Increasing carbon efficiency for DME production from wheat straw and renewable electricity – Analysis of 14 system layouts

Liquid fuels like dimethyl-ether (DME), produced from biomass and electricity are crucial for decarbonizing the shipping industry. In this work, the production of DME from wheat straw through gasification is presented. It was shown how the process can be optimized by using 1) two-stage instead of one-stage DME synthesis, 2) partial oxidation of the produced gas and 3) a hydrogen quench for high-temperature reverse water gas shift reactions. The investigation was conducted by stepwise introducing the different process steps, leading to investigating 14 different plant layouts. This enabled a systematic analysis of the influence of different process steps by looking at the changes in carbon efficiency and energy efficiency. In all plants, DME and bio-ash, which acts as a soil amendment and carbon sink, were produced. 10 of the 14 plants additionally produced high-quality bio-oil. The analysis showed that all the introduced measures increased the carbon efficiency of the plants. At the same time, they increased the net electricity consumption. The highest energy efficiency reached was 57.5 %. A different plant reached the highest carbon efficiency with 84.0 %.,while having the highest net electricity consumption (45.2 MW at a biomass input of 50 MW (LHV)).