Redesign Analysis of a Distillation Column Presented By: Michael Hoepfner University of Utah 2006

Introduction  Why care about redesign?

Outline  Objective  Theory  Experiment  Results  Aspen Analysis  Recommendations  Conclusion / Summary

Objective  Scope Isopropyl Alcohol (IPA) and Water to Ethanol (EtOH) and Water Isopropyl Alcohol (IPA) and Water to Ethanol (EtOH) and Water  Purpose Is the switch possible? Is the switch possible? What are the limitations? What are the limitations?

Outline  Objective  Theory  Experiment  Results  Aspen Analysis  Recommendations  Conclusion / Summary

Theory  Distillation Is among the most common of separations Is among the most common of separations Separates compounds based on volatility Separates compounds based on volatility Utilizes multiple equilibrium separations Utilizes multiple equilibrium separations

Theory (cont.) T-x-y Diagramx-y Diagram Source: Perry’s Chemical Engineering Handbook, 7 th Ed.

Theory (cont.)  McCabe-Thiele Simple and useful tool for defining a distillation column Simple and useful tool for defining a distillation column Three lines can characterize the conditions Three lines can characterize the conditions Source: Seader, 2006

Theory (cont.) Source: Seader, 2006

Theory (cont.)  Efficiency Liquid samples, therefore, liquid efficiency Liquid samples, therefore, liquid efficiency Source: King, 1971

Theory (cont.)  Refractive Index (RI) was used to measure the concentration CRC Handbook of Chemistry and Physics, 64 th Edition Source: CRC Handbook of Chemistry and Physics, 64 th Edition

Outline  Objective  Theory  Experiment  Results  Aspen Analysis  Recommendations  Conclusion / Summary

Experiment  Apparatus 12 Trays with 3 inch bubble caps 12 Trays with 3 inch bubble caps Total Condenser Total Condenser Partial Reboiler Partial Reboiler Thermal couple at every tray Thermal couple at every tray Source: Ong, 1952

Experiment (cont.)  Operate at total reflux Collect samples for efficiency determination Collect samples for efficiency determination  Operate at 2 times the minimum reflux Collect samples for efficiency determination Collect samples for efficiency determination  Model results in Aspen for ethanol and water

Outline  Objective  Theory  Experiment  Results  Aspen Analysis  Recommendations  Conclusion / Summary

Results  Obtained samples on three separate occasions  Samples are numbered by the date collected 10/30/ /30/2006 First run of total refluxFirst run of total reflux 11/01/ /01/2006 Second run of total refluxSecond run of total reflux 11/06/ /06/2006 Only run of partial refluxOnly run of partial reflux

Results (cont.) Concentration of Samples

Results (cont.)  Efficiency Two reasonably reliable data sets Two reasonably reliable data sets All error is at a 95% confidence interval All error is at a 95% confidence interval Total Reflux 10/30/2006 Partial Reflux 11/06/2006 TrayMLErrorMLML FixedError Distillate * * Bottoms Average

Outline  Objective  Theory  Experiment  Results  Aspen Analysis  Recommendations  Conclusion / Summary

Aspen Analysis  Aspen Used average stage efficiency for every stage Used average stage efficiency for every stage It is possible to do separation It is possible to do separation Limited by total condenser load Limited by total condenser load Max condenser load: 278±11 kWMax condenser load: 278±11 kW Max reboiler load: 2410±20 kWMax reboiler load: 2410±20 kW

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 Average Lower

Outline  Objective  Theory  Experiment  Results  Aspen Analysis  Recommendations  Conclusion / Summary

Recommendations  Ethanol separation is possible Max feed 7.55±0.30 GPM of 15 mole % ethanol Max feed 7.55±0.30 GPM of 15 mole % ethanol Reboiler steam required 10.18±0.40 kg/min Reboiler steam required 10.18±0.40 kg/min By redesigning the condenser, capacity can be greatly increased By redesigning the condenser, capacity can be greatly increased Reboiler only at ~1/6 th of capacityReboiler only at ~1/6 th of capacity  Allow more time for partial reflux efficiency

Outline  Objective  Theory  Experiment  Results  Aspen Analysis  Recommendations  Conclusion / Summary

Conclusion / Summary  Redesign analysis is an important part of chemical processing  Distillation column in senior lab is about 25.3 ± 3.7 % efficient  Ethanol and water separation is possible Limited by the total condenser Limited by the total condenser

Sources  Weast, Robert C, Editor. CRC Handbook of Chemistry and Physics, 64th Edition. CRC Press, Inc. Boca Raton, p. D-253.  King, C. Judsen. Separation Processes. McGraw-Hill, New York,1971. p 603.  Ong, John N. Jr, Jack M. Whitney. “The Operation of a Laboratory Bubble-Plate Distillation Column”. University of Utah, June,  Perry, Robert H., Editor. Perry’s Chemical Engineering Handbook. 7th Edition. McGraw-Hill. New York, p  Seader, J. D., Ernest J. Henley. Separation Process Principles, 2nd Edition. John Wiley and Sons. Hoboken, p  Silcox, Geoff. “Basic Analysis of Data”. Unpublished student aid. University of Utah, 1999.

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