Modeling and simulation of an industrial secondary reformer reactor in the fertilizer plants

In this paper, the industrial secondary reformer reactor has been modeled and simulated at steady-state operation conditions. It aims to modify a complete mathematical model of the secondary reformer design. The secondary reformer is a part of a subprocess in a higher scale unit of ammonia synthesis. It is located after the primary reformer in the ammonia plant where it is used in the synthesis of ammonia. The reactions in the secondary reformer reactor are assumed to be carried inside two reactors in series. The first reactor, upper section, is the combustion zone, while the second reactor, bottom section, is the catalyst zone with nickel catalyst based on the alumina. In order to create a reactor design model for the secondary reformer in the industrial ammonia plant, combustion and catalyst zones have been studied. The temperature and compositions of gas in the combustion zone are predicted using the atomic molar balance and adiabatic flame temperature model. In the catalyst zone, the temperature and composition profiles along the axial distance are predicted using a one-dimensional heterogeneous catalytic reaction model with the assumption that the reactions are first order in methane partial pressure. Most of the methane is converted in the part of one fourth to one half of the catalyst zone length from inlet to outlet. The temperature gradient between the gas and catalyst surface decreases along the axial distance, and both temperatures approach the same value at the bottom of the catalyst bed. Finally, the results of this simulation have been compared with the industrial data taken from the existing ammonia unit in the State Company of Fertilizers South Region in the Basra/Iraq, which show a relatively good compatibility.