速溶茶中试冻干过程模拟研究

Simulation study of freeze-drying process in pilot-scale production of instant tea powder

中文关键词:  冷冻干燥  速溶茶  COMSOL Multiphysics  数值模拟

英文关键词:freeze drying  instant tea  COMSOL Multiphysics  numerical simulation

中文摘要:

      目的 采用数值模拟方法预测和优化冻干速溶绿茶粉的中试试验生产工艺。方法 通过有限元法建立二维传热传质相变模型, 模型模拟茶粉冻干过程中温度场、压力场、水分迁移的变化过程。结果 利用模型优化的生产工艺为: 物料铺盘厚度调整为15 mm, 采用阶段升温方法, 在升华干燥0~2.0 h、2.0~4.0 h、4.0~6.0 h、6.0~8.0 h及8.0~26.5 h共计5个时间段中, 调整环境辐射温度为0、10、30、50、60℃。按上述工艺生产所得的速溶绿茶粉的水分含量(质量分数)是(3.9±0.19)%, 各项理化指标符合国家产品标准要求。结论 该模型的预测结果与试验结果相吻合, 采用数值模拟方法可以用于预测和优化冻干速溶茶粉的中试试验生产工艺, 为今后进一步的产业化生产提供参考与借鉴。

英文摘要:

      Objective To predict and optimize the pilot-scale production process of freeze-dried instant green tea powder by numerical simulation methods. Methods A two-dimensional heat and mass transfer phase change model was established using the finite element method, which simulated the changes in temperature field, pressure field, and moisture migration during the freeze-drying process. Results The production process optimized by using the model was: The thickness of the material spread on the tray was adjusted to 15 mm, and a staged heating method was used, the environmental radiation temperature was adjusted to 0, 10, 30, 50, and 60℃, during the 5 time intervals of sublimation drying: 0?2.0 h, 2.0?4.0 h, 4.0?6.0 h, 6.0?8.0 h, and 8.0?26.5 h. The moisture content (mass fraction) of the instant green tea powder produced according to this process was (3.9±0.19)%, and all the physicochemical indicators met the national product standard requirements. Conclusion The model predictions correspond well with the experimental results. The research conclusion shows that the numerical simulation method can predict and optimize the pilot-scale production process of freeze-dried instant tea powder, which can provide a reference for further industrialization in the future.