Method of comminuting minerals for production of a midsize fraction for use in a fluidized bed

Abstract

The present invention relates to a method of comminuting minerals for production of a midsize fraction for use in a fluidized bed, wherein the method comprises the following steps: a) comminuting of the mineral material in a material bed roll mill 30, b) size-selective separation of the material comminuted in step a) and recycling of the coarse fraction to step a), c) size-selective separation of the fine fraction from step b) into a midsize fraction and an ultrafine fraction, d) using the ultrafine fraction as cement substitute, e) using the midsize fraction in a fluidized bed process.

Description

[0001] Provision of a medium size fraction suitable for fluidized bed applications, in particular a calcium fraction

[0002] The invention relates to a method for providing a fluidized bed-suitable size fraction, in particular a calcareous fraction in the particle size range of 100 pm to 1 mm, which is suitable for use in a fluidized bed.

[0003] In a fluidized bed, the particles must not be too large in order to react within the available time. However, a proportion of excessively small particles can also be very detrimental, as this leads to a very high level of dust generation.

[0004] Many industries are currently working intensively on carbon dioxide separation. One method is carbonate looping. In this process, an absorber, particularly CaO, is brought into contact with the exhaust gas and at least partially converted to CaCO₃. The CaCO₃ is then fed into a calciner and, with the input of energy, converted to CaO and CO₂. One option for this process step of converting CaCO₃ to CaO and CO₂ is the use of a fluidized bed. This creates a CO₂-binding absorber material that can then be recycled. This CO₂ can be separated and is then available for further use or storage. It is crucial that the energy input in the calciner does not introduce any other gases, ensuring that the CO₂ remains pure. Therefore, conventional combustion processes are unsuitable.Therefore, there is currently intensive discussion about supplying energy directly via sunlight. However, this requires that the sunlight also reaches a suitable fluidized bed. Strong dust formation prevents this. Therefore, a particularly narrow particle size distribution is necessary for this application.

[0005] However, there are other applications where a material in a suitable particle size distribution is introduced into a fluidized bed, for example, in the color adjustment of calcined clays or the calcination of lime in a drum reactor. For these applications, as previously explained, a correspondingly clean medium particle size distribution is required.

[0006] From DE 101 19 977 A1 a process and a plant for the production of cement clinker are known.

[0007] US patent 2022 / 212992 A1 discloses an advanced process for the carbonation of old concrete and / or the sequestration of CO2.

[0008] The object of the invention is to produce a medium grain size band particularly suitable for the fluidized bed, especially from a calcareous mineral.

[0009] This problem is solved by the method with the features specified in claim 1. Advantageous further developments are described in the dependent claims, the following description, and the drawings.

[0010] The invention relates to a method for comminuting minerals, in particular calcareous minerals, to produce a middle fraction for use in a fluidized bed. The method comprises the following steps: a) comminution of the mineral, in particular the calcareous mineral, in a roller mill; b) size-selective separation of the material comminuted in step a) and recycling of the coarse fraction to step a); c) size-selective separation of the fine fraction from step b) into a middle fraction and a very fine fraction; d) use of the very fine fraction as a cement substitute; e) use of the middle fraction in a fluidized bed process.

[0011] By using a roller mill for comminution, an unnecessarily large fine fraction can be reliably avoided. This optimizes the yield of the desired middle fraction and its use in a fluidized bed process. All of the aforementioned processes are particularly suitable as fluidized bed processes. In a further embodiment of the invention, the fluidized bed process is carbon dioxide separation using the carbonate looping method. Calcination is carried out in a fluidized bed reactor using sunlight. This process particularly benefits from the middle fraction and the resulting low dust generation, as this lessens the interference with sunlight penetration into the fluidized bed reactor and therefore improves energy input.If there is too much dust, the penetration depth of sunlight is reduced, and therefore not the entire space of the fluidized bed reactor is available for the reaction, as parts of the interior are not reached by sunlight.

[0012] In another embodiment of the invention, the fluidized bed process is used for color optimization of activated clays. Clays are usually thermally treated to produce them as cement substitutes, since this process releases very little carbon dioxide from the material itself, and the artificial pozzolans produced in this way have a more favorable CO2 footprint than Portland cement. Unfortunately, however, these pozzolans are often discolored red by iron components, which is why a subsequent reduction is carried out to optimize the color towards a desired gray tone. Such color optimization can preferably be carried out in a fluidized bed. Therefore, it is also advantageous to use the middle fraction for the activation of clays.

[0013] In a further embodiment of the invention, the middle fraction is produced with a size between 0.09 mm and 1 mm, preferably 0.09 mm to 0.65 mm.

[0014] The process according to the invention can, for example, be carried out in a device used for the comminution of minerals, in particular calcareous minerals, to produce a middle fraction for use in a fluidized bed. The most important calcareous mineral is limestone, but the device can also be operated with other mineral feedstocks, for example, recycled cement or clay. For certain applications, especially for the separation of carbon dioxide, for example from exhaust gases, it is important that at least a proportion of free lime can be produced from the calcareous mineral by calcination, which can then be reacted with the exhaust gas to form calcium carbonate. This process is also known as carbonate looping. The device comprises a material feed, a roller mill, and a first size-selective separation device.The system includes a second size-selective separator, a medium fraction outlet, and a fine fraction outlet. The roller mill is particularly well-suited for this purpose because the fine fraction can be minimized very efficiently by adjusting the grinding pressure, thus increasing the yield of the desired medium fraction. The roller mill has a mill inlet and a mill outlet. The first size-selective separator has a first material inlet, a first fine fraction outlet, and a first coarse fraction outlet. The second size-selective separator has a second material inlet, a second fine fraction outlet, and a second coarse fraction outlet. The material feed is connected to the first material inlet. This ensures that fresh material is separated first, and the valuable medium fraction already contained within is immediately separated and not first crushed, thus reducing losses via the fine fraction.The first coarse outlet is connected to the mill inlet; overly coarse material, the coarse fraction, as well as overly coarse feed material, is thus fed to the fine-bed roller mill. The mill outlet is connected to the first material inlet. The first fine outlet is connected to the second material inlet. Here, the mixture of medium and very fine fractions is separated. The second coarse outlet, from which the medium fraction originates, is connected to the medium fraction outlet, from where this fraction can be fed to a fluidized bed process. The second fine outlet is connected to the fine fraction outlet. The very fine fraction is preferably used directly as a cement substitute, for example, for CEM-II cements. Due to its fineness, this material is ideally suited for this purpose. Furthermore, this very fine material does not have to go through the actual clinkering process, where excessively fine particles can also be problematic.In addition, the CO2 remains bound in this material and is not released, which represents the best long-term binding of CO2.

[0015] In a further embodiment of the invention, the first size-selective separation device is a classifier. Classifiers exhibit very good separation efficiency on the order of 1 mm for the desired separation. Depending on the design, the separation limit can be further adjusted via parameters such as the classifying air volume flow rate and the rotational speed of the rotor basket (in the case of rotary basket classifiers). This allows for optimal process control.

[0016] In a further alternative embodiment of the invention, the first size-selective separation device is a sieve. Sieves have a very high separation efficiency but are not flexibly adjustable. Since the coarse fraction is fed back to the comminution process, a dynamic adjustment of the lower limit of the coarse fraction, and thus the upper limit of the medium fraction, is generally not necessary.

[0017] In a further embodiment of the invention, the second size-selective separation device is a classifier.

[0018] In a further alternative embodiment of the invention, the second size-selective separation device is a sieve. A sieve has proven particularly suitable for separating the fine fraction from the medium fraction due to its separation efficiency on the order of 0.1 mm.

[0019] In a further embodiment of the invention, the process is carried out in a cement plant with a clinker production device and a carbon dioxide separation device based on the carbonate looping process, as well as a comminution device as described above. The clinker production device can be designed according to any prior art known to those skilled in the art. The clinker production device has a product outlet for the clinker. According to the invention, the middle fraction outlet is connected to the carbon dioxide separation device. The middle fraction, suitable for the fluidized bed, is thus fed to the carbon dioxide separation device. The fine fraction outlet is connected to the product outlet or to an element arranged downstream of the product outlet, i.e., in the direction of the material flow.Such an element could be, for example, a mill, a storage facility, or the like, in which the cement is mixed from the various components, especially clinker and the fine fraction of limestone, as well as gypsum, for example. The overall combination is particularly advantageous because the material regularly removed from the carbonate looping process can be directly processed further in the cement manufacturing process.

[0020] In a further embodiment of the invention, the carbon dioxide separation device includes a solar-powered fluidized bed reactor for calcination. The solar-powered fluidized bed reactor is particularly susceptible to dust formation, which limits the penetration depth of the light and thus the effectiveness of the solar-powered fluidized bed reactor. Therefore, the provision of the middle fraction according to the invention is particularly advantageous in this case.

[0021] The following section explains in more detail an apparatus for the method according to the invention with reference to exemplary embodiments shown in the drawings.

[0022] Fig. 1 first exemplary device in the system

[0023] Fig. 2 second exemplary device in the system

[0024] Figure 1 shows an exemplary device 1 in combination with a clinker production device 60 and a carbon dioxide separation device 50 according to the carbonate looping process. Limestone is fed via the material feed 10 through the first material inlet 21 of the first size-selective separation device 20, in particular in the form of a classifier. The coarse fraction, in particular everything larger than, for example, 650 pm, is fed via the first coarse outlet 23 and the mill inlet of the roller mill 30 and is crushed there. The crushed material is fed from the roller mill 30 through the mill outlet 32 ​​to the first material inlet 21. The finer fraction, for example below 650 pm, is fed via the first fine outlet 22 and the second material inlet 41 to the second size-selective separation device 40, for example, a screen.The finest fraction is fed to the product outlet 70 via the second fine outlet 42 and thus used as a cement substitute. The medium fraction is fed to the carbon dioxide separator 50 via the second coarse outlet 42.

[0025] The carbon dioxide separation device 50 is constructed according to the carbonate looping process and comprises a carbonator 52, through which the exhaust gas to be freed of carbon dioxide is passed, and a decarbonator 54, which is, for example, designed as a solar-powered fluidized bed reactor and in which the carbon dioxide is released again. Thus, a low-carbon-dioxide exhaust gas stream 56 and a relatively pure carbon dioxide stream 58 exit the carbon dioxide separation device 50.

[0026] The clinker production plant 60, for example, is constructed in the usual manner from a preheater 62, a calciner 64, a kiln 66, and a material cooler 68. The finished clinker then proceeds to the product outlet 70. The carbon dioxide-containing exhaust gases from the clinker production plant 60 are transferred to the carbon dioxide separator 50 for carbon dioxide removal.

[0027] Figure 2 shows the activation of clays. The exemplary device 1 is unchanged from the first example in Figure 1, except that the middle fraction of the clay is introduced directly into the preheater 62 of a clay activation device 80 via the second coarse outlet 43 and subsequently thermally activated in the calciner 64. The material, which is usually reddish in color due to the thermal activation, is introduced into a color optimization fluidized bed reactor 86, in which the optimized particle size of the middle fraction simplifies the color optimization process. The activated and color-optimized clay is then cooled in a material cooler 58 and conveyed to the product outlet 70.

[0028] Reference sign

[0029] 1 Device for crushing calcareous minerals to produce a middle fraction for use in a fluidized bed

[0030] 10 Material feed

[0031] 20 first size-selective separating device

[0032] 21 first material intake

[0033] 22 first fine outlet

[0034] 23 first major exit

[0035] 30 Good bed roller mill

[0036] 31 Mill inlet

[0037] 32 Mill outlet

[0038] 40 Second size-selective separating device 41 Second material inlet

[0039] 42 second fine outlet

[0040] 43 second major exit

[0041] 50 Carbon dioxide separation device 52 Carbonator

[0042] 54 Decarbonator

[0043] 56 Exhaust gas flow

[0044] 58 Carbon dioxide electricity

[0045] 60 Clinker manufacturing device 62 Preheater

[0046] 64 Calcinator

[0047] 66 Oven

[0048] 68 material coolers

[0049] 70 Product outlet 80 Ton activation device

[0050] 86 Color Optimization Fluidized Bed Reactor

Claims

Patent claims 1. A process for comminuting minerals to produce a middle fraction for use in a fluidized bed, comprising the following steps: a) comminuting the mineral in a fine-bed roller mill (30), b) size-selective separation of the material comminuted in step a) and recycling the coarse fraction to step a), c) size-selective separation of the fine fraction from step b) into a middle fraction and a very fine fraction, d) use of the very fine fraction as a cement substitute, e) use of the middle fraction in a fluidized bed process.

2. Method according to claim 1, characterized in that the Fluidized bed process is a color optimization method for activated clays.

3. Method according to claim 1, characterized in that the fluidized bed process is a carbon dioxide separation according to the carbonate looping process, wherein the calcination is carried out in a fluidized bed reactor using sunlight.

4. Method according to one of claims 1 to 3, characterized in that the middle fraction is produced with a size between 0.09 mm and 1 mm, preferably 0.09 mm to 0.65 mm.

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