Separation processes centrifuges

Centrifugal filtration. In this second type of centrifugal separation process, centrifugal filtration occurs which is similar to ordinary filtration where a bed or cake of solids builds up on a screen, but centrifugal force is used to cause the flow instead of a pressure difference. 

The main impurity of the filtrate is the iron(II) sulfate which can be crystallized as the heptahydrate, FeS04-7H2 O, by cooling the solution to a temperature below 15°C. This process is most often carried out in vacuum crystallizers. The crystals of iron sulfate are separated by centrifugation or filtration (qv). To prevent premature hydrolysis of titanium dioxide, the temperature of the above processes should not exceed 70°C. 

Natural menthol is obtained by freezing the essential oU, eg, Mentha arvensis and the menthol crystals ate separated by centrifuging the supernatant hquid away from the crystals. The supernatant oU is then caUed dementholized cornmint oU. Impurities in the crystals come from the essential oU and usuaUy give a slight peppermint aroma to the crystallized menthol. The cornmint oU, rich in (—)-menthone (- 28%) and (—)-menthol (- 32%), can be further processed to give additional natural menthol. 

Reversible Processes. Distillation is an example of a theoretically reversible separation process. In fractional distillation, heat is introduced at the bottom stiUpot to produce the column upflow in the form of vapor which is then condensed and turned back down as Hquid reflux or column downflow. This system is fed at some intermediate point, and product and waste are withdrawn at the ends. Except for losses through the column wall, etc, the heat energy spent at the bottom vaporizer can be recovered at the top condenser, but at a lower temperature. Ideally, the energy input of such a process is dependent only on the properties of feed, product, and waste. Among the diffusion separation methods discussed herein, the centrifuge process (pressure diffusion) constitutes a theoretically reversible separation process. 

Differences in mobilities of ions, molecules, or particles in an electric field can be exploited to perform useful separations. Primary emphasis is placed on electrophoresis and dielec trophoresis. Analogous separation processes involving magnetic and centrifugal force fields are widely apphed in the process industiy (see Secs. 18 and 19). 

Centrifuging of Test material for impact/shock sensitivity and unstable material, thermal hazards shock sensitive, alternate (low energy) separation process for material could shock sensitive/unstable material result in decomposition. CCPS G-13... 

Cyclone collectors are popularly used both for particle removal and for particle sampling (Fig. 13.1). The separation process of a cyclone relies on the centrifugal accelerations that are produced when particle-laden fluid experi-... 

Centrifugation is a well-established liquid-solid separation process popular in commercial and municipal waste treatment facilities. It is usually used to reduce slurry and sludge volumes and to increase the solids concentration in these waste streams. It is a technically and economically competitive process and is commonly used on waste sludges produced from water pollution control systems and on biological sludges produced in industry and municipal treatment facilities. 

In a typical batch suspension process (Figure 12-5), styrene is suspended in water by agitation and use of a stabilizer. The polymer forms beads. The bead/water slurry is separated by centrifugation, dried, and blended with additives. 

Separation processes are based on some difference in the properties of the substances to be separated and may operate kinetically, as in settling and centrifugation, or by establishing an equilibrium, as in absorption and extraction. Typical separation processes are shown in Table 6.1. Better separations follow from higher selectivity or higher rates of transport or transformation. The economics of separation hinges on the required purity of the separated substance or on the extent to which an unwanted impurity must be removed (Figure 6.13). 

HSCCC is attracting attention based on its high separation scale, 100% recovery of sample, and mild operating conditions. It is a chromatographic separation process based on the partition coefficients of different analytes in two immiscible solvent systems (mobile phase and stationary phase) subjected to a centrifugal acceleration field. 

Downstream purification and isolation of proteins and biomolecules is often the most expensive and challenging aspect of their production [91]. Many of the downstream separation processes used by industry today, e.g., ultraliltration, chromatography, and centrifugation, are slow, inherently batch, nonspecific, expensive, overconsume energy, and generate wastes, particularly for downstream product purification, an important cate-... 

Instant tea produced as described above will dissolve completely in hot water but not in cold water, as the caffeine-polyphenol complexes are insoluble under those conditions. Since virtually all instant tea manufacture in the U.S. is for iced tea preparation, process modification is required. This initial extract may be cooled to 5 to 10°C and the cold water insoluble material or cream be allowed to precipitate. Under these conditions, 20 to 35% of the extract solids may be separated by centrifugation. The supernatant solids will reconstitute in cold water after concentration and drying.105 It is also possible to process the cream to make a portion of it compatible with the product and thereby retain the caffeine and some polyphenolic components that are present in this fraction.106 Commercial use of the enzyme Tannase, which removes gallic acid from gallated tea polyphenols107 and reduces cream formation108 can be used to reduce cream losses and manufacture instant teas retaining more of the natural polyphenol content. 

In the Ruthner process,1 the WPL is first concentrated in an evaporator. The concentrate is then pumped to a reactor where it is combined with hydrochloric acid gas, in which ferrous chloride and sulfuric acid are formed. The sulfuric acid is then separated by centrifuging. The ferrous chloride... 

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