Hydrogen production from natural gas using an iron-based chemical looping technology: Thermodynamic simulations and process system analysis

Abstract

Hydrogen (H2) is a secondary fuel derived from natural gas. Currently, H2 serves as an important component in refining operations, fertilizer production, and is experiencing increased utilization in the transportation industry as a clean combustion fuel. In recent years, industry and academia have focused on developing technology that reduces carbon emissions. As a result, there has been an increase in the technological developments for producing H2 from natural gas. These technologies aim to minimize the cost increment associated with clean energy production. The natural gas processing chemical looping technology, developed at The Ohio State University (OSU), employs an iron-based oxygen carrier and a novel gas–solid counter-current moving bed reactor for H2 production. Specifically, this study examines the theoretical thermodynamic limits for full conversion of natural gas through iron-based oxygen carrier reactions with methane (CH4), by utilizing simulations generated with ASPEN modeling software. This study initially investigates the reducer and the oxidizer thermodynamic phase diagrams then derives an optimal auto-thermal operating condition for the complete loop simulation. This complete loop simulation is initially normalized for analysis on the basis of one mole of carbon input from natural gas. The H2 production rate is then scaled to match that of the baseline study, using a full-scale ASPEN simulation for computing cooling loads, water requirements and net parasitic energy consumption. The full scale ASPEN simulation is used to analyze the thermal efficiency of multiple energy recovery schemes, for further validation of the chemical looping process. Resulting from this study, the chemical looping technology is found to produce a cold gas efficiency improvement of more than 5 percentage points and an effective thermal efficiency of more than 6 percentage points over the conventional steam methane reforming process, while producing H2 from natural gas with greater than 90% carbon capture.