Method and arrangement for recovering metal from waste slag

Abstract

A method and an arrangement for recovering metal from waste slag, the method comprising: receiving slag in at least partly molten state, granulating said slag in said at least partly molten state, allowing granulated slag to solidify, separating said granulated slag into at least two fractions such that in a first of said at least two fractions metal content is higher as in a second of said at least two fractions.

Description

BACKGROUND The invention relates to a method for recovering metal from waste slag. The invention further relates to an arrangement for recovering metal from waste slag. E-waste slag is formed during smelting of E-waste that comprises e.g. electronic scrap and circuit boards. Due to the impurities in the slag, it is difficult to find a direct use of the slag, for example as construction material. Due to the highly reducing environment when smelting E-waste, the properties of the E-waste slag differ from the typical primary copper smelter slag. The recovery loss of copper and other metals when smelting E-waste is mainly due to physical inclusions of metallic droplets in the E-waste slag. Due to the high viscosity of the E-waste slag, a pyrometallurgical settling furnace is not ideal for separating the metal from the rest of the E-slag. Solidification and crushing the E-slag is also not ideal solution due to a long process lead time, high equipment costs and higher energy consumption. BRIEF DESCRIPTION Viewed from a first aspect, there can be provided a method for recovering metal from waste slag, the method comprising: - receiving slag in at least partly molten state, - granulating said slag in said at least partly molten state, - allowing granulated slag to solidify, - separating said granulated slag into at least two fractions such that - in a first of said at least two fractions metal content is higher as in a second of said at least two fractions. Thereby a method having a short process lead time and low energy consumption, but still achieving the same process results as the known methods may be achieved. Additionally, the method is more environmentally friendly as it does not produce any direct CO2 emissions and indirect CO2 emissions are lower than in alternative solutions. Viewed from a further aspect, there can be provided an arrangement for recovering metal from waste slag, the arrangement comprising a granulating arrangement arranged for receiving slag in at least partly molten state and granulating said slag in said at least partly molten state, and a first separation unit arranged for separating said granulated slag into at least two fractions, wherein in a first of said at least two fractions metal content is higher as in a second of said at least two fractions. Thereby an arrangement providing a short process lead time and low energy consumption, but still achieving the same process results as the known arrangements may be achieved. Additionally, the arrangement necessitates low capital expenditures and is environmentally friendly as it does not produce any direct CO2 emissions. The arrangement and the method are characterised by what is stated in the independent claims. Some other embodiments are characterised by what is stated in the other claims. Inventive embodiments are also disclosed in the specification and drawings of this patent application. The inventive content of the patent application may also be defined in other ways than defined in the following claims. The inventive content may also be formed of several separate inventions, especially if the invention is examined in the light of expressed or implicit sub-tasks or in view of obtained benefits or benefit groups. Some of the definitions contained in the following claims may then be unnecessary in view of the separate inventive ideas. Features of the different embodiments of the invention may, within the scope of the basic inventive idea, be applied to other embodiments . Various embodiments of the first aspect may comprise at least one feature from the following paragraphs: In one embodiment, the method comprises receiving slag from a furnace, such as a top blown rotary converter. An advantage is that the slag has a high temperature and its premature solidifying may be avoided. In one embodiment, the method comprises discharging slag from the furnace in a vessel and discharging said slag from the vessel for granulating said slag. An advantage is that some flexibility in the layout of the arrangement may be achieved. In one embodiment, at least part of slag originates from at least one source selected from electronic scrap, cable scrap, plastic scrap from electrical or electronic devices, incinerator bottom ash, copper scrap, and Cu alloys. An advantage is that these sources typically include valuable metals that are worth of recycling. In one embodiment, granulating comprises blowing fluid into a stream of slag being in at least partly molten state, such that granules are created. An advantage is that a quick granulation and cooling of the slag may be achieved. In one embodiment, the granulating comprises blowing steam or gas, such as air. An advantage is that produced granules are at least essentially dry. In one embodiment, the granulating comprises blowing liquid, such as water. An advantage is that granules may be effectively cooled and solidified. In one embodiment, the separation comprises a magnetic separation phase. An advantage is that a separation phase having low energy consumption and without producing any direct CO2 emissions may be achieved. In one embodiment, the magnetic separation phase is performed by a low intensity magnetic separator. An advantage is that a low maintenance need and operator attendance may be achieved. In one embodiment, the separation comprises a gravimetric separation phase. An advantage is that an operation having low cost, requiring a simple apparatus and being environmentally friendly may be achieved. In one embodiment, the first fraction contains metal 10 weight-% to 90 weight-%. An advantage is that a cost-effective the separation phase and the method may be achieved. In one embodiment, said metal comprises at least one of copper, silver, gold, palladium, platina. An advantage is that a cost-effective the separation phase and the method may be achieved. In one embodiment, said metal is in a mixture called black copper that is attracted to magnets. An advantage is that non-magnetic metals, such as copper, included in black copper may be separated by a magnetic separation phase. In one embodiment, the method comprises grinding the second fraction and providing thus a grinded second fraction, performing a separation phase of the grinded second fraction into at least two grinded fractions such that in a first of said at least two grinded fractions metal content is higher as in a second of said at least two grinded fractions. An advantage is that metal(s) in the reject of the separation phase may still be separated from the slag. In one embodiment, the separation phase of the grinded second fraction comprises a gravimetric separation of said grinded second fraction into a first sub-fraction and a second sub-fraction. An advantage is that an operation having low cost, requiring a simple apparatus and being environmentally friendly may be achieved. In one embodiment, the method comprises performing a further separation of the first grinded fraction by a flotation method. An advantage is that metal(s) in the reject of the separation phase may still be separated from the slag. In one embodiment, the arrangement comprises a grinding arrangement arranged for grinding the second fraction and providing a grinded second fraction, a second separation unit arranged for performing a separation phase of the grinded second fraction into at least two grinded sub-fractions such that in a first of said at least two grinded subfractions metal content is higher as in a second of said at least two grinded sub-fractions. An advantage is that metal(s) in the reject of the separation phase may still be separated from the slag. In one embodiment, the second separation unit comprises a gravimetric separation apparatus. An advantage is that a second separation unit having low cost, requiring a simple apparatus and being environmentally friendly may be achieved. In one embodiment, the second separation unit comprises a magnetic separation apparatus. An advantage is that a second separation unit having low energy consumption and without producing any direct CO2 emissions may be achieved. In one embodiment, the arrangement comprises a flotation arrangement arranged for performing a further separation of the second grinded sub-fraction. An advantage is that the separation capacity of the arrangement may be further raised. Based on the above mentioned, it should be noted that different embodiments mentioned in the above paragraphs may combined in any possible suitable manner for implementing the present invention. BRIEF DESCRIPTION OF FIGURES Some embodiments illustrating the present disclosure are described in more detail in the attached drawing, in which: Figure 1 is a schematic view of a method and an arrangement for recovering metal from waste slag in partial cross-section, Figure 2 is a schematic side view of a separation unit used in a method and an arrangement for recovering metal from waste slag in partial cross-section, and Figures 3a - 3c are schematic side views of other separation units used in a method and an arrangement for recovering metal from waste slag. In the figure, some embodiments are shown simplified for the sake of clarity. Similar parts are marked with the same reference numbers in the figures. DETAILED DESCRIPTION Figure 1 is a schematic view of a method and an arrangement for recovering metal from waste slag in partial cross-section, Figure 2 is a schematic side view of a separation unit used in a method and an arrangement for recovering metal from waste slag in partial cross-section, and Figures 3a -3c are schematic side views of other separation units used in a method and an arrangement for recovering metal from waste slag. The method is run in an arrangement 100 the main parts or components of which comprise a granulating arrangement 3 and a first separation unit 4. The method and the arrangement 100 are controlled through a control unit 14, which may be a computer, a computation unit or a device comprising at least one processor and a memory. In one embodiment, the granulating arrangement 3 is arranged for receiving slag directly from a furnace 1 in which said slag has been melted. In one embodiment, such as shown in Figure 1, slag is first tapped into a vessel 15, such as a ladle, and then, if required, moved M to a place where slag is poured from the vessel 15 into the granulating arrangement 3. In one embodiment, the slag originates from recycled waste, such as recycled electronic waste. In one embodiment, at least part of the slag originates from at least one source selected from electronic scrap, cable scrap, plastic scrap from electrical or electronic devices, incinerator bottom ash, copper scrap, such as copper pipes used in construction industry, and Cu alloys. Typically, the recycled waste is a combination of wastes originating from different sources. In one embodiment, the furnace 1 is a top blown rotary converter, such as a Kaldo converter. The top blown rotary converter is shaped like an open-ended barrel and inside lined with refractory material. The top blown rotary converter can be rotated about its longitudinal axis X and tilted T about an axis perpendicular to said longitudinal axis X. The slag molten in the top blown rotary converter is discharged through a mouth 2 by tilting. In one embodiment, the furnace 1 is an Isasmelt furnace. In one embodiment, the furnace 1 is an Ausmelt furnace. In one embodiment, the method is run and the apparatus used batch-wise so that molten slag discharged from the furnace 1 is processed as a batch. In another embodiment, the method is run and the apparatus used in a continuous way. In one embodiment, preceding or following discharging slag from the furnace 1, there is a metal discharging step where a melted metal phase is discharged from the furnace 1 into another arrangement (not shown) for further processing. The granulating arrangement 3 receives and granulates slag that is at least partly in molten. The slag may include solid (not melted) particles or fragments in addition to flowable (melted) phase. The granulating arrangement 3 comprises means for pressurizing fluid that is then blown through blowing means into a stream of slag S that is in at least partly molten state. In one embodiment, the blowing means comprises openings or nozzles 17 that are arranged in a blowing box 16, for instance. Fluid F is blown through said openings or nozzles with high speed into the stream of slag S that is in at least partly molten state. In one embodiment, the fluid F is blowed in the stream of slag S that is being poured or discharged from the furnace 1. In one embodiment, the fluid F is blowed in the stream of slag S that is being poured or discharged from a vessel, such as the ladle 15. In one embodiment, the stream of slag S is fed in or on a runner 8 that is arranged to direct said slag in the granulating arrangement 3. In one embodiment, granulation of the slag takes place in a granulation pit 9 provided in the granulating arrangement 3. In one embodiment, the bottom of the granulation pit 9 is at least partly filled with liquid, such as water, and the granules enter and cool down in said liquid. In one embodiment, the fluid F is blowed at least mainly in horizontal direction and the stream of slag S is configured to drop through said fluid. It is to be noted, however, that other arrangements of the fluid F and the stream of slag S may be used in granulation of the slag. In one embodiment, the fluid F comprises steam or gas, such as air. In one embodiment, the fluid F comprises liquid, such as water. In one embodiment, the fluid F provides a high pressure turbulent liquid stream. The characterizing features of the fluid F, such as its velocity, temperature and volume flow, are selected depending on e.g. the characteristics of the molten slag and the flow thereof. In one embodiment, the granulating arrangement 3 comprises a centrifugal granulating apparatus. In this apparatus the stream of slag is poured on a disc that is spinning at high speed. Forces caused by the spinning breaks the slag into granules. In one embodiment, the spinning disc throws the granules in air where they cool down and solidify. In another embodiment, the spinning disc throws the granules in in liquid such as water, where they cool down and solidify. As the slag is being granulated, it also cools so that solid small pieces or droplets are produced. Some heat is removed from the slag by evaporation of liquid (typically water) and / or as heated gas (typically air) and / or liquid. In water granulation, it is possible to use an abundance of water that may then reused and pumped back in the granulation process . In one embodiment, the granulating arrangement 3 produces granules having mean size in range of 0,5 mm to 5 mm. It is to be noted, however, that the size distribution of the granules may be varied, for instance from few microns to over 5 mm. The granules G, i.e. granulated slag, are delivered to a first separation unit 4. In one embodiment, there may be a drying step and a drying apparatus where the granules are dried prior to their feeding in the first separation unit 4. However, the drying step and the drying apparatus are preferably avoided. If the separation step carried out in the first separation unit requires dry material, the granulation step preferably uses dry granulation without any liquid. The first separation unit 4 separates said granules G into at least two fractions. In one embodiment, such as shown in Figure 1, the first separation unit 4 separates the granules G into two fractions, i.e. into a first fraction A and a second fraction B such that the first fraction A has a higher metal content as the second fraction B. In one embodiment, the first fraction A contains metal 10 weight-% to 90 weight-%. In one embodiment, the first fraction A contains metal 30 weight-% to 70 weight-%. In one embodiment, the metal comprises at least one of copper, silver, gold, palladium, platina. In one embodiment, the metal is a mixture comprising copper and ferrous and non-ferrous metals, typically including silver, gold, palladium, platina, so called black copper. Black copper comprises metallic iron, which renders the black copper phase magnetic. In one embodiment, the first separation unit 4 comprises a magnetic separation apparatus and the separation comprises a magnetic separation phase. One embodiment of the magnetic separation apparatus 12 is shown in Figure 2. In one embodiment, the magnetic separation apparatus 12 is a low intensity magnetic separator. The low intensity magnetic separator (LIMS) is a device that is used to recover magnetic material from non-magnetic material, or more magnetic material from less magnetic material. In one embodiment, the magnetic separation apparatus 12 is designed to work with dry separation process. In another embodiment, the magnetic separation apparatus 12 is designed to work with wet separation process. In one embodiment, the magnetic separation apparatus 12 comprises a separator drum 10 that rotates R around its vertically arranged axis. A magnet arrangement 11 is arranged inside the separator drum 10. The magnet arrangement 11 extends only on a part of the length of the circumference of the separator drum. The magnetic or more magnetic material is attracted to the separator drum 10 by the magnet arrangement 11 and is rotated out of the non-magnetic or less magnetic particle stream on the surface of the drum. In one embodiment, the magnetic or more magnetic material detach from the separator drum 10 upon reaching a specific boundary point, such as a baffle, and fall into e.g. a collection container. In one embodiment, the magnetic material discharges from the separator drum when it is rotated out of the magnetic field. Thus, the granules G are separated to the first fraction A and the second fraction B based on magnetic properties thereof. It is to be noted, however, that the magnetic separation apparatus 12 may be constructed in many alternative ways. In one embodiment, the first separation unit 4 comprises a gravimetric separation apparatus 13 and the separation a gravimetric separation phase. One embodiment of the gravimetric separation apparatus 13 is shown in Figure 3a. The working principle of this separation apparatus 13 is based on a centrifugal separation, that means separating substances with different specific gravities by means of centrifugal force. Thus, the granules G are separated to the first fraction A and the second fraction B based on their specific gravities. It is to be noted, however, that the gravimetric separation apparatus 13 may be constructed in many alternative ways. Another embodiment of the gravimetric separation apparatus 13 is shown in Figure 3b. This apparatus 13 is a scavenging spiral where separation of different solid materials or components in slurry is based on solid particle density and particle's hydrodynamic properties. Still another embodiment of the gravimetric separation apparatus 13 is a shaking table or gravity separation table, such as shown in Figure 3c. In this apparatus relative movements against gravitational forces are applied to the particles. The first fraction A provided by the separation phase that is carried out by the first separation unit 4 has a high metal content and it can be transported out from the method and the arrangement 100 to be utilized in any suitable use. In one embodiment, the second fraction B provided by the separation phase and having a low metal content may be considered as waste. In another embodiment, the second fraction B is further processed for further recovery of metal(s) still in the second fraction. In one embodiment, the second fraction B, i.e. granules having low metal content, is grinded into a grinded second fraction, and this grinded second fraction BG is then separated into at least two grinded fractions. The second fraction B is grinded by a grinding arrangement 5 that comprises a suitable grinding or crushing machine. The type of said grinding or crushing machine may be e.g. a jaw crusher, a gyratory crusher, a cone crusher, a ball mill, a rod mill or an impact crusher. In one embodiment, the grinding arrangement 5 is followed by a second separation unit 6 where the grinded second fraction BG is separated into at least two grinded fractions. In one embodiment, the grinded second fraction BG is separated into a first grinded fraction BG1 and a second grinded fraction BG2. The metal content of the first grinded fraction BG1 is higher than of the second grinded fraction BG2. In one embodiment, the second separation unit 6 comprises a magnetic separation apparatus 12. In one embodiment, the second separation unit 6 comprises a gravimetric separation apparatus 13. The same principles of the magnetic separation apparatuses and the gravimetric separation apparatuses described already in connection with the first separation unit apply also here in the second separation unit 6. The first grinded fraction BG1 can be transported out from the method and the arrangement 100 to be utilized in any suitable use. In one embodiment of the method and the arrangement, the second grinded fraction BG2 , i.e. the grinded fraction having a lower metal content, is fed in a flotation arrangement 7 for carrying out a further refining of the fraction. The flotation arrangement 7 separates the grinded fraction BG2 into two fractions such that one of said two fractions has a higher metal content than another of said two fractions. 5 The invention is not limited solely to the embodiments described above, but instead many variations are possible within the scope of the inventive concept defined by the claims below. Within the scope of the inventive concept the attributes of different embodiments and applications can be 10 used in conjunction with or replace the attributes of another embodiment or application. The drawings and the related description are only intended to illustrate the idea of the invention. The invention may 15 vary in detail within the scope of the inventive idea defined in the following claims. REFERENCE SYMBOLS 1        furnace 2       mouth 3       granulating arrangement 4       first separation unit 5       grinding arrangement 6       second separation unit 7       flotation arrangement 8        runner 9       granulation pit 10      separator drum 11      magnet arrangement 12      magnetic separation apparatus 13      gravimetric separation apparatus 14      control unit 15      vessel 16      blowing box 17      opening 100     arrangement A       first fraction B       second fraction BG      grinded second fraction BG1     first sub-fraction of grinded second fraction BG2     second sub-fraction of grinded second fraction F       fluid G       granules M       moving R       rotation S        slag flow T       tilting

Claims

1. A method for recovering metal from waste slag, the method comprising:- receiving slag in at least partly molten state,- granulating said slag in said at least partly molten state,- allowing granulated slag to solidify,- separating said granulated slag into at least two fractions such that- in a first of said at least two fractions metal content is higher as in a second of said at least two fractions.

2. The method as claimed in claim 1, comprising - receiving slag from a furnace (1).

3. The method as claimed in claim 2, comprising - receiving slag from a top blown rotary converter.

4. The method as claimed in claim 2 or 3, comprising- discharging slag from the furnace in a vessel (15), and - discharging from the vessel for granulating said slag.

5. The method as claimed in any of the preceding claims, wherein at least part of slag originates from at least one source selected from - electronic scrap, - cable scrap,- plastic scrap from electrical or electronic devices,- incinerator bottom ash,- copper scrap, and- Cu alloys.

6. The method as claimed in any of the preceding claims, wherein- said granulating comprises blowing fluid into a stream of slag being in at least partly molten state, such that- granules are created.

7. The method as claimed in claim 6, wherein- blowing fluid comprises blowing steam or gas, such as air.

8. The method as claimed in claim 6 or 7, wherein- blowing fluid comprises blowing liquid, such as water.

9. The method as claimed in any of the preceding claims, wherein- the separation comprises a magnetic separation phase.

10. The method as claimed in any of the preceding claims, wherein- the separation comprises a gravimetric separation phase.

11. The method as claimed in any of the preceding claims, wherein- the first fraction contains metal 10 weight-% to 90 weight-%.

12. The method as claimed in any of the preceding claims, wherein- said metal comprises at least one of copper, silver, gold, palladium, platina.

13. The method as claimed in any of the preceding claims, wherein- said metal is in a mixture called black copper.

14. The method as claimed in any of the preceding claims, comprising- grinding the second fraction and providing thus a grinded second fraction.

15. The method as claimed in claim 14, comprising- performing a separation phase of the grinded second fraction into at least two grinded sub-fractions such that- in a first of said at least two grinded sub-fractions metal content is higher as in a second of said at least two grinded sub-fractions.

16. The method as claimed in claim 15, wherein- the separation phase of the grinded second fraction comprises a gravimetric separation.

17. The method as claimed in claim 15, wherein- the separation phase of the grinded second fraction comprises a magnetic separation.

18. The method as claimed in claim 16 or 17, comprising- performing a further separation of the first grinded subfraction by a flotation method.

19. An arrangement for recovering metal from waste slag, the arrangement (100) comprising- a granulating arrangement (3) arranged for receiving slag in at least partly molten state and granulating said slag in said at least partly molten state, and- a first separation unit (4) arranged for separating said granulated slag into at least two fractions, wherein in a first (A) of said at least two fractions metal content is higher as in a second (B) of said at least two fractions.

20. The arrangement as claimed in claim 19, comprising- a vessel (15) arranged for keeping slag in at least partly molten state, and for- discharging said slag in the first separation unit (4).

21. The arrangement as claimed in claim 19 or 20, wherein at least part of slag originates from at least one source selected from- electronic scrap,- cable scrap,- plastic scrap from electrical or electronic devices,- incinerator bottom ash,- copper scrap, and- Cu alloys.

22. The arrangement as claimed in any of claims 19-21, wherein- the granulating arrangement (3) is configured to blow fluid (F) into a stream of slag being in at least partly molten state.

23. The arrangement as claimed in claim 22, wherein- the fluid (F) comprises steam or gas, such as air.

24. The arrangement as claimed in claim 22 or 23, wherein- the fluid (F) comprises liquid, such as water.

25. The arrangement as claimed in any of claims 19-24, wherein- the first separation unit (4) comprises a magnetic separation apparatus.

26. The arrangement as claimed in any of claims 19-24, wherein- the first separation unit (4) comprises a gravimetric separation apparatus.

27. The arrangement as claimed in any of claims 19-26, wherein- said metal comprises at least one of copper, silver, gold, palladium, platina.

28. The arrangement as claimed in any of claims 19-27, wherein- said metal is in a mixture called black copper.

29. The arrangement as claimed in any of claims 19-2 8, comprising- a grinding arrangement (5) arranged for grinding the second fraction (Eh and providing a grinded second fraction (BG) .

30. The arrangement as claimed in claim 29, comprising - a second separation unit (6) arranged for performing a separation phase of the grinded second fraction (BG) into at least two grinded sub-fractions such that- in a first (BG1) of said at least two grinded sub-fractions metal content is higher as in a second (BG2) of said at least two grinded sub-fractions.

31. The arrangement as claimed in claim 30, wherein- the second, separation unit (6) comprises a. second gravimetric separation apparatus .

32. The arrangement as claimed in claim 30, wherein- the second separation unit (6) comprises a second magnetic s e p a r a. t i o n app a r a t u s .

33. The arrangement as claimed in any of claims 2 9 - 32, comprising- a flotation arrangement (7) arranged for performing a further separation of the second (BG2) grinded sub-fraction.RECTIFIED SHEET (RULE 91)

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