Energy & Fuels, Vol.23, No.7, 3745-3752, 2009
Modeling of Stagewise Feeding in Fluidized Bed Reactor of Oxidative Coupling of Methane
The influence of distributed reactant injection on the performance of a fluidized bed reactor of oxidative coupling of methane (OCM) was investigated by means of reactor modeling and simulation. A two-phase hydrodynamic model was coupled with a comprehensive kinetic model of OCM over Mn/Na2WO4/SiO2 catalyst to predict the performance of the reactor. In the stagewise feeding, flow of air is divided into few portions. One portion is introduced to the fluidized bed through the distributor at the bottom, and other portions are injected inside the bed. It was shown that at low temperatures C, yield in the stagewise feeding configuration is higher than the conventional cofeeding, whereas at high temperatures the yield of products in stagewise feeding is lower than cofeeding. Therefore, the optimum operating temperature of the reactor can be decreased from 800 degrees C in cofeeding to 750 degrees C with two secondary air injections while keeping the same conversion and yield. Moreover, it was shown that the oxygen distribution along the bed decreases, making the reactor performance less sensitive to changes in temperature. In general, when applying the stagewise feeding configuration, the reactor can operate at lower temperature, effect of temperature change on the performance of the reactor Would be less, and removing the heat of reaction becomes more effective when compared to a cofeeding configuration. This results in widening the safe range of operating conditions, providing a more stable process with better temperature control and reducing other problems of high-temperature processes in the OCM fluidized bed reactor.