JPS6128915B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to firing or calcination (herein, calcination is expressed as calcination) of carbonaceous products such as electrodes for arc furnaces, electrodes for aluminum electrolytic furnaces, and electrode plates. It is related to a furnace for heating.

In general, these carbonaceous products are molded using pitztar as a binding material, and then used as a product after being calcined or fired at about 1000 to 1400℃, or after being heat-treated in a graphitization furnace after firing. There are some things.

When firing these products, in order to prevent the products from deforming or oxidizing during firing, the products are generally stuffed into the furnace with a filler mainly made of coke powder, and the side walls and intermediate walls are packed together. The product to be fired is heated by combustion gas through the brick wall from the bottom of the furnace, and the volatile components contained in tar and pitch are burned off and carbonized.

For this firing, a large furnace called a single furnace, a spherical furnace, or a ring kiln is generally used, and typical examples include a lead hammer furnace, a Pessine type furnace, and an Alkyant type furnace.
The side walls, intermediate walls, etc. of these firing furnaces are constructed with cavities so that combustion gas can pass through them and heat the object to be fired. Furnace construction work is carried out by assembling or combining small blocks with small cavities, but thousands of blocks are required to construct just one intermediate wall or side wall, Furnace construction work was extremely complicated and required a great deal of labor.

The present invention successfully solves these problems by applying several to more than ten large refractory blocks having cavities on the side walls and/or intermediate walls of the kiln.
This problem was solved, and they succeeded in providing a kiln that greatly simplified the furnace construction work and had sufficient fire resistance.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is an explanatory longitudinal cross-sectional view showing a typical firing furnace consisting of a carbonization chamber, which is a firing chamber for carbonaceous products, and a combustion chamber having a combustion gas passage.

In the drawings, reference numeral 1 denotes a firing chamber, and a carbonaceous product 2, which is an object to be fired, is placed in a chamber filled with coke powder 3. Here, the firing room is
It is divided by a side wall 4 and an intermediate wall 5, and if there is only one firing chamber, the intermediate wall is not necessarily necessary, and if more firing chambers are provided, the number of intermediate walls will increase accordingly.

In these firing furnaces, conventional side walls 4 and intermediate walls 5 are made of small blocks (for example, 460 mm), as described above.
The combustion gas passage 7 was constructed using a large number of bricks 6, for example, usually 2,400 or so.

The combustion gas flows through the gas passage formed in this way roughly in the direction of arrows A→B, and the heat is applied to the firing chamber through fireproof walls such as side walls and intermediate walls, thereby heating the product.

FIG. 2 is a sectional view showing a firing furnace according to the invention, in which several large refractory blocks 8 form one side wall 4.
The large block 8 has at least one cavity 9 that serves as a combustion gas passage 7.

Here, the large blob, which is the main requirement of the present invention, will be explained.

As described above, the large refractory block (hereinafter referred to as "large block") 8 in the present invention has at least one cavity 9 and has a contact surface area (hereinafter referred to as "firing chamber surface area") 10 facing the firing chamber with the firing chamber. is at least 10,000 cm ² or more, and the simplest shape is shown in Figure 3. The one in Figure 3 is, for example, a: 1305.6, b: 900, c: 500, wall thickness
100 (all units are mm), the surface area of the firing chamber is approximately 12,550 ^cm2 , and there is one cavity, and the contact area with the combustion gas of this cavity (hereinafter referred to as gas contact area) is It is approximately ^27700cm2 .

By using such large blocks, walls that had previously been constructed using approximately 2,500 regular-sized bricks,
It is now possible to construct a furnace with only 12 pieces, and the construction work itself using a crane has become easier, and the time required for furnace construction is less than 1/10 of the previous time (for example, 40 hours or 3 hours).
time).

This ease of furnace construction work is most effective when the surface area of the large block firing chamber is at least 10,000 cm ^{2 or} more. However, if it is too large, it will not be easy to manufacture it, it will be difficult to transport it, and it will require more labor than building the furnace, so it has to be limited to a maximum of about 40,000 ^cm2 . do not have.

Because of such a large block, one of the advantages of the present invention is that it is possible to form a large gas flow passage inside with just one block, which not only facilitates the simplicity of furnace construction work but also greatly reduces the The durability of the block can also be improved and the firing efficiency can also be improved.

Considering these points, the gas contact surface area of one cavity is preferably 10,000 cm ² or more,
On the other hand, if it is too large, the strength of the structure will decrease, making it easy for the block to be damaged during transportation or furnace construction, and it is also undesirable because it is likely to break due to mechanical shock when loading and unloading objects to be fired, so the upper limit should be around 30,000 ^cm2 . The goal is to stay.

In addition, in one large block, when the furnace wall is constructed, the opening ratio of the cavity in the cross section, that is, the opening ratio in the cross section perpendicular to the gas passage direction, is approximately 40
~85% is good; if this is too large, the thickness of the part of the large block made of refractory material becomes thinner, which tends to reduce the block's resistance to mechanical shock; if it is too small, gas contact Since the area becomes smaller, the effect of firing the object to be fired is reduced, and there are problems such as increased fuel consumption for firing the object to be fired at a predetermined temperature, a long firing time, etc. This is because it is necessary to heat the object to be fired at a higher temperature through the cavity, which reduces the durability of the large block.

Also, in one large block, the number of cavities is usually one, or two as in many of the examples described below.
It is desirable that the size of the large block be small due to the above-mentioned advantage of increasing the gas contact area in one cavity, and the purpose can be sufficiently achieved at that level. However, if the large block is very large, If the area of the large block that comes into contact with the object to be fired is large and the block is thin, it is advantageous to have a large number of cavities in terms of the strength of the structure.
In addition, it may be advantageous to have a large number of cavities so that the combustion gas uniformly heats the wall surface. For example, in a firing chamber with a surface area of 12,000 cm ² or more, it may be effective to provide 2 to 6 holes.

In any case, it is neither necessary nor desirable to provide ten or more cavities in one large block.

Next, some of the major blocks of the present invention will be explained with reference to FIGS. 4 to 10.

The one shown in FIG. 4 is an example in which protrusions, grooves, or recesses are formed at predetermined positions on the upper and lower sides or on the sides, as in some other examples, and the upper end surface 11 has two The convex protrusion 12 is connected to the lower end surface 13
A recessed groove portion 14 is shown in the figure.

Here, the protrusion is preferably formed on either the upper or lower end surface, preferably along the longitudinal direction,
Concave grooves are formed on the other surfaces of the upper and lower end surfaces on which the projections are formed.

This is because when or when constructing a furnace wall by constructing large blocks, it is easy to construct them next to each other and it is possible to construct them firmly. Effective in use.

The number, position, length, etc. of the protrusions can be determined as appropriate depending on the manner of use, but it is best to form them at least in the longitudinal direction.

Fig. 5 shows an example in which the cavity 9 is formed in two places, for example, a: 1080, b: 945, c: 500, wall thickness.
By using 100 bricks (all units are mm), it is now possible to build something that used to use about 2,400 bricks using about 12 bricks.
Work efficiency has been greatly improved, with furnace construction work now reduced from 40 hours with two people to just three hours with two people.

FIG. 6 shows an example in which the cross-sectional shape of the cavity is triangular. In this case, it is usually advantageous in terms of heating effect to make the opening wider on the firing chamber surface area 10 side.

FIG. 7 shows an example in which a single concave portion 15 is formed on both side surfaces in addition to the protrusions and grooves on the upper and lower end surfaces.

Here, it is preferable that the concave portion on this side surface be formed in the vertical direction especially when constructed in the longitudinal direction of the end surface, and one side surface may have a convex strip 16 (see FIG. 8) depending on the case. You can also leave it as If the concave portion on the side surface and the convex stripe portion on the side surface of the adjacent block are constructed to fit together, a solid furnace wall can be constructed.

FIG. 8 shows six cavities 9, two protrusions 12 in the longitudinal direction and two protrusions 17 in the transverse direction on the upper end surface 11 (corresponding grooves on the lower end surface), and a recess on the side surface. An example in which a portion 15 and a protruding portion 16 are respectively formed is shown.

FIG. 9 shows a protrusion 12 and a groove 1 on each of the upper and lower end surfaces in order to further increase the construction effect.
4, and corresponding grooves and protrusions are formed on the other surface.

FIG. 10 shows an example of a large block located at the lower part of the side wall or intermediate wall, in which a combustion gas inlet/outlet hole 18 is formed on the side surface.

In the present invention, the firing furnace has an intermediate wall and/or a side wall constructed of such large blocks, but of course, in a furnace provided with an intermediate wall, both the side wall and the entire or most part of the wall are constructed with the large block. It goes without saying that it is desirable to construct the block by using the blocks, and it is also natural to use other medium and small blocks in part.

The structure of the present invention has been explained so far, and in order to make the present invention possible, a fireproof molded body with large blocks and high strength is required. The inventors of the present invention have studied various desirable things, and the results can be said to have made the present invention possible.

Although the large refractory blocks that make the present invention possible can be obtained in several ways, the preferred one that makes the present invention possible will be described below.

That is, the large refractory block that makes the present invention possible has alumina cement in the total amount of the refractory material of 1 to 1.
5% by weight, and the refractory material contains ultrafine powder with a particle size of 1μ or less in a ratio of 1 to 17% of the total amount of the refractory material and alumina cement. This type of product is a precast unfired product made by kneading a refractory composition with a small amount of water to form a refractory mixture, and placing this mixture in a predetermined mold to form the product.

According to this method, large precast blocks can be obtained, and these have high strength due to the combination of a small amount of alumina cement and ultrafine powder.

First, the fireproof aggregate should be as hard and dense as possible with fire resistance and corrosion resistance, but various materials can be used, such as silica sand, alumina (electrofused or sintered), calcined clay (bauxite, etc.), etc. is appropriate.

Incidentally, the particle size of this aggregate does not need to be extremely strict, and a range used as ordinary aggregate, for example, about 15 mm to 0.01 mm, is sufficient.

Next, in the total amount of these refractory materials, 1 to 5% of alumina cement, whose main component is calcium aluminate, is mixed to form a refractory composition. We succeeded in reducing the amount to an extremely small amount due to the fine powder.
This enables effects that cannot be obtained with conventional castables.

In other words, it has been considered in the past to construct blocks of this type using castable materials that are easy to construct. Since it has to be used in a large amount (15-30%), it has many pores (approximately 30%) and has disadvantages such as a decrease in strength at 500-1000℃ before ceramic bond formation, which limits its use. In particular, it has been difficult to use large blocks such as those used in the present invention as precast. In the present invention, the content of alumina cement is extremely reduced,
By using a small amount of water and the action of activated fine powder, we were able to reduce the porosity to 10% or less and develop strength, which has excellent hot properties and no strength loss at intermediate temperatures. It has been found that if the amount exceeds 5% of the total amount with the refractory material, this effect will not be sufficiently exhibited, and if the amount is less than 1%, a high-strength product cannot be obtained, which is not preferable.

In addition, the necessity of ultrafine powder in refractory materials means that even with a very small amount of alumina cement, it is possible to provide a refractory structure with remarkable strength and density. This is because it is possible to produce a product with no deterioration in intermediate properties, intermediate strength, or product strength. These characteristics are not desirable if the amount of ultrafine powder is too small, and if it is too large, the filling properties of the molded product will be poor, that is, the compactness will be impaired.

Here, the components of this ultrafine powder are Al ₂ O ₃ ,
Metal oxides such as Cr ₂ O ₃ , ZrO ₂ , TiO ₂ , SiO ₂ or other metal oxides or those having the main component can be preferably used.

According to the present invention, a refractory composition consisting of a predetermined refractory material and a predetermined amount of alumina is kneaded with a small amount of water to form a mixture for obtaining a precast product, and in this case, the amount of water is Generally, 10% or less is sufficient, and in many cases 8% or less is sufficient.

The large refractory block of the present invention is made by putting this irregularly shaped mixture into a mold of a predetermined shape and molding it in advance.This molding can be done in various ways such as pour molding, cast molding, vibration molding, and ram molding. However, it is preferable to use a precast molded body.

The reason why it is necessary to form a molded object in advance even though it has an irregular shape is that it is easier to obtain a sufficient filling degree by vibration molding using a strong mold, and it is better to dry it beforehand. This is because it is preferable. The physical properties of the molded product obtained in this way include a bulk specific gravity of 2.3 or more,
Porosity 13% or less Compressive strength (Kg/cm ² ) in cold
500 or higher, 400 or higher at 1200°C, bending strength of about 100 kg/cm ² even at 1200°C, and softening temperature under load T ₂ of 1450°C or higher.

The present invention thus provides a kiln that significantly simplifies the furnace construction work and has sufficient durability and strength, and has great practical value.

[Brief explanation of the drawing]

FIG. 1 is an explanatory longitudinal cross-sectional view showing an example of a conventional firing furnace, FIG. 2 is an explanatory vertical cross-sectional view showing an example of the firing furnace of the present invention, and FIGS. 3 to 10 are illustrations of the furnace wall of the present invention. A perspective illustration showing several examples of large refractory blocks used is shown. In the drawing, 1 is a firing chamber, 2 is a carbonaceous product to be fired, 4 is a side wall, 5 is an intermediate wall, 7 is a combustion gas passage, 8 is a large refractory block, 9 is a cavity, 10
indicates the surface area of the firing chamber.

Claims (1)

[Claims] 1. Has at least one cavity through which combustion gas can pass and has a gas contact area of 10,000 to 30,000 cm ² , and has a contact area of 10,000 to 40,000 cm ² with the firing chamber, which forms the side surface of the firing chamber. A large refractory block having an aperture ratio of 40 to 85% in a cross section perpendicular to the gas passage direction, the large refractory block containing alumina cement in a total amount of 1 to 5% by weight with the refractory material. and 1μ in the fireproof material.
A refractory composition is formed by kneading a refractory composition consisting of ultrafine powder having the following particle size in a proportion of 1 to 17% of the total amount of refractory material and alumina cement with a small amount of water to form a refractory composition. , a carbonaceous product firing furnace in which the side walls and the intermediate wall are constructed using the large refractory block, which is a tin cast unfired block made by putting this mixture into a predetermined mold and molding it.