EP4308738A1

EP4308738A1 - Method for recovering elements from printed circuit boards and device for carrying out such a method

Info

Publication number: EP4308738A1
Application number: EP22711335.4A
Authority: EP
Inventors: Niels Willem WAGEMAKER; Jan Marinus REITSMA; Martinus Eduard Albertus VAN ZANTEN
Original assignee: Circular Industries BV
Current assignee: Circular Industries BV
Priority date: 2021-03-19
Filing date: 2022-03-17
Publication date: 2024-01-24
Also published as: NL1043973B1; WO2022195527A1; WO2022195527A9

Abstract

Method for recovering elements from printed circuit boards, wherein the method comprises a step (S3) of melting the printed circuit boards (2), as well as a step (S4) of refining or purifying the melted printed circuit boards (2), characterised in that the method further comprises a step (S1) of removing organic material, such as plastic, from the printed circuit boards (2) before the melting step (S3).

Description

Method for recovering elements from printed circuit boards and device for carrying out such a method

The present invention relates to a method for recovering elements from printed circuit boards and a device for carrying out such a method.

Printed circuit boards, or “PCBs” for short, are a typical part of electronic devices such as computers and mobile phones, as they provide a mechanical support for electronic components of such devices and electrically connect the electronic components. The growing use of electronic devices worldwide results in an increase in the amount of electronic waste, including waste from printed circuit boards. Hence there is a need for techniques for recovering elements from printed circuit boards, as they contain many metallic and other elements that are useful and can be reused.

More specifically, the invention relates to a method for recovering elements from printed circuit boards, wherein the method comprises a step of melting the printed circuit boards, as well as a step of refining or purifying the melted printed circuit boards. Such a method is known, but the existing techniques are inefficient and not sustainable. For example, they only recover a limited number of metals from the printed circuit boards, with several elements being lost.

The present invention aims primarily to provide an alternative method for recovering elements from printed circuit boards, with various preferred embodiments providing a more efficient and more sustainable solution which in particular allows more elements to be recovered from the printed circuit boards while minimising the impact on the environment.

To this end, according to a first independent aspect thereof, the invention relates to a method for recovering elements from printed circuit boards, wherein the method comprises a step of melting the printed circuit boards, as well as a step of refining or purifying the melted printed circuit boards, characterised in that the method further comprises a step of removing organic material, such as plastic, from the printed circuit boards before the melting step. Because organic material is removed from the printed circuit boards before the melting step, the steps of melting and/or refining or purifying the printed circuit boards can be carried out more efficiently, so that more elements can be recovered, thus benefiting the environment. For example, fewer problems are encountered in the melting furnace that can be used for the melting process. The removed organic material can be converted into gas. The organic material converted into gas can be transferred to a waste gas process. The organic material can be wholly or partially removed from the printed circuit boards.

The step of removing organic material from the printed circuit boards preferably involves the calcination of the printed circuit boards. Calcination refers to a chemical process in which bound metals are converted into their oxides by heating. Removing organic material from the printed circuit boards via calcination means that the melting process can take place particularly efficiently due to the oxides then present in, for example, the melting furnace. The printed circuit boards are preferably calcined at a temperature between 750 and 1,250 degrees Celsius, more preferably at a temperature between 900 and 1 ,100 degrees Celsius, most preferably at a temperature of approximately 1 ,000 degrees Celsius. At these temperatures the inventors have found that an optimum flux can be obtained in, for example, the melting furnace, in particular when the technique of plasma melting in, for example, a plasma furnace is used to melt the printed circuit boards. Removed organic material such as plastic can be converted into gas particularly advantageously via calcination or another technique. The gas can be transferred to a waste gas process. The gas can be converted into electricity, making it further usable, thus benefiting the environment.

The step of melting the printed circuit boards preferably includes plasma melting of the printed circuit boards, for example in a plasma furnace. Plasma melting is a technique that uses heat from a thermal plasma to melt material. Using plasma melting to melt the printed circuit boards makes it possible to extract more elements from the boards, as higher temperatures can be achieved via plasma techniques compared to conventional melting techniques, such as pyrolysis and combustion. With plasma technology it is possible, for example, to achieve temperatures of up to 3,000 degrees Celsius.

Plasma melting preferably involves the use of plasma torches. Plasma torches produce heat from an electric current passed through a partially ionised gas or plasma. The inventors have found that plasma torches allow very homogeneous and localised heating, so that, on the one hand, few elements are lost in the melting process and, on the other hand, particularly high temperatures are not required. For example, it is sufficient to use temperatures of, for example, up to 1,600 degrees Celsius, yet few elements are lost. The lower the temperature, the less energy is consumed and therefore the better it is for the environment. Another advantage is that melting the printed circuit boards using plasma torches can result in a gas with sufficient calorific value to be converted into electricity and thus be usable in further applications. Yet another advantage of using plasma torches is that the inventors have detected little or no leaching from the plasma rock, making it usable in further applications. The inventors have also found that the use of plasma torches is efficient, as only a limited amount of the raw materials intended to be recovered disappears into the plasma rock.

The method preferably comprises a step of removing iron and/or aluminium from the printed circuit boards before the melting step and preferably after the step of removing organic material. Removing iron and/or aluminium from the printed circuit boards before the melting step improves the efficiency of the melting and/or refining or purification steps. More elements can be recovered from the printed circuit boards because, during the melting of the printed circuit boards, fewer useful elements are able to combine with the iron and/or aluminium. In addition, the most preferred order, that is to say, the order wherein organic material is removed from the PCB first, followed whether or not immediately afterwards by the removal of iron and/or aluminium, has a positive impact on PCB input capacity, in that a larger volume of printed circuit boards can be processed. This is due to the reduction in volume, which can be reduced by half, for example, by removing organic material, in particular by means of calcination. The iron and/or aluminium can be wholly or partially removed from the printed circuit boards.

The inventors have also found that it is not necessary to add copper to the printed circuit boards during the melting step, or any other step in the process, because it has been found that the printed circuit boards processed by the method of this invention include sufficient copper to allow maximum recovery of metals and other elements from the printed circuit boards.

The step of refining or purifying the melted circuit boards can be carried out using various techniques, such as electrolysis and molecular recognition. The inventors have found that it is particularly advantageous to combine the techniques of electrolysis and molecular recognition, preferably using electrolysis first, followed whether or not immediately afterwards by molecular recognition, but not excluding the reverse order. With electrolysis, large flows of elements such as copper, silver, tin and/or nickel can be recovered, while molecular recognition makes it possible to efficiently recover many other elements, such as gold, palladium, platinum and/or boron. With regard to electrolysis, a cylindrical electrochemical cell is preferably used, as it allows improvements in efficiency and durability.

The method preferably also comprises a step of reducing the size of the printed circuit boards before the melting step and more preferably before the step of removing organic material. The printed circuit boards are preferably reduced to an average fragment size of less than 6 millimetres, as this size is advantageous for melting the printed circuit boards. Reducing the size of the printed circuit boards before removing organic material has the advantage that clumping can be avoided during this step.

The method according to the invention is preferably carried out as a continuous process, in particular in a single plant. Because the method, or at least the aforementioned steps, is carried out as a continuous process, a particularly efficient and sustainable process is achieved, which has few or no interruptions. The method preferably comprises a buffering, storage and/or accumulation step between at least two of the above steps of the method. This means that the entire line does not have to be stopped if a problem occurs during one of these steps.

It is also noted that the removal of iron and/or aluminium from the printed circuit boards before the melting step is an inventive idea in itself, separate from the removal of organic material from the printed circuit boards before the melting step. This makes the steps of melting and/or refining or purifying the printed circuit boards more efficient. More elements can be recovered from the printed circuit boards because fewer elements are able to combine with the iron and/or aluminium during the melting process. Therefore, according to a second independent aspect thereof, the invention relates to a method for recovering elements from printed circuit boards, wherein the method comprises a step of melting the printed circuit boards, as well as a step of refining or purifying the melted printed circuit boards, characterised in that the method further comprises a step of removing iron and/or aluminium from the printed circuit boards before the melting step. Preferably, no copper is added to the printed circuit boards during the melting step. The inventors have found that printed circuit boards processed according to the present invention include sufficient copper to allow maximum recovery of metals and other elements from the printed circuit boards.

The use of plasma for melting the printed circuit boards is also an inventive idea in itself, separate from the removal of organic material from the printed circuit boards before the melting step. Using plasma melting has the advantage that more elements can be extracted from the printed circuit boards, as higher temperatures can be achieved via plasma techniques compared to conventional melting techniques, such as pyrolysis and combustion. With plasma technology it is possible, for example, to achieve temperatures of up to 3,000 degrees Celsius. Therefore, according to an independent third aspect thereof, the invention relates to a method for recovering elements from printed circuit boards, wherein the method comprises a step of melting the printed circuit boards, as well as refining or purifying the melted printed circuit boards, characterised in that the step of melting the printed circuit boards comprises plasma melting of the printed circuit boards, for example in a plasma furnace. Plasma melting preferably includes the use of plasma torches. The advantage of plasma torches has already been explained above. Very homogeneous and local heating is thereby obtained, making it possible to reduce the temperature needed to recover as many elements as possible, while still allowing maximum element recovery.

The use of both electrolysis and molecular recognition in the step of refining or purifying the melted printed circuit boards is an inventive idea in itself, separate from the removal of organic material from the printed circuit boards before the melting step. This combination allows more elements to be efficiently recovered compared to conventional techniques. Therefore, according to an independent fourth aspect thereof, the invention relates to a method for recovering elements from printed circuit boards, wherein the method comprises the step of melting the printed circuit boards as well as refining or purifying the melted printed circuit boards, characterised in that the step of refining or purifying is carried out at least by means of electrolysis and molecular recognition, wherein preferably electrolysis is carried out first, followed whether or not immediately afterwards by molecular recognition.

The invention according to its second, third and/or fourth aspects may have one or more features of the invention according to its first aspect, without necessarily being limited to the removal of organic material from the printed circuit boards before the melting step.

According to an independent fifth aspect thereof, the invention further relates to a device for recovering elements from printed circuit boards, with the characteristic that the device comprises means for carrying out the method according to the invention according to one of aspects one to four, or a combination thereof.

The invention is used particularly advantageously on low-value printed circuit boards, but can also be used advantageously on high-value printed circuit boards, or materials other than printed circuit boards.

To better illustrate the features of the invention, certain preferred embodiments are described below, as examples that are not to be understood restrictively, with reference to the accompanying drawing, wherein:

- the figure schematically shows the steps of a method according to the invention.

The figure contains a diagram showing the steps of a method 1 according to the invention. It concerns a method 1 for the recovery of elements from printed circuit boards or PCBs 2, such as low-value PCBs.

Here, the method 1 comprises the step SO of reducing the size of the printed circuit boards 2, the printed circuit boards 2 preferably being reduced to an average fragment size of less than 6 millimetres, as this is advantageous for the further processing of the printed circuit boards 2. This can, for example, minimise or even avoid the risk of clumping in the further steps. A shredder, for example, can be used to reduce the fragment size of the printed circuit boards 2.

A subsequent step in the specific method 1 as shown in the figure is step S1 for the calcination of the printed circuit boards 2. Organic material 3, such as plastic, is wholly or partially removed from the printed circuit boards 2 by means of calcination. The removal of organic material 3 from the printed circuit boards 2 has the advantage that, in particular, the melting and/or refining or purification steps can be carried out more efficiently, so that more elements can be recovered from the printed circuit boards 2. Calcination is a preferred technique in this respect, because it generates oxides which are advantageous in the melting step. Calcination is preferably carried out at a temperature of approximately 1 ,000 degrees Celsius, because the inventors have found that at this temperature an ideal flux of materials is generated, which can be used advantageously in the melting furnace, or in particular the plasma furnace. The removed organic material can be converted into gas, which can be further converted into electricity and thus further used. The calcination step S1 of the printed circuit boards 2 can be carried out in a combustion chamber, for example electrically or fed with fossil fuel. If an electric combustion chamber is used, either batch feeding or continuous feeding of the input current can be chosen.

Whether or not immediately after step S1 , in method 1 a sorting step S2 is then carried out, whereby iron and/or aluminium 4 is wholly or partially removed from the printed circuit boards 2. As a result, fewer elements are able to combine with the iron and/or aluminium in the melting step, which means that more elements can be recovered. The particular position of this step in the process, that is to say, after step S1 , has a positive impact on the PCB input capacity, as it allows larger volumes of printed circuit boards to be processed, given the typical halving of the volume of material after the calcination step S1. The sorting step S2 can, for example, be carried out by means of magnetism for the removal of iron and/or by means of eddy currents for the removal of aluminium.

The next step in the exemplary method 1 is step S3 of melting the printed circuit boards 2, preferably carried out by means of plasma techniques, for example in a plasma furnace. Higher temperatures can be achieved through plasma techniques, thus making it possible to recover more elements. However, the inventors have found that, by using a particular plasma technique, namely plasma torches, the temperature can be limited while nevertheless recovering many elements, because very homogeneous and local heating can be obtained using these plasma torches. The use of plasma torches also results in a gas 5 with sufficient calorific value that it can be converted into electricity, thus making it usable in further applications, and/or in a plasma rock 6 from which there is little or no leaching, thus making it usable in further applications.

Whether or not immediately after step S3, in method 1 a step S4 of refining or purifying the melted printed circuit boards 2 is carried out. At least two techniques are used in the example, that is to say, first electrolysis S41 , followed whether or not immediately afterwards by molecular recognition S42. This results in the efficient recovery of large flows of elements 7, such as copper, silver, tin and/or nickel by electrolysis, followed by molecular recognition to separate further elements 8, such as gold, palladium and platinum, and to recover elements 9, such as boron. With regard to electrolysis, a cylindrical electrochemical cell is preferably used, as it allows improvements in efficiency and durability.

The method 1 according to the invention is preferably carried out as a continuous process, wherein it is advantageous to provide a storage, buffer and/or accumulation step between two or more of steps SO to S4, so that the entire line does not have to be stopped in the event of a problem in one of the steps.

The inventors have carried out a test with a method according to the invention in which printed circuit boards were melted by plasma, more specifically by plasma torches, and before melting the printed circuit boards were calcined at a temperature of approximately 960 degrees. The test showed that at least 35 elements were recovered, including several rare elements that were previously impossible or difficult to recover, such as boron. The present invention is in no way limited to the embodiments described above, but such methods and facilities may be realised according to different variants without going beyond the scope of the present invention. The present invention has been described in relation to the recovery of elements from printed circuit boards, but can be applied more widely. The invention can also be used for recovering elements from materials other than printed circuit boards.

Claims

1. Method for recovering elements from printed circuit boards, wherein the method comprises a step (S3) of melting the printed circuit boards (2), as well as a step (S4) of refining or purifying the melted printed circuit boards (2), characterised in that the method further comprises a step (S1) of removing organic material, such as plastic, from the printed circuit boards (2) before the melting step (S3).

2. Method according to claim 1 , wherein the step (S1 ) of removing organic material from the printed circuit boards (2) includes the calcination of the printed circuit boards (2).

3. Method according to claim 2, wherein the printed circuit boards (2) are calcined at a temperature between 750 and 1,250 degrees Celsius, preferably at a temperature between 900 and 1 ,100 degrees Celsius, more preferably at a temperature of approximately 1,000 degrees Celsius.

4. Method according to any of the preceding claims, wherein the step (S3) of melting the printed circuit boards (2) includes plasma melting of the printed circuit boards (2), for example in a plasma furnace.

5. Method according to claim 4, wherein the plasma melting includes the use of plasma torches.

6. Method according to any of preceding claims wherein the method comprises a step (S2) of removing iron and/or aluminium from the printed circuit boards (2) before the melting step (S3) and preferably after the step (S1) of removing organic material.

7. Method according to any of the preceding claims, wherein no copper is added during the melting step (S3).

8. Method according to any of the preceding claims, wherein the step (S4) of refining or purifying the printed circuit boards (2) is carried out at least by means of electrolysis and molecular recognition. 9. Method according to claim 8, wherein electrolysis is carried out first, followed whether or not immediately afterwards by molecular recognition in order to refine or purify the printed circuit boards (2).

10. Method according to any of preceding claims, wherein the method comprises a step (SO) of reducing the size of the printed circuit boards (2) before the melting step (S3) and preferably before the step (S1) of removing organic material.

11. Method according to any of preceding claims, wherein the method is carried out as a continuous process, or at least the aforementioned steps are carried out as a continuous process, preferably in a single plant.

12. Method for recovering elements from printed circuit boards, wherein the method comprises a step (S3) of melting the printed circuit boards (2), as well as a step (S4) of refining or purifying the melted printed circuit boards (2), characterised in that the method comprises a step (S2) of removing iron and/or aluminium from the printed circuit boards (2) before the melting step (S3).

13. Method for recovering elements from printed circuit boards, wherein the method comprises a step (S3) of melting the printed circuit boards (2), as well as a step (S4) of refining or purifying the melted printed circuit boards (2), characterised in that the step

(53) of melting the printed circuit boards (2) includes plasma melting of the printed circuit boards (2), preferably by means of plasma torches.

14. Method for recovering elements from printed circuit boards, wherein the method comprises a step (S3) of melting the printed circuit boards (2), as well as a step (S4) of refining or purifying the melted printed circuit boards (2), characterised in that the step

(54) of refining or purifying is carried out at least by means of electrolysis and molecular recognition, wherein preferably electrolysis is carried out first, followed whether or not immediately afterwards by molecular recognition.

15. Device for recovering elements from printed circuit boards, the device comprising means for carrying out the method according to any of the preceding claims.