Experimental study and mechanism analysis on low temperature corrosion of coal fired boiler heating surface

Abstract

The low temperature corrosion experiment was made to investigate the phenomena and mechanism in the process of the flue gas deep-cooling. The experiment tube was installed in the flue gas channel between the air preheater and the electrostatic precipitator in the power plant. The scanning electron microscope (SEM), energy spectrum analysis and X-ray diffraction (XRD) experiment were used to the analysis of the ash samples obtained from the outer wall of experiment tube under the different tube wall temperature. By contrasting energy spectrum figures and XRD figures among different ash samples, it has been found that the sulfuric acid corrosion occurred on the surface of the experiment tube under the temperature ranging from 65 °C to 71 °C and the corrosion was caused by SO2 and water vapor under the temperature ranging from 41 °C to 47 °C in the certain types of coal conditions. The wall temperature range was proposed which low temperature heating surface would be capable of long-term operation for the experiment unit. The analysis also showed that the ash particles would gather together under the impact of physical chemistry in the course of deep-cooling flue gas for heat recovery and efficiency gain.