Session: Research Posters

Paper Number: 113258

113258 - In-Situ Observation on Crystallization Behaviors of Blast Furnace Slag in Variable Cooling Conditions 

Iron is one of the most important and common industrial materials. In 2019, about 1253 million tons of pig iron was produced worldwide, and China contributed 61.5% of the total output. The iron and steel making process generates plenty amounts of waste materials, such as slags. Meanwhile, massive thermal energy is transferred to the BF slag, accounting for about 10% of the energy consumption in the iron and steel making process. Different from the common phase change process, the molten BF slag has two separate final solid states; one is the glassy phase which is obtained in a fast cooling condition, the other is the crystal phase which appears a slow cooling condition. Generally, the glassy slag is usually used as cement clinker and has a high economic value. By contrast, the low value-added crystal slag is used as aggregate for road construction and landfilling purposes. At present, to pursue economic benefit water quenching with a high cooling rate is the most popular treatment of BF slag. However, this treatment undergoes many disadvantages, such as thermal energy waste, water consumption, and toxic gases (SO₂ and H₂S) emission. Up to now, centrifugal granulation is the most feasible technology to realize the multi goals of heat recovery, water saving, and pollution mitigation, owing to the compact structure, reliable operation, low power consumption, and high efficiency of heat recovery. The centrifugal granulation and heat recovery system mainly consists of a centrifugal granulation device and waste heat recovery device, and the operational process can be described as follows. The melting BF slag is granulated into small droplets with a diameter of 1-5 mm using a high-speed rotating disk/cup and cooled by air in the granulation cabin simultaneously. Then, the encrusted droplets are cooled to complete solidification in a waste heat recovery device (e.g. fluidized bed or moving bed). It's not hard to see the droplet experiences a complex cooling process in the centrifugal granulation and heat recovery system. Therefore, revealing the crystallization behaviors of BF slag in variable cooling conditions, especially the temperature rebound conditions is the premise to determine the appropriate cooling parameters which meet the multi goals. In this paper, the single hot thermocouple technique (SHTT) was adopted to in-situ explore the effect of rebounding temperature, temperature rebounding rate, and chemical composition on the incubation time, crystallization temperature region, and average growth rate of crystal phase (V_α). The results indicated that the incubation time decreased with an increase in the rebounding temperature, temperature rebounding rate, and corrected optical basicity. Moreover, the governing factor of V_α changed from nucleation growth rate to nucleation rate, resulting in a significant difference in crystallization phenomena between a continuous cooling condition and temperature rebounding condition.

Presenting Author: Bin Ding China University of Petroleum (East China)

Presenting Author Biography: Bin Ding, associate professor in the College of New Energy at China University of Petroleum (East China). He received his B. S. and Ph.D. degrees from Chongqing University in 2012 and 2018, respectively. His research interests include waste heat recovery of molten slag, active or/and passive thermal management of electronic devices, and anti-icing of outdoor equipment. He has published about 50 SCI peer-reviewed papers, which received over 600 citations and 15 H-index. In addition, he won the "Wu Zhonghua Outstanding Graduate Award" in 2018.

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