Hot-air drying behavior and fragmentation characteristic of single lignite particle
Hot-air drying behavior and fragmentation characteristic of single lignite particle
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褐煤单颗粒热风干燥行为及破碎特性
DOI：
10.1016/j.fuel.2019.03.055
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发表时间：
2019-07-01
期刊：
影响因子：
7.4
通讯作者：
Pei, Zhen
中科院分区：
文献类型：
--
作者：
Gao, Mingqiang;Wan, Keji;Pei, Zhen
褐煤的干燥因其较高的经济价值而成为一个非常重要的课题。然而，干燥过程中褐煤的破碎和粉碎也是重要因素，因为它们影响干燥机的运行。本研究的目的是通过图像处理和显微 CT 扫描分析单个褐煤颗粒的干燥行为以及表面和内部裂纹的发展。结果表明，单个褐煤颗粒的干燥曲线可分为三个阶段，即快速干燥阶段（I）、过渡干燥阶段（II）和干燥平衡阶段（III）。随着干燥温度的升高，表面裂纹率增加，表面裂纹数量同时增加。当干燥温度为80℃时，裂纹率（CR）在快速干燥阶段（I）和过渡干燥阶段（II）持续增加。对于更高的干燥温度（110、140和170℃），CR在快速干燥阶段（I）持续增加，并在快速干燥阶段（I）结束时达到最大值。 CR在过渡干燥阶段（II）变化较为平稳，并在该阶段结束时略有下降。干燥初期，表面附近会出现少量裂纹。随着干燥的进行，内部裂纹的数量增加，并且裂纹向核心发展。根据本文的定义，单个褐煤颗粒的抗碎强度（CS）与干燥温度没有明显的依赖性。干燥温度可能会影响样品中的水分含量，从而影响CS。由于水分去除速度快，在高温下更容易发生碎裂。
The drying of lignite is a very significant topic due to its high economic value. However, fragmentation and pulverization of lignite during drying are also important factors because they affect the operation of the dryer. The aim of this study was to analyze the drying behavior of single lignite particle, as well as the development of both surface and internal cracks by image processing and micro-CT scanning. The results showed that the drying curve of single lignite particle can be divided into three stages, namely, a rapid drying stage (I), a transitional drying stage (II) and a drying equilibrium stage (III). The surface cracking rate increases with increasing drying temperature, and the number of surface cracks increases at the same time. Crack rate (CR) increases continuously in rapid drying stage (I) and transitional drying stage (II) when the drying temperature is 80 degrees C. For higher drying temperature (110, 140, and 170 degrees C), CR increases continuously in the rapid drying stage (I) and reaches the maximum near the end of the rapid drying stage (I). CR changes more smoothly in the transitional drying stage (II), and decreases slightly at the end of this stage. A small number of cracks appear near the surface at the beginning of drying. As the drying proceeds, the number of internal cracks increases and cracks develop towards the core. The crushing strength (CS) of single lignite particle, based on the definition in this paper, shows no clear dependence on drying temperature. The drying temperature might affect the moisture content in the sample, thus affecting the CS. Fragmentation is more likely to occur at high temperatures due to the rapid rate of water removal.