Monolithic refractory for dry spraying and dry spraying construction method using the same

Abstract

To provide a monolithic refractory for dry spraying, which is made of all dry powder materials without using any material that is not dry powder, and is dry sprayed using water to form a construction body that has the same air permeability as that of a conventional material that is made of a non-dry powder but contains silica sol added, and dries quickly, thereby reducing the workload. [Solution] This is an unshaped refractory used when water is added to a powder mixture and sprayed from the tip of a nozzle, wherein the powder mixture contains dry powder refractory material, dry powder alumina cement, dry powder alumina gel, and dry powder cement mineral-based quick-setting agent, and the alumina cement is contained in an amount such that the calcium oxide component is within the range of 0.3 to 3.0% outer percentage relative to 100% refractory material, the dry powder alumina gel is contained in an amount within the range of 0.1 to 5.0% outer percentage relative to 100% refractory material, and the cement mineral-based quick-setting agent is contained in an amount within the range of 0.1 to 3.0% outer percentage relative to 100% refractory material. This is an unshaped refractory for dry spraying.

Description

[Technical Field]

[0001] The present invention relates to a technology for monolithic refractories for dry spraying, and more specifically, to a technology for providing a monolithic refractory for dry spraying, which is made entirely of dry powder, using dry powder alumina cement, dry powder alumina gel, and dry powder cement mineral-based quick-setting additives as hardeners, and these as binders (binding agents) for dry powder refractory materials, thereby significantly improving handleability in dry spraying construction and also exhibiting excellent effects in terms of short drying times and explosion resistance of the construction body, as well as a technology for providing a monolithic refractory for dry spraying construction and a dry spraying construction method using the same. [Background technology]

[0002] The construction of refractories involves the pouring of monolithic refractories, painting, and spraying. Of these, pouring is the mainstream, but pouring requires mixing with a large mixer at the construction site, as well as framing and de-framing, making the work complicated and large-scale. On the other hand, the advantage of spraying is that it does not require such complicated work.

[0003] Spraying can be broadly divided into wet spraying and dry spraying. In wet spraying, the refractory material and water are thoroughly mixed using a mixer or other kneading process, and the resulting slurry mixture is then pumped out with air and a quick-setting agent (hardener) at the tip of the spray nozzle, and sprayed. On the other hand, dry spraying is a relatively easy method to work with, as it does not contain water and requires small, simple equipment. After mixing the dry powder, the mixture is pumped out with compressed air, water is added to the dry powder refractory material at the tip of the spray nozzle, and the mixture is mixed inside the nozzle, and then sprayed to obtain the finished product. Therefore, dry spraying is a more convenient and highly useful method of construction.

[0004] Here, if the temperature of monolithic refractory is suddenly raised after installation, the internal steam pressure exceeds the strength of the installed body, causing the body to burst, a phenomenon known as "explosion." It is known that this phenomenon must be prevented. Even in the dry spraying installation, which is a highly useful installation method as described above, when the temperature of the kiln is raised after installation and the material is dried, explosions can occur as the internal steam escapes through the pores of the refractory material, and it is therefore necessary to prevent this explosion.

[0005] For example, a dry-type spray-applied refractory has been proposed that uses dry-type alumina cement and monopotassium phosphate as a binder, resulting in high adhesiveness and enabling application without the need for anchors (see Patent Document 1). However, conventional dry-type spray-applied refractories use dry-type alumina cement as a binder, and immediately before spraying, water is mixed with the dry-type refractory material in a spraying nozzle, and the refractory material is sprayed onto the surface (target object). This poses the following problems: When dry-type spray-applied refractories are applied in this manner, they contain moisture immediately after application. As a result, the moisture must be removed as steam as the furnace heats up, and the refractory must be dried. In the case of conventional dry-type spray-applied refractories that harden at room temperature through the hydration of alumina cement, the surface of the spray-applied refractory has low air permeability. Therefore, to prevent the spray-applied refractory from exploding due to the pressure of internal steam, the furnace must be heated over a long period of time, resulting in a problem of long drying times.

[0006] To address the above issues, a method has been proposed and used to shorten the drying time by increasing the porosity of sprayed refractories: reducing the amount of alumina cement and replacing water with silica sol, which is made by dispersing colloidal silica particles in water. This method shortens the drying time through the following mechanism: When the silica sol hardens through aggregation and gelation, it forms fine cracks that turn into pores, increasing the air permeability. This increases the porosity within the sprayed refractory, allowing internal water vapor to escape through the pores in the refractory material, making it less likely to explode. This allows the furnace temperature to rise faster when the refractory is dried.

[0007] In Patent Document 2, the applicant of the present application proposed a monolithic refractory for dry spraying in which the amount of alumina cement is significantly reduced and silica sol is added. This invention not only increases the furnace temperature rise rate during drying of the applied body, but also solves the problem of low curing strength, which is one of the issues with silica sol-added monolithic refractories for dry spraying. Specifically, the addition of alumina cement and hydraulic alumina has the useful effect of increasing the curing strength of the applied body to 1.0 MPa or more after 24 hours. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-196638 [Patent Document 2] Patent No. 7174184 Summary of the Invention [Problem to be solved by the invention]

[0009] As described above, the silica sol-added monolithic refractory for dry spraying proposed by the present applicant can achieve the above-mentioned excellent effects. However, the inventors recognized that the conventional monolithic refractories for spraying suffer from the complication of storage, handling, and transportation due to the characteristics of the silica sol used as the material, and that if this issue could be improved, the technology would become even more useful. Specifically, when using a silica sol-added monolithic refractory for dry spraying, a non-dry powder silica sol must be added to the dry powder material when spraying it onto the surface to be treated from a spray nozzle. This necessitates various procedures, such as those described below. First, a non-dry powder silica sol in a 18-liter can must be prepared separately from the dry powder material mixture, such as the dry powder refractory material. Then, the required amount of the 18-liter can containing the silica sol must be transported to the treatment site along with the dry powder material. Furthermore, before treatment, a space must be secured at the treatment site to store the 18-liter can containing the silica sol. Furthermore, at the construction site, various tasks must be performed, such as opening the 18L can and pouring the silica sol into a container for storing liquid, and crushing and disposing of the empty 18L can.

[0010] In response to the actual work conditions in the construction described above, the inventors have realized that if it were possible to realize a dry-sprayed monolithic refractory that is made entirely of dry powder, without using silica sol, and that is constructed by simply adding water to the dry powder material and mixing it, and then spraying the mixture onto the surface to be constructed using a spray nozzle, the constructed body would have moderate pores and a high air permeability, just like when a refractory made of the material composition of conventional technology to which silica sol has been added is used, the constructed body would have explosion resistance and be able to dry in a short time, and above all, the complicated work described above would be eliminated, the workload would be significantly reduced, and efficient on-site work would be possible.

[0011] Therefore, the object of the present invention is to provide a practically very useful monolithic refractory for dry spraying, which has a material composition consisting entirely of dry powder without using silica sol that is not a dry powder, and which can be formed by the simple operation of simply mixing water and spraying the mixture with water, thereby having a high air permeability similar to that of a conventional monolithic refractory for dry spraying, which requires the addition of silica sol during application, and which is at least comparable to a conventional monolithic refractory for dry spraying using a conventional material composition that uses silica sol.A further object of the present invention is to provide a monolithic refractory for dry spraying, which has a faster drying rate and is more suppressed in explosion problems than a conventional monolithic refractory for dry spraying having a material composition that requires the addition of silica sol. [Means for solving the problem]

[0012] The above object can be achieved by the present invention, which provides the following monolithic refractory for dry gunning. [1] A dry spraying monolithic refractory used when a powder mixture is mixed with water and sprayed from the tip of a nozzle, The powder mixture comprises a dry powder refractory material, and as a hardener, dry powder alumina cement, dry powder of alumina gel, and dry powder cement mineral-based accelerator; The alumina cement is added in an amount such that the calcium oxide component is in the range of 0.3% by mass or more and 3.0% by mass or less, based on 100% by mass of the refractory material, The dry powder of the alumina gel is added in an amount of 0.1% by mass or more and 5.0% by mass or less, based on 100% by mass of the refractory material. A dry-spraying, unshaped refractory material characterized by containing the cement mineral-based quick-setting admixture in an amount ranging from 0.1% by mass to 3.0% by mass, based on 100% by mass of the refractory material.

[0013] Preferred embodiments of the monolithic refractory for dry spraying are as follows. [2] The monolithic refractory material for dry spraying according to the above [1], wherein the dry powder of alumina gel is a dried product obtained by drying an alumina gel having a pH of 8 to 11 and containing 5 to 25 mass% of Al2O3, 1 to 8 mass% of alkali metal atoms, 5 to 20 mass% of hydroxy acid, and 55 to 85 mass% of water. [3] The monolithic refractory for dry spraying according to [1] or [2] above, wherein the dry powder cement mineral-based quick-setting admixture is a calcium aluminate-based quick-setting admixture or a calcium sulfoaluminate-based quick-setting admixture. [4] The air permeability of the dried monolithic refractory, which is the construction body formed by the above construction, dried at 110 ° C for 24 hours or more after curing is 5 × 10 -15 m 2 The monolithic refractory for dry spraying according to any one of the above [1] to [3].

[0014] As another embodiment, the present invention provides the following dry spraying application method. [5] A construction method for dry spraying by spraying the monolithic refractory for dry spraying according to any one of the above [1] to [4] onto a surface to be treated from a spray nozzle, A dry spraying application method characterized by feeding the powder mixture to the spray nozzle, adding water at the tip of the spray nozzle to mix the powder mixture with water, and spraying the resulting mixture from the tip of the spray nozzle onto the surface to be applied.

[0015] Preferable embodiments of the dry spraying method are as follows. [6] A dry spraying application method according to [5] above, in which the obtained mixture is sprayed onto the surface to be applied from the tip of the spray nozzle, and the application is carried out immediately after adding water to the tip of the spray nozzle to mix the powder mixture with water. [Effects of the Invention]

[0016] According to the present invention, by using a dry powder as the material composition for all materials, it is possible to significantly reduce the significant workload involved in the storage, handling, and transportation of the silica sol material, which was a problem in the dry gunning method using a monolithic refractory for dry gunning that is also used with a silica sol that is not a dry powder. Moreover, the dry gunning-applied body can be dried in a short time, similar to the case of using a monolithic refractory for dry gunning that is also used with a silica sol that is not a dry powder, as previously described as the prior art, thereby shortening the application time and enabling the production of a body with good properties and explosion resistance. Furthermore, according to the present invention, the development of a monolithic refractory for dry gunning that can achieve the above-mentioned excellent effects makes it possible to provide a method of application that allows for quick, practical dry gunning with reduced workload, even in applications and areas where the application of monolithic refractories has been difficult in the past, such as waste incinerators, cement manufacturing facilities, and rotary kilns. [Brief explanation of the drawings]

[0017] [Figure 1] This is a graph showing the air permeability of each of the construction bodies obtained by dry spraying the monolithic refractory for dry spraying of Example 2 and the monolithic refractory for dry spraying of Comparison Example 10 when dried at temperatures of RT (room temperature), 110°C, and 150°C. [Figure 2] This is a graph showing the relationship between drying time and temperature rise rate when the temperature inside the furnace was raised to 800°C under conditions that would not cause explosion and dried the various construction bodies obtained by dry spraying the monolithic refractory for dry spraying of Example 2 and the monolithic refractory for dry spraying of Comparison Example 10. [Figure 3A] This is a schematic diagram to explain the method for measuring the central temperature of each cubic-shaped cast body obtained by kneading monolithic refractory for dry spraying with the same amount of added water as for dry spraying and casting it into a mold of a predetermined shape. [Figure 3B]This graph shows the relationship between the time (seconds) until the central temperature of the cast bodies reaches 200°C after a constant rate drying period, when the cast bodies are placed in an electric furnace maintained at 400°C, and the central temperature of the cast bodies is measured. The cast bodies are cubic in shape, and are obtained by mixing the monolithic refractory for dry spraying of Example 2 and the monolithic refractory for dry spraying using silica sol of the Reference Example with the same amount of added water as in dry spraying, and then casting them into a mold of a predetermined shape. Here, the "constant rate drying period" refers to the region of around 100 to 110°C where the sample temperature remains almost constant. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described in detail below with reference to preferred embodiments. In monolithic refractories for dry gunning, alumina cement is generally used as a binder (binding agent). It is known that reducing the amount of alumina cement and using silica sol in the construction of monolithic refractories for dry gunning makes it possible to introduce pores into the body formed by dry gunning, thereby increasing the air permeability within the body and enabling drying in a short period of time. However, according to the inventors' studies, monolithic refractories for dry gunning that use silica sol have the problem that, unlike other dry powder materials used in combination, silica sol is liquid, making it difficult to handle, and making storage, handling, transportation, and other operations less convenient and cumbersome, thereby reducing the efficiency of dry gunning.

[0019] Under these circumstances, the inventors conducted extensive research to find a useful monolithic refractory for dry spraying that can be made entirely of dry powder without using silica sol, and that, in a dry-sprayed construction, exhibits comparable effects in terms of rapid drying time and explosion resistance to conventional monolithic refractories for dry spraying constructed using silica sol. As a result, the present invention was achieved. Specifically, the inventors discovered that the above-mentioned excellent effects can be achieved by a novel construction that combines dry powder alumina cement with dry powder alumina gel and dry powder cement mineral-based quick-setting additives as hardener components that harden and function as a binder for the refractory base material. The constituent materials of the monolithic refractory for dry spraying of the present invention (hereinafter sometimes simply referred to as "dry-sprayed refractory") are described below.

[0020] The refractory for dry gunning of the present invention is characterized by comprising a dry powder refractory material as a base material, and a dry powder alumina cement, a dry powder alumina gel, and a dry powder cement mineral-based quick-setting admixture as hardener components within specific ranges relative to the refractory material. Each of the materials constituting the present invention will be described below.

[0021] (Fireproof material) The dry powder refractory material constituting the dry gunning refractory of the present invention is not particularly limited, and any common monolithic refractory material can be used. Examples include dry powders of sintered alumina, fused alumina, bauxite, band shale, mullite, andalusite, chamotte, roseki, silica, sintered spinel, fused spinel, chromite, chromium oxide, zircon, zirconia, silicon carbide, graphite, and pitch. In the present invention, one or more materials selected from the group consisting of these materials can be used in combination. In this case, it is preferable to use a refractory material whose particle size has been adjusted to a particle size suitable for gunning, as has been conventionally done. In addition to the above materials, ultrafine refractory powders selected from refractory clay, calcined alumina, silica flour, carbon black, etc. can also be used in combination.

[0022] The refractory material constituting the present invention, selected from the materials listed above, is preferably one having a particle size suitable for spray application. Specifically, the particle size composition of the refractory material constituting the present invention is preferably one containing, for example, fine particles having a particle size of 0.075 mm or less (under) in the range of 15% by mass to 50% by mass. By using such a raw material particle size, the workability as a dry spray application refractory can be maintained in a more stable and favorable state.

[0023] (hardener that acts as a binder) The dry-type gunning refractory of the present invention is characterized by comprising a refractory material as a base material, such as those listed above, and a dry powder of alumina cement, a dry powder of alumina gel, and a dry powder of a cement mineral-based quick-setting admixture, all of which are hardeners that function as binders (binding agents) for the refractory material. These components will be explained below.

[0024] (1) Dry powder alumina cement The dry powder alumina cement constituting the dry gunning refractory of the present invention is a hydraulic cement characterized by rapid hardening and early strength, fire resistance, heat resistance, acid resistance, and chemical resistance, and functions as a useful binder for the base refractory material. The dry powder alumina cement hardens by reacting with moisture added to the dry powder material at the tip of the gunning nozzle during dry gunning. In the dry gunning refractory of the present invention, the blending amount of the dry powder alumina cement is specified so that the calcium oxide component in the alumina cement is contained in an amount ranging from 0.3 to 3.0 mass% outer percent based on 100 mass% of the refractory material.

[0025] The reason for specifying the blending amount of dry powder alumina cement within the above range in the present invention is that, first, if the calcium oxide component of the alumina cement is less than 0.3% by mass (outer percentage) relative to 100% by mass of the refractory material, the blending amount is too small, making it take too long to form the finished product, making it impractical and unlikely to become an industrially applicable technology. On the other hand, if the blending amount of dry powder alumina cement is more than 3.0% by mass (outer percentage) relative to 100% by mass of the refractory material, the finished product will be too dense, which may cause explosions when the internal water vapor escapes through the pores of the refractory material, resulting in poor explosion resistance. These points will be described in detail later.

[0026] (2) Dry powder of alumina gel The dry-type gunning refractory of the present invention is characterized in that, in addition to the dry powder alumina cement described above, it contains a dry powder of alumina gel as a hardener in an amount of 0.1% by mass to 5.0% by mass, based on 100% by mass of the refractory material. The dry powder of alumina gel used in the present invention is preferably a recently developed dry powder of alumina gel, which is a specific alumina gel described in Japanese Patent No. 7510226, powdered by drying at 20 to 200°C. The technology described in the above patent aims to provide a gel material that can rapidly form an aluminum gel without using silica or calcium materials in its production, and that has excellent shape retention.

[0027] In contrast to the above technology, as mentioned above, the present invention aims to solve a major practical problem in conventional dry gunning refractories using silica sol, namely, that the silica sol is not a dry powder, unlike other dry powder materials used in combination, making it difficult to handle, and making storage, handling, transportation, and other operations less efficient and complicated, thereby causing a loss of efficiency in dry gunning.The inventors of the present invention have focused on the fact that the above technology, which was developed on the condition that no silica material is used, can provide a dry powder of alumina gel, and have investigated the applicability of this dry powder of alumina gel as a material for dry gunning refractories.

[0028] First, rapid application is required for use as a constituent material for dry-type gunning refractories. The unique alumina gel dry powder product proposed in the above technology quickly retains water when added to the powder, forming a transparent gel with sufficient shape retention. Furthermore, the gel exhibits a neutral to slightly alkaline pH, making it suitable for use as a material for dry-type gunning refractories. Therefore, we conducted a detailed study on the use of the alumina gel dry powder proposed in the above technology as a constituent material for dry-type gunning refractories. For this study, we used a dried product obtained by drying the alumina gel of the composition described in Patent No. 7510226 at 100°C for approximately two hours. X-ray diffraction analysis of this dried product revealed that it was amorphous.

[0029] According to the inventors' investigations, a refractory for dry spraying was prepared by blending the above-mentioned dry powder of alumina gel with a dry powder refractory material, using dry powder alumina cement as a hardener in an amount such that the calcium oxide component was in the range of 0.3% by mass or more and 3.0% by mass or less, based on 100% by mass of the refractory material, and the inventors found the following: When the above-prepared refractory for dry spraying was used to form a construction body for dry spraying, it was found that the adhesion was poor and the body could not be used as is. Adhesion is an extremely important requirement for a refractory for dry spraying, and unless this requirement is met, it cannot be put into practical use.

[0030] The present inventors conducted extensive research to solve the above-mentioned problems and arrived at the present invention. For the reasons mentioned above, the inventors investigated the use of dry powder alumina cement as a hardening agent in an amount such that its calcium oxide component is in the range of 0.3% by mass to 3.0% by mass, based on 100% by mass of the refractory material, and the addition of the above-mentioned dry powder alumina gel. They also investigated the use of dry powder materials known as cement accelerators or hardening accelerators. As a result, they discovered that the combined use of dry powder alumina gel and a cement mineral-based accelerator under specific blending conditions can improve the adhesion problem of the finished product. Furthermore, they discovered that a dry-type sprayed refractory consisting entirely of dry powder can be produced, which has excellent workability and can produce a finished product in good condition. The following describes the cement mineral-based accelerator used in combination with dry powder alumina cement and alumina gel.

[0031] (3) Dry powder cement mineral-based accelerator The refractory for dry gunning of the present invention is required to contain, in addition to the dry powders of alumina cement and alumina gel described above, a dry powder cement mineral-based quick-setting admixture as a hardening agent in an amount ranging from 0.1% by mass to 3.0% by mass, based on 100% by mass of the refractory material. First, the background to the configuration in which the dry powder refractory material is configured to use the dry powders of alumina cement and alumina gel in combination with a dry powder cement mineral-based quick-setting admixture as a hardening agent will be described.

[0032] As mentioned above, we investigated the application of dry powder alumina gel for dry-sprayed refractories. The results showed that, although this dry powder alumina gel is potentially applicable because it rapidly retains water when added to the dry powder, forming a transparent gel, and has sufficient shape retention, it is poor in adhesion, a fundamental function of dry-sprayed refractories, making it unsuitable for practical use. Furthermore, we found that when a high amount of dry powder alumina gel was used (e.g., 6.0% by mass) relative to 100% by mass of the refractory material, nozzle clogging occurred during dry-sprayed application. This indicates that the dry powder alumina gel cannot be used in large quantities. However, this problem could be solved by specifying a blending amount that does not cause nozzle clogging. However, our investigation revealed that the adhesion problem of the application occurred both when the blending amount of dry powder alumina gel was high and when it was low, suggesting that the use of a new material would be necessary to resolve this issue. In response to this problem, the present inventors have conducted extensive research, thinking that this problem could be solved by using a dry powder cement mineral-based quick-setting admixture (hereinafter sometimes simply referred to as a "cement mineral-based quick-setting admixture") in combination, which has the property of accelerating the solidification and hardening of cement when mixed with cement and undergoing a hydration reaction, thereby causing the cement to set quickly.

[0033] Since the present invention aims to convert all materials into dry powders, powder materials were investigated. Powder (dry powder) sprayed cement mineral-based accelerators include calcium aluminate-based and calcium sulfoaluminate-based accelerators, which are classified as cement mineral-based accelerators, and aluminate-based accelerators, which are classified as inorganic salt-based accelerators. Because aluminate-based accelerators have safety concerns, calcium aluminate-based and calcium sulfoaluminate-based accelerators, which are classified as cement mineral-based accelerators, were used in the present invention. Commercially available powdered cement mineral-based accelerators include Denkanatomic Z (trade name, calcium aluminate-based, manufactured by Denka Co., Ltd.) and powdered Denka ES (trade name, manufactured by Denka Co., Ltd.). The hardening mechanism of Denka ES is the rapid formation of ettringite (calcium sulfoaluminate hydrate, 3CaO·Al2O3·32H2O) upon hydration with cement, which acts to capture and fix hexavalent chromium in the cement components. According to the research conducted by the present inventors, both calcium aluminate-based and calcium sulfoaluminate-based quick-setting admixtures can be used. In the present invention, the research was conducted using the above-mentioned commercially available Denkanatomic Z as a representative dry powder cement mineral-based quick-setting admixture.

[0034] First, a dry-spraying refractory was formulated by adding the aforementioned dry alumina gel powder, and tests were conducted to examine the condition of the resulting refractory. Specifically, the dry-spraying refractory was mixed with 1.2% dry alumina cement by mass. The results showed that both the dry alumina gel powder blended at 2% by mass and the dry alumina gel powder blended at 6% by mass, based on 100% by mass of the refractory, had adhesion problems and were deemed unsuitable for use as a dry-spraying refractory. In both cases, there were no practical problems with nozzle clogging, confirming the feasibility of application.

[0035] Next, we conducted tests to examine the condition of the dry-sprayed refractory materials formed by dry spraying, using the previously described calcium aluminate-based Denkanatomic Z (trade name) as a dry-powder cement mineral-based quick-setting agent, without incorporating the aforementioned dry alumina gel dry powder. Specifically, we used 1.2% dry alumina cement by mass in the dry-powder refractory material, and mixed Denkanatomic Z at 0.5% by mass and 4% by mass, based on 100% by mass of the refractory material. The results showed no problems with adhesion in either formulation. However, in both cases, the resulting refractory materials had low air permeability and were dense, requiring long drying times and thus poor practicality. Furthermore, the resulting refractory materials with low air permeability had another issue: a high risk of explosion, which resulted in poor explosion resistance, making them difficult to commercialize. Furthermore, when the amount of cement mineral-based quick-setting agent was as high as 4% by mass, based on 100% by mass of fire-resistant material, the drying time of the finished product was long, and in addition, nozzle clogging occurred when dry spraying was performed, making it less practical.

[0036] The present inventors have conducted extensive research to find a refractory for dry gunning that has a configuration that solves all of the above-mentioned problems, and as a result, have found that it is necessary for the powder mixture that constitutes the refractory for dry gunning to contain a dry powder refractory material and, as a hardener, dry powder alumina cement, dry powder alumina gel, and dry powder cement mineral-based quick-setting admixture in the following formulation. Specifically, the inventors discovered that the intended effect of the present invention can be achieved by using alumina cement, a hardener blended into a dry powder refractory material, containing calcium oxide in an amount ranging from 0.3% to 3.0% by mass, based on 100% by mass of the refractory material, and by using a dry powder of alumina gel, a hardener, in an amount ranging from 0.1% to 5.0% by mass, based on 100% by mass of the refractory material, and by blending a dry powder of cement mineral-based quick-setting admixture, a hardener, in an amount ranging from 0.1% to 3.0% by mass, based on 100% by mass of the refractory material. Details will be described later.

[0037] The dry-spraying refractory of the present invention comprises the above-described dry-powder refractory material, and the hardening agent functioning as a binder for the refractory material, which includes dry-powder alumina cement, dry powder of alumina gel, and dry-powder cement mineral-based quick-setting admixture, in the above-described formulation. In addition to the above-described components, other components such as flocculants, hardening regulators, thickeners, and fibers may be added as needed. Examples of hardening regulators include at least one compound selected from the group consisting of condensed phosphates, organic acids, and organic acid salts. The hardening regulator is preferably used in an amount ranging from 0.01% to 0.3% by mass, based on 100% by mass of the refractory material. Examples of condensed phosphates include sodium tripolyphosphate, sodium tetrapolyphosphate, sodium pyrophosphate, and sodium hexametaphosphate, and may be used as appropriate. Examples of thickeners include fireclay and bentonite, and may be used as appropriate.

[0038] (Dry spray application method) By applying the dry gunning refractory of the present invention to the dry gunning application method of the present invention, an applied body that exhibits the effects of short-time drying and excellent explosion resistance can be easily obtained. As a result, the dry gunning refractory of the present invention can solve the practical problem of complicated storage, handling, transportation, etc. that arises when dry gunning is performed using a conventional dry gunning refractory that contains an added silica sol that is not a dry powder, without compromising the properties of the applied body.

[0039] The dry gunning application method of the present invention is characterized in that the powder mixture constituting the dry gunning refractory of the present invention is fed to a gunning nozzle, water is added at the tip of the gunning nozzle to mix the powder mixture with water, and the resulting mixture is sprayed from the tip of the gunning nozzle onto the surface to be applied. In this way, a good kneaded mixture can be obtained by the simple procedure of simply adding water to the powder mixture consisting of the specific dry powder specified in the present invention and mixing it, and then the kneaded mixture can be immediately sprayed from the tip of the gunning nozzle onto the surface to be applied, allowing for quick and easy application.

[0040] According to the inventors' investigations, the dry gunning method of the present invention, which allows the formation of a workpiece through the above-mentioned simple operations, allows the following hardening reaction to occur in a favorable state during the formation of the workpiece. That is, as described above, the dry gunning refractory of the present invention is used, water is added to and mixed with dry powder materials in a nozzle, and then, preferably, sprayed immediately thereafter, thereby achieving the following effects. The dry gunning refractory of the present invention is configured to contain a reduced amount of dry powder alumina cement compared to the general amount used as a hardener, and hardening and pore formation occur due to gelation of the dry powder alumina gel and dry powder cement mineral-based quick-setting admixture used in combination. This enables drying in a short time and suppresses the occurrence of explosion in the workpiece, similar to conventional dry gunning refractories configured using silica sol rather than dry powder. By using the dry-spraying refractory of the present invention, it is possible to achieve rapid drying and explosion resistance of the resulting construction by mixing the powder mixture material, which is a specific dry powder as specified in the present invention, with water and applying it by dry spraying, without using silica sol, which is not a dry powder, as a material. As a result, there is no need to use silica sol, which is not a dry powder and is difficult to handle, which increases the workload and equipment load, as occurred in conventional dry-spraying refractories, and this is extremely useful industrially and has extremely high practical value. [Example]

[0041] The present invention will be described in further detail below with reference to examples and comparative examples. The compositions of raw materials for examples of the dry-gunning refractory of the present invention are shown in Tables 1-1 and 1-2 (hereinafter sometimes referred to as "Table 1"), and the compositions of raw materials for comparative examples are shown in Tables 2-1 and 2-2 (hereinafter sometimes referred to as "Table 2"). Each table also shows the evaluation results of each dry-gunning refractory, as evaluated as described below. Unless otherwise specified, "%" below is based on mass.

[0042] [Examples 1 to 7] (Test Overview) In Examples 1 to 7, the dry powders of refractory material, alumina cement, alumina gel, and cement mineral-based quick-setting admixture were used in the amounts shown in Table 1 as the basic formulation. In Examples 1 to 4 shown in Table 1-1, the formulations of refractory material and alumina cement were the same, but the formulations of alumina gel dry powder and dry powder cement mineral-based quick-setting admixture were varied. The amount of alumina gel dry powder varied within a range of 0.1% to 5% relative to 100% refractory material, and the amount of cement mineral-based quick-setting admixture varied within a range of 0.1% to 3% relative to 100% refractory material. These ranges are defined in the present invention. The ratio of the amount of alumina gel dry powder to the amount of cement mineral-based quick-setting admixture was adjusted to be in the range of 1 to 4.

[0043] In Examples 5 to 7 shown in Table 1-2, the refractory material formulation was the same as in Examples 1 to 4, but the alumina gel dry powder and cement mineral-based quick-setting admixture were formulated based on the evaluation results in Table 1-1. The alumina gel dry powder was formulated in an amount of 2% outer percent based on 100% refractory material, and the dry powder cement mineral-based quick-setting admixture was formulated in an amount of 0.5% outer percent based on 100% refractory material, and the amount of alumina cement was gradually changed to produce each Example. Table 1-2 also lists the formulation and evaluation results of Example 2, which was previously described and listed in Table 1-1, in which alumina gel dry powder was formulated in an amount of 2% outer percent based on 100% refractory material.

[0044] The dry powder cement mineral-based quick-setting admixture used above was a calcium aluminate-based Denka Natomic Z (trade name, manufactured by Denka Corporation). Hereinafter, this may be abbreviated as "Natomic." The dry powder of alumina gel used above was a dried product obtained by drying alumina gel obtained by the manufacturing method described in the aforementioned Japanese Patent No. 7510226 at 100°C for 2 hours. The component composition of this dry powder of alumina gel was a ratio of amorphous aluminum hydroxide to lactic acid, a hydroxy acid, of approximately 2:1.

[0045] [Reference example] (Exam overview) In the Reference Examples, the refractory material had the same composition as the dry-sprayed refractories of Examples 1 to 4, and alumina cement and silica sol, not dry powder, were used as the hardener. In the Reference Examples, a dry-powder mixture other than silica sol was fed into the spray nozzle, and the amount of silica sol listed in Table 1-2 was added at the tip of the nozzle to mix and knead with the materials other than silica sol. The mixture was then sprayed from the tip of the nozzle onto the same surface as in the Examples to form an applied body. The cast-in application body was also formed using the same mixing and casting methods as in the Examples.

[0046] [Comparative Examples 1 to 10] (Test Overview) In Comparative Examples 1 to 6, as shown in Table 2-1, the blending ratios of the refractory material and the alumina cement were the same as those in Examples 1 to 4 for comparison with Examples 1 to 4. In Comparative Example 1, neither the dry powder of alumina gel nor the dry powder of cement mineral-based quick-setting admixture was blended; in Comparative Examples 2 and 3, the dry powder of alumina gel was blended; in Comparative Examples 4 and 5, the cement mineral-based quick-setting admixture was blended; and in Comparative Example 6, the blending amounts of the dry powder of alumina gel and the cement mineral-based quick-setting admixture were both greater than the ranges specified in the present invention. The blending amounts of the dry powder of alumina gel used in Comparative Example 3 and the cement mineral-based quick-setting admixture used in Comparative Example 5 were greater than the ranges specified in the present invention. The dry powder of alumina gel and the dry powder of cement mineral-based quick-setting admixture used in the Comparative Examples were the same as those used in the Examples.

[0047] As shown in Table 2-2, in Comparative Examples 7 and 8, the amount of alumina cement blended was less than the range specified in the present invention, while in Comparative Examples 9 and 10, the amount of alumina cement blended was greater than the range specified in the present invention. In Comparative Examples 9 and 10, similar to Example 2, which received a good evaluation in Table 1-1, dry powder of alumina gel was used in an amount of 2% by outer percentage relative to 100% of the refractory material, and dry powder of cement mineral-based accelerator was used in an amount of 0.5% by outer percentage relative to 100% of the refractory material.

[0048] [Fire-resistant materials used in the examples and comparative examples] In both the Examples and Comparative Examples, the refractory material used as the base material was a mixed material consisting of alumina-silica, mullite, alumina, etc., with particle sizes shown in Tables 1-1 and 1-2 (hereinafter collectively referred to as Table 1) and Tables 2-1 and 2-2 (hereinafter collectively referred to as Table 2). As shown in Tables 1 and 2, this mixed material contains approximately 40% alumina-silica, alumina, silica fume, and clay of 0.075 mm or less, classified using a sieve with an opening of 0.075 mm.

[0049] [Methods for spraying refractories for dry spraying in Examples, Reference Examples and Comparative Examples] Powder mixtures with the respective formulations shown in Tables 1 and 2 were prepared to obtain refractories for dry gunning as Examples and Comparative Examples, respectively. Then, dry gunning was performed using the refractories for dry gunning obtained above as Examples and Comparative Examples, each having a different hardener composition, in the manner described below. The conditions during construction of each of the resulting gunned bodies, as well as each of cast bodies obtained by mixing with the same amount of added water as in dry gunning and casting into a formwork of a predetermined shape, separate from the actual dry gunning, were evaluated by the method described below. The results are summarized in Tables 1 and 2. Tables 1 and 2 also include a reference example of a conventional example proposed by the present applicant, which was previously described as prior art, in which dry gunning was performed using a refractory for dry gunning that contained a silica sol, not a dry powder, but a reduced amount of alumina cement as a hardener.

[0050] The dry gunning described above was performed using a gunning nozzle. The dry powder mixtures obtained by premixing the dry powder materials shown in Tables 1 and 2 were used as the dry gunning refractories. Specifically, each dry powder mixture was pumped into the gunning nozzle, and the amount of water shown in Tables 1 and 2 was added to the nozzle tip to mix and knead the powder mixture within the nozzle tip. The kneaded mixture was then sprayed from the nozzle onto the same surface to form the gunned body. The properties of each gunned body, as well as the workability and operability during construction, were evaluated using the methods described below. The evaluation results are summarized in Tables 1 and 2.

[0051] The above-mentioned casting into the formwork was carried out using a kneading mixer, and the dry powder mixtures obtained by pre-mixing the dry powder materials shown in Tables 1 and 2 were used as the dry gunning refractories. Specifically, each powder mixture made of dry powder and the amount of water shown in Tables 1 and 2 were charged into a kneading mixer, and the kneaded mixture obtained by mixing was cast into a predetermined formwork to form a cast body. The properties of each cast body formed were then evaluated by the methods described below, and the evaluation results are summarized in Tables 1 and 2.

[0052] [evaluation] As described above, the refractories for dry gunning prepared in Examples 1 to 7, Comparative Examples 1 to 10, and Reference Example, each having a different formulation, were applied to dry gunning and evaluated, and the evaluation results are summarized in Tables 1 and 2. The refractories for dry gunning of Examples 1 to 7, Comparative Examples 1 to 10, and Reference Example were evaluated by the following methods and according to the following criteria.

[0053] <Ventilation rate of construction body> After dry spraying using each of the dry powder mixtures, the construction was cured at room temperature for 24 hours or more, and the construction was sampled. The sampled construction was dried at 110°C for 24 hours or more, and the dried body was processed into a shape of φ50 mm x height 50 mm to be used as a sample for measuring air permeability. Then, the air permeability (m 2 According to the study by the present inventors, the permeability of the dried body measured as described above was 5 × 10 -15 m 2 When the air permeability is 5 × 10 or more, the product can be dried stably in a short time and has explosive resistance. From the above, it is considered that the condition for the surface condition of the construction body to have an appropriate porosity suitable for achieving the object of the present invention is a permeability of 5 × 10 -15 m 2 If the result is above this, it can be judged to be suitable for practical use. The measured values ​​are summarized in Tables 1 and 2. The symbol "-" in Table 2-2 indicates that the air permeability could not be measured for the following reason. Specifically, when dry spraying was performed, the applied material fell off and washed away before reaching the specified thickness required for measuring the air permeability, making it impossible to collect the applied material, and therefore no sample for measurement could be obtained, and the air permeability could not be measured.

[0054] <Dry spray application> 1.Adhesion Using actual dry spraying equipment (real machine), spray application tests were conducted on each dry powder mixture, and adhesion was judged based on whether or not a coating of the specified thickness could be formed on the surface to be applied. If adhesion was poor, the coating would fall off and wash away from the surface before reaching the specified thickness. The results of the adhesion tests on the coatings conducted using the real machine as described above were visually observed and evaluated according to the following criteria. Tables 1 and 2 summarize the results evaluated according to the following criteria.

[0055] (Evaluation criteria) ⊚: A construction body that reached the specified thickness was formed stably over the entire surface of the construction surface. ◯: A coating having a predetermined thickness was formed over the entire surface of the coating surface in a state that presented no practical problems. △: It was observed that some of the applied surface fell off before reaching the specified thickness. ×: The applied body fell off or washed away from the applied surface before reaching the predetermined thickness.

[0056] 2.Pot life A spray application test was conducted for each dry powder mixture using actual dry spraying equipment (real machine), and the results were judged based on whether the surface of the applied product could be shaped using a trowel or other tool within the desired predetermined time. The actual usable time was determined appropriately based on the balance with the work involved. In the above test, the usable time was set to the typical work time normally performed. The test results for the usable time of each application product formed on the applied surface using the actual machine, as described above, were evaluated according to the following criteria. Tables 1 and 2 summarize the results evaluated according to the following criteria.

[0057] (Evaluation criteria) ⊚: The usable time of the formed construction body was sufficient for the specified time, and the shaping work could be carried out in good condition. ◯: The usable life of the formed construction body was sufficient for the specified time, and the shaping work could be carried out without any practical problems. △: The usable life of the formed construction body was sufficient for the specified time, and shaping work could be carried out without any practical problems, but there were some parts of the construction body with a short usable life, but it was recognized that this was not a problem in practical use. ×: The usable time of the formed construction product was clearly shorter than the predetermined time, and the shaping work could not be carried out sufficiently. -: When dry spraying was performed, the applied product fell off and washed away before reaching the specified thickness, so no applied product was obtained and the usable life could not be evaluated.

[0058] 3. Nozzle clogging Using actual dry spraying equipment (actual machine), spraying tests were conducted on each dry powder mixture, and the clogging condition of the spraying nozzle was visually observed. The evaluation results were judged according to the following criteria and are shown in Tables 1 and 2. (Evaluation criteria) ○: Spraying was possible without nozzle clogging. △: Spraying was possible without any practical problems, but slight nozzle clogging was observed. ×: Nozzle was clogged and good spraying was not possible.

[0059] <Drying time> The evaluation was based on the time required for the applied body of dry spraying refractory material, when applied to a thickness of 200 mm, to reach the drying temperature without exploding. Specifically, the evaluation was based on the time required for the drying temperature to reach 800°C. In this specification, the time required for the above drying is referred to as the drying time, and is shown in Tables 1 and 2. A smaller drying time indicates faster drying. In Table 2, a "-" indicates that the applied body fell off and washed away from the applied surface before reaching the above-mentioned thickness of 200 mm during dry spraying, making it impossible to evaluate the drying time. To achieve efficient application, a drying time of approximately 10 to 15 hours is preferable.

[0060] <Workability> For each of the dry gunning refractories of Examples 1 to 4, Comparative Examples 1 to 6, and Reference Example, the handling (workability) when applied to dry gunning was evaluated based on the following criteria for the storage, transportation, and kneading operations during gunning. The results are summarized in Tables 1 and 2. (Evaluation criteria) ○: Only the dry powder paper bags containing all the materials are stored and transported to the work site. Construction can be completed by simply adding water to the dry powder materials pressure-fed to the nozzle tip and mixing and kneading them. ×: In addition to the paper bag containing the dry powder material, a 18L can containing silica sol is prepared and stored, and the paper bag and the 18L can are transported separately to the work site. The silica sol is transferred from the 18L can to another container, and the silica sol in the prepared container is added to the dry powder material being pressure-fed to the tip of the nozzle, and the mixture is mixed and kneaded before dry spraying.

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[0065] A comparison of Tables 1 and 2 confirmed the following. First, as shown in Table 1, a comparison of Examples 1 to 7 with the Reference Examples shown in Tables 1-2 shows that the dry-sprayed refractories of Examples 1 to 7, which are configured according to the present invention, can be dry-sprayed onto a target surface simply by mixing and kneading the dry powder mixture with water to produce a target body that is comparable in quality to a target body formed using a conventional dry-sprayed refractory using silica sol. Specifically, the dry-sprayed refractories of Examples 1 to 7 provide excellent adhesion to the target surface, and the target body has a sufficient and appropriate usable life, eliminating operational problems. In particular, although depending on the hardener formulation, they exhibit slightly higher air permeability than the target body of the Reference Example, and, like the target body of the Reference Example, drying time can be shortened without causing explosion. Furthermore, the problem of nozzle clogging during application is reduced, resulting in excellent work efficiency in application, similar to the case of obtaining the target body of the Reference Example. The major difference between the use of the refractories for dry gunning in Examples 1 to 7 and the use of the conventional refractories for dry gunning configured using silica sol shown in the Reference Examples is that the workload is significantly reduced. That is, when the refractories of the Reference Examples are used for dry gunning, it is necessary to store and transport the silica sol, which is not a dry powder, in a 18-liter can separately from the dry powder material, and further, during the dry gunning work, it is necessary to transfer the silica sol to another container and dispose of the empty 18-liter can, so the workload on the worker is significantly different compared to when the refractories of the Examples are used.

[0066] A comparison of Tables 1 and 2 confirmed the following. First, when neither the dry powder of alumina gel nor the cement mineral-based quick-setting admixture, which are essential in the present invention, was used, particularly when the cement mineral-based quick-setting admixture was not used, the finished product fell off and washed away before reaching the predetermined thickness during dry spraying, making it impossible to collect the finished product and resulting in no product suitable for practical use. Furthermore, it was found that the use of only the cement mineral-based quick-setting admixture resulted in poor air permeability and the inability to shorten the drying time, making it impossible to achieve the object of the present invention. Furthermore, it was also found that when the amount of cement mineral-based quick-setting admixture was increased, problems with usable time and nozzle clogging occurred, making the resulting finished product unsuitable for practical use.

[0067] [Examples 2, 5-7, Comparative Examples 7-10] - Examination of the amount of alumina cement added As described above, in the dry-spraying refractories of Examples 5 to 7 and Comparative Examples 7 to 10, the formulation of the dry powder refractory material, which is the basic base material, was the same as in Examples 1 to 4 and Comparative Examples 1 to 6. Furthermore, in Examples 5 to 7, the formulation amounts of the hardeners, i.e., alumina cement, alumina gel dry powder, and cement mineral-based quick-setting admixture, were changed, as shown in Table 3. Specifically, the dry powder alumina cement was used in Examples 2, 5 to 7, with the amount gradually changed from 1% to 10% (0.3% to 3% as CaO). In Examples 2, 5 to 7, the amount of alumina gel dry powder was kept constant at 2%, and the amount of Natomic, a cement mineral-based quick-setting admixture, was kept constant at 0.5%, as shown in Table 1-2.

[0068] In comparison with the above Examples 2 and 5 to 7, as shown in Table 3, in Comparative Examples 7 and 8, the blending amount of dry powder alumina cement was less than that specified in the present invention, and in Comparative Examples 9 and 10, the blending amount of dry powder alumina cement was greater than that specified in the present invention. Furthermore, in Comparative Examples 7 and 10, neither dry powder of alumina gel nor Natomic, a cement mineral-based quick-setting admixture, was blended.

[0069] Using the dry gunning refractories of Examples 2, 5 to 7 and Comparative Examples 7 to 10, each having the composition shown in Table 3, evaluation tests were carried out in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 6. The results obtained are summarized in Table 3.

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[0071] The results in Table 3 confirmed the following: As in Comparative Example 10, when the blending amount of alumina cement was higher than that specified in the present invention, and the calcium oxide component in the alumina cement exceeded 3.0%, the constructed body was inferior in terms of air permeability compared to the Examples, and it was found that the drying time could not be shortened. Furthermore, as shown in Table 3, a comparison between Comparative Examples 9 and 10 revealed that even when the blending amount of alumina cement was high, the drying time could be shortened by using alumina gel dry powder and a cement mineral-based quick-setting admixture in combination as a hardener. However, when the amount of alumina cement was high, a practical problem occurred in that the material cost increased, making it uneconomical.

[0072] On the other hand, the results of Comparative Examples 7 and 8 indicate that if the alumina cement formulation contains less than 0.3% calcium oxide, as specified in the present invention, a 200 mm thick concrete body cannot be formed, and even if dry alumina gel powder and a cement mineral-based quick-setting admixture are used in combination, it is not suitable for practical use. In contrast, the results of Table 1-2 indicate that, as in Example 5, even if the alumina cement formulation contains a low amount of calcium oxide, the lower limit specified in the present invention, of 0.3%, by using dry alumina gel powder and a cement mineral-based quick-setting admixture in combination with the hardener, a good concrete body can be formed by dry spraying, with a fast drying rate, good adhesion to the surface, and sufficient usable life. In this case, no nozzle clogging problems were observed. As shown in Table 3, a comparison of Example 7, in which alumina cement was blended so that the calcium oxide content in the alumina cement was 3.0%, with Examples 5, 2, and 6, in which the calcium oxide content in the alumina cement was less than 3.0%, revealed that permeability tends to decrease as the blending amount of alumina cement increases. For this reason, it is more preferable to blend the amount of alumina cement so that the calcium oxide content is within the range of 0.3% to 2.5%, or even 0.3% to 2.0%, in terms of outer percentage relative to 100% of the refractory material.

[0073] [Study example 1 - Ventilation rate of construction body] As described above, the construction body obtained by spraying the dry-type spraying refractory of the embodiment of the present invention exhibits high air permeability, and as a result, the drying time of the construction body after spraying can be significantly shortened. For example, as shown in Table 3, the air permeability of the conventional construction body obtained by spraying the dry-type spraying refractory of Comparative Example 10, which used only alumina cement as a hardener, was 1.0 x 10 -15 m 2 The drying time required to reach 800°C was 36 hours, whereas, as shown in Table 3, the air permeability of the construction body obtained by spraying the dry spraying refractory of Example 2 was 15 × 10 -15 m 2The drying time is reduced to 14 hours, more than half the time required, and the drying speed is significantly improved. The above air permeability values ​​are for the dried body that has been dried at 110°C for 24 hours or more.

[0074] The dry spraying refractory of Example 2 and the dry spraying refractory using a commonly used alumina cement hardener were used, and three types of samples were prepared: a specimen cured at room temperature (RT) for 24 hours or more, a specimen cured at room temperature for 24 hours or more and dried at 110°C for 24 hours or more, and a specimen cured at room temperature for 24 hours or more and dried at 150°C for 24 hours or more. Each specimen was cut into a shape of φ50 mm x height 50 mm, and the permeability (m ) was measured using an air permeability tester in accordance with JIS R2115:2008. 2 ) was measured. The measurement results are shown in Figure 1. As shown in Figure 1, it was confirmed that the air permeability of the body obtained after spraying the dry spraying refractory of Example 2 was significantly higher than that of the body obtained by spraying a commonly used refractory. For example, a dried body dried at 150°C for 24 hours or more showed an air permeability approximately 130 times higher than that of the body obtained by using a commonly used product. Furthermore, as shown in Figure 1, it was confirmed that the body obtained by spraying the dry spraying refractory of Example 2 exhibited high air permeability even at low temperatures, unlike the body obtained by using a commonly used product. This means that the body of the example of the present invention can be dried quickly even at low temperatures.

[0075] [Study example 2 - Drying curve of construction body] The dry-sprayed refractory of Example 2 and the dry-sprayed refractory of Comparative Example 10 were sprayed to obtain 200 mm thick refractory bodies. The furnace temperature for each refractory body was measured from room temperature until the refractory body reached 800 °C and dried in a satisfactory manner without explosion. The results are shown in Figure 2. As shown in Figure 2, for the refractory body according to the present invention, the drying rate increased from 50 °C / hr to 150 °C / hr at the 250 °C boundary, and the refractory body reached 800 °C in 14 hours without explosion. In contrast, for the refractory body according to Comparative Example 10, as shown in Figure 2, the drying rate had to be kept constant at 50 °C / hr. Furthermore, holding times at both 250 °C and 400 °C were required to suppress the temperature rise. Therefore, it took 36 hours to reach 800 °C without explosion.

[0076] [Study example 3 - Short-term drying characteristics of the construction body (internal steam pressure)] The dry-type spraying refractory of Example 2 and the dry-type spraying refractory of Reference Example, which was constructed using silica sol rather than dry powder, were mixed with the water amounts shown in Tables 1 and 2, mixed in a mixer, and cast into a mold in which thermocouples had been placed in the positions shown in Figure 3A to produce cast bodies each consisting of a 60 mm cube with an embedded thermocouple. The cast bodies were cured at room temperature for 24 hours or more and then placed in an electric furnace maintained at 400°C, and the internal temperature of the body was measured after heating began. A graph showing the relationship between the internal temperature and the time it took for the internal temperature to reach 200°C after heating began is shown in Figure 3B.

[0077] The temperature at the boundary between the constant-rate drying period, during which the internal temperature remains almost constant, and the subsequent falling-rate drying period, during which the moisture content reaches equilibrium, marked "Boundary Temperature" in Figure 3B, was read from the graph, and the saturated water vapor pressure was calculated to obtain the internal vapor pressure for each refractory body. The internal vapor pressure for the refractory body in the Example was 0.18 MPa, while that for the refractory body in the Reference Example was 0.24 MPa. It was found that the internal vapor pressure for the refractory body in the Example of the present invention was lower than that for the refractory body in the Reference Example. Thus, the internal vapor pressure for the refractory body in the Example of the present invention was lower than that for the refractory body using a dry-sprayed refractory material composed of silica sol, not dry powder, as shown in the Reference Example. Therefore, the refractory body in the Example of the present invention has a lower risk of explosion during drying than the refractory body in the Reference Example. This means that the refractory body in the Example of the present invention can be expected to dry in a shorter time than the refractory body in the Reference Example, which uses silica sol, not dry powder. In other words, for construction objects made of materials with a high risk of explosion, product yield is maintained by drying them for a long period of time, so being able to reduce the possibility of explosion, as in the construction objects of the examples of the present invention, is of great significance in improving work efficiency. [Industrial Applicability]

[0078] The dry-gunned refractory of the present invention is easy to install and is useful as a dry-gunned refractory for new construction and repair in any type of furnace, such as a waste incinerator, cement manufacturing equipment, or rotary kiln, to which any monolithic refractory can be applied, and its use is expected.

Claims

1. A dry spraying monolithic refractory used when a powder mixture is mixed with water and sprayed from the tip of a nozzle, The powder mixture comprises a dry powder refractory material, and as a hardener, dry powder alumina cement, dry powder of alumina gel, and dry powder cement mineral-based accelerator; The alumina cement is added in an amount such that the calcium oxide component is in the range of 0.3 mass% to 3.0 mass% in terms of outer percentage relative to 100 mass% of the refractory material, The dry powder of the alumina gel is added in an amount of 0.1 mass% or more and 5.0 mass% or less, based on 100 mass% of the refractory material, A dry-spraying amorphous refractory material characterized by containing the cement mineral-based quick-setting admixture in an amount ranging from 0.1 mass% to 3.0 mass% based on 100 mass% of the refractory material.

2. 2. The monolithic refractory for dry spraying according to claim 1, wherein the dry powder cement mineral-based quick-setting admixture is a calcium aluminate-based quick-setting admixture or a calcium sulfoaluminate-based quick-setting admixture.

3. A construction method for dry spraying by spraying the monolithic refractory for dry spraying according to claim 1 or 2 onto a surface to be treated from a spray nozzle, A dry spraying application method characterized by feeding the powder mixture to the spray nozzle, adding water at the tip of the spray nozzle to mix the powder mixture with water, and spraying the resulting mixture from the tip of the spray nozzle onto the surface to be applied.

4. 4. A dry spraying application method according to claim 3, wherein the application by spraying the obtained mixture onto the surface to be applied from the tip of the spray nozzle is carried out immediately after adding water at the tip of the spray nozzle to mix the powder mixture with water.

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