Centrifugation Hydrocyclone

The degree of cell separation is an important parameter to be evaluated in perfusion systems. This can be done through the use of some concepts as cell separation efficiency, grade efficiency, and cut size. These concepts are applicable to any equipment whose performance remains constant if the operational conditions do not change. They are valid, therefore, for equipment such as sedimenting centrifuges, hydrocyclones, gravitational settlers, etc. 

A machine used to separate particles of specified size ranges. Wet classifiers include settling tanks, centrifuges, hydrocyclones, and vibrating screens. Dry classifiers, also termed air classifiers , use gravity or centrifugal settling in gas streams. 

This chapter describes the main unit operations employed for animal cell separation. These are gravity settlers, centrifuges, hydrocyclones, filters, and ultrasonic separators. 

The equipment used for dewatering includes filters and screening devices of various types, centrifuges, hydrocyclones, extrusion and expression presses, water extractors, and thickening, clarifying, and flotation hardware. The processing methods encompass a broad range of water-removal techniques. They... 

Sedimenting centrifuges Filtering centrifuges Hydrocyclones Deep-bed filters Cartridge filters Pressure vessel filters Filter presses Continuous filters Gravity separation equipment... 

Frank et al. (2008) also define systems with solids or surfactants (type 111), or high viscosity (type IVa), or low interfacial tension (IVb), or low density difference (IVc), or formation of a stable emulsion stabilized by solids/surfactants (IVd). Successful setding of type 111 systems that have solids or surfactants present may be possible if solids are removed first by filtration and surfactants by adsorption (see Chapter 181. After the feed and solvent are pretreated, the shaker test should be repeated. Type IV systems probably require a different phase separation system, such as coalescers, centrifuges, hydrocyclones, ultrafiltration or electrotreatment and pretreatment may also be necessary. 

Prethickening of filter feeds can be done with a variety of equipment such as gravity thickeners, hydrocyclones, or sedimenting centrifuges. Even cake filters can be designed to limit or completely eliminate cake formation and therefore act as thickening filters and be used in this thickening duty. 

Time is a critical variable because the magnetite settles if the mixture is held too long in a static condition. Use of hydrocyclones makes possible the separation in a fraction of a minute (21). These devices impart centrifugal force to the system, thereby permitting a separation to be made at a specific gravity less than that required in static, heavy-Hquid separations. 

Centrifuges. Sohd-bowl centrifuges have been proposed as an alternative classifying device to hydrocyclones for cut sizes below 10 pm. The results appear to be mixed (21). In one apphcation, where the cut size was 6.5 pm and the sharpness index 0.7, there was essentially no apparent bypass. However, in other apphcations operating at higher feed concentrations, the cut size ranged from 5—8 pm, but the sharpness index was between 0.3—0.5 and the apparent bypass between 10—30% or higher (22). Smaller cut sizes have also been reported (23). 

In 1981, a novel flotation device known as the air-sparged hydrocyclone, shown in Figure 3, was developed (16). In this equipment, a thin film and swid flotation is accompHshed in a centrifugal field, where air sparges through a porous wall. Because of the enhanced hydrodynamic condition, separation of fine hydrophobic particles can be readily accompHshed. Also, retention times can be reduced to a matter of seconds. Thus, this device provides up to 200 times the throughput of conventional flotation cells at similar yields and product quaHties. 

Cyclones, hydrocyclones and centrifuges utilize centrifugal force to separate material of differing... 

The capacity of filtration centrifuges is very dependent on the solids concentration in the feed. For example, at 10 per cent feed slurry concentration 9 kg of liquid will be centrifuged for every 1 kg of solids separated whereas with a 50 per cent solids concentration the quantity will be less than 1 kg. For dilute slurries it is well worth considering using some form of pre-concentration such as gravity sedimentation or a hydrocyclone. 

Hydrocyclones are used for solid-liquid separations as well as for solids classification, and liquid-liquid separation. It is a centrifugal device with a stationary wall, the centrifugal force being generated by the liquid motion. The operating principle is basically the same as that... 

Hydrocyclones. Particle separation in hydrocyclones uses the centrifugal force as the means of separation. The slurry, consisting of clean soil and contaminated particles, is separated... 

Settling to remove solids from aqueous effluent can be enhanced by the use of centrifugal forces in hydrocyclones. Their design was discussed in Chapter 8. For solids removal, the solids are driven toward the wall of the hydrocyclone and removed from the base. Centrifugation can also be used for solids removal, but restricted to smaller volumes. Solids removal by centrifugation can typically be in the range 50 to 80%, increasing to typically 80 to 95% with chemical addition. 

Centrifugal forces can also be exploited in hydrocyclones. As discussed in Chapter 8, designs are different for the removal of solids and dispersed oil. In contrast to solids... 

Centrifugal force can also be used to separate solid particles from fluids by inducing the fluid to undergo a rotating or spiraling flow pattern in a stationary vessel (e.g., a cyclone) that has no moving parts. Cyclones are widely used to remove small particles from gas streams ( aerocyclones ) and suspended solids from liquid streams ( hydrocyclones ). 

Centrifuges, 22 288. See also Hydrocyclones basket, 11 389-390, 391 filtration equipment, 5 542-548 fixed-bed, 11 389-391 materials of construction and operational stress, 5 522-524 moving-bed, 11 391-392 noise, 5 524-525... 

Solids. Treatment of mustard agents by the SILVER II process results in the precipitation of silver chloride, which, if not removed, could cause cell plugging. This precipitate is removed from the main circuit in a slurry underflow from hydrocyclones in the anolyte feed stream circuit. Subsequently, this slurry is dewatered in a centrifuge to approximately 50 weight percent AgCl, with the remainder of the slurry consisting of water, nitric acid, silver nitrate, and trace amounts of other materials in the anolyte loop. 

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