ROTARY KILN CORROSION-EROSION-RESISTANT LININGS
V. V. Slovikovskii
Translated from Novye Ogneupory, No. 4, pp. 13 – 17, April 2008.
Original article submitted October 30, 2007.
The properties of magnesia refractories are studied with the aim of determining the possibility of their use for
lining rotary kilns. Periclase-chromite refractory PKhPP has been developed with an increased Cr
whose use combined with a laying cement, operating by the principle of self-propagating high-temperature
synthesis, in a developed “slotted” single-layer lay-up of the furnace reaction zone, made it possible to
increase the lining life of industrial rotary kilns by a factor of 1.5 – 1.8.
The most worn lining of a rotary furnace is that of the
Waelz kiln due to the severe operating conditions: high tem
perature (1400 – 1500°C), corrosive charge (considerable
amount of FeÎ, Fe
, Pb, Zn, etc.), low
viscosity of the liquid melt, presence of gas-phase Pb, Zn;
there is a liquid phase in the reaction zone during furnace
operation. Therefore use of linings that operate satisfactorily
in rotary cement furnaces, as practice has shown, is
undesirable in Waelz kilns. In Waelz kilns it is necessary to
use refractory components of metallurgical grades: PKhS,
KhPT, PKhP, etc.
The lining of any Waelz kiln is the most critical part of
its construction. The duration of a campaign and the main
technical and economic indices of processing depend on
lining quality. Currently the duration of a campaign is from
one to three months, as a result of which it is necessary to
carry out partial repair using a considerable amount of
expensive refractory materials and a considerable proportion
of manual labor for highly qualified masons.
The main reasons for the short life of linings of Waelz
– corrosive wear as a result of chemical reaction of
charge reagents with refractory materials during operation;
– abrasive wear caused by the considerable amount of
charge being processed;
– breakdown of the working layer of the lining due to its
small thickness (230 mm), a small throw of articles (3 – 4
mm) as a result of which a refractory component falls from
the lining after wear of about 30 – 40%;
– wear of the heat insulating chamotte layer of a lining as
a result of its rotation with respect to the working layer and
the body of the furnace due to the small weight of the lining,
and also comparatively low mechanical strength of chamotte
– shear of refractory components due to variable thermal
loads and the considerable heating and cooling rate of the
lining, and also occurrence of the zonality of refractory com
ponents as a result of impregnation of them with molten
reagents of the charge to a depth of 150 mm. At the boundary
of the zone cracks form, parallel to the surface of the lining,
due to the different linear thermal expansion coefficients of
– formation in the reaction zone of crusts weighing up to
1500 kg as a result of impregnation of the lining with readily
melting components of the charge followed by separation of
crusts from the lining which leads to failure of the output area
of a kiln and sometimes failure of the loading pouring devices;
– use of oxygen in burner devices.
In order to increase lining life it will be necessary to
study the behavior of different highly resistant refractory
components applied to service conditions in rotary furnaces,
to develop compositions and manufacturing technology of
special refractories for Waelz kilns, and also to select diffe
rent combinations of refractories for lining and creation of
lining structures for Waelz kilns of different sizes. The pro
perties of a number of refractories were studied that are fun
damental in operating the lining of rotary kilns (see Table 1).
Analysis of the thermomechanical properties of refrac
tory materials in the range 20 – 1300°C has shown that
refractory composition, its structure and heating rate have a
marked effect on properties (Figs. 1 and 2). The elasticity
modulus of refractories based on fuzed granular material is
much higher (by a factor of 1.5 – 2) compared with this
index for sintered refractories of similar composition, and
this points to the possibility of low heat resistance during
service of refractories based on fuzed material (type PKhP
modifications PKhPP and PKhPU).
The dependence has been established of deformation for
refractories of magnesia composition on stress before and
after service in a kiln (Fig. 3). Analysis of the dependence
Refractories and Industrial Ceramics Vol. 49, No. 2, 2008
1083-4877/08/4902-0099 © 2008 Springer Science+Business Media, Inc.
GOUVPO UGTU–UPI, Russia.