Abstract:

Most of oxygen-bearing coal-bed methane(CBM)has not been utilized due to the limit in technique for production.The discharged gas leads to not only the waste of resources but also environmental pollution.In this study, a liquefaction process is proposed and designed for the typical CBM.HYSYS software is adopted to simulate the process.The flammability limits are analyzed and calculated based on the flammability limit theory and the simulated results of HYSYS.The results indicate that no flammable hazards exist in the processes of compression, liquefaction and throttling but they may appear at the top of the distillation tower.A method, in which oxygen is first removed from the feed gas with the control of the bottom flowrate(flowrate of the liquid product at column bottom), is adopted to ensure that the methane content is always higher than the flammability limit in the whole liquefaction and distillation processes, so that the operation safety of the whole process is very high.The methane recovery rate and the purity of liquid product are high with low energy consumption.Furthermore, the liquefaction process has good applicability for other gas resources.The simulation results can offer references for the separation of oxygen from CBM and security analysis of liquefied process.

Key words: 含氧煤层气, 液化, 精馏, 爆炸极限

摘要：

大部分含氧煤层气由于技术限制没有被合理利用，而是直接放空，不仅浪费资源，而且污染大气环境。针对某一典型煤层气气源条件和组分特点，设计了一种新型的液化精馏工艺流程，结合HYSYS软件模拟计算结果以及爆炸极限理论，对该液化精馏工艺流程的爆炸极限进行了分析计算，结果表明煤层气中甲烷浓度在压缩、液化以及节流过程中都高于爆炸上限，操作过程安全性比较高。但在精馏塔顶部甲烷浓度开始低于爆炸上限而导致精馏过程存在安全隐患。首先对原料气进行初步脱氧，然后再通过调整精馏塔塔底采出量来控制塔顶杂质气体中甲烷含量，使得其在整个液化及精馏流程中始终高于爆炸上限。分析结果表明，采取安全措施后整个流程都不存在爆炸危险性，甲烷回收率和产品纯度都较高，而且整个流程能耗也比较低。模拟结果显示，所设计的液化及精馏流程对不同气源具有较好的适用性，分析计算结果为含氧煤层气的杂质分离、操作过程的爆炸极限分析以及安全措施的采取提供了一定的参考。

关键词: 含氧煤层气, 液化, 精馏, 爆炸极限