Process Optimization Strategies
Many authors have taken an interest in the design of chemical processes as they became conscious about the environment and numerous methodologies have been proposed (Cano-Ruiz and McRae 1999). An important conclusion of their review is that the adoption of a strategy that considers aggressions against the environment as a design objective and not simply as a constraint on the operations allows us to imagine alternative processes that are effi cient both at the economic and environmental levels. Firstly, system optimization was expanded to incorporate environmental objectives such as the minimization of waste and pollutant emissions (SO2, NOx, COVs …). However, the drawback of these techniques is that they are concentrated on emissions coming only from the plant, without considering other aspects of the life cycle, so that it is then possible to reduce plant emissions together with the increase of environmental impact. Among the most general methods, life cycle assessment (Azapagic 1999; Heijungs and Suh 2002) plays an important role and is the most cited as a multi-attribute interdisciplinary analysis. As a tool to support decisions at the environmental level, its use must be combined with social, political, economic and technical considerations. From the point of view of optimization, multi-objective optimization (Miettinen 1999) seems unavoidable.