Simulation of Methane Steam Reforming Enhanced by in Situ CO2 Sorption Using K2CO3-Promoted Hydrotalcites for H-2 Production

Abstract

The hydrogen production performance of sorption-enhanced methane steam reforming (SESMR) was investigated in this study. Three different K2CO3-promoted hydrotalcites (HTCs), including HTC A, industrial K2CO3-promoted HTC reported in the work by Ding and Alpay (Ding, Y.; Alpay, E. Chem. Eng. Sci. 2000, SS, 3461-3474); HTC B, commercial HTC from SASOL impregnated with K2CO3 in the work by Oliveira et al. (Oliveira, E. L. G.; Grande, C. A.; Rodrigues, A. E. Sep. Purif. Technol. 2008, 62, 137-147); and HTC C, commercial K2CO3-promoted HTC from SASOL, were considered. A set of experiments was carried out to measure CO2 adsorption on HTC C, and a one-dimensional (1D) heterogeneous dynamic fixed-bed reactor mathematical model was developed to simulate the performance of SEMSR. It was observed that the CO2 adsorption characteristics were different among the HTCs, resulting in different sorption-enhanced characteristic curves. The reaction period that can be operated to produce the high-purity hydrogen (99.99%) depends upon the sorbent type and operating conditions. The increase of the steam/methane ratio leads to the increase of the pre-breakthrough period. The increase of the operating pressure results in the increase of the pre-breakthrough period when the S/C value is high enough. The temperature of 863 K is suitable for the operation at a low S/C value, while the temperature of 773 and 740 K is appropriate for higher S/C values. The system using HTC B offers the best performance with the pre-breakthrough period of 720 min at the following operating conditions: F-tot, 0.73 mmol/min; T, 773 K; P, 0.2 MPa; S/C, 11.5; and catalyst/total solid, 0.05, while the system with HTC A offers 126.67 mm, which is better than 20 min of HTC C.