1070-4272/02/7511-1845$27.00C2002 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 75, No. 11, 2002, pp. 1845!1848. Translated from Zhurnal Prikladnoi Khimii, Vol. 75, No. 11,
2002, pp. 1881!1884.
Original Russian Text Copyright + 2002 by A. Levdanskii, Vil’kotskii, E. Levdanskii.
PROCESSES AND EQUIPMENT
OF CHEMICAL INDUSTRY
Multistage Mill with Flow-through Classification for Selective
Comminution of Sylvinite Ore
A. E. Levdanskii, A. I. Vil’kotskii, and E. I. Levdanskii
Belarussian State Technological University, Minsk, Belarus
Received March 14, 2002
Abstract-The process of sylvinite ore comminution in a multistage flow-through mill is analyzed. The po-
tential applications of the mill in preliminary treatment of the sylvinite ore to prepare it for flotation are
In dressing of mineral ores, comminution occupies
a prominent place. The efficiency of ore dressing is
largely determined by the extent to which the com-
ponents are accessible for agents used in dressing.
Therefore, the ore is crushed to the required grain
size, after which the valuable product is recovered.
The flotation technique, based on differences in wet-
tability between minerals, has gained the widest ac-
ceptance for recovery of components from ores.
The sylvinite ore contains three main components:
potassium chloride, sodium chloride, and halopelite.
The valuable recoverable mineral is potassium chlor-
ide, and the other two components are dumped. Halo-
pelite contains various combinations of clayey min-
erals, carbonates, sulfates, chlorides, etc.
The potassium ores from the Starobinsk deposit
contain an increased amount of halopelites, with the
majority of these found in bands. The thickness of
these bands in potassium horizons varies between
fractions of a millimeter and several centimeters. In
addition, a minor amount of halopelite is contained as
microinclusions in rock salt and potassium minerals
[1!4]. The composition of the potassium ore varies
with the bed attitude, being not constant even within a
single bed. In calculations, the following average
component contents were adopted for the beds mined
at the Starobinsk deposit (wt %): KCl 25, NaCl 69,
and halopelite 8 .
The potassium ore extracted by plough machines in
mines has lumps up to 150 mm in size, it is crushed
in impact disintegrators to grain size of 10!15 mm.
Since inclusions of potassium chloride in the sylvinite
mineral are 0.5!3 mm in size, it is necessary to crush
the ore to particle size of less than 3 mm to ensure
total recovery of potassium chloride by flotation. For
this purpose, the final comminution of the ore is done
in rod mills by the wet method. A saturated aqueous
solution of NaCl and KCl is used as liquid phase. The
grinding is done using the closed system: the material
ground in the rod mill is delivered for classification
into an arch screen, wherefrom the undersize product
is removed from the scheme, and the oversize product
is returned into the mill for additional processing. The
comminution by this scheme ensures the minimum
possible overgrinding of the ore. However, water-
insoluble impurities (halopelites) contained in the
potassium ore and mainly represented by clayey!
carbonate materials tend to swell in aqueous media
and, when treated mechanically in a mill, are dis-
persed into fractions with grain size of less than
The presence in the milled ore of a finely dispersed
clayey!carbonate sludge affects adversely the flotation
of potassium salts . This is accounted for by the
fact that minute clay particles have large surface area
onto which the flotation agents are adsorbed. The
adverse influence of the clayey!carbonate sludge on
the flotation is eliminated as follows: (1) mechanical
rubbing-away of the sludges with subsequent removal
of minute particles in hydrocyclones and hydrosepara-
tors; (2) flotation of sludges; (3) depression of sludges
with depressing reagents, which, being adsorbed onto
the surface of clayey!carbonate particles, preclude
adsorption of collectors on these particles.
The scheme with preliminary removal of the major
part of halopelite before delivering the ore into the
drum mill for final comminution is more acceptable.
It was noted in  that comminution of the sylvinite
ore entails selective size distribution of KCl and halo-
pelite: size grades larger than 3 mm are characterized