| As one of the most primary air pollution source in industry fields, steel industries are urgent to realize the ultraclean discharging to solve the environmental problem. The bag-house dust filters have been widely used in the dust extraction process of steel industry for its high efficiency, simple structure, low investment in flue gas purification technology. And the filter materials are the main consumption and core part of bag-house dust filters,In this research, the characteristics of the filtration used in the ultraclean discharging in steel industry manufacture have been studied by experiments which could be outlined as:(1) The reliability tests of the existing filter material in the steel industry were carried out. According to the relevant national and industrial standards, characteristics of mechanics, temperature and erosion resistances are tested for 18 kinds of material involving the Polyester felt, the Polyester woven fabric, the antistatic and the high temperature resisted. The result of the tests shows that the filtration material breaking strength of Polyester felt and the antistatic is above 1200 N, meaning which is strong needle punched felt. The strength of the Polyester woven fabric is higher than that of the Polyester felt normally. In terms of temperature resistance ability and the erosion resistance deriving from the material the filters used, the Polyester should be used under 120℃regularly and the Polyester and the antistatic could be eroded easily in alkali solution above 20% concentration.(2) Tests and researches were conducted on the filtration performance of the existing filter material in the steel industry. According to the tests of aperture, filtration efficiency and dust resistance for 18 types of material belonging to 4 categories, as well as that of two kinds of plastic burning plate filtration material, the result indicates that, the mean apertures of film-coated filtration material are concentrated below 2, while that of non-film-coated are above 20 in a normal distribution. The aperture sizes of the common filter material can arranged as water-weaved filtration material<needle-weaved filtration material≈machine-weaved filtration material, and the classification efficiencies of film-coated material are of much better performance than that of regular non-film-coated ones. As for resistance, needle-weaved material with coated film shows stable trend through operation process.(3) The further analysis of the filtration performance for the exiting material was conducted. Based on parameters of filtration efficiency and resistance, the grey correlation analysis method was adopted to relate the mean permeable aperture of particles on the surface of filtration material with the unanimous air permeability rate CV. The conclusion could be shown as following. Film coated filtration material sees the best filtering quality. In terms of the non-coated material, water-weaved filtration material is the best, and needle-weaved filtration material comes next, and with the worst performance is machine-weaved filtration material. The filtration performance of 120 g composite mesh fabric and 208 lint are poor among these samples.(4) Tracking tests of the longevity and dust removal efficiency were done for the film-coated glass machine-weaved filtration material which were used in lime kiln with different using time. After consecutive tests of air permeability, mechanical property and filtering efficiency for the filtration material, which was used in one filter with service time from 1 to 18 months, the result shows that, the warp and weft breaking strength would arise at the beginning and then dip down with the lasting of their service time. What is satisfied is that all the material show a 75% or above filtering efficiency for the dust particles ranging from 0.23 m~10.0 m, which is higher than the average efficiency in steel industry.(5)The composition of the filtration material samples used in the steel industry were tested to analyze by the Infrared spectrometer(IR) and Differential scanning calorimeter(DSC). In details, three kinds of structure are stripped away involving fabric, surface layer and the covering film layer. IR and DSC curve analysis are two ways to authenticate each other,which can ensure accurate results when detecting filter material composition.Plenty of tests were done to analyze the filtration material reliability and filtration performance for different textile structures and this article provide some important references for the utilization of filtration material in bag-house dust filters. Under the premise of ensuring the reliability, the filtration performance of the coated filter materials is the best and they fit in the steel industry to achieve ultra clean emission. But the realizing of ultraclean discharge needs more optimization for the filter structures, instead of the simple performance of the filtration material itself, and this is essentially true concerning the on-site operating. |
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