The safety of the adsorption process for low concentration (less than 30% ) coal mine methane was analyzed and studied based on the theory of coward explosion triangle, and then a new safe method for enriching low concentration coal mine methane, called the proportion pressure swing adsorption (PPSA) , was put forward. Furthermore , the effects of purge steps on the enrichment process for low concentration coal mine methane based on proportional pressure swing adsorption were investigated experimentally. The results show that purge steps are helpful to decreasing the oxygen and methane concentration in the exhaust gas, and the oxygen and methane concentration decrease with the increase of the purge time. But the purge steps also decrease the methane concentration in the product. So purge steps can be used in the PPSA process to make the oxygen concentration of the exhaust gas in the safe range and ensure the safety of the enrichment for low concentration coal mine. But the purge time should be appropriately controlled to prevent the methane concentration in the desorption gas from reducing too much.%在Coward爆炸三角形的基础上分析研究了低浓度煤层气(甲烷浓度低于30％)吸附富集过程的安全性,提出了一种安全分离富集低浓度煤层气的方法——等比例变压吸附(PPSA)法,并且通过实验研究了用PPSA法时增加反吹过程对低浓度煤层气吸附富集效果和安全性的影响.结果表明:循环步骤中设置反吹过程有利于降低排放气中甲烷和氧气的体积分数.反吹时间越长,排放气中甲烷和氧气体积分数越低,但会使解吸气即产品气中甲烷浓度降低.为了确保低浓度煤层气吸附富集过程的安全性,可以适当地对吸附塔进行反吹,降低排放气中氧气浓度,使之处于安全范围内.但是反吹时间不宜过长,以免使解吸气中甲烷浓度降低过多,使产品气品质不满足后续设备的使用要求.
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