Emissions reduction

© Fraunhofer IPM
Pellet stove (Palazzetti Ecofire Bianca) equipped with electrostatic separator
© Fraunhofer IPM
Tube-shaped thermoelectric generator

Reduction of harmful fine and ultrafine dusts

As local, carbon-neutral raw materials, wood and biomass play an important role in climate protection. However, burning biomass emits large quantities of fine dust, including particles of less than 1 μm in size, which are particularly damaging to health. That is why countries like Germany are imposing increasingly strict limits on how much particulate matter can be emitted. As of 2024, some environmental certificates (e.g. the »Blue Angel«) will also require compliance with limits based on the number of particles – this is already standard for combustion engines today. Therefore, besides effective methods of combustion control, new technologies are needed to reduce the emission of harmful fine dust from combustion plants.

Active instead of passive – Separating instead of filtering

Passive fine dust filters made of ceramic or metal clean the exhaust gases mechanically and chemically. At first glance, they are less expensive than active particle separators. However, they clog up with the filtered particles during operation and must be regularly maintained and replaced.

Fraunhofer IPM therefore relies on active electrical particle separation for its cleaning systems. As standard, we use commercially available electrostatic separators as the core element of our separator solutions. They electrically charge the fine dust particles contained in the exhaust gas stream and subsequently deposit them on the inner walls of the flue pipe. With over 90 percent of the particle count, they provide a very high level of separation efficiency – even for particles down to the nanometer range.

Our particle separator systems are equipped with specially designed self-cleaning devices, which autonomously remove deposits of separated particles from the system. They can be retrofitted into existing installations, or can be integrated into a new installation from the start.

Low-energy plasma technology – for superior separation efficiencies of even ultrafine particles

A still higher fractional separation efficiency of over 99 percent, even for ultrafine particles less than 0.1 μm in size, can be achieved by using low energy plasma separators. These separators provide higher power density and ion concentration in the separation zone than conventional separators because the system operates above breakdown voltage.

Fraunhofer IPM designs plasma separators for various applications, including plasma separators that can be integrated into separation systems for biomass furnaces. In feasibility studies in a commercial pellet stove we were able to achieve separation efficiencies of over 99 percent.

Independent from the power grid thanks to thermoelectric generators

Thermoelectric generators (TEGs) use heat flows to generate their own electricity. They are durable and reliable and can be used even in very small spaces. Integrating a TEG into the flue gas train can generate enough electrical energy to operate a particle separator and a combustion control system. This means that the entire exhaust gas treatment system operates without the need to connect it to the grid.

Our exhaust gas treatment services

Fraunhofer IPM has the expertise and the industrial manufacturing technology required to develop customized emission reduction solutions.

We offer all of the following services from a single source:

  • Advice on designing exhaust gas treatment systems – both as a retrofit solution and as a solution integrated into new installations from the beginning
  • Design and construction of the system
  • Integration of a self-cleaning system to remove the separated particles
  • Integration of thermoelectric generators to provide an off-grid power supply for the exhaust gas treatment system
  • Development of low-energy plasma separators to achieve superior separation efficiencies
  • Measurement of the system’s fractional separation efficiency
  • Acceptance of the complete system in cooperation with accredited testing bodies
  • Referral of suppliers for separator components for series production