Classification of Particles in the Submicron Range in an Impeller Wheel Air Classifier

Abstract

Kurt Leschonski

Separation Characteristics of a Deflector Wheel Classifier in Stationary Conditions and at High Loadings: New Insights by Flow Visualization

“…Since product characteristics and quality are closely related to the particle size, products with a narrow particle size distribution are desired, e.g. for color pigments and abrasive powders (Leschonski K., 1988(Leschonski K., , 1996. In contrast to classifiers with unrestricted flow such as the spiral air classifier with a free vortex, the deflector wheel classifier produces a forced vortex due to the rotating paddles; this has been stated as being less dependent on the mass loading (Leschonski K., 1988(Leschonski K., , 1996Rumpf H. and Raasch J., 1962;Rumpf H. and Leschonski K., 1967;Rumpf H. et al, 1974).…”

“…1) (Rumpf H. and Raasch J., 1962). Coarse particles are deflected on the outer edge of the deflector wheel, while fine particles follow the air flow through the deflector wheel and are separated later from the air flow by an aero-cyclone (Leschonski K., 1988(Leschonski K., , 1996Rumpf H. and Raasch J., 1962;Rumpf H. and Leschonski K., 1967;Rumpf H. et al, 1974). In the last century, Rumpf (Rumpf H. and Raasch J., 1962;Rumpf H. and Leschonski K., 1967;Rumpf H. et al, 1974), Molerus (Molerus O., 1967;Molerus O. and Hoffmann H., 1968), Sender, Schubert (Schubert H., 1968) and Husemann (Husemann K., 1998) developed separation models which describe the particle behavior and the separation efficiency of a deflector wheel classifier only on the basis of geometrical and equilibrium considerations.…”

Assessment of fractional collection efficiency in louvered inertial particle classifiers

“…The inlet velocity, V and the exit dimension Y/A r are of the same magnitude as the nozzle velocity and height reported by [18], implying that the minor flow in the louvered classifier is comparable to the flow through that impactor. The fifth line of the table examines a limestone particle with P comparable to that for the counter-flow centrifugal classifier in Leschonski [28] and Yamada et al [29], but here q o is larger and D p50 is smaller, with the inlet velocity approximately equal to the circumferential velocity reported by [28].…”

“…Specifically the Stokes number in Eq. 3is combined with the ideal gas equation of state, conservation of mass for the gas, Hering's [26] conservation of energy equation for adiabatic flow, and the geometric parameters defining the classifier, , A r , K. The slip correction C(T, P, D p ) is that of Davies [27], as also used by [15,18,28]. A mean free path in the slip correction is from [28], using the kinetic theory of an ideal gas.…”

“…3is combined with the ideal gas equation of state, conservation of mass for the gas, Hering's [26] conservation of energy equation for adiabatic flow, and the geometric parameters defining the classifier, , A r , K. The slip correction C(T, P, D p ) is that of Davies [27], as also used by [15,18,28]. A mean free path in the slip correction is from [28], using the kinetic theory of an ideal gas. If the ambient pressure and temperature (P o , T o ) and inlet mass flow  o q o are known, then the operating pressure of the classifier P, and the "cut diameter" D p50 , specify the height of the classifier inlet Y and the inlet axial gas velocity V. Geometric and hydrodynamic similitude with the experiments of [1 -3] is assured if geometric parameters and Re of the conceptual designs are limited to values consistent with those in Table I.…”