Method for producing carbonate-containing granular material

Abstract

Provided is a method which is for producing a carbonate-containing granular material and by which a carbonate-containing granular material can be produced at a lower cost and more quickly than before.　This method for producing a carbonate-containing granular material comprises a carbonation step for bringing a granular material to be carbonated having a maximum temperature of higher than 0ºC and lower than 100ºC into contact with water, a carbonation accelerator, and at least one among a carbon dioxide-containing substance, carbonate ion-containing water, and hydrogen carbonate ion-containing water, or with a carbonation accelerator and at least one among carbon dioxide-containing water, carbonate ion-containing water, and hydrogen carbonate ion-containing water, wherein: the total amount of the water brought into contact in the carbonation step is at least 1 mass% of the amount of the granular material to be carbonated; the carbonation accelerator contains a sulfur compound or a sulfur compound and a chlorine compound; and the content of sulfur or the total content of sulfur and chlorine in the carbonation accelerator is at least 0.5 mass% of the amount of the granular material to be carbonated.

Description

Method for producing carbonate-containing granular material

[0001] The present invention relates to a method for producing carbonate-containing granular material.

[0002] Steelmaking slag, such as pre-processed slag, converter slag, electric furnace slag, and casting slag, generated at steelworks is discharged onto a pit or steel plate after steel refining and allowed to cool and solidify. After cooling to room temperature, the slag is crushed to adjust its particle size and passed through a magnetic separator to recover the iron content, after which it is widely used for roadbeds, civil engineering and building materials, marine applications, and more.

[0003] Since steelmaking slag contains CaO, if steelmaking slag is used as roadbed material as it is, problems such as expansion will occur. For this reason, when steelmaking slag is used as roadbed material, carbonation treatment of the CaO contained in the steelmaking slag to convert it into calcium carbonate is being considered.

[0004] Patent Document 1 discloses a method for producing a molded body using sulfur-containing slag as a raw material. According to Patent Document 1, the sulfur-containing slag is oxidized to fix at least a portion of the sulfur content in the slag as sulfur compounds, and then a carbon dioxide-containing gas is blown into a packed bed of powder and granules made of the oxidized sulfur-containing slag. As a result, the packed bed of powder and granules solidifies using calcium carbonate produced by carbonation as a binder, thereby obtaining a molded body.

[0005] Patent Document 2 discloses a method for carbonating an aggregate of solid particles containing calcium oxide or calcium hydroxide in a water-containing state as a packed bed. Patent Document 3 discloses a method for carbonating iron and steel slag powder while fluidizing it in treatment water.

[0006] Patent No. 3714229 Patent No. 3624784 Patent No. 5432809

[0007] In the methods disclosed in Patent Documents 1 and 2, slag, calcium oxide, and calcium hydroxide are carbonated as a packed layer, and the calcium carbonate acts as a binder to obtain a compact. However, to produce carbonate-containing granular material, additional steps are required to crush the compact and adjust the particle size. Therefore, the methods disclosed in Patent Documents 1 and 2 have the problem of increasing the production cost of the carbonate-containing granular material and taking a long time to obtain the granular material.

[0008] The method disclosed in Patent Document 3 uses treatment water in which carbon dioxide-containing gas is dispersed as microbubbles, and therefore requires a microbubble generator. Therefore, the method disclosed in Patent Document 3 has the problem of high production costs for carbonate-containing granular material. The present invention has been made in view of these problems of the prior art, and its object is to provide a method for producing carbonate-containing granular material that can produce carbonate-containing granular material more quickly and at lower cost than conventional methods.

[0009] The means for solving the above problems are as follows: [1] A method for producing a carbonate-containing granular material, comprising a carbonation step of contacting a granular material to be carbonated having a maximum temperature greater than 0°C and less than 100°C with water, a carbonation promoter, and at least one of a carbon dioxide-containing substance, carbonate ion-containing water, and bicarbonate ion-containing water, or with a carbonation promoter and at least one of carbon dioxide-containing water, carbonate ion-containing water, and bicarbonate ion-containing water, wherein the total amount of water contacted in the carbonation step is 1% by mass or more of the granular material to be carbonated, the carbonation promoter contains a sulfur compound, or a sulfur compound and a chlorine compound, and the sulfur content, or the total content of sulfur and chlorine, in the carbonation promoter is 0.5% by mass or more of the granular material to be carbonated. [2] A method for producing a carbonate-containing granular material according to [1], wherein the carbonation step further includes contacting the granular material to be carbonated with an ammonia-containing substance. [3] A method for producing a carbonate-containing granular material according to [1] or [2], wherein the granular material to be carbonated and / or water contains the carbonation promoter. [4] A method for producing a carbonate-containing granular material according to any of [1] to [3], wherein the carbon dioxide-containing substance is a gas. [5] A method for producing a carbonate-containing granular material according to any of [1] to [4], wherein the particle size of the granular material to be carbonated satisfies any of the following: a content of particles with a particle size of 0 to 75 μm is more than 25% by mass, a content of particles with a particle size of 0 to 425 μm is more than 30% by mass, a content of particles with a particle size of 0 to 2.36 mm is more than 50% by mass, a content of particles with a particle size of 0 to 4.75 mm is more than 65% by mass, and a content of particles with a particle size of 0 to 13.2 mm is more than 85% by mass. [6] A method for producing a carbonate-containing granular material according to any of [1] to [5], wherein the granular material to be carbonated is steelmaking slag.

[0010] The method for producing carbonate-containing granular material according to the present invention uses a carbonation promoter that promotes the production of carbonates of Ca, Mg, K and Na contained in the granular material to be carbonated, thereby enabling the production of carbonate-containing granular material faster and at lower cost than conventional methods.

[0011] FIG. 1 is a schematic diagram showing an example of a carbonation facility capable of carrying out the carbonation step in the method for producing carbonate-containing granular material according to this embodiment.

[0012] The present invention will be specifically described below through embodiments of the present invention. The following embodiments are preferred examples of the present invention, and the present invention is not limited to these embodiments.

[0013] Fig. 1 is a schematic diagram showing an example of a carbonation facility capable of carrying out the carbonation step in the method for producing carbonate-containing granular material according to this embodiment. The carbonation step in the method for producing carbonate-containing granular material according to this embodiment will be described with reference to Fig. 1.

[0014] The carbonation equipment 10 includes a bottomed cylindrical vessel 12, a spray nozzle 14, a gas ejection nozzle 16, an agitator blade 18, and a thermocouple 20. During the carbonation process, water 22 and a carbonation promoter 24 are supplied to the granular material 100 via the spray nozzle 14. A carbon dioxide-containing gas 26 is blown into the water 22 via the gas ejection nozzle 16, and the water is stirred with the agitator blade 18. This allows carbon dioxide to dissolve in the water 22 as carbonate ions and bicarbonate ions, which then come into contact with the granular material 100. As a result, the carbonation promoter accelerates the carbonation reaction between the oxides, hydroxides, and hydrates contained in the granular material 100 and the carbonate ions and bicarbonate ions, enabling the production of carbonate-containing granular material with higher carbonation efficiency than conventional methods. The carbon dioxide-containing gas 26 shown in FIG. 1 is an example of a gaseous carbon dioxide-containing substance.

[0015] The granular material to be carbonated 100 is composed of CaO, MgO, K ２ O and Na ２ It is preferable that the material contains one or more selected from O. Examples of types of materials that can be used as the granular material to be carbonated 100 are shown in Table 1 below. In Table 1 below, "T-Fe" means the total content of iron contained in iron-containing compounds. "T-S" means the total content of sulfur contained in sulfur-containing compounds.

[0016]

[0017] The granular material to be carbonated 100 is CaO, MgO, K ２ O and Na ２By including one or more selected from O, when water 22 is supplied, Ca, Mg, K and Na are dissolved into the water as ions from the carbonated granular material 100, thereby promoting the production of carbonates of these substances.

[0018] CaO, MgO, K ２ O and Na ２ From the viewpoint of containing one or more selected from O, the granular material to be carbonated 100 is preferably steel slag. Of steel slags, the granular material to be carbonated 100 is more preferably steelmaking slag. As the steelmaking slag, converter slag, electric furnace slag, secondary refining slag, and hot metal pretreatment slag shown in Table 1 above are suitably used.

[0019] Similarly, CaO, MgO, K ２ O and Na ２ The granular material to be carbonated 100 is preferably waste concrete or biomass incineration ash because it contains one or more selected from the group consisting of ammonium nitrate, ...

[0020] The particle size of the granular material to be carbonated 100 preferably satisfies any of the following particle sizes: ・The content of particles with a particle size of 0 to 75 μm is more than 25% by mass ・The content of particles with a particle size of 0 to 425 μm is more than 30% by mass ・The content of particles with a particle size of 0 to 2.36 mm is more than 50% by mass ・The content of particles with a particle size of 0 to 4.75 mm is more than 65% by mass ・The content of particles with a particle size of 0 to 13.2 mm is more than 85% by mass

[0021] When the particle size of the carbonated granular material 100 satisfies any of the above particle sizes, the surface area of ​​the carbonated granular material 100 increases. This increases the contact area between the carbonated granular material 100 and the water 22, accelerating the elution of Ca, Mg, K, and Na ions and the production of carbonates.

[0022] The maximum particle size of the carbonated granular material 100 is more preferably 4.75 mm or less, and even more preferably 2.36 mm or less. Here, the maximum particle size of the carbonated granular material 100 means that when sieved using a sieve with a nominal opening specified in JIS Z 8801-1:2019, the entire amount of the carbonated granular material 100 passes through a sieve with the same nominal opening as the maximum particle size.

[0023] The smaller the maximum particle size of the carbonated granular material 100, the larger the surface area of ​​the carbonated granular material 100, which promotes the elution of Ca, Mg, K, and Na ions. Therefore, there is no need to set a lower limit for the maximum particle size of the carbonated granular material 100. However, since it is difficult to grind the carbonated granular material 100 to a maximum particle size of less than 0.001 mm, it is preferable that the maximum particle size of the carbonated granular material 100 be 0.001 mm or more.

[0024] In the method for producing carbonate-containing granular material according to this embodiment, the granular material to be carbonated 100 is contacted with a carbonation promoter 24 that promotes the carbonation reaction during the carbonation step. In the method for producing carbonate-containing granular material according to this embodiment, a carbonation promoter 24 containing a sulfur compound or a sulfur compound and a chlorine compound is used. The carbonation promoter 24 is a liquid or solid substance containing sulfides, sulfates, and chlorides, which are sulfur compounds or chlorine compounds. Examples of sulfides that can be used include one or more of sodium sulfide, magnesium sulfide, potassium sulfide, and calcium sulfide. Examples of sulfates that can be used include one or more of sodium sulfate, magnesium sulfate, potassium sulfate, and calcium sulfate. Examples of chlorides that can be used include one or more of sodium chloride, magnesium chloride, potassium chloride, and calcium chloride. It is preferable that the granular material to be carbonated 100 and / or the water 22 contain these carbonation promoters.

[0025] The sulfur content or the total sulfur and chlorine content in the carbonation accelerator 24 needs to be 0.5% by mass or more of the granular material to be carbonated 100. When the sulfur content or the total sulfur and chlorine content in the carbonation accelerator 24 is 0.5% by mass or more of the granular material to be carbonated 100, gypsum, ettringite, Friedel's salt, ammonia water, ammonium sulfide, ammonium chloride, ammonium sulfate, sodium bicarbonate, sodium chloride, magnesium chloride, potassium chloride, calcium chloride, sodium sulfate, magnesium sulfate, potassium sulfate, calcium sulfate, sodium sulfide, magnesium sulfide, potassium sulfide, and calcium sulfide are produced, thereby accelerating the elution of metal ions and the carbonation reaction.

[0026] On the other hand, if the sulfur content or the sum of the sulfur and chlorine contents in the carbonation accelerator 24 is less than 0.5% by mass of the granular material 100 to be carbonated, the production of the above substances will be insufficient, and the elution of metal ions and the carbonation reaction will not proceed sufficiently. For this reason, the sulfur content or the sum of the sulfur and chlorine contents in the carbonation accelerator 24 must be 0.5% by mass or more of the granular material 100 to be carbonated. The sulfur content or the sum of the sulfur and chlorine contents in the carbonation accelerator 24 is preferably 1.0% by mass or more of the granular material 100 to be carbonated, and more preferably 2.0% by mass or more. The method for measuring the sulfur content and chlorine content of the carbonation accelerator 24 is not particularly limited, but can be measured, for example, using combustion ion chromatography according to the following steps (1) and (2).

[0027] (1) The sulfur and chlorine components are converted into sulfate ions and chloride ions by a combustion method to prepare an aqueous solution. (2) The sulfate ions and chloride ions in the aqueous solution are quantified by ion chromatography.

[0028] The hot metal pretreatment slag, waste concrete, coal ash, flue gas desulfurization sludge, general municipal waste incineration ash, and biomass incineration ash shown in Table 1 contain sulfur compounds containing 0.5 mass% or more of sulfur. Therefore, these become granular material to be carbonated 100 containing carbonation accelerator 24. In this way, when granular material to be carbonated 100 contains carbonation accelerator 24, it is not necessary to supply carbonation accelerator 24 from injection nozzle 14.

[0029] In the carbonation process, the total amount of water 22 sprayed onto the granular material 100 to be carbonated must be 1% by mass or more of the granular material 100 to be carbonated. By spraying 1% by mass or more of water 22 onto the granular material 100 to be carbonated, the water 22 comes into contact with the surface of the granular material 100 to be carbonated, and the elution of metal ions and the carbonation reaction can proceed.

[0030] On the other hand, if the total amount of water 22 to be sprayed is less than 1% by mass of the granular material 100 to be carbonated, the contact between the granular material 100 and the water 22 will be insufficient, and the elution of metal ions will not proceed sufficiently, which is undesirable. The total amount of water 22 to be sprayed onto the granular material 100 to be carbonated is preferably 5% by mass or more of the granular material 100 to be carbonated, and more preferably 10% by mass or more of the granular material 100 to be carbonated.

[0031] It is preferable to use liquid water 22 as the water 22 to be sprinkled on the granular material 100 to be carbonated. The liquid water 22 to be sprinkled on the granular material 100 to be carbonated may be fresh water, tap water, distilled water, ion-exchanged water, pure water, rainwater, well water, lake water, river water, industrial water, reclaimed water, salt water, brackish water, brine, concentrated seawater, seawater, or hot spring water. An example of the component composition of fresh water, seawater, or hot spring water is shown in Table 2 below. It is preferable to use salt water, brine, concentrated seawater, seawater, or hot spring water as the liquid water 22 to be sprinkled on the granular material 100 to be carbonated. These contain sulfur compounds and chlorine compounds, and therefore become water 22 containing the carbonation promoter 24.

[0032]

[0033] The carbon dioxide content of the carbon dioxide gas-containing gas 26 brought into contact with the granular material 100 is preferably 1% by volume or more of the granular material 100. By supplying carbon dioxide at 1% by volume or more of the granular material 100, the granular material 100 can be sufficiently carbonated. The water 22 supplied from the injection nozzle 14 is prevented from becoming strongly alkaline water, and the generation of strongly alkaline water during the carbonation process can be prevented.

[0034] The carbon dioxide gas-containing gas 26 blown from the gas ejection nozzle 16 may be a mixture of carbon dioxide gas and other gases such as nitrogen, oxygen, carbon monoxide, water vapor, etc. The carbon dioxide gas content in the carbon dioxide gas-containing gas 26 is preferably 0.03% by volume or more, and more preferably 1% by volume or more. By using a carbon dioxide gas-containing gas 26 with a carbon dioxide gas content of 0.03% by volume or more, it is possible to supply the carbon dioxide necessary for the carbonation reaction and promote the carbonation of the granular material 100 to be carbonated. The carbon dioxide content in the carbon dioxide gas-containing gas 26 can be measured by component analysis of the carbon dioxide gas-containing gas 26.

[0035] In the carbonation step, it is preferable to further contact the granular material 100 with an ammonia-containing substance. By contacting the ammonia-containing substance, ammonium salts are produced from the chlorides, sulfates, and sulfides contained in the carbonation promoter 24, and these substances act on the granular material 100 to promote carbonation. By including the ammonia-containing substance, the pH of the water 22 increases and the amount of dissolved carbon dioxide increases, further promoting carbonation of the granular material 100. As the ammonia-containing substance, an ammonia gas-containing gas or ammonia water (aqueous ammonia solution) can be used.

[0036] The maximum temperature of the granular material 100 to be carbonated during the carbonation process must be above 0°C and below 100°C. If the maximum temperature of the granular material 100 to be carbonated is below 100°C, the carbon dioxide dissolved in the water 22 can be used to promote carbonation of the granular material 100. On the other hand, if the maximum temperature of the granular material 100 to be carbonated is above 100°C, the amount of carbon dioxide dissolved in the water 22 will be significantly reduced, making it impossible to efficiently carbonate the granular material 100. The maximum temperature of the granular material 100 to be carbonated during the carbonation process is preferably below 90°C, more preferably below 80°C, and even more preferably below 60°C.

[0037] If the maximum temperature of the granular material 100 to be carbonated falls below 0°C, the water 22 will freeze and the carbon dioxide-containing gas 26 will no longer be able to be blown in, making it impossible to efficiently carbonate the granular material 100. For this reason, the maximum temperature of the granular material 100 to be carbonated during the carbonation process must be above 0°C. The higher the maximum temperature of the water 22 during the carbonation process, the more the carbonation reaction will be promoted. If the maximum temperature of the granular material 100 to be carbonated is above 0°C and below 20°C, the improvement in carbonation efficiency due to the promotion of the carbonation reaction will be greater than the decrease in carbonation efficiency due to a decrease in the amount of dissolved carbon dioxide. For this reason, the maximum temperature of the granular material 100 to be carbonated is preferably above 10°C, and more preferably above 20°C.

[0038] The maximum temperature of the granular material 100 to be carbonated during the carbonation process is measured by a thermocouple 20. The thermocouple 20 is inserted into the water 22. Because the water 22 is being stirred by the stirring blades 18, the water 22 and the granular material 100 to be carbonated have the same temperature. Therefore, by measuring the temperature of the water 22 using the thermocouple 20 during the carbonation process, the maximum temperature of the granular material 100 to be carbonated during the carbonation process can be determined.

[0039] The time for blowing the carbon dioxide-containing gas 26 into the water 22 and allowing it to come into contact with the water 22 is preferably 1 minute or more. This allows the carbon dioxide to come into contact with the granular material 100 to be carbonated, thereby efficiently producing carbonate-containing granular material. The time for supplying the carbon dioxide-containing gas 26 is more preferably 5 minutes or more.

[0040] As described above, in the method for producing carbonate-containing granular material according to this embodiment, carbonate-containing granular material is produced by contacting water 22, carbon dioxide-containing gas 26, and carbonation promoter 24 with granular material to be carbonated. Therefore, carbonate-containing granular material having the same particle size as or a finer particle size than granular material to be carbonated 100 can be produced without the need for a step of crushing compacts to adjust particle size or the use of a microbubble generator. Therefore, the method for producing carbonate-containing granular material according to this embodiment is a method that can produce carbonate-containing granular material more quickly and at lower cost than conventional methods. Furthermore, since carbonate-containing granular material can be produced while promoting the generation of carbonate, carbonate-containing granular material can be produced with high carbonation efficiency.

[0041] The embodiments of the present invention are not limited to the above-described embodiments and various modifications can be made. In the example shown in FIG. 1 , a carbon dioxide gas-containing gas 26 is blown into water 22 containing granular material 100 to produce carbonate-containing granular material, but the present invention is not limited to this. Instead of the carbon dioxide gas-containing gas 26, at least one of carbon dioxide gas-containing water, carbonate ion-containing water, and bicarbonate ion-containing water may be brought into contact with the granular material 100 to produce carbonate-containing granular material. Carbon dioxide gas-containing water, carbonate ion-containing water, and bicarbonate ion-containing water are examples of liquid carbon dioxide gas-containing substances. When carbon dioxide gas-containing water, carbonate ion-containing water, or bicarbonate ion-containing water is used, water 22 need not be used.

[0042] Furthermore, instead of the carbon dioxide gas-containing gas 26, dry ice may be immersed in the water 22 to produce the carbonate-containing granular material. Dry ice is an example of a solid carbon dioxide gas-containing substance. When using carbon dioxide gas-containing water, carbonate ion-containing water, bicarbonate ion-containing water, and dry ice, it is preferable to adjust the supply amounts of these so that the total carbon dioxide content contained therein is 1% by volume or more of the granular material 100 to be carbonated.

[0043] Instead of blowing the carbon dioxide gas-containing gas 26 into the water 22 containing the granular material 100 to be carbonated, the carbonate-containing granular material may be produced by exposing the granular material 100 to be carbonated containing the water 22 to an atmosphere of the carbon dioxide gas-containing gas 26. When an open container is used, it is preferable to use air as the carbon dioxide gas-containing gas from a safety standpoint.

[0044] In this way, the carbonation step can be carried out using gaseous, liquid, and solid carbon dioxide gas-containing substances. Among gaseous, liquid, and solid carbon dioxide gas-containing substances, it is preferable to use gaseous carbon dioxide gas-containing substances because they are inexpensive and easy to handle.

[0045] Next, examples will be described in which carbonate-containing granular materials were produced using steelmaking slag (converter slag, hot metal pretreatment slag), waste concrete, or biomass incineration ash as the granular material to be carbonated. In these examples, steelmaking slag or the like pulverized to a maximum particle size of 2 mm or less was used as the granular material to be carbonated, and the carbonation process was carried out using the carbonation equipment 10 shown in Figure 1, with the stirring blades 18 rotating at 200 rpm to produce the carbonate-containing granular material. The production conditions for the examples and the carbonation efficiency of the carbonate-containing granular material are shown in Tables 3 and 4 below.

[0046]

[0047]

[0048] The temperature shown in the "Maximum temperature of granular material to be carbonated" column in Table 3 is the maximum water temperature measured by inserting a thermocouple into the water during the carbonation process. The "Water spray amount," "Carbonation promoter content," and "Sulfur and chlorine content" in Table 3 are all the water spray amount and content for the granular material to be carbonated.

[0049] In the "Medium" column, "Gas + Liquid" is a manufacturing example in which carbonate-containing granular material is produced using carbon dioxide gas-containing water or carbon dioxide-containing gas-containing water. "Solid + Liquid" is a manufacturing example in which carbonate-containing granular material is produced using dry ice-containing water. "Liquid" is a manufacturing example in which carbonate-containing granular material is produced using carbonate ion-containing water or bicarbonate ion-containing water, liquid carbon dioxide-containing water, or liquid carbon dioxide.

[0050] The value shown in the column "carbonation efficiency" is the value obtained by dividing the carbonate content (mass%) by the amount of carbonate that can be generated (mass%) and multiplying the result by 100. The amount of carbonate that can be generated is determined by the amount of CaO, MgO, K ２ O and Na ２ It was calculated from the content of O. It can be said that the larger the value of this carbonation efficiency, the higher the carbonation efficiency with which the carbonate-containing granular material can be produced.

[0051] As shown in Tables 3 and 4, Production Examples 1 to 4 are examples of the invention in which carbonate-containing granular materials were produced by varying the type of carbonation-promoting material while maintaining the same carbon dioxide content and water spray rate relative to the granular material to be carbonated. Production Examples 1 to 4 achieved carbonation efficiencies of 50.0% or higher. Of these, Production Example 4, which used seawater, had the highest carbonation efficiency at 58.4%.

[0052] Production Example No. 4 is an example of the invention in which a carbonate-containing granular material was produced with a sulfur and chlorine content of 2.0% by mass relative to the granular material to be carbonated. Production Example No. 5 is an example of the invention in which a carbonate-containing granular material was produced with a sulfur and chlorine content of 0.5% by mass relative to the granular material to be carbonated. Production Example No. 24 is a comparative example in which a carbonate-containing granular material was produced with a sulfur and chlorine content of 0.0% by mass relative to the granular material to be carbonated.

[0053] Comparing Production Examples 4, 5, and 24, the carbonation efficiency of Production Example 4 was 58.4%, while the carbonation efficiency of Production Example 5 was 54.1%, and the carbonation efficiency of Production Example 24 was 48.8%. Although the carbonation efficiency decreased with a decrease in the sulfur and chlorine content of the carbonation accelerator, even Production Example 5 maintained a carbonation efficiency of 50.0% or more. These results confirmed that the sulfur content, or the total content of sulfur and chlorine, in the carbonation accelerator should be 0.5% by mass or more relative to the granular material to be carbonated.

[0054] Production Examples 6 to 11 are examples of the invention in which carbonate-containing granular materials were produced using different types of carbon dioxide, while maintaining the same carbon dioxide content and water spray rate relative to the granular material to be carbonated as in Production Example 4. Comparing Production Example 4 with Production Examples 6 to 11, the carbonation efficiency of Production Example 5 was 58.4%, while the carbonation efficiency of Production Examples 6 to 11 was 55.1 to 56.7%. As such, since there was almost no difference in carbonation efficiency between Production Example 4 and Production Examples 6 to 11, it was confirmed that the type of carbon dioxide does not affect the carbonation efficiency of carbonate-containing granular materials.

[0055] Production Example No. 12 is an example of the invention in which a carbonate-containing granular material was produced by changing the maximum temperature of the granular material to be carbonated during the carbonation process, while maintaining the same carbon dioxide content and water spray rate as Production Example No. 4. Comparing Production Example No. 4 and Production Example No. 12, the carbonation efficiency of Production Example No. 4 was 58.4%, while the carbonation efficiency of Production Example No. 12, in which the maximum temperature of the granular material to be carbonated during the carbonation process was increased to 90°C, decreased to 51.0%. As the water temperature increases during the carbonation process, the amount of carbon dioxide dissolved in the water decreases. Therefore, it is believed that the carbonation efficiency decreased as the maximum temperature of the granular material to be carbonated increased.

[0056] Production Example No. 22 is a comparative example in which a carbonate-containing granular material was produced by setting the carbon dioxide content and water spray rate relative to the granular material to be carbonated to the same as those in Production Example No. 4, but setting the maximum temperature of the granular material to be carbonated to 0°C during the carbonation process. Comparing Production Example No. 4 and Production Example No. 22, the carbonation efficiency of Production Example No. 4 was 58.4%, while the carbonation efficiency of Production Example No. 22 was 0.0%. When the maximum temperature of the granular material to be carbonated falls below 0°C during the carbonation process, the water freezes, making it impossible to blow in carbon dioxide gas, which is thought to be why carbonation of the carbonate-containing granular material did not proceed.

[0057] Production Example No. 23 is a comparative example in which a carbonate-containing granular material was produced using the same carbon dioxide content and water spray rate as Production Example No. 4, but with the maximum temperature of the carbonated granular material set to 100°C during the carbonation process. Comparing Production Example No. 4 and Production Example No. 23, the carbonation efficiency of Production Example No. 4 was 58.4%, while the carbonation efficiency of Production Example No. 23 was 1.5%. It is believed that when the maximum temperature of the carbonated granular material exceeds 100°C during the carbonation process, the amount of carbon dioxide dissolved in the water significantly decreases, resulting in a decrease in carbonation efficiency. These results confirm that carbonate-containing granular material can be produced with high carbonation efficiency by contacting a carbon dioxide-containing substance with carbonated granular material set to a maximum temperature above 0°C and below 100°C during the carbonation process.

[0058] Production Examples Nos. 13 to 15 are examples of the invention in which carbonate-containing granular materials were produced by changing the type of granular material to be carbonated, while the carbon dioxide content and water spray amount relative to the granular material to be carbonated were the same as in Production Example No. 4. Comparing Production Example No. 4 with Production Examples Nos. 13 to 15, the carbonate content in Production Example No. 4 was 38.0 mass%, while the carbonate contents in Production Examples Nos. 13 to 15, which used different types of granular material to be carbonated, were 40.0 mass% or more. Compared to converter slag, waste concrete and biomass incineration ash contain not only CaO but also K. ２ O and Na ２ The carbon dioxide also contains a large amount of O. For this reason, the amount of carbonates that can be produced is greater in Production Examples 13 to 15, which used desulfurization slag, waste concrete, or biomass incineration ash, than in Production Example 4, which used converter furnace slag as the granular material to be carbonated, and as a result, the carbonate content also increased.

[0059] Production Examples 16 and 17 are examples of the invention in which carbonate-containing granular material was produced by adding an ammonia-containing substance, while the carbon dioxide content and water spray rate relative to the granular material to be carbonated were the same as those in Production Example No. 4. Comparing Production Example No. 4 with Production Examples 16 and 17, the carbonate content in Production Example No. 4 was 38.0% by mass, whereas the carbonate contents in Production Examples 16 and 17, to which the ammonia-containing substance was added, were 40.0% by mass or more.

[0060] When an ammonia-containing substance is used, ammonium salts are generated from the carbonation promoters chloride, sulfate, and sulfide, which act on the carbonated granules to further promote carbonation. Therefore, Production Examples 16 and 17, which used an ammonia-containing substance, had a higher carbonate content and higher carbonation efficiency than Production Example 4. These results confirmed that it is preferable to bring an ammonia-containing substance into contact with the carbonated granules in the carbonation process.

[0061] Production Example No. 18 is an example of the invention in which carbonate-containing granular material was produced by adding salt water and calcium sulfate, while maintaining the same carbon dioxide content and water spray rate relative to the granular material to be carbonated as Production Example No. 1. Comparing Production Example No. 1 and Production Example No. 18, the carbonation efficiency of Production Example No. 1 was 55.1%, while the carbonation efficiency of Production Example No. 19 was 56.5%. These results confirmed that a higher sulfur and chlorine content in the carbonation promoter added in the carbonation process is preferable.

[0062] Production Example No. 19 is an example of the invention in which a carbonate-containing granular material was produced by setting the carbon dioxide content relative to the granular material to be carbonated to the same as Production Example No. 4, and setting the amount of water sprayed in the carbonation process to 1% by mass. Comparing Production Example No. 4 and Production Example No. 19, the carbonation efficiency of Production Example No. 4 was 58.4%, and the carbonation efficiency of Production Example No. 19 was 54.5%. These results confirmed that the granular material to be carbonated can be carbonated as long as the total amount of water contacted in the carbonation process is 1% by mass or more relative to the granular material to be carbonated.

[0063] Production Examples 20 and 21 are comparative examples in which carbonate-containing granular materials were produced without contact with carbon dioxide. Comparing Production Example 4 with Production Examples 20 and 21, the carbonation efficiency of Production Example 4 was 58.4%, while the carbonation efficiency of Production Examples 20 and 21 was 0.0%. These results confirm that in the carbonation process, it is necessary to contact the granular material to be carbonated with a carbon dioxide-containing substance, carbonate ion-containing water, or bicarbonate ion-containing water, and that this enables the production of carbonate-containing granular materials with high carbonation efficiency.

[0064] REFERENCE SIGNS LIST 10 Carbonation equipment 12 Container 14 Spray nozzle 16 Gas ejection nozzle 18 Stirring blade 20 Thermocouple 22 Water 24 Carbonation promoter 26 Carbon dioxide gas-containing gas 100 Granular material to be carbonated

Claims

1. The carbonation process involves bringing a granular material to be carbonated, with a maximum temperature exceeding 0°C and below 100°C, into contact with water, a carbonation accelerator, and at least one of a carbon dioxide-containing substance, carbonate ion-containing water, and bicarbonate ion-containing water, or a carbonation accelerator and at least one of carbon dioxide-containing water, carbonate ion-containing water, and bicarbonate ion-containing water. The total amount of water brought into contact with the material in the carbonation process is 1% by mass or more of the granular material to be carbonated. A method for producing a carbon oxide-containing granular material, wherein the carbonation accelerator contains a sulfur compound, or a sulfur compound and a chlorine compound, and the sulfur content in the carbonation accelerator, or the total content of sulfur and chlorine, is 0.5% by mass or more of the granular material to be carbonated.

2. The method for producing a carbon oxide-containing granular material according to claim 1, wherein in the carbonation step, an ammonia-containing substance is further brought into contact with the granular material to be carbonated.

3. A method for producing a carbon oxide-containing granular material according to claim 1 or claim 2, wherein the granular material to be carbonated and / or water contains the carbonation accelerator.

4. The method for producing a carbon oxide-containing granular material according to claim 1 or claim 2, wherein the carbon dioxide-containing substance is a gas.

5. The method for producing a carbon oxide-containing granular material according to claim 3, wherein the carbon dioxide-containing substance is a gas.

6. A method for producing a carbon oxide-containing granular material according to claim 1 or claim 2, wherein the particle size of the carbonated granular material satisfies any of the following: the content of particles with a particle size of 0 to 75 μm exceeds 25% by mass, the content of particles with a particle size of 0 to 425 μm exceeds 30% by mass, the content of particles with a particle size of 0 to 2.36 mm exceeds 50% by mass, the content of particles with a particle size of 0 to 4.75 mm exceeds 65% by mass, and the content of particles with a particle size of 0 to 13.2 mm exceeds 85% by mass.

7. The method for producing a carbon oxide-containing granular material according to claim 3, wherein the particle size of the carbonated granular material satisfies any of the following conditions: the content of particles with a particle size of 0 to 75 μm exceeds 25% by mass, the content of particles with a particle size of 0 to 425 μm exceeds 30% by mass, the content of particles with a particle size of 0 to 2.36 mm exceeds 50% by mass, the content of particles with a particle size of 0 to 4.75 mm exceeds 65% by mass, and the content of particles with a particle size of 0 to 13.2 mm exceeds 85% by mass.

8. The method for producing a carbon oxide-containing granular material according to claim 4, wherein the particle size of the carbonated granular material satisfies any of the following: the content of particles with a particle size of 0 to 75 μm exceeds 25% by mass, the content of particles with a particle size of 0 to 425 μm exceeds 30% by mass, the content of particles with a particle size of 0 to 2.36 mm exceeds 50% by mass, the content of particles with a particle size of 0 to 4.75 mm exceeds 65% by mass, and the content of particles with a particle size of 0 to 13.2 mm exceeds 85% by mass.

9. The method for producing a carbon oxide-containing granular material according to claim 5, wherein the particle size of the carbonated granular material satisfies any of the following conditions: the content of particles with a particle size of 0 to 75 μm exceeds 25% by mass, the content of particles with a particle size of 0 to 425 μm exceeds 30% by mass, the content of particles with a particle size of 0 to 2.36 mm exceeds 50% by mass, the content of particles with a particle size of 0 to 4.75 mm exceeds 65% by mass, and the content of particles with a particle size of 0 to 13.2 mm exceeds 85% by mass.

10. The method for producing a carbon oxide-containing granular material according to claim 1 or claim 2, wherein the carbonized granular material is steelmaking slag.

11. The method for producing a carbon oxide-containing granular material according to claim 3, wherein the carbonized granular material is steelmaking slag.

12. The method for producing a carbon oxide-containing granular material according to claim 4, wherein the carbonized granular material is steelmaking slag.

13. The method for producing a carbon oxide-containing granular material according to claim 5, wherein the carbonized granular material is steelmaking slag.

14. The method for producing a carbon oxide-containing granular material according to claim 6, wherein the carbonized granular material is steelmaking slag.

15. The method for producing a carbon oxide-containing granular material according to claim 7, wherein the carbonized granular material is steelmaking slag.

16. The method for producing a carbon oxide-containing granular material according to claim 8, wherein the carbonized granular material is steelmaking slag.

17. The method for producing a carbon oxide-containing granular material according to claim 9, wherein the carbonized granular material is steelmaking slag.