Regular Article

Experimental investigations on tetrahydrofuran – methane – water system: Rapid methane gas storage in hydrates

¹ Gas Hydrate Division, CSIR – National Geophysical Research Institute (CSIR-NGRI), Hyderabad 500007, Telangana, India
² Department of Energy and Resources Engineering and Department of Convergence Study on the Ocean Science and Technology, Ocean Science and Technology (OST) School, Korea Maritime and Ocean University, Busan 606-791, Korea

^* Corresponding author: psrprasad@ngri.res.in

Received: 10 September 2018
Accepted: 20 November 2018

Abstract

This study reports methane (CH₄) gas storage capacity along with TetraHydroFuran (THF) as guest molecules in mixed hydrates. This process has been studied in two reactors of 100 and 400 mL capacity, having 4.5 and 7.5 cm internal diameter respectively, in non-stirred configuration. Experiments were conducted in each reactor at constant initial gas pressure (7.5 MPa) and by increasing the height of the solution from 1 to 8 cm, resulting in volume scale-up factor of 5. The total CH₄ gas uptake (moles) passes through a maximum at around 50% volume of the reactor indicating a transition from gas-rich to solution rich conditions. Observed variations in gas uptake are within ±20% of the maximum, upon different solution volume from 35% to 70% of reactor’s volume. Another set of experiments were conducted keeping the amount of the solution constant and increasing gas pressure in the range of 0.5–11.0 MPa. The gas uptake increased upon an increase in the gas pressure, but this is at least 40% less compared to the theoretical estimate. The stirring of solution or addition of promoter (Sodium Dodecyl Sulfate, SDS) is also not effective in increasing the gas consumption. Kinetics of gas uptake, in both stirred and non-stirred conditions, are quicker and 90% of gas consumption occurs in an hour after the hydrate nucleation event.