Achieving optimal operating conditions in PI controlled biomass-fired boilers: Undemanding way for improvement of small-scale boiler effectiveness

Design of control circuits with standard PI(D) controllers is mostly focused on achieving the best control quality. Assessment of the control quality is usually based on control responses. The responses showing the smallest deviation from the desired value for the shortest time are considered to be those of the best control quality. Seldom any attention is paid to the operating conditions under which the controlled device operates after the desired value of the controlled variable is achieved. However, for the combustion processes especially, temperature of the heated medium and exactness of its keeping is the only viewpoint of a good function of a boiler. Fuel consumption, efficiency at all, harmful emissions are very important aspects even for small-scale boilers. A simple and cheap solution is proposed in the paper aimed at small-scale biomass boilers because we have had such boiler equipped for experiments at disposal and we have used data obtained from the device for testing practicability of the proposed solution.