CONCLUSIONS
In order to promote hydrate formation kinetics under mild conditions, two nano-promoters of -SO3-@PSNS and -COO-@PSNS were prepared, and hydrate formation in a spiral-agitated reactor was carried out, while the synergistic effect of spiral agitation and nano-promoters on hydrate formation kinetics was evaluated. Hydrate nucleation is significantly enhanced by spiral agitation, causing the induction time to be less than 10 min in pure water even at low pressure (3.8 MPa), and this promotion is further improved by nano-promoters. Hydrate growth kinetic is controlled by mass transfer and driving force, although hydrate initial growth kinetics is enhanced by spiral agitation, hydrate later growth is sluggish due to the limitation of mass transfer, especially in pure water under low driving force, giving rise to low methane storage capacity of 79.58 V/V at the inclined angle of 45°. However, this scenario is greatly improved by nano-promoters, and large methane storage capacities of 147.28 V/V and 141.33 V/V are obtained in the systems of -SO3-@PSNS and -COO-@PSNS, respectively, which increase by 85.07% and 77.59%. Ultimately, spiral agitation and nano-promoters contribute to initial and later hydrate formation separately, and their synergistic effect gives rise to enhanced hydrate formation kinetics under mild conditions. Compared with amino acids reported in our previous work, the presented nano-promoters performs better under milder conditions, and considering that the nano-promoters are easy to synthesize and store, their synergistic effect with spiral agitation provides a new insight for the industrial production of SNG technologies.