WO2025009605A1 - Method for producing calcium carbonate particles - Google Patents

Abstract

Provided is a method for producing calcium carbonate particles with which it is possible to continuously produce calcium carbonate particles of high whiteness (high purity) in few steps.　Specifically, the method for producing calcium carbonate particles uses a reaction vessel 10 that is provided with a filter medium 2 compatible with crossflow filtration and is capable of circulating a suspension and circulates a suspension containing Ca-containing waste and carbonate ion-containing aqueous solution through the filter medium 2.

Description

Manufacturing method of calcium carbonate particles

The technology disclosed herein relates to a method for producing calcium carbonate particles.

Generally, the production of high-whiteness (high-purity) calcium carbonate using Ca-containing solid waste as a raw material is carried out through a multi-stage process. In particular, when synthesizing nanoparticles through a solid-liquid reaction, it is difficult to separate the solid raw material from the solid product, so the product must be separated into solid and liquid form and collected after the raw material has completely reacted. In other words, it is produced through batch synthesis. Furthermore, when a solid containing impurities is used as the raw material, a process for separating the impurities by acid extraction or the like is required.

For example, it is known that in the first step, calcium is extracted from calcium-containing solid waste with a strong inorganic acid and then impurities are removed (see, for example, Patent Document 1), or calcium is selectively extracted with a weak inorganic acid (see, for example, Patent Document 2) to obtain a high-purity calcium ion solution, and then in the next step, the calcium ion solution is reacted with carbon dioxide gas or carbonate ions to produce calcium carbonate with high whiteness (high purity).

JP 2008-143765 A JP 2005-097072 A

However, in conventional processes such as those described in Patent Documents 1 and 2, the production of nanoparticles using solids containing impurities as raw materials requires multiple steps, resulting in high production and equipment costs.

The technology disclosed herein has been made in consideration of the above circumstances, and the objective of the technology disclosed herein is to provide a technology relating to a method for producing calcium carbonate particles that can continuously produce calcium carbonate particles with high whiteness (high purity) in a small number of steps, and to solve the above-mentioned problem.

<1> A method for producing calcium carbonate particles, using a reaction vessel equipped with a filter material compatible with cross-flow filtration and capable of circulating a suspension, in which a suspension containing Ca-containing waste and a carbonate ion-containing compound is circulated through the filter material.

<2> The method for producing calcium carbonate particles according to <1>, wherein the filter medium is cylindrical, the suspension is introduced into an inlet at an end in a longitudinal direction of the filter medium, and calcium carbonate particles are separated from a side surface of the filter medium together with a filtrate.
<3> The method for producing calcium carbonate particles according to <1> or <2>, wherein the filter medium is one or more selected from the group consisting of a ceramic filter, a spiral membrane module, and a hollow fiber membrane module.

<4> The method for producing calcium carbonate particles according to any one of <1> to <3>, wherein the suspension contains an organic acid.
<5> The method for producing calcium carbonate particles according to <4>, wherein the organic acid has at least one selected from the group consisting of organic acids having a carboxy group and an organic acid having a sulfo group.
<6> The method for producing calcium carbonate particles according to <4> or <5>, wherein the organic acid is at least one selected from the group consisting of citric acid, acetic acid, formic acid, oxalic acid, stearic acid, glutamic acid, and polyacrylic acid.

<7> The method for producing calcium carbonate particles according to any one of <1> to <6>, wherein the Ca-containing waste is Ca-containing solid waste.
<8> The method for producing calcium carbonate particles according to <7>, wherein the Ca-containing solid waste contains carbide slag.

The technology disclosed herein provides a technology related to a method for producing calcium carbonate particles that can continuously produce calcium carbonate particles with high whiteness (high purity) in a small number of steps.

FIG. 2 is a schematic diagram of a reaction vessel that can be used in the method for producing calcium carbonate particles according to the present disclosure.

The upper and lower limit values of the numerical ranges described in this specification can be combined in any manner. For example, when numerical ranges "A to B" and "C to D" are described, the numerical ranges "A to D" and "C to B" are also included in the scope of the present disclosure.
In addition, unless otherwise specified, a numerical range of "lower limit value to upper limit value" described in this specification means not less than the lower limit value and not more than the upper limit value.

<Method of Manufacturing Calcium Carbonate Particles>
The method for producing calcium carbonate particles according to the present disclosure includes a production step of using a reaction vessel equipped with a filter medium compatible with cross-flow filtration and capable of circulating a suspension, and circulating a suspension containing a Ca-containing waste material and a carbonate ion-containing compound through the filter medium.
In the method for producing calcium carbonate particles according to the present disclosure, a suspension containing a Ca-containing waste and a carbonate ion-containing compound is circulated through a filter medium, whereby calcium carbonate particles can be separated together with the filtrate. The filtrate that has passed through the filter medium is a dispersion in which the coarse particles in the suspension have been removed and the calcium carbonate particles are dispersed.
In this specification, the suspension includes the Ca-containing waste and the carbonate ion-containing compound and refers to the components before passing through the filter medium, and the filtrate that passes through the filter medium and contains calcium carbonate particles is referred to as a dispersion liquid.

As described above, in the method for producing calcium carbonate particles according to the present disclosure, the calcium carbonate particles can be recovered together with the filtrate, and therefore the production step also serves as a recovery step of the calcium carbonate particles.
The method for producing calcium carbonate particles according to the present disclosure may further include a separation step of performing solid-liquid separation of the calcium carbonate particles in the dispersion, a washing step of washing the separated residue, a drying step of drying the residue, and the like.

In the method for producing calcium carbonate particles according to the present disclosure, the term "few steps" refers to a production process up to the production of calcium carbonate particles from Ca-containing waste and a recovery process up to the recovery of calcium carbonate particles from the suspension as a dispersion liquid, and does not include a separation process, a washing process, a drying process, and the like that are optionally performed after the recovery of the calcium carbonate particles.
As described above, in the conventional methods for producing calcium carbonate particles, the production process of calcium carbonate particles requires two or more steps, and further requires many steps such as a recovery step of recovering calcium carbonate particles from a suspension containing coarse particles and a separation step of separating the calcium carbonate particles as a solid component from a dispersion liquid.
In particular, when a solid-liquid reaction is carried out in a batchwise manner, if the reaction time is not allowed to be sufficient to completely react the solid raw material such as the Ca-containing waste, a step of removing the solid raw material becomes necessary.

In contrast, according to the method for producing calcium carbonate particles of the present disclosure, a suspension containing a Ca-containing waste and a carbonate ion-containing compound is circulated while passing through a filter medium, so that the reaction between the Ca-containing waste and the carbonate ion-containing compound proceeds while the generated calcium carbonate particles can be recovered as a dispersion liquid.
Moreover, in the method for producing calcium carbonate particles according to the present disclosure, a product can be continuously obtained even if the solid raw material does not completely react, and the number of steps can be reduced compared to the conventional method.
In this way, since the production and recovery of calcium carbonate particles can be continuously carried out in one step, calcium carbonate particles can be continuously produced in a small number of steps, and production costs and equipment costs can be reduced.

[Reaction vessel]
In the method for producing calcium carbonate particles according to the present disclosure, a reaction vessel is used that is equipped with a filter medium compatible with cross-flow filtration and that can circulate a suspension.
Fig. 1 is a schematic diagram of a reaction vessel 10 that can be used in the method for producing calcium carbonate particles of the present disclosure. The reaction vessel shown in Fig. 1 is an example of a reaction vessel that can be used in the method for producing calcium carbonate particles of the present disclosure, and the reaction vessel that can be used in the method for producing calcium carbonate particles of the present disclosure is not limited to the structure shown in Fig. 1.

The reaction vessel 10 includes a filter medium 2 , a tank 4 , and a flow path 6 .
The filter medium 2 is a filter medium compatible with cross-flow filtration, and may be a ceramic filter, a spiral membrane module, a hollow fiber membrane module, etc. The filter medium 2 may be used alone or in combination of two or more, and when two or more are combined, the same or different types of filter medium may be connected in series or parallel for use.
Ceramic filters may be called different names depending on the manufacturer, for example, ceramic membranes, ceramic membrane filters, ceramic membranes, ceramic membrane filters, etc.

The shape of the filter medium 2 is not particularly limited, but is usually cylindrical.
A filter medium suitable for cross-flow filtration generally has an inlet for introducing a suspension, an outlet for discharging the suspension, and a filtrate outlet having pores. The filter medium 2 may have a variety of structures, such as (a) an inlet and an outlet at the end of the cylindrical filter medium, and a filtrate outlet at the side of the cylindrical filter medium; (b) a filtrate outlet at the end of the cylindrical filter medium, and an inlet and an outlet at the side of the cylindrical filter medium, and there is no particular restriction as to which structure to use.
1 is a cylindrical filter medium of type (a), which has an inlet 2a at one end in the length direction and an outlet 2b at the other end, and has a filtrate outlet 2c on the side of the filter medium 2. When a filter medium of type (b) is used, for example, a suspension is introduced from the side of the filter medium, and calcium carbonate particles can be separated together with the filtrate from the filtrate outlet at the end of the filter medium in the length direction.

It is preferable to select the filter medium 2 as a ceramic filter having a pore size smaller than the particle size of the raw material and larger than the particle size of the intermediate product.
The calcium carbonate particles obtained by the method for producing calcium carbonate particles of the present disclosure usually have a primary particle diameter of 10 nm to 2 μm. In consideration of particle aggregation, the pores at the filtrate outlet of the filter medium 2 preferably have a pore diameter of 1 to 5 μm.
In other words, the filter medium 2 preferably has a filtrate outlet 2c having pores with a pore size of 1 to 5 μm.
The pores of the filtrate outlet 2c preferably have a pore size of 1 to 5 μm, and more preferably 2 to 3 μm.
Furthermore, when pores are provided in the wall surface itself constituting the side surface of the filter medium 2, particles that can pass through the pores are discharged together with the filtrate into the recovery container 8 via the filtrate outlet 2c.
As described above, the pore size of the pores is more preferably 1 to 5 μm, and further preferably 2 to 3 μm.
The particle size of the calcium carbonate particles may be evaluated by photographic observation using a scanning electron microscope (SEM) or a transmission electron microscope (TEM), or may be evaluated by a laser diffraction particle size analyzer or the like.

The tank 4 has a function of storing the suspension, sending out the suspension to the flow path 6, and receiving the suspension discharged from the outlet 2b at the end in the longitudinal direction of the filter medium 2. The shape and size of the tank 4 are not particularly limited.
The flow path 6 has a function of delivering the suspension discharged from the tank 4 to the filter medium 2 and returning the suspension discharged from the filter medium 2 to the tank 4. The shape and size of the flow path 6 are not particularly limited, but a cylindrical flow path is usually used.

F1 to F6 indicate the flow of the suspension. D indicates the flow of the filtrate from the filtrate outlet 2c to the recovery container 8.
By putting the suspension in the tank 4, the suspension flows from the tank 4 through the flow path 6 in the order of F1, F2, F3, F4, and F5 by a pump (not shown), and while the reaction between the Ca-containing waste and the carbonate ion-containing compound proceeds, it is delivered to the inlet 2a at the end in the longitudinal direction of the filter medium 2. In the suspension, small particles such as calcium carbonate particles having a particle size smaller than the pores of the filtrate outlet 2c are collected in the collection container 8 together with the filtrate.
Particles that cannot pass through the pores of the filtrate outlet 2 c flow from the end inlet 2 a in the length direction of the filter medium 2 to the end outlet 2 b, and circulate within the reaction vessel 10.
In the following description, reference numerals in the drawings will be omitted.

[Ca-containing waste]
Although waste concrete is well known as a Ca-containing waste, it is not limited to waste concrete, and coal ash, biomass combustion ash, waste incineration ash, residual concrete, returned concrete, etc. can also be used. Note that residual concrete refers to concrete that remains in an agitator truck after being unloaded at the site. Returned concrete refers to concrete that is not unloaded from an agitator truck and is returned to the ready-mixed concrete plant from which it was shipped, but ready-mixed concrete that is left over or remains unused at a construction site, including returned concrete, is sometimes called residual concrete.
In addition, the Ca-containing waste may be in various forms, such as solid, liquid, muddy, etc., but solid waste is usually more likely to be distributed. Hereinafter, solid Ca-containing waste may be referred to as Ca-containing solid waste.
In the method for producing calcium carbonate particles of the present disclosure, it is preferable to use Ca-containing solid waste.

Examples of Ca-containing solid waste include waste concrete, waste cement, cement sludge, coal ash, biomass combustion ash, waste combustion ash, carbide slag, desulfurization slag, converter slag, and electric furnace slag. From the viewpoint of the calcium hydroxide and calcium oxide content, carbide slag, desulfurization slag, coal ash, biomass combustion ash, and waste combustion ash are more preferred.
Carbide slag is a by-product of acetylene production by the reaction of calcium carbide with water, and refers to a solid whose main component is Ca(OH) _2. Generally, carbide slag contains 70 mass% or more of Ca(OH) ₂ .

[Carbonate ion-containing compounds]
Examples of the carbonate ion-containing compound include carbon dioxide gas ( _CO2 gas), an aqueous solution of carbon dioxide gas, and metal carbonates such as sodium bicarbonate and sodium carbonate.
When carbon dioxide gas is used, the Ca-containing waste may be added to water and then the carbon dioxide gas may be bubbled into the liquid to directly react with the waste, or the carbon dioxide gas may be bubbled into water or an alkaline aqueous solution such as an aqueous NaOH solution to prepare an aqueous solution containing dissolved carbonate ions, which may then be reacted with the Ca-containing waste.
When a metal carbonate is used, the metal carbonate may be prepared in an aqueous solution, and then the Ca-containing waste and the carbonate ion-containing compound may be mixed.
The carbonate ion-containing compound may be used alone or in combination of two or more kinds.

The amount of the carbonate ion-containing compound to be blended varies depending on the Ca content in the Ca-containing waste. In general, the molar ratio (Ca/CO ₃ ²⁻ ) of the Ca content in the Ca-containing waste to the carbonate ions in the carbonate ion-containing compound is preferably 0.6 to 2.0, and more preferably 0.7 to 1.2.

(Organic Acid)
In the method for producing calcium carbonate particles of the present disclosure, in addition to the Ca-containing waste and the carbonate ion-containing compound, an organic acid may be further added to the suspension. When the organic acid is present during the reaction of the Ca-containing waste and the carbonate ion-containing compound, impurities can be easily removed, and the yield of calcium carbonate particles can be increased.
For example, when a suspension of a mixture of Ca(OH) ₂ and _FeCl3 is used as a model of Ca-containing waste _and an aqueous _Na2CO3 solution is used as a carbonate ion-containing compound, Fe(OH) _{3 is} co-precipitated when the suspension is reacted with the aqueous _Na2CO3 solution, resulting in low-purity calcium carbonate. If an organic acid is present during the reaction, the organic acid captures Fe3 ⁺ ions and suppresses the co-precipitation of Fe(OH) ₃ , making it easier to remove impurities and increasing the yield of calcium carbonate particles.

The organic acid is not particularly limited as long as it is an organic compound that has a carboxy group, a sulfo group, a hydroxy group, or the like and exhibits acidity, but it is preferable to use an organic acid having one or more selected from the group consisting of organic acids having a carboxy group and a sulfo group.

Examples of organic acids (carboxylic acids) having a carboxy group include citric acid, acetic acid, formic acid, oxalic acid, stearic acid, glutamic acid, polyacrylic acid, lactic acid, benzoic acid, phthalic acid, fumaric acid, maleic acid, salicylic acid, aspartic acid, and the like. Of these, citric acid, acetic acid, formic acid, oxalic acid, stearic acid, glutamic acid, and polyacrylic acid (PAA) are preferred.
The polyacrylic acid (PAA) preferably has a weight average molecular weight (Mw) of 2,000 to 10,000, and more preferably 3,000 to 7,000.

Examples of organic acids having a sulfo group (sulfonic acids) include toluenesulfonic acid, propylsulfonic acid, polystyrenesulfonic acid, polyvinylsulfonic acid, Nafion, and the like, with toluenesulfonic acid and polystyrenesulfonic acid being preferred among these.
The toluenesulfonic acid may be in the ortho (o-), meta (m-) or para (p-) form, with p-toluenesulfonic acid being preferred.
The weight average molecular weight (Mw) of the polystyrene sulfonic acid is preferably from 50,000 to 100,0000, and more preferably from 70,000 to 200,000.

The organic acid may be used alone or in combination of two or more kinds.
Among the above, from the viewpoint of the strength of the interaction with Ca ions, it is preferable to use a carboxylic acid as the organic acid, and it is more preferable to use one or more selected from the group consisting of citric acid, acetic acid, formic acid, oxalic acid, stearic acid, glutamic acid, and polyacrylic acid.

From the viewpoint of removing impurities and increasing the yield of calcium carbonate particles, the blending amount of the organic acid varies depending on the Ca content in the Ca-containing waste. Generally, the blending amount is preferably 60 to 250 parts by mass, more preferably 60 to 100 parts by mass, and even more preferably 80 to 90 parts by mass, relative to 100 parts by mass of calcium ions in the Ca-containing waste.
Furthermore, when a carboxylic acid is used as the organic acid for the purpose of removing impurities and increasing the yield of calcium carbonate particles, the molar ratio (Ca/COOH) of the Ca content in the Ca-containing waste to the carboxy group content in the organic acid is preferably 0.5 to 2.0, and more preferably 0.6 to 1.7.
The Ca content in the Ca-containing waste can be measured by X-ray fluorescence analysis (XRF) of glass beads made from the Ca-containing waste, or by inductively coupled plasma (ICP) emission spectrometry of a solution in which the Ca-containing waste is dissolved in a strong acid or the like.
On the other hand, from the viewpoint of increasing the whiteness of the calcium carbonate particles, it is preferable not to add an organic acid, and specifically, the amount of the organic acid to be blended is preferably 0 parts by mass per 100 parts by mass of calcium ions in the Ca-containing waste.

(Other ingredients)
The pH of the suspension may be adjusted by adding a pH adjuster such as an aqueous NaOH solution to the suspension.

The calcium carbonate particles produced in the above manner are collected together with the filtrate. The calcium carbonate particles in the filtrate (dispersion liquid) can be separated into solid and liquid using a separation membrane (membrane filter) with a pore size of 0.05 to 2 μm, and obtained as a solid fraction.

The technology disclosed herein will now be described in detail using examples, but the technology disclosed herein is in no way limited by these examples.

<Ingredients used in the production of calcium carbonate particles>
(Ca-containing waste)
Model material of Ca-containing waste: A suspension in which Ca(OH) ₂ , _FeCl3 , and _H2O are mixed in the ratio shown in "Ca-containing waste" in Table 1.

(Carbonate ion-containing compound)
Aqueous sodium carbonate solution obtained by mixing sodium carbonate (Na ₂ CO ₃ ) and H ₂ O in the amounts shown in the “carbonate ion-containing compound” in Table 1.

(Organic Acid)
Compounds shown in the "Additives" column of Table 1

<Equipment used in the production of calcium carbonate particles>
In the production of calcium carbonate particles in Examples 1 and 2, a reaction vessel 10 including a filter medium 2, a tank 4, and a flow path 6 shown in Fig. 1 was used. The filter medium 2 is a ceramic filter ("Cefilt" manufactured by NGK Insulators, pore size 2 µm) compatible with cross-flow filtration, and is provided with an inlet 2a at one end in the length direction and an outlet 2b at the other end, and a filtrate outlet 2c on the side of the filter medium 2. The side of the ceramic filter has pores with a pore size of 2.0 µm, and particles that can pass through the pores are discharged together with the filtrate into a recovery vessel 8. Particles that cannot pass through the pores on the side of the ceramic filter flow from the inlet 2a at the end in the length direction of the filter medium 2 to the outlet 2b at the end, and circulate within the reaction vessel 10.
In Comparative Examples 1 and 2, calcium carbonate particles were produced by a batch method (the compositions were the same as those in Examples 1 and 2, respectively).

<Production of calcium carbonate particles>
Example 1
_Ca (OH) ₂ , _FeCl3 , and _H2O were mixed in the ratio shown in "Ca-containing waste" in Table 1 to obtain a suspension 1. Sodium carbonate ( _Na2CO3 ) and _H2O were mixed in the ratio shown in "carbonate ion-containing compound" in Table 1 to obtain an aqueous sodium carbonate solution.
Suspension 1 and an aqueous sodium carbonate solution were mixed in the ratio shown in Table 1 and placed in a tank. The tank pressure was set to 0.35 MPa, and the suspension was circulated in the reaction vessel to produce calcium carbonate particles of Example 1.

Example 2
Calcium carbonate particles of Example 2 were produced in the same manner as in the production of calcium carbonate particles of Example 1, except that in addition to Suspension 1 and the aqueous sodium carbonate solution, an additive (citric acid) was mixed in the ratio shown in Table 1.

Comparative Example 1
_Ca (OH) ₂ , _FeCl3 , and _H2O were mixed in the ratio shown in "Ca-containing waste" in Table 1 to obtain a suspension 2. Sodium carbonate ( _Na2CO3 ) and _H2O were mixed in the ratio shown in "carbonate ion-containing compound" in Table 1 to obtain an aqueous sodium carbonate solution.
Suspension 2 and an aqueous sodium carbonate solution were mixed in the ratio shown in Table 1, and the reaction was allowed to proceed for 120 minutes while stirring the suspension at 300 rpm using a stirring blade, thereby producing calcium carbonate particles of Comparative Example 1.

Comparative Example 2
Calcium carbonate particles of Comparative Example 2 were produced in the same manner as in the production of calcium carbonate particles of Comparative Example 1, except that suspension 2, the aqueous sodium carbonate solution, and an additive (citric acid) were mixed in the ratio shown in Table 1.

<Evaluation>
In Examples 1 and 2, the filtrate collected in the collection container was filtered through a membrane filter having pores of 0.1 μm to separate the solid matter from the filtrate. The solid matter was dried under reduced pressure to obtain a sample.
In Comparative Examples 1 and 2, the suspension was filtered through a membrane filter having pores of 0.1 μm to separate the solid content from the filtrate, and the solid content was dried under reduced pressure to obtain a sample.

(Whiteness)
The whiteness of the obtained solid was measured according to JIS Z 8715 (1999) using an ultraviolet-visible spectrophotometer "V770" and an integrating sphere unit "ISV-923" manufactured by JASCO Corp. The results are shown in Table 1.

 

As can be seen from the results of Examples 1 and 2 in Table 1, according to the method for producing calcium carbonate particles according to the present embodiment, calcium carbonate particles with high whiteness can be produced continuously from Ca-containing waste in a small number of steps.
On the other hand, the methods for producing calcium carbonate particles according to Comparative Examples 1 and 2 are carried out in a batch manner, which increases production costs and equipment costs.

In addition, in comparison between Example 1 and Example 2, the reason why the whiteness is higher in the system not containing the additive (Example 1) is considered to be due to the following reason.
By adding an additive to the reactor, the additive coordinates with Fe3 ⁺ and is collected together with the filtrate. In other words, Fe3 ⁺ is mixed into the filtrate. Therefore, it is considered that the whiteness of the collected material is higher when no additive is added because the precipitated Fe(OH) ₃ is captured by the filter material.

According to this embodiment, calcium carbonate particles with high whiteness (high purity) can be produced continuously in a few steps from Ca-containing waste. The calcium carbonate particles produced in this way can be used as a raw material for cement materials, asphalt admixtures, polymer fillers, etc.

2 Filter medium 2a Inlet at end of filter medium in longitudinal direction 2b Outlet at end of filter medium in longitudinal direction 2c Filtrate outlet 4 Tank 6 Flow path 8 Recovery vessel 10 Reaction vessel

Claims (8)

A method for producing calcium carbonate particles using a reaction vessel equipped with a filter material compatible with cross-flow filtration and capable of circulating a suspension, in which a suspension containing Ca-containing waste and a carbonate ion-containing compound is circulated through the filter material. The method for producing calcium carbonate particles according to claim 1, wherein the filter medium is cylindrical, the suspension is introduced into an inlet at an end of the filter medium in the longitudinal direction, and calcium carbonate particles are separated from the side of the filter medium together with the filtrate. The method for producing calcium carbonate particles according to claim 1 or 2, wherein the filter medium is one or more selected from the group consisting of a ceramic filter, a spiral membrane module, and a hollow fiber membrane module. The method for producing calcium carbonate particles according to any one of claims 1 to 3, wherein the suspension contains an organic acid. The method for producing calcium carbonate particles according to claim 4, wherein the organic acid is at least one selected from the group consisting of organic acids having a carboxy group and a sulfo group. The method for producing calcium carbonate particles according to claim 4 or 5, wherein the organic acid is one or more selected from the group consisting of citric acid, acetic acid, formic acid, oxalic acid, stearic acid, glutamic acid, and polyacrylic acid. The method for producing calcium carbonate particles according to any one of claims 1 to 6, wherein the Ca-containing waste is Ca-containing solid waste. The method for producing calcium carbonate particles according to claim 7, wherein the Ca-containing solid waste contains carbide slag.

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