Search

US-12624405-B2 - Agglomerated stone for use in an electric furnace

US12624405B2US 12624405 B2US12624405 B2US 12624405B2US-12624405-B2

Abstract

This disclosure relates to an agglomerated stone for use in an electric furnace.

Inventors

  • Ronald Erdmann
  • Sören ELLERIK

Assignees

  • THYSSENKRUPP STEEL EUROPE AG

Dates

Publication Date
20260512
Application Date
20230905
Priority Date
20220922

Claims (11)

  1. 1 . An agglomerated stone for use in an electric furnace, which comprises, in % by weight based on a dry state, 6-15% of a cement binder, 25-60% of a carbon carrier and a metal carrier as remainder, wherein the agglomerated stone has a density of at least 1.90 kg/m 3 , wherein the content of carbon thereof is at least 25% by weight.
  2. 2 . The agglomerated stone according to claim 1 , wherein the metal carriers are in the form of ores, residual materials and/or recycled materials.
  3. 3 . The agglomerated stone according to claim 2 , wherein the metal carriers have a grain size of up to 5 mm.
  4. 4 . The agglomerated stone according to claim 3 , wherein the content of iron thereof is at least 5% by weight.
  5. 5 . The agglomerated stone according to claim 4 , wherein the carbon carriers are in the form of coke dust, coke slack, coke breeze and/or anthracite coal.
  6. 6 . The agglomerated stone according to claim 2 , wherein the carbon carriers have a grain size of up to 5 mm.
  7. 7 . The agglomerated stone according to claim 1 , wherein the cement binder is Portland cement or blast furnace cement.
  8. 8 . The agglomerated stone according to claim 7 , wherein the agglomerated stone may optionally comprise up to 10% by weight based on the dry state of a setting and solidification accelerator selected from water glass, alumina cement, calcium chloride, an alkali metal salt, or a cellulose adhesive.
  9. 9 . The agglomerated stone according to claim 8 , wherein it has a cylindrical, cuboidal or a block shape with a hexagonal, base area.
  10. 10 . The agglomerated stone according to claim 9 , wherein, as a green body before it is dried, it has a water content of less than 25%.
  11. 11 . A method of using the agglomerated stone as claimed in claim 9 comprising: charging the agglomerated stone below a liquid slag into molten pig iron in an electric furnace; increasing the carbon content of the molten pig iron to more than 2.5 wt. %; and processing the pig iron into crude steel.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a U.S. Non-Provisional that claims priority to European Patent Application No. EP 22197096.5, filed Sep. 22, 2022, the entire content of which is incorporated herein by reference. The invention relates to an agglomerated stone for use in an electric furnace. Agglomerated stones for use in blast furnaces are known from the prior art, see DE 10 2004 027 193 A1. In addition to the conventional blast furnace route for the production of pig iron, there is also the route via direct reduction and subsequent smelting of the reduced iron ore (sponge iron) to form pig iron in an electric furnace. Depending on the reducing gas, the sponge iron can be doped with more or with less carbon, particularly with less carbon when hydrogen is used. In order to be able to ensure and maintain existing processes, a minimum content of carbon in the pig iron has proven to be advantageous. For this purpose, carbon can additionally be introduced in the form of coke or coal into the electric furnace, see EP 0 257 450 A2. In contrast to the prior art, the production of pig iron via the direct reduction plant/smelter route uses agglomerated aggregates comprising carbon-containing materials which enable carburization of the sponge iron, downstream of the direct reduction plant in the smelter, to carbon contents >2.5% of a standard pig iron, so that the pig iron can be processed further into crude steel in downstream LD steelworks without any further pretreatment. The invention therefore relates to an agglomerated stone for use in an electric furnace, which comprises, in % by weight based on the dry state, 6-15% of a cement binder, 25-60% of a carbon carrier and a metal carrier as remainder. The composition of the agglomerated stone according to the invention is coordinated in such a way that when the smelting operation is in progress, a carburization of the liquid pig iron by the carbon carrier as well as an additional output of metal or iron by the metal carrier can be effected. The particular composition of agglomerated stones according to the invention makes these stones particularly suitable for the carburization of pig iron in an electric furnace. In order to bring the agglomerated stone directly into contact with the liquid pig iron, which is preferably to be carburized, during the smelting operation below the liquid slag which forms above the liquid pig iron during the smelting operation, the density of the agglomerated stone is at least 1.90 kg/m3 according to one configuration of the invention. The density of the agglomerated stone is in particular at least 1.950 kg/m3, preferably at least 2.0 kg/m3, preferably at least 2.050 kg/m3, particularly preferably at least 2.10 kg/m3, further preferably at least 2.150 kg/m3. According to one configuration of the invention, the metal carriers are in the form of ores, residual and/or recycled materials, in particular containing metal. The metal carriers are preferably iron carriers. The ores are not metallic iron, but rather only pure iron oxide that may be contaminated with a little gangue. The preferred iron ores are present in haematitic (Fe2O3), magnetitic (Fe3O4), wustitic (FeO) modification and/or as goethite (FeO(OH)), having a grain size or grain diameter of up to 5 mm, particularly up to 3 mm, preferably up to 2 mm. The in particular metal-containing residual and/or recycled materials occur for example in steel production and processing in the form of filter dusts, blast furnace dusts or mill scale, having a grain size or grain diameter of up to 5 mm. The metal carriers or iron carriers may also be used in the form of dust or dusts having a grain size of less than 1 mm. Alternatively, iron carriers may in particular also only comprise metallic iron instead of oxidic iron. According to one configuration of the invention, the content of iron in the agglomerated stone is at least 5% by weight in order to promote effective pig iron production. In particular, the content of iron is at least 6% by weight, preferably at least 7% by weight, more preferably at least 8% by weight, particularly preferably at least 10% by weight. It is also possible to adjust the density of the agglomerated stone in a controlled manner by way of the content of iron. Suitable carbon carriers are in principle all materials having free carbon. According to one configuration of the invention, the carbon carriers are in the form of coke dust, coke slack, coke breeze and/or anthracite coal. Coke dust, coke slack and coke breeze are in particular carbon-containing residual and/or recycled materials. The grain size of the carbon carrier is up to 5 mm, in particular up to 3 mm, preferably up to 2 mm. C carriers having such a grain size can be obtained particularly cost-effectively and can be used in iron production only with difficulty. According to one configuration of the invention, the content of carbon in the agglomerated stone is at least 25% by weight.