The present invention relates to a method for grinding a hydraulic binder, such as cement.

The process for preparing a hydraulic binder includes its grinding in order to reduce the particle size of the particles it contains and thus increase its reactivity and give it the desired rheological properties.

The use of a grinding aid makes it possible to improve the grinding yield of the hydraulic binder. Grinding agents allow:

an increase in production during grinding for the same energy consumption and the same fineness, or

an increase in fineness for the same energy consumption.

When a horizontal mill comprising several grinding chambers is used for grinding a hydraulic binder, the grinding agent (s) is (are) introduced into the first chamber of the mill, along with the binder. hydraulic to grind or separately.

There is a need to develop a hydraulic binder grinding process making it possible to improve the quality of the ground hydraulic binder (Blaine fineness and / or particle size distribution in particular) and / or to improve the grinding efficiency in order to lower the costs.

To this end, according to a first object, the invention relates to a method for grinding a hydraulic binder comprising:

a) introduction:

a hydraulic binder, and

of a composition B comprising at least one grinding agent B,

in the first chamber of a horizontal mill comprising several chambers, including a first chamber and a last chamber, each chamber being separated from the adjacent chamber by a diaphragm,

whereby a composition b comprising the hydraulic binder and the composition B is obtained in the first chamber,

b) grinding of composition b in the horizontal mill, whereby composition b passes from the first chamber to the last chamber and a ground composition C is obtained at the outlet of the last chamber,

characterized in that it comprises, during the grinding step, the introduction, into the last chamber, of a composition A comprising at least one grinding agent A comprising an aminoalcohol, the composition A being different from the composition b.

The method uses a horizontal mill comprising several chambers (sometimes also called “compartments”), including a first chamber and a last chamber, each chamber being separated from the adjacent chamber by a diaphragm. Usually the chambers have the same diameter and / or the last chamber is longer than the first chamber. Preferably, the grinding charge (metal balls, etc.) is of a different size from one chamber to another.

The first chamber is the chamber into which the hydraulic binder to be ground is introduced. The last chamber is the chamber out of which the crushed composition C leaves the mill. The ground composition C comprises the ground hydraulic binder, the grinding agent A and the grinding agent B.

During grinding, the hydraulic binder passes from the first chamber to the adjacent chamber, and this up to the last chamber. The diaphragm which separates two adjacent chambers only lets through the particles of hydraulic binder of sufficiently small size to proceed to a finer grinding in the adjacent chamber which follows. The size of the hydraulic binder particles is therefore the highest in the first chamber, and the lowest in the last chamber.

Typically, the mill has only two chambers: the first chamber and the last chamber (which is then the second chamber), these being separated by a diaphragm.

The mill is generally a ball mill. The balls of the first chamber have an average diameter generally greater than those of the last chamber.

The method comprises a step a) of introducing a hydraulic binder and a composition B comprising at least one grinding agent B into the first chamber of the mill.

The term “hydraulic binder” is understood to mean any compound having the property of hydrating in the presence of water and the hydration of which makes it possible to obtain a solid having mechanical characteristics. The hydraulic binder can be a cement according to the EN 197-1 standard of 2012 and in particular a cement of the CEM I, CEM II, CEM III, CEM IV or CEM V type according to the Cement standard NF EN 197-1 of 2012. Cement can therefore in particular comprise mineral additions.

The expression “mineral additions” designates slags (as defined in the Ciment NF EN 197-1 standard of 2012 paragraph 5.2.2), steelworks slags, pozzolanic materials (as defined in the Ciment NF EN standard. 197-1 paragraph 5.2.3), fly ash (as defined in Cement standard NF EN 197-1 paragraph 5.2.4), calcined shale (as defined in Cement standard NF EN 197-1 paragraph 5.2. 5), limestones (as defined in the Cement standard NF EN 197-1

paragraph 5.2.6) or silica fumes (as defined in the Cement standard NF EN 197-1 paragraph 5.2.7) or their compositions. Other additions, not currently recognized by the Cement standard NF EN 197-1 (2012), can also be used. These include metakaolins, such as type A metakaolins in accordance with standard NF P 18-513 of 2012, and siliceous additions, such as siliceous additions of Qz mineralogy in accordance with standard NF P 18-509 of 2012.

In a first embodiment, the grinding agent B comprises a polyol, preferably chosen from:

a diol such as an alkylene glycol preferably comprising from 1 to 20 carbon atoms, in particular from 1 to 10 carbon atoms, and the alkylene group of which may bear a methyl, and being typically chosen from 2-methyl- 1, 3-propanediol, monoethylene glycol, diethylene glycol, triethylene glycol, tetraethyleneglycol, propylene glycol and a mixture thereof,

a triol, preferably glycerol,

- a tetraol, preferably erythritol, and

a mixture of these.

The grinding agent B comprises for example an alkylene glycol, or a mixture of alkylene glycol, and optionally glycerol, the glycerol preferably being present in a proportion of 0 to 5% by weight relative to the weight of the whole. (glycerol and alkylene glycol).

The grinding agent B (and the composition B) is (are) then preferably free from aminoalcohol, in particular one of those listed below.

In a second embodiment, the grinding agent B comprises an aminoalcohol or one of its salts, said aminoalcohol preferably comprising:

- from 2 to 8 carbon atoms, in particular from 4 to 6 carbon atoms, and / or

1, 2 or 3 alcohol functions,

for example chosen from N-methyldiethanolamine (MDEA), diisopropanolamine (DIPA), triisopropanolamine (TIPA), triethanolamine (TEA), ethanoldiisopropanol amine (EDIPA), diethanolisopropanolamine (DEIPA) and a mixture of these . For example, Grinding Agent B includes triisopropanolamine (TIPA), triethanolamine (TEA) or a mixture thereof. The preferred amino alcohol salts are the hydrochlorides, such as TEA. HCl, TIPA.HCI, EDIPA.HCI, and DEIPA.HCI.

In this second embodiment, the grinding agent B (and composition B) is (are) preferably free of polyol, in particular one of those listed above.

This second embodiment is particularly suitable for the grinding of a soft hydraulic binder, on which the polyols could induce an agglomeration which is harmful for the grinding and should therefore be avoided.

In a third embodiment, the grinding agent B comprises a polyol and an aminoalcohol.

In the second and third embodiment (when the grinding agent B comprises an amino alcohol), the grinding agent B may comprise a carboxylic acid or a salt thereof, for example selected from acetic acid or a salt thereof, formic acid or a salt thereof, or a mixture thereof. The grinding agent B then comprises an amino alcohol, a carboxylic acid or a salt thereof and optionally a polyol. The salt can be that formed between the amino alcohol and the carboxylic acid. The carboxylic acid generally makes it possible to adjust the dispersing force of composition B, the latter sometimes being too intense when the amino alcohol is used without carboxylic acid.

Grinding agent B is the active ingredient of composition B. Composition B can comprise one or more grinding agents B.

In addition to grinding agent B, composition B can include a solvent, generally water. Composition B may consist of an aqueous solution of at least one grinding agent B (the latter preferably consisting of one or more polyol (s), one or more aminoalcohol (s), or d 'a mixture of these, and optionally of one or more carboxylic acid (s) or a salt thereof (these)) when the grinding agent comprises an aminoalcohol), or even of a mixture of water and grinding agent B.

The proportion of grinding agent B introduced into the first chamber in step a) is typically from 50 to 2500 g, in particular from 75 to 500 g, preferably from 90 to 250 g per tonne of hydraulic binder introduced into the first chamber during step a). Below, the efficiency of the grinding agent is lower and beyond, the costs become too high. This is the proportion relative to the “dry” grinding agent, without taking into account the possible solvent and any other additives of composition B. When composition B comprises several grinding agents B, it is 'is the sum of their proportions.

The introductions of the hydraulic binder on the one hand and of the composition B on the other hand may or may not be simultaneous. In addition, the introductions of the hydraulic binder and of the composition B can be carried out through separate inlets from the first chamber, or through the same inlet. It is for example possible to introduce into the first chamber the composition b comprising the hydraulic binder and the composition B (introduction of the hydraulic binder and of the composition B simultaneously and through the same inlet). Preferably, composition B and the hydraulic binder are introduced simultaneously through the same inlet of the first chamber. Typically, composition B is dispersed in the hydraulic binder in the hydraulic binder feed hopper, for example by a spray boom or by a pipe dripping onto a hydraulic binder feed hopper. In this case, it is therefore composition b which is introduced into the first chamber of the horizontal mill.

The method comprises a step b) of grinding composition b in the mill, whereby composition b passes from the first chamber to the last chamber and a ground composition C is obtained at the outlet of the last chamber. The average particle size of composition C is therefore smaller than that of composition b. The measurement of the average particle size can be carried out by laser granulometry which gives a size distribution, or by sieving under pressure which typically gives a mass proportion rejected on a defined sieve, typically 32, 45 and / or 63 μm (being understood that the same measurement method must be used to compare sizes).

During step b) of grinding of the process according to the invention, a composition A comprising at least one grinding agent A comprising an amino alcohol is introduced into the last chamber of the grinder.

Typically, composition A is introduced into the last chamber:

either at the level of the diaphragm separating the last chamber from the adjacent chamber, or in the enclosure of the last chamber, in an area generally closer to the diaphragm separating the last chamber from the adjacent chamber than from the outlet of the last chamber,

or at the outlet of the last chamber, typically at the level of the discharge grid with which the outlet of the last chamber is fitted.

Le procédé met en oeuvre au moins deux agents de mouture A et B, qui sont introduits à des endroits distincts du broyeur : l’un dans la première chambre, l’autre dans la dernière chambre.

Les inventeurs ont en effet démontré que les agents de mouture A et B ne se répartissent pas de la même façon dans l’unité de broyage : le dosage de l’agent de mouture le long de l’unité de broyage varie en fonction de la nature de l’agent de mouture. Lorsque les agents de mouture sont introduits tous les deux dans la première chambre du broyeur comme dans l’art antérieur :

la quantité d’agent de mouture retrouvée sur les particules de liant hydraulique est essentiellement gouvernée par la surface spécifique des particules de liant hydraulique dès la sortie de la première chambre du broyeur,

à l’intérieur de la première chambre du broyeur, lorsque l’agent de mouture B comprend un alkylène glycol, il est plus abondant par unité de surface de liant hydraulique que l’agent de mouture A comprenant un aminoalcool,

la quantité d’agent de mouture par unité de surface de liant hydraulique se stabilise dans la seconde chambre du broyeur, et la différence entre les deux agents de mouture s’amenuise dans la dernière chambre.

L’agent de mouture A comprenant un aminoalcool a généralement une bonne capacité à fluidifier l’écoulement des particules, ce qui n’est pas le cas d’un agent de mouture comprenant un alkylène glycol. Sans vouloir être liés par une théorie particulière, au vu des résultats des exemples qui suivent, les inventeurs supposent que :

les agents de mouture sont transportés par les particules de liant hydraulique de forte surface spécifique, et donc les particules de petites tailles,

cet effet serait amplifié si l’agent de mouture a un effet fluidifiant, ce qui est le cas de l’agent de mouture A comprenant un aminoalcool, qui augmente le débit des particules de liant hydraulique de petite taille. L’agent de mouture A comprenant un aminoalcool est ainsi moins abondant en première chambre de broyage, qui comprend des particules de liant hydraulique de taille élevée.

This shows the advantage of introducing the two grinding agents at different places on the grinding line: the grinding agent B in the first chamber to allow a sufficiently long residence time of the hydraulic binder in the grinder, and the 'grinding agent A comprising an aminoalcohol in the last chamber, in order to remove the particles of small sizes from the mill and / or to fluidize the particles of the ground composition C and thus improve its subsequent processability and facilitate any subsequent separation ( second alternative described below).

Composition A is different from composition b. In other words, composition A introduced into the last chamber is not the composition being ground in the mill.

The grinding agent A comprises at least one aminoalcohol preferably comprising:

from 2 to 8 carbon atoms, in particular from 4 to 6 carbon atoms, and / or

1, 2 or 3 alcohol functions,

for example chosen from N-methyldiethanolamine (MDEA), diisopropanolamine (DIPA), triisopropanolamine (TIPA), triethanolamine (TEA), ethanoldiisopropanol amine (EDIPA), diethanolisopropanolamine (DEIPA) and a mixture of these . For example, Grinding Agent A comprises triisopropanolamine (TIPA), triethanolamine (TEA) or a mixture thereof.

The grinding agent A can comprise a carboxylic acid or a salt thereof, for example chosen from acetic acid or one of its salts, formic acid or one of its salts, or a mixture thereof. . The grinding agent A then comprises an amino alcohol and a carboxylic acid or a salt thereof. The salt can be that formed between the amino alcohol and the carboxylic acid. The carboxylic acid generally makes it possible to adjust the dispersing force of composition A, the latter sometimes being too intense when the amino alcohol is used without carboxylic acid.

In one embodiment, the grinding agent A is the same as the grinding agent B. Composition A can be the same as composition B.

In another embodiment, grinding agent A is different from grinding agent B. Composition A is different from composition B.

Grinding agent A is the active ingredient of composition A. Composition A can comprise one or more grinding agents A.

In addition to the grinding agent A, the composition A can include a solvent, generally water. Composition A may consist of an aqueous solution of at least one grinding agent A, or even a mixture of water and grinding agent A.

The proportion of grinding agent A introduced into the last chamber during step b) is typically from 50 to 2500 g, in particular from 75 to 500 g, preferably from 90 to 250 g per tonne of hydraulic binder introduced into the first chamber during step a). Below, the efficiency of the grinding agent is lower and beyond, the costs become too great. This is the proportion relative to the “dry” grinding agent, without taking into account the possible solvent and any other additives of composition A. When composition A comprises several grinding agents A, it is 'is the sum of their proportions.

During grinding step b), air can circulate from the first chamber to the last chamber. Air enters through the first chamber and leaves through the last chamber. This air makes it possible to displace the most volatile particles of composition b which is ground. The method can then comprise, after step b):

i) filtration of the air leaving the last chamber, whereby the most volatile ground hydraulic binder particles are recovered, then

ii) bringing together the most volatile particles recovered with the ground composition C, generally by flow in a current of air.

According to a first alternative, the process comprises, after step b), a step b1) of recovering the ground composition C. The ground composition C then has the desired size / specific surface. The process can then be implemented continuously, semi-continuously or in a batch.

In this first alternative, the main advantage of introducing composition A comprising at least one grinding agent A comprising an aminoalcohol in the last chamber is to fluidify the ground composition C, which improves its subsequent processability because composition C ground is more fluid which facilitates its flow, for example, in a silo, or during the loading and unloading of a truck. Indeed, generally, the required dosage of grinding agent A comprising an amino alcohol in order to have an acceptable fluidity of the ground composition C is greater than that required for efficient grinding of the hydraulic binder. It is therefore advantageous to introduce the grinding agent A into the last chamber of the mill, including in the embodiment where it is introduced at the outlet of the last chamber,

According to a second alternative, the method comprises, after step b):

c) the separation, by a separator, of the composition C ground into fines and in residue from a separator, where the average size of the particles of the residue from the separator is greater than that of the particles of the fines,

d) recovery of fines,

e) returning the residue from the separator to the first chamber of the horizontal mill.

In this second alternative, the process comprises a step c) of separating the composition C ground into fines and as residue from the separator.

The inventors have demonstrated that:

the higher the quantity of grinding agent A or B, the more efficient the separation, until a limit efficiency is reached,

l’efficacité de la séparation dépend de l’agent de mouture utilisé. La séparation est plus efficace pour l’agent de mouture A comprenant un aminoalcool que pour un agent de mouture comprenant un polyol.

Aussi, introduire l’agent de mouture A comprenant un aminoalcool dans la dernière chambre du broyeur permet une meilleure fluidification de la composition C broyée lors de la séparation et rend la séparation plus efficace.

En outre, l’introduction de la composition A comprenant au moins un agent de mouture A comprenant un aminoalcool dans la dernière chambre a également l’avantage de fluidifier la composition C broyée, et les fines récupérées, ce qui améliore leurs processabilités ultérieures car les fines sont plus fluides pour s’écouler, par exemple, dans un silo, ou lors de la charge ou la décharge d’un camion. En effet, généralement, le dosage requis en agent de mouture A comprenant un aminoalcool afin d’avoir une fluidité acceptable des fines récupérées est supérieur à celui requis pour un broyage efficace du liant hydraulique.

Dans cette deuxième alternative, les étapes i) et ii) définies ci-dessus, lorsqu’elles ont lieu, sont de préférence suivies d’une étape iii) de renvoi des particules rassemblées avec la composition C broyée vers le séparateur. Les étapes i), ii) et iii) sont mise en oeuvre entre les étapes b) et c).

Dans cette deuxième alternative, les fines sont récupérées lors de l’étape e). Il s’agit de la composition de liant hydraulique broyée à la taille/la surface spécifique désirée qui est obtenue par le procédé. Typiquement, lorsque le liant hydraulique est du ciment, la surface spécifique, mesurée par la méthode de Blaine, des fines est de l’ordre de 3200 à 4500 cm2/g.

Le refus du séparateur comprend quant à lui des particules de taille trop grosse par rapport à celle désirée. Il est renvoyé dans la première chambre de broyage pour être broyé à nouveau. Aussi, la composition b présente dans la première chambre comprend, voire consiste en, le liant hydraulique, le refus du séparateur et la composition B (sachant que le refus comprend du liant hydraulique, l’agent de mouture A et l’agent de mouture B).

Généralement, dans cette deuxième alternative, le procédé de broyage est mis en oeuvre en continu.

Selon un deuxième objet, l'invention concerne une unité de broyage destinée à la mise en oeuvre du procédé selon l’invention, comprenant :

une source de liant hydraulique,

une source de composition B comprenant au moins un agent de mouture B, une source de composition A comprenant au moins un agent de mouture A comprenant un aminoalcool,

un broyeur horizontal comprenant plusieurs chambres, dont une première chambre munie d’au moins une entrée et une dernière chambre munie d’une sortie, chaque chambre étant séparée de la chambre adjacente par un diaphragme,

caractérisé en ce que la dernière chambre est munie d’une entrée reliée à la source de composition A.

Les modes de réalisation décrits ci-dessus, en particulier pour le broyeur, sont applicables.

Généralement, la dernière chambre s’étend du diaphragme séparant la dernière chambre de la chambre adjacente jusqu’à une grille de décharge, apte à laisser sortir la composition C broyée hors du broyeur. Typiquement, l’entrée la dernière chambre qui est reliée à la source de composition A est :

soit au niveau du diaphragme séparant la dernière chambre de la chambre adjacente,

soit dans l’enceinte de la dernière chambre, dans une zone généralement plus proche du diaphragme séparant la dernière chambre de la chambre adjacente que de la sortie de la dernière chambre,

soit à la sortie de la dernière chambre, typiquement au niveau de la grille de décharge dont est munie la sortie de la dernière chambre.

Lorsque le broyeur est à boulets, la sortie de la dernière chambre est généralement munie d’une grille de décharge configurée pour empêcher les boulets de sortir de la dernière chambre.

Typiquement, le broyeur a uniquement deux chambres : la première chambre et la dernière chambre (qui est alors la deuxième chambre), celles-ci étant séparées par un diaphragme.

Le broyeur est typiquement configuré pour que de l’air puisse circuler depuis une entrée de la première chambre vers la sortie de la dernière chambre. L’unité comprend un filtre relié à la sortie de la dernière chambre et configuré pour filtrer l’air et récupérer les particules de liant hydraulique broyées les plus volatiles.

According to a first alternative, the grinding unit is free of separator. This first alternative of the grinding unit makes it possible to implement the first alternative of the process described above.

In this first alternative of the unit, the filter, when present, is configured to filter the air, recover the most volatile ground hydraulic binder particles and return them to the ground composition C.

In this first alternative, the first chamber is:

either provided with a single inlet connected to the source of hydraulic binder and to the source of composition B,

or provided with two inlets, the first inlet being connected to the source of hydraulic binder and the second inlet being connected to the source of composition B.

According to a second alternative, the grinding unit comprises a separator. The separator is typically a dynamic separator with rotating air chamber, cyclone or static filter or a combination. The outlet of the last chamber of the mill is then generally connected to the inlet of a separator capable of separating particles according to their particle size and provided with two outlets, one of the outlets being connected to an inlet of the first chamber of the horizontal grinder. This second alternative of the grinding unit makes it possible to implement the second alternative of the process described above. The grinding unit then comprises a closed circuit, since the outlet of the last chamber of the grinder is connected to the inlet of the separator, one of the outlets of which is connected to the first chamber of the grinder.

In this second alternative, the first chamber is:

either provided with a single inlet connected to the source of hydraulic binder, to the source of composition B and to an outlet of the separator,

either provided with two inlets, the first inlet being connected to the source of hydraulic binder and to the source of composition, the second inlet being connected to an outlet of the separator,

or provided with three inlets, the first inlet being connected to the source of hydraulic binder, the second inlet being connected to the source of composition B and the third inlet being connected to an outlet of the separator.

In this second alternative of the unit, the filter, when present, is between the last chamber of the mill and the separator. The filter is configured to filter the air, recover the most volatile ground hydraulic binder particles and return them to the separator.

The invention is illustrated in view of the examples which follow and the appended figures.

FIGURES

[Fig 1] Figure 1: Diagram of a grinding unit according to the second alternative of the invention.

[Fig 2] Figure 2: Diagram of a grinding unit according to the prior art and as used in Example 1, with indication of the locations 1, 2, 3, 4 5 and 6 for taking samples for the example 1.

[Fig 3] Figure 3: Example of a Tromp curve. Percentage of the residue from the separator returned to the mill as a function of the particle size in μm.

[Fig 4] Figure 4: Efficiency C of the separator as a function of the quantity of grinding agent entering the separator for each grinding agent and each dosage of grinding agent measured per m 2 of cement. The values ​​indicated on the graphs correspond to the initial dosages in ppm dry of grinding agent relative to the weight of cement. The crosses correspond to the grinding agent A comprising an aminoalcohol, and the circles to the grinding agent B comprising an alkylene glycol.

[Fig 5] Figure 5: Slope b of the fish-hook of the separator as a function of the quantity of grinding agent entering the separator for each grinding agent and each dosage of grinding agent measured per m 2 of cement. The crosses correspond to the grinding agent A comprising an aminoalcohol, and the circles to the grinding agent B comprising an alkylene glycol. The values ​​indicated on the graphs correspond to the initial dosages in ppm dry of grinding agent relative to the weight of cement.

[Fig 6] Figure 6: Dosage of grinding agent (in dry g) measured per m 2 of cement within the chambers of the mill and at the various locations of the unit where the samples were taken. The crosses correspond to the grinding agent A comprising an aminoalcohol, and the circles to the grinding agent B comprising an alkylene glycol.

[Fig 7] Figure 7: Relationship between the quantity of grinding agent (in dry g) measured per tonne of cement measured on the samples and the specific surface of the cement in cm2 / g. The crosses correspond to the grinding agent A comprising an aminoalcohol, and the circles to the grinding agent B comprising an alkylene glycol.

[Fig 8] Figure 8: Diagram of a grinding unit according to the second alternative and places of sampling of example 2.

[Fig 1] Figure 1 illustrates a grinding unit according to the second alternative of the invention, in the case where the grinding unit comprises a filter. A horizontal crusher 1 1 comprising two chambers:

a first bedroom 12 with an entrance 13 and

a second bedroom (last bedroom) 14 with an entrance 15 and an exit 16,

la première chambre 12 étant séparée de la deuxième chambre 14 par un diaphragme 17. L’entrée 13 de la première chambre 12 est reliée à une source 18 de liant hydraulique, à une source 19 de composition B, et à une sortie 24 du séparateur 23. L’entrée 15 de la deuxième chambre 14 est reliée à la source 20 de composition A. Le broyeur 1 est configuré pour que de l’air puisse circuler depuis l’entrée 13 de la première chambre vers la sortie 16 de la deuxième chambre 14. La sortie 16 de la deuxième chambre 14 est reliée :

à un filtre 21 configuré pour filtrer l’air et renvoyer les particules filtrées vers l’entrée 22 d’un séparateur 23, et

à l’entrée 22 du séparateur 23 apte à séparer des particules selon leur granulométrie et muni de deux sorties : une sortie 24, qui est reliée à l’entrée 13 de la première chambre 12 et une sortie 25.

Les points 1 , 2, 3, 4, 5 et 6 ne correspondent pas à des éléments de l’unité, mais indiquent les différents endroits où les échantillons ont été prélevés, en référence aux exemples qui suivent.

Dans les exemples qui suivent, les agents de mouture A et B ont été introduits selon des méthodes variables, soit en première chambre 12 par l’entrée 13, soit au niveau de la grille de décharge dont est munie la sortie 16 de la deuxième chambre, soit à ces deux endroits soit au niveau de la grille de décharge dont est munie la sortie 16 de la deuxième chambre, soit à ces deux endroits. Les expériences réalisées mettent en évidence la répartition de l’agent de mouture A comprenant un aminoalcool ou de l’agent de mouture B comprenant un alkylène glycol, et leur impact sur la granulométrie et l’écoulement du ciment, ainsi que les débits de matière dans le procédé et démontrent l’intérêt d’introduire l’agent de mouture A dans la deuxième chambre 14 du broyeur horizontal 1 1.

EXEMPLE 1

Matériaux

Le ciment étudié était de type CEM I 42.5R (94% de clinker ; 5,5% gypse ; 5,5% calcaire).

Les agents de mouture ont été formulés spécifiquement pour l’étude. Leurs compositions sont fournies dans le tableau 1 ci-dessous :

Tableau 1 : Composition des agents de mouture A et B utilisés dans l’exemple 1.

[Table 1]

L’unité de broyage utilisée est telle qu’illustrée à la figure 2.

Le broyeur horizontal 1 1 utilisé comprenait deux chambres séparées par un diaphragme 17.

Pour un ciment sans agent de mouture, ainsi que sur les ciments contenant chacun des agents de mouture à différentes concentrations, des échantillons ont été prélevés aux différents points du circuit présentés sur la Figure 2, une fois l’état d’équilibre atteint sur la ligne de broyage.

De plus, pour les ciments contenant les agents de mouture, des prélèvements ont été effectués tous les 1 ,2 m dans la première chambre 12 du broyeur horizontal 1 1 et tous les mètres dans la seconde chambre.

Dans ce premier exemple, l’agent de mouture est injecté sous forme liquide par goutte à goutte sur la trémie d’alimentation de liant hydraulique. Le mélange de liant hydraulique et d’agent de mouture a été introduit à l’entrée 13 du broyeur horizontal 1 1 .

Le tableau 2 ci-dessous récapitule les différents prélèvements analysés.

Tableau 2 Prélèvements effectués le long de la ligne de broyage - dosages initiaux

[Table 2]

* Dosage en matière active, sans prise en compte de l’eau

L’essai T3, sans agent de mouture, est la référence de l’étude. Les différents dosages initiaux seront nommés D1 , D2 et D3 ci-après.

Méthodes

Malaxage :

Un malaxeur Kenwood KVC5305S chef Elite a été utilisé pour mélanger le ciment et l’eau ultra pure au ratio eau/ciment (« E/C » ci-après) souhaité. 400 g de ciment ont été introduits dans l’eau ultra pure préparée dans le bol du malaxeur selon la séquence indiquée au tableau 3 :

Tableau 3 Protocole de malaxage

[Table 3]

Lorsqu’il y avait beaucoup de particules grossières dans le ciment, le malaxage a été réalisé à la main. Le ciment a été introduit dans l’eau ultra pure pendant 30 s puis la pâte a été mélangée avec une spatule pendant 2 min.

Dosage des agents de mouture :

Le dosage des agents de mouture a été obtenu par lavage du ciment et mesure de la concentration en carbone dans le jus de ciment.

Le ciment a été mixé avec de l’eau ultra pure suivant le protocole de mélange décrit ci-dessus, puis laissé 30 min au repos. Après homogénéisation manuelle, le coulis a été filtré au Büchner, et le filtrat a été récupéré dans un tube à hémolyse après filtration à 0,2 pm, et acidifié pour s’affranchir de toute carbonatation. Ces solutions ont ensuite été passées à l’analyseur de Carbone Organique Total (« COT » ci-après) pour y déterminer les concentrations en carbone.

La quantité de carbone présente dans le ciment sans agent de mouture a été déduite des mesures effectuées sur les ciments contenant l’agent de mouture.

Afin de vérifier que l’agent de mouture ne présente pas d’isotherme d’adsorption sur la phase solide dans l’eau, les mesures ont été réalisées à deux rapports eau/ciment E/C : 0,4 et 0,6, pour des échantillons de particules fines prélevés à la sortie 25 du séparateur E/C (essais T3, T6, T9, point (6) du circuit de broyage). En l’absence d’isotherme d’adsorption, le ratio carbone en solution/ciment ne dépend pas du rapport E/C initial, et la totalité de l’agent de mouture est dosé.

La mesure de Carbone Organique Total (COT) a été effectuée sur les filtrats acidifiés avec l’analyseur SHIMADZU TOC-VCPN. Le COT a été calculé par différence entre la quantité en carbone total (obtenue par carbonisation de la solution et mesure de la quantité de CO2 dégagée à l’infra-rouge) et la quantité de carbone inorganique (obtenue par acidification de la solution à pH < 1 et dégagement du CO2 dissout par bullage à l’air synthétique). Une courbe de calibration effectuée sur chacun des agents de mouture a permis de déterminer leur concentration dans les jus de ciment. Elle est exprimée en g/L.

Résultats

Les quantités d’agent de mouture sont exprimées en ppm (g sec d’agent de mouture par tonne de ciment) ou en g/m2 (g sec d’agent de mouture par mètre carré de surface de ciment).

Etalonnage du COT

Les courbes d’étalonnage obtenues pour l’agent de mouture A comprenant un aminoalcool et pour l’agent de mouture B comprenant un alkylène glycol présentaient un coefficient de corrélation de 1 , et ont donc pu être utilisées pour calculer la quantité en agent de mouture à partir de la quantité de COT mesurée dans les échantillons.

La concentration en agent de mouture A (CA) comprenant un aminoalcool a ainsi calculée à partir de la valeur de COT selon :

CA = 0,0019 * COT + 0,01 15

La concentration en agent de mouture B (CB) comprenant un alkylène glycol a ainsi calculée à partir de la valeur de COT selon :

CB = 0,0026 * COT + 0,01 1 1

Vérification du lavage du ciment

Afin de s’assurer de l’absence d’isotherme d’adsorption des agents de mouture sur le ciment, des mesures de COT ont été réalisées à deux rapports E/C : 0,4 et 0,6, pour les essais T6 et T9, aux points (6) et les résultats étaient les suivants :

Tableau 4 Efficacité du lavage du ciment - Valeur de COT en fonction du rapport E/C

[Table 4]

Les résultats montrent que les valeurs de COT ne sont pas sensiblement dépendantes du rapport E/C. Les agents de mouture ne s’adsorbent pas à la surface des particules de ciment, et le lavage est donc efficace pour rendre compte de la quantité d’agent de mouture dans les différents échantillons.

Pour les expériences décrites ci-après, les ciments ont été analysés au rapport E/C de 0,4 pour avoir une plus forte concentration de carbone en solution.

TOC on samples not containing grinding agent - T3 test

The TOC was measured at points (2), (3), (4), (5) and (6) of the grinding line and inside the horizontal mill 1 1, on the samples ground without grinding agent (reference). The TOC values ​​related to the weight of cement are given in Tables 5 to 7:

Table 5 TOC values ​​on the different samples outside the mill

[Table 5]

Table 6 TOC in the mill 1 st room

[Table 6]

Table 7 TOC in the mill, 2 nd chamber

[Table 7]

Cement samples from tests performed without grinding agent contained less than 5 ppm TOC along the grinding line.

In the corresponding samples containing grinding agent from the experiments described below, this amount was subtracted in order to account for only the grinding agent.

TOC on samples ground with grinding agents

The results are expressed as a dry dosage of grinding agent per tonne of cement or ppm.

Influence of the Initial dosage

Each grinding agent was introduced at three initial dosages D1, D2 or D3 (Table 2). The quantities of grinding agent measured in the various samples of cement are presented in Table 8 below.

Table 8: Active material by weight of cement for each sample

[Table 8]

It was thus observed that:

- La quantité d’agent de mouture dans le ciment aux différents points de la ligne de broyage augmente avec le dosage initial, à l’exception du filtre 21 dans lequel le dosage mesuré pour le dosage D1 est supérieur à celui mesuré pour le dosage D2, quel que soit l’agent de mouture.

- Dans le filtre 21 , pour l’agent de mouture A comprenant un aminoalcool, au dosage D1 , la quantité d’agent de mouture mesurée dans le ciment est supérieure au dosage initial.

Les inventeurs supposent que cet excès pourrait être dû à la quantité d’agent de mouture qui se trouve à la surface des particules du refus du séparateur réinjectées sur la ligne de broyage ou à l’adsorption de l’agent de mouture en suspension dans le circuit.

- Le dosage en agent de mouture sur les grosses particules (celles du refus du séparateur renvoyé vers le broyeur horizontal 1 1 ) est plus faible que celui sur les particules de petite taille (Fines issues du séparateur). Plus précisément, les inventeurs ont observé que pour les deux agents de mouture, la quantité de matière active des agents de mouture mesurée dans les différents échantillons est corrélée à la surface spécifique des particules de ciment, selon l’équation suivante :

- quantité de matière active (en g/t) =

- 0,0329 * (surface spécifique du ciment (en cm2/g)) - 1 ,637

avec un coefficient de corrélation R2 de 0,9528.

Les quantités d’agent de mouture mesurées ont donc été ramenées à la surface spécifique des particules, et représentées au tableau 9 ci-dessous.

Tableau 9 : Matière active par m2 de ciment pour chacun des prélèvements

[Table 9]

Exprimé en g par m2 de ciment, l’écart entre les quantités d’agent de mouture aux différents points du circuit est amoindri, pour un même dosage initial : la surface spécifique des particules de ciment, et donc leurs granulométries, régit les interactions entre les agents de mouture et le ciment.

Efficacité du séparateur - fish-hook (b) et complément du bypass (C)

The Tromp curve describes the efficiency of a separator. It is calculated for each granular class as the ratio between the flow rate of the waste from the separator (returned to the horizontal grinder 1 1) and the flow rate of the feed to the separator. In the case of perfect efficiency of the separator, the percentage of rejection would be zero until the maximum acceptable particle size is reached, then equal to 100%. In real cases, the Tromp curve of the separator presents the shape of figure 3.

The bypass shows that there is, for all the granular classes, a fraction of particles always reinjected into the horizontal grinder 1 1. The efficiency of the separator is described by:

C = 1 -bypass

the higher C the separator is all the more efficient.

The “Fish Hook” is the part of the curve for which the particle size is smaller than that corresponding to the bypass, and accounts for the leakage of fines to the horizontal grinder 1 1. The lower its slope (b), the less the quantity of fines which returns to the horizontal crusher 11 is important, and the better the efficiency of the separator.

The results shown in Figure 4 and Figure 5 show that the efficiency of the separator depends on the grinding agent used:

C is always higher and b lower with the grinding agent A comprising an aminoalcohol,

b exhibits a non-monotonic variation with the initial dosage of grinding agent B comprising an alkylene glycol and decreases monotonically as the initial dosage of grinding agent A comprising an amino alcohol increases

a limit efficiency of the separator is reached from the intermediate dosage of grinding agent A comprising an aminoalcohol (C no longer varies, b stabilizes)

Inside the crusher - T6 and T9 tests

Samples were taken every 1.2 m in the first chamber 12 and every meter in the second. The dosages of grinding agents per m 2 of cement are shown in Figure 6.

For the grinding agent B comprising an alkylene glycol, the quantity decreases slightly in the first chamber 12 to drop and stabilize in the second chamber 14. For the grinding agent A comprising an aminoalcohol, this quantity increases in the first chamber. 12 and also stabilizes in the second chamber 14.

In the first chamber 12 of the horizontal mill 11, the amount of grinding agent per weight of cement does not change linearly with the specific surface of the cement. This relation becomes true from the second chamber, as shown in Figure 7.

Inside the horizontal mill 11 the two grinding agents differ in the first chamber 12, the grinding agent B comprising an alkylene glycol being more abundant per unit area than the grinding agent A comprising an aminoalcohol. The amount of grinding agent per unit of cement surface stabilizes in the second chamber of the horizontal mill 11, and the difference between the two grinding agents is reduced.

EXAMPLE 2

Materials

The cement studied was of type CEM I 42.5R (94% clinker; 5.5% gypsum; 5.5% limestone).

The grinding agents were formulated specifically for Example 2. Their compositions are provided in Table 10 below. The grinding agent B1 is identical in nature to the grinding agent A. The grinding agent B2 is different.

Table 10: Composition of the grinding agents A, B 1 and B2 used in Example 2.

[Table 10]

The grinding unit used is as shown in Figure 8. Figure 8 is identical to Figure 1, except that:

- sampling points 2 to 6 are shown in figure 8,

the inlet 15 of the second chamber 14, which is connected to the source 20 of composition A, is at the level of the discharge grid with which the outlet 16 of the second chamber is provided. Entrance 15 and exit 16 are therefore at the same place.

The horizontal mill 1 1 used included two chambers separated by a diaphragm 17.

Dans ce second exemple, il, est démontré l’intérêt d’injecter des agents de mouture dans chacune des deux chambres.

Différents cas ont été testés :

- soit aucun agent de mouture n’a été injecté (référence - essai T 1 ),

- soit l’agent de mouture B1 a été injecté par l’entrée 13 de la première chambre et aucun agent de mouture n’a été injecté dans la deuxième chambre (comparatif - essais T2, T3 et T4),

- soit aucun agent de mouture n’a été injecté dans la première chambre et l’agent de mouture A a été injecté par au niveau de la grille de décharge dont est munie la sortie 16 de la deuxième chambre (comparatif - essais T5 et T6),

- soit l’agent de mouture B2 a été injecté par l’entrée 13 de la première chambre et aucun agent de mouture n’a été injecté dans la deuxième chambre (comparatif - essai T8),

- soit un agent de mouture B a été injecté par l’entrée 13 de la première chambre et et l’agent de mouture A a été injecté par au niveau de la grille de décharge dont est munie la sortie 16 de la deuxième chambre, via un tube d’injection dans l’axe de la grille de décharge (invention - essais T7, T9 et T10), avec deux cas distincts :

- soit l’agent de mouture B est B1 (identique à l’agent de mouture A) et les agents de mouture injectés en première et deuxième chambres sont donc de natures identiques (essai T7),

- soit l’agent de mouture B est B2 (différent de l’agent de mouture A) et les agents de mouture injectés en première et deuxième chambres sont donc de natures différentes (essais T9 et T10).

Samples were taken at the various points 2, 3, 4, 5 and 6 of the circuit shown in FIG. 8, once the equilibrium state had been reached on the grinding line.

Table 11 summarizes all the tests carried out, the initial dosages and the injection points.

[Table 11]

The different flow rates at the circuit sampling points were recorded and the circulating load rate calculated as the ratio between the flow rate of fresh material entering the circuit (here 48 tonnes / h in all the tests) and the flow rate of material returning from the circuit. separator from the outlet 24. This rate measures the way in which the process is saturated with material, that is to say its relative size, and directly influences its efficiency. We are trying to reduce this rate to allow ourselves to increase the throughput of the process.

The particle size analyzes of the samples also made it possible to measure the fineness of the cement obtained at the outlet via the rejects on a 45 μm sieve. The lower the refusal, the finer the cement.

The separator bypass values ​​were also recorded during the tests. The higher the parameter C, the better the filtration quality at the separator.

The flow rate at filter 21 was also measured. The filter 21 can easily saturate because it becomes loaded with fine particles. A low flow rate to the filter 21 is therefore preferred.

All the measures are collated in table 12

[Table 12]

The injection of the grinding agent B1 in the first chamber without injecting anything in the second chamber (tests T2 to T4) makes it possible to obtain a fine cement (lower refusal than for the reference test T1) but leads to a strong increase in the circulating charge rate, and a strong degradation of the filtration quality at the separator as shown by the parameter C.

The injection of the grinding agent A in the second chamber,

- either without injecting anything into the first chamber (tests T5 and T6),

- or by injecting the grinding agent B1 into the first chamber (test T7), make it possible to relieve the process, with lower circulating charge rates and better separation factors C than those obtained with tests T2 to T4.

The injection of the grinding agent B2 in the first chamber (test T8) allows a low rate of circulating load and a good quality of filtration in the separator. Nevertheless, the flow rate at the filter 21 is the highest. The T8 test loads this filter more than the T9 and T10 tests, which makes the latter a better compromise.

The most effective combination is the injection of grinding agent B2 in the first chamber and grinding agent A in the second chamber (tests T9 to T10), for which the lowest circulating charge rates, the factors of highest separation C, and cements of acceptable fineness are obtained. The circulating charge rates and the flow rates at the mill outlet filter recorded on tests T9 and T10 make it possible to increase the inlet flow rate, and therefore the general productivity of the process, without running the risk of saturating the process.

Conclusion

These results show that:

the quantity of grinding agent found on the cement particles is essentially governed by the specific surface area of ​​the cement particles as soon as they leave the first chamber 12 of the horizontal grinder 1 1,

The more the initial dosage of grinding agent increases, the more the quantity of grinding agent increases along the grinding line. There is, however, for the grinding agent A comprising an aminoalcohol in intermediate dosage D2, a greater quantity of grinding agent than what is introduced initially. This difference would in fact be due to the fact that the filter 21 selects the particles of smaller size, for which the concentration of grinding agent is the highest because of the developed surface effect.

The loss of grinding agent along the grinding line increases with the initial dosage, which could be explained by a result of dynamic solid-gas adsorption equilibria in the horizontal grinder 11. To limit this loss, it would be necessary to work at a lower dosage, but the grinding agent would not make it possible to optimize the parameters of the horizontal grinder 11 to achieve the desired fineness.

Inside the horizontal mill 11, the two grinding agents differ in their concentrations in the first chamber 12, the grinding agent B comprising an alkylene glycol being the most concentrated.

At the separator, the grinding agent A comprising an amino alcohol has a more favorable effect on the slope of the fish hook (b) and on the complement of the bypass (C) than the grinding agent B comprising an alkylene glycol. The intermediate dosage D2 in grinding agent A comprising an aminoalcohol already makes it possible to reach a plateau of efficiency of the separator, unlike the grinding agent B comprising an alkylene glycol. The injection of the grinding agent A in the second chamber and of the grinding agent B2 in the first chamber made it possible to obtain the best compromise between the efficiency of the

separator, the circulating charge rate, the fineness of the cement and the flow through the filter in comparison with:

- the injection of the grinding agent B1 into the first chamber, without adding the grinding agent in the second chamber,

the injection of the grinding agent B1 in the first chamber and of the grinding agent B2 in the second chamber.

These results show the advantage of introducing the two grinding agents at different places on the grinding line: the grinding agent B at the inlet 13 of the horizontal grinder 1 1 to allow a sufficiently long residence time of the cement. in the horizontal mill 1 1 without removing the fines too quickly, and the grinding agent A comprising an amino alcohol in the second chamber 14 of the horizontal mill 1 1 for better fluidization of the powder in the line of the separator.

CLAIMS

1. Hydraulic binder grinding process comprising:

a) introduction:

a hydraulic binder, and

of a composition B comprising at least one grinding agent B, in the first chamber (12) of a horizontal grinder (1 1) comprising several chambers (12, 14), including a first chamber (12) and a last chamber (14), each chamber (12) being separated from the adjacent chamber (14) by a diaphragm (17),

whereby a composition b comprising the hydraulic binder and the composition B is obtained in the first chamber (12),

b) grinding of composition b in the horizontal mill (1 1), whereby composition b passes from the first chamber (12) to the last chamber (14) and a ground composition C is obtained at the outlet of the last chamber (14), characterized in that it comprises, during the grinding step, the introduction, into the last chamber (14), of a composition A comprising at least one grinding agent A comprising an aminoalcohol, composition A being different from composition b.

2. A method of grinding hydraulic binder according to claim 1, comprising, after step b):

c) the separation, by a separator (23), of the composition C ground into fines and in residue from the separator, where the average size of the particles of the residue from the separator is greater than that of the particles of the fines,

d) recovery of fines,

e) the return of the refusal of the separator in the first chamber (12) of the horizontal crusher (1 1).

3. A method of grinding hydraulic binder according to claim 1 or 2, wherein the horizontal crusher (1 1) has only two chambers (12,14).

4. A method of grinding hydraulic binder according to any one of claims 1 to 3, wherein the hydraulic binder is cement optionally comprising mineral additions.

5. A method of grinding a hydraulic binder according to any one of claims 1 to 4, in which the grinding agent B comprises a polyol, preferably chosen from:

a diol such as an alkylene glycol preferably comprising from 1 to 20 carbon atoms, in particular from 1 to 10 carbon atoms, and the alkylene group of which may bear a methyl, and being typically chosen from 2-methyl- 1, 3- propanediol, monoethylene glycol, diethylene glycol, triethylene glycol, tetraethyleneglycol, propylene glycol and a mixture thereof,

a triol, preferably glycerol, and

a tetraol, preferably erythritol,

or a mixture of these,

preferably the grinding agent B comprises an alkylene glycol preferably comprising from 1 to 20 carbon atoms or a mixture thereof, and optionally glycerol.

6. A method of grinding hydraulic binder according to any one of claims 1 to 5, wherein the grinding agent B comprises:

an aminoalcohol or one of its salts, said aminoalcohol comprising in particular: from 2 to 8 carbon atoms, in particular from 4 to 6 carbon atoms, and / or 1, 2 or 3 alcohol functions,

the aminoalcohol preferably being N-methyldiethanolamine (MDEA), diisopropanolamine (DIPA), triisopropanolamine (TIPA), triethanolamine (TEA), ethanoldiisopropanol amine (EDIPA), diethanolisopropanolamine (DEIPA) or a mixture of those here, and

optionally a carboxylic acid or a salt thereof, for example chosen from acetic acid or one of its salts, formic acid or one of its salts, or a mixture of these.

7. A method of grinding a hydraulic binder according to any one of claims 1 to 6, in which the aminoalcohol of the grinding agent A comprises: from 2 to 8 carbon atoms, in particular from 4 to 6 carbon atoms, and / or 1, 2 or 3 alcohol functions,

the aminoalcohol preferably being N-methyldiethanolamine (MDEA), diisopropanolamine (DIPA), triisopropanolamine (TIPA), triethanolamine (TEA), ethanoldiisopropanol amine (EDIPA), diethanolisopropanolamine (DEIPA) or a mixture of those -this.

8. A method of grinding hydraulic binder according to any one of claims 1 to 7, wherein composition A is introduced into the last chamber:

either at the level of the diaphragm separating the last chamber from the adjacent chamber, or in the enclosure of the last chamber, in an area preferably closer to the diaphragm separating the last chamber from the adjacent chamber than from the outlet of the last chamber,

or at the outlet of the last chamber, preferably at the level of the discharge grid with which the outlet of the last chamber is fitted.

9. Grinding unit intended for implementing the method according to any one of claims 1 to 8, comprising:

a source (18) of hydraulic binder,

a source (19) of composition B comprising at least one grinding agent B, - a source (20) of composition A comprising at least one grinding agent A comprising an aminoalcohol,

a horizontal grinder (1 1) comprising several chambers (12,14), including a first chamber (12) provided with at least one inlet (13) and a last chamber (14) provided with an outlet (16), each chamber (12) being separated from the adjacent chamber (14) by a diaphragm (17),

characterized in that the last chamber (14) is provided with an inlet (15) connected to the source (20) of composition A.

10. Grinding unit according to claim 9, wherein the outlet (16) of the last chamber (14) is connected to the inlet (22) of a separator (23) capable of separating particles according to their particle size and provided two outlets (24,25), one of the outlets (24) being connected to an inlet (13) of the first chamber (12) of the horizontal crusher (1 1).