Research On The Volatile Organic Compounds Emission Control By Multistage Bubbling Fluidized Bed Adsorption

This paper takes the development of volatile organic compounds(VOCs)emission control of multi-stage bubbling fluidized bed adsorption process as the background,which involves the screening of adsorbents,the establishment of multi-stage bubbling fluidized bed and experimental research,and the improvement of multi-stage bubbling fluidized bed and related experimental research.The dynamic adsorption experiments and temperature-programmed desorption curves of the selected three adsorbents were carried out on a self-made fixed bed evaluation device and Labsys Evolution thermogravimetric analyzer,respectively.Combined with the characterization of the adsorbent pore structure and surface oxygen-containing functional groups,the impact of pore structure and surface chemistry of the adsorbent on the adsorption performance were analyzed.Among the three adsorbents selected in this paper,the pitch-based spherical activated carbon(PSAC)adsorbent with the smallest pore size distribution and the maximum bulk density has the best comprehensive adsorption performance.A pilot-scale multistage bubbling fluidized bed adsorption device was designed and constructed.The adsorption of polar ethanol in industrial waste gas using PSAC adsorbent was experimentally studied.And the effects of different operating conditions,such as bed height,superficial gas velocity,ethanol concentration,adsorbent circulation rate and desorption temperature,on the adsorption efficiency of ethanol were examined critically.The results show that the self-built two-stage bubbling fluidized bed adsorption device can continuously and stably carry out the adsorption and purification of organic waste gas.The purification efficiency of the two-stage bubbling fluidized bed to the exhaust gas varies from 81.3%to 94.5%when the desorption is complete within the range of selected operating variables,which has good industrial application potential.To further improve the purification efficiency,the two-stage bubbling fluidized bed was modified into a four-stage bubbling fluidized bed.And the effects of different operating conditions,such as superficial gas velocity,inlet concentration,adsorbent circulation rate and the type of adsorbate,on the adsorption efficiency of ethanol were examined critically under the total bed height of 80 mm.The results show that after the two-stage bubbling fluidized bed is improved to a four-stage bubbling fluidized bed,the purification efficiency of the four-stage bubbling fluidized bed for ethanol varies from 94.6%to 97.9%and xylene varies from 95.4%to 98.6%within the range of selected operating variables.The purification efficiency of the VOCs exhaust gas in the four-stage bubbling fluidized bed has been greatly improved and almost does not change with the change of operating conditions such as superficial gas velocity,inlet concentration,adsorbent circulation rate and adsorbent type,which has high adaptability and stability to changes in adsorption conditions and is very suitable for industrial waste gas treatment.