K. Thermal Desalination

8/10/2019 K. Thermal Desalination

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Thermal Desalination

Antiscalant

Indonesia Customer Seminar

June 13 & 14 2012

Jakarta Indonesia


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Overview

Scaling & Its Impact

Type of Scale in Thermal Desalination

Factors Influences Scale formation

Scale Inhibitor Technology Overview

PC-2040T Features

Performance

Comparison with other technology

Advantages & Benefit


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Why Scale Occur in Thermal Desalination?

Condition in thermal desalination generate supersaturatedcondition for some minerals salt in sea water

Factors:

Increasing of temperature

Evaporative concentration

Release of CO2from the brine which induces further shift ofbicarbonate ion to the carbonate to the hydroxide ion through theincrease in pH

4HCO3

2-+ Ca2+ + Mg2+CaCO3(s)

+ Mg(OH)2(s)

+ 3CO2 (g)

+ H2O


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Scale Formation in MSF

LP steam

MP steam

Seawater

Seawater

Distilled water

Brine discharge

1-deaerator2-brine heater3-heat recovery4-heat rejection5-vacuum6-brine recirculation pump

Condensate

1

2

3

4

5

6

~30C

Hard scale (CaSO4) and alkaline scale (CaCO3 and MgOH2) in brine

heater which has highest temperature

Calcium carbonate scale and sludge in flash chamber and demister


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Mainly alkaline scale (CaCO3) on tube surfaces where saturation index is

the highest .

Scale Formation in MED


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Effects of Scaling in the Brine Heater

Decreased brine temperature at a constant steampressure

Increased steam pressure to maintain top brinetemperature

Reduced flow rates for constant top temperature

Loss of production if no compensation has beenmade for 1 and 3


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Effects of Scaling in the Heat Recovery Section

Lower temperature rise through the section and henceincreased steam demand in the brine heater to maintainproduction levels


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Effects of Scaling in the Demisters

Physical blocking of the mesh resulting in an increasein vapour pressure drop across the demister. Thisdecreases the steam temperature in the recoverystage, reducing the heat transfer and so reducing theexit temperature of the brine and eventually reducing

the inlet temperature to the brine heater.


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Overall Effect of Scaling

Increased operational costCost of cleaning

Decreased distillate production

Decreased system reliability


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Effect of Scale on MSF Heat Consumption

Source: Effect of Scaling on Design and Operation of Thermal Seawater Desalination Plant, Dr. Rainer Greggarath, SECRC COMO GmbH


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Factors Influencing Scale

Water temperatureAlkalinity

Thermally dissolved solids Type of dissolved products

Presence of nucleation particles Silt from intake water

Flow and velocity

TimeAlkaline scales (CaCO3, Mg(OH)2) will form more quickly than

CaSO4(Anhydride). CaSO4x H2O (hemi-hydrate) will form veryquickly.


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Effect of Temperature on Scaling

80C 90C 120C

CaCO3 Mg(OH)2

CaCO3

CaSO4

Mg(OH)2CaCO3

Increased hardness, more difficult to remove


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Deposit composition in sea water evaporator

010

20

30

40

50

6070

80

90

100

60 66 71 77 82 88 93 99 104

Evaporator water temperature, C

Compositiono

fscale

CaSO4

CaCO3

Mg(OH)2

Nominal temperaturedifference - 27 C

Concentration factor = 2

Scale Type vs Temperature


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Concentrationfactor

Temperature (C)

0 50 100 150 200

1

2

3

4

5

CaSO4Scale Formation in MSF Operation

Data from:Mulford, Scale control in seawater evaporators

TDS 35


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Scaling Tendency in MSF

Source: Fouling Phenomena in MSF Distiller, M, Abdul0Kareem Al-Sofi


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Effect of Velocity - MSF (CaSO4)


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Effect of Flow - MED

In the tubes, the hot vapors arecontinuously passing uniformly atthe same mass and heat flow

But if the on the outside tubes, ifsea water flow has locallyreduced , supersaturation ofsalts does occur

- evaporation of water

- localized continued heating

- removal of carbon dioxide)

Source: Effect of Scaling on Design and Operation of Thermal Seawater Desalination Plant, Dr. Rainer Greggarath, SECRC COMO GmbH


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Effect of FlowMED (No of Tubes Row)


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Scaling Tendency MSF vs MED

Parameter MSF MED

Operating Temperature 90120 0C


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Scale Control in Thermal Desalination

CaCO3scale control

Mg(OH)2 scale control

CaSO4scale control

Dispersion capabilities


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Inhibition of crystal growth

Crystal modification

Crystal growth inhibition

Scale dispersion

Inhibit adherence

Scale Inhibitor Activity

Modesofdefense

Need Inhibitor that Work in All Fronts

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Antiscalant Technology Development

PolyphosphatePhosphonate/Polyacrylate

PolymaleicAcid

ModifiedPolymaleic

Acid

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Antiscalant Performance Comparison

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Chemistry T

ToleranceCaCO3

(Deposition)

CaCO3(Growth)

Disper

sancy

Mg(OH)2 CaSO4

Phosphonate Medium Good Mediocre Poor Poor Poor

Polyacrylate Medium Good Poor Good Fair Poor

PMA

Homopolymer

High Poor Good Mediocre Fair Good

PMA

Copolymer

High Poor Good Good Poor Mediocre

PMA

Terpolymer

High Poor Poor Good Good Poor

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Antiscalant: The Needs

Effective scale & deposition control for both soft scale(CaCO3& Mg(OH)2) and hard scale (CaSO4)

Good dispersancy

High temperature and calcium tolerance

Easy to measure/detect On line measurement & control capability

Cost-effective

Environmental friendly

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PolyphosphatePhosphonate

/ PolyacrylatePolymaleic

Acid

ModifiedPolymaleic

Acid

NovelAntiscalant

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Antiscalant Technology Development


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PC-2040T: The Features

PC-2040T is antiscalant program for the control of softscale (calcium carbonate and magnesium hydroxide) andhard scale (calcium sulfate) in all types of sea waterdistillation plants

It is specifically formulated for use in high Top BrineTemperature plants where the predominant scale potentialis from calcium sulfate

PC-2040T is utilizing TRASAR technology for easydetection, monitoring and control (future)

NSF Approved

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PC-2040T: The Chemistry

Blend of Nalco Patented:Phosphino Carboxylic Acid

- Stable, reverse proof chemistry

- Excellent CaCO3and CaSO4and deposition control

- Good Mg(OH)2scale control

- Environmental friendly

High Stress Polymer (HSP)

- Terpolymer PAA

- High stress tolerance dispersant for silt, iron, phosphate; etc

TRASAR technology

- Tracer material for easy detection & monitoring

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PC-2040T: Performance

Laboratory Testing

SWCC Plant Trial

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PC-2040T : Lab Testing CaSO4Inhibition

0

70

%inhibition

PC-2040Competitor A

0.5 ppm

PC-2040 more effective than competitor A in CaSO4inhibition

Especially at lower dose

no effect


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Effect PC-2040T on the Formation of CaSO4

Dramatic decrease in crystal number(>100000 vs. 2 in treated sample)

Decrease in crystal size and shape

CaSO4crystal

CaSO4crystal grownPC-2040T

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SWCC

The Saline Water Conversion Corporation (SWCC) ofSaudi Arabia is one of the most internationally recognizedauthority in the industry for evaluating thermal desalinationantiscalant

The Research & Development Center (RDC) in Al-Jubailhas been intensively involved in the evaluation ofcommercial scale inhibitor of most of recognized watertreatment companies in the world


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PC-2040T :SWCC Plant Evaluation

Phase #1TBT : 110 0C

Dosage: 2 ppm

Phase #2

TBT : 110 0C

Dosage: 1 ppm

Phase #3

TBT : 119 0C

Dosage: 0.8 ppm

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SWCC Plant Evaluation Certification

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PC-2040T Dosage Guide Line (MSF)

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PC-2040T Additional Dosage: Turbidity

0

0,2

0,4

0,6

0,8

1

0 1 2 3 4 5 6 7 8 9 10

Turbidity (NTU)

Doseincrea

se(ppm)

0

0,2

0,4

0,6

0,8

1

0 1 2 3 4 5 6 7 8 9 10

Turbidity (NTU)

Doseincrea

se(ppm)

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Antiscalant Dosage & Control

It is necessary to follow very closely the injectionof the chemical by analysis or by feed flow ratecontrol

Just few hours of under-dosage are enough to

produce scale in the brine heater with resultantloss of production

Technology to measure & control antiscalantresidual in real time basis is not available

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PC-2040T: What is TRASAR?

Patented Technology from Nalco

Use widely in boiler and cooling water system

A specifically chosen ingredient (a tracer) is blended intoNalco product at precise concentration

Once the product is fed, the tracer is optically excited andeasily detected in system water

The signal generated by this process is used to monitor

and control chemical addition on a real time basis

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PC-2040T: How Trasar Work?


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PC-2040T: 3DT Automation (Future.)

PC-2040T


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Summary PC-2040T Performance

Effective scale inhibitor & deposition control ofCaCO3, Mg(OH)2and CaSO4at vary operatingcondition

Broad temperature range

Broad range of concentration factors

Outperform antiscalant technology available in themarket

Capability for having on-line measurement, realtime & control (by Trasar)

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PC-2040T: Advantages

Effective scale & deposition control for all type ofscales up to maximum operating condition ofthermal desalination

Easy to monitor & control

NSF approved

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PC-2040T: Benefits

Cleaner heat transfer surfaceLower steam consumption

Lower cleaning frequency

Higher plant efficiency

Higher plant reliability

Comply with SHE


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Thank You !

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K. Thermal Desalination

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