Modelling, Identification and Control of a Grate Boiler

Grate boilers are widely used as active steam generation units in Finnish pulp and paper mills to control the steam network of the plant. The fuels burned on grates are typically bark and waste-wood. To ensure good stability and load following properties for grate boilers both drying and combustion processes must be well controlled. This presumes good instrumentation for the grate, special measurement and control systems for combustion power and good knowledge of the process behaviour. This paper presents the principles for modelling the grate boiler. Simulation model is developed on the basis of process experiments. The methods and devices, including a microprocessor based data collection system, for modelling and simulation are also handled. The paper further proposes a control system for supply and combustion parts of a grate boiler.