ENGINEERING 536

MASS TRANSFER OPERATIONSFALL 1997

TEAM MEMBERS:

Dr. Jim Henry, P.E.

Sean Cunningham

Mark Koss, P.E.

Sandy Koss

Tara Ostrander, E.I.

Nittaya Pittayataree

Beth Ruta

Nitipol Suksathaporn

IntroductionIntroduction

Study of mass transfer operations using the distillation column

Approach to the study of the distillation column included

- Literature search

- Operating the column- Computer modeling

+ Ponchon-Savarit

+ PROII

This report will cover

- column calibrations

- experimental results- computer modeling

DISTILLATION COLUMNDISTILLATION COLUMN

1

2

3

4

5

6

7

8

9

10

11

12Reboiler

TI

TI

TI

TI

TI

TI

TI

TI

TI

TI

TI

TI

Product Cooler

Electromagnetic Reflux Control

Feed Tank(Product Tank)

Cooling Water SupplyCondenser

Reboiler Pump

Distillate Pump

Feed Pump

LI

Cooling Water Return

TI

TI LI

PI

TI

TITI

COLUMN COLUMN DESCRIPTIONSDESCRIPTIONS

Condenser Reflux valve Trays RTDs Pumps - Feed pump

- Reboiler pump - Distillate pump - Auxiliary pump Reboiler Level Control - Condenser

- Reboiler FEED LOCATIONS

Column Column CalibrationsCalibrations

Heat loss studyHeat loss study RTD calibrationRTD calibration Pump and cooling Pump and cooling

water calibrationwater calibration

Heat Loss StudyHeat Loss Study

Previous heat loss calculations seemed excessive

Parameters of the study are - selected reboiler amperage

- 100% reflux - no condensate produced Column losses are equal to the

energy input into the column Minimum amperage to

maintain the temperature on tray 1 is between 6 and 7 amps

Estimated column heat loss is between 1230 Watts and 1435 Watts

Reboiler Amps = 7

65.0

65.2

65.4

65.6

65.8

66.0

70 72 74 76 78 80

Time

Tem

pera

ture

(C)

Reboiler Amps = 6

63.0

63.5

64.0

64.5

65.0

65.5

78 79 80 81 82 83 84 85

Time

Tem

pera

ture

(C)

Temperature of tray 1 at 7 amps

Temperature of tray 1 at 6 amps

RTD CalibrationRTD Calibration

Temperature is calculated by multiplying the voltage by the scale and then adding the offset

Steps to calibrate RTDs

- fill reboiler with pure

methanol- allow steady state- set offset to zero- set scale to one- collect voltage readings- repeat with water

Voltage is taken at 100oC (pure water) and 64.5oC (pure methanol)

Straight line was fit between the two points

Slope of the line is the scale

y intercept is the offset

Pump and Cooling Pump and Cooling Water CalibrationWater Calibration

Pump and cooling water calibrations seem to be reliable

Pump calibration - by measuring the outflow of the pump for a timed period Cooling water calibration - by measuring the flow at the cooling water system

drain at various valve openings

Pump Calibration Pump Calibration CurveCurve

Feed Pump Calibration Curve

F = -2.3996M2 + 98.326M - 81.102

R2 = 0.9942

0

100

200

300

400

500

600

0 2 4 6 8 10

Pump Setting

Flo

wra

te (

ml/

min

)

Pump : 7017-21 Pattern No. 3.358.609

Conclusions Conclusions (calibrations)(calibrations)

Pump and cooling water calibrations seem to be reliable

Calibrations performed on the glass RTDs were unsuccessful ( repeated several times)

Replacement of the glass RTDs with stainless steel improved the calibrations

- three RTDs do not give

reliable temperature indication

Recommendation Recommendation (calibrations)(calibrations)

Perform calibrations- after a period of inactivity

- whenever equipment is changed

or modified

Reduce time spent on calibrations

- Calibrate the RTDs individually

with ice and boiling water

- UTC engineering/maintenance

personnel should complete

calibrations

Experimental Experimental ResultsResults

Energy and mass Energy and mass balancebalance

Capacity testCapacity test Feed location impactFeed location impact Reflux ratio impactReflux ratio impact

Energy and Mass Energy and Mass BalanceBalance

Excel spreadsheet was developed to facilitate mass and energy calculations

Calculations showed an increase in water and a decrease in methanol

Column had not reached steady-state conditionsFlowrate (gms/min)

Mixture Methanol WaterFeed 321 315 12Bottoms 205 168 12Distillate 116 147 0

DISTILLATION COLUMN EXPERIMENT (10/15/97)MASS BALANCE

InputsReflux Ratio= 1.78 Tank Temp= 30.00Distillate: Reboiler: Feed:Pump Setting: 1.20 Pump Setting: 2.10 Pump Setting: 5.00RTD Reading: 64.57 RTD Reading: 75.67 %MeOH(Molar): 0.50Density: 0.79 Density: 0.94 Density 0.92

Distillate Reboiler: Feed Pump:%MeOH (Molar) 99.55 %MeOH (Molar) 39.15 %MeOH (Molar) 50.00Frac (Wt) 1.00 Frac (Wt) 0.53 Frac (Wt) 0.64Flow Rate (ml/min) 15.05 Flow Rate (ml/min) 336.57 Flow Rate (ml/min) 350.54Mass flow rate (g/min) 11.91 Mass flow rate (g/min) 315.13 Mass flow rate (g/min) 320.95Mass MeOH (g/min) 11.88 Mass MeOH (g/min) 168.14 Mass MeOH (g/min) 205.41Mass H2O(g/min) 0.03 Mass H2O(g/min) 147.00 Mass H2O(g/min) 115.54

water balance 31.48 gm/minMeOH balance -25.39 gm/min

ENERGY BALANCEENERGY IN AT REBOILERReboiler (Amps) 15.43Energy In(watts) 3394.60

CONDENSER RE BOILERCool Water Temp-in(°C) 19.74 Delta T 45.67Cool Water Temp-out (°C) 20.63Cool Water Flow (ml/min) 9000.00Water Cp (KJ/KgoK) 4.18 MeOH Cp 2.55Energy Out Cond(watts) 557.94 Qcond Reboiler Energy 794.47 QrLatent Heat(watts) 615.07 Qlatent

Capacity TestCapacity Test

Performed to determine the maximum capacity of the column to produce distillate

Parameters for the test are -- reboiler was filled with a mixture of methanol and water

- reboiler current set at 20 amps (maximum) - reflux set 95 % Methanol distillate

- steady-state conditions were established

- Set various feed pump settings- Set various feed pump settings

- Set various reflux ratios- Set various reflux ratios

-- Determine distillate and reboiler Determine distillate and reboiler

flowrateflowrate

- Column did not produce distillate at- Column did not produce distillate at

pump setting of 7 pump setting of 7

Feed Pump Feed Flowrate Percent Distillate ReboilerSetting (ml/min) Reflux Flowrate Flowrate

(ml/min) (ml/min)3 192 76 25 1805 350 75 32 3326 420 76 21 3907 490 - - -

Capacity Test Capacity Test ComparisonComparison

Feed Location Feed Location ImpactImpact

ParameterParameter

- Pump setting of 3- Pump setting of 3

- Reboiler amps at 20- Reboiler amps at 20

- 70% reflux- 70% reflux ResultsResults

- Tray 4 - 89% - Tray 4 - 89%

- Tray 5 - 93% - Tray 5 - 93%

- Tray 6 - 97%- Tray 6 - 97%

Reflux ImpactReflux Impact

Parameter Parameter

- Feed location tray 4- Feed location tray 4

- Pump setting of 3- Pump setting of 3

- Reboiler amps at 20- Reboiler amps at 20 ResultsResults

- Reflux 50% - 78% at 43- Reflux 50% - 78% at 43

ml/minml/min

- Reflux 70% - 89% at 23- Reflux 70% - 89% at 23

ml/min ml/min

Conclusions Conclusions (Experimental (Experimental Results)Results)

Design and execution of experiments

- useful way of gaining experience

- found column performed in a predictable manner - increased the students’ level of confidence

energy and mass balance calculations demonstrated

- purity of the product was surpassed with a reduction in the quantity of

the product

Based on observations from the capacity test

- maximum output of the reboiler heaters

could not maintain boiling conditions above a feedwater flowrate of

420ml/min

Based on observations from the feed location experiment

- optimum feed tray location - tray 6

- due to the higher methanol composition

in the distillate

Based on observations from the percent reflux experiment

- between 50- and 70-percent reflux

* two times the distillate flowrate* 1.6 times the amount of methanol

Recommendation Recommendation (Experimental (Experimental Results)Results)

Review the RTD calibrations to account for the discrepancies in the mass balance

Perform additional feed location impact experiments

Take physical measurement of the distillate flow (not pump flowrates)

Computer ModelingComputer Modeling

Pro IIPro II Ponchon-SavaritPonchon-Savarit

PRO IIPRO II

Steady-state heat and material balance simulator

Simulates any number of components, streams, units, and recycle loops

Requirement- Feed stream

- composition

- temperature- flowrate

- pressure - Tray efficiency

Specify two of the following parameters

- Any specific tray temperature

- Heat duty of the condenser- Temperature of the distillate- Composition of the distillate- Flowrate of the distillate- Reflux ratio- Temperature of the bottoms- Composition of the bottoms- Flowrate of the bottoms- Heat duty of the reboiler

PROII will calculate remaining

parameters

PRO II - Optimizing Distillation ColumnPRO II - Optimizing Distillation ColumnStream Name 1 2 3Stream DescriptionPhase Liquid Liquid LiquidTemperature C 25 65.53888 99.82745Pressure ATM 0.994603 0.994603 0.994603Flowrate G-MOL/MIN 12.00385 6.488153 5.515693Composition MEOH 0.5 0.925 6.91E-05 H2O 0.5 0.075 0.999931Total StreamRate G-MOL/MIN 12.00385 6.488153 5.515693

G/MIN 300.4381 201.0676 99.37048Std. Liq. Rate CM3/MIN 350 250.4837 99.51627Temperature C 25 65.53888 99.82745Pressure ATM 0.994603 0.994603 0.994603Molecular Weight 25.0285 30.98997 18.01597Enthalpy M*J/MIN 0.023033 0.034942 0.041537

J/G 76.66611 173.7827 417.998Mole Fraction Liquid 1 1 1Reduced Temperature 0.514083 0.647976 0.576169Reduced Pressure 0.006671 0.011017 0.004556Acentric Factor 0.45835 0.552148 0.348015UOP K-Value 9.962891 10.55651 8.76176Std. Liquid Density G/CM3 0.858395 0.802717 0.998535 Sp. Gravity 0.859242 0.803509 0.999521 API Gravity 33.18008 44.60248 10.06786VaporRate G-MOL/MIN n/a n/a n/a

G/MIN n/a n/a n/aCM3/MIN n/a n/a n/a

Molecular Weight n/a n/a n/aZ (from Density) n/a n/a n/aEnthalpy J/G n/a n/a n/aCP J/G-C n/a n/a n/aDensity G/CM3 n/a n/a n/aTh. Conductivity KCAL/HR-M-Cn/a n/a n/aViscosity CP n/a n/a n/aLiquidRate G-MOL/MIN 12.00385 6.488153 5.515693

G/MIN 300.4381 201.0676 99.37048CM3/MIN 352.8752 265.9261 103.6818

Molecular Weight 25.0285 30.98997 18.01597Z (from Density) 0.001195 0.001467 0.000611Enthalpy J/G 76.66611 173.7827 417.998CP J/G-C 3.115483 2.895487 4.21597Density G/CM3 0.851401 0.756103 0.958418Surface Tension DYNE/CM n/a n/a n/a

Ponchon-Savarit Ponchon-Savarit TheoryTheory

Graphical Method Graphical Method • Plots Enthalpy Against Plots Enthalpy Against

CompositionComposition Provides Exact SolutionsProvides Exact Solutions Incorporates Effects of Incorporates Effects of

Heat Losses Heat Losses • Inputs of Individual Tray Inputs of Individual Tray

LossesLosses• Inherent Material and Inherent Material and

Energy BalancesEnergy Balances

Ponchon-Savarit Ponchon-Savarit Diagram on ExcelDiagram on Excel

Inputs Needed (highlighted in yellow)• Distillate and Bottoms

Compositions Desired• Distillate and Bottoms

Flowrates• Heat Losses on Each Tray

Works For Up To 13 Stages Tested For Bottoms

Concentrations down to 0.01% and Distillate Concentrations up to 97.9%

ConclusionConclusion(Computer (Computer Modeling)Modeling)

PROII- user friendly

- fast- not accurate- limited by constraints

Ponchon-Savarit- heat loss on individual

trays must be known- only valid for methanol-

water mixtures

RecommendationsRecommendations(Computer (Computer Modeling)Modeling)

Modify the PROII model to more closely approximate the UTC distillation column

Conduct training for students on the use of modeling tools

Determine the heat losses on the individual trays (Ponchon-Savarit)

ConclusionsConclusions(Final)(Final)

Technical - Study of mass transfer operations using the distillation column - Approach to the study of the distillation column included

- Literature search

- Operating the column

- Computer modeling

* Ponchon-Savarit

* PROII

- Each student had the opportunity to participate in

- operation

- calibration- repair

- Provided a better understanding

through - research

- classroom discussion- design of experiments

Accomplishments- Ponchon-Savarit spreadsheet

developed- PROII model developed - Energy and mass balance spreadsheet developed- Determination of the column capacity- Determination of heat lost to the environment- Performed feed input experiments

RecommendationsRecommendations(Final)(Final)

Allow for more continuous laboratory time - Modify class schedule

- Maintain the distillation column components - Establish course objectives,

perform calibrations, research literature, and familiarize

students with modeling programs

within the first month of the semester