Modeling Gas Hydrates Using the Equation of State and the vdW-P Model
Date Issued
2009
Date
2009
Author(s)
Lin, Chi-Hung
Abstract
Gas hydrates are ice-like crystalline solids in which water molecules form a three-dimensional structure that is stabilized by the encapsulation of small gas molecules like methane, ethane and carbon dioxide. The motivation of this work is to develope a calculation model to predict vapor-liquid-hydrate-three-phase equilibrium condition with a better degree of predictability. n this study, the van der Waals and Platteeuw (vdW-P) model is applied to describe the hydrate phase and both Peng-Robinson-Stryjek-Vera (PRSV) equation of state (EoS) and Cubic Plus Association equation of state (CPA EoS) are chosen to describe the vapor and liquid phases. In the vdW-P model, the Langmuir adsorption behavior is assumed to model the adsorption of gas molecules in the hydrate cages and the Langmuir constant is defined as a function of spherically symmetric cell potential function. In this study, the Langmuir constant is described by a two-parameter temperature-dependent function. It is found that the vapor-liquid-hydrate-three-phase equilibria can be well described by this simple model. And the model also can be applied to predict the competition of different gases when forming binary-guest gas hydrate and predict the phase equilibrium condition of gas hydrate with inhibitor.
Subjects
Gas hydrate
Langmuir constnat
Type
thesis
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