Vacuum process filters

Sterile Filtration of Gases. Primary appHcations for sterile gas filtration are the sterilization of fermentor inlet air, fermentor vent gas, vents on water for injection tanks, and vacuum break filters during lyophilization. Operational and process considerations apply. Typically, the membrane in gas... 

The main features in which the Radford process differs from the batch operation are in thermal dehydration and compounding. Water-wet nitrocellulose on a continuous vacuum belt filter is vacuum-dried followed by hot air transfusion (80°C) to reduce the moisture to less than 2%. After cooling, alcohol is sprayed on the nitrocellulose to a concentration of 15—20%. The alcohol-wet nitrocellulose is then transferred from a surge feeder to a compounder by a continuous weigh-belt along with the other ingredients of the composition, which are also weighed and added automatically. 

One of the oldest filters applied throughout the chemical processing industry is the rotary vacuum drum filter, which is illustrated in Figure 8. This machine belongs to the group of bottom feed configurations. Rotary drum filters are typically operated in the countercurrent mode of operation. The principle advantage of these machines is the continuity of their operation. 

Processes are classified by their rate of cake buildup in a laboratory vacuum leaf filter rapid, 0.1-10.0 cm/sec medium, 0.1-10.0cm/min slow, 0.1-lO.Ocm/hr. 

Filtration is a unit operation commonly employed nowadays in biotechnological processes. In this unit operation, a filter medium acts as a physical barrier to particles larger than its pores. Traditional filtration devices such as filter presses and rotary vacuum drum filters have so far found no application for the separation of animal cells. Nevertheless, membrane filters are commonly employed, as well as some alternative filter designs such as spin-filters. In the next sections, the most common types of filters used for animal cell separation will be discussed. 

Filter the white precipitate using a Buchner filtration apparatus and discard the precipitate. Concentrate the remaining clear solution to approximately 50 mL using a rotary evaporator. Precipitate the product from the concentrate by drop-wise addition into the vortex walls of rapidly stirred cold diethyl ether (250 mL). Filter the white precipitate from the solvent using a Buchner filtration apparatus. Dissolve the precipitate in toluene (50 mL) and repeat the precipitation process. Filter the white precipitate again and dry under vacuum to remove all traces of solvent. The final product should be stored under dry nitrogen in the dark. Yields >90% are usual. 

The selection depends to a great extent on the rate of growth of the cake. This rate has a major effect on the following choices batch versus continuous process pressure or vacuum gravity filters and separation technique (filters, centrifuges, etc.). Table 22.8 (features of slurry), Table 22.9 (selection of filters), and Table 22.10 (comparison of separation processes) aid in this effort. 

The use of vacuum to filter liquids and to distill materials at more reasonable temperatures is central to many of the processes in this book. With the great importance assumed by a reliable source of vacuum for these operations, it would well serve any explosive manufacturer to become familiar with convenient sources of vacuum, and the hidden problems they pose. 

Solvent Fractionation—is the most efficient fractionation process. Crystallization is performed in the presence of a solvent, usually acetone, at a ratio of between 3 and 5 to 1 (solvent to oil). Separation is usually performed on a vacuum belt filter. The high separation efficiency and the purity and yield of the solid fraction are the main advantages of solvent fractionation. The high investment and operating costs prevented the adoption of this process for commodity products such as margarines and shortenings. 

The crystallization processes used to produce p-xylene are generally carried out in two stages. The feedstock material is first dried to a residual water content of around 10 ppm, to avoid the formation of ice, then cooled to around -55 to -70 °C, and separated from the mother liquor in centrifuges or rotating vacuum drum filters. The mother liquor from the first stage is transferred to an isomerization unit. The crystallizate of the first stage with a p-xylene content of around 90% is melted, then cooled again and separated from the mother liquor. The purity of the produced p-xylene surpasses 99%. 

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