In this study, we characterized a batch distillation column to determine the optimal operating conditions for the extraction of a valuable dye from a binary ethanol-water mixture. We tested the column at varying charge compositions and heat input values to determine the most effective and economical column conditions. We measured the composition of the liquid on each tray and used a refractometer to correlate ethanol composition with the refractive index of each sample. Using this composition data, we calculated the Murphree stage efficiency and overall column efficiency using the McCabe-Thiele graphical method. We generated McCabe-Thiele diagrams for each trial using MathWork's MATLAB software. We also measured the temperature profile of the trays to establish the effect of the different heating values and the overall heat loss from the column.
We found that the column operated most effectively when 0.8 kW was applied to the reboiler vessel. For tests conducted at total reflux, the column was more efficient at lower reboiler compositions, and the column achieved a higher overall separation for higher reboiler compositions, due to the equilibrium behavior at higher compositions of ethanol. Individual tray efficiencies tended to decrease as the tray number increased and the vapor moved up the column. Considering the downward trend of the individual tray efficiencies as the stage number increased, the main source of inefficiency was heat loss from the column.
[...] Chemical Engineering Science 1985;40(11):2087- Wankat PC. Separation process engineering. Pearson Education; Dong, Jin-Quan; Lin, Rui-Sen; Yen, Wen-Hsing. Canadian Journal of Chemistry vol p Vitvitskii, A. I. Russian Journal of Applied Chemistry vol p - 508 Zhurnal Prikladnoi Khimii (Sankt-Peterburg, Russian Federation) vol p VLE-Calc: Calculator of vapor-liquid and liquid-liquid phase equilibria [Internet]. [updated 2013 Oct 19; cited 11 November 11]. Available from: http://vle-calc.com/index.html. APPENDIX Ethanol Refraction Index Standard Curve Figure 12: Ethanol refraction index standard curve. [...]
[...] Murphree liquid and vapor efficiencies for each tray and overall efficiency of the column for each trial. APPENDIX Sample Calculations Calculation of mole fraction from net refractive index Calculation of mole fraction from net refractive index: Where k is the mass fraction of the diluted sample, z is the net refractive index, and q is the slope of the linear range of the sample. Seeing that Where a is the mass of ethanol in the sample, b is the original mass of water in the undiluted sample, and c is the mass of dilution water. [...]
[...] We charged the column with approximately 16 L of ethanol-water mixture for both tests. Selecting a Binary Mixture A benzene-toluene mixture would have provided a near-ideal mixture, which would have been the best to characterize the column. However, we avoided using a benzene-toluene mixture because of the health and safety risks associated with both compounds. Instead, we chose between a methanol-water mixture, a 1-propanol-water mixture, and an ethanol-water mixture. Of the three remaining choices, ethanol was the least toxic and provided the best choice for a model system, although it forms an azeotrope at high concentrations. [...]
[...] greater amount of distillate). Table of Contents Abstract 2 Definition of Symbols 4 Introduction 5 Background 5 Experimental Methods 13 Results 16 Discussion 23 Conclusions and Recommendations 25 Literature Cited 27 APPENDIX Ethanol Refraction Index Standard Curve 29 APPENDIX MATLAB Code 30 APPENDIX McCabe-Thiele Diagrams 34 APPENDIX Murphree and Overall Efficiency Data/Graphs 37 APPENDIX Detailed Apparatus Diagrams 39 APPENDIX Sample Calculations 41 APPENDIX Laboratory Notes 45 Definition of Symbols Introduction The purpose of this study was to characterize a pilot scale batch distillation column discovered on a property recently acquired by WasteNot Chemicals to separate solvent mixtures containing dyes. [...]
[...] [Equation The hydrodynamic flow properties, mass transfer rate, and the column size affect the overall efficiency. When the column is operating at total reflux, the overall efficiency should ideally be close to one because these conditions will produce the highest separation with the fewest number of required stages. The Murphree liquid efficiency is the actual change in mole fraction divided by the change for an equilibrium stage (Equation [Equation Where is the liquid mole fraction in equilibrium with actual vapor mole fraction . [...]
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