High-Pressure Chemical Looping Reforming Processes: System Analysis for Syngas Generation from Natural Gas and Reducing Tail Gases

Abstract

Reforming technologies produce syngas that serves as an important intermediate in the production of fuels and chemicals in the chemical and petrochemical industry. Only recently has reforming technology based on the chemical looping concept been attempted. Most chemical looping studies have been performed under ambient pressure conditions, but most processes that use syngas operate at an elevated pressure. Understanding the effect that pressure has on syngas generation in a chemical looping reactor is essential to the design of the overall system. This study characterizes and compares the effect of pressures on syngas yields under various chemical looping reforming operating conditions. Specifically, in this study, an iron-based oxygen carrier is used for the chemical looping partial oxidation reaction of methane to form syngas. The equilibrium simulation is of direct relevance to process applications, as demonstrated by the methane and metal oxide co-current reactor system, where in previous studies, experimental product yields were shown to be appropriately represented by equilibrium conditions. The results of syngas generation at 1 atm are used in this study as the basis for comparison to those obtained under pressurized conditions. The isothermal syngas generation is first examined qualitatively and quantitatively for pressures ranging from 1 to 30 atm. The adiabatic syngas generation is then examined under autothermal operating conditions. The sensitivity studies are performed to describe the changes in product yields as the temperature and pressure along with steam and CO2 inputs are varied. The results of the analysis illustrate the various competing factors that dictate the high-pressure syngas yield and purity. The study also provides insight into choice of operating conditions that enable thermodynamic syngas yields at higher pressure to be comparable to those at atmospheric pressures.