Computationally efficient CFD model for scale-up of bubbling fluidized bed reactors applied to sorption-enhanced steam methane reforming

Abstract

Sorption-Enhanced Steam Methane Reforming (SE-SMR) represents a novel and energy-efficient hydrogen production route with in situ CO2 capture. A comprehensive Eulerian-Eulerian CFD model of SE-SMR in a bubbling fluidized bed reactor, that uses dolomite and other solid sorbents as CO2 acceptors, has been developed. Kinetic models for steam methane reforming and CO2 capture have been implemented. In addition, a new particle drag model has been derived from customary formulas in order to reduce the computational cost. Two different scales have been studied: laboratory and semi-industrial. Results of the computation are in good agreement with literature data at both scales (SMR H2=76–78% vs. SE-SMR H2=90–96% dry basis mole fraction). Numerical simulations demonstrate that CO2 capture is the kinetic limiting step of the SE-SMR mechanism, as compared to steam methane reforming. Temperature is shown to be the key parameter of the SE-SMR chemical process at large scales, and an optimal T=625°C is estimated. Additionally, compared with the classical approaches, the new drag model provides seemingly realistic predictions within the multiple bubble regime, at a low computational cost and using a coarse grid. This represents a further advance for the scaling-up of the reactor to industrial sizes based on numerical simulation.