Feasibility assessment of transition metal carbides applied to chemical looping reforming – A proof-of-concept for tungsten carbide

Abstract

This paper is the first study to present an innovative technology for hydrogen and syngas production named Carbide Chemical Looping Reforming (CCLR). Nine different Transition Metal Carbides (TMC) were assessed in a thermodynamic study to evaluate potential materials to be applied in the system that could possibly form hydrogen and carbide when in the presence of methane. Out of all the materials, tungsten proved to be the best suitable due to its known high resistance to carbon deposits [1], low-temperature range to form carbides (at least 750 °C), no formation of undesired compounds, and considerably high hydrogen quality in syngas range. A sensitivity analysis is performed in order to assess the better conditions of temperature, pressure and methane ratio for the process to maximize the formation of hydrogen. A study of the heat balance between the air reactor and fuel reactor is shown to prove the system can work as an autothermal process and exclude external heat sources as well as an analysis of the carbon emission potential to prove the technology accounts for lower emission when compared to current technologies, such as Steam Methane Reforming and Steam Methane Reforming with Carbon Capture and Storage. Experimental thermogravimetric analysis showed a high formation of hydrogen and carbide in the system with high selectivity towards hydrogen/syngas reactions, proving the formation of carbides in a process and replicability of the system. Lastly, an economic assessment is performed with tungsten carbide to show that the application of tungsten in CCLR could achieve a competitive level to current technologies with a hydrogen cost price of USD 3.23, with the potential to be reduced even more depending on the process configuration.