Simulation study on seasonal recovery of waste heat and water resources in flue gas and slurry after WFGD

Efficient utilization of low-grade waste heat is pivotal for advancing energy savings and emissions reduction in power stations. However, the heat and water contained in flue gas and slurry post wet flue gas desulfurization (WFGD) have traditionally been underutilized. The flash-heat pump-heat exchanger (FHH) system and heat exchanger-heat pump (HH) system were proposed, employing heat exchangers (HE), flash column (FC), and absorption heat pumps (AHP) to utilize waste heat for seasonal heating and air heating purposes. A comprehensive evaluation of the systems was conducted, encompassing thermal performance, exergy analysis, economics, and environmental impact. The study revealed that the improved systems were more energy-efficient and environmentally friendly than before. The HH system recovered more low-temperature waste heat than the FHH system by 16.15–25.75 MW, and provided a shorter payback period of 2.37 years. The addition of FC and HE to WFGD improved exergy efficiency by 40 %. Both the FHH and HH systems achieved notable coal savings, with improvements ranging from 36 % to 37 % and 45–49 %, respectively, over the original system. Water of 14.18–38.9 t·h⁻¹ and 362 t·h⁻¹ were recovered through HE and FH, respectively. Overall, the improved systems provide guidance for the effective utilization of low temperature waste heat and in power plants.