Comparative Study of Tetra-N-Butyl Ammonium Bromide and Cyclopentane on the Methane Hydrate Formation and Dissociation

Warintip Chanakro,Pramoch Rangsunvigit,Chutikan Jaikwang,Santi Kulprathipanja,Katipot Inkong

doi:10.3390/en13246518

Warintip Chanakro, Pramoch Rangsunvigit + Show 3 more

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https://doi.org/10.3390/en13246518

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Abstract

Two widely investigated methane hydrate promoters, tetra-n-butyl ammonium bromide (TBAB) and cyclopentane (CP), for methane hydrate formation and dissociation were comparatively investigated in the quiescent reactor at 2.5 °C and 8 MPa. The results indicated that the increase in the mass fraction TBAB decreased the induction time. However, it did not significantly affect the methane uptake. In the presence of CP, the increase in the CP concentration resulted in an increase in the induction time due to the increasing thicknesses of the CP layer in the unstirred reactor. Moreover, the methane uptake was varied proportionally with the CP concentration. The addition of TBAB resulted in a higher methane uptake than that of CP, since the presence of TBAB provided the cavities in the hydrate structure to accommodate the methane gas during the hydrate formation better than that of CP. On the contrary, the presence of CP significantly increased the induction time. Although the methane recovery remained relatively the same regardless of TBAB and CP concentrations, the recovery was higher in the presence of TBAB.

Highlights

In recent years, the global energy demand has been continually increasing due to the growth of human society
In the first step of this work, fresh water without a promoter was examined in order to comprehend the fresh water effects on the methane hydrate formation kinetics
The results showed that the presence of both promoters outstandingly enhanced the methane hydrate formation by improving the hydrate formation kinetics—induction time and methane hydrate formation rate—and methane consumption in comparison with pure water

Summary

Introduction

The global energy demand has been continually increasing due to the growth of human society. More than 76% of energy come from carbon-based sources such as gas, oil, and coal. Among these three carbon-based energy sources, natural gas is present at the appropriate ratio compared to other sources of fossil energy [1,2]. Natural gas hydrates play an important role in the largest resource of methane gas on Earth and are a possible energy resource for the coming age due to the demand for clean energy sources. The main challenges to use hydrates technology for natural gas storage and transportation in industrial processes include the slow kinetics of hydrate formation with a longer hydrate nucleation time and low hydrate formation rate during the hydrate growth, and low conversion of gas to methane hydrates leading to poor storage capacity [5]

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