Internal Flow Field Research And Structure Optimization Of The Straight-Through Type Under Inlet Bag Filter

China has become one of the most heavily polluted countries in the world,atmospheric particulate matter could bring great harm to human health and the growth of crops, which has relation with the people’s well-being. The energy structure of our country determines the main status of coal-fired plants in the power industry, which caused smoke pollution has become the main form of air pollution in China. In recent years, with the national emission standards for particulate matter becoming more strictly, the bag filter with high efficiency dust removal has gradually become the key equipment of dust removal in coal fired power plant. particulate pollution has been controlled under a certain degree, but also exposed some problems. Through the investigation and analysis of the actual use of bag filter in coal-fired power plants, found that the non-uniformity of the flow field in the bag filter increased the running resistance of the equipment, reduced the service life of the filter bag and seriously affected the dust removal efficiency and stable operation of the bag type dust collector.Because of the bag filter requires strict sealing in actual use, and thestructure is more complex, directly using experimental method to study the flow field is difficult. In this paper, the inner flow field was simulated using computational fluid dynamics(CFD) software, FLUENT, to explore the effect of the airflow distribution under different filtration velocity, the causes of filter bag breakage and the location of filter bag is easy to break. the reasonable range of filtration velocity was put forward.According to the nonuniform internal flow field of bag filter under reasonable filtration velocity, by comparing the distribution of the velocity field,pressure field, multiple sets of structural optimization schemes are proposed,including the optimization of air inlet pipe structure and guiding device arranged in the hopper, after a lot of calculation and analysis, the Structural optimization design method was confirmed, could realize the uniformity of air flow distribution in straight through type under inlet bag filter. Euler Lagrange discrete phase model was Used to compare the movement law of different size particle was studied in before and after structure optimization, to verify the effectiveness of the structure optimization.The results shown that for the straight through type under inlet bag filter,the uniformity of internal airflow distribution was severely affected by filtration velocity. With the filtration velocity increased, the jet inlet was enhanced,causing the scour to the bottom of the bag and the non-uniform phenomenon of airflow distribution was exacerbate, the front of bag processed less gas, the hind bag processed more gas; the suitable working conditions of filtration velocityrange is 0.5~0.8m/min; in the structural optimization of the air inlet pipe, the effects of jet flow could be reduced by using guide plate Bend, the scour to the bottom of the bag was effectively avoided, which could prolong the service life of the filter bag; the design of three guide device in the hopper, could effectively improve the uniformity of airflow distribution, especially the running resistance of trapezoidal guide plate was minimum, the organization of flow field in the bag filter is most uniform and has reasonable clearance speed, the σ=0.1895<0.2was calculated by RMS air flow Uniformity evaluation standard, suggesting that air flow distribution is good; with the same filtration velocity, particles size below 100 μm is arrested better in the structure optimized model and each bag trapping particles evenly, the particulate size about 150 μm partially is arrested by the bottom of bag, partially settled in the hopper, 300μm large particles settled in the hopped by action of gravity, the effectiveness of structural optimization was confirmed.The conclusions of this study provides references for improving the uniformity of the flow field in the straight through type under inlet bag filter,improving the efficiency of dust removal and prolonging the service life of the filter bag.