Study On Improvement Of Injection Structure And Optimization Of Internal Flow Field Of Bag Filter In Flue Gas Purification System Of Aluminum Electrolysis Plant

The subject of this paper is the pulse-jet bag filter in the flue gas purification system of aluminum electrolysis plant.In view of the problems occurring in the operation of bag filter,numerical simulation and experimental verification were adopted to study and some improvement measures were put forward.The filter bag cleaning is affected by five factors,including filter bag length and diameter,nozzle type,injection pressure and injection height.In actual engineering application,the combination design of these five factors is mostly depend on experience,so it is difficult to save air consumption and ensure the safety of filter bag while satisfying the pulse-jet cleaning strength.In order to find the optimum combination of five factors,a single bag filter was numerically simulated.The influence of five factors on the cleaning effect was investigated by orthogonal experimental design.According to the method of optimum combination,five factors are aggregated.An experimental platform was built to verify the combination of five factors.The results obtained were in agreement with the numerical results.Nonuniform nozzle injection results in nonuniform cleaning of a row of filter bags.Numerical simulation of the flow field inside the nozzle is carried out.A viewpoint was put forward that cleaning distribution in a row of filter bag is affected by the momentum flux distribution at the outlet of each nozzles.The simulation of the ejection space flow field validated this viewpoint.In order to achieve uniform nozzle injection,the momentum flux distribution at each nozzle outlet should be uniform.Nozzle diameter was optimized by repeated iteration,and the momentum flux distribution was optimized after optimization.The nozzle with optimized nozzle diameter was experimentally verified.The experimental results showed that the optimized nozzles were uniform.The eccentric angle of the nozzle will cause the highly velocity airflow to wash one side of the filter bag directly,leading to the failure of the filter bag.In order to reduce the damage of the filter bag caused by the eccentric angle of air flow,the variation law of the nozzle eccentric angle under different influencing factors must be explored.Nozzle flow field simulation results showed that the eccentric angle is caused by that potency dimension of the static presure at spray,which can deflected airflow velocity direction,is not enough.The closer the nozzle inlet is,the greater the eccentricity angle is.The smaller parameter of the gas pressure,the number of nozzles,the nozzle diameter and the nozzle inner diameter are,the smaller the eccentric angle is.While,the larger parameter of the nozzle length is,the smaller the eccentricity angle is.The flow field inside the bag filter without a deflector is very nonuniform.In order to optimize the uniformity of the internal flow field,the vertical deflector is used to average divide the air flow into several small areas.The numerical simulation results showed that the uniformity of flow field has been improved after adding the vertical deflector.