Vane classifiers

Fig. 7. Vane classifier where ( ) represents particle flow (a) side view and (b) cross-sectional view showing the vanes.

The Mikro-ACM pulverizer is a pin mill with the feed being carried through the rotating pins and recycled through an attached vane classifier. The classifier rotor is separately driven through a speed control which may be adjusted independently of the pin-rotor speed. Oversize particles are carried downward by the internal circulating airstream and are returned to the pin rotor for further reduction. The... 

Axial fans are classified as propeller, tube-axial, and vane-axial (Fig. 9). The choice of fan requited is determined by the resistance (static pressure) the fan must work against as well as the volume flow requited. PtopeUet fans usually discharge iato a plenum or directly iato the atmosphere. Tube-axial fans are usually mounted ia ducts as ia an air conditioning system. Vane-axial fans are also mounted ia ducts but feature a stationary guide vane on the discharge side that straightens the air flow to improve efficiency. Tube-axial fans can work at static pressures up to 623 Pa (2.5 ia. H2O) vane-axial fans can work up to 2000 Pa (8 ia. H2O). 

There are several mechanical air classifiers designed to operate in the superfine 10- to 90- Im range. Two of these are the Mikroplex spiral air classifier MP T Hosokawa Micron Powder Systems Div.) and the classifier which is an intregal part of the Hurricane pulverizer-classifier ABB Raymond Div, Combustion Engineering Inc.) described under Hammer Mills. Others are the Majac classifier Hosokawa Micron Powder Systems Div.), the Sturtevant Superfine Air Separator, and the Bradley RMC classifier. These also use a vaned rotor, but operate at higher speed with higher power input and lower throughput. 

Volume 1 explains that pumps ean be classified as either positive-displacement or kinetie. The same is true for compressors. In a positive displacement compressor the gas is transported from low pressure to high pressure in a device that reduces its volume and thus inereases its pressure. The most common type of positive displacement eompressors are reeiprocating and rotary (serew or vane) just as was the ease for pumps. Kinetic compressors impart a veloeity head to the gas, which is then converted to a pressure head in accordance with Bernoulli s Law as the gas is slowed down to the velocity in the discharge line. Just as was the case with pumps, centrifugal compressors are the only form of kinetic compressor commonly used. 

In much the same manner as pumps, compressors are classified as one of two general classes positive displacement or dynamic (see Figure 3-68) [23]. These two general classes of compressors are the same as that for pumps. The positive displacement class of compressors is an intermittent flow device, which is usually a reciprocating piston compressor or a rotary compressor (e.g., sliding vane, screws, etc.). The dynamic class of compressor is a continuous flow device, which is usually an axial-flow or centrifugal compressor (or mix of the two). 

The development of positive displacement downhole motors began in the late 1950s. The initial development was the result of a United States patent filed by W. Clark in 1957. This downhole motor was based on the original work of a French engineer, Rene Monineau, and is classified as a helimotor. The motor is actuated by drilling mud pumped from the surface. There are two other types of positive displacement motors that have been used, or are at present in use today the vane motor and the reciprocating motor. However, by far the most widely used positive displacement motor is the helimotor [79,83]. 

Rotary compressors are classified into three general groups sliding vane, helical lobe, and liquid-seal ring. 

This type of compressor is classified as a constant volume, variable-pressure machine that is quite similar to the vane-type rotary in general characteristics. Both have a built-in compression ratio. 

Fluid motors are usually classified according to the type of internal element which is directly actuated by the pressurized flow. The most common types of elements are gears, vanes and pistons. All three of these types are... 

Impingement separators, 246, 257 Chevron style, 248, 255 Efficiencies, 246 Knitted wire mesh, 246 York-vane efficiencies, 248 Inertial centrifugal separators, 266, 268 Kinetic energy, pump system, 187 Lamella plate classifiers, 239 Line sizing work sheet, 107... 

The composition of protein and starch fractions produced from pin milling and air classification are related to a number of variables variability in composition of field pea cultivars, number of passes through pin mill and air classifier, vane settings and protein content of peas, and seed moisture (5,9,23,31). 

Rotary compressors are generally classified as of the straight-lobe type, screw type, sliding-vane type, and liquid-piston type. 

Two main types of these classifiers are known, distinguished by method of creating air rotation. In vortex classifiers the air is rotated by stationary vanes (or tangential pipes) in rotor classifiers this is done by rotating blades. The latter devices may have open or closed aerodynamic cycle. 

Circulating air classifiers are widely used, mainly in cement industry. One type of such devices produced by Sturte-vant [22] (Fig. 5c) consists of two coaxial exterior and interior vessels. Particles entering the device from the top onto the plate are scattered within the interior vessel by a rotating plate. There they rotate and move to periphery. The fan creates a circulating air flow that rises within the interior vessel and descends within the intermediate space between the two. The air stream returns into the inner vessel through the vanes. Coarse particles fall down in the inner vessel be-... 

Fig. 5.4 Simplified schematic diagram of the Bahco microparticle classifier showing its major components I, electric motor 2, threaded spindle 3, symmetrical disc 4, sifting chamber 5, container 6, housing 7, top edge 8, radial vanes 9, feed point 10, feed hole 11, rotor 12, rotary duct 13, feed slot 14, fanwheel outlet 15, grading member 16, throttle.

Because of the particle-wall and particle-classifier impacts, one drawback of this type of mill is the potential for buildup of compressed product in the mill or on the classifier. This can affect milled particle size by changing the open volume in the mill or open area in the classifier, especially if classifier vanes or gas nozzles become plugged or blocked. Buildup at the exit of the mill or in the classifier typically results in a gradual increase in the average-milled particle size over time owing to reduced classification efficiency. Specifically,... 

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