Study On Formation Mechanism And Ash Accumulation Characteristics Of SO₂ In Pressurized Oxy-fuel Combustion Of Bio-mass Mixed Coal

The greenhouse effect poses a great challenge to human living environment.Seeking effective CO₂ capture technology is an important method to mitigate the greenhouse effect and improve climate environment.The biomass mixed coal pressurized oxy-fuel combustion process integrates the ad-vantages of biomass energy utilization and pressurized oxy-fuel combustion technology,which is a promising carbon capture technology.However,during the combustion process,the mixture of bio-mass and the increase of combustion pressure make the SO₂ emission and ash formation characteris-tics of fuel change compared with that of atmospheric oxy-fuel combustion.In order to investigate the effects of combustion pressure,biomass mixing ratio and combustion atmosphere on the for-mation mechanism of SO₂ and ash formation characteristics in the pressurized oxy-fuel combustion of biomass mixed coal,In this paper,the combustion process was simulated by Chemkin and Fact Sage software from the perspectives of kinetics and thermodynamics,aiming at obtaining the emission law and ash accumulation characteristics of SO₂ in the pressurized oxy-fuel combustion process of bio-mass mixed coal,and providing theoretical reference and technical support for the practical applica-tion of biomass mixed coal pressurized oxy-fuel combustion technology.The formation mechanism of sulfur to SO₂ in biomass mixed coal during pressurized oxy-fuel combustion was studied.With the increase of combustion pressure,SO₂ emission rate and total emis-sion decrease.The mixing of biomass can inhibit the precipitation of SO₂ to a certain extent.The higher the mixing ratio of biomass,the lower the total emission of SO₂ in flue gas.The emission rate and total emission of SO₂ in 21%O₂/79%CO₂ atmosphere are slightly lower than those in air atmos-phere,and the emission rate and emission of SO₂ in oxygen concentration increase significantly in O₂/CO₂ atmosphere.Based on the above research results,the Rate of Production（ROP）method is used to analyze that when the combustion pressure increases from 0.1 MPa to 1.6 MPa,the reduction total SO₂ emission is the result of the joint influence of eight main reactions,and the main reaction path of sulfur element migration in the process of biomass mixed coal pressurized oxygen-rich com-bustion is identified.The transformation characteristics of potassium into gas phase K₂SO₄ in biomass mixed coal during pressurized oxy-fuel combustion were investigated,and the formation path of K₂SO₄ before and after pressurized combustion was analyzed.Increasing combustion pressure can inhibit the for-mation of K₂SO₄ in flue gas and reduce the emission of K₂SO₄.K₂SO₄ emission increases with the increase of mixing ratio.The total emission of K₂SO₄ in 21%O₂/79%CO₂ atmosphere is not different from that in air atmosphere.The change of atmosphere has little influence on the generation of K₂SO₄,and the emission of K₂SO₄ decreases when the oxygen concentration is increased in O₂/CO₂ atmos-phere.According to ROP analysis,the change of pressure affects the formation of KO₂,which makes the reactions of the main elements involved in the transformation of K₂SO₄ different before and after pressure,and the main transformation path also changes accordingly.The characteristics of ash deposition in biomass mixed coal during pressurized oxygen-rich com-bustion were investigated.Under different combustion pressure,combustion atmosphere and mixing ratio,the mineral species in ash are not changed obviously,but the content of minerals is affected.The increase of pressure inhibited the decomposition of Ca SO₄,which reduced the contents of Cal-cium Akermanite and Merwinite,and also reduced the production of KAl Si₂O₆.The mixing ratio mainly affects the formation of Ca SO₄ and KAl Si₂O₆,but has no significant effect on other mineral phases.The formation of KAl Si₂O₆ and the decomposition of Ca SO₄are inhibited by oxygen enriched atmosphere.