| With the advancement of dust collector technology,bag filter is not only used in industrial ventilation process,but also occupies an important position in large-scale industrial kiln flue gas purification to ensure the emission efficiency of fine particles,and the multi-pollutant collaborative control process based on bag dust removal has gradually become the mainstream technical route.Bag filter has been used in high temperature alumina roasting,garbage pyrolysis and other industries,and the high temperature flue gas generated during the process is a key factor affecting the service life of the bag filter bag.The application of metal filter bags in high-temperature bag filters can effectively avoid problems such as shortening the life of filter bags caused by temperature,but at present,there may be filter bag paste phenomenon caused by temperature in the application of metal filter bags,and the residual resistance of filter bags increases due to improper selection of ash cleaning parameters,and the operating resistance of bag filter dust collectors increases.Aiming at the problems of ash cleaning failure in the operation of metal filter bags,metal fiber filter bags are selected,and the penetration of microscopic dust on filter material under the filter bag filtration state is studied by numerical simulation real experiments,and on this basis,the peak wall pressure and maximum reverse acceleration distribution law of different measurement points along the bag length direction of the filter bag are studied by joint physical test and numerical simulation method,and the factors affecting the ash cleaning performance are analyzed through orthogonal tests under the premise of verifying the reliability and accuracy of the model.Through numerical simulation experiments,the influence of pulse jet cleaning air flow on condensation in the mouth area of filter bags under high temperature conditions was studied,and the following conclusions were mainly drawn:(1)Based on the microscopic numerical simulation under the filter material filtration condition,the penetration degree of particles to different filter materials is clarified.When the filter media is filtered,particles with a small particle size are easier to penetrate the filter media.Under the same particle size conditions,the penetration distance of organic fiber filter material particles is small compared with that of metal filter material,the longest penetration distance of metal filter material is 0.13 mm,and the maximum penetration distance of organic fiber filter material is 0.11 mm.The filter material with fine fiber has a short particle penetration distance;When the penetration distance is the same,the particle penetration amount of organic fiber filter material is significantly greater than that of metal filter material.With 0% penetration of membrane media,surface filtration can be fully realized.(2)Based on the pulse injection physical model test of metal filter bag,the change law of filter bag cleaning performance in axial direction under different cleaning parameters was clarified.Changing the injection parameters,the peak pressure of the wall along the length of the bag,the pressure rise rate and the maximum reverse acceleration show the same change law: the peak pressure of the wall of the filter bag increases with the increase of the injection pressure value,and the maximum value appears at about 0.5m in the upper part of the filter bag,and then the pressure value gradually decreases along the length of the filter bag,and continues to gradually decrease after increasing at 2 m from the bag mouth until the bottom of the bag rebounds and increases.Under the same test parameters as the physical model test,the numerical simulation test was carried out,except for 0.3 m and 1.5 m at the bag mouth,the simulated values of other points were basically the same as the experimental values,and the deviation was within 10%,which verified the reliability of the numerical analysis method.By comparing the test values of the ash cleaning evaluation index of the metal filter bag and the organic fiber filter bag,under the influence of fundamental factors such as the quality of the filter material and the particle layer and the elastic coefficient of the filter material material,the separation force on the surface of the two filter bags during spraying is different,showing that the peak pressure,peak pressure arrival time and free movement displacement and maximum reverse acceleration of the filter bag wall are different.(3)Based on the two-dimensional single-bag numerical simulation design,the orthogonal test obtained the degree of influence of injection pressure,filter bag length,spray time,spray distance and spray aperture on the cleaning performance of metal filter bag.The influence of injection pressure on peak pressure showed a straight upward trend;The peak pressure of the filter bag wall decreases as the length of the filter bag increases.During the gradual increase of the injection distance,the peak pressure of the wall generally showed an increasing trend,and there was an optimal injection distance in the pulse injection process,that is,200 mm.100 ms is the optimal spray time,and the spray time has little effect on the peak pressure.The pressure rise rate of injection pressure,injection distance and filter bag length is the same as that of wall peak pressure,and decreases with the increase of injection time.The maximum reverse acceleration trend plot is the same as the peak wall pressure,in which the influence of injection pressure,spray distance and filter bag length is the most significant,while the influence of spray time is small.(4)Based on the numerical simulation test of pulse injection under high temperature conditions of metal filter bag,the influence of compressed air temperature on condensation in the mouth area of the filter bag was analyzed.Different temperature pulse injection air flow spray to the high temperature filter bag will cause the temperature change in the front section of the filter bag,with the increase of pulse jet air flow temperature,the temperature of the first half of the filter bag gradually increases and the cooling area gradually decreases.The minimum temperature of the filter bag is pulse injection 40 ms,and the filter bag temperature decreases first and then increases when the air flow is sprayed to the filter bag.When the temperature of the injection gas flow is 0 °C,the temperature at 0.5 m～2 m of the filter bag is lower than 100 °C,and there is a risk of condensation at the mouth of the filter bag.Heating the compressed air and increasing the air flow temperature at the pulse injection nozzle to about 50 °C can effectively prevent the condensation of the filter bag mouth caused by the compressed air temperature being too low. |
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