Research and application of key technologies for pre-removal of coarse particle fly ash in compact space before denitration of a 300 MW unit
Due to factors such as coal quality and combustion,coarse fly ash particles in flue gas of coal-fired boiler can easily cause varying degrees of wear and tear on tail flue and denitrification catalysts.An"A-V-T"type pre-removal structure for coarse particle fly ash before denitrification is established using the flue from the economizer outlet to the denitrification system inlet of a 300 MW unit as the research object.The structure is composed of"A-type baffle enrichment+V-type high-efficiency ash collection+T-type coarse ash channel"and is placed in a large cross-section low flow velocity flue at the economizer outlet.The influence rules of different particle size distribution trajectories,removal effects and resistance before and after the arrangement of the coarse particle fly ash pre-removal device are studied through numerical simulation,and engineering application is conducted to verify the effectiveness.The numerical simulation results indicate that,the use of coarse particle removal technology has little effect on flow field state of the original system at flue gas side.As the particle size of fly ash increases,the removal rate of fly ash increases.The removal rates of fly as particles with size of 50,200,500,and 1 000 μm are 12.15%,59.40%,87.01%,and 93.62%,respectively.The removal efficiency for coarse particles with size of 200 μm and above is 85.15%.The overall ash collection rate is 15.50%,with an additional resistance of 78 Pa.For this 300 MW unit,the tests after retrofitting show that,the removal rate of coarse ash particles with size of 200 μm and above is 83.96%,the overall removal rate of ash is 14.91%,and the net increase in resistance is 73 Pa.The experimental results verify the rationality of the numerical simulation results.
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