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Increased combustion stability in modulating biomass boilers for district heating systems



The main objective of this project is to improve the combustion stability for small and medium sized biomass fired boilers aimed for small district heating networks. Investigated boilers in the thermal output range of 0.5 to 10 MW, show too high levels of harmful emissions at low and at varying loads and different ways to overcome this problem will be investigated within the project. This includes the development, design and construction of different combustion units to improve the conditions under which the combustion takes place. New means to monitor and control the combustion is included in the project and software will be developed to better describe the combustion process. The improvements will be verified by measurements and the different approaches compared by their impact efficiency and emissions of NOx, VOC and particles over the entire load range.


Three different combustion units will be designed and constructed in order to maintain high combustion stability at low and at varying load, namely: - pulsating combustion with a 500 kW prototype boiler - stationary vortex combustion with acoustic stimulation in a 150 kW boiler - 500 kW boiler with partitioned combustion chamber and heat storage. New and low-investment equipment to monitor the combustion process will be used together with simplified simulation software, fast enough to be utilised in the control system for boilers of actual size. Software to simulate the pyrolysis and gasification of fuels on the bed will be developed and the software CFX together with developed routines for the combustion of the gas phase will be used to predict the influence from geometry and boundary conditions on the formation of harmful emissions.


After completion of the project, different ways to overcome the problems identified when boilers are run at low and at varying loads will be demonstrated. New biomass fired boiler concepts, new and inexpensive control equipment and reliable simulation tools will be made available to boiler manufacturers and to energy utilities, thereby speeding up the changeover from fossil to biomass fuels and making it possible to reduce emissions of CO2 without increasing other harmful emissions. It is expected that after the end of the project two years are needed to transform the results into fully developed industrial products for the market.

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Luleä University of Technology
971 87 Luleä

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Participants (4)

Foundation for Appropriate Technologyand Social Ecology
12,schwengistrasse 12
4438 Langenbruck

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Högskolan i Växjö
23 A,pg Vejdes Väg
351 95 Växjö

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Technical Research Centre of Finland
40101 Jyväskylä

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Technische Universität Graz
8010 Graz

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