Abstract
The restructuring of the chemical industry towards the use of CO2 and intermittent, renewable energy sources poses a significant challenge for chemical engineers. Based on a systematic screening of current carbon-based chemical processes, we identify a promising combined reversible solid oxide cell (RSOC) and sorption-enhanced DME synthesis (SEDMES) process which produces dimethyl ether from captured CO2 and wind-generated electricity. Existing flowsheet alternatives are researched and a novel process design is proposed and simulated using Aspen Plus® and MATLAB®.
The optimization is divided into a design and a demand side management problem, solved by a genetic algorithm and the linear programming solver CPLEX, to determine the optimal operation and optimal production regime dependent on dynamic renewable electricity availability and price. The thermodynamic, economic, and ecological performance is assessed and compared to a selected fossil based state-of-the-art and biomass based state-of-research DME process. Thermodynamically, the RSOC/SEDMES process outperforms the exergetic efficiency of the state-of-the-art (37.7%) and state-of-research (50.8%) process with an exergetic efficiency of 53.2%. The necessary product break-even price of 2.14e/kgDME is approximately five times larger than for the fossil based state-of-the-art process (0.4e/kgDME), but is more economically viable than the state-of-research process (2.64e/kgDME). Emitted greenhouse gases calculated via a cradle-to-gate life cycle assessment (LCA) using the GREET® database of −1.973 kgCO2eq/kgDME is comparable with the state-of-research process (−1.813 kgCO2eq/kgDME), and represents a massive improvement over the state-of-the-art process (2.066 kgCO2eq/kgDME).