Study On Cleaning Mechanism Of Chamber Type Jet Injection Bag Filter

Bag filter was a kind of dust separator with high efficiency. It was widespread applied in various dust-cleaning processes. Choosing suitable filter material and effective dust-cleaning mode were key factors for successful bag filter. Filter material directly determined life-span of filter-bag. Dust-cleaning technique affected the stability of bag filter. Chamber type jet injection bag filter was a new pattern. Its dust-cleaning mode was that electromagnetic pulse valve started when dust-cleaning began. High-pressure gas jetted from nozzle. In the meanwhile a great deal of air from the exhaust passage was injected. The air entered chamber air box from injection aperture. Reversal air velocity formed in filter-bag. Dust on the surface of filter-bag was peeled off. Then the purpose of dust-cleaning was obtained. Comparing chamber type jet injection bag filter with air chamber type pulse-jet bag filter, the former mode was an on-line system. It omitted air switching valve. So its frame was simple comparatively and running was more reliable.Aiming at chamber type jet injection bag filter, firstly velocity and mass air amount were deduced applied coercible gas heat insulating energy equation; Then applying free-jet stream theory, air amount and average energy of injecting profile were studied; Finally according to the relationship of reversal air velocity and air amount and average energy, the calculation formulas of necessary jetting pressure, nozzle diameter, ejecting distance, injection aperture diameter and side mouth diameter under a certain dust load were obtained. The mathematical describe for dust-cleaning course of chamber type jet injection bag filter settled theoretical basis for the design of dust-cleaning system.In order to check the theory fruit and review the infection of correlative factors for dust-cleaning effect, the dust-cleaning efficiency respective under different dust load, jetting pressure and nozzle diameter was tested by experiment. The experimental results indicated that:under a certain jetting pressure, dust-cleaning efficiency increased quickly with increment of dust load. When the dust load was lager than 1.4kg/m2, the increment of efficiency went to slowness; under a certain dust load, dust-cleaning efficiency increased quickly with increment of jetting pressure. When the jetting pressure was lager than 0.3MPa, the increment of efficiency went to slowness Under the same jetting pressure and dust load, dust-cleaning efficiency with 3mm nozzle diameter was bigger than that with 2mm nozzle diameter. By analyzing experimental data it discovered that between detachment stress and dust-cleaning efficiency there was a good correlation. So it proved that sticky detachment stress was the main power for dust-cleaning effect.Based on theoretical and experimental research for chamber type jet injection bag filter, the design method of dust-cleaning system was put forward:Firstly based on prospective efficiency, detachment stress was determined according to relationship between detachment stress and dust-cleaning efficiency; Reversal air velocity was calculated based on detachment stress; Then necessary injection aperture diameter, ejecting distance, and air demand were obtained based on the formula of reversal air velocity. Systemic dust-cleaning design method established essential foundation for overall structure design of bag filter.