Composition for monolithic refractories and method for producing monolithic refractories

Abstract

The present invention provides a composition for monolithic refractories and a method for producing monolithic refractories that yield construction materials with high explosion resistance and recyclable monolithic refractories. [Solution] A composition for amorphous refractory materials comprising: refractory aggregate; a binder; at least one of an organic acid salt and an inorganic acid salt; aluminum lactate; and organic fibers, wherein the binder contains alkaline earth metal oxide fine powder, the content of the alkaline earth metal oxide fine powder is greater than 0.05% by mass and less than 11% by mass relative to the total amount of the amorphous refractory material composition, the particle size of the alkaline earth metal oxide fine powder is greater than 0.2 μm and less than 35 μm, and if the amorphous refractory material composition contains alumina cement, the content of calcium oxide is 0.2% by mass or less relative to the total amount of the amorphous refractory material composition.

Description

Technical Field

[0001] The present disclosure relates to a composition for monolithic refractories and a method for manufacturing monolithic refractories.

Background Art

[0002] Since alumina cement has excellent fire resistance, it has been conventionally used in cement castables. However, in conventional cement castables, as the content of alumina cement increases, problems such as a decrease in the heat resistance and corrosion resistance of the obtained monolithic refractory and deterioration of strength have occurred.

[0003] Therefore, a low-cement castable has been developed, which has a lower content of alumina cement compared to conventional cement castables and has a dramatic improvement in the heat resistance and corrosion resistance of the obtained monolithic refractory. A monolithic refractory is constructed by adding water to a low-cement castable, molding it, raising the temperature, and drying it. However, if the low-cement castable is rapidly heated, the free water inside the constructed body vaporizes into steam, causing the internal steam pressure of the constructed body to rise rapidly. If this steam pressure exceeds the strength of the constructed body, the constructed body will burst. In particular, low-cement castables have a smaller amount of water added compared to conventional cement castables, and the structure of the constructed body tends to be dense, so bursting is likely to occur, and more precise temperature control is required. Therefore, an amorphous refractory composition containing silicon carbide, aluminum lactate, and organic fibers has been disclosed as an amorphous refractory composition that is less likely to burst even when rapidly heated (Patent Document 1).

[0004] Furthermore, a powder composition for amorphous refractories has been disclosed that can form a refractory excellent in thermal stability and corrosion resistance, substantially containing no alumina cement, and containing an aggregate, a low-reactive alkaline earth metal oxide and a water-soluble organic or inorganic acid salt as a binder, and alumina fine powder (Patent Document 2).

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-101285 [Patent Document 2] Japanese Patent Publication No. 2011-47563 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, in order to shorten construction periods and for other reasons, there is a need for high spall resistance that prevents explosion even with rapid temperature increases.

[0007] Furthermore, conventionally, unprocessed monolithic refractories (for example, old industrial furnaces) were discarded as industrial waste after dismantling without being recycled. Even if attempts were made to recycle the pulverized monolithic refractories obtained from dismantling as raw materials for monolithic refractory compositions, the resulting material would tend to have a lower melting point and reduced heat resistance, or reduced corrosion resistance. However, in recent years, from the perspective of SDGs, the recycling of monolithic refractories has become necessary.

[0008] This disclosure is made in view of the foregoing, and relates to a composition for monolithic refractories and a method for manufacturing monolithic refractories, which yields a construction body with high explosion resistance and a recyclable monolithic refractories. [Means for solving the problem]

[0009] This disclosure includes the following aspects: <1> It contains fire-resistant aggregate, a binder, at least one of an organic acid salt and an inorganic acid salt, aluminum lactate, and organic fibers. The binder contains alkaline earth metal oxide fine powder, the content of which is greater than 0.05% by mass and less than 11% by mass relative to the total amount of the composition for amorphous refractories, and the particle size of which is greater than 0.2 μm and less than 35 μm. When a composition for monolithic refractories contains alumina cement, the calcium oxide content is 0.2% by mass or less relative to the total amount of the monolithic refractory composition. Composition for monolithic refractories. <2> The aforementioned alkaline earth metal oxide fine powder is magnesia fine powder. <1> A composition for amorphous refractories as described above. <3> The aforementioned fire-resistant aggregate contains at least one of alumina and silica. <1> or <2> A composition for amorphous refractories as described above. <4> The content of the aforementioned refractory aggregate is 65% to 90% by mass relative to the total amount of the composition for amorphous refractories. <1> ~ <3> A composition for amorphous refractory materials as described in any one of the following. <5> The total content of the organic salts and inorganic salts is 0.05% to 0.3% by mass relative to the total amount of the composition for amorphous refractories. <1> ~ <4> A composition for amorphous refractory materials as described in any one of the following. <6> The content of aluminum lactate is 0.1% to 0.9% by mass relative to the total amount of the composition for amorphous refractories. <1> ~ <5> A composition for amorphous refractory materials as described in any one of the following. <7> The content of the aforementioned organic fibers is 0.005% to 0.7% by mass relative to the total amount of the composition for amorphous refractories. <1> ~ <6> A composition for amorphous refractory materials as described in any one of the following. <8> Furthermore, it contains bentonite, <1> ~ <7> A composition for amorphous refractory materials as described in any one of the following. <9> The bentonite content is 0.5% to 3% by mass relative to the total amount of the monolithic refractory composition. <8> A composition for amorphous refractories as described above. <10> Furthermore, it contains fire-resistant powder, <1> ~ <9> A composition for amorphous refractory materials as described in any one of the following. <11> The aforementioned fire-resistant aggregate is <1> ~ <10> Contains crushed monolithic refractories produced from any one of the monolithic refractory compositions described in any one of the following: <1> ~ <10> A composition for amorphous refractory materials as described in any one of the following. <12> It is for spray application. <1> ~ <11> A composition for amorphous refractory materials as described in any one of the following. <13> <1> ~ <12> A method for producing an unshaped refractory, comprising producing an unshaped refractory using an unshaped refractory composition described in any one of the following. <14> <1> ~ <12> A method for producing an amorphous refractory, comprising: adding water to an amorphous refractory composition described in any one of the above; molding the amorphous refractory composition to which water has been added; and drying the molded amorphous refractory composition. [Effects of the Invention]

[0010] This disclosure provides a composition for monolithic refractories and a method for manufacturing monolithic refractories, which yields a construction body with high explosion resistance and a recyclable monolithic refractories. [Modes for carrying out the invention]

[0011] One embodiment of this disclosure is described in detail below. However, this disclosure is not limited to the embodiment described below. In the following disclosure, the components (including elemental steps, etc.) are not essential unless otherwise explicitly stated. The same applies to numerical values ​​and their ranges, and do not limit this disclosure.

[0012] In this disclosure, the numerical range indicated using "~" includes the numbers before and after "~" as the lower and upper limits, respectively. In numerical ranges described in stages within this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described within this disclosure, the upper or lower limit of that range may be replaced with the values ​​shown in the examples. In this disclosure, the content of each component in the composition means the total content of the multiple substances present in the composition, unless otherwise specified, if multiple substances corresponding to each component are present in the composition. Where multiple elements are listed using "or" or "or," unless otherwise explicitly stated, this does not preclude selecting multiple elements in combination, provided that it does not result in a technical inconsistency. Even when an element is described in the singular form in the present disclosure, unless otherwise expressly stated, the existence of a plurality is not excluded as long as there is no technical contradiction. In the present disclosure, a plurality of exemplary embodiments described separately may be combined with each other to form a new embodiment as long as they do not contradict each other.

[0013] In the present disclosure, the "composition for monolithic refractories" refers to the composition for monolithic refractories before water is added. The "monolithic refractory" refers to an object obtained by adding water to the composition for monolithic refractories, molding it, and further drying it. The "constructed body" includes an object during construction and a monolithic refractory obtained by construction.

[0014] ≪Composition for Monolithic Refractories≫ The composition for monolithic refractories of the present disclosure contains a refractory aggregate, a binder, at least one of an organic acid salt and an inorganic acid salt, aluminum lactate, and organic fibers. The binder contains alkaline earth metal oxide fine powder, the content rate of the alkaline earth metal oxide fine powder is more than 0.05% by mass and less than 11% by mass with respect to the total amount of the composition for monolithic refractories, and the particle diameter of the alkaline earth metal oxide fine powder is more than 0.2 μm and less than 35 μm. When the composition for monolithic refractories contains alumina cement, the content rate of calcium oxide is 0.2% by mass or less with respect to the total amount of the composition for monolithic refractories.

[0015] According to the composition for monolithic refractories of the present disclosure, a constructed body having high spalling resistance and a recyclable monolithic refractory can be obtained. The action of the composition for monolithic refractories of the present disclosure is presumed as follows.

[0016] The water inside the construction body exists as free water or structural water. Free water is the water that does not undergo a hydration reaction among the water added to the composition for amorphous refractories and exists inside the construction body as liquid water (i.e., H2O) as it is. Since the boiling point of water is 100 °C, when heated (for example, during the temperature rise for drying the construction body), the vapor pressure due to the free water inside the construction body rapidly rises near 100 °C, and the construction body is likely to burst. In particular, low-cement castables are likely to have a dense structure. Therefore, when heated, the escape routes for water vapor and the like generated inside the construction body are likely to be lost, and it is likely to burst. Both aluminum lactate and organic fibers contained in the composition for amorphous refractories of the present disclosure improve the air permeability of the construction body. Therefore, the construction body obtained from the composition for amorphous refractories of the present disclosure has high spalling resistance.

[0017] And when the amorphous refractory contains a certain amount or more of a mineral having calcium oxide (CaO) in its composition (for example, anorthite: CaO·Al2O3·Si2O8), even if the pulverized product of this amorphous refractory is recycled as a raw material for the composition for amorphous refractories, the product obtained by recycling has a liquid-phase formation temperature of less than 1250 °C, and the melting point and heat resistance are reduced. The binder used in the composition for amorphous refractories of the present disclosure contains fine powder of alkaline earth metal oxide in which a mineral having CaO in its composition is not generated. Furthermore, in the amorphous refractory using fine powder of alkaline earth metal oxide, a mineral having a higher melting point than anorthite is likely to be generated. Furthermore, the composition for amorphous refractories of the present disclosure is set so that the CaO content is very small, 0.2 mass% or less with respect to the total amount of the composition for amorphous refractories. Therefore, even when the composition for amorphous refractories of the present disclosure contains alumina cement that generates a mineral having CaO in its composition, the amorphous refractory obtained from the composition for amorphous refractories is unlikely to have a low melting point. That is, it is possible to recycle the pulverized product of the amorphous refractory obtained from the composition for amorphous refractories of the present disclosure as a raw material for the composition for amorphous refractories, and the product obtained by recycling can be used as an amorphous refractory. Furthermore, this disclosure is not limited in any way to the estimation mechanism described above.

[0018] <Refractory aggregate> The monolithic refractory composition disclosed herein contains refractory aggregate. The monolithic refractory composition disclosed herein may contain two or more types of refractory aggregate. In this disclosure, the particle size of the "refractory aggregate" is 10 μm or larger from the viewpoint of exhibiting its function as an aggregate, preferably 10 μm to 10 mm, more preferably 30 μm to 7 mm, and even more preferably 45 μm to 5 mm. In this disclosure, the particle size of the refractory aggregate can be measured by a sieving test in accordance with JIS Z 8815:1994, and is the particle size at which the cumulative volume becomes 50%. The "refractory aggregate" in this disclosure and the "refractory powder" described later are distinguished by the difference in particle size.

[0019] The refractory aggregate is not particularly limited as long as it can be used in the manufacture of monolithic refractories. The monolithic refractory composition of this disclosure may contain two or more types of refractory aggregate. The refractory aggregate preferably contains at least one element selected from the group consisting of aluminum, silicon, chromium, zirconium, magnesium, boron, and carbon. The refractory aggregate is more preferably at least one selected from the group consisting of carbon such as alumina, high-purity alumina, bauxite, diaspore, mullite, kyanite, ban shale, chamotte, silica, silica, pyrophyllite, sillimanite, andalusite, chromite, spinel, magnesia, zirconia, zircon, chromia, silicon nitride, aluminum nitride, silicon carbide, boron carbide, graphite, titanium boride, and zirconium boride. Furthermore, the Al2O3 content in high-purity alumina is 90% by mass or more, in bauxite it is 80% to 89% by mass, in mullite it is around 60% by mass, and in chamotte it is 40% to 50% by mass.

[0020] From the viewpoint of heat resistance, corrosion resistance, and cost, refractory aggregates preferably contain at least one of alumina and silica, and silica-alumina-based raw materials are more preferable. Silica-alumina-based raw materials are refractory raw materials mainly composed of silica and / or alumina. That is, refractory aggregates preferably contain at least one selected from the group consisting of alumina, high-purity alumina, bauxite, diaspore, mullite, kyanite, ban shale, chamotte, silica, siliceous rock, pyrophyllite, sillimanite, andalusite, spinel, zircon, silicon nitride, aluminum nitride, and silicon carbide.

[0021] The refractory aggregate may contain crushed monolithic refractories produced from the monolithic refractory composition of the present disclosure. In other words, the refractory aggregate may be aggregate obtained by recycling monolithic refractories of the present disclosure, as described later. The particle size of the crushed monolithic refractories produced from the monolithic refractory composition of this disclosure is 10 μm or larger, preferably 10 μm to 10 mm, more preferably 30 μm to 7 mm, and even more preferably 45 μm to 5 mm, from the viewpoint of exhibiting its function as an aggregate. In this disclosure, the particle size of the crushed monolithic refractories can be measured by a sieving test in accordance with JIS Z 8815:1994, and is the particle size at which the cumulative volume is 50%.

[0022] From the viewpoint of improving explosion resistance, the lower limit of the refractory aggregate content is preferably 65% ​​by mass or more, more preferably 70% by mass or more, and even more preferably 75% by mass or more, based on the total amount of the composition for amorphous refractory materials. From the viewpoint of improving explosion resistance, the upper limit of the refractory aggregate content is preferably 90% by mass or less, more preferably 87% by mass or less, and even more preferably 85% by mass or less, relative to the total amount of the composition for amorphous refractory materials.

[0023] <Binder> The monolithic refractory composition disclosed herein contains a binder. The monolithic refractory composition disclosed herein may contain two or more binders.

[0024] (Alkaline earth metal oxide fine powder) The binder includes the alkaline earth metal oxide fine powder of this disclosure having a particle size greater than 0.2 μm and less than 35 μm. The amorphous refractory composition of this disclosure may contain two or more types of the alkaline earth metal oxide fine powder of this disclosure. Alkaline earth metal oxide fine powder and at least one of the organic acid salts and inorganic acid salts described later bind the refractory aggregates together to form a dense structure.

[0025] In this disclosure, fine powder refers to powder with a particle size of less than 35 μm. The lower limit of the particle size of fine powder is not particularly limited, and is, for example, greater than 0 μm. In this disclosure, the particle size of fine powder can be measured by a laser diffraction particle size distribution method in accordance with JIS Z 8825:2013, and is the particle size at which the cumulative volume is 50%.

[0026] The alkaline earth metal oxide fine powders disclosed herein are low-reactivity alkaline earth metal oxide fine powders. In this disclosure, "low-reactivity" means that the material itself is not reactive. The opposite of "low-reactivity," "active," means that the material itself is reactive.

[0027] The alkaline earth metal oxide fine powder of this disclosure, having a particle size greater than 0.2 μm and less than 35 μm, is a low-reactivity alkaline earth metal oxide fine powder. That is, the alkaline earth metal oxide fine powder of this disclosure does not have the effect of curing the amorphous refractory composition by its own addition, but cures by contact with at least one of an inorganic acid salt and an organic acid salt. For example, activated magnesia differs from the alkaline earth metal oxide fine powders of this disclosure in that it effectively promotes the hardening of the amorphous refractory composition itself. Also, for example, magnesia aggregate and calcia aggregate differ from the alkaline earth metal oxide fine powders of this disclosure in that, although they are alkaline earth metal oxides, they cannot harden the amorphous refractory composition themselves, nor do they harden when in contact with inorganic or organic acid salts.

[0028] From the viewpoint of heat resistance, the alkaline earth metal oxide fine powder of this disclosure is preferably at least one selected from the group consisting of calcia fine powder (CaO), magnesia fine powder (MgO), and strontium oxide fine powder (SrO), with magnesia fine powder being more preferred.

[0029] The particle size of the alkaline earth metal oxide fine powder in this disclosure is less than 35 μm, and is preferably less than 30 μm, and more preferably less than 25 μm, from the viewpoint of making the amorphous refractory composition easier to cure and facilitating the removal of the construction body. The particle size of the alkaline earth metal oxide fine powder in this disclosure is greater than 0.2 μm, preferably greater than 0.3 μm, and more preferably greater than 0.5 μm, from the viewpoint of extending the pot life. Pot life is the time from when water is added to the composition for amorphous refractories until the mixture loses its fluidity. When the particle size of the alkaline earth metal oxide fine powder is greater than 0.2 μm, the surface area of ​​the particles does not become too large, resulting in a low-reactivity alkaline earth metal oxide fine powder. In this disclosure, the particle size of the alkaline earth metal oxide fine powder can be measured by a laser diffraction particle size distribution method in accordance with JIS Z 8825:2013, and is the particle size at which the cumulative volume is 50%.

[0030] The content of alkaline earth metal oxide fine powder in this disclosure is more than 0.05% by mass relative to the total amount of the composition for monolithic refractories, and more than 0.1% by mass is preferred, and more than 0.5% by mass is preferred, from the viewpoint of facilitating the curing of the composition for monolithic refractories. The content of alkaline earth metal oxide fine powder in this disclosure is less than 11% by mass relative to the total amount of the composition for amorphous refractories. From the viewpoint of not requiring too much water to be added during the mixing of the composition for amorphous refractories and thus facilitating the curing of the composition for amorphous refractories, it is preferably less than 10% by mass, and more preferably less than 9% by mass.

[0031] Furthermore, the particle size of alkaline earth metal oxide fine powder in compositions for amorphous refractories can be measured by combining a scanning electron microscope (SEM) and an energy-dispersive X-ray spectrometer (EDS). For example, the particle size can be calculated by using an EDS to identify the alkaline earth metal oxide fine powder with an SEM and then taking the average of the particles within the field of view at approximately 2000x magnification. The content of alkaline earth metal oxide fine powder in the composition for monolithic refractories can also be measured from the composition for monolithic refractories in accordance with JIS R 2216 "Fluorescent X-ray Analysis Method for Refractory Products". The content can be determined by, for example, calculating the elemental concentration from the X-ray intensity using the relationship formula between the elemental concentration of the above-mentioned alkaline earth metal oxide (e.g., MgO) and the X-ray intensity. Specifically, a calibration curve can be created using multiple samples with relatively similar components as standard samples, and the concentration of the unknown sample can be determined by interpolation in principle. The content of alkaline earth metal oxide fine powder in the monolithic refractories can be obtained by multiplying the determined content of alkaline earth metal oxide fine powder by the ratio of the monolithic refractories composition fine powder to the total monolithic refractories composition. Note that monolithic refractories composition fine powder is the monolithic refractories composition from which the refractory aggregate has been removed.

[0032] (Alumina cement) The binder may include alumina cement. Alumina cement is a cement containing CaO·Al2O3. Alumina cement can maintain the strength of monolithic refractories manufactured over a wide temperature range, from room temperature to high temperatures.

[0033] When the binder contains alumina cement, from the viewpoint of raising the melting point of the resulting monolithic refractory, the alumina cement content is preferably 0.7% by mass or less, more preferably 0.4% by mass or less, and even more preferably 0.1% by mass or less, relative to the total amount of the monolithic refractory composition. The alumina cement content may be greater than 0% by mass relative to the total amount of the composition for monolithic refractories.

[0034] When the binder contains alumina cement, from the viewpoint of improving suitability for rapid temperature rise and improving explosion resistance, the CaO·Al2O3 content is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, relative to the total amount of alumina cement. From a cost perspective, the CaO·Al2O3 content is preferably 99% by mass or less relative to the total amount of alumina cement.

[0035] When the binder contains alumina cement, the calcium oxide (CaO) content is 0.2% by mass or less relative to the total amount of the composition for amorphous refractories, preferably 0.1% by mass or less, and more preferably 0.05% by mass or less, from the viewpoint of raising the melting point. The calcium oxide content may be greater than 0% by mass relative to the total amount of the composition for amorphous refractories. When the binder contains alumina cement, the content of calcium oxide (CaO) derived from the alumina cement is preferably 0.2% by mass or less relative to the total amount of the composition for amorphous refractories.

[0036] The calcium oxide content in the monolithic refractory composition can be measured by quantitative analysis of chemical components using a calibration curve method. For example, a method can be applied in which the elemental concentration is calculated from the X-ray intensity using a relationship formula between the calcium oxide concentration and the X-ray intensity. Specifically, a calibration curve can be created using multiple samples with relatively similar components as standard samples, and the concentration of the unknown sample can be determined in principle by interpolation. The calculated calcium oxide content can be multiplied by the ratio of the monolithic refractory composition fine powder to the total monolithic refractory composition to obtain the calcium oxide content in the monolithic refractory composition.

[0037] Furthermore, if the binder does not contain alumina cement, the content of calcium oxide (CaO) relative to the total amount of the composition for amorphous refractories is not particularly limited.

[0038] <Organic acid salts, inorganic acid salts> The compositions for amorphous refractories disclosed herein contain at least one of an organic acid salt and an inorganic acid salt. The compositions for amorphous refractories disclosed herein may contain two or more organic acid salts, or two or more inorganic acid salts.

[0039] For organic acid salts, water-soluble organic acid salts are preferred, and for inorganic acid salts, water-soluble inorganic acid salts are preferred. In this disclosure, water solubility means dissolving 10 g or more in 1 L of water at 25°C.

[0040] The water-soluble organic salts and water-soluble inorganic salts can be any salts that elute ions in water and react with alkaline earth metal oxide fine powders. Examples of water-soluble organic acid salts include water-soluble organic acids such as carboxylic acids or sulfonic acids, carboxylate salts and sulfonates, and preferably sodium carboxylate, sodium polycarboxylate, potassium carboxylate, potassium polycarboxylate, sodium sulfonate, and potassium sulfonate. Examples of water-soluble inorganic salts include phosphates, carbonates, sulfates, and hydrochlorides, which consist of an inorganic acid and an alkali metal atom. Preferably, sodium phosphate, sodium tripolyphosphate, potassium phosphate, sodium carbonate, and potassium carbonate are included.

[0041] Organic acid salts and inorganic acid salts function as dispersants in the amorphous refractory compositions of this disclosure. Organic and inorganic acid salts, when combined with alkaline earth metal oxide fine powder, promote the elution of cations from the alkaline earth metal oxide fine powder. Refractory aggregates (e.g., alumina and silica) are negatively charged and repel each other in water, remaining dispersed without agglomerating due to their own van der Waals forces. When cations generated from the alkaline earth metal oxide fine powder act on the refractory aggregate, the refractory aggregate is electrically neutralized, inhibiting its dispersion, and the alkaline earth metal oxide fine powder and refractory aggregate agglomerate due to van der Waals forces. Therefore, the amorphous refractories of this disclosure are thought to form a dense structure.

[0042] From the viewpoint of obtaining an amorphous refractory with a dense structure, the total content of organic acid salts and inorganic acid salts is preferably more than 0.05% by mass, more preferably more than 0.06% by mass, and even more preferably more than 0.07% by mass, relative to the total amount of the amorphous refractory composition. From the viewpoint of corrosion resistance, the total content of organic salts and inorganic salts is preferably less than 0.3% by mass, more preferably less than 0.27% by mass, and even more preferably less than 0.25% by mass, relative to the total amount of the composition for amorphous refractories.

[0043] <Aluminum lactate> The monolithic refractory composition disclosed herein contains aluminum lactate. The monolithic refractory composition disclosed herein may contain two or more types of aluminum lactate. Examples of aluminum lactate include aluminum lactate normal salt represented by Al(OCOCH(OH)CH3)3, basic aluminum lactate represented by Al(OH)(OCOCH(OH)CH3)2 or Al(OH)2(OCOCH(OH)CH3), and hydrates thereof. Among those mentioned above, aluminum lactate is preferably at least one selected from the group consisting of basic aluminum lactate and hydrated basic aluminum lactate. Aluminum lactate may also be a composite salt with citric acid or glycolic acid, etc.

[0044] From the viewpoint of improving the permeability of the monolithic refractory material and further enhancing its suitability for rapid temperature rise, the aluminum lactate content is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more, based on the total amount of the composition for the monolithic refractory material. From the viewpoint of improving the strength of monolithic refractories and further suppressing the occurrence of curing shrinkage cracks in monolithic refractories, the aluminum lactate content is preferably 0.9% by mass or less, more preferably 0.8% by mass or less, and even more preferably 0.7% by mass or less, based on the total amount of the composition for monolithic refractories.

[0045] <Organic Fibers> The monolithic refractory composition disclosed herein contains organic fibers. The monolithic refractory composition disclosed herein may contain two or more types of organic fibers. The type of organic fiber is not particularly limited, but at least one selected from the group consisting of polypropylene fibers, polyethylene fibers, polyester fibers, polyvinyl alcohol fibers, and cellulose fibers is preferred, with polypropylene fibers being preferred from the viewpoint of suitability for rapid temperature rise.

[0046] From the viewpoint of further improving suitability for rapid temperature rise, the fiber length of the organic fiber is preferably 10 μm or more, more preferably 100 μm or more, and even more preferably 1.0 mm or more. From the viewpoint of further improving the transportability by an airflow-type sprayer when spraying compositions for amorphous refractories, the fiber length of the organic fibers is preferably 20 mm or less, more preferably 15 mm or less, and even more preferably 10 mm or less. The monolithic refractory compositions disclosed herein may contain two or more organic fibers with different fiber lengths. The fiber length shall be measured in accordance with JIS L 1015:2010.

[0047] From the viewpoint of further improving suitability for rapid temperature rise, the fineness of the organic fiber is preferably 0.1 dtex or higher, more preferably 0.5 dtex or higher, and even more preferably 1 dtex or higher. From the viewpoint of further improving the transportability by an airflow-type sprayer when spraying compositions for amorphous refractories, the fineness of the organic fibers is preferably 20 dtex or less, more preferably 15 dtex or less, and even more preferably 10 dtex or less. Fineness is measured in accordance with JIS L 1015:2010.

[0048] From the viewpoint of improving the breathability of amorphous refractories and further enhancing their suitability for rapid temperature rise, the content of organic fibers is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.05% by mass or more, and particularly preferably 0.1% by mass or more, relative to the total amount of the composition for amorphous refractories. From the viewpoint of improving the strength of monolithic refractories and further improving the transportability by air-flow-type sprayers when spraying compositions for monolithic refractories, the content of organic fibers is preferably 0.7% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.4% by mass or less, and particularly preferably 0.3% by mass or less, relative to the total amount of the compositions for monolithic refractories.

[0049] <Bentonite> The monolithic refractory composition disclosed herein preferably contains bentonite. The monolithic refractory composition disclosed herein may contain two or more types of bentonite. Bentonite is a weakly alkaline clay rock whose main component is the clay mineral montmorillonite. Bentonite may contain silicate minerals such as quartz, α-cristobalite, and opal as minor components. Furthermore, bentonite may be associated with silicate minerals such as feldspar, mica, and zeolite, carbonate minerals such as calcite, dolomite, and gypsum, sulfate minerals, and sulfide minerals such as pyrite.

[0050] From the viewpoint of reducing dust generation during spraying, the bentonite content is preferably 0.5% by mass or more, more preferably 0.8% by mass or more, and even more preferably 1% by mass or more, based on the total amount of the composition for monolithic refractories. From the viewpoint of further improving the strength, corrosion resistance, and transportability by air-flow spraying machines of monolithic refractories, the bentonite content is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less, based on the total amount of the composition for monolithic refractories.

[0051] From the viewpoint of rapid setting action, the particle size of bentonite is preferably 45 μm or less, and more preferably 10 μm or less. The particle size of bentonite may be 1 μm or more. In this disclosure, the particle size of bentonite can be measured by a laser diffraction particle size distribution method in accordance with JIS Z 8825:2013, and is the particle size at which the cumulative volume is 50%.

[0052] <Refractory powder> The compositions for monolithic refractories disclosed herein preferably contain refractory powders. The compositions for monolithic refractories disclosed herein may contain two or more types of refractory powders. In this disclosure, the particle size of the "refractory powder" is less than 10 μm. In this disclosure, the particle size of the refractory powder can be measured by a laser diffraction particle size distribution method in accordance with JIS Z 8825:2013, and is the particle size at which the cumulative volume is 50%.

[0053] The type of refractory powder is not particularly limited, as long as it can penetrate the gaps between the refractory aggregates and bond them together. The refractory powder is preferably at least one selected from the group consisting of alumina, titania, bauxite, diaspore, mullite, van shale, chamotte, pyrophyllite, sillimanite, andalusite, silica, chromite, spinel, magnesia, zirconia, zircon, chromia, silicon nitride, aluminum nitride, silicon carbide, boron carbide, titanium boride, zirconium boride, and amorphous silica such as silica. The materials described above may be used in a colloidal state, either entirely or partially, dispersed in a liquid.

[0054] From the viewpoint of further improving the strength and corrosion resistance of monolithic refractories, the content of refractory powder is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, based on the total amount of the composition for monolithic refractories. From the viewpoint of reducing dust generation when spraying the monolithic refractory composition and further improving the transportability by an airflow-type spraying machine, the content of refractory powder is preferably 24% by mass or less, more preferably 22% by mass or less, and even more preferably 20% by mass or less, based on the total amount of the monolithic refractory composition.

[0055] <Additives> The monolithic refractory composition disclosed herein may contain additives other than those described above. The monolithic refractory composition disclosed herein may contain two or more additives. Examples of additives include dispersants other than the organic and inorganic salts mentioned above, inorganic binders other than CaO·Al2O3, antioxidants, shrinkage-reducing agents, thickeners, pH adjusters, surfactants, and defoamers. Other inorganic binders besides CaO·Al2O3 include 12CaO·7Al2O3, CaO·2Al2O3, CaO·Al2O·CaSO4, CaO·Al2O3·Fe2O3, CaO·Al2O3·CaF2, and CaO·Na2O·Al2O3.

[0056] <Application> The monolithic refractory composition disclosed herein is used in the manufacture of monolithic refractories. The manufacture of monolithic refractories may be carried out by spraying, pouring, or casting, and the monolithic refractory composition disclosed herein is preferably for spraying.

[0057] ≪Unshaped refractories≫ The monolithic refractories disclosed herein are manufactured using the monolithic refractory composition disclosed herein. In this disclosure, the manufacture of monolithic refractories from the monolithic refractory composition may be carried out by spraying, pouring, or casting.

[0058] The flexural strength of the monolithic refractory material disclosed herein is preferably 6.0 MPa or higher, more preferably 7.0 MPa or higher, and even more preferably 8.0 MPa or higher. In this disclosure, the bending strength is measured by the following method. Each 10,000 g of the composition for monolithic refractories is dry-kneaded for 1 minute, then 1,000 g of water is added as needed and kneaded for 3 minutes to obtain a mixture. The mixture is then pressed into a 160 mm × 40 mm × 40 mm mold to produce three rectangular parallelepiped test specimens. After curing at 20°C for 24 hours, the specimens are dried at 110°C for 24 hours to obtain monolithic refractories. The bending strength (in MPa) of the monolithic refractories is measured according to the strength test for castable refractories in accordance with JIS R 2553:1992.

[0059] In this disclosure, the liquid phase formation temperature is 1250°C or higher, and from the viewpoint of superior heat resistance, 1300°C or higher is preferred, and 1350°C or higher is more preferred. In this disclosure, the liquid phase formation temperature is estimated by the following method. Each of the 10,000 g compositions for amorphous refractories is dry-kneaded for 1 minute, then 1,000 g of water is added as needed and kneaded for 3 minutes to obtain a mixture. The mixture is then pressed into a 160 mm × 40 mm × 40 mm mold to produce one rectangular parallelepiped test specimen at a time. After curing at 20°C for 24 hours, the specimens are dried at 110°C for 24 hours, and then fired at 1200°C for 3 hours to obtain amorphous refractories. This amorphous refractory material is pulverized into a powder, and X-ray diffraction (XRD) measurements are performed using a Bruker D8 ADVANCE. From the XRD measurements, low-melting-point minerals contained in the amorphous refractory material after firing at 1200°C are identified, and the liquid phase formation temperature is estimated. For example, when alumina cement is incorporated into a composition for amorphous refractories, the liquid phase formation temperature of the candidate formulation is estimated from the anorthite portion of the three-component phase diagram of CaO-Al2O3-SiO2. For example, when magnesia fine powder is incorporated into a composition for amorphous refractories, the liquid phase formation temperature of the candidate formulation is estimated from the cordierite portion of the three-component phase diagram of MgO-Al2O3-SiO2.

[0060] ≪Manufacturing Method for Shaped Refractories≫ A method for manufacturing an amorphous refractory material according to the present disclosure involves manufacturing an amorphous refractory material using the amorphous refractory material composition according to the present disclosure. The method for manufacturing an amorphous refractory material according to the present disclosure includes adding water to the amorphous refractory material composition according to the present disclosure, molding the amorphous refractory material composition to which water has been added, and drying the molded amorphous refractory material composition.

[0061] <Dry kneading> The method for producing an amorphous refractory material described herein may include dry-kneading the amorphous refractory material composition before the kneading described later. The method of dry-kneading is not particularly limited.

[0062] <Adding water> The method for producing monolithic refractories described herein includes adding water to a composition for monolithic refractories. The method of adding water is not particularly limited.

[0063] In the method for producing monolithic refractories according to the present disclosure, it is preferable to add 1 to 20 parts by mass of water to 100 parts by mass of monolithic refractory composition, more preferably 3 to 15 parts by mass of water, and even more preferably 5 to 13 parts by mass of water.

[0064] <Kneading> The method for producing monolithic refractories disclosed herein may include kneading a composition for monolithic refractories with added water. The mixing method is not particularly limited, as long as the amorphous refractory composition and water are mixed homogeneously. For mixing, an omni-mixer, paddle mixer, Nauta mixer, Eilich mixer, vortex mixer, or continuous mixing device can be used.

[0065] In the mixing process, the composition for amorphous refractories and water may be mixed together with pH adjusters, surfactants, or defoamers, in addition to the composition itself.

[0066] <Molding> A method for producing an amorphous refractory material according to the present disclosure includes molding an amorphous refractory material composition to which water has been added. In the method for manufacturing monomorphic refractories disclosed herein, the molding method may be spray application, pouring application, or casting application. The above monomorphic refractory composition is suitable for spray application, and from the viewpoint of shortening the construction period, molding is preferably carried out by spray application.

[0067] (Spray application) The spray application process includes spraying the above-mentioned amorphous refractory composition onto the object to be applied (i.e., the object to be sprayed). In spray application, application water may be added to the monolithic refractory composition before spraying onto the workpiece. Water is preferred as the application water from the viewpoint of workability. Spray application may be dry or wet.

[0068] The following describes an example of spray application. The spray application apparatus comprises an airflow conveyor, a conveying pipe, a means for adding application water, an application water addition section, a spray nozzle, and a compressor.

[0069] The airflow conveyor transports the powdered monolithic refractory composition into a transport pipe at a predetermined solid / gas ratio using compressed air from a compressor. The transported monolithic refractory composition is then transported from one end of the transport pipe (i.e., the airflow conveyor side) to the other end (i.e., the spray nozzle side). The compressor supplies compressed air to the airflow conveyor. The monolithic refractory composition is conveyed through the conveying pipe by the compressed air supplied from the compressor in the airflow conveyor.

[0070] The monolithic refractory composition, once fed into the conveying pipe, is transported through the pipe towards the spray nozzle by compressed air supplied to the airflow conveyor. The transport pipe is a passage for transporting powdered amorphous refractory composition to the spray nozzle using compressed air. Furthermore, even if construction water is added to the monolithic refractory composition during transport, causing the monolithic refractory composition to become wet, the monolithic refractory composition is transported to the spray nozzle by compressed air.

[0071] The construction water addition means involves adding construction water to a transport pipe in which the powdered monolithic refractory composition is being transported, thereby wetting the monolithic refractory composition. The wet monolithic refractory composition is then transported to the spray nozzle by compressed air from an airflow conveyor.

[0072] The spray nozzle is attached to the end of the transport pipe and sprays the monolithic refractory composition, to which construction water has been added, onto the object to be constructed. The compressed air used for transport is released into the outside air by the impact when it is sprayed onto the workpiece. After degassing, the sprayed monolithic refractory composition rapidly aggregates and then hardens to form a monolithic refractory, creating a strong furnace wall. Formwork or the like may be used as needed during the manufacture of the monolithic refractory.

[0073] <Curing> A method for producing an amorphous refractory material according to the present disclosure may include curing a molded amorphous refractory material composition. Curing can be carried out by any of the following methods: natural curing (i.e., room temperature curing), wet curing (i.e., water curing), steam curing, heated curing, autoclave curing, or spray curing.

[0074] <Drying> A method for producing a monolithic refractory in this disclosure includes drying a molded monolithic refractory composition. The drying method is not particularly limited, and the heating rate is preferably 40°C / hour to 80°C / hour, more preferably 50°C / hour to 70°C / hour, and even more preferably 60°C / hour. Drying is preferably carried out by raising the temperature to 400°C to 800°C, more preferably to 500°C to 700°C, and even more preferably to 600°C. More specifically, drying is preferably carried out by raising the temperature to 600°C at a heating rate of 60°C / hour (i.e., the drying time is 10 hours). [Examples]

[0075] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to the following examples unless it exceeds the spirit of the disclosure. Examples 2 to 17 are examples, and Examples 1 and 18 to 21 are comparative examples.

[0076] <Preparation of compositions for amorphous refractories> Compositions for amorphous refractories, as shown in Examples 1-21, were prepared by mixing various components according to the formulations shown in Table 1. In Table 1, the units of the numerical values ​​for each component are parts by mass, and "-" indicates that the component was not included. The details of the various components shown in Table 1 are as follows: • Fire-resistant aggregate: Mullite • Bentonite: Particle size less than 10 μm • Other refractory powders (i.e., refractory powders other than refractory aggregates and bentonite, with a particle size of less than 10 μm): alumina, silica • Inorganic salts: Sodium tripolyphosphate • Aluminum lactate: Basic aluminum lactate • Organic fibers: Polypropylene fibers • Alumina cement: Alumina cement with a CaO·Al2O3 content of 84% by mass. Alkaline earth metal oxides: Magnesia earth metal oxide fine powder (activated) with a particle size of 0.2 μm Magnesia earth metal oxide fine powder with a particle size of 0.33 μm (low reactivity) Magnesia earth metal oxide fine powder with a particle size of 2 μm (low reactivity) Magnesia earth metal oxide fine powder with a particle size of 28 μm (low reactivity) Magnesia earth metal oxides with a particle size of 35 μm (low reactivity)

[0077] <Mixing Evaluation> 10,000 g each of the amorphous refractory compositions from Examples 1 to 21 was dry-kneaded for 1 minute, then 1,000 g of water was added as needed, and the mixture was kneaded for 3 minutes to obtain a kneaded product. The mixed materials were evaluated based on the following evaluation criteria. The evaluation results are shown in Table 1. (Evaluation Criteria) A: Usable time is more than 3 minutes. B: Pot life is 3 minutes or less.

[0078] <Excluding the framework evaluation> The aforementioned mixture was pressed into a cylindrical mold measuring 100 mm in height and 100 mm in diameter to produce two cylindrical test specimens. After curing in a 20°C environment for 24 hours, the molds were removed. The removed construction structures were evaluated based on the evaluation criteria described below. The evaluation results are shown in Table 1. (Evaluation Criteria) A: After removing the formwork, a cylindrical structure was obtained. B: The construction material was too soft and could not be removed from the formwork. *: The compound could not be obtained and therefore could not be evaluated.

[0079] <Rapid Temperature Rise Suitability Assessment> The removed construction material was placed in an electric furnace at a 1400°C atmosphere, and after 30 minutes it was removed to obtain an unshaped refractory material. The presence or absence of spalling in the unshaped refractory material was observed visually. The suitability for rapid temperature rise was evaluated based on the evaluation criteria below. The evaluation results are shown in Table 1. (Evaluation Criteria) A: No explosions were observed in the amorphous refractory materials. *: The construction sample could not be obtained and therefore could not be evaluated.

[0080] <Bending strength evaluation> Each of the 10,000 g compositions for monolithic refractories was dry-kneaded for 1 minute, then 1,000 g of water was added as needed and kneaded for 3 minutes to obtain a mixture. The mixture was then pressed into a 160 mm × 40 mm × 40 mm mold to produce three rectangular parallelepiped test specimens. After curing at 20°C for 24 hours, the specimens were dried at 110°C for 24 hours to obtain monolithic refractories. The bending strength (in MPa) of the monolithic refractories was measured according to the strength test for castable refractories in accordance with JIS R 2553:1992. The bending strength was evaluated based on the evaluation criteria below. The evaluation results are shown in Table 1. (Evaluation Criteria) A: The bending strength of the monolithic refractory material was 7.0 MPa or higher. B: The bending strength of the monolithic refractory material was less than 7.0 MPa. *: Unformed refractory material could not be obtained and therefore could not be evaluated.

[0081] <Recycling Assessment> Each of the 10,000 g compositions for amorphous refractories was dry-kneaded for 1 minute, then 1,000 g of water was added as needed and kneaded for 3 minutes to obtain a mixture. The mixture was then pressed into a 160 mm × 40 mm × 40 mm mold to produce one rectangular parallelepiped test specimen. After curing at 20°C for 24 hours, the specimens were dried at 110°C for 24 hours, and then fired at 1200°C for 3 hours to obtain amorphous refractories. This amorphous refractory was pulverized into a powder, and X-ray diffraction (XRD) measurements were performed using a Bruker D8 ADVANCE. From the XRD measurements, low-melting-point minerals contained in the amorphous refractory after firing at 1200°C were identified, and the liquid phase formation temperature was estimated. In Example 1, which incorporates alumina cement, the liquid phase formation temperature of the candidate formulation was estimated from the anorthite portion of the three-component phase diagram of CaO-Al2O3-SiO2. For Examples 2-16, which incorporated magnesia powder, the liquid phase formation temperature of the candidate formulations was estimated from the cordierite portion of the three-component phase diagram of MgO-Al2O3-SiO2. In Example 17, which incorporates alumina cement and magnesia fine powder, the liquid phase formation temperature of the candidate formulation was estimated from the anorthite portion of the three-component phase diagram of CaO-Al2O3-SiO2 and the cordierite portion of the three-component phase diagram of MgO-Al2O3-SiO2. The recyclability / non-recyclability was evaluated based on the following evaluation criteria. The evaluation results are shown in Table 1. Note that when discarded amorphous refractory materials are collected, crushed, and granulated for recycling as refractory aggregate, they can be considered usable as refractory aggregate if the liquid phase formation temperature is 1250°C or higher. (Evaluation Criteria) A: The liquid phase formation temperature is estimated to be 1250°C or higher, making it recyclable. B: The liquid phase formation temperature is estimated to be below 1250°C, making monolithic refractories unrecyclable. *: Unformed refractory material could not be obtained and therefore could not be evaluated.

[0082] [Table 1]

[0083] From the above, Examples 2 to 17 yielded compositions for monolithic refractories that provide construction materials with high explosion resistance and recyclable monolithic refractories.

Claims

1. It contains fire-resistant aggregate, a binder, at least one of an organic acid salt and an inorganic acid salt, aluminum lactate, and organic fibers. The binder contains alkaline earth metal oxide fine powder, the content of which is greater than 0.05% by mass and less than 11% by mass relative to the total amount of the composition for amorphous refractories, and the particle size of which is greater than 0.2 μm and less than 35 μm. When a composition for monolithic refractories contains alumina cement, the calcium oxide content is 0.2% by mass or less relative to the total amount of the monolithic refractory composition. Composition for monolithic refractories.

2. The composition for amorphous refractories according to claim 1, wherein the alkaline earth metal oxide fine powder is magnesia fine powder.

3. The composition for amorphous refractories according to claim 1 or 2, wherein the refractory aggregate contains at least one of alumina and silica.

4. The composition for monomorphic refractory materials according to claim 1 or 2, wherein the content of the refractory aggregate is 65% by mass to 90% by mass with respect to the total amount of the composition for monomorphic refractory materials.

5. The composition for monolithic refractories according to claim 1 or 2, wherein the total content of the organic acid salt and inorganic acid salt is 0.05% by mass to 0.3% by mass relative to the total amount of the composition for monolithic refractories.

6. The composition for monomorphic refractories according to claim 1 or 2, wherein the content of aluminum lactate is 0.1% by mass to 0.9% by mass relative to the total amount of the composition for monomorphic refractories.

7. The composition for monomorphic refractory materials according to claim 1 or 2, wherein the content of the organic fibers is 0.005% by mass to 0.7% by mass relative to the total amount of the composition for monomorphic refractory materials.

8. The amorphous refractory composition according to claim 1 or 2, further containing bentonite.

9. The monolithic refractory composition according to claim 8, wherein the bentonite content is 0.5% to 3% by mass relative to the total amount of the monolithic refractory composition.

10. The composition for amorphous refractories according to claim 1 or 2, further containing refractory powder.

11. The refractory aggregate contains crushed monolithic refractories produced from the monolithic refractory composition described in claim 1, wherein the monolithic refractory composition is as described in claim 1.

12. A composition for amorphous refractory materials according to claim 1 or 2, for use in spray application.

13. A method for producing an amorphous refractory, comprising producing an amorphous refractory using the amorphous refractory composition described in claim 1 or 11.

14. A method for producing an amorphous refractory, comprising: adding water to an amorphous refractory composition according to claim 1 or 11; molding the amorphous refractory composition to which water has been added; and drying the molded amorphous refractory composition.

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