Dr. Jim Henry, P.E. Professor of Engineering University of Tennessee at Chattanooga 615 McCallie Avenue Chattanooga, TN Dr.

Transcription

1 Aubrey Gunter Green Team - Distillation College of Engineering and Computer Science University of Tennessee at Chattanooga 615 McCallie Avenue Chattanooga, TN To: Dr. Jim Henry, P.E. Professor of Engineering University of Tennessee at Chattanooga 615 McCallie Avenue Chattanooga, TN Dr. Henry: The following report provides a detailed account of the Green Team s experimental work and all other relevant information related to their study of the distillation column at the University of Tennessee at Chattanooga located in Grote room 115. Aubrey Gunter Green Team Senior Undergraduate Student Chemical and Environmental Engineering University of Tennessee at Chattanooga

2 Distillation Column Experiments, Batch and Continuous University of Tennessee at Chattanooga College of Engineering and Computer Science Engineering 435 Chemical Process Laboratory Section 001 Author: Aubrey Murray Gunter Co-Authors: Alok Patel, Paul Pearman To: Dr. Jim Henry Cc: Dr. Frank Jones October 24, 2002

3 ABSTRACT: A distillation column was studied at the University of Tennessee at Chattanooga, School of Engineering and Computer Science for the binary system of methanol and water. The purpose of this study of the distillation column was to determine the composition of methanol in the distillate collected for various reflux percentages under conditions of continuous and batch distillation. Two methods were used to determine the composition of the distillate, density and temperature. The distillate flow rate for various reflux percentages under conditions of continuous and batch distillation was also studied. Two methods were used to study the distillate flow rate. The first method was performed by manually observing the collected distillate level over time. The second method involved a flow meter and the LabVIEW program that calculates the flow rate. The composition of each tray for various reflux percentages under conditions of continuous and batch distillation was also studied. The temperature method was used to study this tray composition. An energy study was also performed on the condenser. The relationship between the manual study and computer study of distillate flow rate is given in the following equation: Q Manual = (1.68±1.08)Q LabVIEW - 188(±11.5), where Q is the flow rate is L/min. The methanol composition of the distillate and for each tray was found to have a proportional relationship to the reflux percentage for both batch distillation and continuous distillation experiments. The energy study revealed that the energy removed by the condenser is higher for batch distillation than for continuous distillation.

4 TABLE OF CONTENTS: Page Introduction x Theory x Equipment..x Procedure x Results x Discussion of Results..x Conclusions.x Recommendations...x Nomenclature..x References...x Appendices..x

5 INTRODUCON: The purpose of this study of the distillation column by the Green Team was to determine the composition of the distillate collected for various reflux percentages under conditions of continuous and batch distillation. Two methods were used to determine the composition of the distillate, density and temperature. The Green Team also studied the distillate flow rate for various reflux percentages under conditions of continuous and batch distillation. Two methods were used to study the distillate flow rate. The first method was performed by manually observing the collected distillate level over time. The second method involved a flow meter and the LabVIEW program that calculates the flow rate. The composition of each tray for various reflux percentages under conditions of continuous and batch distillation was also studied. The temperature method was used to study this tray composition. The Green Team also performed an energy study on the condenser. Binary distillation is the process in which a mixture of 2 chemicals are separated based upon each chemical s vapor pressure, or how easily each chemical vaporizes. For the purposes of this experiment, only a binary mixture of methanol and water was studied. When two pure chemicals are mixed and heated to boiling, the chemical with the lowest vapor pressure, i.e. the lowest boiling point, will vaporize first. This component of the binary mixture is called the light component, and commonly referred to as component A the mixture. The other component of the binary mixture is called the heavy component, and is commonly referred to as component B of the mixture. A distillation column is a column composed of a series of trays stacked vertically, with a condenser, reboiler, and a feed. The feed is the mixture of chemicals, in this case methanol and water, which is fed into the middle section of the distillation column. The reboiler provides energy to the distillation column in the form of heat to cause the light component, component A, of the binary mixture to vaporize first. The reboiler is located at the bottom of the distillation column. The product stream of the reboiler is known as the bottoms product. The condenser is located at the top of the distillation column and removes energy from the distillation column. The purpose of the condenser is to condense the vapor leaving the top tray of the column. Reflux percent is the percent of liquid condensed in the condenser that is allowed to be collected as distillate. The distillate is the product stream from the top of the distillation column, which is rich in component A of the binary mixture. The remaining liquid that is not collected as distillate, termed reflux, is returned to the distillation column for further separation. A distillation column can be run via batch operation or continuous operation. In batch distillation, a batch of chemicals, in this case methanol and water, is first fed into the column and the liquid part of this mixture settles in the reboiler. Once the reboiler is filled with the desired finite batch of the binary mixture, energy is added to the reboiler in the form of heat to start the experiment. In continuous distillation, the feed enters the column continuously. Heat is constantly supplied to the reboiler, and a continuous flow of distillate and bottoms product is collected or returned to the feed tank.

6 THEORY: The composition of the distillate collected was analyzed in two ways. One method for determining composition is density. This calculated density was then compared with a tabulated list of densities located in Perry s Handbook. To find the density, a measured volume of collected distillate was weighed. The formula for density is given below. Density = Mass/volume (1) The second method for determining composition of the distillate collected, and the composition for each tray, is temperature. Using a vapor-liquid equilibrium diagram from tabulated data in Perry s Handbook for methanol and water mixture, the known temperature of the liquid in each tray can be used to find the composition of the liquid and vapor. The following diagram in Figure 1 illustrates this method Perry's Data for Methanol-Water Vapor Equilibrium Line Data x Data y 90.0 Temperature, oc Liquid Equilibrium Line x,y Figure 1. Vapor-Liquid Equilibrium Diagram for Methanol and Water For example, at a temperature of 78.0 o C, the composition of liquid of the light component, in this case methanol, is 0.30 mole fraction, and the composition of methanol in the vapor is 0.67 mole fraction.

7 Reflux percentage is the percent of liquid condensed in the condenser that is allowed to be collected as distillate. The distillate is the product stream from the top of the distillation column, which is rich in component A of the binary mixture. The remaining liquid that is not collected as distillate, termed reflux, is returned to the distillation column for further separation. At 95% reflux, 5% of the condensed liquid from the condenser is collected as distillate. The remaining 95% of the condensed liquid is returned to the distillation column for further separation. Therefore, the higher the reflux percentage, the greater amount of liquid is sent back to the distillation column for further separation. It follows then that the highest composition of the light component collected in the distillate is proportional to the highest possible reflux percentage. Unfortunately, at 100% reflux no distillate is collected. The figure below is an illustration of reflux. Reflux Condenser 1 Distillate collected 4 Figure 2. Diagram Illustrating Reflux.

8 An energy study on the distillation column can be simplified if an overall energy balanced is used on the distillation column. A simplified illustration of the distillation column is given in the following figure, Figure 3. Q condenser Q loss Q reboiler Figure 3. Simplified Model of the Distillation Column At steady-state, the energy added to the distillation column is equal to the energy removed from the distillation column minus any heat loss in the distillation column. The following equation was used to find the overall heat loss in the distillation column. Q reboiler = Q condenser + Q loss (2). Q reboiler is the energy added to the distillation column from the reboiler, Q condenser is the energy removed by the condenser, and Q loss is the energy loss in the distillation column.

9 m Q condenser Condensation Droplets T out m T in Vapor from Tray 1 Condensed Liquid Figure 4. Simplified Model of the Condenser Located at the Top of the Distillation Column In order to perform an energy balance on the condenser, the following equation was used: Q = mc T (3), P where Q is the energy in watts removed by the condenser, m is the mass flow rate of the entering cold water, and C p is the heat capacity of water. T is the change in temperature in degree Celsius, or more specifically, T = T out - T in (4).

10 EQUIPMENT: The distillation column is approximately 15 feet high with a diameter of approximately 6 inches. There are 12 trays within the distillation column. The section of the distillation column above the feed is known as the rectifying section. The section of the distillation column below the feed is known as the stripping section. The reboiler is located at the bottom of the column. Inside the reboiler is a heating unit composed of calrod heaters that is used to heat the mixture that is fed into the distillation column. When this mixture is heated the light component, the component of the mixture that has the lowest boiling point, vaporizes and condenses on the tray directly above the reboiler. From the heat added to the reboiler, each subsequent tray undergoes vaporization and condensation so that the top of the column has a high concentration of the lightest component and the bottom of the column has a high concentration of the heavy component (the component with the higher boiling point). Figure 4 best illustrates this separation. Liquid from tray above Vapor leaving tray Typical Tray Liquid leaving tray Vapor from tray below Figure 5. A Typical Tray. This distillation column can be run via batch operation or continuous operation. In batch distillation, a batch of chemicals, in this case methanol and water, is first fed into the column and the liquid part of this mixture settles in the reboiler. Once the reboiler is filled with the desired finite batch of the binary mixture, energy is added to the reboiler in the form of heat to start the experiment. A schematic drawing of the distillation column under batch distillation is given in Figure 6. In continuous distillation, the feed enters the column continuously. Heat is constantly supplied to the reboiler, and a continuous flow of distillate and bottoms product is collected or returned to the feed tank. A schematic drawing of the distillation column under continuous distillation is given in Figure 7.

11 Heat Removed from the Condenser Reflux Condenser 1 Distillate collected Distillate Pump Rectifying Section Feed Tank Reboiler Pump Vapor Boil-up Reboiler filled with batch of binary mixture Reboiler Heat added to the Reboiler Bottom s Product

12 Figure 6. Distillation Column Under Batch Operation Heat Removed from the Condenser Reflux Condenser 1 Distillate collected Rectifying Section Distillate Pump Feed Feed Pump Feed Tank Reboiler Pump Stripping Section Vapor Boil-up Reboiler Heat added to the Reboiler Bottom s Product

13 Figure 7. Distillation Column Under Continuous Distillation PROCEDURE: Seven experiments were ran for batch operation. The inputs required for batch distillation include Reflux Percent and Heat Added to the Reboiler. Table 1 depicts the experiments ran for batch operation of the distillation column. Table 1. Experiments for Batch Distillation Experiment Number Reflux Rate Heat Added to Reboiler, Watts Composition of batch, wt % methanol 1 100% % 2 95% % 3 95% % 4 90% % 5 70% % 6 50% % 7 20% % Four experiments were run for continuous distillation. The inputs for continuous operation include Reflux Percent, Heat added to the Reboiler, and a feed pump setting. It should be noted that a P-only controller maintained a level of approximately 11 liters in the reboiler. Table 2 depicts the experiments ran for continuous operation of the distillation column. Table 2. Experiments for Continuous Distillation Experiment Number Feed Pump Setting Reflux Rate Heat Added to Reboiler, Watts Composition of Feed, wt % methanol % % % % % % % % Distillate Flow Rate Study For batch distillation, the flow rate for the distillate was found by two different methods, manually and computer. Manual Method - The real distillate flow rate was recorded physically by manually recording the level of the distillate collected in the 1000mL beaker every 5 minutes. Computer Method The distillate flow rate given by the computer, i.e. LabVIEW is automatically recorded to a raw data sheet that is downloadable at

14 Composition of Methanol in the Distillate The composition of the distillate was found using two different methods, density and temperature data. For density calculations for batch and continuous distillation experiments, the initial distillate that was collected in the 1000mL beaker was transferred to a 50mL beaker. This distillate was used to wash a 5mLgraduated cylinder. After 3 washings, the collected distillate was poured into the 5mL-graduated cylinder to the 5mL mark. This graduated cylinder was then weighed on a triple beam balance to the nearest 100 th of a gram. Then, using the following equation, Density = Mass/volume (1) the density was found. Then, using a list of tabulated data by Perry s Handbook, 7 th edition, the composition of the distillate was found. To calculate the composition of the distillate by temperature data, the temperature of the top tray was used in conjunction with the chart given in Figure 1. The composition of the distillate was recorded as the composition of the vapor at the tray 1 of the distillation column. For batch distillation experiments, the composition of the distillate calculated from temperature data was found approximately 5 minutes after the first distillate started to flow. For continuous distillation experiments, the composition of the distillate calculated from temperature data was found at steady-state. Composition of Methanol on Each Tray Temperature data in conjunction with the chart given in Figure 1was used to find the composition of methanol in each tray. For batch distillation experiments, the composition of the distillate was found approximately 5 minutes after the first distillate started to flow. For continuous distillation experiments, the composition of the distillate calculated was found at steady-state. Energy Study on the Condenser The needed information for conducting an energy study on the condenser was Cold Water Flow Rate to the condenser, the Cold Water Supply Temperature to the condenser, and the Cold Water Return Temperature to the condenser. The following equation was used to calculate the energy removed by the condenser, Q = mc T (3), P where Q is the energy in watts removed by the condenser, m is the mass flow rate of the entering cold water, and C p is the heat capacity of water. T is the change in temperature in degree Celsius, or more specifically, T = T out - T in (4). where T in is the Cold Water Supply Temperature and T out is the Cold Water Return Temperature.

15 Overall Energy Loss in the Distillation Column At steady-state, the energy added to the distillation column is equal to the energy removed from the distillation column minus any heat loss in the distillation column. The following equation was used to find the overall heat loss in the distillation column. Q reboiler = Q condenser + Q loss (2). Q reboiler is the energy added to the distillation column from the reboiler, Q condenser is the energy removed by the condenser, and Q loss is the energy loss in the distillation column. RESULTS: The distillate flow rate was found for batch distillation manually (manually recording the distillate collected in the 1000mL beaker every 5 minutes) and then compared to the data recorded by LabVIEW (the distillate level calculated by the LabVIEW program using a pressure sensor at the bottom of the beaker containing the distillate). Table 3 and Table 4 give the results of the flow rate analysis. Table 3. Distillate Flow Rate for Batch Distillation for a Constant Reflux Rate Heat Added to Reboiler, Watts Reflux Rate LabVIEW Flow Rate, ml/min Manual Flow Rate, ml/min % % Table 4. Distillate Flow Rate for Batch Distillation for a Constant Heat Added to Reboiler Reflux Rate Heat Added to Reboiler, Watts LabVIEW Flow Rate, ml/min Manual Flow Rate, ml/min 95% %

16 Figure 8 displays the difference in flow rate of the distillate for batch distillation at a constant reflux percentage of 95%. The data displayed below represents the manually collected data. Heat added to the reboiler is the variable studied in Figure 8. As noticed in the figure below, the higher distillate flow rate is for 2500 Watts added to the reboiler. Batch Distillation Flow Rate for 2000 Watts vs. 2500Watts (95% Reflux) Watts V = 5.1t Volume of Distillate (ml) Watts V = 3.9t Time (min) Figure 8. Manual Distillate Flow Rate for Constant Reflux Rate

17 Figure 9 represents the data collected manually for batch distillation at a constant wattage supplied to the reboiler of 2500 Watts. Reflux percentage is the variable of interest. As noticed in the figure below, the higher distillate flow rate is associated with the lower reflux percentage. Batch Distillation Flow Rate of 95% vs. 20% Reflux (2500Watts) % Reflux V = 60.7t Volume of Distillate (ml) % Reflux V = 5.1t Time (min) Figure 9. Manual Distillate Flow Rate for Constant Heat Added to Reboiler

18 Figure 10 represents the comparison of the manual data and computer data for the distillate flow rate for batch distillation. The wattage supplied to the reboiler and the Reflux Percentage are held constant at 2000Watts and 95%, respectively. As noticed in the figure below, the higher distillate flow rate is associated with the manual data. Batch Distillation Manual vs. LabVIEW (2000 Watts, 95% Reflux Rate) LabVIEW V = 2.5t Volume of Distillate (ml) Manual V = 3.9t Time (min) Figure 10. Comparison of Manual and LabVIEW Distillate Flow Rate

19 Figure 11 represents the comparison of the manual data and computer data for the distillate flow rate for batch distillation. The wattage supplied to the reboiler and the Reflux Percentage are held constant at 2500Watts and 20%, respectively. As noticed in the figure below, the higher distillate flow rate is associated with the manual data. Batch Distillation Manual vs. LabVIEW (2500 Watts, 20% Reflux Rate) 2500 Manual 2000 V = 60.7t Volume of Distillate (ml) LabVIE W V = 30.8t Time (min) Figure 11. Comparison of Manual and LabVIEW Distillate Flow Rate

20 Figure 12 represents the comparison of the manual data and computer data for the distillate flow rate for batch distillation. The wattage supplied to the reboiler and the Reflux Percentage are held constant at 2500Watts and 95%, respectively. As noticed in the figure below, the higher distillate flow rate is associated with the manual data. Batch Distillation Manual vs. LabVIEW (2500 Watts, 95% Reflux Rate) LabVIEW V = 3.4t Volume of Distillate (ml) Manual V = 5.1t Time (min) Figure 12. Comparison of Manual and LabVIEW Distillate Flow Rate

21 As noticed in Figures 10 through 12, the manually collected data does not match the computer data for distillate flow rate. Assuming that the manually collected data for the distillate flow rate is the true distillate flow rate, an equation needs to be created that corrects the computer data to match the manual data. Heat Added to Reboiler, Watts Reflux Percentage Table 5. Ratio of Flow Rates for Manual and LabVIEW LabVIEW Flow Rate, ml/min Manual Flow Rate, ml/min Ratio of Flow Rates, Manual/LabVIEW Intercepts % % % Average Student T Error ±1.08 ±11.5 Relationship between Manual Flow Rate and LabVIEW Flow Rate: Manual Flow Rate = (1.68±1.08)*LabVIEW Flow 188(±11.5) Density study for methanol composition It was first believed that density would prove to be a good comparison with the temperature method for methanol composition in the distillate. However, in light of the obvious high error in density calculations, comparisons are not made between the temperature calculations for methanol composition and density calculations for methanol composition. Table 6 summarizes the error analysis for the density data at a Reflux of 50%. Reflux Percentage Table 6. Percent Methanol in Distillate from Density Calculations Volume in Graduated Cylinder (ml) Weight of Distillate (grams) Density of Distillate (grams/ml) Composition of Distillate (wt%) 50% % 50% % 50% % 50% % Students T- Error 17.1%

22 Table 7 summarizes the density calculations for batch distillation. It should be noted that these methanol compositions appear to be bogus. Table 7. Density Calculations for Methanol Composition in the Distillate for Batch Distillation Reflux Percentage Composition of Distillate (wt%) 95% 110% 90% 98% 70% 89% 50% 61% 20% 89% Table 8 summarizes the density calculations for continuous distillation. It should be noted that these methanol compositions also appear to be bogus. Table 8. Density Calculations for Methanol Composition in the Distillate for Continuous Distillation Reflux Percentage Composition of Distillate (wt%) 90% 61% 70% 57% 50% 106% Table 9 summarizes the distillate composition found for batch distillation using the temperature method. It should be noted that these calculations were conducted approximately 5 minutes after the first distillate started to flow. Table 9. Comparison of Distillate Composition for Batch Distillation with 2500 Watts added to the Reboiler Reflux Percentage Composition of Distillate, mole fraction Methanol 95% % % % % 0.18

23 Table 10 summarizes the distillate composition found for continuous distillation using the temperature method. It should be noted that these calculations were performed once the continuous distillation experiment reached steady-state. Table 10. Comparison of Distillate Composition for Continuous Distillation with 2500 Watts added to the Reboiler Reflux Percentage Composition of Distillate, mole fraction Methanol 90% % % 0.23 Table 11 presents the comparison between calculated compositions of methanol in the distillate for batch distillation and continuous distillation. Batch distillation calculations were conducted approximately 5 minutes after the first distillate started to flow. Continuous distillation calculations were conducted once steady-state was reached. Table 11. Comparison of Distillate Composition for Continuous Distillation and Batch Distillation with 2500 Watts added to the Reboiler Reflux Percentage Composition of Batch Distillate, mole fraction Methanol Composition of Continuous Distillate, mole fraction Methanol 90% % %

24 Figure 13 is graph of the methanol composition in the liquid for each tray. Figure 13 illustrates the difference in liquid composition for batch distillation with a constant reflux percentage of 95%. The variable of interest is the wattage added to the reboiler, which in this graph is 2000Watts and 2500Watts. It should be noted that these calculations were conducted approximately 5 minutes after the first distillate started to flow. Batch Distillation at 95% Reflux Liquid Composition Watts 0.8 mole fraction methanol Watts Tray Figure 13. Liquid Composition of Methanol in Each Tray for Batch Distillation

25 Figure 14 is graph of the methanol composition in the liquid for each tray. Figure 14 illustrates the difference in liquid composition for batch distillation with a constant wattage supplied to the reboiler of 2500Watts. The variable of interest is the reflux percentage. It should be noted that these calculations were conducted approximately 5 minutes after the first distillate started to flow. Batch Distillation at 2500 Watts added to Reboiler - Liquid Composition % Reflux 90% Reflux 0.7 mole fraction methanol % Reflux 95% Reflux % Reflux Tray Figure 14. Liquid Composition of Methanol in Each Tray for Batch Distillation

26 Figure 15 is graph of the methanol composition in the liquid for each tray. Figure 15 illustrates the difference in liquid composition for continuous distillation with a constant wattage supplied to the reboiler of 2500Watts. The variable of interest is the reflux percentage. It should be noted that these calculations were performed once the continuous distillation experiment reached steady-state. Continuous Distillation at 2500 Watts added to Reboiler - Liquid Composition % Reflux mole fraction methanol % Reflux 70% Reflux % Reflux Tray Figure 15. Liquid Composition of Methanol in Each Tray for Continuous Distillation

27 Energy Balance on the Condenser and Heat Loss in the Distillation Column It should be noted that during the course of this study, it was found that the cold water flow rate displayed by the computer is incorrect. Table 12 summarizes theses results Table 12. Cold Water Flow Rate Study Cold Water Flow Rate Displayed Cold Water Flow Rate found Ratio of Manual/LabVIEW by LabVIEW (L/min) Manually (L/min) Therefore, it follows that the correction factor for the flow rate given by the computer is 2.8 Table 13 is a summary of the energy study for batch distillation experiments. Table 13. Summary of Energy Study for Batch Distillation Reflux Rate Heat Added to Reboiler, Watts Heat Removed by Condenser, Watts Heat Loss in Column, Watts 100% % % % % % Table 13 is a summary of the energy study for the continuous distillation experiments Table 13. Summary of Energy Study for Continuous Distillation Reflux Rate Heat Added to Reboiler, Watts Heat Removed by Condenser, Watts Heat Loss in Column, Watts 95% % % %

28 Figure 16 is a graph comparing the heat absorbed by the condenser for batch distillation experiments and continuous distillation experiments. The wattage supplied to the reboiler is 2500 Watts for all data graphed below. Heat absorbed by Condenser Vs. Reflux % Heat absorbed by condenser (Watts) Batch Continuous Reflux % Figure 16. Comparison of Heat Absorbed by Condenser for Batch and Continuous Distillation

29 DISCUSSION OF RESULTS: When comparing the distillate flow rates for the Manual and LabVIEW methods, the distillate flow rate displayed by the computer, i.e. LabVIEW, is consistently lower than the real distillate flow rate, i.e. Manually. Specifically, the real distillate flow rate is 1.68±1.08 times the computer distillate flow rate. The correction for this discrepancy was found to be Q corrected = (1.68±1.08)Q LabVIEW - 188(±11.5), where Q is the flow rate. When comparing the distillate flow rates for batch distillation at different reflux percentages but at a constant wattage supplied to the reboiler, the higher distillate flow rate is due to the lower reflux percentage, as expected in the theory. When comparing the distillate flow rates for batch distillation at different wattages added to the reboiler but at a constant reflux percent, the higher distillate flow rate is due to a higher wattage supplied to the reboiler. The composition of the methanol in the distillate was found using two different methods, density and temperature. The compositions found using the density calculations proved to be bogus with a Student-T error of 17.4% for batch distillation with 50% reflux and 2500Watts added to the reboiler. Commonly the composition of the methanol exceeded 100 wt%. Obviously, it is impossible to have greater than 100 wt% methanol in the distillate. Also, the composition of methanol in the distillate would inconsistently increase or decrease as the reflux percentage decreased. Therefore, the density calculations proved erroneous. The composition of methanol in the distillate found from temperature calculations proved to be consistent with the theory. An increase in percent methanol is related to an increase in reflux percentage, and a decrease in percent methanol in the distillate is related to a decrease in reflux percentage. Batch distillation experiments give a higher composition of methanol in the distillate than continuous distillation experiments when reflux percentage and heat added to the reboiler are equal. It should be noted that batch distillation compositions occurred approximately 5 minutes after the first distillate started to flow and the continuous distillation compositions occurred at steady-state. The composition of methanol in each tray found from temperature calculations also proved to be consistent with the theory. Tray 1 contained the highest percent methanol and each subsequent tray contained successively less methanol. There is little difference in corresponding tray compositions for reflux percentages of 90% and 95% for batch distillation. The same phenomenon was also observed for continuous distillation experiments at 90% and 95% reflux. When comparing the methanol composition on each tray for batch distillation at different wattages added to the reboiler but at a constant reflux percent, the methanol concentration in the lower trays (7 through 12) are lower for the higher wattage supplied to the reboiler. This is due to the fact that there is a greater flow rate of vapor to the top of the column with a higher wattage supplied to the reboiler. For batch distillation experiments, the energy removed by the condenser is greater than the energy removed from the condenser during continuous distillation experiments.

30 CONCLUSIONS: The distillate flow rate found by LabVIEW, i.e. the computer is incorrect and does not match the manually calculated flow rate, which is accepted as the real distillate flow rate. The correction for this discrepancy was found to be Q corrected = (1.68±1.08)Q LabVIEW - 188(±11.5), where Q is the flow rate is L/min. Methanol concentration increases in the trays as it ascends in the distillation column. Batch distillation experiments give a higher initial methanol composition in the distillate than continuous distillation experiments. At lower reflux percentages, the distillate flow rate is higher for both continuous distillation experiments and batch distillation experiments. Also, at lower reflux percentages, the concentration of methanol is less in the stripping section (trays 7 through 12) of the distillation column for both batch and continuous distillation experiments. At higher watts added to the reboiler, there is a corresponding lower concentration of methanol in the lower trays (trays 7 through 12) of the distillation column for batch distillation experiments. RECOMMENDAONS: It would be of interest to observe continuous distillation at a constant reflux percentage but varying the wattage supplied to the reboiler. Also, it would be of interest to observe continuous distillation for different feed pump settings. In addition, a study should be conducted to determine why the heat absorbed by the condenser is less for continuous distillation than for batch distillation. REFERENCES: Unit Operations of Chemical Engineering, 6 th Ed., Warren L. McCabe, Julian C. Smith and Peter Harriott, McGraw-Hill, Boston, Perry, Robert H. and Don W. Green. Perry s Chemical Engineers Handbook, 7 th Edition, June 1, McGraw-Hill Professional Cunningham, James R. Dr. Lecture Notes Fall 2002 for ENCH 432 at the University of Tennessee at Chattanooga. UTC Engineering Controls Lab Online. University of Tennessee at Chattanooga. Appendices

31 Batch Distillation at 95% Reflux Vapor Composition Watts Tray Batch Distillation at 2500 Watts added to Reboiler - Vapor Composition % Reflux 100% 95% % 90% % Reflux Tray

32 Continuous Distillation at 2500 Watts added to Reboiler - Vapor Composition % % 90% % Tray