WO2014015539A1

WO2014015539A1 - Method of recycling of waste easy-open aluminum cans

Info

Publication number: WO2014015539A1
Application number: PCT/CN2012/079789
Authority: WO
Inventors: 张深根; 刘波; 潘德安; 田建军; 刘阳
Original assignee: 北京科技大学
Priority date: 2012-07-26
Filing date: 2012-08-07
Publication date: 2014-01-30
Also published as: CN102912140A; CN102912140B

Abstract

A method of recycling waste easy-open aluminum cans uses waste easy-open aluminum cans as raw materials and performs crushing, iron removal through magnetic separation, preprocessing paint removal, melting, component adjustment, modification processing, filtering, and casting to eventually obtain aluminum alloy for easy-open cans.

Description

Method for recycling green recycling of waste aluminum cans

The invention provides a method for recycling aluminum aluminum cans, belonging to the field of circular economy technology and environmental protection, and particularly relates to a method for recycling green recycling of waste aluminum cans. Background technique

It is estimated that the recovery rate of waste aluminum cans in China is over 96%, and at least 400,000 tons of waste cans are recovered every year, plus a small amount of imports, totaling around 500,000 tons. The existing waste aluminum cans are low in recycling and reuse, and the environmental pollution in the reuse process is serious. The main reason is that the recycling technology is low and the technical difficulty is high. The following five technical difficulties need to be solved: (1) The can body of the waste aluminum can is different from the aluminum alloy of the cover and the pull ring, and it is difficult to separate the body, the cover and the ring; (2) The inner and outer surface paint of the waste aluminum can is easily produced. Pollution, and affect the quality and recovery rate of recycled aluminum alloy; (3) Waste aluminum cans have thin texture, large surface area, severe smelting and oxidation loss, and low metal recovery rate; (4) Waste aluminum cans have wide sources and difficult pretreatment. It is easy to introduce impurities into the aluminum alloy melt during smelting, which makes the alloy composition complicated and the adjustment difficulty is increased. (5) The aluminum alloy ingot can be difficult to control the structure of the aluminum alloy ingot.

The can body of the waste aluminum can is different from the aluminum alloy of the cover and the pull ring (see Table 1). Theoretically, the separation, recycling and reuse of the can body, the cover and the pull ring are beneficial for re-use and reuse. Due to the serious deformation of the recovered aluminum cans, it is usually packed and compacted for convenient transportation. From the economic and practical conditions, it is impossible to separate the tank, the cover and the pull ring, and directly return the parts of the aluminum cans. Percentage)

The inner and outer surface paints of waste aluminum cans are prone to pollution during recycling and affect the quality of recycled aluminum alloys. Therefore, the broken aluminum cans must be stripped. Take off The lacquer method and paint stripping rate directly affect the quality of the finished aluminum or aluminum alloy material as well as the cost of use and environmental pollution. In the recycling of waste aluminum cans, stripping is one of the core technologies for the recycling of used aluminum cans, and it is also one of the difficulties.

The waste aluminum can has a thin texture and a large surface area. In order to reduce the smelting oxidation loss and improve the metal recovery rate, the double-chamber reverberatory furnace is generally used to melt, so that the aluminum piece is not in contact with the flame but directly added to the molten aluminum liquid, thereby avoiding waste. The burning of aluminum improves the metal recovery rate.

The waste aluminum cans have a wide range of sources, and are difficult to pretreat. It is easy to introduce impurities into the aluminum alloy melt during smelting, resulting in complex alloy composition and difficulty in adjusting composition and structure.

Waste aluminum can recycling and recycling technology is one of the important areas for comprehensive utilization of renewable resources. Since the widespread use of scrap aluminum cans, people have spontaneously recycled and reused cans, forming relevant technologies and intellectual property rights.

As early as September 29, 1989, Jin Dacheng and Guan Hongguo applied for the Chinese invention patent "Recycling cans and their sorting device" (Application No. 89107289.6), which disclosed a method for cutting and separating the lid and the bottom of the can. The side body of the can is ground into a separate collection method and device. Due to the thin and dispersed nature of the cans, the patented technology has not been widely used. On March 5, 2007, Wang Junyi, Hao Junwen and others applied for the utility model patent “Waste cans metal separation and recovery machine” (application No. 200720067610.9), designed a can metal separation and recovery machine, which can completely separate the two metals of cans. Due to the serious deformation of the recovered waste aluminum cans, this patented technology is difficult to be popularized and applied. On October 14, 2009, Chen Dingfang, Zhang Zhengyan and others applied for the Chinese invention patent "an automatic separation and crushing of iron aluminum cans" (Application No. 200910062072.8), which discloses a separation of iron and aluminum cans, The flattening technology device is actually an electromagnetic sorting and crushing technique.

On October 30, 2008, Li Quanxiang, Cheng Bowen and others applied for the Chinese invention patent "A Waste Can Surface Treatment Agent" (Application No. 200810152559.0), which discloses a surface treatment for the simultaneous removal of the surface of the can coating and the anticorrosive film of the inner wall. The agent is composed of dichloromethane, trifluoroacetic acid and water. On July 8, 2009, Kang Weimin, Chen Banglie and others applied for the Chinese invention patent "a kind of waste cans surface paint removal agent" (Application No. 200910069633.7), which disclosed a method for removing the surface of the cans at the same time. Agent, which is composed of formic acid, dichloromethane and water. The two patents use a chemical stripping process and have a heavy environmental burden.

On January 25, 2008, Befesa Aluminio Bilbao of Canada applied for Process for Recycling Spent Pot Linings (SPL) From Primary Aluminium Production European Patent (Application No. EP08380016.9), and applied for International Specialties through PCT (PCT/EP2009/000189). An acid hydrolysis method for recycling waste aluminum can products is disclosed. After crushing, pickling, and magnetic separation, aluminum raw materials widely used in the industry are obtained. On November 14, 2001, Russian, Abdurakhmanov AD applied for Method and Plant for Reworking Aluminium Tins (Application No. 2001131605/02), which discloses a method for treating waste aluminum cans, including crushing, magnetic separation, and organic removal. After the process, the scrap aluminum scrap is finally obtained. On January 8, 2003, Azrat Abdurakhmanov te Den Haag of the Netherlands applied for Methode en installatie voor de verwerking van aluminium blikjes, which disclosed the technology of crushing, sorting and washing of waste, cans. On November 28, 1995, Fry applied for the US patent Collector for empty used recyclable beverage cans (USP 5,469,783), which disclosed that the recycling device for the beverage cans in Hezhong can distinguish between iron cans, non-ferrous metal cans, and plastic cans. Automatic classification, with photoelectric sensors to provide quantitative information in the recycling device.

It can be seen that the existing patented technology for recycling and processing waste aluminum cans is a process technology, and some technologies have serious secondary pollution, and the obtained aluminum alloy products are degraded. Therefore, there is an urgent need to develop green recycling of waste aluminum cans for use in cans of aluminum alloys. Summary of the invention

The invention aims at the complex composition of the waste aluminum can, the organic coating on the inner and outer surfaces, and the complicated source. The crushing, magnetic separation and iron removal, pretreatment stripping, smelting, rapid detection of melt components, composition adjustment, modification treatment, filtration , casting, etc., and finally get aluminum alloy for cans. In order to achieve the standard discharge, the dioxin is decomposed by the secondary combustion of flue gas, the flue gas is quenched, and the technology is such as bag dust removal, activated carbon adsorption, and desulfurization (nitrogen).

(1) Crushing: The form of the recycled cans has been destroyed and broken into blocks. Therefore, before stripping, it is necessary to break up and crush to a certain particle size, which is conducive to the subsequent magnetic separation and stripping. .

(2) Stripping: Loose waste cans (including broken waste cans) directly enter the paint stripping kiln for stripping. The stripping paint is treated by a rotary paint stripping kiln. At the beginning, a certain amount of heat energy needs to be added. After reaching a certain temperature, the heat energy mainly depends on the exothermic heat of the surface paint of the can. In the rotary paint stripping kiln, the paint layer of the can is carbonized, relies on the vibration of the rotating process, the paint layer falls off, and finally the special vibration equipment is used to make the carbon particles fall off. In order to prevent the oxidation loss and overheating of the aluminum flakes, it is necessary to strictly control the temperature in the kiln and the secondary combustion of the flue gas containing oxygen: the gas from the rotary paint stripping kiln and the carbon particles are passed into the high temperature furnace for secondary combustion. The combustion is in the anoxic reduction zone, the temperature is controlled at about 850 °C, the flue gas continues to be sent to the secondary combustion chamber for complete oxidative decomposition, and the temperature in the secondary combustion chamber is relatively high, usually above 1000 °C. After the flue gas is burned at high temperature in the secondary combustion chamber, the dioxin-like substances have been basically eliminated. Studies have shown that the dioxin removal rate can reach 99.999%. When the flue gas enters the control equipment from the outlet of the secondary combustion chamber, the quenching technology is used to rapidly cool the flue gas temperature to 90-130 °C through the heat exchanger, and quickly pass over the temperature zone which is easy to generate dioxin, thereby suppressing it again. synthesis. The cooled flue gas is dedusted by bag, activated carbon adsorption and purification of flue gas after combustion, can absorb newly formed dioxins, reduce the content of dioxins in the flue gas, and finally reach the environmental protection requirements through the treatment of desulfurization and denitration tower.

(3) Smelting: The waste cans which have been pretreated and stripped are fed into a melting furnace for smelting. An advanced regenerative double chamber reverberatory furnace is used. The double-chamber reverberatory furnace is divided into inner and outer chambers, and the molten aluminum liquid is heated in the inner chamber, flows into the outer chamber, contacts the solid waste aluminum, and melts it, and the temperature is lowered, and then enters the inner chamber for heating, and the circulation is specially made. The ceramic pump is carried out. Since the waste aluminum is not in direct contact with the flame, it is directly added to the molten aluminum liquid, thereby avoiding the burning of the waste aluminum and improving the metal recovery rate.

(4) Adjustment of alloy composition: Controlling the chemical composition of aluminum alloy is the key to ensuring the reutilization of waste aluminum cans. It is necessary to strictly control the content of impurities Si, Fe, Cu, Mn, Zn, Cr, and Mg to suppress the brittleness caused by the element Na. The direct reading spectrometer is used to quickly detect the composition of the aluminum alloy melt, and the melt composition is adjusted according to the monitoring data, and finally meets the requirements for the aluminum alloy for the can.

(5) Degassing and removing impurities: Degassing is mainly one of the key processes for determining the quality of recycled aluminum alloys by removing hydrogen, sodium and calcium from molten aluminum. High temperature nitrogen or argon is used as the deaerator. The deaerator forms fine bubbles in the molten aluminum solution, and the bubbles contact the aluminum liquid, adsorbing the surrounding hydrogen and oxides such as calcium and sodium, and then flowing over the aluminum liquid.

(6) Metamorphism and refinement of grain treatment: In order to improve the morphology and size of the eutectic silicon, the formation of coarse needles and plate-like eutectic silicon is prevented, and the microstructure of the alloy is refined, and Al-Ti-B or Al-Ti is added. -C grain refiner to prevent cracking of ingots.

(7) Static insulation: The refined aluminum liquid is allowed to stand in the furnace for a certain period of time. First, it is convenient for the refining carrier to float and remove the gas and fine non-metallic inclusions in the aluminum liquid from the upper surface of the aluminum liquid, and the second is to facilitate the sinking of large non-metallic inclusions to the bottom of the furnace.

(8) Filtration: The aluminum alloy melt is filtered using a foam ceramic filter to remove inclusions.

(9) Casting: Continuously and smoothly casting with advanced semi-continuous ingot casting machine. Lubricating oil and casting gas permeate through the graphite ring to the surface of the crystallizer, forming a layer of oil and gas film between the aluminum alloy melt and the crystallizer, making casting The crystal grains of the ingot are fine and uniform, and the surface is smooth.

The invention has the advantages that the stripping treatment of the inner and outer surfaces of the waste aluminum can and the subsequent flue gas treatment are realized, and the environmental pollution of the recycling process is eliminated; the aluminum alloy for the cans is produced by using the waste aluminum cans as the raw material, and the relegation is achieved. Recycling; easy to industrialize, with significant economic, environmental and social benefits. DRAWINGS

Figure 1 is a flow chart showing the overall process of the method of the present invention. detailed description

The present invention will be further described in conjunction with the embodiments, but the present invention is not limited to the following embodiments.

Example 1

The scrap aluminum cans are mechanically broken up and shredded to obtain scattered pieces, and then the ferromagnetic metal mixed in the cans is separated by a magnetic separator to avoid mixing into subsequent processes.

The cans were hot stripped for 120 min at an oxygen partial pressure of 8% and a temperature of 450 °C. The flue gas generated during the hot stripping process is sent to the combustion furnace through the flue gas pipeline, and the dioxin-like substance is eliminated after burning at a temperature of 1000 ° C or higher. The temperature of the flue gas is rapidly cooled to below 130 ° C by a heat exchanger to suppress the re-synthesis of dioxins. The cooled flue gas is treated by bag dust removal, activated carbon adsorption, desulfurization and denitration tower treatment, and discharges after meeting environmental protection requirements. The hot-drawn paint cans are shaken to remove the adhered carbon particles by vibrating the sieve to prevent secondary pollution caused by the combustion of the carbon particles during the smelting process.

After the stripping of the aluminum sheet is packed, it is pressed into the molten aluminum liquid in the outer chamber of the regenerative double chamber reverberating furnace to be melted, so as to avoid direct contact of the flame with the aluminum sheet to reduce the recovery rate. Outer chamber aluminum liquid temperature control At about 700 ° C, the temperature of the aluminum liquid in the inner chamber is controlled at about 850 ° C. The molten aluminum in the inner and outer chambers is circulated by means of a ceramic pump.

After the aluminum sheet in the reverberatory furnace is completely melted and the aluminum liquid is evenly stirred, the aluminum alloy composition sample is extracted on-line, and the content of Si, Fe, Cu, Mn, Mg, Zn and Ti in the aluminum liquid and the impurity content are analyzed by a direct reading spectrometer. The Si, Fe, Cu, Mn, Mg, Zn and Zn alloy elements reach the range required for the aluminum alloy for cans, and the content of the single impurity element is less than 0.05%, and the total impurity content is less than 0.15%. Using 500 ° C nitrogen as a deaerator, it is evenly introduced into the aluminum alloy melt to form fine bubbles, which absorb hydrogen and calcium, sodium and other oxides in the aluminum liquid, and then float above the aluminum liquid.

Add 0.5% Α1ΤΪ5Β1 to the aluminum alloy melt for modification, improve the morphology and size of the eutectic silicon, prevent the formation of coarse needles and plate-like eutectic silicon, and refine the microstructure of the alloy. A grain refiner is added to prevent cracking of the ingot. After the metamorphism treatment, the composition and the impurity content satisfying the requirements of the 3104 aluminum alloy are allowed to stand in the holding furnace for a period of time, the refining carrier is floated, and the gas and the fine non-metallic inclusions in the aluminum liquid are taken out of the upper surface of the aluminum liquid. And removing, the large non-metallic inclusions sink to the bottom of the furnace; then the aluminum alloy melt is filtered by a ceramic filter to remove inclusions; the filtered aluminum alloy flows into the semi-continuous casting machine Continuous continuous casting, lubricating oil and casting gas penetrate into the surface of the crystallizer through the graphite ring, forming a layer of oil and gas film between the aluminum alloy melt and the crystallizer, so that the crystal grains of the ingot are fine and uniform, and the surface is smooth. Table 2 shows the composition of the aluminum alloy prepared in this example, which meets the requirements of the 3104 aluminum alloy composition specified in "GB/T3190-2008 Chemical composition of deformed aluminum and aluminum alloy".

Table 2 Comparison Table of Compositions of Aluminum Alloy and 3104 Aluminum Alloy Prepared in This Example (% by Weight)

Example 2

The waste aluminum cans are mechanically broken up and shredded to obtain scattered pieces, and then the ferromagnetic metal mixed in the cans is separated by a magnetic separator to avoid mixing into subsequent processes. The cans were hot stripped for 80 min at a partial pressure of oxygen of 0 and a temperature of 500 °C. The flue gas generated during the hot stripping process is sent to the combustion furnace through the flue gas pipeline, and the dioxin-like substance is eliminated after burning at a high temperature of 1000 ° C or higher. The temperature of the flue gas is rapidly cooled to below 130 ° C by a heat exchanger to suppress the re-generation of dioxins. The cooled flue gas is treated by bag dust removal, activated carbon adsorption, desulfurization and denitrification tower, and discharged after meeting environmental protection requirements. The cans of the cans after hot stripping are shaken to remove the adhered carbon particles by the vibrating screen to prevent secondary pollution caused by the combustion of the carbon particles during the smelting process.

After the stripping of the aluminum sheet is packed, it is pressed into the molten aluminum liquid in the outer chamber of the regenerative double chamber reverberating furnace to be melted, so as to avoid direct contact of the flame with the aluminum sheet to reduce the recovery rate. The temperature of the aluminum liquid in the outer chamber is controlled at about 750 °C, and the temperature of the aluminum liquid in the inner chamber is controlled at about 900 °C. The molten aluminum in the inner and outer chambers is circulated by means of a ceramic pump.

After the aluminum sheet in the reverberatory furnace is completely melted and the aluminum liquid is evenly stirred, the aluminum alloy composition sample is extracted on-line, and the content of Si, Fe, Cu, Mn, Mg, Zn and impurities in the aluminum liquid is analyzed by a direct reading spectrometer, and Si, Fe is required. The Cu, Mn, Mg, and Zn alloy elements are within the range required for the aluminum alloy for cans, and the content of the single impurity element is less than 0.05%, and the total impurity content is less than 0.15%. Using 600 °C nitrogen as a deaerator, the aluminum alloy melt is uniformly introduced to form fine bubbles, which adsorb hydrogen and calcium, sodium and other oxides in the aluminum liquid, and then float above the aluminum liquid.

0.1% ΑΓΠ5Β1 was added to the molten aluminum alloy for modification, which improved the morphology and size of the eutectic silicon, prevented the formation of coarse needles and plate-like eutectic silicon, and refined the microstructure of the alloy. A grain refiner is added to prevent cracking of the ingot. After the metamorphism treatment, the composition and the impurity content satisfying the requirements of the 3004 aluminum alloy are allowed to stand in the holding furnace for a period of time, the refining carrier is floated, and the gas and the fine non-metallic inclusions in the aluminum liquid are carried out of the upper surface of the aluminum liquid. And removing, the large non-metallic inclusions sink to the bottom of the furnace; then the aluminum alloy melt is filtered by a ceramic filter to remove inclusions; the filtered aluminum alloy flows into the semi-continuous casting machine Continuous continuous casting, lubricating oil and casting gas penetrate into the surface of the crystallizer through the graphite ring, forming a layer of oil and gas film between the aluminum alloy melt and the crystallizer, so that the crystal grains of the ingot are fine and uniform, and the surface is smooth. Table 3 shows the composition of the aluminum alloy prepared in this example, which meets the composition requirements of the 3004 aluminum alloy specified in "Chemical Composition of Modified Aluminum and Aluminum Alloys of GB/T3190-2008".

Table 3 Comparison Table of Components of Aluminum Alloy and 3004 Aluminum Alloy Prepared in the Present Example (% by Weight) Alloy composition Si Fe Cu Mn Mg Zn Ti Al This example 0.22 0.55 0.21 1.24 1.08 0.18 0.008

3004 can body 0.30 0.70 0.25 1.00-1.50 0.80-1.30 0.25 1 佘 quantity Example 3

The cans were hot stripped for 60 min at an oxygen partial pressure of 4% and a temperature of 550 °C. The flue gas generated during the hot stripping process is sent to the combustion furnace through the flue gas pipeline, and the dioxin-like substance is eliminated after burning at a high temperature of 1000 ° C or higher. The temperature of the flue gas is rapidly cooled to below 130 °C by a heat exchanger to suppress the re-generation of dioxins. The cooled flue gas is treated by bag dust removal, activated carbon adsorption, desulfurization and denitrification tower, and discharged after meeting environmental protection requirements. The hot-painted cans of the cans are vibrated by vibrating screen to remove the adhered carbon particles to prevent secondary contamination of the carbon particles during the smelting process.

After the stripping of the aluminum sheet is packed, it is pressed into the molten aluminum liquid in the outer chamber of the regenerative double chamber reverberating furnace to be melted, so as to avoid direct contact of the flame with the aluminum sheet to reduce the recovery rate. The temperature of the aluminum liquid in the outer chamber is controlled at about 800 °C, and the temperature of the aluminum liquid in the inner chamber is controlled at about 900 °C. The molten aluminum in the inner and outer chambers is circulated by means of a ceramic pump.

After the aluminum sheet in the reverberatory furnace is completely melted and the aluminum liquid is evenly stirred, the aluminum alloy composition sample is extracted on-line, and the content of Si, Fe, Cu, Mn, Mg, Cr, Zn and Ti and the impurity content in the aluminum liquid are analyzed by a direct reading spectrometer. It is required that the Si, Fe, Cu, Mn, Mg, Cr, Zn and Ti alloy elements reach the required range of the aluminum alloy for cans, the content of the single impurity element is less than 0.05%, and the total impurity content is less than 0.15%. Argon gas at 650 ° C is used as a deaerator, and fine aluminum bubbles are uniformly introduced into the aluminum alloy melt to adsorb hydrogen and calcium, sodium and the like in the aluminum liquid, and then float above the aluminum liquid.

Adding 0.25% AlTi5Cl to the aluminum alloy melt for modification, improving the morphology and size of the eutectic silicon, preventing the formation of coarse needles and plate-like eutectic silicon, and refining the microstructure of the alloy. A grain refiner is added to prevent cracking of the ingot. After the metamorphism treatment, the composition and the impurity content satisfying the requirement of the 5182 aluminum alloy are allowed to stand in the holding furnace for a certain period of time, and the refining carrier is floated to bring the gas and the fine non-metallic inclusions in the aluminum liquid out of the upper surface of the aluminum liquid. Remove, big The non-metallic inclusions of the block sink to the bottom of the furnace; then the aluminum alloy melt is filtered by a ceramic filter to remove inclusions; the filtered aluminum alloy flows into the semi-continuous casting machine for continuous smooth casting. The lubricating oil and the casting gas permeate through the graphite ring to the surface of the crystallizer, and a gas film is formed between the aluminum alloy melt and the crystallizer, so that the crystal grains of the ingot are fine and uniform, and the surface is smooth. Table 4 The composition of the aluminum alloy prepared in the present example meets the composition requirements of the 5182 aluminum alloy specified in "GB/T3190-2008 Modified Aluminum and Aluminum Alloy Chemical Composition".

Table 4 Comparison Table of Compositions of Aluminum Alloy and 5182 Aluminum Alloy Prepared in This Example (% by Weight)

Example 4

The cans were hot stripped for 20 min at an oxygen partial pressure of 4% and a temperature of 640 °C. The flue gas generated during the hot stripping process is sent to the combustion furnace through the flue gas pipeline, and the dioxin-like substance is eliminated after burning at a high temperature of 1000 ° C or higher. The temperature of the flue gas is rapidly cooled to below 130 °C by a heat exchanger to suppress the re-generation of dioxins. The cooled flue gas is treated by bag dust removal, activated carbon adsorption, desulfurization and denitrification tower, and discharged after meeting environmental protection requirements. The hot-painted cans of the cans are vibrated by vibrating screen to remove the adhered carbon particles to prevent secondary contamination of the carbon particles during the smelting process.

After the stripping of the aluminum sheet is packed, it is pressed into the molten aluminum liquid in the outer chamber of the regenerative double chamber reverberating furnace to be melted, so as to avoid direct contact of the flame with the aluminum sheet to reduce the recovery rate. The temperature of the aluminum liquid in the outer chamber is controlled at about 850 °C, and the temperature of the aluminum liquid in the inner chamber is controlled at about 950 °C. The molten aluminum in the inner and outer chambers is circulated by means of a ceramic pump.

After the aluminum sheet in the reverberatory furnace is completely melted and the aluminum liquid is evenly stirred, the aluminum alloy composition sample is extracted on-line, and the content of Si, Fe, Cu, Mn, Mg, Cr, Zn and Ti and the impurity content in the aluminum liquid are analyzed by a direct reading spectrometer. , requires Si, Fe, Cu, Mn, Mg, Cr, Zn, and Ti alloy elements to reach the required range of aluminum alloy for cans, and a single impurity element The amount is less than 0.05%, and the total impurity content is less than 0.15%. Argon gas at 700 °C is used as a deaerator, and fine aluminum bubbles are uniformly introduced into the aluminum alloy melt to adsorb hydrogen and calcium, sodium and the like in the aluminum liquid, and then float above the aluminum liquid.

0.75% AlTi5Cl was added to the molten aluminum alloy for modification, which improved the morphology and size of the eutectic silicon, prevented the formation of coarse needles and plate-like eutectic silicon, and refined the microstructure of the alloy. A grain refiner is added to prevent cracking of the ingot. After the metamorphism treatment, the composition and the impurity content satisfying the requirements of the 5042 aluminum alloy are allowed to stand in the holding furnace for a period of time, and the refining carrier is floated to bring the gas and the fine non-metallic inclusions in the aluminum liquid out of the upper surface of the aluminum liquid. Remove, the large non-metallic inclusions sink to the bottom of the furnace; then use the foam ceramic filter to filter the aluminum alloy melt, and remove the inclusions; the filtered aluminum alloy flows into the semi-continuous casting machine continuously Smooth casting, lubricating oil and casting gas penetrate into the surface of the crystallizer through the graphite ring, forming a layer of oil and gas film between the aluminum alloy melt and the crystallizer, so that the crystal grains of the ingot are fine and uniform, and the surface is smooth. Table 5 shows the composition of the aluminum alloy prepared in this example, which meets the composition requirements of the 5042 aluminum alloy specified in "Chemical Composition of Modified Aluminum and Aluminum Alloys of GB/T3190-2008".

Table 5 Comparison Table of Compositions of Aluminum Alloy and 5042 Aluminum Alloy Prepared in This Example (% by Weight)

Example 5

The cans were hot stripped for 100 min at an oxygen partial pressure of 6% and a temperature of 600 °C. The flue gas generated during the hot stripping process is sent to the combustion furnace through the flue gas pipeline, and the dioxin-like substance is eliminated after burning at a high temperature of 1000 ° C or higher. The temperature of the flue gas is rapidly cooled to below 130 ° C by a heat exchanger to suppress the re-generation of dioxins. The cooled flue gas is treated by bag dust removal, activated carbon adsorption, desulfurization and denitrification tower, and discharged after meeting environmental protection requirements. The cans of the cans after hot stripping are shaken to remove the adhered carbon particles by the vibrating screen to prevent secondary pollution caused by the combustion of the carbon particles during the smelting process. After the stripping of the aluminum sheet is packed, it is pressed into the molten aluminum liquid in the outer chamber of the regenerative double chamber reverberating furnace to be melted, so as to avoid direct contact of the flame with the aluminum sheet to reduce the recovery rate. The temperature of the aluminum liquid in the outer chamber is controlled at about 800 °C, and the temperature of the aluminum liquid in the inner chamber is controlled at about 880 °C. The molten aluminum in the inner and outer chambers is circulated by means of a ceramic pump.

After the aluminum sheet in the reverberatory furnace is completely melted and the aluminum liquid is evenly stirred, the aluminum alloy composition sample is extracted on-line, and the content of Si, Fe, Cu, Mn, Mg, Zn, Ti and impurities in the aluminum liquid is analyzed by a direct reading spectrometer, and Si is required. The Fe, Cu, Mn, Mg, Zn and Ti alloy elements are within the range required for the aluminum alloy for cans, the content of the single impurity element is less than 0.05%, and the total impurity content is less than 0.15%. Using 600 ° C of nitrogen as a deaerator, the aluminum alloy melt is uniformly introduced to form fine bubbles, which adsorb hydrogen in the aluminum liquid and oxygen such as calcium and sodium, and then float above the aluminum liquid.

Adding 1.0% ΑΓΠ5Β1 to the aluminum alloy melt for modification, improving the morphology and size of the eutectic silicon, preventing the formation of coarse needles and plate-like eutectic silicon, and refining the microstructure of the alloy. A grain refiner is added to prevent cracking of the ingot. After the metamorphism treatment, the composition and the impurity content satisfying the requirements of the 3104 aluminum alloy are allowed to stand in the holding furnace for a certain period of time, so that the refining carrier floats to bring the gas and the fine non-metallic inclusions in the aluminum liquid out of the upper surface of the aluminum liquid. Remove, the large non-metallic inclusions sink to the bottom of the furnace; then use the foam ceramic filter to filter the aluminum alloy melt, and remove the inclusions; the filtered aluminum alloy flows into the semi-continuous casting machine continuously Smooth casting, lubricating oil and casting gas penetrate into the surface of the crystallizer through the graphite ring, forming a layer of oil and gas film between the aluminum alloy melt and the crystallizer, so that the crystal grains of the ingot are fine and uniform, and the surface is smooth. Table 6 shows the composition of the aluminum alloy prepared in this example, which meets the composition requirements of 3104 aluminum alloy specified in "Chemical Composition of Modified Aluminum and Aluminum Alloys of GB/T3190-2008".

Table 6 Comparison Table of Compositions of Aluminum Alloy and 3104 Aluminum Alloy Prepared in This Example (% by Weight)

Claims

claims

1. A method for green recycling, upgrading and reuse of scrap aluminum cans. The specific steps are as follows:

(1) Crushing: Scatter and shred scrap aluminum cans;

(2) Magnetic separation and iron removal: Pass the crushed scrap aluminum can fragments through a magnetic separator to separate the ferromagnetic metal from the can fragments;

(3) Pretreatment paint removal: Put the can fragments into the paint removal kiln for paint removal, the paint layer will be carbonized, and then go through special vibration equipment to make all the carbon particles fall off;

(4) Melting: A regenerative double-chamber reverberatory furnace is used. After the stripped aluminum sheets are packed, molten aluminum is pressed into the outer chamber for melting. The molten aluminum is heated by the flame of the reverberatory furnace in the inner chamber. The molten aluminum liquid in the outer chamber is circulated by a ceramic pump; the temperature of the aluminum liquid in the outer chamber is 700°C-850°C, and the temperature of the aluminum liquid in the inner chamber is 850°C-950°C;

(5) Composition adjustment: The described composition adjustment is to control the content of Si, Fe, Cu, Mn, Mg, Cr, Zn and Ti in the aluminum alloy to meet the requirements of aluminum alloy for cans; the content of a single impurity element is less than 0.05%, and the impurity The total content is less than 0.15%;

(6) Modification treatment: The described modification treatment is to add 0.1%-1% AΓΠ5B1 or AlTi5Cl to the molten aluminum liquid to improve the morphology and size of the eutectic silicon, and prevent the formation of thick needles and plate-shaped eutectic silicon, so that The structure of the alloy is refined, and grain refiners are added to prevent ingot cracks;

(7) Filtration and casting: The modified aluminum liquid is allowed to stand in the holding furnace for a certain period of time, so that the refining carrier floats and the gas and small non-metallic inclusions in the aluminum liquid are brought out of the upper surface of the aluminum liquid for removal. Large pieces of non-metallic inclusions sink to the bottom of the furnace; then a foam ceramic filter is used to filter the aluminum alloy melt to further remove the inclusions; the filtered aluminum alloy flows into the semi-continuous ingot casting machine for continuous and smooth casting. Lubricating oil and casting gas penetrate into the surface of the crystallizer through the graphite ring, forming an oil and gas film between the aluminum alloy melt and the crystallizer, making the grains of the ingot fine and uniform, and the surface smooth, and finally the aluminum alloy for cans is obtained.

2. The method according to claim 1, characterized in that: the pretreatment paint removal in step (2) is performed by a rotary paint removal kiln, the oxygen partial pressure is not higher than 8%, and the temperature is 450°C - 640 °C, perform thermal paint removal for 20min-120min.

3. The method according to claim 1, characterized in that: after the flue gas generated during the thermal depainting process in step (2) is burned at a high temperature above 1000°C, the dioxin-like substances are eliminated. The heat exchanger quickly cools the flue gas temperature below 130°C, suppressing the Oxins are synthesized again; the cooled flue gas is bag dusted, activated carbon adsorbed, and processed through a desulfurization and denitrification tower before being discharged to meet environmental protection requirements.

4. The method according to claim 1, characterized in that: the component adjustment in step (5) uses 500°C-700°C high-temperature nitrogen or argon as a degassing agent, and is formed in the aluminum liquid that is uniformly passed through The tiny bubbles absorb hydrogen and oxides such as calcium and sodium in the aluminum liquid, and then float to the top of the aluminum liquid.