Freeze chamber-condenser valve

Figure 29 Scheme of a water vapor condenser of a freeze-drying plant. A, diameter of opening between chamber and condenser B, cylindrical area, when valve is open C area between condenser wall and valve plate D, valve plate, valve drive E, condenser coils F, refrigerant inlet and outlet G, pipe to VPS H, water outlet p pressure in the chamber, condenser. (AMSCO Finn-Aqua GmbH, D-50354 Hiirth, Germany.)... 

In the plant, this separation is accomplished with an isolation valve that separates the ice condenser from the drying chamber this valve is also able to permit (a) the pressure rise test at the end of the freeze drying cycle, (b) the simultaneous discharging and loading of the product and condenser defrosting, and (c) the reduction of cross-contamination between batches to a minimum. All the internal parts of the freeze dryer are of stainless steel type AISI 304L or 316L with a finished surface of 300 mesh or more. In the modern plants, the internal sterilization of the... 

Fig. 2.10. Freeze drying plant of the type in Fig. 2.9 (a). 1600 cm2 temperature-controlled shelf area stoppering device for vials on four shelves, valve between chamber and condenser, for BTM and DR-measure-ments, freezing is possible between the condenser coils or in the shelves if they are cooled and heated by brine from a thermostat, Tco down to -55 °C (LYOVAC GT 2, AMSCO Finn-Aqua, D-50354 Hurth). 

Fig. 2.49.2. Schema of a freeze drying production plant with approx. 20 m2 shelf area. The chamber and condenser are in the same vacuum chamber, separated by a wall in which the valve is built, providing the shortest possible path for the water vapor. The condenser and the brine heat exchanger are cooled by LN2. The condenser surface is made from plates (Fig. 2.49.3), its temperature can be controlled between -110 °C and -60 °C. The shelves can be controlled by the circulated brine between -70 °C and +50 °C. The trays with product can be automatically loaded and unloaded from a trolley. The shelves can be pressed together in one block and the trays are loaded to the shelves by pushing one shelf after another in front of the trolley.

The merit of Malinin s work is the comparative study of water content of bones by reproducible methods. The measurement of water vapor pressure during the drying cannot be used dirctly to determine the RM, as Malinin correctly states. Measurement of the description rates (DR) provide a means to follow quantitatively the course of desorption drying. The method is described in Section 1.2.2, but cannot be applied in an installation used by Malinin because the condenser cannot be separated from the chamber by a valve. By using the data given in the paper of Malinin it is possible to estimate the freeze drying process of bone transplants as follows ... 

Fig. 1.86. Scheme for the estimation of the water vapor transport in a freeze-drying plant. 1, Frozen product 2, vial or the end of a shelf 3, open surface (FI) for the water vapor flow between 2 and 4 4, chamber wall 5, valve with an open area F2 6, condenser chamber 7, cooling and condensing surface in the con-... 

Typical laboratory plants can be used for different purposes if equipped accordingly. One example is shown in Figure 28. In this unit, small product quantities can be freeze-dried in ampules, vials, or trays, and also flasks can be connected to it. The laboratory plant as shown in Figure 29 is equipped for multiple purposes Shelves can be cooled down to -35°C for freezing the product. A valve is installed between chamber and condenser. Thus it is possible to measure the sublimation surface temperature by BTM, to determine the end of main drying and to control secondary drying. The pressure can be controlled, the temperature of the shelves or the product can be recorded, and vials can be closed with stoppers. 

In pilot freeze-drying plants the connection between the chamber and the condenser has usually a diameter large enough for the transport of the water vapor. In large production plants this diameter has to be estimated. Theoretically the maximum flow density (g/h cm2) is achieved if the following conditions are met The diameter of the connection d has to be large, compared with its length /, / J, a smooth outlet from the chamber and a smooth inlet into the condenser with no obstacles in the connection (e.g., no valve plate) and s This flow density... 

Figure 34 Freeze-drying plant condenser and shelves cooled with LN2. Clean-in-place system in chamber and condenser. 1, LN2 inlet to condenser and heat exchanger 2, N2 outlet from the condenser and heat exchanger 3, heat exchanger for the brine in shelves 4, brine to and from shelves 5, pressure plate for stoppering of vials 6, piston rod with bellows 7, hydraulic piston for 5 and 6 8, hydraulically operated valve 9, hydraulic system 10 and 13, water and steam inlet 11, pumping system 12, water outlet. (AMSCO Finn-Aqua GmbH, D-50354 Hiirth, Germany.)...

Figure 1 Schematic of a typical industrial freeze-drying plant, showing the chamber and the adjoining condenser, which can be separated by a valve each unit is served by its own refrigerationjheating plant. Adapted from M. J. Pikal (unpublished work)...

By far the largest number of the industrial freeze dryers in operation is of the vacuum batch type with freeze drying of the product in trays. There are two main types, depending on the type of condenser used. In the first type, the condenser plates are alongside the tray-heater assembly and in the same chamber in the second type the condenser is in a separate chamber joined to the first by a wide, in general, butterfly valve. This latter type of plant is always used in pharmaceutical industries, but it can also be used for the freeze drying of foods. Because of the wide variety and complexity of the... 

FIGURE 45.19 Continuous vibrogravitational freeze dryer for liquid and pastes (1) vacuum granulator (2) material feed (3) condenser (4) vacuum pump (5) feeding valve (6) drying chamber (7) radiators and (8) vibrating trays. (From Novikov, P.A. et al., Continuous freeze-dryer for liquid materials, Russian Patent No. 273,734, 1970.)... 

The laboratory freeze-drying plant did not have automatic BTM and DR measurements. The hydraulic valve between the chamber and condenser was closed and opened manually. The time of closure was measured by a stop watch. The pressure rises were recorded on a high-speed printer, and Tice extrapolated from the pressure plot at the change of slope. The pressure was measured by a capacitive gauge. The relationship between Pc, T h, and Tice is only viable for the laboratory plant (lab plant) it will be different for the pilot plant and most likely also for the production plant. 

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