Experimental study on the effect of direct co-firing salix psammophila pellets in a 660MW coal-fired power plant

YANG Fuxin; ZHAO Xu; TAN Houzhang; WANG Xuebin

doi:10.13225/j.cnki.jccs.2024.1169

Abstract：Biomass is considered as a zero-carbon,renewable energy source.Co-firing biomass fuels in large-scale power plants not only enables the highly efficient large-scale utilization of biomass energy but also significantly reduces CO2 emissions.In this study,a co-firing experiment was conducted using salix psammophila biomass pellets in a 660 MW ultra-low emission coal-fired power plant,utilizing the existing pulverization and combustion systems of the power plant.Two combustion modes were proposed:"single mill and single burning",where biomass was pulverized separately,and"single mill and mixed burning",where coal and biomass were co-pulverized.The study analyzed the effects of co-firing biomass on the operation of coal mills,combustion characteristics of the plant,boiler thermal efficiency,pollutant emissions,and the characteristics of fly ash.The results indicate that the biomass pellet co-firing can be achieved using the existing pul-verization and combustion equipment.In the"single mill and single burning"mode,a biomass feed rate of 15 t/h to 20 t/h is recommended,while a biomass co-firing ratio of 3％to 5％is optimal for the"single milling and mixed burning"mode.The HP coal mill demonstrates good adaptability to biomass pellets,and meets the operational requirements.The operat-ing current of mill is lower when the biomass is milled alone or with coal.During the testing,the burners operate stably,with no premature ignition or slagging observed.When co-firing,the furnace temperature decreases slightly by about 15 ℃ to 32 ℃,while the temperature of flue gas at air preheater inlet shows little change.The thermal efficiency of boiler re-mains in the range of 92.83％to 93.93％,nearly equivalent to the thermal efficiency under pure coal conditions.The burnout performance of boiler is satisfactory when co-firing,with minimal impact on thermal efficiency.Oxygen content is identified as a key factor influencing NOx formation.By adjusting the air supply parameters,co-firing biomass can re-duce the formation of NOx.The fly ash produced under various conditions with"single mill and single burning"meets the strength activity index requirements,with values exceeding 70％,and fulfill the standards for building materials.