Modeling of suspended pyroelectric particles in wastewater for dye decomposition driven by low-grade waste heat in tubular heat exchanger

Pyroelectric dye decomposition is a potential technology to convert low-grade waste heat into oxidation charges for the removal of pollutants in wastewaters. Herein, a tubular heat exchanger was utilized to transfer the heat energy from hot water to the dye wastewater with suspended pyroelectric particles for dye decomposition. A CFD model integrated pyroelectric kinetics was firstly established to simulate the heat transfer and dye degradation of dye wastewaters. The effects of the flow rate of the dye wastewater q v,c (0.5 – 16 L/h), the flow rate of hot water q v,h (1 – 16 L/h), and the inlet temperature of the hot water T in,h (35 – 80°C) on the heat recovery Q and the dye degradation rate R of the tubular heat exchanger have been investigated. Moreover, the mass of indigo carmine (IC) degradation per heat transfer power η wQ has been investigated to analyze the energy efficiency of the pyroelectric dye degradation process. Comprehensive consideration the dye removal η , the depth of heat recovery of the hot water η T , and the heat recovery Q , the optimal R of IC solution (2.93 g·h -1 ) was appeared at the q v,h of 4 L/h and the q v,c of 8 L/h, while the η T was 74.4% at the T in,h of 80°C.