METHOD, PROCESS, AND SYSTEM OF USING A MILL TO SEPARATE METALS FROM FIBROUS FEEDSTOCK

Abstract

A method for recovering metals from waste in which material is roughly or coarsely separated to leave a fibrous feedstock, the feedstock is comminuted with a mill (e.g., a ball mill) to liberate and separate the fibrous feedstock to obtain a mix of a metal fraction and residue, and the metals fraction and the residue are collected. There is a system employing the same to treat such materials.

Claims

1. A method of recovering metals from a fibrous feedstock, the method comprising: receiving a fibrous feedstock comprising organic and/or plastic fibers with entrained or embedded metals and having a metal content of less than about 5% by weight; comminuting the fibrous feedstock in a media mill selected from a ball mill or a rod mill to liberate the fibers from the metals and to produce a comminuted mixture; separating the comminuted mixture to produce at least a metals fraction and a fibrous residue fraction based on one or more of size or density; and collecting the metals fraction and collecting the fibrous residue fraction.

2. The method of claim 1, wherein the comminuting is performed as a wet process in the presence of water to form a slurry.

3. The method of claim 1, wherein the comminuting is performed as a dry process without added liquid.

4. The method of claim 1, further comprising magnetic separation of ferrous material downstream of the media mill prior to said separating.

5. The method of claim 1, wherein separating comprises sizing the comminuted mixture through a discharge screen on the mill at a first cut size between 10 mm and 25 mm to produce a coarse stream and a fines stream.

6. The method of claim 5, further comprising secondary sizing of at least the fines stream at a cut size of about 0-4 mm.

7. The method of claim 5, wherein the coarse stream is subjected to fluidized or inertial separation on an inertia table to advance heavier particles and retard lighter fibrous particles.

8. The method of claim 6, wherein the fines stream is subjected to gravity separation selected from hydrocyclones, spiral separators, jigs, sink-float tanks, kinetic density separators, and rising current separators.

9. The method of claim 1, wherein the fibrous feedstock is obtained from aspirated lights produced by one or more upstream operations selected from air aspirators including Z-box aspirators, dry destoners, friction separators, ballistic separators, air tables, cyclones, blowers, and air-knife separators, or from wet roughers including pre-concentrators, water tables, Wilfley/Diester tables, sink-float vessels, DMS separators, hydro-cyclones, barrel washers, and heavy-media processes.

10. The method of claim 1, wherein comminuting pulverizes and densifies copper conductors to preferentially sink in a liquid medium and flattens aluminum to preferentially float, thereby facilitating subsequent specific-gravity separation of copper from aluminum.

11. A process for producing a non-ferrous metal concentrate from aspirated fibrous waste, the process comprising: feeding an aspirated lights fraction containing fibrous organic or plastic material with embedded metals to a rubber-lined wet ball mill equipped with water inlets; operating the wet ball mill to liberate fibers from metallic particles and form a slurry; removing ferrous metals by wet magnetic separation; sizing the slurry at a first cut between 10 mm and 25 mm and directing the oversize to inertial or fluidized separation and the undersize to fines classification; classifying at least a portion of the undersize at about 0-4 mm using hydrocyclones and/or spiral separators to produce a non-ferrous metals concentrate and a fibrous/light residue; and clarifying and recycling process water to the wet ball mill.

12. The process of claim 11, wherein the ball mill is rubber-lined and charged with grinding media to reduce fiber length and detach fibers from metallic surfaces.

13. The process of claim 11, wherein the feed to the wet ball mill comprises rejects from eddy-current separation combined with the lights fraction from upstream air classification.

14. The process of claim 11, wherein the wet ball mill is positioned downstream of a shredding line that includes air classification of lights, magnetic recovery of ferrous metals, trommel sizing, and eddy-current separation of non-ferrous metals, and wherein rejects from the eddy-current separation are directed to the wet ball mill.

15. The process of claim 11, further comprising polishing the recovered metals fraction to increase purity and marketability.

16. A system for recovering metals from fibrous waste, comprising: a source of fibrous feedstock having a metals content of less than about 5 wt %; a media mill selected from a ball mill or rod mill positioned downstream of the source and configured to liberate metallic particles from fibers; a discharge sizing device coupled to the media mill and configured to provide a first size cut between 10 mm and 25 mm; a magnetic separator downstream of the media mill; a density-based separator selected from an inertia table, hydrocyclone, spiral separator, jig, sink-float device, kinetic density separator, or rising-current separator; and one or more conveyors and/or screws arranged to deliver the fibrous feedstock to the media mill and to route sized streams to the density-based separator, the system being configured to produce a metals fraction and a fibrous residue fraction from the fibrous feedstock.

17. The system of claim 16, wherein the media mill includes water inlets and the system further comprises a water clarifier configured to receive process water from downstream separation and to return clarified water to the media mill.

18. The system of claim 16, wherein the discharge sizing device comprises a nose-cone screen mounted at the mill discharge.

19. The system of claim 16, wherein the source is arranged to receive material from a shredding facility that performs air classification of lights, magnetic ferrous recovery, trommel sizing, and eddy-current non-ferrous recovery, and wherein rejects from eddy-current separation and/or the lights fraction are combined and fed to the media mill.

20. The system of claim 16, wherein the metals fraction comprises one or more of aluminum, copper, zinc, tin, nickel, silver, gold, iron, and stainless steel, and the system further comprises a polishing station configured to raise purity of the metals fraction after density-based separation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 illustrates an exemplary method employing comminution of fibrous feedstock.

[0011] FIG. 2 illustrates another exemplary method employing comminution of fibrous feedstock together with an inertia table.

[0012] FIG. 3 illustrates another exemplary method employing comminution of fibrous feedstock together with a gravity separator.

[0013] FIG. 4 illustrates an exemplary system employing a ball mill to liberate and separate metals from fibrous feedstock.

DETAILED DESCRIPTION

[0014] Specific applications include methods and systems relate to the recovery of metals from any wet process or dry process. Such wet processes may include streams from, e.g., preconcentrators, water table concentrators, gold shaking tables such as produced by diester, Wilfery table concentrators, sink float tanks, sink float vessels, snail drums, barrel washers, wet processes using heavy media, DMS separators, hydro-cyclones, and other processes. Such dry processes, e.g., roughers such as an air aspirator Z box aspirator (broadly used in the EU for pre-concentrating auto mobile shredder residue, the light fraction containing embedded/entangled metals with the fibrous materials, such as carpet, foam, fiber and or fabrics), dry destoners, friction separators, ballistic separators, air tables, cyclones, blowers, air knife separators or dry separation devices that separate lights from heavies and the lights contain fuzz and fibrous materials that have metal embedded within material, also known as light fractions. Other wet and dry processes are known to those with skill in the art.

[0015] This application includes methods and systems for recovering metals, e.g., copper and precious metals, through the use of comminution (e.g., a ball mill or rod mill). Specific embodiments may be carried out in wet processes or dry processes. That is, a wet process can include a slurry or dry mix of fibrous feedstock (e.g., a having fibrous organic and plastic material and metals). Specific embodiments include the processing of fibrous feedstock that is aspirated lights (light material from an aspirator) and/or lights from a wet rougher or process, e.g., a heavy media plant, or a rising current separation using water.

[0016] In one embodiment, the processes and systems were found to be highly effective in recovering metal from feedstock that was aspirated waste, which is common in the European Union from processes that do not involve incineration. Aspirators are well known in the classifying art and result in a light fraction having organic material with limited amounts of metal and such metal tends to be buried/embedded/entangled with the organic fibers. Often, the fibrous feedstock has buried, embedded, or entangled plastic therein. This type of waste is referred herein as aspirated fibrous feedstock.

[0017] One method for recovering metals from waste includes roughly or coarsely separating the metals from the waste to leave a fibrous feedstock, comminuting the fibrous feedstock with a mill to liberate and separate the fibrous feedstock to obtain a mix of a metal fraction and residue, and collecting the metals fraction and collecting the residue.

[0018] The comminution step can be after or downstream of the rough or course separation step. In one example, the course processing does not include processing with a ball mill or rod mill. In many instances, the fibrous feedstock is a type where the additional metals cannot be economically reclaimed from the material and the material is usually discarded.

[0019] FIG. 1 shows the three main steps of one specific embodiment of this invention. The first step 10 is the introduction of materials having fibrous materials, which may be a product of course or rough processing. The second step 20 is to apply or comminute with a mill (e.g., a ball mill) to the material or fibrous feedstock, which effectively separates fibers or fuzz from or embedded in the metal. The comminution can be performed in a mill that uses media (e.g., a ball mill, a tumbling mill, a drum mill, or a rod mill). The next step 30 is to separate the comminuted or crushed material using techniques such as specific gravity separation, including centrifugal, inertial, and gravity classifications. In one embodiment, the material may be sorted or screened and then further processed to recover materials. In other embodiments, the feedstock material or the crushed material may be treated may have been treated with a wet magnet and screened accordingly. In some examples, the course processing may be aligned with the mill so that that course processing feedsthe mill.

[0020] In one specific example, the fibrous feedstock is conveyed to a ball mill for comminution or crushing. After which, the material may be treated with a wet magnet to remove iron and then is screened or cut (e.g., between 0-4 mm). The material greater than the cut may be treated by fluidized separation or an inertia table and the material less than the cut may be treated using other techniques (e.g., hydrocyclones or spiral separators).

[0021] In another specific example, the material greater than the cut or from the mill may be treated by fluidized separation or an inertia table 40 shown in FIG. 2. The separation may include an inertia table that includes a frame, a tray or tilt tray, a cam, and a motor. The tray can be secured to (e.g., pneumatic) cylinders/springs/spring-type elements, which can be secured to the frame. Materials processed by the upstream delivery station are accumulated on or conveyed by a tray, which separates and moves material by creating a moment of inertia and/or rotary motion translated into reciprocating/oscillating motion (e.g., a stroke/follower motion). As a result, heavier materials are carried forward and the lighter materials are carried backwards. One exemplary inertia table is now available from TAV Holdings, Inc.

[0022] Another embodiment includes a method of recovering a metal product with a given particle size distribution. This method includes loading feedstock with fibrous organic material into a ball mill and operating the ball mill to mill the feedstock to separate or liberate the organic fibrous material from the metals. The ball milling was able to liberate, separate or remove the fibrous feedstock and was found to result in a higher metal recovery efficiency.

[0023] In another embodiment shown in FIG. 3, the material processed by the ball mill or the rod mill is further processed using a gravity separator 50 (e.g., jigs, hydrocyclones, gravity sink/float tanks, and kinetic density separators). A gravity separator uses the differences in density for the separation of solid particles that have different densities from a generally homogeneous mixture of solids. Because residue is very heterogeneous and its contents have overlapping densities and shapes, gravity separation of shredder residue, as-is, cannot yield products from shredder residue, except for metals, as practiced in some wet shredder facilities. Such separators can be operated by using water or a heavy media.

[0024] In one example, the ball mill was operated as a wet ball mill. In some examples, the mill or ball mill can be a rod mill, a ball mill, and other equivalents that will occur to those of skill in the art. The mill may be rubber lined, which gave unexpectedly good results or resulted in substantial separation of the metals from the fibers. In at least some such examples, crushed material is moved by a conveyor and discharged into a unit where the materials are reduced in size or further processed.

[0025] In one embodiment, the ball mill application can be downstream from the shredding process, which operations may vary from site to site, but the basic process involves air classification of thelights fraction followed by one or more stages of magnetic separation to recover the ferrous metals. Trommels can be used to remove smaller particles, followed by one or more stages of eddy current separations to recover the nonferrous metals. Conveyors are used to move materials around. In one example, the rejects from the eddy currents can be combined with the lights fraction and conveyed to a ball mill. Aggregates and glass are pulverized into smaller fractions than aluminum, copper, and other metals and can be effectively screened.

[0026] The fibrous feedstock can be a material having fibrous organic or plastic material. Such material includes ASR material treated to recover light materials. In other examples, the material may be electronic waste. In one example, the fibrous feedstock can be municipal waste. In other examples, the fibrous feedstock can be the light materials from other processes and include materials mixed with organic fibers.

[0027] In other examples, the fibrous feedstock may be the drops from an eddy current, which include metals and fibrous organic or plastic material. In some examples, the fibrous feedstock had about 0% organic material. In other examples, the fibrous feedstock has greater than 50% organic or plastic material. In other examples, the fibrous feedstock has greater than 75% organic or plastic material. In yet other examples, the fibrous feedstock may be greater than 90% or 95% organic or plastic material. That amount of organic or plastic material in the fibrous feedstock may vary from about 0 to about 100%. Fibrous feedstock may have less than 10 or 6%, 5% or 4% or 3% or 2% or 1% of metals by weight or volume. In some examples, the fibrous feedstock contains greater than 95% plastics or organics.

[0028] In many examples, the fibrous feedstock includes metals such as aluminum, zinc, copper, tin, nickel, silver, gold, iron and alloys thereof such as gold bronze, an alloy of copper and zinc, alloys of tin with aluminum, gallium and/or indium, or stainless steel, an alloy composed mainly of iron. The recovered metals can be polished to increase purity, value, and marketability.

[0029] FIG. 4 shows one example of a system incorporating or executing methods described herein. The system 200 may have multiple tools, conveyors, and devices. For illustration only, the ball mill or mill 210 is downstream from the waste stream, i.e., the entering feedstock has a reduced metal content and fibers. In a basic embodiment, the fibrous feedstock 250 is conveyed to the ball mill 210 (e.g., wet or dry), and from the ball mill 210, the material can be divided, separated, and/or further processed. For example, the fibrous feedstock 250 can be conveyed to the ball mill 210 (e.g., wet or dry), and from the ball mill 210, the material can exit from an exemplary screen 230 (e.g., a nose cone), which can separate the material into smaller sized material and larger sized material (e.g., at a size between 10 mm and 25 mm). In one example, the material may be damped with water inlets 235 and include a water clarifier 240.

[0030] The larger sized material can be processed separately from the smaller sized portion, that is, for example, the smaller sized portion may be processed through a fine circuit 267 and the larger sized materials may be processed through heavier equipment 265. Some or all of the components shown therein may be used to effect the object of metal separation. The system can have optional water clarification systems 240, e.g., when the feedstock is combined with water prior to the ball mill 210 application. As can be seen, the system can incorporate wet magnets, screen, conveyors, screws, and other elements to improve the separation process. The process cycles can be selected based on desires and space constrictions of the operator.

[0031] In the separation process in accordance with the present embodiment, copper (e.g., tubes and wires) are pulverized and flattened into denser structures, which then sink in water or media (e.g., heavy media), whereas the aluminum component is flattened, which increases floatation properties. The aluminum, glass and copper can be efficiently separated, e.g., by an ordinary screening operation. The aluminum, glass and copper can also be efficiently separated into their components, e.g., by specific gravity separation, such as centrifugal, inertial, and gravity classifications. Other separation processes are known in the art.

[0032] Although specific embodiments of the disclosure have been described above in detail, the description is merely for purposes of illustration. It is to be understood that the present description illustrates those aspects of the invention relevant to a clear understanding of the invention. Certain aspects of the invention that would be apparent to those of ordinary skill in the art and that, therefore, would not facilitate a better understanding of the invention have not been presented in order to simplify the present description. Although embodiments of the present invention have been described, one of ordinary skill in the art will, upon considering the foregoing description, recognize that many modifications and variations of the invention may be employed. All such variations and modifications of the invention are intended to be covered by the foregoing description.