Study On Mineral Transformation Mechanism During High-silicon Coal Combustion And Agglomeration Of Fine Particles

Particulate matter (PM) is the dominant pollutant in most Chinese cities,and has brought about serious impacts on human health and the ecological environment.Coal combustion is the major source of PM in Chinese ambient air and accounts for more than 33% in PM mass.The knowledge of PM formation and emission contributes a lot to the risk assessment of PM pollution,legislation and emission control.Xuanwei is high incidence of lung cancer.Foreign experts have done some research on the harm from the high-silicon coal-fired,but have not involved mineral transformation and PM formation mechanism of high-silicon coal.In this article,the mineralogy and microstructure and density separation fraction of 7 kinds of typical high silicon coals and 2 kinds of fly ashes from different power plants were studied by X-ray diffraction and scanning electronic microscopy with energy dispersive X-ray analysis.PM formation mechanisms were investigated by systematic drop tube furnace (DTF) experiments. Agglomeration of fly ash from high silicon coal-fired was studied by experiment.The mainly silicon -bearing minerals in coal include:quartz and kaolinite.there is more quartz in fine particles.Mullite mostly comes from kaolinite.Quartz is irregular crystals with smooth surface.The resistance of high-silicon coal is increased with increasing temperature.The resistance arrives maximum when the temperature is 150℃.Afer this temperature,the value of resistance reduces.The smaller the size of fly ash is,the largerThe value of resistance becomes.Collection efficiency is lower.DTF experiment results show that:the number of fine particals increases with the temperature.The emission concentration of PM₁₀ is also increases with the temperature.SiO₂ in crude particle is more then fine particle,while the distribution of SO₃ is opposite to it.The mainly elements in PM_1.0 are S and O,S mainly exists sulfate in the form of sulfate.The main mechanism of chemical agglomeration is the adsorption bridging process. PAM,XTG,and CMC can contribute to the agglomeration of fine particles from high-silicon coal-combustion.XTG has best effect,but the concentration should not exceed 0.1g·L^-1.Nonionic surfactants can contribute to the agglomeration of fine particles, but as for the anionic surfactants, agglomeration of fine particles is restrained by phosphoric acid.