Study On Oxygen Removal From Coal Mine Methane By VPSA

In this paper, a safe and effective oxygen removal and methane enrichment process is proposed which is based on vapor pressure swing adsorption (VPSA). A mixture of methane and air, in which the oxygen content is13vol%, was used as the feed gas, and five kinds of commercial carbon molecular sieve (CMS) as adsorbents. The oxygen removal from coal mine methane was studied in a laboratory scale two-column VPSA unit with adsorption-rinse-pressure equalization-desorption cycle.The influences of adsorption time, flow of feed gas, rinse time and rinse pressure on the degree of oxygen removal were comparatively investigated for the VPSA process with different CMS. CMS-1showed the best oxygen removal performance, in which the oxygen content was reduced to0.25%in product gas, the methane recovery reached to96.5%while the concent of methane in product gas increased by11.8%. CMS-3owned the best methane enrichment with an increase of33.4%in methane content, while oxygen content of1.33%in the product gas and methane recovery of88.7%were obtained.Then a novel VPSA process with layered beds was applied for purifying coal mine methane with CMS-1and CMS-3. The layered pressure swing adsorption (LPSA) process was composed of the CMS-1to selectively remove Oxygen followed by a layer of CMS-3to make the separation of nitrogen from methane. The mass ratio of CMS-1/CMS-3layers was also varied to analyze the effect of this parameter in overall unit performance. Oxygen content of the product gas and methane enrichment through the layered beds showed an intermedia behavior between CMS-1beds and CSM-3beds. The higher mass ratio produced lower oxygen content, higher methane recovery in product gas, and lower methane enrichment. Under the optimized ratio of2:1, the oxygen in product gas and the methane recovery were0.40%and91.8%, respectively, and the methane concent in product gas was20.6%higher than that in feed gas.