ABSTRACT:

The decomposition of methane hydrate in aqueous solute is modeled and analyzed numerically. To simplify this problem, a single spherical pellet of the hydrate is considered and flows over the pellet are solved by a 3-D CFD method by using unstructured grid system. The decomposition at the surface of the MH pellet is modeled to consist of two parts, one is mass transfer from interface to an imaginary buffer layer and the other is that from the buffer layer to the solution. This model was adopted in our CFD method and performed some promising simulations that will be continued to future experimental work for its parameterization.

INTRODUCTION

Methane hydrate (MH) is clathrate composition, which traps a vast amount of gas in the lattice of hydrate under the conditions of high pressure and low temperature. It is realized that MH is like a treasure house underground resources. A numbers of researches have been conducted to understand and model the thermodynamics and/or kinetics of formation and/or decomposition of MH, such as Sloan (1998), Ji et al. (2001), Wim et al. (1999), Yousif and Sloan (1991), Holder and Angert (1982a), and Holder et al. (1982b). In particular, we are interested in the work of Kim et al. (1987), who modeled the decomposition of MH at quite low Reynolds number area. At present, their model is widely used in various numerical simulations on the field scales, such as Masuda et al. (1999). However, it seems to the authors that the use of the model of Kim et al. (1987) is sometimes beyond its limitations and may affect the accuracy of numerical predictions. In the present study, we tried to model the decomposition of MH in the macroscopic view by employing microscopic cell-based numerical calculation.

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