Aluminum electrolysis solid waste resource utilization method

Abstract

The invention discloses an aluminum electrolysis solid waste resource utilization method, and relates to the technical field of waste resource utilization. Comprising the following steps: pre-mixing the pre-treated aluminum electrolysis solid waste with concentrated sulfuric acid to obtain an acidic blend, and collecting hydrogen fluoride generated in the pre-mixing process; adding a reaction aid calcium salt into the acidic blend, uniformly mixing, adding into a rotary kiln, reacting at high temperature, and collecting hydrogen fluoride generated in the reaction process. According to the method, the concentrated sulfuric acid and the aluminum electrolysis solid waste are premixed firstly, the dissolution rate of fluorine in the aluminum electrolysis solid waste is increased, and then the utilization rate of fluorine in the aluminum electrolysis fluorine-containing solid waste is increased; by adding a reaction aid calcium salt into an acidic blend obtained by premixing, hydrogen fluoride is recovered by reaction at high temperature in a rotary kiln, and the reaction aid calcium salt plays a role in lubrication and dispersion, so that the caking phenomenon of the mixture after reaction is reduced, and the method is suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of waste resource utilization, and in particular to a method for resource utilization of aluminum electrolysis solid waste. Background Art

[0002] With the rapid development of the electrolytic aluminum industry, a large amount of solid waste has been generated, such as waste electrolyte, waste cathode, carbon slag, covering material and overhaul slag. According to the production of 1t of aluminum, 10-20kg of solid waste will be generated, and the annual fluorine-containing solid waste will be as high as 4 million tons. These solid wastes are rich in valuable elements such as fluorine and aluminum, and have high resource utilization value. According to the existing technology, only harmless treatment is carried out, but the tailings are still hazardous waste. In recent years, with the enhancement of awareness of resource conservation and environmental protection, the resource utilization of solid waste has become the focus of the industry.

[0003] The production of anhydrous hydrogen fluoride mainly depends on fluorite resources. my country's fluorite resources are relatively abundant, but there are more poor ores, fewer rich ores, and a large proportion of associated ores. The ore grade is generally 35%-40%, and rich ores with an ore grade greater than 65% account for about 20% of the total. Fluorite ores associated with metal minerals generally have an ore grade of 7%-20%. High-grade fluorite resources have become scarce due to mining and large-scale exports in the past 30 years. Therefore, with the increasing shortage of fluorite resources, it is of great significance to develop new fluorine resources to produce anhydrous hydrogen fluoride. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0005] In order to solve the above problems, the present invention provides a method for resource utilization of aluminum electrolysis solid waste, comprising:

[0006] premixing the pretreated aluminum electrolysis solid waste with concentrated sulfuric acid to obtain an acidic mixture, and collecting hydrogen fluoride generated during the premixing process;

[0007] A reaction aid calcium salt is added to the acidic blend and mixed evenly, and then added to a rotary kiln for reaction at high temperature, and hydrogen fluoride generated during the reaction is collected.

[0008] Furthermore, after pretreatment, the aluminum electrolysis solid waste has a particle size of 50 μm to 500 μm.

[0009] Furthermore, the mass ratio of the aluminum electrolysis solid waste to concentrated sulfuric acid is 1:1-7, wherein the mass concentration of the concentrated sulfuric acid is not less than 98%.

[0010] Furthermore, the premixing temperature is 20°C to 150°C and the time is 0.5h to 3h.

[0011] Furthermore, the reaction aid calcium salt is one or more of calcium sulfate, calcium carbonate and calcium oxide.

[0012] Furthermore, the amount of the reaction aid calcium salt added is calculated according to the mass of the aluminum electrolysis solid waste, and the mass ratio of the reaction aid calcium salt to the aluminum electrolysis solid waste is 0.05 to 0.1:1.

[0013] Furthermore, the reaction auxiliary calcium salt is three kinds of calcium sulfate, calcium carbonate and calcium oxide; wherein the mass ratio of calcium sulfate, calcium carbonate and calcium oxide is 2.8-3.2:2.8-3.2:3.8-4.2.

[0014] Furthermore, the reaction is carried out at a high temperature of 200°C to 500°C and for a time of 12h to 26h.

[0015] Furthermore, the recovery rate of fluorine in the aluminum electrolysis solid waste reaches more than 97%.

[0016] Furthermore, the fluorine recovery rate is the sum of the first recovery rate and the second recovery rate;

[0017] Wherein, the first recovery rate is generated from the hydrogen fluoride recovered during the premixing process, and the first recovery rate is 10% to 25%;

[0018] The second recovery rate is generated by hydrogen fluoride recovered during the reaction process at the high temperature.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] The present invention provides a method for resource utilization of aluminum electrolysis solid waste. The method comprises the following steps: premixing concentrated sulfuric acid with the aluminum electrolysis solid waste to improve the dissolution rate of fluorine in the aluminum electrolysis solid waste, thereby improving the utilization rate of fluorine in the aluminum electrolysis fluorine-containing solid waste; adding a reaction aid calcium salt to the acidic blend obtained by premixing, reacting at high temperature in a rotary kiln to recover hydrogen fluoride, and the reaction aid calcium salt plays a role of lubrication and dispersion, which helps to reduce the agglomeration phenomenon of the mixture after the reaction, and is suitable for industrial production. DETAILED DESCRIPTION

[0021] In order to better understand the above-mentioned technical scheme, the technical scheme of the embodiment of the present application is described in detail through specific embodiments below. It should be understood that the embodiment of the present application and the specific features in the embodiment are detailed descriptions of the technical scheme of the embodiment of the present application, rather than limitations on the technical scheme of the present application. In the absence of conflict, the embodiment of the present application and the technical features in the embodiment can be combined with each other.

[0022] The embodiment of the present invention provides a method for resource utilization of aluminum electrolysis solid waste, comprising:

[0023] premixing the pretreated aluminum electrolysis solid waste with concentrated sulfuric acid to obtain an acidic mixture, and collecting hydrogen fluoride generated during the premixing process;

[0024] A reaction aid calcium salt is added to the acidic blend and mixed evenly, and then added to a rotary kiln for reaction at high temperature, and hydrogen fluoride generated during the reaction is collected.

[0025] The inventors have found in practice that if hydrogen fluoride is recovered only by reacting aluminum electrolysis solid waste with concentrated sulfuric acid, in order to obtain a higher recovery rate, the reaction temperature generally needs to be controlled above 150°C or even above 200°C. However, there are still a large amount of aluminum and sodium elements in aluminum electrolysis solid waste, which react with concentrated sulfuric acid at high temperature to produce a large amount of aluminum sulfate and sodium sulfate. Aluminum sulfate and sodium sulfate have high viscosity, which will cause the reactor to stagnate and the material to agglomerate in actual applications, which not only has low reaction efficiency, but also cannot be continuously reacted and cannot be industrialized.

[0026] The method for resource utilization of aluminum electrolytic solid waste provided by the embodiment of the present invention comprises the following steps: premixing concentrated sulfuric acid with aluminum electrolytic solid waste to fully mix the concentrated sulfuric acid and the aluminum electrolytic solid waste, thereby improving the dissolution rate of fluorine in the aluminum electrolytic solid waste, and further improving the utilization rate of fluorine in the aluminum electrolytic fluorine-containing solid waste; adding a reaction aid calcium salt to the acidic blend obtained by premixing, and reacting and recovering hydrogen fluoride at high temperature in a rotary kiln. The reaction aid calcium salt plays a role of lubrication and dispersion, which helps to reduce the agglomeration phenomenon of the mixture after the reaction, and is suitable for industrial production.

[0027] Specifically, concentrated sulfuric acid and calcium salt react at high temperature to generate calcium sulfate particles with larger particle size, which can act as crystal seeds. The product after the reaction is coated on the surface of the calcium sulfate particles, which helps to further reduce the viscosity of the mixture after the reaction and improve its fluidity, thereby reducing the possibility of agglomeration; it effectively solves the problems of wall formation and agglomeration of materials after the reaction, low reaction efficiency, and inability to carry out continuous production.

[0028] It is understandable that if aluminum electrolyte solid waste and concentrated sulfuric acid are not premixed and directly reacted at high temperature, there will be a problem of uneven mixing. Because there is no stirring device in the rotary kiln in actual production, it will cause the local reaction to be too strong or too weak, thus affecting the overall reaction effect, and uneven mixing may also cause a large amount of heat to be generated locally, causing side reactions or product agglomeration, and reducing the recovery rate of fluorine.

[0029] In some embodiments, the aluminum electrolysis solid waste has a particle size of 50 μm to 500 μm after pretreatment.

[0030] Specifically, aluminum electrolytic solid waste is a substance formed at high temperature during the aluminum electrolysis process. It is in block form, with complex composition and structure, and is uneven. Therefore, before the aluminum electrolytic solid waste is recycled, it is ground and crushed, and then sieved to make the particle size between 50μm and 500μm, so as to achieve uniform reaction and improve reaction efficiency. Preferably, after pretreatment, the particle size of the aluminum electrolytic solid waste is 200μm to 400μm.

[0031] In some embodiments, the mass ratio of the aluminum electrolysis solid waste to concentrated sulfuric acid is 1:1-7, wherein the mass concentration of the concentrated sulfuric acid is not less than 98%.

[0032] Specifically, we analyzed the content of each valuable element in aluminum electrolysis solid waste, calculated the theoretical amount of concentrated sulfuric acid used, and then verified the final reaction efficiency under the theoretical amount of concentrated sulfuric acid used through experiments. The results showed that the recovery rate of fluorine in aluminum electrolysis solid waste was low under the theoretical amount of concentrated sulfuric acid used. When the amount of concentrated sulfuric acid used was continuously increased to the theoretical amount (several times to several times), the recovery rate of fluorine in aluminum electrolysis solid waste could reach more than 97%, and further increasing the amount of concentrated sulfuric acid used did not further improve the recovery rate of fluorine in aluminum electrolysis solid waste.

[0033] In some embodiments, the premixing temperature is 20°C to 150°C and the premixing time is 0.5h to 3h.

[0034] Specifically, our experiment started from 20°C and continuously increased the premixing temperature to examine the recovery rate of fluorine in aluminum electrolytic solid waste after mixing for different times. We found that with the increase of premixing temperature, the recovery rate of fluorine in aluminum electrolytic solid waste also continued to increase until the premixing temperature reached 150°C. When the premixing temperature was further increased, the recovery rate of fluorine in aluminum electrolytic solid waste no longer increased, as shown in Table 1.

[0035] Table 1

[0036]

[0037] In some embodiments, the reaction aid calcium salt is one or more of calcium sulfate, calcium carbonate and calcium oxide.

[0038] Specifically, the selection of our reaction aids is based on: first, no other elements can be introduced; second, the byproducts obtained by the introduced elements can be effectively treated; third, the cost issue must be considered comprehensively, and it must be easy to purchase and as low in price as possible. Therefore, the reaction aid calcium salts we choose are one or more of calcium sulfate, calcium carbonate and calcium oxide, and the effect is good after addition.

[0039] In some embodiments, the amount of the reaction aid calcium salt added is calculated according to the mass of the aluminum electrolysis solid waste, and the mass ratio of the reaction aid calcium salt to the aluminum electrolysis solid waste is 0.05 to 0.1: 1. Preferably, the reaction aid calcium salt is calcium sulfate, calcium carbonate and calcium oxide; wherein the mass ratio of calcium sulfate, calcium carbonate and calcium oxide is 2.8 to 3.2: 2.8 to 3.2: 3.8 to 4.2, and preferably, the mass ratio of calcium sulfate, calcium carbonate and calcium oxide is 3: 3: 4.

[0040] Specifically, in order to further optimize the type of reaction aid calcium salt and the amount of reaction aid calcium salt added, we conducted a large number of experiments on the type of reaction aid, the mass ratio of aluminum electrolysis solid waste to reaction aid, the fluorine recovery rate, and the agglomeration of materials during the reaction process. Some of the experimental results are listed in Table 2. As can be seen from Table 2, combined with the cost of reaction aid calcium salt, the mass ratio of reaction aid calcium salt to aluminum electrolysis solid waste is 0.05-0.1:1, and the most preferred reaction aid is a mixture of calcium sulfate, calcium oxide and calcium carbonate, wherein the mass ratio of calcium sulfate, calcium oxide and calcium carbonate is 3:3:4. It is understandable that the amount of reaction aid added will affect the mixing effect between the reactants. Too much additive may cause uneven dispersion of the reactants and affect the reaction efficiency; while too little additive may not be able to fully exert its promoting effect. Using theories such as chemical reaction kinetics and thermodynamics, the reaction process is simulated and calculated to predict the reaction effect under different addition amounts, providing a reference for experimental verification. Then, through a series of experiments, the reaction efficiency, yield, by-product generation, product quality and other indicators were tested under different additive addition amounts, so as to determine the optimal addition amount range as the mass ratio of reaction additive calcium salt to aluminum electrolysis solid waste of 0.05 to 0.1:1.

[0041] Table 2

[0042]

[0043]

[0044] In some embodiments, the reaction is carried out at a high temperature of 200°C to 500°C, preferably 260°C to 400°C, and the reaction time is 12h to 26h.

[0045] Specifically, the reaction between aluminum electrolysis solid waste and concentrated sulfuric acid is a multiphase reaction, including mass transfer and reaction processes between the solid phase (aluminum electrolysis solid waste) and the liquid phase (concentrated sulfuric acid), and the reaction is an endothermic reaction. Increasing the temperature can significantly increase the reaction rate, but too high a temperature may lead to increased evaporation and decomposition of sulfuric acid. By increasing the reaction temperature by 200°C to 500°C, the reaction rate is increased while ensuring sufficient sulfuric acid to participate in the reaction. Through experiments and production practice, we have concluded that after adding the reaction aid calcium salt to the acidic blend and mixing evenly, it is added to the rotary kiln and reacted at a temperature of 200°C to 500°C for 12 to 26 hours, preferably at a temperature of 260°C to 400°C for 20 hours to 24 hours.

[0046] In some embodiments, the recovery rate of fluorine in aluminum electrolysis solid waste reaches more than 97%; wherein the recovery rate of fluorine is the sum of the first recovery rate and the second recovery rate, as follows:

[0047] The first recovery rate is generated from the hydrogen fluoride recovered during the premixing process, and the first recovery rate is 10% to 25%;

[0048] The second recovery rate is generated by the hydrogen fluoride recovered during the reaction process at the high temperature.

[0049] Specifically, concentrated sulfuric acid is premixed with aluminum electrolysis to make the solid phase and liquid phase mix evenly, and increasing the premixing temperature is beneficial to increasing the dissolution rate of fluorine in aluminum electrolysis solid waste. Experiments have found that when the premixing temperature is 20°C to 150°C and the time is 0.5h to 3h, the first recovery rate is between 10% and 25%.

[0050] The present invention is further described below through specific examples. It should be noted that the aluminum electrolysis solid waste in Examples 1 to 6 and Comparative Examples 1 to 2 is: fluorine-containing solid waste generated by an aluminum electrolysis plant, wherein the main elements are F 30.06%, Al 10.11%, Na 21.05%, K 0.35, Ca 0.1%, Mg 0.041%, Fe 0.45%, C 30.04%, and Cr 0.009% by mass percentage.

[0051] Example 1

[0052] A method for resource utilization of aluminum electrolysis solid waste, comprising the following steps:

[0053] (1) First, the aluminum electrolytic solid waste is ground in a grinder to a particle size of 150 μm;

[0054] (2) The ground aluminum electrolytic solid waste is pre-mixed with 98% concentrated sulfuric acid at a mass ratio of 1:1.5, and 200 g of aluminum electrolyte solid waste and 300 g of 98% concentrated sulfuric acid are pre-mixed at 20° C. for 0.5 h to obtain an acidic blend; the gas phase generated during the pre-mixing process is collected, dusted and cooled to obtain crude liquid hydrogen fluoride.

[0055] (3) Add 12 g of calcium sulfate to the acidic blend of step (2) at a mass ratio of aluminum electrolysis solid waste to calcium sulfate of 1:0.06, mix well and add to a rotary kiln, adjust the reaction temperature to 200°C, and the reaction time to 14 hours. Collect the gas generated by the reaction for dust removal, and cool it to obtain crude liquid hydrogen fluoride.

[0056] (4) The crude liquid hydrogen fluoride is distilled to remove impurities to obtain anhydrous hydrogen fluoride. According to calculations, the recovery rate of fluorine in aluminum electrolysis solid waste is 97.5%.

[0057] Example 2

[0058] A method for resource utilization of aluminum electrolysis solid waste, comprising the following steps:

[0059] (1) First, the aluminum electrolytic solid waste is ground in a grinder to a particle size of 250 μm;

[0060] (2) The ground aluminum electrolytic solid waste is pre-mixed with 98% concentrated sulfuric acid at a mass ratio of 1:2.5, and 500 g of aluminum electrolyte solid waste and 1250 g of 98% concentrated sulfuric acid are pre-mixed at 50° C. for 1.5 hours to obtain an acidic blend; the gas phase generated during the pre-mixing process is collected, dusted and cooled to obtain a crude liquid hydrogen fluoride.

[0061] (3) Add 35 g of calcium carbonate to the acidic blend of step (2) at a mass ratio of aluminum electrolysis solid waste to calcium carbonate of 1:0.07, mix well and add to a rotary kiln, adjust the reaction temperature to 300°C, and the reaction time to 18 hours. Collect the gas generated by the reaction for dust removal, and cool it to obtain crude liquid hydrogen fluoride.

[0062] (4) The crude liquid hydrogen fluoride is distilled to remove impurities to obtain anhydrous hydrogen fluoride. According to calculations, the recovery rate of fluorine in aluminum electrolysis solid waste is 97.8%.

[0063] Example 3

[0064] A method for resource utilization of aluminum electrolysis solid waste, comprising the following steps:

[0065] (1) First, the aluminum electrolytic solid waste is ground in a grinder to a particle size of 300 μm;

[0066] (2) The ground aluminum electrolytic solid waste is pre-mixed with 98% concentrated sulfuric acid at a mass ratio of 1:3.5, and 1000 g of aluminum electrolyte solid waste and 3500 g of 98% concentrated sulfuric acid are pre-mixed at 80° C. for 2 h to obtain an acidic blend; the gas phase generated during the pre-mixing process is collected, dusted and cooled to obtain crude liquid hydrogen fluoride.

[0067] (3) Add 80 g of calcium oxide to the acidic blend of step (2) at a mass ratio of aluminum electrolysis solid waste to calcium oxide of 1:0.08, mix well and add to a rotary kiln, adjust the reaction temperature to 360°C, and the reaction time to 20 hours. Collect the gas generated by the reaction for dust removal, and cool it to obtain crude liquid hydrogen fluoride.

[0068] (4) The crude liquid hydrogen fluoride is distilled to remove impurities to obtain anhydrous hydrogen fluoride. According to calculations, the recovery rate of fluorine in aluminum electrolysis solid waste is 98.1%.

[0069] Example 4

[0070] A method for resource utilization of aluminum electrolysis solid waste, comprising the following steps:

[0071] (1) First, the aluminum electrolytic solid waste is ground in a grinder to a particle size of 400 μm;

[0072] (2) The ground aluminum electrolytic solid waste is mixed with 98% concentrated sulfuric acid at a mass ratio of 1:4.5, and 2000 g of aluminum electrolyte solid waste and 9000 g of 98% concentrated sulfuric acid are pre-mixed at 110° C. for 2.5 hours to obtain an acidic blend; the gas phase produced by the reaction is collected, dusted and cooled to obtain crude liquid hydrogen fluoride.

[0073] (3) Add 90 g of calcium sulfate and 90 g of calcium oxide to the acidic blend of step (2) in a mass ratio of 1:0.09 of aluminum electrolysis solid waste to a mixture of calcium sulfate and calcium oxide, mix well, and then add to a rotary kiln, adjust the reaction temperature to 400°C, and the reaction time to 24 hours. Collect the gas generated by the reaction for dust removal, and cool it to obtain crude liquid hydrogen fluoride.

[0074] (4) The crude liquid fluorine is distilled to remove impurities and obtain anhydrous hydrogen fluoride. According to calculations, the recovery rate of fluorine in aluminum electrolysis solid waste is 98.3%.

[0075] Example 5

[0076] A method for resource utilization of aluminum electrolysis solid waste, comprising the following steps:

[0077] (1) First, the aluminum electrolytic solid waste is ground in a grinder to a particle size of 500 μm;

[0078] (2) The ground aluminum electrolytic solid waste is pre-mixed with 98% concentrated sulfuric acid at a mass ratio of 1:5.5, and 5000 g of aluminum electrolyte solid waste and 27500 g of 98% concentrated sulfuric acid are pre-mixed at 130° C. for 3 hours to obtain an acidic blend; the gas phase generated during the pre-mixing process is collected, dusted and cooled to obtain crude liquid hydrogen fluoride.

[0079] (3) Add 250 g of calcium sulfate and 250 g of calcium oxide to the acidic blend of step (2) in a mass ratio of 1:0.1 of aluminum electrolysis solid waste to calcium carbonate and calcium oxide, mix well and add to a rotary kiln, adjust the reaction temperature to 500°C, and the reaction time to 26 hours. Collect the gas generated by the reaction for dust removal, and cool it to obtain crude liquid hydrogen fluoride.

[0080] (4) The crude liquid hydrogen fluoride is distilled to remove impurities to obtain anhydrous hydrogen fluoride. According to calculations, the recovery rate of fluorine in aluminum electrolysis solid waste is 98.2%.

[0081] Example 6

[0082] A method for resource utilization of aluminum electrolysis solid waste, comprising the following steps:

[0083] (1) First, the aluminum electrolytic solid waste is ground in a grinder to a particle size of 450 μm;

[0084] (2) The ground aluminum electrolytic solid waste is pre-mixed with 98% concentrated sulfuric acid at a mass ratio of 1:7, and 10,000 g of aluminum electrolyte solid waste and 70,000 g of 98% concentrated sulfuric acid are pre-mixed at 150° C. for 2.5 hours to obtain an acidic blend; the gas phase generated during the pre-mixing process is collected, dusted and cooled to obtain crude liquid hydrogen fluoride.

[0085] (3) Add 150 g of calcium sulfate, 200 g of calcium oxide, and 150 g of calcium carbonate to the acidic blend of step (2) in a mass ratio of 1:0.1 of the mixture of aluminum electrolytic solid waste and calcium sulfate, calcium oxide, and calcium carbonate, mix well, and add to a rotary kiln, adjust the reaction temperature to 400° C., and the reaction time to 24 h. Collect the gas generated by the reaction for dust removal, and cool it to obtain crude liquid hydrogen fluoride.

[0086] (4) The crude liquid hydrogen fluoride is distilled to remove impurities to obtain anhydrous hydrogen fluoride. According to calculations, the recovery rate of fluorine in aluminum electrolysis solid waste is 98.5%.

[0087] Comparative Example 1

[0088] A method for resource utilization of aluminum electrolysis solid waste, comprising the following steps:

[0089] (1) First, the aluminum electrolytic solid waste is ground in a grinder to a particle size of 300 μm;

[0090] (2) The ground aluminum electrolytic solid waste is directly added to the rotary kiln with 98% concentrated sulfuric acid at a mass ratio of 1:5.5 and aluminum electrolytic solid waste and calcium oxide at a mass ratio of 1:0.08 without pre-mixing, and the reaction temperature is adjusted to 380°C and the reaction time is 20 hours. The gas generated by the reaction is collected for dust removal and cooled to obtain crude liquid hydrogen fluoride.

[0091] (3) The crude liquid hydrogen fluoride is distilled to remove impurities and obtain anhydrous hydrogen fluoride. According to calculations, the recovery rate of fluorine in aluminum electrolysis solid waste is 85%.

[0092] Comparative Example 2

[0093] A method for resource utilization of aluminum electrolysis solid waste, comprising the following steps:

[0094] (1) First, the aluminum electrolytic solid waste is ground in a grinder to a particle size of 450 μm;

[0095] (2) The ground aluminum electrolytic solid waste is pre-mixed with 98% concentrated sulfuric acid at a mass ratio of 1:6.5, and 2000 g of aluminum electrolyte solid waste and 12000 g of 98% concentrated sulfuric acid are pre-mixed at 140° C. for 2.5 hours to obtain an acidic blend; the gas phase generated during the pre-mixing process is collected, dusted and cooled to obtain crude liquid hydrogen fluoride.

[0096] (3) Add the acidic blend of step (2) into a rotary kiln without adding a reaction aid, adjust the reaction temperature to 400°C, and the reaction time to 26 hours. Collect the gas produced by the reaction for dust removal, and cool it to obtain crude liquid hydrogen fluoride.

[0097] (4) The crude liquid hydrogen fluoride is distilled to remove impurities and obtain anhydrous hydrogen fluoride. According to calculations, the recovery rate of fluorine in aluminum electrolysis solid waste is 70%. In addition, after the reaction, there is a large amount of material adhering to the wall of the rotary kiln, which needs to be stopped for manual removal, and the slag is agglomerated in large quantities.

[0098] Results and Discussion:

[0099] It can be seen from Examples 1 to 6 that the recovery rate of fluorine in aluminum electrolysis solid waste reaches more than 97%, and there is basically no material sticking to the rotary kiln wall after the reaction in Examples 1 to 6.

[0100] It can be seen from Comparative Example 1 that the recovery rate of fluorine in aluminum electrolysis solid waste is greatly reduced without premixing of aluminum electrolysis solid waste and concentrated sulfuric acid. The reason for this is that after premixing, the electrolyte solid waste and sulfuric acid are evenly dispersed. Because the actual production rotary kiln only has a feeding screw but no stirring device, uneven mixing will cause the local reaction to be too strong or too weak, thus affecting the overall reaction effect. Uneven mixing may also cause a large amount of heat to be generated locally, triggering side reactions or product agglomeration, further reducing the recovery rate of fluorine.

[0101] Comparative Example 2 shows that without adding the reaction aid calcium salt, on the one hand, the fluorine recovery rate is greatly reduced, on the other hand, after the reaction, there is a large amount of bonding material on the rotary kiln wall, and the slag is agglomerated in large quantities. The reason for the analysis is: without adding the reaction aid, the sodium sulfate and calcium sulfate generated by the reaction of some materials with concentrated sulfuric acid quickly adhere to the wall and agglomerate, which is equivalent to forming a dense covering layer on the surface of the unreacted electrolyte solid waste, hindering the further contact between the concentrated sulfuric acid and the unreacted electrolyte solid waste. The formation of the reaction group will hinder the heat and mass transfer process between the reactants, causing the reaction rate to decrease. This further reduces the reaction efficiency and increases the reaction time.

[0102] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed. The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application. The above are only preferred implementation methods of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present application, and these improvements and variations should also be regarded as the protection scope of the present application.

Claims

1. A method for resource utilization of aluminum electrolysis solid waste, characterized in that: include: premixing the pretreated aluminum electrolysis solid waste with concentrated sulfuric acid to obtain an acidic mixture, and collecting hydrogen fluoride generated during the premixing process; A reaction aid calcium salt is added to the acidic blend and mixed evenly, and then added to a rotary kiln for reaction at high temperature, and hydrogen fluoride generated during the reaction is collected.

2. The method for resource utilization of aluminum electrolysis solid waste according to claim 1, characterized in that: After pretreatment, the aluminum electrolysis solid waste has a particle size of 50 μm to 500 μm.

3. The method for resource utilization of aluminum electrolysis solid waste according to claim 1, characterized in that: The mass ratio of the aluminum electrolysis solid waste to the concentrated sulfuric acid is 1:1-7, wherein the mass concentration of the concentrated sulfuric acid is not less than 98%.

4. The method for resource utilization of aluminum electrolysis solid waste according to claim 1, characterized in that: The premixing temperature is 20° C. to 150° C. and the premixing time is 0.5 h to 3 h.

5. The method for resource utilization of aluminum electrolysis solid waste according to claim 1, characterized in that: The reaction aid calcium salt is one or more of calcium sulfate, calcium carbonate and calcium oxide.

6. The method for resource utilization of aluminum electrolysis solid waste according to claim 5, characterized in that: The amount of the reaction aid calcium salt added is calculated according to the mass of the aluminum electrolysis solid waste, and the mass ratio of the reaction aid calcium salt to the aluminum electrolysis solid waste is 0.05 to 0.1:

1.

7. The method for resource utilization of aluminum electrolysis solid waste according to claim 6, characterized in that: The reaction auxiliary calcium salts are calcium sulfate, calcium carbonate and calcium oxide; wherein the mass ratio of calcium sulfate, calcium carbonate and calcium oxide is 2.8-3.2:2.8-3.2:3.8-4.

2.

8. The method for resource utilization of aluminum electrolysis solid waste according to claim 1, characterized in that: The high temperature reaction is carried out at a temperature of 200° C. to 500° C. and a time of 12 h to 26 h.

9. The method for resource utilization of aluminum electrolysis solid waste according to any one of claims 1 to 8, characterized in that: The recovery rate of fluorine in the aluminum electrolysis solid waste reaches more than 97%.

10. The method for resource utilization of aluminum electrolysis solid waste according to claim 9, characterized in that: The fluorine recovery rate is the sum of the first recovery rate and the second recovery rate; Wherein, the first recovery rate is generated from the hydrogen fluoride recovered during the premixing process, and the first recovery rate is 10% to 25%; The second recovery rate is generated by hydrogen fluoride recovered during the reaction process at the high temperature.

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