Freeze Drying Adviser Basics and Applications

Freeze Drying Adviser Basics And Applications-Free PDF

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Freeze Drying Adviser,Basics and Applications, Freeze drying is the most gentle process to dry maintaining the initial shape archaeology flowers. various types of perishable materials The principle or product conditioning for further use e g fruits. of freeze drying is based on the direct transition of in yogurt. a substance from the solid to the gaseous state, called sublimation Initially the product is frozen The initial freezing process creates ice crystals. and then dried by sublimation in an environment within and on the surface of the product By. of reduced pressure The low pressure enables turning into ice the individual water molecules. direct changeover of the frozen solvent into vapor lock up into a well defined grid Figure 2 As the. In most freeze drying applications the solvent to water molecules sublimate from the product they. be removed from the product is water However leave little pores and gaps within the product and. other solvents can be used to a certain extent thus maintain its shape and structure Rehydration. such as ethanol of the product is therefore quick and simple a. particularly important feature in pharmaceutical, Freeze drying is mainly used for preservation of applications Freeze dried products can last many. delicate materials that are subject to degradation years at room temperature if they are well sealed. or decomposition Product stability is massively and protected against moisture and oxygen. increased by reducing its water content due, to the direct link between water presence and Sublimation Solid to gaseous. biological and chemical activity which are mainly Sublimation describes the direct transition. responsible for product degradation Compared to of a substance from the solid phase to the. other dehydration methods freeze drying causes gaseous phase while bypassing the liquid phase. less product damage and avoids shrinkage or completely Sublimation can only occur at low. agglomeration of the material Figure 1 Common pressure and low temperature The ideal freeze. preservation methods use high temperatures that drying conditions strongly depend on the sample. affect the shape and colour of a product as well to be freeze dried as well as on the solvent to. as its flavour smell and nutritional content Freeze be removed from the product The main solvent. drying is a very gentle process and particularly being water the three states are ice water and. suitable for heat sensitive and precious products water vapor Freeze drying is fundamentally based. Freeze drying is applied in many different areas on the phase diagram Figure 3 The phase. with various objectives such as preservation of diagram illustrates the three physical states of. product characteristics e g pharmaceuticals water as a function of pressure and temperature. Figure 1 Common preservation methods apply heat to the Figure 2 In freeze drying ice directly transitions into water. product leading to structural changes loss of colour taste vapor by sublimation allowing to maintain product structure. and smell as well as nutritional constituents e g vitamins and characteristic Freeze drying is a very gentle process. 221 bar Critical point,0 00611 bar Triple point,0 C 100 C 374 C.
Temperature, Figure 3 Phase diagram of water as a function of pressure and temperature All states coexist at the triple point Freeze drying. occurs below the triple point and requires low pressures as well as temperatures. Phase transitions occur at the lines separating the in the following section For the primary drying. different states the so called phase boundaries stage conditions for efficient sublimation need to. As shown in Figure 3 water goes through all be established At the same time it is essential to. physical states solid liquid and gaseous as long maintain product characteristics by ensuring the. as the prevalent pressure is above 6 11 mbar At product s temperature remains below a distinct. exactly 6 11 mbar the three states coexist triple temperature the so called critical temperature. point and below 6 11 mbar water occurs only as Above this temperature the product structure. ice or water vapor The product to be freeze dried collapses leading to shrinkages or cracks Ideally. is initially often a liquid Considering the phase freeze drying is performed at temperatures. diagram the freeze drying process leads via two just below the critical temperature The drying. phase changes first to the solid and further to the chamber pressure is decreased to activate the. gaseous phase red arrow For sublimation to take drying process The prevailing pressure and. place once the product is completely frozen the temperature readings are now both below the. pressure must be below the triple point as shown triple point Figure 3 point B. in Figure 3,Sublimation creates water vapor in the drying. Pressure and temperature chamber If not removed from the system the. The crucial parameters in freeze drying are water vapor equilibrates and no further ice particles. pressure and temperature Typically the freeze sublimate The vapor particles are removed by. drying process involves three stages freezing means of the ice condenser a cooling device. primary drying and secondary drying Each running at temperatures far below the critical. process step has distinctive requirements in product temperature Figure 3 point C The. terms of pressure and temperature Initially the vapor pressure resulting from the low temperature. product is frozen at a temperature low enough to of the ice condenser is therefore lower than the. guarantee it is completely frozen Figure 3 point vapor pressure of the product and naturally forces. A The freezing phase is discussed in more detail the water molecules to travel towards the ice. Freeze Drying Adviser,Basics and Applications, Figure 4 Different ways of heat transfer exist conduction a convection b and radiation c Using heated shelves heat is. directly carried over through the surface by conduction whereas ambient heat is transferred by convection and radiation. additionally Manifold application apply heat from the environment only. condenser Consequently the water vapor as well difference than combination B product at 25 C. as other condensable gases freezes on the ice ice condenser at 45 C It is therefore beneficial. collector forming ice to work as close to the triple point as possible. The rate of sublimation is basically defined by the Driving force heat. difference in vapor pressures the vapor pressure Sublimation is an endothermic process requiring. over the product on one hand and the vapor energy in the form of heat The product. pressure over the ice condenser on the other experiencing sublimation therefore gives off heat. hand Generally the larger the difference the and would eventually cool down if the required. faster the sublimation At the same time the closer heat is not supplied otherwise As learned above. the product temperature is to the triple point the higher product temperatures lead to larger. larger is the pressure difference As example pressure differences and hence to a more efficient. Figure 5 illustrates that combination A product at sublimation process The additional input of heat. 5 C ice condenser at 25 C results in a larger boosts the sublimation and represents the real. driver of freeze drying,Heat transfer methods include conduction. convection and radiation Figure 4 Direct heat,VAPOR PRESSURE mbar.
conduction is applied in shelf drying with shelf,4 heating ability Convection and radiation are. p2 A 3 important in terms of indirect heat input from the. 2 surrounding environment In manifold drying heat, p1 1 is entirely provided by ambient heat in the form. T 20 C B T 20 C,of convection and radiation In shelf drying the. 60 50 40 30 20 10 0,TEMPERATURE C,dominant transfer method is thermal conduction. however effects from convection and radiation are, Figure 5 Example of variations in sublimation speed noticeable and should be considered particularly.
for samples close to the drying chamber boundary,Main components of a freeze dryer. Drying chamber,For sample placement,e g in vials or trays. Vapor path,Water vapor migrates towards,lower vapor pressure. Control unit,Regulation of pressure,and temperature. Ice condenser,Water vapor forms ice and,aggregates at condenser.
Vacuum pump,Maintain very low,system pressure,sample to be freeze dried is either placed in a. The amount of heat added to the system system of shelves inside the drying chamber or. requires vigilant control the product temperature it is filled into single flasks that are attached to. may increase but must not exceed the critical the manifold The vacuum pump is connected. temperature The amount of heat required depends to the drying chamber via ice condenser and is. upon the product volume and arrangement as responsible for evacuation of the drying chamber. well as on the vessel used Heated shelves allow Additionally the vacuum pump acts as remover of. for precise control of the heat input with a defined all non condensable gases that did not aggregate. gradient and set temperature Manifold drying on at the ice condenser. the other hand offers little control in terms of heat. input The main task of the ice condenser is the collection. of the water vapor and all other condensable, Freeze dryer setup gases Water molecules travel naturally towards. The main components of a freeze dryer are the the ice condenser encouraged by the difference. drying chamber or specific drying attachments in vapor pressure The ice condenser temperature. the vacuum pump and the ice condenser The must be significantly lower than the frozen product. Freeze Drying Adviser,Basics and Applications,Freezing Primary Drying Secondary Drying. 80 Water content 5 10 1 5,od Product shelf,Temperature. B Pressure,er C Condenser, Figure 6 The freeze drying process includes three main stages freezing primary drying and secondary drying The initial.
water content is usually reduced to more than 95, temperature i e minimum 15 C colder The system automatically switches between the two. operating temperature of the Lyovapor L 200 of condensers after a defined time While the fresh. 55 C is therefore well suited for most applications condenser is collecting ice automated hygienic. Using organic solvents instead of water demands steam cleaning is applied to the loaded condenser. even colder temperatures to guarantee removal making it ready for further use The alternation. of the sublimated particles For this reason the concept allows for continuous operation with. Lyovapor L 300 is capable of cooling to 105 C unlimited volumes of ice avoiding down time to. Additionally an adequate control system supports defrost the ice condenser. the pressure and heat regulation Control systems, range from basic to very advanced B CHI s Process overview. Infinite Control offers unprecedented features The main steps in the freeze drying process are. far beyond just pressure and temperature control freezing primary drying and secondary drying. Figure 6 Freezing takes place in a deep freezer, Infinite Control in liquid nitrogen or using a low temperature bath. This feature allows for maximum control of the The freezing temperature should be chosen well. Lyovapor at the instrument at any connected below the critical point eutectic temperature or. work station as well as on mobile devices glass transition point of the formulation to ensure. Real time process monitoring data recording the sample gets fully frozen Figure 3 and 6. and customized reports provide maximum point A At the end of external freezing the freeze. convenience at any time The dedicated app dryer is prepared for operation by initializing the. enables remote monitoring and instant informing condenser cooling Figure 3 and 6 point C. by push notification,Once freezing is completed the samples are. Infinite Technology placed in the drying chamber or the vessels. The Lyovapor L 300 is the first dual condenser containing the samples are attached to the. freeze dryer with unlimited capacity in laboratory manifold ports The drying chamber is then. scale Two ice condensers alternately collect ice evacuated and the application specific vacuum. and defrost the accumulated ice automatically The settings are applied If heatable shelves are used. the shelf temperature will be raised leading to a endure during the freeze drying process Applying. temperature increase of the product However vacuum to an incompletely frozen eutectic mixture. the product temperature must remain below the may result in the destruction of the product as. critical temperature Figure 3 and 6 point B unfrozen components expand when placed under. The sublimation process is now activated In the vacuum. following each process step of freeze drying will, be discussed in more detail The other class of mixtures is amorphous and.
form glassy states when frozen With decreasing, Freezing temperature the formulation becomes more and. Most liquid products or formulations freeze by more viscous and eventually freezes to a vitreous. forming ice crystals Size and shape of the ice solid at the glass transition point For amorphous. crystals depend on the cooling speed and define products the critical point in terms of stability. the freeze drying ability rapid cooling results in is called collapse temperature The collapse. Freeze Drying Adviser Basics and Applications Freeze drying is the most gentle process to dry various types of perishable materials The principle of freeze drying is based on the direct transition of a substance from the solid to the gaseous state called sublimation Initially the product is frozen and then dried by sublimation in an environment

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