Disturbance Analysis of the Fuel Feed System in Multi-Fuel Combustion

J. Mononen, I. Lerssi, and K. Leppakoski (Finland)


Fluidized bed boiler, biomass, signal analysis, filtering, cross correlation, power spectra


The fluctuations in combustion conditions in industrial multi-fuel boilers are mainly due to the variations in the fuel properties. This paper considers measurements conducted in industrial power plants where the fuel silos were equipped with discharging screws. These measurements show oscillations in the steam pressure and temperature. Tools of signal processing and analysis were used to find and analyze the sources of those disturbances. The oscillation frequency correlates with the radial cycle time of the discharging screws. In addition, it will also be discussed how an inappropriate filtering of signals in the fuel feed and airflow control can severely degrade the boiler control. Together with variations in fuel properties, these result in undesired oscillations in the steam pressure and temperature, and make it difficult to optimize the boiler efficiency and the flue gas emissions by the means of selection of the fuel mixture, or by reducing excess air.

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