RU2321462C2 - Method of processing of electronic and cable scrap - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: invention relates to dry processing of electronic and cable scrap and it can be widely used in processing of radioelectronic junk and game playing machines with separation of metals and sorting out plastics. Proposed method of processing of electronic and cable scrap consists of two stages of milling in impact mills, sieve sizing to get particles of +5 mm and -5 mm, directing +5 mm particles to second stage of milling, electrostatic separation with obtaining middlings in form of locked concretions. Then gravity separation of - 5 mm particles is carried out on concentration table and tailings, together with middlings from electrostatic separator, are directed to second stage to unlock middlings. All flow of milled and partially separated scrap is directed for magnetic separation, and nonmagnetic product, for electrostatic separation.

EFFECT: increased capacity, extraction and quality of metal concentrate, higher degree of junk cleaning from dielectric, reduced energy consumption and cost of process.

1 dwg

Description

The invention relates to dry processing of electronic and cable scrap and can be most widely used for the processing of electronic scrap and gaming machines with the extraction of metals and sorting of plastics.

The organization of recycling industrial and household waste today has stopped the further increase in the extraction of raw materials.

The task of processing electronic scrap is today especially urgent, since a twofold increase in the volume of these wastes occurs every 5 years. Electronic scrap is an especially valuable material containing almost all metals, including precious ones. It is ten times cheaper to extract these metals from electronic scrap than from ore. Many plastics are already acquiring the value of metals, and electronic scrap contains at least 70% of plastics that can be removed in parallel with metals.

The known method of pyrometallurgical processing of scrap is aimed at burning plastics, however, it is not possible to catch all the emitted dioxins, therefore firms using this method are switching to other technologies.

Processing electronics in heavy suspensions is also harmful to the environment.

The most rational and environmentally friendly methods are electromechanical technologies, which make it possible to obtain a polymetallic concentrate without using liquids, free it from non-metals, and then direct this concentrate to pyrohydrometallurgical processes to produce individual metals.

A known method of processing an insulated cable (US patent No. 4362276 from 1982.12.07), including crushing it in a knife crusher, in an impact mill, separation in an electrodynamic separator and processing on a vibrating pneumatic concentration table.

In the known method, pieces of wire are cut into small particles in a knife crusher and fed to a vibration concentration table, through the holes in which air is supplied providing gravitational separation of the cable: heavy metal and light insulation particles are directed along the table surface in different directions, and particles in which the wire is covered with insulation; they occupy an intermediate position at unloading. When rubbing against the table, the insulation receives an electrostatic charge and slows down due to adhesion to the table surface, and metal particles give off the charge of the grounded table surface and are unloaded unhindered without slowing down. Fine particles of insulation are carried away by the air flow through the exhaust hood.

Further, the intermediate stream of particles of wires with insulation enters the electrodynamic separator, which operates on the basis of Foucault currents. On it, metal particles are discarded further than particles completely coated with insulation. The latter fall into the impact mill, where they are partially cleaned of insulation and returned again to the concentration table for cleaning.

The known method is characterized by high productivity, but the complexity and need for a large number of equipment and is not suitable for processing electronic scrap due to the low (up to 90%) recovery of metal concentrate.

A known method of processing circuit boards from electrical and electronic devices (US patent No. 5683040 from 1997.11.04). The method includes knife crushing of scrap, its further selective cryogenic regrinding, air separation, screen classification, heating of the product, drying, subsequent electrostatic separation and magnetic separation with the release of collective metal concentrate.

In accordance with the known method, after the knife crusher, the pieces of electronic scrap are cooled with liquid nitrogen in a special chamber, and then they are periodically loaded into the hammer mill, to which liquid nitrogen is also fed. The small product that passed through the openings of the grill of the crusher is sent for classification, then for heating, drying, and each size class is sent to all types of separation. Large particles that have not passed through the grinder of the hammer mill are discharged from it periodically and sent to a magnetic separator, where after separation of the hard-crushed iron, the remaining part of the product is sent for grinding to the grinder. After the first magnetic separator, the product is cleaned in an electrodynamic separator based on Foucault eddy currents. The same process occurs after the electrostatic separator: magnetic and electrodynamic separation.

The advantage of this method over the previous analogue is the high recovery (95%) of the metal.

The disadvantage of this method is low productivity, very high complexity and a large amount of equipment. In particular, the method includes the use of cryogenic technology before crushing in a hammer mill. Such an operation not only makes the process more expensive, but also does not lead to high-quality product disclosure. Since the plastic separated from the metal components is well embrittled and separated by impact, and the plastic in contact with the metal is poorly cooled, since the metal has good thermal conductivity and quickly heats up during crushing, reducing embrittlement. Therefore, the selectivity of the disclosure is sharply reduced and requires various types of separation after crushing. The periodic crushing cycle also complicates the processing scheme. However, further complicating the scheme is the need for heating and drying the ground scrap before electrostatic separation after deep cooling of the scrap. The cold product, leaving the hammer mill, immediately becomes condensed due to the inevitable loss of moisture from the surrounding air. Electrical separation is not possible with this humidity. Hence the need for additional energy-intensive operations requiring extra equipment. The cooling and drying operations do not allow to achieve the most complete release of metal.

Known for the prototype method for processing electronic and cable scrap (patent RU 2166376 C1, 05/10/2001, B03C 7/08), including crushing, grinding, size classification and separation, in which the grinding process is carried out selectively in hammer crushers, by impact and intralayer grinding in a closed cycle, with air and sieve classification, while the particles of the material are made smaller than 5 mm and sent as a monolayer to a conveyor with a metal belt, to which high-voltage corona ele rozaryady simultaneously doizmelchaya particles and charging the electrostatically charged particles and separating it at the outlet from the conveyor to a conductive metal, and a dielectric intermediate fraction which is recycled to the metal strip for re-separation.

Verification of this method showed insufficient selectivity for the disclosure of scrap and not a high percentage of metal recovery from the feedstock.

The objective of the present invention is to ensure maximum metal recovery (up to 98%), improving the quality of the concentrate, that is, increasing the degree of its purification from dielectrics and increasing the productivity of the method.

The problem is solved by the proposed method for processing electronic and cable scrap, including crushing, impact selective grinding, screen classification, separation on a concentration table, as well as electrostatic and magnetic separation with the release of collective metal concentrate, in which, in accordance with the present invention, the tails of gravity separation together with the intermediate product of the electrostatic separator is sent for regrinding in a shock mill, while the magnetic sep Aration of the entire product is carried out before electrostatic separation.

The drawing shows a process diagram of the implementation of the method.

In accordance with the invention, the source material in the form of a cable, gaming machines, computers or other products is loaded into a knife crusher 1, from which it enters the high-speed hammer mill 2 of the 1st stage. The product of the mill 2 (smaller than 25 mm) is sent for classification to the drum screen 3, from which particles larger than 5 mm enter the hammer mill 4 of the II stage. Particles smaller than 5 mm from the screen 3 are sent to a concentration table 5, the tails of which are fed to the mill 4 for opening the splices, and then to the magnetic separator 6. Magnetic concentrate from the separator 6 is sent to the shipment, and non-magnetic enters the electrostatic separator 7. Monolayer material flow on this separator is subjected to processing by high-voltage corona pulsed electric discharges of 40 kV from the high-voltage generator 8.

Corona electro-pulse discharges pass mainly along the contact surfaces of a metal and a dielectric in intergrowths of particles and destroy them along these surfaces, providing good separation selectivity. At the same time, the particles receive an electrostatic charge, but the metal immediately gives it to the tape of the electrostatic separator as a low-voltage electrode and falls from the tape as a neutral bulk material. The dielectric adheres to the tape of the separator 7 due to the residual charge and comes off already under it, forming its own flow. The intermediate product, which is an unopened splices, falls into the mill 4 for regrinding and additional disclosure of splices.

Selective disclosure of scrap is provided in special high-speed impact hammer mills, in which each rotor carries more than two hundred flat impact elements, striking with their pointed ends on pieces of scrap and destroying its weak bonds, due to different inertia of the dielectric and metal. The remaining intergrowths are selectively crushed in a layer against each other and beat according to the principle of forced self-grinding. Reaching the size of the holes in the grill of the mill, they enter a drum screen, where during its rotation there is not only classification, but also tumbling (cleaning) of metal particles from the remaining dielectric particles on them, then particles smaller than 5 mm are sent to a concentration table, whose tails are guided into a mill 4, into which particles larger than 5 mm from a drum screen enter.

In the process of grinding in mills, fans create a vacuum or ejection, which ensures the transfer of light dielectric particles into the suction system. If it is necessary to separate the tails into separate grades of plastics, additional electrostatic separators are installed with special settings for a specific grade of plastics.

Concentration table 5 processes part of the finished product by size and divides it into concentrate and tailings, which are re-milled, and then into an electrostatic separator. The entire stream of crushed and partially separated scrap passes through a magnetic separator, which releases at least 30% of the concentrate and thereby simplifies the operation of the electric separator 7.

Thus, the proposed method due to the interaction of the claimed operations allows us to solve the tasks: increase productivity, improve the quality of the concentrate and the degree of metal extraction from the feedstock up to 98%.

Claims (1)

A method of processing electronic and cable scrap, including two stages of grinding in impact mills, sieve classification to obtain particles +5 mm and -5 mm, directing particles +5 mm to the second stage of grinding, electrostatic separation to obtain an intermediate product in the form of unopened splices, characterized the fact that they carry out gravitational separation of -5 mm particles on a concentration table, the tails of which, together with the intermediate product of the electrostatic separator, are sent to the second grinding stage for splices, while the entire stream of crushed and partially separated scrap is sent to magnetic separation, and the non-magnetic product of the latter to electrostatic separation.