Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B3/00—General features in the manufacture of pig-iron
  • C21B3/02—General features in the manufacture of pig-iron by applying additives, e.g. fluxing agents
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B11/00—Making pig-iron other than in blast furnaces
  • C21B11/10—Making pig-iron other than in blast furnaces in electric furnaces
• • 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
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B13/00—Making spongy iron or liquid steel, by direct processes
  • C21B13/008—Use of special additives or fluxing agents
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B13/00—Making spongy iron or liquid steel, by direct processes
  • C21B13/12—Making spongy iron or liquid steel, by direct processes in electric furnaces
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B13/00—Making spongy iron or liquid steel, by direct processes
  • C21B13/14—Multi-stage processes processes carried out in different vessels or furnaces
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B3/00—General features in the manufacture of pig-iron
  • C21B3/04—Recovery of by-products, e.g. slag
  • C21B3/06—Treatment of liquid slag
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B2200/00—Recycling of non-gaseous waste material
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B2400/00—Treatment of slags originating from iron or steel processes
  • C21B2400/02—Physical or chemical treatment of slags

Definitions

• the invention relates to a method for producing a phosphorus-containing pig iron melt.
• the DD 44 860 A5 how the conversion of phosphorus-rich pig iron into steel and the conversion of Thomas iron into steel are carried out in a converter.
• the DE 10 15 839 A1 describes a process for producing carbon steels by refining phosphorus-rich pig iron in a converter vessel.
• Table 10.16 on page 239 provides values for carbon, phosphorus, etc., and their temperature reduction coefficients, which, with the aid of formula 10.26 on page 238, can be used to calculate the approximate melting point of a steel depending on its constituents.
• the task is to provide a process for producing a phosphorus-containing pig iron melt, which in particular proposes an alternative variant for closing phosphorus cycles and/or preferably can have a positive influence on reducing CO2 emissions in steel production.
• iron carriers and additives are melted in an electric melter to form a smelter slag covering the pig iron melt, wherein, to adjust the phosphorus content in the pig iron melt to between 0.150 and 5.0 wt.%, organic substances in the form of iron carriers and/or additives with a phosphorus and/or phosphate content of at least 1.0 wt.% are added and melted together.
• the phosphorus content in the pig iron melt can be, in particular, at least 0.250 wt.%, 0.350 wt.%, preferably at least 0.450 wt.%, 0.550 wt.%, more preferably at least 0.60 wt.%, 0.70 wt.%, and most preferably at least 0.750 wt.%, 0.850 wt.%, or 1.0 wt.%.
• the higher the phosphorus content the more organic substances with a phosphorus and/or phosphate content of at least 1.0 wt.% can be added, and in particular, the carbon content in the pig iron melt can also be reduced, preferably while maintaining and/or adhering to a predetermined melting point.
• the phosphorus and/or phosphate content of the organic substance can be, in particular, at least 1.2, 1.4, 1.6 wt.%, preferably at least 1.8, 2.0, 2.2 wt.%, preferably at least 2.4, 2.6, 2.8 wt.%.
• the phosphorus and/or phosphate content of the organic substance can be a maximum of 10.0 wt.%, in particular a maximum of 9.0, 8.0 wt.%, preferably a maximum of 7.0, 6.0, 5.0 wt.%.
• the phosphorus content in the pig iron melt can be, in particular, a maximum of 4.0 wt.%, 3.50 wt.%, preferably a maximum of 3.0 wt.%, 12.50 wt.%, preferably a maximum of 2.0 wt.%, 1.80 wt.%, and especially preferably a maximum of 1.60 wt.%, 1.40 wt.%, 1.20 wt.%, in order to avoid, for example, excessively frequent slag removal (slag replacement).
• the molten pig iron can contain, in addition to phosphorus (P), the following components in wt.%: carbon (C): 1.2 to 5.0%, silicon (Si): 0.015 to 3.0%, manganese (Mn): 0.020 to 6.0%, balance: iron (Fe), and impurities, which together total 100 wt.%.
• the impurities can include one or more of the elements Al, Mg, Ti, S, N, and O, listed here by way of example (and this list is not exhaustive), with a total of up to 1.0 wt.% or less.
• P would also be considered an impurity; however, the essential advantages of P, as described, are utilized, among other things, in the present invention.
• iron carriers are required. These include or consist of reduced iron, unreduced iron, ferrous scrap, ferrous residues and/or recycled materials.
• Reduced iron is produced from iron ores containing iron oxides with gangue minerals such as silicon, aluminum, and magnesium in oxide form. The concentrations of these individual components can vary depending on the ore's origin.
• a hot reducing gas which may contain or consist of CO and/or H2
• the cooled reduced iron can then be supplied as direct reduced iron (DRI), which can optionally be passivated to prevent reoxidation and loss of metallization.
• DRI direct reduced iron
• the reduced iron can be briquetted while still warm to form hot briquetted iron (HBI). Passivation is not necessary in this case, and HBI can also be supplied as an iron carrier.
• the DRI and/or HBI has a metallization degree of at least 75%, in particular at least 80%, preferably at least 88%, and can ideally be up to 100%, in particular up to 99%.
• the DRI and/or HBI can have a carbon content between 0 and 4.0 wt.%, in particular > 0.10 wt.%, preferably > 0.30 wt.%, preferably > 0.50 wt.%, and in particular a maximum of 3.50 wt.%, preferably a maximum of 3.0 wt.%, preferably a maximum of 2.0 wt.%.
• the gangue structure during the metallization of iron ore to reduced iron by passing the iron ore through a reducing gas is not significantly affected or removed, so that it remains essentially unchanged.
• non-reduced iron i.e., iron ore or only partially reduced iron, and thus in this case, iron oxide
• the feed rate can be up to 100 kg, in particular up to 90 kg, preferably up to 80 kg, preferably up to 70 kg per ton of pig iron melt produced, or even 0.
• Partially reduced iron for example, has a metallization degree of at most 70%, in particular at most 50%, preferably at most 30%, and preferably at most 15%. In particular, sufficient reduction potential is present.
• the degree of metallization of a substance is familiar to those skilled in the art, whereby the degree of metallization is defined as the quotient of the mass of elemental iron (Fe ⁇ sub>elemental ⁇ /sub>) and the total mass of iron present. Iron (Fe total) .
• Oxide iron in the pig iron melt can have the advantage that the oxygen separates from the oxide iron and combines, for example, with dissolved silicon in the pig iron melt. The resulting silicon dioxide has a lower density compared to the surrounding pig iron melt and rises to the interface with the pig iron melt, thus being transferred into the smelting slag above. Additional compounds with other components of the pig iron melt, especially impurities (Al, Mg, Ti), can also be transferred into the smelting slag via the same mechanism.
• ferrous scrap can also be provided as an iron carrier.
• up to 200 kg, especially up to 150 kg, preferably up to 100 kg, and preferably up to 50 kg of ferrous scrap can be added per ton of molten pig iron produced.
• the feed rate can also be zero.
• iron-containing residues and/or recycled materials can also be provided as iron carriers.
• these iron-containing residues and/or recycled materials which contain or consist of oxygen compounds, are in oxide form. Examples include iron-containing agglomerates or oxide recycled materials or metallurgical products generated in a smelting plant complex, particularly residues/dusts from a coking plant, sintering plant, and/or burden preparation facility.
• the advantage of these iron-containing residues and/or recycled materials, preferably in oxide form is that they can be reduced to iron and thus substitute components such as silicon, as well as other elements, in the pig iron melt, thereby increasing the iron yield. In particular, sufficient reduction potential is present.
• additives are required. These include or consist of at least one slag former and/or at least one reducing agent.
• Slag formers comprise or consist of at least one component from the group consisting of SiO2 , CaO, MgO, and Al2O3 . They are used to bind silicates and phosphates and to promote the slag flow of the smelter slag produced in the electric remelter.
• the gangue leads to the formation of the smelter slag and contributes in particular to its composition. the smelting slag, which forms on the pig iron melt during the smelting process.
• At least one reducing agent can be added as a further additive.
• the reducing agent comprises or consists of at least one carbon-containing substance in gaseous, liquid, and/or solid form with reducible free carbon, which can be introduced into an electric melter.
• Suitable solids include, for example, coke dust, coke slurry, coke grit, and/or (bio)coal particles.
• Suitable liquids include, for example, ethanol, methanol, and other (suitable) hydrocarbons.
• Suitable gases include, for example, carbon-containing gases such as carbon dioxide, methane (natural gas), carbon monoxide, propane, and butane.
• reducing agents can be added in combination with an iron-containing residue and/or recycled material present in oxide form and/or unreduced iron, in order to reduce these to iron and, for example, increase the iron yield.
• the organic materials which may be contained in the form of iron carriers and/or additives and enter the electric melter, may include or consist of components from sewage sludge, reduced and/or non-reduced iron, carbon-containing residues, such as briquetted dusts from metallurgical residues.
• Sewage sludge is rich in nutrients, among other things, because microorganisms in the biological treatment stage use the wastewater constituents to build biomass, thus concentrating the nutrients contained in the wastewater. Nitrate, phosphate (especially with a P2O5 content of, for example, between 1.0 and 8.0 wt% based on dry matter), and other plant nutrients are of particular importance for agriculture.
• sewage sludge also contains microplastics, nanomaterials, and pharmaceutical residues, which preclude its direct agricultural use. Portions of the sewage sludge that are not directly used in agriculture can be effectively recycled using alternative technologies, and the phosphorus and/or phosphate content contained in the sewage sludge can be reused, thus preventing it from ending up in landfills, for example. Sewage sludge, as an organic matter containing phosphorus and/or phosphate, could therefore be used as an additive.
• iron ores can be contaminated with high levels of phosphorus and/or phosphate, for example, at least 0.8 wt%. Due to their high phosphorus content, these types of iron ores are rarely used for steel production and/or are mixed with ores containing less phosphorus. Therefore, alternatively or additionally, reduced and/or unreduced iron contaminated with phosphorus and/or phosphate can be added in the form of an iron carrier.
• the additive can additionally or alternatively contain not only phosphorus and/or phosphate as an organic substance, but also free carbon, thus contributing to the enrichment of the pig iron melt to be produced in the form of a reducing agent containing phosphorus and/or phosphate.
• reduced iron as an iron carrier, particularly as the main component of the iron carrier with at least 60%, more specifically at least 70%, preferably at least 80%, and, for example, a maximum possible 100%, also entails slag-forming components that are naturally present in the iron ore and cannot be driven off in a prior reduction process (gangue). If the gangue provided by the reduced iron is insufficient, further slag formers can be added as additional additives to produce a remelter slag suitable for further processing. Slag formers are preferably added such that a basicity B4 in the remelter slag is established between 0.7 and 1.8. B4 can be at least 0.8, preferably at least 0.9, and particularly at most 1.7, preferably at most 1.6.
• the basicity B4 corresponds to the ratio (CaO+MgO) to (SiO 2 +Al 2 O 3 ), whereby the determination of the characteristic quantities is generally known to those skilled in the art in solid slags.
• an electric melter has several electrodes that can be energized with electricity, thus providing the necessary energy to convert the materials into a liquid phase comprising molten pig iron and melting slag.
• three, four, five, six, or more than six electrodes can be used.
• the energy required for melting is preferably provided, at least in part, from renewable energy sources (solar, wind, water, biomass). If the required energy is available in sufficient quantities, and if it is available entirely from renewable sources, the process would be ideal. If energy can be provided, the electric melter can be operated in a climate-neutral (or more) manner.
• the electric melter can preferably be an electric furnace of the OSBF (Open Slag Bath Furnace) type.
• SAF furnaces the electrodes are immersed in the charge and/or melting slag.
• the electric reduction furnaces can be designed as alternating current arc reduction furnaces (SAFac) or direct current arc reduction furnaces (SAFdc).
• EAFs Electro Arc Furnaces
• EAFac alternating current arc melting furnace
• EAFdc direct current arc melting furnace
• LF ladle furnace
• the molten pig iron can have a temperature between 1300 °C and 1650 °C.
• Important states of matter can be derived from an iron-carbon diagram known to those skilled in the art. If the production of pig iron and its further processing into crude steel or steel must take place indirectly via suitable and known containers, for example, torpedo ladles or the like, a molten pig iron temperature with a certain buffer above the liquidus temperature is required to ensure that the molten pig iron does not (partially) solidify during transport in the suitable containers. The addition of phosphorus can lower the liquidus temperature of a molten pig iron, regardless of the carbon content of the molten pig iron.
• the temperature during tapping from the electric melter can be a maximum of 1600 °C, preferably a maximum of 1550 °C, more preferably a maximum of 1500 °C, and more preferably a maximum of 1450 °C.
• a buffer of at least 75 K, in particular at least 100 K, and preferably at least 125 K can be provided so that the critical liquidus temperature cannot be reached during normal operation.
• the invention also comprises a method for producing a phosphorus-containing converter slag comprising the steps of: - providing a phosphorus-containing pig iron melt produced according to the invention; - Treating the phosphorus-containing pig iron melt in a converter by adding at least one slag former and/or at least one reducing agent and by oxygen bubbling, wherein at the end of the treatment a steel melt comprising the following components in wt.%: C: 0.0010 to 0.80%, Si: 0.015 to 3.0%, Mn: 0.020 to 6.0%, P: up to 0.10%, balance Fe and impurities, which together amount to 100 wt.%, is tapped, wherein during the treatment and/or optionally at the end of the treatment a phosphorus-containing converter slag comprising or consisting of the following components in wt.%: FeO: up to 40%, MnO: up to 10%, SiO2 : 5 to 40%, CaO: 35 to 65%, MgO: up to 8%,
• the FeO content can be 0 or > 0, in particular > 1 wt.%, preferably > 2 wt.%. FeO can be a maximum of 35 wt.%, preferably a maximum of 30 wt.%, preferably a maximum of 25 wt.%.
• the MnO content can be 0 or > 0, in particular > 1 wt.%, preferably > 2 wt.%. MnO can be a maximum of 8 wt.%, preferably a maximum of 6 wt.%, preferably a maximum of 4 wt . %.
• the Al2O3 content can be 0 or > 0, in particular > 0.5 wt.%. Al2O3 can be a maximum of 15 wt.%, preferably a maximum of 12 wt.%, preferably a maximum of 10 wt.%.
• the method of removing the converter slag can be customized depending on the converter's operation and/or design.
• the converter slag generated in the converter by oxygen bubbles can be removed during the treatment process, i.e., after a predetermined treatment time, and optionally at the end of the treatment process, thus being removed at least twice.
• the first removal during treatment can yield converter slag containing the aforementioned components
• the second or, for example, final removal can yield converter slag whose composition differs from that of the first removal, at least in its phosphate content.
• This slag may contain up to 4.0 wt.% P2O5 , more specifically up to 3.0 wt.%, and preferably up to 2.0 wt.% P2O5 .
• the converter slag can be removed only once, which means that, especially at the end of the treatment, a converter slag containing the aforementioned components can be provided.
• FIG. 1 shows a process flow diagram for producing a pig iron melt (11) with a phosphorus content between 0.150 and 5.0 wt.% and a smelting slag (12) covering the pig iron melt (11) in an electric melter (10).
• Iron carriers and additives are melted in the electric melter (10), whereby, to adjust the phosphorus content in the pig iron melt (11) between 0.150 and 5.0 wt.%, organic substances in the form of iron carriers and/or additives with a phosphorus and/or phosphate content of at least 1.0 wt.% are added and melted along with the smelting.
• Figure 1 shows Figure 1 also, how a phosphorus-containing converter slag (22) is produced by treating the phosphorus-containing pig iron melt (11) by adding at least one slag former and/or at least one reducing agent and by oxygen bubbles in a converter (20).
• a steel melt (21) comprising the following components in wt.%: C: 0.0010 to 0.80%, Si: 0.015 to 3.0%, Mn: 0.020 to 6.0%, P: up to 0.050%, balance Fe and impurities, which together make up 100 wt.%, is tapped, wherein during the treatment and/or optionally at the end of the treatment, a phosphorus-containing converter slag (22) comprising or consisting of the The following components in wt.%: FeO: up to 40%, MnO: up to 10%, SiO2 : 5 to 40%, CaO: 35 to 65%, MgO: up to 8%, Al2O3 : up to 20%, P2O5 : 4 to 30% and impurities totaling 100 wt .% are produced, which is drawn off before tapping of the molten steel (21).
• the withdrawn smelting slag (12) and converter slag (22) are fed into a further conventional route known to those skilled in the art, not shown here. In particular, they can optionally be subjected to granulation.
• the converter slag (22), which can optionally be granulated, can preferably be used for agricultural purposes, and more preferably further processed into a fertilizer.
• the tapped steel melt (21) is fed to another conventional route known to those skilled in the art, not shown here.
• pig iron melt (11) with a phosphorus content of 0.65 wt.% and a carbon content of 4.1 wt.% was produced in an electric melter (10) of type SAF, wherein reduced iron with a metallization degree of 94% (87.1% of the impurity), which was reduced with 100% H2 , was used as an iron carrier with a total Fe content of 88.9% wt.%, 83.5% Fe metal , 0.050% S, 0.01% P, balance SiO2 , Al2O3 , CaO, MgO, containing 80 wt.
• sewage sludge 5.7% of the impurity as an organic substance with a P content of 8.67 wt.% as a further additive.
• the sewage sludge contained CaO at 10 wt% and MgO at 1.5 wt%
• further slag formers (3.2% of the slag content) was necessary to melt a smelter slag (12) with a basicity B4 of 1.1.
• the temperature of the pig iron melt (11) was 1380 °C.
• the theoretical liquidus temperature T ⁇ sub>liq ⁇ /sub> would be 1110 °C, resulting in a buffer of 270 K (temperature of the pig iron melt (11) - liquidus temperature).
• the resulting remelting slag (12) was removed, allowing the pig iron melt (11) containing 0.25 wt% Mn, 0.6 wt% Si, and 0.005 wt% S, with the balance being Fe and unavoidable impurities, to be fed into a laboratory-scale converter (20).
• the phosphorus-containing pig iron melt (11) from the electric remelter (10) was treated by adding at least one slag former and/or at least one reducing agent and by oxygen bubbling.
• a steel melt (21) comprising the following components in wt%: C: 0.05%, Mn: 0.06%, P: 0.052%, balance Fe and impurities. produced and tapped.
• a phosphorus-containing converter slag (22) comprising or consisting of the following components in wt.%: FeO: 20.7%, MnO: 2.3%, SiO2 : 9.8% , CaO: 41.5%, MgO : 3.8%, Al2O3 : 0.7%, P2O5 : 21.2%, and impurities totaling 100 wt.%, was produced, which was drawn off before the steel melt (21) was tapped.

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Citations (5)

• 2024
  • 2024-04-30 EP EP24173275.9A patent/EP4644574A1/fr active Pending

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