WO2024166385A1 - Sulfur oxide removal material, method for removing sulfur oxide, and sulfur oxide removal device - Google Patents

Abstract

The present invention provides: a sulfur oxide removal agent which is an aluminum dross water treatment product and contains aluminum hydroxide; a method for removing sulfur oxide, comprising bringing the sulfur oxide removal agent into contact with a sulfur oxide; and a sulfur oxide removal device inside which the abovementioned sulfur oxide removal agent is provided.

Description

Sulfur oxide removing material, sulfur oxide removing method, and sulfur oxide removing device

The present invention relates to a sulfur oxide removal material, a sulfur oxide removal method, and a sulfur oxide removal device.

Sulfur oxides, such as sulfur dioxide, are known to be generated when fossil fuels that contain sulfur, such as petroleum and coal, are burned. Because sulfur oxides are the cause of asthma and acid rain, there is a need to remove sulfur oxides from exhaust gases and other sources.

For example, _a method of removing sulfur oxides using gelled aluminum hydroxide represented by the chemical formula Al(OH) _3.xH2O is known (for example, Patent Document 1). Specifically, Patent Document 1 discloses a high-temperature wet treatment method in which an aqueous suspension containing Al(OH) ₃ is placed in a flask as an adsorbent, the aqueous suspension is heated to about 100°C, and sulfur dioxide gas is introduced into the aqueous suspension, thereby causing the Al(OH) ₃ slurry to absorb the sulfur dioxide gas.

Also, as a method for treating exhaust gas containing hydrogen sulfide or sulfur dioxide, a method is known in which desulfurization media particles containing aluminum oxide or aluminum hydroxide are used to treat the exhaust gas through the Claus reaction (for example, Patent Document 2). Specifically, a method is known in which a mixed gas is prepared by adding the missing hydrogen sulfide or sulfur dioxide gas to the exhaust gas so that the ratio of hydrogen sulfide and sulfur dioxide in the exhaust gas becomes a predetermined ratio, the mixed gas is passed through a moving bed filled with the desulfurization media particles, and is heated to a temperature equal to or higher than the melting point of sulfur, and hydrogen sulfide and sulfur dioxide are reacted, and then the mixed gas is cooled to a temperature below the melting point of sulfur.

In addition, there is a demand for more effective use of resources, including the fossil fuels mentioned above, such as by recycling them. As a reusable resource, aluminum is attracting attention as it is recycled using a method that involves melting aluminum products. The total annual domestic demand for aluminum in the aluminum industry is said to be 4 million tons.

U.S. Pat. No. 4,256,712 Japanese Patent Application Publication No. 55-13620

However, the methods of Patent Documents 1 and 2 involve heating, and do not allow for easy disposal of sulfur oxides.

Also, the aluminum hydroxide described in Patent Documents 1 and 2 is precipitated from an aluminum solution extracted from bauxite, an aluminum ore, using a large amount of energy. On the other hand, the disposal of approximately 200,000 tons of aluminum dross generated annually as industrial waste during the aluminum heating and melting process is an issue. When aluminum dross is exposed to rainwater, etc., it generates ammonia through a heat-generating reaction, making some kind of disposal necessary.

The present invention was made in consideration of the above circumstances, and aims to provide a sulfur oxide remover, a sulfur oxide removal method, and a sulfur oxide removal device that can remove sulfur oxides using a simple method that does not involve heating.

The present invention provides the following means to solve the above problems.

(1) The sulfur oxide remover according to one embodiment of the present invention is a water-treated aluminum dross product and contains aluminum hydroxide.

(2) In the sulfur oxide removing agent of (1) above, the aluminum hydroxide may be one or both of Al(OH) ₃ and AlOOH.

(3) The sulfur oxide remover of (1) or (2) above may be a remover for removing sulfur dioxide.

(4) In one embodiment of the method for removing sulfur oxides according to the present invention, the sulfur oxides may be contacted with a sulfur oxide remover that is a water-treated product of aluminum dross and contains aluminum hydroxide.

(5) In the method for removing sulfur oxides according to (4) above, the aluminum hydroxide may be one or both of Al(OH) ₃ and AlOOH.

(6) The method for removing sulfur oxides described above in (4) or (5) may involve contacting sulfur dioxide with the sulfur oxide remover.

(7) In any of the above methods for removing sulfur oxides (4) to (6), the sulfur oxides may be contacted with the sulfur oxide remover at room temperature.

(8) A sulfur oxide removal device according to one embodiment of the present invention includes a sulfur oxide removal agent according to any one of (1) to (3) above.

The present invention provides a sulfur oxide remover, a sulfur oxide removal method, and a sulfur oxide removal device that can remove sulfur oxides using a simple method that does not involve heating.

FIG. 1 is a diagram showing an example of the configuration of an apparatus for treating aluminum dross, which is an apparatus used in a method for removing sulfur oxides according to an embodiment of the present invention. FIG. 1 is a diagram showing an example of the configuration of an apparatus used in a method for removing sulfur oxides according to one embodiment of the present invention, the apparatus removing sulfur oxides by a sulfur oxide removing agent. 1 is a SEM image of the sulfur oxide removing agent of Example 1. 4 is an SEM image of the sulfur oxide removing agent of Example 1, which is an enlarged image of FIG. 3. 2 shows the results of analyzing the sulfur oxide removing agent of Example 1 by X-ray diffraction method. 1 is an SEM image of the aluminum dross of Comparative Example 1. 4 is an SEM image of the aluminum dross of Comparative Example 1, which is an enlarged image of FIG. 3. 1 shows the results of analyzing the aluminum dross of Comparative Example 1 by X-ray diffraction. 1 shows the results of analyzing the gas removing agent of Comparative Example 2 by X-ray diffraction. 1 is a graph showing the change in sulfur dioxide concentration over time when the samples of Example 1, Comparative Example 2, and Comparative Example 3 were contacted with sulfur dioxide. 1 is a graph showing the change in sulfur dioxide concentration over time when sulfur dioxide was contacted with samples of Comparative Examples 4 to 8.

Below, an example of an embodiment of the present invention is described. The present invention is not limited to the following example.

[Sulfur oxide remover]
The sulfur oxide removing agent according to the embodiment of the present invention is a water treatment product of aluminum dross and contains aluminum hydroxide. The sulfur oxide removing agent according to the embodiment of the present invention is used when removing sulfur oxides ( _SOx) . The sulfur oxide removing agent according to the embodiment of the present invention is used when removing, for example, _SO2 (sulfur dioxide).

The sulfur oxide removing agent contains, for example, one or both of Al(OH) ₃ (aluminum hydroxide) and AlOOH (aluminum oxide hydroxide) as the aluminum hydroxide. The sulfur oxide removing agent preferably contains at least Al(OH) ₃ as the aluminum hydroxide.

The sulfur oxide removing agent contains, for example, Al(OH) ₃ , AlOOH, _MgAl2O4 (magnesium _aluminate ), and _Al2O3 (alumina), and may further contain inevitable impurities such as _MgF2 (magnesium fluoride), MgO (magnesium oxide) _, KCl (potassium chloride), NaCl (sodium chloride), unburned carbon, etc.

The ratio of the constituent components (mass%) of the sulfur oxide removing agent is, for example, {Al(OH) ₃ + AlOOH}: MgAl ₂ O ₄ : Al ₂ O ₃ : inevitable impurities = 10-65%: 10-34%: 10-61%: 0-5%, or may be 12-63%: 11-60%: 13-60%: 0-1%. Here, the sulfur oxide removing agent is configured so that the sum of the above constituent components is 100%. The ratio of the constituent components of the sulfur oxide removing agent is, for example, {Al(OH) ₃ + AlOOH}: (MgAl ₂ O ₄ + Al ₂ O ₃ ): inevitable impurities = 10-65%: 30-86%: 0-5%, preferably 40-65%: 30-55%: 0-5%, and more preferably 42-65%: 30-55%: 0-1%.

The aluminum hydroxide contained in the sulfur oxide removing agent is a flaky substance. In the sulfur oxide removing agent, the aluminum hydroxide is unevenly distributed on the surface. In the sulfur oxide removing agent, for example, MgAl ₂ O ₄ and Al ₂ O ₃ are formed on the inside, and Al(OH) ₃ and AlOOH are unevenly distributed on the surface. In the sulfur oxide removing agent, for example, a plurality of flaky aluminum hydroxides are arranged in parallel and spaced apart from each other, forming a group. In the sulfur oxide removing agent, for example, a plurality of the above groups are provided. By having the above-mentioned configuration, the sulfur oxide removing agent has a structure having a high specific surface area.

The BET specific surface area of the sulfur oxide removing agent is, for example, 60 [m ² /g] or more, preferably 80 [m ² /g] or more, and more preferably 100 [m ² /g] or more. The BET specific surface area of the sulfur oxide removing agent may be, for example, less than 220 [m ² /g], and may be less than 150 [m ² /g]. By having the above structure, the sulfur oxide removing agent has such a high specific surface area and can remove sulfur oxides highly efficiently for a long period of time.

The median diameter (d ₅₀ ) of the sulfur oxide removing agent may be greater than 3, and may be 6 or greater and 100 or less, or 8 or greater and 20 or less.

Aluminum dross contains, for example, _{MgAl2O4 , Al2O3} , metallic aluminum, AlN _, etc., and is a residue generated when metallic aluminum is heated and dissolved. When aluminum dross comes into contact with water, AlN and the aluminum component of metallic aluminum are dissolved into the water, which is the solvent, and when the concentration of the aluminum component in the water increases, aluminum hydroxide is precipitated according to the degree of supersaturation in that environment. As a result, when AlN reacts with water, it reacts according to the following reaction formula (1) to form aluminum hydroxide and generate ammonia.
AlN+ _3H2O →Al(OH) ₃ + _NH3 ...(1)

Specifically, the reaction represented by the above formula (1) occurs as the reactions represented by the following formulas (2) and (3) proceed: In a high-temperature environment, the reaction represented by the following formula (3) is followed by a reaction in which Al(OH) ₃ changes to AlOOH+ _H2O .
AlN+ _2H2O →AlOOH+ _NH3 ...(2)
AlOOH+ _H2O →Al(OH) ₃ ...(3)

When managing aluminum dross, which is an industrial waste product, the generation of ammonia from AlN can be extremely harmful to the surrounding environment, so the AlN in the aluminum dross needs to be converted into another stable substance through some kind of process.

As described above, the sulfur oxide remover according to this embodiment has aluminum hydroxide unevenly distributed on the surface, giving it a high specific surface area and allowing it to adsorb and remove a large amount of sulfur oxide from the space in which it is contained.

The sulfur oxide remover according to this embodiment has been confirmed to exhibit excellent removal efficiency when in contact with sulfur dioxide, and is suitable for use as a remover for removing sulfur dioxide.

[Method for Removing Sulfur Oxides]
The method for removing sulfur oxides will be described below.
The method for removing sulfur oxides according to this embodiment includes a step of contacting sulfur oxides with a sulfur oxide-removing agent, which is a water-treated product of aluminum dross and contains aluminum hydroxide.

The sulfur oxide remover is prepared, for example, by the following method. The sulfur oxide remover is prepared, for example, by using a specified treatment device. Figure 1 is a schematic diagram showing an example of the configuration of an aluminum dross treatment device used in a sulfur oxide removal method according to one embodiment of the present invention.

The processing device 200 shown in FIG. 1 includes a flask 22, a gas supply pipe 23, a gas flow meter 24, an air pump 25, an ORP meter 26, a pH meter 27, an exhaust pipe 28, a rubber stopper 29, a water bath 30, and a heater 31.

Gas supply pipe 23 is fixed to flask 22 and extends to near the bottom of flask 22. Air pump 25 is connected to gas flow meter 24, and supplies a fixed amount of air to flask 22 via gas supply pipe 23 using a valve mounted inside the gas flow meter.

The ORP meter 26 and the pH meter 27 are each fixed to the flask 22 and extend to a position where they are fully immersed in the water slurry contained in the flask 22.

The exhaust pipe 28 is fixed to the flask 22 and opens at a position that forms the gas phase inside the flask 22. A rubber stopper 29 airtightly seals the opening of the flask 22. In the processing device 200, the flask 22 serves as an airtightly sealed tank.

The water bath 30 contains water as a heat medium, and is positioned relative to the flask 22 in such a way that the heat medium is in sufficient contact with the periphery of the liquid contained in the flask. The heater 31 is a mechanism that can appropriately heat the water in the water bath 30.

In the flask 22, for example, a water slurry 40 containing aluminum dross 41 and water is contained. In the flask 22, a wet treatment of the aluminum dross 41 is carried out to remove halogens from the aluminum dross 41. In the treatment device 200, a sulfur oxide remover can be produced by a method including a wet treatment process.

The method for producing the sulfur oxide remover includes, for example, a process of blowing air into the water slurry 40 to dilute the harmful ammonia gas and promote the release of the dissolved ammonia in the solution into the gas phase (ammonia dilution and removal process).

For example, in the processing device 200, air is supplied from the gas supply pipe 23 to the water slurry 40 in the flask 22. The introduced air is supplied to the water slurry 40 in an amount sufficient to achieve the stirring effect of the water slurry 40. The bubbles generated from the gas supply pipe 23 stir the water slurry 40, increasing the frequency of contact between the aluminum dross and the water-based catalyst.

When aluminum dross comes into contact with water, AlN and metallic aluminum are dissolved. When AlN reacts with water, it reacts according to the following reaction formula (1) to form aluminum hydroxide and generate ammonia.
AlN+ _3H2O →Al(OH) ₃ + _NH3 ...(1)

Furthermore, when metallic aluminum reacts with water, the reaction proceeds according to the following formula (4) to form aluminum hydroxide and generate hydrogen.
2Al+6H ₂ O→2Al(OH) ₃ +3H ₃ ...(4)

The gas supplied from the gas supply pipe 23 also comes into sufficient contact with the water slurry 40. In other words, the harmful ammonia gas is diluted and the dissolved ammonia in the solution is released into the gas phase.

The water bath 30 works in conjunction with the heater 31 to maintain the temperature of the water slurry 40 in the flask 22 at a desired temperature (e.g., 25°C). Such temperature control is preferable from the viewpoint of sufficiently increasing the stability and efficiency of the processing in this embodiment.

The physical properties of the water slurry 40 can be confirmed from the detection values of the ORP meter 26 and pH meter 27.

The sulfur oxide remover is produced by treating aluminum dross with water using the method described above.

FIG. 2 is a schematic diagram showing an example of the configuration of an apparatus used in a method for removing sulfur oxides according to one embodiment of the invention, which removes sulfur oxides using a sulfur oxide remover. The method for removing sulfur oxides according to this embodiment can be carried out, for example, using a treatment apparatus 100 as shown in FIG. 2. The treatment apparatus 100 is also called a sulfur oxide removal apparatus. The treatment apparatus 100 contains the sulfur oxide remover according to the above embodiment.

The treatment device 100 includes, for example, a first gas source 1 containing sulfur oxide gas, a second gas source 2 containing a second gas excluding sulfur oxide gas, a first flow meter 3 of the first gas source 1, a second flow meter 4 of the second gas source 2, a first gas pipe 5 through which sulfur oxide gas flows, a second gas pipe 6 through which the second gas flows, a first valve 7 for controlling the flow rate of the first gas pipe 5, a second valve 8 arranged downstream of the first valve 7 and capable of controlling the flow rates of the sulfur oxide gas and the second gas, a third gas pipe 9 arranged downstream of the second valve 8, a gas bag 11 capable of containing a sulfur oxide remover 10 and in which sulfur oxide gas is sealed, a fourth gas pipe 12 arranged downstream of the gas bag 11 and through which exhaust gas discharged from the gas bag 11 flows, and a third valve 13 for controlling the airtightness of the gas bag 11 by opening and closing the fourth gas pipe 12.

In the method for removing sulfur oxides according to this embodiment, for example, the sulfur oxide removing agent 10 is accommodated in a gas bag 11, and the flow rate of the gas is controlled by controlling the opening and closing of a first valve 7, a second valve 8, and a third valve 13, thereby bringing the sulfur oxide gas into contact with the sulfur oxide removing agent 10. As the sulfur oxide gas, a sulfur oxide gas represented by the general formula _SOx can be used, and examples of the sulfur oxide gas that can be used include sulfur monoxide, sulfur dioxide, and sulfur trioxide.

The gas to be contacted with the sulfur oxide remover may be a gas containing sulfur oxides, for example, a sulfur oxide gas containing a mixture of sulfur oxides and an inert gas such as nitrogen, or may be exhaust gas containing sulfur oxides. The gas may be any gas containing sulfur oxides, such as a gas emitted by the combustion of fossil fuels. The second gas source 2 shown in FIG. 2 contains, for example, air, and may contain nitrogen, oxygen, carbon dioxide, or argon. The air as the second gas is used, for example, before and after the use of the sulfur oxide gas.

In the processing device 100, for example, the first gas source 1 can be adjusted to be open, the second gas source 2 to be closed, and the first valve 7 and the second valve 8 to be open. After sulfur oxide gas is sealed in the gas bag 11, the third valve 13 can be closed, and after a predetermined time has passed, the third valve 13 can be opened. By controlling the valves in this way in the processing device 100, the gas containing sulfur oxides can be brought into sufficient contact with the sulfur oxide removing agent 10, thereby increasing the efficiency of sulfur oxide removal.

The temperature at which the sulfur oxides are brought into contact with the sulfur oxide remover 10 is, for example, room temperature.

According to the method for removing sulfur oxides according to this embodiment, it is possible to remove sulfur oxides by contacting sulfur oxide gas with the sulfur oxide remover 10, even in a method that does not involve heating. Furthermore, the method for removing sulfur oxides according to this embodiment can remove sulfur oxides in a dry manner.

Note that while FIG. 2 shows a treatment device 100 having only one gas bag 11 containing sulfur oxide removing agent 10, the sulfur oxide removal method and sulfur oxide removing device according to this embodiment are not limited to the above example. For example, the sulfur oxide removing device can have a structure in which multiple gas bags 11 containing sulfur oxide removing agent 10 are arranged in series, thereby realizing a configuration in which the sulfur oxide concentration is lower downstream.

The sulfur oxide removal device according to this embodiment may have a structure including a column instead of the gas bag 11, and the inside of the column may be filled with a sulfur oxide removing agent. The valve may be controlled to an open state, and the inside of a member in which sulfur oxide gas is provided, such as the inside of a column, may be continuously ventilated. A mechanism may be provided in which sulfur oxide gas is supplied to the inside of a member, such as a column, in which a sulfur oxide removing agent is provided, and the sulfur oxide concentration in the sulfur oxide gas is controlled to be lowered according to the flow direction of the sulfur oxide gas. The sulfur oxide removal device according to this embodiment is not limited to the above example, and may have other structures as long as it is provided with the sulfur oxide removing agent according to the above embodiment.

As described above, the sulfur oxide remover according to the above embodiment contains aluminum hydroxide modified from metallic aluminum and aluminum nitride, and the aluminum hydroxide and aluminum hydroxide oxide contained in this modified aluminum hydroxide have a high specific surface area. Since the aluminum hydroxide is unevenly distributed on the surface of the sulfur oxide remover, the sulfur oxide remover can remove sulfur oxides with high removal efficiency on the surface of the modified aluminum hydroxide even at room temperature.

The following describes examples of the present invention. The present invention is not limited to the following examples.

[Example 1]
First, aluminum dross was prepared. The prepared aluminum dross was subjected to water treatment using an apparatus similar to that shown in Fig. 1 to produce a sulfur oxide removing agent which was a water-treated product of the aluminum dross and contained aluminum hydroxide.

The sulfur oxide removing agent of Example 1 was observed by a scanning electron microscope (SEM). FIG. 3 is an SEM image of the sulfur oxide removing agent of Example 1. FIG. 4 is an SEM image of the sulfur oxide removing agent of Example 1, which is an enlarged image of FIG. 3. From the SEM images of FIG. 3 and FIG. 4, the sulfur oxide removing agent of Example 1 has a large amount of scaly material formed on the surface. When the sulfur oxide removing agent of Example 1 was observed, it was confirmed that the entire particle was covered with scaly material. Furthermore, from FIG. 4, it was confirmed that in the sulfur oxide removing agent of Example 1, a group was formed in which a plurality of scaly Al(OH) ₃ particles were spaced apart from each other and arranged in parallel, and a plurality of such groups were provided.

Furthermore, the constituent phases of the sulfur oxide removing agent of Example 1 were analyzed by X-ray diffraction (XRD). The analysis of the constituent phases by X-ray diffraction was carried out under the following conditions.
・X-ray source: Cu line (output: 45kV, current: 200mA)
Scanning range: 2θ=10° to 80°
Step time: 0.12 s/step
Scan speed: 10°/min
Step width: 0.02°
・Detector: HyPix-3000 (1D detector mode)

Fig. 5 shows the results of X-ray diffraction analysis of the sulfur oxides-removing agent of Example 1. As can be seen from Fig. 5, the sulfur oxides-removing agent of Example 1 contains Al(OH) ₃ , _AlOOH , _{MgAl2O4 ,} and _Al2O3 .

[Comparative Example 1]
The same aluminum dross as that used in Example 1 was prepared and used as Comparative Example 1. As in Example 1, the aluminum dross of Comparative Example 1 was observed by a scanning electron microscope and the constituent phases were analyzed by the X-ray diffraction method.

Figure 6 is an SEM image of the aluminum dross of Comparative Example 1. Figure 7 is an SEM image of the aluminum dross of Comparative Example 1, which is an enlarged image of Figure 3. As can be seen from Figures 6 and 7, the aluminum dross of Comparative Example 1 does not have scale-like members formed on its surface, unlike the sulfur oxide remover of Example 1.

Fig. 8 shows _{the results of analyzing the aluminum dross of Comparative Example 1 by X-ray diffraction. As can be seen from Fig. 8, the aluminum dross of Comparative Example 1 contains MgAl2O4, Al2O3 , AlN ,} metallic aluminum, MgO, KCl, and NaCl. From the XRD analysis result of the aluminum dross of Comparative Example 1, among the peaks confirmed in the XRD measurement result of the sulfur oxide removing agent of Example ₁ , the peaks of _MgAl2O4 and _Al2O3 were confirmed, but the peaks of aluminum hydroxides (Al(OH) ₃ and AlOOH) were not confirmed _. Therefore, it is considered that the aluminum dross does not contain the above aluminum hydroxides.

5 and 8, it is understood that the scaly substance formed on the surface of the sulfur oxide removing agent of Example 1 but not on the surface of the aluminum dross of Comparative Example 1 is aluminum hydroxide. In addition, as will be described later, a large amount of similar scaly substances is formed in Example 1, which has a small amount of AlOOH, and therefore it is understood that the aluminum hydroxide in Example 1 is Al(OH) ₃ .

As described later, the sulfur oxide removing agent of Example 1 is not made of _aluminum hydroxide. Although the sulfur oxide removing agent of Example 1 contains _Al2O3 and _MgAl2O4 , the particle surfaces are covered with a scaly substance _, and it is _understood that the scaly substance is unevenly distributed on the surfaces of _{Al2O3 and MgAl2O4} .

First, a total of 11 samples similar to those in Comparative Example 1 were prepared, and the proportions of the constituent phases of the aluminum dross of Comparative Example 1 were analyzed based on chemical analysis. Specifically, the aluminum dross of Comparative Example 1 was dissolved in iodine methanol, and the Al component dissolved in the iodine methanol was identified as metallic Al. The residue that did not dissolve in the iodine methanol did not contain metallic Al, but contained Al components other than metallic Al (Al ₂ O ₃ , AlN) and magnesium components (MgO, MgAl ₂ O ₄ ). The Mg component when this residue was acid leached was taken as MgO, and N was analyzed by distillation separation and back titration, and the amount of analyzed N was calculated as all AlN. From the Al component and Mg component when the residue that did not dissolve in the iodine methanol was completely dissolved by alkali melting, Al ₂ O ₃ and MgAl ₂ O ₄ were calculated by taking into account the amounts of MgO and AlN. Others is the remainder that does not fall under these, and is composed of other materials, and includes halides, unburned carbon, etc.
In Example 1, the case where the aluminum dross of Comparative Example 1 is treated with water, and all of the metal Al and AlN in the aluminum dross react according to formulas (1) and (4) is considered. The Al(OH) ₃ in Example 1 was calculated from formulas (1) and (4) based on the respective contents of metal Al and AlN in the raw aluminum dross. Assuming that the aluminum dross is treated with water, and most of the aluminum halides are dissolved and removed into the solvent water, in Example 1 _{, Al2O3} , _MgAl2O4 , and MgO that do not react by water treatment, and the remainder of the Al(OH) ₃ are designated as "Others." That is, Table 1 for Example 1 reflects the reaction of metal Al and _AlN according to formulas (1) and (4) and the dissolution and removal of halides, and adjusts the ratio of values according to the change in the total mass, in comparison with Table 2 for Comparative Example 1. The analysis results of the sulfur oxide removing agent of Example 1 are summarized in Table 1, and the analysis results of the aluminum dross of Comparative Example 1 are summarized in Table 2. The sample numbers in Table 1 correspond to those in Table 2. Tables 1 and 2 show the mass % ratios of each constituent phase.

Incidentally, an AlOOH peak was confirmed from the XRD analysis result of the sulfur oxide removing agent of Example 1, but an AlOOH peak was not confirmed from the XRD analysis result of the aluminum dross of Comparative Example 1, and therefore AlOOH is not contained in the aluminum dross of Comparative Example 1. In Example 1 as well, it can be determined from the peak intensity that a small amount of AlOOH is present, and it is presumed to be precipitated as Al(OH) ₃ , and is treated as being included in Al(OH) ₃ in Table 1.

[Sulfur oxide removal test]
The sulfur oxide removing agent of Example 1, the gas removing agents of Comparative Example 2 and Comparative Example 3 prepared for comparison, and samples of Comparative Examples 4 to 7 were prepared. These samples were contacted with sulfur oxides by a method described in detail below, and a sulfur oxide removal test was conducted. Note that in the sulfur oxide removal test, the sample with the above sample number No. 1 was used as the sulfur oxide removing agent of Example 1.

[Comparative Example 2]
An iron oxide-based gas removing agent was prepared as a sample of Comparative Example 2. X-ray diffraction was performed on the gas removing agent of Comparative Example 2 under the same conditions as those for the sulfur oxide removing agent of Example 1. Fig. 9 shows the analysis results of the gas removing agent of Comparative Example 2 by the X-ray diffraction method. As shown in Fig _. 9, it was confirmed that the gas removing agent of Comparative Example ₂ contains _Fe3O4 , _{Fe3.71O4 ,} and _Fe2O3 .

[Comparative Example 3]
As a sample of Comparative Example 3, an activated carbon gas removing agent was prepared.

[Comparative Examples 4 to 7]
As a sample of Comparative Example 4, a reagent composed of Al ₂ O ₃ was prepared.
As a sample of Comparative Example 5, a reagent composed of MgAl ₂ O ₄ was prepared.
As a sample of Comparative Example 6, a reagent composed of Al(OH) ₃ was prepared.
As a sample of Comparative Example 7, a reagent composed of AlOOH was prepared.

The BET specific surface area and median diameter were measured in advance for the sulfur oxide removing agent of Example 1 and the samples of Comparative Example 2 to Comparative Example 7. The BET specific surface area was calculated by the BET method in accordance with JIS Z8830:2013. The median diameter is the average particle diameter d ₅₀ calculated based on the particle size distribution measured in accordance with a conventional method using an SK Laser Micron Sizer LMS-2000e (Seishin Enterprise Co., Ltd.). The measured BET specific surface areas [m ² /g] and median diameters d ₅₀ [μm] are summarized in Table 3.

As shown in Table 3, it was confirmed that the sulfur oxide removing agent of Example 1 had a higher BET specific surface area than the reagents used in Comparative Examples 4 to 6. When the sulfur oxide removing agent of Example 1 and the sample of Comparative Example 6 were observed with a scanning electron microscope, the shape of Al(OH) ₃ unevenly distributed on the surface of the sulfur oxide removing agent of Example 1 prepared by subjecting aluminum dross to a specified water treatment was different from the shape of Al(OH) ₃ as the reagent. Therefore, it was confirmed that the sulfur oxide removing agent of Example 1 is a composition formed by subjecting aluminum dross to a specified water treatment, in which Al(OH) ₃ having a specific shape is unevenly distributed on the surface. The sulfur oxide removing agent of Example 1 has the above structure and thus has a significantly higher BET specific surface area than the samples of Al ₂ O ₃ , MgAl ₂ O ₄ , and Al(OH) ₃ .

On the other hand, as described above, the sulfur oxide removing agent of Example 1 has _a high specific surface area due to the uneven distribution of Al(OH) ₃ on the surface, and also contains _Al2O3 and _MgAl2O4 , so the median diameter _{d50 also} shows a relatively high value.

The samples of Example 1 and Comparative Example 1 to Comparative Example 7 were placed in a gas bag of a processing device similar to the processing device 100 shown in FIG. 2, and sulfur dioxide gas containing sulfur dioxide was sealed in the gas bag. The gas bag was then left to stand for a predetermined time in a closed space with no gas flow, and the change in sulfur dioxide concentration in the gas bag over time was measured using a detector tube installed at the outlet of the gas bag. Specifically, a petri dish with 1.0 g of sample placed on it was first placed in an aluminum gas bag. Next, 10 L of sulfur dioxide gas consisting of sulfur dioxide and nitrogen and with a sulfur dioxide concentration of 0.10 vol. % was sealed in as the sulfur dioxide gas, creating a closed space. In this state, the gas bag was left to stand for 24 hours at room temperature, and the sulfur dioxide concentration in the gas bag was measured using a detector tube.

For comparison, comparative example 8 was prepared by measuring the change in sulfur dioxide concentration over time in the gas bag of the processing device without placing a sample in the gas bag. In other words, comparative example 8 is the test result for a blank.

Figure 10 is a graph showing the change in sulfur dioxide concentration over time when sulfur dioxide is brought into contact with the samples of Example 1, Comparative Example 2, and Comparative Example 3, and Figure 11 is a graph showing the change in sulfur dioxide concentration over time when sulfur dioxide is brought into contact with the samples of Comparative Examples 4 to 8.

As shown in Figure 10, it was confirmed that when the sulfur oxide remover of Example 1 was used, more sulfur dioxide could be removed than when Comparative Example 2 and Comparative Example 3 were used.

11, in Comparative Example 4 using the reagent Al ₂ O ₃ and Comparative Example 5 using the reagent MgAl ₂ O ₄ , the change in sulfur dioxide concentration over 24 hours was the same as that of Comparative Example 8, which is the blank experimental data, and it is considered that Al ₂ O ₃ and MgAl ₂ O ₄ do not contribute to the removal of sulfur dioxide. In addition, Comparative Example 6 using the reagent Al(OH) ₃ , which has a slightly higher specific surface area than Al ₂ O ₃ and MgAl ₂ O ₄ , is considered to show a slightly higher sulfur dioxide removal efficiency than Al ₂ O ₃ and MgAl ₂ O _4. In addition, it was found that Comparative Example 7 using the reagent AlOOH, which has a significantly higher specific surface area and a significantly smaller median diameter than the other comparative examples, showed a significantly higher sulfur dioxide removal efficiency than Comparative Examples 4 to 6.

In addition, when the experimental data was examined using the sulfur oxide remover of Example 1 and the sample of Comparative Example 7, it was confirmed that the sulfur oxide remover of Example 1 exhibited a sulfur dioxide removal efficiency equal to or greater than that of the sample of Comparative Example 7.

The above results confirm that Example 1, which is the sulfur oxide removing agent of the above embodiment, can achieve excellent sulfur dioxide removal efficiency by subjecting aluminum dross to a specified water treatment, resulting in _{a structure in which scaly Al(OH)3 is} unevenly distributed on the surface even though it contains _MgAl2O4 and _{Al2O3 ,} and which has a high BET specific surface area even though it has a large median diameter.

Aluminum dross, which is generated in large quantities as industrial waste during the aluminum heating and melting process and generates ammonia when it reacts with water, can be used to remove sulfur oxides, which can cause asthma and acid rain. In addition, the use of aluminum dross can lead to the creation of a new environmental industry and the provision of sulfur oxide removers that are cheaper than conventional ones.

1 First gas source 2 Second gas source 3 First flow meter 4 Second flow meter 5 First gas pipe 6 Second gas pipe 7 First valve 8 Second valve 9 Third gas pipe 10 Sulfur oxide remover 11 Gas bag 12 Fourth gas pipe 13 Third valve 22 Flask 23 Gas supply pipe 24 Gas flow meter 25 Air pump 26 ORP meter 27 pH meter 28 Exhaust pipe 29 Rubber stopper 30 Water bath 31 Heater 40 Water slurry 41 Aluminum dross 100 Treatment device 200 Treatment device

Claims (8)

A water-treated product of aluminum dross,
A sulfur oxide remover containing aluminum hydroxide. The sulfur oxide removing agent according to claim 1 , wherein the aluminum hydroxide is one or both of Al(OH) ₃ and AlOOH. The sulfur oxide remover according to claim 1, which is a remover for removing sulfur dioxide. A method for removing sulfur oxides by contacting the sulfur oxides with a sulfur oxide remover that is a water-treated product of aluminum dross and contains aluminum hydroxide. The method for removing sulfur oxides according to claim 4, wherein the aluminum hydroxide is one or both of Al(OH) ₃ and AlOOH. The method for removing sulfur oxides according to claim 4, wherein the sulfur oxide remover is contacted with sulfur dioxide. The method for removing sulfur oxides according to claim 4, wherein the sulfur oxides are contacted with the sulfur oxide remover at room temperature. A sulfur oxide removal device having the sulfur oxide removal agent according to claim 1 inside.

Images