Method for producing hydraulic cement

Abstract

Disclosed is a method for producing a hydraulic cement, the method including: a step A for obtaining a molten mixture by mixing at least one slag (I) that has a CaO / SiO2 mass ratio of less than 3.0 and at least one slag (II) that has a CaO / SiO2 mass ratio of 3.0 or more, which are selected from among slags produced during the process of iron steel production, in a state where at least one of the slag (I) and the slag (II) is in a molten state; a step B for obtaining a clinker by rapidly cooling and solidifying the molten mixture obtained in the step A; and a step C for adding gypsum and a pulverization assistant to the clinker obtained in the step B and grinding the resulting mixture.

Description

Manufacturing method of hydraulic cement

[0001] The present disclosure relates to a method for making hydraulic cement.

[0002] Japan's crude steel production volume in 2023 is expected to be 87 million tons, of which 63 million tons are produced using the blast furnace method. The carbon dioxide (CO ２ If the CO emissions from the production of 63 million tons of crude steel are assumed to be 2.0 tons, ２ This is the total CO2 emissions for the whole country in 2023, which is 126 million tons. ２ This corresponds to 11.7% of the total CO emissions of approximately 1.08 billion tons. At the same time, as by-products of crude steel production using the blast furnace method, 19.6 million tons of blast furnace slag and 9.2 million tons of converter slag will be generated in 2022. To address these burdens, the shift from the blast furnace method to the electric furnace method and the reduction of CO emissions are expected to be significant. ２ There are various efforts underway to develop steelmaking methods that generate less waste, and there are also various initiatives to utilize blast furnace slag and converter slag.

[0003] Blast furnace slag is almost entirely used as a cement raw material, cement admixture, road material, etc. However, it cannot be said that the added value of any of these uses is sufficiently high, and there is a demand for technologies to utilize blast furnace slag with even greater value. There have been attempts to use converter slag in various ways, such as as road material, civil engineering material, fertilizer, and seaweed bed formation material, but compared to blast furnace slag, its development into established uses is limited. There is a demand for technologies to utilize both blast furnace slag and converter slag in uses with even higher added value than currently available.

[0004] Japan's cement production volume in 2021 is 55.7 million tons, and CO per ton of cement is ２ If the emissions are 0.75 tonnes, that would be 41.8 million tonnes of CO ２ This means that the total CO2 emitted by the country is ２ This corresponds to about 3.9% of emissions, or about one-third of emissions from steel production, but is a significant CO ２ Therefore, the CO emitted during cement production ２ Various efforts are being made to reduce the occurrence of such incidents.

[0005] CO during cement production ２ Regarding CO2 reduction, there remains unused technology for utilizing slag from steel manufacturing, such as blast furnace slag and converter slag. Since both blast furnace slag and converter slag are produced in a molten state, if hydraulic cement could be manufactured from these molten slag as raw materials, the energy required for current cement manufacturing, which involves heating raw materials to 1,450°C using a rotary kiln, would become almost unnecessary. In addition, since both blast furnace slag and converter slag are already decarbonated materials, CO2 from the raw materials would be reduced. ２ Emissions from energy could also be nearly zero. ２ and CO from the raw material ２ This raises the possibility of developing environmentally friendly cement that generates almost no carbon dioxide.

[0006] As a technique for obtaining hydraulic cement by utilizing slag discharged from steel manufacturing, for example, a method for producing hydraulic cement by adding at least SiO to molten reduced slag produced in the reduction and casting process of the electric furnace steelmaking process is proposed. ２ and a composition adjuster containing CaO is added to the molten reduced slag, which is then rapidly cooled and solidified to produce clinker, after which gypsum is added and the resulting mixture is pulverized to produce a hydraulic cement composition (see Patent Document 1). ２ Source: Al ２ O ３ Source: Fe ２ O ３ Patent Document 2 discloses a method for producing clinker by adding at least one of the above-mentioned sources as an auxiliary raw material to form a molten mixture, and Patent Document 3 discloses a method for producing a fine powder having latent hydraulic properties by mixing blast furnace slag and converter slag, at least one of which is in a molten state, in a ratio of 95 to 70 / 5 to 30 mass%, quenching the mixture with water, and pulverizing the mixture.

[0007] Patent Document 1: Japanese Patent No. 3240053 Patent Document 2: Japanese Patent Publication No. 2011-520756 Patent Document 3: Japanese Unexamined Patent Publication No. 8-337448

[0008] Patent Document 1 describes a method for producing a molten electric furnace reduction slag produced in an electric furnace steelmaking process as a main raw material, and using at least SiO ２ and CaO as auxiliary raw materials to form a molten mixture, which is then rapidly cooled and solidified to obtain clinker. In the method described in Patent Document 1, a large amount of auxiliary raw materials is added to the molten mixture so that the blending ratio is the same as that of conventional Portland cement. According to an example in Patent Document 1, 50 kg of CaO, SiO, and 40 kg of electric furnace reduced slag are added. ２ A total of 70 kg of auxiliary materials, 17 kg of slag and 3 kg of FeO, were added to develop hydraulic properties. ２ Furthermore, the effect of reducing the energy required to burn cement obtained by using molten slag is also small. Furthermore, as disclosed in Reference 1 below, electric furnace reduced slag contains approximately 10% to 15% MgO, and if used as is, Mg(OH) ２ This may cause expansion and reduce the stability of the hardened body, but no attention has been paid to this point.

[0009] "Tadashi Kuwayama, Atsuhiro Honda, Masaru Yamada, and Sadao Mise; Hydraulic Properties and Utilization of Electric Furnace Reduced Slag, Journal of the Japan Society of Waste Management, Vol. 1, No. 1, pp. 19-26, 1990" (Reference 1).

[0010] Patent Document 2 describes a method for producing a molten slag from a steelmaking process, which is used as a main raw material, and which contains a CaO source, SiO ２ Source: Al ２ O ３ Source: Fe ２ O ３ The document describes a method for producing clinker by adding at least one of the above-mentioned sources as an auxiliary material, forming a molten mixture, and rapidly solidifying the mixture. It also describes the use of one of molten blast furnace slag, converter slag, and electric furnace slag as the slag. However, the document does not focus on the composition of the slag used as the raw material, and does not disclose a method for controlling the composition to obtain hydraulic cement. Furthermore, as described in the examples of Patent Document 2, the CO emitted during production is ２The amount of CO obtained is the same as that of general-purpose blast furnace cement. ２ Patent Document 2 discloses a range of the degree of lime saturation as a composition range for obtaining hydraulic cement, but according to the inventor's investigation, the range includes many ranges in which it is difficult to obtain hydraulic cement, and there is no explicit description of a method for developing hydraulic properties and achieving a sufficient carbon dioxide reduction effect.

[0011] Patent Document 3 proposes a method for producing a fine powder with latent hydraulic properties by mixing at least one of molten blast furnace slag and converter furnace slag in a mass ratio of 90-70 / 5-30, rapidly solidifying with water, and pulverizing the mixture. However, the resulting material does not have hydraulic properties by itself, but rather has latent hydraulic properties. The fact that the material obtained by the above method has latent hydraulic properties can also be seen from the fact that the mixture ratio of blast furnace slag to converter furnace slag is 95-70 / 5-30 by mass, and that the material is in the acidic range, which has properties similar to those of blast furnace slag.

[0012] The object of one embodiment of the present disclosure is to use, as a main raw material, a plurality of molten slags generated in the steel manufacturing process, and to reduce CO emitted from the firing energy required during manufacturing. ２ , and CO emitted from the raw material ２ The present invention aims to provide a method for producing hydraulic cement in which the above-mentioned problems are reduced.

[0013] The means for solving the problems include the following embodiments: <1> CaO / SiO selected from slag generated in the steel manufacturing process ２ At least one slag (I) having a mass ratio of less than 3.0 and CaO / SiO ２ and at least one type of slag (II) having a mass ratio of 3.0 or more as main raw materials, the method comprising: step A of mixing at least one of the slag (I) and the slag (II) in a molten state to obtain a molten mixture; step B of rapidly solidifying the molten mixture obtained in step A to obtain clinker; and step C of adding gypsum and a grinding aid to the clinker obtained in step B and grinding the resulting mixture.

[0014] <2> The method for producing hydraulic cement according to <1>, wherein both the slag (I) and the slag (II) are in a molten state produced in a steel production process. <3> The step A further comprises the step of adding, as auxiliary raw materials, a component adjuster consisting of one component of CaO, a component consisting of CaO and Al ２ O ３ A component adjuster consisting of two components, CaO and SiO ２ and a component adjuster consisting of two components, CaO and Al. ２ O ３ and SiO ２ <1> or <2>, comprising a step (A-1) of selecting at least one component adjuster selected from the group consisting of the following three components:

[0015] <4> The molten mixture in the step A is a molten mixture containing slag (I) and slag (II), or a molten mixture containing slag (I), slag (II), and at least one kind of component adjuster, and CaO, Al contained in the molten mixture ２ O ３ , and SiO ２ When the total content of CaO, Al is taken as 100 mass %, ２ O ３ , and SiO ２ The method for producing hydraulic cement according to any one of <1> to <3>, further comprising a step (A-2) of adjusting the composition of the molten mixture so that the content of CaO in the total content of the above is equal to or greater than the value calculated by the following formula (1) and equal to or less than the value calculated by the following formula (2). ２ O ３ (mass%) + 69 Formula (2) CaO (mass%) = -0.34×Al ２ O ３ (mass%)+73

[0016] <5> The step A is performed by adding Fe contained in the molten mixture ２ O ３ The method for producing hydraulic cement according to <1> or <2> further comprises a step (A-3) of adjusting the iron content, calculated as 1.0% by mass or more to 10.0% by mass or less, and adjusting the MgO content to 5.0% by mass or less.

[0017] <6> The method for producing hydraulic cement according to <5>, wherein the step (A-3) includes at least one treatment selected from the following (i), (ii), and (iii): (i) a mixing treatment in which the types and mixing ratio of slag (I) and slag (II) are adjusted and mixed, (ii) a mixing treatment in which the types and mixing ratio of slag (I) and slag (II) are adjusted and the type and amount of a component adjuster as an auxiliary raw material is selected and mixed, and (iii) a weight reduction treatment in which slag (I) is reduced.

[0018] <7> The method for producing a hydraulic cement composition according to any one of <1> to <5>, wherein step A further comprises step (A-4) of feeding the molten mixture into a melting furnace having a mixing mechanism and a heating mechanism, heating the mixture, and forming and maintaining a molten state. <8> The method for producing hydraulic cement according to <7>, wherein step (A-4) is a step of continuously producing the molten mixture using a continuous mixing and heating furnace lined with basic firebricks and equipped with a heating mechanism. <9> The method for producing hydraulic cement according to <7>, wherein step (A-4) is a step of batchwise producing the molten mixture using a batch-type mixing and heating furnace lined with basic firebricks and equipped with a heating mechanism.

[0019] <10> The method for producing hydraulic cement according to any one of <1> to <9>, wherein step B further comprises step (B-1) of slowly cooling the molten mixture obtained in step A to obtain granules, and wherein the granules obtained in step (B-1) are rapidly cooled and solidified to produce clinker. <11> The method for producing hydraulic cement according to any one of <1> to <9>, wherein step B further comprises step (B-2) of granulating the molten mixture obtained in step A by causing it to flow down and spraying an air jet against it, and wherein the granulated mixture obtained in step (B-2) is rapidly cooled and solidified to produce clinker.

[0020] <12> The method for producing hydraulic cement according to any one of <1> to <11>, wherein the gypsum used in step C is gypsum dihydrate, a mixture of gypsum dihydrate and type II anhydrous gypsum, or a mixture of type II anhydrous gypsum and type III anhydrous gypsum.

[0021] <13> The method for producing hydraulic cement according to any one of <1> to <12>, wherein step C comprises the step of introducing at least one compound selected from the group consisting of diethylene glycol, triethanolamine, isopropanolamine, diethanolisopropanolamine, and methyldiethanolamine through an opening on the material inlet side of the grinding device. In step C of the method for producing hydraulic cement according to <13>, if an admixture is further added as desired, it is preferable to carry out the step of introducing at least one compound selected from the group consisting of a polycarboxylic acid-based cement dispersant, a lignin-based cement dispersant, calcium chloride, calcium nitrite, sodium gluconate, and sucrose through an opening on the ground material outlet side of the grinding device.

[0022] <14> The CaO / SiO ２ The method for producing hydraulic cement according to <4>, wherein the slag (I) having a mass ratio of less than 3.0 contains, as a main raw material, at least one selected from the group consisting of electric furnace oxidizing slag and electric furnace reducing slag produced in an electric furnace steelmaking process, and at least one treatment selected from the following (i), (ii), and (iv) is carried out to adjust the CaO content in the obtained hydraulic cement to a range that satisfies the above formulas (1) and (2): (i) a mixing treatment in which the types and mixing ratio of the slag (I) and the slag (II) are adjusted and mixed, (ii) a mixing treatment in which the types and mixing ratio of the slag (I) and the slag (II) are adjusted and the type and amount of a component adjuster as an auxiliary raw material is selected and mixed, or (iv) a mixing treatment in which the composition of the clinker obtained in the above step B is analyzed and multiple types of clinker are mixed.

[0023] <15> The CaO / SiO ２ The slag (I) having a mass ratio of less than 3.0 contains at least one selected from the group consisting of blast furnace slag, electric furnace oxidizing slag, and electric furnace reducing slag as a main raw material, and the CaO / SiO ２ <1> to <13>, wherein the slag (II) having a mass ratio of 3.0 or more contains, as a main raw material, converter slag produced in a steelmaking process by a blast furnace method.

[0024] <16> The CaO / SiO ２ The slag (I) having a mass ratio of less than 3.0 contains at least one selected from the group consisting of blast furnace slag, electric furnace oxidizing slag, and electric furnace reducing slag as a main raw material, and the CaO / SiO ２ The method for producing hydraulic cement according to <5>, wherein the slag (II) having a mass ratio of 3.0 or more contains, as a main raw material, converter slag produced in a steelmaking process by a blast furnace method, and the step (A-3) includes at least one treatment selected from the following (i), (ii), and (iii): (i) a mixing treatment in which the types and mixing ratio of the slag (I) and the slag (II) are adjusted and mixed, (ii) a mixing treatment in which the types and mixing ratio of the slag (I) and the slag (II) are adjusted and the type and amount of a component adjuster as an auxiliary raw material is selected and mixed, and (iii) a weight reduction treatment in which the slag (I) is reduced.

[0025] <17> The CaO / SiO ２ The slag (I) having a mass ratio of less than 3.0 contains, as a main raw material, at least one selected from the group consisting of electric furnace oxidizing slag and electric furnace reducing slag produced in an electric furnace steelmaking process, and ２ The method for producing hydraulic cement according to <4>, wherein the slag (II) having a mass ratio of 3.0 or more contains, as a main raw material, converter slag produced in a steelmaking process by a blast furnace method, and at least one treatment selected from the following (i), (ii), and (iv) is carried out to adjust the CaO content in the obtained hydraulic cement to a range that satisfies the above formulas (1) and (2): (i) a mixing treatment in which the types and mixing ratio of the slag (I) and the slag (II) are adjusted and mixed, (ii) a mixing treatment in which the types and mixing ratio of the slag (I) and the slag (II) are adjusted and the type and amount of a component adjuster as an auxiliary raw material is selected and mixed, or (iv) a mixing treatment in which the composition of the clinker obtained in the above step B is analyzed and multiple types of clinker are mixed.

[0026] According to one embodiment of the present disclosure, a plurality of molten slags generated in the steel manufacturing process are used as the main raw materials, and CO emitted from the firing energy required during manufacturing is reduced. ２ , and CO emitted from the raw material ２A method for producing hydraulic cement having reduced

[0027] Fig. 1 is a conceptual diagram showing all steps of the manufacturing method according to the present disclosure. ２ , Al ２ O ３ 1 is a conceptual diagram showing the compositions of the raw materials slag (I) and slag (II) and the compositions of the hydraulic cements of Examples 1 to 5 and Comparative Example 1 obtained by the production method according to the present disclosure, in a ternary phase diagram according to the present disclosure.

[0028] The method for producing hydraulic cement of the present disclosure will be described in detail below. The following description of the components may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments.

[0029] In the present disclosure, the use of "to" indicating a numerical range means that the numerical values ​​before and after it are included as the upper and lower limits. In numerical ranges described in stages in the present disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in numerical ranges described in the present disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. In the present disclosure, the term "step" includes not only independent steps, but also steps that cannot be clearly distinguished from other steps, as long as the intended purpose of the step is achieved.

[0030] In this disclosure, the term "main raw material" refers to slag produced in the steel manufacturing process, which is used in an amount exceeding 50% by mass of the total content of the hydraulic cement raw materials. The term "auxiliary raw material" refers to a component adjuster other than slag, which is used in an amount not exceeding 50% by mass of the total content of the hydraulic cement raw materials.

[0031] The first embodiment of the method for producing hydraulic cement of the present disclosure (hereinafter also referred to as the "production method according to the present disclosure") is a method for producing hydraulic cement by extracting CaO / SiO 2 from slag produced in the steel production process. ２ At least one slag (I) having a mass ratio of less than 3.0 and CaO / SiO２ The method includes: a step A of using as a main raw material at least one of the slag (I) and the slag (II) in a molten state to obtain a molten mixture by mixing them; a step B of rapidly cooling and solidifying the molten mixture obtained in the step A to obtain clinker; and a step C of adding gypsum and a grinding aid to the clinker obtained in the step B and grinding the resulting mixture.

[0032] Slags produced in steelmaking processes include blast furnace slag produced in the pig iron production process using the blast furnace method, converter slag produced in the steelmaking process using the blast furnace method, molten pig iron pretreatment slag produced in the steelmaking process using the blast furnace method, electric furnace oxidizing slag produced in the oxidation refining and casting process in the electric furnace steelmaking process, and electric furnace reducing slag produced in the reduction refining and casting process in the electric furnace steelmaking process. Furthermore, new slags are emerging in response to advances in environmental impact reduction technologies for steelmaking. As such, there are a variety of slags produced in steelmaking processes. The manufacturing method disclosed herein provides a technology for suitably using slags to produce hydraulic cement by combining appropriate slags while taking into account the characteristics of the desired slags, using composition adjusters as necessary, and adjusting the type and content of each raw material to a range suitable for producing hydraulic cement. That is, the manufacturing method according to the present disclosure specifically relates to a method for manufacturing hydraulic cement that contains, as a raw material, slag produced in the steel manufacturing process.

[0033] Table 1 shows examples of the compositions of steel slags, including blast furnace slag, converter slag, electric furnace oxidizing slag, and electric furnace reducing slag. All of these slags contain CaO, SiO, and other elements necessary for imparting hydraulic properties to cement. ２ , Al ２ O ３ and Fe ２ O ３ Contains:

[0034]

[0035] The compositions of blast furnace slag and converter slag were referenced in "Japan Iron and Steel Slag Association Website: Chemical Properties of Steel Slag (as of March 2024) (Reference 2)." The composition of electric furnace oxidizing slag was referenced in "Yamato Hiroaki, Noguchi Yosuke, Sanno Chinao, Torii Kazuyuki; Physical and Chemical Stability of Concrete Using Electric Furnace Oxidizing Slag, Proceedings of the Japan Concrete Institute, Vol. 26, No. 1, pp. 1641-1646, 2004 (Reference 3)," and "Taguchi Haruki, Ito Yosuke, Kawabe Nobuhito, Yasui Hideyuki; Effect of Water Content and Material Age on the Radio Wave Absorption Performance of Mortar Using Electric Furnace Oxidizing Slag as Aggregate, Proceedings of the Japan Concrete Institute, Vol. 40, No. 1, pp. 537-542, 2018 (Reference 4)." The composition of electric furnace reducing slag was referenced in the above-mentioned Reference 1.

[0036] General-purpose hydraulic cement is made of limestone (CaCO ３ ), silica (SiO ２ It is known that slags such as SiO2, SiO3, and SiO4 are used as raw materials, but it is important in the manufacturing method of the present disclosure to use slags of various compositions produced in the steel manufacturing process in an appropriate amount for hydraulic cement. ２ The mass ratio is about 3.0. The main component responsible for strength development in general-purpose hydraulic cement is 3CaO.SiO ２ (Tricalcium silicate), and the CaO / SiO of tricalcium silicate ２ The mass ratio is also 3.0. That is, to obtain hydraulic cement, CaO / SiO ２ Slag (I) having a mass ratio of less than 3.0, i.e., CaO / SiO ２ At least one slag having a composition positioned on the acidic side of the mass ratio of 3.0 and CaO / SiO ２ Slag (II) having a mass ratio of 3.0 or more, i.e., CaO / SiO ２ By combining it with slag that is more basic than the mass ratio of 3.0, a composition similar to general-purpose cement, i.e., CaO / SiO ２ It is important to obtain a molten mixture with a mass ratio of about 3.0.

[0037] When calculated based on the slag composition shown in Table 1 above, the CaO / SiO ２ The mass ratio is 1.2, 4.2 for converter slag, 1.6 for electric furnace oxidizing slag, and 1.7 for electric furnace reducing slag. Therefore, it can be seen that a combination of blast furnace slag and converter slag has the potential to be a main raw material for hydraulic cement, and that a combination of electric furnace oxidizing slag and converter slag, and a combination of electric furnace reducing slag and converter slag also have the potential to be suitable as a main raw material for hydraulic cement. As mentioned above, the CaO / SiO ２ By taking the mass ratio into consideration, combinations that are not suitable for producing hydraulic cement, such as blast furnace slag and electric furnace oxidizing slag, blast furnace slag and electric furnace reducing slag, and electric furnace oxidizing slag and electric furnace reducing slag, can be eliminated. The first embodiment of the production method according to the present disclosure makes it easy to select slag that can be used as a raw material for hydraulic cement from the various slags discharged in the steelmaking process.

[0038] After selecting the combination of the main raw materials, step A is carried out. Step A is a step of obtaining a molten mixture by mixing slag (I) and slag (II), at least one of which is in a molten state, and using the resulting mixture as the main raw material. From the viewpoint of energy reduction, it is desirable to obtain the molten mixture while both slag (I) and slag (II) are in the molten state generated in the steel production process. In a second embodiment of the production method of the present disclosure, both slag (I) and slag (II) are used in the molten state generated in the steel production process. However, considering the convenience of production, i.e., the transportation of molten slag to the mixing process, if at least one slag is in a molten state, the other slag can be partially solidified. The solidified slag in the present disclosure includes powder, granules, sand-like, or gravel-like fine particles obtained from slag solidified by cooling or the like. When at least one of the slags (I) and (II) used in step A is in a molten state as produced, and the other is a solidified slag, it is preferable that a molten mixture in a molten state can be formed by mixing or mixing and heating.

[0039] Step B is a step of rapidly cooling and solidifying the molten mixture obtained in step A to obtain clinker, and step C is a step of adding gypsum and a grinding aid to the clinker obtained in step B and grinding it.

[0040] According to the first embodiment of the manufacturing method of the present disclosure, a method is provided for appropriately obtaining hydraulic cement by selecting a combination of multiple slags that can be used as main raw materials for manufacturing hydraulic cement from slags generated in the steel manufacturing process.

[0041] In a third embodiment of the manufacturing method of the present disclosure, the step A further comprises adding a component adjuster consisting of one component of CaO, a component adjuster consisting of CaO and Al ２ O ３ A component adjuster consisting of two components, CaO and SiO ２ and a component adjuster consisting of two components, CaO and Al. ２ O ３ and SiO ２ The method includes a step (A-1) of selecting at least one component adjuster selected from the group consisting of the following three components: (1) a component adjuster for adding to the mixture of the main raw materials slag (I) and slag (II) when preparing the molten mixture in step A; and (2) a component adjuster for adding to the mixture of the main raw materials slag (I) and slag (II). By adding the component adjuster selected in step (A-1), it is possible not only to adjust the mixing ratio of slag (I) and slag (II), but also to adjust the composition of the molten mixture to that of hydraulic cement having better hydraulic properties by selecting an appropriate component adjuster.

[0042] The component adjuster may be a component adjuster consisting of only one component, CaO, or a component adjuster consisting of CaO and Al. ２ O ３ A component adjuster consisting of two components, CaO and SiO ２ and a component adjuster consisting of two components, CaO and Al. ２ O ３ and SiO ２ It is preferable that the component adjuster is at least one of the following three components:

[0043] If the molten mixture is still on the acidic side after adjusting the mixing ratio of the slag (I) and slag (II) obtained in step A, a composition adjuster consisting of one component, CaO, is added as a composition adjuster. By adding the composition adjuster, the molten mixture can be placed in a region with good hydraulic properties. CaO and Al are added as composition adjusters to the molten mixture. ２ O ３ When a component adjuster consisting of these two components is added, Al ２ O ３ In addition, the molten mixture may contain CaO and SiO. ２ By adding a component adjuster consisting of two components, Al ２ O ３ Therefore, when step A includes step (A-1), it becomes easier to adjust the hydraulic cement obtained by the production method according to the present disclosure to have a composition closer to a target composition by selecting a component adjuster, making it easier to obtain hydraulic cement with a suitable composition.

[0044] In a fourth embodiment of the manufacturing method according to the present disclosure, the molten mixture in the step A is a molten mixture containing slag (I) and slag (II), or a molten mixture containing slag (I), slag (II), and at least one kind of component adjuster, and CaO, Al contained in the molten mixture ２ O ３ , and SiO ２ When the total content of CaO, Al is taken as 100 mass %, ２ O ３ , and SiO ２ The method further includes a step (A-2) of adjusting the composition of the molten mixture so that the content of CaO in the total content of the above is equal to or greater than the value calculated by the following formula (1) and equal to or less than the value calculated by the following formula (2): Formula (1) CaO (mass%) = -0.30 × Al ２ O ３ (mass%) + 69 Formula (2) CaO (mass%) = -0.34×Al ２ O ３ (mass%)+73

[0045] In a fifth embodiment of the manufacturing method of the present disclosure, the step A is ２ O ３ The method further includes a step (A-3) of adjusting the iron content, calculated as Fe, to 1.0 mass % or more and 10.0 mass % or less, and adjusting the MgO content to 5.0 mass % or less. ２ O ３ The hydraulic cement obtained by the manufacturing method according to the present disclosure contains approximately 20% by mass to 25% by mass of iron oxide, calculated as Fe. ２ O ３ When the content of MgO, especially free MgO, is high, the hardened cement composition may have a black color. ２ Since the formation of MgO can cause the structure to expand and become unstable, it is preferable to also control the content of MgO contained in the hydraulic cement.

[0046] It is known that the MgO contained in the molten mixture is free MgO derived from the slag, which is the main raw material. Free MgO reacts more easily with water than non-free MgO, and the reaction product, magnesium hydroxide (Mg(OH) ２ ) causes undesired hydration expansion, destabilizing the hardened hydraulic cement obtained. Therefore, it is preferable that the content of MgO, especially free MgO, contained in the molten mixture is 5.0 mass % or less. In this way, in order to produce hydraulic cement using steel slag as a raw material, it is necessary to control the content of Fe contained in the slag. ２ O ３ Preferably, the method further comprises a step of controlling the content of at least one of Fe and MgO. ２ O ３ It is preferable that the amount of Fe is 10 mass % or less and the amount of MgO is 5 mass % or less. ２ O ３ Since it constitutes a liquid phase component during cement production and has an effective effect in producing hydraulic cement, the minimum amount is preferably 1.0 mass % or more.

[0047] The above step (A-3) is carried out to remove Fe, which may cause undesired coloring or expansion of hydraulic cement. ２ O ３ In a sixth embodiment of the manufacturing method of the present disclosure, the Fe content and / or the MgO content are controlled. ２ O ３ Specifically, the Fe content in step (A-3) and the MgO content in step (A-4) are controlled as follows: ２ O ３ The control of the content of at least one of the elements (I) and (MgO) is performed for the total amount of the main raw material and the auxiliary raw material, not for each individual slag, and can be performed by at least one of the following treatments (i), (ii), and (iii).

[0048] (i) Mixing treatment of adjusting the types and mixing ratio of slag (I) and slag (II) The mixing treatment described in (i) is performed by adjusting the types and mixing ratio of slag (I) and slag (II) contained in the main raw materials, i.e., Fe, ２ O ３ When at least one of the Fe content and the MgO content exceeds the target value, ２ O ３ By increasing the mixing ratio of other slags with lower Fe and MgO contents, the Fe content in the main raw material slag can be reduced. ２ O ３ and a method of relatively reducing the content of MgO.

[0049] (ii) A mixing process in which the type and mixing ratio of slag (I) and slag (II) are adjusted, and the type and amount of a component adjuster as an auxiliary material are selected and mixed. In addition to the mixing process described in (i) above, which adjusts the type and content of the main raw materials, slag (I) and slag (II), the type and amount of a component adjuster as an auxiliary material is selected and mixed, thereby reducing the Fe content of the mixture as a whole. ２ O ３ and a method of relatively reducing the content of MgO.

[0050] (iii) Weight reduction treatment of slag (I) The weight reduction treatment of (iii) is performed by reducing the Fe content of one or more slags used as the main raw material. ２ O ３ When at least one of the Fe content and the MgO content exceeds the above-mentioned preferable value, the Fe content is reduced by the reduction treatment of the slag. ２ O ３ and a method of reducing the content of MgO, i.e., decreasing the amount.

[0051] The reduction treatment (iii) above can be carried out using a non-metallic reducing agent such as carbon. Metallic reducing agents are preferably avoided as they leave behind metal oxides. MgO is a soluble form of Fe. ２ O ３ Since MnO is more difficult to reduce with carbon than Fe, reduction at high temperatures may be necessary. ２ O ３ As with the above, it may affect blackening, so Fe ２ O ３ However, MnO may require the same consideration as Fe. ２ O ３ At the same time, it tends to be reduced by carbon, so reduction treatment is easy. ２ O ３ The control of the content of at least one of Fe and MgO is performed for the entire molten mixture, and therefore, it can be performed by either the mixing treatment or the reduction treatment, or by combining both of them. ２ O ３ By controlling the content, even when the amount of iron oxide contained in the converter furnace slag, which is the slag (II), varies, adjustment can be easily made, and blackening of the hardened product can be suppressed.

[0052] The non-metallic reducing material used in the reduction treatment of iron oxide is preferably at least one selected from the group consisting of carbon, carbon monoxide, hydrogen, ammonia, and methane. Only one type of non-metallic reducing material may be used, or two or more types may be used. The principle of the reduction treatment of iron oxide using carbon is the same as that of the reduction treatment of iron oxide using the conventional blast furnace method. Furthermore, the principle of the reduction treatment using carbon, carbon monoxide, hydrogen, ammonia, and methane is also the same as that using carbon.

[0053] In a seventh embodiment of the production method according to the present disclosure, step A further includes step (A-4) of feeding the molten mixture into a melting furnace having a mixing mechanism and a heating mechanism, heating the mixture, and forming and maintaining a molten state. Here, adjusting the molten mixture to an appropriate temperature results in a more uniform molten mixture. That is, the mixture is fed into a melting furnace having a mixing mechanism and a heating mechanism and maintained at an appropriate temperature to form a molten mixture. This appropriate temperature depends on the slag and auxiliary materials used as the main raw material, but is preferably 1300°C to 1800°C, more preferably 1400°C to 1700°C. As described in the eighth embodiment of the production method according to the present disclosure, step (A-4) may be a continuous mixing and heating furnace lined with basic firebricks and equipped with a heating mechanism, in which the molten mixture is continuously produced.

[0054] Furthermore, as described in the ninth embodiment of the production method according to the present disclosure, step (A-4) may be a step of producing a molten mixture in a batch-type mixing and heating furnace lined with basic firebricks and equipped with a heating mechanism.

[0055] Next, a method for producing hydraulic cement using selected slags (I) and (II) as the main raw materials will be described. As described above, neither slag (I) nor slag (II) alone has a composition that can produce hydraulic cement. However, by mixing these slags to produce a mixture, a composition that can produce hydraulic cement is achieved. The resulting mixture is then adjusted to an appropriate temperature to produce a molten mixture, which is then rapidly cooled and solidified to produce clinker. Finally, gypsum and a grinding aid are added to the clinker, which is then ground to produce hydraulic cement. A conceptual diagram of steps A, B, and a step preceding step C included in the production method of the present disclosure is shown in FIG. 1. FIG. 1 is a conceptual diagram of the entire process, including the above steps and additional preferred steps.

[0056] Step A for obtaining a molten mixture further includes a step (A-1) of selecting and adding auxiliary materials to the molten mixture, a step (A-2) of selecting a ratio for mixing the main and auxiliary materials to obtain hydraulic cement, a step (A-3) of reducing the amount of components that may cause blackening or instability of the hardened cement body, and a step (A-4) of forming a molten mixture at an appropriate temperature to obtain hydraulic properties.

[0057] The type and amount of the composition adjuster in the step (A-1) are as described above. The step (A-2) is a step of selecting a composition for obtaining hydraulic cement by mixing multiple types of slag, composition adjusters, etc., and the following formulas (1) and (2) define the range of the amount of CaO depending on the raw materials. Note that, as long as the slag generated in the steel manufacturing process is used for hydraulic cement, the amount of Al ２ O ３ There is no need to set a limit for the formula (1): CaO (mass%) = -0.30 × Al ２ O ３ (mass%) + 69 Formula (2) CaO (mass%) = -0.34×Al ２ O ３ (mass%)+73

[0058] The step (A-4) includes a step of forming a molten mixture at an appropriate temperature. That is, the molten mixture is charged into a melting furnace having a mixing mechanism and a heating mechanism, and maintained at an appropriate temperature to form the molten mixture. This appropriate temperature can be appropriately selected depending on the raw materials, and is generally preferably 1300°C to 1800°C, and more preferably 1400°C to 1700°C.

[0059] In the above step (A-4), the apparatus for forming the molten mixture may be either a continuous type or a batch type. As the heating and mixing furnace, a continuous rotary kiln with a burner installed at the outlet can be used. The basic refractory brick is used to withstand the basicity of the hydraulic cement, and it is preferable to use chromium-free refractory bricks such as magnesia-spinel, magnesia-calcium, and magnesia-dolomite.

[0060] The equipment that can be used in step A is preferably an equipment that can form a molten mixture and maintain the molten mixture at the target temperature. The molten slag and, if necessary, the solid composition adjuster can be mixed by either mixing them before charging them into the rotary kiln or mixing them inside the rotary kiln after charging. Mixing inside the rotary kiln can be performed by using heat-resistant balls installed inside the kiln or by blowing nitrogen gas into the kiln to increase the mixing efficiency.

[0061] A converter used in the steelmaking process using the blast furnace method can be used as the batch-type mixing and heating furnace in the above step (A-4). Acidic slag and auxiliary materials are added to the remaining converter slag after the molten steel has been discharged, and the mixture is heated to form a molten mixture. A gas mixing method such as nitrogen gas injection can be used as the mixing mechanism. A method such as combustion heating gas injection, internal gas combustion, or carbon electrode insertion can be used as the heating mechanism.

[0062] Next, step B will be described. Step B is a step of rapidly solidifying the molten mixture obtained in step A to form a structure for obtaining hydraulic cement. As described in a ninth embodiment of the manufacturing method according to the present disclosure, two methods can be applied: a method in which the molten mixture obtained in step A is first slowly cooled to obtain granules (step (B-1)), and the granules obtained in step (B-1) are rapidly solidified to produce clinker; and a method in which an air jet is blown onto the molten mixture obtained in step A in a flowing state to granulate the molten mixture, and the granules obtained in step (B-2) are rapidly solidified to directly produce clinker, as described in a tenth embodiment of the manufacturing method according to the present disclosure. While step (B-1) is clear in terms of structure formation, step (B-2) not only achieves substantially the same performance, but also has the advantage of being more efficient as a manufacturing technique.

[0063] Next, step C will be described. Step C is a step in which gypsum and a grinding aid are added to the clinker obtained in step B and the resulting mixture is ground to obtain hydraulic cement. As described in the eleventh embodiment of the manufacturing method according to the present disclosure, it is preferable to use gypsum dihydrate, or gypsum dihydrate and type II anhydrous gypsum, or type II anhydrous gypsum and type III anhydrous gypsum as the gypsum. By using gypsum dihydrate to adjust the setting time and further using type II anhydrous gypsum in combination, effects such as improved strength of the hardened cement body can be expected. This effect is particularly expected when blast furnace slag is added to form a mixed cement. Type III anhydrous gypsum, like dihydrate gypsum, is effective in adjusting the setting time. Furthermore, by using type III anhydrous gypsum and type II anhydrous gypsum in combination, both effects of adjusting the setting time and improving the strength of the hardened cement body can be expected.

[0064] In the above step C, as described in the thirteenth embodiment of the manufacturing method according to the present disclosure, it is preferable to further include a step of adding at least one selected from the group consisting of diethylene glycol, triethanolamine, isopropanolamine, diethanolisopropanolamine, and methyldiethanolamine through an opening on the material input side of a grinding device such as a ball mill or rod mill used for grinding. In addition, in step C, when an admixture is further added as needed in addition to the grinding aid, it is preferable to include a step of adding at least one selected from the group consisting of polycarboxylic acid cement dispersants, lignin sulfonate cement dispersants, calcium chloride, calcium nitrite, sodium gluconate, and sucrose through an opening on the ground material discharge side of the grinding device.

[0065] By adding the additives as grinding aids, it is possible to reduce grinding energy and at the same time add various performances to cement. Diethylene glycol is often used as a grinding aid, but by using amines such as triethanolamine, isopropanolamine, diethanolisopropanolamine, and methyldiethanolamine as grinding aids, it is possible to increase the efficiency of clinker grinding, reduce energy consumption, and reduce CO ２ A reduction effect can be expected.

[0066] In step C, the grinding aid used to improve grinding efficiency is effectively added from the early stage of grinding for that purpose. It is preferable to add it from the opening on the material input side of the grinding device, such as a ball mill or rod mill, i.e., the inlet side of the grinding device. However, adding admixtures to improve performance such as cement fluidity and strength from the inlet side reduces their effectiveness due to heat and physical impact during grinding. To address this issue, adding these admixtures from the opening on the grinding device's outlet side, i.e., the outlet side of the grinding device, reduces the residence time of the admixture in the grinding device and suppresses the decrease in effectiveness. Examples of admixtures include, but are not limited to, polycarboxylic acid-based cement dispersants, lignin sulfonate-based cement dispersants, calcium chloride, calcium nitrite, sodium gluconate, sucrose, etc., and known admixtures can be used. According to the thirteenth embodiment of the manufacturing method of the present disclosure, the fluidity and strength of hydraulic cement can be further improved, and CO2 emissions can be reduced by reducing the amount of hydraulic cement used, etc. ２ A reduction effect is expected.

[0067] In the electric furnace steelmaking process, scrap iron is used as the raw material, so there is a large variation in the composition of the raw material and the impurities, and as a result, there is a large variation in the composition of the electric furnace slag. According to the description in the above-mentioned Reference 1, the main components of the electric furnace reducing slag are, in mass terms, CaO = 35% to 55%, SiO ２ =25%~35%, Al ２ O ３ According to the "Japan Society of Civil Engineers: Guidelines for the Design and Construction of Concrete Using Electric Arc Furnace Oxidizing Slag Aggregate (Draft) 2003 (Reference 5)," the variations in electric arc furnace oxidizing slag, including variations between businesses, are as follows: CaO = 41% to 7%, SiO ２ =30%~6%, Al ２ O ３ Therefore, in order to use electric furnace slag as a raw material, it is preferable to carry out some kind of treatment.

[0068] The fourteenth embodiment of the manufacturing method according to the present disclosure is the above CaO / SiO ２The method includes the steps of: (i) mixing slag (I) having a mass ratio of less than 3.0, which contains, as a main raw material, at least one selected from the group consisting of electric furnace oxidizing slag and electric furnace reducing slag produced in an electric furnace steelmaking process; and (ii) adjusting the CaO content in the resulting hydraulic cement to a range that satisfies the above formulas (1) and (2) by performing at least one treatment selected from the following (i), (ii), and (iv): (i) a mixing treatment in which the types and mixing ratio of slag (I) and slag (II) are adjusted and mixed; (ii) a mixing treatment in which the types and mixing ratio of slag (I) and slag (II) are adjusted and the type and amount of a composition adjuster as an auxiliary raw material is selected and mixed; and (iv) analyzing the composition of the clinker obtained in the above step B and mixing multiple types of clinker.

[0069] The mixing processes (i) and (ii) above are as described above. The mixing process described in (iv) above is a mixing process in which the composition of the clinker obtained in the above step B is analyzed and multiple types of clinker are mixed. That is, the CaO content in the hydraulic cement can be controlled within an appropriate range by selecting the type and mixing ratio of the slag as the main raw material, the type and amount of the composition adjuster, and also by selecting and mixing the type and amount of the clinker. The mixing process (iii) above is a mixing process in which the composition of the clinker obtained in step B is analyzed, stored, and multiple types of clinker are mixed to adjust the CaO content in the resulting hydraulic cement to a range that satisfies the above formulas (1) and (2).

[0070] For example, it is effective to combine two or more of the mixing treatments (i), (ii), and (iii) to control the CaO content in the hydraulic cement within a preferred range.

[0071] According to the above-mentioned (i) mixing process, for example, by mixing equal amounts of electric furnace slag and other main raw material slag, the coefficient of variation of a certain composition can be reduced from 5% to 2.5%. The above-mentioned (ii) mixing process is suitable for fine adjustment of the composition variation, and the use of Al as a component adjuster is effective. ２ O ３ The amount is adjusted by adding CaO and Al.２ O ３ The addition of CaO and SiO ２ The mixing treatment of (iii) above is a method in which a certain degree of variation in composition is allowed during the production of clinker in step B, and multiple types of clinker with different compositions are mixed at the end of the process to ultimately control the composition of hydraulic cement within a preferred range.

[0072] The target value when adjusting the composition by the above method is, as mentioned above, the CaO and Al contained in the hydraulic cement. ２ O ３ and SiO ２ When the total amount of CaO, Al is taken as 100 mass % ２ O ３ and SiO ２ The content of CaO relative to 100 mass% of the total content of the above components is controlled to be equal to or greater than the value calculated by the above formula (1) and equal to or less than the value calculated by the above formula (2).

[0073] The method for selecting the multiple slags generated in the steel manufacturing process and the method for manufacturing hydraulic cement using them have been described above, but the steps to be performed vary depending on the combination of slags selected. Therefore, specific slags from which hydraulic cement can be obtained are presented below, and the steps for manufacturing hydraulic cement from them are also described below.

[0074] According to Table 1 above, the CaO / SiO ratio of blast furnace slag generated in the pig iron manufacturing process using the blast furnace method is ２ The mass ratio of CaO / SiO of electric furnace oxidizing slag produced in the oxidation refining process of the electric furnace steelmaking process is 1.2. ２ The mass ratio of CaO / SiO of electric furnace reduction slag produced in the reduction refining process is 1.6. ２ The mass ratio is 1.7, so these are CaO / SiO ２ The slag (I) having a CaO / SiO mass ratio of less than 3.0 can be used. ２ Since the mass ratio is 4.2, the converter slag is CaO / SiO２ Hydraulic cement can be produced by using converter slag as the slag (II) having a mass ratio of 3.0 or more. That is, hydraulic cement of a suitable composition can be produced by combining converter slag with one or more selected from blast furnace slag, electric furnace oxidizing slag, and electric furnace reducing slag as the main raw slag.

[0075] The slag (I) does not necessarily have to be a single slag selected from the group consisting of blast furnace slag, electric furnace oxidizing slag, and electric furnace reducing slag, but can be a mixture of two or three of these slags. Therefore, the type of slag (I) can be appropriately selected depending on the location of blast furnaces and electric furnaces within a factory or between adjacent factories.

[0076] Among the slags selected from the three types of slag (I) and one type of slag (II), Fe is selected depending on the slag used as the main raw material. ２ O ３ The difference between the two types of slag is whether or not a treatment to reduce the content of at least one of MgO and MgO is necessary and the treatment method. When electric furnace slag is used, it is preferable to suppress the variation in composition.

[0077] When electric furnace oxidizing slag, electric furnace reducing slag, and converter slag are used as the main raw material, at least one of the above methods is carried out to obtain the Fe content of the hydraulic cement. ２ O ３ It is preferable to adjust the content of MgO within the above range.

[0078] When electric furnace oxidizing slag or electric furnace reducing slag is used as the slag (I), at least one mixing treatment selected from the above-mentioned mixing treatment (i), mixing treatment (ii), and mixing treatment (iv) is carried out to remove CaO, Al contained in the hydraulic cement. ２ O ３ and SiO ２ When the total amount of CaO, Al is 100 mass % ２ O ３ and SiO ２It is preferable to control the composition so that the content of CaO relative to 100 mass% of the total content of the above is equal to or greater than the value calculated by the above formula (1) and equal to or less than the value calculated by the above formula (2).

[0079] These slags are used as raw materials, and the combination amount is adjusted, and the type and amount of component adjuster is also adjusted. ２ O ３ and MgO, ２ Another feature of the manufacturing method according to the present disclosure is that it is possible to produce the desired hydraulic cement while reducing the amount of waste generated.

[0080] The manufacturing method of the present disclosure will be described below using specific examples, but it goes without saying that the present disclosure is not limited to the following examples, and various modifications are possible. In the following examples, % means % by mass, and parts means parts by mass, unless otherwise specified.

[0081] <Examples 1 to 5, Comparative Example 1> Examples 1 to 5 shown in Table 2 are CaO / SiO ２ Slag (I) having a mass ratio of less than 3.0 and CaO / SiO ２ The slag (II) having a mass ratio of 3.0 or more is 40% to 60% by mass, and CaO or SiO is used as a component adjuster. ２ in the amounts shown in Table 2. In Table 2, "-" indicates that the component in question is not included. Comparative Example 1 is a cement equivalent to ordinary Portland cement. The compositions of the blast furnace slag, converter slag, electric furnace oxidizing slag, and electric furnace reducing slag used in the examples are as shown in Table 1 above.

[0082]

[0083] The compositions of Examples 1 to 5 and Comparative Example 1 shown in Table 2 are CaO, SiO ２ , Al ２ O ３ The composition in which the total amount of the three components is 100 mass % and Fe ２ O ３ The percentage of Fe and MgO content relative to the total amount of hydraulic cement is shown. ２O ３ The composition of MgO is Fe and MgO, which are obtained by reduction treatment in converter slag. ２ O ３ The composition of the electric furnace oxidizing slag is shown after the weight of Fe and MgO is reduced and mixed with the acidic slag (I) and the component adjuster. ２ O ３ The figures show the composition of converter slag after reduction treatment with reduced MgO and MgO, and after mixing with a composition adjuster. For electric furnace reduced slag, the weight reduction treatment by reduction of MgO is taken into consideration.

[0084] Example 1 is a composition in which blast furnace slag and converter slag are combined and 14 mass % of CaO is added as a component adjuster, Example 2 is a combination of electric furnace reducing slag and converter slag, and Example 3 is an example in which a combination of electric furnace oxidizing slag and converter slag is used as a raw material. The compositions of the hydraulic cements obtained in each of the above examples and Comparative Example 1 are as follows: CaO, SiO ２ , Al ２ O ３ The composition of the converter slag is shown in a ternary phase diagram in FIG. 2. In FIG. 2, the composition of the blast furnace slag is shown as "Slug (II)," the composition of the electric furnace oxidizing slag is shown as "Slug (I-1)," the composition of the electric furnace reducing slag is shown as "Slug (I-2)," and the composition of the electric furnace reducing slag is shown as "Slug (I-3)." In FIG. 2, the compositions of Examples 1 to 5 are shown as "E1" to "E5," respectively, and the composition of Comparative Example 1 is shown as "C1." In the ternary phase diagram, formulas (1) and (2) are shown as straight lines represented by (1) and (2), respectively. The hydraulic cements of Examples 1 to 5 all have compositions close to the above formula (2), and the hydraulic cements of Examples 3 and 4 all have compositions close to the above formula (1).

[0085] The blast furnace slag, converter slag, electric furnace oxidizing slag, and electric furnace reducing slag used in the production of hydraulic cement in Examples 1 to 5 and Comparative Example 1 were determined by referring to the compositions of each slag shown in Table 1. ３ , SiO ２ , Al ２ O ３ and Fe of the reagent ２O ３ and MgO. ３ As the powder, industrial limestone powder with a content of 98.8 mass% was used. ２ As the silica powder, an industrial silica powder having a content of 98.7% by mass was used. ２ O ３ The powder was pulverized in a jet mill to obtain a CaCO ３ The average particle size of the powder is 10 μm, and SiO ２ and Al ２ O ３ The powders used had an average particle size of 5 μm. ２ O ３ A reagent with a content of 96.0% by mass was used as is, and a reagent with a content of 96.0% by mass was used as is for MgO. ２ O ３ The powder had an average particle size of 0.2 μm, and the MgO powder had an average particle size of 1.7 μm, so they were used as they were to prepare the slag without being crushed.

[0086] A mixture of the above materials was granulated into 1 mm to 5 mm pellets and heated to form a uniform melt, and a molten mixture was prepared with the blending ratios shown in Table 2 (Step A). ​​The melt was then left to cool in indoor air to obtain clinker (Step B). Gypsum dihydrate was added to the obtained clinker and pulverized (Step C), to obtain hydraulic cement.

[0087] In the above step A, 150 g of pellets obtained by granulating each of the above mixtures to a diameter of 1 mm to 5 mm were placed in a circular dish-shaped platinum crucible and heated to 1450°C in an uncontrolled atmosphere electric furnace to obtain a uniform molten mixture. The temperature was increased at a rate of 25°C / min, and after holding at 1000°C for 60 minutes, the temperature was increased to 1450°C and held at this temperature for 90 minutes to obtain a uniform molten mixture. Thereafter, the crucible containing the obtained molten mixture was removed and allowed to cool and solidify in air to obtain clinker (step B).

[0088] In step C, the solidified clinker obtained in step B is mixed with gypsum dihydrate in a ball mill to a fineness of 2900 cm ２ / g to 3000 cm ２The amount of gypsum dihydrate added was 100g / g, and the resulting mixture was crushed to 100g / g to obtain hydraulic cement. ３ This is calculated as 2% by mass.

[0089] [Strength Evaluation] Mortar was prepared using the hydraulic cements of Examples 1 to 5 and Comparative Example 1, and the performance of the hydraulic cement was evaluated. The water-cement ratio of the mortar was 50% by mass, and silica sand No. 6 was used as the fine aggregate, resulting in a sand-cement mass ratio of 1.8. The size of the test specimen for the compressive strength test was 15 mm x 15 mm x 30 mm. After demolding, the specimen was cured in water at 20°C, and then a rectangular parallelepiped test specimen of the above size was obtained. An Instron 5567 universal testing machine (Instron Japan) was used as the testing machine. The two sides of the test specimen that were in contact with the formwork were set horizontally, one above the other. A 15 mm x 15 mm x 10 mm steel loading plate was placed in the center of the top and bottom surfaces so that the 15 mm x 15 mm surface of the plate was in contact with the test specimen. A compressive load was then applied from above and below via the loading plate. The loading rate was the loading rate per unit area specified in JIS R 5201-2015, Physical Testing Methods for Cement. "JIS" is an abbreviation for Japanese Industrial Standards. Using the above method, compressive strength was measured at ages of 3, 7, and 28 days. The color tone of the hardened body was also evaluated using the formwork surface of the compressive strength test specimen. Furthermore, free lime was evaluated from the X-ray diffraction results of the hydraulic cement to estimate its stability.

[0090] Table 3 shows the compressive strength at ages of 3, 7, and 28 days and the strength ratio to the 28-day strength. The 28-day compressive strength of Examples 1 to 3 is equal to or slightly higher than that of the Comparative Example, which corresponds to ordinary Portland cement. Example 4 has a lower strength than the Comparative Example, but exhibits clear hydraulic properties. Example 5 exhibits a higher strength than the Comparative Example and other Examples. Looking at the strength ratio (%) to the 28-day compressive strength, Examples 1 to 3 are almost the same as Comparative Example 1, and show the same strength development. Examples 4 and 5 tend to have a slightly slower strength development rate than Comparative Example 1.

[0091]

[0092] The evaluation of the color tone of the formwork surface of specimens subjected to compressive strength tests at ages of 3, 7, and 28 days revealed no difference between the Examples and Comparative Examples. X-ray diffraction results indicated that there was no or only trace amounts of free lime, suggesting that stability was not an issue. Performance evaluation tests of the Examples and Comparative Examples indicated that hydraulic cement could be produced by combining blast furnace slag and converter slag, electric furnace oxidizing slag and converter slag, and electric furnace reducing slag and converter slag. Furthermore, since cements with compositions close to formulas (1) and (2), which were established as the preferred compositional conditions for producing hydraulic cement, all possess hydraulic properties, it was confirmed that suitable hydraulic cements can be obtained by controlling the content of each component according to the above two formulas.

[0093] The above results show that hydraulic cement can be obtained by using any one of blast furnace slag, electric furnace reducing slag, and electric furnace oxidizing slag as the acidic slag and converter slag as the basic slag.

[0094] The above three types of hydraulic cement contain CaO, SiO, as shown in Figure 2. ２ , Al ２ O ３ In the ternary phase diagram, the positions of Examples 1, 2, and 3 are shown. From Fig. 2, it can be seen that the positions of the Examples are near the line connecting the positions of the acidic slag and the basic slag.

[0095] Next, a description will be given of the case where multiple acidic slags are mixed. In Figure 2, a mixture of blast furnace slag and electric furnace reducing slag is located between the blast furnace slag and the electric furnace reducing slag. Similarly, a mixture of blast furnace slag and electric furnace oxidizing slag is located between the two slags, and a mixture of electric furnace reducing slag and electric furnace oxidizing slag is also located between these two. A mixture of blast furnace slag, electric furnace reducing slag, and electric furnace oxidizing slag is also located between these two.

[0096] Because the acidic slag mixture is in the above position, the hydraulic cement composition obtained by combining the acidic slag mixture with converter furnace slag is intermediate between those of Examples 1, 2, and 3. Since it was confirmed that hydraulic cement can be obtained from Examples 1, 2, and 3, it is believed that hydraulic cement can also be obtained from intermediate positions. In other words, it is estimated that hydraulic cement with good hardening properties can be obtained from the fourteenth to seventeenth embodiments of the production method according to the present disclosure, which combines multiple slags (I) located on the acidic side with converter furnace slag [slag (II)].

[0097] Next, CO2 emissions from the production of hydraulic cement in Examples 1 to 5 and Comparative Example were analyzed. ２ The amount of CO generated per ton of ordinary Portland cement in Comparative Example 1 is approximately 0.75 tons. ２ In contrast, the hydraulic cement of the present embodiment uses multiple molten slags that have been decarbonated as raw materials, so CO ２ Furthermore, since the raw materials are used in a molten state, the energy required to sinter the raw materials is almost zero. In other words, almost no CO is generated from the raw materials and energy. ２ However, in the process of obtaining CaO used as a component adjuster, CO ２ occurs.

[0098] CO to obtain CaO ２ However, CO from the raw material ２ is CO ２ / CaO molecular weight mass ratio, and CO from production energy ２ "Lime Manufacturing Association: Global warming countermeasures in the lime manufacturing business (Low Carbon Action Plan 2016 performance report)" (Reference 6) for fiscal 2018 (0.255 ton CO ２ / ton CaO) from Examples 1 to 5. ２ 0.11 to 0.18 tonnes CO ２ / ton hydraulic cement. Therefore, the CO ２The reduction rate is 78% to 85%. Furthermore, when 50% by mass of ground granulated blast furnace slag is substituted for blast furnace cement, CO ２ The reduction rate is 89% to 93%, and CO2 emissions in the production of hydraulic cement are ２ The incidence is close to zero.

[0099] The manufacturing method according to the present disclosure improves the added value of blast furnace slag and converter slag, which are by-products generated in large quantities during steel production, and reduces CO emissions from cement production. ２ As described above, according to each embodiment of the manufacturing method of the present disclosure, a plurality of molten slags generated in the steel manufacturing process are used as the main raw materials, and CO emissions from the firing energy required during manufacturing are reduced. ２ , and CO emitted from the raw material ２ It can be seen that a method for producing hydraulic cement with reduced

[0100] The disclosure of Japanese Patent Application No. 2024-073233, filed on April 26, 2024, is incorporated herein by reference. All documents, patent applications, and technical standards mentioned in this disclosure are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. CaO / SiO selected from slag produced in the steel manufacturing process ２ At least one slag (I) having a mass ratio of less than 3.0 and CaO / SiO ２ and at least one type of slag (II) having a mass ratio of 3.0 or more as main raw materials, the method comprising: step A of mixing at least one of the slag (I) and the slag (II) in a molten state to obtain a molten mixture; step B of rapidly solidifying the molten mixture obtained in step A to obtain clinker; and step C of adding gypsum and a grinding aid to the clinker obtained in step B and grinding the resulting mixture.

2. The method for producing hydraulic cement according to claim 1, wherein both the slag (I) and the slag (II) are in a molten state produced in the process of steel production.

3. The step A further includes the use of a component adjuster consisting of one component of CaO, a mixture of CaO and Al, as an auxiliary raw material. ２ O ３ A component adjuster consisting of two components, CaO and SiO ２ and a component adjuster consisting of two components, CaO and Al. ２ O ３ and SiO ２ The method for producing hydraulic cement according to claim 1 or claim 2, further comprising a step (A-1) of selecting at least one component adjuster consisting of the following three components:

4. The molten mixture in the step A is a molten mixture containing slag (I) and slag (II), or a molten mixture containing slag (I), slag (II), and at least one kind of component adjuster, and CaO, Al contained in the molten mixture ２ O ３ , and SiO ２ When the total content of CaO, Al is taken as 100 mass %, ２ O ３ , and SiO ２ The method for producing hydraulic cement according to claim 1 or 2, further comprising a step (A-2) of adjusting the composition of the molten mixture so that the content of CaO in the total content of the above is equal to or greater than the value calculated by the following formula (1) and equal to or less than the value calculated by the following formula (2). ２ O ３ (mass%) + 69 Formula (2) CaO (mass%) = -0.34×Al ２ O ３ (mass%)+73 5. The step A is carried out by ２ O ３ The method for producing hydraulic cement according to claim 1 or 2, further comprising a step (A-3) of adjusting the iron content, calculated as 1.0% by mass or more and 10.0% by mass or less, and adjusting the MgO content to 5.0% by mass or less.

6. The method for producing hydraulic cement according to claim 5, wherein step (A-3) includes at least one treatment selected from the following (i), (ii), and (iii): (i) a mixing treatment in which the types and mixing ratio of slag (I) and slag (II) are adjusted and mixed, (ii) a mixing treatment in which the types and mixing ratio of slag (I) and slag (II) are adjusted and the type and amount of a component adjuster as an auxiliary raw material is selected and mixed, and (iii) a weight reduction treatment in which slag (I) is reduced.

7. The method for producing a hydraulic cement composition according to claim 1 or 2, wherein step A further comprises step (A-4) of charging the molten mixture into a melting furnace having a mixing mechanism and a heating mechanism, heating the mixture, and forming and maintaining a molten state.

8. The method for producing hydraulic cement according to claim 7, wherein step (A-4) is a step of continuously producing a molten mixture using a continuous mixing and heating furnace lined with basic firebricks and equipped with a heating mechanism.

9. A method for producing hydraulic cement according to claim 7, wherein step (A-4) is a step of producing a molten mixture in a batch-type mixing and heating furnace lined with basic firebricks and equipped with a heating mechanism.

10. A method for producing hydraulic cement according to claim 1 or 2, wherein step B further comprises step (B-1) of slowly cooling the molten mixture obtained in step A to obtain granules, and step B is a step of rapidly cooling and solidifying the granules obtained in step (B-1) to produce clinker.

11. A method for producing hydraulic cement according to claim 1 or 2, wherein step B further comprises step (B-2) of granulating the molten mixture obtained in step A by allowing it to flow down and spraying an air jet onto it, and the granulated mixture obtained in step (B-2) is rapidly cooled and solidified to produce clinker.

12. A method for producing hydraulic cement according to claim 1 or 2, wherein the gypsum used in step C is gypsum dihydrate, a mixture of gypsum dihydrate and type II anhydrous gypsum, or a mixture of type II anhydrous gypsum and type III anhydrous gypsum.

13. A method for producing hydraulic cement according to claim 1 or 2, wherein step C includes a step of introducing at least one selected from the group consisting of diethylene glycol, triethanolamine, isopropanolamine, diethanolisopropanolamine, and methyldiethanolamine through an opening on the material introduction side of the grinding device.

14. The CaO / SiO ２ 5. The method for producing hydraulic cement according to claim 4, wherein the slag (I) having a mass ratio of less than 3.0 contains, as a main raw material, at least one selected from the group consisting of electric furnace oxidizing slag and electric furnace reducing slag produced in an electric furnace steelmaking process, and the method comprises carrying out at least one treatment selected from the following (i), (ii), and (iv) to adjust the CaO content in the resulting hydraulic cement to a range that satisfies the formulas (1) and (2): (i) a mixing treatment in which the types and mixing ratio of the slag (I) and the slag (II) are adjusted and mixed, (ii) a mixing treatment in which the types and mixing ratio of the slag (I) and the slag (II) are adjusted and the type and amount of a component adjuster as an auxiliary raw material is selected and mixed, and (iv) a mixing treatment in which the composition of the clinker obtained in step B is analyzed and multiple types of clinker are mixed.

15. The CaO / SiO ２ The slag (I) having a mass ratio of less than 3.0 contains at least one selected from the group consisting of blast furnace slag, electric furnace oxidizing slag, and electric furnace reducing slag as a main raw material, and the CaO / SiO ２ 3. The method for producing hydraulic cement according to claim 1 or 2, wherein the slag (II) having a mass ratio of 3.0 or more contains, as a main raw material, converter slag produced in a steelmaking process by a blast furnace method.

16. The CaO / SiO ２ The slag (I) having a mass ratio of less than 3.0 contains at least one selected from the group consisting of blast furnace slag, electric furnace oxidizing slag, and electric furnace reducing slag as a main raw material, and the CaO / SiO ２ The method for producing hydraulic cement according to claim 5, wherein the slag (II) having a mass ratio of 3.0 or more contains, as a main raw material, converter slag produced in a steelmaking process by a blast furnace method, and the step (A-3) includes at least one treatment selected from the following (i), (ii), and (iii): (i) a mixing treatment in which the types and mixing ratio of the slag (I) and the slag (II) are adjusted and mixed, (ii) a mixing treatment in which the types and mixing ratio of the slag (I) and the slag (II) are adjusted and the type and amount of a component adjuster as an auxiliary raw material is selected and mixed, and (iii) a weight reduction treatment in which the slag (I) is reduced.

17. The CaO / SiO ２ The slag (I) having a mass ratio of less than 3.0 contains, as a main raw material, at least one selected from the group consisting of electric furnace oxidizing slag and electric furnace reducing slag produced in an electric furnace steelmaking process, and the CaO / SiO ２ The method for producing hydraulic cement according to claim 4, wherein the slag (II) having a mass ratio of 3.0 or more contains, as a main raw material, converter slag produced in a steelmaking process by a blast furnace method, and the method comprises carrying out at least one treatment selected from the following (i), (ii), and (iv) to adjust the CaO content in the obtained hydraulic cement to a range that satisfies the above formulas (1) and (2): (i) a mixing treatment in which the types and mixing ratio of the slag (I) and the slag (II) are adjusted and mixed, (ii) a mixing treatment in which the types and mixing ratio of the slag (I) and the slag (II) are adjusted and the type and amount of a component adjuster as an auxiliary raw material is selected and mixed, and (iv) a mixing treatment in which the composition of the clinker obtained in the above step B is analyzed and multiple types of clinker are mixed.

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