Measurement of slagging thickness on the heating surfaces of a 330 MW subcritical boiler based on mid-infrared imaging technology

Abstract

In this paper, a mid-infrared thermal imager and a Complementary Metal Oxide Semiconductor (CMOS) imaging device were employed to measure the slagging thickness on the heating surface in a 330 MW subcritical drum boiler. A way to establish the relationship between the slagging temperature and emissivity was proposed based on the Boom emissivity model and the Hadley thermal conductivity model, and then the slagging thickness was calculated by the Newtonian iterative method. In the superheater area, the average slagging thickness of the lower section was 8.6 mm, and it was 1.71 mm higher than that of the upper section. In the water-cooled wall area, the average slagging thickness of the right wall was 10.8 % larger than that of the left wall. To verify the accuracy of the calculated slagging thickness, the slagging image was measured by the direct visual probe, and the relative error was 7.69 %.