FR3053675A1 - TABLET-COMPOSITION COMPRISING VITAL CALCO-MAGNESIVE COMPOUNDS, PROCESS FOR OBTAINING SAME AND USE THEREOF - Google Patents

Abstract

Composition based on bright calco-magnesium compounds in the form of tablets, characterized in that said composition comprises quicklime in the form of ground particles at a concentration of at least 10% by weight and at most 100% by weight with respect to the weight of said composition, said tablet composition having a test Shatter number of less than 10% and its method of preparation and its use.

Description

Holder (s): S.A. LHOIST RESEARCH AND DEVELOPMENT.

Extension request (s)

Agent (s): GEVERS & ORES.

COMPOSITION IN THE FORM OF TABLETS COMPRISING LIVE CALCO-MAGNESIAN COMPOUNDS, PROCESS FOR OBTAINING SAME AND THEIR USE.

FR 3 053 675 - A1 (fi) Composition based on living calcium-magnesium compounds in the form of tablets, characterized in that the said composition comprises quicklime in the form of ground particles at a concentration of at least 10% by weight and at most 100% by weight relative to the weight of said composition, said composition in the form of tablets having a Shatter test index of less than 10% and its preparation process and its use.

i

The present invention relates to a composition in the form of tabs comprising at least one bright calcium magnesium compound, said composition having from 40% to 100% by weight of CaO + MgO equivalent, preferably 60% to 100% by weight of 'CaO + MgO equivalent, relative to the weight of said composition.

For the purposes of the present invention, the term “bright calcium magnesium compound” means a mineral solid material the chemical composition of which is mainly calcium oxide and / or magnesium oxide. The quick calco-magnesian compounds within the meaning of the present invention therefore include quicklime (calcium lime), quick magnesium lime, quicklime dolomitic lime or quick burnt dolomite, also called cooked dolomite. The living calcium-magnesium compounds contain impurities, namely, compounds such as 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 in reality appear in different phases. It also generally contains a few percent of residual CaCO ₃ or MgCO ₃ , called incuits, and a few percent of residual Ca (OH} ₂ or Mg (OH) ₂ , due to the partial hydration of the living products during cooling, handling and / or storage phases.

Quicklime is understood to mean a mineral solid, the chemical composition of which is mainly calcium oxide, CaO. Quicklime is commonly obtained by calcination of limestone, mainly consisting of CaCO ₃ . Quicklime contains impurities, namely, compounds such as magnesium oxide, MgO, ia silica, SiO ₂ or alumina, Al ₂ O ₃ , etc ..., up to a few for -hundreds. It is understood that these impurities are expressed in the aforementioned forms but may in reality appear in different phases. It also generally 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 calcium oxide CaO during the cooling phases, handling and / or storage.

According to the present invention, the term “briquette” is understood to mean a compact having an oblong shape, having a mass of approximately 5 to 100 g per briquette, inscribed in an ellipsoid of flattened or elongated revolution (in English oblate ellipsoid of revolution or proiate ellîpsoid of revolution). Typically, briquettes are in the form of a bar of soap or are qualified as “egg briquettes”.

By contrast, a distinction is made between tablets which are typically in the form of pellets, as produced by the “Titan” presses of the “Eurotab” company. By definition, tablets for industrial use are regular in shape, more particularly in the form of a cylinder of low height.

Such compositions are well known in the art, see for example the document WO2015007661. According to this document, compacts (namely briquettes or tablets) are described comprising particles of calcium-magnesium compound comprising at least 50% of bright calcium-magnesium compound.

According to this document, the mechanical resistance to fall is measured by means of a shatter test. The compacts described generally have a Shatter test index of less than 10%.

By the terms “Shatter test index” is meant the percentage by mass of fines less than 10 mm generated after 4 falls of 2 m from 10 kg of product. These fines are quantified by sieving through a 10 mm square mesh screen after 4 falls of 2 m.

A detailed analysis of the examples and counterexamples of this document indicates that raw tablets having mechanical resistance to falling were obtained using at least 50% of live products, and that these tablets also have resistance to aging in a humid atmosphere. On the other hand, when briquettes of living compounds are obtained using living compounds, the shatter test index representing the mechanical resistance remains high (between 13 and 15%) and it is necessary to carry out a fairly long heat treatment and typically above 1200 ° C if a test shatter index lower than

10%.

Document 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 possibly a lubricant. The briquettes disclosed in document US 5186742 are tested for their resistance to fall, a test which is not comparable to the test for measuring the Shatter index test and have a compressive strength between 150 and 300 pounds (pounds). , which corresponds to a Shatter test index well above 10%.

Calco-magnesian compounds are used in many industries, such as the steel industry, gas treatment, water and sludge treatment, agriculture, construction 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 size). In some industries, the pebble shape is nevertheless preferred.

This is the case, for example, in the steel industry, when adding calcium and magnesium compounds in oxygen converters or electric arc furnaces.

During the production of these pebbles and pieces, many fines are generated. These fines typically have a limited potential for use because they are difficult to transport and handle.

For several years, the objective, in a number of sectors, has been to transform compounds initially in powder form into compacts (briquettes or tablets) to facilitate and secure their transport, handling and use.

The chaufourniers always maintain a balance of materials between the calco-magnesian compounds in pebbles and the fines generated before and during its calcination as well as during the manipulations and subsequent operations. However, in some cases, an excess of fines is produced.

These fines can then be agglomerated to each other in the form of briquettes, tablets or the like, which not only gives the possibility of eliminating the excess fines but also of artificially increasing the production of calcium and magnesium compounds in pebbles. by adding these briquettes, tablets or the like to the pebbles.

The document by Barnett et al (Roll-press briquetting: Compacting fines to reduce waste-handlîng costs, powder and buik engineering, vol.24, n ° 10, October 2010, 1-6) describes a process for manufacturing raw briquettes from lime. However, this document is silent as to the production conditions as well as the mechanical properties of the briquettes obtained. Briquettes based on excess fines, tablets or the like generally have a lower mechanical resistance than the pebble calcium and magnesium compounds. They also have a resistance to aging during storage or handling which is much lower than that of the calcium and magnesium compounds in pebbles.

This explains the fact that, in practice, the briquetting or tabletting of the fines of calcium and magnesium compounds is not widely used at present. In particular, given the low quality of the briquettes formed by this type of process, it is estimated that briquetting provides a yield of less than 50%, due to the presence of a very large number of unusable briquettes at the outlet of this type of process, which requires a recycling step.

Lubricants and binders are additives often used in agglomeration processes in the form of briquettes, tablets or the like.

Lubricants can be of two types, internal or external. The internal lubricants are intimately mixed with the materials to be briquetted. They promote on the one hand the flowability of the mixture during the feeding of the briquetting machine and on the other hand the rearrangement of particles in the mixture during compression. External lubricants are applied to the surfaces of the briquetting machine rollers and mainly help with mold release. In both cases, they reduce friction on the surface and therefore wear. The lubricants can be liquids such as mineral oils, silicones, etc. or solids such as the pillowcase, graphite, paraffins, stearates, etc. In the case of compositions based on living calcium-magnesium compounds, stearates are preferred and more particularly calcium stearate or magnesium stearate.

Binders are substances which have 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 or animal origin (celluloses, starches, gums, alginates, pectin, glues, ...), of synthetic origin (polymers, waxes , ...). In many cases, they are used and implemented with water which activates their agglomeration properties.

Over the years, several of these additives have been used to increase the strength and durability of briquettes, tablets or the like of calcium and magnesium compounds, for example calcium stearate or paper fibers, (see for example US5186742 ), but without this leading to sufficient improvements. In addition, in many cases, the use of additives currently used for other shaped industrial products is limited, as is the case in particular for the manufacture of briquettes or tablets of calcium-magnesium compounds, either because calcium-magnesium compounds react violently with water, either because of a potentially negative effect of these additives on the end use of briquettes of calcium-magnesium compounds.

US Patent 7,105,114 claims a briquetting process for slaked lime fines (dolomitic) using 0.5 to 5% by weight of binders containing pseudoplastic carbon chains which clearly improve the mechanical properties of briquettes and which do not don't have the disadvantages mentioned earlier. However, this process only leads to obtaining briquettes, half of which already break after a fall from a height between 0.9 and 1.8 m (a fall from a height between 3 and 6 feet ), which represents a totally insufficient mechanical resistance.

Briquettes, tablets or the like based on calcium-magnesium compounds can also be consolidated by means of a very high temperature heat treatment which leads to the sintering of said briquettes, tablets or the like. For example, in the case of cooked dolomite briquettes, it is known that a heat treatment of one to several hours at a temperature above 1200 ° C, and even ideally above 1300 ° C, leads to an increase in properties. mechanical of said briquettes. This heat treatment at very high temperature nevertheless leads to a chronological evolution of the texture characteristics of the aforementioned briquettes, it leads in particular to a sharp reduction in both the specific surface and the porous volume. Ceia is also accompanied by a sharp reduction in water reactivity, as explained in standard EN 459-2: 2010 E, which has many drawbacks for certain applications.

Consequently, there is a real need to develop tablets of calcium-magnesium compound which can be distinguished from the products such as the tablets which we know today by a very marked improvement in their resistance to falling and also, preferably, by a better resistance to aging in a humid atmosphere, while preserving the intrinsic properties (structural characteristics) of the calcium and magnesium compound before shaping, in particular its specific surface and / or its pore volume, but above all its reactivity to the water.

The object of the invention is to overcome the drawbacks of the state of the art by providing a composition in the form of tablets as mentioned at the start, characterized in that said quick calcium-magnesium compound comprises quicklime in the form of particles. ground to a concentration of at least 10% by weight and at most 100% by weight relative to the total weight of said composition, said composition in the form of tablets having a Shatter test index of less than 10%.

Quicklime in the form of crushed particles is called lime fines from the grinding of quicklime and therefore corresponding to a dimensional reduction of the lime in rock. Grinding can be

Ί indifferently carried out at the start of the all-out at the exit of the oven (taken out of the oven) and / or at the exit of the silo (taken out of the silo) or else at the start of the general-purpose at the exit of the oven and / or at the exit of previously screened silo. The grinding can be carried out using different types of grinders (hammer mill, impact mill ...), either in open circuit (no recirculation loop), or in closed circuit (recirculation loop).

Quicklime in the form of crushed particles is distinguished from screening lime. Lime fines from the lime screening are called screening lime. The particle size is defined by the size of the screen. For example, a lime screened at 3 mm leads to the production of a screening lime 0-3 mm. Thus the screening on the all coming out of the oven leads to a "primary" screening lime. The screening on the all coming from the storage silo leads to a "secondary" screening lime.

For the purposes of the present invention, quicklime in the form of crushed particles is understood to mean lime fines generally containing more very fine than the screening lime fines. Thus, if we consider for example 0-3mm fines, quicklime fines in the form of crushed particles will typically contain at least 30% by weight, most often at least 40% by weight, even at least 50% by weight of very fine less than 100 μm, while the screening lime fines will often contain at most 25% by weight, or even at most 15% by weight of very fine less than 100 μm.

The chemical composition of grinding lime fines is generally more homogeneous than that of screening lime fines. Thus, if we consider for example a lime in rock 10-50 mm cooked with a fuel which generates ashes such as coal (lignite, coal, anthracite ...) or even petroleum coke, and that the 0 ~ 3mm fines from the grinding or screening of this lime in rock are characterized, it will be seen that the 0200 μm fraction of the 0-3 mm fines from the grinding has a chemistry similar to that of the 200 μm ~ 3 mm fraction, while the 0-200 µm fraction of 0-3 mm fines from screening contains more impurities than that of the 200 µm-3 mm fraction.

Grinding lime fines are generally more reactive than screening lime fines. Thus, for quick-cooked quicklime, if we measure the water reactivity (standard EN459) of fines 0-3 mm, the grinding fines typically have t ₆₀ values less than 5 min where the primary screening fines often have t ₆₀ values greater than 5 min.

The term "tablets" denotes, as indicated above, within the meaning of the present invention, shaped objects with an industrial compacting or compression technology of fines by the combined action of two punches (one in the high position , the other in the low position} on said fines placed in a cavity. The term "tablets" therefore includes all of the shaped objects belonging to the family of tablets and lozenges and more generally, objects with various global shapes three-dimensional like, for example, substantially cylindrical, octagonal, cubic or rectangular shapes with a slight asymmetry between the lower part (bottom) and the upper part (top) of said shaped objects. Said technology generally uses rotary presses or presses hydraulic.

This type of industrial compacting (tabletting) process offers a productivity greater than or equal to 0.1 t / h (tonnes per hour), preferably greater than or equal to 0.5 t / h, advantageously greater than or equal to it / h by compacting device (press). Industrial tablets produced in such a process, such as for example by means of a hydraulic press or a rotary press, such as the Titan rotary press from Eurotab, have a surface differential between their lower part and their upper part. Consequently, the compact industrial product of the present invention in the form of tablets will have an asymmetrical shape, which will make it possible inter alia to obtain a high level of productivity making it possible to achieve an industrial application but also an industrial acceptance of the tablets according to the present invention. Indeed, the asymmetrical shape also leads to a reduction in defects in finished shelves.

More particularly, in the case of a tablet having a generally cylindrical three-dimensional shape, this asymmetry will lead to a tablet which can be seen as a truncated cone, if we accentuate the phenomena.

Advantageously, the difference between the surface of the upper part (surface of the upper part) and that of the lower part (surface of the lower part) of the tablet is greater than or equal to 0.5%, preferably greater than or equal to 1%, and less than or equal to 10%, preferably less than or equal to 5%, in particular less than or equal to 3%, in particular around 2%.

The difference is a relative difference calculated by decreasing the surface (upper) of the upper part by the surface (lower) of the lower part and dividing the result by the middle section of the shelf according to [(surface of the upper part - surface of the lower part) / middle section of the tablet], The upper part (upper part) has been designated herein as being larger than the lower part (lower part) of the tablet. The median diameter corresponds to the diameter measured in the middle of the height of the shelf. The surface of the upper part is that which faces upwards during manufacture, when the tablet is in the die in a representative embodiment, while the surface of the lower part is that which faces downwards. Of course, depending on the manufacturing process of the tablets and the hardware, the opposite is also possible. Similarly, when resting on a surface such as the floor or a table, the surface of the top may also be oriented downward or in any other orientation.

As can be seen, the tablets according to the present invention have a particularly advantageous Shatter test index, of less than 10%, thereby conferring on the tablets sufficient mechanical strength to allow industrial use in most processes using the compounds. calco-magnésîens in the form of pebbles, alone or in mixtures with pebbles.

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It has indeed appeared, surprisingly, without it being possible at present to explain the reasons, that the addition of quicklime in the form of ground particles at a concentration of at least 10% by weight relative to the weight composition! obtained a mechanical resistance to fall greatly improved. A content as restricted as 10% by weight allows a significant improvement in your mechanical strength to be obtained, although the content of ground particles can go up to 100% by weight.

Within the meaning of the present invention, said vivid calcomagnesium compound comprises one or more vivid calco-magnesian compound (s). The quick calco-magnesian compound is chosen from the group consisting of quicklime (calcium), magnesian lime, quicklime, calcined dolomite and their mixtures, preferably in the form of particles, such as particles. from screening, grinding, filter dust and their mixing. Said lively caio-magnesian compound can therefore be considered as a calco-magnesian component of the composition in the form of tablets, which may contain other compounds. Within the meaning of the present invention, the calcium-magnesium compound is present in the composition at a concentration of at least 50% by weight, preferably at least 60% by weight, more preferably at least 70% by weight , more particularly at least 80% by weight, your own at least 90% by weight relative to the total weight of said composition.

By the terms "Shatter test index" is meant within the meaning of the present invention the mass percentage of fines less than 10 mm generated after 4 falls of 2 m from 10 kg of product (tablets). are quantified by sieving through a 10 mm square screen at the end of the 4 2 m falls.

The% by weight of CaO + MgO equivalent is determined by X-ray fluorescence spectrometry (XRF) as described in standard EN 15309. Chemical analysis, semi-quantitative, by XRF to determine the relative mass concentration of elements whose atomic mass is between 16 (oxygen) and 228 (uranium), is produced from samples ground at 80pm and shaped into pellets. The samples are introduced into a PANalytical / MagiX PRO PW2540 apparatus, operating in wavelength dispersion. The measurement is carried out with a power of 50kV and 80 mA, with a Duplex detector.

The results of the analysis give the calcium and cagnesium content and these measurements are reported by weight of CaO and MgO equivalent.,

Advantageously, in the composition in the form of plates according to the present invention, said vivid calco-magnesian compound is soft cooked or medium cooked, preferably soft cooked.

Quick calc-magnesian compounds, such as quicklime, are industrially produced by baking natural limestones in different types of ovens such as straight ovens (regenerative double-flow ovens, annular ovens, standard straight ovens ...) or even rotary ovens. The quality of the catco-magnesian compound, such as, for example, quicklime, in particular its reactivity to water, and the consistency of this quality, are partly linked to the type of oven used, to the conditions of use of the oven, the nature of the limestone from which the living calcium-magnesium compound is derived in itself, or even the nature and quantity of the fuel used. Thus, it is theoretically possible to produce a whole range of quick calcomagnesian compounds, such as for example quicklime with water reactivities allying the most explosive to the slowest.

In general, obtaining a quicklime by gentle cooking (900-1000 ° C) makes it possible to obtain a rather reactive lime while obtaining a less reactive lime requires an overcooking at a higher temperature (1200-1400 ° C). Overcaking often leads to producing quicklime of less stable quality in terms of water reactivity because the calcination operation is carried out in a thermal zone where the textural evolution of quicklime is fairly sensitive. This overcooked quicklime is also more expensive to produce than a softer quicklime because it requires the use of higher temperatures but also because, except when using dedicated ovens, the production of this quicklime cooked leads to production intercampagnes to alternate with the production of soft quicklime which are more commonly used, which is not without posing problems of stabilization of the calcination conditions and therefore problems of stabilization of the quality.

The quicklime obtained by gentle cooking generally has 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 ISO 9277: 2010E standard greater than 1 m ² / g, while overcooked quicklime generally has surfaces well below 1 m ² / g.

In the context of this invention, the reactivity of quicklime is measured using the water reactivity test of European standard EN 459-2: 2010 E. Thus, 150g of quicklime are added with stirring in a Dewar cylindrical 1.7 dm ³ capacity containing 600 cm ³ of permuted water at 20 ° C. Quicklime is brought in the form of fines ranging in size from 0 to 1 mm. The stirring at 250 revolutions per minute is carried out using 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. We can deduce from this curve the value t ₆ o which is the time necessary to reach 60 ° C. The reactivity of cooked dolomite, also called living dolomite, is measured using this same reactivity test. In this case, 120 g of cooked dolomite are added with stirring in a cylindrical Dewar of 1.7 dm ³ of capacity containing 400 cm ³ of water permuted at 40 ° C. The cooked dolomite is brought in the form of fines of size between 0 and 1 mm. The stirring at 250 revolutions per minute is carried out using 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. We can deduce from this curve the value t ₇₀ which is the time necessary to reach 70 “C.

The composition according to the present invention advantageously comprises a calco-magnesian compound with gentle or medium cooking, preferably gentle which is therefore necessarily relatively reactive, thus providing reactive tablets.

According to the present invention, a lively caico-magnesian compound with gentle or medium cooking, preferably gentle, is characterized by a value t ₆ o less than 10 min, preferably 8 min, preferentially 6 min, and still preferentially 4 min when the compound quick caico-magnesian is quick lime and with a value of t; o less than 10 min, preferably 8 min, preferably 6 min, and even more preferably 4 min when the quick caico-magnesian compound is a cooked dolomite.

In an advantageous embodiment of the composition according to the present invention, said quicklime in the form of crushed particles is quicklime quick cooking or medium cooking, preferably soft cooking.

Advantageously, said quicklime in the form of crushed particles according to the present invention has a high reactivity to water characterized by a value of tgo of less than 10 min, preferably of less than 8 min, preferably of less than 6 min and even more preferably of less than 4 min.

In a particular embodiment, said shelves have a highest dimension of at most 50 mm, preferably at most 40 mm, more preferably at most 30 mm.

This means that the tablets of the composition in the form of tablets pass through a square mesh screen with a side of 50 mm, preferably 40 mm, and in particular 30 mm, respectively.

Preferably, said tablets have a highest dimension of at least 10 mm, preferably at least 15 mm, more preferably at least 20 mm.

By the terms a most elevated dimension is meant a characteristic dimension of the tablet which is the largest, namely the diameter, the length, the width, the thickness, ...

In one embodiment of the composition in the form of tablets according to the present invention, said tablets are raw tablets and have a BET specific surface greater than or equal to 1 m ² / g, preferably greater than or equal to 1.2 m ² / g, more preferably greater than or equal to 1.4 m ² / g.

In another embodiment of the composition in the form of tablets according to the present invention, said tablets are cooked tablets and have a BET specific surface greater than or equal to 0.4 m ² / g, preferably greater than or equal to 0, 6 m ² / g, more preferably greater than or equal to 0.8 m ² / g.

By BET specific surface is understood within the meaning of the present invention, the specific surface 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 such as described in standard ISO 9277: 2010E and expressed in m ² / g.

In another embodiment of the composition based on living calcium-magnesium compounds in the form of tablets according to the invention, said tablets are raw tablets or cooked tablets, and have a porosity greater than or equal to 30%, preferably greater than or equal to 32%, more preferably greater than or equal to 34%.

Porosity is understood to mean, within the meaning of the present invention, the total pore volume of mercury determined by porosimetry by mercury intrusion according to part 1 of ISO 15901-1: 2005E which consists in dividing the difference between the skeletal density, measured at 30,000 psia, and the apparent density, measured at 0.51 psia, by the skeletal density.

Alternatively, the porosity measurement can also be measured by petroleum intrusion porosimetry. The density and porosity of the briquettes are determined by intrusion of kerosene, according to a measurement protocol based on standard EN ISO 5017. The measurements are carried out on 5 briquettes.

The density of the briquettes is calculated according to the formula ml / (m3 - m2) x Dp and the porosity in percent according to the formula (m3 - ml) / (m3 - m2) x 100.

ml is the mass of these 5 briquettes, m2 is the mass of these 5 briquettes immersed in petroleum and rrs3 is the mass of these 5 “wet” briquettes, that is to say impregnated with petroleum. Dp is the density of oil.

In a particular embodiment according to the present invention, the composition is in the form of raw tablets and the tablets have a high reactivity to water defined by a teo value of less than 10 min, preferably less than 8 min, preferably less than 6 min, and still preferably less than 4 min.

In another embodiment according to the present invention, the composition is in the form of cooked tablets and the tablets have a high water reactivity defined by a value of t _{60 of} less than 10 min, preferably less than 8 min, preferably less 6 min, and still preferably less than 4 min.

More particularly, according to the present invention, when the composition is in the form of raw tablets and the calcomagnesian compound is mainly quicklime, said composition has a reactivity value t ₆ o of less than 10 min, preferably less than 8 min , preferably less than 6 min and even more preferably less than 4 min. If fluxes are present or for example an iron oxide, to take into account the content of fluxes, such as for example an iron-based compound in the composition, a little more than 150 g of said composition is added in the test for reactivity to have the equivalent of 150g of quicklime added,

Advantageously, according to the present invention, when the composition is in the form of raw tablets and the calcomagnesian compound is mainly cooked dolomite, said composition has a reactivity value t _{70 of} less than 10 min, preferably less than 8 min, of preferably less than 6 min and even more preferably less than 4 min. If fluxes are present or, for example, an iron oxide, to take account of the flux content such as, for example, of iron-based compound in the composition, slightly more than 120 g of said composition are added in the reactivity test for have the equivalent of 120g of cooked dolomite added.

More particularly, according to the present invention, when the composition is in the form of cooked tablets and the calcomagnesian compound is mainly quicklime, said composition has a t ₆₀ value of less than 10 min, preferably less than 8 min, preferably less than 6 min and even more preferably less than 4 min. If fluxes are present or, for example, an iron oxide, to take into account the content of fluxes, such as for example of iron-based compound in the composition, a little more than 150 g of said composition is added in the reactivity test. to have the equivalent of 150g of "free" quicklime added. By "free" quicklime is meant quicklime which has not reacted with iron oxide to lead to calcium ferrites CaFe ₂ O ₄ and / or Ca ₂ Fe2O ₅ .

In an advantageous embodiment of the composition according to the present invention, said quicklime in the form of ground particles is present at a concentration of at least 15% by weight, preferably at least 20% and more preferably of at least 30%, in particular at least 40% by weight relative to the total weight of said composition.

Advantageously, in the composition according to the present invention, said quicklime in the form of ground particles is present at a concentration of at most 90% by weight, preferably at most 80%, preferably at most 70%, more preferably at most 50% by weight relative to the total weight of said composition.

In a preferred form of the present invention, the composition based on living calcium-magnesium compounds in the form of tablets further comprises a binder or a lubricant, preferably in the form of a powder or of concentrated aqueous suspension, more particularly chosen from the group consisting of binders of mineral origin such as cements, clays, silicates, binders of plant or animal origin, such as celluloses, starches, gums, alginates, fa pectin, glues, binders 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, stearate magnesium, and mixtures thereof, preferably calcium stearate and / or magnesium stearate, in a content of between 0.05 and 0.50% by weight, preferably between 0.05 and 0.30% by weight , so e more preferred between 0.10 and 0.20% by weight relative to the total weight of said composition.

More particularly, according to the invention, said tablets have an average weight per tablet of at least 5 g, preferably at least 10 g, more preferably at least 12 g, and in particular at least 15 g.

Advantageously, according to the invention, said tablets have an average weight per tablet 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.

In another preferred embodiment according to the present invention, said tabs 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 .

In a particular embodiment according to the present invention, said bright calco-magnesian compound further comprises fine particles of calco-magnesian compound chosen from fine particles rejected in the screening of the production of the rollers of said bright calcomagnesian compound, calcium dust filter magnesians and their mixture, at a concentration of at least 10% by weight and at most 90% by weight relative to the total weight of said composition.

Advantageously, in the composition in the form of tablets according to the present invention, said fine particles rejected during the screening of production of pebbles of calcium-magnesium compound are fine particles of living dolomite.

In a preferred variant, said fine particles rejected in the screening for the production of pebbles of calcium-magnesium compound are fine particles of quicklime.

Advantageously, in the composition of tablets according to the present invention, said fine particles rejected by screening are fine particles rejected by screening at 7 mm during said production of rollers of said caico-magnesian compound.

More particularly, in your composition of tablets according to the present invention, said fine particles rejected by screening are fine particles rejected by screening at 5 mm during said production of rollers of said caico-magnesian compound.

Even more advantageously, said fine particles rejected during screening are fine particles rejected during screening at 3 mm during said production of rollers of said caico-magnesian compound.

In a particular embodiment of the present invention, said fine particles rejected by screening are a mixture of fine particles rejected by screening at 7 mm during said production of rollers of said caico-magnesian compound and / or fine particles rejected by screening at 5 mm during said production of rollers of said caico-magnesium compound and / or of fine particles rejected by screening at 3 mm during production of rollers of said caico-magnesium compound.

The fine particles rejected during screening therefore advantageously have a dioo particle size less than or equal to 7 mm, in particular less than or equal to 5 mm, more particularly less than or equal to 3 mm; a d ₉₀ less than or equal to 3 mm and a d ₅₀ less than or equal to 1 mm.

For the purposes of the present invention, unless otherwise specified, the notation d _x represents a diameter expressed in pm, measured by laser granulometry in methanol without sonication, relative to which x% by volume of the particles measured are less than or equal.

In another particular embodiment according to the present invention, said composition in the form of tablets further comprises one or more compound (s) based on iron at a concentration of at least 3% by weight and at most 60% by weight expressed in Fe ₂ O ₃ equivalent relative to the total weight of said composition.

In a preferred embodiment of the present invention, at least one of the iron-based compound (s) is a compound based on iron oxide, preferably active iron, present at a concentration of at least 3% by weight and at most 60% by weight expressed in Fe ₂ O ₃ equivalent relative to the total weight of said composition.

Advantageously, said composition in the form of tablets comprises at least 50% by weight of calcium expressed in the form of CaO equivalent, relative to the total weight of said composition.

In particular, said composition in the form of tablets comprises a Ca / Mg molar ratio greater than or equal to 1, preferably greater than or equal to 2, more preferably greater than or equal to 3.

In a very particular embodiment of the present invention, in which the green tablets contain an iron-based compound which is a compound based on iron oxide, said green tablets can advantageously be subjected to a heat treatment at a temperature between 700 ° C and 1200 ° C, preferably between 900 ° C, or even 1050 ° C and 1200 ° C, particularly around 1100 ° C, for a predetermined period, for example between 5 and 20 minutes, preferably longer or equal to 7 minutes and less than or equal to 15 minutes, with the formation and obtaining of cooked tablets in which the compound based on iron oxide is converted, at least partially, into calcium ferrites.

Within the meaning of the present invention, said an iron-based compound may be formed of one or more iron-based compounds, totaling together in the composition a content of 3 to 60% by weight relative to the total weight of said composition.

In a particular embodiment, the composition according to the present invention is 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.

More particularly, said tablets have a slightly asymmetrical three-dimensional shape, preferably substantially frustoconical, in which the difference between the surface of the upper part and that of the lower part of the tablet is greater than or equal to 0.5%, preferably greater or equal to 1%, and less than or equal to 10%, preferably less than or equal to 5%, in particular less than or equal to 3%, in particular around 2%.

In an advantageous variant of the present invention, the composition in the form of tablets consists of raw tablets having a Shatter test index of less than 8%, preferably less than 6%, and more preferably less than 5%, in particular less than 4%.

In another advantageous variant of the present invention, the composition in the form of tablets consists of cooked tablets having a Shatter test index of less than 6%, preferably less than 4%, and more preferably less than 3%, particular less than 2%, or even less than 1.5%.

Other embodiments of the composition in the form of tablets according to the invention are indicated in the appended claims.

The invention also relates to a process for manufacturing a composition in the form of tablets.

The method is characterized in that it comprises the following steps:

a) supplied with a homogeneous pulverulent mixture comprising at least 40% by weight of CaO + MgO equivalent relative to the weight of said homogeneous pulverulent mixture, and comprising at least one bright calco-magnesium compound, said at least one calco-magnesium compound quicklime comprising quicklime in the form of ground particles at a concentration of at least 10% by weight and at most 100% by weight relative to the total weight of said homogeneous pulverulent mixture,

b) feeding of said homogeneous pulverulent mixture in a confinement space between two punches having a section of between 1 and 40 cm ² , advantageously between 1 and 20 cm ² , preferably between 1 and 10 cm ² , in particular between 2 and 10 cm ² ,

c) compacting said homogeneous mixture to form a product in the form of tablets of a three-dimensional shape, by applying a compaction pressure of between 200 MPa and 800 MPa, preferably between 250 MPa and 600 MPa, more preferably between 300 and 500 MPa, and even more preferably between 350 and 500 MPa,

d) release of the compaction pressure and

e) ejection of said product in the form of tablets from said confinement space.

In a particular form of the invention, said pulverulent mixture comprises at most 100% by weight, preferably at most 90% by weight, preferably, at most 88%, in certain embodiments, at most 80% by weight , more preferably, at most 60% by weight of CaO + MgO equivalent relative to the weight of said composition.

Optionally, in the process according to the present invention, step a) is carried out in the presence of a binder or a lubricant, preferably in the form of a powder or of concentrated aqueous suspension, more particularly chosen from the group consisting of binders of mineral origin such as cements, clays, silicates, binders of plant or animal origin, such as celluloses, starches, gums, alginates, pectin, glues, binders of origin synthetic, 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 their mixtures, preferably calcium stearate and / or magnesium stearate, in 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 per ra weight of the total weight of said tablets.

Advantageously, the method according to the present invention further comprises a heat treatment of said collected raw tablets, at a temperature between 700 ° C and 1200 ° C, preferably around 900 ° C for a predetermined period between 5 and 20 minutes , preferably greater than or equal to 7 minutes and less than or equal to 15 minutes, with the formation and obtaining of cooked tablets.

Preferably, (edict homogeneous mixture brought into the process according to the invention comprises a kcal-magnesian compound with gentle or medium cooking, preferably with gentle cooking.

Advantageously, said quicklime in the form of crushed particles, of said homogeneous mixture brought into the process according to the invention, is quicklime with soft cooking or with medium cooking, preferably with soft cooking.

Advantageously, said quick calcium-magnesium compound is quicklime.

In another advantageous embodiment, said quicklime in the form of crushed particles, of said homogeneous mixture brought into the process according to the invention, exhibits a high water reactivity characterized by a teo value of less than 10 min, preferably less 8 min, preferably less than 6 min and more preferably less than 4 min.

In yet another advantageous embodiment, said quicklime in the form of crushed particles, of said homogeneous mixture brought into the process according to the invention, is obtained by grinding from quicklime in rock whose size is greater than 3 mm, preferably greater than 5 mm, preferably greater than 7 mm, and more preferably greater than 10 mm, and less than 120 mm, preferably 100 mm, preferentially less than 80 mm, and still preferentially less than 60 mm.

In a preferred embodiment, said at least one quick calcomagnesium compound comprises quicklime in the form of ground particles at a concentration of at least 15% by weight, in particular at least 20% by weight, more preferably d '' at least 30% by weight, particularly preferably at least 40% by weight relative to the total weight of said homogeneous pulverulent mixture.

In another preferred embodiment, the said homogeneous mixture based on living calco-magnesian compounds brought into the process according to the invention comprises quicklime in the form of ground particles at a concentration of at most 90% by weight, in particular at most 80% by weight, more preferably at most 70% by weight, particularly preferably at most 50% by weight relative to the total weight of said homogeneous pulverulent mixture.

In a particular embodiment of the present invention, said live caico-magnesian compound further comprises fine particles of caico-magnesian compound chosen from fine particles rejected in the screening of the production of the rollers of said live caicomagnesium compound, filter magnesians and their mixture, at a concentration of at least 10% by weight and at most 90% by weight relative to the total weight of said homogeneous pulverulent mixture.

Advantageously, said fine particles rejected in the screening for the production of pebbles of caico-magnesian compound are fine particles of living dolomite.

In a preferred variant, said fine particles rejected in the screening for the production of pebbles of caico-magnesian compound are fine particles of quicklime.

Advantageously, said fine particles rejected during screening are fine particles rejected during screening at 7 mm during said production of rollers of said caico-magnesian compound.

More particularly, said fine particles rejected during screening are fine particles rejected during screening at 5 mm during said production of rollers of said caico-magnesian compound.

Even more advantageously, said fine particles rejected during screening are fine particles rejected during screening at 3 mm during said production of rollers of said caico-magnesian compound.

In a particular embodiment of the present invention, said fine particles rejected by screening are a mixture of fine particles rejected by screening at 7 mm during said production of rollers of said caico-magnesian compound and / or fine particles rejected by screening at 5 mm during said production of rollers of said caico-magnesium compound and / or of fine particles rejected by screening at 3 mm during production of rollers of said calco-magnesian compound.

The fine particles rejected during screening therefore advantageously have a particle size less than or equal to 7 mm, in particular less than or equal to 5 mm, more particularly less than or equal to 3 mm; a d ₉₀ less than or equal to 3 mm and a d ₅₀ less than or equal to 1 mm.

Within the meaning of the present invention, unless otherwise specified, the notation d _x represents a diameter expressed in pm, measured by laser granulometry in ie methanol without sonication, relative to which x% by volume of the particles measured are less than or cheers.

In another particular embodiment according to the present invention, said homogeneous pulverulent mixture further comprises one or more compound (s) based on iron, at a concentration of at least 3% by weight and at most 60% by weight expressed in Fe ₂ O ₃ equivalent relative to the weight of said mixture.

In a preferred embodiment of the present invention, at least one of the iron-based compound (s) is an iron oxide-based compound present in a concentration of at least 3% by weight and at most 60 % by weight expressed in Fe ₂ O ₃ equivalent relative to the weight of said homogeneous mixture, preferably active iron.

Advantageously, said homogeneous mixture based on living caico-magnesian compounds comprises at least 50% by weight of calcium expressed in the form of CaO equivalent, relative to the total weight of said mixture.

In particular, said homogeneous mixture based on living calco-magnesian compounds comprises a Ca / Mg ratio greater than or equal to 1, preferably greater than or equal to 2, more preferably greater than or equal to 3.

In a very particular embodiment of the present invention, in which the raw tablets contain an iron-based compound which is a compound based on iron oxide, the method further comprises a heat treatment of said collected raw tablets, to a temperature between 700 ° C and 1200 ° C, preferably between 900 ° C, or even 1050 ° C and 1200 ° C, more particularly around HOO'C, for example for a predetermined period of between 5 and 20 minutes, preferably greater than or equal to 7 minutes and less than or equal to 15 minutes, more particularly greater than or equal to 8 minutes and less than or equal to 13 minutes with the production of cooked tablets in which the compound based on iron oxide is converted , at least partially, of calcium ferrites.

In a preferred embodiment of the invention, the method further comprises, before said supply of a homogeneous pulverulent mixture,

a) supplying a mixer with said at least one living calcium-magnesium compound and

b) a mixture for a predetermined period, sufficient to obtain a homogeneous pulverulent mixture of said at least one bright calco-magnesian compound.

Other embodiments of the process according to the invention are indicated in the appended claims.

The present invention also relates to a process for manufacturing a composite material comprising several successive layers in order to form a multilayer structure in which at least one layer is formed with said product in the form of tablets of the composition by the process of the present invention and further comprising an additional step of compacting said at least one layer of said compact product in the form of tablets and another compact layer before said ejection step.

The present invention also relates to the use of raw or cooked tablets according to the present invention, in the steel industry, in particular in the manufacture of steel in elementary oxygen converters, in electric arc furnaces, or else in the secondary metallurgy, in the treatment of flue gases, in water treatment, in sludge and wastewater treatment, in agriculture, in the building industry and in public works, such as for stabilization soils.

A subject of the invention is also the use of a composition in the form of raw tablets or in the form of cooked tablets according to the present invention in the steel industry, in particular in oxygen converters or else in electric arc furnaces.

More particularly, the raw or cooked tablets according to the present invention are used in oxygen converters or in electric arc furnaces, in admixture with tablets of bright calcomagnesian compounds or with rollers of bright calco-magnesian compounds.

In fact, during the first minutes of the refining process, there is not enough slag available in the reaction tank for the dephosphorization reaction to effectively start in the processes of the prior art. The use of the composition according to the present invention, therefore doped with fluxes, turns out to melt faster than lime into rocks, and helps to form a liquid slag earlier at the start of the process, in comparison with the conventional processes, due to 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 slag components with high melting point such as calcium silicates which usually form during the above-mentioned prior art process.

A subject of the invention is also the use of a composition in the form of raw tablets or in the form of cooked tablets in a process for refining molten metal, in particular for dephosphorization of molten metal and / or desulfurization of molten metal and / or reduction of loss of refined metal in the slag.

The use of a composition in the form of raw tablets or in the form of cooked tablets according to the present invention in a process for refining molten metal comprises at least one step of introducing hot metal and optionally iron-based waste into a tank, at least one step of introducing a composition in the form of raw tablets or in the form of cooked tablets according to the present invention, preferably in the form of cooked tablets according to the present invention, at least one step of blowing oxygen in said tank, at least one step of forming a slag with said composition of tablets in said tank, at least one step of obtaining refined metal having a reduced content of phosphorus and / or sulfur compounds and / or a content increased in refined metal from the hot metal by dephosphoration and / or desulfurization, and at least one step of discharging said refined metal having a reduced content of phosphorus and / or sulfur components res and / or augmented in refined metal.

The use according to the present invention further comprises a step of adding quicklime, preferably quicklime in rock or compacts of quicklime, in particular tablets or quicklime tablets.

Other forms of use according to the invention are indicated in the appended claims.

Other characteristics, details and advantages of the invention will emerge from the description given below, without implied limitation and with reference to the examples.

The present invention relates to a method for tabulating a composition comprising at least one quick caico-magnesian compound comprising quicklime in the form of ground particles at a concentration of at least 10% by weight and at most 100% by weight relative to the total weight of said composition.

The tabetting process according to the invention comprises supplying a homogeneous pulverulent mixture comprising at least one living caico-magnesian compound.

Depending on the intended use of the tablets, it is possible to add additives, for example, in the case of use in the steel industry, of fluxes, such as for example B2O3, NaC> 3, calcium aluminate, calcium silicate, a calcium ferrite such as Ca ₂ Fe ₂ O ₅ or CaFe ₂ O ₄ , Al metal, Mg metal, Fe metal, Mn metal, Mo metai, Zn metai, Cu metal, Si elementary, CaF ₂ , C , Cac ₂ , alloys such as CaSi, CaMg, CaFe, FeMn, FeSi, FeSiMn, FeMo; TiO ₂ , a molybdenum-based oxide, a copper-based oxide, a zinc-based oxide, a molybdenum-based hydroxide, a copper-based hydroxide, a zinc-based hydroxide and their mixture.

Preferably, when iron oxide is present in the raw tablets, this is present in the form of an iron-based compound present in a content of at least 3%, preferably at least 12%, more preferably at least 20%, preferably at least 30%, more preferably at least 35% by weight of Fe ₂ O ₃ equivalent relative to the weight of said composition, said iron-based compound having a very fine particle size distribution characterized by a median size d _{50 of} less than 100 μm, preferably 50 μm as well as a size of d _{90 of} less than 200 μm, preferably of less than 150 μm, preferably of less than 130 μm, more preferably of less than 100 μm.

By the terms an iron-based compound is meant, for example, an iron-based compound, preferably based on iron oxide, characterized by a median size d _{50 of} less than 100 μm, preferably 50 μm as well as a size d ₉₀ less than 200 µm, preferably less than 150 µm, preferably less than 130 µm, more preferably less than 100 µm. We can then qualify this active iron oxide of 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 this iron oxide present in the peripheral layer of the grains of the iron-based compound, this peripheral layer being defined by a thickness of 3 μm. This defines a volume fraction of iron oxide on the surface of the iron oxide particles, which can react to be converted to ferrite during heat treatment or directly in situ in the converter.

The particle size distribution of the iron-based compound in the tablet-like composition is determined by scanning electron microscopy and X-mapping, coupled with image analysis.

The measurement is based on the property of the particles of the iron compound to emit, when subjected to high energy radiation (for example, a high intensity electron beam), energy X radiation. specific (6.398 keV). The detection of this radiation, coupled with exact knowledge of the position of the electron beam for each point observed, makes it possible to specifically map the particles of the iron-based compound.

Each particle identified is then characterized by its particle diameter with equivalent surface (X _a J, as defined in standard ISO 13322-1. The particles are then grouped by particle size fraction of particle size.

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 μm. For each particle size fraction and therefore for each particle size, we can therefore calculate the fraction of iron in the peripheral layer by the formula:

^ Fifth tif _ac / particu! E ⁼ fVJf-Vint) / ^ ext where V _Exi is the particle's volume based iron compound and V _int ΐθ volume in the heart of the particle more than 3 microns from the surface, that is to say the volume corresponding to a spherical particle having a reduced radius of 3 μm.

As the particles are considered to be perfectly spherical, the following formula is obtained for particles whose diameter is greater than 6 μm:

% ^ teacti // part £ cu £ e> 6pjn [C ^ ext) fôext 6) l / C ^ ext) ³ where D _exi is the diameter of the particle expressed in pm, or the size of the particle in the sense of laser particle size.

The following formula is obtained for particles whose diameter is less than 6 μm:

⁰ ^ P ^ actÎf / particle <6iim ~~ 1θθ%

The fraction of total active iron within the meaning of the invention is therefore the sum over all the particle size fractions of the fraction of active iron multiplied by the volume percentage of each particle size fraction obtained by laser particle size

Consequently, to have sufficient active iron oxide in the iron-based compound present in the tablets produced by the process according to the present invention, the% of active iron must be at least 40%.

As can be seen, according to the present invention, having a fine particle size is not enough, if it is really necessary to reach the% of active iron oxide within the iron-based compound present in the tablets, which makes it possible to reach sufficient ferrite conversion during prior heat treatment or in a converter.

In addition, in the method according to the present invention, it has been found that te! active iron oxide did not penalize the mechanical strength of the tablets formed, even at a high content of 60% by weight relative to the total weight of the raw tablets. The formation of such raw tablets containing a high amount of active iron oxide also makes it possible to have tablets which simultaneously provide fluxes such as iron oxide (Fe ₂ O ₃ ), but also the required ferrites, provided that if the tablets are raw and that they do not directly contain ferrites, the ferrites are formed directly in situ, for example in the converters in which the tablets are used.

The process according to the present invention therefore makes it possible to obtain tablets of calcium-magnesium compound whose mechanical resistance is not penalized by the addition of fluxes, even without heat treatment, of which the iron oxide is active, but which in addition is very flexible and efficient, without bringing the above constraints.

Preferably, according to the present invention, said an iron-based compound containing from 3% to 40% of Fe ₂ O ₃ equivalent supplied in the form of a homogeneous mixture comprises at least 50% of active iron oxide, advantageously , at least 60% of active iron oxide, in a particularly preferred manner, at least 70% of active iron oxide, relative to the total weight in Fe ₂ O ₃ equivalent.

The homogeneous pulverulent mixture thus formed is fed into a confinement space between two punches of a Eurotab titan type rotary press having a section between 1 and 40 cm ² , advantageously between 1 and 20 cm ² , preferably between 1 and 10 cm ² , in particular between 2 and 10 cm ² .

The homogeneous powder mixture is then compacted to form a product in the form of tablets of a three-dimensional shape, by application of a compacting pressure comprising 200 MPa and 800 MPa, preferably between 250 MPa and 600 MPa, more preferably between 300 and 500 MPa, and even more preferably between 350 and 500 MPa, optionally in the presence of a binder or a lubricant, preferably supplied in the form of a powder or of concentrated aqueous suspension, more particularly chosen from the group binders of mineral origin such as cements, clays, silicates, binders of plant or animal origin, such as celluloses, starches, gums, alginates, pectin, glues, binders synthetic origin, such as polymers, waxes, liquid lubricants such as mineral oils or silicones, solid lubricants such as talc, graphite, paraffins, stearates, in particular l e calcium stearate, magnesium stearate, and mixtures thereof, preferably calcium stearate and / or magnesium stearate, in a content of between 0.05 and 0.50% by weight, preferably between 0.05 and 0.30% by weight, more preferably between 0.10 and 0.20% by weight relative to the total weight of said mixture. The compaction pressure is then released and the product in the form of tablets is ejected to allow its collection.

The rotary press of the Titan type comprises a die having an internal wall defining at least said confinement space having a section which is reduced towards the bottom. The lower section of the confinement space in which the product is housed in the form of a tablet is less than the upper section of the confinement space in which the product is housed in the form of a tablet, to facilitate the ejection of the product in the form of a containment space tablet, and provides productivity of at least 100 rpm (tablet per minute). Beginning with about thirty kilograms of fines of slaked lime from 0 to 3 mm, 12.7 g of this mixture are successively poured into each of the dies of the tool, which has a substantially cylindrical shape having a section which reduces towards the bottom. for the shelves and with a diameter of approximately 21 mm. The compression is carried out under a compression of 500 MPa, with an approach speed of the punches of 115 mm / s and a holding time of 100 ms.

Several kilograms of product are obtained in the form of substantially cylindrical tablets, each having a weight of 12.6 g and a median diameter of an average value of 21.4 mm. The upper diameter of the top (top) of the shelves has an average value of 21.51 mm and the bottom diameter of the bottom (bottom) of the shelves has an average value of 21.29 mm, which leads respectively to a upper surface of the upper part with an average value of 363 mm ² and a lower surface of the lower part with an average value of 356 mm ² . Consequently, the difference between the average upper surface and the average lower surface of the tablets compared to the average median section of the product in tablet form is equal to 2.06% [(average upper surface of the upper part-lower surface of the lower part) / middle section of the product in tablet form], The height is 15.9 mm and the density is 2.20 g / cm ³ . These tablets are of uniform quality and are free from macroscopic defects.

These compacts in the form of tablets develop a BET specific surface (measured by manometry with nitrogen adsorption after degassing in vacuo at 190 ° C. for at least two hours and calculated according to the multipoint BET process described in standard ISO 9277: 2010E) of 1.4 m ² / g and have a total pore volume with mercury of 34% (determined by porosimetry by introduction of mercury according to part 1 of standard ÎSO 15901-l: 2005E which consists in dividing the difference between the density of skeleton , measured at 30,000 psia, and the apparent density, measured at 0.51 psia, by your density of skeleton).

An impact resistance test is carried out, starting with 5 0.5 kg of these tablets and successively carrying out 4 drops of two meters. We weigh the quantity of fines less than 10 mm produced at the end of these 4 falls. An impact resistance index of 2.8% is obtained.

In a preferred embodiment of the method according to the present invention, the collected raw tablets are heat treated at a temperature between 700 ° C and 1200 ° C, preferably between 700 ° C and 1000 ° C, preferably between 800 ° C and 1000 ° C, for a predetermined period of time.

The raw tablets are therefore brought into a high temperature oven where they undergo a heat treatment of these tablets at a temperature less than or equal to 1200 ° C., preferably less than or equal to 1000 ° C. They are then cooled and collected in the form of baked tablets to, among other things, improve their resistance to aging as well as their resistance to falling.

The heat treatment time is linked to the temperature of the heat treatment (the shorter the temperature the higher the temperature) and the thickness of the bed of shelves {the time increases with the thickness of the bed to allow the time for the heat to diffuse inside the bed). Thus in “monolayer” conditions, the heat treatment is preferably carried out at around 900 ° C. 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, more particularly greater. or equal to 7 minutes and less than or equal to 13 minutes, obtaining cooked tablets. In the condition "monolayer", each decrease in the temperature of the heat treatment ^50th C leads to double the heat treatment time.

When the heat treatment is carried out in a “multilayer” condition, that is to say that the tablets are in the form of a static bed of tablets of a certain thickness, it is understood that the heat treatment time must be increased. to allow time for the heat to penetrate the heart of the bed of shelves. As an indication, for a bed thickness of 100 mm, the heat treatment is preferably carried out around 900 ° C for a predetermined period of between 6 and 40 minutes, preferably greater than or equal to 10 minutes and less than or equal to 30 minutes, more particularly greater than or equal to 14 minutes and less than or equal to 26 minutes.

For example, a heat treatment for a period of 10 to 20 minutes at 900 ° C is sufficient for a layer of tablets up to 100 to 150 mm thick in the oven. Typically it is necessary to double the heat treatment time for a 50 ° C drop in temperature.

The live calco-magnesian compound is advantageously a calco-magnesian compound with gentle or medium cooking, preferably with gentle cooking.

In a very particular embodiment of the present invention, in which the raw tablets contain an iron-based compound which is a compound based on iron oxide, the method further comprises a heat treatment of said collected raw tablets, to a temperature between 900 ° C and 1200 ° C, preferably between 1050 ° C and 1200 ° C, in particular around 1100 ° C, for a predetermined period with the formation and obtaining of cooked tabs in which the compound based on iron oxide is converted, at least partially, to calcium ferrites.

The raw tablets are therefore brought into a high temperature oven where they undergo a heat treatment of these tabs at a temperature below or equal to 1200 ° C. They are then cooled and collected in the form of cooked tablets to, inter alia, promote the formation of calcium ferrites, sought after in iron and steel applications, and improve their resistance to aging as well as their resistance to dropping.

The heat treatment time is related to the temperature of the heat treatment (the shorter the temperature, the higher the temperature) and the thickness of the bed of shelves (the time increases with the thickness of the bed to allow the time for the heat to diffuse inside the bed). Thus in “monolayer” conditions, the heat treatment is preferably carried out around 1100 ^e C 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, more particularly greater or equal to 7 minutes and less than or equal to 13 minutes, obtaining cooked tablets, in which said active iron oxide is converted into calcium ferrite. In the “monolayer” condition, each decrease in the temperature of the heat treatment by 50 ° C. leads to doubling the time of heat treatment.

When the heat treatment is carried out in a "multilayer" condition, that is to say that the tablets are in the form of a static bed of tablets of a certain thickness, it is understood that the heat treatment time must be increased. to allow time for the heat to penetrate the heart of the bed of shelves. As an indication, for a bed thickness of 100 mm, the heat treatment is preferably carried out around 1100 ° C for a predetermined period of between 6 and 40 minutes, preferably greater than or equal to 10 minutes and less than or equal to 30 minutes, more particularly greater than or equal to 14 minutes and less than or equal to 26 minutes.

To carry out these heat treatments, a horizontal oven such as for example a tunnel oven, a passage oven, a rack oven, a roller oven or a mesh belt oven can be used. As a variant, any other type of conventional oven, but which does not lead to the alteration of the integrity of the compacts, for example due to excessive attrition, can be used. The cooling can either be carried out in a conventional manner in the downstream part of the furnace, or outside of the furnace, as for example in a vertical counter-current cooler for the cooling air or in a cooler in a fluidized bed by the cooling air in the event of quenching.

In one particular mode, the cooling at the end of the heat treatment is carried out rapidly in less than 15 min, preferably in less than 10 min, in a bed fluidized by the cooling air.

In a preferred form according to the present invention, the process comprises, before said supply of a homogeneous pulverulent mixture,

a) feeding a mixer with said at least one living caico-magnesian compound and

b) a mixture for a predetermined period, sufficient to obtain a homogeneous pulverulent mixture of said at least one bright calco-magnesian compound.

In a variant of the invention, the homogeneous mixture based on calcium-magnesium compound comprises at least 10% by weight of ground quicklime particles, preferably at least 20% by weight, more particularly at least 30% by weight and at most 100% by weight relative to the total weight of said mixture.

The “raw” tablets are advantageously based on quicklime (possibly dolomitic) in the form of particles rejected during screening during the manufacture of pebbles and quicklime in the form of crushed particles.

They are also characterized by a mass content of calcium and magnesium of at least 40%, preferably at least 60%, preferably at least 70% and at most 100%, preferably 95% expressed in CaO equivalent and MgO. The chemical analysis is carried out by RFX.

The% by weight of CaO + MgO equivalent and Fe ₂ O ₃ is determined by X-ray fluorescence spectrometry (RFX) as described in standard EN 15309. Chemical analysis, semi-quantitative, by RFX for 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 ground at 80 pm and shaped in the form of pellets. The samples are introduced into a PANalyticaf / MagiX PRO PW2540 apparatus, operating in wavelength dispersion. The measurement is carried out with a power of 50kV and 80 mA, with a Duplex detector.

The results of the analysis give the content of calcium, magnesium and iron and these measurements are reported respectively by weight of CaO and MgO equivalent, and by weight of Fe ₂ O ₃ equivalent.

They preferably contain 0.05 to 0.50% of lubricant, for example stearate such as calcium or magnesium stearate, preferably 0.10 to 0.20% by weight.

They are in the form of tablets (typical shapes of soap bars, balls, wafers ... known to those skilled in the art and from tangential roller presses) and have a size of at least 10mm, preferably at least at least 15mm and at most 50mm, preferably at most 40mm, preferably at most 30mm, in the direction of their passage through a square mesh screen.

The raw tablets of the composition have good mechanical strength characterized by a Shatter Test index (“STI”, ie mass percentage of fines less than 10 mm after 4 falls of 2 m) less than 8%, preferably less than 6%, 5% , 4%.

They are also characterized by a BET specific surface 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 tablets is greater than or equal to 30%, preferably greater than or equal to 32%, more preferably greater than or equal to 34%.

Raw tablets have an apparent density between 2.0 and 3.0, preferably between 2.2 and 2.8.

Raw tablets have good resistance to aging. Thus, when they are exposed to a humic atmosphere containing for example 5 to 15 g / m ³ of absolute humidity, the degradation of their mechanical properties (STI) occurs only after 1.5% of setting mass, preferably 2% mass gain, and still preferably 2.5% mass gain, following the hydration reaction of quicklime CaO into slaked lime Ca (OH) ₂ .

The cooked tablets of the present invention have a Shatter Test index (“STI”, i.e. mass percentage of fines less than 10 mm after 4 drops of 2 m) less than 6%, preferably less than 4%, 3%, 2%. In fact, in certain embodiments of the process according to the present invention, the cooked briquettes have a Shatter test index of less than 8%, sometimes less than 6%, less than 4%, less than 3%, or even around 2 %.

They are also characterized by a BET specific surface greater than or equal to 0.4 m ² / g, preferably greater than or equal to 0.6 m ² / g, more preferably greater than or equal to 0.8 m ² / g

The porosity is greater than or equal to 30%, preferably greater than or equal to 32%, more preferably greater than or equal to 34%.

The cooked tablets have an apparent density of between 2.0 and 3.0, preferably between 2.2 and 2.8.

Cooked tablets have good resistance to aging. Thus, when they are exposed to a humic atmosphere containing for example 5 to 15 g / m ³ of absolute humidity, the degradation of their mechanical properties (STI) occurs only after 4% of mass gain , preferably 4.5% mass gain, and still preferentially 5% mass gain, following the hydration reaction of quicklime CaO into slaked lime Ca (OH} ₂ .

Example 1.- Quicklime tablets, obtained from quicklime grinding fines

The quicklime grinding fines were prepared from a soft-cooked rock lime produced in a regenerative parallel-flow oven. 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 grinding quicklime fines contain 71% of particles greater than 90 µm, 37% of particles greater than 500 µm, 21% of particles greater than 1 mm and 1% of particles between 2 and 3 mm. The t ₆ o value of the water reactivity test is 0.9 min. The BET specific surface (measured by nitrogen adsorption manometry after degassing under vacuum at 190 ° C. for at least two hours and calculated according to the BET multi-point method as described in standard ISO 9277: 2010E) is 1.7 m ² / g. These quicklime grinding fines contain 95.7% CaO and 0.8% MgO by weight.

A Gericke GCM450 powder mixer is used, with a capacity of 10 dm ³ , equipped with standard blades of 7 cm radius used in rotation at 350 revolutions per minute (ie 2.6 m / s). This mixer is used in continuous mode to prepare a mixture consisting of:

99.9% by weight of these quicklime grinding fines,

- 0.1% by weight of calcium stearate powder.

The total flow rate of the powder is 300 kg / h and the residence time is 3.5 s. The mixture obtained is very homogeneous.

A rotary press equipped with a turret with a diameter of 1700 mm is used. On the peripheral part of the turret are distributed 67 frustoconical cavities with a diameter of 26 mm with, on both sides, 67 lower punches and 67 upper punches. This press is equipped with a system for feeding the mixture to be compacted (feeding zone), lower and upper compression rollers (compression zone) and extraction rollers (extraction and collection zone).

From 10 tonnes of the mixture, the rotary press is fed so that the filling time of the cavities is 0.6 s and compacted at a speed of 13 revolutions per minute (i.e. a linear speed of

1.14 m / s) at a surface pressure of 410 MPa (220 kN) with an approach speed of the punches of 100 mm / s and a holding time of 100 ms.

9.7 tonnes of tablets are obtained, having an average weight of 27.7 g and an average density of 2.05. These shelves have a diameter of

26.6 mm and a height of 24.3. These tablets develop a BET specific surface of 1.6 m ² / g and have a total pore volume of mercury (determined by mercury intrusion porosimetry according to part 1 of the ISO 15901-1: 2005E standard which consists in dividing the difference between the skeletal density, measured at 30,000 psia, and the apparent density, measured at 0.51 psia, by skeletal density) of 37%.

The water reactivity of the tablets is determined by adding 150 g of these tablets, previously ground in the form of fines of size between 0 and 1 mm, to 600 cm ³ of water at 20 ° C. The value ΐεο is 1.1 min.

We make a Shatter Test starting from 10 kg of these tablets by successively making 4 drops of 2 m. We weigh the quantity of fines less than 10 mm generated after these 4 falls. A 2.7% Shatter Test Index is obtained.

Example 2 - Quick Lime Tablets, Made from a Mixture of Quick-Cook Grinding Quick Lime Fine and Screening Quick Lime Fine

The quicklime grinding fines are those of Example 1. The quicklime sieving fines were recovered at the end of the screening through a sieve 3 mm from the bulk at the outlet of an oven. rotary equipped with a preheater. These quicklime screening fines contain a cumulative 74% of particles greater than 90 µm, 60% of particles greater than 500 µm, 47% of particles greater than 1 mm and 18% of particles between 2 and 3 mm. The t ₆ o value of the water reactivity test is 4 min. The BET specific surface is 1.2 m ² / g. These quicklime screening fines contain 97.1% CaO and 0.7% MgO by weight.

The mixture, produced according to the method of Example 1, consists of:

0.1% by weight of calcium stearate powder,

99.9% by weight of a 50:50 mixture by weight of these fines of quicklime grinding and these fines of quicklime of cribiage.

The tablets are produced from this mixture according to the method of Example 1. 9.5 tonnes of tablets are obtained, having an average weight of 27.4 g and an average density of 2.05. These shelves have a diameter of 26.6 mm and a height of 24.1. These tablets develop a BET specific surface of 1.4 m ² / g and have a total pore volume of mercury of 36%.

The water reactivity of the tablets is determined by adding 150 g of these tablets, previously ground in the form of fines of size between 0 and 1 mm, to 600 cm ³ of water at 20 ° C. The teo value is 1.8 min.

We do a Shatter Test starting from 10 kg of these tablets by successively performing 4 falls of 2 m. We weigh the quantity of fines less than 10 mm generated after these 4 falls. A 3.2% Shatter Test Index is obtained.

Example 3.- Tablets of quicklime dolomitic, obtained from a mixture of quicklime fine-grinding lime fines and cooked dolomite fines

The quicklime grinding fines are those of Example 1.

The cooked grinding dolomite fines were prepared from a rock baked dolomite produced in a regenerative furnace with parallel flow. The grinding was carried out in a hammer mill. These cooked grinding dolomite fines contain a cumulative 91% of particles greater than 90 μm,

44% of particles greater than 500 µm, 31% of particles greater than 1 mm and 17% of particles greater than 2 mm and 8% of particles between 3 and 5 mm. The t ₇₀ value of the water reactivity test is 3.1 min, The BET specific surface is 2.8 m ² / g · These cooked grinding dolomite fines contain 58.5% CaO and 38, 4% MgO by weight.

The mixture, produced according to the method of Example 1, consists of:

0.1% by weight of calcium stearate powder,

- 99.9% by weight of a 70:30 by weight mixture of these quicklime grinding fines and these cooked dolomite fines.

The tablets are produced from this mixture according to the method of Example 1. 9.6 tonnes of tablets are obtained, having an average weight of 27.8 g and an average density of 2.04. These tablets have a diameter of 26.6 mm and a height of 24.5. These tablets develop a BET specific surface of 2.2 m ² / g and have a total pore volume of mercury of 36%,

We do a Shatter Test starting from 10 kg of these tablets by successively performing 4 falls of 2 m. We weigh the quantity of fines less than 10 mm generated after these 4 falls. We obtain a Shatter Test Index of 3.9%.

Free 4, - Tablets of quicklime, obtained from a mixture of quick-lime grinding quicklime fines and iron oxide fines

The quicklime grinding fines are those of Example 1. The iron oxide fines come from the grinding of an iron ore of the hematite type Fe2O3 passing through a sieve at 150 μm and characterized by Coulter laser granulometry ( based on light diffraction and following the theories of Fraunhofer and Mie} by a dio of 0.5 pm, a dso of 12.3 pm and a dgo of 35.7 pm. These fines of iron oxide contain 64.6% Fe.

The mixture, produced according to the method of Example 1, consists of:

- 0.1% by weight of calcium stearate powder,

- 99.9% by weight of a 90:10 mixture by weight of these quicklime grinding fines and these iron oxide fines.

The tablets are produced from this mixture according to the method of Example 1. 9.7 tonnes of tablets are obtained, having an average weight of 29.3 g and an average density of 2.15. These shelves have a diameter of 26.6 mm and a height of 24.5. These tablets develop a BET specific surface of 1.7 m ² / g and have a total pore volume of mercury of 36%.

The water reactivity of the tablets is determined by adding 166.7 g of these tablets, previously ground in the form of fines of size between 0 and 1 mm, to 600 cm ³ of water at 20 ° C. The 166.7 g of tablets correspond to 150 g of quicklime. The value t _6û is 1.2 min.

We do a Shatter Test starting from 10 kg of these tablets by successively performing 4 falls of 2 m. We weigh the quantity of fines less than 10 mm generated after these 4 falls. We obtain a Shatter Test Index of 3.6%.

The volume fraction of iron oxide on the surface of the 10 iron oxide particles in the tablet composition is 85

%. Iron oxide therefore contains 85% active iron.

The tablets are also characterized by carrying out a heat treatment of 10 min at 11OOT (hot charging / diversion) on 3 of these tablets at the end of which a powder with a particle size of less than 80 μm is prepared. This is characterized by X-ray diffraction and a quantification of the phases is carried out by Rietveld analysis. 83% of the total iron is in the form of calcium ferrites CaFe2O ₄ or Ca2Fe20s, and 17% is always in the form of Fe ₂ O ₃ .

Example 5 - Quick Lime Tablets, Derived from Quick Grinding Lime Fine, Heat Treated

From 1 ton of tablets of Example 1, placed in boxes so that the thickness of the bed of tablets is 100 mm, a heat treatment of 20 min at 900 ° C. is carried out, with ramps of temperature rise and fall by 40 ° C per minute.

Tablets are obtained having an average weight of 27.5 g and an average density of 2.04. These shelves have a diameter of 26.6 mm and a height of 24.3. These tablets develop a BET specific surface of 1.3 m ² / g and have a total pore volume of mercury of 38%.

The water reactivity of the tablets is determined by adding 150 g of these tablets, previously ground in the form of fines of size between 0 and 1 mm, to 600 cm ³ of water at 20 ° C. The tgo value is 1.0 min.

We do a Shatter Test starting from 10 kg of these tablets by successively performing 4 falls of 2 m. We weigh the quantity of fines less than 10 mm generated after these 4 falls. A 1.8% Shatter Test Index is obtained.

Example 6: Tablets of quicklime, obtained from a mixture of quick-lime grinding quicklime fines and iron oxide fines, heat treated

From 1 tonne of tablets of Example 4, placed in boxes so that the thickness of the bed of tablets is 100 mm, a heat treatment of 20 min is carried out at 1100 ° C., with ramps of rise and fall in temperature of 50 ° C. per minute.

Tablets are obtained having an average weight of 29.0 g and an average density of 2.13. These shelves have a diameter of 26.6 mm and a height of 24.5. These tablets develop a BET specific surface of

1.1 m ² / g and have a total pore volume of mercury of 38%.

We do a Shatter Test starting from 10 kg of these tablets by successively performing 4 falls of 2 m. We weigh the quantity of fines less than 10 mm generated after these 4 falls. We obtain a Shatter Test Index of 1.1%.

The volume fraction of iron oxide on the surface of the iron oxide particles in the composition in tablet form is 87%. The iron-based compound therefore contains 87% active iron.

From 30 of these heat-treated tablets, a powder with a particle size of less than 80 μm is prepared. This is characterized by X-ray diffraction and a quantification of the phases is carried out by Rietveld analysis. 82% of the total iron is in the form of calcium ferrites CaFe ₂ O ₄ or Ca ₂ Fe20s, and 18% is always in the form Fe ₂ O ₃ .

The water reactivity of the tablets is determined by adding 178.2 g of these tablets, previously ground in the form of fines of size between 0 and 1 mm, to 600 cm ³ of water at 20 ° C. The 178.2 g of tablets correspond to 150 g of free quicklime (that is to say not being in the form of calcium ferrites). The teo value is 1.5 min.

It is understood that the present invention is in no way limited to the embodiments described above and that many modifications can be made thereto without departing from the scope of the appended claims.

Claims (36)

"CLAIMS" 1. Composition in the form of tablets comprising at least one bright calco-magnesian compound, said composition having at least 40% by weight of CaO-rMgO relative to the weight of said composition, characterized in that said calco-magnesian compound comprises quicklime in the form of ground particles at a concentration of at least 10% by weight and at most 100% by weight relative to the total weight of said composition, said composition in the form of tablets having a Shatter test index less than 10%. 2. Composition in the form of tablets according to claim 1, in which said quicklime in the form of crushed particles is quicklime quick cooking or medium cooking, preferably soft cooking. 3. Composition according to claim 1 or claim 2, wherein said tablets have the highest dimension of at least 10 mm, preferably at least 15 mm, more preferably at least 20 mm. 4. Composition in the form of tablets according to any one of the preceding claims, in which said tablets have a highest dimension of at most 50 mm, preferably at most 40 mm, more preferably at most 30 mm. 5. Composition in the form of tablets according to any one of claims 1 to 4, in which said tablets are raw tablets and have a BET specific surface greater than or equal to 1 m ² / g, preferably greater than or equal to 1, 2 m ² / g, more preferably greater than or equal to 1.4 m ² / g. 6. Composition based on live calcium-magnesium compounds in the form of tablets according to any one of claims 1 to 4, in which said tablets are cooked tablets and have a BET specific surface greater than or equal to 0.4 m ² / g, preferably greater than or equal to 0.6 m ² / g, more preferably greater than or equal to 0.8 m ² / g. 7. Composition in the form of tablets according to any one of claims 1 to 6, in which the said tablets have a porosity greater than or equal to 30%, preferably greater than or equal to 32%, more preferably greater than or equal to 34 %. 8. Composition based on living caico-magnesian compounds in the form of tablets according to any one of claims 1 to 7, in which said quicklime in the form of ground particles is present at a concentration of at least 15%, preferably at least 20%, and more preferably at least 30%, in particular at least 40% by weight relative to the total weight of said composition. 9. Composition in the form of tablets according to any one of claims 1 to 8, in which said quicklime in the form of ground particles is present at a concentration of at most 90% by weight, preferably at most 80%, preferably at most 70%, more preferably at most 50% by weight, relative to the total weight of said composition. 10. Composition in the form of tablets according to any one of claims 1 to 9, further comprising a binder or a lubricant, more particularly chosen from the group consisting of binders of mineral origin such as cements, clays, silicates , binders of plant 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, ie magnesium stearate, and their mixtures, preferably calcium stearate and / or magnesium stearate, at a content of between 0.05 and 0.50% by weight, preferably between 0.05 and 0.30% by weight, more preferably between 0.10 and 0.20% by weight per relative to the total weight of said composition. 11. Composition in the form of tablets according to any one of claims 1 to 10, in which said tablets have a 5 average weight per tablet of at least 5 g, preferably at least 10 g, more preferably at least 12 g, and in particular at least 15 g. 12. Composition in the form of tablets according to any one of claims 1 to 11, in which said tablets have an average weight per tablet of less than or equal to 100 g, preferably less than or 10 equal to 60 g, more preferably less than or equal to 40 g and in particular less than or equal to 30 g. 13. Composition in the form of tablets according to any one of claims 1 to 12, in which said tablets have an apparent density of between 2 g / cm ³ and 3.0 g / cm ³ , advantageously 15 between 2.2 g / cm ³ and 2.8 g / cm ³ . 14. Composition in the form of tablets according to any one of the preceding claims, characterized in that said bright calco-magnesian compound further comprises fine particles of calco-magnesian compound chosen from fine particles rejected at Screening of the production of the rollers of said live calco-magnesian compound, of calc-magnesian filter dust and their mixture, at a concentration of at least 10% by weight and at most 90% by weight relative to the total weight of said composition. 15. Composition in the form of tablets according to one 25 any of the preceding claims, characterized in that said composition further comprises one or more iron-based compound (s) at a concentration of at least 3% by weight and at most 60%, for example at least plus 40% by weight expressed in Fe ₂ O ₃ equivalent relative to the total weight of said composition. 30 16. Composition in the form of tablets according to any one of claims 1 to 15, 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. 17. Composition in the form of tablets according to any one of claims 1 to 16, in which said tablets have a slightly asymmetrical three-dimensional shape, preferably substantially frustoconical, in which the difference between the surface of the upper part and that of the part lower of the tablet is greater than or equal to 0.5%, preferably greater than or equal to 1%, and less than or equal to 10%, preferably less than or equal to 5%, in particular less than or equal to 3%, in particular around 2%. 18. Composition in the form of tablets according to any one of claims 1 to 5 and 7 to 17, in which the tablets are raw tablets having a Shatter test index of less than 8%, preferably less than 6%, and more preferably less than 5%, in particular less than 4%. 19. Composition in the form of tablets according to any one of claims 1 to 4 and 6 to 17, in which the tablets are cooked tablets having a Shatter test index of less than 6%, preferably less than 4%, and of more preferably less than 3%, in particular less than 2%. 20. A method of manufacturing a composition in the form of tablets, comprising the following steps: a) supplied with a homogeneous pulverulent mixture comprising at least 40% by weight of CaO + MgO equivalent relative to the weight of said homogeneous pulverulent mixture, and comprising at least one bright calcium-magnesium compound, said at least one calcium-magnesium compound quicklime comprising quicklime in the form of ground particles at a concentration of at least 10% by weight and at most 100% by weight relative to the weight of said homogeneous powdery mixture, b} feeding of said homogeneous powdery mixture in a space confinement between two punches having a section between 1 and 40 cm ² , advantageously between 1 and 20 cm ² , preferably between 1 and 10 cm ² , in particular between 2 and 10 cm ² , c) compacting said homogeneous mixture to form a product in the form of tablets of a three-dimensional shape, by applying a compaction pressure of between 200 MPa and 800 MPa, preferably between 250 MPa and 600 MPa, more preferably between 300 and 500 MPa, and even more preferably between 350 and 500 MPa, d) release of the compaction pressure and e) ejection of said product in the form of tablets from said confinement space. 21. A method of manufacturing a composition in the form of tablets according to claim 20, wherein said compression step is carried out in the presence of a binder or a lubricant, preferably supplied in the form of powder or aqueous suspension. concentrated, more particularly chosen from the group of binders of mineral origin such as cements, clays, silicates, binders of plant 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, in a content of between 0.1 and 1% by weight, preferably between 0.15 and 0 , 6% by weight, of more preferably between 0.2 and 0.5% by weight relative to the total weight of said mixture. 22. A method of manufacturing a composition in the form of tablets according to claim 20 or claim 21 „further comprising a heat treatment of said collected raw tablets, at a temperature between 700 ° C and 1200C, preferably around 900 ° C. 23. A method of manufacturing a composition in the form of tablets according to any one of claims 20 to 22, comprising a step of heat treatment of said tablets for a predetermined period of between 5 and 20 minutes, preferably greater than or equal to 7 minutes and less than or equal to 15 minutes, with the formation and obtaining of cooked tablets. 24. A method of manufacturing a composition in the form of tablets according to claim 20 or claim 21, wherein said quicklime in the form of crushed particles is quicklime with soft or medium cooking, preferably with soft cooking, 25. A method of manufacturing a composition in the form of tablets according to any one of claims 20 to 24, wherein said quicklime in the form of crushed particles has a high reactivity to water characterized by a value of teo less than 10 min, preferably less than 8 min, preferably less than 6 min and more preferably less than 4 min. 26. A method of manufacturing a composition in the form of tablets according to any one of claims 20 to 25, wherein said quicklime in the form of crushed particles is obtained by grinding from quicklime in rock whose size is greater to 3 mm, preferably greater than 5 mm, preferably greater than 7 mm, and still preferentially greater than 10 mm, and less than 120 mm, preferentially less than 100 mm, preferentially less than 80 mm, and still preferentially less than 60 mm. 27. A method of manufacturing a composition in the form of tablets according to any one of claims 20 to 26, wherein said at least one quick caico-magnesian compound comprises quicklime in the form of grinded particles in a concentration of at least 15% by weight, in particular at least 20% by weight, more preferably at least 30% by weight, particularly preferably at least 40% by weight relative to the total weight of said mixture homogeneous powder. 28. A method of manufacturing a composition in the form of tablets according to any one of claims 20 to 27, wherein said at least one quick lime-magnesium compound comprises quicklime in the form of particles ground to a concentration of at most 90% by weight, in particular at most 80% by weight, more preferably at most 70% by weight, more preferably at most 50% by weight, relative to the total weight of said homogeneous powder mixture. 29. A method of manufacturing a composition in the form of tablets according to any one of claims 20 to 28, in which said bright calco-magnesian compound further comprises fine particles of calco-magnesian compound chosen from fine particles rejected at screening of the production of the rollers of said live calco-magnesian compound, of calc-magnesian filter dust and their mixture, at a concentration of at least 10% by weight and at most 90% by weight relative to the total weight of said composition . 30. A method of manufacturing a composition in the form of tablets according to any one of claims 20 to 29, wherein said pulverulent homogeneous mixture further comprises one or more compound (s) based on iron, at a concentration of at least 3% by weight and at most 60% by weight expressed in Fe ₂ O ₃ equivalent relative to the weight of said mixture. 31. A method of manufacturing a composition in the form of tablets according to claim 30, in which said tablets are raw tablets and in which at least one of the iron-based compound or compounds is an iron oxide, preferably a active iron oxide present at a concentration of at least 3% by weight and at most 60% by weight expressed as Fe ₂ O ₃ equivalent relative to the weight of said mixture. 32. A method of manufacturing a composition in the form of tablets according to claim 30 and claim 31, further comprising a heat treatment of said collected raw tablets, at a temperature between 700 ° C and 1200 ° C, preferably around of 5 HOO’C. 33. A method of manufacturing a composition in the form of tablets according to any one of claims 30 to 32, for a predetermined period of between 5 and 20 minutes, preferably greater than or equal to 7 minutes and less than or equal to 15 minutes , more 10 particularly greater than or equal to 8 minutes and less than or equal to 13 minutes with baked tablets obtained in which the compound based on iron oxide is converted into calcium ferrites. 34. A method according to any one of claims 20 to 30, further comprising, before said supply of a pulverulent mixture 15 homogeneous, a) supplying a mixer with said at least one living calcium-magnesium compound and b) mixing for a predetermined period, sufficient to obtain a homogeneous powder mixture of said at least one 20 vivid calco-magnesian compound. 35. Method for manufacturing a composite material comprising several successive layers in order to form a multilayer structure in which at least one layer is formed with said product in the form of tablets of the composition by the method according to one 25 any of claims 20 to 34 and further comprising an additional step of compacting said at least one layer of said compact product and another compact layer before said ejection step. 36. Use of the composition according to claims 1 to 30 19 or from the process according to claims 20 to 35, in the steel industry, in particular in the manufacture of steel in elementary oxygen converters, in electric arc furnaces, or in secondary metallurgy, in the treatment flue gases, in water treatment, in sludge and wastewater treatment, in agriculture, in the building industry and in public works, as for example for 5 ia soil stabilization.