Experimental And Numerical Research On The Characteristics Of Bag Filter

The flue gas emission of coal-fired power plant is one of the major sources of atmospheric pollutant.Especially in those years,pollution of fine particles like PM2.5 is getting worse,which has brought great threats to the health of human beings.It’s imperative to improve the collection efficiency of particles especially to fine particles.The paper investigated on bag filter in order to offer help for the design optimization of bag filters.Both methods of experiment tests and numerical simulations were investigated on the traditional and rotating bag filters.The results of two methods were proved to be consistent with each other by comparing the running resistance.A new method of wet bag filter was put proposed in this paper.Theoretical analysis shows that when wetting the filter bag,the porosity decreases,the screening effect gets enhanced.At the same time,water droplets occupy the space of pores of the filter bags,which will reduce the filling of dust particles.As a result of that,the filter mode will transit from depth filtration to surface filtration much earlier.The mode of surface filtration can improve the dust removal efficiency effectively,and it’s easier to clean the dust layer on the surface of filter bags.What’s more,when spraying water into the system,the adhesion force of dust particles increases.Small particles will agglomerate into larger ones,which is favorable for the dust removal.In summary,the wet type bag filter can improve the dust removal efficiency,but the working resistance will increase with it too.So this paper investigated on the working resistance and dust removal efficiency under different conditions of bag filters.The uniformity of airflow is one of the evaluation standards for the design of traditional bag filters.The paper analyzed the flow low and uniformity of airflow according to the simulation results.Three standards of Flow Distribution Coefficient,Maximum Flow Amplitude and Average Flow Amplitude were applied to evaluate the uniformity of airflow.The results showed that,all the targets meet the request,so it could be reckoned to be uniform.For the traditional bag filter,nine filtration velocities between 1.00m/min and 3.00m/min were investigated.The effects of velocity on the pressure drop and dust removal efficiency were analyzed.The results indicated that with the increasing velocity,the working resistance increased,dust removal efficiency decreased firstly and then increased.When using the wet bag filter,the working resistance increased about three times of the dry bag filter.There was an obvious increase in the dust removal efficiency.The growing rate was among 0.6%to 0.8%.The dust emissions decreased,the decreasing rate was among 75%-82.9%.For the rotating bag filter,the numerical simulation method was firstly used for the structural optimum design.According to the simulation results,the specific spacing of 20 and the filling ratio of 14 were selected for experimental investigation.Eight face velocities between 0.3m/s to 1.4m/s were investigated by the experiment.The results showed that both the working resistance and dust removal efficiency increased with the face velocity.When using the wet bag filter,both the working resistance and dust removal efficiency increased.The working resistance of wet bag filter was 2.6～2.7 times of the dry.The dust removal efficiency growing rate was among 0.4%-0.6%.The dust emissions decreased to 82.8%～91.1%.The wet bag filter technology presented in this paper could enhance the dust removal efficiency,reduce the dust emissions.But it also leaded to a sharp increase in the working resistance.So the wet bag filter can be used as a secondary dust removing equipment,aiming at trapping the fine particles in the gas.Considering the performance of the rotating bag filter,the working resistance was low,and it was remarkable in dealing with huge amount of gas flow.But the dust removal efficiency dropped.Above all,the rotating bag filter was suitable for conditions whose requests for dust removal and dust characteristics were low.It could be also used as a primary dust collector.Besides,it was also feasible to improve the dust removal efficiency of rotating bag filter by adding the number of filtering layers.The investigations in this paper offered some help for the development and application of the wet bag filter technology and optimization design of bag filters.So the study has a certain reference research and practical value.