Press Release 023/2015

Towards Dust-free Wood Combustion

Particle Emissions of Wood Combustion Systems Reduced by 90% - KIT Researchers Present Innovative Carola precipitator at the ISH 2015 Trade Fair
The Carola®-precipitator (light green) is installed into the flue gas passage reduces the concentration of soot and fine dust by up to 90%. (Bild: KIT/P. Langer)

About 15 million wood-fired stoves and combustion systems exist in Germany, including central-heating boilers for apartment houses. They are subject to strict clean air regulations. New wood-fired boilers exceeding emission limits for particles have to be equipped with precipitators since the beginning of 2015. Next week, KIT scientists will present the Carola®-precipitator for boilers at the ISH trade fair, Frankfurt.


“All wood-fired boilers can be equipped with our compact, low-maintenance precipitator,” Dr. Hanns-Rudolf Paur, one of the inventors and scientist of Karlsruhe Institute of Technology (KIT), says. The Carola®-precipitator is installed into the flue gas passage between the boiler and the stack and reduces the concentration of soot and fine dust by up to 90%. If necessary, several systems can be connected in parallel or in series. The CCA system was developed to maturity for boiler systems of 25 to 1000 kW in cooperation with boiler manufacturers.


The functioning principle of the patented Carola®-precipitator is rather simple: The precipitator consists of two chambers. In the ionization chamber the particles of the flue gas are electrically charged by corona discharge. A natural corona discharge can be observed on e.g. masts of ships during thunderstorms. In the downstream collector chamber of the CCA system the charged soot and dust particles are deposited on a helical brush. It rotates regularly over a scraper and the collected particles fall into the collection vessel. “The only maintenance work to be done by the user is to empty the vessel every few months,” Paur explains.


“The advantages of our precipitator over other principles are obvious,” Dr. Hans P. Rheinheimer, Managing Director of CCA GmbH, a startup of KIT, says. The system is nearly maintenance-free, can be integrated into the boiler, and consumes less energy than a bulb. Contrary to HEPA filters, it is not necessary to exchange wear parts and the cross section of the stack is hardly reduced. With a separation efficiency of up to 90%, modern boilers can comply with the limits given by the Federal Emission Control Ordinance (1. BImSchV) for 2015.


KIT’s startup company CCA-Carola Clean Air GmbH is based on the know-how on precipitator systems for wood fired boilers. For the innovative process, the inventors were granted several awards, such as the Innovation Award of the Karlsruhe Chamber of Industry and Commerce and the Environmental Award of the Sparkasse Pforzheim Calw. Under a cooperation project with the boiler manufacturer HDG Bavaria, the precipitator was tested successfully.


KIT will present (stand 9.1 F OY02) the Carola®-precipitator at the world’s biggest trade fair for energy-efficient heating technology and renewable energies, ISH 2015, Frankfurt, from March 10 to 14, 2015.


Homepage of the KIT startup CCA GmbH:



Being “The Research University in the Helmholtz Association”, KIT creates and imparts knowledge for the society and the environment. It is the objective to make significant contributions to the global challenges in the fields of energy, mobility, and information. For this, about 10,000 employees cooperate in a broad range of disciplines in natural sciences, engineering sciences, economics, and the humanities and social sciences. KIT prepares its 22,800 students for responsible tasks in society, industry, and science by offering research-based study programs. Innovation efforts at KIT build a bridge between important scientific findings and their application for the benefit of society, economic prosperity, and the preservation of our natural basis of life. KIT is one of the German universities of excellence.

kes, 03.03.2015

Margarete Lehné
Chief Press Officer (acting)
Phone: +49 721 608-41105
Fax: +49 721 608-43658
presse does-not-exist.kit edu

Contact for this press release:

Margarete Lehné
Press Officer
Phone: +49 721 608-41157
Fax: +49 721 608-41157
margarete lehne does-not-exist.kit edu
The photo in the best quality available to us may be requested by
presse does-not-exist.kit edu or phone: +49 721 608-41105.

The press release is available as a PDF file.