Method for extracting calcium

Abstract

A method for extracting calcium according to one embodiment of the present disclosure comprises: a first preparation step for preparing a material containing calcium and a solvent for extraction of calcium from the material; a first standing step for bringing the material into contact with the solvent and letting the same stand; and a first separation step for, following the standing step, separating from the material a calcium extract liquid obtained by the contact with the material.

Description

Calcium Extraction Method

[0001] The present disclosure relates to a method for extracting calcium.

[0002] In recent years, carbon dioxide is considered to have a large impact on global warming. Carbon dioxide fixation technology has attracted attention as an effective measure against this global warming problem. A method for fixing carbon dioxide by supplying carbon dioxide gas to an alkaline earth metal-containing substance in contact with a solvent is known (Japanese Patent Laid-Open Publication No. 2005-097072).

[0003] Japanese Patent Application Laid-Open No. 2005-097072

[0004] In Patent Document 1, a mixed solution of water and an aqueous solution of a salt of a weak base and a strong acid is used as the solvent for extracting calcium from an alkaline earth metal-containing substance (material) that fixes carbon dioxide, and the material is introduced into this solvent and stirred to extract the calcium. The use of the aqueous solution promotes the dissolution of components other than calcium in the material into the solvent, which may relatively suppress the extraction rate of calcium.

[0005] In view of the above circumstances, an object of the present disclosure is to provide a calcium extraction method that can easily improve the calcium extraction rate.

[0006] A calcium extraction method according to one aspect of the present disclosure that solves the above-mentioned problems includes a first preparation step of preparing a calcium-containing material and a solvent for extracting calcium from the material, a first standing step of contacting the material with the solvent and standing the material, and a first separation step of separating the calcium extract obtained by contacting the material with the solvent from the material after the first standing step.

[0007] The calcium extraction method of the present disclosure can easily improve the calcium extraction rate.

[0008] Fig. 1 is a graph showing the extraction rate of calcium extract obtained by a calcium extraction method according to an embodiment of the present disclosure and the extraction rate of calcium extract obtained by other extraction methods. Fig. 2 is a graph showing the extraction rate of calcium extract obtained in Test Examples 1 and 3 of Fig. 1. Fig. 3 is a graph showing the solid concentration in the calcium extract obtained in Test Examples 1, 2, and 3 of Fig. 1.

[0009] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] (1) A calcium extraction method according to one aspect of the present disclosure includes a first preparation step of preparing a calcium-containing material and a solvent for extracting calcium from the material, a first standing step of contacting the material with the solvent and standing the material, and a first separation step of separating the calcium extract obtained by contacting the material with the solvent from the material after the first standing step.

[0011] This calcium extraction method (hereinafter simply referred to as the "extraction method") involves contacting a prepared calcium-containing material with a solvent prepared for extracting calcium from the material and allowing them to stand. That is, the contacting material and the solvent are left standing without stirring or passing the solvent through, and calcium is extracted from the material. Because the solvent continues to contact the material, calcium in the material can be efficiently extracted, improving the extraction rate. In addition, it is possible to reduce the amount of material fragments that are generated by collisions between the materials due to stirring or solvent flow, thereby improving the purity of the calcium extract. This calcium extraction method does not require relatively large facilities for extracting calcium from the material, and therefore allows calcium to be extracted easily and efficiently at relatively low cost.

[0012] (2) In the above (1), the method may further include a second preparation step of further preparing a solvent for extracting calcium, a second standing step of contacting the material from which the calcium extract has been separated with the solvent prepared in the second preparation step and standing the material, and a second separation step of separating the calcium extract obtained by contact with the material from the material after the second standing step. By further contacting the material from which calcium has been extracted by contact with the solvent with a new solvent, calcium remaining in the material can be easily extracted.

[0013] (3) In the method (1) or (2), the first settling step may involve contacting the material with the solvent in a tank and allowing them to stand, and the first separation step may involve discharging the calcium extract from an outlet provided in the tank to separate it from the material, and the material filtering out foreign matter in the calcium extract through the outlet. By filtering out foreign matter in the solvent with the material, the purity of the calcium extract can be easily improved.

[0014] (4) In any of the above (1) to (3), the material may be steelmaking slag. By using steelmaking slag as the calcium-containing material, a calcium extract can be obtained at a relatively low cost, and the steelmaking slag can be reused.

[0015] (5) In any of (1) to (4), the first standing step may involve contacting a plurality of the materials with the solvent, and the plurality of materials may be in the form of granules or powder having an average particle size of 10 mm or less. By contacting the materials in the form of granules or powder having an average particle size of 10 mm or less with the solvent, the calcium extraction rate can be further improved.

[0016] (6) In any one of (1) to (5), the solvent may contain a polyol compound. By containing the polyol compound in the solvent, the calcium extraction rate can be further improved.

[0017] (7) In the above (6), the polyol compound may be glycerin. By using glycerin as the polyol compound, the calcium extraction rate can be further improved.

[0018] (8) In the above (4), when the ratio of the total weight of the solvent in contact with the steel slag to the weight of the steel slag is defined as the liquid-solid ratio, the contact time between the material and the solvent may be 1.0 [time / liquid-solid ratio] or more. By doing so, calcium can be efficiently extracted from the steel slag.

[0019] Here, the term "polyol compound" refers to an organic compound having a plurality of alcoholic hydroxyl groups (groups in which hydrogen atoms of an aliphatic hydrocarbon are substituted with hydroxy groups (-OH)).

[0020] [Details of the Mode for Carrying Out the Invention] Hereinafter, one embodiment of the calcium extraction method will be described in detail.

[0021] The extraction method includes a first preparation step of preparing a calcium-containing material and a solvent for extracting calcium from the material, a first standing step of contacting the material with the solvent and standing the material, and a first separation step of separating the calcium extract obtained by contacting the material with the solvent from the material after the first standing step.

[0022] The extraction method may further include a second preparation step of preparing a solvent for extracting calcium, a second standing step of contacting the material from which the calcium extract has been separated with the solvent prepared in the second preparation step and standing the solvent, and a second separation step of separating the calcium extract obtained by contact with the material from the material after the second standing step.

[0023] [First Preparation Step] The material prepared in the first preparation step is not particularly limited as long as it contains calcium. Natural minerals may be used, but from an environmental perspective, waste materials are preferred. Examples of such waste materials include construction waste, incineration ash, and by-products generated during manufacturing processes, such as industrial waste, household waste, and disaster waste. Examples include waste cement, concrete waste, glass waste, gypsum board waste, and interior waste materials such as calcium silicate boards, carbide slag, woody biomass waste, coal ash, incineration ash from garbage (municipal waste, industrial waste, disaster waste, etc.) or sludge, collected dust ash from an incinerator or kiln dust collector, woody biomass incineration ash, paper sludge incineration ash, cinders, soot, steelmaking slag, blast furnace slag, paper sludge, and sieve residue. In these materials, calcium exists, for example, in the form of calcium oxide (CaO). Among these, steelmaking slag is preferred. The steelmaking slag is a slag such as converter slag or electric furnace slag that is produced in the steelmaking process and contains a relatively large amount of calcium. Furthermore, by drying the steelmaking slag after calcium extraction, it can be reused as, for example, roadbed material (road material) or fertilizer resource.

[0024] The material is preferably in the form of granules or powder with an average particle diameter of 10 mm or less. The material may be in a lump form, but the lump is preferably pulverized to form granules with an average particle diameter of 10 mm or less. By making the material have an average particle diameter of 10 mm or less, the contact area with the solvent can be increased, thereby improving the calcium extraction efficiency. The lower limit of the average particle diameter of the material is not particularly limited, and may be 3 mm or 5 mm. The average particle diameter refers to the value based on the 50% cumulative volume (D50 value) measured using a laser scattering particle size distribution analyzer.

[0025] The solvent to be prepared is not particularly limited as long as it can extract calcium from the material, but preferably contains a polyol compound. The polyol compound is an organic compound having multiple alcoholic hydroxyl groups. The alcoholic hydroxyl groups are hydroxyl groups that replace hydrogen atoms of aliphatic hydrocarbons, and do not include hydroxyl groups that replace hydrogen atoms of hydrocarbons that constitute aromatic rings (e.g., hydroxyl groups of phenols).

[0026] Furthermore, it is preferable that the solvent further contains water. That is, it is preferable that the solvent is a mixed solution of a polyol compound and water. The upper limit of the concentration of the polyol compound in this mixed solution is preferably 60% by mass, more preferably 50% by mass, and even more preferably 40% by mass. The lower limit of the concentration is preferably 20% by mass, and more preferably 30% by mass. By setting the polyol compound concentration within the above range, a sufficient amount of calcium can be extracted from the material into the solvent. The water is not particularly limited, and examples thereof include pure water.

[0027] The polyol compound is not particularly limited as long as it is an organic compound having a plurality of alcoholic hydroxyl groups, but is preferably a diol compound or a triol compound. These diol compounds and triol compounds are usually liquid at room temperature and normal pressure, so they can be mixed with the water relatively easily. Note that the term "diol compound" refers to an organic compound having two of the above alcoholic hydroxyl groups, and the term "triol compound" refers to an organic compound having three of the above alcoholic hydroxyl groups.

[0028] The diol compound is not particularly limited as long as it is an organic compound having two alcoholic hydroxyl groups. Examples of the diol compound include ethylene glycol, propylene glycol, diethylene glycol, butanediol, and diethanolamine. Among these, the diol compound is preferably one or more selected from the group consisting of ethylene glycol, propylene glycol, and diethylene glycol.

[0029] The triol compound is not particularly limited as long as it is an organic compound having three alcoholic hydroxyl groups, but is preferably glycerin, which can further improve the efficiency of calcium extraction from the material.

[0030] [First Standing Step] In the first standing step, the material and the solvent are brought into contact and allowed to stand. The material and the solvent may be brought into contact, for example, by adding the material to a tank (container) and then injecting the solvent, or by injecting the solvent into a tank and then adding the material. The material may be premixed with a portion of the solvent to form a slurry, and this slurry may be brought into contact with the remainder of the solvent. The solvent is preferably poured so that the entire material or slurry in the tank is immersed. One or more relatively large chunks of material may be added to the tank, but it is preferable to add multiple granular or powdery materials.

[0031] In the first standing step, the material and the solvent are allowed to remain in the tank without stirring the material and the solvent in contact with each other in the tank, and without continuously injecting the solvent so that the solvent flows through the tank. In other words, the material and the solvent are left in contact with each other in the tank. This allows the solvent to maintain contact with the material, and calcium in the material can be efficiently dissolved in the solvent. The solvent changes into a calcium extract as calcium dissolves.

[0032] The time during which the contacting material and the solvent are allowed to stand in contact with each other, i.e., the actual time (standing time) during which the contact state continues, is not particularly limited and may be determined depending on the characteristics and amount of the material and the solvent. When the material is steelmaking slag, the contact between the material and the solvent is preferably 1.0 [hours / liquid-solid ratio] or more, where the ratio of the total weight of the solvent in contact with the steelmaking slag to the weight of the steelmaking slag is defined as the liquid-solid ratio (hereinafter, the contact time relative to the liquid-solid ratio is referred to as the "contact time"). The lower limit of the contact time may be 1.2 [hours / liquid-solid ratio] or 1.5 [hours / liquid-solid ratio]. The upper limit of the contact time for the steelmaking slag is not particularly limited, but may be 3.0 [hours / liquid-solid ratio] or 2.5 [hours / liquid-solid ratio]. By setting the contact time within the above range, the reliability of calcium extraction at a high extraction rate can be improved.

[0033] [First Separation Step] In the first separation step, the calcium extract obtained by contact with the material after the first settling step is separated from the material. The separation method is not particularly limited, and a known solid-liquid separator may be used, for example, but separation is preferably performed by discharging the calcium extract from an outlet provided at the bottom or side of the tank. The side outlet is preferably provided below the tank.

[0034] The calcium extract liquid is preferably free of foreign matter, such as fragments generated by collisions between the materials when they are introduced into the tank and impurities adhering to the materials. If foreign matter is present in the calcium extract liquid, it may be necessary to remove the foreign matter in order to improve the purity of the calcium extract liquid. To remove such foreign matter in advance, a filter or other filtering material may be placed at the outlet.

[0035] In the first separation step, the calcium extract is separated by being discharged from the outlet of the tank, and the material preferably filters out the foreign matter in the calcium extract. That is, the material preferably functions as a filter for the foreign matter. By filtering the foreign matter with the material, the purity of the calcium extract discharged from the outlet can be easily improved. When the material is in the form of granules or powder with an average particle diameter of 10 mm or less, the effect of removing fine foreign matter can be improved, and the purity of the calcium extract can be further improved.

[0036] If the material has a lower specific gravity than the solvent, that is, if the material floats or rises in the solvent, the solvent may be poured so that it does not exceed the top surface (height) of the material poured into the tank. By preventing the solvent from exceeding the top surface of the material poured into the tank, the material can be prevented from floating or rising in the solvent, and foreign matter can be effectively filtered out.

[0037] [Second Preparation Step] The solvent prepared in the second preparation step may be different from the solvent prepared in the first preparation step, but is preferably the same as the solvent prepared in the first preparation step.

[0038] [Second Standing Step] In the second standing step, the material from which the calcium extract solution has been separated is brought into contact with the solvent prepared in the second preparation step and allowed to stand. That is, the material from which the calcium extract solution has been separated is further brought into contact with a new solvent for extracting calcium. By repeatedly bringing the material into contact with the calcium-extracting solvent, the amount of calcium extracted from the material can be increased.

[0039] [Second Separation Step] After the second standing step, the method for separating the calcium extract obtained by contact with the material from the material may be different from that used in the first separation step, but is preferably the same method.

[0040] In this extraction method, a calcium-containing material is contacted with a solvent that extracts calcium from the material and allowed to stand, thereby maintaining continuous contact between the material and the solvent, allowing for efficient extraction of calcium from the material and improving the extraction rate. Even if the material has a relatively low specific gravity, the solvent is not circulated within the tank, preventing the material from leaking out of the tank, allowing for efficient extraction of calcium and improving the extraction rate. Furthermore, even if the material is brittle, for example, collisions between the materials do not occur due to stirring or solvent flow, and even if the material is a piece of paper, it does not dissolve in the solvent due to stirring or solvent flow, preventing parts of the material from being mixed into the calcium extract. Therefore, this extraction method improves the purity of the calcium extract.

[0041] The calcium extract obtained by this extraction method may be used for carbon dioxide fixation. That is, in a method for fixating carbon dioxide comprising the steps of obtaining a calcium extract, contacting the calcium extract with a gas containing carbon dioxide, and separating a precipitate from the calcium extract that has been contacted with carbon dioxide, the step of obtaining the calcium extract may be the extraction method. This extraction method can extract calcium at a high extraction rate, thereby increasing the amount of carbon dioxide fixed to calcium in the obtained calcium extract and increasing the amount of carbon dioxide reduction. Furthermore, carbon dioxide can be fixed at low cost, and the amount of the obtained precipitate (calcium carbonate) can be increased. The calcium extract from which the precipitate has been separated in the separation step may be used as a solvent for the extraction method.

[0042] [Other Embodiments] The above-described embodiments do not limit the configuration of the present invention. Therefore, the above-described embodiments may include omissions, substitutions, or additions of components based on the description in this specification and common general technical knowledge, and all of these should be construed as falling within the scope of the present invention.

[0043] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0044] The calcium-containing material includes unreacted CaO and unreacted Ca(OH). ２ A steelmaking slag containing 3% to 4% by mass of calcium carbonate was prepared and pulverized to an average particle size of 10 mm. As a solvent for extracting calcium from the steelmaking slag, glycerin having a purity of 84% to 87% and water were prepared and mixed so that the glycerin concentration was 40% by mass.

[0045] (Test Example 1) 35 kg of the material was placed in a tank with internal dimensions of 500 mm wide x 250 mm long x 500 mm high, and the solvent was poured into the tank at a flow rate of 0.7 kg / min until the top of the material was submerged. The tank was then left to stand for 30 minutes. After standing, the calcium extract was drained from the bottom of the tank and separated from the material. The time until the calcium extract ceased to flow (the time until drainage was complete) was approximately 30 to 45 minutes. After drainage was complete, the solvent was poured into the tank under the same conditions, and the tank was allowed to stand and separated under the same conditions. This procedure was repeated until the total weight of the solvent poured into the tank and in contact with the material was approximately five times the weight of the material.

[0046] (Test Example 2) 100 kg of the material was placed in a tank having the same internal dimensions as the tank, and the solvent was continuously supplied at 0.7 kg / min so as to flow through the tank. The calcium extract was allowed to overflow from the top of the tank and collected. The solvent was continuously supplied until the total weight was five times the weight of the material.

[0047] Test Example 3 Calcium was extracted under the same conditions as in Test Example 1, except that 100 kg of the material was placed in a tank having the same internal dimensions as the tank, and the solvent was supplied at a flow rate of 1.5 kg / min.

[0048] The calcium content of the calcium extracts obtained in Test Examples 1, 2, and 3 was ２＋ By measuring the concentration, the calcium extraction rate for each sample was calculated using the following formula 1. The results are shown in Table 1. The contact time for each test example in Table 1 is expressed as the liquid-solid ratio, which is the ratio of the total weight of the solvent in contact with the material to the weight of the material. Ca [mol] in calcium extract / Ca [mol] in material × 100 (1)

[0049]

[0050] As can be seen from Table 1, Test Example 1, in which calcium was extracted by standing still, had a higher calcium extraction rate despite the shorter contact time than Test Example 2, in which calcium was extracted by passing a liquid through. This is thought to be because the solvent was more efficiently allowed to flow into and come into contact with the materials (gaps between the materials) by standing still rather than by passing a liquid through.

[0051] Figure 1 shows the relationship between test time (the time from the start to the end of the test) and calcium extraction rate in Test Examples 1 and 3. Test Example 3, in which the standing time (actual time during which contact is maintained) per test was 5 minutes, had a higher calcium extraction rate than Test Example 1 when compared based on the time to completion of the test (2.25 hours). On the other hand, when test times were 5 hours or longer, Test Example 1 had a higher calcium extraction rate than Test Example 3. This indicates that when the standing time was shortened, the interval between the injection of the solvent and the discharge of the calcium extractant was short, resulting in frequent flow of the solvent and calcium extractant between the materials. This suppresses the calcium extraction effect due to continuous contact between the solvent and the materials, improving the calcium extraction rate per unit time, but resulting in a relatively small improvement in the calcium extraction rate per standing time. This suggests that the calcium extraction rate can be further improved by ensuring an appropriate standing time for calcium extraction and setting an appropriate number of standing times.

[0052] The relationship between contact time and calcium extraction rate in Test Examples 1 and 3 is shown in Figure 2. A straight line connecting Test Examples 1 and 3 indicates that the calcium extraction rate exceeded 60% when the contact time was set to 1.0 [hours / liquid-solid ratio], which is equal to or greater than that of Test Example 2, in which calcium was extracted by passing the liquid through the solution. Furthermore, a high extraction rate of approximately 70% was achieved when the contact time was set to 1.55 [hours / liquid-solid ratio].

[0053] The calcium extracts of each test example that had been discharged and separated from the material were filtered under reduced pressure, and the foreign matter in each calcium extract was dried to evaluate the concentration (solid concentration) of foreign matter in each calcium extract. The results are shown in Figure 3. As shown in Figure 3, the solid concentrations of Test Example 2, in which the overflowed calcium extract was recovered, were similar to those of Test Example 1. Since most of the foreign matter is thought to precipitate in the solvent, the solid concentration of Test Example 2, in which the overflowed calcium extract was recovered, is thought to be relatively low. The fact that the solid concentration of the calcium extract of Test Example 1 discharged from the bottom of the tank was similar to that of Test Example 2 indicates that the material functioned as a filter media, thereby suppressing the incorporation of foreign matter into the calcium extract discharged from the bottom.

[0054] The calcium extraction method of the present disclosure can efficiently extract calcium without using special equipment, and is therefore suitable for use in recycling industrial waste and fixing carbon dioxide in the extracted calcium extract.

Claims

1. A calcium extraction method comprising: a first preparation step of preparing a calcium-containing material and a solvent for extracting calcium from the material; a first standing step of contacting the material with the solvent and standing the material; and a first separation step of separating, from the material, the calcium extract obtained by contact with the material in the first standing step.

2. The extraction method according to claim 1, further comprising: a second preparation step of further preparing a solvent for extracting calcium; a second standing step of contacting the material from which the calcium extract has been separated with the solvent prepared in the second preparation step and standing the material; and a second separation step of separating the calcium extract obtained by contact with the material from the material after the second standing step.

3. The calcium extraction method according to claim 1, wherein in the first standing step, the material and the solvent are brought into contact with each other in a tank and allowed to stand, and in the first separation step, the calcium extract is discharged from an outlet provided in the tank and separated from the material, and foreign matter in the calcium extract is filtered out by the material when discharged from the outlet.

4. The calcium extraction method according to claim 1, wherein the material is steel slag.

5. A calcium extraction method as described in claim 3 or claim 4, wherein in the first standing step, a plurality of materials are brought into contact with the solvent and allowed to stand, and the plurality of materials are in the form of granules or powder having an average particle size of 10 mm or less.

6. The calcium extraction method according to claim 1, wherein the solvent contains a polyol compound.

7. The calcium extraction method according to claim 6, wherein the polyol compound is glycerin.

8. The calcium extraction method according to claim 4, wherein in the first settling step, the contact time between the material and the solvent is 1.0 [time / liquid-solid ratio] or more, where the ratio of the total weight of the solvent in contact with the steel slag to the weight of the steel slag is defined as the liquid-solid ratio.

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