Development of a direct contact heat exchanger for energy and water recovery from humid flue gas

•On site research and development of packed tower after WFGD system.•In-situ measurement on the temperature of high humidity flue gas.•Optimized design of packed tower as a direct contact heat exchanger.•The packed tower has small resistance and high heat transfer coefficient. A large amount of water and energy can be recovered in the flue gas after wet desulfurization. In order to explore the performance of the packed tower as a direct contact heat exchanger between flue gas and water, we measured the resistance and temperature field distribution of packed tower through on site pilot scale experiments, filled the gap in previous studies that lacked field trials and high humidity flue gas temperature data. The experimental results show that using packed tower as the heat exchanger can achieve low resistance and high heat exchange efficiency, indicating that packed tower is suitable for cooling the flue gas after wet desulfurization to achieve the purpose of energy and water recovery. The research results can guide the design and operation of the packed tower, liquid to gas ratio of 4.0 L/Nm3 and packing layer thickness of 1.20 m are optimal design parameters for packed tower. The selection of packing type and gas velocity, and the adjustment of operating parameters under variable load conditions can also refer to the experimental data in this article.