| As the requirement to environmental protection is getting higher and higher, ESP is faced with reformation. The ESP designed according to old criteria fails to meet the new emission regulations, because it can not increase electric field due to the limitation of ground. And as the development of filter material and mature filtering technology, bag filter's market share in the precipitation industry increases greatly. It's of very good environmental and economic benefit to replace ESP with bag filter. The new design will affect the distribution of gas flow, so it is necessary to research the gas-flow distribution after the reconstruction of ESP.According to concentration distribution of the pollutant diffusion on cylinder in the static fluid,build diffusion model on the base of Fick first low and flow function in Lame fields to get concise efficiency expression, and further discuss the relation between filter efficiency and filter velocity.In addition, this paper uses computer flow dynamic software (CFX) to solve flow field distribution inside the bag filter. The numerical calculation of gas flow distribution inside bag filter is accomplished through simplifying the physics model of bag filter, ascertaining the types of grid ,adjusting grid density, choosing turbulent flow model, calculation method and data disposing method and so on. The result indicates that the distribution of gas-flow entering the filtrating house is very asymmetrical. This not only decreases the efficiency of filtration, but also severely shortens the natural life of fabric. According to the result of numerical calculation, the article improves the distribution of the gas-flow by setting board that can lead gas-flow. The second and the third results of numerical calculation indicate gas-flow distribution is much better than before after setting board. It provides good instruction to the design of structure optimization.
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