Baffled-type thermochemical reactor for high-efficient hydrogen production by methanol steam reforming

Abstract

A baffled-type thermochemical reactor (BTR) for high-efficient hydrogen production by methanol steam reforming (MSR) based on the novel concept of methanol-based solar-driven hydrogen station is proposed and numerically investigated in terms of geometric and operating conditions with a multi-physics coupled model. It is found that the radius of heat-exchanging tube shows a significant impact on hydrogen yield (YH2) whereas the radius of heat-exchanging tube array shows little effect. Both the inlet velocity (Vin,HTF) and temperature (Tin,HTF) of heat transfer fluid (HTF) affect the reactor performance by influencing the heat transfer inside BTR. Excessively higher Vin,HTF and higher Tin,HTF would promote the side reaction of methanol decomposition (MD) against the main reaction of MSR, which finally decreases YH2. Moreover, it is also found that for each gas hourly space velocity (GHSV) there is a corresponding optimal value of Vin, HTF to maximize YH2. Based on this, an optimal operating curve has been obtained via data-fitting, where YH2 decreases while the hydrogen production rate (RH2) increases nonlinearly against GHSV, and the corresponding maximal values of 97.84% and 1.66 mol h−1 have been achieved separately. The results suggest that the practical operating conditions should follow the optimal operating curve with the compromise between YH2 and RH2. Finally, based on the performance evaluation against the traditional tubular reactor, the hydrogen yield of BTR is up to 1.79% higher than that of the tubular reactor due to (30.44%) more uniform temperature distribution, (15.30%) longer contact time and (7.46%) higher thermal-to-hydrogen energy conversion efficiency.