Biogas from anaerobic digestion and producer gas from wood gasification can be further converted to produce renewable methane or heat and electricity, the latter by using gas engines, gas turbines or high temperature fuel cells. The gas streams from biomass contain not only carbon oxides, methane, steam and hydrogen, but also higher hydrocarbons (often unsaturated), sulphur compounds and further impurities such as particulates, siloxanes, and ammonia.
The conversion steps require specific feed gas quality, e.g. to remove sulphur upstream of catalytic reactors or siloxanes and particulates upstream of engines and turbines. Therefore, for each conversion of biomass to energy carriers, gas cleaning steps with sufficient performance have to be found, while being cost-efficient for relatively small plants. Our research focuses on both adsorption based and catalytic gas cleaning steps, and on world class diagnostic tools which allow the measurement of low concentrations of contaminants (down to sub-ppm range) in difficult gas streams containing particulates, steam and/or tars. The diagnostic tools cover on-line particle measurements, suitable sampling methods and analytic tools ranging from mass spectrometry to gas chromatographs with multiple detectors (FID, SCD, MS), IR spectrometry, UV-vis and ICP-MS.
Besides measurement campaigns in the field, long duration tests with real gases (TRL 5) and laboratory experiments (TRL 2-3) with model compounds allow for a deeper understanding the performance of specific gas cleaning units. These findings are integrated in integrated in simulations of complete process chains to determine optimal process concepts with respect to energy efficiency and economics.
Field campaigns
- Successful long duration test at 10 kW scale (Container based demo plant COSYMA at TRL 5) converting raw biogas from the 6 MW biogas plant in Zürich Werdhölzli in collaboration with energie360°. More than 1100 hours of stable desulfurization and thus operation without catalyst deactivation (spring/summer 2017).
Watt d’Or 2018 awarded by the Swiss Federal Office for Energy for the project team “Direct methanation of Biogas” - Supporting scale-up of the wood-to-SNG process to 1 MWSNG scale within the EU-project Bio-SNG and commissioning of the Pilot & Demonstration Unit, several measurement campaigns (2006-2009).
Watt d’Or 2009 awarded by the Swiss Federal Office for Energy and Schweighofer Prize 2009 for the project team “Methane from wood” - Successful long duration test at 10 kW scale (Container based demo plant COSYMA at TRL 5) converting producer gas from the commercial wood gasifier in Güssing/Austria to Synthetic Natural gas (SNG). More than 1000h of stable desulfurization, tar removal and thus operation without catalyst deactivation (spring/summer 2007)
Key findings
- Gas cleaning is one of the key technology steps to use fuel gases derived from biomass by anaerobic digestion or by gasification. The gas cleaning has to be optimised within the specific process chains, be it for a synthesis, be it for combined heat and power production in turbines, motors and fuel cells
- To enable advanced experiments and field campaigns, unique combinations of sampling systems and analytics have been developed, several of them operating on-line, to determine trace species even in hot, humid, tar-laden gas streams, e.g. measuring hydrocarbons or sulphur species down to the low ppm range
- Thermo-economic analyses for several process chains (comprising rate based models for both, producing methane, or combined heat and power) showed that less temperature changes (e.g. by implementing hot gas cleaning) improve the overall process performance
- Kinetics and performance for several gas cleaning materials have been successfully determined in laboratory experiments and field campaigns: sorbents, hydrodesulphurisation catalysts, reforming catalysts and reactive bed materials
Funding
SCCER Biosweet (Innosuisse), Energy System Integration platform (ESI), Swiss Federal Office for Energy (BfE), Swiss National Science Foundation, Competence Center for Energy and Mobility (CCEM), swisselectric research, Swiss Gas Association (FOGA), European Union, energie360°
Publications
Book and Book chapters
C.F.J. König, M. Nachtegaal, T.J. Schildhauer, Integrated desulfurization and methanation concepts for SNG production, in Synthetic Natural Gas from Coal, Dry Biomass, and Power-to-Gas Applications, T.J. Schildhauer, S.M.A. Biollaz (Eds.), Wiley & Sons, New York, 293-306 (2016)
Completed PhD theses
- D. Kuzmenko, Development of a catalyst for methanation in the presence of sulphur to simplify the production of Synthetic Natural Gas from wood (Diss. ETH Zürich No. 26326, 2015 – 2019, with C. Copéret, ETHZ and M. Nachtegaal, PSI)
- C. König, In situ XAS investigations of attrition resistant reactive bed materials under fluidised-bed conditions (Diss. ETH No. 21209, 2013, with M. Nachtegaal, PSI)
- U. Rhyner, Reactive hot gas filter for B-IGFC systems (Diss. ETH No. 21102, 2013)
- M. Rechulski, Catalysts for High Temperature Gas Cleaning in the Production of Synthetic Natural Gas from Biomass (Thèse EPFL, n° 5484, 2012)
- J. Judex, Grass for Power Generation. Extending the Fuel Flexibility for IGCC Power Plants (Diss. ETH Zürich No. 18865, 2010)
- F. Nagel, Electricity from wood trough the combination of gasification and solid oxide fuel cells (Diss. ETH Zürich No. 17856, 2008)
- J. Pecho, Oxygen transfer materials with catalytic properties for biomass gasification (Diss. ETH Zürich No. 17302, 2007)