Technical-economic-environmental analysis of biomass direct and indirect co-firing in pulverized coal boiler in China

An analysis was conducted on two integrated models involving direct co-firing and pyrolysis co-firing systems within a typical 600 MW coal-fired power generation plant. The study assessed the performance of various biomass sources (sawdust, corn straw, and rice husk) using distinct co-firing ratios (5%, 10%, 15%, 20%) across technological, environmental, and economic dimensions. The findings revealed that in terms of thermal and exergy efficiency, the pyrolysis co-firing approach exhibited lower results compared to direct co-firing. Notably, among the biomasses tested, sawdust demonstrated the least impact on boiler efficiency. The CO2 emission was estimated by the Life Cycle Assessment method. The emission of the conventional boiler, along with direct and pyrolysis co-firing of corn straw at a 20% ratio, resulted in CO2 emissions of 1.075 kg, 0.954 kg, and 0.942 kg per 1kWh of electricity, respectively. The different feeding methods were also discussed, providing technically and economically rational options for coal-fired power plants. The economic feasibility of both co-firing systems was also proposed. At carbon tax rates of 410 CNY/t and 464 CNY/t for the direct co-firing and pyrolysis co-firing models respectively, the operational cost of the co-firing systems becomes comparable to that of a coal-fired boiler. However, when the by-product price exceeds 3700 CNY/t, the pyrolysis co-firing model becomes the more economically favorable option. This study primarily concentrates on investigating the real-world application and effective utilization of biomass co-firing systems within the specific framework of China's energy scenario.