Abstract
Coalbed methane (CBM) is a kind of unconventional gas. CBM often contains a great deal of air when it comes out of the well. So, it must be condensed and purified before it can be applied. In this paper, raw clinoptilolite (Cp) was treated with grinding, gravimetric concentration, and ion-exchange using different aqueous solutions of salts. Then, the modified Cp powder was prepared into particles as adsorbents. Then, the adsorbents were used for nitrogen/methane separation in pressure swing adsorption (PSA) at the same condition of 0.2 MPa and 298 K. Research results indicated that there were micropores and lots of mesopores in the Cp, and the pores were mainly slit holes formed by sheet stacking. The adsorbents of NH4-Cp, Cs-Cp, and Cu-Cp showed good equilibrium selectivity for CH4, and the equilibrium separation factors of CH4 and N2 were 2.56, 2.31, and 1.95, respectively. The adsorbents of Na-Cp and Ag-Cp showed good equilibrium selectivity for N2, and the equilibrium separation factors of N2 and CH4 were 7.25 and 6.53, respectively. Consequently, the adsorbent of Na-Cp was suitable for nitrogen/methane mixture separation, which could make the concentration of methane concentrated from 19.7% to 30.72%.
Highlights
For a long time, coalbed methane (CBM) has been discharged into the atmosphere from coal mines for the safe of coal production
Cp has been studied with a view to its use in natural gas purification
The natural clinoptilolite was crushed to 200 mesh by wet-grinding, and the milled pulp was poured into a centrifuge to remove any heavy impurities
Summary
For a long time, coalbed methane (CBM) has been discharged into the atmosphere from coal mines for the safe of coal production. The equilibrium adsorption capacity of activated carbon to methane is higher than that of nitrogen, and the separation coefficient is higher. Materials 2018, 11, x FOR PEER REVIEW carbon is circulation, powdered, which often blockage equipment It characterized by large by large gas low efficiency, andcauses high costs. There is difficulty in separating methane and effect isThe the zeolite opposite. Because of molecular sieve is a very promising adsorbent Zeolites, because of their inherent porosity, crystallinity, inherent porosity, crystallinity, and the presence of hydrated aluminosilicates of alkali and alkaline and the presence of hydrated aluminosilicates of alkali and alkaline earth cations, can absorb as polar earth cations, can absorb polar molecules and small molecules: they have long been considered molecules and small molecules: have long considered candidate materials excellent candidate materials for thethey separation of been gases. 0.55 × 0.40 nm) [5]
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