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

Abstract

The present invention relates to a device for the thermal treatment of a mineral material, wherein the device comprises an activation device 30, the activation device 30 being designed as a fluidized bed 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.

Description

[0001] The invention relates to a device and a method for producing an activated mineral material, in particular a clay, especially as a low-CO2 emission cement component with a particularly high proportion of substitute fuel for the greatest possible avoidance of fossil fuels, and to such an activated material.

[0002] In traditional cement production, limestone (CaCO3) is burned to produce clinker (CaO), a major source of human-generated carbon dioxide. Therefore, mineral materials, particularly clays, are increasingly being activated. These materials have similar binding properties but do not produce the same amount of carbon dioxide during activation. Thus, in clay activation, the primary source of carbon dioxide is the fuel used to generate the necessary temperatures and energy. To further reduce this source of human-generated carbon dioxide, alternative fuels are increasingly being used instead of fossil fuels. This conserves resources such as coal, oil, and gas. These fossil fuels are being replaced by CO2-neutral or low-CO2 alternative fuels with particular preference. Alternative fuels are diverse and widely used, ranging from plastic waste to biomass.

[0003] From DE 10 2013 105 096 A1 a process for the heat treatment of a material stream and for the drying of a carbon-containing material stream is known.

[0004] Energy recovery during the cooling of color-optimized activated clays is known from DE 10 2020 211 750 A1.

[0005] WO 2017 / 125 579 A1 discloses a U-shaped incinerator and a method for use in a cement plant.

[0006] From EP 2 735 554 A1 a method and a device for drying solid waste by means of gas from a clinker cooler are known.

[0007] From WO 2007 / 017 748 A2 a method and a device for utilizing alternative fuels in clinker and cement production are known.

[0008] From EP 582 394 A1 a process for burning waste in a cement plant is known.

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

[0010] A key aspect of the combustion of alternative fuels is that they consistently require high temperatures for reliable ignition and combustion. 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. This means that conventional fuels can currently only be partially replaced by alternative fuels. However, there is a desire to replace conventional fuels as completely as possible, or ideally, entirely.

[0011] The object of the invention is to provide a device that allows for an increased proportion of substitute fuel as an energy source.

[0012] This problem is solved by the device with the features specified in claim 1. Advantageous further developments are described in the dependent claims, the following description, and the drawings.

[0013] 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 includes an activation unit. The activation unit is designed as a fluidized bed reactor. Here, the material to be activated is transported in cocurrent flow with a gas stream and activated by the temperature. The activation unit is connected to a separation cyclone for separating the activated mineral material from the gas stream. The separated gas stream is then typically directed into a preheater to transfer heat to the mineral material to be activated, which can thus be preheated before being fed to the activation unit, thereby reducing the energy consumption in the activation unit. The device includes a material cooler.In the material cooler, the activated mineral material is cooled, and the heat is simultaneously transferred to a gas stream, which is then fed to the activation unit. The separation cyclone is connected to the material cooler via a first material line for transferring the activated material. The material cooler is connected via a gas line, for example, to the activation unit or an upstream drying unit, to supply a gas stream preheated in the material cooler. The activation unit includes a combustion device for a substitute fuel. The combustion device provides the energy necessary for activation. The combustion device can be designed in various ways. It can be relatively simple if the substitute fuel is fully biogas-capable. In that case, the combustion device essentially consists only of a feed for the substitute fuel.Typically, the combustion unit has a section that is, for example, angled and designed for burning solid, non-aircraftable alternative fuels. Alternatively, a horizontally arranged combustion unit can be used, for example, with a conveying system located in the ground. Another alternative is a combustion unit with a fluidized bed.

[0014] According to the invention, the separation cyclone is equipped with a second material line. This second material line is connected to the activation device or the gas line for transferring activated material into the activation device. Thus, a portion of the hot activated material is returned directly or indirectly to the activation device. There, the hot activated material can transfer its heat to the gas stream coming from the material cooler, thereby warming it. This makes it possible to heat the gas stream using reliably ignitable fossil fuels without the need for additional combustion via a hot gas generator, thus significantly reducing the proportion of fossil fuels required. A disadvantage is that the returned material increases the gas stream in the activation device, and this partial return results in a broadening of the material's residence time spectrum within the activation device.

[0015] 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 stream preheated in the material cooler, may, for example, have a gas diverter to direct part of the gas stream preheated in the material cooler to another location or process where this heat is to be used.

[0016] In a further embodiment of the invention, the combustion device for the substitute fuel is arranged within the activation device. This direct internal arrangement ensures that the energy is generated and delivered precisely where it is needed and consumed for activation. This reliably prevents temperature spikes and thus also the potential deactivation of the material due to excessive temperature. 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.

[0017] In a further embodiment of the invention, a classifier is located upstream and / or downstream of the separation cyclone, and / or the separation cyclone itself is designed as a classifier. The rationale is that size-selective separation and recycling can be advantageous, particularly 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 alternative fuels can produce an incompletely burned residue. This residue 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 configured such that a fraction of approximately 30 wt.% is separated and recycled as the fine fraction. 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 larger than 2 mm. Such large particles are relatively likely to contain large, unburned pieces of the alternative fuel. Therefore, it is advantageous to separate and recycle this coarse fraction. Recycling enables virtually complete combustion, which in turn offers two advantages. Firstly, the entire energy content of the alternative fuel can be utilized, and secondly, the carbon content in the finished product is reduced.

[0018] In a further embodiment of the invention, the classifier is designed to separate a coarse fraction, a medium fraction, and a fine fraction. This separation into three fractions allows both the incompletely burned residue via the fine fraction and unburned pieces of the alternative fuel to be recycled, while the medium fraction exhibits a particularly pure product. Therefore, the second material line is preferably connected to the classifier in such a way that both the fine and coarse fractions are recycled. The first material line, on the other hand, is connected to the classifier in such a way that the medium fraction is transferred to the material cooler.

[0019] In a further embodiment of the invention, the device includes a hot gas generator. The hot gas outlet of the hot gas generator is connected to the gas line. This connection is located downstream of the connection between the second material line and the gas line in the direction of gas flow. This allows the gas flow to be heated first by the recirculated activated material and, if necessary, 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.

[0020] In a further embodiment of the invention, the device includes a hot gas generator. The hot gas outlet of the hot gas generator is connected to the gas line. This connection is located upstream of the connection between the second material line and the gas line, in the direction of gas flow. This arrangement ensures thorough mixing of the gas flows.

[0021] 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.

[0022] In another 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 range has proven advantageous with regard to optimizing the color of the activated material, but is significantly too low to reliably ignite and then combust alternative 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 reliable ignition and complete combustion of the alternative fuel. The minimum temperature for the reliable ignition of alternative fuels is typically assumed to be 700 °C. Thus, the gas stream exiting the material cooler is at least 100 °C too low.To sufficiently heat the gas stream, 15 to 60 wt% of the activated material from the separation cyclone is returned to 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 alternative fuels in the overall process.

[0023] 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 alternative fuel. This can be adjusted via the proportion of recycled activated material.

[0024] In a further embodiment of the invention, the proportion of the alternative fuel to the total amount of fuel is at least 80%, preferably at least 85%, more preferably at least 90%, and particularly preferably at least 95%. This proportion is based on the calorific value in order to be able to weight different fuels in a targeted manner. It is therefore possible to achieve a further increase in the proportion of alternative fuels compared to conventional plants using the method according to the invention.

[0025] In a further embodiment of the invention, the alternative fuel consists of at least 60% by weight, preferably at least 70% by weight, of volatile components. The advantage of a volatile alternative fuel is that it combusts easily in the gas stream and thus in close proximity to the mineral material to be activated, thereby releasing energy that is absorbed by the mineral material and used for the activation process, significantly reducing temperature peaks and troughs.

[0026] In a further embodiment of the invention, the substitute fuel consists of at least 20 wt.%, preferably at least 30 wt.%, of biogenic fuel.

[0027] For example, the alternative fuel can consist of 30% biomass. This is considered CO2-neutral because the released CO2 was previously absorbed from the atmosphere through plant growth and can therefore be regarded as particularly climate-friendly. The remaining 70% could consist of, for example, shredded plastic waste, which is particularly suitable for air transport, has a comparatively constant calorific value, and virtually no moisture (requiring energy for water evaporation during combustion). This allows for a balance 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, and particularly preferably less than 6 s. The shorter the residence time, the more critical the complete combustion of an alternative fuel becomes, and the greater the potential proportion of carbon and / or incompletely combusted fuel in the finished product. However, since, according to the invention, at least a portion is recycled, thus extending the residence time of the fuel, especially if the recycling is preferably size-selective, reliable combustion can be achieved even with such short residence times and thus high throughputs. This optimally utilizes the calorific value of the alternative fuel and leads to improved product quality with a low carbon content.

[0029] In a further embodiment of the invention, the coarse fraction with a diameter greater than 2 mm is returned via the second material line. This coarse fraction can contain comparatively large amounts of unburned alternative fuel, so that selectively returning this largest coarse fraction specifically returns the carbon load. This ensures optimal utilization of the alternative fuel's calorific value and also improves 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. The fine fraction, in particular, can contain a high proportion of carbon, especially in the form of incompletely combusted residue, and be returned for further combustion. This allows for optimal utilization of the calorific value of the alternative fuel and also improves product quality by reducing the carbon content.

[0031] In a further embodiment of the invention, the hot gas generator is used only for starting up the device. During start-up, the overall system, usually starting from ambient temperature, does not yet have sufficient heat for the combustion of substitute fuels. Therefore, it is advantageous to initially introduce the required heat into the system via a hot gas generator. Since the hot gas generator is thus operated relatively infrequently and therefore has only a very small impact on the overall CO2 balance, it can, for example, be 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 increased temperature, the actual volume is approximately three to four times larger, plus the additional gas volume from water vapor, which is gaseous and not liquid at these high temperatures.

[0033] In a further aspect, the invention relates to an activated material produced according to the inventive method, wherein the activated material has less than 1, preferably less than 0.5, and more preferably less than 0.2 wt% carbon. The inventive method thus makes it possible to produce a product that has both a very low to no CO2 footprint and a very low carbon content.

[0034] A device for carrying out the method according to the invention therefore preferably has a control unit, in particular a device for electronic data processing, with executable program instructions for carrying out the method according to the invention.

[0035] The device according to the invention is explained in more detail below with reference to the exemplary embodiments shown in the drawings. Fig. 1 first exemplary embodiment Fig. 2 second exemplary embodiment Fig. 3 third exemplary embodiment

[0036] In Fig. Figure 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, where it is activated by means 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 an inclined bottom for the combustion of the substitute fuel, for example biomass. After activation of the material, it is separated in the separation cyclone 40. For example, 70 wt.-% of the separated activated material is fed to the material cooler 60 via the first material line 51, cooled there, and discharged via the product outlet 70. The remaining, for example, 30 wt% of the separated activated material is fed to the gas line 80 via the second material line 52 and heats the gas stream coming from the material cooler 60.

[0037] The gas flow is essentially in the opposite direction to the material flow. The gas enters the material cooler 60 via the gas supply 100 and is heated, for example, to 550 °C. The gas leaves the material cooler 60 via the gas line, where it is mixed with the activated material from the second material line 52, thereby increasing its temperature by, for example, 250 °C to 800 °C. The gas flow, now 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 is 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 discharged via the gas outlet (after optional exhaust gas cleaning, in particular dust removal).

[0038] For starting 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.

[0039] The in Fig. The second exemplary embodiment shown in 2 differs from the one shown in Fig. 1 first exemplary embodiment shown in that the preheated material 11 from the preheater is combined with the material flow of the second material line 52 and introduced together into the activation device.

[0040] The in Fig. The third exemplary embodiment shown in 3 differs from the one shown in Fig.1 first exemplary embodiment shown in that the combustion device 31 is designed as an inclined area within the activation device 30, thereby achieving a greater proximity 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 more uniform temperature profile within the activation device 30. Reference sign 10 Material supply 11 preheated material 20 preheaters 30 Activation device 31 Burning device 40 separation cyclones 51 first material management 52 second material line 60 material coolers 70 Product outlet 80 Gas pipeline 90 hot gas generators 100 Gas supply 101 Hot gas 102 Gas release QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. 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

[0000] DE 10 2013 105 096 A1

[0003] DE 10 2020 211 750 A1

[0004] WO 2017 / 125 579 A1

[0005] EP 2 735 554 A1

[0006] WO 2007 / 017 748 A2

[0007] EP 582 394 A1

[0008] KR 2005 079 028 A

[0009] DE 10 2021 203 071 A1

[0016] DE 10 2021 203 072 A1

[0016] DE 10 2021 203 073 A1

[0016] DE 10 2021 203 074 A1

[0016]

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 byin 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). [2] Device according to claim 1, characterized by 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 by that a separator is arranged upstream or downstream of the separating cyclone (40) or that the separating cyclone (40) is designed as a separator. [4] Device according to claim 3, characterized by 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 byin 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] 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). [7] Method according to claim 6, characterized bythat the gas flow from the material cooler (60) is heated by 100 °C to 200 °C by the returned activated material before the gas flow reaches the combustion device (31) for the substitute fuel. [8] Method according to one of claims 6 to 7, characterized by that the proportion of the 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%. [9] Method according to one of claims 6 to 8, characterized by that the substitute fuel consists of at least 60 wt.%, preferably at least 70 wt.%, of airworthy components. [10] Method according to one of claims 6 to 9, characterized by that the substitute fuel consists of at least 20 wt.%, preferably at least 30 wt.%, of biogenic fuel. [11] Method according to one of claims 6 to 10, characterized bythat 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 by 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 by that the fine fraction is returned via the second material line (52). [14] Method according to one of claims 6 to 13, characterized by that the heating gas generator is only used to start up the device. [15] Method according to one of claims 6 to 14, characterized by that the gas loading in the activation device (30) is 500 to 4000 g per standard cubic meter. [16] Activated material prepared by the process according to any one of claims 6 to 15, wherein the activated material comprises less than 1 wt% carbon.

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