Research On Pressure Drop Characteristics And Pulse Cleaning Performance Of Pleated Filter Bags

The ultra-low emission of bag filter under the background of emission peak and carbon neutrality targets plays an important role in the field of industrial dust removal.Pleated filter bag has the obvious advantages of larger filter area in limited space,and is more favored than conventional filter bag.Therefore,reducing the filtration resistance of the pleated filter bag and improving the dust-cleaning performance of the filter bag are conducive to achieving low carbon goals.Based on this,this paper takes the pleated filter bag as research object,and conducts research on the pressure drop characteristics and cleaning performance.In addition,the structure of the pleated filter bag and the nozzle of the pulse cleaning system are optimized and improved.The research results can provide theoretical basis and data support for the practical application of pleated filter bag dust removal.In this paper,an experimental test platform for a pleated filter bag filter is set up,and the effects of different structural parameters(the number of pleats N,pleat ratioα)and operating parameters(air volume F)on the filtration pressure drop and filtration efficiency are analyzed.In addition,the distribution law of filtration pressure drop along the axial direction of the vertically installed pleated filter bag in the dust collector is studied,and the effects of different pulse injection pressure P,pulse width T and pleat ratioαon the axial distribution of the peak pressure of the filter bag sidewall are explored.Then,a new type double-pleated filter bag is proposed,and the pressure drop distribution law of the double-pleated filter bag along the axial direction is analyzed by CFD numerical simulation.Finally,a new nozzle(double Laval annular slit nozzle)is designed,and the effect of the new nozzle on the dust removal effect of the pleated filter bag is analyzed by CFD numerical simulation.The dust removal effect of the new nozzle with different structural parameters and the conventional circular nozzle are compared and analyzed.The results show that:(1)When the air flow rate is 3000 m~3/h～5000 m~3/h,the filtration efficiency of N=8,10 and 12 filter bags decreases by 3.49%,3.37%and 3.35%;the filtration efficiency shows a downward trend with the increase of the treated air flow rate,and the decline rate becomes larger.The filter pressure drop increases with the increasing of the air flow rate;the filter pressure drop of N=8,10,and 12 filter bags increases by42.8%,34.1%and 31.8%with the change of air flow rate.When the pleat ratio is0.58～0.86,the increase of pleat ratioαwill weaken the decrease of filtration pressure drop caused by the increase of pleat number.As the air flow rate increases,the effect of the pleat ratioαin hindering the reduction of the filtration pressure drop becomes more significant,and the magnitude of pressure drop reduction is weakened by 33%to 66%.The filtration pressure drop distribution along the axial direction of the pleated filter bag is non-uniform,and the pressure drop near the bag mouth is larger;the non-uniformity of pressure drop distribution becomes more obvious with the increase of air flow rate.(2)The sidewall peak pressure of the pleated filter bag decreases along the length of the filter bag(from the bag mouth to the bottom of the bag),and increases slightly near the bottom of the bag.When the pulse pressure is 0.4 MPa～0.6 MPa,the increase of the pressure peak in the upper region of the filter bag is significantly higher than that in the middle and lower regions.When the pleat ratioα=0.71～0.86,the sidewall peak pressure in the middle and lower regions of the filter bag decreases significantly.When the pulse pressure is 0.4 MPa～0.6 MPa and the pulse width is 100 ms～200 ms,the filter bag with a pleat ratio ofα=0.71 has better cleaning uniformity.The dynamic shedding process of dust is consistent with the variation law of the peak pressure of the sidewall of the filter bag.(3)Compared with the conventional pleated filter bag,the simulation results display that the static pressure difference distribution along the axial direction of the double-pleated filter bag is more uniform.The double pleated filter bag reduces the difference of filtration pressure drop between the bag mouth and the bag bottom by13.6%～20.4%,and the pressure drop at the top of the filter bag is reduced by11.2%～15.4%,and the unevenness of the filter pressure drop distribution is reduced.The pressure drop distribution of the double pleated filter bag is relatively uniform,therefore the filter pressure drop of the dust collector can be reduced by up to 13.5%,which effectively reduces the operating energy consumption of the dust collector.(4)The pressure peak of the double Laval annular slit nozzle pulse jet filter bag is significantly larger than that under the circular nozzle,and the sidewall peak pressure becomes larger with the increase of the opening area and throat slit width of the double Laval annular slit nozzle.The pulse cleaning intensity of double Laval annular slit nozzles(No.1～5 new nozzles)is 1.73 times to 3.61 times that of circular nozzles.The optimal structural parameters of the double Laval annular slit nozzle are:throat slit width 2 mm,outer tube inlet diameter 40 mm and outer tube outlet diameter35 mm.