Research And Application Of Modification Techniques In Bag Filters Transformed By ESP In Coal-Fred Power Plants

Most of China’s electricity provision is coal-fired power, more than90%of early coal-fired boiler flue gas treatment devices are electrostatic precipitator, but the efficiency of ESP changes with the variety of coal, and with the improvement of environmental standards and the mature of bag filter technology, the ESP into bag filter becomes the first choice of energy-saving, environmental protection, and high efficiency. Some problems associated with airflow organization like filter bags seriously damaged, frequent cleaning, too large resistance and uneven ash content appear after running for a period of time after ESP into bag filter. This paper intends to adopt the methods of theoretical analysis and CFD simulations to explore the reasons of problems caused by transforming ESP into bag filter by filed investigation and discussion, and make simulation study for transformation and optmization techniques in ESP into bag filter, and reference flow simulation results to guide engineering practice.The topic regards a bag filter transformed by ESP in a thermal power plant as research object, by analyzing the airflow organization in bag filter transformed by ESP gets that the airflow process is too long, the speed of airflow is too large, especially the speed below the bottom of the filter bags, air rising speed is higher than the limit sedimentation velocity corresponding to most of the particle size. The flow load is uneven between compartments, the first few rows and the last few rows filter bags in precipitator have the risk of overall broken, and others haves high risk of broken in bottom of filter bags.Make simulation analysis of the technical means which aim at solving the problems caused by ESP into bag filter, respectively simulate and analyze the airflow organization in extended program, extension and elevation program, and research their features and effects, put forward a side into program and make simulation for it. The numerical results show that the airflow uniformity in compartments of side into bag filter is the best, followed by extension and elevation program, and the extension program is the worst. Extend bag filter not be able to change the problem of too high airflow speed in precipitator, the contrary, the speed bellow the bottom of filter bags becomes larger and its airflow uniformity turns worse, but can effectively reduce the rising speed of airflow relatively. The elevation and extension program can effectively reduce the speed and rising speed of airflow, but the airflow uniformity becomes worse. After the transformation of side into program, the air flow progress becomes shorter and the speed falls significantly, compared with original ESP into bag filter, the airflow uniformity of side air intake drops.Against the uneven uniformity of side into program, propose two optimization programs: increase airflow uniformity panels and math compartments with different filter bag penetration. Using the orthogonal experiment method to analyze the airflow uniformity effects caused by airflow panels, the results show that the extent of relative influence is uniformity panels n>width L>deflection angle θ in three factors affect the airflow uniformity. On the significant impact, the number n has an extremely significant impact, width L has a significant impact, deflection angle0has a relatively impact. Matching different chamber with corresponding permeability of filter bags with can improve the uniformity of bag filter.Combine engineering practice and subject sources, transform the bag filter transformed by ESP in a coal-fired power plant and optimize its airflow organization, simulation analysis and measure test show that there’s a good effect after transformation, which provides reference to other transformation cases.