Optimizing Wastewater Heat Recovery Systems in Textile Dyeing Processes Using Pinch Analysis

Textile manufacturing discharges plenty of wastewater that contains large amounts of thermal energy. In particular, the textile dyeing process consists of several and complex processes, and each process has a different operating time, temperature, and water usage. A large amount of energy is consumed for heating fresh water and cooling wastewater owing to the absence of a suitable wastewater heat recovery (WWHR) system in the textile dyeing process. Therefore, recovering wastewater while satisfying the operating conditions of each process is crucial. Herein, we suggest an optimal design of WWHR systems to maximize the energy efficiency in the textile dyeing process using pinch analysis. A novel two-step approach was used to design an optimum WWHR system in which the WWHR was maximized. First, after defining the scenarios for all feasible WWHR methods, the WWHR systems were designed accordingly by integrating the heat pump and the heat exchanger. Second, the heat exchanger network of the developed WWHR systems was modified based on pinch analysis to maximize the waste-heat recovery efficiency. Finally, to derive the cost-optimal WWHR system, a techno-economic analysis was conducted for the modified systems. The total annualized cost (TAC), based on the capital cost and operating cost, was determined based on both the current and potential future economies. Thus, TAC was reduced by 41.82 %, and the economic efficiency of the proposed energy-saving measures demonstrated a payback period of up to 8.73 months