Multi-objective Optimization Of FCCU Absorption-stabilization System

In practical chemical process, we not only want to increase the yield of products, but also hope to reduce energy cost and pollution, this is a multi-objective optimization problem. For multi-objective optimization problems, there are not absolute optimal solutions but a serious of solutions which could not be compared with simply, these solutions are called none-dominated solutions or Pareto optimal solution. At present, process simulation software, such as PRO/Ⅱ, Aspen Plus, only has single-objective optimization. So multi-objective optimization has become very important.In this paper, the combination of the optimization software, modeFRONTIER, and the chemical process simulator PRO/II is used to simulate absorption-stabilization system. The Pareto curve and optimal point are obtained, which is helpful for the operation of absorption-stabilization system. It is of great importance for getting the engineers out of many trivial individual processes, saving simulation time, improving work efficiency and reducing production cost.Interface is set up between modeFRONTIER and PRO/Ⅱby programming. PRO/Ⅱis to simulate the process as a simulator, interface is responsible for transferring the date between the process simulator and multi-objective algorithm. Based on the report of the simulator PRO/Ⅱ, multi-objective optimization modeFRONTIER calculates the fitness and updates the population, the new population then modifies input document of PRO/Ⅱ. The circulation does not end until fitting for the settings. Thus multi-objective optimization and process simulation can work together, it will serve the actual engineering better.Based on the multi-objective optimization model established, MOGAⅡis adopted to optimize the quality of products and energy consumption of absorption-stabilization system. Pareto optimal solutions are founded, compared with practical operation, we find that practical operation is not optimal, and we can get better dry gas quality(molar content≥C3 in dry gas) using the same energy. A bi-objective optimization study is also performed involving the profit and energy cost of absorption-stabilization system. After optimization, the results are obviously better than practical operation in the factory.In this paper, the method used is applicable not only to optimize absorption-stabilization system, but can be applied to other arbitrary chemical process optimization. For China's chemical industry, This has important practical and strategic significance to improve economic efficiency and reduce energy consumption, to reduce pollution and to reduce the gap between our country and foreign advanced countries.