Liquid-Liquid and Vapor-Liquid Equilibrium for the Design of Extraction and Distillation Columns

Abstract

Liquid-Liquid extraction is a separating unit operation process which is well known and well investigated, however, the equilibrium data For mutual solubility and tie lines are difficult to correlate and be applied. Many workers including Othmer and Tobias, Ishida, and Hand introduced methods that predict Liquid-Liquid tie-line data, but the mutual solubility data is still plotted on binodal curve on equilateral triangle. The construction of the tie –line on the binodal curve to determine the number of theoretical stages, has to be made graphically using the relevant correlations. This requires experimental determination of the mutual solubility and tie-line data.Treybal even prior to Hand and other workers introduced a method of construction without using tie-lines data of binodal curves to determine the number of theoretical stages. This method is investigated and proved to be correct, rapid and does not require experimental determination of tie-line data. Treybal method is used in the present work and proved to be accurate and easy to apply. The number of stages is determined using this method and all other design parameters of a sieve tray extraction column are obtained. A complete design by hand calculation procedure is realized and Outlined. The number of theoretical stages is calculated using ASPEN PLUS SOFT WARE and it is found to be in agreement with the method investigated in this thesis. This work also investigates the preparation of the data required to design a distillation column .It is known from the literature and practice that distillation is well known and well investigated ,However, different techniques have been used to determine the design parameters. These include the minimum reflux ratio, the actua reflux ratio, the number of theoretical stages, the number of actual stages, the feed stage location, ,the flooding velocity,the liquid-vapor flow factor,the maximum volumetric flow rate,the net area,the active area ,the hole area,the weir length,the entertainment,the weeping,the weir crest and actual minimum vapor velocity are lastly determined. The design of adistillation column requires experimental determination and correlation of equilibrium data. The equilibrium data and component balance are used to calculate the number of theoretical stages and consequently the other design parameters. An adequate literature is cited covering the activity coefficient models such as NRTL, UNIOUAC and UNIFAC. Data obtained by these methods are used to design a distillation using ASPEN PLUS SOFTWARE .The design is also made through hand calculations and found to be asatisfactory agreement with ASPEN PLUS SOFTWARE result .Acomplete procedure by hand calculations for designing extraction and distillation columns .