JP2000313682A - Coating agent for refractory for high temperature furnace and its application - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating agent capable of forming excellent glaze layer capable of providing improved flatness and durability to a refractory by a low temperature application by formulating a specific proportion of a thickening agent to an aqueous solution of an alkali silicate to regulate the viscosity of the aqueous solution at a specified temperature so as to be a specific value. SOLUTION: This coating agent for a high temperature refractory, regulated so that the viscosity of the aqueous solution at 20 deg.C may be 800-10,000 cp is produced by formulating 0.2-10 wt.% thickening agent with an aqueous solution of an alkali silicate. An inorganic thickening agent such as sepiolite and bentonite, and an organic thickening agent such as a carboxymethylcellulose and methylcellulose are cited as the thickening agent. Sodium metasilicate, potassium metasilicate, sodium orthosilicate, potassium orthosilicate or the like is cited as the alkali silicate. An alkali borate (e.g. sodium metaborate) can be used together with the alkali silicate, and 5-15 wt.% B2O3 is preferably included in the glaze layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating agent for high-temperature furnace refractories represented by various industrial furnaces such as a ceramic furnace, a coke oven, and a carbon oven. Melting point and a predetermined coating thickness, thereby covering the surface of refractories exposed to high temperatures and subject to friction, thereby improving the durability and various types of refractories such as bricks that have been thermally degraded. TECHNICAL FIELD The present invention relates to a coating agent for high-temperature furnace refractories which can be used for repairing, and the like, and a method for applying the same.

[0002]

2. Description of the Related Art Bricks, joints, and other refractories used in furnaces, furnace lids, furnace doors, etc. of high-temperature furnaces represented by various industrial furnaces such as ceramic furnaces, coke furnaces, carbon furnaces, etc. Due to severe deterioration due to exposure to high temperatures, repairs using various repair agents are frequently performed on a daily basis. When performing such repairs, there are two types of work: hot work performed during furnace operation and low-temperature (normal temperature) work performed before furnace operation. In general, mortar is mainly used for hot work. A repair agent which is a slurry obtained by mixing a small amount of water with a powder as a component is directly sprayed onto a portion to be repaired. Further, as described in Japanese Patent Publication No. 2748328, there is a method in which glaze is hot-coated on the inner wall surface of a coke oven, and a glaze layer is formed by welding on the surface of the refractory to repair the surface. On the other hand, low temperature (normal temperature)
As an example of construction, a clay-like glaze containing a refractory powder (generally a composition similar to a brick component such as mortar) as a main component, and a frit-like glaze that melts at a high temperature is blended with the refractory powder. A method of applying (adhering) at low temperature (normal temperature) on the surface of an object, drying, and then firing at high temperature is adopted.

[0003]

However, low-temperature (normal temperature) construction using the conventional clay-like glaze has the following problems. Since the melting point of the glaze is high, it was necessary to apply (attach) a clay-like glaze to the surface of the refractory and then heat it to 1000 to 1500 ° C. Since the glaze is almost solid, has low fluidity, and is a kneaded mixture of inorganic component powders, the surface of the refractory cannot be uniformly and thinly coated.

When a hot-applied repairing agent is applied at a low temperature (normal temperature), for example, a repairing agent obtained by mixing a small amount of water or the like with a powder composition mainly composed of mortar is applied at a low temperature (normal temperature). When applied to the refractory surface, the refractory surface is extremely porous, so that it penetrates from the refractory surface to the inside, in particular, the liquid component penetrates, and the fine powder, which is an inorganic component, remains dotted on the surface. Had been in a state. Therefore, a uniform and thin glaze layer having a uniform composition could not be formed. In addition, the same state is obtained when the above-mentioned clay-like glaze is diluted with water and applied. Patent Publication No. 274832
In the method described in No. 8, the glaze layer can be uniformly and thinly formed by welding when hot, but the following phenomenon occurs when the coating is performed at a low temperature (normal temperature). When a completely dissolved aqueous solution type glaze is applied at a low temperature (normal temperature), the glaze will generally be present within the refractory within a few minutes to tens of minutes, depending on the refractory composition, shape and degree of drying. The glaze cannot be formed on the surface of the refractory because it penetrates. When a slurry type glaze is applied at low temperature (normal temperature), the solution part in the glaze is very easy to penetrate from the refractory surface to the inside, while the solid part (undissolved part) in the glaze remains on the refractory surface. The prescribed glaze layer composition cannot be formed on the refractory surface. Generally, only the slurry component (solid component) remains as powder on the surface because the flux component penetrates. Therefore, in order to perform the low-temperature (normal temperature) construction for both the aqueous solution type and the slurry type, the refractory is heated to about 300 ° C. or more in advance, or is applied at a low temperature (normal temperature) and then immediately heated to a high temperature. Had to be placed in a heating furnace. Therefore, although it can be applied to, for example, a brick alone, there is a limit to the size of a refractory and the like, and it cannot be applied to repair of various industrial furnaces such as a ceramic furnace, a coke furnace, and a carbon furnace.

[0005]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned problems, and relates to a low-temperature (normal-temperature) application method applied to repair of various high-temperature furnace refractories and a coating agent therefor. The glaze can be easily formed even when the temperature is raised several days after application at (normal temperature). In addition, the glaze can have a predetermined composition, a predetermined melting point, and a predetermined coating thickness, and can form an excellent glaze layer which improves the smoothness and durability of the refractory at low temperature (normal temperature). In addition, the low temperature (normal temperature) in the present invention refers to a normal temperature such as a room temperature that is not a high temperature environment during operation of the furnace, room temperature, etc.
Not affected by heating furnaces at 800 ° C or higher)
It means the temperature environment, and it is 5 to dare notation
It is a temperature environment of about 200 ° C. The coating agent for high-temperature furnace refractories according to the present invention has a viscosity of 800 to 1000 at 20 ° C. by adding a thickener of 0.2 to 10 wt% to an aqueous solution of alkali silicate.
It is adjusted to 0 cp, and by adjusting the viscosity of the coating agent, the penetration of the coating agent from the surface of a refractory such as a porous brick into the inside is suppressed.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The coating agent of the present invention is basically prepared by adding a thickener to an alkali silicate and adjusting the viscosity to 800 to 10000 cp to obtain a refractory coating material after low-temperature application. Although it has already been described that the permeation into the interior is suppressed, not only does the role of the thickener, but also acts as a property modifier of the glaze layer.

The thickeners usable in the present invention include inorganic thickeners such as sepiolite and bentonite, carboxymethylcellulose (CMC), methylcellulose (M
Organic thickeners such as C). The sepiolite is a hydrous magnesium silicate, the chemical structural formula is shown in _{Si 12 Mg 8 O 30 (OH} ) 4 (OH 2) 4 · 8H 2 O, thicken due to the thixotropy conventionally in various fields, sedimentation It is used for prevention and sagging prevention. Bentonite also has a different composition from sepiolite, but its basic properties are similar to sepiolite, such as paints, inks,
It is used as a thickener for other liquid compositions. Methylcellulose is obtained by methylation of cellulose ether, and carboxymethylcellulose (CMC) can be said to be a derivative thereof, and these have been conventionally used mainly for sizing agents in many applications.

[0008] The coating agent for high temperature furnace refractories containing these thickeners of the present invention has a high viscosity and is sometimes gelled. When applied to porous refractories such as bricks at low temperatures such as room temperature, in low-viscosity aqueous solutions or slurries that do not contain thickeners, the amount of water that permeates into the interior over time and remains on the surface is reduced. In the case of a slurry, the solution part penetrates into the inside, and disadvantages such as the fine powder part remaining on the surface occur. The composition of the present invention can solve these problems and can be fixed as a uniform composition on the surface as a whole.

The alkali silicates usable in the present invention include, for example, sodium metasilicate, potassium metasilicate, sodium orthosilicate, potassium orthosilicate and hydrates thereof, No. 1 water glass, No. 2 water glass, No. 3 There is water glass and the like. Furthermore, besides alkali silicate, Si
Examples of the compound serving as an O ₂ source include SiO ₂ , kaolin minerals, pottery stone, rubble, celite, diatomaceous earth, and the like. Fine powder can be added as a slurry to these minerals.

In the present invention, an alkali borate may be used in combination with the alkali silicate as a glass-forming component. Particularly, B ₂ O ₃ in the glaze layer contains ₅ to 15 watts.
It is desirable that t content be contained. As the alkali borate, for example, sodium and potassium salts such as metaboric acid, orthoboric acid, and tetraboric acid, and those obtained by reacting boric acid with sodium hydroxide and / or potassium hydroxide may be used.

Further, Li is used as a flux for forming a glaze layer.
OH ・ H_TwoO, Li_TwoCO_Three, LiNO _Three, LiCl, etc.
An i-compound can also be added.

In the present invention, a property modifier may be added and compounded.
It has the role of changing the properties of the glaze layer formed at high temperatures, such as reducing the hot tack of the glaze layer surface, improving the peelability of the glaze layer and carbon, improving the smoothness of the glaze layer surface, It shows characteristics such as improvement of hot shock resistance of the layer surface. Specifically, as the property modifier, a phosphate compound, a barium compound, a strontium compound,
Iron compounds, aluminum compounds, magnesium compounds,
One or more of a calcium compound, a zirconium compound, a titanium compound, a lead compound, and a zinc compound can be used.

Examples of the phosphoric acid compound used as a property modifier include sodium and potassium salts such as tertiary phosphoric acid, secondary phosphoric acid, metaphosphoric acid, pyrophosphoric acid, and polymerized phosphoric acid (tripolyphosphoric acid, hexametaphosphoric acid). There is.
Further, when all or a part of the P ₂ O ₅ source is derived from at least one selected from the group consisting of calcium phosphate, magnesium phosphate, aluminum phosphate, barium phosphate, and iron phosphate, Is preferred because it does not react with water glass based glass at a high temperature and forms a high melting point glass surface on the surface of the glass layer.

A phosphoric acid compound used as a property modifier
Other compounds other than the above are also exemplified below. barium
(Ba) Compounds include BaO, Ba (OH)_Two, Ba
CO_Three, BaCl_Two, Ba (NO_Three)_TwoOxides, such as hydroxide
Substances, carbonates, chlorides, nitrates, etc. can be used
You. As the strontium (Sr) compound, SrO,
Sr (OH)_Two, SrCO_Three, SrCl_Two, Sr (NO_Three)_Twoetc
Oxides, hydroxides, carbonates, chlorides, nitrates, etc.
Can be. Examples of iron (Fe) compounds include Fe_Two
O_Three, Fe_ThreeO_Four, FeOOH, ferrocyanide potassium
, Potassium ferricyanide, sodium ferrocyanide
Ferrous phosphate, phosphorus, sodium ferricyanide, etc.
Ferric acid, iron chelate of EDTA (Na, K, NH
_FourEtc.) can be used. Aluminum (A
l) The compound is Al_TwoO_Three, Al (OH)_Three, Al_TwoO
_Three・ H _TwoO, Al_TwoO_Three・ 3H_TwoO, AlCl_Three, Al (N
O_Three)_Three, AlPO_FourOxides, hydroxides, chlorides, nitrates, etc.
Acid salts and phosphates can be used. magnesium
(Mg) compounds include MgO, Mg (OH)_Two, Mg
CO_Three, MgCl_Two, Mg (NO_Three)_TwoOxides, such as hydroxide
Substances, carbonates, chlorides, nitrates, etc. can be used
You. Calcium (Ca) compounds include CaO, Ca
(OH)_Two, CaCO_Three, CaCl_Two, Ca (NO_Three)_Two, Ca_Three
(PO_Four)_Two, Ca_TwoP_TwoO₇, Ca (PO_Three)_TwoOxides such as water
Use oxides, carbonates, chlorides, nitrates, phosphates, etc.
Can be As a zirconium (Zr) compound
Is ZrO_Two, ZrSiO_Four, Zr (NO_Three)_Four, ZrC
l_Two, ZrCl_Four, Zircon sand (composition ZrO_Two66%, S
iO_Two33%) oxides, chlorides, nitrates, spinels
A structure or the like can be used. Titanium (Ti) compound
The thing is TiO_Two, TiO, Ti_TwoO_Three, TiO_Two・ H_Two
O, TiO_Two・ 2H_TwoO, TiCl_Two, TiCl_ThreeOxidation of etc.
, Chloride and the like can be used. Lead (Pb) compound
As an object, Pb_ThreeO_Four, PbO, Pb_TwoO_Three, PbO_Two,
Pb_ThreeO _Two(OH)_Two, PbCO_Three, PbCl_Four, Pb (NO_Three)
_TwoOxides, hydroxides, carbonates, chlorides, nitrates, etc.
Can be used. As a zinc (Zn) compound,
ZnO, Zn (OH)_Two, ZnCO_Three, ZnCl_Two, Zn (N
O_Three)_Two, Zn_Three(PO_Four)_Two, Zn_TwoP_TwoO₇Oxides, hydroxyl, etc.
Use chlorides, carbonates, chlorides, nitrates, phosphates, etc.
be able to.

Furthermore, the present invention may be 0.2～3Wt% added blended with SO ₃ relative to sulphate (SO ₄₎ compounds, this SO ₄ compound, coating agent melt of the present invention When it becomes, it moves to the surface of the molten glass as an SO ₃ component, and at that time, convection and diffusion are caused in the vitreous composition in a molten state, thereby promoting homogenization of the vitreous by a mixing action. When the coating agent of the present invention vitrifies in the melting process, CO ₂ , H ₂ O, O ₂ ,
It generates gas components such as SO ₂ and generates small bubbles in the molten vitreous composition, but the SO ₃ component significantly reduces the surface tension of the molten vitreous surface. it can. Further, when the SO ₃ component reaches the surface of the molten glass, a high-melting substance mainly composed of Na ₂ SO ₄ or K ₂ SO ₄ is formed as a spot pattern on the surface. Due to these effects, when the SO ₄ compound is added, the process from the molten state to vitrification is short, and the adhesiveness of the glass surface at high temperature can be reduced in a short time.
From these facts, it is a matter of course that even when carbon adheres to the vitreous surface, the carbon has good releasability, so that the coke extrusion resistance can be reduced at an early stage. As described above, this SO ₄ compound is contained in an amount of 0.2 to ₃ wt% based on SO ₃ ,
If it is less than 3 wt%, the effect of the above-mentioned SO ₄ component addition cannot be expected. Further, if it is added in excess of 3 wt%, the smoothness of the vitreous surface is lost, and the sliding performance is reduced.

These SOs_FourAs a compound, lithium sulfate
Um (Li_TwoSO_Four), Sodium sulfate (Na_TwoSO_Four),
Potassium sulfate (K_TwoSO_Four), Iron sulfate (FeSO_Four, Fe
_Two(SO_Four) _Three), Barium sulfate (BaSO)_Four), Sulfate sulfate
Ntium (SrSO_Four), Aluminum sulfate (Al_Two(S
O_Four)_Three), Aluminum potassium sulfate (AlK (S
O_Four)_Two), Magnesium sulfate (MgSO4)_Four), Magnesium sulfate
Potassium potassium (K_TwoMg_Two(SO_Four) _Three), Calcium sulfate
(CaSO_Four), Lead sulfate (PbSO_Four), Zinc sulfate (Zn
SO _Four), Copper sulfate (CuSO_Four), Nickel sulfate (NiS
O_Four) And sulfuric acid.

The application object of the coating agent of the present invention is not particularly limited, but the following high-temperature furnace refractories are more preferable than high-temperature furnaces of a type that operates continuously for a long period of time. That is, 1. 1. High-temperature furnace refractories that repeat heating and cooling, such as small industrial furnaces and ceramic furnaces. 2. The refractory of a high-temperature furnace, in which the shape of the furnace is not uniform and hot work cannot be performed with a coating machine inserted. 3. High temperature furnace refractories, where repairs are limited. Refractory parts that are frequently replaced, such as high temperature furnace doors. In particular, in places where the opening and closing are repeated frequently, such as in a coke oven door, an iron core is generally placed inside the refractory to reinforce cracks and breakage of the refractory. ₂ iron core, etc.
The refractory has deteriorated and is being repaired within about two years. Therefore, when the coating agent according to the present invention is applied to the above-mentioned application objects, the smoothness of the surface of the refractory is improved, the intrusion of atmosphere components, such as carbon, CO, O ₂ , SO _2, etc., into the inside of the refractory is prevented, and It has the effects of preventing adhesion of the refractory, improving the hot impact resistance of the refractory, and improving the durability of the refractory.

In the method of applying a coating agent of the present invention, for example, a door of a coke oven or the like is sprayed with a coating agent aqueous solution having the above-mentioned structure on a surface of a high temperature furnace refractory cooled to room temperature or sprayed with a brush, a spatula, a trowel or the like. 0.2-5kg /
m ² , and left for several hours to several days at room temperature. Then, after holding at a high temperature equal to or higher than the melting point of the glaze for several hours or more to fix and form the glaze layer on the surface of the refractory, it is left to cool and then mounted in a furnace.

[0019]

EXAMPLE First water glass (Na ₂ O: 17 to 19% by weight, SiO ₂ : 35) specified in JIS K 1408
３８38% by weight, water: remaining weight%, No. 2 water glass (Na ₂
O: 14~15 weight%, SiO _2: 34~36% by weight,
Water: residual weight%), No. 3 water glass (Na ₂ O: 9 to 10 weight%, SiO ₂ : 28 to 30 weight%, water: residual weight%), potassium metasilicate as the main component, and hydroxylation An aqueous solution or slurry was prepared by adding lithium, boric acid compound, metal phosphate, barium sulfate, strontium compound, magnesium carbonate, aluminum oxide, titanium dioxide, zinc oxide, etc. and water. Further, a thickener was gradually added to this solution to prepare an aqueous solution or slurry having high viscosity. Table 1 shows the composition of the thickener, and Table 2 shows the composition of the composition.
It is described in Table 3. Tables 4 and 5 show the oxides of the components (excluding components that evaporate at a high temperature) in this blended composition. Since the SO ₃ component moves to the glaze layer surface at a high temperature, the theoretical amount of the formulation is not included in the glaze layer composition, but is shown in Table 4.
5 is shown. The highly viscous aqueous solution or slurry shown in Tables 2 and 3 was applied to the surface of the sample refractory brick at room temperature with a brush.
The components of the refractory brick are as shown in Table 6. The application amount is
It was 1 kg per m ^{2 of} surface area. Two days after standing at room temperature, the surface of the brick of the coating composition was visually observed, and then the sample refractory brick was kept at 950 ° C. for 60 minutes and cooled naturally. Tests were conducted on the peelability of the glaze layer and the brick after cooling, the smoothness of the glaze layer surface, and the hot shock resistance of the glaze layer surface. The test method and its evaluation are as follows. In addition, the same test was carried out for a comparative example (conventional example) showing the composition of the composition in Table 7, and the results are shown. Table 8 shows oxides (excluding components that evaporate at high temperatures) of the components of the compounds in Table 7 in terms of oxides.

(A) Adhesion between glaze layer and brick Test method: The brick after cooling was dropped from a height of 2 m, and the state was observed. Evaluation method: ：: Complete adhesion ○: About 10% peeling △: About 20% peeling

(B) Smoothness of glaze layer surface Test method: Judgment was made by visual observation and finger observation of the cooled brick. Evaluation method: ：: Totally smooth ○: Partially concave △: Surface irregularity

(C) Hot impact resistance of glaze layer surface Test method: The glaze layer was cut off with a sharp iron column while the brick was kept at 950 ° C., and the state at that time was observed and evaluated. Evaluation method: ：: Hard surface and no scratches ○: Hard surface but some scratches △: Cracks occur at impact part

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

[Table 4]

[0027]

[Table 5]

[0028]

[Table 6]

[0029]

[Table 7]

[0030]

[Table 8]

According to visual observation and finger touch observation, Examples 1 to 1
Each of the coating liquids of No. 4 is uniformly applied on the brick surface, and a part of the coating liquid is crystallized in white (powder), but has elasticity when touched with a finger, and the outer part is dried. Even so, the inside was kept hydrated. On the other hand, in Comparative Examples 1 to 3, the coating liquid completely penetrated inside, and hardly remained on the surface. In Comparative Example 4, the white fine powder remained on the entire surface of the brick, but it was easily peeled off when touched with a finger, and the subsequent surface state was the same as Comparative Examples 1 to 3.
That is, in Comparative Example 4, the solid content of the slurry remained on the brick surface after being separated over time, and the liquid component had permeated into the brick.

[0032]

As described above, the coating agent for high temperature furnace refractories of the present invention has higher strength at room temperature application than the conventional coating agent, and has high impact resistance, excellent smoothness, and durability. And long-term protection of refractory bricks in high-temperature furnaces became possible.

Claims (10)

[Claims] A thickener is added to an aqueous solution of an alkali silicate salt.
A coating agent for high temperature furnace refractories, wherein 2 to 10 wt% is blended and the viscosity of the aqueous solution at 20 ° C. is adjusted to 800 to 10000 cp. 2. The coating agent for high temperature furnace refractories according to claim 1, further comprising a borate. 3. The coating agent for a high-temperature refractory according to claim 1, wherein a property modifier is added and blended. 4. The property modifying agent is one or two of a phosphoric acid compound, a barium compound, a strontium compound, an iron compound, an aluminum compound, a magnesium compound, a calcium compound, a zirconium compound, a titanium compound, a lead compound, and a zinc compound. The high temperature furnace refractory coating agent according to claim 3, characterized in that: 5. The sulfate compound is converted to an SO ₃ amount of 0.
2. The composition according to claim 1, wherein 2 to 3 wt% is added.
The high temperature furnace refractory coating agent according to any one of claims 4 to 4. 6. The sulfate compound is lithium sulfate, sodium sulfate, potassium sulfate, iron sulfate, barium sulfate, strontium sulfate, aluminum sulfate, potassium aluminum sulfate, magnesium sulfate, potassium magnesium sulfate, calcium sulfate, lead sulfate, zinc sulfate. The high temperature furnace refractory coating agent according to claim 5, wherein the coating agent is at least one of copper, nickel sulfate, nickel sulfate, and sulfuric acid. 7. The glaze layer formed on the surface of a high temperature furnace refractory, wherein B ₂ O ₃ is contained in a composition of ₅ to 15 wt%. Item 7. The coating agent for high temperature furnace refractories according to Item. 8. The method of claim 8, wherein the thickener is sepiolite, bentonite,
The high temperature furnace refractory coating agent according to any one of claims 1 to 7, wherein the coating agent is at least one of carboxymethylcellulose and methylcellulose. 9. The coating agent for a high-temperature furnace refractory according to claim 1, wherein the high-temperature furnace refractory is at least one of bricks, joints, and irregular-shaped refractories. 10. The glaze has a melting point of 500 to 1000 ° C., and the coating agent according to any one of claims 1 to 9 is applied to the surface of a high temperature furnace refractory at room temperature, and then has a melting point of not lower than the melting point. A method for applying a coating agent for high-temperature furnace refractories, which comprises raising the temperature and forming a glaze layer by welding.