REFRACTORIES IN HEAT UNITS
WEAR OF BASIC REFRACTORIES IN THE LINING
OF WAELZ KILNS IN THE PRODUCTION OF ZINC
L. A. Kazanbaev,
P. A. Kozlov,
A. V. Kolesnikov,
and D. A. Ivakin
Translated from Novye Ogneupory, No. 3, pp. 19 – 21, March, 2003.
Operating conditions of the refractory lining for Waeltz kilns in the production of zinc are considered. Results
of an examination of post-service periclase-spinellide refractories for the Waelz kiln lining are given and ma
jor factors involved in the wear and failure of refractory materials are discussed.
The refractory lining of rotary Waelz kilns for use in zinc
and lead fuming technologies operates under heavy-duty
conditions and is subjected to mechanical (abrasive) and
chemical factors associated with the rotation of the kiln and
the movement of materials loaded in it.
In the kiln, as the charged material is moving in it, the
following zones and processes associated therewith can be
identified: (i) drying, (ii) sulfate decomposition, (iii) reac-
tive, and (iv) clinker formation. The first zone (drying zone)
10 – 15 m in length is lined with chamotte components; here
the lining thickness is 230 mm (the total kiln length is 41 m).
The service life of the chamotte lining is typically 2 – 2.5
years; here the wear is mainly due to attrition by particles of
the mixture as it moves in the rotating kiln.
The other kiln zones (25 – 30 m in length) are lined with
materials more resistant to high temperature, mechanical
wear, and chemical attack — chromite-periclase, periclase-
chromite, periclase-spinellide, periclase-spinel, and corun
dum refractories. At the Chelyabinsk Zinc Smeltery
Joint-Stock Co. (ChZS JSC), two variants of the lining were
in use: a single-layer lining using PKhS-, PShS-grade or
KhTP-grade components, and a two-layer lining using
chamotte components (heat-insulating layer 65 mm thick)
and PKhS-, PShS-grade or KhTP-grade components (work
ing (hot) layer 230 mm thick in direct contact with the mix
ture). At present, the two-layer lining is only used, with the
hot layer made from periclase-spinellide or periclase-chro
mite refractory components, commercially available from
domestic manufacturers (Kombinat Magnezit JSC and
Nizhny Tagil Iron and Steel Works).
The service life of the basic lining may vary from
2.5 – 3 months to 2 years depending on the kiln zone. The
minimum service life (3 – 4 months on average) is typical of
the lining of the discharge cone and the adjacent area of
10 – 15 m (clinker formation zone). The demand in basic
refractories for a single Waelz-kiln with dimensions of
2.5 ´ 41 m at the ChZS JSC is 250 – 270 tons per year, and
chamotte refractories — about 50 tons per year per kiln. At
present, the cost of replacement of the lining in Waelz kilns
at the ChZS JSC accounts for 18 – 20% of the cost of cake
processing, therefore extending the service life of the lining
remains a challenging issue.
As is known, the main factors responsible for the wear
and failure of the refractories in Waelz kilns are mechanical
stresses that arise from the rotation of the kiln and deforma
tion of its casing, attrition by materials in motion, periodic
thermal shocks (associated with torch heat-up, hot kiln shut
down, material overheat) and from chemical attack of the re
active mixture. During service, the chemical and mineral
composition and, correspondingly, physicomechanical prop
erties of the refractory materials (heat conductivity, resis
tance to abrasive wear, etc.) undergo change.
The refractories that were in use in Waelz kilns were
tested for corrosion. The wear rate of the lining in the clinker
formation zone was 2 – 3 times the wear rate in the reaction
zone. Average chemical composition of the clinker in this
zone was: Fe
, 25 – 40%; FeO, 15 – 30%; SiO
, 5 – 12%;
CaO, 2 – 6%; Zn, 2 – 15%; Cu, 3 – 7%; S, 4 – 8%; and C,
10 – 25%. The clinker phase composition was mainly repre
sented by fayalite, franklinite, chalcosine, bornite, sphalerite,
and metallic iron reguli. The temperature of the reaction mix
Refractories and Industrial Ceramics Vol. 45, No. 4, 2004
1083-4877/04/4504-0225 © 2004 Springer Science+Business Media, Inc.
Chelyabinsk Zinc Smeltery Joint-Stock Co., Chelyabinsk, Russia.