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
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/04—Removing impurities by adding a treating agent
  • C21C7/076—Use of slags or fluxes as treating agents
• • 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
• • 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
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/0037—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 by injecting powdered material
• • 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
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
• • 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
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/04—Removing impurities by adding a treating agent
  • C21C7/06—Deoxidising, e.g. killing
• • 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
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/04—Removing impurities by adding a treating agent
  • C21C7/064—Dephosphorising; Desulfurising
  • C21C7/0645—Agents used for dephosphorising or desulfurising
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B1/00—Preliminary treatment of ores or scrap
  • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
  • C22B1/24—Binding; Briquetting ; Granulating
  • C22B1/242—Binding; Briquetting ; Granulating with binders
  • C22B1/244—Binding; Briquetting ; Granulating with binders organic
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
  • C22B7/02—Working-up flue dust
• • 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
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
  • C21C2007/0062—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires with introduction of alloying or treating agents under a compacted form different from a wire, e.g. briquette, pellet

Definitions

• the present invention relates to a composition for use in steel making process.
• the present invention further relates to the method for production of the composition, to the use of the composition as raw material in steel making process and to a premix for producing the composition.
• wastes also called by-products, such as slag, dust, and sludge are generated, which contain hazardous chemicals and metals. If not handled correctly, these wastes can contaminate the environment, harm human health, and damage ecosystems. These wastes are currently mostly disposed of to landfill. However, disposal of large volumes of metallic solid waste may disturb the environmental balance of soil and groundwater.
• Recycling is becoming very important. Recycling is a process using materials (waste) into new products to prevent waste of potentially useful materials, reduce the consumption of fresh raw materials, reduce energy usage, reduce air pollution (from incineration) and water pollution (from landfilling) by reducing the need for "conventional" waste disposal. Recycling is a key component of modern waste reduction.
• the European Union is also currently updating its legislation on waste management to promote a shift to a more sustainable model known as the circular economy.
• BOF and LAF slag's into cement, concrete and road base infrastructure markets, leading to significant reductions in environmental impact, along with high-efficiency metal recovery and the manufacture of co products from the residual slag's.
• EP0687309 A1 also discloses a process and a device for recovering iron and carbon from blast furnace scrubber sludge (dust, particulates and sludge). After a series of treatments such as separations by filtration or hydro cyclones, the recovered iron and carbon are recycled to the iron making operation
• the steel making industry is also affected by the concerns of recycling and circular economy and is currently undergoing an energy transition. It must notably adapt its dependence on raw materials in line with constantly changing regulations.
• composition (C), herein after] wherein said composition (C) is prepared by mixing :
• the present invention further provides a method for the manufacturing of a composition for a use in steel making process, as detailed above, a premix for manufacturing the composition, as detailed above and use of the composition as raw material in a steel making process, as detailed above.
• compositions comprising A and B should not be limited to the composition consisting only of A and B. It means that with respect to the present invention, the only compositional components of the composition are A and B. Accordingly, the terms “comprising” and “including” encompass the more restrictive terms “consisting essentially of” and “consisting of”.
• the terms "optional” or “optionally” means that a subsequently described event or circumstance can or cannot occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.
• composition [composition (C), herein after] is for use in a steel making process.
• the present invention relates to a composition (C) suitable to be used as a raw material in a steel making process.
• steel making process refers to a process for producing steel.
• Non-limiting examples of such steel making process are basic oxygen furnace (BOF) process, electric arc furnace (EAF) process and argon oxygen decarburization process (AOD).
• BAF basic oxygen furnace
• EAF electric arc furnace
• AOD argon oxygen decarburization process
• the composition (C) is particularly suitable to be used as a raw material in an electric arc furnace (EAF) process.
• composition according to the present invention is prepared from at least one steel scale by-product [compound SSB, herein after].
• the expression “at least one steel scale by-product [compound SSB, herein after]” is intended to denote one or more than one steel scale by-product. Mixtures of steel scale by-product can also be used for the purpose of the invention.
• steel scale by-product is understood, for the purposes of the present invention, both in the plural and the singular form.
• the compound (SSB) is intended to refer to a by-product, also called a waste, of a steel making process.
• Scale is formed on the surface of steel during their high temperature thermal treatments after casting.
• steel is immersed in an acidic bath (also called pickling process) to remove scale present at the surface of the steel.
• the acidic solution is then collected.
• lime is added to this acidic solution to reach a pH of about 10 and to precipitate dissolved metals.
• the resulting sludge which contained the precipitated metals is collected and subjected to a press process in order to separate the solid phase from the liquid phase.
• the solid phase comprises at least metals such as iron (Fe), chromium (Cr), nickel (Ni), molybdenum (Mo).
• this solid phase also comprises a high content of moisture and is also called steel scale by-product, steel scale waste or filter cake.
• the compound (SSB) is a by-product from stainless steel process or carbon steel process or mixture thereof.
• the compound (SSB) can be in different forms such as a paste, a powder, scraps or mixture thereof.
• the compound (SSB) is a paste.
• the compound (SSB) can also be chunked, milled, crushed or powdered.
• said at least one steel scale by-product comprises equal to or more than 35.0 wt. % of free water, relative to the total weight of the compound (SSB).
• the expression “free water” is intended to refer to the portion of water which evaporates upon heating.
• the expression “bound water” refers to the water which remains bounded to the compound upon heating. It is understood that the skilled person in the art will measure the amount of free water according to standard and general practice known by said skilled person in the art. Preferably, unless otherwise mentioned or indicated, according to the present invention, the measurement of free water is performed by subjecting the sample to a heating step at 80 °C. In general, the measurement of free water is performed until a constant weight of the sample subjected to said measurement is reached.
• said compound (SSB) comprises, or equal to or more than 40.0 wt. %, or equal to or more than 45.0 wt. %, or equal to or more than 50.0 wt. %, or equal to or more than 55.0 wt. %, of free water, relative to the total weight of the compound (SSB).
• the upper limit of free water in the compound (SSB) is advantageously equal to or less than 80.0 wt. %, or equal to or less than 75.0 wt. %, or equal to or less than 70.0 wt. %, relative to the total weight of the compound (SSB).
• free water is present in the compound (SSB) in an amount from 35.0 wt. % to 80.0 wt. %, or from 35.0 wt. % to 75.0 wt. %, or from 40.0 wt. % to 75.0 wt. % or from 45.0 wt. % to 75.0 wt. %, or from 50.0 wt. % to 70.0 wt. % or from 55.0 wt. % to 70.0 wt. %, relative to the total weight of the compound (SSB).
• the compound (SSB) may further comprise equal to or more than 0.2 wt. % of fluorine, expressed as CaF 2 , relative to the total dry weight of the compound (SSB).
• fluorine also refers to the ionic form, F-, fluoride.
• dry weight is intended to refer to the weight of the compound (SSB) after the evaporation of the free water, as detailed above.
• the presence of fluorine, expressed as CaF 2 , in the compound (SSB) may come from the steel making process from which the steel scale by-product is derived.
• CaF 2 is produced during the addition of lime to neutralize the acidic solution. Its content in the compound (SSB) is thus dependent on the conditions used during the steel making process from which the steel scale by-product is derived.
• said compound (SSB) may comprise equal to or more than 1.0 wt. %, or equal to or more than 5.0 wt. %, or equal to or more than 7.0 wt. %, of fluorine, expressed as CaF 2 , relative to the total dry weight of the compound (SSB).
• the upper limit of fluorine, expressed as CaF 2 , in the compound (SSB) may advantageously be equal to or less than 15.0 wt. %, or equal to or less than 12.0 wt. %, or equal to or less than 10.0 wt. %, or equal to or less than 8.0 wt. %, relative to the total dry weight of the compound (SSB).
• fluorine expressed as CaF 2 , as detailed above, is present in the compound (SSB) in an amount from 0.2 wt. % to 15.0 wt. %, or from 1.0 wt. % to 12.0 wt. %, or from 5.0 wt. % to 10.0 wt. %, relative to the total dry weight of the compound (SSB).
• the compound (SSB) can further comprise metals such as iron (Fe), chromium (Cr), nickel (Ni), molybdenum (Mo).
• metals such as iron (Fe), chromium (Cr), nickel (Ni), molybdenum (Mo).
• the compound (SSB) may further comprise iron, expressed as Fe 2 O 3 , in an amount equal to or more than 10 wt. %, preferably equal to or more than 20 wt. %, equal to or more than 30 wt. %, relative the total dry weight of the compound (SSB). It is further understood that the expression “iron” refers to iron in all its forms (ionic forms) present in the compound (SSB).
• the upper limit of iron, expressed as Fe 2 O 3 , in the compound (SSB) is equal to or less than 60 wt. %, preferably equal to or less than 50 wt. %, equal to or less than 60 wt. %, relative the total dry weight of the compound (SSB).
• iron expressed as Fe 2 O 3
• SSB iron, expressed as Fe 2 O 3
• iron is preferably present in the compound (SSB) in an amount from 10 wt.% to 60 wt. %, preferably from 20 wt. % to 50 wt. %, preferably from 30 wt. % to 40 wt. %, relative the total dry weight of the compound (SSB).
• the upper limit of chromium in the compound (SSB) is equal to or less than 15.0 wt. %, preferably equal to or less than 12.0 wt. %, equal to or less than 10.0 wt. %, relative the total dry weight of the compound (SSB).
• the upper limit of nickel in the compound (SSB) is equal to or less than 15.0 wt. %, preferably equal to or less than 12.0 wt. %, preferably equal to or less than 10.0 wt. %, relative the total dry weight of the compound (SSB).
• nickel is present in the compound (SSB) in an amount from 0.02 wt. % to 15.0 wt.%, or from 0.06 wt.% to 12.0 wt. %, preferably from 0.1 wt. % to 10 wt. %, relative the total dry weight of the compound (SSB).
• the compound (SSB) may further comprise molybdenum in an amount equal to or more than 0.02 wt. %, preferably equal to or more than 0.05 wt. %, preferably equal to or more than 0.1 wt. %, relative the total dry weight of the compound (SSB).
• the upper limit of molybdenum in the compound (SSB) is equal to or less than 15.0 wt. %, preferably equal to or less than 12.0 wt. %, preferably equal to or less than 10 wt. %, relative the total dry weight of the compound (SSB).
• molybdenum is present in the compound (SSB) in an amount from 0.02 wt. % to 15.0 wt.%, or from 0.06 wt.% to 12.0 wt. %, preferably from 0.1 wt. % to 10 wt. %, relative the total dry weight of the compound (SSB).
• chromium, nickel and molybdenum are present in the compound (SSB) in a cumulated amount from 0.1 wt. % to 50 wt. %, preferably from 0.2 wt. % to 40 wt. %, preferably from 0.5 wt. % to 30 wt. % relative to the total dry weight of the compound (SSB).
• composition (C), as detailed above, is prepared by mixing the compound (SSB), as detailed above, with at least one first additive.
• the expression “at least one first additive” is intended to denote one or more than one first additive. Mixtures of first additive can also be used for the purpose of the invention.
• first additive is understood, for the purposes of the present invention, both in the plural and the singular form.
• composition (C), as detailed above, is prepared by mixing the compound (SSB), as detailed above, with at least one first additive in an amount providing a weight ratio of calcium oxide to the free water present in the compound (SSB) equal to or more than 1.50.
• the first additive is mixed with the compound (SSB) in such a way to have a weight ratio of calcium oxide to free water of the compound (SSB) equal to or more than 1.50; wt .
• the lower limit of the amount of the first additive which is mixed with the compound (SSB) should be sufficient to provide the amount of calcium oxide, as detailed above.
• the first additive is mixed with the compound (SSB) in an amount providing a weight ratio of calcium oxide to the free water present in the compound (SSB) equal to or more than 1.75, preferably equal to or more than 1.80, more preferably equal to or more than 1.90, even more preferably equal to or more than 2.00.
• the first additive is mixed with the compound (SSB) in an amount providing a weight ratio of calcium oxide to the free water present in the compound (SSB) equal to or less than 2.50, preferably equal to or less than 2.25, more preferably equal to or less than 2.15 even more preferably equal to or less than 2.10.
• the first additive is advantageously mixed with the compound (SSB) in an amount providing a weight ratio of calcium oxide to the free water present in the compound (SSB) from 1.50 to 2.50, more preferably from 1.80 to 2.25, most preferably from 2.0 to 2.15.
• the first additive comprises calcium oxide in an amount of at least 80.0 wt. %, relative to the total weight of the first additive.
• first additive is intended to refer to a compound comprising at least 80.0 wt. % of calcium oxide or a composition comprising at least 80.0 wt. % of calcium oxide or a mixture thereof.
• the first additive comprises calcium oxide in an amount of at least 85.0 wt. %, preferably in an amount of at least 90.0 wt. %, more preferably in an amount of at least 95.0 wt. %, even more preferably in an amount of at least 98.0 wt. %, relative to the total weight of the first additive.
• the first additive is a compound comprising or consisting essentially of calcium oxide, as detailed above, wherein the total amount of the calcium oxide is equal to or more than 80.0 wt.%, or more than 85.0 wt.% or more than 90.0 wt.% or more than 95.0 wt.% or desirably more than 98.0 wt.% relative to the total weight of the compound.
• the first additive may further comprise at least one calcium salt, other than calcium oxide, in an amount equal to or less than 20 wt. %, preferably equal to or less than 15 wt. %, more preferably equal to or less than 10 wt. %, relative to the total weight the first additive.
• at least one calcium salt is intended to denote one or more than one calcium salt. In the rest of the text, the expression “at least one calcium salt” is understood, for the purposes of the present invention, both in the plural and the singular. Non-limiting examples of such calcium salts are calcium carbonate, calcium hydroxide, calcium sulfate, or calcium nitrate.
• the first additive may further comprise at least one magnesium salt selected from the group consisting of magnesium carbonate, magnesium oxide, and magnesium hydroxide.
• at least one magnesium salt is intended to denote one or more than one magnesium salt. In the rest of the text, the expression “at least one magnesium salt” is understood, for the purposes of the present invention, both in the plural and the singular.
• the content of magnesium, expressed as magnesium oxide, present in the first additive is equal to or less than 10.0 wt. %, preferably equal to or less than 7.0 wt. %, more preferably equal to or less than 5.0 wt. %, relative to the total weight of the first additive.
• the first additive according to the present invention may further comprise impurities in an amount equal to or less than 5.0%, preferably equal to or less than 4.0 wt. %, more preferably equal to or less than 2.5 wt. %, relative to the total weight of the first additive.
• impurities are silicon, aluminum, iron, sodium, potassium, sulfur, phosphorous alone or in combination.
• the impurities may also be in salt form, in oxide form, in combination with calcium or combination thereof.
• Said first additive may be a compound or a composition or mixture thereof.
• Said first additive may be synthetically prepared by a variety of methods known in the art or can be of natural origin.
• Non-limiting examples of first additive of natural origin may be made from mined (raw) minerals such as limestones.
• limestone comprises CaCOs in a total amount of more than 95.0 wt.%, or more than 96.0 wt.%, or more than 97.0 wt.%, or desirably more than 98.0 wt.%, relative to the total weight of the limestone.
• the first additive is a quicklime.
• quicklime is made from limestones, in particular by calcining limestones.
• the quicklime when the first additive is a quicklime, said quicklime has a reactivity, t 60 , of at most 10 minutes.
• the quicklime reactivity is evaluated with the European reactivity on slaking test, EN 459-2: Building lime - Part 2: Tests methods.
• the quicklime reactivity is expressed as t 60 , which is the time needed to reach 60 °C when 150 g of quicklime is added to 600 cm 3 of water.
• the quicklime complies with the chemical requirements of a calcium lime CL80-R5 according to the European standard EN 459-1.
• composition (C) is prepared by mixing the compound (SSB), as detailed above, with the at least one first additive, as detailed above, in an amount providing a weight ratio of calcium oxide to the free water present in the compound (SSB) equal to or more than 1.50, the free water of the resulting composition (C) is significantly reduced.
• the composition (C), after mixing the compound (SSB), as detailed above, with the at least one first additive, as detailed above, comprises free water in an amount equal to or less than 5.0 wt. %, relative to the total weight of the composition (C).
• composition (C) of the present invention can be safely used in a steel making process.
• a free water equal to or less than 5 wt. % in the composition (C) is an important figure as this is the threshold for safely reintroducing this composition as a raw material in a steel making process.
• a low content of free water in the raw material is mandatory in a steel making process to avoid rapid expansion of the free water into gas. Due to the high temperatures used in a steel making process, the free water becomes a gas which takes up a greater volume. This rapid expansion of the liquid water into a gas can be so sudden that the liquid steel is ejected out of the vessel. This causes a major safety risk and potentially damages equipment.
• the use of the first additive according to the invention is cost-effective since it avoids the use of further drying steps. Moreover, it allows the recycling and the reuse of the by-product, notably of the high value metals and alloys that are contained in the compound (SSB).
• the present invention provides a solution for the recovering and recycling of steel scale by-product and facilitating the subsequent reuse of this by-product in a steel making process while improving the performance of this process.
• the present invention has an important economic potential.
• said composition (C) comprises equal to or less than 4.5 wt. %, equal to or less than 4.0 wt. %, preferably equal to or less than 3.5 wt. %, more preferably equal to or less than 3.0 wt. %, most preferably equal to or more than 2.5 wt. %, most preferably equal to or more than 2.0 wt. %, even more preferably equal to or less than 1.5 wt. %, of free water relative to the total weight of the composition (C).
• the lower limit of free water in the composition (C) is advantageously equal to or more than 0.0 wt. % or equal to or more than 0.2 wt. %, preferably equal to or more than 0.3 wt. %, preferably equal to or more than 0.4 wt. %, more preferably equal to or more than 0.5 wt. %, even more preferably equal to or more than 0.7 wt. %, most preferably equal to or more than 1.0 wt. %, relative to the total weight of the composition (C).
• free water is advantageously present in the composition (C) in an amount from 0.0 wt. % to 5.0 wt. %, preferably from 0.2 wt. % to 4.5 wt. %, preferably from 0.3 wt. % to 4.0 wt. %, more preferably from 0.5 wt. % to 3.5 wt. %, more preferably from 0.7 wt. % to 3.0 wt. % from 1.0 wt. % to 3.0 wt. % or from 1.0 wt. % to 2.0 wt. %, relative to the total weight of the composition (C).
• the composition (C), after mixing the compound (SSB), as detailed above, with the at least one first additive, as detailed above, further comprises fluorine, expressed as CaF 2 , in an amount equal to or less than 20.0 wt.%, preferably equal to or less than 15.0 wt. %, preferably equal to or less than 10.0 wt. %, relative to the total dry weight of the composition (C).
• a second additive may be added to the composition (C), as detailed above, wherein said second additive is comprising, relative to the total weight of said second additive, at least 20.0 wt. % of magnesium, expressed as magnesium oxide.
• the amount added to the composition (C), as detailed above, is determined by the amount of fluorine, expressed as CaF 2 , in the composition (C) and the nature of the second additive.
• the second additive is added in an amount providing in the composition (C) a weight ratio of magnesium, expressed as magnesium oxide, to fluorine, expressed as CaF 2 , equal to or more than 5.0.
• the expression “at least on second additive” is intended to denote one or more than one second additive. Mixtures of second additive can also be used for the purpose of the invention.
• second additive is understood, for the purposes of the present invention, both in the plural and the singular form.
• second additive is intended to refer to a compound comprising at least one magnesium salt or a composition comprising at least one magnesium salt or a mixture thereof.
• At least one magnesium salt is intended to denote one or more than one magnesium salt.
• Non-limiting examples of suitable magnesium salts may be made of magnesium carbonate, magnesium hydroxide, magnesium oxide, magnesium sulphate, magnesium silicate or magnesium nitrate.
• the at least one magnesium salt is selected from the group consisting of magnesium carbonate, magnesium oxide, and magnesium hydroxide.
• composition of the present invention may be prepared by using at least one second additive in an amount providing in the composition (C) a weight ratio of magnesium, expressed as magnesium oxide, to fluorine, expressed as CaF 2 , equal to or more than 5.0.
• the second additive is used in such a way to have a composition (C) wherein the weight ratio of magnesium, expressed as magnesium oxide, to fluorine, expressed as CaF 2 , is equal to or more than 5.0; wt . Mg ,expressed as MgO compo C Fluorine ,expressed as CaF 2 compo C ⁇ 5.0
• the amount of the second additive is dependent on the content of magnesium in the second additive and on the fluorine, expressed as CaF 2 , in the composition (C) after mixing the compound (SSB), as detailed above, with the at least one first additive, as detailed above.
• the composition (C) is prepared by further adding the second additive in an amount from 400 wt. % to 2500 wt. %, preferably from 1000 wt. % to 2000 wt. %, preferably from 1500 wt.% to 1800 wt. %, relative to the weight of fluorine, expressed as CaF 2 , in the composition, after mixing the compound (SSB), as detailed above, with the at least one first additive, as detailed above.
• the lower limit of the amount of the second additive which is used should be sufficient to provide the content of magnesium, expressed as magnesium oxide, as detailed above.
• the second additive is used in an amount providing in the composition (C) a weight ratio of magnesium, expressed as magnesium oxide, to fluorine, expressed as CaF 2 , equal to or more than 7.0, preferably equal to or greater than 10.0, more preferably equal to or greater than 12.0, most preferably equal to or greater than 15.0, even more preferably equal to or greater than 20.0.
• the second additive is used in an amount providing in the composition (C) a weight ratio of magnesium, expressed as magnesium oxide, to fluorine, expressed as CaF 2 , equal to or less than 25.0, preferably equal to or less than 20.0, more preferably equal to or less than 15.0, most preferably equal to or less than 12.0, even more preferably equal to or less than 10.0.
• the second additive is used in an amount providing in the composition (C) a weight ratio of magnesium, expressed as magnesium oxide, to fluorine, expressed as CaF 2 , from 5.0 to 25.0, preferably from 7.0 to 20.0, more preferably from 10.0 to 15.0, most preferably from 12.0 to 15.0, or from 7.0 to 10.0.
• said second additive comprises magnesium, expressed as magnesium oxide, in an amount of at least 20.0 wt. %, relative to the total weight of the second additive.
• magnesium expressed as magnesium oxide
• the second additive comprises or consists essentially of a magnesium salt, as detailed above, wherein the total amount of magnesium, expressed as magnesium oxide, is of at least at least 25.0 wt.%, or of at least 30.0 wt.%, or of at least 35.0 wt. %, or desirably of at least 35.0 wt.% relative to the total weight of the second additive.
• the magnesium content is less than 90.0 wt.%, or less than 80.0 wt.%, or less than 70.0 wt.%, or less than 60.0 wt.%, or less than 55.0 wt.%, or less than 50.0 wt.%, or desirably less than 45.0 wt.%, relative to the total weight of the second additive.
• the second additive may further comprise at least one calcium salt selected from the group consisting of calcium carbonate, calcium oxide, and calcium hydroxide.
• the second additive comprises or consists essentially of the magnesium salt, as detailed above and the calcium salt, as detailed above, wherein the total amount of magnesium, expressed as magnesium oxide, and calcium, expressed as calcium oxide, is more than 80.0 wt.%, or more than 85.0 wt.% or more than 90.0 wt.% or more than 95.0 wt.% or desirably more than 98.0 wt.% relative to the total weight of the compound, and wherein the magnesium content, expressed as magnesium oxide, is of at least 20.0 wt.%, or of at least 25.0 wt.%, or desirably of at least 30.0 wt.%, relative to the total weight of the second additive.
• the magnesium content is less than 90.0 wt.%, or less than 80.0 wt.%, or less than 70.0 wt.%, or less than 60.0 wt.%, or less than 55.0 wt.%, or less than 50.0 wt.%, or desirably less than 45.0 wt.%, relative to the total weight of the second additive.
• the calcium content is less than 80.0 wt.%, or less than 70.0 wt.%, or less than 60.0 wt.%, or less than 50.0 wt.%, or less than 40.0 wt.%, or less than 30.0 wt.%, or desirably less than 20.0 wt.%, relative to the total weight of the second additive.
• the magnesium content expressed as magnesium oxide, varies from 20.0 wt. % to 80.0 wt.%, or from 20.0 wt.% to 70.0 wt.%, or from 25.0 wt.% to 60.0 wt.% or from 30.0 wt.% to 50.0 wt.%, or from 30.0 wt.% to 45.0 wt.%, relative to the total weight of the second additive.
• Said second additive may be synthetically prepared by a variety of methods known in the art or can be of natural origin.
• Non-limiting examples of second additive of natural origin may be made of mined (raw) minerals such as dolomite and dolomitic limestones.
• dolomitic limestone comprises MgCOs and CaCOs, in which the MgCOs and CaCOs are present in a total amount of more than 95.0 wt.%, or more than 96.0 wt.%, or more than 97.0 wt.%, or desirably more than 98.0 wt.%, relative to the total weight of the dolomitic limestone, and wherein the MgCO3 content may vary from 20.0 wt.% to 45.0 wt.%, or from 25.0 wt.% to 40.0 wt.%, or from 30.0 wt.% to 40.0 wt.% relative to the total weight of MgCOs and CaCOs.
• dolomite comprises MgCOs and CaCOs, in which the MgCOs and CaCOs are present in a total amount of more than 95.0 wt.%, or more than 96.0 wt.%, or more than 97.0 wt.%, or desirably more than 98.0 wt.%, relative to the total weight of the dolomitic limestone, and wherein the MgCOs and CaCOs content are present in a 1:1 molar ratio.
• Non-limiting examples of synthetically prepared second additive suitable to be used in the composition of the present invention may be partly or fully burnt dolomite consisting of calcium oxide and magnesium oxide (also called calcined dolomite or dolomitic quick lime or dolime), calcium hydroxide and magnesium oxide (also called semi-hydrated dolomitic lime) or calcium hydroxide and magnesium hydroxide (also called type S hydrated lime).
• dolomite consisting of calcium oxide and magnesium oxide (also called calcined dolomite or dolomitic quick lime or dolime), calcium hydroxide and magnesium oxide (also called semi-hydrated dolomitic lime) or calcium hydroxide and magnesium hydroxide (also called type S hydrated lime).
• the second additive consists essentially of at least one magnesium salt, as detailed above.
• the term "consisting essentially of” is to be understood to mean that any additional component different from the magnesium salt, as detailed above, is present in an amount of at most 1.0 wt.%, or at most 0.5 wt.%, or at most 0.1 wt.%, based on the total weight of the second additive.
• Non-limiting examples of such additive are magnesia, magnesite, olivine and brucite.
• first additive and the second additive according to the present invention are two different compounds or compositions.
• the inventors have surprisingly found that when a second additive, as detailed above, is used to prepare the composition (C), as detailed above, the negative impact of CaF 2 on the slag viscosity during the steel making process is reduced. It has been found that CaF 2 is a slag fluidizer. This means that when a composition containing a high quantity of CaF 2 is used as raw material in a steel making process, the viscosity of the slag generated during the process is low. This slag having a low viscosity no longer correctly covers the liquid steel which results in a reduction of the thermal insulation and increases the risk of nitrogen pick that can then reduce the yield for the process. Therefore, the use of the second additive according to the invention results in an improvement of the yield of the steel making process while using a by-product as raw material.
• the composition (C), after mixing the compound (SSB), as detailed above, with the at least one first additive, as detailed above, and with the at least one second additive, as detailed above, further comprises fluorine, expressed as CaF 2 , in an amount equal to or less than 10.0 wt. %, relative to the total dry weight of the composition (C).
• composition (C) of the present invention can be safely used as raw material in a steel making process and that the yield of said process is improved and the need of further additives during the process is reduced.
• the lower limit of fluorine, expressed as CaF 2 , in the composition (C) is advantageously equal to or more than 0.0 wt. % or equal to or more than 0.2 wt. %, preferably equal to or more than 0.5 wt. %, preferably equal to or more than 0.7 wt. %, more preferably equal to or more than 1.0 wt. %, even more preferably equal to or more than 1.5 wt. %, most preferably equal to or more than 2.0 wt. %, relative to the total dry weight of the composition (C).
• fluorine expressed as CaF 2, , as detailed above, is advantageously present in the composition (C) in an amount from 0.0 wt. % to 10.0 wt. %, preferably from 0.2 wt. % to 8.0 wt. %, preferably from 0.5 wt. % to 7.0 wt. %, more preferably from 0.7 wt. % to 6.0 wt. %, more preferably from 1.0 wt. % to 5.0 wt. % or from 1.5 wt. % to 5.0 wt. % or from 2.0 wt. % to 5.0 wt. %, relative to the total dry weight of the composition (C).
• the composition (C) is in the form of a solid composition.
• solid composition is intended to refer to a composition in the form of powders, fibers, dusts, tablets, pellets, aggregates, compacts or briquettes or a granular form such as granules or crumbs,.
• said composition (C) is in a form selected from the group consisting of powders, aggregates, briquettes or mixtures of two or more thereof.
• said composition (C) is in a form selected from the group consisting of aggregates, briquettes or mixtures of two or more thereof.
• composition (C) are also an aspect of the present invention.
• the method for the manufacturing of the composition (C), as detailed above comprises mixing of (a) at least one compound (SSB), as detailed above, (b) at least one first additive, as detailed above and (c) optionally at least one second additive, as detailed above.
• composition (C) prepared according to the invention is particularly suitable for use as raw material in a steel making process.
• composition (C) any order of mixing of the various components as comprised in the composition (C), as detailed above, is acceptable.
• the first additive and the second additive are separately mixed with the compound (SSB)
• the first additive and the second additive can be mixed simultaneously, or, if desired, the second additive can be mixed after the first additive.
• composition (C) may be introduced in the form of a powder or dust, however, it may also be present in a compressed form such as tablets, pellets or granules to manufacture the composition (C).
• mixing may be carried out by using a variety of mixing means known in the art.
• mixing means are for example mechanical mixing such as traditional mixers and blenders, high intensity mixers and electric stirrers, said mixers, blenders and stirrers which can be equipped with at least one dispersion disk.
• a high sheer force can be applied during the mixing in order to improve the homogeneity of the composition (C).
• said mixing is carried out until a homogeneous mixture is obtained.
• said composition (C), after mixing, is then subjected to a shaping step.
• a shape is given to the composition (C).
• Various shaping process are known in the art and non-limiting examples of such a shaping process are pelletizing, compacting, slip casting, aggregating, extrusion.
• the shaping process is a compacting process.
• Non-limiting examples of compacting processes are cold isostatic pressing, tabletting, briquetting, roll compaction.
• the shaped composition (C) can take various forms such as compacts, tablets, briquettes, pellets, extrudates.
• the shaped composition (C) takes the form of briquettes or aggregates.
• the premix of the first additive, as detailed above, and the second additive, as detailed above, is another aspect of the present invention.
• composition (C), as detailed above, as raw material in a steel making process is another aspect of the invention.
• composition (C) as raw material in a steel making process.
• the amount of fluorine was measured after the measurement of free water, described above. Fluorine was thus measured on a "dry sample", after the evaporation of the free water, as detailed above.
• the measurements of fluorine were performed by using wavelength dispersive X-ray fluorescence spectrometer device from Malvern Panalytical Zetium.
• the quicklime reactivity was evaluated with the European reactivity on slaking test, EN 459-2: Building lime - Part 2: Tests methods.
• the reactivity t 60 was determined as the time needed to reach 60 °C when 150 g of quicklime was added to 600 cm 3 of water.
• the mass loss occurring between 350°C and 550°C corresponds therefore to the amount of "bound water” (expressed as H 2 O) according to the invention.
• the carbonate compound(s) comprised in the composition of the invention decompose(s) between 550°C and 950°C (or constant mass) by releasing CO 2 .
• the mass loss occurring between 550°C and 950°C (or constant mass) corresponds therefore to the amount of total carbonate (expressed as CO 2 ) according to the invention.
• Example 1 was realized using the raw materials having the composition and properties as described in tables 1-3.
• Table 1 Steel scale by-product compound (compound SSB) Wt. % Free water* 55.0 CaF 2 ** 36.2 Fe 2 O 3 ** 30.4 Cr** 5.3 Ni** 4.1 Mo** 0.1 * relative to the total weight of the compound SSB ** relative to the total dry weight of the compound SSB
• Table 2 First additive - composition Amount (wt.
• the compound SSB, described in table 1, was mixed with a first additive, as detailed in tables 2 and 3, in an amount providing a weight ratio of calcium oxide to the free water present in the compound (SSB) of 1.62.
• the mixing was performed with an Eirich intensive mixer type R01, at 300 rpm stirrer speed and 42 rpm bowl speed.
• 1.5 kg of compound SSB was add to the mixer together with 500g of the first additive, as detailed in table 1 and 2, and mixed during 30 min. Then, an additional 500g of first additive was added and mixed during 30 min. Then, an additional 500g of first additive was added and mixed during 30 min.
• the resulting composition was sampled after 2h from the start to measure its free water content which was of 4.7 wt%, relative to the total weight of the composition. This result shows that the addition of the first additive allows to obtain a composition having a content of free water less than 5 wt. %, which can thus be used as raw material in a steel making process.
• Example 2 was realized by mixing the composition obtained in example 1 with a second additive presenting the composition as detailed in table 4.
• Table 4 Second additive - composition Amount (wt. %*) H 2 O free ⁇ 0.01 MgO 27.5 CaO 40.0 Fe 2 O 3 1.8 F ⁇ 0.01 SO 3 1.8 SiO 2 3.0
• the content of fluorine, expressed as CaF 2 , in the composition obtained in example 1 was measured, as detailed above, and was of 8.8 wt. %, relative to the total dry weight of the composition. Then 216.6g of the second additive, as detailed in table 4, was added and mixed with 200g sampled from the composition obtained in example 1.
• the mixing was performed using a WAB Turbula ® mixer for 10 min at 72 rpm.
• the free water of the resulting composition was of 2.2 wt. %, relative to the total weight of the composition.
• the weight ratio of the magnesium, expressed as magnesium oxide, to the fluorine, expressed as CaF 2 was 5.0. This result shows that the addition of the second additive allows to obtain a composition which can be safely used as raw material in a steel making process.
• the compound SSB, described in table 1 was mixed with a first additive, as detailed in tables 2 and 3, in an amount providing a weight ratio of calcium oxide to the free water present in the compound (SSB) of 1.1.
• the mixing was performed with a fast shear mixer as described in standard NF P 94-093.
• 1.5 kg of compound SSB was add to the mixer together with 500g of the first additive, as detailed in table 1 and 2, and mixed during 30 min. Then, an additional 500g of first additive was added and mixed during 30 min.
• Example 4 was realized using the composition obtained in example 1.

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