GB2400847A

GB2400847A - Treatment of waste CFC-containing equipment

Info

Publication number: GB2400847A
Application number: GB0309253A
Authority: GB
Inventors: Limited Norfrost; Associates Limite Breckenridge; John Taylor Breckenridge
Original assignee: Norfrost Ltd
Current assignee: Norfrost Ltd
Priority date: 2003-04-24
Filing date: 2003-04-24
Publication date: 2004-10-27

Abstract

A method of recycling CFC-containing equipment, such as refrigeration units, comprises shredding the material forming the equipment and pyrolysing the shredded product. The shredding step may be performed in an enclosure so that any air contaminated with CFCs is prevented from escaping into the atmosphere. The contaminated air can be fed to a catalyst bed or to a microwave or plasma generator to decompose any CFCs. The catalyst may be a tungsten oxide/titanium dioxide catalyst or a sulphate-modified titanium dioxide/zirconia catalyst. The CFCs may be broken down to HCl and HF, which can then be removed using a scrubber. The pyrolysis may be conducted by passing the shredded material through an externally heated rotary pyrolyser to produce a gaseous mixture, which may undergo further treatment to remove CFCs. The treated gaseous mixture may also be used to fuel a generator. An apparatus for carrying out the method is also disclosed.

Description

PATENTS ACT 1977 A1081 1GB - GMD Title: Method and Apparatus for Recycling

CFC Containing Equipment

Description of Invention

This invention relates to the recycling of chlorofluorocarbon (CFC) containing equipment, such as refrigeration equipment. More particularly the invention relates to a method and apparatus for recycling redundant refrigeration equipment in such a way as to prevent release of CFCs to the atmosphere. In being aimed at dealing with CFCs, the invention may be able to deal with other ozone depleting substances, e.g. other halocarbons, and references to CFCs shall be taken to include such other substances.

Known methods of recycling redundant refrigeration equipment include the steps of manually dismantling the equipment, mechanically shredding it and separating the residues into streams of scrap metal, such as steel, aluminium and copper, plastics materials and insulating foam. These residues are then subsequently recycled or incinerated as appropriate. The method is carried out in a controlled enclosure, which includes systems to capture released CFCs.

The CFCs from the cooling circuit of the refrigeration equipment are generally captured with high efficiency during the dismantling step, although it is necessary for CFCs released from the insulating foam to be stripped from the ambient air within the enclosure.

The typical method may comprise the following steps: 1. Physically dismantling the refrigeration equipment to remove doors, lids and internal fitments, such as mercury tilt switches, and separating these into material types ready for transport to another location for recycling; Shari. 2. physicalremovalofthe compressor unit; ). Draining and collection of CFC refrigerant from the system; i 4. Draining and collection of compressor oil from the compressor unit; i 5. Degassing the compressor oil and collection of the evolved CFCs; 6. Shredding the carcass of the refrigeration equipment; 7. Separating the steel, copper, aluminium, insulating foam and plastics materials of the refrigeration equipment by mechanical, magnetic, eddy current and air separation techniques; 8. Briquetting of the insulating foam to expel any entrained CFCs and allow for their collection; 9. Removal and treatment of ambient process air from enclosure to condense andlor destroy any entrained CFCs; 10. Disposal of the collected, briquetted foam and degassed compressor oil by conventional incineration; 11. Transportation of collected CFCs for incineration at a high- temperature incineration facility; and 12. Sale of separated metal and plastics materials to commercial recyclers.

There are a number of processes used to collect the fugitive CFCs released during the dismantling and shredding processes, such as cryogenic CFC collection, catalytic CFC treatment using a precious metal- based catalyst _to convert the CFCs into hydrofluoric and hydrochloric acids and CFC collection in oil such as a mineral oil scrubber prior to incineration of the saturated oil.

Steps 2 to 8 of the typical method of recycling redundant refrigeration equipment all result in the release of CFCs and hence must be carried out in a controlled enclosure. Also given that steps 2 to 5 are manual operations, the controlled enclosure must contain the evolved CFCs and also provide a safe working environment for the operatives involved. Step 10 can provide further economic and environmental issues as the briquetted insulating foam may still contain trace amounts of CFCs and while the potential emissions from the briquetted insulating foam are below current legislative limits, and hence may be land filled or conventionally incinerated, they still provide a long-term disposal problem. Also, the degassed, recovered compressor oil may be recovered through oil recycling processes although in the long term this will be environmentally unacceptable owing to the difficulty of reducing the CFC content of this oil to within the proposed legislative limits. Additionally, step S 11, where the accumulated CFCs from the process must be transported to a high temperature incineration facility, can introduce additional risk of accidental release of CFCs to the atmosphere.

There are many problems with such methods, such as they are energy intensive. A typical facility may have with a power consumption of around 500kW. Also the residues of the shredded metal and plastics materials are still contaminated with a&Bring insulating foam, which contains CFCs which will be released to atmosphere during subsequent processing. The methods are very inefficient and do not wholly address the problem of releasing CFCs to the atmosphere.

It has been estimated that some three million pieces of refrigeration equipment are in need of disposal each year in the UK, which means that any increases in efficiency of such methods, or reduction in energy usage could present enormous cost savings.

It is therefore the object of the present invention to provide a method of recycling CFC containing equipment, and apparatus for same, which seeks to overcome the problems and disadvantages of known methods of recycling CFC containing equipment.

According to a first aspect of the invention there is provided a method of recycling CFC containing equipment, comprising subjecting at least some the material forming the equipment to at least one shredding step, wherein at least some of the shredded material is subjected to a pyrolysis treatment.

The pyrolysis treatment may be effected by passing the at least some of the shredded material through an externally heated rotary pyrolyser, to produce a gaseous mixture which is subject to further treatment to remove CFCs therefrom.

The gaseous mixture may contain hydrocarbons which may be used as a fuel for a generator.

Any CFCs in the gaseous mixture may be removed from the gaseous mixture prior to supply thereof to the generator.

The CFCs may removed from the gaseous mixture by passing the gaseous mixture through a catalyst bed to convert the CFCs to hydrogen chloride and hydrogen fluoride, which may be subsequently removed to provide a mixture containing hydrocarbons and no or little CFCs.

The catalyst bed may comprise a Tungsten Oxide/Titanium Dioxide catalyst, such as, for example, having a WO3 to TiO2 ratio in the range of 0.5:1 to 0.01:1, and specific surface areas in the range of 10m2/g to 150m2/g.

Alternatively the catalyst bed may comprise a Sulphate-modified Titanium Dioxide/Zirconia catalyst, such as, for example, having a Ti to Zr mole ratio in the range of 10:1 to 0.01:1. Such catalysts act on the CFCs, but not on hydrocarbons.

The gaseous mixture containing CFCs may be supplied to the generator and the exhaust from the generator may be treated to remove CFCs therefrom.

The shredding step of the method may be carried out in a controlled enclosure, the controlled enclosure inhibiting air contaminated with CFCs, which has been released from the equipment during the shredding step, from escaping to atmosphere.

The contaminated air from the controlled enclosure may be fed to a catalyst bed to break down any CFCs therein.

The generator may be used to provide sufficient power to operate any equipment used in the method.

The generator may be a diesel engine or gas turbine generator.

The exhaust gas from the generator may be fed to a microwave or other plasma generator to break down any CFCs therein, the microwave or other plasma generator producing a mixture containing HCI and HF.

Alternatively the exhaust gas may be fed to a catalyst bed to break down any CFCs therein, the catalyst bed producing a mixture containing HCI and HF.

The contaminated air from the controlled enclosure may be fed to a microwave or other plasma generator to break down any CFCs therein, or to a catalyst bed to break down any CFCs therein, the catalyst bed or microwave or other plasma generator producing a mixture containing HCI and HF.

The mixture produced by the microwave or other plasma generator or the catalyst bed may be fed into a HCI/HF scrubber to remove HCI and HE therefrom.

According to a second aspect of the invention there is provided an apparatus for carrying out the method according to the first aspect of the invention, comprising: shredding means adapted to shred the material forming the equipment; and pyrolysis means, arranged to receive at least come of the shredded material and adapted pyrolytically to decompose susceptible materials of the shredded material introduced therein.

The pyrolysis means may be an externally heated rotary pyrolyser, which may produce a gaseous mixture.

The apparatus may include a generator which uses hydrocarbons in the gaseous mixture as a Mel.

The apparatus may comprise means for removing any CFCs from the gaseous mixture prior to supply thereof to the generator.

The apparatus may include a catalyst bed adapted to receive the gaseous mixture and remove any CFCs therefrom by converting the CFCs to hydrogen chloride and hydrogen fluoride, which may be subsequently removed to provide a mixture containing hydrocarbons and no or little CFCs.

The catalyst bed may comprise a Tungsten Oxide/Titanium Dioxide catalyst, such as, for example, having a WO3 to TiO2 ratio in the range of 0.5:1 to 0.01:1, and specific surface areas in the range of l0m2/g to 150m2/g.

Alternatively the catalyst bed may comprise a Sulphate-modified Titanium Dioxide/Zirconia catalyst, such as, for example, having a Ti to Zr mole ratio in the range of 10:1 to 0.01:1.

Means may be provided for treating the exhaust from the generator to remove CFCs therefrom.

The apparatus may include a microwave or other plasma generator adapted to receive the exhaust gas from the generator and break down any CFCs therein, the microwave or other plasma generator producing a mixture containing HCI and HF.

Alternatively the apparatus may include a catalyst bed adapted to receive the exhaust gas from the generator and break down any CFCs therein, the catalyst bed producing a mixture containing HCI and HF.

The apparatus may include a controlled enclosure in which the shredding step is carried out, the controlled enclosure may inhibit air contaminated with CFCs, which may have been released from the equipment during the shredding step, from escaping to atmosphere.

Means may be provided for supplying the contaminated air from the enclosure to the microwave or other plasma, or a catalyst bed, to break down any CFCs therein.

A catalyst for treating the exhaust from the generator to break down CFCs therein, and/or for treating contaminated air from the controlled enclosure, may comprise a tungsten/titanium or zirconium/titanium catalyst as above referred to, or a precious metal catalyst an example of which is described hereafter.

The apparatus may include a HCI/HF scrubber adapted to receive the mixture and remove HCl and HE therefrom.

The generator may be a diesel engine, gas turbine or other electrical generator.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 illustrates schematically a method and apparatus according to the invention for recycling refrigeration equipment, in which a microwave or other plasma destructor is used, Figure 2 illustrates schematically a further method and apparatus according to the invention for recycling refrigeration equipment, in which a catalyst bed is used, and Figure 3 illustrates schematically a modified version of the method illustrated in Figure 2.

Figure 1 shows a method 10 of recycling refrigeration equipment including the use of a microwave or other plasma destructor 34 to break down CFCs. The method 12 illustrated in Figure 2 is similar to the method 10 of Figure 1, except that the microwave or other plasma destructor 34 has been replaced by a catalyst bed 32.

A typical piece of refrigeration equipment comprises a compressor unit, having compressor oil, a cooling circuit and a carcass or frame structure, which typically comprises steel, aluminium, copper, plastics materials, such as polystyrene, acrylonitrile butadiene styrene and PVC, synthetic rubbers and insulating foam such as polyurethane and/or expanded polystyrene.

The first stage of both methods, which takes place in a controlled enclosure (not shown), includes a dismantling step wherein the piece of refrigeration equipment is dismantled, the compressor unit (not shown) is removed from the carcass and the compressor oil 14 from the compressor. The cooling circuit (not shown), which is integral with the equipment, is drained of CFCs. The carcass is then shredded, together with the drained cooling circuit, to provide fragmented scrap which is fed, together with the compressor oil 14, into an externally heated rotary pyrolyser 22.

The pyrolyser 22 decomposes the plastics, rubber and foam components of the fragmented scrap and compressor oil 14, into a gaseous mixture of hydrogen and assorted hydrocarbons with chain lengths of between 1 and 35 carbon atoms. The shredded metal, free of its decomposed associated plastics etc. components, is then transferred from the pyrolyser 22 to a mechanical separation step 24, which separates the steel, aluminium and copper using magnetic and eddy-current techniques, for further separation and recycling at 26.

The gaseous mixture from the pyrolyser 22 is then ducted to either a diesel or a gas turbine generator where it is combusted to generate electricity 30. The exhaust gases from the diesel engine or gas turbine are fed into a proprietary microwave or other plasma generator 34 (as shown in Figure 1) where the organic molecules, CFCs etc. therein. are broken down to carbon dioxide, water, hydrogen fluoride and hydrogen chloride. The gas from the microwave or other plasma generator 34 is then ducted in sequence to a cooling tower (not shown) and HC1/HF scrubber 38, where any hydrogen fluoride and hydrogen chloride contained in the gas are trapped as sodium fluoride and sodium chloride respectively. The exhaust air 18 from the controlled enclosure is also fed into the diesel engine or gas turbine exhaust stream and the entrained CFCs similarly destroyed.

In Figure 2, the microwave or other plasma generator 34 has been replaced by a catalyst bed 32 into which the exhaust gases from the diesel engine or gas turbine are fed, along with the exhaust air 18 from the controlled enclosure together with steam at a temperature in the range of 450 to 600 C.

The gas passes through the catalyst bed 32 where the organic molecules, CFCs etc. are broken down into carbon dioxide, water, hydrogen fluoride and hydrogen chloride.

The gas from the catalyst bed 32 is then dueled in sequence to a cooling tower (not shown) and HCl/HF scrubber 38, where any hydrogen fluoride and hydrogen chloride contained in the gas is trapped as sodium fluoride and sodium chloride respectively.

The catalyst bed 32 may be a precious metal-based catalyst such as a Pd/ZnO/y-AI2O3 catalyst with a surface area of at least 50m2/g (as disclosed in US patent No. 5817896). Other suitable catalysts may comprise palladium, platinum, rhodium, ruthenium, silver, gold or gallium, either alone or in combination with a different metal such as zinc, aluminium, silver, platinum, nickel, gold or gallium, which may be present in an oxygenated form. The ratio of the active catalyst material to the total amount of catalyst may range from 10:1 to 1:1 or 1:5 to 1:2.

Alternatively, the catalyst bed 32 may be selected from any of the following; palladium on activated carbon; palladium on aluminium fluoride; palladium chloride on activated carbon; or catalysts containing palladium in concentrations by weight ranging from 0.5% w/w to 10% w/w on substrates of alumina, zirconia, zirconia coated alumina or activated carbon.

The power output generated by the diesel-electric or other generator in a plant processing around 60 units/hour in both methods is in the region of 650kW which is sufficient to power the dismantling, shredding and treatment stages with a surplus which can be used elsewhere or sold. However, the energy generated by the process is a function of the capacity of the plant and the quantity of plastics pyrolysed.

Referring to Figure 3 there is illustrated a modified and preferred embodiment of the invention which uses a highly selective catalyst 33a to convert the entrained CFCs in the gaseous mixture from the pyrolyser 22 to HCI, HE, CO2 and H2O without destroying the accompanying hydrocarbons.

The gaseous mixture from the pyrolyser 22 is fed directly into a Tungsten Oxide/Titanium Dioxide catalyst (having a WO3 to TiO2 ratio in the range of 0.5:1 to 0.01: 1, and specific surface areas in the range of l0m2/g to 150m2/g) or a Sulphate-modified Titanium Dioxide/Zirconia catalyst (having a Ti to Zr l mole ratio in the range of 10:1 to 0.01:1). The above mentioned catalysts destroy any CFCs in the gaseous mixture, but do not destroy the hydrocarbons in the mixture. Therefore after the catalysed mixture has been fed through the HCl/HF scrubber 24 to remove hydrogen chloride and hydrogen fluoride therefrom, the remaining hydrocarbons can be supplied to a diesel engine or gas turbine at 30, for electricity generation.

The exhaust air 18 from the controlled enclosure is fed into a further i catalyst 33b, which also converts the entrained CFCs to HCl, HE, CO2 and H2O. The gas from the catalyst bed 33b is then ducted in sequence to a cooling tower (not shown) and HC1/HF scrubber 38.

The catalyst bed 33b may be a precious metal-based catalyst such as a Pd/ZnO/y-Al2O3 catalyst with a surface area of at least 50m2/g (as disclosed in; US patent No. 5817896). Other suitable catalysts may comprise palladium, platinum, rhodium, ruthenium, silver, gold or gallium, either alone or in combination with a different metal such as zinc, aluminium, silver, platinum, nickel, gold or gallium, which may be present in an oxygenated form. The ratio of the active catalyst material to the total amount of catalyst may range from 10:1 to 1:1 or 1:5 to 1:2.

Alternatively, the catalyst bed 33b may be selected from any of the following; palladium on activated carbon; palladium on aluminium fluoride; palladium chloride on activated carbon; or catalysts containing palladium in concentrations by weight ranging from 0.5% w/w to 10% w/w on substrates of alumina, zirconia, zirconia coated alumina or activated carbon.

Further, alternatively, the catalyst bed 32 and 33b may be Tungsten Oxide/Titanium Dioxide catalysts (having a WO3 to TiO2 ratio in the range of 0.5:1 to 0.01:1, and specific surface areas in the range of 1Om2/g to 150m2/g) or a Sulphate-modified Titanium Dioxide/Zirconia catalysts (having a Ti to Zr mole ratio in the range of 10:1 to 0.01:1).

The aforementioned methods of recycling CFC containing equipment provide an environmentally satisfactory process where the CFC containing equipment is reduced to scrap steel, aluminium and copper, carbon dioxide, water and electrical energy. The in-line nature of the steps of the method reduces disposal costs and reduces if not eliminates the risk of accidental and fugitive CFC release which is inherent in known methods.

In the present specification "comprises" means "includes or consists of'' and "comprising" means "including or consisting of''.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A method of recycling CFC containing equipment, comprising subjecting at least some the material forming the equipment to at least one shredding step, wherein at least some of the shredded material is subjected to a pyrolysis treatment.

2. A method according to claim 1 wherein the pyrolysis treatment is effected by passing the at least some of the shredded material through an externally heated rotary pyrolyser.

3. A method according to claim 2 wherein the pyrolyser produces a gaseous mixture which is subject to further treatment to remove CFCs therefrom.

4. A method according to claim 3 wherein hydrocarbons in the gaseous mixture are used as a fuel for a generator.

5. A method according to claim 4 wherein CFCs in the gaseous mixture are removed from the gaseous mixture prior to supply thereof to the generator.

6. A method according to claim 5 wherein the CFCs are removed from the gaseous mixture by passing the gaseous mixture through a catalyst bed to convert the CFCs to hydrogen chloride and hydrogen fluoride, which are subsequently removed to provide a mixture containing hydrocarbons and no or little CFCs.

7. A method according to claim 4 wherein the gaseous mixture containing CFCs is supplied to the generator and the exhaust from the generator is treated to remove CFCs therefrom.

8. A method according to any preceding claim wherein at least the shredding step is carried out in a controlled enclosure, which inhibits air contaminated with CFCs, which have been released from the equipment during the shredding step, from escaping to atmosphere.

lO

9. A method according to claim 8 wherein the contaminated air from the controlled enclosure is fed to a catalyst bed to break down any CFCs therein.

10. A method according to any one of claims 4 to 9 wherein the generator is used to provide sufficient power to operate any equipment used in the method.

1 1. A method according to any one of claims 4 to 10 wherein the fuel is used to power a diesel engine or gas turbine generator.

12. A method according to claim 7 or any claim appendant thereto wherein the exhaust gas is fed to a microwave or other plasma generator to break down any CFCs therein, the microwave or other plasma generator producing a mixture containing HCl and HF.

13. A method according to claim 7 or any claim appendant thereto wherein the exhaust gas is fed to a catalyst bed to break down any CFCs therein, the catalyst bed producing a mixture containing HCl and HF.

14. A method according to claim 12 or 13, as appendant to claim 8, wherein the contaminated air from the controlled enclosure is fed to a or the microwave or other plasma generator to break down any CFCs therein, the microwave or other plasma generator producing a mixture containing HCl and HF.

15. A method according to claim 12 or 13, as appendant to claim 8, wherein the contaminated air from the controlled enclosure is fed to a or the catalyst bed to break down any CFCs therein, the catalyst bed producing a mixture containing HCl and HF.

16. A method according to claim 13 or claim 15 wherein the catalyst is a precious metal based catalyst.

17. A method according to claim 6, 13 or 15, or any claim appendant thereto wherein the catalyst bed comprises a Tungsten Oxide/Titanium Dioxide catalyst.

18. A method according to claim 17 wherein WO3 to TiO2 ratio is in the range of 0.5:1 to 0.01:1, and has specific surface areas in the range of l0m2/g to 150m2/g

19. A method according to claim 6, 13 or 15, wherein the catalyst bed comprises a Sulphate-modified Titanium Dioxide/Zirconia catalyst.

20. A method according to claim 19 wherein the Ti to Zr mole ratio is in the range of 10:1 to 0.01:1.

21. A method according to any one of claims 12 to 20 wherein the mixture is fed into a HC1/HF scrubber to remove HCI and HE therefrom.

22. An apparatus for carrying out the method according any one of claims 1 to21 comprising: shredding means adapted to shred the material forming the equipment; and pyrolysis means, arranged to receive at least some of the shredded material and adapted pyrolytically to decompose susceptible materials of the shredded material introduced therein.

23. An apparatus according to claim 22 wherein the pyrolysis means is an externally heated rotary pyrolyser.

24. An apparatus according to claim 22 or 23 wherein the pyrolysis means produces a gaseous mixture.

25. An apparatus according to claim 24 wherein the apparatus includes_a generator which uses hydrocarbons in the gaseous mixture as a fuel.

26. An apparatus according to claim 25 wherein means is provided for removing any CFCs from the gaseous mixture prior to supply thereof to the generator.

27. An apparatus according to claim 26 wherein a catalyst bed in provided to receive the gaseous mixture and remove any CFCs therefrom by converting the CFCs to hydrogen chloride and hydrogen fluoride, which are subsequently removed to provide a mixture containing hydrocarbons and no or little CFCs.

28. An apparatus according to claim 25 wherein means is provided for supplying the gaseous mixture containing CFCs to the generator.

29. An apparatus according to claim 28 wherein means is provided for treating the exhaust from the generator to remove CFCs therefrom.

30. An apparatus according to claim 29 wherein a microwave or other plasma generator is provided, adapted to receive the exhaust gas from the generator and break down any CFCs therein, the microwave or other plasma generator producing a mixture containing HCl and HF.

31. An apparatus according to claim 29 wherein a catalyst bed is provided, adapted to receive the exhaust gas from the generator and break down any CFCs therein, the catalyst bed producing a mixture containing HCl and HF.

32. An apparatus according to claim 27 or claim 31 wherein the catalyst comprises a Tungsten Oxide/Titanium Dioxide Catalyst.

33. An apparatus according to claim 32 wherein the WO3 to TiO2 ratio is in the range of 0.5:1 to 0.1:1, and has specific surface areas in the range of 10m2/g to 150m2/g.

34. An apparatus according to claim 27 or claim 31 wherein the catalyst comprises a Sulphate-modified Titanium Dioxide/Zirconia catalyst.

35. An apparatus according to claim 34 wherein the Ti to Zr ratio is in the range of 10:1 to 0.01:1.

36. An apparatus according to claim 31 wherein the catalyst is a precious metal-based catalyst.

37. An apparatus according to any one of claim 22 to 36 including a controlled enclosure in which the shredding step is carried out, the controlled enclosure inhibiting air contaminated with CFCs, which has been released from the equipment during the shredding step, from escaping to atmosphere.

38. An apparatus according to claim 37 as appendant to claim 30 wherein means is provided for supplying the contaminated air from the enclosure to the microwave or other plasma generator to break down any CFCs therein.

39. An apparatus according to claim 37 as appendant directly or indirectly to claim 31 wherein means is provided for supplying the contaminated air from the enclosure to a or the catalyst bed to break down any CFCs therein.

40. An apparatus according to any one of claims 30 to 39 wherein a HC1/HF scrubber is provided to remove HC1 and HE from the mixture.

41. An apparatus according to any one of claims 25 to 40 wherein the generator is a diesel engine, gas turbine or other electrical generator.

42. A method or apparatus substantially as hereinbefore described with he; - . 25 reference to and as shown in the accompanying drawings. .

43. Any novel feature or novel combination of features described herein andlor in the accompanying drawings.