Hydrogen and/or syngas production through combined dry and steam reforming of biogas in a membrane reactor: A thermodynamic study

Abstract

The possibility of valorizing biogas by producing pure H2 and/or syngas while minimizing the net CO2 emissions was analyzed, combining both dry and steam reforming of biogas. For this purpose, a multifunctional membrane reactor (MR) with a hydrogen permselective membrane was used. The MR, which allows obtaining ultra-pure hydrogen in the permeate side, is compared with a conventional reactor (CR). All analyses were performed from thermodynamic equilibrium calculations based on the Gibbs free energy minimization method. The temperature was varied up to 800 °C and 550 °C for the CR and the MR, respectively. The influence of water addition in the feed on the productivity of hydrogen and CO2 reduction was assessed as well. Results showed that the CR is more suitable to obtain syngas with high purity (only CO and H2) because it allows operating at very high temperatures. The syngas H2/CO ratio can be adjusted for further applications depending on the co-fed amount of water. However, in the permeate side of the MR high-purity hydrogen with a productivity of 73 mol per 100 mol of biogas fed can be obtained. This productivity is equivalent to an H2 production of 131 kg/h, assuming the biogas generation capacity of an existing landfill plant; still, by CO2 recycling, net CO2 emission can be reduced up to 50%.