Researchers from University of California assessed the structure of flames that use laboratory-produced methane hydrates as fuel to identify their key combustion characteristics
Gas clathrate hydrates are crystalline water-based solids that physically resemble ice. Gas clathrate hydrates contain small non-polar molecules or polar molecules with large hydrophobic moieties that are trapped inside ‘cages’ of hydrogen bonded, frozen water molecules. Significant reserves of methane stored in the form of methane clathrates are found in sediment in the ocean’s continental shelves and in permafrost. Hydrates represent a unique fuel that is remarkably diluted but still flammable and can be thermal sources for additional hydrate dissolution and clean power.
Now, a team of researchers from University of California assessed the gas hydrate burning process and analyzed the ignition step and flame visualization during hydrate combustion. The team created artificial methane hydrate samples from ground ice solid phases with a 5.75 hour heating cycle modified from a standard hydrate formation procedure that operated around a peak pressure of 1500 psi. A series of hydrate ignition test experiments were conducted to comprehend the hydrate as it released cold flammable gases during dissociation in surroundings at room temperature and pressure. The team found that the hydrate ignited at the temperature around −65 °C, while the gas temperature above was −4 °C for the half-covered tests.
The team presented measurements of the visible optical spectrum of direct methane hydrates in combustion. For stable burning, the sample should reach some minimum temperature and the temperature can vary depending on the shape of the hydrate sample. The spectral measurements demonstrated that the proportion of the total flame luminosity arising from the different species remains nearly constant throughout the burn. The team concluded that methane hydrate combustion can be considered as a potential option for future cleaner. The research was published in the journal MDPI Energies on May 21, 2019.