Vacuum filtration batch filters

The other new technique which must be mastered to produce nitromannite is vacuum filtration. This technique is needed because nitromannite is a solid with very fine fluffy needlelike crystals. It has to be separated from its reaction mixture or recrystallization liquors by filtration. These long, fine needle crystals can only be filtered properly by having a vacuum force the flow of material through the filter. Without this, filtering the batches could take hours, and the results would be poor. This technique is very simple and can be improvised using household equipment. It too will be explained in detail when the time comes. 

Set up a 50-mm Buchner funnel for vacuum filtration using a 125-mL filter flask. Filter the mixture through a piece of Whatman 2 filter paper (4.25 cm). The filtration process may be slow. You can push the solid down a bit with a bent spatula to remove as much of the liquid as possible. Keep the filtrate, and add another 5 mL of 3 M aqueous HCl to the filtrate in the filter flask. The second addition of HCl produces more solid, but not as much as what you obtained after the first addition of HCl. Set up another vacuum filtration apparatus using your partner s 125-mL filter flask and 50-mm Buchner funnel. Refilter the mixture through a fresh piece of filter paper. Discard the solids that you collected on the filter papers. Remember you want to keep the filtrates. Combine the tivo batches of filtrates. The filtrate consists of the product dissolved in toluene and the aqueous layer. 

When constant pressure/vacuum filtrations are performed in batch filters the rate of filtration is generally a maximum at the start and then progressively decreases. A decision must be taken as to when the filter cycle should be ended. In Section 6.2.1.1, for example, the end of filtration was specified by the formation of a known mass of cake solids and the duration of subsequent phases was specified via a time or specific cake condition. An alternative way of making these decisions is to define an average filtration rate on the basis of the total cycle time. By incorporating equation (6.9) the overall production rate (F) can be written as... 

Efficient and rapid removal of solvent and antisolvent is a vital component of the successful MBPprocess. Once the precipitation has been completed (concurrently for continuous process and at the end of the solvent addition for the semi-batch process), the MBP is filtered from the suspension. This is generally performed by any of the standard filtration processes such as vacuum filtration ranging from Buchner funnel to Nutsche filter or centrifugal filter. Centrifugal filters are preferred for filtration of MBP suspension because of the particle size, the hydrogel nature of the polymer, and the effectiveness in solid/liquid separation... 

Various designs are used to achieve either a clarification of liquors, or a significant increase in solids concentration resulting in the production of a wet solid filter cake of minimal moisture content. This can be driven by either an applied pressure to the substrate over a porous filter medium (i.e. pressure filtration), or a vacuum applied behind the filter medium (vacuum filtration). The process can be on a batch basis, or via a continuous operation where, by a mechanical rotary means, new filtration areas are offered to the substrate. Chemical conditioning, including flocculation and coagulation, can be used to increase throughput, cake solids or fines capture. 

The SulFerox sulfur-cake matrix tends to be quite compressible and reportedly lends itself well to filtration via plate-and-fiame filters or automated batch filter presses with recessed membranes for post-filtration sulfur-cake squeezing. It is claimed that only small amounts of wash water are needed to displace the residual process solution from the filtercake. Rotary drum vacuum filters were used in all early SulFerox applications, but variations in feed slurry characteristics due to differing inlet gas contaminants and required additive levels made their performance inconsistent. It is repotted that filtration by pressurized-feed filter presses has eliminated the problem of cake quality variation and has substantially reduced iron chelate losses (Anon., 1994). The sulfur filtercake from pressurized-feed filter presses is reported to contain 10 to 23 wt% moisture (Allen, 1995). 

Vacuum filters are available in a variety of types, and are usually classified as either batch operated or continuous. An important distinguishing feature is the position of the filtration area with respect to gravity, ie, horizontal or non-horizontal filtering surface. 

Filtration. In many mineral processing operations, filtration follows thickening and it is used primarily to produce a soHd product that is very low in moisture. Filtration equipment can be either continuous or batch type and either constant pressure (vacuum) or constant rate. In the constant pressure type, filtration rate decreases gradually as the cake builds up, whereas in the constant rate type the pressure is increased gradually to maintain a certain filtration rate as the cake resistance builds. The size of the device is specified by the required filter surface area. 

Since most batch-type filters operate under pressure rather than vacuum, the following discussion will apply primarily to pressure filtration and the various types of pressure filters. 

Plate filters are suitable for filtration of batch fermentation broth accumulated biomass must be cleaned periodically. A rotary dram vacuum filter is used for a continuous system. 

Against this, it may be necessary with a batch vacuum filter to provide holding vessels for feed, and possibly filtrate and wash. The discharge of solids is intermittent and this may lead to complications in feeding the solids to a continuous dryer or to some other continuous process, and cake hoppers and a feeding arrangement may have to be provided. 

Finely chop the glands with a razor blade or pulverize in a blender. Extract the adrenalin into a small excess of hot H2O concentrate in a vacuum. Remove the salts and proteins (if proteins are not removed, they will give the same effect as blood poisoning from a rattle snake bite, but worse) by precipitating with alcohol and remove this precipitate by filtration. The filtrate is then distilled in vacuo to remove the adrenalin (1 would perform the filtration above, at room temp). Add a little ammonia to precipitate the active compound and filter from the water. The amount of ammonia depends on the amount of substance. To experiment, to get the proper amount, add a very little amount of ammonia to the distillate and filter off any precipitate if any forms. Add a little more ammonia and filter. Repeat until no more precipitate is formed, remember the amount of ammonia used and use this amount on the same amount of filtrate during the extraction of the next batch. 

The reactor and filter are rinsed with 186 L of isopropyl alcohol and 2.7 kg of anhydrous hydrogen chloride is added to the combined filtrate. The batch is heated to reflux for 2 hours. The temperature is adjusted to 65°C and the solution is seeded with bevantolol hydrochloride crystals. The mixture is held at this temperature with stirring until a heavy sand-like slurry is present. The mixture is allowed to cool to ambient temperature without stirring or artificial cooling. It is then cooled to 20°C. The slurry is centrifuged and the product rinsed with isopropyl alcohol until the filtrate is colorless. After being vacuum dried at 50-55°C the product is milled if necessary yield of bevantolol hydrochloride 22.7 kg (78.6%) melting point 137-138°C. 

The crystals are filtered on a Buchner funnel, some solution being constantly maintained over the crystals. A second batch of crystals is obtained by adding ethanol to the filtrate until crystallization begins. This second crop is added to the original batch of crystals. The product is washed with 95 % ethanol and dried in a vacuum desiccator. Recrystallization does not improve the purity of the product. Yield, 90%. Anal. Calcd. for Fe(HC00)2-2H20 Fe, 30.70 C, 13.19 H, 3.32. Found Fe, 30.61 C, 13.17 H, 3.50. Qualitative test for ferric ion negative. 

The filter cake is removed continuously by scraping from the vacuum filters or batch-wise after completion of the filtration with membrane filters. After removal in either system, the stearin fraction is melted for further handling and processing. 

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