Development Of Adsorbents For Volatile Organic Compounds Used In Fluid Bed

Volatile organic compounds(VOCs)are the most common air pollutants emitted by petroleum,chemical industry and related industries.They participate in the formation of haze,seriously destroy the ecological environment and affect human health.The fluid bed adsorption device with the advantages of high gas-solid contact efficiency,high heat transfer rate,high operating gas velocity,is a promising development direction of the treatment of high-volume,low-concentration industrial exhaust gas.The study of adsorbent for fluid bed is basically in blank.The lack of dedicated adsorbents limits the popularization of the fluid bed adsorption purification device.In this thesis,adsorbents,specifically adsorption resins and spherical activated carbons,with low-cost,high abrasion strength,high adsorption capacity and rate,as well as good performance of adsorption and desorption cycle,have been developed to solve the problem of shortage of adsorbents used in fluid bed.Additionally,the design parameter of the fluid bed was calculated with the adsorption resins as adsorbents.Polystyrene was used as raw material to synthesize hypercrosslinked polymers(HCPs)through chloromethylation reaction and post-crosslinking reaction.The pore size of HCPs was controlled effectively by adding n-hexane in the reaction process which served as mesoporous template agent.The average pore size of the resin rises with the increase of the amount of mesoporous template agent;the mesoporous specific surface area increased first and then decreased with the increase of the amount of n-hexane.HCPs with high rigidity and strong wear resistance(abrasion index r168<0.1%),satisfy the requirement of fluid bed.HCPs also have a high specific surface area and pore volume,strong hydrophobicity,and high adsorption capacity of VOCs.Breakthrough curves of were measured by fixed bed adsorption experiments in order to obtain the total mass transfer coefficient,internal and external diffusion coefficients.As calculation result shown,the internal diffusion coefficient of HCPs is 4.68 times of the commercial adsorption resins,indicating HCP-5 have smaller mass transfer resistance and faster adsorption rate.Using HCPs as raw material,polymer-based activated carbon beads(PCBs)with different pore structure was prepared by water vapor activation,ZnCl2 activation and synergistic activation of water vapor-ZnCl2.Vapor activation was favorable for the production of microporous structure,while ZnCl2 activation is conducive to the production of mesoporous structure.PCBs presented excellent wear resistance and hardness with abrasion index less than 0.1%and crushing strength greater than 18 N/particle,able to meet the requirement of fluid bed.PCBs also have high adsorption capacity of VOCs,and their xylene,ethyl acetate and acetone adsorption capacity are all higher than imported commercialized activated carbon used as adsorbents in fluid bed.The total mass transfer coefficient,internal and external diffusion coefficients of PCBs were calculated from breakthrough curves.The internal diffusion coefficient of the PCBs activated by water vapor is 1.66 times of the commercialized fluid bed activated carbon,with a great advantage in mass transfer.In the design of fluid bed using HCPs as adsorbents,to complete the design task of exhausted gas with ethyl acetate concentration of 0.5 g/m3 and flow rate of 30000 m3/h,the required diameter of fluid bed was 5.46 m with 2 layers,and the solid flow rate was 108.43 kg/h.