Preventing Gas Hydrate Agglomeration with Polymer Hydrogels

Abstract

This study investigates the potential to use hydrogel particles for simultaneously inhibiting the formation of gas hydrates and preventing their agglomeration after they form. The particles were synthesized specifically for this application and swell to a controlled degree in water and remain discrete. A stirred autoclave was used to determine the hydrate onset time, subcooling temperature, initial growth rate, and torque changes during hydrate formation with the water absorbed in the hydrogel particles. The system also included a liquid decane phase which simulates a condensate. In comparison to water (with no particles) + decane mixture, the hydrate onset time was delayed and the subcooling temperature increases. In addition, both the initial growth rate and hydrate fraction were lower for polymer hydrogels. Stable torque is observed for polymer hydrogels while there are sharp increases in torque before the stirrer stops for water + decane mixture, suggesting that the hydrogel particles (and hence hydrate particles) are well-dispersed in the decane phase. Experimental observations show that the hydrates form as a surface shell on the hydrogel particles and grow inward. The hydrate shell-covered hydrogel particles do not agglomerate or deposit under stirring because the particles remain discrete due to the polymer network. In order to further investigate the ability of the hydrogel particles to prevent agglomeration, the stirring was stopped after confirming the formation of hydrate was complete. After 4 h, additional hydrate formation was negligible, and no serious torque increase or stirrer blockage was observed when the stirring was restarted. These results suggest that the synthesized polymer in this work has the potential to prevent hydrate agglomeration without using surfactants, which is a new concept.