A Multi-Scale Two-Dimensional Packed Bed Reactor Model for Catalytic Steam Methane Reforming

Abstract

Steam methane reforming (SMR) is the primary source of synthesis gas (CO/H2) production for use in direct reduction of iron-ore. The endothermic and equilibrium-limited SMR reaction is carried out in multiple tubes packed with reforming catalyst. The models available in the literature for SMR packed bed reactor are one dimensional homogeneous and pseudo-homogeneous. The homogeneous model calculates the reaction at bulk fluid concentration and pseudo-homogeneous employs catalyst effectiveness factor. These models do not take into account the reaction and diffusion in the catalyst particle, and therefore predict inaccurate conversion and selectivity of products. This talk presents a steady state 2D multi-scale packed bed reformer model that takes into account the solid-gas phase mass and energy diffusional limitations along the reactor length. In lieu of using the catalyst effectiveness factor, mass and energy balance in the 3D catalyst particle is calculated and coupled with gas phase model. The gas phase model takes into account the axial and radial dispersion as well as finite solid-fluid mass and heat transfer coefficients; calculated using empirical correlations available in the literature. The pressure drop in the packed bed is calculated employing the Ergun equation and compared with the Eisfeld-Schnitzlein equation that takes into account the wall effects. The molar expansion during reaction is also taken into account using a differential equation for average molecular weight along reactor length. This talk presents the simulation results for different case studies employing the model. First, we will present the 2D non-isothermal model results and compare with 1D model results. Second, we will compare the simulation results using two different pressure drop equations. Finally, we will compare the results without taking into account the mole effects on velocity during reaction.