Cyclone design factor

The collection efficiency of cyclones varies as a function of particle size and cyclone design. Cyclone efficiency generally increases with (1) particle size and/or density, (2) inlet duct velocity, (3) cyclone body length, (4) number of gas revolutions in the cyclone, (5) ratio of cyclone body diameter to gas exit diameter, (6) dust loading, and (7) smoothness of the cyclone inner wall. Cyclone efficiency will decrease with increases in (1) gas viscosity, (2) body diameter, (3) gas exit diameter, (4) gas inlet duct area, and (5) gas density. A common factor contributing to decreased control efficiencies in cyclones is leakage of air into the dust outlet (EPA, 1998). 

The mechanism of interaction between catalyst and gas in a large fluidized bed is complex and is not well correlated with design factors. In the bed itself, large bubbles of a foot or more in diameter form and are irrigated with a rain of catalyst particles. This process occurs in parallel with a well-mixed fluidized bed. Above the bed level and before the entrained catalyst is recovered in cyclones, the reaction continues in dilute phase plug flow. Since even the physical behavior of fluidized beds is not well understood, the design of such... 

Zenz [13] has shown that the velocity given by the latter differs from the former by a factor of 2 to 2.5. Kalen and Zenz [14] have applied the saltation concept to cyclone design by assuming ... 

Varying operating conditions change dust-collection efficiency only by a small amount. The primary design factor that controls collection efficiency is cyclone diameter. A small-diameter unit operating at a fixed pressure drop... 

Obviously this model has some restrictions in its range of applications. As the model stands, it is only suitable for cyclones with slot inlet and a low loading. This is because the effect of the dust on the wall on the friction factors is not reliably quantified as the authors state. If the effect of the solids is to be accounted for, the friction factors at the different walls are likely to differ. Another restriction is that it is only applicable to the conventional cylinder-on-cone cyclone design, and therefore not to cylindrical swirl tubes. 

A number of attempts to relate the geometric design parameters of a cyclone to the pressure drop have led to various empirical formulas for the loss factor Cf. One of the simplest formulas is an expression proposed by Sheperd and Lapple ... 

Six-tenths factor, 47 Yearly cost indices, 47 Critical flow, safety-relief, 438 Back pressure, 440 Sonic flow, 438 Critical flow, see Sonic Cyclone separators, 259-269 Design, 260-265 Efficiency chart, 263 Hydroclones, 265-267 Pressure drop, 263, 264 Scrubber, 269 Webre design, 265 Deflagration venting nomographs,... 

An alternative method of using the scaling factor, that does not require redrawing the performance curve, is used in Example 10.4. The cyclone should be designed to give an inlet velocity of between 9 and 27 m/s (30 to 90 ft/s) the optimum inlet velocity has been found to be 15 m/s (50 ft/s). 

Three different spray chamber designs (Fig. 3.6) are most often used for ICP-MS the Scott [15] (double-barrel) chamber, a conical chamber with an impact bead, and a cyclonic chamber [14,16,17]. The cyclonic spray chamber typically provides a slightly (up to about a factor of 2 or 3) higher analyte transport efficiency as well as somewhat shorter washout times. In some cases the spray chamber is cooled (such as on the HP 4500 ICP-MS double-pass spray chamber, which is cooled to 4°C) to reduce the amount of water vapor that enters the ICP further so that signals from polyatomic ions containing oxygen are reduced. The cooled spray chamber also helps maintain a stable spray chamber temperature. 

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