A METHOD AND APPARATUS FOR AT LEAST PARTIALLY DRAINING AN OPERATING SYSTEM

Abstract

A method for at least partially draining an operating system containing a working fluid (comprising carbon dioxide (R744) and a halogenated hydrocarbon). The method comprises transferring the working fluid from the operating system to a destination vessel, where the working fluid is brought into contact with an absorbent bed.

Description

A METHOD AND APPARATUS FOR AT LEAST PARTIALLY DRAINING AN OPERATING SYSTEM The present invention relates to a method for at least partially draining an operating system, which contains a working fluid. Refrigeration systems are commonplace. Examples of refrigeration systems include refrigerated storage containers, such as those found in supermarkets, for holding food or other materials that must be kept refrigerated / frozen to prevent / delay spoilage before sale. Such refrigeration systems typically comprise a working fluid that, together with a refrigeration / air conditioning unit, provides the desired cooling effect. Working fluids typically include hydrocarbons, carbon dioxide, ammonia, and halogenated hydrocarbons (chlorinated and / or fluorocarbons). Often, the working fluid comprises a mixture of two or more agents. There are times when the working fluid must be removed from the cooling system. This removal can be due to routine maintenance, where the fluid needs to be replaced, either as part of a scheduled service or due to fluid degradation from use. Other reasons for removal arise when the cooling system is taken out of service. Since many working fluids are potentially harmful due to one or more issues, including toxicity, flammability, and global warming / ozone depletion, it is necessary to dispose of the fluid safely, both to ensure the safety of the disposal operator and to prevent the release of potentially harmful chemicals into the atmosphere. Safe disposal of the working fluid and its transfer to a storage vessel achieves these objectives. Furthermore, such disposal is beneficial because the working fluid can be reused after disposal, for example, in a secondary cooling system. Conventional recovery equipment for halocarbon refrigerants works by combining liquid recovery followed by vapor recovery. For the liquid recovery stage, the refrigerant is removed from the system as a liquid and transferred to a storage container. For the vapor recovery stage, the vapor is pumped out of the system and then compressed and condensed in a small condenser heat exchanger, which is part of the recovery unit. The condensed refrigerant is then returned to a recovery cylinder for reuse or disposal. The condenser can be cooled with ambient air, or a small onboard refrigeration circuit can be used in the recovery unit. The refrigeration system's compressor can be used to assist in this pumping process, or the vapor can be drawn in and then compressed by a dedicated compressor that is part of the recovery unit. Working fluid disposal becomes more complex when the working fluid comprises a mixture of two or more agents. The complexity arises because, by the time of disposal, the working fluid specification has typically changed since its initial application, meaning reuse is not straightforward. Furthermore, there may be a desire to reuse certain components of the working fluid, rather than the entire mixture, requiring separation of the working fluid. These complications can lead to improper disposal of the working fluid instead of addressing the underlying problems. This is a particular issue when one of the mixture components comprises a halogenated hydrocarbon, the release of which to the atmosphere is highly regulated, and another component comprises an agent whose release to the atmosphere is less or not regulated (such as carbon dioxide). It is an object of the present invention to avoid or mitigate the problems described above. According to a first aspect of the invention, a method is provided for at least partially draining an operating system, which contains a working fluid (comprising carbon dioxide (R744) and a halogenated hydrocarbon), the method comprising transferring the working fluid from the system to a destination vessel, wherein the working fluid is brought into contact with an absorbent bed. The method of the invention has been found to be remarkably effective in the removal of working fluids comprising a mixture of carbon dioxide (R744) and a halogenated hydrocarbon. By using the method of the invention, it is possible to recover at least the halogenated component of the mixture for reuse or disposal. Generally, the operating system comprises a vapor-compression cycle for air conditioning, heat pumping, or refrigeration. A preferred example of such a system is a medium-temperature refrigeration system. Therefore, the preferred working fluid comprises a refrigerant. The working fluid may come into contact with the absorber bed more than once. In this method, the composition can be brought into contact with two or more absorbent beds. In such a case, the beds can be the same or different. Where the beds are different, one bed can be for the absorption of the halogenated hydrocarbon and a second bed can be for the absorption of carbon dioxide. Generally, the contact stage is carried out, at least in part, at a temperature of approximately 0 °C to approximately 200 °C, more preferably at a temperature of approximately 20 °C to approximately 100 °C, more preferably at a temperature of approximately 20 °C to approximately 60 °C, preferably at a temperature of approximately 40 °C. Generally, the contact stage is performed at a pressure of approximately 0.1 to 50 Bara. The absorbent bed may require treatment prior to the contact stage. The treatment stage preferably comprises a heat treatment stage involving heating the bed to remove adsorbed gases, optionally followed by a cooling stage to reduce the temperature of the solid adsorbent material and thus improve its fluid absorption capacity. nn? Lnn / zznz / E / Yi The treatment stage of the absorbent bed may comprise an exposure stage comprising exposing the adsorbent to one or more inert gases, preferably N2 or one or more noble gases. The absorbent bed treatment stage (before the contact stage) can be operated under a total / partial vacuum. The absorbent bed can be dried before use. The absorbent bed may require treatment after the contact stage. It should be noted that the absorbent material may need treatment after the device has been used to drain an operating system. Such treatment may be necessary to regenerate the absorbent material and remove the absorbed material from it. Regeneration of the absorbent material may involve exposing the absorbent material to elevated temperature and / or reduced pressure or vacuum. This regeneration process preferably captures the released material. The method of the invention is suitable for the recovery of liquids and / or vapors. Generally, the working fluid comprises a halogenated refrigerant, comprising at least R32 (difluoromethane). Preferably, the working fluid has the composition comprising: (a) from approximately 10 percent to approximately 35 percent by weight of R-32; (b) from approximately 65 percent to approximately 90 percent by weight of R744 (carbon dioxide), based on the weight of components (a) to (b). Optionally, the halogenated refrigerant comprises quantities of other refrigerants, such as R-1132a (1,1-difluoroethene), R-1123 (trifluoroethene), R-134a (1,1,1,2-tetrafluoroethane), R-152a (1,1-difluorotane), R-125 (pentafluoroethane), R-227ea (1,1,1,2,3,3,3-heptafluoropropane), R-1234ze(E) (trans-1,1,1,3-tetrafluoropropene), R-1234yf (2,3,3,3-tetrafluoropropene), R-1311 (iodotrifluoromethane), or mixtures of one or more of these. Preferably, the total proportion of halogenated refrigerant in the mixture is approximately 10 to 35% by weight of the total composition. The refrigerant may also comprise smaller quantities of one or more hydrocarbons selected from: propane (R-290); propene (R-1270); isobutane (R-600a); or n-butane (R-600), wherein the proportion of hydrocarbon in the total mixture is less than approximately 5% by weight. According to a second aspect of the invention, an apparatus is provided for at least partially draining an operating system containing a working fluid (comprising carbon dioxide (R744) and a halogenated hydrocarbon), wherein the apparatus is suitable for connection to the operating system via a conduit, the apparatus comprising a) an absorbent bed, and b) A storage container. It will be appreciated that the characteristics of the first aspect of the invention will apply mutatis mutandis to the second aspect of the invention. Preferably, the absorbent bed is located upstream of the storage container. nn? Lnn / z^nz / B / Yi Preferably, the absorbent bed comprises an absorbent material. Generally, the absorbent material comprises openings that have a size in their largest dimension of approximately 2 Å to approximately 12 Å. Generally, the absorbent material comprises an adsorbent containing aluminum, activated carbon, or a mixture thereof. Preferably, the absorbent material comprises alumina or aluminosilicate; most preferably, the absorbent material comprises aluminosilicate. Preferably, the aluminosilicate comprises a molecular sieve (zeolite) having pore sizes in the range of 2 to 12 Angstroms, for example, about 3Å to about 6Å, such as having an average pore size of about 3Å or about 4Å. According to a third aspect of the invention, the use of an apparatus according to the second aspect of the invention is provided in carrying out a method according to the first aspect of the invention.

Claims

1. A method for at least partially draining an operating system containing a working fluid (comprising carbon dioxide (R744) and a halogenated hydrocarbon), the method comprising transferring the working fluid from the operating system to a destination vessel, wherein the working fluid is brought into contact with an absorbent bed.

2. The method of claim 1, wherein the operating system is a cooling system.

3. The method according to claim 1 or 2, wherein the operating system is a medium temperature cooling system.

4. The method according to any preceding claim, wherein the fluid is brought into contact with the absorbent bed more than once.

5. The method according to any preceding claim, wherein the fluid is brought into contact with two or more absorbent beds.

6. The method according to any of the preceding claims, wherein the contact step is carried out, at least in part, at a temperature of approximately 0 °C to approximately 200 °C.

7. The method according to any preceding claim, wherein the contact stage is performed at a pressure of approximately 0.1 to 50 Bara.

8. The method according to any preceding claim, comprising an absorbent bed treatment step prior to the contact step.

9. The method according to claim 8, wherein the absorbent bed treatment step comprises a heat treatment step comprising heating the adsorbent to a maximum temperature of at least 150 °C, preferably at least 200 °C.

10. The method according to claim 9, wherein the heat treatment step comprises heating the adsorbent to the maximum temperature at a rate of 0 °C / minute to 60 °C / minute, preferably at a rate of 20 °C / minute to 40 °C / minute.

11. The method according to claim 9 or 10, wherein the heat treatment step nn? Lnn / zznz / E / Yi comprises holding the absorbent bed at or around the maximum temperature for a time from 1 second to 1 hour.

12. The method according to claim 8, 9, 10 or 11, wherein the absorbent bed treatment step comprises an exposure step, comprising exposing the absorbent bed to one or more inert gases, preferably N2 or a noble gas.

13. The method according to claim 8, 9, 10, 11 or 12, wherein the absorbent bed treatment step comprises an exposure step comprising exposing the adsorbent to a vacuum.

14. The method according to any preceding claim, comprising an absorbent bed treatment step after the contact step.

15. The method according to claim 14, wherein the treatment step of the absorbent bed after the contact step comprises exposing the absorbent material to elevated temperature and / or vacuum.

16. The method according to any of the preceding claims, wherein the working fluid comprises R-32 (difluoromethane).

17. The method according to claim 16, wherein the working fluid comprises: (a) from approximately 10 percent to approximately 35 percent by weight of R-32; (b) from approximately 65 percent to approximately 90 percent by weight of R744 (carbon dioxide), based on the weight of components (a) to (b).

18. An apparatus for at least partially draining an operating system, containing a working fluid (comprising carbon dioxide (R744) and a halogenated hydrocarbon), wherein the apparatus is suitable for connection to the operating system through a conduit, the apparatus comprising a) An absorbent bed, and b) A storage container.

19. An apparatus according to claim 18, wherein the absorbent bed comprises an absorbent material.

20. An apparatus according to claim 19, wherein the absorbent material comprises openings having a size in their largest dimension of approximately 2Å to approximately 12Å nn? Lnn / zznz / E / Yi 21. An apparatus according to claim 19 or 20, wherein the absorbent material comprises an adsorbent containing aluminum, activated carbon, or a mixture thereof. 5 22. An apparatus according to claim 21, wherein the absorbent material comprises a molecular sieve (zeolite) having pore sizes in the range of 2 to 12 Angstroms, for example, approximately 3A to approximately 6A.

23. Use of an apparatus according to any of claims 18 to 22 wherein an operating system containing a working fluid (comprising carbon dioxide (R744) and a halogenated hydrocarbon) is at least partially drained.

24. Use of an apparatus according to any of claims 18 to 22 in accordance with a method according to any of claims 1 to 17.