JP3128213B2 - Glaze for forming glassy glaze layer on refractory surface in furnace and method for forming glassy glaze layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for hot or cold construction of refractory bricks, irregular refractories, joints, etc., which are walls of a high-temperature furnace, to form a glass-like glaze layer on the surface of the refractory. And a method for forming a glassy glaze layer.

[0002]

BACKGROUND OF THE INVENTION High temperature furnaces, such as coke ovens, produce coke by steaming coal at about 1100 DEG C. for 20 to 25 hours. Tar-like substances and hydrocarbon gases are generated during the coal distillation process. These are the inner wall of the coke oven,
It penetrates into gaps such as furnace lids and coal inlets, and open pores of the furnace refractory, and undergoes pyrolytic carbonization to form strong carbon deposits. The carbon firing furnace produces carbon by firing carbon raw materials. When the carbon raw material is fired, a part of the carbon is scattered and firmly grows on the refractory in the furnace.

[0003] The carbon deposits lower the melting point of the refractory and cause embrittlement of the refractory. In addition, the deposited carbon deposits make it difficult to open and close the furnace lid and deteriorate the hermeticity of the furnace lid to the furnace. For this reason, the adhered carbon is mechanically removed, but the adherence is so strong that the removal operation takes a long time and the working environment is poor. Further, during the removal operation, the surface of the refractory itself may be scraped off. As another method, burning is performed by blowing air or oxygen gas, but in this method, the working range is limited to the vicinity of the furnace port. To clean the entire area of the furnace, the furnace must be shut down and the furnace left empty to burn down. However, the burn-off operation itself is a severe high-temperature operation, and the combustion heat at the time of burn-down brings a local high-temperature state to the refractory of the furnace body,
It may cause furnace body damage. In addition, a coke oven, for example, is subject to joint breakage due to long-term use.

In order to cope with such a situation, various studies have been made on a refractory to which carbon does not easily adhere and a method for coating the surface of the refractory with a coating film to which carbon does not easily adhere and for repairing joint breakage. For example, Japanese Patent Publication No. 62-19777: A composition comprising silicon carbide, silicon nitride or graphite particles and an inorganic binder is applied to a lining brick in a coke oven. JP-A-62-197371: A heat-resistant and tar-based substance permeation preventive agent made of silicon carbide, silicon nitride, or the like, a binder made of phosphate, yttrium oxide, or the like, and a heat-insulating agent made of potassium titanate fiber Is applied to the inner wall surface of the coke oven. JP-B-63-40463: A graphite powder and an inorganic binder such as colloidal silica and alumina sol are applied to a lining refractory for a door of a coke oven. JP-A-63-236783: Simultaneously firing a glaze and a brick to produce a refractory brick for a coke oven having a glaze layer formed thereon.

[0005] Among the above-mentioned methods, the method using silicon carbide, silicon nitride or graphite, etc., has poor adhesion between the particles and the binder, has insufficient adhesion strength, and the coating layer peels off during operation. There is a problem of doing.

[0006] The method of using a brick on which a glaze layer is formed is as follows.
It has good adhesion and does not fall off during operation. Also, since there are almost no pores in the glaze layer coating, carbon is not penetrated and this is a very effective method. However, when a coke oven or a furnace lid is newly manufactured, this method is applicable, but it is impossible to form a glaze layer on the surface of the refractory of the furnace while operating the furnace.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been described in the art.
It is an object of the present invention to provide a glaze that is formed by hot or cold glazing to form a dense and durable glass-like glaze layer on a wall refractory, and a method of forming a glass-like glaze layer.

[0008]

Means for Solving the Problems The present invention provides a composition for forming a glaze, on an oxide basis, R ₂ O (R represents Na or K, the same applies hereinafter) is 10 to 40 wt%, the balance To S
A glaze that contains iO ₂ and has a melting point of 900 ° C. or less, and a glassy glaze layer is formed on a surface of a refractory in a furnace by hot working or cold working.

The present inventors have tested the availability of various metal oxide combinations as glazes when used with silicon oxide, and melted at a temperature of 900 ° C. or less, and some of the components after melting. Volatilized or diffused below the operating temperature of the high-temperature furnace, the melting point thereof increased, and a metal oxide that did not melt at the operating temperature of the high-temperature furnace was found, thus completing the present invention.

[0010] In the present specification, the glaze refers to a chemical applied to the surface of a refractory constituting a furnace body of a high-temperature furnace. It is sufficient that the metal oxide contains a metal salt or a metal compound which is converted into an oxide after the application and a silicate compound, and it is not always necessary to include the oxide before the application.

According to the present invention, the glaze comprises R ₂ O of 10-4.
It contains 0% by weight and the balance SiO ₂ . R ₂ O is Na ₂ O
Alternatively, it may be composed of K ₂ O, and may be a mixture of both.
If the content of R ₂ O is less than 10% by weight, the melting point of the glaze will not be 900 ° C. or less, and if it exceeds 40% by weight, the melting point will be too low, and it will take time for the melting point to rise after construction, so that it will be applied to the vertical surface. When it is done, it causes a drooping phenomenon. Furthermore, the amount of volatiles from the glaze layer increases, and a dense glaze layer cannot be formed.

Suitable precursors to be converted to the oxides are hydroxides, carbonates, nitrates, phosphates of the same metal,
Sulfate, chloride and the like can be mentioned. The precursor can be converted to an oxide after application, preferably at a temperature of about 600 ° C. or higher.

As a precursor of Na ₂ O, sodium hydroxide, sodium carbonate, sodium hydrogen carbonate, sodium nitrate, sodium phosphate, sodium sulfate, sodium chloride, sodium silicate and the like are preferable.

As precursors of K ₂ O, potassium hydroxide, potassium carbonate, potassium hydrogen carbonate, potassium nitrate,
Potassium phosphate, potassium sulfate, potassium chloride, potassium silicate and the like are preferred.

In the present invention, the reason why the melting point of the glaze rises after the application at a temperature lower than the operating temperature of the high-temperature furnace is considered to be that some of the components in the composition volatilize or diffuse with time. Although the details of this mechanism do not limit the present invention, when R ₂ O coexists with SiO ₂ , the melting point (Si
(O ₂ alone, 1728 ° C) significantly decreases. Since these alkali metal oxides have a large diffusion coefficient and a relatively high vapor pressure, they diffuse and volatilize over time after application, and the composition of the glaze layer approaches the SiO ₂ film, and as a result, the melting point increases.

In the present invention, as a composition for forming a glaze layer, Li ₂ O is 0 to 10% by weight and B ₂ O ₃
There 0-10 wt%, and R ₂ O is 10 to 40 wt%, and a SiO ₂ to the remainder, and the glassy glaze into the furnace refractory surface, wherein the melting point of 900 ° C. or less Glaze formed by hot or cold work.

Further, the present invention is characterized in that it contains 0.2 to 10% by weight of Li ₂ O. The present invention, the B ₂ O _3, characterized in that it comprises 0.5 to 10 wt%.

The glaze according to the invention is based on oxides, Li
₂ O, 0 to about 10% by weight, B ₂ O ₃ , 0 to about 10% by weight
It is preferable to include Furthermore Li ₂ O, 0.2 to about 10 wt% and / or B ₂ O _3, it is particularly preferred to include about 10 wt% 0.5.

Therefore, the composition of the glaze is represented by R ₂
O, in addition to 10 to 40 wt% and the balance as the basic composition consisting of SiO _2, the composition of a first preferred glaze,
Li ₂ O, 0.2 to 10% by weight, R ₂ O, 10 to 40% by weight and the balance being SiO ₂ , and B ₂ O ₃ , 0.5 to 10% by weight, R ₂
O, 10 to 40% by weight, with the balance being SiO _2, and a third suitable glaze composition, Li ₂ O, 0.
2-10 wt%, B ₂ O _3, 0.5~10 wt%, R
₂ O, 10 to 40% by weight, with the balance being SiO ₂ .

Li ₂ O and B ₂ O ₃ are effective in lowering the melting point of the glaze, and are easily volatilized by increasing the temperature after the glaze layer is formed. Li ₂ O, B ₂ O ₃ ratio of 10% by weight
If it exceeds, the melting point becomes too low, which is not preferred.

The melting point of the glaze used in the present invention must be set at a temperature not higher than the actual furnace temperature and at about 900 ° C. or less in consideration of the peripheral portion of the refractory on the inner wall of the furnace. It is also one embodiment of the present invention to appropriately adjust the component ratio of the composition so that the melting point is equal to or lower than the set value. Specifically, in the case of a ternary system of Li ₂ O—Na ₂ O—SiO ₂ , the state diagram (for example, FCKracek,
J. Am. Chem. Soc., 61,2871 (1939)).
The weight percent of each component is determined in an appropriate region of 00 ° C. or lower, and precursors of Li ₂ O, Na ₂ O, and SiO ₂ are mixed in specified amounts so as to give a desired component ratio, thereby obtaining a glaze of the present invention. be able to.

[0022] Li ₂ O, B ₂ O ₃ is used to glaze as an aqueous solution or slurry in the form of R ₂ O and also precursors.
As the precursor of Li ₂ O, lithium hydroxide, lithium carbonate, lithium hydrogen carbonate, lithium nitrate, lithium phosphate, lithium sulfate, lithium chloride, lithium silicate and the like are preferable. As a precursor of B ₂ O ₃ , boric acid, sodium borate, potassium borate and the like are preferable.

As described above, the glaze according to the present invention is R ₂ O
From 10 to 40% by weight, and Li ₂ O from 0 to 10% by weight,
B comprises ₂ and O ₃ 0-10 weight%, and SiO ₂ in the remainder. That is, it does not prevent inclusion of substances other than R ₂ O, Li ₂ O, B ₂ O ₃ and SiO ₂ . R ₂ O, Li ₂ O, B
Substances other than ₂ O ₃ and SiO ₂ include Al ₂ O ₃ and Mg.
O, CaO, ZrO ₂ , and TiO ₂ (hereinafter, referred to as Al ₂ O ₃ ) are preferable. Al ₂ O ₃ etc., when the glaze forms a glaze layer on the surface of the refractory, improves the familiarity between the refractory and the glaze layer, and cracks the glaze layer due to the difference in thermal expansion between the refractory and the glaze layer. To prevent the occurrence of

[0024]

[0025]

[0026]

[0027]

[0028]

Further, the present invention is characterized in that the compound forming SiO _{2 comprises} at least one compound selected from the group consisting of sodium silicate, potassium silicate and lithium silicate, and an alkali siliconate.

In the present invention, the alkali siliconate is sodium methylsiliconate, and CH ₃ SiO _1.5
It is characterized in that it is 2% by weight to 30% by weight on the basis.

According to the invention, as the compound for forming the SiO ₂ (SiO ₂ precursor), the foregoing is preferred. Also particularly preferred sodium methyl siliconate alkali siliconate titanate, which is particularly preferably one containing 2 to 30% by weight of the compound forming the SiO ₂ in CH ₃ SiO _1.5 standards.

[0032] The invention is also characterized in that the refractory in the furnace is selected from the group consisting of refractory bricks, joints and irregular refractories.

According to the present invention, the refractory in the furnace for forming a glaze layer by applying a glaze is not particularly limited, but is preferably used for refractory bricks, joints and irregular refractories.
Particularly, it is preferable for repairing joint breakage by hot.

The present invention is also a method for forming a glassy glaze layer, wherein the glaze is hot-worked on the surface of a refractory in a furnace.

In order to apply the glaze according to the present invention to the surface of the refractory constituting the inner wall surface of the high-temperature furnace, a standard application method such as applying or spraying the glaze on a predetermined surface with a brush or a trowel is used. . Therefore, in order to apply the glaze uniformly on the surface of the refractory, the glaze is desirably made into an aqueous solution or a slurry close to the aqueous solution. Among the above-mentioned metal salts and metal compounds, water-soluble ones can be easily prepared in an aqueous solution so that the metal has a desired composition ratio. Those insoluble or hardly soluble in water are finely pulverized, dispersed in water and used as a slurry.

The concentration of the solid content in terms of metal oxide in the aqueous solution to be applied is usually about 5 to about 50% by weight, preferably about 10 to about 50% by weight.
Adjust to about 40% by weight. When the concentration is about 50% by weight or more, gelation is likely to occur due to heat during construction, and the spray nozzle is clogged. On the other hand, when the content is less than about 5% by weight, a large amount of the aqueous solution of the composition is required to form a sufficient film, and the efficiency of construction is reduced. The thickness of the glaze layer is not particularly limited, but may be practically about 3 mm or less.

According to the present invention, the glaze is applied at a high temperature near its melting point. Therefore, at the time of application, moisture evaporates, the glaze melts on the surface of the refractory, and a uniform and dense glassy glaze layer is formed on the surface of the refractory. The molten glaze layer has a high viscosity and does not hang down in a short time even if formed on a vertical wall surface. The melting point of the glaze layer rises with time and becomes higher than the operating temperature of the high-temperature furnace, so that it becomes a firm film and does not melt again. High-temperature construction can be performed without stopping the furnace operation, but must be performed from outside the furnace using a long-handled iron, brush or spray tool, and is suitable for small-scale repairs.

Further, the present invention provides a method for forming a glass-like glaze layer, wherein the glaze is cold-worked on the surface of the refractory in the furnace and then heated to a temperature not lower than the melting point of the glaze and not higher than the operating temperature of the furnace. It is.

According to the present invention, the glaze is applied at a low temperature of 100 ° C. or less. The shape of the glaze is in the form of an aqueous solution or slurry as in hot working. In low-temperature application, the temperature of the coke oven is raised after application, moisture evaporates first, and then the glaze melts at the melting temperature of the glaze, forming a uniform and dense glaze layer on the surface of the refractory. Before the temperature is raised, the melting point of the glaze layer increases, and a firm glaze layer film is formed. The low-temperature coating can be performed in a good working environment, so that complete coating can be performed. However, the operation of the coke oven has to be temporarily stopped, which is suitable for large-scale repair.

In the prior art, various glazes are known, but since the composition does not take into account the melting point, the glaze layer melts and hangs down after construction, exposing refractories, and It cannot be kept glassy and looks like syrup and promotes adhesion of carbon. Also, the glaze layer may be scraped off by the carbon particles, so that satisfactory results cannot be obtained. On the other hand, the glaze of the present invention takes into consideration the melting point as described above, and after the application, the glaze is melted to form a glaze layer which is firmly welded to the surface of the refractory, and a part of the glaze layer is formed below the furnace operating temperature. Component evaporates and the melting point rises, forming a glass-like glaze layer having a melting temperature higher than the operating temperature of the high-temperature furnace.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail with reference to the following examples, but the present invention is not limited by these examples. In the examples, all “%” represent% by weight.

Example 1 No. 3 water glass (Na ₂ O)
8.7%, SiO ₂ 27.8%, water 63.5%) 1
00 parts by weight, lithium silicate (2.2% Li ₂ O, Si
50 parts by weight of O _{2 (} 20%) were mixed and stirred until a completely transparent liquid was obtained. This is designated as solution A.

Lithium hydroxide (LiO) was added to 959 parts by weight of water.
H) 96 parts by weight were added and dissolved. Then, 318 parts by weight of boric acid powder (H ₃ BO ₃ ) was added, and the mixture was stirred to make a completely transparent liquid. This is designated as solution B.

Sodium methylsiliconate (Na ₂
(10.7% of O, 20% of CH ₃ SiO _1.5 : 17.9% as SiO ₂ ) 12.5 parts by weight of the liquid B was added to 100 parts by weight, and the mixture was stirred until a transparent liquid was obtained. This is designated as liquid C.

To 100 parts by weight of the liquid A, 30 parts by weight of the liquid C was added and stirred until a transparent liquid was obtained. This is designated as solution D.

In these preparations, heating at 70 to 80 ° C. to increase the speed did not change the results.

When the obtained glaze composition became an oxide, the glaze composition was 21.7% of Na ₂ O and Li ₂ O
_{2.2%, B 2 O 3 1.1} %, was SiO ₂ 75.0%. A commercially available castable brick containing 36% of SiO _{2 and} 54% of Al ₂ O ₃ was cut into 100 × 100 × 40 mm to prepare a test refractory piece.

The test piece was placed in a furnace at 900 ° C. and heated.
After confirming that the temperature of the brick had risen to 900 ° C., the brick was taken out and, at the same time, the liquid D was sprayed on the brick surface with a spray gun. Initially, the brick foamed, but after about one minute, it melted and a uniform, strong glass coating was formed. This was placed again in a furnace at 900 ° C. and held for 2 hours.

A slurry comprising 5 parts of coal powder and 3 parts of coal tar was applied to the brick on which the glaze layer film was formed in this manner, and heated and maintained at 800 ° C. for 3 hours in an inert atmosphere (for example, under nitrogen). After cooling, the adhesion carbon was easily peeled off using an adhesive tape, and the carbon was easily peeled off.

On the other hand, in the sample to which the glaze composition of the present invention was not applied, carbon was firmly adhered to the brick surface and could not be completely removed even by applying a mechanical force.

(Example 2) No. 3 water glass (Na ₂ O)
9.6%, SiO ₂ 27.8%, water 62.6%) 1
00%, lithium silicate (2.2% Li ₂ O, SiO ₂
(20%, water 77.8%) 4.4 parts by weight were mixed and stirred until a completely transparent liquid was obtained, which was used as Liquid A.

To 100 parts by weight of liquid A, 10.1 parts by weight of water was added, and then 2.7 parts by weight of liquid B having the same composition as in Example 1 were added. Finally, sodium methylsiliconate (Na ₂
O 10.7%, CH ₃ SiO _1.5 20.0%: SiO ₂
17.9%) and stirred until a clear liquid was obtained. This is designated as solution D.

When the obtained glaze composition turned into an oxide, the glaze composition was Na ₂ O 25.8%, Li ₂ O
_{0.4%, B 2 O 3 1.0} %, was SiO ₂ 72.8%. The composition before the methyl group of sodium methylsiliconate disappeared was SiO ₂ 67.8%,
Li ₂ O 0.4%, Na ₂ O 25.6%, B ₂ O ₃
1.0% and CH ₃ SiO _1.5 5.2%. Test refractory pieces similar to those in Example 1 were prepared.

This test piece was placed in a furnace at 900 ° C. and heated. After confirming that the temperature of the brick had risen to 900 ° C., the brick was taken out and, at the same time, the liquid D was sprayed on the brick surface with a spray gun. Initially, the brick foamed, but after about one minute, it melted and a uniform, strong glass coating was formed.

A solution having substantially the same composition except that the amount of sodium methylsiliconate was reduced to 1/5 was used as solution E.

The obtained solution E had a glaze composition of 25.0% Na ₂ O, 0.5% Li ₂ O,
B ₂ O _{3 was} 1.1% and SiO _{2 was} 73.5%.

The composition before the methyl group of sodium methylsiliconate disappeared was SiO ₂ 72.4
%, Li ₂ O 0.5%, Na ₂ O 24.9%, B ₂ O ₃
1.3% and CH ₃ SiO _1.5 1.1%.

This was tested in the same manner as in Example 1. As a result, a uniform and strong glass film was formed. However, when it was applied to a vertical surface of a brick, a considerable portion was drooped.

(Examples 3 to 6) A glaze composition was prepared in the same manner as in Example 1 so that the composition of the glaze was as shown in Table 1. Was evaluated for peeling. Table 1 shows the composition and evaluation results.
Shown in

Example 7 100 parts by weight of Solution D of the glaze composition of Example 1 and 20 parts by weight of alumina powder having an average particle size of 5 μm were mixed to form a slurry to obtain a glaze.

This slurry was sprayed on bricks in the same manner as in Example 1. The formed film was not transparent, but the surface was glossy and glassy.

(Comparative Examples 1-2) A composition was prepared in the same manner as in Example 1 so that the composition of the glaze was as shown in Table 1, and the obtained glaze layer was evaluated. Table 1 shows the compositions and evaluation results.

[0063]

[Table 1]

The melting points are 600 ° C., 700 ° C., 800 ° C., 9
When heat-treated at 00 ° C. and 1000 ° C., it was estimated by visual observation whether the glaze melted and formed a glaze layer.

From the test results shown in Table 1, the glazes of the examples have excellent film formation and a remarkable effect of preventing carbon adhesion.
It became clear that the glaze of the comparative example was inferior in both.

(High Temperature Holding Test) The brick covered with the glaze layer obtained in Example 1 was held at a temperature of 900 ° C. for about 5 hours, and the components in the glaze layer coating of the fired brick were analyzed.
The molar ratio of ₂ / Na ₂ O was 3.5, which was higher than the initial 3.0.
₂ O tended to decrease.

Further, when the temperature was maintained at 1100 ° C. for 1 hour, the molar ratio was 7.5, and a remarkable decrease in Na ₂ O was observed. At this time, B ₂ O ₃ and Li ₂ O were not detected. The melting point of this glaze layer was 1300 ° C. or higher, and a remarkable melting point increasing effect was observed from the initial melting point of 800 ° C. or lower.

[0068]

As described above, according to the present invention, a glaze containing R ₂ O and SiO ₂ and having a melting point of 900 ° C. or less.
These glazes of the present invention are hot-worked or cold-worked and then melt at a temperature equal to or higher than the melting point to form a glassy glaze layer. As time passes, the melting point of the glaze layer increases below the operating temperature of the high-temperature furnace and does not melt again at the operating temperature of the high-temperature furnace. As a result, a dense and uniform glass-like glaze layer is firmly formed on the surface of the refractory constituting the high-temperature furnace, and carbon generated by high-temperature operation hardly adheres to the surface of the refractory, and a small amount of the carbon adheres. The removed carbon can be easily peeled off and the surface of the refractory can be easily repaired.

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Claims (11)

(57) [Claims] 1. A composition for forming a glaze layer, which contains, on an oxide basis, 10 to 40% by weight of R ₂ O (R represents Na or K), the balance containing SiO ₂ and a melting point of 900. ° C
A glaze for forming a glassy glaze layer on a refractory surface in a furnace by hot working, characterized by the following. 2. The composition for forming a glaze layer contains, on an oxide basis, 10 to 40% by weight of R ₂ O (R represents Na or K), the balance being SiO ₂ and a melting point of 900. ° C
A glaze that forms a glassy glaze layer on the surface of a refractory in a furnace by cold working, characterized in that: 3. A composition for forming a glaze layer, wherein, based on oxides, Li ₂ O is 0 to 10% by weight, B ₂ O ₃ is 0 to 10% by weight, and R ₂ O (R represents Na or K). ) Contains 10 to 40% by weight, the balance being SiO ₂ and having a melting point of 900 ° C.
A glaze for forming a glassy glaze layer on a refractory surface in a furnace by hot working, characterized by the following. 4. A composition for forming a glaze layer, wherein, based on oxides, Li ₂ O is 0 to 10% by weight, B ₂ O ₃ is 0 to 10% by weight, and R ₂ O (R represents Na or K). ) Contains 10 to 40% by weight, the balance being SiO ₂ and having a melting point of 900 ° C.
A glaze that forms a glassy glaze layer on the surface of a refractory in a furnace by cold working, characterized in that: 5. The glaze according to claim 3, comprising 0.2 to 10% by weight of Li ₂ O. 6. The glaze according to claim 3, comprising 0.5 to 10% by weight of B ₂ O ₃ . 7. The glaze according to claim 1, wherein the compound forming SiO ₂ is at least one selected from the group consisting of sodium silicate, potassium silicate and lithium silicate, and an alkali siliconate. 8. The glaze according to claim 7, wherein the alkali siliconate is sodium methylsiliconate and is 2% to 30% by weight based on CH ₃ SiO _1.5 . 9. The glaze according to claim 1, wherein the refractory in the furnace is selected from the group consisting of refractory bricks, joints and irregular refractories. 10. A method for forming a glassy glaze layer, wherein the glaze according to claim 1 is hot-worked on the surface of a refractory in a furnace. 11. The method according to claim 1, wherein the glaze according to any one of claims 1 to 9 is cold-worked on the surface of the refractory in the furnace, and then heated to a temperature equal to or higher than the melting point of the glaze and equal to or lower than the operating temperature of the furnace. A method for forming a glass-like glaze layer.