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EP-4680586-B1 - OPTIMIZATION OF COLOR IN THE MECHANOCHEMICAL ACTIVATION OF CLAYS

EP4680586B1EP 4680586 B1EP4680586 B1EP 4680586B1EP-4680586-B1

Inventors

  • WILCZEK, MICHAEL
  • HINDER, DANIEL
  • FYLAK, Marc
  • NEUMANN, THOMAS
  • MAIER, OLIVER
  • LAMPE, KARL
  • SACHSE, CARSTEN
  • STROTMANN, Jan
  • WILLMS, EIKE
  • RUDOWSKI, LUC
  • MÖLLER, Hendrik
  • HAMM, ANDREAS

Dates

Publication Date
20260513
Application Date
20240311

Claims (13)

  1. A method for the mechanochemical activation and simultaneous color optimization of mineral material, characterized in that the mechanochemical activation and simultaneous color optimization take place in a first high-energy mill (40), wherein the mineral material is ground together with a solid reducing agent in the first high-energy mill (40) and wherein the mechanochemical activation of the mineral material causes an increase in the R3 value (7d) according to ASTM C1897-20 by at least 150 J/g, preferably by at least 250 J/g.
  2. The method according to claim 1, characterized in that a metal with an electronegativity of less than 1.8 is selected as the reducing agent.
  3. The method according to one of the preceding claims, characterized in that a metal with a lower (more negative) normal potential than that of iron is selected as the reducing agent.
  4. The method according to one 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. The method according to one of the preceding claims, characterized in that 0.01 to 1 mol of reducing agent is added per kg of mineral material added.
  6. The method according to one 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 0.03 to 0.33 times the amount of Fe 3+ contained in the mineral material.
  7. The method according to one of the preceding claims, characterized in that the reducing agent is added with a particle size of less than 100 µm.
  8. The method according to one of claims 1 to 6, characterized in that the reducing agent is added through abrasion of grinding media.
  9. The method according to claim 1, characterized in that the reducing agent is selected from the group comprising tin(II) sulfate (ZnSO 4 ), antimony trioxide (Sb 2 O 3 ), iron(II) sulfate (FeSO 4) , iron(II) sulfate monohydrate (FeSO 4 · H 2 O), and iron(II) sulfate heptahydrate (FeSO 4 · 7 H 2 O).
  10. The method according to claim 1, characterized in that elemental carbon from the group comprising coal, graphite, anthracite, carbon black, or petroleum coke in the presence of carbon dioxide is selected as the reducing agent elemental.
  11. The method according to claim 1, characterized in that elemental carbon 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 is selected as the reducing agent.
  12. The method according to one of the preceding claims, characterized in that the method comprises a control circuit, wherein the amount of reducing agent added is controlled, wherein, for example, the L*a*b* color value is determined from the activated material that is produced with the method, wherein the amount of reducing agent added is increased if the a* value exceeds 2 and wherein the amount of reducing agent added is reduced if the a* value falls below 1.
  13. Process according to one of the preceding claims, characterized in that a partial thermal activation is carried out before the mechanochemical activation.

Description

The invention relates to a method for color optimization during the mechano-chemical activation of clays. Activated clays have become established as additives, particularly in the cement industry. The currently common method involves drying and calcining the clays, i.e., thermal activation. This process requires energy for heating, and excessively high temperatures can cause further material changes that may be undesirable. The firing conditions during thermal activation in an oxidizing atmosphere cause naturally occurring iron compounds in the clays to transform, in particular, into red iron oxides. This results in a reddish coloration of the activated clays, which significantly reduces the market acceptance of cements produced with them. The iron content, or rather the content of iron in its strongly coloring trivalent oxidation state ( Fe³⁺ ), largely 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 the typically gray cement. Lower-quality ("lean") clays, in particular, can have Fe₂O₃ contents averaging 2 to 9 wt.%. In so-called "red clays , " the Fe₂O₃ content can even reach 15 to 20 %. These high iron contents can lead to a very intense and usually undesirable red discoloration of the artificial pozzolan produced and the composite cements made from it during calcination, while iron-poor clays result in a pinkish color. For this reason, in the calcination or post-calcination section of plants for the production of calcined clays, for example, combustion conditions with reducing gas atmospheres are established to achieve, in particular, the conversion of Fe₂O₃ in red-colored minerals, such as hematite, to black magnetite ( Fe₃O₄ ) . Establishing reducing combustion conditions, in turn , requires readily combustible fossil fuels, which are expensive and CO₂ -intensive, such as natural gas, petroleum, lignite, or hard coal. The creation of reducing combustion conditions for color change is therefore... From a process engineering perspective, this is actually contrary to combustion conditions for optimal fuel conversion. In particular, so-called secondary fuels require consistently oxidizing combustion conditions for effective combustion, which in turn necessitates complex post-treatment of the trivalent iron species to eliminate or reduce the undesirable red coloration in the thermally activated clay. From the WO 2017 / 008 863 A1 A process and a plant arrangement for processing and activating a raw material are known. From the EP 3 909 682 A1 A method and a roller mill for the thermomechanical activation of a clay mixture are known. From the DE 10 2015 106 109 A1 A method for the tribochemical activation of binders and additives is known. A general overview of the state of the art can be obtained, for example, from the following scientific publications: Bolm, Carsten; Hernändez, José G. (2018): Mechanochemistry of Gaseous Reactants (Angew. Chem. Int. Ed, 58). Available online at http://dx.doi.org/10.1002/anie.201810902 . Fernandez, 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 . Ilić, Biljana; Radonyanin, Vlastimir; Maleshev, Mirjana; Zdujić, Miodrag; Mitrović, Aleksandra (2016): Effects of mechanical and thermal activation on pozzolanic activity of kaolin containing mica. In: Applied Clay Science 2016 (123), pp. 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. In: 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. In: Materials (Basel, Switzerland) 2018 (11). DOI: 10.3390/ma11101860 From the DE 10 2017 114 831 A1 A process for processing fly ash and a process for producing cement are known. From the CN 109 954 485 A A manufacturing process for activated clays is known. From the CZ 307 528 B6 A method for treating kaolin, clay, or a mixture thereof is known. From the JP H08 67803 A is an epoxy resin and its production is known. From the CN 111 362 602 A A method for changing the color of clay-containing cementing material is known. From the WO 97/01614 A1 The activation of clay with metal salts is known. From the RU 2 209 824 C2 A method for producing sludge powders is known. From the 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 RESEARC