Batch cleaning systems process time

For continuous processes, the lowest possible system dead volume will enable the operation with low average holding times. This may be important in some applications, especially those involving bacteria-laden liquids. Low system dead volume is also desirable for batch or continuous processes to minimize the volumes of cleaning solutions required during a cleaning cycle. 

Table 1 shows that the maximum ethanol concentration in this test was 67.7 g/1, in the outlet of the third reactor, for a flow rate of 8.1 ml/h. In this condition, the TRS and glucose concentrations were 3.3 and 0.8 g/1, respectively. The system is stable for all flow rates. The lowest flow rate, 8.1 ml/h, was more difficult to control, which was what led to some more pronounced oscillation of the variable values in this condition. It was expected in the continuous run that similar results than the ones obtained in the batch run will be achieved. As in batch operation, the cycle time is considerably longer than the reaction time, if the continuous process had reached a similar performance than the one obtained with the batch run in the continuous operation, we could save cycle time (times to clean, to fill ant to empty the reactor). Therefore, from the industrial point of view, the continuous process would lead to higher productivities. 

Reaction times can be as short as 10 minutes in a continuous flow reactor (1). In a typical batch cycle, the slurry is heated to the reaction temperature and held for up to 24 hours, although hold times can be less than an hour for many processes. After reaction is complete, the material is cooled, either by batch cooling or by pumping the product slurry through a double-pipe heat exchanger. Once the temperature is reduced below approximately 100°C, the slurry can be released through a pressure letdown system to ambient pressure. The product is then recovered by filtration (qv). A series of wash steps may be required to remove any salts that are formed as by-products. The clean filter cake is then dried in a tray or tunnel dryer or reslurried with water and spray dried. 

Obviously, GMP requirements, especially extensive personnel training, calibration, qualification and validation, enhanced documentation, extensive cleaning and sanitation, and sharpened in-process control must considerably influence process organization and output. All these GMP-related activities are costly and time consuming, and will result in decreased productivity and increased production costs. On the other hand, a quality assurance system contributes to consistent production with a lower number of rejected batches and complaints. 

The sequence of process steps shown in Fig. 4 produces three batches of spent resin (a total of about 4 L) and introduces about 50 kg of LiCl into the liquid waste system. The initial product recovery steps require about two weeks of operating time, and the clean rework recovery requires another 2 weeks. 

The use of trays during lyophilization is less common, nevertheless, ring trays with removable bottoms are sometimes used to transfer vials to/from the lyophilizer. Where trays are used, they must be cleaned and sterilized prior to each batch. Large lyophilization facilities will sometimes use an automated loading/unloading system in which all shelves or a shelf at a time are processed. Regardless of the practice, ISO 5 conditions are required for all areas of the facility in which partially stoppered containers are transferred or handled. As previously mentioned, it may be possible in some operations to transfer containers in a manner that they are not exposed to the environment during transfer. 

In summary, the problems associated with this system were related to the fact that supercritical fluids had been used previously for batch extraction processes and there had been no significant development to this time of supercritical fluid extractors for the specific application of precision cleaning. These problems were exacerbated by an unwillingness of the vendors to discuss many of the problems they had already encountered and solved, based on proprietary process concerns. 

The drawbacks depend on the system scale. The reactor has to be loaded, unloaded, and cleaned, sometimes resulting in longer time than the reaction itself. The batch reactor requires less labor, however, requires special care to avoid contamination. Batch reactors are utilized in pharmaceutical industry, fine chemicals, natural products, and processes little known. 

Another parameter affecting the treatment efficiency in PMRs is the operational mode (Table 6.3).TTie PMRs can work either in batch or continuous modes. Sometimes, semi-batch systems are also applied. In batch mode, the feed tank is filled with the treated solution at the beginning of the process and no refilling of the tank before the end of the operation is done. The permeate is collected in a permeate tank and the retentate (concentrate) is recycled back to the feed tank. At the end of the batch process, a small volume of concentrate remains in the feed tank. Then the system is drained, the membranes can be cleaned if necessary, and the tank is refilled with a new batch. A modification of the batch mode is the semi-batch system. In this case the feed tank is refilled with fresh feed solution as the permeate is removed, in order to keep a constant volume in the feed tank. After a defined time, or once a predetermined concentration or flux is reached, the supply of fresh feed is stopped and the remaining solution in the tank is concentrated, as in batch mode. In continuous mode the feed solution is continuously supplied to the feed... 

Enclosed vapor degreasers from each firm operate continuously, repeating cycles of some cleaning processes (Chapter 2.19), but parts must be loaded and unloaded in batches. As shown in Figures 2.25 and 2.26, two or more work chambers may be used with the same solvent processing facilities and control system to have one work chamber implementing a cleaning process at all times. 

Chemical cleaning sequences are often contained in conveyorized spray equipment with rinsing between each step. Batch processing in a tank system is also used, with a hoist for basket movement between solutions. Uniformity of the etching of panels within a basket must be measured, but is generally quite good and reproducible as long as the immersion time is short and the bath s chemical composition is consistent. 

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