The Drying Chamber

It may be assumed that outlet gas composition from the coating and the dry chambers are independent of the entering gas compositions. 

The most important data during main drying is the temperature at the moving sublimation front which cannot be measured by Ths or RTDs. In 1958, Neumann and Oetjen 11.651 showed that the barometric temperature measurement (BTM) measures exactly this data. In Fig. 1.77 this is schematically shown if the drying chamber is separated from the condenser by a valve for a short time the pressure in the chamber rises to the saturation vapor pressure (ps) corresponding to the temperature of the sublimation front. ps can be converted into the ice temperature by the water vapor- temperature diagram (e. g. 0.3 mbar = -30 °C). Data for accurate conversion are given in Table 1.11 the temperatures between -100 and -1 °C. 

Transport out of the container (2) into the drying chamber produces no measurable pressure drop if the product surface is equal to the opening of the container (e. g. with trays). Vials without stoppers in the vial neck do not produce a measurable pressure drop, if e. g. 1 g/h water at a Tice of -20 °C and a pressure difference of 0.6 mbar are transported. In this example the velocity of water vapor is a few m/s. 

All these plants are of the chamber type (see Fig. 1.88 (c)) with cooled and heated shelves and a condenser which can be separated from the drying chamber by a valve. Refrigeration and vacuum systems should be laid out for temperatures and pressures which can be expected under extreme experimental conditions, even if these extreme data may not be used in the production process. Pilot plants for pharmaceutical or medical products should be laid out differently than those used for food. 

Fig. 2.48.2. Water vapor flow from the drying chamber (left) to the condenser.

In some cases all the product is conveyed from the dryer by the exhaust gases and collected outside the drying chamber. This method is liable to cause breakage of the... 

Attempts to obtain regular spherical shaped particles by spray drying were unsuccessful. Apparently, collisions of not completely solidified particles in the jet stream supplying primary droplets into the drying chamber result in their coalescence and/or distortion of shape. The perspective of obtaining microspheres with well-controlled shape, diameter, and diameter... 

VAC TRAX is different from other thermal desorption processes in that it is a vacuum dryer. By sealing the drying chamber and reducing the air pressure, a vacuum is created. The vacuum allows a much lower temperature to be used in the dryer, enabling the use of smaller, more transportable equipment. 

The drying chamber is rectangular in shape and is equipped with a door. It is vacuum- and pressure-resistant and designed for the freeze-drying process and sterilization with pure steam at an overpressure of (provide value) bar corresponding to (provide temperature in °C). 

This combination of seals makes sure that if there should ever be a leak in the hydraulic cylinder, it will not be possible for oil to penetrate into the inner area of the drying chamber. 

This system is used for heating and cooling the product shelves in the drying chamber to effect the following functions ... 

Nominal pumping speed is approximately 1 (provide value) mVh Operating data lowering of pressure in the drying chamber from (provide value) to 10 mbar approximately (provide value) minutes ... 

This system is designed to clean the freeze-drying chamber and condenser with water for injection. Spraying with WFI at an inlet temperature of (provide value) °C effects cleaning of the chamber. There are jet rods installed in the drying chamber and the pathway to the condenser. The position of these rods as well as the distribution of the spray jets provides good coverage all over the interior surfaces of the chamber with WFI. The jet rods are equipped with full cone and flat jet nozzles. 

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