New type of reactor for biological methanation successfully tested as a flexible energy storage

Trickle-bed reactor of the BTU Cottbus methanisiert either carbon dioxide or raw biogas being boosted with hydrogen - methane formation rate, high product quality, low energy consumption

In a research project, the Brandenburg Technical University (BTU) Cottbus Senftenberg has further optimized its 2012 developed continuous trickle-bed reactor for the biological methanation and tested under realistic conditions. The procedure is potentially well suited for flexible storage of energy as a contribution to the energy revolution.

Power-to-gas (PtG) procedures are regarded as key technologies for the storage of renewable energy. This water into hydrogen (H2) and oxygen is split into Electrolysers with help of excess renewable electricity. The hydrogen can then with CO2 in methane (CH4) convert (SNG), which is almost equal to natural gas and can be easily feed into the existing gas networks. Classic, chemical physical methanation process are due to the required high pressures and temperatures comparatively expensive. To compensate for the fluctuation of renewable energies such as wind power and photovoltaic, the biological methanation appears as a suitable alternative. This single-celled organisms called Archaea, transform H2 and CO2 under ambient conditions to CH4.

The BTU has developed a new, continuous trickle bed reactor already 2012 the biological methanisation. The now patented reactor is characterised by a particularly high methane concentration by 98 percent in the product gas and a low power and heat demand. The relatively low ratio of methane formation was improved. The project presented here, the BTU developed the approach tested in the pilot plant for the coupling of organic, solar and wind energy in practice. By increasing the working pressure 5 bar, it the ratio of methane formation at relatively low could increase energy overhead. A further increase in pressure, however, led to no increased sales of hydrogen. In addition, the researchers determined the optimal operating parameters and tested successfully not purified biogas as an alternative to the output gas CO2. By adding a practical nutrient solution, they reached a stable long-term operation of the reactor. “Noteworthy is also the very good control of the process, the formation of methane can be directly started or interrupted. Thus it is possible, on the demand for natural gas and the availability of input gases to react flexibly”, explains project manager Dr. Marko Burkhardt.

Overall, the researchers evaluated the anaerobic trickle bed reactor as economically competitive with other Methanisierungsverfahren, with significant strengths in the energy efficiency and product quality. According to their estimates, the reactor itself for a flexible, demand-oriented driving style is well suited, the interaction of the entire process chain from the electrolysis to methane feed must be examined on a practical scale but further. R & d demand even in the use of control and control technology for the SNG under increased pressure, because here the exact setting of the CO2: H ratio is particularly important.

The project was funded by the Federal Ministry of food and Agriculture (BMEL) about the project carrier specialist agency renewable raw materials e. V. (FNR). The final report is available on 22407112 available at the grant number.

Source: FNR, press release, 2018-04-04.