Energy & Fuels, Vol.26, No.9, 5626-5632, 2012
Effectiveness of Alcohol Cosurfactants in Hydrate Antiagglomeration
Hydrates are crystalline inclusion compounds where hydrogen bonded water molecules form cages to trap small hydrocarbon and nonhydrocarbon molecules. Under high subcooling conditions, these crystals grow rapidly into large pieces and may cause enormous problems in transport and deepwater oil capture. One of the most effective methods to address gas hydrate problems is through the formation of small hydrate particles in the nanometer or micrometer range dispersed in the fluid phase. In this approach, special surfactants are required, which are called antiagglomerants (AAs). However, there are major limitations when salt is present in water and when volume ratio of water in fluid (i.e., watercut) is high. In this work, we investigate a wide range of alcohols as cosurfactants along with the rhamnolipid as AA in a multiple screening-tube rocking apparatus by monitoring the temperature of vials and morphology of mixtures. The results show medium-sized alcohols, such as isopropanol (IPA), are effective cosurfactants. Small quantities of IPA reduce the effective dosage of surfactant in the formation of hydrate particles in both water and brines. Our emulsion size measurements, by dynamic light scattering, and interfacial tension measurements reveal the effectiveness of alcohol cosurfactants in stabilizing oil-in-water emulsions, therefore enhancing the hydrate antiagglomeration effect.