Experimental study on the ash deposit thermal conductivity for ammonium bisulfate and fly ash blend with an in situ measurement technology

Experimental investigation of the strength characteristics of low‐temperature fouling containing ammonium bisulfate in boilers

“…According to previous studies, some ABS in the flue gas will react with other compounds in ash particles to form new compounds so to change the microstructure to connect the originally discrete ash particles into a whole, while some ABS will realize this process by forming a liquid phase with strong viscosity, that is, the liquid phase will provide a liquid-bridge force to greatly enhance the strength of the ash deposition. [29][30][31]44 The enhancement of ash deposition strength by ABS may be realized from two aspects: chemical action and physical action. 14 In addition, the fouling with higher ABS content has a more compact microstructure, which may be also mean a higher deposition strength.…”

“…9,29 The deposit sample is prepared with a muffle furnace since it is difficult to collect the deposit from the boiler sample area completely and the shape of the deposit is irregular. In order to accurately control the proportion of ABS in experimental samples, and refer to the practice of previous researchers, 29,31,34,35 and also the strength of low-temperature fouling is mainly determined by the content of ABS in the deposit and the ambient temperature, 14,30 in this paper, the ABS is also directly premixed with the fly ash because we are paying attention to the effect of ABS content on low-temperature ash fouling strength. According to the previous research results, although the mass ratios of ABS to ash in the flue gas of the utility boilers is in the range of 1:50-1:200, a high ABS concentration is detected in the bottom part of low-temperature fouling due to the selective deposition of ABS-bearing fly ash, which the mass proportion of ABS in the bottom layer of fouling can be as high as about 35% and in the upper layer is about 20%.…”

“…According to the previous research results, although the mass ratios of ABS to ash in the flue gas of the utility boilers is in the range of 1:50-1:200, a high ABS concentration is detected in the bottom part of low-temperature fouling due to the selective deposition of ABS-bearing fly ash, which the mass proportion of ABS in the bottom layer of fouling can be as high as about 35% and in the upper layer is about 20%. 31,42 Therefore, three blending rates are prepared in this experiment to study the influence of ABS content on the deposition strength, ABS: ash (wt) = 1:2, 1:3, and 1:5, respectively.…”

Measuring surface temperatures of different types of fly ash samples using a CCD camera

“…Directly visible morphological features can be used to describe the status of the ash deposition, and these features can be monitored using imaging devices; however, protecting camera lenses from high temperatures and dust remains a key problem. Zhou et al [5,6] used a digital imaging system protected by cooling water and compressed air to monitor the growth of ash deposition. Additionally, surface temperature plays an important role in ash deposition [7][8][9][10].…”

“…Ash deposits also provide thermal resistance, and the surface temperatures of ash deposits increase with growth [12]. Zhou et al [6] also calculated the effective thermal conductivity, which is a key parameter in ash deposition modeling and boiler design. In the calculations, the surface temperature was measured by thermocouples using a method developed by Zheng et al [13].…”