Solid-phase washing of secondary aluminosphate and treatment of washing water

Abstract

This invention provides a process for obtaining a harmless solid phase and a harmless liquid phase from a slurry, which is a solid-liquid integrated substance obtained by reacting secondary aluminum dross with water to remove the harmful gas phase. [Solution] The present invention divides the solid phase washing process of a slurry, which is a solid-liquid integrated substance obtained by reacting secondary aluminum dross with water to remove harmful gas phases, into first, second, and third washing processes. In each washing process, the slurry from the previous process is separated into solid and liquid phases, a washing solution is mixed with the solid phase, a pH adjusting agent is added to adjust the pH value, and then washing is performed by stirring. After washing, a specified value for the impurity ion content is measured. In addition, in each washing process, the liquid phase obtained by solid-liquid separation is collected separately for each washing process, carbon dioxide is dissolved in each collected liquid phase to adjust the pH to 6-10, and the treated water is used as the washing solution for the first or second washing process, or the detoxified liquid phase substance is discharged as wastewater.

Description

[Technical Field]

[0001] The present invention relates to a method for detoxifying the solid phase of secondary aluminodross by washing, and also for detoxifying the washing water used in the detoxification process. [Background technology]

[0002] In the aluminum production process, a residue called aluminum dross (aluminum ash) is generated, and it is said that tens of thousands of tons of this aluminum dross are produced annually in Japan. The biggest problem with the disposal of aluminum dross is that if it is left as is (stored) or during processing, the aluminum nitride, metallic aluminum, and water it contains react, generating heat, ammonia, and hydrogen, which can cause fires, explosions, foul odors, and health problems.

[0003] Therefore, numerous methods for treating aluminum dross, which had not been established before, have been proposed, and these can be broadly classified into dry treatment and wet treatment. Dry treatment is a method in which the residual ash is heated to a high temperature of 1000°C or more in a rotary kiln or the like, and the constituent phases can be converted into oxides by combustion oxidation, which can be used as oxide raw materials, but it has the problem of high energy consumption and high cost. On the other hand, the wet treatment proposed in this application is a method in which aluminum dross is reacted with water, and is more cost-effective than the dry treatment method, but it is accompanied by the generation of ammonia, so the removal of the discharged ammonia has been a problem.

[0004] The main composition and mass fraction of aluminum dross is 10-30% metallic aluminum, 20-40% alumina, 7-15% silicon, magnesium, and iron oxides, and 15-30% potassium, sodium, calcium, magnesium chlorides, and other trace amounts of fluorides.

[0005] Aluminum dross is classified into primary aluminum dross and secondary aluminum dross, depending on the number of times metallic aluminum or aluminum alloys are recovered in the recycling process and their content.

[0006] Primary alumina dross is an insoluble slag produced in the process of producing metallic aluminum using electrolytic alumina. The metallic aluminum content in primary alumina dross is 30-85%, and it also contains other substances such as fluorides, alumina, and aluminum nitride.

[0007] Secondary aluminum dross is waste slag produced in the remelting process of primary aluminum dross, or in the process of recovering metallic aluminum from spruced aluminum. The metallic aluminum content in secondary aluminum dross is 5-20%, and it also contains alumina, aluminum nitride, chloride compounds such as fluorine, and silicon dioxide.

[0008] Methods for treating secondary aluminum dross into harmless substances are divided into dry methods involving the high-temperature heat treatment described above and wet methods involving chemical reaction treatment using water. However, the wet methods covered in this application include methods that use not only water but also acids and alkalis for reaction treatment. In this wet treatment method, when secondary aluminum dross is reacted with water and acids or alkalis of a specific concentration, it is decomposed into aluminum nitride, metallic aluminum, and other aluminum compounds.

[0009] Detoxifying the solid phase of secondary aluminum dross ultimately means removing heavy metal components and impurity ions contained in the solid phase, essentially treating it to a state that has no adverse effects on the environment or human health. Conventionally, there is a treatment technology that detoxifies secondary aluminum dross by removing heavy metal components and impurity ions contained in the solid phase through "washing".

[0010] As processing techniques for removing heavy metal components and impurity ions contained in the solid phase of the above-mentioned secondary aluminodros by "washing," for example, Patent Document 1 (Japanese Patent Publication No. 11-319753), Patent Document 2 (Japanese Patent Publication No. 2002-45824), and Patent Document 3 (Japanese Patent No. 7249075) are known.

[0011] However, conventional methods, including those described in Patent Documents 1-3, have shown that even if the solid phase of secondary aluminum dross can be rendered harmless, the washing water is not rendered harmless, posing a problem for the disposal of the liquid phase. Even if fresh water is added and the water is recycled, the amount of wastewater increases as a result of adding fresh water, and if fresh water is not added, the concentration of washed heavy metal components and impurity ions gradually increases in purity. In particular, when wastewater is recycled, the final discharge of wastewater becomes more troublesome, equipment deterioration is accelerated, and the intended reaction with secondary aluminum dross may not occur. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Application Publication No. 11-319753 [Patent Document 2] Japanese Patent Publication No. 2002-45824 [Patent Document 3] Patent No. 7249075 [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] The problem we are trying to solve is that even if the solid phase of secondary aluminum dross can be rendered harmless by washing, the wastewater treatment of the water used during washing is insufficient, and simply disposing of it as wastewater has a negative impact on the environment. Furthermore, even if reuse is attempted, adding fresh water for recycling increases the amount of wastewater, and if fresh water is not added, the concentration of harmful substances gradually increases. In addition, when recycling is used, the final discharge of wastewater becomes more troublesome, equipment deterioration is accelerated, and the intended reaction with secondary aluminum dross may not occur. [Means for solving the problem]

[0014] To solve the above problems, the method for solid-phase washing of secondary aluminum dross and treatment of washing water according to the present invention is a treatment for obtaining a harmless solid phase and a harmless liquid phase from a slurry which is a solid-liquid integrated substance in a state where harmful gas phase has been removed by reacting secondary aluminum dross with water. The washing process of the solid phase in the slurry is divided into first, second, and third washing steps. In the first, second, and third washing steps, the slurry of the previous step is separated into solid and liquid, a washing liquid is mixed with the solid phase, a pH adjuster is added to adjust the pH value, and then washing is performed by stirring. After washing, there is a procedure for measuring the specified value of the impurity ion content. Further, in the first, second, and third washing steps, the liquid phase at the time of solid-liquid separation is separately collected for each of the first, second, and third washing steps, and for each of the separately collected liquid phases, carbon dioxide is dissolved to adjust the pH to 6-10 to obtain treated water, which is used as the washing liquid for the first or second washing step, or there is a procedure for discharging it as a harmless liquid phase substance.

Advantages of the Invention

[0015] The present invention can render the secondary aluminum dross in the solid phase harmless by washing, and the washing liquid used for washing the solid phase can be rendered harmless by separate treatment during solid-liquid separation. And the harmless liquid phase can be discharged if it is unnecessary, but it can also be recycled and used as the washing water for the solid phase. When recycled and used, since it is always rendered harmless, the concentration of harmful substances will not gradually increase, and the possibility of accelerating equipment deterioration or making it impossible to perform the intended washing of secondary aluminum dross can be reduced.

Brief Description of the Drawings

[0016] [Figure 1] It is a flowchart showing the schematic process of the method of the present invention. [Figure 2] It is a flowchart showing the first washing step. [Figure 3] It is a flowchart showing the second washing step. [Figure 4] It is a flowchart showing the third washing step. [Figure 5]It is a flowchart showing the washing water processes (1), (2), and (3). [Figure 6] It is a diagram showing the schematic configuration of the first to third washing kettles used in the method of the present invention.

Embodiment for Carrying Out the Invention

[0017] The method for washing and detoxifying secondary aluminum dross of the present invention is carried out as shown in FIG. 1. (Washing kettle) The washing kettle shown in FIG. 6 is provided with three units from the upstream process to the downstream process according to the procedure of the method of the present invention. In this example, the volumes of the three washing kettles are all the same. This washing kettle is for washing the solid phase of secondary aluminum dross after the previous process, that is, after reacting the solid phase of secondary aluminum dross with water to generate and extract hydrogen.

[0018] The washing kettle includes an inlet 1, a water intake 2, a kettle body 3, an ultrasonic stirrer 4, stirring blades 5, a discharge valve 6, a slurry pump 7, a liquid level gauge 8, a speed reducer 9, a motor 10, an annular air supply pipe 11, and an air supply pipe 12.

[0019] The ultrasonic stirrer 4 is for generating vibration and vortex in the slurry in the kettle body 3 in order to improve the washing efficiency. The ultrasonic stirrer 4 is controlled to generate ultrasonic waves in the range of 20 - 80 kHz for vibration, and optimally in the range of 30 - 50 kHz. Also, the ultrasonic stirrer 4 is controlled to generate a vortex in the opposite direction to the rotation of the stirring blades 5 for the vortex.

[0020] The stirring blades 5 are controlled within the range of a rotational speed of 20 - 80 r / min, and optimally at 40 - 60 r / min. Also, the annular air supply pipe 11 is provided at the inner bottom of the kettle body 3 and is made of porous ceramics, and ejects carbon dioxide sent from the air supply pipe 12.

[0021] (Process overview) In the solid-phase washing of secondary aluminum dross and treatment of washing water method of the present invention described below, the target of treatment is secondary aluminum dross in a solid-liquid integrated state (hereinafter referred to as slurry) in which the harmful gas phase has already been removed by reacting secondary aluminum dross with water in an upstream process. As shown in Figure 1, the present invention removes heavy metals such as Pb, Cd, Cr, Cu, Ni, Zn, Mn, and Cl from the secondary aluminum dross through a first-to-third cleaning process. - F - , K - na + Removes impurity ions.

[0022] (First cleaning process): Figure 2 The slurry is sent to a pressure filter for solid-liquid separation. The water content of the solid phase after pressure filtration is 15-25%. This solid phase is sent to the first washing kettle, and the liquid phase, along with the liquid phase separated in the second washing process described later, is treated with washing water (1) and may be used in the reaction between the secondary aluminum dross and water in the upstream process. However, in this example, we will show an example of using it as a "washing liquid" as described below.

[0023] The solid phase and the "cleaning liquid" are placed in the first cleaning kettle. The solid-liquid ratio (mass ratio) in the first cleaning kettle at this time is set to 1:3-10 for solid phase:liquid phase. This solid-liquid ratio is finely adjusted within the above range for each treatment in the second and third cleaning kettle. The liquid level inside the kettle body 3 at this time is set to be in the range of 50-80% of the internal height.

[0024] The "washing solution" in the first washing step is obtained by combining the liquid phase separated in the solid-liquid separation step and the liquid phase separated in the second washing step and performing washing water treatment (1). Washing water treatment (1), (2), and (3) will be described later.

[0025] The cleaning process begins by activating the agitator blade 5 and the ultrasonic stirrer 4. The rotation speed of the agitator blade 5 is controlled within the range of 20-80 r / min, with the optimal range being 40-60 r / min. Meanwhile, the ultrasonic stirrer 4's ultrasonic frequency is controlled within the range of 20-80 kHz, with the optimal range being 30-50 kHz. While stirring as described above, carbon dioxide supplied via the aeration pipe 12 is ejected from the annular gas phase pipe 11 until the slurry reaches a pH of 6 or higher and less than 7. Furthermore, after the slurry reaches a pH of 6 or higher and less than 7, one or more types of sulfuric acid, nitric acid, or organic acids are injected as a adjusting agent until the pH reaches 2 or higher and less than 6.

[0026] After this, further washing is performed until the tracer ion content is less than 10%. Specific ions (heavy metals or impurity ions) are "selected as tracer ions," samples are taken at predetermined intervals, and the tracer ion content is examined. The first washing process is terminated when the change in tracer ion content between two samples is less than 10%.

[0027] The following explains the "Selection of Tracer Ions" process. The content of heavy metals and impurity ions in the solid phase of the washing kettle is inspected and recorded as A1. A1 / A2 is calculated, and the ion with the highest value is selected as the tracer ion.

[0028] (Second cleaning process): Figure 3 The slurry from the first washing kettle after the first washing process is sent to a pressure filter for solid-liquid separation. The solid phase is loaded into the second washing kettle, and the liquid phase, as described above, is used as the washing water for the solid phase in the first washing process after the washing water treatment (1) in this example. The solid phase and the "cleaning liquid" are placed in the second cleaning kettle. The liquid level inside the kettle body 3 of the second cleaning kettle is set to a range of 50-80% of the internal height. The aforementioned "cleaning solution" is the liquid phase that was finally separated into solid and liquid phase in the third cleaning process described later, and which has undergone cleaning water treatment (3).

[0029] The cleaning process begins by activating the agitator blade 5 and the ultrasonic stirrer 4. The rotation speed of the agitator blade 5 is controlled within the range of 20-80 r / min, with the optimal range being 40-60 r / min. Meanwhile, the ultrasonic stirrer 4's ultrasonic frequency is controlled within the range of 20-80 kHz, with the optimal range being 30-50 kHz. While stirring as described above, one or more types of sulfuric acid, nitric acid, or organic acids are added as adjusting agents until the pH reaches 2-6.

[0030] After this, further washing is performed until the tracer ion content is less than 10%. A specific ion (heavy metal or impurity ion) is selected as a tracer ion, and samples are taken at predetermined intervals to check the tracer ion content. The second washing process is terminated when the change in tracer ion content between two samples is less than 10%.

[0031] (Third cleaning process): Figure 4 After the second washing process, the slurry from the second washing kettle is sent to a pressure filter for solid-liquid separation. The solid phase is sent to the third washing kettle, and the liquid phase, as described above, in this example, is used as the washing solution for the solid phase in the first washing process after the washing water treatment (2). The solid phase and the "cleaning liquid" are placed in the third cleaning kettle. The liquid level inside the kettle body 3 of the third cleaning kettle is set to a range of 50-80% of the internal height. The aforementioned "cleaning solution" uses clean water, or fresh water, as a top-up.

[0032] The cleaning process begins by activating the agitator blade 5 and the ultrasonic stirrer 4. The rotation speed of the agitator blade 5 is controlled within the range of 20-80 r / min, with the optimal range being 40-60 r / min. Meanwhile, the ultrasonic stirrer 4's ultrasonic frequency is controlled within the range of 20-80 kHz, with the optimal range being 30-50 kHz. While stirring as described above, one or more types of adjusting agents such as lime hydroxide, sodium hydroxide, oxalic acid, (calcium) carbide slag, and electrostatic slag are injected until the pH is less than 7-12, and ideally 9-11.

[0033] After this, further washing is performed until the tracer ion content is less than 10%. A specific ion (heavy metal or impurity ion) is selected as a tracer ion, and samples are taken at predetermined intervals to check the tracer ion content. When the change in tracer ion content between two samples is less than 10%, the washing is terminated.

[0034] In the third washing process, after the above washing, the slurry is sent to a pressure filter for solid-liquid separation. Pressure filtration is used to reduce the water content of the solid phase to 15-25%, and it is measured whether the solid phase meets, for example, environmental standards. If the solid phase does not meet the standards, the process returns to the washing process in the third washing process and is repeated until it meets the standards.

[0035] On the other hand, the liquid phase separated at this stage undergoes washing water treatment (3) and is used as the washing solution for the second washing process. Furthermore, if the solid phase separated at this stage meets the standards, it can be used as a solid phase raw material. As a raw material, it is particularly suitable for use in concrete materials. Of course, it can also be treated as general waste.

[0036] Wash water treatment (1)(2)(3): Figure 5 The washing water treatment (1), (2), and (3) are carried out in separate facilities, but the treatment itself is the same. First, the pH of the collected liquid phase is measured, and if the pH is less than 6-10, the process proceeds to the solid-liquid separation treatment described later. The reason for using separate facilities is that the properties of the liquid phase collected in each process and the destinations of the treated water from washing water treatment (1), (2), and (3) are different.

[0037] On the other hand, if the collected liquid phase has a pH of 6-10, an adjusting agent is added to adjust it to the pH range of 6-10, and it is allowed to stand for 2-5 hours. After that, solid-liquid separation is performed, and the small amount of solid phase is stored until it reaches a certain amount. Meanwhile, the liquid phase from the solid-liquid separation is used in each treatment. Of course, the liquid phase that has undergone this washing water treatment (1)(2)(3) can also be used as general wastewater.

[0038] Thus, with the present invention, by providing an ultrasonic stirrer 4 and a stirring blade 5 together, dispersing the solid phase cleaning process in the first to third stages, adjusting the pH value of the slurry to dissolve heavy metals and impurity ions in the liquid phase to the maximum extent, the cleaning efficiency of heavy metals and impurity ions is significantly improved, and the solid phase can be rendered harmless. Furthermore, by providing cleaning water treatment steps (1)-(3) in each of the first to third cleaning stages to render the cleaning solution harmless, it becomes possible to render both the solid phase and the liquid phase used to clean the solid phase harmless.

[0039] Furthermore, by employing the tracer ion selection method, it is possible to quickly determine the cleaning effect and whether the heavy metal and impurity ions after cleaning meet the standards. Additionally, by using carbon dioxide as a pH adjuster, it can contribute to the realization of a negative carbon process. [Examples]

[0040] Examples 1-3 will be described below, but first, the washing water treatment (1), (2), and (3) in each example will be explained. -Wash water treatment (1)(2)(3)- The washing water treatment (1), (2), and (3) all aim to detoxify the treated water to a level where it can be disposed of as general waste (drainage), to circulate this treated water within the first to third washing processes to reduce the amount of fresh water used, and furthermore, to ensure that the concentration of harmful substances does not increase even when the amount of fresh water used is reduced and the treated water is circulated, thereby eliminating the possibility of the final wastewater discharge becoming more complicated, equipment deterioration accelerating, or the intended reaction with secondary aluminum dross not occurring.

[0041] • Wash water treatment (1) involves collecting and treating the liquid phase after solid-liquid separation in the first washing process and the liquid phase after solid-liquid separation in the second washing process in this treatment equipment, and using the treated water as the washing solution in the first washing process. • Wash water treatment (2) involves collecting and treating the liquid phase after solid-liquid separation of the slurry that has been moved to the third washing kettle in the third washing process in this treatment equipment, and using the treated water as the washing liquid in the first washing process. • Wash water treatment (3) involves collecting and treating the liquid phase after solid-liquid separation of the slurry that has been tracer ion-tested in the third washing kettle in the third washing process using the equipment for this treatment, and using the treated water as the washing solution in the second washing process.

[0042] The liquid phases collected in each process (1), (2), and (3) were tested for pH. In this example, if the pH was not between 6 and 10, carbon dioxide was dissolved in the slurry as a adjusting agent to adjust it to 6 or 10. The slurry, with a pH of 6-10, was allowed to stand for 2-5 hours, followed by solid-liquid separation. The resulting liquid phase was used as the washing solution in each of the washing steps described above. Alternatively, it was drained if unnecessary.

[0043] The solid phase of the solid-liquid separation described above is collected in each process (1), (2), and (3), which is the liquid phase that has been separated in each washing step. However, the collected liquid phase is not completely separated from the solid phase, and a small amount has solidified in each process (1), (2), and (3) due to the reaction with the adjusting agent during pH adjustment. Therefore, solid-liquid separation is ultimately performed in each process (1), (2), and (3). The solid phase obtained from the above solid-liquid separation is collected in each process (1), (2), and (3). Once a certain amount has been collected, it is rendered harmless by a separate process and then disposed of as general waste.

[0044] (Example 1) -First Washing Process- • In the upstream process, the slurry, which had already been reacted with secondary aluminum dross and water to remove harmful gases, was subjected to solid-liquid separation to obtain a solid phase with a water content of 18%. The solid phase was sent to the first washing kettle, and the liquid phase was sent to the washing water treatment (1). • In the first washing kettle, treated water from washing water treatment (1) and (2) was added as the washing liquid at a mass ratio of 3.4 to the solid phase 1, and the liquid level in the first washing kettle was raised to 55%. The rotation speed of the stirring blade 5 was controlled to 55 r / min. The frequency of the ultrasonic stirrer 4 was also controlled to 40 kHz. • Carbon dioxide was supplied to the washing kettle to adjust the pH to 6.5. After the pH reached 6.5, nitric acid was added as a adjusting agent to adjust the pH to 3. The solution was adjusted to pH 3 and then washed for 18 minutes. During the 18-minute washing time, chloride ions (Cl - ) was selected as a tracer ion, and samples were taken at 5-minute intervals to examine the tracer ion content. The chloride ion content was adjusted to pH 3 and washed repeatedly between two consecutive samplings until it fell below 10%. The first washing process was terminated when the chloride ion content fell below 10%.

[0045] -Second cleaning process- The slurry sent from the first washing kettle was separated into solid and liquid phases. The solid phase was sent to the second washing kettle, and the liquid phase was sent to the washing water treatment (1). The solid phase and treated water from the washing water treatment (3) are injected into the second washing kettle as the washing liquid, and the liquid level in the second washing kettle is raised to 55%. The rotation speed of the stirring blade 5 was controlled to 55 r / min. The frequency of the ultrasonic stirrer 4 was also controlled to 40 kHz. Nitric acid was added as a adjusting agent to adjust the pH to 2. The solution was adjusted to pH 2 and then washed for 22 minutes. During the 22-minute washing time, chloride ions (Cl - ) was selected as a tracer ion, and samples were taken at 5-minute intervals to examine the tracer ion content. The chloride ion content was adjusted to pH 2 and washed repeatedly between two consecutive samplings until it fell below 10%. Once it fell below 10%, the second washing process was terminated.

[0046] -Third cleaning process- The slurry sent from the second washing kettle was separated into solid and liquid phases. The solid phase was sent to the third washing kettle, and the liquid phase was sent to the washing water treatment (2). The solid phase and fresh water were injected into the third washing kettle as the washing solution, and the liquid level in the third washing kettle was raised to 55%. The rotation speed of the stirring blade 5 was controlled to 55 r / min. The frequency of the ultrasonic stirrer 4 was also controlled to 40 kHz. • Limewater was added as a adjusting agent to adjust the pH to 8. The solution was adjusted to pH 8 and then washed for 22 minutes. During the 22-minute washing time, chloride ions (Cl - ) was selected as a tracer ion, and samples were taken at 5-minute intervals to examine the tracer ion content. The chloride ion content was adjusted to pH 8 and washed repeatedly between two consecutive samplings until it fell below 10%. Once it fell below 10%, the next treatment was performed. The next step involves solid-liquid separation of the slurry in the third washing kettle. The liquid phase after solid-liquid separation is sent to the washing water treatment (3), and the treated water processed in the washing water treatment (3) is reused as the washing solution for the second washing step. On the other hand, the solid phase after the solid-liquid separation was tested for heavy metal and impurity ion content using a prescribed testing method. If it met the prescribed standards, the process was terminated. If it did not meet the standards, the process was repeated by returning to the initial washing after solid-liquid separation in the third washing step (returning the solid phase) and repeating the subsequent processes. • Although solid phases that meet the specified standards can be disposed of as general waste, in this example they were reused as concrete material.

[0047] (Example 2) -First Washing Process- • In the upstream process, the slurry, which had already been reacted with secondary aluminum dross and water to remove harmful gases, was subjected to solid-liquid separation to obtain a solid phase with a water content of 22%. The solid phase was sent to the first washing kettle, and the liquid phase was sent to the washing water treatment (1). • In the first washing kettle, treated water from washing water treatment (1) and (2) was added as the washing liquid at a mass ratio of 4.2 to the solid phase 1, and the liquid level in the first washing kettle was raised to 60%. The rotation speed of the stirring blade 5 was controlled to 60 r / min. The frequency of the ultrasonic stirrer 4 was also controlled to 60 kHz. • Carbon dioxide was supplied to the washing kettle to adjust the pH to 6.8. · After reaching pH 6.8, nitric acid was added as an adjuster to adjust the pH to 3.5. · After adjusting to pH 3.5, it was washed for 25 minutes. · During the 25 - minute washing time, chloride ions (Cl - ) were selected as tracer ions, sampled at 5 - minute intervals, and the content of the tracer ions was inspected. · The washing after adjusting to pH 3.5 was repeated until the change in the chloride ion content became less than 10% between two consecutive samplings, and when it became less than 10%, the first - stage washing process was terminated.

[0048] - Second - stage washing process - · The slurry sent from the first washing kettle was subjected to solid - liquid separation. The solid phase was sent to the second washing kettle, and the liquid phase was sent to the washing water treatment (1) respectively. · The solid phase and the treated water from the washing water treatment (3) were injected into the second washing kettle as washing liquid, and the liquid level height in the second washing kettle was made 60%. · The rotation speed of the stirring blade 5 was controlled to 60 r / min. Also, the frequency of the ultrasonic stirrer 4 was controlled to 60 kHz. · Nitric acid was added as an adjuster to adjust the pH to 2.5. · After adjusting to pH 2.5, it was washed for 28 minutes. · During the 28 - minute washing time, chloride ions (Cl - ) were selected as tracer ions, sampled at 5 - minute intervals, and the content of the tracer ions was inspected. · The washing after adjusting to pH 2.5 was repeated until the change in the chloride ion content became less than 10% between two consecutive samplings, and when it became less than 10%, the second - stage washing process was terminated.

[0049] - Third - stage washing process - · The slurry sent from the second washing kettle was subjected to solid - liquid separation. The solid phase was sent to the third washing kettle, and the liquid phase was sent to the washing water treatment (2) respectively. · The solid phase and pure water were injected into the third washing kettle as washing liquid, and the liquid level height in the third washing kettle was made 60%. The rotation speed of the stirring blade 5 was controlled to 55 r / min. The frequency of the ultrasonic stirrer 4 was also controlled to 40 kHz. • Calcium hydroxide was added as a adjusting agent to adjust the pH to 9. The solution was adjusted to pH 9 and then washed for 25 minutes. During the 25-minute washing time, chloride ions (Cl - ) was selected as a tracer ion, and samples were taken at 5-minute intervals to examine the tracer ion content. The chloride ion content was adjusted to pH 9 and washed repeatedly between two consecutive samplings until it fell below 10%. Once it fell below 10%, the next treatment was performed. The next step involves solid-liquid separation of the slurry in the third washing kettle. The liquid phase after solid-liquid separation is sent to the washing water treatment (3), and the treated water processed in the washing water treatment (3) is reused as the washing solution for the second washing step. On the other hand, the solid phase after the solid-liquid separation was tested for heavy metal and impurity ion content using a prescribed testing method. If it met the prescribed standards, the process was terminated. If it did not meet the standards, the process was repeated by returning to the initial washing after solid-liquid separation in the third washing step (returning the solid phase) and repeating the subsequent processes. • Although solid phases that meet the specified standards can be disposed of as general waste, in this example they were reused as concrete material.

[0050] (Example 3) -First Washing Process- • In the upstream process, the slurry, which had already been reacted with secondary aluminum dross and water to remove harmful gases, was subjected to solid-liquid separation to obtain a solid phase with a water content of 22%. The solid phase was sent to the first washing kettle, and the liquid phase was sent to the washing water treatment (1). • In the first washing kettle, treated water from washing water treatment (1) and (2) was added as the washing liquid in a mass ratio of 5 to the solid phase 1, and the liquid level in the first washing kettle was raised to 65%. The rotation speed of the stirring blade 5 was controlled to 60 r / min. The frequency of the ultrasonic stirrer 4 was also controlled to 35 kHz. • Carbon dioxide was supplied to the washing kettle to adjust the pH to 6.2. After the pH reached 6.2, nitric acid was added as a adjusting agent to adjust the pH to 3.8. The solution was adjusted to pH 3.8 and then washed for 32 minutes. During the 32-minute washing time, chloride ions (Cl - ) was selected as the tracer ion, and samples were taken at 8-minute intervals to examine the tracer ion content. The chloride ion content was adjusted to pH 3.8 and washed repeatedly between two consecutive samplings until it fell below 10%. The first washing process was terminated when the chloride ion content fell below 10%.

[0051] -Second cleaning process- The slurry sent from the first washing kettle was separated into solid and liquid phases. The solid phase was sent to the second washing kettle, and the liquid phase was sent to the washing water treatment (1). The solid phase and treated water from the washing water treatment (3) are injected into the second washing kettle as the washing liquid, and the liquid level in the second washing kettle is raised to 65%. The rotation speed of the stirring blade 5 was controlled to 60 r / min. The frequency of the ultrasonic stirrer 4 was also controlled to 35 kHz. Nitric acid was added as a adjusting agent to adjust the pH to 3.2. The solution was adjusted to pH 3.2 and then washed for 28 minutes. During the 28-minute washing time, chloride ions (Cl - ) was selected as the tracer ion, and samples were taken at 8-minute intervals to examine the tracer ion content. The chloride ion content was adjusted to pH 3.2 and washed repeatedly between two consecutive samplings until it fell below 10%. The second washing process was terminated once the chloride ion content was below 10%.

[0052] -Third cleaning process- The slurry sent from the second washing kettle was separated into solid and liquid phases. The solid phase was sent to the third washing kettle, and the liquid phase was sent to the washing water treatment (2). The solid phase and fresh water were injected into the third washing kettle as the washing solution, and the liquid level in the third washing kettle was raised to 65%. The rotation speed of the stirring blade 5 was controlled to 55 r / min. The frequency of the ultrasonic stirrer 4 was also controlled to 35 kHz. Carbide slag was added as a adjusting agent to adjust the pH to 10. The solution was adjusted to pH 10 and then washed for 28 minutes. During the 28-minute washing time, chloride ions (Cl - ) was selected as the tracer ion, and samples were taken at 8-minute intervals to examine the tracer ion content. The chloride ion content was adjusted to pH 10 and washed repeatedly between two consecutive samplings until it fell below 10%. Once it fell below 10%, the next treatment was performed. The next step involves solid-liquid separation of the slurry in the third washing kettle. The liquid phase after solid-liquid separation is sent to the washing water treatment (3), and the treated water processed in the washing water treatment (3) is reused as the washing solution for the second washing step. On the other hand, the solid phase after the solid-liquid separation was tested for heavy metal and impurity ion content using a prescribed testing method. If it met the prescribed standards, the process was terminated. If it did not meet the standards, the process was repeated by returning to the initial washing after solid-liquid separation in the third washing step (returning the solid phase) and repeating the subsequent processes. • Although solid phases that meet the specified standards can be disposed of as general waste, in this example they were reused as concrete material.

[0053] (Example 4) -First Washing Process- • In the upstream process, the slurry, which had already been reacted with secondary aluminum dross and water to remove harmful gases, was subjected to solid-liquid separation to obtain a solid phase with a water content of 22%. The solid phase was sent to the first washing kettle, and the liquid phase was sent to the washing water treatment (1). • In the first washing kettle, treated water from washing water treatment (1) and (2) was added as the washing liquid in a mass ratio of 6 to the solid phase 1, and the liquid level in the first washing kettle was raised to 70%. The rotation speed of the stirring blade 5 was controlled to 65 r / min. The frequency of the ultrasonic stirrer 4 was also controlled to 40 kHz. • Carbon dioxide was supplied to the washing kettle to adjust the pH to 6.2. After the pH reached 6.2, acetic acid and oxalic acid were added as adjusting agents to adjust the pH to 4.2. The solution was adjusted to pH 4.2 and then washed for 20 minutes. During the 20-minute washing time, chloride ions (Cl - A tracer ion was selected, and samples were taken at 6-minute intervals to examine the tracer ion content. The chloride ion content was adjusted to pH 4.2 and washed repeatedly between two consecutive samplings until it fell below 10%. The first washing process was terminated when the chloride ion content fell below 10%.

[0054] -Second cleaning process- The slurry sent from the first washing kettle was separated into solid and liquid phases. The solid phase was sent to the second washing kettle, and the liquid phase was sent to the washing water treatment (1). The solid phase and treated water from the washing water treatment (3) are injected into the second washing kettle as the washing liquid, and the liquid level in the second washing kettle is raised to 70%. The rotation speed of the stirring blade 5 was controlled to 65 r / min. The frequency of the ultrasonic stirrer 4 was also controlled to 40 kHz. Acetic acid and oxalic acid were added as adjusting agents to adjust the pH to 3.2. The solution was adjusted to pH 3.2 and then washed for 28 minutes. During the 28-minute washing time, chloride ions (Cl - A tracer ion was selected, and samples were taken at 6-minute intervals to examine the tracer ion content. The chloride ion content was adjusted to pH 3.2 and washed repeatedly between two consecutive samplings until it fell below 10%. The second washing process was terminated once the chloride ion content was below 10%.

[0055] -Third cleaning process- The slurry sent from the second washing kettle was separated into solid and liquid phases. The solid phase was sent to the third washing kettle, and the liquid phase was sent to the washing water treatment (2). The solid phase and fresh water were injected into the third washing kettle as the washing solution, and the liquid level in the third washing kettle was raised to 70%. The rotation speed of the stirring blade 5 was controlled to 55 r / min. The frequency of the ultrasonic stirrer 4 was also controlled to 40 kHz. • Electrostatic slag was added as a adjusting agent to adjust the pH to 10. The solution was adjusted to pH 10 and then washed for 25 minutes. During the 25-minute washing time, chloride ions (Cl - A tracer ion was selected, and samples were taken at 6-minute intervals to examine the tracer ion content. The chloride ion content was adjusted to pH 10 and washed repeatedly between two consecutive samplings until it fell below 10%. Once it fell below 10%, the next treatment was performed. The next step involves solid-liquid separation of the slurry in the third washing kettle. The liquid phase after solid-liquid separation is sent to the washing water treatment (3), and the treated water processed in the washing water treatment (3) is reused as the washing solution for the second washing step. On the other hand, the solid phase after the solid-liquid separation was tested for heavy metal and impurity ion content using a prescribed testing method. If it met the prescribed standards, the process was terminated. If it did not meet the standards, the process was repeated by returning to the initial washing after solid-liquid separation in the third washing step (returning the solid phase) and repeating the subsequent processes. • Although solid phases that meet the specified standards can be disposed of as general waste, in this example they were reused as concrete material.

[0056] Thus, with the present invention, the solid phase remaining after the harmful gas phase is removed by reacting secondary aluminum dross with water can be rendered harmless, and the washing water used in this process can also be rendered harmless, making it suitable for disposal (drainage) or reuse. Furthermore, according to the treatment of the present invention, the fresh water used in the third washing step accounts for only a few percent of the total washing solution, and even if it is rendered harmless and then drained, it will only amount to a few percent including the aforementioned fresh water. [Explanation of Symbols]

[0057] 3 Pot body 4. Ultrasonic stirrer 5. Agitation blades 11 Annular air supply pipe

Claims

[Claim 1] A process for obtaining a harmless solid phase and a harmless liquid phase from a slurry, which is a solid-liquid integrated substance obtained by reacting secondary aluminum dross with water to remove the harmful gas phase, The solid phase cleaning process in the slurry is divided into first, second, and third cleaning processes. The first, second, and third washing steps each involve separating the slurry from the previous step into solid and liquid phases, mixing the washing solution with the solid phase, adjusting the pH value by adding a pH adjusting agent, washing by stirring, and then measuring the specified value of the impurity ion content. A method for solid-phase washing of secondary aluminosphate and treatment of washing water, comprising the steps of: collecting the liquid phase obtained from solid-liquid separation in the first, second, and third washing steps separately for each of the first, second, and third washing steps; dissolving carbon dioxide in each of the collected liquid phases to adjust the pH to 6-10 and using the treated water as washing water for the first or second washing step, or discharging it as a harmless liquid phase substance.

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