Intelligent instrumentation of solid fuel power plants

Large variations in moisture content and heat value of fuels (peat, bark, coal) can cause stability problems in combustion. Some computer-based methods to improve the measurement and control of solid fuel boilers have been developed. A microprocessor-based four-beam infrared moisture measurement system has been developed, which has advantages compared with ordinary two-beam sensors. The paper also presents a digital measuring station for estimating the fuel power of the plant. Furthermore, flame monitors might give a false "flame-off" indication even if the fuel is still burning. The system developed herein estimates the changes of the combustion process by comparing the amount of flue gases generated in the process with the fuel and air feed. By adding this information to the signals obtained from the flame monitoring system, the existence of the flame can be verified. Finally, load level and combustion conditions in industrial power plants vary continuously, and when solid fuels are used, the optimal excess air in the flue gas does not stay constant. We have developed and tested a method for minimizing the losses of the boiler.