Among the various drying methods used in the pharmaceutical industry, freeze drying has become the most widespread, allowing the best way to preserve the beneficial properties of the dried products. Freeze drying, also called freezing, molecular, or lyophilic, is a popular and rapidly developing technological process of the last few decades. The reason for this is the high quality of the products obtained and the indispensability of freeze drying, primarily in the pharmaceutical, food industry, biotechnology for drying thermolabile, oxidizing and expensive medecines (hormonal medecines, antibiotics, vitamins, enzyme preparations, as well as blood preparations, serums and vaccines). The powders obtained by freeze drying are very hygroscopic and easily soluble.
A significant role in improving heat and mass transfer is played by the evaporation surface and the thickness of the frozen material layer. An increase in the evaporation surface is achieved by increasing the dispersion and specific surface area of the material. This can be done by spraying and additional grinding of the frozen product, which makes it possible to obtain a product of high dispersion. According to preliminary estimates, the cost of removing 1 kg of moisture by spray drying is 6 times less than sublimation. At the same time, transportation costs are significantly lower, and the condition of the products is stable during long-term storage. However, as the study showed, the use of spray drying is possible only for microorganisms that can withstand...
Fluidized bed drying is a very effective type of drying of solids. To dry the material in a periodic mode, the wet source product is placed in batches in the receiving tank of the drying unit. There it is mixed in an ascending turbulent flow of heated gas and maintained in a suspended state. In this case, the product is dried in a process with high heat and mass transfer coefficients to the required residual humidity.
The vacuum sublimation dehydration method combines the advantages of two well—known dehydration methods - freezing and vacuum drying. During freezing, undesirable changes in the properties of the product are minimal, and during subsequent drying, frozen moisture is removed, which allows the products to be stored in appropriate packaging (for a year or more) at an unregulated ambient temperature. The energy costs of organizing the sublimation process in vacuum are 15-20 times higher than the similar costs of thermal drying.
The vacuum sublimation dehydration method combines the advantages of two well—known dehydration methods - freezing and vacuum drying. During freezing, undesirable changes in the properties of the product are minimal, and during subsequent drying, frozen moisture is removed, which allows the products to be stored in appropriate packaging (for a year or more) at an unregulated ambient temperature. The energy costs for organizing the sublimation process in vacuum are 15-20 times higher than the similar costs for thermal drying.
Atmospheric freeze drying of frozen spherical particles can also be carried out in a fluidized bed apparatus. This technology makes it possible to obtain new products consisting of smooth spherical particles with a unique porous structure that promotes their rapid dissolution, which is very important for new generation pharmaceutical products. A modified Mini-Glatt laboratory unit developed at the Institute of Pharmaceutical Technologies of the University of Moscow is presented. Basel (Switzerland) together with Glatt (Germany), for freeze drying of the material in active hydrodynamic mode. Similar equipment is presented at the International Educational and Scientific Center for the Transfer of Pharmaceutical and Biotechnologies at the D.I. Mendeleev Russian State Technical University (Moscow). The laboratory installation is a periodic device consisting of cylindrical and conical parts.
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