WO2024090580A1

WO2024090580A1 - Method for producing hydraulic cement composition using blast furnace slag and converter furnace slag

Info

Publication number: WO2024090580A1
Application number: PCT/JP2023/038999
Authority: WO
Inventors: 敏男米澤; 光男木之下
Original assignee: グローバル・マテリアルリサーチ株式会社
Priority date: 2022-10-28
Filing date: 2023-10-27
Publication date: 2024-05-02

Abstract

A method for producing a hydraulic cement composition, the method comprising: a step (A) for mixing a blast furnace slag generated in a pig iron production step in a blast furnace process and a converter furnace slag generated in a steel making step, in a state where at least one of the blast furnace slag and the converter furnace slag is molten, to obtain a molten mixture; a step (B) for rapidly quenching and solidifying the molten mixture obtained in the step (A) to produce a clinker; and a step (C) for adding, to the clinker obtained in the step (B), gypsum and pulverizing the same.

Description

Method for producing hydraulic cement composition using blast furnace slag and converter slag

This disclosure relates to a method for producing a hydraulic cement composition using blast furnace slag produced in the pig iron production process using the blast furnace method and converter slag produced in the steelmaking process as raw materials.

Japan's crude steel production volume was 83 million tons in 2020, of which 62 million tons were produced by the blast furnace method. If the carbon dioxide (hereinafter also referred to as _CO2 ) emissions associated with the production of 1 ton of crude steel by the blast furnace method are 2.0 tons, the _CO2 emitted by the production of 62 million tons of crude steel will be 124 million tons. This is equivalent to 10% of the country's total _CO2 emissions, which are approximately 1.2 billion tons. At the same time, 20 million tons of blast furnace slag and 9.5 million tons of converter slag were generated as by-products of crude steel production by the blast furnace method in 2020. In response to these loads, there are various movements, such as the conversion from the blast furnace method to the electric furnace method and the development of steelmaking methods that generate less _CO2 . There are also various efforts to utilize blast furnace slag and converter slag.

Blast furnace slag is used almost 100% as a cement raw material, cement admixture, road material, etc. However, the added value of none of these is sufficiently high, and there is a demand for technology to utilize it in ways that provide even greater value. There have been attempts to use converter slag in a variety of ways, such as as a road material, civil engineering material, fertilizer, and seaweed bed formation material, but compared to blast furnace slag, there has been limited development into established uses. There is a demand for technology to utilize both blast furnace slag and converter slag in ways that provide even greater added value than at present.

Meanwhile, Japan's cement production volume in 2020 was 56 million tons, and assuming that _CO2 emissions per ton of cement are 0.75 tons, this means that 42 million tons of _CO2 were emitted. This is equivalent to approximately 3.5% of the country's total _CO2 emissions and approximately one-third of the emissions from steel production, which is a considerable amount of _CO2 . For this reason, various efforts are being made to reduce _CO2 emissions from cement manufacturing.

Regarding the reduction _{of CO2} during cement production, there remains an unused technology for utilizing blast furnace slag and converter slag. Since both blast furnace slag and converter slag are produced in a molten state, if a cement composition can be produced from the molten state, the energy required for the current cement production, which is produced by heating raw materials to 1450°C using a rotary kiln, will be almost unnecessary. In addition, since both blast furnace slag and converter slag are already decarbonated materials, there is a possibility that _CO2 emissions from the raw materials will be almost zero. In other words, there is a possibility of an environmentally friendly cement that generates almost no _CO2 from energy and almost no _CO2 from the raw materials. The present invention was made based on the prospect of this possibility, and aims to provide a technology that improves the added value of blast furnace slag and converter slag, which are by-products produced in large quantities from steel production, and significantly reduces _CO2 emissions from cement production.

As technologies related to the present invention, for example, there are a method for producing hydraulic cement using solidified blast furnace slag and converter slag as raw materials, utilizing the effect of iron oxide contained in converter slag to reduce the calcination energy required for cement production using a conventional rotary kiln (see JP 50-10314 A), a method for producing a hydraulic cement composition by adding a component adjuster containing at least SiO ₂ and CaO to molten reduced slag produced in the reduction and casting process of the electric furnace steelmaking process, rapidly cooling and solidifying the molten reduced slag to produce clinker, and then adding gypsum and pulverizing the mixture (see JP 3240053 A), and a method for producing a hydraulic cement composition by adding a component adjuster consisting of CaO or SiO ₂ to molten blast furnace slag, and producing a CaO/SiO ₂ The following techniques have been disclosed: a method in which blast furnace slag and converter slag, at least one of which is in a molten state, are mixed in a ratio of 95 to 70/5 to 30 mass %, quenched with water, and then pulverized to produce a fine powder having latent hydraulic properties (see JP-A-6-115998); a method in which molten blast furnace slag and converter slag, at least one of which is in a molten state, are mixed in a ratio of 95 to 70/5 to 30 mass %, quenched with water, and pulverized to produce a fine powder having latent hydraulic properties (see JP-A-8-337448); a method in which solidified granular or powdered converter slag is mixed with molten blast furnace slag, melted, slowly cooled, solidified, crushed and pulverized to produce concrete aggregate or roadbed material; or, conversely, a method in which solidified granular or powdered blast furnace slag is mixed with molten converter slag and melted, and then similarly treated to produce concrete aggregate or roadbed material (see JP-A-10-279331).

However, although the method described in JP 50-10314 A shows that a hydraulic cement composition can be obtained from blast furnace slag and converter slag, it is a method of producing the composition by heating solidified slag to 1,300-1,450°C using a conventional rotary kiln, and does not result in a reduction in the amount of energy required for firing.

The method described in Japanese Patent No. 3240053 is a technology that uses molten reduced slag produced in an electric furnace steelmaking process, and since the slags to be used are different, the composition of the mixture is different from that of a mixture of molten blast furnace slag and molten converter slag. Furthermore, although the method uses _SiO2 and CaO simultaneously as composition adjusters, the idea of simultaneously using _SiO2 , an acidic material, and CaO, a basic material, is not clear, and it is difficult to recognize the rationality of the method. Furthermore, since the temperature of the slag is lowered by adding the composition adjuster to the molten slag, a process of uniformly mixing the slag and the composition adjuster is required, making the manufacturing method complicated.

The method described in JP-A-6-115998 is a method of adding a component adjuster made of CaO or _SiO2 to molten blast furnace slag, followed by quenching and pulverization to produce a fine powder with latent hydraulic properties. In other words, this material does not have hydraulic properties by itself, but when mixed with Portland cement, it develops hydraulic properties, and no hydraulic material is obtained. The fact that the material obtained by the above method does not have hydraulic properties by itself can be understood from the fact that the CaO/ _SiO2 (molar ratio) is 0.8 to 1.5, which is in the same range as the raw material ground granulated blast furnace slag.

The method described in JP 8-337448 A involves mixing at least one of blast furnace slag and converter slag in a molten state in a mass ratio of 90-70/5-30, rapidly solidifying with water, and pulverizing to produce a fine powder with latent hydraulic properties. However, the material obtained is a material with latent hydraulic properties that does not have hydraulic properties by itself. The fact that the material obtained by this technology is a material with latent hydraulic properties can also be seen from the fact that the mixture ratio of blast furnace slag and converter slag is 95-70/5-30 by mass, which means that the material is in the acidic range closer to blast furnace slag.

The method described in JP 10-279331 A is a technique in which molten blast furnace slag is mixed with solidified granular or powdered converter slag, melted, slowly cooled to solidify, and then crushed and pulverized to produce concrete aggregate or roadbed material. Conversely, this technique also includes a method in which molten converter slag is mixed with solidified granular or powdered blast furnace slag, melted, and similarly processed to produce concrete aggregate or roadbed material. Therefore, although this method is appreciated for utilizing molten blast furnace slag or converter slag, it is difficult to produce a cement composition with hydraulic properties.

As described above, all of the conventional methods use molten blast furnace slag and molten converter slag as raw materials, but there is a problem that they are not sufficiently effective in reducing _CO2 emitted from energy during production and _CO2 emitted from the raw materials due to decarbonation.

An object of one embodiment of the present disclosure is to provide a method for producing a hydraulic cement composition using blast furnace slag and converter furnace slag as raw materials, in which CO ₂ emitted from the energy required during production and CO ₂ emitted from the raw materials are reduced.

Means for solving the above problems include the following embodiments.

<1> [First embodiment of the present disclosure]
A method for producing a hydraulic cement composition, comprising: a step (A) of mixing blast furnace slag produced in a pig iron production process using a blast furnace method with converter slag produced in a steelmaking process, with at least one of the blast furnace slag and the converter slag in a molten state, to obtain a molten mixture; a step (B) of rapidly cooling and solidifying the molten mixture obtained in step (A) to produce clinker; and a step (C) of adding gypsum to the clinker obtained in step (B) and pulverizing the clinker.
<2> [Second embodiment]
The method for producing a hydraulic cement composition according to <1>, wherein in the step (A), the blast furnace slag and the converter furnace slag are both in a molten state.
<3> [3-1st embodiment]
The method for producing a hydraulic cement composition according to <1> or <2>, wherein the step (B) further includes a step (B-1) of slowly cooling and granulating the molten mixture obtained in the step (A) to obtain a granulated product, and a step of rapidly cooling and solidifying the granulated product obtained in the step (B-1) to produce a clinker.
<4> [Third-2nd embodiment]
The method for producing a hydraulic cement composition according to <1> or <2>, wherein the step (B) is a step (B-2) of blowing an air jet in a flowing state onto the molten mixture obtained in the step (A) to granulate the molten mixture and rapidly cooling and solidifying it.

<5> [Fourth embodiment]
The method for producing a hydraulic cement composition according to any one of <1> to <4>, further comprising a step (D) of adding a component adjuster to the molten mixture obtained in the step (A).
<6> [Fifth embodiment]
The method for producing a hydraulic cement composition according to <5>, wherein the component adjuster is a component adjuster consisting of only CaO, a component adjuster containing two components, CaO and Al ₂ O ₃ , or a component adjuster containing two components, CaO and SiO ₂ .
<7> [Sixth embodiment]
_The method for producing a hydraulic cement composition according to any one of <1> to <4>, wherein the CaO content in the molten mixture of the blast furnace slag and the converter slag is equal to or greater than the value calculated by formula ( ₁ ) and equal to or less than the value calculated by formula (2) when the total amount of CaO, Al ₂ O ₃ , and SiO 2 contained in the mixture is taken as 100% by mass, and the Al ₂ O 3 content in the mixture is 1.0% by mass or more and 15% by mass or less when the total amount of CaO, Al ₂ O ₃ , and SiO ₂ contained in the mixture is taken as 100% by mass.

<8> [Seventh embodiment]
The method for producing a hydraulic cement composition according to _<5> , wherein the CaO content in the mixture obtained by further adding the component adjuster to the molten mixture of the blast furnace slag and the converter _slag is equal to or greater than the value calculated by formula (1) and equal to or less than the value calculated by formula (2) when the total amount of CaO, Al ₂ O 3, and SiO ₂ contained in the mixture is taken as 100 mass%, and the Al 2 O ₃ content in the mixture is 1.0 mass% or more and 15 mass% or less when the total amount of CaO, Al ₂ O ₃ , and SiO ₂ contained in the mixture is taken as 100 mass%.

<9> [Eighth embodiment]
The method for producing a hydraulic cement composition according to any one of <1> to <8>, further comprising a step (E) of feeding the mixture of molten blast furnace slag and molten converter slag into a melting furnace having a mixing mechanism and a heating mechanism, maintaining the mixture at a temperature at which the molten state is maintained, and then quenching the mixture.
<10> [Ninth embodiment]
The method for producing a hydraulic cement composition according to <8>, wherein the mixture of the molten blast furnace slag and the molten converter slag further contains the component adjuster.
<11> [Tenth embodiment]
The method for producing a hydraulic cement composition according to any one of <1> to _<10> , wherein the content of iron oxide in the obtained hydraulic cement composition is 1.5 mass% or more and 10 mass% or less in terms of _Fe2O3 .

<12> [Eleventh embodiment]
The method for producing a hydraulic cement composition according to <11>, wherein the converter furnace slag in the step (A) is in a molten state and is converter furnace slag that has been subjected to a treatment to reduce the amount of iron oxide by a treatment to reduce the iron oxide using a nonmetallic reducing material.
<13> [Twelfth embodiment]
The method for producing a hydraulic cement composition according to <12>, wherein the nonmetallic reducing material used in the reduction treatment of the iron oxide is at least one selected from the group consisting of carbon, carbon monoxide, hydrogen, ammonia and methane.
<14> [Thirteenth embodiment]
<1> to <13>, wherein in the step (C), before or after the grinding of the clinker, at least one selected from the group consisting of ground granulated blast furnace slag, fly ash, and Portland cement is further added. The method for producing a hydraulic cement composition according to any one of <1> to <13>.

According to one embodiment of the present disclosure, there is provided a method for producing a hydraulic cement composition using blast furnace slag and converter furnace slag as raw materials, in which CO ₂ emitted from the energy required during production and CO ₂ emitted from the raw materials are reduced.

FIG. 1 is a CaO—SiO ₂ —Al ₂ O ₃ ternary phase diagram illustrating the resulting compositional ranges of hydraulic cement compositions obtained by the manufacturing methods of the present disclosure. FIG. 2 is a diagram showing the positions of the compositions of Examples 1 to 7 and Comparative Examples 1 to 6 in a CaO—SiO ₂ —Al ₂ O ₃ ternary phase diagram, based on the composition range of the hydraulic cement composition obtained by the manufacturing method of the present disclosure. FIG. 3 is a diagram showing one embodiment of a flow chart of a method for producing a hydraulic cement composition of the present disclosure.

In the present disclosure, a numerical range expressed using "to" means a range that includes the numerical values before and after "to" as the lower and upper limits.
In the numerical ranges described in the present disclosure in stages, 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. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value of the numerical range may be replaced with a value shown in the examples.
In the drawings of the present disclosure, components indicated by the same reference numerals are meant to be the same components. The sizes in the drawings do not necessarily represent the actual sizes, and may be enlarged or reduced as necessary.

The manufacturing method of the hydraulic cement composition disclosed herein (hereinafter also simply referred to as the manufacturing method disclosed herein) will be described in detail below.

As a means for solving the above problems of the present disclosure, materials that constitute a hydraulic cement composition by using molten blast furnace slag, molten converter slag, and adding a component adjuster as necessary can be used. Here, the composition and amount of materials that impart hydraulic properties to the composition have been examined, and preferred solutions include the first to seventh embodiments of the present disclosure.

As a means for solving the above problems, an apparatus for producing a hydraulic cement composition was studied. That is, in order to add blast furnace slag and converter slag, at least one of which is in a molten state (step (A)), and add a component adjuster as necessary (step (D)), it is necessary to suppress the temperature drop caused by mixing and adding the additives, form a uniform molten material, and maintain it at a predetermined temperature, and the eighth embodiment is one such means for achieving this.
The apparatus applied to the manufacturing method of the present disclosure will be described in detail in the Examples.

As a means for solving the above problem, with regard to the iron oxide contained in the converter slag, the content of the iron oxide can be optimized.
Iron oxide has an effective effect on cement production, such as aiding in the generation of molten liquid components, but it has been found that if the amount of iron oxide is too large, the hardened cement body obtained from the hydraulic cement composition turns black, and the appearance of the structure deteriorates. Although there is no problem with the performance of the hardened body itself, in order to give the hardened body a better appearance, it is preferable to use, as a preferred embodiment, converter slag with a controlled iron oxide content, instead of converter slag with a high iron oxide content (see the tenth to twelfth embodiments).

As a more preferred embodiment of the solution to the above problem, the hydraulic cement composition obtained by the manufacturing method disclosed herein was investigated as a mixed cement. In order to more suitably use the hydraulic cement composition obtained by the manufacturing method disclosed herein as a general-purpose cement, it is necessary that it can be applied to various infrastructure structures and buildings. A thirteenth embodiment is a preferred embodiment for using the hydraulic cement composition obtained by the manufacturing method disclosed herein as a mixed cement.

[Manufacturing method of the present disclosure]
The first embodiment of the present disclosure includes a step (A) of mixing blast furnace slag produced in a pig iron production process using a blast furnace method with converter slag produced in a steelmaking process, with at least one of the blast furnace slag and the blast furnace slag being in a molten state, to obtain a molten mixture; a step (B) of rapidly cooling and solidifying the molten mixture obtained in step (A) to produce clinker; and a step (C) of adding gypsum to the clinker obtained in step (B) and pulverizing it.
Here, it is preferable from the viewpoint of uniform mixing that the blast furnace slag and the converter furnace slag used in step (A) are both in a molten state.

First, the materials and amounts constituting the hydraulic cement composition obtained by the manufacturing method of the present disclosure will be considered.
Fig. 1 is a CaO- _SiO2 - _Al2O3 _ternary phase diagram showing the composition range of hydraulic cement compositions obtained by the manufacturing method of the present disclosure, in which the positions of the raw materials blast furnace slag and converter slag, the position of a mixture of blast furnace slag and converter slag, and the position of ordinary Portland cement (OPC) are shown.
Table 1 below shows examples of the chemical compositions of blast furnace slag, converter slag, and commonly used ordinary cement.

Based on the chemical compositions shown in Table 1 above, the positions of the compositions of blast furnace slag, converter slag, a mixture of blast furnace slag and converter slag, and ordinary Portland cement (OPC) in the ternary phase diagram of the three components CaO, SiO ₂ , and Al ₂ O ₃ of blast furnace slag, converter slag, and ordinary cement are shown in FIG. 1.
FIG. 1 also shows the positions in a ternary phase diagram of the compositions of mixtures in which the blast furnace slag and converter furnace slag in Table 1 are mixed in mass ratios of 70/30, 50/50, 15/85, and 2/98.

As can be seen from Figure 1, blast furnace slag is a material that is on the acidic side compared to ordinary cement, and converter slag is a material that is on the basic side. When the two are mixed, with a mixing ratio of blast furnace slag/converter slag = 15/85, the composition of this mixture is close to that of ordinary cement on the ternary phase diagram.
When a mixture of the two materials in the above-mentioned mixing ratio is used, a molten mixture is formed under temperature conditions of 1400°C to 1700°C (step (A)), this mixture is rapidly cooled and solidified to obtain clinker (step (B)), and the clinker is further mixed with gypsum and pulverized (step (C)), thereby obtaining a hydraulic cement composition.
The above mixture ratio is one example, and by mixing blast furnace slag and converter slag in various ratios depending on the purpose, it is possible to adjust the components and obtain hydraulic cement compositions of various compositions.
In addition, a molten mixture can be obtained by having at least one of the blast furnace slag and the converter slag in a molten state. From the viewpoint of obtaining a uniform mixture, it is preferable that both the blast furnace slag and the converter slag are in a molten state.

At present, when considering a balance between the usage amounts of blast furnace slag, which is generated annually at approximately 20 million tons, and converter furnace slag, which is generated at 9.5 million tons, a ratio of 70/30 is used, which approaches the range of blast furnace slag, which is vitreous and has latent hydraulic properties; however, as described in the fourth to sixth embodiments, by adding an appropriate amount of a component adjuster containing at least CaO (step (D)), the obtained composition can be shifted to the basic side, and a hydraulic cement composition that exhibits good hydraulic properties can be obtained.
That is, the production method of the present disclosure may further include a step (D) of adding a composition adjuster to the molten mixture obtained in the step (A).
As described above, one of the advantages of the present disclosure is that a hydraulic cement composition having good hydraulic properties can be obtained not only by adjusting the mixing ratio of blast furnace slag and converter furnace slag but also by using, for example, a component adjuster.

The fourth to sixth embodiments of the present disclosure, that is, the step (D) of adding a component adjuster, will be described in detail.
The component regulator is preferably a component regulator containing only CaO, a component regulator containing two components, _CaO and _Al2O3 , or a component regulator containing two components, CaO and _SiO2 .

In the case where the molten mixture of blast furnace slag and converter slag obtained in step (A) is a mixture located on the acidic side, the mixture can be brought into the hydraulic region by adding a component adjuster consisting of only CaO as a component adjuster.
When a component adjuster consisting of two components, CaO and Al ₂ O _3, is added to the mixture, a hydraulic cement composition with a high content of Al ₂ O ₃ can be obtained.
Furthermore, by adding CaO to the mixture in excess of the amount necessary for the resulting hydraulic cement composition to become hydraulic, thereby shifting the composition to a basic state, and then adding _SiO2 to return the composition to the hydraulic region, a hydraulic cement composition with _less _Al2O3 can be obtained.
As described above, the component regulator is preferably one consisting of only CaO, or one consisting of two components, _CaO and _Al2O3 , or one consisting of two components, CaO and _SiO2 , and the chemical composition of the hydraulic cement composition can be controlled by selecting and using these. By selecting a component regulator in the step (D) of adding the component regulator, it becomes possible to change the properties of the hydraulic cement composition obtained by the manufacturing method of the present disclosure, to bring the composition closer to a target composition, and the like, and it also becomes easier to control the quality of the hydraulic cement composition.

Next, the specific composition range of the hydraulic cement composition will be described.
In the conventional production of Portland cement by burning in a rotary kiln, a number of conditions must be satisfied, such as the formation of a molten liquid, the production of _C3S ( _3CaO.SiO2 ) and _C2S ( _2CaO.SiO2 ), the prevention of the formation of a coating inside the kiln due to excess molten liquid, and the formation of clinker pellets. Therefore, the composition range in which Portland cement can be produced is very close to the composition range of ordinary cement (OPC), the example of which is shown in Table 1 above.
In contrast, the present inventors have found that, according to the manufacturing method of the present disclosure, a hydraulic cement composition is produced by forming a homogeneous molten mixture by adding blast furnace slag, converter slag, and an optional component adjuster, and then carrying out a quenching step (step (B)). This hydraulic cement composition has a wider composition range than Portland cement and has good hydraulic properties, allowing for better formulation flexibility.

Next, specific preferred composition ranges for the mixture of blast furnace slag and converter slag (first to third embodiments) and the mixture obtained by adding an optional component adjuster (sixth and seventh embodiments) will be described.
It is preferable that the CaO content (%) in the mixture of blast furnace slag and converter furnace slag (fourth embodiment) or the CaO content (%) in the mixture of blast furnace slag, converter furnace slag, and a component adjuster be such that it satisfies the conditions shown below.

It is preferable that the CaO content in the mixture is equal to or greater than the value calculated by formula (1) and equal to or less than the value calculated by formula ( ₂ ) when the total amount of CaO, Al ₂ O ₃ , and SiO 2 contained in the mixture is 100 mass%, and that the Al ₂ O ₃ content in the mixture is equal to or greater than 1.0 mass% and equal to or less than 15 mass%, when the total amount of CaO, Al ₂ O ₃ , and SiO ₂ contained in the mixture is 100 mass%.

When the total amount of CaO, Al ₂ O ₃ , and SiO ₂ in the mixture is taken as 100 mass%, the amount is equal to or greater than the value calculated by the above formula (1) and equal to or less than the value calculated by formula (2), and at the same time, the amount of Al ₂ O ₃ in the 100% ranges from 1.0 mass% to 15 mass%, so that a hydraulic cement composition with better hydraulic properties can be produced.

When the amount of CaO and the amount of _SiO2 in the hydraulic cement composition are within the above composition range, the composition changes from a blast furnace slag having glass properties to a cement, and more stable hydraulic properties can be obtained.
Furthermore, when the amount of CaO is more and the amount of _SiO2 is less than the composition range specified in the preceding paragraph, the amount of CaO becomes excessive, making it difficult to obtain stable hydraulic properties.
When the Al ₂ O ₃ content is 1.0 mass% or more, the molten liquid components are sufficiently obtained, and it becomes easier to obtain a hydraulic cement composition. When the Al ₂ O ₃ content is 15 mass% or less, the strength of the obtained hardened material is sufficiently exhibited.

There are no particular limitations on the manufacturing apparatus used in the manufacturing method of the present disclosure, but the hydraulic cement composition obtained by the manufacturing method of the present disclosure is manufactured by quenching a molten mixture of blast furnace slag and converter slag, which further contains a component adjuster. In other words, this manufacturing method may be called a melt quenching method.
Therefore, it is preferable that the production equipment is capable of producing a uniform molten material and is capable of maintaining the melting temperature even when a composition adjuster is added.
In the manufacturing method disclosed herein, it is preferable to further include a step (E) of feeding the molten mixture of blast furnace slag and converter slag into a melting furnace having a mixing mechanism and a heating mechanism, maintaining the mixture at a temperature at which the molten state is maintained, and then rapidly cooling the mixture. The molten mixture of blast furnace slag and converter slag may further include the component adjuster.
That is, as an apparatus to be used in the manufacturing method of the present disclosure, an apparatus having a stirring mechanism and a heating mechanism as described in the eighth embodiment is suitable, and in particular, an apparatus in which the mixture is fed into a melting furnace to maintain the molten state is preferred.
As long as the device has the above-mentioned mechanism, there is no particular limitation, but a melting furnace equipped with a horizontal electrode and a stirring mechanism can be used.
The stirring mechanism may be either a mechanical type or a gas injection type. Furthermore, a melting furnace may be used in which the molten slag and the composition adjuster are continuously fed into the rotary kiln for continuous production.

The temperature for forming the molten mixture is preferably set in the range of 1400°C to 1700°C, more preferably in the range of 1450°C to 1600°C, taking into consideration the discharge temperature and composition of the molten slag.
After forming the homogeneous molten mixture, the process of quenching the melt (step (B)) is important in the manufacturing method of the present disclosure.
It is also effective to recover the waste heat generated by the rapid cooling of the high-temperature molten material and use it to preheat the composition adjuster.

It is preferable that step (B) further includes step (B-1) of slowly cooling and granulating the molten mixture obtained in step (A) to obtain granules, and that the granules obtained in step (B-1) are rapidly cooled and solidified to produce clinker.
In addition, step (B) may be an embodiment in which an air jet is blown in a flowing manner onto the molten mixture obtained in step (A), the molten mixture is granulated, and the molten mixture is rapidly cooled and solidified (B-2).

Both the method of immediately quenching the molten mixture and the method of first slowly cooling the molten mixture to obtain granules and then quenching the obtained granules are suitable, but since the inherent crystal structure, etc. differs depending on the cooling temperature conditions, the process should be selected according to the desired physical properties of the resulting hydraulic cement composition.

In this disclosure, "quenching" refers to a method of cooling a molten mixture containing high-temperature slag using a medium. The cooling medium typically used is water, oil, air, etc. By using a medium for cooling, the mixture is rapidly cooled from the point of contact with the medium.

On the other hand, "slow cooling" refers to a method of cooling slowly without contact with a medium, such as by leaving it outdoors, indoors, or in a furnace.

Next, the problem of iron oxide contained in converter slag will be described. Converter slag contains _about 20% by mass to 25% by mass of iron oxide calculated as _Fe2O3 .
In the manufacturing method of the present disclosure, since converter furnace slag is included as a raw material, the physical properties of the hardened product of the obtained hydraulic cement composition are not affected, but the hardened product of the cement composition may be black in color.
For this reason, in order to impart an appearance suitable for use in various structures, the iron oxide content in the obtained hydraulic cement composition is preferably 1.5% by mass or more and 10% by mass or less, calculated as Fe ₂ O ₃ .
In order to achieve the above-mentioned iron oxide content, for example, a method of adjusting the mixing ratio of converter furnace slag in a mixture of blast furnace slag and converter furnace slag can be mentioned.
As another method, there can be mentioned a method in which the content of iron oxide in the hydraulic cement composition is controlled within the above range by separating or reducing the amount of iron oxide through reduction treatment of the converter slag.
Specifically, in this embodiment, the converter furnace slag in step (A) is in a molten state, and the converter furnace slag is used after a treatment to reduce the amount of iron oxide by a reduction treatment of the iron oxide using a non-metallic reducing material.
The latter reduction treatment for controlling _the _Fe2O3 content allows easy adjustment even when the amount of iron oxide contained in the converter slag varies, and can suppress blackening of the hardened product. The content of iron oxide in the hydraulic cement composition is preferably 10 mass% or less, and more preferably ₈ mass% or less, calculated as _Fe2O3 . By achieving this condition, a hardened product can be obtained at a level where the effect of blackening is unlikely to be a problem.
Although there is no particular lower limit for the iron oxide content, it is desirable to set the iron oxide content to 1.5 mass% or more, since this makes it easier for the molten slag to form a molten liquid and facilitates the process of rapidly cooling the molten mixture to obtain clinker.

The non-metallic reducing material used in the reduction treatment of the iron oxide is preferably at least one selected from the group consisting of carbon, carbon monoxide, hydrogen, ammonia and methane.
The nonmetallic reducing material may be used alone or in combination with two or more kinds. The principle of the reduction treatment of iron oxide using carbon is the same as that of the conventional blast furnace method. The reduction treatments using carbon monoxide, hydrogen, ammonia, and methane are also based on the same principle as carbon.

A method using a metal reducing agent such as Al is known as a reduction treatment method for reducing converter slag to reduce the amount of iron oxide. However, although the iron oxide is reduced and the Fe can be separated by metal reduction, this method is not desirable because it leaves behind metal oxide.

When the hydraulic cement composition obtained by the manufacturing method of the present disclosure is used as a mixed cement, in step (C), a method can be adopted in which at least one selected from the group consisting of ground granulated blast furnace slag, fly ash, and Portland cement is further added before or after crushing the clinker.
By mixing the hydraulic cement composition obtained by the manufacturing method of the present disclosure with ground granulated blast furnace slag and fly ash, it is possible to produce concrete that generates less _CO2 and has excellent heat generation properties, fluidity, strength properties and durability.
In order to reduce _CO2 emissions from Portland cement, the use of blended cement using ground granulated blast furnace slag is becoming more widespread. However, even in this case, a considerable amount of _CO2 is generated due to the use of Portland cement.
In contrast, in a mixed cement using the hydraulic cement composition obtained by the manufacturing method of the present disclosure, almost no _CO2 is generated from the cement itself, so that the mixed cement can also utilize the effects of blast furnace slag and fly ash without generating almost no _CO2 .
When using blast furnace slag as an admixture, the addition rate of blast furnace slag should be 30% to 60% by mass, the same as that of conventional blast furnace cement Type B, to obtain the benefits of the durability and thermal properties of blast furnace slag.
Also, in the case of fly ash, by using 10% by mass to 20% by mass, which is the same as that of conventional type B cement, it is possible to obtain effects in terms of thermal properties and fluidity.
Additionally, it can be mixed with conventional Portland cement to reduce the iron oxide content.

Next, a description will be given with reference to a drawing showing one embodiment of the manufacturing method of the hydraulic cement composition of the present disclosure. FIG. 3 shows one embodiment of the manufacturing method of the hydraulic cement composition. In FIG. 3, 1 shows an example of an iron oxide reduction and weight reduction device (hereinafter also referred to as reduction treatment device 1) for reducing iron oxide from converter slag to separate and reduce the weight. 2 is a schematic diagram showing an example of a heating melting and mixing furnace having a heating mechanism for mixing molten blast furnace slag and molten converter slag, and adding a component adjuster as necessary, to form a uniform molten material at a predetermined temperature. 3a, 3b, and 3c show devices for stocking, measuring, and adding three types of component adjusters (CaO, Al ₂ O ₃ , SiO ₂ ) to the melting furnace. The devices including 3a, 3b, and 3c are collectively referred to as a component adjuster measuring, supplying, and preheating device 3. 4 shows a device for rapidly cooling the molten material produced in the melting and mixing furnace 2 to produce granular clinker (hereinafter also referred to as clinker production device 4). Reference numeral 5 denotes a grinding device (hereinafter also referred to as a mixing and grinding device 5) for adding gypsum to particulate clinker and grinding the mixture to obtain a hydraulic cement composition.

The above manufacturing apparatus will be further described. In FIG. 3, the reduction treatment apparatus 1 is an apparatus for performing reduction treatment for separating iron oxide, and is a reduction treatment apparatus using a nonmetallic reducing material that does not generate residual oxides in the slag. The melting and mixing furnace 2 is a heating, melting and mixing furnace for mixing molten blast furnace slag, molten converter slag, and optionally adding a composition adjuster to form a uniform molten material at a predetermined temperature. 3a, 3b, and 3c represent silos for measuring and adding the composition adjusters CaO, Al ₂ O ₃ , and SiO ₂ , and an apparatus including these silos is called the measuring, supply, and preheating apparatus 3. The clinker manufacturing apparatus 4 is an apparatus for granulating the molten mixture formed in the melting and mixing furnace 2 by slowly cooling it, and then rapidly solidifying the granulated material by spraying air, thereby manufacturing granular clinker. The waste heat generated during rapid cooling is recovered and supplied to the

composition adjuster silos

3a, 3b, and 3c, and used to preheat the composition adjuster.
In step (B), the molten mixture formed in the melting and mixing furnace may be allowed to flow down, and then granulated by blowing air jets thereon, and the molten mixture may be rapidly cooled and solidified to produce clinker.
The mixing and grinding device 5 is a grinding device for adding and mixing the particulate clinker produced in 4 (i.e., step (B)) and gypsum, and grinding and mixing them to produce a hydraulic cement composition. A ball mill type device is suitable for the mixing and grinding device 5.

According to the manufacturing method of the present disclosure, the manufacturing method of hydraulic cement composition using blast furnace slag and converter slag is carried out by mixing blast furnace slag produced in the pig iron manufacturing process and converter slag produced in the steelmaking process to use as raw materials, or adding a component adjuster to the blast furnace slag to use as raw materials. Therefore, at least one of the original raw materials is at a high temperature that allows cement production, and heat energy to heat to about 1450°C as in the conventional Portland cement production is almost unnecessary. In addition, while conventional Portland cement uses a large amount of limestone as a raw material and generates a large amount of _CO2 by decarbonation, in the manufacturing method of the present disclosure, the addition of limestone is limited to a component adjuster used as needed, and the _CO2 generated from the raw materials is also greatly reduced. In other words, it becomes possible to recycle converter slag, which has been used only in a limited way, and not only does the use of blast furnace slag become high-added-value, but it also becomes an environmentally friendly material that greatly contributes to reducing _CO2 from cement.

It was also found that the composition regulator used for the molten mixture of blast furnace slag and converter slag is preferably one consisting of only CaO, or one consisting of two components, CaO and _Al2O3 , or _one consisting of two components, CaO and _SiO2 .

According to conventional manufacturing methods, a cement composition is manufactured by determining the chemical composition of a mixture of blast furnace slag, converter slag, and an optional component adjuster. In contrast, according to the manufacturing method of the present disclosure, it is possible to determine _a region in the ternary phase diagram of CaO, _Al2O3 , and _SiO2 in which a general-purpose hydraulic cement composition can be obtained, and it is also possible to determine the amount of component adjuster to be added depending on the type of component adjuster.

In the manufacturing method disclosed herein, which uses two types of slag and preferably the above-mentioned component adjuster as raw materials, it has been found that it is preferable to mix these materials to form a uniform molten material and maintain it at a predetermined temperature. Therefore, the eighth embodiment provides a more preferable manufacturing method.

In order to use converter slag for various purposes as a raw material for hydraulic cement compositions, it is necessary to suppress the effects of the iron oxide contained in large amounts in this slag and avoid the problem of blackening of the hardened body. According to the tenth embodiment of the present disclosure, the mixed use of converter slag and blast furnace slag and the separation or reduction of the iron oxide in the converter slag by reduction treatment provide a solution to this problem. Furthermore, the eleventh and twelfth embodiments provide specific methods and materials for the reduction treatment.

Conventional Portland cement has been adapted to a variety of uses by using various admixtures, but according to the thirteenth embodiment of the present disclosure, it is possible to make the hydraulic cement composition obtained by the manufacturing method of the present disclosure into a mixed cement, which will enable a variety of applications.

The manufacturing method of the present disclosure will be explained 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.

<Examples 1 to 8, Comparative Examples 1 to 5>
In Examples 1 to 4 and Comparative Example 4, the compositions shown in Table 2 were prepared using five components, namely, CaO, SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ and MgO. In these five compositions, the amount of Fe ₂ O ₃ was 7.3%, the amount of MgO was 5.4%, and the composition ratios (%) of CaO, SiO ₂ and Al ₂ O ₃ when the amounts excluding these are taken as 100% are shown in Table 2.
The raw material for CaO was industrial limestone powder with a _CaCO3 content of 98.8%. For _SiO2 , industrial silica powder with a _SiO2 content of 98.7% was used, and for _Al2O3 , industrial alumina powder with _an _Al2O3 content of 98.5% was used. These powders were pulverized with a jet mill, _and the average particle size of _CaCO3 was ₁₀ μm, and the average particle sizes of _SiO2 and _Al2O3 were each 5 μm.
A reagent with a content of 96.0 mass% of _Fe2O3 and a reagent _{with a content of 96.0 mass% of MgO were used. The average particle size of Fe2O3} _was _0.2 μm and the average particle size of MgO was 1.7 μm, and they were used as they were.

In Examples 5 to 8 and Comparative Examples 1 to 3, a mixture of ground granulated blast furnace slag and powdered converter slag was used in the ratio shown in Table 2. The chemical compositions of the blast furnace slag and converter slag are shown in Table 1, and none of the slag contained gypsum.
The blast furnace slag had a fineness of 4000 cm ² /g, and the converter slag was crushed to an average particle size of 10 μm before use.
In Examples 5 to 7, CaO and _SiO2 shown in Table 2 were further added as component adjusters in the amounts shown in Table 2. The amounts of the component adjusters shown in Table 2 are shown as % of the total material.
The materials used for the component adjusters were the same as those in Examples 1 to 4.
Comparative Example 5 is a commercially available ordinary Portland cement, described as a control example.
In Table 2, when ground granulated blast furnace slag and powdered converter slag are used, their composition ratios (%) are shown. For Examples 1 to 4 and Comparative Example 5, which were prepared using a reagent, the composition ratio column is left blank.

Each of the above mixtures was processed into pellets having a diameter of 1 to 5 mm and heated to form a homogeneous melt (step (A)).
Thereafter, the mixture was quenched with water to obtain clinker (step (B)).
Gypsum was added to the obtained clinker and pulverized (step (C)), to obtain a hydraulic cement composition.

In the step (A), 2 kg of pellets obtained by processing each of the above mixtures into pellets having a diameter of 1 to 5 mm were placed in a graphite crucible and heated to 1600° C. in a high-temperature electric furnace in a nitrogen atmosphere, and then maintained at this temperature for 40 minutes to obtain a homogeneous melt.
Thereafter, the mixture was gradually cooled and held at 1000° C. for 30 minutes to obtain the mixture of step (A).

In step (B), the mixture obtained in step (A) was poured into a water-filled steel box, and rapidly cooled and solidified while spraying water thereon to obtain clinker.
In step (C), the solidified clinker was coarsely crushed with a jaw crusher, gypsum was added, and the mixture was crushed to a fineness of 3,400 ^cm2 /g with a ball mill to obtain a hydraulic cement composition. The amount of gypsum added was 4% as a standard, and 9% in Examples 2, 4, and 7 and Comparative Examples 1, 2, and 5.

The configurations of the examples and comparative examples are shown in Table 2.
The positions of the Examples and Comparative Examples in Table 2 in the ternary phase diagram are shown in FIG.
Examples 1 to 4 are compositions suitable for general-purpose hydraulic cement compositions, which are located at the four corners of the composition range defined in the sixth and seventh embodiments, and are entirely composed of industrial powders and reagents. Comparative Example 5 is also similarly composed of industrial powders and reagents.
In these five conditions, a 70:30 mixture of blast furnace _slag and converter slag shown in Table 1 is assumed, with _Fe2O3 = 7.3%, MgO = 5.4%, and the remainder being the _three components CaO, _SiO2 , and _Al2O3 .
In Table 2, the notation "-" indicates that the component is not included.

Examples 5 to 8 in Table 2 above are blast furnace slag and converter slag to which a component adjuster has been added, and are within the composition range of the components of Examples 1 to 4. Comparative Example 5 is ordinary Portland cement as a control example, and is within this composition range.
Example 8 is an example that is located within the composition range of the components of Examples 1 to 4, but the content of Fe ₂ O ₃ is higher than the preferred range.
Both Comparative Example 1 and Comparative Example 2 are outside the composition range of Examples 1 to 4, and are in the acidic region with a high _SiO2 content. Comparative Example 3 is also outside the composition range, and is in the basic region with a high _CaO content. Comparative Example 4 is also outside the composition range, and is in the region with a high _Al2O3 content.

For Examples 1 to 8 and Comparative Examples 1 to 5, the presence or absence of hydraulic properties, stability (JIS R5201), color tone of the hardened body surface, and compressive strength (JIS R5201) were evaluated. The results are shown in Table 3.
The hydraulic properties were evaluated as "A" when they showed hydraulic properties, and "B" when they did not show hydraulic properties.
The stability was rated as "A" when it was acceptable for practical use, and "B" when it was problematic for practical use.
Regarding the color tone of the hardened body, the Portland cement hardened body (grayish white), which was the control example, was rated as an extremely good "AA" level, the hardened body (grayish) that had no problem in appearance was rated as "A", and the hardened body (grayish black) that was too black in appearance and problematic in practical use was rated as "B".
In Table 3, for those evaluated as "no hydraulicity", no other evaluations are recorded. Also, for those evaluated as having poor stability, the evaluation results of color tone and compressive strength are not recorded.
In Table 3, "-" indicates that the evaluation was not performed.

In the evaluation results shown in Table 3, Comparative Example 5 is a normal ordinary Portland (i.e., a control example).
The hydraulic cement compositions obtained by the manufacturing methods of Examples 1 to 8 all showed evaluation results similar to those of Comparative Example 5, and were evaluated to have the same performance as general-purpose hydraulic cement compositions in terms of compressive strength, etc.
The hardened bodies obtained by the manufacturing methods of Examples 1 to 4 are located at the four corners of the composition range as described above, but these four conditions and three conditions within those composition ranges are evaluated as being equivalent to general-purpose hydraulic cement compositions. Therefore, it was confirmed that by setting each component within the above composition range, a hydraulic cement composition with good versatility can be manufactured.
Example 8 was evaluated as exhibiting performance usable as a hydraulic cement composition, but the Fe ₂ O ₃ content exceeded 10%, and the surface of the hardened body was gray-black. From the above evaluation results, it can be seen that by setting the Fe ₂ O ₃ content in the total mass to the range of 1.5% to 10%, not only the physical properties but also the appearance of the hardened body obtained by the manufacturing method of the present disclosure are improved.

Comparative Examples 1 and 2 are evaluated as having no hydraulic properties.
Comparative Example 3 is evaluated as having poor stability, although it has hydraulic properties, presumably due to the high CaO content.
Comparative Example 4 has no problems with hydraulic properties, stability, and color tone, but has low compressive strength and is therefore considered difficult to apply to general-purpose hydraulic cement compositions.

Next, the amount of _CO2 generated during the production of the compositions of Examples 1 to 8 and Comparative Examples 1 to 5 will be described.
The ordinary Portland cement of Comparative Example 5 generates about 0.75 tons of _CO2 per ton from raw materials and energy. In contrast, all examples except for Examples 5 to 7, which use CaO as a component adjuster, use molten slag as a raw material, so both the _CO2 from raw materials and the _CO2 from energy are evaluated to be almost zero.
When the amount of _CO2 generated in Examples 5 to 7 is calculated from the materials in terms of the _CO2 /CaO molecular weight ratio and from the production energy in terms of the value in Reference 1 (0.255 ton _CO2 /ton CaO), the value is reduced by 65% to 70% compared to ordinary Portland cement. If this is used as a mixed cement with 50% ground granulated blast furnace slag as described in the eighth embodiment of the present disclosure, the amount of _CO2 generated will be reduced by 80% to 85%.
In this way, by producing a hydraulic cement composition using the production method of the present disclosure, the amount of _CO2 generated during production is almost zero if no component adjuster is used, and even if one is used, it is reduced by 65% to 70% compared to conventional Portland cement. If a blended cement is used, the amount of _CO2 generated can be reduced by 80% or more.

[Reference 1] Lime Manufacturing Association: Global warming countermeasures in the lime manufacturing industry (Low Carbon Society Implementation Plan 2016 performance report), 2018

[Explanation of symbols]
1. Iron oxide reduction and weight reduction device (reduction treatment device)
2 Heating, melting and mixing furnace 3 Component adjustment material measurement, supply and preheating device 4 Quenching device (clinker production device)
5. Crushing equipment (mixing and crushing equipment)

The disclosure of Japanese Patent Application No. 2022-185276, filed on October 28, 2022, is incorporated by reference into this disclosure.
All publications, patent applications, and standards mentioned in this disclosure are incorporated by reference into this disclosure to the same extent as if each individual publication, patent application, or standard was specifically and individually indicated to be incorporated by reference.

Claims

A step (A) of mixing blast furnace slag produced in a blast furnace pig iron production process with converter slag produced in a steelmaking process, with at least one of the blast furnace slag and the converter slag being in a molten state, to obtain a molten mixture;
A step (B) of rapidly cooling and solidifying the molten mixture obtained in the step (A) to produce clinker;
Step (C) of adding gypsum to the clinker obtained in step (B) and pulverizing it;
A method for producing a hydraulic cement composition comprising the steps of:
The method for producing a hydraulic cement composition according to claim 1, wherein in step (A), the blast furnace slag and the converter slag are both in a molten state.
The method for producing a hydraulic cement composition according to claim 1 or 2, wherein step (B) further includes step (B-1) of slowly cooling and granulating the molten mixture obtained in step (A) to obtain granules, and the granules obtained in step (B-1) are rapidly cooled and solidified to produce clinker.
The method for producing a hydraulic cement composition according to claim 1 or 2, wherein step (B) is step (B-2) of blowing a jet of air onto the molten mixture obtained in step (A) in a flowing state, granulating the molten mixture, and rapidly cooling and solidifying it.
The method for producing a hydraulic cement composition according to claim 1 or 2, further comprising step (D) of adding a component adjuster to the molten mixture obtained in step (A).
The method for producing a hydraulic cement composition according to claim 5, wherein the component adjuster is a component adjuster consisting of only CaO, a component adjuster containing two components, CaO and Al2O3 , or a component adjuster containing two components, CaO and SiO2 .
The CaO content in the molten mixture of the blast furnace slag and the converter furnace slag is in a range of not less than the numerical value calculated by formula (1) and not more than the numerical value calculated by formula (2) when the total amount of CaO, Al 2 O 3 , and SiO 2 contained in the mixture is taken as 100 mass%,
The method for producing a hydraulic cement composition according to claim 1 or 2 , wherein the content of Al2O3 contained in the mixture is 1.0 mass% or more and 15 mass% or less when the total amount of CaO, Al2O3 , and SiO2 contained in the mixture is 100 mass%.
the content of CaO in the mixture obtained by further adding the component adjuster to the molten mixture of the blast furnace slag and the converter slag is in a range equal to or greater than the value calculated by formula (1) and equal to or less than the value calculated by formula (2) when the total amount of CaO, Al 2 O 3 , and SiO 2 contained in the mixture is taken as 100 mass%,
The method for producing a hydraulic cement composition according to claim 5 , wherein the content of Al2O3 contained in the mixture is 1.0 mass% or more and 15 mass% or less when the total amount of CaO, Al2O3 , and SiO2 contained in the mixture is 100 mass%.
The method for producing a hydraulic cement composition according to claim 1 or 2 further comprises a step (E) of feeding the mixture of molten blast furnace slag and molten converter slag into a melting furnace having a mixing mechanism and a heating mechanism, maintaining the mixture at a temperature at which the molten state is maintained, and then quenching the mixture.
The method for producing a hydraulic cement composition according to claim 9, wherein the mixture of molten blast furnace slag and molten converter slag further contains the component adjuster.
3. The method for producing a hydraulic cement composition according to claim 1 or 2, wherein the content of iron oxide in the obtained hydraulic cement composition is 1.5 mass % or more and 10 mass % or less, calculated as Fe2O3 .
The method for producing a hydraulic cement composition according to claim 11, wherein the converter slag in step (A) is in a molten state and is converter slag that has been subjected to a process for reducing the amount of iron oxide by a process for reducing the iron oxide using a nonmetallic reducing material.
The method for producing a hydraulic cement composition according to claim 12, wherein the nonmetallic reducing material used in the reduction treatment of the iron oxide is at least one selected from the group consisting of carbon, carbon monoxide, hydrogen, ammonia, and methane.
The method for producing a hydraulic cement composition according to claim 1 or 2, wherein in step (C), at least one selected from the group consisting of ground granulated blast furnace slag, fly ash, and Portland cement is further added before or after the clinker is crushed.