Modelling and experimental validation of a CO2methanation annular cooled fixed-bed reactor exchanger

Abstract A simulation model of a fixed‐bed reactor‐exchanger dedicated to CO 2 methanation on an industrial Ni/γ‐Al 2 O 3 catalyst has been built on the basis of experimental characterization of heat transfer and kinetic parameters. An effective thermal conductivity of the bed and a wall heat transfer coefficient are determined from cooling experiments of different Ar‐H 2 mixtures (thermal conductivity 0.02–0.25 W · m −1 · K −1 ) at different Reynolds numbers (particle Reynolds number 1–50). The flow dependent component of the Nusselt number correlates to the gas Prandtl number as Pr 0.72 . These heat transfer parameters and a kinetic model adapted to the Ni/γ‐Al 2 O 3 catalyst are integrated in mass, heat, and momentum balance equations in the bed and at the particle scale to build a 2D heterogeneous model of the fixed‐bed reactor. CO 2 methanation experiments in an annular fixed‐bed reactor‐exchanger filled with 400 g of Ni/γ‐Al 2 O 3 catalyst at pressures from 0.4 to 0.8 MPa and coolant temperatures from 473 to 548 K (200 to 275 °C) are described in this paper and simulated by the model. CO 2 conversion rate and CH 4 selectivity at the reactor outlet and temperature elevations in the reactor are simulated by the model with a discrepancy lower than 10 %. For pressures above 0.4 MPa, a strong mass diffusion limitation inside the catalyst particles is shown and the efficiency decrease of the three reactions is explained.