Gao Mingqiang, Xiao Yawen, Miao Zhenyong, Pel Leo, Wan Keji, He Qiongqiong, Xue Shuwen
School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, Jiangsu, China.
National Engineering Research Center of Coal Preparation and Purification, China University of Mining and Technology, Xuzhou 221116, Jiangsu, China.
ACS Omega. 2021 Jul 16;6(29):18702-18710. doi: 10.1021/acsomega.1c01519. eCollection 2021 Jul 27.
The research on moisture transfer characteristics and surface crack development of a single lignite particle (SLP) driven by humidity difference is helpful to achieve a better understanding of the fragmentation characteristics of lignite during the moisture transfer process. This is of great significance to the safe operation of a drying system. The characteristics of moisture transfer within SLP driven by humidity difference were studied in different stages. Six drying equations commonly used in the literature were selected to describe the moisture transfer behavior. The apparent diffusion coefficient ( ) of moisture in each stage was calculated to compare the driving forces of moisture transfer in different stages. The surface crack rate (CR) was used to quantitatively analyze the fragmentation characteristics of SLP caused by moisture transfer. The results showed that the moisture transfer process of SLP driven by humidity difference can be divided into three stages, and stage I is the main moisture removal stage. The larger the particle size, the longer the stage I, while less moisture is removed in this stage. A logarithmic drying equation best simulates the moisture transfer process of SLP. The larger the particle size, the larger the value in each stage. The driving force of moisture transfer in stage I is the largest, which is the opposite of a thermal drying process. CR for SLP has experienced a rapid increase - stable at the highest value - rapid decrease - stable during the moisture transfer process driven by the humidity difference.
研究湿度差驱动下单颗褐煤颗粒（SLP）的水分传递特性及表面裂纹发展情况，有助于更好地理解褐煤在水分传递过程中的破碎特性。这对干燥系统的安全运行具有重要意义。研究了不同阶段湿度差驱动下SLP内部的水分传递特性。选取了文献中常用的六个干燥方程来描述水分传递行为。计算了各阶段水分的表观扩散系数（ ），以比较不同阶段水分传递的驱动力。采用表面裂纹率（CR）对湿度差驱动水分传递导致的SLP破碎特性进行定量分析。结果表明，湿度差驱动下SLP的水分传递过程可分为三个阶段，其中阶段I是主要的水分去除阶段。粒径越大，阶段I持续时间越长，但该阶段去除的水分越少。对数干燥方程能最好地模拟SLP的水分传递过程。粒径越大，各阶段的 值越大。阶段I的水分传递驱动力最大，这与热干燥过程相反。在湿度差驱动的水分传递过程中，SLP的CR经历了快速增加 - 在最高值稳定 - 快速下降 - 稳定的过程。
