The world’s first small scale, CO2 neutral pyrolysis plant was launched by Danish-based biomass power production company, Stirling Denmark on 24 October 2008. The system is based on the pyrolysis process in which wood chips are heated to a high temperature without admitting oxygen. This creates pyrolysis gases which are then burned in a boiler to produce heat. Some of this heat drives a Stirling engine that generates electricity. And Danfoss products help to keep the plant burning safely and efficiently.

From low-value biomass to high-value CO2 neutral energy

Founded in 2004, Stirling Denmark is the result of 15 years of research into and development of Stirling engine technology by the Technical University of Denmark. The company develops and manufactures Stirling engines that convert low-value biomass into high-value CO2 neutral electricity and heat.
What makes the Stirling Denmark pyrolysis plant unique is where combustion takes place: not in the engine’s cylinder, but in an external combustion chamber fuelled by the gases produced during the pyrolysis process. And Danfoss products help monitor and maintain the correct temperatures during operation.

The Danfoss effect

So how did Danfoss get involved in the development of a pyrolysis plant that converts biomass to electricity? Stirling Denmark was familiar with Danfoss products and was impressed by their quality. So when a subcontractor working on the plant’s water circulation system recommended other Danfoss products, Stirling Denmark took action. In September 2007, a team from Stirling Denmark visited the Danfoss stand at the Herning Industrial Exhibition. The rest is recent history. Danfoss currently supplies Stirling Denmark with valves and switches for temperature and pressure control.
Danfoss products are primarily used for safety functions in the plant’s water system, which delivers the heat generated from the biomass to the central heating grid. This involves a) the transfer of excess heat to an emergency cooler, b) the detection of water leaks that can cause a drop in pressure and c) the protection of an additional traditional boiler against freezing. But Danfoss’ contribution doesn’t stop there. At present, Danfoss is working to develop a new thermostatic valve, the BVTS valve. The BVTS will monitor burn back in the woodchip screw conveyor which feeds the pyrolysis process (where the woodchips are heated and charred at temperatures up to 600°C). If a fire starts and burns back into the conveyor, the BVTS will release a jet of water that will put the fire out.

Set for success

The world’s first small-scale commercial pyrolysis plant burns wood chips from discarded wooden crates, but other biomass materials such as straw and coconut shells are currently being tested. The char residue from the current burn-off process is then returned to the soil as a nutrient, completing the CO2 neutral process – and effect – on the environment. This CO2 neutral form of energy production is generating a lot of interest. Since the pyrolysis plant’s launch in October 2008, the hits on Stirling Denmark’s website have almost doubled, and the phones have hardly stopped ringing. If you’d like to learn more about Danfoss products, please contact your nearest Danfoss office.

The process of heating material in a controlled atmosphere where there is not enough oxygen to initiate burning.
The process produces gases that can be used as fuel.

Jan Kofoed Laursen, sales engineer