Method for producing calcium-based carbonate compound, cao-containing composition, calcium-based carbonate compound, and inorganic molded body

Abstract

Provide are: 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. 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% by 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.

Description

Method for producing calcium carbonate compound, CaO-containing composition, calcium carbonate compound, and inorganic molded body

[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 formed body.

[0002] With the recent increase in environmental awareness, attempts have been made to reuse by-products and by-produced energy, such as waste materials, exhaust gases, and waste heat, generated in industrial processes. A technology for producing calcium carbonate by carbonating calcium-containing waste materials from concrete waste with carbon dioxide has been proposed (Japanese Patent Laid-Open Publication No. 2006-69860).

[0003] Japanese Patent Application Laid-Open No. 2006-69860

[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 carbonate compound using a CaO-containing composition suitable for carbonation reaction, a CaO-containing composition, a calcium carbonate compound, and an inorganic formed body.

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

[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 performed in a wet manner. This allows the free CaO particles (or free (CaO) ｍ ・(H ２ O) 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 pulverization step of pulverizing the CaO-containing raw material. ｍ ・(H ２ O) ｎ By pulverizing the carbon dioxide particles, the reactivity with the carbon dioxide particles can be improved, and more advantageous carbon dioxide fixation can be achieved.

[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. ２ / g or more 50m ２ / g or less. By using a finely divided or highly activated CaO-containing composition, the content of free CaO can be further increased.

[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 relates to a CaO-containing composition for producing a calcium-based carbonate compound, 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] In yet another embodiment, the present invention relates to calcium-based carbonate compounds that are carbonates of the CaO-containing compositions.

[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 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 may be used. Thus, elements may 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. The same applies to 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] <Ethylenediaminetetraacetic acid disodium titration method> 1 g of calcium carbonate compound (dried for 2 hours at 105°C) was weighed as a sample and suspended in 50 mL of water. 10 mL of hydrochloric acid (a 1:1 mixture of concentrated hydrochloric acid and water by volume) was added and heated to dissolve. After cooling, the suspension was transferred to a 250 mL volumetric flask and made up to the same volume with water. A 5.00 mL aliquot was taken from this and water was added to bring the total volume to approximately 50 mL. 5 mL of buffer solution (a 1,000 mL solution prepared by dissolving 500 g of potassium hydroxide in water) was added, followed by commercially available Dotite NN diluted powder. The titration was terminated when the solution changed color from red to blue. Calculate the calcium carbonate content (% by mass) using the following formula:

[0030] (In the formula, f is the titration reagent factor. The factor is determined by standardization with the titration reagent using a BT indicator. V is the amount of titration reagent consumed (mL). W is the amount of sample taken (0.02 g of calcium carbonate compound).)

[0031] CO ２ FIG. 1 is a cross-sectional view schematically showing an apparatus for measuring the content of calcium carbonate. FIG. 2 is a SEM photograph of the calcium carbonate compound of Example 1-1 of the present invention. FIG. 3 is a SEM photograph of the calcium carbonate compound of Example 1-2 of the present invention. FIG. 4 is a SEM photograph of the calcium carbonate compound of Example 1-3 of the present invention. FIG. 5 is a SEM photograph of the calcium carbonate compound of Comparative Example 1-1 of the present invention. FIG. 6 is a partial perspective view schematically showing a heating tester.

[0032] The method for producing a calcium carbonate compound, the CaO-containing composition, the calcium carbonate compound, and the 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 for producing a calcium-based carbonate compound> The method for producing a calcium-based 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 taking into consideration the content and particle size of free CaO in the CaO-containing raw material to be treated and the target CaO-containing composition. Below, an embodiment including a sieving step and a pulverization step, which are preferred steps as the preparation step, will be described.

[0034] (Sieving step) In the sieving step, the CaO-containing raw material is sieved and the portion that passes through the sieve is collected. Although it is possible to use the CaO-containing raw material itself, which is a waste product, by subjecting the CaO-containing raw material to the sieving step, it is possible to prepare a CaO-containing composition having 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 factories, concrete sludge discharged from concrete product factories, concrete waste materials 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. In terms of the content of free CaO, 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 free CaO content in the CaO-containing raw material is generally low and varies depending on the process in which the waste is generated. The free CaO content in the CaO-containing raw material is not particularly limited, but is generally 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 opening 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 one step, or in multiple steps, using sieves with large openings to sieves with small openings.

[0038] The sieving step may be carried out by either 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 (H ２ O) ｎ A wet method is preferred in that 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 in consideration of 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 thoroughly mixed with the water. The stirring time is preferably from 1 minute to 3 hours, 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 carry out concentration in the next step, it is preferable to leave the mixture to stand until the particles settle. The standing time is not particularly limited, but is preferably from 10 minutes to 3 hours, more preferably from 20 minutes to 2.5 hours, and even more preferably from 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] (Pulverization step) In the pulverization step, the CaO-containing raw material is pulverized. The pulverization step also produces free CaO particles (or free (CaO) ｍ (H ２ O) ｎ By miniaturizing the CaO-containing raw material (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 been subjected to a sieving step or an unsieved product that has not been subjected to a sieving step.

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

[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 a 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 or more and 600 g or less, more preferably 80 g or more and 500 g or less, and even more preferably 120 g or more and 400 g or less.

[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 that contains a high content of free CaO and has 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, and is therefore suitable for use in producing calcium carbonate compounds. As described above, the CaO-containing composition is preferably a sieved or pulverized product of a CaO-containing raw material. However, both the sieved product and the pulverized product may also be subjected to a sieving process.

[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 making it possible to obtain a CaO-containing composition having high reactivity with carbon dioxide.

[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 composed of moisture and CO ２ It comes from minutes.

[0054] SiO in CaO-containing compositions ２ The content of is preferably 0.4% by mass or more and 5.0% by mass or less, more preferably 0.6% by mass or more and 4.5% by mass or less, and even more preferably 0.8% by mass or more and 4.0% by mass or less.

[0055] Fe in CaO-containing compositions ２ O ３ The content is preferably 0.14% by mass or more and 0.80% by mass or less, more preferably 0.16% by mass or more and 0.60% by mass or less, and even more preferably 0.18% by mass or more and 0.40% by mass or less.

[0056] Al in CaO-containing compositions ２ O ３ The content is preferably 0.2% by mass or more and 1.8% by mass or less, more preferably 0.3% by mass or more and 1.5% by mass or less, and even more preferably 0.4% by mass or more and 1.2% by mass or less.

[0057] SO in CaO-containing compositions ３The content of is preferably 0.8% by mass or more and 3.0% by mass or less, more preferably 0.9% by mass or more and 2.5% by mass or less, and even more preferably 1.0% by mass or more and 2.0% by 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] CO in CaO-containing compositions ２ The upper limit of the content of CO is preferably 30% by mass, more preferably 20% by mass, and even more preferably 10% by mass. ２ Although a lower content of CO is preferable, it may be 0.1 mass %, 0.2 mass %, or 0.3 mass %. ２ is mainly derived from calcium carbonate. By keeping this value low, the content of free CaO can be increased.

[0060] (Carbonation Step) 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 obtained by dispersing the CaO-containing composition in water to carbonate it is typically preferred.

[0061] The solids concentration of the CaO-containing composition in the dispersion may be appropriately set taking into consideration 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 so that the concentration of the resulting suspension of the CaO-containing composition falls 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] Taking into consideration carbonation efficiency, the concentration of carbon dioxide in the exhaust gas in the carbonation step is preferably 1 vol% or more and 50 vol% or less, more preferably 3 vol% or more and 40 vol% or less, and even more preferably 5 vol% or more and 30 vol% or less.

[0064] In consideration of carbonation efficiency, the temperature in the carbonation step (the temperature of the dispersion) 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] When carbonation efficiency and production capacity are taken into consideration, the flow rate of carbon dioxide gas is preferably 10 L / min to 200 L / min per 10 kg of the charged raw material CaO, 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, alkali (NaOH, amine, etc.) and CO ２ By reacting with Na ２ CO ３First, amine carbonate is prepared and reacted with CaO to obtain CaCO ３ Also suitable are solution processes which produce:

[0069] By going through the above steps, a calcium-based carbonate compound can be produced as a carbonate of the CaO-containing composition. The resulting calcium-based carbonate compound may be filtered and dried to form a powder, or may be used as a calcium-based 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 as 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 2 m 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 has a molecular weight of 1000 or less. 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] SiO in calcium carbonate compounds ２ The content is preferably 0.20% by mass or more and 2.00% by mass or less, more preferably 0.40% by mass or more and 1.80% by mass or less, and even more preferably 0.60% by mass or more and 1.60% by mass or less.

[0076] Fe in calcium carbonate compounds ２ O ３ The content of is preferably 0.12% by mass or more and 1.20% by mass or less, more preferably 0.14% by mass or more and 1.00% by mass or less, and even more preferably 0.15% by mass or more and 0.80% by mass or less.

[0077] Al in calcium carbonate compounds ２ O ３ The content of is preferably 0.10% by mass or more and 1.50% by mass or less, more preferably 0.20% by mass or more and 1.20% by mass or less, and even more preferably 0.30% by mass or more and 1.00% by mass or less.

[0078] SO in calcium carbonate compounds ３ The content is preferably 0.75% by mass or more and 2.00% by mass or less, more preferably 0.80% by mass or more and 1.60% by mass or less, and even more preferably 0.85% by mass or more and 1.40% by 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] CO in calcium carbonate compounds ２The lower limit of the content of CO 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. ２ 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 mass%, more preferably 70 mass%, and even more preferably 80 mass%. The upper limit of the production rate is preferably 100 mass%, but may also be 98 mass%, 95 mass%, or 90 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%, even more preferably 4 mass%, and particularly preferably 2 mass%. The lower limit of the unreacted CaO content is preferably 0 mass%, but may 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 an industrial process can be reused, which can contribute to reducing carbon dioxide emissions throughout the entire industrial process.

[0084] <Uses of calcium-based carbonate compounds> The uses of calcium-based carbonate compounds are not particularly limited. For example, they are suitable as high-performance additives for inorganic molded bodies, such as building materials, and fillers for resins. Hereinafter, embodiments in which calcium-based carbonate compounds are used in inorganic molded bodies will be described.

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

[0086] (Molded Board for Building Material) The molded board preferably contains a hydraulic material, a siliceous material, a reinforcing fiber material, and a calcium carbonate compound.

[0087] (Hydraulic Materials) 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 or more and 45% by mass or less, more preferably 8% by mass or more and 42% by mass or less, and even more preferably 10% by mass or more and 40% by mass or less, 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 suppress an increase in the bulk density of the molded board, thereby improving workability during construction.

[0089] (Silicate Material) Examples of siliceous materials include silica sand, silica powder, silica fume, fly ash, diatomaceous earth, layered silicates (e.g., mica, talc, kaolin, bentonite), wollastonite, lightweight aggregates (e.g., fly ash balloons, perlite, shirasu balloons, glass foams, etc.), and other SiO ２ 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, which will be described later.

[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. In addition, 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, in order to prevent the bulk density from becoming too light and weakening strength such as bending strength and peel strength, 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.

[0091] (Reinforcing Fiber Material) Examples of reinforcing fiber materials that can be used include pulps such as softwood pulp, hardwood pulp, fibrillated pulp 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] In order 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 exhibit a sufficient reinforcing effect while suppressing the protrusion of fibers on the surface of the molded board, thereby improving smoothness. When an inorganic reinforcing fiber material having an average length of 1 mm to 50 mm is blended as the reinforcing fiber material, it is preferable to use other reinforcing fiber materials in combination so that their 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-Based Carbonate Compound) As the calcium-based carbonate compound, the calcium-based 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 the low thermal conductive calcium carbonate compound at a content within the above range, the strength and fire resistance of the molded board can be improved.

[0095] (Optional Components) In addition to the above materials, various materials 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. can be blended into the molded board depending on the purpose in order to impart various functions. It is also possible to appropriately add recycled materials obtained by crushing scraps generated during the processing of the molded board.

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

[0097] (Method for manufacturing molded plate) The method for manufacturing the molded plate according to this embodiment is not particularly limited, and commonly used methods such as papermaking, extrusion molding, 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 or the like, followed by curing at room temperature, steam curing, autoclave curing, or the like. The molded plate may then be dried and, if necessary, shaped or painted.

[0098] (Uses of molded board) The uses of the molded board are not particularly limited, and it can be suitably used as a performance maintaining material for wall construction materials, flooring materials, roofing materials, various boards, external 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 cement-based molded board containing a cementitious material, and more preferably a calcium silicate molded body.

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

[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, and 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 a range of 1 mass % to 60 mass %, preferably 3 mass % to 50 mass %, and more preferably 5 mass % to 40 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, the 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 having a molecular weight of 1 / g.

[0104] The expansive material may be, for example, an expansive material 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" may be used. Furthermore, quicklime becomes slaked lime when it comes into contact with water, so quicklime specified in JIS R9001 "Industrial Lime" may be used instead of slaked lime. In this case, it is advisable to correct the amount of water required to convert quicklime into slaked lime. For example, fly ash conforming to JIS A6201 "Fly ash for concrete" may be used.

[0106] Ordinary Portland cement is used as the 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 these 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 ３2.0g / cm or more ３ It is preferable that the density is 0.8 g / cm or less. ３ 1.8g / cm or more ３ More preferably, it is 0.9 g / cm or less. ３ 1.6g / cm or more ３ It is even more preferable that:

[0111] The present invention will be described in detail below using examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. Measurements and evaluations of physical properties, etc. were carried out as follows.

[0112] <Evaluation of CaO-containing composition and calcium-based carbonate compound> The CaO-containing composition and calcium-based carbonate compound (hereinafter, both are also collectively referred to as "sample") obtained in the examples and comparative examples were analyzed as follows. When the sample was a suspension, the wet material collected by filtration was dried at 110°C for 12 hours before being used for evaluation. The analytical results for the CaO-containing composition are shown in Table 1, and the analytical results for the calcium-based carbonate compound are shown in Table 2. SEM photographs of the calcium-based carbonate compound are shown in Figures 2 to 5.

[0113] (Ignition Loss) Approximately 2 g of sample was placed in a pre-weighed porcelain crucible that had been brought to a constant mass, and the total mass was accurately weighed. This was heated in an electric furnace at 900°C ± 25°C for at least 3 hours. The sample was cooled to room temperature in a desiccator, accurately weighed, and the difference in mass before and after heating was calculated as the weight loss. The ignition loss (mass basis) was calculated using the following formula: L (%) = (D / S) × 100 (where L is the ignition loss (%), D is the weight loss (g), and S is the weight (g) of the sample before heating.)

[0114] (CaO Content) The sample was treated according to the "ethylenediaminetetraacetic acid disodium titration method," which is a method for measuring the content of calcium carbonate in the calcium-based carbonate compound, and the CaO content (mass%) in the sample was calculated using the following formula.

[0115] (In the formula, f is the titration reagent factor. The factor is determined by standardization with the titration reagent using a BT indicator. V is the amount of titration reagent consumed (mL). W is the amount of sample taken (0.02 g of sample).)

[0116] (SiO ２ , Fe ２ O ３ , Al ２ O ３ and SO ３ (content) <ICP-AES method> 0.2 g of sample was weighed out, moistened with water, and 14 mL of hydrochloric acid (a 1:1 volumetric mixture of concentrated hydrochloric acid and water) was added using a dispenser, followed by heating and dissolution. After cooling, the solution was transferred to a 100 mL volumetric flask and water was added to make up to 100 mL. 5 mL of this solution was then dispensed into a 50 mL volumetric flask, and water was added to make up to 50 mL to prepare the sample solution for measurement. Separately, 5 mL of the aqueous solution made up to 100 mL was dispensed into a 50 mL volumetric flask, and standard solutions of each element (Si, Fe, Al, and S) were added as desired to prepare standard solutions for calibration curves with different concentrations. 1000 ppm atomic absorption standard solutions (commercially available) were used as the standard solutions for each element.

[0117] The calibration standard solutions containing different concentrations of each element and the sample solution for measurement were placed in the autosampler of an inductively coupled plasma atomic emission spectrometry (ICP-AES) analyzer (Hitachi High-Tech Science Corporation, "SPECTROBLUE FMS36 Model"), and the amounts of Si, Fe, Al, and S (ppm) 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 Liquid type: Aqueous solution Number of integrations: 3 Sample order: For each sample Measurement method: Standard addition method Calibration curve weighting: None Measurement wavelengths: 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 calculated from the amount of each element, and each was converted into an oxide to give SiO ２ , Fe ２ O ３ , Al２ O ３ and SO ３ The content (mass%) of

[0119] (Hydrochloric Acid Insolubles) 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 warmed solution was filtered using No. 5B filter paper. The insoluble matter adhering to the inner wall of the beaker was scraped off and collected with a policeman (a laboratory instrument with a rubber-covered tip of a glass rod) and combined with the insoluble matter on the filter paper. The insoluble matter on the filter paper was washed with at least 300 mL of hot water at approximately 70°C. The insoluble matter, 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 be incinerated. The sample was removed from the electric furnace and cooled on a porcelain dish. The porcelain crucible (including insoluble matter) was placed on a precision balance using resin tweezers, and zero point adjustment was performed (zero load). The insoluble matter was removed from the porcelain crucible with a brush, and the crucible was placed back on the precision balance and the weight loss (minus mark on the scale) was measured. 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 (where H is the hydrochloric acid insoluble matter (mass %), R is the weight loss (g) when the insoluble matter was removed, and S is the weight of the sample (g).)

[0120] (CO ２ (content of barium hydroxide) The reagents used for the measurement were prepared as follows. ・1 / 10N barium hydroxide solution: 15.8 g of barium hydroxide (octahydrate) was dissolved in ultrapure water to make a total of 1000 mL. After sealing and shaking well, the solution 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: 1 g of phenolphthalein was dissolved in ethanol to make a total of 100 mL.

[0121] FIG. 1 shows the CO ２1 is a schematic diagram showing a measurement device for the content of . Gas was circulated inside the measurement device by a circulation pump, and an airtight state was maintained during circulation. In the figure, arrows indicate the direction of gas flow.

[0122] Using the measuring device shown in FIG. ２ The content of was determined by the following procedure. 20.0 mL of 1 / 10 N barium hydroxide solution was placed in a 100 mL medium bottle, 2 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 90 minutes or more, 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. CO was calculated based on the following formula: ２ The content (mass%) of

[0123] (Wherein C is CO ２ is the content (mass%) of HCl. k is a coefficient (=0.0022). f is the factor of 1 / 10N hydrochloric acid standard solution. a is the titer (mL) of the sample. b is the titer (mL) of the control. s is the sample amount (g).

[0124] (Free CaO Content in CaO-Containing Composition) The free CaO content Z (mass%) in the CaO-containing composition is calculated by the ignition loss, CaO content, and SO ３ Content rate and CO ２ The content data was used to calculate the following formula, where "%" represents "% by mass."

[0125] (In the formula, p is the CaO content (mass%) in the CaO-containing composition. q is the CO ２ r is the content (mass%) of SO in the CaO-containing composition. ３ x is the water content (mass%) that is lost on ignition in the CaO-containing composition; and y is the loss on ignition in the CaO-containing composition (mass%).

[0126] (BET Specific Surface Area) A sample powder was pretreated in a nitrogen gas atmosphere at about 130°C for about 30 minutes using an 8-tube preheat unit (manufactured by MOUNTECH Co., Ltd.), and the BET specific surface area (m ２ / g) was measured.

[0127] (Average particle size by laser diffraction method) 50 mL of ethanol was placed in a 100 mL beaker, and about 0.2 g of the sample powder was added to the 100 mL beaker. The mixture was subjected to ultrasonic treatment (UD-201, manufactured by Tomy Seiko Co., Ltd.) for 3 minutes to prepare a dispersion. The volume-based 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 diameter (μm).

[0128] (Production rate of calcium carbonate compound that contributed to fixation of carbon dioxide) The production rate E (mass %) of calcium carbonate compound that contributed to fixation of carbon dioxide was calculated by the following formula. (wherein d is the CO in the calcium carbonate compound) ２ e is the CO content (mass%) in the CaO-containing composition. ２ The content is expressed as a percentage by mass.

[0129] (Content of Unreacted CaO in Calcium-Based Carbonate Compound) The content G (mass %) of unreacted CaO in the calcium-based carbonate compound was calculated by the following formula. (where g is the CaO content (mass%) in the calcium carbonate compound; h is the CO ２ The content (mass%) of the calcium carbonate compound is ３ Content (mass%)

[0130] (Scanning electron microscope observation) Double-sided tape was attached to an aluminum sample stage, and the sample powder was applied to the tape by tracing it with a spatula. After platinum deposition, particle images of the sample powder were photographed at 5,000 magnifications using a scanning electron microscope (FE-SEM: S-4700 manufactured by Hitachi, Ltd.). Figures 2 to 5 show SEM photographs of the examples and comparative examples.

[0131] Preparation of CaO-Containing Composition and Production of Calcium Carbonate Compound Example 1-1 20 L of water was poured into a 30 L plastic container, and 1.5 kg of lime slag (hydrated lime-based wet product) was added under stirring. After stirring for 1 hour, the mixture was sieved through a 4 mm mesh sieve by a wet method. The suspension that passed through the sieve was allowed to stand for 1 hour, and then approximately 10 L of supernatant was removed to concentrate the suspension to 10 L with a solids concentration of approximately 130 g / L. This 10 L suspension was placed in a 20 L pot mill filled with 5 kg of 8 mm diameter zirconia balls and wet-ground at 90 rpm for 4 hours to prepare a CaO-containing composition. For analysis, the slurry was filtered, and the wet product was dried at 110°C for 12 hours.

[0132] The pulverized slurry was removed from the pot mill, and 6 L of the pulverized slurry was placed in an 8 L SUS container with a baffle plate at a solids concentration of 130 g / L. The temperature was then raised to 40°C, and the mixture was stirred at that temperature using a stirrer equipped with one turbine blade at a rotation speed of 350 rpm. An exhaust gas extraction pipe was connected to the exhaust outlet of a steam production boiler fueled by LNG, and the exhaust gas was drawn in using a test blower. ２ When measured using a concentration meter (XP-3140 manufactured by New Cosmos Electric Co., Ltd.), CO ２ The concentration was 10% by volume. The exhaust gas was introduced into the aforementioned 8-liter SUS vessel using a test blower at a rate of 3.3 L / min, and the reaction was carried out for 10 hours. The mixture was then filtered, and the separated wet matter was dried at 110°C for 12 hours and pulverized to obtain a sample powder of a calcium carbonate compound.

[0133] [Example 1-2] 2 kg of lime slag (quicklime-based dried 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. The same procedure as in Example 1 was carried out, except that 780 g of the dry-ground product was placed in an 8 L SUS container equipped with a baffle and filled with 6 L of water, to obtain a sample powder of a calcium carbonate compound.

[0134] Example 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 the CaO-containing composition.

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

[0136]

[0137]

[0138] From the results in Tables 1 and 2, the content of free CaO in the CaO-containing compositions of the examples and the CO ２ The production rates of calcium carbonate compounds that contributed to immobilization were all 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. The amounts of the components used are all expressed in "parts by mass" unless otherwise specified. 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 stirred and mixed to obtain a raw material slurry. The calcium carbonate compound of Example 1-1 was used as the calcium carbonate compound. 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 performing suction filtration 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 molded 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 molded 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 molded 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 molded 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 Articles> 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 performed using the following equipment and procedure. FIG. 6 is a partial perspective view showing a schematic diagram of a heating tester. As shown in FIG. 6, an electric heater was used as a heat source, and a fireproof material was installed between the test specimen and the heat source so that the temperature could be stabilized at around 900°C, and the temperature of the back surface of the test specimen could be measured with a thermocouple. Specifically, an 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, and preheating was performed up to 902°C, followed by heating once. (2) After the temperature of the heated surface had dropped below 200°C, the test specimen was inserted. (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 board (approximately 30 mm x 70 mm) and a weight were placed on top to secure it in place. (4) Heating was initiated, and the specimen was left for a predetermined time (45 minutes), and the temperatures of the front and back surfaces were recorded with a data logger. During this time, the temperature of the electric heater was set to 902°C on the heated surface side, and was controlled by a temperature controller with a lower limit of 900°C. The data logger also measured the temperature every 10 seconds, and data was recorded at this interval. (5) After the test was completed, the test 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 heated surface were measured with vernier calipers. The area of ​​the heated surface (mm ２ ) was calculated, and the heated surface shrinkage (%) was calculated based on the following formula: Heating surface shrinkage (%) = {|S １ -S ０ | / S ０}×100 (in the formula, S ０ is the area of ​​the heating surface before the test (mm ２ ) and S １ 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]

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

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

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

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

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. A 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. 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. A method for producing a calcium carbonate compound as described in 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. 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 used for inorganic moldings.

16. An inorganic molding containing the calcium carbonate compound according to claim 14.

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