Optimization of H2 production with CO2 capture by steam reforming of methane integrated with a chemical-looping combustion system

Abstract

Methane steam reforming (SR) integrated with a chemical-looping combustion (CLC) system is a new process for producing hydrogen from natural gas, allowing carbon dioxide capture with a low energy penalty. In this study, mass and enthalpy balances of an SR-CLC system were carried out to determine the autothermal operating conditions for optimal H2 production. The evaluation was conducted using iron-based oxygen carriers. Two configurations were analysed, firstly with the reformer tubes inside the fuel reactor and, secondly, with the reformer tubes inside the air reactor. This paper analyses the effect of two parameters affecting the SR process, namely the conversion of methane in the reformer (XCH4) and the efficiency of the hydrogen separation of a pressure swing adsorption (PSA) unit (ηPSA), as well as two parameters affecting the CLC system, namely the Fe2O3 content in the oxygen carrier and its conversion variation (ΔXOC), on the H2 yields. Moreover, it also analyses the reduction of Fe2O3 to Fe3O4 or to FeAl2O4. The results shown that a H2 yield value of 2.45 mol H2 per mol of CH4 can be obtained with the reformer tubes located inside the air reactor and with Fe2O3 being reduced to Fe3O4. This corresponds to a CH4 to H2 conversion of 74.2%, which is similar to state-of-the-art H2 production technologies, but with inherent CO2 capture in the SR-CLC process.