Note: Descriptions are shown in the official language in which they were submitted.
1046Z~9
1 This invention relates to a method for constructing a
runner for transferring molten metal or molten slag which is
attached to a metal melting furnace such as a blast furnace.
Runners of blast furnaces have previously been constructed
by stamping a mixture of the fine part~cles of chamotte or silica
sand, fire clay particles (as a binder), and water. In recent
years, the pressure of the furnace at its top has become higher
with an increase in the size of blast furnaces and the advance of
the furnace operating techniques. Thus, the amount of pig iron
produced in one furnace cycle and the number of pig iron tapping
operations per day have increased, and also the temperature of
molten iron or molten slag has become high~r. In addition, because
there has been employed a method wherein molten iron and molten
slag are transferred simultaneously through the same runner,
refractory materials used as linings of the runners are drastically
attacked by the molten pig iron and molten slag both chemically
and mechanically. Carbon bond refractories using as a binder a
carbonaceous material containing volatile matters such as pitch,
tar or resin have higher softening temperature under load, higher
modulus or rupture at high temperature, and higher abrasion re-
sistance at high temperature than the above~mentioned ceramic
bond refractories using the fire clay particles as a binder. Since
the binder material is carbonaceous and neutral and has a high
resistance to chemical attack by molten slag, a method has also
been utilized in which a runner is constructed by stamping a re-
fractory material comprising as a binder a carbonaceous substance
containing volatile matters.
When the runner is made by stamping a mixture consisting
of chamotte or silica sand particles, fire clay as a binder, and
water, the runner can be used by drying it until the water added
-1- ~ '
10~ 49
1 is removed. However, when it is made by stamping a mixture of
chamotte particles and as a binder, a carbonaceous substance con-
taining volatile matters such as pitch or tar or resin, the product
must be heated for longer period of time by gradually elevating
the temperature in order to remove the volatile matters, and there-
by to coke and solidify the product. However, the time allowed for
the construction of the runner and its drying or heat solidification
in front of the biast furnace is determined by the operation of the
blast furnace. Of late, with an increase in the number of molten
metal tapping operations per day as a result of the increasing size
of the blast furnace and the advance of the furnace operating
techniques, this construction time is greatly shortened, and
especially it is not possible to permit long pexiods of time for
the drying of the runner or heat solidifying it after construction.
Furthermore, it is difficult to micro-adjust the heating burner
in an operation in front of the furnace. Accordingly, since the
runner is heated abruptly at high temperatures after construction,
heavy smokes and bad smell are generated from the pitch or tar to
pollute the working environment in front of the blast furnace.
Further, since large quantities of the volatile matters are dis-
sipated at a time, the runner becomes porous, and since it is
heated in air, the surface of the runner is oxidized and burnt to
reduce its strength.
An attempt has also been made to avoid its contact with
air during heating by coating the surface of the constructed
runner with a paste comprising coke powder t chamotte powder, and
clay, etc. But since the control of temperature rise cannot be
performed in view of the situation mentioned above, satisfactory
results cannot be obtained. There is also a method in which blocks
of a runner are formed in advance, and gradually heated to remove
10'~249
1 the volatile matter and solidify them, and the blocks are then
connected to make a runner. However, it is difficult to choose
a joint material for the connecting parts of the blocks, the
corrosion of the joint parts is remarkable, and much labor is
required for assembling the blocks. ;
The present invention provides a method for constructing
a runner for a metal melting furnace such as a blast furnace by
using a refractory material comprising as a binder a carbonaceous
substance containing volatile substances.
As previously stated, when the runner is constructed with
a ceramic bond refractory material comprising a mixture of powdery
refractory material such as chamotte particles, fire clay powder
as a binder, and water, it is necessary to dry the product before
use in order to remove the water. On the other hand, when the
runner is constructed with a carbon bond refractory material com-
prising refractory powder such as fire clay powder, and a carbo-
naceous substance containing volatile matters such as pitch, tar
or resin as a binder, the product must be coked and solidified
by gradually heating it before use to remove the volatile matters.
When the drying procedure is compared with the solidification by
coking, the following can be said.
At the drying the ceramic bond refractory material, the
drying of the inside of the materials should be least different
from that of the surface since the difference in the extent of
drying between the inside and the surface of the refractory
material will result in cracks. The rate of evaporation of water
from the surface of the refractory material is dependent upon the
temperature of the outer atmosphere (heating temperature), humidity
and the rate of air flow, and the rate of diffusion of moisture
within the refractory material differs according to such factors
104~;;249
1 as the temperature of the refractory material, the amount, shape
and size of pores, the temperature difference of the refractory
material between the inside and the surface, or the moisture con-
tent. Accordingly, the drying conditions such as heating should
be determined in the light of these factors. However, since the
material to be removed is water, the drying can be considered to
have been completed if the temperature of the entire refractory
material has reached at least 100C to diffuse moisture on the
surface, and the time required for evaporation has elapsed.
The solidification of the carbon bond refractory material
by coking is performed by heating the refractory material thereby
to remove the volatile matters such as pitch, or tar added as a
binder. The volatile matters contained in pitch or tar dirfer
from each other in volatilization temperature as, for example,
cresol has a boiling point of 200C, naphthalene 218C, light oil
250C, phenanthrene 340Cr and anthracene 342C. Accordingly,
for coking and solidifying the carbon bond refractory material,
the material may be maintained at temperatures at which the
individual substances are volatilized until these substances are
volatilized completely. The time required for the completion of
the volatile matters contained in a carbonaceous substance such
as pitch or tar used as a binder for the refractory material is
dependent upon the amounts of the volatile substances, and the
amount, shape or size of the pores of the refractory material
Therefore, the rate of heating the carbon bond refractory material
is determined in the light of these factors. However, generally,
up to at least about 600C, the temperature must be raised undex
a thoroughly controlled condition. The firing of a carbon product
of the carbon bond type such as electrodes is performed after
filling coke breeze around the product in order to prevent its
- 4 -
- 104f~249
1 deformation during heating and also its oxidation during firing.
When a refractory material comprising as a binder a car-
bonaceous substance, such as pitch or tar, which contains volatile
matters was formed by the stamping method and solidified by coking,
there was a large weight loss if it was heated in air to a tempera-
ture of at least 300C, and the strength of the material is
drastically reduced. Specifically, a mixture of 10% of natural
graphite, 48% of silicon carbide, 30~ of chamotte, and as a binder
12% of pitch and tar combined is heated to a temperature of not
more than 200C, kneaded, placed in a mold and formed into an
article having a diameter of 50 mm and a height of 50 mm by the
stamping method. The article formed was heated in air at a
temperature between 100C and 1000C indicated in Table 1. Se-
parately, a similar test piece was placed in a vessel made of
a refractory material, and coke breeze was filled between the
vessel and the test piece to shut off air. Then, the test piece
was gradually elevated up to 1000C in the course of 40 hours.
The heated products obtained are tested as to their physical
properties. The results are shown in Table 1.
TABLE 1
_ _ _ _ _ . , .
Heating Temper- Retain- Weight Amount Compres- Porosity
temper- ature ing time loss of sive (%)
ature rise (hours) (%) wear strength
(C) (hours) (ml) (Kg/cm2)
100 1 3 1.1 0.6 14 11.2
200 1 3 2.9 1.1 87 15.1
300 1 3 6.2 2.2 45 19.8
500 1 3 7.8 4.5 13 32.5
800 2 3 14.5 Meas~ rement im~ ~ossible
1000 2.5 3 16.0 Measurement impossible
_ _ _
Comparison Example in which coke breeze was filled
1000 14.0 I ~ 1 6.0 1 0.8 1 135 1 21.7
1046249
1 The temperature raising time of 1 to 2.5 hours and the
retaining time Gf 3 hours were prescribed on the basis of the
conjecture of the situation in which the runner is constructed in
front of the blast furnace and heated by gas or heavy oil burners.
The amount of wear is measured as follows: A steel ball having a
diameter of 2.3 mm and weighing 8.4 Xg is passed through a ver-
tically erected tube having an inside diameter of 24 mm, and let
fall onto the surface of a test piece from the height of 4 m.
Then, the amount of wear of the surface of the test piece is
measured and expressed by volume (milliliters). Larger values of
the amount of wear show greater mechanical wear. T~e compression
strength and the porosity are measured by conventional methods
used for fire brick.
When the carbon bond refractory material comprising pitch
or tar as a binder is heated in air, the weight loss becomes
greater at a temperature higher than 300C and the amount of wear
becomes greater at a temperature of 200C or above, as compared
with the case of heating it in the absence of air. The compression
strength is at a maximum when the temperature is 200C, and
decreases when the temperature is lower than it. The porosity
increases with increasing temperature. Especially at a temperature
of 800C or above, the test piece becomes crumb-like, and the
amount of wear, compression strength and porosity can not be
measured. This is because the rapid heating causes abrupt vola-
tilization of the volatile matters in the binder, and the coked
carbon and the added graphite also burn.
The present invention was accomplished on the basis of
the results of this experiment. Thus, the invention provides a
method for constructing a runner for a blast furnace, for example,
3 by using a refractory material comprising as a binder carbonaceous
- .
: ~ ~ . ....
`` lO~Z~9
1 substances containing volatile matters such as pitch or tar, and
heating the resulting trough to solidify it sufficiently as a
result of coking.
The invention will be described further by reference to
the accompanying drawings in which:
Figure 1 is a schematic sectional view of a runner in
accordance with the method of this invention;
Figure 2 is a schematic sectional view of a runner in
accordance with a conventional method;
Figure 3 is a curve diagram showing the temperature rise
at the time of heating the runner in accordance with the method
of this invention; and
Figure 4 is a curve diagram showing the temperature rise
- at the time of heating the runner by the conventional method.
Referring to Figure 1, the reference numeral 1 represents
an ordinary fire brick, 2, a carbon bond refractory material con-
taining as a binder carbonaceous substances containing volatile
matters, and 3, a ceramic bond containing clay as a binder. A
gas burner for heating is shown at 4. The reference numeral 5
designates an iron covering which can be omitted by increasing the
thickness of fire brick when the runner is of the fixed type.
The characterstic feature of this invention is that a refractory
material of the carbon bonded type is formed by stamping or ramming
to produce a runner, and the surface of the runner which comes in
contact with molten pig iron and molten slag is coated with a
ceramic bond refractory material containing clay as a binder in a
smaller thickness than in the case of the first-mentioned refractory
material. The carbon-bond refractory material used is a mixture
of, by weight, 10% of natural graphite, 48% of silicon carbide,
30~ of chamotte, and 12% of pitch and tar combined, which is then
1046~i~49
1 kneaded at a temperature of not higher than 200C. The ceramic
bond refractory material is a kneaded mixture of, by weight, 7%
of natural graphite, 40~ of chamotte, 20% of siliceous sand, 15%
of silicon carbide, 18% of clay, and water. In this case, the
thickness of the ceramic bond refractory material is 50 mm. The
ceramic bond refractory material must cover the entire surface so
that the carbon bond refractory material may not be exposed. How-
ever, in order to release the volatile matters in the carbon bond
refractory material, gas extracting pores or spaces may be provided
at places which do not come into contact with molten pig iron and
slag. Points A to D show the positions of a thermocouple inserted
for temperature measurement. The distances from these points to
the surface to which the carbon bond refractory material has been
applied are 70 mm for point A, 150 mm for point B, 200 mm for point
C, and 250 mm for point D. Point E designates a thermocouple
inserted in contact with the surface of the refractory material in
order to measure the heating temperature.
Referring to Figure 2, the reference numeral 1 shows an
ordinary fire brick, 2, a carbon bond refractory material, 4, a
gas burner for heating, and S, an iron covering. Points A' to D'
show the positions of a thermocouple inserted for temperature
measurement. The distances from the surface to which the refractory
material has been applied are 70 mm for point A', 150 mm for point
B', 200 mm for point C', and 250 mm for point D'. Point E' de-
signates a thermocouple inserted in contact with the surface of
the refractory material in order to measure the heating temperature.
The points A to E and points Al to E' are arranged on the line
crossing the refractory material applied surface at right angles.
Although not shown in the drawings, a space above the
gas burner is covered with an iron plate, and the gas burner is
~O~Z49
1 ignited. The gas is burned while controlling the burner so that
the temperatures at the points E and E' are 800C, and then the
temperatures at the points A to D and A' to D' are measured~ The
results of temperature measurement are shown in Figure 3 (present
invention), and Figure 4 (the conventional method). In Figures 3
and 4, the temperature at the starting point is about 80C. This
is because the carbon bond refractory material is kneaded at
elevated temperatures and stamped while being hot. When the con-
ventional method is used, the temperatures of the points A' and
B' abruptly rise after igniting the burner, as shown in Figure 4.
It is deemed that a part nearer the refractory applied surface
than point A' rapidly attains a temperature near 800C. On the
other hand, according to the method of this invention as shown
in Figure 3, the temperature rise of point A is very linear, and
the average rate of temperature rise up to 600C is about 29 & /hr.,
which is only slightly higher than the average temperature rising
rate (25C/hr.) in the case of heating after coke breeze is filled
up. For some time after ignition, no rise in temperature is seen
because moisture contained in the ceramic bond refractory material
evaporates during this time. The difference in temperature rise
between the conventional method and the method of the present
invention is that in the method of this invention, heat is gradually
transferred to the carbon bond refractory material by the heat
transfer resistance of the ceramic bond refractory material since
the thermal conductivity of the ceramic bond refractory material
stamped on the carbon bond refractory material is 2 K cal/m.h. C,
while the thermal conductivity of the carbon bond refractory
material is 4 K cal/m.h. G. After heating, test samples are
collected from points A, B, A' and B', and the physical properties
of these samples are measured. The results are shown in Table 2
below.
" 104~i249
1 TABLE 2
Total car- Amount Compressive Porosity
bon content of wear strength (~)
(%) (ml) (Kg/cm2)
. __ _ . .
Method of
present ln-
vention
Point A 17.5 1.0 122 19.2
Point B 18.1 1.5 103 17.4
. .. . ........ _
Conventional
method
Point A' 15.4 8.7 32 24.5
Point B' 17.3 5.5 61 22.0
Since the total carbon content calculated of the carbon
bond refractory material (the sum of the amounts of graphite and
coked pitch and tar) is 17%, it is believed that point A in accord-
ance with the method of this invention has been substantially
completely coked, and at point B, some amount of the volatile
matters is still present. At point A' in accordance with the
conventional method, the total carbon content decreases, and this
is believed to be due to a partial oxidation and combustion of
the binder material. In accordance with the method of this in-
vention; the amount of wear and the compressive strength are
similar to the case of heating the refractory material after
filling coke breeze. Furthermore, according to the method of this
invention, no smoking and offensive smell occur during heating,
and the situation is quite the same as in the case of drying only
a ceramic bond refractory. However, in the conventional method,
a large amount of gas is evolved from the refractory applied ~urface,
and the combustion of the gas near the surface is observed to
cause heavy black smokes and bad smell. The absence of smokes and
-- 10 --
~046Z49
1 offensive smell in the method of this invention is considered due
to the fact that the volatile matters which are gradually evolved
- from the carbon bond refractory material come into contact with
the heated ceramic bond refractory material to burn or decompose
and be converted to a harmless gas consisting mainly of C02. In
other words, the method of this invention is very effective for
heating carbon bond refractory materials. It is possible to begin
to tap molten pig iron after the drying of the ceramic bond re-
fractory material, and to coke and solidify the carbon bond re-
fractory material gradually by the heat of the molten pig iron.
Experiments show that if the thickness of the ceramic
bond refractory material is less than 30 mm, the rate of temperature
rise of the carbon bond refractory material is high and the shut-
off of air cannot be effected completely. If the thickness of the
ceramic bond refractory material applied exceeds 150 mm, the trans-
fer of heat to the carbon bond refractory material is poor, and
considerable time is needed to solidify the carbon bond refractory
material by coking. Furthermore, if the thickness of the ceramic
bond refractory material is less than 150 mm, moisture easily
evaporates, and therefore, there is no special necessity to control
the burner during heating.
- The carbon bond refractory material that can be used in
the present invention may be any refractory material comprising a
powdery raw material and as a binder carbonaceous materials con-
taining volatile matters. The powdery raw material may be those
having fire resistance, but in view of the corrosion resistance
to molten pig iron and molten slag, it is prefer~ed to use at least
one member of each of the following three groups. The first group
comprises chamotte, mullite, a-alumina, siliceous sand and zircon
sand. The second group includes silicon carbide, ferro-silicon
.
- 11-
~04~2~9
1 nitride, and silicon nitride. The third group includes natural
graphite, artificial graphite, and amorphous carbon.
The ceramic bond refractory material is produced by
mixing a powdery raw material, a clay substance as a binder such
as fire clay or bentonite, and water. The powdery raw material
may be those having fire resistance. However, it should not be
corroded so much by molten pig iron and molten slag, because the
ceramic bond refractory material needs to cover the carbon bond
refractory material until the solidification of the carbon bond
refractory material by coking is completed. In order to increase
its corrosion resistance, it is effective to add graphite and
silicon carbide. However, if the amount of graphite exceeds 20%
by weight or the amount of silicon carbide exceeds 50% by weight,
the thermal conductivity becomes excessively high.
The method of this invention can be used not only for
constructing runners of blast furnaces but also for the construction
of runner of metal melting furnaces.
EXAMPLE 1
.,
A runner was constructed by stamping a carbon bond re-
fractory material consisting of, by weight, 10% of natural graphite,
48% of silicon carbide, 30% of chamotte, and 12% of pitch and tar
combined as a binder. On top of it, a ceramic bond refractory
material consisting of, by ~eight, 7% of natural graphite, 40%
of chamotte, 20% of siliceous sand, 15% of silicon carbide, 18%
of clay, and water was stamped in a th~ckness of 70 mm to form a
runner in accordance with this invention. The runner was heated
for 4 hours by a gas burner, and then molten pig iron was trans-
ferred through it. Without repair, 80,000 tons of molten pig iron
could be transferred.
When the runner was built only by using the carbon bond
- 12 -
" 104~;~49
1 refractory material, the amount of pig iron tapped was at most
40,000 tons. Accordingly, the runner in accordance with this
invention was about two times as durable as that in accordance
with the conventional method.
i No smokes and offensive smell occurred during heating by
the gas burner and after the beginning of transferring molten pig
iron. Same as in the case of constructing the runner only with
the ceramic bond refractory material, very good working environment
could be maintained.
EX~MPLE 2
A runner was constructed by stamping a carbon bond re-
fractory material consisting of, by weight, 8% of natural graphite,
4~ of anthracite as amorphous carbon, 35% of silicon carbide, 15%
of ferro-silicon nitride, 21% of mullite, 6~ of zircon sand, and
11% of pitch and tar combined. On top of it, a ceramic bond re-
fractory material consisting of, by weight, 10% of natural graphite,
45% of chamotte, 5% of siliceous sand, 20% of silicon carbide, 20%
of fire clay, and water was stamped in a thickness of 100 mm to
form a runner in accordance with this invention. After heating
for 4 hours by a gas burner, the trough permitted the transferring
of 98,000 tons of pig iron without repair. The durability of
this runner was more than two times as high as that constructed
only with the carbon bond refractory material in which the amount
of molten pig iron transferred was at most 45,000 tons.
While the invention has been described in detail and with
reference to specific embodiments thereof, it will be apparent to
one skilled in the art that various changes and modifications can
be made therein without departing from the spirit and scope thereof.
- 13 -
