Multistage devices

To illustrate the principle of an equilibrium-stage cascade, two typical countercurrent multistage devices, one for distillation and one for leaching, are described here. Other types of mass-transfer equipment are discussed in later chapters. 

Gas absorption/stripping in multistage devices having an overall countercurrent flow pattern... 

Extraction of a dilute solute between immiscible solvents in a continuous countercurrent multistage device/ cascade... 

Often solvent extraction is carried out continuously in a countercurrent multistage device/cascade. The sieve-plate tower is an example of one multistage device, whereas Figure 8.1.37(a) illustrates a multistage arrangement of N mixer-settler devices (one such device is studied in Section 6.4.1.2). First, we analyze a dilute solution of solute i in a feed-extract phase system assumed to be essentially insoluble in each other (Cussler, 1997). Then we will analyze extraction systems with some mutual solubility of the feed and the extraction solvent. 

Operation. The absolute separator is a multistage device utilizing all of the forces employed in mechanical separation—gravity, centrifugal force, inertial impaction, direct interception, and Brownian diffusion. 

Distillation. Distillation (qv) is by far the most common separation technique because of its inherent advantages. Its phase separation is clean, its equihbrium is closely approached in each stage, and its multistage countercurrent device is relatively easy to build. 

Operational Factors In industrial use, peiwaporation is a continuous-flow single-stage process. Multistage cascade devices are unusual. Peiwaporation is usually an adjunct separation, occasionally a principal one. It is used either to break an azeotrope or to concentrate a minor component. Large stand-alone uses may develop in areas... 

The quadrupole mass filter is the most abundant mass analyser today and RF-only multipoles are used as transmission devices/collision regions in various instrumental configurations. The mass filter is used extensively as a stand-alone mass analyser and as an analyser in multistage mass spectrometers. 

In some industry branches semicontinuous production occurs together with both multistage joint production (often with multiple side products per stage that have to be processed further just like the main product) and the opportunity to vary the throughputs of the production devices. 

Interstage bushings and thrust-balancing devices on multistage pumps may have the manufacturer s standard clearances, provided these clearances are stated as exceptions to this standard (see 2.6.4.2) in the proposal and are approved by the purchaser. When the manufacturer s standard clearances are based on material combinations exhibiting superior wear characteristics, supporting data shall be included in the proposal. 

The multistage in-well aerator is an inexpensive, low-maintenance device that simultaneously treats and extracts contaminated groundwater using only compressed air. Air stripping is based... 

As the potentialities of liquid extraction as a separation method were developed, the need for efficient, continuously operated, multistage equipment became apparent. It was natural therefore to turn to devices which had been so successful in other similar fluid-contacting operations, such as the bubble-tray tower and the packed tower of distillation. These devices have proved to be disappointing in liquid-extraction service, however for example, bubble-tray towers provide tray efficiencies in liquid-extraction operations of less than 5% (S7), and conventional packed towers show heights of transfer units of 10 to 20 ft. or more (T3). 

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