A method for resource utilization of high-iron aluminous ash
By using coarse crushing, ball milling, screening, and mixed smelting methods, high-iron aluminum ash is separated into secondary aluminum ash and iron-containing materials, solving the problem of resource waste in existing technologies, realizing efficient utilization of iron and aluminum resources, and improving economic benefits.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHONGQING LINLANG ENVIRONMENTAL PROTECTION TECH CO LTD
- Filing Date
- 2023-09-27
- Publication Date
- 2026-06-12
AI Technical Summary
In existing methods for utilizing aluminum ash from high-speed rail, the iron obtained from magnetic separation contains a large amount of aluminum ash and must undergo physical and chemical treatment or be used directly as a deoxidizer in steel plants, resulting in resource waste and low economic benefits.
By employing coarse crushing, ball milling, screening, magnetic separation, and mixed smelting, high-iron aluminum ash is separated into secondary aluminum ash, coarse material, and fine material. Aluminum-containing material and iron-containing material are obtained through magnetic separation, and then mixed and smelted with quicklime to form calcium aluminate melt and molten iron, thus achieving efficient separation and recovery of iron and aluminum.
It improves the resource utilization rate of high-speed rail aluminum ash, with an iron recovery rate of 87.78% and an aluminum recovery rate of 85.45%, and significantly reduces processing energy consumption and procedures. The product purity meets national standards and can be sold directly.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of solid waste treatment and comprehensive utilization of resources in the aluminum alloy processing industry, specifically to a method for the resource utilization of high-speed rail aluminum ash. Background Technology
[0002] As a hazardous waste, aluminum ash has been the subject of extensive research for resource recycling, resulting in a plethora of effective treatment methods and the development of a significant industry. However, electrolytic aluminum ash (hazardous waste code 321-024-48) constitutes a very small proportion of the total aluminum ash; the vast majority is alloy ash (hazardous waste code 321-026-48). Within alloy ash, iron-aluminum alloy ash constitutes a substantial proportion. This is because the iron added during the production of iron-aluminum alloys often originates from heavily corroded scrap iron. The high smelting temperatures during production generate a large amount of iron-containing aluminum ash slag. Particularly during the smelting of ferroalloys, large chunks of iron-rich pot bottoms are produced. When this high-iron aluminum ash is reused, a significant amount of iron is mixed into the remelted aluminum ingots (reaching over 10% iron content with increasing remelting temperature), severely impacting the quality of the remelted aluminum ingots.
[0003] Currently, the common method used is to separate these high-speed rail aluminum ash wastes using magnetic separation. However, the separated iron, because it carries a large amount of aluminum ash, is still classified as hazardous waste. Therefore, the aluminum ash must undergo physical and chemical treatment before landfilling, wasting a significant amount of valuable resources. To utilize this aluminum-containing high-speed rail aluminum ash, some steel mills use it directly as a deoxidizer due to its aluminum content. However, because its iron-aluminum content is highly unstable, its addition is entirely based on experience, which significantly impacts the stability of steel product quality. Consequently, the economic value of these iron-aluminum-containing magnetically separated materials is greatly underestimated, and some are even provided free of charge.
[0004] In summary, developing a high-speed rail aluminum ash resource utilization method with high resource utilization rate, simple process, and low energy consumption can not only effectively make up for the shortcomings of existing high-speed rail aluminum ash recycling processes, but also improve the resource utilization rate of high-speed rail aluminum ash, greatly enhance its economic benefits, and is of great significance for the recycling and utilization of high-speed rail aluminum ash resources. Summary of the Invention
[0005] The present invention aims to provide a method for the resource utilization of high-speed rail aluminum ash, in order to solve the technical problem that the iron obtained from the magnetic separation of high-speed rail aluminum ash contains a large amount of aluminum ash and must be landfilled after physical and chemical treatment, or simply used as a deoxidizer in steel plants, resulting in resource waste.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for the resource utilization of high-speed rail aluminum ash, comprising the following steps: (i) a coarse crushing, ball milling and screening stage, wherein the high-speed rail aluminum ash is coarsely crushed, ball milled and screened to obtain secondary aluminum ash, coarse material and fine material; (ii) a magnetic separation stage, wherein the aforementioned coarse material and fine material are magnetically separated to obtain aluminum-containing material and iron-containing material; (iii) a mixing and smelting stage, wherein the aforementioned secondary aluminum ash, iron-containing material and quicklime are mixed to obtain a mixture, and the mixture is smelted to obtain calcium aluminate melt and molten iron.
[0007] The principles and advantages of this scheme are:
[0008] 1. Compared to existing technologies, the iron obtained from magnetic separation, which contains a large amount of aluminum ash, must undergo physical and chemical treatment before being landfilled or simply used by steel plants, resulting in resource waste and no economic benefit. This solution, however, effectively improves the resource utilization rate of high-speed iron aluminum ash by mixing and smelting the iron-containing material after magnetic separation with secondary aluminum ash to recover iron resources in the form of molten iron. Specifically, using this method to recover and utilize 33t of high-speed iron aluminum ash (15.8% Fe, 5.3% Fe2O3, 19.6% Al, 45.5% Al2O3) (totaling 6.47t of iron and 6.47t of elemental aluminum), 6.10t of iron ingots, 5.70t of aluminum ingots, and 32.86t of calcium aluminate can be obtained. The iron recovery rate is as high as 87.78%, and the elemental aluminum recovery rate is as high as 85.45%, effectively realizing the resource utilization of high-speed iron aluminum ash.
[0009] 2. This solution separates high-speed iron aluminum ash into secondary aluminum ash, coarse material, and fine material through coarse crushing, followed by several ball milling and sieving processes. Then, magnetic separation can be used to separate the aluminum-containing and iron-containing materials in the coarse and fine materials. The aluminum-containing material obtained by magnetic separation has high purity, and subsequent smelting can yield aluminum ingots with a purity greater than 97% (meeting the aluminum purity requirements of the national standard "Recycled Cast Aluminum Alloy Raw Materials" (GB / T38472-2019)). The high quality ingots can be sold directly, effectively improving the recycling efficiency of aluminum in aluminum ash.
[0010] 3. This solution involves smelting a mixture of secondary aluminum ash, iron-containing materials, and quicklime in a single furnace. Compared to existing technologies that process iron-containing materials and secondary aluminum ash separately, this solution not only effectively saves processing steps and shortens processing time, but also simultaneously processes two types of hazardous waste (secondary aluminum ash and iron-containing materials), significantly reducing energy consumption and improving production efficiency.
[0011] 4. This method, through mixed smelting of iron-containing materials and secondary aluminum ash, thoroughly separates iron and aluminum into different products with significant density differences for recycling. This results in more thorough separation and recycling of iron and aluminum in high-speed iron aluminum ash, improving the resource recovery rate of iron and aluminum. The inventors' experiments revealed that the iron ingots cast from the molten iron recovered using this method have a purity greater than 93.1%, meeting the national standard for "Foundry Pig Iron" (GB / T718-2005) and can be directly sold as a product. Furthermore, the resulting calcium aluminate melt meets the requirements of the ferrous metallurgical industry standard for "Pre-melted Calcium Aluminate for Steelmaking" (YB / T4265-2011).
[0012] Preferably, the (a) ball milling and sieving stage includes the following steps:
[0013] S1. Coarse crushing and ball milling: After coarse crushing and ball milling, the high-speed iron aluminum ash is passed through a 90-mesh sieve and a 50-mesh sieve in sequence, and the ash under the 90-mesh sieve, the ash under the 50-mesh sieve and the ash on the 50-mesh sieve are collected respectively.
[0014] S2. Repeated ball milling and screening: Send the ash under the 50-mesh sieve into the temporary storage bin. After a batch of material has been ball milled and screened, put the ash under the 50-mesh sieve in the temporary storage bin back into the ball mill for screening. Repeat step S1 2-3 times. Combine the ash under the 90-mesh sieve obtained from multiple screenings to form secondary aluminum ash. The ash under the 50-mesh sieve from the last screening is fine material. Combine the ash over the 50-mesh sieve obtained from multiple screenings to form coarse material.
[0015] Beneficial effects: The above-mentioned setup facilitates the separation of agglomerated aluminum and iron particles encased in aluminum ash through ball milling, which in turn facilitates subsequent magnetic separation of iron-containing and aluminum-containing materials. Through long-term experiments, the applicant discovered that after coarse crushing and ball milling, most of the attached alumina ash was removed from large aluminum and iron blocks; however, fine aluminum particles remained trapped within the large amount of alumina ash and required further grinding. Therefore, ash passing through a 50-mesh sieve was selected for multiple ball milling processes to separate the aluminum particles encased in the ash, facilitating recycling and reuse.
[0016] Preferably, in S1, the feeding speed of the screening is 300-500 kg / min. In this scheme, the screening is completed in a screening machine, which includes a shell and a drum screen arranged coaxially in the horizontal direction. The drum screen is arranged at an inclination. A feed inlet is provided on the upper part of one side of the shell, and a three-stage discharge outlet is provided at the bottom of the shell. Along the material pushing direction, the discharge outlets are the first discharge outlet, the second discharge outlet, and the third discharge outlet. A first screen is provided on the side wall of the drum corresponding to the first discharge outlet, a second screen is provided corresponding to the second discharge outlet, and no screen is provided corresponding to the third discharge outlet. The first screen is a 90-mesh screen, and the second screen is a 50-mesh screen.
[0017] Beneficial effects: The ash undersize from the first discharge port is secondary aluminum ash, the ash undersize from the second discharge port is fine powder, and the ash directly discharged from the third discharge port is coarse powder. This scheme, using the above settings, facilitates rapid sieving of the mixture obtained from ball milling through a 90-mesh sieve and a 50-mesh sieve to obtain secondary aluminum ash, fine powder, and coarse powder. The inventors discovered through experiments that if the feeding speed is too fast, some small-diameter powder (such as less than 90 mesh) may enter the subsequent sieving process, becoming ash undersize or oversize ash on the 50-mesh sieve. This increases the volume of repeated ball milling and sieving, increases ball milling and sieving energy consumption, and reduces ball milling and sieving efficiency, thereby reducing production efficiency. Even worse, it reduces the sieving effect, resulting in a large amount of small-diameter powder remaining as fine or coarse powder after multiple sievings, leading to an increase in fine ash impurities in the aluminum-containing material after magnetic separation, thus affecting the quality of aluminum ingots. Conversely, if the feeding speed is too slow, it will significantly reduce production efficiency.
[0018] Preferably, the (ii) magnetic separation stage includes S3, which involves separately magnetically separating coarse and fine materials, and then combining and collecting the aluminum-containing and iron-containing materials obtained from the magnetic separation; the magnetic separation speed of the coarse material is 8-10 t / h, and the magnetic separation speed of the fine material is 10-12 t / h.
[0019] Beneficial effects: The above settings in this scheme facilitate the adjustment of the magnetic separation speed according to the magnetic separation effect of the components in the fine and coarse materials, thereby improving the magnetic separation effect, separating iron and aluminum as much as possible, and preventing iron from entering the aluminum-containing material and affecting the purity of the aluminum ingots cast subsequently.
[0020] Preferably, the screening and magnetic separation are carried out continuously. The process also includes testing the components in the coarse material, fine material, iron-containing material and aluminum-containing material. The ball mill screening endpoint is determined when the total aluminum and iron content in the fine material under the 50-mesh sieve reaches more than 60%. After magnetic separation, a certain amount of secondary aluminum ash, coarse material and fine material are obtained from the output.
[0021] Beneficial effects: The above-mentioned setup facilitates the separation of iron and aluminum in high-speed rail aluminum ash, and ensures that most of the iron is magnetically separated into the iron-containing material, thereby improving the iron recycling rate. Through long-term experiments, the applicant discovered that as the number of repeated ball millings of the ash under the 50-mesh sieve increases, the iron and aluminum content in the fine material (the ash under the last 50-mesh sieve) gradually increases. The applicant analyzed that the reason is that after coarse crushing and ball mill vibration, most of the alumina ash attached to the large aluminum and iron blocks is removed; however, the fine aluminum particles (and some iron particles) are trapped in the ash and need to be ground again. As the number of re-grindings increases, the fine aluminum ( / iron) particles are separated from the ash, and some fine aluminum and iron particles are ground into finer particles that can be detected in the fine material along with the ash. Therefore, the applicant chose to define the ball milling end point as "the total aluminum and iron content in the fine material under the 50-mesh sieve reaches more than 60%". This fully demonstrates that most of the aluminum and iron particles trapped in the ash under the 50-mesh sieve have been separated from the ash. At this point, stopping the repeated ball milling not only results in a higher recovery rate of aluminum and iron but also saves energy in the ball mill and improves production efficiency.
[0022] Preferably, the (iii) mixing and smelting stage includes the following steps:
[0023] S4. Ingredients: Mix secondary aluminum ash, quicklime and iron-containing materials in a mass ratio of 4-5:4-5:2-3 to obtain a mixture.
[0024] S5. Melting: Melt the above mixture to obtain calcium aluminate melt and molten iron;
[0025] S6. Discharge: After the mixture has completely melted, let it stand and separate into layers, then discharge the calcium aluminate melt and molten iron separately.
[0026] Beneficial effects: This solution uses the above-mentioned proportions of secondary aluminum ash, quicklime, and iron-containing materials, which facilitates the formation of calcium aluminate products after high-temperature smelting. Through long-term experiments, the applicant has found that if too much secondary aluminum ash is added, the excess will produce free alumina, resulting in excessively high alumina content in the calcium aluminate product and affecting product quality. If too much quicklime is added, free calcium oxide will be produced, causing the calcium aluminate product to pulverize, affecting product quality and even rendering it unusable. If too much iron-containing material is added, the excessive iron oxide content will prevent too much iron oxide from being reduced to elemental iron, and the residual iron oxide mixed in the calcium aluminate product will also affect the quality of calcium aluminate.
[0027] Preferably, in step S4, the content of Fe2O3 and elemental Al in the mixture is detected so that the Fe2O3 content is less than 2.96 times the mass of elemental Al when calculating the batching ratio.
[0028] Beneficial effects: The above settings in this scheme facilitate the addition of excess elemental Al while maintaining a Fe2O3 to elemental Al ratio of 1:2.96 in the mixture (the amount of quicklime added is calculated based on the amount of secondary aluminum ash fed, such as 1:1, according to the different grades of calcium aluminate products). Part of the excess elemental aluminum will gasify or oxidize, and the remaining small amount of elemental Al will form an alloy with iron, which facilitates the complete reaction of iron oxide. This results in the smelting of molten iron with high purity and effectively avoids iron oxide mixed in the calcium aluminate product, thus reducing product quality.
[0029] Preferably, in S5, the smelting is carried out in an electric arc furnace, which includes a furnace body and graphite electrodes. The furnace body includes a furnace cover and a furnace body. A calcium aluminate discharge port is opened at the furnace body, 20-30 cm away from the furnace bottom. A molten iron discharge port is opened laterally at the lowest point of the furnace bottom. The molten iron discharge port and the calcium aluminate discharge port are located on both sides of the furnace body.
[0030] Beneficial effects: The above-mentioned setup facilitates the separation of the calcium aluminate melt and molten iron after smelting, allowing them to separate into two layers and be discharged from different outlets.
[0031] Preferably, the electrode temperature during melting is 3000-4000℃, and the edge temperature of the electric arc furnace is 1600-1650℃.
[0032] Beneficial effects: The above-mentioned setup facilitates the smelting of secondary aluminum ash, quicklime, and iron-containing materials into molten iron and calcium aluminate. Through long-term experiments, the applicant discovered that if the electrode temperature is too low, the edge temperature of the electric arc furnace will be lower than the iron melting temperature, thus affecting the smelting process of the mixture at the edge of the electric arc furnace.
[0033] Preferably, in S6, the settling time is 5-10 minutes.
[0034] Beneficial effects: The above-mentioned setup facilitates the thorough stratification of the calcium aluminate melt and molten iron. Through long-term observation, the applicant has found a significant density difference between the calcium aluminate melt and molten iron. If the settling time is too short, slag inclusions will occur in the molten iron; if the settling time is too long, time and energy will be wasted. Attached Figure Description
[0035] Figure 1 This is a process flow diagram of the high-speed rail aluminum ash resource utilization method in Embodiment 1 of the present invention.
[0036] Figure 2 This is a cross-sectional view of the screening machine in Embodiment 1 of the present invention.
[0037] Figure 3 This is a cross-sectional view of the electric arc furnace in Embodiment 1 of the present invention. Detailed Implementation
[0038] The following detailed description illustrates the specific implementation method:
[0039] The reference numerals in the accompanying drawings include: outer shell 1, feed inlet 11, first discharge outlet 12, second discharge outlet 13, third discharge outlet 14, drum screen 2, first screen 21, second screen 22; graphite electrode 3, furnace body 4, furnace bottom 5, calcium aluminate discharge outlet 61, molten iron discharge outlet 62.
[0040] The following example, using a batch of high-speed rail aluminum ash, illustrates the method described in this invention. The main components of this batch of high-speed rail aluminum ash are: Fe: 15.8%, Al: 19.6%, Fe2O3: 5.3%, Al2O3: 45.5%, and others: 13.8%.
[0041] Example
[0042] This embodiment is basically as follows: Figure 1 The following is a method for the resource utilization of aluminum ash from high-speed rail, comprising the following steps:
[0043] (I) Coarse crushing, ball milling, and screening stage: After coarse crushing and ball milling, the high-speed iron aluminum ash is screened to obtain secondary aluminum ash, coarse material, and fine material; specifically, it includes the following steps:
[0044] S1. Coarse crushing ball milling and screening: First, the high-speed iron aluminum ash is coarsely crushed by a jaw crusher, and then sent to a ball mill for further ball milling and crushing. The mixed powder obtained after ball milling is sent to a drum-type double screening machine for screening. The mixed powder passes through a 90-mesh sieve and a 50-mesh sieve in sequence, and the ash under the 90-mesh sieve, the ash under the 50-mesh sieve, and the ash on the 50-mesh sieve are collected respectively.
[0045] In this solution, the screening machine is as follows: Figure 2 As shown, the device includes a horizontally coaxial outer shell 1 and a drum screen 2. The drum screen 2 is inclined, and the material moves forward by its own gravity when rotating. The upper left side of the outer shell 1 has a feed inlet 11, and the bottom of the outer shell 1 has three discharge outlets, which are the first discharge outlet 12, the second discharge outlet 13, and the third discharge outlet 14 in sequence along the material propulsion direction. The side wall of the drum screen 2 has a first screen 21 corresponding to the first discharge outlet 12 and a second screen corresponding to the second discharge outlet 13. No screen is set for the third discharge outlet 14, so that all the material can be discharged through the three discharge outlets.
[0046] In this scheme, the first screen 21 is a 90-mesh screen, the second screen is a 50-mesh screen, the ash under the first discharge port 12 is the ash under the 90-mesh screen, the ash under the second discharge port 13 is the ash under the 50-mesh screen, and the ash on the third discharge port 14 is the ash on the 50-mesh screen.
[0047] Furthermore, during the sieving process, the feeding speed at the inlet is 300-500 kg / min, which facilitates the thorough sieving of the ball-milled mixed powder according to particle size.
[0048] S2. Repeated ball milling and sieving: Repeat step S1 2 to 3 times with the ash under the 50-mesh sieve; combine the ash under the 90-mesh sieve obtained from multiple sievings to form secondary aluminum ash, and finally obtain the ash under the 50-mesh sieve as fine material, and combine the ash over the 50-mesh sieve obtained from multiple sievings as coarse material.
[0049] (ii) Magnetic separation stage: coarse and fine materials are separated by magnetic separation to obtain aluminum-containing material (i.e., remelted material) and iron-containing material;
[0050] S3. Separately magnetically separate coarse and fine materials, and collect aluminum-containing and iron-containing materials separately and then combine them; wherein, the magnetic separation speed of coarse material is 8-10 t / h, and the magnetic separation speed of fine material is 10-12 t / h.
[0051] In this scheme, screening and magnetic separation are carried out continuously. The process also includes testing the components in coarse materials, fine materials, iron-containing materials and aluminum-containing materials. When the total aluminum and iron content in the ash under the 50-mesh sieve reaches more than 60% (selectable range is 60-65%), it is determined as the endpoint of ball milling and screening. Ball milling and screening can be stopped to obtain a certain amount of secondary aluminum ash, and iron-containing materials and aluminum-containing materials are obtained through magnetic separation.
[0052] The total weight of the high-speed rail aluminum ash in this project is 33t. The weight of the "coarse material" obtained by screening is 9.7t and the weight of the "fine material" is 7.8t, with a total weight of 17.5t. The weight of the secondary aluminum ash is 15.4t. After magnetic separation, the weight of the iron-containing material is 7.8t and the weight of the aluminum-containing material is 9.7t.
[0053] The main components in high-speed rail aluminum ash, secondary aluminum ash, coarse material, fine material, iron-containing material, and aluminum-containing material were detected, and the results are shown in Table 1.
[0054] Table 1. Main components of high-speed rail aluminum ash, secondary aluminum ash, coarse material, fine material, iron-containing material, and aluminum-containing material.
[0055]
[0056] (III) Mixed smelting stage: Secondary aluminum ash, iron-containing materials, and quicklime are mixed to obtain a mixture. The mixture is smelted to obtain calcium aluminate melt and molten iron. The calcium aluminate melt is cooled to obtain pre-dissolved refining slag and calcium aluminate product. The molten iron is cooled to obtain iron ingots. The specific steps include the following:
[0057] S4. Batching: Mix secondary aluminum ash, quicklime, and iron-containing materials in a mass ratio of 4-5:4-5:2-3 to obtain a mixture. After batching, the mixture's elemental Al and Fe2O3 content is tested to ensure that the Fe2O3 content is less than 2.96 times the mass of elemental Al, i.e., m... Fe2O3 <2.96m Al .
[0058] In this embodiment, the mass ratio of secondary aluminum ash, quicklime, and iron-containing material is 4:4:2. According to the test results, in this batch of secondary aluminum ash and iron-containing material, the weight of elemental aluminum is 1.2t, and the weight of iron oxide is 1.5t, with a ratio of elemental aluminum to iron oxide of 1:1.25 (iron oxide is 1.25 times that of elemental aluminum). Theoretically, according to the chemical equation:
[0059] 2Al + Fe₂O₃ → Al₂O₃ + 2Fe
[0060] The ratio of elemental aluminum to iron oxide is 1:2.96 (54:160), and in this embodiment, elemental aluminum is in excess. A portion of the excess elemental aluminum vaporizes, a portion oxidizes, and the remainder forms an alloy with iron, facilitating the complete reaction of the iron oxide.
[0061] S5. Melting: The above mixture is fed into an electric arc furnace for melting at a temperature of 1600-1700℃ to obtain calcium aluminate melt and molten iron.
[0062] This method uses an electric arc furnace to melt the mixture, such as Figure 3 As shown, the electric arc furnace includes a furnace body and graphite electrodes. The furnace body includes a barrel-shaped furnace body 4 and an elliptical furnace bottom 5. A calcium aluminate discharge port 61 is opened at a distance of 20-30cm from the furnace bottom 5. A molten iron discharge port 62 is opened laterally at the lowest point of the furnace bottom 5. The molten iron discharge port 62 and the calcium aluminate discharge port 61 are located on both sides of the furnace body.
[0063] Before smelting, graphite electrodes need to be inserted into the electric arc furnace. After the mixture is fed into the electric arc furnace, the power supply to the graphite electrodes is turned on to start heating. Because the electric arc furnace is large, and the heat transfer in the mixture is delayed after the graphite electrodes are heated, and the furnace wall is thick, the temperature at the outer edge of the furnace is always much lower than the electrode temperature. Therefore, in this embodiment, the electrode temperature is controlled at 3000-4000℃ and the edge temperature of the electric arc furnace is controlled at 1600-1650℃, so that the mixture in the center and edge of the electric arc furnace can be smelted into calcium aluminate melt and molten iron.
[0064] S6. Discharge: After the mixture has completely melted, let it stand for 5-10 minutes to separate into layers, and then discharge the calcium aluminate melt and molten iron separately.
[0065] Because the volume difference between the calcium aluminate melt and molten iron formed in a single smelting process is significant (the calcium aluminate melt is larger than the molten iron), after each smelting and settling for 5-10 minutes, the smelting mixture can be quickly separated into an upper layer of calcium aluminate melt and a lower layer of molten iron. At this point, only the upper layer of calcium aluminate melt can be discharged from the calcium aluminate outlet 61, while the lower layer of molten iron can be accumulated through multiple smelting processes and then discharged from the molten iron outlet 62 at the bottom of the electric arc furnace. Specifically, when the molten iron accumulates to the upper liquid level near the calcium aluminate outlet 61, it is discharged in the order of "calcium aluminate melt - molten iron." In this way, the molten iron can be significantly improved through multiple smelting processes, thereby increasing the purity of the molten iron and the iron purity in the iron ingots. Specifically, in this embodiment, 33 tons of high-iron aluminum ash raw material yielded a total of 6.1 tons of iron ingots, of which the elemental iron content was 93.1%; a total of 32.86 tons of calcium aluminate was produced, with a purity of over 90%.
[0066] In addition, the aluminum-containing material was also sent to the remelting workshop to be smelted into aluminum liquid, and cooled to obtain 5.70 tons of aluminum ingots, of which the content of elemental aluminum was 97%.
[0067] In the comparative examples, all high-speed iron aluminum ash came from the same high-speed iron aluminum ash produced by the same enterprise and were tested under different working conditions. Each batch of feed was determined to be 33t based on the volume of the existing temporary storage silo. The quicklime added each time calcium aluminate was smelted came from the same batch of quicklime from the same manufacturer. In all examples, the slag removed after aluminum melting in the remelting workshop was not treated or statistically analyzed. In all examples, the dust removal ash was not treated.
[0068] Examples 2-3 and Comparative Examples 1-10 are basically the same as Example 1, except that the values of some parameters differ during the process. For details of the parameter differences in Examples 1-3 and Comparative Examples 1-10, please refer to Table 2.
[0069] Table 2. Differences in parameters in Examples 1-3 and Comparative Examples 1-10
[0070]
[0071]
[0072] The purity of the iron ingots, aluminum ingots, and calcium aluminate obtained from the treatment of high-iron-content ash in Examples 1-3 and Comparative Examples 1-10, as well as the iron and aluminum recovery rates, are detailed in Table 3.
[0073] In the recovery rate calculation, iron is calculated as elemental iron, and aluminum is calculated as elemental aluminum. The recovery rate calculation formula is as follows:
[0074] Iron recovery rate % = Amount of elemental iron in the recovered iron ingot / Total amount of iron in the raw material * 100%.
[0075] Elemental aluminum recovery rate % = Amount of elemental aluminum in the recovered aluminum ingot / Equivalent amount of elemental aluminum in the raw material * 100%.
[0076] Table 3 shows the treatment results of high-speed rail aluminum ash in Examples 1-3 and Comparative Examples 1-10.
[0077]
[0078] Experimental data shows that in this scheme, high-speed iron aluminum ash, after crushing, ball milling, screening, and magnetic separation, yields secondary aluminum ash, iron-containing material, and aluminum-containing material. The aluminum-containing material is then remelted to obtain aluminum ingots. Furthermore, by batching secondary aluminum ash, iron-containing material, and quicklime, molten iron and calcium aluminate melt are obtained, effectively recovering iron and aluminum. When exploring factors affecting iron and aluminum recovery rates, the applicant found that factors such as ball milling feed rate, ball milling endpoint, magnetic separation speed, batching ratio, the ratio of elemental aluminum to iron oxide, and smelting temperature all affect the iron and aluminum recovery rates in the following ways:
[0079] 1. Ball mill screening feed speed: If the feed speed is too fast (as in Comparative Example 2), the ball mill efficiency is low, and the number of ball milling cycles is more frequent. Although it does not significantly affect the recovery rate of iron and aluminum, the overall process is more time-consuming and energy-intensive, thereby reducing the company's production efficiency. If the feed speed is too low (as in Comparative Example 3), the impact of the ball mill on aluminum particles and iron oxide will be greater. Some elemental aluminum and iron oxide will be crushed and enter the secondary aluminum ash, resulting in a decrease in the aluminum recovery rate (only 78.36%). However, since the iron oxide in the secondary aluminum ash can be utilized, the iron recovery is not affected.
[0080] 2. Endpoint of ball milling: The lower the aluminum and iron content in the fine material (i.e., ash under the 50-mesh sieve) at the end of ball milling (as in Comparative Example 1), the heavier the ash content in the fine material, which increases the difficulty of subsequent aluminum remelting, increases energy consumption, and thus reduces production efficiency; the higher the aluminum and iron content in the fine material (i.e., ash under the 50-mesh sieve) at the end of ball milling (as in Comparative Example 6), the more intense the ball milling, and the more elemental aluminum and iron oxide enter the secondary aluminum ash, which greatly affects the aluminum recovery rate (as in Comparative Example 6, the aluminum recovery rate is only 81.13%); however, because the iron oxide in the secondary aluminum ash can be utilized, the iron recovery rate is not affected.
[0081] 3. Magnetic separation speed: If the magnetic separation speed is too fast (as in Comparative Example 4), it will lead to incomplete separation of iron and aluminum, with some iron entering the remelted aluminum material. This will not only reduce the purity of the aluminum ingots but also reduce the iron recovery rate. Specifically, in Comparative Example 4, the iron ingot output was only 5.8t, while the aluminum ingot output increased to 5.8t, but the purity of the aluminum ingots decreased to 94.8%, which cannot meet the purity requirements of aluminum in the national standard "Recycled Cast Aluminum Alloy Raw Materials" (GB / T38472-2019). On the other hand, if the magnetic separation speed is too low (as in Comparative Example 5), although iron can be magnetically separated from aluminum, it will be time-consuming and energy-intensive, resulting in more harm than good.
[0082] 4. The mass ratio of secondary aluminum ash, quicklime, and iron-containing materials (i.e., the ratio of elemental aluminum to iron oxide): Since quicklime can be added according to product requirements, its amount affects the grade of calcium aluminate in the product, but has little impact on the aluminum and iron recovery rates. For example, in Comparative Examples 7-8, neither excessive nor insufficient quicklime affects the iron recovery rate. However, the ratio of elemental aluminum to iron oxide in the secondary aluminum ash and iron-containing materials significantly affects the aluminum and iron recovery effect. In the embodiments and comparative examples of this scheme, elemental aluminum is in excess. Therefore, as long as the mass ratio of elemental aluminum to iron oxide is greater than 1:2.96, the iron ingot product is not affected. However, the applicant's previous experiments found that if the mass ratio of elemental aluminum to iron oxide is less than 1:2.96, the iron oxide is not completely reduced to iron, which significantly reduces the iron recovery rate.
[0083] 5. Melting Temperature: If the melting temperature is too low (as in Comparative Example 10), the fluidity of the molten material in the electric arc furnace will decrease, resulting in more slag inclusions in the molten iron, which will affect the purity of the iron ingots. For example, the iron ingots in Comparative Example 10 have an iron content of only 88.1%, which cannot meet the iron ingot sales standards (iron content of more than 90%). If the melting temperature is too high (as in Comparative Example 9), in addition to extra energy consumption, it will also have a negative impact on the refractory materials of the furnace body. Moreover, if the melting temperature is too high, although the iron purity will be slightly improved, the iron production will be reduced (the iron ingot production in Comparative Example 9 is only 5.8t), thereby reducing the iron recovery rate (only 83.82%).
[0084] In summary, this scheme effectively improves the resource utilization rate of high-iron aluminum ash by mixing and smelting the iron-containing material after magnetic separation with secondary aluminum ash to recover iron resources in the form of molten iron. Specifically, using this method to recover and utilize 33t of high-iron aluminum ash (15.8% Fe, 5.3% Fe2O3, 19.6% Al, 45.5% Al2O3) (totaling 6.47t of Fe and 6.47t of elemental aluminum), 6.1t of iron ingots, 5.70t of aluminum ingots, and 32.86t of calcium aluminate can be obtained. The iron recovery rate is as high as 87.78%, and the aluminum recovery rate is as high as 85.45%, effectively realizing the resource utilization of high-iron aluminum ash. In addition, this solution involves smelting a mixture of secondary aluminum ash, iron-containing materials, and quicklime in a single furnace. Compared to existing technologies that separately process and simply utilize iron-containing materials and secondary aluminum ash, this solution not only effectively saves processing steps and shortens processing time, but also simultaneously processes two types of hazardous waste (secondary aluminum ash and iron-containing materials), significantly reducing energy consumption and improving production efficiency.
[0085] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.
Claims
1. A method for the resource utilization of aluminum ash from high-speed rail, characterized in that: Includes the following steps: (a) The coarse crushing, ball milling, and screening stage involves coarsely crushing, ball milling, and screening of the high-speed iron aluminum ash to obtain secondary aluminum ash, coarse material, and fine material; including the following steps: S1. Coarse crushing and ball milling: After coarse crushing and ball milling, the high-speed iron aluminum ash is passed through a 90-mesh sieve and a 50-mesh sieve in sequence, and the ash under the 90-mesh sieve, the ash under the 50-mesh sieve and the ash on the 50-mesh sieve are collected respectively. S2. Repeated ball milling and screening: The ash under the 50-mesh sieve is sent to the temporary storage bin. After a batch of material is ball milled and screened, the ash under the 50-mesh sieve in the temporary storage bin is put back into the ball mill for screening. This process is repeated 2-3 times. The ash under the 90-mesh sieve obtained from multiple screenings is secondary aluminum ash. The ash under the 50-mesh sieve from the last screening is fine material. The ash over the 50-mesh sieve obtained from multiple screenings is coarse material. (ii) Magnetic separation stage: the aforementioned coarse and fine materials are magnetically separated to obtain aluminum-containing and iron-containing materials; S3. Separately magnetically separate the coarse and fine materials, and combine and collect the aluminum-containing and iron-containing materials obtained from the magnetic separation; the magnetic separation speed of the coarse material is 8-10 t / h, and the magnetic separation speed of the fine material is 10-12 t / h. The screening and magnetic separation are carried out continuously. The process also includes testing the components in the coarse material, fine material, iron-containing material and aluminum-containing material. The ball mill screening endpoint is determined when the total aluminum and iron content in the fine material under the 50-mesh sieve reaches more than 60%. After magnetic separation, a certain amount of secondary aluminum ash, coarse material and fine material are obtained from the output. (III) Mixing and smelting stage: The aforementioned secondary aluminum ash, iron-containing material, and quicklime are mixed to obtain a mixture, which is then smelted to obtain calcium aluminate melt and molten iron; including the following steps: S4. Ingredients: Mix secondary aluminum ash, quicklime and iron-containing materials in a mass ratio of 4-5:4-5:2-3 to obtain a mixture. S5. Melting: Melt the above mixture to obtain calcium aluminate melt and molten iron; S6. Discharge: After the mixture has completely melted, let it stand and separate into layers, then discharge the calcium aluminate melt and molten iron separately.
2. The method for resource utilization of high-speed rail aluminum ash according to claim 1, characterized in that: In S1, the feeding speed of the screening is 300-500 kg / min, and the screening is completed in the screening machine. The screening machine includes a shell and a drum screen arranged coaxially in the horizontal direction. The drum screen is arranged at an inclination. The upper part of one side of the shell is provided with a feed port, and the bottom of the shell is provided with three discharge ports, which are the first discharge port, the second discharge port and the third discharge port in sequence along the material pushing direction. The drum side wall is provided with a first screen corresponding to the first discharge port, a second screen corresponding to the second discharge port, and no screen corresponding to the third discharge port. The first screen is a 90-mesh screen and the second screen is a 50-mesh screen.
3. The method for resource utilization of high-speed rail aluminum ash according to claim 2, characterized in that: S4 also includes detecting the Fe2O3 and elemental Al content in the mixture, ensuring that the Fe2O3 content is less than 2.96 times the mass of elemental Al.
4. The method for resource utilization of high-speed rail aluminum ash according to claim 3, characterized in that: In S5, the smelting is carried out in an electric arc furnace, which includes a furnace body and graphite electrodes. The furnace body includes a furnace cover and a furnace body. A calcium aluminate discharge port is opened in the furnace body, 20-30cm away from the furnace bottom. A molten iron discharge port is opened laterally at the lowest point of the furnace bottom. The molten iron discharge port and the calcium aluminate discharge port are located on both sides of the furnace body.
5. The method for resource utilization of high-speed rail aluminum ash according to claim 4, characterized in that: The electrode temperature during the smelting process is 3000–4000℃, and the edge temperature of the electric arc furnace is 1600–1650℃.
6. The method for resource utilization of high-speed rail aluminum ash according to claim 5, characterized in that: In S6, the settling time is 5-10 minutes.