Investigation On Pressure Characteristics In Radial Bed Dust Collector

The radial fixed bed has been widely used in many processes,e.g.,by its advantages of low pressure drop,high process capacity and easy to large-scale.In the gas collection and distribution channels of the radial bed,the variable mass flow of gas makes it difficult for the pressure to maintain a constant value in the axial direction.It greatly affects the bed efficiency by increasing the nonuniformity of the gas velocity distribution in the bed.Thus,with the studying of the pressure distribution characteristics in the mainstream channels,the momentum exchange coefficient K is determined by many scholars.The coefficient is used to calculate the pressure change in the mainstream channels.The pressure characteristics can then be obtained.However,the previous studies mainly focused on the overall momentum exchange coefficient rather than the local momentum exchange coefficient distribution with the axial direction,which will definitely affect the calculation accuracy of the pressure distribution in the mainstream channels.The CP-Πand CP-Z radial fixed bed are built in this project.By measuring and analyzing the pressure distribution in the gas collection and distribution channels,the overall pressure drop of the particle bed is got as well as the overall momentum exchange coefficient in the flow channels.Afterwards,with the analysis of the Ergun equation,the mass and momentum balances in the element body,the gas radial velocity distribution along the axial direction in the particle bed is obtained as well as the gas velocity in the flow channels.According to the experimental data,the computation model of the local momentum exchange coefficient is finally fitted in the flow channels.Besides,the flow fields are investigated after introducing the talc particles with the concentration of 0,0.5,and 1.5 g/m³in a CP-Πradial fixed bed.Above methods are used to discuss the influence of the dust concentration and time on the flow fields,e.g.,pressure and local momentum exchange coefficients in channels.The dust removal efficiency is then obtained.The calculation model of pressure drop is also established.It is found that the flow fields have many similaritiesin the radial fixed bed with/without the introduction of talc particles.The pressure increases along the gas flow directionin the distribution channel of the radial bed;while it decreases in the collection channel.Based on the pressure drop and gas radial velocity in the particle bed,the CP-Πtype is slightly better than the CP-Z type.Considering that the sensitivity of the momentum exchange coefficient to the pressure measurement error,the distribution channel has smaller value than the collection channel.The flow field is mainly analyzed in the distribution channel.In the distribution channel,the overall momentum coefficient almost invariant with the operating modes,gas flow volume,axial position,dust concentration and time.The local momentum exchange coefficient is only a function of the local flow rate ratio u/u₀,which decreases with the ratio firstly and then becomes nearly unchangable.According to the experimental results,the computation model of the local momentum exchange is established by regression method within±11%error.Compared to the clean bed,the pressure in the channels changes with the dust concentration and removaltime in the bed with talcum particles.With the increasing of dust concentration and time,the amounts of dust deposition gradually grows in the particle bed.It makes the bed porosity to decrease,which raises the overall pressure drop of the particles and the evenness of the gas velocity distribution.The momentum exchange coefficient is nearly unaffected,which indicates the computaion model of local momentum exchange coefficient also works in the bed with talcum particles.The dust removal efficiency reached 100%under the experimental conditions in this project.In addition,based on the pressure drop formula used in clean bed,the sedimentation rate and the bed voidage,the empirical formula of pressure drop is established within±15%error in the bed with talcum particles.It is expected to provide a reference for the designation of radial bed dust collector..