| In this paper,three coal-based activated carbons were used as adsorbents to conduct single-component fixed-bed adsorption experiments,combined with toluene and butanone as adsorbents.Its purpose is to study the effect of both physical properties of activated carbon and adsorption parameters on adsorption behavior.Meanwhile,the cyclic adsorption and desorption experiments of three activated carbons were performed with toluene and butanone to implore the impact of the pore structure of activated carbon.The main research contents and conclusions in this paper are as follows:1.The fixed bed adsorption experiments of three kinds of activated carbon on toluene and butanone were carried out,and the influence of pore structure of activated carbon on adsorption was discussed.The results show that:The adsorption of toluene and butanone on activated carbon has an effective pore volume.The specific surface area,total pore volume and micropore volume are not the key factors determining the adsorption performance of activated carbon;With the increasing of inlet gas concentration,the effective adsorption pore size range is increased in the activated carbon increases.When the toluene concentration is lower than 1000mg/m3,the main adsorption occurs at the micro-pore structure?<0.7 nm,<1.4 nm?.But pore structure of 0.72.8 nm in activated carbon plays an important role in adsorption with concentration of toluene higher than 2000 mg/m3.When the butanone concentration is below1500 mg/m3,the pore volume of<0.65 nm is the effective for butanone adsorption in activated carbon.Meanwhile,the pore volume of<1.3 nm in activated carbon plays a key role in adsorption with concentration of toluene higher than 1500 mg/m3.The saturated vapor pressure of adsorbate is different in capillary condensation occurs in different pore sizes of activated carbon.Under the experimental concentration range,the maximum pore sizes the condensation are 2.4 nm and 1.8 nm according to toluene and butanone,respectively.2.With the increasing of inlet gas concentration,the breakthrough time is significantly shortened and the length of mass transfer zone is gradually increased,plus the utilization ratio of bed first decreases,then increases and then decreases,which is relate to effective adsorption pore volume of activated carbon.The relationship between the breakthrough time of toluene and butanone adsorbed by activated carbon and the concentration of inlet gas is consistent with the formula of Lntb=ALnc0+B.3.The effects of temperature,space velocity and activated carbon particle size on adsorption performance were investigated.The results suggest that the adsorption performance on the three activated carbons is decreased with the increasing of temperature,and the bed pressure drop has no change.In addition,the adsorption performance of AC-2 is less affected with temperature,and is superior with temperature higher than 35°C.With the increase of space velocity,the breakthrough time,breakthrough adsorption capacity and utilization ratio of activated carbon for toluene and butanone decreased,while the bed pressure drop and height of mass transfer zone increased,but the saturated adsorption capacity remained unchanged.AC-2is most affected by space velocity,and toluene is less affected by space velocity than butanone.At the same space velocity,the bed utilization rate is related to the properties of adsorbate and the physical properties of activated carbon.The activated carbon with 12 mm particle size has the best adsorption performance for toluene and butanone.The mass transfer zone has the lowest height and the bed utilization rate is the highest.The SPSS software was used to obtain the model by multivariate linear regression of the adsorption capacity of toluene and butanone,concentration of the inlet,adsorption temperature,effective adsorption pore volume.4.The adsorption kinetics of toluene and butanone were investigated under different conditions,including adsorption time,inlet concentration,adsorption temperature and space velocity.The adsorption behavior of activated carbon under different temperature and space velocity conditions was simulated by pseudo-first-order and pseudo-second-order and Bangham kinetic models.The results show that the fitness of the Bangham kinetic model is greater than 0.99.The three kinetic models have no obvious relationship with the pore structure characteristics of the three activated carbons.The applicability in this experiment is Bangham>pseudo-first-order>pseudo-second-order.5.Three activated carbons were subjected to cyclic vacuum desorption experiments at different temperatures to study the effect of pore structure on desorption.The results showed that with the increasing of desorption temperature,the desorption rate of activated carbon to toluene and butanone increased,the amount of cyclic adsorption increased,the breakthrough time prolonged,and the closeness of regenerated carbon and new carbon increased.The desorption rate of butanone is higher than that of toluene at the same temperature.The desorption rate of butanone can reach 99%at the desorption temperature of 90?.The order of desorption rate is AC-2>AC-3>AC-1 in three activated carbons at the same temperature.Meanwhile,the pore structure with 0.72.8 nm has a certain positive effect on the desorption of toluene,and the pore structure with 0.652.6 nm plays an active role in the effective desorption of butanone.During the cyclic adsorption and desorption process,the adsorbate can be completely desorbed without affecting the pore structure of activated carbon.The adsorption capacity and breakthrough time has no changed basically in of each cycle.At the same desorption temperature,the cyclic adsorption capacity of AC-2 and AC-3 for toluene is higher than that of AC-1,and the order of the cyclic adsorption capacity of butanone is AC-1>AC-3>AC-2.There are 38 figures,37 tables and 87 references in this thesis. |
PDF Full Text Request