DE102022133349A1 - Device for color optimization of activated tones - Google Patents

Abstract

The present invention relates to a device for the thermal activation of mineral materials, wherein the device comprises a calciner 40, a reduction device and a material cooler 70, wherein the calciner 40 and the reduction device are connected to one another for the transfer of calcined material, wherein the reduction device is connected to the material cooler 70 for the transfer of color-optimized material, characterized in that the reduction device is a fluidized bed reactor 50.

Description

The invention relates to a device and a method for color optimization of activated clays.

The cement industry is a major emitter of carbon dioxide. An important point is the carbon dioxide released from limestone. In order to reduce carbon dioxide emissions, clinker substitutes are used, which preferably do not release carbon dioxide when activated. Activated clays are therefore an important product. One problem with clays, however, is that they often contain iron, for example, which is usually (at least partially) oxidized when activated under oxidizing conditions and, as Fe ^III , gives the clay a strong red color. However, this is usually not accepted by customers. In order to obtain a cement- or clinker-like color, which is accepted by customers, the activated clay is often treated under reducing conditions to reduce the oxidized iron again and thus give the activated clay a cement-like color.

From the EN 10 2016 104 738 A1 A method and a device for the thermal treatment of granular solids is known.

From the EN 10 2008 020 600 B4 A process and a plant for the heat treatment of fine-grained mineral solids is known.

From the EN 10 2011 014 498 A1 A clinker substitute is known.

From the US 2012 / 160 135 A1 A process for producing synthetic pozzolans is known.

From the WO 2021 / 224 055 A1 Color optimization is known in the production of activated clays.

However, there are two problems with color optimization. Firstly, a longer residence time of the already activated clays at high temperatures is bad because it can lead to deactivation. This effect also depends on the particle size. Deactivation occurs more quickly with smaller particles. Secondly, the reduction and thus the color optimization also depends on the particle size. The smaller the particles, the faster the decolorization takes place, the larger the particles, the longer the reduction takes. This means that an optimum must be found in which the smallest particles are not deactivated and the largest particles are still decolorized. This optimum is achieved by choosing the narrowest possible particle size distribution, i.e. keeping the difference between the smallest particle and the largest particle small. This in turn is complex and energy-intensive, which in turn creates a new potential source of carbon dioxide, since renewable energy is only available to a limited extent for the processes for producing a narrow grain band.

The object of the invention is to provide a device and a method in which color optimization is also possible with a significantly broader particle size distribution.

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

The device according to the invention is used for the thermal activation of mineral materials, in particular clays. The device has a calciner, a reduction device and a material cooler. The calciner and the reduction device are connected to one another for the transfer of calcined material. The reduction device is connected to the material cooler for the transfer of color-optimized material. According to the invention, the reduction device is a fluidized bed reactor. This fluidized bed reactor or fluidized bed reactor has proven to be extremely advantageous as a reduction device when there is a broad particle size distribution (a broad grain range). On the one hand, extremely small particles are discharged very quickly with the fluidization gas. On the other hand, the particle size also has an influence on the transport speed in the fluidized bed reactor. The fluidized bed reactor therefore enables color optimization in a simple manner, since small particles that are quickly color-optimized are also discharged more quickly, whereas large particles that require a longer treatment time also have a longer residence time. This makes it possible to save considerable energy in the comminution and fractionation of the particle size distribution.

In addition, a preheater can be arranged upstream of the calciner. This allows the heat carried out of the calciner with the gas flow to be transferred to the material to be thermally activated.

In a further embodiment of the invention, the reduction device has a first material outlet and a second material outlet. In particular, the first material outlet and the second material outlet are arranged at different heights. For example, the first material outlet can be located on the underside of the fluidized bed. This means that a coarse fraction of the color-optimized material is discharged through the first material outlet. For example, the second material outlet can be located on the top of the fluidized bed. This means that a fine fraction of the color-optimized material is discharged through the second material outlet. In this way, in addition to targeted color optimization, separation by size can also be carried out. The two fractions can then be processed separately or together.

In a further embodiment of the invention, the first material outlet and the second material outlet are each connected to the material cooler for transferring color-optimized material. The first material flow from the first material outlet and the second material flow from the second material outlet are preferably introduced into the material cooler at different points. This also allows for customized cooling, particularly if the first material flow and the second material flow have a different particle size distribution.

In a further embodiment of the invention, the device has a deagglomeration device. The deagglomeration device is connected to the calciner for transferring deagglomerated material. For example and preferably, the deagglomeration device is connected to the calciner for transferring deagglomerated material via a riser dryer. The deagglomeration device is further preferably a hammer mill, vertical roller mill, impact mill, pendulum roller mill or agitator mill. The deagglomeration device is particularly preferably a hammer mill.

In a further embodiment of the invention, the device has a color detection device. The color detection device is designed to detect the color of the product. The color detection device is arranged in or along the product flow after the material cooler. By detecting the color, a reduction and thus a color optimization can be carried out to the necessary extent, but can also be limited to the necessary extent, whereby reducing agent can be saved.

In a further embodiment of the invention, the device has a reducing agent supply. The reducing agent supply is connected to the reducing device for supplying reducing agent. Various gaseous, liquid or solid substances can be used as reducing agents. Typical gaseous reducing agents are methane, hydrogen or carbon monoxide. Examples of liquid reducing agents are liquid hydrocarbons. An important example of a solid reducing agent is coal, in particular coal dust or biomass. If the reducing agent is a fuel, combustion usually takes place in the absence of oxygen, so that a reducing atmosphere is created, for example and in particular carbon monoxide. The device also has a control device. The control device is designed to regulate the amount of reducing agent supplied by the reducing agent supply. For this purpose, the control device is connected to the reducing agent supply in a corresponding manner for transmitting control commands or by directly controlling, for example, servomotors. The control device is also designed to regulate the amount of reducing agent depending on the color detected by the color detection device. For this purpose, the control device has in particular a data connection to the color detection device in order to obtain the color of the product detected by the color detection device. The control device also has, for example, a color threshold value. If the color threshold value is exceeded, for example if the sample is too reddish, the supply of reducing agent is increased in order to achieve greater decolorization. If the color threshold value is not reached, the supply of reducing agent is reduced in order to avoid unnecessary consumption. For example, the color threshold value can also be specified in the form of a range. Alternatively, the control device can have an allocation table in which the amount of reducing agent is specified for different color value ranges. Overall, the minimum amount of reducing agent required to achieve sufficient decolorization and thus market acceptance can thus be used.

It can be provided that both a reducing agent and a fuel are provided. For example, biomass is used as the fuel, with approximately stoichiometric combustion taking place. As a result, the residual oxygen content after combustion is usually low. Hydrogen is then added as a reducing agent, for example. As a small molecule, this has excellent diffusion properties, but would be more expensive as a fuel than biomass.

In a further embodiment of the invention, a gas-sealing material lock is arranged between the reduction device and the material cooler.

In a further embodiment of the invention, a gas-sealing material lock is arranged between the calciner and the reduction device.

In a further embodiment of the invention, the device has a gas supply to the reduction device. The gas supply can be regulated with regard to volume flow and gas velocity. The device has a control device. The device also has a particle size specification device. The particle size specification device can be designed, for example, in that the particle size distribution is determined by a particle size measuring device and passed on to the particle size specification device. Alternatively, the particle size specification device can be an input device in the conventional sense, in which an operator enters the particle size distribution either directly or via a selection from predetermined distributions. The particle size specification device can also be an interface to a central database system, which, for example, has data from laboratory analysis or on supplied products and can thus pass on the particle size distribution, for example based on the supplied material. The control device is designed to control the gas supply in such a way that the control device controls the volume flow and gas velocity depending on the particle size of the material specified by the particle size specification device. The particle size distribution has an influence on the loosening speed (loosening point), i.e. the point at which the gas flow just begins to fluidize the solid. Since the device is preferably operated with a fluidization speed of the gas flow that corresponds to 5 to 15 times the loosening speed, it is helpful to record a value such as the particle size so that a change in the loosening speed of the fluidized bed can be easily recognized.

In a further embodiment of the invention, the particle size specification device has a particle size measuring device or is connected to it. For example, the particle size measuring device can determine the particle size and particle size distribution by means of light scattering in or before the calciner. Alternatively, samples can be taken before or after the reduction device and fed to the particle size measuring device.

In a further alternative embodiment of the invention, the particle size specification device is an input device via which the information can be manually entered by the plant personnel. As a further alternative, the particle size specification device is an interface via which information on the particle size distribution can be taken over, for example from an analytical laboratory system.

In a further embodiment of the invention, the reduction device has guide elements for guiding the material flow. For example, these can be arranged in the lower region of the fluidized bed to extend the path of the largest particles and thereby extend the residence time of these largest particles in the reduction device.

In a further embodiment of the invention, the reduction device has guide elements for guiding the gas flow. This serves in particular to keep the gas flow that has already emerged from the fluidized bed and the finest particles carried away with the gas flow in the reduction device for a minimum time and thus ensure reliable reduction and color optimization. This can be done, for example, using a labyrinth guide.

In a further embodiment of the invention, the reduction device has a gas outlet. The gas outlet is connected to a filter device. The finest fraction of the activated and color-optimized material is separated in the filter device. This fraction is usually also the most active fraction. This can either be recombined with the other activated and color-optimized material. This finest fraction can also be further processed separately, for example for particularly demanding applications.

In a further embodiment of the invention, a gas sensor is arranged fluidically behind the gas outlet, which is designed to detect the concentration of one or more substances selected from the list comprising carbon monoxide, carbon dioxide, hydrogen, methane. These substances can either be used directly as reducing agents or are created in the reduction device. Therefore, the detected concentration at the outlet can be used as an indicator of an excess of reducing agent. The carbon dioxide concentration is preferably detected together with the carbon monoxide concentration, in particular to determine the ratio.

In a further embodiment of the invention, the device has a bypass between the calciner and the material cooler to bypass the reduction device.

This bypass is preferably used exclusively for starting up and shutting down the device. The activated material at the reduction device can be transferred directly to the material cooler via the bypass.

In a further embodiment of the invention, the reduction device has a dip tube for supplying activated material. The dip tube preferably extends into the fluidized bed. This introduces the activated material directly into the interior of the fluidized bed, so that the residence time is slightly extended, particularly for the finest particles, and color optimization is thus ensured even for the finest particles.

In a further aspect, the invention relates to a method for color optimization of an activated material using a device according to the invention. A broad particle size distribution is selected for color optimization in the reduction device, the broad particle size distribution being characterized by at least 10% by weight of the particles being smaller than 50 µm and at least 10% by weight of the particles being larger than 250 µm. Such a broad grain range (particle size distribution) is unusual and cannot be processed by the existing systems. In existing systems, the very small particles would already be deactivated before the very large particles are color-optimized. However, the use of a fluidized bed reactor allows the use of this broad particle size distribution. This means that a lot of energy can be saved during comminution or deagglomeration and/or a size separation step can be dispensed with.

In a further embodiment of the invention, the particle size distribution is selected such that all particles are smaller than 2 mm.

In a further embodiment of the invention, the particle size distribution is selected such that at least 5 wt.% of the particles are larger than 900 µm.

In a further embodiment of the invention, the particle size distribution is selected such that at least 5 wt.% of the particles are smaller than 20 µm.

In a further embodiment of the invention, at least 10% by weight of the material flow from the reduction device is discharged via the gas flow through the gas outlet and separated in the filter device. This means that the finest fraction with a particularly small particle size makes up at least 10% by weight. In a conventional process, this proportion would most likely lose activity in the reduction device. In a fluidized bed reactor according to the invention, however, this fraction is discharged very quickly via the fluidization gas, so that color optimization occurs but no deactivation occurs. This effect of the fluidized bed simultaneously separates the finest fraction.

In a further embodiment of the invention, the fluidization speed in the reduction device is selected so that the fluidization speed is 5 to 15 times the loosening speed. The loosening speed or the loosening point is the flow speed of the fluidization gas at which fluidization of the material occurs, i.e. the theoretically lowest speed for the formation of the fluidized bed. This higher fluidization speed significantly supports the different residence times of the particles depending on their size, which means that the finest particles in particular, which are color-optimized very quickly and which would also lose activity again accordingly quickly, are carried away again very quickly with the gas, i.e. only have a comparatively short residence time.

In a further embodiment of the invention, the fluidizing gas supplied to the reduction device has a temperature of at least 700 °C. For example and in particular, an exhaust gas with an oxygen content of less than 15 vol.% can be used as the gas. The lower the oxygen content and the higher the temperature of the exhaust gas used, the less it needs to be heated, which means that less fuel (and thus reducing agent) is required. However, the exhaust gas preferably has an oxygen content of more than 0.5 vol.% in order to enable combustion and thus energy release. The process of color optimization, for example the reduction of trivalent iron, is endothermic, so that the temperature would drop. In addition, the reduction device radiates heat. In particular, in order to be able to compensate for these two effects in the reduction device and not to allow cooling in the reduction device, the gas preferably has a corresponding residual oxygen content.

In a further embodiment of the invention, a reducing agent is introduced directly into the reduction device. For example, coal, in particular coal dust, or biomass can be introduced into the reduction device via a direct feed. This creates the reducing atmosphere directly in the reactor. On the one hand, the heat is generated by a layer of fuel, and on the other hand, the heat is also made available directly through combustion, thus maintaining a constant temperature. Alternatively, hydrogen or methane, for example, can be introduced directly into the reduction device.

In a further embodiment of the invention, a reducing agent is introduced into the reduction device with the gas flow. Gaseous reducing agents such as hydrogen and methane are particularly suitable for this, but also liquid reducing agents, for example liquid hydrocarbons.

In a further embodiment of the invention, a reducing agent is introduced into the reduction device with the material flow. This is preferred for solid reducing agents, such as coal, in particular coal dust. Here, the reducing agent is mixed with activated material before it is introduced into the reduction device, so that the reducing atmosphere is the same for all particles right from the start.

In a further embodiment of the invention, in iron-containing minerals, in particular clays, with an Fe ₂ O ₃ content of more than 20 wt.%, a reduction of at least 80% of the iron is carried out.

In a further embodiment of the invention, a reduction of 50 to 80% of the iron is carried out in iron-containing minerals, in particular clays, with an Fe ₂ O ₃ content between 10 wt.% and 20 wt.%. The proportion of the iron to be reduced is increased from 50% at 10 wt.% to 80% at 20 wt.%. This can be done, for example, linearly or in stages.

In a further embodiment of the invention, in the case of iron-containing minerals, in particular clays with an Fe ₂ O ₃ content of less than 10 wt.%, only a reduction of up to 50% of the iron is carried out.

• 1 erstes Ausführungsbeispiel
• 2 zweites Ausführungsbeispiel
• 3 drittes Ausführungsbeispiel

The device according to the invention is explained in more detail below using an embodiment shown in the drawings.

• 1 first embodiment
• 2 second embodiment
• 3 third embodiment

In 1 a first embodiment of a device according to the invention for producing color-optimized activated material, in particular clays, is shown. The material first goes into a hammer mill and is deagglomerated there. This creates a comparatively broad particle size distribution. The deagglomerated material is then raised and dried in a riser dryer. The material then goes via a preheater into a calciner and is thermally activated there. During activation under oxidizing conditions, however, oxidation of iron to Fe ^III also occurs, for example, so that the material turns reddish. The oxidation does not necessarily take place quantitatively, i.e. not all iron atoms are necessarily oxidized to Fe ^III . In order to reverse this, the thermally activated material is introduced into a fluidized bed reactor 50. To fluidize the fluidized bed, fluidization gas is supplied to the fluidized bed reactor 50 from a fluidization gas supply 100 via a combustion chamber 90, wherein, for example, coal dust is supplied to the combustion chamber 90 via a reducing agent supply 110 in excess of the oxygen supplied with the fluidization gas, so that carbon monoxide is produced in the combustion chamber. For example, an oxygen-poor exhaust gas from a process, for example from the preheater 30, can be used as the fluidization gas. The fluidized bed reactor is operated, for example, in such a way that the fluidization speed corresponds to 5-15 times the loosening speed. As a result, the finest particles, which also reduce the fastest and are thus color-optimized, are quickly discharged through the gas outlet and reach the filter device 60, in which they are then separated. The fluidized bed reactor also has two outlets for the color-optimized material. One of these outlets is located on the underside and is used to remove the largest particles, the second outlet is located in the upper area of the fluidized bed and is used to remove the medium particle fraction. All three fractions of the color-optimized material are fed to a material cooler 70. After cooling, the color is determined in the color detection device 80. This allows the addition of reducing agent via the reducing agent feed 110 to be regulated so that as little reducing agent as possible is added, but sufficient decolorization is still achieved.

2 shows a second embodiment, which differs from the first in 1 shown embodiment in that the reducing agent is mixed with the activated material before the fluidized bed reactor 50 and is introduced together with it into the fluidized bed reactor 50. For example, coal dust is supplied via the reducing agent supply 110. As a result, the heat supply is also generated directly in the fluidized bed of the fluidized bed reactor 50 by combustion. This embodiment is preferred, when the fluidization gas supplied by the fluidization gas supply 100 is already close to (just below) the treatment temperature.

In 3 A third embodiment is shown, which differs from the first in 1 shown embodiment in that a gas sensor 120 is arranged behind the gas outlet, so that in addition to the color detection in the color detection device 80, the reducing components still present in the exhaust gas can also be used as a control variable. For example, the gas sensor 120 can be a carbon monoxide sensor. In addition, the finest material fraction is separated from the filter device 60. This often has the highest reactivity and can therefore be used for particularly high-quality products.

Reference symbols

10

Hammer mill

20

Riser dryer

30

Preheater

40

Calciner

50

Fluidized bed reactor

60

Filter device

70

Material cooler

80

Color detection device

90

Combustion chamber

100

Fluidization gas supply

110

Reducing agent supply

120

Gas sensor

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely to provide the reader with better information. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 102016104738 A1 [0003]
• DE 102008020600 B4 [0004]
• DE 102011014498 A1 [0005]
• US 2012160135 A1 [0006]
• WO 2021224055 A1 [0007]

Claims (26)

Device for the thermal activation of mineral materials, the device comprising a calciner (40), a reduction device and a material cooler (70), the calciner (40) and the reduction device being connected to one another for transferring calcined material, the reduction device being connected to the material cooler (70) for transferring color-optimized material, characterized in that the reduction device is a fluidized bed reactor (50). Device according to Claim 1 , characterized in that the reduction device has a first material outlet and a second material outlet, wherein the first material outlet and the second material outlet are each connected to the material cooler (70) for transferring color-optimized material. Device according to one of the preceding claims, characterized in that the device comprises a deagglomeration device, wherein the deagglomeration device is connected to the calciner (40) for transferring deagglomerated material. Device according to Claim 3 , characterized in that the deagglomeration device is connected to the calciner (40) via a riser dryer (20) for transferring deagglomerated material. Device according to one of the Claims 3 until 4 , characterized in that the deagglomeration device is a hammer mill (10), vertical roller mill, impact mill, pendulum roller mill or agitator mill. Device according to Claim 5 , characterized in that the deagglomeration device is a hammer mill (10). Device according to one of the preceding claims, characterized in that the device has a color detection device (80), wherein the color detection device (80) is designed to detect the color of the product, wherein the color detection device (80) is arranged in or along the product flow after the material cooler (70). contraption Claim 7 , characterized in that the device has a reducing agent supply, wherein the reducing agent supply is connected to the reduction device for supplying reducing agent, wherein the device has a control device, wherein the control device is designed to regulate the amount of reducing agent supplied by the reducing agent supply, wherein the control device is designed to regulate the amount of reducing agent depending on the color detected by the color detection device (80). Device according to one of the preceding claims, characterized in that a gas-sealing material lock is arranged between the reduction device and the material cooler (70). Device according to one of the preceding claims, characterized in that the device has a gas supply to the reduction device, wherein the gas supply is controllable with regard to volume flow and gas velocity, wherein the device has a control device, wherein the device has a particle size specification device, wherein the control device is designed to control the gas supply, wherein the control device controls volume flow and gas velocity depending on the particle size of the material specified by the particle size specification device. Device according to Claim 10 , characterized in that the particle size setting device is a particle size measuring device. Device according to one of the preceding claims, characterized in that the reduction device has guide elements for guiding the material flow. Device according to one of the preceding claims, characterized in that the reduction device has a gas outlet, wherein the gas outlet is connected to a filter device (60). Device according to Claim 13 , characterized in that a gas sensor (120) is arranged fluidically behind the gas outlet, wherein the gas sensor (120) is designed to detect the concentration of one or more substances selected from the list comprising carbon monoxide, carbon dioxide, hydrogen, methane. Device according to one of the preceding claims, characterized in that the device has a bypass between the calciner (40) and the material cooler (70) for bypassing the reduction device. Device according to one of the preceding claims, characterized in that the Reduction device has a dip tube for the supply of activated material. Method for color optimization of an activated material with a device according to one of the preceding claims, wherein a broad particle size distribution is selected for the color optimization in the reduction device, wherein the broad particle size distribution is characterized in that at least 10 wt. % of the particles are smaller than 50 µm and at least 10 wt. % of the particles are larger than 250 µm. Procedure according to Claim 17 , characterized in that at least 5 wt.% of the particles are larger than 900 µm. Method according to one of the Claims 17 until 18 , characterized in that at least 10 wt. % of the material flow from the reduction device is discharged via the gas flow through the gas outlet and separated in the filter device (60). Method according to one of the Claims 17 until 19 , characterized in that the fluidization speed in the reduction device is selected such that the fluidization speed is 5 times to 15 times the loosening speed. Method according to one of the Claims 17 until 20 , characterized in that the gas supplied to the reduction device has a temperature of at least 700 °C. Method according to one of the Claims 17 until 21 , characterized in that a reducing agent is introduced directly into the reduction device. Method according to one of the Claims 17 until 21 , characterized in that a reducing agent is introduced into the reduction device with the gas stream. Method according to one of the Claims 17 until 21 , characterized in that a reducing agent is introduced into the reduction device with the material flow. Method according to one of the Claims 17 until 24 , characterized in that for iron-containing minerals with an Fe ₂ O ₃ content of more than 20 wt.% only a reduction of at least 80% of the iron is carried out. Method according to one of the Claims 17 until 24 , characterized in that for iron-containing minerals with an Fe ₂ O ₃ content of less than 10 wt.% only a reduction of up to 50% of the iron is carried out.

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