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
  • C21B13/0006—Making spongy iron or liquid steel, by direct processes obtaining iron or steel in a molten state
  • C21B13/0013—Making spongy iron or liquid steel, by direct processes obtaining iron or steel in a molten state introduction of iron oxide into a bath of molten iron containing a carbon reductant
  • C21B13/002—Reduction of iron ores by passing through a heated column of carbon

Definitions

• the invention relates to a method for removing sulfur in the melting of pig iron in a coal fluidized bed.
• the invention now aims to avoid such a separate desulfurization of the melt and to carry out most or all of the desulfurization work in the melting reactor.
• the invention essentially consists in introducing lumpy and / or granular desulfurizing agent into the fluidized bed of carbon and optionally additionally into the slag layer.
• the use of dusty fine lime in the form of hydrated lime or quicklime has proven to be disadvantageous, since dusty fine lime is largely discharged again with the blown-in gas and only a small amount is available for desulfurization in the melting chamber.
• the exclusive use of lumpy lime leads to insufficient dissolution in the mostly acidic slag from the coal ash due to the formation of a dicalcium silicate layer on the grain surface.
• the desulfurization reaction with CaO is endothermic and preferably takes place in the direction of higher temperatures. If the oxygen activity or the FeO content of the slag is high, then an impairment of the desulfurization efficiency must be expected, above all because the Si content of the molten metal is low.
• the feedstocks intended for post-desulfurization are now metered into the meltdown generator in granular and / or lumpy form and whirled together with the coal in accordance with their grain size. They bind the carbon sulfur in a solid, liquid or sublimed state of aggregation or, in the case of coarser grains, immediately fall through the fluidized bed and slowly dissolve in the slag layer in close contact with the melting iron sponge.
• the heavy weight of the desulfurization reaction can be shifted into the fluidized bed or into the slag layer by varying the lumpy or granular fraction of the desulfurization agent.
• manganese calcium, magnesium, alkalis or rare earths in the form of oxides, carbides, carbonates, alloys, mixed metals or in metallic form can be used as the desulfurizing agent.
• the use of calcium carbonate alone has the disadvantage that, when charging directly into the gasifier, not inconsiderable amounts of energy are required for the expulsion and conversion of C0 2 .
• Calcium carbide is therefore used according to the invention in a particularly preferred manner as a desulfurization agent. The desulfurization reaction with CaC 2 takes place with the release of energy and preferably in the direction of low temperatures.
• Calcium carbide also acts as a deoxidizer to reduce the FeO content in the slag.
• the reaction products CaO and CaS are taken up by the slag.
• Ladder provides a control option by combined loading of the desulfurization rooms (fluidized bed for coal desulfurization and slag layer for iron desulfurization).
• the grain size and quality of the desulfurization agent play an important role here.
• Such a control option is advantageously achieved by introducing the proportion of the desulfurizing agent for the coal fluidized bed in the grain size range of 0.5-5 mm and the proportion of the desulfurizing agent for the slag in the grain size range of 5 - 50 mm, these two parts in wide limits can be varied and in this way an adjustment of the heavy weight of the desulfurization reaction to the fluidized bed or the slag layer can be achieved.
• the process according to the invention is advantageously carried out in such a way that the granular and the lumpy portion of the desulfurizing agent is introduced above or laterally into the carbon fluidized bed.
• the desulphurising agent can be easily introduced together with coal, aggregates or recycling materials.
• the desulfurizing agents are at least partially introduced in agglomerated form.
• the invention is explained in more detail below using an exemplary embodiment.
• About 1000 kg of coal were used in a smelting gasifier per ton of pig iron.
• the coal had a sulfur content of 1.0%.
• the sulfur was composed of 60% organically bound sulfur and 40% inorganic sulfur (pyrite, sulfide, sulfate-S). Most of the inorganic sulfur was released when the coal was degassed and went into the reducing gas.
• the remaining sulfur approx. 6 - 7 kg / t pig iron, was converted into the gaseous state in the fluidized bed during combustion in front of the nozzles or gasification of the coked coal (S-Dampf, S0 2 , COS).
• the reaction product CaS dissolved in the slag.
• the sulfur content of the slag was between 2 and 3% and the sulfur in pig iron was 0.1%.

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• 1983
  • 1983-05-04 AT AT0164683A patent/AT387036B/de not_active IP Right Cessation
• 1984
  • 1984-04-26 EP EP84890076A patent/EP0128131B1/fr not_active Expired
  • 1984-04-26 DE DE8484890076T patent/DE3462925D1/de not_active Expired
  • 1984-04-30 US US06/605,282 patent/US4566902A/en not_active Expired - Fee Related
  • 1984-05-04 JP JP59090086A patent/JPS59208007A/ja active Granted

Patent Citations (5)

Non-Patent Citations (1)

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