1. Increased Combustion Stability in Modulating Biomass Boilers for District Heating Systems
R.Hermansson, J.Dahl, J.Lundgren, M.Lundqvist, G.Eriksson, B.Lundqvist
Division of Energy Engineering
The Division of Energy Engineering at Luleå University of Technology has developed a boiler design giving stabilised combustion at varying thermal outputs with very low emissions of pollutants over a wide thermal output range, 50 kW to 500 kW. The work has been carried out in close cooperation with a local industrial company, AB Swebo Flis och Energi in Boden, Sweden.
A number of applications for boilers in the capacity range MW can be identified. Some potential users are heat supply to
-Public buildings, like schools, home for older people, etc.
-Small industries, shopping centres
-Small district heating networks for villages of suitable size
The purpose could be to change from fossil fuels in existing plants or to build completely new installations. Another application is to convert from electrical heating to district heating.
The main conclusions from the project are that it is possible to run the boiler down to 10% of maximum load with low emissions of CO and THC even when wood-chips with high moisture content are used. This can reduce both the investment and operating costs for small district heating plants. The most appropriate solution for a small district-heating system is to use a water heat store to match the heat load variations, while the furnace operates at as constant thermal output as possible.
The primary combustion chamber
Picture from the test site in Boden
Fluent calculation of the temperature distribution in the secondary zone
Typical emissions in the thermal output range kW
The research is partly funded by the European Commission in the framework of the Non Nuclear Energy Programme JOULE III and partly by the Swedish National Energy Administration.