Study On Oxygen Removal From Coal Mine Methane By VPSA And Preparation Of CMS

In the study, oxygen removal from coal mine methane (CMM) by vacuum pressure swing adsorption(VPSA) and preparation of carbon molecular sieves (CMS) by chemical vapor deposition(CVD) were investigated.Five kinds of CMS were characterized by XRD and element analysis to determine their microstructure and element composition. In order to determine which CMS is suitable for oxygen removal from CMM by VPSA, the dynamic selectivity of O2/N2/CH4of the CMSs were measured, and air separations were taken by PSA. The results showed that CMS-5was the best adsorbent for oxygen removal from CMM, which possessed selectivity coefficients of O2/N2and O2/CH4were3.15and infinite, respectively. A series of experiments were carried out with CMS-5as the adsorbents by a novel two-column VPSA unit. The simulative coal mine methane consisted of air and methane in which oxygen content was about12%. For the process, the effects of influences of adsorption time, rinse time, rinse pressure, feed flow, and pressure equalization time on the performance of oxygen removal were investigated. It was found that with adsorption time of80s, rinse time of40s, rinse pressure of0.33MPa, feed flow of850mL/min and pressure equalization time of3s, the oxygen concentration of product gas was0.3%, methane content of product gas was52.3%, which increased by10.2%compared with the feed gas.,and methane content in effluent was2.7%with the recovery of95.5%, which confirmed that the process for oxygen removal using CMS as adsorbent was an effective and safe technology.In the present work, an effert has been made to develop a suitable CMS for oxygen removal from oxygen-bearing CMM. The CMS has been prepared through CVD of benzene on activated carbon precursor. Two methods were used to manufacture CMS by CVD:the one is that CMS was obtained by one-step CVD, which possessed a certain air separation effect. During the operation, the effects of CVD temperature, time and benzene flow rate on the CMS pore structures have been examined in detail. The result showed that with optimum operation conditions of the CVD temperature850℃, CVD time30min and benzene flow rate1.5mL/min, N2concentration in the product can reach to96%by PSA with as-prepared CMS as the adsorbents. Another way is that during the CVD process, the slow-release agent is added to the benzene vapor, and the flow rate and deposition time are investigated. The result showed that with the slow release flow rate19.72mL/h and deposition time32min, N2concentration in the PSA product can get upto97%from air with the CMS. Although the air separation results from prepared CMSs were not very well, the relation between air separation and the CVD conditions was attained which can guide the future experiments for prepared CMSs.