Development of newly designed wood burning systems with low emissions and high efficiency

• Forschungsstelle: EU FRP
• Projektnummer: 95.0210
• Projekttitel Englisch: Development of newly designed wood burning systems with low emissions and high efficiency

Schlüsselwörter (Englisch)

Wood combustion; wood chips; particulate emission; vortex; air staging

Alternative Projektnummern (Englisch)

EU project number: JOR3-CT95-0056

Forschungsprogramme (Englisch)

EU-programme: 4. Frame Research Programme - 5.1 Nonnuclear energies

Kurzbeschreibung (Englisch)

See abstract

Partner und Internationale Organisationen (Englisch)

Institute for Process Engineering and Power Plant Technology (IVD), Universität Stuttgart (DE), Luleå Institut of Technology, Luleå, (SE), Schmid AG (CH), Tulisydän Oy (FIN)

Abstract (Englisch)

The process development unit (PDU) has been tested with various fuels. The PDU combines a pri-mary thermal conversion chamber and a secon-dary combustion chamber with hot cyclone and vortex-burner.
The PDU was feed with different fuels. There was a softwood (mainly spruce, Picea abies Karst.) and a hardwood (beech, Fagus sylvatica L.) chips burnt. The hardwood was supplied by IVD in-stitute at the University of Stuttgart as reference fuel, which was tested in all combustion equipment of the project partners. The PDU was operated at fuel inputs at an hourly feed rate of 17 to 31 kg. Combus-tion air supply was varied to get excess air ratios of 1.4 up to 2. The combustion/gasification process in the primary thermal conversion chamber produced a fuel gas riche flame with carbon monoxide contents (CO) between 7 to 10 Vol%. The air ratio achieved values between 0.7 and 0.8. The hot cy-clone temperature raised up to 1150 degree Celsius. The retention time of the hot gases in the cyclone varied from 0.9 (31 kg/h feed) up to 1.7 seconds (17 kg/h feed). 77 % of the energy in the fuel was converted in the cyclone. The specific heat load in the cyclone achieved values of 240 up to 446 kW/mn3.
The combustion in the vortex-burner was homogenous. The products of incomplete combus-tion (PIC), here as carbon monoxide, were very low, typically between 6 to 200 mg/mn3 (European Standards limit CO at 873 mg/mn3 @ 13% oxygen). The nitrogen oxides in the flue gas varied considerable. The nitrogen oxides in the flue gas were in the range of 90 mg/mn3 to 190 mg/mn3 (Swiss Standard limits NOx at 200 mg/mn3). The total particle surface (TPS) of the PDU is of an order of magnitude smaller (softwood 6.7 E-02 cm2/cm3; hardwood 5.34 E-02 cm2/cm3) than the one of the commercial burners (131 E-02 cm2/cm3). The Nano-particles mobility diameter has been in the range up to 120 nm with mean diameters of 80 to 90 nm. Particle surface attracts polycyclic aromatic hydrocar-bons (PAH). Any decrease in particle surface reduces transport of carcinogens compounds in to the lungs.
The IVD in-stitute at the University of Stuttgart did some velocity profile measurements with the Laser Doppler Velocimeter (LDV). The flow patterns proved the vortex shaped swirl in the combustion chamber.
The results show some very promising approaches to the established questions at the commencement of the project. The basic layout of the process development unit covers most of the required features of innovative wood combustion systems such as:
-Complete combustion with low emissions of unburned compounds (PIC)
-Low particulate emissions
-Low nitrogen emissions (NOx)
-Ash fractions with low content of heavy metals
What still needs to be improved is the combustion stability over the entire heat load range.

Datenbankreferenzen (Englisch)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 95.0210