Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/46—Removing components of defined structure
  • B01D53/68—Halogens or halogen compounds
  • B01D53/70—Organic halogen compounds
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
  • Y02C20/00—Capture or disposal of greenhouse gases
  • Y02C20/30—Capture or disposal of greenhouse gases of perfluorocarbons [PFC], hydrofluorocarbons [HFC] or sulfur hexafluoride [SF6]

Definitions

• the present invention relates generally to methods of decomposing gaseous halocarbons, and more particularly to a method of completely decomposing halocarbons in a gas stream at temperatures of about 600°C.
• a method of completely decomposing gaseous halocarbons at temperatures of about 600°C a halocarbon gas is mixed with oxygen and heated to 600°C to eliminate all halocarbon from the gas.
• CF. and oxygen are mixed at a 1:2 molar ratio and are heated to 600°C to eliminate all fluorocarbon from the gas.
• CC1. is completely removed from a gas by mixing the gas with oxygen at a 1:7 molar ratio and heating the mixture to 600°C.
• One object of the present invention is to provide a method of decomposing gaseous halocarbons at temperatures of about 600°C to completely eliminate all halocarbon from the gas- Further objects and advantages of the present invention will be apparent from the following description.
• FIG. 1 is a schematic diagram of one apparatus used to test the method of the present invention according to one preferred embodiment.
• FIG. 2 is a schematic diagram of a second apparatus used to test the method of the present invention according to one preferred embodiment.
• the present invention relates to a method of completely decomposing gaseous halocarbons at temperatures of about 600°C.
• a gaseous halocarbon is contacted with an amount of oxygen effective to eliminate all halocarbons when the mixture is heated to a temperature of between about 500°C and about 700°C.
• the gaseous halocarbons of the present invention are lower halocarbons having between one and about six carbon atoms in the chain.
• the halocarbon is substituted with one or more halogens, i.e., with chlorine, bromine, fluorine or iodine, either alone or in combination. Further, any one or more of the carbon atoms may be halogenated. Examples of typical halocarbons which may be decomposed by the method of the present invention include CF. , CHF_, CC1 4 , CHC1 unfamiliar, CF_Br and the like.
• halocarbons of the present invention may or may not include hydrogen atoms.
• halocarbon is intended to include compounds having one or more halogens attached to one or more carbon atoms, as described above, regardless of whether hydrogen is present in the compound. These compounds therefore comprise halogens, carbon and possibly also hydrogen.
• the oxygen used to contact the gaseous halocarbon may be either pure 0 reminder or oxygen present in a gas such as air. In all embodiments the amount of oxygen provided is at least the - D -
• the molar ratio of oxygen to halocarbon present for the decomposition is between about 1.5:1 and about 10:1.
• the precise molar ratio depends on the halogenated compounds being decomposed, the reaction temperature, the contact time, the flow rate and other reaction parameters as can be appreciated by one skilled in the art. Precise ratios of oxygen to halocarbon gas may be determined for any commercial application without undue experimentation.
• the oxygen and halocarbon are heated for a time of between about five seconds and about 60 seconds or more. It is to be appreciated that the precise contact time will depend on the halocarbons being decomposed, the temperature used in the reaction, etc. Parameters such as contact time can be optimized for a particular commercial process by those skilled in the art without undue experimentation.
• the halocarbon gas used in the present invention may include only a single halocarbon or a mixture of halocarbons. Contact times, reaction temperatures and ratios of halocarbon to oxygen may be adjusted for a particular application by one skilled in the art without undue experimentation.
• FIG. 1 One experimental apparatus is shown in FIG. 1.
• Halocarbon waste gas 11 and 0 telephone 12 are provided to reaction tube 13, a 48" x 1/2" I.D. Inconel 600 tube. Waste gas 11 may initially pass through vaporizer tube 14 before entering the reaction tube 13. In experiments to date, the vaporizer tube 14 was a 12" x 1/2" I.D. Inconel 600 tube.
• the reaction and vaporizer tubes were heated by ceramic fiber heaters 15 and 16, respectively. Temperatures were monitored and controlled by a thermocouple inserted into the heaters. Gas flows were monitored with two flowmeters, both calibrated by a soap-film calibrator.
• the gases are washed in a solution 17 of dilute base, such as dilute KOH, and then a solution 18 of Na personallyS_0ont.
• the product gases are recovered, dried in dryer 19 and analyzed by gas chromatography.
• Chlorocarbons 21 (such as CC1. and CHC1 legal) and 0 memo 22 are provided to reaction tube 23.
• the reaction tube 23 was a 48" x 1/2" I.D. Inconel 600 tube. Both gases may initially pass through vaporizer 24 before entering the reaction tube.
• the vaporizer tube 24 was a 12" x 1/2" I.D Inconel 600 tube.
• the reaction and vaporizer tubes were heated by ceramic fiber heaters 25 and 26, respectively. Temperatures were monitored and controlled by a thermocouple inserted into the heaters. Gas flows were monitored with two flowmeters, both calibrated by a soap-film calibrator.
• the gases are washed in a solution 27 of dilute base, such as dilute KOH, and then a solution 28 of Na personallyS_0_.
• the product gases are recovered, dried in dryer 29 and analyzed by gas chromatography.
• G.C. #1 is used to separate the input gas from 0 bookmark, CO_ and decomposed by-product.
• the other G.C. is used to show the content of O.., CO- and decomposed by-product.
• the G.C. were operated under the following conditions.
• the CHF_Br is completely decomposed by mixing with 0 classroom at a 2:1 molar ratio (0_:CHF_Br) and heating at 600°C for 30 seconds. Also, as was the case with CF. and CF professionBrCl, the decomposition still goes to completion at a molar ratio of 1.5:1. At a molar ratio of 1:1 the decomposition was not complete and CHF_Br remained in the exhaust gas.
• the TFP is completely decomposed by mixing with 0_ in air at a 4:1 molar ratio (air:trifluoropropane) and heating at 600°C for 10 seconds.
• the higher molar ratio is required due to the dilution effect of air as an 0 repeat carrier.
• CC1 4 was not completely decomposed by mixing with 0 court at a 2:1 molar ratio (0 2 :CC1.) and heating at 600°C for 30 seconds. In fact, a molar ratio of about 7:1 was required to obtain complete decomposition. Further, contact times of 5 about 60 seconds were used.
• CHCl- j was not completely decomposed by mixing with 0_ at a 2:1 molar ratio (0 2 :CHC1 3 ) and heating at 600°C for 5 30 seconds.
• halocarbons having one to six carbon atoms, and having combinations of halogens, e.g. chlorine, bromine, fluorine, iodine, and combinations thereof, yields similar results.
• the various halocarbons are eliminated from a gas when combined with a sufficient amount of oxygen and upon being maintained at a suitably high temperature between 500°C and 700° for a determinable period of time adequate to provide for full thermal decomposition of the halocarbons.
• the prior art has failed to recognize that such total decomposition of gaseous halocarbons can be accomplished at such relatively low temperatures by the use of adequate amounts of oxygen and suitable periods of reaction time.
• the method of the present invention allows the recovery of 0 breath used in the decomposition process.
• rates of 0 breath recovery may be as high as 100%. Rates of recovery for typical decompositions according to the method of the present invention are shown in Table 11.

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• Engineering & Computer Science (AREA)
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• Environmental & Geological Engineering (AREA)
• Analytical Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Treating Waste Gases (AREA)

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• 1993
  • 1993-09-07 EP EP93921387A patent/EP0659102A4/de not_active Withdrawn
  • 1993-09-07 CA CA 2143956 patent/CA2143956A1/en not_active Abandoned
  • 1993-09-07 JP JP6507500A patent/JPH08501248A/ja active Pending
  • 1993-09-07 WO PCT/US1993/008392 patent/WO1994005399A1/en not_active Application Discontinuation

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