The focus of our research is on Water, Energy & Environment (WEE) pertaining to clathrate (gas) hydrates. 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. The significance of gas hydrate research is summarized in the following schematic:
Our research interests pertaining to clathrates or gas hydrates are:
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 sequestration of carbon dioxide as clathrates in the ocean. Some of the challenges to scale 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).
There is a need to design and test innovative reactor configurations and concepts to scale up the clathrate process for carbon capture due to the non-suitability of stirred tank reactor configuration. Recently, we have introduced polyurethane foam (very cheap and has good interconectivity of interstitial pore space) as a medium for enhanced kinetics [Babu et al. Environ Sci Technol (2013), 47 (22), 13191-13198].
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 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 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.
The focus of our research is on identifying low dosage kinetic hydrate inhibitors (LDHI's) for risk management in oil and gas production and transport facilities. Our facility here can be used to identify and evaluate the performance of chemicals under a controlled environment of hydrate formation/decomposition. Our recent work (Daraboina et al. 2013) on a well known LDHI employing a new contact mode revealed that it delays the induction time of crystallization significantly and reduces the rate of hydrate growth significantly thus preventing plug formation in oil and gas production and transport facilities. The advantages of LDHI's is that they can be employed at low concentrations compared to traditional thermodynamic hydrate inhibitors like glycols.
Energy Storage and Transport
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 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)
Research Highlight: SNG (solidified natural gas) technology is a cost effective and environmentally benign option to store natural gas at a large scale and in a safe manner. In this study, we report a simple method to produce methane hydrates rapidly for the first time employing an unstirred reactor configuration in presence of tetrahydrofuran (THF) as a promoter. We report about 70% of water conversion to hydrates in just 60 min after nucleation with methane storage capacity of 4.2 ± 0.2 kmol of methane/m3 of water. For the first time, THF is reported to act both as a thermodynamic and kinetic promoter. We further elucidate the mechanism for this behavior by morphology observations during hydrate formation. Further, we demonstrated a volumetric scale up of 220 times and diameter scale up of 10 times in this work without significant reduction in the methane storage capacity. This work has been published Pin Chemical Engineering Journal on January 22, 2016 [doi:10.1016/j.cej.2016.01.026]
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 sand can be exploited for application of clathrate process for seawater desalination. It is possible to achieve water recovery of upto 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 to the clathrate process. The schematic of hydrate based desalination (HBD) process is shown in figure.
Schematic of the HBD process (Babu et al. Chem Eng Sci, 2014)
Experimental Thermodynamics and Multi-Phase Equilibrium
The focus of our research is on experimental investigation of vapor-liquid equilibria (VLE), vapor--liquid-liquid equilibria (VLLE) and vapor-liquid-solid equilibria (VLSE). Some of the systems of interest are phase behavior of carbon dioxide, hydrocarbons and brines; phase behavior of hydrocarbons and water at high pressures and low temperatures.