Comprehensive energy, exergy, economic and environmental assessment of integrating waste tire pyrolysis with supercritical coal-fired power plants

To enhance the operational flexibility of coal-fired power plants (CFPPs) under increasing penetration of variable renewable energy, waste tire pyrolysis is investigated as an auxiliary pathway to stabilize combustion during low-load operation while enabling solid waste valorization. In this study, four integration schemes coupling waste tire pyrolysis with a 600 MW supercritical CFPP are proposed and systematically evaluated, including electrical heating, flue gas heating, steam extraction heating, and partial pyrolysis gas combustion heating. A comprehensive assessment framework integrating energy, exergy, techno-economic, and environmental analyses is developed to quantify system performance under varying load conditions. The results indicate that the pyrolysis gas combustion heating system achieves the highest energy and exergy efficiencies, reaching 42.83% and 41.78% respectively, mainly due to the efficient internal energy circulation that avoids high-grade steam extraction and electrical pyrolysis heating. This pathway also exhibits the most favorable economic performance, reducing the levelized cost of electricity (LCOE) by 3.26-6.09% compared with the baseline system, while decreasing the specific coal consumption rate by 5.88-18.33% under different load conditions. Economic sensitivity analysis further indicates that the LCOE is most sensitive to coal price, annual operating time, and boiler capital cost, whereas waste tire price and pyrolysis system capital cost have relatively limited impacts. Environmentally, this integration system achieves the lowest GWP among the systems investigated, ranging from 252.20 to 721.53 kg CO2-eq/MWh across different load conditions. The proposed integration systems can improve low-load fuel utilization and reduce specific coal consumption, thereby providing a potential pathway for low-load operation of CFPPs.