EP0659102A1 - Method of decomposing gaseous halocarbons - Google Patents
Method of decomposing gaseous halocarbonsInfo
- Publication number
- EP0659102A1 EP0659102A1 EP93921387A EP93921387A EP0659102A1 EP 0659102 A1 EP0659102 A1 EP 0659102A1 EP 93921387 A EP93921387 A EP 93921387A EP 93921387 A EP93921387 A EP 93921387A EP 0659102 A1 EP0659102 A1 EP 0659102A1
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- EP
- European Patent Office
- Prior art keywords
- gas
- oxygen
- halocarbons
- mixture
- halocarbon
- Prior art date
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- 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.
- halocarbons at temperatures of about 600 °C .
- a ha locarbon gas is mixed with oxygen and heated to 600°C to eliminate all halocarbon from the gas.
- CF 4 and oxygen are mixed at a 1:2 molar ratio and are heated to 600°C to eliminate all fluorocarbon from the gas.
- CCl 4 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.
- 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 4 , CHF 3 , CCl 4 , CHCl 3 ,
- 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 O 2 or oxygen present in a gas such as air. In all embodiments the amount of oxygen provided is at least the stoichiometric amount. In preferred embodiments, 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
- 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
- Halocarbon waste gas 11 and O 2 12 are provided to reaction tube 13, a 48" ⁇ 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" ⁇ 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.
- FIG. 2 Another experimental apparatus is shown in FIG. 2.
- Chlorocarbons 21 such as CCl 4 and CHCl 3
- O 2 22 are provided to reaction tube 23.
- the reaction tube 23 was a 48" ⁇ 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" ⁇ 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.
- CF 3 Br may be completely decomposed at 600°C so that no halocarbon remains.
- the reaction is effectively performed with a contact time of 30 seconds when the molar ratio of O 2 :CF 3 Br is 2:1.
- CHF 3 is completely decomposed by mixing with O 2 at a 2:1 molar ratio (O 2 :CHF 3 ) and
- CHF 3 Br is completely decomposed by mixing with O 2 at a 2:1 molar ratio (O 2 :CHF 3 Br) and heating at
- EXAMPLE 7 Decomposition of Trifluoropropane. This experiment was performed with the apparatus shown in FIG. 1, except that since trifluoropropane (TFP) is a flammable gas, the tests were performed with air instead of 100% O 2 . TFP and O 2 in air were combined at the desired flow rates and
- the TFP is completely decomposed by mixing with O 2 in air at a 4:1 molar ratio (air : trifluoropropane) and heating at 600°C for 10 seconds.
- air air : trifluoropropane
- the higher molar ratio is required due to the dilution effect of air as an O 2 carrier.
- CCl 4 was not completely decomposed by mixing with O 2 at a 2:1 molar ratio (O 2 :CCl.) and heating at 600°C for
- CHCl 3 was not completely decomposed by mixing with O 2 at a 2:1 molar ratio (0 2 :CHCl 3 ) and heating at 600°C for 30 seconds.
- a molar ratio of about 4.5:1 with a contact time of about 60 seconds, was required to obtain complete decomposition.
- CCl 4 was not completely decomposed by mixing with O 2 in air at a 12:1 molar ratio (air:CCl 4 ) and heating at
- halocarbons having one to six carbon atoms, and having combinations of halogens, e.g. chlorine, bromine, fluorine, iodine, and combinations thereof, yields similar results.
- halogens e.g. chlorine, bromine, fluorine, iodine, and combinations thereof.
- the various halocarbons are
- rates of O 2 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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Abstract
A method of completely decomposing gasesous halocarbons at temperatures of between about 500 °C and about 700 °C, preferably about 600 °C. The gaseous halocarbons may initially pass through a vaporizer tube (14), before entering the reaction tube (13). The reaction and vaporizer tubes are heated by ceramic fiber heaters (15 and 16). Temperatures were monitored and controlled by a thermocouple inserted into the heaters. Gas flows are monitored with two flowmeters. This sytem for decomposing gaseous halocarbons has the advantage of mixing the halocarbon gas with oxygen and maintaining the temperature at 600 °C for a length of time sufficient to eliminate all halocarbons from the gas.
Description
METHOD OF DECOMPOSING GASEOUS HALOCARBONS
BACKGROUND OF THE INVENTION
Field of the Invention:
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.
Description of the Prior Art:
A variety of halocarbon gases are produced during common commercial processes. In the prior art, it is known to combust these waste gases at temperatures on the order of 1200°C and higher in order to thermally decompose the gases to more environmentally benign products. Unfortunately, the high temperature required for these prior art processes reduces the commercial applicability of prior art methods and precludes their employment in many commercial applications.
Recently, a variety of factors have increased the
desirability of removing all halocarbons from an exhaust gas stream. In some circumstances the cost of producing
halocarbon emissions has increased, while in other
circumstances such emissions are prohibited altogether. A need has therefore remained for a method of decomposing gaseous halocarbons in an exhaust gas stream so that no halocarbons remain in the stream. The present invention addresses this need.
SUMMARY OF THE INVENTION
Briefly describing the present invention, there is provided a method of completely decomposing gaseous
halocarbons at temperatures of about 600 °C . In one aspect of the present invention , a ha locarbon gas is mixed with oxygen and heated to 600°C to eliminate all halocarbon from the gas. In a preferred embodiment, CF4 and oxygen are mixed at a 1:2 molar ratio and are heated to 600°C to eliminate all fluorocarbon from the gas. In another embodiment, CCl4 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.
BRIEF DESCRIPTION OF THE DRAWINGS
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.
DESCRIPTION OF THE PREFERRED EMBODIMENT
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the preferred embodiment and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the method, and such further applications of the principles of the invention being contemplated as would normally occur to one skilled in the art to which the invention relates.
The present invention relates to a method of completely decomposing gaseous halocarbons at temperatures of about 600°C. In one aspect of the invention, 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 CF4, CHF3, CCl4, CHCl3,
CF3Br and the like.
The halocarbons of the present invention may or may not include hydrogen atoms. In this description of the invention the term "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 O2 or oxygen present in a gas such as air. In all embodiments the amount of oxygen provided is at least the
stoichiometric amount. In preferred embodiments, 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.
In the process of the present invention, 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.
Reference will now be made to specific examples using the process described above. It is to be understood that these examples are provided to more completely describe and explain the preferred embodiments, and that no limitation to the scope or breadth of the invention is thereby intended.
Experimental Procedure One experimental apparatus is shown in FIG. 1.
Halocarbon waste gas 11 and O2 12 are provided to reaction tube 13, a 48" × 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" × 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.
After reaction, the gases are washed in a solution 17 of dilute base, such as dilute KOH, and then a solution 18 of Na2S2O3. The product gases are recovered, dried in
dryer 19 and analyzed by gas chromatography.
Another experimental apparatus is shown in FIG. 2.
Chlorocarbons 21 ( such as CCl4 and CHCl3) and O2 22 are provided to reaction tube 23. In experiments to date, the reaction tube 23 was a 48" × 1/2" I.D. Inconel 600 tube.
Both gases may initially pass through vaporizer 24 before entering the reaction tube. In experiments to date, the vaporizer tube 24 was a 12" × 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.
After reaction, the gases are washed in a solution 27 of dilute base, such as dilute KOH, and then a solution 28 of Na2S2O3. The product gases are recovered, dried in
dryer 29 and analyzed by gas chromatography.
In all experiments, two gas chromatography analyzers are used. One G.C. is used to separate the input gas from O2, CO2 and decomposed by-product. The other G.C. is used to show the content of O2, CO2 and decomposed by-product.
The G.C. were operated under the following conditions.
G.C. #1:
Column: 3% SP-1500 on carbopack B, O.D. 5 mm × L. 3.1m, glass Detector temperature: 150°C
Detector type: TCD @ 100mA
Injector temperature: 100°C
He: 25 mL/min
Program: 30°C/4 min / 15°C/min / 110°C/3 min
G.C. #2:
Column: Carbosieve G, O.D. 5mm × L. 3.1m, glass.
Detector temperature: 180°C
Detector type: TCD @ 100mA
Injector temperature: 180°C
He: 40 mL/min
Program: 30°C/3 min / 10°C/min / 120°C/8 min The reaction contact time (θ) is calculated as follows θ = Reactor volume (155 mL) / Total flow of O2 and
halocarbon gas
EXAMPLE 1
Decomposition of CF3Br. This example was performed with the apparatus shown in FIG. 1. Experiments were carried out by combining O2 and CF3Br (Halon 1301) at the desired flow rates and temperature for one hour. The outlet gas was then sampled and analyzed by gas chromatography. Results are summarized in Table 1.
It can be seen that CF3Br may be completely decomposed at 600°C so that no halocarbon remains. The reaction is effectively performed with a contact time of 30 seconds when the molar ratio of O2:CF3Br is 2:1.
The effect of molar ratio can be seen by comparing entries six through nine. In this Example, a molar ratio of 1.5:1 was not effective to completely decompose CF3Br, while a molar ratio of 2:1 provided complete decomposition.
TABLE 1
DECOMPOSITION OF CF3Br
Flow(mL/min) Ratio Outlet Gas Content(%)
Entry Temp.(°C) Time(sec ) 1301* O2 O2:1301 O2+CO2 1301 F-14
1 645 ~ 657 50 62 124 2:1 100 0 0
2 " 30 103 207 " 100 0 0
3 " 20 155 310 " 98.97 0 1.03
4 II 15 207 413 " 96.68 0.33 2.99
5 596 ~ 609 30 103 207 " 100 0 0
6 " 20 155 310 " 98.96 0.48 0.56
7 " 30 124 186 1.5:1 98.57 0.06 1.37
8 " " 155 155 1:1 94.56 0.18 5.26
9 " " 185 125 1:1.5 84.54 0.94 14.51
10 664 ~ 656 " 185 125 " 88.50 0 11.50
11 543 ~ 556 " 124 186 1.5:1 96.78 1.99 1.23
* Halon 1301 ( CF3Br )
The effect of contact time can be seen by comparing entries one through four. In this Example, a reaction contact time of 20 seconds was not effective to completely decompose CF3Br, while a reaction contact time of 30 seconds provided complete decomposition.
The effect of temperature can be seen by comparing entry 3 with entry 6, entry 7 with entry 11 and entry 9 with entry 10. As would be expected, the higher the temperature the better the decomposition. EXAMPLE 2
Decomposition of CF3Cl. This experiment was
performed with the apparatus shown in FIG. 1. CF3Cl and O2 were combined at the desired flow rates and temperatures for one hour. The outlet gas was then sampled and analyzed by gas chromatography. The results are summarized in Table 2.
It can be seen that CF3Cl is completely decomposed by mixing with O2 at a 2:1 molar ratio (O2:CF3Cl) and
heating at 600°C for 30 seconds. At a molar ratio of 1.5:1 the decomposition was not complete. When the reaction
(contact) time was only 20 seconds the decomposition was not complete.
EXAMPLE 3
Decomposition of CHF3. This experiment was performed with the apparatus shown in FIG. 1. CHF3 and O2 were combined at the desired flow rates and temperatures for one hour. The outlet gas was then sampled and analyzed by gas chromatography. The results are summarized in Table 3.
It can be seen that CHF3, is completely decomposed by mixing with O2 at a 2:1 molar ratio (O2:CHF3) and
heating at 600°C for 30 seconds. At a molar ratio of 1.5:1 the decomposition was not complete and CHF3 remained in the
TABLE 2
DECOMPOSITION OF CF3CI
Flow(mL/min) Ratio Outlet Gas Content(%)
Temp.(°C) Time(sec.) F-13* O2 O2:F-13 O2+CO2 F-13 F-14**
596 ~ 608 30 103 207 2:1 100 0 0
" 20 155 310 2:1 99.69 3.31 0
" 30 124 186 1.5:1 99.96 0.04 0 " 30 155 155 1:1 98.18 1.82 0
* F-13 (CF3CI)
** F-14 (CF4)
TABLE 3
DECOMPOSITION OF CF3H
Flow(mL/min) Ratio Outlet Gas Content(%)
Temp.(°C) Time(sec.) F-23* O2 O2:F-23 O2+CO2 F-23 F-14
596 - 608 30 103 207 2:1 100 0 0 " 30 124 186 1.5:1 99.95 0.047 0 " 30 155 155 1:1 88.89 11.09 0 " 30 207 103 1:2 76.31 23.40 0.29
* F-23 (CF3H)
exhaust gas. At a molar ratio of 1:2 the decomposition was not complete and both CHF3 and CF4 remained in the
exhaust gas.
EXAMPLE 4 Decomposition of CF4. This experiment was performed with the apparatus shown in FIG. 1. CF4 and O2 were
combined at the desired flow rates and temperatures for one hour. The outlet gas was then sampled and analyzed by gas chromatography. The results are summarized in Table 4.
It can be seen that CF. is completely decomposed by mixing with O2 at a 2:1 molar ratio (O2:CF4) and
heating at 600°C for 30 seconds. Further, at a molar ratio of 1.5:1 the decomposition still goes to completion and no halocarbon remained in the exhaust gas. At a molar ratio of 1:1 the decomposition was not complete and CF4 remained in the exhaust gas.
EXAMPLE 5
Decomposition of CF3BrCl. This experiment was
performed with the apparatus shown in FIG. 1. CF3BrCl and 0-*, were combined at the desired flow rates and temperatures for one hour. The outlet gas was then sampled and analyzed by gas chromatography. The results are summarized in Table 5
It can be seen that CF2BrCl is completely decomposed by mixing with O2 at a 2:1 molar ratio (O2:CF2BrCl) and
heating at 600°C for 30 seconds. Further, at a molar ratio of 1.5:1 the decomposition still goes to completion and no halocarbon remained in the exhaust gas. At a molar ratio of 1.2:1 the decomposition was not complete and CF3BrCl
remained in the exhaust gas.
TABLE 4
DECOMPOSITION OF CF4
Flow(mL/min) Ratio Outlet Gas Content(%) Temp.(°C) Time(sec) F-14* O2 O2:F-14 O2+CO2 F-14
596 - 608 30 103 207 2:1 100 0
" 30 124 186 1.5:1 100 0
" 30 155 155 1:1 89.51 10.49
F-14 (CF4)
TABLE 5
DECOMPOSITION OF CF2BrCl
Flow(mL/min) Ratio Outlet Gas Content(%)
Temp. (°C) Time(sec.) 1211* O2 O2:1211 O2+CO2 1211 by-product
596 - 608 30 103 207 2:1 100 0 0
" 30 124 186 1.5:1 10 0 0 " 30 155 155 1.2:1 94.29 0 5.71
* Halon 1211 (CF2BrCl)
F-13:4.21%, 1301 : 0.024%, F-14: 1.48%
EXAMPLE 6
Decomposition of CHF3Br. This experiment was
performed with the apparatus shown in FIG. 1. CHF3Br and O2 were combined at the desired flow rates and temperatures for one hour. The outlet gas was then sampled and analyzed by gas chromatography. The results are summarized in Table 6
Again, the CHF3Br is completely decomposed by mixing with O2 at a 2:1 molar ratio (O2:CHF3Br) and heating at
600°C for 30 seconds. Also, as was the case with CF4 and CF2BrCl, 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 CHF3Br remained in the exhaust gas.
EXAMPLE 7 Decomposition of Trifluoropropane. This experiment was performed with the apparatus shown in FIG. 1, except that since trifluoropropane (TFP) is a flammable gas, the tests were performed with air instead of 100% O2. TFP and O2 in air were combined at the desired flow rates and
temperatures for one hour. The outlet gas was then sampled and analyzed by gas chromatography. The results are
summarized in Table 7.
The TFP is completely decomposed by mixing with O2 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 O2 carrier.
EXAMPLE 8
Decomposition of CCl4. This experiment was performed with the apparatus shown in FIG. 2. CCl4 and O2 were
combined at the desired flow rates and temperatures for one hour. The outlet gas was then sampled and analyzed by gas chromatography. The results are summarized in Table 8.
TABLE 6
DECOMPOSITION OF CHFBr2
Flow(mL/min) Ratio Outlet Gas Content(%)
Temp.(°C) Time(sec) FM-100 O2 O2:FM-100 O2+CO2 FM-100 by-product
596 ~ 608 30 110033 220077 2:1 100 0 0
" 30 112244 118866 1.5:1 100 0 0 " 30 115555 115555 1:1 99.31 0 0.69
F-13:0.057%, 1301 : 0.037%, F-14:0.597%
TABLE 7
DECOMPOSITION OF TFP
Flow(mL/min) Ratio Outlet Gas Content (%)
Temp.(°C) Time(sec.) TFP Air Air:TFP O2+CO2 TFP by-product
596 ~ 608 10 85 845 10:1 100 0 0
" 10 155 775 5:1 100 0 0 " 10 186 744 4:1 100 0 0 " 10 233 698 3:1 Explosion danger
TABLE 8
DECOMPOSITION OF CCI4
(600ºCº
Feed Rate Ratio Outlet Gas Content CCl4
Entry Time O2 CCl4 O2:CCl4 O2+CO2 CCl4 Others in water
(sec.) (mL/mm) (g/min) (7o) (ppm)
1 60 138 0.111 8.5:1 100 0 0 0
2 60 138 0.122 7.8:1 100 0 0 -
3 60 133 0.130 7.0:1 100 0 0 0
4 60 133 0.165 5.5:1 98.52 1.448 0.036 -
5 45 180 0.199 6.2:1 96.90 3.077 0.027 -
6 90 81 0.124 4.5:1 99.66 0.309 0.028 -
CCl4 was not completely decomposed by mixing with O2 at a 2:1 molar ratio (O2:CCl.) 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 about 60 seconds were used.
EXAMPLE 9
Decomposition of CHCl3. This experiment was
performed with the apparatus shown in FIG. 2. CHCl3 and O2 were combined at the desired flow rates and a
temperature of about 600°C for one hour. The outlet gas was then sampled and analyzed by gas chromatography. The results are summarized in Table 9.
CHCl3 was not completely decomposed by mixing with O2 at a 2:1 molar ratio (02:CHCl3) and heating at 600°C for 30 seconds. Here, a molar ratio of about 4.5:1, with a contact time of about 60 seconds, was required to obtain complete decomposition.
EXAMPLE 10
Decomposition of CCl. with air. This experiment was performed with the apparatus shown in FIG. 2. CCl4 and
O2 in air were combined at the desired flow rates and
temperatures for one hour. The outlet gas was then sampled and analyzed by gas chromatography. The results are
summarized in Table 10.
CCl4 was not completely decomposed by mixing with O2 in air at a 12:1 molar ratio (air:CCl4) and heating at
600°C for 30 seconds. However, at a molar ratio of about 12.5:1 and a contact time of 45 seconds complete
decomposition was obtained.
TABLE 9
DECOMPOSITION OF CHCI3
Feed Rate Ratio Outlet Gas Content CHCl3/CCl4
Time O2 CHCl3 O2:CHCl3 O2+CO2 CCl3 CCl4 Others in water
(sec.) (mL/min) (g/min) (%) (ppm)
60 133 0.158 4.5:1 100 0 0 0 0/0.145
30 206 0.532 2:1 99.68 0 0.315 0 -
TABLE 10
DECOMPOSITION OF CCl4 WITH AIR
Feed Rate Ratio Outlet Gas Content CCl4
Entry Time Air CCl4 Air:CCl4 Air+CO2 CCl4 Others in water
(sec.) (mL/min) (g/min) (%) (ppm)
1 45 192 0.105 12.5:1 100 0 0 0
2 30 286 0.163 12:1 99.09 0.890 0.019 -
EXAMPLE 11
Repetition of the foregoing examples with other lower halocarbons, e.g. halocarbons having one to six carbon atoms, and having combinations of halogens, e.g. chlorine, bromine, fluorine, iodine, and combinations thereof, yields similar results. Advantageously, 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.
It is to be appreciated that the method of the present invention allows the recovery of O2 used in the
decomposition process. Depending on the halocarbon being decomposed, rates of O2 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.
While the invention has been illustrated and described in detail in the foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and
modifications that come within the spirit of the invention are desired to be protected.
TABLE 11
Required O2/CFC moles and resulting O2 recovery.
CF4 + 2 O2 ╌> CO2 + 2 OF2
2 H2O + 2 OF2 ╌> 4 HF + 2 O2 10O% 0 mol
C2F6 +7/2 O2 ╌>2 CO2 + 3 OF2
3 H2O + 3 OF2 ╌> 6 HF + 3 O2 86% 0.5 mol
C2F4 + 3 O2 ╌>2 CO2 + 2 OF2
H2O + 2 OF2 ╌> 4 HF + 2 O2 67% 1 mol
CF3Br + 2 O2 ╌> CO2 + 3/2 OF2 + 1/2 OBr2
2 H2O + 3/2 OF2 + 1/2 OBr2
- - - > HBr + 3 HF + 2 O2 100% 0 mol
CHF3 +3/2 O2 ╌> CO2 + OF2 + HF
2 H2O + OF2 + HF
- - -> 3 HF + 1/2 O2 50% 1 mol
CH2F2 + O2 ╌> CO2 + 2 HF 0% 1 mol
CH3F +3/2 O2 ╌> CO2 + HF + H2O 0% 1.5 mol
C3H3F3 + 3 O2 ╌>3 CO2 + 3 HF 0% 3 mol
Claims
1. A method of eliminating gaseous halocarbons from a gas containing such compounds, comprising
(a) providing a mixture of air and of the gas containing one or more gaseous halocarbons, the mixture including oxygen in an amount effective to thermally decompose all of the halocarbons in the mixture when the mixture is maintained at a temperature of between about 500°C and about 700°C;
(b) heating the gas and oxygen to a temperature of between about 500°C and about 700°C; and
(c) maintaining the mixture of gas and oxygen at about 500°C to about 700°C for a time sufficient to provide
elimination of the halocarbons.
2. The method of claim 1 wherein the mixture of oxygen and gas containing halocarbon includes an amount of oxygen effective to eliminate all halocarbons from the gas when the gas and oxygen mixture are maintained at a temperature of about 600°C, and wherein each of said heating and said maintaining is at a temperature of about 600°C.
3. The method of claim 1 wherein the molar ratio of oxygen to halocarbon is between about 1.5:1 and about 10:1.
4. The method of claim 1 wherein said maintaining is for a time of between about 5 seconds and about 90 seconds.
5. The method of claim 1 wherein said gas consists essentially of fluorocarbons.
6. The method of claim 5 wherein the molar ratio of oxygen to halocarbon is at least about 2:1.
7. The method of claim 6 wherein said maintaining is for a time of at least about 30 seconds.
8. The method of claim 1 wherein said gas consists essentially of chlorocarbons.
9. The method of claim 8 wherein the molar ratio of oxygen to halocarbon is at least about 7:1.
10. The method of claim 9 wherein said maintaining is for a time of at least about 60 seconds.
AMENDED CLAIMS
[received by the International Bureau on 27 January 1994 (27.01.94);
original claim 1 amended; other claims unchanged (1 page)]
1. A method of eliminating gaseous halocarbons from a gas containing such compounds, consisting essentially of
(a) providing a mixture of air and of the gas
containing one or more gaseous halocarbons, the mixture including oxygen in an amount effective to thermally
decompose all of the halocarbons in the mixture when the mixture is maintained at a temperature of between 500°C and 700°C;
(b) heating the gas and oxygen to a temperature of between 500°C and 700°C; and
(c) maintaining the mixture of gas and oxygen at 500°C to 700°C for a time sufficient to provide elimination of the halocarbons.
2. The method of claim 1 wherein the mixture of oxygen and gas containing halocarbon includes an amount of oxygen effective to eliminate all halocarbons from the gas when the gas and oxygen mixture are maintained at a
temperature of about 600°C, and wherein each of said heating and said maintaining is at a temperature of about 600°C.
3. The method of claim 1 wherein the molar ratio of oxygen to halocarbon is between about 1.5:1 and about 10:1.
4. The method of claim 1 wherein said maintaining is for a time of between about 5 seconds and about 90 seconds.
5. The method of claim 1 wherein said gas consists essentially of fluorocarbons.
6. The method of claim 5 wherein the molar ratio of oxygen to halocarbon is at least about 2:1.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US94300492A | 1992-09-09 | 1992-09-09 | |
US943004 | 1992-09-09 | ||
PCT/US1993/008392 WO1994005399A1 (en) | 1992-09-09 | 1993-09-07 | Method of decomposing gaseous halocarbons |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0659102A1 true EP0659102A1 (en) | 1995-06-28 |
EP0659102A4 EP0659102A4 (en) | 1995-08-16 |
Family
ID=25478949
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP93921387A Withdrawn EP0659102A4 (en) | 1992-09-09 | 1993-09-07 | Method of decomposing gaseous halocarbons. |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0659102A4 (en) |
JP (1) | JPH08501248A (en) |
CA (1) | CA2143956A1 (en) |
WO (1) | WO1994005399A1 (en) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6162957A (en) * | 1997-03-24 | 2000-12-19 | Showa Denko K.K. | Catalytic decomposition of perfluoro-compound |
JP3593875B2 (en) * | 1997-03-24 | 2004-11-24 | 昭和電工株式会社 | Method for catalytic decomposition of perfluoro compounds |
JPH11218318A (en) * | 1998-02-03 | 1999-08-10 | Air Liquide Japan Ltd | Exhaust gas treating facility |
CN107569985B (en) * | 2017-09-27 | 2020-09-01 | 徐州工程学院 | Reaction cracker |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3845191A (en) * | 1972-06-02 | 1974-10-29 | Du Pont | Method of removing halocarbons from gases |
GB1350727A (en) * | 1972-06-12 | 1974-04-24 | Shell Int Research | Process and apparatus for the disposal of halogenated organic material |
JPH0326384A (en) * | 1989-06-21 | 1991-02-04 | Central Glass Co Ltd | Treatment of fluorine-containing organic compound |
-
1993
- 1993-09-07 JP JP6507500A patent/JPH08501248A/en active Pending
- 1993-09-07 EP EP93921387A patent/EP0659102A4/en not_active Withdrawn
- 1993-09-07 CA CA 2143956 patent/CA2143956A1/en not_active Abandoned
- 1993-09-07 WO PCT/US1993/008392 patent/WO1994005399A1/en not_active Application Discontinuation
Non-Patent Citations (2)
Title |
---|
No further relevant documents disclosed * |
See also references of WO9405399A1 * |
Also Published As
Publication number | Publication date |
---|---|
JPH08501248A (en) | 1996-02-13 |
CA2143956A1 (en) | 1994-03-17 |
WO1994005399A1 (en) | 1994-03-17 |
EP0659102A4 (en) | 1995-08-16 |
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