Abstract

Objectives and problems to be solved:

The project focuses on the solution of problems related to aerosols and fly ashes in fixed-bed biomass combustion systems namely particulate emissions and deposit formation. Characteristics and the behaviour of aerosols should be investigated considering different biomass fuels. Mechanisms governing deposit formation in furnaces and boilers and the corrosive potential of these deposits should be explored. Based on this knowledge, technologies reducing the problems mentioned should be developed. Efficient aerosol precipitators should be enhanced by setting up an aerosol data base for filter manufacturers accompanied by techno-economic recommendations as well as by optimising the RPS, which is an innovative dust precipitator for small-scale applications. Additives to influence aerosol formation and growth will be investigated. Finally, environmental and health risks of aerosol emissions from biomass combustion should be evaluated as a basis for the recommendation of emission limits.

Description of the work:

At first, aerosols formed during the combustion of different biomass fuels (bark, wood chips, waste wood) should be characterised. Test runs at a pilot plant and a large-scale CHP-plant i ncluding aerosol, fly-ash and deposit sampling with subsequent chemical analyses and analyses by electron microscopy should provide information about particle size distribution, shape and chemical composition of aerosols and fly-ashes. Based on these data, the mechanisms of aerosol and ash formation and behaviour should be investigated with computer aided mathematical models. Additionally, mathematical flow simulation will be used to describe the motion and deposit formation of aerosols and fly ashes in furnaces and boilers. The knowledge gained from this basic research should be used as a basis for the following investigations concerning aerosol precipitation and reduction of corrosive deposits. To optimise ESP and bag house filters, which are mainly used in large-scale biomass combustion units, an aerosol data base as well as relevant design data for filter manufacturers should be worked out and techno-economically evaluated. Concerning small-scale combustion units, the rotational particle separator (RPS), an innovative dust separator, should be optimised. Moreover, additives injected into the furnace in order to influence formation, growth and chemical composition of aerosols should be developed and tested. The effectiveness and techno-economic evaluation of additive injection will be performed based on the results from test runs.

Finally, the ecological and health risks of aerosol emissions from biomass combustion will be evaluated and compared to aerosol emissions from other sources as a basis for the recommendation of appropriate emission limits. Expected Results and Exploitation Plans: Based on an increase of the knowledge about aerosol and fly-ash formation and behaviour during fixed-bed biomass combustion by identifying the most important influencing variables, primary and secondary measures should be found to reduce aerosol emissions from biomass combustion units. Guidelines for the design of more advanced dust precipitators should be one major result from the project. Furthermore, additives, which influence the formation and growth of aerosols should be developed to reduce deposit formation in furnaces and boilers as well as to reduce the potential for corrosion of these deposits. Finally, an ecological evaluation of the data about aerosol emissions collected during the project, should lead to recommendations for future emission limits.

Contacts

Coordinator

• Otto WOLFBAUER / Graz University of Technology Institute of Chemical Engineering Fundamentals and / AUSTRIA

Participant

• Margareta NYBACKA WILLNER / AABO Akademi University Faculty of Chemical Engineering / FINLAND
• Gerard PASMANS / Eindhoven University of Technology Department of Mechanical Engineering
• Emissions Reduzierungs Concepte GMBH GERMANY
• Claus STEURER / Mawera Holzfeuerungsanlagen GMBH & CO KG
• Wolfgang VOSS / Standardkessel Lentjes Fasel GMBH GERMANY
• Knud OSTERGAARD / Technical University of Denmark Department of Chemical Engineering / DENMARK