Optimization of preparation parameters of biomass briquette and emission characteristics of combustion pollutants

A large number of pollutants are produced by the inefficient combustion of civil solid fuels. According to China’s economic development level and the reality of various regions，the consumption of clean solid fuels suitable for rural areas and towns is an effective way to reduce the emission of non-point source air pollutants. Anthracite was mixed with different proportion of biomass (wheat，corn and rice) straw to prepare civil solid fuel. The process parameters of cold briquetting of anthracite-straw biomass briquette were optimized by orthogonal experiment. The combustion thermal efficiency and main pollutant emission factors of biomass briquette were tested and analyzed on typical civil stove. The experimental results show that the maximum compressive strength of briquette is 15.98 kN/pellet，and the corresponding drop strength is 99.87% under the optimized conditions of biomass dosage 20%，particle size upper limit 1 mm，molding pressure 25 MPa，binder 10%; The thermal efficiency of biomass briquette was increased by 81%～137%，the reductions of emission factors were 90～98% for PM2.5 and 48%～92% for CO，and the emission factors of NO2，SO2 and toxic elements As，Se and Pb in PM2.5 were greatly reduced as well. The synergistic effect of biomass and anthracite is an important reason for energy saving and emission reduction. The addition of biomass reduces the pyrolysis temperature，ignition point and burn out temperature of briquette. The pyrolysis gas of biomass supports the combustion of anthracite particles. Besides，the volume of biomass shrinks and is porous after burning out，which provides a developed gas channel for further combustion of anthracite. Due to the full contact between oxygen and solid phase，the combustion is full，the thermal efficiency is improved，and the emission of pollutants is reduced.