有序介孔材料上水合物法富集低浓度煤层气甲烷

The usage of methane captured from gas drainage in operational mines is very difficult because of the low concentration of methane and the scattered location of mines. Low temperature rectify,as a conventional method,is not economical. PSA is supported to be a good choice for its low investment, flexible maneuverability and low energy cost. But the main problem, low selectivity of adsorbent, is not resolved. The present project proposes a new method for the separation of methane, nitrogen and oxygen in the ordered mesoporous materials on the basic of different formation pressure of gas hydrate. The operational pressure of coalbed gas is controlled to make the partial pressure of methane reach the pressure at which methane hydrate forms, and the partial pressures of nitrogen and oxygen are lower than the pressures at which their hydrate form. This work uses mesoporous materials whose pores are filled with accelerant aqueous solution as high selective reagents. With the co-catalysis of accelerant（such as tetrahydrofuran） and adsorption potential field in nanospace, the formation pressure of gas hydrate decreases and the velocity of hydrate formation and decomposition speed up. The present work tunes up the pore size of ordered mesoporous material to build up an appropriate nanospace and selects the species and concentration of accelerant. It focuses on studying the formation/decomposition equilibrium and dynamics of hydrates of pure gas and coalbed gas, building rational thermodynamics and dynamics models, and then probes the mechanism of hydrated separation on porous materials. On the basic of study above mentioned, factors which affect the recovery and concentration of methane product are cleared in principle and experiment. The mechanism of hydrated enrichment is introduced into PSA cycle. Substituting a cycle of hydrate formation/ decomposition for the conventional cycle of adsorption/refreshment in PSA, therefore the continuous operation of coalbed methane enrichment is achieved.

我国低浓度抽放煤层气规模不等且分散，很难集中利用，传统技术难以分离且极不经济。本项目利用水合物促进剂（如四氢呋喃等）和纳米尺度空间吸附势场的双重催化作用，在有序介孔材料孔内形成水合物，利用甲烷与氮气和氧气水合物生成压的较大差异，控制煤层气的操作压力，使其满足甲烷水合物的生成压力，而氮气和氧气的分压低于各自水合物的生成压力,从而强化甲烷/空气的分离。研究将制备系列具有不同表面性质的介孔材料，采用孔径调节等手段构建合理的纳米尺度空间，通过对纯组分气体和模拟煤层气水合物生成和解析过程的平衡研究和动力学研究，建立热力学和动力学模型，探讨纳米空间内水合物分离机理，明确各因素对产品气甲烷纯度和收率的影响。以填充促进剂水溶液的有序介孔材料为高效甲烷/空气分离剂，将水合物分离原理引入变压吸附分离工艺，实现低浓度煤层气甲烷富集的连续运行。

我国低浓度抽放煤层气规模不等且分散，很难集中利用，传统技术难以分离且极不经济。变压吸附作为革新技术具有操作灵活、投资小,能耗低等优点，但其主要缺点在于吸附剂分离选择性不高。本项目提出利用纳米尺度空间吸附势场的催化作用，在有序介孔材料孔内形成水合物，利用甲烷与氮气和氧气水合物生成压的较大差异，控制煤层气的操作压力，使其满足甲烷水合物的生成压力，而氮气（和氧气）的分压低于各自水合物的生成压力,从而强化甲烷/空气的分离。并将水合物分离原理与变压吸附工艺相结合，实现低浓度煤层气甲烷富集的连续运行。考虑到气体水合物的生成压均较高，实际分离的操作压力一般很难满足其生成压力，因此本研究以四氢呋喃THF作为促进剂降低气体水合物的生成压，以填充促进剂水溶液的介孔材料为高效甲烷/空气分离剂，配制CH4浓度为30%-50%的模拟煤层气，对分离过程进行研究。.研究内容分为三部分。一是介孔材料的制备，前期研究工作表明当介孔材料的孔径在2-5nm时有利于气体水合物的形成和分解，因此本研究制备了有序介孔碳材料CMK-3，其规则的孔结构（孔径3.5nm）适宜水合物的形成。考虑到水热合成法制备介孔材料的成本较高，本研究利用化学和物理法相结合，制备了具有很高介孔比例的活性炭，作为纳米尺度空间的供体。二是纯组分气体水合物在多孔材料上的生成和解析平衡研究，通过测定气体的吸入和平衡等温线，考察了促进剂比例、载水量、压力、温度等条件对水合物形成和分解的影响，并进行了理论分析。三是分离研究，利用纯组分静态实验结果筛选出适宜混合气分离的实验条件，从而实现甲烷的富集。考察了操作压力，吸附时间，原料气浓度等因素对分离效果的影响，并且将水合物的分离原理与变压吸附工艺相结合，进行了多周期的分离实验，考察了工艺的稳定性。.研究结果表明，利用甲烷和氮气水合物生成压力的差异可以将模拟煤层气甲烷浓度提高20%以上，且该原理与变压吸附分离工艺相结合可以实现多周期的稳定运行。本研究为甲烷/氮气的分离提供了一种新的技术选择，亦为其它种类的气体分离提供了可供借鉴的方法和基础数据。