A thermofluid network based methodology for integrated system simulation of heat transfer and combustion in a coal-fired furnace

Abstract

Coal-fired power plant boilers are made up of several complex and interdependent subsystems that all need to work together properly to ensure plant availability, efficiency and safety, while limiting emissions to the environment. Having a process model where the relevant subsystems are coupled, and the interdependencies can be ascertained, is therefore invaluable. Such an integrated model may be based on a one-dimensional thermofluid network approach to model the water to steam cycle and the coal and air to flue gas cycle. If quick solution times are required, for instance in model based on-line process condition monitoring, such an integrated model cannot capture the same level of detail that would typically be available in a three-dimensional CFD model. However, even in a reduced model a three-dimensional approach may be required, for instance when modelling the thermal radiation heat transfer in the furnace. This paper proposes a network based methodology which combines the zonal method to model the radiation heat transfer in three dimensions with a one-dimensional burnout model for the heat generation, and characteristic flow maps for the mass transfer. The methodology was applied to the single burner furnace of the IFRF’s experimental facility at Ijmuiden in the Netherlands, for which extensive empirical data is available. The new model was used to predict the radial temperature profile near the furnace exit and the heat absorbed through the walls, as well as the temperature, carbon burnout, oxygen and carbon dioxide profile along the centerline of the furnace. To better understand the benefits and limitations associated with the specific combination of models implemented here, a CFD model was also developed and used for comparison. The results obtained with the new model compare well with the CFD benchmark, as well as the experimental results. This provides confidence that the combination of models applied here can be used to model the integrated behavior in the single burner furnace and forms the basis for expansion to utility scale boilers.