467196 CFD Modeling of an Industrial Furnace Reformer and 3D Multi Scale Model for Packed Bed Reactor for Synthesis Gas Production
Sunday, November 13, 2016: 3:45 PM
Franciscan D (Hilton San Francisco Union Square)
Extended Abstract: File Not Uploaded
Synthesis gas (Syn gas) is used in many industrial applications such as Direct Reduction of Iron (DRI), Fischer-Tropsch synthesis, and also a source for environmental-friendly clean fuels and chemicals. In Midrex DRI process, syn gas is used to remove the chemically bound oxygen from raw iron-ore without melting. Syn gas is primarily produced from natural gas reforming in a large number of tubular packed bed reactors suspended in a furnace. Combustion of fuel takes places in the furnace supplying the requisite heat for the endothermic reforming reactions. The reactor tubes are made of special alloys and their failure due to uneven temperature or hotspots leads to the production loss or plant shutdown. Therefore, an accurate prediction of tube wall temperature is vital for preventing such tube failures. Computational Fluid Dynamics (CFD) is a powerful tool that can be used to simulate the turbulence, radiation and combustion in furnace reformer and the tube wall temperature is predicted without employing empirical heat transfer coefficients.
This talk presents a 3D CFD model of an industrial Midrex furnace reformer employing k-ε turbulence model, Discrete Ordinates (DO) radiation model, and finite rate/Eddy Dissipation combustion model. The reactor tubes are fully meshed in 3D and heat transferred from the furnace side to tube side is directly coupled at the tube wall. This step avoids the use of empirical heat transfer coefficients and also directly takes into account the varying tube wall heat flux due to shadowing and proximity to the burners. The flow reactor tubes are described using laminar flow porous media model with pressure drop described using Ergun equation and the reforming reaction rates are taken from the literature. The model in the tube constitutes an effective media packed bed model where a catalyst effectiveness is employed. We will present the results showing the temperature, velocity and species profiles inside the furnace as well as the performance of the packed bed reformer.
This talk also presents a 3D multiscale packed bed reformer model of a single tube developed using multiscale approach. The model takes into account dispersion in axial and radial directions as well as catalyst-fluid phase mass and energy limitations along the length of the reactor. The varying heat flux in the angular direction due to shadowing of tubes also is taken into account. Reaction, mass and heat transfer inside the catalyst are directly coupled with fluid phase equations using 1D pellet model, and thus avoiding the use of a catalyst effectiveness factor. This reactor model results will then be compared with the simpler model used to describe in the furnace reformer model. The model results will also be compared with a 2D multiscale model not accounting for varying heat flux in angular direction.