A que distância estamos da cinética máxima no processo tradicional de reforma de metano?

Abstract

Methane steam reforming is one of the main industrial routes for syngas and hydrogen production, due to its reliability and relatively low costs. Theseproducts are widely applied in important commodities productions, such as methanol and ammonia, as well as its derivatives. Given the importance of his system to the chemical industry, it has become the focus of several studies. A variety of models has been proposed in the literature for describing a steam reformer. In this sense, there is an interest in the improvement of the catalytic systems due to the economical expected impact. The present work aims to study the influence of internal and external transfer limitations on the catalyst particle, observing the distance of industrial reactors to one where such effects were reduced considering reaction kinetics sufficiently fast.For the evaluation of such behaviors, different models derived from different hypothesis were investigated. For the problem formulation, mass, energy and momentum balances were applied. According to the models features, different resolution methods were selected.For the analysis of the catalytic bed performance, temperature, pressure and methane conversion profiles throughout the rector length were evaluated. The manipulation of process variables effects and of the reduction of transfer limitations were analyzed. It was observed that, for typical industrial conditions, there is a high inefficiency related to the intraparticular transferlimitations and/or low kinetic rate,allowing yet the improvement of the reactor performance towards maximum kinetics (theoretical rate without any diffusional effects, with negligible mass transfer resistance, achieving conversions close to that of thermodynamic equilibrium). In our investigations, for typical conditions of industrial reformer, it was observed that accelerating kinetics asymptotically to very high values could reduce 40% of the reactor length.