Pore Structure Evolvement And Its Influence On Particles Creation During Coal Combustion

At present, the environment pollution due to inhalable particles is the main pollutions to the atmosphere, among the cities that exceed standard of the air quality, 68 percents of them existing the problems of inhalable particles pollution, it has important influence on the living qualities of the human beings. It is indicated in researches: inhalable particles in the atmosphere have seriously destroyed the human's health and ecological environment. Coal combustion is the main emission source for inhalable particles. There are many factors in affecting the forming of inhalable particles, the fragmentations of the coal particles is one. The fragmentation has a great influence on the burnout time, particles size distribution, boiler residue and attrition. Therefore, intensifying the mechanism research of coal fragmentation and its effect on the forming of particles has important science and practice meaning. In this thesis, the porous structure evolvement and its influence on the ash particles characteristic during coal combustion is preliminarily studies by theory simulation and experiment study. Above all the thesis summarizes the overview of the coal fragmentation, and researches some main kinds of models describing the pore structure. On the basis of the front work, the critical fragmentation porosity is modeled using the percolation theory, the results is compared with the literature experiment; the infection of varied factors on the change of the pore structure are calculated, such as the temperature, the coal particle size, the fragmentation place and the thermal conductivity etc. In the next place, we experiment separately in the Drop Tube Furnaces and the new one. The preliminary experiments mainly aim at the affection of temperature and atmosphere on the micro granules creation, preparing for the next experiments. Then in the new DTF, with the condition changed including temperature, atmosphere, coal particles size, analyzed ash particles by LPI and char by SEM after sampled, the experiments summarize the pore structure evolvement in char, ash granules size distribution and the inhalable particles emission amount under different conditions. It is obtained that the influence of the combustion conditions on the char pore structure changes and the inhalable particles creation characteristic, establishing the foundation for controlling the emission of the inhalable particles effectively.