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WO2025245069A1 - Système secondaire d'injection d'oxygène, cubilot et procédés de fonctionnement - Google Patents

Système secondaire d'injection d'oxygène, cubilot et procédés de fonctionnement

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Publication number
WO2025245069A1
WO2025245069A1 PCT/US2025/030130 US2025030130W WO2025245069A1 WO 2025245069 A1 WO2025245069 A1 WO 2025245069A1 US 2025030130 W US2025030130 W US 2025030130W WO 2025245069 A1 WO2025245069 A1 WO 2025245069A1
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WO
WIPO (PCT)
Prior art keywords
oxygen injection
cupola furnace
primary
hour
scfm
Prior art date
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Pending
Application number
PCT/US2025/030130
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English (en)
Inventor
David J. KASUN
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Atd Engineering & Machine LLC
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Atd Engineering & Machine LLC
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Filing date
Publication date
Application filed by Atd Engineering & Machine LLC filed Critical Atd Engineering & Machine LLC
Publication of WO2025245069A1 publication Critical patent/WO2025245069A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B13/00—Making spongy iron or liquid steel, by direct processes
    • C21B13/02—Making spongy iron or liquid steel, by direct processes in shaft furnaces
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B13/00—Making spongy iron or liquid steel, by direct processes
    • C21B13/0006—Making spongy iron or liquid steel, by direct processes obtaining iron or steel in a molten state
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B7/00—Blast furnaces
    • C21B7/16—Tuyéres
    • C21B7/163—Blowpipe assembly
    • 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
    • F27B1/00—Shaft or like vertical or substantially vertical furnaces
    • F27B1/10—Details, accessories or equipment specially adapted for furnaces of these types
    • 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
    • F27B3/00—Hearth-type furnaces, e.g. of reverberatory type; Electric arc furnaces ; Tank furnaces
    • F27B3/10—Details, accessories or equipment, e.g. dust-collectors, specially adapted for hearth-type furnaces
    • F27B3/22—Arrangements of air or gas supply devices
    • F27B3/225—Oxygen blowing
    • 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
    • F27D17/10—Arrangements for using waste heat
    • 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
    • F27D17/20—Arrangements for treatment or cleaning of waste 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
    • F27D3/00—Charging; Discharging; Manipulation of charge
    • F27D3/16—Introducing a fluid jet or current into the charge
    • 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
    • F27D7/02—Supplying steam, vapour, gases or liquids
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B5/00—Making pig-iron in the blast furnace
    • C21B5/001—Injecting additional fuel or reducing agents

Definitions

  • the present teachings generally relate to secondary oxygen injection systems; cupola furnaces, particularly coke-fired cupolas; and methods of operating the same.
  • Cupola furnaces are conventionally used in iron production processes, primarily for foundries.
  • Cupolas have a furnace shaft that is loaded with weighed batches, or charges, each containing coke, flux, and metallic material (e.g., metallic scrap, various metallurgical alloys, etc.).
  • Combustion of the coke in the bottom of the cupola shaft furnace is relied upon to melt the metallics, and to calcine the fluxes, typically at temperatures of about 2200 °C to about 3050 °C in the combustion zone of the cupola.
  • Oxygen for combustion is typically added using blast of ambient air, and often with additional high purity oxygen injection or enrichment via primary tuyeres to maintain melt conditions for the metallics. This is referred to as primary blast and injection.
  • the charges are converted to liquid metal (e.g., iron), draining down to the bottom of the cupola where they are tapped out, additional charges are added into the top of the cupola over the duration of a production session.
  • liquid metal e.g., iron
  • the cupola operates continuously, provided that primary blast and oxygen injection is provided into the primary tuyeres. Melting will suspend, or stop, when the primary blast and oxygen injection is stopped.
  • Waste gasses that includes a relatively high calorific value composition due to the primary content of carbon monoxide and a comparatively lower content of hydrogen. Hydrocarbons and volatile organic compounds may also be volatilized from some charge materials that are added to the furnace. The waste gasses rise through the cupola, preheating the descending charges, and cooling rapidly as they rise, before ultimately exiting the system. Waste gasses present two primary challenges, both related to emission discharge air quality. The first is due to the high particulate content, which must be scrubbed or filtered prior to emission. The second is due to the gaseous pollutant content of the gas, where carbon monoxide, volatile compounds, and hydrogen, must be incinerated prior to emission.
  • the present disclosure relates to a secondary oxygen injection system which may address at least some of the needs identified above.
  • the secondary oxygen injection system may be used in a cupola furnace.
  • the secondary oxygen injection system may comprise: one or more oxygen injection devices; a first supply line in fluid communication with the one or more oxygen injection devices and supplying oxygen to the one or more oxygen injection devices.
  • the oxygen may influence combustion of waste gasses produced by a primary combustion within the cupola furnace.
  • the one or more oxygen injection devices may be arranged in one or more levels above a melting zone of the cupola furnace and below a charging door of the cupola furnace, each of the one or more levels being defined by a height along the cupola furnace, such as a height above primary tuyere holders of the cupola furnace.
  • Each of the one or more levels may provide a ratio of the oxygen to a total primary oxygen of about 0.02 to about 0.5.
  • the oxygen and the total primary oxygen may be represented as the molecular oxygen volume. Stated differently, the ratio is of the molecular oxygen volume of the oxygen of the secondary oxygen injection system and the molecular oxygen volume of the total primary oxygen.
  • the total primary oxygen may include oxygen in the blast (ambient oxygen, which is typically about 21% oxygen) enrichment oxygen and/or injection oxygen, as described herein.
  • Each of the one or more levels may provide a flow rate of the oxygen of at least about 25 SCFM (standard cubic feet per minute, relative to a reference temperature of 60 °F (about 16 °C) (about 40 Nm 3 /hour), but more preferably about 100 SCFM (about 161 Nm 3 /hour) to about 400 SCFM (about 643 Nm 3 /hour).
  • the one or more oxygen injection devices may include three to six of the one or more oxygen injection devices per each of the one or more levels.
  • the secondary oxygen injection system may comprise two, three, four, five, or even six of the one or more levels.
  • the one or more oxygen injection devices may be spatially distributed generally equally around a perimeter of the cupola furnace.
  • the one or more levels may be situated in the cupola furnace in a region where an operating temperature of the cupola furnace is about 1,500 °F (about 815 °C) to about 2,000 °F (about 1,093 °C).
  • a first level of the one or more oxygen injection devices may be located at least about 36 inches (about 90 centimeters) to about 72 inches (about 183 centimeters), more preferably about 45 inches (about 114 centimeters) to about 60 inches (about 152 centimeters), or even more preferably about 55 inches (about 140 centimeters) above the top of the primary tuyere holders of the cupola furnace.
  • Each of the one or more levels are separated by about 12 inches (about 30 centimeters) to about 36 inches (about 91 centimeters).
  • the one or more oxygen injection devices may eject the oxygen at an average speed of from about Mach 1 to about Mach 2.5.
  • Each of the one or more oxygen injection devices may be adapted and configured to deliver oxygen at a flow rate of about 30 SCFM (about 48 Nm 3 /hour) to about 70 SCFM (about 113 Nm 3 /hour), more preferably about 50 SCFM (about 80 Nm 3 /hour) to about 70 SCFM (about 113 Nm 3 /hour)
  • Each of the one or more oxygen injection devices may be adapted to deliver oxygen at a pressure of about 60 pounds per square inch (PSI) (0.41 MegaPascal) to about 120 PSI (0.83 MegaPascal).
  • PSI pounds per square inch
  • the oxygen may be supplied with a purity of at least about 88%, more preferably at least about 90%, more preferably at least about 95%, or even more preferably at least about 99%.
  • the one or more oxygen injection devices may comprise an adapter including external threads for cooperating in a threaded engagement with the cupola furnace, or may comprise a quick disconnect coupling.
  • the secondary oxygen injection system may further comprise a second supply line for supplying nitrogen to a region of the one or more injection devices for at least managing a temperature of the one or more injection devices.
  • the second supply line may be in fluid communication with one or more ports in which, respectively, the one or more oxygen injection devices may be located.
  • the second supply line may provide for a flow rate of the nitrogen of about 1 SCFM (about 1.6 Nm 3 /hour) to about 3 SCFM (about 4.8 Nm 3 /hour).
  • the one or more oxygen injection devices may be characterized by one or more of the following: a channel defined by an inner diameter and a length, the ratio of the inner diameter to the length being about 0.042 to about 0.058; the adapter defined by a diameter, wherein a ratio of the length of the channel to the diameter of the adapter is about 10 to about 30; a nozzle having an inlet, a reduction, and an outlet, each being defined by a diameter and a length; and being a supersonic direct injection nozzle (e.g., a de Laval nozzle).
  • a ratio of the inlet diameter to the reduction diameter may be about 2.4 to about 2.8, a ratio of the inlet diameter to the outlet diameter may be about 1.8 to about 2.2, a ratio of the reduction diameter to the outlet diameter may be about 0.5 to about 0.9, a ratio of the inlet length to the reduction length may be about 2.3 to about 2.7, a ratio of the inlet length to the outlet length may be about 0.6 to about 1.0, and/or a ratio of the reduction length to the outlet length may be about 0.1 to about 0.5.
  • the secondary oxygen injection system may comprise one or more flow rate detection devices.
  • the secondary oxygen injection system may comprise one or more pressure sensors.
  • the secondary oxygen injection system may comprise one or more temperature sensors.
  • the secondary oxygen injection system may comprise a gas composition analysis device for providing feedback from the waste gasses escaping the cupola.
  • the waste gasses may comprise carbon monoxide, carbon dioxide, oxygen, hydrogen, or any combination thereof.
  • the gas composition analysis device may be capable of detecting one or any combination of these waste gasses. Multiple gas composition analysis devices may be employed, each for detecting a particular waste gas.
  • the secondary oxygen injection system may comprise one or more first flow control devices for increasing or decreasing the flow rate and/or a pressure of the oxygen in the first supply line; and/or one or more second flow control devices for increasing or decreasing the flow rate and/or a pressure of the nitrogen in the second supply line.
  • the secondary oxygen injection system may comprise one or any combination of the foregoing devices.
  • the secondary oxygen injection system may comprise a controller for implementing computerexecutable instructions.
  • One or more inputs may be provided from the one or more flow rate detection devices, the one or more pressure sensors, the one or more temperature sensors, or any combination thereof.
  • One or more outputs are determined therefrom, the one or more outputs relating to a physical state of the one or more first and/or second flow control devices.
  • the controller may be in signal communication with the one or more first and/or second flow control devices.
  • the present disclosure relates to a cupola furnace which may address at least some of the needs identified above.
  • the cupola furnace may comprise the secondary oxygen injection system characterized by one or any combination of the foregoing paragraphs. As described herein, the cupola furnace may
  • the one or more levels of the secondary oxygen injection system may be situated in the cupola furnace in a region where an operating temperature of the cupola furnace is about 1,500 °F (about 815 °C) to about 2,000 °F (about 1,093 °C).
  • the cupola furnace may comprise one or more ports for respectively receiving the one or more oxygen injection devices.
  • the second supply line may fluidly communicate with the one or more ports and supply the nitrogen to the one or more ports, for managing the temperature of the one or more oxygen injection devices, purging the one or more ports, or both.
  • the one or more oxygen injection devices, engaged with the cupola furnace may be oriented at an angle of about 0 degrees to about 15 degrees.
  • the one or more oxygen injection devices may be oriented parallel to a surface upon which the cupola furnace is situated or downward at the angle of up to about 15 degrees.
  • the cupola furnace may be defined by one or any combination of the following characteristics: hot blast, having a water-cooled cascade shell (e.g., a steel shell), having a full refractory lining, a tuyere circle diameter of about 60 inches (about 152 centimeters), a furnace inner diameter (“ID”) (shell diameter) of about 104 inches (about 264 centimeters), a working ID of about 86 inches (about 218 centimeters), a refractory lining thickness of about 9 inches (about 23 centimeters), a tuyere outlet diameter of about 4 inches (about 10 centimeters), a blast flow rate of about 6,800-7,200 SCFM (about 10,932- 11,576 Nm 3 /hour), supersonic direct oxygen injection rate of about 3-4%, a stack height of about 29 feet (about 9 meters), and a typical (without the secondary oxygen injection described herein) melt rate of about 33 short tons (about 30 metric tons).
  • a water-cooled cascade shell e
  • a cupola furnace with characteristics being +/-30% or less, +/-20% or less, or even +/-10% or less of one or any combination of the foregoing numerical values is also contemplated, but the present teachings are not intended to be limited in this regard.
  • the present teachings are not intended to be limited by these characteristics of cupola furnace.
  • the present teachings may be applied to any suitable cupola-style furnace.
  • the foregoing characteristics may be understood as merely exemplary, to provide context to process improvements described herein (e.g., melt rate, efficiency, etc.).
  • an exemplary cupola furnace described herein may have a typical melt rate of about 30 metric tons per hour
  • a cupola furnace having a typical melt rate of about 10 metric tons per hour may proportionately realize the process improvements of the secondary oxygen injection system described herein (e.g., increased by at least about 3% to at least about 50% as described herein).
  • the foregoing is applicable to all embodiments.
  • a coke rate of the cupola furnace may be decreased by at least about 15% and up to about 45% relative to a cupola furnace without the secondary oxygen injection system.
  • a melt rate of the cupola furnace may be increased by at least about 3% and up to about 60% relative to a cupola furnace without the secondary oxygen injection system.
  • a primary blast rate and/or primary oxygen injection or primary oxygen enrichment rate of the cupola furnace may be decreased by at least about 3% and up to about 40% relative to a cupola furnace without the secondary oxygen injection system.
  • the present disclosure relates to a method of operating a cupola furnace which may address at least some of the needs identified above.
  • the method may comprise supplying a primary blast and a primary oxygen injection or enrichment via a first supply line, and additionally supplying a secondary oxygen injection via a second supply line at one or more levels above the primary blast and primary oxygen injection or enrichment.
  • the method may comprise providing by each of the one or more levels a ratio of the oxygen to a total primary oxygen of about 0.02 to about 0.5, as described above.
  • the method may comprise providing the secondary oxygen injection at a flow rate of at least about 25 SCFM (about 40 Nm 3 /hour), but more preferably about 100 SCFM (about 161 Nm 3 /hour) to about 400 SCFM (about 643 Nm 3 /hour).
  • the method may comprise delivering the secondary oxygen injection into a region of the cupola furnace that is about 36 inches (about 90 centimeters) to about 72 inches (about 183 centimeters), more preferably about 45 inches (about 114 centimeters) to about 60 inches (about 152 centimeters), or even more preferably about 55 inches (about 140 centimeters) above the top of the primary tuyere holders of the cupola furnace.
  • the method may comprise reducing a primary blast rate and flow rate of the primary oxygen injection or enrichment, in proportion to the flow rate of the secondary oxygen injection, when the secondary oxygen injection is turned on, to avoid overproduction in the melting zone.
  • the flow rate of the primary oxygen injection or enrichment may be reduced by about 15% to about 30%.
  • the flow rate of the primary oxygen injection or enrichment may be about 310 SCFM (about 498 Nm 3 /hour) to about 400 SCFM (about 643 Nm 3 /hour).
  • the secondary oxygen injection may be provided at an average speed of about Mach 1 to about Mach 2.5.
  • the secondary oxygen injection may be supplied after initiation of the primary blast and primary oxygen injection or enrichment.
  • the secondary oxygen injection may be supplied no sooner than about 5 minutes after initiation of the primary blast and the primary oxygen injection or enrichment.
  • the primary blast may be at a rate of about 6,800 SCFM (about 10,929 Nm 3 /hour) or less, about 6,400 SCFM (about 10,286 Nm 3 /hour) or less, about 6,000 SCFM (about 9,643 Nm 3 /hour) or less, about 5,600 SCFM (about 9,000 Nm 3 /hour) or less, or at least about 5,200 SCFM (about 8,357 Nm 3 /hour).
  • the cupola furnace may be operated at a coke rate of about 480 lb (pounds) (about 218 kg (kilograms)) per charge or less, about 460 lb (about 209 kg) per charge or less, about 440 lb (about 200 kg) per charge or less, or at least about 420 lb (about 191 kg) per charge.
  • the cupola furnace may be operated at a melt rate of about 35 short tons (about 32 metric tons) per hour or more, about 37 short tons (about 34 metric tons) per hour or more, about 39 short tons (about 35 metric tons) per hour or more, about 41 short tons (about 37 metric tons) per hour or more, about 43 short tons (about 39 metric tons) per hour or more, even about 45 short tons (about 41 metric tons) per hour or more.
  • the method may comprise receiving one or more inputs from one or more flow rate detection devices, one or more pressure sensors, one or more temperature sensors, one or more gas composition analysis devices, or any combination thereof.
  • the first and/or second flow control devices may be actuated based on the one or more inputs.
  • the one or more levels may be selectively activated and/or deactivated based on the one or more inputs.
  • the method may comprise increasing or decreasing the flow rate and/or the average speed of the oxygen via a first flow control device.
  • the method may comprise increasing or decreasing the flow rate and/or the average speed of the nitrogen via a second flow control device.
  • the method may comprise increasing or decreasing the flow rate and/or the average speed of the primary blast and primary oxygen injection or enrichment.
  • the method may be performed, at least in part, by one or more controllers implementing one or more computer-executable instructions.
  • the one or more computer-executable instructions may be stored on a non-transitory memory storage medium.
  • the one or more computer-executable instructions may take one or more inputs from one or any combination of the above-described devices.
  • the one or more computer-executable instructions may perform one or more operations on the one or more inputs (e.g., executing an algorithm, referencing a look-up table, extrapolating from an empirical model, or the like). Based on the one or more operations, one or more control signals may be generated.
  • the one or more control signals may be used to ultimately change a physical state of one or more of the abovedescribed devices. Stated differently, the one or more control signals may contribute to the practical application of operating a cupola furnace.
  • the cupola furnace may be operated at a coke rate that is decreased by at least about 15% and up to about 45% relative to a cupola furnace without the secondary oxygen injection system.
  • the cupola furnace may be operated at a melt rate that is increased by at least about 3% and up to about 60% relative to a cupola furnace without the secondary oxygen injection system.
  • the cupola furnace may be operated at a primary blast rate that is decreased by at least about 3% and up to about 40% relative to a cupola furnace without the secondary oxygen injection system.
  • the method may comprise supplying nitrogen to the one or more oxygen injection devices when the cupola furnace is idling or turned off. [0060] The foregoing method may be performed, at least in part, with the secondary oxygen injection system described in one or any combination of the foregoing paragraphs.
  • the foregoing method may be performed, at least in part, with the cupola furnace described in one or any combination of the foregoing paragraphs.
  • FIG. 1 is a schematic of the secondary oxygen injection system according to the present teachings.
  • FIG. 2 is a perspective view of an oxygen injection device according to the present teachings.
  • FIG. 3 is a plan view of the oxygen injection device.
  • FIG. 4 is a sectional view the oxygen injection device.
  • FIG. 5 is a plan view of an adapter of the oxygen injection device.
  • FIG. 6 is a sectional view of an adapter of the oxygen injection device.
  • FIG. 7 is a sectional view of a nozzle of the oxygen injection device.
  • FIG. 8 is a sectional view of an exemplary cupola furnace.
  • the present teachings generally relate to a cupola shaft furnace for cast iron production in foundries.
  • the present teachings are not intended to be limited to cupola shaft furnaces, but may relate to other cupola furnaces, such as those for the reduction and melting of carbon-bearing oxide wastes, those for the melting of virgin rock, stone, concrete, bricks, blast furnace slag, or other materials conventionally used for mineral wool production.
  • Cupola furnaces (“cupolas” or “cupola-style furnaces”) may comprise a chamber divided into combustion, melting, reducing, preheating, and stack zones.
  • the chamber is vertically-extending and generally is provided as a generally cylindrical shape.
  • a charging door or charging throat is provided in the upper stack zone and functions to receive coke, flux, and metallics and/or alloys, to charge the chamber.
  • the present application may describe specific applications with iron production, the production of other metals via other furnace configurations is contemplated.
  • the present teachings contemplate metal materials including recycled materials from prior uses.
  • the chamber may be charged with an initial quantity of the same, and may be replenished from time-to-time during a session, referred to as charges.
  • Alternating layers of coke, flux, and metal may extend from the charging door, through the preheating zone, to the melting zone.
  • a coke bed occupies the combustion, melting, and reducing zones.
  • carbon monoxide is produced and, in concert with other gasses, mitigates oxidation of the metallics and/or alloys.
  • metallics and/or alloys are melted, where liquid metal trickles through the coke bed, and is ultimately tapped from the cupola.
  • the material located in the preheating zone is progressively heated by the sensible heat transfer resulting from the heat generated in the lower section from the thermodynamic processes occurring in lower layers. Generally, a temperature gradient is observed extending through the preheating zone.
  • the present teachings contemplate that supplemental heating of the preheating zone may ultimately reduce the coke requirements in the combustion, melting, and reducing zones, to maintain the requisite operating temperatures of the cupola.
  • the present teachings propose combusting (oxidizing) the waste gasses rising through the preheating zone.
  • the present teachings refer to this concept as secondary oxygen (02) injection or secondary gas combustion. That is, the system of the present teachings may be understood as distinct from the primary gas injection and/or combustion systems operating in at least the combustion zone of the typical cupola shaft furnace.
  • the primary gas injection and/or combustion system may provide enrichment oxygen and/or injection oxygen, as described herein.
  • the waste gasses include significant concentrations of carbon monoxide (CO), hydrogen (H2), one or more hydrocarbons (HCs), one or more volatile organic compounds (VOCs), or any combination thereof.
  • CO carbon monoxide
  • H2 hydrogen
  • HCs hydrocarbons
  • VOCs volatile organic compounds
  • the waste gasses may be generated based on combustion of coke, flux, metallics, alloys, or any combination thereof; chemical reactions downstream of combustion; moisture presence; or any combination thereof.
  • Hydrocarbons and volatile organic compounds may also be present to a significant degree, depending on the composition of the charge.
  • waste products such as used special scrap steels sought to be reclaimed for their metal content, may contribute to hydrocarbon vapor and volatile organic compound content in the waste gasses.
  • the hydrocarbons and volatile organic compounds may contribute to heating in the preheat zone via the secondary combustion described herein.
  • the present teachings may provide benefits with charges containing such waste products, by combusting a significant portion of the associated waste gasses.
  • additional heat is reclaimed, and transferred to the metallics and/or alloys in the charges that are descending down the cupola shaft, and this increased heat recovery will result in coke reductions in the charges, with a resulting decrease in calorific heating value and total waste gas volume before recapture or final emission venting into the atmosphere.
  • Nitrogen may be present with the waste gasses, as a portion of the primary blast combustion air. Although, nitrogen is inert, so it does not contribute to the secondary combustion of described herein.
  • the present teachings contemplate that substantial or complete combustion of the waste gasses may occur. That is, about 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, or even 95% or more of the waste gasses generated, from primary blast and injection, may be combusted. In this regard, downstream systems for managing gases that would otherwise be expelled from the cupola may remain, but the system of the present teachings may reduce the demands on such gas management systems.
  • the time delay between adding a charge and when it becomes affected by the secondary oxygen injection may be determined. This time delay may be as low as about 15 minutes but can be about 2 hours or more, depending on the furnace throughput, diameter, height, and the like. A minimum threshold of coke in the coke bed may be desirable in the event the cupola is idled for an extended period of time.
  • the minimum threshold of coke is not maintained, or it is desired to reduce coke below the minimum threshold, then it may be beneficial to have a supplemental heating source through the primary tuyeres of the cupola, in the form of sensible heat or combustion heat.
  • a supplemental heating source through the primary tuyeres of the cupola, in the form of sensible heat or combustion heat.
  • natural gas torches may be used.
  • the cupola furnace employing the secondary oxygen injection system described herein may exhibit improved process efficiencies.
  • the improvement described herein upon coke rate may depend upon the configuration of the cupola furnace, such as the configuration and/or physical dimensions thereof. That is, the coke rate may be improved by a percentage relative to a cupola furnace having a similar configuration, but without the secondary oxygen injection system described herein.
  • the coke rate of some conventional cupola furnaces may be about 6% to 15%.
  • the coke rate may be reduced by about 15% or more, more preferably about 25% or more, more preferably about 35% or more, or even more preferably about 45% or more, relative to a cupola furnace having approximately the same configuration and/or physical dimensions, but without the secondary oxygen injection system described herein.
  • the improvements may be realized by complete secondary combustion of waste gasses.
  • Increased melt rates and increased efficiency may typically need to be offset by reduced primary blast rate and primary oxygen injection or enrichment rates, corresponding to the reduced coke rates.
  • the improvement described herein upon melt rate may depend upon the configuration of the cupola furnace, such as the configuration and/or physical dimensions thereof. That is, the melt rate may be increased by a percentage relative to a cupola furnace having a similar configuration, but without the secondary oxygen injection system described herein.
  • the melt rate of some conventional cupola furnaces may be about 3 short tons (about 3 metric tons) per hour to 140 short tons (about 127 metric tons) per hour.
  • the melt rate may be increased by at least about 3%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, or at least about 50%, relative to a cupola furnace having approximately the same configuration and/or physical dimensions, but without the secondary oxygen injection system described herein.
  • the present teachings contemplate an increase in melt rate of up to about 60%.
  • the improvement described herein upon blast rate may depend upon the configuration of the cupola furnace, such as the configuration and/or physical dimensions thereof. That is, the blast rate may be decreased by a percentage relative to a cupola furnace having a similar configuration, but without the secondary oxygen injection system described herein.
  • the blast rate of some conventional cupola furnaces may be about 3,000 SCFM (about 4,821.60 Nm 3 /hour) to 20,000 SCFM (about 32,144.01 Nm 3 /hour).
  • the blast rate may be decreased by about 3% or more, about 10% or more, about 20% or more, about 30% or more, or about 40% or more, relative to a cupola furnace having approximately the same configuration and/or physical dimensions, but without the secondary oxygen injection system described herein.
  • the degree of improvements described above may be proportional to the configuration of the secondary oxygen injection system described herein, such as the quantity of oxygen injection devices in a level, the quantity of levels of oxygen injection devices, the flow rates thereof, or the like.
  • the secondary oxygen injection system of the present teachings may reduce coke demands by about 20 lb (about 9.07 kg) per charge or more, 30 lb (about 13.61 kg) per charge or more, 40 lb (18.14 kg) per charge or more, or even 50 lb (about 22.67 kg) per charge or more.
  • a charge may be about 2,000 lb (about 907.18 kg) to about 15,000 lb (about 6,803.89 kg), and about 9 to about 13 charges may be provided per hour.
  • a charge may be about 2,000 lb (about 907.18 kg) to about 15,000 lb (about 6,803.89 kg), and about 9 to about 13 charges may be provided per hour.
  • the secondary oxygen injection system may be installed in a cupola furnace.
  • the secondary oxygen injection system may function to cause combustion secondary to a primary combustion of coke, combust at least a portion of waste gasses generated as a result of the primary combustion, increase the efficiency of the cupola furnace, reduce a quantity of coke required during melting of the cupola furnace, or any combination thereof.
  • the secondary oxygen injection system may comprise one or more oxygen injection devices.
  • the one or more oxygen injection devices may function to deliver gas to the cupola furnace.
  • the one or more oxygen injection devices may be referred to herein as lances.
  • the one or more oxygen injection devices may be arranged above the melting zone and below the charging door of the cupola furnace.
  • the one or more oxygen injection devices may be arranged in the preheating zone.
  • the one or more oxygen injection devices may deliver oxygen to the cupola furnace.
  • the oxygen may influence a secondary combustion within the cupola furnace.
  • the oxygen may influence combustion (oxidation) of waste gasses produced by a primary combustion within the cupola furnace.
  • the one or more oxygen injection devices may be arranged at one or more levels above the melting zone and below the charging door. Each of the one or more levels may be defined by a height along the cupola furnace. The one or more levels may be located at different heights along the cupola furnace.
  • the one or more oxygen injection devices may include two or more, more preferably three or more, more preferably four or more, more preferably five or more, or more preferably six or more oxygen injection devices per level. Typically, there may be three to six of the oxygen injection devices per level.
  • the oxygen injection devices within each level may be spatially distributed around a perimeter of the cupola furnace.
  • the oxygen injection devices within each level may be generally equally spatially distributed around a perimeter of the cupola furnace.
  • the one or more levels may include one, two, three, four, five, or even six or more levels.
  • the one or more levels may be selectively activated or deactivated, or operate continuously. Operation of each of the levels may be determined by operating parameters of the cupola furnace, described in greater detail below.
  • the thermal profile of the cupola furnace may change during melting. Such fluctuations may result from physical characteristics of the charge, such as the quantity (e.g., weight) of coke, flux, metal, or any combination thereof; the density of the charge; or any combination thereof. Such fluctuations may result from the composition of materials entering the cupola furnace.
  • the waste gasses may rise through the charge and cause cooling of the same, in counteraction to the heat that rises through the charge, originating from the primary combustion. Density of the charge may influence the permeation of the waste gasses and thus, the thermal profile.
  • the secondary oxygen injection system may operate in one or more regions of the cupola furnace where the temperature is below the combustion temperature of the coke and near or above the autoignition temperature of one or more of the waste gasses.
  • the secondary oxygen injection system may operate in one or more regions of the cupola furnace having a temperature of about 1500 °F (about 815 °C) to about 2000 °F (about 1093 °C).
  • no ignition source is required, although the present teachings contemplate that the system may include an ignition source.
  • Said one or more regions may be above the point where the primary coke bed Boudouard reaction is complete.
  • one or more levels may be selectively activated and/or deactivated such that the secondary oxygen injection system operates within the regions having the above-described thermal profile. Although, it is contemplated that no such activation and/or deactivation may be required during melting.
  • the one or more oxygen injection devices may be located at least about 36 inches (about 90 centimeters) to about 72 inches (about 183 centimeters) above a top of primary tuyere holders of the cupola furnace. Where multiple levels of the one or more oxygen injection devices are provided for, the lower mostly-located oxygen injection devices may be provided at this height. [0099] Each level may be separated by about 12 inches (about 30 centimeters) to about 36 inches (about 91 centimeters).
  • Each of the one or more levels may provide a ratio of the oxygen to a total primary oxygen of about 0.02 to about 0.5, about 0.05 to about 0.45, about 0.1 to about 0.40, about 0.15 to about 0.35, or even about 0.2 to about 0.3.
  • the oxygen and the total primary oxygen may refer to the molecular oxygen.
  • Each of the one or more levels may provide a flow rate of oxygen of at least about 25 standard cubic feet per meter (SCFM) (about 40. 18 Nm 3 /hour). Each of the one or more levels may be provided a flow rate of oxygen of less than 500 SCFM (about 803.60 Nm 3 /hour). More preferably, the flow rate of oxygen may be about 100 SCFM (about 160.72 Nm 3 /hour) to about 400 SCFM (about 642.88 Nm 3 /hour).
  • SCFM standard cubic feet per meter
  • Activation of about six levels, where the flow rate of oxygen in each level is about 100 SCFM, may provide for almost complete combustion (e.g., about 95% or more, or even about 99% or more) of the waste gasses.
  • the cupola furnace may be operated to provide for less- than-complete combustion of the waste gasses.
  • the flow rate of oxygen may be modulated to avoid the cupola furnace being undercoked.
  • an auxiliary heat input source associated with the primary tuyeres may be used to bring the cupola furnace up to operating temperatures.
  • the one or more oxygen injection devices may eject oxygen at an average speed of from about Mach 1 to about Mach 2.5.
  • the speed of the oxygen injection may cause the oxygen to penetrate through the charge and cause a generally even distribution of the oxygen through the charge at or proximate to each level.
  • the one or more oxygen injection devices may comprise an adapter for engaging the cupola furnace.
  • the adapter may include external threads for cooperating in a threaded engagement with the cupola furnace.
  • the adapter may include a quick disconnect coupling.
  • the quick disconnect coupling may include a ball latching coupling (otherwise referred to as a snap type coupling), a bayonet style coupling, or the like.
  • the one or more oxygen injection devices may be added to and removed from the cupola furnace in accordance with requirements of a session.
  • the one or more oxygen injection devices may be inserted into a fitting with a valve, such as an isolation ball valve, which may be shut to the interior of the cupola when the lance is extracted.
  • the one or more oxygen injection devices may extend through the wall of the cupola furnace and optionally through a cooling (e.g., water-cooled) jacket of the cupola furnace.
  • a cooling jacket may be provided on one side of an expansion joint, and so it is contemplated that some may extend through the cooling jacket while some do not.
  • the outlet of the one or more oxygen injection devices may locate proximate to or flush with the inner perimeter of the cupola furnace. In this regard, the speed of the oxygen may ensure adequate penetration and distribution into the charge.
  • the one or more oxygen injection devices may comprise a channel defined by an inner diameter and a length. The ratio of the inner diameter to the length may be about 0.042 to about 0.058 (e.g., 0.050).
  • the one or more oxygen injection devices may comprise a nozzle having an inlet, a reduction, and an outlet, each being defined by a diameter and a length.
  • the nozzle may be a converging/diverging nozzle.
  • the nozzle may be a supersonic direct injection nozzle.
  • the supersonic direct injection nozzle may be a de Laval nozzle.
  • the nozzle may be welded to the lance.
  • a ratio of the inlet diameter to the reduction diameter may be about 2.4 to about 2.8.
  • a ratio of the inlet diameter to the outlet diameter may be about 1.8 to about 2.2.
  • a ratio of the reduction diameter to the outlet diameter may be about 0.5 to about 0.9.
  • a ratio of the inlet length to the reduction length may be about 2.3 to about 2.7.
  • a ratio of the inlet length to the outlet length may be about 0.6 to about 1.0.
  • a ratio of the reduction length to the outlet length is about 0.1 to about 0.5 (e.g., 0.350).
  • the adapter may be defined by a diameter.
  • a ratio of the length of the channel to the diameter of the adapter may be about 10 to about 30.
  • the one or more oxygen injection devices may be fabricated from metal (e.g., stainless steel or other metallic materials), ceramic, or both.
  • the one or more oxygen injection devices may be fluid cooled (e.g., water cooled).
  • the secondary oxygen injection system may comprise one or more first supply lines.
  • the one or more first supply lines may function to supply oxygen to the one or more oxygen injection devices.
  • the one or more first supply lines may be in fluid communication with the one or more oxygen injection devices.
  • the oxygen may be supplied to the one or more oxygen injection devices at a purity of at least about 88%, more preferably at least about 90%, more preferably at least about 95%, or even more preferably at least about 99%.
  • the oxygen may include pure industrial grade cryogenic oxygen or Vacuum Swing Adsorption (VSA) generated oxygen, or any other similar oxygen generation method.
  • VSA Vacuum Swing Adsorption
  • the secondary oxygen injection system may comprise one or more second supply lines.
  • the one or more second supply lines may function to supply an inert gas to one or more ports in which the one or more oxygen injection devices are respectively located.
  • the inert gas may include nitrogen.
  • the inert gas may function to manage a temperature of the one or more oxygen injection devices, purge the one or more ports.
  • the nitrogen may be provided with a flow rate of at least about 1 SCFM (about 1.61 Nm 3 /hour), but less than about 3 SCFM (about 4.82 Nm 3 /hour); preferably about 2 SCFM (about 3.21 Nm 3 /hour).
  • An inert gas such as nitrogen
  • nitrogen may be supplied to the one or more first supply lines while the cupola furnace is idling or off. That is, oxygen flow may be ceased and nitrogen flow may be initiated.
  • Each level may be provided with its own gas train.
  • the gas trains may flow to distribution headers with three to six taps to accommodate the oxygen injection devices.
  • Flexible hose connections may extend from the taps to the oxygen injection devices.
  • the flexible hose connections may be about 36 inches (91.44 centimeters) to about 72 inches (182.88 centimeters) in length. In this regard, easy installation, removal, and service of the oxygen injection devices may be provided for.
  • the system may comprise one or more low pressure switches.
  • the one or more low pressure switches may function to detect piping break, piping problems, or instrument or valve control problems, as related to insufficient supply pressure.
  • the system may comprise one or more high pressure switches.
  • the one or more high pressure switches may function to detect run-away or over pressure conditions, liquid oxygen in lines, or instrument or valve control problems, as related to excess pressure.
  • Each of the gas trains may comprise a pressure sensor at an inlet thereof.
  • Each of the gas trains may comprise a pressure sensor at an outlet thereof.
  • Each of the gas trains may be maintained with a pressure of about 100 PSI (about 0.69 MPa) to about 150 PSI (1.03 MPa), but preferably no greater than 125 PSI (0.86 MPa).
  • the secondary oxygen injection system may comprise one or more flow rate detection devices.
  • the one or more flow rate detection devices may be located in the one or more first supply lines, the one or more second supply lines, or both.
  • the secondary oxygen injection system may comprise one or more pressure sensors.
  • the one or more pressure sensors may be located in in the one or more first supply lines, the one or more second supply lines, or both.
  • the secondary oxygen injection system may comprise one or more temperature sensors.
  • the temperature sensors may be located in one or more regions of the cupola furnace. Preferably, one or more of the temperature sensors are located within or proximate to one of the levels of the one or more oxygen injection devices.
  • the temperature sensors may include thermocouples.
  • the secondary oxygen injection system may comprise one or more gas composition analysis devices.
  • the one or more gas composition analysis devices may function to provide feedback from the waste gasses escaping the cupola.
  • the waste gasses may comprise carbon monoxide, carbon dioxide, oxygen, hydrogen, or any combination thereof.
  • the gas composition analysis device may be capable of detecting one or any combination of these waste gasses. Multiple gas composition analysis devices may be employed, each for detecting a particular waste gas.
  • the secondary oxygen injection system may comprise one or more first flow control devices.
  • the one or more first flow control devices may function to increase or decrease the flow rate and/or pressure of oxygen.
  • the one or more first flow control devices may be located in the one or more first supply lines.
  • the one or more first flow control devices may include valves (e.g., ball valve, v-notch ball valve, or the like).
  • the secondary oxygen injection system may comprise one or more second flow control devices.
  • the one or more second flow control devices may function to increase or decrease the flow rate and/or pressure of nitrogen.
  • the one or more second flow control devices may be located in the one or more second supply lines.
  • the one or more second flow control devices may include valves (e.g., ball valve, v-notch ball valve, or the like).
  • the one or more flow rate detection devices, pressure sensors, temperature sensors, gas composition analysis devices, or any combination thereof may be employed for the actuation of the one or more first and/or second flow control devices. That is, during melting, flow of oxygen and/or nitrogen may be increased, decreased, shut-off, or any combination thereof. As described herein, flow in one or more levels may be modulated or ceased during melting, based at least in part on a thermal profile of the cupola furnace and/or the gas composition escaping the cupola furnace.
  • the secondary oxygen injection system may comprise one or more controllers.
  • the one or more controllers may function to implement computer-executable instructions.
  • the computer-executable instructions may generally follow the method described in greater detail below. Ultimately the method may cause actuation of the one or more first and/or second flow control devices.
  • One or more inputs into the computer-executable instructions may be provided from the one or more flow rate detection devices, the one or more pressure sensors, the one or more temperature sensors, or any combination thereof.
  • One or more outputs from the computer-executable instructions may relate to a physical state of the one or more first and/or second flow control devices.
  • the controller may signally communicate with the one or more first and/or second flow control devices.
  • the present disclosure provides for a method of operating the secondary oxygen injection system and/or the cupola furnace.
  • the method may comprise supplying oxygen via a first supply line to one or more oxygen injection devices arranged at one or more levels, as described herein.
  • the oxygen may be provided at a flow rate of about 25 SCFM (about 40.18 Nm 3 /hour) to about 150 SCFM (about 241.08 Nm 3 /hour), more preferably about 50 SCFM (about 80.36 Nm 3 /hour) to about 100 SCFM (about 160.72 Nm 3 /hour).
  • the oxygen may be provided at an average speed of about Mach 1 to about Mach 2.5
  • the method may comprise supplying nitrogen via a second supply line to one or more ports in which, respectively, the one or more oxygen injection devices are located, as described herein.
  • the nitrogen may be provided at a flow rate of at least about 1 SCFM (about 1.61 Nm 3 /hour), but less than 3 SCFM (about 4.82 Nm 3 /hour).
  • the method may comprise selectively activating and/or deactivating the one or more levels such that the oxygen is supplied to a region of the cupola furnace having an operating temperature of about 1500 °F (about 815 °C) to about 2000 °F (about 1093 °C).
  • the method may comprise increasing or decreasing the flow rate and/or the average speed of the oxygen via a first flow control device.
  • the method may comprise increasing or decreasing the flow rate and/or the average speed of the nitrogen via a second flow control device.
  • the method may comprise receiving one or more inputs from one or more flow rate detection devices, one or more pressure sensors, one or more temperature sensors, one or more gas composition analysis devices, or any combination thereof.
  • the method may comprise actuating the first and/or second flow control devices based on the one or more inputs.
  • the method may comprise activating and/or deactivating the one or more levels based on the one or more inputs.
  • the method may be performed, at least in part, by one or more controllers implementing one or more computer-executable instructions; and wherein the one or more computer-executable instructions are stored on a non-transitory memory storage medium. That is, one or more inputs may be received by the one or more controllers, which may perform one or more functions on said inputs and provide one or more outputs. The one or more outputs may determine said actuation of the first and/or second flow control devices; activation and/or deactivation of the one or more levels, or both.
  • the oxygen may be supplied after initiation of a primary combustion system of the cupola furnace; more preferably no sooner than 5 minutes after initiation of the primary combustion system.
  • the method may comprise reducing a primary blast rate and oxygen flow rate of the primary combustion system in proportion to the flow rate of the secondary combustion, to avoid overproduction in the melting zone.
  • the oxygen flow rate of the primary combustion system may be reduced by about 15% to about 30% of the oxygen flow rate associated with the secondary oxygen injection system.
  • Primary blast rate and primary oxygen flow rate may be adjusted together, proportionately, to maintain their ratio within a pre-defined range.
  • the method may comprise supplying nitrogen via the first supply line to the one or more oxygen injection devices when the cupola furnace is idling or turned off.
  • the present teachings contemplate that the foregoing method may be performed by the secondary oxygen injection system according to the present teachings, the cupola furnace according to the present teachings, or both.
  • FIG. 1 is a schematic of the secondary oxygen injection system 10 according to the present teachings.
  • the secondary oxygen injection system 10 has a first supply line 12 for carrying oxygen and a second supply line 14 for carrying nitrogen.
  • the first and second supply lines 12, 14 deliver their respective gasses, respectively, to first and second headers 16, 18, which are adapted to circumscribe a cupola furnace, extending around an exterior dimension (e.g., circumference) thereof.
  • the first and second headers 16, 18 deliver their respective gasses, respectively, to first, second, and third oxygen injection devices 20, 22, 24.
  • Auxiliary connection points 26 are provided in the first and second headers 16, 18 for the addition of up to three more oxygen injection devices per header 16, 18. It is also contemplated that any of the oxygen injection devices 20, 22, 24 shown may be removed, any number of the auxiliary connection points 26 may be occupied by oxygen injection devices, or both. Thus, the present teachings are not intended to be limited to the illustrated arrangement.
  • first and second headers 16, 18, and associated oxygen injection devices 20, 22, 24 are associated with a single level, adapted to locate along a height of a cupola furnace. As described herein, up to six, or perhaps more, levels may be utilized in a cupola furnace. It is contemplated that additional levels may be supplied by the first and second supply lines 12, 14, or separate dedicated supply lines may be provided for each level.
  • FIG. 2 through FIG. 4 illustrate an oxygen injection device 28 comprising an adapter 30, a nozzle 32, and a channel 34.
  • FIG. 4 is a sectional view of the oxygen injection device 28 along line A- A, showing an inner diameter 36 and length 38 of the channel 34.
  • FIG. 5 and FIG. 6 show an adapter 30.
  • the adapter 30 has externally oriented threading 40 to provide for a threaded engagement with a port in a cupola furnace.
  • the oxygen injection device 28 can be readily applied to or removed from the port, providing for a modular configuration.
  • the adapter 30 has a first fitting 42 for receiving an element of the first supply line 12, and a second fitting 44 for receiving the channel 34, as shown in FIG. 4.
  • the first fitting 42 is defined by a diameter 46 and the second fitting 44 is defined by a diameter 48.
  • the adapter 30 has a passage 50 extending between the first and second fittings 42, 44.
  • the passage 50 is defined by a diameter 52.
  • FIG. 7 is a sectional view of a nozzle 32.
  • the nozzle 32 has an inlet 54, a reduction 56, and an outlet 58.
  • An inner surface of the nozzle 32 tapers down from the inlet 54 to the reduction 56, and tapers up from the reduction 56 to the outlet 58.
  • the inlet 54 is defined by a diameter 60
  • the reduction 56 is defined by a diameter 62
  • the outlet 58 is defined by a diameter 64.
  • the nozzle 32 may cooperate with conditions (e.g., flow rate, pressure, and the like) of the supply lines described herein to provide for Mach speeds of the gas into the cupola furnace.
  • FIG. 8 is a schematic of a cupola furnace 66 according to the present teachings.
  • the cupola furnace 66 extends vertically and is typically generally cylindrical in shape.
  • the cupola furnace 66 is divided into a number of zones, including, from top-to-bottom, a preheating zone 68, a reducing zone 70, a melting zone 72, and a primary combustion zone 74.
  • the cupola furnace 66 is loaded, via a charging door 76 and charging throat 78 with metallics and/or alloys, coke, and flux 80. As these materials are consumed within the cupola furnace 66, additional charges can be introduced.
  • the cupola furnace 66 provides for combustion with primary tuyeres 86 located below alternating charges, which provides oxygen to the primary combustion zone 74, supplied by an air blast inlet. As described herein, this primary gas injection system is distinct from the secondary oxygen injection system described herein. The primary gas injection system provides for the melting and subsequent tapping of the metal product of the cupola furnace 66. However, the present disclosure describes a secondary gas injection system that is distinct in location, configuration, and technical effects, relative to the primary gas injection system. Oxygen injection devices 84, as described herein, are located in the preheating zone 68. The present teachings are not intended to be limited to the depicted arrangement. Melted metal 86 seeps down through a coke bed and is tapped via a metal spout 88. Slag exits via a slag spout 90.
  • a cupola furnace having the following configuration was operated: hot blast, a water-cooled cascade shell (e.g., steel shell), full refractory lining, a tuyere circle diameter of about 60 inches (about 152 centimeters), a furnace inner diameter (“ID”) (shell diameter) of about 104 inches (about 264 centimeters), a working ID of about 86 inches (about 218 centimeters), a refractory lining thickness of about 9 inches (about 23 centimeters), a tuyere outlet diameter of about 4 inches (about 10 centimeters), a blast flow rate of about 6,800-7,200 SCFM (about 10,932-11,576 Nm3/hour), supersonic direct oxygen injection rate of about 3-4%, a stack height of about 29 feet (about 9 meters), below/above charge takeoff, and a typical (without the secondary oxygen injection described herein) tons per hour melt rate of about 33 short tons (about 30 metric tons).
  • ID furnace inner diameter
  • ID shell diameter
  • the cupola furnace described was typically used for melting ductile base iron (ASTM grade D65412 being the predominant grade, aside from about 5-7 other grades of ductile base iron), with external continuous desulfurization. While the examples herein were predominantly performed with D654512, the present teachings contemplate that the secondary oxygen injection system described herein can also be used for all other grades of ductile iron, although subject to variations (for which the present teachings provide suitable guidance to perform) in: specific primary blast and primary oxygen injection or enrichment rates, and secondary oxygen injection rates. It is also contemplated that relative process parameter improvements may vary slightly, as related to the variations in different makeups of the various charges for the various grades of ductile iron.
  • the cupola furnace included a primary oxygen injection system in the tuyeres, and was additionally outfitted with the secondary oxygen injection system according to the present teachings.
  • the secondary oxygen injection system included 3 lances generally evenly spaced around the perimeter of the cupola furnace.
  • the lances were inserted through the cooling jacket and into ports formed in the wall of the cupola furnace.
  • the lances were oriented generally perpendicular to the central axis (along the height) of the cupola furnace.
  • the lances were located about 55 inches above the tuyeres.
  • Each of the lances were fitted with low flow nozzles (adapted to provide about 33 standard cubic feet per minute (SCFM) each) or high flow nozzles (adapted to provide about 66 SCFM each).
  • the cupola furnace was operated for three different sessions.
  • the first session functioned as a baseline, where the secondary oxygen injection system was not operational, and the secondary oxygen injection system was operational during the second and third sessions.
  • the secondary oxygen injection system was operative intermittently during the second and third sessions. That is, the secondary oxygen injection system was turned OFF when the cupola furnace was put on spill (molten metal ceased to flow out) and turned back ON after the cupola furnace was put back on blast (primary blast system operational).
  • the first session included two portions where: in the earlier portion, the target blast rate was set to 7,300 SCFM (about 11,736 Nm 3 /hour) and the target primary oxygen injection was set to 290 SCFM (about 466 Nm 3 /hour); and in the latter portion, the target blast rate was set to 7,100 SCFM (about 11,415 Nm 3 /hour) and the target primary oxygen injection was set to 280 SCFM (about 450 Nm 3 /hour).
  • the secondary oxygen injection system operated in three portions where: in the earlier portion, the target blast rate was set to 7,400 SCFM (about 11,897 Nm 3 /hour), the target primary oxygen injection was set to 400 SCFM (about 643 Nm 3 /hour), and the target secondary oxygen injection was set to 103 SCFM (about 166 Nm 3 /hour); in the middle portion, the target blast rate was set to 7,300 SCFM (about 11,736 Nm 3 /hour), the target primary oxygen injection was set to 350 SCFM (about 563 Nm 3 /hour), and the target secondary oxygen injection was set to 90 SCFM (about 145 Nm 3 /hour); and in the latter portion, the target blast rate was set to 7,100 SCFM (about 11,415 Nm 3 /hour), the target primary oxygen injection was set to 300 SCFM (about 482 Nm 3 /hour), and the target secondary oxygen injection was set to 80 SCFM (about 129 Nm 3 /hour).
  • the target blast rate was set to 7,400 SCFM (about 11,897 Nm 3 /hour) and the target primary oxygen injection was set to 380 SCFM (about 611 Nm 3 /hour).
  • the target secondary oxygen injection was set to 103 SCFM (about 166 Nm 3 /hour).
  • the target secondary oxygen injection was set to 95 SCFM (about 153 Nm 3 /hour).
  • the cupola furnace was operated in three sessions. In each session, there were two portions, one in which the secondary oxygen injection system was OFF and one in which the secondary oxygen injection system was ON. The secondary oxygen injection system had the low flow nozzles for the first and second sessions and for the third session, the low flow nozzles were replaced with high flow nozzles. In the first session, the cupola furnace was charged with D654512 and in the second and third sessions, the cupola furnace was charged with D654512. Process parameters are summarized in TABLE 1. The values in this and the following tables are expressed as an average over each time period indicated.
  • a TPK of 4.24 is a remarkably high efficiency in the industry, and comparable efficiencies can only be conventionally met with significant increases in hot blast preheating, reductions in charge steel content (%), decreases in classic sensible cupola heat losses, or some combination thereof, but these parameters were not changed in these sessions.
  • a greater impact was observed with the 191.4 SCFM (about 308 Nm 3 /hour) secondary oxygen injection rate compared with the 99.5 SCFM (about 160 Nm 3 /hour) secondary oxygen injection rate. Without intending to be bound by theory, this may be due to the comparatively higher pressures associated with 191.4 SCFM (about 308 Nm 3 /hour) and thus better oxygen penetration into the charges.
  • Carbon and silicon content during periods of secondary oxygen injection operation were not statistically significantly different from the content during periods when secondary oxygen injection was not operational. Carbon content was about 3.25 weight percent to about 3.37 weight percent, and silicon content was about 1.54 weight percent to about 1.66 weight percent. Unless otherwise indicated herein, weight percent is relative to the total weight of a sample.
  • the secondary oxygen injection system had the high flow nozzles installed.
  • the cupola furnace was operated in three sessions (SI, S2, S3).
  • the target blast rate was 6,800 SCFM (about 10,932 Nm 3 /hour) (@ 4% primary oxygen), when the secondary oxygen injection system was OFF, and 6,200 SCFM (about 9,968 Nm 3 /hour) (@ 4% primary oxygen), while the secondary oxygen injection system was ON.
  • the coke charges were 490 Ib/charge (about 222 Kg/charge), when the secondary oxygen injection system was OFF, and 440 Ib/charge (about 200 Kg/charge), while the secondary oxygen injection system was ON.
  • the charge recipe was adjusted in each session. A reduction in special scrap steels in the recipe, from 600 lb (about 272 Kg) in sessions 1 and 2, to 200 lb (about 91 Kg) in session 3, was performed to study the effects on combustor temperature.
  • the recipes were as follows:
  • SI special scrap steels (600 lb (about 272 Kg)); steel (1,700 lb (about 771 Kg)); D654512 pig (800 lb (about 363 Kg)); D805506 return (400 lb (181 Kg)); D654512 return (2,000 lb (about 907 Kg)); Si alloy (110 lb (about 50 Kg)); coke (440 lb (about 200 Kg)); stone (100 lb (about 45 Kg))
  • S2 special scrap steels (600 lb (about 272 Kg)); steel (1,700 lb (about 771 Kg)); D654512 pig (800 lb (about 363 Kg)); D805506 return (400 lb (about 181 Kg)); D654512 return (2,000 lb (about 907 Kg)); Si alloy (95 lb (about 43 Kg)); coke (440 lb (about 200 Kg)); stone (100 lb (about 45 Kg))
  • S3 special scrap steels (200 lb (about 91 Kg)); steel (2,100 lb (about 953 Kg)); D805506 return (400 lb (about 181 Kg)); D654512 return (2,800 lb (about 1,270 Kg)); Si alloy (110 lb (about 50 Kg)); coke (490 lb (about 222 Kg) / 440 lb (about 200 Kg)); stone (110 lb (about 50 Kg) / 100 lb (about 45 Kg))
  • the cupola furnace and secondary oxygen injection system were physically configured as in EXAMPLE 1 except the low flow nozzles were replaced with high flow nozzles (adapted to provide about 66 SCFM (about 106 Nm 3 /hour) each).
  • the combined flow rate of the lances can be up to about 198 SCFM (about 318 Nm 3 /hour). Actual flow rate was up to about 206 SCFM (about 331 Nm 3 /hour).
  • D654512 (recipe 5): special scrap steels (200 lb (about 91 Kg)); steel (1,900 lb (about 862 Kg)); D805506 return (400 lb (about 181 Kg)); D654512 return (3,000 lb (about 1,361 Kg)); Si alloy (60/70 lb (about 27/32 Kg)); coke (450/430 lb (about 204/195 Kg)); stone (100 lb (about 45 Kg))
  • D654512 (recipe 4): special scrap steels (200 lb (about 91 Kg)); steel (2,100 lb (about 953 Kg)); D654512 pig (800 lb (about 363 Kg)); D805506 return (400 lb (about 181 Kg)); D654512 return (2,200 lb (about 998 Kg)); Si alloy (60 lb (about 27 Kg)); coke (430/450 lb (about 195/204 Kg)); stone (100 lb (about 45 Kg)) [0180] TABLE 3
  • the initial baseline TPK of 4.00 was higher than the typical baseline of about 3.8, due to a low coke bed situation, that was eventually corrected with a coke booster prior to initiating subsequent sessions 3 through 8.
  • the TPK value of 3.94 was measurably low, due to a discovered mechanical process problem that caused a significant drop in hot blast preheating temperature, that was corrected, for subsequent sessions 3 through 8.
  • Combustor temperature declined after the reduced special scrap steel charge reached the coke bed, but otherwise were stable and within acceptable ranges.
  • the spout chemistry was stable.
  • the cupola furnace and secondary oxygen injection system were physically configured as in EXAMPLE 1 except the low flow nozzles were replaced with high flow nozzles (adapted to provide about 66 SCFM (about 106 Nm 3 /hour) each).
  • the combined flow rate of the lances can be up to about 198 SCFM (about 318 Nm 3 /hour). Actual flow rate was up to about 206 SCFM (about 331 Nm 3 /hour).
  • D654512 (recipe 1): special scrap steels (200 lb (about 91 Kg)); steel (1,900 lb (about 862 Kg)); D805506 return (400 lb (about 181 Kg)); D654512 return (3,000 lb (about 1361 Kg)); Si alloy (60 lb (about 27 Kg)); coke (430 lb (about 195 Kg)); stone (100 lb (about 45 Kg))
  • D654512 (recipe 2): special scrap steels (200 lb (about 91 Kg)); steel (1,900 lb (about 862 Kg)); D654512 pig (800 lb (about 363 Kg)); D805506 return (400 lb (about 181)); D654512 return (2,200 lb (about 998 Kg)); Si alloy (60 lb (about 27 Kg)); coke (430 lb (about 195 Kg)); stone (100 lb (about 45 Kg))
  • the cupola furnace and secondary oxygen injection system were physically configured as in EXAMPLE 1 except the low flow nozzles were replaced with high flow nozzles (adapted to provide about 66 SCFM (about 106 Nm 3 /hour) each). However, the flow rate in this session was set at less than the maximum theoretical 198 SCFM (about 318 Nm 3 /hour), noted below.
  • This session used a lesser coke reduction (450 Ib/charge (about 204 Kg/charge)), a higher blast rate while the secondary oxygen injection system is ON (6,500 SCFM (about 10,450 Nm 3 /hour) @ 4% oxygen), and lesser secondary oxygen injection system flow rate (106 SCFM (about 170 Nm 3 /hour)).
  • 450 Ib/charge about 204 Kg/charge
  • SCFM about 10,450 Nm 3 /hour
  • 106 SCFM about 170 Nm 3 /hour
  • the charge recipe was as follows: [0196] D654512: special scrap steels (200 lb (about 91 Kg)); steel (1,900 lb (about 862 Kg)); D805506 return (400 lb (about 181 Kg)); D654512 return (3,000 lb (about 1361 Kg)); Si alloy (60 lb (about 27 Kg)); coke (430 lb (about 195 Kg)); stone (100 lb (about 45 Kg))
  • the cupola furnace and secondary oxygen injection system were physically configured as in EXAMPLE 1 except the low flow nozzles were replaced with high flow nozzles.
  • the charge recipe was as follows:
  • D654512 drums and rotors (400 lb (about 181 Kg)); special scrap steels (500 lb (about 227 Kg)); steel (1,600 lb (about 726 Kg)); D805506 return (400 lb (about 181 Kg)); D654512 return (2,600 lb (about 1,179 Kg); Si alloy (60 lb (about 27 Kg)); coke (440 lb (about 200 Kg)); stone (100 lb (about 45 Kg))
  • Combustor temperature and secondary oxygen injection system port temperatures were stable, but combustor temperature was lower by about 300 °F (e.g., about 1632 °F vs. 1905 °F) when the secondary oxygen injection system was ON.
  • Melt rate is the quantity, in weight, of molten metal that is tapped from the cupola furnace per unit time. Melt rate is represented herein in tons per hour (TPH). Unless otherwise indicated, tons per hour refer to short tons per hour. Although, references to melt rate are generally presented herein with both the short tons per hour and metric tons per hour values.
  • Efficiency is a measure of the melt rate in context with the equivalent primary blast rate and is defined as: melt rate / (equivalent blast rate / 1,000). Efficiency is represented herein in tons per thousand (TPK). TPK represented as a percentage relative to baseline may refer to the increase of efficiency when the secondary oxygen injection is on relative to the efficiency when the secondary oxygen injection is off.
  • Blast rate is a measure of flow of atmospheric air into the cupola furnace.
  • blast rate is expressed as an average (“avg.”) blast rate of the recorded blast rates within each time period.
  • blast rate is represented herein in standard cubic feet per minute (SCFM).
  • SCFM cubic feet per minute
  • Equivalent (“Eq.”) blast rate (“EBR”) is a measure of flow of all oxygen into the cupola furnace, including the flow of atmospheric air (typically assumed as about 21% oxygen) and primary oxygen injection or enrichment (variable, but in some examples herein about 4%). Unless otherwise indicated, equivalent blast rate is represented herein in standard cubic feet per minute (SCFM). Although, references to equivalent blast rate are generally presented herein with both SCFM and Nm 3 /hour values. Equivalent blast rate may be referred to herein as primary equivalent blast rate.
  • SCFM cubic feet per minute
  • Injection oxygen refers to injecting high purity (e.g., 80% pure or more) oxygen into the primary combustion zone via tuyeres.
  • Enrichment oxygen refers to increasing the oxygen content of the primary blast, by mixing high purity oxygen with the atmospheric air.
  • Coke rate refers to the quantity of coke added to the cupola furnace. Coke rate is typically expressed as a weight of coke per charge. Herein, where indicated as a percentage, coke rate may be expressed as a percentage relative to metallics in the charges (coke weight / (total metallics weight + total metallic alloys weight)).
  • Primary oxygen injection or enrichment refers to the flow rate of oxygen into the tuyeres expressed as a percentage of the additional oxygen relative to 21% of the ambient oxygen. Primary and secondary oxygen injection was measured using mass flow meters.
  • Total primary oxygen refers to the sum of the primary blast (ambient oxygen) and primary injected or enrichment oxygen.
  • On blast refers to when the primary blast and primary oxygen injection or enrichment are operational, and melt is occurring.
  • On spill refers to when the primary blast and primary oxygen injection or enrichment are non-operational, to pause melt.
  • Carbon content (expressed as a percentage by weight (wt. %) relative to the spout sample) was determined with a LECO 744 Series Combustion Analysis for Carbon and Sulfur (commercially available from LECO Corporation).
  • Silicon content (expressed as a percentage by weight (wt. %) relative to the spout sample) was determined with a SPECTROMAXx Arc/Spark OES Analyzer (commercially available from SPECTRO AMTEK).
  • Coke content was calculated as a total percentage of the charge weight.
  • the coke used was foundry coke with a 6 inch by 9 inch sizing.
  • the composition of the coke was 8% ash, 0.6% sulfur, 0.7% volatiles, and 91% fixed carbon.
  • Combustor temperature refers to the temperature in the combustor of the emissions system, which functions at least in part to convert carbon monoxide to carbon dioxide.
  • SCFM standard cubic feet per minute
  • D654512 and D805506 refer to ASTM grades of iron, as understood by skilled artisans.
  • pig and “return” may refer to physical forms of the iron, particularly differing in one or more physical dimensions thereof.
  • Relative combustor temperatures correspond to relative calorific heating value of cupola effluent gasses, since all gasses herein maintained a constant exhaust system volumetric flow.
  • the terms “generally” or “substantially” to describe angular measurements may mean about +/- 10° or less, about +/- 5° or less, or even about +/- 1° or less.
  • the terms “generally” or “substantially” to describe angular measurements may mean about +/- 0.01° or greater, about +/- 0.1° or greater, or even about +/- 0.5° or greater.
  • the terms “generally” or “substantially” to describe linear measurements, percentages, or ratios may mean about +/- 10% or less, about +/- 5% or less, or even about +/- 1% or less.
  • the terms “generally” or “substantially” to describe linear measurements, percentages, or ratios may mean about +/- 0.01 % or greater, about +/- 0.1 % or greater, or even about +/- 0.5 % or greater.
  • any numerical values recited herein include all values from the lower value to the upper value in increments of one unit provided that there is a separation of at least 2 units between any lower value and any higher value.
  • the amount of a component, a property, or a value of a process variable such as, for example, temperature, pressure, time and the like is, for example, from 1 to 90, from 20 to 80, or from 30 to 70
  • intermediate range values such as (for example, 15 to 85, 22 to 68, 43 to 51, 30 to 32 etc.) are within the teachings of this specification.
  • individual intermediate values are also within the present teachings.

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Abstract

La présente invention concerne un système secondaire d'injection d'oxygène pour un cubilot. Le système d'injection d'oxygène secondaire comprend un ou plusieurs dispositifs d'injection d'oxygène et une première conduite d'alimentation en communication fluidique avec le ou les dispositifs d'injection d'oxygène. La première conduite d'alimentation fournit de l'oxygène au ou aux dispositifs d'injection d'oxygène pour influencer la combustion de gaz résiduaires produits par une combustion primaire à l'intérieur du cubilot.
PCT/US2025/030130 2024-05-20 2025-05-20 Système secondaire d'injection d'oxygène, cubilot et procédés de fonctionnement Pending WO2025245069A1 (fr)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1182645A (fr) * 1981-01-21 1985-02-19 Union Carbide Corporation Injection supersonique d'oxygene dans les fours a cubilot
EP0793071A2 (fr) * 1996-03-01 1997-09-03 The BOC Group plc Combustion contrÔlée des gaz d'échappement d'un four

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1182645A (fr) * 1981-01-21 1985-02-19 Union Carbide Corporation Injection supersonique d'oxygene dans les fours a cubilot
EP0793071A2 (fr) * 1996-03-01 1997-09-03 The BOC Group plc Combustion contrÔlée des gaz d'échappement d'un four

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
BOSCH R ET AL: "Controlled supersonic injection of oxygen", FOUNDRY TRADE JOURNAL, INSTITUTE OF CAST METALS ENGINEERS, WEST BROMWICH, GB, vol. 178, no. 3611, 1 January 2004 (2004-01-01), pages 18 - 19, XP001518243, ISSN: 0015-9042 *
POWELL J ET AL: "A REVIEW OF CUPOLA MELTING", FOUNDRY TRADE JOURNAL, INSTITUTE OF CAST METALS ENGINEERS, WEST BROMWICH, GB, vol. 171, no. 3533, 1 August 1997 (1997-08-01), pages 340 - 346, XP000726330, ISSN: 0015-9042 *

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