CFD simulation of hydrodynamics and methanation reactions in a fluidized-bed reactor for the production of synthetic natural gas

Numerical investigations of hydrodynamics and kinetic reactions in a fluidized bed methanation reactor are carried out by coupling methanation kinetics with the two-fluid flow model. The gas-solid reacting flow models are implemented within OpenFOAM software. The grid resolution is investigated using two-dimensional and three-dimensional (2D and 3D) meshes. The bed height is reasonably predicted with the Gidaspow and Syamlal models. Simulated results are compared against experimental data in the literature. The simulated axial species concentrations agree well with the measured results at the end of the bed. The effects of different operating parameters are evaluated using the established models. The increase in the gas inlet velocity results in more dilute solid concentration and larger bed expansion. The weak bed expansion results from the methanation reaction with gas volume reduction. The methane concentration is increased when increasing catalyst inventory in the reactor. The addition of water into the feedstock with low H₂/CO ratio benefits the methanation reaction.