(578e) Simulation of Start-up in a Double-Jacketed Membrane Reactor on Methanol Steam Reforming

Hydrogen production using a membrane reactor has been widely studied in recent years. Most of studies focus on the steady state operation. However, the start-up operation and response condition are important in practice, and still unclear. In this study, the start-up strategy of methanol steam reforming in a double-jacketed membrane reactor(Fig. 1) was simulated using a one-dimensional, non-isothermal model. Methanol mixed with air was directed into the oxidation tube and provided the energy for the endothermic steam reforming reaction. The temperature variation between catalyst bed and inlet gas stream was considered under two conditions: In condition 1(Fig. 2), the catalyst bed is at room temperature(298.15K), and the inlet gas stream is fed at working temperature(543.15K); In condition 2(Fig. 3), the catalyst bed is preheated to working temperature(543.15K), and the inlet gas stream is fed at steam temperature(373.15K). The results showed that both operating conditions reached steady state within 10 minutes. When the inlet concentrations of the oxidation tube were changed, it took several seconds to reach steady state. The reaction rate of condition 1 increased as time increases, whereas the reaction rate of condition 2 decreased with time. Operating under condition 1 could get higher equilibrium temperature than that of condition 2, i.e. operating under condition 1 has higher conversion and hydrogen yield than those of condition 2. In addition, the methanol conversion was compared using a co-current and counter-current reactor and it was concluded that the co-current reactor had the best results.(Fig. 4) Furthermore, the optimum superficial velocity ratio of the oxidation tube and reforming tube was evaluated to be 0.1 to reach the highest methanol conversion.

Keywords: double-jacketed membrane reactor, methanol steam reforming, unsteady state, simulation model.

Fig. 1 Scheme diagram of double-jacketed membrane reactor.

Fig. 2 Temperatures in reformer using condition 1. WHSV is 14, water to methanol molar ratio is 1.2, inlet gas temperature is 543.15K, and initial catalyst bed temperature is 298.15K.

Fig. 3 Temperatures in reformer using condition 2. WHSV is 14, and water to methanol molar ratio is 1.2, inlet gas temperature is 373.15K, and initial catalyst bed temperature is 543.15K.

Fig. 4 Comparisons of co-current and counter-current operation. Time is 600 seconds, WHSV is 10, and water to methanol molar ratio is 1.2.