Fuel-quality soft sensor using the dynamic superheater model for control strategy improvement of the BioPower 5 CHP plant

This paper presents an enhanced method for estimating fuel quality in a BioGrate combustion process and the method’s use in control strategy improvement. This method is based on a dynamic model that makes use of combustion power estimates – which can be calculated based on the furnaces oxygen consumption – and that makes use of a nonlinear dynamic model of the secondary superheater. The paper focuses to estimate the most essential combustion parameters: fuel moisture and fuel flow. The time delay for detecting a change in fuel moisture and fuel flow is small enough for the method to be used for controlling both air and fuel feed, preventing any steam and pressure oscillations. The proposed control strategy is compared with the method currently used in the BioPower 5 CHP plant. Finally, the results are analyzed and discussed.

► The fuel quality soft-sensor utilizes combustion power dynamic model of the secondary superheater.
► The fuel quality soft-sensor is a promising feasible and effective way to measure changing fuel quality.
► The enhanced control strategy efficiently stabilizes the combustion process.