Chamber Production Plants

Both installations have full-size doors which are opened during loading and unloading. The loading of 50 000 or 100 000 vials takes some time, and the shelves should therefore be at room temperature to avoid condensation of ice from the humidity of the atmosphere. 

The condensers are directly flanged to the chambers and have an ice capacity of 500 kg each (photograph AMSCO Finn-Aqua, D-50354 Hurth). 

If the loading of vials has to be done on cold shelves, a smaller loading door as shown in Fig. 2.50 and 2.51.1 should be built in to reduce the amount of air diffusing into the chamber. In addition, a small overpressure of sterile air or N2 in the chamber reduces the condensation of ice. If N2 is used, the 02 content near the loading door should be monitored. 

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The process data from manifold installations can hardly be transferred to chamber-type plants. This applies, practically, also to the process transfer from belljar-type installations to chamber plants. Results obtained in laboratory plants of the chamber type must be analyzed carefully, if they are be transferred to another plant. If the product, the layer thickness of the product and the vials or trays are identical, the following conditions should be observed and compared ... 

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 two adsorbent chambers contain the zeolitic adsorbent, the liquid xylenes and p-diethylbenzene desorbent. Proper loading of the adsorbent into the large diameter vessels in industrial production plants is of critical importance to maximize adsorbent mass in the fixed vessel volume and not generate low and high density areas within the adsorbent bed. Density inconsistencies could adversely affect liquid flow distribution and thereby have a detrimental effect on the performance of the process. Adsorbent loading methods are a matter of proprietary know how of the technology licensors. However, Seko has published a paper on the practical matters involved in an actual problem case [20]. 

In a production plant the valve beween the chamber and condenser could have a diameter of 1 m or more, and it cannot be closed in 1 s or less. However, the method can be applied with some changes in the software The movement of the valve is controlled for its reproducibility and accuracy and the pressure rise is used for the cal-clation of 71 after the valve has reached a certain position. Table 1.12.2 shows such measurements for a valve with adiameter of 1.1 m. 

The lead-chamber process is more economical than the contact process, but it produces a more dilute and less pure product. Thus, the chamber process can compete only in the market that can use a relatively impure and dilute acid. Although chamber-acid plants now in use will undoubtedly be operated for many years to come, it seems probable that all sulfuric acid plants constructed in the future will employ the contact process or some still more efficient process. 

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... 

The vacuum pumping system in a freeze-drying production plant consists of several pumps in series. It has three functions (1) to evacuate chamber and condenser in an acceptable time (10-20 min) to the operation pressure and (2) pump out the gas dissolved in the product at a pressure, which has to be small compared with... 

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. 

Commercially, the burner chamber and the absorber cooler sections are combined as a single unit for small-scale production. However, in large capacity plants, these units are separated. A typical commercial unit is schematically described in Figure 5 (32). 

Because the highest possible interfacial area is desired for the heterogeneous reaction mixture, advances have also been made in the techniques used for mixing the two reaction phases. Several jet impingement reactors have been developed that are especially suited for nitration reactions (14). The process boosts reaction rates and yields. It also reduces the formation of by-products such as mono-, di-, and trinitrophenol by 50%. First Chemical (Pascagoula, Mississippi) uses this process at its plant. Another technique is to atomize the reactant layers by pressure injection through an orifice nozzle into a reaction chamber (15). The technique uses pressures of typically 0.21—0.93 MPa (30—135 psi) and consistendy produces droplets less than 1 p.m in size. The process is economical to build and operate, is safe, and leads to a substantially pure product. 

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