Device and method for temperature-optimized mechano-chemical activation

Abstract

The present invention relates to a device for the mechanical activation of a mineral material, wherein the device has a mill 10, wherein the mill 10 has a drive 20, wherein the device has at least a first temperature sensing element 30, wherein the first temperature sensing element 30 is arranged in or on the mill 10, wherein the device has a control device 40, wherein the device has a material feed 50 for feeding ground material to the mill 10, wherein the control device 40 is connected to the first temperature sensing element 30 for transmitting the detected temperature, wherein the control device 40 is connected to the drive 20 for regulating the drive power and to the material feed 50 for regulating the supplied quantity of ground material.

Description

The invention relates to an apparatus and a method for thermally controlled mechanochemical activation of mineral materials, in particular clays.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 mechanical activation or mechanochemical activation by intensive grinding is increasingly discussed.In mechanochemical activation, water bound in crystalline form beforehand is retained in the mineral material, for example, as inner layer water (Xerox gels). This differentiation into thermally activated materials is an essential quality feature of mechano-chemically activated substances when used as a cement aggregate, since this results in improved binder properties, in particular a low water requirement. This has an improving effect on, for example, strength development and processing of the binder-containing mortar or concrete without the need to use expensive cement additives such as superplasticizers.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 mechanical 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 mechanical 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.An advantage of mechanochemical activation is that clays with a lower kaolin content can also be mechanochemically activated, which are not suitable for thermal activation. This broadens the available raw material base.One of the challenges for mechanical activation is that only about 25% of the introduced milling energy is actually converted to chemical energy (activation), about 75% is converted to heat. This heat naturally leads to heating of the product. There is therefore the risk that the material will be heated too much and thus may lose its advantageous properties. However, it is difficult in this case that the energy for the sufficient mechanical activation has to be introduced precisely into the material, that is to say a simple reduction of the introduced energy is not possible.It is an object of the invention to provide a process which is as gentle as possible and nevertheless leads to a sufficiently activated product.This object is achieved by the device having the features specified in claim 1 and by the method having the features specified in claim 5. Advantageous further developments are evident from the dependent claims, the following description and the drawing.The device according to the invention serves for the mechanical activation of a mineral material, for example a clay. Conventionally, the activation is carried out thermally, wherein the mineral material is heated to 900° C. to 1000° C., for example. The aim of activation is achieved in the case of mechanical activation by very intensive grinding, with substantially more energy being introduced than is required for comminution. In this region of mechanical activation, particle growth can rather be detected by grinding. Specifically, it is meant that, despite further absorption of energy by the particles, an coarsening of the grain band is established by the conventional analytical methods. The apparatus comprises a mill. Preferably, the mill is an agitator 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 102023 106 222 or DE 10 2023 123 525. The mill has a drive. The energy is introduced into the mill via the drive. The device has at least one first temperature detection element. A temperature sensing element can be contact-type or contactless. The temperature detection element can be, for example, a thermocouple, and it can likewise be designed as an IR sensor. The device preferably has a plurality of temperature detection elements. The first temperature sensing element is arranged in or on the mill. In the simplest case, it is arranged on the outside on the housing of the mill. The advantage is the simple arrangement, the ease of connection, the avoidance of wear due to grinding material and the like. For this purpose, the measurement is the inaccurate and averaged by the total mass of the mill and delayed in time. A contactless detection of the temperature of the grinding material inside the mill would be particularly accurate, for example by IR sensors. The challenge here is in particular dust formation, adhesion and wear due to the grinding material. The device has a control device. The device further comprises a material supply for supplying grinding material to the mill. The control device is connected to the first temperature detection element for transmitting the detected temperature. Furthermore, the control device is connected to the drive for regulating the drive power and to the material feed for regulating the amount of grinding material fed in. It is essential that both the energy introduced (control of the drive power) and the amount of the grinding material supplied are controlled, since an approximate constancy of a high grinding energy introduced of, for example, 200 kWh / t of grinding material is necessary for the mechanical activation. Thus, only reducing the energy introduced would lead to no activation occurring any longer.In a further embodiment of the invention, the mill has a cooling device. The cooling device is arranged in or on the housing of the mill or is a component of the housing. In addition, the cooling device can also be arranged, for example, in the shaft in the mill. The control device is connected to the cooling device for regulating the cooling capacity. The cooling device is usually operated with a cooling fluid, in particular water, and is therefore also capable of absorbing and transporting large amounts of heat. Due to the external arrangement, the cooling is slow, in particular with respect to regulation. On the other hand, the cooling fluid inlet temperature may be subject to fluctuations, for example due to weather. If, for example, the cooling water temperature rises as a result of weathering, the efficiency of cooling by a cooling device can decrease and thus lead to an increase in the temperature in the interior.In a further embodiment of the invention, the first temperature sensing element is arranged at a position selected from the group comprising housing of the mill, shaft of the mill, product outlet of the mill. As already stated, an arrangement on the housing is simple. An arrangement on or in the shaft is likewise simple, but here wear can occur as a result of the mechanical load. A further option is therefore to record the product temperature directly at the product outlet of the mill and thus outside the grinding chamber. Of course, any combinations can preferably also be selected if a plurality of temperature detection elements are used.In a further embodiment of the invention, the first temperature detection element is designed for contactless temperature detection of the temperature of the ground material in the mill. This most complicated and challenging detection has the advantage, however, that the temperature of the ground material is detected directly. As a result, on the one hand, a time delay due to the thermal inertia of the overall system has no influence. In addition, an upper temperature limit T G can be set according to material knowledge and is not to be adapted to the thermal behavior of the entire device. Preferably, the contactless temperature detection takes place by means of infrared measurement.In a further embodiment of the invention, the mill has an internal volume of at least 1 m 3.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 a method for mechanically activating a mineral material with a mill. Such methods 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 method has the following steps: a) Specification of an upper temperature limit T G, b) Continuous detection of the temperature T of the mill and / or of the grinding material, c) Comparison of the detected temperature T with the upper temperature limit T G, d) Adaptation of the drive power of the mill and of the fed grinding material quantity as a function of the comparison in step c).In addition to the conventional method, temperature monitoring is performed. This prevents the product from overheating and losing the valuable properties of mechanical activation and becoming similar to a thermally activated product.It is essential here that in step d) the grinding energy and the amount of the grinding material are adjusted, so that the high energy input for the mechanical activation remains ensured. Likewise, for example, at a lower temperature, the throughput can also be increased by increasing both the energy input and the material input.The detection in step b) can be effected in the simplest form on the outer side of the housing of the mill. As a result, the integration is simple and wear is avoided. For this purpose, this detection is the most inaccurate because of the inertia of the entire system. In addition, the temperature detected here is lower than the temperature of the grinding material itself. The best method is to detect the grinding material within the mill, for example by means of a contactless IR sensor. What is challenging here is the integration into the grinding chamber with its strong mechanical loads and the development of dust in the interior of the grinding chamber. Furthermore, the measurement can be recorded, for example, on the product exiting the mill.The comparison in step c) can be effected digitally. Exceeding leads to a reduction in the drive power and the supplied amount of grinding material in step d) and dropping below leads to an increase in the drive power and the supplied amount of grinding material in step d). Preferably, however, an adaptation can also be effected as a function of the distance of the temperature detected in step b) from the upper temperature limit T G. For example, the closer the detected temperature T approaches the upper temperature limit T G the more the driving power and the supplied grinding material amount are reduced in step d). On the other hand, the farther the detected temperature T is away from the upper limit temperature T G downward, the higher the driving power and the supplied grinding material amount in step d) is.During the adaptation in step d), the energy introduced per amount of grinding material can preferably be kept constant, for example at 500 kWh / t. As a result, a constant activation quality is ensured.However, a direct relationship between the drive power and the amount of grinding material supplied is not absolutely necessary, since there are also other adjustment possibilities, for example additional cooling.The upper temperature limit T G is particularly preferably predefined between 250° C. and 300° C.In a further embodiment of the invention, a temperature operating range is additionally predefined. The temperature range is preferably below the upper temperature limit T G or can have this. The temperature operating range includes an upper limit range T BO and a lower limit range T BU. Here, the upper temperature limit T BO may be equal to the upper temperature limit T G. When the temperature T detects that the lower limit range T BU is undershot, the drive power and the supplied amount of grinding material are increased. When the upper limit range T BO is detected to be exceeded by the temperature T, the driving power and the supplied amount of the grinding material are decreased. The use of such a temperature range facilitates control.In a further embodiment of the invention, the temperature of the grinding material exiting the mill is detected. The detection at the output is simpler than the detection directly in the mill. A disadvantage is that a time offset occurs as a result of the transport through the mill, i.e. the detection then takes place only after the completion of the grinding operation.In a further embodiment of the invention, the gas stream passed through the mill is adapted as a function of the comparison in step c). A part of the heat can be dissipated by the gas flow through the mill and thus cooling can be achieved. However, due to the low heat capacity of the gas stream, this is limited.In a further embodiment of the invention, the cooling capacity of the mill is adjusted as a function of the comparison in step c). In this case, the cooling is preferably effected in the housing of the mill. Optionally, the cooling can also be provided in the shaft.In a further embodiment of the invention, when the upper temperature limit T G is exceeded, direct cooling is carried out by water injection in order to achieve rapid and efficient cooling.In a further embodiment of the invention, the reactivity of the grinding material exiting from the mill is detected. Here, the reactivity can be detected in-line, but because of the complexity, analysis is preferably carried out after sampling; in particular, the setting behavior is investigated. Especially when temperature is detected only on the housing of the mill, this can be an essential additional indicator for the exceeding of the upper temperature limit T G.In a further embodiment of the invention, the adaptation in step d) additionally also takes place as a function of the detected reactivity. An exceeding of the upper temperature limit T G, is recognizable in a decreasing reactivity or an increased water requirement.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 device according to the invention is explained in more detail below with reference to an exemplary embodiment shown in the drawing. FIG. 1 shows a device with a control deviceAn exemplary device is shown in FIG. 1. The core of the mechanical activation is a mill 10, for example and preferably an agitator ball mill. The mill is driven by a drive 20. The ground material is supplied via a material supply 50 and gas can be supplied via a gas supply 60. The milled product is examined by means of a reactivity measuring device 70. The reactivity measurement device 70 is, for example, a calorimeter. The mill 10 also has a cooling jacket 80.Furthermore, the device has a control device 40, which is connected in particular to the temperature detection element 30. According to the temperature T detected there and a comparison with an upper temperature limit T G the control of the further components takes place. If the temperature T rises to the vicinity of or above T G, the coolant flow through the cooling jacket 80 and / or the gas flow through the gas feed 60 can be increased first, for example. However, it is essential that the power of the drive 20 and the supplied quantity of grinding material can also be reduced by the material feed 50. If the temperature T falls, the device can be raised again and the power of the drive 20 and the supplied quantity of grinding material can be increased again by the material feed 50.Reference numerals denote reference numerals10 Mill 20 Drive 30 Temperature detection element 40 Control device 50 Material feed 60 Gas feed 70 Reactivity measurement device 80 Cooling jacketReferences 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 [0005, 0014, 0023]DE 10 2023 106 217 [0006, 0014, 0023]DE 10 2023 106 221 [0007, 0014, 0023]DE 10 2023 106 222 [0008, 0014, 0023]DE 10 2023 123 525 [0009, 0014, 0023]

Claims

Device for mechanically activating a mineral material, wherein the device has a mill (10), wherein the mill (10) has a drive (20), wherein the device has at least one first temperature detection element (30), wherein the first temperature detection element (30) is arranged in or on the mill (10), wherein the device has a control device (40), wherein the device has a material feed (50) for feeding grinding material to the mill (10), wherein the control device (40) is connected to the first temperature detection element (30) for transmitting the detected temperature, wherein the control device (40) is connected to the drive (20) for regulating the drive power and to the material feed (50) for regulating the amount of grinding material fed.Device according to claim 1, characterised in that the mill (10) has a cooling device, wherein the cooling device is arranged in the housing of the mill (10), wherein the control device (40) is connected to the cooling device for regulating the cooling capacity.Device according to one of the preceding claims, characterized in that the first temperature detection element (30) is arranged at a position selected from the group comprising housing of the mill (10), shaft of the mill (10), product outlet of the mill (10).Device according to one of the preceding claims, characterized in that the first temperature detection element (30) is designed for contactless temperature detection of the temperature of the ground material in the mill (10).Method for mechanically activating a mineral material with a mill (10), wherein the method has the following steps: a) Presetting an upper temperature limit T G, b) Continuously recording the temperature T of the mill (10) and / or of the grinding material, c) Comparing the recorded temperature T with the upper temperature limit T G, d) Adapting the drive power of the mill (10) and the fed grinding material quantity as a function of the comparison in step c).Method according to Claim 5, characterized in that a temperature operating range is additionally predefined, wherein the temperature operating range has an upper range limit T BO and a lower range limit T BU wherein, when the temperature T detects that the lower range limit T BU is undershot, the drive power and the fed grinding material quantity are increased, wherein, when the temperature T detects that the upper range limit T BO is exceeded, the drive power and the fed grinding material quantity are decreased.Method according to one of Claims 5 to 6, characterized in that the temperature of the grinding material exiting from the mill (10) is detected.Method according to one of Claims 5 to 7, characterized in that, as a function of the comparison in step c), the gas stream fed through the mill (10) is adapted.Method according to one of Claims 5 to 8, characterized in that the cooling capacity of the mill (10) is adapted as a function of the comparison in step c).Method according to one of Claims 5 to 9, characterized in that the reactivity of the grinding material exiting from the mill (10) is detected.Method according to claim 10, characterised in that the adaptation in step d) additionally also takes place as a function of the detected reactivity.

Images