ENERGY CONSERVATION IN SEPARATION SYSTEMS

Abstract

This thesis brings out a theoretical investigation on Energy Conservation in Distillation by considering two methods of energy conservation; namely, feed optimization and the use of heat ' pump with conventional columns. Using the conventional McCabe Thiele procedure for determining minimum ref lux ratio, total consumption of utilities (cooling water in condenser and steam in reboiler) has been related to feed quality. It has been found that thermal condition of feed has a marked effect upon total cost of utilities. The total utility cost has been optimized with respect to feed quality to determine the optimal value of feed quality for the seperation of a mixture of benzene-toluene of a given initial feed compOsition and distillate/feed ratio. Low pressure steam which is generally cheaper than process steam has been used as a supplement to process steam in feed .preheater to reduce the total cost of utilities in the plant. Application of feed preheater has necessitated the use of feed of poorer quality in the column than that used in the case without preheater. ii However, it also depends upon initial feed composition and distillate/feed ratio for a given system. Use of heat pump as a method of energy conservation has been described by replacing condenser with a vapor compression unit and using compressed vapor as heating medium in reboiler. Temperature difference in reboiler has been found to play an important role to affect the costs of reboiler and compressor. The total annual cost of column coupled with heat pump has been compared with that of conventional column for the separation of propane-propylene system to determine the range of applicability of heat pump in distillation. The present analysis has been extended to futuristic of fixed- and operating- costs by properly accounting inflation in them.