Method for optimized operation of a mill for mechano-chemical activation

Abstract

The present invention relates to a method for mechano-chemical activation in a mill, wherein the method has at least two operating states, wherein in a first operating state a first energy input per mass of ground material takes place, wherein in a second operating state a second energy input per mass of ground material takes place, wherein the first energy input is higher than the second energy input, wherein the first operating state is selected when electrical energy is cheaper or more available than in the long-term average, wherein the second operating state is selected when electrical energy is more expensive or less available than in the long-term average.

Description

[0001] The invention relates to a method for mechano-chemical activation taking into account optimal energy utilization.

[0002] Activated clays have established themselves as an additive, particularly in the cement industry. The current standard method is drying and calcining the clays, i.e., thermal activation. This requires energy for heating, and the high temperature can also cause further, potentially undesirable, changes in the material. Furthermore, the thermal process requires flue gas purification to capture the resulting nitrogen oxide and sulfur oxide emissions. Furthermore, the thermal process will require the use of processes to capture and, if necessary, purify the carbon dioxide produced or released.

[0003] Cement aggregates are now used to reduce clinker and thus carbon dioxide emissions. According to DIN EN 450-1, the activity index describes the ratio (in %) of the compressive strengths of standardized mortar prisms tested at the same age, which contain a mass fraction of 75% test cement and a mass fraction of 25% cement aggregate, and standardized mortar prisms produced exclusively with test cement. The test cement used is a Portland cement (type CEM I) with a strength class of 42.5 or higher. The cement aggregate (supplementary cementitious material, SCM) to be evaluated can be less or more powerful than the test cement. An SCM considered inert, such as limestone, results in an activity index of 75%, meaning the SCM makes no contribution to strength development. However, high-performance SMCs such as granulated blast furnace slag can also achieve activity values ​​of more than 100 up to about 120.If the activity index is above 100, this means that the clinker content in the binder can be reduced even further, namely by exactly the amount necessary to achieve an activity index of 100. The clinker content is usually replaced by an inert, finely ground filler such as limestone, which is considerably cheaper to produce than clinker.

[0004] Therefore, so-called mechanochemical activation through intensive grinding is increasingly being discussed. The process of mechanochemical activation can be used to produce cement aggregates that can optionally replace other secondary cementitious materials, i.e., SCMs. Ideally, SCMs possess pozzolanic, latent hydraulic, or even hydraulic properties, allowing these materials to contribute to the strength development when the finished binder is mixed with water. Inert materials such as limestone do not exhibit this additional strength development when mixed with water.

[0005] During mechanochemical activation, previously crystalline water remains in the mineral material, for example, as inner-layer water (xerogels). This differentiation from thermally activated materials is an essential quality feature of mechanochemically activated materials when used as cement aggregates, as it results in improved binding properties, particularly low water requirements. This has an improved effect on, for example, the strength development and processing of the binder-containing mortar or concrete, without the need for expensive cement additives such as superplasticizers.

[0006] From the subsequently published DE 10 2023 106 210 a process for grinding and pozzolanic activation in a stirred ball mill is known.

[0007] From the subsequently published DE 10 2023 106 217 a process for grinding and pozzolanic activation in two separate stages of a stirred ball mill is known.

[0008] From the subsequently published DE 10 2023 106 221, the combination of mechanochemical and thermal activation in at least one agitator ball mill is known.

[0009] From the subsequently published DE 10 2023 106 222, the color optimization in the mechano-chemical activation of clays is known.

[0010] A cement additive made from old concrete is known from the subsequently published DE 10 2023 123 525.

[0011] One advantage of mechanochemical activation is that even clays with a lower kaolin content, which are not suitable for thermal activation, can be mechanochemically activated. This broadens the available raw material base.

[0012] Because clays are a complex system (especially compared to the firing of limestone), different activation processes result in different products (activated clays) with different properties. Likewise, the diversity of the clays that can be used means that not every process is suitable for every clay.

[0013] Mechanochemical activation differs fundamentally from thermal activation in terms of the understanding of the processes involved. While thermal activation is primarily determined by temperature and time, mechanochemical activation in a mill appears to be considerably more complex and dependent on many more parameters. Furthermore, a large portion of the input grinding energy is converted into heat.

[0014] A key difference from conventional thermal activation is that the required energy does not come from fuel fed into the reactor, but rather as drive power to the mill and is therefore preferably provided as electrical energy. However, the process is subject to fluctuations in the electrical energy supply, whether in terms of price via a utility grid or due to the availability of electricity from renewable sources, such as wind power or photovoltaics.

[0015] The object of the invention is to adapt the process of mechano-chemical activation to the fluctuations in the electrical energy supply.

[0016] This object is achieved by the method having the features specified in claim 1. Advantageous further developments emerge from the subclaims, the following description and the drawings.

[0017] The method according to the invention serves for mechanochemical activation in a mill. Conventionally, activation is carried out thermally, whereby the mineral material is heated, for example, to 900°C to 1000°C. The objective of activation is achieved with mechanical activation through very intensive grinding, whereby significantly more energy is input than is required for comminution. In this range of mechanical activation, particle growth can be detected through grinding. Specifically, this means that, despite further energy absorption by the particles, a coarsening of the grain size range can be detected using conventional analytical methods. The device comprises a mill. The mill is preferably an agitated ball mill. 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.These known methods are being further developed in order to improve them. The method according to the invention has at least two operating states. In a first operating state, a first energy input per mass of ground material takes place, in a second operating state, a second energy input per mass of ground material takes place. The first energy input is higher than the second energy input. This means that in the first operating state, greater activation of the ground material is achieved, i.e. a higher activity index is achieved. The first operating state is selected when electrical energy is cheaper or more available than the long-term average. The second operating state is selected when electrical energy is more expensive or less available than the long-term average.

[0018] If, for example, electrical energy generated from renewable sources is used for activation, the availability of the electrical energy is subject to fluctuations. If the electrical energy is provided by photovoltaics, the well-known day-night rhythm arises with a pattern throughout the day (neglecting cloud cover). With wind power, the situation is more complex. Typically, attempts are made to minimize these effects by combining wind and solar energy, for example, to achieve a more consistent energy supply. In addition, energy storage systems such as batteries are usually used to achieve uniformity. However, there remains a dependency on the amount of generation. These cycles also lead to corresponding price developments on the electricity market, which today are largely attributable to this variable amount of generation.The simplest and easiest way to illustrate this is with the example of photovoltaics and its daily rhythm. At night, there is no electricity, and the mill is idle. At midday, the maximum amount of electricity is available (more in summer, less in winter). At this time, the mill can produce the maximum amount with the best quality. In the period immediately after sunrise and before sunset, the available electrical energy is too low, making it unprofitable to operate the mill. Now, with constant quality, the amount of material fed in can be scaled with the available amount of electricity, yielding a constant result. The disadvantage is that energy is no longer sufficient relatively early in the day; for example, if the mass flow through the mill is below 50%, it is no longer viable to operate the mill. As already explained, this more complex situation also applies to other (fluctuating) electricity sources, be it in terms of availability or (therefore) in price.

[0019] Therefore, at least a second operating mode is introduced, which still produces activated product even at lower availability, but with a lower activation. In the simplest case, the "good" and "bad" fractions can then be mixed, thus achieving medium activity with an increased production volume. Alternatively, the higher-value product can be sold at a higher price. The key point is that the two operating modes produce two different products based on the activity index, thus achieving better overall utilization of the mill.

[0020] Of course, multiple operating states are also possible, for example, three operating states. This can be useful, for example, if the fluctuation is solely due to price fluctuations, but electricity from the grid is always available. In this case, an operating state for an average electricity price can be selected for medium activation, an operating state for maximum activation at a low electricity price, and a low activation at a high electricity price. This ensures optimal utilization of the mill.

[0021] Secondly, different products can be stored more easily than electricity can be buffered. The goal is therefore to advantageously convert power fluctuations into controlled quality levels and thus achieve an optimum. Likewise, a very large number of operating states can be implemented to enable particularly good dynamic adaptation.

[0022] In a further embodiment of the invention, the first energy input is selected to be greater than 500 kWh / t, and the second energy input is selected to be less than 500 kWh / t. For example, in the case of three operating modes, the energy inputs are selected from the windows 200 to 400 kWh / t, 400 to 500 kWh / t, and greater than 500 kWh / t.

[0023] In a further embodiment of the invention, the first energy input and the second energy input have a difference of at least 50 kWh / t, preferably at least 100 kWh / t.

[0024] In a further embodiment of the invention, the long-term average is considered a forecasting average for 1 to 10 days. This optimally reflects price predictability on the spot market.

[0025] In a further embodiment of the invention, the long-term average is considered to be an annual average. For renewably generated electrical energy, a long-term average of 5 to 30 years is preferably used.

[0026] In a further embodiment of the invention, in the second operating state, the product already activated in the mill is fed back to the mill for further activation. This reduces the product quantity but increases the activation and thus the product quality.

[0027] In a further embodiment of the invention, a forecast is made for the availability of electrical energy. This allows early planning of the operating states and also the required product quantities. Preferably, the reactivation by returning to the mill in the second operating state can also be taken into account. Again taking photovoltaics as an example, more electricity is available in summer, so the amount of high-quality product from the first operating state will be higher. In winter, the second operating state will predominate. In order to obtain a sufficiently high-quality product, a sufficient proportion is reactivated and thus refined. With a forecast, it can therefore be decided, for example, in the second operating state whether a simple product or a higher-quality product through reactivation is produced in order to ultimately achieve the desired mixture of both qualities.

[0028] In a further embodiment of the invention, in the first operating state the maximum material flow is driven through the mill and in the second operating state 50% of the maximum material flow is driven through the mill.

[0029] In a further embodiment of the invention, in the first operating state, the millbase is activated to an activity index of 100 to 120, preferably 110 to 120, and in the second operating state, the millbase is activated to an activity index of 80 to 100, preferably 80 to 90. The activity index is defined according to DIN EN 450-1.

[0030] In a further embodiment of the invention, the process is carried out in a mill having an internal volume of at least 1 m 3 carried out.

[0031] In a further embodiment of the invention, the process is carried out in a mill with an energy density of at least 200 kW / m 3 carried out.

[0032] In a further embodiment of the invention, the process is carried out in a mill having a length of at least 2 m, preferably of at least 2.5 m.

[0033] 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 at least 0.75 m 2 , on.

[0034] In a further embodiment of the invention, the process is carried out in a mill having a length to diameter ratio of at least 3, preferably of at least 3.5.

[0035] In a further embodiment of the invention, the mill is operated with a residence time of the material to be ground in the mill of at least 5 minutes, preferably at least 10 minutes, particularly preferably at least 20 minutes.

[0036] The method according to the invention is explained in more detail below using an embodiment shown in the drawings. Fig. 1 summer Fig. 2 winters

[0037] The figures show an example of photovoltaic power generation in a highly simplified and schematic form. The power generation is shown at the top (highly simplified). The activity index is shown at the bottom. An example shows a first operating state that achieves an activation index A of 120, and a second operating state that achieves an activation index A of 80.

[0038] In Fig. 1 shows the condition in summer, in Fig. 2 the winter. In addition to the shorter sunshine duration, a lower maximum intensity is indicated in winter. Compared to summer in Fig. 1 it is also evident that in winter in Fig.2, the ratio of well-activated material to less activated material also changes significantly. Therefore, especially in winter, it can be advantageous to activate material a second time in the second operating state to achieve a better ratio. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2023 106 210 [0006, 0017] DE 10 2023 106 217 [0007, 0017] DE 10 2023 106 221 [0008, 0017] DE 10 2023 106 222 [0009, 0017] DE 10 2023 123 525 [0010, 0017]

Claims

[1] Method for mechano-chemical activation in a mill, the method having at least two operating states, wherein in a first operating state a first energy input per mass of ground material takes place, wherein in a second operating state a second energy input per mass of ground material takes place, the first energy input being higher than the second energy input, the first operating state being selected when electrical energy is cheaper or more available than in the long-term average, the second operating state being selected when electrical energy is more expensive or less available than in the long-term average. [2] Method according to claim 1, characterized by that the first energy input is selected with more than 500 kWh / t and the second energy input is selected with less than 500 kWh / t. [3] Method according to one of the preceding claims, characterized bythat the first energy input and the second energy input have a difference of at least 50 kWh / t, preferably at least 100 kWh / t. [4] Method according to one of the preceding claims, characterized by that is, the long-term average is considered the forecast average for 1 to 10 days. [5] Method according to one of claims 1 to 3, characterized by that the long-term average is considered as an annual average. [6] Method according to one of the preceding claims, characterized by that in the second operating state the product already activated in the mill is fed to the mill for further activation. [7] Method according to one of the preceding claims, characterized by that a forecast for the availability of electrical energy is made. [8] Method according to one of the preceding claims, characterized bythat in the first operating state the maximum material flow is driven through the mill, whereas in the second operating state 50% of the maximum material flow is driven through the mill. [9] Method according to one of the preceding claims, characterized by that in the first operating state the ground material is activated to an activity index of 100 to 120, preferably 110 to 120, wherein in the second operating state the ground material is activated to an activity index of 80 to 100, preferably 80 to 90.

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