Complete Ca/Cu cycle for H2 production via CH4 sorption enhanced reforming in a Lab-Scale fixed bed reactor

Abstract

The three main reaction stages of a H2 production process based on the combination of the CaO/CaCO3 and Cu/CuO loops have been experimentally studied in a lab scale fixed bed reactor. The solid bed contained the three functional materials required to run the process, namely a commercial Ni-based catalyst, a CaO-Ca12Al14O33 CO2 sorbent and a CuO-Al2O3 material in a proportion that resulted in a bed with 43.3% wt. CuO, 25.6% wt. CaO and 1.7% wt. Ni. The system was able to convert 13.5 kg CH4 h−1 kg Ni−1, at 675 °C producing a gas stream with a 93.5% vol. H2 at 10 bar. The Cu-based material presented high oxidation kinetics, being totally converted in a narrow reaction front with a highly diluted air stream at 10 bar. The Cu-based material presented also fast reduction kinetics and it was completely converted with a fuel gas with typical composition of a Steam Methane Reforming stage at high temperature. A Cu/Ca molar ratio of 2 allowed for calcination efficiencies over 85% molar basis at the CO and H2 break-through, and 95% of the CO2 from CaCO3 exited the reactor at CH4 break-through. The experimental results have been validated with an existing pseudo homogeneous reactor model that had been developed in previous works for the three reaction stages. The model was able to predict product gas compositions, bed breakthrough, and temperature profiles along bed.