WO1993010037A1 - Improvements in halogen generators - Google Patents

Improvements in halogen generators Download PDF

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Publication number
WO1993010037A1
WO1993010037A1 PCT/GB1992/002151 GB9202151W WO9310037A1 WO 1993010037 A1 WO1993010037 A1 WO 1993010037A1 GB 9202151 W GB9202151 W GB 9202151W WO 9310037 A1 WO9310037 A1 WO 9310037A1
Authority
WO
WIPO (PCT)
Prior art keywords
halogen
source
generator
container
cell
Prior art date
Application number
PCT/GB1992/002151
Other languages
French (fr)
Inventor
Andrew John Kearsley
Thomas Neville Walton Salkeld
Alan Howard Ferguson
Gerard Sean Mcgrady
Original Assignee
Oxford Lasers Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Oxford Lasers Limited filed Critical Oxford Lasers Limited
Publication of WO1993010037A1 publication Critical patent/WO1993010037A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B7/00—Halogens; Halogen acids
    • C01B7/01—Chlorine; Hydrogen chloride
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B7/00—Halogens; Halogen acids
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B7/00—Halogens; Halogen acids
    • C01B7/19—Fluorine; Hydrogen fluoride
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/02—Constructional details
    • H01S3/03—Constructional details of gas laser discharge tubes
    • H01S3/036—Means for obtaining or maintaining the desired gas pressure within the tube, e.g. by gettering, replenishing; Means for circulating the gas, e.g. for equalising the pressure within the tube
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/22—Gases
    • H01S3/223—Gases the active gas being polyatomic, i.e. containing two or more atoms
    • H01S3/225—Gases the active gas being polyatomic, i.e. containing two or more atoms comprising an excimer or exciplex

Definitions

  • This invention relates to halogen and hydrogen halide generators (herein referred to as 'halogen generators') , which are devices for producing a supply of halogen gas.
  • Halogen generators based on the heating of metal halides or the heating of zeolite containing a halogen compound, such as hydrogen chloride, have been known for some time. See, for example, US Patent 3,989,808 (Asprey) .
  • FIG. 1 shows such a halogen generator cell 10 which comprises a metal cylinder 11 providing a cylindrical compartment 12 for the halogen donor (herein referred to as a 'source').
  • an outlet 14 When the source within compartment 12 is heated halogen is released and the gas is removed via an outlet 14, this outlet also being used for all other access to the cell, such as an initial loading of the source and its periodic replacement.
  • the design of such a cell suffers from four main disadvantages,
  • the cylinder wall is thin and the material of the wall, which is chosen for its chemical properties rather than its thermal properties, is a poor conductor of heat.
  • the temperature uniformity of the walls is poor and the ability of the wall material to conduct heat to the source is also poor and the source is not heated uniformly.
  • the surface area of the wall in contact with the source is small and this limits the heat flow from the cell walls into the source.
  • the source itself is intrinsically a poor conductor of heat and, because the source must be loosely packed into the cell with voids to permit passage of the gas, the heat path to the centre of the cell is long and the source is not uniformly heated. Thus, the source is heated and cooled only very slowly through a large thermal resistance.
  • the halogen is preferentially drawn off the source nearest the exhaust port or outlet 14 and the source in this area is depleted first. This depletion can change the halogen partial pressure / temperature relationship of the cell making accurate control of the halogen partial pressure difficult.
  • the overall effect of these four disadvantages is that temperature uniformity in the cell is poor and the source takes a long time to come into equilibrium. As a result the temperature, which determines the rate at which the halogen is evolved, is difficult to control and hence control of the halogen partial pressure is also rendered difficult. Devices of this kind are reasonably useful for research but are impractical as general purpose halogen sources.
  • a halogen generator comprising a container, a halogen source from which the halogen is to be given off arranged to be disposed in said container, the walls of said container being arranged to provide a short heat path to said halogen source and means for heating said container, said container being constructed from thick-walled material having a high thermal conductivity and having a large surface area,.
  • Figure 2 is a longitudinal section through a halogen generator constructed in accordance with the present invention
  • Figure 3 is a section along the line A-A of Figure 2
  • Figure 4 is a longitudinal section through a further halogen generator also constructed in accordance with the present invention
  • Figure 5 is a section along the line B-B of Figure 4, and, Figure 6 is a longitudinal section through another halogen generator constructed in accordance with the present invention.
  • cell 20 is constructed from a large diameter bar 21 of a material having a high thermal conductivity such as copper, aluminium, nickel, alumina or beryllia.
  • a heater 22 surrounds the bar 21.
  • Bar 21 has an internal opening along its length created by boring out three holes 23, 24 and 25, each of which partly overlaps the other two; all of which extend along the full length of the bar 21. This creates an opening along the centre of the bar 21 into which the halogen source is packed.
  • the opening has a large surface area and sports ridges 26 all along its length, which together ensure that the heat path from the bar 21 to all parts of the source is short.
  • the shape of bar 21 provides a relatively large surface area in a long cell with a wall thickness which is relatively thick, being of the order of 2mm or greater, to ensure adequate temperature uniformity.
  • the cell 30 has three volumes 31, 32, 33, each of rectangular cross-section, in which the halogen source is packed. Each of these volumes is enclosed in a thick-walled material, having a wall thickness of the order of 2mm or greater, made of a high thermal conductivity material such as copper, aluminium, nickel, alumina or beryllia.
  • the volumes are joined at their ends to a common outlet 34 through which the halogen gas is extracted and which is also used for common access to the cell.
  • the cell has heaters 36, 37, 38, 39 positioned one on each of the flat sides of the rectangular cross-section; its construction ensures that the thermal resistance path from the heaters to all parts of the source is low. Whilst this structure can be fabricated either from sheet or solid material, the shape of the cell is particularly suited to manufacture from an extrusion and a halogen- resistant coating can be applied to the inside surfaces of the cell during manufacture.
  • the low thermal resistance heat paths provide uniform heating of the source and a reliable, controllable output of halogen gas. Problems caused by initial depletion of the salt nearest the inlet, described in (iv) above, can be overcome with a cell in which the gas flow resistance is low from all parts of the cell to the exhaust port, thereby facilitating flow of halogen between all parts of the cell.
  • a cell 40 is shown in Figure 6, in which a void 41 is left above the source 42 to collect the halogen.
  • Relatively short fingers 43 transport heat from the cell walls into the source 42.
  • a second method can be used in service to ameliorate the problem described in (iv) above. This involves isolation of the cell followed by heating. Heating will then be released by undepleted source and absorbed by depleted source so re-establishing uniform halogen coverage of the source. If desired, the initially depleted source can be cooled first so giving that source a preferential charge of halogen for future use.

Abstract

An improved form of halogen generator in which the heat path from the interior walls to the halogen source is made short so as to improve uniformity of heating of the source and to obtain a more uniform and controllable output from the generator.

Description

TITLE: Improvements in Halogen Generators
This invention relates to halogen and hydrogen halide generators (herein referred to as 'halogen generators') , which are devices for producing a supply of halogen gas. Halogen generators based on the heating of metal halides or the heating of zeolite containing a halogen compound, such as hydrogen chloride, have been known for some time. See, for example, US Patent 3,989,808 (Asprey) .
Figure 1 shows such a halogen generator cell 10 which comprises a metal cylinder 11 providing a cylindrical compartment 12 for the halogen donor (herein referred to as a 'source'). The cylinder 11, which is surrounded by a heater 13, is made of a halogen resistant metal and is relatively thin walled, having a wall thickness of the order of less than 2 mm. When the source within compartment 12 is heated halogen is released and the gas is removed via an outlet 14, this outlet also being used for all other access to the cell, such as an initial loading of the source and its periodic replacement. The design of such a cell suffers from four main disadvantages,
(i) the cylinder wall is thin and the material of the wall, which is chosen for its chemical properties rather than its thermal properties, is a poor conductor of heat. As a result the temperature uniformity of the walls is poor and the ability of the wall material to conduct heat to the source is also poor and the source is not heated uniformly. (ii) the surface area of the wall in contact with the source is small and this limits the heat flow from the cell walls into the source.
(iii) the source itself is intrinsically a poor conductor of heat and, because the source must be loosely packed into the cell with voids to permit passage of the gas, the heat path to the centre of the cell is long and the source is not uniformly heated. Thus, the source is heated and cooled only very slowly through a large thermal resistance.
(iv) the halogen is preferentially drawn off the source nearest the exhaust port or outlet 14 and the source in this area is depleted first. This depletion can change the halogen partial pressure / temperature relationship of the cell making accurate control of the halogen partial pressure difficult. The overall effect of these four disadvantages is that temperature uniformity in the cell is poor and the source takes a long time to come into equilibrium. As a result the temperature, which determines the rate at which the halogen is evolved, is difficult to control and hence control of the halogen partial pressure is also rendered difficult. Devices of this kind are reasonably useful for research but are impractical as general purpose halogen sources.
According to the present invention there is provided a halogen generator comprising a container, a halogen source from which the halogen is to be given off arranged to be disposed in said container, the walls of said container being arranged to provide a short heat path to said halogen source and means for heating said container, said container being constructed from thick-walled material having a high thermal conductivity and having a large surface area,.
Embodiments of the present invention will now be described, by way of example only, with reference to Figures 2 to 6 of the accompanying drawings, in which, Figure 2 is a longitudinal section through a halogen generator constructed in accordance with the present invention,
Figure 3 is a section along the line A-A of Figure 2, Figure 4 is a longitudinal section through a further halogen generator also constructed in accordance with the present invention,
Figure 5 is a section along the line B-B of Figure 4, and, Figure 6 is a longitudinal section through another halogen generator constructed in accordance with the present invention. In Figures 2 and 3, cell 20 is constructed from a large diameter bar 21 of a material having a high thermal conductivity such as copper, aluminium, nickel, alumina or beryllia. A heater 22 surrounds the bar 21. Bar 21 has an internal opening along its length created by boring out three holes 23, 24 and 25, each of which partly overlaps the other two; all of which extend along the full length of the bar 21. This creates an opening along the centre of the bar 21 into which the halogen source is packed. Because of its shape the opening has a large surface area and sports ridges 26 all along its length, which together ensure that the heat path from the bar 21 to all parts of the source is short. The shape of bar 21 provides a relatively large surface area in a long cell with a wall thickness which is relatively thick, being of the order of 2mm or greater, to ensure adequate temperature uniformity.
A coating of a halogen-resistant material, such as nickel, is applied to the inside of the opening in bar 21.
Referring now to Figures 4 and 5, the cell 30 has three volumes 31, 32, 33, each of rectangular cross-section, in which the halogen source is packed. Each of these volumes is enclosed in a thick-walled material, having a wall thickness of the order of 2mm or greater, made of a high thermal conductivity material such as copper, aluminium, nickel, alumina or beryllia. The volumes are joined at their ends to a common outlet 34 through which the halogen gas is extracted and which is also used for common access to the cell.
The cell has heaters 36, 37, 38, 39 positioned one on each of the flat sides of the rectangular cross-section; its construction ensures that the thermal resistance path from the heaters to all parts of the source is low. Whilst this structure can be fabricated either from sheet or solid material, the shape of the cell is particularly suited to manufacture from an extrusion and a halogen- resistant coating can be applied to the inside surfaces of the cell during manufacture.
The low thermal resistance heat paths provide uniform heating of the source and a reliable, controllable output of halogen gas. Problems caused by initial depletion of the salt nearest the inlet, described in (iv) above, can be overcome with a cell in which the gas flow resistance is low from all parts of the cell to the exhaust port, thereby facilitating flow of halogen between all parts of the cell. Such a cell 40 is shown in Figure 6, in which a void 41 is left above the source 42 to collect the halogen. Relatively short fingers 43 transport heat from the cell walls into the source 42. A second method can be used in service to ameliorate the problem described in (iv) above. This involves isolation of the cell followed by heating. Heating will then be released by undepleted source and absorbed by depleted source so re-establishing uniform halogen coverage of the source. If desired, the initially depleted source can be cooled first so giving that source a preferential charge of halogen for future use.
The above techniques enable rapid response, large volume devices to be constructed.

Claims

CLAIMS A halogen generator comprising a container, a halogen source from which halogen or hydrogen halide is to be evolved, adapted to be disposed within said container, and means for heating said container, said container providing a short heat path to said halogen source. A halogen generator as claimed in claim 1, having a large surface area in contact with said halogen source or other halogen containing material. A halogen generator as claimed in claim 2, in which the large surface area is formed by a plurality of interconnecting holes in a bar of suitable material. A halogen generator as claimed in claim 3, in which the suitable materail has a halogen-resistant protective coating. A halogen generator as claimed in claim 2, in which the large surface area is formed by a plurality of channels. A halogen generator as claimed in claim 2, in which the large surface area is formed by a long, thin container. A halogen generator as claimed claim 5, in which the container has a circular cross-section. A halogen generator as claimed in any one of the preceding claims, which is constructed from thick- walled material. A halogen generator as claimed in any one of the preceding claims, where the wall material has a high thermal conductivity. A halogen generator as claimed in any one of the preceding claims where the container is constructed such that there is low resistance to gas flow from all parts of the cell. A method which can be used on any halogen generator as claimed in any of the preceding claims, wherein the source is isolated and heated to re-establish a uniform halogen coverage of the source.
PCT/GB1992/002151 1991-11-23 1992-11-20 Improvements in halogen generators WO1993010037A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB919124949A GB9124949D0 (en) 1991-11-23 1991-11-23 Improvements in halogen generators
GB9124949.0 1991-11-23

Publications (1)

Publication Number Publication Date
WO1993010037A1 true WO1993010037A1 (en) 1993-05-27

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1992/002151 WO1993010037A1 (en) 1991-11-23 1992-11-20 Improvements in halogen generators

Country Status (2)

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GB (1) GB9124949D0 (en)
WO (1) WO1993010037A1 (en)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3989808A (en) * 1975-07-28 1976-11-02 The United States Of America As Represented By The United States Energy Research And Development Administration Method of preparing pure fluorine gas
US4284617A (en) * 1979-11-30 1981-08-18 The United States Of America As Represented By The Secretary Of The Navy Solid compositions for generation fluorine and gaseous fluorine compounds
US4958356A (en) * 1988-10-04 1990-09-18 Fuji Electric Co., Ltd. Excimer laser apparatus
WO1991018433A1 (en) * 1990-05-23 1991-11-28 Oxford Lasers Limited Halogen generator

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3989808A (en) * 1975-07-28 1976-11-02 The United States Of America As Represented By The United States Energy Research And Development Administration Method of preparing pure fluorine gas
US4284617A (en) * 1979-11-30 1981-08-18 The United States Of America As Represented By The Secretary Of The Navy Solid compositions for generation fluorine and gaseous fluorine compounds
US4958356A (en) * 1988-10-04 1990-09-18 Fuji Electric Co., Ltd. Excimer laser apparatus
WO1991018433A1 (en) * 1990-05-23 1991-11-28 Oxford Lasers Limited Halogen generator

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
R.B.BIRD ET AL. 'Transport Phenomena' 1960 , JOHN WILEY & SONS , NEW YORK *

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Publication number Publication date
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