Modeling and Optimization of Simultaneous Waste Heat Utilization and Wastewater Treatment Processes

Abstract

Huge amounts of low-temperature waste heat, which can be utilized to improve the energy efficiency in various ways, are available in the process industries. Organic Rankine Cycle (ORC) is one of the promising technologies to convert low-temperature waste heat into electricity. Other than waste heat, wastewater is abundant in the process industries. The treatment of wastewater is a crucial problem in industry. Reverse Osmosis (RO) membrane desalination is an option for wastewater treatment. In this study, an integrated system for simultaneous waste heat utilization and wastewater treatment is proposed and optimized. An ORC is adopted to recover waste heat and then the electricity (or mechanical energy) generated by the ORC is used to drive the RO membrane desalination process. The waste heat comes from a complex chemical process. Hot water as an intermedium recovers waste heat in the chemical process and then releases heat to the organic working fluid in an ORC. A two-stage desalination process is integrated with the background chemical process. The integration model involves a heat integration model, an ORC model and a RO desalination model that interact with each other. The optimal design of the integrated process can be derived based on the proposed mathematical model.