Syngas Chemical Looping Process: Design and Construction of a 25 kWth Subpilot Unit

The syngas chemical looping (SCL) process employing the gas solid counter-current flow pattern demonstrates an innovative approach to generate hydrogen and/or electricity from syngas accompanied with in situ carbon capture. Iron-based oxygen carriers donate oxygen for complete syngas conversion in the reducer. The reduced oxygen carriers are then oxidized by steam and/or air to generate hydrogen and/or heat in the oxidizer and/or the combustor, respectively. Previous studies have reported the performance of the iron-based oxygen carriers, the advantages of a moving bed reducer and oxidizer, and simulation of various parametric effects on the reactor design of the reducer, oxidizer, and combustor for a continuous system. In this study, a 25 kW(th) subpilot SCL unit was designed based on the simulated criteria and constructed to demonstrate the feasibility of generating high purity hydrogen with in situ carbon capture. Two test runs were presented using 4.5 mm x 2.5-4.5 mm cylindrical oxygen carriers comprising of 60 wt % iron oxide (Fe2O3). The first test resulted in a syngas conversion of 99.96% and trace amounts of hydrogen generation highlighting the importance of the extent of oxygen carrier conversion. The second test demonstrated the continuous production of hydrogen with an average purity of 94.4% and a maximum of 98.4% when the conversion of the oxygen carriers exiting the reducer was 35.54%. The initial test results support the concept of continuous hydrogen generation with in situ carbon capture using the SCL process and also highlight the advantage of adopting the countercurrent moving bed reactor design.