Packed Bed Distillation Column Lab Report

EKB 2131 – Chemical Engineering Lab - IIIBachelor of Chemical Engineering (Hons) LAB REPORT EKB 2131 - CHEMICAL ENGINEERING LAB - III EXPERIMENT TITLE PACKED BED DISTILLATION COLUMN NAME OF CANDIDATE SHAMINI SATHIVEL WITH REG NO. SESSION DATE 22th OCTORBER 2015, Thursday DATE OF SUBMISSION 29TH OCTORBER 2015, Thursday NAMES OF GROUP MEMBERS No REG No. NAME . 1 1000013 Sangidha Jegathesan 2 1000045 Sasi Varnan 3 MARKING SIGNATURES MARKS DETAILS TOTAL AWARDED Participation and Attitude (Name of Faculty Supervising) TABLE OF CONTENTS Mr.Arasu Uttaran Lab Report CHEM. ENGG. LAB-IV INCHARGE Total (Dr. TVN. Padmesh/Arasu Uttran) Page 1 EKB 2131 – Chemical Engineering Lab - III S. NO. DESCRIPTION PAGE NO. Abstract 3 1 Introduction 3 2 Materials and Methods 5 3 Results and Discussions 7 4 Conclusions and Recommendations 8 5 References 9 Appendix 9 ABSTRACT Page 2 EKB 2131 – Chemical Engineering Lab - III The experiment was carried out to study the process of packed bed distillation column. The experiment was conducted under total reflux condition. The moles fraction of methanol in feed, residue and distillate was determined by the graph of R.I vs. x corresponding to refractive indexes respectively. The mole fraction of methanol in feed, F was determined to be 0.37 moles. The mole fraction of methanol of residue B was determined to be 0.25 moles. The mole fraction of methanol of distillate D was to be 0.057. The error that was calculated is 2.61. The value of minimum plates, Nm that was calculated is 0.84. 1. INTRODUCTION 1.1. Distillation Distillation is defined as a process in which a liquid or vapour mixture of two or more substances having different vapour pressures is separated into its component fractions of desired purity, by the application of heat [1]. When the vapours of the boiling mixture is cooled and condensed, the condensate will contain more volatile components (low boiling point). As distillation progresses, the original mixture will contain more of less volatile material (high boiling point). Depending on the concentrations of the components present, the liquid mixture will have different boiling point characteristics. Distillation occurs because of vapour pressures of the components in the liquid mixture. If relative volatility is very close to 1, they have similar vapour pressures and hence, it will be difficult to separate the two components by distillation [1]. Distillation is a unit operation capable of producing pure substance from liquid mixtures. 1.1.2 Application of Distillation  Distillation has long been used as the separation process in chemical and petroleum industries  Distillation technology is applied in pharmaceutical, chemical, food, and alcohol industries  Distillation is used in refineries for fractionating crude oil to produce many chemicals  It is used in distillery for producing alcohol 1.1.3 Types of Distillation Columns Page 3 EKB 2131 – Chemical Engineering Lab - III There are many types of distillation columns, each designed to perform specific types of separations and each design differs in terms of complexity. A few common types are given below:  As batch and continuous processes based on how they are operated.  As binary or multi-component distillation processes based on the number of components in the feed.  As tray or packed distillation columns based on the type of column internals. 1.2 Packed Bed Column Packed bed columns are used most often for absorption, liquid-liquid extraction and distillation. This experiment was conducted to study the operation of packed bed distillation column. The packing provides a large surface area for vapour - liquid contact. The feed mixture contains components of different volatilities, and enters the column approximately at the middle. The liquid flows downward through the packing, and the vapour flows upward through the column [2]. Differences in concentration cause the less-volatile components to transfer from the vapor phase to the liquid phase. After the feed mixture enters the column it flows down the column through the packing counter currently and contacts the rising vapour stream. The liquid at the bottom enters a reboiler. Two streams exit the reboiler; a vapour stream, which returns to the column, and a liquid product stream. The vapour stream flows upward through the packing, picks up the more volatile components, exits the column, and enters a condenser. After the vapour condenses, the stream enters a reflux drum, where it is split into an overhead product stream, known as the distillate, and a reflux stream that is recycled back to the column [2]. 1.2.1. Advantages of Packed Bed Column  Most cost-efficient distillation column when the diameter of the column is less than 0.6 m.  Because packing can be made from inert materials, packed beds are able to handle corrosive materials [2].  Lower pressure drop than in plate columns.  Good for thermally sensitive liquids Page 4 EKB 2131 – Chemical Engineering Lab - III 1.2.2. Disadvantages of Packed Bed Column  Packing can break during installation, or due to thermal expansion.  Not cost efficient for high liquid flow rates.  Contact efficiencies are decreased when the liquid flow rate is too low [2]. 2. MATERIALS AND METHODS VALVE V1 Feed Supply Valve for Funnel V2 Air Vent Valve of Vessel V3 Water Flow Control Valve V4 Air Vent Valve of Condenser V5 Valve for Distillation Collection V6 Drain Valve of Vessel 2.1 Starting Procedure 1. Methanol water solution is prepared by mixing known amount of water and methanol 2. The total amount of solution is 15L 3. The volume of water and methanol was noted down 4. V1- V6 valves was closed 5. All the switches on the panel were ensured to be at OFF position. 6. The water is filled in the cold water tank 7. The reboiler was filled with methanol water solution by opening the valve V 1 and air vent valve V2 8. Valve V1 and V2 was closed 9. The electricity was connected to the set. 10. The process temperature was set at 90 C. 11. The heater and cooling water pump was started. 12. The cold water flow was adjusted by the rotameter valve to a moderate value. 13. The cyclic temperature was set for total reflux. 14. Wait 25-30 minute for the system to achieve steady state. 15. Samples from the bottom & distillate stream were taken out. 16. The samples were cooled to room temperature and the refractive indices were measured 2.2 Closing Procedure 1. The water supply was stopped when the experiment was over. Page 5 EKB 2131 – Chemical Engineering Lab - III 2. The pump, heater and the main power supply was switched off. 3. Column, reflux drum, receiving tank and water tank were drained. 4. The vessels were drained after the temperature fell down to atmospheric pressure by opening valve V6. 2.3 Formulae used To calculate the moles of methanol in feed M (1) F ρV To calculate the moles of methanol in residue x FxD B ×F (2) x BxD F xF (3) BxB F 1x F αIn (4) B 1x B To calculate the error F xF F 1x F E= - αIn (5) BxB B 1x B To calculate minimum number of plates x D 1x B x B 1x D –1 (6) Nm Inα Figure 1 shows the block diagram of packed bed distillation column. The set-up consists of packed column, which is packed with glass rasching rings. An electrically heated reboiler is installed at the Page 6 EKB 2131 – Chemical Engineering Lab - III bottom of the column. A tank is provided to collect the bottom product. Shell and tube type condenser is provided to condensate the vapour. A tank with pump and rotameter is provided for circulation of cooling water. Reflux drum is provided to collect the condensate. Receiving tank is for collecting the distillate. Drain valves are provided for drainage purpose. Figure 1: Block Diagram of Packed Bed Distillation Column 3. RESULTS AND DISCUSSION From the graph shown in Figure 2 as shown in Appendix, the mole fraction of methanol in feed, F was determined to be 0.38 moles. The mole fraction of methanol of residue B was determined to be 0.25 moles. The mole fraction of methanol of distillate D was to be 0.057. Table 1 shows the readings of refractive index of the sample taken for every 5 min interval. From table 1 it can be seen that the temperature increases as the time increase and decrease at the final time taken. The refractive index changes throughout the experiment. This error could be occurred while taking the readings in decimal places through refractometer as the difference between the consecutive readings are very small. Page 7 EKB 2131 – Chemical Engineering Lab - III Table 1: Refractive index reading Total reflux condition Time T oC R. I 5 85.1 1.3330 10 87.2 1.3348 15 89.6 1.3369 20 90.2 1.3360 25 89.3 1.327 Table 2 shows the theoretical and experimental values of mole fraction of methanol in liquid phase. It can be seen that the values of mole fraction of methanol experimental are higher values than the values of mole fraction in theoretical. This could be due to some errors during the experiment. The error could be while calculating the readings with decimal places to solve the following required variables. Table 2: Theoretical and Experimental values of mole fraction of methanol in liquid phase Time X X the 10 0.0544 0.225 20 0.0558 0.320 30 0.1856 0.662 40 0.1281 0.444 50 0.0369 0.156 60 0.0538 0.215 4. CONCLUSIONS AND RECOMMENDATION The experiment was carried out to study the process of packed bed distillation column. The experiment was conducted under total reflux condition. The error that was calculated is 2.61. The value of minimum plates, Nm that was calculated is 0.84. There is little recommendation that should be considered for this experiment. More readings should be taken to see the steady state of the distillation process. A proper source of light should be provided while taking the readings of refractive index through the refractometer. Page 8 EKB 2131 – Chemical Engineering Lab - III 5. REFERENCES 1. Treybal, R. E. (1981). Mass Transfer Operation. McGraw Hill. 2. http://encyclopedia.che.engin.umich.edu/Pages/SeparationsChemical/DistillationColumns/D istillationColumns.html 3. https://www.scribd.com/doc/219202796/Application-of-Packed-Bed-Column-Distillation- in-Industry APPENDIX Data Relative volatility α 3.32 Molecular weight of methanol MM 32 g/mole Molecular weight of Water MW 18 g/mole Enthalpy of feed HF 0 kJ/kmole Packed height Z 0.90 m Figure 2: R.I vs x Page 9 EKB 2131 – Chemical Engineering Lab - III Table 3: Value of R.I based on theoretical mole fraction of methanol Total Reflux Condition R 1 V 2.5 Litre Tf 90°C R.I F 1.3300 R.I B 1.3356 R.I D 1.327 The property of methanol of methanol (ρ) at temperature T_F from data book: ρV = 782.771 kg/m3 XF = 0.38 XD = 0.057 Page 10 EKB 2131 – Chemical Engineering Lab - III XB = 0.25 M M × 1000 (1) F ρV 782.771 X 15 = 32 x 1000 = 0.37 kmole x FxD B ×F (2) x BxD 0.380.057 = ×0.37 0.2500.057 = 0.619 k.mole F xF (3) BxB 0.37 × 0.37 = In [ 0.040× 0.240 ] = 10.33 F 1x F αIn (4) B 1x B 0.37 10.036 =3.32 In 0.04010.240 = 8.17 F xF F 1x E= BxB - αIn B 1x F (5) B = 10.33 -8.17 Page 11 EKB 2131 – Chemical Engineering Lab - III = 2.16 x D 1x B x B 1x D –1 (6) Nm Inα 0.056 10.240 = 0.240 10.056 -1 3.32 = 0.84 Page 12 EKB 2131 – Chemical Engineering Lab - III Page 13