[China Aluminum Network] The United States, Japan, Germany, Australia and other developed countries in the aluminum scrap pretreatment technology research and application started earlier, has achieved the mechanization and automation of aluminum scrap pretreatment, can limit the removal of metal And non-metallic impurities, improve production efficiency and sorting quality, reduce production costs. The pretreatment process used includes sorting, disassembling, packing, drying and degreasing, organic coating on the surface, and the like. 1.1 Sorting Sorting methods mainly include morphological sorting, mechanical sorting, heavy medium sorting, fire sorting and electrostatic sorting. 1.1.1 Form separation Morphological sorting refers to physical sorting, that is, sorting according to appearance marks (color, section characteristics, hardness, mass density, magnetism, etc.) and physical marks (part names, winning prizes, etc.). Visual methods can be used, but also by spot analysis, spectroscopic analysis and special instruments. For example, iron, copper, and aluminum alloys can be distinguished by color; white gold The genus can distinguish aluminum, magnesium, zinc, lead, cupronickel, tin, etc. according to the difference in the surface color after cleaning; the material of the parts with the same size can be distinguished according to the different mass densities, for example, the magnesium parts are lighter than the aluminum parts. Use magnetic to determine the steel parts that are aluminized or aluminized. When the color, density and magnetic properties cannot be identified, spot analysis, spectral analysis, and special instruments can be used for sorting. In the spot analysis method, chemicals are dropped on the smooth surface of the metal or alloy, and the presence of a certain element can be judged according to the displayed color. The type of the alloy can be determined by sequentially dropping different reagents. Such as using CdSO. (5 g), NaCl (10 g), and hydrochloric acid (20 mL) were mixed with an aqueous solution (100 mL) on the surface of the metal. If it appeared black after 10-20 s, it indicated that it was a magnesium alloy; if it was gray, It is an aluminum-zinc alloy, and for aluminum and aluminum alloys, it is a transparent color. At the same time, it can also roughly estimate the content of an element based on the depth of the color. Droplet analysis is simple and easy to use. For some special parts, if you need to accurately determine the chemical composition, you must use spectral analysis. 1.1.2 Mechanical sorting Mechanical sorting includes particle size sorting, wind selection, magnetic separation, flotation, and vortex selection. 1.1.2.1 Granular sorting method When it is necessary to sort the fine or large component elbow from the aluminum scrap, a size sorting method may be adopted. Sorting process - generally using screening machines, including fixed sieves, trommel and vibrating screens. There are grid type and horizontal type fixed sieves, suitable for sorting aluminum scrap with particle size J larger than 50 mm. The screening machine shall not be less than 350 when sifting bulk materials, and not less than 50 when sorting flat-shaped materials or damp pieces. . The screening efficiency of the grid-type screening machine does not exceed 65%. The required sieve area F can be calculated as follows: F=Q/2.4a Where Q - sorting capacity by raw scrap /t·h-1 a-Screen strip gap width/mm The following principles should be followed when selecting the size of the grid-type screen: The width of the screen should be greater than twice the size of the larger material; the length of the screen should be at least 2 times its width. The trommel is a cylindrical rotating drum with perforations. There are several screens in the drum (diameter of the sieve holes are not -). They are installed in series or in parallel. If the aluminum waste contains a lot of dust, a plurality of water spray heads are usually installed in the drum for wet screening. Roller screens are suitable for screening large and medium blocks (blocks with a particle size of less than 250-). They can be used to produce screened products with a particle size of not less than 25 inches. The drum tilt angle is 2. ~8. The speed is 10-15 r/nlin. Vibrating screens are widely used for grain size separation of aluminum scrap. According to the shaking of the sieve, the shaker can be divided into inertial sieve, automatic balance sieve and resonance sieve. The inertial screen has one or two replaceable screen boxes mounted on a spring hanger or a metal frame. The vibration of the screen is achieved by the rotation of the shaft; the automatic balance screen is commonly used for dehydration and suspension of aluminum scrap. Separation and washing of weighting agents; resonant sieves are suitable for sifting aluminum scraps with a particle size of up to 300 mm. They have strong sorting power, high reliability and low energy consumption. 1.1.2.2 Wind-selection Wind separation is the use of air flow to separate aluminum and aluminum alloys from non-metallic inclusions such as less dense paper scraps, plastic films, wood blocks, and dust. The winnowing method is the ideal method to separate light non-metallic inclusions. 1.1.2.3 Magnetic Separation Magnetic separation can be used to sort out ferromagnetic inclusions and parts with large amounts of iron inlays from aluminum scrap. It has been widely used in foreign countries. This method is suitable for aluminum scraps, slag, aluminum scrap, broken cables, scraps and stamping scraps with a particle size below 450 mm. Iron is a harmful impurity in aluminum and aluminum alloys, and its performance is also greatly affected. Therefore, the inclusion of iron should be sorted out to a greater extent in the pretreatment process. Whether or not ferromagnetic inclusions can be completely separated depends on the particle size, layer thickness, build-up, and inclusion rate of the waste, as well as the strength of the magnetic field and the speed at which the material moves within the magnetic field. Magnetic separators mainly include suspended separators and electromagnetic wheels. The suspended sorter is installed along the conveyor in the longitudinal or transverse direction. The iron-containing material is sucked by the separator into the discharge belt and then transported to the discharge end. The suspended sorter cannot sort ferromagnetic materials with a size less than 5 nlln and a weight less than 80 g or more than 20 kg; the electromagnetic wheel is suitable for sorting ferromagnetic substances in bulk or bulk materials, and the conveyor belt performs better. The speed is 1.25 to 2.00 m/s, and it is maintained at a speed of 50-60 r/min with the electromagnetic wheel. The particle size of the material to be separated and the thickness of the material layer on the conveyor belt must not exceed 150 nUll. 1.1.2.4 Flotation Flotation is also called water selection. The method uses water as the suspending medium and uses the buoyancy of water to separate the light materials such as plastics, wood blocks, rubber, etc. contained in the waste materials from the aluminum material and take them away by the water with a constant flow rate, meanwhile, the soil and the dust The water is also carried away into the sedimentation tank. This method can completely separate lightweight materials with low density and is easy to use. 1.1.2.5 Vortexing Different metals have different electromagnetic forces when they move in an alternating electric field, so the resulting throwing distance is also different. The vortex selection method is based on this principle and separates aluminum from non-aluminum metal by the action of electromagnetic force. The more commonly used equipment is an eddy current separator. Although this equipment has a large investment, the separation efficiency is high (the general trash removal rate is more than 99%) and the production cost is low. 1.1.3 Heavy Media Sorting Heavy media sorting is sorting with heavy media made of weighting agent, suspending agent and water. For example, when the density of heavy media is 3 150 kg/rm?, heavy metals and aluminum with fixtures sink, aluminum and aluminum alloy wastes float; when the density of heavy media is 2 780 kg/in3, the copper-zinc alloy sinks. When the density of heavy media is 2 690 kg/ITl3, aluminum-copper alloy sinks; heavy media When the density is 2 550 kg/IIl3, the aluminum-silicon alloy sinks, while the aluminum-magnesium alloy and aluminum-magnesium-silicon alloy float. The heavy medium sorting method requires special heavy medium preparation equipment. The separation efficiency is low (-generally less than 90%), and the production cost is high. Currently, it has rarely been adopted. 1.1.4 Fire sorting The pyrometallurgical separation is the use of aluminum and aluminum alloys with different melting points of iron, tin, zinc, and lead, which are separated by controlling the smelting temperature in stages during the smelting process. When the melting temperature is controlled at 200 to 250%, tin first melts and flows out; at 300 to 350°C, lead melts and flows out; at 400 to 450°C, zinc melts and flows out; and then the melting temperature rises to above 580% until After melting aluminum and aluminum alloys, high-melting metals such as iron are pulled out. Separation of cast aluminum alloys from wrought aluminum alloys and can bodies and can lids can also be separated by pyrometallurgical separation. 1.1.5 Electrostatic separation Electrostatic separation uses the effect of an electric field to separate metallic conductors from insulating objects. Objects in the electric field, regardless of their composition, are charged, and the magnitude of the charge depends on the polarity of the halo motor and the characteristics of the material. With the same electric field, the metal conductor has a larger charge than the insulating object. When the charged object releases its own charge when it comes in contact with the ground conductor, the amount of discharged electricity depends on the resistance, capacitance and contact time. For metal conductors, due to their low electrical resistance, the charge they carry will quickly release when contacted with a grounded conductor and will not be adsorbed, while the insulating object will retain its own charge for a long time, and thus it is easily adsorbed. This is the basic principle of electrostatic separation. The metal object on the surface of the drum of the electrostatic separator instantaneously releases its own electric charge and falls into the drum. The insulator then rotates with the drum and remains on the surface of the drum, and then falls into another drum. Electrostatic separation is mostly used for the pretreatment of waste wire and cable. 1.2 Disintegration The disassembly is to transform the Cu, Fe, Mg, zn and other metals embedded in the bulk aluminum scrap into a free body to facilitate separation and to reduce the scrap and weight of the scrap for subsequent processing. Disintegration can be divided into dismantling disintegration and destruction disintegration two. Dismantling and dismantling can recover valuable parts and products (such as rolling bearings, fasteners, etc.) from waste parts. This method is more common in China's Zhejiang and other places. When disassembling and disassembling, use fitter tools and electric nut wrenches. The disintegration of aluminum or aluminum alloy waste or scraps mostly uses destruction and disintegration. The destruction of disintegration is divided into shear disintegration and disintegration. The shear disintegration is applicable to the disintegration of deformed aluminum and aluminum alloy scraps. The small scrap is usually cut by a guillotine shear, while the shear material with a large shear cross section is mostly hydraulic shears; the disintegration of broken pieces is suitable for the dismantling of aluminum alloy castings. Depending on the size of the broken product, the crusher can be divided into three types: coarse crusher (250-300 mm), intermediate crusher (25-30 mill) and crusher (less than 3 mm). General crushers mainly include drop hammer crushers, jaw crushers, roller crushers and hammer crushers. Drop hammer crusher is suitable for crushing large aluminum alloy castings, slags, etc. The weight of drop hammer ranges from 500 to 1 000 slaves to 6.15 t. The larger size of broken material blocks is 1500 to 2 000 mm. The larger size of the rear block is 500-300mm; Jaw crusher is suitable for coarse crushing of slag, the reduction rate is 3-5, the operation reliability is strong, and it is convenient to use; the roller crusher is suitable for processing grain size less than 3mm. The slag and other materials can be used to recover the aluminum in the slag. The hammer crusher is broken by a hammer hinged on a rotating rotor. The size of the crushing impact force depends on the size of the hammer and the rotation speed of the rotor. Productivity High, large reduction (up to 50). Led Integrated Emergency Device Led Lamp Automatic Emergency Device,Led Automatic Emergency Device,Led Emergency Device,Led Light Emergency Device,Emergency Driver For Led Lights Foshan Nai An Lighting Electric Co.,ltd , https://www.articalight.com
Foreign aluminum waste pretreatment process