Cleaning Mechanism And Cleaning Performance Optimization Of Flat Box Cartridge Filter

Flat cartridge filter has broad prospect and great potential in application for powder collection because of its small area occupied,high dust removal efficiency and flexible installation.The present studies show that the traditional pulse-jet ash cleaning method always lead to a serious ash accumulation in the upper and lower ends of the flat cartridge,indicating that a large area of ash cleaning failure is caused and the dust removal efficiency is significantly reduced,which restrict the application and development of the flat cartridge filter.In order to improve the cleaning uniformity of the flat cartridge filter,in this paper,different types of blowing hole were developed based on the characteristics of the pulse airflow and pressure distribution inside the filter.The effect of different pulse ash jet flow field structure on the performance of the flat filter dust collector was studied systematically.The attenuation law and superposition effect of the air flow inside the flat filter cylinder under the conditions of both symmetric and asymmetric jet blowing were analyzed.The impacting mechanism of the pressure distribution characteristic inside the filter by different blowing conditions were revealed.The cleaning performance of the filter was optimized.The main research contents and conclusions are as follows:（1）The design idea of replacing the conventional pulsed circular jet with plane jet was proposed.The results showed that the velocity attenuation rate of plane jet along the flow was less than that of circular jet.The free hysteresis points were 5 and 35 mm by the plane jet and the circular jet,respectively.The flat filter completely located in the intersection and superposition area of the air flow by the plane jet.In this way,the blowing airflow was better distributed,which is more conducive to the upper cleaning of the flat filter.At 0.3 MPa pressure of plane jet,the pressures at all measuring points were greater than 306 Pa,which met the basic cleaning requirement.At the jet distance of 60 mm,the maximum relative standard deviation of the peak pressure on the inner wall was 413,indicating that the cleaning uniformity is the worst.When the jet distance was 20 mm,the average peak pressure was the largest（901.2 Pa）,but there was still a problem of insufficient cleaning capacity in the lower part of the flat filter.（2）In order to optimize the airflow field distribution at the bottom of the flat filter,the impacting laws of different length-width ratio of slotted holes on the airflow field distribution were systematically studied.The results showed that the peak pressure by the two-slit blow hole（99×2 mm）at the measuring points at the non-positive-to-blow hole area cannot reach the minimum cleaning strength requirement under any condition.At 0.2 MPa jet pressure,the average peak pressure of the three-slit hole（66×2 mm）was 1725 Pa and the minimum peak pressure of the measuring point is 1013 Pa,which was better than that of the four-slit hole（50×2 mm）and five-slit hole（40×2 mm）.The results of coating experiments showed that under the conditions of three-slit blow hole,200 g/m³gas-solid concentration,and 1.0 m/min filtered wind speed,the cleaning performance was the best.The problem of ash trapping at the bottom was solved.At the same time,the skew of air flow by plane jet was found.Schlieren test results showed that the maximum deflection angle of the airflow by plane jet was 30°,and the maximum deflection angle of the airflow by circular jet was 5°.（3）The blowpipe with several groups of circular jet holes was established to study their flow field distribution of in the process of pulse-jet deashing.The results showed that the peak pressures at the measuring points of P4 and P5 which are located at the non-positive-to-blow hole area could not meet the requirements of minimum cleaning strength under any condition by the group of four circular blowing holes with a diameter of 5mm.For the group of seven circular blowing holes with a diameter of 4 mm,the average peak pressure of the flat filter is 1274 Pa under the conditions of 0.3 MPa jet pressure and 40mm jet distance.When the jet distance is 100 mm,the relative standard deviation of the measuring point inside the flat filter is the smallest（413）,and the uniformity of the flat filter cartridge is the best.The structure of the blowpipe with several groups of circular jet holes can greatly improve the skew of the jet flow,and optimize the uniformity of the pressure distribution of the jet flow in the inner part of the flat filter,especially in the bottom area,and it was better than plane jet in the cleaning strength.（4）In order to further improve the uniformity of pulse jet flow,the physical model of uniformly distributed holes with small diameter was established.The results showed that the distribution of the air flow jetted by the blowpipe with uniformly distributed holes with small diameter formed an air curtain which entered into the flat filter at the moment of the jet flow ejecting was homogeneous.Under 0.1 MPa jet pressure and 10–20 mm the optimal jet distance,the peak pressure at each measuring point can meet the basic cleaning requirement,and the uniformity of cleaning is good.A theoretical model of induced air flow was established,and the maximum induced air flow at the optimum injection distance was verified.It is concluded that the induced distance is proportional to the induced flow rate and inversely proportional to the average velocity of the jet section.（5）The lithium iron phosphate powder(D₅₀=6.24μm)was collected in the coating experiments in industrial scale to verify the dust removal effect by the proposed structure of the blowpipe with uniformly distributed holes with small diameter.The results show that the filter flow velocity is the main factor affecting the operating resistance of the system,followed by the gas-solid concentration and the pressure of the jet flow.When the filter flow velocity is no more than 0.6 m/s,the low jet pressure can realize the efficient operation of the dust removal system（0.1 MPa）.When the filter flow velocity reaches 0.8 m/s and the gas-solid concentration increases to 200 g/m³,0.2 MPa jet pressure can meet the requirement of maintaining the stable and continuous operation of the dust removal system.This work provides a series of new methods for the opening mode of the blowing hole,contributing to a new way for the running of flat filter cartridge with high efficiency and low energy consumption,and a foundation for wider application of the flat filter cartridge in environmental protection.