Method for preparing refractory raw material by utilizing innocent treatment of secondary aluminum ash

Abstract

The invention belongs to the technical field of refractory materials, and discloses a method for preparing a refractory raw material by utilizing harmless treatment of secondary aluminum ash, which comprises the following steps: selecting hazardous solid waste secondary aluminum ash rich in potassium, sodium, fluorine, chlorine and other harmful substances as a treatment object, grinding, sieving, mixing with sulfite paper pulp waste liquid, and pressing into a porous honeycomb aluminum ash standard brick. Preparing a refractory raw material through the processes of normal-temperature maintenance, heat treatment in a high-temperature nitrogen environment and the like; the technological process is simple, and during high-temperature heat treatment, fluorine, chlorine, potassium, sodium and other alkali ions contained in the aluminum ash are volatilized under the high-temperature driving effect; under the protection of nitrogen atmosphere, the binding capacity between alkali ions such as potassium and sodium and silicon oxide and aluminum oxide in the aluminum ash during volatilization is reduced, and the alkali ions are promoted to effectively escape, so that the alkali removal effect is achieved, and a harmless refractory raw material is obtained; the method is low in production cost, high in aluminum ash treatment efficiency, high in dealkalization rate and good in effect, secondary pollution caused in the aluminum ash treatment process is avoided, and the resource utilization level is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of refractory materials, and particularly relates to a method for preparing refractory raw materials by utilizing secondary aluminum ash harmless treatment. Background Art

[0002] Aluminum ash is a waste product of the aluminum industry. It is formed during the aluminum smelting, processing, and regeneration process by the oxidation of aluminum and the mixing of slag. The aluminum and its alloy content is 10-30%. The secondary aluminum ash after the metal aluminum is recovered mainly consists of Al, AlN, Al2O3, oxides of (Fe, Si, Mg) and chlorides of (K, Na, Ca, Mg). The aluminum oxide content is 20-40%, and it is powdery and gray-black. my country produces a large amount of aluminum ash every year. It is a hazardous waste listed in the "Catalogue of Hazardous Chemicals". Its main hazards are: (1) aluminum ash contains harmful substances such as fluoride and chloride, which pollute the environment; (2) aluminum ash stored in the open air will undergo hydration reaction due to the AlN contained in it, emitting a large amount of ammonia gas, polluting the air; (3) the storage of aluminum ash occupies a large amount of land, polluting the land.

[0003] Currently, there are two main methods for harmlessly treating aluminum ash: pyrolysis and hydrolysis. The pyrolysis method involves calcining the aluminum ash in a high-temperature kiln, causing the fluorine and chlorine contained in it to volatilize at high temperatures and the aluminum nitride and metallic aluminum to oxidize to form aluminum oxide, thereby removing hazardous waste from the aluminum ash. However, during this treatment process, alkali ions such as potassium and sodium preferentially bind to the silicon oxide and aluminum oxide in the aluminum ash, leaving most of them unremoved. This limits its use as a refractory raw material. While reports suggest that ammonium salt-based dealkalizers can be used to remove potassium and sodium, these methods suffer from low removal rates, high costs, and complex exhaust gas composition, which can easily corrode pipelines during discharge, impacting exhaust purification.

[0004] Chinese patents disclose a method for harmless aluminum ash treatment (CN110723746A), a method for harmless aluminum ash treatment (CN115959672A), and a method for secondary harmless aluminum ash utilization (CN109052445A). These methods all employ wet treatment methods, first washing the aluminum ash with water or acid, then removing harmful substances through leaching or chemical reactions to extract the desired useful substances. However, this process is complex and generates large amounts of wastewater and waste liquid, which can easily cause secondary pollution. Furthermore, the process is inefficient and costly, making large-scale aluminum ash treatment unsuitable.

[0005] Compared to the wet process, the dry process can completely remove harmful substances such as metallic aluminum, aluminum nitride, fluorine, and chlorine from secondary aluminum ash through high-temperature calcination. This process is simple and cost-effective. However, alkaline ions such as potassium and sodium are difficult to effectively remove. The key to its resource utilization is to effectively remove potassium and sodium from aluminum ash during pyrometallurgical treatment and apply it as a refractory raw material in the refractory materials industry. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a method for preparing refractory raw materials by harmlessly treating secondary aluminum ash. Secondary industrial aluminum ash, which is a hazardous solid waste rich in harmful substances such as potassium, sodium, fluorine and chlorine, is selected as the treatment object. The bricks are pressed into porous honeycomb aluminum ash standard bricks after being ground, screened and mixed with sulfite pulp waste liquid. The bricks are then cured at room temperature and heat treated in a high-temperature nitrogen environment. The high temperature promotes the escape of fluorine, chlorine, potassium and sodium contained in the secondary aluminum ash. The protective atmosphere provided by nitrogen is used to reduce the binding ability between alkali ions such as potassium and sodium and silicon oxide and aluminum oxide in the aluminum ash when they volatilize, thereby promoting the effective escape of alkali ions, and promoting their discharge and removal, thereby achieving the de-alkali effect and obtaining a harmless refractory raw material.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: a method for preparing refractory raw materials by using secondary aluminum ash harmless treatment, which specifically includes the following steps: Step 1: Weigh a certain weight of secondary aluminum ash powder and put it into a ball mill equipped with alumina grinding balls for fine grinding. After 3 to 5 hours, stop the machine, sieve, and take the sieve-free material for use; Step 2: Place the sieved secondary aluminum ash in a blender and add a binder while stirring. The amount of binder added is 4-5% of the weight of the secondary aluminum ash. After 5 minutes, the materials are evenly mixed and then discharged. Step 3: Place the mixed materials into a special steel mold and use a hydraulic press to press and shape them into aluminum gray standard bricks; then place them in an air environment and cure at room temperature for 24 hours; Step 4: Place the aluminum ash standard brick after curing in a nitrogen atmosphere furnace, then close the air inlet valve and exhaust valve connected to the furnace chamber to form a closed system, start to evacuate the furnace chamber, stop evacuating after the pressure reaches -0.1Pa, open the air inlet valve and start to introduce nitrogen until the pressure reaches 1.0×10 5 After Pa, open the exhaust valve and continue to introduce nitrogen to maintain the nitrogen atmosphere in the furnace chamber and stabilize it at normal pressure; heat at a heating rate of 5℃ / min, and stop heating after heating to 1400~1500℃, and keep warm for 3 hours; then turn off the heating system and let the furnace cool naturally. When the temperature drops to 1000℃, stop introducing nitrogen and wait until it is completely cooled to room temperature to produce the refractory raw material.

[0008] Among them, the main chemical components of secondary aluminum ash are Al2O3≥60%, SiO2≤8%, CaO≤1.5%, MgO≤2.5%, Na2O+K2O≤8%, and F+Cl≤20%.

[0009] Wherein, the particle size of the secondary aluminum ash in step 1 is finely ground to -100 mesh.

[0010] Among them, the binder in step 2 uses a specific gravity of 1.05-1.1g / cm 3 of sulfite pulp waste liquor.

[0011] Among them, the machine pressing pressure in step 3 is 100 MPa; and the aluminum ash standard bricks with a size of 300×150×65 mm are made.

[0012] Among them, the steel mold structure in step three is a rectangular array composed of 36 φ20mm circular steel columns on the mold base, which forms an aluminum ash standard brick with a porous honeycomb structure after machine pressing.

[0013] Among them, in step 4, the nitrogen flow rate is controlled within the range of 50~150L / h by using a nitrogen flow meter connected to the intake valve; when the heating temperature reaches between 800-1400℃, the nitrogen flow rate is adjusted to 100-150 L / h, and in the remaining stages, the nitrogen flow rate is adjusted to 50-100 L / h.

[0014] According to the composition of secondary aluminum ash, the high-aluminum material after dealkalization treatment can be directly used as a refractory raw material to prepare refractory materials, and can also be used to synthesize other refractory raw materials, such as spinel, cordierite, etc.

[0015] During secondary aluminum ash treatment, while the commonly used oxygen-enriched calcination effectively removes aluminum nitride, promotes the oxidation of metallic aluminum to aluminum oxide, and promotes the volatilization of harmful substances such as fluorine and chlorine, the alkali metal ions, such as potassium and sodium, contained in the aluminum ash are only partially removed at high temperatures. This is because, under high-temperature oxidizing conditions, these alkali metal ions have a strong affinity and strong binding capacity with the silicon oxide and aluminum oxide in the aluminum ash, easily forming sodium silicate glass or β-alumina, making them difficult to effectively remove.

[0016] The working mechanism of this invention primarily utilizes heat treatment under a high-temperature nitrogen atmosphere to promote the removal of harmful substances such as fluorine, chlorine, potassium, and sodium from secondary aluminum ash through decomposition, evaporation, and volatilization. By controlling the nitrogen atmosphere, the high-temperature volatilization of potassium and sodium reduces their ability to bind to silicon oxide and aluminum oxide, accelerating their escape process and thus improving their removal rate. Utilizing this principle, by designing an appropriate treatment temperature and nitrogen atmosphere, the efficient removal of harmful substances from secondary aluminum ash is promoted.

[0017] The present invention mixes secondary aluminum ash and sulfite pulp waste liquid and presses the mixture into porous honeycomb-shaped aluminum ash standard bricks. The porous honeycomb shape provides a channel for removing impurities in the secondary aluminum ash, and promotes the removal of harmful substances in the secondary aluminum ash through decomposition, evaporation, volatilization, etc. The aluminum ash standard bricks are made to facilitate the stacking of secondary aluminum ash on a kiln car during sintering, thereby improving production efficiency. The added sulfite pulp waste liquid is used as a binder to make the aluminum ash bricks, thereby increasing the uniformity and adhesion of the mixture, reducing the moisture content of the mixture and the energy consumption during drying, and simultaneously improving the plasticity of the aluminum ash standard brick body and the strength of the body after drying, thereby reducing the scrap rate in production and improving various properties of the refractory raw materials after the aluminum ash standard bricks are fired.

[0018] The potassium and sodium in secondary aluminum ash exist mainly in the form of chloride and fluoride. The melting point of sodium chloride is 801℃ and the decomposition temperature is 1080℃. Therefore, it can be assumed that potassium and sodium begin to volatilize after 800℃. Fluorine and chlorine also volatilize in large quantities at this stage. After treatment at 1100℃, harmful substances such as fluorine and chlorine can be basically completely removed. According to experimental results, the loss of sodium is the largest between 800-1400℃. Therefore, the nitrogen flow rate can be increased to 100-150L / h in this range; at higher temperatures such as 1400℃, volatilization will decrease, and the nitrogen flow rate can be reduced at this time; the nitrogen flow rate is adjusted according to different removal stages to reduce production costs, increase the dealkalization rate, avoid secondary pollution during the secondary aluminum ash treatment process, and improve the level of resource utilization.

[0019] The beneficial effects of the present invention are as follows: the present invention selects secondary industrial aluminum ash as solid waste, grinds, sieves, and mixes with sulfite pulp waste liquid, presses it into porous honeycomb aluminum ash standard bricks, cures it at room temperature, and then performs high-temperature nitriding heat treatment to produce refractory raw materials. By heat-treating the secondary aluminum ash under a high-temperature nitrogen atmosphere, the high temperature promotes the escape of fluorine, chlorine, potassium, and sodium contained in the secondary aluminum ash; the protective atmosphere provided by nitrogen is used to hinder the combination of potassium and sodium with silicon oxide, aluminum oxide, etc., promote their emission and removal, and obtain a harmless refractory raw material after efficient dealkalization. The treatment process is simple, and the nitrogen flow rate can be adjusted according to different removal stages. The production cost is low, the dealkalization rate is high, and secondary pollution caused by the secondary aluminum ash treatment process is avoided, thereby improving the level of resource utilization. The aluminum ash treated by the present invention is tested to obtain: Na2O+K2O≤0.5%, and no F and Cl are detected. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic top view of the inner cavity of the steel mold of the present invention; Figure 2 This is a diagram showing the composition changes of the secondary aluminum ash after heat treatment under nitrogen. DETAILED DESCRIPTION

[0021] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0022] To avoid repetition, the raw materials involved in this specific implementation method are first described in a unified manner and will not be repeated in the examples: the main chemical components of the secondary aluminum ash used are Al2O3: 65.81%, SiO2: 3.96%, CaO: 0.68%, MgO: 2.23%, Fe2O3: 0.22%, K2O: 0.48%, Na2O: 6.94%, F: 17.44%, Cl: 2.24%.

[0023] The top view of the inner cavity of the special steel mold used in this specific embodiment is as follows Figure 1 As shown in the figure, 36 φ20mm circular steel columns are fixed on the steel mold base and arranged in a rectangular array. The horizontal or vertical vertical distance between the center outer edge of the steel column on the periphery of the array and the outer edge of the mold is 20mm, and the vertical distance between the center outer edges of two adjacent steel columns is 10mm. When the machine is pressed, a porous honeycomb structure aluminum ash standard brick is formed. Example 1

[0024] A method for preparing refractory raw materials by using secondary aluminum ash harmless treatment comprises the following steps: Step 1: Weigh a certain weight of secondary aluminum ash powder and put it into a ball mill equipped with alumina grinding balls for fine grinding. After 3 to 5 hours, stop the machine, pass it through a -100 mesh sieve, and take the sieve-less material for later use; Step 2: Place the sieved secondary aluminum ash into the mixer and add the aluminum ash with a specific gravity of 1.05-1.1g / cm 3 The sulfite pulp waste liquid is added in an amount of 4%; after 5 minutes, the materials are mixed evenly and then discharged; Step 3: Place the mixed materials into a special steel mold and use a hydraulic press to press and form them at a molding pressure of 100 MPa to produce a porous honeycomb aluminum ash standard brick with a size of 300×150×65 mm; then take it out and place it in an air environment for room temperature curing for 24 hours; Step 4: Place the aluminum ash standard brick after curing in a nitrogen atmosphere furnace, then close the air inlet valve and exhaust valve connected to the furnace chamber to form a closed system and start vacuuming the furnace. Stop vacuuming after the pressure reaches -0.1 Pa, open the air inlet valve and start introducing nitrogen until the pressure reaches 1.0×10 5After Pa, open the exhaust valve and continue to introduce nitrogen at a nitrogen flow rate of 50L / h to maintain the nitrogen atmosphere in the furnace chamber and stabilize it at normal pressure; heat at a heating rate of 5℃ / min, adjust the nitrogen flow rate to 100L / h after reaching 800℃, and adjust the nitrogen flow rate to 80L / h after reaching 1400℃. Stop heating after reaching 1400℃ and maintain this temperature for 3 hours; then turn off the heating system and let the furnace cool naturally. When the cooling temperature drops to 1000℃, stop inputting nitrogen until it is completely cooled to room temperature to prepare the refractory raw material.

[0025] The chemical composition of the sample was detected as Al2O3: 89.53%, SiO2: 4.34%, CaO: 1.05%, MgO: 2.71%, Fe2O3: 0.39%, K2O: 0.06%, and Na2O: 0.42%. Example 2

[0026] A method for preparing refractory raw materials by using secondary aluminum ash harmless treatment comprises the following steps: Step 1: Weigh a certain weight of secondary aluminum ash powder and put it into a ball mill equipped with alumina grinding balls for fine grinding. After 3 to 5 hours, stop the machine, pass it through a -100 mesh sieve, and take the sieve-less material for later use; Step 2: Place the sieved secondary aluminum ash into the mixer and add the aluminum ash with a specific gravity of 1.05-1.1g / cm 3 The sulfite pulp waste liquid is added in an amount of 5%; after 5 minutes, the materials tend to be mixed evenly and then discharged; Step 3: Place the mixed materials into a special steel mold and use a hydraulic press to press and form them at a molding pressure of 100 MPa to produce a porous honeycomb aluminum ash standard brick with a size of 300×150×65 mm; then take it out and place it in an air environment for room temperature curing for 24 hours; Step 4: Place the aluminum ash standard brick after curing in a nitrogen atmosphere furnace, then close the air inlet valve and exhaust valve connected to the furnace chamber to form a closed system and start vacuuming the furnace. Stop vacuuming after the pressure reaches -0.1 Pa, open the air inlet valve and start introducing nitrogen until the pressure reaches 1.0×10 5 After Pa, open the exhaust valve and continue to introduce nitrogen at a nitrogen flow rate of 80L / h to maintain the nitrogen atmosphere in the furnace chamber and stabilize it at normal pressure; heat at a heating rate of 5℃ / min, adjust the nitrogen flow rate to 120L / h after reaching 800℃, adjust the nitrogen flow rate to 100L / h after reaching 1400℃, and stop heating after reaching 1450℃, and maintain this temperature for 3 hours; thereafter, turn off the heating system and let the furnace cool naturally. When the cooling temperature drops to 1000℃, stop inputting nitrogen until it is completely cooled to room temperature, and the refractory raw material is thus prepared.

[0027] The chemical composition of the sample was detected as Al2O3: 90.59%, SiO2: 4.24%, CaO: 0.96%, MgO: 2.76%, Fe2O3: 0.28%, K2O: 0.06%, and Na2O: 0.38%. Example 3

[0028] A method for preparing refractory raw materials by using secondary aluminum ash harmless treatment comprises the following steps: Step 1: Weigh a certain weight of secondary aluminum ash powder and put it into a ball mill equipped with alumina grinding balls for fine grinding. After 3 to 5 hours, stop the machine, pass it through a -100 mesh sieve, and take the sieve-less material for use; Step 2: Place the sieved secondary aluminum ash into the mixer and add the aluminum ash with a specific gravity of 1.05-1.1g / cm 3 The sulfite pulp waste liquid was added in an amount of 4.5%; after 5 minutes, the materials tended to be mixed evenly and then discharged; Step 3: Place the mixed materials into a special steel mold and use a hydraulic press to press and form them at a molding pressure of 100 MPa to produce a porous honeycomb aluminum ash standard brick with a size of 300×150×65 mm; then take it out and place it in an air environment for room temperature curing for 24 hours; Step 4: Place the aluminum ash standard brick after curing in a nitrogen atmosphere furnace, then close the air inlet valve and exhaust valve connected to the furnace chamber to form a closed system and start vacuuming the furnace. Stop vacuuming after the pressure reaches -0.1 Pa, open the air inlet valve and start introducing nitrogen until the pressure reaches 1.0×10 5 After Pa, open the exhaust valve and continue to introduce nitrogen at a nitrogen flow rate of 100L / h to maintain the nitrogen atmosphere in the furnace chamber and stabilize it at normal pressure; heat at a heating rate of 5℃ / min, adjust the nitrogen flow rate to 150L / h after reaching 800℃, adjust the nitrogen flow rate to 50L / h after reaching 1400℃, and stop heating after reaching 1500℃, and maintain this temperature for 3 hours; thereafter, turn off the heating system and let the furnace cool naturally. When the cooling temperature drops to 1000℃, stop inputting nitrogen until it is completely cooled to room temperature, and the refractory raw material is thus prepared.

[0029] The chemical composition of the sample was detected as Al2O3: 90.20%, SiO2: 4.06%, CaO: 1.07%, MgO: 2.45%, Fe2O3: 0.28%, K2O: 0.04%, and Na2O: 0.31%.

[0030] After secondary aluminum ash is treated in high temperature nitrogen atmosphere, its composition changes as follows Figure 2 The comparison of the chemical composition content in the secondary aluminum ash and the samples of Examples 1-3 is shown in the following table: Comparison of chemical composition before secondary aluminum ash treatment and after treatment in Examples 1-3 (wt%)

Claims

1. A method for preparing refractory raw materials by using secondary aluminum ash harmless treatment, characterized in that: Secondary aluminum ash rich in harmful substances such as potassium, sodium, fluorine, and chlorine is selected and ground, sieved, mixed with sulfite pulp waste liquid, and then pressed into porous honeycomb aluminum ash standard bricks. The refractory raw materials are made through processes such as normal temperature curing and heat treatment in a high-temperature nitrogen environment. The specific steps include: Step 1: Weigh a certain weight of secondary aluminum ash powder and put it into a ball mill equipped with alumina grinding balls for fine grinding. After 3 to 5 hours, stop the machine, sieve, and take the sieve-free material for use; Step 2: Place the sieved secondary aluminum ash in a blender and add a binder while stirring. The amount of binder added is 4-5% of the weight of the secondary aluminum ash. After 5 minutes, the materials are evenly mixed and then discharged. Step 3: Place the mixed materials into a special steel mold and use a hydraulic press to press and shape them into aluminum ash standard bricks. After taking them out, place them in an air environment and cure them at room temperature for 24 hours. Step 4: Place the aluminum ash standard brick after curing in a nitrogen atmosphere furnace, then close the air inlet valve and exhaust valve connected to the furnace chamber to form a closed system, start to evacuate the furnace chamber, stop evacuating after the pressure reaches -0.1Pa, open the air inlet valve and start to introduce nitrogen until the pressure reaches 1.0×10 5 After Pa, open the exhaust valve and continue to introduce nitrogen to maintain the nitrogen atmosphere in the furnace chamber and stabilize it at normal pressure; heat at a heating rate of 5℃ / min, and stop heating after heating to 1400~1500℃, and keep warm for 3 hours; then turn off the heating system and let the furnace cool naturally. When the temperature drops to 1000℃, stop introducing nitrogen and wait until it is completely cooled to room temperature to produce the refractory raw material.

2. The method for preparing refractory raw materials by using secondary aluminum ash harmless treatment according to claim 1, characterized in that: The main chemical components of secondary aluminum ash are Al2O3≥60%, SiO2≤8%, CaO≤1.5%, MgO≤2.5%, Na2O+K2O≤8%, F+Cl≤20%.

3. The method for preparing refractory raw materials by using secondary aluminum ash harmless treatment according to claim 1, characterized in that: In step 1, the particle size of the secondary aluminum ash is finely ground to -100 mesh.

4. The method for preparing refractory raw materials by using secondary aluminum ash harmless treatment according to claim 1, characterized in that: The binder in step 2 has a specific gravity of 1.05-1.1 g / cm 3 of sulfite pulp waste liquor.

5. The method for preparing refractory raw materials by using secondary aluminum ash harmless treatment according to claim 1, characterized in that: In step 3, the machine pressing pressure is 100 MPa; aluminum ash standard bricks with a size of 300×150×65 mm are produced.

6. The method for preparing refractory raw materials by using secondary aluminum ash harmless treatment according to claim 1, characterized in that: In step 3, the steel mold structure is a rectangular array consisting of 36 φ20mm circular steel columns on the mold base, which forms an aluminum gray standard brick with a porous honeycomb structure after machine pressing.

7. The method for preparing refractory raw materials by using secondary aluminum ash harmless treatment according to claim 1, characterized in that: In step 4, the nitrogen flow meter connected to the intake valve is used to control the nitrogen flow rate to be within the range of 50~150 L / h.

8. The method for preparing refractory raw materials by using secondary aluminum ash harmless treatment according to claim 7, characterized in that: When the heating temperature reaches 800-1400℃, adjust the nitrogen flow rate to 100-150L / h. In the remaining stages, adjust the nitrogen flow rate to 50-100 L / h.

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