Multi-cycle methane hydrate formation in micro droplets of gelatinous dry solution.

Transition from bulk surfactant solution to gelatinous surfactant dry solution and the behavior of the methane uptake in GDS droplets during the repeated hydrate formation. • GDS droplets have the merits of the dry water, the surfactant solution and the gelling agent. • The droplets can provide abundant gas channels, considerable gas–liquid contact area and stable gel-like structure. • The droplets facilitate rapid and reversible methane storage in clathrate hydrate. • The droplets maintained relatively high methane storage capacities until the ninth cycle. A gelatinous dry solution (GDS) was prepared by blending sodium dodecyl sulfate solution, gellan gum powder, and hydrophobic silica nanoparticles in air at a high speed. It is essentially a pile of free-flowing micro surfactant droplets supported by a gelling agent. The GDS has the dispersion characteristics of dry water, activity of the surfactant solution and stability of the gel. The flour-like droplets can provide abundant micro channels for gas transfer, a considerable surface area for gas–liquid contact and stable gel-like structure for repeated hydrate formation. Multi-cycle methane consumption experiments were conducted in a stainless steel vessel at 5.0–8.1 MPa and 273.2 K, in order to study the repeated kinetics of methane hydrate formation in GDS. The results demonstrated that the dispersed GDS facilitated rapid and reversible methane storage in clathrate hydrate by enhancing the gas–liquid contact and the stability of the regular droplets. Methane uptake (152.2–163.2 m3·m−3) and maximum uptake rates (4.522–5.690 m3·m−3·min−1) were achieved in the first storage cycle at the experimental pressures. GDS maintained relatively high methane storage capacities (114.3–118.0 m3·m−3) until the ninth cycle, and the capacities only were attenuated by 24.92–27.70% with respect to the first cycle at the above pressures. A hypothesis of "droplets breakage by released gas" was proposed to illustrate the attenuation of gas storage capacity of the droplets. [ABSTRACT FROM AUTHOR]