METHOD FOR PRODUCING CALCIUM-BASED CARBONATE COMPOUND, CaO-CONTAINING COMPOSITION, CALCIUM-BASED CARBONATE COMPOUND, AND INORGANIC MOLDED BODY

Abstract

To provide a method for producing a calcium-based carbonate compound using a CaO-containing composition suitable for carbonation reactions, a CaO-containing composition, a calcium-based carbonate compound, and an inorganic molded body.SOLUTION: This method for producing a calcium-based carbonate compound involves: a preparation step for preparing a CaO-containing composition having a free CaO content of 50 mass% or more; and a carbonation step for bringing the CaO-containing composition into contact with carbon dioxide to form a calcium-based carbonate compound.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for producing a calcium carbonate compound, a CaO-containing composition, a calcium carbonate compound, and an inorganic molded product. [Background technology]

[0002] With the recent increase in environmental awareness, attempts are being made to reuse by-products and by-produced energy, such as waste, exhaust gas, and waste heat, generated in industrial processes. A technology has been proposed for producing calcium carbonate by carbonating calcium-containing waste from concrete waste with carbon dioxide (JP 2006-69860 A). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-69860 Summary of the Invention [Problem to be solved by the invention]

[0004] However, since waste contains various components, it is not easy to efficiently promote the carbonation reaction.

[0005] An object of the present invention is to provide a method for producing a calcium-based carbonate compound using a CaO-containing composition suitable for a carbonation reaction, a CaO-containing composition, a calcium-based carbonate compound, and an inorganic formed body. [Means for solving the problem]

[0006] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by the following configuration, and have thus completed the present invention.

[0007] In one embodiment, the present invention provides A preparation step of preparing a CaO-containing composition having a free CaO content of 50% by mass or more; a carbonation step in which the CaO-containing composition is contacted with carbon dioxide to form a calcium carbonate compound; The present invention relates to a method for producing a calcium carbonate compound, comprising:

[0008] As a result of investigations, the present inventors have found that the carbonation reaction can be efficiently promoted by using a CaO-containing composition having an increased content of free CaO, which contributes to the carbonation reaction, as the CaO-containing composition to be subjected to carbonation. In this method for producing a calcium carbonate compound, a CaO-containing composition having a free CaO content of 50 mass% or more is used as the CaO-containing composition to be subjected to carbonation, so that the carbonation reaction can be efficiently promoted without the need to add seed crystals or perform other operations during the carbonation step.

[0009] In one embodiment, the preparation step preferably includes a sieving step of sieving the CaO-containing raw material and recovering the fraction that passes through the sieve. By subjecting the CaO-containing raw material, typically waste from various industrial processes, to the sieving step, it is possible to remove fractions that are relatively large in size and have a low content of free CaO, thereby increasing the content of free CaO in the CaO-containing composition.

[0010] In one embodiment, the sieving step is preferably carried out in a wet manner. This allows the free CaO particles (or free (CaO) m (H2O) n This can promote the dissolution and pulverization of the CaO particles, thereby further increasing the content of free CaO in the CaO-containing composition.

[0011] In one embodiment, the preparation step preferably includes a grinding step of grinding the CaO-containing raw material. m (H2O) n By pulverizing the carbon dioxide particles, the reactivity with carbon dioxide can be improved, resulting in more effective carbon dioxide fixation.

[0012] In one embodiment, the CaO-containing raw material may be derived from a waste product from a process involving calcination and slaking of limestone. Among various waste products, the waste product derived from this process has a relatively high content of free CaO, and therefore can easily and efficiently provide a CaO-containing composition.

[0013] In one embodiment, the CaO-containing composition has an average particle size of 1 μm or more and 30 μm or less as measured by a laser diffraction method. In one embodiment, the CaO-containing composition has a BET specific surface area of ​​10 m 2 / g or more 50m 2 / g or less. The content of free CaO can be further increased by using a finely divided or highly activated CaO-containing composition.

[0014] In one embodiment, from the viewpoint of efficiency of the carbonation step, the concentration of carbon dioxide in the carbonation step is preferably 1% by volume or more and 50% by volume or less.

[0015] In one embodiment, the carbon dioxide used in the carbonation step is preferably carbon dioxide emitted from a combustion engine, which allows carbon dioxide secondarily generated in an industrial process to be reused, thereby contributing to a reduction in carbon dioxide emissions throughout the entire industrial process.

[0016] In one embodiment, in terms of efficiency of the carbonation step, the temperature in the carbonation step is preferably 5°C or higher and 95°C or lower.

[0017] In another embodiment, the present invention provides The present invention relates to a CaO-containing composition for producing calcium-based carbonate compounds, which has a free CaO content of 50 mass % or more.

[0018] The CaO-containing composition having a high content of free CaO is suitable for producing calcium carbonate compounds because it allows the carbonation reaction to proceed in high yield.

[0019] In one embodiment, the CaO-containing composition is preferably a sieved or pulverized product of a CaO-containing raw material, from the viewpoint of increasing the content of free CaO and increasing the activity of the reaction with carbon dioxide.

[0020] In one embodiment, the CaO-containing raw material may be derived from waste from a process involving the calcination and slaking of limestone in terms of its content of free CaO.

[0021] The present invention, in yet another embodiment, comprises: The present invention relates to a calcium carbonate compound, which is a carbonate of the CaO-containing composition.

[0022] The use of carbonates of CaO-containing compositions as calcium carbonate compounds with a wide range of uses can contribute to the reduction and effective use of waste and the reduction of carbon dioxide emissions.

[0023] In one embodiment, the calcium carbonate compound is suitable for use in inorganic moldings.

[0024] In one embodiment, the present invention provides The present invention relates to an inorganic formed body containing the calcium carbonate compound.

[0025] Inorganic molded bodies are molded bodies that are mostly composed of inorganic substances such as hydraulic materials and siliceous materials, and because they have properties such as fire resistance, light weight, high strength, and workability, they are widely used for exterior wall materials, roof underlayment materials, eaves ceiling materials, etc. for houses, etc. They are also widely used for foundations, walls, pillars, floors, etc. of buildings that require strength and fire resistance. By using specific calcium-based carbonate compounds in such a wide range of inorganic molded bodies, it is possible to reduce the environmental impact of the entire industrial process.

[0026] In this specification, standard abbreviations of elements from the periodic table of elements can be used.Therefore, elements can be represented by these abbreviations.For example, Ca means calcium; O means oxygen; H means hydrogen; Si means silicon; Fe means iron; Al means aluminum; S means sulfur; Mg means magnesium.Similarly for other elements.

[0027] In this specification, "free CaO" refers to unreacted CaO (calcium oxide) that has not combined with other substances. The methods for measuring the content of free CaO, as well as the composition and physical properties, are as described in the Examples unless otherwise specified.

[0028] In this specification, the term "calcium-based carbonate compound" refers to a compound containing calcium carbonate as a main component, which is a concept that allows the inclusion or coexistence of other subcomponents that may be incorporated during the manufacturing process, etc. The calcium carbonate content in the calcium-based carbonate compound is preferably 80 mass% or more. The calcium carbonate content in the calcium-based carbonate compound can be suitably measured by the ethylenediaminetetraacetic acid disodium titration method.

[0029] <Disodium ethylenediaminetetraacetic acid titration method> Weigh out 1 g of calcium carbonate sample (dried at 105°C for 2 hours) and suspend it in 50 mL of water. Add 10 mL of hydrochloric acid (a 1:1 mixture of concentrated hydrochloric acid and water by volume) and heat to dissolve. After cooling, transfer to a 250 mL volumetric flask and add water to the same volume. Take a 5.00 mL aliquot from this and add water to bring the total volume to approximately 50 mL. Add 5 mL of buffer solution (a 1,000 mL solution of 500 g of potassium hydroxide dissolved in water), then add commercially available Dotite NN diluted powder. Titrate with titration reagent (a 1,000 mL solution of approximately 3.8 g of disodium ethylenediaminetetraacetate dissolved in water). The titration is terminated when the color of the solution changes from red to blue. Calculate the calcium carbonate content (% by mass) using the following formula:

[0030]

number

[0031] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic diagram of a measuring device for measuring the content of CO2. [Figure 2] 1 is an SEM photograph of the calcium carbonate compound of Example 1-1 of the present invention. [Figure 3] 1 is a SEM photograph of the calcium carbonate compound of Example 1-2 of the present invention. [Figure 4] 1 is an SEM photograph of the calcium carbonate compound of Example 1-3 of the present invention. [Figure 5] 1 is an SEM photograph of the calcium carbonate compound of Comparative Example 1-1 of the present invention. [Figure 6] FIG. 2 is a partial perspective view schematically showing a heating tester. DETAILED DESCRIPTION OF THE INVENTION

[0032] A method for producing a calcium carbonate compound, a CaO-containing composition, a calcium carbonate compound, and an inorganic molded body according to one embodiment of the present invention will be described below, but the present invention is not limited to these embodiments.

[0033] <Method of manufacturing calcium carbonate compounds> The method for producing a calcium carbonate compound includes a preparation step and a carbonation step. The preparation step preferably includes at least one step selected from the group consisting of a sieving step and a pulverization step. Which step is to be performed as the preparation step may be determined in consideration of the content and particle size of free CaO in the CaO-containing raw material to be treated and the target CaO-containing composition. Hereinafter, an embodiment including a sieving step and a pulverization step, which are preferred preparation steps, will be described.

[0034] (sieving process) In the sieving step, the CaO-containing raw material is sieved and the fraction that passes through the sieve is collected. Although it is possible to use the waste CaO-containing raw material itself, by subjecting the CaO-containing raw material to the sieving step, it is possible to prepare a CaO-containing composition with a high content of free CaO.

[0035] As the CaO-containing raw material, various waste materials generated in industrial processes can be used as long as they contain CaO. Specific examples of the CaO-containing raw material include waste materials from processes involving the calcination and slake of limestone, paper sludge incineration ash discharged from paper mills, concrete sludge discharged from concrete product factories, concrete waste generated during the demolition of concrete structures, coal ash generated by the combustion of coal at coal-fired power plants and waste incineration plants, steel slag generated in steel manufacturing processes, and carbide slag discharged from acetylene gas manufacturing processes. From the viewpoint of the free CaO content, the CaO-containing raw material is preferably derived from waste materials from processes involving the calcination and slake of limestone (hereinafter also referred to as "lime slag"). The limestone slag mainly includes an undersize fraction (hereinafter also referred to as "quicklime-based limestone slag") produced by sieving after calcining limestone, and an oversize fraction (hereinafter also referred to as "slaked lime-based limestone slag") produced by sieving after slaking, which is the next step.

[0036] The content of free CaO in the CaO-containing raw material is generally low and varies depending on the process in which the waste is generated. The content of free CaO in the CaO-containing raw material is not particularly limited, but is 10% by mass or more and 90% by mass or less.

[0037] The sieve opening size can be appropriately set depending on the size of the CaO-containing raw material to be treated and the size of the target CaO-containing composition. The sieve opening size can suitably be a nominal size conforming to JIS Z 8801-1. Representative sieve opening sizes include, but are not limited to, 8 mm, 6.7 mm, 5.6 mm, 4 mm, 2 mm, and 1 mm. Sieving may be performed in a single step, or in multiple steps, using sieves with large openings to sieves with small openings.

[0038] The sieving step may be carried out either by a dry method or a wet method, but the fine free CaO particles (or free (CaO)) adhering to the sieved fraction may be removed. m (H2O) n A wet method is preferred because it is easy to dissolve the CaO-containing raw material (particles). When the sieving step is performed by a wet method, water is usually used as the dispersion medium. The concentration of the CaO-containing raw material when dispersed in water can be appropriately set taking into consideration the dispersion efficiency, sieving efficiency, etc. The amount of the CaO-containing raw material mixed per liter of water is preferably 10 g or more and 300 g or less, more preferably 15 g or more and 250 g or less, and even more preferably 20 g or more and 200 g or less.

[0039] After adding the CaO-containing raw material to the water, it is preferable to stir the CaO-containing raw material so that the CaO-containing raw material is fully mixed with the water. The stirring time is preferably from 1 minute to 3 hours, and more preferably from 5 minutes to 2 hours.

[0040] When the sieving step is performed in a wet system, the sieved fraction is often in the form of a dilute suspension, and therefore, in order to concentrate it in the next step, it is preferable to leave it to stand until the particles settle. The standing time is not particularly limited, but is preferably 10 minutes to 3 hours, more preferably 20 minutes to 2.5 hours, and even more preferably 30 minutes to 2 hours.

[0041] Depending on the treatment in the next step, after the standing, a predetermined amount of the supernatant may be removed (the dispersion may be concentrated), or the dispersion may be further dehydrated and dried.

[0042] When the content of free CaO in the particles after the sieving step is 50% by mass or more, the particles can be treated as a CaO-containing composition. When the content of free CaO in the particles after the sieving step is less than 50% by mass, the particles are preferably subjected to the pulverization step as a CaO-containing raw material. When the CaO-containing raw material is slaked lime-based lime slag, a CaO-containing composition can sometimes be obtained by the sieving step alone.

[0043] (Crushing process) In the grinding process, the CaO-containing raw material is ground. The grinding process also produces free CaO particles (or free (CaO) m (H2O) n By miniaturizing the CaO particles, it is possible to prepare a CaO-containing composition having high reactivity with carbon dioxide. The CaO-containing raw material may be either a sieved product that has undergone a sieving process or an unsieved product that has not undergone a sieving process.

[0044] The pulverization method is not particularly limited, and a method using a known pulverizer can be adopted. Examples of pulverizers include roller mills, jet mills, high-speed rotary pulverizers such as hammer mills and pin mills, container-driven mills such as rotary mills, vibration mills and planetary mills, and media-agitating mills such as attritors, bead mills, ball mills and rod mills.

[0045] The grinding time can be appropriately set taking into consideration the content and particle size of free CaO in the target CaO-containing composition. The grinding time is preferably from 5 minutes to 10 hours, more preferably from 10 minutes to 8 hours, and even more preferably from 30 minutes to 6 hours. When a rotary mill such as a ball mill or pot mill is used as the grinder, the rotation speed is preferably from 40 rpm to 300 rpm, more preferably from 50 rpm to 200 rpm, and even more preferably from 60 rpm to 150 rpm.

[0046] The pulverization step may be carried out by either a dry method or a wet method. When the pulverization step is carried out by a wet method, water is usually used as a dispersion medium. The concentration of the CaO-containing raw material when dispersed in water can be appropriately set in consideration of pulverization efficiency, etc. The amount of the CaO-containing raw material mixed per liter of water is preferably 50 g to 600 g, more preferably 80 g to 500 g, and even more preferably 120 g to 400 g.

[0047] When the grinding step is carried out wet, the suspension may be directly subjected to the next step, the carbonation step, or may be dried before being subjected to the next step.

[0048] As described above, by carrying out at least one step selected from the group consisting of a sieving step and a pulverization step as a preparation step, a CaO-containing composition having a high content of free CaO and high reactivity with carbon dioxide can be suitably prepared.

[0049] (CaO-containing composition) The CaO-containing composition prepared in the preparation step has a free CaO content of 50 mass% or more, making it suitable for use in producing calcium carbonate compounds. As described above, the CaO-containing composition is preferably a sieved or pulverized product of the CaO-containing raw material. However, the sieved product may also be subjected to a pulverization step, and the pulverized product may also be subjected to a sieving step.

[0050] The free CaO content in the CaO-containing composition may be 50% by mass or more, with the lower limit being preferably 60% by mass, more preferably 70% by mass, even more preferably 75% by mass, and particularly preferably 80% by mass. The upper limit of the free CaO content is preferably as high as possible, but may be 98% by mass, 95% by mass, 92% by mass, or 90% by mass.

[0051] The average particle size of the CaO-containing composition measured by a laser diffraction method is preferably 1 μm or more and 30 μm or less, more preferably 1.5 μm or more and 20 μm or less, and even more preferably 2 μm or more and 10 μm or less, thereby enabling a CaO-containing composition having high reactivity with carbon dioxide to be obtained.

[0052] The BET specific surface area of ​​the CaO-containing composition is 10 m 2 / g or more 50m 2 / g or less, and 2 / g or more 40m 2 / g or less is more preferable, and 15m 2 / g or more 30m 2 / g or less, it is more preferable that the CaO content is 1 / g or less. This makes it possible to obtain a CaO-containing composition having high reactivity with carbon dioxide.

[0053] The upper limit of the ignition loss of the CaO-containing composition is preferably 40% by mass, more preferably 35% by mass, and even more preferably 30% by mass. Although a lower ignition loss is preferable, it may be 1% by mass, 3% by mass, or 5% by mass. The ignition loss is mainly derived from moisture and CO2.

[0054] The SiO2 content in the CaO-containing composition is preferably 0.4 mass% or more and 5.0 mass% or less, more preferably 0.6 mass% or more and 4.5 mass% or less, and even more preferably 0.8 mass% or more and 4.0 mass% or less.

[0055] The content of Fe2O3 in the CaO-containing composition is preferably 0.14 mass% or more and 0.80 mass% or less, more preferably 0.16 mass% or more and 0.60 mass% or less, and even more preferably 0.18 mass% or more and 0.40 mass% or less.

[0056] The content of Al2O3 in the CaO-containing composition is preferably 0.2 mass% or more and 1.8 mass% or less, more preferably 0.3 mass% or more and 1.5 mass% or less, and even more preferably 0.4 mass% or more and 1.2 mass% or less.

[0057] The content of SO3 in the CaO-containing composition is preferably 0.8 mass% or more and 3.0 mass% or less, more preferably 0.9 mass% or more and 2.5 mass% or less, and even more preferably 1.0 mass% or more and 2.0 mass% or less.

[0058] The hydrochloric acid insoluble content of the CaO-containing composition is preferably 1.0 mass % or more and 16.0 mass % or less, more preferably 1.5 mass % or more and 14.0 mass % or less, and even more preferably 2.0 mass % or more and 12.0 mass % or less.

[0059] The upper limit of the CO2 content in the CaO-containing composition is preferably 30 mass%, more preferably 20 mass%, and even more preferably 10 mass%. Although a lower CO2 content is preferable, it may be 0.1 mass%, 0.2 mass%, or 0.3 mass%. CO2 is mainly derived from calcium carbonate. By keeping this value low, the free CaO content can be increased.

[0060] (carbonation process) In the carbonation step, the CaO-containing composition from the preparation step is brought into contact with carbon dioxide (hereinafter also referred to as "carbon dioxide gas") to form a calcium carbonate compound. Although the carbonation method is not particularly limited, a carbon dioxide gas method in which carbon dioxide gas is blown into a dispersion liquid in which the CaO-containing composition is dispersed in water to carbonate the composition is typically preferred.

[0061] The solids concentration of the CaO-containing composition in the dispersion may be appropriately set in consideration of carbonation efficiency, but is preferably 10 g / L to 500 g / L (Ca concentration of 5.4% to 27.0%), more preferably 20 g / L to 400 g / L (Ca concentration of 10.8% to 21.6%), and even more preferably 30 g / L to 350 g / L (Ca concentration of 16.2% to 18.9%). When the sieving step and the pulverization step are performed dry, the resulting CaO-containing composition may be dispersed in water to achieve the above-mentioned concentration range. When the sieving step and the pulverization step are performed wet, water may be added or removed to achieve the concentration of the resulting suspension of the CaO-containing composition within the above-mentioned concentration range.

[0062] As the carbon dioxide gas to be used in the carbon dioxide gas method, flue gas from a lime kiln installed in the vicinity of a calcium carbonate compound production plant or the like, or exhaust gas containing carbon dioxide gas emitted from a combustion engine such as a boiler or a garbage incinerator can be used.

[0063] In consideration of carbonation efficiency, the concentration of carbon dioxide in the exhaust gas in the carbonation process is preferably 1% by volume or more and 50% by volume or less, more preferably 3% by volume or more and 40% by volume or less, and even more preferably 5% by volume or more and 30% by volume or less.

[0064] In consideration of carbonation efficiency, the temperature in the carbonation step (the temperature of the dispersion liquid) is preferably 5°C or higher and 95°C or lower, more preferably 15°C or higher and 85°C or lower, and even more preferably 25°C or higher and 75°C or lower.

[0065] Considering carbonation efficiency and production capacity, the flow rate of carbon dioxide gas is preferably 10 L / min to 200 L / min per 10 kg of raw material CaO charged, more preferably 20 L / min to 180 L / min, and even more preferably 30 L / min to 150 L / min.

[0066] In the carbonation step, stirring is preferably carried out in conjunction with blowing in carbon dioxide gas. When stirring is carried out using a stirring blade, the rotation speed is preferably 100 rpm or more and 600 rpm or less, more preferably 150 rpm or more and 550 rpm or less, and even more preferably 200 rpm or more and 500 rpm or less.

[0067] The carbonation reaction time may be appropriately set so that the carbonation reaction proceeds sufficiently, taking into consideration the concentration of the CaO-containing composition, the concentration and flow rate of carbon dioxide gas, etc. The carbonation reaction time is not limited, but is preferably 0.5 hours or more and 20 hours or less, more preferably 1 hour or more and 18 hours or less, and even more preferably 2 hours or more and 15 hours or less.

[0068] In addition to the carbon dioxide gas method, a solution method is also suitable in which an alkali (NaOH, amine, etc.) is reacted with CO2 to produce Na2CO3 or an amine carbonate, which is then reacted with CaO to produce CaCO3.

[0069] By going through the above steps, a calcium carbonate compound can be produced as a carbonate of the CaO-containing composition. The resulting calcium carbonate compound may be filtered and dried to form a powder, or may be used as a calcium carbonate compound source in the form of a slurry or cake without being filtered and dried.

[0070] <Calcium carbonate compounds>

[0071] The average particle size of the calcium carbonate compound measured by a laser diffraction method is preferably 1 μm or more and 30 μm or less, more preferably 1.5 μm or more and 20 μm or less, and even more preferably 2 μm or more and 10 μm or less, thereby improving the physical properties of the object to which the calcium carbonate compound is applied.

[0072] The BET specific surface area of ​​calcium carbonate compounds is 2m 2 / g or more 25m 2 / g or less, and 2 / g or more 20m 2 / g or less is more preferable, and 6m 2 / g or more 15m 2 / g or less, it is more preferable that the calcium carbonate compound is used in an amount of 1000 to 15000 kJ / g. This makes it possible to improve the physical properties of the object to which the calcium carbonate compound is applied.

[0073] The upper limit of the ignition loss of the calcium carbonate compound is preferably 55% by mass, more preferably 50% by mass, and even more preferably 45% by mass. The lower limit of the ignition loss is preferably 30% by mass, more preferably 35% by mass, and even more preferably 40% by mass. This allows the physical properties of the object to which the calcium carbonate compound is applied to be improved. Furthermore, the above range is preferable in terms of the purity of the calcium carbonate compound.

[0074] The CaO content in the calcium carbonate compound is preferably 40% by mass or more and 65% by mass or less, more preferably 45% by mass or more and 60% by mass or less, and even more preferably 50% by mass or more and 55% by mass or less.

[0075] The SiO2 content in the calcium carbonate compound is preferably 0.20 mass% or more and 2.00 mass% or less, more preferably 0.40 mass% or more and 1.80 mass% or less, and even more preferably 0.60 mass% or more and 1.60 mass% or less.

[0076] The content of Fe2O3 in the calcium carbonate compound is preferably 0.12 mass% or more and 1.20 mass% or less, more preferably 0.14 mass% or more and 1.00 mass% or less, and even more preferably 0.15 mass% or more and 0.80 mass% or less.

[0077] The content of Al2O3 in the calcium carbonate compound is preferably 0.10 mass% or more and 1.50 mass% or less, more preferably 0.20 mass% or more and 1.20 mass% or less, and even more preferably 0.30 mass% or more and 1.00 mass% or less.

[0078] The content of SO3 in the calcium carbonate compound is preferably 0.75 mass% or more and 2.00 mass% or less, more preferably 0.80 mass% or more and 1.60 mass% or less, and even more preferably 0.85 mass% or more and 1.40 mass% or less.

[0079] The hydrochloric acid insoluble content of the calcium carbonate compound is preferably 0.4% by mass or more and 12.0% by mass or less, more preferably 0.7% by mass or more and 10.0% by mass or less, and even more preferably 0.9% by mass or more and 8.0% by mass or less.

[0080] The lower limit of the CO2 content in the calcium carbonate compound is preferably 25% by mass or more and 55% by mass or less, more preferably 30% by mass or more and 50% by mass or less, and even more preferably 35% by mass or more and 45% by mass or less. CO2 is mainly derived from calcium carbonate. By setting this value within the above range, the physical properties of the object to which the calcium carbonate compound is applied (for example, fire resistance when applied to an inorganic molded body) can be improved.

[0081] The higher the production rate of calcium carbonate compounds that contribute to the fixation of carbon dioxide, the better, and the lower limit is preferably 60% by mass, more preferably 70% by mass, and even more preferably 80% by mass. The upper limit of the production rate is preferably 100% by mass, but may also be 98% by mass, 95% by mass, or 90% by mass.

[0082] The lower the content of unreacted CaO in the calcium carbonate compound, the better, and the upper limit is preferably 8 mass%, more preferably 6 mass%, further preferably 4 mass%, particularly preferably 2 mass%. The lower limit of the unreacted CaO content is preferably 0 mass%, but may also be 0.05 mass%, 0.1 mass%, or 0.2 mass%.

[0083] In view of the synthesis procedure, the calcium carbonate compound is preferably a synthetic calcium carbonate compound. By using a synthetic calcium carbonate compound that is a reaction product of a CaO-containing composition and carbon dioxide as the calcium carbonate compound, carbon dioxide that is secondarily generated in industrial processes can be reused, which can contribute to reducing carbon dioxide emissions throughout the entire industrial process.

[0084] <Applications of calcium carbonate compounds> The use of the calcium carbonate compound is not particularly limited. For example, it is suitable as a high-performance additive for inorganic molded bodies, such as building materials, a filler for resins, etc. Hereinafter, an embodiment in which the calcium carbonate compound is used in an inorganic molded body will be described.

[0085] <Inorganic molded body> The inorganic molded body is not particularly limited, and typical examples include molded boards for building materials, concrete structures (concrete molded bodies), etc. Applicable compositions and the like will be described in detail below according to the application.

[0086] (molded board for building materials) The molded board preferably contains a hydraulic material, a siliceous material, a reinforcing fiber material, and a calcium carbonate compound.

[0087] (hydraulic material) Examples of hydraulic materials include cementitious materials, gypsum, lime, slag, etc. Examples of cementitious materials include commonly used cements, such as ordinary Portland cement, high-early-strength cement, moderate-heat cement, fly ash cement, blast furnace slag cement, and alumina cement. Examples of gypsum include anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum. Examples of slag include blast furnace slag and converter slag. These hydraulic materials can be used alone or in combination of two or more.

[0088] The content of the hydraulic material is preferably 5% by mass to 45% by mass, more preferably 8% by mass to 42% by mass, and even more preferably 10% by mass to 40% by mass, based on the total amount of materials constituting the molded board. By setting the content of the hydraulic material within the above range, it is possible to improve the physical properties of the molded board, such as bending strength and peel strength, and to prevent the molded board from becoming too high in bulk density, thereby improving workability during construction.

[0089] (siliceous material) Examples of siliceous materials include materials containing a large amount of SiO, such as silica sand, silica powder, silica fume, fly ash, diatomaceous earth, layered silicates (e.g., mica, talc, kaolin, bentonite), wollastonite, and lightweight aggregates (e.g., fly ash balloons, perlite, shirasu balloons, glass foam, etc.). These siliceous materials can be used alone or in combination of two or more. Talc, mica, and wollastonite can also be used as reinforcing fiber materials, as described below.

[0090] The content of the siliceous material is preferably 10% by mass or more and 55% by mass or less, more preferably 12% by mass or more and 50% by mass or less, and even more preferably 15% by mass or more and 45% by mass or less, based on the total amount of materials constituting the molded board. If the content of the siliceous material is within the above range, it becomes possible to set the bending strength, bulk specific gravity, water absorption rate, dimensional stability, etc. of the molded board within the desired range. Incidentally, as the siliceous material, perlite, fly ash balloons, shirasu balloons, etc., having a unit volume mass of 0.5 g / cm are preferred. 3 When mixing the following lightweight aggregates, it is preferable to use other siliceous materials in combination so that the content of lightweight aggregate is 20 mass% or less, based on the total amount of materials constituting the molded board, in order to prevent the bulk density from becoming too light and weakening strength such as bending strength and peel strength.

[0091] (reinforcing fiber material) Examples of reinforcing fiber materials that can be used include pulps such as softwood pulp, hardwood pulp, fibrillated pulps thereof, and pulp obtained by defibrating waste paper, organic reinforcing fiber materials such as vinylon fiber, acrylonitrile fiber, and polypropylene fiber, and inorganic reinforcing fiber materials such as rock wool and glass fiber. These reinforcing fiber materials can be used alone or in combination of two or more.

[0092] To improve the strength and toughness of the molded board, the content of the reinforcing fiber material is preferably 2% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 26% by mass or less, and even more preferably 4% by mass or more and 22% by mass or less, based on the total amount of materials constituting the molded board. By setting the content of the reinforcing fiber material within the above range, it is possible to achieve a sufficient reinforcing effect while suppressing the protrusion of fibers from the surface of the molded board, thereby improving smoothness. When an inorganic reinforcing fiber material with an average length of 1 mm to 50 mm is blended as the reinforcing fiber material, it is preferable to use another reinforcing fiber material in combination so that the content is 10% by mass or less, based on the total amount of materials constituting the molded board, in order to improve the smoothness of the molded board.

[0093] (Calcium carbonate compounds) As the calcium carbonate compound, the calcium carbonate compounds described above can be suitably used.

[0094] The content of the calcium carbonate compound is preferably 5% by mass or more and 60% by mass or less, more preferably 8% by mass or more and 55% by mass or less, and even more preferably 12% by mass or more and 50% by mass or less, based on the total amount of materials constituting the molded board. By blending a calcium carbonate compound with low thermal conductivity at a content within the above range, the strength and fire resistance of the molded board can be improved.

[0095] (optional ingredient) In addition to the above materials, various materials can be blended into the molded board depending on the purpose to impart various functions, such as hollow resin bodies, wood chips, wood flour, resin powder, antifoaming agents, flocculants, water repellents, thickeners (methyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, etc.), dispersants, etc. It is also possible to add recycled materials made by crushing scraps generated during the processing of the molded board as appropriate.

[0096] The bulk density of the molded plate is 0.7 g / cm 3 More than 2.0g / cm 3 Preferably, it is 0.8 g / cm or less. 3 More than 1.8g / cm 3 More preferably, it is 0.9 g / cm or less. 3 More than 1.6g / cm 3 It is even more preferable that:

[0097] (Method of manufacturing molded plate) The method for producing the molded plate according to this embodiment is not particularly limited, and commonly used methods such as papermaking, extrusion, flow-on molding, casting, and press (compression) molding can be used. The molded plate can be obtained by subjecting a green sheet molded by these methods to press dehydration or patterning by embossing, etc., followed by curing at room temperature, steam curing, autoclave curing, etc. The molded plate can then be dried and, if necessary, shaped or painted.

[0098] (Uses of molded boards) The uses of the molded board are not particularly limited, and it can be suitably used as a performance maintaining material for wall construction, flooring, roofing, various boards, exterior decorative members, interior and exterior finishing materials such as fittings, sealing materials, heat insulating materials, sound absorbing materials, waterproofing materials, etc. The molded board is preferably a cementitious molded board containing a cementitious material, and more preferably a calcium silicate molded body.

[0099] (concrete structures) The concrete structure is composed of a hardened hydraulic composition. The hydraulic composition is made of a powder containing a calcium carbonate compound and at least one of blast furnace slag, expansive agent, slaked lime, quicklime, fly ash, and Portland cement. The calcium carbonate compound may be any of the calcium carbonate compounds described above.

[0100] In addition to the hydraulic composition, aggregates such as sand and gravel, chemicals such as chemical admixtures for concrete, and fiber materials made of metals or polymeric materials may be blended to form a hydraulic composition mixture.

[0101] The hardened hydraulic composition is obtained by hardening a paste obtained by kneading the hydraulic composition with water. The hardened hydraulic composition mixture is obtained by hardening a mixture (equivalent to fresh mortar or fresh concrete) obtained by kneading the hydraulic composition mixture with water, and corresponds to mortar or concrete.

[0102] The ratio of the calcium carbonate compound in the powder (the ratio of the calcium carbonate compound to the cement) is within the range of 1% by mass to 60% by mass, preferably 3% by mass to 50% by mass, and more preferably 5% by mass to 40% by mass.

[0103] It is desirable to use ground granulated blast furnace slag used in JIS (Japanese Industrial Standards) R5211 "Blast furnace cement" or ground granulated blast furnace slag conforming to JIS A6206 "Blast furnace slag for concrete." In addition, blast furnace slag should have a specific surface area of ​​2000 to 10000 cm. 2 / g, preferably 3500 to 7000 cm 2 It is desirable to use one with a saturation of 0.15 to 0.25 g.

[0104] The expansive material may be, for example, one specified in JIS A6202 “Expansive materials for concrete.” The expansive material is preferably added in an amount of 2 to 9 mass % based on the total amount of the hydraulic composition.

[0105] For example, slaked lime specified in JIS R9001 "Industrial Lime" can be used. Furthermore, because quicklime becomes slaked lime when it comes into contact with water, quicklime specified in JIS R9001 "Industrial Lime" can be used instead of slaked lime. In this case, it is advisable to adjust the amount of water required to convert quicklime into slaked lime. The fly ash used may be one that conforms to JIS A6201 "Fly ash for concrete," for example.

[0106] Ordinary Portland cement is used as Portland cement, but other types of Portland cement such as high-early-strength Portland cement, ultra-high-early-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, and sulfate-resistant Portland cement, as specified in JIS R5210 "Portland cement," and JIS R5214 "Ecocement" can also be used.

[0107] When the hydraulic composition contains Portland cement, the proportion of Portland cement in the powder other than the calcium carbonate compound is 70% by mass or less, and preferably 30% by mass or less.

[0108] Furthermore, when Portland cement and blast furnace slag or fly ash are used, the components may be pre-mixed, for example, JIS R5211 "blast furnace cement" or, for example, JIS R5213 "fly ash cement," and the pre-mixed components may be used alone or in combination.

[0109] Since the calcium carbonate compound having the above characteristics is used, the hydraulic composition and the hydraulic composition mixture exhibit good fluidity, and the hardened concrete produced from the composition can exhibit excellent compressive strength.

[0110] The density of the concrete structure is 0.7 g / cm 3 More than 2.0g / cm 3 Preferably, it is 0.8 g / cm or less. 3Above 1.8 g / cm 3 It is more preferable that it is below, and 0.9 g / cm 3 Above 1.6 g / cm 3 It is even more preferable that it is below.

Examples

[0111] Hereinafter, the present invention will be described in detail using examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded. The measurement and evaluation of physical properties and the like were performed as follows.

[0112] <Evaluation of CaO-containing composition and calcium-based carbonate compound> For each of the CaO-containing compositions and calcium-based carbonate compounds (hereinafter, both are also collectively referred to as "samples") obtained in the examples and comparative examples, the following analysis was performed. When the sample was a suspension, the filtered wet product was dried at 110 ° C for 12 hours and used for evaluation. The analysis results for the CaO-containing composition are shown in Table 1, and the analysis results for the calcium-based carbonate compound are shown in Table 2. SEM photographs of the calcium-based carbonate compound are shown in FIGS. 2 to 5.

[0113] (Loss on ignition) Approximately 2 g of the sample was put into a previously weighed magnetic crucible, and the total mass was precisely weighed. This was heated in an electric furnace at 900 ° C ± 25 ° C for 3 hours or more. It was cooled to room temperature in a desiccator and precisely weighed, and the difference in mass before and after heating was determined as the loss amount. Based on the following formula, the loss on ignition (mass basis) was determined. L(%) = (D / S) × 100<第0000447号>(In the formula, L is the loss on ignition (%). D is the loss amount (g). S is the weight of the sample before heating (g).)

[0114] (CaO content) It was processed according to the "disodium ethylenediaminetetraacetate titration method", which is a method for measuring the content ratio of calcium carbonate in the calcium-based carbonate compound, and the CaO content (%) in the sample was determined by the following formula.

[0115] [Number] (In the formula, f is the factor of the titrant. The factor is determined by standardizing with the BT indicator using the titrant. V is the consumption volume (mL) of the titrant. W is the sampling amount of the sample (0.02 g of the sample).)

[0116] (Contents of SiO2, Fe2O3, Al2O3 and SO3) <ICP-AES method> Weighed 0.2 g of the sample, moistened it with water, added 14 mL of hydrochloric acid (a solution prepared by mixing concentrated hydrochloric acid and water in a volume ratio of 1:1) using a pipette, and heated and dissolved it. After cooling, it was transferred to a 100 mL volumetric flask, and water was added to make up to 100 mL. 5 mL was taken from this and transferred to a 50 mL volumetric flask, and water was added to make up to 50 mL to obtain the test solution for measurement. On the other hand, 5 mL was taken from the 100 mL made-up aqueous solution described above and transferred to a 50 mL volumetric flask, and standard solutions of each element (Si, Fe, Al and S) were arbitrarily added to prepare calibration standard solutions with different concentrations. Note that the standard solutions of each element used were 1000 ppm standard solutions for atomic absorption (commercially available).

[0117] The calibration standard solutions with different concentrations to which each element was added and the test solution for measurement were set in the autosampler of an inductively coupled plasma atomic emission spectrometry (ICP-AES) apparatus (manufactured by Hitachi High-Technologies Corporation, "SPECTROBLUE FMS36 type"), and the amounts (ppm) of Si, Fe, Al and S were measured under the following conditions. <Measurement conditions> High-frequency output: 1.4 kW Carrier gas (humidified) flow rate: 0.9 L / min Plasma gas flow rate: 13.0 L / min Auxiliary gas flow rate; 1.0 L / min Liquidity: Aqueous solution Number of integrations: 3 times Sample order: For each sample Measurement method: Standard addition method Weighting of calibration curve: None Measurement wavelength: Si: 251.612 nm Fe: 238.204 nm Al: 167.078 nm S: 182.034 nm

[0118] Finally, the content (mass%) of each element was determined from the determined amount of each element, and the contents (mass%) of SiO2, Fe2O3, Al2O3 and SO3 were calculated in terms of their oxides.

[0119] (hydrochloric acid insoluble matter) 5.00 g of sample was weighed into a 200 mL beaker and moistened with water. 50 mL of hydrochloric acid (a 1:1 volume mixture of concentrated hydrochloric acid and water) was added and heated to approximately 100 °C for approximately 5 minutes to dissolve the sample. This solution was filtered while still warm using No. 5B filter paper. The insoluble material adhering to the inner wall of the beaker was scraped off with a policeman (a laboratory instrument with a rubber-covered tip of a glass rod) and collected, and then combined with the insoluble material on the filter paper. The insoluble material on the filter paper was washed with at least 300 mL of hot water at approximately 70 °C. The insoluble material, along with the filter paper, was dried, placed in a porcelain crucible, and combusted on a heater. It was then heated in an electric furnace (900 °C) for at least 20 minutes to incinerate the material. The sample was removed from the electric furnace and cooled on a porcelain dish. The porcelain crucible (including the insoluble material) was placed on a precision balance using plastic tweezers, and the zero point was adjusted (zero load was set). The insoluble matter was removed from the porcelain crucible with a brush, and the crucible was placed on the precision balance again to measure the weight loss (the scale was marked with a minus sign). The weight loss corresponds to the mass of the hydrochloric acid insoluble matter. The hydrochloric acid insoluble matter (mass%) was calculated using the following formula. H(mass%)=(|R| / S)×100 (In the formula, H is the hydrochloric acid insoluble matter (mass%), R is the weight loss (g) when the insoluble matter is removed, and S is the weight of the sample (g).)

[0120] (CO2 content) The reagents used in the measurement were prepared as follows. 1 / 10N barium hydroxide solution: 15.8 g of barium hydroxide (octahydrate) was dissolved in ultrapure water to a total volume of 1000 mL. After sealing and shaking well, the container was left to stand for at least one day, and the supernatant was taken and used as the solution. Sulfuric acid: A solution was prepared by mixing concentrated sulfuric acid and water in a 1:1 volume ratio. 1 / 10N hydrochloric acid standard solution: Prepared by diluting 1N hydrochloric acid 10 times. PP indicator: Dissolve 1 g of phenolphthalein in ethanol to make a total of 100 mL.

[0121] Figure 1 is a schematic diagram showing the CO2 content measurement device. Gas was circulated inside the measurement device by a circulation pump, and an airtight state was maintained during circulation. In the figure, the arrows indicate the direction of gas flow.

[0122] Using the measurement device shown in Figure 1, the CO2 content was determined using the following procedure. 20.0 mL of 1 / 10 N barium hydroxide solution was placed in a 100 mL medium bottle, two drops of PP indicator were added, and the bottle was sealed. Separately, 0.1 g of sample was placed in a 500 mL medium bottle, and water was added to bring the total volume to 200 mL. 10 mL of sulfuric acid was added to the dish using a measuring cup, the bottle was immediately sealed, and the circulation pump was started. After operating for more than 90 minutes, the 100 mL medium bottle was removed from the device and titrated directly with 1 / 10 N hydrochloric acid standard solution. The same procedure was repeated without adding the sample to the 500 mL medium bottle as a control. The CO2 content (mass%) was calculated using the following formula.

[0123]

number

[0124] (Free CaO content in CaO-containing composition) The content Z (mass%) of free CaO in the CaO-containing composition was calculated using the data of the ignition loss, CaO content, SO3 content, and CO2 content obtained above, according to the following formula, where "%" represents "mass%."

[0125]

number

[0126] (BET specific surface area) The sample powder was pretreated in an 8-well preheat unit (MOUNTECH) at approximately 130°C for approximately 30 minutes under a nitrogen gas atmosphere. The BET specific surface area (m) was measured by nitrogen gas adsorption using a Macsorb HM Model-1208 (MOUNTECH) BET specific surface area measuring device. 2 / g) was measured.

[0127] (Average particle size by laser diffraction method) 50 mL of ethanol was placed in a 100 mL beaker, and approximately 0.2 g of the sample powder was placed in the beaker. The mixture was subjected to ultrasonic treatment (UD-201, manufactured by Tomy Seiko Co., Ltd.) for 3 minutes to prepare a dispersion. The volumetric D of this dispersion was measured using a laser diffraction particle size distribution analyzer (Microtrac HRA Model 9320-X100, manufactured by Nikkiso Co., Ltd.). 50 The value was measured as the average particle size (μm).

[0128] (Production rate of calcium carbonate compounds that contributed to the fixation of carbon dioxide) The production rate E (mass%) of calcium carbonate compounds that contributed to the fixation of carbon dioxide was calculated using the following formula.

number

[0129] (Unreacted CaO content in calcium carbonate compounds) The content rate G (mass %) of unreacted CaO in the calcium-based carbonate compound was determined from the following formula. [Number] (In the formula, g is the CaO content rate (mass %) in the calcium-based carbonate compound. h is the CO2 content rate (mass %) in the calcium-based carbonate compound. i is the SO3 content rate (mass %) in the calcium-based carbonate compound.)

[0130] (Scanning electron microscope observation) A double-sided tape was attached to the aluminum sample stage, and the sample powder was applied thereon in a manner of tracing with the spatula blade. After platinum evaporation, a photograph of the particle image of the sample powder was taken at 5,000 times magnification using a scanning electron microscope (FE-SEM: S-4700 manufactured by Hitachi, Ltd.). SEM photographs of the examples and comparative examples are shown in FIGS. 2 to 5.

[0131] [Preparation of CaO-containing composition and production of calcium-based carbonate compound] [Example 1-1] 20 L of water was poured into a 30 L plastic container, and further 1.5 kg of lime sludge (hydrated lime-based wet product) was added under stirring. After stirring for 1 hour, screening was performed with a sieve having a mesh size of 4 mm by the wet method. After the suspension passing through the sieve was allowed to stand for 1 hour, about 10 L of the supernatant was removed and concentrated to 10 L of a suspension having a solid content concentration of about 130 g / L. 10 L of this suspension was put into a 20 L capacity pot mill filled with 5 kg of zirconia balls having a diameter of 8 mm, and wet pulverized at a rotation speed of 90 rpm for 4 hours to prepare a CaO-containing composition. For analysis, after filtering this slurry, a wet product dried at 110 °C for 12 hours was used.

[0132] The ground slurry was removed from the pot mill and placed in an 8-L stainless steel container with a baffle. The mixture was then heated to 40°C and stirred at 350 rpm using a stirrer equipped with a single turbine blade. A flue gas extraction pipe was connected to the exhaust outlet of an LNG-fueled steam production boiler, and the flue gas was drawn in using a test blower. Measurements using a CO2 concentration meter (XP-3140, manufactured by New Cosmos Electric Co., Ltd.) indicated a CO2 concentration of 10% by volume. The flue gas was introduced into the 8-L stainless steel container at a rate of 3.3 L / min using a test blower and allowed to react for 10 hours. The mixture was then filtered, and the separated wet material was dried at 110°C for 12 hours and pulverized to obtain a calcium carbonate powder sample.

[0133] [Example 1-2] 2 kg of lime slag (quicklime-based dry product) was dried at 110°C for 12 hours to produce a dried product, which was then dry-ground in a Bantam mill at a feed rate of approximately 100 g / min to obtain a dry-ground product as a CaO-containing composition. A sample powder of calcium carbonate compound was obtained by the same procedure as in Example 1, except that 780 g of the dry-ground product was placed in an 8 L stainless steel container equipped with a baffle and filled with 6 L of water.

[0134] [Examples 1-3] A sample powder of a calcium carbonate compound was obtained in the same manner as in Example 1, except that the suspension that passed through a sieve with 4 mm openings was used as it was in the carbonation reaction as a CaO-containing composition.

[0135] [Comparative Example 1-1] Sample powders of a CaO-containing composition and a calcium carbonate compound were obtained in the same manner as in Example 1, except that a suspension of the sieved fraction was used instead of the fraction that passed through a sieve with 4 mm openings.

[0136] [Table 1]

[0137] [Table 2]

[0138] From the results in Tables 1 and 2, the content of free CaO in the CaO-containing composition of the examples and the production rate of calcium carbonate compounds that contributed to CO2 fixation were both higher than those of the comparative examples.

[0139] <Production of inorganic molded body> Inorganic molded bodies were produced by a papermaking method according to the following procedure. Unless otherwise specified, the amounts of the components used are all expressed in parts by mass. In the table below, "-" indicates that the corresponding component was not used.

[0140] [Example 2-1] Production of inorganic molded body by papermaking method The materials shown in Table 3 below were placed in a plastic container and mixed under stirring to obtain a raw material slurry. The calcium carbonate compound used was the calcium carbonate compound of Example 1-1. The raw material slurry was divided and placed in a filter lined with felt, and a laminated board (long side 28 mm x short side 24 mm x thickness 14 mm) was produced while suction filtering was performed using a vacuum pump. The laminated board was removed from the filter and subjected to dehydration pressing. The thickness after pressing was 13 mm. Autoclave curing (curing pressure (gauge pressure) 9 kgf / cm 2 After curing for 12 hours, the pressed body was dried in a dryer (105°C) for 24 hours. Both sides were polished with a sander to adjust the thickness to 12 mm, and an inorganic molded body was obtained.

[0141] [Example 2-2] Production of inorganic molded body by papermaking method An inorganic formed body was obtained in the same manner as in Example 2-1, except that the calcium carbonate compound of Example 1-2 was used as the calcium carbonate compound.

[0142] [Example 2-3] Production of inorganic molded body by papermaking method An inorganic formed body was obtained in the same manner as in Example 2-1, except that the calcium carbonate compound of Example 1-3 was used as the calcium carbonate compound.

[0143] [Comparative Example 2-1] Production of inorganic molded body by papermaking method An inorganic formed body was obtained in the same manner as in Example 2-1, except that the calcium carbonate compound of Comparative Example 1-1 was used as the calcium carbonate compound.

[0144] [Comparative Example 2-2] Production of inorganic molded body by papermaking method An inorganic formed body was obtained in the same manner as in Example 2-1, except that no calcium carbonate compound was used.

[0145] <Evaluation of inorganic molded bodies> The inorganic molded articles produced by papermaking in the examples and comparative examples were evaluated as follows. The results are shown in Table 3.

[0146] (bulk density) The bulk density was measured in accordance with JIS A 5430.

[0147] (heating test) The heating test was carried out using the following equipment and procedure. Figure 6 is a partial perspective view that shows a schematic diagram of the heating tester. As shown in Figure 6, an electric heater was used as the heat source, and fireproof material was installed between the test specimen and the heat source to stabilize the temperature at around 900°C, and a thermocouple was used to measure the temperature on the backside of the test specimen. Specifically, the electric heater (1.2 kW heater) was fixed as the heat source equipment so that the distance between the heating surface of the test specimen and the heat source was approximately 70 mm.

[0148] The test procedure was as follows. (1) A scrap board was placed, preheated to 902°C, and then heated once. (2) The specimen was inserted after the heated surface had cooled to below 200°C. (3) A thermocouple was placed in the center of the back surface (top surface in the figure) of the test specimen, and a calcium silicate plate (approximately 30 mm x 70 mm) and a weight were placed on top and fixed in place. (4) Heating was started, and the sample was left for the specified time (45 minutes), after which the temperatures on the front and back sides were recorded with a data logger. During this time, the temperature setting of the electric heater was set to 902°C on the heating surface side, and the temperature was controlled with a temperature controller with a lower limit of 900°C. The data logger also measured the temperature every 10 seconds, and the data was recorded at this interval. (5) After the test was completed, the specimen was removed and the following items were measured (each item was also measured before the test): Dimensions: The length and width of the back surface and heating surface were measured with a vernier caliper. The area of ​​the heating surface (mm 2 ) was calculated, and the heating surface shrinkage (%) was calculated based on the following formula. Heating surface shrinkage (%) = {|S1-S0| / S0} x 100 (where S0 is the area of ​​the heating surface before the test (mm 2 ) and S1 is the area of ​​the heated surface after the test (mm 2 ) Warpage: The specimen was placed on an iron surface plate, and the height of the center of each side of the specimen from the iron surface plate was measured with a thickness gauge, and the average value (mm) was calculated. This average value was taken as the warpage (mm) after heating.

[0149] [Table 3]

[0150] The inorganic molded bodies of the Examples were superior to the Comparative Examples in terms of shrinkage on the heated surface, temperature rise on the reverse surface, and warpage after heating, demonstrating good fire resistance. Furthermore, the inorganic molded bodies of the Examples did not develop cracks after heating (not shown).

Claims

1. A preparation step of preparing a CaO-containing composition having a free CaO content of 50% by mass or more; a carbonation step of contacting the CaO-containing composition with carbon dioxide to form a calcium carbonate compound; A method for producing a calcium carbonate compound, comprising:

2. 2. The method for producing a calcium-based carbonate compound according to claim 1, wherein the preparation step includes a sieving step of sieving the CaO-containing raw material and recovering the fraction that passes through the sieve.

3. The method for producing a calcium carbonate compound according to claim 2, wherein the sieving step is carried out in a wet system.

4. The method for producing a calcium-based carbonate compound according to claim 1 , wherein the preparation step includes a pulverization step of pulverizing a CaO-containing raw material.

5. The method for producing a calcium-based carbonate compound according to any one of claims 2 to 4, wherein the CaO-containing raw material is derived from waste from a process involving calcination and slaking of limestone.

6. 2. The method for producing a calcium carbonate compound according to claim 1, wherein the CaO-containing composition has an average particle size of 1 μm or more and 30 μm or less as measured by a laser diffraction method.

7. The BET specific surface area of ​​the CaO-containing composition is 10 m ２ / g or more 50m ２ The method for producing a calcium carbonate compound according to claim 1, wherein the calcium carbonate content is 0.01g or less.

8. 2. The method for producing a calcium carbonate compound according to claim 1, wherein the concentration of carbon dioxide in the carbonation step is 1% by volume or more and 50% by volume or less.

9. 2. The method for producing a calcium carbonate compound according to claim 1, wherein the carbon dioxide used in the carbonation step is carbon dioxide emitted from a combustion engine.

10. 2. The method for producing a calcium carbonate compound according to claim 1, wherein the temperature in the carbonation step is 5°C or higher and 95°C or lower.

11. A CaO-containing composition for producing calcium-based carbonate compounds, having a free CaO content of 50% by mass or more.

12. The CaO-containing composition according to claim 11, which is a sieved or crushed product of a CaO-containing raw material.

13. 13. The CaO-containing composition of claim 12, wherein the CaO-containing raw material is derived from waste from a process involving the calcination and slaking of limestone.

14. A calcium carbonate compound, which is a carbonate of the CaO-containing composition according to any one of claims 11 to 13.

15. The calcium carbonate compound according to claim 14, which is for use in inorganic molded bodies.

16. An inorganic formed body comprising the calcium carbonate compound according to claim 14.

Images