Fragmentation Mechanism Of PM_2.5 Fine Particulate Matter Formation During Coal Particles Combustion

In recent years, more and more serious air pollution, has caused a great impact onpeople’s daily lives, are extremely harmful to human health. Fine particulate air pollutants ingreat harm to humans, the burning of coal combustion and petrochemical combustion is amajor source of fine particulate matter. Therefore, the process of generation principle studyfine particles of coal combustion has become an important part of treatment of fine particlepollution from the roots.Pulverized coal combustion process occurs in a complex physical changes, such aschanges in the internal pore structure, specific surface area changes, and ultimately brokencomplete combustion of carbon occurs, the series of the change process is difficult to directlyobserve hot now the basic experimental studies are based, is more difficult to test for thermalcoal particles burn the whole process of research, the basic thrust reversers are from thecombustion products of combustion processes, coupled with the burning time during manychemical reactions short, exacerbated the difficulty of the study. In this paper, the volatilepyrolysis of coal particles during the thermal stress analysis of stresses within the materialand the expansion of the coal particles is itself broken research focus, without consideringthe volatile matter combustion and after the precipitation process can be seen in an inert gasatmosphere. Model is constructed on the basis of earlier studies summarized with the newcalculation method to simulate the high reliability of the model, compared to the relevantexperimental verification can prove the correctness of the calculation method.The innovation of this paper is the original model of optimization, improved methodsfor characterizing the degree of fragmentation: quality ratio as a measure of the degree offragmentation of standards; well as through new meshing method: concentric mannermeshing, simulation the crushing process is followed by the ring from the outside in the formof gradual, more in line with the actual situation in the combustion process.Found through simulation: a main factor affecting the coal particles are broken: the coal particle size, concentration of volatiles, combustion temperature, and the porosity of the coalparticles. Particle size of the coal particles is the most important factor affecting the coalparticle breakage, the main influence of particle size on the results of the expansion ofcrushing stress acting on the specific surface area of the coal particles from the reaction, thesmaller the particle size, the same expansion stress the greater the pressure to produce,crushing effect is more obvious. Volatiles after the crushing effect of particle impact, thegreater the content of volatile matter, the greater the thermal analysis of the stress generatedduring the expansion, while the gaseous and volatile solid char produced from larger wallporosity rate, further reducing the yield strength of the particles of coal itself. The larger theexpansion stress, the yield strength is reduced, making it easier to produce crushed. Effect oftemperature effect on the thermal fragmentation is reflected in terms of stress andtemperature gradient, the higher the furnace temperature, the greater the initial stage of thetemperature gradient; Meanwhile, volatile analyze the faster, the greater the expansion stress,so that the fragmentation occurs. Little effect on the porosity of the broken, the main role ofporosity changes in the performance of the material stress changes the coal particles, thegreater influence of porosity on the other hand the precipitation rate of volatilization. Thehigher the porosity, the analysis of volatile pyrolysis stage, the easier, the lower the yieldstrength of the coal particles, so that a higher degree of fragmentation rate.