JP5563350B2 - Cooling structure at the bottom of the blast furnace - Google Patents

Description

  The present invention relates to a cooling structure at the bottom of a blast furnace furnace bottom.

In the blast furnace, a refractory made of carbon is installed on the inside of the iron skin, and the carbon refractory directly contacts the hot metal and wear increases. From the blast furnace reaches the end of its life.
In order to extend the life of the blast furnace, a cooling structure for refractories will be installed. For example, the side surface portion of the blast furnace as shown in FIG. 10, stave cooler 6 having the water cooling structure inside the furnace shell 5 is installed, are I line the cooling of the carbonaceous refractory from the outer periphery. In addition, a water cooling pipe 8 is disposed on the bottom of the bottom plate, and the carbon refractory is cooled from the lower surface.
As described above, the carbonaceous refractory is cooled from the surroundings, so that a protective layer is formed at the contact portion with the hot metal, wear is reduced, life is extended, and improvement in cooling ability is an important factor.
Among such background arts, there are Patent Documents 1 and 2 as conventional blast furnace bottom structure.

The content of the above-mentioned patent document 1 uses a water-based press-in material instead of the conventional non-aqueous graphite press-in material as a press-in material under the bottom plate of the blast furnace body, and has a thermal conductivity equivalent to the conventional press-in material, The purpose is that it is easy to install and does not cause poor filling.
In FIG. 11, the high thermal conductivity filler 16 is formed in the gap between the cooling pipe 8 and the secondary concrete layer 15 on the foundation 10, and then the high thermal conductivity filler 17 is formed thereon and cured. Then, the bottom plate 7 of the blast furnace body is installed by welding or the like.
At this time, a gap of 0.5 to 5 mm is secured between the high thermal conductivity filler 17 and the blast furnace body bottom plate 7. Then, the press-fitting material 20 is press-fitted from the pressure inlets 19 installed at a plurality of locations.
As the press-fitting member 20, the chemical components prior to the addition of water, SiC: 20 mass% or more, graphite: from 10 to 30 _wt%, Al ₂ O 3: 20 wt% or less, _SiO 2: 15 wt% or less, The total content of SiC, graphite, Al ₂ O ₃ and SiO ₂ is 95% by mass or more, and the thermal conductivity at room temperature is 4.5 W / m · K or more.

  Further, Patent Document 2 discloses a structure at the bottom of the blast furnace bottom of a two-layer structure in which a stamp material is applied to the upper layer and mortar is applied to the lower layer with a water-cooled pipe provided below the bottom plate of the blast furnace body as a boundary. .

JP 2008-156133 A JP 2009-120945 A

However, in the technique of the Patent Document 1, in the construction of the bottom of the blast furnace bottom, the press-fitting material 20 is filled in a narrow space of 0.5 to 5.0 mm below the bottom plate of the blast furnace furnace. In order to fill the material without gaps, the amount of water in the press-fitted material must be increased, and as a result, the thermal conductivity is lowered despite the large amount of graphite being 10 to 30%. It is judged that the upper limit is about 5.2 W / m · K described in 1.
That is, since the press-fitting material is filled in the narrow space as described above, extremely high fluidity is required, so that a large amount of moisture is required and the thermal conductivity cannot be increased.
Further, if the moisture content is decreased in order to increase the thermal conductivity, the fluidity is deteriorated and an air gap is generated in some places on the bottom plate, so that heat transfer from the water-cooled pipe is inhibited.

In the technique of Patent Document 2, since the bottom plate is applied after filling the upper layer of the stamp material, a gap is formed between the lower surface of the bottom plate and the upper surface of the stamp material, and heat transfer from the water-cooled pipe is hindered.
As described above, in the techniques of the conventional Patent Documents 1 and 2, since heat transfer from the water-cooled pipe is hindered, the cooling ability of the carbon bricks arranged at the bottom of the furnace is lowered, and thereby the life of the blast furnace is shortened. Shorter.

  The object of the present invention is to solve the problems of the prior art, and provide a cooling structure for the bottom of the blast furnace that can provide good cooling performance, thereby prolonging the life of the blast furnace. It is.

The feature of the cooling structure at the bottom of the blast furnace bottom according to the present invention is that it is constructed between the bottom plate disposed on the lower surface of the main body of the blast furnace and the foundation of the blast furnace, and has a water cooling pipe for cooling inside. The cooling structure has a boundary line at a predetermined position in the vertical direction of the cooling structure, and the boundary line is provided from the lower end to the center of the water-cooled pipe. In the portion up to the bottom plate, the alumina material is 10 to 60% by mass, the graphite is more than 0 and 5% by mass or less, the silicon carbide material is 35% by mass or more, and the thermal conductivity is 6 to 20 W / m. -The pumping material which is K is filled, and the part from the boundary line to the base of the blast furnace is filled with an amorphous material having a lower thermal conductivity than the pumping material.

In the present invention, the graphite that is difficult to wet with water is suppressed to 5% by mass or less, thereby preventing an increase in the amount of water necessary for imparting the desired fluidity to the pressure-feeding material, and adding 35% of the silicon carbide raw material. Good thermal conductivity can be achieved by containing more than mass%. In addition, since the graphite raw material becomes a factor which reduces fluidity as mentioned above, it is better that the addition amount is small, and it is better not to add other than the unreacted carbon raw material contained in the silicon carbide raw material. desirable.
Contains 35% by mass or more of silicon carbide raw material, which is a raw material with a low apparent specific gravity, but ensures fluidity (self-flowing property) due to its own weight in the pumping material by including 10-60% by mass of an alumina raw material with a high apparent specific gravity. can do. Thereby, although it contains many silicon carbide raw materials, a pumping material can be filled up without any gap. If the alumina raw material is less than 10% by mass, the fluidity becomes insufficient.
If the alumina material exceeds 60% by mass, the silicon carbide material is limited by that amount, so that the thermal conductivity is lowered. Examples of the alumina raw material include electrofused alumina, sintered alumina, calcined alumina, and alumina cement. Examples of graphite include scaly graphite and earthy graphite. The upper limit of the silicon carbide raw material is naturally less than 90% by mass.
In addition to the alumina raw material, graphite, and silicon carbide raw material, in the press-fitted material, inevitable impurities that enter from the respective raw material manufacturing processes and the press-fitted material manufacturing process described above, and good thermal conductivity (6 ˜20 W / m · k) and other components that do not adversely affect the fluidity due to their own weight.

In the present invention, a boundary line is provided at a predetermined position in the vertical direction of the cooling structure. Between the boundary line and the bottom plate, the high thermal conductivity refractory material, and between the boundary line and the foundation concrete, heat conduction is performed by the high thermal conductivity refractory material. A non-standard material with a low rate is used. For this reason, heat from the bottom of the furnace is hardly transmitted to the foundation concrete located below the boundary line, and heat removal from the lower surface side of the pipe can be suppressed.
In the present invention, the boundary line is provided from the lower end to the center of the water-cooled pipe. The distance from the lower end to the center of the water-cooled pipe is the distance in the extending direction. Thereby, the heat from the bottom of the furnace is not easily transmitted to the foundation concrete side, and the heat removal from the lower surface side of the pipe can be further suppressed.
As described above, the cooling structure at the bottom of the blast furnace bottom according to the present invention has a function of high thermal conductivity and imparts fluidity at the time of filling, and generates an air gap in the lower space of the blast furnace bottom plate at the time of filling. It is a safe cooling structure.

In addition, the structure of the bottom of the blast furnace furnace according to the present invention is preferable when the silicon carbide raw material includes particles obtained by spheroidizing treatment.
Since the spheroidized particles have an effect of reducing friction between the particles, the amount of water necessary for imparting a desired fluidity to the pumping material can be further reduced. For this reason, thermal conductivity can be further improved.

The structure of the bottom of the blast furnace furnace according to the present invention is such that the amorphous material has a thermal conductivity of 2 W / m · K or less, and is one of refractory castable, adiabatic castable, refractory concrete and ready-mixed concrete. It is desirable to be composed of seeds or two or more kinds. The thermal conductivity of the amorphous material provided between the foundations from the boundary line of the cooling pipe is 2 W / m · K or less, and the amorphous material is one or more of refractory castable, refractory concrete and ready-mixed concrete. Composed.
This makes it difficult for heat from the bottom of the furnace to be transferred from the boundary line of the cooling pipe to the foundation between the foundations, that is, below the boundary line. It is possible to extract heat from the bottom of the furnace.

Further, in the structure of the bottom of the blast furnace furnace according to the present invention, the water cooling pipes are arranged in a plurality of stages in the horizontal direction, and the boundary line is a water cooling in the lowest pipe in the vertical direction among the water cooling pipes in the plurality of stages. It is preferably provided between the lower end and the center of the pipe.
That is, as shown in FIG. 1, FIG. 5, and FIG. 6 described in detail in the embodiment, in the case where a plurality of water-cooled pipes are arranged in the vertical direction in the lower space of the blast furnace bottom plate, the boundary is the bottom pipe. It is preferable to provide it. The construction range of the pressure-feeding material having a thermal conductivity of 6 to 20 W / m · K is intended to cool the bottom plate side, so that the upper side from the center of the cooling pipe is preferable as shown in FIG. Since the arrangement and size of the cooling pipes are various as shown in FIG. 4, the boundary is set in the range from the center to the lower end of the cooling pipe. Although the boundary position may be slightly above the center, it is not preferable because the heat removal area is reduced by the amount upward. Although the boundary position may be slightly below the lower end, it is not preferable because heat removal from below increases as much as it goes downward.
In actual construction, the installation level (height and inclination) of the cooling pipe also varies, and the construction level of the amorphous material provided between the boundary line and the foundation also varies, so the boundary line level is partitioned by beams. There may be a step between the adjacent zones, and in some parts, the area may deviate from the boundary line.

The cooling structure at the bottom of the blast furnace bottom according to the present invention has a function of high thermal conductivity, imparts fluidity during filling, and does not cause an air gap in the bottom space of the blast furnace bottom plate during filling. It is.
The structure of the bottom of the blast furnace furnace according to the present invention preferably includes particles obtained by spheroidizing the silicon carbide raw material. In this case, the spheroidized particles have an effect of reducing friction between particles. Therefore, the amount of water required to impart the desired fluidity to the pumping material can be further reduced. For this reason, thermal conductivity can be further improved.
Further, in the structure of the bottom of the blast furnace furnace according to the present invention, it is preferable to use a material having a thermal conductivity of 2 W / m · K or less as an indeterminate material used downward from the boundary line. Can prevent excessive heat removal. Furthermore, when the cooling pipes are arranged in multiple stages, the amount of heat absorbed from the cooling pipes increases, wear of the carbon block is suppressed, and the life of the blast furnace can be extended.

Cross section of cooling structure at the bottom of the blast furnace showing the first embodiment of the present invention BB cross section of FIG. AA cross section of FIG. CC cross section of FIG. Cross section of cooling structure at the bottom of the blast furnace showing the second embodiment of the present invention Cross section of the cooling structure at the bottom of the blast furnace bottom showing the third embodiment of the present invention Cross section of the cooling structure at the bottom of the blast furnace bottom showing the fourth embodiment of the present invention Schematic diagram of hermetic vessel used for testing of blast furnace bottom of the present invention The graph which showed the relationship between the heat conductivity of the pumping material used for the boundary line upper part of this invention, and the amount of heat absorbed from a cooling pipe Cross section of conventional cooling structure at the bottom of the blast furnace Overview of conventional blast furnace bottom

Embodiments of the present invention will be described below with reference to FIGS. 1 to 7 and Table 1. FIG.
FIG. 1 shows a cross section of the cooling structure at the bottom of the blast furnace bottom, which is the first embodiment of the present invention. 2 shows a BB cross section of FIG. 1, FIG. 3 shows a AA cross section of FIG. 1, and FIG. 4 shows a CC cross section of FIG.

  In the first embodiment, in each drawing, the lower end of the water-cooled pipe 8 is used as a boundary line. Between the boundary line and the foundation concrete 10, a refractory castable, a heat insulating castable, a refractory concrete, a raw concrete, An indeterminate material 25 composed of one or more of the concrete is a pressure-feeding material 21 having a thermal conductivity of 6 to 20 W / m · K between the boundary line and the bottom plate 7. 11 is filled.

Conventionally, as shown in FIGS. 1 to 4, a beam assembly structure is used to install a water cooling pipe 8 between the bottom plate 7 and the foundation concrete 10. The lower part of the water-cooled pipe 8 forms a box-like structure with the main beam 22 and the cross beam 23, and the part where the water-cooled pipe 8 is arranged is a unidirectional main beam 22 and an auxiliary beam 24.
That is, the portion where the water-cooled pipe 8 is installed does not have the cross beam 23 in the middle thereof, so when the press-fitting material 21 is press-fitted from the press-fitting hole 11 as shown in FIG. 4, the press-fed material 21 is discharged through the confirmation hole 12. While being discharged from the hole 3, the space can be filled without any gap.

  FIG. 5 is a sectional view of the cooling structure at the bottom of the blast furnace bottom showing the second embodiment of the present invention, and the lower levels of the large and small water-cooled pipes 8 are different. In this case, the boundary line between the pumping material 21 and the amorphous material 25 is set at the lower level of the large cooling pipe 8.

  FIG. 6 is a sectional view of the cooling structure at the bottom of the blast furnace furnace showing the third embodiment of the present invention, in which water-cooled pipes 8 of the same size are arranged in three stages at different heights in the vertical direction. In this case, the boundary line between the pumping material 21 and the amorphous material 25 is set to the lower level of the cooling pipe 8 at the lowest stage.

  FIG. 7 is a sectional view of the cooling structure at the bottom of the blast furnace furnace showing the fourth embodiment of the present invention. The center level of the cooling pipe 8 is the boundary line between the pumping material 21 and the amorphous material 25. It is set at the center level.

Then, the test result using various raw materials is demonstrated using the airtight container 31 shown in FIG.
In Table 1 and Table 2, the silicon carbide-based raw material, graphite, and alumina raw material are mixed in various proportions, and the thermal conductivity and fluidity are evaluated in each case where the silicon carbide-based raw material is spheroidized. The results are shown.

  The thermal conductivity is a value measured according to JIS-R2618. The test piece obtained by casting the pumping material of each example into a mold having the dimensions specified in JIS-R2618, removing the frame after curing, and drying at 110 ° C. for 24 hours was used as a measurement object.

The fluidity was evaluated as follows.
An airtight container 31 having a width of 30 cm, a height of 20 cm, and a length of 10 m shown in FIG. 8 is formed by a transparent acrylic plate, an injection port 32 is provided at one end in the length direction of the airtight container 31, and a discharge port 33 is provided at the other end. Provide. The pumping material is injected from the injection port 32. After the inside of the airtight container 31 was filled with the pumping material and the pumping material was discharged from the discharge port 33, the pumping condition was visually observed. If the fluidity of the pumping material is poor, an air gap 34 is seen. The following criteria were used for four-level evaluation.
The size of the airtight container 31 is assumed to be, for example, a space portion having a depth between the floor beam 13 shown in FIG. 5 and the adjacent floor beam 13, that is, the same size as that of the actual machine size. Set the size.

Evaluation was performed according to the following criteria.
◎… There is no air gap.
○: A minute air gap having a volume of about 1 mm × 1 mm × 1 mm or less is observed.
Δ: The following air gap is observed when the volume is 10 mm × 10 mm × 10 mm.
X ... A large air gap with a volume exceeding 10 mm x 10 mm x 10 mm is observed.

The method of the spheroidizing treatment of the present invention and its definition are as follows.
By applying a spheroidizing process, specifically, a process of smoothing the corners of the surface by an abrasion process, the fluidity is improved. The abrasion treatment can be performed with a ceramic raw material pulverizer such as a sand mill, a ball mill, a fret mill, and a tube mill.
The spheroidized particles refer to particles that have been subjected to an abrasion treatment that brings the particle shape closer to a sphere after pulverizing the ingot, or particles having a sphericity of 0.7 or more.

The sphericity is obtained by measuring an image of a sample particle photographed with a stereomicroscope (for example, SMZ-10 manufactured by Nikon Corporation) or a scanning electron microscope (for example, JXA-8600M manufactured by JEOL Ltd.) as an image analyzer (for example, Nippon Avionics Co., Ltd.) ) And obtain it as follows. A projected area S _A of the sample particles from the image of the sample particles are measured and the perimeter L. When the area of a perfect circle of the circumference L is S _B , the sphericity of the sample particle is defined as S _A / S _B. The sphericity is measured for any 100 particles in the target powder, and the average value is taken as the sphericity of the target powder.

[Example 2 to Example 5]
Examples 2 to 5 in the table are based on the present invention.
In Examples 2 to 5, the silicon carbide raw material, graphite, and alumina raw material are blended in the range defined in claim 1 of the present invention, and the amount of water added is 9% by weight in terms of the outer percentage. It is. The silicon carbide raw material used was not spheroidized. As is clear from the table, good results are shown in both thermal conductivity and fluidity.

[Comparative Examples 1 and 6]
Comparative Example 1 and Comparative Example 6 show conventional techniques for Examples 2 to 5 based on the present invention.
In Comparative Example 1, 65% by mass of the alumina raw material is added in excess of the upper limit of 60% by mass according to claim 1 of the present invention. Thereby, the mixing of the silicon carbide raw material is limited. Therefore, although fluidity | liquidity is favorable, thermal conductivity falls and is unpreferable.
In Comparative Example 6, 5% by mass of the alumina-based raw material is less than the lower limit of 10% by mass according to claim 1 of the present invention. If the alumina material is less than 10% by mass, the amount of silicon carbide material having low fluidity is increased. Therefore, although heat conductivity is favorable, fluidity | liquidity becomes inadequate.

[Examples 7 to 8]
Examples 7 to 8 in the table are based on the present invention.
In Examples 7 to 8, graphite is increased based on Example 3 of the present invention, and the blending percentage of the silicon carbide based raw material, graphite, and alumina based raw material is within the scope of claim 1 of the present invention. In addition, 9% by mass of the added water amount is added as an outer percentage. As is clear from the table, the thermal conductivity and fluidity also show good results.

[Comparative Example 9, Comparative Example 10]
Comparative Example 9 and Comparative Example 10 in the table show conventional techniques for Examples 7 to 8 based on the present invention.
In Comparative Example 9 and Comparative Example 10, the graphite content is 7 to 10% by mass exceeding the upper limit of 5% by mass according to claim 1 of the present invention. Since graphite that is difficult to wet with water exceeds 5% by mass, the thermal conductivity is good, but both are unfavorable because the fluidity is lowered.

[Example 11, Example 12]
Examples 11 and 12 in the table are based on the present invention and are examples for confirming the effect of the spheroidizing treatment of the silicon carbide raw material.
Example 11 shows the result of spheroidizing treatment of 40% by mass of the silicon carbide raw material 59% by mass in the range of 75 μm to 3 mm in Example 3 of the present invention. When both Example 3 and Example 11 which are examples of the present invention are compared, Example 11 can reduce the added water by 1%, increase the thermal conductivity by about 10%, and improve the fluidity. ing. Thus, the effect of the spheroidizing treatment of the silicon carbide raw material has been clarified.
Example 12 shows the result of spheronization treatment of 70% by mass of the silicon carbide-based raw material of 89% by mass in the range of 75 μm to 3 mm in Example 5 of the present invention. In Example 12, the added water can be reduced by 1%, the thermal conductivity is increased by about 10%, and the fluidity is also improved. Thus, the effect of the spheroidizing treatment of the silicon carbide raw material has been clarified.

1 and 5 to 7, the foundation 10 is made of ready-mixed concrete, and an amorphous material 25 having a thermal conductivity of 2 W / m · K or less is used between the boundary line and the foundation.
The amorphous material 25 was selected from among refractory castable, adiabatic castable, refractory concrete, and ready-mixed concrete. Since the thermal conductivity is 2 W / m · K or less, heat from the furnace bottom is difficult to be transmitted downward from the boundary line, and heat extraction from below the water-cooled pipe can be suppressed.

FIG. 9 is a graph showing the relationship between the thermal conductivity λ of the refractory material used in the upper part of the boundary of the cooling pipe 8 portion of the present invention and the amount of heat removal Q from the cooling pipe 8.
As shown in FIG. 9, it can be seen that as λ increases, the amount of heat removal Q increases. Note that the amount of heat Q deprived from the cooling pipe 8 varies depending on the size and position of the pipe, the thickness of the laying beam portion, the temperature and amount of cooling water, etc.
In FIG. 9, the ◯ marks indicate the amount of heat removal when the refractory material of λ = 12 W / m · K of Example 3 is used in the airtight container 31 of FIG. Further, in the present invention (marked with asterisks) having the multistage pipe structure shown in FIG.

1: Blast furnace 5: Iron skin 6: Stave cooler 7: Bottom plate 8: Water-cooled pipe 9: Carbon refractory 10: Basic concrete 11: Pressure inlet 12: Confirmation port 13: Floor beam 15: Secondary concrete layer 16: High heat conduction Filling material 17: High thermal conductivity filling material 19: Press-in port 20: Press-in material 21: Pumping material 22 of the present invention: Main beam 23 of the spread beam: Cross beam 24 of the spread beam 25: Auxiliary beam 25 of the spread beam: Indeterminate Material 31: Airtight container 32: Injection port 33: Discharge port 34: Air gap

Claims (4)

A cooling structure at the bottom of the blast furnace bottom, which is constructed between a bottom plate arranged on the lower surface of the main body of the blast furnace and the foundation of the blast furnace and includes a water-cooling pipe for cooling inside,
Having a boundary at a predetermined position in the vertical direction of the cooling structure;
The boundary line is provided between the lower end and the center of the water-cooled pipe;
Above the boundary line, the portion from the boundary plate to the bottom plate is composed of 10 to 60% by mass of alumina material, more than 0 to 5% by mass of graphite, and 35% by mass or more of silicon carbide material, and heat conduction. Filled with a pumping material with a rate of 6-20 W / m · K,
A cooling structure at the bottom of the blast furnace bottom, wherein an amorphous material having a lower thermal conductivity than that of the pumping material is filled below the boundary line up to a base of the blast furnace. The cooling structure at the bottom of the blast furnace furnace according to claim 1 , wherein the silicon carbide material includes particles that have been spheroidized. The amorphous material has a thermal conductivity of 2 W / m · K or less, and is composed of one or more of refractory castable, adiabatic castable, refractory concrete, and ready-mixed concrete. The cooling structure at the bottom of the blast furnace furnace according to claim 1 or 2 . The water-cooled pipes are arranged in a plurality of stages in the horizontal direction, and the boundary line is provided between the lower end and the center of the water-cooled pipe in the lowest-stage pipe in the vertical direction among the plurality of stages of water-cooled pipes. The cooling structure of the lower part of a blast furnace bottom of any one of Claims 1-3 characterized by the above-mentioned.

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