WO2013127869A1 - Procédé d'amélioration de performances d'écumage de laitier pendant un processus de désulfuration d'un métal chaud - Google Patents

Procédé d'amélioration de performances d'écumage de laitier pendant un processus de désulfuration d'un métal chaud Download PDF

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Publication number
WO2013127869A1
WO2013127869A1 PCT/EP2013/053952 EP2013053952W WO2013127869A1 WO 2013127869 A1 WO2013127869 A1 WO 2013127869A1 EP 2013053952 W EP2013053952 W EP 2013053952W WO 2013127869 A1 WO2013127869 A1 WO 2013127869A1
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WO
WIPO (PCT)
Prior art keywords
slag
hot metal
glass
desulphurisation
slag modifier
Prior art date
Application number
PCT/EP2013/053952
Other languages
English (en)
Inventor
Zushu LI
Andy Ferguson
John Smith
Original Assignee
Tata Steel Uk Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tata Steel Uk Limited filed Critical Tata Steel Uk Limited
Publication of WO2013127869A1 publication Critical patent/WO2013127869A1/fr

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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
    • C21C1/025—Agents used for 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
    • C21C7/0087—Treatment of slags covering the steel bath, e.g. for separating slag from the 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
    • C21C7/0645—Agents used for 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
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/072—Treatment with gases

Definitions

  • the invention relates to a method for the desulphurisation of hot metal and to a slag modifier for the modification of desulphurisation slag.
  • soda ash was used in conjunction with magnesium deep injection (known as "soda ash-Mg process") in the hot metal desulphurisation process in BOF steelmaking plants.
  • soda ash-Mg process magnesium deep injection
  • a certain amount of soda ash is added into the hot metal stream as the metal is being poured from a torpedo into a transfer ladle.
  • the soda ash acted as a slag modifying agent to aid slag skimming as well as a desulphurising agent.
  • the term "hot metal” is used to indicate the molten iron product from the blast furnaces which is normally transported to the steel works in a so-called torpedo ladle.
  • the soda ash-Mg process is often upgraded to a lime/magnesium co-injection hot metal desulphurisation process. This cuts the desulphurisation time by up to 50%, or sometimes even more.
  • the use of lime and magnesium has increased the slag bulk, altered the slag consistency and deteriorated slag conditions. Efficient slag skimming was sometimes not possible without slag modification for the heats with low hot metal temperature ( ⁇ 1300 °C) and high CaO/Mg injection for producing ultra low sulphur steel grades. This also increased the steel yield loss as the total iron (TFe) content in the slag was sometimes found to be 80 wt% in the form of entrapped iron droplets and direct skimming iron loss was increased due to extended skimming operation.
  • TFe total iron
  • the slag on top of the hot metal before desulphurisation is mainly composed of blast furnace slag and the remaining slag from previous heats.
  • the other sources include spalling from the iron runner, heat insulation and a fraction of oxides formed by reaction between Fe, Mn, Si, V and Ti in the hot iron with oxygen in the air.
  • the desulphurisation by CaO-Mg co-injection brings the CaO and MgO into the slag.
  • slag modifying agents are often added with the desulphurising agent or directly into the hot metal ladle before or after hot metal pouring to decrease the viscosity and melting temperature of the post- desulphurisation slag.
  • Various materials have been used as slag modifying agents such as fluorspar, dolomitic lime, silica, sodium carbonate, sodium chloride, potassium chloride, potash, cryolite, potassium cryolite, colemanite, calcium chloride, calcium aluminate, sodium fluoride, anhydrous borax, nepheline syenite and soda ash.
  • the object of this invention is to provide a method of improving slag skimming performance in hot metal desulphurisation process in BOF steelmaking.
  • a method for the desulphurisation of hot metal comprising intermixing the hot metal to be desulphurised with a slag containing as the principal ingredients lime, magnesium and a slag modifier, wherein the slag modifier is glass comprising at most 5% of Al 2 0 3 , preferably comprising at most 2.6% of Al 2 0 3 .
  • the skimming time is reduced significantly. Therefore, direct skimming iron loss was much reduced.
  • the iron content in the slag is reduced considerably from about 80% in the slag without glass addition to the hot metal to a value of between 20 to 40% in the slag with addition of glass as a slag modifier to the hot metal.
  • glass was used as a slag modifier the build up on skim blades was considered better as less jack hammering was required and easier removal of skulls from the blade was reported. No effect was noticed on the build up on the lances.
  • the slag modifier has a low alumina content or below 5% and preferably of at most 2.6%. It is preferable that no additional soda ash and/or no silica sand and/or no Fe 3 0 4 and/or no exothermic agent of metallic aluminium (for heating the slag) is added to or present in the glass to be used as a slag modifier.
  • the composition of the slag changes when glass is added. Without glass, the typical iron content of the slag is 80% and the non-metallic slag fraction is typically 43% Fe, 24% CaO, 10% Si0 2 and ⁇ 0.08% Na 2 0. With a glass addition there is typically 20-40% Fe and the non-metallic slag fraction is typically 25- 35% Fe, 15-30% CaO, 25-35% Si0 2 and 2-6% Na 2 0.
  • the phase diagram of the CaO-MgO-Si0 2 -AI 2 0 3 system shows that the melting point of the slag is over 1500°C and increases as the amount of lime is added, i.e. the slag will be more solid for lower steel sulphur aims.
  • Typical iron temperatures arriving at a BOS plant are 1250-1400°C and therefore the slag is likely to be mainly solid at these temperatures.
  • the amount of Si0 2 is increased and consequently the melting temperature of the slag is reduced towards the iron temperatures seen in production. This is observed as a more fluid slag and consequently the slag appears easier to skim off.
  • the glass or the recycled glass, or mixtures thereof comprise:
  • the slag modifier comprises no Pb, Sr, BaO, Zr0 2 or fluoride component except as an unavoidable impurity. These elements are considered particularly harmful for the resulting steel and their presence should be avoided. Also when glass contains elements such as BaO and Pb these also transfer across to the slag; this may limit the uses of the material from the skim pit and therefore it is recommended to avoid glass with these contaminants.
  • the Na 2 0 content of the slag modifier is at most 10%, more preferably at most 9%.
  • Fluorine-containing modifiers are detrimental to both environment and hot metal ladle refractories; and Na 2 C0 3 and K 2 C0 3 additions (used as the raw materials of slag modifiers) is also not good for environment, ladle lining life and waste gas cleaning system. Also, because of the complex preparation process and its cost of raw materials, these slag modifying agents can be much more expensive than the glass, recycled or otherwise.
  • At least 1% CaO is present in the slag modifier.
  • the glass is added in the form of powder or cullet or granules.
  • glass cullet of 5-10 mm in size is used. No fumes were observed during hot metal pouring onto the glass cullet and slag skimming when using material of this size.
  • cullet with a maximum size of between 10 to 50 or 10 to 25 mm showed a similar performance to 5-10 mm cullet, but these larger sizes are currently more costly than the 5-10 mm size fraction. Therefore, although from a technical performance the glass works just as well as the 5 to 10 mm cullet, it is currently less cost efficient to use the 10-25mm size.
  • the invention is also embodied in glass or recycled glass for use as slag modifier for the modification of desulphurisation slag in the desulphurisation of hot metal, said glass comprising at most 5% of Al 2 0 3 , and preferably at most 2.6% of Al 2 0 3 .
  • the slag modifier for the modification of desulphurisation slag the slag modifier comprises no Pb, Sr, BaO, Zr0 2 or fluoride component except as an unavoidable impurity, and/or the slag modifier comprises at least 1% CaO.
  • Table 1 provided a typical slag chemistry with and without glass addition
  • Table 2 provides an analysis of the glass used as slag modifiers.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Analytical Chemistry (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)

Abstract

La présente invention concerne un procédé de désulfuration d'un métal chaud consistant à mélanger le métal chaud devant être désulfuré à un laitier contenant, à titre de composants principaux, de la chaux, du magnésium et un agent modificateur de laitier, l'agent modificateur de laitier étant du verre, et audit agent modificateur de laitier.
PCT/EP2013/053952 2012-03-01 2013-02-27 Procédé d'amélioration de performances d'écumage de laitier pendant un processus de désulfuration d'un métal chaud WO2013127869A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP12157715.9 2012-03-01
EP12157715 2012-03-01

Publications (1)

Publication Number Publication Date
WO2013127869A1 true WO2013127869A1 (fr) 2013-09-06

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2013/053952 WO2013127869A1 (fr) 2012-03-01 2013-02-27 Procédé d'amélioration de performances d'écumage de laitier pendant un processus de désulfuration d'un métal chaud

Country Status (1)

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WO (1) WO2013127869A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3170908A1 (fr) * 2015-11-18 2017-05-24 Roman Wolf Procédé de traitement de scorie lors de la production d'acier

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3981721A (en) * 1974-02-27 1976-09-21 Aikoh Co., Ltd. Method for desulfurizing molten iron
JPS54136502A (en) * 1978-04-17 1979-10-23 Sumitomo Metal Ind Ltd Treating method for slag produced in sodiummtype desulfurization of molten cast iron
DE10344543A1 (de) * 2002-10-04 2004-04-15 Visteon Global Technologies, Inc., Dearborn Grünglasmischung

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3981721A (en) * 1974-02-27 1976-09-21 Aikoh Co., Ltd. Method for desulfurizing molten iron
JPS54136502A (en) * 1978-04-17 1979-10-23 Sumitomo Metal Ind Ltd Treating method for slag produced in sodiummtype desulfurization of molten cast iron
DE10344543A1 (de) * 2002-10-04 2004-04-15 Visteon Global Technologies, Inc., Dearborn Grünglasmischung

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
HIROKI OHTA ET AL: "Activities of SiO2 and Al2O3 and activity coefficients of FetO and MnO in CaO-SiO2-Al2O3-MgO slags", METALLURGICAL AND MATERIALS TRANSACTIONS B, SPRINGER-VERLAG, NEW YORK, vol. 29, no. 1, 28 February 1998 (1998-02-28), pages 119 - 129, XP019696839, ISSN: 1543-1916 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3170908A1 (fr) * 2015-11-18 2017-05-24 Roman Wolf Procédé de traitement de scorie lors de la production d'acier

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