Research On Synergistic Particulate Matter/SO₃ Removal By Precipitators From Coal-fired Flue Gas

At present,the ultra-low emission transformation of coal-fired power plants has been basically completed,and the purpose of reducing particulate matter,sulfur dioxide and nitrogen oxides has been achieved,but the harmful effects of SO₃ emissions from coal-fired power plants are attracting more and more attention,so it is of great significance to study the impact of ultra-low emission transformation of coal-fired power plants on SO₃ emissions.Dust removal equipment is an important part of ultra-low emission in coal-fired power plants,in which low-temperature electrostatic precipitator technology has basically become one of the"standard"technologies to achieve ultra-low emission.The study of dust removal equipment,especially low-temperature electrostatic precipitator technology,is of great significance to the cooperative removal of particulate matter and SO₃.This paper selects 22 domestic units with different dust removal technologies to test the performance of dust removers,analyzes the removal effect of different dust removal technology facilities on particulate matter and SO₃,focuses on the law of cooperative removal of particulate matter and SO₃ by low-temperature electrostatic precipitator,explores its cooperative removal mechanism.The influence of operating parameters of low and low temperature electrostatic precipitator on the removal efficiency of particulate matter and SO₃ was studied.The main results are as follows:First of all,according to the performance test equipment of 22 domestic dust collectors with different dust removal technologies,it is found that low-temperature electrostatic precipitators and electrostatic-fabric integrated precipitator have higher dust and SO₃ removal efficiency than high-efficiency electrostatic precipitators,and their SO₃ removal efficiency is 50.17%-73.58%"and 65.70%-78.62%,respectively,and the SO₃ removal rate of high-efficiency electrostatic precipitators is only 16.48%-24.04%.Due to the differences in layout,design parameters and coal-fired composition,the dust collector has a great difference in the removal effect of particulate matter and SO₃.Secondly,The performance test of a domestic low-temperature electrostatic precipitator and the study on the physical and chemical properties of fly ash,the results show that along the flue gas direction,the fly ash matrix is mainly silicate,mixed with some metal compounds.most of them are distributed on the surface of fly ash particles in the form of oxides.Large particles contain more silicon-aluminum oxides and clay minerals,while small particles contain more metal oxides.The particle size of fly ash increases at first and then decreases gradually,and the final electric field fly ash particles are basically round or spherical,with a particle size of about 3.12μm.The proportion of large particles in fly ash particles along the way increases and decreases at first,and the sudden change of particle size and the proportion of large particles occurs in the flue gas cooling section.Due to the decrease of flue gas temperature,the agglomeration between sulfuric acid droplets and particles is obvious.Sulfuric acid fog condenses and agglomerates to form submicron particles,and small particles collide and adhere to form larger particles.Along the way,the element content of fly ash changes regularly,the content of Si decreases gradually,and the content of Na,Mg,Al,S,Ca and Fe tends to increase.With the decrease of particle size,with the decrease of particle size,except for the relatively stable content of Ti,the content of Si decreases gradually,while the content of K,Na,Ca,Mg and Fe tends to increase.The physical and chemical properties of the final electric field fly ash show that the escape of the dust collector fly ash is closely related to the particle size and chemical composition.Finally,the influence of operating parameters of low temperature electrostatic precipitator on SO₃ removal and the composition of fly ash is studied.The results show that the operating temperature of low temperature economizer has the greatest influence on SO₃ removal of low temperature electrostatic precipitator,followed by the ratio of ash to sulfur in inlet flue gas,and the influence of operating voltage of electrostatic precipitator is the least.The operating parameters of low temperature electrostatic precipitator have influence on the chemical composition of fly ash.The sulfur ratio of inlet flue gas has a significant negative effect on the enrichment of sulfur in fly ash,and the influence degree is the greatest.The operating voltage of electrostatic precipitator has no significant effect on the enrichment of sulfur in fly ash.In the later electric field along the way,the influence of ash-sulfur ratio and low temperature economizer operating temperature on the enrichment of sulfur in fly ash is also gradually decreasing,and the last stage electric field basically has no significant effect.