(439c) Process System Analysis of a High-Pressure Chemical Looping Based Hydrogen Production System

The iron-based moving bed based chemical looping technology developed at the Ohio State University (OSU) is a promising candidate to reduce costs associated with Steam Methane Reforming (SMR) for H₂ production. The OSU system performs the natural gas utilization and H₂ production in two separate reactors. As a result, it eliminates the need for multiple processing units to purify H₂. Initial estimates have shown an improvement in hydrogen production (2.4 moles of H₂ per mole of carbon in natural gas for chemical looping as opposed to 2.2 moles of H₂ per mole of carbon in natural gas for SMR system)¹. The earlier chemical looping investigations quantified the thermodynamics of the chemical looping system for atmospheric pressure. So, while the earlier results are promising, it should be noted that various H₂ utilization applications require H₂ at pressures of ~30-50 bar.

This study seeks to quantify the thermodynamic feasibility associated with high-pressure chemical looping applications for Hydrogen production. This study initially quantifies the H₂ production potential of the chemical looping system for higher pressures under isothermal operating conditions. Identified optimal isothermal operating conditions are used for simulating a commercially relevant adiabatic reactor operation. Investigation of variation in the pre-heats of natural gas, the supports (wt%) to synchronize the endothermic reducer reactor and the exothermic combustor reaction show maxima in trends associated with each reducer inlet temperature and system operating pressure. The study will investigate the individual and synergistic effects of variables like the number of compressor and expander stages, variation in reactant space hourly velocities and the trade-offs associated with using pinch and transshipment type technology for heat exchanger network synthesis. Preliminary results show that operating chemical looping system at higher pressures is feasible. An autothermal production achieved at pressures of 32 and 64 bar while maintaining a better performance than the conventional SMR systems and atmospheric chemical looping systems.

1. Kathe, M. V., Empfield, A., Na, J., Blair, E., & Fan, L. S. (2016). Hydrogen production from natural gas using an iron-based chemical looping technology: Thermodynamic simulations and process system analysis. Applied Energy, 165, 183-201.