Computational modelling of pulverised fuel burnout in tangentially fired furnaces

Two operating furnaces are completely modelled computationally to investigate incomplete fuel burnout. Combustion parameters for a range of coals are obtained from laboratory data. The burnout predictions for seven operating conditions are found to agree very well with the test data. Unburned carbon in the ash hopper is also predicted accurately. This study validates the computational model carbon burnout predictions and shows that laboratory derived coal combustion data can be used to predict full-scale furnace performance. Carbon burnout is found to be quite sensitive to the flow distribution between burners. A cause for incomplete carbon burnout is found to be low local oxygen concentrations for some of the conditions in these tangentially fired furnaces. Particle trajectories concentrate near the furnace walls because of the cyclonic action of the swirling flow causing high local oxygen demand.