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This paper describes some problems concerning control of small-scale biomass boilers. A commercially available boiler equipped with additional instrumentation has been used as an experimental platform for research purposes. In the paper are discussed grate sweeping effects on fluctuations in boiler operation that have been weakened by algorithm alternations. Another problem discussed in the paper is transient states generation during on/off control of the boiler heat output. These states cause decrease in overall efficiency of the boiler and they can be also source of increased emissions of gaseous pollutants in the flue gas. As a solution the on/off algorithm has been replaced by continuous linear controller that is able to control the transient states in a desired manner.

This paper reports on an attempt to achieve maximum efficiency and lowest possible emissions for a small-scale biomass boiler. This aim can be attained only by changing the control algorithm of the boiler, and in this way not raising the acquisition costs for the boiler. This paper describes the experimental facility, the problems that arose while establishing the facility, and how we have dealt with them. The focus is on discontinuities arising after periodic grate sweeping, and on finding the parameters of the PID control loops. Alongside these methods, which need a lambda probe signal for proper functionality, we inroduce another method, which is able to intercept the optimal combustion working point without the need to use a lambda sensor.