IMPROVING THERMAL INSULATION FOR GRAPHITIZATION FURNACES
V. A. Vedin
1
and V. I. Pirogov
2
Translated from Novye Ogneupory,No.12,pp.3–5,December, 2008.
Original article submitted April 15, 2008.
Alternative materials are proposed for the lateral thermal insulation in graphitization furnaces. It is possible to
reduce the loss of heat and the consumption of electricity by using carbon dust for insulation, and it is also pos
-
sible to use plates of thermally and electrically insulating carbon material to hold it in the furnace.
Artificial graphite is made in resistance furnaces, which
are classified in Acheson and Kastner types in terms of the
method of heating (Figs. 1 and 2). There are also continu
-
ous-graphitization furnaces, which have restricted use [1].
Kastner furnaces are mainly used throughout the world in
graphitizing electronic products, which use direct heating to
reduce the electricity consumption by 20 – 30% and reduce
the heating time by a factor 3 – 4, which increases the
throughput considerably. On the other hand, Acheson resis-
tance furnaces are extensively used for graphitizing various
forms of carbon. In Russia, they remain the main equipment
for obtaining artificial graphite. By comparison with Kastner
furnaces, they consume more electricity and packing materi-
als. Then an effective way of reducing the costs of making
carbon products is to reduce the losses of electricity and heat
by improving the thermal insulation.
The thermal insulation mixture is an auxiliary material in
making graphite electrodes to reduce the loss of heat and to
protect the side walls from the effects of high temperatures.
Those walls are usually made of refractory concrete blocks
or firebrick. The thickness of the thermal insulation is chosen
from the need to restrict the internal surface temperature of
the firebrick wall. When the temperature at the wall reaches
1300 – 1350°C, the firebrick becomes impregnated with car
-
bon and carbide eutectics are formed, and the furnace be
-
comes no longer viable [1]. The total volume of insulating
material is about 70 – 75% of the internal space, with about
50% of the total volume occurring in the side insulation.
Temperatures of up to 2600 – 3000°C are attained on the
thermoinsulation packing, so only carbon materials can be
used for that purpose, sometimes mixed with sand and saw
-
dust. Anthracite or coke fines are the main materials cur
-
rently used as side insulation.
Economy is provided in these packing materials by mix
-
ing recycled material with fresh material that has not been
exposed to high temperatures. The ratio of the fresh and re
-
cycled materials is determined by the specifications for the
Refractories and Industrial Ceramics Vol. 49, No. 6, 2008
416
1083-4877/08/4906-0416 © 2008 Springer Science+Business Media, Inc.
1
Energy Industry Management Ltd, Moscow, Russia.
2
Russian Aluminum Company, Moscow, Russia
Fig. 1. Scheme for Acheson graphitization furnace: 1 ) end wall;
2 ) current-carrying electrodes; 3 ) refractory blocks; 4 ) core pack
-
ing; 5 ) thermal insulation packing.
Fig. 2. Kastner graphitization furnace scheme: 1 ) head of furnace;
2 ) column of blanks; 3 ) carbon packing; 4 ) carbon insert; 5 )hy
-
draulic system for compressing electrodes.
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