System and process for treating SLAG from waste incineration plants

Abstract

Material treatment plant (1) for separating non-ferrous metals (6) from partly-treated slag (2, 3) of different particle size fractions with one single processing line including one single eddy current separator (4), which separator has an inlet (9) for untreated slag, an outlet (7) for a mineral slag fraction (8), and an outlet (5) for a separated non-ferrous metal fraction (6), wherein before the inlet (9) for untreated slag, two storage buffers (10, 11) are arranged in parallel with an outlet (12, 13) for untreated slag (2, 3) from the 2 parallel storage buffers with a common conveying line (14) from the two outlets (12,13) to the inlet (9) of the eddy current separator (4).

Description

[0001] BW1368R - 1 -

[0002] SYSTEM AND PROCESS FOR TREATING SLAG FROM WASTE INCINERATION PLANTS

[0003] DESCRIPTION

[0004] Field of the invention

[0005] The present invention relates to an apparatus, or system, and a process for separating non-ferrous metals from incinerator waste, also known as slag. Typical non-ferrous metals that can be separated are aluminium, copper, silver, gold, lead, zinc, tin and palladium.

[0006] The apparatus and method may operate as a subsystem and a substep, respectively, within a comprehensive slag treatment procedure.

[0007] Background of the invention

[0008] The separation of non-ferrous metals from incineration waste is known in the art and may be performed using an eddy current separator.

[0009] In particular, after the slag is discharged from the incinerator, it primarily consists of mineral slag particles and various metals.

[0010] In typical slag processing procedures, in a first step larger particles, usually greater than 300 mm in size, and large iron scrap particles are separated from the remainder of the slag. The slag is then divided into different fractions using a separation device, such as a screening device. Each fraction is further treated in a respective, individual line. In each line, the iron-containing fractions are separated, as well as slag particles with magnetic properties. These preliminary process steps before the non-ferrous metal separation can be arranged differently depending upon the plant. In any case, regardless of the sequence, these steps are completed before proceeding, in each of said lines, to the separation of non-ferrous metals from the mineral slag fraction. As mentioned above, the separation of non-ferrous metals is usually done using an eddy current separator. Such separation of non-ferrous metals is a crucial factor for the economic returns of the slag processing plant operator and significantly impacts the profitability of the facility. In waste incineration slag separation technology, the goal is to recover as many non-ferrous metals as possible with high purity, typically in a range of about 70-95% of the total metals included in the slag. BW1368R - 2 -

[0011] As mentioned, each processing line in a slag treatment plant normally operates with its own distinct process and includes a ferrous separation step, a magnetic slag separation step and a non-ferrous metal separation step. However, the Inventors have noted that the known art slag treatment plants and processes are not applicable for smaller waste-to-energy (WtE) facilities or in general small amounts of slag, mainly due to the high costs associated with each individual processing line. In particular, in these smaller facilities the revenue generated from producing secondary materials by processing slag is insufficient to create a viable business case. A smaller WtE plant is defined as a plant that produces yearly approximately from 5,000 tons to 50,000 tons of slag.

[0012] Summary of the invention

[0013] The technical problem underlying the present invention is therefore to overcome the drawbacks and satisfy the need mentioned above with reference to the state of the art.

[0014] The above problem is solved by a system according to claim 1 and by a method according to claim 9.

[0015] Preferred features of the invention are object of the dependent claims.

[0016] According to preferred embodiments, the invention provides a slag material treatment system, plant and method for separating non-ferrous metals from untreated slag of different particle size fractions with one single processing line.

[0017] Therefore, the invention provides a system in which different slag fractions can be processed with a same processing line, used alternatively for one fraction or the other(s). In this way, independent processing lines for each slag are no longer needed. Accordingly, the invention significantly reduces the costs associated with slag treatment in an incineration plant and allows an efficient application of separator systems and methods also to smaller waste-to-energy (WtE) facilities. In particular, this invention allows for a viable business case even with smaller quantities of slag, ranging approximately from 5,000 to 50,000 tons, by processing the slag into reusable secondary materials, specifically non-ferrous metals.

[0018] Moreover, also in case of plants handling larger quantities of material, having only one processing line for multiple slag fractions according to the invention reduces the investment size of the complete plant and the cost of the associated treatment process.

[0019] In preferred embodiments, different slag fractions coming from an incineration process BW1368R - 3 - are stored in different storage buffers and downstream such buffers a single, one common treatment line is provided. During operation, there is always only one slag fraction being fed and treated in the single treatment line, while the other fractions are stored in the respective buffers.

[0020] The common line may comprise one or more eddy current separator devices, of a type generally known in the art. Providing multiple eddy current separator devices arranged in series may ensure a more complete separation of all non-ferrous metals out of the slag fraction and increases the overall system efficiency.

[0021] In particular, one, or each, eddy current separator is generally based upon the repulsion property caused by the electrical conductivity of individual non-ferrous metal particles, which is induced by a changing magnetic field. The electrical conductivity of the particles is, of course, crucial for the strength of the particle repulsion, allowing them to surpass the separation plate / splitter. The successful separation of non-ferrous metals in the eddy current separator(s) depends upon the interaction between the electrical conductivity, the material’s density, the particle size and the geometry of the individual particles. Therefore, processing different slag fractions with one common eddy current separator device may require different eddy current set ups. Advantageously, the eddy current separator(s) set-up can be automatically adjusted through a dedicated control system that contains pre-programmed parameters for each respective slag fraction that is to be processed. In this way, when a different storage buffer is feeding the respective slag fraction towards the eddy current separator, the parameters can be (automatically) adjusted in a way that allows and favours the separation efficiency of that specific fraction.

[0022] There are different types of eddy current separators suitable to be used in the system according to the invention.

[0023] Such separators may mainly include, for example, an eccentric or concentric magnetic drum, a plurality of magnets within the magnetic drum and a splitter, which separates non-ferrous metals from the mineral slag fraction and which may be adjustable.

[0024] Advantageously, parameters such as the throughput of incoming slag, the speed of a conveyor belt in the eddy current separator, the position of the splitter and the rotational speed of the magnetic drum can be adjusted. In an eddy current separator with an eccentric magnetic drum the position of the magnets inside the drum can also be varied.

[0025] While all slag fractions are being stored with the dedicated storage buffers, one slag BW1368R - 4 - fraction is inserted into the treatment line via the outlet of the storage buffer and transported by a conveying system. The untreated slag fraction fed to the common line is than treated with the eddy current separator, which separates the non-ferrous metal fraction from a mineral slag fraction.

[0026] Preferably, a hopper is installed before the separator device. This hopper may ensure a constant, or anyhow controlled, slag feed towards the separator to enhance the separation efficiency of the non-ferrous metals from the mineral slag fraction.

[0027] Preferably, iron-containing and / or magnetic particles are separated from the slag flow upstream the non-ferrous metal separator device(s) either in the common line or upstream the buffers. In fact, iron-containing and magnetic materials might negatively affect the process of separating non-ferrous metals and may damage any magnetic drum possibly provided in the (eddy current) separation device according to the known art. In case there is no magnetic separation device installed prior the main storage buffers for each fraction, a magnetic separation device is installed between the storage buffers and the eddy current separator device.

[0028] In a preferred embodiment, a classification device is installed after the outlet of the separator device(s) for the separated non-ferrous metal fraction. In this way the separated non-ferrous metals can be classified in different fractions of various sizes, which ensure an enhanced situation for any subsequent processing of the non-ferrous metals.

[0029] Therefore, downstream the treatment system discussed above, there remain essentially two products to be processed: the mineral slag, which is generally the dominant fraction, and the separated non-ferrous metal(s).

[0030] As mentioned above, the invention provides a system that allows creating a viable process even with smaller amounts of slag coming from the incineration plant.

[0031] Other advantages, features and use modes of the present invention will result evident from the following detailed description of some embodiments, provided by way of example and not with limitative purpose. BW1368R - 5 -

[0032] Brief description of the drawings

[0033] Reference will be made to the figures of the annexed drawings, wherein:

[0034] ■ Figure 1 shows a schematic block diagram, or flow chart, of a system for separating non-ferrous metals from incinerator waste according to a first embodiment of the invention which provides a simple arrangement with two slag fractions to be treated;

[0035] ■ Figure 2 shows a schematic block diagram, or flow chart, of a system for separating non-ferrous metals from incinerator waste according to a second embodiment of the invention which provides an arrangement with three slag fractions to be treated;

[0036] ■ Figure 3 shows a schematic block diagram, or flow chart, of a system for separating non-ferrous metals from incinerator waste according to a third embodiment of the invention which provides an arrangement with additional slag fractions to be treated;

[0037] ■ Figure 4 shows a schematic block diagram, or flow chart, of a system for separating non-ferrous metals from incinerator waste according to a variant embodiment including a magnetic separator and a hopper arranged upstream an eddy current separator device and a classification device arranged downstream the separator device for the non-ferrous metals;

[0038] ■ Figure 5 shows a schematic block diagram, or flow chart, of a system for separating non-ferrous metals from incinerator waste according to a variant embodiment with respect to that of Figure 4, wherein multiple eddy current separator devices are provided.

[0039] Detailed description of preferred embodiments of the invention

[0040] Several embodiments and variants of the invention will be described below, with reference to the figures already introduced.

[0041] Generally speaking, analogous components are indicated in the various figures using corresponding reference numbers.

[0042] Further embodiments and variants other than those already described will be explained solely in conjunction with the relevant differences, if any, with respect to the preceding ones.

[0043] Moreover, the features of the various embodiments and variants described below are to be understood as combinable. BW1368R - 6 -

[0044] Figure 1 refers to a first embodiment of a system for treating slag in a waste incineration plant according to the present invention. The treatment system is globally denoted with 1 and is configured to separate non-ferrous metals from the slag. Typical non-ferrous metals that can be separated are aluminium, copper, silver, gold, lead, zinc, tin and palladium.

[0045] Preferably, the slag to be treated in system 1 has a moisture content of less than 10 wt.%.

[0046] Preferably, the slag particles to be treated in system 1 have a size of less than 100 mm.

[0047] Operation of the system 1 can be obtained by a control unit 100 internal or external to the system 1 and / or to the incineration plant the system 1 is part of.

[0048] System 1 includes a first and a second storage containers, buffers or buffer containers, denoted by 10 and 11, respectively, arranged in parallel and each configured to receive a respective fraction, 2 and 3 respectively, of untreated, or partially treated, incineration waste, or slag.

[0049] Fractions 2 and 3 may differ for particle size, for granulometry and / or for their composition and are preferably selectively separated from a common flow coming from an incineration chamber by dedicated separation means arranged upstream buffers 10 and 11. Fractions 2 and 3 may also differ in alternative respects or simply be the result of a subdivision of a main flow in two sub-flows.

[0050] Fractions 2 and 3 are fed to the respective buffers 10 and 11 by conveying or transport means known in the art and not shown in the figures.

[0051] Downstream buffers 10 and 11 , a common conveying, or transport, line 14 is provided. The conveying line 14 can be implemented, e.g., by a conveyor belt, a vibrating feeder, a bucket elevator or other. The outlet 12, 13 of each buffer 10, 11 is in direct material flow communication with line 14, possibly through a respective sub-line.

[0052] The outlet 12, 13 of each storage buffer 10, 11 is controlled so that the respective fraction 2, 3 is fed to the line 14 in selected operative conditions, e.g. when the buffer 10, 11 has reached its nominal capacity and the line 14 is not handling material coming from the other buffer 11, 10.

[0053] Along the line 14 a non-ferrous metal separation device 4 is arranged. In the present example - and most preferably - the device 4 is an eddy current separator device having an inlet 9.

[0054] In the separator device 4, the slag fraction 2 or 3 is processed, and two material BW1368R - 7 - streams are generated. The separated non-ferrous metals 6 are transported via a first outlet 5. The mineral slag fraction 8 is discharged through a second outlet 7.

[0055] As mentioned, according to preferred operating conditions, when processing untreated slag 2 from storage buffer 10, no untreated slag 3 exits storage buffer 11. Still according to preferred operating conditions, once a specific amount of untreated slag 2 has been processed by separator device 4, producing non-ferrous metals 6 and mineral slag fraction 8, the outlet of storage buffer 10 is closed. Once the outlet of storage buffer 10 is closed, untreated slag 2 is stored again in storage buffer 10. After the outlet 12 of storage buffer 10 is closed, the outlet 13 of storage buffer 11 can be opened, allowing untreated slag 3 to move from storage buffer 11 through its outlet 13 via line 14 towards the inlet 9 of separator device 4. The device 4 treats the untreated slag 3, producing two fractions: non-ferrous metals 6 and mineral slag fraction 8. Once storage buffer 10 reaches its capacity with incoming untreated slag 2, the outlet 13 of storage buffer 11 is closed. Incoming slag 3 is stored again in storage buffer 11, while untreated slag 2 exits storage buffer 10 towards device 4. During the process, only one of the outlets 12, 13 of the storage buffers 10, 11 is open at any time. In other words, untreated slag 2 and 3 are never conveyed simultaneously via line 14 towards the separator device 4.

[0056] Depending upon which slag material fraction 2, 3 is being treated, treatment parameter(s) of the separator device 4 can be changed automatically by the control unit 100. In case of an eddy current separator device, a splitter position can be changed, for separating non-ferrous metal fractions of different particle size.

[0057] In the configuration of Figure 2, an additional, third storage buffer 16 for another slag fraction 15 to be treated has been added. Fraction 15 can enter the separator device 4 via outlet 17 and be transported by the conveying line 14.

[0058] Figure 3 refers to an extension of the configuration of Figure 2 with multiple, third and fourth additional storage buffers 20 and 21 that store respective slag fractions 18, 19 to be treated, which can enter the conveying line 14 via respective outlets 22 and 23.

[0059] Figure 4 refers to an extension of the configuration of Figure 1. In particular, in case no magnetic separation has been taken place upstream the buffers, a magnetic separator 24 can be integrated before the separator device 4. The magnetic separator 24 processes incoming untreated slag 2, 3, one fraction at a time, and separates a BW1368R - 8 - magnetic and ferritic slag fraction 26 that exits the magnetic separator 24 by a magnetic material outlet 25. The non-magnetic slag 28 exits the magnetic separator 24 by a non-magnetic material outlet 27.

[0060] Moreover, preferably a hopper 29 is provided immediately upstream to, and configured to feed, the separator device 4. Hopper 29 temporarily stores the non-magnetic slag 28 before its processing by device 4.

[0061] According to a preferred embodiment, a classification device 30 is provided after the outlet 5 of the separator device 4 for the non-ferrous metals 6 to screen the separated non-ferrous metals 6 into different non-ferrous fractions 31, 32, 33. Classification of the non-ferrous metals 6 with the help of classification device 30 into different fraction 31, 32, 33 can improve the subsequent processes.

[0062] Figure 5 refers to a configuration based on that of Figure 4, wherein additional separator devices, denoted by 34, 35 and 36, respectively, are arranged in series among them and with separator device 4. After the non-magnetic fraction 28 is treated by the first separator device 4, the mineral slag fraction that exits from the outlet 7 enters addition separator device 34 where the remaining non-ferrous metals 6 are separated. To recover all non-ferrous metals 6, the remaining mineral slag fraction can be processed with additional separator devices 35, 36 to enhance the recovery efficiency of the non-ferrous metals 6. All separated non-ferrous metals 6 from all separator devices 4, 34, 35, 36 can be transported to the classification device 30 to be divided in different non-ferrous metal fractions 31, 32, 33.

[0063] The present invention has been described so far with reference to preferred embodiments. It is intended that there may be other embodiments which refer to the same inventive concept as defined by the scope of the following claims.

[0064] BW1368R -9-

Claims

BW1368R - 10 -CLAIMS1. A material treatment system (1) for separating non-ferrous metals (6) from other slag material (8), configured to be installed in an incineration waste treatment plant and comprising:- separation means, configured to separate a single flow of slag material into a plurality of fractions (2, 3);- a plurality of buffer containers (10, 11) arranged in parallel downstream said separation means, each having an inlet for receiving a respective slag material fraction (2, 3) coming from said separation means and an outlet (12, 13) for discharging said respective slag material fraction (2, 3);- a conveyor device (14) arranged downstream said buffer containers (10, 11) and common to all of them, which conveyor device (14) is configured for receiving a slag material fraction (2, 3) discharged by each of said buffer containers (10, 11);- at least one non-ferrous metal separator device (4) arranged downstream said conveyor device (14) and having an inlet (9) for receiving slag material, a first outlet (5) for discharging non-ferrous metals (6) separated from a remainder of the inlet slag material and a second outlet (7) for discharging the remainder slag material (8);- control means (100), configured for controlling charging and discharging of slag material from said buffer containers (10, 11) so that only one buffer container (10, 11) at a time discharges respective slag material to said conveyor device (14) and towards said non-ferrous metal separator device (4), so that said conveyor device (14) and said non-ferrous metal separator device (4) are fed alternatively by one or another buffer container (10, 11).

2. The system (1) according to claim 1 , wherein each of said buffer container (10, 11) is configured to receive a slag material fraction (2, 3) made of particles of a respective size.

3. The system (1) according to any of the preceding claims, comprising a plurality of separator devices (4, 34) arranged in series downstream said buffer containers (10, 11), the second outlet (7) of each separator device (4) being in flow communication with the inlet (5) of an adjacent, downstream separator device (34).

4. The system (1) according to any of the preceding claims, wherein said, or each, non-ferrous metal separator device is an eddy current separator device (4).

5. The system (1) according to any of the preceding claims, comprising a hopper (29) arranged upstream said, or a first, separator device (4) and configured for receiving slag material from said conveyor device (14) and for feeding slag material to saidBW1368R - 11 - separator device (4) according to a controlled, preferably constant, material flow.

6. The system (1) according to any of the preceding claims, comprising a magnetic separator device (24) arranged upstream to said separator device or devices (4) and / or upstream to said hopper (29).

7. The system (1) according to any of the preceding claims, comprising a classification device (30) arranged downstream said separator device or devices (4, 34, 35, 36) and configured for receiving the separated non-ferrous metal from said separator device or devices (4, 34, 35, 36) and for sorting the input non-ferrous metals into different fractions according to particle size.

8. The system (1) according to any of the preceding claims, wherein said control means (100) are configured to automatically adjust the set-up of said non-ferrous metal separator device (4) according to pre-programmed parameters for each respective slag fraction that is to be processed.

9. An incineration waste treatment plant, comprising a treatment system according to any of the preceding claims.

10. The incineration waste treatment plant according to claim 9, which has a capacity of approximately 5,000 tons to 50,000 tons of slag.

11. A material treatment method for separating non ferrous-metal from other waste material, suitable for use in an incineration waste treatment plant and comprising the following steps:- storing a plurality of slag material fractions (2, 3) into a respective plurality of buffer containers (10, 11) arranged in parallel, each having an inlet for receiving a respective slag material fraction (2, 3) and an outlet (12, 13) for discharging said respective slag material fraction (2, 3);- providing a non-ferrous metal separator device (4) arranged downstream said buffer containers (10, 11) and having an inlet (9) for receiving slag material, a first outlet (5) for discharging the non-ferrous metal (6) and a second outlet (7) for discharging the remainder slag material (8);- conveying each slag material fraction (2, 3) at a time from the respective buffer container (10, 11) to the separator device (4) through a conveying line (14) common to all the buffer containers (10, 11) of said plurality, so as to perform a non-ferrous metal separating step, wherein only one buffer container (10, 11) at a time discharges respective slag material to said conveyor line (14) and towards said non-ferrous metal separator device (4), so that said conveyor line (14) and said non-ferrous metal separator device (4) are fed alternatively by one or another buffer container (10, 11).BW1368R - 12 -12. The method according to claim 11, wherein each of said buffer containers (10, 11) receives a slag material fraction (2, 3) made of particles of a respective size.

13. The method according to claim 11 or 12, providing a plurality of non-ferrous metal separating steps applied in sequence.

14. The method according to any of claims 11 to 13, wherein the slag material is fed to said separator device (4) according to a controlled, preferably constant, material flow.

15. The method according to any of claims 11 to 14, comprising a magnetic separation step upstream to said non-ferrous metal separating step.

16. The method according to any of claims 11 to 15, comprising a classification step downstream said non-ferrous metal separation step and configured for sorting the separated non-ferrous metals (6) from said separator device or devices (4) into different fractions according to particle size.

17. The method according to any of claims 11 to 16, wherein the non-ferrous metal is one or more of aluminium, copper, silver, gold, lead, zinc, tin and palladium.

18. The method according to any of claims 11 to 17, wherein the slag material of said buffer containers (10, 11) is treated in a batch process.

19. The method according to any of claims 11 to 18, wherein during the treatment of the material outing from one buffer container (11), incoming untreated slag material (3) is stored in one or more of the other buffer containers.

20. The method according to any of claims 11 to 19, wherein the slag material fractions have a moisture content of less than 10 wt.%.

21. The method according to any of claims 11 to 20, wherein the slag material fractions have a size of less than 100 mm.

22. The method according to any of claims 11 to 21 , which is used for treating grate ash from waste incineration.

23. The method according to any of claims 11 to 22, which uses a system according to any of claims 1 to 8.

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