PROCESS SYNTHESIS OF MULTI-COMPONENT DISTILLATION COLUMNS

Abstract

This dissertation presents a theoretical investigation on process synthesis of various sequential arrangements for the separation of multi-component mixtures and the selection of an optimal configuration based on duties of condenser and reboiler in various columns of the arrangement and also its efficiency. Two types of problems of 5-component and 3-component mixtures have been considered in this investigation. Both of them have specified compositions of feed mixture and requirement of 98.5% purity of each component as product. Using various heuristic rules developed by several investigators, the number of possible sequential arrangements has been reduced to six and three for a 5-component and a 3-component mixture, respectively. RADFRAC model of ASPEN PLUS software has been employed for the separation of above two mixtures. As a result, number of equilibrium stages, temperature and composition of each component on each stage of each column of the sequential arrangement and condenser and reboiler duties have been determined. The results of a'sequential arrangement have been compared with that of Shah & Kokossis [33] who have solved the above 5-component mixture problem by using HYSIS software. The agreement between the two has been satisfactory. Thus the method employed for the analysis has been validated. As a result of data analysis it had been found that sequential arrangement which involves the separation of more volatile component in the beginning requires least amount of condenser and reboiler duties. Naturally such an arrangement has to be preferred. In fact this is in confirmation to an already existing heuristic rule. Based on the duties of condenser and reboiler of various sequential arrangements, optimal configurations for the separation of 5-component and 3-component mixtures have been selected.