Research On Adsorption Of Ventilation Air Methane By Activated Carbon

The development and utilization of lean methane in coalbed methane are very important for ecological and environmental protection,and profitable.The difficulty in its development and utilization is that the CH4 concentration in the ventilation air methane(VAM)system is very lean,the flow rate is large,and the emission is unstable.Using adsorption method,methane in the VAM was concentrated,which results in high utilization efficiency and low cost.The state of art of adsorption method is not suitable for VAM concentration.In this paper,the systematic study on the concentration process of VAM is carried out.The specific work contents are as follows:(1)Study of the characteristics of VAM concentration adsorbents.The breakthrough curves and adsorption capacity of CH4 molecules on 18 activated carbon adsorbents were studied under the conditions that the methane concentration is 0.4%and the air volume is 500mL/min(the specific speed is 0.106m/s),and three kinds of activated carbon samples were analyzed by BET characterization and FTIR test.The larger specific surface area is the premise of activated carbon with higher methane adsorption capacity,and the proper pore distribution and pore structure are the key to determine methane adsorption.(2)Study of the process of VAM concentration adsorbents.The effects of experimental temperature,experimental pressure,activated carbon particle size,wind speed and methane concentration on CH4/air separation were investigated.The amount of breakthrough and saturated adsorption of methane does not change much with the decrease of particle size,and the adsorption effect of activated carbon with 20-40 mesh is the best;When the experimental temperature is lower,the pressure is higher,the wind speed of the raw material gas is smaller and the concentration of adsorbed gas is higher,then the adsorption penetration time of activated carbon adsorbent on methane is longer and the corresponding adsorption capacity is larger,which has a certain mathematical relationship between them.(3)Study of the modification of VAM concentration adsorbents.The effects of high temperature modification,water vapor treatment,HNO3 oxidation modification and ammonia reduction modification on the adsorption performance of activated carbon for methane were investigated.The water vapor treatment and high temperature modification had little effect on the surface properties and penetration time of activated carbon,but had a slight effect on the saturated adsorption of it.After the modification of HN03 oxidation,the total specific surface area of activated carbon decreased,and the acidic functional group is enough still,which is not conducive to the adsorption of methane;the modification of activated carbon with 10%ammonia can improve the methane adsorption performance,and as the ammonia concentration increases,the methane adsorption effect of activated carbon first becomes better and then decreases.