THF对高浓度CH_4瓦斯水合分离效果影响实验

Experimental for the influence of THF on the hydrate separation effect of high concentration CH_4 gas

为改善高浓度CH_4瓦斯水合分离效果,进行了3种初始压力(1.5,2.5,3.5 MPa)影响下高浓度CH_4瓦斯(60%CH_4,32%N_2,8%O_2)在摩尔分数为2.5%~5.5%的THF溶液中的水合分离实验,结合气相色谱分析结果,考察THF摩尔分数、初始压力对CH_4回收率和分离因子的影响;利用Raman光谱技术分析高浓度CH_4瓦斯在THF摩尔分数5.5%、初始压力1.5 MPa、温度2℃实验条件下水合产物微观晶体结构特征。结果表明:同一压力下,CH_4回收率和分离因子随THF摩尔分数升高呈递增趋势;THF摩尔分数在2.5%~4.5%时,CH_4回收率随着初始压力的升高先增大后减小,THF摩尔分数为5.5%时,CH_4回收率随着初始压力的升高而增大,4种浓度THF溶液中分离因子均随着初始压力的升高而减小;THF参与水合反应并占据大孔穴(5^(12)6~4),为瓦斯气体提供小孔穴(5^(12))骨架,CH_4优于N_2,O_2占据小孔穴,THF—CH_4—H_2O生成II型水合物。

In order to improve the hydrate separation effect of highly concentrated CH_4 gas,authors studied the hydrateseparation experiment on a high concentration CH_4gas（60% CH_4,32% N_2 and 8% O_2） under the condition of dif-ferent concentrated THF solutions whose concentration were 2. 5%-5. 5%,and three kinds of initial pressures（1. 5,2. 5 and 3. 5 MPa）. In combination with the analysis results of gas chromatography,the effect of THF concentrationand initial pressure on the recovery and separation factor of CH_4 were investigated,the hydration products of microcrystalline structure characteristics of the high concentration CH_4 gas were analyzed by Raman spectroscopy,under thecondition that the THF concentration was 5. 5%,the initial temperature was 2 ℃,and the pressure was 1. 5 MPa. Theresults indicate that the CH_4 recovery and separation factor increase with the increase of THF concentration at the samepressure. When the concentration of THF is 2. 5%-4. 5%,the CH_4 recovery increases at first and then decreases withthe increase of initial pressure. When the concentration of THF is 5. 5%,the CH_4 recovery increases with the increaseof initial pressure,the separation factor decreases with the increase of initial pressure in the four concentration of THFsolution. THF is involved in the hydration reaction and occupies the large cages（5^126^4）,then provides the small cages（5^12） skeleton for gas,CH_4 has precedence to N_2 and O_2,THF—CH_4—H_2O forms the hydrate of structure II.