KR101551896B1 - Preparation method of high purity calcium carbonate using direct aqueous carbonation - Google Patents

Abstract

The present invention relates to a method for producing high purity calcium carbonate using a direct carbonation reaction, and more particularly, to a method for producing high-purity calcium carbonate by drying a flue gas desulfurization gypsum in an ammonia solution; Supplying carbon dioxide to the ammonia solution in which the flue gas desulfurization gypsum is dissolved to carry out carbonation reaction, and then filtering the carbon dioxide; And filtering the precipitated calcium carbonate after allowing the filtered liquid to stand. The present invention also relates to a method for producing high purity calcium carbonate using the direct carbonation reaction.

Description

[0001] The present invention relates to a method for preparing high purity calcium carbonate using a direct carbonate-

The present invention relates to a process for preparing high purity calcium carbonate using a direct carbonate reaction.

As the industry develops and the life becomes more abundant, power consumption is increasing every year, so the fossil fuels needed to produce electricity are consumed more and accordingly the emission of sulfur dioxide gas is also increasing. Accordingly, the installation of the flue gas desulfurization equipment for removing the sulfur dioxide gas has been continuously increased, and accordingly, the amount of the flue gas desulfurization gypsum to be treated is gradually increasing. In order to utilize these flue gas desulfurization gypsum, ammonium sulfate fertilizer has been produced, and at the same time, calcium carbonate has been produced as a by-product. Such calcium carbonate can be used commercially depending on purity and shape. Conventional flue gas desulphurization gypsum is treated in two successive stages as shown in the following chemical formula 1.

[Chemical Formula 1]

CO ₂ (g) + 2NH ₄ OH → (NH ₄ ) ₂ CO ₃ (aq)

CaSO ₄ .2H ₂ O + (NH ₄ ) ₂ CO ₃ (aq) → CaCO ₃ (s) + (NH ₄ ) ₂ SO ₄ + 2H ₂ O

This reaction can produce ammonium sulfate in high yield and high purity, and the purity of the ammonium sulfate is increased because most of the residue of the flue gas desulfurization gypsum remains as a solid residue. When impurities remaining in ammonium sulfate are present, the impurities can be removed by a simple filtration method. Considering the solubility of ammonium sulphate and calcium carbonate, ammonium sulphate has high solubility and is present in the solution, and most of the calcium carbonate is not dissolved and precipitates. Therefore, the ammonium sulfate crystals of high purity can be obtained by removing insoluble impurities by filtration and then precipitating. On the other hand, since the solubility of calcium carbonate is low, there is a problem that high purity calcium carbonate can not be obtained by the above method.

As a prior art related to this, there is "a method of immobilizing carbon dioxide using gypsum plaster" disclosed in Korean Patent Laid-Open Publication No. 10-2010-0008342 (published on Jan. 25, 2010).

Accordingly, it is an object of the present invention to provide a method for producing calcium carbonate of high purity using a direct carbonate reaction.

The problems to be solved by the present invention are not limited to the above-mentioned problem (s), and another problem (s) not mentioned can be understood by those skilled in the art from the following description.

In order to solve the above problems, the present invention provides a method for producing a desulfurized gypsum, comprising: drying an exhaust gas desulfurization gypsum in an ammonia solution; Supplying carbon dioxide to the ammonia solution in which the flue gas desulfurization gypsum is dissolved to carry out carbonation reaction, and then filtering the carbon dioxide; And filtering the precipitated calcium carbonate after leaving the filtered liquid. The present invention also provides a method for producing high purity calcium carbonate using the direct carbonation reaction.

At this time, the carbonation reaction is performed for 5 to 20 minutes.

The solid-liquid ratio (S / L) of the flue gas desulfurization gypsum is 5 - 20 g / L.

And the ammonia concentration in the ammonia solution is 3.7 to 4.1% by volume.

And the flue gas desulfurization gypsum dissolution in the ammonia solution is performed by stirring at 350 - 450 rpm for 5 minutes.

And the carbon dioxide is supplied at 1 - 3 L / min.

The carbonation reaction is performed at room temperature and atmospheric pressure.

Characterized in that the carbonation reaction is completed at pH 7.

The filtration is performed by a 0.2 μm membrane filter, and the membrane filter is made of cellulose acetate.

The present invention also provides a method for producing a desulfurized gypsum, comprising: drying a flue gas desulfurization gypsum in an ammonia solution; Supplying carbon dioxide to the ammonia solution in which the flue gas desulfurization gypsum is dissolved to carry out carbonation reaction, and then filtering the carbon dioxide; And a step of filtering the precipitated calcium carbonate after allowing the filtered liquid to settle. The present invention also provides calcium carbonate including a calcite crystal form prepared by the process for producing high purity calcium carbonate using the direct carbonation reaction.

The knife site is characterized by being rhombic.

According to the present invention, the carbonation reaction of the flue gas desulfurization gypsum is improved by performing the direct carbonation reaction at room temperature and atmospheric pressure, and after the carbonation reaction is performed for a certain period of time (induction period), the filtered liquid is settled, Calcium carbonate can be produced.

FIG. 1 is a flowchart showing a method for producing high purity calcium carbonate using a direct carbonation reaction according to the present invention.
2 is a schematic view showing an apparatus for producing high purity calcium carbonate using a direct carbonation reaction according to the present invention.
3 is a graph showing the XRD analysis results of the flue gas desulfurization gypsum.
FIG. 4 is a graph showing changes in pH and concentration of dissolved sulfate ions according to carbonation reaction time in a method for producing high purity calcium carbonate using the direct carbonateification reaction according to the present invention.
5 shows an FE-SEM photograph of the solid residue produced during the carbonation reaction in the process for producing high purity calcium carbonate using the direct carbonation reaction according to the present invention.
6 is a graph showing the results of EDX mapping of solid residues after carbonation reaction for 15 minutes in the process for producing high purity calcium carbonate using the direct carbonation reaction according to the present invention.
FIG. 7 is a graph showing the XRD results of solid residues according to carbonation reaction time in the process for producing high purity calcium carbonate using the direct carbonation reaction according to the present invention.
8 is a graph showing changes in the content of the baterite phase of the solid residue according to the carbonation reaction time in the process for producing high purity calcium carbonate using the direct carbonateification reaction according to the present invention.
FIG. 9 shows XPS C1s spectra of solid residues according to carbonation reaction time in the process for producing high purity calcium carbonate using the direct carbonation reaction according to the present invention.
10 is a graph showing changes in the calcite concentration of calcium carbonate precipitated in the filtered liquid according to the carbonation reaction time in the method for producing high purity calcium carbonate using the direct carbonateification reaction according to the present invention.
11 is an FE-SEM photograph of calcium carbonate precipitated in the filtered liquid according to the carbonation reaction time in the method of producing high purity calcium carbonate using the direct carbonation reaction according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving it will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings.

The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

The present invention relates to a method for producing a desulfurized gypsum, comprising: drying an exhaust gas desulfurization gypsum in an ammonia solution;

Supplying carbon dioxide to the ammonia solution in which the flue gas desulfurization gypsum is dissolved to carry out carbonation reaction, and then filtering the carbon dioxide; And

And filtering the precipitated calcium carbonate after the filtered liquid is allowed to stand. The present invention also provides a method for producing high purity calcium carbonate using a direct carbonation reaction.

The process for producing high purity calcium carbonate using the direct carbonation reaction according to the present invention is carried out at room temperature and atmospheric pressure and thus has high carbonation reaction ability of the flue gas desulfurization gypsum. In the induction period before the calcium carbonate is precipitated during the carbonation reaction, , The calcium carbonate can be produced by a carbonation reaction in a period of time until the precipitation reaction starts in earnest due to the presence of the calcium carbonate, and calcium carbonate can be produced at a high rate from the flue gas desulfurization gypsum.

FIG. 1 is a flowchart showing a method for producing high purity calcium carbonate using a direct carbonation reaction according to the present invention. Hereinafter, the present invention will be described in detail with reference to Fig.

The method for producing high purity calcium carbonate using the direct carbonation reaction according to the present invention includes a step (S100) of drying the flue gas desulfurization gypsum and then dissolving the gypsum in the ammonia solution.

The flue gas desulfurization gypsum discharged after removing SO _x from the thermal power plant is composed of CaSO ₄ · 2H ₂ O, and the flue gas desulfurization gypsum thus discharged can be made into fertilizer. At this time, the solid-liquid ratio (S / L) of the flue gas desulfurization gypsum is preferably 5 - 20 g / L. When the solid ratio of the flue gas desulfurization gypsum is less than 5 g / L, it is difficult to recover the produced calcium carbonate because the amount of produced calcium carbonate is small, and when it exceeds 20 g / L, the calcium carbonate formation rate drops to 60% have.

The concentration of ammonia in the ammonia solution is preferably 3.7 to 4.1 vol.%. If the concentration of ammonia is less than 3.7% by volume, the formation of calcium carbonate may be deteriorated. If the concentration of ammonia is more than 4.1% by volume, a large amount of ammonia may be consumed to increase the cost.

The flue gas desulfurization gypsum dissolution in the ammonia solution can be performed by stirring at 350 - 450 rpm for 5 minutes. Specifically, the stirring can be performed using a mechanical impeller. When the mixing ratio is less than 350 rpm, the flue gas desulfurization gypsum does not sufficiently dissolve in the ammonia solution, It is preferable that the flue gas desulfurization gypsum is no longer dissolved in the ammonia solution and is 450 rpm or less in terms of energy efficiency.

Next, a method for producing high purity calcium carbonate using the direct carbonation reaction according to the present invention includes a step (S200) of supplying carbon dioxide to the ammonia solution in which the flue gas desulfurization gypsum is dissolved, followed by carbonation reaction and filtering.

In the method for producing high purity calcium carbonate using the direct carbonation reaction according to the present invention, the direct carbonation reaction includes gaseous carbon dioxide, a liquid ammonia solution, and a solid flue gas desulfurization gypsum. A specific reaction to this can be represented by the following formula (2).

(2)

CaSO ₄ · 2H ₂ O + 2NH ₄ OH (aq) + CO ₂ (g) → CaCO ₃ (s) + (NH ₄ ) ₂ SO ₄ + 2H ₂ O

It is preferable that the carbon dioxide is supplied at 1 - 3 L / min. When the carbon dioxide is supplied at a rate of less than 1 L / min, the reaction rate is slowed to increase the carbonation reaction time. When the carbon dioxide exceeds 3 L / min, the carbonation reaction proceeds rapidly, There is a problem in that separation of the solution is not easy.

At this time, the carbonation reaction is preferably carried out for 5 to 20 minutes. When the carbonation reaction is carried out for less than 5 minutes, there is a problem in that the amount of calcium carbonate present in the form of a liquid is small and the recovery rate is low. If it exceeds 20 minutes, calcium carbonate may contain impurities.

The carbonation reaction can be carried out at room temperature and atmospheric pressure, thereby increasing the carbonation reaction reactivity of the flue gas desulfurization gypsum, so that calcium carbonate can be produced by a simple method and the process cost can be reduced.

The carbonation reaction can be completed at pH 7. The initial pH after dissolving the flue gas desulfurization gypsum in the ammonia solution is 12, but when the carbon dioxide is supplied and the carbonation reaction proceeds, the pH gradually decreases and the carbonation reaction is completed at 7.

When the carbonation reaction is completed, the solution is filtered. The filtration can be performed with a 0.2 μm membrane filter, and the membrane filter can be made of cellulose acetate.

The method for producing high purity calcium carbonate using the direct carbonation reaction according to the present invention includes a step (S300) of filtering the precipitated calcium carbonate after leaving the filtered liquid.

High purity calcium carbonate is present as a liquid phase in the filtered liquid. In order to obtain it in a solid phase, it is necessary to carry out a step of standing. The high purity calcium carbonate filtered by filtering the precipitated calcium carbonate can be washed with deionized water, Lt; / RTI >

2 is a schematic view showing an apparatus for producing high purity calcium carbonate using a direct carbonation reaction according to the present invention. 2, the solid particles of the flue gas desulfurization gypsum were agitated with an impeller at 350 - 450 rpm for 5 minutes, dissolved in an ammonia solution, CO ₂ gas was injected for carbonation reaction, and the filtered liquid was allowed to stand to precipitate Calcium carbonate can be obtained by filtration. pH and temperature can be measured by using pH meter and thermocouple. At this time, the liquid ratio (S / L) of flue gas desulphurization gypsum is 5 - 20 g / L and CO ₂ gas is flow rate of 1 - 3 L / min And the ammonia concentration in the ammonia solution is 3.7 - 4.1% by volume. High purity calcium carbonate filtered and filtered through a membrane filter can be further washed with deionized water and then dried.

The present invention also provides a method for producing a desulfurized gypsum, comprising: drying a flue gas desulfurization gypsum in an ammonia solution; Supplying carbon dioxide to the ammonia solution in which the flue gas desulfurization gypsum is dissolved to carry out carbonation reaction, and then filtering the carbon dioxide; And filtering the precipitated calcium carbonate after leaving the filtered liquid. The present invention provides calcium carbonate including a calcite crystal form, which is produced by a process for producing high purity calcium carbonate.

Calcium carbonate has an anhydrous crystalline form of calcite, aragonite and vaterite, but in the present invention only crystals of calcite and baterite are precipitated and no aragonite phase is formed . Specifically, in the method for producing high purity calcium carbonate using the direct carbonation reaction according to the present invention, calcium carbonate in the form of calcite crystals can be produced in an amount of 5% by weight of the flue gas desulfurization gypsum dissolved in the ammonia solution have. At this time, the knife site is rhombic.

Example 1: Preparation of high purity calcium carbonate

The flue gas desulfurization gypsum was obtained from Yeongheung Thermal Power Plant located in Incheon, Korea and dried at 45 ℃ overnight to remove the water present on the surface. The dried flue gas desulfurization gypsum was placed in an ammonia solution and stirred with an impeller at 400 rpm for 5 minutes to dissolve the flue gas desulfurization gypsum. At this time, 200 g of flue gas desulfurization gypsum and 3.9% (v / v) of ammonia solution were used. The ammonia concentration was adjusted by using 25% by weight ammonia solution, and the liquid ratio was 15%. After dissolving the flue gas desulfurization gypsum in the ammonia solution, CO ₂ (99.99%) was injected into the ammonia solution in which the flue gas desulfurization gypsum was dissolved at a feeding rate of 1 - 3 L / min, followed by carbonation reaction. ). ≪ / RTI > The filtered liquid was allowed to stand for 10 hours to precipitate calcium carbonate of high purity and then filtered to obtain a solid calcium carbonate. All the steps were carried out at room temperature and atmospheric pressure.

Comparative Example 1: Preparation of calcium carbonate using the conventional method

Ammonia bicarbonate was prepared by supplying carbon dioxide at a flow rate of 1 L / min to 3.9% (v / v) ammonia solution, cooled to room temperature, and reacted with the flue gas desulfurization gypsum.

Experimental Example 1: Elemental analysis of flue gas desulfurization gypsum

XRD analysis of flue gas desulfurization gypsum obtained from Yeongheung Thermal Power Plant located in Incheon, Korea revealed that the minor phases contained kerosite (KAl ₂ Si ₃ AlO ₁₀ (OH) ₂ ) and dolomite (CaMg (CO ₃ ) ₂ ) Calcium sulfate dihydrate (see Fig. 3). The purity of the calcium sulfate dihydrate was about 97.5% and 0.7% SiO ₂ , 0.4% Al ₂ O ₃ , 0.2% Fe ₂ O ₃ and 0.1% K ₂ O were trace impurities. Pb, Ag, No heavy metal impurities such as Hg, Zn, Mn and Cd were detected. The particle size was in the range of 1 - 100 ㎛ with a volume mean diameter of 32.9 ㎛, but the majority of particles over 80% were below 74 ㎛ in size.

Experimental Example 2: Carbonation of flue gas desulfurization gypsum

The flue gas desulfurization gypsum produced ammonium sulfate and calcium carbonate with high carbonation reaction at normal temperature and pressure. The calcium carbonate formed by the carbonation reaction had a mixed crystal of calcite and baterite. Since most of the undissolved impurities are easily filtered, ammonium sulfate dissolved in the solution can be produced with high purity. In the filtered solution, metal impurities of Si, K, Na, Al and Mg were contained at a concentration of 10 mg / L or less, and Fe was 0.01 mg / L or less. It is believed that this is due to the undissolved minerals such as dolomite and dolomite. Therefore, the purity of ammonium sulfate produced was more than 98%, and therefore, it was a purity suitable for commercial use.

FIG. 4 is a graph showing the pH and the concentration of dissolved sulfate ion according to the carbonation reaction time in the method for producing high purity calcium carbonate using the direct carbonateification reaction according to the present invention (the solid line in FIG. 4 shows a change in pH, Indicates a change in concentration of sulfate ion).

The initial pH of the ammonia solution after supplying the flue gas desulfurization gypsum was 12. The concentrations of dissolved calcium and sulfate ions before and after CO ₂ were 560 mg / L (or 14.0 mM) and 1350 mg / L (or 14.0 mM), respectively. The CO ₂ gas was readily dissolved in CO ₃ ^{2 -} at an initial pH of 12. The carbonation reaction was carried out by monitoring the pH of the solution and the concentration of the sulfate ion. As shown in FIG. 4, when the carbonation reaction was completed, the concentration of sulfate ions reached a constant value of about 800 mM, and the pH also reached a constant value of about 7.0. The dissolution rate of flue gas desulfurized gypsum increased with CO ₂ feed rate. An increase in the CO ₂ feed flow rate facilitates the carbonation reaction by facilitating the supply of carbonate ions in the solution that reacts with the calcium ions. In addition, agitation can be improved by increased CO ₂ feed flow rate to increase the dissolution of flue gas desulfurization gypsum.

FIG. 5 shows FE-SEM photographs of the solid residue filtered during the carbonation reaction, and it can be seen that the shape of the reaction product changed over time. The magnitude of the flue gas desulfurization gypsum was drastically reduced between 10 and 15 minutes in the low magnification (× 500) photomicrograph. The low magnification (× 1000) photomicrographs show that the calcium carbonate precipitate was separated from the desulfurization gypsum and the carbonation reaction proceeded through the separation of the flue gas desulfurization gypsum particles. It was found that the calcium carbonate precipitate was formed by separating from the flue gas desulfurization gypsum in the micrograph of high magnification (占 0000) and was not formed on the surface of the flue gas desulfurization gypsum. These results are also shown in the EDX mapping results of the solid residue after the carbonation reaction for 15 minutes in the method of producing high purity calcium carbonate using the direct carbonate reaction according to the present invention of FIG. 6A is an SEM photograph (× 10000), FIG. 6B is an EDS mapping result (CK _α , and C is an EDS mapping result (Al-K _α , After reaction EDS mapping result (SK _? ). In the photographs of CK _α (CaCO ₃ ) and SK _α (CaSO ₄ ), calcium carbonate was not formed on the surface of the flue gas desulfurization gypsum.

Experimental Example 3: Morphology Analysis of Calcium Carbonate

Of the three forms of calcium carbonate, baterite is the most thermodynamically unstable phase. The form of calcium carbonate in the present invention depends on the carbonation reaction sequence, the carbonation reaction time, and the like. The phase change with the carbonation reaction time was analyzed at CO ₂ feed rate of 1 L / min. FIG. 7 is a graph showing the XRD results of solid residues according to carbonation reaction time in the process for producing high purity calcium carbonate using the direct carbonation reaction according to the present invention. Calcium carbonate was not found in the XRD results when the carbonation reaction time was less than 15 minutes. 8 is a graph showing changes in the content of the baterite phase depending on the carbonation reaction time in the process for producing high purity calcium carbonate using the direct carbonateification reaction according to the present invention. In the direct carbonation reaction, the baterite phase increased with the passage of time, which can be confirmed by the FE-SEM in Fig. As shown in Fig. 8, the vaterite phase rapidly increased and stagnated after 45 minutes. The lack of calcium ions leads to the production of thermodynamically stable calcite sites. Accordingly, CO ₂ The partial pressure affects the crystallization and when the calcium ion is higher than 80 mM, CO ₂ Baterite is formed at partial pressure. As CO ₂ flow increases, the proportion of baterite increases because of the high CO ₃ ^{2 -} concentration. As shown in FIG. 4, the concentration of sulfate ion was relatively low (120 mM, 15% of the total amount) at 20 minutes, but rapidly increased to 89% of the total amount (720 mM) at 30 minutes. The concentration of dissolved sulfate ions is changed corresponding to the amount of dissolved calcium ions. As a result, when calcium ions are insufficiently dissolved, more calcite sites that are thermodynamically stable through late nucleation and growth during the initial stage are precipitated. On the other hand, when the reaction time was 30 minutes, 89% of the total amount of sulfate ion was dissolved. This provides sufficient calcium ions after 20 minutes and increases the tendency for the baterite phase to precipitate.

Experimental Example 4: Calcium carbonate formation analysis according to induction period

Calcium carbonate is present as a pair of ions dissolved during the induction period (carbonation reaction time) before the start of precipitation. The induction period is generally observed when the precipitation process is slow. That is, the concentration ratio of calcium to carbonate ion is stoichiometrically small.

9 is a XPS C1s spectral result of the solid residue generated according to the carbonation reaction time in the method of producing high purity calcium carbonate using the direct carbonation reaction according to the present invention. The intensity of the Cls peak of CaCO ₃ increases with the progress of the carbonation reaction. The carbonation was clearly observed after 20 minutes and the binding energy of C1s at 15 minutes was found to be small because the crystal growth was not completely completed, which is consistent with the XRD result of FIG.

FIG. 10 is a graph showing a change in the calcite concentration of calcium carbonate produced according to the carbonation reaction time in the method for producing high purity calcium carbonate using the direct carbonateification reaction according to the present invention. As shown in Fig. 10, the induction period is shortened as the CO ₂ gas flow rate is increased. This is because rapid chemical adsorption of CO ₂ gas accelerates precipitation of calcium carbonate as well as dissolution of flue gas desulfurization gypsum. In contrast, in the case of the conventional two-step reaction, since there are sufficient amounts of calcium ions and bicarbonate ions to form a calcium carbonate precipitate even after a reaction time of 5 minutes, there is no induction period in the manufacture of two- Due to these differences, it can be seen that the direct carbonation reaction according to the present invention can precipitate high purity calcium carbonate from the solution during the induction period (carbonation reaction time).

Experimental Example 5: Precipitation of high purity calcite

High-purity calcium carbonate crystals can be precipitated according to the reaction time in the direct carbonation reaction. Most of the impurities in the flue gas desulfurization gypsum are not dissolved and removed in the filtration process, so that no impurities are present in the solution. Therefore, pure calcium carbonate can be prepared from the filtered solution during the induction period.

To confirm this, the solution was allowed to stand for about 10 hours and the solid precipitate was recovered by filtration. From FE-SEM and XRD analysis, it was confirmed that the precipitate was a single crystal calcite crystal. 11 is an FE-SEM image of calcium carbonate precipitated in the filtered liquid after the carbonation reaction in the process for producing high purity calcium carbonate using the direct carbonation reaction according to the present invention. Fig. 11 (A) is an FE-SEM photograph of the calcite deposited in the filtered liquid after 5 minutes of carbonation reaction, Fig. 11 (B) FE-SEM photograph of the site.

The calcite crystals were several ㎛ in size and high purity, and most impurities were detected below the detection limit. The amount of high-purity calcite crystals obtained by the direct carbonation reaction according to the present invention was about 5% by weight of the flue gas desulfurization gypsum. It is considered that the crystallization rate of calcium carbonate should be delayed and the induction period should be prolonged in order to increase the yield of calcium carbonate and prepare high purity calcium carbonate.

Although the present invention has been described with respect to a specific embodiment of the method for producing high purity calcium carbonate using the direct carbonation reaction according to the present invention, it is apparent that various modifications can be made without departing from the scope of the present invention.

Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

It is to be understood that the foregoing embodiments are illustrative and not restrictive in all respects and that the scope of the present invention is indicated by the appended claims rather than the foregoing description, It is intended that all changes and modifications derived from the equivalent concept be included within the scope of the present invention.

Claims (12)

Drying the flue gas desulfurization gypsum and dissolving it in an ammonia solution;
Supplying carbon dioxide to the ammonia solution in which the flue gas desulfurization gypsum is dissolved to carry out carbonation reaction, and then filtering the carbon dioxide; And
Filtering the precipitated calcium carbonate after allowing the filtered liquid to settle,
Wherein the concentration of ammonia in the ammonia solution is 3.7 to 4.1 vol.%.
The method according to claim 1,
Wherein the carbonation reaction is carried out for 5 to 20 minutes.
The method according to claim 1,
(S / L) of the flue gas desulfurization gypsum is 5 - 20 g / L.
delete The method according to claim 1,
Wherein the flue gas desulfurization gypsum dissolution in the ammonia solution is performed by stirring at 350 - 450 rpm for 5 minutes.
The method according to claim 1,
Wherein the carbon dioxide is supplied at a rate of 1 - 3 L / min.
The method according to claim 1,
Wherein the carbonation reaction is carried out at room temperature and atmospheric pressure.
The method according to claim 1,
Wherein the carbonation is completed at a pH of about 7.
The method according to claim 1,
Wherein the filtration is carried out by a 0.2 μm membrane filter.
10. The method of claim 9,
Wherein the membrane filter is made of cellulose acetate. ≪ RTI ID = 0.0 > 11. < / RTI >
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