Dong Ziwen, Yu Wenhui, Jia Tinggui, Guo Shengli, Geng Weile, Peng Bin
School of Materials and Chemical Engineering/School of Safety Engineering, Ningbo University of Technology, Ningbo, Zhejiang 315211, China.
Institute of Mining and Coal, Inner Mongolia University of Science & Technology, Baotou, Inner Mongolia 014010, China.
ACS Omega. 2021 Jul 22;6(30):19409-19418. doi: 10.1021/acsomega.1c01031. eCollection 2021 Aug 3.
Significant volume shrinkage and drying cracking of high-water-content lignite will occur during low-temperature drying. To determine the variation behaviors of the drying shrinkage rate and desiccation crack surface width in the process of low-temperature drying, low-temperature and low-humidity drying experiments were conducted, and the variations of the surface widths of the desiccation crack with time and water content of old lignite were examined. The results showed that the slow drying of lignite at low temperatures caused significant volume shrinkage and desiccation crack formation, and the occurrence and development of desiccation cracks were highly nonuniform. Three stages of the variation of surface widths of the desiccation cracks were observed with the water content decrease: an initial rapid increase stage, a second slow decrease stage, and a final stable stage, and the average width of the desiccation cracks increased in a Gaussian function. The higher the evaporation rate and volume drying shrinkage rate, the lower the surface width of the desiccation cracks under low-temperature drying conditions. To achieve safe and green mining, storage, transportation, processing, and utilization of lignite, the moisture content of old lignite should be controlled to be above 13-15%.
高含水量褐煤在低温干燥过程中会出现显著的体积收缩和干燥开裂现象。为了确定低温干燥过程中干燥收缩率和干裂表面宽度的变化行为，进行了低温低湿干燥实验，并研究了老褐煤干裂表面宽度随时间和含水量的变化情况。结果表明，褐煤在低温下缓慢干燥会导致显著的体积收缩和干裂形成，且干裂的发生和发展极不均匀。随着含水量降低，观察到干裂表面宽度变化的三个阶段：初始快速增加阶段、第二缓慢减少阶段和最终稳定阶段，且干裂的平均宽度呈高斯函数增加。在低温干燥条件下，蒸发速率和体积干燥收缩率越高，干裂的表面宽度越低。为实现褐煤的安全绿色开采、储存、运输、加工和利用，老褐煤的含水量应控制在13 - 15%以上。
