Research On The Pre-separation Of Dust In The Settling Chamber Of Dual Layer Granule Bed Filter

Air pollution destroyed the ecosystem and would directly affect human health.Industrial waste gas was one of the most important causes of air pollution.Therefore,more and more attention has been paid to the purification of industrial waste gas.The filtration technology of dual layer granule bed had high efficiency,high temperature resistance,energy saving and emission reduction.The dual layer granule bed is composed of two layers of chemically stable solid particles.Dust containing gas first passes through the upper layer,for crude filtering,and then through the lower one for fine filtering.During back-flushing,The dust intercepted by the granule bed were blown out.In the dual layer granular bed filter,generally adopts a plurality of granule bed for dust removal.When the dust intercepted by a granule bed were blown out,then they would be easy to get into another granule bed again and resulted in a heavier burden on granule bed.In this study,the gas-solid two-phase flow field in the settling chamber was numerically simulated by using the RNG k-? model and the discrete phase model in the FLUENT software.In order to prevent the coarse dust particles from entering the dual layer granular bed and to reduce the filtration burden of the granular bed,the method of installing the guide-plate at the entrance of the granular bed was adopted to improve the inertia separation of dust.The effect of different types of guide plate on particle settling efficiency was studied.In order to solve the problem that more particles entered the bottom granule bed,the way of the downward extension of the guide-plate and the design of the bottom pumping system were studied.Simulation results showed that,installing appropriate guide-plates in the settling chamber could effectively reduce the burden of dual layer granule bed,and the coarse dust particles settled to the bottom ash bucket directly.The bottom gas circulatory system with proper air velocity could reduce the particle entering the bottom granular bed and improved the sedimentation rate of the particles at the bottom ash bucket.Using the improved settling chamber with different density of dust particles in different gases caused good settlement effect.In the improved settling chamber filled with 500? gas,the density of 1.2g/cm3 dust particles with the particle size of more than 125?m,which will not enter the filter bed and directly settle to the bottom.According to the simulation results,the minimum back-flushing speed of the granular bed was calculated,so all the dust of intercepted by the granular bed could be cleaned out,ensured the regeneration effect of the filter material,which could provide a reference for the optimal design of the dual layer granular bed filter.