Simultaneous water and energy conservation in non-isothermal processes – A case study of thermal power plant

Abstract

A modified methodology is proposed for simultaneous water and energy conservation in non-isothermal system. It consists of two major steps i.e. to design water allocation network and then to generate water allocated heat exchanger network. In the present study, the modified approach for non-isothermal system is illustrated through an example and results are validated with that of published work. It is observed that the minimum freshwater requirement and wastewater generation is independent of change in inlet and outlet temperatures of the process. Further, the approach is used to conserve simultaneous water and energy in thermal power plant where multiple contaminants i.e. TDS and TSS are available. The results indicate savings in freshwater by 5.15% and reduction in wastewater by 21.55%. Water allocated heat exchanger network (WAHEN) of multi-contaminant case of thermal power plant is investigated and modified based on actual process constraints. In the modified WAHEN, there is no requirement of heater or cooler; however, one heat exchanger is required in power plant. The economic analysis also indicates that this modification requires significantly less payback period as compared to value reported in the literature. Thus, the modified methodology accounts process constraints of the plant easily, if required.