Abstract
The self-preservation property of CH4 hydrates is beneficial for the transportation and storage of natural gas in the form of gas hydrates. Few studies have been conducted on the effects of chemicals (kinetic and thermodynamic promoters) on the self-preservation properties of CH4 hydrates, and most of the available literature is limited to pure water. The novelty of this work is that we have studied and compared the kinetics of CH4 hydrate formation in the presence of amino acids (hydrophobic and hydrophilic) when the temperature dropped below 0 °C. Furthermore, we also investigated the self-preservation of CH4 hydrate in the presence of amino acids. The main results are: (1) At T < 0 ℃, the formation kinetics and the total gas uptake improved in the presence of histidine (hydrophilic) at concentrations greater than 3000 ppm, but no significant change was observed for methionine (hydrophobic), confirming the improvement in the formation kinetics (for hydrophilic amino acids) due to increased subcooling; (2) At T = −2 °C, the presence of amino acids improved the metastability of CH4 hydrate. Increasing the concentration from 3000 to 20,000 ppm enhanced the metastability of CH4 hydrate; (3) Metastability was stronger in the presence of methionine compared to histidine; (4) This study provides experimental evidence for the use of amino acids as CH4 hydrate stabilizers for the storage and transportation of natural gas due to faster formation kinetics, no foam during dissociation, and stronger self-preservation.
Highlights
Natural gas continues to play an essential role in meeting the ever-increasing global demand for energy
Constant ramp and isothermal temperature schemes are applied to measure the kinetics of formation and dissociation of CH4 hydrate in terms of the change in concentrations of L-methionine and L-histidine amino acids and driving force
At least 2–3 replicates are performed in the presence of kinetic inhibitors to account for the stochastic nature of hydrate formation, this may not be necessary for the presence of promoters, as their presence decreases the stochastic nature of hydrate formation
Summary
Natural gas continues to play an essential role in meeting the ever-increasing global demand for energy. To meet the ever-increasing demand, scientists have started exploring unconventional resources such as shale gas, hydrates, and coal seam gas to secure gas supply. With the increasing demand from developing countries and unconventional sources, long-term efficient, safe, environmentally friendly, and sustainable transportation and natural gas storage are becoming increasingly important. Technologies, such as CNG and LNG, seem to be suitable for long-distance transportation. These technologies have problems, such as the extremely low temperature (111 K) required for storage and transportation, leakage due to vaporization, explosiveness due to high pressure, and high operating and safety costs. Hydrate-based natural gas storage (solidified natural gas–SNG) is considered to be the environmentally friendly technology of the future.
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