The DVGW

Your network of excellence in the gas and water industry

The DVGW supports the gas and water industry in all technical and scientific areas. The main focus of the Association’s work is on safety and hygiene as well as environmental and consumer protection. The DVGW elaborates technical rules designed to promote the technical self-management of the German gas and water industry, thus ensuring the safe and secure supply of gas and water according to the highest international standards. The Association, which was founded in 1859, currently has approximately 14,000 members. The DVGW is free from economic and political influences.

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DVGW Research Center at Engler-Bunte-Institut of Karlsruhe Institute of Technology (KIT)
DVGW Research Center at Engler-Bunte-Institut of KIT
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Technical Center Hall

Production of renewable gases

The DVGW Research Center explores methods for producing renewable gases. Together with partners from research and industry, experiments and modelling are used to advance the various production paths and evaluate these paths from an energy and economic perspective.

New processes for the production and processing of renewable gases are being investigated in the pilot plant.; © Matthias Bitsch
Contribution of renewable gases for the success of the energy transition
Topics related to the generation of renewable gases
We explore renewable gas generation from concept to commercialization. © DVGW-EBI

The DVGW intends to use the “Energie Impuls” [Energy Momentum] dialogue series to encourage discussion on how to ensure the success of the energy transition across sectors. An important step of the “Energie Impuls” is to continuously increase the share of renewable gases, such as green methane and hydrogen, in the existing gas supply. This step contributes to the creation of a sustainable climate-neutral energy supply across all sectors of the energy system.
In light of this, the DVGW Research Center takes an integrated look at various technologies to supply renewable gases.

The Process Engineering working group explores the supply of renewable gases from biogas and Power-to-Gas technology. The goal is to develop a complete process, from the initial idea through to the application of the technology. The various processes include two-stage pressure fermentation, CO2 separation and supply with ionic liquids as well as biological and catalytic methanation. But the process development also needs to be accompanied by a detailed investigation of the individual aspects. These include the characterisation of substance properties (e.g. solubility, viscosity, etc.), the description of the reaction kinetics as well as the investigation of the hydrodynamics and the mass transfer in multi-phase apparatus (e.g. gas scrubbers, bubble columns). The development of the process also involves  technical and economic analyses of the overall process chains as well as their comparison with the state of the art.

Process chain for the production of liquefied methane from biomass and renewable electricity using the two-stage pressure fermentation process. © ProBioLNG

Biogas is comprised of 50% methane (CH4) and 50% carbon dioxide (CO2). In Germany, biogas is primarily used for on-site power generation. At around 250 of over 9,000 biogas plants, treated biogas is fed into the natural gas network for a range of applications in various sectors. This removes the temporal and geographic link between production and use, which is a critical advantage for the energy transition. To be able to supply biogas, CO2 as well as sulphur compounds and water must be removed and the biogas must be compressed to the pressure used in the natural gas network. The compression accounts for 30% of the costs required for the entire biogas treatment. To counter this challenge, we worked together with the State Institute of Agricultural Engineering at the University of Hohenheim for several years to develop two-stage pressure fermentation in the ProBioLNG research project, among others.

Three innovations optimise the two-stage pressure fermentation for the feed-in to the natural gas network:

  • Reduction of the residence time of the liquid through the spatial separation of the individual steps to decompose the biomass and adapt the reactor conditions (e.g. pressure and pH value) to the microorganisms
  • Biogas production under pressure produces biomethane with a very high methane content (> 80 Vol.%) and reduces the energy needed for treatment and compression
  • Integration of green hydrogen in biological methanation in the pressure reactor enables operation as a Power-to-Gas plant and therefore as an integrated energy management element.

The entire process chain enables an energy saving of 40 – 60 % compared to the depressurised method. In addition, the biomethane production costs are reduced by around 10% compared to the current state of the art.

Process for the production of renewable ("green") hydrogen © DVGW-EBI

Hydrogen as a chemical energy source can play a key role in a climate-neutral energy system. As a result, the European Union and the German federal government have developed a European and national hydrogen strategy. The DVGW supports the use of climate-neutral hydrogen and promotes research in reliable supply in the “Hydrogen innovation programme”.

The DVGW Research Center explores the production and supply of renewable hydrogen and climate-neutral hydrogen.

There are a range of options for producing renewable (“green”) hydrogen (see picture). The production methods for hydrogen from biomass and from renewable electrical energy based on water electrolysis have already reached a very advanced stage. The production methods are constantly analysed from a techno-economical perspective in consideration of the latest technical developments.

The production methods for climate-neutral (“blue”) hydrogen via steam reforming with CO2 separation and for turquoise hydrogen via methane pyrolysis are further areas of focus of the current research (RoadMapGas). We explain the “hydrogen colour theory” in a separate info box.

Gas scrubber for CO2 separation from air
Gas scrubber for CO2 separation from air in the pilot hall © Matthias Bitsch

Large-scale processes predominantly make use of gas scrubbing to separate CO2 from gases. If the CO2 in the gas is under low partial pressure, chemical gas scrubbers are more appropriate, as they enable comparatively high loads compared to physical gas scrubbers, even under low partial pressure conditions. For a number of years, the DVGW Research Institute has been investigating ionic liquids (IL) as scrubbing liquids for CO2 separation. ILs are characterised by a negligible vapour pressure. This means that large gas flows can be brought into contact with the IL and regenerated at higher temperatures in a vacuum without themselves vaporising to any significant extent. The proof of suitability for CO2 separation in connection with biogas treatment has already been provided at the DVGW Research Centre in laboratory and field tests. Further applications are currently being investigated as part of the RECODE and MethFuel research projects:

  • CO2 separation from fuel gases
  • CO2 supply from ambient air

CO2 separation from ambient air (direct air capture, see picture) is a particular challenge given the extremely low CO2 component of around 400 ppm.

Demo SNG container
Container of the demo SNG plant with 100 kW power © DVGW-EBI

In the Methanation Process, green hydrogen is combined with CO or CO2 and converted to methane and water. Methanation is a strongly exothermic reaction and the conversion is limited based on the equilibrium at high temperatures.

On an industrial scale, methanation is usually chemical-catalytic, executed in a series of adiabatic fixed-bed reactors with intermediate cooling. Novel reactor concepts enable good heat dissipation, where renewable methane suitable for supply can only be produced in a single reactor stage or in a series of two reactors with intermediate condensation. This type of process is demonstrated at the DVGW Research Center in cooperation with the KIT based on a mobile demo SNG plant in a 100 kW scale. The heart of this plant are honeycomb reactors, whose catalyst-coated metal structure enables good heat management as well as a high reaction speed. The plant has already been operated on a wood gasifier in Sweden (press release) and is being fitted with a new generation of honeycomb segments in the H2Mare project.

Besides catalytic methanation, biological methanation is another area of investigation at the DVGW Research Center. In the biological method, CO2 and H2 are converted to CH4 at low temperatures by microorganisms. The advantage of this method is a high tolerance to typical catalyst poisons. What’s more, the low process temperature means that no equilibrium limitation exists and full conversion is possible in a single process stage.

Bubble column
Bubble flow in bubble column in technical center © Matthias Bitsch

Research on RE gases extends to the design of suspension bubble column reactors (methanation) and gas scrubbers (chemisorption with ionic liquids). Despite intensive research activities over recent decades, the design of these multi-phase apparatus for large-scale production still presents a challenge. The design always requires the description of the chemical reaction as well as the mass transfer and the hydrodynamics. The mass transfer between the phases in the apparatus is defined by the hydrodynamics. The hydrodynamics involves the movement behaviour and the distribution of all of the phases in the reactor: gas phase, liquid phase and solid phase (e.g. catalyst particles). The goal is to investigate the hydrodynamics at defined positions and times, and establish the fundamental physical relationships. To do so, modern measurement methods based on tomography and laser metrology as well as imaging measurement methods for the experimental investigation of hydrodynamics are being developed and used in the Technology Centre (see InnoSyn research project). The fundamental physical relationships are then used to develop physically established calculation rules.

Power-to-gas plant in Falkenhagen
The power-to-gas plant in Falkenhagen is fully integrated into the surrounding energy infrastructure. © Uniper

To supply RE gases, individual technologies are used to create process chains. The centrepiece of Power-to-Gas (PtG) process chains are: water electrolysis, CO2 supply, methanation as well as compression or liquefaction.

National and European projects have provided extensive experience with various PtG technologies. The DVGW Research Centre predominantly conducts experimental research on processes for CO2 supply and methanation and has done so for years. Theoretical considerations and modelling of various technology configurations extend to energy optimisation and the evaluation of process chains as well as the analysis of investment and operating costs.

The data and experience gained from the project context are combined in a process chain tool and enable a detailed techno-economic analysis of various process chains. This takes account of site-specific factors so that the plants can be optimised for the local conditions from both an energy as well as economic perspective.

Current research projects on the techno-economic evaluation of PtG process chains:

The DVGW Research Centre uses the knowledge gained to advise on issues concerning RE gas supply in the form of studies and feasibility analyses on specific issues.

Whether studies or feasibility analyses: consulting starts with ideas

Contacts
If you have any questions on renewable gases, please contact
Friedemann Mörs
Gas Technology ∙ Group Manager Process Engineering

Phone+49 721 608-41274