A method of separating and concentrating CH4 from coal bed methane (CBM) by hydrate formation was proposed. The separation experiments of CBM simulation gas (13.11vol% CH4+86.89vol% N2) were carried out by adding promoter solution of 5.8mol% Tetrahydrofuran (THF)?0.03mol% Sodium dodecyl sulfate (SDS). The effect of pressure, temperature and reaction time on gas consumption, reaction rate, methane concentration in the hydrate, methane recovery and separation factor were investigated. The concentrations of methane in the residual gas phase and the decomposed gas phase were determined by chromatographic analysis. The results indicated that the higher pressure, lower temperature, longer reaction time facilitated gas consumption, methane recovery and separation factor. With the increase of pressure, the recovery of CH4 and the separation factor of CH4 increased. It illustrated that higher pressure resulted in better separation efficiency for CBM. As the temperature decreased, nitrogen competed with methane to enter hydrate crystals, which led to the reduction of methane concentration in the hydrate phase. The temperature was the key factor affecting the methane separation factor, and the increase of temperature was propitious to improve the selectivity of methane hydrate. The maximum methane recovery rate was up to 98.65%, and the maximum separation factor was 14.83. With the increase of reaction time, the concentration of CH4 in decomposition gas increased. This indicated that CH4 and N2 molecules entered the hydrate lattice with the reaction proceeding, but the amount of CH4 entering the hydrate was more than that of N2 in the later stage of the reaction. This technology can effectively separate methane from low concentration coal bed methane and was valuable to storage and transportation of CBM and to disposal of mine methane.
[1]Sun Q, Guo XQ, Liu AX, et al.Experimental study on the separation of CH4 and N2 via hydrate formation in TBAB solution[J].Industrial & Engineering Chemistry Research, 2011, 50(4):2284-2288
[2]曲思建, 董卫国, 李雪飞, 等.低浓度煤层气脱氧浓缩工艺技术开发与应用[J].煤炭学报, 2014, 39(8):1539-1544
[3]Qu S J, Dong W G, Li X F, et al.Research and application of the low concentrated coal bed methane upgrading technique[J].Journal of China Coal Society, 2014, 39(8):1539-1544
[4]杨仲卿, 张力, 唐强.超低浓度煤层气能源化利用技术研究进展[J].天然气工业, 2010, 30(2):115-118
[5]Yang Z Q, Zhang L, Tang Q.Research progress in the utilization of ventilation air methane as an energy source[J].Natural Gas Industry, 2010, 30(2):115-118
[6]朱耀剑, 梁海峰, 车雯, 等.基于水合物法浓缩低浓度煤层气的研究进展[J].现代化工, 2013, 33(11):31-35
[7]Zhu Y J, Liang H F, Che W, et al.Progress of condensation of low-concentration coal-bed methane based on hydrate-based[J].Modern Chemical Industry, 2013, 33(11):31-35
[8]Zhong D L, Ye Y, Yang C.Equilibrium conditions for semiclathrate hydrates formed in the CH4 + N2 +O2 +tetra-n-butyl ammonium bromide systems[J].Journal of Chemical and Engineering Data, 2011, 56(6):2899-2903
[9]Zhong D L, Englezos P.Methane separation from coal mine methane gas by tetra-n-butyl ammonium bromide semiclathrate hydrate formation[J].Energy & Fuels, 2012, 26(4):2098-2106
[10]Zhong D L, Ye Y, Yang C, et al.Experimental investigation of methane separation from low-concentration coal mine gas (CH4/N2/O2) by tetra-n-butyl ammonium bromide semiclathrate hydrate crystallization [J]. Industrial & Engineering Chemistry Research, 2012, 51:14806-14813.[J].Industrial & Engineering Chemistry Research, 2012, 51:14806-14813
[11]Zhong D L, Kun D, Jin Y, et al.Influence of cyclopentane and SDS on methane separation from coal mine gas by hydrate crystallization[J].Energy Fuels, 2013, 27(12):7252-7258
[12]Sun Q, Guo X Q, Liu A X, et al.Experiment on the separation of air-mixed coal bed methane in THF solution by hydrate formation [J]. Energy Fuels, 2012, 26:4507-4513.
[13]Zhang B Y, Wu Q.Thermodynamic promotion of tetrahydrofuran on methane separation from low-concentration coal mine methane based on hydrate[J].Energy Fuels, 2010, 24(4):2530-2535
[14]Zhang B Y, Cheng Y P, Wu Q.Sponge effect on coal mine methane separation based on clathrate hydrate method[J].Chinese Journal of Chemical Engineering, 2011, 19(4):610-614
[15]Wu Q, Gao X, Zhang B Y.SDS effect on CH4/N2/O2 hydrate formation rate for CMM separation and storage [J]. Advanced Materials Research, 2011, 201-203:471-475.
[16]Li X S, Cai J, Chen Z Y, et al.Hydrate-based methane separation from the drainage coal-bed methane with tetrahydrofuran solution in the presence of sodium dodecyl sulfate [J]. Energy & Fuels, 2012, 26:1144-1151.
[17]陈广印, 孙强, 郭绪强, 等.水合物法连续分离煤层气实验研究[J].高等化学工程学报, 2013, 27(4):561-566
[18]Chen G Y, Sun Q, Guo X Q, et al.Experimental study on the continuous separation process of coal bed methane via forming hydrate[J].Journal of Chemical Engineering of Chinese Universities, 2013, 27(4):561-566
[19]赵建忠, 赵阳升, 石定贤.溶液水合物技术提纯含氧煤层气的实验[J].煤炭学报, 2008, 33(12):1419-1424
[20]Zhao J Z, Zhao Y S, Shi D X.Experiment on the methane concentration from oxygen-containing coal bed gas by THF solution hydrate formation[J].Journal of China Coal Society, 2008, 33(12):1419-1424
[21]吴强, 朱玉梅, 张保勇.低浓度瓦斯气体水合分离过程中十二烷基硫酸钠和高岭土的影响[J].化工学报, 2009, 60(5):1193-1198
[22]Wu Q, Zhu Y M, Zhang B Y.Effects of sodium dodecyl sulfate and kaolin on low-concentration mine gas hydration separation[J].Journal of Chemical Industry and Engineering, 2009, 60(5):1193-1198
[23]吴强, 张保勇, 王海桥.煤矿瓦斯固化防突及低浓度瓦斯固化分离新技术[J].黑龙江科技学院学报, 2010, 20(1):23-27
[24]Wu Q, Zhang B Y, Wang H Q.New hydrate-based technique for coal and gas outburst prevention and low-concentration coal mine gas separation[J].Journal of Heilongjiang Institute of Science & Technology, 2010, 20(1):23-27
[25]吴剑锋, 孙兆虎, 公茂琼.从含氧煤层气中安全分离提纯甲烷的工艺方法[J].天然气工业, 2009, 29(2):113-116
[26]Wu J F, Sun Z H, Gong M Q.Security technology of methane recovery from coalbed gas with oxygen[J].Natural Gas Industry, 2009, 29(2):113-116
