JP3981994B2 - Refractory repair and strengthening method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for repairing and strengthening a refractory within a sealable space.
[0002]
[Prior art]
In general, refractories constituting the inner walls of industrial furnaces and molten metal containers are damaged by cracks and the like due to thermal spalling and the like. As a refractory repair method, a method of spraying a mixture of refractory powder and water to a damaged portion, that is, a wet spray method is known. However, since this method is performed after the furnace temperature is lowered, it takes time to cool the furnace and raise the temperature after repair work. Therefore, it is necessary to stop the operation of the furnace for a long time. In addition, this wet spraying method does not exhibit sufficient bonding strength to the sprayed refractory, and thus is easily peeled off with a slight impact. Therefore, this method is only used as a temporary measure.
[0003]
Therefore, thermal spraying has been proposed as a repair method for refractories. In this method, the refractory powder is made to be in a semi-molten or molten state in a flame composed of oxygen and fuel gas, or by burning aluminum or silicon, and adhered to the damaged part of the refractory. For example, Japanese Patent Application Laid-Open No. Sho 62-15508 discloses a flame sprayed material applied for such a purpose.
[0004]
Japanese Patent Publication No. 3-9185 discloses a high-silica material composed of a specific ratio of SiO ₂ , Al ₂ O ₃ , CaO, Fe ₂ O ₃ and Na ₂ O and forming a thermal spray repair body that can withstand long-term use. A thermally sprayed material is disclosed. In construction, these thermal spray materials are melted by a flame, collide with a repaired portion, and rapidly solidify to form a thermal spray body mainly composed of a glass phase.
[0005]
In an industrial furnace or the like, when the quartz brick that constitutes the furnace wall is severely damaged, transshipment of the damaged brick is performed. Brick transshipment is performed hot to avoid damage associated with cooling of existing bricks. For example, Japanese Patent Laid-Open No. 5-132355 discloses a hot-repaired quartzite brick for use in hot-replacement repair of a coke oven wall brick, which has excellent heat resistance and wear resistance. Yes.
[0006]
[Problems to be solved by the invention]
However, the sprayed body mainly composed of the glass phase described in Japanese Patent Application Laid-Open No. 62-15508 or Japanese Patent Publication No. 3-9185 crystallizes in the cooling process and transitions to the crystalline phase. Since the volume shrinks during this phase transition, cracking occurs. For this reason, the thermal spray repair body is insufficiently bonded to the base material and cannot be used for a long time. In particular, when the base material is denatured and the strength is reduced, cracks develop from the base material side and the thermal spray repaired body falls off. Accordingly, the life of the thermal spray repaired body is not determined only by the strength of the thermal spray itself or the spalling resistance, and there is a problem of such a problem that the thermal spray repaired body falls off, and the life is about half a year.
[0007]
Moreover, in order to apply this method, it is necessary to specify a damaged part beforehand. However, the region is not limited to a portion that can be observed from the outside, and it is generally difficult to identify the damaged portion by observing the inside of the furnace.
[0008]
The hot transshipment repair technique described in Japanese Patent Application Laid-Open No. 5-132355 is a more reliable method than the flame spraying method, but involves a high-temperature heavy reinforcement work in the hot state and has a problem in the work environment. In addition, since the work takes a long time, it is necessary to stop the operation of the furnace for a long time.
[0009]
The present invention has been made to solve the above problems, can be repaired hot, can be easily carried out without specifying a damaged portion, and prevents the repaired body from falling off the repaired portion. Provide refractory repair methods that can be used.
[0010]
[Means for Solving the Problems]
Gas this invention, an industrial furnace having a furnace lid, in the repair method of strengthening refractory within a sealable space container of molten metal, a first said space is evacuated, then, contains a metal or a metal compound Or one of the reactive gases that react with the metal or metal compound to precipitate another solid metal compound, and then supply the other gas into the space. Thus, there is provided a method for repairing and strengthening a refractory, wherein the solid metal compound is deposited as a refractory on a damaged portion of the refractory.
[0011]
Here, the space which can be sealed is, for example, an equipment having a refractory inside such as an industrial furnace having a furnace lid, a container of molten metal and the like. About the container etc. of a molten metal, the inside becomes the space which can be sealed by preparing a suitable lid.
[0012]
Next, for a gas containing a metal or a metal compound, a metal having a high vapor pressure such as Mg is desirable as the metal gas, and the metal compound gas is an alkyl metal bonded to an alkyl group, a halide, an oxyhalide, Various compounds such as hydrohalides and alkoxides can be used.
[0013]
For example, examples of the alkyl metal include Al (CH ₃ ) ₃ , Al (C ₂ H ₅ ) ₃ , Si (CH ₃ ) ₄ , Si (C ₂ H ₅ ) _{4 and the} like. Examples of the alkoxide include Al (C ₃ H ₇ O) ₃ , Si (CH ₃ O) ₄ , Si (C ₂ H ₅ O) _{4 and the} like. Examples of the halide include AlCl ₃ , SiCl ₄ , TiCl ₄ , and ZrCl ₄ . Examples of oxyhalides include Si ₂ OCl ₆ and ZrOCl ₂ . Hydrohalides SiH ₂ Cl _{2 and the} like.
[0014]
These may be used only with a gas of a metal or a metal compound, or may be used after being diluted with a gas that does not react with the metal or the metal compound. As the diluent gas, for example, N ₂ or Ar may be used, and dry air can also be used when it does not react with H ₂ O and O ₂ .
[0015]
As the reactive gas, a gas that reacts with a gas (metal or metal compound) containing the above metal or metal compound metal to precipitate a solid of another metal compound is used. Here, the other solid metal compound may have a function as a refractory, but it is desirable that the coefficient of thermal expansion and the like are as equal as those of the refractory to be repaired. Therefore, it is preferable to use the same metal compound as the refractory to be repaired.
[0016]
As the reactive gas, for example, O ₂ , H ₂ O, CO ₂ , N ₂ , NH ₃ , N ₂ O, and various hydrocarbons can be used. Examples of the various hydrocarbons are alkanes such as CH ₄ , C ₂ H ₅ and C ₃ H ₇ , alkenes such as C ₂ H ₄ and C ₃ H ₆ , and alkynes such as C ₂ H ₂ .
[0017]
When O ₂ is used as the reactive gas, a metal oxide solid can be precipitated by reaction with various metals or metal compounds. The individual reactions are shown below.
[0018]
Mg + 1 / 2O ₂ → MgO
Al ₂ Cl ₆ + 3 / 2O ₂ → Al ₂ O ₃ + 3Cl ₂
SiH ₄ + O ₂ → SiO ₂ + 2H ₂
MgCl ₂ + 1 / 2O ₂ → MgO ₃ + Cl ₂
TiCl ₄ + O ₂ → TiO ₂ + 2Cl ₂
ZrCl ₄ + O ₂ → ZrO ₂ + 2Cl ₂
Al (CH ₃ ) ₃ + 15 / 2O ₂ → 1 / 2Al ₂ O ₃ + 3CO ₂ + 9 / 2H ₂
[0019]
When H ₂ O is used as the reactive gas, a metal oxide solid can be precipitated by reaction with various metals or metal compounds. The individual reactions are shown below.
[0020]
Mg + H ₂ O → MgO + H ₂
MgCl ₂ + H ₂ O → MgO + 2HCl
SiCl ₄ + H ₂ O → SiO ₂ + 4HCl
TiCl ₄ + H ₂ O → TiO ₂ + 4HCl
ZrCl ₄ + H ₂ O → ZrO ₂ + 4HCl
Al ₂ Cl ₆ + 3H ₂ O → Al ₂ O ₃ + 6HCl
Al (C ₂ H ₅ ) ₃ + 3H ₂ O → 1/2 Al ₂ O ₃ + 3C ₂ H ₆
Si (CH ₃ O) ₄ + 2H ₂ O → SiO ₂ + 4CH ₃ OH
Si (C ₂ H ₅ O) ₄ + 2H ₂ O → SiO ₂ + 4C ₂ H ₅ OH
[0021]
When CO ₂ is used as the reactive gas, a metal oxide solid can be precipitated by reaction with various metals or metal compounds. The individual reactions are shown below.
[0022]
Mg + CO ₂ → MgO + CO
SiH ₄ + 2CO ₂ → SiO ₂ + 2CO + 2H ₂
[0023]
When a mixed gas of CO ₂ and H ₂ is used as the reactive gas, a metal oxide solid can be precipitated by reaction with various metals or metal compounds. The individual reactions are shown below.
[0024]
MgCl ₂ + CO ₂ + H ₂ → MgO + CO + 2HCl
Al ₂ Cl ₆ + 3CO ₂ + 3H ₂ O → Al ₂ O ₃ + 3CO + 6HCl
[0025]
When a mixed gas of N ₂ and H ₂ is used as the reactive gas, a metal nitride solid can be precipitated by reaction with various metals or metal compounds. The reaction is shown below.
[0026]
Al ₂ Cl ₆ + N ₂ + 3H ₂ → 2AlN + 6HCl
[0027]
When NH ₃ is used as the reactive gas, a metal nitride solid can be precipitated by reaction with various metals or metal compounds. The individual reactions are shown below.
[0028]
SiH ₄ + 4 / 3NH ₃ → 1/3 Si ₃ N ₄ + 4H ₂
3SiH ₂ Cl ₂ + 10NH ₃ → Si ₃ N ₄ + 6NH ₄ Cl
SiCl ₄ + 16 / 3NH ₃ → 1 / 3Si ₃ N ₄ + 4NH ₄ Cl
TiCl ₄ + 4 / 3NH ₃ → TiN + 4HCl + 1 / 6N ₂
ZrCl ₄ + 4 / 3NH ₃ → ZrN + 4HCl + 1 / 6N ₂
[0029]
When CH ₄ is used as the reactive gas, a metal carbide solid can be precipitated by reaction with various metals or metal compounds. The individual reactions are shown below.
[0030]
SiH ₄ + CH ₄ → SiC + 4H ₂
TiCl ₄ + CH ₄ → TiC + 4HCl
TiI ₄ + CH ₄ → TiC + 4HI
[0031]
When a mixed gas of C ₂ H ₅ and H ₂ is used as the reactive gas, a metal nitride solid can be deposited by reaction with various metals or metal compounds. The reaction is shown below.
[0032]
TiI ₄ + 1 / 2C ₂ H ₅ + 3 / 2H ₂ → TiC + 4HI
[0033]
When a mixed gas of CH ₄ and H ₂ is used as the reactive gas, a solid metal carbide can be precipitated by reaction with various metals or metal compounds. The reaction is shown below.
[0034]
CrCl ₃ + 3 / 2CH ₄ + 1 / 3H ₂ → 1/3 Cr ₃ C ₂ + 3HCl
[0035]
The metal or metal compound gas may be a mixture of a plurality of metals and a plurality of metal compound gases. Also, as for the reactive gas, a mixed gas other than the above-mentioned mixed gas of reactive gas may be used. In these cases, a precipitate composed of a plurality of components can be obtained according to the composition of each gas.
[0036]
The appropriate reaction temperature of the metal or metal compound gas and the reactive gas differs depending on the combination of the two.
[0037]
For combinations of alkyl metals with O ₂ and H ₂ O, temperatures in the range of 300-800 ° C. are desirable. This is because the reaction rate is too slow at less than 300 ° C., while the alkyl metal is thermally decomposed at temperatures exceeding 800 ° C., making it difficult to achieve the intended reaction.
[0038]
For combinations of alkoxide and H ₂ O, temperatures in the range of 200-700 ° C. are desirable. This is because the reaction rate is too slow at less than 200 ° C., while the alkoxide is thermally decomposed at temperatures exceeding 700 ° C., making it difficult to achieve the intended reaction.
[0039]
The combination of halide, oxyhalide, or hydrohalide with O ₂ , H ₂ O, CO ₂ , N ₂ , NH ₃ , N ₂ O, and various hydrocarbons is a temperature of 600 ° C. or higher. Is desirable. This is because the reaction rate is too slow below 600 ° C.
[0040]
In the combination of Mg vapor and O ₂ , H ₂ O, and CO ₂ , a temperature of 700 ° C. or higher is desirable. This is because part of the Mg vapor is likely to condense at the stage of transfer to the reaction site at less than 700 ° C., so that Mg cannot be effectively used for the intended reaction.
[0041]
Mg vapor may be generated by heating molten Mg. In this case, the heating temperature is preferably in the range of 700 to 1200 ° C. This is because the generation rate of Mg vapor is too slow below 700 ° C., whereas the generation of Mg vapor becomes intense when it exceeds 1200 ° C., and it becomes difficult to control the flow rate and pressure of the gas containing this. It is.
[0042]
Mg as a starting material may be ingot or powder. When Mg is a powder, it may be a single Mg or a mixed powder of Mg—CaO and Mg—Al. Since Mg powder is easily ignited, mixed powder is preferable.
[0043]
Mg vapor may be generated by reacting MgO and Al as follows.
3MgO + 2Al → 3Mg + Al ₂ O ₃
In this case, the reaction temperature is preferably in the range of 850 to 1700 ° C. This is because the reaction rate is too slow below 850 ° C., while on the other hand, when it exceeds 1700 ° C., the generation of Mg vapor becomes violent, making it difficult to control the flow rate and pressure of the gas containing this.
[0044]
The concentration of the metal or metal compound contained in the gas (dilution gas) containing the metal or metal compound is 0.1 vol. % Or more is desirable. This is 0.1 vol. This is because the reaction rate is too slow at less than%.
[0045]
The concentration of the reaction gas contained in the gas containing the reaction gas (dilution gas) is 1 vol. % Or more is desirable. This is 1 vol. This is because the reaction rate is too slow at less than%.
[0046]
As a gas containing the reaction gas (dilution gas), when two or more kinds of gases are selected from O ₂ , H ₂ O, CO ₂ , and N ₂ , a pure gas may be mixed. Various combustion gases may be used. As the combustion gas, any gas obtained by burning natural gas, liquefied petroleum gas, kerosene, heavy oil, coal, coke oven gas, blast furnace gas, converter gas, or the like with air or oxygen can be used. Moreover, you may use the exhaust gas of various heating furnaces as needed. When CH ₄ is used as the reaction gas, natural gas or coke oven gas may be heated before use.
[0047]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view showing a cross section of a crack in a refractory. In the figure, 1 is a refractory, 2a is a fine crack, 2b is a large crack, and 60 is a deposit layer. The gas containing metal or metal compound filled in the cracks 2a and 2b reacts with the reaction gas mainly on the surface of the refractory, and solids on the surface of the refractory inside the damaged portion, that is, on the fracture surface of the crack. 60 is deposited.
[0048]
If this reaction continues, the gas containing the metal or metal compound is consumed, so that the reaction gas gradually enters the interior of the crack or the like. In this way, while the reaction interface of the two kinds of gases advances deep into the damaged part such as a crack, the solid 60 is deposited inside the crack and the fine crack 2a is buried. In this way, it is possible to repair fine cracks that are difficult to find.
[0049]
Even in the case of the large crack 2b, the reaction between the gas containing the metal or the metal compound and the reaction gas continues on the surface of the refractory 1, and solid deposition continues on the surface of the refractory. Therefore, a layer of precipitate 60 is formed on the surface of the refractory. Thereby, the surface (fracture surface) of the crack 2b is covered with the layer of a solid precipitate, and is protected.
[0050]
Hereinafter, embodiments of the coke oven will be described. The wall of the coke oven (also called a partition wall) is usually made of silica brick. Therefore, a silicon compound is suitable as a metal compound for repair. Of the silicon compounds, SiCl ₄ is a thermally stable substance and is particularly desirable because it does not thermally decompose within the entire range of 900-1450 ° C., which is the furnace wall temperature during coke oven operation. As dilution gas or carrier gas of SiCl ₄ , dry air, N ₂ , inert gas, or the like can be used.
[0051]
H ₂ O is most desirable as a reactive gas component to be reacted with SiCl ₄ . This is because H ₂ O has a very high reaction rate with SiCl _{4 in the} above temperature range, so that the reaction proceeds unless the supply amount of H ₂ O falls below the stoichiometric value.
[0052]
As the H ₂ O gas, that is, water vapor, one generated in an ironworks can be used. Moreover, water vapor is contained in combustion gas such as an industrial furnace, and can be used. For example, if coke oven gas or blast furnace gas is burned with air, H ₂ O is changed to 1 to 25 vol. %, 5~30vol the CO _2. % Containing gas is obtained. At this time, if it is burned with excess air, a gas containing O ₂ can also be prepared. If O ₂ is enriched and steam is blown, the concentration of H ₂ O, CO ₂ and O ₂ can be increased while maintaining an appropriate temperature.
[0053]
FIG. 2 is a cross-sectional view showing a cross section of the coke oven. In the figure, 10 is a furnace wall, 11 is a heating chamber, 12 is a heated chamber, 36 is a combustion gas inlet, 37 is a gas introduction port, 47 is an introduction gas, and 49 is a combustion gas.
[0054]
First, the heated chamber 12 is evacuated to remove internal air. Next, a gas 47 containing SiCl ₄ is introduced from the gas inlet 37. Since the air in the heated chamber 12 is removed including a damaged portion such as a crack of the refractory, the gas 47 containing a metal or a metal compound penetrates deeply into the damaged portion such as a crack. In this state, a gas 47 containing water vapor is introduced into the heated chamber 12. At this time, the reaction between the two gases also occurs, but the remaining water vapor reaches the damaged part.
[0055]
A gas containing SiCl ₄ and water vapor enter the inside of a crack or the like, and a solid is deposited inside the crack to fill the fine crack. Even in the case of a large crack, the reaction continues on the surface of the crack, and solid deposition continues on the surface of the refractory (the fracture surface of the crack). Therefore, the surface of the crack is covered and protected with a layer of precipitate.
[0056]
【The invention's effect】
In the present invention, since the refractory is repaired by precipitating another solid metal compound from the gas containing the metal or metal compound, it can be repaired hot and simple without specifying the damaged portion. Can be implemented. Further, by depositing a metal compound having the same refractory and thermal expansion coefficient as another solid metal compound, it is possible to solve the problem of dropping off the repaired portion of the repaired body.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a cross section of a refractory crack.
FIG. 2 is a cross-sectional view showing a cross section of a coke oven.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Refractory 2a Fine crack 2b Large crack 10 Furnace wall 11 Heating chamber 12 Heated chamber 36 Gas for combustion 37 Gas inlet 47 Gas for introduction 49 Gas for combustion 60 Deposit layer

Claims (1)

Industrial furnace having a furnace lid, in the repair method of strengthening refractory within a sealable space container of molten metal, the space is evacuated first, and then, gas, or the metal containing metal or a metal compound Alternatively, any one of the reactive gases that react with the metal compound to precipitate another solid metal compound is supplied into the space, and then the other gas is supplied into the space to provide a refractory. A method for repairing and strengthening a refractory, comprising depositing the solid metal compound as a refractory on a damaged portion of the refractory.

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