Method for comprehensive utilization of secondary aluminum dross

Abstract

The application relates to the technical field of comprehensive treatment of industrial solid wastes, and particularly discloses a comprehensive utilization method of secondary aluminum ash, which specifically comprises the following steps: deoxidizing the secondary aluminum ash; performing hydrolysis treatment on the deoxidized secondary aluminum ash, and performing solid-liquid separation to obtain mixed gas, hydrolysis slurry solid phase and high-salt-alkali ammonia-nitrogen hydrolysis liquid; separating and purifying the mixed gas to obtain hydrogen; performing at least twice acid pickling treatment and at least once alkali cleaning treatment on the hydrolysis slurry solid phase to obtain a solid-phase product for concrete admixture; performing ammonia-nitrogen separation on the high-salt-alkali ammonia-nitrogen hydrolysis liquid, and performing gradient acidification treatment to obtain aluminum hydroxide and inorganic salt crystals. By implementing the application, high-value overall utilization of the secondary aluminum ash can be realized.

Description

Technical Field

[0001] This invention relates to the field of comprehensive treatment technology for industrial solid waste, and in particular to a method for the comprehensive utilization of secondary aluminum ash. Background Technology

[0002] Secondary aluminum ash is the ash residue generated during the remelting of primary aluminum ash or the recovery of elemental aluminum from scrap aluminum in the secondary aluminum industry. The elemental aluminum content in secondary aluminum ash ranges from 5% to 20%, and it also contains alumina, aluminum nitride, salts (fluorides and chlorides, etc.), and silicon dioxide. The main hazardous component of secondary aluminum ash is aluminum nitride, along with small amounts of inorganic salts such as fluorides, sulfides, sulfates, and chlorides. Direct discharge of secondary aluminum ash will cause serious air, soil, and water pollution.

[0003] The disposal methods for secondary aluminum ash are mainly divided into pyrometallurgical and wet methods (primarily hydrolysis). The wet method includes acid-alkali treatment, which involves reacting the secondary aluminum ash with a specific concentration of acid or alkali to hydrolyze aluminum nitride, elemental aluminum, and other aluminum compounds. After alkaline treatment, the liquid phase has a pH greater than 14 and mainly contains aluminates, chlorides, sulfides, sulfates, and small amounts of fluorides and ammonia nitrogen. Currently, acid or alkali leaching is commonly used to treat secondary aluminum ash, achieving efficient hydrolysis of aluminum nitride and leaching soluble salts. However, a large amount of recyclable resources still remain in the acidic or alkaline hydrolysate. The heavy metal and impurity ion content of secondary aluminum ash treated by hydrolysis is not significantly reduced, making it unsuitable as an auxiliary cementitious material in concrete. This poses difficulties for the utilization of the secondary aluminum ash residue after hydrolysis. Furthermore, the products obtained from the current treatment of alkaline aluminum ash hydrolysate are relatively limited, resulting in low resource utilization of the aluminum ash hydrolysate. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a comprehensive utilization method for secondary aluminum ash, which can realize the high-value-added resource utilization of secondary aluminum ash and greatly improve its utilization rate.

[0005] To address the aforementioned technical problems, this invention provides a method for the comprehensive utilization of secondary aluminum ash, comprising:

[0006] Deoxidize the secondary aluminum ash;

[0007] The deoxidized secondary aluminum ash was hydrolyzed and then separated into solid and liquid phases to obtain a mixed gas, a hydrolyzed mud solid phase, and a high-salt, alkaline, ammonia-nitrogen hydrolysate.

[0008] The mixed gas was separated and purified to obtain hydrogen.

[0009] The hydrolyzed mud solid phase is subjected to at least two acid washing treatments and at least one alkali washing treatment to obtain a solid phase product for use as a concrete admixture.

[0010] The high-salt, alkaline ammonia-nitrogen hydrolysate was subjected to ammonia-nitrogen separation and a stepwise acidification treatment to obtain aluminum hydroxide and inorganic salt crystals.

[0011] As an improvement to the above technical solution, in the step of hydrolyzing the deoxidized secondary aluminum ash to obtain a mixed gas, a hydrolyzed slurry solid phase, and a high-salt, alkaline, ammonia-nitrogen hydrolysate:

[0012] Secondary aluminum ash and water are mixed at a solid-liquid ratio of 1:(2-10), and calcium hydroxide and catalyst are added. The mixture is hydrolyzed at 5-99℃ for 5-48 hours. The gas collected during the hydrolysis process is the mixed gas. The liquid phase obtained by solid-liquid separation of the hydrolysis product is a high-salt, alkaline, ammonia-nitrogen hydrolysate, and the solid phase obtained is the hydrolysis mud solid phase.

[0013] The weight ratio of calcium hydroxide to deoxidized secondary aluminum ash is (1-10):100, and the weight ratio of catalyst to deoxidized secondary aluminum ash is (1-10):100.

[0014] The catalyst comprises, by weight, 0-10 parts sodium carbonate, 0-10 parts potassium carbonate, 10-80 parts sodium hydroxide, 0-50 parts potassium hydroxide, 5-30 parts carbide slag, and 0.01-5 parts sodium stannate.

[0015] As an improvement to the above technical solution, the temperature during the hydrolysis process is determined according to the following procedure:

[0016] Secondary aluminum ash, water, catalyst and calcium hydroxide are added to the reactor. When the temperature inside the reactor rises to 70-90℃, a cooling medium is used to cool it so that the rate of temperature rise inside the reactor is controlled at 0.1-3℃ / min.

[0017] When the rate of temperature rise in the reactor decreases, gradually reduce the amount of cooling medium to maintain the temperature in the reactor at 80-90℃.

[0018] When the temperature inside the reactor begins to drop, a heating medium is used for heating, and the amount of heating medium is adjusted to maintain the temperature inside the reactor at 80-90℃; wherein the temperature difference between the heating medium and the temperature inside the reactor is 1-10℃.

[0019] As an improvement to the above technical solution, the step of deoxidizing the secondary aluminum ash includes:

[0020] The secondary aluminum ash is graded to ensure that the residue on a 125μm sieve is 1-10%.

[0021] The secondary aluminum ash was deoxidized by nitrogen replacement.

[0022] As an improvement to the above technical solution, the step of subjecting the hydrolyzed mud solid phase to at least two acid washing treatments and at least one alkali washing treatment to obtain a solid product for use in concrete admixtures includes:

[0023] The solid phase of the hydrolyzed mud is subjected to at least two acid washing treatments, and the slurry obtained from the acid washing treatment is subjected to solid-liquid separation to obtain a sub-solid phase and a first sub-liquid phase; the sub-liquid phase is used for secondary aluminum ash hydrolysis treatment or the previous acid washing treatment.

[0024] The solid phase is subjected to at least one alkaline washing treatment, and the slurry obtained from the alkaline washing treatment is subjected to solid-liquid separation to obtain a solid product and a second sub-liquid phase, which is used for acid washing treatment.

[0025] The content of tracer ions was measured in both the acid-washed and alkaline-washed slurries. The tracer ions were selected from heavy metals and / or impurity ions.

[0026] The heavy metals include one or more of Pb, Cd, Cr, Cu, Ni, Zn, and Mn, and the impurity ions include Cl. - F - K + Na + One or more of them.

[0027] As an improvement to the above technical solution, the step of subjecting the hydrolyzed mud solid phase to at least two acid washing treatments and at least one alkali washing treatment to obtain a solid product for use in concrete admixtures includes:

[0028] The first washing liquid is injected into the primary washing tank, and the hydrolyzed mud solid phase is sent in for washing. The first washing liquid comes from the second liquid phase after the slurry is filtered at the outlet of the secondary washing tank.

[0029] A first gas is introduced into the primary washing tank until the pH of the washing solution reaches the first preset value;

[0030] Acidic solution is introduced into the primary washing tank until the pH of the washing solution reaches the second preset value;

[0031] After the primary washing tank is completed, the slurry is subjected to solid-liquid separation to obtain a first liquid phase and a first solid phase. The first liquid phase can be used for secondary aluminum ash hydrolysis treatment.

[0032] A second washing liquid is injected into the secondary washing tank, and the first solid phase is introduced to continue washing. The second washing liquid comes from the third liquid phase after the slurry is filtered at the outlet of the tertiary washing tank.

[0033] Acidic solution is introduced into the secondary washing tank until the pH of the washing solution reaches the second preset value;

[0034] After the secondary washing tank is completed, the mud is subjected to solid-liquid separation to obtain a second liquid phase and a second solid phase;

[0035] A third washing liquid is injected into the three-stage washing tank, and the second solid phase is introduced for washing. The third washing liquid is water.

[0036] An alkaline substance is introduced into the three-stage washing tank until the pH of the washing solution reaches the third preset value;

[0037] After the three-stage washing tank is completed, the mud is subjected to solid-liquid separation to obtain a third liquid phase and a third solid phase;

[0038] The content of heavy metals and impurity ions in the third solid phase is tested. If it meets the prescribed standards, the washing is completed and the third solid phase is the solid phase product. If it does not meet the prescribed standards, the washing process in the three-stage washing tank is repeated.

[0039] As an improvement to the above technical solution, the solid-liquid ratio of the primary washing tank, the secondary washing tank, and the tertiary washing tank is 1:(3-10) by mass.

[0040] The liquid level of the washing liquid in the primary, secondary, and tertiary washing tanks is 50-80% of the internal height of the washing tank.

[0041] As an improvement to the above technical solution, the first gas is CO2, and the first preset value of pH is 6-7;

[0042] The acidic solution is one or a combination of sulfuric acid, nitric acid, and organic acids, and the second preset value of pH is 2-6;

[0043] The alkaline substance is one or a combination of calcium hydroxide, sodium hydroxide, and carbide slag, and the third preset value of pH is 7-12.

[0044] As an improvement to the above technical solution, the criteria for determining the end of each wash cycle include:

[0045] Select one or more heavy metal or impurity ions as tracer ions and sample at preset intervals;

[0046] The content of the tracer ions is detected. If the change in the content of tracer ions between two consecutive tests is less than the preset value, the washing process ends.

[0047] The preset value for the ions is 5-10%.

[0048] As an improvement to the above technical solution, the first-stage washing tank, the second-stage washing tank, and the third-stage washing tank are used for washing by turning on the ultrasonic generator and the agitator, wherein the rotation speed of the agitator is 20-80 r / min, and the ultrasonic frequency of the ultrasonic generator is 20-80 kHz.

[0049] As an improvement to the above technical solution, the steps of separating ammonia nitrogen from the high-salt-alkali ammonia nitrogen hydrolysate and performing a stepwise acidification treatment to obtain aluminum hydroxide and inorganic salt crystals include:

[0050] The high-salt-alkali ammonia nitrogen hydrolysate is subjected to ammonia nitrogen separation to obtain a gas phase and a first-stage liquid phase;

[0051] Carbon dioxide is dissolved in the first-stage liquid phase until a specified pH value is reached to obtain the second-stage liquid phase;

[0052] Carbon dioxide is dissolved in the second-stage liquid phase until a specified pH value is reached to obtain the third-stage liquid phase;

[0053] An extraction solvent is added to the third-stage liquid phase and carbon dioxide is dissolved until a specified pH value is reached. After extraction and separation, a fourth-stage liquid phase consisting of an organic phase and an inorganic phase is obtained.

[0054] The water in the fourth-stage liquid phase of the inorganic phase is evaporated;

[0055] The fourth stage liquid phase of the organic phase is back-extracted to separate inorganic and organic liquid phases. The water in the inorganic liquid phase is evaporated, and the organic liquid phase is returned to the third stage liquid phase for processing.

[0056] As an improvement to the above technical solution, in the step of separating ammonia nitrogen from the high-salt-alkali ammonia nitrogen hydrolysate to obtain a gas phase and a first-stage liquid phase:

[0057] The high-salt, alkaline, ammonia-nitrogen hydrolysate is introduced into a reactor at a rotation speed of 40-150 r / min, and aeration is performed by introducing air at a flow rate of 10-30 m³ / min. 3 The reaction rate is 0.5-3 h, and the resulting ammonia gas is passed into the absorption tower to produce ammonia water.

[0058] The high-salt, alkaline ammonia nitrogen hydrolysate has a temperature of 80-95℃, an alkalinity of 0.20-2.0 mol / L, a total salt content of 5-25%, and an ammonia nitrogen concentration of 200-2000 mg / L.

[0059] The reactor rotation speed is set to 40-150 r / min, and air is introduced for aeration at a flow rate of 10-30 m³ / min. 3 The reaction rate is 0.5-3 h, and the resulting ammonia gas is passed into the absorption tower to produce ammonia water.

[0060] As an improvement to the above technical solution, in the step of dissolving carbon dioxide in the first-stage liquid phase until a specified pH value is reached to obtain the second-stage liquid phase:

[0061] Carbon dioxide is introduced into the first-stage liquid phase, with a flow rate of 1000-3000 mL / min and a rotation speed of 30-150 r / min. The reaction is stopped when the pH of the reaction decreases from 12-14 to 7-8. The slurry is then subjected to solid-liquid separation to obtain aluminum hydroxide and the second-stage liquid phase.

[0062] As an improvement to the above technical solution, in the step of dissolving carbon dioxide in the second-stage liquid phase until a specified pH value is reached to obtain the third-stage liquid phase:

[0063] The second-stage liquid phase is transferred into the reactor, and carbon dioxide is introduced into the reactor. The carbon dioxide flow rate is set to 1000-3000 mL / min, and the rotation speed is set to 40-150 r / min. The reaction is stopped when the pH of the reaction decreases from 7-8 to 5-6. The slurry is then subjected to solid-liquid separation to obtain sodium bicarbonate and the third-stage liquid phase.

[0064] As an improvement to the above technical solution, in the step of adding an extraction solvent to the third-stage liquid phase and dissolving carbon dioxide until a specified pH value is reached, and obtaining a fourth-stage liquid phase consisting of an organic phase and an inorganic phase after extraction and separation:

[0065] The third-stage liquid phase is transferred to a reaction vessel, and carbon dioxide is introduced into the vessel while an extraction solvent is added. The volume ratio of organic phase to inorganic phase is set to (1-2):(2-3), and the solubility of carbon dioxide is set to 0.05-0.08 mol / L. The reaction is stopped when the pH of the reaction decreases from 5-6 to 3-4. After extraction and separation, a fourth-stage liquid phase of organic phase and a fourth-stage liquid phase of inorganic phase are obtained. The fourth-stage liquid phase of organic phase contains chlorine.

[0066] As an improvement to the above technical solution, the extraction solvent comprises an extractant and a diluent, wherein the extractant is one or more selected from alkyl primary amines, secondary amines, trioctylalkyl tertiary amines, and trioctylmethyl quaternary ammonium salts; and the diluent is one or more selected from kerosene, tributyl phosphate, n-pentanol, n-hexanol, n-octanol, and isooctanol.

[0067] The flow rate of the carbon dioxide is 1000-3000 mL / min;

[0068] The rotation speed of the reactor is set to 40-150 r / min, the reaction temperature is 20-25℃, and the reaction pressure is 1-3 MPa.

[0069] As an improvement to the above technical solution, in the step of evaporating the water in the fourth-stage liquid phase of the inorganic phase:

[0070] The fourth stage liquid phase of the inorganic phase is discharged from the bottom of the reactor and heated to 90-100°C. Then it is pumped into the MVR evaporator and the compressor is started. When the sodium sulfate is supersaturated, sodium sulfate and mother liquor are produced.

[0071] When the sodium sulfate concentration in the mother liquor decreases to 3-7% and the temperature drops to 45-55℃, the mother liquor is transported to the MVR evaporator, the compressor is turned on, and sodium chloride is obtained after concentration and supersaturation.

[0072] As an improvement to the above technical solution, the step of back-extraction separation of the fourth-stage liquid phase of the organic phase to obtain an inorganic liquid phase and an organic liquid phase, evaporating the water in the inorganic liquid phase, and returning the organic liquid phase to the third-stage liquid phase processing is as follows:

[0073] Ammonia water is added to the fourth stage liquid phase of the organic phase, and the volume ratio of organic phase to inorganic phase is set to (1-2):(0.5-1). The rotation speed is 40-150 r / min, and back-extraction separation is performed to obtain inorganic liquid phase and organic liquid phase. The water in the inorganic liquid phase is evaporated to obtain ammonium chloride. The organic liquid phase is then returned to the third stage liquid phase for processing.

[0074] Implementing this invention has the following beneficial effects:

[0075] 1. In the comprehensive utilization method of secondary aluminum ash in this invention, the secondary aluminum ash is deoxidized and hydrolyzed to obtain a mixed gas, a hydrolyzed slurry solid phase, and a high-salt-alkali ammonia-nitrogen hydrolysate. The mixed gas is separated and purified to obtain hydrogen. The hydrolyzed slurry solid phase undergoes at least two acid washing treatments and at least one intermittent treatment to remove heavy metals and impurity ions, making it usable as a concrete admixture. The high-salt-alkali ammonia-nitrogen hydrolysate, after ammonia-nitrogen separation and graded acidification treatment, yields aluminum hydroxide, as well as inorganic salt crystals such as sodium bicarbonate, sodium chloride, sodium sulfate, and ammonium chloride, thereby achieving high-value-added utilization of the secondary aluminum ash.

[0076] 2. In the comprehensive utilization method of secondary aluminum ash of the present invention, the secondary aluminum ash is first subjected to low-temperature hydrolysis treatment (5-99℃), and then the hydrolyzed slurry solid phase obtained from the hydrolysis treatment is subjected to at least two acid washing treatments (room temperature) and at least one alkali washing treatment (room temperature). Based on this technical route, firstly, it prevents a sudden rise in temperature during the hydrolysis process, which would generate a large amount of foam and reduce the difficulty of controlling the hydrolysis reaction. Secondly, the low-temperature hydrolysis process reduces the generation of water vapor, preventing a large amount of water vapor from mixing into the mixed gas and reducing the difficulty of separating the mixed gas in the later stage. Thirdly, the subsequent acid washing and alkali washing treatments can separate impurity ions and heavy metals, and also completely decompose the gas-producing impurities in the secondary aluminum ash, making the solid phase product applicable to high-value-added concrete.

[0077] 3. In the comprehensive utilization method of secondary aluminum ash in this invention, a specific temperature control program is adopted according to the characteristics of the hydrolysis reaction of secondary aluminum ash. Specifically, in the early stage of hydrolysis, a cooling medium is introduced for cooling, and in the later stage of hydrolysis, a heating medium is introduced for heating. This makes the reaction temperature control more precise, avoids excessive reaction, reduces the difficulty of control, and reduces the difficulty of separating the mixed gas.

[0078] 4. In the comprehensive utilization method of secondary aluminum ash in this invention, the solid phase of the hydrolyzed mud is washed multiple times during treatment. After each washing, solid-liquid separation is performed. The resulting liquid is recycled for use in the hydrolysis or washing process, while the resulting solid is used in concrete. Furthermore, heavy metal and impurity ions are monitored during each washing process. Based on this process, not only is water consumption effectively reduced, but the elution efficiency of heavy metals and impurity ions is also improved, facilitating the high-value-added utilization of the hydrolyzed mud solid phase.

[0079] Furthermore, this invention adjusts the pH of the slurry by introducing different substances at different stages, thereby maximizing the dissolution of heavy metals and impurity ions in the liquid phase and improving the elution efficiency of heavy metals and impurity ions. Moreover, this invention uses CO2 as a pH adjuster, converting CO2 into carbonates, achieving a negative carbon process. Attached Figure Description

[0080] Figure 1 This is a flowchart illustrating a method for the comprehensive utilization of aluminum dichloroash in one embodiment of the present invention.

[0081] Figure 2 This is a schematic diagram of the structure of the washing kettle body in one embodiment of the present invention;

[0082] Figure 3 This is a schematic diagram of the aeration pipe in one embodiment of the present invention;

[0083] Figure 4 This is a flowchart of a method for treating the solid phase of hydrolyzed mud according to an embodiment of the present invention;

[0084] Figure 5 A flowchart of a method for treating high-salt, alkaline, ammonia nitrogen hydrolysate according to one embodiment of the present invention. Detailed Implementation

[0085] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below with reference to the accompanying drawings.

[0086] See Figure 1 This invention discloses a method for the comprehensive utilization of secondary aluminum ash, which includes the following steps:

[0087] S100, deoxidize the secondary aluminum ash;

[0088] Specifically, deoxidation can be achieved through an inert gas replacement process, but it is not limited to this. Preferably, in one embodiment, secondary aluminum ash is placed in a reactor and nitrogen gas is introduced for replacement to achieve deoxidation. Deoxidation avoids the risk of explosion caused by the combination of hydrogen and oxygen generated later.

[0089] Preferably, in some embodiments, step S100 includes:

[0090] S101. Grade the secondary aluminum ash.

[0091] Specifically, grading can be performed by sieving or cyclone grading, but is not limited to these methods. Preferably, in one embodiment, grading is performed by cyclone grading.

[0092] The residue on a 125μm sieve of the secondary aluminum ash obtained after grading is 1-10wt%; preferably 1-5wt%. Using the fraction with a particle size smaller than 125μm for hydrolysis significantly improves the hydrolysis reaction rate and reduces the content of metallic aluminum and aluminum nitride in the residue after hydrolysis.

[0093] It should be noted that in conventional secondary aluminum ash processing, the secondary aluminum ash is usually ground to enhance reactivity, which consumes a great deal of energy. However, the comprehensive utilization method based on this invention eliminates the need for a grinding process, significantly reducing energy consumption.

[0094] S102. The secondary aluminum ash is deoxidized by nitrogen replacement.

[0095] S200: The deoxidized secondary aluminum ash is hydrolyzed and then separated into solid and liquid phases to obtain a mixed gas, a hydrolyzed mud solid phase, and a high-salt-alkali ammonia nitrogen hydrolysate.

[0096] Preferably, in one embodiment, secondary aluminum ash and water are mixed at a solid-liquid ratio of 1:(2-10) and added to a reactor. The water can be pure water, water obtained from a subsequent hydrolysis slurry solid-phase treatment process, or cooling water, but is not limited to these. Preferably, the solid-liquid ratio is 1:3-1:6. More specifically, approximately one-third of the total water volume is first added to the reactor, then the deoxidized secondary aluminum ash is added, and finally the remaining water is added.

[0097] At the start of hydrolysis, calcium hydroxide and a catalyst are added to the reactor. Specifically, the weight ratio of calcium hydroxide to deoxidized secondary aluminum ash is (1-10):100 to achieve a supersaturated state, resulting in a pH of 12-13 in the reaction solution. Specifically, the weight ratio of the catalyst to deoxidized secondary aluminum ash is (1-10):100; preferably 3:100-8:100.

[0098] Preferably, in one embodiment, the catalyst comprises, by weight, 0-10 parts sodium carbonate, 0-10 parts potassium carbonate, 10-80 parts sodium hydroxide, 0-50 parts potassium hydroxide, 5-30 parts calcium carbide slag, and 0.01-5 parts sodium stannate. Based on this catalyst, more aluminum nitride and aluminum hydrolysis can be completed at a lower temperature (5-99°C) and in a shorter time (5-48h).

[0099] Specifically, the hydrolysis reaction temperature is 5-99℃, preferably 80-90℃. The hydrolysis reaction time is 5-48h, preferably 5-24h. Based on these reaction conditions, the elemental aluminum and aluminum nitride in the secondary aluminum ash can reach a near-complete concentration.

[0100] It should be noted that the hydrolysis reaction of secondary aluminum ash with water can be divided into an induction period, an acceleration period, and a deceleration period. During the induction period, approximately 0.5-1 hour after the start of the hydrolysis reaction, the reaction rate is slow with no significant exothermic reaction. During the acceleration period, approximately 0.5-1 hour after the start of the hydrolysis reaction, the reaction rate increases rapidly, accompanied by significant exothermic reaction. During the deceleration period, both the reaction rate and the rate of exothermic reaction decrease. Therefore, during the acceleration period, the internal temperature of the reactor exceeds the boiling point of water (100°C at normal pressure) within a few hours of the start of the hydrolysis reaction. A large amount of water vapor enters the gas phase, which makes subsequent hydrogen purification difficult. Furthermore, the rapid temperature rise also generates a large amount of foam, making the reaction difficult to control. During the deceleration period, the internal temperature of the reactor begins to decrease, and the hydrolysis reaction rate begins to decrease significantly. Therefore, this invention controls the temperature of the hydrolysis reaction to be below 100°C, preferably between 5-99°C, and more preferably between 80-90°C.

[0101] To achieve the above temperature control, in one embodiment, the temperature during the hydrolysis process is controlled according to the following procedure:

[0102] Secondary aluminum ash, water, catalyst and calcium hydroxide are added to the reactor. When the temperature inside the reactor rises to 70-90℃, a cooling medium is used to cool it so that the rate of temperature rise inside the reactor is controlled at 0.1-3℃ / min. Specifically, the cooling medium can be water, but is not limited to it.

[0103] When the rate of temperature rise in the reactor decreases, gradually reduce the amount of cooling medium to maintain the temperature in the reactor at 80-90℃.

[0104] When the temperature inside the reactor begins to drop, a heating medium is used to reheat it, and the amount of heating medium is adjusted to maintain the temperature inside the reactor at 80-90℃; the temperature difference between the heating medium and the reactor temperature is 1-10℃. Specifically, the heating medium can be hot water, but is not limited to this.

[0105] Accordingly, the structure of the reactor was modified to achieve the aforementioned temperature control. Internal coils, external coils, or jackets also need to be installed on the conventional reactor to allow the introduction of cooling or heating media.

[0106] S300: Separate and purify the mixed gas to obtain hydrogen.

[0107] Specifically, during the hydrolysis reaction, the generated gases are collected to obtain a mixed gas. The specific processing flow for this mixed gas is as follows: using water as the absorbent gas, multi-stage absorption is performed to absorb NH3 from the mixed gas. Hydrogen is then purified by pressure swing adsorption (PSA) to achieve a purity of over 99.99 wt%. The impurity gases (CH4, H3P, H2S, etc.) removed by PSA are sent to a regenerative thermal oxidizer (RTO) for combustion to provide heat energy for heating the water. The heated water can then be used as a heating medium to heat the reactor during the deceleration phase of the hydrolysis reaction. Specifically, the temperature of the heated water is 81-99℃.

[0108] Specifically, after hydrolysis, the resulting slurry undergoes solid-liquid separation to obtain a hydrolyzed mud solid phase and a high-salt, alkali, ammonia-nitrogen hydrolysate. The hydrolyzed mud solid phase has a water content of 15-25 wt% and contains heavy metals such as Pb, Cd, Cr, Cu, Ni, Zn, and Mn, as well as Cl... - F - K + Na + Impurity ions. Preferably, the high-salt, alkaline ammonia nitrogen hydrolysate has a temperature of 80-95℃, an alkalinity of 0.20-2.0 mol / L, a total salt content of 5-25%, and an ammonia nitrogen concentration of 200-2000 mg / L. More preferably, the high-salt, alkaline ammonia nitrogen hydrolysate has a temperature of 85-90℃, an alkalinity of 0.25-1.5 mol / L, a total salt content of 10-20%, and an ammonia nitrogen concentration of 200-2000 mg / L.

[0109] S400. The solid phase of hydrolyzed mud is subjected to at least two acid washing treatments and at least one alkali washing treatment to obtain a solid phase product for use as a concrete admixture.

[0110] Preferably, in one embodiment: step S400 includes:

[0111] The solid phase of the hydrolyzed mud is subjected to at least two acid washing treatments, and the slurry obtained from the acid washing treatment is subjected to solid-liquid separation to obtain a sub-solid phase and a first sub-liquid phase; the sub-liquid phase is used for secondary aluminum ash hydrolysis treatment or the previous acid washing treatment.

[0112] The solid phase is subjected to at least one alkaline washing treatment, and the slurry obtained from the alkaline washing treatment is subjected to solid-liquid separation to obtain a solid product and a second sub-liquid phase, which is used for acid washing treatment.

[0113] The content of tracer ions was measured in both the acid-washed and alkali-washed slurries. The tracer ions were selected from heavy metals and / or impurity ions.

[0114] This invention involves multiple washings of the solid phase of hydrolyzed mud, followed by solid-liquid separation after each washing. The resulting liquid is recycled for use in either the hydrolysis or washing process, while the solid is utilized in concrete. Furthermore, heavy metal and impurity ions are monitored during each washing process. This process effectively reduces water consumption and improves the elution efficiency of heavy metals and impurities, facilitating the high-value utilization of the hydrolyzed mud solid phase.

[0115] It should be noted that the multiple washing in this invention can be two washings or more than three washings, preferably three to five washings, and the number of washings can be determined according to the actual situation of the secondary aluminum ash.

[0116] It should be noted that a washing vessel with a specific structure is used for washing to improve the efficiency of treating the solid phase of hydrolyzed mud. For details, please refer to [link to relevant documentation]. Figure 2 and Figure 3 The washing tank includes a washing tank body 100, which includes a tank body 10, a feeding port 20 and a water inlet 30 located on the upper part of the tank body 10, a discharge valve 40 and a mud pump 50 located on the lower part of the tank body 10, an ultrasonic wave baffle 60, a stirrer 70 and an aeration pipe 80 located inside the tank body 10, and an electric power unit 90 for controlling the rotation of the stirrer, which includes a motor 91 and a reducer 92.

[0117] The ultrasonic wave baffle 60 is disposed on the inner wall of the vessel 10 to generate vibration and eddies in the slurry within the vessel 10, thereby improving cleaning efficiency. The ultrasonic wave baffle 60 is controlled to generate ultrasonic waves in the range of 20-80 kHz for vibration, preferably in the range of 30-50 kHz. The ultrasonic waves provide oscillation of the liquid phase, and the baffle creates eddies inside the washing vessel; together, they improve washing efficiency, significantly enhancing the elution efficiency of heavy metals and impurity ions.

[0118] In addition, the ultrasonic stirrer 4 is controlled to generate vortices in the opposite direction to the rotation of the stirring blades 5.

[0119] The aeration pipe 80 is located at the bottom of the vessel. The aeration pipe includes a main aeration pipe 81 and an annular aeration pipe 82. The annular aeration pipe 82 includes multiple concentric annular sub-pipes, all of which are connected to the main aeration pipe 81. The annular aeration pipe 82, located at the bottom of the vessel, is made of porous ceramic and is used to spray carbon dioxide.

[0120] Specifically, in one embodiment, step S400 includes:

[0121] S401. Inject the first washing liquid into the primary washing tank and send the hydrolyzed mud solid phase for washing. The first washing liquid comes from the second liquid phase after the mud is filtered at the outlet of the secondary washing tank.

[0122] Preferably, the agitator and ultrasonic generator are turned on for washing, wherein the agitator speed is 20-80 r / min, preferably 40-60 r / min, and the ultrasonic frequency is 20-80 kHz, preferably 30-50 kHz.

[0123] Preferably, the solid-liquid ratio (mass ratio) in the primary washing tank is set to 1:(3-10). The first washing liquid is injected into the primary washing tank, and the liquid level reaches 50-80% of the internal height of the washing tank. The first washing liquid comes from the second liquid phase after the mud is filtered at the outlet of the secondary washing tank.

[0124] The solid phase of the hydrolyzed mud after pressure filtration is added to the primary washing vessel. The amount of solid phase is determined based on the amount of washing liquid and the predetermined liquid-solid ratio.

[0125] S402. Introduce the first gas into the primary washing tank until the pH of the washing liquid reaches the first preset value.

[0126] Preferably, the first gas is CO2, which is introduced into the primary washing vessel until the pH of the washing solution is 6-7.

[0127] This invention first introduces CO2, which is converted into carbonate, to perform the first pH adjustment. The pH is controlled at 6-7, which allows heavy metals and impurity ions to dissolve to a greater extent in the liquid phase, thus improving the elution efficiency of heavy metals and impurity ions. Moreover, by using CO2 as a pH adjuster, the conversion of CO2 into carbonate achieves a carbon negative process.

[0128] S403. Pass an acidic solution into the primary washing tank until the pH of the washing solution reaches the second preset value;

[0129] Preferably, the acidic solution is one or a combination of sulfuric acid, nitric acid, and organic acids, and the second preset pH value is 2-6, but not limited thereto. In this invention, after introducing the first gas, an acidic solution is introduced into the primary washing vessel to adjust the pH to 2-6, which allows heavy metals and impurity ions to dissolve to a greater extent in the liquid phase.

[0130] The temperature of the primary washing tank is preferably controlled between 15-40℃, more preferably between 20-35℃. After introducing the acidic solution, washing begins, and the washing time is preferably 5-50 minutes, more preferably 5-30 minutes.

[0131] It should be noted that the washing time is determined based on the rate of change in the concentration of heavy metals and impurity ions in the liquid phase.

[0132] The S403 washing cycle ends when the tracer ion content changes less than the preset value between two consecutive wash cycles.

[0133] This step involves selecting one or more heavy metal or impurity ions as tracer ions and sampling them at preset intervals. The content of the tracer ions is then detected. If the change in the content of the tracer ions between two consecutive samples is less than a preset ion value, the washing process ends. The preset interval is 5-20 minutes, preferably 5-10 minutes; the preset ion value is 5-10%, preferably 5-8%.

[0134] Specifically, the heavy metals used as tracer ions include one or more of Pb, Cd, Cr, Cu, Ni, Zn, and Mn, and the impurity ions used as tracer ions include Cl. - F - K + Na + One or more of them.

[0135] S404 After the washing in the primary washing tank is completed, the mud is subjected to solid-liquid separation to obtain a first liquid phase and a first solid phase. The first liquid phase can be used for secondary aluminum ash hydrolysis treatment.

[0136] Preferably, after washing, the mud in the primary washing tank is pumped into a filter press for solid-liquid separation. The solid phase after filtration contains about 15-25% water. The first solid phase enters the secondary washing tank for further washing, and the first liquid phase is used for secondary aluminum ash hydrolysis treatment. This effectively reduces water consumption and improves the elution efficiency of heavy metals and impurity ions.

[0137] S405. Inject the second washing liquid into the secondary washing tank and send the first solid phase in for continued washing. The second washing liquid comes from the third liquid phase after the mud is filtered at the outlet of the tertiary washing tank.

[0138] Preferably, the agitator and ultrasonic generator are turned on for washing, wherein the agitator speed is 20-80 r / min, preferably 40-60 r / min, and the ultrasonic frequency is 20-80 kHz, preferably 30-50 kHz.

[0139] Preferably, the solid-liquid ratio (mass ratio) in the secondary washing tank is set to 1:(3-10). The second washing liquid is injected into the secondary washing tank, and the liquid level reaches 50-80% of the internal height of the washing tank. The second washing liquid comes from the third liquid phase after the mud is filtered at the outlet of the tertiary washing tank.

[0140] The first solid phase is added to the secondary washing tank. The amount of solid phase is determined based on the amount of washing liquid and the predetermined liquid-solid ratio.

[0141] S406. Pass an acidic solution into the secondary washing tank until the pH of the washing solution reaches the second preset value;

[0142] Preferably, the acidic solution is one or a combination of sulfuric acid, nitric acid, and organic acids, and the second preset pH value is 2-6, but not limited thereto. In this invention, after the first-stage washing, an acidic solution is introduced into the second-stage washing vessel to adjust the pH to 2-6, which allows heavy metals and impurity ions to dissolve to a greater extent in the liquid phase.

[0143] The temperature of the secondary washing tank is preferably controlled at 15-40℃, and more preferably at 20-35℃.

[0144] After introducing the acidic solution, begin washing. The washing time is preferably 5-50 minutes, more preferably 5-30 minutes.

[0145] It should be noted that the washing time is determined based on the rate of change in the concentration of heavy metals and impurity ions in the liquid phase.

[0146] The S406 washing cycle ends when the tracer ion content changes less than the preset value between two consecutive wash cycles.

[0147] This step involves selecting one or more heavy metal or impurity ions as tracer ions and sampling them at preset intervals. The content of the tracer ions is then detected. If the change in the content of the tracer ions between two consecutive samples is less than a preset ion value, the washing process ends. The preset interval is 5-20 minutes, preferably 5-10 minutes; the preset ion value is 5-10%, preferably 5-8%.

[0148] Specifically, the heavy metals used as tracer ions include one or more of Pb, Cd, Cr, Cu, Ni, Zn, and Mn, and the impurity ions used as tracer ions include Cl. - F - K + Na + One or more of them.

[0149] S407 After the secondary washing tank is completed, the mud is subjected to solid-liquid separation to obtain a second liquid phase and a second solid phase;

[0150] Preferably, after washing, the mud in the secondary washing tank is pumped into a filter press for solid-liquid separation. The solid phase after filtration contains about 15-25% water. The second solid phase enters the tertiary washing tank for further washing, and the second liquid phase is used to wash the hydrolyzed mud solid phase in the primary washing tank. This effectively reduces water consumption and improves the elution efficiency of heavy metals and impurity ions.

[0151] S408. Inject the third washing liquid into the three-stage washing tank and send the second solid phase in for washing. The third washing liquid is water.

[0152] Preferably, the agitator and ultrasonic generator are turned on for washing, wherein the agitator speed is 20-80 r / min, preferably 40-60 r / min, and the ultrasonic frequency is 20-80 kHz, preferably 30-50 kHz.

[0153] Preferably, the solid-liquid ratio (mass ratio) in the three-stage washing tank is set to 1:(3-10), and a third washing liquid is injected into the three-stage washing tank until the liquid level reaches 50-80% of the internal height of the washing tank. The third washing liquid is water.

[0154] The second solid phase is added to the three-stage washing tank. The amount of solid phase is determined based on the amount of washing liquid and the predetermined liquid-solid ratio.

[0155] S409. Introduce an alkaline substance into the three-stage washing tank until the pH of the washing solution reaches the third preset value.

[0156] Preferably, the alkaline substance is one or a combination of calcium hydroxide, sodium hydroxide, and carbide slag, and the second preset pH value is 7-12, preferably 8-11, but not limited thereto. In this invention, after the secondary washing, an alkaline substance is introduced into the tertiary washing vessel, which allows heavy metals and impurity ions to dissolve to a greater extent in the liquid phase, and can also react with small amounts of residual or encapsulated aluminum, aluminum nitride, etc. The temperature of the tertiary washing vessel is preferably controlled at 15-40℃, more preferably 20-35℃.

[0157] After introducing the alkaline substance, begin washing. The washing time is preferably 5-50 minutes, and more preferably 5-30 minutes.

[0158] It should be noted that the washing time is determined based on the rate of change in the concentration of heavy metals and impurity ions in the liquid phase.

[0159] The S409 washing cycle ends when the tracer ion content changes less than the preset value between two consecutive wash cycles.

[0160] This step involves selecting one or more heavy metal or impurity ions as tracer ions and sampling them at preset intervals. The content of the tracer ions is then detected. If the change in the content of the tracer ions between two consecutive samples is less than a preset ion value, the washing process ends. The preset interval is 5-20 minutes, preferably 5-10 minutes; the preset ion value is 5-10%, preferably 5-8%.

[0161] Specifically, the heavy metals used as tracer ions include one or more of Pb, Cd, Cr, Cu, Ni, Zn, and Mn, and the impurity ions used as tracer ions include Cl. - F - K + Na + One or more of them.

[0162] After the S410 three-stage washing tank is completed, the mud is subjected to solid-liquid separation to obtain a third liquid phase and a third solid phase;

[0163] Preferably, after washing, the slurry in the three-stage washing tank is pumped into a filter press for solid-liquid separation. The solid phase after filtration contains about 15-25% water. The third liquid phase is used to wash the solid phase in the two-stage washing tank, which effectively reduces water consumption and improves the elution efficiency of heavy metals and impurity ions.

[0164] S411. Detect the content of heavy metals and impurity ions in the third solid phase. If it meets the specified standards, the washing is completed. If it does not meet the specified standards, repeat the washing process in the three-stage washing tank.

[0165] S500: The high-salt, alkaline ammonia nitrogen hydrolysate is subjected to ammonia nitrogen separation and graded acidification treatment to obtain aluminum hydroxide and inorganic salt crystals.

[0166] It should be noted that steps S400, S500, and S600 are not sequential and can be executed simultaneously, or one or both of them can be executed first, followed by the remaining steps.

[0167] Preferably, in one embodiment of the present invention, step S500 includes:

[0168] S501. The high-salt-alkali ammonia nitrogen hydrolysate is subjected to ammonia nitrogen separation to obtain a gas phase and a first-stage liquid phase;

[0169] Preferably, in step S501, the high-salt-alkali ammonia nitrogen hydrolysate is aerated by passing air through it to obtain a gas phase and a first-stage liquid phase. The gas phase is dissolved in water to obtain ammonia water.

[0170] More preferably, the high-salt, alkaline ammonia nitrogen hydrolysate is introduced into a reaction vessel, the reaction vessel rotation speed is set to 40-150 r / min, and air is introduced for aeration at a flow rate of 10-30 m³ / min. 3 The reaction rate is 0.5-3 h, and the resulting ammonia gas is passed into the absorption tower to produce ammonia water.

[0171] This invention utilizes air aeration to remove ammonia gas from high-salt, alkaline ammonia nitrogen hydrolysate, breaking down its buffer system and preparing for subsequent pH adjustment. Furthermore, the resulting ammonia gas is utilized in the subsequent back-extraction process, achieving resource recycling. Moreover, air aeration simultaneously oxidizes pollutants such as reducing sulfides or thiosulfates in the high-salt, alkaline ammonia nitrogen hydrolysate into sulfates, increasing the purity of the subsequent sulfates.

[0172] S502. Dissolve carbon dioxide in the first-stage liquid phase until the specified pH value is reached to obtain the second-stage liquid phase;

[0173] Preferably, carbon dioxide is dissolved in the first-stage liquid phase until a specified pH value is reached, and the first-stage liquid phase is separated from aluminum hydroxide to obtain aluminum hydroxide and a second-stage liquid phase.

[0174] More preferably, carbon dioxide is introduced into the first-stage liquid phase, with the carbon dioxide flow rate set to 1000-3000 mL / min and the rotation speed set to 30-150 r / min. The reaction is stopped when the pH of the reaction decreases from 12-14 to 7-8, and the slurry is then subjected to solid-liquid separation to obtain aluminum hydroxide and the second-stage liquid phase.

[0175] S503. Dissolve carbon dioxide in the second-stage liquid phase until the specified pH value is reached to obtain the third-stage liquid phase;

[0176] Preferably, carbon dioxide is dissolved in the second-stage liquid phase until a specified pH value is reached, so that sodium bicarbonate is separated from the second-stage liquid phase to obtain sodium bicarbonate and a third-stage liquid phase.

[0177] More preferably, the second-stage liquid phase is transferred into a reactor, and carbon dioxide is introduced into the reactor. The carbon dioxide flow rate is set to 1000-3000 mL / min, and the rotation speed is set to 40-150 r / min. The reaction is stopped when the pH of the reaction decreases from 7-8 to 5-6. The slurry is then subjected to solid-liquid separation to obtain sodium bicarbonate and the third-stage liquid phase.

[0178] This step, by adjusting the pH using carbon dioxide, achieves the following objectives: firstly, it can convert aluminate ions into aluminum hydroxide precipitate; secondly, it does not increase the amount of water to be treated; and thirdly, in high-salt-alkali systems, it can utilize the principle of alkali production to generate sodium bicarbonate, a high-valence salt.

[0179] Aluminum hydroxide can be washed with water to remove a small amount of sodium bicarbonate crystals. The resulting sodium bicarbonate washing solution can be saturated with sodium chloride to precipitate sodium bicarbonate crystals, thus achieving resource recycling.

[0180] S504. Add extraction solvent to the third-stage liquid phase and dissolve carbon dioxide until the specified pH value is reached. After extraction and separation, a fourth-stage liquid phase of organic phase and a fourth-stage liquid phase of inorganic phase are obtained.

[0181] Preferably, an extraction solvent is added to the third-stage liquid phase and carbon dioxide is dissolved until a specified pH value is reached, chlorine is extracted and separated, and then a fourth-stage liquid phase consisting of an organic phase and an inorganic phase is obtained.

[0182] More preferably, the third-stage liquid phase is transferred to a reaction vessel, carbon dioxide is introduced into the vessel, and an extraction solvent is added at the same time. The volume ratio of organic phase (i.e., extraction solvent) to inorganic phase (i.e., third-stage liquid phase) is set to (1-2):(2-3), and the solubility of carbon dioxide is set to 0.05-0.08 mol / L. The reaction is stopped when the pH of the reaction decreases from 5-6 to 3-4. After extraction and separation, the fourth-stage liquid phase of organic phase and the fourth-stage liquid phase of inorganic phase are obtained.

[0183] More preferably, the third-stage liquid phase is transferred to a reaction vessel, and carbon dioxide is introduced into the vessel at a flow rate of 1000-3000 mL / min. Simultaneously, an extraction solvent is added, and the volume ratio of organic phase to inorganic phase is set to (1-2):(2-3). The solubility of carbon dioxide is set to 0.06-0.07 mol / L. The rotation speed of the reaction vessel is set to 40-150 r / min, the reaction temperature is 20-25℃, and the reaction pressure is 1-3 MPa. The reaction is stopped when the pH of the reaction decreases from 5-5.5 to 3-3.5. After extraction and separation, the fourth-stage liquid phase of organic phase and the fourth-stage liquid phase of inorganic phase are obtained.

[0184] More preferably, the third-stage liquid phase is transferred to a reaction vessel, and carbon dioxide is introduced into the vessel at a flow rate of 1000-2000 mL / min. Simultaneously, an extraction solvent is added, and the volume ratio of organic phase to inorganic phase is set to 1:2. The solubility of carbon dioxide is set to 0.06-0.07 mol / L. The rotation speed of the reaction vessel is set to 40-150 r / min, the reaction temperature is 20-25℃, and the reaction pressure is 1-3 MPa. The reaction is stopped when the pH of the reaction drops from 5 to about 3. After extraction and separation, the fourth-stage liquid phase of organic phase and the fourth-stage liquid phase of inorganic phase are obtained.

[0185] The extraction solvent comprises an extractant and a diluent. The extractant is preferably one or more of alkyl primary amines, secondary amines, trioctylalkyl tertiary amines, and trioctylmethyl quaternary ammonium salts, but is not limited thereto. The diluent is preferably one or more of kerosene, tributyl phosphate, n-pentanol, n-hexanol, n-octanol, and isooctanol, but is not limited thereto.

[0186] It should be noted that the extraction solvent of this invention can be selected according to actual needs.

[0187] This step involves introducing carbon dioxide while simultaneously adding an extraction solvent for extraction and separation, which can efficiently extract and separate chlorine. The extraction principle of chloride ions is as follows:

[0188]

[0189] Wherein, R3N is the extractant, H + Provided by pressurized carbon dioxide, Cl - It is provided by chloride ions in the liquid phase.

[0190] This invention continues to use pressurized carbon dioxide extraction to extract chlorine, which can yield ammonium chloride with high purity. The extractant can also be recycled after back-extraction.

[0191] S505. Evaporate the water in the fourth stage liquid phase of the inorganic phase.

[0192] Preferably, the fourth stage liquid phase of the inorganic phase is subjected to MVR separation to evaporate the water and obtain sodium chloride and sodium sulfate.

[0193] More preferably, the fourth-stage liquid phase of the inorganic phase is discharged from the bottom of the reactor and heated to 90-100°C, then pumped into the MVR evaporator, and the compressor is started. When the sodium sulfate is supersaturated, sodium sulfate and mother liquor are produced.

[0194] When the sodium sulfate concentration in the mother liquor decreases to 3-7% and the temperature drops to 45-55℃, the mother liquor is transported to the MVR evaporator, the compressor is turned on, and sodium chloride is obtained after concentration and supersaturation.

[0195] More preferably, step S106 includes:

[0196] The fourth stage liquid phase of the inorganic phase is discharged from the bottom of the reactor and heated to 90-100℃. Then it is pumped into the MVR evaporator and the compressor is started. When the sodium sulfate is supersaturated, sodium sulfate and mother liquor are produced.

[0197] When the sodium sulfate concentration in the mother liquor decreases to 4-6% and the temperature drops to 50-55℃, the mother liquor is transported to the MVR evaporator, the compressor is turned on, and sodium chloride is obtained after concentration and supersaturation.

[0198] This step, through MVR separation, yields high-quality sodium chloride and sodium sulfate with high yield and high purity.

[0199] S506. The fourth stage liquid phase of the organic phase is back-extracted to separate inorganic liquid phase and organic liquid phase, the water in the inorganic liquid phase is evaporated, and the organic liquid phase is returned to the third stage liquid phase treatment.

[0200] Preferably, ammonia is added to the fourth stage liquid phase of the organic phase for back-extraction separation to obtain an inorganic liquid phase and an organic liquid phase, wherein the water in the inorganic liquid phase is evaporated to obtain ammonium chloride; and the organic liquid phase is returned to the third stage liquid phase for processing.

[0201] More preferably, in the back-extraction separation process of adding ammonia to the fourth stage liquid phase of the organic phase, the volume ratio of organic phase to inorganic phase is set to (1-2):(0.5-1), and the rotation speed is 40-150 r / min. It should be noted that the organic phase here refers to the fourth stage liquid phase of the organic phase, and the inorganic phase refers to the added extraction solution (such as ammonia).

[0202] More preferably, ammonia is added to the fourth stage liquid phase of the organic phase, and the volume ratio of organic phase to inorganic phase (ammonia) is set to 1:0.5. The rotation speed is set to 40-150 r / min for back-extraction separation to obtain inorganic liquid phase and organic liquid phase. The fourth stage liquid phase of the organic phase is recycled to the third stage liquid phase treatment in step S504 to evaporate the water in the inorganic liquid phase and obtain ammonium chloride.

[0203] It should be noted that the ammonia water added here can be the ammonia water obtained in step S501.

[0204] After the third-stage liquid phase extraction and separation, the present invention yields a fourth-stage liquid phase consisting of an organic phase and an inorganic phase. The final inorganic fourth-stage liquid phase contains a small amount of sulfate and chloride. The present invention achieves zero wastewater discharge through MVR evaporation, while the organic fourth-stage liquid phase is back-extracted with ammonia to obtain ammonium chloride.

[0205] The present invention will be further described below with reference to specific embodiments.

[0206] Example 1

[0207] This embodiment provides a method for the comprehensive utilization of secondary aluminum ash, and the specific implementation methods are given in three parts below:

[0208] (a) Hydrolysis reaction and treatment of mixed gas

[0209] 1. Powder classification: The secondary aluminum ash is classified using a powder classifier. After classification, the residue on a 125μm sieve is 3.5%.

[0210] 2. Deoxidation: Place the secondary aluminum ash in the reactor and purge it with nitrogen to perform deoxidation treatment;

[0211] 3. Hydrolysis: Feeding is carried out at a solid-liquid ratio of 1:3.5. First, add approximately 1 / 3 of the total water volume to the reactor, then add the deoxidized secondary aluminum ash, followed by the remaining water. Then, add calcium hydroxide until the pH of the reaction solution reaches 12.5. Simultaneously, add catalyst at 3 wt% of the weight of the secondary aluminum ash to begin the reaction. The catalyst formula is: 10 parts sodium carbonate, 20 parts sodium hydroxide, 10 parts carbide slag, and 0.03 parts sodium stannate.

[0212] The initial reaction temperature was 15℃, and the pressure was atmospheric pressure. When the temperature inside the reactor reached 75℃, cooling water was introduced into the internal coils of the reactor, and the flow rate of the cooling water was controlled to maintain the temperature rise rate at 1.2℃ / min. As the temperature rise rate of the reactor began to decrease, the cooling water flow rate was gradually reduced until it was completely shut off. After shutting off, the internal temperature of the reactor was approximately 87℃. When the internal temperature of the reactor began to drop, hot water was introduced into the jacket. The hot water came from a regenerative thermal incinerator. The temperature of the hot water was 91℃. The flow rate of the hot water entering the jacket was adjusted to maintain the internal temperature of the reactor at approximately 88℃.

[0213] 4. Gas Collection and Purification: The hydrolysis reaction takes 22 hours. During the hydrolysis process, the gas discharged from the reactor is collected. A multi-stage absorption tower is used to absorb, separate, and dry the mixed gas, which is mainly composed of NH3. The gas after absorption by the multi-stage absorption tower is mainly hydrogen. The absorbent in the multi-stage absorption tower is purified water. The absorbent, which is mainly composed of ammonia, exits the absorption tower for further utilization.

[0214] The gas separated by the multi-stage absorption tower is mainly hydrogen. Pressure swing adsorption (PSA) is used to purify the hydrogen, achieving a purity (mass fraction) of 99.995%. The impurity gases removed by PSA enter a regenerative thermal oxidizer (RTO) for combustion, with the heat energy used to heat the cooling water (internal coil) from the reactor. The heated water is then used to maintain the reactor's temperature. The heated water temperature is 93°C.

[0215] 5. Collection and Separation of Liquid and Solid Phases: The slurry obtained after the hydrolysis reaction is subjected to solid-liquid separation to obtain a hydrolyzed mud solid phase and a high-salt, alkali, ammonia nitrogen hydrolysate. The high-salt, alkali, ammonia nitrogen hydrolysate has the following concentrations: hydroxide 0.6 mol / L, aluminum ion 15 g / L, total salinity 12%, chloride ion 27.7 g / L, ammonia nitrogen 2000 mg / L, sulfide and thiosulfate concentrations 1.98 g / L and 13.5 g / L, respectively. The water content of the hydrolyzed mud solid phase is 18 wt%.

[0216] (II) Treatment of high-salt, alkaline, ammonia nitrogen hydrolysate

[0217] 1. The high-salt-alkali ammonia nitrogen hydrolysate is subjected to ammonia nitrogen separation to obtain gaseous ammonia gas and a first-stage liquid phase. The gaseous ammonia gas is dissolved in water to obtain ammonia water.

[0218] In this process, ammonia nitrogen separation is carried out in a reaction vessel using a high-salt, alkaline ammonia nitrogen hydrolysate. The reaction vessel rotation speed is set to 40 r / min, and air is introduced for aeration at a flow rate of 10. 3 / min, reaction time 1h.

[0219] 2. Dissolve carbon dioxide in the first-stage liquid phase until the specified pH value is reached to obtain the second-stage liquid phase;

[0220] Carbon dioxide is introduced at a flow rate of 1000 mL / min and a rotation speed of 40 r / min. The reaction is stopped when the pH drops from 14 to about 7. The slurry is then transferred to a belt filter press for solid-liquid separation to obtain aluminum hydroxide and a second-stage liquid phase.

[0221] 3. Dissolve carbon dioxide in the second-stage liquid phase until the specified pH value is reached to obtain the third-stage liquid phase;

[0222] The second-stage liquid phase is transferred to the reactor, and carbon dioxide is introduced into the reactor at a flow rate of 1200 mL / min and a rotation speed of 40 r / min. The reaction is stopped when the pH drops from 7 to about 6. The slurry is then transferred to a plate and frame filter press for solid-liquid separation to obtain sodium bicarbonate and the third-stage liquid phase.

[0223] 4. Add extraction solvent to the third-stage liquid phase and dissolve carbon dioxide until the specified pH value is reached. After extraction and separation, a fourth-stage liquid phase consisting of an organic phase and an inorganic phase is obtained.

[0224] In this process, the third-stage liquid phase is transferred to a reaction vessel, and carbon dioxide is introduced into the vessel at a rotation speed of 40 r / min and a flow rate of 1100 mL / min. Simultaneously, an extraction solvent (alkyl primary amine extractant + kerosene diluent) is added. The organic phase to inorganic phase volume ratio is set to 1:2. The reaction temperature in the reaction vessel is 20℃, the reaction pressure is 1.85 MPa, and the carbon dioxide solubility is set to 0.07 mol / L. The reaction is stopped when the pH of the reaction drops from 6 to about 3. After extraction and separation, the fourth-stage liquid phase of the organic phase and the fourth-stage liquid phase of the inorganic phase are obtained.

[0225] 5. Evaporate the water in the fourth stage liquid phase of the inorganic phase;

[0226] The process involves releasing the solution from the bottom of the reactor, heating it to 100°C, and then pumping it into an MVR crystallizer evaporator. The compressor is then started, and sodium sulfate and mother liquor are produced when the sodium sulfate concentration in the mother liquor is supersaturated. When the concentration of sodium sulfate in the mother liquor decreases to 5%, the temperature is lowered to 50°C, and the mother liquor is transported to the MVR evaporator. The compressor is then turned on, and sodium chloride is obtained after concentration and supersaturation.

[0227] 6. The fourth stage liquid phase of the organic phase is subjected to back-extraction separation to obtain an inorganic liquid phase and an organic liquid phase. The water in the inorganic liquid phase is evaporated, and the organic liquid phase is returned to the third stage liquid phase processing.

[0228] In step 4, after separating the inorganic fourth-stage liquid phase, some of the ammonia water from step 1 is added to the organic fourth-stage liquid phase. The volume ratio of organic phase to inorganic phase is set to approximately 1:0.5, and the rotation speed is set to 40 r / min for back-extraction separation. The organic fourth-stage liquid phase is then reused in step 4. The obtained inorganic fourth-stage liquid phase is then concentrated and evaporated to obtain ammonium chloride.

[0229] In this embodiment, after treatment with the high-salt, alkaline ammonia nitrogen hydrolysate, the yields of the various products are as follows:

[0230]

[0231] (III) Treatment of solid phase of hydrolyzed mud

[0232] The solid-liquid ratio (mass ratio) in each washing tank is set to 1:3.4. The first washing liquid is injected into the first-stage washing tank until the liquid level reaches 55% of the tank's internal height. This first washing liquid comes from the second liquid phase after sludge filtration at the outlet of the second-stage washing tank.

[0233] The solid phase of the hydrolyzed mud after pressure filtration is added to the primary washing vessel. The amount of solid phase is determined based on the amount of washing liquid and the predetermined liquid-solid ratio.

[0234] Turn on the agitator and the ultrasonic generator to perform the washing process. The agitator speed is 55 r / min and the ultrasonic frequency is 40 kHz.

[0235] CO2 was introduced into the primary washing tank until the pH of the washing solution reached 6.5.

[0236] Nitric acid is introduced into the primary washing tank until the pH of the washing solution reaches 3.

[0237] Start washing; washing time is 18 minutes. Chloride ion (Cl) is selected. - As tracer ions, samples were taken at 5-minute intervals to test the tracer ion content. The washing process ended when the change in chloride ion content between two consecutive tests was less than 10%.

[0238] After washing, the slurry in the primary washing tank is pumped into a filter press for solid-liquid separation. The first solid phase enters the secondary washing tank for further washing, and the first liquid phase is used for secondary aluminum ash hydrolysis.

[0239] The second washing liquid is injected into the secondary washing tank until the liquid level reaches 55% of the internal height of the washing tank. The washing liquid in the secondary washing tank comes from the third liquid phase after the slurry is filtered from the outlet of the tertiary washing tank.

[0240] The first solid phase after pressure filtration is added to the secondary washing vessel. The amount of the first solid phase is determined according to the predetermined liquid-solid ratio.

[0241] Turn on the agitator and the ultrasonic generator to perform the washing process. The agitator speed is 55 r / min and the ultrasonic frequency is 40 kHz.

[0242] Nitric acid is introduced into the washing vessel until the pH of the washing solution reaches 2.

[0243] Start washing; washing time is 22 minutes. Chloride ion (Cl) is selected. - As tracer ions, samples are taken at 5-minute intervals to test the chloride ion content. The washing process ends when the change in tracer ion content between two consecutive tests is less than 10%.

[0244] After washing, the mud in the secondary washing tank is pumped into a filter press for solid-liquid separation. The second solid phase enters the tertiary washing tank for further washing, and the second liquid phase is used as the washing liquid in the primary washing tank.

[0245] The third washing liquid is injected into the three-stage washing tank until the liquid level reaches 55% of the internal height of the washing tank. The third washing liquid in the three-stage washing tank is clean water.

[0246] The second solid phase from the second-stage washing tank after pressure filtration is added to the third-stage washing tank. The amount of the second solid phase is determined according to the predetermined liquid-solid ratio.

[0247] Turn on the agitator and the ultrasonic generator to perform the washing process. The agitator speed is 55 r / min and the ultrasonic frequency is 40 kHz.

[0248] Add calcium hydroxide to the washing vessel until the pH reaches 8.

[0249] Start washing; washing time is 22 minutes. Chloride ion (Cl) is selected. - Using ions as tracers, samples were taken at 5-minute intervals to test the chloride ion content. The washing process ended when the change in tracer ion content between two consecutive tests was less than 10%.

[0250] After washing, the mud in the three-stage washing tank is pumped into a filter press for solid-liquid separation to obtain a third liquid phase and a third solid phase. The third liquid phase is used as the washing liquid in the second-stage washing tank.

[0251] The washing process is completed after testing for the content of heavy metals and impurity ions. If the content meets the specified standards, the washing process is finished.

[0252] The solid phase obtained in this embodiment (i.e., the third solid phase) can be reused as a concrete material.

[0253] Specifically, the third solid phase has a moisture content of 22 wt%. This moisture content solid phase is transported to the concrete batching plant. At the concrete batching plant, it is diluted to a moisture content of 50 wt%. During dilution, 0.003 wt% cellulose ether is added. The diluted slurry is metered and added to the concrete mixer at a ratio of 18 wt% (wet basis) of the concrete cementitious material.

[0254] Example 2

[0255] This embodiment provides a method for the comprehensive utilization of secondary aluminum ash, and the specific implementation methods are given in three parts below:

[0256] (a) Hydrolysis reaction and treatment of mixed gas

[0257] 1. Air classification: The secondary aluminum ash was classified using an air classifier. After classification, the residue on a 125μm sieve was 4.2%.

[0258] 2. Deoxidation: Place the secondary aluminum ash in the reactor and purge it with nitrogen to perform deoxidation treatment;

[0259] 3. Hydrolysis: Feeding is carried out at a solid-liquid ratio of 1:3.8. First, add approximately 1 / 3 of the total water volume to the reactor, then add the deoxidized secondary aluminum ash, followed by the remaining water. Then, add calcium hydroxide until the pH of the reaction solution reaches 12.3. Simultaneously, add 5 wt% of the catalyst (based on the weight of the secondary aluminum ash) to begin the reaction. The catalyst formulation is as follows: 12 parts sodium carbonate, 18 parts sodium hydroxide, 14 parts calcium carbide slag, and 0.04 parts sodium stannate.

[0260] The initial reaction temperature was 24℃, and the pressure was atmospheric pressure. When the temperature inside the reactor reached 88℃, cooling water was introduced into the internal coils of the reactor, and the flow rate of the cooling water was controlled to maintain the temperature rise rate at 0.5℃ / min. As the temperature rise rate of the reactor began to decrease, the cooling water flow rate was gradually reduced until it was completely shut off. After shutting off, the internal temperature of the reactor was approximately 93℃. When the internal temperature of the reactor began to drop, hot water was introduced into the jacket. The hot water came from a regenerative thermal incinerator. The temperature of the hot water was 95℃. The flow rate of the hot water entering the jacket was adjusted to maintain the internal temperature of the reactor at approximately 92℃.

[0261] 4. Gas Collection and Purification: The hydrolysis reaction takes 27 hours. During the hydrolysis process, the gas discharged from the reactor is collected. A multi-stage absorption tower is used to absorb, separate, and dry the mixed gas, which is mainly composed of NH3. The gas after absorption by the multi-stage absorption tower is mainly hydrogen. The absorbent in the multi-stage absorption tower is purified water. The absorbent, which is mainly composed of ammonia, exits the absorption tower for further utilization.

[0262] The gas separated by the multi-stage absorption tower is mainly hydrogen. Pressure swing adsorption (PSA) is used to purify the hydrogen, achieving a purity (mass fraction) of 99.997%. The impurity gases removed by PSA enter a regenerative thermal oxidizer (RTO) for combustion, with the heat energy used to heat the cooling water (internal coil) from the reactor. The heated water is then used to maintain the reactor's temperature at 97°C.

[0263] 5. Collection and Separation of Liquid and Solid Phases: The slurry obtained after the hydrolysis reaction is subjected to solid-liquid separation to obtain a hydrolyzed mud solid phase and a high-salt, alkali, ammonia nitrogen hydrolysate. The high-salt, alkali, ammonia nitrogen hydrolysate has the following concentrations: hydroxide 0.55 mol / L, aluminum ion concentration 16 g / L, total salinity 13%, chloride ion concentration 28 g / L, ammonia nitrogen concentration 1900 mg / L, and sulfide and thiosulfate concentrations of 1.88 g / L and 12 g / L, respectively. The water content of the hydrolyzed mud solid phase is 22 wt%.

[0264] (II) Treatment of high-salt, alkaline, ammonia nitrogen hydrolysate

[0265] 1. The high-salt-alkali ammonia nitrogen hydrolysate is subjected to ammonia nitrogen separation to obtain gaseous ammonia gas and a first-stage liquid phase. The gaseous ammonia gas is dissolved in water to obtain ammonia water.

[0266] In this process, ammonia nitrogen separation is carried out in a reaction vessel using a high-salt, alkaline ammonia nitrogen hydrolysate. The reaction vessel rotation speed is set to 50 r / min, and air is introduced for aeration at a flow rate of 12 m³ / min. 3 / min, reaction time 1.5h.

[0267] 2. Dissolve carbon dioxide in the first-stage liquid phase until the specified pH value is reached to obtain the second-stage liquid phase;

[0268] In this process, carbon dioxide is introduced at a flow rate of 1200 mL / min and a rotation speed of 30 r / min. The reaction is stopped when the pH drops from 14 to about 7. The slurry is then transferred to a belt filter press for solid-liquid separation to obtain aluminum hydroxide and a second-stage liquid phase.

[0269] 3. Dissolve carbon dioxide in the second-stage liquid phase until the specified pH value is reached to obtain the third-stage liquid phase;

[0270] The second-stage liquid phase is transferred to the reactor, and carbon dioxide is introduced into the reactor at a flow rate of 1300 mL / min and a rotation speed of 55 r / min. The reaction is stopped when the pH drops from 7 to about 6. The slurry is then transferred to a plate and frame filter press for solid-liquid separation to obtain sodium bicarbonate and the third-stage liquid phase.

[0271] 4. Add extraction solvent to the third-stage liquid phase and dissolve carbon dioxide until the specified pH value is reached. After extraction and separation, a fourth-stage liquid phase consisting of an organic phase and an inorganic phase is obtained.

[0272] In this process, the third-stage liquid phase is transferred to a reaction vessel, and carbon dioxide is introduced into the vessel at a rotation speed of 50 r / min and a flow rate of 1450 L / min. Simultaneously, an extraction solvent (extractant secondary amine + diluent tributyl phosphate) is added. The organic phase to inorganic phase volume ratio is set to 1:2.2. The reaction temperature in the reaction vessel is 21℃, the reaction pressure is 1.8 MPa, and the carbon dioxide solubility is set to 0.065 mol / L. The reaction is stopped when the pH of the reaction drops from 5 to about 3. After extraction and separation, the fourth-stage liquid phase of the organic phase and the fourth-stage liquid phase of the inorganic phase are obtained.

[0273] 5. Evaporate the water in the fourth stage liquid phase of the inorganic phase;

[0274] The solution is discharged from the bottom of the reactor, heated to 100°C, and then pumped into the MVR crystallization evaporator. The compressor is started, and sodium sulfate and mother liquor are produced when sodium sulfate is supersaturated. When the concentration of sodium sulfate in the mother liquor decreases to 5%, the temperature is lowered to 50°C, and the mother liquor is transported to the MVR evaporator. The compressor is turned on, and sodium chloride is obtained after concentration and supersaturation.

[0275] 6. The fourth stage liquid phase of the organic phase is subjected to back-extraction separation to obtain an inorganic liquid phase and an organic liquid phase. The water in the inorganic liquid phase is evaporated, and the organic liquid phase is returned to the third stage liquid phase processing.

[0276] In step 4, after separating the inorganic phase, some of the ammonia water from step 1 is added to the fourth-stage liquid phase of the organic phase. The volume ratio of organic phase to inorganic phase is set to approximately 1:0.45, and the rotation speed is set to 35 r / min for back-extraction separation. The resulting fourth-stage liquid phase of the organic phase is reused in step 4. The resulting fourth-stage liquid phase of the inorganic phase is concentrated and evaporated to obtain ammonium chloride.

[0277] In this embodiment, after treatment with the high-salt, alkaline ammonia nitrogen hydrolysate, the yields of the various products are as follows:

[0278]

[0279] (III) Treatment of solid phase of hydrolyzed mud

[0280] The secondary aluminum ash was hydrolyzed, and then filtered to obtain a hydrolyzed slurry solid phase with a water content of 22%. The filtered solid phase was then sent to a washing tank for washing.

[0281] The solid-liquid ratio (mass ratio) in each washing tank is set to 1:4.2. The first washing liquid is injected into the first washing tank until the liquid level reaches 60% of the internal height of the washing tank. The first washing liquid comes from the second liquid phase after the mud is filtered at the outlet of the second washing tank.

[0282] The solid phase of the hydrolyzed mud after pressure filtration is added to the primary washing vessel. The amount of solid phase is determined based on the amount of washing liquid and the predetermined liquid-solid ratio.

[0283] Turn on the agitator and the ultrasonic generator to perform the washing process. The agitator speed is 60 r / min and the ultrasonic frequency is 60 kHz.

[0284] CO2 was introduced into the primary washing vessel until the pH of the washing solution reached 6.8.

[0285] Nitric acid was introduced into the primary washing tank until the pH of the washing solution reached 3.5.

[0286] Start washing; washing time is 25 minutes. Select Cl. - As tracer ions, samples were taken at 5-minute intervals to test their concentration. When two Cl samples were close together... - Washing ends when the content change is less than 10%.

[0287] After washing, the slurry in the primary washing tank is pumped into a filter press for solid-liquid separation. The first solid phase enters the secondary washing tank for further washing, and the first liquid phase is used for secondary aluminum ash hydrolysis.

[0288] The second washing liquid is injected into the secondary washing tank until the liquid level reaches 60% of the internal height of the washing tank. The washing liquid in the secondary washing tank comes from the third liquid phase after the slurry is filtered from the outlet of the tertiary washing tank.

[0289] The first solid phase after pressure filtration is added to the secondary washing vessel. The amount of the first solid phase is determined according to the predetermined liquid-solid ratio.

[0290] Turn on the agitator and the ultrasonic generator to perform the washing process. The agitator speed is 60 r / min and the ultrasonic frequency is 60 kHz.

[0291] Nitric acid is introduced into the washing tank until the pH of the washing solution reaches 2.5.

[0292] Start washing; washing time is 28 minutes. Select Cl. - As tracer ions, samples were taken at 5-minute intervals to test for Cl. - The washing process ends when the change in tracer ion content between two consecutive washes is less than 10%.

[0293] After washing, the mud in the secondary washing tank is pumped into a filter press for solid-liquid separation. The second solid phase enters the tertiary washing tank for further washing, and the second liquid phase is used as the washing liquid in the primary washing tank.

[0294] The third washing liquid is injected into the three-stage washing tank until the liquid level reaches 60% of the internal height of the washing tank. The third washing liquid in the three-stage washing tank is clean water.

[0295] The second solid phase from the second-stage washing tank after pressure filtration is added to the third-stage washing tank. The amount of the second solid phase is determined according to the predetermined liquid-solid ratio.

[0296] Turn on the agitator and the ultrasonic generator to perform the washing process. The agitator speed is 55 r / min and the ultrasonic frequency is 40 kHz.

[0297] Add calcium hydroxide to the washing vessel until the pH reaches 9.

[0298] Start washing; washing time is 25 minutes. Select Cl. - As tracer ions, samples were taken at 5-minute intervals to test for Cl. - The content of tracer ions. The washing process ends when the change in tracer ion content between two consecutive washes is less than 10%.

[0299] After washing, the mud in the three-stage washing tank is pumped into a filter press for solid-liquid separation to obtain a third liquid phase and a third solid phase. The third liquid phase is used as the washing liquid in the second-stage washing tank.

[0300] Test the content of heavy metals and impurity ions in the third solid phase. If it meets the specified standards, the washing process is complete.

[0301] The solid phase obtained in this embodiment (i.e., the third solid phase) can be reused as a concrete material.

[0302] Specifically, the third solid phase has a moisture content of 24 wt%. This moisture content solid phase is transported to the concrete batching plant. At the concrete batching plant, it is diluted to a moisture content of 50 wt%. During dilution, 0.0025 wt% cellulose ether is added. The diluted slurry is metered and added to the concrete mixer at a ratio of 22 wt% (wet basis) of the concrete cementitious material.

[0303] Example 3

[0304] This embodiment provides a method for the comprehensive utilization of secondary aluminum ash, and the specific implementation methods are given in three parts below:

[0305] (a) Hydrolysis reaction and treatment of mixed gas

[0306] 1. Powder classification: The secondary aluminum ash is classified using a powder classifier. After classification, the residue on a 125μm sieve of the secondary aluminum ash is 5.7%.

[0307] 2. Deoxidation: Place the secondary aluminum ash in the reactor and purge it with nitrogen to perform deoxidation treatment;

[0308] 3. Hydrolysis: Feeding is carried out at a solid-liquid ratio of 1:4.2. First, add approximately 1 / 3 of the total water volume to the reactor, then add the deoxidized secondary aluminum ash, followed by the remaining water. Then, add calcium hydroxide until the pH of the reaction solution reaches 12.6. Simultaneously, add catalyst at 5 wt% of the weight of the secondary aluminum ash to begin the reaction. The catalyst formula is: 8 parts sodium carbonate, 24 parts sodium hydroxide, 12 parts calcium carbide slag, and 0.04 parts sodium stannate.

[0309] The initial reaction temperature was 21℃, and the pressure was atmospheric pressure. When the temperature inside the reactor reached 92℃, cooling water was introduced into the internal coils of the reactor, and the flow rate of the cooling water was controlled to maintain the temperature rise rate at 0.9℃ / min. As the temperature rise rate of the reactor began to decrease, the cooling water flow rate was gradually reduced until it was completely shut off. After shutting off, the internal temperature of the reactor was approximately 91℃. When the internal temperature of the reactor began to drop, hot water was introduced into the jacket. The hot water came from a regenerative thermal incinerator. The temperature of the hot water was 95℃. The flow rate of the hot water entering the jacket was adjusted to maintain the internal temperature of the reactor at approximately 91℃.

[0310] 4. Gas Collection and Purification: The hydrolysis reaction takes 33 hours. During the hydrolysis process, the gas discharged from the reactor is collected. A multi-stage absorption tower is used to absorb, separate, and dry the mixed gas, which is mainly composed of NH3. The gas after absorption by the multi-stage absorption tower is mainly hydrogen. The absorbent in the multi-stage absorption tower is purified water. The absorbent, which is mainly composed of ammonia, exits the absorption tower for further utilization.

[0311] The gas separated by the multi-stage absorption tower is mainly hydrogen. Pressure swing adsorption (PSA) is used to purify the hydrogen, achieving a purity (mass fraction) of 99.995%. The impurity gases removed by PSA enter a regenerative thermal oxidizer (RTO) for combustion, with the heat energy used to heat the cooling water (internal coil) from the reactor. The heated water is then used to maintain the reactor's temperature. The heated water temperature is 97°C.

[0312] 5. Collection and Separation of Liquid and Solid Phases: The slurry obtained after the hydrolysis reaction is subjected to solid-liquid separation to obtain a hydrolyzed mud solid phase and a high-salt, alkali, ammonia nitrogen hydrolysate. The high-salt, alkali, ammonia nitrogen hydrolysate has a hydroxide concentration of 0.57 mol / L, an aluminum ion concentration of 13 g / L, a total salinity of 16%, a chloride ion concentration of 25 g / L, an ammonia nitrogen concentration of 1888 mg / L, and sulfide and thiosulfate concentrations of 1.7 g / L and 11 g / L, respectively. The water content of the hydrolyzed mud solid phase is 22 wt%.

[0313] (II) Treatment of high-salt, alkaline, ammonia nitrogen hydrolysate

[0314] 1. The high-salt-alkali ammonia nitrogen hydrolysate is subjected to ammonia nitrogen separation to obtain gaseous ammonia gas and a first-stage liquid phase. The gaseous ammonia gas is dissolved in water to obtain ammonia water.

[0315] In this process, ammonia nitrogen separation is carried out in a reaction vessel using a high-salt, alkaline ammonia nitrogen hydrolysate. The reaction vessel rotation speed is set to 46 r / min, and air is introduced for aeration at a flow rate of 13 m³ / min. 3 / min, reaction time 1.3h.

[0316] 2. Dissolve carbon dioxide in the first-stage liquid phase until the specified pH value is reached to obtain the second-stage liquid phase;

[0317] Carbon dioxide was introduced, with a flow rate of 1314 mL / min and a rotation speed of 38 r / min. The reaction was stopped when the pH dropped from 14 to about 7. The slurry was then transferred to a belt filter press for solid-liquid separation to obtain aluminum hydroxide and a second-stage liquid phase.

[0318] 3. Dissolve carbon dioxide in the second-stage liquid phase until the specified pH value is reached to obtain the third-stage liquid phase;

[0319] The second-stage liquid phase is transferred to the reactor, and carbon dioxide is introduced into the reactor at a flow rate of 1500 mL / min and a rotation speed of 45 r / min. The reaction is stopped when the pH drops from 7 to about 6. The slurry is then transferred to a plate and frame filter press for solid-liquid separation to obtain sodium bicarbonate and the third-stage liquid phase.

[0320] 4. Add extraction solvent to the third-stage liquid phase and dissolve carbon dioxide until the specified pH value is reached. After extraction and separation, a fourth-stage liquid phase consisting of an organic phase and an inorganic phase is obtained.

[0321] In this process, the third-stage liquid phase is transferred to a reaction vessel, and carbon dioxide is introduced into the vessel at a rotation speed of 54 r / min and a flow rate of 1520 mL / min. Simultaneously, an extraction solvent (trioctyl tertiary amine extractant + n-pentanol diluent) is added. The organic phase to inorganic phase volume ratio is set to 1:2.3. The reaction temperature in the reaction vessel is 23℃, the reaction pressure is 1.77 MPa, and the carbon dioxide solubility is set to 0.06 mol / L. The reaction is stopped when the pH of the reaction decreases from 6 to about 3. After extraction and separation, the fourth-stage liquid phase of the organic phase and the fourth-stage liquid phase of the inorganic phase are obtained.

[0322] 5. Evaporate the water in the fourth stage liquid phase of the inorganic phase;

[0323] The solution is discharged from the bottom of the reactor, heated to 100°C, and then pumped into the MVR crystallization evaporator. The compressor is started, and sodium sulfate and mother liquor are produced when sodium sulfate is supersaturated. When the concentration of sodium sulfate in the mother liquor decreases to 5%, the temperature is lowered to 50°C, and the mother liquor is transported to the MVR evaporator. The compressor is turned on, and sodium chloride is obtained after concentration and supersaturation.

[0324] 6. The fourth stage liquid phase of the organic phase is subjected to back-extraction separation to obtain an inorganic liquid phase and an organic liquid phase. The water in the inorganic liquid phase is evaporated, and the organic liquid phase is returned to the third stage liquid phase processing.

[0325] In step 4, after separating the inorganic phase, some of the ammonia water from step 1 is added to the fourth-stage liquid phase of the organic phase. The volume ratio of organic phase to inorganic phase is set to approximately 1:0.43, and the rotation speed is set to 48 r / min for back-extraction separation. The resulting fourth-stage liquid phase of the organic phase is reused in step 4. The resulting fourth-stage liquid phase of the inorganic phase is concentrated and evaporated to obtain ammonium chloride.

[0326] In this embodiment, after treatment with the high-salt, alkaline ammonia nitrogen hydrolysate, the yields of the various products are as follows:

[0327]

[0328] (ii) Treatment of solid phase in hydrolyzed mud

[0329] The solid-liquid ratio (mass ratio) in each washing tank is set to 1:4.2. The first washing liquid is injected into the first-stage washing tank until the liquid level reaches 65% of the tank's internal height. This first washing liquid comes from the second liquid phase after sludge filtration at the outlet of the second-stage washing tank.

[0330] The solid phase of the hydrolyzed mud after pressure filtration is added to the primary washing vessel. The amount of solid phase is determined based on the amount of washing liquid and the predetermined liquid-solid ratio.

[0331] Turn on the agitator and the ultrasonic generator to perform the washing process. The agitator speed is 60 r / min and the ultrasonic frequency is 35 kHz.

[0332] CO2 was introduced into the primary washing vessel until the pH of the washing solution reached 6.2.

[0333] Nitric acid was introduced into the primary washing tank until the pH of the washing solution reached 3.8.

[0334] Start washing; washing time is 32 minutes. Chloride ion (Cl) is selected. - As tracer ions, samples were taken at 8-minute intervals to test the tracer ion content. The washing process ended when the change in chloride ion content between two consecutive tests was less than 10%.

[0335] After washing, the slurry in the primary washing tank is pumped into a filter press for solid-liquid separation. The first solid phase enters the secondary washing tank for further washing, and the first liquid phase is used for secondary aluminum ash hydrolysis.

[0336] The second washing liquid is injected into the secondary washing tank until the liquid level reaches 65% of the internal height of the washing tank. The washing liquid in the secondary washing tank comes from the third liquid phase after the slurry is filtered from the outlet of the tertiary washing tank.

[0337] The first solid phase after pressure filtration is added to the secondary washing vessel. The amount of the first solid phase is determined according to the predetermined liquid-solid ratio.

[0338] Turn on the agitator and the ultrasonic generator to perform the washing process. The agitator speed is 60 r / min and the ultrasonic frequency is 35 kHz.

[0339] Nitric acid was introduced into the washing vessel until the pH of the washing solution reached 3.2.

[0340] Start washing; washing time is 28 minutes. Chloride ion (Cl) is selected. - As tracer ions, samples were taken at 8-minute intervals to test their content. The washing process ended when the change in chloride ion content between two consecutive tests was less than 10%.

[0341] After washing, the mud in the secondary washing tank is pumped into a filter press for solid-liquid separation. The second solid phase enters the tertiary washing tank for further washing, and the second liquid phase is used as the washing liquid in the primary washing tank.

[0342] The third washing liquid is injected into the three-stage washing tank until the liquid level reaches 65% of the internal height of the washing tank. The third washing liquid in the three-stage washing tank is clean water.

[0343] The second solid phase from the second-stage washing tank after pressure filtration is added to the third-stage washing tank. The amount of the second solid phase is determined according to the predetermined liquid-solid ratio.

[0344] Turn on the agitator and the ultrasonic generator to perform the washing process. The agitator speed is 55 r / min and the ultrasonic frequency is 35 kHz.

[0345] Add carbide slag to the washing vessel until the pH reaches 10.

[0346] Start washing; washing time is 28 minutes. Chloride ion (Cl) is selected. - As tracer ions, samples were taken at 8-minute intervals to test the tracer ion content. The washing process ended when the change in chloride ion content between two consecutive tests was less than 10%.

[0347] After washing, the mud in the three-stage washing tank is pumped into a filter press for solid-liquid separation to obtain a third liquid phase and a third solid phase. The third liquid phase is used as the washing liquid in the second-stage washing tank.

[0348] Test the content of heavy metals and impurity ions in the third solid phase. If it meets the specified standards, the washing process is complete.

[0349] The solid phase obtained in this embodiment (i.e., the third solid phase) can be reused as a concrete material.

[0350] Specifically, the third solid phase has a moisture content of 18 wt%. This moisture content solid phase is transported to the concrete batching plant. At the concrete batching plant, it is diluted to a moisture content of 50 wt%. During dilution, 0.003 wt% cellulose ether is added. The diluted slurry is metered and added to the concrete mixer at a ratio of 21 wt% (wet basis) of the concrete cementitious material.

[0351] Example 4

[0352] This embodiment provides a method for the comprehensive utilization of secondary aluminum ash, and the specific implementation methods are given in three parts below:

[0353] (a) Hydrolysis reaction and treatment of mixed gas

[0354] 1. Powder classification: The secondary aluminum ash is classified using a powder classifier. After classification, the residue on the 125μm sieve of the secondary aluminum ash is 2.6.

[0355] 2. Deoxidation: Place the secondary aluminum ash in the reactor and purge it with nitrogen to perform deoxidation treatment;

[0356] 3. Hydrolysis: Feeding is carried out at a solid-liquid ratio of 1:3.8. First, add approximately 1 / 3 of the total water volume to the reactor, then add the deoxidized secondary aluminum ash, followed by the remaining water. Then, add calcium hydroxide until the pH of the reaction solution reaches 12.8. Simultaneously, add catalyst at 4 wt% of the weight of the secondary aluminum ash to begin the reaction. The catalyst formula is: 5 parts sodium carbonate, 16 parts sodium hydroxide, 14 parts carbide slag, and 0.01 parts sodium stannate.

[0357] The initial reaction temperature was 18℃, and the pressure was atmospheric pressure. When the temperature inside the reactor reached 82℃, cooling water was introduced into the internal coils of the reactor, and the flow rate of the cooling water was controlled to maintain the temperature rise rate at 1.1℃ / min. As the temperature rise rate of the reactor began to decrease, the cooling water flow rate was gradually reduced until it was completely shut off. After shutting off, the internal temperature of the reactor was approximately 84℃. When the internal temperature of the reactor began to drop, hot water was introduced into the jacket. The hot water came from a regenerative thermal incinerator. The temperature of the hot water was 87℃. The flow rate of the hot water entering the jacket was adjusted to maintain the internal temperature of the reactor at approximately 85℃.

[0358] 4. Gas Collection and Purification: The hydrolysis reaction takes 16 hours. During the hydrolysis process, the gas discharged from the reactor is collected. A multi-stage absorption tower is used to absorb, separate, and dry the mixed gas, which is mainly composed of NH3. The gas after absorption by the multi-stage absorption tower is mainly hydrogen. The absorbent in the multi-stage absorption tower is purified water. The absorbent, which is mainly composed of ammonia, exits the absorption tower for further utilization.

[0359] The gas separated by the multi-stage absorption tower is mainly hydrogen. Pressure swing adsorption (PSA) is used to purify the hydrogen, achieving a purity (mass fraction) of 99.995%. The impurity gases removed by PSA enter a regenerative thermal oxidizer (RTO) for combustion, with the heat energy used to heat the cooling water (internal coil) from the reactor. The heated water is then used to maintain the reactor's temperature. The heated water temperature is 91°C.

[0360] 5. Collection and Separation of Liquid and Solid Phases: The slurry obtained after the hydrolysis reaction is subjected to solid-liquid separation to obtain a hydrolyzed mud solid phase and a high-salt, alkali, ammonia nitrogen hydrolysate. The high-salt, alkali, ammonia nitrogen hydrolysate has a hydroxide concentration of 0.59 mol / L, an aluminum ion concentration of 15 g / L, a total salinity of 18%, a chloride ion concentration of 29 g / L, an ammonia nitrogen concentration of 1650 mg / L, and sulfide and thiosulfate concentrations of 1.5 g / L and 16 g / L, respectively. The water content of the hydrolyzed mud solid phase is 22 wt%.

[0361] (II) Treatment of high-salt, alkaline, ammonia nitrogen hydrolysate

[0362] 1. The high-salt-alkali ammonia nitrogen hydrolysate is subjected to ammonia nitrogen separation to obtain gaseous ammonia gas and a first-stage liquid phase. The gaseous ammonia gas is dissolved in water to obtain ammonia water.

[0363] In this process, ammonia nitrogen separation is carried out in a reaction vessel using a high-salt, alkaline ammonia nitrogen hydrolysate. The reaction vessel rotation speed is set to 48 r / min, and air is introduced for aeration at a flow rate of 15 m³ / min. 3 / min, reaction time 1.5h.

[0364] 2. Dissolve carbon dioxide in the first-stage liquid phase until the specified pH value is reached to obtain the second-stage liquid phase;

[0365] Carbon dioxide was introduced, with a flow rate of 1517 mL / min and a rotation speed of 44 r / min. The reaction was stopped when the pH dropped from 14 to about 7. The slurry was then transferred to a belt filter press for solid-liquid separation to obtain aluminum hydroxide and a second-stage liquid phase.

[0366] 3. Dissolve carbon dioxide in the second-stage liquid phase until the specified pH value is reached to obtain the third-stage liquid phase;

[0367] The second-stage liquid phase is transferred to the reactor, and carbon dioxide is introduced into the reactor at a flow rate of 1750 mL / min and a rotation speed of 56 r / min. The reaction is stopped when the pH drops from 7 to about 6. The slurry is then transferred to a plate and frame filter press for solid-liquid separation to obtain sodium bicarbonate and the third-stage liquid phase.

[0368] 4. Add extraction solvent to the third-stage liquid phase and dissolve carbon dioxide until the specified pH value is reached. After extraction and separation, a fourth-stage liquid phase consisting of an organic phase and an inorganic phase is obtained.

[0369] In this process, the third-stage liquid phase is transferred to a reaction vessel, and carbon dioxide is introduced into the vessel at a rotation speed of 60 r / min and a flow rate of 1780 mL / min. Simultaneously, an extraction solvent (trioctylmethyl quaternary ammonium salt + n-hexanol) is added. The organic phase to inorganic phase volume ratio is set to 1:2.11. The reaction temperature in the reaction vessel is 25℃, the reaction pressure is 1.8 MPa, and the carbon dioxide solubility is set to 0.07 mol / L. The reaction is stopped when the pH of the reaction decreases from 5 to about 3. After extraction and separation, the fourth-stage liquid phase of the organic phase and the fourth-stage liquid phase of the inorganic phase are obtained.

[0370] 5. Evaporate the water in the fourth stage liquid phase of the inorganic phase;

[0371] The solution is discharged from the bottom of the reactor, heated to 100°C, and then pumped into the MVR crystallization evaporator. The compressor is started, and sodium sulfate and mother liquor are produced when sodium sulfate is supersaturated. When the concentration of sodium sulfate in the mother liquor decreases to 5%, the temperature is lowered to 50°C, and the mother liquor is transported to the MVR evaporator. The compressor is turned on, and sodium chloride is obtained after concentration and supersaturation.

[0372] 6. The fourth stage liquid phase of the organic phase is subjected to back-extraction separation to obtain an inorganic liquid phase and an organic liquid phase. The water in the inorganic liquid phase is evaporated, and the organic liquid phase is returned to the third stage liquid phase processing.

[0373] In step S105, after separating the inorganic phase, a portion of the ammonia water from step S102 is added to the fourth-stage liquid phase of the organic phase. The volume ratio of organic phase to inorganic phase is set to approximately 1:0.49, and the rotation speed is set to 50 r / min for back-extraction separation. The resulting fourth-stage liquid phase of the organic phase is reused in step S105. The resulting fourth-stage liquid phase of the inorganic phase is concentrated and evaporated to obtain ammonium chloride.

[0374] In this embodiment, after treatment with the high-salt, alkaline ammonia nitrogen hydrolysate, the yields of the various products are as follows:

[0375]

[0376] (ii) Treatment of solid phase in hydrolyzed mud

[0377] The solid-liquid ratio (mass ratio) in the primary washing tank is set to 1:6. The first washing liquid is injected into the primary washing tank until the liquid level reaches 70% of the internal height of the washing tank. The first washing liquid comes from the second liquid phase after the mud is filtered at the outlet of the secondary washing tank.

[0378] The solid phase of the hydrolyzed mud after pressure filtration is added to the primary washing vessel. The amount of solid phase is determined based on the amount of washing liquid and the predetermined liquid-solid ratio.

[0379] Turn on the agitator and the ultrasonic generator to perform the washing process. The agitator speed is 65 r / min and the ultrasonic frequency is 40 kHz.

[0380] CO2 was introduced into the primary washing vessel until the pH of the washing solution reached 6.2.

[0381] A mixture of acetic acid and oxalic acid is introduced into the primary washing tank until the pH of the washing solution reaches 4.2.

[0382] Start washing; washing time is 20 minutes. Select Cl. - As tracer ions, samples were taken at 6-minute intervals to test their concentration. When two Cl samples were close together... - Washing ends when the content change is less than 10%.

[0383] After washing, the slurry in the primary washing tank is pumped into a filter press for solid-liquid separation. The first solid phase enters the secondary washing tank for further washing, and the first liquid phase is used for secondary aluminum ash hydrolysis.

[0384] The second washing liquid is injected into the secondary washing tank until the liquid level reaches 70% of the internal height of the washing tank. The washing liquid in the secondary washing tank comes from the third liquid phase after the slurry is filtered from the outlet of the tertiary washing tank.

[0385] The first solid phase after pressure filtration is added to the secondary washing vessel. The amount of the first solid phase is determined according to the predetermined liquid-solid ratio.

[0386] Turn on the agitator and the ultrasonic generator to perform the washing process. The agitator speed is 65 r / min and the ultrasonic frequency is 40 kHz.

[0387] A mixture of acetic acid and oxalic acid is introduced into the washing tank until the pH of the washing solution reaches 3.2.

[0388] Start washing; washing time is 28 minutes. Select Cl. - As tracer ions, samples were taken at 6-minute intervals to test their concentration. When two Cl samples were close together... - Washing ends when the content change is less than 10%.

[0389] After washing, the mud in the secondary washing tank is pumped into a filter press for solid-liquid separation. The second solid phase enters the tertiary washing tank for further washing, and the second liquid phase is used as the washing liquid in the primary washing tank.

[0390] The third washing liquid is injected into the three-stage washing tank until the liquid level reaches 70% of the internal height of the washing tank. The third washing liquid in the three-stage washing tank is clean water.

[0391] The second solid phase from the second-stage washing tank after pressure filtration is added to the third-stage washing tank. The amount of the second solid phase is determined according to the predetermined liquid-solid ratio.

[0392] Turn on the agitator and the ultrasonic generator to perform the washing process. The agitator speed is 55 r / min and the ultrasonic frequency is 40 kHz.

[0393] Add carbide slag to the washing vessel until the pH reaches 10.

[0394] Start washing; washing time is 25 minutes. Select Cl. - As tracer ions, samples were taken at 6-minute intervals to test their concentration. When two Cl samples were close together... - Washing ends when the content change is less than 10%.

[0395] After washing, the mud in the three-stage washing tank is pumped into a filter press for solid-liquid separation to obtain a third liquid phase and a third solid phase. The third liquid phase is used as the washing liquid in the second-stage washing tank.

[0396] Test the content of heavy metals and impurity ions in the third solid phase. If it meets the specified standards, the washing process is complete.

[0397] Specifically, the third solid phase has a moisture content of 24 wt%. This moisture content solid phase is transported to the concrete batching plant. At the concrete batching plant, it is diluted to a moisture content of 50 wt%. During dilution, 0.002 wt% cellulose ether is added. The diluted slurry is metered and added to the concrete mixer at a ratio of 22 wt% (wet basis) of the concrete cementitious material.

[0398] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A comprehensive utilization method of secondary aluminum dross, characterized by, The application relates to a method for preparing a solid-phase product for concrete admixture. The method comprises the following steps: deoxidizing secondary aluminum ash; carrying out hydrolysis treatment on the deoxidized secondary aluminum ash, and carrying out solid-liquid separation to obtain mixed gas, hydrolysis slurry solid phase and high-salt-alkali ammonia-nitrogen hydrolysis liquid; carrying out separation and purification on the mixed gas to obtain hydrogen gas; carrying out at least twice acid washing treatment and at least once alkali washing treatment on the hydrolysis slurry solid phase to obtain the solid-phase product for concrete admixture; carrying out ammonia-nitrogen separation and gradient acidification treatment on the high-salt-alkali ammonia-nitrogen hydrolysis liquid to obtain aluminum hydroxide and inorganic salt crystals; wherein the step of carrying out at least twice acid washing treatment and at least once alkali washing treatment on the hydrolysis slurry solid phase to obtain the solid-phase product for concrete admixture comprises the following steps: injecting a first washing liquid into a first-stage washing kettle, the first washing liquid being obtained from the second liquid phase after the slurry of the second-stage washing kettle is filtered, and sending the hydrolysis slurry solid phase into the first-stage washing kettle for washing; introducing a first gas into the first-stage washing kettle until the pH of the washing liquid is a first preset value; wherein the first gas is CO2, and the first preset value of the pH is 6-7; introducing an acidic solution into the first-stage washing kettle until the pH of the washing liquid is a second preset value; after the washing of the first-stage washing kettle is completed, carrying out solid-liquid separation on the slurry to obtain a first liquid phase and a first solid phase, and the first liquid phase can be used for the hydrolysis treatment of secondary aluminum ash; injecting a second washing liquid into a second-stage washing kettle, the second washing liquid being obtained from the third liquid phase after the slurry of the third-stage washing kettle is filtered, and sending the first solid phase into the second-stage washing kettle for continuous washing; introducing an acidic solution into the second-stage washing kettle until the pH of the washing liquid is the second preset value; after the washing of the second-stage washing kettle is completed, carrying out solid-liquid separation on the slurry to obtain a second liquid phase and a second solid phase; injecting a third washing liquid into a third-stage washing kettle, the third washing liquid being water, and sending the second solid phase into the third-stage washing kettle for washing; introducing an alkaline substance into the third-stage washing kettle until the pH of the washing liquid is a third preset value; after the washing of the third-stage washing kettle is completed, carrying out solid-liquid separation on the slurry to obtain a third liquid phase and a third solid phase; detecting the content of heavy metal and impurity ions in the third solid phase, if the content meets the specified standard, the washing is completed, and the third solid phase is the solid-phase product, if the content does not meet the specified standard, the washing of the third-stage washing kettle is repeated; 2. The comprehensive utilization method of secondary aluminum dross according to claim 1, characterized by, wherein the acidic solution is one or a combination of sulfuric acid, nitric acid and organic acid, the second preset value of the pH is 2-6, the alkaline substance is one or a combination of calcium hydroxide, sodium hydroxide and calcium carbide slag, and the third preset value of the pH is 7-12. in the step of carrying out hydrolysis treatment on the deoxidized secondary aluminum ash to obtain mixed gas, hydrolysis slurry solid phase and high-salt-alkali ammonia-nitrogen hydrolysis liquid, mixing the secondary aluminum ash with water according to a solid-liquid ratio of 1: (2-10), adding calcium hydroxide and a catalyst, and carrying out hydrolysis at 5-99 DEG C for 5-48 h; the gas collected during the hydrolysis process is the mixed gas, the liquid phase obtained through solid-liquid separation of the hydrolysis product is the high-salt-alkali ammonia-nitrogen hydrolysis liquid, and the solid phase obtained is the hydrolysis slurry solid phase; wherein the weight ratio of the calcium hydroxide to the deoxidized secondary aluminum ash is (1-10):100, and the weight ratio of the catalyst to the deoxidized secondary aluminum ash is (1-10):

100. The catalyst comprises, by weight parts: sodium carbonate 0-10 parts, potassium carbonate 0-10 parts, sodium hydroxide 10-80 parts, potassium hydroxide 0-50 parts, carbide slag 5-30 parts, sodium stannate 0.01-5 parts.

3. The comprehensive utilization method of secondary aluminum dross according to claim 1 or 2, characterized by, The temperature in the hydrolysis process is controlled according to the following procedure: The secondary aluminum ash, water, catalyst and calcium hydroxide are added into the reaction kettle, when the temperature in the reaction kettle rises to 70-90℃, the cooling medium is used for cooling, so that the temperature rising rate in the reaction kettle is controlled to be 0.1-3℃ / min; When the temperature rising rate in the reaction kettle decreases, the amount of the cooling medium is gradually reduced, so that the temperature in the reaction kettle is maintained at 80-90℃; When the temperature in the reaction kettle begins to decrease, the heating medium is used for heating, and the amount of the heating medium is adjusted, so that the temperature in the reaction kettle is maintained at 80-90℃; wherein the difference between the temperature of the heating medium and the temperature in the reaction kettle is 1-10℃.

4. The comprehensive utilization method of secondary aluminum dross according to claim 1, characterized by, The step of deoxidizing the secondary aluminum ash comprises: The secondary aluminum ash is subjected to grading treatment, so that the sieve residue of 125μm sieve is 1-10%; The secondary aluminum ash is subjected to deoxidation treatment by nitrogen replacement.

5. The comprehensive utilization method of secondary aluminum dross according to claim 1, characterized by, The solid-liquid ratio of the primary washing kettle, the secondary washing kettle and the tertiary washing kettle is 1:(3-10) by mass ratio; The liquid level height of the washing liquid of the primary washing kettle, the secondary washing kettle and the tertiary washing kettle is 50-80% of the internal height of the washing kettle; The primary washing kettle, the secondary washing kettle and the tertiary washing kettle are opened for washing by the ultrasonic generator and the stirrer, wherein the rotation number of the stirrer is 20-80r / min, and the ultrasonic frequency of the ultrasonic generator is 20-80kHz.

6. The comprehensive utilization method of secondary aluminum dross according to claim 1, characterized by, The step of obtaining aluminum hydroxide and inorganic salt crystals by hydrolyzing the high-salinity-alkaline ammonia-nitrogen solution, separating ammonia-nitrogen, and performing gradient acidification treatment comprises: The high-salinity-alkaline ammonia-nitrogen solution is subjected to ammonia-nitrogen separation to obtain a gas phase and a first-stage liquid phase; Carbon dioxide is dissolved in the first-stage liquid phase until a first specified pH value is reached to obtain a second-stage liquid phase; Carbon dioxide is dissolved in the second-stage liquid phase until a second specified pH value is reached to obtain a third-stage liquid phase; An extraction solvent is added to the third-stage liquid phase and carbon dioxide is dissolved until a third specified pH value is reached, and after extraction separation, an organic phase fourth-stage liquid phase and an inorganic phase fourth-stage liquid phase are obtained; The water content of the inorganic phase fourth-stage liquid phase is evaporated; The organic phase fourth-stage liquid phase is subjected to back-extraction separation to obtain an inorganic liquid phase and an organic liquid phase, the water content in the inorganic liquid phase is evaporated, and the organic liquid phase is returned to the third-stage liquid phase treatment.

7. The comprehensive utilization method of secondary aluminum dross according to claim 6, characterized by, In the step of separating ammonia-nitrogen from the high-salinity-alkaline ammonia-nitrogen solution to obtain a gas phase and a first-stage liquid phase: The high-salt-alkali ammonia-nitrogen hydrolysate is fed into a reactor, the rotation speed of the reactor is set to 40-150 r / min, air is fed for aeration, the air flow is 10-30 m 3 / min, the reaction time is 0.5-3 h, the obtained ammonia gas is fed into an absorption tower, and ammonia water is prepared. The temperature of the high-salinity-alkaline ammonia-nitrogen solution is 80-95℃, the alkalinity is 0.20-2.0mol / L, the total salt content is 5-25%, and the concentration of ammonia-nitrogen is 200-2000mg / L; In the step of dissolving carbon dioxide in the first-stage liquid phase until a first specified pH value is reached to obtain a second-stage liquid phase: Carbon dioxide is introduced into the first-stage liquid phase, the flow rate of the carbon dioxide is set to 1000-3000 mL / min, the rotation speed is set to 30-150 r / min, the reaction is stopped when the pH of the reaction solution decreases from 12-14 to 7-8, the slurry is subjected to solid-liquid separation, and aluminum hydroxide and a second-stage liquid phase are obtained; In the step of dissolving carbon dioxide in the second-stage liquid phase until a second specified pH value is reached to obtain a third-stage liquid phase: The second-stage liquid phase is transferred into a reaction kettle, carbon dioxide is introduced into the kettle, the flow rate of the carbon dioxide is set to 1000-3000 mL / min, the rotation speed is set to 40-150 r / min, the reaction is stopped when the pH of the reaction solution decreases from 7-8 to 5-6, the slurry is subjected to solid-liquid separation, and sodium bicarbonate and a third-stage liquid phase are obtained; In the step of adding an extraction solvent to the third-stage liquid phase and dissolving carbon dioxide until a third specified pH value is reached, and then extracting and separating to obtain an organic phase of a fourth-stage liquid phase and an inorganic phase of a fourth-stage liquid phase: The third-stage liquid phase is transferred into a reaction kettle, carbon dioxide is introduced into the kettle, and an extraction solvent is added, the volume ratio of the organic phase to the inorganic phase is set to (1-2):(2-3), the solubility of the carbon dioxide is set to 0.05-0.08 mol / L, the reaction is stopped when the pH of the reaction solution decreases from 5-6 to 3-4, and then extracting and separating to obtain an organic phase of a fourth-stage liquid phase and an inorganic phase of a fourth-stage liquid phase; the organic phase of the fourth-stage liquid phase contains chlorine.

8. The comprehensive utilization method of secondary aluminum dross according to claim 7, characterized by, The extraction solvent comprises an extractant and a diluent, wherein the extractant is one or more of alkyl primary amine, secondary amine, trioctyl tertiary amine, and trioctylmethyl quaternary ammonium salt; and the diluent is one or more of kerosene, tributyl phosphate, n-pentanol, n-hexanol, n-octanol, and isooctanol; The flow rate of the carbon dioxide is 1000-3000 mL / min; When the third-stage liquid phase is transferred into the reaction kettle, the rotation speed of the reaction kettle is set to 40-150 r / min, the reaction temperature is 20-25°C, and the reaction pressure is 1-3 MPa.

9. The comprehensive utilization method of secondary aluminum dross according to claim 6, characterized by, In the step of evaporating the water in the inorganic phase of the fourth-stage liquid phase: The inorganic phase of the fourth-stage liquid phase is discharged from the bottom of the reaction kettle, heated to 90-100°C, and then pumped into an MVR evaporator, and a compressor is started to produce sodium sulfate and mother liquor when the sodium sulfate is supersaturated; When the concentration of sodium sulfate in the mother liquor decreases to 3-7%, the temperature is lowered to 45-55°C, the mother liquor is transported to the MVR evaporator, and the compressor is started, and sodium chloride is obtained after the supersaturation is concentrated.

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