Phenomenological modeling of a fluidized-bed reactor for catalytic decomposition of methane

Modeling and simulation of a fluidized-bed reactor for methane decomposition over Ni–Cu–Al catalyst were investigated. The products of the reactions are carbon nanotubes and hydrogen. The axisymmetric 2D phenomenological model of the reactor developed in this research comprises gas-phase methane and hydrogen mass balances, solid particle mass balance, energy balance and momentum balance. Axial and radial dispersion concepts are applied on the description of the non-ideal flow pattern of gas phase and solid particle in the reactor. The solid particle dispersion takes into account agglomeration as a result of carbon nanotubes growth on the catalyst surface. The dynamic simulation of the solid particle mass balance was performed to investigate the solid particle distribution in the reactor bed. Furthermore, the dynamic simulation of all other balances was carried out. Simulation results exhibit that at the inlet pressure of 1 atm, the inlet velocity of 0.017 m/s, the bed diameter of 0.28 m and the catalyst particle diameter of 0.1 mm, the bed length where the minimum fluidization occurs is 0.79 m. The increase in the inlet pressure from 1 atm to 2 atm decreases the methane conversion from 77% to 51%, and increases the carbon yield from 0.66 g/g catalyst to 0.90 g/g catalyst. The increase in the wall temperature from 873 K to 1023 K magnifies the methane conversion from 25% to 97%.