Analysis and Simulation of Catalytic Steam Prereforming of Hydrocarbons in Adiabatic Tubular Reactors

Abstract

This work presents a dynamic model describing the catalytic steam prereforming of hydrocarbons (natural gas and naphtha) in adiabatic packed-bed tubular reactors. Pre-reforming is an additional step typically used in hydrogen industrial sites before steam reforming to reduce the catalyst deactivation. The proposed model comprises a set of differential equations, based on the momentum, energy, and mass balances, describing the reactions performed in a fixed catalyst-bed reactor, where hydrocarbons and water are mainly converted into a mixture of hydrogen and carbon oxides. The effect of operating conditions such as the steam/ carbon and hydrogen/hydrocarbon ratios on the conversion, temperature, and composition stationary profiles was analyzed for both natural gas and naphtha catalytic prereforming. Besides, the consistency of temperature and composition axial profiles were analyzed via comparison with the adiabatic temperature and composition computed from thermodynamic equilibrium. Simulated results indicated that the proposed model can accurately describe the steam prereforming process operating with both natural gas and naphtha. The main results showed that proper modeling of the effectiveness factor for natural gas and naphtha prereforming is an important task in the industrial operation of these reactors. Additionally, the simulated results showed that these reactors operate close to thermodynamic equilibrium at the beginning of the campaign, as seen at industrial sites. Besides, only methanation and water−gas-shift reactions seem to be controlled by the diffusive effects.