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
  • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
  • C21C5/28—Manufacture of steel in the converter
• • 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
  • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
  • C21C5/28—Manufacture of steel in the converter
  • C21C5/36—Processes yielding slags of special composition
• • 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
  • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
  • C21C5/28—Manufacture of steel in the converter
  • C21C5/36—Processes yielding slags of special composition
  • C21C2005/366—Foam slags
• • 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
  • C21C2300/00—Process aspects
  • C21C2300/04—Avoiding foam formation

Definitions

• This invention relates to a slag defoaming composite for example, for use in steel manufacture, which may preferably be in briquette or pellet form.
• the invention is not restricted to steel manufacture and may be suitable in a number of applications where the defoaming of slag or the reduction of oxides to the metallic state is required.
• iron from a blast furnace is converted to steel by placing the iron in a basic oxygen furnace.
• the quantity of iron can vary. Typically, it is about 200 tonnes.
• Oxygen is blown into the iron by an oxygen lance and the removal of impurities such as carbon, silicon, manganese, etc., converts the iron to steel.
• impurities such as carbon, silicon, manganese, etc.
• the present invention seeks to ameliorate the abovementioned disadvantages and provide an efficient and rapid defoaming agent.
• the present invention provides a slag defoaming composite, comprising: a carbon source; a source of exothermic material, such as aluminium; a dense insert granular material, such as calcium alumina silicate; and a binder, optionally provided; characterised in that, said composite is selected to have a density sufficient to penetrate the slag layer during processing.
• said composite is manufactured in the form of briquettes pellets, and/or the like.
• said slag defoaming composite is substantially non-combustible.
• the density of said composite is selected to be in the range of 1.0 to 2.6 g/cc.
• the slag defoaming composite comprises: a carbon source which yields a final carbon content cf the composite in the range of 3 to 50% w/w; a source of aluminium which yields a final aluminium content of the composite within the range of 5 to 60% w/w; a calcium alumino silicate or a similar dense inert granular material within the range of 10 to 50% w/w; and a binder within the range of 0 to 20% w/w.
• said binder is sodium silicate or similar silicate derivatives, be they organic or inorganic, or clay, lime, or the like.
• the composite further comprises a lubricant material.
• said lubricant material is a stearate, such as calcium stearate.
• said lubricant material is provided within the range of 0 to 2% w/w.
• said composite further comprises a slag fluidiser.
• said slag fluidiser is provided in the range of 0 to 30% w/w.
• the composite further comprises: cellulose based raw material; and flame retardent.
• said cellulose based raw material is provided in the range of 3 to 30% w/w.
• typical ingredients include fine granular premelted calcium alumino silicate, fine powder alumina/aluminium, a silica/carbon fine powder admixture, sodium silicate binder and calcium stearate lubricant.
• the ingredients are mixed together, and then compressed, ideally to a briquette form. Details of the ingredients are as follows, with a suitable composition range for the slag defoaming composite being listed in Example 1, whilst Example 2 provides an example of a typical specific composition.
• the calcium alumino silicate, or like material has a very important role in the manufacturing of the briquette. It is a non-absorbent/inert material which coarsens the mix and thus adjusts the particle size distribution which allows for the briquetting of the mixture.
• the binder material is important to bind the various components together.
• a silicate such as sodium silicate or other similar silicate may be used, or alternatively, materials such as clay or lime, which have a binding effect may be used.
• a specialised binder material may not need to be added. That is, the other components of the composite may have a binding effect on the ingredients of the composite, such that a specialised binder material is unnecessary.
• a suitable briquette - an example of which is now described.
• the ingredients such as calcium alumino silicate, alumina/aluminium and the carbon silica mixture are firstly weighed separately and added into a mixing mill. They are dry mixed typically for three to five minutes. Sodium silicate, which acts as a binder, is finely sprayed into the mix while the mill is blending and this proceeds for a further six to eight minutes. In the last one minute of mixing, the calcium stearate lubricant is added and mixed in. The long mixing time yields a relatively dry mix characterised by good flowability which is essential in the manufacturing process.
• slag fluidiser cellulose based raw materials and flame retardents may also be included.
• the composite may contain carbon in the range of 3 to 50% w/w. s ag fluidiser in the range of 0 to 30% w/w, and cellulose based raw materials, such as wood chips in the range of 3 to 30%.
• flame retardent is added to prevent auto combustion in the hopper above the BOF.
• a preferred method of forming the briquette is to place the low moisture mixture in a hydraulic press and then to compress it to a pressure in excess of 20 tonnes per square inch to form a hard briquette with compression strength above 1000 kPa.
• a typical size for cylindrically shaped briquettes may be in the range of 65-75 mm in diameter and a 35-50mm in height.
• the typical density for the briquette in Example 2 would be in the vicinity of 2.4 g/cc; however densities in the range of 1.0 to 2.6 are quite acceptable.
• the density can generally be adjusted by varying the quantity of the dense inert granular material, eg., calcium alumino silicate present, the content of cellulose based-material or other variations in composition or processing.
• the briquettes are manufactured with different densities to suit different needs. For example, for steels with very viscous slag, briquettes of high density are required. Also the defoaming composite could be in various briquette shapes and sizes as well as in pellet and other forms. For example, the shape could be cylindrical, half cylindrical, rectangular, certain shapes being more preferable for transportation purposes, etc., as will be understood to persons skilled in the art.
• the slag defoaming composite as described herein has the advantage that the density of a slag defoaming composite - 1 - briquette can be chosen so as to penetrate the surface of the slag, but not sink into the steel. Being suspended within the slag layer results in an efficient exothermic reaction therefore improving the release of gases and reduction of slag viscosity which is desired in order to achieve defoaming. As mentioned this.typical density range is in the vicinity of 1.0 to 2.6 g/cc.
• Variation in the reactivity of the composite is controllable by variation in the composition thereof.
• the very fine division of the ingredients used causes good dispersion of reactive elements and thus promotes a highly exothermic reaction to thin the slag.
• the size, shape and hardness of the briquettes allows them to be handled and placed into hoppers which are held above the basic oxygen furnace without breakage, and to freefall into the furnace without loss of product or thermal reaction, before penetrating the slag.
• a final important advantage of the slag defoaming composite is that it will not combust when stored in a hopper above the basic oxygen furnace and nor will it react exothermically with powdered lime which may enter into the hopper containing the composite.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)
• Processing Of Solid Wastes (AREA)
• Treatment Of Steel In Its Molten State (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=3776692

Family Applications (1)

Country Status (5)

Families Citing this family (18)

• 1994
  • 1994-02-04 EP EP94906093A patent/EP0682717A4/de not_active Withdrawn
  • 1994-02-04 NZ NZ26127794A patent/NZ261277A/en not_active IP Right Cessation
  • 1994-02-04 JP JP6517443A patent/JPH08506144A/ja active Pending
  • 1994-02-04 WO PCT/AU1994/000049 patent/WO1994018347A1/en not_active Application Discontinuation
• 1995
  • 1995-08-07 OA OA60696A patent/OA10453A/en unknown

Non-Patent Citations (2)

Also Published As

Similar Documents

Legal Events