Experiment on the Separation of Air-Mixed Coal Bed Methane in THF Solution by Hydrate Formation

Abstract

Because of the technology limitation and safety requirement, a large amount of air-mixed coal bed methane is released directly to the atmosphere. It leads to severe waste of resources and exacerbates the greenhouse effect. This work tries to alleviate this problem by separating CH 4 from a mixture of CH 4 and N 2 via hydrate separation method. Several experiments were systematically carried out in 6 mol % tetrahydrofuran (THF) solution to separate CH 4 /N 2 gas mixtures containing 4.90 to 71.23 mol % CH 4 . The results that THF can significantly reduce the formation pressure of CH 4 −N 2 hydrate materialize the possibility of separating CH 4 and N 2 using hydrate separation technology in industrial scale. CH 4 can be separated effectively from CH 4 /N 2 mixture and concentrated in hydrate phase with the presence of THF. The recovery of CH 4 ranges from 34.06% to 58.16% and the separation factor is between 2.29 and 5.17. A two-stage separation process of 46.28 mol % CH 4 /53.72 mol % N 2 with recycle is designed to increase the recovery of CH 4 . The calculated results indicate that CH 4 concentration in hydrate gas could reach 82.61 mol % with a recovery yield of 47.28%. Hydrate separation technology is an effective way to process and utilize the airmixed coal bed methane. Multistage separation process does have wide application prospects.

Continuous separation of CH4/N2 mixture via hydrates formation in the presence of TBAB

“…4 and 5 show the pressure effect on the separation results with 37.5 mol% CH 4 /N 2 under constant temperature, feed gas flow (240 L/h), liquid flow (40 L/h), and TBAB solution (10 wt%). We can find that the concentration of CH 4 in both unhydrated gas and dissociated gas decreases with the pressure, which is in good agreement with the results of the equilibrium separation of CH 4 /N 2 via hydrates formation [9].…”

“…With the advantages of simple process, mild operation conditions, low cost and energy consumption, hydrate separation method is widely applied to remove CO 2 , and recover H 2 and hydrocarbons, etc. [6][7][8][9][10][11][12].…”

Separation of the N2/CH4 Mixture through Hydrate Formation in Ordered Mesoporous Carbon

“…According to studies on pure water, promoters, such as tetrahydrofuran (THF), cyclopentane, propane and isobutene, reduce the hydrate-formation pressure (Sabil et al 2010). Sun et al (2012) found that THF significantly reduced the gas hydrate-formation pressure in the separation of N 2 and CH 4 . This method can also be applied for reducing the hydrate-formation pressure in porous media.…”

“…Besides, the stored methane can be released immediately when pressure is reduced and the amount of methane released increases with time at almost a constant rate. The porous media with a pore size of 2-6 nm was shown to be more suitable for the hydrate formation (Zhou et al 2005b(Zhou et al , 2010Liu et al 2006a;Sun et al 2007;Liu et al 2011;Wei et al 2014). Porous media with high surface areas provide improved access for both the water and the gases.…”

Hydrate‐Based Gas Separation for Methane Recovery from Coal Mine Gas using Tetrahydrofuran

“…Furthermore, this method is also ideal to recover CH 4 from air-mixed CBM because the presence of water could effectively reduce the possible explosion between CH 4 and air. [23] In this study, we investigated the separation of a CH 4 /N 2 mixture by hydrate formation of THF solution and dissociation to develop a viable pathway for future industrial application.…”