A harmless regeneration treatment method for aluminum ash residue

Abstract

The present invention discloses a harmless regeneration treatment method for aluminum ash slag, which relates to the field of solid waste treatment and includes: S1 raw material ratio, S2 homogenization and pulping, S3 extraction of metallic aluminum, S4 specific gravity separation by diversion electric wave, S5 dynamic reaction, S6 utilization of reaction tail gas, S7 ion separation, S8 drying treatment, S9 roasting and phase transformation, S10 recovery of chloride salts and sulfate salts, and S11 Raymond grinding and powder making; the present invention can extract tiny metallic aluminum in the aluminum ash slag for use as raw materials for aluminum alloy production; it can recycle soluble salts in the aluminum ash slag to produce products such as industrial-grade sodium chloride salt and aluminum alloy flux; it can convert harmful nitrogen in the aluminum ash slag into ammonia water for recycling; it can utilize the hydrogen generated when the aluminum ash slag meets water as a heat source, and can also produce an alternative material for alumina, namely regenerated alumina, which can be applied in fields such as refractory materials, abrasives, coatings, ceramic materials, white cement raw materials, etc.; realizing the comprehensive utilization of aluminum ash slag.

Description

Technical Field

[0001] The present invention relates to the field of solid waste treatment, and in particular to a harmless regeneration treatment method for aluminum ash slag. Background Art

[0002] Aluminum ash is a waste generated during the production process of the aluminum industry. The chemical components in aluminum ash can cause harm to the environment and human health. Aluminum nitride, metallic aluminum, and aluminum carbide are contained in aluminum ash. When aluminum nitride encounters water or humid air, it is extremely prone to hydrolysis reaction, generating ammonia gas with a pungent smell, polluting the air; when metallic aluminum reacts with water, hydrogen is generated, and when aluminum carbide reacts with water, methane is generated. Both hydrogen and methane have the risk of combustion and explosion. Aluminum ash also contains relatively high levels of alkali metal oxides, as well as fluorides, chlorides, etc. Long-term accumulation will pollute the soil and groundwater, seriously affecting the ecological environment and the health and safety of the people. It has obvious toxicity (T) and reactivity (R).

[0003] Aluminum ash can be divided into primary aluminum ash and secondary aluminum ash according to the different degrees of treatment and disposal. Primary aluminum ash is mainly the aluminum ash directly produced in the electrolytic aluminum section and the molten aluminum recycling section. It is manifested as the aluminum slag directly discharged from the molten section and the floating slag generated in the electrolytic aluminum oxide section. Metal aluminum has not been extracted, and the main components are substances such as metallic aluminum, fluoride salts, aluminum oxide, and aluminum nitride, which have relatively high recycling value of metallic aluminum; secondary aluminum ash is the waste after extracting metallic aluminum from the melting of primary aluminum ash or the aluminum-containing waste residue generated during the aluminum refining process. The content of metallic aluminum contained is significantly lower than that of primary aluminum ash, and general extraction methods can no longer extract metallic aluminum. Therefore, secondary aluminum ash no longer has recycling value and is directly disposed of as hazardous waste.

[0004] Therefore, it is necessary to design a harmless regeneration treatment method for aluminum ash slag for secondary aluminum ash. Summary of the Invention

[0005] The present invention overcomes the above deficiencies and provides a technical solution that can solve the above problems.

[0006] A harmless regeneration treatment method for aluminum ash slag includes the following steps:

[0007] Step S1: Pre-match the composition of the aluminum ash slag so that the aluminum ash slag contains 25 - 55% aluminum, 2.8 - 10% magnesium, 0.8 - 5% silicon, 0.8 - 3.5% chlorine, 0.3 - 1.2% potassium, 0.8 - 2.2% sodium, 0.1 - 1% calcium, and 0.3 - 3.2% nitrogen;

[0008] Step S2, adding low-temperature water at 3-30°C to the aluminum ash slag for pulping, wherein the liquid-to-solid ratio of the pulping is 3-8:1, and adding a reaction inhibitor at a ratio of 1.8-6.2‰ during the pulping, wherein the reaction inhibitor forms a polymerized mucous film between the water and the metal surface;

[0009] Step S3, putting the slurry into an extraction system, which includes a diameter expansion processing device, a diversion device and a screening device. The diameter expansion processing device is provided with grinding balls, and the aluminum ash material in the slurry is repeatedly crushed and impacted by the high-hardness grinding balls. The grinding balls rotate continuously for 15-60 minutes, and then enter the diversion device. Finally, the metal aluminum with a particle size less than 200 mesh is screened out by the screening device;

[0010] Step S4, putting the slurry into a sorting device, wherein the sorting device is provided with a guide channel, wherein the guide channel has two or more diversion channels, wherein the two or more guide channels are arranged into a composite multiple spiral shape according to the magnetic field strength characteristics, and a mesh structure is interlaced in the middle of the guide channel, and the total length of the guide channel is 10-20 meters, and the slurry flows slowly in the guide channel, and the slurry removes the dyed metal oxide with the magnetic medium under the action of the high-intensity magnetic field;

[0011] Step S5, placing the slurry and the catalyst into a denitrification reactor at the same time to react and remove nitrogen, the denitrification reactor adopts a horizontal cylindrical ball mill;

[0012] Step S6: During the reaction process of the nitrogen removal reactor in step S5, a mixed gas is generated. The mixed gas includes ammonia, hydrogen and water vapor. The temperature of the mixed gas is 90-115°C. The mixed gas is cooled by heat exchange in the primary heat exchanger of the steam boiler and then enters the ammonia absorption tower. The ammonia absorption tower absorbs the ammonia into ammonia water with a concentration of 18-32%. The remaining hydrogen is used as the fuel gas source of the steam boiler. When the steam boiler is working, steam is generated. Part of the steam is used in the wastewater treatment device, and the excess steam is incorporated into the park. When the steam is stopped, the hydrogen enters the high-temperature phase-transition tunnel kiln and mixes with the natural gas to assist the combustion of the natural gas.

[0013] Step S7, after the deamination reaction, the liquid-solid ratio of the slurry is 3-6:1, and then the slurry is placed in an ion separation device, and the ion separation device washes and separates the soluble salt in the slurry;

[0014] Step S8, after ion separation, the water content of the slurry is 18-55%, and the slurry is dried to obtain a low-temperature regenerated alumina product;

[0015] Step S9: Press the material with a water content of 5 - 15% into bricks, stack them on the kiln car, and input them into the tunnel kiln through the kiln car for roasting at a temperature of 1000 - 1400 °C for 10 - 20 hours. After high-temperature roasting, hydrated alumina is converted into α-Al2O3, and at the same time, the residual anions in the material can be removed by high-temperature roasting;

[0016] Step S10: Volatile chlorine and sulfate ions are generated during high-temperature roasting. These gases are absorbed and dissolved by the circulating water spray in the waste gas tower as tail gas. When the concentration of the circulating water reaches the treatment standard, it is sent to the MVR wastewater treatment system for recovering chloride salts and sulfates;

[0017] Step S11: After roasting and cooling, alumina products with high purity and whiteness are obtained. Then, they are coarsely broken by a coarse crusher and then put into a Raymond mill to be ground into products with a particle size of 100 - 1200 mesh.

[0018] Further, in step S3, the temperature of the extraction system is maintained below 15 °C, and a temperature measurement, pH control device, and automatic makeup device for controlled-temperature water are set inside the extraction system to keep the pH value of the slurry below 10.

[0019] Further, in step S3, the temperature of the extraction system is maintained below 25 °C, and a temperature measurement, pH control device, and automatic makeup device for controlled-temperature water are set inside the extraction system to keep the pH value of the slurry below 10.

[0020] Further, in step S4, the magnetic flux of the diversion channel in the sorting device is 20000 - 30000 gauss.

[0021] Further, in step S5, a spiral baffle with a height of 2 / 3 of the diameter is set inside the denitrification reactor, and high-aluminum grinding balls are installed in the denitrification reactor. The denitrification reactor is driven to rotate continuously at a speed of 5 - 30 revolutions per minute, and the temperature during the deammoniation reaction is controlled at 60 - 110 °C. The residence time of the slurry in the denitrification reactor is 30 - 75 minutes, and the particle size of the slurry increases to 300 - 600 mesh after the deammoniation reaction.

[0022] Further, in step S5, under the action of the catalyst, aluminum nitride and metallic aluminum in the slurry will undergo the following reactions:

[0023] S501: AlN + 3H2O = Al(OH)3 + NH3↑;

[0024] S502: 2Al + 6H2O → 2Al(OH)3 + 3H2↑;

[0025] S503. 2Al + 2NaOH + 2H2O = 2NaAlO2 + 3H2↑.

[0026] Further, in step S7, the ion separation device includes a high-speed centrifugal separation device, a filter press device, and a vacuum filtration device.

[0027] S701. The slurry first enters the high-speed centrifugal separation device and rotates at a high speed using the high-speed centrifugal separation device. Its rotation speed is maintained at 3000 - 5000 revolutions per minute. The water in the slurry is centrifuged out, and the slurry is dehydrated into filter residue with a water content of 20 - 30%. Then, low-salt water is added to the filter residue for stirring and pulping. The liquid-solid ratio of pulping is 3 - 5:1, and the dissolution and stirring time is 10 - 20 minutes.

[0028] S702. The slurry is input into the filter press device for filtration. The filter press device applies high pressure to the slurry, with a pressure of 3 - 5 Mpa, to let the filtrate drain out and obtain filter residue with a water content of 30 - 40%. Then, low-salt water is added to the filter residue for stirring and pulping. The liquid-solid ratio of pulping is 3 - 5:1, and the dissolution and stirring time is 10 - 20 minutes.

[0029] S703. The slurry is input into the vacuum filtration device. The vacuum filtration device dehydrates the slurry under the action of atmospheric pressure to obtain filter residue with a water content of 35 - 50%.

[0030] S704. After separation by the ion separation device, a slurry with a soluble salt removal rate of over 95% is obtained. The filtrate obtained during the dehydration process is subjected to multi-stage washing in a circulating water manner to obtain salt-containing water containing soluble salts.

[0031] S705. The salt-containing water is input into the MVR wastewater treatment system for evaporation and condensation treatment. The treated low-salt water will enter the ion separation device for reuse, and salt substances will produce industrial-grade sodium chloride and raw materials for aluminum alloy flux.

[0032] Further, in step S8, the drying treatment includes the following two parts:

[0033] S801. Centrifugal spray drying; The slurry is pressurized and input into the centrifugal atomization drying device. The slurry will be output from the nozzle of the centrifugal atomization drying device. As the nozzle rotates at a high speed, the slurry is sprayed into a mist of mud droplets under the action of pressure and centrifugal force. At this time, the mud droplets will be sprayed onto the hot flue of the hot blast stove. The temperature of the hot flue is 550 - 800 °C. The mud droplets will come into contact with the high temperature and be instantly dried into approximately spherical particles. Then, the spherical particles are cooled by the cooler at the bottom of the tower until the temperature drops to 40 - 100 °C. At this time, they are discharged, and the water content of the discharged material will be reduced to 15 - 45%.

[0034] S802. Input the granular material into a rotary drying device for further drying. The rotary drying device uses a rotary kiln. The material is heated by the high-temperature flame and rotary motion inside the rotary kiln to evaporate the moisture. When the moisture content of the material drops to the stage of 5 - 15%, a discharging device is set up for discharging. The discharged material will enter the next process. At the same time, part of the material still remains in the rotary kiln until it is dried to a moisture content < 0.5%, and a low-temperature regenerated alumina product is obtained.

[0035] Further, in step S9, the following reactions will occur to the material in the tunnel kiln:

[0036] S901. NaAlO2 + 2H2O = Al(OH)3 + NaOH;

[0037] S902. 2Al(OH)3 = Al2O3 + 3H2O;

[0038] S903. 2NaOH = Na2O + H2O;

[0039] S904. Al2O3 → α - Al2O3;

[0040] S905. C + O2 = CO2.

[0041] Further, in step S11, products with particle sizes of 100 - 200 mesh, 200 - 250 mesh, 250 - 300 mesh, 300 - 500 mesh, 500 - 800 mesh, and 800 - 1200 mesh are respectively ground using a Raymond mill.

[0042] Compared with the prior art, the beneficial effects of the present invention are:

[0043] 1. The metallic aluminum in the secondary aluminum ash can be further recovered, and the extraction rate can reach 40 - 71%. The extracted metallic aluminum particles can be used as raw materials for recycled aluminum to produce aluminum alloy rods, improving the utilization value of the secondary aluminum ash.

[0044] 2. For the secondary aluminum ash after extracting metallic aluminum, during the subsequent harmless treatment process, the generation amount of hydrogen can be reduced, improving the safety of the treatment equipment.

[0045] 3. The hydrogen and ammonia generated by the reaction achieve the effect of full resource utilization. Ammonia can be prepared into ammonia water for use in denitrification production. The surplus ammonia water can also be used as a product for external sales. Hydrogen can be used as the heat source for a steam boiler or mixed with natural gas in the tunnel kiln for combustion to reduce the consumption of natural gas.

[0046] 4. The soluble salts in the aluminum ash slag can be fully recycled, and products such as industrial-grade sodium chloride and aluminum alloy flux can be produced.

[0047] 5. The comprehensive utilization of aluminum ash slag is realized, and low-temperature regenerated alumina and high-temperature regenerated alumina products are produced, with the production yield rate reaching over 98%. The application fields can cover refractory materials, abrasives, coatings, ceramic materials, raw materials for white cement, etc.

[0048] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0050] Figure 1 is a schematic diagram of the method of steps S1 - S10 of the present invention;

[0051] Figure 2 is a schematic diagram of the operation process of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the specific embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0053] Embodiment 1

[0054] As Figure 1-2 shown, a method for harmless regeneration treatment of aluminum ash slag of the present invention includes the following steps:

[0055] Step S1. Pre-match the composition of the aluminum ash slag so that the aluminum ash slag contains 30 - 50% aluminum, 1 - 8% magnesium, 1 - 4% silicon, 1 - 3% chlorine, 0.5 - 1% potassium, 1 - 2% sodium, 0.1 - 1% calcium, and 0.5 - 3% nitrogen;

[0056] Step S2. Add low-temperature water at 5 - 30 °C to the aluminum ash slag for pulping. The liquid-solid ratio of pulping is 3 - 8:1, and a reaction inhibitor is added at a ratio of 2 - 6‰ during pulping. The reaction inhibitor forms a polymeric mucosal layer between the surface of water and metal.

[0057] Step S3: Put the slurry into the extraction system. The extraction system includes a diameter-expanding treatment device, a shunt device, and a screening device. There are grinding balls in the diameter-expanding treatment device. The aluminum ash material in the slurry is repeatedly rolled and impacted by the high-hardness grinding balls. The continuous rotation time of the grinding balls is 20 - 60 minutes, and then it enters the shunt device. Finally, the metallic aluminum with a particle size less than 200 mesh is screened out by the screening device. Preferably, the metallic aluminum with a particle size less than 160 mesh is screened out.

[0058] In step S3, the temperature of the extraction system is maintained below 15°C, and a temperature measurement, a PH control device, and a temperature-controlled water automatic replenishment device are set inside the extraction system to keep the PH value of the slurry below 10.

[0059] Step S4: Put the slurry into the sorting device. There is a diversion channel inside the sorting device. The diversion channel is divided into 3 - 6 branches. The diversion channel is set as a composite multi-helical shape according to the magnetic field intensity characteristics, and there is a criss-crossing mesh structure in the middle of the diversion channel. The total length of the diversion channel is 10 - 20 meters. The slurry slowly flows in the diversion channel, and the dyed metal oxides with magnetic media are removed under the action of a high-intensity magnetic field.

[0060] In step S4, the magnetic flux of the diversion channel in the sorting device is 20000 - 30000 gauss.

[0061] Step S5: Put the slurry and the catalyst into the denitrification reactor simultaneously for denitrification reaction. The denitrification reactor uses a horizontal cylindrical ball mill.

[0062] In step S5, a spiral diversion baffle with a height of 2 / 3 of the diameter is set inside the denitrification reactor, and high-aluminum grinding balls are installed in the denitrification reactor. The denitrification reactor is driven to rotate continuously at a speed of 5 - 30 revolutions per minute, and the temperature during the deammoniation reaction is controlled at 60 - 110°C. The residence time of the slurry in the denitrification reactor is 30 - 75 minutes. After the deammoniation reaction, the particle size of the slurry increases to 300 - 600 mesh.

[0063] In step S5, under the action of the catalyst, the aluminum nitride and metallic aluminum in the slurry will undergo the following reactions:

[0064] S501: AlN + 3H2O = Al(OH)3 + NH3↑;

[0065] S502: 2Al + 6H2O → 2Al(OH)3 + 3H2↑;

[0066] S503: 2Al + 2NaOH + 2H2O = 2NaAlO2 + 3H2↑.

[0067] Step S6: During the reaction process of the nitrogen removal reactor in step S5, a mixed gas is generated. The mixed gas includes ammonia, hydrogen and water vapor. The temperature of the mixed gas is 95-110° C. The mixed gas is cooled by heat exchange in the primary heat exchanger of the steam boiler and then enters the ammonia absorption tower. The ammonia absorption tower absorbs the ammonia into ammonia water with a concentration of 20-30%. The remaining hydrogen is used as the fuel gas source of the steam boiler. When the steam boiler is working, steam is generated. Part of the steam is used in the wastewater treatment device, and the excess steam is incorporated into the park. When the steam is stopped, the hydrogen enters the high-temperature phase-transition tunnel kiln and mixes with the natural gas to assist the combustion of the natural gas.

[0068] Step S7, after the deamination reaction, the liquid-solid ratio of the slurry is 3-6:1, and then the slurry is placed in an ion separation device, and the ion separation device washes and separates the soluble salt in the slurry;

[0069] In step S7, the ion separation device includes a high-speed centrifugal separation device, a filter press device and a vacuum filtration device;

[0070] S701, the slurry first enters a high-speed centrifugal separation device, and is rotated at a high speed by the high-speed centrifugal separation device, and the speed is maintained at 3000-5000 rpm. The water in the slurry is thrown out under the action of the centrifuge, and the slurry is dehydrated into a filter residue with a water content of 20-30%. Then, low salt water is added to the filter residue for stirring and slurrying. The liquid-to-solid ratio of the slurry is 3-5:1, and the dissolution stirring time is 10-20 minutes;

[0071] S702, input the slurry into a filter press device for filtration, the filter press device performs high pressure extrusion on the slurry, the pressure of which is 3-5Mpa, and the filtrate is discharged to obtain a filter residue, the water content of which is 30-40%, and then low salt water is added to the filter residue for stirring and slurrying, the liquid-to-solid ratio of the slurrying is 3-5:1, and the dissolution stirring time is 10-20 minutes;

[0072] S703, inputting the slurry into a vacuum filtration device, which dehydrates the slurry under the action of atmospheric pressure to obtain filter residue, wherein the water content of the filter residue is 40-45%;

[0073] S704, after separation by an ion separation device, a slurry with a soluble salt removal rate of more than 95% is obtained, and the filtrate obtained in the dehydration process is subjected to multi-stage washing by circulating water to obtain a salt water containing soluble salts;

[0074] S705, inputting the salt water into the MVR wastewater treatment system for evaporation and condensation treatment, the treated low-salt water will enter the ion separation equipment for repeated use, and the salt substances will produce sodium chloride industrial-grade salt and aluminum alloy flux raw materials;

[0075] Step S8: After ion separation, the water content of the slurry is 20 - 50%. At this time, the slurry is dried to obtain a low-temperature regenerated alumina product;

[0076] In step S8, the drying process includes the following two parts:

[0077] S801: Centrifugal spray drying; The slurry is pressurized and fed into a centrifugal atomization drying device. The slurry will be output from the nozzle of the centrifugal atomization drying device. As the nozzle rotates at high speed, the slurry is sprayed into mist-like slurry droplets under the action of pressure and centrifugal force. At this time, the slurry droplets will be sprayed onto the hot flue of the hot blast stove. The temperature of the hot flue is 600 - 750°C. The slurry droplets will come into contact with the high temperature and be instantly dried into approximately spherical particles. Then, the spherical particles are cooled by a cooler at the bottom of the tower until the temperature drops to 40 - 100°C. At this time, they are discharged, and the water content of the discharged material will drop to 20 - 40%;

[0078] S802: The granular material is fed into a rotary drying device for further drying. The rotary drying device uses a rotary kiln. The material is heated by the high-temperature flame and rotary motion inside the rotary kiln to evaporate the water. When the water content of the material drops to 5 - 15%, a discharging device is set up for discharging. The discharged material will enter the next process. At the same time, part of the material still remains in the rotary kiln until it is dried to a water content < 0.5% to obtain a low-temperature regenerated alumina product;

[0079] Step S9: The material with a water content of 5 - 15% is pressed into bricks and stacked on a kiln car. The kiln car is used to feed it into a tunnel kiln for roasting at a temperature of 1000 - 1400°C for 10 - 20 hours. After high-temperature roasting, trihydrate aluminum is converted into α - Al2O3. At the same time, high-temperature roasting can remove the residual anions in the material;

[0080] In step S9, the following reactions will occur to the material in the tunnel kiln:

[0081] S901: NaAlO2 + 2H2O = Al(OH)3 + NaOH;

[0082] S902: 2Al(OH)3 = Al2O3 + 3H2O;

[0083] S903: 2NaOH = Na2O + H2O;

[0084] S904: Al2O3 → α - Al2O3;

[0085] S905: C + O2 = CO2.

[0086] Step S10: Volatile chlorine and sulfate ions are generated during high-temperature roasting. These gases are absorbed and dissolved through the circulating water spray of the waste gas tower as tail gas. When the concentration of the circulating water reaches the treatment standard, it is sent to the MVR wastewater treatment system for the recovery of chloride salts and sulfates.

[0087] Step S11: After roasting and cooling, alumina products with high purity and whiteness are obtained. Then, they are coarsely crushed by a coarse crusher and then put into a Raymond mill. The Raymond mill is used to grind them into products with a particle size of 100 - 1200 mesh.

[0088] In step S11, products with particle sizes of 100 - 200 mesh, 200 - 250 mesh, 250 - 300 mesh, 300 - 500 mesh, 500 - 800 mesh, and 800 - 1200 mesh are respectively ground by the Raymond mill.

[0089] Example Two

[0090] As Figure 1-2 shown, a harmless regeneration treatment method for aluminum ash slag of the present invention includes the following steps:

[0091] S1. Raw material ratio

[0092] The aluminum ash slag is pre-formulated according to the requirements of the product. The requirements for the formulated items are: aluminum 30 - 40%, magnesium 1 - 5%, silicon 1 - 4%, chlorine 1 - 3%, potassium 0.5 - 1%, sodium 1 - 2%, calcium 0.1 - 1%, nitrogen 0.5 - 3%, etc.

[0093] The formulation is determined through multiple formulation experiments based on the characteristics of each element component in the aluminum ash slag and the reaction mechanism in the subsequent production process. Through a specific batching formula, the production system can be maintained stable and efficient, and various types of and special application field regenerated alumina products can be prepared. The application fields cover refractory materials, abrasives, coatings, ceramic materials, white cement raw materials, etc.

[0094] S2. Homogenization and pulping

[0095] The production system uses low-temperature water as the dispersion medium and pulps with a liquid-solid ratio of 3:1. There are also alternative solid-liquid ratio schemes, which are 5:1 and 8:1 respectively. The low-temperature water is obtained through a circulating refrigeration device, and the temperature is controlled at 5 - 30°C. The low-temperature water can effectively inhibit the water reactivity of the aluminum ash slag, and a reaction inhibitor is added in a proportion of 2 - 6‰. The inhibitor is prepared from several organic polymers, and the main components are carbon, hydrogen, oxygen, and nitrogen. It can form a polymer mucous membrane between water and the metal surface to prevent the aluminum ash slag from reacting with water prematurely and ensure the extraction rate of metallic aluminum particles.

[0096] S3. Extraction of metallic aluminum

[0097] The extraction system is divided into a diameter-expanding treatment device, a shunt device, and a screening device. The rotating device of the diameter-expanding treatment device is equipped with alumina grinding balls. Through the repeated rolling and impact of the high-hardness grinding balls on the aluminum ash material, the particle size of the metallic aluminum particles is increased, and the rotation duration is 20 - 60 minutes. Then it enters the shunt device. In the multi-stage screening device, the metallic aluminum with a particle size smaller than 160 mesh is screened out. An alternative is to screen out the metallic aluminum with a particle size smaller than 200 mesh.

[0098] Temperature measurement, pH control devices, and automatic makeup devices for temperature-controlled water are configured at multiple equipment points within the extraction system to ensure that the temperature throughout the process is below 15°C. An alternative is below 25°C. The pH value of the medium material needs to be controlled below 10 to ensure the inhibition of the hydrolysis reaction of the material.

[0099] S4. Guided-wave specific gravity separation

[0100] There is a diversion channel with a magnetic flux of 20,000 gauss in this device, and there is also an alternative diversion channel with a magnetic flux of 30,000 gauss. The diversion channel is divided into 3 - 6 branches, distributed in a composite multi-helical shape according to the intensity characteristics of the magnetic field, and there is an intersecting mesh structure in the middle. The total length is 10 - 20 meters. The material slowly flows in the diversion channel. Under the action of the high-intensity magnetic field, the colored metal oxides such as iron, manganese, and nickel in the material are sorted and removed. Through this process treatment, the roasting whiteness of the material can be increased by 10 - 20%.

[0101] S5. Dynamic reaction

[0102] The denitrification reaction is carried out on the material treated by the above process in a specially designed reactor. The main body of the reactor is a horizontal cylindrical ball mill. It is equipped with a spiral baffle with a height of 2 / 3 of the diameter inside the reactor and filled with high-aluminum grinding balls. Through the continuous rotation of the reactor, the rotation speed is 5 - 30 revolutions per minute. Under the action of the catalyst, the following reactions occur for aluminum nitride and metallic aluminum in the material:

[0103] AlN + 3H2O = Al(OH)3 + NH3↑;

[0104] 2Al + 6H2O → 2Al(OH)3 + 3H2↑;

[0105] 2Al + 2NaOH + 2H2O = 2NaAlO2 + 3H2↑.

[0106] In the reactor, the materials react rapidly under the action of the catalyst, and the temperature is controlled at 60 - 110 °C. Due to the continuous rotation of the equipment, the grinding balls continuously stir and grind the materials. Under the action of the diversion baffle, the materials are discharged from the tail of the reactor at a uniform speed, ensuring that the residence time of the materials in the reactor is controlled within 30 - 75 minutes. During this time, the materials can fully react, and the particle size can be increased to 300 - 600 mesh, with the median particle size being 500 mesh.

[0107] S6. Utilization of reaction tail gas

[0108] During the deamination reaction, a mixed tail gas containing ammonia, hydrogen, and water vapor is generated, with a temperature of 95 - 110 °C. The mixed gas passes through the primary heat exchanger of the steam boiler equipped in the production system, and after heat exchange and cooling, it enters the ammonia absorption tower. The ammonia absorption tower absorbs ammonia to form ammonia water with a concentration of 30%. The remaining hydrogen is used as the fuel source for the steam boiler to produce steam. The steam is used in the wastewater treatment device within the production system, and the excess steam is incorporated into the park for use. When the steam production is stopped, the hydrogen can enter the tunnel kiln for high-temperature phase conversion and be mixed with natural gas for combustion, which can reduce the natural gas consumption by 30 - 45%.

[0109] S7. Ion separation

[0110] The liquid-solid ratio of the material slurry after the reaction is 3:1, and there are alternative liquid-solid ratios of 5:1 and 6:1. In the ion separation system equipment, the soluble salts in the materials are washed and separated. There are three types of solid-liquid separation devices in the ion separation system:

[0111] The first type is a high-speed centrifugal separation device. By high-speed rotation at a speed of 3000 - 5000 revolutions per minute, the moisture in the slurry is centrifuged out, and the slurry is dehydrated into filter cake with a moisture content of 20 - 30%. The soluble salts are separated with the water. The filter cake is then stirred and slurried with low-salt water, and the liquid-solid ratio of the slurrying is 3 - 5:1, and the dissolution and stirring time is 10 - 20 minutes.

[0112] The second type is a filter press device. The slurry is filtered in the filter press device. When the throughput reaches the predetermined amount, the slurry feeding is stopped, and high-pressure extrusion is carried out using the filter press device at a pressure of 3 - 5 Mpa to discharge the filtrate. The moisture content of the remaining filter cake is 30 - 40%. The filter cake is then stirred and slurried with low-salt water, and the liquid-solid ratio of the slurrying is 3:1, and there is an alternative of 5:1. The dissolution and stirring time is 10 - 20 minutes.

[0113] The third type is a vacuum filtration device. The slurry is put into the vacuum filtration device, and under the action of atmospheric pressure, the slurry is dehydrated to obtain filter cake with a moisture content of 40 - 45%.

[0114] The ion separation system is a combination of these three types of solid-liquid separation equipment, which can remove soluble salts in the slurry, with a removal rate of over 95%. The recycled water is then washed through multiple uses to gradually increase the concentration of soluble salts; finally, the brine with the highest concentration is input into the MVR wastewater treatment system for evaporation and condensation treatment. The low-salt water after treatment enters the three solid-liquid separation devices in the ion separation system for reuse. Salt substances can produce industrial-grade sodium chloride and raw materials for aluminum alloy fluxes.

[0115] S8. Drying treatment

[0116] After ion separation, the water content of the slurry is 20 - 50%, and drying treatment is still required to remove the remaining moisture. The slurry drying system is divided into two parts. One is centrifugal spray drying. The equipment for this process is a centrifugal atomization drying device. The slurry is pressurized and fed into the nozzle position. Through the high-speed rotation of the nozzle, the slurry is sprayed into a mist under the action of pressure and centrifugal force. The contact area between the slurry mist droplets and the gas is very large. When encountering the hot flue gas generated by the hot blast stove, the gas temperature of the hot flue gas is 600 - 750°C, and it will be dried into approximately spherical particles in a very short time. The particles are cooled to 40 - 100°C by the cooler at the bottom of the tower and then discharged. At this time, the water content of the material will drop to 20 - 40%.

[0117] The granular material is put into a rotary drying device for further drying. The rotary drying device uses a rotary kiln. The rotary kiln heats the material through high-temperature flames and rotary motion to evaporate the moisture in it, thereby achieving the purpose of drying. The fuel and the primary air for combustion support are sent into the combustion chamber through the burner at the kiln head to form high-temperature flames and release a large amount of heat. These heats are then transferred to the material to increase its temperature and evaporate the moisture.

[0118] In the rotary drying device, as the drying process continues, when the material is dried to near dryness and the water content of the material drops to the stage of 5 - 15%, a discharging device is also set up to discharge part of the material with a water content of 5 - 15%. The discharged material will enter the next process, while the remaining material continues to be dried to a water content of <0.5%, which can be used as low-temperature regenerated alumina products. The characteristics of this part of the regenerated alumina products are that they contain aluminum trihydrate and can be used as raw materials for aluminosilicate refractory materials.

[0119] S9. Roasting and phase transformation

[0120] The material with a water content of 5 - 15% is pressed into bricks and stacked on the kiln car. The kiln car enters the tunnel kiln for roasting at a temperature of 1000 - 1400°C for 10 - 20 hours. In the tunnel kiln, the following reaction occurs to the material:

[0121] NaAlO2 + 2H2O = Al(OH)3 + NaOH;

[0122] 2Al(OH)3 = Al2O3 + 3H2O;

[0123] 2NaOH = Na2O + H2O;

[0124] Al2O3 → α-Al2O3;

[0125] C + O2 = CO2.

[0126] S10. Recovery of chlorides and sulfates

[0127] After high-temperature roasting, aluminum trihydroxide is converted into α-Al2O3. At the same time, high-temperature roasting can remove residual anions such as chlorine, fluorine, and sulfate in the material. The tail gas generated by volatile chlorine and sulfate ions will be absorbed and dissolved by the circulating water spray of the waste gas tower. When the concentration of the circulating water reaches the treatment standard, it will be sent to the MVR wastewater treatment system to recover chlorides and sulfates, achieving the full recycling of resources.

[0128] S11. Raymond grinding for powder production

[0129] The material after roasting and cooling is alumina product with high purity and whiteness. It is then roughly broken and ground by Raymond mill into powder with a wide particle size distribution range, and then subjected to multi-stage screening to finally produce products with various particle sizes, including products with particle sizes of 100 - 200 mesh, 200 - 250 mesh, 250 - 300 mesh, 300 - 500 mesh, 500 - 800 mesh, and 800 - 1200 mesh, which can meet the needs of different customers.

[0130] In the above two embodiments of the present invention, both are applicable to the resource-based recycling of various substances in aluminum ash waste, achieving the following technical effects:

[0131] 1. Tiny metallic aluminum in aluminum ash can be extracted and used as raw material for aluminum alloy production.

[0132] 2. Soluble salts in aluminum ash can be recycled to produce industrial-grade sodium chloride salt, aluminum alloy flux and other products.

[0133] 3. Harmful nitrogen in aluminum ash can be converted into ammonia water for recycling.

[0134] 4. Hydrogen generated when aluminum ash meets water can be used as a heat source.

[0135] 5. Alternative materials for alumina can be produced: recycled alumina, and its application fields cover refractory materials, abrasives, coatings, ceramic materials, raw materials for white cement, etc.

[0136] It is obvious to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention.

Claims

1. A harmless regeneration method for aluminum ash slag, characterized in that: The steps include: Step S1, pre-proportioning the aluminum ash slag so that the aluminum slag contains 25-55% aluminum, 2.8-10% magnesium, 0.8-5% silicon, 0.8-3.5% chlorine, 0.3-1.2% potassium, 0.8-2.2% sodium, 0.1-1% calcium, and 0.3-3.2% nitrogen; Step S2, adding low-temperature water at 3-30°C to aluminum ash slag for pulping, wherein the liquid-to-solid ratio of the pulping is 3-8:1, and adding a reaction inhibitor at a ratio of 1.8-6.2‰ during the pulping, wherein the reaction inhibitor forms a polymerized mucous film between the water and the metal surface; Step S3, putting the slurry into an extraction system, which includes a diameter expansion processing device, a diversion device and a screening device. The diameter expansion processing device is provided with grinding balls, and the aluminum ash material in the slurry is repeatedly crushed and impacted by the high-hardness grinding balls. The grinding balls rotate continuously for 15-60 minutes, and then enter the diversion device. Finally, the metal aluminum with a particle size less than 200 mesh is screened out by the screening device; Step S4, putting the slurry into a sorting device, wherein the sorting device is provided with a guide channel, wherein the guide channel has two or more diversion channels, wherein the two or more guide channels are arranged into a composite multiple spiral shape according to the magnetic field strength characteristics, and a mesh structure is interlaced in the middle of the guide channel, and the total length of the guide channel is 10-20 meters, and the slurry flows slowly in the guide channel, and the slurry removes the dyed metal oxide with the magnetic medium under the action of the high-intensity magnetic field; Step S5, placing the slurry and the catalyst into a denitrification reactor at the same time to react and remove nitrogen, the denitrification reactor adopts a horizontal cylindrical ball mill; Step S6: During the reaction process of the nitrogen removal reactor in step S5, a mixed gas is generated. The mixed gas includes ammonia, hydrogen and water vapor. The temperature of the mixed gas is 90-115°C. The mixed gas is cooled by heat exchange in the primary heat exchanger of the steam boiler and then enters the ammonia absorption tower. The ammonia absorption tower absorbs the ammonia into ammonia water with a concentration of 18-32%. The remaining hydrogen is used as the fuel gas source of the steam boiler. When the steam boiler is working, steam is generated. Part of the steam is used in the wastewater treatment device, and the excess steam is incorporated into the park. When the steam is stopped, the hydrogen enters the high-temperature phase-transition tunnel kiln and mixes with the natural gas to assist the combustion of the natural gas. Step S7, after the deamination reaction, the liquid-solid ratio of the slurry is 3-6:1, and then the slurry is placed in an ion separation device, and the ion separation device washes and separates the soluble salt in the slurry; Step S8, after ion separation, the water content of the slurry is 18-55%, and the slurry is dried to obtain a low-temperature regenerated alumina product; Step S9, pressing the material with a water content of 5-15% into bricks, stacking them on a kiln car, and transporting them into a tunnel kiln through the kiln car for roasting at a temperature of 1000-1400° C. for 10-20 hours. After high-temperature roasting, aluminum trihydrate is converted into α-Al2O3, and high-temperature roasting can remove residual anions in the material; Step S10: During high-temperature roasting, volatile chlorine and sulfate ions are generated. These gases are absorbed and dissolved by the circulating water spray of the exhaust tower as tail gas. When the circulating water concentration reaches the treatment standard, it is sent to the MVR wastewater treatment system for the recovery of chloride and sulfate. Step S11, after roasting and cooling, the alumina product with high purity and whiteness is obtained, which is then roughly crushed by a coarse crusher, and then put into a Raymond mill, and ground into a product with a particle size of 100-1200 mesh by the Raymond mill.

2. The harmless regeneration method of aluminum ash slag according to claim 1 is characterized in that: In step S3, the temperature of the extraction system is maintained below 15°C, and a temperature measurement, pH control device and an automatic temperature-controlled water replenishing device are provided in the extraction system to keep the pH value of the slurry below 10.

3. The harmless regeneration method of aluminum ash slag according to claim 1 is characterized in that: In step S3, the temperature of the extraction system is maintained below 25°C, and a temperature measurement, pH control device and an automatic temperature control water replenishment device are provided in the extraction system to keep the pH value of the slurry below 10.

4. The harmless regeneration method of aluminum ash slag according to claim 1 is characterized in that: In step S4, the magnetic flux of the guide channel in the sorting device is 20000-30000 Gauss.

5. The harmless regeneration method of aluminum ash slag according to claim 1 is characterized in that: In step S5, a spiral guide baffle with a height of 2 / 3 of the diameter is set inside the denitrification reactor, and high-aluminum grinding balls are installed in the denitrification reactor to drive the denitrification reactor to rotate continuously at a speed of 5-30 rpm, and the temperature during the deamination reaction is controlled at 60-110°C, the residence time of the slurry in the denitrification reactor is 30-75 minutes, and the particle size of the slurry after the deamination reaction increases to 300-600 mesh.

6. A harmless regeneration method for aluminum ash slag according to any one of claims 1 or 5, characterized in that: In step S5, under the action of the catalyst, the aluminum nitride and the metal aluminum in the slurry undergo the following reaction: S501, AlN+3H2O=Al(OH)3+NH3↑; S502, 2Al+6H2O→2Al(OH)3+3H2↑; S503, 2Al+2NaOH+2H2O=2NaAlO2+3H2↑.

7. The harmless regeneration method of aluminum ash slag according to claim 1 is characterized in that: In step S7, the ion separation device includes a high-speed centrifugal separation device, a filter press device and a vacuum filtration device; S701, the slurry first enters a high-speed centrifugal separation device, and is rotated at a high speed by the high-speed centrifugal separation device, and the speed is maintained at 3000-5000 rpm. The water in the slurry is thrown out under the action of the centrifuge, and the slurry is dehydrated into a filter residue with a water content of 20-30%. Then, low salt water is added to the filter residue for stirring and slurrying. The liquid-to-solid ratio of the slurry is 3-5:1, and the dissolution stirring time is 10-20 minutes; S702, input the slurry into a filter press device for filtration, the filter press device performs high pressure extrusion on the slurry, the pressure of which is 3-5Mpa, and the filtrate is discharged to obtain a filter residue, the water content of which is 30-40%, and then low salt water is added to the filter residue for stirring and slurrying, the liquid-to-solid ratio of the slurrying is 3-5:1, and the dissolution stirring time is 10-20 minutes; S703, inputting the slurry into a vacuum filtration device, which dehydrates the slurry under the action of atmospheric pressure to obtain filter residue, wherein the water content of the filter residue is 35-50%; S704, after separation by an ion separation device, a slurry with a soluble salt removal rate of more than 95% is obtained, and the filtrate obtained in the dehydration process is subjected to multi-stage washing by circulating water to obtain a salt water containing soluble salts; S705. The salt water is input into the MVR wastewater treatment system for evaporation and condensation treatment. The treated low-salt water will enter the ion separation equipment for repeated use. The salt substances will produce industrial-grade sodium chloride salt and aluminum alloy flux raw materials.

8. The harmless regeneration method of aluminum ash slag according to claim 1 is characterized in that: In step S8, the drying process includes the following two parts: S801, centrifugal spray drying; the slurry is pressurized and input into a centrifugal atomization drying device. The slurry is output from the nozzle of the centrifugal atomization drying device. As the nozzle rotates at high speed, the slurry is sprayed into mist-like mud droplets under the action of pressure and centrifugal force. At this time, the mud droplets are sprayed onto the hot flue of the hot blast furnace. The temperature of the hot flue is 550-800°C. The mud droplets are instantly dried into approximately spherical particles when in contact with the high temperature. The spherical particles are then cooled by a cooler at the bottom of the tower until the temperature drops to 40-100°C. At this time, the slurry is discharged, and the moisture content of the discharged material is reduced to 15-45%; S802. The granular material is input into the rotary drying device for further drying. The rotary drying device adopts a rotary kiln. The material is heated by the high temperature flame and rotary motion in the rotary kiln to evaporate the water. When the water content of the material drops to 5-15%, a discharging device is set to discharge the material. The discharged material will enter the next process. At the same time, some of the material will remain in the rotary kiln until it is dried to a water content of less than 0.5%, thereby obtaining a low-temperature regenerated alumina product.

9. The harmless regeneration method of aluminum ash slag according to claim 1, characterized in that: In step S9, the materials in the tunnel kiln will produce the following reactions: S901, NaAlO2+2H2O=Al(OH)3+NaOH; S902, 2Al(OH)3=Al2O3+3H2O; S903, 2NaOH = Na2O + H2O; S904, Al2O3→α-Al2O3; S905, C+O2=CO2.

10. The harmless regeneration method of aluminum ash slag according to claim 1, characterized in that: In step S11, a Raymond mill is used to grind products with particle sizes of 100-200 mesh, 200-250 mesh, 250-300 mesh, 300-500 mesh, 500-800 mesh, and 800-1200 mesh, respectively.

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