Process for the recycling of waste batteries and waste printed circuit boards in molten salts or molten metals

Abstract

Disclosed is a system and method for the recycling of waste composite feed materials such as printed circuit boards (PCBs), batteries, catalysts, plastic, plastic composites such as food packaging materials, for example Tetra Pak, mattresses, compact disks (CDs, DVDs), automobile shredder residue (ASR), electric cable wastes, liquid display panels, mobile phones of various sizes or combinations of the above using a new pyrolysis system and method.

Claims

1. A system of recycling of waste composite feed material, the system comprising: a separation/pyrolysis chamber (8) for containing a separation/pyrolysis liquid (7) during operation, the separation/pyrolysis chamber having: a top (44), a bottom (45) opposed the top, a first side wall (46) and a second side wall (47) opposed the first side wall, the first and second side wall each extending between the top and the bottom, the first side wall having an upper part (46a) adjacent the top and a lower part (46b) adjacent the bottom, and the second side wall having an upper part (47a) adjacent the top and a lower part (47b) adjacent the bottom; a charging vessel (1, 30) equipped with means for charging the feed material from the charging vessel into the separation/pyrolysis chamber; the charging vessel being in communication with the separation/pyrolysis chamber at a charging end (48) of the separation/pyrolysis chamber, the charging end being located at the top (44) adjacent the upper part of the first side wall or at the upper part of the first side wall (46a) adjacent the top; a heater (11) for heating and maintaining the separation/pyrolysis liquid in a liquid state at a temperature at which the feed material undergoes pyrolysis to form pyrolysis vapours, top dross, and bottom dross; the bottom (45) of the separation/pyrolysis chamber being sloped downward relative to said first side wall (46) and the top (44) and sloping away from the charging end of the separation/pyrolysis chamber, thereby defining a low area (D) of the bottom of the separation/pyrolysis chamber at which bottom dross collects; a vapour removal line (23) in fluidic communication with the separation/pyrolysis chamber via the top for removing pyrolysis vapours from the separation/pyrolysis chamber; a top dross removal device (32) being in communication with the separation/pyrolysis chamber for removing said top dross from the surface of said separation/pyrolysis liquid; and a solids removal device (16, 17) extending into the low area of the separation/pyrolysis chamber for removing said bottom dross from the separation/pyrolysis chamber.

2. The system of claim 1 characterised in that said bottom of the separation/pyrolysis chamber is sloped at an angle of between 10 and 60 degrees relative to the top of the separation/pyrolysis chamber.

3. The system of claim 2 characterised in that said bottom is sloped at two or more different angles relative to the top of separation/pyrolysis chamber.

4. The system of claim 1, further comprising a cyclone for separating said pyrolysis vapours from said top dross.

5. The system of claim 1 characterised in that said separation/pyrolysis chamber is equipped with a drain located at or near said low area.

6. The system of claim 1 characterised in that the solids removal device is removable from said separation/pyrolysis chamber.

7. The system of claim 1 characterised in that said charging vessel is installed vertically, horizontally or sloped between 90 and zero degrees with respect to the separation/pyrolysis chamber.

8. The system of claim 1 characterised in that said charging vessel comprises a plurality of vessels.

9. The system of claim 1 characterised in that the separation/pyrolysis chamber includes an auger configured to remove said top dross from said separation/pyrolysis chamber.

10. The system of claim 4 characterised in that said cyclone is comprised of filters, cyclones, zig-zag sifters, or eddy flow separators installed in series or in parallel or combinations thereof.

11. The system of claim 1, further comprising one or a plurality of plungers extending through the top of said separation/pyrolysis chamber for submerging heavy materials floating on the surface of said separation/pyrolysis liquid.

12. The system of claim 1 characterised in that said separation/pyrolysis chamber is equipped with a gate configured to ensure that a contact or reaction time of the feed material with the separation/pyrolysis liquid is a sufficient length of time so that complete separation is achieved.

13. The system of claim 1, further comprising a filter and means for re-circulating said separation/pyrolysis liquid through the filter.

14. A method of recycling of waste composite feed material using the system of claim 1, the method comprising: obtaining a system of claim 1; charging said feed material from said charging vessel into said separation/pyrolysis chamber containing a separation/pyrolysis liquid and pyrolyzing said feed material to form pyrolysis vapours, top dross, and bottom dross; allowing the bottom dross and top dross resulting from pyrolysis of said feed material to separate within said separation/pyrolysis liquid; removing the pyrolysis vapours via the vapour removal line from the surface of said separation/pyrolysis liquid; removing said bottom dross from below the surface of said separation/pyrolysis liquid with the solids removal device; and removing said top dross from the surface of said separation/pyrolysis liquid with the top dross removal device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The characteristics and advantageous characteristics of the present invention are detailed in this section based on the accompanying drawings, given as a non-restrictive example, with reference to the attached drawings wherein:

(2) FIG. 1 is a cross sectional drawing of the separation chamber of the battery recycling process utilising a molten metal;

(3) FIG. 2 gives a process flow diagram of the proposed battery recycling process utilising a molten metal;

(4) FIG. 3 is a cross sectional drawing of the separation/pyrolysis chamber of the PCBs recycling process utilising a molten metal;

(5) FIG. 4 gives a process flow diagram of the proposed PCBs recycling process utilising a molten metal;

(6) FIG. 5 is a cross sectional drawing of the separation/pyrolysis chamber of the battery recycling process utilising a molten salt;

(7) FIG. 6 gives a process flow diagram of the proposed battery recycling process utilising a molten salt;

(8) FIG. 7 is a cross sectional drawing of the separation/pyrolysis chamber of the PCBs recycling process utilising a molten salt;

(9) FIG. 8 gives a process flow diagram of the proposed PCBs recycling process utilising a molten salt; and

(10) FIG. 9 is a drawing of a number of different extractors.

DRAWINGS LEGEND

(11) 1. Charging chamber 2. Charging chamber cold valve 3. Charging chamber hot valve 4. Nitrogen 5. Vacuum pump 6. Vacuum pump exhaust 7. Separation/pyrolysis liquid 8. Separation/pyrolysis chamber 9. Level of top dross in leg A 10. Level of separation liquid in leg A 11. Heater 12. Leg A and B separator 13. Vacuum line 14. Motor 15. Solids removal device 16. Solids removal device (chain or similar) 17. Solids removal device (basket or similar) 18. Leg B cover 19. Upper drain 20. Middle drain 21. Lower drain 22. Extractor 23. Vapour removal line 24. Cyclone 25. Cyclone rotary valve 26. Solid removal line 27. Vapour line 28. Fan 29. Vapours to further processing 30. Charging vessel 31. Conveyor 32. Top dross removal device 33. Condenser 34. Pyrolysis oil condensate 35. Plunger 36. Motor/gearbox and drive train for plunger 37. Pump suction pipe 38. Pump 39. Pump discharge pipe 40. Filter 41. Filter discharge 42. Gate 43. Mechanism to operate gate 44. Top 45. Bottom 46. First Side Wall 46a. First Side Wall Upper Portion 46b. First Side Wall Lower Portion 47. Second Side Wall 47a. Second Side Wall Upper Portion 47b. Second Side Wall Lower Portion 48. Charging End D. Lower Area of Bottom

DETAILED DESCRIPTION

(12) Referring now to FIGS. 1 to 8, illustrating preferred embodiments of the invention, showing waste batteries and waste PCBs to be treated. In the figures, the same constitutional elements or components are represented by the same reference numerals as given in the drawings legend above.

(13) For the following non-restrictive examples, the present invention is described by the example of waste household batteries and PCBs. The process is characterised as a metal concentration, gravity separation and a pyrolysis process executed in one step. The metals such as mischmetal, gold, palladium, nickel, lead either form an alloy with the molten metal, separate as a distinct phase or form top or bottom dross, whereas plastic, paint and paper are pyrolysed. In the following examples it is assumed that a separation/pyrolysis liquid 7 of the battery recycling example is a molten metal, for example zinc, whereas for the example of the PCB recycling process the separation/pyrolysis liquid 7 is a molten salt, for example the eutectic (58.2 mol % LiCl and 41.8 mol % KCl) or near eutectic mixture of LiClKCl. Specific information on this salt is provided by: A. S. Basin, A. B. Kaplun, A. B. Meshalkin and N. F. Uvarov, The LiClKCl Binary System, Russian Journal of Inorganic Chemistry, 2008, Vol. 53, No. 9, pp. 1509-1511). Other salts such as ternary nitrate-nitrite salts, for example sodium nitrate-sodium nitrite-potassium nitrate (NaNO.sub.3NaNO.sub.2KNO.sub.3), having, for instance, been used as s heat transfer media on an industrial scale in solar power installations. The physical properties of these and many other salts may be found in: G. J. Janz, C. B. Allen, N. P. Bansal, R. M. Murphy and R. P. T. Tomkins, Physical Properties Data Compilations Relevant to Energy Storage. II Molten Salts: Data on Single and Multi-Component Salt Systems, Tech. Rep. NSRDS-NBS61-II, US Department of Commerce, 1979.

(14) The waste battery recycling process works as follows: In a first step (see FIG. 2) the received waste batteries are sorted according to size or according to the machine which slices them. Custom made batteries and AAA, AA, C, D and 9V batteries are cut into slices about 0.5 to 1 cm long or longer, whereas button cell batteries may not require cutting or they may to be cut into sections about 0.5 cm or shorter. The batteries may also be cut along their longitudinal axis.

(15) The batteries cut or not cut are fed into charging vessel 1 (see FIG. 1; charging vessel 30 is not used in this example). Once the charging vessel 1 is full, the charging vessel cold valve 2 is closed; the air in the vessel is removed by vacuum pump 5 and subsequently broken with nitrogen 4 and repeated until charging vessel 1 is inerted.

(16) Then the charging chamber hot valve 3 is opened and the batteries are charged into separation/pyrolysis liquid 7. Due to the high temperature of the separation/pyrolysis liquid 7 (typically >350 C.), the batteries readily decompose and separate into vapour, top and bottom dross.

(17) The light solids, commonly named top dross, are allowed to build up in the separation/pyrolysis chamber 8 to a level until the top dross must be removed either manually or by other means (see FIG. 1; top dross removal device 32) via opening the top section of the separation/pyrolysis chamber 8.

(18) The top dross may be composed of graphite, cobalt oxide, aluminium oxide, zinc oxide, manganese oxide and other materials less dense than the separation/pyrolysis liquid 7 and may be treated by others.

(19) The vapours and some of the top dross are continuously removed from the separation/pyrolysis chamber 8 by vapour/top dross removal line 23. There may be an extractor 22 protruding into the separation/pyrolysis chamber 8. Solids entrained in the vapour stream are removed from the vapour stream by a cyclone 24. The collected solids exit the system via cyclone rotary valve 25 and solids removal line 26 for further processing. The vapours are also routed for further processing 29 or may provide energy 11 for the process. The suction driving force for the vapour removal is provided by fan 28.

(20) Heavy compounds such as rare earths or mischmetal, cobalt, nickel, manganese, stainless steel and cadmium oxide separate to the bottom of the separation/pyrolysis chamber 8 and, due to the slope of this wall, accumulate in area D (see FIG. 1) where they can be removed by a number of drain points 20, 21 or by solids removal device 15-17.

(21) Lead, aluminium and other metals may form an alloy with the separation/pyrolysis liquid 7. These materials will be removed once it has been determined that the separation/pyrolysis liquid 7 is exhausted. Then the melt is removed via drains 20, 21 or by solids removal device 15-17 for further processing.

(22) The bottom product i.e. the stainless steel casings of the spend batteries can be removed from the separation/pyrolysis chamber 8 (area D) with solids removal device 15-17. Zinc attached to the casings and other steel or metal parts may be removed by another unit operation.

(23) A plunger 35 may be used to submerge heavy materials floating on the surface of the separation/pyrolysis liquid 7.

(24) A gate 42 can be closed to ensure that the contact or reaction time of the batteries with the separation/pyrolysis liquid 7 is sufficiently long. This is important for the process so that complete separation is achieved. Gate 42 can be opened periodically so that the treated batteries can move by gravity from Leg A to Leg B.

(25) Batteries may also be charged to the separation/pyrolysis chamber 8 via charging vessel 30, which may be equipped with a conveyor 31. The charging vessel 30 is inerted via nitrogen 4 and vacuum line 13.

(26) In summary, the battery recycling process is a metal concentration and gravity separation process combined with pyrolysis representing a new approach to battery recycling. The precious and other metals are collected as top or bottom dross or form an alloy with the molten zinc in the separation/pyrolysis chamber 8. Periodically the metal alloy/mixture accumulating in the chamber is drained and may be treated by another unit operation. Capital and operational cost are reduced as the batteries do not need to be shredded or pulverised.

(27) The PCB recycling process disclosed is a concentrating process for precious and low value metals and at the same time a pyrolysis process for the epoxy, plastic, paper and other materials. As a result also low and medium grade PCBs may be economically treated. Pyrolysis oil may also be produced by this process offering an additional revenue stream to the recovery of the metals.

(28) The PCBs recycling process works as follows: The waste PCBs are charged without mechanical pre-treatment that is, generally, intact into charging vessel 30 (see FIGS. 7 and 8 for a block flow diagram of the process; charging vessel 1 is not used in this example) the air is removed by vacuum pump 5 and broken by nitrogen 4. The PCBs are charged with conveyor belt 31 into the separation/pyrolysis liquid 7. Due to the high temperature of the separation/pyrolysis liquid 7, the PCBs readily decompose and separate into vapour, top and bottom dross.

(29) The light solids such as glass and some metals may collect in the separation/pyrolysis chamber 8 above the collected metal i.e. in area C above level D (see FIG. 7) from where this material is removed periodically by solids removal device 15-17.

(30) The solids removal device 15-17 may operate on a batch basis. During times when 15-17 is idle, the solids removal device 15-17 may be removed from the separation/pyrolysis chamber 8. The top of leg B may be closed with covers 18 to minimise heat losses and for safety reasons.

(31) The vapours and some of the top dross are continuously removed from the separation/pyrolysis chamber 8 by vapour/top dross removal line 23. There may or may not be an extractor 22 protruding into the separation/pyrolysis chamber 8. Solids entrained in the vapour stream are removed from the vapour stream by cyclone 24 or by other means for example a bag filter. The collected solids exit the system via removal line 26 as product or for further processing. The vapours are also routed for further processing 29 or may provide energy 11 for the process. The suction driving force for the vapour removal is provided by fan 28.

(32) Some of the heavy compounds such as stainless steel, copper, gold or palladium but also metals molten at the operating temperature such as zinc, tin or lead separate to the bottom of the separation/pyrolysis chamber 8 and, due to the slope of this wall, accumulate in area D where they may be removed by a number of drain points 20 or 21 or by solids removal device 15-17.

(33) The bottom dross or bottom product such as stainless steel, copper, molten metal and glass may be removed from the separation/pyrolysis chamber 8 (area C, D) with solids removal device 15-17.

(34) Plunger 35 may be used to submerge heavy materials floating on the surface of the separation/pyrolysis liquid 7.

(35) A gate 42 can be closed to ensure that the contact or reaction time of the PCBs with the separation/pyrolysis liquid 7 is sufficiently long. This is important for the process so that complete separation is achieved. Gate 42 can be opened periodically so that the treated PCBs can move by gravity from Leg A to Leg B.

(36) The solids removal device 15-17 may operate on a batch basis. During times when 15-17 is idle, the solids removal device 15-17 may be removed from the separation/pyrolysis chamber 8. The top of leg B may be closed with covers 18 to minimise heat losses and for safety reasons.

(37) As the pressure inside the separation/pyrolysis chamber 8 is only slightly above atmospheric (generally not more than 100 mbar), the liquid level of leg B is nearly equal to the liquid level in leg A. This is due to the fluid statics principle of legs A and B being filled with a continuous fluid.

(38) Some top dross may also form on top of leg B. This dross would also be periodically removed by drossing the surface of the separation/pyrolysis liquid 7.

(39) Some particles may not separate as bottom or top dross. Instead some particles may remain suspended within the separation/pyrolysis liquid 7. These particles are removed by filter 40. Pump 38 is used to pump the molten salt through filter 40 and back to the separation/pyrolysis chamber 8.

(40) In summary this PCB recycling process provides a metal concentration and gravity separation process combined with pyrolysis representing a new approach to PCB recycling. The precious and other metals are collected as top or bottom dross or form an alloy in the separation/pyrolysis chamber 8. Periodically the top and bottom dross are removed from the separation/pyrolysis chamber 8 and the metal alloy/mixture may, for instance, be sold to a third party or treated in a follow on unit operation.

(41) FIG. 9 illustrates a number of different embodiments that can be used as an extractor, where a show a simple lance type extractor, b a lance extractor with broader opening at one end, and c a manifold type extractor adapted for removing the pyrolysis vapours and light solid pyrolysis products from the surface of the separation/pyrolysis liquid 7.

(42) A desirable characteristic of the present invention is that all types of dry batteries may be treated with this system eliminating the requirement of sorting the batteries to types. Another desirable characteristic of the present invention is that the batteries do not need to be crushed or pulverised or dried reducing energy requirements in comparison to other processes. Another desirable characteristic of the present invention is that the stainless steel battery casings are recovered as scrap increasing the economics of the process.

(43) Another desirable characteristic of the present invention is that low value PCBs can be recycled economically as the process concentrates the metals and may also generate pyrolysis oil. Another desirable characteristic of the present invention is that the PCBs do not need to be shredded prior to processing, minimising the energy requirements of this process.

(44) Another desirable characteristic of the present invention is that VOC emissions do not occur from separation/pyrolysis chamber 8 (see FIG. 5, 7). Hence this part of the separation/pyrolysis chamber 8 may be opened to the atmosphere without causing VOC emissions which otherwise may have to be abated. Another desirable characteristic of the present invention is that the process is readily scalable.

(45) It will be appreciated that the invention can be applied to printed circuit boards (PCBs), batteries, catalysts, plastic, plastic composites such as food packaging materials, for example Tetra Pak, mattresses, compact disks (CDs, DVDs), automobile shredder residue (ASR), electric cable wastes, liquid display panels, hoses and other composite material for example platinum-coated silicon materials, carbon composites, mobile phones or combinations of the above.

(46) In the specification the terms comprise, comprises, comprised and comprising or any variation thereof and the terms include, includes, included and including or any variation thereof are considered to be totally interchangeable and they should all be afforded the widest possible interpretation and vice versa.

(47) The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail.