University of Oulu

Advanced control of an industrial circulating fluidized bed boiler using fuzzy logic

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Author: Karppanen, Erkki1
Organizations: 1University of Oulu, Faculty of Technology, Department of Process and Environmental Engineering
Format: ebook
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2 MB)
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Language: English
Published: 2000
Publish Date: 2000-01-10
Thesis type: Doctoral Dissertation
Defence Note: Academic Dissertation to be presented with the assent of the Faculty of Technology, University of Oulu, for public discussion in Raahensali (Auditorium L 10), Linnanmaa, on February 4th, 2000, at 12 noon.
Reviewer: Doctor Timo Hyppänen
Doctor Enso Ikonen


Circulating Fluidized Bed (CFB) boilers are widely used for multi-fuel combustion of waste and bio-fuels. When several non-homogeneous fuels, having varying heat values, are burned simultaneously, the boiler control system can be affected by various control challenges, especially since it is not feasible to reliably measure the energy content of the multi-fuel flow. In order to fulfill energy production needs and maintain the ability to burn low grade fuels, co-firing with high heat value fuels such as gas, oil or coal is needed.

Fuzzy Logic Control (FLC) has been successfully used for solving control challenges, where operators’ process expertise can be transformed into automation. Real life control objects are often non-linear because the dynamics change with the operating point, or there might be other essential non-linearities in the combustion process.

The proposed fuzzy control applications were developed to solve control challenges the operators meet in daily operation of a 150 MW(th) CFB at Varenso Oy’s (Stora Enso Oyj) K6 boiler in Varkaus Finland. Before implementing the applications in the full scale boiler, they were tested at a 2 MW(e) pilot plant boiler at Foster Wheeler Energia Oy’s Research Center in Karhula, Finland.

According to the industrial experiments, the four applications (steam pressure control, compensation of fuel quality fluctuation, fuel-feed optimization and increased bed inventory monitoring) discussed in this thesis, showed satisfactory performance and various improvements to the boiler control were achieved. Fuzzy logic control was shown to be a notable tool to improve the multi-fuel CFB boiler control.

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Series: Acta Universitatis Ouluensis. C, Technica
ISSN-E: 1796-2226
ISBN: 951-42-5519-4
ISBN Print: 951-42-5518-6
Issue: 145
Copyright information: © University of Oulu, 2000. This publication is copyrighted. You may download, display and print it for your own personal use. Commercial use is prohibited.