Construction and energy-consumption analysis of a carbon capture heating system based on waste heat utilization in a coal-fired power plant

Conventionally, the heat of the reboiler in monoethanolamine (MEA)-based post-combustion CO 2 capture (PCC) system is supplied by intermediate-pressure extraction steam which temperature is higher than the needed, causing energy losses and capture cost increases. This study develops a staged, synergistic heat-supply scheme for a 600 MW unit, featuring exhaust-steam dominance, flue-gas-heat compensation and minimal extraction steam as backup. Low-pressure exhaust-steam heat is upgraded by a compression heat pump and converted to reboiler via flashing, while the waste heat of tail-end flue-gas is recovered through a closed-cycle water loop and delivered to the reboiler via water-water heat exchange and flashing; the extraction steam is introduced only to minimally close the heat balance when waste heat is insufficient. A coupled unit-PCC model is established in Ebsilon and Aspen Plus, and steady-state simulations are performed at 100%/75%/60%/50%/40% THA, followed by improved grey wolf optimizer (IGWO) optimization with the levelized cost of CO 2 capture (LCOC) as the objective. At 0.01 MPa back pressure, the proposed waste-heat strategy reduces LCOC by 19.96%, 13.57%, 11.59%, 9.64% and 6.63% across the five THA conditions relative to the benchmark, while increasing the overall energy utilization rate by 11.4% on average. At 100% THA, the waste heat utilization rate remains 92%-94% and the specific capture energy decreases from 3.20 to 3.06 GJ·tCO 2 −1 . The results demonstrate that the proposed staged framework enables effective substitution of high-grade extraction steam by in-plant low-grade waste heat over a wide load range, providing a practical pathway for cost-effective decarbonization retrofits of coal-fired units.