Synergistic promotion mechanisms
As mentioned above, hydrate growth kinetics is significantly enhanced by the synergistic effect of spiral agitation and nano-promoters under mild conditions. Since methane uptake rate corresponds to hydrate kinetics, its variation under different conditions was analyzed, and the schematic diagram of methane uptake rate for different scenarios were given in Figure 5(a). For high pressure (5 MPa), the rate curve is divided into two sections, a fast uptake stage with stirring (Stage I) and a slow uptake stage for hydrate static formation (Stage II). In comparison, it is clear from Figures 5(b) and 5(c) that the rate profiles can be divided into three stages at 3.8 MPa. An initial stage for hydrate stable growth (Stage I), following by a hydrate quick growth stage (Stage II), and finally a hydrate slow growth stage occurs under static condition (Stage III). In addition, compared with pure water and -COO-@PSNS systems, an obvious “secondary uptake” stage appears in -SO3-@PSNS systems as seen in Figure 5(c).