Redesign Analysis of a Redesign Analysis of a Distillation ColumnDistillation Column

Presented By: Michael HoepfnerPresented By: Michael Hoepfner

University of Utah 2006University of Utah 2006

IntroductionIntroduction

Why care about redesign?Why care about redesign?

OutlineOutline

ObjectiveObjective TheoryTheory ExperimentExperiment ResultsResults Aspen AnalysisAspen Analysis Recommendations Recommendations Conclusion / Summary Conclusion / Summary

ObjectiveObjective

ScopeScope Isopropyl Alcohol (IPA) and Water to Ethanol Isopropyl Alcohol (IPA) and Water to Ethanol

(EtOH) and Water(EtOH) and Water PurposePurpose

Is the switch possible?Is the switch possible? What are the limitations?What are the limitations?

OutlineOutline

ObjectiveObjective

TheoryTheory ExperimentExperiment ResultsResults Aspen AnalysisAspen Analysis Recommendations Recommendations Conclusion / Summary Conclusion / Summary

TheoryTheory

DistillationDistillation Is among the most common of separationsIs among the most common of separations Separates compounds based on volatilitySeparates compounds based on volatility Utilizes multiple equilibrium separationsUtilizes multiple equilibrium separations

Theory (cont.)Theory (cont.)

175

180

185

190

195

200

205

210

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Mole Fraction IPA

Tem

erat

ure

(ºF

)

Bubble Line

Dew Line

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.65

0.7

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7Liquid Fraction IPA

Va

po

r r

Fra

cti

on

IP

A

Equilibrium Line

45 Degree Line

T-x-y Diagram x-y Diagram

Source: Perry’s Chemical Engineering Handbook, 7th Ed.

Theory (cont.)Theory (cont.)

McCabe-ThieleMcCabe-Thiele Simple and useful Simple and useful

tool for defining a tool for defining a distillation columndistillation column

Three lines can Three lines can characterize the characterize the conditionsconditions

Source: Seader, 2006

Theory (cont.)Theory (cont.)

Source: Seader, 2006

Theory (cont.)Theory (cont.)

EfficiencyEfficiency Liquid samples, therefore, liquid efficiencyLiquid samples, therefore, liquid efficiency

nini

niniML xx

xxE

,1,

,1,

*

Source: King, 1971

Theory (cont.)Theory (cont.)

Refractive Index (RI) Refractive Index (RI) was used to was used to measure the measure the concentrationconcentration

1.33

1.335

1.34

1.345

1.35

1.355

1.36

1.365

1.37

1.375

1.38

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

Mole Percent IPA

Re

fra

cti

ve

In

de

x

Source: CRC Handbook of Chemistry and Physics, 64CRC Handbook of Chemistry and Physics, 64thth Edition Edition

OutlineOutline

ObjectiveObjective TheoryTheory

ExperimentExperiment ResultsResults Aspen AnalysisAspen Analysis Recommendations Recommendations Conclusion / Summary Conclusion / Summary

ExperimentExperiment

ApparatusApparatus 12 Trays with 3 12 Trays with 3

inch bubble inch bubble capscaps

Total CondenserTotal Condenser Partial ReboilerPartial Reboiler Thermal couple Thermal couple

at every trayat every tray

Source: Ong, 1952

Experiment (cont.)Experiment (cont.)

Operate at total refluxOperate at total reflux Collect samples for efficiency determinationCollect samples for efficiency determination

Operate at 2 times the minimum refluxOperate at 2 times the minimum reflux Collect samples for efficiency determinationCollect samples for efficiency determination

Model results in Aspen for ethanol and Model results in Aspen for ethanol and waterwater

OutlineOutline

ObjectiveObjective TheoryTheory ExperimentExperiment

ResultsResults Aspen AnalysisAspen Analysis Recommendations Recommendations Conclusion / Summary Conclusion / Summary

ResultsResults

Obtained samples on three separate occasionsObtained samples on three separate occasions Samples are numbered by the date collectedSamples are numbered by the date collected

10/30/200610/30/2006• First run of total refluxFirst run of total reflux

11/01/200611/01/2006• Second run of total refluxSecond run of total reflux

11/06/200611/06/2006• Only run of partial refluxOnly run of partial reflux

Results (cont.)Results (cont.)Concentration of SamplesConcentration of Samples

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

0 1 2 3 4 5 6 7 8 9 10 11 12

Tray Number

Mo

le P

erc

en

t IP

A

Total Reflux 10/30/2006

Total Reflux 11/01/2006

Partial Reflux 11/06/2006

Results (cont.)Results (cont.)

EfficiencyEfficiency Two Two

reasonably reasonably reliable data reliable data setssets

All error is at a All error is at a 95% 95% confidence confidence intervalinterval

 Total Reflux10/30/2006

Partial Reflux 11/06/2006

Tray ML Error ML ML Fixed Error

Distillate  -  -  -  -  -

2 15.7 6.5 109.8 0 -

3 20.2 4.1 94.9 94.9 156.3

4 32.4 3.1 480.3 0 -

5 18.6 2.5 -93.2 0 -

6 27.0 2.0 -7.4 0 -

7 97.8 0* 4885.2 0 -

8 91.5 0* -84.2 0 -

9 0 - 82.5 82.5 125.9

10 0 - 492.5 0 -

11 0 - 132.6 0 -

12 0 - 20.2 20.2 26.0

Bottoms 0 - -113.8 0 -

Average 25.3 3.7   18.0 102.8

OutlineOutline

ObjectiveObjective TheoryTheory ExperimentExperiment ResultsResults

Aspen AnalysisAspen Analysis Recommendations Recommendations Conclusion / Summary Conclusion / Summary

Aspen AnalysisAspen Analysis

AspenAspen Used average stage Used average stage

efficiency for every efficiency for every stagestage

It is possible to do It is possible to do separationseparation

Limited by total Limited by total condenser loadcondenser load

• Max condenser load: Max condenser load: 278±11 kW 278±11 kW

• Max reboiler load: Max reboiler load: 2410±20 kW 2410±20 kW

COMPLEXFEEDC

TOPSC

BOTTC

Aspen Analysis (cont.)Aspen Analysis (cont.)

 

Feed Flow (gpm)

Condenser Duty (kW)

Distillate Flow

(kmol/hr)

Bottoms Flow

(kmol/hr)

Reboiler Duty (kW)

Steam Flow

(kg/min)

Upper 7.85 289.19 20.68 53.93 401.09 10.58

Average 7.55 278.29 19.90 51.89 385.96 10.18

Lower 7.26 267.27 19.11 49.84 370.70 9.78

OutlineOutline

ObjectiveObjective TheoryTheory ExperimentExperiment ResultsResults Aspen AnalysisAspen Analysis

Recommendations Recommendations Conclusion / Summary Conclusion / Summary

RecommendationsRecommendations

Ethanol separation is possibleEthanol separation is possible Max feed 7.55±0.30 GPM of 15 mole % Max feed 7.55±0.30 GPM of 15 mole %

ethanolethanol Reboiler steam required 10.18±0.40 kg/minReboiler steam required 10.18±0.40 kg/min By redesigning the condenser, capacity can By redesigning the condenser, capacity can

be greatly increasedbe greatly increased• Reboiler only at ~1/6Reboiler only at ~1/6thth of capacity of capacity

Allow more time for partial reflux efficiencyAllow more time for partial reflux efficiency

OutlineOutline

ObjectiveObjective TheoryTheory ExperimentExperiment ResultsResults Aspen AnalysisAspen Analysis Recommendations Recommendations

Conclusion / Summary Conclusion / Summary

Conclusion / SummaryConclusion / Summary

Redesign analysis is an important part of Redesign analysis is an important part of chemical processingchemical processing

Distillation column in senior lab is about Distillation column in senior lab is about 25.3 ± 3.7 % efficient25.3 ± 3.7 % efficient

Ethanol and water separation is possibleEthanol and water separation is possible Limited by the total condenserLimited by the total condenser

SourcesSources Weast, Robert C, Editor. CRC Weast, Robert C, Editor. CRC Handbook of Chemistry and Physics, Handbook of Chemistry and Physics,

64th Edition64th Edition. CRC Press, Inc. Boca Raton, 1983. p. D-253.. CRC Press, Inc. Boca Raton, 1983. p. D-253. King, C. Judsen. King, C. Judsen. Separation ProcessesSeparation Processes. McGraw-Hill, New . McGraw-Hill, New

York,1971. p 603.York,1971. p 603. Ong, John N. Jr, Jack M. Whitney. “The Operation of a Laboratory Ong, John N. Jr, Jack M. Whitney. “The Operation of a Laboratory

Bubble-Plate Distillation Column”. University of Utah, June, Bubble-Plate Distillation Column”. University of Utah, June, 1952.1952.

Perry, Robert H., Editor. Perry, Robert H., Editor. Perry’s Chemical Engineering Handbook. Perry’s Chemical Engineering Handbook. 7th Edition.7th Edition. McGraw-Hill. New York, 1999. p. 115. McGraw-Hill. New York, 1999. p. 115.

Seader, J. D., Ernest J. Henley. Seader, J. D., Ernest J. Henley. Separation Process Principles, 2nd Separation Process Principles, 2nd Edition.Edition. John Wiley and Sons. Hoboken, 2006. p. 193-294. John Wiley and Sons. Hoboken, 2006. p. 193-294.

Silcox, Geoff. “Basic Analysis of Data”. Unpublished student aid. Silcox, Geoff. “Basic Analysis of Data”. Unpublished student aid. University of Utah, 1999.University of Utah, 1999.

Questions?Questions?