Behavior of Fouling Deposits Formed on a Probe with Different Surface Temperatures

Zhun Dong (ZD) coal, which is characterized by high sodium levels, was burned in a pilot-scale furnace to investigate the behavior of fouling deposits on an oil-cooled probe with different surface temperatures. In this study, the fouling deposits were collected at 1298 K furnace temperature. In addition, the inlet temperatures of the conduction oil were set as 543, 493, and 443 K, which were comparable to the feedwater temperature in the coal-fired boiler economizer. The surface temperatures of the deposition probe varied in the ranges of 733-594, 714-571, and 671-507 K. A digital imaging technique was used to monitor variations in deposit thickness and deposit morphology over time for the three cases. The results revealed that the probe surface temperature had a significant effect on the growth, mineralogy, and microstructure of the fouling deposit. The stable thicknesses of the three fouling deposits fluctuated in the ranges of 9.63-9.82, 12.48-12.54, and 15.31-15.53 mm in the 543, 493, and 443 K cases, respectively. In addition, a low probe surface temperature resulted in the absence of significant sintering in the fouling deposit for the 443 K case.