BE1021863B1 - RALENTIATED REACTIVITY LIME, METHOD OF MANUFACTURE AND USE THEREOF - Google Patents

Abstract

Quicklime with slowed reactivity exhibiting a reactivity with water t6o according to the reactivity test EN 459-2: 2010 E greater than or equal to 5 minutes, characterized in that said quicklime with slow reactivity exhibits a reactivity with water t60 less than or equal to 18 minutes and is a soft-cooking quicklime, composition based on this slow-reactive quicklime, its manufacturing process and its uses.

Description

"Quicklime quicklime, its manufacturing process and its use"

The present invention relates to quicklime with reduced reactivity having a reactivity with water t6o according to the EN 459-2: 2010 E reactivity test greater than or equal to 5 minutes.

For the purposes of the present invention, quicklime is understood to mean a mineral solid material, the chemical composition of which is mainly calcium oxide, CaO. Quicklime is commonly obtained by calcination of limestone, mainly consisting of calcium carbonate, CaCO 3. This quicklime may also contain, for up to a few percent, impurities such as phases derived from MgO, SiO 2, Al 2 O 3, Fe 2 O 3, MnO, P 2 O 5, K 2 O and / or SO 3, brought by the initial limestone and / or by the fuel calcination. It is understood that these impurities are expressed in the aforementioned forms but may actually appear in different phases.

Quicklime is used in a large number of applications such as, for example, iron and steel industry, non-ferrous metal mining, construction and civil engineering, fume treatment, water and sludge treatment, agriculture or else the chemical industry in general.

Quicklime is industrially produced by cooking natural limestones in different types of furnaces such as straight furnaces (regenerative furnaces with double flow, ring furnaces, standard straight furnaces ...) or even rotary kilns.

The quality of quicklime, especially its reactivity to water, and the consistency of this quality are partly related to the type of oven used, the conditions of use of the oven, the nature of the limestone from which the quicklime comes itself, or the nature and quantity of the fuel used.

Thus, it is theoretically possible, by controlling the calcination conditions, to produce a whole range of quicklime with reactivities to water ranging from the most explosive to the slowest. In general, obtaining a rather reactive quick lime goes through a gentle baking (900-1000 ° C) while obtaining a quick lime reactive requires overcooking at higher temperature (1200-1400 ° C). VS). The quick lime resulting from a gentle cooking is better known under the name of "soft-burnt quicklimes" and has a weight of typically less than 5 minutes whereas the quicklime resulting from an overcooking is better known under the name of "mid-burnt quicklimes". - / hard-burnt quicklimes "and have a t60 typically greater than or equal to 5 minutes.

The quicklime obtained by gentle cooking generally has specific surface areas greater than 0.8 m 2 / g, in particular greater than 1 m 2 / g, whereas overworked quicklime generally has surfaces well below 1 m 2 / g, in particular less than 0.8 m2 / g.

As part of the present application, the water reactivity of quicklime is measured using the water reactivity test of the European standard EN 459-2: 2010 E. Thus, 150 g of quicklime are added with stirring in a cylindrical dewar of 1.7 dm3 capacity containing 600 cm3 of water permuted at 20 ° C. The stirring at 250 rpm is carried out by means of a specific blade (blade stirrer as described in said standard). The evolution of the temperature is measured as a function of time, which makes it possible to draw a curve of reactivity. From this curve, it is possible to deduce in particular the values T2, T5, Tio, Tm - which are respectively the temperatures reached after 2 min, 5 min, 10 min and the maximum temperature - or else the value t6o which represents the time necessary to reach 60 ° C. For the sake of simplification, the maximum temperature observed, named T'max in the EN 459-2: 2010 E standard, will be referred to in the present application. In the context of this invention, the reactivity is always measured on ground quicklime whose particle size is therefore mainly between 0 and 90 .mu.m.

In the context of the present application, the specific surfaces are measured by nitrogen adsorption manometry after degassing under vacuum at 190 ° C. for at least 2 hours and calculated according to the multi-point BET method as described in the ISO standard. 9277: 2010 E.

The characteristics and properties of quicklime are globally adapted case by case to meet the requirements of each of its applications. One of the typical properties of quicklime is its strongly exothermic reaction with water that can be put to use in some manufacturing processes. This is for example the case for the manufacture of cellular concrete. This is obtained from a mixture of silica-rich raw materials (crushed sands or fly ash), cement, a sulphate source such as gypsum or anhydrite, a quicklime, a raising powder such as aluminum in metallic form and water.

At first, quicklime reacts with water to form hydrated lime, which generates a certain amount of heat. The heat released leads to an increase in the temperature which favors the formation of hydrogen gas by reaction of the water in contact with the metallic aluminum, which thus leads to an expansion of the mixture and the obtaining of a porous medium commonly called "cake".

At the same time, the hydrated lime reacts with the other constituents, which leads to the formation of hydrated calcium silicates (CSH) and thus to the consolidation of the porous structure of the cake.

The speed of the hydration reaction between quicklime and water is decisive because it will partly determine the success of the manufacturing process of cellular concrete. It should not be too fast, the risk of leading to a release of too violent heat causing a rise in temperature of the cake itself too fast which leads to too strong expansion of the cake before consolidation and therefore its collapse. Nor should it be too slow, at the risk of having too early a consolidation before the expansion is completed (appearance of cracks during the expansion).

When the cake is well consolidated, it is cut into the form of bricks and the cellular concrete is obtained after a hydrothermal autoclave treatment that gives it its final mechanical properties.

Currently, the quicklime most commonly used in the manufacture of cellular concrete is more commonly called "quicklime slow reactivity." They have a hydration kinetics in water and therefore a heat release profile, quite well adapted to the process of manufacturing cellular concrete, ie a relatively linear water reactivity curve and a t6o value relatively high, usually between 5 and 12 minutes. For example, quicklime reactivity slowed down can be characterized by the following frames: 5 <t6o <8min; 36 <T2 <51 ° C; 54 <T5 <65 ° C; 64 <Ti0 <74 ° C; 71 <T2o <78 ° C; Tm> 69 ° C, and quicklime with more slowed reactivity can be characterized by the following boxes: 8 <t6o <12min; 26 <T2 <35 ° C; 34 <T <46 ° C; 51 <Ti0 <63 ° C; 66 <T20 <75; Tm> 69 ° C.

Moreover, for the production of cellular concretes, it is advantageous to maintain a relatively high value of Tm, because it is this value which accounts for the exothermic potential of quicklime. A value of Tm too low would lead to having to over-dose the amount of quicklime used in the manufacture of cellular concrete. This value of Tm is mainly influenced by the amount of calcium oxide (CaO) available in quicklime, which itself depends on the chemical purity of quicklime and its degree of cooking. Quicklime reactive quicklime prepared from soft-burning quicklime has been developed especially for applications in cellular concretes, such as quicklime with slow reactivity used in WO98 / 02391 (see for example Figure 3). . The latter claims a process for the production of cellular concrete using quick-cooking quick-lime, modified with a chemical agent which is of organic or mineral origin and / or simply water, and whose main objectives are to limit the rapid increase in temperature in the first seconds of the reactivity test and thus to limit the agglomeration of lime during its implementation, but still insufficient, especially for optimal use in the production of cellular concrete. Moreover, the extent of the modification of said quicklime remains too limited. Indeed, either the value of Tm is slightly reduced following this modification but in this case the value of t60 is slightly increased, the value of t60 is greatly increased but in this case, the value of the Tm is very significantly decreased. In addition, in the latter case, the additive used is of organic type and the amount of additive used is quite important, which is detrimental either in economic terms or by that it makes the modified lime more difficult to application environment. Other fast-reacting quicklime prepared from soft quick-cooking lime has also been described in the literature. Their manufacturing processes are mainly based on a partial modification of the chemical nature of quicklime or on a modification of the surface chemistry of quicklime by a mineral-type treatment.

For example, it is possible to cite document GB 1 585 483 which proposes a modification of quicklime with a soft cooking by a process which consists in partially hydrating the surface of the quicklime by adding water at ambient temperature and then carbonating it. by contacting with gaseous carbon dioxide.

However, although the treatment is effective in slowing the reactivity of the lime (in particular by increasing the value of the t0o), a major disadvantage of the process described is that the modification of the quicklime leads to a significant decrease in the value of the Tm, which means that a fairly significant part of the product is no longer quicklime but probably hydrated lime. In addition to limiting the potential of the product in the application, including its ability to generate a significant exothermic reaction with water, this highlights the lack of homogeneity of the surface treatment of quicklime which is detrimental when placing used in the manufacturing process of cellular concrete. In particular because of all the aforementioned drawbacks, but also because the treatments have always been carried out imperfectly and inhomogeneously, fast-reacting quicklime prepared from freshly baked quick-cooking lime has so far never been possible. implemented in cellular concrete type applications. Currently, the production of cellular concrete must therefore resort to the use of lime burnt which also has a t6typiquement greater than 5 minutes.

More specifically, the type of quicklime, generally used in the manufacturing process of cellular concrete is a quicklime burnt slowed reactivity, that is to say that not only is it a quicklime of the type overcooked, but overcooked such that the reactivity curve of said quicklime in water is relatively linear.

Unfortunately, quicklime burnt in general and quicklime burnt lime in particular are more difficult and more expensive to produce than quicklime cooking lighter because they require the use of specific straight furnaces (such as furnaces such as "Normal Shaft Kilns"), higher temperatures, but also because, except for using dedicated ovens, the production of these quick-reacted burnt lime leads to inter-production campaigns, which is not the case. without causing problems of stabilization of calcination conditions and thus problems of stabilization of quality.

In addition, overcooking often leads to produce quicklime of less stable quality in terms of reactivity to water because the calcination operation is carried out in a high temperature zone where a small variation in the calcination temperature generally leads to to a great variation of the texture of the quicklime produced (in particular a great variation of the size of the grains and thus of the specific surface, the pore volume and the density) and consequently to a great variation of the value of the

Given the constraints and difficulties in producing this type of quicklime reactivity slowed by the usual overcooking processes, and also taking into account the excessive energy consumption and therefore the negative environmental footprint in terms of CO2 generation, it is easy to understand that there is a need to develop a new type of fast-reactive quicklime that does not have the disadvantages of overcooked lime. The invention aims to overcome the drawbacks of the state of the art by providing quicklime slow reactivity whose characteristics are stable and controlled, allowing in particular optimal use in cell concrete type applications.

To solve this problem, it is provided according to the invention quicklime slowed reactivity as mentioned at the beginning, that is to say having a reactivity to water t6o according to the reactivity test EN 459-2: 2010 E greater than or equal to 5 minutes, characterized in that said quicklime reactivity slowed has a water reactivity t6o less than or equal to 18 minutes and is quicklime soft cooking.

As can be seen, quicklime with slowed reactivity according to the present invention has a reactivity with water t6o of between 5 and 18 minutes, that is to say a reactivity to water particularly suitable for applications of the type cellular concretes, such as the reactivity with water, which is likely to be obtained for quicklime, but which is much better controlled.

In fact, overcooking has many disadvantages, in addition to energy consumption and environmental impact, such as for example to provide quicklime that is of less stable quality in terms of reactivity to water because the calcination operation is performed in a high temperature zone where a small variation in the calcination temperature can lead to a large variation in the texture of the quicklime produced. As a result, the burnt quicklime resulting from the calcination is not homogeneous in terms of textural quality and has more or less fired particles, some of which will therefore have reactivities with water t6o much too high and others much too much low.

The quicklime with slowed reactivity according to the present invention being obtained from quicklime soft cooking, it therefore has a reactivity to water much better controlled. This means that when the quicklime reactive lime of the present invention is contacted with an aqueous phase, the temperature of the aqueous phase increases predictably and substantially linearly with time.

In this way, the temperature increase of the aqueous phase is controlled and occurs at a rate suitable for use in cellular concretes, where finally the water reactivity characteristics / constraints are dictated by the concrete compositions. and the needs of the manufacturers of cellular concretes.

These characteristics / constraints are related to the manufacturing process of the cellular concretes used and may also vary depending on the end user. The existing processes for the manufacture and formulation of cellular concretes are optimized for lime that has been made available locally, which are often lime burnt, obtained in a very specific and controlled manner and are therefore generally produced in straight furnaces of the type "Normal shaft kiln", namely, as mentioned above, energy consuming ovens and pollutants that the heaters need to use less and less.

As a result, according to the present invention, surprisingly, quicklime reactive lime based on quicklime quicklime has been developed which exhibits a water reactivity behavior similar to that of overcured live lime.

These quick-cooking quick-cooking lime used as raw material in order to obtain fast-reacting quicklime according to the present invention initially have t6o typically between 1 and 5 minutes whereas the end-user prerequisites reside in the fact. use quick lime instead with a ΐβο 5 to 12 minutes. According to the present invention, quick-cooking hot lime with slow reactivity has been obtained.

They have a t6o in the range of 5 minutes to 18 minutes. In this way, it has been possible according to the present invention to obtain quick-cooking hot lime having water reactivities similar to those of quicklime burnt, but which are therefore less expensive to produce, more suitable for modern ovens the most commonly used and which are part of the current cooking processes, to avoid inter-campaigns overcooking in the midst of more conventional mild cooking campaigns, optimized and sought to reduce the environmental footprint.

Moreover, the fast-reactive quicklime lime of the present invention are also able to retain all their potential for release of heat in contact with water and do not require the use of organic additives.

Thus, quicklime with slowed reactivity according to the present invention makes it possible, on the one hand, to provide a slowing down in the sufficient hydration reaction (t 6o greater than or equal to 5 minutes) to create the optimal porosity in the applications of cellular concretes, without induce excessive hydrogen evolution during the reaction with aluminum and secondly not too important to allow optimal cohesion and the formation at the right moment of calcium silicates.

The quicklime with slowed reactivity according to the invention also has the advantage of minimizing the formation of large agglomerates of hydrated lime (grits) when it is used in processes for the manufacture of hydrated calcium silicates in general, in particular tobermorite , and more particularly in the process of manufacturing cellular concrete. This characteristic is of considerable importance because, in the process of manufacturing cellular concrete for example, the suspension used to produce the "cake" contains a certain amount of calcium sulfate such as gypsum or anhydrite. However, it is known that, during the extinction of quicklime, the presence of sulphates generally leads to forming large agglomerates of hydrated lime. These are harmful for obtaining a good quality cellular concrete.

To characterize the tendency of quicklime to form large agglomerates in the presence of sulphate-containing extinguishing water, the reactivity test according to EN 459-2: 2010 E, in which water is used, is used. substituted with water saturated with calcium sulphate (2.4 g of gypsum in 600 cm3 of water).

When this test is carried out with fast-reactive quicklime according to the invention, the quantity of large agglomerates formed during the quenching is low. Indeed, after sieving the lime milk resulting from the reactivity test carried out in the presence of the sulphates, the amount of the agglomerates whose size is greater than or equal to 200 μm is less than or equal to 10% by weight, and preferably less than or equal to at 5% by weight, relative to the amount of said quicklime reactive lime implemented in this test.

The term "quantity of agglomerates whose size is greater than or equal to 200 μm" means the solid material which does not pass through a sieve of 200 μm and whose quantity is determined after drying at 105 ° C. for a period of night.

Preferably, quicklime with slowed reactivity according to the present invention has a reactivity with t60rev water after heat treatment at 700 ° C in a muffle furnace for 30 minutes of 200 g of said quicklime reactive lime less than or equal to 1/3 of his t6o measured according to the EN 459-2: 2010 E reactivity test.

In another preferred embodiment according to the present invention, quicklime with slowed reactivity has a Tm measured according to EN 459-2: 2010E greater than or equal to Tmrev -5 ° C where Tmrev represents the value of Tm of the quicklime with slowed reactivity after heat treatment at 700 ° C in a muffle furnace for 30 minutes of 200 g of said fast-reactive quicklime.

Advantageously, quicklime with slowed reactivity according to the present invention has a Tm measured according to EN 459-2: 2010 E greater than or equal to Tmrev - 3 ° C where Tmrev represents the Tm value of quicklime reactivity slowed down after heat treatment at 700 ° C. in a muffle furnace for 30 minutes with 200 g of said fast-reacting quicklime.

More preferably, quicklime with reduced reactivity according to the invention has a Tm measured according to EN 459-2: 2010 E greater than or equal to Tmrev - 2 ° C where Tmrev represents the Tm value of quicklime reactivity slowed down after heat treatment at 700 ° C. in a muffle furnace for 30 minutes with 200 g of said fast-reacting quicklime.

Preferably, quicklime with reduced reactivity has a Tm measured according to EN 459-2: 2010 E greater than or equal to 65 ° C, preferably greater than or equal to 67 ° C, and more preferably greater than or equal to 69 ° C. ° C.

In addition, advantageously, quicklime with slowed reactivity according to the present invention has a t6o value of between 8 and 12 min.

Preferably, quicklime with a reduced reactivity according to the invention also has a T5 value of between 25 and 50 ° C, preferably between 30 and 45 ° C.

In particular, quicklime with slowed reactivity according to the invention has a value of T2 between 21 and 40 ° C, preferably between 25 and 35 ° C.

In an advantageous variant according to the invention, the quicklime with slowed reactivity has a value of t ^ of between 5 and 8 min.

In this variant, quicklime with reduced reactivity according to the invention also has a value of T5 preferably between 35 and 65 ° C, in particular between 40 and 60 ° C.

In this variant, quicklime with reduced reactivity according to the invention also has a value of T2 preferably between 25 and 55 ° C, in particular between 35 and 50 ° C.

In another advantageous variant according to the invention, quicklime with slowed reactivity according to the invention has a t6o value of between 12 and 18 min.

In this other variant, quicklime with slowed reactivity according to the invention also has a value of Ts preferably between 21 and 40 ° C, in particular between 25 and 30 ° C.

In this variant, quicklime with slowed reactivity according to the invention also has a value of T2 preferably between 21 and 30 ° C, in particular between 21 and 25 ° C.

In an advantageous embodiment, the quicklime with slowed reactivity according to the invention has a specific surface area measured by nitrogen adsorption manometry after degassing under vacuum at 190 ° C. for at least 2 hours and calculated according to the BET method. multi-point as described in ISO 9277: 2010 E greater than or equal to 0.8 m2 / g, preferably greater than or equal to 1 m2 / g

In another advantageous embodiment, quicklime with slowed reactivity according to the present invention has a CaO content greater than or equal to 90% by weight, preferably greater than or equal to 92% by weight, and even more preferably higher or equal to 95% by weight relative to the total weight of said fast-reacting quicklime.

Advantageously, the H 2 O content of quicklime with slowed reactivity according to the invention, present in hydroxide form, in particular in the form of Ca (OH) 2; is less than or equal to 3% by weight, preferably less than or equal to 2% by weight, more preferably less than or equal to 1.5% by weight relative to the total weight of said quicklime reactive lime.

In an advantageous embodiment, the CO 2 content of the fast-reactive quicklime according to the present invention, present in the form of carbonate, in particular in the form of CaCO 3, is less than or equal to 3% by weight, preferably lower or equal to 2% by weight, more preferably less than or equal to 1.5% by weight relative to the total weight of said quicklime reactive lime.

In addition, according to the invention, quicklime with reduced reactivity has a sulfur content of less than or equal to 0.2% by weight, preferably less than or equal to 0.1% by weight relative to the total weight of lime. quick to slow down.

In addition, still according to the invention, quicklime slowed reactivity has an organic carbon content less than or equal to 1% by weight, preferably less than or equal to 0.5% by weight and more preferably less than or equal to 0 , 2% by weight, in particular less than or equal to 0.1% by weight relative to the total weight of fast-reactive quicklime.

The respective levels of H 2 O, CO 2, sulfur and organic carbon of quicklime reactive lime according to the present invention can easily be determined by conventional methods. For example, the content of H 2 O can be determined by a measurement of the loss on ignition. This consists in measuring, according to EN 459-2: 2010 E, the loss of mass generated at 550 ° C.

The CO 2 content can be determined by measuring the volumetric CO 2 according to EN 459-2: 2010 E.

The sulfur and total carbon contents can be respectively determined by carbon / sulfur (C / S) analysis according to the ASTM C25 (1999) standard.

Finally, the percentage of organic carbon present in the quick-reactive quicklime of the present invention can be calculated by the difference between the percentage of total carbon (determined by the C / S analysis) and the percentage of carbon of mineral origin, in other words, the CO2 content. Other embodiments of quicklime reactivity slowed according to the invention are indicated in the appended claims. The invention also relates to a composition based on quicklime slowed reactivity according to the invention. The composition according to the invention may then comprise additives such as gypsum, anhydrite, cement, sand and / or other lime. The subject of the invention is also a process for the production of quicklime with slow reactivity comprising the following steps: (i) feeding a quicklime having a water reactivity value ΐβο, measured according to the reactivity test described in the standard EN 459-2: 2010 E between 1 and 5 min, and preferably between 1 and 4 min, at a predetermined temperature greater than or equal to 50 ° C, preferably greater than or equal to 70 ° C, and less than or equal to 300 ° C, preferably less than or equal to 250 ° C, (ii) supplying a gas comprising water vapor at a percentage by volume of between 1 and 25% relative to the total volume of said gas and carbon dioxide at a volume percentage between 5 and 40% relative to the total volume of gas, said gas having a predetermined temperature greater than or equal to 50 ° C, preferably greater than or equal to 70 ° C, and lower or equal to 300 ° C , preferably less than or equal to 250 ° C, (iii) treatment of said quicklime brought by a flow of said gas before, during or after said supply to said temperature of said quicklime and for a predetermined period of time to form said lime fast reactivity slowed, and (iv) cooling of said fast-reactive quicklime in a confined medium substantially free of water, water vapor and carbon dioxide.

Advantageously, said step (iii) is carried out until a slow-reactivity quicklime is obtained which has a reactivity with water t60 according to the EN 459-2: 2010 E reactivity test greater than or equal to 5 minutes and less or equal to 18 minutes.

As can be seen, in the process according to the present invention, the gas for the treatment of quicklime comprises water vapor at a volume percentage of between 1 and 25% relative to the total volume of said gas and also comprises carbon dioxide at a volume percentage of between 5 and 40% relative to the total volume of gas. This gas has a predetermined temperature of between 50 ° C and 300 ° C. The predetermined temperature of the gas is chosen in the aforementioned range to be sufficient so that the water vapor contained in the gas does not condense (absence of liquid water).

The quicklime is brought to a predetermined temperature also between 50 ° C and 300 ° C, and is treated with gas. The predetermined temperature of the quicklime is also chosen in the above-mentioned temperature range to be sufficient so that the water vapor contained in the gas does not condense on contact during the treatment of the quicklime with the gas ( lack of liquid water).

These predetermined temperatures will also be chosen as a function of the selected volume percentages of water vapor and CO2 in the treatment gas as soon as the dew points of the gas are modified as a function of their concentration.

The choice of these temperatures is clearly dictated by the desired absence of liquid water during the treatment of quicklime by the gas flow.

Indeed, it has been observed according to the present invention that when liquid water is present, it directly impacts the value of tm of quicklime with slowed reactivity obtained by decreasing relatively strongly, as in the case for example of the patent GB 1 585 483, as well as when the concentrations of water vapor or CO 2 are not optimized in the aforementioned ranges.

According to the present invention, the predetermined time period of treatment of quicklime by the gas flow is the period of time sufficient to obtain a quicklime with slowed reactivity in which the amount of water captured by said quicklime during said treatment is less than or equal to 0.5% by weight, preferably less than or equal to 0.3% by weight relative to the weight of fast-reacted quicklime and in which the amount of CO 2 captured by said quicklime is less or equal to 0.8% by weight, preferably less than or equal to 0.6% by weight relative to the weight of quicklime with reduced reactivity.

Upon cooling, the slower-reacted quicklime is then confined in a storage space substantially free of CO 2 and water as well as water vapor so that the total amount of water and CO 2 captured during cooling by said quicklime is less than or equal to 0.1% by weight and that the total amount of water and CO2 captured by said quicklime during the entire process according to the invention is between 0.1 and 1% by weight. weight relative to the weight of quicklime with slowed reactivity.

In a preferred embodiment of the method according to the present invention, said quicklime brought is a quicklime taken from a cooking oven at said predetermined temperature. Indeed, when the structure of the oven allows it, the quicklime can be directly taken from a sampling zone, before being cooled, directly to the predetermined temperature or to a temperature above the predetermined temperature so as to be treated directly. at the furnace exit by the gas flow.

In another embodiment according to the invention, the treatment of said quicklime by said gas is carried out directly in the cooling zone of a lime kiln having a temperature of between 50 ° C. and 300 ° C.

In a variant of the process according to the invention, said quicklime brought is from a preheating at said predetermined temperature.

Advantageously, in the process according to the present invention, said quicklime brought is in the form of fine particles of quicklime having a diox of less than or equal to 10 mm, preferably less than or equal to 5 mm, and preferably less than or equal to 3 mm. mm.

The method according to the present invention makes it possible to develop a range of small particles produced in a relatively large amount during the calcareous rock baking and which however are currently little exploited. In fact, during the baking treatment of limestone rocks, the abrasion caused by the movement of the rocks in the furnace produces a quantity of relatively fine particles which are often discarded.

In an equally advantageous variant of the process according to the present invention, said quicklime brought is in the form of crushed lime, said ground material having a d95 of less than or equal to 200 μm, preferably less than or equal to 100 μm.

According to the present invention, it is also possible to use fine particles which are then ground or ground using, for example, a hammer mill, a ball mill, a vertical pendulum mill or the like. a grinding mill, to obtain a homogeneous mixture in particle size rather powdery.

The ground material may therefore be derived from a mixture of different sizes of quicklime particles, but not necessarily. According to the present invention, it is also envisaged that the treatment of quicklime by the gas flow is directly carried out in a grinding chamber, possibly heated, or by recovering the heat resulting from the friction of the particles during grinding.

Advantageously, said treatment of said quicklime brought by said flow of said gas is carried out with stirring, for example using a powder mixer such as a ribbon mixer, screw, blade or plow, or still well paddle, to improve the solid-gas contact.

In an advantageous variant of the process according to the invention, said treatment by said flow of said gas of said quicklime brought is carried out using a fluidized bed.

In yet another embodiment of the process according to the present invention, said quicklime is in the form of quicklime pebbles having a diO greater than or equal to 5 mm, preferably greater than or equal to 100 μm and preferably greater than or equal to 20 μm. mm and a dioo less than or equal to 60 mm, preferably less than or equal to 50 mm and preferably less than or equal to 40 mm.

In a preferred alternative mode according to the present invention, the treatment of said quicklime brought by said gas flow is carried out statically, for example by passing said gas through a fixed bed of quicklime.

Advantageously, said gas comprises at least flue gases from calcareous cooking furnaces and / or combustion gases from a fuel such as, for example, natural gas, lignite, anthracite or coke powder.

In any case, according to the present invention, it is preferable for said gas to have a sulfur content of less than or equal to 0.05% by volume relative to the total volume of said gas.

In yet another particular embodiment according to the present invention, said preheating of quicklime is carried out using a double jacket.

In a variant according to the invention, said preheating of quicklime is achieved by bringing said quicklime into contact with a preheated gas such as for example air or with said quicklime treatment gas.

Advantageously, the preheating of the gas is carried out using a heat exchanger such as a preheating screw, a ribbon mixer, a screw mixer, a blade mixer or ploughshare or even a mixer. pallets.

In another variant according to the invention, the quicklime is brought to ambient temperature and said treatment gas is brought to a sufficiently high temperature to allow rapid heating of said quicklime and thus to avoid the condensation of steam. water contained in said gas during its contact with the lime.

In a preferred form of the process according to the present invention, the preheating of the quicklime is carried out using a heat exchanger such as a preheating screw, a ribbon mixer, a screw mixer, a stirring mixer. blades or plow or alternatively a vane mixer.

In one embodiment of the process according to the present invention, the quicklime is treated by said flow of said gas in a discontinuous manner.

In another embodiment of the process according to the present invention, the quicklime is treated by said flow of said gas continuously. Other embodiments of the method according to the present invention are mentioned in the appended claims.

The present invention also relates to a use of fast-reactive quicklime according to the invention in a process for manufacturing calcium silicate hydrate (SCH).

Advantageously, quicklime with slowed reactivity according to the invention is used in a process for manufacturing cellular concrete.

In another form of use, quicklime with slowed reactivity is used in a process for producing animal bedding. Other uses are mentioned in the appended claims. Other features, details and advantages of the invention will emerge from the description given below, without limitation and with reference to examples.

The present invention therefore relates to quicklime slow reactivity which firstly is characterized, according to the European standard EN 459-2: 2010 E reactivity test, by a t6o value between 5 and 18 min. Another method of characterizing quicklime reactive lime from quicklime is the measurement of a reversibility property, ie, when this quicklime is heat treated at 700 ° C, the resulting t6o value , henceforth called teorev, is at least 3 times smaller than the value of the t60 of said fast-reacting quicklime and the value of the resulting Tm, henceforth referred to as Tmrev, is greater than the value of the Tm of said reactive quicklime slowed down but not increased by more than 5 ° C, preferably 3 ° C, and more preferably 2 ° C, relative to the Tm value of said quicklime reactivity slowed.

The heat treatment carried out during this reversibility test is carried out at 700 ° C. in an electric muffle furnace. More precisely, 200 g of ground lime with slow reactivity is spread in a 30 cm by 20 cm dish and is charged directly to 700 ° C in a muffle furnace. After 30 minutes, the heat treatment is stopped and the ground quicklime is transferred into a closed metal bucket where it is allowed to cool for 2 hours. The quicklime with slowed reactivity according to the invention is moreover preferably characterized by a Tm value greater than 65 ° C, preferably greater than or equal to 67 ° C, and still preferably greater than or equal to 69 ° C.

Said quicklime with slowed reactivity according to the invention is also characterized preferentially by a relatively linear reactivity curve.

The quicklime with slowed reactivity according to the present invention has the peculiarity of having, according to the European standard EN 459-2: 2010 E reactivity test, a relatively high t6o value of between 5 and 18 min while presenting a property. reversibility which is easily evidenced by a heat treatment at 700 ° C and which leads to a resulting t6o, henceforth t60rev, at least 3 times lower than its initial t60.

This characteristic distinguishes quick lime with slow reactivity resulting from soft cooking of quicklime with slowed reactivity.

Furthermore, quicklime with slowed reactivity according to the present invention is distinguished from quicklime reactive lime resulting from a soft cooking according to the prior art while maintaining a relatively high value of Tm compared to the value of Tm of lime In addition, quicklime with slowed reactivity according to the present invention does not contain any organic additives except those potentially used for the grinding of the initial quicklime such as diethylene glycol, triethanol amine and the like and mixtures thereof. contents of the order of 0.05% to 0.1% by weight, relative to the total weight of the quicklime This does not mean that it is not possible to add a posteriori, but this means that the addition of organic additives is not necessary to obtain said fast-reacting quicklime according to the present invention.

The quicklime with slowed reactivity according to the invention also has the advantage of minimizing the formation of large agglomerates of hydrated lime (grits) in the presence of silicate-containing extinguishing water. This characteristic is particularly advantageous for the manufacture of cellular concrete, since, in this process, the suspension used to produce the "cake" contains a certain amount of calcium sulphate such as gypsum or anhydrite and that the presence large agglomerates should be avoided since, on the one hand, they reduce the amount of lime that can react with the other raw materials used in the process of manufacturing cellular concrete and, on the other hand, they prevent the obtaining a good quality cellular concrete.

The quicklime with slowed reactivity according to the invention thus has, to a certain extent, the appearance of a quicklime, but is actually a quicklime resulting from a mild calcination, modified by a surface after-treatment. Said surface treatment consists of very slightly moisturizing and carbonating the entire surface accessible to the gas of said quicklime.

Whatever the quicklime considered, it can be naturally already partially hydrated and / or carbonated at its surface, in particular because during its manufacture or after its manufacture, it has been in contact with the atmosphere (humid ambient air, atmosphere more or less rich in carbon dioxide ...). Hydration and / or partial carbonation of the surface means here that in certain areas of the surface, hydration and / or carbonation is real while in other areas, it is zero or almost zero. It is therefore an inhomogeneous surface treatment and it is well understood that for the entire surface of quicklime accessible to the gas to be hydrated and / or carbonated, it would be necessary for the rate of hydration and / or carbonation to be very important. which would significantly alter the reactivity of quicklime in water, notably by causing a decrease in the value of Tm.

The particularity of quicklime with slowed reactivity according to the present invention is that the hydration and the surface carbonation are carried out homogeneously and quantitatively. Thus, the process of obtaining is optimized so that the surface treatment is as effective as possible while limiting as much as possible the increase in the content of H 2 O and CO 2 in the final product. The surface treatment according to the present invention led to greatly slow the reactivity of the initial quicklime while maintaining a relatively high value of Tm compared to the Tm value of the initial quicklime.

Starting from a given quicklime (characterized by a value of 160 between 1 and 5 min and preferably between 1 and 4 min), it is the intensity of the treatment that defines the final characteristics of quicklime reactivity slow down.

The higher the treatment, the more the reactivity is slowed down. By important treatment is meant a treatment, for example longer, or even carried out using a higher concentration of water vapor in the gas, or even carried out at a higher temperature, which increases the kinetics of the reactions of hydration and re-carbonation.

But the reactivity of lime slowed according to the present invention can also be modified and / or optimized by carrying out mixtures. For example, a highly slowed lime according to the present invention can be mixed in variable proportion with a lime less strongly slowed according to the present invention, which makes it possible to adjust the final reactivity of quicklime with slowed reactivity.

The process for manufacturing quicklime with slow reactivity according to the present invention comprises the following steps:

i) a supply of quicklime characterized, according to the European Standard EN 459-2: 2010 E reactivity test, by a t6o value of between 1 and 5 min, and preferably between 1 and 4 min, at a predetermined temperature greater than or equal to 50 ° C, preferably greater than or equal to 70 ° C, and less than or equal to 300 ° C, preferably less than or equal to 250 ° C ii) A supply of a gas, containing among others, steam having a volume percentage of between 1 and 25% and carbon dioxide having a volume percentage of between 5 and 40%, said gas having a predetermined temperature greater than or equal to 50 ° C, preferably greater than or equal to 70 ° C, and less than or equal to 300 ° C, preferably less than or equal to 250 ° C and in particular at least sufficient so that the water vapor contained in the gas does not condense ( lack of liquid water); iii) Possibly preheating said quicklime to reach the predetermined temperature of between 50 ° C. and 300 ° C. and more particularly at a temperature at least sufficient for the water vapor contained in the gas of step ii not to reach do not condense to its contact at step iv (no liquid water); iv) A treatment of said quicklime under flow of said gas before, during or after said supply to said temperature of said quicklime, so that the amount of water captured by said quicklime is less than or equal to 0.5% by weight, preferably less than or equal to 0.3% by weight, that the amount of CO 2 captured by said quicklime is less than or equal to 0.8% by weight, preferably less than or equal to 0.6% by weight , and in particular such that the total amount of water and CO2 captured by said quicklime during this treatment is between 0.1 and 1.0% by weight, based on the weight of fast-reactive quicklime ; v) cooling in a confined environment free of water, water vapor and carbon dioxide, in particular such that the total amount of water and CO2 captured by said quicklime during cooling is less than or equal to 0.1% by weight relative to the weight of quicklime with slowed reactivity.

Preferred but non-limiting aspects of this process for producing a fast-reacting quicklime according to the present invention, taken alone or in combination, are as follows: the quicklime brought is in the form of fines having a size of less than 10 mm preferably less than 5 mm, and preferably less than 3 mm; the quicklime brought is ground or ground and has a size of less than 200 μm, preferably less than 100 μm; the quicklime brought is in the form of pebbles and has a dio particle size greater than or equal to 5 mm, preferably greater than or equal to 10 mm and preferably greater than or equal to 20 mm and a particle size di0o less than or equal to 60 mm, preferably less than or equal to 50 mm and preferably less than or equal to 40 mm; the gas flow used to treat quicklime comes from calcareous kilns (oven fumes); the flow of gas used for the treatment of quicklime comes directly from the combustion of a fuel such as for example natural gas, lignite, anthracite or coke powder; the flow of gas used for the treatment of quicklime contains a quantity of sulfur less than or equal to 0.05% by volume relative to the total volume of said gas; the flow of gas used for the treatment of quicklime comes from a preheated gas, for example with the aid of a heat exchanger; the possible preheating of the quicklime is carried out using a double envelope; the optional preheating of the quicklime is carried out using a heat exchanger such as a preheating screw, a ribbon mixer, screw, blade or plow, or even a vane mixer; the possible preheating of the quicklime is carried out by placing in contact with a preheated gas such as for example nitrogen, air or the gas of step (ii); the treatment of the quicklime by the gas flow is carried out with stirring, for example by means of a powder mixer to promote the solid / gas contact, the lime then being more particularly or in the form of fines having a size less than 10 mm, preferably less than 5 mm, and preferably less than 3 mm, or in the form of a ground powder having a size of less than 200 μm, preferably less than 100 μm; the treatment of quicklime by the gas flow is carried out using a fluidized bed, the lime then being more particularly or in the form of fines having a size of less than 10 mm, preferably less than 5 mm, and preferably less than 3 mm, either in the form of a ground powder having a size less than 200 μm, preferably less than 100 μm; the treatment of the quicklime by the gas flow is carried out statically, for example by passing said gas through a fixed bed of quicklime, the lime then being preferably in the form of pebbles having a larger size or equal to 5 mm, preferably greater than or equal to 10 mm and preferably greater than or equal to 20 mm and a size less than or equal to 60 mm, preferably less than or equal to 50 mm and preferably less than or equal to 40 mm. the treatment of the quicklime by the gas flow is carried out directly in a grinding chamber, the lime then being more particularly or in the form of fines having a size of less than 10 mm, preferably less than 5 mm, and preferably less than 3 mm, or in the form of pebbles having a size greater than or equal to 5 mm, preferably greater than or equal to 10 mm and preferably greater than or equal to 20 mm and a size less than or equal to 60 mm, preferably less than or equal to 50 mm and preferably less than or equal to 40 mm;

The process for producing quicklime with slowed reactivity according to the invention has the particularity of using as a raw material a quicklime characterized, according to the European Standard EN 459-2: 2010 E reactivity test, by a value of t 60. between 1 and 5 min and preferably between 1 and 4 min, so a lime that can be described as quicklime "soft cooking". The low limit of the value of ΐβο is related to the difficulty of shifting the t60 value significantly between 5 and 18 min by the process of the present invention from a quicklime having a lower t60 value. at 1 min without strongly impacting the value of Tm. The upper limit of the value of ίβο is mainly related to technical and economic aspects. A quicklime which has a value of t60 greater than 5 min, preferably greater than 4 min, is a quick-lime that has a more limited gas accessible surface, and therefore a quicklime that by nature is less sensitive to the process of the present invention. The technical and economic interests of implementing the method of the present invention would therefore not be obvious a priori.

Cellular concrete is produced in a manner well known to those skilled in the art. This is obtained from a mixture of silica-rich raw materials (crushed sands or fly ash), cement, a sulphate source such as gypsum or anhydrite, a quicklime, a raising powder such as aluminum in metallic form and water. At first, quicklime reacts with water to form hydrated lime, which generates a certain amount of heat. The heat released leads to an increase in the temperature which favors the formation of hydrogen gas by reaction of the water in contact with the metallic aluminum, which thus leads to an expansion of the mixture and the obtaining of a porous medium commonly called "cake". At the same time, the hydrated lime reacts with the other constituents, which leads to the formation of hydrated calcium silicates (CSH) and thus to the consolidation of the porous structure of the cake. The speed of the hydration reaction between quicklime and water is decisive because it will partly determine the success of the manufacturing process of cellular concrete. It should not be too fast, the risk of leading to a release of too violent heat causing a rise in temperature of the cake itself too fast which leads to too strong expansion of the cake before consolidation and therefore its collapse. Nor should it be too slow, at the risk of having too early a consolidation before the expansion is completed (appearance of cracks during the expansion). When the cake is well consolidated, it is cut into the form of bricks and the cellular concrete is obtained after a hydrothermal autoclave treatment that gives it its final mechanical properties.

In practice, the consolidation of the "cake" must be carried out in an appropriate period of time. The hydration reaction between the quicklime and the water gives off heat but it is necessary to control this release of heat which must be neither too fast nor too slow. The quicklime burnt is thus very widely used for the manufacture of cellular concrete, because it has a kinetics of hydration and therefore of heat release rather well suited to the manufacturing process of the cellular concrete. However, because the quicklime is not chemically very reactive, the consolidation time of the "cake" is relatively long, which slows down the manufacturing process. The quicklime with slowed reactivity according to the present invention makes it possible to optimize the consolidation time of the "cake".

EXAMPLES

Example 1.- ground quicklime with slow reactivity t6o = 5.7 min

Starting from industrial quick lime fines 2-8 mm from the secondary rock lime screen produced in the Parallel Flow Regenerative Kiln (PFRK) and PRK kilns (Pre-heated Rotary Kiln) in the Lhoist group's Flandersbach plant a 0-90 μm lime is prepared.

The ground lime thus obtained, called "Weissfeinklak-la", contains more than 95% by weight of particles smaller than 90 μm. It contains 95% by weight of CaO, 1.3% by weight of MgO, 0.6% by weight of residual CO2 (present in the form of calcium carbonate) and 0.9% by weight of residual H 2 O (present in the form of calcium hydroxide). It has t60 values of 1.9 min, T2 of 63.3 ° C, T5 of 73.7 ° C and Tm of 75.1 ° C in the European standard EN 459-2 reactivity test. : 2010 E.

A MR type Lödige powder mixer (internal volume of 20 dm3) equipped with an inlet and an outlet for gases and a double jacket for indirect heating by recirculation of oil is used. This is filled with 6 kg of ground quicklime and the mixture is stirred at 2.5 m / s (end speed).

Preheating is carried out for 30 minutes under a flow of nitrogen of 22 dm3 / min previously heated to 200 ° C. and using an oil recirculation at 200 ° C., so that ground quicklime is at a temperature of 170 ° C. The nitrogen flow of 22 dm3 / min, preheated to 200 ° C., is replaced by a flow of 22 dm3 / min of nitrogen, itself preheated to 200 ° C., containing 15% by volume of CO2 and 2.5% by weight. in volume of H20.

After 17 minutes, the treatment is stopped and the ground quicklime is transferred to a closed metal bucket where it is allowed to cool for 2 hours. The ground quicklime thus obtained is called according to the invention ground quicklime with slowed reactivity. It contains 1.0% by weight of residual CO 2 and 1.2% by weight of residual H.sub.2 O and has T o values of 5.7 min, T 2 of 35.3 ° C., T 5 of 52.9 ° C. C and Tm of 73.4 ° C in the European Standard EN 459-2: 2010 E reactivity test. It also has a BET specific surface area of 1.2 m 2 / g and contains 0.03% by weight of sulfur and less than 0.0015% by weight of organic carbon.

A reversibility test is then performed. For this, 200 g of ground lime with slow reactivity are spread in a 30 cm by 20 cm and are charged directly to 700 ° C in a muffle furnace. After 30 minutes, the heat treatment is stopped and the ground quicklime is transferred to a closed metal bucket where it is left to cool for 2 hours.

The resulting ground quicklime has t60rev values of 1.6 min, T2rev of 64.8 ° C, T5rev of 74.2 ° C and Tmrev of 75.0 ° C measured according to the reactivity test. Water EN 459-2: 2010 E.

Example 2.- Ground quicklime with slowed reactivity t6o = 8.0 min

A ground quicklime with slowed reactivity is obtained according to the same protocol as in example 1 but the treatment is carried out using a flow of 22 dm3 / min of nitrogen containing 15% by volume of CO2 and 7.5% by volume of H 2 O previously heated to 200 ° C. Ground lime with slow reactivity thus obtained contains 1.2% by weight of residual CO 2 and 1.1% by weight of residual H 2 O. It has values of 160 minutes, T2 of 25.1 ° C, T5 of 34.7 ° C and Tm of 73.6 ° C.

This fast-reactive quicklime is also characterized by the reactivity test according to EN 459-2: 2010 E, in which the water is substituted with water saturated with calcium sulphate (2.4 g of gypsum in the 600 cm3 of water). At the end of this test, the milk of lime produced is filtered through a sieve of 200 .mu.m. The solid material recovered on the sieve is dried at 105 ° C for 1 night. A final mass of 4.8 g is thus obtained, which represents an amount of agglomerates greater than 200 μm in size equal to 3.2% by weight relative to the 150 g of quicklime reactive lime used in this process. test.

In the reversibility test, the values of tereor were 1.7 min, T2rev of 63.8 ° C, T5rev of 74.0 ° C and Tmrev of 75.4 ° C.

Example 3.- Ground quicklime with slowed reactivity t60 = 9.4 min

Ground lime with slow reactivity is obtained according to the same protocol as in Example 2, but the treatment is carried out for 22 min instead of 17 min. Ground lime with slow reactivity thus obtained contains 1.2% by weight of residual CO 2 and 1.2% by weight of residual H 2 O. It has t60 values of 9.4 min, T2 of 24.6 ° C, T5 of 33.0 ° C and Tm of 73.0 ° C. It also has a BET specific surface area of 1.2 m 2 / g and contains 0.03% by weight of sulfur and less than 0.0015% by weight of organic carbon.

In the reversibility test, Iorv values of 1.6 min, T2rev of 64.0 ° C, T5rev of 74.1 ° C and Tmrev of 75.2 ° C were observed.

Example 4 - ground quicklime with slowed reactivity t6o = II, 2 min

Ground lime with slowed reactivity is obtained according to the same protocol as in Example 1 but using a 0-90 μm ground quicklime from the grinding of the 0-10 mm fraction of another industrial furnace. The latter contains 98% by weight of CaO, 0.5% by weight of MgO, 0.1% by weight of residual CO 2 (present in the form of calcium carbonate) and 0.6% by weight of residual H 2 O ( present as calcium hydroxide). It has t6o values of 3.5 min, T2 of 49.9 ° C, T5 of 61.5 ° C and Tm of 74.3 ° C.

The resulting slower reacted ground lime contains 0.2% by weight of residual CO 2 and 0.8% by weight of residual H.sub.2 O. It has ΐβο values of 11.2 min, T2 of 31.7 ° C, T5 of 41.0 ° C and Tm of 74.0 ° C. It also has a specific surface area of 1.4 m 2 / g and contains 0.03% by weight of sulfur and less than 0.0015% by weight of organic carbon.

In the reversibility test, values of 3.5 min, 52.7 ° C for T2rev, 62.9 ° C for T5rev and 76.0 ° C for Trevre were observed.

Example 5 Production of Cellular Concrete P2-0.40 A quick-reacted batch of quicklime made according to Example 3 is used as a raw material for producing laboratory concrete blocks on a laboratory scale by a standardized method, simulating industrial production.

The other raw materials used for this production are listed below: - Quartz sand (Millisil W10, Quarzwerke Frechen) - Portland CEM I - 42.5 R from PLZ Wittekind plant in Erwitte (D) - Anhydrite from Cirkel in Haltern (D) - Schlenck Aquapor 9004 Aluminum Powder

One day before production at the laboratory scale, return sludge was prepared to simulate the recycling of residues from the production of industrial cellular concrete. They were prepared in a bucket of 10 dm3 with stirring by adding successively in 2.00 kg of water, 2.20 kg of sand, 1.00 kg of cement, 0.60 kg of quicklime with slowed reactivity and 0 , 20 kg of anhydrite, and then were kept stirring in this closed bucket until their use the next day.

A mixture of cement, slow-reacted lime and anhydrite is prepared using 1.00 kg of cement, 0.60 kg of slow-reacting lime and 0.20 kg of anhydrite.

A suspension of aluminum at 10% by weight is prepared by mixing 32 g of aluminum powder and 288 g of water. The suspension is kept stirring.

Starting from the 6 kg of sludge prepared the day before and placed in a 30 dm 3 bucket, 10.71 kg of water at 70 ° C. are added successively with stirring at 900 rpm, followed by 8.80 kg of water. Sand, then 1.80 kg of the cement mixture, slow-reacting lime and anhydrite. The mixture is stirred for 2 minutes and then the 320 g of the aluminum suspension is added. The suspension is stirred for a further 20 seconds and is poured into a mold where it is left to sit under cover for 4 hours, which leads to the formation of a cake. This is placed in an autoclave at 185 ° C under a steam pressure of 11 bar where it undergoes a hydrothermal treatment for 6 hours. Cellular concrete cubes are obtained by cutting the initial block into pieces of 10 * 10 * 10 cm3 (1 dm3). These cubes are then dried at 80 ° C. for several hours until they contain a residual moisture of 4 to 8% by weight, expressed relative to the weight of these same cubes when they are completely dried by an additional treatment. at 105 ° C for 24 hours (a few cubes are sacrificed to determine the drying time required to reach this residual moisture at 80 ° C).

Six cubes dried at 80 ° C are then characterized. The results that are shown are the average of the results obtained on these six cubes. The density of the cubes is 0.39 (i.e., their density is 0.39 g / cm 3) and the compressive strength, measured perpendicular to the direction of cake growth, is 2. , 6 N / mm2.

Example 6. Production of P2-0.35 Cellular Concrete

A cellular concrete is produced according to Example 5 using the same raw materials and the same protocol but by changing the recipes.

The return sludge was prepared with 1.94 kg of water, 2.00 kg of sand, 1.12 kg of cement, 0.56 kg of fast-reacting quicklime and 0.2 kg of anhydrite.

The mixture of cement, slow-reacted lime and anhydrite is prepared using 1.12 kg of cement, 0.68 kg of slow-reacting lime and 0.2 kg of anhydrite.

The aluminum suspension at 10% by weight is prepared by mixing 44 g of aluminum powder and 396 g of water.

At the beginning of the 6 kg of sludge are added 11.26 kg of water at 70 ° C, then 8.00 kg of sand, then the 2.00 kg of the mixture of cement, slow-reacting lime and anhydrite, then 440 g of the aluminum suspension.

The density of the cubes of cellular concrete is 0.33 and the compressive strength, measured perpendicular to the direction of growth of the cakes, is 2.1 N / mm 2.

Comparative example 1, - quicklime "Poro C"

Ground commercial ground lime, brand name 'Poro C, hardburnt type', is used as a reference. It is produced from rock limestone by overbaking in a straight furnace. It contains 1.0% by weight of residual CO 2 and 0.2% by weight of residual H 2 O. It has t6o values of 11.3 min, T2 of 30.1 ° C, T5 of 38.2 ° C and Tm of 71.1 ° C in the European standard EN 459-2 reactivity test. : 2010 E.

Poro C lime is also characterized by the reactivity test according to EN 459-2: 2010 E in which water is substituted by water saturated with calcium sulphate (2.4 g of gypsum in 600 cm3 of water). At the end of this test, the milk of lime is filtered through a sieve of 200 .mu.m. The solid material recovered on the sieve is dried at 105 ° C for 1 night. This gives a final mass of 6.8 g, which represents 4.5% by weight of agglomerates of size greater than 200 μm, compared to 150 g of Poro C lime used in this test.

A reversibility test is then performed. For this, 200 g of this quicklime are spread in a 30 cm by 20 cm and are charged directly at 700 ° C in a muffle furnace. After 30 minutes, the heat treatment is stopped and the quicklime is transferred to a closed metal bucket where it is left to cool for 2 hours.

The reactivity of the resulting quicklime has not substantially changed since the latter has values of t60rev of 11.2 min, T2rev of 30.5 ° C, T5rev of 39.1 ° C and Tmrev of 71, 2 ° C measured according to the water reactivity test EN 459-2: 2010 E.

Comparative Example 2. Quicklime slowed with liquid water The ground quicklime of Example 1 was hydrated by adding water in liquid form with stirring to reach a hydration of 4.6%, as described in the document GB 1,585,483. 3 kg of this lime were then placed in the Lödige mixer and then treated with stirring for 14 minutes under a nitrogen flow of 40 dm3 / min containing 20% by volume of CO2. This fast-reactive quicklime has t60 values of 12.8 min, T2 of 22.5 ° C, T5 of 24.5 ° C and Tm of 63.8 ° C in the standard reactivity test. European standard EN 459-2: 2010 E. The value of Tm is particularly low compared to the Tm value of the mother lime (75.1 ° C).

In the reversibility test, teorev values of 0.9 min, T2rev of 70.7 ° C, T5rev of 75.6 ° C and Tmrev of 76.9 ° C were observed. The value of Tmrev is particularly large compared to the Tm value of this fast-reactive quicklime.

Comparative Example 3, Production of P2-0,40 Cellular Concrete Example 5 is carried out by substituting the slow-reacted quicklime of Example 3 with the "PoroC" hardened quicklime of Comparative Example 1. The density cubes of cellular concrete is 0.41 and the compressive strength, measured perpendicular to the direction of growth of the cakes, is 2.8 N / mm 2.

Comparative Example 4. Production of P2-0.35 Cellular Concrete Example 6 is carried out by substituting the slow-reacted quicklime of Example 3 with the "PoroC" hardened quicklime of Comparative Example 1. The density cubes of cellular concrete is 0.34 and the compressive strength, measured perpendicular to the direction of growth of the cakes, is 2.2 N / mm 2.

Comparative Example 5. Ground Quick-Grilled Quick Ground T0o = 1/9 min.

The quicklime ground used in Example 1 before treatment according to the invention (t6o = 1.9 min) is characterized with the reactivity test according to the standard EN 459-2: 2010 E in which the water is substituted with water saturated with calcium sulphate (2.4 g of gypsum in 600 cm3 of water). At the end of this test, the lime milk obtained is filtered through a sieve of 200 .mu.m. The solid material recovered on the sieve is dried at 105 ° C for 1 night. This gives a final mass of 59 g, which represents 39% by weight of agglomerates of size greater than 200 pm, compared with 150 g of quicklime reactivity slowed implemented in this test.

Comparative Example 6. Lime Additized with 0.4% Ca-Lignosulphate 12 g of calcium lignosulphonate were added to 3 kg of ground quicklime used in Example 1 before treatment according to the invention (t 60 = 1.9 min). The mixture was homogenized in a paddle mixer for 5 minutes. The resulting lime has t60 values of 12.0 min, T2 of 30.8 ° C, T5 of 33.5 ° C and Tm of 71.3 ° C.

It is also characterized with the reactivity test according to EN 459-2: 2010 E in which the water is substituted by water saturated with calcium sulphate (2.4 g of gypsum in the 600 cm3 of water). water). At the end of this test, the milk of lime is filtered through a sieve of 200 .mu.m. The solid material recovered on the sieve is dried at 105 ° C for 1 night. This gives a final mass of 48 g, which represents 32% by weight of agglomerates of size greater than 200 μηη, compared with 150 g of lime used in this test.

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

Claims (44)

1. Quicklime reactive lime having a reactivity to water ΐεο according to the EN 459-2: 2010 E reactivity test greater than or equal to 5 minutes, characterized in that said quicklime reactivity lime has a reactivity to the water t6o less than or equal to 18 minutes and is quicklime soft cooking. 2. Slow-reacted quicklime according to claim 1, having a reactivity with water torev after heat treatment at 700 ° C for 30 minutes of 200 g of said quicklime reactivity slowed less than or equal to 1/3 said measured teo according to the EN 459-2: 2010 E reactivity test. 3. quicklime reactivity slowed according to claim 1 or claim 2, having a Tm measured according to EN 459-2: 2010 E greater than or equal to Tmrev - 5 ° C where tmrev represents the value of Tm of quicklime with slowed reactivity after heat treatment at 700 ° C. for 30 minutes of 200 g of said fast-reacting quicklime. 4. Quicklime reactive lime according to any one of claims 1 to 3, having a Tm measured according to EN 459-2: 2010 E greater than or equal to Tmrev - 3 ° C where Tmrev represents the value of Tm of the quicklime with slowed reactivity after heat treatment at 700 ° C. for 30 minutes of 200 g of said fast-reacting quicklime. 5. Quicklime reactive quicklime according to any one of claims 1 to 4, having a Tm measured according to EN 459-2: 2010 E greater than or equal to Tmrev - 2 ° C where Tmrev represents the value of Tm of the quicklime with slowed reactivity after heat treatment at 700 ° C. for 30 minutes of 200 g of said fast-reactive quicklime 6. Quicklime with reduced reactivity according to any one of claims 1 to 5, having a Tm measured according to EN 459-2 2010 E greater than or equal to 65 ° C, preferably greater than or equal to 67 ° C, and more preferably greater than or equal to 69 ° C. 7. Quicklime reactive quicklime according to any one of claims 1 to 6, having a t6o value between 8 and 12 min. 8. quicklime reactive lime according to claim 7, having a T5 value of between 25 and 50 ° C, preferably between 30 and 45 ° C. 9. Quicklime reactive quicklime according to claim 7 or claim 8, having a value of T2 between 21 and 40 ° C, preferably between 25 and 35 ° C. 10. Quicklime reactive quicklime according to any one of claims 1 to 6, having a t6o value of between 5 and 8 min. 11. quicklime reactive lime according to claim 10, having a T5 value between 35 and 65 ° C, preferably between 40 and 60 ° C. 12. Quicklime reactive lime according to claim 10 or claim 11, having a value of T2 between 25 and 55 ° C, preferably between 35 and 50 ° C. 13. quicklime reactive lime according to any one of claims 1 to 6, having a t6o value of between 12 and 18 min. 14. quicklime reactive lime according to claim 13, having a T5 value between 21 and 40 ° C, preferably between 25 and 30 ° C. 15. Quicklime reactive lime according to claim 13 or claim 14, having a value of T2 between 21 and 30 ° C, preferably between 21 and 25 ° C. 16. Quicklime reactive quicklime according to any one of the preceding claims, having a specific surface area measured by nitrogen adsorption manometry after degassing under vacuum at 190 ° C for at least 2 hours and calculated according to the BET method. points as described in ISO 9277: 2010 E greater than or equal to 0.8 m2 / g, preferably greater than or equal to 1 m2 / g. 17. Quicklime reactive lime according to any one of the preceding claims having a CaO content greater than or equal to 90% by weight, preferably greater than or equal to 92% by weight, and still more preferably greater than or equal to 95% by weight. % by weight relative to the total weight of said fast-reactive quicklime. 18. Quicklime reactive lime according to any one of the preceding claims, having an S content less than or equal to 0.2% by weight, preferably less than or equal to 0.1% by weight relative to the total weight of the quicklime with slow reactivity. Lime with a slowed reactivity according to any one of the preceding claims, having an organic carbon content of less than or equal to 1% by weight, preferably less than or equal to 0.5% by weight and more preferably less than or equal to 0.2% by weight, in particular less than or equal to 0.1% by weight relative to the total weight of fast-reactive quicklime. 20. Quicklime reactive lime according to any one of the preceding claims having, in the reactivity test according to EN 459-2: 2010 E in which the water is substituted with water saturated with calcium sulphate ( 2.4 g of gypsum in 600 cm 3 of water), a quantity of agglomerates whose size is greater than or equal to 200 μm, less than or equal to 10% by weight, preferably less than or equal to 5% by weight, in relation to the amount of said quicklime reactive lime implemented in said test. 21. Slow-reacted quicklime composition according to any one of claims 1 to 20. 22. A process for producing quicklime with slowed reactivity, comprising the following steps: (i) feeding a quicklime having a water reactivity value t oo, measured according to the reactivity test described in standard EN 459 -2: 2010 E between 1 and 5 min, and preferably between 1 and 4 min, at a predetermined temperature greater than or equal to 50 ° C, preferably greater than or equal to 70 ° C, and less than or equal to 300 ° C, preferably less than or equal to 250 ° C, (ii) supplying a gas comprising water vapor at a volume percentage of between 1 and 25% relative to the total volume of said gas and carbon dioxide at a volume percentage between 5 and 40% relative to the total volume of gas, said gas having a predetermined temperature greater than or equal to 50 ° C, preferably greater than or equal to 70 ° C, and less than or equal to 300 ° C , preferably lower or equal to 250 ° C, (iii) treatment of said quicklime brought by a flow of said gas before, during or after said supply to said temperature of said quicklime and for a predetermined period of time to form said fast-reactive quicklime, and (iv) cooling said fast-reacted quicklime in a contained medium substantially free of water, water vapor and carbon dioxide. 23. The manufacturing method according to claim 22, wherein said step (iii) is carried out until a quicklime with reduced reactivity having a reactivity with water t6o according to the reactivity test EN 459-2: 2010. E greater than or equal to 5 minutes and less than or equal to 18 minutes. 24. The manufacturing method according to claim 22 or claim 23, wherein the predetermined temperatures of steps (i) and (ii) are at least sufficient so that the water vapor contained in the gas does not condense (absence of liquid water). 25. The manufacturing method according to any one of claims 22 to 24, wherein step (iii) is carried out so that the amount of water captured by said quicklime is less than or equal to 0.5% by weight, preferably less than or equal to 0.3% by weight, that the amount of CO 2 captured by said quicklime is less than or equal to 0.8% by weight, preferably less than or equal to 0.6% by weight, and such that the total amount of water and CO2 captured by said quick lime is between 0.1 and 1.0% by weight based on the weight of fast-reacted quicklime. 26. The manufacturing method according to any one of claims 22 to 25, wherein said quicklime brought is a quicklime taken from a baking oven at said predetermined temperature. 27. The manufacturing method according to any one of claims 22 to 26, wherein said quicklime brought is from a preheating at said predetermined temperature. 28. The manufacturing method according to any one of claims 22 to 27, wherein said treatment of said quicklime brought by said flow of said gas is carried out with stirring, for example using a powder mixer, including a ribbon mixer, screw, blade or plow, or even pallet. 29. The manufacturing method according to any one of claims 22 to 27, wherein the treatment of quicklime is carried out using a fluidized bed. 30. The manufacturing method according to any one of claims 22 to 27, wherein the treatment of said quicklime brought by said gas stream is made statically, for example by passing said gas through a fixed bed of quicklime. 31. Manufacturing method according to any one of claims 22 to 27, wherein said treatment of said quicklime brought by said flow of said gas is carried out during the crushing or during the grinding of said quicklime, for example using a hammer mill, a ball mill, a vertical pendulum mill or a grinding mill. 32. A method of manufacture according to any one of claims 22 to 29 or 31, wherein said quicklime brought is in the form of fine particles of quicklime having a less than or equal to 10 mm, preferably less than or equal to 5 mm, and preferably less than or equal to 3 mm. 33. The manufacturing method according to any one of claims 22 to 29, wherein said quicklime brought is in the form of crushed lime having a dg5 less than or equal to 200 pm, preferably less than or equal to 100 pm. 34. A method of manufacture according to any one of claims 22 to 27 or 30 to 31, wherein said quicklime is in the form of quicklime pebbles having a di0 greater than or equal to 5 mm, preferably greater than or equal to 10 mm and preferably greater than or equal to 20 mm and a minimum of 60 mm, preferably less than or equal to 50 and preferably less than or equal to 40 mm. 35. The manufacturing method according to any one of claims 22 to 34, wherein said gas comprises at least flue gases from calcareous kilns. 36. Manufacturing method according to any one of claims 22 to 35, wherein said gas comprises at least combustion gases of a fuel such as for example natural gas, lignite, anthracite or coke powder. . 37. Manufacturing process according to any one of claims 22 to 36, wherein said gas has a sulfur content less than or equal to 0.05% by volume relative to the total volume of said gas. 38. The manufacturing method as claimed in any one of claims 22 to 37, wherein said gas is preheated to the predetermined temperature, for example by means of a heat exchanger. 39. Manufacturing process according to any one of claims 27 to 38, wherein said preheating of quicklime is carried out using a double jacket. 40. Manufacturing process according to any one of claims 27 to 39, wherein said preheating of quicklime is achieved by contacting said quicklime with a preheated gas such as for example air or with said process gas for quicklime. 41. Manufacturing method according to any one of claims 27 to 40, wherein the preheating of quicklime is performed using a heat exchanger such as a preheating screw, ribbon mixer, a mixer screw, a blade mixer or plow, or even a vane mixer. 42. Use of fast-reactive quicklime according to any one of claims 1 to 20, or resulting from the process according to any one of claims 22 to 41, or the composition according to claim 21, in a manufacturing process. hydrated calcium silicate (SCH). 43. Use according to claim 42 in a process for manufacturing cellular concrete. 44. Use according to claim 42 in a method of manufacturing animal bedding.