Economic and Environmental Criteria and Trade-Offs for Recovery Processes

Volatile organic component (VOC) and solvent recovery processes are two industrially important processes to limit the release of potentially harmful components into the environment. The extent of environmental contamination depends on the recovery system used for the harmful components, which indirectly contributes to the cost of process. Recently, VOC and solvent recovery systems have been optimized for multiple economic and environmental criteria such as profit before tax (PBT), net present worth (NPW), and potential environmental impact (PEI). Besides PEI, there are other aggregate environmental indicators such as IMPact Assessment of Chemical Toxics 2002+ (IMPACT), green degree (GD), and inherent environmental toxicity hazard (IETH). In this study, we consider the optimization of VOC and solvent recovery processes for PBT, NPW, PEI, IETH, GD, and IMPACT as well as their individual components as simultaneous objectives, to explore the trade-offs among them. The two processes are simulated using a commercial simulator, and then optimized using the elitist nondominated sorting genetic algorithm in a spreadsheet along with an interface to the simulator. From the results, it can be concluded that optimization of aggregated IMPACT indicator is similar to optimization of its individual end-point damage categories. In the case of other environmental indicators, optimization for individual categories may be necessary to explore trade-offs among them.