Method for simultaneously removing sodium and potassium in aluminum and chromium residue dust by mild hydrothermal method of carbide slag

Abstract

The application discloses a method for simultaneously removing sodium and potassium in aluminum-chromium residue dust by mild hydrothermal method, and belongs to the technical field of industrial solid waste resource utilization. The method comprises the following steps: collecting aluminum-chromium residue dust generated in the preparation of metal chromium by the aluminum thermal method; fully dissolving calcium carbide waste residue generated in the preparation of polyvinyl chloride or vinyl acetate products by the calcium carbide acetylene method in water to prepare a calcium carbide residue aqueous solution; adding the aluminum-chromium residue dust into the calcium carbide residue aqueous solution, uniformly mixing, and then transferring into a reaction kettle; continuously stirring and heating the reaction kettle, opening the cooling water after heat preservation, cooling the reaction slurry, filtering, solid-liquid separation, washing the obtained filter cake with hot water, suction filtration, and drying. The method can fully utilize the calcium carbide residue solid waste, simultaneously reduce the Na and K in the aluminum-chromium residue dust, meet the use requirements of chromium corundum high-grade refractory materials, and provide a new way for low-pollution emission and high-value resource utilization of the aluminum-chromium residue dust and the calcium carbide residue.

Description

Technical Field

[0001] This invention belongs to the field of industrial solid waste resource utilization technology, and relates to a method for simultaneously removing sodium and potassium from aluminum chromium slag dust using a mild hydrothermal method with calcium carbide slag. Background Technology

[0002] Metallic chromium is an important alloying element, mainly used in the preparation of high-temperature alloys, resistance alloys, precision alloys, and other non-ferrous alloys. The aluminothermic process for producing metallic chromium uses metallic aluminum as a reducing agent to reduce chromium from chromium trioxide. Due to the vigorous reaction, a significant amount of aluminum-chromium slag dust is generated around the reactor and at the end of the dust removal system. Furthermore, a considerable amount of aluminum-chromium slag dust is also generated during the crushing of the lumpy aluminum-chromium slag. Aluminum-chromium slag has a high alumina content and contains a certain amount of chromium oxide, making it widely used in the refractory materials field. In the non-ferrous metallurgy field, after sorting and crushing, aluminum-chromium slag, combined with various auxiliary materials, can be pressed and fired to produce chromium corundum bricks, used in zinc smelting kilns. In the iron and steel metallurgy field, aluminum-chromium slag can be used to produce blast furnace tapping trough castables, medium-frequency furnace ramming materials, and permeable bricks. Currently, aluminum-chromium slag has achieved certain successes in both non-ferrous and iron and steel metallurgy, but some problems have also been encountered during its use. The aluminum-chromium slag dust generated in the above process contains high levels of alkali metal oxides such as Na₂O and K₂O. Excessive levels of these oxides severely affect the quality of refractory materials, including their refractoriness, strength, and service life. Therefore, refractory material manufacturers strictly limit the Na₂O and K₂O content in aluminum-chromium slag. This results in large-scale stockpiling of dust with excessive Na₂O and K₂O content, causing continuous harm to the environment and human health, while also impacting the economic benefits and storage costs of chromium production enterprises. Therefore, how to achieve low-cost and high-efficiency dealkali treatment of aluminum-chromium slag dust has become a key technology for expanding its utilization rate.

[0003] Calcium carbide slag mainly originates from the production of polyvinyl chloride (PVC) and vinyl acetate using the calcium carbide process. Approximately 1.45 tons of calcium carbide are consumed to produce 1 ton of PVC or vinyl acetate, and the hydrolysis of each ton of calcium carbide produces over 1 ton of calcium carbide slag. Therefore, the production of 1 ton of PVC or vinyl acetate results in the discharge of over 2 tons of calcium carbide slag. The large quantity of calcium carbide slag, if discharged untreated, will clog sewers, accumulate in riverbeds, and harm fisheries. On land, it occupies land and pollutes the environment. If calcium carbide slag solid waste can be fully utilized, and sodium and potassium can be simultaneously removed from aluminum-chromium slag dust, a new approach can be provided for the low-pollution emission and high-value resource utilization of both aluminum-chromium slag dust and calcium carbide slag, thereby achieving the goal of treating waste with waste and synergistic resource utilization of multiple solid wastes.

[0004] Therefore, how to develop a method for the simultaneous removal of sodium and potassium from aluminum chromium slag dust using a gentle hydrothermal process with carbide slag is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method for simultaneously removing sodium and potassium from aluminum chromium slag dust using a mild hydrothermal method with carbide slag.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for simultaneously removing sodium and potassium from aluminum chromium slag dust using a gentle hydrothermal process with carbide slag includes the following steps:

[0008] (1) Collect the aluminum chromium slag dust generated during the aluminothermic process for the preparation of metallic chromium for later use;

[0009] (2) Dissolve the calcium carbide waste residue generated during the preparation of polyvinyl chloride or vinyl acetate products by the calcium carbide acetylene method in water to prepare a calcium carbide waste residue aqueous solution;

[0010] (3) Add the aluminum chromium slag dust from step (1) to the calcium carbide slag aqueous solution from step (2), mix thoroughly and evenly, and then transfer to the reactor;

[0011] (4) The reactor is continuously stirred and heated. After the temperature is maintained, the cooling water is turned on to cool the reaction slurry.

[0012] (5) After the reaction slurry in step (4) is cooled down, it is filtered while hot and the solid and liquid are separated. The resulting filter cake is washed with hot water, then filtered and dried.

[0013] Furthermore, the aluminum-chromium slag dust is one or a mixture of several of the following: dust generated near the furnace mouth during the aluminothermic process for preparing metallic chromium, dust collected by the dust removal system, or dust generated during the crushing of blocky aluminum-chromium slag.

[0014] Furthermore, the aluminum chromium slag dust and calcium carbide waste do not require additional treatment to meet the required particle size requirement of ≤150 mesh and can be used directly.

[0015] Furthermore, the concentration of the calcium carbide slag aqueous solution in step (2) is 16-20 wt%, and the mass ratio of aluminum chromium slag dust to calcium carbide slag aqueous solution in step (3) is 1:(5-7).

[0016] The beneficial effects of adopting the above-mentioned further technical solutions are: ensuring a suitable concentration of carbide slag, and guaranteeing the effectiveness and efficiency of subsequent treatment.

[0017] Limiting the mass ratio of aluminum chromium slag dust to calcium carbide slag aqueous solution ensures an appropriate proportion of Ca(OH)2 concentration introduced from the aluminum chromium slag dust and calcium carbide slag. This avoids both excessive introduction of impurities from calcium carbide slag and insufficient calcium carbide slag, which would prevent inefficient replacement of insoluble alkali.

[0018] Furthermore, the chemical composition of the aluminum chromium slag dust is required to be Al2O3 ≥ 80wt%, Cr2O3 ≥ 13wt%, CaO ≤ 0.30wt%, Fe2O3 ≤ 0.30wt%, MgO ≤ 0.30wt%, and SiO2 ≤ 0.30wt%, while the chemical composition of the carbide slag is required to be CaO ≥ 70wt%, Fe2O3 ≤ 0.30wt%, MgO ≤ 0.30wt%, and SiO2 ≤ 1.30wt%.

[0019] The beneficial effects of adopting the above-mentioned further technical solutions are: limiting the chemical composition requirements of aluminum-chromium slag dust can expand the sources of aluminum-chromium slag dust to be treated and make its initial composition meet the requirements for the use of chromium corundum refractory materials.

[0020] Limiting the chemical composition requirements of carbide slag ensures sufficient calcium source to meet treatment concentration requirements, while avoiding excessive impurities that could affect the quality of chromium corundum refractory materials.

[0021] Furthermore, in step (4), the heating rate of the reactor is 5℃ / min, the temperature is raised to 160~180℃, the holding time is 90~120min, the stirring rate is 200 rpm, and the reaction pressure is 0.20~0.40MPa.

[0022] The beneficial effects of adopting the above-mentioned further technical solution are: within this treatment condition range, the structure of insoluble bases (sodium and potassium) can be efficiently destroyed, allowing Na and K to enter the solution. This provides a prerequisite for subsequent removal.

[0023] Furthermore, in step (5), when the reaction slurry from step (4) is cooled to 85-95°C, hot filtration and solid-liquid separation are started, and the resulting filter cake is washed 3-5 times with hot water at 85-95°C, then filtered and dried until the water content is less than 3wt%.

[0024] The beneficial effects of adopting the above-mentioned further technical solution are: ensuring that sodium and potassium ions entering the hot aqueous solution are fully washed away and avoided from being adsorbed. This is because when the aqueous solution temperature is low, Na and K in the solution will revert to the formation of insoluble alkalis, affecting the removal efficiency.

[0025] Furthermore, in step (5), the mass ratio of hot water to filter cake used for each wash is (1.5~2.5):1.

[0026] Furthermore, the liquid phase after solid-liquid separation in step (5) and the liquid phase obtained after washing and filtration are collected in a unified manner. After being adsorbed by Tulsimer T-42H strong acid cation exchange resin, the liquid phase can be returned to step (2) or step (5) for recycling.

[0027] The beneficial effects of adopting the above-mentioned further technical solutions are: saving water costs and achieving water recycling.

[0028] Furthermore, the chemical composition of the aluminum-chromium slag obtained after drying in step (5) is Al2O3≥80wt%, Cr2O3≥13wt%, CaO+MgO≤4.50wt%, Fe2O3≤0.45wt%, SiO2≤0.50wt%, Na2O≤0.25wt%, K2O≤0.75wt%, which meets the requirements for the composition of chromium corundum advanced refractory materials.

[0029] The beneficial effects of adopting the above-mentioned further technical solutions are: ensuring that the composition requirements for high-grade chromium corundum refractory materials are met.

[0030] The beneficial effects of this invention are as follows: This invention utilizes a low-temperature, low-pressure hydrothermal method with calcium carbide slag to simultaneously remove Na₂O and K₂O from aluminum-chromium slag dust. Its advantages lie in the relatively mild temperature and pressure conditions, which allow for full utilization of calcium carbide slag solid waste, reducing Na₂O to below 0.25% and K₂O to below 0.75% in the aluminum-chromium slag dust, meeting the requirements for use in high-grade chromium corundum refractory materials. Simultaneously, the aqueous solvent in the reaction medium can be recycled within the system, making it highly operable for industrial implementation with low operating costs. This process achieves energy conservation, emission reduction, and high-value utilization of aluminum-chromium slag dust, representing a dealkali treatment process with low-cost, large-scale industrial application prospects. The Na₂O removal rate reaches over 90%, and the K₂O removal rate reaches over 70%.

[0031] The technical concept of this invention is as follows: Potassium and sodium in aluminum chromium slag dust exist in both insoluble and soluble alkali forms. Soluble alkalis can be removed by water leaching, while insoluble alkalis are very difficult to remove by water leaching and are the main forms of Na and K in aluminum chromium slag dust. Calcium carbide slag contains abundant calcium resources, which can continuously provide Ca in solution. 2+ Calcium ions can form precipitates with basic anions, thereby displacing sodium and potassium ions from insoluble bases and releasing them into the solution, where they are removed through solid-liquid separation and repeated washing. Its displacement effect is similar to that of Ca... 2+ The effects of ion concentration (amount of calcium carbide slag added, mass ratio of calcium carbide slag solution to aluminum chromium slag dust), temperature, system pressure, and washing method are closely related. This invention, under mild hydrothermal reaction conditions (temperature range 160–180℃, holding time 90–120 min, system reaction pressure 0.20–0.40 MPa, and washing hot water temperature 85–95℃), uses calcium carbide slag solid waste as a calcium source. This effectively disposes of calcium carbide slag solid waste and removes potassium and sodium from aluminum chromium slag dust, achieving synergistic high-value utilization of multiple solid wastes. Attached Figure Description

[0032] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1

[0035] A method for simultaneously removing sodium and potassium from aluminum-chromium slag dust using a gentle hydrothermal process with carbide slag includes the following steps:

[0036] (1) First, mix the dust generated near the furnace mouth during the aluminothermic process for preparing metallic chromium with the dust collected by the dust removal system and set aside. Then, fully dissolve the calcium carbide waste residue generated during the calcium carbide-acetylene process for preparing polyvinyl chloride and vinyl acetate products in water to prepare a calcium carbide slag aqueous solution with a concentration of 18wt%.

[0037] Main raw material composition: The content of each component of the aluminum chromium slag dust obtained after uniform mixing is as follows: Cr2O3 13.42wt%, Al2O3 80.64wt%, CaO 0.15wt%, SiO2 0.26wt%, Fe2O3 0.15wt%, MgO 0.13wt%, Na2O 2.48wt%, K2O 2.53wt%, and others 0.24wt%.

[0038] The main components of the calcium carbide waste residue are: CaO 71.28 wt%, Fe2O3 0.15 wt%, MgO 0.16 wt%, SiO2 1.22 wt%, Al2O3 1.75 wt%, moisture content 24.23 wt%, and other components 1.21 wt%.

[0039] (2) Add the well-mixed aluminum-chromium slag dust from step (1) to the calcium carbide slag aqueous solution prepared in step (1). The mass ratio of aluminum-chromium slag dust to calcium carbide slag aqueous solution is 1:5. After thorough mixing, transfer the mixture to a reactor. Then, heat the mixture to 170°C at a rate of 5°C / min and hold it at that temperature for 100 min. The stirring rate is 200 rpm throughout the process, and the system reaction pressure is maintained at 0.30 MPa. After the holding time is up, turn on the cooling water to cool the mixture down and open the pressure relief valve to release the system pressure. Stop stirring during the cooling process. When the temperature of the reaction slurry drops to 90°C, open the reactor, filter the mixture while it is still hot, and perform solid-liquid separation. Wash the resulting filter cake four times with hot water at 90°C. The mass ratio of hot water used for each wash to the mass of the filter cake is 2.0:1. After washing, filter the mixture and dry it until the water content is less than 3 wt%, thus obtaining the de-alkali aluminum-chromium slag.

[0040] (3) The liquid phase after solid-liquid separation and the liquid phase obtained after washing and filtration are adsorbed by Tulsimer T-42H strong acid cation exchange resin and can be returned to the previous process that requires water solvent for recycling.

[0041] (4) The aluminum-chromium slag dust obtained after drying contains 13.51 wt% Cr2O3, 80.58 wt% Al2O3, 4.05 wt% CaO, 0.49 wt% SiO2, 0.14 wt% Fe2O3, 0.14 wt% MgO, 0.22 wt% Na2O, 0.74 wt% K2O, and 0.12 wt% other components. The removal rate of Na2O reaches 91.13%, and the removal rate of K2O reaches 70.75%.

[0042] Example 2

[0043] A method for simultaneously removing sodium and potassium from aluminum-chromium slag dust using a gentle hydrothermal process with carbide slag includes the following steps:

[0044] (1) First, mix the dust generated near the furnace mouth during the aluminothermic process for preparing metallic chromium and the dust collected during the crushing of blocky aluminum-chromium slag evenly for later use. Then, fully dissolve the calcium carbide waste residue generated during the calcium carbide-acetylene process for preparing polyvinyl chloride and vinyl acetate products in water to prepare a calcium carbide slag aqueous solution with a concentration of 20wt%.

[0045] Main raw material composition: The content of each component of the aluminum chromium slag dust obtained after uniform mixing is as follows: Cr2O3 13.71 wt%, Al2O3 80.52 wt%, CaO 0.14 wt%, SiO2 0.22 wt%, Fe2O3 0.14 wt%, MgO 0.14 wt%, Na2O 2.50 wt%, K2O 2.51 wt%, and others 0.22 wt%.

[0046] The main components of the calcium carbide waste residue are: CaO 70.32 wt%, Fe2O3 0.16 wt%, MgO 0.18 wt%, SiO2 1.24 wt%, Al2O3 1.86 wt%, moisture content 24.91 wt%, and other components 1.33 wt%.

[0047] (2) Add the well-mixed aluminum-chromium slag dust from step (1) to the calcium carbide slag aqueous solution prepared in step (1). The mass ratio of aluminum-chromium slag dust to calcium carbide slag aqueous solution is 1:6. After thorough mixing, transfer the mixture to a reactor. Then, heat the mixture to 180°C at a rate of 5°C / min and hold it at that temperature for 90 min. The stirring rate throughout the process is 200 rpm, and the system reaction pressure is maintained at 0.40 MPa. After the holding time is up, turn on the cooling water to cool the mixture down and open the pressure relief valve to release the system pressure. Stop stirring during the cooling process. When the temperature of the reaction slurry drops to 95°C, open the reactor, filter the mixture while it is still hot, and perform solid-liquid separation. Wash the resulting filter cake three times with hot water at 95°C. The mass ratio of hot water used for each wash to the mass of the filter cake is 2.5:1. After washing, filter the mixture and dry it until the water content is less than 3 wt%, thus obtaining the de-alkali aluminum-chromium slag.

[0048] (3) The liquid phase after solid-liquid separation and the liquid phase obtained after washing and filtration are adsorbed by Tulsimer T-42H strong acid cation exchange resin and can be returned to the previous process that requires water solvent for recycling.

[0049] (4) The aluminum-chromium slag dust obtained after drying contains 13.67 wt% Cr2O3, 80.46 wt% Al2O3, 4.16 wt% CaO, 0.41 wt% SiO2, 0.13 wt% Fe2O3, 0.13 wt% MgO, 0.19 wt% Na2O, 0.71 wt% K2O, and 0.14 wt% other components. The removal rate of Na2O reaches 92.40%, and the removal rate of K2O reaches 71.71%.

[0050] Example 3

[0051] A method for simultaneously removing sodium and potassium from aluminum-chromium slag dust using a gentle hydrothermal process with carbide slag includes the following steps:

[0052] (1) First, mix the dust generated near the furnace mouth during the aluminothermic process for preparing metallic chromium with the dust collected by the dust removal system and set aside. Then, fully dissolve the calcium carbide waste residue generated during the calcium carbide-acetylene process for preparing polyvinyl chloride and vinyl acetate products in water to prepare a calcium carbide slag aqueous solution with a concentration of 16wt%.

[0053] Main raw material composition: The content of each component of the aluminum chromium slag dust obtained after uniform mixing is as follows: Cr2O3 13.66wt%, Al2O3 80.34wt%, CaO 0.16wt%, SiO2 0.26wt%, Fe2O3 0.16wt%, MgO 0.15wt%, Na2O 2.52wt%, K2O 2.54wt%, and others 0.21wt%.

[0054] The main components of the calcium carbide waste residue are: CaO 71.93 wt%, Fe2O3 0.14 wt%, MgO 0.15 wt%, SiO2 1.19 wt%, Al2O3 1.81 wt%, moisture content 23.54 wt%, and other components 1.24 wt%.

[0055] (2) Add the well-mixed aluminum-chromium slag dust from step (1) to the calcium carbide slag aqueous solution prepared in step (1). The mass ratio of aluminum-chromium slag dust to calcium carbide slag aqueous solution is 1:7. After thorough mixing, transfer the mixture to a reactor. Then, raise the temperature to 160°C at a rate of 5°C / min and hold for 120 min. The stirring rate is 200 rpm throughout the process, and the system reaction pressure is maintained at 0.20 MPa. After the holding time is up, turn on the cooling water to cool down and open the pressure relief valve to release the system pressure. Stop stirring during the cooling process. When the temperature of the reaction slurry drops to 85°C, open the reactor, filter while hot, and perform solid-liquid separation. Wash the obtained filter cake repeatedly with hot water at 85°C five times. The mass ratio of hot water used for each wash to the mass of the filter cake is 1.5:1. After washing, filter and dry until the water content is less than 3 wt% to obtain dealkalized aluminum-chromium slag.

[0056] (3) The liquid phase after solid-liquid separation and the liquid phase obtained after washing and filtration are adsorbed by Tulsimer T-42H strong acid cation exchange resin and can be returned to the previous process that requires water solvent for recycling.

[0057] (4) The aluminum-chromium slag dust obtained after drying contains 13.62 wt% Cr2O3, 80.29 wt% Al2O3, 4.21 wt% CaO, 0.40 wt% SiO2, 0.16 wt% Fe2O3, 0.16 wt% MgO, 0.23 wt% Na2O, 0.73 wt% K2O, and 0.13 wt% other components. The removal rate of Na2O reaches 90.87%, and the removal rate of K2O reaches 71.26%.

[0058] Example 4

[0059] A method for simultaneously removing sodium and potassium from aluminum-chromium slag dust using a gentle hydrothermal process with carbide slag includes the following steps:

[0060] (1) First, mix the dust generated near the furnace mouth during the aluminothermic process for preparing metallic chromium, the dust collected by the dust removal system, and the dust collected during the crushing of blocky aluminum-chromium slag evenly for later use. Then, fully dissolve the calcium carbide waste residue generated during the calcium carbide-acetylene process for preparing polyvinyl chloride and vinyl acetate products in water to prepare a calcium carbide slag aqueous solution with a concentration of 17wt%.

[0061] Main raw material composition: The content of each component of the aluminum chromium slag dust obtained after uniform mixing is as follows: Cr2O3 13.22 wt%, Al2O3 81.02 wt%, CaO 0.14 wt%, SiO2 0.21 wt%, Fe2O3 0.13 wt%, MgO 0.13 wt%, Na2O 2.47 wt%, K2O 2.50 wt%, and others 0.14 wt%.

[0062] The main components of the calcium carbide waste residue are: CaO 71.62 wt%, Fe2O3 0.15 wt%, MgO 0.16 wt%, SiO2 1.23 wt%, Al2O3 1.80 wt%, moisture content 23.83 wt%, and other components 1.21 wt%.

[0063] (2) Add the well-mixed aluminum-chromium slag dust from step (1) to the calcium carbide slag aqueous solution prepared in step (1). The mass ratio of aluminum-chromium slag dust to calcium carbide slag aqueous solution is 1:6.5. After thorough mixing, transfer the mixture to the reactor. Then, heat the mixture to 175°C at a rate of 5°C / min and hold it at that temperature for 95 min. The stirring rate is 200 rpm throughout the process, and the system reaction pressure is maintained at 0.25 MPa. After the holding time is up, turn on the cooling water to cool the mixture down and open the pressure relief valve to release the system pressure. Stop stirring during the cooling process. When the temperature of the reaction slurry drops to 88°C, open the reactor, filter the mixture while it is still hot, and perform solid-liquid separation. Wash the resulting filter cake four times with hot water at 88°C. The mass ratio of hot water used for each wash to the mass of the filter cake is 1.5:1. After washing, filter the mixture and dry it until the water content is less than 3 wt%, thus obtaining the de-alkali aluminum-chromium slag.

[0064] (3) The liquid phase after solid-liquid separation and the liquid phase obtained after washing and filtration are adsorbed by Tulsimer T-42H strong acid cation exchange resin and can be returned to the previous process that requires water solvent for recycling.

[0065] (4) The aluminum-chromium slag dust obtained after drying contains 13.15 wt% Cr2O3, 80.96 wt% Al2O3, 4.11 wt% CaO, 0.41 wt% SiO2, 0.14 wt% Fe2O3, 0.15 wt% MgO, 0.24 wt% Na2O, 0.74 wt% K2O, and 0.10 wt% other components. The removal rate of Na2O reaches 90.28%, and the removal rate of K2O reaches 70.40%.

[0066] Example 5

[0067] A method for simultaneously removing sodium and potassium from aluminum-chromium slag dust using a gentle hydrothermal process with carbide slag includes the following steps:

[0068] (1) First, collect the dust collected in the dust removal system during the aluminothermic process for preparing metallic chromium and set it aside for later use. Then, fully dissolve the calcium carbide waste generated during the calcium carbide-acetylene process for preparing polyvinyl chloride and vinyl acetate products in water to prepare a calcium carbide slag aqueous solution with a concentration of 19 wt%.

[0069] Main raw material composition: The content of each component in the dust collector ash is as follows: Cr2O3 14.13 wt%, Al2O3 80.21 wt%, CaO 0.12 wt%, SiO2 0.20 wt%, Fe2O3 0.14 wt%, MgO 0.14 wt%, Na2O 2.46 wt%, K2O 2.49 wt%, and others 0.11 wt%.

[0070] The main components of the calcium carbide waste residue are: CaO 70.38 wt%, Fe2O3 0.16 wt%, MgO 0.14 wt%, SiO2 1.24 wt%, Al2O3 1.79 wt%, moisture content 25.11 wt%, and other components 1.18 wt%.

[0071] (2) Add the well-mixed aluminum-chromium slag dust from step (1) to the calcium carbide slag aqueous solution prepared in step (1). The mass ratio of aluminum-chromium slag dust to calcium carbide slag aqueous solution is 1:5.5. After thorough mixing, transfer the mixture to a reactor. Then, heat the mixture to 168°C at a rate of 5°C / min and hold it at that temperature for 105 min. The stirring rate is 200 rpm throughout the process, and the system reaction pressure is maintained at 0.35 MPa. After the holding time is up, turn on the cooling water to cool the mixture down and open the pressure relief valve to release the system pressure. Stop stirring during the cooling process. When the temperature of the reaction slurry drops to 92°C, open the reactor, filter the mixture while it is still hot, and perform solid-liquid separation. Wash the resulting filter cake three times with hot water at 92°C. The mass ratio of hot water used to filter cake used in each wash is 2.5:1. After washing, filter the mixture and dry it until the water content is less than 3 wt%, thus obtaining the de-alkali aluminum-chromium slag.

[0072] (3) The liquid phase after solid-liquid separation and the liquid phase obtained after washing and filtration are adsorbed by Tulsimer T-42H strong acid cation exchange resin and can be returned to the previous process that requires water solvent for recycling.

[0073] (4) The aluminum-chromium slag dust obtained after drying contains 14.08 wt% Cr2O3, 80.16 wt% Al2O3, 4.04 wt% CaO, 0.42 wt% SiO2, 0.13 wt% Fe2O3, 0.13 wt% MgO, 0.21 wt% Na2O, 0.71 wt% K2O, and 0.11 wt% other components. The removal rate of Na2O reaches 91.46%, and the removal rate of K2O reaches 71.49%.

[0074] Example 6

[0075] A method for simultaneously removing sodium and potassium from aluminum-chromium slag dust using a gentle hydrothermal process with carbide slag includes the following steps:

[0076] (1) First, the dust generated during the crushing of the blocky aluminum-chromium slag formed in the aluminothermic process for the preparation of metallic chromium is collected for later use. Then, the calcium carbide waste generated in the preparation of polyvinyl chloride and vinyl acetate products by the calcium carbide-acetylene process is fully dissolved in water to prepare a calcium carbide slag aqueous solution with a concentration of 16wt%.

[0077] Main raw material composition: The content of each component of the dust generated during the crushing of blocky aluminum chromium slag is as follows: Cr2O3 13.14 wt%, Al2O3 81.15 wt%, CaO 0.14 wt%, SiO2 0.18 wt%, Fe2O3 0.14 wt%, MgO 0.15 wt%, Na2O 2.48 wt%, K2O 2.53 wt%, and others 0.09 wt%.

[0078] The main components of the calcium carbide waste residue are: CaO 71.96 wt%, Fe2O3 0.17 wt%, MgO 0.13 wt%, SiO2 1.26 wt%, Al2O3 1.82 wt%, moisture content 23.48 wt%, and other components 1.18 wt%.

[0079] (2) Add the well-mixed aluminum-chromium slag dust from step (1) to the calcium carbide slag aqueous solution prepared in step (1). The mass ratio of aluminum-chromium slag dust to calcium carbide slag aqueous solution is 1:5. After thorough mixing, transfer the mixture to a reactor. Then, heat the mixture to 162°C at a rate of 5°C / min and hold it for 110 min. The stirring rate is 200 rpm throughout the process, and the system reaction pressure is maintained at 0.25 MPa. After the holding time is up, turn on the cooling water to cool down the mixture and open the pressure relief valve to release the system pressure. Stop stirring during the cooling process. When the temperature of the reaction slurry drops to 85°C, open the reactor, filter the mixture while it is still hot, and perform solid-liquid separation. Wash the resulting filter cake five times with hot water at 85°C. The mass ratio of hot water used to filter cake for each wash is 1.5:1. After washing, filter the mixture and dry it until the water content is less than 3 wt%, obtaining the de-alkali aluminum-chromium slag.

[0080] (3) The liquid phase after solid-liquid separation and the liquid phase obtained after washing and filtration are adsorbed by Tulsimer T-42H strong acid cation exchange resin and can be returned to the previous process that requires water solvent for recycling.

[0081] (4) The aluminum-chromium slag dust obtained after drying contains 13.10 wt% Cr2O3, 81.13 wt% Al2O3, 4.05 wt% CaO, 0.43 wt% SiO2, 0.16 wt% Fe2O3, 0.13 wt% MgO, 0.19 wt% Na2O, 0.73 wt% K2O, and 0.08 wt% other components. The removal rate of Na2O reaches 92.34%, and the removal rate of K2O reaches 71.15%.

[0082] Example 7

[0083] A method for simultaneously removing sodium and potassium from aluminum-chromium slag dust using a gentle hydrothermal process with carbide slag includes the following steps:

[0084] (1) First, collect the dust generated near the furnace mouth during the aluminothermic process for preparing metallic chromium and set it aside for later use. Then, fully dissolve the calcium carbide waste residue generated during the calcium carbide-acetylene process for preparing polyvinyl chloride and vinyl acetate products in water to prepare a calcium carbide slag aqueous solution with a concentration of 20 wt%.

[0085] Main raw material composition: The content of each component of the dust collected near the furnace mouth is as follows: Cr2O3 14.29 wt%, Al2O3 80.15 wt%, CaO 0.16 wt%, SiO2 0.22 wt%, Fe2O3 0.14 wt%, MgO 0.14 wt%, Na2O 2.38 wt%, K2O 2.42 wt%, and others 0.10 wt%.

[0086] The main components of the calcium carbide waste residue are: CaO 70.28 wt%, Fe2O3 0.16 wt%, MgO 0.18 wt%, SiO2 1.19 wt%, Al2O3 1.76 wt%, moisture content 25.18 wt%, and other components 1.25 wt%.

[0087] (2) Add the well-mixed aluminum-chromium slag dust from step (1) to the calcium carbide slag aqueous solution prepared in step (1). The mass ratio of aluminum-chromium slag dust to calcium carbide slag aqueous solution is 1:7. After thorough mixing, transfer the mixture to a reactor. Then, heat the mixture to 178°C at a rate of 5°C / min and hold it at that temperature for 95 min. The stirring rate is 200 rpm throughout the process, and the system reaction pressure is maintained at 0.40 MPa. After the holding time is up, turn on the cooling water to cool the mixture down and open the pressure relief valve to release the system pressure. Stop stirring during the cooling process. When the temperature of the reaction slurry drops to 95°C, open the reactor, filter the mixture while it is still hot, and perform solid-liquid separation. Wash the resulting filter cake three times with hot water at 95°C. The mass ratio of hot water used for each wash to the mass of the filter cake is 2.0:1. After washing, filter the mixture and dry it until the water content is less than 3 wt%, thus obtaining the de-alkali aluminum-chromium slag.

[0088] (3) The liquid phase after solid-liquid separation and the liquid phase obtained after washing and filtration are adsorbed by Tulsimer T-42H strong acid cation exchange resin and can be returned to the previous process that requires water solvent for recycling.

[0089] (4) The aluminum-chromium slag dust obtained after drying contains 14.21 wt% Cr2O3, 80.12 wt% Al2O3, 4.05 wt% CaO, 0.35 wt% SiO2, 0.11 wt% Fe2O3, 0.14 wt% MgO, 0.22 wt% Na2O, 0.71 wt% K2O, and 0.09 wt% other components. The removal rate of Na2O reaches 90.76%, and the removal rate of K2O reaches 70.66%.

[0090] Comparative Examples 1-6: Compared with Example 1, Comparative Examples 1-6 are identical to Example 1 in all experimental materials and conditions except for the reaction temperature in step (2). The removal rates of Na2O and K2O are shown in Table 1 below.

[0091] Table 1. Reaction temperature and removal rates of Na₂O and K₂O for Comparative Examples 1-6

[0092] Comparative Example 1 140℃ 71.17％ 50.91％ Comparative Example 2 145℃ 77.41％ 57.45％ Comparative Example 3 150℃ 82.84％ 62.73％ Comparative Example 4 155℃ 87.23％ 66.82％ Comparative Example 5 185℃ 91.35％ 70.96％ Comparative Example 6 190℃ 91.51％ 71.04％

[0093] Comparative Examples 7-11: Compared with Example 1, Comparative Examples 7-11 and Example 1 differed only in step (2) of the heat preservation time; all other experimental materials and conditions were the same as in Example 1. The removal rates of Na2O and K2O are shown in Table 2 below.

[0094] Table 2 Comparative Examples 7-11: Incubation Time and Removal Rates of Na2O and K2O

[0095] Comparative Example 7 30min 67.21％ 45.76％ Comparative Example 8 50min 78.33％ 58.82％ Comparative Example 9 70min 86.62％ 67.24％ Comparative Example 10 140min 91.28％ 70.91％ Comparative Example 11 160min 91.46％ 70.98％

[0096] Comparative Examples 12-16: Compared with Example 1, Comparative Examples 12-16 and Example 1, except for the system reaction pressure, had the same experimental materials and conditions. The removal rates of Na2O and K2O are shown in Table 3 below.

[0097] Table 3 shows the system reaction pressure and the removal rates of Na2O and K2O in Comparative Examples 12-16.

[0098] Comparative Example 12 0.05MPa 70.12％ 51.41％ Comparative Example 13 0.10MPa 79.46％ 61.25％ Comparative Example 14 0.15MPa 85.93％ 66.73％ Comparative Example 15 0.45MPa 91.94％ 71.36％ Comparative Example 16 0.50MPa 92.08％ 71.49％

[0099] Comparative Examples 17-21: Compared with Example 1, Comparative Examples 17-21 and Example 1 are identical in all experimental materials and conditions except for the temperature of the hot water used to wash the filter cake in step (2). The removal rates of Na2O and K2O are shown in Table 4 below.

[0100] Table 4 Comparative Examples 17-21: Hot water temperature for washing and removal rates of Na2O and K2O

[0101] Comparative Example 17 60℃ 73.55％ 56.43％ Comparative Example 18 70℃ 81.71％ 62.32％ Comparative Example 19 80℃ 87.62％ 66.85％ Comparative Example 20 98℃ 91.79％ 71.29％ Comparative Example 21 100℃ 91.87％ 71.41％

[0102] The description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for simultaneously removing sodium and potassium from aluminum-chromium slag dust using a mild hydrothermal method with calcium carbide slag, characterized in that, Includes the following steps: (1) Collect the aluminum chromium slag dust generated during the aluminothermic process for the preparation of metallic chromium for later use; (2) Dissolve the calcium carbide slag produced during the preparation of polyvinyl chloride or vinyl acetate products by the calcium carbide acetylene method in water to prepare an aqueous solution of calcium carbide slag; (3) Add the aluminum chromium slag dust from step (1) to the calcium carbide slag aqueous solution from step (2), mix thoroughly and evenly, and then transfer to the reactor; (4) The reactor is continuously stirred and heated. After the temperature is maintained, the cooling water is turned on to cool the reaction slurry. (5) After the reaction slurry in step (4) is cooled down, it is filtered while hot and the solid and liquid are separated. The resulting filter cake is washed with hot water, then filtered and dried. The concentration of the calcium carbide slag aqueous solution in step (2) is 16~20 wt%, and the mass ratio of aluminum chromium slag dust to calcium carbide slag aqueous solution in step (3) is 1:(5~7). In step (4), the heating rate of the reactor is 5 ℃ / min, the temperature is raised to 160~180 ℃, the holding time is 90~120 min, the stirring rate is 200 rpm, and the reaction pressure is 0.20~0.40 MPa; In step (5), when the reaction slurry from step (4) is cooled to 85-95 ℃, hot filtration and solid-liquid separation are started, and the resulting filter cake is washed 3-5 times with hot water at 85-95 ℃, then filtered and dried until the water content is less than 3 wt%.

2. The method for simultaneously removing sodium and potassium from aluminum-chromium slag dust using a mild hydrothermal method based on carbide slag according to claim 1, characterized in that, The aluminum-chromium slag dust is one or a mixture of several of the following: dust generated near the furnace mouth during the aluminothermic process for preparing metallic chromium, dust collected by the dust removal system, or dust generated during the crushing of blocky aluminum-chromium slag.

3. The method for simultaneously removing sodium and potassium from aluminum-chromium slag dust using a mild hydrothermal method based on carbide slag according to claim 1, characterized in that, The aluminum chromium slag dust and carbide slag do not require additional treatment to meet the required particle size requirement of ≤150 mesh and can be used directly.

4. The method for simultaneously removing sodium and potassium from aluminum-chromium slag dust using a mild hydrothermal method based on carbide slag according to claim 1, characterized in that, The chemical composition requirements for the aluminum chromium slag dust are: Al2O3 ≥ 80 wt%, Cr2O3 ≥ 13 wt%, CaO ≤ 0.30 wt%, Fe2O3 ≤ 0.30 wt%, MgO ≤ 0.30 wt%, SiO2 ≤ 0.30 wt%. The chemical composition requirements for the carbide slag are: CaO ≥ 70 wt%, Fe2O3 ≤ 0.30 wt%, MgO ≤ 0.30 wt%, SiO2 ≤ 1.30 wt%.

5. The method for simultaneously removing sodium and potassium from aluminum-chromium slag dust using a mild hydrothermal method based on carbide slag according to claim 1, characterized in that, In step (5), the mass ratio of hot water to filter cake used for each wash is (1.5~2.5):

1.

6. A method for simultaneously removing sodium and potassium from aluminum-chromium slag dust using a mild hydrothermal method according to claim 1 or 5, characterized in that, The liquid phase after solid-liquid separation in step (5) and the liquid phase obtained after washing and filtration are collected together. After being adsorbed by Tulsimer T-42H strong acid cation exchange resin, the liquid phase can be returned to step (2) or step (5) for recycling.

7. The method for simultaneously removing sodium and potassium from aluminum-chromium slag dust using a mild hydrothermal method based on carbide slag according to claim 1, characterized in that, The chemical composition of the aluminum-chromium slag obtained after drying in step (5) is Al2O3 ≥ 80 wt%, Cr2O3 ≥ 13 wt%, CaO+MgO ≤ 4.50 wt%, Fe2O3 ≤ 0.45 wt%, SiO2 ≤ 0.50 wt%, Na2O ≤ 0.25 wt%, K2O ≤ 0.75 wt%, which meets the composition requirements for use in high-grade chromium corundum refractory materials.

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