Analysis and interaction of exergy, environmental and economic in multi-objective optimization of BTX process based on evolutionary algorithm

In this paper sustainability analysis (exergy, environmental and economic) and multi-objective optimization for an aromatic plant are provided and interactions between decision variables are discussed. Environmental evaluation shows that the cancer human toxicity and global warming are the most important environmental concerns and the weight of EIs (environmental impacts) are mainly due to process wastes. The optimizations results demonstrate parameters like reactor temperature have a wide range in the optimizations while some variables, such as extraction unit variables have the same value. Utility EI reduction occurred in economic and exergy optimizations rather than environmental optimization so if the environmental concerns of the plant are due to utility consumption, exergy and economic optimizations reduce EI and there is no need for an explicit environmental optimization. While whenever the environmental concerns correspond to process waste, process optimization should be done based on EI itself. Furthermore multi-objective optimizations are carried out and the objectives trade-offs are illustrated through Pareto curves in four scenarios. In the proposed green scenario 3.8% of plant's EI decreases while annual cost rises up to 2%. In the proposed economic scenario annual cost reduces by 3.6% however plant's EI deteriorates up to 13.7%. (C) 2013 Elsevier Ltd. All rights reserved.