CH4/N2Adsorptive Separation by a ZSM-5 Zeolite Packed Multicolumn VPSA Process with the SMB Operation Mode for High-Purity Methane Production

Abstract

ZSM-5 zeolites with a high Si/Al molar ratio are commercially available sorbents with a high specific surface area, well-developed microporous structure, good hydrophobic properties, and water resistance, which would be safer and more efficient sorbents to deal with the recovery of flammable methane gas from coalbed gas, shale gas, etc. In this article, ZSM-5 zeolites are used as sorbents, matched with the multicolumn vacuum pressure swing adsorption (VPSA) process with the simulated moving bed (SMB) operation mode to separate CH4/N2 for high-purity methane production. Based on the process design, five-column, six-column, and seven-column VPSA experimental apparatuses have been set up in the laboratory, which are operated with the SMB mode at a fully automatic control platform. According to experimental results, it is found that the switching time of inlet and outlet stream ports can be shortened, and the column number may be also reduced in the proposed VPSA process with ZSM-5 zeolites as sorbents. High-purity methane product gas (99% CH4) can be obtained continuously from 30–60% CH4 feed gas with an above 90% methane recovery efficiency and 1.06–1.64 mol/kg/h methane productivity at 250 kPa and ambient temperature by the developed VPSA process with ZSM-5 zeolites. Compared with our previous work using activated carbon sorbents, the separation performance of CH4/N2 by ZSM-5 zeolites is improved obviously, having a broad prospect for the recovery of low-grade methane gas from unconventional natural gases.