Study On Particulate Matter Enrichment With Arsenic And Chromium In The Fly Ash During Coal Combustion

An important environmental issue is the emission of toxic metals, such as arsenic(As) and chromium(Cr), from the combustion of coal. This thesis discusses the serious harm of particulate matter emission on human and inhabitation environment, which means it's important and necessary to study particulate matter formation and controlling method. According to the research work on the formation fundamental theories and control ways of particulate matter enriched with trace elements up to date in detail, their advantages and disadvantages are systematically analyzed.For understanding the mechanism of particulate matter enrichment with toxic metals during coal combustion, a mathematical model for predicting the fate of toxic heavy metals is presented. The model can discovery that gasification rate, translation rate of adsorption and reaction, temperature, density are important for particulate matter enrichment with toxic metals.In order to investigate and study the distribution and enrichment of trace elements in the fly ash from coal combustion, a coal combustion experiment is carried out on a drop furnace with several kinds of coal, which were air dried and sized to a range of 74μm. The data on different combustion conditions, such as temperature and existing form, are analyzed comparatively. The result shows that, combustion conditions and existing form of As in coal are the main factors of influencing enrichment of As in fly ash, Cr distribution is main relating with the existing form.By researching the relation of trace elements distribution and the fly ash particle size(13 ranks, from 0.0281μm to 9.8μm diameter), the result of this work also confirms a recent understanding, which suggests that pulverized coal fly ash particle formation is best described as a tri-modal particle size distribution that includes a submicron fume region, a fine fragmentation region centered at approximately 0.03μm～0.7μm diameter, and a bulk fragmentation region. And the research about the fine fragmentation region is an important step to mitigating the environmental impact of coal combustion.