JP2011169498A - Wet-spraying method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve poor usability due to low solubility of calcium hydroxide as a lime component of a lime slurry to water, in a wet-spraying method using the lime slurry including calcium chloride. <P>SOLUTION: In this spraying method by force-feeding a monolithic refractory kneaded in advance with water of application, to a nozzle 2, and adding an accelerating agent at or just before the nozzle 2, the lime slurry including calcium chloride is used as the accelerating agent, and the calcium hydroxide as the lime component of the lime slurry has an average particle size of 6-20 μm and a specific surface area of 15 m<SP>2</SP>/g or more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wet spraying method for an amorphous refractory containing refractory powder and alumina cement.

  With reference to FIG. 1, the procedure of the wet spraying construction of an irregular refractory is demonstrated. An irregular refractory is kneaded with water in advance to form mud. The mud is pumped to the nozzle 2 through the pipe 3 by the pump 1. A quick setting agent is added to the mud at the nozzle 2 or in front of it. The quick setting agent is added to the mud together with the compressed air from the quick setting agent tank 4 via the quick setting agent supply pipe 5.

  The primary role of the quick-setting agent is to reduce the fluidity of the mud to prevent the mud that has the fluidity that can be pumped from falling from the work surface S at the moment of spraying. It is to disappear instantaneously. This loss of fluidity is manifested by the rapid setting agent agglomerating the particles in the mud. Hereinafter, the action of agglomerating particles in the mud and causing the fluidity to disappear instantaneously will be referred to as a quick setting action.

  The spray construction body formed on the work surface S by the rapid setting action does not have fluidity, but has a softness that can be trimmed to level the surface using a trowel or the like. Yes. This spray construction body hardens through a hydration reaction of alumina cement during the curing period.

  The second role of the quick-setting agent is to promote hardening by hydration of the alumina cement in the spray construction body, thereby preventing the curing period from becoming too long and cracking the spray construction body during curing. And preventing peeling and the like. Hereinafter, this action of accelerating the hydration of alumina cement will be referred to as a hardening accelerating action.

  Conventionally, as the quick setting agent used in the wet spraying method, alkali aluminate solution, alkali silicate solution (see Patent Document 1), calcium chloride solution (see Patent Document 2), calcium hydroxide powder and water The lime slurry (refer patent documents 3 and 4) which consists of these, or the lime slurry containing calcium chloride (refer patent document 5) is known.

  Of these, alkali aluminates and silicic acid alkali salts have high basicity including caustic soda, and may be irritated when touched directly, and may cause rhinitis when inhaled. For this reason, it is desirable not to use these as much as possible.

  Calcium chloride has an excessively rapid setting action and solidifies before the mud reaches the work surface S, so the amount of rebound of the mud from the work surface S tends to increase, and the hardening is promoted. Therefore, it is necessary to secure the curing period as long as several days, for example, and the strength of the spraying body during curing is small, so that the spraying body is cracked or sprayed on the ceiling. In this case, there is a problem that the sprayed construction body is easily peeled off during curing.

  On the other hand, calcium hydroxide is excellent in curing acceleration effect, but is poor in rapid setting effect. Then, as seen in Patent Document 5, the above-mentioned problem seen in the single use of calcium chloride is alleviated by combining calcium hydroxide with calcium hydroxide.

  That is, at the moment of spraying, the calcium hydroxide excessively reduces the rapid setting action of calcium chloride, or the expression of the setting action of calcium chloride is delayed for about 1 to 2 seconds, thereby reducing the rebound loss. After spraying, calcium hydroxide supplements the hardening promoting effect of calcium chloride.

JP-A-10-118762 JP-A-10-95678 JP 2001-114542 A JP 2001-278664 A Japanese Patent No. 426317

  Calcium chloride powder is easily soluble in water, but calcium hydroxide is difficult to dissolve in water, so it cannot be used in an aqueous solution and must be used in the form of a slurry. Calcium hydroxide particles separate from water in the quick setting agent tank 4 and easily settle, so it is difficult to keep the calcium hydroxide concentration in the quick setting agent constant. Such troubles are likely to occur.

  In this regard, Patent Document 5 explains that the precipitation can be suppressed by making the particles of calcium hydroxide powder fine. Specifically, in Patent Document 5, the average particle size of the calcium hydroxide powder is set to 5.8 μm or less.

  However, when the calcium hydroxide powder is made finer with an average particle size of 5.8 μm or less, it becomes difficult to settle, but once it settles on the bottom of the quick setting agent tank 4 due to the interruption of the spraying operation, the particles are fine. Therefore, it accumulates densely at the bottom of the quick-setting agent tank 4, and it becomes difficult to re-disperse even if the quick-setting agent tank 4 is shaken. In addition, there may be a problem that calcium hydroxide powder is clogged in the quick setting agent supply pipe 5.

  In addition, when the calcium hydroxide powder is fined to an average particle size of 5.8 μm or less, the addition of an amount that can alleviate or delay the excessive rapid setting action of calcium chloride tends to cause excessive hardening promoting action on alumina cement. It is difficult to secure a sufficient period for trimming the sprayed body.

  An object of the present invention is to alleviate the difficulty in use due to the low solubility of calcium hydroxide, which is a lime component of a lime slurry, in water in a wet spraying method using a lime slurry containing calcium chloride. .

According to one aspect of the present invention, a mud that is kneaded by adding water to an irregular refractory containing a refractory powder and alumina cement is pumped toward a nozzle through a pipe, Alternatively, in a wet spraying method in which a quick setting agent comprising a lime slurry containing calcium chloride is added to the mud in the pipe, the lime component of the lime slurry has an average particle size of 6 to 20 μm and a specific surface area of 15 m. There is provided a wet spraying method characterized by using ² / g or more calcium hydroxide powder.

In general, the larger the particle size, the higher the settling speed. However, the calcium hydroxide powder used in the present invention has a large specific surface area of 15 m ² / g or more, although it has an average particle size larger than the conventional one, and the contact area with water Because of the large sedimentation resistance, separation and sedimentation hardly occur in the lime slurry. Since the average particle size of calcium hydroxide powder is large, even if it precipitates, it is difficult to form a dense deposit at the bottom of the quick setting agent tank, and it can be easily redispersed by shaking the quick setting agent tank. .

  Moreover, since the average particle diameter of the calcium hydroxide powder is made larger than before, the hardening accelerating action on the alumina cement is unlikely to be excessive, and the period for trimming the sprayed construction body can be ensured appropriately. If the average particle size of the calcium hydroxide powder is only increased, the solubility in water will be reduced, so the effect of alleviating or delaying the excessive rapid setting action of calcium chloride will be poor, but at the same time the specific surface area was increased. Thus, the effect of relieving or delaying the rapid setting action of calcium chloride at the moment of spraying is hardly impaired, and rebound loss can be suppressed.

It is the schematic which shows a wet spray construction apparatus. It is a graph which shows the time change of the dispersion degree of the lime slurry used as a quick setting agent.

  The amorphous refractory includes refractory powder and alumina cement. The amorphous refractory may contain a binder other than alumina cement, a dispersant, organic fibers, metal powder, a thickener, and the like.

  Examples of the refractory powder include alumina materials such as fused alumina, sintered alumina, bauxite, diaspore, clay shale, and calcined alumina, silica stone, silica sand, amorphous silica (for example, microsilica, silica flour, etc. Siliceous raw materials such as fumed silica and white carbon), alumina silica raw materials such as wax, chamotte, clay, andalusite, sillimanite, kyanite and mullite, coal, coke, pitch, artificial graphite, natural graphite (for example, Carbonaceous raw materials such as carbon black, fused spinel, sintered spinel, magnesia raw materials such as magnesia clinker, dolomitic raw materials such as dolomite clinker, fused zirconia, etc. Zirconia materials, zircon materials such as zircon sand, nitriding From raw materials, aluminum nitride raw materials, silicon carbide raw materials, boron carbide raw materials, titanium boride raw materials, zirconium boride raw materials, etc., and pulverized refractory waste materials mainly composed of at least one of them One or more selected can be used.

  Alumina cement functions as a binder, and the addition amount thereof is preferably 0.5 to 20% by mass, more preferably 2 to 10% by mass, based on 100% by mass of the refractory powder. When it is 0.5% by mass or more, the strength of the obtained refractory near normal temperature becomes particularly good, and when it is 20% by mass or less, good corrosion resistance can be maintained. In addition, the alumina cement preferably has an average particle size of 10 μm or less because the pumpability of the mud can be improved.

  Examples of binders other than alumina cement include aluminum lactate, calcium lactate, aluminum glycolate, lactic acid-aluminum glycolate, hydraulic alumina, magnesia cement, Portland cement, phosphate, and silicate. When these are used in combination, it is appropriate that the amount added is, for example, 20% by mass or less as an outer coating with respect to 100% by mass of the refractory powder.

  The dispersant has the effect of increasing the fluidity of the mud. Specific examples thereof include sodium tripolyphosphate, sodium hexametaphosphate, sodium polyacrylate, sodium polyacrylate, polycarboxylic acid, sodium lignin sulfonate, and carboxyl group-containing polyether. If the addition amount is too small, the effect of improving the fluidity cannot be obtained. If the addition amount is too large, the fluidity is adversely affected. Therefore, 0.01 to 1.5% by mass is applied to 100% by mass of the refractory powder. preferable.

  Examples of the organic fiber include polypropylene fiber, nylon fiber, PVA fiber, polyethylene fiber, acrylic fiber, polyester fiber, and pulp. The addition amount is preferably 0.02 to 1% by mass based on 100% by mass of the refractory powder.

  Examples of the thickener include bentonite, CMC, isoban and the like, and the addition amount is preferably 5% by mass or less as an outer coating with respect to 100% by mass of the refractory powder.

  Examples of the metal powder include aluminum, silicon, ferrosilicon, an aluminum alloy, a silicon alloy, and the like, and the addition amount is preferably 0.01 to 3% by mass based on 100% by mass of the refractory powder.

  The amorphous refractory is kneaded with water in advance and adjusted to a mud shape during wet spraying. The amount of water to be added is not particularly limited, but from the balance between the fluidity imparted to the mud and the corrosion resistance of the obtained refractory, it is, for example, 3 to 15% by weight on the basis of 100% by weight of the amorphous refractory. Preferably, 5 to 12% by mass is more preferable.

  As shown in FIG. 1, such mud is pumped to the nozzle 2 through the pipe 3 by the pumping pump 1, a quick setting agent is added before the nozzle 2 or the nozzle 2, and sprayed on the work surface S. For the purpose of uniformly adding the quick setting agent to the mud and increasing the spraying speed of the mud, it is preferable to add the quick setting to the mud with compressed air.

As the quick setting agent, a slurry obtained by adding at least calcium chloride to a lime slurry (hereinafter referred to as the present slurry) is used. The lime slurry refers to a suspension composed of calcium hydroxide powder and water. As the calcium hydroxide powder that is the lime component of the slurry, one having an average particle diameter of 6 to 20 μm and a specific surface area of 15 m ² / g or more is used. Although the addition amount of this slurry is not specifically limited, From the viewpoint of optimization of quick setting action and hardening acceleration | stimulation action, 0.3-1.5 mass% is preferable with respect to 100 mass% of amorphous refractories.

  In this specification, the average particle diameter means the volume average particle diameter corresponding to the central cumulative value (D50) of the cumulative curve measured with a laser diffraction / scattering particle size distribution meter.

  If the average particle size of the calcium hydroxide powder is less than 6 μm, even if the specific surface area is large, the redispersibility after precipitation is poor and the hardening promoting action on alumina cement is excessive, so trimming the sprayed construction body It is difficult to ensure a sufficient period of time. On the other hand, when the average particle diameter of the calcium hydroxide powder exceeds 20 μm, even if the specific surface area is large, the effect of relaxing or delaying the excessive rapid setting action of calcium chloride becomes poor.

  In this specification, the specific surface area refers to a BET value obtained by a nitrogen adsorption method. The specific surface area can be measured by, for example, a nitrogen adsorption method using a Micromeritics Flow Soap II 2300 manufactured by Shimadzu Corporation.

When the specific surface area of the calcium hydroxide powder is less than 15 m ² / g, separation and sedimentation cannot be suppressed when the average particle size is 6 to 20 μm.

  As an industrial method for producing calcium hydroxide powder, generally, a dry method is used in which quick lime is digested by contacting with water, water is evaporated using heat generated by digestion, and the resulting dried product is pulverized. ing. However, with this dry method, it is difficult to obtain calcium hydroxide powder having a large specific surface area as defined in the present invention.

  Therefore, for example, in the dry method described above, water used for digestion of quicklime is citric acid, oxycarboxylic acid, oxycarboxylate, saccharide, monohydric alcohol, polyhydric alcohol, nonionic surfactant, alcohol amine, succinic acid. Of the calcium hydroxide powder obtained by adding a water-soluble compound such as metal succinate, lignin sulfonate, primary amine, or secondary amine and allowing the digestion to proceed in the presence of these water-soluble compounds. The specific surface area can be increased.

  Since this specific method is publicly known, detailed description thereof is omitted (see, for example, JP-A-10-25112, JP-A-10-152352, JP-A-9-278435, etc.). For example, the particle surface roughness of the calcium hydroxide powder can be adjusted by the amount of the water-soluble compound added. Moreover, the average particle diameter of the calcium hydroxide obtained can be adjusted by the way of grinding and classification of the dried product.

  However, the production method of the calcium hydroxide powder used in the present invention is not particularly limited to the above-described method. For example, by adjusting the temperature of water used for quick lime digestion, etc., the present invention also defines the conventional dry method. Calcium hydroxide powder can be obtained.

  The mass ratio of calcium chloride / calcium hydroxide as a solid content (residue when water as a solvent is evaporated) in the slurry is preferably 30/70 to 90/10. Thereby, the effect of relieving or delaying the excessive rapid setting action of calcium chloride by calcium hydroxide and the effect of supplementing the hardening promoting action of calcium chloride by calcium hydroxide become particularly remarkable.

  The concentration of calcium hydroxide and calcium chloride as solids in the slurry is preferably adjusted so that the total amount of calcium hydroxide and calcium chloride is, for example, 10 to 70% by mass. By making it into this range, further optimization of the quick setting agent and the curing acceleration effect is achieved.

  The solid content of the slurry is preferably such that the total amount of calcium chloride and calcium hydroxide, which is a lime component, occupies 95% by mass or more. Examples of components other than calcium chloride and calcium hydroxide include a precipitation inhibitor in addition to known quick setting agents other than these.

  Examples of the precipitation inhibitor include a dispersion state stabilizer and a foaming agent in addition to the same dispersant as that contained in the above-mentioned amorphous refractory. The addition amount of the precipitation inhibitor is an outer coating with respect to the total amount of 100% by mass (solid content) of calcium chloride and calcium hydroxide in the slurry, and the total amount is preferably 0.05 to 5% by mass.

  As a dispersion state stabilizer, it is adsorbed on the surface of calcium hydroxide particles, inorganic thickeners such as silicic anhydride and clay, which have the effect of increasing the viscosity of water as a solvent and reducing the sedimentation rate of calcium hydroxide particles. Layered, and has the effect of suppressing the sedimentation by forming a sterically loose crosslinking bond between adjacent particles in the entire slurry, for example, CMC, PVA, polyacrylate having a molecular weight of 20,000 or more, etc. There are water-soluble polymers, and one or more substances having the same effect as these can be selected and added according to the use conditions.

  The foaming agent has an effect of causing bubbles to adhere to the particle surface of calcium hydroxide and suppressing sedimentation by the buoyancy of the bubbles. For example, various surfactants such as lauryl sulfate can be selected and added from one or more substances having the same effect as these.

  Measurement using a standard sieve specified in JIS-Z8801, electrofused alumina with a particle size of 8 to 1 mm: 35% by mass, porphyry shale with a particle size of 1 mm or less: 56% by mass, clay: 3% by mass, calcined alumina : 3% by mass, and evaporated silica: 3% by mass of refractory powder 100% by mass, 4% by mass of alumina cement and 0.1% by mass of sodium tripolyphosphate, respectively. The product was kneaded with a mixer with water of 6% by weight of the outer shell to form a slurry.

  The obtained mud is subjected to wet spraying using the apparatus of FIG. The pressure pump 1 is an Allentown 10PRO swing valve double piston pump, the piping 3 is a pressure-resistant hose with an inner diameter of 2 inches and a length of 100 feet, and the nozzle 2 is a pre-pressed rubber nozzle with a length of 200 mm. Was used.

The quick setting agent is supplied using a MONO pump having a snake pump, and the quick setting agent supply pipe 5 connected to the nozzle 2 from the quick setting agent tank 4 using compressed air of 0.55 MPa and 8.5 m ³ / min as a carrier. Went through. The addition amount of the quick setting agent was adjusted so that the outer coating was 0.6% by mass relative to 100% by mass of the amorphous refractory.

  For the quick setting agent, a slurry comprising a solid content in which calcium chloride powder and calcium hydroxide powder are combined so that the mass ratio of calcium chloride / calcium hydroxide is 10/8 and water as a solvent is used. It was. The concentration of the solid content in the slurry is 18% by mass.

  Table 1 shows the evaluation results when the average particle diameter and specific surface area of the calcium hydroxide powder in the slurry as the quick setting agent are variously changed in this case.

  The difficulty of precipitation was evaluated in the following manner. Put the slurry as a quick setting agent in a graduated graduated cylinder, stir well and leave it cloudy. When allowed to stand for a certain period of time (hereinafter referred to as the standing time), the calcium hydroxide powder settles, and a transparent water layer begins to be formed on the surface layer portion of the slurry. The ratio of the height of the cloudy portion excluding the transparent portion in the total height of the slurry is the dispersity. Based on the degree of dispersion when the standing time was 50 hours, the difficulty sedimentation was relatively evaluated in four stages: ◎, ○, Δ, and ×.

  The redispersibility after precipitation was evaluated in the following manner. A slurry as a quick setting agent is put in a plastic container so that calcium hydroxide powder is completely precipitated on the bottom of the container. The container in this state is placed on a flow table specified in JIS-R2521, and tapped. Based on the small number of tappings required until the slurry in the container became uniformly cloudy, the easy redispersibility was relatively evaluated in four stages: 、, ○, Δ, and ×.

  Rebound loss is sprayed on a vertical surface in an environment with an air temperature of about 20 ° C., and is obtained according to the formula: “Adhesion rate = (total amount of repair material sprayed−rebound amount) / total amount of repair material sprayed”. According to the adhesion rate, relative evaluation was made in four stages: ◎, ○, Δ, ×.

  Curing time is measured for penetration resistance using a penetration hardness meter with a tip of 6 mmφ for the construction body obtained by spraying in an environment with an air temperature of about 20 ° C., until the penetration resistance reaches about 3.5 MPa. Depending on the time, 10 to 45 minutes, ◎, 45 minutes to 60 minutes or less ○, 60 minutes to 120 minutes or less △ less than 10 minutes or more than 120 minutes × .

  The calcium hydroxide powders of Examples 1 to 4 were produced by a general dry method, and the average particle size was adjusted by the manner and classification of the dried product obtained by digesting quick lime. The treatment for roughening the particle surface of the obtained calcium hydroxide powder is not performed, and the specific surface area tends to increase as the average particle size decreases.

  In Example 1, since the average particle diameter of the calcium hydroxide powder is small, the characteristics of the calcium hydroxide powder that the hardening accelerating action is strong appear excessively, and sufficient time for trimming cannot be secured, and precipitation occurs. In some cases, a dense deposit is formed, and the redispersibility after precipitation is poor. Further, since the specific surface area is not sufficiently large for the small average particle diameter, the sedimentation resistance is small and the difficulty of sedimentation is poor.

  In Examples 2 and 4, since the average particle size was larger than that in Example 1, the redispersibility after the precipitation was improved. However, simply increasing the average particle size increases the sedimentation rate and remarkably inferior sedimentation property. Further, simply increasing the average particle size is inferior in solubility in water and inferior in the effect of alleviating or delaying the excessive rapid setting action of calcium chloride, resulting in an increase in rebound loss.

  In Example 3, as a precipitation inhibitor in Example 2, sodium polyacrylate having a molecular weight of 100,000 was added in an amount of 0.1% by mass on the basis of 100% by mass (solid content) of calcium chloride and calcium hydroxide in the slurry. However, the difficulty sedimentation could not be improved to an acceptable level.

  The calcium hydroxide powders of Examples 5 to 14 are obtained by digesting quick lime using an aqueous solution of citric acid, aging for 1 hour, drying, and grinding the dried product. The average particle size was adjusted by the grinding method and classification, and the specific surface area was adjusted by the concentration of citric acid. According to this production method, the specific surface area can be controlled independently of the average particle diameter.

  In Example 5, the average particle size is the same as in Examples 2 and 3, but the specific surface area is increased. The rebound loss was improved because the effect of alleviating or delaying the excessive rapid setting action of calcium chloride was improved by increasing the specific surface area, but this is insufficient.

  In Example 6, the specific surface area was further increased. Further improvement in rebound loss was observed, and the sedimentation resistance was increased by increasing the specific surface area. .

  Examples 7 to 13 are examples in which the specific surface area is further increased and the average particle size is also increased, and are excellent in all evaluations of difficulty sedimentation, redispersibility after precipitation, rebound loss, and curing time.

  In Example 14, although the specific surface area was large, the average particle size was too large, so that the difficulty of sedimentation was insufficient. In addition, if the average particle size is too large, even if the specific surface area is large, the solubility in water is inferior, so that the excessive rapid setting action of calcium chloride cannot be reduced or delayed, the rebound loss increases, and the curing time is increased. The result was a little too long. If the curing time is too long, the ratio of occurrence of cracks and peeling off in the sprayed construction body is increased, which is not preferable.

From the results of Table 1, it is considered that the average particle diameter of the calcium hydroxide powder is generally preferably 6 to 20 μm and more preferably 7.5 to 20 μm. In addition, the calcium hydroxide powder preferably has a particle size constitution in which the content of particle size less than 5 μm is less than 40% by mass. The specific surface area of the calcium hydroxide powder is preferably 15 m ² / g or more, and more preferably 20 m ² / g or more.

  FIG. 2 shows the change over time in the degree of dispersion of the slurry according to Example 1 (Comparative Example) and the slurry according to Example 11 (Example) in Table 1. The broken line A shows the time variation of the degree of dispersion of Example 11, and the broken line B shows the change of the degree of dispersion of Example 1. In Example 1 (Comparative Example), the degree of dispersion is 50% or less after 150 hours, while Example 11 (Example) retains a degree of dispersion of 80% or more after 150 hours. .

  The present invention includes, for example, a molten metal container such as a blast furnace, a kneading wheel, a converter, a ladle, or a tundish, or a waste melting furnace, a waste ash melting furnace, an incinerator, a cement plant furnace, a soaking furnace, Alternatively, it can be widely applied to the formation of an initial lining of an industrial furnace such as a heating furnace or the repair of an already formed lining.

  DESCRIPTION OF SYMBOLS 1 ... Pressure feed pump, 2 ... Nozzle, 3 ... Piping, 4 ... Quick setting agent tank, 5 ... Quick setting agent supply pipe.

Claims (1)

Mud that is kneaded by adding water to an irregular refractory containing refractory powder and alumina cement is pumped to the nozzle through the pipe, and the mud is placed in the nozzle and / or in the pipe. In the wet spraying method of adding a quick setting agent comprising a lime slurry containing calcium chloride, as the lime component of the lime slurry, a calcium hydroxide powder having an average particle size of 6 to 20 μm and a specific surface area of 15 m ² / g or more A wet spraying construction method characterized by using the above.

Images