(728f) Hydrate Based Gas Separation of CH4-CO2 gas Mixture in Fixed Bed Reactor

Hydrate
based gas separation of CH₄-CO₂
gas
mixture in fixed bed reactor

Namrata
Gaikwad¹,
Gaurav Bhattacharjee³,
Omkar S. Kushwaha¹,
Praveen Linga³,
Jitendra Sangwai²,
Rajnish Kumar¹*

¹Department
of Chemical Engineering, Indian Institute of Technology, Chennai,
600036, India

²Department
of Ocean Engineering, Petroleum Program, Indian Institute of
Technology, Chennai, 600036, India

³Department
of Chemical and Biomolecular Engineering, National University of
Singapore, 117585, Singapore

Corresponding
author: rajnish@iitm.ac.in

Keywords:
Gas hydrates, CO₂
Capture,
CH₄
Storage, Hydrate Kinetics, Hydrate Dissociation.

Abstract

Past
work on hydrate based gas separation (HBGS) process for separation of
CO₂-CH₄
gas mixtures has shown low separation efficiencies. In this work, two
additives were identified such that they would modify the system to
preferentially allow the enclathration of only one of the two gases
into the hydrate phase. These additives were expected to a) enhance
the kinetics of hydrate formation and b) enhance the separation
efficiency of the HBGS process. An amino acid Tryptophan was used
which has shown promise as a kinetic promoter for hydrate growth. A
50 % CO₂-50
% CH₄
gas mixture was used in a horizontal fixed bed reactor (HFBR).
Hydrate formation was studied at two different initial pressures, 3.5
MPa and 5.0 MPa to study the effect of driving forces on the kinetics
of hydrate formation and the separation efficiency of the process.
Average gas uptake, the average rate of hydrate formation, average
induction time, split fraction and separation factor have been
studied in detail at two different pressure conditions in pure water
and using Tryptophan as a kinetic promoter. From the hydrate
formation studies, we observed that the presence of Tryptophan can
significantly increase the rate of hydrate formation. Furthermore,
the addition of cyclo-octane as a large molecule guest substance
(LMGS) further increased the gas uptake by forming mixed sI and sH
hydrate. Owing to more gas storage capacity of sH hydrate compared to
sI hydrate, and also due to lower equilibrium hydrate formation
pressure this additive has better potential for scale-up. Gas
separation by forming sH hydrate opens up a new era in gas separation
via hydrate based crystallization.