Research On Emission Characteristics Of Particulate Matter And Main Gaseous Pollutants From Open-Air Coal Combustion

Coal resources are an important part of China’s energy structure and an indispensable mineral energy source for China and the world,but coal combustion is also one of the main sources of PM₁₀ pollutants and gaseous pollutants worldwide.While coal resources promote national economic construction and improve residents’life,its uncontrollable spontaneous combustion and artificial combustion also bring very serious environmental pollution.In this thesis,the particle size distribution characteristics and main influencing factors of particulate matter in combustion flue gas of different types of coal samples,the emission patterns of gaseous pollutants under complete combustion of coal samples,the emission factors of PM₁₀,CO and CO₂ gas from combustion of different types of coal samples are analyzed and calculated using a laboratory coal combustion test system designed and produced by ourselves.The emission factors of CO and CO₂ gas of different coal samples are analyzed and calculated,and the morphological and component characteristics of the particulate matter emitted from different coal samples are studied and analyzed from the microscopic perspective,and the concentration distribution patterns of coal combustion pollutants under different conditions are simulated and analyzed by MATLAB software.The thesis uses a combination of experimental and simulation calculations to obtain its main conclusions as follows.The particle size distribution of coal emissions from coal combustion is affected by temperature,coal type and coal particle size.Lignite and bituminous coal generate more particle agglomerates at lower temperatures and incomplete combustion,and their masses are much larger than those at higher temperatures,and the overall particle size distribution is concentrated in the range of 0.32-0.56μm,0.18-0.32μm and 0.056-0.10μm.Due to the difference in coal types,the particle generation of bituminous coal and lignite is much larger than that of anthracite coal.Based on the competing effects of particle generation mechanisms,the effect of different coal particle sizes on the particle size distribution showed different results,the reduction of coal sample size promoted the generation of more PM₁ in lignite particles,and shifted the peak particle size range of anthracite coal from 0.056-0.10μm to 0.10-0.18μm.The PM₁₀ emission factors of five different coal samples are measured by the self-designed coal combustion dilution sampling system,and the PM₁₀ emission factors of lean coal,gas coal,long-flame coal,lignite and anthracite are 13.90mg/g,13.07mg/g,12.10mg/g,10.81mg/g and 5.93mg/g,respectively.According to the gas concentration data measured by the gas sensor in the test system,the CO gas emission factors of lean coal,long-flame coal,gas coal,anthracite and lignite are 80.1mg/g,60.6mg/g,50.4mg/g,48.7mg/g and 45.7mg/g,respectively,based on the gas concentration data measured by the gas sensors in the test system,which roughly divided the three combustion stages of the five experimental coal samples,and obtained that the CO gas emission of the combustion stage accounted for more than 80%of the whole combustion process,and measured the emission factors of CO₂ gas for long flame coal,lignite,anthracite,lean coal and gas coal are 1134.8mg/g,1004.1mg/g,987.6mg/g,970.1mg/g and 933.1mg/g,respectively,in which the CO₂ gas emission in the combustion stage accounted for more than 60%of the whole combustion process.The microscopic morphology and elemental composition of the particulate matter emitted from the combustion of lean coal,gas coal,long-flame coal and lignite are analyzed,and it is found that the morphological characteristics of the particulate matter from the combustion of the four coal samples are mainly spherical,spherical-chain and irregular,among which spherical and spherical-chain shapes accounted for most of them;the spherical and spherical-chain particles emitted from the combustion of coal are carbonaceous particles with C as the main constituent element,and the irregular particles are mainly Ca-rich and Si-rich particles.which are composed of Ca,Si,Mg and Al in addition to C.The results of energy spectrum analysis show that the elemental composition of the particles emitted from the four coal samples all contain C,O,Si and S elements.Combined with the results of basic experiments,the Gaussian dispersion model is chosen to simulate and study the dispersion of coal-fired particulate matter and major gaseous pollutants.The dispersion of coal-fired particulate matter and gaseous pollutants in the open environment is closely related to the effective height of flue gas and wind speed;the higher the effective height of flue gas from coal-fired sources,the lower the concentration of pollutants on the ground,the wider the distribution area of pollutants,and the highest concentration distribution area of pollutants The farther away from the source,the greater the wind speed in the atmospheric environment,the lower the concentration of pollutants,but the impact on the highest concentration of pollutants concentration distribution area is not significant;comparative analysis of ground and near-ground pollutant concentration distribution law found that coal-fired sources with low effective height of flue gas have higher values of concentration distribution on the ground and near the ground,for such coal-fired sources should be particularly prevented and managed.The thesis has 62 figures,9 tables,and 96 references.