Experimental Study On The Performance Of Pleated Filter Bag Pulse Blowing Dust Removal

Compared with the circular filter bag of the same specification,the pleated filter bag increases the filtration area by folding design along the circumferential direction.In the same filtration unit,the surface area can be increased by 1.5～2 times.It can reduce the filter wind speed and the equipment resistance and prolong the service life of the filter bag.However,the narrow channel between folds leads to dust accumulation and poor dust cleaning effect in the application process.In this paper,the cleaning process of pleated filter bag is investigated by physical test and numerical simulation,which provides basis for the selection of cleaning parameters and the structural design of filter bag.The main conclusions can be drawn as follows:(1)Under the condition of 22 mm in diameter of the nozzle and 100 ms of the pulse time,different blowing pressures(0.2MPa,0.3MPa,0.4MPa)and blowing distance(180mm,200 mm,220mm),the change of the peak value of the fold filter bag(8 folds,7m long)along the length direction is the same as that of a circular filter bag;the relative deviation of the peak pressure on the three measuring points of the same section of the wave peak,the middle,and the valley is within ± 10%.In addition,the increase of the blowing pressure and the diameter of the nozzle leads to the increase in the pressure of different measuring points of the side wall of the filter bag;the peak pressure measured at 200 mm in spray distance is the largest.The peak pressure reaching time is reduced with the increase of the spray pressure.The greater the distance between the measuring point and the mouth of the bag,the more significant the impact;the diameter of the nozzle and the spray distance are not the main factor affecting the peak pressure reaching time.(2)The equal circulation area method and the equal filtration area method are used to simplify the pleated filter bag with 8 pleats into a circular filter bag.The numerical calculation results of the simplified two-dimensional and three-dimensional models with equal circulation area method are closer to the experimental results,and the deviations of the wave peak,wave middle and wave trough are less than 10%;the relative deviation between measurement points of the same section in the three-dimensional pleated filter bag simulation is within ±5%,and the influence of the pleat shape on the peak pressure at the wall is smaller.Combining Wall peak pressure,induced airflow,bag mouth static pressure and mass flow rate,the rationality of the simplified methods and models is verified.(3)Under the condition of 22 mm in diameter of the nozzle,a two-dimensional model design orthogonal test is used to study the impact of pleated,filter bag length,spray time,and blowing distance on the ash performance of the fold filter bag.It can be seen that the peak wall pressure increases with the increase of the spraying pressure,and decreases with the increase of the length of the filter bag,and decreases with the increase in the number of folds;the spray distance 200 mm is the best distance;blowing time in the 60～120ms conditions of the peak wall pressure shows a trend of first increase and then decrease.The pressure rising rate decreases with the increase of the spray time,and the number of folds has no significant impact on it;the changes in each influencing factors on the maximum reverse acceleration are the same as the pressure.(4)When studying the cleaning performance under the dust covering conditions through numerical simulation methods,the reliability of the calculation model is verified based on the changes of filter pressure drop by the length of the filter bag,and the filtration speed and the number of pleats on the influence of the filter pressure drop are further analyzed.The results show that the pressure drop increases with the increase of the filter bag length under different filter bag length,face velocity,and fold numbers.The pressure drop is mainly concentrated at one third away from the mouth of the bag,and the variation pattern is consistent with that of the circular filter bag.At the same time,the dust deposition on the surface of the folded filter bag was not uniform in the gas-solid two-phase flow simulation.Under the condition of the same deposition area,the proportion of dust load in the crest and trough of the particles with different particle sizes was similar and larger than that in the middle of the wave.The proportion of large particles with a particle size of 50 μm caught due to inertia and gravity does not exceed10 %,while small particles with a particle size of 2 μm easily move with the airflow and are caught in the bag area with a proportion of 18 %.As the dust thickness increases during the cleaning process,the blowing intensity gradually increases and the coefficient of variation gradually decreases,indicating that the formation of a primary dust layer enhances the cleaning effect.