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

Burla Sai Kiran,Kandadai Sowjanya,Ji-Ho Yoon,Pinnelli S.R Prasad

doi:10.2516/ogst/2018092

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 CH4gas 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.

Highlights

Clathrate hydrates are the ice-like crystalline solids, often found in low temperature and high-pressure regions, namely in the certain arctic zone and oceanic sediments
Our motivation is to investigate the hydrate formation process with different amounts of aq-THF solution and initial gas pressure to understand the role of surface area, the volume of solution and driving force as these are a relevant parameter in the gas storage process
The mixed hydrates system with THF is interesting for methane gas storage and transportation applications

Summary

Introduction

Clathrate hydrates are the ice-like crystalline solids, often found in low temperature and high-pressure regions, namely in the certain arctic zone and oceanic sediments. Veluswamy et al [38, 39] have conducted studies on storage capacity and gas uptake kinetics in CH4 + THF + H2O system and have reported process scale-up using three different reactors, namely, in small (dia: 1.3 cm), medium (dia: 5.1 cm) and large (dia: 10.2 cm) using 2, 53 and 220 mL of aq-THF solution at comparable methane gas pressure. Such scale-up is deceptive as both diameter and volume (height) of the solution vary. Our motivation is to investigate the hydrate formation process with different amounts of aq-THF solution and initial gas pressure to understand the role of surface area, the volume of solution (height) and driving force (at a fixed volume of solution) as these are a relevant parameter in the gas storage process

Experimental method

Results and discussion

Methane uptake at higher pressure

Kinetics of methane uptake at higher pressure

Conclusion