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

Definitions

• Desulphurization of pig iron outside the blast furnace is an essential necessity due to the increasing sulfur content in the ores and black matter. Numerous means and processes have already been known for this, with which sufficient degrees of desulfurization can be achieved. Mixtures based on calcium carbide with diamide lime (DE-PS 17 58 250) and with additives which split off hydrogen (DE-PS 22 52 796) or water (DE-PS 22 52 795) are preferably used. Calcium-containing compounds in combination with hydrocarbons such as oil or paraffin (FR-PS 11 66 389 and US-PS 28 63 755) have already been proposed.
• the purpose of the gas-releasing component is to distribute the finely ground particles of the basic desulfurization agent in the molten iron.
• a commercially available product with contents of 70 to 85% CaC 2 is normally used as calcium carbide, but so-called eutectic carbide with contents of 65% CaC 2 and below can also be used.
• Solid, liquid or gaseous hydrocarbons can be used as the hydrogen-releasing compounds.
• solid hydrocarbons at room temperature are, for. B. polyethylene, polypropylene, polyvinyl chloride or polystyrene.
• liquid hydrocarbons which may contain halogen
• z. B. those with boiling points between 50 and 350 ° C
• These liquid substances are preferably used in the form of a porous organic or inorganic material, which can contain up to a multiple of its own weight of hydrocarbon.
• Preferred porous Materials for this purpose are those that can also split off hydrogen themselves or favorably influence the formation of slag, such as. B. polyurethane foam, peat or expanded minerals. If gaseous hydrocarbons are used, some or all of them can serve to blow the solid desulfurization mixture into the molten iron. Those hydrocarbons or mixtures thereof which contain little or no oxygen are preferred.
• component A can also have 1 to 10% by weight of other constituents which have a favorable effect on the properties of the slag, such as, for example, B. fluorspar, alumina, cryolite or colemanite.
• additives which release carbon dioxide such as, in particular, calcium carbonate, dolomite or diamide lime, individually or as a mixture, can preferably also be mixed in with component A.
• carbon dioxide such as, in particular, calcium carbonate, dolomite or diamide lime, individually or as a mixture
• component A additives which release carbon dioxide
• additives which release carbon dioxide can preferably also be mixed in with component A.
• their amount must be so limited that the volume of carbon dioxide developed therefrom and any other Co 2 -producting substances present is less than the volume of hydrogen developed from the compounds which release hydrogen.
• These substances that release carbon dioxide can be ground together with the calcium carbide. If the specified quantity conditions are adhered to, they cause practically no oxidation of the magnesium or calcium carbide in the molten iron, but they increase the beneficial effect of the split off hydrogen through the CO 2 formed (which is also formed in certain quantities by the hydrocarbon).
• component A may be expedient to additionally mix component A with brown or gas coal, anthracite or hard coal, which also have a gas-releasing effect.
• component A can also be added in small amounts (about 0.01 to 0.5% by weight) with commercially available flow improvers such as graphite, long-chain organic amines, alcohols, esters or silicones.
• the constituents of component A are ground and mixed intensively, the mixing process advantageously being carried out in a mill, which is preferably a tube mill, under an inert gas blanket.
• the constituents are preferably comminuted to such an extent that 90% of the mixture has a grain size ⁇ 90 ⁇ m and about 50% has a grain size ⁇ 50 ⁇ m. Certain deviations from this are irrelevant to the desulfurization effect.
• the magnesia can be added to the component in powder form in the mill or afterwards until component A contains a ratio of 70 to 99% by weight calcium carbide and 1 to 30% by weight essentially hydrogen-donating compounds.
• M an can mix components A and B (Mg) before blowing into the iron melt, so that they are conveyed pneumatically into the melt as a mixture.
• component A it has often proven to be expedient to store component A separately from the magnesium after its production and to combine it with the magnesium only in the delivery line or in the lance and to introduce it together into the melt.
• the process according to the invention is characterized in that a mixture of calcium carbide and a hydrogen-releasing compound as component A is blown into the pig iron together with component B, the magnesium.
• components A and B in a ratio of 40 to 95 to 5 to 60% by weight.
• carbon dioxide-releasing substance such as alkaline earth metal carbonate, dolomite or diamide lime and hydrogen-releasing substance such as hydrocarbon
• fluorspar and small amounts up to 0.5% by weight
• the process is advantageously carried out in such a way that a blowing rate of 10 to 100 kg, preferably 15 to 80 kg, per minute of desulfurizing agent, consisting of component A and magnesium, is blown into the iron melt.
• a blowing rate of 10 to 100 kg, preferably 15 to 80 kg, per minute of desulfurizing agent, consisting of component A and magnesium is blown into the iron melt.
• the desulfurizing agent is preferably blown pneumatically into the molten iron as deeply as possible using a submersible lance.
• carrier gases come inert gases such as argon or nitrogen alone or as a mixture, or reactive gases that split off hydrogen and / or contain CO 2 such as, for. B. propane or natural gas alone or as a mixture in question.
• the desulfurization agent according to the invention is suitable in connection with the blowing process described just as well for hot metal desulfurization in the transfer pan as in the transport pan (torpedo pan).
• the particularly low requirement for injection gas has a particularly advantageous effect; the composition of the agent guarantees sufficient distribution so that a high degree of utilization of the desulfurizing agent is achieved.
• the desulfurization agent according to the invention has considerable advantages over the known agents in connection with the method according to the invention. According to the invention, a significant increase in the degree of desulfurization is achieved or a noticeably reduced amount of desulfurizing agent is required to achieve the same desulfurization effect.
• the compounds which desulfurize the iron melt that is to say the calcium carbide and the alkaline earth metal, are completely available for the desulfurization reaction in combination with the compounds which essentially release hydrogen, since they are not consumed by oxidation processes.
• Table 1 below describes various desulfurizing agents, their use and the results achieved with them. The results are averages from at least 3 desulfurization treatments each.
• Examples 1 to 4 are comparative examples which were carried out using known desulfurization agents based on calcium carbide and diamide lime or calcium hydroxide and carbon.

Landscapes

• 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)
• Manufacture And Refinement Of Metals (AREA)
• Catalysts (AREA)
• Carbon And Carbon Compounds (AREA)
• Manufacture Of Macromolecular Shaped Articles (AREA)
• Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
• Compounds Of Iron (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)

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Citations (6)

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• 1984
  • 1984-11-16 CA CA000468038A patent/CA1240842A/fr not_active Expired
  • 1984-12-13 US US06/681,174 patent/US4592777A/en not_active Expired - Lifetime
• 1985
  • 1985-05-10 ZA ZA853556A patent/ZA853556B/xx unknown
  • 1985-05-13 AT AT85105870T patent/ATE35153T1/de not_active IP Right Cessation
  • 1985-05-13 DE DE8585105870T patent/DE3563360D1/de not_active Expired
  • 1985-05-13 EP EP85105870A patent/EP0164592B2/fr not_active Expired - Lifetime
  • 1985-05-14 IN IN364/CAL/85A patent/IN162816B/en unknown
  • 1985-05-14 NO NO851924A patent/NO165765C/no not_active IP Right Cessation
  • 1985-05-15 FI FI851943A patent/FI78736C/fi not_active IP Right Cessation
  • 1985-05-16 AU AU42542/85A patent/AU568056B2/en not_active Ceased
  • 1985-05-16 ES ES543217A patent/ES8606504A1/es not_active Expired

Patent Citations (6)

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