Intensifying chemical looping dry reforming: Process modeling and systems analysis

Abstract

Dry reforming of methane (DRM) to synthesis gas is one of the most well-developed CO2 utilization approaches, but it suffers from low efficiency. This paper explores the use of “chemical looping dry reforming” (CLDR) to intensify DRM by improving its carbon balance and energy efficiency and producing inherently separated syngas (CO and H2) streams. Performance models are presented for a comparative evaluation of four different process configurations, based on different schemes for supplying the heat needed for the endothermal reforming reaction: Combustion of auxiliary methane feed, combustion of some of the produced CO, or internal combustion of a fraction of the carbon formed in the cracking step, either with air or with pure oxygen. Our results show that the CLDR processes can significantly exceed the efficiency of conventional dry reforming in terms of syngas yield and CO2 utilization. The configurations with internal carbon combustion showed the highest efficiency, confirming the importance of heat transfer limitations for dry reforming and highlighting the ability to overcome these limitations via innovative process designs that are enabled by the flexibility offered by the separated reaction steps in chemical looping schemes. Furthermore, all CLDR processes produce inherently separated syngas streams, which makes them a flexible option for a range of downstream technologies without the need for additional process steps to adjust the H2/CO ratio required in conventional dry reforming of methane. Overall, the results confirm that CLDR is a technically viable and strongly intensified process alternative to conventional DRM as a CH4-conversion and CO2-utilization technology.