Effects Of MWCNT, PU Foam And New Dry Water On Methane Hydrate Formation

Hydrate technology has been applied in gas storage and transportation, gas separation, air conditioning, waste water treatment, desalination, solution concentration and other industrial fields. However, hydrate formation rate is slow naturally, which limits the application of hydrate technology to a great extent. To enhance hydrate formation is the key to realize industrialization of hydrate technology. In this paper, new materials were introduced into the static reaction system and constant volume method was used to study the enhancement effect and mechanism of different materials. The main points are summarized as follows:First, multi-walled carbon nanotubes-0.03wt% SDS solution was prepared, and its enhancement effect was studied under different concentrations and pressure. The results show that, within concentration range of 0.002wt%-0.04wt%, as the concentration increases, methane uptake and maximum rate increases and t90 got shortened, with the highest methane uptake being 165V/V, the largest rate being 12.3 m3·m-3·min-1 and the shortest t90 being only 26.8 min. Under the same concentration and temperature, as pressure increases, methane uptake and the maximum rate increases as well. The mechanism can be summarized as adsorption, enhancement of heat transfer and mass transfer.Secondly, polyurethane foam with different pore sizes were introduced into the system of 0.03wt% SDS solution. The effect of pore sizes on the hydration process and the recycling properties of PU foam, and the performance of composite materials, which is the mixture of carbon nanotubes solution and PU foam, was under research. The results show that, PU foam has excellent recycle properties, and there is an optimum pore size for the strongest enhancement of methane uptake and maximum gas rate. The highest methane uptake 179 V/V was achieved with PU-1.0, and the largest rate 9.7 m3·m-3·min-1 was achieved with PU-2.0. With the carbon nanotubes solution to improve the thermal conductivity of the composite material, the highest gas storage capacity, 184 V/V, was achieved. Being hydrophobic itself, with high specific area and good connectivity of the pore space, PU foam is able to enhance the mass transfer during the hydration process.Finally, copper dry water(copper DW), frozen dry water(frozen DW) and frozen copper dry water(frozen copper DW) were introduced into hydration system. Maximum rate in copper DW is 35.69% higher than in dry water(DW), but methane uptake decreased because the intake passage is blocked by the copper powder and mass transfer process got hindered. Frozen DW can achieve a higher methane uptake, which is 148 V/V, but the maximum rate decreased by 43.90%, which is due to the delay of the removal of a great amount of hydration heat generated during the hydration process. Frozen copper DW could achieve high methane uptake and maximum rate at the same time, which is the result of the enhanced heat and mass transfer.