Mechano-chemical activation of mineral materials

Abstract

The present invention relates to the selection of the size of a mill for the economically viable mechano-chemical activation, in particular of clays, for example in the cement industry.

Description

The invention relates to the selection of the size of a mill for the economically viable mechanochemical activation, in particular of clays, for example in the cement industry.Activated clays have become established as an additive, particularly in the field of the cement industry. The currently customary way is drying and calcining of the clays, i.e. thermal activation. In this case, on the one hand, energy is required for the heating, and on the other hand, the high temperature can also bring about further material changes, which are possibly undesirable. Furthermore, the thermal process requires flue gas purification for the separation of the nitrogen oxide and sulfur oxide emissions formed. In addition, the thermal process requires the use of methods for separating out and optionally purifying the carbon dioxide generated or released in the future.Therefore, the so-called mechanochemical activation by intensive milling is increasingly discussed.From post-published DE 10 2023 106 210 a method for grinding and pozzolanic activation in an agitator ball mill is known.From post-published DE 10 2023 106 217, a method for grinding and pozzolanic activation is known in two separate stages of an agitator ball mill.The combination of mechanochemical and thermal activation in at least one stirred ball mill is known from post-published DE 10 2023 106 221.The color optimization in the mechanochemical activation of clays is known from post-published DE 10 2023 106 222.From post-published DE 10 2023 123 525 a cement additive made of old concrete is known.Since clays are a complex system (especially as compared to limestone firing), different activation methods result in different products (activated clays) with different properties. Also, the diversity of clays that can be used results in not every method being usable for each clay.Mechanochemical activation is fundamentally different from thermal activation as far as understanding of the operations is concerned. While thermal activation is primarily determined by temperature and time, mechanochemical activation in a mill appears to be substantially more complex and dependent on substantially more parameters. Furthermore, a large part of the grinding energy introduced is converted into heat, so that here an optimization potential entirely exists.The object of the invention is to optimize mechanochemical activation in a mill in such a way that the activation (reactivity of the product) per amount of energy used for the mill is the highest.This object is achieved by a device for mechanochemical activation having the features specified in claim 1, the use of a mill having the features specified in claim 7 and by the method having the features specified in claim 10. Advantageous refinements emerge from the dependent claims, the following description and the drawings.The device according to the invention is suitable for mechanochemical activation. Clays, for example, but also old concrete or other substances can be activated thermally, but also mechanochemically, and then have a suitable setting behavior and further properties in order to be able to be used, for example, as clinker substitute or additive. Such devices are known, for example, from DE 10 2023 106 210, DE 10 2023 106 217, DE 10 2023 106 221, DE 10 2023 106 222 or DE 10 2023 123 525.The apparatus comprises a mill. This mill is operated for mechanochemical activation in a region where clearly more grinding energy is introduced than is required for comminution and in which a size growth during grinding can already be observed again. It has surprisingly been found that a mill which has an internal volume of at least 1 m 3 can be used for activation particularly efficiently and thus particularly economically. This difference in efficiency leads to mills with an internal volume of less than 100 I being completely inefficient and only having an economically viable efficiency with an internal volume of more than 1 m 3. Surprisingly, it has been shown by means of technical tests that the ratio between the achieved activation and the energy introduced is highly dependent on the overall size of the machine, so that this results in a minimum size of the machine for economic operation. This means that a comparatively large mill must be selected precisely independently of the throughput to be achieved.In a further embodiment of the invention, the mill is an agitator ball mill.In a further embodiment of the invention, the mill has an energy density of at least 200 kW / m 3.In a further embodiment of the invention, the mill has a length of at least 2 m, preferably of at least 2.5 m.In a further embodiment of the invention, the mill has a cross-sectional area perpendicular to the longitudinal axis of at least 0.71 m 2, preferably of at least 0.75 m 2.In a further embodiment of the invention, the mill has a ratio of length to diameter of at least 3, preferably of at least 3.5.In a further aspect, the invention relates to the use of a mill having an internal volume of at least 1 m 3 for mechanochemical activation.In another embodiment of the invention, the mill used is an agitator ball mill.In a further embodiment of the invention, the mill used has an energy density of at least 200 kW / m 3.In a further aspect, the invention relates to a method for mechanochemical activation, for example of clays for use in the cement industry. For mechanochemical activation, a mill having an inner volume of at least 1 m 3 is selected.In a further embodiment of the invention, an agitator ball mill is selected as the mill.In a further embodiment of the invention, the mill is operated at an energy density of at least 200 kW / m 3.In a further embodiment of the invention, the mill is operated with a residence time of the grinding material in the mill of at least 5 min, preferably at least 10 min, particularly preferably at least 20 min.The relationship between the size of the interior space and the activation efficiency is shown below. FIG. 1 shows measurement data of two exemplary millsIn Fig. 1 two exemplary mills are shown which differ only in the size of the interior space. The interior of B is here 10 times as large as the interior of A. The energy input is plotted in kWh / t on the abscissa, the degree of activation achieved on the ordinate, 100% meaning the maximum activation achievable.It is readily apparent that the course for the mill A and the mill B runs parallel, but in the larger mill a significantly higher activation is achieved with the same energy input or, in other words, the same activation is achieved with a significantly lower energy input per ton of product.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2023 106 210 [0004, 0013]DE 10 2023 106 217 [0005, 0013]DE 10 2023 106 221 [0006, 0013]DE 10 2023 106 222 [0007, 0013]DE 10 2023 123 525 [0008, 0013]

Claims

An apparatus for mechanochemical activation, the apparatus comprising a mill, characterized in that the mill has an internal volume of at least 1 m 3.Device according to claim 1, characterised in that the mill is an agitator ball mill.Device according to one of the preceding claims, characterized in that the mill has an energy density of at least 200 kW / m 3.Device according to one of the preceding claims, characterized in that the mill has a length of at least 2 m, preferably of at least 2.5 m.Device according to one of the preceding claims, characterized in that the mill has a cross-sectional area perpendicular to the longitudinal axis of at least 0.71 m 2, preferably of at least 0.75 m 2.Device according to one of the preceding claims, characterized in that the mill has a length to diameter ratio of at least 3, preferably of at least 3.5.Use of a mill having an internal volume of at least 1 m 3 for mechanochemical activation.Use according to Claim 7, characterized in that the mill is an agitator ball mill.Use according to any of claims 7 to 8, characterized in that the mill has an energy density of at least 200 kW / m 3.A method of mechanochemical activation, wherein a mill having an internal volume of at least 1 m 3 is selected for mechanochemical activation.Method according to claim 10, characterised in that an agitator ball mill is selected as the mill.Method according to one of Claims 10 to 11, characterized in that the mill is operated at an energy density of at least 200 kW / m 3.Method according to one of Claims 10 to 12, characterized in that the residence time of the grinding material in the mill is at least 5 min, preferably at least 10 min, particularly preferably at least 20 min.

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