Research on CCUS-molten salt TES-microalgal carbon fixation coupling and circular development pathways in thermal power sector

Under the synergistic policy framework of carbon peaking， carbon neutrality and the circular economy， existing carbon capture， utilization and storage （CCUS） projects in coal-fired power plants （CFPPs） continue to face significant challenges， including high regeneration energy demand， reliance on turbine steam extraction， limited carbon utilization pathways， poor economic viability and difficulties in by-product management. To address these limitations， this study proposed an integrated low-carbon retrofitting strategy that couples molten-salt thermal energy storage （TES） and microalgal carbon fixation systems with existing CCUS facilities under minimal plant modification. A closed-loop carbon and energy utilization framework was established， integrating waste heat recovery， primary CO₂ capture， secondary biological carbon fixation and biomass fuel recycling. The proposed system operates through a gradient synergistic mechanism： （i） recovered waste heat is stored in a molten-salt TES unit to provide regeneration energy， thereby replacing conventional steam extraction； （ii） CO₂ is initially captured by the CCUS process； （iii） residual CO₂ is further utilized by microalgae for deep carbon fixation； and （iv） the harvested algal sludge is converted into biomass fuel for co-firing within the power plant， completing the carbon recycling loop. The technical architecture， coupling mechanisms， scenario-specific implementation pathways and operational risk control strategies were systematically evaluated. The results indicate that the integrated system can reduce energy consumption by approximately 30% to 40% per unit of CO₂ captured， increase the overall carbon fixation efficiency by 15% to 20%， and shorten the investment payback period to less than five years. Furthermore， the proposed framework enables the transformation of conventional coal-fired power plants from single-purpose energy producers into multifunctional circular systems integrating energy generation， carbon cycling and resource recovery. Owing to the technological maturity of its constituent components， strong adaptability to different plant capacities and geographical conditions， and a clear deployment roadmap from pilot demonstration to large-scale implementation， this integrated solution provides a practical， replicable and scalable pathway for the low-carbon and circular transition of China's thermal power sector.