Liquefied Natural Gas Gels: Structure, Rheology, and Production Energy Requirements

摘要

Liquefied natural gas was gelled with two gelants, water and methanol, using a vapor condensation technique. Gelant particle structure analysis, by X-ray diffraction, composition determination and microscopic observation showed that the particles were crystalline clathrate solids with hydrogen bonding between gel particles likely responsible for the observed gel structure. Rheological properties of the gels, derived from their responses to an oscillating shear field, revealed Bingham plastic behavior. Gel yield shear stresses varied from 1 to 100 N/m2 and were dependent upon gelation conditions, increasing both with increasing gelant concentration in the gel and with reduced gelant loading in the carrier gas. LNG gels may offer safety benefits in transporting natural gas. Measurements of LNG gel vaporization from a water surface showed that the gels boiled at rates about one-half those of normal LNG. With rheological data used to predict gel spreading behavior, it was estimated that a typical gel could reduce the maximum distance for flammable mixtures fivefold. Energy requirements for production of LNG gels were estimated. With water as gelant, a gel of yield shear stress 50 N/m2 would require at least 0.073 kg gelant/kg LNG in gel. Production of such a gel by the present vapor condensation process would entail boiling off approximately one kg of LNG for every kg of LNG gelled; thus the energy requirement for producing gelled LNG would be double that for production of normal LNG, an increase of 100 percent.