REFRACTORIES AT THE USER
MECHANICAL EFFECTS ON THE LINING OF ROTARY CEMENT KILNS
V. I. Shubin
Translated from Ogneupory i Tekhnicheskaya Keramika, No. 6, pp. 41 – 48, June, 2001.
Results of studies concerned with mechanical effects on the lining of cement rotary kilns are reviewed.
Stresses arising from strains of the kiln casing and from slippage of the lining against the kiln casing are con
sidered, and mechanical effects exerted by the calcined material on the lining are discussed.
The refractory lining in rotary cement kilns is subjected
to a variety of mechanical effects such as impact, erosion,
and attrition owing to the motion of the calcined material in-
side the rotary kiln or cyclone-type heat exchangers. Other
mechanical effects are radial and axial deformations of the
kiln casing and torques generated in the lining, especially in
starting and stopping the kiln.
STRESSES IN THE LINING CAUSED BY THE
STRAIN OF THE ROTARY KILN CASING
Radial and axial deformations (strains) of the casing of
rotary cement kilns are distinguished. The elastic strains
arise periodically at each rotation of the kiln. Radial bending
strains of the cylindrical shell are most important for generat
ing stresses in the lining. Also, one should not overlook axial
plastic strains of the kiln casing that might arise because of
the accidental misalignment of the kiln during installation, or
because of the high temperature, especially in the sintering
zone, during kiln operation.
The irrecoverable axial distortion of the kiln casing dur
ing rotation generates a nonuniform load in individual roller
bearings, with the resulting occurrence of appreciable local
elastic strains in kiln tires and tire shells.
The main strains that may be generated in the casing of a
rotary kiln are characterized in Table 1. The strain values
may vary in a wide range. Departures of the generatrix of the
kiln casing from the circular line may reach 12 – 13 mm .
They cause a change in loading of the lining. At large strains,
the compressive, bending, or tensile stresses generate cracks
and cause spalling (shelling) in the refractory material. The
shift of refractory bricks with respect to one another causes
the brickwork joints to open; occasionally, individual bricks
or even entire sections of the lining may fall out. Under these
conditions, formation of the protective scull (slag lining) pro-
duced form the calcined material on the lining surface is
strongly hampered, which degrades the resistance of the lin-
ing and promotes spalling. As a consequence, thermal shocks
are generated, directed against the underlying layer of the
lining. With time, the kiln lining, exposed to relatively high
temperatures in the sintering zone, loses stiffness. With ex
tended service time, the mechanical loadings on the refrac
tory lining increase.
During service, the kiln casing develops a deflection in
the longitudinal direction because of the temperature differ
ence over the lateral cross-section to which the nonuniform
wear of lining and variation in scull thickness contribute.
In kilns of diameter 5 m and length 185 m, the tempera
ture difference of the kiln casing may in places reach ³ 100°C.
For a through-the-thickness temperature difference of 100°C
Refractories and Industrial Ceramics Vol. 42, Nos.5–6, 2001
1083-4877/01/0506-0245$25.00 © 2001 Plenum Publishing Corporation
For the previous paper of this series see Nos. 3, 4, and 5 (2001).
NIItsement Research Institute Joint-Stock Company, St. Peter
TABLE 1. Characterization of Strains
Radial Elastic Lateral stresses Roller bearings
Bending moment Roller bearings and
space between them
Axial Plastic Installation faults,
disturbance of nor