WO2008047010A2 - Method for treating waste containing precious metals and device for implementing said method - Google Patents

Abstract

The invention relates to a method for treating waste containing precious metals, said method comprising the following successive steps: the waste is brought into contact with a composition based on molten lead; the mixture obtained is skimmed; and the skimmed mixture is refined by electrolysis in such a way as to recover the precious metals. The invention also relates to a waste treatment installation for implementing said method.

Description

 PROCESS FOR PROCESSING WASTE CONTAINING PRECIOUS METALS AND DEVICE FOR IMPLEMENTING SAID METHOD

FIELD OF THE INVENTION

The present invention relates to a waste treatment method containing precious metals and a device for implementing this method.

TECHNICAL BACKGROUND The increasing use of calculators, mobile telephones, electronic equipment and other short-lived high-tech appliances is generating an increasing amount of waste containing precious and rare metals. This situation poses the problem of recovering and treating the metals contained in these wastes. Thus, such waste is a real deposit of non-ferrous metals, rare and valuable. E-waste is currently being collected, exported and processed in large non-ferrous industrial complexes that often require multiple plants in lead, copper and zinc extraction cascades where these high-value materials are diluted in raw material flows. of mining or secondary origin. Current processes are therefore optimized to produce large quantities of lead, copper or pure zinc, but they are poorly suited to produce rare and precious metals, present in small quantities.

It is therefore desirable to design a waste treatment process making it possible to recover a large proportion of the precious metals contained in the waste.

SUMMARY OF THE INVENTION The invention firstly relates to a waste treatment method containing precious metals, comprising the following successive steps:

- contacting the waste with a composition based on molten lead;

skimming of the mixture obtained; and

- Refining the foam mixture by electrolysis so as to recover the precious metals.

According to a particular embodiment, the residues which are treated by: contacting the residues with a second composition based on molten lead are recovered at the skimming stage; skimming of the mixture obtained; and recovering the froth mixture to provide at least a portion of the aforementioned molten lead composition. According to a particular embodiment, the step of refining the foam mixture comprises the following substeps:

- Pouring the foam mixture into anodes;

electrolysis of a fluosilicic acid solution using said anodes; and - recovery of anode sludge containing the precious metals.

According to a particular embodiment, the aforementioned method comprises before, simultaneously with or after the anode sludge recovery step, the following step: recovery of cathodic deposits of lead and optionally tin to provide at least a part of the composition based on molten lead and / or the second molten lead composition.

According to a particular embodiment, the step of refining the foam mixture comprises, after the sub-step of recovering anode sludge, the following additional substeps: melting anode sludge recovered in the presence of oxygen; - skimming of melted anode sludge; and casting into ingots molten and foamed anode sludge.

According to a particular embodiment, each molten lead composition comprises 0 to 50% tin, preferably 0 to 20% tin.

According to a particular embodiment, the aforementioned method comprises, prior to the step of bringing the waste into contact with a composition based on molten lead, the following step: copper extraction of the waste by selective dissolution.

According to a particular embodiment, the copper extraction step comprises the following substeps: selective dissolution of the waste in the presence of sulfuric acid, iron sulphate and oxygen; treatment of the solution obtained by filtration and / or electrolysis and / or precipitation; recovery of copper on the one hand and other metallic impurities on the other. According to a particular embodiment, the aforementioned method comprises, prior to the copper extraction step, the following step: combustion of waste by pyrolysis, producing carbonaceous gases; and possibly afterburning of the carbonaceous gases.

According to a particular embodiment, the above-mentioned method also comprises a preliminary step of grinding the waste and / or analyzing crushed waste. According to a particular embodiment, the precious metals comprise one or more metals chosen from gold, silver, platinum, palladium, rhodium, ruthenium, iridium, osmium and their mixtures. According to a particular embodiment, the waste is chosen from catalytic exhaust pipes and electronic waste such as electronic cards.

According to a particular embodiment, more than 90% by weight, preferably more than 99% by weight, precious metals contained in the waste are recovered according to the aforementioned method.

According to a particular embodiment, the supernatants comprise ceramics, glass fibers and / or ferrites.

The invention also relates to a waste treatment plant containing precious metals, comprising: - at least one filling vessel; a melted lead composition feed line connected to the inlet of the filling vessel;

a feed line for pretreated materials, connected at the inlet of the stuffing vessel; skimming means associated with the stuffing vessel; a scum mixture withdrawal line, connected at the outlet of the stuffing vessel;

means for refining the foam mixture by electrolysis, fed by the foam mixture withdrawal line; and

a precious metals withdrawal line connected at the outlet of the refining means of the foam mixture.

According to a particular embodiment, the aforementioned treatment plant further comprises: a skimming residue withdrawal line, connected at the outlet of the skimming means; at least one additional filling vessel, fed on the one hand by the skimming residue withdrawal line and on the other hand by an additional molten lead composition feed line; additional skimming means associated with the additional stuffing vessel; and an additional froth mixture withdrawal line connected at the outlet of the additional filling vessel and supplying the molten lead composition feed line.

According to a particular embodiment, the means for refining the foam mixture by electrolysis comprise: anode casting means; - Betts electrolysis means; and means for recovering anode sludge. According to a particular embodiment, the means for refining the foam mixture by electrolysis comprise: lead-tin recovery means, supplying the supply line with additional molten lead composition. According to a particular embodiment, the aforementioned treatment plant further comprises: copper extraction means, an output of which is connected to the feed line of pretreated materials; and a feed line of primary materials, connected at the input of the copper extraction means.

According to a particular embodiment, the copper extraction means comprise: at least one selective dissolution vessel fed by the feed line of primary materials; a lean electrolyte supply line connected to the inlet of the selective dissolution vessel; electrolysis means; rich electrolyte transfer means, connecting the selective dissolution vessel to the electrolysis means; stripping means of the cathodes; and - poor electrolyte recycling means connected at the output of the electrolysis means.

According to a particular embodiment, the above-mentioned treatment plant further comprises: waste pyrolysis means connected at the outlet to the feed line of primary materials; a waste feed line feeding the pyrolysis means; and eventually ; a gas exhaust line at the outlet of the pyrolysis means and feeding afterburner means. According to a particular embodiment, the aforementioned treatment plant further comprises: grinding and analysis means fed by a raw waste feed line and feeding the waste feed line.

According to a particular embodiment, the aforementioned method is implemented in the aforementioned installation. According to a particular embodiment, the aforementioned installation is intended for implementing the aforementioned method. The present invention overcomes the disadvantages of the state of the art. In particular, it provides a specific process for the treatment and recovery of waste containing precious metals, which harmoniously combines the metallurgical sequences and avoids diluting the metals contained in a primary metal production stream. The invention also provides a unique facility for separating the constituents of waste and in particular recovering precious metals.

According to some particular embodiments, the invention also has the advantageous features listed below.

The method according to the invention is very flexible and makes it possible to adapt to the foreseeable changes in the composition of the electronic cards.

The method according to the invention does not have the disadvantage of using the usual technique of extraction of precious metals by oxidation of lead, called cupellation operation, and followed by the operation of the reduction of lead oxide. The invention makes it possible to keep the metals in metallic form as much as possible: the precious metals are preserved in metallic form throughout the process, and the lead and the tin are kept in metallic form until step (d) included. This makes it possible to minimize the entrainment of the precious metals by metal oxides. The invention makes it possible to collect precious metals at a single outlet. The invention can be implemented with a controlled environmental impact.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 schematically shows an example of waste treatment plant according to the invention. FIG. 2 represents an example of grinding and analysis means that can be used in the context of the waste treatment installation according to the invention. Dashed arrows denote gaseous flows. The arrows in double lines denote solid flows.

FIG. 3 represents an example of pyrolysis and afterburner means that can be used in the context of the waste treatment installation according to the invention. Dashed arrows denote gaseous flows. The arrows in simple black line designate the liquid flows. The arrows in double lines denote solid flows.

FIG. 4 represents an example of copper extraction means that can be used in the context of the waste treatment installation according to the invention. Dashed arrows denote gaseous flows. The arrows in simple black line designate the liquid flows. The arrows in double lines denote solid flows.

FIG. 5 represents a particular example of a filling receptacle that can be used in the context of the invention. FIG. 6 represents an example of refining means that can be used in the context of the waste treatment installation according to the invention. Dashed arrows denote gaseous flows. The arrows in simple black line designate the liquid flows. The arrows in double lines denote solid flows.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The invention is now described in more detail and without limitation in the description which follows.

Waste treatment facility

Referring to Figure 1, a waste treatment plant according to the invention schematically comprises the following elements.

At the inlet of the treatment plant, a waste feed line 1 is provided. This waste feed line 1 may optionally be connected to the output of grinding and analyzing means fed by a feed line. raw waste Ibis.

The waste feed line 1, like all other feed lines, transfer or withdrawal mentioned in the present description, may comprise a single path or multiple channels (branches) in parallel.

According to one embodiment, the waste feed line 1 feeds pyrolysis means 2. At the outlet of the pyrolysis means 2 there are provided means for feeding primary materials 6, which feed the copper extraction means 37 At the outlet of the copper extraction means 37 is provided a pre-treated material supply line 14, which feeds a stuffing container 15. This embodiment is particularly well suited to the processing of used electronic cards. According to one variant, the pyrolysis means 2 are absent, and the waste feed line 1 directly feeds the copper extraction means 37 (in this case it is considered that the waste feed line 1 is merged with the supply line of primary materials 6).

According to another variant, the copper extraction means 37 are absent, and the supply line of primary materials 6 directly feeds the stuffing vessel 15 (in this case it is considered that the supply line of primary materials 6 is confused with the feed line of pretreated materials 14).

According to yet another variant, both the pyrolysis means 2 and the copper extraction means 37 are absent, and the waste feed line 1 directly feeds the stuffing vessel 15 (in this case it is considered that the waste supply line 1 and the feed line of pretreated materials 14 are combined). This variant is particularly suitable for the treatment of used catalytic converters, since these contain no or virtually no copper.

When they are present, the pyrolysis means 2 can be connected at the output to a gas exhaust line 4, which can feed post-combustion means 5. When present, the copper extraction means 37 can comprise a selective dissolution vessel 7 fed at the inlet by the feed line of pretreated materials 6 and fed on the other hand by a poor electrolyte supply line 11. The feed line of pretreated materials 14 is then connected at the outlet of the selective dissolution vessel 7, while a rich electrolyte transfer line 8 feeds electrolysis means 9. Stripping means of the cathodes 13 are provided in association with the electrolysis means 9, and a LOW electrolyte recycling line 10 is provided at the output of the electrolysis means 9. This lean electrolyte recycling line 10 can feed the poor electrolyte supply line 11 and / or a line of line poor electrolyte 12.

The filling vessel 15, which is fed by the feed line of pretreated materials 14, is also fed by a feed line of molten lead composition 24. Foaming means 16 are associated with the feed container. Filling 15. At the outlet of the filling vessel 15 is provided a foam mixture withdrawal line 21, which feeds means for refining the foam mixture 36. A precious metals withdrawal line 38 is provided at the outlet of the refining means. It is also possible to provide a skimming residue withdrawal line 17 at the outlet of the skimming means 16, which can feed an additional filling vessel 18. This additional stuffing vessel 18 is then also supplied with fuel. by an additional molten lead composition feed line 31. Additional skimming means 19 are provided in association with the additional stuffing vessel 18, e an additional scum mixture withdrawal line 22 is provided at the outlet of the additional filling vessel 18. This additional scum mixture withdrawal line 22 can supply, like the scum mixture withdrawal line 21, the scouring means However, according to a preferred alternative, the additional scum mixture withdrawal line 22 feeds the molten lead composition feed line 24. A complementary source of molten lead composition 23 may be provided in a suitable manner. optional to complete this diet. An additional skimming residue withdrawal line 20 may be provided at the outlet of the additional skimming means 19.

The means for refining the foam mixture 36 more specifically comprise anode casting means 25, an anode transfer system 26, Betts electrolysis means 27. At the level of the Betts electrolysis means 27 are provided means lead-tin recovery 29 and anode sludge recovery means 28. The lead-tin recovery means 29 feeds (optionally together with a fresh lead feed line 30 which may optionally be provided) the feed line of additional molten lead composition feed 31.

The means for recovering anode sludge 28 feed melting means 33, which are additionally provided with an oxygen supply 32. Final skimming means 34 are provided in association with the melting means 32. The withdrawal line Precious metals 38 are connected at the outlet of the melting means 32, which also include a waste discharge line 35.

Referring now to FIG. 2, a possible example is described in more detail below for the first part of the waste treatment facility, dedicated to receiving, grinding and analyzing incoming waste. (see references Ibis, lter of Figure 1).

According to this example, the installation comprises means for receiving waste 101, which may in particular comprise an unloading hall, and which are for example adapted to receive trucks. Weighing means 102 are provided at these waste receiving means 101, as well as storage means 103. At the outlet of the storage means 103 are provided dosing means 104 adapted to discharge the waste on a main conveyor 105 (carpet or the like). The main conveyor 105 distributively feeds a first secondary conveyor 106, a second secondary conveyor 107 and a third secondary conveyor 108.

The first secondary conveyor 106 feeds a coarse mill 109. A fine mill 11 1 is also provided, supplied on the one hand by the second secondary conveyor 107 and on the other hand by a transfer line 110 coming from the outlet of the coarse mill 109 The grinders 109, 111 may have a typical capacity of 5 to 10 t / h each. A collecting conveyor January 12 is provided at the end of the fine grinder 1 11 and joins the third secondary conveyor 108. In the path of the third secondary conveyor 108 are also provided sampling means 113 (for example a ladle), which make it possible to supplying means of analysis 1 14.

Furthermore, the third secondary conveyor 108 distributes a first tertiary transporter 115 and a second tertiary transporter 1 17 in a distributive manner. The first tertiary transporter 115 feeds a waste storage silo 1 16. As for the second tertiary transporter 1 17, it feeds a container January 18, at the output of which a return conveyor 119 feeds the storage means 103. An air purification system 120 is installed at the level of the coarse mill 109 and the fine mill 111 and feeds a bag filter 121 , which can have a typical capacity of 5000 Nm ³ / h. The bag filter 121 is connected to a stack 123 and to a fine recovery line 122, which feeds the waste storage bin 1 16. It is obvious that the skilled person will adapt the means thus described to the needs of the installation, for example by varying the number or type of grinders or the capacity of the various means used.

Referring now to FIG. 3, a possible example will be described in more detail below for that portion of the treatment plant that lies between the waste supply line 1 (hereinafter 201) and the feed line of primary materials 6 (hereinafter 205a, 205b).

According to this example, the waste feed line 201 is provided at the outlet of the above-mentioned waste storage silo 116 and feeds three pyrolysis furnaces 202a, 202b, 202c arranged in parallel via hoppers. The pyrolysis furnaces 202a, 202b, 202c may be screw-type kiln furnaces heated externally electrically. By way of example, it is possible to use furnaces with a length of 5 m and a diameter of 40 cm, with a power of 100 kW, having a variable screw speed. The number of ovens can be varied according to the needs of each installation. A calcined waste collection line 203 is provided at the outlet of the pyrolysis furnaces 202a, 202b, 202c and feeds two calcined waste storage silos 204a, 204b. The number of these storage silos can be varied according to the needs of each facility. The calcined waste collection line 203 may be a jacketted conveyor provided with means for cooling with water. At the outlet of each calcined waste storage silo 204a, 204b is provided a respective primary material supply line 205a, 205b (these two lines together constitute the primary material supply line 6).

Furthermore, at the outlet of each pyrolysis furnace 202a, 202b, 202c is provided a respective gas exhaust pipe 206a, 206b, 206c (all of these pipes corresponding to the above-mentioned exhaust gas line 4). Each gas exhaust pipe 206a, 206b, 206c supplies a respective afterburner chamber 207a, 207b, 207c. A typical example of afterburner chamber volume 207a, 207b, 207c is 15 m ³ . Each afterburner chamber 207a, 207b, 207c is further supplied by a respective air supply line 208a, 208b, 208c. A flue gas collection conduit 209 connects the outlet of the afterburner chambers 207a, 207b, 207c to the inlet of a vertical cooling chamber 210. A cooling water supply line 211 is also provided at the inlet of the cooling chamber 210. For example, spray bars located in the upper part of the chamber can be provided. A pre-cooled gas sampling line 212 is provided at the outlet of the cooling chamber 210, and supplies a bag filter 214. An air supply line 213 is connected to the pre-cooled gas sampling line. 212. The bag filter 214 may for example have a capacity of 40000 Nm ³ / h. A fine withdrawal line 215 on the one hand and a purified gas withdrawal line 216 are connected at the outlet of the bag filter 214. The purified gas withdrawal line 216 feeds a stack 217.

Referring now to FIG. 4, a possible example is described in more detail below for that part of the treatment plant which essentially comprises the copper extraction means 37.

Each primary material supply pipe 205a, 205b supplies a respective selective dissolution vessel 301a, 301b, which may be, for example, a closed reactor of 20 m ³ made of epoxy resin / glass fiber of great thickness, provided with 'a lid and a

LO variable speed stirrer. It is possible to provide one such container or on the contrary a larger number, depending on the production needs. Each selective dissolution vessel 301a, 301b is also fed by a poor electrolyte supply line 303. An oxygen supply 304 is further provided at the bottom of each selective dissolution vessel 301a, 301b.

A respective selective post-dissolution drain line 305a 305b is provided at the outlet of each selective dissolution vessel 301a, 301b, which supplies a respective filter press 306a, 306b. A solids collection system 307 is placed at the outlet of the filter presses 306a, 306b and feeds a drying oven 308, at the outlet of which is the pre-treated material supply line 309 (corresponding to the reference 14 on the figure 1). The

Drying oven 308 may be a screw oven similar to those used for pyrolysis.

Furthermore, each filter press 306a, 306b is provided at the outlet of a filtered liquid withdrawal pipe 310a, 310b respectively which feeds a single tank 302. This latter, in turn, feeds, via a transfer line 311, a rich electrolyte storage tank 312, which may have for example a capacity of 60 m ³ .

The other major component of this part of the plant is the electrodeposition unit 314. This electrodeposition unit 314 comprises a number of electrolysis vessels 315a, 315b, 315c, 315d, 315e, the number of five in this example, the number of tanks that can be adapted to the needs of production. Each electrolysis cell 315a, 315b, 315c, 315d, 315e comprises a number of electrolysis cells according to the

10 needs of the production, for example eight in the present example. For example, each electrolysis cell can have a useful volume of 4 m ³ and contain 31 stainless steel cathodes and lead / calcium anodes of useful surface area 1 m ² per side. The electrolysis vessels 315a, 315b, 315c, 315d, 315e are fed in parallel through a rich electrolyte transfer line 313 connected at the outlet of the rich electrolyte storage tank 312. The electrodeposition unit 314 is completed by a stripping system of the cathodes 316.

At the outlet of the plating unit 314 is provided a poor electrolyte recycling line 317, which feeds a first poor electrolyte storage tank. 318 (for example 60 m ³ ) and a second poor electrolyte storage tank

319 (for example of capacity 25 m ³ ). The first lean electrolyte storage tank 318 constitutes the supply source of the lean electrolyte supply line 303. The second lean electrolyte storage tank 319 feeds a first purification reactor 320 (for example capacity 15 m ³ ). This first purification reactor 320 is also fed by a lime feed line 321. At the outlet of the first purification reactor 320 is connected a first pulp withdrawal line 323, which feeds an additional filter press 324.

Furthermore, the fines extraction pipe 215 described with reference to FIG. 3 feeds a second purification reactor 325 (example of capacity: 5 m ³ ) equipped with a water and lime supply (not shown). At the outlet of the latter there is a second pulp withdrawal line 326, which also feeds the additional filter press 324. At the outlet of the additional filter press 324 are connected a washed fines withdrawal line 327, a withdrawal line. of lime sulphate 328 and an acid juice withdrawal line 329. The washed fines withdrawal line 327 can supply one of the selective dissolution containers 301a, 301b or both. The acid juice withdrawal line 329 can feed a tank, not shown, with downstream additional devices for treating halides.

A gas purification system 330 passes through all the storage tanks 312, 318, 319, selective dissolution vessels 301a, 301b and purification reactors 320, 325 and feeds a washing tower 331. The tanks storage 312, 318, 319, the purification reactors 320, 325 and the washing tower 331 may be epoxy resin / glass fiber of standard thickness. The washing tower 331 comprises at the outlet an additional acidic juice withdrawal line 332, which can feed back the poor electrolyte storage tank 318. The washing tower 331 can have a capacity of 5 m ³ , be equipped with a standard lining and work with water.

Referring again generally to FIG. 1, the potting vessel 15 and the additional potting vessel 18 may be as shown in FIG. 5. Each vessel then comprises a cauldron 401 (50 ton capacity example) surrounded by a heating chamber 402 provided with burners 403. An agitator 404 (for example a propeller with a vertical axis propeller) is immersed in the kettle 401. The kettle 401 is fed by a feeder 407, which, depending on the case, is connected to the inlet of the feed line of pre-treated materials 14 or to the skimming residue withdrawal line 17. On the side of the kettle 401 is provided a skimming machine 405 consisting of a squeegee articulated steel fixed to an inclined plane. A cowling 406 isolates the surface of the contents of the kettle and is adapted to provide nitrogen inerting. Suction means 408 are provided above the cauldron 401 and are connected to a not shown bag filter. Flue gas evacuation means 409 adapted to collect the gases emitted by the burners are connected to the heating chamber 402. The stirrer 404 is advantageously removable in order to allow the transfer of the contents of the kettle 401. Downstream of the Filling containers 15, 18, are the anode casting means 25, which include in particular a kettle of the type described in Figure 5, but without necessarily frothing and stirring devices. This cauldron can include a cowling and a suction.

The last major part of the present installation relates to the refining and notably includes the references 27, 33, 34 of FIG. 1. This is described below with reference to FIG.

This part of the plant comprises a Betts electrolysis unit 501, which contains a plurality of rows 502a, 502b of Betts electrolysis cells (two in this example). Each row 502a, 502b may comprise, for example, five cells, each cell having 30 anodes and 31 cathodes of useful surface area 1 m ² per face, for a useful cell volume of 4 m ³ . The rows 502a, 502b are supplied in parallel with electrolyte from a Betts 503 reactor. A return pumping system may be provided to facilitate the circulation of the electrolyte. The Betts 503 reactor is fed on the one hand by a fluosilicic acid feed line 504 and on the other hand by a litharge feed line 505. At the outlet of the Betts electrolysis unit 501, a line used Betts electrolyte collection

506 returns to the second poor electrolyte storage tank 319 of FIG.

An electrolysis sewer system 507 collects the gases at the Betts electrolysis unit 501 and at the Betts 503 reactor, and conveys them to a washing tower 508, with a typical volume of 5 m ³ . A washing juice collection line 509 provides a return to the second poor electrolyte storage tank 319 of FIG. 4.

The betts electrolysis unit 501 is also provided with cathode stripping means 510. The cathode stripping means 510 provide a cathode supply line 51 1 which itself feeds a cathode 512 cauldron . The cauldron 512 is of the type described in FIG. 5, but without necessarily the frothing and stirring devices. This cauldron 512 may include a cowling and a suction. It feeds via a lead-tin supply line 513, possibly together with a fresh lead feed line 30, the additional melted lead composition feed line 31 (see Fig. 1). The set of references 510 to 513 correspond to the lead-tin recovery means 29. The Betts electrolysis unit 501 is furthermore provided with means for scraping anode butts 514 which feed an anode sludge collection line. 516 (the assembly constituting an example of means for recovering anode sludge 28). This line of Anode sludge collection 516 feeds an anode sludge treatment unit 517 which may include washing means, weighing means and / or storage means. A washed sludge transfer line 518 connects the anode sludge processing unit 517 to an oxidation furnace 520 (eg 800 kW power, 1 ton capacity), which also receives a feed line of 519. At the outlet of the oxidation furnace 520, an ingot collection line 521 can provide a return to the trunk storage means of the anode sludge treatment unit 516. The line of FIG. Litharge supply 505 is also connected at the outlet of oxidation furnace 520. A flue gas collection line 522 is also provided at oxidation furnace 520, it can be connected to the same filtration system as that provided for in FIG. level of the filling receptacles.

Waste treatment process

An example of a waste treatment method containing precious metals is described below, in the case where the waste is used electronic cards. In this example, the process comprises 5 main phases: grinding; pyrolysis; copper extraction by selective dissolution (or leaching); 20 - the filling; and refining.

This example corresponds to the use of the treatment plant described above in connection with FIGS. 1 to 6. The production capacity is of the order of 25,000 tons per year or of the order of 72 tons of waste per day. In the case where the waste is for example

In the case of catalytic converters, steps of pyrolysis and copper extraction can advantageously be dispensed with.

The electronic cards are received at the level of the waste reception means 101. The electronic cards arrive at the entrance of the installation in batches (containers, big bags, drums), which are weighed at the weighing means 102, labeled, recorded and stored at the level

Storage means 103.

Cards can come in three main forms:

1) whole cards requiring double grinding before any treatment;

2) pre-milled cards requiring simple grinding before any treatment; and

3) properly milled cards to less than 5 mm in size, requiring no additional grinding before processing.

Therefore, using the transport system described above, the cards are directed according to their nature: either successively to the coarse crusher 109 and the fine crusher 11 1 (case 1 above); either directly to the fine grinder 111 (case 2 above); or directly the waste storage silo 116 (case 3 above). The coarse crusher 109 crushes or crushes waste reducing it to a size less than 25 mm, while the fine crusher 111 crushes or crushes waste reducing it to the required size less than 5 mm. Moreover, prior to the entry of the correctly ground cards into the waste storage silo 116, they undergo an automated sampling at the sampling means 113, which periodically cut the flow of cards. For example, 300 kg of sample can be taken in a batch of 24 t. Then the sample is analyzed by the analysis means 114 after quartering in the laboratory to reach a final sample mass of 4 to 5 kg. It is preferred to treat a given batch of waste only when the result of the analysis is known, in order to adapt the parameters of the treatment. Therefore, before the sample analysis has been performed, the cards return via the return conveyor 119 to the storage means 103.

The premises of the grinders 109, 11 are cleaned, and the fines suspended in the air are recovered and reinjected into the waste storage silo 116.

The grounded electronic boards are then extracted at the base of the waste storage bin 1 16 and supply the hoppers located above the inlet of each of the three pyrolysis furnaces 202a, 202b, 202c. The bulk density of the product is 0.7 at the entrance of the furnaces. Pyrolysis is useful for degrading and eliminating organic matter in cards. This is a gentle combustion of the carbon chains, which is carried out while keeping the metals of the waste in the metallic state.

The residence time in the furnaces may be between 20 and 90 min and is preferably 30 min. The operating temperature can be between 350 and 55O ⁰ C and is preferably about 400 ⁰ C. The control of temperatures, vacuum and speed of the screw allows to control the operation. Each furnace typically has a processing capacity of 1 t / h. The pyrolysis gases rich in phenol compounds leave at 400 ^° C. of each oven.

The calcined cards leaving each oven are cooled on the calcined waste collection line 203 (jacketted conveyor) and are then stored in the silos 204a, 204b feeding the copper leaching. The product has a black appearance due to residual carbon from the pyrolysis of plastics. It has a density of about 0.5.

The pyrolysis gases from each furnace are burned at high temperature in the afterburner chamber 207a, 207b, 207c (residence time 2 s) in order to destroy all the carbonaceous molecules and any dioxins and furans. Thus, almost all carbon chains are recovered as energy that can be recovered and used in the process itself. Combustion air is preheated to 400 ° C to ensure good gas ignition. Additional controlled air is needed to regulate the chamber outlet temperature at 1100 ° C and avoid the formation of NOx. An additional 800 kW burner ensures that the temperature is sufficient for the combustion to take place, especially during the transient phases. Continuous control of the inlet and outlet temperatures of the afterburner is achieved and regulates the dilution air inlet. The gases to HOO ⁰ C arrive in the cooling chamber 210 to undergo quenching with water. The cooling water is brought to a flow rate of 10 minutes. Water is completely transformed into water vapor by capturing a good deal of the gas energy. The cooled gases leave the chamber at 200 ^° C. The control of the outlet temperature makes it possible to regulate the flow of water injected. These gases are then finely cooled in air at about 150 ^° C. before entering the bag filter 214. The handles retain the fine solid particles containing in particular halides. Purge is carried out in the next sector of copper leaching. The totally purified gases are discharged at the chimney 217. A continuous control is carried out there (analysis of the gases, rate of dust ...). With regard to the extraction of copper, this is carried out through a series of hydrometallurgical operations: leaching in oxidizing acid medium, filtration of the residue, electroplating copper requiring the use of several reactors, storage tanks, filters, pumps and a set of electrolysis cells and current generators.

The daily flow rate of calcined cards from the silos 204a, 204b containing 12 t of copper is treated in the selective dissolution vessels 301 to 301b (closed reactors) in leachings of 4 hours each. The operation is as follows: transfer to the pump of 15 m ³ of copper-poor electrolyte and rich in acid (at 85 ° C) from the poor electrolyte storage tank 318. It is then proceeded to the introduction of 4.8 t of calcined cards with a fine bubbling of oxygen at the bottom of the reactor. The lean electrolyte is a solution containing sulfuric acid (from 50 to 200 g / l, preferably about 100 g / l) and soluble iron in the form of iron sulphate (5 to 20 g / l, preferably about 10 g / 1) which must be maintained in the Fe ³⁺ form (with oxygen) to effectively attack copper.

The temperature is maintained by injecting live steam. Finally, the contents of the reactor are filtered on the filter press 306a or 306b or both. The copper-rich juices are transferred to the rich electrolyte storage tank 312 feeding the electrolysis cells.

The electrolyte is enriched with iron and nickel, which dissolve at the same time as copper. It is necessary to carry out a daily purge on the poor electrolyte leaving the electrolysis cells. It is sent to the second poor electrolyte storage tank 319 and its treatment is carried out in the first purification reactor 320 twice a day. These very acidic juices containing iron, nickel and some copper are treated with lime up to pH 8.5. It precipitates calcium sulphate resulting in the metal hydroxides. This pulp is filtered on the additional filter press 324. The resulting residue (10 to 15 t / d) is placed in a controlled landfill. The juices are recycled to the first poor electrolyte storage tank 318.

The fines of the pyrolysis filter are treated in the second purification reactor 325 every 2 days in the presence of water and a little lime at pH 9. The halides (chlorides and bromides

5 mainly) go into solution. The pulp is filtered on the additional filter press 324: the residue (500 kg) is recycled to the selective dissolution vessels 301a, 301b and the juices (3 m ³ ) enriched in halides are stored in a tank for further processing.

All the reactors, storage tanks, filters are sanitized and the vapors and vesicles are captured by the washing tower 331. The acidic juices obtained are regularly purged and recycled to the poor electrolyte storage tank 318.

In the process, the poor electrolyte is heated and maintained at 85 ° C by means of a steam-fed coil. The rich electrolyte is cooled at 50 ^° C. by a coil fed with cold water. This cold water can then be used in the hot gas vaporization chamber of the post-combustion pyrolysis.

The wet solid residues (40 t / d) from filter presses 306a and 306b are rich in precious metals. They are dried in the drying oven 308. They are pulverulent and have a black color, the glass fibers which constitute the main compound being broken during the stirring in the attack tank. Solid and liquid flows are sampled regularly and analyzed.

With regard to the electroplating step, the stream from the rectifiers passes in series from electrolysis cell to electrolysis cell and in parallel to the electrode levels of each cell. The current density can be from 50 to 400 A / m ² , preferably about 200 A / m ² and the temperature of the electrolyte can be from 20 to 80 ⁰ C, preferably from 45 to 50 ⁰ C. The concentration in ferric ions is kept as low as possible, and in any case at a level below 10 g / l. When the total iron concentration reaches a value of 10 to 30 g / 1, a portion of the electrolyte is purified by precipitation of iron and filtration of the precipitate.

The rich electrolyte from the tank for storing rich electrolyte 312 is sent to the ^st row of eight cells. The cells are arranged in cascade to allow the circulation of the electrolyte and a pump returns the juice of the last cell to the first.

The circulating flow is of the order of 15 mVh. The electrolyte takes 24 hours to run out of copper which settles on the cathodes. The addition of a surfactant makes it possible to obtain a fine and regular copper deposit. The spent electrolyte is pumped to the poor electrolyte storage tank 318. The cells are then refilled with rich electrolyte. Each row can be emptied and filled with electrolyte every 4.5 to 5 hours.

Every 5 days a row of cells is stripped. Recovered copper cathodes

(12 t) are rinsed with water and the copper is separated from its stainless support by a suitable mechanical tool. The resulting copper is sampled and stored. It should also be noted that all the solid and liquid flows are advantageously sampled regularly and analyzed.

The step of selective extraction of copper is important when the starting material contains a significant proportion of copper. Indeed, copper is capable of forming stable compounds insoluble in liquid lead, said compounds often containing precious metals. This is why it is necessary to get rid of as much copper as possible before starting the subsequent stages of filling and refining, otherwise a large quantity of precious metals will be lost in said stable compounds.

Moreover, the step of selective extraction of copper makes it possible to extract almost all of the copper selectively in the form of a merchantable product (cathodes of pure copper), which can be remelted in the form of ingots.

The metals dissolved in the electrolyte (iron, aluminum, nickel) can be advantageously removed during periodic electrolyte regeneration operations.

It should be noted that copper electroplating can be replaced by a copper sulfate crystallization process, a commercial product.

Depending on the type of waste, one can do without either of the pyrolysis and copper extraction stages by selective dissolution, or both. This is the case for example when the waste consists of catalytic converters. In this case, the content of carbon and copper chains does not justify the presence of these two stages, and the used crushed catalytic converters undergo directly the stuffing step.

The stuffing step comprises contacting the pre-treated materials (i.e., after grinding, optional pyrolysis, possible copper extraction) with a molten lead composition in the stuffing vessel 15. The molten lead composition comprises predominantly lead and may comprise from 0 to 50% tin, preferably less than 20% tin. This composition is in the liquid state. It serves as a collector and extractor of precious metals, which are solubilized in non-oxidized form. The lead and possibly the tin of this composition come partly from the filler metals contained in the electronic cards, and partly from the metals recovered thereafter. The dissolution is carried out as follows: stirring is started and creates a vortex of molten lead in the cauldron. The feeder 407 pours the materials to be filled into the vortex core. The operation lasts about 15 minutes. The temperature can then be between 350 and 55O ⁰ C and is preferably about 500 ° C.

Subsequently, a skimming phase or phase of separation of the elements without affinity with the lead begins. In this phase, the stirring is stopped, and the inert parts washed of their precious metals (ceramics, glass fibers, ferrites ...) go back to the surface where they float. The skimming machine 405 is then started up and makes it possible to recover the supernatants. When these supernatants have been removed from the lead bath, the operation is repeated. Foaming can be carried out at a temperature of between 250 and 45 ^° C., for example about 270 ° C. for a lead-tin alloy containing 30% tin by weight.

The supernatants can be treated again in the same manner in the additional filling vessel 18. Indeed, a small amount of lead (and precious) is entrained with the supernatant material during skimming, and is therefore useful repeat the operation in a second cauldron to avoid losing precious metals.

The inerts collected at skimming at the additional filling vessel 18 are sent to landfill as ultimate waste after possibly being sampled and analyzed. The molten lead composition contained in the additional filling vessel 18 has a low concentration of precious metals

(Less than 100 g per ton) and is pumped back to the stuffing vessel 15.

The filling phase can last several days. It is considered that it is completed when the precious metal content in the molten lead composition reaches a threshold value, for example between 2 and 4 kg per tonne of lead.

An optional decoupling operation can then be performed, consisting of adding sulfur to the vortex of the lead-based composition, to form copper mattes, which are returned to a selective dissolution vessel 301a, 301b for copper extraction. .

Then the molten lead composition, with the solubilized precious metals, is sent to a storage cauldron from which this composition is poured into anodes.

(This constitutes the means for casting anodes 25).

The subsequent Betts refining step releases the precious metals contained in the anodes thus cast. In this step, the lead and tin are removed from the anodes by electrolysis in a fiuosilicic medium, which is known as the Betts process, at the Betts 501 electrolysis unit. The electrolysis cells are fed with an electrolyte containing, for example, about 90 g / l of lead and 80 g / l of free acid. This electrolyte is prepared by solubilizing litharge (PbO) in fluosilicic acid at the Betts 503 reactor. The electrolysis can be carried out for example at a current density of 350 A / m ² and at a temperature of electrolyte of 40 ° C. During electrolysis, the solid lead and tin of the anodes dissolve in the electrolyte, while lead and tin deposits accumulate on the cathodes. The addition of surfactant in the electrolyte makes this deposit fine and regular. Precious metals remain at the level of the anodes.

In this configuration, the electrolyte does not concentrate or few impurities. A total purge may only be performed once or twice a year. In this case, the electrolyte is sent to the second poor electrolyte storage tank 319 for lime treatment in the first purification reactor 320, and a new electrolyte is prepared. A purge may be required to lower the lead content with sulfuric acid in the Betts 503 reactor.

The reactor 503 and the electrolysis cells are cleaned up and the gaseous effluents are sent into the washing tower 508. The washing liquors are treated in the first purification reactor 320 via the second poor electrolyte storage tank 319.

In the example described here, the two rows of five cells contain 60x5 = 300 anodes of 450 kg each. It takes six days to consume 80% of the anodes which release their precious metals (432 kg) in the form of anode sludge, that is to say of residues of dissolved anodes. The anode sludge may, depending on the case, fall into dust in baskets or have an adherent cellular structure. Preferably, the electrolysis is interrupted before complete dissolution of the anodes. It is thus possible to recover the anode sludge by scraping.

The cathodes of Pb / Sn produced are 108 t for these six days.

Advantageously, two cathode strippings are carried out every three days and two scrapings of the anodes at the same time. The cathodes are recycled to cauldron 512 to produce ingot merchantable tin-tin and / or to supply molten lead-based composition to the additional stuffing vessel 18.

The anode sludge is washed, weighed and stored in a trunk. Advantageously, the anode sludge is melted once or twice a week in the oxidation furnace 520 at a temperature of 1000 ^° C. This melting step of the anode sludge, in the presence of gaseous oxygen (or air) makes it possible to oxidizing at least a portion of the lead and tin still contained in the anode sludge. Litharge (PbO) is formed on the surface: it is cast in plates and makes it possible to dope the lead electrolyte when necessary. The oven fumes are channeled to the fudge filter. The precious liquid alloy can be poured into ingots (25 kg) which are stored in a box. All ingots are sampled and weighed before being marketed.

The process described above is designed to minimize precious metal losses at all stages of the process. Thus: the fine recovery line 122 makes it possible to reintroduce into the system the fine fragments of crushed waste which pass into the ambient air at the grinding stage; the fine withdrawal line 215 makes it possible to recover the metal fraction entrained with the carbonaceous gases during the pyrolysis; the washed fines withdrawal line 327 makes it possible to reinject into the main circuit the fragments of materials to be treated which are entrained with the electrolyte or electrolytes; the use of an additional bunker 18 in addition to the bunker 15 makes it possible to recover the precious metals accidentally entrained with the inert materials during the main filling; similarly copper which has not been extracted during the selective extraction step by dissolution is recovered as copper mattes at the filling vessel 15 and is reinjected into the main circuit.

Thus, the process makes it possible to recover in fine more than 90 or even 95% by weight, preferably more than 99% by weight, advantageously more than 99.9% by weight of the precious metals initially contained in the waste.

Tables 1 and 2 below give an estimate of the chemical composition of the products during the various stages of the treatment process, in the case where the waste is typical used electronic boards.

Table 1 - Chemical composition during the process (the ^era ection

Table 2 - Chemical com osition during the process (2 è ^{e m} e ^part)

Claims

A method for treating waste containing precious metals, comprising the following successive steps: contacting the waste with a molten lead composition; skimming of the mixture obtained to recover supernatants; and - Refining the foam mixture by electrolysis so as to recover the precious metals. 2. The process according to claim 1, wherein the skimming stage includes recovering residues which are treated by: contacting the residues with a second molten lead composition; skimming of the mixture obtained; and recovering the froth mixture to provide at least a portion of the molten lead composition of claim 1. 3. Method according to claim 1 or 2, wherein the step of refining the froth mixture comprises the following substeps: pouring the froth mixture into anodes; electrolysis of a fluosilicic acid solution using said anodes; and - recovery of anode sludge containing precious metals. 4. The method of claim 3, comprising before, simultaneously or after the anode sludge recovery step, the following step: recovery cathodic deposits of lead and optionally tin to provide at least a portion of the composition based on molten lead and / or the second molten lead composition. 5. The method of claim 3 or 4, wherein the step of refining the foam mixture comprises, after the substep of anode sludge recovery, the following additional substeps: melting of the anode sludge recovered in the presence of oxygen ; skimming of melted anode sludge; and - ingot casting of molten and foamed anode sludge. The process according to one of claims 1 to 5, wherein each molten lead composition comprises 0 to 50% tin, preferably 0 to 20% tin. 7. Method according to one of claims 1 to 6, comprising, prior to step 5 of bringing the waste into contact with a composition based on molten lead, the following step: copper extraction of waste by selective dissolution. 8. The method of claim 7, wherein the copper extraction step L 0 comprises the following substeps: selective dissolution of waste in the presence of sulfuric acid, iron sulfate and oxygen; treatment of the solution obtained by filtration and / or electrolysis and / or precipitation; L5 - recovery of copper on the one hand and other metallic impurities on the other hand. 9. The method of claim 7 or 8, comprising, prior to the copper extraction step, the following step: combustion of waste by pyrolysis, producing carbonaceous gases; and optionally afterburning of the carbonaceous gases. 10. Method according to one of claims 1 to 9, further comprising a preliminary step of grinding the waste and / or crushed waste analysis. 11. Process according to one of claims 1 to 10, in which the precious metals comprise one or more metals chosen from among gold, silver, platinum, palladium, rhodium, ruthenium, iridium, osmium and mixtures thereof. 12. Method according to one of claims 1 to 1 1, wherein the waste is selected from catalytic exhaust pipes and electronic waste such as electronic cards. 13. Process according to one of Claims 1 to 12, in which more than 90% by weight, preferably more than 99% by weight, of the precious metals contained in the waste are recovered. 14. Process according to one of claims 1 to 13, in which the supernatants comprise ceramics, glass fibers and / or ferrites. 15. Waste treatment plant containing precious metals, comprising: - at least one stuffing vessel (15); a feed line of molten lead composition (24), connected at the inlet of the stuffing vessel (15); a feed line of pretreated materials (14), connected at the inlet of the stuffing vessel (15); skimming means (16) associated with the filling vessel (15); a scum mixture withdrawal line (21) connected at the outlet of the bunker (15); means for refining the foam mixture by electrolysis (36), fed by the foam mixture withdrawal line (21); and - a precious metals withdrawal line (38) connected at the outlet of the refining means of the foam mixture (36). 16. Processing plant according to claim 15, further comprising: a skimming residue withdrawal line (17) connected at the outlet of the skimming means (16); at least one additional filling vessel (18) supplied on the one hand by the skimming residue withdrawal line (17) and on the other by an additional molten lead composition feed line ( 31); additional skimming means (19) associated with the additional stuffing vessel (18); and an additional froth mixture withdrawal line (22) connected to the outlet of the additional filling vessel (18) and feeding the molten lead composition feed line (24). 17. Processing plant according to claim 15 or 16, wherein the means for refining the electrolysis foam mixture (36) comprise: anode casting means (25); Betts electrolysis means (27); and means for recovering anode sludge (28). 18. Processing plant according to claim 17, wherein the means for refining the electrolysis foam mixture (36) comprise: lead-tin recovery means (29) supplying the additional molten lead composition feed line (31). 19. Processing plant according to one of claims 15 to 18, further comprising: copper extraction means (37), an output of which is connected to the feed line of pretreated materials (14); and a feed line of primary materials (6), connected at the inlet of the copper extraction means (37). L O 20. Treatment plant according to claim 19, wherein the copper extraction means (37) comprises: at least one selective dissolution vessel (7) fed by the primary material supply line (6); A lean electrolyte supply line (1 1), connected at the inlet of the selective dissolution vessel (7); electrolysis means (9); rich electrolyte transfer means (8), connecting the selective dissolution vessel (7) to the electrolysis means (9); ! 0 - cathode stripping means (13); and lean electrolyte recycling means (10) connected at the output of the electrolysis means (9). 21. Treatment plant according to claim 19 or 20, further comprising: - waste pyrolysis means (2) connected at the output to the primary material supply line (6); a waste supply line (1) supplying the pyrolysis means (2); and optionally an exhaust line of the gases (4) at the outlet of the pyrolysis means (2) and> 0 feeding the afterburner means (5). 22. Treatment plant according to one of claims 15 to 21, further comprising: - Milling and analysis means (lter) fed by a feed line 5 of raw waste (Ibis) and feeding the waste feed line (1).