叶丝气流干燥过程中水分和丙三醇迁移特性

为了在叶丝气流干燥过程中有效调控物料的水分和丙三醇含量，考察丙三醇含量和干燥温度对叶丝中丙三醇和水分迁移的影响，利用固定床气流干燥装置，在100～145℃下对丙三醇含量为0～6.6%的叶丝进行干燥试验，得到了叶丝中丙三醇和水分释放规律。结果表明：(1)添加丙三醇后叶丝水分迁移规律基本一致，叶丝的干燥速率受丙三醇初始含量的影响较小。干燥过程分为两个阶段，第一阶段（0～100 s）和第二阶段（100～600 s）。(2)叶丝表面温度与干燥温度正相关，与丙三醇的初始含量无关。(3)丙三醇初始含量对其脱除无显著影响。第一阶段丙三醇的损失量基本相同，约占总损失量的50%以上；第二阶段不同丙三醇初始含量的损失速率无明显差异，且随着干燥时间的增加不断减小。(4)干燥温度对丙三醇脱除有显著影响。第一阶段不同干燥温度下丙三醇损失量均为0.6百分点左右，损失速率随干燥时间线性降低，损失速率的变化率与干燥温度呈负相关关系；第二阶段丙三醇损失量随干燥温度的升高而增大，损失速率基本保持稳定。

Migration characteristics of moisture and glycerol in cut tobacco strips during pneumatic drying

To regulate the moisture and glycerol contents in cut tobacco strips effectively during pneumatic drying, the effects of glycerol content and drying temperature on the migration of glycerol and moisture in cut strips were investigated. The drying experiments on cut strips with 0-6.6% glycerol were conducted on a pneumatic dryer with a fixed bed at 100-145 ℃, and the release laws of glycerol and moisture in cut strips were obtained. The results showed that: 1) The migration law of moisture in cut strips was basically unchanged after the addition of glycerol. The influence of initial glycerol content on drying rate of cut strips was minor. The drying process was divided into two stages, the first stage was from 0 to 100 s and the second stage from 100 to 600 s. 2) The surface temperature of cut strips positively correlated to the drying temperature and was independent of the initial glycerol content. 3) The initial content of glycerol had no significant effect on its removal. The loss of glycerol at the first stage accounted for more than 50% of its total loss. At the second stage, the loss rate of glycerol with different initial contents did not differed significantly and decreased with the increase of drying duration. 4) Drying temperature significantly affected glycerol removal. At the first stage, the loss of glycerol at different drying temperatures was about 0.6 percentage point and its loss rate decreased linearly with the drying time, and the change rate of the loss rate negatively correlated with drying temperature. At the second stage, the loss of glycerol increased with the rise of drying temperature, and its loss rate remained essentially constant.