Optimal Synthesis of Property-Based Wastewater Network with Multiple Regenerators in Coal-Based Chemical Plants

Abstract

Coal-based chemical industries usually generate wastewater containing various compositions and high concentration of pollutants. This causes more intensely environmental and social concerns compared with other process industries like oil refineries. This work addresses the synthesis and optimization of superstructure-based multi-contaminant wastewater network with the consideration of reuse, recycle, and regeneration of wastewater streams in coal-based chemical plants. This wastewater network is formulated as multiple unit-specific shortcut models of wastewater regenerators including electrocoagulation, biodegradation, and reverse osmosis in place of conventional regeneration models with fixed outlet concentration (or contaminant removal ratio) to describe the mass transfer and cost functions. The physical and chemical properties (such as pH, temperature, and the concentrations of phenols and sodium chloride in the wastewater) are taken into account in the proposed wastewater network. A disjunctive programming formulation is developed to address the influences of wastewater compositions and treatment technologies on the costs for wastewater management system, freshwater consumption, and wastewater network design. The effectiveness and feasibility of the proposed model is demonstrated in two case studies of practical coal-based chemical industry.