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US20140190312A1 - Method and apparatus for dephosphorising liquid hot metal such as liquid blast furnace iron - Google Patents

Method and apparatus for dephosphorising liquid hot metal such as liquid blast furnace iron Download PDF

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Publication number
US20140190312A1
US20140190312A1 US14/234,980 US201214234980A US2014190312A1 US 20140190312 A1 US20140190312 A1 US 20140190312A1 US 201214234980 A US201214234980 A US 201214234980A US 2014190312 A1 US2014190312 A1 US 2014190312A1
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US
United States
Prior art keywords
hot metal
stream
metal
refining unit
liquid
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US14/234,980
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English (en)
Inventor
Maurice Stuart Millman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Tata Steel UK Ltd
Original Assignee
Tata Steel UK Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
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Assigned to TATA STEEL UK LTD reassignment TATA STEEL UK LTD ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: MILLMAN, Maurice Stuart
Publication of US20140190312A1 publication Critical patent/US20140190312A1/en
Abandoned legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C1/00—Refining of pig-iron; Cast iron
    • C21C1/02—Dephosphorising or desulfurising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0037—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 by injecting powdered material
    • C21C7/0043—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 by injecting powdered material into the falling stream of molten metal
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/064—Dephosphorising; Desulfurising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/076—Use of slags or fluxes as treating agents
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • This invention relates to a method and apparatus for dephosphorising liquid hot metal such as liquid blast furnace iron or liquid metal with a composition equivalent to blast furnace iron, hereafter referred to as hot metal.
  • liquid hot metal such as liquid blast furnace iron or liquid metal with a composition equivalent to blast furnace iron, hereafter referred to as hot metal.
  • Previous hot metal phosphorus pre-treatment production processes included silicon removal in the blast furnace runner followed by phosphorus removal in the torpedo ladle by injection of powdered and gaseous dephosphorising reagents. This procedure led to the removal of silicon from the hot metal (chemical energy) together with a significant drop in temperature in the torpedo ladle (heat energy) and consequently, a requirement for a high hot metal ratio at charge (for example >90%). For plants designed to use significant amounts of scrap in their input materials and therefore having a typical hot metal ratio at charge of between 70% to 85%, such as the majority of the European steel plants, this method is not practically viable.
  • ‘a spare’ BOS converter can be used for hot metal phosphorus pre-treatment whereby hot metal (no scrap) is blown more or less normally in a ‘dephosphorising’ converter, with lime or pre-fused slag for a very short treatment time (e.g. less than eight minutes). In general, this is enough time to transfer a large portion of the phosphorus load to the slag. The dephosphorised metal is then tapped conventionally into a ladle and then charged together with scrap to a ‘decarburising’ converter. However, this procedure is not an option when there is no ‘spare’ BOS-converter.
  • the object of the invention is to provide a method which allows the use of higher phosphorus ores.
  • Another object is to provide a method which can be readily integrated into current steelmaking operating practices.
  • Still another object of the invention is to provide an apparatus for carrying out the inventive method.
  • liquid hot metal such as liquid blast furnace iron or liquid metal with a composition equivalent to blast furnace iron
  • a pouring stream of the hot metal is discharged from a vessel containing the hot metal into a refining unit (a.k.a.
  • one or more streams of additives for forming a molten slag and one or more gaseous streams for breaking up the pouring stream of hot metal into molten metal droplets are directed into the pouring stream wherein one or more of the gaseous streams and/or one or more of the streams of additives comprises oxygen in gaseous form or in compounded form, to allow a dephosphorisation reaction between the metal droplets, the oxygen and the molten slag during the fall of the molten droplets before being collected into a receiving vessel positioned below the refining unit as described in independent claim 1 .
  • the apparatus comprises a vessel for containing the liquid hot metal, such as liquid blast furnace iron or liquid metal with a composition equivalent to blast furnace iron, which hot metal is preferably already desulphurised, the vessel comprising means for discharging a pouring stream of the hot metal into a refining unit, the refining unit having a single reaction chamber, wherein the refining unit is provided with at least one first injection means for injecting a gaseous stream into the pouring stream of the hot metal to break up the pouring stream into molten metal droplets, and with at least one second injection means for injecting a stream of additives into the pouring stream and/or into the molten droplets and with an outlet for waste process gas, and an outlet for allowing the molten droplets to be collected into a receiving vessel.
  • the apparatus comprises a vessel for containing the liquid hot metal, such as liquid blast furnace iron or liquid metal with a composition equivalent to blast furnace iron, which hot metal is preferably already desulphurised, the vessel comprising means for discharging a pouring
  • the pouring stream preferably exits the vessel containing the liquid hot metal in a substantially vertical direction and enters the refining unit also in a substantially vertical direction before being broken up into molten metal droplets by the gaseous stream from the at least one first injection means.
  • the invention is also embodied in an apparatus wherein the at least one injection means for injecting a gaseous stream and/or the at least one second injection means for injecting a stream of additives into the pouring stream are mounted in an angle ⁇ to the pouring stream of between 0° (parallel to the pouring stream) and 75°, preferably wherein the angle is at least 10° and/or at most 60°. A preferred maximum is 45°. It is the intention that the gaseous stream and the stream of additives contact the pouring stream at the angle at which the respective injection means are mounted with respect to the vertical. The choice of a is made so as to achieve a completely broken-up pouring stream into metal droplets that have an average diameter and size range required for optimum dephosphorisation performance.
  • the condition should be to break up the stream to the desired droplet size and to achieve the required level of oxidation and slag basicity for maximum dephosphorisation at a controlled, minimal level of decarburisation and iron yield loss.
  • the angle of the first and/or second injection means can be changed during the dephosphorisation, preferably independently, to enable optimisation of the breaking up of the pouring stream and/or the injection of the additives into the pouring stream.
  • the hot metal which is discharged from the vessel into the refining unit is preferably desulphurised prior to being dephosphorised according to the invention.
  • the one or more gaseous streams may comprise gaseous oxygen or oxygen containing gaseous compounds.
  • the one or more streams of additives may comprise oxygen in compounded form, e.g. in the form of an oxide or carbonate.
  • the hot metal dephosphorising method according to the invention is preferably positioned in the steelmaking process route between the hot metal desulphurisation plant and the BOS-converter.
  • the vessel containing hot metal preferably desulphurised, preferably unskimmed, provides a pouring stream of the hot metal, e.g. by bottom-pouring, into a refining unit.
  • the pouring could be done otherwise, e.g. by tilting the vessel and pouring it from a taphole in the sidewall or even by pouring it like a bucket, the bottom-pouring gives the best conditions for a stable pouring stream in terms of consistency and stability, and the best conditions for shielding the pouring stream from the influences of the surrounding atmosphere.
  • the refining unit is preferably equipped with several individual multi purpose burner modules or nozzles containing one or more injection features for injecting one or more of gaseous compounds such as oxygen, nitrogen, natural gas or other gas, or solid compounds such as lime powder, flux powder or other powder that point directly into the pouring stream either from discrete positions or from an annular ring so that the pouring stream is completely broken-up into metal droplets that have an average diameter and size range required for optimum dephosphorising performance.
  • gaseous compounds such as oxygen, nitrogen, natural gas or other gas
  • solid compounds such as lime powder, flux powder or other powder that point directly into the pouring stream either from discrete positions or from an annular ring so that the pouring stream is completely broken-up into metal droplets that have an average diameter and size range required for optimum dephosphorising performance.
  • lime, flux or other powder granules could be used.
  • the nozzles provide supersonic or subsonic jets of the gaseous and/or solid compounds.
  • the droplet size is preferably at
  • Additional individual multi purpose burner modules or nozzles of the aforementioned type and for the aforementioned purpose may be placed at other positions in the refining unit as required.
  • the oxygen input rate and lime powder/flux powder/other powder input rates to the refining process are matched to the hot metal pouring rate and to the required state of oxidation and chemistry of the resulting slag.
  • Total Fe in the slag is preferably between 10% and 40% and the slag basicity (CaO/SiO2) is preferably between 1.0 and 4.0.
  • Phosphorus is transferred from the metal droplets to the slag at a high level of efficiency of at least 50% because the design of the method ensures a very high reaction surface; a relatively low temperature (between 1200° C. and 1500° C.
  • a high state of oxidation that is at or near an optimum condition for oxidation of phosphorus
  • a slag composition that is at or near optimum condition for high phosphorus capacity
  • a smaller containment vessel hereafter known as a tundish may be provided to allow the dephosphorisation process in the refining unit to be not directly linked to the vessel containing the hot metal, and to continue while the vessel containing the hot metal is emptied and replaced by a full vessel.
  • the ferrostatic head of the hot metal may be held constant by sustaining a constant height of liquid metal in the tundish. In this way, the flow condition of the pouring stream may be effectively maintained.
  • the stream of hot metal to be broken up in molten metal droplets is discharged into the refining unit from the tundish rather than directly from the vessel.
  • the dispersed metal droplets are exposed to an oxidising and basic slag environment ensuring very fast silicon and phosphorus removal together with Fe oxidation and a significant rise in temperature.
  • the carbon content of the dispersed hot metal droplets may also be reduced albeit by a variable amount and dependent upon their average diameter and size range.
  • High yield losses from fume in the off gas and FeO and metallic shot in the slag may occur when the average diameter of the dispersed metal droplets is low and the size range wide. Therefore the size of the metal droplets preferably is between 1 ⁇ m and 20 mm.
  • a suitable minimum droplet size is 100 ⁇ m.
  • a suitable maximum droplet size is 3000 ⁇ m.
  • the metal pouring stream geometry and the number, flow conditions, nozzle geometry and relative direction of the subsonic streams or supersonic streams from the nozzles are major factors in the determination of the average droplet diameter and size range. Therefore, the number of nozzles is preferably at least one and at most eight and more preferably at least two. A suitable maximum is four nozzles.
  • the pouring stream shape may be irregular or may be round or rectangular or a combination of both; the supersonic core length of the stream or streams can be greater than, equal to or less than the nozzle to stream distance; the relative direction of the stream of additives or gaseous streams to the pouring stream can be between 0° (parallel to the pouring stream) and 75°. Preferably this angle ( ⁇ , see FIG.
  • the stream of additives or gaseous streams are directed perpendicularly to the pouring stream in case of the angle ⁇ being 90°, and are tilted downwardly in case of an angle between 0 and 90°.
  • the choice of ⁇ is made so as to achieve a completely broken-up pouring stream into metal droplets that have an average diameter and size range required for optimum dephosphorisation performance.
  • the condition should be to break up the stream to the desired droplet size and to achieve the required level of oxidation and slag basicity for maximum dephosphorisation at a controlled, minimal level of decarburisation and iron yield loss.
  • the angle of the first and/or second injection means can be changed during the dephosphorisation, preferably independently, to enable optimisation of the breaking up of the pouring stream and/or the injection of the additives into the droplet stream.
  • means are provided between the refining unit and the receiving vessel for collecting the dephosphorised metal which enable continuous use of the refining unit without having to stop for changing the receiving vessel when this is full.
  • These means may consist of a buffer vessel or buffer tundish able to collect the dephosphorised metal while the full receiving vessel is exchanged for an empty one.
  • the advantage of the method according to the invention is that it can be implemented with relatively low capital and running costs; minimal logistical impact; high productivity; and, the simple and effective concept of rapid refining, particularly of relatively small volumes of hot metal per unit time, via the controlled generation of hot metal droplets within a regulated oxidising and basic environment.
  • the injected additives may be recovered decarburising converter slag that has been suitably processed to injectable grade. As such, the lime flux will be pre-fused and therefore easily melted.
  • injected additives may be alloy or ferro-alloy fines.
  • the chemistry of the ambient conditions can be additionally altered.
  • These alloy or ferro-alloy fines may be recovered alloy or ferro-alloy fines.
  • FIG. 1 shows a schematic drawing of an apparatus for carrying out the process according to the invention.
  • FIG. 3 shows a more realistic drawing of an apparatus for carrying out the process according to the invention.
  • FIG. 2 shows the angle ⁇ in relation to the pouring stream (PS) and one nozzle (n).
  • FIG. 1 shows an apparatus according to the invention with a tundish between the vessel containing the hot metal and the refining unit (indicated in FIG. 1 with refining vessel).
  • the inlets indicated with oxygen injection and lime injection in FIG. 1 are the gaseous streams and stream of additives in the context of this invention.
  • the apparatus is placed in-line between the hot metal desulphurising plant and the BOS-converter.
  • Hot metal (not skimmed) and preferably desulphurised, contained in a bottom-pouring vessel is bottom-poured into a tundish and then bottom-poured from the tundish as a pouring stream into the refining unit.
  • the flow rate of the pouring stream into the refining unit can be monitored and controlled via load cells.
  • One or more supersonic or subsonic gas jets as outputs from oxygen/nitrogen/other gas/lime powder/flux powder/other powder/natural gas burner modules or nozzles which can be either combined into a single multi purpose module or nozzle or as separate injectors point directly into the pouring stream either from discrete positions or from an annular ring.
  • Additional individual multi purpose burner modules or nozzles containing one or more injection features for injecting supersonic or subsonic oxygen, nitrogen, other gas, lime powder, flux powder or other powder or natural gas may be placed at other positions in the top or sidewall of the refining unit as required.
  • the oxygen input rate and lime powder/flux powder/other powder input rates to the refining process are matched to the pouring rate of the pouring stream.
  • the metal droplets, oxygen and molten slag will chemically react during the time it takes for the metal droplets to fall under gravity into the receiving vessel. Silicon and phosphorus refining will be accompanied by iron oxidation and a rapid rise in temperature. Further refining reactions will also take place between the slag and metal in receiving ladle. This can be gas-stirred to ensure that the slag and metal approach chemical equilibrium. Some carbon oxidation is also expected and this could lead to appreciable slag foaming within the receiving ladle. Consequently, the receiving vessel will require a suitably large freeboard to accommodate this.
  • the receiving ladle (now the transfer ladle or charging ladle), will be moved away and the slag removed with a slag skimmer unit or other slag removal device.
  • the slag may require pre-conditioning prior to slag skimming or slag removal to reduce metallic iron yield loss.
  • the dephosphorised and partially-decarburised hot metal which generally has a temperature of between about 1250° C. and 1500° C., will then be transferred and charged to the decarburising converter that already contains its required scrap charge.
  • the oxygen flow rate can be significantly higher than current practice, and have values of up to 1500 Nm 3 /min. Consequently, it is expected that the converter processing time will be substantially shorter than current practice, leading to significant gains in productivity.
  • the phosphorus content of the slag skimmed (i.e. removed) from the receiving ladle, which is now the charging ladle for the decarburisation process, may well be high enough to ensure that such slag could be used as a basis for a fertiliser product.
  • the control systems preferably include flexible and independent control of one, more or all of the following: injectant inputs, pouring stream rate, metal and slag composition sampling and control, temperature measurement and/or off-gas analysis monitoring.
  • the temperature affects the performance by affecting the slag capacity for phosphorus and the metal droplet size. Too high temperature may cause the dephosphorising reaction to slow, stop, or reverse. On the other hand, the reaction vessel is required to be suitably pre-heated to ensure low levels of temperature loss. Hot metal temperature changes may be influenced by a combination of chemical heat (silicon and Fe (+carbon, manganese) oxidation), chemical heat (natural gas burner) and conductive, convective and radiative thermal losses.
  • decarburisation time in the BOS converter can be reduced by utilising a high oxygen blowing rate. This will help to increase converter productivity. Less aggressive slag could be used which will reduce the need for slag splashing and refractory maintenance and in turn will lower converter heat losses. A high flow rate oxygen lance could be employed for the converter.
  • the decarburisation slag could be recycled to the dephosphorising reactor where it could be injected as a pre-fused flux addition.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
  • Carbon Steel Or Casting Steel Manufacturing (AREA)
US14/234,980 2011-08-05 2012-07-31 Method and apparatus for dephosphorising liquid hot metal such as liquid blast furnace iron Abandoned US20140190312A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP11176753 2011-08-05
EP11176753.9 2011-08-05
PCT/EP2012/064953 WO2013020858A1 (en) 2011-08-05 2012-07-31 Method and apparatus for dephosphorising liquid hot metal such as liquid blast furnace iron

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US (1) US20140190312A1 (es)
EP (1) EP2739757A1 (es)
JP (1) JP2014521837A (es)
KR (1) KR20140053195A (es)
CN (1) CN103814142A (es)
BR (1) BR112014002610A2 (es)
CA (1) CA2843798A1 (es)
MX (1) MX2014001293A (es)
WO (1) WO2013020858A1 (es)

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CN104711393B (zh) * 2013-12-12 2017-04-12 Posco公司 处理钢液的设备和利用其处理钢液的方法
CN105420490B (zh) * 2015-11-25 2017-11-17 内蒙古科技大学 一种对转炉渣进行脱磷的方法
CN105671248B (zh) * 2016-03-22 2018-04-24 首钢集团有限公司 一种转炉高效脱磷的冶炼方法

Citations (1)

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Publication number Priority date Publication date Assignee Title
JPS5594431A (en) * 1979-01-13 1980-07-17 Nippon Steel Corp Spray steel making method

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Publication number Priority date Publication date Assignee Title
CH394263A (de) * 1959-07-10 1965-06-30 Fischer Ag Georg Verfahren zum In-Berührung-Bringen von Stoffen mit Metallschmelzen, insbesondere Stahlschmelzen
FR2558482B1 (fr) * 1984-01-25 1989-10-27 Siderurgie Fse Inst Rech Procede d'elaboration de l'acier par preaffinage de la fonte
US4664701A (en) * 1986-01-15 1987-05-12 Blaw Knox Corporation Method and plant for fully continuous production of steel strip from ore
JPS6318009A (ja) * 1986-07-10 1988-01-25 Sumitomo Metal Ind Ltd 溶銑の予備処理方法および装置
JPH01136917A (ja) * 1987-11-21 1989-05-30 Nippon Steel Corp 溶銑予備処理法
US5868817A (en) * 1994-06-30 1999-02-09 Nippon Steel Corporation Process for producing steel by converter
CN1392272A (zh) * 2001-06-14 2003-01-22 莱芜钢铁股份公司炼钢厂 一种钢铁生产工艺及其专用设备

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5594431A (en) * 1979-01-13 1980-07-17 Nippon Steel Corp Spray steel making method

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EP2739757A1 (en) 2014-06-11
WO2013020858A1 (en) 2013-02-14
JP2014521837A (ja) 2014-08-28
BR112014002610A2 (pt) 2017-03-01
KR20140053195A (ko) 2014-05-07
CN103814142A (zh) 2014-05-21
CA2843798A1 (en) 2013-02-14
MX2014001293A (es) 2014-05-13

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Owner name: TATA STEEL UK LTD, UNITED KINGDOM

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:MILLMAN, MAURICE STUART;REEL/FRAME:032142/0487

Effective date: 20140131

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