Carbonation process and carbonation apparatus

Abstract

To provide a carbonation process and a carbonation apparatus that can reduce a use amount of a heavy metal stabilizer.SOLUTION: A carbonation process for performing carbonation by bringing carbon dioxide into contact with a carbonation object includes: a water supply step for supplying a water content to a carbonation object; and a carbon dioxide supply step for supplying and bringing the carbon dioxide into contact with the carbonation object, after the water supply step. Prior to the carbon dioxide supply step, a heavy metal stabilizer for restricting elution of heavy metal contained in the carbonation object is added to the carbonation object.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a carbonation process and a carbonator. [Background technology]

[0002] Carbonation targets, such as fly ash generated by incinerating household and industrial waste, contain alkaline components such as calcium, which are unreacted components of slaked lime used to neutralize exhaust gases. Therefore, when the target is brought into contact with carbon dioxide, the target reacts with carbonate ions, resulting in carbonation. The carbonates thus produced can be used as aggregates for concrete and other products. However, the target may contain heavy metals such as lead and cadmium, and treatment to prevent the heavy metals from leaching out is required before the target can be used.

[0003] Patent Document 1 describes a method for suppressing the elution of heavy metals contained in a material to be carbonated by adding a heavy metal stabilizer to the material to be carbonated. The carbonation process described in Patent Document 1 includes a water supply step for supplying water to the material to be carbonated, a carbon dioxide supply step for bringing the material to be carbonated into contact with carbon dioxide, and a granulation step for granulating the material to be carbonated after carbonation is complete, and the heavy metal stabilizer is added during carbonation of the material to be carbonated or after carbonation is complete. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-273374 Summary of the Invention [Problem to be solved by the invention]

[0005] If the heavy metal stabilizer is added during or after the carbonation of the object to be carbonated, as in Patent Document 1, anions such as carbonate ions inhibit contact between the heavy metal stabilizer and the heavy metals, making it impossible to efficiently suppress the elution of heavy metals. This increases the amount of heavy metal stabilizer used, leading to increased treatment costs.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to provide a carbonation process and a carbonation apparatus that can reduce the amount of heavy metal stabilizer used. [Means for solving the problem]

[0007] The characteristic configuration of the carbonation process of the present invention is a carbonation process in which carbonation is carried out by bringing carbon dioxide into contact with the object to be carbonated, and includes a water supply step in which water is supplied to the object to be carbonated, and a carbon dioxide supply step in which carbon dioxide is supplied to and brought into contact with the object to be carbonated after the water supply step, and a heavy metal stabilizer that suppresses the leaching of heavy metals contained in the object to be carbonated is added to the object to be carbonated prior to the carbon dioxide supply step.

[0008] According to this configuration, in the carbonation process, the heavy metal stabilizer is added to the material to be carbonated before the carbon dioxide supply step, in which the material to be carbonated is brought into contact with carbon dioxide. This allows the heavy metals to be stabilized before the material to be carbonated, so that the stabilization of the heavy metals is not hindered by anions such as carbonate ions generated in the carbon dioxide supply step. In this way, by adding the heavy metal stabilizer at the appropriate time, the reaction efficiency of the heavy metal stabilizer can be maximized, thereby reducing the amount of heavy metal stabilizer used.

[0009] A further characteristic feature of the present invention is that the heavy metal stabilizing agent is in the form of a powder, and is added prior to the water supply step.

[0010] According to this configuration, by adding the powdered heavy metal stabilizer before the water supply step, the heavy metal stabilizer and the material to be carbonated can be uniformly mixed, which prevents localized uneven distribution of the heavy metal stabilizer and increases the contact area between the heavy metal stabilizer and the heavy metals contained in the material to be carbonated, thereby improving the reaction efficiency of the heavy metal stabilizer.

[0011] A further characteristic feature of the present invention is that the heavy metal stabilizing agent is liquid, and is added in the water supply step.

[0012] According to this configuration, adding a liquid heavy metal stabilizer in the water supply step allows the water, the material to be carbonated, and the heavy metal stabilizer to be mixed uniformly. Because the liquid heavy metal stabilizer easily disperses in water, adding it in the water supply step can prevent localized uneven distribution of the heavy metal stabilizer compared to adding it in the pre-mixing step. This increases the contact area between the heavy metal stabilizer and the heavy metals contained in the material to be carbonated, thereby improving the reaction efficiency of the heavy metal stabilizer.

[0013] A further characteristic configuration of the present invention is that it further includes a measuring step of measuring the heavy metal content of the object to be carbonated, and adds the heavy metal stabilizer in powder or liquid form depending on the heavy metal content.

[0014] Powder heavy metal stabilizers are chemicals themselves, so they have high concentrations but are difficult to handle. Liquid heavy metal stabilizers are easy to handle, but are chemicals dissolved in a solvent, so their concentrations are low. Therefore, according to this configuration, the heavy metal content of the carbonation target is measured in the measurement step, and either a powder heavy metal stabilizer or a liquid heavy metal stabilizer is used depending on the measured value, thereby enabling the heavy metal stabilizer to be added efficiently. For example, by adding a powder heavy metal stabilizer when the heavy metal content is high and adding a liquid heavy metal stabilizer when the heavy metal content is low, the handleability of the heavy metal stabilizer can be improved.

[0015] A further characteristic feature of the present invention is that the heavy metal includes hexavalent chromium.

[0016] Among the heavy metals contained in the carbonation target, lead, zinc, etc. are stabilized and their elution is suppressed by carbonation, but hexavalent chromium is not stabilized by carbonation. According to this configuration, hexavalent chromium, which is not stabilized by carbonation, is stabilized by the heavy metal stabilizer and its elution is suppressed, thereby reducing the amount of chemical used.

[0017] The characteristic configuration of the carbonation device of the present invention is a carbonation device that carbonates an object to be carbonated by bringing carbon dioxide into contact with the object, and includes an agitation unit that agitates and mixes the object to be carbonated, a water supply unit that supplies water to the object to be carbonated, a carbon dioxide supply unit that supplies carbon dioxide to the object to be carbonated, a heavy metal stabilizer addition unit that adds a heavy metal stabilizer that suppresses the leaching of heavy metals contained in the object to be carbonated, and a control unit that controls the addition of the heavy metal stabilizer, wherein the control unit controls the addition of the heavy metal stabilizer before the carbon dioxide is supplied to the object to be carbonated.

[0018] According to this configuration, the control unit controls the addition of the heavy metal stabilizer before carbon dioxide is supplied to the material to be carbonated. This allows the heavy metals to be stabilized before the material to be carbonated, so that the stabilization of the heavy metals is not hindered by anions such as carbonate ions generated during carbonation. In this way, by adding the heavy metal stabilizer at the appropriate time, the reaction efficiency of the heavy metal stabilizer can be maximized, thereby reducing the amount of heavy metal stabilizer used.

[0019] A further characteristic feature of the present invention is that it further comprises a measuring unit that measures the heavy metal content of the carbonation object, and the control unit controls the addition of the powder or liquid heavy metal stabilizer depending on the heavy metal content measured by the measuring unit.

[0020] Powdered heavy metal stabilizers are chemicals themselves, so they have high concentrations but are difficult to handle. Liquid heavy metal stabilizers are easy to handle, but are chemicals dissolved in a solvent, so their concentrations are low. Therefore, with this configuration, the measurement unit measures the heavy metal content of the carbonation target, and the control unit selectively uses either the powdered or liquid heavy metal stabilizer depending on the measurement value, thereby enabling the heavy metal stabilizer to be added efficiently. For example, by adding a powdered heavy metal stabilizer when the heavy metal content is high and adding a liquid heavy metal stabilizer when the heavy metal content is low, the handleability of the heavy metal stabilizer can be improved.

[0021] A further characteristic feature of the present invention is that, when adding the heavy metal stabilizer in powder form, the control unit controls the addition of the heavy metal stabilizer before the supply of the moisture and the carbon dioxide.

[0022] According to this configuration, by adding the powdered heavy metal stabilizer to the material to be carbonated before the supply of water and carbon dioxide, the heavy metal stabilizer and the material to be carbonated can be mixed uniformly. In particular, by adding the heavy metal stabilizer before the supply of water and then mixing and stirring the heavy metal stabilizer and the material to be carbonated, it is possible to suppress localized uneven distribution of the heavy metal stabilizer. This increases the contact area between the heavy metal stabilizer and the heavy metals contained in the material to be carbonated, thereby improving the reaction efficiency of the heavy metal stabilizer.

[0023] A further characteristic feature of the present invention is that, when the heavy metal stabilizing agent is added in liquid form, the control unit controls the addition of the heavy metal stabilizing agent simultaneously with the supply of the water.

[0024] According to this configuration, adding a liquid heavy metal stabilizer simultaneously with the supply of water allows the water, the material to be carbonated, and the heavy metal stabilizer to be mixed uniformly. Because liquid heavy metal stabilizers easily disperse in water, adding the heavy metal stabilizer simultaneously with the supply of water can suppress localized uneven distribution of the heavy metal stabilizer compared to adding the heavy metal stabilizer before the supply of water. This increases the contact area between the heavy metal stabilizer and the heavy metals contained in the material to be carbonated, thereby improving the reaction efficiency of the heavy metal stabilizer. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a schematic diagram showing the device configuration of a carbonation device according to an embodiment. [Figure 2] FIG. 1 is a process block diagram of a carbonation process according to a first embodiment. [Figure 3] FIG. 1 is a process block diagram of a carbonation process according to a second embodiment. [Figure 4] FIG. 10 is a process block diagram of a carbonation process according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the carbonation process and carbonation device according to the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and various modifications are possible within the scope of the present invention.

[0027] First Embodiment A carbonation process and a carbonation device 10 according to this embodiment will be described with reference to Figures 1 and 2. As shown in Figure 1, the carbonation device 10 has an agitation unit 1, a water supply unit 2, a carbon dioxide supply unit 3, and a heavy metal stabilizing agent addition unit 4. The carbonation target A, water, and carbon dioxide are supplied to the agitation unit 1 and agitated, thereby carbonating the carbonation target A. Furthermore, the addition of a heavy metal stabilizing agent to the agitation unit 1 suppresses the elution of heavy metals contained in the carbonation target A.

[0028] Carbonation target A is, for example, bottom ash or fly ash generated when general garbage or industrial waste is incinerated in an incinerator, or incineration ash from woody biomass power generation. Carbonation target A may also be slag generated in the steel manufacturing process, or recycled aggregate, sludge, or dust generated in the concrete recycling process. Carbonation target A may also be a mixture of these. Such carbonation target A contains calcium derived from slaked lime, etc., and heavy metals such as lead and cadmium.

[0029] The stirring unit 1 is a known mixer such as a twin-shaft mixer with stirring blades, a vortex mixer, a paddle mixer, etc. The material A to be carbonated supplied to the stirring unit 1 is mixed and stirred in the stirring unit 1, thereby being uniformly broken down into small particles.

[0030] The water supply unit 2 supplies water, such as purified water or industrial water, to the agitation unit 1. The water supply unit 2 may have a pump for pressurizing the water, a nozzle for spraying water toward the agitation unit 1, or the like. The amount of water supplied to the agitation unit 1 may be determined based on the weight of the object A to be carbonated, etc. By agitating the object A to be carbonated and the water in the agitation unit 1, they are mixed uniformly and the object A to be carbonated and the water come into contact with each other.

[0031] The carbon dioxide supply unit 3 supplies, for example, air or exhaust gas to the agitation unit 1 to supply carbon dioxide to the agitation unit 1. The exhaust gas may be, for example, gas generated from an incinerator that produces the carbonation target A. The carbon dioxide supply unit 3 may also supply only carbon dioxide to the agitation unit 1. The carbon dioxide supplied to the agitation unit 1 by the carbon dioxide supply unit 3 dissolves in water to produce carbonic acid, which then ionizes to produce carbonate ions. The carbonate ions react with components in the carbonation target A, thereby carbonating the carbonation target A. When carbonation of the carbonation target A is performed using exhaust gas, the carbon dioxide in the exhaust gas can be fixed, making it possible to reduce carbon dioxide emissions from the incinerator that produces the carbonation target A.

[0032] The carbonation target A carbonated in this manner is granulated by various granulation methods, such as tumbling granulation, stirring granulation, and extrusion granulation, and then used as aggregate for concrete, for example. Meanwhile, the granulated product obtained by carbonating and granulating the carbonation target A may contain heavy metals. While some heavy metals, such as lead, are stabilized and prevented from leaching by carbonation, some heavy metals, such as hexavalent chromium, cannot be prevented from leaching by carbonation. Therefore, the carbonation device 10 according to this embodiment includes a heavy metal stabilizer adding unit 4 that adds a heavy metal stabilizer that prevents the leaching of heavy metals, such as hexavalent chromium, and a control unit 5 that controls the heavy metal stabilizer adding unit 4.

[0033] The heavy metal stabilizer adding unit 4 adds a heavy metal stabilizer such as a phosphate-based agent or a chelating agent to the stirring unit 1. The heavy metal stabilizer adding unit 4 may include a tank for storing the heavy metal stabilizer, and a pump or nozzle for pressure-feeding the tank to the stirring unit 1. The heavy metal stabilizer in this embodiment is preferably one that reduces hexavalent chromium contained in the carbonation target A to trivalent chromium, and specifically, ferrous sulfate can be used. Furthermore, the heavy metal stabilizer in this embodiment is a powder. When the heavy metal stabilizer is a powder, the powder itself can be used as a chemical agent, thereby increasing the concentration of the heavy metal stabilizer.

[0034] The control unit 5 has a processor and controls the operation of the heavy metal stabilizing agent adding unit 4. The processor includes an ASIC, an FGPA, a CPU, or other hardware for executing applications and the like stored in a memory unit (not shown) of the carbonation device 10.

[0035] The control unit 5 controls the heavy metal stabilizer adding unit 4 to supply the heavy metal stabilizer to the stirring unit 1 before carbon dioxide is supplied to the stirring unit 1. Adding the heavy metal stabilizer after carbon dioxide is supplied to the stirring unit 1 may reduce the reaction efficiency between the heavy metal stabilizer and the heavy metal. This is thought to be because anions such as carbonate ions generated by the supply of carbon dioxide inhibit the reaction between the heavy metal stabilizer and the heavy metal. Specifically, ferrous sulfate added to the stirring unit 1 reacts with hexavalent chromium to form a precipitate, and the presence of carbonate ions at this time is thought to inhibit the reaction between ferrous sulfate and hexavalent chromium. Therefore, adding the heavy metal stabilizer after carbon dioxide is supplied can improve the reaction efficiency between the heavy metal stabilizer and the heavy metal, thereby reducing the amount of heavy metal stabilizer used.

[0036] More specifically, the control unit 5 controls the heavy metal stabilizer adding unit 4 to supply the heavy metal stabilizer to the stirring unit 1 before water and carbon dioxide are supplied to the stirring unit 1. This allows the material A to be carbonated and the heavy metal stabilizer to be stirred and mixed in the stirring unit 1 in the absence of water and carbon dioxide, thereby preventing the heavy metal stabilizer from being locally distributed unevenly in the material A to be carbonated. Uniform mixing of the material A to be carbonated and the heavy metal stabilizer increases the contact area between the heavy metal stabilizer and the heavy metal contained in the material A to be carbonated, thereby increasing the efficiency of their reaction. The timing of adding the heavy metal stabilizer may be before the material A to be carbonated is supplied to the stirring unit 1, or may be simultaneous with or after the supply of the material A to be carbonated.

[0037] The carbonation apparatus 10 may further include a measurement unit 6 that measures the type and concentration of heavy metals contained in the carbonation target A. In this embodiment, the measurement unit 6 is provided on a supply path that supplies the carbonation target A to the stirring unit 1, but the installation location of the measurement unit 6 is not limited thereto and the measurement unit 6 may be provided in the stirring unit 1. The type and concentration of heavy metals contained in the carbonation target A may be measured before the carbonation target A is supplied to the carbonation apparatus 10. The control unit 5 may increase or decrease the amount of heavy metal stabilizer to be added based on the heavy metal content measured by the measurement unit 6. For example, if the concentration of hexavalent chromium in the carbonation target A supplied to the stirring unit 1 is low, the amount of heavy metal stabilizer added may be reduced. This allows the amount of heavy metal stabilizer used to be optimized.

[0038] Next, the carbonation process according to the first embodiment will be described with reference to Figure 2. The carbonation process is performed by a control unit (not shown) that controls the carbonation device 10. First, a step of supplying the carbonation target A is performed, in which the carbonation target A is supplied to the agitation unit 1 and agitated and mixed (#01). Next, a step of adding a heavy metal stabilizer is performed, in which a powdered heavy metal stabilizer is added to the agitation unit 1 and agitated and mixed (#02). This allows the carbonation target A and the heavy metal stabilizer to be uniformly mixed.

[0039] Next, a water supply step is performed, in which water is supplied to the stirring unit 1, and the carbonation target A and the water are stirred and mixed (#03). This brings the carbonation target A into contact with the water. Finally, a carbon dioxide supply step is performed, in which carbon dioxide is supplied to the stirring unit 1, and the carbonation target A and other components are stirred and mixed (#04). The carbon dioxide supplied to the stirring unit 1 dissolves in water, and the resulting carbonate ions react with components contained in the carbonation target A, resulting in the carbonation of the carbonation target A. In the carbon dioxide supply step, the generated carbonate ions tend to inhibit the reaction between the heavy metal stabilizer and the heavy metals. However, in this embodiment, the heavy metal stabilizer is added before the water supply step, so the heavy metals are stabilized and their elution is suppressed before the carbon dioxide supply step. Therefore, it is possible to carbonate the carbonation target A without reducing the reaction efficiency of the heavy metal stabilizer. Note that stirring in the stirring unit 1 is performed continuously during the carbonation process.

[0040] Second Embodiment Next, a carbonation device 10 and a carbonation process according to a second embodiment will be described with reference to Figures 1 and 3. In the second embodiment, a liquid heavy metal stabilizer is used. The liquid heavy metal stabilizer is a chemical dissolved in a solvent, so it has a low concentration but is easy to handle. For example, ferrous sulfate dissolved in water can be used as such a liquid heavy metal stabilizer.

[0041] In the second embodiment, the control unit 5 controls the heavy metal stabilizer adding unit 4 to add the heavy metal stabilizer to the agitator 1 simultaneously with the supply of water by the water supply unit 2. Because liquid heavy metal stabilizers easily disperse in water, localized uneven distribution of the heavy metal stabilizer in the carbonation target A can be suppressed compared to adding the heavy metal stabilizer to the agitator 1 before the supply of water. This increases the contact area between the heavy metal stabilizer and the heavy metals contained in the carbonation target A, thereby improving the reaction efficiency of the heavy metal stabilizer. Furthermore, as in the first embodiment, the heavy metal stabilizer is added before the supply of carbon dioxide, so the reaction between the heavy metal stabilizer and the heavy metals in the carbonation target A is not inhibited by carbonate ions. The heavy metal stabilizer may be added simultaneously with the supply of water or after the supply of water but before the supply of carbon dioxide. Other configurations of the carbonation device 10 are the same as those in the first embodiment, and therefore detailed description of the same configurations as those in the first embodiment will be omitted.

[0042] Next, the carbonation process according to the second embodiment will be described with reference to Figure 3. First, a carbonation object supply step is performed, in which the carbonation object A is supplied to the agitation unit 1 and stirred and mixed (#11). Next, a water supply step is performed, in which moisture is supplied to the agitation unit 1 (#12), and a heavy metal stabilizer addition step is performed, in which a liquid heavy metal stabilizer is added to the agitation unit 1 and the carbonation object A, moisture, and heavy metal stabilizer are stirred and mixed (#13). As a result, the surface of the carbonation object A comes into contact with water, and the heavy metals contained in the carbonation object A react with the heavy metal stabilizer, suppressing elution of the heavy metals.

[0043] Finally, a carbon dioxide supply step is performed, in which carbon dioxide is supplied to the stirring unit 1 and the carbonation target A and other components are stirred and mixed (#14). The carbon dioxide supplied to the stirring unit 1 dissolves in water to produce carbonate ions, which react with components contained in the carbonation target A, thereby carbonating the carbonation target A. In the carbon dioxide supply step, the reaction between the heavy metal stabilizer and the heavy metals is likely to be inhibited by the carbonate ions generated. However, in this embodiment, the heavy metal stabilizer is added before the water supply step, so the heavy metals are stabilized before the carbon dioxide supply step. Therefore, it is possible to carbonate the carbonation target A without reducing the reaction efficiency of the heavy metal stabilizer.

[0044] Third Embodiment Next, a carbonation device 10 and a carbonation process according to a third embodiment will be described with reference to FIGS. 1 and 4. A control unit 5 according to the third embodiment controls the heavy metal stabilizer adding unit 4 to add a powdered heavy metal stabilizer and / or a liquid heavy metal stabilizer to the stirring unit 1 in accordance with the heavy metal content of the carbonation target A measured by the measurement unit 6. Specifically, the control unit 5 controls the heavy metal stabilizer adding unit 4 to add a powdered heavy metal stabilizer when the heavy metal concentration measured by the measurement unit 6 is equal to or greater than a predetermined value, and to add a liquid heavy metal stabilizer when the heavy metal concentration measured by the measurement unit 6 is less than the predetermined value. The predetermined value may be determined based on, for example, an upper limit on the amount of liquid heavy metal stabilizer that can be added. Alternatively, the control unit 5 may control the heavy metal stabilizer adding unit 4 to add both a liquid heavy metal stabilizer and a powdered heavy metal stabilizer to the stirring unit 1.

[0045] Next, the carbonation process according to the third embodiment will be described with reference to Figure 4. First, a measurement step is performed, in which the heavy metal content contained in the carbonation target A is measured by the measurement unit 6 (#21). Next, a carbonation target supply step is performed, in which the carbonation target A is supplied to the agitation unit 1 and agitated and mixed (#22).

[0046] The control unit 5 controls the heavy metal stabilizer adding unit 4 to add a powder or liquid heavy metal stabilizer depending on the heavy metal content measured in the measurement step. For example, if the heavy metal content is equal to or greater than a predetermined value, the control unit 5 controls the heavy metal stabilizer adding unit 4 to add a powder heavy metal stabilizer (Yes in #23), and if the heavy metal content is less than the predetermined value, the control unit 5 controls the heavy metal stabilizer adding unit 4 to add a liquid heavy metal stabilizer (No in #23). When the control unit 5 controls the heavy metal stabilizer adding unit 4 to add a powder heavy metal stabilizer, a heavy metal stabilizer adding step is performed, in which the powder heavy metal stabilizer is added to the agitation unit 1, and the carbonation target A and the heavy metal stabilizer are agitated and mixed (#24). Thereafter, a water supplying step is performed, in which water is supplied to the agitation unit 1, and the carbonation target A, the heavy metal stabilizer, and the water are agitated and mixed (#25). As a result, the object to be carbonated A comes into contact with water, and the heavy metal reacts with the heavy metal stabilizer, thereby suppressing elution of the heavy metal.

[0047] If the heavy metal content of the carbonation target A is less than a predetermined value, the control unit 5 controls the heavy metal stabilizer adding unit 4 to add a liquid heavy metal stabilizer (#23). In this case, a water supply step is performed after the carbonation target A supply step (#26), and a heavy metal stabilizer adding step is performed (#27) to add a liquid heavy metal stabilizer simultaneously with or after the water supply step. This allows the carbonation target A, water, and heavy metal stabilizer to be stirred and mixed, and the heavy metals react with the heavy metal stabilizer, suppressing elution of the heavy metals.

[0048] Finally, a carbon dioxide supply step is performed, in which carbon dioxide is supplied to the stirring unit 1 and the carbonation target A and other substances are stirred and mixed (#28). The carbon dioxide supplied to the stirring unit 1 dissolves in water to produce carbonate ions, which react with components contained in the carbonation target A, thereby carbonating the carbonation target A.

[0049] When the control unit 5 controls the heavy metal stabilizer adding unit 4 to add both a powder heavy metal stabilizer and a liquid heavy metal stabilizer to the stirring unit 1, the powder heavy metal stabilizer is preferably added to the stirring unit 1 before the water supply step, and the liquid heavy metal stabilizer is preferably added to the stirring unit 1 simultaneously with the water supply step.

[0050] The heavy metal stabilizing agent adding unit 4 according to the third embodiment may have tanks for storing the powder and liquid heavy metal stabilizing agents, respectively.

[0051] [Example] Examples of the present invention will be described below, but the present invention is not limited to the descriptions of these examples.

[0052] Woody biomass combustion ash was used as the carbonation target A, and powdered ferrous sulfate was used as a heavy metal stabilizer to carbonate the carbonation target A of the example. Specifically, the carbonation target A was stirred and mixed in the stirring unit 1, and then the heavy metal stabilizer was added and mixed with the carbonation target A. Thereafter, moisture and exhaust gas were supplied to the stirring unit 1 to carbonate the carbonation target A, resulting in the example.

[0053] Woody biomass combustion ash that had not been subjected to carbonation treatment was used as Comparative Example 1. Furthermore, moisture and exhaust gas were supplied to the carbonation target A to carbonate it, and then a heavy metal stabilizer was added to the carbonate, which was then stirred and mixed to prepare Comparative Example 3.

[0054] Table 1 shows the values ​​of each component eluted in the elution amount test based on Environmental Notification No. 46 for the Examples and Comparative Examples 1 and 2, along with the standard values. Focusing on hexavalent chromium, the values ​​were 0.15 mg in Comparative Example 1 and 0.16 mg in Comparative Example 2, both exceeding the standard values, while the values ​​were less than 0.05 mg in the Examples, indicating that the elution of hexavalent chromium was suppressed. Therefore, it can be said that adding a heavy metal stabilizer prior to the carbon dioxide supply step can improve the reaction efficiency between hexavalent chromium and the heavy metal stabilizer.

[0055] [Table 1]

[0056] As for fluorine, its elution is suppressed by carbonation, so the values ​​are the same between Example and Comparative Example 2. As for boron, both Example and Comparative Example 2 exceed the standard value, but this can be reduced by adjusting the pH. [Industrial Applicability]

[0057] INDUSTRIAL APPLICABILITY The present invention can be used in a carbonation process and a carbonation device that carbonates a material to be carbonated by bringing carbon dioxide into contact with the material. [Explanation of symbols]

[0058] 1: Stirring section 2:Water supply section 3: Carbon dioxide supply unit 4: Heavy metal stabilizer addition section 5: Control section 6: Measuring part 10: Carbonation device A: Carbonation target

Claims

1. A carbonation process in which carbonation is carried out by contacting a carbonation target with carbon dioxide, a water supply step of supplying water to the object to be carbonated; a carbon dioxide supply step of supplying carbon dioxide to the object to be carbonated and bringing the object into contact with carbon dioxide after the water supply step, A carbonation process in which a heavy metal stabilizer that suppresses the elution of heavy metals contained in the material to be carbonated is added to the material to be carbonated prior to the carbon dioxide supply step.

2. the heavy metal stabilizer is a powder, 2. The carbonation process of claim 1, wherein the addition of the heavy metal stabilizer occurs prior to the water supply step.

3. the heavy metal stabilizer is a liquid; 2. The carbonation process of claim 1, wherein the heavy metal stabilizer is added during the water supply step.

4. Further comprising a measuring step of measuring the heavy metal content of the carbonation object, 2. The carbonation process of claim 1, wherein the heavy metal stabilizer is added in powder or liquid form depending on the heavy metal content.

5. 10. The carbonation process of claim 1, wherein the heavy metal comprises hexavalent chromium.

6. A carbonation device that carbonates a material to be carbonated by bringing carbon dioxide into contact with the material, A stirring unit that stirs and mixes the carbonation object; a water supply unit that supplies water to the object to be carbonated; a carbon dioxide supply unit that supplies carbon dioxide to the object to be carbonated; a heavy metal stabilizer adding unit that adds a heavy metal stabilizer that suppresses the elution of heavy metals contained in the carbonation object; a control unit that controls the addition of the heavy metal stabilizer, The control unit performs control to add the heavy metal stabilizing agent before the carbon dioxide is supplied to the object to be carbonated.

7. Further provided is a measuring unit for measuring the heavy metal content of the carbonation object, The carbonation device according to claim 6 , wherein the control unit performs control to add the heavy metal stabilizer in powder or liquid form depending on the heavy metal content measured by the measurement unit.

8. When the heavy metal stabilizer in powder form is added, the control unit 8. The carbonation device according to claim 7, wherein control is performed to add the heavy metal stabilizer before the water and the carbon dioxide are supplied.

9. When the heavy metal stabilizing agent is added in liquid form, the control unit 8. The carbonation apparatus according to claim 7, wherein control is performed to add the heavy metal stabilizer simultaneously with the supply of water.

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