Tunnels, freezing

Fig. 2.52. Schematic comparison of two commonly used tunnel freeze drying systems for the freeze drying of food and luxury food.

FIGURE 23.15 Schematic diagram of a typical tunnel freeze dryer. 

The total capacity of a tunnel freeze dryer can be increased as the volume of business increases. Large commercial plants for processing cottage cheese and coffee have been built up in this way. 

The tunnel freeze dryers have the same advantages of plant capacity utilization that can be achieved as in multibatch plants, but the flexibility for simultaneous production of different products or in switching from one product to another is lacking. 

FIGURE 12.6 Schematic diagram of a typical tunnel freeze dryer. (From Mellor, J.D., Fundamentals of Freeze Drying, Academic Press, London, U.K., 1978.)... 

Military interest stimulated the development of biosensors for the determination of methane, ammonia, nitrogen dioxide, and sulphur dioxide. Biosensors for carbon dioxide and monoxide [33] will also find application in the civilian sector (chemical industry, mines, underground carparks, road tunnels, freezing stores and factories, chemical laboratories, etc.). 

As a general rule, any product which will be eaten without cooking, or only very brief cooking (such as green peas), should be quick-frozen in a blast-freezing tunnel or similar device. Other foodstuffs need not be frozen so quickly, and may be left in a coldroom at a suitable temperature until frozen. 

Figure 19.1 Freezing tunnel, fluidized bed (Courtesy of APV-Parafreeze Ltd)...

Figure 19.2 Freezing tunnel, belt (low fan energy) (Courtesy of S. Forbes Pearson)...

Fig. 2.9. Basic types of freeze drying chambers. A, bell jar or vertical cylinder b, rectangular or cylindrical chamber with one (or 2) door(s) c, tunnel dryer, in which the trays are transported in and out by a system (shown as a carrier on a monorail).

Fig. 2.13.1. Freeze drying tunnel plant. Upper part in front monorail of the transport system. In the tunnel transport rail for the carrier with trays. In the tunnel heated shelves in between which the carrier with trays is moved. When the carrier is position, the trays are lowereed on to the shelves by lowering the carrier (System CQC , ALD Vacuum Technologies GmbH, D-63526 Erlensee).

Basically the chamber plants described in Section 2.4 can be used for foodstuffs and other products, as described in Sections 5.1 and 5.2. Freeze drying plants for food and similar products have to handle large quantities of product. The cleaning requirements remain, but no sterilization is necessary. The product can be transported in trays as described in Section 2.2.2 and dried in cylindrical tunnels. Figure 2.52 shows the two systems most commonly used to day. Their characteristic features are ... 

Fig. 2.55. Freeze drying plant, type CQC, as shown in Fig. 2.53. In this plant, two carriers are moved in parallel through the tunnel. The photograph shows the two heated shelves systems. The sliding gate valve is located in the large extension on the left side. In this plant approx. 5000 tonnes of freeze dried coffee granulate can be produced annually (photograph ALD Vacuum Technologies GmbH, D-63526 Erlensee).

The cryocooling bath is modeled after commercial food-freezing tunnels. Key design parameters for each cryofracture train are given in Table 5-2. Projectiles... 

AREA Loading freeze dryer Room No. (Class WO) Reference sampling point Loading freeze dryer Room No. Class (100/1000) Reference sampling point Solution Room Room No. (Class 100) Reference sampling point Sterilization tunnel Room No. (Class 100) Reference sampling point ... 

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