Increasing the proportion of substitute fuels in the production of activated clays

Abstract

The present invention relates to a device for heat-treating a mineral material, wherein the device has an activation device (30), wherein the activation device (30) is designed as an entrained flow reactor, wherein the activation device (30) is connected to a separation cyclone (40) to separate the activated mineral material from the gas flow, wherein the device has a material cooler (60), wherein the separation cyclone (40) is connected, via a first material line (51), to the material cooler (60) to transfer activated material, wherein the material cooler (60) is connected, via a gas line (80), to the activation device (30) to supply a gas flow which is preheated in the material cooler (60), wherein the activation device (30) has a combustion device for a substitute fuel, characterised in that the separation cyclone (40) is connected to a second material line (52), wherein the second material line (52) is connected to the activation device (30) or the gas line (80) to transfer activated material into the activation device (30).

Description

[0001] Increasing the proportion of substitute fuels in the production of activated clays

[0002] The invention relates to a device and a method for producing an activated mineral material, in particular a clay, in particular as a low-CO2 emission cement component with a particularly high proportion of substitute fuel to largely avoid the use of fossil fuels, as well as to a material activated in this way.

[0003] In cement production, limestone (CaCO3) is traditionally burned to produce clinker (CaO), which is a major source of carbon dioxide released by humans. Therefore, mineral materials, particularly clays, are increasingly being activated. These materials have similar binding properties but do not produce the same amounts of carbon dioxide upon activation. Thus, in the activation of clays, the main source of carbon dioxide is the fuel used to generate the necessary temperatures and energy. To reduce this source of man-made carbon dioxide, substitute fuels are increasingly being used instead of fossil fuels. This conserves resources such as coal, oil, and gas. These fossil fuels are being replaced with CO2-neutral or low-CO2 substitute fuels, particularly those with low CO2 emissions. Substitute fuels are widely known and used, ranging from plastic waste to biomass.

[0004] From DE 10 2013 105 096 A1 a method for heat-treating a material stream and for drying a carbon-containing material stream is known.

[0005] DE 10 2020 211 750 A1 discloses energy recovery during the cooling of color-optimized activated clays.

[0006] WO 2017 / 125 579 A1 discloses a U-shaped burner and a method for use in a cement plant.

[0007] EP 2 735 554 A1 discloses a method and device for drying solid waste using gas from a clinker cooler. WO 2007 / 017 748 A2 discloses a method and device for utilizing alternative fuels in clinker and cement production.

[0008] EP 582 394 A1 discloses a process for incinerating waste in a cement plant.

[0009] A process for producing solid fuels using plastic waste is known from KR 2005 079 028 A.

[0010] From US 5 174 749 A a method and a device for heat treatment of a powdered material is known.

[0011] A device for burning materials is known from US 4 167 390 A.

[0012] An important consideration when burning substitute fuels is that they regularly require high temperatures to ignite and burn safely. Therefore, hot gas generators are often used today to further heat the gases coming from a material cooler, using conventional fuels such as natural gas. As a result, conventional fuels can currently only be partially replaced by substitute fuels. However, there is a desire to replace conventional fuels as extensively as possible, or even completely.

[0013] The object of the invention is to provide a device that enables an increased proportion of substitute fuel as an energy source.

[0014] This object is achieved by the device having the features specified in claim 1. Advantageous further developments emerge from the subclaims, the following description, and the drawings.

[0015] The device according to the invention serves for the thermal treatment of a mineral material, for example and in particular clays for production as a clinker substitute. The device comprises an activation device. The activation device is designed as an entrained-flow reactor. Here, the material to be activated is transported cocurrently with a gas stream and activated by the temperature. The activation device is connected to a separation cyclone for separating the activated mineral material from the gas stream. The separated gas stream is then typically fed into a preheater to transfer the heat to the mineral material to be activated, which can then be preheated and fed to the activation device, thereby reducing the energy requirement in the activation device. The device comprises a material cooler.In the material cooler, the activated mineral material is cooled and simultaneously the heat is transferred to a gas stream, which is then fed to the activation device. The separation cyclone is connected to the material cooler via a first material line for transferring activated material. The material cooler is connected via a gas line, for example, to the activation device or an upstream drying device for supplying a gas stream preheated in the material cooler. The activation device has a combustion device for a substitute fuel. The combustion device provides the energy required for activation. The combustion device can be designed in different ways. The combustion device can be comparatively simple if the substitute fuel is fully airworthy. In this case, the combustion device essentially consists only of a feed for the substitute fuel.Typically, however, the combustion device has a section that is, for example, inclined and designed for the combustion of solid and non-airworthy alternative fuels. Alternatively, a horizontally arranged combustion device can be used, for example, with an in-ground conveyor system. A further alternative is a combustion device with a fluidized bed.

[0016] According to the invention, the separation cyclone is equipped with a second material line. The second material line is connected to the activation device or the gas line for transferring activated material into the activation device. The combustion device for a substitute fuel is arranged above the connection of the second material line to the activation device or the gas line. Thus, the hot activated material is proportionally returned directly or indirectly to the activation device. On the path between the feed and the combustion device, the returned material heats the gas stream coming from the material cooler. There, the hot activated material can thus transfer its heat to the gas stream coming from the material cooler and heat it, for which no fuel is required.This makes it possible to heat the gas stream using reliably ignited fossil fuels without the need for additional firing via a hot gas generator, which at least significantly reduces the proportion of fossil fuels. The disadvantage is that the recirculated material in the gas stream increases the amount of fuel in the activation device, and this partial recirculation results in a broadening of the residence time spectrum of the material in the activation device. It is therefore essential that the recirculated material is fed in upstream of the combustion device and that a distance and thus a residence time for heat exchange is provided between the feed, i.e. the outlet of the second material line, and the combustion chamber. This means that the gas stream reaches the combustion device warmer, which enables the safe combustion of substitute fuels.

[0017] The gas line, via which the material cooler is connected, for example, to the activation device or an upstream drying device for supplying a gas flow preheated in the material cooler, can, for example, have a gas switch in order to bring part of the gas flow preheated in the material cooler to another location or to another process where this heat is to be used.

[0018] In a further embodiment of the invention, the combustion device for the substitute fuel is arranged within the activation device. Due to the direct arrangement within, the energy is generated and released exactly where it is needed and consumed for activation. This more reliably prevents temperature peaks and thus also possible deactivation of the material due to excessively high temperatures. Such an implementation can be found, for example, in DE 10 2021 203 071 A1, DE 10 2021 203 072 A1, DE 10 2021 203 073 A1 or DE 10 2021 203 074 A1. In a further embodiment of the invention, a classifier is arranged upstream and / or downstream of the separation cyclone and / or the separation cyclone is designed as a classifier. The background to this is that size-selective separation and recirculation can be useful, in particular to reduce the proportion of carbon and / or incompletely combusted fuel in the finished product.There are two main sources for this. Firstly, the combustion of the substitute fuels can produce an incompletely burnt residue. This is very small and very light and can therefore be separated as the finest fraction (light fraction) and optionally recycled. For example, the classifier can be set up so that a fraction of around 30 wt.% is separated as the finest fraction and recycled. The remaining 70 wt.% of the coarse fraction (heavy fraction) then contains only a very small amount of carbon. Alternatively or additionally, the classifier can be designed to separate a coarse fraction with particle sizes over 2 mm. Such large particles are relatively likely to contain large, unburned pieces of the substitute fuel. It is therefore advantageous to separate this large fraction and recycle it.The recycling then enables almost complete combustion, which in turn has two advantages: Firstly, the entire energy content of the substitute fuel can be utilized, and secondly, the carbon content in the finished product is reduced.

[0019] In a further embodiment of the invention, the separator is designed to separate a coarse fraction, a medium fraction, and a fine fraction. By separating the material into three fractions, both the incompletely burned residue via the fine fraction and unburned pieces of the refuse-derived fuel can be recycled, and the medium fraction has a particularly pure product. Therefore, the second material line is preferably connected to the separator in such a way that both the fine fraction and the coarse fraction are recycled. The first material line, on the other hand, is connected to the separator in such a way that the medium fraction is transferred to the material cooler.

[0020] In a further embodiment of the invention, the device comprises a hot gas generator. The hot gas outlet of the hot gas generator is connected to the gas line. The connection is arranged downstream of the connection of the second material line to the gas line in the gas flow direction. As a result, the gas stream is initially heated by the recirculated activated material and can, if desired, be further heated in a second step via a hot gas generator. This can be useful, for example, to compensate for fluctuations in the calorific value of the substitute fuel. It can also be useful for starting up the device.

[0021] In a further embodiment of the invention, the device comprises a hot gas generator. The hot gas outlet of the hot gas generator is connected to the gas line. The connection is arranged upstream of the connection of the second material line to the gas line in the gas flow direction. This arrangement leads to thorough mixing of the gas streams.

[0022] In a further embodiment of the invention, a reduction device for color optimization is arranged in the first material line between the separation cyclone and the material cooler.

[0023] In a further aspect, the invention relates to a method for operating a device according to the invention. The device is operated such that the gas stream leaves the material cooler at a temperature of 350°C to 900°C, preferably 400 to 600°C. This temperature window has proven advantageous with regard to color optimization of the activated material, but is significantly too low to safely and reliably ignite and then combust substitute fuels at this temperature. Activation in the activation device is carried out at 750°C to 950°C. This ensures both reliable activation of the mineral material and safe ignition and complete combustion of the substitute fuel. The lowest temperature for safe ignition of substitute fuels is usually assumed to be 700°C. Thus, the gas stream exits the material cooler at at least 100°C, which is too low.To sufficiently heat the gas stream, 15 to 60 wt.% of the activated material from the separation cyclone is fed back into the activation device, and the remaining 40 to 85 wt.% of the activated material is fed to the material cooler. This enables a simple energy transfer that heats the gas stream without the use of fossil fuels, thus significantly increasing the proportion of substitute fuels in the overall process. Between the connection of the second material line to the activation device or the gas line and the combustion device for a substitute fuel, the gas coming from the material cooler is heated by the material returned through the second material line. Heating by means of a combustion process and thus the use of a fuel is thus dispensed with.The aim is to heat the gas stream sufficiently to enable safe combustion of the substitute fuels while at the same time avoiding the use of other fuels.

[0024] In a further embodiment of the invention, the gas stream from the material cooler is heated by the recycled activated material by 50°C to 400°C, preferably 100°C to 200°C, before the gas stream reaches the combustion device for the substitute fuel. This can be adjusted by the proportion of recycled activated material.

[0025] In a further embodiment of the invention, the proportion of substitute fuel in the total amount of fuel is at least 80%, preferably at least 85%, more preferably at least 90%, particularly preferably at least 95%. This proportion is based on the calorific value in order to allow for targeted weighting of different fuels. Thus, the process according to the invention makes it possible to further increase the proportion of substitute fuels compared to conventional systems.

[0026] In a further embodiment of the invention, the substitute fuel consists of at least 60 wt.%, preferably at least 70 wt.%, of airworthy components. The advantage of an airworthy substitute fuel is that it burns easily in the gas stream and thus in close proximity to the mineral material to be activated, releasing energy that is in turn absorbed by the mineral material and used for the activation reaction, significantly reducing temperature peaks and dips.

[0027] In a further embodiment of the invention, the substitute fuel consists of at least 20 wt.%, preferably at least 30 wt.%, biogenic fuel. For example, the substitute fuel can consist of 30% biomass. This is considered carbon dioxide-neutral because the CO2 released from the atmosphere was previously bound by plant growth and can therefore be considered particularly climate-friendly. The remaining 70% consists, for example, of shredded plastic waste, which is particularly airworthy, has a relatively constant calorific value, and contains virtually no moisture (energy required for the evaporation of water during combustion). This allows a balance to be achieved between climate protection, costs, and stable process conditions.

[0028] In a further embodiment of the invention, the residence time in the activation device is less than 10 s, preferably less than 8 s, particularly preferably less than 6 s. The shorter the residence time, the more critical the complete combustion of a substitute fuel is and the greater the proportion of carbon and / or incompletely combusted fuel in the finished product can be. However, since according to the invention at least a portion is recycled and thus the residence time for the fuel is extended, particularly if the fuel is preferably recycled in a size-selective manner, reliable combustion can be achieved even with such short residence times and thus high throughputs, which both optimally utilizes the calorific value of the substitute fuel and leads to improved product quality with a low carbon content.

[0029] In a further embodiment of the invention, the coarse fraction larger than 2 mm is returned via the second material line. The coarse fraction in particular can contain comparatively large amounts of unburned substitute fuel, so the selective recirculation of this largest coarse fraction returns the carbon load, thereby optimally utilizing the calorific value of the substitute fuel and increasing product quality by reducing the carbon content.

[0030] In a further embodiment of the invention, the fine fraction is returned via the second material line. This fine fraction, in particular, can contain a high proportion of carbon, particularly in the form of incompletely combusted residue, and can be returned for further combustion. This not only optimally utilizes the calorific value of the refuse-derived fuel, but also increases product quality by reducing the carbon content.

[0031] In a further embodiment of the invention, the hot gas generator is used only to start up the device. During start-up, the entire system usually does not yet have sufficient heat from ambient temperature to burn substitute fuels. Therefore, it is advantageous to initially supply the required heat to the system via a hot gas generator. Since the hot gas generator is operated comparatively little and thus has only a very minimal impact on the overall CO2 balance, it can be, for example, a simple natural gas burner, which is easy to operate and relatively simple in design.

[0032] In a further embodiment of the invention, the gas loading in the activation device is 500 to 4000 g per standard cubic meter, preferably 1000 to 2500 g per standard cubic meter. The standard cubic meter refers to the (dry) gas volume at ambient pressure and temperature. Due to the elevated temperature, the actual volume is approximately three to four times larger, plus the additional gas volume due to water vapor, which is gaseous and not liquid at the high temperatures.

[0033] In a further aspect, the invention relates to an activated material produced by the process according to the invention, wherein the activated material has less than 1, preferably less than 0.5, and more preferably less than 0.2 wt.% carbon. The process according to the invention thus makes it possible to produce a product that has both a very low to no carbon footprint and a very low carbon content.

[0034] A device for implementing the method according to the invention therefore preferably comprises a control unit, in particular a device for electronic data processing, with executable program instructions for implementing the method according to the invention. The device according to the invention is explained in more detail below with reference to exemplary embodiments illustrated in the drawings.

[0035] Fig. 1 first exemplary embodiment

[0036] Fig. 2 second exemplary embodiment

[0037] Fig. 3 third exemplary embodiment

[0038] Fig. 1 shows a first exemplary embodiment of a device according to the invention. Material to be activated, for example clay, is fed to a preheater 20 via the material feed 10. The preheater 20 can, for example, be designed as a cascade of two to six co-current heat exchangers with a subsequent separation cyclone. The preheated material 11 is transferred to the activation device 30, in which it is activated with the help of the heat released by the combustion of a substitute fuel in the combustion device 31. In the example shown, the combustion device 31 is a laterally attached chamber with a sloping floor for the combustion of the substitute fuel, for example biomass. After the material has been activated, it is separated in the separation cyclone 40. For example, 70 wt.-% of the separated activated material is fed via the first material line 51 to the material cooler 60, cooled there, and discharged via the product outlet 70. The remaining, for example, 30 wt.% of the separated activated material is fed via the second material line 52 to the gas line 80, where it heats the gas stream coming from the material cooler 60.

[0039] The gas flow essentially runs in the opposite direction to the material flow. The gas enters the material cooler 60 via the gas inlet 100 and is heated to, for example, 550°C. The gas leaves the material cooler 60 via the gas line, where the gas flow is mixed with the activated material from the second material line 52 and is thereby heated by, for example, 250°C to 800°C. The gas flow, thus heated to 800°C, enters the activation device 30, is loaded with the preheated material 11, and is further heated to, for example, 900°C by the combustion of the substitute fuel in the combustion device 31. After the activated material has been separated in the separation cyclone 40, the hot gas 101 is transferred to the preheater 20, where it releases most of its heat. The gas is then released again via the gas outlet (after optional exhaust gas purification, in particular dust removal).

[0040] For start-up, the device has a hot gas generator 90, which can introduce hot gas into the gas line 80 to heat the gas flow and thus the entire device.

[0041] The second exemplary embodiment shown in Fig. 2 differs from the first exemplary embodiment shown in Fig. 1 in that the preheated material 11 from the preheater is combined with the material flow of the second material line 52 and is introduced together into the activation device.

[0042] The third exemplary embodiment shown in Fig. 3 differs from the first exemplary embodiment shown in Fig. 1 in that the combustion device 31 is designed as an inclined region within the activation device 30, whereby a greater proximity is achieved between the exothermic combustion of a solid substitute fuel and the endothermic activation taking place above it in the gas phase, which in turn leads to a homogenization of the temperature profile within the activation device 30.

[0043] Reference symbol

[0044] 10 Material supply

[0045] 11 preheated material

[0046] 20 preheaters

[0047] 30 Activation device

[0048] 31 Burning device

[0049] 40 Separation cyclone

[0050] 51 first material line

[0051] 52 second material line

[0052] 60 material coolers

[0053] 70 Product outlet

[0054] 80 gas pipeline

[0055] 90 Hot gas generator Gas supply Hot gas Gas outlet

Claims

Patent claims 1. A device for the thermal treatment of a mineral material, the device comprising an activation device (30), the activation device (30) being designed as an entrained-flow reactor, the activation device (30) being connected to a separation cyclone (40) for separating the activated mineral material from the gas stream, the device comprising a material cooler (60), the separation cyclone (40) being connected to the material cooler (60) via a first material line (51) for transferring activated material, the material cooler (60) being connected to the activation device (30) via a gas line (80) for supplying a gas stream preheated in the material cooler (60), the activation device (30) comprising a combustion device for a substitute fuel, characterized in that the separation cyclone (40) is connected to a second material line (52).wherein the second material line (52) is connected to the activation device (30) or the gas line (80) for transferring activated material into the activation device (30), wherein the combustion device for a substitute fuel is arranged above the connection of the second material line (52) to the activation device (30) or the gas line (80).

2. Device according to claim 1, characterized in that the combustion device for the substitute fuel is arranged within the activation device (30).

3. Device according to one of the preceding claims, characterized in that a separator is arranged upstream or downstream of the separating cyclone (40) or the separating cyclone (40) is designed as a separator.

4. Device according to claim 3, characterized in that the classifier is designed to separate a coarse fraction, a medium fraction and a fine fraction.

5. Device according to one of the preceding claims, characterized in that the device comprises a hot gas generator (90), wherein the hot gas outlet of the hot gas generator (90) is connected to the gas line (80), wherein the connection is arranged in the gas flow direction behind the connection of the second material line (52) to the gas line (80).

6. A method for operating a device according to one of the preceding claims, wherein the device is operated such that the gas stream leaves the material cooler (60) at a temperature of 400°C to 600°C, wherein the activation in the activation device (30) is carried out at 750°C to 950°C, wherein 15 to 60 wt.% of the activated material is fed from the separation cyclone (40) back into the activation device (30) and the remaining 40 to 85 wt.% of the activated material is fed to the material cooler (60), wherein between the connection of the second material line (52) to the activation device (30) or the gas line (80) and the combustion device for a substitute fuel, the gas coming from the material cooler (60) is heated by the material fed back through the second material line (52).

7. The method according to claim 6, characterized in that the gas stream from the material cooler (60) is heated by the returned activated material by 100 °C to 200 °C before the gas stream reaches the combustion device (31) for the substitute fuel.

8. Method according to one of claims 6 to 7, characterized in that the proportion of the substitute fuel in the total amount of the fuel is at least 80%, preferably at least 85%, further preferably at least 90%, particularly preferably at least 95%.

9. A method according to any one of claims 6 to 8, characterized in that the substitute fuel consists of at least 60% by weight, preferably at least 70% by weight, of airworthy components.

10. Process according to one of claims 6 to 9, characterized in that the substitute fuel consists of at least 20% by weight, preferably at least 30% by weight, of biogenic fuel.

11. Method according to one of claims 6 to 10, characterized in that the residence time in the activation device (30) is less than 10 s, preferably less than 8 s, particularly preferably less than 6 s.

12. Method according to one of claims 6 to 11, characterized in that the coarse fraction with more than 2 mm is returned via the second material line (52).

13. Method according to one of claims 6 to 12, characterized in that the fine fraction is returned via the second material line (52).

14. Method according to one of claims 6 to 13, characterized in that the heating gas generator is used only for starting up the device.

15. Method according to one of claims 6 to 14, characterized in that the gas loading in the activation device (30) is 500 to 4000 g per standard cubic meter.

16. Activated material produced by the process of any one of claims 6 to 15, wherein the activated material comprises less than 1 wt% carbon.

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