Numerical Modeling of Victorian Brown Coal Combustion in a Tangentially Fired Furnace

A computational fluid dynamics (CFD) model of a 375 MW brown-coal-fired furnace in the Latrobe Valley, Australia, has been developed using ANSYS CFX 12.0. To improve the model predictions, a coal combustion model that takes into consideration carbon monoxide reactions has been utilized in ANSYS CFX 12.0. A level of confidence in the current CFD model has been established by carrying out a mesh independence test and validation against the furnace gas exit temperature (FGET), concentration of flue gas components, total boiler heat supply, and the wall incident heat fluxes measured in the power plant. The validated CFD model is then applied to investigate the effects of several operating conditions at full load, such as different out-of-service firing groups and different combustion air distributions on the coal flame. It is found that the selection of out-of-service firing groups has a considerable effect on coal combustion in terms of high-temperature zone shape and location and distribution of incident radiation heat flux on furnace walls. Model results also indicate that redistributing and increasing the velocity of the combustion air can change the location of the high-temperature zone in the furnace, therefore reducing the peak incident heat flux on the furnace walls. A reduction in peak heat flux is likely to lead to a reduction in furnace wall slagging. This study provides a basis for further assessment of future operation of dried brown coal in the existing furnaces in the Latrobe Valley, which were designed and currently operate using raw brown coal.