My research program in NUS centers on gas (clathrate) hydrates spanning both fundamental and applied research. The vision of “Linga Lab”, is to advance clathrate hydrate technology as an effective, and feasible solution for the critical needs of safe and clean water, cleaner energy, and environmental stewardship. Clathrate or gas hydrates are ice-like inclusion crystals formed by water and small gas molecules like methane, ethane, carbon dioxide, hydrogen at suitable temperature and pressure.

Our research featured in Amazing Ideas Awesome Innovations series of NUS Engineering!

Carbon dioxide capture and storage (CCS)
Our research focus is on carbon dioxide capture, storage, and utilization. More specifically, our focus is on developing an integrated carbon dioxide capture facility by employing existing technologies and developing promising technologies that would optimize the capture costs and increase the separation efficiency of the process. A novel method to capture carbon dioxide is by employing the Hydrate Based Gas Separation (HBGS) process from pre-combustion and post-combustion streams. Our group also focuses on the sequestration of carbon dioxide as clathrates in the ocean. Some of the challenges to scaling up the HBGS process are; to enhance the kinetics of hydrate formation; to reduce the operating conditions (pressure) of the hydrate reactor. One possible approach to enhance the hydrate formation kinetics is to develop and test innovative reactor designs. The operating pressure of the hydrate reactor can be reduced by identifying a suitable additive that does not compromise the separation efficiency (carbon dioxide recovery and separation factor) and reaction yields (reaction rate, conversion of water to hydrates).

Linga Lab Video: Enhanced hydrate formation kinetics in PU foam (DOI:10.1021/es403516f)

Energy Recovery from Natural Gas Hydrates
Natural gas hydrates found in the earth’s crusts range between 10,000 and 40,000 trillion cubic meters (TCM). Considering that there are about 370 TCM of natural gas available in the world, natural gas hydrates are potentially a huge energy resource. Our research focus is to simulate hydrate formation in sediments at the laboratory in order to develop potential recovery methods. It is also of our interest to understand the formation and decomposition phenomena since it is expected that global warming could lead to the release of methane to the atmosphere from the deposits. An exciting project that we are working on is to simultaneously sequester carbon dioxide and produce methane from these naturally occurring hydrate deposits.

Solidified Natural Gas (SNG) Technology
Converting natural gas to hydrate pellets is a profitable means of storage and transportation of natural gas from stranded gas fields (50% of the natural gas fields worldwide are stranded) compared to liquefied natural gas (LNG) and compressed natural gas (CNG). 1 m3 of natural gas hydrate can store about ~170 m3 of natural gas at STP conditions. Hence, hydrates are in a compressed state and non-explosive (see video below showing burning NGH sample prepared in our lab). The focus of our research is to develop and test innovative reactor designs that would enhance the crystallization rate and reduce the process costs associated with the crystallization process. Our interest is also on hydrogen storage via hydrate crystallization.

Burning natural gas hydrates (non-explosive and can sustain flame)!
Rapid mixed methane hydrate formation with THF as a dual functionality promoter (DOI: 10.1016/j.cej.2016.01.026)
Our recent breakthrough work introduces 1,3-Dioxolane (DIOX) as a replacement for THF as a dual functional promoter and a combination of an additive mixture that can enable the ultrafast formation of SNG hydrates.

Ultra-rapid methane hydrate formation with DIOX as a dual functionality promoter (DOI: 10.1039/D0EE02315A)
Another body of work that my team extensively worked and contributed new knowledge is the use of amino acids as kinetic promoters for several systems of interest for gas hydrates. We were the first to observe and report a peculiar morphology pattern of hydrates formed in the presence of amino acid (L-Leucine) whereby the crystals showed very flexible behavior. This finding led to the introduction of an innovative hybrid reactor operation that will greatly reduce induction time stochasticity and accelerate hydrate growth even at quiescent conditions.

Methane hydrate formation in presence of amino acid, L-Leucine (DOI:10.1021/acs.cgd.6b00997)

Hydrate based Desalination (HyDesal)
The focus of our research is to develop a novel technology based on the clathrate process to desalinate seawater by employing the cold energy from LNG (-161 C, 1 atm) re-gasification. Recently, we identified an unusual behavior of hydrate formation in silica sand with gas mixtures containing propane as a co-guest. Based on morphology study we observed that propane as a co-guest has the ability to draw water dispersed in silica sand to the hydrate formation region (gas phase above the bed) and showed a tendency to result in drastic hydrate growth due to the migration of water molecules to the gas phase region. This behavior of propane as co-guest in the sand can be exploited for the application of a clathrate process for seawater desalination. It is possible to achieve a water recovery of up to 60% in one hour. In addition to enhanced kinetics, there will be a natural separation of hydrate crystals from the brine solution. Moreover, by using the cold energy from LNG re-gasification terminal we can offset the cold energy requirement, thus addressing the parasitic energy penalty that was associated with the clathrate process. The schematic of the hydrate based desalination (HBD) process is shown in the figure below.

Unusual behaviour of hydrate formation in presence of propane as a co-guest (DOI: 10.1016/j.ces.2014.06.044)