本平台为互联网非涉密平台,严禁处理、传输国家秘密或工作秘密

烟草干燥动力学特性及水分预测模型研究

Drying kinetic characteristics and moisture release prediction model for tobacco redrying

  • 摘要: 为深入了解干燥过程中烟丝内部水分变化规律,对烟丝干燥机理、干燥动力学参数影响因素、水分预测模型及现有滚筒干燥数值模拟研究方法进行梳理总结。结果表明,烟丝干燥过程包括预热干燥、恒速干燥和降速干燥3个阶段,干燥速率、有效水分扩散系数和表观活化能是描述烟丝内部水分迁移和扩散情况的3个干燥动力学参数。实验室规模下烟丝干燥时的有效水分扩散系数集中在1.35×10-11~7.72×10-10 m2/s,活化能大小为12.57~38.64 kJ/mol;干燥动力学参数值大小主要受烟丝物理特性和干燥条件影响,其中物理特性包括孔隙率、厚度、品种、部位和产地等,同时干燥条件作为外部因素也会显著影响烟丝水分扩散速率;烟草水分预测模型主要包括薄层干燥模型和反应工程(REA)模型2种,其中薄层干燥模型应用最为广泛,然而目前仍缺乏一个通用性的烟丝干燥过程水分预测模型;现有数值模拟工作中主要对滚筒干燥内部温湿度分布规律以及筒内烟丝滞留时间和混合情况进行研究。

     

    Abstract: To gain a deeper understanding of the moisture changes in tobacco leaves during the drying process, tobacco drying mechanisms, the influencing factors of drying kinetic parameters, moisture prediction models and existing numerical simulation methods for roller drying were summarized and reviewed. The results showed that: 1) The tobacco drying process includs three stages: preheating drying, constant-speed drying and speed-down drying. Drying rate, effective moisture diffusion coefficient and apparent activation energy are three drying kinetics parameters that describe the migration and diffusion of internal moisture in cut tobacco. The effective moisture diffusion coefficients during lab-scale tobacco drying are in the range of 1.35×10-11 to 7.72×10-10 m2/s and the activation energies are between 12.57 and 38.64 kJ/mol. The parameters of tobacco drying kinetics are mainly affected by the physical properties of cut tobacco and drying conditions. The physical properties include the porosity, thickness, variety, stalk position and origin, while the drying conditions significantly influence the moisture diffusion rate in cut tobacco as external factors. Thin layer drying model and reaction engineering approach (REA) model are the two main moisture prediction models for tobacco, and the thin layer drying model is the most widely utilized. However, there is a lack of a universal moisture prediction model for the drying process for cut tobacco. Existing numerical simulation studies mainly focus on the internal temperature and humidity distribution patterns of roller drying process and the retention time and degree of mixing for cut tobacco within the roller.

     

/

返回文章
返回