Hydrogen can be used not only as a fuel, but also for the chemical processing. One of the applications is as a synthesis gas in the gas-to-liquid (GTL) process which produces liquid fuel from a gaseous one and has tremendous potential for the future energy industry. Steam methane reforming (SMR) is one of the major methods of hydrogen production. To optimize SMR, pressure dependence is important since the Fischer-Tropsch (FT) process, which is the oil production process in GTL, favors high pressure. In this study, using the rate expressions of SMR, which are obtained by experiment using a nickel-based catalyst supported on a metal plate in a rectangular channel, two-dimensional (2-D) simulation was performed at four different pressures ranging from 0.1 to 0.4 MPa in addition to one-dimensional (1-D) simulation. The reaction rates deduced from the experimental results on the basis of pseudo-bulk reaction naturally fit the 1-D simulation. The more precise 2-D simulation, however, inevitably needs some modification to reasonably predict the phenomena on the basis of the data from the pseudo-bulk reaction. As a result, the discrepancy between the results could be fixed by adjusting the reaction rate for the related pressure, and the adjusted factors show consistency between 1-D and 2-D calculations. Finally, the proper rate equations were estimated.
This study presents a method that can be employed to obtain the reaction rate and be widely applied to the simulation of steam methane reforming in a channel with a catalyst on the wall. Prior to the numerical simulation, an experiment was performed in an annular channel, in which the catalyst was deposited on the outer surface of the inner tube. In addition to varying the temperature and composition of the reactants, the velocity was also varied in order to investigate the range where the reaction-limiting condition occurs. Next, the results from the bulk concentration of the products were interpreted to determine the reaction rate of the surface catalyst. The reaction rate was properly introduced into the numerical simulation in two dimensions, although this method for obtaining the reaction rate is generally applied to a field that is supposed to be one-dimensional as a packed catalyst. On the other hand, a discrepancy between the experimental and simulation results was observed at a low velocity. The reason for this was investigated by considering the concentration and profile of the reactants. As a result, we concluded that it was necessary to pay close attention in a case where the amount of the reaction varied with the velocity, because the actual phenomena were controlled by other mechanisms that were not introduced into the numerical simulation.
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