Pulverized Fuel Control using Biased Flow Measurements

This paper describes the design, implementation, and use of a pulverized fuel flow observer for a coal fired power plant. The observer is based on a state of the art pulverized fuel flow sensor, which adds transient information previously unavailable. Unfortunately, the flow measurement is subject to an uncertain and slowly changing bias, which makes it unsuitable for direct feedback control. The effect of the bias is effectively removed by combining a stochastic sensor error model with a simple coal mill model in a state observer. The designed observer is implemented on 12 coal mills at two Danish coal fired power plants, and the results show that it can be used to effectively attenuate firing disturbances, when used in a feedback control loop around the coal mills. Focus is kept on building a simple observer and control structure to accommodate easy implementation and maintenance.