Germany-headed biogas plant operators and technology suppliers EnviTec Biogas AG has revealed that it has achieved another milestone in the German biogas upgrading market with the completion of a 700 Nm3 per hour EnviThan upgrading plant in Solschen, Lower Saxony.“In just five years, we have planned and completed a total of 20 plants with this efficient and environmentally-friendly membrane technology,” revealed Jürgen Tenbrink, Chief Technology Officer at EnviTec Biogas.
Flexible membrane technology
Fuel gases are subdivided into two types: H-gas (high calorific gas) and L-gas (low calorific gas). L- and H-gas are transported using separate pipeline systems. L-gas produced by German and Dutch plants currently supplies around 30 percent of the German natural gas market. The upgrading process can produce any level of calorific value as desired, which is measured by using the ‘Wobbe index’.
Our customers have been particularly impressed by the flexibility of our membrane technology. Production output is declining, however, so affected network areas will have to move to H-gas in the future, said Stefan Laumann, Head of Gas Upgrading at EnviTec.
In the course of this ‘marketplace migration’, the Solschen EnviThan plant will also need to convert from L- to H-gas. The plant is already well-prepared for this step, however, since it has adequate slots reserved for the additional membranes.
Joint development with Evonik
Developed jointly by EnviTec and Evonik Industries, the EnviThan process has now been successfully deployed in the UK, France, China and Denmark following its German market launch in 2012. Laumann explained that the technology has seen a series of improvements over the last five years.
While we initially installed the membranes vertically, we ultimately switched over to a new, horizontal arrangement – and this is now the standard membrane design. Three out of four projects now use a horizontal membrane layout, Laumann said.
By using this horizontal arrangement, EnviTec is now able to install almost three times as many modules in a single container. Another change was introducing the option to source the feed-in compressor from EnviTec as well.
First deployed as part of a project in France, this compressor boosts the pressure of the biomethane produced from around 12 bar to the network pressure required by the various destination gas networks. The booster compressor is delivered as a fully-equipped, ready-to-go unit along with the high-pressure gas lines needed, if needed by the client, to connect the plant to the network operator’s feed-in point.
Laumann reveals that progress has also been made in developing smaller, more compact plants. The company now offers a single-container model for biogas plants up to 300 Nm³/h. The new container design also provides dedicated space for up to two membrane racks: this is much more cost-effective since it not only avoids using a second container but also saves on pipework, cabling and base.