冷凍真空乾燥之乾燥層與乾燥率分析

冷凍真空乾燥技術廣泛使用於食品、製藥、微奈米材料等，其原理是在真空狀態下，利用低溫低壓使冰昇華之原理，使預先凍結物料中的水分不經過融化而直接以冰昇華為水蒸氣除去，獲得在外觀及品質上皆較優良之乾燥製品。一般在製藥乾燥時常使用凍晶瓶，在過程中會觀察到物料有一冰線隨著製程逐漸下降至物料底部，一般文獻中鮮少對其性質進行研究分析。本論文使用棚板式冷凍真空乾燥設備，針對重量百分濃度20%葡萄糖溶液進行冷凍乾燥製程研究，設定兩種預凍方式，冷凍櫃預凍以及棚板預凍，配合三種棚板溫度-30℃、-20℃和-10℃進行試驗，藉由CCD觀察試驗過程中物料冰線的變化，利用影像等比例放大得到乾燥層高度，並分析各情況下乾燥層高度與製程時間之關係，再測量出各乾燥層高度所對應的失水重量，進而計算出各條件下乾燥層高度與製程時間、失水比例與乾燥率之間關係。從實驗得知使用冷凍櫃預凍方式之失水比例及乾燥率皆較使用棚板預凍方式有效率，但在物料外觀及品質上，使用棚板預凍方式則明顯較為優良。設定棚板溫度愈高乾燥率愈高，但藉由觀察乾燥層高度之失水比例則與理想值距離愈遠；物料外觀上，棚板溫度愈低，物料品質愈穩定。

關鍵字

凍真空乾燥；初級乾燥；乾燥層；失水比例；乾燥率

並列摘要

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.

並列關鍵字

freeze drying ； primary drying ； dry layer ； water loss ratio ； drying rate

參考文獻

[18] 簡裕晉，“棚板式冷凍真空乾燥機設計研究”，碩士論文，國立臺北科技大學冷凍空調工程系碩士班，台北，2007。

[3] Litchfield, R.J., Liapis, A.I. “An adsorption-sublimation model for a freeze dryer”, Chemical Engineering Science 34 (9) , pp. 1085-1090, 1979.

[4] S. Rambhatla, R.Romat, C.Bhugra, M.J. Pikal, “Heat and mass transfer scale-up issues during freeze drying: II. Control and characterization of the degree of supercooling”, AAPS PharmSciTech . 5 (4) , pp. e58, 2004.

[6] C.Ratti, “Hot air and freeze-drying of high-value foods: A review”, Journal of Food Engineering 49 (4) , pp. 311-319, 2001.

[7] Alessio Carullo, Alberto Vallan, “Measurement uncertainty issues in freeze-drying processes”, Measurement: Journal of the International Measurement Confederation 45 (7) , pp. 1706-1712, 2012.

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冷凍真空乾燥之乾燥層與乾燥率分析

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