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To produce pipeline-quality methane with a high level of adsorbent productivity from landfill gas, the pressure swing adsorption (PSA) process with carbon molecular sieve (CMS) was investigated experimentally and theoretically by using CO 2 /CH 4 feed (50/50 vol %). Due to the high throughput as well as the high heat of adsorption of the faster diffusing component (CO 2 ), the isothermal assumption was no longer valid and energy balance equations were inevitable for accurate prediction. Owing to the strong concentration dependency of sorption rate, the adsorption dynamics of the CMS bed in the PSA process were predicted by using a modified LDF model with concentration-dependent diffusivity. The nonisothermal and nonadiabatic model successfully predicted the performance of the CMS PSA process, which was operated by the Skarstrom cycle with cocurrent equalization. The purity was significantly affected by the changes in the adsorption pressure and adsorption step time, while the change in the recovery due to these operating variables was relatively small. The purgeto-feed ratio played a key role in improving the productivity based on the production of 90+% CH 4 from the CH 4 /CO 2 mixture.

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To produce O2 with a high purity of 99+% and a high productivity from various oxygen-rich feeds, a parametric study was done on a six-step pressure swing adsorption (PSA) purifier using carbon molecular sieve (CMS). The cyclic performances of the PSA process such as purity, recovery, and productivity were compared under nonisothermal conditions. To study the effects of N2 amount on the PSA purifier, various feeds with 90% O2 or more were experimentally and theoretically applied for the PSA process. Since N2 plays a key role in product purity, the maximum purity of the PSA was 99% O2 with 51.5% recovery from a higher nitrogen feed (O2:Ar:N2; 90:4:6 vol %) and 99.8% O2 with 56.9% recovery from a lower nitrogen feed (O2:Ar:N2; 95:4:1 vol %) within the experimental range. The adsorption step time and feed flow rate served as key operating variables in the purification of the oxygen-rich feeds because the concentration wave fronts of minor impurities such as N2 and Ar were controlled by kinetic selectivity. To produce 99% O2 purity from feeds with various amounts of N2, the optimum operating variables were set to maximize the recovery and productivity within the experimental ranges. A high feed flow rate accompanied by a short adsorption step time could increase both purity and productivity. Without any serious loss of recovery and productivity, the process could purify the feed with higher than 91% O2 to the product with higher than 99% O2. The nonisothermal model incorporating mass, energy, and momentum balance together with a concentration-dependent rate model could accurately predict the performance results.