1070-4272/05/7812-1970 + 2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 12, 2005, pp. 1970!1976. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 12, 2005,
Original Russian Text Copyright C 2005 by Mil’chenko, Domanskii, Vorob’ev-Desyatovskii.
PROCESSES AND EQUIPMENT
OF CHEMICAL INDUSTRY
Design of Large-Volume Agitators
for Polydisperse Suspensions
A. I. Mil’chenko, I. V. Domanskii, and N. V. Vorob’ev-Desyatovskii
St. Petersburg State Technological Institute, St. Petersburg, Russia
POLIMETALL INZhINIRING (Polymetal Engineering) Private Company, St. Petersburg, Russia
Received July 7, 2005
Abstract-Specific features of designing of large-volume agitators for mechanical agitation of concentrated
polydisperse suspensions are considered. Mathematical models and results of model experiments are applied
to obtain calculational relations that can be use to determine technical parameters of industrial agitators.
The designing procedure is confirmed by the experience of industrial use of agitators with a capacity of up
to 1000 m
Processes of mechanical agitation in fluid3solid
and fluid3solid3gas systems are widely employed in
chemical and mining-and-smelting industries. As ex-
amples of processes of this kind can serve leaching-
out of gold and silver from ores with sodium cyanide
and of sodium aluminate from bauxites with an alkali,
biooxidation of sulfide ores, manufacture of extraction
phosphoric acid in sulfuric acid treatment of apatite,
and many others. It should be noted that many pro-
cesses are not only large-tonnage, but also require
a long time (up to 4 days). All these factors make
necessary development of cascaded agitators or chains
of agitators working in the rotary mode. The capacity
of single agitators in such cascades or chains has
reached a value of 5000 m
. A specific feature of
agitators of this kind is also that the solid phase is
Fig. 1. Integral dispersion composition of the ore (1) before
and (2) after leaching. (d) Particle diameter.
a polydisperse medium (Fig. 1), whose particle size,
as a rule, does not exceed 200 mm, and the agitation
process is performed at a nearly zero excess pressure
in the agitators.
Designing of such unconventional large-volume
agitators meets certain difficulties, which have been
insufficiently discussed in the special literature .
The influence exerted by centrifugal forces on
the distribution of the solid phase along the agitators
radius in agitation of finely dispersed suspensions is
insignificant. Therefore, it is advisable to use for
this purpose low-energy-intensive smooth-walled agi-
tators. The scheme of the agitators we recommend,
with account of the minimum expenditure for its
fabrication and use, is shown in Fig. 2. This is an ap-
Fig. 2. Design of a large-volume agitators.