ENERGY-SAVING PNEUMATIC LIFT
S. Ya. Davydov
and I. D. Kashcheev
Translated from Novye Ogneupory, No. 5, pp. 10 – 14, May, 2011.
Original article submitted September18, 2010.
This article examines the state of a gas suspension during vertical pneumatic transport upward. A comparison
is made between pneumatic lifts with screw-type pneumatic pumps, chamber-type pneumatic pumps, and
pneumatic-chamber air-lift pumps. The material is lifted in high concentrations and at low velocities in the gas
mixture. Thus, the consumption of compressed gas is also low.
Keywords: pneumatic lift, tube, grate, swirl velocity, two-phase flow, fluidized bed.
A quantity called swirl velocity is used to account for the
aerodynamic properties of the particles in a pneumatic lift
when the parameters of the conveyor are being calculated.
The aerodynamic properties of the particles are taken into
consideration automatically when swirl velocity is deter-
mined experimentally. In formulas used to calculate swirl ve-
locity - formulas which are usually derived with the assump-
tion that the particles are spherical - the deviation of the par-
ticles from a perfect sphere and the condition of their surface
are accounted for by introducing static and dynamic shape
We will examine an ascending flow of a gas in a vertical
channel . It will be assumed that the flow is steady and
that its velocity along and across the channel are constant.
The channel is of infinite length. We introduce a solid body
(particle) into the gas flow. The body will be acted upon by
three forces: gravity, the buoyancy force, and aerodynamic
resistance. The equation of motion of the body under the in-
fluence of these forces has the form
is the mass of the body; u
are the velocities
of the gas and the particle relative to the walls of the channel;
t is time; r
are the densities of the gas and the parti-
cle; g is acceleration due to gravity; C
is the empirical drag
coefficient, which depends on the form of the body and the
Reynolds number; S
is the cross-sectional area of the parti
If the velocity of the ascending flow is high enough, the
aerodynamic resistance force (drag) will exceed the force of
gravity. As a result, the particle undergoes an acceleration
/dt > 0 and begins to rise. If the velocity of the ascending
flow is low, then the force of gravity will be greater than the
drag force. As a result, the body undergoes the acceleration
du/dt and begins to fall. After a certain time interval, the re-
sultant acting in the body decreases to zero, i.e. the body
moves downward at a constant velocity in the ascending gas
flow. Thus, depending on the velocity of the gas, a solid body
(particle) placed in a vertically ascending gas flow will rise,
fall, or remain stationary (i.e. the body swirls in the ascend-
ing gas flow). This velocity is called the swirl velocity u
The dependence of C
on the Reynolds number Re has
been established by numerous experiments for bodies of
spherical form. It has been shown that the formula
is valid for the laminar regime of gas flow
about a body, when Re £ 0.6. In the laminar region
0.6<Re£ 800, numerical values of C
should be found by
experiment. At 800 < Re £ 2·10
changes from 0.35 to
0.48 and the value 0.4 is often taken for this parameter in cal-
culations. The value of C
decreases sharply from 0.4 to 0.15
in the range Re=2·10
. Experimental values of C
for spheres were given in  for different values of Re.
To calculate swirl velocity, it is necessary to have numer-
ical values of C
. The drag coefficient depends on the
aerodynamic characteristics of the body and the velocity of
the incoming flow, i.e. the swirl velocity. The value of S
a body of irregular form depends on the body’s orientation in
the gas flow.
The function C
= f(Re) has been determined experi
mentally for a sphere. It is proposed that the following rela
Refractories and Industrial Ceramics Vol. 52, No. 3, September, 2011
1083-4877/11/05203-0165 © 2011 Springer Science+Business Media, Inc.
Ural Federal University, Ekaterinburg, Russia.