2. ENGINEERING 536 MASS TRANSFER OPERATIONS FALL 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

3. Introduction b b Study of mass transfer operations using the distillation column b b Approach to the study of the distillation column included - Literature search - Operating the column - Computer modeling + Ponchon-Savarit + PROII b b This report will cover - column calibrations - experimental results - computer modeling

4. DISTILLATION COLUMN 1 2 3 4 5 6 7 8 9 10 11 12 Reboiler TI Product Cooler Electromagnetic Reflux Control Feed Tank (Product Tank) Cooling Water Supply Condenser Reboiler Pump Distillate Pump Feed Pump LI Cooling Water Return TI LI PI TI

5. COLUMN DESCRIPTIONS b b Condenser b b Reflux valve b b Trays b b RTDs b b Pumps - Feed pump - Reboiler pump - Distillate pump - Auxiliary pump b b Reboiler b b Level Control - Condenser - Reboiler b b FEED LOCATIONS

6. Column Calibrations b Heat loss study b RTD calibration b Pump and cooling water calibration

7. Heat Loss Study b b Previous heat loss calculations seemed excessive b b Parameters of the study are - selected reboiler amperage - 100% reflux - no condensate produced b b Column losses are equal to the energy input into the column b b Minimum amperage to maintain the temperature on tray 1 is between 6 and 7 amps b b Estimated column heat loss is between 1230 Watts and 1435 Watts

8. Temperature of tray 1 at 7 amps Temperature of tray 1 at 6 amps

9. RTD Calibration b b Temperature is calculated by multiplying the voltage by the scale and then adding the offset b b 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

10. b b Voltage is taken at 100 o C (pure water) and 64.5 o C (pure methanol) b b Straight line was fit between the two points b b Slope of the line is the scale b b y intercept is the offset

11. Pump and Cooling Water Calibration b b Pump and cooling water calibrations seem to be reliable b b Pump calibration - by measuring the outflow of the pump for a timed period b b Cooling water calibration - by measuring the flow at the cooling water system drain at various valve openings

12. Pump Calibration Curve

13. Conclusions (calibrations) b b Pump and cooling water calibrations seem to be reliable b b Calibrations performed on the glass RTDs were unsuccessful ( repeated several times) b b Replacement of the glass RTDs with stainless steel improved the calibrations - three RTDs do not give reliable temperature indication

14. Recommendation (calibrations) b b Perform calibrations - after a period of inactivity - whenever equipment is changed or modified b b Reduce time spent on calibrations - Calibrate the RTDs individually with ice and boiling water - UTC engineering/maintenance personnel should complete calibrations

15. Experimental Results b Energy and mass balance b Capacity test b Feed location impact b Reflux ratio impact

16. Energy and Mass Balance b b Excel spreadsheet was developed to facilitate mass and energy calculations b b Calculations showed an increase in water and a decrease in methanol b b Column had not reached steady- state conditions

18. Capacity Test b b Performed to determine the maximum capacity of the column to produce distillate b b 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

19. - 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 flowrate flowrate - Column did not produce distillate at - Column did not produce distillate at pump setting of 7 pump setting of 7 Capacity Test Comparison

20. Feed Location Impact b Parameter - Pump setting of 3 - Reboiler amps at 20 - 70% reflux b Results - Tray 4 - 89% - Tray 5 - 93% - Tray 6 - 97%

21. Reflux Impact b Parameter - Feed location tray 4 - Pump setting of 3 - Reboiler amps at 20 b Results - Reflux 50% - 78% at 43 ml/min ml/min - Reflux 70% - 89% at 23 ml/min ml/min

22. Conclusions (Experimental Results) b Design and execution of experiments - useful way of gaining experience - found column performed in a predictable manner - increased the students’ level of confidence b energy and mass balance calculations demonstrated - purity of the product was surpassed with a reduction in the quantity of the product

23. b b 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 b b Based on observations from the feed location experiment - optimum feed tray location - tray 6 - due to the higher methanol composition in the distillate b b 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

24. Recommendation (Experimental Results) b b Review the RTD calibrations to account for the discrepancies in the mass balance b b Perform additional feed location impact experiments b b Take physical measurement of the distillate flow (not pump flowrates)

25. Computer Modeling b Pro II b Ponchon-Savarit

26. PRO II b b Steady-state heat and material balance simulator b b Simulates any number of components, streams, units, and recycle loops b b Requirement - Feed stream - composition - temperature - flowrate - pressure - Tray efficiency

27. b b 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 b b PROII will calculate remaining parameters

28. PRO II - Optimizing Distillation Column

29. Ponchon-Savarit Theory b Graphical Method Plots Enthalpy Against CompositionPlots Enthalpy Against Composition b Provides Exact Solutions b Incorporates Effects of Heat Losses Inputs of Individual Tray LossesInputs of Individual Tray Losses Inherent Material and Energy BalancesInherent Material and Energy Balances

30. Ponchon-Savarit Diagram on Excel b b Inputs Needed (highlighted in yellow) Distillate and Bottoms Compositions Desired Distillate and Bottoms Flowrates Heat Losses on Each Tray b b Works For Up To 13 Stages b b Tested For Bottoms Concentrations down to 0.01% and Distillate Concentrations up to 97.9%

31. Conclusion (Computer Modeling) b b PROII - user friendly - fast - not accurate - limited by constraints b b Ponchon-Savarit - heat loss on individual trays must be known - only valid for methanol-water mixtures

32. Recommendations (Computer Modeling) b b Modify the PROII model to more closely approximate the UTC distillation column b b Conduct training for students on the use of modeling tools b b Determine the heat losses on the individual trays (Ponchon- Savarit)

33. Conclusions (Final) b b 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

34. - E ach student had the opportunity to participate in - operation - calibration - repair - P rovided a better understanding through - research - classroom discussion - design of experiments

35. b b 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

36. Recommendations (Final) b b 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