Controlled Formation and Flowability of Clathrate Hydrate Suspensions from Frozen Emulsions

Suspensions of clathrate hydrates are of great importance in oil and gas exploration where hydrates are thermodynamically stable at operating conditions normally encountered in deepwater fields, posing great danger to flow assurance operations. At the same time, synthetic clathrate hydrates offer enormous potential for transport and storage of gases such as methane, carbon dioxide or hydrogen, and production of suspensions of particles for hydrate synthesis could improve the viability of enclathration as a mode of continuous production. Here we show how to controllably and continuously produce flowable cyclopentane hydrate suspensions starting from frozen emulsions. Working at atmospheric pressure allows us to use microscopic imaging to determine the particles' features, such as size and size distribution. We show that hydrate formation can be reliably controlled by the use of spherical ice particles obtained by exploiting the hydrodynamic instabilities of liquid jet breakup. When suspended in a liquid oil phase also containing the hydrate-former, clathrate induction times of just a few seconds can be attained. Once formed in suspension, rheometry and microscopy show that these small hydrate particles inevitably sinter over time forming a single porous solid structure, unless an appropriate antiagglomerant is added. The sintering process is similar both in the presence or absence of surfactants and by modeling the evolution of the suspension viscosity over time we determine a single characteristic sintering time scale for each chemical composition, independent of the shear rate imposed during formation. This result provides us with a simple model that can be used to evaluate the effectiveness of chemical additives in preventing or promoting sintering. The novel process presented here for producing atmospheric cyclopentane hydrates in either a flowable slurry or solid form can, in principle, be extended to the production of high-pressure gas hydrates.