AT THE ENTERPRISES AND INSTITUTES
UDC 666.3.041.55-431
CAUSE-AND-EFFECT RELATIONS WITH RESPECT
TO DEFECTS IN BRICK FIRING IN TUNNEL KILNS
O. B. Gol’tsova,
1
V. S. Klekovkin,
1
O. B. Nagovitsyn,
1
and N. L. Dmitriev
1
Translated from Steklo i Keramika, No. 3, pp. 26 – 28, March, 2005.
The cause-and-effect relations in firing brick in tunnel kilns are investigated and the causes of defects depend
-
ing on the rate of heat treatment of brick in the kiln are identified. Current gas burners do not satisfy the re
-
quirements imposed on firing velocity regimes. The kiln has to be upgraded: Vulkan-gaz burners should be
replaced by state-of-the-art gas burners with automatic control of the heat regime of the kiln, and the thermal
regime in the preparation zone of the tunnel kiln has to be improved.
The goal of saturating the ceramic brick market implies
setting up new factories and reconstructing the existing brick
factories, as well as the development of new thermotechnical
machinery meeting the contemporary requirements on pro-
duction efficiency.
The present study offers theoretical and practical analy-
sis of defect causes and ways for improving production effi-
ciency in firing brick in tunnel kilns at the Al’tair Works of
Construction Materials.
A tunnel kiln with a flat roof of capacity 30 million
bricks per year was designed by the Yuzhgiprostroii Institute
and installed in 1990. The total length of the kiln is 134.7 m,
width 3.5 m, and height 1.8 m, including a preparation zone,
a firing zone with a hardening zone, and a cooling zone.
Brick is heated by Vulkan-gaz gas-plasma heaters (95 heat
-
ers) installed in the tunnel kiln roof according to the tempera
-
ture schedule shown in Fig. 1. The plot of the actual kiln per
-
formance is constructed by measuring temperatures in all
zones of the kiln, whereas the theoretical plot is taken
from [1].
The study of the temperature regime along the kiln indi
-
cates that the temperature in the preheating zone is below the
prescribed value and in front of the firing zone it sharply in
-
creases, i.e., the rate of the temperature rise on this particular
site exceeds the theoretical rate and the brick is subjected to
an abrupt thermal shock, which impairs the quality of firing
and increases the quantity of defects.
The analysis of the kiln performance included consider-
ation of the following physicochemical processes:
– the technological process related to modifications of
the physicochemical properties of initial materials and pro-
ducts in the course of heating and cooling;
– thermal engineering process ensuring the combustion
of gas and heat exchange between heated gases and the sur-
face of bricks (external heat exchange), as well as propaga
-
tion of heat within the brick (internal heat exchange);
– the aerodynamic process that regularizes the gas mo
-
tion across the section of the loaded kiln;
– the mechanical process responsible for the movement
of materials in the kiln tunnel.
To achieve an appropriate technological process, all
other processes should be subordinated to the former in order
to ensure its optimum qualitative and quantitative para
-
meters.
Glass and Ceramics Vol.62, Nos.3–4, 2005
89
0361-7610/05/0304-0089 © 2005 Springer Science+Business Media, Inc.
1
Izhevsk State Technical University, Izhevsk, Russia; Al’tair Works of
Construction Materials Joint-Stock Company, Izhevsk, Russia.
1000
900
800
700
600
500
400
300
200
100
0
2 6 10 14 18 22 26 28 32 34 38 42 46 48
1
2
Preparation zone
Firing zone
Cooling zone
Temperature, °C
Fig. 1. Theoretical (1 ) and actual (2 ) temperature regimes of the
tunnel kiln.