Heat generation & emission reductions at landfills
Today, up to 2 percent of total greenhouse gas emissions in Sweden originate from older landfills, where by-product methane gas is released untreated. Vocsidizer™, a regenerative thermal oxidizer (RTO) system from Dürr Megtec, can make a crucial contribution to reducing these emissions. The Swedish location of Dürr Megtec, headquartered in Gothenburg, is a subsidiary of the Dürr Group. Sweden is the first country that uses this technology in a particularly sustainable way: The occurring process energy is recovered for district heating.
The energy supplier Gotland Energy AB (GEAB) has been using incineration to treat the landfill gas from the Visby landfill in cooperation with the Gotland region since the 1980s. The waste heat is then used for district heating generation. However, a reduction in the percentage of organic waste in the landfill meant an accompanying reduction in the methane gas concentration.
“We have determined that the methane gas concentration is now under 30 percent. As a result, the existing plant can no longer be operated in an energy-efficient manner. The low methane gas concentration makes it even difficult to ignite the flame in the existing incinerator, and then we need to help it along with gas or liquefied petroleum gas to get the incineration going. That’s neither modern nor environmentally friendly,” says Lisa Larsson, waste engineer for the Gotland region.
GEAB therefore urgently needed to find a new technology to avoid untreated methane gas being released. Lisa Larsson explains that until then, no technology for treating landfill gas with low methane concentrations was known in Sweden:
“We turned to the Chalmers University of Technology, and it established contact with Dürr Megtec”. The company deals in particular with regenerative thermal oxidation. Its technology was already in use at landfill sites in Germany. “I thought that if it works there, it’ll work here in Sweden too”, underlines the waste engineer.
Last year, the flameless regenerative thermal oxidizer (F-RTO) → Vocsidizer™ for treating industrial hydrocarbon emissions was then installed by Dürr Megtec in Visby.
The Vocsidizer™ system is unique in comparison with conventional regenerative thermal oxidizers, since it doesn’t need a flame.
Martin Poulsen, General Manager, Dürr Megtec in Sweden
“The Vocsidizer™ system is unique in comparison with conventional regenerative thermal oxidizers, since it doesn’t need a flame. This means that only extremely small quantities of typical flame or incineration residues such as nitrogen oxide or carbon monoxide are emitted,” explains Martin Poulsen, General Manager at Dürr Megtec in Sweden, adding:
“The Vocsidizer™ has a thermal efficiency of up to 98 percent, making it extremely energy efficient, and is powered by the energy supplied from the process gases. Integrated pipework ensures an efficient exchange of heat between the excess energy and the water.”
Gotland is the first region to use this technology for treating landfill gas, making Sweden the first country in the world to use the excess energy from an RTO system in the district heating network.
“It’s very satisfying to be able to use the energy available in the old landfill with Vocsidizer™. Because we can use it to heat a hundred homes in Visby all year long. And the resulting income covers the system’s running costs – a real win-win situation,” says Lisa Larsson.
GEAB received repeated awards for the project developed together with Dürr Megtec. In addition to the national Quality Innovation Award in 2019 of the Swedish Institute for Quality (SIQ), GEAB's performance was also honored at a global stage with the International Quality Innovation Award. This award was presented in February 2020 and is given among all participating international quality institutes.
The Vocsidizer™ uses a unique regenerative heat exchange principle. Compared with conventional RTO systems there is no burner or combustion chamber. This innovative, patented design uses a flameless single bed for process oxidation. Due to its flameless operation principle, it generates zero thermal NOx.
More than 2500 units have been meanwhile delivered.
The Vocsidizer™ at a glance:
- Unique flameless operating principle – zero thermal NOx generation
- 98% thermal efficiency – low operating costs
- Operating temperature at 900 to 980 °C – efficient destruction
- Compact skid-container system design – minimize investment and site requirements