EA043132B1 - METHOD FOR GRINDING HYDRAULIC BINDER - Google Patents

Description

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

The method for preparing a hydraulic binder includes milling to reduce the particle size of the binder, thereby increasing reactivity and imparting desired rheological properties.

The use of a dispersant added to the material to be ground (grinding additive) makes it possible to increase the yield of the hydraulic binder to be ground. Dispersants added to the material to be ground provide an increase in grinding capacity with the same energy input and the same degree of dispersion, or an increase in the degree of dispersion with the same energy consumption.

When a horizontal multi-chamber grinding mill is used to grind the hydraulic binder, the grinding aid(s) are (are) introduced into the first chamber of the grinding mill together with the hydraulic binder to be ground or separately.

There is a need to develop a method for grinding a hydraulic binder that can improve the quality of the crushed hydraulic binder (in particular, the degree of dispersion according to Blaine and/or particle size distribution) and/or improve the yield of the crushed material to reduce costs.

To accomplish this task, the first object of the invention is a method of grinding a hydraulic binder, including:

a) introducing a hydraulic binder, and composition B, containing at least one dispersant B added to the material to be ground, into the first chamber of a horizontal grinder containing several chambers, including the first chamber and the last chamber, each chamber being separated from the adjacent chamber by a diaphragm, at the same time, composition β is obtained in the first chamber, containing a hydraulic binder and composition B,

b) grinding composition β in a horizontal grinder, wherein the composition β is transferred from the first chamber to the last chamber, and at the outlet from the last chamber, a crushed composition C is obtained, characterized in that during the grinding step it includes introducing into the last chamber composition A containing at least one dispersing agent A added to the ground material containing an amino alcohol, wherein the composition A differs from the composition β.

The method uses a horizontal shredder containing multiple chambers (sometimes referred to as compartments), including a first chamber and a last chamber, each chamber separated from the adjacent chamber by a diaphragm. Typically, the chambers are of the same diameter and/or the last chamber is longer than the first. Preferably, the grinding bodies in the mill (metal balls...) differ in size from one chamber to another.

The first chamber is the chamber in which the hydraulic binder to be ground is placed. The last chamber is the chamber from which the ground composition C exits the grinder. The ground composition C contains a ground hydraulic binder, a dispersant A, and a dispersant B added to the ground material.

During the grinding process, the hydraulic binder moves from the first chamber to the adjacent chamber until it reaches the last chamber. The diaphragm separating two adjacent chambers allows only hydraulic binder particles to pass that are sufficiently reduced in size for finer grinding in the next adjacent chamber. Thus, the particle size of the hydraulic binder is largest in the first chamber and smallest in the last chamber.

Typically, a chopper has only two chambers: the first chamber and the last chamber (which in this case is the second chamber) separated by a diaphragm.

The grinder is usually a ball mill. The average ball diameter in the first chamber is usually larger than the average ball diameter in the last chamber.

The method includes step a) for introducing a hydraulic binder and composition B containing at least one dispersant B into the first chopper chamber.

By the term "hydraulic binder" is meant any compound having the property of hydration in the presence of water, the hydration of which makes it possible to obtain a solid having mechanical characteristics. The hydraulic binder may be a cement in accordance with EN 197-1 of 2012, and in particular of type CEM I, CEM II, CEM III, CEM IV or CEM V in accordance with NF EN 197-1 for cement of 2012. Therefore, the cement may in particular contain mineral additives.

The expression mineral additives means slag (as defined in NF EN 197-1 standard for cement of 2012, paragraph 5.2.2), steelmaking slag, pozzolanic materials (such as defined in NF EN 197-1 standard for cement paragraph 5.2.3), fly ash (e.g. as defined in NF EN 197-1 cement standard, paragraph 5.2.4), calcined shale (e.g. as defined in NF EN 197-1 cement standard, paragraph 5.2.5 ), limestone (eg as defined in cement standard NF EN 197-1 paragraph 5.2.6) or fumed silica (such as defined in NF EN 197-1 cement standard paragraph 5.2.7) or compositions thereof. Other additives may also be used which are not currently recognized by the NF EN 197-1 standard for cement (2012). These are mainly metakaolins, such as type A metakaolins, according to NF P 18-513 2012, and siliceous additives of mineralogical composition Qz, according to NF P 18-509 2012.

In the first embodiment of the invention, the dispersing agent B contains a polyol, preferably selected from the following:

a diol such as an alkylene glycol, preferably having 1-20 carbon atoms, in particular 1-10 carbon atoms, its alkylene group, optionally bearing methyl and usually selected from 2-methyl 1,3-propanediol, monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol and mixtures thereof, triol, preferably glycerol, tetraol, preferably erythritol, and mixtures thereof.

The dispersing agent B added to the material to be ground contains, for example, an alkylene glycol or a mixture of alkylene glycols and optionally glycerol, the glycerol being preferably contained in a proportion of 0-5% by weight relative to the weight of the assembly (glycerol and alkylene glycol (alkylene glycols)).

The dispersant B added to the material to be ground (and formulation B) is preferably free of amino alcohols, in particular one of the amino alcohols listed below.

In a second embodiment of the invention, the dispersing agent B added to the material to be ground contains an amino alcohol or one of its salts, said amino alcohol preferably containing from 2 to 8 carbon atoms, in particular 4 to 6 carbon atoms, and/or

1, 2 or 3 alcohol groups selected, for example, from N-methyldiethanolamine (MDEA), diisopropanolamine (DIPA), triisopropanolamine (TIPA), triethanolamine (TEA), ethanoldiisopropanolamine (EDIPA), diethanolisopropanolamine (DEIPA) and mixtures thereof. For example, dispersant B contains triisopropanolamine (TIPA), triethanolamine (TEA), or a mixture thereof. Preferred amino alcohol salts are hydrochlorides such as TEA-HCl, TIPA-HCl, EDIPA-HCl and DEIPA-HCl.

In this second embodiment, the dispersant B added to the material to be ground (and composition B) preferably does not contain a polyol, and in particular one of those listed above.

This second embodiment is particularly well suited for grinding soft hydraulic binders on which polyols can cause agglomeration which is detrimental to grinding and should therefore be avoided.

In a third embodiment of the invention, the dispersant B added to the material to be ground contains a polyol and an amino alcohol.

In the second and third embodiments of the invention (when the dispersant B contains an amino alcohol), the dispersant B added to the ground material may contain a carboxylic acid or a salt thereof selected, for example, from acetic acid and one of its salts, formic acid or one of its salts, or mixtures thereof. The dispersing agent B added to the material to be ground in this case contains an amino alcohol, a carboxylic acid or a salt thereof, and optionally a polyol. The salt may be a salt formed from an amino alcohol and a carboxylic acid. The carboxylic acid generally allows the dispersing power of Formulation B to be adjusted, this power is sometimes too strong when the amino alcohol is used without the carboxylic acid.

The dispersant B added to the material to be ground is the active material of composition B. The composition B may contain one or more dispersants B.

In addition to the dispersant B, formulation B may contain a solvent, typically water. Composition B may consist of an aqueous solution of at least one dispersing agent B (this adjuvant preferably consists of one or more polyols, one or more amino alcohols or a mixture thereof, and optionally one or more carboxylic acids or a salt thereof, when the dispersant contains and amino alcohol), even from a mixture of water and dispersant B.

The proportion of dispersing agent B added to the material to be ground, which is introduced into the first chamber in step a), is usually 50-2500 g, in particular 75-500 g, preferably 90-250 g, per ton of hydraulic binder fed into the first chamber in step A). Below this value, the effectiveness of the dispersant decreases, and above this value the costs become too high. The percentage indicated refers to the dry dispersant without taking into account any solvent or optional other additives in composition B. When composition B contains several dispersants B added to the material to be ground, the sum of their relative contents (shares) is taken into account.

The supply of hydraulic binder and composition B may or may not be simultaneous. In addition, the supply of hydraulic binder and composition B can be carried out through separate inlets of the first chamber or through the same inlet. For example, the first chamber may be loaded with composition β containing a hydraulic binder and composition B (introducing the hydraulic binder and composition B at the same time 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 a hydraulic binder feed hopper, for example through a spray frame with nozzles or through a pipe that carries droplets into the hydraulic binder feed hopper. In this case, composition β is introduced into the first chamber of the horizontal grinder.

The method comprises the step b) grinding the composition β in the grinder, whereby the composition β moves from the first chamber to the last chamber, and the crushed composition C is obtained at the outlet from the last chamber. Therefore, the average particle size of composition C is smaller than that of composition β. Particle size measurement can be done by laser particle size measurement to obtain a particle size distribution, or by pressure sieving, which typically gives the mass fraction of rejected particles on a particular sieve mesh, typically 32, 45 and/or 63 µm (with the understanding that that you must use the same measurement method to compare sizes).

In the grinding step b) of the process according to the invention, a composition A containing at least one dispersant A added to the material to be ground containing an amino alcohol is introduced (injected) into the last chamber of the grinder.

Usually, composition A is injected (injected) into the last chamber:

or at the diaphragm separating the last chamber from the adjacent chamber, or within the enclosure of the last chamber in an area usually closer to the diaphragm separating the last chamber from the adjacent chamber than to the outlet from the last chamber, or at the outlet from the last chamber, usually on the discharge grate, which is equipped with an outlet from the last chamber.

This method uses at least two dispersing agents A and B, which are introduced at different points in the grinder, one into the first chamber and the other into the last chamber.

The inventors have shown that the dispersing agents A and B added to the material to be ground are not distributed in the same way within the grinding device: the dosage of the dispersing agent along the grinding device varies depending on the type of dispersing agent. When both dispersants added to the material to be ground are introduced into the first chamber, as in the prior art:

the amount of dispersant added to the material to be ground and present on the particles of the hydraulic binder is mainly determined by the specific surface area of the particles of the hydraulic binder as soon as they leave the first chamber of the grinder;

inside the first chamber of the grinder, when the dispersant B added to the grinded material contains alkylene glycol, it is more present per unit surface area of the hydraulic binder than the dispersant A added to the grinded material containing amino alcohol, the amount of dispersant added to the grinded material, per unit surface area of the hydraulic binder is stabilized in the second chamber of the grinder, and the difference between the two dispersants is reduced in the last chamber.

A dispersant added to the ground material containing an amino alcohol generally has a good ability to fluidize the particle stream, which cannot be said for a dispersant containing an alkylene glycol. Without wishing to be bound by any particular theory, in light of the following examples, the inventors assume that the dispersants added to the material to be ground are carried by hydraulic binder particles with high specific surface area and hence small particle size;

this effect will be enhanced if the dispersant has a thinning effect, as in the case of dispersant A containing an amino alcohol, which increases the flow rate of the small size hydraulic binder particles. Dispersant A added to the material to be ground containing an amino alcohol is therefore less common in the first grinding chamber of the grinder, which contains large size hydraulic binder particles.

This demonstrates the advantage of introducing two grinding aids in different

- 3 043132 points of the grinding line: dispersant B added to the ground material in the first chamber to ensure a sufficiently long residence time of the hydraulic binder in the grinder, and dispersant A added to the ground material containing amino alcohol in the last chamber to remove particles small size from the grinder and/or to fluidize the particles of the crushed composition C, thereby improving its subsequent processability and facilitating any subsequent separation (the second alternative is described below).

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

The dispersing agent A added to the material to be ground contains at least one amino alcohol, preferably containing from 2 to 8 carbon atoms, in particular 4 to 6 carbon atoms, and/or 1, 2 or 3 alcohol groups, for example selected from the following : N-methyldiethanolamine (MDEA), diisopropanolamine (DIPA), triisopropanolamine (TIPA), triethanolamine (TEA), ethanoldiisopropanolamine (EDIPA), diethanolisopropanolamine (DEIPA) and mixtures thereof. For example, dispersant A contains triisopropanolamine (TIPA), triethanolamine (TEA), or a mixture thereof.

The dispersing agent A added to the material to be ground may contain a carboxylic acid or a salt thereof selected, for example, from acetic acid or one of its salts, formic acid or one of its salts, or a mixture thereof. Thus, the dispersing agent A contains an amino alcohol and a carboxylic acid or a salt thereof. The salt may be a salt formed from an amino alcohol and a carboxylic acid. The carboxylic acid generally allows the dispersing power of mixture A to be controlled, which is sometimes too strong when the amino alcohol is used without the carboxylic acid.

In one embodiment, the dispersant A added to the material to be ground is the same as the dispersant B. Composition A may be the same as composition B.

In another embodiment, the dispersant A added to the material to be ground is different from the dispersant B. Composition A is different from composition B.

Dispersant A added to the ground material is the active material of Formulation A. Formulation A may contain one or more dispersants A added to the ground material.

In addition to the dispersant A, formulation A may contain a solvent, typically water. Composition A may consist of an aqueous solution of at least one dispersant A, even a mixture of water and dispersant A.

The proportion (percentage) of dispersing agent A added to the material to be ground, introduced into the last chamber in step b) is usually 50-2500 g, in particular 75-500 g, preferably 90-250 g, per tonne of hydraulic binder fed into the first chamber at step a). Below this value, the effectiveness of the dispersant decreases, and above this value, the costs become too high. This proportion refers to the dry dispersant without taking into account any solvent and optional other additives to composition A. When composition A contains several dispersants A added to the material to be ground, the sum of their proportions is taken into account.

In the grinding step b) air can be circulated from the first chamber towards the last chamber. Air enters through the first chamber and exits through the last chamber. This air makes it possible to displace the most volatile particles of the composition β subjected to grinding. After step b) the method may include:

i) filtering the air leaving the last chamber, thereby recovering the most volatile hydraulic binder particulates; then ii) bundling the recovered most volatile particles with pulverized composition C, typically in a stream under an air stream.

In a first alternative, after step b) the method comprises step b1) of recovering the pulverized composition C. The pulverized composition C then has the desired size/specific surface area. In this case, the method may be carried out using a continuous, semi-continuous or batch process.

In this first alternative, the main advantage of introducing composition A, containing at least a dispersant A added to the ground material containing amino alcohol, into the last chamber is to allow the ground composition C to be fluidized, which improves its subsequent processability, since the ground composition C is more fluid, facilitating the flow of the composition, for example into a bunker, or when loading or unloading a truck. In general, the required dosage of dispersant A containing an amino alcohol to obtain a suitable fluidity of the milled formulation C is higher than the dosage required to efficiently mill the hydraulic binder. Therefore, it is preferable to introduce dispersing agent A into the last chamber of the grinder, including in the embodiment of the invention, in

- 4 043132 in which the dispersing agent A is introduced at the outlet of the last chamber, as a rule, on the discharge grate, which is equipped with the outlet of the last chamber.

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

c) separating, by means of a separator, the pulverized composition C into fine particles and reject particles of the separator, wherein the average size of the particles rejected from the separator is larger than that of the fine particles;

d) recovery of fine particles;

e) returning the rejected particles of the separator to the first chamber of the horizontal grinder.

In this second alternative, the method includes step c) separating between finely divided composition C and discarded separator particles. The inventors have shown that:

the separation is more effective, the greater the amount of dispersant A or B, until the maximum efficiency is reached;

separation efficiency depends on the dispersing agent used, added to the ground material. Separation is more effective with dispersant A containing an amino alcohol than with a dispersant containing a polyol.

Therefore, the introduction of the dispersant A containing amino alcohol into the last chamber of the grinder makes it possible to better liquefy the ground composition C during the separation and makes the separation more efficient.

In addition, the introduction of composition A, containing at least one dispersant A containing amino alcohol, into the last chamber also has the advantage of fluidizing the ground composition C and recovered fine particles, which improves its subsequent processability, since fine particles have a greater fluid flow. environment, such as in a bunker or while loading or unloading a truck. In general, the required dosage of dispersant added to the amino alcohol containing material to be ground to obtain acceptable fluidity of the recovered fines is greater than that required to effectively grind the hydraulic binder.

In this second alternative, steps i) and ii) as defined above are preferably followed by step iii) for returning the particles grouped with the ground composition C back to the separator. Steps i), ii) and iii) are performed between steps b) and c).

In this second alternative, fine particles are recovered in step e). It is a mixture of hydraulic binder, ground to the desired size/specific surface area, which is obtained using this method. Typically, when the hydraulic binder is cement, the specific surface area of the fine particles measured by the Blaine method is in the order of 3200-4500 cm ² /g.

The discarded separator particles contain particles that are too large for the desired size. They return to the first grinding chamber for re-grinding. Therefore, composition β contained in the first chamber contains, even consists of a hydraulic binder, rejected separator particles and composition B (given that the rejected particles contain a hydraulic binder, a dispersant A added to the material to be ground, and a dispersant B, added to the crushed material).

In general, in this second alternative, the grinding process is a continuous process.

The second object of the invention is a grinding device designed to implement the method of the invention, containing a source of hydraulic binder;

a source of composition B containing at least one dispersant B added to the material to be ground;

a source of composition A containing at least one dispersing agent A added to the ground material containing an amino alcohol;

a horizontal grinder containing several chambers, including a first chamber having at least one inlet and a last chamber having an outlet, each chamber being separated from an adjacent chamber by a diaphragm, characterized in that the last chamber is equipped with an inlet connected to a composition source A.

The above-described embodiments of the invention are applicable, in particular, to the grinder.

As a rule, the last chamber extends from the diaphragm that separates the last chamber from the adjacent chamber, to the discharge grate, which allows the crushed composition C to be discharged from the grinder. Typically, the inlet of the last chamber connected to the source of composition A is positioned:

or at 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 to the outlet from the last chamber;

- 5 043132 or on the outlet from the last chamber, usually on the discharge grate, which is equipped with the outlet from the last chamber.

If the grinder is a ball grinder, the outlet of the last chamber is usually equipped with a discharge grate configured to prevent the grinding balls from escaping from the grinder.

Typically, a grinder has only two chambers: a first chamber and a last chamber (which in this case is the second chamber) separated by a diaphragm.

The chopper is typically configured to allow air to circulate from the inlet of the first chamber towards the outlet of the second chamber. The grinding device contains a filter connected to the outlet of the last chamber and is configured to filter air and extract the most volatile particles of the crushed hydraulic binder.

In the first alternative, the grinding device does not have a separator. This first alternative chopping device makes it possible to realize the first alternative variant of the method described above.

In this first alternative arrangement, the filter, if any, is configured to filter air to extract the most volatile particles of the hydraulic binder to be ground and return them to the ground composition C.

In this first alternative, the first chamber is either equipped with one inlet connected to a source of hydraulic binder and a source of composition B, or equipped with two inlets, the first inlet is connected to the source of hydraulic binder, and the second inlet is connected to the source of composition B.

In a second alternative, the grinding device comprises a separator. The separator is typically a dynamic air or rotary chamber cyclone separator, or a static filter separator, or a combination of the two. The outlet of the last chamber of the grinder is usually connected to the inlet of a separator capable of separating particles according to size and is provided with two outlets, one of the outlets being connected to the inlet of the first chamber of the horizontal grinder. This second alternative of the shredding device makes it possible to realize the second alternative of the method described above. In this case, the grinding device comprises a closed circuit, since the outlet of the last grinding chamber 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 or is equipped with one inlet connected to a source of hydraulic binder, to a source of composition B, and to a separator outlet;

or equipped with two inlets, the first inlet is connected to the source of hydraulic binder and the source of composition B, and the second inlet is connected to the outlet of the separator;

or equipped with three inlets, the first inlet is connected to a source of hydraulic binder, the second inlet is connected to the source of composition B, and the third inlet is connected to the outlet of the separator.

In this second alternative arrangement, the filter, if any, is positioned between the last chopper chamber and the separator. The filter is designed to filter air, extract the most volatile particles of the hydraulic binder and return them to the separator.

The invention is illustrated in conjunction with the following examples and the accompanying figures.

figures

Fig. 1 is a block diagram of a shredding device according to a second alternative embodiment of the invention.

Fig. 2 is a block diagram of a prior art grinder and how it is used in Example 1, showing sampling points 1, 2, 3, 4, 5 and 6 for Example 1.

Fig. 3 is an example of a Tromp curve. Percentage of rejected separator particles returned to the grinder, as a function of particle size in µm.

Fig. 4 shows separator efficiency C as a function of the amount of dispersant added to the material to be ground, introduced into the separator, for each dispersant and each metered portion of the dispersant, measured in m ² of cement. The values indicated on the graphs correspond to the initial dry dosages in ppm (parts per million) of the dispersant in relation to the weight of the cement. Crosses correspond to dispersant A containing amino alcohol, and circles to dispersant B containing alkylene glycol.

Fig. 5 - tilt β of the fish-hook separator depending on the number of dis

- 6 043132 perg added to the crushed material, introduced into the separator for each „ „ „ 2 dispersant and each dosed portion of the dispersant, measured in m of cement. Crosses correspond to dispersant A containing amino alcohol, and circles to dispersant B containing alkylene glycol. The values indicated on the graphs correspond to the initial dry doses of the dispersant in parts per million (ppm) in relation to the weight of the cement.

Fig. 6 is the dosage of dispersant (in dry grams) measured per m ² of cement in the grinder chambers and at various points in the apparatus where samples were taken. Crosses correspond to dispersant A containing amino alcohol, and circles to dispersant B containing alkylene glycol.

Fig. 7 is the ratio between the amount of dispersant (in dry grams) measured per ton of cement on the samples and the specific surface area of the cement in cm ² /g. Crosses correspond to dispersant A containing amino alcohol, and circles to dispersant B containing alkylene glycol.

Fig. 8 is a block diagram of a grinder according to the second alternative and the positions of the sampling points in Example 2.

In FIG. 1 illustrates a shredding device according to a second alternative of the invention in the case where the shredding device comprises a filter. Horizontal grinder 11 contains two chambers:

a first chamber 12 provided with a first inlet 13; and a second chamber (last chamber) 14 equipped with an inlet 15 and an outlet 16, the first chamber 12 is separated from the second chamber 14 by a diaphragm 17. The inlet 13 of the first chamber 12 is connected to a hydraulic opening 24 of the separator 23. The inlet 15 of the second chamber 14 is connected to the source 20 of composition A. The chopper 11 is configured in such a way that air can circulate from the inlet 13 of the first chamber towards the outlet 16 of the second chamber 14. The outlet 16 of the second chamber 14 connected to a filter 21 configured to filter the air and return the filtered particles to the inlet 22 of the separator 23; and an inlet 22 of the separator 23 capable of separating particles according to particle size and equipped with two outlets; the outlet 24 is connected to the inlet 13 of the first chamber 12, and the outlet 25.

Points 1, 2, 3, 4, 5 and 6 do not correspond to the elements of the device, but indicate various points where samples are taken, with reference to the following examples.

Examples

In the following examples, the dispersing agents A and B added to the material to be ground were supplied in various ways either to the first chamber 12 through the inlet 13, or through the discharge grate provided with the outlet 16 of the second chamber, or both. The experiments carried out prove the distribution of dispersant A containing amino alcohol or dispersant B containing alkylene glycol and their effect on particle size and cement flow, as well as material flow rates in the process, and also show the advantage of introducing dispersant A into the second chamber 14 of the horizontal grinder 11.

Example 1

Materials.

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

The dispersing agents added to the ground material were specially developed for the study. Their compositions are given in table. 1 below:

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Table 1

The composition of the dispersants A and B added to the ground material used in example 1

Connections Active material (%) Dispersant A containing amino alcohol Water Triethanolamine 8.33 Triisopropanolamine (diluted) 33.33 Dispersant B containing alkylene glycol Water diethylene glycol 22.70 Glycerin (diluted) 12.09

The grinding device used is the same as that illustrated in FIG. 2.

The horizontal grinder 11 contains two chambers separated by a diaphragm 17.

For cements without dispersants and for cements each containing dispersants at different concentrations, samples were taken at different points along the contour of the block diagram shown in FIG. 2 after reaching the state of equilibrium reached in the grinding line.

In addition, for cements containing dispersants, samples were taken every 1.2 m in the first chamber 12 of the horizontal grinder 11 and every meter in the second chamber.

In this first example, the dispersant added to the material to be ground, in liquid form, was added dropwise to the hydraulic binder feed funnel. A mixture of hydraulic binder and dispersant was supplied to the inlet 13 of the horizontal grinder 11.

In table. 2 below are the various analyzed samples.

table 2

Samples taken on the grinding line - initial dosages

Trial Dispersant Initial dosage (ppm) Dry* dosage (ppm) Dosage link Samples taken in the grinder Contour samples Items 2, 3, 4, 5, 6) TK No 0 0 X X (standard) T4 Dispersant A containing amino alcohol 250 104 D1 X T5 350 146 D2 X Tb 450 187 D3 X X T7 Dispersant B containing alkylene glycol 300 104 D1 X T8 400 139 D2 X T9 500 174 D3 X X

* Dosage of the active substance excluding water.

Test T3 without dispersant is the reference for the study. Hereinafter, various initial dosages are referred to as D1, D2 and D3.

Ways.

Mixing.

A Kenwood Chef Elite KVC5305S mixer was used to mix cement and ultrapure water at the desired water/cement (W/C) ratio. 400 g of cement was added to ultrapure water prepared in a mixer bowl, following the sequence shown in table. 3.

Table 3

P mixing protocol Time Speed (rpm) Action O’-ZO” 43 powder powder 30”-G 96 Mixing G-GZO 0 Edge trimming 1'30-2'30 96 Mixing

If there were many large particles in the cement, mixing was done manually. The cement was added to ultrapure water for 30 seconds, after which the paste was stirred with a spatula for 2 minutes.

The study of dispersants added to the crushed material.

The study of dispersants added to the ground material was carried out by washing the cement and measuring the carbon concentration in the cement slurry.

The cement was mixed with ultrapure water according to the mixing protocol described above, then left for 30 minutes. After manual homogenization, the solution was filtered through a Buchner and the filtrate was collected in a hemolysis tube after 0.2 µm filtration and acidified to overcome any carbonate formation. These solutions were passed through a total organic carbon (TOC) analyzer to determine the carbon concentration.

The amount of carbon in cement without dispersant was subtracted from measurements made on cements containing dispersant.

To ensure that the dispersant added to the material to be ground does not have an adsorption isotherm on the solid phase in water, measurements were made with two water/cement W/C ratios of 0.4 and 0.6, on samples of fine particles taken at outlet 25 from the W/C separator (tests T3, T6, T9, point (6) on the grinding circuit). In the absence of an adsorption isotherm, the slurry/cement carbon ratio is independent of the initial W/C ratio and all dispersant added to the material to be ground is examined.

Total organic carbon (TOC) was measured on acidified filtrates using a SHIMADZU TOC-VCPN analyzer. TOC was calculated from the difference between the amount of total carbon (obtained by carbonizing the solution and measuring the amount of emitted CO ₂ in the infrared) and the amount of inorganic carbon (obtained by acidifying the solution to pH <1 and releasing the dissolved CO ₂ using sparging with synthetic air). The calibration curve for each of the dispersants made it possible to determine their concentration in cement slurries. It is expressed in g/l.

Results.

The amounts of dispersants are expressed in parts per million (g dry weight of dispersant per ton of cement) or g/m ² (g dry weight of dispersant per square meter of cement surface area).

TOC calibration.

The calibration curves obtained for dispersant A containing amino alcohol and for dispersant B containing alkylene glycol showed a correlation coefficient of 1 and could therefore be used to calculate the amount of dispersant from the amount of TOC measured in the samples.

The concentration of the dispersant A (C _A ) containing the amino alcohol was therefore calculated based on the TOC value according to the expression

Ca \u003d 0.0019 * TOC + 0.0115

The concentration of dispersant B (CB) containing alkylene glycol was therefore calculated based on the TOC value according to

C _B \u003d 0.0026 * TOC + 0.0111

Cement flush test.

To ensure that there is no adsorption isotherm of dispersants on cement, TOC measurements were made with two W/C ratios: 0.4 and 0.6, for tests T6 and T9, at points (6), and the results were as follows:

Table 4

Cement flushing efficiency - TOC value versus W/C ratio

Trial TOC value at W/C 0.4 (ppm) TOC value at W/C 0.6 (ppm) TV (6) 149 146 T9(6) 132 137

The results show that the TOC values are not significantly affected by the W/C ratio. Dispersants added to the ground material do not adsorb on the surface of the cement particles, so washing is effective in determining the amount of dispersants in different samples.

For the experiments described below, the cements were analyzed with a W/C ratio of 0.4 to obtain a higher concentration of carbon in solution.

TOC on samples without dispersant - test T3.

TOC was measured at points (2), (3), (4), (5) and (6) on the grinding line and inside the horizontal grinder 11 on samples crushed without a dispersant added to the grinding material (reference). TOC values related to the weight of cement are given in table. 5-7.

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Table 5

TOC values for various samples taken outside the grinder

Point on the grinding line TOC (parts per million for cement) (2) Excess chopper 2.8 (3) Filter 4.6 (4) Separator feed 3 (5) Rejected separator particles returned to grinder 2.4 (6) Small particles leaving the separator 3.5

Table 6

CBT inside the chopper, 1st chamber

Distance from inlet (m) TOC (parts per million for cement) 0 1.3 1.2 4.2 2.4 2.1 3.6 1.9

Table 7

CBT inside the chopper, 2nd chamber

Aperture distance 17 (m) TOC (parts per million for cement) 0 2.2 1 3.1 2 2.5 3 2.8 4 5.0 5 2.5 5.9 3.1

The cement of the samples in tests conducted without a dispersant added to the ground material contained less than 5 ppm TOC along the grinding line.

In the respective samples containing the dispersant in the experiments described below, this amount was subtracted in order to take into account only the dispersant added to the ground material.

TOC on samples ground with dispersants.

The results are expressed as dry dispersant dosage per tonne of cement or parts per million.

Influence of the initial dosage.

Each dispersant was applied in three initial dosages DI, D2 or D3 (Table 2). The amount of dispersant measured in various samples of cement, are given in table. 8 below.

Table 8

Active material by weight of cement for each of the samples

Initial dosage of dispersant A containing amino alcohol Initial dosage of dispersant B containing alkylene glycol D1 D2 D3 D1 D2 D3 Active material by weight of cement (g/t, BWOC) (2) Excess chopper 65 80 97 61 64 84 (3) Filter 134 108 150 97 92 120 (4) Submission separator 72 86 107 52 63 85 (5) Rejected separator particles returned to grinder 33 35 44 32 37 40

- 10043132

(6) Small particles leaving the separator 92 108 142 93 99 123

It has been observed that:

the amount of dispersant in the cement at various points along the grinding line increases from the initial dosage, except for filter 21, in which the dosage measured for dosage D1 is higher than the dosage measured for dosage D2, regardless of the dispersant.

In the dispersant A filter 21 containing the amino alcohol at a dosage of D1, the amount of dispersant measured in the cement exceeds the initial dosage. The inventors speculate that this excess may be related to the amount of dispersant on the surface of the discarded separator particles being reintroduced into the grinding line, or to adsorption of the dispersant in the slurry in the loop.

The dosage of grinding agent for large particles (rejected separator particles returned to the horizontal grinder 11) is lower than for small particles (fine particles leaving the separator). More specifically, the inventors have observed that for both dispersants added to the material to be ground, the amount of active material of the dispersants measured in different samples correlates with the specific surface area of the cement particles according to the following equation:

amount of active material (g/t) = 0.0329 * (specific surface area of cement (cm ² /g)) - 1.637 with a correlation coefficient R ² of 0.9528.

Thus, the measured amounts of dispersant were related to the specific surface area of the particles and are given in table. 9 below.

Table 9

Active material per m ² of cement for each of the samples

Initial dosage of dispersant A containing amino alcohol Initial dosage of dispersant A containing alkylene glycol D1 D2 D3 D1 D2 D3 active material (2) Excess chopper 2.0 2.5 3.2 2.1 2.5 3.0 (d) per m ² (3) Filter 2.5 2.4 3.1 2.4 2.3 2.9 cement (4) Submission separator 2.1 2.5 3.3 1.7 2.0 2.9 (5) Rejected separator particles returned to grinder 1.9 2.3 3.0 1.8 2.2 2.7 (6) Small particles leaving the separator 2.3 2.7 3.6 2.4 2.6 3.3

Expressed in g per m ² of cement, the difference between the amounts of dispersant at different points in the circuit decreases for the same initial dosage: the specific surface area of the cement particles and therefore the size of these particles determines the interaction between the dispersants and the cement.

Separator efficiency - fish hook (β) and bypass addition (C).

The Tromp curve describes the efficiency of a separator. It is calculated for each particle size class as the ratio between the separator reject stream (returned to the horizontal grinder 11) and the separator feed stream. In the case of an ideal separator efficiency, the percentage of particles rejected will be zero until the maximum allowable particle size is reached, in which case it is equal to 100%. In real cases, the Tromp curve for a separator has the shape shown in FIG. 3.

The bypass indicates that for each particle size class there is a particle fraction that is always reintroduced into the horizontal grinder 11. The efficiency of the separator is described as follows:

C = 1-bypass separator is more efficient, the higher the value of C.

The fish hook is that part of the curve where the particle size is smaller than the size corresponding to the bypass, and indicates the leakage of fine particles towards the horizontal

- 11 043132 grinder 11. The more gentle the slope (β), the smaller the number of returned fine particles to the horizontal grinder 11, and the higher the efficiency of the separator.

The results shown in FIG. 4 and 5 show that separator efficiency depends on the dispersant used:

C is always higher and β lower when using a dispersant A containing an amino alcohol;

β exhibits a non-monotonic change at the initial dosage of the alkylene glycol-containing dispersant B and decreases monotonically when the initial dosage of the amino alcohol-containing dispersant A increases;

the maximum efficiency of the separator is reached at and after an intermediate dosage of the dispersing agent A containing amino alcohol (C no longer changes, β stabilizes).

Inside the grinder - tests T6 and T9.

Samples were taken every 1.2 m in the first chamber 12 and every meter in the second. The dosages of the dispersing agent per 1 m ² of cement are shown in FIG. 6.

For the alkylene glycol containing dispersant B, the amount decreases slightly in the first chamber 12 and then drops and stabilizes in the second chamber 14. For the amino alcohol containing dispersant A, the amount increases in the first chamber 12 and stabilizes in the second chamber 14.

In the first chamber 12 of the horizontal grinder 11, the amount of dispersant by weight of cement does not vary linearly with the specific surface area of the cement. This relationship becomes true starting from the second chamber, as illustrated in FIG. 7.

Inside the horizontal grinder 11, the two dispersants added to the material to be ground differ, in the first chamber 12, the dispersant B containing alkylene glycol is contained in a larger amount per unit surface area than the dispersant A containing amino alcohol. The amount of dispersant per unit surface area of the cement is stabilized in the second chamber of the horizontal grinder 11, and the difference between the two dispersants is reduced.

Example 2

Materials.

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

Dispersants added to the ground material were specially formulated for Example 2. Their compositions are given in table. 10 below. The dispersant B1 is of the same type as the dispersant A. The dispersant B2 is different.

Table 10

Composition of dispersants A, B1 and B2 used in Example 2

Connections Active material (%) Dispersant A containing amino alcohol Water Triethanolamine 8.33 Triisopropanolamine (diluted) 33.33 Dispersant B1 containing amino alcohol Water Triethanolamine 8.33 Triisopropanolamine (diluted) 33.33 Dispersant Β2 containing alkylene glycol Water diethylene glycol 22.70 Glycerin (diluted) 12.09

The grinding device used was as shown in FIG. 8. FIG. 8 is identical to FIG. 1, except that sampling points 2 through 6 are shown in FIG. 8;

the inlet 15 of the second chamber 14, which is connected to the source 20 of composition A, is positioned at the discharge grate supplying the outlet 16 of the second chamber. Therefore, the inlet 15 and the outlet 16 are in the same position.

The used horizontal grinder 11 contains two chambers separated by a diaphragm 17.

This second example shows the advantage of introducing dispersants added to the material to be ground into each of the two chambers.

Various cases have been tested:

or no dispersant was added (reference test T1);

- 12 043132 or dispersant B1 was introduced into the inlet 13 of the first chamber, while the dispersant was not introduced into the second chamber (comparative tests T2, T3 and T4);

or no dispersing agent was introduced into the first chamber, and the dispersing agent A was introduced onto the discharge grate equipped with the outlet 16 of the second chamber (comparative tests - T5 and T6);

or the dispersant B2 was introduced through the inlet 13 of the first chamber, while the dispersant was not introduced into the second chamber (comparative test - T8);

or dispersing agent B was introduced through the inlet 13 of the first chamber, and the dispersing agent A was introduced to the discharge grate, equipped with the outlet 16 of the second chamber, through the injection tube on the axis of the discharge grate (invention - tests T7, T9 and T10) with two separate cases:

or the dispersing agent B is B1 (same as the dispersing agent A) and therefore the dispersants introduced into the first and second chambers are of the same type (test T7), or the dispersing agent B is the B2 agent (different from the dispersing agent A ), and the dispersants introduced into the first and second chambers are of different types (tests T9 and T10).

Samples were taken at various points 2, 3, 4, 5 and 6 of the block diagram circuit illustrated in FIG. 8 after reaching the state of equilibrium reached in the grinding line.

In table. 11 shows all tests carried out, initial dosages and points of administration.

Table 11

1st camera 2nd camera Samples taken in the grinder Samples taken at points 2, 3, 4, 5, 6 Trial Auxiliary B1 dosage (ppm) Auxiliary B2 dosage (ppm) Auxiliary B2 dosage (ppm) T1 (reference) 0 0 0 X X T2 (compar.) 250 0 0 X TK (compar.) 350 0 0 X T4 (compar.) 450 0 0 X X T5 (compar.) 0 0 262 X TB (compar.) 0 0 350 X T7 (invent) 250 0 138 X T8 (compar.) 0 300 0 X T9 (invent) 0 300 FROM X T10 (invent) 0 300 199 X X

Various flows were recorded at the sampling points of the flowchart loop and the percentage circulating load was calculated as the ratio between the flow of fresh material entering the flowchart loop (here 48 t/h in all tests) and the flow of material returned by the separator from the outlet holes 24. This percentage measures the degree of saturation of the process with material, i.e. its relative workload, and directly affects efficiency. Therefore, one should strive to reduce this percentage so that the flow rate of the process can be increased.

Particle size analysis on the samples also measured the fineness of the cement obtained at the outlet through the rejected particles on a 45 µm sieve. The smaller the rejected particles, the finer the cement.

Separator bypass values were also measured during testing. The higher the value of parameter C, the better the filtration quality on the separator.

The flow rate on the filter was also measured. Filter 21 is easily saturated because it is charged with fine particles. Therefore, it is preferable to have a low flow rate on the filter 21.

All measurements are grouped in Table. 12.

- 13 043132

Table 12

Trial Circulating load percentage C=1-bypass Rejected particles at 45 µm Filter flow rate 21 (ton/h) T1 (reference) 44.56% 94% 5.0 19.73 T2 (comparative) 86.67% 90% 4.2 8.28 TK (comparative) 136.96% 83% 2.8 13.53 T4 (compare) 244.75% 73% 1.0 7.25 T5 (compare) 97.02% 89% 3.2 13.38 Tb (comparative) 114.58% 87% 2.0 13.74 T7 (invent) 98.83% 89% 2.0 3.53 T8 (compare) 68.04% 91% 3.4 16.86 T9 (invent) 77.96% 90% 4.0 8.61 T10 (invent) 71.79% 91% 2.8 11.00

The introduction of the dispersant B1 added to the material to be ground into the first chamber without any introduction of the dispersant into the second chamber (tests T2-T4) produces a fine cement (less rejected particles than for the reference test T1), but results in a large increase in circulating load and a strong deterioration in the quality of filtration on the separator, as indicated by parameter C.

Introduction of dispersant A, added to the material to be ground, into the second chamber:

without introduction into the first chamber (tests T5 and T6), or with the introduction of dispersant B1 added to the material to be ground into the first chamber (test T7), allows for a simplification of the process with lower circulation loads and better separation coefficients C than those were obtained in trials T2-T4.

The introduction of the dispersant B2, added to the material to be ground, into the first chamber (test T8) reduces the circulation load and ensures good filtration quality in the separator. However, the flow rate at filter 21 is the highest. The T8 test puts more stress on this filter than the T9 and T10 tests, meaning that the latter offers the best compromise.

The most effective combination is the introduction of dispersant B2 into the first chamber and dispersant A into the second chamber (tests T9 and T10), which achieve the lowest circulating loads, the highest separation coefficients C and cements with an acceptable degree of dispersion. The circulating loads and flow rate at the grinder outlet filter measured in tests T9 and T10 allow the flow rate of the feed materials to be increased, hence the overall throughput of the process, without the risk of saturation of the process.

Conclusion

These results show that the amount of dispersant added to the pulverized material on the cement particles is mainly determined by the specific surface area of the cement particles as soon as they leave the first chamber 12 of the horizontal grinder 11;

the more the initial dosage of the dispersant added to the material to be ground increases, the more the amount of the dispersant increases along the grinding line. However, for the dispersant A added to the ground material containing amino alcohol, in the intermediate dosage D2, there is more dispersant than originally added. This difference may be due to the fact that the filter 21 selects the smallest particles for which the dispersant concentration is the highest, in addition to the developed area effect.

The loss of dispersant added to the material to be ground along the grinding line increases with the initial dosage, which may be the result of gas-solid adsorption at dynamic equilibrium in the horizontal grinder 11. To limit this loss, lower dosages should be used, but the dispersant in this case will not allow to optimize the parameters of the horizontal grinder 11 to achieve the desired degree of fineness.

Inside the horizontal grinder 11, the two dispersants added to the ground material differ in their concentration in the first chamber 12, with the dispersant B added to the ground material containing alkylene glycol being the most concentrated.

In the separator, the dispersant A added to the ground material containing an amino alcohol has a more favorable effect on the slope (β) in the form of a fishhook and on the bypass addition (C) than the dispersant B added to the ground material containing alkylene glycol. The intermediate dosage D2 of the dispersant A containing the amino alcohol already allows an efficiency plateau to be reached in the separator, in contrast to the dispersant B containing the alkylene glycol.

The introduction of dispersant A, added to the ground material, into the second chamber and dispersant B2, added to the ground material, into the first chamber made it possible to obtain the best compromise between separator efficiency, circulating load, cement fineness and filter flow rate compared to the introduction of a dispersing agent. means B1 into the first chamber without supplying a dispersant to the second chamber;

introducing the dispersant B1 into the first chamber and the dispersant B2 into the second chamber.

These results show the advantage of introducing two dispersants added to the material to be ground at different points along the grinding line: the dispersing agent B2 at the inlet 13 of the horizontal grinder 11 to allow sufficient residence time of the cement in the horizontal grinder 11 without removing fines too quickly , and dispersing agent A containing amino alcohol, into the second chamber 14 of the horizontal grinder 11 for better fluidization of the powder in the separator line.

Claims (10)

1. A method for grinding a hydraulic binder, comprising: a) introducing a hydraulic binder, composition B, containing at least one dispersant B added to the material to be ground, into the first chamber (12) of a horizontal grinder (11) containing several chambers (12, 14), including the first chamber (12) and the last chamber (14), with each chamber (12) separated from the adjacent chamber (14) by a diaphragm (17), whereby in the first chamber (12) a composition β containing a hydraulic binder and composition B is obtained, b) grinding the composition β in a horizontal grinder (11), wherein the composition β is transferred from the first chamber (12) to the last chamber (14) and a crushed composition C is obtained at the outlet from the last chamber (14), characterized in that at the stage grinding, it includes introducing into the last chamber (14) composition A containing at least one dispersant A added to the crushed material containing amino alcohol, while composition A differs from composition β. 2. The method of grinding the hydraulic binder according to claim 1, comprising after step b): c) separating with a separator (23) the crushed composition C into fine particles and rejected particles of the separator, where the average particle size of the particles rejected from the separator is larger than that of fine particles; d) recovery of fine particles; e) returning the rejected separator particles to the first chamber (12) of the horizontal grinder (11). 3. Method for grinding the hydraulic binder according to claim 1 or 2, wherein the horizontal grinder (11) has only two chambers (12, 14). 4. A process for grinding a hydraulic binder according to any one of claims 1 to 3, wherein the hydraulic binder is a cement optionally containing mineral additives. 5. A process for grinding a hydraulic binder according to any one of claims 1 to 4, wherein the dispersing agent B added to the material to be ground contains a polyol, preferably selected from the following: a diol, such as an alkylene glycol, preferably having 1-20 carbon atoms, in particular 1-10 carbon atoms, the alkylene group, optionally bearing methyl, being usually selected from 2-methyl-1,3propanediol, monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol and mixtures thereof, a triol, preferably glycerol, and a tetraol, preferably erythritol, or a mixture thereof, preferably a dispersant B, added to the ground material contains an alkylene glycol, preferably containing 1-20 carbon atoms, or a mixture thereof, and optionally glycerin. 6. The method of grinding the hydraulic binder according to any one of claims 1 to 5, wherein the dispersing agent B added to the material to be ground contains - 15 043132 amino alcohol or one of its salts, and the specified amino alcohol, in particular, contains from 2 to 8 carbon atoms, in particular 4-6 carbon atoms, and/or 1, 2 or 3 alcohol groups, the amino alcohol is preferably N- methyldiethanolamine (MDEA), diisopropanolamine (DIPA), triisopropanolamine (TIPA), triethanolamine (TEA), ethanoldiisopropanolamine (EDIPA), diethanolisopropanolamine (DEIPA) or a mixture thereof, and optionally, a carboxylic acid or a salt thereof selected, for example, from acetic acid or one of its salts, formic acid or one of its salts, or mixtures thereof. 7. Method for grinding a hydraulic binder according to any one of claims 1 to 6, wherein the amino alcohol of the dispersing agent A added to the material to be ground contains from 2 to 8 carbon atoms, in particular 4 to 6 carbon atoms, and/or 1, 2 or 3 alcohol groups, the amino alcohol is preferably N-methyldiethanolamine (MDEA), diisopropanolamine (DIPA), triisopropanolamine (TIPA), triethanolamine (TEA), ethanoldiisopropanolamine (EDIPA), diethanolisopropanolamine (DEIPA), or a mixture thereof. 8. The method of grinding the hydraulic binder according to any one of paragraphs.1-7, in which the composition A is introduced into the last chamber; or at 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 to the outlet of the last chamber, or at the outlet from the last chamber, preferably on the discharge grate, which is equipped on the outlet of the last chamber. 9. A grinding device for carrying out the method according to any one of claims 1 to 8, containing a source (18) of a hydraulic binder, a source (19) of composition B containing at least one dispersant B added to the material to be ground, a source (20 ) composition A containing at least one dispersant A added to the material to be ground, containing an amino alcohol, a horizontal grinder (11) containing several chambers (12,14), including a first chamber (12) equipped with at least one inlet (13), and the last chamber (14) equipped with an outlet (16), wherein each chamber (12) is separated from the adjacent chamber (14) by a diaphragm (17), characterized in that the last chamber (14) is equipped with an inlet ( 15) connected to the source (20) of composition A. 10. The grinding device according to claim 9, in which the outlet (16) of the last chamber (14) is connected to the inlet (22) of a separator (23) capable of separating particles in accordance with their size and equipped with two outlets (24, 25 ), wherein one of the outlets (24) is connected to the inlet (13) of the first chamber (12) of the horizontal grinder (11).