FlexDME - Flexible Demonstration System for the Generation of DME from Biogas and Hydrogen

Contact: M.Sc. Caroline Otto

Dimethyl ether (DME, C₂H₆O) is expected to replace fossil liquid gas in the fuel market in the long term. It can be used in adapted gasoline and diesel engines. Due to its sufficiently high energy density of 19 MJ/l (comparison: diesel: 35 MJ/l, LPG: 25 MJ/l), uncomplicated handling and excellent combustion properties, DME is regarded as a future option for the further use of diesel engines for heavy-duty transport (road and water), for construction vehicles and stationary CHP units. According to the state of the art, DME is produced in a two-step process via methanol from synthesis gas, which is produced from fossil raw materials (mainly coal, natural gas, petroleum residues).

The aim of the FlexDME project is to develop a modular, container-integrated demonstration plant for DME production from renewable raw materials (biogas) and electrolysis hydrogen.

Biogas with the main components methane and carbon dioxide provides the carbon basis in the process. By means of dry reforming, the biogas is first converted into synthesis gas (CO and H₂):

Dry reforming: CH4 + CO2 → 2 CO + 2 H2

DME synthesis then takes place in the subsequent synthesis step:

DME synthesis:4 H2 + 2 CO → C2H6O + H2O

The special feature of the process is a flexible mode of operation, in which "green" hydrogen is additionally introduced into the process during periods of high renewable electricity supply. In this way, the DME yield can be increased by up to 50 % compared to the biogas mode. The biogas-only mode during periods without H2 from renewable electricity ensures a high year-round utilization of the plant. This flexible mode of operation also allows the plant to contribute to the stabilisation of the electricity grid by providing useful negative secondary control power.