Measurements on flame temperature and its 3D distribution in a 660 MWe arch-fired coal combustion furnace by visible image processing and verification by using an infrared pyrometer

Abstract

In order to verify the 3D temperature distribution of combustion in large-scale, coal-fired boiler furnaces visualized through a visible flame image processing system, a carefully calibrated portable flame temperature measuring system adopting the same flame image processing technique was developed, which is more convenient for industrial flame measurements. Furthermore, the temperatures and emissivities measured by the portable system were compared with the results by an infrared pyrometer which was used to measure the equivalent blackbody temperatures of the flames. The relative differences of the predicted temperatures and emissivity for a blackbody furnace by the portable system are less than 1% and 3%, respectively, showing a good accuracy for its application in the combustion industry. The equivalent blackbody temperatures deduced from the flame temperatures and emissivities measured by the portable system from 12 flame-observing ports in a 660 MWe arch-fired boiler in three horizontal sections at different elevations were compared with those measured by the infrared pyrometer. The relative differences are less than 7%, an acceptable agreement for measurements in the case of a coal-fired furnace. The cross-section-averaged temperatures deduced from the 3D temperature distribution acquired by the visualizing system were verified by those measured by the portable flame measuring system, and the two sets of results matched each other reasonably. This revealed that the coal combustion in the furnace was suffering from seriously delayed ignition of coal, leading to a lower efficiency of fuel utilization.