Method for treating wastewater generated when producing hydrogen from secondary aluminum dross.

Abstract

Harmless and useful chemical raw materials are obtained from wastewater generated during hydrogen production from secondary aluminum dross. [Solution] The present invention comprises the steps of: separating the gas phase and primary liquid phase of wastewater after hydrogen generation; dissolving carbon dioxide in the primary liquid phase until it reaches a predetermined pH value to obtain a secondary liquid phase; filtering the secondary liquid phase and dissolving carbon dioxide in the secondary liquid phase until it reaches a predetermined pH value to obtain a tertiary liquid phase; adding an extraction solvent to the tertiary liquid phase and dissolving carbon dioxide until it reaches a predetermined pH value to obtain a quaternary liquid phase separated into an organic phase and an inorganic phase by pressurized extraction; evaporating the water in the quaternary liquid phase of the inorganic phase; adding a solvent to the water in the quaternary liquid phase of the organic phase and performing back-extraction separation to obtain an inorganic liquid phase and an organic liquid phase, evaporating the water in the inorganic liquid phase while returning the organic liquid phase to the tertiary liquid phase.

Description

[Technical Field]

[0001] This invention relates to a method for obtaining harmless and useful chemical raw materials from wastewater generated during hydrogen production from secondary aluminum dross. [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 high-temperature heat treatment and wet methods involving chemical reaction treatment using water, as described above. The wet method targeted in this application includes 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] The liquid phase used in the wet treatment of secondary aluminum dross to render it harmless has a pH exceeding 14 and contains aluminates, chlorides, sulfides, sulfates, small amounts of fluorides, and ammonia nitrogen. This highly basic liquid phase is typically treated by adding carbon dioxide or hydrochloric acid to directly recover aluminum hydroxide or produce polyaluminum chloride.

[0010] Furthermore, during the wet treatment process to render secondary aluminum dross harmless, the secondary aluminum dross reacts with water or moisture in the initial stages. This reaction generates a gas phase, consisting of toxic, harmful, and flammable gases such as ammonia (NH3), methane (CH4), phosphine (PH3), hydrogen (H2), and hydrogen sulfide (H2S). Of these gases, hydrogen is actively collected and utilized. In the subsequent solid phase washing, the water used to generate the gas phase is reused, but the water used to wash the solid phase may also be reused to generate the gas phase again.

[0011] For example, Patent Document 1 (Japanese Unexamined Patent Publication No. 2010-1175), Patent Document 2 (Japanese Unexamined Patent Publication No. 2017-217606), Patent Document 3 (Japanese Patent Publication No. 7252683), and Patent Document 4 (Japanese Patent Publication No. 7249076) disclose technologies for generating and extracting hydrogen by reacting secondary aluminum dross with water.

[0012] However, conventionally, including in Patent Documents 1-4, even if the above wastewater is recycled by adding fresh water, the amount of wastewater increases as a result of adding fresh water, and if fresh water is not added, the concentration of highly basic substances 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]

[0013] [Patent Document 1] Japanese Patent Publication No. 2010-1175 [Patent Document 2] Japanese Patent Publication No. 2017-217606 [Patent Document 3] Patent No. 7252683 [Patent Document 4] Patent No. 7249076 [Patent Document 5] Patent No. 7249076 [Overview of the project]

Problems to be Solved by the Invention

[0014] <​​​​​​​​​​​​​​​​

Brief Description of the Drawings

[0017] [Figure 1] It is a flowchart showing the steps in the method of the present invention.

Embodiments for Carrying Out the Invention

[0018] The present invention is processed as follows. FIG. 1 is a flowchart showing the procedure of the wastewater treatment method for hydrogen generation of the present invention. The procedure of wastewater treatment of the water required to generate hydrogen from secondary alumidros is described. The secondary alumidros, which is the solid phase after hydrogen generation, is detoxified by separate treatment.

[0019] Also, in the following description, since the secondary alumidros and water are stirred and reacted, the "liquid phase" means the slurry, and the "solid phase" means the solid component obtained by removing or separating the moisture in this slurry.

[0020] (1): Separation of the gas phase and the first liquid phase of the wastewater after hydrogen generation Hydrogen is generated and collected from the gas phase generated by reacting secondary alumidros and water. The subsequent liquid phase, that is, the high ammonia nitrogen salt aqueous solution, is collected in an aeration reaction kettle equipped with porous pottery at the bottom.

[0021] The high ammonia nitrogen salt aqueous solution is transferred to another reaction kettle. In the reaction kettle, aeration treatment is carried out at a rotation speed of 40 - 150 r / min and an air flow rate of 10 - 30 m 3 / min for a reaction time of about 0.5 - 3 h to separate into ammonia gas (gas phase) and high salt alkaline water (first liquid phase).

[0022] (Ammonia water production) The ammonia gas in the gas phase fraction separated above is introduced into an absorption tower to obtain ammonia water. The "ammonia aqueous solution (ammonia water)" obtained here can be used as a general raw material for metal surface cleaners and pharmaceuticals.

[0023] (2): First liquid phase → Second liquid phase Meanwhile, the primary liquid phase (highly alkaline aqueous solution) of the residual aqueous solution after the separation of ammonia gas as a gaseous component is transferred to another reaction vessel. In this reaction vessel, carbon dioxide is supplied at a rate of 1000-3000 mL / min while stirring the contents of the vessel at a rotation speed of 40-150 r / min until the pH of the primary liquid phase reaches pH 6 or higher to pH 7.

[0024] (aluminum hydroxide) The primary liquid phase after the above treatment is separated by filtration into a solid phase and a liquid phase (secondary liquid phase). The solid phase obtained by this filtration separation is "aluminum hydroxide," which can be used as a general raw material for pharmaceuticals, adsorbents, and pigments.

[0025] (3):Second liquid phase → Tertiary liquid phase The secondary liquid phase separated above is transferred to another reaction vessel, and carbon dioxide is supplied at a rate of 1000-3000 mL / min while stirring the vessel at a rotation speed of 40-150 r / min until the pH of the secondary liquid phase is between 5 and less than 6.0. (Sodium bicarbonate) The secondary liquid phase after the above treatment is separated by filtration into a solid phase and a liquid phase (tertiary liquid phase). The solid phase obtained by this filtration separation is "sodium bicarbonate," which can be used as a general raw material for polishing, saponification, and washing.

[0026] (4)Third liquid phase → fourth liquid phase The tertiary liquid phase is transferred to another reaction vessel, where the reaction temperature is maintained at 20-25°C and the reaction pressure at 1.85 MPa, while stirring the vessel at a rotation speed of 40-150 r / min. Carbon dioxide is supplied at a rate of 1000-3000 mL / min with a carbon dioxide solubility of 0.06-0.07 mol / L, and one of the following extraction solvents is added to separate and extract the organic phase (quaternary liquid phase) and the inorganic phase (quaternary liquid phase). The volume ratio is organic phase:inorganic phase = 1:2.

[0027] The above-mentioned extraction solvent includes an extractant and a diluent. The extractant may be one or more of alkyl primary amines, secondary amines, trioctylamines, or trioctylmethylammonium salts. The diluent may be one or more of kerosene, tributyl phosphate, positive pentanol, positive hexanol, positive octanol, or isooctanool.

[0028] (Sodium chloride and sodium sulfate) The inorganic phase solution described above is heated to 90-100°C and then sent to a self-vapor mechanical compressor (MVR) apparatus. The compressor is operated until the sodium sulfate becomes supersaturated, at which point "sodium sulfate" and the mother liquor are obtained. When the sodium sulfate concentration in the mother liquor drops to 5%, the temperature is lowered to 50-55°C. This mother liquor is then sent to the self-vapor mechanical compressor (MVR) apparatus, the compressor is operated, and supersaturated "sodium chloride" is obtained.

[0029] In the self-contained mechanical compression apparatus described above, the water vapor generated at this stage has had all common toxic and harmful substances removed, so it may be released into the atmosphere or supplied as fresh water equivalent for the subsequent detoxification treatment of secondary aluminodros. The sodium sulfate obtained here can be used as a general raw material for desiccants, and the sodium chloride can be used as a general material for medical products, etc.

[0030] (5) Fourth liquid phase of the organic phase → inorganic liquid phase / organic liquid phase The fourth liquid phase of the organic phase described above is transferred to another reaction vessel. In this reaction vessel, an aqueous ammonia solution (ammonia water) obtained by dissolving the gas phase described in (1) in water is added to the fourth liquid phase. The reaction vessel is stirred at a rotation speed of 40-150 r / min, and back-extraction separation is performed to return the substances extracted into the organic phase from the solvent to the liquid phase. After separation, an organic liquid phase and an inorganic liquid phase are obtained. The volume ratio of the organic liquid phase to the inorganic liquid phase is approximately 1:0.5.

[0031] (Ammonium chloride) The above organic liquid phase is returned to the tertiary liquid phase. Meanwhile, the above inorganic liquid phase is concentrated and evaporated to obtain ammonium chloride. Ammonium chloride can be used as a general material for plating, fertilizers, etc. Furthermore, the water vapor separated during the evaporation of the inorganic liquid phase has had all common toxic and harmful substances removed, so it can be released into the atmosphere or supplied as fresh water equivalent for the subsequent detoxification treatment of secondary aluminodros.

[0032] Thus, all wastewater used in generating hydrogen from secondary alumina dross is repurposed as a general material, the water component is safely released into the atmosphere as water vapor, and is supplied as fresh water equivalent for the subsequent detoxification treatment of secondary alumina dross. This prevents an increase in wastewater volume by adding new fresh water, and also prevents the concentration of highly alkaline substances from gradually increasing in purity by not adding new fresh water.

[0033] More specifically, it has the following effects: By employing air aeration, ammonia can be removed from the liquid phase. This disrupts the buffering system of the liquid phase, making subsequent pH adjustment easier. Furthermore, the ammonia can be used in subsequent back-extraction, allowing for the complete reuse of wastewater.

[0034] Furthermore, by employing air aeration, contaminants such as reducing sulfides and thiosulfates in the liquid phase can be oxidized to sulfates, thereby improving the purity of the subsequent sulfates.

[0035] Furthermore, by adjusting the pH value using carbon dioxide, it is possible to precipitate aluminate ions as aluminum hydroxide, without increasing the amount of treated water, and to produce high-value salts such as sodium bicarbonate using an alkali production method in the highly basic liquid phase. [Examples]

[0036] (First embodiment) The wastewater generated when hydrogen is produced from secondary aluminum dross containing the following components, i.e., a high-ammonia nitrogen salt aqueous solution (30 ml). 3 Processed. • Components of high ammonia nitrogen salt aqueous solution pH14 Hydroxide ion concentration: 0.6 mol / L Aluminum ion concentration: 15 g / L Total salt concentration: 12% Chloride ion concentration: 27.7 g / L Ammonia nitrogen concentration: 2000 mg / L Sulfide and thiosulfate concentrations: 1.98 g / L and 13.5 g / L

[0037] (1) Separation of the gas phase and primary liquid phase of wastewater after hydrogen generation. The following conditions were used to obtain "ammonia water" in this process. Reaction vessel rotation speed: 40 r / min Airflow rate for aeration: 10 m 3 / min Aeration time: 1 hour Gas-liquid separation was performed, and the ammonia in the gas phase was passed through an absorption tower to obtain "ammonia water," while the liquid phase (primary liquid phase) was transferred to another reaction vessel for the next step.

[0038] (2) 1st liquid phase → 2nd liquid phase The following conditions were used to obtain "aluminum hydroxide" in this process. Carbon dioxide flow rate: 1000 mL / min Reaction vessel rotation speed: 40 r / min The treatment was continued under the above conditions until the pH reached 7. After the pH reached 7, the primary liquid phase was subjected to solid-liquid separation using a pressure filter press to obtain "aluminum hydroxide" as the solid phase, while the liquid phase (secondary liquid phase) was transferred to another reaction vessel for the next step.

[0039] (3) 2nd liquid phase → 3rd liquid phase The following conditions were used to obtain "sodium bicarbonate" in this process. Carbon dioxide flow rate: 1200 mL / min Reaction vessel rotation speed: 40 r / min The treatment was continued under the above conditions until the pH reached 6. After the pH reached 6, the secondary liquid phase was subjected to solid-liquid separation using a pressure filter press to obtain "sodium bicarbonate" as the solid phase, while the liquid phase (tertiary liquid phase) was transferred to another reaction vessel for the next step. (4)Third liquid phase → fourth liquid phase The following conditions were used to obtain "sodium chloride" and "sodium sulfate" in this process. Carbon dioxide flow rate: 1100 mL / min Reaction vessel rotation speed: 40 r / min Extraction solvent: Extractant: alkyl primary amine; Diluent: kerosene Add the organic phase and inorganic phase so that their volume ratio is approximately 1:2. Reaction temperature: 20°C Pressure inside the reaction vessel: 1.85 MPa Solubility of carbon dioxide: 0.07 mol / L The process was continued under the above conditions until the pH reached 3. The tertiary liquid phase, after reaching pH 3, was extracted and separated to obtain a quaternary liquid phase consisting of an organic phase and a quaternary liquid phase consisting of an inorganic phase. The quaternary liquid phase of the organic phase was then transferred to another reaction vessel for the next step.

[0040] The fourth liquid phase of the inorganic phase described above was removed from the bottom of the reaction vessel and sent to a self-vapor mechanical compressor (MVR) apparatus. In this apparatus, it was heated to 100°C, and the compressor was operated to supersaturate it with sodium sulfate to obtain "sodium sulfate" and "mother liquor".

[0041] As described above, once the sodium sulfate concentration in the mother liquor was reduced to 5% by the extraction of sodium sulfate, the temperature was lowered to 50°C, and the mother liquor was sent to another self-vapor mechanical compression (MVR) apparatus. In this apparatus, the compressor was operated to concentrate and supersaturate the mixture to obtain sodium chloride.

[0042] (5) Fourth liquid phase of the organic phase → inorganic liquid phase / organic liquid phase The following conditions were used to obtain "ammonium chloride" in this process. To the fourth liquid phase of the organic phase described above, an aqueous ammonia solution obtained by dissolving the gas phase described in (1) in water was added so that the volume ratio of the organic phase to the inorganic phase was approximately 1:0.5. The fourth liquid phase of the organic phase after the addition of aqueous ammonia was subjected to back-extraction and separation treatment with the reaction vessel rotation speed set to 40 r / min. The inorganic liquid phase separated above was concentrated and evaporated to obtain "ammonium chloride," while the organic liquid phase was returned to the tertiary liquid phase in step (4) above.

[0043] The wastewater treated by the first example was as follows. All obtained general chemical raw materials (excluding ammonia water) had a purity of 90% or higher, and a high-ammonia nitrogen salt aqueous solution was used in 30 ml. 3 The entire volume was processed, and no wastewater treatment was necessary. In addition, the water evaporated in steps (4) and (5) above was safely released into the atmosphere as water vapor. Aluminum hydroxide 1.30 t Sodium bicarbonate 2.20 t Ammonium chloride 0.10 t Sodium chloride 0.80 t Sodium sulfate 1.40 t Ammonia solution 0.30 t (concentration range 5-15%)

[0044] (Second example) The wastewater generated when hydrogen is produced from secondary aluminum dross containing the following components, i.e., a high-ammonia nitrogen salt aqueous solution (30 ml). 3 Processed. • Components of high ammonia nitrogen salt aqueous solution pH14 Hydroxide ion concentration: 0.55 mol / L Aluminum ion concentration: 16 g / L Total salt concentration: 13% Chloride ion concentration: 28 g / L Ammonia nitrogen concentration: 1900 mg / L Sulfide and thiosulfate concentrations: 1.88 g / L and 12 g / L

[0045] (1) Separation of the gas phase and primary liquid phase of wastewater after hydrogen generation. The following conditions were used to obtain "ammonia water" in this process. Reaction vessel rotation speed: 50 r / min Airflow rate for aeration: 12 m 3 / min Aeration time: 1.5 hours Gas-liquid separation was performed, and the ammonia in the gas phase was passed through an absorption tower to obtain "ammonia water," while the liquid phase (primary liquid phase) was transferred to another reaction vessel for the next step.

[0046] (2) 1st liquid phase → 2nd liquid phase The following conditions were used to obtain "aluminum hydroxide" in this process. Carbon dioxide flow rate: 1200 mL / min Reaction vessel rotation speed: 30 r / min The treatment was continued under the above conditions until the pH reached 7. After the pH reached 7, the primary liquid phase was subjected to solid-liquid separation using a pressure filter press to obtain "aluminum hydroxide" as the solid phase, while the liquid phase (secondary liquid phase) was transferred to another reaction vessel for the next step.

[0047] (3) 2nd liquid phase → 3rd liquid phase The following conditions were used to obtain "sodium bicarbonate" in this process. Carbon dioxide flow rate: 1300 mL / min Reaction vessel rotation speed: 55 r / min The treatment was continued under the above conditions until the pH reached 6. After the pH reached 6, the secondary liquid phase was subjected to solid-liquid separation using a pressure filter press to obtain "sodium bicarbonate" as the solid phase, while the liquid phase (tertiary liquid phase) was transferred to another reaction vessel for the next step. (4)Third liquid phase → fourth liquid phase The following conditions were used to obtain "sodium chloride" and "sodium sulfate" in this process. Carbon dioxide flow rate: 1450 mL / min Reaction vessel rotation speed: 50 r / min Extraction solvent: Extractant: Secondary amine; Diluent: Tributyl phosphate Add the organic phase and inorganic phase so that their volume ratio is approximately 1:2.2. Reaction temperature: 21°C Pressure inside the reaction vessel: 1.80 MPa Solubility of carbon dioxide: 0.065 mol / L The process was continued under the above conditions until the pH reached 3. The tertiary liquid phase, after reaching pH 3, was extracted and separated to obtain a quaternary liquid phase consisting of an organic phase and a quaternary liquid phase consisting of an inorganic phase. The quaternary liquid phase of the organic phase was then transferred to another reaction vessel for the next step.

[0048] The fourth liquid phase of the inorganic phase described above was removed from the bottom of the reaction vessel and sent to a self-vapor mechanical compressor (MVR) apparatus. In this apparatus, it was heated to 100°C, and the compressor was operated to supersaturate it with sodium sulfate to obtain "sodium sulfate" and "mother liquor".

[0049] As described above, once the sodium sulfate concentration in the mother liquor was reduced to 5% by the extraction of sodium sulfate, the temperature was lowered to 50°C, and the mother liquor was sent to another self-vapor mechanical compression (MVR) apparatus. In this apparatus, the compressor was operated to concentrate and supersaturate the mixture to obtain sodium chloride.

[0050] (5) Fourth liquid phase of the organic phase → inorganic liquid phase / organic liquid phase To the fourth liquid phase of the organic phase described above, an aqueous ammonia solution obtained by dissolving the gas phase described in (1) in water was added so that the volume ratio of the organic phase to the inorganic phase was approximately 1:0.45. The fourth liquid phase of the organic phase after the addition of aqueous ammonia was subjected to back-extraction and separation treatment with the reaction vessel rotation speed set to 35 r / min. The inorganic liquid phase separated above is concentrated and evaporated to obtain "ammonium chloride," while the organic liquid phase is returned to the tertiary liquid phase in step (4) above.

[0051] The wastewater situation processed by the second embodiment was as follows. All the obtained general chemical raw materials (excluding aqueous ammonia) had a purity of 90% or more, and 30 m of the high ammonia nitrogen salt aqueous solution 3 was completely processed, and no wastewater treatment was required. Aluminum hydroxide 1.50 t [[ID=^]] Sodium bicarbonate 2.00 t Ammonium chloride 0.09 t Sodium chloride 0.90 t Sodium sulfate 1.30 t Aqueous ammonia 0.33 t (concentration range 5 - 15%)

[0052] (Third Embodiment) The wastewater generated when producing hydrogen from the secondary aluminum dross of the following components, that is, 30 m of the high ammonia nitrogen salt aqueous solution 3 was treated. · Components of the high ammonia nitrogen salt aqueous solution pH 14 Hydroxide ion concentration: 0.57 mol / L Aluminum ion concentration: 13 g / L Total salt concentration: 16% Chloride ion concentration: 25 g / L Ammonia nitrogen concentration: 1888 mg / L Sulfide and thiosulfate concentrations: 1.7 g / L and 11 g / L

[0053] (1) Separation of the gas phase and the first liquid phase of the wastewater after hydrogen production It was treated under the following conditions, and "aqueous ammonia" was obtained in this step. Rotation speed of the reaction kettle: 46 r / min Air flow rate for aeration: 13 m 3 / min Aeration time: 1.3 h Gas-liquid separation was performed. Ammonia in the gas phase passed through the absorption tower to obtain "aqueous ammonia", while the liquid phase (the first liquid phase) was transferred to another reaction kettle for the next step.

[0054] (2) First liquid phase → Second liquid phase The following conditions were used to obtain "aluminum hydroxide" in this process. Carbon dioxide flow rate: 1314 mL / min Reaction vessel rotation speed: 38 r / min The treatment was continued under the above conditions until the pH reached 7. After the pH reached 7, the primary liquid phase was subjected to solid-liquid separation using a pressure filter press to obtain "aluminum hydroxide" as the solid phase, while the liquid phase (secondary liquid phase) was transferred to another reaction vessel for the next step.

[0055] (3) 2nd liquid phase → 3rd liquid phase The following conditions were used to obtain "sodium bicarbonate" in this process. Carbon dioxide flow rate: 1500 mL / min Reaction vessel rotation speed: 45 r / min The treatment was continued under the above conditions until the pH reached 6. After the pH reached 6, the secondary liquid phase was subjected to solid-liquid separation using a pressure filter press to obtain "sodium bicarbonate" as the solid phase, while the liquid phase (tertiary liquid phase) was transferred to another reaction vessel for the next step. (4)Third liquid phase → fourth liquid phase The following conditions were used to obtain "sodium chloride" and "sodium sulfate" in this process. Carbon dioxide flow rate: 1520 mL / min Reaction vessel rotation speed: 54 r / min Extraction solvent: Extractant: Trioctylamine; Diluent: Pentamol Add the organic phase and inorganic phase so that their volume ratio is approximately 1:2.3. Reaction temperature: 23°C Pressure inside the reaction vessel: 1.77 MPa Solubility of carbon dioxide: 0.06 mol / L The process was continued under the above conditions until the pH reached 3. The tertiary liquid phase, after reaching pH 3, was extracted and separated to obtain a quaternary liquid phase consisting of an organic phase and a quaternary liquid phase consisting of an inorganic phase. The quaternary liquid phase of the organic phase was then transferred to another reaction vessel for the next step.

[0056] The fourth liquid phase of the inorganic phase described above was removed from the bottom of the reaction vessel and sent to a self-vapor mechanical compressor (MVR) apparatus. In this apparatus, it was heated to 100°C, and the compressor was operated to supersaturate it with sodium sulfate to obtain "sodium sulfate" and "mother liquor".

[0057] As described above, once the sodium sulfate concentration in the mother liquor was reduced to 5% by the extraction of sodium sulfate, the temperature was lowered to 50°C, and the mother liquor was sent to another self-vapor mechanical compression (MVR) apparatus. In this apparatus, the compressor was operated to concentrate and supersaturate the mixture to obtain sodium chloride.

[0058] (5) Fourth liquid phase of the organic phase → inorganic liquid phase / organic liquid phase The following conditions were used to obtain "ammonium chloride" in this process. To the fourth liquid phase of the organic phase described above, an aqueous ammonia solution obtained by dissolving the gas phase described in (1) in water was added so that the volume ratio of the organic phase to the inorganic phase was approximately 1:0.43. The fourth liquid phase of the organic phase after the addition of aqueous ammonia was subjected to back-extraction and separation treatment with the reaction vessel rotation speed set to 48 r / min. The inorganic liquid phase separated above was concentrated and evaporated to obtain "ammonium chloride," while the organic liquid phase was returned to the tertiary liquid phase in step (4) above.

[0059] The wastewater treated by the third example was as follows. All obtained general chemical raw materials (excluding ammonia water) had a purity of 90% or higher, and a high-ammonia nitrogen salt aqueous solution was used. 3 The entire volume was processed, and no wastewater treatment was necessary. In addition, the water evaporated in steps (4) and (5) above was safely released into the atmosphere as water vapor. Aluminum hydroxide 1.20 t Sodium bicarbonate 1.90 t Ammonium chloride 0.07 t Sodium chloride 0.70 t Sodium sulfate 1.10 t Ammonia solution 0.30 t (concentration range 5-15%)

[0060] (Fourth embodiment) The wastewater generated when hydrogen is produced from secondary aluminum dross containing the following components, i.e., a high-ammonia nitrogen salt aqueous solution (30 ml). 3 Processed. • Components of high ammonia nitrogen salt aqueous solution pH14 Hydroxide ion concentration: 0.59 mol / L Aluminum ion concentration: 15 g / L Total salt concentration: 18% Chloride ion concentration: 29.0 g / L Ammonia nitrogen concentration: 1650 mg / L Sulfide and thiosulfate concentrations: 1.5 g / L and 16 g / L

[0061] (1) Separation of the gas phase and primary liquid phase of wastewater after hydrogen generation. The following conditions were used to obtain "ammonia water" in this process. Reaction vessel rotation speed: 48 r / min Airflow rate for aeration: 15 m 3 / min Aeration time: 1.5 hours Gas-liquid separation was performed, and the ammonia in the gas phase was passed through an absorption tower to obtain "ammonia water," while the liquid phase (primary liquid phase) was transferred to another reaction vessel for the next step.

[0062] (2) 1st liquid phase → 2nd liquid phase The following conditions were used to obtain "aluminum hydroxide" in this process. Carbon dioxide flow rate: 1517 mL / min Reaction vessel rotation speed: 44 r / min The treatment was continued under the above conditions until the pH reached 7. After the pH reached 7, the primary liquid phase was subjected to solid-liquid separation using a pressure filter press to obtain "aluminum hydroxide" as the solid phase, while the liquid phase (secondary liquid phase) was transferred to another reaction vessel for the next step.

[0063] (3) 2nd liquid phase → 3rd liquid phase The following conditions were used to obtain "sodium bicarbonate" in this process. Carbon dioxide flow rate: 1750 mL / min Reaction vessel rotation speed: 56 r / min The treatment was continued under the above conditions until the pH reached 6. After the pH reached 6, the secondary liquid phase was subjected to solid-liquid separation using a pressure filter press to obtain "sodium bicarbonate" as the solid phase, while the liquid phase (tertiary liquid phase) was transferred to another reaction vessel for the next step. (4)Third liquid phase → fourth liquid phase The following conditions were used to obtain "sodium chloride" and "sodium sulfate" in this process. Carbon dioxide flow rate: 1780 mL / min Reaction vessel rotation speed: 60 r / min Extraction solvent: Extractant: Trioctylmethylammonium salt; Diluent: Positive hexanol Add the organic phase and inorganic phase so that the volume ratio is approximately 1:2.11. Reaction temperature: 25°C Pressure inside the reaction vessel: 1.8 MPa Solubility of carbon dioxide: 0.07 mol / L The process was continued under the above conditions until the pH reached 3. The tertiary liquid phase, after reaching pH 3, was extracted and separated to obtain a quaternary liquid phase consisting of an organic phase and a quaternary liquid phase consisting of an inorganic phase. The quaternary liquid phase of the organic phase was then transferred to another reaction vessel for the next step.

[0064] The fourth liquid phase of the inorganic phase described above was removed from the bottom of the reaction vessel and sent to a self-vapor mechanical compressor (MVR) apparatus. In this apparatus, it was heated to 100°C, and the compressor was operated to supersaturate it with sodium sulfate to obtain "sodium sulfate" and "mother liquor".

[0065] As described above, once the sodium sulfate concentration in the mother liquor was reduced to 5% by the extraction of sodium sulfate, the temperature was lowered to 50°C, and the mother liquor was sent to another self-vapor mechanical compression (MVR) apparatus. In this apparatus, the compressor was operated to concentrate and supersaturate the mixture to obtain sodium chloride.

[0066] (5) Fourth liquid phase of the organic phase → inorganic liquid phase / organic liquid phase The following conditions were used to obtain "ammonium chloride" in this process. To the fourth liquid phase of the organic phase described above, an aqueous ammonia solution obtained by dissolving the gas phase described in (1) in water was added so that the volume ratio of the organic phase to the inorganic phase was approximately 1:0.49. The fourth liquid phase of the organic phase after the addition of aqueous ammonia was subjected to back-extraction and separation treatment with the reaction vessel rotation speed set to 50 r / min. The inorganic liquid phase separated above was concentrated and evaporated to obtain "ammonium chloride," while the organic liquid phase was returned to the tertiary liquid phase in step (4) above.

[0067] The wastewater treated by the fourth example was as follows. All obtained general chemical raw materials (excluding ammonia water) had a purity of 90% or higher, and the high-ammonia nitrogen salt aqueous solution was 30 ml. 3 The entire volume was processed, and no wastewater treatment was necessary. In addition, the water evaporated in steps (4) and (5) above was safely released into the atmosphere as water vapor. Aluminum hydroxide 1.20 t Sodium bicarbonate 1.90 t Ammonium chloride 0.07 t Sodium chloride 0.70 t Sodium sulfate 1.10 t Ammonia solution 0.30 t (concentration range 5-15%)

[0068] (Fifth example) The wastewater generated when hydrogen is produced from secondary aluminum dross containing the following components, i.e., a high-ammonia nitrogen salt aqueous solution (30 ml). 3 Processed. • Components of high ammonia nitrogen salt aqueous solution pH14 Hydroxide ion concentration: 0.46 mol / L Aluminum ion concentration: 13.3 g / L Total salt concentration: 16% Chloride ion concentration: 23 g / L Ammonia nitrogen concentration: 1764 mg / L Sulfide and thiosulfate concentrations: 1.3 g / L and 14 g / L

[0069] (1) Separation of the gas phase and primary liquid phase of wastewater after hydrogen generation. The following conditions were used to obtain "ammonia water" in this process. Reaction vessel rotation speed: 67 r / min Airflow rate for aeration: 19 m 3 / min Aeration time: 1 hour Gas-liquid separation was performed, and the ammonia in the gas phase was passed through an absorption tower to obtain "ammonia water," while the liquid phase (primary liquid phase) was transferred to another reaction vessel for the next step.

[0070] (2) 1st liquid phase → 2nd liquid phase The following conditions were used to obtain "aluminum hydroxide" in this process. Carbon dioxide flow rate: 1866 mL / min Reaction vessel rotation speed: 58 r / min The treatment was continued under the above conditions until the pH reached 7. After the pH reached 7, the primary liquid phase was subjected to solid-liquid separation using a pressure filter press to obtain "aluminum hydroxide" as the solid phase, while the liquid phase (secondary liquid phase) was transferred to another reaction vessel for the next step.

[0071] (3) 2nd liquid phase → 3rd liquid phase The following conditions were used to obtain "sodium bicarbonate" in this process. Carbon dioxide flow rate: 1487 mL / min Reaction vessel rotation speed: 65 r / min The treatment was continued under the above conditions until the pH reached 6. After the pH reached 6, the secondary liquid phase was subjected to solid-liquid separation using a pressure filter press to obtain "sodium bicarbonate" as the solid phase, while the liquid phase (tertiary liquid phase) was transferred to another reaction vessel for the next step. (4)Third liquid phase → fourth liquid phase The following conditions were used to obtain "sodium chloride" and "sodium sulfate" in this process. Carbon dioxide flow rate: 1974 mL / min Reaction vessel rotation speed: 66 r / min Extraction solvent: Extractant: Secondary amine; Diluent: Tributyl phosphate Add the organic phase and inorganic phase so that the volume ratio is approximately 1:2.14. Reaction temperature: 24°C Pressure inside the reaction vessel: 1.78 MPa Solubility of carbon dioxide: 0.07 mol / L The process was continued under the above conditions until the pH reached 3. The tertiary liquid phase, after reaching pH 3, was extracted and separated to obtain a quaternary liquid phase consisting of an organic phase and a quaternary liquid phase consisting of an inorganic phase. The quaternary liquid phase of the organic phase was then transferred to another reaction vessel for the next step.

[0072] The fourth liquid phase of the inorganic phase described above was removed from the bottom of the reaction vessel and sent to a self-vapor mechanical compressor (MVR) apparatus. In this apparatus, it was heated to 100°C, and the compressor was operated to supersaturate it with sodium sulfate to obtain "sodium sulfate" and "mother liquor".

[0073] As described above, once the sodium sulfate concentration in the mother liquor was reduced to 5% by the extraction of sodium sulfate, the temperature was lowered to 50°C, and the mother liquor was sent to another self-vapor mechanical compression (MVR) apparatus. In this apparatus, the compressor was operated to concentrate and supersaturate the mixture to obtain sodium chloride.

[0074] (5) Fourth liquid phase of the organic phase → inorganic liquid phase / organic liquid phase To the fourth liquid phase of the organic phase described above, an aqueous ammonia solution obtained by dissolving the gas phase described in (1) in water was added so that the volume ratio of the organic phase to the inorganic phase was approximately 1:0.501. The fourth liquid phase of the organic phase after the addition of aqueous ammonia was subjected to back-extraction and separation treatment with the reaction vessel rotation speed set to 50 r / min. The inorganic liquid phase separated above is concentrated and evaporated to obtain "ammonium chloride," while the organic liquid phase is returned to the tertiary liquid phase in step (4) above.

[0075] The wastewater treated by the fifth example was as follows. All obtained general chemical raw materials (excluding ammonia water) had a purity of 90% or higher, and the high-ammonia nitrogen salt aqueous solution was 30 ml. 3 The entire volume was processed, and no wastewater treatment was necessary. Aluminum hydroxide 1.44 t Sodium bicarbonate 1.90 t Ammonium chloride 0.05 t Sodium chloride 0.80 t Sodium sulfate 1.40 t Ammonia solution 0.27 t (concentration range 5-15%)

[0076] (Sixth embodiment) The wastewater generated when hydrogen is produced from secondary aluminum dross containing the following components, i.e., a high-ammonia nitrogen salt aqueous solution (30 ml). 3 Processed. • Components of high ammonia nitrogen salt aqueous solution pH14 Hydroxide ion concentration: 0.61 mol / L Aluminum ion concentration: 14.3 g / L Total salt concentration: 14% Chloride ion concentration: 22 g / L Ammonia nitrogen concentration: 1774 mg / L Sulfide and thiosulfate concentrations: 1.4 g / L and 12 g / L

[0077] (1) Separation of the gas phase and primary liquid phase of wastewater after hydrogen generation. The following conditions were used to obtain "ammonia water" in this process. Reaction vessel rotation speed: 68 r / min Airflow rate for aeration: 20 m 3 / min Aeration time: 1.06 h Gas-liquid separation was performed, and the ammonia in the gas phase was passed through an absorption tower to obtain "ammonia water," while the liquid phase (primary liquid phase) was transferred to another reaction vessel for the next step.

[0078] (2) 1st liquid phase → 2nd liquid phase The following conditions were used to obtain "aluminum hydroxide" in this process. Carbon dioxide flow rate: 1466 mL / min Reaction vessel rotation speed: 42 r / min The treatment was continued under the above conditions until the pH reached 7. After the pH reached 7, the primary liquid phase was subjected to solid-liquid separation using a pressure filter press to obtain "aluminum hydroxide" as the solid phase, while the liquid phase (secondary liquid phase) was transferred to another reaction vessel for the next step.

[0079] (3) 2nd liquid phase → 3rd liquid phase The following conditions were used to obtain "sodium bicarbonate" in this process. Carbon dioxide flow rate: 1473 mL / min Reaction vessel rotation speed: 68 r / min The treatment was continued under the above conditions until the pH reached 6. After the pH reached 6, the secondary liquid phase was subjected to solid-liquid separation using a pressure filter press to obtain "sodium bicarbonate" as the solid phase, while the liquid phase (tertiary liquid phase) was transferred to another reaction vessel for the next step. (4)Third liquid phase → fourth liquid phase The following conditions were used to obtain "sodium chloride" and "sodium sulfate" in this process. Carbon dioxide flow rate: 1687 mL / min Reaction vessel rotation speed: 67 r / min Extraction solvent: Extractant: Trioctylamine; Diluent: Isooctanol Add the organic phase and inorganic phase so that the volume ratio is approximately 1:2.15. Reaction temperature: 24°C Pressure inside the reaction vessel: 1.78 MPa Solubility of carbon dioxide: 0.081 mol / L The process was continued under the above conditions until the pH reached 3. The tertiary liquid phase, after reaching pH 3, was extracted and separated to obtain a quaternary liquid phase consisting of an organic phase and a quaternary liquid phase consisting of an inorganic phase. The quaternary liquid phase of the organic phase was then transferred to another reaction vessel for the next step.

[0080] The fourth liquid phase of the inorganic phase described above was removed from the bottom of the reaction vessel and sent to a self-vapor mechanical compressor (MVR) apparatus. In this apparatus, it was heated to 100°C, and the compressor was operated to supersaturate it with sodium sulfate to obtain "sodium sulfate" and "mother liquor".

[0081] As described above, once the sodium sulfate concentration in the mother liquor was reduced to 5% by the extraction of sodium sulfate, the temperature was lowered to 50°C, and the mother liquor was sent to another self-vapor mechanical compression (MVR) apparatus. In this apparatus, the compressor was operated to concentrate and supersaturate the mixture to obtain sodium chloride.

[0082] (5) Fourth liquid phase of the organic phase → inorganic liquid phase / organic liquid phase The following conditions were used to obtain "ammonium chloride" in this process. To the fourth liquid phase of the organic phase described above, an aqueous ammonia solution obtained by dissolving the gas phase described in (1) in water was added so that the volume ratio of the organic phase to the inorganic phase was approximately 1:0.504. The fourth liquid phase of the organic phase after the addition of aqueous ammonia was subjected to back-extraction and separation treatment with the reaction vessel rotation speed set to 66 r / min. The inorganic liquid phase separated above was concentrated and evaporated to obtain "ammonium chloride," while the organic liquid phase was returned to the tertiary liquid phase in step (4) above.

[0083] The wastewater treated by the sixth example was as follows. All obtained general chemical raw materials (excluding ammonia water) had a purity of 90% or higher, and the high-ammonia nitrogen salt aqueous solution was 30 ml. 3 The entire volume was processed, and no wastewater treatment was necessary. In addition, the water evaporated in steps (4) and (5) above was safely released into the atmosphere as water vapor. Aluminum hydroxide 1.30 t Sodium bicarbonate 1.60 t Ammonium chloride 0.45 t Sodium chloride 0.70 t Sodium sulfate 1.10 t Ammonia solution 0.23 t (concentration range 5-15%)

Claims

1. A wastewater treatment method after hydrogen is produced by the reaction of secondary aluminum dross with water, A process to separate the gas phase and primary liquid phase of wastewater after hydrogen generation, A step of dissolving carbon dioxide in the primary liquid phase until a predetermined pH value is reached to obtain a secondary liquid phase, This secondary liquid phase is filtered and carbon dioxide is dissolved in it until a predetermined pH value is reached to obtain a tertiary liquid phase. The process involves adding an extraction solvent to this third liquid phase and dissolving carbon dioxide until the pH reaches a predetermined value, thereby obtaining a fourth liquid phase separated into an organic phase and an inorganic phase by pressurized extraction. A step of evaporating the water in the fourth liquid phase of the inorganic phase, The process involves adding a solvent to the water in the fourth liquid phase of the organic phase and performing back-extraction separation to obtain an inorganic liquid phase and an organic liquid phase, evaporating the water in the inorganic liquid phase while returning the organic liquid phase to the third liquid phase, A method for treating wastewater generated when producing hydrogen from secondary aluminum dross containing [a specific material].

2. A method for treating wastewater generated when hydrogen is produced from secondary aluminum dross, according to claim 1, wherein in the step of separating the gas phase and primary liquid phase of wastewater after hydrogen production, the gas phase is absorbed into water to obtain ammonia water.

3. A method for treating wastewater generated when producing hydrogen from secondary aluminum dross according to claim 1, wherein in the step of obtaining the secondary liquid phase, solid-liquid separation is performed in the primary liquid phase in which carbon dioxide has been dissolved until a predetermined pH value is reached, and aluminum hydroxide is obtained from the solid phase.

4. A method for treating wastewater generated when producing hydrogen from secondary aluminum dross according to claim 1, wherein in the step of obtaining the third liquid phase, carbon dioxide is dissolved in the second liquid phase until a predetermined pH value is reached, and solid-liquid separation is performed to obtain sodium bicarbonate from the solid phase.

5. A method for treating wastewater generated when producing hydrogen from secondary aluminum dross according to claim 1, wherein in the step of evaporating water in the fourth liquid phase of the inorganic phase, sodium chloride and sodium sulfate are obtained from the solid phase remaining after water evaporation.

6. A method for treating wastewater generated when producing hydrogen from secondary aluminum dross according to claim 1, wherein ammonium chloride is obtained from the solid phase remaining after evaporation of water in the step of evaporating the water in the inorganic liquid phase.

7. A method for treating wastewater generated when producing hydrogen from secondary aluminum dross, according to claim 1, wherein the step of evaporating the water in the quaternary liquid phase of the inorganic phase and the step of evaporating the water in the inorganic liquid phase are performed, and the wastewater generated when evaporating the water to produce hydrogen from secondary aluminum dross is not discharged into the atmosphere but is released into the atmosphere in a harmless and safe state.

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