An Analysis of the Dry Layer and Drying Rate of Vacuum Freeze-drying

• Main Authors: Jia-Ren Liu, 劉嘉仁
• Other Authors: Hung-Pin Cheng
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/26jqxa

碩士 === 國立臺北科技大學 === 能源與冷凍空調工程系碩士班 === 101 === Vacuum freeze-drying technology is widely used in the production of food, pharmaceuticals, and micro-nano-materials. The principle is that in a vacuum state, due to the ice sublimation caused by low temperature and pressure, the moisture previously froze in the material can be removed in the form of water vapor in sublimation without melting, so that dried products of good appearance and quality can be obtained. Crystal bottle is often used in pharmaceutical freeze-drying. In the process, a line of ice of the material can be observed to gradually decrease to the bottom of the material under processing. Few studies have analyzed the nature of the line of ice. By using the shed plate freeze-drying equipment, this study examined the freeze-drying process of the glucose solution of weight percentage concentration of 20%. In settings of two pre-freezing methods including the pre-freezing by freezer and the pre-freezing by shed plate, and shed plate temperatures at -30℃, -20℃ and -10℃, this experiment used CCD to test and observe the changes in the line of ice of the material during the testing process. By enlargement of scaling of the images, the dry layer heights were obtained, and the relationship between dry layer heights and processing time was analyzed. The water loss weights corresponding to the dray layer heights were measured. The relationship between dry layer height and processing time, as well as the relationship between water loss ratio and drying rate, as calculated. The experimental results indicated that pre-freezing by freezer is more efficient than pre-freezing by shed plate in terms of water loss ratio and drying rate. However, the pre-freezing by shed plate is apparently better in terms of material appearance and quality. When the shed plate temperature and drying rate are greater, the water loss ratio is further away from the ideal values. Regarding material appearance, when the shed plate temperature is lower, the material quality is more stable.