Study On Direct Thermal Integration In Neibor Processes Tudy On Direct Thermal Integration In Neighbor Processes Study Of Direct Thermal Integration Between Neighbour Processes

Processes Industrial plants are usually made up of several sets of units.Due to the different characteristics of the processes,the heat balance between the different units is different.Some units have the excess heat,while others are lack of heat.When isolated with the energy system,it will inevitably lead to low energy efficiency,cooling load,high-level utility consumption.So it's necessary to implement heat integration between the heat-lacking units and heat-source units.In this paper,a thermal integration problem between a set of heat-lacking unit and heat-source units which are adjacent and synchronous with the heat-lacking operation.The main research work is as follows:?1?Analyze the actual direct thermal integration case in the refinery,and propose the engineering characteristics of the direct thermal integration.The thermodynamic target of the direct thermal integration is summarized by the T-H diagram and the ?-H diagram of the heat transfer process.The first one is highest temperature in heat transfer process(t_c2,max).the second one is the maximum effective energy harvest(S_2,max).The concept of excess temperature(t_i,j)is proposed.And a superstructure flow of direct thermal integration is established,which provides a basis for subsequent studies.?2?Based on the assumption: 1)Only the external thermal flow above the heat pinch temperature of the heat-lacking unit can participate in the heat integration.And the minimum heat transfer temperature difference and the cold utility works are unchanged;2)The combined hot streams don't split and only have one chance to transfer its heat.A direct heat integration model?MILP?with the goal of minimizing the hot utility consumption is constructed.Genetic algorithm?GA?is applied to solve the problem and determin the optimal intermediate temperature(t_i,j,opt).And the thermodynamic and engineering constraint evaluation methods are proposed in view of the multi-solution characteristics of the problem.?3?On the basis of the above MILP model,the direct thermal integration model?MIN LP?with the goal of minimizing the hot utility consumption and the exergy loss during the process is constructed.The non-dominated sorting genetic algorithm?NSGA-II?based on elite strategy to obtain the Pareto optimal solution frontier is applied to solve the problem.?4?A direct heat interation problem of a heat-lacking unit is studied.The hot streams are divided into three cases.The single-objective optimization MILP model and the multi-objective optimization MIN LP model are used to calculate the optimal intermediate temperature(t_i,j,opt)of the hot streams.And the two models are proved feasible which can be applied to guide the program design.