Calcium extraction method, carbon dioxide fixation method, and carbon dioxide fixation apparatus

Abstract

To provide a method for fixing carbon dioxide, which can fix carbon dioxide easily in a calcium extract obtained by extracting calcium in slag efficiently while suppressing generation of fine powder of slag and which can improve purity of the solvent and carbonate salt after fixing carbon dioxide.SOLUTION: A method for fixing carbon dioxide according to one aspect of the present invention comprises: a circulation step of circulating a solvent containing a polyol compound through a slag layer formed by filling slag containing calcium into a container; an aeration step of aerating a calcium extract, obtained by passing the solvent through the slag layer according to the circulation step, with a gas containing carbon dioxide; and a separation step of carrying out solid-liquid separation of precipitates deposited from a mixture obtained by the aeration step. In the circulation step, the solvent is circulated at a speed at which the slag layer does not flow.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for extracting calcium, a method for fixing carbon dioxide, and a carbon dioxide fixing apparatus.

Background Art

[0002] In recent years, climate change due to global warming has become a problem. Carbon dioxide (CO2) in the atmosphere is one of the greenhouse gases and is considered a major cause of global warming. Therefore, reduction of CO2 emissions and the like are demanded.

[0003] As one of the means for reducing CO2 emissions, there is a technology for fixing CO2. As a target for fixing CO2, a CO2 immobilization method using an alkaline earth metal-containing substance such as slag is known (Japanese Patent Application Laid-Open No. 2005-097072).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

[0005] In Patent Document 1, the above-mentioned alkaline earth metal-containing substance is put into an aqueous solution containing a weak base and a salt of a strong acid in a first reaction vessel and stirred, and the stirred aqueous solution containing calcium chloride (CaCl2) is transferred to a second reaction vessel and aerated with carbon dioxide gas to generate calcium carbonate (CaCO3) to fix CO2, and at the same time, a carbonate is obtained.

[0006] In Patent Document 1, because stirring is performed, fine particles of the alkaline earth metal-containing substance may be present in the aqueous solution. The aqueous solution and the resulting carbonate after aeration with carbon dioxide may have reduced purity due to the inclusion of these fine particles, potentially limiting their applications. Furthermore, because the stirring and aeration are performed in different reaction vessels, the carbon dioxide fixation process may become complicated.

[0007] In view of these circumstances, the present invention aims to provide a calcium extraction method that can efficiently extract calcium from slag into a solvent while suppressing the generation of fine slag particles, and a carbon dioxide fixation method and apparatus that can easily fix carbon dioxide in the calcium extract obtained by this extraction method and improve the purity of the solvent and carbonate after carbon dioxide fixation. [Means for solving the problem]

[0008] A calcium extraction method according to one aspect of the present invention, which solves the above problems, comprises a flow step of flowing a solvent containing a polyol compound through a slag layer formed by filling a container with calcium-containing slag, wherein the solvent is flowed through the flow step at a rate that does not cause the slag layer to flow.

[0009] A carbon dioxide fixation method according to another aspect of the present invention that solves the above problems comprises a flow step of flowing a solvent containing a polyol compound through a slag layer formed by filling a container with calcium-containing slag; an aeration step of aerating a carbon dioxide-containing gas into a calcium extract obtained by the passage of the solvent through the slag layer in the flow step; and a separation step of solid-liquid separation of precipitates precipitated from the mixed liquid obtained in the aeration step, wherein in the flow step, the solvent is flowed at a rate that does not cause the slag layer to flow.

[0010] A carbon dioxide fixation apparatus according to yet another aspect of the present invention, which solves the above problems, comprises a container for filling with calcium-containing slag to form a slag layer, a supply unit for supplying a solvent containing a polyol compound to the container, an adjustment unit for adjusting the amount of solvent supplied so that the slag layer does not flow, a storage unit for storing a calcium extract that passes through the slag layer and is discharged from the container, an aeration unit for aerating the extract stored in the storage unit with a gas containing carbon dioxide, and a separation unit for solid-liquid separation of precipitates in the mixed liquid obtained by aeration by the aeration unit. [Effects of the Invention]

[0011] The calcium extraction method of the present invention can efficiently extract calcium from slag into a solvent while suppressing the generation of fine slag particles. The carbon dioxide fixation method and apparatus of the present invention can easily fix carbon dioxide in the calcium extract obtained by the above extraction method, and can improve the purity of the solvent and carbonate after carbon dioxide fixation. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a conceptual diagram showing a carbon dioxide sequestration device according to one embodiment of the present invention. [Figure 2] Figure 2 is a conceptual diagram showing the test apparatus used in the embodiment of the present invention. [Figure 3] Figure 3 is a graph showing the relationship between the empty velocity and pressure drop of the solvent flowing through the slag layer formed in the container of the test apparatus shown in Figure 2. [Modes for carrying out the invention]

[0013] A calcium extraction method according to one aspect of the present invention comprises a flow step in which a solvent containing a polyol compound is flowed through a slag layer formed by filling a container with calcium-containing slag, and in the flow step, the solvent is flowed at a rate that does not cause the slag layer to flow.

[0014] The calcium extraction method (hereinafter also referred to as "the extraction method") involves flowing a solvent containing a polyol compound through the slag layer of calcium (Ca)-containing slag and bringing it into contact with the slag layer. Therefore, the calcium can be efficiently extracted as calcium ions into the solvent. The solvent is flowed at a speed that does not cause the slag layer to flow, thus suppressing the generation of fine powder (slag fragments) caused by collisions between slag particles in the solvent.

[0015] Another embodiment of the present invention relates to a carbon dioxide fixation method comprising: a flow step of flowing a solvent containing a polyol compound through a slag layer formed by filling a container with calcium-containing slag; an aeration step of aerating a carbon dioxide-containing gas into a calcium extract obtained by the passage of the solvent through the slag layer in the flow step; and a separation step of solid-liquid separation of precipitates precipitated from the mixed solution obtained in the aeration step, wherein in the flow step, the solvent is flowed at a rate that does not cause the slag layer to flow.

[0016] This carbon dioxide fixation method allows for efficient extraction of calcium from the slag during the extraction process, thus enabling the fixation of a larger amount of carbon dioxide into the calcium. Furthermore, since the generation of slag fragments is suppressed during the extraction process, the decrease in the purity of the solvent after carbon dioxide fixation, and the purity of the carbonate obtained by fixing carbon dioxide, can be suppressed.

[0017] The carbon dioxide fixation method may further include a reuse step in which the separated liquid separated in the separation step is reused as at least part of the solvent in the flow step. By circulating and reusing the solvent in this way, the carbon dioxide fixation method can be carried out at a low cost.

[0018] In the above-described flow process, it is preferable to flow the solvent so that the pressure loss of the solvent flowing through the slag layer is 14 kPa / m or less. Doing so can further suppress the generation of slag fragments.

[0019] In the above-described circulation process, it is preferable to circulate the solvent so that the superficial velocity of the solvent flowing through the slag layer is 0.4 mm / s or less. By doing so, the generation of slag pieces can be further suppressed.

[0020] The polyol compound is preferably a diol compound or a triol compound. By doing so, calcium in the slag can be more efficiently extracted as calcium ions.

[0021] The diol compound is preferably one or more selected from the group consisting of ethylene glycol, propylene glycol, and diethylene glycol. By doing so, calcium in the slag can be more efficiently extracted as calcium ions.

[0022] The triol compound is preferably glycerin. By doing so, calcium in the slag can be more efficiently extracted as calcium ions.

[0023] A carbon dioxide fixing device according to another aspect of the present invention includes a container for filling slag containing calcium to form a slag layer, a supply unit for supplying a solvent containing a polyol compound to the container, an adjustment unit for adjusting the supply amount of the solvent so that the slag layer does not flow, a storage unit for storing a calcium extract discharged from the container through the slag layer, an aeration unit for aerating a gas containing carbon dioxide into the extract stored in the storage unit, and a separation unit for solid-liquid separating precipitates in the mixed liquid obtained by the aeration by the aeration unit.

[0024] Since the carbon dioxide fixing device includes an adjustment unit for adjusting the supply amount of the solvent supplied to the slag layer to an amount at which the slag does not flow, the generation of slag pieces can be suppressed and carbon dioxide can be efficiently fixed.

[0025] Here, "polyol compound" refers to an organic compound having multiple alcoholic hydroxyl groups (groups in which a hydrogen atom of an aliphatic hydrocarbon is replaced with a hydroxyl group (-OH)). Similarly, "diol compound" refers to an organic compound having two of the above alcoholic hydroxyl groups, and "triol compound" refers to an organic compound having three of the above alcoholic hydroxyl groups.

[0026] [Details of the embodiment for carrying out the invention] The present invention will be described in detail below with reference to the drawings as appropriate. Note that the drawings are for illustrative purposes only, and each component (each member) is conceptually depicted; the shape, scale, etc., may differ from the actual product. Components such as pumps for transferring liquids (solvents, etc., described later) or valves for transferring liquids at appropriate timings may be omitted. Furthermore, this specification may describe multiple upper and lower limits as numerical ranges for the components of the present invention. These multiple upper and lower limits are described in such a way that one of them can be arbitrarily selected, or they can be arbitrarily combined.

[0027] [Carbon dioxide fixation methods] The carbon dioxide fixation method mainly comprises a flow step of flowing a solvent containing a polyol compound through a slag layer formed by filling a container with calcium-containing slag; an aeration step of aerating a carbon dioxide-containing gas into the calcium extract obtained by the passage of the solvent through the slag layer in the flow step; and a separation step of separating the precipitate precipitated from the mixture obtained in the aeration step into solid and liquid form. In the flow step, the solvent is flowed at a rate that does not cause the slag layer to flow.

[0028] The carbon dioxide fixation method further comprises a reuse step in which the separated liquid separated in the separation step is reused as at least a portion of the solvent in the flow step. The carbon dioxide fixation method is carried out using a carbon dioxide fixation apparatus as shown in Figure 1.

[0029] <Carbon dioxide fixation device> The carbon dioxide fixation apparatus mainly comprises a container 1 for filling with calcium-containing slag to form a slag layer S, a supply unit 2 for supplying a solvent M containing a polyol compound to the container 1, an adjustment unit 3 for adjusting the supply rate of the solvent M so that the slag layer S does not flow, a storage unit 4 for storing the calcium extract M1 that passes through the slag layer S and is discharged from the container 1, an aeration unit 5 for aerating the extract M1 stored in the storage unit 4 with a gas C containing carbon dioxide, and a separation unit 6 for solid-liquid separation of precipitates D in the mixed liquid M2 obtained by aeration by the aeration unit 5.

[0030] The carbon dioxide fixation device further includes a circulation unit 7 that circulates the separated liquid M3, obtained by separating the precipitate D in the separation unit 6, back to the supply unit 2.

[0031] <Slag> Slag is not particularly limited as long as it contains calcium, but examples include blast furnace slag, steelmaking slag, cement, concrete waste, glass waste, coal ash, and sludge incineration ash. The blast furnace slag mentioned above is slag produced during the ironmaking process, and the steelmaking slag mentioned above is slag produced during the steelmaking process, such as converter slag or electric furnace slag. In these slags, calcium exists, for example, in the form of calcium oxide (CaO).

[0032] <Solvent> Solvent M contains a polyol compound. The polyol compound is a medium for extracting calcium from the slag. The polyol compound is an organic compound having multiple alcoholic hydroxyl groups. The alcoholic hydroxyl groups are hydroxyl groups obtained by substituting hydrogen atoms of aliphatic hydrocarbons, and do not include hydroxyl groups obtained by substituting hydrogen atoms of hydrocarbons constituting an aromatic ring (e.g., the hydroxyl group of phenol).

[0033] The polyol compound is not particularly limited as long as it is an organic compound having multiple alcoholic hydroxyl groups, but diol compounds or triol compounds are preferred.

[0034] The above-mentioned diol compound is not particularly limited as long as it is an organic compound having two alcoholic hydroxyl groups, and examples include ethylene glycol, propylene glycol, diethylene glycol, butanediol, or diethanolamine. Of these, the above-mentioned diol compound is preferably one or more selected from the group consisting of ethylene glycol, propylene glycol, and diethylene glycol.

[0035] For example, it is generally known that the solubility of calcium in ethylene glycol is about 10 times that of calcium in water. In other words, the solubility of calcium in diol compounds is far greater than that in water. Therefore, if the diol compound is one or more selected from the above group, calcium can be extracted more efficiently from the slag layer S.

[0036] The above triol compound is not particularly limited as long as it is an organic compound having three alcoholic hydroxyl groups, but glycerin is preferred. By using glycerin, calcium can be extracted more efficiently from the slag layer S.

[0037] The upper limit of the concentration of the polyol compound in the solvent M flowing through the slag layer S is preferably 60% by mass, more preferably 50% by mass, and even more preferably 40% by mass. If the concentration of the polyol compound exceeds the upper limit, the precipitation of precipitates (carbonates) in the aeration process described later may be reduced. In other words, the efficiency of carbon dioxide fixation may be reduced. The lower limit of the concentration of the polyol compound in the solvent M in the flow process is preferably 20% by mass, and more preferably 30% by mass. If the concentration of the polyol compound is less than the lower limit, a sufficient amount of calcium may not leach from the slag layer S into the solvent M.

[0038] The solvent M preferably further contains water. Since the diol compound and triol compound are usually liquid at room temperature and pressure, they can be relatively easily mixed with the water and flow through the slag layer S. The water contains protons (H) for ionizing carbon dioxide (carbonate ionization). + ) becomes a source of carbon dioxide. Furthermore, in the distribution process described later, calcium ions extracted by the polyol compound migrate (diffuse) into water, and carbon dioxide is added to this water as carbonate ions (CO3). 2- It dissolves as ). As a result, calcium ions and carbonate ions react with this water as the reaction site, and precipitate as calcium carbonate. Such water is not particularly limited as long as it functions catalytically as described above, for example, pure water.

[0039] [Distribution process] In the distribution process, a solvent M containing a polyol compound is circulated through a slag layer S formed by filling a container 1 with calcium-containing slag. The container 1 is not particularly limited as long as it can be filled with slag to form a slag layer S and through which the solvent M containing the polyol compound can be circulated.

[0040] In the distribution process, the solvent M is distributed at a speed that does not cause the slag layer S to flow. That is, the solvent M is distributed at a speed that does not cause the slag in the slag layer S to move relative to each other within the container 1 and collide. If the slag collides with each other as the solvent M is distributed, the fragments (slag pieces) will be mixed into the solvent M discharged from the container 1. The inclusion of these slag pieces in the solvent M may reduce the purity of the solvent M after carbon dioxide fixation, potentially limiting its uses or reuse. In addition, carbonate is obtained from the solvent M discharged from the container 1 through carbon dioxide fixation, but if these carbonates are also mixed with the slag pieces, their purity may decrease, potentially limiting their uses. To improve the purity of the solvent M discharged from the container 1, a process to remove the slag pieces is necessary, which may increase the cost of using or reusing the solvent M and carbonate discharged from the container 1.

[0041] The carbon dioxide fixation apparatus comprises a supply unit 2 for supplying solvent M and an adjustment unit 3 for adjusting the amount of solvent M supplied. The adjustment unit 3 adjusts the flow rate of solvent M supplied by the supply unit 2 to the container 1, controlling the flow velocity of solvent M within the container 1 so that the slag layer S does not flow. The supply unit 2 is not particularly limited and can be, for example, a pump for liquids. The adjustment unit 3 is not particularly limited and can be, for example, an adjustment valve with a variable opening diameter. The adjustment unit 3 is installed in a solvent supply pipe P1 that connects the container 1 and the supply unit 2.

[0042] In the flow process, it is preferable to flow the solvent M through the slag layer S such that the pressure drop of the solvent M flowing through the slag layer S is 14 kPa / m or less. The upper limit of the pressure drop of the solvent M flowing through the slag layer S is more preferably 12 kPa / m, even more preferably 10 kPa / m, and particularly preferably 6 kPa / m. If the pressure drop of the solvent M flowing through the slag layer S exceeds the above upper limit, the slag in the slag layer S may move relative to each other within the container 1 and collide with each other.

[0043] Furthermore, in the flow process, it is preferable to flow the solvent M through the slag layer S such that the empty velocity of the solvent M flowing through the slag layer S is 0.4 mm / s or less. A more preferable upper limit for the empty velocity of the solvent M flowing through the slag layer S is 0.3 mm / s. If the empty velocity of the solvent M flowing through the slag layer S exceeds the above upper limit, the slag in the slag layer S may move relative to each other within the container 1, potentially causing collisions. There is no particular lower limit for the empty velocity of the solvent M flowing through the slag layer S, but for example, it is 0.08 mm / s.

[0044] Slag from which calcium has been removed during the distribution process can be used as a resource such as roadbed material (road material) or fertilizer, for example, if the slag is steelmaking slag, by removing it from container 1 and drying it.

[0045] [Aeration process] In the aeration process, gas C containing carbon dioxide is aerated into the calcium extract obtained by the passage of solvent M through the slag layer S in the above-mentioned flow process. Specifically, the solvent (calcium extract) M1 discharged from container 1 is stored in storage section 4, and gas C containing carbon dioxide is aerated into the stored calcium extract M1. Storage section 4 is a tank that stores the calcium extract M1 supplied from container 1 via extract supply pipe P2. The aeration section 5 aerates gas C into the calcium extract M1 stored in storage section 4. The aeration section 5 is not particularly limited and, for example, is a known gas blowing device. It is preferable to aerate gas C by the aeration section 5 while stirring the calcium extract M1 in storage section 4.

[0046] Solvent M containing the polyol compound, upon contact with the slag, released many calcium ions (Ca 2+ The calcium extract M1 containing the calcium ions is discharged from container 1. By aerating this calcium extract M1 with gas C containing carbon dioxide, the carbon dioxide dissolves in the calcium extract M1 as carbonate ions. When the calcium ions and carbonate ions react, a carbonate (calcium carbonate: CaCO3) precipitates as a precipitate. This carbon dioxide fixation method can fix a large amount of carbon dioxide because the calcium extract M1 contains a large amount of calcium ions.

[0047] As the carbon dioxide-containing gas C mentioned above, it is preferable to use exhaust gas containing carbon dioxide emitted from industrial activities such as factories, power plants, and transportation. The concentration of carbon dioxide in gas C is not particularly limited and may be the same as the concentration of carbon dioxide in the atmosphere or the exhaust gas mentioned above, or it may be a diluted or concentrated version of these concentrations. Gas C may consist solely of carbon dioxide.

[0048] [Separation process] The separation step involves solid-liquid separation of the precipitate D precipitated from the mixed liquid M2 obtained by the aeration step. Specifically, the calcium extract (mixed liquid) M2 after the aeration step, supplied via the mixed liquid supply pipe P3, is separated into solid (precipitate D) and liquid (separated liquid M3) in the separation unit 6. The separation unit 6 is not particularly limited and can be, for example, a known centrifuge.

[0049] The precipitate D and separated liquid M3 separated in the separation unit 6 have high purity because the inclusion of slag fragments is suppressed, and can be used or reused in a wide range of applications. Separated liquid M3 can be reused as part of solvent M in the above-mentioned flow process, for example, as described later. Precipitate D (carbonate) can be used, for example, as a filler for resins.

[0050] [Reuse process] In the reuse process, the separated liquid M3 is reused as at least a portion of the solvent M in the above-mentioned flow process. The separated liquid M3 is circulated to the supply unit 2 in the circulation unit 7 and used as part of the solvent mixture that comes into contact with the slag layer S. The circulation unit 7 includes a separated liquid supply pipe P4. The circulated separated liquid M3 has the same quality as the solvent M before it came into contact with the slag layer S because the inclusion of slag fragments is suppressed and the precipitate D has been removed in the above-mentioned separation process.

[0051] 〔advantage〕 In this carbon dioxide fixation method, a solvent containing a polyol compound is passed through calcium-containing slag during the flow process, allowing for efficient extraction of calcium from the slag. As a result, the slag after the solvent has passed through has a reduced calcium content and can be efficiently utilized or reused. The solvent after contact with the slag contains a large amount of calcium and can efficiently fix carbon dioxide by aerating it with a carbon dioxide-containing gas. Furthermore, in this carbon dioxide fixation method, the solvent is passed through at a rate that prevents the slag from flowing during the flow process, thus suppressing the mixing of slag fragments into the solvent after the flow. As a result, the precipitate formed by aeration and the solvent after aeration have high purity, allowing for low-cost utilization or reuse of the precipitate and the solvent after aeration in a wide range of applications.

[0052] [Other embodiments] The embodiments described above do not limit the configuration of the present invention. Accordingly, the embodiments may omit, substitute, or add components of each part of the embodiments based on the description herein and common technical knowledge, and all such additions should be interpreted as falling within the scope of the present invention.

[0053] In the above-described embodiment, the carbon dioxide fixation device was described as including a supply unit and an adjustment unit, but the supply unit may also incorporate the adjustment unit. In other words, a supply unit with an integrated adjustment unit may be used.

[0054] The solvent may contain polyol compounds, other solutions besides water, and additives, to the extent that they do not impede the calcium extraction efficiency from the slag. Examples of other solutions include hydrophilic solutions. Examples of hydrophilic solutions include ethanol and methanol. Furthermore, in the distribution process, a mixture of the polyol compound and an aqueous solution obtained by dissolving additives other than the solvent in water may be used.

[0055] The above reuse process is not an essential step in the carbon dioxide fixation method, and the separated liquid may be used for other purposes.

[0056] As for the method of filling the container of the carbon dioxide fixation device with slag, the supply of solvent may be started after filling the container with slag, or the slag and solvent may be supplied (filled) into the container simultaneously.

[0057] Furthermore, the solvent may be supplied to the container at a constant flow rate, or at a varying flow rate. The solvent may also be supplied continuously or intermittently.

[0058] Obstacles may be provided inside the container to prevent the solvent from flowing in a straight line. In other words, obstacles may be provided inside the container to cause the solvent to flow turbulently, either partially or entirely. [Examples]

[0059] The present invention will be further described below with reference to examples, but the present invention is not limited to these examples.

[0060] The following comparative tests were conducted using the test apparatus shown in Figure 2. 450g of steelmaking slag, adjusted to a particle size of 10mm or less using a sieve, was packed into a container 11 with an inner diameter of 42mm and a height of 230mm to form a slag layer S1.

[0061] The properties of the above slag are such that it contains 13% by mass of f-CaO. Here, f-CaO refers to unreacted calcium oxide (CaO) and unreacted calcium hydroxide (Ca(OH)2). The component content of the above slag is shown in Table 1. The percentages are rounded to three decimal places.

[0062] [Table 1]

[0063] As the solvent M11 containing the polyol compound, glycerin (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity exceeding 99.5%) was mixed with water to a concentration of 40% by mass. In Test Examples 1 and 2 shown in Table 2 below, the solvent M11 was supplied to container 11 and circulated through the slag layer S1 to extract calcium. The solvent M11 was stored in solvent container 12 and supplied to container 11 by pressurizing the solvent container 12 with nitrogen gas N. In Test Examples 1 and 2, the flow rate (supply rate) of the solvent M1 was controlled by the supply amount of nitrogen gas N, resulting in different empty column velocities. The supply amount of nitrogen gas N was adjusted with valve V while being monitored with a flow meter 13.

[0064] The solvent (calcium extract) M12 discharged from the container 11 on which the slag layer S1 was formed was sampled at predetermined time intervals, and the calcium extraction rate E was calculated by measuring the calcium ion concentration in the solution. The calcium extraction rate E [%] was calculated using the following formula 1. E = B / S × 100 ····(1) Here, B is the amount of calcium in the calcium extract [mol], and S is the amount of calcium in the slag [mol].

[0065] In Test Example 3, 400 g of the above solvent M11 and 40 g of the above slag were placed in another container (beaker), and calcium was extracted by stirring. Stirring was performed at room temperature and under a nitrogen atmosphere using a stirrer at 300 rpm for 1.5 hours. The solvent (calcium extract) after stirring was subjected to vacuum filtration (filter medium: filter paper type 5A), the calcium concentration in the filtrate was quantified, and the extraction rate was calculated.

[0066] The presence or absence of fine powder (slag fragments) in the calcium extract in Test Examples 1, 2, and 3 was visually confirmed by the turbidity of the calcium extract. The evaluations of Test Examples 1, 2, and 3 are shown in Table 2.

[0067] [Table 2]

[0068] In Test Example 3, the calcium extraction rate is equivalent to that of Test Example 1, but because there is fine powder in the calcium extract, a process to remove the fine powder is necessary in order to use or reuse this calcium extract. On the other hand, in Test Examples 1 and 2, the amount of fine powder in the calcium extract is very small, so the calcium extract can be reduced to a solvent and used or reused without any process to remove the fine powder.

[0069] Next, as Test Example 4, the test was conducted under the same conditions as Test Example 1, except for the empty column velocity. The empty column velocity was varied between 0 mm / s and 1.4 mm / s or less during the test. The test was performed in run 1 with a relatively fast empty column velocity and run 2 with a relatively slow empty column velocity. The pressure drop of the solvent in container 11 was measured using a manometer. The pressure drop was calculated by measuring the height at which the liquid in the manometer crossed the top of the slag layer S1, and the change was read. Figure 3 shows the relationship between the change in the empty column velocity of the solvent and the change in pressure drop.

[0070] Figure 3 shows that there is a point of inflection in the pressure loss at an empty velocity of 0.4 mm / s. In other words, it can be seen that slag flow begins when the empty velocity exceeds 0.4 mm / s. Therefore, from Figure 3, it can be seen that it is best to keep the empty velocity of the solvent M11 flowing through the slag layer S1 below 0.4 mm / s and the pressure loss below 14 kPa / m. [Industrial applicability]

[0071] This invention allows for the efficient and low-cost fixation of carbon dioxide, thereby enabling the effective utilization of calcium-containing slag. Furthermore, it allows for high purity of the solvent and precipitates after carbon dioxide fixation, facilitating the utilization or reuse of the solvent and precipitates. Therefore, this invention is suitably used for carbon dioxide fixation. [Explanation of Symbols]

[0072] 1,11 container 2 Supply section 3 Adjustment part 4. Storage section 5. Aeration section 6 Separation section 7 Circulation section 11 Container 12 Solvent containers 13 Flow meter D Precipitate M, M11 solvent M1, M12 Calcium Extract M2 mixture M3 separation liquid N Nitrogen gas P1 Solvent supply tube P2 Extract supply pipe P3 Mixed liquid supply pipe P4 Separated liquid supply pipe S,S1 Slag Layer V-valve

Claims

1. The system includes a flow process in which a solvent containing a polyol compound is circulated through a slag layer formed by filling a container with calcium-containing slag. A method for extracting calcium, wherein in the above-described flow process, the solvent is flowed such that the empty velocity of the solvent flowing through the slag layer is less than or equal to the value of the inflection point shown in the graph illustrating the relationship between the empty velocity and the pressure loss of the solvent flowing through the slag layer.

2. A flow process involves filling a container with calcium-containing slag to form a slag layer, and then flowing a solvent containing a polyol compound through this slag layer. An aeration step is performed in which a gas containing carbon dioxide is aerated into the calcium extract obtained by the passage of the solvent through the slag layer in the above-mentioned flow process, A separation step is performed to separate the precipitate precipitated from the mixture obtained by the above aeration step into solid and liquid form. Equipped with, A method for fixing carbon dioxide, wherein in the above-described flow process, the solvent is flowed such that the empty velocity of the solvent flowing through the slag layer is less than or equal to the value of the inflection point shown in the graph illustrating the relationship between the empty velocity and the pressure loss of the solvent flowing through the slag layer.

3. The carbon dioxide fixation method according to claim 2, further comprising a reuse step of reusing the separated liquid separated in the above separation step as at least a part of the solvent in the above flow step.

4. The carbon dioxide fixation method according to claim 2, wherein in the above flow process, the solvent is flowed such that the pressure loss of the solvent flowing through the slag layer is 14 kPa / m or less.

5. The carbon dioxide fixation method according to claim 2 or claim 4, wherein in the above flow process, the solvent is flowed such that the empty velocity of the solvent flowing through the slag layer is 0.4 mm / s or less.

6. The carbon dioxide fixation method according to claim 2 or claim 3, wherein the polyol compound is a diol compound or a triol compound.

7. The carbon dioxide fixation method according to claim 6, wherein the diol compound is one or more selected from the group consisting of ethylene glycol, propylene glycol, and diethylene glycol.

8. The carbon dioxide fixation method according to claim 6, wherein the above triol compound is glycerin.

9. A container for filling with calcium-containing slag to form a slag layer, This container includes a supply unit that supplies a solvent containing a polyol compound, An adjustment unit for adjusting the empty velocity of the solvent flowing through the slag layer so that it is less than or equal to the value of the inflection point shown in the graph illustrating the relationship between this empty velocity and the pressure loss of the solvent flowing through the slag layer, A storage section for storing the calcium extract that has passed through the slag layer and been discharged from the container, This storage section includes an aeration section that aerates the above extract stored in this storage section with a gas containing carbon dioxide, A separation unit separates the precipitate in the mixed liquid obtained by aeration by the above aeration unit into solid and liquid components. A carbon dioxide fixation device equipped with the following features.

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