KR20200077065A - A method for preparing calcium carbonate using sludge generated during annealing and pickling process of stainless steel, and a calcium carbonate prepared by the same - Google Patents

Abstract

A calcium carbonate production method of the present invention utilizes waste resources by using sludge generated after an annealing and pickling process, thereby efficiently producing calcium carbonate and simultaneously removing carbon dioxide.

Description

Method for manufacturing calcium carbonate using annealing pickling sludge and calcium carbonate prepared accordingly {A METHOD FOR PREPARING CALCIUM CARBONATE USING SLUDGE GENERATED DURING ANNEALING AND PICKLING PROCESS OF STAINLESS STEEL, AND A CALCIUM CARBONATE PREPARED BY THE SAME}

Disclosed herein is a method for producing calcium carbonate using annealed sludge, and calcium carbonate prepared accordingly.

Among carbon dioxide treatment technologies, mineral carbonation is a method of converting and storing solid carbonate minerals by reacting cations such as calcium and magnesium in an aqueous solution with carbon dioxide.

Currently, research on storage, capture, and conversion (biological and chemical) is actively underway to reduce greenhouse gas carbon dioxide, but collection/storage technology is difficult to secure storage facilities and has limited transportation, and bioconversion is insignificant.

On the other hand, the carbon dioxide conversion method using the mineral carbonation method is an excellent technique that can not only process a large amount of carbon dioxide but also produce calcium carbonate to secure economic efficiency.

Accordingly, it is possible to access various sources of calcium for mineral carbonization, and in particular, by using calcium contained in the waste, it is possible to overcome the environmental problems caused by waste treatment and significantly reduce the environmental burden, thereby producing high value-added materials.

Korean Registered Patent No. 10-1375735 Korean Registered Patent No. 10-1854116

In one aspect, an object of the present invention is to use waste annealing sludge containing a large amount of calcium ions to effectively use waste resources, economically and efficiently reduce carbon dioxide, and simultaneously produce calcium carbonate.

In one aspect, the present invention comprises the steps of recovering and drying the annealed sludge; Adding the dried annealed sludge to an acidic solution containing chloride ions to produce an elution solution containing calcium ions; Removing impurities from the elution solution; And producing calcium carbonate by supplying carbon dioxide to the elution solution from which the impurities have been removed.

In another aspect, the present invention provides calcium carbonate prepared according to the above-described calcium carbonate manufacturing method.

In one aspect, the method for producing calcium carbonate of the present invention uses annealing acid sludge containing a large amount of calcium ions, so that it can supply raw materials economically.

In addition, calcium carbonate can be produced only by supplying chloride ions to increase the solubility of calcium without high concentrations of acids and bases, thereby minimizing production costs and securing economic efficiency.

In another aspect, the method for producing calcium carbonate of the present invention removes carbon dioxide at the same time as the production of calcium carbonate, and thus can be applied in a purification field to prevent warming.

Figure 1, in the embodiment of the present invention, when the dried annealed sludge 10g and hydrochloric acid (HCl) 10M, 1M, ammonium chloride (NH ₄ Cl) 2.5M, 1M each reacted by 100ml, the content of the eluted calcium ion It is a schematic diagram showing.
FIG. 2 shows the amount of calcium carbonate produced over time by injecting carbon dioxide into an elution solution (1M hydrochloric acid) having the best elution efficiency in an embodiment of the present invention.

Term Definition

In the present specification, when a part “includes” a certain component, it means that the component may further include other components, rather than excluding other components, unless otherwise specified.

Exemplary Of implementations Explanation

Hereinafter, the present invention will be described in detail.

In exemplary embodiments of the present invention, recovering and drying the annealed sludge; Adding the dried annealed sludge to an acidic solution containing chloride ions to produce an elution solution containing calcium ions; Removing impurities from the elution solution; And producing calcium carbonate by supplying carbon dioxide to the elution solution from which the impurities have been removed.

In this specification, "annealed pickling sludge" is sludge generated after neutralization treatment after the annealing pickling process. Specifically, due to washing of stainless steel, hydrofluoric acid, etc., various minerals are dissolved in water to discharge low pH annealed sludge, and an active treatment method using slaked lime is used to neutralize it.

Due to this, a large amount of unreacted calcium ions are contained in the annealed sludge, and if using the mineral carbonization method using this, it is possible to economically and efficiently reduce carbon dioxide and simultaneously produce calcium carbonate.

In one aspect, the annealed sludge may be recovered and dried, crushed into a rubber hammer. Specifically, the dried annealed sludge may be further subjected to a sieving step after a crushing process to be in a powder form, filtered through a 100 mesh sieve, and provided in a powder form having a uniform particle size and an increase in specific surface area, elution solution and carbon dioxide, which will be described later. The reaction with can be generated efficiently.

In one aspect, the annealing acid sludge may be an annealing acid sludge of less than pH 7, for example, less than pH 7, pH 6.9 or less, pH 6.7 or less, pH 6.5 or less, pH 6.3 or less, pH 6.1 or less, pH 5.9 or less, pH It may be 5.7 or less, pH 5.5 or less, pH 5.3 or less, pH 5.1 or less, pH 4.9 or less, pH 4.7 or less, pH 4.5 or less, pH 4.3 or less, pH 4.1 or less, pH 3.9 or less or pH 3.5 or less.

In one embodiment, the dried annealed sludge includes a metal or metalloid element, fluorine, and sulfur, and the metal or metalloid element may be one or more selected from the group consisting of Ca, and Fe, and Cr. .

Therefore, when the dried annealed sludge is added to the acidic solution containing the chloride ions, the metal or metalloid element, fluorine, and sulfur contained in the annealed sludge in the aqueous solution are eluted in the form of ions. This will elute.

After the elution, the step of removing impurities can be performed by adjusting the pH. In the case of other major ions (Fe, Cr) contained in the annealing pickling sludge, precipitates at pH 11~11.5, and in the case of calcium (Ca) ions, they exist in the ionic phase at pH 11. By doing so, impurities can be removed. In one embodiment, when the annealed sludge is analyzed by X-ray fluorescence spectrometry (XRF), the content of Ca is 20% or more based on the weight of all metal or metalloid elements, fluorine, and sulfur. It may be, for example, 25% or more, 30% or more, 35% or more, or 37% or more.

When the Ca in the annealed sludge of the present invention contains a large amount, when using it to produce calcium carbonate, it can be confirmed that a large amount of calcium carbonate can be produced.

In one embodiment, the acidic solution containing chloride ions may be at least one selected from the group consisting of hydrochloric acid, ammonium salt solution, ammonium acetate solution, and ammonium chloride solution, and if it contains chloride ions capable of eluting calcium ions It is not limited to this.

In one embodiment, the dried annealed sludge and the acidic solution containing the chloride ions may be mixed at a solid-liquid ratio (S/L) of 50 to 150 g/L. When the solid-liquid ratio is less than 50 g/L, there is a problem in that the process cost is increased by excessively containing an acidic solution containing chloride ions, and if it is more than 150 g/L, the calcium carbonate yield may not increase proportionally.

In one embodiment, the concentration of the acidic solution containing the chloride ion may be 0.1 to 15 M, for example, 0.5 M or more, 0.7 M or more, or 1 M or more, 10 M or less, 5 M or less, or 3 M or less. When the concentration of the acidic solution is less than 0.1M, it is difficult to sufficiently extract calcium ions, and when it is more than 2M, iron and chromium ions may be dissolved in addition to calcium ions.

At this time, since the elution solution contains a large amount of impurities, it is preferable to perform a filtering process, and the filtering process is not limited to this, as long as it is a method capable of separating impurities other than calcium ions.

After the elution, the step of removing impurities may be performed by adjusting the pH. In the case of other ions (Fe, Cr) contained in the annealed acid sludge, precipitates at pH 11 to 11.5, and in the case of calcium (Ca) ions, they exist in the ionic phase even at pH 11, thereby increasing the pH to remove impurities. When the carbon dioxide is injected later, it is possible to form pure calcium carbonate.

In addition, after the pH is adjusted, an aqueous solution of the supernatant having only calcium ions is separated from other solidified ions to react with carbon dioxide, and solid-liquid separation may be primarily performed using a syringe filter. Subsequently, when solid-liquid separation is performed using a syringe filter, substances of 0.2 μm or less may escape, thereby affecting the purity, and thus additional impurities (solidified other ions) are obtained by performing solid-liquid separation of the eluent through centrifugation. ) Can be removed.

Thereafter, carbon dioxide is supplied to the elution solution from which the impurities are removed to produce calcium carbonate. As a mineral carbonation reaction, the carbon dioxide reacts with calcium ions contained in the elution solution to produce calcium carbonate.

In one embodiment, the step of producing the calcium carbonate may be performed at pH 9 to 11.5, for example, pH 9.5 or higher, pH 10 or higher, pH 10.5 or higher, pH 11 or lower, pH 10.5 or lower, pH 10 or lower Can. When the pH is less than 9, other heavy metals or cations do not precipitate and aggregate, so impurities may be formed, and if it is more than 11.5, Ca may be dissolved to reduce calcium carbonate production efficiency. The method for producing calcium carbonate according to the present invention can maintain the pH range without adding a pH adjusting agent.

In one aspect, the carbon dioxide may be supplied at 100ml/min to 1500ml/L, for example, 300 ml/min or more, 500 ml/min or more, or 700 ml/min or more, 1400 ml/min or less, 1300 ml /min or less, or 1200 ml/min or less. When the carbon dioxide is supplied at less than 100 ml/min, the mineral carbonation reaction time is excessively long, and when it exceeds 1500 ml/min, the unreacted carbon dioxide is excessively discharged.

In exemplary embodiments of the present invention, calcium carbonate prepared according to the above-described calcium carbonate manufacturing method is provided.

Hereinafter, the present invention will be described in more detail through the following examples. However, the following implementations are provided for the purpose of illustration only to aid understanding of the present invention, and the scope and scope of the present invention are not limited thereto.

Example

Example One: Annealed acid sludge Recovery and moisture content measurement

The annealing pickling sludge used sludge sediment generated in a facility for neutralizing stainless washing wastewater in POSCO, and was used without any other manufacturing process. The recovered annealed sludge was measured for moisture content using a weight difference before and after drying at 105°C for 2 hours, and exhibited a moisture content of about 30%.

Example 2 : Annealed pickling Sludge Checking the presence of calcium and preparing calcium elution

The annealed sludge prepared in Example 1 was dried and sieved through a 100 mesh standard sieve, and subjected to XRF analysis for elemental analysis. As a result of XRF analysis, it was confirmed that Ca 37% and Fe 30% were distributed, and it was confirmed that a sufficient amount of calcium for producing calcium carbonate was included in the annealed sludge.

Component Ca Fe F S Cr Ni Mg Si Al Na Mn Inclusion amount in annealed sludge (wt%) 37.90 30.40 13.50 6.60 6.47 2.02 1.07 0.67 0.32 0.29 0.26

10 g of the dried annealed sludge 10 g, without separate pre-treatment, were mixed in a plastic bottle with 100 ml each of each extract type (HCl 10M, 1M, ammonium chloride (NH ₄ Cl) 2.5M, 1M), and then mixed. The mixture was stirred for 1 hour at 150 rpm at 25°C in a constant temperature horizontal shaking reactor.

After completion of the reaction, the pH of the eluate was adjusted to pH 11 or higher, and then a solid was removed using a 0.4 um PVDF filter, and a sample that passed through the filter was used as an analytical sample. The sample for analysis was analyzed through ICP-OES, and the extraction efficiency was evaluated by calculating the extraction amount per g using the analyzed concentration. When using 10M hydrochloric acid, the amount of hydrochloric acid used was higher than that of elution. Specifically, referring to FIG. 1, when using hydrochloric acid solution 1M, extraction efficiency of 11% was shown, and about 30% of Ca (37.9%) contained in the annealed sludge could be extracted.

Example 3: Calcium carbonate production through carbon dioxide reaction

Ca was extracted as in Example 2 for the annealed sludge prepared in Example 1, and after the reaction was completed, the pH of the eluent was adjusted to pH 11 or higher, and solids in the extraction solution were removed using a 0.4 um PVDF filter. The solution that passed through the filter was used as a carbon dioxide reaction sample.

The concentration of the resulting calcium carbonate was confirmed by injecting without a separate device in an aqueous solution at a rate of 1 L/min using 100% of commercially available carbon dioxide. The amount of calcium carbonate produced was collected in 10 ml of aqueous solution during the reaction, and centrifuged (3000 rpm 20 min) to remove the supernatant, dried at 105° C. for 2 hours, and then checked for weight.

FIG. 2 shows the amount of calcium carbonate produced per hour by injecting carbon dioxide. Referring to this, it can be confirmed that the amount of calcium carbonate increases over time, but does not increase any more after 30 minutes.

Claims (9)

Recovering and drying the annealed sludge;
Adding the dried annealed sludge to an acidic solution containing chloride ions to produce an elution solution containing calcium ions;
Removing impurities from the elution solution; And
Method for producing a calcium carbonate comprising; supplying carbon dioxide to the elution solution from which the impurities are removed to generate calcium carbonate.
According to claim 1,
The annealing pickling sludge is produced by neutralizing the wastewater after washing stainless, the method for producing calcium carbonate.
According to claim 1,
The dried annealed sludge contains metal or metalloid elements, fluorine, and sulfur,
The metal or metalloid element is characterized in that at least one selected from the group consisting of Ca, and Fe, and Cr, calcium carbonate manufacturing method.
According to claim 1,
When the dried annealed sludge is analyzed by X-ray flourescence spectrometry (XRF), the content of Ca is 20% or more based on the weight of all metal or metalloid elements, fluorine, and sulfur. Calcium carbonate production method.
According to claim 1,
The dried annealed acid sludge and the acidic solution containing the chloride ions, characterized in that mixed in a solid-liquid ratio (solid-liquid ratio, S / L) of 50 to 150 g / L, calcium carbonate production method.
According to claim 1,
The concentration of the acidic solution containing the chloride ion is characterized in that 0.1 to 15 M, calcium carbonate manufacturing method.
According to claim 1,
The acidic solution containing the chloride ion is characterized in that at least one selected from the group consisting of hydrochloric acid, ammonium salt solution, ammonium acetate solution, and ammonium chloride solution, calcium carbonate production method.
According to claim 1,
The step of producing the calcium carbonate is characterized in that performed at pH 9 to 11.5, calcium carbonate production method.
Calcium carbonate prepared according to the method for producing calcium carbonate according to any one of claims 1 to 8.

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