| As a major pollutant produced during the incineration and disposal of municipal solid waste,particulate matter has caused serious harm to ecological environment and also threatened the safety of boiler operation.Based on the deficiencies in research and the generation and control of particulate matter during the combustion of municipal solid waste,this thesis has carried out in-depth research on the emission characteristics,formation mechanism,additive control and high temperature corrosion characteristics of particulate matter during the combustion of municipal solid waste.The particle size distribution results showed that the PM10 generated by the combustion of municipal solid waste all present a three-peak distribution.Both the yields of PM1 and the yield ratio of PM1/PM10 showed a strong positive correlation with the fuel ash ratio of(Na2O+K2O)/(Si O2+Al2O3).Increasing combustion temperature could reduce the distribution ratio of Na in submicron particles,and at the same time promoted the migration of elements such as Si,Al,Mg,Ca,Fe,Ti and P into fine particles.In the nucleation process of submicron particles,alkali sulfate particles were more likely to be distributed within a particle size of less than 0.2μm,while alkali chloride,carbonate and hydroxide particles were more likely to be distributed within a particle size in 0.2-1 μm.When alkali chlorides and alkali sulfates coexist in high-temperature flue gas,the heterogeneous nucleation and agglomeration effects of alkali salt particles would cause more alkali salt particles to be distributed in the particle size range of 0.2-0.5 μm.The additive control experiment showed that,at a combustion temperature of 1100°C,the Si/Al-based additive had the best removal effect on PM0.3 emission,and the removal efficiency increases with the increase of the additive Si/Al ratio.The higher Si/Al ratio additives had a higher conversion efficiency of alkali sulfate minerals in the flue gas of MSW combustion,and could effectively reduce the nucleation probability of PM0.3.The Ca in Ca O and Ca CO3 additives competed with the alkali elements in MSW to react with S,which inhibited the formation of volatile alkali sulfates in high-temperature flue gas.The Ti O2 additive reacted with the Na salt and Ca salt in the MSW fuel composition at high temperature to form Na4 Ti O4 and Ca Ti O3,respectively.The Na4 Ti O4 conversion process inhibited the conversion of Na to Na Cl and Na2SO4,while the formation of Ca Ti O3 increased the ash melting point of the coarse particles.The increase of the characteristic temperature of ash melting inhibited the "fragmentation" of coarse mineral particles in the ash,and at the same time weakens the agglomeration ability between fine particles.The study found that during the MSW combustion process,the concentrations of volatile trace elements such as Cu,Zn,and Pb gradually increased with the decrease of particle size,while the concentrations of less volatile trace elements such as Ti,Co,and Ba decrease with the decrease of particle size.The emission reduction efficiency and directional control ability of Si/Al-based additives for trace elements in submicron particles decrease with the increase of the additive Si/Al ratio.The migration paths of different trace elements in the particles were also different after the effect of additives.The high-temperature corrosion rate of 304 stainless steel increased significantly as the particle size decreases.At 600°C,the corrosive ability of PM1 to 304 stainless steel was about 3-5 times that of PM10+.After 5% of kaolin was added,the overall corrosion ability of the particulate matter generated by MSW combustion on 304 stainless steel was reduced by 12%.When calculating with the particulate matter composition of the heated surface slag layer and ash deposit layer after stable formation,the corrosion control efficiency was increased to 71%.It was found that the high-temperature corrosion process of particulate matter was mainly dominated by Na Cl,KCl,Ca Cl2,Na2SO4 and K2SO4,the corrosion of alkali and alkaline earth metal chloride was generally stronger than that of sulfate at 600°C.In addition,this study also discussed the corrosion mechanism of corrosion cracking,pitting corrosion,molten salt corrosion process in which alkali chloride and sulfate coexist. |
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