CN109402423B - Method for reducing harmful waste residues generated in remelting and refining waste aluminum - Google Patents
Method for reducing harmful waste residues generated in remelting and refining waste aluminum Download PDFInfo
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- CN109402423B CN109402423B CN201811449029.2A CN201811449029A CN109402423B CN 109402423 B CN109402423 B CN 109402423B CN 201811449029 A CN201811449029 A CN 201811449029A CN 109402423 B CN109402423 B CN 109402423B
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C1/00—Making non-ferrous alloys
- C22C1/02—Making non-ferrous alloys by melting
- C22C1/026—Alloys based on aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/06—Making non-ferrous alloys with the use of special agents for refining or deoxidising
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
- C22C21/02—Alloys based on aluminium with silicon as the next major constituent
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Abstract
The invention discloses a method for reducing harmful waste residues in remelting and refining waste aluminum, which comprises the following steps of adding a fluoride-free nitrate-based refining agent into waste aluminum in the process of remelting and refining; the fluoride-free nitrate-based refining agent is formed by blowing high-purity nitrogen into an aluminum melt through a seamless steel pipe and blowing twice in a smelting furnace; and after slagging off and standing the melt, casting to obtain a cast ingot product. The front end of the seamless steel pipe for blowing is tightly coated with an inorganic high-temperature adhesive before blowing so as to reduce melt iron increase. When the aluminum-silicon alloy press cast ingot such as ADC12 is produced by remelting the waste aluminum impurity, the method can greatly reduce harmful waste residues, even eliminate fluorine-containing harmful waste residues, reduce the environmental protection pressure, improve the quality of the regenerated aluminum silicon ingot and have good application prospect.
Description
Technical Field
The invention belongs to the technical field of aluminum alloy smelting, and particularly relates to a method for reducing harmful waste residues generated in remelting and refining waste aluminum.
Background
Aluminum and aluminum alloys have been widely used in various fields of national economy, and a large amount of aluminum scrap is inevitably produced after the end product has been finished in service life. The recovery and recycling of aluminum and aluminum alloy are one of the main sources of aluminum resources, and have become an important link in the aluminum processing industry chain. At present, many enterprises in the waste aluminum recycling industry in China generally lack precise instruments and equipment, cannot carry out fine sorting and classification on waste aluminum, and can only be used for preparing ADC12 isobaric cast aluminum alloy ingots after remelting, so that degraded recycling is realized. Because the surface of the waste aluminum product is usually coated or oxidized, and the mixing is serious, the impurity content is very high during remelting, and the metallurgical quality of the die-casting aluminum ingot can be ensured only by performing strengthening refining.
At present, aluminum-silicon alloy pressed cast ingots are produced in China by remelting waste aluminum, then adopting chloride and villiaumite as refining agents, blowing nitrogen and the refining agents into an aluminum melt through a steel pipe to realize degassing and deslagging of the aluminum melt, and then casting and molding. In the process, a large amount of smelting waste slag is necessarily generated. Since the common refining agent contains high fluorine salt, fluoride is inevitably contained in the waste slag. The fluoride is harmful to the environment, so the waste slag generated by remelting and refining belongs to harmful waste slag, and aluminum-silicon pressure ingot production enterprises bear high environmental protection pressure and waste slag treatment cost. Therefore, research and development of a feasible method for reducing harmful waste residues generated by remelting and refining waste aluminum, particularly fluorine-containing harmful waste residues, are important problems in the aluminum processing industry at present.
Disclosure of Invention
The invention provides a method for reducing harmful waste residues generated by remelting and refining waste aluminum, aiming at solving the problem that a large amount of fluorine-containing harmful waste residues are generated during the regeneration of the waste aluminum in the current industry. The method can reduce the harm of the smelting waste slag to the environment, and can effectively improve the metal recovery rate and the product quality.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method for reducing harmful waste slag in remelting and refining waste aluminum comprises the following steps:
the method comprises the following steps: the recovered and sorted waste mixed aluminum, industrial pure aluminum, silicon agent and other raw materials are proportioned according to the specified proportion of alloy brand, and then added into a gas furnace for remelting according to the specified sequence;
step two: after the raw materials are completely melted and properly stirred, blowing a fluoride-free nitrate-based refining agent into the aluminum melt through a seamless steel tube by adopting high-purity nitrogen for primary refining, wherein the refining time is 15-20 minutes; the blowing flow of the refining agent is 2.0-2.5 kg/min.
Step three: slagging off the aluminum melt after primary refining, standing for 10-30 minutes, blowing nitrogen and a fluorine-free nitrate-based refining agent into the aluminum melt by using a blowing pipe to perform secondary refining, wherein the refining time is 15-20 minutes; the blowing flow of the refining agent is 2.0-2.5 kg/min.
Step four: slagging off the aluminum melt after secondary refining, and standing for 20-30 minutes; and then starting the casting machine for casting to obtain the aluminum-silicon alloy cast ingot.
The method for reducing the harmful waste residues generated in remelting and refining the waste aluminum is characterized in that the addition amount of the fluoride-free nitrate-based refining agent is 0.10-0.15% of the mass of the molten aluminum during the first refining, and the addition amount of the fluoride-free nitrate-based refining agent is 0.10% of the mass of the molten aluminum during the second refining. The fluorine-free nitrate-based refining agent comprises the following components in percentage by mass: 30% of sodium nitrate, 35% of potassium nitrate, 5% of activated carbon, 5% of magnesium chloride, 5% of calcium chloride, 5% of hexachloroethane, 10% of potassium chloride and 5% of sodium chloride. The purity of the high-purity nitrogen reaches more than 99.99 percent, and the dew point is below 70 ℃ below zero. Before refining, the inner and outer surfaces of the front end (the end extending into the aluminum melt) of the seamless steel pipe for blowing are tightly coated with an inorganic high-temperature glue. The inorganic high-temperature adhesive is a commercially available DB5010 single-component high-temperature inorganic adhesive; the coating and curing operations were performed according to the product instructions.
Compared with the prior art, the invention has the following advantages: (1) the adoption of a fluoride-free nitrate-based refining agent can effectively reduce harmful waste residues. The invention adopts an environment-friendly fluorine-free refining agent which takes nitrate as a main component and matches with chloride and carbon in a proper amount. The nitrate reacts with carbon at high temperature to generate nitrogen and carbon dioxide gas, and the gas carries impurities and gas (mainly hydrogen) out of the melt when floating upwards in the aluminum melt, thereby realizing the degassing and deslagging of the aluminum melt. The chlorine salt and the activated carbon are added to the refining agent in order to enhance the adsorption capacity to bubbles and impurities, improve the refining effect, and properly reduce the reaction speed. (2) And high-purity nitrogen is adopted for blowing twice, so that the refining effect is enhanced. By increasing the purity of the nitrogen, oxygen and moisture in the nitrogen are reduced, thereby reducing the oxide inclusions in the melt. Before the method is adopted, an enterprise generally carries out primary blowing refining, and the adding amount of a refining agent is about 0.20-0.25% of the mass of an aluminum melt. Most of the refining agent components end up as smelting slag, so the more refining agent is added, the more slag is added. The invention adopts the idea of 'multipurpose nitrogen and less salt', ensures the melt refining effect and controls the total amount of the molten slag by blowing and refining twice under the condition of equivalent total consumption of the refining agent. Before the method is adopted, only one-time blowing refining is carried out, the produced smelting waste slag is about 13.5kg per ton of melt, and after the method is adopted, two-time blowing refining is carried out, and the produced smelting waste slag is about 15.0kg per ton of melt. Although the total amount of the waste residue is increased, the waste residue is generated without fluorine and harm. The aluminum content in the waste residues is high, and fine frying can be carried out subsequently, and the aluminum in the waste residues is deeply recycled. The waste residue (secondary aluminum ash) after fine frying does not contain fluorine, and can be used as a raw material for other industries for recycling. (3) The air injection steel pipe is coated by inorganic high-temperature glue, so that the increase of iron in a melt is avoided, and the quality of the aluminum-silicon die-cast ingot is ensured. The blowing refining is carried out twice at high temperature, and the ablation degree of the blowing steel pipe is inevitably increased, therefore, the invention adopts the high-temperature inorganic glue which can resist 1200 ℃ to tightly coat the inner surface and the outer surface of the steel pipe which is deep into one end of the melt, so as to reduce the ablation of the steel pipe in the aluminum melt, prevent the melt from increasing iron and simultaneously prolong the service life of the steel pipe.
Detailed Description
The present invention is further illustrated by the following specific examples.
Example 1
A method for reducing harmful waste slag in remelting and refining waste aluminum comprises the following steps:
the method comprises the following steps: 20 tons of recycled and sorted raw materials such as waste aluminum, industrial pure aluminum, silicon agent and the like are proportioned according to the specified proportion of ADC12 alloy mark, and then added into a gas furnace for remelting according to the specified sequence;
step two: after the raw materials are completely melted and properly stirred, a fluoride-free nitrate-based refining agent is blown into an aluminum melt through a seamless steel tube by adopting high-purity nitrogen gas to carry out primary degassing, deslagging and refining, wherein the refining time is 10-15 minutes, and the blowing flow of the refining agent is 2.0-2.5 kg/min.
Step three: and after slagging off, standing for 10-30 minutes, blowing nitrogen and a fluorine-free nitrate-based refining agent into the aluminum melt subjected to primary refining by using a blowing pipe for secondary refining, wherein the refining time is 10-20 minutes, and the blowing flow of the refining agent is 2.0-2.5 kg/min.
Step four: slagging off the aluminum melt after secondary refining, and standing for 20-30 minutes; and then starting the casting machine for casting to obtain the aluminum-silicon alloy cast ingot.
The adding amount of the fluoride-free nitrate-based refining agent in the second step is 0.15 percent of the mass of the aluminum liquid, and the adding amount of the fluoride-free nitrate-based refining agent in the third step is 0.10 percent of the mass of the aluminum liquid.
The fluorine-free refining agent in the second step and the third step comprises the following components in percentage by mass: 30% of sodium nitrate, 35% of potassium nitrate, 5% of activated carbon, 5% of magnesium chloride, 5% of calcium chloride, 5% of hexachloroethane, 10% of potassium chloride and 5% of sodium chloride.
The purity of the high-purity nitrogen in the second step and the third step reaches more than 99.99 percent, and the dew point is below 70 ℃ below zero.
Before refining, the inner and outer surfaces of the front end (the end extending into the aluminum melt) of the seamless steel pipe for blowing in the second step and the third step are tightly coated by an inorganic high-temperature glue. The inorganic high-temperature adhesive is a commercially available DB5010 single-component high-temperature inorganic adhesive; the coating and curing operations were performed according to the product instructions.
Examples 2 to 3
Other production tests of pressed ingots were carried out in the same manner as in example 1, except that: the product from the trial of example 2 was an ADC10 die cast ingot, and the product from the trial of example 3 was an ADC14 die cast ingot.
Comparative example 1
The difference from the embodiment 1 is only that the addition amount of the fluoride-free nitrate-based refining agent in the second step and the third step is more and is 0.2 percent of the mass of the aluminum liquid, and the other processes are the same.
Comparative example 2
The difference from the embodiment 1 is only that the addition amount of the fluoride-free nitrate-based refining agent in the second step and the third step is less, and is 0.05 percent of the mass of the aluminum liquid, and the other processes are the same.
Comparative example 3
The difference from the embodiment 1 is only that the addition amount of the fluoride-free nitrate-based refining agent in the step two is 0.25 percent of the mass of the molten aluminum, and the refining agent is left for 10 to 15 minutes after slagging-off without secondary refining treatment; the rest processes are the same.
Comparative example 4
The only difference from the example 1 is that the refining agent in the second step and the refining agent in the third step are changed into the fluorine-containing refining agent, and the refining agent consists of the following components in percentage by mass: 47% of potassium chloride, 30% of sodium chloride and 23% of cryolite (anhydrous sodium fluoroaluminate); the rest processes are the same.
Comparative example 5
The difference from the example 1 is only that the purity of the nitrogen in the second step and the third step is 99.95 percent, the dew point is below 30 ℃, and the rest processes are the same.
Comparative example 6
The only difference from example 1 is that the seamless steel pipe for blowing described in the second and third steps was not subjected to any surface layer protection treatment, and the remaining processes were the same.
The test results of examples 1-3 and comparative examples 1-6 are tabulated below:
TABLE 1 summary of test results for examples and comparative examples
From the above table test data, it can be seen that:
the addition amount of the fluoride-free nitrate-based refining agent can influence the amount of waste residues generated in the remelting process and the quality of cast ingot products, the amount of the waste residues can be increased when the refining agent is more, but the defects generated by the cast ingot are correspondingly reduced;
the adoption of the fluorine-containing refining agent can ensure the product quality, but can generate fluorine-containing harmful slag which can cause damage to both human bodies and the environment;
the purity of the nitrogen also has certain influence on the quality of the product, the higher the purity is, the lower the oxygen content and the water content are, the oxide content and the pore defects of the ingot casting product can be reduced, and the product quality is improved;
the spraying treatment of the inorganic high-temperature glue on the inner and outer surfaces of the seamless steel pipe for injection can reduce the iron content of cast ingot products and obviously prolong the service life of the steel pipe.
In a word, the invention adopts an environment-friendly fluoride-free nitrate refining agent and high-purity nitrogen gas twice blowing to strengthen the remelting and refining of the aluminum scrap, although a small amount of smelting waste residue is increased, the waste residue is fluoride-free and harmless, and can be recycled; the method of coating the air injection steel pipe with the inorganic high-temperature glue can avoid the increase of iron in the melt and prolong the service life of the injection pipe. The method of the invention can stably produce a plurality of aluminum-silicon alloy pressed ingots with excellent quality.
Claims (1)
1. A method for reducing harmful waste slag in remelting and refining waste aluminum is characterized by comprising the following steps:
the method comprises the following steps: the recovered and sorted waste mixed aluminum, industrial pure aluminum and silicon agent raw materials are proportioned according to the specified proportion of alloy brands and then added into a gas furnace for remelting according to the specified sequence;
step two: after the raw materials are completely melted and properly stirred, blowing a fluoride-free nitrate-based refining agent into the aluminum melt through a seamless steel tube by adopting high-purity nitrogen for primary refining, wherein the refining time is 15-20 minutes; the blowing flow of the refining agent is 2.0-2.5 kg/min;
step three: slagging off the aluminum melt after primary refining, standing for 10-30 minutes, blowing nitrogen and a fluorine-free nitrate-based refining agent into the aluminum melt by using a blowing pipe to perform secondary refining, wherein the refining time is 15-20 minutes; the blowing flow of the refining agent is 2.0-2.5 kg/min;
step four: slagging off the aluminum melt after secondary refining, and standing for 20-30 minutes; then starting a casting machine for casting to obtain an aluminum-silicon alloy cast ingot;
the addition amount of the fluoride-free nitrate-based refining agent is 0.10-0.15% of the mass of the aluminum liquid during the first refining, and the addition amount of the fluoride-free nitrate-based refining agent is 0.10% of the mass of the aluminum liquid during the second refining;
the fluorine-free nitrate-based refining agent comprises the following components in percentage by mass: 30% of sodium nitrate, 35% of potassium nitrate, 5% of activated carbon, 5% of magnesium chloride, 5% of calcium chloride, 5% of hexachloroethane, 10% of potassium chloride and 5% of sodium chloride;
the purity of the high-purity nitrogen in the second step and the third step reaches more than 99.99 percent, and the dew point is below 70 ℃ below zero;
before refining, the inner surface and the outer surface of one end of the seamless steel pipe for injection, which extends into the aluminum melt, are tightly coated with an inorganic high-temperature adhesive, wherein the inorganic high-temperature adhesive is a DB5010 single-component high-temperature inorganic adhesive.
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Denomination of invention: A method for reducing harmful waste residue in remelting refining of waste aluminum Effective date of registration: 20220531 Granted publication date: 20191227 Pledgee: Yujiang branch of the Industrial Commercial Bank of China Ltd. Pledgor: JIANGXI BAOTAI NON-FERROUS METAL GROUP Co.,Ltd. Registration number: Y2022980006723 |