Multi-objective optimization of chemical process plant layout considering economy and inherent safety

Economy and safety are important factors for the layout design of chemical process plants. However, safety factors are often translated into economic indicators as a part of the objective function for layout optimization in previous studies. This may result in safety performance of chemical process plants does not meet the actual production requirements. In this paper, a multi-objective optimization method for chemical process plant layout is proposed to obtain series of solutions that can achieve the trade-off between economy and safety. The economic objective function is characterized by the total capital cost, including land cost, pipe cost, protection device cost and expected property loss from accidents. The safety objective function involves inherent safety which is evaluated by the Comprehensive Inherent Safety Index (CISI). The proposed multi-objective optimization model solved by non-dominated sorting genetic algorithm II (NSGA-II) is applied for layout optimization of an acrylic acid production plant. The results show a strong trade-off between competing economic and safety objectives according to the Pareto curve. The optimal solution ranges from 236,099 $ to 379,622 $ for total cost, corresponding to 87.7-132 for CISI. Safety will be improved significantly in the low-safety layout scheme when the capital investment increases slightly.