Classifications

• • 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
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
  • C04B18/02—Agglomerated materials, e.g. artificial aggregates
  • C04B18/021—Agglomerated materials, e.g. artificial aggregates agglomerated by a mineral binder, e.g. cement
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
  • C04B14/02—Granular materials, e.g. microballoons
  • C04B14/30—Oxides other than silica
  • C04B14/308—Iron oxide
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B22/00—Use of inorganic materials as active ingredients for mortars, concrete or artificial stone, e.g. accelerators or shrinkage compensating agents
  • C04B22/06—Oxides, Hydroxides
  • C04B22/062—Oxides, Hydroxides of the alkali or alkaline-earth metals
  • C04B22/064—Oxides, Hydroxides of the alkali or alkaline-earth metals of the alkaline-earth metals
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B22/00—Use of inorganic materials as active ingredients for mortars, concrete or artificial stone, e.g. accelerators or shrinkage compensating agents
  • C04B22/06—Oxides, Hydroxides
  • C04B22/066—Magnesia; Magnesium hydroxide
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/26—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on ferrites
  • C04B35/2683—Other ferrites containing alkaline earth metals or lead
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
  • C04B35/63—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B using additives specially adapted for forming the products, e.g.. binder binders
• • 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
  • C22B1/243—Binding; Briquetting ; Granulating with binders inorganic
• • 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
  • 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
  • C22B1/245—Binding; Briquetting ; Granulating with binders organic with carbonaceous material for the production of coked agglomerates
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
  • C04B2111/00732—Uses not provided for elsewhere in C04B2111/00 for soil stabilisation
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
  • C04B2111/00758—Uses not provided for elsewhere in C04B2111/00 for agri-, sylvi- or piscicultural or cattle-breeding applications
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
  • C04B2111/0087—Uses not provided for elsewhere in C04B2111/00 for metallurgical applications
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
  • C04B2111/0087—Uses not provided for elsewhere in C04B2111/00 for metallurgical applications
  • C04B2111/00887—Ferrous metallurgy
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/3205—Alkaline earth oxides or oxide forming salts thereof, e.g. beryllium oxide
  • C04B2235/3206—Magnesium oxides or oxide-forming salts thereof
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
  • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
  • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
  • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
  • C04B2235/3205—Alkaline earth oxides or oxide forming salts thereof, e.g. beryllium oxide
  • C04B2235/3208—Calcium oxide or oxide-forming salts thereof, e.g. lime

Definitions

• the present invention relates to a process for producing a composition in the form of briquettes containing a bright calco-magnesium compound and an iron-based compound, to raw briquettes containing the bright calco-magnesium compound and the oxide of iron, cooked briquettes containing the bright calco-magnesium compound and ferrites of caicium and their use.
• solid magnesium compound means a solid mineral material whose chemical composition is mainly calcium oxide and / or magnesium oxide.
• the living calco-magnesium compounds in the sense of the present invention therefore comprise quicklime (calcium lime), bright magnesium lime, dolomitic lime or bright calcined dolomite.
• the living calco-magnesium compounds contain impurities, that is, compounds such as silica » Si0 2 or alumina, Al2O3, etc., up to a few percent. It is understood that these impurities are expressed in the aforementioned forms but may actually appear in different phases.
• Lime means a mineral solid whose chemical composition is mainly calcium oxide, CaO.
• Quicklime is commonly obtained by calcination of limestone, mainly consisting of CaCO 3 .
• Quicklime contains impurities, that is, compounds such as magnesium oxide, MgO, silica, SiO 2 or alumina, Al 2 O 3, etc., up to a few percent. It is understood that these impurities are expressed in the aforementioned forms but may actually appear in different phases. It also usually contains a few percent of residual CaCO 3 , called incuits, and a few percent of residual Ca (OH) 2 , due to the partial hydration of CaO calcium oxide during the cooling, handling and / or storage phases.
• the term "briquette” means a compact having an oblong shape, having a mass of about 5 to 100 g per briquette, inscribed in an ellipsoid of flattened or elongated revolution (in English oblate ellipsoid of revolution gold prolate ellipsoid of revolution).
• the briquettes are in the form of soap or are called briquettes "egg” (in English “egg briquettes”)
• Briquettes are known from the state of the art, see for example WO2015007661. According to this document, compacts (namely briquettes or tablets) are described comprising particles of calco-magnesium compound comprising at least 50% of bright calco-magnesium compound. The compacts (in the form of briquettes or tablets) disclosed may also contain additives, particularly iron oxide.
• the mechanical resistance to the fall is measured by means of a test shatter.
• the compacts described generally have a test Shatter index of less than 10%.
• the term "Shatter test number” is used to mean the mass percentage of fines less than 10 mm generated after 4 drops of 2 m from 10 kg of product. These fines are quantified by sieving through a 10 mm square screen at the end of the 4 drops of 2 m.
• US5186742 discloses lime briquettes containing from 55 to 85% by weight of lime, from 10 to 40% by weight of ash and from 0.1 to 10% by weight of paper fibers as well as optionally a lubricant.
• the briquettes disclosed in US 5186742 are tested for drop resistance, which test is not comparable to the test for measuring the Shatter test index and has a compressive strength between 150 and 300 pounds. , which corresponds to a test Shatter index well above 10%.
• Calco-Magnesium compounds are used in many industries, such as iron and steel, gas processing, water and sludge treatment, agriculture, building industry, public works and others. They can be used either in the form of pebbles or pieces, or in the form of fines (generally less than 7 mm). In some industries, the shape of pebble is nevertheless preferred.
• the heaters always maintain an equilibrium of the materials between the calco-magnesian compounds in rollers and the fines generated before and during the caic interation as well as during the manipulations and subsequent operations. Nevertheless, in some cases, an excess of fines is produced. These fines can then be agglomerated to one another in the form of briquettes or the like, which not only gives the possibility of removing excess fines but also artificially increasing the production of calcium and magnesium compounds by adding pebbles. these briquettes or the like with pebbles.
• the Barnett et al Kingi-press briquetting: Compacting fines to reduce vended-handiing costs, powder and bulk engineering, vol.24, No.
• Lubricants and binders are additives often used in agglomeration processes in the form of briquettes or the like.
• Lubricants can be of two types, internal or external. Internal lubricants are intimately mixed with briquetting materials. They favor on the one hand the flowability of the mixture during the feeding of the briqueteuse and on the other hand the rearrangement of the particles within the mixture during the compression. External lubricants are applied to the surfaces of the briquetting rollers and primarily assist in the demolding. In both cases, they reduce the friction on the surface and thus the wear. Lubricants can be liquids such as mineral oils, silicones, etc. or solids such as talc, graphite, paraffins, stearates, etc. In the case of compositions based on living calco-magnesium compounds, stearates are preferred and more particularly calcium stearate or magnesium stearate.
• Binders are substances having the property of agglomerating the particles together, either by adhesion forces or by a chemical reaction. They can be of mineral origin (cements, clays, silicates %), of vegetable origin or animal (celluloses, starches, gums, alginates, pectin, glues, %), of synthetic origin (polymers, waxes, ). In many cases, they are used and implemented with water that activates their agglomeration properties.
• a composition of bright calco-magnesium compounds such as quicklime and / or live dolostone and scrap are introduced into a converter to control the kinetics and chemistry of the reaction. slag formation, thus facilitating the removal of impurities and protecting the refractory lining of the oven against excessive wear.
• the bright calco-magnesium compounds introduced float on the hot metal bath thus forming an interface.
• the molten metal is introduced into the tank in which scrap can also be introduced.
• the molten metal from the melting of metal compounds typically has an initial carbon content of 40 to 45 kg per ton of molten metal and an initial phosphorus content of 0.7 to 1.2 kg per ton of molten metal.
• the bright calco-magnesium compounds are loaded and float above the bath of molten metal. Oxygen is blown for a predetermined period of time in order to burn off the carbon and oxidize directly and / or indirectly the phosphorus compounds and the silicon. During insufflation, the calcium-magnesium compounds are immersed in the molten metal bath and dissolve / melt slightly at the interface with the molten metal, the calco-magnesian compounds still floating.
• Slag is the layer of oxides floating above the bath and results from the formation of SiO2 due to the oxidation of silicon, the formation of other oxides (MnO and FeO) during the blowing, the addition bright calco-magnesium compounds to neutralize the action of Si0 2 on the refractory lining and to liquefy and activate the slag, and MgO from the wear of the refractory lining.
• a metal / gas reaction occurs in which the carbon is burned to form CO and CO 2 gas.
• the carbon content is reduced to about 0.5 kg per ton of molten metal, which means about 500 ppm.
• a metal / slag reaction is produced to dephosphor the molten metal.
• the phosphorus content is about 0.1 kg or less per ton of molten metal, which means about 100 ppm or less.
• FeO (iron oxide) and phosphorus come from hot metal, while CaO is added to the converter. This reaction is exothermic and the goal is to shift the balance to the right side. This can be done by reducing the temperature, fluidizing the slag as much as possible, homogenizing the metal bath (performed by insufflation of argon and / or nitrogen by the bottom in most cases), maintaining the basicity CaO / SiO 2 between 3 and 6 (ratio by weight of calcium oxide to silica which is acidic), maintenance of the level of magnesite at less than 9% in the slag, and creation of sufficient quantities of slag.
• Magnesite is typically present in the slag and comes from the wear of the refractory lining, which can be reduced by the controlled addition of live dolomite. However, to promote the kinetics of the reaction in the slag, the magnesite level should be kept below 9%.
• the refining of hot metal is not so easy, and ii should perform its optimization for a given quantity of liquid metal, by mass action on the balance of the metai, a given chemical analysis "by acting on the mass balance of oxygen (oxidation reaction ⁇ , and a given temperature at the end of the insufflation (action on thermal equilibrium).
• the complexity of improving the dephosphorization during hot metal refining is due, among other things, to the simultaneous respect of the three equilibria.
• This patent focuses on the improvement of the dephosphorization during a process in a slag cooling converter in the second half of the process.
• the technico-economic point of view is penalized (specific furnace, energy consumption, loss of production capacity, partial sintering, ie reduction of the specific surface area and reduction porous volume).
• the present invention aims to solve at least some of these disadvantages by providing a method to significantly reduce the loss of lime and improve the efficiency of lime in slag formation.
• a method of manufacturing a calco-magnesian composition in the form of briquettes comprising the following steps: i. supplying a pulverulent mixture comprising at least one bright calco-magnesium compound, said mixture comprising at least 40% by weight of CaO + MgO equivalent relative to the weight of said composition and having a Ca / Mg molar ratio greater than or equal to 1, preferably greater than or equal to 2, more particularly greater than or equal to 3 and an iron-based compound present at a content of at least 3%, preferably at least 12%, more preferably at least 20%, so preferred at least 30%, more preferably at least 35% by weight equivalent Fe 2 O 3 based on the weight of said composition, said iron-based compound having a very fine particle size distribution characterized by a median size d less than 100 ⁇ , preferably less than 50 ⁇ and a size of 90 less than 200 ⁇ % preferably less than 150 ⁇ , preferably less than 130 ⁇ , pl us preferential
• said at least one bright calco-magnesium compound comprising at least 40% by weight of CaO + MgO equivalent comprises a fraction of calco-magnesium compound particles having a particle size of less than 90 ⁇ , which comprises at least 20% by weight of CaO equivalent relative to the weight of said powder mixture and wherein said powder mixture further comprises less than 10% of particles of bright calco-magnesium compound having a particle size> 90 ⁇ "and ⁇ 5 mm relative to to the total weight of said powder mixture.
• the aforementioned distinction is materialized by using a section of a briquette according to the invention, on which scanning electron microscopy is performed, coupled with dispersive energy analysis.
• the particles of calco-magnesian compound also appear in two dimensions on the plane of section.
• the two-dimensional sizes are calculated by a program making for each particle of bright calco-magnesium compound dispersed in the continuous matrix of calcium ferrite the sum of the smallest and the largest dimension divided by two of its cutting surface. . This sum divided by two represents the diameter of the equivalent disk.
• the particles of bright calco-magnesium compound melt or merge in said matrix (continuous phase) of calcium ferrite or calco-magnesium compound after cooking) when said particles of bright calco-magnesium compound have a two-dimensional size less than 63 ⁇ , observable by scanning electron microscopy coupled to the energy dispersive analysis, in a section of the briquette.
• inclusions of bright calco-magnesium compound are present in the calcium ferrite based matrix, when particles of bright calco-magnesium compound having a two-dimensional size greater than 63 pm, observable by scanning electron microscopy coupled in dispersive energy analysis, in a section of the briquette cover at least 20% of said cut.
• the process according to the invention of briquettes devoid of true inclusions of living calco-magnesium compounds, in particular quicklime dispersed in the continuous phase (matrix) of calcium ferrite or calco-magnesium compound, as described above.
• the iron content in the briquette is high, the bright calco-magnesium compound is then available in situ where the calcium ferrites have promoted the formation of the slag, acting as a flux to allow the calcium compound Magnesian keen to act immediately.
• the briquettes obtained by the process according to the present invention have a relative grain size homogeneity, namely that the briquette, when cut, has a granular composition in most of its volume.
• a continuous phase formed of calcium ferrite, calco-magnesium compound, such as for example quicklime and optionally iron-based compound, such as iron oxide, depending on the initial content in the raw briquette of calc-magnesium compound, calcium component therein, of iron-based compound.
• Briquettes of calcium ferrites without significant presence of inclusion of bright calco-magnesium compounds are therefore usable in the iron and steel industry, in particular as a converter for the refining of molten metal in order to facilitate the formation of slag. Such briquettes therefore clearly offer an advantage of accelerating the formation of slag and increasing its fluidity.
• said powder mixture comprises at most 97% by weight, preferably at most 90% by weight, more preferably at most 88%, in some embodiment at most 60% by weight. equivalent CaO + gO with respect to the weight of said composition.
• step i. is carried out in the presence of a binder or a lubricant, preferably in the form of a concentrated aqueous powder or suspension, more particularly chosen from the group consisting of binders of mineral origin such as cements, clays, silicates binders of vegetable or animal origin, such as celluloses, starches, gums, aiginates, pectin, glues, binders of synthetic origin, such as polymers, waxes, liquid lubricants such as mineral oils or silicones, solid lubricants such as talc, graphite, paraffins, stearates, in particular calcium stearate, magnesium stearate and mixtures thereof, preferably calcium stearate and / or magnesium stearate, at a content of between 0.1 and 1% by weight, preferably between 0 and 15 and 0.6% by weight, more preferably between 0.2 and 0.5% by weight relative to the total weight of said briquettes.
• binders of mineral origin such as cements, clay
• the determination of the% by weight of equivalent CaO + MgO, but also Fe 2 0 3 is carried out by X-ray fluorescence spectrometry (XRF) as described in the EN 15309 standard.
• XRF X-ray fluorescence spectrometry
• Chemical analysis, semi-quantitative, by XRF to determine the relative mass concentration of the elements whose atomic mass is between 16 (oxygen) and 228 (uranium) is made from the samples milled at 80 ⁇ and shaped into a pellet form.
• the samples are introduced into a PANaiytical / agiX PO PW2540 apparatus, operating in wavelength dispersion.
• the measurement is carried out with a power of 50kV and 80 mA, with a Duplex detector.
• the particle size distribution of the iron-based compound that is used in the process is determined by laser particle size. The measurement is therefore based on the diffraction of light and follows the theories of Fraunhofer and Mie.
• the particles are spherical non-porous and opaque.
• the measurement is carried out according to ISO 13320 in methanol, without sonication.
• an iron-based compound iron-based compound with a very fine particle size distribution
• an iron-based compound preferably based on iron oxide, characterized by a median size of less than 50%. at 100 ⁇ % preferably 50 ⁇ and a size of 90 less than 200 ⁇ , preferably less than 150 ⁇ , preferably less than 130 im, more preferably less than 100 ⁇ .
• This iron oxide can be described as active iron, which implies in particular that there is, relative to the total amount of iron oxide present in the iron-based compound, at least 40% of the iron oxide.
• the iron-based compound is in the form of a mixture of iron-based compound, which mixture of iron-based compounds may comprise one or more iron oxide, which may comprise at least one in turn 50% by weight, preferably 60% by weight, preferably 70% by weight of active iron oxide relative to the total weight of said iron-based compound.
• the particle size distribution of the iron-based compound in the briquette composition is determined by scanning electron microscopy and X-ray mapping, coupled with image analysis,
• the measurement is based on the property of iron-based compound particles to emit, when subjected to high energy radiation (eg, a high intensity electron beam), energy X radiation specific (6.398 keV).
• high energy radiation eg, a high intensity electron beam
• energy X radiation specific 6.398 keV
• Each identified particle is then characterized by its equivalent surface particle diameter (X 3 ⁇ 4i ), as defined in ISO 13322-1.
• the particles are then grouped by size fraction particle size fraction.
• the active iron fraction within the meaning of the invention is in the peripheral layer of each particle of the iron-based compound, in the outer layer with a thickness of 3 ⁇ .
• V ext is the volume of the particle of the iron-based compound and V int the volume at the heart of the particle at more than 3 ⁇ m from the surface, i.e. the volume corresponding to a spherical particle having a reduced radius of 3 ⁇ m.
• D ext is the diameter of the particle expressed in ⁇ m, or the size of the particle in the direction of the laser particle size.
• the total active iron fraction within the meaning of the invention is therefore the sum over all the granuiometric fractions of the active iron fraction muttiplied by the percentage by volume of each particle size fraction obtained by particle laser granulometry particle-% F e active particle
• the% active iron must be at least 40%.
• having a fine particle size is not enough, it is actually necessary to achieve the% of active iron oxide in the iron-based compound present in the briquettes, which allows to achieve a sufficient ferrite conversion during a pre-heat treatment or in a converter.
• Such raw briquettes containing a high quantity of iron oxide also makes it possible to have briquettes simultaneously supplying the fluxes, such as iron oxide (Fe 2 O 3 ), but also the ferrites required, provided that if briquettes are raw and do not directly contain ferrites, ferrites can be formed directly in situ, for example in converters in which the briquettes are used.
• the fluxes such as iron oxide (Fe 2 O 3 )
• ferrites can be formed directly in situ, for example in converters in which the briquettes are used.
• the method according to the present invention thus makes it possible to obtain calco-magnesian compound briquettes whose mechanical strength is not penalized by the addition of fluxing agents, even without heat treatment for iron oxide contents of less than 40% by weight.
• weight of the raw briquette composition the iron oxide of which has a very fine particle size distribution characterized by a median size d 50 of less than 100 ⁇ m, preferably less than 50 ⁇ m and a size of 90 less than 200 ⁇ , of preferably less than 150 ⁇ , preferably less than 130 ⁇ , more preferably less than 100 ⁇ m, and which furthermore is very flexible and efficient, without providing the above-mentioned constraints.
• an iron-based compound may be formed from one or more iron-based compounds, totaling together in the composition a content of at least 3%, preferably at least 12%, more preferably at least 20%, more preferably at least 30%, more preferably at least 35% by weight.
• said an iron-based compound has a granuiometric distribution characterized by a d 50 of less than or equal to 80 ⁇ , preferably less than or equal to 60 ⁇ .
• the notation x represents a diameter in ⁇ , as measured by laser particle size in methanol without sonication, relative to which x% by volume of the particles measured are less than or equal.
• the method of measuring the granulometry is by sieving and not by laser diffraction.
• the process according to the present invention further comprises a heat treatment of said green briquettes collected at a temperature between 900 ° C and 1200 ° C, preferably between 1050 ° C and 1200 ° C inclusive, plus preferably between 1100T and 1200T inclusive
• the heat treatment time is preferably carried out for a predetermined period of between 3 and 20 minutes, preferably greater than or equal to 5 minutes and less than or equal to 15 minutes, with formation and obtaining of cooked briquettes wherein said iron oxide is converted to calcium ferrite, i.e., cooked briquettes comprising a bright calco-magnesium compound and an iron-based compound comprising at least calcium ferrite, the compound based on of iron comprising at least calcium ferrite being present at a content of at least 3%, preferably at least 12%, more preferentially at least 20%, preferably at least 30%, more preferably at least 35% Fe 2 0 3 equivalent.
• the heat treatment time can be increased to allow time for the heat to penetrate the heart of the briquette bed.
• the treatment thermal process makes it possible to obtain cooked briquettes comprising a calc-magnesium compound and an iron-based compound containing calcium ferrite, whose porosity and specific surface area is not or only slightly impaired and whose mechanical strength is found therein improved. In other words, at these temperatures, the phenomenon of sintering the briquettes is avoided.
• briquettes obtained by the process according to the present invention not only have a sufficiently high calcium ferrite content, but that the briquettes exhibit a mechanical strength represented by the Shatter index test of particular interest.
• the cooked briquettes have a test Shatter index of less than 8%, sometimes less than 6%, less than 4%, less than 3%, or even around 2%. %.
• said bright calco-magnesium compound is a calco-magnesian compound with soft or medium cooking, preferably soft cooking.
• the calco-magnesian compound brought in the form of a homogeneous mixture is also sufficiently reactive, so as to form cohesive briquettes with the iron-based compound after heat treatment.
• the bright calco-magnesium compound is sufficiently reactive.
• the living calco-magnesian compounds such as quicklime are industrially produced by cooking natural limestones in different types of ovens such as straight furnaces (regenerative furnaces with double flow, ring furnaces, standard straight furnaces ...) or even rotary kilns.
• the quality of the calcium-magnesium compound, such as for example quicklime, especially its reactivity to water, and the consistency of this quality, are partly related to the type of oven used, the conditions of use of the oven, to the nature of the limestone from which the living calco-magnesium compound originates, or even to the nature and quantity of the fuel used.
• said bright calco-magnesium compound is quicklime.
• obtaining a quicklime by a gentle firing makes it possible to obtain a rather reactive lime while obtaining a low reactive lime goes through overcooking at a higher temperature ( 1200-1400 ° C).
• Overcooking often leads to produce quicklime of less stable quality in terms of reactivity to water because the calcination operation is carried out in a thermal zone where the textural evolution of quicklime is quite sensitive.
• This over-cooked quicklime is also more expensive to produce than a quicker quicklime because it requires the use of higher temperatures but also because, except to use dedicated ovens, the production of this quicklime sur- Cooking leads to production intercropagnes to alternate with the production of quicklime that is more commonly used, which is not without problems of stabilization of the calcination conditions and thus problems of stabilization of the quality.
• the quick lime obtained by gentle firing generally have specific surfaces measured by nitrogen adsorption manometry after degassing under vacuum at 190 ° C. for at least 2 hours and calculated according to the multi-point BET method as described in the standard.
• ISO 9277: 2010E greater than 1 m 2 / g whereas over-cooked quicklime generally has surfaces well below 1 m 2 / g
• the reactivity of quicklime is measured using the water reactivity test of the European standard EN 459-2: 2010 E.
• 150g of quicklime are added with stirring in a Dewar cylindrical of 1.7dm 3 of capacity containing 600cm 3 of permutated water at 20 ° C.
• the quicklime is brought in the form of fines of size between 0 and 1 mm.
• the stirring at 250 rpm is carried out by means of a specific pale.
• the evolution of the temperature is measured as a function of time, which makes it possible to draw a curve of reactivity. From this curve can be deduced the teo value which is the time necessary to reach 60X.
• the reactivity of the cooked dolomite is measured using this same reactivity test.
• 120 g of cooked dolomite are added with stirring in a cylindrical dewar of 1.7 dm 3 capacity containing 400 cm 3 of deionized water at 40 ° C.
• the cooked dolomite is brought in the form of fines of size between 0 and 1 mm.
• the stirring at 250 rpm is carried out by means of a specific pale.
• the evolution of the temperature is measured as a function of time, which makes it possible to draw a reactivity curve. From this curve can be deduced the value t 70 which is the time necessary to reach 70 ° C.
• composition according to the present invention comprises a calco-magnesium compound with soft or medium cooking, preferably soft, which is therefore necessarily relatively reactive thus providing reactive briquettes.
• a calco-magnesian compound with soft or medium cooking is characterized by a value t so less than 10 min, preferentially 8 min, preferentially 6 min, and still more preferably 4 min when the calco- magnesian is a quicklime and by a value of t ? o less than 10 min, preferably 8 min, preferably 6 min, and more preferably 4 min when the calco-magnesian compound is a cooked dolomite.
• the process comprises, before said feeding of a powder mixture:
• said fraction of particles of calco-magnesian compound have a particle size ⁇ 90 ⁇ . ⁇ which contains at most 60% by weight of CaO equivalent relative to the weight of said powder mixture
• binder or lubricant can be added directly to the feed of the roller press, said binder or lubricant is added to the mixer, wherein said binder or lubricant is included in said powder mixture, preferably homogeneous.
• said calco-magnesium compound contains at least 10% by weight of quicklime in the form of crushed particles relative to the weight of said composition.
• said calco-magnesium compound according to the present invention contains at least 40% by weight, preferably at least 50% by weight, preferably at least 60% by weight, particularly at least 65% by weight, in particular at least 70% by weight. weight, preferably at least 80% by weight, advantageously at least 90% by weight, or even 100% by weight of quicklime in the form of crushed particles relative to the weight of said composition.
• Quicklime in the form of crushed particles is called lime fines from the grinding of quicklime and therefore corresponding to a dimensional reduction of lime rock.
• the grinding can be indifferently made from the all-out oven and / or output silo or from the all-out oven and / or output silo previously screened.
• the grinding can be carried out using different types of mill (impact mill, hammer mill, double rotor mill, conical mill, ...), either in open circuit (no recirculation loop), or in closed circuit (recirculation loop).
• Quicklime in the form of crushed particles is distinguished from lime screen.
• Screen lime is called lime fines from lime screen.
• the particle size is defined by the size of the screen. For example, a lime screened at 3 mm results in a 0-3 mm screening lime. Thus the screening on the all-out oven led to a "primary” screening lime. Screening on the all-out storage silo leads to a "secondary" screening lime.
• quicklime in the form of crushed particles lime fines generally containing more than very fine lime fines screening.
• quicklime fines in the form of crushed particles will typically contain at least 30% by weight, most often at least 40% by weight, or even at least 50% by weight. by weight of very fine less than 100 ⁇ , while the screening lime fines often contain at most 25% by weight, or even at most 15% by weight of very fine less than 100 ⁇ .
• the chemical composition of crushing lime fines is generally more homogeneous than that of lime fines.
• a lime rock 10-50 mm cooked with a fuel that generates ash such as coal (lignite, coal, anthracite ...) or petroleum coke, and which is characterized the 0-3mm fines resulting from the crushing or screening of this rock lime
• the fraction 0-200 ⁇ of the fines 0-3 mm resulting from the grinding has a chemistry similar to that of the fraction 200 ⁇ 3 mm
• the 0-200 ⁇ fraction of the 0-3 mm fines resulting from the screening contains more impurities than that of the 200 ⁇ -3 mm fraction.
• Crushing lime fines are generally more reactive than fines lime screen.
• the grinding fines typically have teo values of less than 5 min where the fines primary screening often have t 6 o values greater than 5 min.
• said quicklime in the form of ground particles is a quicklime softbake or average cooking, preferably fresh baking said quicklime in the form of crushed particles being characterized by a value t 6 o less than 10 min, preferably less than 8 min, preferentially less than 6 min, and still preferably less than 4 min.
• the process further comprises pretreatment of the modified atmosphere briquettes containing at least 2% by volume of CC3 ⁇ 4 and at most 30% by volume of C0 2 , preferably at most 25% by weight. % by volume of C0 2 , preferably at most 20% by volume of C0 2 , more preferably at most 15% by volume of C0 2 , more preferably still at most 10% by volume of C0 2 with respect to said modified atmosphere.
• said at least one iron-based compound is present at a content greater than or equal to 20% by weight relative to the total weight of said powder mixture in Fe 2 O 3 equivalent.
• the content of iron-based compound is at least 20% by weight relative to the weight of the powder mixture, but also the presence of CaO in the Calco-magnesian compound in the form of very fine particles (dao ⁇ 90 ⁇ ) is at least 20% by weight, not only is the formation of calcium ferrite improved and has a conversion efficiency of iron oxide to ferrite calcium about 90%, but also the balance between the mono-calcium ferrites and ferrites dicalcium formation is directed towards ia formation of dicalcium ferrite, particularly when the contents of CaO and Fe equivalent? 03 ⁇ 4 very fine equilibrium. It has indeed proved interesting from an industrial point of view to be able to control the proportion of di-calcium ferrites with respect to the proportion of mono-caicic ferrites according to needs and vice versa.
• the% by weight of CaO equivalent in the fraction of calco-magnesium compound having a particle size ⁇ 90 ⁇ relative to the total% by weight of quicklime in the fraction of calco-magnesium compound having a particle size ⁇ 90 ⁇ and the Fe20% equivalent 3 of said iron compound of very fine particle size distribution is> 30%, preferably> 32%, more preferably> 34% particularly preferably> 36%.
• the% by weight of CaO equivalent in the fraction of bright calco-magnesium compound having a particle size ⁇ 90 ⁇ relative to the total of% by weight of quicklime in the fraction of calco-magnesian compound having a particle size ⁇ 90 ⁇ and the% Fe 2 0 3 equivalent of said very fine granuiometric distribution iron compound is> 30%, preferably> 32%, more preferably> 34%, particularly preferably>36%.; briquette cooking will favor the formation of di-calcium ferrite (Ca 2 Fe 2 O 5 ).
• PI represents the percentage in the powder mixture for briquetting particles of the bright calco-magnesium compound whose size is less than 90 ⁇ (fraction of caico-magnesium compound having a particle size ⁇ 90 ⁇ ),
• P2 represents the percentage in the powder mixture intended for briquetting particles of the caico-magnesium compound whose size is greater than 90 ⁇ m
• Cl represents the percentage of CaO equivalent in the particles of kiesel-magnesium compound whose size is less than 90 ⁇
• C2 represents the percentage of CaO equivalents in the particles of kiesel-magnesium compound whose size is greater than 90 ⁇
• C3 represents the percentage of Fe 2 0 3 equivalent in the iron-based compound
• the mass ratio "PI / (P1 + P3)" is a key parameter that must be controlled to form either predominantly major mono-calcium ferrites or is predominantly di-calcium ferritic majority, it comes more generally than the weight ratio "P1.C1 / (P1.C1 + P3.C3)” is one of the possibits of the formation of monocalcic ferrite majority or di-calcium ferrite majority,
• said heat treatment is preferably a heat treatment at a temperature greater than or equal to 100 ° C., preferably greater than or equal to 1150 ° C., more particularly less than or equal to 1200 ° C., preferably according to the relationship (predetermined heat treatment time) / ⁇ heat treatment temperature - 1000 ° C)> 5.
• the percentage P2 is a key parameter that must be controlled to form briquettes with or without inclusions of bright CaCO-magnesium compound having a bidimensional size greater than 63 ⁇ ,
• said iron-based compound comprises at least 50% by weight, preferably at least 60% by weight, more preferably at least 70% by weight, more preferably at least 80% by weight and so more than 95% by weight of magnetite as iron oxide Fe30 particular 4 relative to the total weight of the iron-based compound expressed in equivalent Fe 2 0 3,
• the% by weight of said particles of quicklime having a particle size ⁇ 90 ⁇ relative to the total of the% by weight of said particles of quicklime having a particle size ⁇ 90 ⁇ and said iron-based compound is ⁇ 40, preferably ⁇ 38, more preferably ⁇ 36% and> 20%, preferably> 22%, preferably 24% to influence briquette formation, mono-calcium ferrites.
• said heat treatment is a heat treatment at a temperature less than or equal to 1150 ° C, preferably less than or equal to UOOT, more particularly greater than or equal to 900T, preferably according to the relation (predetermined duration) / (heat treatment temperature - 1000X)> 5, which makes it possible to further promote the formation of mono-calcium ferrites.
• said iron-based compound comprises at least 50% by weight, preferably at least 60% by weight, more preferably at least 70% by weight, more preferably at least 80% by weight. % by weight and in particular more than 95% by weight of iron oxide in the form of Fe 2 0 3 hematite relative to the total weight of the iron-based compound expressed in Fe 2 O 3 equivalent.
• the subject of the invention is also a composition in the form of raw briquettes comprising at least one bright calco-magnesium compound and an iron-based compound characterized in that the composition comprises at least 40% by weight of CaO + MgO equivalent per relative to the weight of said composition " said composition having a molar ratio Ca / Mg greater than or equal to 1, preferably greater than or equal to 2, more preferably greater than or equal to 3 and characterized in that said iron-based compound is present at a level of at least 3%, preferably at least 12%, more preferably at least 20%, most preferably at least 30%, more preferably at least 35% by equivalent weight Fe 2 0 3 by weight of said composition, said compound based on iron having a very fine particle size distribution characterized by a median size of less than 100 o 5 ⁇ , preferably less than 50 ⁇ and a size d 90 of less than 200 ⁇ , preferably less than 150 pm, preferably less than 130 ⁇ plus preferably less than 100 .mu.m, in which said bright CaCO
• said bright calco-magnesium compound comprises one or more bright calco-magnesium compounds.
• the bright caico-magnesium compound is selected from the group consisting of quick lime (calcium), magnesium lime, bright dolomitic lime, calcined dolomite and mixtures thereof, preferably in the form of particles, such as particles from screening, grinding, filter dust and mixing.
• Said bright magnesium calco compound can therefore be considered as a calco-magnesian component of the composition in the form of briquettes, which may contain other compounds.
• the composition in the form of raw briquettes according to the present invention comprises at most 97% by weight, preferably at most 90% by weight, more preferably at most 88%, in some form of realization, at most 60% by weight of equivalent CaO + MgO with respect to the weight of said composition.
• the% by weight of CaO equivalent in the fraction of bright calco-magnesium compound having a particle size ⁇ 90 ⁇ m relative to the total of% by weight of quicklime in the fraction of calco-magnesian compound having a particle size ⁇ 90 pm and the equivalent% Fe 2 0 3 of said compound based on very fine particle size distribution of iron is> 30%, preferably> 32%, more preferably> 34%, particularly preferably> 36%.
• the composition in the form of raw briquettes according to the present invention further comprises at least 50% by weight, preferably at least 60% by weight, more preferably at least 70% by weight, more preferably at least 80% by weight. by weight and in particular more than 95% by weight of ferric oxide in magneton form Fe 3 O 4 relative to the total weight of the iron-based compound expressed as Fe 2 O 3 equivalent.
• magnesium having a particle size ⁇ 90 ⁇ and the Fe 2 03 equivalent of said iron-based compound of very fine particle size distribution is ⁇ 40, preferably ⁇ 38, more preferably ⁇ 36%.
• composition in the form of briquettes according to the present invention further comprises at least 50% by weight, preferably at least 60% by weight, more preferably at least 70% by weight, more preferably at least 80% by weight. weight and in particular more than 95% by weight of iron oxide in the form of Fe 2 0 3 hematite relative to the total weight of the iron-based compound expressed in Fe 2 O 3 equivalent,
• the present invention also relates to a composition in the form of cooked briquettes, comprising at least one iron-based compound, said composition comprising at least 40% by weight of CaO + MgO equivalent relative to the weight of said composition and exhibiting a Ca / g molar ratio greater than or equal to 1, preferably greater than or equal to 2, more preferably greater than or equal to 3, characterized in that said iron-based compound is present at a content of at least 3%, preferentially at least 12%, more preferably at least 20%, preferably at least 30%, more preferably at least 35% by weight of equivalent Fe 2 (3 ⁇ 4 relative to the weight of said composition, said iron-based compound comprising at least 60% of calcium ferrite, expressed by weight of equivalent Fe 2 O 3 , relative to the total weight of said iron-based compound expressed by weight of Fe 2 equivalent C3 ⁇ 4 and further comprising particles of bright calco-magnesium compound, preferably lime having a bidimensional size greater than 63 ⁇ m and less than 5 mm, observable by scanning electron microscopy
• Calcium ferrite is represented by the following formulas: CaFe 2 0 4 (mono-calcium ferrite) and / or Ca 2 Fe 2 O 5 (di-caicic ferrites)
• said powder mixture comprises at most 97% by weight, preferably at most 90% by weight, more preferably at most 88%, in some embodiment at most 60% by weight. equivalent CaO + MgO with respect to the weight of said composition.
• said bright calco-magnesium compound comprises at least 10%, preferably 20%, more preferably 30%, more preferably 40% by weight. equivalent weight CaO + MgO, relative to the total weight of said composition.
• said bright calco-magnesium compound comprises fine particles of calco-magnesium compound chosen from fine particles rejected by screening its pebble production of said bright calco-magnesium compound.
• Calco-magnesium filter dusts at a concentration of 0% by weight to 90% by weight, based on the total weight of the calc-magnesium compound and 10 and 100% by weight of quicklime in the form of crushed particles, by relative to the total weight of said bright calco-magnesium compound.
• said bright calco-magnesium compound contains from 0 to 100% by weight of quicklime in the form of particles ground from the rolls of said calco-magnesium compound.
• said bright calco-magnesium compound contains from 0 to 90% by weight of fine particles rejected in the cobalt production screen of said calco-magnesium compound. and 10 and 100% by weight of quicklime in the form of crushed particles, based on the total weight of said calco-magnesium compound.
• said quicklime in the form of crushed particles is present at a concentration of at least 15% by weight, in particular at least 20% by weight, more preferably at least 20% by weight. 30% by weight, particularly preferably at least 40% by weight relative to the weight of the composition.
• said bright calco-magnesium compound is a calco-magnesian compound with soft or medium cooking, preferably soft cooking.
• quicklime in the form of crushed particles is quicklime soft cooking or medium cooking, preferably soft cooking.
• composition when the composition is in the form of raw briquettes, said composition has a BET specific surface area greater than or equal to 1 m 2 / g, preferably greater than or equal to 1.2 m 2 / g, of more preferentially greater than or equal to 1.4 m 2 / g.
• said composition when the composition is in the form of raw briquettes, said composition has a porosity greater than or equal to 20%, preferably greater than or equal to 22%, more preferably greater than or equal to 24%.
• porosity of the composition in the form of briquettes is meant for the purpose of the present invention, the total pore volume of mercury determined by mercury intrusion porosimetry according to part 1 of the ISO 15901-1: 2005E standard which consists of dividing the difference between the skeletal density, measured at 30000 psia, and the apparent density, measured at 0.51 psia, by the skeletal density.
• the measurement of porosity can also be measured by oil intrusion porosimetry.
• the density and the porosity of the briquettes are determined by intrusion of kerosene, according to a measuring protocol resulting from the EN ISO 5017 standard. The measurements are carried out on 5 briquettes.
• the density of the briquettes is calculated according to the formula ml / (m3 - m2) x
• ml is the mass of these 5 briquettes
• m2 is the mass of these 5 briquettes immersed in oil
• m3 is the mass of these 5 "wet" briquettes, that is to say impregnated by oil.
• Dp is the density of oil.
• the composition when the composition is in the form of green briquettes and that the calco-magnesian compound is mainly of quicklime, said composition has a reactivity worth t 6 o less than 10 min, preferably less than 8 min, preferably less than 6 min and even more preferably less than 4 min.
• a little more than 150 g of said composition is added in the reactivity test to have the equivalent of 150 g of quicklime added.
• the composition when the composition is in the form of raw briquettes and the calco-magnesium compound is mainly cooked dolomite, said composition has a reactivity value t 70 less than 10 min, preferably less than 8 min. preferably less than 6 minutes and even more preferably less than 4 minutes.
• t 70 a reactivity value t 70 less than 10 min, preferably less than 8 min. preferably less than 6 minutes and even more preferably less than 4 minutes.
• slightly more than 120 g of said composition is added in the reactivity test to have the equivalent of 120 g of cooked dolomite added.
• composition when the composition is in the form of cooked briquettes, said composition has a BET specific surface area greater than or equal to 0.4 m 2 / g, preferably greater than or equal to 0.8 m 2 / g. more preferably greater than or equal to 0.8 m 2 / g.
• said composition when the composition is in the form of cooked briquettes, said composition has a porosity greater than or equal to 20%, preferably greater than or equal to 22%, more preferably greater than or equal to 24%.
• the composition when the composition is in the form of fired briquettes and that the calco-magnesian compound is mainly of quicklime, said composition has a value t 6 o less than 10 min, preferably less than 8 min preferably less than 6 minutes and even more preferably less than 4 minutes.
• t 6 o less than 10 min, preferably less than 8 min preferably less than 6 minutes and even more preferably less than 4 minutes.
• a little more than 150 g of said composition is added in the reactivity test to have the equivalent of 150 g of "free" quicklime added.
• quicklime "free” is meant quicklime that has not reacted with iron oxide to lead to calcium ferrites CaFe 2 0 4 and / or Ca 2 Fe 2 0 5 .
• said at least one calcium-magnesium compound is formed of particles smaller than 7 mm.
• said at least one calco-magnesium compound is formed of particles smaller than 5 mm.
• said at least one calco-magnesium compound is formed of particles smaller than 3 mm.
• said at least one calco-magnesium compound is a mixture of particles smaller than 7 mm and / or particles smaller than 5 mm and / or or particles smaller than 3 mm.
• the composition in the form of raw or cooked briquettes further comprises a binder or a lubricant, more particularly chosen from the group consisting of binders of mineral origin such as cements, clays, silicates, binders of vegetable or animal origin, such as celluloses, starches, gums, alginates, pectin, glues, binders of synthetic origin, such as polymers, waxes, liquid lubricants such as mineral oils or silicones, solid lubricants such as talc, graphite, paraffins, stearates, in particular calcium stearate, magnesium stearate and mixtures thereof, preferably calcium stearate and / or magnesium stearate, at a content of between 0.1 and 1% by weight, preferably between 0.15 and 0.6% by weight, more preferably between 0.2 and 0.5% by weight relative to to the total weight of the composition.
• binders of mineral origin such as cements, clays, silicates
• binders of vegetable or animal origin such as
• the composition according to the present invention is a composition of raw or cooked briquettes produced in industrial volumes and packaged in types of containers having a volume of content greater than 1 m 3 such as large bags, containers, silos and the like, preferably sealed.
• the briquettes of the composition in the form of raw briquettes have a test Shatter index of less than 10%, for iron oxide contents of less than 20% by weight of the composition.
• the briquettes of the composition in the form of cooked briquettes have a test Shatter number of less than 8%, more particularly less than 6%, irrespective of the content of iron-based compound.
• said briquettes have the highest dimension, at most 50 mm, preferably at most 40 mm, more preferably at most 30 mm.
• the briquettes of the composition in the form of briquettes pass through a sieve with square mesh of 50 mm, preferably 40 mm, and in particular 30 mm, side respectively.
• said raw or cooked briquettes have a larger dimension of at least 10 mm, preferably at least 15 mm, more preferably at least 20 mm.
• highest dimension is meant a characteristic dimension of the raw or cooked briquette which is the largest, namely the diameter, the length, the width, the thickness, preferably in the longitudinal direction of the briquette. oblong shape.
• said at least one calco-magnesium compound is live dolomite.
• said at least one calco-magnesian compound is quicklime.
• said raw or cooked briquettes have a mean weight per briquette of at least 5 g, preferably at least 10 g, more preferably at least 12 g, and in particular at least 15 g.
• said raw or cooked briquettes have a mean weight per briquette less than or equal to 100 g, preferably less than or equal to 60 g, more preferably less than or equal to 40 g and in particular less than or equal to 30 g .
• said raw or cooked briquettes have an apparent density of between 2 g / cm 3 and 3.0 g / cm 3 , advantageously between 2.2 g / cm 3 and 2.8 g / cm 3 .
• the cooked briquettes according to the present invention further comprise particles of bright calco-magnesium compound, preferably quicklime having a two-dimensional size greater than 63 ⁇ and less than 5 mm, observable by electron microscopy with scanning coupled to the energy dispersive analysis, in a section of said briquette and covering at most 20% of the cutting surface of said briquette, preferably at most 10% of the cutting surface of said briquette.
• the briquettes baked according to the present invention comprise at least 20% by weight of calcium ferrite relative to the weight of said composition in the form of a cooked briquette, in which said calcium ferrite forms a matrix in which particles of compound are dispersed. bright calco-magnesian ..
• Said matrix must be understood as being a continuous phase based on calcium ferrite in which particles of bright calco-magnesium compound, in particular quicklime, are dispersed.
• particles of bright calco-magnesium compound are of small size so that they melt visually into the matrix based on calcium ferrite in the case where particles of bright calco-magnesium compound are larger. appearing as inclusions of bright calco-magnesium compound in said matrix.
• the aforementioned distinction is materialized by using a section of a briquette according to the invention, on which scanning electron microscopy is performed, coupled with dispersive energy analysis.
• the particles of calco-magnesian compound also appear in two dimensions on the plane of section.
• the particles of bright calco-magnesium compound melt or merge in said matrix (continuous phase) of calcium ferrite when said particles of bright calco-magnesium compound have a two-dimensional size less than 63 ⁇ , observable by scanning electron microscopy coupled with dispersive energy analysis, in a section of the briquette.
• the briquettes baked according to the present invention comprise at least 40% by weight, preferably 50% by weight of said calcium ferrites are in the form of mono-calcium ferrite CaFe 2 0 4 .
• the briquettes baked according to the present invention comprise at least 40% by weight, preferably 50% by weight of said calcium ferrites are in the form of di-calcium ferrite Ca 2 Fe 2 O 5 .
• compositions in the form of raw or cooked briquettes according to the invention are indicated in the appended claims.
• the invention also relates to a use of a composition in the form of raw briquettes or in the form of briquettes cooked according to the present invention in the iron and steel industry, in particular in oxygen converters or in electric arc furnaces.
• the raw or cooked briquettes according to the present invention are used in oxygen converters or in electric arc furnaces, mixed with briquettes of bright calco-magnesium compounds or with rolls of bright calco-magnesium compounds.
• composition according to the present invention which is therefore doped with fluxing agents, is found to melt faster than lime in rocks, and helps to form a liquid slurry earlier at the beginning of the process, in comparison with the conventional processes, because of a homogeneous mixture and the shaping of this homogenized mixture which makes it possible to further accelerate the slag formation process and to minimize the formation of components high melting slags such as the calcium silicates which are usually formed during the aforementioned method of the state of the art.
• the invention also relates to the use of a composition in the form of raw briquettes or in the form of briquettes cooked in a process for refining molten metal, in particular dephosphorizing molten metal and / or desulphurizing molten metal and / or reduction of loss of refined metal in the slag.
• compositions in the form of raw briquettes or in the form of briquettes cooked according to the present invention in a process for refining molten metal comprises
• At least one unloading step of said refined metal having a reduced content of phosphorus and / or sulfur compounds and / or increased refined metal.
• the use according to the present invention further comprises a step of adding lime, preferably quicklime rock or compacts of quicklime, especially tablets or briquettes of quicklime.
• Figure 1 is a graph of the BET specific surface area and oil intrusion porosity depending on the equivalent content of Fe 2 0 3 in the briquettes according to the present invention.
• Figure 2 is a graph of the Shatter Test Index (STI) as a function of the Fe 2 equivalent content (3 ⁇ 4 in the cooked and raw briquettes according to the present invention.
• STI Shatter Test Index
• Figure 3 is a plot of Fe 2 % (3 3 converted to calcium ferrites versus Fe 2 0 3 equivalent content in cooked briquettes according to the present invention.
• FIG. 4 is a graph of the evolution of the calcium ferrite content expressed as Fe 2 0 3 equivalent in the briquettes fired as a function of the iron oxide content expressed as Fe 2 0 3 equivalent in the raw briquettes before treatment thermal.
• Figure 5 shows the photographs of the briquette sections of Examples 2 to 9.
• the present invention relates to a method for briquetting fine particles of calco-magnesian compounds and iron-based compound, said iron-based compound having a very fine particle size distribution characterized by median size d so less than 100 ⁇ , preferentially less than 50 ⁇ and a d90 size less than 200 ⁇ % preferably less than 150 ⁇ % preferably less than 130 ⁇ , more preferably less than 100 ⁇ .
• the briquetting process according to the invention comprises a feed of a substantially homogeneous powder mixture comprising at least 40% by weight of equivalent CaO + gO of a bright calco-magnesium compound and at least 3%, preferably at least 12%, more preferably at least 20%, more preferably at least 30%, more preferably at least 35% by weight of a iron-based compound expressed as Fe 2 O 3 equivalent based on the weight of said composition, wherein said bright calco-magnesium compound wherein said at least one bright caico-magnesium compound comprises at least 40% by weight of equivalent CaO + ivIgO comprises a fraction of caico-magnesian compound particles having a particle size of less than 90 ⁇ m, which comprises at least 20% by weight of CaO equivalent relative to the weight of said powder mixture and wherein said powder mixture comprises in part in addition, between 10% and 60% of particles of bright calco-magnesium compound having a particle size of> 90 ⁇ m and ⁇ 5 mm relative to the total weight of said powder mixture.
• said powder mixture comprises at most 97% by weight, preferably at most 90% by weight, more preferably at most 88%, in some embodiment at most 60% by weight. of equivalent CaO + MgO with respect to the weight of said composition
• the homogeneous mixture in which the iron-based compound is homogeneously distributed is supplied to a roller press, also sometimes referred to as a tangential press, for example a Komarek press, Sahut Konreur, Hosokawa Bepex, Kopern.
• the substantially homogeneous powder mixture is compressed, optionally in the presence of a binder or a lubricant, more particularly chosen from the group consisting of binders of mineral origin such as cements, clays, silicates binders of vegetable or animal origin, such as celluloses, starches, gums, alginates, pectin, glues, binders of synthetic origin, such as polymers, waxes, liquid lubricants such as mineral oils or silicones, solid lubricants such as talc, graphite, paraffins, stearates, in particular calcium stearate, magnesium stearate, and mixtures thereof, preferably calcium stearate and / or magnesium stearate, at a content of between 0.1 and 1% by weight, preferably between 0.15 and 0.6% by weight, more preferably between 0.2 and 0.5% by weight relative to to the weight al said briquettes.
• a binder or a lubricant more particularly chosen from the group consisting of binders of mineral origin
• the rollers of the roller press develop linear speeds at the periphery of the rolls of between 10 and 100 cm / s, preferably between 20 and 80 cm / s, and linear pressures of between 60 and 160 kl / l. cm, preferably between 80 and 140 kN / cm, and even more preferably between 80 and 120 kN / cm.
• a surface pressure can be calculated which is equal to the linear pressure divided by (1 ⁇ 2.JI.D) / 360 where D is the diameter of the frets expressed in cm.
• the surface pressure is between 300 and 500 MPa, preferably between 300 and 450 MPa, and more preferably between 350 and 450 MPa.
• the calco-magnesian composition in the form of raw briquettes is obtained and these are collected.
• the collected raw briquettes are heat treated at a temperature between 900X and 1200 ° C, preferably between 1050 ° C and 1200T, more preferably between 1100 ° C and 1200 ° C included.
• the heat treatment time is preferably carried out for a predetermined time of between 3 and 20 minutes, to obtain cooked briquettes in which said iron oxide is converted into calcium ferrite, that is to say cooked briquettes comprising a bright calco-magnesium compound and a calcium ferrite compound present at a content of at least 3%, preferably at least 12%, more preferably at least 20%, preferably at least 30%, more preferably at least 35% equivalent Fe 2 0 3.
• said heat treatment of raw briquettes is carried out in a rotary kiln at high temperature.
• the rotary kiln is used for the heat treatment of briquettes whose iron oxide content is less than 40%.
• the heat treatment is carried out in a horizontal oven such as a tunnel oven, a passage oven, a rack oven, a roller oven or a mesh belt furnace.
• a horizontal oven such as a tunnel oven, a passage oven, a rack oven, a roller oven or a mesh belt furnace.
• any other type of conventional oven but not leading to the alteration of the integrity of the compacts, for example due to too much attrition, can be used.
• Cooling can either be carried out conventionally in the downstream part of the furnace or outside the furnace, for example in a countercurrent vertical cooler for the cooling air or in a fluidized bed cooler. cooling air in case of quenching.
• the cooling after the heat treatment is carried out rapidly in less than 15 min, preferably in less than 10 min, in a fluidized bed by cooling air.
• the process comprises, before said feeding of a homogeneous powdery mixture,
• said bright calco-magnesium compound comprising at least 40% by weight of equivalent CaO + MgO also comprises at least one fraction of particles of bright calco-magnesium compound having a particle size ⁇ 90 ⁇ % which comprises at least 20% by weight s of equivalent CaO with respect to the weight of said powder mixture and between 10% and 60% of particles of bright calco-magnesium compound having a particle size> 90
• the calco-magnesium compound comprises at least 10% by weight of crushed quicklime particles, preferably at least 20% by weight, more particularly at least 30% by weight and at most 100% by weight. weight relative to the total weight of said calco-magnesium compound.
• "Raw" briquettes are based on quick lime (possibly dolomitic) and ultrafine iron oxide particles. They are characterized by a mass content of iron of at least 3%, preferably at least 12%, more preferably at least 20%, preferably at least 30%, more preferably at least 35% by weight, expressed as Fe 2 equivalent. 0 3 .
• the raw briquettes are also characterized by a mass content of calcium and magnesium of at least 40% by weight, expressed as CaO and MgO equivalents. Chemical analysis is performed by X-ray fluorescence spectrometry (XRF) according to EN 15309.
• XRF X-ray fluorescence spectrometry
• the chemical analysis, semi-quantitative, by XRF to determine the relative mass concentration of the elements whose atomic mass is between 16 (oxygen) and 228 (uranium) is carried out starting from the samples crushed to ⁇ and shaped in form pastille.
• the sample is excited by a high energy source (primary X-ray) and by recovering its original excitation state, the sample emits secondary X-rays, characteristic of the chemical elements composing the sample.
• the samples are introduced into a PANalytical / MagiX PRO PW2540 apparatus, operating in wavelength dispersion.
• the measurement is carried out with a power of 50 kV and 80 mA, with a Duplex detector.
• the semi-quantitative analysis of the iron-based compounds is carried out on the basis of a diffractogram of radii X by the Rietveld method.
• This method consists in simulating a diffractogram from a crystallographic model of the sample, and then adjusting the parameters of this model so that the simulated diffractogram is as close as possible to the experimental diffractogram.
• the total amount of iron expressed in Fe 2 0 3 equivalent does not differ by more than 10% from the values obtained by XRF.
• the percentage of total iron in the form of calcium ferrites is obtained by a simple division (Fe in ferrites divided by Fe in the whole of iron-based compounds).
• the raw briquettes are also characterized by a BET specific surface area greater than or equal to 1 m 2 / g, preferably 1.2 m 2 / g, preferably 1.4 m 2 / g
• the porosity of the raw briquettes is greater than or equal to 20%, preferably 22%, preferably 24%.
• the green briquettes have a bulk density of between 2.0 and 3.0 and preferably between 2.2 and 2.8.
• the briquettes have good resistance to aging. Thus, when they are exposed to a humid atmosphere containing, for example, 5 to 15 g / m 3 of absolute humidity, the degradation of their mechanical properties (STI) only occurs above 1.5% mass, preferably 2% weight gain, and even more preferably 2.5% mass gain, following the hydration reaction of CaO quicklime Ca (OH) 2 slaked lime.
• STI mechanical properties
• the baked briquettes comprise a calco-magnesium compound, for example quick lime (dolomitic) and an iron-based compound, containing ultrafine iron oxide particles and CaFe 2 0 4 and / or Ca 2 Fe calcium ferrites. 0 5 2.
• a calco-magnesium compound for example quick lime (dolomitic) and an iron-based compound, containing ultrafine iron oxide particles and CaFe 2 0 4 and / or Ca 2 Fe calcium ferrites. 0 5 2.
• the baked briquettes are characterized by a mass content of iron of at least 3%, preferably at least 12%, more preferably at least 20%, preferably at least 30%, more preferably at least 35% by weight expressed in equivalent. Fe 2 O 3 . They are also characterized by a mass content of calcium and magnesium of at least 40% by weight, expressed as CaO and MgO equivalents.
• the chemical analysis is carried out as previously mentioned by XRF.
• At least 40%, preferably at least 50%, preferably at least 60% and even more preferably at least 70% of the total iron is in the form of calcium ferrites.
• Quantification of the calcium ferrites is carried out by XRD / Rietveld analysis after crushing the briquettes, as for the raw briquettes.
• the baked briquettes of the present invention exhibit a
• Shatter Test ie percentage by mass of fines less than 10mm after 4 drops of 2m
• STI Shatter Test
• They are also characterized by a specific surface greater than or equal to 0.4 m 2 / g. preferably 0.5 m 2 / g, preferably 0.6 m 2 / g.
• the porosity is greater than or equal to 20%, preferably 22%, preferably 24%.
• the cooked briquettes have an apparent density of between
• Cooked briquettes have good resistance to aging. Thus, when they are exposed to a humid atmosphere containing, for example, 5 to 15 g / m 3 of absolute humidity, the degradation of their mechanical properties (STI) occurs only above 4% of mass preferably 4.5% of weight gain, and more preferably 5% of weight gain, following the hydration reaction of CaO quicklime Ca (OH) 2 .
• STI mechanical properties
• Crushed quick lime fines were prepared from a soft-baked rock lime produced in a parallel-flow regenerative furnace.
• the grinding is carried out in a hammer mill equipped with a 2 mm screen and a recirculation loop for sizes greater than 2 mm.
• These fine bright grinding lime contains 29% of particle size of particles less than 90 .mu.m (d 30 ⁇ 90 pm), 71% of greater than 90 .mu.m particles, 37% of greater than 500 prn particles, 21% particles greater than 1 mm and 1% of particles between 2 and 3 mm.
• the t 60 value of the water reactivity test is 0.9 min.
• the BET specific surface area (measured by nitrogen adsorption manometry after degassing under vacuum at 190 ° C. for at least two hours and calculated according to the BET multipoint method as described in the ISO 9277: 2010E standard) is 1.7 m2 / g.
• These crushed quicklime fines contain 95.7% CaO and 0.8%
• a Gericke GC 450 powder mixer with a capacity of 10 dm 3 is used , equipped with standard 7 cm radius blades used in rotation at 350 rpm (ie 2.6 m / s). This mixer is used in continuous mode to prepare a mix consisting of: - fines of quicklime, possibly lime fines of grinding,
• the total flow rate of the powder is 300 kg / h and the residence time is
• the mixture obtained is very homogeneous. This means that the Fe content for different 10 g samples taken from the final mixture is always within plus or minus 5% of the average value.
• the tangential press is fed and compacted at a speed of 12 revolutions per minute (ie a linear velocity of 38 cm / s) at a linear pressure of 120 kN / cm (ie a calculated surface pressure). 455 MPa for 0.5 degree angle).
• briquettes Nearly several tons of briquettes are obtained with an average volume of 8.4 cm 3 , an average weight of 21.4 g and an average density of 2.4. These briquettes have a length of about 36 mm, a width of about 26 mm and a thickness of about 15.8 mm. These briquettes develop a total pore volume of mercury (determined by mercury intrusion porosimetry according to part 1 of ISO 15901-1: 2005E which consists of dividing the difference between skeletal density, measured at 30000 psia, and apparent density. , measured at 0.51 psia, by skeletal density).
• the water reactivity of the briquettes is determined by adding a predetermined quantity of these briquettes, previously crushed in the form of fines of size between 0 and 1 mm, to 600 ml of water at 20 ° C., so as to correspond to 150 g of quicklime ..
• the briquettes are also characterized by performing a heat treatment (charging / hot deflection) on several of these briquettes at the end of which a powder of particle size less than 80 ⁇ is prepared. This is characterized by X-ray diffraction and phase quantification is performed by Rietveld analysis.
• Raw briquettes are produced according to the invention with crushed quicklime containing particles of sizes between 0 and 2 mm, but having different particle size profiles and iron oxide contents of hematite type, expressed in Fe 2 equivalent. 3 ranging from 10% to 60%.
• the iron oxide used in these examples is characterized by a d i0 of 0.5 ⁇ , d 5 o of 12.3 ⁇ and 0% of 35.7 ⁇ .
• the grinding quicklime particles of size between 0 and 2 mm have at least 30% of particles that are less than 90 ⁇ .
• the preparation protocol is described in Example 1.
• Figure 1 presents a graph showing:
• Figure 2 presents a graph showing:
• the Shatter test indices are less than 20% for raw briquettes with iron compound contents expressed in Fe 2 C 1 ⁇ 2 equivalent less than 40%, whereas for cooked briquettes, all Shatter tests are less than 10% or even 6%.
• FIG. 3 presents a graph showing the evolution of the yield of iron-based compound (iron oxide) converted to ferrite of caicium, as a function of the iron oxide content expressed in Fe 2 0 3 equivalent, as well as the amounts of iron oxide converted to mono-calcium ferrite and di-calcium ferrite.
• the heat treatment is carried out in a static bed for 20 min at 1100 ° C. in a tunnel oven over 100 mm thick briquettes.
• the calcium ferrite conversion efficiency starts to decrease for iron oxide contents expressed in equivalent Fe 2 0 3 greater than 40%.
• the percentage of mono-calcium ferrites goes through a maximum for iron oxide contents of 40%.
• the percentage of formation of di-calcium ferrites decreases with the content of iron oxide
• Figure 4 shows the evolution of the calcium ferrite content expressed in ⁇ 2 equivalent (3 ⁇ 4 in briquettes fired according to the iron oxide content expressed as Fe 2 0 3 equivalent in the raw briquettes before heat treatment.
• Example 4 baked briquettes having a conversion efficiency to calcium ferrite of 98% and containing 55.3% by weight of mono- calcium ferrite relative to the amount of calcium ferrites are produced after heat treatment at 1200. ° C for 20 minutes on raw briquettes containing about 40% by weight of hematite and 60% by weight of quicklime having a d 97 equal to 2 mm and a d 30 equal to ⁇ , the presence of 0.25% by weight of calcium stearate, relative to the total weight of the raw briquettes.
• Example 6 baked briquettes having a conversion yield of 90% calcium ferrite and containing 69.9% by weight of mono- calcium ferrite relative to the amount of calcium ferrites are produced after 1100 heat treatment. ° C for 20 minutes on green briquettes containing about 50% by weight of hematite and 25% by weight of quicklime having a d 97 equal to 2 mm and a d 30 equal to 90 ⁇ ⁇ ⁇ and 25% by weight of lime vivid having a dg 7 equal to 90 ⁇ , the presence of 0.25% by weight of calcium stearate, relative to the total weight of raw briquettes.
• Example 7 cooked briquettes having a 96% ferrite conversion yield and containing 47.2% by weight of mono- calcium ferrite relative to the amount of calcium ferrites are produced after heat treatment at 1100. C. for 20 minutes on raw briquettes containing approximately 50% by weight of hematite and 50% by weight of quicklime having a dioo equal to 90 ⁇ .
• Example 8 baked briquettes having a conversion efficiency to ferrite of Calcium of 99% and containing 43.9% by weight of mono-calcium ferrite relative to the amount of calcium ferrites are produced after heat treatment at 1200 ° C.
• the mono-calcium ferrite yield can be increased by lowering the temperature of the heat treatment to 1100 ° C., the presence of 0.25% by weight of calcium stearate, relative to the total weight of the raw briquettes.
• Example 9 cooked briquettes having a conversion efficiency to calcium ferrite of 61% and containing 82.6% by weight of mono- calcium ferrite relative to the amount of calcium ferrites are produced after heat treatment at 1100. ° C for 20 minutes on raw briquettes containing about 50% by weight of hematite and 50% by weight of quicklime having a d 97 equal to 2 mm and a d 30 equal to 90 ⁇ .
• the mono-calcium ferrite yield can be increased by increasing the amount by weight of quicklime having a dioo equal to 90 ⁇ m, in the presence of 0.25% by weight of calcium stearate, based on the total weight of the raw briquettes. .
• FIG. 5 shows the photographs of the sections of briquettes of examples 2 to 9.
• the textures of the cooked briquettes of examples 2 to 9 were analyzed by scanning electron microscopy coupled to the energy dispersive analysis by cutting these briquettes, encapsulating these briquettes in a resin, and polishing the cutting surface. These analyzes make it possible to reconstruct a mapping of the distribution of each element in a section of the briquettes.
• An image analysis software makes it possible to combine the maps obtained for each element and to measure the size distribution and the relative coverage of each element.
• the calcium ferrite forms a matrix (or continuous phase) in which particles of quicklime (discontinuous phase) are dispersed.
• a calcium ferrite matrix may be obtained after heat treatment for 20 minutes at temperatures between 900 ° C and 1200X, preferably between 1050 and 1200T of raw briquettes containing at least 20% by weight of calco-magnesian compound particles, preferably in the form of quicklime and at least 20% by weight of iron oxide having a d90 of less than 200 ⁇ m, preferably less than 150 ⁇ m, more preferably less than 100 ⁇ m and a dso of less than 50.
• the two-dimensional sizes of the lime particles dispersed in The matrix is calculated by a program averaging the smallest and highest dimension of each lime particle in the calcium ferrite matrix.
• the particles are classified into a first group of particles whose two-dimensional size is less than 63 ⁇ m and greater than the detection limit of the measuring apparatus, and a second group of particles whose two-dimensional size is greater than 63 ⁇ m.
• Table 2 shows, for the briquettes of Examples 2 to 9, the relative covers of its calcium ferrite matrix, particles of quicklime less than 63 ⁇ m and particles of quicklime greater than 63 ⁇ m in the section. cutting each briquette.
• the surface coverage percentages of quicklime particles greater than 63 ⁇ are less than 25% for cooked briquettes having calcium ferrite contents greater than 60% by weight of the composition.
• Raw briquettes were made with 38.85% by weight iron oxide in the form of magnetite Fe 3 O 4 having a dy of 150 ⁇ m and with 60.9% by weight of quicklime having a d97 equal to 2 mm. and a d 30 equal to 90 ⁇ and 0.25% by weight of calcium stearate, based on the weight of the briquette.
• the heat treatment was performed on a static bed of three layers of briquettes for 20 min at 1100 ° C to obtain the fired briquettes and the weight percent of iron converted to mono-calcium ferrite is 8%, while percentage of Iron converted to di-calcium ferrite is 82%.
• Raw briquettes were made with 39.9% by weight of iron oxide in hematite form FeiO-j having one characterized by a d 10 of 0.5 ⁇ , d 50 of 12.3 ⁇ m and dg 0 of 35. , 7 ⁇ and with 59.85% by weight of quicklime having a d 97 equal to 2 mm and a dût) equal to 90 ⁇ and 0.25% by weight of caicium stearate relative to the weight of the briquette.
• the raw briquettes obtained were heat-treated under the same conditions as in Example 17 in order to obtain cooked briquettes. In this case, the The percentage of iron converted to mono-calcium ferrite is 65% by weight and the percentage of iron converted to di-calcium ferrite is 24% by weight.
• Examples 12 to 28 Pretreatment in Modified Atmosphere Containing C3 ⁇ 4 Corresponding respectively to Tests 1 to 17 in Table 3.
• the tests for the compressive strength of the briquettes were carried out with the aid of FIG. a Pharmatron Multitest 50, one of whose plates is equipped with a tip. The presence of a tip decreases the force required to break the briquettes compared to a compression test performed without tip.
• pre-treatment tests with varying parameters as shown in Table 4.- are performed by charging each time 10 new raw briquettes in an electric 11-liter muffle furnace. All these pretreatments are carried out between 20 and 450 ° C under a flow of 10 liters per minute of a gas mixture formed of N 2 , H 2 O and CO 2 . The temperature ramps are between 2 and 100 / min.
• the volume concentrations of H 2 O in the gas are between
• the volume concentrations of CO 2 in the gas are between 0.9 and 9.1%.
• the 10 briquettes are characterized by the compressive strength test.
• the entirety of the 10 pretreated briquettes is also analyzed to determine the weight gains relating to the hydration dm (H 2 O) / m and carbonation dm (CO 2) / m.
• the overall results are summarized in Table 3.-.
• the Shatter test scores were compared to the compressive strength on several raw briquette samples to establish the correlation between the test Shatter index and the compressive force.
• the raw briquettes tested included quicklime with a particle size ranging from 0 to 3 mm with different iron oxide contents, from 0 to 60% by weight and different lubricant contents, ranging from 0.125 to 0.5%. by weight, based on the total weight of the briquettes.
• the parameters of the briquetting process were also modified to ensure that the population for correlation was sufficiently wide.
• a compressive force greater than 144 kg is required, corresponding to 317.5 pounds for briquettes having a test Shatter number of less than 10%.

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