温度和相对湿度对褐煤干燥动力学特性的影响

Effects of temperature and relative humidity on drying kinetics of lignite

为确定褐煤干燥最佳工艺参数,在恒温恒湿热风干燥实验台上进行了温度为50～90℃,相对湿度为10%～30%条件下的褐煤颗粒热风干燥实验。将实验数据与9种经验、半经验模型进行拟合,利用相关系数、方差、均方根误差3种统计学参数对不同模型进行评价。结果表明:Page模型相比其他模型更适合用于描述干燥过程中褐煤颗粒水分随时间的变化关系。对实验数据进行动力学分析,获得了不同温湿度条件下的有效水分扩散系数,并对传统Arrhenius公式进行修正,获得了温度和相对湿度对褐煤干燥特性影响的半经验公式。

Abstract： In order to identify the optimal drying conditions for Ningxia lignite, the effects of temperature and relative humidity on the drying kinetics were investigated. Drying experiments of lignite were carried out on the rig with constant temperature and relative humidity under 15 conditions involving 5 different temperatures （50°C, 60°C, 70°C, 80°C and 90°C） and 3 relative humidity values （10%, 20% and 30%） at a constant airflow. It was found that the drying rate of lignite increased markedly as the air temperature increased in the range of 50--70°C and as the relative humidity decreased from 30% to 10%. Different mathematical models were applied to simulate the lignite drying curves. Three statistical parameters including the square of the coefficient of determination, reduced chi-square and root mean square error were compared to evaluate the models. The results indicate that the Page model is better to describe the change of the water content of lignite with the drying time. The effective moisture diffusivities were determined with a diffusion model. The traditional Arrhenius-type equation, which only takes the effect of temperature into consideration, was modified to express the effect of both temperature and humidity on the effective moisture diffusivities.