An evaluation of direct dimethyl ether (DME) synthesis from hydrogen and carbon dioxide based on CFD reactor simulations
Nils Beltermann, Stefan Weiske, Rafael Becka, Remzi Can Samsun, Ralf Peters, Detlef Stolten, Thomas E. Müller
Abstract
To mitigate the effects of anthropogenic climate change, various options for decarbonizing the transport sector are under investigation. One promising approach is the chemical production of energy carriers and fuels from renewable sources. Among various options, dimethyl ether (DME) is discussed as one of the top candidates. However, the production of DME from a renewable raw material supply is associated with certain challenges. This study analyzes the direct synthesis of DME from CO2 and H2 based on computational fluid dynamics (CFD) simulations of the relevant reactors. For the CFD simulations, the software ANSYS Fluent was applied. Kinetic models were integrated by user-defined functions to describe the multiple heterogeneous catalyzed reactions in the synthesis reactor. Several kinetic models were tested with respect to their accuracy and applicability with regard to describing DME formation. A quasi-isothermal reactor model was implemented as base case. It is shown that the progressive formation of water slows down the reaction of direct DME formation. Moreover, a model for a membrane reactor was developed and analyzed in detail. In comparison to the base case, a significant increase in reactor performance was obtained. In conclusion, it can be stated that, for the direct conversion of CO2 to DME, techniques for reducing the accumulation of water need to be adopted such as in-situ water removal or implementing an upstream reverse water-gas shift reactor.