Freezing installation

The freezing of a product in the vacuum chamber by the evaporation of 15-25 % of its water would reduce the process time, the investment- and the operation cost, since the evaporation of this water could be done in a very short time, and no extra freezing installations are required. Oetjen [4.4, 4.5] points out, that this process has substantial disadvantages for the quality of the product and is only applicable for a limited number of products. Therefore this process is no longer used (see Section 2.1.5). The freezing processes for food are discussed in the Sections 2.1.1 and 2.1.3, and the possible freezing rates in Section 1.1.1. The decisive quantities for the freezing rastes are ... 

Water in a hydrocarbon stream can cause plugging by increasing corrosion rates, forming hydrates, or freezing. Install and use low point drains. Draw water regularly from vessels and tanks. Automatic draws may be appropriate for some problem areas. 

It is very important that a melt-ont riser be installed whenever tank contents are expected to freeze on prolonged shutdown. The purpose is to provide a molten chimney through the ernst for relief of thermal expansion or cavitation if fluids are to be pumped ont or recirculated through an external exchanger. An external heat tracer, properly... 

It is obvious that further strengthening of brine has no effect, and can cause a different reaction—salt sometimes freezes out in the installations where concentration is too high. 

Samples may separate into two or more phases as they cool in the sample line precipitate, coagulate, and freeze. Laboratory sampling may result in nonrepresentative compositions. Heat tracing may be required and may not be installed on the nonroutine sample locations. 

Install insulation/tracing of piping to minimize solid deposition (freezing/precipitation)... 

For installations in cold climates, as well as applications in which prod-net freezing, polymerization, or crystallization is a concern, the flame arrester and piping shonld be insnlated and, and where reqnired, heat... 

It is possible to install an air filled soft tube ( balloon ) in the borehole between the two other tubes as shown in Figure 62. This elastic balloon is compressed more easily than the brine filled pipe and will therefore take the pressure from the formation of ice. The amount of water will also decrease because of the space of the balloon, which decreases the risk of freezing. 

The primary characteristic necessary for a liner, cover, or cutoff wall is low permeability, which essentially enables them to slow down the seepage or diffusion of chemicals. Clay is therefore the main material used to construct these containment systems. The thickness and chemical compatibility of containment systems are of concern in assessing the performance of a system. For example, clay liners are constructed as a simple liner that is 2 to 5 ft thick. In composite and double liners, the compacted clay layers are usually between 2 and 5 ft thick, depending on the characteristics of the underlying geology and the type of liner to be installed. Regulations specify that the clay used can only allow water to penetrate at a rate of less than 1.2 in./yr. However, the effectiveness of clay liners can be reduced by fractures induced by freeze-thaw cycles, drying out, and the presence of some chemicals. 

Artificial ground freezing involves the installation of freezing loops in the ground and a self-confined refrigeration system that pumps coolant around the freezing loop. This method is useful only as a temporary treatment approach because of the high thermal maintenance expense. 

Fig. 2.2. Automatic filling of a product to be freeze dried in vials, which are cooled by LN2. In the installation the following steps are carried out with a speed of up to 9000 vials per hour Precooling of the vials down to -180 °C, filling of the vials, shock freezing of the product, placing the stoppers on the vials (photograph Groninger Co. GmbH, D-7180 Crailsheim).

A typical grinding and sieving system (Fig. 2.5) produces dust which has to be collected. If in addition a CIP (cleaning in place) installation is installed, the total preparation equipment becomes a major part of the whole freezing and freeze drying installation. Figure 2.6 shows only the collecting container for the dust, which is sorted by size while below the container is the vibration transport system. 

Figure 2.7.1. shows the schema of a process for freezing pellets for freeze drying and Fig. 2.7.2 illustrates the details of the freezing chamber. Such installations are offered under the trade name Cryopel with throughputs between 10 and 250 kg/h. 

The leak rates of a freeze drying plant can be measured at the empty plant with the condenser cooled and the shelves heated by measuring the pressure rise per time multiplied by the installation volume in the dimension (mbar L/s). It should be noted, that the plant has to be evacuated for several hours, e. g. down to 10-2 mbar, before the pressure rise measurements, to avoid the influence of small amounts of ice and the desorption of gas from the surfaces. Furthermore, the pressure rise should be measured up to 0.2 or 0.4 mbar to detect possible gas desorption. Only if the pressure rise has been for some time proportional with time (Fig. 2.33.1), it represents a leak rate, which is defined as... 

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