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The Effects of Process Water Selection on Lime-Limestone Flue Gas

Desulfurization Chemistry

CS-2451 Co:-~tract TPS 80-730

Final Report, July 1982

Prepared by

RADIAN CORPORATION 8501 MoP<~" ...soulevard

Austin, Texas 78759

Principal Investigators 0. W. Hargrove W. S. Seames

R. L Glover T. R. Blair

Prepared for

Electric Power Research Institute 3412 Hillview Avenue

Palo Alto, California 94304

EPRI Project Manager D. A. Stewart

Desulfurization Processes Program Coal Combustion Systems Division

·~ ... -~--· 1).

ORDERING INFORMATION

Requests for copies of this report should be directed to Research Reports Center {RRC). Box 50490. Palo Alto, CA 94303, (415) 965·4081. There i:;; no charge for reports requested by EPRI member utilities and affiliates, contributing nonmembers, U.S. '!.ltility assccmtions. U.S. government agencies (federal, state, and local), media, and foreign organiz:atrons with which EPRI has an information exchange agreement. On request, RRC will send a catalog of EPRI reports.

Copyngh\ 1982 Etectnc Power Research lnS\Jtute. Inc. All ngh\s reserved

NOTICE ThiS report was prepared by the orgamzalion(s) named beiow as an account of work sponsored by lhe Electric Power Research lnst.tute Inc. (EPRll NeJther EPRI. members or E'PRI. the orgamzahonls) named below, nor any perscfl actmg on behalf ol any ol them (a) makes any warranty. express or 1mphed, w1th respect to the use of any mform;~tion. apparatt.s. method. or process dJ3closed in thiS report or that such use may not infringe private ly owned nghts. or (bl assumes any hab11111es Wllh respect to the use of. or for damages resulting from the use of, any mtormaliOn, apparatus. method. or process d•sc!osed ;n th;s report

Prepared by Rad1an CorporatiOn Austin, Texas

ABSTRACT

The electric utility industry is interested in power plant water management both to

conserve wttter and reduce waste water discharge to a minimum. For those power

plants operating flue gas desulfurization systems, the water management becomes more

complex, but utilization of waste water in the FGD system is )Ossible. Calculations

of the effects of the various waste water streams on operation of lime and limestone

wet scrubbing processes have shown that in many cases the so2 removal is enhanced by

using these streams as makeup water to the system. The results of calculations using various combinations of makeup water, reagents, and flue gas compositions are given in this report.

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EPRI PERSPECTIVE

PROJECT DESCRIPTION

Water management has become more important to electric utilities as regulations for

discharge of waste water have become more restrictive. In the case of power plants

in the western United States, conservation of 'lllater is also a factor. For those

power plants that also include a flue gas desulfurization (FGD) system, integration

of the various other water systems with the FGD process is important. It is possi­

ble that waste water streams or water treatment products c:an be used in the FGD

system without adverse effects by altering operating conditions of an existing FGD

system or designing a new system to accommodate these waste streams.

The work described in this final report for TPS 80-730 calculated FGD stream

compositions and some operating conditions when using various combinations of coal,

limestone, lime, and makeup waste waters. Radian's Process Simulation Model was

used for the calculations around the FGD system, and a cooling tower model d~veloped

for EPRI under RP1261-l was used to calculate cooling tower blowdown and other

treatment WS$te compositions. The raw water compositions were obtained from an EPRI

study of plant water management, RP909-l.

PROJECT OBJECTIVES

The goals of this planning study were to predict FGD liquor compositions when using

waste water from other power plant water systems and to determine the likely effects

on operating conditions, scaling, and so2 removal, using these waste waters at

various points in the FGD system.

PROJECT RESULTS

The so2 removal for these calculations was set such that nel.r source performance

standards would be met--i.e., 70% so2 ~emoval for western coal cases and 90% removal

for eastern coal cases. The variables that were allol.red to change with conditions

were liquid-to-gas (L/G) ratio and reaction tank size. These variables would not be

used in this way in actual design situations; therefore, these data should not be

used for deRign purposes.

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The model calculations showed that the major effect of using cooling tower blowdown

and/or treated waste streams is to increase the concentration of ions which react

with dissolved so2 (alkalinity). This increased alkalinity decreases the L/G

required for the specified so2 removal. This beneficial effect is reduced as

chloride in the coal increases the soluble HCl content of the flue gas. The reac­

tion tank size was allowed to vary to control gypsum scaling in the system. Accord­

ingly, the greater th~ concentration .of sulfate entering the system, the larger the

reaction tank. However, the required size only va~ied by a maximum of 20k over the

fairly broad range of water compositions used in the calculations.

These results were intended primarily for use by EPRI in planning work in this ar(.J,

but they should be useful to FGD operating personnel who are currently using or

contemplating using waste water streams in existing FGD systems. Architect­

engineering firms and electric utilities designing new plants with FGD processes

sho~ld find the data of interest to indicate possible effects of water integration on the FGD system.

Further studies are under way in the laboratory under RP1031-4 to supplement and

confirm the calculations from this work by investigating effects of actual

dissolved-solids concentration levels on so2 removal, equilibrium solid-liquid phase

relationships, calcium sulfite and calcium sulfate nucleation and growth rates, and

crystal habit (size and shape) of the solid phases. These data are being used to

plan the test program for the wet scrubber in the Integrated Environmental Control Pilot Plant at the Arapahoe power plant (RP1646-4).

Dorothy A. Stewart, Project Manager Coal Combustion Sy~tems Division

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CONTENTS

Section

1. INTRODUCTION

Backgrouud

Objective

Approach

Study Basis

Variable Matrix

Process Simulation.s

Report Content

2 • MODELING APPROACH

3.

Lime/Limestone Process Description

Flue Gas Cleaning

Reaction Tank

Dewatering

Radian Process Model

Spray Tower (SCRUBS)

Reaction Tank (RATHLD)

Thicken~r/Filter (FILTER)

Modeling

RESULTS

Results Summary

Effect of Makeu~ Water Source

Effect of Water Source in Eastern Coal Cases

Effect of Water Source in Western Coal Cases

Effects of Reagent Feed Source

Lime Versus Limestone

Effect of Reactive Magnesium Content in FGD Systems

Vii

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Page

1-1

1-1

1-2

1·-2

1-2

1-9

1-13

1-13

2-1

2-1

2-4

2-8

2-10

2-11

2-11

2-15

2-16

2-16

3-1

3-2

3-4

3-4

3-7

3-11

3-1).

3-13

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Section

CONTENTS

(continued)

Effect of Coal Chloride Content

Effect of a Prescrubber in High Chloride Coal/Lime FGD Systems

Mist Eliminator Wash Loop Results

Effect of Makeup Water on Operation of an Existing FGD System

Effect of Typical Low Volume Wastewater on FGD System Process Chemistry

Alternative Design Concepts

4.. CONCLUSIONS AND RECOMMENDATIONS

Conclusions

Recommendations

5. GLOSSARY OF TERMS

6. REFERENCES

APPENDIX A - RESULTS FOR ALL SIMULATION CASES

Viii

Page

3-17

3-17

3-19

3-23

3-25

3-27

4-1

4-1

4-1

5-1

6-1

A-1

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ILLUSTRATIONS

Figu:t'e

2-1 FGD System Flow Diagram

2-2 Process Model Flow Plan

3-1 Effect of Liquid Phase Alkalinity on L/G Ratio for Spray Tower Designs

3-2 FGD System Flow Diagram Including Prescrubber

ix

Page

2-2

2-12

3-3

3-20

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TABLES

Table Page

1-1 Representative Makeup Water Compositions 1-4

1-2 Waste Stream Makeup Wator Composition 1-5

1-3 Alkaline Reagent Compositions 1-7

1-4 Coal and Flue Gas Compositions for Typical Eastern and Western 1-8 Coals Fired in a 500 MWe Steam Plant

1-5 Matrix of Main Loop Cases Studied for Eastern Coals 1-10

1-6 Matrix of Main Loop Cases Studied for Western Coals 1-11

1-7 Additional C~se Studies 1-12

2-1 Summary of Scrubber Design Concerns 2-6

2-2 Summary of Slurry Sy,stem Design C•.mcerns 2-9

3-1 Effects of ~fakeup Water Source on Eastern Coal, High Magnesium 3-6 Limestone FGD Systr~ms

3-2 Effects of Makeup Water Source on Western Coal, High Magnesium 3-9 Limestone FGD Systems

3-3 Comparison of High Mg Limestone and Lime for Eastern Coal and 3-12 FGD Systems

3-4 Effects of Mg Availability in Limestone on Eastern Coal Systems 3-14

3-5 Effects of Mg Availability in Limestone on Western Coal FGD Systems 3-16

3-6 Effects of Co1al Chloride Content on Lime Eastern Coal FGD Systems 3-18

3-7 Effects of Using a Prescrubber for Chloride Removal on High Mg 3-21 Lime Eastern Coal FGD Systtims -Main Loop Results

3-8. Results of Simulations of Prescrubbers Upstream of Higher Magnesium 3-22 Lime FGD Systems

3-9 Results of Mist Eliminator Wash Loop Modeling 3-24

3-10 Effect of Makeup Water Source on Operation of Existing Western 3-26 Coal, Low Magnesium Limestone FGD Systems

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TABLES

(continued)

Table !~~

3-11 Effects of Typical Low Flow Rate Wastewaters on ~~Eastern, Low 3-28 Magnesium Limestone FGD System

3-12 Effects of Typical Low Flow Rate Wastewaters on a Western Coal, Low b!agnesiu.m Limestone FGD System

Xii

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SUMMARY

Electric Utilities are currently making efforts to balance and minimize water

usage in power plants. This will both conserve water and reduce waste water

discharge. Integrating the cooling water systems with flue gas desulfurization

(FG.Il) systems is one means to reduce fresh water demand. !faterial balance

calculations of integrated systems have been made to predict the effects of

different process water compositions on FGD system chemistry and process design

for both Eastern coal (10,100 Btu/lb (23,500 :r/g) and 4.0 pe;-:cent sulfur) and

'i!estern coa1 (8,080 Btu/lb (18,800 J/g) and 0.48 percent sulfur) applications.

The process simulation model developed by Radian was used for these calcula-tions. The water sources selected for study included Santee River water

(76 mg/L total dissolved solids (TDS)), Mississippi River ·water at St. Louis

(457 mg/L TDS), and Lake Sakajawea water (3500 mg/L TDS). Two different models

of cooling tower operation were also simulated using Lake Sakajawea and

Mississippi River water as makeup, and the cooling tower blowdown streams were

used as alternative makeup sources for the FGD system. Candidate low volume

wastewater (demineralizer regeneration waste and pretreatment softener clarifier

blowdown) were also briefly examined to supplement makeup water requirements tc

the FGD system. A study plan was designed so that a range of possible operating

conditions was examined in both Eastern and Western coal cases. Other important

chemical variables such as reagent selection (lime or limestone), reactive

magnesium content of the reagent, and chloride content of the coal were also

:i.nvestigated as part of the program.

The chemical effects predicted for ¥GD system operation were: (1) the alkalinity

(total amount of chemical species which are basic with respect to SOz) required

to meet SOz absorption requirements (sets the l:i.;;tuid/gas ratio), and (2) the

system's chemical scn.ling tendency (sets reaction tank size). A spray tower

system with a single ruaction tank was the design configuration used to examine

effects on a consistent basis. In each case, the liquid-to-gas (L/G) ratio was

determined based on the alkalinity required to achieve the desired S02 absorp-

S-1

tion, and the reaction tank was then sized to prevent gypsum scaling conditions

in ·the absorb~r. Additionally, mist eliminator wash loop performance, using poor

quality wash water, and the effect of a prescrubber on FGD system chemistry were

briefly examined.

The results of this study should not be applied directly to actual design

applications since important considerations such as physical S03 mass transfer

limitations were not addressed quantitatively. As a result, unrealistic L/ G' s

for spray towers were simulated {bss than 30 gal/Macf (4.5 m3/Nm3) in some

Western cases and greater than 200 g.al/Macf (30 m11 /Nm3 ) in some Eastern casets).

However, the results of the study emphasize the importance of considering pro­

cess chemistry variables in the design or. modification of FGD systems. If cer­

tain key process variables s.re not :b.andled properly in the design phase of a new

system or are altered in an existing system, the FGD system may not meet desired

SOz removal or reliability goals wUhout expensive alteration to eqtdpment and/

or addition of chemical additives.

The major effect of alternate wate1c sources, reagent magnesium content, or coal

chloride is o.t the liquid phase alkalinity and the resulting L/G required for

S03 sorption. These chemical var~ables caused L/G values to change by as much

as a factor of 8 while the maximum·variation in the reaction tank size was about

20 percent.

In general, the L/G in an Eastern r.:oal system will be higher than in a Western

coal system both because of the higher sulfur level and because a higher SOz

removal percentage is requir.ed by regulation, For a consistent coal sulfur

composition, however, the liquid phase alkalinity is the primary variable which

influences the L/G requirements. In systems operating without organic addi­

tives, the liquid phase alkalinity is affected primarily by the concentrations

of the soluble species, magnesium, sodium, and chloride. Systems ·which. operate

with: (1) higher concentrations of reactive magnesium in the limestone (2) pro­

cess makeup water high in magnesium and sodium relative to chloride, and

(3} relatively low coal chloride-to-sulfur ratios require lower L/G values to

achieve equivalent SOz removal efficiency.

S-2

The main effect of process makeup water composition is to alter the liquid phase

alkalinity although the process ch1...nistry changes may also modify gypswn scaling

tendency. Cha:nges in makeup quality resulilted in variations in L/G req·tlirements

of a factor of two for the Eastern cases amd a factor of 8 for the Western cases

Using blowdown from a cooling tower, using1; Mississippi water with lime/~oda ash

sidestream softening as makeup to an FGD :system, results in the highest liquid

phsse alkalinity and lowest L/G ratio of all the: Eastern coal cases examined.

The sodium treatment results in a much more alk!aline scrubbing solution when

this blowdown is used in a l!ime or limestone FGD system. This emphasizes that

high TDS makeup water is no·t necsssarily detrimental to FGD system performance.

However, the full effects on the prooess chemistry of all unit operations should

be considered before makin& the process water selection fer a specific applica­

tion since process water quality also has an effect on design of equipment such

as the mist eliminator wash loop.

Other important process chemistry variables include the chloride-to-sulfur

(Cl/S) ratio in the coal and the amount of reactive magnesium in the limestone.

If the coal's Cl/S ratio is high, the dissolved chloride concentration is high

and SOz removal (and liquid phase alkalinity) is lowe::ed. Conversely, high

reactive magnesium concentrations in the limestone tend to increase the S02

removal efficiency. Variations in these properties can cause the design L/G in

a spray tower to more than double, although process design changes are likely in

high chloride situations. One modification is addition of a chloride prescrub­

ber to lower the chloride concentration in the main scrubbing loop which lowers

the L/G requirement.

The effect of adding low volume demineralizer regeneration and pretreatment

softener blowdown wastewater streams should have little effect on FGD system

operation if the rate of addition is averaged over time. On a time-averaged

basis, the wastewater streams are small compared to the FGD system's water re-­

quirements, but surges in these wastewater flows could cause some significant

changes in the FGD process chemistry.

S-3

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The performance of a once-through mist eliminator wash loop, using untreated

Lake Sakajnea water (gypsum relative saturation of 0.4) for washing, was also

modeled. The wash requirements using this water were within the constraints for

achieving zero discharge. However, if the wash water is saturated with respect

to gypsum (e.g., some cooling tower blowdown streams), an alternate wa£h scheme

may be necessary to prevent scale buildup. Dilution with other process water or

a deluge wash sequence are two possible !llternatives. The main point to be em­

phasized is that the effect of the wash water chemistry on mist eliminator wash

loop design should be considered.

Caution should be exercised before applying these results to any existing plant

situation. The model has not been fully validated a~ all high ionic strength

(high TDS) conditions; and, while the trends should be consistent, the actual

magnitude of the effects may not be accurately quantified. Efforts are continu­

ing in validation for high TDS solutions.

S-4

·~

Section 1

INTRODUCTION

BACKGROUND

Electric utilities have considerable interest in water management at the present

time. As new power plants are planned and built, pressures to minimize water

discharge rates and water consumption increase. Shortages in water resources in

the West and in some locations in the East and increasingly stringent water dis­

charge regulations contribute to these pressures.

The increased emphasis on minimizing water consumption and effluents creates the

need for fully integrated power plant water systems. Flue gas desulfurizntion

(FGD) systems are a net consumer of water and, therefore, can play a key role in

the overall integration scheme, In particular, lime and limestone FGD systems are

of interest 1) beca1tse they are the predominate systems currently in use and pro­

jected for use in the near future and 2) because they can tolerate higher levels of

dissolved impurities than most regenerable FGD systems.

The potential of using a cascading water system to achieve zero blowdown is recog­

nized. Plant water systems that require high quality water (e.g., boiler feed

water, cooling systems, etc.) can send their blowdown to the FGD system for use as

makeup water thus effectively reusing water and minimizing fresh water makeup

requirements. However, the overall water system including the FGD system must be

properly designed and operated to avoid problems created by chemical scaling.

Actually, the integrated water system is a complex chemical system and must be

treated as such to succes~fully minimize water discharge whil~ achieving reliable

operation. EPRI commissioned Radian to use its process simulation capabilities to

examine the effect that different water sources can have on FGD system process

chemistry and how integration of the cooling tower and other water systems with the

FGD system might alter the process chemistry.

1-1

•·

OBJECTIVE

This project was designed to provide insight into the effects of different process

makeup water qualities on the process chemistry of lime/limestone FGD systems, It

is apparent that the makeup water sources cannot be studied independently of other

important chemical variables such as coal composition and alkaline reagent composi­

tion, so a plan was developed to examine the effect these important variables have

on FGD performance, TWo specific objectives were enumerated:

•

•

characterize liquid and solid phase compositions of major FGD process streams for different makeup wat~·rs, and

predict the relative effects of different makeup waters on lime/limestone system process chemistry.

The major FGD process design variables, liquid-to-gas (L/G) ratio, and reaction

tank size, were used to monitor changes in the process chemistry and. measure

relative effects of different makeup water and other chemical variables, It was

not the objective to obtain optimum process designs for each case examined in this

study. Rather, a consistent design configuration was employed, a single spray

tower contractor with a single reaction tank. Changes in I./G or tank size are

therefore directly related to process chemistry chahges, but in some instances

result in unrealistic L/G ratios. This simply reflects that an alternate config­

uration design (for example, double loop system or packed absorber) should be

considered, if these FGD cases were actually to be constructed.

APPROACH

Three basic steps were taken in meeting the project's objective. First, a study

basis was developed which included specifying process makeup water compositions,

coal compositions, and reagent compositions and setting a plant size of 500 mega­

watts (llw), net. Then, a matrix of cases was composed to examine a wide range of

variables which affect FGD process chemistry. Finally, process chemistry compari­

sons were made ·with the assistance of th~ Radian Inorganic Process Simulation Model.

St.udy Basis

osi­Tho study bosis wos ••loctod to ••••uro tho offoct of proc

0,, nokoup wator conp

tion ha, on FGD 'Y•t .. procos, ch,.i,try. Dowevor, interactions betwoon the nokoup

wator composition and othor chonicot voriabte, wero recognizod. ond an appropriato matrix was set up to include:

1-2

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•

•

process makeup water composition- untreated waters, cooling tower blowdown, softener blowdown, demineralizer regeneration waste;

reagent composition - lime and limestone each with high and low reactive magnesium contents; and

coal composition- Eastern and Western coals with variation of chloride content in the Eastern coal.

Makeup Water Compositions, Santee River, Mississippi River, and Lake Sakajawea

were the water sources chosen to represent power plant water sources that contain

low, medium, and high levels of total dissolved solids (TDS) which may be found

across the country. Santee River water is very low in TDS [76 ppm(w)] and repre­

s~nts clean water sources which are found in some locations in the East. Missis­

sippi River water taken near East St. Louis, Illinois, was analyzed to have 457

ppm(w) TDS which is representative of water quality which can be found generally in

the East and in some locations in the West. Lake Sakajawea has 3500 ppm(w) TDS and

represents waters which may be found in the rather arid portions of the Western u.s.

Two cooling water treatment options were modeled for the Mississippi and Lake

Sakajhwea mak~up water sources to generate cooling tower blowdown streams which

could be evaluated as makeup water sources for FGD systems. The effect of two

levels of treatment on cooling tower operation and resulting blowdown compositions

were examined: (1) acid addition and (2) acid addition with sidestream softening.

The cooling towe-· modeling was performed by Radian on a supporting EPRI project, RP

1261-1. The compositions of the untreated water source and cooling tower blowdown

streams are shown in Table 1-1.

The first cooling tower operatiounl scheme using acid addition models n typical set

of conditions for the cooling tower. Four cycles of concentration were set as a

goal with sulfuric acid added to control pH and prevent ~alcium carbonate scaling.

Mississippi River water can be cycled to four in this sch~~,; however, gypsum

scaling would occur if Lake Sakajawea water were concentrated to that degree.

Therefore, the acid addition case for Lake Sakajawea was modeled ~t 1.5 cycles of

concentration to remain below the saturation value for gypsum.

An additi~nal cooling water treatment scheme involving both acid addition and

lime/soda ash sidestream softening was also modeled. The sulfuric acid is added to

control pH and therefore calcium carbonate scaling. The lime/soda softening is

designed to remove calcium from the recirculning water to minimize the Jhances of

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gypsum scaling. A slips~ream equal to one percent of the total rec.

rate was treated in this case. Mississippi River water could only be

to about 8 cycles to maintain a gypsum relative saturation below 1.0. L

cycles of concentration were possible with the Lake Sakajawea water due to

relatively high sulfate concentration of the untreated water. Even so, the & .

rel2tive saturation in the recirculating cooling water in this case was almost •

which approaches the 1.3 to 1.4 level when incipient nucleation and possible equi~­ment scaling begins, Careful control would have to be maintained to operate the

cooling tower in this manner and conservative practice would be to reduce the

cycles of concentration to achieve a gypsum relative saturation of about 1.0. San­

tee River cooling tower blowdown was not used as makeup water in this stuny since

the TDS levels resulting from using Santee cooling tower blowdown are covered by

the other cases examined in the project.

In addition to these major water sources, the effect of two additional minor waste­

water streams were evaluated. A typical cation/anion demineralizer regeneration

waste and a typical pretreatment softener waste were combined to f~rm a 53 liters/

min (14 gpm) makeup water stream. 1~e composition of this composite waste stream

is presented in Table 1-2.

T .ole 1-2

WASTE STiffiAM MAKEUP WATER COMPOSITION

Component Concentration im&L1l Ca++ 168

Mg++ 6.6

Na++ 157

Cl- 73

NOg- 0.2

S04= 3,'190

10.0 pH

This wastewater was used as makeup to the FGD system iu both ~n Eastern ~nd a

Western coal case.

1-5

Alkaline Reagent Compositions. Lime and li~~~ton~ reagents were selected primar­

ily to give a :range of reactive magnesium values. Table 1-3 shows the compositions

of the reagents selected. The limestone chosev was Fredonia limestone which has a

magnesium-to-calcium molar ratio of 0.018 and is currently being examined in EPRI's

limestone dissolution project, EPRI Technical Planning Study No, 79-747. Since the

dissolution of magnesium from limestone is not fully understood and litiu3stones have

different reactive magnesium contents, higher and lower magnesium availability

cases were studied. For the higher magnesium cases, the magnesium was assumed to

dissolve at the same Mg/Ca ratio as exists in the solid limestone. To model lower

magnesium reactivities or lower magnesium conceutration limestones, a limestone

with a 0.0018 reactive Mg/Ca ratio was used. The two lime compositions studied

were obtained from Wallace and Tiernan publications. Actual lime compositions were

selected to reflect higher and lower reactive magnesium levels corresponding to 0.023 and 0.0075 Mg/Ca molar ratios.

Coal Composition. The effects of the different process waters were studied for

both an Eastern and Western coal situation. Table 1-4 shows the compositions of

the coals selected and the flue gas composition which results from combustion

conditions. These coals are the same as those selected in a previous EPRI study

(!), and the assumptions made in performing the combustion calculation are detailed there.

These two coals result in two different sets of FGD system design requirements.

The primary reason is the different coal sulfur content. The New Source Perform­

ance Standard, revised in 1979 (~), requires 90 percent reduction in sulfur

emissions for the Eastern coal and 70 percent sulfur xeduction in the Western coal

system. As this study shows, the combination of lower sulfur removal and reduced

sludge processing in the Western cases can emphasize differences in the process water selected.

In •ddition to tho boso oool '••o•, tho effoot of highor ohlorido compo,ition in

tho £o•torn •••I on FGD proco,, ohemi,try wa, ox .. inod in a fow co,e,, The chlor­

ide contont wa, triplod resulting in o oool with 0,3 porcont C1 rothor thon 0.1 and

a fluo Sa• containing 210 pnrt, por million (ppm) HC! rathor thon 70 ppm,

1-6

-.\

LIMESTONE

Component

CaC03

MgC03

Inerts

Jfg/Ca Mole Ratio

LIME :

Component

Ca(OH)2

!1lg(OH) 2

Inerts

lrfg/Ca Mole Ratio

Table 1-3

ALKALINE REAG~T COMPOSITIONS

------------~C~o~mp~o~s~.ion (percent (w) Higher Magnesium Lower Magnesium

96.63 96.63

1.50 0.15

1.87 3,22

0.018 0.0018

94.90 95.20

1.66 0.55

3.44 4.25

0.023 0.0075

1-7

f

~f.

·~ r f-':

Table 1-4

COAL AND FLUE GAS COMPOSITIONS FOR TYPICAL EASTERN AND WESTERN COALS FIRED IN A 500 lt!We STEAM PLAm'

Component

Carbon Hydrogen Nitrogen Chloride Sulfur Ash Oxygen .Moisture

TOTAL

RHV {Btu/Ib)

Component

so2 H20 C02 NO N~

L

02 HCl

lUTAL

Flow rate (acfm) Flow rate {scfm) Tem2erature (°F)

0

COAL COMPOSITIONS

Ultimate Analysis (weight %~ Eastern Western

57.5 47.85 .3.7 3.40 0.9 0.62 0.1 0.03 4.0 0.48

16.0 6.40 5.8 10.83

12.0 30.40

100.0 100.00

lO,lOu 8,020

FLUE GAS COMPOSITIONS

Compositinn (mole fraction! Eestern Western

0.2959 0.0402 8.190 11.92 11.95 11.88 0.0504

0.0478 14.68 70.46 5.824 5.656 0.00704 0.00252

100.0 100.0

1.713,.000 1,881,00(\ 1.172,000 1,287,0tJ0 301)

300

1-8

Variable Matrix

Once the process variables were delineated, a study matrix was outlined. Tables 1-5

and 1-6 show the variables which were examined to assess their effects on the primary

FGD system scrubbing loop. The cases selected for study were prioritized to pro­

vide the necessary information in a cost-effective manner rather than to examine

the full matrix of possible cases. First, a cross-section of variable effects in

both East.ern and Western coal cases were selected to study. Then moxe detailed

attention was devoted to specific cases which arc likely to occur in each geograph­

ic region. For instance, all three raw water sources were studied ::or the Eastern

coal cases. Then more attention was focused on the use of Mississippi River water

(untreated and two cooling tower blowdown treatment schemes) with different reagent

types since the Mississippi water is more representative of the water likely to be

encountered in the East. Likewise, the effect of higher chloride content coal was

only studied in the Eastern cases since Eastern coals are more likely to have the

higher chloride concentrations. Ou the other hand, more attention was focused on

Lak" Sakajawea water in the Western cases since this water is more typical of the

situation likely to be encountered in the West. The Santee River water was not

simulated in the Western case studies since this water quality is not generally availa'ble in the West.

Some additional cases were run to examine situations outside of the primary vari­

able matrix. These cases are summarized in Table l-7. The first set of cases 1ras

designed to measure the effect of a 53 liter/min (14 gpm) wastewater stream (demin­

eralizer regeneration and softener blowdown wastes) on FGD system process chemis­

try. Cases E16 and Wl9 can be compared with the results of Cases E09 and W07,

respectively, to determine the effect of this fairly small wastewater stream. The

second set of additional cases models the effects of changing the process makeup

water on fixed FGD system designs (e.g., for existing systems). In one case the

S02 removal efficiency and gypsum relative saturation were calculated based on

fixed L/G and tank size. In the other case, the L/G and gypsum relative s~t~r~tion were calculated for a specified S02 removaJ, and fixed reaction tank size. The

gypsum relative saturations calculated in these cases were evaluated for scaling

tendency. In all other cases the tank size and L/G were adjusted to achieve non­

scaling ~onditions and specified S02 r~movals. In the third set of cases shown

in Table 1-7, the effect of a prescrubber for chloride removal was modeled for a

high sulfur Eastern coal application. Two ,Process waters were use.d in this pre­

scrubber modeling. Finally, the wash rate required to maintain scale-free mist

eliminator ,Performance was mode.led using untreated Lake Sakajavrea as the system's makeup water.

1-9

- .. ,; ifl ' ,I

i

Table 1-5

MATRIX OF MAIN LOOP CASES STUDIED FOR EASTERN COM S

Water Treatment Alkaline Feed Source Case Water Source Cooling Tower Lime Limestone Designation Santee .Mississippi Lake Sakajawea Untrea_ted Acid Treated ~· High Mg Low Mg High Mg Low Mg

Eastern Coal

Low Cl

\} j EO! X X X EOZ X X X E03 X X :X ...... E04 X X X I ......

0 EOS X X X E06 X X X E07 X X X EOS X X

X E09 X X :X E10 X X X Ell X X X

H.:5;1t Cl

El~ X X X E13 X X EH X X X X E15 X X

X

~Sidestream Softened

Table 1-6

MATRIX OF MAIN LOOP CASES STUDIED FOR WESTERN COALS

Water Treatment Alkaline Feed Source Case Water Source Cooling Tower Lime Limestone Designation Santee ltlississiJ!I!.i Lake Sakajawea Untreated Acid Treated -ill* High Mg_ Low Mg High Mg Low Mg

Western Coal

WOl X X X W03 X X X W04 X

X X

..... wos X X X

I

' .... f-o.

W06 X X

X W07 X

X X wos X X

X W09 X X X ~

WlO X X X

Wll X X

X W12 X

X X

W13 X X

X W14 X X

X W15

X X

X W16 X X X X

*Sidestream Softened

r--. I

""' Ul

""' .0

~

tl) (.:l

~ tl)

(.:l tl)

t3

~

i

0 ):

.3 "I ' .,, ~

loft -"' :::o• " ej ... ;,: .

' .. ... i l:J

81

.. u .. " 0

"' 0 ~ ....

~

g ... .. " ~ .. .. II It 0 -" .. 0 .. .. " ll ... ~

~I ~I ..,

!; ., .. .. .. 11<

~ .... .. .. ~ .. • II

.Q ... ...

.Q

0

" 0 .. .. " II ... ~

~:;• -;:

< .........

i .. e ~ :; .. E! 11< 0 0

> ... . = ~ " .. 10 ... ... . . "' ..., :r;: !' .:l .. .. :;~· ,::: rn E ., - .. .. ... "' :r;:

.. ... .. ...:l

.. ~

... 0 .. -...... = .. " ..

0 .. .. .. " .. . : ...

... .. " Q

" .. .. <.>

"' ~ 10 ;;l

.. .. .. ,.. .J

" .. ... .. .. Q

"' .. H ... "' ... ....

gl ~ .. .. = .. 0• ...

~ " ... ..

(1!1 14 : ~~ .; "'

<>!

~1 ~· -· -"' ... <

11 .. " ~

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~ .. " " ... .. B ): 0 ... l

0

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" .... .. " > ... :.:

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'd .... .. < e ... .. > ... ~

... ... c. "' "' "' ...... .. ..

.!! .: .. .. .. ..

... ... :.: :.:

0 ., ~ .. .. .. C!

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':! ~ "d

" H ... t:,

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g ... .. " " .. .. !I ,. 0 ... 0

= 0 ... .. .. II ... ~

'd ... u ~

t .. .. .,. .. Cl''

~· .... !' .. .. ... .. .. ... ::.:

t:O ',) "d <I .. ... " ~ 'd <> .. ... t:,

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.. .. E! 'Z "'

" 0 ... .... .. " ... .. " Q .. .. ..

t)

l-12

.Q .. ... A

.. ~ ... ..... .... ""O ., .... •.a l::lu

9 ... .. .. " .. • II 10 0 ... .. II ...

...:l

" " 0 <:1 1:; .. > ... :.: ... ~ ... .. .. ... .. .. ...

:r;:

a "' "'

...: .. ...

...: I

e .. ... .. .. l:J

~ .. .. " "' .. n .. 0 .....

" II ... ~

"' "' rn

~ ... .. ! :.: ... ~ ... .. .. ... .. .. ...

::.:

g "' "'

.. .. '" .. u ...: .. .. llo

It 0 ... .. " ... !l ... .1<1 .... .. ~

> ....

0

::: " 0 til ... .. s

" u ... "' 0

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.!! .... " ~

... <I .. E ... .. .. ~

a It 0 ... .. :

9 .... .. 0 <I .. .. H

.Q .. ...

...: I 0 <I 0 ... .. 0 H ... ~

"I .. ., 0

""i = ::.: ";;' ... ... .. ii (t:

... " .. ~ "' .. ...:l

~~ a :: Sl Q ., .. "" u

:;;-.. .. .. .., 0 .. -.. a ... a ...

"'~ 0 ..,.,. J< " 0 = ......

<Q ... .... ... 0

""' 10

~!l " .., ..

a .... ... .. .... .. O"d o ... Utll

I I

e~ ......

Process Simulatioqs

Each of the cases outlined in the va~iable matrix in Tables 1-5, 1-6 and 1-7 was

modeled using the Radian Process Model. This model is described in more detail in

Section 2, Modeling Approach. The Radian model was developed primarily for concep­

tual design applications; therefore, design variable such as L/G and reaction tank

size were employed as indicators of process chemistry r.hanges. A single confisur­

ation, spray tower contactor with a single reaction tank, was used to model all

cases so that evaluation of process chemistry changes would be more straightfox­

ward. It is emphasized here that this design configuration is not practical lor

some of the cases examined. For certain water/re&gent/coal combinations more

efficient contactors would have to be designed to achieve the desired S02 removal

at more reasonable L/G ratios. However, it was not within the scope of this study to obtain an optimum design for each case •

REPORT CONTENT

The scope outlined in this section is described in more detail in the following

sections. Section 2 briefly describes important aspects of lime/limestone FGD

system process design considerations and the Radian process model used to simulate

the matrix of cases. Then Section 3 presents and discusses the results and explains some important chemistry effects •

~

l-13

C·

Section 2

MODELING APPROACH

The lime a;~d limestone systems considered here and the Radian modeling approach and

assumptions have been described in a previous EPRI report (~). As a result. only

the highlights will be addressed in this section. First, some im<\'>rtant process

design considerations for a lime/limestone system are discussed. 'Then the Radian

process model is related to the FGD system and important assumptions are identi­fied.

LIME/LIMESTONE PROCESS DESCRIPTION

A schematic of a lime/limestone FGD system is shown in Figure 2-1. Lime or lime­

stone is added to the reaction tank. and a slurry of calcium salts is contacted

with the flue gas in the absorber where S02 is transferred to the slurry. The

S02 ladened absorber effluent is then recycled back to the rea~tion tank where

alkaline reagent is added continuously. and the bulk of the precipitation of insol­

uble salts, calcium sulfite and calcium sulfate, is accomplished. A slip stream

from the reaction tank is sent to the dewatering area where solid-liquid separation

occurs. The sludge so1:d cake or concentrated slurry is generally disposed of in a

landfill or pond oite.

The overall reactions process chemistry reactions are shown below:

Limestone System:

X 1 . 1 S02 (g) + CaC03

(s) + 202 + 2H20+Ca[(1-x)S03

•xso4

J·2H20(s} +

C02(g) (2-1)

S02 (g) + CaC03

(s) + ~02 + 2H20+CaS04

•2H20(s) + co

2(g) (2-2)

Lime System:

1 1 1 so2

(g) + CaO(s) + 2o2 + 2H2o+ca[(l-x)S03xso4J • 2H20(s) (2-3)

so2 (g) + CaO(s) + ~02 + 2H2o+caso4·2H20(s) (2-4)

co2

(g) + CaO(s) + CaC03(s) (2-5)

2-1

"'

i.J-

~1

J.,

:~ ~

~ i

o': Ul;;.;

1 ~

.o.; ..... =~ ~ E~

,;,

j 1.

;. .... .... ·: ..., 1 ... .,., .., ... : 5' Ci e:J

~ .: .... ";j

"" :;:

2-2

;>. :,:Jt~~itf'Jfi\

.... 1:1 <? 0 g. ....

Q

g

.. H~ ~ ~· ; k

.: tnt"" 0 -.'~ 't$- ·~ ..u: ' ~ .._, ..:I 1!3 .:C t.7 I J.l

~t: '0:!1~ ~~ 0 l~

UJ

. ~ 10

•1"1 'tl

~ 1;:1

~ .u

~ rn

~ • .-!

~ C)

~ •1"1 ~

The main difference in the overall reactions for lime/limestone FGD sy$tems is that

C02 is evolved in limestone systems while some 002 is absorbed in lime syatems.

Note that two equations are written for the precipitation of sulfur solids in lime

and limestone systems. The first indicates the formation of a calcium sulfite/sul­

fate solid solution. Some oxygen is sorbed into the scrubbing slurry which reacts

with absorbed sulfite species and forms liquid phase sulfate. If the fraction of

the absorbed sulfur that is oxidized is less than about 15 percent, then the sul­

fate formed is included in calcium sulfite lattice as a solid solution. The amount

of sulfate formed in excess of 15 percent is preciyitated as CaS04

•2H2

o (gypsum).

A system functioning in the latter mode of operation is said to be operating super­saturated with respect to gypsum •

The level of oxidation is important since one of the more difficult chemical prob­

lems handle in lime/limestone FGD systems is control of chemical scaling, As the

S02 is absorbed the dissolved concentrations of relatively insoluble calcium

sulfite and sulfate build up and the liquor becomes supersaturated. The degree of

supersaturation may be measured by the relative supe~saturation (generalized as

relative saturation to cover subsaturated cases as well). The relative saturation

of gypsum is defined as follows:

RSGyp = [aca++J[aso4 = J[aa2oJ 2

Ksp,Gyp

where RSGyp is the relative saturation of gypsum; aca++, aS04=, and aHzO

(2-5)

are the activities of calcium, sulfate, and water, respectively; and Ksp,Gyp is

the solubility product of gypsum at tho solution tempe~ature. If the relative

saturation of gypsum exceeds about 1.3, gypsum solids begin to form as small

nuclei and solids may begin to precipitate on equipment surfaces.. The critical

relative saturation for calcium sulfite nucleation is not as well deftned but is

known to be a factor of five to eight times higher. This chemical scaling should

be avoided if possible since severe or prolonged scaling conditions can result in

a forced equipment outage.

The objective in designing an efficient lime/limestone FGD system is to (1) achieve

the desired SOz removal, (2) minimize the chances of spontaneous nucleation and

scaling, (3) produce an easily handled solid waste product, and (4) minimize

2-3

capital and operating costs while achieving the first three goals. In this ProJect

however, the goal was to compare the effect of different process water

effective, prActical system design.

As a prelude to the discussion of the modeling approach used in this study, a brief

discussion of the important FGD process areas is provided here. The processes can be generally categorized as:

• flue gas cleaning - gas-liquid contact occurs urator, and mist eliminator; in absorber, presnt-

•

•

solids dissolution and precipitation - primarily occurs in the reaction tank;

solids separation and disposal - occurs in thickener, filter, and/or pond.

Flue Gas Cleaning

Gas-liquid contacting occurs in the presaturator, mist eliminator, and absorber.

1he presaturator is generally used to quench the hot flue gas before it enters the

main absorber to protect absorber lining and to control the wet-dry interface

outside of the main scrubber vessel. Sometimes the presaturator loop is separated

from the main slurry loop to remove HCl from the gas and segregate dissolved. chloride.

The mist eliminatox is generally designed to remove entrained slurry from the

cleaned gas by impaction prior to the gas stream's entry into the stac~. The

entrained slurry contains some alkalinity which promotes some additional S02 removal across the mist eliminator. However, the biggest ator reliability is washing the entrained

to prevent scaling or plugging problems.

concern with mist elimin­slurry fro~ the mist eliminator surfaces

types Mo" of tho 802 rouovd occur. in tho main ahorbor vouol. Thoro are many

or ab,orbor, which havo boon propo•od and u•od in comuorcial FGD •ystou•. These

inoludo •Pray towers. packad beds, turbulent contnct ab,orbers (TCA), ventur" • . s

2-4

and combinations of these including multiple contactors in series such as the

double-loop design. Because of its open design which is resistent to scaling and

plugging problems, spray towers have been used in many recent designs and was >tsed

as the design concept in this study.

Absorber design concerns are summarized in Table 2-1. The main function of the

absorber is to achieve the desired S02 r.emoval in a scale free mode of operation.

Important concepts related to S02 removal are alkalinity to maintain a driving

force for S02 mass transfer and physical gas-liquid contact capability. Scaling

control is achieved by considering the reaction tanl:. design in conjunction with

scrubber design.

Alkalinity. Alkalinity can come from either the liquid or solid phase although

alkalinity in the liquid phase can react with S02 more quickly which is important

in determining the optimum slurry rate. The S02 sorption step is shown in Eq. 2-6.

so2 (g) + n2o:tn+ + nso; (2-6)

Any species which can neutralize the n+ formed in this sorption step will shift

the reaction to the right and will maintain the drivin& force for S02 sorption.

Dissolved species in the scrubbing liquor which are alkaline with respect to S02

absorption include:

so; CaS03

(l!.) MgS03

(£) Naco;

HC03 caeo3

(~.) + MgHC03

NaHC03

($1.)

co; + MgC0

3 ($1.) . CaHC0

3

An important variable which has a major impact o~ the liquid alkalinity is the

relative amount of soluble sodium and magnesium compared to dissolved chloride

content. First, consider that the liquor must have an equal number of positive and

negative charges. If only the major dissociated ions (no ion pairs) are considered

and if the relative amounts of n+ and on- ions are small compared to the other

dissolved species which is normally the case in most FGD systems, then the charge

balance can be written:

2[Mg++] + [Na+] + 2[Ca++]

2[c; J + rnco; 1 + [Cl-l

2[so;1 + 2[SO~l + rnso;J +

2-5

(2-7)

Table 2-1

SUMMARY OF SCRUBBER DESIGN CONCERNS

Concerns

Alkalinity

~lass Transfer Capability G/Ll Distribution GIL Interfacial Area GIL Residence Time

Scale Control

1GIL - gas-liquid

Variables

Liquid Rate

Liquid Composition

Slurry Concentration

Spray Levels

Nozzle Arrangement and Type

Scrubber Dimensions

O.xidalion

Rearranging Eq. 2-7 so that the more soluble species are on the left and species

constrained by solubility in lime/limestone systems are on the right yields:

2[Mg++] + [Na+]

2[CO~l + rnco;1

[Cl-J = 2[so;J + 2[so;J + [Hso;J +

2[Ca ++]

Eq. 2-8 shows that as Mg++ and Na+ incroas'' relative to Cl- the soluble

alkaline spec~es su~h as so; and co; must ~~crease to maintain the charge

balance. <so; is not alkaline but it also in~'teases.) Since these calcium

(2-8)

salts are constrained by solubility, the calcium con~entratiQn decreases as the

Mg++ and Na+ concentrations rise. In addition to tb.is effect, magnesium and sodium

also complex with sulfite and carbonate species to further increase the dissolved alkalinity.

Increases in dissolved chloride have the opposite effect. As Cl- increases

relative to Mg++ and Na+, the Ca++ concentration must increase to maintain the

charge balance. Solubility constraints force the dissolved sulfite and carbonate

concentrations to decrease which decreases the dissolved alkalinity

The alkalinity is also influenced by the calcium carbonate and calcium sulfitr

solids which dissolve in the scrubber. As S02 is absorbed, the pH drops and au

environment which is conducive to solid carbonate and sulfite dissolution is cre­

ated. Significant amounts of solids can dissolve at these lower absorber pH's even

though the slurry residence time in the absorber is relatively short. However,

since solids dissolution involves an additional mass transfer step, solids alkalin­

ity does not have as much influence as the liquid alkalinity in the ·determination

of the L/G required for a specified S02 removal in a given spray tower design.

Mass Transfer Capability. The importance of the mass transfer variables which

affect gas-liquid distribution, interfacial area, and contact time should not be

understated. Physical absorber layout including nozzle and header placement and

nozzle selection are equally important in scrubb~r design. However, for purposes

of this process chemistry study, these factors have not been considered as vari­

ables.

Scale Control. The major concern here is control of gypsum scaling. Calcium

sulfite can also form scale, but this is not generally a problem and reduced pH can

dissolve sulfite scale whereas gypsum is insoluble at pH's achieved in lime/lime­

stone FGD systems. Control of scaling is achieved by integrating absorber and

2-6 -· 2-7

. ~ .~

roootioo tonk design•. Tho reection tank is diacussed in tho next suboootion. Some general guidelines for scale control include:

maintain sufficent seed crystal inventory for solids precipitation 0

in scrubber,

• maintain a ~ufflciently low scrubher feed relative saturation, and

• maintain a sufficiently high L/G so that solids dissolution and sulfur sorption do not result in scaling.

Fnrtbor disonssions concerning scolo control are included in tho reaoUon lank

sootion sinoo rooction tank design is a significant factor in developing o control strategy for chemical scaling.

~action Tan~

Important design concern, for tho slurry systen (reaction tank and dowatering)

oro shown in Table 2-2. Tho importont rooctions which occur in the reaction tad

oro proclpitation of calcium solfito nod colcium snlfate and dissolution of lime or limestone,

A>. l"J>ortant variablo in r"oUon lank dosign is the level of 'Ystom oxida lion. As

'" discussod proviousty, if tho oxidation is lou thou about 15 percent, the sys­

ton oporatos .ub,. tnrotod With rospect to gypsum. This is important sinco gypsun

•••ling presonts a more significant problem and subsaturated operation greatly

rednoes the ohonoes of scaling evon with increases in rotative saturation acres• the scrubber.

The Procipitation rates of gyp, .. or calcittm sulfite/sulfato solid eolution can be represented in the following form:

Precipitation Rate = k(t) a V C B (RS-l)n

•her • k( tl is a temp ora turo depondont r. to constant, , i, tho •poc.i£ i c surface area

•£ t~c P<ocipitatiug specios (om2/g), V is tho Volume of tho ronction tonk (lit-

oro, Cis tho •lur<Y ooncontration (g/1), B is tho fraction tho precipituting ••lid

is Of tho total •olids (g/g), Rs i• tho rolative saturation Of the procipitating

'P••ies, nnd n is •n oxpcnant aesooiated with the re!otive saturation driving force Whieh con he Variod to detarmino tho 'PPropriato correlating form.

(2-9)

2-8

h

Table 2-2

SUMMARy OF SLURRY SYSTEM DESIGN CONCERNS

Concerns

REACTION TANK :

Precipitation/D~supersaturation of Calci·~ Sulfite and Sulfate

Lime/Limestone Dissolution

DEWATERING :

Settleability

Filtering Rates

2-9

Variables

Tank Volume

Tanks in Series

System Oxidatirn

Slurry Concentration

Reagent Feed Ratio

Particle Size

Slurry Concentration

Particle Size

System Oxidation

T':le primary design 'l'.ariable is the ,reaction ta:U:: volu.me. 'lhe precipitation rate is

JHlt t;y t1:e S02 renovd rate achieved in the absorber. Nor1llally.. the slnr.ry RADIAN PROCESS MODEL

The process model employed in this study is essentially the same as the one used in

a previous EPRI study which investigated the effects of increased S02 removal

efficiency on FGD system design (1). For this reason, only the major programs

inputs and assumptions pertinent to evaluating the current project's results are discussed in this section.

sphds c~ncentra: ticn is <Jbout 10 to 12 weight perc{!nt. Much lower ;Sl-urxy concen­

trllt!Ct:i.s co ntli provide a sufficient solids iDYentory for reasonable tau :voltll!les,

s:cd !:11rher slo.:u·y concentrations can lead to operating difficnl ties :snell. as

:z::.crea~ed ero.s.ic.n. The slurry ccncentration can be varied to fine tune the scale

:.~:::trd lcop once the systetl has been built. The distribution ">L sulfite and

t.:;;.i.fate s~Hds is set by the oxidaticn fraction. Thus, tl:Je major design variable

'' <>• reaction tank voloco, • Figure 2-2 •hows the flow soh .. e employed in the modoling of tho main scrubbing

~e spec1fic solid surface area and relative saturation generally change depending

:n t:!:e :.tber ¥ariables in I::Ost designs. For instance. if the reaction tank vollll!le

were de~reased for a specific design~ the surface area and relative saturation

>r~'::!d tend tc 1nc:rease. The tank 1::ust be sized such L a.t the relative saturation

entenx:g the scrubber is sufficiently low :that the increase across the scrubber

~hu Il';!t cause scaling. In addition, the t:&nk must also be sized such that the

sc,l;ic particle size is large enough to b.e handled easily in dewatering (surface

area is u:ve:rsely related to particle di2l:leter). Sot1e particle size control

s:?ames s::ch as particle grinding or reactors which control nucleation have been

~,:r::..;:;se:i but in general ~:ost systems do nat presently include these control ~..;1--' t l-':.:: s ;f.

L~~est~ne dissoluti~n is also a concern in reaction tank sizing in limestone sys-tees ..

L~e is s~ reactive that lioe dissolution rate is not generally a tank

s~zing criteria. The limestone dissolution rate depends on limestone reactivity~ !:~estcne grind, and licestone-to-absorbed S02 ratio which is desired.

DeYatE!ri::g

Lesign of dewatering eq~ipcent is sized based on settling and filtering rates >rbic~ in turn are pritlarily influenced by the

The czidaticn rate is not a control variable,

chrect!y i;y the reaction tank ~dzec and

2~10

oxidation rate and the particle size.

but the particle size is affected

loop in this project. By rearranging the process modules, many different proce::::s

configurations may also be simulated. Subroutines FLUGSl, ALKINP, and WTRMKP

simulate process inputs of flue gas, alkaline additive, and makeup water, respect­

ively. Subroutine SCRUBS models the spray tower, and RATHLD simulates a stirred

reaction tank. Subroutines DIVDER and DIVDR3 simulate stream splitters, and FILTER

models a thickener-filter system. Subroutine SYSTBS is an ancillary routine which

performs material balance calculations around the entire system. One important sub­

routine not shown is the Radian eq,uilibrium program which is used to calculate the

kinetic driving forces for all of the chemical mass transfer steps.

Important inputs and assUmptions made in each process model and then the modeling

sequence used to arrive at a converged case are presented in the following subgec­tions.

Spray Tower (SCRUBS)

Important input parameters specified for the spray tower model incluue (1) S02

removal efficiency desired, (2) level of sulfite oxidation, {3) amount of alkaline

solids dissolution, and (4) the liquid-to-gas (L/G) ratio. In this particular

study, the L/G was a parameter adjusted to maintain tlle proper driving force for

S02 -~sorption. This is discussed later in the Modeling Approach Section.

The Radian model was first developed as a tool to assist in design of F'GD systems

so normally the required S02 removal efficiency is a specified input and other

design variables are adjusted until this criterion is met.

required removal was 90 percent for the Eastern coal cases

Western cases which correspond to the removal rcquir,•ments

New Source Performance Standards promulgated in June 1979.

2-11

In this study the

and 70 percent in the

stated in the Federal

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2-12

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The sulfite oxidation is a key performance variable since this determines whether

the system performs in a mode such that the liquor is subsaturated (less than about

15 percent oxidation) or supersaturated (greater than about 15 percent oxidation)

with respect to gypsum, If the liquor is supersaturated with respect to gypsum but

a minimum amount of gypsum seed crystals are present (18 to 25 percent oxidation)

gypsum scaling is more likely to occur. In cases in which the absorber feed liquor

is subsaturated or where there is a high concentration of gypsum solids available

to act as precipitation sites, gypsum scaling is less likely to occur. As stated

previously, gypsum scaling is the most difficult scaling problem normally encount­

ered in lime and limestone FGD systemG. Unfortunately, a model which successfully

predicts oxidation for all applications has not yet been developed although some

variables which affect the oxidation level have been identified. For instance

experience has shown that the oxidation level is generally lower in Eastern coal

applica tion.s compared to Western coa:L. This may be a result of the higher S02 to

02 concentrations in the liquid film of the droplets in the absorber for the

Easte.rn cases.. In Western cases, th;e S02 t.nnsfer is lower while the driving

force for 02 transfer is similar to 'Eastern situatilons, Thus, the oxidation

tends to be higher in the Western systems. Likewine, oxidation is generally

slightly lower in lime systems than limestone. ThJls may be caused uy the more

reactive sorbent whi.;b. allows a slightly higher soJ~ption of S02 pe.r volume of

ltiquor which also raises the S.02/02 ratio in the lilquid film. Several other

variahles, such as s;pecific ab1sorber d.esign featur1:s and soluble trace elements

that can act as ox. ida tion pt:omot.ers or inhibitors, also influence ox:ida tion rates,

but th:ese effects are no:t ye1t. cO'.mple:tely unde:cstoo1i,

In this study, the a':x:ida:tiOlll lev,el m:odeled for Eas~cern coal limeston.e FGD systems

was 20 percent while the ox:ildati10n selected for lime s]rstems was sli,gihtly lower at

15 percent. In the 'Western case;:;, both lime and l:imes1tone systems we:r~ modeled

assumil1g 90 percent oxidation simce the di1iference in 10xidation tWoula. have less

effect on system des:ign at the h:igher oxidmtion le1;els,,

Ano1thcr key design VTariable is tile amount oif alkalilne solids whilch dii,ssolve in the

absorber. Even in tihe spray towier contact:o~r where ga:s-liquid cent:ac~t time is

failr:ly short comt?are:d to other contacto.rs, the soHd phase o.lkalini.t:;r is a signifi­

cant contributor to .the ·total available alJklalinity, Although sign~if:i.Jcant fly ash

alkalinitY is availa:hle in some lFGD system1s, partic:ularly with Weste:rn "'1::1, a high

efficiency fly ash c:ollector was assumed up1;tream o1f the FGD system 1md no alkalin­

ity was assumed to b1e available r"ia this source.

2-13

· ...... "~; .• ::~-~ ' .. ·.·.~~- :·::.:.~· .::;·;: ~·1·:!· ·. ···~· ·:··:.~ .• 1 ... ··.: .~. ·:.' .... ·.·><.\I~J> :~: *"' ;;), \ • • $; _, ~ " ' ' ••• 1t . i'lo' •c! " ~ .._ ,. .... ,. ..:~t.llt'~'~.:. of#> 'If ,.let'•«; ~;o;,. . . ' . . ' . . • 1

t:::.---------··--· ...

Based on past pilot and full scale experience, Radin.n set the limestone dissolu­

tion equal to 1 percent of the total recirculating limestone in the Eastern cases

and 0.5 percent in the Western cases. The lower diuolution in the Western cases

results from a lower dissolution driving force due to less S02 sorption~ In limo

FGD systems, calcium sulfite/sulfate solid solution i.s the alkaline species which

dissolves (the calcium sulfite portion is alkaline with respect to S02 absorp­

tion}. A value of 0.2 percent dissolution of solid solution resulted in a reason­

able driving force for dissolution in the Eastern cases. A value of slightly above

0.5 percent was employed in the Western cases since the relative amount of solid

solution solids is lower compared to the total recirculating solids. Thus a larger

fraction dissolves in the Western system to yield an equivalent dissolution driving

force as in the Eastern cases, As with sulfite oxidation, additional work is

required to accurately quantify the phenomena of solid dissolution in the absorber.

Reaction Tank (RATHLD)

The reaction tank is modeled as a well-mixed vessel in which limestone dissolu­

tion, calcium sulfite/$ulfate solid solution precipitation, and gypsum precipita-tion are the important mass transfer steps.

The limestone dissolution in this study was not a factor in sizing the reaction

tank. This implies that sufficient CaC03 dissolution would occur at a alkaline

feed ratio of 1.1 moles CaC03 per mole S02 absorbed, Assumptions implicit in

this result include selection of a fairly reactive stone (Fredonia) with relatively

smnH average particle size. Note that the reaction tank may be limited by lime­stone dissolution rate in some FGD system designs,

Precipitation of calcium sulfite/sulfate solid solution for the Eastern lime cases

and precipitation of gypsum for all other cases were the reactions which determined

reaction tank. sizing. A precipitation rate form previously shown in Eq, 2-9 is

employed in the Radian process model to compute precipitation rates. Rate con­stants derived from lab studies and verified in pilot

used in coujunction with representative

cipi ta tion kinetics in this model,

~

and full scale programs were particle size distributions to model pre-

2-14

.IhickenerLFilter !(FILTER)

The dewatering equipment was assumed to produce a sludge of 50 percent solids in

all cases examined in this project. This was done to study the effect of different

process waters in systems which functioned with the same degree of closed-loop

operation. In actuality some differences in dewatering efficiency would occur due

to different oxidation fractions or particle sizes. This would cause different

sludge solids concentrations or neoessitate different dewatering equipment designs

to achieve the same level of dewatering for the different cases examined here.

Modeling

Main Loop Simulations. Th~ two parameters used to directly compare the effects

of different chemical variables on the process chemistry of the main scrubbing loop

are the L/G and reaction tank size. The same calculation sequence was used in all

cases so that the effects of the different variables could be evaluated as directly

as possible. This sequence involved first setting the L/G ratio to obtain the

alkalinity necessary for S02 sorption and then adjusting the reaction tank size

to avoid scaling conditions.

The L/G ratio was set to achieve a sufficient mass transfer driving force. The L/G

was adjusted until the equilibrium partial pressure of S02 above the scrubber

effluent was ten times lower than the partial pressure of S02 in the scrubbed

flue gas leaving tho absorber. This ten-to-one driving force assumption is based

on Radian experience with limestone spray towers, primarily in high sulfur coal

situations. Physical mass transfer requirements were not considered since this

complicates direct comparison of chemical effects. Ignoring physical mass transfer

considerations means that several of the cases are not realistic. In some cases In the L/G is too low to supply the interfacial area needed for mass transfer.

other cases, the L/G is too high for spray tower operation and gas and slurry

surges would result in unsatisf4ctory operation, However, the approach used in

this project is effective in comparing chemical effects, and the limitations to

actual design situations must be recognized.

After the L/G was set, the reaction tank size was adjusted to meet the apJ?ropriate

non-scaling criterion. In the cases in which the oxidation was greater than 15 The tank was adjusted until a

percent, gypsum scaling became the limiting concern.

2-15

gypsu:n: .relative saturation of 1.3 was reached in the scrubber effluent stream. In

the lime systems <-perating with high sulfur coal, the oxidation was estimated to be

IS percent and gypstll:l scaling was not a problem in any of the particular ca.ses

st~~ied here. Instead. the reaction tank was sized to give a calcium sulfite relative saturaticn of 3.0 in the sccubber feed.

Prescrubher ana Mist Eliminator Modeling. In addition to the main sc.rnbbin& loop

sic>Ilalit'ns, a few prescrubber and tlist eliminator wash loop cases were also stud­

ied. In the p:t:escrubber cases, the makeup water feed rate and. discharge rate were

se:: baued on three criteria: {1) a maxim= chloride concentration of 10,000 ppm in

t!::e 1iq:1or, (2} a l:linimt:.m fH of 2.0 in the recycled slurry, and (3) a maximtll!1

gypsum relative saturation of 1.3 in the liquor. Ninety percent of the HCl enter­

ing the prescrubber was assumed to be removed. The .remaining HCl was r.emoved in the main absorber.

The cist eHninator wash loop was model~d as a co'ntinuous wash with the wash liqnoz

sent to the reaction tank {no wash water recycle). The wash rate was increased

tt:ctil a &Y.Pst:m relative saturation of 1.3 was achieved. Assnmptions here included

an esti=ated slurry carryover rate to the mist eliminat~.r of 105 gpm and dissolu­

ticn of calcium carbonate solids reaching the mist eliminator. These assumptions

are based on previous Radian mist el~inatc.r experience which are primarily on

Easter~ coal Fr.D syste:1s which generally have higher L/G 1 s than Western systems.

2-15

=------· - ... =.ii/

Section 3

RESULTS

This section p~esents a summary and discussion of important results and trends

noted during the project. The parameters studied in the high sulfur

Eastern coal cases included:

• makeup water source~

• reagent feed source,

• coal chloride content,, and

• prescrubber chloride removal in the high coal chloride cases •

Parameters examined in the Western r.oal cases included:

e. makeup water source,

• tlo

• •

reagent feed source,

mist eliminator wash loop performance for one case,

effect of makeup water in a fixed FGD system design, and

a low volume wastewater streum as supplementary makeup source •

For most cases, the required S02 removal efficiency was specified and the L/G

adjusted to yield an adequate alkalinity driving force for S02 mass transfer.

lne reaction tank size was adjusted to avoid scaling conditions. However, in two

of the Western cases the effects of differ~nt makeup waters on fixed designs were

examined.

It should be reiterated here that the purpose of these simulations was to compare

the process chemistry changes resulting from chang~s in process water source and

design considerations such as physical other important variables. Important

absorber design were not included as part of this study and the results should not

be used directly for design application. A brief discussion of some alternate

designs other than a single spray tower is included at the end of this section,

3-1

EE-:11S S~~i'

n:e :t:t:;o: e:ffe>:;t of altern&te -rater sources,. reagent ll&gnesit:a content, or coal

:J;;:-:rz.::!e u ":.:.l tf.;e Hqtdd phase Alkalinity and the resulting L/G required .for ·502 t::.:;.!:;:::. These cheoical variables caused a l::laxi::Hn!! variation in the reaction she

::.! a':::.::: z::; i'er<:e~t Yithin each set of coal/reagent saulations 'll'.hile L/G• s changed

'::? u :::.::eb. u a factor of S. The tatJ.k sizes Yere determined prharily by t'tte

u::.;.::t :.: W; abscrbed and the fraction of S02 oxidized and subsequently p:r·e­

:;zp!;ll't~:! u gyps>;: cr calcit;n sulfite!snlfate solid solution. Note that these

:!::.!!e:re::::es are substantial in detemining equipment size requirezents.. If changes

:::. vue: cco;ositi~.;n or other variables are !!lade in an existing syste:a, additional

-:.:: d:ffe:er.t p-.::ops !:light be required as well as incre11sed slurry header capacity.

!.:d::tz.~::a: reaction tank capaei ty could also be required to ac.hi~e reliable opera­

tz~::. ~~e effect of 1iq~id phase alkalinity on L!G is sucmarized in Figure 3-1 for

=::.:~ Eastern a~d western coal FGD systems. In general, the L/G in an Eastern coal

Fr.::. syste~ cesign Till be higher than in a Western coal design because the S02

re:~•al req~Ireoant is significantly higher, 90 percent recoval from a 4.0 percent

n:;.~f:;r cc;al cr:::pared to 70 percent recoval froc a 0.48 percent sul.fur coal. Within

ez:coh set ~f cases ho-Kever, the liquid phase alkalinity is the pxisary variable Y~Ich i~fluences the L/G.

I:= ~:yste:s operating Yithou organic additiYes, the liquid phase alkalinity is

affected I=-ril:larily by the concentrations of the soluble species, magnesium, sodium,

a~d chlcride. Magnesium and sodiun tend to hold alkaline species in solution which

-::?:bride tends to displace the less soluble sulfite and caxbona te species from

sr.h•hcn. As a result, systems which operate with high concentrations of reactive

r:ag:.:::.esi~. with process makeup water high in !!lagnesium and sodi!li:l concentr11tions

re:ative to chloride, and with relatively low coal chloride concentrations exhibit

1~ver L!G's to achieve an equivalent SOl removal efficiency.

that these effects result in a factor of three difference in

cases a:.:::.d a factor of eight in the Western cases.

Figure 3-1 shows

L!G1 s for the Eastern

l"~e reaction tank size vas set primarily by the S02 sorption and sulfite o.xlda­

HGn and S:llbseqnent precipitation of calcium-suliur salts. The largest single

effect is seen in the Eastern coal cases where the selection of lime results in a

fact<:Jr of 5 decrease i!l the tanl: size compared to limestone cases. This is due to

a slightly lever predicted sulfite oxidation for the lime case which allows that

3-2

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the FGD system. It was felt that the Mississippi River water was more representa­

tive of the water which might be used in cooling towers in the East than the other

water sources examined. Table 3-1 summarizes, the res·alts of using these waters in

the higher magnesium limestone, East~rn coal FGD applications. The results of

using these waters in lo·w-magnesium limestone and both lower and higher magnesium

lime cases showed similar trends to those seen in Table 3-1 •

First, examine the effect of the water source on the liquid phase alkalinity and

the resulting L/G. Waters with lower magnesium and sodium concentrations relative

to the chloride concentration result in FGD systems with higher L/G's. Untreated

Santee and ~lississippi River waters required L/G's of 135 gal/Mac£ (18.1 m3/

Jw3) and 133 gal/Macf (17.8 m3/Mn3), respectively, to supply the alkalinity

needed for S02 mass transfer. The Mississippi acid treated cooling tower blow­

down case required a slightly lower L/G of 127 gal/Mac£ (17.0 m3JMm3). The

untreated Lake Sakajawea water case showed an L/G of 96 gal/acf (12.9 m3/Mm3),

and the Mississippi sidestream softened case had the lowest L/G at 78 gal/Macf

(10.5 m3/Mm3). Untreated Lake Sakajawea water has a fairly high soluble magne­

sium and sodium content and sidestream treating with soda ash markedly improves the

Mississippi water's alkalinity. Note that the liquid phase alkaline species for

each absorber feed stream were tabulated in Table 3-1, and these correlated well

with the L/G's. The Santee case had the highest L/G (135 gal/Mac£) and the lowest

alkaline species tota 1 (.005 N) while the sidestream softened case had the low~st

L/G (78 gal/Macf) and the highest alkaline species total (0.01 N).

A difference in reaction tank size is also noted although the maximum difference is

only about 8 percent from the smallest to the largest tank. The Santee River,

Mississippi River, and Mississippi acid-treated cases showed tank sizes in the

740,000 to 750,000 gallon (2800 to 2840 m3) range. Lake Sakajawea and Missis­

sippi sidestream softened cases showed the larger tank size at 772,000 gallons

(2900 m3) and 799,000 gallons (3020 m3), respectively.

The reason for the larger tanks in the higher liquid alkalinity cases can be ex­

plained by examining the factors which influence the increase in gypsum relative

saturation across the absorber. The Santee River case shows that the increase in

calcium ion activity (due to Ca003 dissolution) and increase in sulfate ion

act· · 1V1 tY (due to sorption of S02 and subsequent oxidation) are about equal.

However, the Mississippi sidestream softened cooling tower blowdown case shows that

the change in makeup wster has changed the process chemistry somewhat. In the

higher soluble magnesium and sodium cases (sidestream softened case for instance),

3-5

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the absorber feed sulfate ion concentration incraases relative to that in untreated

Mississippi case to maintain the ionic charge balance, and the calcium concentra­

tion decreases because of solubility constraints. As a result, the one percent

calcium carbonate dissolution in the absorber drives the gypsum relative saturation

up proportionately more in the sidestream softened case than in tlle untreated

Mississippi water case. Note also that although the amount of sulfate absorbed per

volume has increased by more than 70 percent, the increase in sulfate ion activity

across the absorber has actually decreased to about 40 percent of the value in the

untreated Mississippi case. This decrease in the change in sulfate activity is due

to the large increase in soluble sulfate caused by the magnesium and sodium. In

this case, the effect of the increased calcium activity more than offsets the

decrease in sulfate and the roaction tank size must increase so that the rise in

gypsum relative saturation across the absorber does not create scaling conditions •

An example calculation may clarify this. The increase in gypsum relative satura­

tion across the absorber may be calculated as follows:

RSGyp = (1 + ca++)(1 + so;> (3-1)

This change for the untreated Mississippi water case i.s:

RSGyp = (1.018)(1.014) = 1.032 or 3.2 percent

while the absorber relative saturation increase for the Mississippi side-stream softened case is:

RSGyp (1.047)(1.0054) = 1.052 or 5.2 percent

Thus, the absorber feed gypslll!l relative saturation, must be lower for the sidestream

softened case which translates to a larger reaction tank to prevent scaling in this

case. In some instances. increasingly high TDS lowers the absorber feed relative

saturation for equivalent-sized reaction tanks hy further altering the process

chemistry.

Effect of Water Sources in Western Coal Cases

In the Western cases, only Laka Sakajawea and Mississippi River water ~ere studi~d

sJace the low TDS water, as typified by the Santee River water, is not routinely

encountered in the West. Both wate~s were used. as makeup in simulated cooling

tower cases, and the blowdown streams from these cases were used as FGD system

makeup water sources.

3-7

Prier to ~he discu~sion of the effect of waters on the Western coal FGD systems,

several differences between thF Eastern and Western cases sh~uld be emphasized.

First, the Eastern case requirement of 90 percent S02 removal from a higher

sulfur flue gas result~ in an S02 removal r&te of about 3700 gmole/min (8.2

lbmole/min) compared to the 430 gmole/min (0.95 lbmole/min) requirement for the

Western cases. Again, the basis for these figures is a net 500 ~~ steam plant.

Although 90 percent of the absorbed S02 is oxidized to sulfate in the Western

cases compared to 20 percent in the Eastern cases, the sulfate pickup in the West­

ern cases is only 3~0 gmole/mi~ ccmpa~ed t~ 740 gmole/min in the Eastern cases.

The net result is that lower L/G's and smaller reaction tank sizes are required in

the Western cases. Also note that the makeup water rates are similar for both

Eastern and Western cases since most of the water makeup is required for replacing

water lost through evaporation. However, the sludge production rate in the Western

systems is about 15 percent of the Eastern system sludge production rate so the

dissolved solids entering with the makeup water are concentrated to a much greater

degree in the Wastern cases. As a result, the differences in process water source

can be magnified in the Western cases.

Table 3-2 summarizes the effects of makeup wat~r source on Western coal, FGD 3ys­

tems using higher magnesium limestone. Note that the L/G for the untreated Missit­

sippi River water case I65 gal/b1acf (8.4 m3/Mm3)] has decreased to less than

half of that shown in the Ea~tern case for the same water [133 gal/Macf (17.8 m3/

~w3)] and the tank size has also been redu~ed a factor of six~ However, the

etfects of the different makeup waters on the process chemistry of Eastern and

Western ~ases is in many ways very similar.

The trends in requi:!:ed L/G are the same in the Western cases as in the Easter.n

cases. The untreated Lake Sakajawea water contains a much higher concentration of

soluble magnesium and sodium than does the untreated Mississippi River water. As a

result, the required L/G for the untreated Lake Sakajawea case is 15 gal/Mac£ (2.0

m3/Mm3) compared to 63 gt\l/J.!acf (8.4 m3/Mm3) for the untreated Mississippi

River water case. Use of cooling tower blowdown resulted in lowex L/G's for both

waters, but the effect of sidestream softening had a much larger influence in the

Mississippi cues than in the Jake Sakajaweu cases. The acid-treated Mississippi

case predicts a L/G of 53 gal/Macf and the sidestream softened case predicts an L/G

of 14 gal/Mncf. The L/G's for similar Lake Sakajawea cases are 12 and 8 gal/Macf,

respectively. The additit)n of soda ash to the cooling tower using Mississippi

River water changes the liquid phase alkalinity to a greater extent than in the

3-8

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Lake Sakajawea case since the untreate4 Mississippi watex has P ~uch lower magne­

sium and sodium content than does the untreated Lake Snk~jawea water. As with the

Eastern cases, the required L/G's correspond closely with the liquid alkaline

species. The untr~ated Mississippi case has the lowest quantity of alkaline spe­

cies (0.0017 N) and the highest L/G (63 gal/~acf}. The sidestream softened Lake

Sakajawea case has the highest quantity ~i alkaline species (0.029 N) and the

lowest L/G (8 ial/Macf).

Note here that L/G's of less than about 30 to 40 gal/Macf (4.0 to 5.4 m3/Mm3)

are not generally practical for spray tower system designs. At the low slurry faed

rates of 8 to 15 gal/Macf examined in the Lake Sakajawea and sidestream softened

Mississippi cooling tower blowdown cases, the interfacial axea required for mass

transfer cannot be attained with reasonable nozzle design and slurry dr.oplet sizes.

How&ver, the trends noted are valid for the process chemistry comparisons desired

in this project.

Note also that the ionic strength in three of the Western cases are above 1.5.

Extensive validation work of Radian's equilibrium model has been conducted with

solutions of ionic strength below 1.5 which are typi~al of most lime/limestone FGD

installations. Radian and EPRI are continuing efforts to validate the model at

higher ionic strengths. However, at this time absolute effects cannot be predicted

with great confidence although trends can be gauged for the comparative pn~po~e~ of

this st~dy.

'!he effect of process water selection on reaction tank size is n<:'t as significant

percentage··wise as the change in L/G. The maximum difference in tank size shown in

Table 3-2 h about 20 percent with 142,000 gallons (540 m3) being the largest

tank. Th:o is more than 5 times smaller than the tanks shown in Table 3-1 for the Eastern cases.

Note that the increase in relative saturation across the absorber is larger for the

two sidestream softened cooling tower blowdown cases. In the Mississippi case, the

higher TDS liquor has altered the process chemistry sufficiently to offset this

increase. However, the relative saturation increase in the Lake Sakajawea case is

so large that a larger reaction tank is required in spite of the change in process chemistry.

3-10

EFFECTS OF REAGENT FEED SOURCE

The cha~acteristics of t.be ~lkalinc reagent have a major effect on a FGD system's

abi.lity to function as specified by the user. The two major variables associated

with the alkaline feed source examined in this st~dy were:

• selection of lime versus limestone as the alkaline source, and

• concentration of reactive magnesium within the alkaline source •

The effects of these variables were studied for both Eastern and Western coal cases

to d~termine if trends were consistent.

Lime Versus Limeston~

As was discussed in the modeling approach, the're are several subtle but important

differences between lime and limestonu systems. Limo solids are more reactive and

lime dissolution is not buffered in the pH ranges encountered in lime/lim~:i$-;.one FGD

systems. As a result, lime dissolution is not a rate limiting step and the scrub­

ber feed slurry pH is generally controlled at about 8.0 to minimize recarbonation

of the lime by sorption of C02 in the absorber. On the other hand, limestone

dissolution rates are generally much slower and the scrubber feed pH normal1y

remains between 5.5 anl1 6.5 du.e to the effect of carbonate buffering. In addition,

solid phase alkalinity is derived from the calcium sulfite portion of the solid

solution in lime systems while calcium carbonate dissolution is of primary import­

ance in limestone systems. The freshly precipitated solid solution may be more

reactive than the limestone solids. As a result of these differences, lime systems

ge~erally have slightly lower L/G's than do limestone systems.

Table 3-3 shows the compariscns of higher magnesium content lime and limestones for

Eastern and Western coal cases. The makeup water in the Eastern cases was un­

treated Mississippi River water while untreated Lake Sakajawea water was used in

the Western cases. TAe trends shown in Table 3-3 should be similar for other water

sources as well. The Eastern lime system has an L/G of 99 gal/Macf (13.3 m3/

Mm3) compared to 133 gal/Macf (17.8 m3/Mm3) for the limestone system. In the

Western cases, the lime system shows an LIG of 11 compared to 15 gal/Macf (1.5 to

2,0 m3/Mm3) for the li .. ~e.:<,tone system. Although the absolute L/G' s are quite

different, the percentage reduction due to lime usage is about the same for the

Eastern and Western cases. Part of these differences between lime and limestone

3·-11

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are due to the slightly higher Mg/Ca molar ratio in the lime selected (0.023)

compared to the limestone (0.018) and part is due to the characteristics of the more reactive lime reagent.

There is also a large reduction in reaction tank size in the Eastern !ime case.

Here the tank size is about 140,000 gallons (530 m3) compared to over 740,000

gallons (2800 m3) in the Eastern limestone case. This difference is due m~inly to the different o~idation rates assumed for the two systems. Lower oxidation

rates are typically measured in lime systems, and in this particular study, 15%

oxidation was assumed for lime FGD systems operating in Eastern coal plants com­

pared to 20% for l~~est~ne systems. Therefore, the Eastern coal lime systems

operate subsaturated with respect to gypsum and much smaller reaction tanks are

predicted. The differences in tank size between lime and limestone in Western coal

applications were not judged to be as significant due to the high levels of oxida­

tion normally encountered for both reagents ar.d therefore all cases were based on a

90% oxidation level. Only a slight differenu,~ is noted in the reaction tank size in the Western cases.

Effect of Reactive Magnesium Content in FGD Systems

The primary effect of increased reactive magnesium in the limeston: is to provide

additional liquid phase alkalinity in the FGD system. As the soluble magnesium

concentration is increased compared to the dissolved chloride concentration, alka­

line species such as sulfite and carbonate io.ns increase in solution thereby in­

creasing the driving force for S02 sorption in the absorber. In the Eastern

cases, the increase in reactive magnesium caused a dramatic reduction in L/G, but

the effect was much less noticeable in the Western limestone cases. Since the

effect of magnesium in the lime cases was essentially the same as in the limestone

cases, the results are not summarized here. Details are provided in tbe Appendix.

Effect of Reactive Magnesium in Eastern Limestone Cases. Table 3-4 summarizes

the results of changes in the reactive magnesium co,ncentration in the Eastern

cases. The trend is similar for both untreated Mississippi water and acid-treated

blowdown. The lowe;r magnedum cases show an L/G of 234 gal/Macf (31.4 m3/Mm3)

is required to provide alkalinity for S02 absorption. Use of higher magnesium

limestone lowers the required L/G to 133 gal/Macf (17.8 m3/Mm3) in the un-

treated water case and to 127 gal/Macf (17.0 m3/Mm3) in the acid-treated cool-

ing tower blowdown case. These decreased L/G's result from the increase in the

3-13

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concentration (equivalence) of magnesium compared to the concentration (equiva­

lence) of chloride in the scrubbing liquor. As a Mg/Cl eqni.vnlence ratio of one is

approached, an improvement in liquid phase alkalinity would b~ expected. ~is is

noted in a slight decrease in L/G due to the use of acid treated blowdown. In the

low magnesium cases, no differen~e is noticed between the two water sources since

the Mg/Cl rati'D is so low that the liquid phase alkalinity is about the same and

much of the requir~d alkalinity comes from the solid phase dissolution.

The reaction ta~k sizes for the higher magnesium cases are one to two percent lower

than for the lower magnesium cases. The main reason for this is the higher soluble

sulfate level that is ~arried out in the liquid associated with the sludge in the

high masnesium c.ases. This means that less gypsum must be precipitated in the high

magnesium Cl.',ses and the tanks can therefore be reduced in size slightly.

Effect oi Magnesium in Westorn Limestone C~~~. Table 3-5 summarizes the effect

of magnesium availability on the Western limestone cases. Note the effect of

increased magnesium content is much reduced in these cases compared to the Eastern

limestone cases, The low magnesium limestone cases show L/G's of 66 gal/Macf .(8.8

m3/b~3) for both the Mississippi untreated and acid-treated cooling tower blow­

down water sources. The high mngnesium case for the untreated water shows a

slightly reduced L/G of 63 gal/Macf (8.4 m3/Mm3) with essentially the same

liquid phase alkalinity as the low magnesium cases. The high magnesi~un limestone,

cooling tower blowdown case has a L/G of 53 gal/Macf (7.1 m3/Mm3) and a some­

what higher liquid phase alkalinity •

The ruain reason the magnesium had less effect in the Western cases is because of

the increased chloride concentration in these cases compared to the Eastern cases.

AlthougA the Western coal only contains ahout 30 percent of the chloride that the

Eastern coal contains, the sludge rate in the Western cases is only about 15 per­

cent of that in the Eastern cases. This means that the HCl absorbed from the

Western plant's flue gas is concentrated by a factor of six times more in the

Western system than in the Eastern system. The result is that the dissolved chlo­

ride content in the Western cases is over twice that calculated for the Eastern cases •

The higher chloride concentration means that the increased magnesium dissolution

from the limestone initially displaces the less soluble calcium from solution with

little effect on the liquid phase alkalinity. Only as the magnesium (plus sodium)

concentration (equivalence) approaches the chloride concentration does the liquid

3-15

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3-16

~ l ,,r./t&i~4~.a~ ·>i."!N:a.w;w .JJ Qr.ta:-,u « iW ~--

I~ase alkalinity begin to increase noticeably. Above this threshold, further

increases in magnesium xesult in more substantial increases in liquid-phase alka­

linity. The acid treated cooling tower blowdown in combination with the higher

magnesium limestone results in a scrubbing liquox which approaches the threshold,

and therefore, the alkalinity increases slightly and the L/G decreases slightly.

The reaction tank sizes for the higher magnesium casos are somewhat lower than the

corresponding lower magnesium cases, This trend is similar to that r1oted in the Eastern limestone cases.

EFFECT OF COAL CHLORIDE COZ...TENT

The concentration of chloride in th.e coal has a sig· . .ificant effect on FGD system

design since the bulk of the HCl formed in the boiler is removed from the flue gas

in the absorber. As has been discussed in Section 2, and previously in Section 3,

increased chloride ion concentra~ion in the scrubbing liquor reduces the liquid

phase alkalinity and increases the required L/G. The effects of chloride content

were studied for Eastern coal steam plants employing both lime and limestone FGD

systems for cleanup. Two coal chloride concentrations were studied, 0.1 percent

(w) (base case Eastern coal for the program) and 0.3 percent (w). The inerts were

adjusted to compensate for the increased chloride content, but otherwise, th.e coal compositions were identical.

Table 3-6 summarizes the effects of coal chloride content for lower and higher

magnesium content lime syst<Jm:; employing untreated !fississippi River water as

makeup, These results indicate that significantly higher L/G's are required in the

high Cl cases than in the low Cl cases. In the 0.1 percent (w) chloride cases~ the

difference in lime magnesiuo content has a marked effect on the L/G with the higher

magnesium case showing an L/G of 99 gal/ Macf (13.2 m3/Mm3) compared to 215

(28,8 m3/Mm3) for the lower magnesium case. However, in the high chloride

cases, the lime magnesium content has no effect on L/G with both high and low

magnesium cases showing L/G's of 249 gal/Macf (33.4 m3/Mm3). The high liquid

phase chloride concentrations have greatly reduced the liquid phase alkalinity and

a major portion of the alkalinity required for S02 sorptiore is derived from

alkaline solids dissolution in the absorber.

Effect of a Prescrubber in High Chloride Coal/Lime FGD Systems

Two prescrubber cases were simulated to determine the affect of removing the chlo­

rides from the flue gas upstream of the primary G02 absorber. A flow schematic

3-17

Table 3-6

EFFECTS OF COAL CHLORIDE CONTENT ON LIME EASTERN COAL FGD SYSTE.'dS

Untreated Mississiupi Ri·ver Water

Coal Chloride Content 0.1 0.3 0.1 0.3

Lime Mg(OH) Content (weight %) 1.66 1.66 0.55 0.55

Liquid-to-Gas Ratio (gal/macf) 99 249 215 249

Reaction Tank Size (gal) 141,000 180,000 166,000 194,000

Absorber Feed TDS (wppm) 20,200 31,300 11,900 32,300

Total Alkaline Species in the 0.0077 0.0019 0.0025 0.0021 Absorber Feed Liquor (N)

Ionic Strength of Absorber 0.46 0.91 0.32 0.90 Feed

Absorber Feed pH 8.4 7.4 8.0 7.4

Absorber Effluent pH 4.7 4.2 4.4 4.1

3-18

---·----::----.......,_,_-~..,............___,.,~-~ --··-

is shown in Figure 3-2. Both untreated and acid-treated Mississippi River water

were used in high magnesium lime systems treating Ligh chloride content flue gases.

A portion of the thickener overflow "~s aiso sent to the prescrubber as makeup.

Ninety percent of the HCl was assumed to be removed in the prescrubber with the

remaining 10 percent HCl removed in the S02 absorber. Other criteria for the

prescrubber simulations included 0.1% SOz removal, a minimum recycle liquor pH of

2.0, a ruaximum dissolved chloride content of 10,000 ppm, and maximum gypsum rela­tive saturation of 1.3.

The effects of the prescrubber on the main absorber loop design are summarized in

Table 3-7. This table shows that removal of the chlorides in the prescrubber

reduces the required L/G by about 35 percent for both types of water. Note also

that the reaction tanks have been reduced by 20 to 25 percent in the main scrubbing

loop. Any savings here however would be offset by the additional prescrubber equipment.

On the negative side, the total system makeup water requirements have about

doubled. In addition, the prescrubber blowdown must be either disposed of or

treated in some manner. Thickener overflow was used as part of the makeup to the

prescrubber loop, Other schemes, such as collecting mist eliminator wash water to

use as prescrubber feed, may have provided a more optimized system. However, the

prescrubber cases modeled reflect the trends that can be expected in the main scrubbing loop.

Table 3-8 presents results specific to the prescrubber simulations. Note the

relatively high makeup and discharge rates and the relatively low chloride concen­

tration. The prescrubber discharge was set by the gypsum relative saturation which

was in turn increased by the need to add lime to control pH. A more optimized

:;~·stem could provide additional residence time and some gypsum seed crystals to aid

in scale control and possibly reduce the discharge rate. Alternately, the system

could be designed with materials to resist corrosion at lowe~ pH's reducing calcium

concentrations. The system modeled here assumed no gypsum precipitation which

represents a worst case situa·tion.

MIST ELIMINATOR WASH LOOP llliSULTS

A mist eliminator wash loop was simulated in conjunction with the main absorber

loop for a Western coal, high magnesium limestone system. Th.e mist eliminator was

modeled as a continuous wash with the effluent draining iv.to the main absorber

3-19

' > ' . . I -~ • - . . • . I

w I

N ......

w I

N 0

• ~. ! • .. ~

F!u~ Gas

r-' Solld3 to

Dist cs:U

Alkalinc5 .,., 1 1 M<lltivc

Makeup W;>ter r-----,llloot----.......1

Bleed to Wa~te Ol!J~'<'J.Sal

Suttled Solids ~

.--------a ... Gas to Stack

J I 1\lk.>llr& s ,., i :Wiitl.VO

MlkeUI• li->ter S lll>l

'

Ucc'!ln-:i Stagu

Gy!ltet"l Slowdown

Soli~-Liquid ~----------~ Separator

' Solid Cake to Regen.~ eration or Disposal

Figure 3-2~ FGD syste. flow diagra. including prescrubber.

Table 3-7

EFFECTS OF USING A PRESCRUBBER FOR CHLORIDE RmiOVAL ON HIGH MG LIME EASTERN COAL FGD SYSTEMS - MAIN LOOP RESULTS

Mississippi Acid Treated Untreated Mississi~~i Water Cooling Tower Blowdown Without With Without With Makeup Water Source Pre scrubber Pre scrubber Pre scrubber Prescrubb&r

Main Loop Makeup Water Flow 586 586 588 588 (gpm)

Total System Makeup Wate.t" Flow 586 (gpm) ~.o~o 588 1,325

Prescrubber Blowdowu Rat.!} (gpm) 424 -- -- 737 Liquid-to-Gas Ratio (gal/macf) 249 156 253 166 Reaction Tank Size (gal) 180,000 148,000 194,000 ~45,000

Absorber Feed TDS (wppm) 31,300 4,700 32,400 5,2!!C Total Alkaline Species i:n; the 0.0019 0.0031 0.0020 0.0032 Absorber Feed Liquor nn

Ionic Strength of Absorber Feed 0.74 0.093 0.92 0.1.0 Absorber Feed pH 7.4 8.0 7.5 8.0 Absorber Effluent pH 4.2 4.6 4.1 4.6

:W..ft.AfltM:~:

' .i

...,_,,__.,_. -.. ·- \

. ' : ' I

Table 3-8

RESULTS OF SIMULATIONS OF PRESCRUBBERS UPSTREAM OF HIGHER MAGNESIUM LI?tiE FGD SYSTEMS

Makeup Water Source

Thickener Overflow Rate to Prescrubber (gpm)

Additional ~Iakeup Water (gpm)

Prescrubber Blowdown Rate (gpm)

Lime Feed Rate for Pre­scrubber {lb/min)

Prescrubber Effluent Conditions:

pH

TDS (wppm)

Cl Content (wppm)

Ionic Strength

CaS04 Relativu Saturation

Untreated Mississippi River Water

463

426

424

18.00

2.1

12,900

6,400

0.31

1.30

1Hssissippi River Water Acid Treated

Cooling Tower Blowdown

464

737

739

19.5

2.3

9,050

3,800

0.21

1.30

loop. The wash water was untreated Lake Saknjawea water which was also used to

provide the remainder of the makeup to the main absorber loop. The results of this simulation are shown in Table 3-9.

Tb.e results indicate that the mist eliminator has little effect on the process

chemistry of the main absorber loop. The mist eliminator wash rate is only 338 gpm

(1.3 m3/min) compared to the total requirement of 514 gpm (1.9 m3/min) in the

main absorber loop. ltlist eliminator wash is a common method of introducing makeup

water into FGD systems. Therefore, additional makeup requirements for pump seals

and limestone grinding can be provided without exceeding the overall water balance

for the FGD system. If mist eliminator wash requirements had been significantly

greater, the FGD system could not have been operated in a closed-loop mode without mist eliminator scaling.

The carryover rate modeled is based on previous Radian experience (high sulfur,

relatively high L/G situations) and should be verified in future full scale sampl­

ing programs. For Western coal, lower L/G systems, this carryover rate should be

conservatively high. The driving force ~or S02 absorption results in 14 percent

of the .remaining S02 in the flue gas (4 percent of the total SOz entering the

FGD system) being absorbed in the mist eliminator. All of the calcium carbonate

deposited on the mist eliminator surface was assumed to dissolve. The wash water

rate was then set to prevent gypsum scaling conditions.

Other water sources, such as cooling tower blowdown streams which are almost satu­

rated with respect to gypsum, may not function as well as mist eliminator wash.

Other mist ~liminator wash schemes, such as closed loop wash cycles or intermittent

deluge wash sequences, might be required but were not included in the scope of this

study.

EFFECT OF MAKEUP WATER ON OPERATION OF AN EXISTING FGD SYSTEM

Three cases were simulated to gain perspective of the effect a change in makeup

water could have on the operation of an existing FGD system with the Western coal,

low-magnesium limestone foxming the basis for this comparison, First, the L/G and

tank size were determined for the case in which untreated Mississippi River water

was used for makeup {base case). Then, the makeup water source was changed to the

Mississippi sidestream softened cooling tower blowdown. l~e second and third cases

were run with the sidestrearo softened water to observe the effect of changing

process water. In one case, the reaction tank size was held constant and the L/G

3-22 3-23

Table 3-9

RESULTS OF MIST ELIMINATOR WASH LOOP ltiODELING

P&rameter

Total Absorber Makeup Water Rate (gpm)

Mist Eliminator Water Rate (gpm)

Carryover Rate (gpm)

% Solids in Carryover

Absorber L/G (gal/Macf)

Absorber Reaction Tank Size (gal)

SOz Removal in Mist Eliminator (%)

Rel~tive Saturation CaC03 in:

Absorber Feed (carryover) Absorber Effluent Mist Eliminator Effluent

Relative Saturation CaS03 in:

Absorber Feed (carryover) Absorber Effluent Mist Eliminator Effluent

Relative Saturation Ca804 in:

Absorber Feed (carryover) Absorber Effluent Mist Eliminator Effluent

3-24

Value

514

338

105

10

15

124.000

14

0.40 0.003

0.0004

2.40 0.72 0.17

1.23 1.30 1.30

was adjusted to maintain the alkalinity required for 70% SOz removal, a~d in the

other case the reaction tank and L/G were both set at the base case conditions and

the S02 removal and scaling tendency were both predicted. The first case simu­

lates an existing system in which the absorber feed rate can be controlled (vari­

able speed pumps or isolation valves for spray headers). The latter case repre­

sents a situation in which the makeup water source is changed in a system with no

capability to control the absorber feed rate.

Table 3-10 summarizes the results from the fixed design cases for existing systems.

The base case shows a L/G of 66 gal/Mac£ (8.8 m3/Mm3) and a reaction tank of

141,000 gallons (530m3), Changing the makeup water from untreated to sidestream

softened cooling tower blowdown Mississippi water changes the liquid phase alkalin-­

ity as has been demonstrated. in previous cases. For a fixed tank size, the L/G

could be reduced to 17 gal/Macx (2.3 m3/Mm3) and still maintain the alkalinity

required for 70 percent 802 removal. In this case, the process chemistry has

changed such that the gypsum relative saturation of the absorber effluent is 1.25

which is adequate since it is less than the 1.3 scaling threshold. Therefore, both

the L/G and scaling tendency have been reduced.

In the case in which the tank and L/G were fixed at base case values, the 802

removal efficiency was predicted to be 98 percent. The increased S02 removal

<.:aused a gypsum relative saturation of 1.32 in the absorber effluent which repre­

sents operation in a possible scaling regime. Scaling ~ay be controlled in this

case by increasing the slurry solids concentration above 10 percent to provide

additional seed crystals for precipitation. The 98 percent S02 removal was

predicted assuming that the 10:1 alkalinity driving force is valid for high removal

efficiency, low S02 concentration mass transfer situations. In all likelihood,

the gas film resistance will become controlling at these conditions and the removal

would be lower.

EFFECT OF TYPICAL LOW VOLUME WASTEWATER ON FGD SYSTEM PROCESS CHEMISTRY

Two cases were simulated to study the effects of adding low volume wastewat~rs to

the FGD system. The two wastewaters chosen were a typical demineralizer regenera­

tion wastewater and a cooling tower pretreatment softener blowdown. The combined

composition of these streams is present in Table 1-2 in Section 1.

3-25

0

'( m

tl)

1"i ,c

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g;~ oz til~ s ~= ~s

ffi ~ ~ 8 ~

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1l I .. ~ d !C!: s:: .... ....:: 0 u 0 "' 0

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v.t • ...... ~ .... til 0 -: ~ ~ ;I) i-' ~ ~~ ~ o , "1:1 ~ -Aa ~ ~ '-4 d '"!1 0 .... I:. ~

~t:l~to__.._, Q i) ...., t E-4 ~ d d~ v 1t.1 ca 0 > .114 1U ~ ~ • r ~ ~ ~ ~f ;

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3-26

~ '<>

": \o

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'a 'tl .. 0

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"! ...,

cc

...

1:1 ... "' d

" "' ... .... ... 1"1 .. .. ..0 .. 0 .. ~

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"' .... 0 ., d 0 -... "' .. "' ... .. "' ., " " ;..., .... u ... "

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.. ... d '"'<rt.l H .. rz:

"1'"1'00 • • N

0 N • ....

........ "' ..... 0 N • ....

....... o . . ... ON • ....

.. ... d

" " ... .... ::J .. " "' f'''l;t'f) v "-

8SlSl g as a:t .o ,o

t.Jr...JtJ <

,!;

... ... <'! ........ . .... Q ....

.......... COON 0 •• •o,.,.

Q

"'"'"' con., co • . ..... co

"'"'"" 8 00

"'"' .. .. .. uuu

In the first case chosen, the two wastewaters were added to an Eastern coal system

using the low Mg reactivity limestone and Mississippi acid-treated cooling tower

blowdown. The results are shown in Table 3-11. The addition of these low volume

w-astewaters does not affect the design of the system significantly. This is due to

the fact that these additional wastewaters account for less than 3% of the total

makeup water added to the system.

The second case simulated with the additional wastewaters was a Western coal system

using the low Mg reactivity limestone and Lake Sakajawea blowdown from the side-·

stream softened cooling tower system. The results, shown in Table 3-12, indicate

that the additional wastewaters do not effect the design of Western system. As in

the Eastern case, the additional waters account for less than 3% of the total

makeup water added to the system.

It should be noted that these simulations Assumed a constant low vola~e flo~.

Surge capacity should be included in an actual design so that the FGD system would

not receive too large of ~ quantity of these waste streams or these cases would not

simulate the appropriate operating conditions.

ALTERNATIVE DESIGN CONCEPTS

The fact that some of the simulation results represent unreasonable actual system

designs has been emphasized in this report. Some of the Western coal cases' have

L/G's less than 20 gal/Macf (2.1 m3/Mm3) with a few in the 10 gal/Macf (1.3

m3/~fm3) range. Some of the Eastern cases have L/G's in the 250 gal/Macf (3.4

m3/Mm3) range. Both of these situations are unreasonable for operation of a

single spray tower absorber in a lime/limestone FGD system. This section addresses

some concepts which might be employed by a designer to overcome system limitations,

but the concepts proposed represent by no means an exhaustive discussion of the

solutions which may exist.

In the Western cases in which L/G's of less than 20 gal/Macf providd sufficient

alkalinity for S02 absorption, the spray tower FGD system becomes limited by

physical mass transfer considerations. Generally speaking. L/G's in this range

cannot supply sufficient interfacial mass transfer aro~ to accomplish the required

SOz transfer, Nozzle selection and design can produce smaller droplets and

improve the interfacial area per volume of slurry, but this corrective action is

limited by excessive entrainment of very fine droplets in the flue gas exiting the

system. Cne way of supplying the required transfer area is to simply increase the

3-27

Table 3-11

EFFEC'l"S OF TYPICAL LOW FLOW RATE WASTEWATERS ON AN EASTERN, LOW MAGNESIUM LIMESTONE FGD SYSTEM

Primary Makeup Water

Demineraliz~r Waste Flow (gpm)

Softener Wastewate= Flow (gpm)

Makeup Water Flow (gpm)

% Makeup Water from Wastewaters

L1qllid-to-Gas Ratio (gal/macf)

Rer.ction Tank Size (~Ill}

Absorber Feed TDS (Wppm)

Total Alkaline Species in Absorber F~ed Liquor (N)

Ionic Strength

Absorber Feed pH

Absorber Effluent pH

3-28

Mississippi River Water Acid­Treated Cooling Tower Blowdown

619

234

161),t)00

13,300

0.0023

n "'"' v.oJ.,

5.8

4.3

10.5

4

605

2.3

233

771,000

13,400

0.0023

0.32

5.8

4.4

__ L --~~- ---"" .....

Table 3-12

EFFECTS OF TYPICAL LOW FLOW BATE WASTEWATERS ON A WESTERN COAL, LOW MAGNESIUM LIMESTONE FGD SYSTEM

Primary Makeup Water

Demineralizer Waste Flow (gpm)

Softener Wastewater Flow (gpm)

Makeup Water Flow (gpm)

% ?tfakeup Water from Wastewaters

Liquid-to-Gas Ratio (!41/macf)

Reaction Tank Size (gal)

At,.sorber Feed TDS (wppm)

T(!)t~., Alkaline Species in Absorber Feed Liquor (N)

Ionic Stren.~th

Absorber Feed pH

Absorber Effluent pH

3-29

Lake Sakajawea Sidestream Soften~d Cooling Tower Blowdown

10.5

4

514 500

2.8

9.8 9.8

126,000 126,000

202,900 200,700

0.023 O.OZ3

3.97 3.92

6.6 6.6

5.4 5.4

I

spray tower L/G above that needed for alkalinity to a level sufficient to provide

mass transfer area without excessive entrainment. This is a very practical solu­

tion since the pumping requirements will still be reasonable and since spray towers

are less susceptible to scaling and plugging problems which have plagued many other

lime/limestone system designs. The tradeoff of a slightly ltigher liquid rate may

be more than offset by increased capital costs a4d operating problems of alterna­

tive designs operatin~ ~t minimum liquid rates,

The Eastern coal cases, particularly the higher chloride coal cases, present prob­

lems on the other end of the spectrum, L/G's in the 200 gal/ltfacf (27 m3/Mm3)

range and above are not that attractive since these high L/G's can cause gas and

liquid surges throug~ the contactor and also result in much higher pressure dLops

than desired in spray towers. One method of reducing the slurry pumping require­

ment would be to use a packed bed design of some type. The additional gas-sl~ry

residence time would provide time required for alkaline solids dissolution so that

de~ired removals could be achieved at reduced L/G's. However, c~re must be taken

in the packed tower design since higher dissolved sulfate and. calcium ion concen­

trations may result and can promote chemical scaling. Some packings are also

susceptible to physical plugging with slurry solids.

Another concept, which can be used with either the spray tower or packed designs, is two or more contactors in serles. If the water system is handled properly, the majority of the chlorides can be isolated in the first loop and resulting overall

L/G may be reduced since the second loop has a much higher liquid phase alkalinity. In some cases, ~ne additional cost

the savings i·. operating expenses. of the extra equipment is more than offset by

The prescr~bber concept is one type of double-loop type s~s~~m in which only the

chlorides are removed in the first loop. A relatively small prescrubbe:r contactor

is designed so the cost of materials for handling chloride laaened liquor can be

minimized, The ~ain loop can be built of less exotic materi~ls, and the L/G

required for alkalinity will be less since the chlorides have been isolated in the

prescrubber loop as illustrated in cases examined in this ~tudy. The prescrubber

system will have a '~''astewater stream which must be disposed of in some manner (in

the a~h pond on in a brine concentrator for e~ample). The prescrubber should be de~igned tc naximize these benefits and minimize water usage.

3-30

~ --~-----~---::~-~---~~·---~-..._.~~~·-----~.~~-~;»~,~ '~~,~~

The n•3ed for lower L/0' s in eastern coal c&n also be met by using additiv~t.< that

improve 1iquid phase alkalinity. Addition of magnesium or sodium compounds such as

MgO, MgS04, or NaC03 will improve the slurry alkalinity in many C"\~es. Here

the selection of the proper vrater source is essential since alk.aline reagents are

sometimes added to wahr streams other than in the FGD system, Proper selection of

the water source can minimize water usage and reagent costs. Use of organic acids

such as adipic acid will also improve liquid phase alkalinity. 'i'he organic acids

are less affected by the sulfite oxidation or chloride level than are the inorganic

additives, but the organic ar.ids are generally somewhat more exP,ensive. All of

these additives may have an influence on the morphology of the solids formed in the

FGD system which has an effect on sludge processing and disposal. All of the

factors must be considered in d"sian of an additive-enhanced lime/limestone FGD

system.

3-31

":· :~~.~~~~ .. ~~~.

Sectior.t 4

CONCLUSIONS AND .RECO~JDATIONS

f!ONCLUSIONS

The followinzs conclusions can be dra·Rn from work performed on this project:

•

•

•

•

•

Process water selection has a significant effect on the process chemistry. The TDS of the makeup water is not the major determining factor in evaluating the impact of makeup water on process chem­istry. Waters with high Mg++ or Na+ concentrations relative to Cl- result in higher liquid phase alkalinity and lower L/G's.

Other varianles such as coal Cl content and reactive magnesium concentration in the alkaline reagent have an equally important role in determining process chemistry effects.

Process water selection has an important but less significant effect on the system's scaling tendency than on alkalinity. In most cases, these effects can be compensated for by changing the suspended solid concentration to adjust the seed crystal inventory.

In selecting the optimum use of water sources in an FGD system, one must examine the process chemistry effect on the specific unit operation such as the mist eliminator or lime slaker as well as on the main absorber loop.

Process water selection can effect the optimum FGD system design • Additionally, the feasibility of some designs can be effected by the makeup water used.

RECOMMENDATIONS

The recommendations stated here are mainly ones which concern validation of the

modeling which has been performed to date. The phase relationship have been fairly

well validated for the more dilute solutions, but extensive wox~ ~as not been

performed with the concentration solutions expected from using high TDS cooling

tower blowdown in FGD systems. Specific recommendations include:

4-1

• Verify the Radian equilibrium program results with field sampling and analysis data. Determine if magnesium or sodium are precipi­tated or occluded in the solids in a form not presently accounted for •

• Determine the effects that high 'IDS cooling tower bllJwdown liquors have on solids precipitation and crystal morphology. Any scaling inhibitors used in cooling tower should also be investigated for effects on crystal morphology.

•

•

•

Continue efforts to determine the effects of high IDS liquors on tho dissolution rate of MgCOg from limestone.

Investigate the effect of integration of other plant water systems on FGD system performance (e.g., ash pond blowdown as makeup water, lime softener sludge as alkaline reagent) and consider in more detail the proper point of addition to the system (e.g •• mist elimi­nator wash, presaturator, etc.).

Investigate the impact of minor chemical species on FGD system design and performance. T!ace metals introduced from some roakeup water sources {e.g., cooling tower additives, ash leachate, etc.) could effect sulfite oxidation rates and crystal morphologies (e.g., solid waste characteristics).

4-2.

A

c

I.S.

Ksp

R(t)

L/G

M

N

percent(w)

ppm (w)

RSGyp

13

OTIIER TERMS

calcium sulfite/ sulfate

gypsum

subsaturated conditions

supersaturated conditions

Section S

GLOSSARY OF TERMS

specific solid surface area (cm2/g)

s~lids content of a slurry (g/Q)

ionic strength = -21EM. Z. 2 where ~li is the molar

t . f . . l. 1 • . d z . th h concen rat1on o 1on1c spec1es 1 an i 1s e c arge associated with species i

solubility product constant

temperature dependent precipitation rate constant

liquid-to-gas ratio (generally

fsctor of 103 (one thousand)

expressed as gal/1000

normality (equivalents per liter)

weight percent

parts per million by weight (appro~imately milligrams per liter in dilute solutions)

relative saturation of gypsum

r (aCa++)(aso4=)(aH20)2]

[ Ksp, Gyp

defined as

equal to

acf)

ratio of precipitating solid species to total solids (g/g)

solid solution of calcium sulfate hemihydrate in calcium sulfite hemihydrate crysta1 lattice (maximum sulfate content is about 15 percent of the total sulfur)

calcium sulfate dihydrate (CaS04•2H20)

relative saturation less than 1.0 (generally the scrubbing liquor is subsaturated with respect to gypsum when sulfite oxidation is less than 15 percent)

relative saturation greater than 1.0 (generally the scrubbing liquor is supersaturated with respect to gypsum when oxidation is greater than 15 percent)

5-1

"'

Section 6

REFERENCES

1. Arnold, C. W., Jr., et. al, Investigation of High SOz Removal Design and Economics. Final Report. CS-1439, Volllll\e I Technical Planning Study TPS 760. Austin, Texas: Radian Corporation, June 1980.

2. Federal Register. Part II, Environmental Protection Agency, Hew Stationa:~:y

Sources Performanc·e Standards; Electric Utility Steam Generating Units, 40 CFR Part 60. June, 191"9.

3. Arnold, C. W., Jr. et. al, Investigation of High S02 Remo~al Design and Economics. Final Report. CS-1439, Volume I Technical Planning Study TPS 78-760. Austin, Texas: Radian Corporation, June, 1980.

6··1

• ,._

• ;..

••

' '.

• • # ~:.

• •

., •

' :

• •

• •

=~ .

. . .

. .

. -.

~=---~ .-

ell ~

ell

< 0 ~

H

E-4

<

~ X

•.-I

H

"d

ell

s:: QJ

,..:t ......

~

,..:t .l:

~

< ~

0 fzl e

ll

~ C/l ~ ~

Appendix A

RESULTS FOR ALL SHlULATIOU CASES

This appPndix presents the results from each case simulated du~ing the project.

Tables A-1 through A-9 present design and operating parameters for the cases. Next

Tables A-10 through A-45 present the chemical compositions of the absorber feed,

absorber effluent, sludge waste streams and prescrubber effluent streams for each cas~.

Note that some abbreviations have been made in this appendix. For instance, 11Lake

Saka11

stands for Lake Sakajawea water and 11CTB 11 stands for cooling tower blowdown.

A-2

'!'able A-1

DESIGN PARAMETERS FOR EASTERN COAL HIGH MAGtmSIUM LIMESTONE CASES

Parameter

.t-1akeu.tl Water Source Treatment Flow Rate (gpm)

so2 Removal (%) Sulfite Oxidation (%) Coal Chloride Content (wt%)

Alkaline Feed Source stoichiometry Flow Rate (lb/min) Reactiva Mg Concentration (wt%)

Required L/G (gal/mac£) Required Reaction Tank (gal)

Absorber Feed Rate (gpm) pH R.S. of CaC03 R.S. of CaS03 R.S. of CaS04

Total Alkaline Species in Liquid klhase (N) TDS (wppm) Ionic Strength

Absorber Effluent pH R.S. of CaC03 :&.S. of CaS03 R.S. of CaS04 TDS (wppm) Ionic Strength

Solids Dissolution in the Absorber (%)

Sludge Flow Rate (lb/min) pH TDS (wppm)

EOl

Raw Lake Saka

616

90 20 0.1

Limestone 1.1 937 1.5

A-3

96 772,000

136,000 6.1 0.40 2.48 1.25

0.0078

27,800 0.55

4.7 <0.001

0.44 1.30

28,200 0.56

1.0

2400 6.4

27,300

E02

Raw Santee River

616

90 20 CJ.l

Limestone 1.1 937 1.5

135 739,000

191,000 6.0 0.40 2.49 1.26

0.0050

18,100 0.42

4.7 <0.001 0.49 1.30

18,300 0.43

1.0

2400 6.2

17,300

i .'1

Table A-1 (continued}

'DESIGN PARA:.\lETERS !:'OR EASTERN COAL HIGH 1-!AGNESIU!'·l I.INESTONE CASES

}~';~E~~t~:;:

f·l.Jkeu1 h'atcr ~ourt:t:• Trt:atm"nt

F'lt.lit: Ratr• {g].,·!':l)

Sv~ .R,;:::t:Nal ( :,) Sulfit~ OXiJat1on <~> ~o.:.l Ch1oride .::ontt.:nt

.t1lk~l i ~\..; l'.t:t.::j Sc.ur~t..· •:~::.oi;:.!liOl!!'itr~ ..

ltd·~;

l,la:: !\u.tt.: tlt .. /r:linl E·.;~L:tive..: !~l:J Con..;-..:~ltrcttion

h1t 0)

EJ3 -Ra\-.," :·Iis:.J.

615

90 :w 0.1

Limestone Ll :!37 1.5

RE!~J>.<ircd !./1; {gal/mac:f) R·.c•l': ir•.;;d Rt1acticn Tunk {'ru.l) 133

7•1G, 'JOt>

li1J~tu:bt=r !·l:.,.~d !•!I

F'J.te (;,;r.t)

r:.s, of R.s. of H.s. ()f -..:as~J ..

Total Al;:alirt'~ Sr·t;;.~.: ·"'..:s in Liquid rha"'t: (!n TD3 {t;l-!-;r:}

Ioniu 3t:t·taqth

ALsr;l::Lcr Effluent 1H l'.S. of i;<J :03 R.s. of Ga:·Ki3 r~· .. ~~ .. of Ca!::G4 TDD (~-:g.n)

IrJnit: Struu•;t:,

Soliu<: DL·:Jolutian in th•;; Ab<;o:rtur (':;)

::ilud·~u FltM Hate I·l!

T!J3 ( ill.Vtm)

(1L/min}

lBJ,:;uo G.•J 0.4 ., -..: ... ,.-"u

1.2&

0. {J(j':.l

P,3JO ~J.4;::

4.7 <!). ;: '1 0.4) 1.::;'

1~;, 71)• ..

, ... ·,~' .. t;!:;;

l. '

2400 G.3

17, 60iJ

A·-i

E07 -Niss. CTB

At•id Addition

617

,, .. ~ '•·-' 20 (l.l

Lir.lt..;::,;tono l.l 937 1.!'

lJ7 7-J:t,OOO

181,~ (\) 6. {_1

\ 'r • 4-2,57 1.26

G. t)~.)S4

l'} I 'HlO : ~. 4 ~

4.::. <(;.t}ijl

0.34 L3ti

2U,0lhJ

'l.34

l.o

24t)ij £.3

l'J 1 00()

E04 -I-1iss, CTB

Acid Addition and Sidestream Soft~::t:d

618

90 20 0.1

Limestone Ll 937 1.5

78 7!:.l'J,OOO

110,000 6.2 0.4 2.22 1.24

0.010 45,800 0.53

4.9 <0.001 0.54 1.30

46,200 0.83

1.0

2400 6.5

45,400

Table A-2

DESIGN PARAMETERS FOR EASTER~ COAL LOW Mll,GNESIUM LIMESTONE CASES

~~ Hak.uup Wat('r Som:~e

Treatment

:now Rate (gpm)

SO:.> Removal (%) sulfite Oxidation (%) Coal Chloride Content (wt%)

Alkaline E'ced Source Stoichiometry Flow Rate (lb/rnin) Reactive Mg Concentration

(wtr~)

H~quircd L/G (gal/macf) Required Reaction Ta.uk {gal)

Absorber Feed Ra.te (gpm) vH R.S. of CaCOa R.S. of CaSOa R.S. of CaS04

Total Alkaline Species in Liquid Phase (N) TDS (wl'I'm) ~onic Strength

Absorb~r Effluent pH R.S. of CaC03 R.S. of CaS03 R.S. of CaS04 TDS (W},>tJm) Ionic Strength

Solids Dissolution in tho Absorber (%)

Sludge Flow i\~tc (lb/min) pH •ros (wppm)

E08

Raw Miss.

617

90 20

0.1

Limestone 1.1 937

0.15

234 765,000

331,000 5.8

0.40 2.68 1.26

0.0023

12,600 0.31

4.2 <0.001

0.27 1.30

12,800 0.31

1.0

2400 6.0

12,100

E09 El5 E16

Miss. CTB Miss. CTB Miss. Acid Acid Addition Acid Addition Addition CTB

and Wastewaters

619

90 20

0.1

Limestone 1.1 937

0.15

234 760,000

332,000 5.8

0.40 2.52 1.26

0.0023

13,300 0.32

4.3 <v.001

0.35 1.30

13,400 0.35

1.0

2400 6.0

12,800

A-5

613

90 20

0 • .3

Limestone 1.1 937

0.15

274 739,000

388,000 5.5

0.40 2.47 1.26

0.0022

32,900 0.88

3.7 <u.OOl

0.13 1.30

33,100 o.8a

1.0

2400 5.7

32,600

614

90 20

0.1

r.imestone 1.1 937

0.15

233 771,000

330,000 5.8

0.40 2.53 1.26

0.0023

13,400 0.32

4.4 <0.001

0.37 1.30

13,500 0.32

1.0

2400 6.0

12,800

Tat-le A-3

DESIGN PAIW1ETERS FOR EASTERN COAL HIGH MAGNESIUM ! nm CASES (BOTH Hir.H AND LON COAL CHLOP3.DE CONJ:i::NT CASES)

;~,£~?:· t:~E~

Hctlt(;Uf' ~-:utf·r Suurc(.'! Tr~;~<Lblen~

r'lo\.; Hate (gpn)

so2 Rct::ov..11 < ~> Sulfi t~.: O:<i.lu.ti... { ;:.) Coal Chl'VriJ·~· -.:ont•.:nt (wti.)

Alkaline E't:;;c::d So:.trcc St..oic!liO::lutry Flo;-; F.atu (lb/ntb; Reactive !·l'J Concentration

('f;t:: l

F.Dquirt:d L/G lgal/.:::i:icf} Requir· J Rea::::tion Tank (gal)

Absorber F~~-:,J Rate liJ!:I:I) r .. H

.H.s. c!' '::'aco3 R.s .. of CaS:J3 :r. .• .:o;. of caso,.

·rotul Alkalin;: Sr:•:ciF.;s in Liquid Phv.st.: (N) TDS (:,;u .:::)

Ionic Stnmgth

~"sutLer Effluent l•H

R. s. of caco3 R.S. of CaSOa R.s. of caso4 TDS (wpr:m) Ionic Strength

CaS03 Solids Dissolution in the Al;osrber {~)

Sludge Flow Rata (lb/min} f'U T!JS {Wf;~I:Il

ElO

!-2iss. River

5<10

}f.)

15 ~;...~ .1

Lirnt"l l.OS l''33 1. Co

~9

141,000

14;J,OOO 8.4 9.C 3.0

~1.51

0.0077

2li,200 (J.4G

4.7 -:rJ. 0()1

('.3;, 0.67

21,1~)!)

0.48

0.20

::no 8.1

19,000

A-6

Ell ill !>1iss CTB

Acid Addition 591

Miss. River

586

90 1 <;

~·

0.1

LimP 1.06 683 1.6&

113 148,GJO

160,GJO 8.4 B.r; ., ;.t. >}

0.64

0.0065

2l,HOO *).4)

4.7 •'O.·l\Jl

0.35 0.71

22,500 o.so

0.2Q

2320 8.3

2o,soo

90 15 0.3

Lime 1.06 683 1.66

249 180,000

353,000 7.4 10 3.0

o. 7l':

0.001!)

31,30:.) 0.91

4.2 •:u.oo1

0.26 0.78

31,800 0.91

0.20

22'JU 6.6

29,~WO

El4 -Miss. CTB

Acid Addition 588

90 15 0.3

Lime 1.06 683 1.66

253 194,000

358,000 7.5 10 3.0 1.0

0.0020

32,400 0.92

4.1 <0.001

0.21 1.04

33,000 0.93

0.20

2300 6.6

32,400

Table ~4

DESIGN PARAMETERS FOR EASTERN COAL LOW MAGNESIUM LIME CASES (BOTH LOW AND HIGH COAL/CHLORIDE CONTENT CASES)

Parameter

Makeup Water Source Treatment Flow Rate (gpm)

SOz Removal (%) Sulfite oxidation (%) coal Chloride Content (wt%)

Alkaline Feed Source Stoichiometry Flow Rate (lb/min) Reactive Hg Concentration

(wt%) Required L/G (gal/macf) Required Reaction Tank (gal)

Absorber Feed Rate (gpm) pH R.S. of CaCOa R.s. of caso3 R.S. of CaSOtt

Total Alkaline Species in Liquid Phase (N) TDS (wppm) Ionic Strength

Absorber Effluent pH R.S. of CaCOa R.S. of CaS03 R.s. of caso4 TDS (wppm) Ionic Strength

caso3 Solids Dissolution in Absorber (%)

Sludge Flow Rate (1b/min) pH TDS (wppm)

E05

Hiss. River

592

90 15

0.1

:t.ime 1.06 681 0.55

215 166,000

305,000 8.0 25 3.0 0.69

0.0025

11,900 0.32

4.4 <0.001

0.37 0.73

12,500 0.32

0.20

2320 6.9

10,100

A-7

E06

Miss CTB Acid Addition

591

90 15

0.1

JJime 1.06 681 0.55

213 168,000

303,000 7.9 25 3.0 1.0

0.0024

13,700 0.34

4.5 <0.001

0.36 1.04

14,200 0.35

0.20

2330 6.7

13,600

E13

Hiss River

586

90 15 0.3

Lime 1.06 681 0.55

249 194,000

352,000 7.4 20 3.0 0.83

0.0021

32,300 0.90

4.1 <0.001

0.37 0.89

32,700 0.90

0.20

2280 6.3

31,300

..,.

Table A-S

!·lAH7 LC'OP DESIGN PARi'>J.lETEl~S FOR !::ASTERN COAL LIME SYSTEMS

E:OlPLCIYING A PRESCRUBBER FOP. Cl Rm10VAL

! J.rdr:·~:-:·.:t'

:-:J;:·_.·l;. ~-t.l~> ... r ~~l.!r~t: :·r._ ~t::'_,t, t

:-!~i=·~ :.-... _.:;!· I-·lc:·~- E.J:t·; \:~~:a;

T.J!:u.l z.;~:~t·"'-~ Flu:·: ~.at~ \.:! m) ~):· ~"~·,;:~·~~val {'~J

~:llfit ~- .... xid~~i~-·:. t. ..:! ,;va. ·..:~·.:.:ori J._ 2::':~t·..:nt~ (t-.·t ..~)

;~l~~.l:i:~·....: t~_.:-...:d £~\..~ur ... >:: 3~~1 ::.::i.i{;r:.·~:..r / !·2~·~-; ~.~t.£: (lL- · ~i::.d r~ .. .;~~~iV*~ :-:~ :.: . ..Jrl·.>..::itratl..;;~

F.'.: !Ui.I>:.:j ~- '.·; ~~~1, r.ta,;f}

:-.~..:~Iuir•_d r.-·.:u.~ti".:n. ::"i:J: (~J.:il:'

.;; ~<JrL-,r r··:::·..:;l i:<:~t·., (;; I:l} 'H

~,~; :·tJ.·:;:r~

? .. 2. ·,.;f Ca.~.L..' ·~ i .3. of ...:a3 · .•

T:..:t,.;t! Al}:ulin-.:.; ..::: ·.:;:.:i·_:~ ir • .::..1.-"r-1i:l t·l.da .. ~,._: \:n T:S >:·:!;t1: rc:ii :; ~tr' .. :::..f:it.~ ~

Z~s.:..r~~~-.;r ::.:ff.:~-;::J.t t i!

:.·.3. ~._f ,...:acJ; , •• ::;. :.>f ~..:aso~ !< ... ~. ~.:...t :..:as:: ... TD.3 ~;~;!.;~::1)

!or~.tc Str•.:.n:;t!l

•::01.3:." ;~vlid~ Di::~~-olution ir" ti.·..: I>l;.;vrL,;:r ( .;j

311..l"if:J~ f'lv·~·: ~r:;.t~..; {1L/mir.; rH 'ri:.>3 '.:·;Ht~l

{:·:t -.~)

A-8

~ !11i~H;issipi'i River

:J86 LH2

'}J 1' .)

1.3

1.,16 ub3

1.66

1:56 14d, -.'•)0

"") ..... _,..J.,' •:!d

8. ~J l<}

3. '. :;,4

• '.11)3•J

H2·J i ,1_)-·J3

4.ti <ti. )';l

(J. ,:;:;

iJ. 63 :034fJ

0.1))'_:

fJ. 2

~2:JU

7.6 373fJ

PE02 -His!J CTB

Acid Addition 588

1325 90 15

0.3

1.06 683

1.66

166 145,000

234,000 8.0 10

3.0 0.59

i"). 003-..~

5180 0.10

4.6 <0.001

0.27 0.68 5850 0.11

0.2

2290 7.7

4081

Table A-5 (continued)

PRESCRUBBER LOOP DESIGN PARAMETERS FOR EASTERN COAL LIME SYSTEMS EMPLOYING A PRESCRUBBER FOR Cl REMOVAL

J?arame~

Nak.eup Water Source Treatment

Prescrubbcr Loop Makeup Water Rate (gpm) Thickunor ovcrf10\'l Water Rate (gpm)

S02 Removal (%) sulfite Oxidation (%)

Alkaline Feed source :now Rate (lb/min) Raactiva Mg Concentration (wt%)

R.:quired L/G ( gal/macf) Pruscrubbar Effluent Rate (gpm)

pH R.S. of CaCOa R. S. of CaS03 R.S. of CaSO~ Cl Co:1tcnt (wppm) TDS (wppm) Ionic Strength

A-9

P.I::Ol

Raw Hississippi

426 463

<0.1 90

Lime 18.0 1.66

0.30 424 2.1

2.8 X 10-~ 7.8 X 10-4

l. 30 6400

12,900 0.31

PE02

Hissisnippi CTB ACid Addition

737 464

<0.1 90

Lime 19.5 1.66

0.52 739 2.3

3.4 X 10- 9

6.7 X 10-4

1.30 3800 9050 0.21

Table A-6

DESIGN PJH~AMETEP~ FOR l'f'ES'l'ERN C~;liL HIGH HAGNE'~!UN L!NESTONE CAGES

Para.meter --~~ke Watar Source

Treatment i"lml' Rate (gpm)

SO, Remov<il Sulfite vxidation (%)

AlkalinG Feed Source Btoichiometry Plc,~ Rate Ub/min) aouctive ~1g Concentration

(wt%} Required I.!G (gal/.111.a.:cf} Required Reaction Tunk {gcil)

AbsorbE:r Fee'i P..ate (gpm) pH

Relative Saturation of CaCo" Relative Saturation of casoa Relative Saturation of caso~ Total Alkalin~ Srecies in Liquid Phase (N) TDS (\.,ppm} Ionic Strength

Absorber Effluent PH

:..~ia··~.,,~ Saturation of Caco 3

Relative Saturation of Caso; Relative Saturation of CaS04 TDS (v.rpmJ Ion{ Strength

SQlids 0issolutjon in AJ:..sorber (~)

Sl·. Je Flow ~te (lb/min) PH TDS (\\ppm)

~

Raw Lake Saka

534

70 90

Limestone 1.1 109 1.5

15 124,000

23tOOO 6.3 0.40 2.40 1.23

o.ou

7.:.,SOJ 1.4

4.9 <u. 'J(h

C'.37 L3o

-5,100 1,4

o.s

350 6.6

73,100

A-10

!!Q£

Lake Saka CT.B A.:ict Addition

515

70 90

J..oirnestone 1.1 109 1.5

12 121,000

18,000 6.4 0.40 2.27 1 23

0.015

106,000 1.9

s.o 0.0017

0.47 1.30

1oa,ooo 2.0

0.5

360 6.8

lOG,OOO

W07 -t.ake Saka CTB

Sidestream S"ftened 514

70 90

Limestone 1.1 109 1.5

8 142,000

13,0(10 6.6 0.40 2.14 1.18

0.029

216,000 4.2

5.4 0.0023

1.16 1.30

222,000 4.3

0.5

370 7.0

216,000

Table A-6 (continued)

DESIGN PARAMETERS FOR WESTEPN COAt HIGH MAGNESIUM LIMESTONE CASES

Parameter

Nakeup Water Source Treatment Flow Rate (gpm)

so2

Removal (%) Sulfite Oxidation (%)

Alka~· Feed Source Stcichiometry Flow R".te (lb/min) Reactive Ng Concentration

(wt%)

Required L/G (gal/macf) Required Reaction Tank (gal)

Absorber Feed Rate (gpm) pH Relative Se.turation of CaC0 3 Relative Saturation of CaSO Relative Saturation of caso:

Total Alkaline Species in Liquid Phase (N) TDS (wppm) Ionic Strt;ngth

Absorber Effluent pH Relative Saturation of CaC03 Relative Saturation of CaSOa Relative Saturation of CaSO~ TDS (wppm) Ionic Strength

Solids Dissolution in Absorber (%)

Sludge Flow Rate (lb/min) pH TDS (wppm)

W03

Raw Miss.

513

70 90

Li: ~stone 1.1 109 l. f.i

163 124,000

9!3,300 '5.8 0.40 1.62 1.23

0.0017

29,900 0.82

3.7 <0.001

0.028 1.30

30,10G 0.83

0.5

340 6.0

29,700

A-ll

W04 W05

Miss. CTB Miss. CTB Acid Addition Sldestream Softened

515 516

70 90

Limestone 1.1 109 1.5

53 124,000

83,600 5.8 0.40 2.05 1.24

0.0023

33,600 0.88

3.9 <0.001

0.046 l. 30

33,800 0.89

0.5

350 6.0

33/100

70 90

Limestone 1.1 109 1.5

14 116,000

21,500 6.7 0.40 2.38 1.22

0.014

175,000 3.5

5.4 0.0053 1.08 1.30

177,000 3.5

0.5

370 7.1

175,000

Table A-7

DFSIGN PARA."lETERS FOR WESTERN COli,L LON MAGNESIUH LIMESTONE CASES

~Q~

!·1ake~p i"iater Source Treatment Ho-..; Rate (9fi:l}

SO, Removal {;;,) Sulfite Oxidar:...,n (r.;}

~lkalinc Feed Source Stoic1li~motrr FloH Rate (lb/n:in} Reactive ~1g Concentration

R""qui red L/ G (gal/mac f)

Required Reaction Tank (gal)

Absorber Feej RatQ (gpm} ~

~9!ativ~ Saturation of CaC03 Relative Saturation of CaS0

3 Relative Saturation of CaSC~

'lbtal Alkalinf; Sr•eci.-·;; in Liquid P:!uS•,: {N} '.!'Dt h>Tpm) Ic-nic St.t'ength

•lbsc~b9r Effluent pH

Felative 3aturation of CaC03 Relat~ve Satutacion of CaS03 P.elative Saturation of CaSo4

TDS (t.;ppi:l}

Ionic ~trength

Solids Dissolution in the 1U..o;orb£·r {'~)

Sludge Flo;-; Rate !lb/rnL1) pH TDS (\>ippm)

~.~~:;:'~::.:.;::

WlQ

Raw ~liss.

513

70 90

Limestone 1.1 109

0.15

66 141,000

l04,JOO 5.6

0 .. 40 2.27 1.20

D.U017

30,700 O.Bl

3.8 0.0059 0.059 1.30

30,'300 0.82

0.5

340 5.8

30,300

A-12

~ '-:·

Wll

t-1iss. C1:.'B Acid n~.:t.i.don

515

70 90

Limestone Ll 109

r..1s

66 131,000

106,CIOO 5.7

0.41) 2.1R 1.22

o.u017

33,400 0.86

:J.9 <0.001

0.061 1. 30

33,600 0.87

0.5

3JQ 5.9

<:3, 000

W12

Miss. C'l'B S1destream Softened

516

70 90

r.imestone 1.1 109

0.15

18 110,000

27.,800 6.7

0.40 2.20 1.24

0.0094

162,000 3.3

5.4 0.0052 0.93 1.30

164,000 .'3.3

0.5

370 7.1

162,000

Table A-7 (continued)

DESIGN PARAMETERS FOR WESTE~1 COAL LOW MAGNESIUM LIMESTONE CASES

rarameter

H:Jkeup \~ater source Treatment

Flow nate (gpml

S\lz Removal ('1.) Sulfite oxidation (\)

blkaline Feed source stoichiometrv F!~« !V'te (lb/min) heactive !'.!! c.mcentration

(wt\)

Required L/G (gal/macf) RNUi.red Eeaction Tank {gall

Absorber Fccrl Rate (gp:n) ;·ll n.s. of caC03 R.S. of CaS03 R.S. of caso ..

Total Alkaline Species in Liquid Phase (Nl Tll5 (wpr.m) Ioni<:: 5trength

Absorber Effluent fll R.s. of caco1 n.s. of casoa R.S. of CaSO~ 'OS ( -..-pf:m) l'Jnl.c Strength

St,l;.d.; Dissolution in the 1.03orl>cr ( '0}

SluJJU Flow P.ato (lb/ml.n) f!l TDS (W:.Jp::l)

.!:!£

Raw Lake Saka

515

70 90

:t.:.•u~stone

l.l 109 0.15

19 122,000

29,700 6.3

0.40 2.52 1,24

0.0078

62,200 1.2

5.0 <0.001

0.40 1.30

63,300 1.2

0.5

360 6.6

61,700

.!ill. Lake Saka C'l'B Acid Addition

516

70 90

Limestone 1.1 109 0.15

13 123,000

20,300 6.4

0.40 2.53 1.23

0.013

94,500 1.7

5.1 0.0018

o.ss 1.30

96,400 1.'?-

0.5

360 6 .. 7

94,200

A-13

~

Lake Saka CTB SidestrP.am Soften.Jd

514

70 90

Limestone 1.1 109 0.15

10 126,000

15,300 6.6

0.40 2.17 1.20

0.023

203,000 4.0

5.4 0.0037

1.16

208,000 4.1

o.s

370 7.8

203,000

!:!!2. .L.aku Saka. CTB Side• stream Soft~ned and Wastew~ters

70 90

Limestone 1.1 109 O.l:i

10 126,000

15,400 6.6

0.40 2.18 1.20

0.023

201,000 3.9

5.4 0.0035

1 ,.

1.30 205,000

4.0

0 .. 5

370 7.0

201,000

Table A-8

DESIGN PARAi'IETERS FOR ~'VESTERN COAL LOW !>!AGNESIUH LIHESTONE CASES

(FIXED DESIGN CASES)

Parameter

!·1akeup l•iater Source '!'re.>atment Flow Rate (gpm)

SO: RemoV'l.l (;:,) Sulfite (1xidation (\;)

Alkaline Feed Source Stcichicmt>try

Wl7 --Hiss. CTB

Sidestream Softened 516

70 90

l-'10\v F .. te !J.b/min) Reactive !•1g Concentration h'lt%)

Limestone 1.1 109

0.15

L/G {gal;'macf) Rea~ticn Tank (qall

Ahso:r:ber Feed Rate (gpm) pH Relative s~turation of CaC0 3 Relative Saturation of Ca~o 3 Relative Saturation of case~

Total Alkalin~ Species in Liquid Phase <m TDS (\''!-·r:m} !rrni,:- Str1.mgth

Ahs~rbe:::· Effluent pH

Relative Saturation of Caco5 Relative Saturation of casc;3 Relative Sat4ration of CaS04 Tr:s {>vi;pm)

Scl1Js Dissolution in the Absorber (%)

Sludg~ Flow P~t~ (lt/min) .PH TDS (w1fm}

17 141,000

::!6,800 6. ~ 0.4(.1 2.13 1.19

0.0094

162,000 3.3

5.3 0,0033 0.83

164,00.; 3.3

0.5

370 7.1

162,000

A-14

Wl8 -Miss. CTB

Sidestream Softened 526

98 90

Limestonp. 1.1 152

0.15

66 141,000

104,000 6.G 0.40 2.35 1.28

0.010

121,000 2.3

6.2 0.11 2.07

121,000 2.3

0.5

510 7.0

121,000

<j

Table A-9

DESIGN PARAMETERS FOR WESTERN COAL LIME CASES

Parameter

!-1akeup Water sou:rce •rreatment FlC"''.'! Rcn::.e (gpm)

SO 2

R(;'moval (%) Sulfite oxidation (%)

Alkaline Feed source Stoicf.iometry ~low Rate (lb/min) Reactive Mg Concentration

(wt%)

Required L/G (gal/macf) Required Reaction Tank (gal)

Absorber Feed Rate (gpm) pH Relative Saturation of CaCOs RrE.lative Saturation of CaS03 Relative Saturation of CaS04

Total Alkaline Species in Liquid Phase (N)

TDS hipprn) Ionjc Strength

Absorber Effluent pH Relative saturation of caCO! Relative Saturation of caS03 Relative Saturation of CaS011 TDS {wppm) Ionic Strength

CaS03 Solids Dissolution in the Absorber (%)

Sludge Flow Rate (lb/min) pH TDS (wppm)

woe

Lake Saka

512

70 90

Lime 1.06 78.9 0.55

14 121,000

22,600 8.2

10 3.62 1.23

0.010

66,700 1.3

5,.0 0.002 0.45 LJC

68,100 1.3

o.54

350 7.4

66,400

A-15

W09

Lake Saka CTB Sidestream Softened

511

70 90

r.ime 1.06 78.9 0.55

14 103,000

22,500 8.0 1..20 1.90 1.24

0.016

210,000 4.1

5.3 0.002

0.79 1.30

214,000 4.2

0

363 8.0

210,000

':..-:, .nOr ,,., • -c -""* ,__.r ... a_:t=f_.-~ ~~z •- -- 1::

W16

Lake Saka

512

70 90

Lime 1.06 79.1 1.66

11 117,000

17,300 8.1

10 3.8 1.24

0.015

77,400 1.5

5.1 0.005

0.59 ]..30

79,000 1.5

0.54

346 7.3

77,200

Table A-10

STREAM COMPOSITIONS FOR C.ASE E01. EASTERN LOW Cl COAL, HIGH Mg LIMESTo''E RAW LAKE SAKAJAWEA WATER .~., I

Component

Ca

Mg

Na

Cl

C02

NO 3

803 so

4

Col_!lponer:!

caro3

CaS03 tso4

• H2

0

caso4 • 2H1_o

Inerts

.Eguid Phase Concent.:ration [I!2m{w~ J Ahsorb~r Feed Absorber Effluent

Sludge Wasti

856 891 685

3890 3900 3890

2540 2550 2540 6790 6820 6800 346 81 446 52 52 52

392 828 149 12,900 13,000 12,500

sorher .t<eea Absorber Effluent Sludge Waste

7.49

85.0

5.97

1.56

A-16

7.42

85.0

5.98

1.56

7.24

84.8

6.42

1.55

TaMe A-l:l.

STREAM COMl'OSITlONS FOR CASE ll02. EASTERN LOW Cl COAL, HIGH Mg LIMESTONE, RAW I,Al'ffi SANTEE WATER

Ca

Mg

Na

Cl

co 2 N03 so3 so4

Component

CaCo3 Caso

3tso

4 • H20

CaS04

• 2H20

Inerts

.· ation [~2m~w}] Liquid Pha~ce~cr Sludge Waste

Absorber Peed Absorber Effluent -

1130 1380 1350 3150 3150 3140

50 so ~0

6820 6840 345

6820 85

3.5 274 3.5

3.5 91 584

5640 260 6230

6120

~n11~ Phase Concentration [percent(WlJ -A~~--~-~ Sludge Waste

~bsorber Fee4 Ab~'!fber Effluent

7.39 7.33

7.18

35.3 85.8

85.7 6.01 1

5.29 5,30

1.55 1.57

1.51

A• .7

Table A-12

STREA?tl COMPOSITIONS FOR CASE E03. EASTERN LOW Cl COAL, liiGH Mg LIMESTONE RAW MISSISSPPI RIVER WATER '

Liguid Puase Concentration [2P.m{w~J .£Q!tpone: t Absorber Feed Absorber Effluent ~udge\fu~

Ca 1300 1340

1040 Afg 3200 3210

3200 Na 98

99 99 Cl 6530

6540 6530 C0

2 251 93

326 N03 30

30 30 so

3 287 561

94 so4 6690

6190 6150

---~~a~~un Lpercent{w~J ColllPonent

nu~oroer Feed Absorber Effltlent

Sludge Waste Caco3 1.53

7.47 1.31 CaSO/S04

• H2o

85.1 85.8 85.2 caso

4 • zu

2o

5.15 5.15 5.94

lnerts 1.57

1.57 1.55

A-18

1

r 1 1: 1 t {

f ,j ,!! t.

1-

Table A-13

sTREAM COMPOSITIONS FOR CASE E04. EASTERN LOW Cl COAL, HIGH Mg LIMESTONE, MISSISSIPPI ACID-TRR\Tr CTB

t tion [ppm(w)] Lignid Phar-e Concen ~ra t Sludge Waste AQ_~orber Feed Absorber Ef~luen

~2.2nent

497 638 603 3270 ·Ca 3280· 3270 9650 Mg

%80 7210

96,50 7230

Na 7200

513 97 Cl

407 352 co2 352 352 190 942

N03

441 23,600 so3 24,000

23,700 so4

Absorber Feed Absorber Effluent -~n11d. Pn.ase Concentration [percent(Wl.

~· -~ Sludge Waste

Colilponent

CaC03

CaS03/S04 • H20

Caso4

• 2H20

Inert.s

7.40 7.33

7.15

84.3 M.4

84.4

6. 72, 6. 73

6.93

1.54 1.55

1.54

A-19

Table A-14

STREAM COMPOSITIONS FOR CASE EOS • EASTERN LOW Cl COAL, LOW Mg LIM, RAW MISSISSIPPI RIVER WATER

Comp~

Ca

Mg

Na

Cl

C02 N03 so3

so4

ComJ2onent

CaC03

CaS03tso4

• H2

0

Inerts

Liguid Phase Concen.tration [I!I!m{w}] Absoriber Feed Absorber Effluent Sludge Waste

2fl\70 2140 1520 1410 1410 1420

91 .98 98 6710 6720 6720

54 63 33

29 '29 29

17 423 35

1480 1550 245

Solid Phase Concentration [percent(w)] w~-;te Absorber Feed Absorber Effluent Sludge .. ,..,.

4.29

93.2

2.54

A-20

4.30

9.3.2

2.55

4~27

93.2

2.50

<*- Mi~'j zr•

5 )

'

l t

l 1

l

Table A-15

STREAM COMPOSITIONS FOR CASE E06. EASTERN L(lif Cl COAL, LOW Mg LIME, ACID-TREATED MISSISSIPPI CTB WATER

Liguid Phase Co~centration [I!I!S~!l]

_£omponent Absorber Feed Ab~f~flu~nt Sludge Waste

Ca 2110 2180 2100

Mg 1600 1600 1600 ,

Na 331 332 331

Cl 7010 7020 7010

C02 65 74 41

N03

172 173 172

so3 55 401 34

2380 2340 so

4 2300

Solid Phase Concentration [per~ce~n~t~(~w~}~l ________ ___ Absorber Feed Absorber Effluent Sludge Waste Component

CaC03

CaS03/S04

• H20

C,aS04. 2H20

Inerts

4.11 4.11 4.15

93.0 93 .o 93.0

0.402 0.402 0.342

2.49 2.50 2.49

A-21

. ' ~~:---·~.......,...-.-·~~~"" ~1;'; J. :·. ~; ,;;e-·:--.-.-•.•• -.- -· •

""

Table A-16

, OR CASE E07. EASTE~.N f,OW Cl COAL, HIGH Mg LIMESTONE, ST!!BAM COMPOSJT!ONS F SIDESTREA!! SOFTENIID AND ACID TRJ!A'I!ID MISSISSIPPI Cll

Component

Ca

Mg

Na

Cl

C02

NO 3

so3

so4

Component

CaC03

CaS03tso

4 • H

20

CaS04 • 2H2o

Inerts

Li uid Phase ConcentratJ.on Absorber Feed Absorber Effluent

1230 1267 1000 3370 3380 3380 333 334 334 6790 6810

6800 267 85 342 174 174 174 286 599 100

7220 7320 6130

Solid Phase Concentration [percent(w)J - .. Absorber .t<eea aosorber Effluent Sludge Waste

7.39 7.33 7.17

85.3 85.3 84.8

5.19 5.80 6.50

1.56 1.56 1.54

A-22

0

\)

,,

G,

Table />.-17

STREAM COMPOSITIONS FOR CASE EIJS. EASTERN LOW Cl COAL, LOW Ms LDIESTONE, RAW MXSS!SSIPPl RIVER WATFR

Component

Ca

f.tg

Na

Cl

C02 N03 so3 so4

Component

CaC03 CaS0

3/S0

4 • li20

CaSO 4

• 2H20

Inerts

Liguid Phase Conce~tion [~~m~w}] ~ Absorber Effluent Sludge Waste Absorber~,g

,3700 3730 3550

aao 380 380

98 98 98

6480 6490 6490

170 75 207

30 30 30 39

134 315 1240

1580 1630

Snlid Phase Concentration [~ercent(w)) -- SLu~&~ ~~=t~ Absorber Feed Absorber Effluent

6.23 6.11 6.12

85.0 85.0

84.6

6.27 6.27 6.77

2.53 2.53

2.51

A-23

Table A-18

STREAM COMPOSITIONS FOR CASE E09. EASTERN LOW Cl COAL. LOW Mg LIMESTONE, ACID-TREATED MISSISSIPPI CTB WATER

CoiJll)onent

Ca

Mg

Na

C1

C02

NO 3

so3

804

Component

ca·co3 CaS Oaf SO

4 • H2 0

CaS04

• 2H2o

Ine:rts

Liguid Phase Concentration [~~m(w)] Absorber Feed Absorber Effluent Sludge Waste

3430 3460 3280 568 568 568 332 332 332

6740 6750 6740 169 76 206

17l 173 173 129 306 40

1700 1760 1370

Solid Phase Concentration {1l_!:l_J:I:ent(w)] Absorber Feed Absorber Effluent Sludge Waste

6.10

84.5

6.91

2.51

A-:4

6.04

84.5

6.91

2.51

5.98

84.1

7.40

2.50

i

',-..~..,/-. ---·-----. ~ ~ ' -~~~,. ~-- w td .. ~ . '-'

Table A-19

STREAM COMPOSITIONS FOR CASE E10. EASTERN LOW Cl COAL, HIGH Mg LIME, RAW MISSISSIP~I RIVER WATER

Component

Ca

Mg Na

Cl

co2

N03 so

3 804

Component

Caco3 CaSOgf SO

4 • n

2 0

CaSO 4

• 2H2

0

Inerts

Liguid Phase Concentration [nEm(w}] Absorber Feed Absorber Effluent Sludge Waste

551 61!> 165

4160 4170 4170

98 98 98

6750 6770 6760

69 92 35

29 29 29

315 959 382

8210 8350 7360

Solid Phase Concentration [ptr~c::..!e:.=n~t_,_(w.::..>wl~.-___ _ Absorber Fe3d Absorl>ef_Effluent Sludge Waste

5.40 5.41 5.41

92.5 92.5 92.6

0.002 0.002 0.001

2.06 2.06 2.04

A-25

Table A-20

STREAM COMPOSTI'IONS FOR C..ASE Ell. EASTERN LOW Cl COAL, HIGH Mg Lllr!E, ACID-TREATED MISSISSIPPI CTB WATER

Component

Ca

Mg

Na

Cl

C02

N03

so3

so4

Com~onent

Caco3

CaS03Jso

4 • H

2o

Caso4

• 2H2

o

Inerts

Liguid Phase Concentration [~~m{w2J Absorber Feed Absorber Efflu~ Sludge Waste

556 619 168

4330 4340 4340 331 332 331

7040 7030 7030

64 83 27 172 173 172 298

197 394 9000 9120 8050

Solid Phase Concentration [percent(w)J ,_ - J<O

sorber ~eea ~osorber Effluent Sludge Waste

5.28 5.29 s .30 92.7

92.6 92.7 0.009

0.009 0.001 2.05 2.06 2.03

A-26

,,

l :j

Table A-21

STREAM COlJPOSITIONS FOR CASE E12. EASTERN HIGH Cl COAL, HIGH Mg LIME, RAW MISSISSIPPI RlVER WATER

Liguid Phase Concentration [~~m~w)]

~m11onent Absorber Feed Absorber Effluent Sludge Waste

4530 4980 506D Ca

4290 4280 4270 ~!g 203 203 203 Na

20.400 20,400 Cl 20,300

43 26 38 61

C02 61 61 33

N03 34 84 503 803

~ 1570 1510 so4

Component

Caco3 3.68 3.69 3 .~:J

CaS03/so4 • n2o 94.2 94.2 94.;;

Inerts 2.08 2.08 2.05

A-27

Table A-22

STREAK COMPOSITIONS FOR CASE E13. .EASTERi'1' HIGH Cl COAL, LO'If Mg LIME, ACID-TREATED MISSISSIPPI CTB WATER

Cc;cpo:aent

Ca:

Mg

Na

CI

to2

NO_ .$

so3

so4

Componen~

Caco3

•"!asos~so4 • n2o

I:nerts

L" "d Absorber Feed 1gn1 Phase Concentration [~Bm{w2J

Absorber Effluent S ludge Waste

9490 9560

9200 1450 1450

99 1450 99

20,400 99 20.400 20,400 54

57 30 40

30 53 30

336 894 24

953 249

.__.. Solid. Phase Concentration [percent(w)) Abstrber Feed Absorber Effluent Sludge Waste

2.43 2.44

2.44 95.00 95,()1

95.0 2.57 2.57

2.54

A-28

I

Table A-23

STREAM COMPOSITIONS FOR CASE El4. EASTERN HIGH Cl COAL, HIGH Mg LIME, ACID-TREATED MISSISSIPPI CTB WATER

fQ!!!PQ.nen t

Ca

big

Na

Cl

co2 N03 803 so4

Component

Caco3

caso3tso

4• n

2o

CaSO 4

• 2JI2 0

Inerts

Liguid Phase Concentration [~~m(w}] Absorber Feed Absorber Effluent Sludge Waste

5030 5100 5010

4390 4390 4390

333 334 333

20,500 20,500 20,500

42 50 30

173 174 174

66 449 31

2060 2140 2080

Solid Phase Conuentration [percent(w} J ~bsorber Feed Absorber Effluent Sludge Waste

3.43 3.44 3.46

94.0 94.0 94.0

0.508 0.509

0.453

2.05 2.05

2.05

A-29

Table A-24

STREAM CO~WOSITIONS FOR CASE E15. EASTERN HIGH Cl COAL, HIGH Mg LIMESTONE, ACID-TREATED MISSISSIPPI CTB WATER

Component

Ca

Mg

Na

Cl C0

2 N0

3 so3 so

4

£\:"!!!!Ponent

CaC03

CaS03/so4

·H2o

Caso4 • 2H2o

Inerts

~ -----~ ..... a .. ~POmlw ____ &--~ Absorber Effluent Sludge Waste

10,600 10,600

578 519

336 336

19,~!00 19,900

174 85

175 115

129 284

1200 1240

Solid Phase Concentration lnA~n~-~ Absorber Feed •·

4.37 4.33

85.8 85.9

7.27

2.55 7.27

2.55

A-30

10,500

578

336

19,800

213

175

39

970

Waste

4.27

85.5

7.65

2.54

.~---~·~--·--·------·~-·-.-----~.:-------. -~ '~t}.~:i,~J\:~~:.;~ij.s:d'~"'( ,· ··~;~

Table A-25

STREAM COMPOSITIONS FOR CASE E16. EASTERN LOW Cl COAL, LOW ~lg LIMESTONE, ACID-TREATED MISSISSIPPI CTB AND WASTEWATERS

Component

Ca

Mg

Na Cl

co2 N0

3 so3 so4

~onent

Caco3 l.., "0':1/804. Il20

Caso4

• 2H2

0

Inerts

Liauid Phase Concentration [ppm(w) 1 Absorber Feed Absorber Effluent. Sludge Wasta

3310 3340 3160

568 569 568

480 481 481

6730 6740 6740

170 76 207

169 169 169

130 308 40

1750 1800 1400

Solid Phase Concentration [percent(w)] Absorber Feed Absorber Effluent Sludge Waste

6.10 6.04

5.98

84.5 84.5

84.1

6.93 6.93

7.44

2.51 2.51

2.50

A.-31

£.Q_mpoi1ent

Ca

Mg

Na

Cl

co3

N03 so

3 so

4

f!2ml:lonent

CaCO 3

CaSO /SO .. H 0 3 4 2 Inerts

t.,ble A-26

SOLUTION COMPOSITIONS FOR l'ASE PE01. SYSl'E.M WITII PRESCRUBBER, EASTERN HIGH Cl COAl, HIGH .M3 LBffi. RAW JIISSISSIPPI RIVER WATER

Pre scrubber Absorber

Sludge Effluent

Absorber Feed Effluent

_futst.!L.

4840 380

440 94 820

7JJ.O 710 710 270

2.3 2.3 2.3 6310

390 390

390 124 126 110 6.2

0.3 0.3 0.3 180

128 580 170 590

2980 3 iii'G 2210

Sol 'd Ab 1 Phase sorber Feed

Sludge Waste 0.96

97.0 .96

2.03 97.0

0.97

91.0 2.03

2.01

A-32

~poneat

Ca

Mg

Na

Cl

co3 N03 so3

804

Component

CaC03

Table A-27

SOLUTION COMPOSITIONS FOR CASE PE02. SYSTEM WITII PRESCRUBBER, EASTERN HIGH Cl COAL, HIGH Mg LIME, ACID-TREATED MISSISSIPPI CTB WATER

Absorber Sludge Effl1l_~nt Waste Pre scrubber

Absorber Feed Effluent

90 480 400 1980 750 750 750 560

80 80 80 460

130 460 460

90 3770

110 110 20 90

20 20 170 30

600 130 2400 3360

110 3240 1380

Solid Phase Composition [percent(w)]

Absorber Absorber

Feed Effluent

Sludge Waste

.96 .96

.98

97.0 97.0

CaS03/SO • H 0 4 2

97.0 2.0

2.0

Inerts 2.0

A-33

Table A-28

STREAM COMPOSITIONS FOR CASE W01. WESTERN COAL, HIGH Mg LIMESTONE, RAW LAKE SAKA.TAWEA WATER

!;'proponent Absorber Feed Li uid Ph c ase oncentration

Absorber Effluent Ca

Sludge Wast.!! 623

Mg 6820

644

Na 6940 492

14,500 Cl 14,800

6810

19,400 14,500 C0

2 252 19,700

19,400 N03

66 293 337

so3 298

581 293 so

4 627

31.400 32,300

258

31,200

Component Absorber Feed

Waste caco3 4.51

4.48 4.31

CaS03/so4

'H2o

7.79 7.79

8.31 Caso4 • 2H

2o

86.5 86.5

86.2 Inerts

1.22 1.23

1.22

A-34

Table A-29

sTREAM COMPOSITIONS FOR CASE W03. WESTERN COAL, HIGH Mg LIMESTONE, RAW MISSISSIPPI RIVER WATER

Liguid Phase Concentration [~~m(w}]

£g_!npon@.i AQ.:'1orber Feed Absorber Ef_fluent Sludge~

Ca 5860 5900 5800

2990 2970 Mg 2970

582 580 Na 580

Cl 18,400 18.500 :1.8,40il

118 co2

91 57 175

N03 175 175

39 81 91

803 1630 so4

1780 1890

· ceu~~u~~~~ ·r-Solid Phuse ~on ft~··---+ Sludge Waste

Component Absorber Feed 4.67

4.70 8.69 4.72

8.64 85.4

CaC03 8.64

85.4 1.2'.1

CaS03/S04 • H20 85.4

1.27 CaS0

4 • 2H

20

1.27 Inerts

A-3S

Table A-30

STREAbl COMPOSITIONS FOR CASE W04. WESTERN COAL, HIGH Mg LIMESTONE, ACID-TREATED MISSISSIPPI CTB WATER

Component

Ca

!Ig

Na

Cl

C02

No3

so3

so4

Component

CaC03

CaS03Jso

4 • H

20

Caso4 • 2H2o

Ine1:ts

Absorber Feed Liquid Ph ase Concentrat·

Absorber Effl 10n [ppm(w)J ,uent Sludge Wasii'

4350 4380

3980 4000

4210

1910 3980 1920

19,600 19,700

1910

122 1.s',600 80

995 152 1000

124 996 133

2640 48 2750

2320

Solid Phase Concentration 1 nernAn+• ... Absorber Feed ... - · -Sludge W~st£

4.05

3.97 4.03

8.32

86.4 8.32

8.40

1.23 86.4

86.4 1.23

1.23

A-36

(l

\1

Table A-31

STREAM COMPOSITIONS FOR CASE WOS. WESTERN COAl., HIGH Mg LIMESTONE, SIDESTREAM S011'TENP.!> MISSISSIPPI C'lll WATER

Liquid Phase Concentration [ppm(<:l)]

£.Q.IIIPO~l!i Absorber Feed Absorbe~ Effluent Sludge Waste

Ca 249 261 198

Mg 3340 3390 3340

Na 53,600 54,300 53,600

Cl 21,400 21,700 21,4V'l

C02 232 96 275

N03 1960 1990 1960

so3 720 756 354

so4 94,000 95,600 94,200

Solid Phase Concentration (percent(w)J Absorber Feed Absorber Effluent Sludge Waste

Component

Caco3 casog~ so 4 • n2 o Caso

4 • 2H20

Inerts

4.00 3.98

3.91

7.47 7.47

8.09

87.3 87.4

86.8

l.i9 1.19

1.19

A-37

Table A-32

STREAM COMPOSITIONS FOR CASE W06. WESTERN COAL, HIGH Mg LIMESTONE, ACID-'I'P.EATED LAKE SAKAJAWEA CTB WATER

Component

Ca

],fg

Na

Cl

C02

N03

so3

so4

Component

CaC03

CaS03 /so4

• H2o

Caso4

• 2H2

0

Inerts

Absorber Feed Li uid Ph ase Concentration

Absorber Effl uent

446 464

8680 8830

22,500 22,900

20,100 20,500

267 89

423 430

192

53,600 840

54,900

Solid Phase Concentration rnAPh~-L Absorber Feed •~

4.11

7.50 4.09

87.2 7.50

1.21 87.2

1.21

A-38

Sludge Waste

354

8680

22,500

20,100

351

423

390

53,700

Waste

3.93

8.18

86.7

1.20

Table A-33

STREAM COMPOSITIONS FOR CASE W07 • WESTERN COAL, HIGH Mg LIMESTONE, SIDESTREAM SOFTENED LAKE SAKAJAWEA CTB WATER

£Qmpone!!i

Ca

~lg

Na

Cl

co2 N03 so

3 so4

Component

CaC03

Caso3tso

4' H

20

Caso4

• 2H20

Inerts

Liquid Phase Concentration [ppm(w)]

Absorber Feed Absorber Ef_fluent .SludgeJVaste

197 211 163

10,100 10,300 10,100

56,500 58,000 56,500

22,500 23,100 22,500

331 64 398

782 802 782

1210 1290 643

125,000 129,000 126,000

Solid Phase Concentration (]ercent(wl ' Absorber Effluent Sludge Waste

~orher r:cea

3.94 3.92

3.81

6.96 6.96

7.94

87.1

87.9 87,9

1.18

1.18 1.18

A-39

Table A-34

STREAM Cm!POSITIONS FOR CASE WOS. WESTERN COAL, LOW Mg LHIE, RAW LAKE SAKAJAWEA lVATER

Comooneztt

Ca

~lg

Na Cl

C02

No3 so3 so

4

~mEEnen_t

C'aco3 caso3Jso

4 • H

2o

Caso4

• 2H2

o

Inerts

Absorber Feed Li uid Pha se Concentration

Absorber Effl uent

672 697

5410 5490

14,600 14,800

19,500 19,800

107 112

295 299

523

25,900 585

26,600

Solid Phase Concentration lnA-ftft-L Absorber Feed h

1.61

7.85 1.61

88.6 7.81

1.92 88.7

1.92

A-40

Sludge Wast.!

531

5410

14,600

19,500

51

295

182

26,100

Waste

1.72

8.41

87.9

1.92

T1>'bh A.-35

'S'f.iB.A,.,'\1 {'..o1tiP'~ITI().l>.~ FOl C..\SE \~J9.. JES'ttmN COAII, LOW Mg LUU.h smESn:E.4ll S~ L\KE SAUl i'~fi'U C'l'U WA'rER

~

Cs

Hg

Na

Cl

co., ... !\03

so3

so~

CO!l!j?Ollent.

CaC03

caso3,aso

4 ~ B

2o

CaSO, • 2B.,.O ... ;;.

Ine.rts

Liqn.id Phue Conoenttntipn [pprn(wU_ ..

E}ls~rber Feed ~\bsorbu Effluent [!Jj!dg!! Wute

n4 208 165

S"'J3{} 8880 8730

SS.:SO:.'I 57.800 56,800

2Z.'ji0tl 23 ,100 22,1(}0

49 54 11

185 800 786

819 913 570

12l.1Ull 123,600

121,500

SoHd Phase Concentration [percentt'l'!. ~ ...... --- ~~""'A"'"~ tl11~t:e

Abs~rber Feed Absorber Efuuent

1.32 1.32

7.:50 7.53

89.3 89.3

1 .. '85 1.85

1..3Z

8,03

ss.s l.,SS

A-41

~

Table A-36

STREAM COMPOSITIONS FOR CASE WlO. WESTERN COAL. LOW Mg LIMESTONE RAW .ltf!SSISSIPPI RIVER WATiR I

C_omponent

Ca

Mg

Na

Cl

C02

N03

so 3

so4

Component

CaC03

CaS03/so

4 • H

2o

Caso4

• 2H2

o

Inerts

Absorber Feed Liguid Phase Concentration

Absorber Effluent

9450 9500 662 665 580

582 18,400

18,500 115

73 175

175 109

118 1240

1340

Solid Phase Concentration tuercent1w Ahsorber Feed ••

3.80 3.78

8.60 8.60

85.5 85.5

2.08 2.08

A-42

9350

662

580

18.400

144

175

36

1020

3.72

8.69

85.5

2.07

~,

'i

I I

! I I

Table A-37

STREAM COMPOSITIONS FOR CASE W11. WESTERN COAL, LOW Mg LIMESTONE, ACID-TREATED MISSIS~IPPI CTB WATER

Conmonent

Ca

Mg

Nn

Cl

C02 N0

3 so3 804

Com~onent

CaC03 CaS0

3/S0

4 • n

2o

CaS04

• 2H20

Inerts

Liguid Phas~ Concentration [~~m~w}] Absorber Feed Absorber Effluent Sludge ll'll_ste

7560 7600 7450

1740 175 1740

1910 1920 1910

19.600 191700 19,600

105 61 131

995 1000 995

104 113 37

~..;::10 1530 1640

Solid Phase Concentration [~ercent(w)] Absorber Feed Absorber Effluent Sludge Waste

3.12 3.10 3.05

8.32 8.32

8.40

86.6 86.6 86.6

2.01 2.01

2.00

A-43

Table A-38

STREAM COMPOSITIONS FOR CASE W12. WESTERN COAL, LOW Mg LIMESTONE SIDESTRWf SOFTENED MISSISSIPPI CrB WATER '

Compon(lnt

Ca

Ms Na

Cl

C02 N0

3 so

3 so

4

C..-mponent

caro3 CaSO/so4 • tr2o

CaS04

• 2H20

Inerts

-""'""-·-----'''"'"..,....._....,... ____ ,~,.....___ __ ,~·.~·-----'"~·

Liquid Phase Concentr~t· [ 1on ~pm(w)J Absorber Feed Absorber Effluent Sludge Wast;'

259 269 211 1150 1170 1150

52,900 53,400 52,900 21,100 21,400 21,100

192 89 223 1940 1960 1940

508 533 265 84,700 85,800 84,800

Solid Phase Concentration [percent(w)] A. bsorber Feed Absorber Effluent Sludge Waste

3.04 3.03 2.98 7.60 1.60 8.00

87.4 87.5 87.1 1.91 1.92 1.91

A-44

l I I

I !

l

Table A:-39

sTREAM COMPOSITIONS FOR CASE W13. WESTERN COAL, LOW Mg LIMESTONE, RAW LAKE SAKAI AWEA WATER

CgmEonent

Ca

Mg

Na

Cl

C02 N0

3 so3 ~04

Com~onent

Caco3 Caso

3;so4• n2o

Caso4 • 2H20

Inerts

Liquid Phase Concentration [~~m~w)] Absorber Feed

Absorber Efflueni Sludge Waste

727 746 572

4530 4610

4540

14,300 14,500

14,300

19,100 19,400

19,100

54 284

212 294

290

289 179 468

432

22,800 23,500

22,600

Solid Phase Concentration Lperce_~n.!o.t~(vr!!-.!)~1-----Absorber Feed Absorber Effluent Sludge Waste

3.36

3 .53 3.51

7.82 7.82

8.21

86.7 86.7

86.5

1.97 1.96

1.97

A-45 0

Table A-40

STREAM COMPOSITIONS FOR CASE W14. WESTERN COAL, LOW Mg LIMESTONE ACID-TREATIIENT LAKE SAKAJAWEA CTB WATER '

Component

Ca

Mg

Na

Cl

co2 N03 soj so

4

Component

Caco3 CaS0/S0

4 • n

2o

CaS04

• 2H2o

Inerts

Liguid Phase Concentration [~~m{w)] Absorber Feed Absorber Effluent Slud W -

ge asli

494 510 387

6400 6520 6400 22,200 22,600 22,200 19,800 20,200 19,800

259 16 344 417 425 418 700 747 307

44,600 45,800 44,600

Solid Phase Concentration [percent(_w)] Absorber ¥eed Absorber Effluent Sludge Waste

3.11 3.16 2.99 7.42 7.42 8.08

87.5 87.5 87.0 1.94 1.94 1.93

A-46

I t l

l l f ' ! l

1 [ l

Table A-41

STREAM COMPOSITXONS FOR CASE W15. WESTERN COAL, LOW Mg LIMESTONE, SilJESTREAM SOFTENED LAKE SAKAJAWEA CTB WATER

g,ompo_nent

Ca

lrlg

Na

Cl

C02 N03 so

3 804

Component

CaC03 CaS0

3tso4 • H20

Caso4

• 2B20

Inerts

Liguid Phase ConcentratiQn Absorber Feed Absorber Effluent

209 221 172

7820 8000 7820

55,800 57,000 55,800

22,200 22,700 22,200

296 69 354

772 789 772

1040 1100 547

116,000 119,000 116,100

Solid Phase Concentration [percent(w Absorber Feed Absorber Effluent Sludge Waste

3.01

7.00

88.1

1.89 •

A-47

2.99

7.00

88.1

1.89

2.89

7.85

87.4

1.89

Table A-42

STREA.M COMPOSITIONS FOR CASE W16. WESTERN COAL, HIGH Mg LIME RAW LAKE SAKA.TAWEA WATER '

Component

Ca

.Mg

Na

Cl

co2

NO 3

so3

so4

Comp~nt

Caco3

CaS0/S04

• H2o

CaS04

• 2B2

0

Inerts

Liguid Phase Concentration [~~m{w~J Absorber Feed Absorber Effluent

Sludge Wa~

598 621 467

7590 7700 1590 14,700 14,900 14,700 19,700 20,000 19,700

146 154 71

291 302 297

151 814 256 34,000 34.,800 34,400

Solid Phase Concen~ration (perce~t(w}] Absorber .t•eea Absorber Effluent Sludge Waste

2.46 2.46 2.61 1.63 1.59 8.48

88.3 88.4 87.3 1.57 1.58 1.51

A-48

Table A-43

STREAM COMPOSITIONS FOR CASE W17. WESTERN COAL, LOW Mg LIMESTONE, SIDESTRF..AM SOFTENED LAKE SAKAJAWEA

Component

Ca

Mg

Na

Cl

C02 N03 so3

804

Component

CaC03 Caso

3;so

4 • H20

CaS04

• 2H20

Inerts

Liguid Phase Concentration [EEm{w~] Absorber Feed Absorber Effluent Sludge Waste

256 266 211

1150 1170 1150

52,900 53,500 52,900

21,100 21,400 21,100

193 74 223

1940 1960 1940

499 528 265

84,700 85,900 84,800

Solid Phase Concentration [percent(w Sludge Waste Absorber Feed Absorber Effluent

3.05 3.03

1.59 7.59

87.5 87.5

1.92 1.92

2.98

8.00

87.1

1.91

Table A-44

STREAM COMPOSITIONS FOR CASE W18. WESTERN COAL, LOW Mg LIMESTONE, SIDES~! SOFTENED LAKE SAKAJAWEA CTB, USING TANK SIZE FOR CASE WlO

AND L/G FOR CASE WlO '

Component

Ca

Mg

Na

Cl

C02 NO

3 eo

3 so

4

Component

CaC03

CaS03/so4

• n2o

CaS04 • 2H2

o

Inerts

Absorber Feed. Liguid Phase Concentration [~~m{w)]

Absorber Effluent _ Sludge Waste -----

363 3741 280 918 922 918

39,000 39,200 39,000 15,400 15,400 15,400

214 162 260 1430 1440 1430 452 465 223

63,300 63,700 63,300

Solid Phase Concentration [percent{w) ] ____ _ Absorber Feed Absorber Effluen-t Sludge Waste

3.92 3 .• 90 3.82 7.76 7.76 8.13

86.4 86.4 86.1 1.95 1.95 1.95

A-50

'·'"-•

·,

Table A-45

STREAM COMPOSITIONS FOR CASE W19. WESTERN COAL, LOW Mg LIMESTONE, SJDESTREAM SOFTENER LAKE SAJU.JAWEA CTB AND WASTE WATERS

Liguid Phase Concentration [~~m~w~]

£_omponent Absorber Feed Absorber Effluent Sludge Waste

Ca 212 224 174

.r.lg 7660 7830 7660

Na 55,300 56,500 55,300

Cl 22,100 22,600 22,100

co2

295 67 352

N03

751 768 751

so3 1030 1090 538

so4 114.200 117,200 114,600

Component Absorber Feed .,.___ ------ ~...-....-- ......... Sludge Waste

CaC03

3.02 3.00 2.90

CaS03

/S04 • H20 7.02 7.02 7.86

Caso4

• zn2o 88.1 88.1 87.3

Inerts 1.89 1.89 1.89