Color optimization in the mechanochemical activation of clays

Abstract

The present invention relates to a method for the mechanochemical activation and simultaneous optimization of the color of a mineral material, characterized in that the mechanochemical activation and simultaneous optimization take place in a first high-energy mill (40), the mineral material being ground together with a solid reducing agent in said first high-energy mill (40).

Description

Color optimization in the mechanochemical activation of clays The invention relates to a procedure for optimizing color in the mechanochemical activation of clays. In the cement industry, activated clays have become a well-established additive. The most common method used today is drying and calcining the clays, a process known as thermal activation. This requires energy for heating, and excessively high temperatures can also cause other, potentially undesirable, changes in the material. Due to the firing conditions during thermal activation in an oxidizing atmosphere, the iron compounds naturally present in clays are transformed, in particular, into red iron oxides. This results in a reddish coloration of the activated clays, significantly reducing the market acceptance of cements made from them. The iron content, specifically the content of iron in its trivalent oxidation state (Fe3+), which is a strong coloring agent, decisively determines the color of a calcined clay. Color is an important quality parameter for the potential use of these activated clays as a component of typically gray cement. In particular, lower-quality ("lean") clays can have Fe2O3 contents of between 2 and 9% by weight on average. In so-called "red clays," the Fe2O3 content can reach between 15 and 20%.These high iron contents can cause, during calcination, a very intense and generally undesirable red coloration of the artificial pozzolan obtained in this way and of the composite cements made with it, while clays with low iron content lead to a pinkish coloration. For this reason, in the calcination or post-calcination zone of plants for the production of calcined clays, for example, reducing gaseous combustion conditions are adjusted to achieve, in particular, the transformation of the Fe₂O₃ present in red-colored minerals, such as hematite, into black magnetite (Fe₃O₄). Establishing reducing combustion conditions, in turn, requires highly combustible, expensive, and CO₂-intensive primary fossil fuels, such as natural gas, oil, lignite, or bituminous coal.Generating reducing combustion conditions for color modification is therefore, from a process engineering perspective, incompatible with the combustion conditions required for optimal fuel conversion. In particular, so-called secondary fuels require continuously oxidizing combustion conditions for efficient combustion, which, in turn, necessitates complex post-treatment of trivalent ferric species to eliminate or reduce the unwanted red coloration in the thermally activated clay. WO 2017 / 008863 A1 discloses a procedure and installation arrangement for conditioning and activating a raw material. EP 3909682 A1 discloses a procedure and a tubular mill for the thermomechanical activation of a clay mixture. DE 102015106109 A1 discloses a procedure for the tribochemical activation of binders and additives. An overview of the state of the art can be obtained, for example, from the following scientific publications: Bolm, Carsten; Hernandez, Jose G. (2018) : Mechanomystification of Gaseous Reactants (Angew. Chem. Int. Ed, 58) . Available online at http: / / dx.doi.org / 10.1002 / anie.201810902. Fernändez, Rodrigo; Martirena, Fernando; Scrivener, Karen L. (2011) : The origin of the pozzolanic activity of calcined clay minerals: A comparison between kaolinite, illite and montmorillonite. In: Cement and Concrete Research 2011 (41), pp.113-122. DOI: 10.1016 / j.cemconres.2010.09.013. Ili, Biljana; Radonjanin, Vlastimir; Male?ev, Mirjana; Zduji, Miodrag; Mitrovi, Aleksandra (2016) : Effects of mechanical and thermal activation on pozzolanic activity of kaolin containing mica. En: Applied Clay Science 2016 (123) , S.173-181. DOI: 10.1016 / j.clay.2016.01.029. Tole, Ilda; Habermehl-Cwirzen, Karin; Cwirzen, Andrzej (2019) : Mechanochemical activation of natural clay minerals: an alternative to produce sustainable cementitious binders - review. En: Miner Petrol 2019 (113) , pp.449-462. DOI: 10.1007 / s00710-019-00666-y. Tole, Ilda; Habermehl-Cwirzen, Karin; Rajczakowska, Magdalena; Cwirzen, Andrzej (2018) : Activation of a Raw Clay by Mechanochemical Process-Effects of Various Parameters on the Process Efficiency and Cementitious Properties. En: Materials (Basilea, Suiza) 2018 (11) . DOI: 10.3390 / ma11101860 DE 10 2017 114 831 A1 discloses a procedure for the treatment of fly ash and a procedure for the manufacture of cement. CN 109954485 A discloses a manufacturing process for activated clays. CZ 307528 B6 discloses a procedure for the treatment of kaolin, clay or a mixture thereof. JP H0867803 A discloses an epoxy resin and its manufacturing process. CN 111362602 A discloses a procedure for modifying the color of a cementitious material containing clay. WO 97 / 01614 A1 discloses the activation of clays using metallic salts. RU 2209824 C2 discloses a process for the manufacture of mud powders. De SIMON BLOTEVOGEL: "Ability of the R3 test to evaluate differences in early age reactivity of 16_industrial ground granulated blast furnace slags (GGBS) ", CEMENT AND CONCRETE RESEARCH. vol.130, 1 de abril. 2020 (2020-04-01) , página 105998, XP93161349, US ISSN: 0008-8846, DOI: 10.1016 / j.cemconres.2020.105998 Encontrado en Internet: URL:https: / / www.sciencedirect.com / science / article / pii / S0008884619311421 / pdfft?md5=-d44e758bb1164f2d480c3a3ede769488&pid =1-s2.0-S0008884619311421-rnain.pdf> [encontrado el 2024-05-13] la prueba R3 es conocida. From TOLE ILDA ET AL: "Mechanochemical activation of natural clay minerals: an alternative to produce sustainable cementitious binders - review", MINERALOGY AND PETROLOGY, SPRINGER VIENNA, VIENNA, vol.113, no. 4, May 8, 2019 (2019-05-08), pp.449-462, XP036833323, ISSN: 0930-0708, DOI: 10.1007 / S00710-019-00666-Y [accessed 2019-05-08] the mechanochemical activation of clays is known. Since clays constitute a complex system (particularly compared to calcined limestone), different activation procedures lead to different products (activated clays) with different properties. Furthermore, the diversity of usable clays means that not every procedure is applicable to every clay. The invention aims to enable simple color optimization and, in particular, to allow the use of clays with a high iron content that would otherwise be unusable. This objective is achieved by the process with the characteristics indicated in claim 1. Advantageous improvements follow from the dependent claims, the description that follows, and the drawings. The process according to the invention serves for the mechanochemical activation and simultaneous color optimization of mineral material. It involves, on the one hand, mechanochemically activating the mineral material in a first high-energy mill, rather than through a thermal process. On the other hand, it involves simultaneously achieving color optimization with the activation, and not performing it in a subsequent stage, as is typical in thermal activation. Therefore, simultaneous activation and color optimization in a single milling operation, and thus in a single machine unit, is essential. The mechanochemical activation and simultaneous color optimization are carried out in a first high-energy mill. For this purpose, the mineral material is milled together with a solid reducing agent in the first high-energy mill. Mechanochemical activation consists of three phases or stages: In the first stage, particle size decreases (more or less linearly) with the addition of energy. Put simply, the more the material is ground, the finer the product becomes (Rittinger zone). However, this has a limit, a particle size that can hardly be reduced further. From this point, a second stage begins, in which particle size does not change with an additional input of energy (aggregation zone). In this stage, crystallographic structures are destroyed through the breaking of atomic bonds; individual atoms or entire groups of atoms are replaced by other atoms or groups of atoms.In particular, on the particle surfaces, the initial crystalline structure, as well as the bond type and oxidation states of the atoms, are modified due to the high energy transfer and subsequent chemical reactions. For economic reasons, in conventional milling, where the sole aim is to generate surface area, the transition from the first to the second stage is therefore avoided. However, this step is necessary for mechanochemical activation. If the energy input is further increased, a third stage can be reached, in which an increase in particle size can again be observed due to nanoparticle agglomeration (agglomeration zone), which has a positive impact on the processability of activated clay-based mortars and cement concretes.Therefore, in conventional grinding this area will be avoided even further, since with less effort a better result can be achieved in relation to the particle size distribution. However, it has been shown that with high energy inputs, i.e., in the second stage, modifications occur in the material itself. For example, in clays, similar to thermal activation, these modifications lead to a reactivity that allows the material to be used as a binding agent (and thus as a substitute for clinker). Therefore, with energy inputs of this magnitude, subsequent heat treatment can be omitted. However, it has been shown that the energy demand for purely mechanochemical activation can be higher than that of thermal activation. Therefore, the process according to the invention initially appears disadvantageous compared to conventional thermal activation. However, it has been demonstrated that the process according to the invention is advantageous despite the comparatively high energy demand, particularly for clay activation. Specifically in the case of complex raw materials, such as clays, thermal activation regularly leads to several negative effects. On the one hand, it is known that, for example, clays can release gaseous substances at high temperatures, which necessitates more complex exhaust gas cleaning, particularly in the event of additional CO2 separation (carbon capture) that may be required in the future.This can be avoided by using lower temperatures. On the other hand, at high activation temperatures, coloring components, such as iron compounds, frequently oxidize, which in the case of iron leads to an undesirable red coloration of the product. In fact, simultaneous grinding with a solid reducing agent even allows the use of already strongly colored materials, particularly materials containing Fe₂O₃, such as clays known as "red clays," as starting materials, transforming them into a colorless product. Thus, although the energy demand for the activation step itself increases in the process according to the invention, the treatment of exhaust gases is simplified, and a separate process step with subsequent reduction can be avoided. In this way, the entire activation process for manufacturing a marketable binder can be efficiently simplified.Furthermore, different clay minerals exhibit different optimum activation temperatures. For example, minerals from the kaolin and chlorite groups activate at considerably lower temperatures than, for instance, minerals from the mica group (muscovite, illite, and others). If, in the case of clays containing minerals from these groups, the optimum activation temperature of kaolinite is selected for thermal activation, minerals such as muscovite and illite will still not activate. Conversely, if the considerably higher activation temperature of muscovite and illite is selected for thermal activation, the formation of new mineral phases, particularly spinels, leads to over-calcination of the kaolinite, resulting in its deactivation.In contrast, this differentiation of clay minerals with respect to the optimum activation temperature disappears in mechanochemical activation. Coloring components, for example, iron compounds, frequently oxidize at higher activation temperatures, which in the case of iron leads to an increase in the undesirable red coloration of the product. Unlike the thermal activation of clay, in which the clay minerals are dehydroxylated and the generated water is completely released, in the mechanochemical process according to the invention, it can be shown that the water or, respectively, the hydroxyl groups of the clay minerals remain conserved in the mineral structure and are made available for a reaction, for example, with a solid metal such as aluminum powder or zinc powder. The hydrogen generated in this reaction enables the transformation of Fe₂O₃ to Fe₃O₄ in the clay minerals, in particular according to the following chemical reactions: 2 Al + 3 H2O --> Al2O3 + 3 H2 9 Fe2O3 + 3 H2 --> 6 Fe3O4 + 3 H2O Total: 2 Al + 9 Fe2O3 --> Al2O3 + 6 Fe3O4 As can be seen from the reaction equations, this is an autocatalytic reaction. This means that the water required for the first reaction step is not completely consumed. According to the invention, the color optimization process is particularly efficient because the kinetics of the chemical reduction reaction of Fe₂O₃ to Fe₃O₄ are enhanced by the availability of the water molecules or hydroxyl groups necessary for the reduction reaction in the clay minerals. This effect is based on the high energy level during mechanochemical activation and the resulting surface chemistry. In contrast, after thermal activation, the water or hydroxyl groups required for such transformations are not present. The high mixing effect of the material during mechanochemical activation is due to the high rotational speed of the agitator in the first high-energy mill. According to the invention, the mechanochemical activation of the mineral material causes an increase in the R3(7d) value, determined according to ASTM C1897-20 for the evaluation of reactivity or pozzolanicity, of at least 150 J / g, preferably at least 250 J / g, compared to the starting material. The activation is therefore sufficiently high to use the materials activated in this way as supplementary cementitious materials (SCMs). ASTM C1897-20 is a standard commonly used in the cement industry for analyzing the reactivity of cement additives or, respectively, for characterizing setting behavior. In another embodiment of the invention, the grinding and mechanochemical activation are carried out with an energy input per grinding chamber volume of at least 100 kW / m³, preferably at least 200 kW / m³. A typical value for a ball mill, as an example of a fine mill, is usually closer to 20 kW / m³ and is therefore considerably lower (and more energy-efficient). In this respect, the grinding chamber volume should be understood as the available volume inside the first high-energy mill, i.e., the free volume when there is no material or, for example, balls in the first high-energy mill. Therefore, components belonging to the mill, such as a shaft or agitator tools and the like, arranged in a movable manner inside, are not considered part of the grinding chamber volume, since this volume cannot be occupied by material. In another embodiment of the invention, after milling, selective size separation is carried out into a coarse fraction and a fine fraction. The fine fraction is reintroduced into the first high-energy mill, and the coarse fraction is extracted as product. For example, the separation is performed using a classifier. In this respect, the fine fraction is recirculated, since activation is associated with an increase in particle size. This differs fundamentally from conventional separation and recirculation in a mill, where the coarse fraction is typically recirculated. In another embodiment of the invention, the second selective size separation is carried out in such a way that the size boundary between the second coarse fraction and the second fine fraction corresponds to the smallest particle size achievable with the second high-energy mill multiplied by a factor of 2. In another embodiment of the invention, the first high-energy mill is operated continuously. This means that both the mineral material is continuously fed into the first high-energy mill and, simultaneously, activated mineral material is continuously extracted. Preferably, the first high-energy mill is therefore operated as a through-mill with an inlet and an outlet. In another embodiment of the invention, the first high-energy mill is selected from the group comprising vibrating mills, planetary ball mills, and agitated ball mills. Preferably, the first high-energy mill is selected from the group comprising planetary ball mills and agitated ball mills. These types of mills have proven to be particularly suitable for mechanochemical activation, as particularly high energy densities can be achieved with them.A dry-operated agitated ball mill is especially preferred as the first high-energy mill. In another embodiment of the invention, a ball agitator mill with a length-diameter ratio of 2.5 to 5 is selected. In another embodiment of the invention, the first high-energy mill is filled with grinding media to a volume fill level of between 50% and 95%, preferably between 60% and 70%. In this respect, the apparent volume of the grinding media refers to the volume of the first high-energy mill. Since, in a simple filling, the fill level is approximately 64%, and in a denser sphere packing arrangement, approximately 74%, even with a theoretical grinding media fill level of 100%, a corresponding free space remains that can be occupied, for example, by the mineral material to be activated.However, since the degree of filling of a charge of grinding media depends significantly on the shape and uniformity of the grinding media, in practice it is simpler to refer here to the degree of filling of the grinding media to the apparent volume rather than the actual (filled) volume. In another embodiment of the invention, grinding media made of iron or an iron alloy, or of aluminum or an aluminum alloy, are selected. Preferably, grinding media made of iron or an iron alloy are selected. In particular, steel grinding media are selected. In another embodiment of the invention, ceramic grinding bodies are selected. In another embodiment of the invention, grinding bodies with a diameter of between 1 mm and 10 mm are selected. In another embodiment of the invention, the ball agitator mill is operated with a peripheral speed of between 2 m / s and 6 m / s, preferably between 3 m / s and 5 m / s, and most preferably between 3.5 m / s and 4.5 m / s. In another embodiment of the invention, the agitated ball mill is operated with a volumetric gas flow rate and a material flow rate. The ratio between the volumetric gas flow rate and the material flow rate is adjusted such that the ratio between the volumetric gas flow rate and the material flow rate is between 0.0001 m³ / kg and 5 m³ / kg, preferably between 0.1 m³ / kg and 2 m³ / kg. In another embodiment of the invention, the mineral material is dried before being introduced into the first high-energy mill and is crushed to achieve a residual moisture content of less than 1% by weight and a grain size of less than 2 mm. In another embodiment of the invention, the mineral material is selected from the group comprising clay, ash, in particular fly ash, belite cement clinker, fine fractions of recycled concrete, slag, phyllosilicates, and tectosilicates. Clay, or a mixture of clay and one or more additional materials selected from the group comprising ash, in particular fly ash, belite cement clinker, fine fractions of recycled concrete, slag, phyllosilicates, and tectosilicates, as well as limestone, is particularly preferred as the mineral material. In another embodiment of the invention, the mineral material is mechanochemically activated together with between 0.1 and 50% by weight of quartz or corundum. In another embodiment of the invention, the material is analyzed after activation and color optimization to determine the activation. For the analysis, one or more procedures are selected from the group comprising IR spectroscopy, Raman spectroscopy, X-ray diffraction analysis, heat flow calorimetry, thermogravimetry, scanning electron microscopy, particle size and / or particle shape analysis, NMR spectroscopy, and color measurement. Preferably, one or more procedures are selected for the analysis from the group comprising IR spectroscopy, Raman spectroscopy, X-ray diffraction analysis, heat flow calorimetry, and color measurement.In another embodiment of the invention, the gas for the gas flow through the first high-energy mill is selected and used, comprising one or more gases selected from the group comprising nitrogen, argon, carbon dioxide, water vapor, carbon monoxide, hydrogen, and hydrocarbons, particularly methane, ethane, propane, and butane. Preferably, the gas contains primarily (more than 50% by volume) nitrogen, carbon dioxide, or water vapor. Preferably, the gas contains less than 1% by volume, and preferably less than 0.1% by volume, of oxygen. In another embodiment of the invention, a metal with an electronegativity of less than 1.8, preferably less than 1.7, is selected as the reducing agent. This ensures the reliable reduction of trivalent iron. In another embodiment of the invention, a metal with a lower (more negative) standard potential than iron is selected as the reducing agent. In another embodiment of the invention, a reducing agent is selected from the group comprising aluminum, zinc, magnesium, and calcium. These metals have proven suitable for several reasons. First, these elements are not detrimental to the final cement product, as most are already present in it anyway. Second, they, for example aluminum, are readily and inexpensively available. Moreover, these metals are particularly well-suited to the process according to the invention. In another embodiment of the invention, 0.01 to 1 mol of reducing agent is added per kg of amount of mineral material fed. In another embodiment of the invention, the amount of reducing agent is selected such that the electrons released by the oxidation of the metal correspond to between 0.03 and 0.33 times the amount of Fe3+ contained in the mineral material. Theoretically, it would be sufficient to transform one-third of all iron atoms into divalent iron with the formation of magnetite. However, it has been found that even 10% produces discoloration that results in an acceptable product. Therefore, within this range, product optimization (from acceptable to optimal) is possible in relation to costs (the lower the cost, the more economical), depending on the target market. In another embodiment of the invention, the reducing agent is added with a particle size of less than 100 µm. Preferably, the reducing agent is added with a particle size greater than 0.1 µm. In another embodiment of the invention, the reducing agent is supplied by abrasion of the grinding media. For this purpose, aluminum grinding media are preferably used. This is preferred when the required amount of reducing agent is small, particularly in the case of clays with low iron content. In another embodiment of the invention, the reducing agent is selected from the group comprising tin(II) sulfate (ZnSO4), antimony trioxide (Sb2O3), iron(II) sulfate (FeSO4), iron(II) sulfate monohydrate (FeSO4·H2O), and iron(II) sulfate heptahydrate (FeSO4·7H2O). Preferably, the reducing agent is selected from the group comprising tin(II) sulfate (ZnSO4) and antimony trioxide (Sb2O3). In another embodiment of the invention, elemental carbon is selected as the reducing agent from the group comprising coal, graphite, anthracite, carbon black or petroleum coke, in the presence of carbon dioxide. In another embodiment of the invention, elemental carbon from the group comprising coal, graphite, anthracite, carbon black, or petroleum coke is selected as the reducing agent, in the presence of carbonates from the group comprising dolomite, magnesite, calcite, aragonite, iron carbonate, or alkali carbonates. In another embodiment of the invention, the process comprises a control circuit, regulating the amount of reducing agent added. That is, the amount of reducing agent added is actively regulated. The Lab color value (also CIELAB or L*a*b*) is determined from the activated material produced by the process. In the Lab color value, the lightness value L* is perpendicular to the color plane (a*, b*) and is defined by EN ISO 11664-4 "Colorimetry Part 4: CIE 1976 L*a*b* Color space". The amount of reducing agent added increases when the a* value exceeds 3 and decreases when the a* value is less than 1.In this way, the product is optimized in terms of market acceptance and the consumption of reducing agent is minimized. Active regulation also allows for optimal adaptation to the typically fluctuating composition of, for example, natural clays. In another embodiment of the invention, the process comprises a regulating circuit, whereby the added quantity of reducing agent is regulated. That is, the added quantity of reducing agent is actively regulated. The Lab color value (also CIELAB or L*a*b*) is determined from the activated material produced by the process. In the Lab color value, the lightness value L* is perpendicular to the color plane (a*, b*) and is defined by EN ISO 11664-4 "Colorimetry Part 4: CIE 1976 L*a*b* Color space". The amount of reducing agent added is increased when the color index, determined as the root of the sum of (a*) 2 and (b*) 2, is greater than 5, preferably greater than 10. Correspondingly, the amount of reducing agent added is reduced when the color index, determined as the root of the sum of (a*) 2 and (b*) 2, is less than 10, preferably less than 5. In another embodiment of the invention, a partial thermal activation is carried out prior to the mechanochemical activation. Preferably, the thermal activation is performed at a temperature below 600 °C, and more preferably below 500 °C. In purely thermal activation, temperatures of, for example, 900 °C are typical. In this way, energy can be saved and the energy demand for the mechanochemical activation at least partially reduced. Furthermore, the reduction of the maximum temperature also has other positive effects; for example, the thermal formation of nitrogen oxides is reduced, and undesirable modifications of the product, such as color changes due to the oxidation of coloring components, are avoided. The procedure according to the invention is then explained in more detail by means of an exemplary embodiment shown in the drawings. Fig.1 Flowchart Figure 1 shows a highly schematic representation of the process. Clay is extracted from a clay deposit 10 as a mineral material for activation and color optimization. This clay is conveyed past a chemical analysis sensor 20 to determine its Fe3+ content. The determined Fe3+ content is transmitted to a control unit 70. The control unit 70 regulates the dosage of aluminum from an aluminum deposit 30 into the clay. The clay and aluminum mixture is then transferred to a first high-energy mill 40, where it is ground and simultaneously activated and its color is optimized internally within the process. The material from the first high-energy mill 40 is analyzed in a color analyzer 50, and the L*a*b* color value is determined and transmitted to the control unit 70. The finished product is then transferred to a product deposit 60. Alternatively, instead of chemical analysis 20, another color analysis corresponding to color analysis 50 can also be used. This considerably simplifies the procedure. It uses the color value of the clay and, based on experience, assigns an Fe3+ content to that color value. The procedure can then be carried out otherwise without modification. Numerical references 10 clay deposit 20 chemical analysis 30 aluminum tank 40 first high energy mill 50 color analysis 60 product deposit 70 control unit

Claims

1. A method for the mechanochemical activation and simultaneous optimization of the color of mineral material, characterized in that the mechanochemical activation and simultaneous color optimization are carried out in a first high-energy mill (40), the mineral material being ground together with a solid reducing agent in the first high-energy mill (40), the mechanochemical activation of the mineral material causing an increase in the R3 (7d) value according to ASTM C1897-20 of at least 150 J / g, preferably at least 250 J / g.

2. A method according to claim 1, characterized in that a metal with an electronegativity less than 1.8 is selected as the reducing agent.

3. A method according to any of the preceding claims, characterized in that a metal with a standard potential lower (more negative) than that of iron is selected as the reducing agent. 4.A process according to any of the preceding claims, characterized in that a metal from the group comprising aluminum, zinc, magnesium, and calcium is selected as the reducing agent.

5. A process according to any of the preceding claims, characterized in that 0.01 to 1 mol of reducing agent is added per kg of mineral material fed.

6. A process according to any of the preceding claims, characterized in that the amount of reducing agent is selected such that the electrons released by the oxidation of the metal correspond to between 0.03 and 0.33 times the amount of Fe3+ contained in the mineral material.

7. A process according to any of the preceding claims, characterized in that the reducing agent is added with a particle size of less than 100 µm.

8. A process according to any one of claims 1 to 6, characterized in that the reducing agent is supplied by abrasion of the grinding media. 9.A process according to claim 1, characterized in that the reducing agent is selected from the group comprising tin(II) sulfate (ZnSO4), antimony trioxide (Sb2O3), iron(II) sulfate (FeSO4), iron(II) sulfate monohydrate (FeSO4·H2O), and iron(II) sulfate heptahydrate (FeSO4·7H2O).

10. A process according to claim 1, characterized in that elemental carbon is selected as the reducing agent from the group comprising coal, graphite, anthracite, carbon black, or petroleum coke, in the presence of carbon dioxide.

11. A process according to claim 1, characterized in that elemental carbon is selected as the reducing agent from the group comprising coal, graphite, anthracite, carbon black, or petroleum coke, in the presence of carbonates from the group comprising dolomite, magnesite, calcite, aragonite, iron carbonate, or alkali carbonates. 12.A method according to any of the preceding claims, characterized in that the method comprises a control circuit, regulating the added amount of reducing agent, determining, for example, the color value L*a*b* of the activated material manufactured by the method, increasing the added amount of reducing agent when the value a* exceeds 2 and reducing the added amount of reducing agent when the value a* is less than 1.

13. A method according to any of the preceding claims, characterized in that a partial thermal activation is carried out before the mechanochemical activation.

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