RELATED APPLICATIONS

The present application claims priority from Australian provisional patent application No. 2020902936 filed on 18 August 2020, the entire contents of which are incorporated herein by reference.

FIELD OF INVENTION

The present invention relates generally to method and apparatus for recovering metal copper from waste material, and in particular, to a method and apparatus for recovering metal copper from cathode bars used in the smelting of aluminium.

BACKGROUND OF THE INVENTION

For industrial processes such as the smelting of primary aluminium, cathode or collector bars are employed in large numbers. Such collector bars typically comprise a steel body having a copper insert. The copper insert has been found to significantly increase the conductivity of the collector bar and to reduce energy/power consumption by improving the distribution of electrical current along the collector bar during use.

The process for the smelting of primary aluminium is referred to as the Hall- Heroult process. Such a process involves passing an electrical current, at an amperage of up to 600kA, through a bath or pot containing an electrolyte comprising a mixture of cryolite and alumina. The pot typically has a carbonaceous material lining, with the bottom of the pot serving as a cathode upon which the molten aluminium collects during the process. The electrolyte is typically placed in the pot to form a cell and the current is passed through the cell from an anode (typically consumable carbon electrodes partially emerged into the molten electrolyte at the top of the cell), through the electrolyte and into the cathode. Cathode collector bars are typically arranged in the bottom of the cell and are connected to the current source to complete the circuit. In such a process, the alumina is dissociated by the current so that aluminium is deposited at the bottom of the pot and drawn off and collected by way of a vacuum crucible or the like, and oxygen is liberated at the carbon anode, forming CO and CO2.

A pot has a typical life of around 2,000 days, which is largely dependent upon on the structural formation of the pot lining and the cathode assembly. Thus, for smelters having 100 pots, a pot may be replaced every 20 days. As the collector bars are not consumed in the process, the replacement and relining of the pots generates a high number of used collector bars, which contain a significant amount of copper therein.

Copper and copper alloys have long been used in a large variety of important applications. As such, the copper and copper alloy industry is highly dependent upon the economic recycling of surplus products containing copper. This has been the case since the Middle Ages where it was common practice after wars to melt down the bronze cannons to make more useful items. Similarly today, copper is recycled to provide an economical cost price for the material.

Most commercial supplies of pure copper are used in electrical applications where it is essential that purity is reproducibly maintained in order to ensure high conductivity, consistent annealability and freedom from breaks during rod production and subsequent wire drawing. For non-electrical applications, copper is also used to make large quantities of plumbing tube, roofing sheet and heat exchangers. In such applications, high electrical conductivity is not mandatory and other quality requirements are not strictly required. As such, secondary copper can be used for the manufacture of these materials, though still within stipulated quality limits for impurities.

In any event, there is a need to provide a method and apparatus to recover copper from waste materials, such as cathode or collector bars used in industry, where the copper is present in high quantities and of high levels of purity.

The above references to and descriptions of prior proposals or products are not intended to be, and are not to be construed as, statements or admissions of common general knowledge in the art. In particular, the above prior art discussion does not relate to what is commonly or well known by the person skilled in the art, but assists in the understanding of the inventive step of the present invention of which the identification of pertinent prior art proposals is but one part.

STATEMENT OF INVENTION

The invention according to one or more aspects is as defined in the independent claims. Some optional and/or preferred features of the invention are defined in the dependent claims. Accordingly, in one aspect of the invention there is provided an apparatus for recovering metal copper from a product material, comprising: a vertically orientated tubular body having a central core formed therein and a coil mounted within the body and arranged to extend in a vertical axis so as to extend about the central core; a collecting crucible mounted beneath said core of the body for collecting metal copper from the wats material; and a hoisting apparatus mounted with respect to the body, the hoisting apparatus being configured to lower the product material into the central core of the body and to suspend the product material therein; wherein, the coil is configured to receive a current to generate a magnetic field in the body such that the magnetic field generates eddy currents within the product material causing the product material to heat, thereby releasing the metal copper in a molten form from the product material into the collecting crucible for recovery.

In an embodiment, the apparatus may further comprise a control system for controlling power supplied to the coil based on a temperature reading of the product material. The control system may comprise a sensor mounted within the body to monitor the product material and generate the temperature reading of the product material. The temperature reading of the product material may be delivered by the sensor to a controller that controls an amount of power supplied to the coil to achieve a target temperature of the product material

In one embodiment, the sensor may be a pyrometer.

The target temperature of the product material may be a temperature of the product material that is above a melting temperature of the metal copper to facilitate release of the metal copper in a molten form from the product material, but which is below a melting temperature of the product material.

In one embodiment, the coil is suspended within a refractory material to maintain the coil in a fixed position within the body. The body may further comprise upper and lower layers of castable refractory material between which the coil extends.

The central core comprises a replaceable lining extending about the surface thereof. The replaceable lining may be made from a refractory cement material. The product material may be a cathode or collector bar having a copper core.

In accordance with another aspect, there is provided a method of recovering metal copper from a product material, comprising: positioning the product material within an induction coil activating the induction coil to generate a magnetic field about the product material to cause the product material to increase in temperature; controlling the temperature of the product material to achieve a target temperature that is above a melting temperature of the metal copper but below a melting temperature of the product material; and collecting the metal copper from the product material in a molten form.

The product material may be suspended within the induction coil such that the product material extends substantially vertically within the induction coil.

The temperature of the product material may be controlled by sensing the temperature of the product material and controlling an amount of power delivered to the induction coil to achieve and maintain the product material at a target temperature.

The metal copper may be collected from the product material under gravity in a collection vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be better understood from the following non-limiting description of preferred embodiments, in which:

Fig. 1 is a cross-sectional view of a copper recovery apparatus in accordance with an embodiment of the present invention;

Fig. 2 is a depiction of the control system for controlling the operation of the copper recovery apparatus of Fig. 1; and

Fig. 3 is a flow chart depicting the method of controlling the copper recovery apparatus of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Preferred features of the present invention will now be described with particular reference to the accompanying drawings. However, it is to be understood that the features illustrated in and described with reference to the drawings are not to be construed as limiting on the scope of the invention.

The apparatus and method of the present invention will be described below in relation to its application for use in recovering copper from cathode bars used in the smelting of aluminium. However, it will be appreciated that the apparatus and method of the present invention could be employed in extracting copper, and other metals, from a variety of different products where the material is contained or otherwise held within a carrier material.

Referring to Fig. 1, an apparatus 10 in accordance with one embodiment of the present invention is depicted. The apparatus 10 comprises a main body 12 in the form of a cylinder having a central opening 14 into which a product 5 that contains the copper 6 to be reclaimed, is inserted.

In the embodiment where the product 5 is a cathode bar used in smelting of aluminium, the product 5 is typically made from an Ultra-Low Resistivity Steel (ULR) body having a copper core 6 that functions to increase the electrical conductivity of the ULR body. The product 5 typically has a length of between 2000 - 4000mm with the copper insert extending within the product for a distance or around 900 - 1700 mm from an end thereof. It will be appreciated that the actual dimensions of the product 5 and the copper insert 6 will vary between products and are defined herein for illustrative purposes only.

In a preferred form, the body 12 is configured to extend, at least partially, below a floor surface 2 to reduce the working height of the body 12. In the embodiment as depicted in Fig. 1, the body 12 extends above the floor surface 2 and has a height of around 1200 mm. The body 12 extends below the floor surface 2 for around 600 mm, such that the total length of the body 12 is around 1800mm. In other embodiments, it will be appreciated that the body 12 may be fully positioned above or below a ground surface 2, as required.

The central opening 14 extends through the body 12 from an upper surface 12a to a lower surface 12b. A collector 15, in the form of a crucible or similar container, is positioned beneath the central opening 14 to collect the copper 6 as it is released from the product 5, in the manner to be described in more detail below.

The body 12 houses a coil 20 that extends vertically about the central opening 14. A layer of castable refractory material 22 is provided at the top and bottom ends of the body 12 such that the coil 20 extends between the layers of refractory material 22. This refractory material may comprise a mixture of perlite, cement and vermiculite to minimise heat conductivity from the apparatus 10. To further insulate the body 12, a shield plate 23 extends across the upper surface 12a of the body. In one embodiment, the shield plate 23 is a water-cooled flux shield that ensures that the temperature of the upper end of the body 12 is maintained at a safe temperature.

The internal surface of the central opening 14 has a removable lining 24 that extends from the lower layer of the castable refractory material 22 to the upper layer of castable refractory material 22, as shown. The lining 24 may also be made from a refractory cement material that is durable and able to withstand a degree of wear due to the product 5 bumping and scaping the surface of the lining 24 as it is lowered into the central opening 4.

The coil 20 is suspended within a mixture of castable refractory material 25, having a composition similar to that described above. The material 25 functions to separate and support the coil so as to maintain separation of the coil windings at the predetermined coil spacings. A non-conductive vertical support 26 extends behind the coil 20 to securely support the coil 20 in the vertical orientation as shown. The outer wall 28 of the body 12 may comprise a steel sheet formed into a cylindrical shape to enclose the system and accommodate the features of the apparatus 10, as shown.

The apparatus 10 employs electromagnetic induction to recover the copper 6 from the product 5. An electric current is passed through the coil 20 to induce a magnetic field around the coil 20, which is concentrated in the centre of the coil, namely within the central opening 14 of the apparatus 10.

The product 5, typically the ULR steel body with the copper core 6, is lowered into the central opening 14 of the apparatus 10 by way of a hoist arrangement 30. The hoist arrangement 30 is controllable by conventional means to suspend the product 5 within the central opening 14 in the manner as shown. In this position, an electric current is applied to the coil to generate the magnetic field. As the magnetic field flows through the product 5, eddy currents are induced in the product 5 due to the conductive nature of the ULR steel body. As the eddy currents travel through the ULR steel body of the product 5, the energy is dissipated in the form of heat, thus causing the body of the product 5 to increase in temperature. As the ULR steel body temperature increases, the temperature will cause the copper present therein to melt, as the copper has a lower melting point than the ULR steel. The molten copper will then flow from the core 6 of the product 5 and be captured in the crucible 15, which is positioned beneath the central opening 14 of the apparatus 10.

Following recovery of the copper from the product 5, the product 5 can then be raised from the central opening 14 of the apparatus 10 and removed. The copper collected in the crucible 15 from the core of the product 5 can then be recycled for use in other applications.

In a preferred form, the process performed by the apparatus 10 is controlled by way of a control system 40, as depicted in Fig. 2 in accordance with the method 50 shown in Fig. 3.

In step 52 of the method 50 the waste material is positioned within the induction coil 20 of the apparatus 10 in the manner as previously described. The induction coil 20 is then activated in step 54 to generate the magnetic field.

In step 56, the control system 40 is provided to control the waste material temperature as follows.

The control system 40 comprises a sensor member 42, such as a pyrometer, which is mounted within the apparatus 10 to extend through the body 12 and into the central core 14 such that it is able to continuously read the temperature of the product 5.

A controller 44, such as a computer processor having a CPU and data storage for operating programmable software algorithms, receives the temperature signal 43 from the sensor 42 and compares the temperature of the product 5 against a target temperature that is stored within the data storage of the processor. The target temperature stored by the processor is representative of a desired temperature of the product that facilitates melting of the copper core but is below the melting temperature of the main body of the product 5, namely the ULR steel body.

If the sensed temperature of the product 5 is determined as being below the desired target temperature, the controller 44 calculates the amount of electrical power required by the induction coil 20 to generate the desired amount of energy to heat the product 5 to the target temperature and to maintain the product 5 at this target temperature.

The controller 44 then sends a power control signal 45 to the induction coil power supply unit 46 to cause the unit 46 to increase the power supply to the coil 20. Such an increase in power supply will cause the magnetic filed generated by the induction coil 20 to increase in magnitude to generate the required magnetic field capable of causing the temperature of the nroduct 5 to reach the desired temperature.

The molten copper is then able to be collected from the waste material product in step 58, as previously discussed.

Such a closed loop system 40 is able to regulate the power delivered to the induction coil 20, which is determined on raising and maintaining the temperature of the product 5 to a pre-set level to facilitate release of the copper therefrom. The system 40 ensures that the power levels are optimised to achieve the desired purpose, thereby creating a more efficient and reliable copper extraction process.

It will be appreciated that the apparatus 10 can be simply employed for recovering copper from a product in a simple and effective manner. There is no requirement to cut the steel product, which can be difficult due to the hardness of the steel and the size of the bars. The apparatus can also be employed for bars of varying cross-sectional shapes and thicknesses as well as lengths, and the apparatus can be simply adapted as required.

Throughout the specification and claims the word “comprise” and its derivatives are intended to have an inclusive rather than exclusive meaning unless the contrary is expressly stated or the context requires otherwise. That is, the word “comprise” and its derivatives will be taken to indicate the inclusion of not only the listed components, steps or features that it directly references, but also other components, steps or features not specifically listed, unless the contrary is expressly stated or the context requires otherwise.

It will be appreciated by those skilled in the art that many modifications and variations may be made to the methods of the invention described herein without departing from the spirit and scope of the invention.