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

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 fullscale 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.

[1]  S. J. Koffman,et al.  Control of a fluidized bed combustor using fuzzy logic , 1996 .

[2]  Anders Lyngfelt,et al.  Low N2O, NO and SO2 emissions from circulating fluidized bed boilers , 1995 .

[3]  菅野 道夫,et al.  Industrial applications of fuzzy control , 1985 .

[4]  U. Kortela,et al.  Dynamic model for a bubbling fluidized bed coal combustor , 1994 .

[5]  F. A. Lootsma.  Applications of fuzzy set methodologies in industrial engineering , 1990 .

[6]  M. G. Alliston,et al.  Experience with the combustion of alternate fuels in a CFB pilot plant , 1995 .

[7]  Witold Pedrycz,et al.  Fuzzy control and fuzzy systems , 1989 .

[8]  Piero P. Bonissone,et al.  Industrial applications of fuzzy logic at General Electric , 1995, Proc. IEEE.

[9]  J. Makansi.  CFB`s make waste-to-energy, recycling `perfect together` , 1997 .

[10]  C. K. Jotshi,et al.  Fluidized-bed incineration of waste materials , 1994 .

[11]  K. B. Lee,et al.  Water Level Controls for a Drum-Type Boiler System using Fuzzy Logic Approach , 1995 .

[12]  Janet Efstathiou,et al.  Applications of fuzzy set methodologies in industrial engineering , 1990 .

[13]  菅野 道夫,et al.  Applied fuzzy systems , 1994 .

[14]  H. Martin.  Zukünftige Entwicklung von Wirbelschichtanlagen , 1991 .

[15]  J. R. Howard,et al.  Fluidized beds : combustion and applications , 1983 .

[16]  R. M. Tong,et al.  A control engineering review of fuzzy systems , 1977, Autom..

[17]  Kaddour Najim,et al.  Fuzzy neural networks and application to the FBC process , 1996 .

[18]  Marion Hersh,et al.  A study of advanced control systems in the work place , 1996 .

[19]  J. Werther,et al.  Kinetics of the main stages of fluidized bed combustion of a wet biomass particle , 1997 .

[20]  Prabir Basu,et al.  Circulating Fluidized Bed Boilers: Design and Operations , 1991 .

[21]  Li-Xin Wang,et al.  Adaptive fuzzy systems and control - design and stability analysis , 1994 .

[22]  L. A. Sanchez,et al.  Steam Temperature Fuzzy Controller in Fossil Power Plant , 1995 .

[23]  E. Kakaras,et al.  Pollutant emissions from circulating atmospheric fluidised beds burning low-grade coal , 1995 .

[24]  H. Zimmermann,et al.  Fuzzy Set Theory and Its Applications , 1993 .

[25]  B. Armstrong-Hélouvry,et al.  Fuzzy logic control-a taxonomy of demonstrated benefits , 1995, Proc. IEEE.

[26]  Prabir Basu,et al.  Heat transfer to walls of a circulating fluidized-bed furnace , 1996 .

[27]  S. G. Dukelow,et al.  The Control of Boilers , 1986 .