Research On Solving Method Of Many-objective Optimization Problems For Heat Exchanger Networks

The heat exchanger network is an important part in the process industry system,and it is the key subsystem of energy recycling.The rationality of its design directly determines the reliability,efficiency and economy of high energy-consuming process industries such as energy power and petrochemical industry.For the rapid development of today’s society,the original heat exchanger networks can not meet the high standards and high requirements of existing energy recycling.However,these heat exchanger networks still have great energy saving potential after optimization and retrofitting.Therefore,optimizing and retrofit of the heat exchanger network is an important measure to reduce system energy consumption and improve system reliability and economy.The optimization and retrofit method for existing heat exchanger network usually use economic objects such as utility costs and annualized total costs as optimization indicators.However,the loss of product profits brought by modification and the environmental impact of the retrofitted system are not considered.For practical industrial systems,the research of multi-objective optimization problems has high value for engineering application,but the common evolutionary optimization algorithms(based on Pareto dominant relationship to select population individuals)are getting worse and worse with the increase of the objective function.Therefore,this paper proposes a solving method with many-objective optimization problem for heat exchanger networks.For this study,the following works are mainly carried out:1.Considering the high product profit loss caused by system shutdown and the feasibility of the retrofit,this paper quantifies the retrofit engineering quantity and uses it as an optimization indicator;and the composition of environmental impact of the heat exchanger network before and after the retrofit is analyzed.The objective function,the minimum environmental impact,is established.2.The MINLP model of the stage-wise superstructure with non-isothermal mixed is set up with the objective functions of capital cost,utility,environmental impact and retrofit engineering quantity.The systematic solution strategy and calculation method are proposed.The model established above is solved by NSGA-III,and the heat exchanger network structure and specific parameters are obtained.3.Applying the mathematical model and solution strategy established above,the many-objective optimization problems of the original heat exchanger networks are carried out,and the retrofit results are compared and analyzed.The effectiveness and superiority of the proposed method are verified.