Synthesis Of Heat Exchanger Network Based On Life Cycle Energy Saving

Heat exchanger network is very important for energy recovery and saving in the petrochemical industry.A heat exchanger network consists of many heat exchangers.During the operation life cycle of the heat exchanger network,fouling of the heat exchanger will get more and more serious.Moreover,the fouling resistance will keep increasing.Thus,the heat transfer coefficient will continue to decrease,and the heat transfer performance of the heat exchanger network will gradually decline.In order to avoid effects of heat exchanger fouling,many scholars from different perspectives proposed different solutions to obtain an optimal heat exchanger network,such as the margin design,design and analysis of flexibility and resiliency,and multiple periods optimization etc..However,these methods usually aim to meet the operating requests as the fouling of the heat exchanger becomes worst,which is the optimization at the end of the life cycle.However,the fouling itself is slow time-varying and long-periodic,so that the resulting optimized heat exchanger network can not achieve a energy-saving effect during the whole life cycle.To solve the above problems,this paper presents a method based on a dynamic mathematical model of fouling,building a mathematical expression of cumulative total cost of the heat exchanger network in whole life cycle,and analyzing the relationship between life cycle cumulative total cost and the heat exchanger network's cost,and its affects on the continuous energy saving.The objective function is the minimum cumulative total cost,and the life cycle running time is divided into several intervals to simple the optimization.Then,the margin design of heat exchanger network is proposed.Based on dynamic simulation of the heat exchanger network,to minimize the cumulative total cost,an optimization method for margin design of the heat exchanger network is studied.By building a superstructure model of the heat exchanger network,the heat exchanger network is synthesized and optimized to save system energy continuously.