Adsorption And Desorption Of Foreon 11 And Cyclohexane On Activated Carbon Bed

Aiming at the mechanical leakage problem of fixed bed absorption device which has attracted the attention of domestic and foreign institutions,non-destructive evaluation has been widely applied and popularized.In this paper,freon-11 and cyclohexane were selected as tracer gases for mechanical leakage detection of absorption device,and the adsorption and desorption process of the two gases on activated carbon material for chemical protection was studied.BET,FTIR and XPS were used to characterize the physical structure and surface chemical characteristics of three kinds of activated carbons for chemical protection.The adsorption equilibria of cyclohexane,water and freon-11 on the adsorbent were measured.The effects of different air flow velocity,air relative humidity,initial concentration and bed thickness on the adsorption penetration of cyclohexane and freon-11 on carbon bed were investigated.Wheeler equation,Shilov equation and Yoon-Nelson equation were used to describe the adsorption kinetics.Air flow rate,temperature and bed water content on the removal effect of tracer gas were discussed as the influence mechanism,and the desorption process were described by LDF and Freundlich desorption kinetics models.The results show that:（1）The three kinds of activated carbons are microporous adsorbents,and the main surface oxygen-containing functional groups of the three activated carbons are hydroxyl and ether groups,and may contain a small amount of carbonyl,quinone,carboxyl and ester groups.The sequence of pore volume and BET surface area of the three activated carbons are BC>ASC-T>ASZM-T;（2）The adsorption of freon-11 and cyclohexane by activated carbon is mainly physical adsorption.The L-F equation can fit the I-type adsorption isotherm of cyclohexane better,and DR equation and Langmuir equation can fit the adsorption equilibrium data of freon-11 on ASZM-T and cyclohexane at low concentration.（3）The adsorption kinetics was mainly controlled by external diffusion.The quantitative relationship between the protective time of freon-11 and cyclohexane on ASZM-T and specific velocity,bed thickness and initial concentration was determined.The effect of humidity on the penetration behavior is mainly reflected in the curl of the breakthrough curve caused by the competitive adsorption between gas adsorbents and water molecules.（4）The desorption rate of freon-11 was positively correlated with temperature and bed water content,desorption temperature 25-30℃and air flow rate 0.8 L·min^-1·cm^-2are the best conditions for industrial mechanical leakage test desorption The desorption rate of cyclohexane gas is positively correlated with air flow rate and temperature,and negatively correlated with bed water content.The industrial test temperature condition should not be less than 50℃,and high specific velocity condition should be adopted.The research results of this subject reveal the adsorption and desorption regulars of the two tracer gases freon-11 and cyclohexane in the activated carbon bed,and supply a vital theoretical foundation and technical assistance for establishing non-destructive inspection method of mechanical leakage in fixed bed adsorption device.