Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
  • C21D9/54—Furnaces for treating strips or wire
  • C21D9/663—Bell-type furnaces
  • C21D9/667—Multi-station furnaces
  • C21D9/67—Multi-station furnaces adapted for treating the charge in vacuum or special atmosphere
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
  • C21D1/76—Adjusting the composition of the atmosphere
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/30—Details, accessories, or equipment peculiar to furnaces of these types
  • F27B9/40—Arrangements of controlling or monitoring devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
  • F27D17/008—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases cleaning gases
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D19/00—Arrangements of controlling devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D7/00—Forming, maintaining, or circulating atmospheres in heating chambers

Definitions

• the present invention is a method of removing oxygen molecules present in a furnace atmosphere comprising the step of: reacting the oxygen molecules from the furnace atmosphere on one or more catalytic reactors.
• the present invention is a method for using a catalytic deoxygenation reactor having a furnace atmosphere comprising hydrogen gas (up to 100%) in order to avoid oxygen build-up in the furnace.
• the reactor may be placed inside the furnace and may be located along the pathway of ingressing gas whereby the oxygen in the ingressing gas will be catalytically converted with hydrogen from the furnace's atmosphere to water vapor (H 2 O).
• the reactor comes into contact with the oxygen molecules in the atmosphere by the movement of the gases in the furnace atmosphere.
• atmosphere moving equipment for example, fans, pumps, or vacuums
• fans, pumps, or vacuums can be provided to move the gases in the furnace atmosphere to foster the contact between the oxygen and hydrogen molecules and the reactor.
• fan(s), pump(s) or vacuum(s) could be used to draw the atmosphere into a reactor that is located external to the furnace, and the atmosphere gases with the reduced molecular oxygen content could be reintroduced into the furnace downstream of the reactor.
• the reactor may be located adjacent to or mounted onto the furnace and the gases having the reduced molecular oxygen content could be immediately returned to the furnace atmosphere after passing through the reactor.
• the invention can lower oxygen levels in the furnace and may prevent oxidation of materials that are being processed in and by the furnace.
• this invention provides a furnace comprising an atmosphere and at least one catalytic reactor for removing oxygen molecules present in the atmosphere.
• furnaces and methods for safe operation of furnaces (avoiding the accumulation of oxygen to an unsafe level in the furnace) having a hydrogen-containing atmosphere; furnaces and methods that may avoid or reduce the number of shut-downs and/or nitrogen purgings of furnaces due to air ingression; furnaces and methods that eliminate or reduce the amount of unwanted oxidation of the materials processed in furnaces; furnaces and methods that increase the productivity of furnaces; and furnaces and methods that decrease the production costs of the materials treated in furnaces.
• FIG. 1 is a schematic longitudinal cross-sectional view of the exit end of a furnace with the installation of a reactor according of the present invention.
• FIG. 2 is a schematic longitudinal cross-sectional view of the exit end of a furnace with the installation of a reactor according of the present invention.
• FIG. 3 is a schematic transverse cross-sectional view of a reactor useful in the present invention.
• Fig. 4 is a schematic longitudinal cross-sectional view of the entrance end of a furnace showing the placement of a reactor in the front end of the furnace.
• Fig. 5 is a schematic longitudinal cross-sectional view of the entrance end of a furnace showing the placement of a reactor in the supply line to a recovery system from the front end of the furnace.
• This invention is directed to a method of using a catalytic reactor typically inside a furnace, for example at the exit end curtain area of a furnace or kiln.
• the furnace comprises hydrogen gas in its atmosphere (up to 100%).
• the reactor catalytically converts to water any oxygen leaking-in from the outside of the furnace or internal sources within the furnace.
• furnace will be used to mean any piece of thermal process equipment with protective or reactive atmosphere capability.
• furnaces may include heat- treating furnaces, continuous belt furnaces, rotary furnaces, box furnaces, strand furnaces, strip furnaces, roller-hearth furnaces, float glass furnaces, ceramic kilns, and others that would be known to the art. These furnaces can be used in processing metal, composites or ceramic materials, including sintering, annealing, carburizing, decarburizing, hardening, brazing, nitriding, melting, glass-making and the like.
• the atmosphere in the furnace is typically a hydrogen-containing atmosphere.
• the desired hydrogen-containing atmosphere can contain any amount of hydrogen, typically between 5 and 100%.
• the balance of the hydrogen-containing atmosphere can be made up of inert gases and/or reactive gases depending upon the process requirements.
• inert gases can be nitrogen, argon and helium.
• reactive gases may include CO, CO 2 , propane, methane, ethane, and other alkanes, natural gas, silane, ammonia, and the like.
• This invention is used to maintain a desired atmosphere within the furnace.
• the reactor and method of this invention may be used in conjunction with separate atmosphere generating equipment that may be located inside or outside the furnace. The atmosphere generating equipment will have one or more sources outside the furnace for the gases to be fed, or to be generated and then fed, into the furnace atmosphere.
• the term ingressing gas will be used to describe an undesired source of oxygen into the furnace atmosphere.
• the present invention is a method to prevent undesired ingressing gas from causing a build up of oxygen in a furnace having a hydrogen-containing atmosphere.
• the ingressing gas can be air that enters the furnace, or it can be a gas that is present as an impurity or impurities in a source for the atmosphere of the furnace (for example, oxygen in a hydrogen gas supply or unreacted oxygen from atmosphere generating equipment).
• Ingress of air can be from leaking flanges, pipe connections, ports, the entrance and exit for the materials to be processed in the furnace or other openings into the furnace.
• Ingressing gas, particularly air may result from furnace design, furnace wear, or from changing the size or shape of a material to be processed in a furnace.
• the source of the ingressing gas may be from the material being processed in the furnace.
• the catalytic reactor comprises catalytic materials, such as platinum, palladium, nickel, noble-metals, rhodium, ruthenium, or other materials that promote the reaction of hydrogen and/or reactive gases/hydrocarbons (if present in the furnace atmosphere) with oxygen.
• the reactor may comprise catalyst alone or a support to hold the catalyst or onto which the catalyst may be coated or adhered. Examples of support materials include alumina, or other ceramic or metallic powders, strips, honeycombs, screens, semi- conductive materials, porous silicon, other porous materials and designs or other support forms.
• the reactor may be located anywhere in the furnace. Typically the reactor is located near a source of the ingressing gas which is often at the entrance or exit of the furnace.
• the reactor is near the source of the ingressing gas so that a majority of the ingressing gas contacts the reactor before it has dispersed within the atmosphere as a whole.
• the reactor is considered near the source for the ingressing gas if it is less than ten feet away from the source of the ingressing gas.
• the reactor is particularly useful in furnaces or in sections of furnaces having a hydrogen-containing atmosphere and/or in sections of the hydrogen-containing atmosphere where the temperature of the atmosphere is lower than the auto-ignition temperature of the gases in the atmosphere, such as in the exit end or cooling zone of a furnace.
• the temperature of the furnace may be below 579 0 C at atmospheric pressure (auto-ignition temperature for hydrogen).
• the auto-ignition temperature for the atmosphere will depend on the composition of gases in the atmosphere and the pressure in the furnace. At temperatures below the auto-ignition temperature for the composition of the atmosphere, if the reactor of this invention were not present, the oxygen in the ingressing gas (for example, air) would not react with the hydrogen (and hydrocarbons) in the furnace atmosphere to form water vapor (and CO or CO 2 ), and would consequently accumulate inside the furnace.
• the oxygen in the ingressing gas for example, air
• the catalytic reactor could also take the form of a furnace curtain material or coating on a curtain material, for example a fiberglass curtain material, or other air ingress blocking means, such as a flap or flexible or inflexible physical barrier being constructed out of catalytically active material.
• the catalyst could be powders or beads or catalytic coatings on beads or powders that are used to block the furnace exit, which would ensure that oxygen is reacted at the point of entering the furnace or upon initially mixing with the furnace atmosphere with the hydrogen or hydrocarbon to form water vapor or carbon dioxide or carbon monoxide, which is less reactive than oxygen to the materials being processed and safer if present in a hydrogen-containing atmosphere.
• the catalytic reactor comprises the catalytic materials packed inside a support which can be made of stainless steel and can have two screened walls on opposite ends of the reactor that allow gas to readily pass through the reactor.
• the reactor can be sized, for example having the same width as the width of the interior of the furnace, and otherwise designed for maximum ingressing-gas contact, and located in the furnace that a large portion or a majority of the ingressing gas cannot by-pass the reactor.
• the operation of the catalytic reactor inside the furnace can be monitored by placing a thermocouple inside the catalytic reactor, and another thermocouple outside the catalytic reactor inside the furnace, for example, facing the furnace exit end as shown in Figure 1.
• a thermocouple inside the catalytic reactor
• another thermocouple outside the catalytic reactor inside the furnace, for example, facing the furnace exit end as shown in Figure 1.
• H 2 +O 2 - H 2 O
• heat will be generated inside or on the surface of the reactor and the reactor's temperature will rise. Therefore, the temperature difference between the two thermocouples (or multiple sets of thermocouples) can be used as an indication of the presence and/or the amount of oxygen inside the furnace.
• oxygen monitors can be used to measure (directly or indirectly) the oxygen concentration or dew point inside the furnace at the appropriate location(s), which can be used to indicate if deoxygenation reactions due to the presence of the reactor are occurring.
• reactor of this invention can be used for removing oxygen from the gases in the atmosphere that pass through the reactor at low pressures, for example, less than 1 psig or less than 0.5 psig.
• the pressures in or near the inlet piping to the recycling system from the furnace may be less than 1 psig or less than 0.5 psig.
• Figure 1 shows a schematic representation of the exit end of a continuous belt furnace 10 for processing a material 15 in the furnace, for example, annealing of metallic powders 15.
• the furnace includes a hydrogen-containing gas inlet 12 to supply hydrogen- containing gas atmosphere for the furnace, a solid conveyor belt 11 to carry metallic powders 15 through the furnace, an inert gas, for example nitrogen, purge inlet 13, a physical curtain 14 at the exit end of the furnace to prevent air from leaking into the furnace, and an oxygen content monitoring sample port 16.
• the atmosphere 112 is all the gas inside the furnace containing the materials 15 to be processed in the furnace.
• the material to be processed in the furnace may move in the direction indicated by arrow A, the gas in the atmosphere may move in the direction indicated by arrow B.
• the furnace When the oxygen monitor 16 shows a high oxygen level in the furnace, the furnace will be shut down and purged with the inert gas; however, the reactor 17 will help to reduce the frequency for an inert gas safety purge and shut down.
• the shut-down and/or purge steps may be fully automated by a processing means (for example, a computer and electronic controls) that is not shown. Alternatively, the shut down and/or purge steps may be controlled by an operator.
• the door 19 and physical curtain 14 (as depicted in Figure 1 ) of the current furnace design cannot adequately prevent all the ingressing gas (for example, air) from entering the furnace 10.
• an in situ catalytic deoxygenation reactor 17 in accordance with the present invention and an optional differential thermocouple monitor 18 are provided in the furnace.
• the operation of the catalytic reactor 17 is monitored by the differential thermocouple 18 based on the exothermic characteristic of the chemical reaction between oxygen and hydrogen.
• the reactor could comprise catalytic material coated on the physical curtain 14 alone or in addition to the reactor 17 as shown. If desired, catalyst could be provided on one or more other fixtures or structures within the furnace and/or on the internal surfaces of the furnace walls if desired.
• Figure 2 shows a similar furnace 20 as in Figure 1 but as shown the furnace 20 has a powder, bead, or shell barrier or lock 24 instead of a physical curtain 14 as shown in Figure 1.
• the furnace 20 has an in situ catalytic deoxygenation reactor 27 and an optional differential thermocouple monitor 28.
• the catalytic reactor is shown as located within the furnace 20. With the invented method, any oxygen leaking through the physical curtain 24 will be catalytically converted in or on the catalytic reactor 27 to water vapor by reacting the oxygen molecules with hydrogen present in the furnace's atmosphere 122.
• the additional elements of the furnace 20 shown in Figure 2 are the hydrogen inlet 22, the gas sample port 26 for the atmosphere 122, and the exit door 29 for the furnace.
• FIG 3 shows the front view of the catalytic reactor 70 similar to the one shown in a side view in Figure 1 or 2.
• the reactor includes a catalytic material 71, for example, a palladium metal supported on aluminum oxide (AI 2 O 3 ) powders, packed inside a porous container support 72, for example, a stainless steel container with two screened openings 74 on its front and back walls facing each other to allow gases to pass through the reactor.
• a flexible foil or flap 73 which may comprise stainless steel or any useful composition, is attached and may contact the material to be processed in a furnace to prevent ingressing gas or oxygen molecules in the atmosphere from passing under the reactor 70.
• the reactor 70 may be sized so that the top 76 of the reactor contacts and/or may be mounted on the ceiling of the furnace, the sides 77 and 78 of the reactor contact and/or may be mounted on the side walls of the furnace and the bottom 75 is in contact with or nearly contacting the material to be processed by the furnace.
• oxygen accumulation in the furnace may be reduced or may not occur, and the furnace can run continuously for a longer campaign without the need for shutting down and purging the furnace with inert gas. Additionally less of the material to be processed by the furnace may be oxidized.
• FIG 4 shows the front end of a furnace 40 similar to the furnaces previously shown, but with the installation of an in situ catalytic deoxygenation reactor 47 according to the present invention located in the front end of the furnace.
• the reactor located at the entrance end 49 of the furnace may be used to reduce the amount of oxygen in the furnace 40.
• the materials 45 being processed in the furnace may move in the direction indicated by arrow A on the conveyor belt 41.
• the gases in the atmosphere 142 mayflow in the direction indicated by arrow B.
• Figure 5 shows an embodiment in which a reactor 57 is used in the intake pipe 81 of a recovery or recycling system.
• the recycling system 80 of the hydrogen-containing atmosphere from the furnace is used to remove impurities from the hydrogen-containing atmosphere, typically to create a recycled hydrogen gas stream with less than 5%, less than 3% or less than 1 % impurities, and then the hydrogen may be reused in the furnace atmosphere.
• the reactor 57 is placed in the intake pipe 81 as shown.
• the reactor could be placed across the entrance 82 to the intake pipe or multiple reactors could be used, for example the reactor shown in Figure 4 could be used with the reactor shown in Figure 5.
• One or more reactors can be used in a furnace to remove the oxygen from the atmosphere. If multiple reactors are used they can be located in various locations and have different designs.
• the reactor shown in Figure 1 can be used in conjunction with the reactor shown in Figure 5, or the reactor shown in Figure 1 can be used with a reactor that is coated on an exit curtain (not shown) and/or with the reactor shown in Figure 4.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Environmental & Geological Engineering (AREA)
• Furnace Details (AREA)

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• 2006
  • 2006-11-08 US US11/594,477 patent/US20070107818A1/en not_active Abandoned
  • 2006-11-10 KR KR1020087013941A patent/KR20080084942A/ko not_active Application Discontinuation
  • 2006-11-10 WO PCT/US2006/060764 patent/WO2007114853A2/en active Application Filing
  • 2006-11-10 CA CA002628610A patent/CA2628610A1/en not_active Abandoned
  • 2006-11-10 EP EP06850135A patent/EP1971693A2/de not_active Withdrawn

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