Recycling furnace

Abstract

The present invention relates to a multipurpose recycling furnace designed for processing metal-containing waste material. The furnace comprises a vessel with a mouth section for receiving recyclable material, a lance extending through the mouth section for introducing an oxidising gas, and an electrically powered heating arrangement for melting the material. The invention further provides a method for recycling metal-containing waste, involving introducing the waste into the vessel, melting it using electrical energy, refining the molten material with an oxidising gas, and subsequently discharging the refined material. This system enhances efficiency and effectiveness in metal recycling processes.

Description

[0001] RECYCLING FURNACE

[0002] BACKGROUND TO THE INVENTION

[0003] This invention relates to a furnace, and more particularly but not exclusively to a multipurpose recycling furnace.

[0004] Waste containing metallic materials, including slags formed during a primary smelting process, are often recycled to recover both base metals and precious metals. Recycling metals from waste materials helps conserve natural resources, reduce energy consumption, and minimize environmental impact compared to extracting metals from raw ores. Efficient recovery of metals from waste materials is not only desirable for their economic value, but also for reducing reliance on primary mining, which can have significant environmental impacts.

[0005] Base metals like iron, aluminum, lead, nickel, cobalt and copper are commonly recovered from various waste streams such as scrap metal, electronic waste (e-waste), batteries (lead acid batteries and lithium batteries), slags, and industrial by-products. Precious metals like gold, silver, and platinum are also recovered from electronic waste and other sources through specialized recycling processes. Recycling efforts for platinum group metals (PGMs) primarily focus on recovery from automotive catalytic converters, which contain significant amounts of platinum, palladium, and rhodium. These metals are extracted through various refining techniques from used catalytic converters and other sources of PGM-containing waste, such as electronic scrap and industrial catalysts.

[0006] Metal-containing waste products undergo a systematic recycling process starting with collection from various sources such as households, businesses and industries. Once collected, these materials are sorted to separate different types of metals and alloys, employing both manual and automated techniques. Following sorting, the waste undergoes processing which may involve shredding, crushing, or melting in preparation for further treatment. Shredding and crushing reduce bulky items like scrap metal and electronic waste, while melting extracts metals from materials such as aluminum cans and steel scrap. Once collected, sorted and processed, the processed material undergoes smelting / melting and refinement.

[0007] The present invention relates to the smelting / melting and refinement part of the recycling process. At present, various processes are utilized to achieve these steps.

[0008] Before the existing processes are described in more detail, reference must be made to some relevant equipment known in the art.

[0009] An electric furnace is a type of furnace that uses electricity as its primary source of heat energy for industrial processes such as melting, heating, and refining metals, and are commonly used in metallurgy, foundries, and materials processing industries due to their efficiency, versatility, and precise temperature control.

[0010] A top blown rotary converter (TBRC) is a type of metallurgical furnace used for smelting and refining various types of metal-bearing materials. It's a versatile furnace that can handle a wide range of feed materials, including ores, concentrates, recycled materials, and intermediate products from other processes. A conventional TBRC furnace consists of a rotating, cylindrical refractory-lined vessel equipped with a fuel lance for use in melting the feed material or providing heat to the process, and an oxygen lance for use during the refinement of the molten feed material. The rotation of the vessel helps to mix the feed materials thoroughly and ensure uniform heating and processing.

[0011] Turning now to existing recycling processes available in the marketplace, in one existing process a two-step approach is followed. The first step entails a melting / smelting and first pass separation process, and typically takes place in an electric furnace. The second step is then a refining and converting process that typically takes place in a top blown rotary converter (TBRC) or similar apparatus to further concentrate the recovered metals in an alloy prior to further downstream processing and refining. The two-step process increases the capital cost as well as the operating costs due to the requirement for two distinct vessels.

[0012] In another existing recycling process, both the melting / smelting and refining can be done in a single top blown rotary converter (TBRC) or similar apparatus. However, in this case the melting / smelting process require the use of a carbonaceous fuel such as fuel oil, pulverized coal or similar, or natural gas. This leads to high CO2 emission levels, which is not desirable from an environmental perspective. It is also not possible for the melting / smelting step of this process to be converted to be reliant on green energy.

[0013] Currently, most recycling is done by large operators - usually traditional primary producers of the metals to be recovered. These operators have existing plants that are usually large and well established. These plants are far away from all the collection points for the materials to be recycled, and the logistics of collecting, sorting and transporting the materials to these plants form a large part of the overall processing costs. The current recycling ecosystem is therefore not optimal and leaves significant room for improvement. It is accordingly an object of the invention to provide a recycling furnace that will, at least partially, alleviate the above shortcomings.

[0014] It is also an object of the invention to provide a recycling furnace which will be a useful alternative to existing recycling furnaces.

[0015] It is a further object of the invention to provide a new recycling process and method that will, at least partially, alleviate the above shortcomings, and / or which will be a useful alternative over existing processes and methods.

[0016] SUMMARY OF THE INVENTION

[0017] According to the invention there is provided a recycling furnace including: a vessel, suitable for receiving material to be recycled, the vessel having a mouth section; a lance operatively extending through the mouth section for introducing an oxidizing gas into the vessel; and an electrically powered heating arrangement for supplying heat to the material to be recycled.

[0018] In one embodiment the electrically powered heating arrangement may be in the form of an induction heating arrangement. There is provided for the induction heating arrangement to be in the form of induction coils located on or inside walls of the vessel, for example in the refractory lining of the vessel.

[0019] In another embodiment the electrically powered heating arrangement may be in the form of two electrodes. A first electrode may be incorporated into a base of the vessel and a second electrode may extend into the vessel through the open end of the vessel. Alternatively, both electrodes may extend into the vessel through the open end of the vessel. In a still further embodiment, the electrically powered heating arrangement may be in the form of a plasma torch with an end portion operatively arranged within the vessel for supplying heat to the material to be recycled.

[0020] There is provided for the plasma torch to be displaceable relative to the vessel between an operative position in which end portion of the plasma torch is located inside the vessel, and an inoperative position in which the end portion of the plasma torch is located outside of the vessel.

[0021] When the lance is in the operative condition, an end of the lance may be located above a surface of the molten material, or below the surface of the molten material.

[0022] The plasma torch may be suitable for generating a non-transferred plasma arc. The end portion of the plasma torch may comprise a cathode having a tip located in a gas chamber and an anode arranged proximate the tip of the cathode, the anode comprising an opening for a plasma arc operatively to pass through. The end portion may include an electric arc or spark generator. The cathode may comprise a tungsten electrode and the anode may comprise a copper nozzle. The gas chamber may operatively be fed with a plasma forming gas.

[0023] In accordance with one embodiment of the invention there is provided for the vessel to be a rotatable vessel. There is also provided for the vessel to be tiltable.

[0024] According to a further aspect of the invention, there is provided a method of recycling metal containing waste material, the method including the steps of:

[0025] - introducing the waste material into a recycling vessel;

[0026] - melting the waste material in the recycling vessel using electrical energy; refining the molten material by introducing an oxidizing gas into the same vessel; discharging the refined material.

[0027] There is provided for the vessel to be stationary or to rotate during the melting step.

[0028] There is also provided for the vessel to rotate during the refinement step.

[0029] The melting step and the refinement step may happen concurrently, with the vessel being rotated while melting using electrical energy and refinement using the oxidizing gas take place at the same time, or at least partially overlap.

[0030] Preferably, the vessel is continuously rotated at a variable speed.

[0031] There is provided for the oxidizing gas to be oxygen or an oxygen rich gas mixture, with the gas being introduced into the vessel using a lance.

[0032] There is provided for an end of the lance in use to be located above a surface of the molten material, or below the surface of the molten material.

[0033] The step of discharging the refined material may entail tilting the vessel in order for the material to be discharged under gravity.

[0034] The method may also include a holding step after the refinement step. The holding step may include using electrical energy to maintain the temperature of the molten and refined material above a predetermined temperature. The vessel is preferably stationary during the holding step. The step of melting the waste material in the recycling vessel using electrical energy may entail the use of an induction heating system, electrical elements electrodes or a plasma torch.

[0035] BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Embodiments of the invention are described by way of non-limiting examples, and with reference to the accompanying schematic drawings in which:

[0037] Figure 1 is a schematic cross-sectional view of an existing TBRC as is known in the art, with the process in the refinement state;

[0038] Figure 2 shows the TBRC of figure 1 in a tilted configuration for discharging the refined material;

[0039] Figure 3 is a schematic cross-sectional view of a recycling furnace according to one embodiment of the invention;

[0040] Figure 4 is a schematic cross-sectional view of a recycling furnace according to another embodiment of the invention;

[0041] Figure 5 is a schematic cross-sectional view of a third embodiment of a recycling furnace in accordance with the invention, with the furnace being in an upright position;

[0042] Figure 6 is a schematic cross-sectional view of the furnace of Figure 5 with the furnace in a tilted position and an oxygen lance in an operative configuration; Figure 7 is a schematic cross-sectional view of the furnace of Figure 5 with the furnace in a discharge position and the oxygen lance removed;

[0043] Figure 8 is a schematic cross-sectional view of a fourth embodiment of a recycling furnace in accordance with the invention, with the furnace being in an upright position, including a detailed view of an end portion of a plasma torch;

[0044] Figure 9 is a schematic cross-sectional view of the furnace of Figure 8 with the furnace in a tilted position and an oxygen lance and the plasma torch in an operative configuration; and

[0045] Figure 10 is a schematic cross-sectional view of the furnace of Figure 8 with the furnace in a discharge position and the oxygen lance and plasma torch removed.

[0046] DETAILED DESCRIPTION OF INVENTION

[0047] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms "mounted", "connected", "engaged" and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings and are thus intended to include direct connections between two members without any other members interposed therebetween and indirect connections between members in which one or more other members are interposed therebetween. Further, "connected" and "engaged" are not restricted to physical or mechanical connections or couplings. Additionally, the words "lower", "upper", "upward", "down" and "downward" designate directions in the drawings to which reference is made. The terminology includes the words specifically mentioned above, derivatives thereof, and words or similar import. It is noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the," and any singular use of any word, include plural referents unless expressly and unequivocally limited to one referent. As used herein, the term “include” and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items.

[0048] Referring to Figures 1 and 2, a TBRC as is known in the trade is generally indicated by reference numeral 10. The TBRC includes a vessel 12 having an opening 13 defining a mouth, and a hollow interior 14. In use, a material to be processed is introduced into the vessel 12 through the opening 13. The vessel 12 can rotate about a longitudinal axis as indicated by arrow A, and can also pivot or tilt about a transverse axis, as indicated by arrow B. The vessel 12 can tilt from an upright position through about 270 degrees.

[0049] The vessel 12 is usually positioned in an upright position (not shown) during feeding of material, especially cold feed material, or at an angle if molten feed is added. The vessel is then angled at approximately 45 degrees during the smelting / melting / heating process, as shown in Figure 1. During the melting phase, heat is imparted using a fuel lance 16. During the refining process, oxygen or oxygen enriched air is introduced into the vessel 12 using an oxygen lance 17. The lances (16 and 17) are pneumatically / hydraulically I or similarly inserted and extracted from the vessel opening 13. As shown in Figure 2, when the lances (16 and 17) have been extracted, the vessel 12 can be tilted in order for first the slag, and then the refined metal I matte I alloy, to be emptied into a ladle 18.

[0050] In addition to tilting, the vessel also rotates (arrow A) whilst in operation. The rotation assists with mixing the feed and molten material, firstly to expose it to the burner flame from the fuel lance 16 for melting / smelting, and secondly to better expose the melt to the oxygen from the oxygen lance 17 for refining through selective oxidation and slag forming. As impurities and other unwanted products react with the fluxes and form oxides, they rise to the surface due to their lighter density compared to the molten metal. This separation is also facilitated by the rotation of the TBRC vessel, which helps to agitate the contents and promote the separation of slag from the metal.

[0051] As mentioned above, in an alternative arrangement (not shown) the refinement step take place in a furnace as described with reference to Figures 1 and 2 (but without the fuel lance 16), but with the melting taking place in a separate furnace, for example an electrical furnace.

[0052] Referring now to Figures 3, 4 and 5, in which like numerals indicate like features, a non-limiting and simplified example of a recycling furnace in accordance with the present invention is shown schematically, and using the same reference numerals as used for Figures 1 and 2. It should be noted that these drawings only show the parts pertinent to the invention, and other standard TBRC components like the extraction hood, frame, variable speed motor, gears and loading chute are omitted.

[0053] The invention differs from the prior art in that the recycling furnace 10 does not include a fuel lance 16. Instead, the furnace includes an electrically powered heating arrangement, which can be in the form of an electrode arrangement 20 (shown in Figure 3 and 4), an induction heating arrangement 50 (as shown in Figures 5 to 7) or a plasma torch (shown in Figures 8 to 10) for use in providing heat energy for melting the charge 15. The new furnace still includes an oxygen lance 17, which is also still retractable as is known in the art. It should be understood that a fuel lance may still be used in combination with the electrically powered heating arrangement, but it is not required. The presence or lack of a fuel lance therefore has no specific bearing on the scope of the invention.

[0054] In the embodiment shown in Figure 3, the electrically powered heating arrangement is in the form of an electrode arrangement 20 that comprises a cathode 21 and an anode 22, with the cathode 21 extending into the vessel 12 through the mouth of the vessel (similar to the fuel lance 16). The anode 22 is located in or at the bottom of the vessel 12. In a second embodiment of the invention, shown in Figure 4, the electrical heating arrangement is also in the form of an electrode arrangement 20, but here both the anode 22 and the cathode 21 are inserted through the opening 13 of the vessel.

[0055] In the embodiment shown in Figures 5, 6 and 7 the furnace 10 includes induction coils 50 embedded in the wall of the vessel, instead of an electrode arrangement as shown in Figures 3 and 4. In Figure 5, the vessel is shown in an upright position during which melting occurs. In Figure 6 the vessel is in a titled configuration with an oxygen lance 17 also extending into the vessel, and in Figure 7 the vessel is in a discharge configuration, with the lance 17 again retracted from the vessel. In this embodiment, the furnace also includes a fuel lance 16.

[0056] A fourth embodiment, shown in Figure 8 to 10, differs from the first three embodiments in that the recycling furnace 10 includes a plasma arc torch 100 as a replacement for the electrode arrangement 20 (shown in Figure 3 and 4), or the induction heating arrangement 50 (as shown in Figures 5 to 7). The plasma arc torch 100 is provided for operatively providing heat energy for melting the charge 15. Again, the furnace according to the fourth embodiment still includes an oxygen lance 17, which is also still retractable as is known in the art. Similarly, the plasma arc torch 100 is retractable between an operative condition, in which an end portion 102 thereof is located within the inside the vessel 12 (typically by extending through the opening 13 or mouth of the vessel 12) and an inoperative condition in which the end portion 102 is displaced out of the vessel 12. Again, a fuel lance may still be used in combination with the arc torch 10, but it is not required. The presence or lack of a fuel lance therefore has no specific bearing on the scope of the invention.

[0057] The plasma arc torch 100 is configured for generating a non-transferred plasma arc.

[0058] The end portion 102 of the plasma torch 100 comprises a cathode 103 in the form of a tungsten electrode, an end portion 104 of which terminating in a tip 106. The end portion 104 is encapsulated within a gas chamber 108. An anode 110, typically in the form of a copper nozzle having an opening 112, is arranged proximate the end portion 104 of the cathode 103. The anode 1 10 is electrically insulated from the gas chamber 108. In use, plasma forming gas is fed through a gas supply line 1 14 towards the gas chamber 108.

[0059] In Figure 8, the vessel 12 is shown in an upright position during which loading and / or melting occurs. In Figure 9 the vessel is in a titled configuration with the oxygen lance 17 also extending into the vessel, and in Figure 10 the vessel is in a discharge configuration, with the lance 17 and plasma arc torch 100 again retracted from the vessel 12.

[0060] In use, the material to be recycled is loaded into the vessel 12 while the vessel is in an upright position.

[0061] The melting phase then commences, and electricity is supplied to the electrical heating arrangement, i.e, to the electrode arrangement 20 (Figure 3 and 4), the induction coils 50 (Figures 5 to 7) or the plasma torch 100 (Figures 8 to 10). When an electrode arrangement is used, electrical power is supplied to heat and melt the feed material in the vessel using either AC or DC power, most likely with the top electrode or cathode 21 immersed in the molten material 15, but potentially with an end of the cathode being located above the material, thus drawing an open arc. When immersed, heating is achieved through resistance heating (I2R), and when drawing an open arc, heating is achieved through both resistance heating and arc radiation. The vessel is not rotated while the feed material is heated up and melted, and also does not have to be tilted to the position shown in Figure 1 .

[0062] When the plasma torch 100 is used, a voltage is supplied over the anode 1 10 and cathode 103, gas is supplied to the gas chamber 108 and an arc or spark is created proximate the opening 112, causing a plasma arc to be generated to heat and melt the feed material in the vessel 12. The plasma arc is directed towards the material in the vessel. It will be appreciated that the melting phase may occur in either the upright position of figure 8, or the tilted position of figure 9. Also, and advantageously, the vessel 12 may be rotated during the melting phase, resulting in better heat distribution and more even heating.

[0063] Once the melting step has been completed, the vessel 12 starts to rotate while in the tilted position, and oxygen or an oxygen rich gas is introduced through the oxygen lance 17. During this step, the furnace is used like a conventional TBRC. When the refinement step has been completed, and metal and slag layers have formed, the vessel can be tiled further to the discharge position shown in Figure 2, at which point the slag (if formed) is skimmed, and the metal decanted into a ladle 18.

[0064] The invention provides for the possibility of an intermediate holding step during which the molten and refined material is kept hot, again using the electrode arrangement or plasma arc torch 100, as the case may be, which ensures adequate separation between the alloy / matte / metal and the slag that may form. The electrode arrangement or plasma arc torch 100, as the case may be, can also be used to heat up already molten material fed to the vessel.

[0065] The invention provides a way in which the two-step melting and refinement process can be performed in the same vessel, without the use of fuel introduced through a fuel lance. The invention will result in a reduction of the overall capital cost compared to the two-step process, and potentially reduces the CO2 emissions and carbon footprint compared to the existing single step TBRC process if green electricity is available. The single, lower- cost and lower-emission process will be more suitable for smaller scale operations located closer to the source of the materials to the recycled, usually closer to residential areas.

[0066] It should be noted that the invention is not limited to the use of a rotating vessel, and will also find application when the vessel is used in a top submerged lance configuration (i.e. upright vessel with a submerged lance, instead of TBRC configuration). The important requirement is that the process should still utilize a combination of electrical energy for heating (directly using the electrodes, or by means of the plasma arc torch) and lancing (introducing oxidizing gas) for refinement. The use of the submerged lance renders rotation of the vessel unnecessary, as the process results in sufficient mixing. It will, however, still be useful for the vessel to be tiltable in order to discharge slag and alloy / matte.

[0067] The use of induction heating, as described above with reference to Figures 5 to 7, result in further potential benefits. As mentioned above, induction heating may for example be achieved by embedding an induction coil in the refractory lining of the vessel to heat the charge using electrical induction. The vessel can tilt and rotate, and the oxygen lance can be used simultaneously while electrical heating takes place through the induction coils. The combination of electric induction heating used concurrently with the lance is of particular interest when considering a converting operation for copper scrap / waste recycling. There is little to no sulphur in the alloy that can provide the energy for heating during the converting process. Normally sulphur is oxidised when oxygen is blown into or onto the melt during a typical primary smelting converting process, but in this case the heating will be done using induction heating.

[0068] The fourth embodiment results in similar advantages as mentioned in respect of the induction heating version, in that heating can be done whilst in the inclined position and whilst the TBRC is rotating, resulting in more even heating of the charge.

[0069] The fourth embodiment has further advantages over and above those of the other embodiments, in that it doesn’t comprise potentially vulnerable hardware such as embedded induction coils or bottom anodes.

[0070] It will be appreciated that the above is only one embodiment of the invention and that there may be many variations without departing from the spirit and / or the scope of the invention. It is easily understood from the present application that the particular features of the present invention, as generally described and illustrated in the figures, can be arranged and designed according to a wide variety of different configurations. In this way, the description of the present invention and the related figures are not provided to limit the scope of the invention but simply represent selected embodiments.

[0071] The skilled person will understand that the technical characteristics of a given embodiment can in fact be combined with characteristics of another embodiment, unless otherwise expressed or it is evident that these characteristics are incompatible. Also, the technical characteristics described in a given embodiment can be isolated from the other characteristics of this embodiment unless otherwise expressed.

Claims

CLAIMS:1 . A recycling furnace including: a vessel, suitable for receiving material to be recycled, the vessel having a mouth section; a lance operatively extending through the mouth section for introducing an oxidizing gas into the vessel; and an electrically powered heating arrangement for supplying heat to the material to be recycled.

2. The recycling furnace according to claim 1 wherein the electrically powered heating arrangement is in the form of an induction heating arrangement.

3. The recycling furnace according to claim 2 wherein the induction heating arrangement is in the form of induction coils located on or inside walls of the vessel.

4. The recycling furnace according to claim 1 wherein the electrically powered heating arrangement is in the form of two electrodes.

5. The recycling furnace according to claim 4 wherein a first electrode is incorporated into a base of the vessel and a second electrode extends into the vessel through the open end of the vessel.

6. The recycling furnace according to claim 4 wherein both electrodes extend into the vessel through the open end of the vessel.

7. The recycling furnace according to claim 1 wherein the electrically powered heating arrangement is in the form of a plasma torch with an end portion operatively arranged within the vessel for supplying heat to the material to be recycled.

8. The recycling furnace according to claim 7 wherein the plasma torch is displaceable relative to the vessel between an operative position in which an end portion of the plasma torch is located inside the vessel, and an inoperative position in which the end portion of the plasma torch is located outside of the vessel.

9. The recycling furnace according to any one of the preceding claims wherein the vessel is a rotatable vessel.

10. The recycling furnace according to any one of the preceding claims wherein the vessel is a tiltable vessel.1 1. A method of recycling metal containing waste material, the method including the steps of:- introducing the waste material into a recycling vessel;- melting the waste material in the recycling vessel using electrical energy; refining the molten material by introducing an oxidizing gas into the same vessel; and- discharging the refined material.

12. The method according to claim 1 1 wherein the vessel is stationary during the melting step.

13. The method according to claim 1 1 wherein the vessel is rotating during the melting step.

14. The method according to any one of claims 1 1 to 13 wherein the vessel rotates during the refinement step.

15. The method according to any one of claims 11 to 14 wherein the melting step and the refinement step happen concurrently, with the vessel beingrotated while melting using electrical energy and refinement using the oxidizing gas take place at the same time, or at least partially overlap.

16. The method according to any one of claims 1 1 to 15 wherein the vessel is continuously rotated at a variable speed.

17. The method according to any one of claims 1 1 to 15 wherein the oxidizing gas is oxygen or an oxygen rich gas mixture, with the gas being introduced into the vessel using a lance.

18. The method according to claim 17 wherein an end of the lance is located above a surface of the molten material, or below the surface of the molten material.

19. The method according to any one of claims 1 1 to 18 wherein the step of discharging the refined material entails tilting the vessel in order for the material to be discharged under gravity.

20. The method according to any one of claims 1 1 to 19 including a holding step after the refinement step, wherein the holding step includes using electrical energy to maintain the temperature of the molten and refined material above a predetermined temperature.21 . The method according to any one of claims 1 1 to 20 wherein the step of melting the waste material in the recycling vessel using electrical energy entail the use of an induction heating system, electrical elements electrodes or a plasma torch.

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