Separation Of The CH₄/CO₂ Mixture By Adsorption Method

CO₂ is the primary component of fuel gas and the product of combustion, and the primary greenhouse gas, so its purification is given great attention.In this paper, the main aim was to find an excellent adsorbent to separate CO₂ and CH₄. Firstly, triethanolamine (TEA), N-Methyldiethanolamine (MDEA) and diisopropanolamine (DIPA) with high boiling point and different concentration were selected to modify the surface of silica gel, which were researched by adsorption and desorption experiments for the mixtures of CO2 and CH4 respectively. The breakthrough curves, desorption curves, and the parameters of separation factors and purging ratios were obtained. In addition, 13X and Y molecular sieves were researched by adsorption and desorption experiments for the mixtures of CO2 and CH4 respectively, whose breakthrough curves, desorption curves, and the parameters of separation factors and purging ratios were obtained.The compare and analysis for adsorption and desorption performances of different sorbents showed: when the spreading concentrations of three liquid films were 75%, their separation factors were optimal and were 11.2, 12.5 and 12.2 respectively. For the 13X and Y molecular sieves, the separation factors were 6.28 and 7.11 respectively. When the CH4 being purging gas, CO2 in the adsorption bed filled with these sorbents were not desorbed very well. However, when vacuum desorption method was used, the first regeneration ration of MDEA was higher than 80%, which was the optimal desorption, that of TEA and 13X molecular sieve were the second. The regeneration ration of DIPA and Y molecular sieve were about 50%.In conclusion, the silica gel spreaded 75% TEA and 75% MDEA for separation of CO2 and CH4 were best.