Investigation on Growth Kinetics of Hydrate on the Surface of an AC-QS Porous Media Composite System in an SDS System

The anionic surfactant sodium dodecyl sulfate (SDS) used in industry is a kinetic accelerator that helps to form hydrates, but the hydrates formed are extremely unstable and cannot be well preserved and transported. Hydrates stored in porous media environments can serve as a means of transportation. In this work, SDS is combined with two porous media (quartz sand (QS) and activated carbon (AC) of different particle sizes) to form a composite system to study the effect of particle size on hydrate formation characteristics. Experimental results show that when a small particle size quartz sand layer is added to a 100% saturated sodium dodecyl sulfate solution, the hydrate gas storage capacity is 0.320 mol, while the surfactant solution without a porous medium layer is only 0.263 mol. Under the same particle size, the maximum water intake amounts of the QS layer and AC layer are 0.192 and 0.143 mol, respectively. The small size of activated carbon as a gas reservoir is not conducive to the formation and storage of hydrates. The AC layer gap composed of activated carbon with a particle size of 100 mu m does not hinder the mass transfer of methane gas but only hinders the formation and storage of hydrates. The good adsorption capacity of the activated carbon layer can be used as a capture layer to capture the upward migration of unreacted liquid, which is beneficial to the storage of hydrates. In the AC-QS composite system, the AC layer is used to transfer the effect of SDS to drive hydrate growth along the wall to the upper layer. The gas storage capacity of the AC-QS composite system of different sizes is basically higher than the 172 mol/(mol of the separate QS system). And the average reaction rate is 2.65 mol/min. At the same time, under the QS-AC system, 100 mesh AC can increase the gas storage capacity by up to 21.6%. At the same time, experiments found that compared with the large-particle QS system as a hydrate generation layer, the small-particle QS system and the AC system with different particle sizes can better improve the hydrate gas storage capacity. This function of capturing migrating liquid through the AC layer can solve the problem of insufficient gas storage capacity caused by exposure of a large amount of hydrates to the gas phase environment.