gas hydrate - CCOP

Sequestering Carbon Dioxide into Complex Structures of Naturally
Occurring Gas Hydrates
Young-June Park 1) , Do-Youn Kim 1) , Jong-Won Lee 2) , Dae-Gee Huh 3) ,
Keun-Pil Park 3) , Jaeh-Young Lee 3) , and Huen Lee 1)
1) Department of Chemical & Biomolecular Engineering,
Korea Advanced Institute of Science and Technology, Dejeon, Korea
2) Department of Environmental Engineering, Kongju National University,
Cheonan, Korea
3) Korea Institute of Geoscience and Mineral Resources, Daejon, Korea
ABSTRACT: Large amounts of CH 4 in the form of solid hydrates are stored on
continental margins and in permafrost regions. If these CH 4 hydrates could be
converted into CO 2 hydrates, they would serve as both as a source of CH 4 as and
CO 2 storage sites. We investigate the exchange phenomenon occurring in sI and sII
CH 4 hydrate deposits through spectroscopic analyses and explore its potential
application to CO 2 sequestration at the preliminary phase. The current outcome of
an 85% CH 4 recovery rate in sI CH 4 hydrate achieved by the direct use of binary N 2
+ CO 2 guests is quite surprising when compared with a rate of 64% for a pure CO 2
guest attained in previous approaches. The direct use of a mixture of N 2 + CO 2
eliminates the requirement of a CO 2 separation/purification process. In addition, the
simultaneously occurring dual mechanism of CO 2 sequestration and CH 4 recovery
is expected to provide the physicochemical background required for developing a
promising large-scale and economically feasible approach.
In the case of sII CH 4 hydrates, we observe a spontaneous structure transition of sII
to sI during the replacement and a cage-specific distribution of guest molecules. A
significant change of the lattice dimension due to structure transformation induces
the relative number of small cage sites to reduce, resulting in the considerable
increase of CH 4 recovery rate. The mutually interactive pattern of targeted guestcage
conjugates possesses important implications for the diverse hydrate-based
inclusion phenomena as clearly illustrated in the swapping process between CO 2
stream and complex CH 4 hydrate structure.
Keywords: clathrate, CO 2 sequestration, methane, swapping phenomenon, NMR.
INTRODUCTION
Because the total amount of natural gas hydrate in deposits worldwide was estimated to be
about twice as much as the energy contained in fossil fuel reserves (Collett, 1998; Makogon,
1988), many researchers have tried to find a way to exploit CH 4 hydrates as a new energy
source. Recently, the replacement of CH 4 hydrate with CO 2 has been suggested as an
alternative option for recovering CH 4 gas. When CO 2 itself is put under a certain pressure, a
solid CO 2 hydrate can be formed according to the stability regime (Brewer, 1999). In addition,
the formation condition of CO 2 hydrate is known to be more stable than that of CH 4 hydrate.
Therefore, the swapping process between the two gaseous guests is considered to be a
favorable approach toward long-term storage of CO 2 . Because CH 4 hydrate maintains the
New Energy Resources in the CCOP Region - Gas Hydrates and Coalbed Methane 97