Method for producing carbonate-including substance

Abstract

Provided is a method for producing a carbonate-including substance, wherein a carbonate-including substance can be produced with higher carbonation efficiency than before.　This method for producing a carbonate-including substance has: a hydration step in which water or ice is brought into contact with a substance for carbonation that has a maximum temperature of 100°C to 600°C, and a hydration process is performed; and a carbonation step in which either water and a carbon dioxide-including substance, or at least one of carbon dioxide-including water, carbonate ion-including water, and hydrogencarbonate ion-including water is or are brought into contact with the substance for carbonation that has been subjected to the hydration process and has a maximum temperature of greater than 0°C and less than 100°C, wherein the total water quantity of the water or ice that is brought into contact with the substance for carbonation in the hydration step is greater than or equal to 1 vol% of the substance for carbonation.

Description

Method for producing carbonate-containing material

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

[0002] Steelmaking slag, such as pre-processed slag, converter slag, electric furnace slag, and casting slag, generated at steelworks is discharged onto a dump 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, passed through a magnetic separator to recover the iron, and then widely used as roadbed material, civil engineering and construction materials, marine applications, and more. Because steelmaking slag contains CaO, using steelmaking slag directly as roadbed material can cause problems such as expansion. Therefore, when using slag as roadbed material, carbonation of the CaO contained in the slag to convert it into calcium carbonate has been considered.

[0003] As a technique for carbonating slag, Patent Document 1 describes a method of carbonating CaO in slag by spraying water at a high temperature of 600°C or higher and generating carbon dioxide gas by utilizing the water-gas reaction and shift reaction. According to Patent Document 1, since the water-gas reaction is an endothermic reaction, spraying water at a high temperature of 600°C or higher can rapidly progress the water-gas reaction.

[0004] Patent Document 2 describes a method in which limestone is burned to obtain quicklime, an aqueous suspension of slaked lime is obtained by wet slake, and a carbon dioxide-containing gas is blown into the suspension to carbonate the suspension at 50 to 80° C. Patent Document 3 describes a method in which iron and steel slag powder is carbonated while being fluidized in treatment water.

[0005] Patent Document 4 describes a method of aging in which water is sprayed onto high-temperature slag in a sealed container to hydrate the slag. Patent Document 5 describes a method in which water is sprayed onto high-temperature steelmaking slag in a sealed container to cool it, and carbon dioxide gas is introduced at the same time, promoting a reaction between the slag, steam, and carbon dioxide, thereby causing the slag to self-crush and shortening the aging period.

[0006] Patent No. 4870063 Publication JP 2011-225390 Patent No. 5432809 JP 58-55093 JP JP 06-184610

[0007] In the method disclosed in Patent Document 1, CaO in the slag is subjected to a carbonation reaction in a high-temperature range of 600°C or higher. However, carbonates such as calcium carbonate that are expected to be produced decompose into calcium oxide and carbon dioxide at temperatures above 600°C. Therefore, at high temperatures above 600°C, the carbonates produced by carbonation decompose, making it impossible to produce a carbonate-containing substance with high carbonation efficiency.

[0008] The method disclosed in Patent Document 2 requires obtaining a highly concentrated aqueous suspension of slaked lime from limestone in a low temperature range of 100° C. or less, and therefore requires a long time to obtain the aqueous suspension of slaked lime.The method disclosed in Patent Document 3 requires a long time to carbonate the minerals contained in the slag, as the powder of the steel slag is directly carbonated in water in a low temperature range of 100° C. or less.

[0009] The method disclosed in Patent Document 4 does not include a carbonation step. Therefore, although the method disclosed in Patent Document 4 can stabilize the slag and shorten the aging period, it has the problem of not being able to produce a carbonate-containing substance. In the method disclosed in Patent Document 5, steelmaking slag is carbonated using carbon dioxide gas at a high temperature range with a maximum temperature of 150°C or higher and 900°C or lower, while adjusting the pressure. As such, the method disclosed in Patent Document 5 requires an airtight container for adjusting the pressure in the carbonation treatment, and is therefore not suitable for mass production.

[0010] The present invention has been made in consideration of the problems of the conventional technology, and its object is to provide a method for producing a carbonate-containing substance that can produce a carbonate-containing substance with higher carbonation efficiency than conventional methods.

[0011] Means for solving the above problems are as follows. [1] A method for producing a carbonate-containing material, comprising: a hydration step of contacting water or ice with a substance to be carbonated having a maximum temperature of 100°C or higher and 600°C or lower to perform a hydration treatment; and a carbonation step of contacting water and a carbon dioxide-containing material, or at least one of carbon dioxide-containing water, carbonate ion-containing water, and bicarbonate ion-containing water, with the hydrated substance to be carbonated having a maximum temperature of higher than 0°C and lower than 100°C, wherein the total amount of water or ice contacted with the substance to be carbonated in the hydration step is 1% by volume or more of the substance to be carbonated. [2] A method for producing a carbonate-containing material according to [1], wherein the total content of carbon dioxide contained in at least one of the carbon dioxide-containing substance, the carbonate ion-containing water, and the bicarbonate ion-containing water is 1% by volume or more of the substance to be carbonated. [3] A method for producing a carbonate-containing material according to [1] or [2], wherein the carbon dioxide-containing substance is in a gaseous state. [4] The method for producing a carbonate-containing material according to any one of [1] to [3], wherein the particle size of the substance 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. [5] The method for producing a carbonate-containing material according to any one of [1] to [4], wherein the substance to be carbonated is steelmaking slag.

[0012] In the method for producing a carbonate-containing material according to the present invention, the production of hydroxides and hydrates of Ca, Mg, K, and Na contained in the substance to be carbonated is promoted, and the carbonate-containing material is produced from the hydroxides and hydrates. Because metal hydroxides and hydrates are more easily carbonated than the metals themselves, by carrying out the method for producing a carbonate-containing material according to the present invention, it is possible to produce a carbonate-containing material with higher carbonation efficiency than conventional methods, without using a sealed container.

[0013] Fig. 1 is a schematic diagram showing a hydration facility capable of carrying out the hydration step in the method for producing a carbonate-containing material according to this embodiment. Fig. 2 is a schematic diagram showing a carbonation facility capable of carrying out the carbonation step in the method for producing a carbonate-containing material according to this embodiment.

[0014] 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.

[0015] 1 is a schematic diagram showing a hydration facility 10 capable of carrying out the hydration step in the method for producing a carbonate-containing material according to this embodiment. First, the hydration step in which a substance to be carbonated 100 is hydrated to produce hydroxides and hydrates will be described using FIG.

[0016] The hydration equipment 10 has a sprinkler nozzle 12 and a plurality of thermocouples 16. The sprinkler nozzle 12 is a nozzle that sprinkles a predetermined amount of water 14 onto the substance 100 to be carbonated from above. A plurality of sprinkler nozzles 12 may be provided so that water 14 can be sprinkled onto all of the substance 100 to be carbonated.

[0017] Within this hydration facility 10, water 14 is sprayed from spray nozzles 12, bringing the water 14 into contact with the substance to be carbonated 100, which has been stacked in a yard and has a maximum temperature of 100°C or higher and 600°C or lower. This causes metal ions such as Ca, Mg, K, and Na to elute from the substance to be carbonated 100, producing hydroxides or hydrates of the metals. The hydration process is the process of producing hydroxides or hydrates of the metals Ca, Mg, K, and Na contained in the substance to be carbonated 100.

[0018] The carbonation material 100 is composed of CaO, MgO, K ２ O and Na ２ It is preferable that the substance contains one or more selected from O. Examples of types of substances that can be used as the substance to be carbonated 100 are shown in Table 1 below.

[0019]

[0020] The substance to be carbonated 100 is CaO, MgO, K ２ O and Na ２By including O, when water 14 is supplied, Ca, Mg, K, and Na are dissolved as ions from the substance to be carbonated 100 into the water, and hydroxides and hydrates of these substances are produced. Examples of hydroxides produced by the hydration process include calcium hydroxide, sodium hydroxide, potassium hydroxide, and katoite. Examples of hydrates produced by the hydration process include amorphous calcium silicate hydrate, amorphous calcium aluminate hydrate, potassium hydroxide hydrate, and sodium hydroxide hydrate.

[0021] CaO, MgO, K ２ O and Na ２ From the viewpoint of containing one or more selected from the group consisting of slag, iron and steel slag, it is preferable that the substance to be carbonated 100 is iron and steel slag. Of iron and steel slags, it is more preferable that the substance to be carbonated 100 is steelmaking slag. As the steelmaking slag, converter slag, electric furnace slag, secondary refining slag, electric furnace slag, and hot metal pretreatment slag shown in Table 1 above are suitably used.

[0022] Similarly, CaO, MgO, K ２ O and Na ２ The substance to be carbonated 100 is preferably waste concrete, waste geopolymer, or waste alkali-activated material because it contains at least one selected from the group consisting of ammonium nitrate, ...

[0023] The particle size of the substance 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

[0024] When the particle size of the substance to be carbonated 100 satisfies the above, the surface area of ​​the substance to be carbonated 100 increases, and the contact area with water 14 increases, thereby facilitating the elution of metal ions in the hydration process. The maximum particle size of the substance to be carbonated 100 is more preferably 4.75 mm or less, and even more preferably 2.36 mm or less. The maximum particle size of the substance to be carbonated 100 means that when sieved using a sieve with a nominal opening specified in JIS Z 8801-1:2019, the entire amount of the substance to be carbonated 100 will pass through a sieve with the same nominal opening as the maximum particle size.

[0025] The smaller the maximum particle size of the substance to be carbonated 100, the greater the surface area of ​​the substance to be carbonated 100, which promotes the elution of metal ions during the hydration reaction. For this reason, there is no need to set a lower limit for the maximum particle size of the substance to be carbonated 100. However, since it is difficult to grind the substance to be carbonated 100 to a maximum particle size of less than 0.001 mm, it is preferable that the maximum particle size of the substance to be carbonated 100 be 0.001 mm or more.

[0026] The substance to be carbonated 100 may be crushed by spraying hot water on the substance to be carbonated 100, or by using a crusher or grinder to crush or pulverize the substance to be carbonated 100. By crushing or pulverizing the substance to be carbonated 100 using these methods, the maximum particle size of the substance to be carbonated 100 can be adjusted.

[0027] The total amount of water 14 sprayed onto the substance to be carbonated 100 needs to be 1% or more by volume of the substance to be carbonated 100. By spraying 1% or more by volume of water 14 onto the substance to be carbonated 100, the water comes into contact with the surface of the substance to be carbonated 100, allowing the elution of metal ions and the hydration reaction to proceed. On the other hand, if the amount of water 14 sprayed is less than 1% by volume of the substance to be carbonated 100, the water 14 will not come into sufficient contact with the substance to be carbonated 100, preventing the elution of metal ions and the hydration reaction from proceeding sufficiently, which is undesirable. The amount of water 14 sprayed onto the substance to be carbonated 100 is preferably 5% or more by volume of the substance to be carbonated 100, and more preferably 10% or more by volume.

[0028] The time for which water is in contact with the surface of the substance to be carbonated 100 is preferably 10 minutes or more. By allowing water to be in contact with the surface of the substance to be carbonated 100 for 10 minutes or more, the elution of metal ions and the hydration reaction can be sufficiently promoted. The time for which water is in contact with the surface of the substance to be carbonated 100 is preferably 20 minutes or more, and more preferably 30 minutes or more. By extending the time for which water is in contact with the surface of the substance to be carbonated 100, the particle size of the carbonated oxide 100 becomes finer due to hydration or thermal stress, improving the carbonation rate in the subsequent carbonation process. Furthermore, the finer particle size also improves the handleability of the resulting carbonate-containing substance.

[0029] It is preferable to use liquid water as the substance that promotes the hydration reaction of the substance to be carbonated 100. Fresh water, tap water, distilled water, ion-exchanged water, pure water, rainwater, well water, lake water, river water, brackish water, salt water, seawater, or hot spring water may be used as the water 14 supplied to the substance to be carbonated 100. An example of the component composition of fresh water, seawater, or hot spring water is shown in Table 2 below.

[0030]

[0031] The maximum temperature of the substance 100 to be carbonated with the water 14 must be 100° C. or higher and 600° C. or lower. When the substance 100 to be carbonated has a maximum temperature of 600° C. or lower, water is brought into contact with the substance 100 to be carbonated to form hydroxide or hydrate.

[0032] When water comes into contact with a high-temperature substance to be carbonated, the water boils. At temperatures above the Leidenfrost point, which is film boiling, a vapor layer forms between the substance to be carbonated 100 and the water 14, inhibiting the elution of metal ions. Carbonated substances with low thermal conductivity, such as steelmaking slag and waste concrete, have a Leidenfrost point higher than approximately 600°C. Therefore, if the maximum temperature of the substance to be carbonated 100 is 600°C or lower, no vapor layer will form between the substance to be carbonated 100 and the water 14, allowing the elution of metal ions and the hydration reaction to proceed.

[0033] From the viewpoint of promoting the elution of metal ions, it is preferable that the maximum temperature of the substance to be carbonated 100 is as high as possible, provided that it is not higher than 600°C. On the other hand, the Ca(OH) produced by the hydration reaction ２and Mg(OH) ２ From the viewpoint of suppressing the decomposition of Ca(OH), the temperature is preferably 400° C. or less, and more preferably 300° C. or less. By setting the maximum temperature of the substance to be carbonated 100 to 300° C. or less, Ca(OH) ２ and Mg(OH) ２ It is also possible to suppress the decomposition of NaOH and KOH, which decompose at a lower temperature than the above.

[0034] Considering both the promotion of the elution of metal ions and the suppression of decomposition of the substance produced by the hydration reaction, the maximum temperature of the substance to be carbonated 100 in the hydration step is preferably 250° C. or higher and 400° C. or lower. This is disadvantageous from the viewpoint of promoting the elution of metal ions, but it is advantageous in preventing the decomposition of Ca(OH) produced by the hydration reaction. ２ and Mg(OH) ２ It is also preferable that the maximum temperature of the substance to be carbonated 100 in the hydration step is more than 400°C and not more than 600°C. This is because the decomposition of Ca(OH) produced by the hydration reaction is suppressed. ２ and Mg(OH) ２ This is because, although it is disadvantageous from the viewpoint of inhibiting the decomposition of the metal ions, it is advantageous from the viewpoint of promoting the elution of metal ions. By setting the maximum temperature of the substance to be carbonated 100 in the hydration step to 250°C or higher and 400°C or lower, or higher than 400°C and lower than 600°C, it is possible to produce a carbonate-containing substance with high carbonation efficiency.

[0035] The maximum temperature of the substance 100 to be carbonated during the hydration process can be measured by a plurality of thermocouples 16. The plurality of thermocouples 16 are inserted from the top toward the center of the substance 100 to be carbonated, and measure the temperature at a plurality of positions in the center of the substance 100 to be carbonated. The substance 100 to be carbonated stacked in the yard is cooled from the surroundings by spraying water or by leaving it to cool. For this reason, the temperature of the substance 100 to be carbonated during cooling is higher near the center than at the surface.

[0036] The degree of cooling of the substance to be carbonated 100 varies depending on the location during cooling. Therefore, the maximum temperature of the substance to be carbonated 100 can be measured by measuring the temperature at multiple locations in the center of the substance to be carbonated 100 and identifying the highest temperature at these multiple locations.

[0037] Instead of the multiple thermocouples 16, a thermograph may be used to measure the maximum temperature of the substance to be carbonated 100. When using a thermograph, the temperature difference between the center and the surface is determined in advance, the surface temperature of the substance to be carbonated 100 is measured by the thermograph, and the maximum temperature of the center calculated from the measured value and the temperature difference may be used as the maximum temperature of the substance to be carbonated 100.

[0038] The hydration process may be carried out while the maximum temperature of the substance to be carbonated 100 is kept constant, or may be carried out while the maximum temperature of the substance to be carbonated 100 is varied. When hydration is carried out while cooling, the maximum temperature of the substance to be carbonated 100 may be reduced to 600°C or less by spraying water on the substance to be carbonated 100 whose maximum temperature exceeds 600°C and cooling it. In the hydration process, the substance to be carbonated 100 whose maximum temperature is 100°C or more may be cooled to less than 100°C. In other words, when hydration is carried out while cooling the substance to be carbonated 100, it is sufficient that water 14 comes into contact with the substance to be carbonated 100 whose maximum temperature reaches 100°C or more and 600°C or less during the hydration process.

[0039] 2 is a schematic diagram showing a carbonation facility 20 capable of carrying out the carbonation step in the method for producing a carbonate-containing material according to this embodiment. The carbonation step in the method for producing a carbonate-containing material according to this embodiment will be described with reference to FIG.

[0040] The carbonation equipment 20 includes a cylindrical container 22 with a bottom, a spray nozzle 24, a gas ejection nozzle 28, an agitator blade 32, and a thermocouple 34. During the carbonation process, water 26 is supplied from the ejection nozzle 24 to a hydrated substance 100 to be carbonated, the maximum temperature of which is less than 100°C, contained in the container 22. A carbon dioxide-containing gas 30 is then blown into the water 26 from the gas ejection nozzle 28, and the water is stirred with the agitator blade 32. This allows carbon dioxide to dissolve in the water 26 as carbonate ions or bicarbonate ions and contact the substance 100. As a result, a carbonation reaction between metal hydroxides or hydrates contained in the substance 100 and carbonate ions or bicarbonate ions progresses, producing a carbonate-containing substance. The carbon dioxide-containing gas 30 shown in FIG. 2 is an example of a gaseous carbon dioxide-containing substance.

[0041] The carbon dioxide content of the carbon dioxide gas-containing gas 30 that is brought into contact with the substance to be carbonated 100 is preferably 1% by volume or more of the substance to be carbonated 100. By supplying carbon dioxide at 1% by volume or more of the substance to be carbonated 100, the substance to be carbonated 100 can be sufficiently carbonated. The water 26 supplied from the injection nozzle 24 is prevented from becoming strongly alkaline water, and the generation of strongly alkaline water during the carbonation process can be prevented.

[0042] The carbon dioxide gas-containing gas 30 blown from the gas ejection nozzle 28 may be a mixed gas 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 30 is preferably 0.03% by volume or more, and more preferably 1% by volume or more. By using a carbon dioxide gas-containing gas 30 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 substance to be carbonated 100. The carbon dioxide content in the carbon dioxide gas-containing gas 30 can be measured by component analysis of the carbon dioxide gas-containing gas 30.

[0043] The maximum temperature of the substance to be carbonated 100 in the carbonation step must be above 0°C and below 100°C. If the maximum temperature of the substance to be carbonated 100 exceeds 100°C, the temperature of the water will rise and the amount of carbon dioxide that can be dissolved will decrease, making it impossible to efficiently produce a carbonate-containing substance. The maximum temperature of the substance to be carbonated 100 in the carbonation step is preferably 90°C or less, more preferably 80°C or less, and even more preferably 60°C or less.

[0044] On the other hand, if the maximum temperature of the substance to be carbonated 100 falls below 0°C, the water 26 will freeze and it will no longer be possible to blow in the carbon dioxide gas-containing gas 30, making it impossible to produce a carbonate-containing substance. For this reason, the maximum temperature of the substance to be carbonated 100 in the carbonation process must be above 0°C. The higher the temperature of the water 26 in the carbonation process, the more the carbonation reaction will be promoted. If the maximum temperature of the substance to be carbonated 100 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 substance to be carbonated 100 is preferably above 10°C, and more preferably above 20°C.

[0045] The maximum temperature of the substance 100 to be carbonated during the carbonation process is measured by a thermocouple 34. The thermocouple 34 is inserted into the water 26. Because the water 26 is being stirred by the stirring blades 32, the water 26 and the substance 100 to be carbonated have the same temperature. Therefore, by measuring the temperature of the water 26 using the thermocouple 34, the temperature of the substance 100 to be carbonated during the carbonation process can be determined.

[0046] The carbonation process may also be carried out while keeping the maximum temperature of the substance to be carbonated 100 constant, or may be carried out while varying the maximum temperature of the substance to be carbonated 100. When the carbonation process is carried out while cooling the substance to be carbonated 100, water may be sprayed on the substance to be carbonated 100, which has a maximum temperature of 100°C or higher, to cool it down so that the maximum temperature of the substance to be carbonated 100 is less than 100°C. In other words, when the carbonation process is carried out while cooling the substance to be carbonated 100, it is sufficient that a state in which the carbon dioxide-containing substance comes into contact with the substance to be carbonated 100, whose maximum temperature has reached above 0°C and less than 100°C during the carbonation process, is included.

[0047] The time for blowing the carbon dioxide-containing gas 30 into the water 26 and contacting it is preferably 1 minute or more. This allows the carbon dioxide to come into contact with the substance to be carbonated 100, allowing the carbonate-containing substance to be produced efficiently. The time for supplying the carbon dioxide-containing gas 30 is more preferably 10 minutes or more.

[0048] As described above, in the method for producing carbonate according to this embodiment, water 14 is brought into contact with a substance to be carbonated 100 having a maximum temperature of 600°C or less to produce a hydroxide- and hydrate-containing substance. Carbon dioxide is then supplied at a maximum temperature of less than 100°C to produce a carbonate-containing substance. This promotes the production of hydroxides and hydrates, while allowing the carbonate-containing substance to be produced from the hydroxides and hydrates. Because metal hydroxides and hydrates are more easily carbonated than the metals themselves, the method for producing a carbonate-containing substance according to the present invention can produce a carbonate-containing substance more efficiently than conventional methods without using a sealed container.

[0049] The embodiments of the present invention are not limited to the above embodiment and various modifications can be made. In the example shown in FIG. 1 , water 14 is brought into contact with the substance to be carbonated 100 to promote the hydration reaction, but the present invention is not limited to this. Instead of water 14, ice may be brought into contact with the substance to be carbonated 100 to promote the hydration reaction. When ice is brought into contact with the high-temperature substance to be carbonated, the heat of fusion from ice to water is required, further increasing the Leidenfrost point. As described above, the evaporation rate of ice is slower than that of water, so contacting ice with the substance to be carbonated 100 can further promote the elution of metal ions from the substance to be carbonated 100. When ice is used instead of water 14, the supply amount of water is adjusted so that the total amount of water contained in the ice is 1% or more by volume of the substance to be carbonated 100.

[0050] 2 shows an example in which a carbonate-containing substance is produced by blowing a carbon dioxide gas-containing gas 30 into water 26 containing a substance to be carbonated 100, but this is not limiting. Instead of the carbon dioxide gas-containing gas 30, at least one of carbon dioxide-containing water, carbonate ion-containing water, and bicarbonate ion-containing water may be brought into contact with the substance to be carbonated 100 to produce a carbonate-containing substance. Carbon dioxide-containing water, carbonate ion-containing water, and bicarbonate ion-containing water are examples of carbon dioxide-containing substances that are liquids. When carbon dioxide-containing water, carbonate ion-containing water, and bicarbonate ion-containing water are used, water 26 does not need to be used. Carbon dioxide gas-containing water or carbon dioxide-containing gas-containing water may be used as the carbon dioxide-containing water.

[0051] Furthermore, instead of the carbon dioxide gas-containing gas 30, dry ice may be immersed in water 26 to produce the carbonate-containing substance. Dry ice is an example of a solid carbon dioxide-containing substance. When carbon dioxide gas-containing water, carbonate ion-containing water, bicarbonate ion-containing water, and dry ice are used, 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 substance 100 to be carbonated.

[0052] In this way, the carbonation step can be carried out using gaseous, liquid, and solid carbon dioxide-containing substances. Among gaseous, liquid, and solid carbon dioxide-containing substances, it is preferable to use gaseous carbon dioxide-containing substances because they are inexpensive and easy to handle.

[0053] Next, an example will be described in which a carbonate-containing substance was produced using steelmaking slag (converter furnace slag) as the substance to be carbonated. In this example, steelmaking slag pulverized to a maximum particle size of 2 mm or less was used as the substance to be carbonated, and carbonate-containing substances were produced under various conditions using the hydration equipment 10 shown in FIG. 1 and the carbonation equipment 20 shown in FIG. 2. In the carbonation equipment 20, the agitator blades 32 were rotated at 200 rpm to carry out the carbonation step. The production conditions for the hydration step are shown in Table 3 below, and the production conditions and carbonation efficiency for the carbonation step are shown in Table 4 below.

[0054]

[0055]

[0056] The temperature shown in the column "Maximum temperature of material to be carbonated at the start of hydration treatment" in Table 3 is the highest temperature among the multiple temperatures measured by inserting multiple thermocouples from the top surface to the center of the steelmaking slag piled in the yard at the start of hydration treatment. The temperature shown in the column "Minimum temperature of material to be carbonated at the end of hydration treatment" is the lowest temperature among the multiple temperatures measured by multiple thermocouples at the end of hydration treatment. The temperature shown in the column "Maximum temperature during carbonation process" in Table 4 is the highest water temperature measured by inserting a thermocouple into water during the carbonation treatment.

[0057] In the "medium" column, "gas" is a production example in which a carbonate-containing substance was produced by bringing carbon dioxide gas into contact with steelmaking slag. "gas + liquid" is a production example in which a carbonate-containing substance was produced using water containing carbon dioxide gas. "solid" is a production example in which a carbonate-containing substance was produced using dry ice. "liquid" is a production example in which a carbonate-containing substance was produced using water containing carbonate ions or water containing bicarbonate ions.

[0058] The values ​​shown in the "Water Sprinkler Amount" column are the total amount of water contained in the water 14 or ice supplied from the water sprinkler nozzle 12. The values ​​shown in the "Carbonation Efficiency" column are the values ​​obtained by dividing the carbonate content (mass%) by the amount of carbonated substances that can be produced (mass%) and multiplying this by 100. The amount of carbonated substances that can be produced is determined by the amount of CaO, Na ２ O.K. 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 substance can be produced.

[0059] As shown in Tables 3 and 4, Production Examples 1 to 8 are examples of the invention in which carbonate-containing substances were produced by varying the maximum temperature of the substance to be carbonated at the start of hydration, while maintaining the same carbon dioxide content and water spray rate relative to the substance to be carbonated. Production Examples 1 to 5 in which the temperature at the start of hydration was 250 to 600°C achieved a carbonation efficiency of 75.0% or higher. Of these, Production Example 4, in which the temperature at the start of hydration was 300°C, achieved the highest carbonation efficiency of 80.8%.

[0060] In contrast, in Production Example No. 6, where the temperature at the start of the hydration treatment was 200°C, the carbonation efficiency decreased to 72.0%. Furthermore, in Production Example No. 7, where the temperature of the substance to be carbonated was 150°C, the carbonation efficiency decreased to 69.1%. These results confirmed that the temperature of the substance to be carbonated is preferably 250°C or higher and 600°C or lower, and more preferably 250°C or higher and 400°C or lower. When the temperature of the substance to be carbonated is 250°C or higher, although some of the hydroxides or hydrates of Na and K decompose, the rate of production of hydroxides or hydrates of Ca, Mg, Na, and K increases, thereby increasing the rate of production of hydroxides or hydrates throughout the system and increasing the amount of these produced. This is thought to be the reason for the high carbonation efficiency in Production Examples No. 1 to No. 5.

[0061] Production Example No. 4 is a production example in which a carbonate-containing substance was produced by adjusting the carbon dioxide concentration in the carbon dioxide-containing gas to 100% by volume. On the other hand, Production Example No. 9 is a production example in which a carbonate-containing substance was produced by adjusting the carbon dioxide concentration in the gas to 0.03% by volume. Comparing Production Example No. 4 and Production Example No. 9, the carbonation efficiency of Production Example No. 4 was 80.7%, while the carbonation efficiency of Production Example No. 9 was 1.7%. Although the carbonation efficiency decreased with the decrease in carbon dioxide concentration, a carbonation efficiency of 1.0% or more was ensured. From these results, it was confirmed that the carbon dioxide concentration in the carbon dioxide-containing gas is preferably 0.03% by volume or more.

[0062] Production Examples 10 to 12 are examples of the invention in which carbonate-containing substances were produced using different types of carbon dioxide while maintaining the same carbon dioxide content and water spray rate relative to the substance to be carbonated. Comparing Production Example 4 with Production Examples 10 to 12, the carbonation efficiency of No. 4 was 80.7%, while Nos. 10 to 12, which used different types of carbon dioxide, also had carbonation efficiencies of 78.6% or higher. These results confirm that carbonate-containing substances can be produced with high efficiency regardless of the type of carbon dioxide, as long as the carbon dioxide concentration is the same.

[0063] Production Example No. 4 is an example of the invention in which a carbonate-containing substance was produced by spraying 10% by volume of water relative to the steelmaking slag. On the other hand, Production Example No. 13 is an example of the invention in which a carbonate-containing substance was produced by spraying 1% by volume of water relative to the steelmaking slag. Comparing Production Example No. 4 and Production Example No. 13, the carbonation efficiency of Production Example No. 4 was 80.7%, while the carbonation efficiency of Production Example No. 13 was 4.2%. These results confirmed that a carbonate-containing substance can be produced with high efficiency by spraying 10% or more by volume of water relative to the steelmaking slag, which is the substance to be carbonated.

[0064] Production Examples 14 to 16 are examples of the invention in which carbonate-containing substances were produced using different types of water while maintaining the same carbon dioxide content and water spray rate relative to the substance to be carbonated. Comparing Production Example 3 with Production Examples 14 to 16, the carbonation efficiency of Production Example 3 was 75.4%, while Production Examples 14 to 16, which used ice instead of water, had a carbonation efficiency of over 80%. In Production Example 14, the use of ice likely increased the temperature at the Leidenfrost point, prolonging the time it took for the water to reach film boiling and increasing the rate of hydroxide and hydrate production. In Production Examples 15 and 16, seawater and hot spring water were used, and the chlorides, sulfides, and sulfates contained in the seawater and hot spring water promoted carbonation, confirming that carbonate-containing substances could be produced with high efficiency.

[0065] Production Examples Nos. 17 and 18 are examples of the invention in which carbonate-containing substances were produced by changing the type of substance to be carbonated while maintaining the same carbon dioxide content and water spray rate relative to the substance to be carbonated. Comparing Production Example No. 4 with Production Examples 17 and 18, the amount of carbonated substance produced in Production Example No. 4 was 52.6 mass%, while the amount of carbonated substance produced in Production Examples 17 and 18, which used different types of substance to be carbonated, was 60 mass% or more. Compared to steelmaking 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, Production Examples 17 and 18, which used waste concrete or biomass incineration ash as the substance to be carbonated, were able to produce a larger amount of carbonated substances than Production Example 4, which used steelmaking slag as the substance to be carbonated, and as a result, the amount of carbonated substances produced also increased.

[0066] Production Examples 19 to 22 are examples of the invention in which carbonate-containing substances were produced by varying the maximum temperature of the substance to be carbonated during the carbonation process while maintaining the same carbon dioxide content and water spray rate relative to the substance to be carbonated. Comparing Production Example 4 with Production Examples 19 to 21, the carbonation efficiency of Production Example 4 was 80.7%, whereas the carbonation efficiency of Production Examples 19 to 21, in which the maximum temperature of the substance to be carbonated during the carbonation process was increased to 60 to 90°C, decreased to less than 80%. Among Production Examples 19 to 21, the carbonation efficiency increased as the maximum temperature of the substance to be carbonated was decreased from 90°C to 60°C.

[0067] As the water temperature increases during the carbonation process, the amount of carbon dioxide that can be dissolved in water decreases. Therefore, it is believed that the carbonation efficiency gradually decreased as the maximum temperature of the substance to be carbonated increased. Meanwhile, the carbonation efficiency of Production Example No. 22, in which the maximum temperature of the substance to be carbonated during the carbonation process was 10°C, was slightly lower than that of Production Example No. 4. In the carbonation process, the carbonation reaction is promoted more when the water temperature is higher. When the maximum temperature of the substance to be carbonated 100 is above 0°C but below 20°C, the improvement in carbonation efficiency due to the promotion of the carbonation reaction is greater than the decrease in carbonation efficiency due to the decrease in the amount of dissolved carbon dioxide caused by the increase in temperature. This is believed to be why the carbonation efficiency of Production Example No. 4 was higher than that of Production Example No. 22.

[0068] From these results, it was confirmed that the maximum temperature of the substance to be carbonated in the carbonation step is preferably 90° C. or less, more preferably 80° C. or less, and even more preferably 60° C. or less. It was confirmed that the lower limit temperature of the maximum temperature of the substance to be carbonated in the carbonation step is preferably 10° C. or more, and more preferably 20° C. or more.

[0069] Production Examples 23 and 24 are comparative examples in which a carbonate-containing substance was produced by increasing the maximum temperature at the start and minimum temperature at the end of the hydration step to greater than 600°C. Comparing Production Example 4 with Production Examples 23 and 24, the carbonation efficiency of Production Example 4 was 80.7%, while the carbonation efficiency of Production Examples 23 and 24 was 0.0%. These results confirmed that when the maximum temperature of the substance to be carbonated in the hydration step exceeds 600°C, the produced hydroxides and hydrates decompose, making it impossible to produce a carbonate-containing substance.

[0070] Production Examples 25 and 26 are comparative examples in which a carbonate-containing substance was produced without contact with carbon dioxide. Comparing Production Example 4 with Production Examples 25 and 26, the carbonation efficiency of Production Example 4 was 80.7%, while the carbonation efficiency of Production Examples 25 and 26 was 0.0%. These results confirmed that in the carbonation step, a carbonate-containing substance can be produced with high carbonation efficiency by contacting a hydrated substance to be carbonated with a carbon dioxide-containing substance, carbonate ion-containing water, or bicarbonate ion-containing water.

[0071] Production Examples 27 and 28 are comparative examples in which a carbonate-containing substance was produced by contacting water with a carbonate-containing substance having a maximum temperature of 90°C or 0°C, followed by contact with carbon dioxide at 20°C or 0°C. Comparing Production Example 4 with Production Examples 27 and 28, the carbonation efficiency of Production Example 4 was 80.7%, while the carbonation efficiencies of Production Examples 27 and 28 were 0.9% and 0.0%, respectively. It is believed that when the maximum temperature of the substance to be carbonated in the hydration step is less than 100°C, the rate of metal ion elution slows, resulting in a decrease in the amount of hydroxide and hydrate produced, which in turn reduces the amount of carbonate-containing substance produced. These results confirm that a carbonate-containing substance can be produced with high carbonation efficiency by contacting water with a substance to be carbonated at a maximum temperature of 100°C or higher but not higher than 600°C in the hydration step.

[0072] Production Example No. 29 is a comparative example in which a carbonate-containing substance was produced by setting the maximum temperature of the substance to be carbonated in the carbonation step to 100°C. Comparing Production Example No. 4 and Production Example No. 29, the carbonation efficiency of Production Example No. 4 was 80.7%, while the carbonation efficiency of Production Example No. 29 was 0.8%. It is believed that when the maximum temperature of the substance to be carbonated in the carbonation step is 100°C or higher, the amount of carbon dioxide that can be dissolved in water is significantly reduced, resulting in a decrease in carbonation efficiency. These results confirm that a carbonate-containing substance can be produced with high carbonation efficiency by contacting a carbon dioxide-containing substance with a substance to be carbonated whose maximum temperature is above 0°C and below 100°C in the carbonation step.

[0073] Furthermore, in Production Examples 1 to 22, the hydration time was set to 10 minutes or more, and the maximum particle size after hydration was 1.9 mm or less, which improved the carbonation rate in the carbonation step and also improved the handleability of the carbonate-containing material.

[0074] 10 Hydration equipment 12 Spray nozzle 14 Water 16 Thermocouple 20 Carbonation equipment 22 Container 24 Spray nozzle 26 Water 28 Gas ejection nozzle 30 Carbon dioxide gas-containing gas 32 Stirring blade 34 Thermocouple 100 Substance to be carbonated

Claims

1. A method for producing a carbonate-containing substance, comprising: a hydration step in which water or ice is brought into contact with a substance to be carbonated and the maximum temperature of which is between 100°C and 600°C to hydrate it; and a carbonation step in which water and a carbon dioxide-containing substance, or at least one of carbon dioxide-containing water, carbonate ion-containing water, and bicarbonate ion-containing water, are brought into contact with the hydrated substance to be carbonated and the maximum temperature of which is between 0°C and 100°C, wherein the total amount of water or ice brought into contact with the substance to be carbonated in the hydration step is 1% by volume or more of the substance to be carbonated.

2. A method for producing a carbonate-containing material as described in claim 1, wherein the total content of carbon dioxide contained in at least one of the carbon dioxide-containing material, the carbonate ion-containing water, and the bicarbonate ion-containing water is 1% by volume or more of the material to be carbonated.

3. The method for producing a carbonate-containing material according to claim 1 or 2, wherein the carbon dioxide-containing material is a gas.

4. A method for producing a carbonate-containing substance according to any one of claims 1 to 3, wherein the particle size of the substance 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.

5. A method for producing a carbonate-containing material according to any one of claims 1 to 4, wherein the material to be carbonated is steelmaking slag.

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