Systematic freeze-drying Fundamentals, process management, and applications

Systematic freeze-drying Fundamentals, process management, and applications

4.1 Overview 10 4.2 Freezing 12 4.3 Primary drying and final drying  16 5 5.1 Warm up / Cool down  22 5.2 Shell freezing and spin freezing  22 5.3 Achievable vacuum levels  23 5.4 Determining end of drying / PAT  24 6 Process management summary  28 Application examples

While food products such as instant coffee make up the largest application by volume for freeze-drying, biotech and pharma products such as vaccines require machines and equipment that meet the highest quality 1 Introduction Freeze-drying, or lyophilisation, is the most gentle method for drying materials. The underlying physical phenomenon of sublimation refers to the direct transition from a solid to a vapor state, bypassing the liquid state. The frozen product is thus dried under vacuum without thawing out. The method has a wide range of potential applications: • Maintaining product characteristics...

Laboratory freeze-drying systems • Ice condenser capacity from 2 to 24 kg • Air-cooled chilling systems • Wide range of accessories for a variety of applications • Typically for drying pre-frozen products Pilot freeze-drying systems • • • • Ice condenser capacity from 4 to 16 kg air or water cooled refrigeration systems Freezing and drying in the drying chamber on liquid-cooled shelves Insulator integration is possible Production freeze-drying systems • • • • • • Ice condenser capacity from 20 to 500 kg Water-cooled chilling systems Freezing and drying in the drying chamber on liquid-cooled shelves...

The historic use of freeze-drying under atmospheric conditions – by Eskimos, for example – is a legend. In fact, this is a conventional "series circuit" of melting and evaporation processes. The latter occurs so rapidly that no visible liquid phase is formed. The principle of sublimation is explained below using the phase diagram for water. In practice, the process is nearly always used for aqueous systems, but in recent years the popularity of freeze-drying special solvent/water mixtures has increased. Krit. Punkt In a phase diagram of a pure material, the three states of vapor, liquid, and...

The units of measure typically used for conversion are:

A freeze-dryer or lyophilisator consists essentially of the receiver product chamber), the separator for water vapor, ( (ice condensor), and a pump evacuation device (vacuum pump). There is a wide variety of technical solutions derived from this concept. 3 System structure The basic components of a freeze-drying system are: Extensive accessories can be added to the basic components, such as: Vacuum drying chamber Vacuum pump for evacuating air from the drying chamber (gas pump) and regulating the drying vacuum with a pressure control valve Ice condensor with temperatures from –55 °C to –105 °C...

For both lab systems and commercial production freeze-drying systems, a distinction is made between single and dual chamber systems. The principle is presented here at the laboratory scale: As shown in Figure 3.2, in the single chamber system, freezing and subsequent drying of the product are performed in the ice condenser chamber. The sample is frozen due to the low temperature of the ice condenser (–55 °C or –105 °C). The interior can be chilled down to about –20 °C or –40 °C. A significant improvement in cold transfer from the ice condenser to the sample can be achieved with the use of a fan...

separately in a deep-freeze unit in the lab area (dual chamber method) 4.1 Freeze-drying process flow sequence As a rule, freezing takes place at atmospheric pressure, similar Before the various process steps for freeze-drying are described in detail, this section is intended to provide an overview of the process flow sequence. to a conventional freezer. Drying the product in round-bottom flasks or closeable wide-mouth filters is popular and has the advantage of being Prior to loading a new product, the freeze-drying system must be dry and any residual water from the previous run must be removed...

Figure 4.2 shows a process graph for a ceramic suspension. Due Optional final drying involves lowering the vacuum to the to its freezing point near 0 °C and uncomplicated product most severe, lowest possible value in conjunction with properties, it can be freeze-dried using a fairly rough vacuum increased shelf temperature. These two measures improve of 1 mbar, with a high energy input (shelf temperature +40 °C). desorption. For this desorption step, other thermodynamic The product temperature probes in the suspension (yellow, principles apply than those in the actual sublimation. green, blue...

PROZESSF Process Theeutectic point refers to the point at which a homogeneous mixed phase transitions directly from the liquid to the solid state, so that no crystalline mixture consisting of different phases is produced. In contrast, amorphous substances are characterized by a lack of any crystal boundaries, similar to a supercooled melt, such The freezing phase defines the microstructure of the solidified as window glass. Heating up such a solidified solution also solution and thus also that of the product to be dried. Two does not cause abrupt melting, but rather causes the softened fundamentally...

Ultrapure water Ultrapasteurized milk Skim milk Glucose bouillon Malt extract bouillon 10 Freezing point -21.6 °C Vacuum per vapor pressure curve 0.884 mbar Suggested drying vacuum 0.538 mbar Yeast solution Intersection with asymptote -96.9% Litmus solution Recorded duration Product tempera- For a flatter rise of the LyoRx value during solidification, to be on the safe side, the value for product temperature determined from this illustration Figure 4.5 Graphic construction for determining the freezing point: should be Figure 4.4 Solidification point (SP) of various culture considered to be the...