JPS6362473B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a new basis for a furnace used in metallurgy, more particularly a new basis for a furnace with a crucible (heart) containing a liquid metal or liquid alloy heated to a high temperature. Pertains to.

More particularly, the present invention relates to blast furnaces and electrometallurgical furnaces, especially those in which a cooling bottom is formed below the lining of the crucible, the temperature level of which is controlled by the circulation of water, oil or other fluids. Regarding the furnace. The invention further relates to a metallurgical furnace having a crucible in which at least a portion of the refractory lining consists of an integral combination of graphite and/or carbon blocks. Experiments have shown that, especially in the case of blast furnaces, crucibles with the above structure have an extremely long lifespan, as long as the lining blocks are assembled very precisely and maintain perfect stability over time. found.

To this end, it is important that the base supporting the refractory lining of the crucible maintains excellent planarity and mechanical resistance over time. As the technology for machining the flat surfaces of carbon-containing blocks with an accuracy of ±0.2 mm is currently known,
The above characteristics are also strongly required for the substrate.

In addition, the crucible lining must be cooled to prevent liquid metal penetration, which can corrode the lining and even puncture the lining and leak out of the furnace over a long period of time. It was also confirmed that

Particularly in the area near the axis of the furnace, it is important to promote cooling in this way, and the base is therefore designed to facilitate the flow of heat between the graphite and/or carbon blocks constituting the lining and the cooling means. must be done. In the case of refractory linings of this kind, especially for blast furnace hearths, many manufacturing methods have already been proposed for suitable substrates on which to place them.

Two major types of these foundations are particularly well known.

The first type of foundation is fireproof concrete composed of oxide-based aggregates, such as silico-alumina refractories with cement as a binder. This type of concrete is relatively simple to manufacture and has hydraulic properties.

However, even if the surface is carefully leveled after concrete is poured so that the concrete layer has a nearly horizontal and smooth surface, experimental results show that differences in height of several millimeters will almost inevitably occur in some areas. The result is clear. Therefore, if you want to accurately place a lining made of processed blocks on such a base, the entire surface of the base must be ground to eliminate such height differences.
Although this requires considerable effort, it is still extremely difficult to make the surface sufficiently smooth. Furthermore, such a substrate has a low thermal conductivity of about 1 W.m ^-1 .K ^-1 .
It is possible to increase this thermal conductivity by using corundum-based aggregates, but this increases costs and, due to the hardness of the aggregates, requires grinding. becomes even more difficult.

The second type of foundation consists of refractory tiles several centimeters thick laid on, for example, a cement floor.

French Patent No. 2,104,389 discloses a method for precisely laying such refractory tiles so that the upper surfaces lie in the same plane. According to this, reference tiles are placed at precisely predetermined intervals on a cement or mortar bed which has been previously extended on a base plate, and optical means well known to those skilled in the art are used. The height of the surface of the tiles is adjusted by submerging them more or less into the mortar so that the tile surface coincides with a reference plane controlled by the method. Once the base point is set in this way, all that is left to do is to use a flat ruler to adjust the top surface so that it is positioned on the reference plane, and then you can fit other tiles in between. If the surface properties of the tiles are sufficient and they are placed with sufficient care, it is possible in this way to achieve a foundation with a very precise reference surface. To increase the thermal conductivity of the substrate, tiles made of carbon-containing material, especially graphite, may be laid.

However, this method is expensive due to the high cost of thin graphite tiles and, as mentioned above, the reference surface must be completely flat so that the blocks forming the lining can be placed with the desired accuracy. Great care must be taken in the installation. In some cases, tiles that cannot be placed in accordance with the reference level may have to be further ground, for example using a pendulum milling cutter. However, when using the milling cutter described above, the reference surface may also be slightly curved.

Normally, with the two types of bases mentioned above, a satisfactory result cannot be obtained unless the work is carried out carefully over time, and the quality of the result is largely determined by the skill level of the worker. In addition, the thermal conductivity of these foundations is often insufficient due to the use of refractory mortar or concrete, which have relatively low thermal conductivity. The use of pise' based on carbon-containing materials instead of mortar or concrete increases thermal conductivity, but flatness remains a problem.

Until now, in the base of a metallurgical furnace with a cooling bottom, the upper surface reliably forms a horizontal reference plane with an extremely small deviation from the theoretical plane, and a simple method has been used to achieve economical results in a short time. Attempts have been made to develop a new type of base that can be easily manufactured, easily put into practical use, and whose effects can be completely reproduced.

Attempts have also been made to create a substrate with high thermal conductivity to reduce the temperature of the lining.

Furthermore, there is a favorable heat transfer between the bottom of the furnace and the means for cooling, for example when cooling by air circulation under the base plate or by circulating liquid in conduits arranged above the base plate. Attempts have also been made to create a foundation that will cause coupling.

The substrate that is the subject of the invention has at least 80% by weight
a clay layer in direct contact with the cooling bottom surface, the clay layer containing at least 40% graphite fines and a synthetic resin-based binder; It consists of a thin layer of grade grout covering the soil.

As described below, the present invention also relates to a method of manufacturing the substrate.

Graphite-based clays contain natural graphite, such as graphite from Ceylon or Madagascar, artificial graphite, or a mixture of these two types of graphite.

The binder contains a resin such as a thermosetting resin in an amount of about 8 to 15% by weight, and a catalyst is usually added so that the clay solidifies at room temperature. The clay layer placed at the bottom of the blast furnace must have sufficient thickness to form a non-deformable base after hardening. This thickness depends to some extent on the diameter of the blast furnace and the arrangement of the cooling means.

Cooling fluid conduits are often located on the base plate, in which case it is necessary to surround and cover these conduits with the clay.

In practice, the thickness of the clay layer after close packing amounts to approximately 5 to 20 cm, depending on the case. In order to minimize the thickness of the ground leveling grout layer covering the clay, it is necessary to make the upper surface of the clay a relatively smooth and horizontal surface.

The base plate and, as the case may be, the cooling conduits, are tightly packed together so that the clay is in full contact with the base plate and, as the case may be, the upper surface matches the reference plane as much as possible and has minimal irregularities. Various methods can be used for filling.

A method of manufacturing a base has been developed which is particularly effective in closely packing the clay into the conditions described above. This method forms part of the present invention and will be described later.

According to the present invention, a base having an upper surface constituting a substantially perfect horizontal surface is obtained by covering a layer of soil with a thin layer for leveling composed of a fluid grout. Such grout is easily distributed over slight irregularities and depressions and fills these areas, so that a perfectly horizontal reference surface is obtained. The thickness of the grout is limited to the minimum necessary, but usually its average value is 1 to 5 mm. The grout is made of finely powdered natural graphite or powdered artificial graphite with a particle size of less than 0.3 mm.
Contains 40 to 70% by weight. The remainder is a thermosetting resin, usually with a solvent added to increase its fluidity.

The grout is often mixed with a suitable catalyst so that it solidifies at room temperature.

The base manufacturing method developed according to the invention is a method for realizing a base whose upper surface is constituted by a horizontal plane whose deviation from the ideal mean plane after grout hardening is usually less than a millimeter at all points. However, this will be explained later.

As a result of measuring the mechanical properties imparted to the substrate according to the invention, it was found that the substrate has a minimum crushing strength of 8 MPa when it is based on natural graphite. This minimum value reaches 20 MPa if the substrate is based on artificial graphite.

The thermal conductivity of the base depends in part on the relative thicknesses of the fill and grout layers.

Since the thermal conductivity of the grout is lower than that of the clay, it is extremely important to reduce the thickness of the grout to a minimum, which is one of the main advantages of the base manufacturing method, which is another object of the present invention. This is precisely because the average thickness of the grout can be reduced to just a few millimeters.

In this way, the thermal conductivity of the base can be determined by the properties of the graphite used, the composition of the clay expressed in weight percent,
and depending on the degree of compaction (tight packing), usually 10 to
Indicates a value between 20W.m ^-1 .K ^-1 .

In this method, a plurality of straight leveling rods are placed at suitable intervals from each other so as to divide the surface to be coated into several areas, and with an average height equal to the desired thickness of the clay from the bottom of the furnace upwards. Place at a distance.
Optionally, the adjustment rods may be arranged parallel to each other at approximately equal distances, or arranged in a square grid, or in any other suitable arrangement. The height of the adjustment rods can be adjusted so that the upper surface of each rod is the same by installing removable adjustable coupling means between these rods and the bottom of the furnace to adjust the vertical distance between them. Adjusted to lie on a horizontal plane. A simple way to do this is to
A fixing means well known to those skilled in the art, such as a vertical shaft, is welded in place on the base plate, and the fixing means, which is thus attached to the bottom of the furnace, is connected to the bottom of the connecting means, such as a threaded vertical rod. There is a method of joining the upper end of the connecting means to the horizontal adjustment rods so that the height of the horizontal adjustment rods can be adjusted while the ends are fixed. If a threaded rod is used, the upper end of the rod may be engaged in a hole formed at the tip of the leveling rod, in which case the height adjustment of the rod may be adjusted, for example by a nut, as known to those skilled in the art. have it carried out in a method. Once the leveling rod has been adjusted, the height of the first reference plane, which is to be coincident with the upper surface of the mulch, can be adjusted using conventional methods, such as by means of pneumatic close packing, which are well known to those skilled in the art. Fill the bottom part by continuously forming layers using the method described in the following.

The soil layer is adjusted so that the entire surface completely reaches the level of the adjustment rod. In this case, a movable horizontal ruler is used in a known manner, and the tip of the ruler is moved on the adjustment rod in a sliding manner. The level of the clay between these adjustment rods may be adjusted.

Next, the leveling rod is readjusted to the height of the second reference plane, that is, the plane that is located higher than the first reference plane and corresponds to the final height of the top surface of the substrate. Therefore, the average distance between the first and second reference planes corresponds to the thickness of the ground for leveling that covers the ground.

In order to carry out the second adjustment, the position of the adjustment rod along the adjustable coupling means may be adjusted. If the means is a threaded rod, the adjustment is made via a nut which fixes the adjusting rod to the rod.

In some cases, taking into account the desired accuracy, relatively inexpensive adjustment rods with medium accuracy are used for setting the first reference plane, and these adjustment rods are used for setting the second reference plane. Instead, use another set of precision adjustment rods and adjust the height of these adjustment rods very carefully. For adjustment in this way, a water level and/or
Alternatively, means well known to those skilled in the art, such as leveling optical devices, may be used. After setting the second reference surface, a thin film of ground leveling ground is poured. Due to the high fluidity of the grout, the surface is very easily leveled, so that a perfectly flat surface is formed at the same height as the upper surface of the adjustment rod. Once the grout has solidified, the adjustment rod and connecting means are typically removed and the resulting void is filled with a small amount of clay and/or grout.

The manufacturing method described above has the great advantage of being extremely simple to work with, and at the same time allows the manufacturing of the base to be carried out extremely accurately and in an extremely short time, but it is possible to modify the manufacturing method in various ways. It is possible.

In fact, it is often desirable to reduce manufacturing time in order to minimize the time required to rebuild extremely large furnaces. For example, when rebuilding a state-of-the-art blast furnace, the interruption in operation time due to construction will result in significant production losses.
It is extremely important to reduce this interruption time as much as possible.

Hereinafter, an experimentally produced blast furnace base according to the present invention will be cited as a specific example without limiting the present invention,
This will be explained with reference to the attached drawings.

Figures 1 and 2 show the base plate 1 of the blast furnace.
(A part of the thin metal bottom plate tole de fond) is shown. Steel cooling conduits such as 2 are fixed at intervals on the base plate by flanges such as 3, and threaded rods 5 are connected to the plate via nuts 4 welded to the plate. is fixed.

A hole is formed in the adjusting rod such as 6, and the upper end of the rod 5 passes through this hole. The height of the adjustment rod is adjusted to the reference plane through nuts such as 7 and 8 that hold it. It will be clear that by tightening or loosening the nut on the threaded rod, the height of the adjustment rod upper surface 9 can be adjusted to match the height of the first horizontal reference plane. The average distance between the base plate and the reference surface is about 12 cm. This adjustment is controlled by optical collimation using a spirit level in a manner well known to those skilled in the art. After adjusting the adjustment rod to the height of the first reference plane, fill it with clay composed of 87% by weight of artificial graphite, 10% by weight of phenol formaldehyde resin, and 3% of coagulation catalyst. Using a pneumatic rammer (dame) with a flat veneer of 20 x 20 cm, the compaction process is divided into several steps and repeated continuously to form layers. In this case, the clay is compacted until its density is approximately 1.7. The thickness of the clay layer is adjusted by the method described above so that its surface coincides as perfectly as possible with the first reference plane defined by the upper surface of the adjustment rod.

Once the clay has hardened, remove the adjustment rod used to set the first reference plane and replace it with a rod of the same size but higher precision and a deflection of 0.1.
Install a second set of adjustment rods that do not exceed mm/m. The adjustment rod is first engaged with a threaded rod at its tip;
The height is then adjusted so that the upper surface coincides with a second reference horizontal plane located an average distance of about 3 mm upward from the first reference plane. The adjustment means itself is the same for the second adjustment rod as for the first adjustment rod.

Next, pour grout for leveling into the soil. The grout is composed of 60% by weight of fine powder of artificial graphite with a particle size of less than 0.3 mm, 30% of phenol formaldehyde resin, and 10% of coagulation catalyst, and is used as a ground leveler by sliding it along the Joetsu adjustment rod. A ruler is poured into the gap between the adjustable rods so that the height of the surface corresponds to the height of the upper edge of the adjustable rod. After the grout has hardened, the adjustment rod and threaded rod are removed and the resulting void is filled with a small amount of grout to create a perfectly smooth surface. If there are any irregularities, flatten them by grinding. In this way, a base is created, as shown in FIG. 3, consisting of the clay 10 and the grout layer 11 covering it, the upper surface 12 of which is completely horizontal. On said surface 12 it is possible to place the bottom of the crucible very precisely. Since the surface 12 is completely flat, graphite or semi-graphite blocks or very accurately machined carbon-containing blocks can be assembled in one piece without any bonding agent and with almost no deformation. This is particularly advantageous for mounting in such a way that it can be used for a long period of time without any problems. This combination of blocks creates a favorable thermal contact between the base and the base plate on the one hand, and between the block made of graphite or other carbon-containing material and the base on the other hand, thereby improving the heat flow in the shaft area of the blast furnace. is transmitted extremely smoothly toward the base plate. As a result of measuring the thermal conductivity of a sample of the substrate manufactured in this manner, the average value was 18 W.m ^-1 .K ^-1 .

As for the manufacturing method of the substrate which is the object of the present invention, various manufacturing methods other than the above-mentioned method are possible within the scope of the present invention.

[Brief explanation of drawings]

FIG. 1 is a plan view of the device according to the present invention, FIG. 2 is a sectional view taken along the line AA in FIG. 1, and FIG. 3 is an explanatory view of the base according to the present invention after removing the adjustment rod and the connecting rod. 1...Base plate, 2...Cooling conduit, 3
... Flange, 4, 7, 8 ... Nut, 5 ... Rod, 6 ... Adjustment rod, 9 ... First reference surface, 10 ...
...Made soil layer, 11... Grout layer, 12... Second reference surface.

Claims (1)

[Scope of Claims] 1 Consisting of a layer of clay containing at least 80% graphite and a binder based on a synthetic resin and in direct contact with the hearth bottom, the clay layer containing at least 40%
A base for a blast furnace hearth, characterized in that the base is coated with a thin layer of ground level grout containing finely powdered graphite and a solvent-diluted synthetic resin. 2. The base according to claim 1, wherein the thickness of the clay layer is 5 to 20 cm, and the average thickness of the grout layer is 1 to 5 mm. 3. Placing a group of horizontal rods at an appropriate distance above the hearth bottom, defining a horizontal reference plane with the upper edge of the horizontal rod group, and placing graphite as a base in the space between the reference surface and the hearth bottom. 1. A method for producing a base for a blast furnace, which comprises compactly filling the drilled soil, and covering the dregs with a thin layer of ground leveling grout. 4. Install fixing means on the bottom of the furnace at predetermined intervals, connect the lower end of the connecting means to the fixing means, and connect the upper end to the tip of the horizontal rod so that the height can be adjusted. The manufacturing method according to claim 3, characterized in that the height is adjusted. 5. Adjust the horizontal bar so that it first aligns with the first reference plane, and then, after filling with soil, adjust the horizontal bar so that it is at least 1 mm away from the first reference plane and at the level of the top surface of the grade grout. 5. The manufacturing method according to claim 4, wherein the manufacturing method is made to match a corresponding second reference plane. 6. Claim 5, characterized in that after filling with clay, the horizontal rod used to set the first reference surface is replaced with a precision rod with a deflection of 0.1 mm/m or less to define the second reference surface. The manufacturing method described in section. 7. The manufacturing method according to any one of claims 3 to 6, characterized in that the horizontal bar is removed after the base is solidified. 8. The manufacturing method according to any one of claims 3 to 7, wherein the furnace bottom is made of base pellet. 9. The manufacturing method according to any one of claims 3 to 8, characterized in that the furnace bottom has cooling means for circulating liquid and/or gaseous fluid. 10. The manufacturing method according to claim 9, wherein the cooling means is a tube and is arranged on the base plate.