A zoned heat transfer model of a large tangentially fired pulverized coal boiler

Abstract

A mechanistic model of a tangentially-fired pulverised-fuel furnace of 900 MW thermal input is described, in which a zoned method of computation predicts the temperature distribution within the chamber and the heat absorbed by the water-tube walls. The cylindrical model, comprising 45 gas and 21 surface zones, approximates the furnace, which is rectangular in cross section. The flow pattern within the chamber is assumed but the treatment of coal combustion and the complexities of radiative inter-change are rigorous within the liminations of the method. A series of simulations to demonstrate the effect of variation in gas flow pattern, boiler load and ash content in the coal is presented. These show that variation in the specific surface of the ash has a dominating influence, whereas the effect of the flow pattern is smally by comparison. Measurements taken on the actual furnace provide a check on the validity of the model. Comparisons are generally good although temperature predicted close to the furnace walls at burner level are consistently low. Investigations to improve the comparisons, and the method in general, are recommended.