Color optimization of activated clay

Abstract

The invention relates to a device for activating and optimizing the color of a mineral material, wherein the device has an activation and color optimization device. The invention is characterized in that the device has a tubular reactor (30) behind the color optimization device (20) in the material flow direction, wherein the tubular reactor (30) has a solid material inlet (34), said solid material inlet (34) being connected to the color optimization device (20) in order to transfer the activated and color-optimized material, and the tubular reactor (30) has a gas inlet (36). The tubular reactor (30) has a length (32) of 5 m to 50 m, the tubular reactor (30) is connected to a deflecting device (40) at the tubular reactor end, and the deflecting device (40) has a solid material outlet (42) and a gas outlet (44).

Description

[0001] thyssenkrupp Polysius GmbH 1 thyssenkrupp AG

[0002] Color optimization of activated tones

[0003] The invention relates to a device and a method for obtaining the optimized coloration of an activated clay obtained during a reduction of an activated clay.

[0004] Activated clays have established themselves as additives, particularly in the cement industry. The current method is drying and calcining the clays, a thermal activation process. This requires energy for heating and thermal activation, and excessively high temperatures can also cause further material changes that may be undesirable.

[0005] Due to the firing conditions during thermal activation in an oxidizing atmosphere, naturally occurring iron compounds in the clays are converted, particularly into hematite iron oxides. This causes 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 (Fe 3+), largely determines the color of a calcined clay. The color is an important quality parameter for the potential use of these activated clays as a component of the typically gray cement. In particular, lower-quality ("lean") clays can have Fe2O3 contents of an average of 2 to 9 wt.%. In the so-called "red clays," the Fe2O3 content can be up to 15% or higher. These high iron contents can lead to a very intense and usually undesirable red discoloration of the artificial pozzolan produced in this way and the composite cements manufactured with it during calcination. For this reason, reducing firing conditions are set in the cooling area of ​​plants for the production of calcined clays, for example, to achieve the formation of black magnetite.To achieve reducing firing conditions, readily combustible fossil and CO2-intensive primary fuels such as natural gas, crude oil, lignite, or hard coal are required. So-called secondary fuels, in particular, require consistently oxidizing firing conditions for effective firing, 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.

[0006] From DE 10 2016 104 738 A1 a method and a device for the thermal treatment of granular solids is known.

[0007] DE 10 2008 020 600 B4 discloses a process and a plant for the heat treatment of fine-grained mineral solids.

[0008] A clinker substitute is known from DE 10 2011 014 498 A1.

[0009] A process for producing synthetic pozzolans is known from US 2012 / 160 135 A1.

[0010] WO 2021 / 224 055 A1 discloses a color optimization in the production of activated clays.

[0011] The activation itself and the color optimization in a reducing atmosphere are well known to those skilled in the art and can be performed in a variety of variations. A critical point, however, is how the hot, activated, and color-optimized material is cooled to preserve its properties, especially the color. In addition to cooling in a reducing atmosphere or in the absence of air, rapid cooling up to 100 K / s in an oxygen-containing gas, such as air, is also known. Each of these processes has advantages and disadvantages.

[0012] The object of the invention is to provide a simple and extremely reliable method for cooling an activated and color-optimized clay.

[0013] This object is achieved by the device having the features specified in claim 1 and by the method having the features specified in claim 13. Advantageous further developments emerge from the subclaims, the following description and the drawing. The device according to the invention serves to activate and color optimize a mineral material, in particular clays. The device has an activation and color optimization device. The activation and color optimization device can be designed in two parts or consist of a combined activation and color optimization device. In the activation and color optimization device or the activation device, a thermal treatment takes place which leads, for example, to the clay developing the necessary properties to be used, for example, as a cement aggregate.Such activated materials are also sometimes referred to as artificial pozzolans. The activation is known from the prior art and can be carried out using any method known from the prior art. The activation device can thus be designed in any configuration known to those skilled in the art. For example, the activation and color optimization device or the activation device can be an entrained-flow calciner. The same applies to the color optimization device. This is also known to those skilled in the art and can be designed in any manner known to those skilled in the art from the prior art. By way of example only, the color optimization device can be designed as a fluidized-bed reactor. As an example of a combined activation and color optimization device, a prior-art activation device operated under reducing conditions may be mentioned.Further by way of example, in another embodiment, the color optimization device can be designed as a flow-flow reactor.

[0014] According to the invention, the device comprises a tubular reactor downstream of the color optimization device in the direction of material flow. The tubular reactor has a solids inlet, which is connected to the color optimization device for transferring the activated and color-optimized material. The tubular reactor also has a gas inlet. The gas inlet is preferably arranged upstream of the solids inlet in the direction of gas flow. The tubular reactor has a length of 5 m to 50 m, whereby the length refers to the distance between the solids inlet and the end of the tubular reactor and thus, together with the flow velocity, defines the residence time within the tubular reactor. The tubular reactor is connected at the end to a deflection device. The deflection device has a solids outlet and a gas outlet.In the deflection device, the flow dynamics are strongly influenced by the deflection and the carrying capacity of the gas flow for the solid is massively reduced, resulting in very rapid separation.

[0015] The inventive combination of a tubular reactor with a deflection device is advantageous over conventional cooling systems, such as a cyclone separator, because it allows for much faster cooling rates and re-separation of the activated material. The tubular reactor enables a very narrow residence time distribution, enabling uniform and uniform cooling for all particles of the activated material. Dead volumes and the resulting significant differences in residence times, resulting in different cooling rates and, in turn, different product qualities due to varying degrees of reoxidation, are reliably and easily avoided.Due to the very simple design compared to the usually long and complex residence time behavior in a separation cyclone, a much higher cooling rate of over 200 K / s is possible according to the invention, which reduces reoxidation but at the same time allows the installation space to be kept comparatively small, since a shorter residence time also requires a smaller volume.

[0016] The usually lower separation efficiency of a deflection device compared to, for example, a separation cyclone can be accepted because the exhaust gas from a separation cyclone usually has to be subjected to further dedusting to completely remove the activated material, so that no or no significant additional effort is required for subsequent purification of the gas.

[0017] In a further embodiment of the invention, the deflection device has a deflection of the gas flow of 135° to 225°, preferably of 170° to 190°, particularly preferably of 180°. This strong deflection achieves a sufficiently high deposition of the activated material.

[0018] In a further embodiment of the invention, the tubular reactor is arranged such that the gas flow in the tubular reactor is directed downward. "Downward" means along the force of gravity, i.e., toward the earth. In particular, a 180° deflection occurs in the deflection device, so that the gas flow is directed upward after the deflection. In this way, the influence of gravity is additionally utilized to improve the separation of the activated material from the gas flow. The disadvantage of the high construction is acceptable in this case.

[0019] In a further embodiment of the invention, the tubular reactor is constructed in two parts. A first part of the tubular reactor is arranged horizontally, and a second part, adjacent to the deflection device, is arranged vertically, so that the gas flow in the second part of the tubular reactor is directed downward. This achieves an optimum of separation and installation height.

[0020] In a further embodiment of the invention, the solids outlet of the deflection device is arranged at the lowest point of the deflection device.

[0021] In a further embodiment of the invention, a separation cyclone and / or a dust filter is arranged downstream of the deflection device. This makes it possible to achieve the low solids loading of the gas required for discharge to the environment or transfer to other processes.

[0022] In a further embodiment of the invention, a gas conveying device is arranged upstream of the gas inlet. This makes it easier to achieve the high flow velocity of 15 to 50 m / s preferred for the tubular reactor. In the simplest case, the gas conveying device is a fan that conveys sufficient ambient air into the gas inlet to achieve the flow velocity in the tubular reactor. The use of ambient air also easily creates a cool starting point for the gas.

[0023] In a further embodiment of the invention, the solids outlet is connected to a cooling device. For example, the activated material can leave the deflection device at 300°C to 500°C. The cooling device then cools it to below 100°C (or to ambient temperature), allowing the product to be easily stored or bottled. Since reoxidation is no longer a concern in this temperature range, the type and speed of cooling are relatively arbitrary, and those skilled in the art will be familiar with what such a cooling device looks like.

[0024] In a further embodiment of the invention, the deflection device has a first cross-sectional area at the inlet and a second cross-sectional area in the middle. The second cross-sectional area is 2 to 5 times, preferably 3 to 4 times, the size of the first cross-sectional area. The increase in cross-sectional area reduces the velocity, which in turn facilitates the separation of the activated material from the gas stream synergistically with the inertia of the material during deflection.

[0025] In a further embodiment of the invention, the device comprises a gas temperature measuring device downstream of the deflection device. By measuring the gas temperature, the cooling effect can be easily monitored and the process can be regulated, for example, by adjusting the loading. Since the activated material should fall below a temperature of 500 °C during deposition, a lower gas temperature, for example, a maximum of 450 °C, would be a suitable control parameter.

[0026] In a further embodiment of the invention, the device comprises a first solid temperature measuring device downstream of the solid outlet of the deflection chamber. This also allows for a simple check as to whether the activated material has been safely cooled below 500°C. The first solid temperature measuring device is preferably designed as an infrared thermometer.

[0027] In a further embodiment of the invention, the device comprises a first solid color measuring device downstream of the solid outlet. In addition to sufficiently rapid cooling, this also allows for the color optimization in the color optimization device to be monitored as directly as possible, since excessively high temperatures can disrupt optical detection and thus color recognition. Color detection is preferably used to regulate fuel addition and thus, for example, to regulate the stoichiometric conditions in the color optimization reactor. This allows, for example, optimization of the color value and minimization of fuel consumption.

[0028] In a further aspect, the invention relates to a method for activating and color optimizing a mineral material. The method comprises the following steps: a) thermally activating the mineral material, b) color optimizing the activated mineral material under reducing conditions, c) cooling the color-optimized mineral material in a tubular reactor, d) depositing the cooled mineral material in a deflection device, wherein the cooling in the tubular reactor occurs at a rate of 200 K / s to 650 K / s.

[0029] Steps a) and b) are known to those skilled in the art in a wide variety of embodiments. These can be carried out in any manner known to those skilled in the art. What is essential is that at the end of step b), a hot, usually between 700°C and 1000°C, activated and color-optimized material is present.

[0030] The difference between the invention and the prior art lies in the rapid, efficient, reliable, and robust cooling according to steps c) and d), which enable an extremely high cooling rate of more than 200 K / s and thus significantly higher cooling rates than, for example, the separation cyclones known in the prior art with up to 100 K / s. At the same time, the basic operation of a tubular reactor achieves a very narrow residence time distribution, so that the cooling rate is also achieved for the entire product and not just on average, which in turn enables a uniform product.

[0031] In a further embodiment of the invention, an oxygen-containing gas, such as air, is selected for the gas stream in the tubular reactor. The use of ambient air is preferred due to its ease of provision as a cooling gas stream. Due to the high cooling rate, even in the presence of oxygen, no significant reoxidation occurs, and thus no renewed and undesired discoloration of the activated material occurs. Furthermore, complex cooling under protective gas is eliminated.

[0032] In a further embodiment of the invention, the gas velocity in the tubular reactor is set at 15 m / s to 50 m / s. This velocity range has proven to be optimal. Combined with the length, this results in a residence time of 0.2 s to 2.5 s. Shorter residence times are preferred at higher cooling rates (< 650 K / s) and longer residence times at lower cooling rates (> 200 K / s).

[0033] In a further embodiment of the invention, the velocity of the gas phase in the deflection device is reduced to 1.5 to 3.4 m / s. This is achieved by expanding the cross-section. This massive velocity reduction rapidly reduces the carrying capacity of the gas phase and thus leads to a good separation result for the activated material from the gas in the deflection device.

[0034] In a further embodiment of the invention, the temperature of the mineral material deposited in the deflection device is below 500°C, for example, in a range from 300°C to 500°C. This has two advantageous reasons. Firstly, a high cooling rate can be achieved particularly at high temperatures; excessive cooling (i.e., to a final temperature that is too low) makes it more difficult to achieve the very high cooling rates required according to the invention, since higher cooling rates are usually easier to achieve at higher temperatures than at lower temperatures. Secondly, this also means that the gas phase leaves the deflection device at a correspondingly higher temperature, i.e., it is higher-quality heat that can be better utilized elsewhere in a system than low-calorific heat. For these two reasons, the target range of 300°C to 500°C has proven advantageous.

[0035] In a further embodiment of the invention, after separation in step d), residual separation of the cooled mineral material from the gas stream leaving the deflection device takes place. The residual separation can take place, for example, in a separation cyclone and / or a dust filter. The goal is to be able to further use the gas stream without any solids load or to release it into the environment.

[0036] In a further embodiment of the invention, the material separated in the residual separation is combined with the material separated in step d). While both fractions can also be processed separately, since the fraction obtained in the residual separation has finer (smaller particles) and can therefore be sold as a separate product, combining them simplifies the effort required for final cooling, processing, storage, and packaging into a single product line.

[0037] In a further embodiment of the invention, the material temperature is measured at the transition from the tubular reactor to the deflection device or after discharge from the deflection device. This enables active control, for example, of the amount of gas supplied to the tubular reactor.

[0038] In a further embodiment of the invention, the material color is detected after it has been discharged from the deflection device. This enables targeted control of the color optimization device, particularly to keep the consumption of reducing agent as low as possible.

[0039] The device according to the invention is explained in more detail below using an embodiment shown in the drawing.

[0040] Fig. 1 Device

[0041] Fig. 1 shows an exemplary device schematically and not to scale. Clay, for example, is fed to an activation device 10 via a material feed 12. The activation device 10 can, for example, comprise a comminution device, a drying device, a preheater, and an entrained-flow calciner. Such activation devices 10 are extensively known from the prior art. During thermal activation, iron, in particular, which is often contained in clays, is oxidized to Fe2O3, which has an undesirable reddish color. Therefore, the activated clay is treated in a color optimization device 20 in a reducing atmosphere, whereby the III-valent iron is reduced to other iron compounds, which produce a gray color in the clay and thus allow a saleable product to be obtained. This reduction takes place, for example, at 850°C.The activated and color-optimized clay is fed via the solids inlet at 850°C to the tubular reactor 30, which is arranged vertically with the gas flowing downwards. Air from the air supply 52 and the gas conveying device 50 are fed to the tubular reactor via the gas inlet 36. The gas velocity in the tubular reactor 30 is, for example, 35 m / s. The length 32 is, for example, 35 m, resulting in a residence time of 1 s. The gas flow is deflected by 180° in the deflection device 40, i.e., upwards. This dramatically reduces the load-bearing force, so that the activated clay, cooled to, for example, 450°C, is deposited. This results in a cooling rate of 400 K / s. The deposited clay is fed via the solids outlet 42 to the cooling device 70. The gas stream leaving the deflection device 40 via the gas outlet 44 is fed to a dust filter 60 in which fine activated clay is separated from the gas stream.This separated clay is combined with the clay separated in the deflection device 40 and also fed to the cooling device 70.

[0042] Reference symbol

[0043] 10 Activation device

[0044] 12 Material supply

[0045] 20 Color optimization device

[0046] 30 tube reactor

[0047] 32 length

[0048] 34 Solids inlet

[0049] 36 Gas inlet

[0050] 40 deflection device

[0051] 42 Solids outlet

[0052] 44 Gas outlet

[0053] 50 Gas conveying device

[0054] 52 Air supply 60 Dust filter

[0055] 70 Cooling device

Claims

Patent claims 1. A device for activating and color optimizing a mineral material, the device comprising an activation and color optimizing device, characterized in that the device has a tubular reactor (30) downstream of the color optimizing device (20) in the material flow direction, the tubular reactor (30) having a solids inlet (34), the solids inlet (34) being connected to the color optimizing device (20) for transferring the activated and color-optimized material, the tubular reactor (30) having a gas inlet (36), the tubular reactor (30) having a length (32) of 5 m to 50 m, the tubular reactor (30) being connected at the end to a deflection device (40), the deflection device (40) having a solids outlet (42) and a gas outlet (44).

2. Device according to claim 1, characterized in that the activation and color optimization device comprises a separate activation device (10) and a separate color optimization device (20).

3. Device according to one of the preceding claims, characterized in that the deflection device (40) has a deflection of the gas flow of 135° to 225°, preferably of 170° to 190°.

4. Device according to one of the preceding claims, characterized in that the tubular reactor (30) is arranged such that the gas flow in the tubular reactor (30) is directed downwards.

5. Device according to claim 4, characterized in that the solids outlet (42) of the deflection device (40) is arranged at the lowest point of the deflection device (40).

6. Device according to one of the preceding claims, characterized in that a separation cyclone and / or a dust filter (60) is arranged behind the deflection device (40).

7. Device according to one of the preceding claims, characterized in that a gas conveying device (50) is arranged in front of the gas inlet (36).

8. Device according to one of the preceding claims, characterized in that the solids outlet (42) is connected to a cooling device (70).

9. Device according to one of the preceding claims, characterized in that the deflection device (40) has a first cross-sectional area at the inlet, wherein the deflection device (40) has a second cross-sectional area in the middle, wherein the second cross-sectional area is 2 to 5 times, preferably 3 to 4 times, as large as the first cross-sectional area.

10. Device according to one of the preceding claims, characterized in that the device has a gas temperature measuring device behind the deflection device (40).

11. Device according to one of the preceding claims, characterized in that the device has a first solid temperature measuring device behind the solid outlet (42).

12. Device according to one of the preceding claims, characterized in that the device has a first solid color measuring device behind the solid outlet (42).

13. A method for activating and color optimizing a mineral material, the method comprising the following steps: a) thermally activating the mineral material, b) color optimizing the activated mineral material under reducing conditions, c) cooling the color-optimized mineral material in a tubular reactor (30), d) depositing the cooled mineral material in a deflection device (40), wherein the cooling in the tubular reactor (30) takes place at a rate of 200 K / s to 650 K / s.

14. The method according to claim 13, characterized in that the gas velocity in the tubular reactor (30) is set at 15 m / s to 50 m / s.

15. Method according to one of claims 13 to 14, characterized in that the temperature of the mineral material deposited in the deflection device (40) is below 500 °C.

16. Method according to one of claims 13 to 15, characterized in that after the separation in step d), a residual separation of the cooled mineral material from the gas stream leaving the deflection device (40) takes place.

17. The method according to claim 16, characterized in that the material deposited in the residual deposition is combined with the material deposited in step d).

18. Method according to one of claims 13 to 17, characterized in that the material temperature is detected at the transition from the tubular reactor (30) to the deflection device (40) or after discharge from the deflection device (40).

19. Method according to one of claims 13 to 18, characterized in that the material color is detected after discharge from the deflection device (40).

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