METHOD FOR OPERATING A PLANT FOR THE THERMAL TREATMENT OF A MINERAL SUBSTANCE

Description

[0001] The invention relates to a method for operating a plant for the thermal treatment of mineral substances, for example and in particular clay and pozzolans from artificial or natural rocks, for example and in particular from silicon dioxide, alumina, limestone, iron oxide and alkaline substances, aluminium and / or silicon-containing residues from metal processing, the ceramics and / or paper industry or dredging and harbor sludge, for example for the production of artificial pozzolans as a substitute for cement production, wherein alternative fuels can be used completely and no additional fossil fuels are required.

[0002] The use of alternative fuels to reduce CO₂ emissions is well-established and now widespread in many sectors. However, alternative fuels often exhibit fluctuating properties, particularly their calorific values. Furthermore, some fuels have a high moisture content, meaning they are often not self-igniting. This varying moisture content also results in different energy requirements for water vaporization, which in turn affects the temperature. Additionally, the particle size of alternative fuels varies. Smaller particles burn faster and more readily combust completely, while larger particles burn more slowly and may not burn completely. Therefore, particle size also influences the temperature.Therefore, auxiliary burners for rapidly adjustable fossil fuels are often used in plants fired with alternative fuels to compensate for fluctuations in calorific value (calorific value here and in the following refers specifically to all the aforementioned factors influencing temperature) and the resulting temperature fluctuations. Furthermore, in some energy-intensive thermal treatment processes, it is advantageous to have at least part of the combustion, and thus the energy generation, directly at the point of thermal treatment. The input of fossil fuels is more easily metered and dispersed, resulting in a more homogeneous distribution and better interaction with the materials being treated. Gas or pulverized coal are preferred for this purpose. Thus, nowadays often only 60 to 80% of the fuel is used in the form of alternative fuel, while 20 to 40% is still fossil fuel.

[0003] From DE 10 2012 013 877 A1 a process for treating biomass as fuel in a plant for the production of cement clinker is known, in which the biomass is first pre-dried by the exhaust gases of a heat exchanger of the plant and in which carbonization of the biomass takes place in a reactor.

[0004] A plant for the production of cement clinker is known from WO 2012 / 056 178 A2. In addition to alternative fuels, a proportion of high-grade fuels is used in the process, with coal and petroleum coke being specified as high-grade fuels.

[0005] A process and a plant for the production of cement clinker are known from WO 2008 / 120 109 A1.

[0006] A method and a device for clinker production are known from WO 2008 / 120 109 A1.

[0007] A device for clinker production is known from WO 2012 / 056 178 A1.

[0008] The object of the invention is to provide a device that enables the exclusive use of alternative fuels and thus makes it possible to completely dispense with fossil fuels.

[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 system for carrying out the process according to the invention serves for the thermal treatment of a mineral substance. An example of such thermal treatment can be, for instance, and in particular, the thermal treatment of clay and clay-like materials to produce pozzolanic substances. The system includes a device for thermal treatment. This device can be referred to as an activator. For instance, and in particular, it can be designed as a fluidized-flow calciner. A preheater is usually arranged upstream of the device for thermal treatment. The preheater often consists of a cascade of co-current heat exchangers with a separation cyclone. Furthermore, a reduction device for color optimization of the product and, typically, at least one product cooler are connected downstream of the device for thermal treatment to return the heat to the process. The product cooler can also be designed in multiple stages.The system includes a combustion chamber. Fuel is burned in the combustion chamber to provide the thermal energy for the thermal treatment. For this purpose, the combustion chamber is connected to the thermal treatment device to transfer the combustion gases generated within it. The combustion chamber also includes a solids discharge system. Solid residues that are not converted to gaseous products during combustion are discharged via this system. Solids discharge is preferably achieved by dropping the material via a chute and a subsequent discharge device, but can also be carried out directly mechanically, for example, with a screw conveyor or a slide gate. Solids discharge can also be achieved pneumatically or fluidically using a gas stream. The thermal treatment device includes at least one combustion chamber.A combustion zone can be located within the actual thermal treatment, for example, in a fluidized bed calciner. The advantage is that the heat is then generated directly at the point where it is consumed by the thermal treatment of the material. However, the combustion zone can also be arranged in a separate heating device, for example, to supply preheated gas to a device, such as a combustion chamber. Thus, in the context of the invention, a combustion zone is not limited to a structurally separate combustion device but can also be integrated into other devices. The combustion zone is connected to a fuel supply device. Fuel is supplied to the combustion zone via the fuel supply device, thereby maintaining combustion within the combustion zone.The thermal treatment device can also have two or more combustion zones and thus two or more fuel supply devices, particularly at different locations. Fuel is supplied directly to the thermal treatment device via the fuel supply device. The thermal treatment device can, for example, have a reaction zone and a treatment zone. In this case, the fuel is supplied to the reaction zone via the fuel supply device. This allows the temperature in the treatment zone to be kept more constant, since the thermal treatment, especially in the reaction zone, typically extracts energy from the gas stream, thereby cooling it. Furthermore, this allows the temperature inside the thermal treatment device to be controlled more precisely and quickly.Nowadays, alternative fuels are often used in the combustion chamber, which have a fluctuating calorific value (including moisture, particle size, and other influencing factors), resulting in temperature fluctuations. To compensate for these, for example, pulverized coal is introduced directly into the thermal treatment device to specifically counteract the fluctuations and thus precisely control the temperature, in particular to keep it constant.

[0011] According to the invention, the combustion chamber is designed to produce an incompletely combusted solid residue. The aim is to ensure that the fuel supplied to the combustion chamber is only partially combusted. This produces an incompletely combusted solid residue, which can then be burned elsewhere in the system. An advantage of this is that the combustion chamber is particularly well-suited for the combustion of lower-grade fuels such as alternative fuels, which, for example, in the case of biomass, can have a high moisture content. Therefore, these alternative fuels are comparatively demanding in terms of ignition and the duration of combustion required for reliable conversion. The incomplete combustion produces a solid that is both dry and has a high calorific value.This combustible solid can therefore be used within the plant in areas where safe combustion of alternative fuels is not possible and where, for example, pulverized coal has previously been used as fuel. The solid discharge from the combustion chamber is connected to a comminution device. The combustible solid (or high-calorific solid) discharged from the combustion chamber, which contains, in particular, high-calorific and partially pyrolyzed components, is thus comminuted. The comminution device shreds the solid discharged from the combustion chamber. Without prior cooling, the use of a crusher for comminution is preferred. This combustible solid then represents a thermally usable, processed combustible solid that can be used similarly to pulverized coal.Therefore, the comminution device is connected directly or, preferably, indirectly via a storage device to the fuel supply device. This makes it possible to completely eliminate the need for fossil fuels. The high-calorific fuel required for this is thus produced within the process itself. This enables the complete replacement of high-quality, especially primary, fuels such as gas, oil, or coal with lower-quality alternative fuels.

[0012] A crusher or a grinder can be used as a shredding device. Since the partially pyrolyzed material is often very brittle and porous, sufficient shredding can often be achieved in a technically very simple way using a grinder.

[0013] In a further embodiment of the invention, the solids discharge from the combustion chamber is connected to a cooling device. The combustible solid (or solid containing calorific value), which in particular contains components with high calorific value and is partially pyrolyzed, is thus cooled. Cooling prevents unwanted oxidation, for example, with atmospheric oxygen. The cooling device is therefore designed to cool the combustible solid discharged from the combustion chamber. The cooling device is connected to the comminution device. In the comminution device, the combustible solid discharged from the combustion chamber and cooled in the cooling device is comminuted, in particular ground.

[0014] In a further embodiment of the invention, a storage device is arranged between the comminution device and the fuel supply device. The storage device enables the time-controlled addition of the comminuted, in particular ground, combustible solid, and thus precise control, particularly with regard to the temperature in the thermal treatment device. This also allows for targeted responses to fluctuations in the calorific value of the substitute fuel introduced into the combustion chamber. Furthermore, any surplus of comminuted, in particular ground, combustible solid can be easily used elsewhere, for example, by being fed into another system.

[0015] In a further embodiment of the invention, a metering device is arranged between the comminution device and the fuel supply device. This embodiment is advantageous if not only the fuel supply device but also other devices are supplied with the comminutioned combustible solid. This embodiment is particularly preferred if, for example, another device is a power generator that can easily be operated with fluctuating loads. In this case, any excess is fed directly into the power generator, so that the plant itself always has precisely the required amount of comminutioned combustible solid available and no excess is produced, since it is always directly converted in the power generator.

[0016] In a further embodiment of the invention, the cooling device incorporates gas cooling. Cooling with an oxygen-containing gas has the advantage that the heated gas can be easily integrated into other processes, thus allowing the energy to be readily fed back into the process. For example, the cooling device has a connection to the combustion chamber for transferring the preheated oxygen-containing gas. In this example, air, oxygen-enriched air, or oxygen is used as the cooling gas. A gas with a reduced oxygen content, for example, only 5 to 10%, can also be used. This gas can, for instance, originate from the overall process itself. The advantage of the reduced oxygen content is that unwanted oxidation of the combustible solid being cooled can be avoided.

[0017] In an alternative embodiment, a gaseous reducing agent is used to cool the partially pyrolyzed fuel instead of the oxygen-containing gas. This gaseous reducing agent can, for example, be supplied to a reduction device for color optimization.

[0018] In a further embodiment, the system includes at least one reduction device downstream of the thermal treatment device. In the reduction device, for example, iron compounds contained in the product are reduced from Fe III to Fe II by means of a gaseous reducing agent, which results in a color adjustment of the product from red towards black. In this embodiment, the cooling device has a connection to the reduction device for transferring the gaseous reducing agent preheated in the cooling device. In this embodiment, for example, hydrocarbon-containing gases and / or CO or mixtures of these gases, as well as mixtures of these gases, particularly with inert gases such as nitrogen or carbon dioxide, can be used as the cooling gas, which is then used as the gaseous reducing agent in the downstream reduction device.

[0019] In a further embodiment of the invention, the cooling device features water injection. This enables very rapid cooling. Preferably, the steam generated in this process is used in further processes to utilize the energy.

[0020] In a further embodiment of the invention, the cooling device includes a heat exchange medium. The cooling device has a separating element for separating the heat exchange medium from the discharged combustible solid. For example, the heat exchange medium can flow through a pipe jacket, and inside the pipe, the combustible solid discharged from the combustion chamber is conveyed, for example, by a screw conveyor. An advantage of this embodiment is that it can be operated with a significantly reduced air supply, thus preventing oxidation or even combustion. In this case, the energy transferred from the heat exchange medium in the cooling device can be used, for example, to heat a gaseous reducing agent.

[0021] In a further embodiment of the invention, the combustion chamber includes a fuel transport device. The residence time of the fuel in the combustion chamber can be precisely controlled by this transport device. Examples of such transport devices in combustion chambers include, for example, separately movable strip elements, a circulating conveyor belt made of chain elements, or even push elements or screw conveyors. Alternatively, the transport device can also be pneumatically or fluidically operated. For example, a fluidizing gas, preferably flowing along the conveying direction, can be supplied from below.

[0022] In a further embodiment of the invention, the system includes an auxiliary combustion device. The auxiliary combustion device is connected to the combustion chamber for the transfer of hot combustion gases. This can be used, for example, for start-up to bring the combustion chamber up to a starting temperature. Similarly, supplemental firing can also occur during normal operation to ensure, for example, a sufficiently high ignition temperature, such as with moist alternative fuels. The auxiliary combustion device is connected to the shredding device. This connection can be made directly or via a storage device. This feeds the shredded combustible solid to the auxiliary combustion device.

[0023] In a further embodiment of the invention, the system comprises a fluidized bed calciner. The combustion chamber is located in or on the fluidized bed calciner. In particular, the combustion chamber is located in the lower third of the fluidized bed calciner. Two or more fuel feed devices can also be provided to the lower third of the fluidized bed calciner in order to achieve the most uniform heat generation possible in parallel with the thermal reaction, thus maintaining a temperature as constant as possible across the reaction section.

[0024] The inventive method for operating a plant as described above. Only alternative fuels are used as fuel for the plant. The alternative fuel is fed into the combustion chamber. By using the crushed, in particular ground, combustible solid discharged from the combustion chamber as a further fuel, the use of fossil fuels can be eliminated, and only alternative fuels can be used. If the alternative fuels originate from renewable sources, such as biomass including wood, the combustion is CO₂-neutral. Since no or very little CO₂ is released from the clays, the process represents a possibility for further reducing the climate impact in this highly relevant area of ​​the cement industry. An incompletely combusted solid residue is produced from the alternative fuel.This incompletely burned solid residue represents a combustible solid, which generally has a higher calorific value than alternative fuels, but above all, better ignition properties. Furthermore, this combustible solid is easy to make airborne and therefore, unlike alternative fuels, can be easily used in other locations where alternative fuels cannot be burned or cannot be burned safely.

[0025] When a substitute fuel is burned in the combustion chamber, flammable gaseous substances are typically released. These, along with the fuel gases heated in the combustion chamber, are fed to the thermal treatment device and can be combusted further there. This is advantageous because heat is needed in the area where the fuel gases are fed, for example, for the thermal conversion; otherwise, the fuel gases would not be directed there.

[0026] In a further embodiment of the invention, the combustion of the substitute fuel is carried out such that the incompletely combusted solid residue, as a combustible solid, has a carbon content of at least 30 wt.%, preferably at least 50 wt.%, and particularly preferably at least 70 wt.%. This creates a combustible solid whose properties allow for a similarly wide range of applications as coal dust does today. In particular, this makes combustion in a flue gas stream possible.

[0027] In a further embodiment of the invention, only incompletely burned solid residue is supplied to the combustion chamber as fuel. This completely eliminates the need for valuable primary fuels such as gas, oil, or coal.

[0028] In a further embodiment of the invention, the combustible solid is measured, for example by means of NIR spectroscopy. The combustion in the combustion chamber is controlled according to the measured data in order to obtain a combustible solid with predetermined properties, for example a predetermined carbon content.

[0029] In a further embodiment of the invention, combustion in the combustion chamber is carried out under oxidizing conditions. This means that the combustion gases leaving the combustion chamber still contain residual oxygen. The aim is stoichiometric or slightly superstoichiometric combustion of the fuel used, whereby a portion of the substitute fuel is pyrolyzed, i.e., practically carbonized. This carbon fraction of the combustible solid can then be reused as fuel in the process after grinding.

[0030] In a further embodiment of the invention, clay, artificial or natural rocks, for example and in particular silicon dioxide, alumina, limestone, iron oxide and alkaline substances, aluminum- and / or silicon-containing residues from metal processing, ceramics and / or paper industries are used as the mineral material. Clay is particularly preferred as the mineral material.

[0031] In a further embodiment of the invention, biomass, preferably wood or a wood product, is used as a substitute fuel.

[0032] In a further embodiment of the invention, the discharged combustible solid is ground to a particle size suitable for airborne transmission. Particles smaller than 500 µm, preferably smaller than 250 µm, and most preferably smaller than 100 µm, are considered suitable for airborne transmission within the meaning of the invention. This allows for simple subsequent integration into the process. At the same time, it enables the continued use of these particles in existing systems, for example, in combustion devices or conveying units for coal dust.

[0033] In a further embodiment of the invention, the ground and cooled combustible solid is temporarily stored. This temporary storage allows for targeted control of the process, particularly in order to precisely control the temperature.

[0034] Additionally, this can help to compensate for fluctuations in the calorific value of the alternative fuel. Furthermore, an auxiliary combustion unit can be operated with the combustible solid stored in the intermediate storage area. This allows, for example, the auxiliary combustion unit to establish a sufficiently high temperature for combustion of the alternative fuel before or at the inlet of the combustion chamber. Intermediate storage also makes it possible to distribute the material flows differently between the various uses, thus enabling a more flexible response. Moreover, an existing supply of combustible solid stored in intermediate storage can be used for subsequent start-up operations.

[0035] In a further embodiment of the invention, the gas supply to the combustion chamber is regulated such that the oxygen content in the combustion gases is between 1% and 5%. The percentage is based on the volume fraction in the dry gas under standard conditions. This enables clean combustion. Furthermore, combustion is also possible in the downstream thermal treatment device, as sufficient oxygen remains available.

[0036] In a further embodiment of the invention, the proportion of combustible solid discharged is adjusted via the residence time of the fuel in the combustion chamber. Since the substitute fuel does not have a constant and clearly predictable composition, moisture content, particle size, and thus combustion behavior, targeted control of the residence time is advantageous. Controlling this via the proportion of combustible solid discharged, for example, via the mass of the discharged combustible solid, offers a simple and targeted method without requiring precise knowledge of the combustion processes inside the combustion chamber itself. Furthermore, this ensures that a sufficient supply of shredded, particularly ground, combustible solid is always available as additional fuel. This decoupling offers the advantage of consistent operation of the thermal treatment system.

[0037] In a further embodiment of the invention, the gas supply to the combustion chamber has an oxygen content of at least 50%, preferably at least 90%, and particularly preferably at least 95%. As a result, the exhaust air at the end of the entire process consists mainly of water and carbon dioxide. This makes the carbon dioxide relatively easy to separate and allows it to be reused or stored to further minimize CO₂ emissions and thus, if necessary, to easily offset other CO₂ emissions from other processes.

[0038] In a further embodiment of the invention, the crushed, in particular ground, combustible solid is supplied with a gas stream for combustion to the device for thermal treatment.

[0039] In a further embodiment of the invention, the combustible solid, in particular ground, is fed into the combustion chamber. This is done particularly in an auxiliary combustion device, which ensures a sufficient ignition temperature for the substitute fuel. The auxiliary combustion device can also be located upstream of the combustion chamber, so that only hot gases from the auxiliary combustion device are introduced into the combustion chamber.

[0040] In a further embodiment of the invention, the residence time of the fuel in the combustion chamber is controlled in such a way that the temperature of the gases leaving the combustion chamber is regulated, and thus the temperature in the thermal treatment device. For example, the residence time is increased to achieve more complete combustion and thus a higher temperature, or the residence time is shortened to achieve less complete combustion and thus a lower temperature. As a side effect, the amount of combustible solid discharged is also changed.

[0041] In a further embodiment of the invention, the combustible solid is fed to the reduction device. Here, the combustible solid can be used to generate a reducing atmosphere.

[0042] The system for carrying out the method according to the invention is explained in more detail below with reference to an exemplary embodiment shown in the drawings. Fig. 1 first exemplary embodiment Fig. 2 second exemplary embodiment Fig. 3 third exemplary embodiment

[0043] In Fig. 1 A first exemplary embodiment of the apparatus according to the invention is shown, with reference to which the method according to the invention will be explained. The material stream of the mineral substance to be thermally treated, for example and in particular a clay, is introduced into the preheater 11, preheated, and then enters the thermal treatment device 12, for example a fluidized bed calciner. There, the thermal treatment, in particular the activation of the clay, takes place at high temperatures, for example between 700°C and 1200°C. Subsequently, the material stream enters a reduction device 13, where, in a reducing atmosphere containing, for example, hydrocarbons, hydrogen, and / or carbon monoxide, color-imparting components, for example Fe III, are converted to less colored substances, for example Fe II.The finished product, which is used, for example, in the cement industry, is then cooled in a product cooler 14.

[0044] To provide the energy required for the thermal treatment device 12, the system includes a combustion chamber 20. A substitute fuel, for example biomass, is fed into the combustion chamber 20 and partially combusted there. However, a portion of the substitute fuel also undergoes pyrolysis only within the combustion chamber 20. The ratio between combustion and pyrolysis can be adjusted, in particular, by the amount of substitute fuel fed into the combustion chamber 20 and / or by the transport or residence time of the substitute fuel through the combustion chamber 20. As a first approximation, the shorter the residence time in the combustion chamber 20, the higher the proportion of pyrolyzed material. The hot combustion gases are directed from the combustion chamber 20 into the thermal treatment device 20.For this purpose, the combustion chamber 20 and the thermal treatment device 12 can be directly adjacent to one another; in particular, the combustion chamber 20 is attached laterally directly to the thermal treatment device 12. The material pyrolyzed in the combustion chamber 12 is discharged from the combustion chamber 20 and transferred to a cooling device 30. For example, the cooling device 30 can have a water injection system. This cools the pyrolyzed material very rapidly, thus quickly preventing further unwanted oxidation. The cooled material is transferred from the product cooler 30 to the mill 40 and ground there. The ground material is stored in the storage device 50. From the storage device 50, a portion of the pyrolyzed, cooled, and ground material is fed into the thermal treatment device 12 via a fuel supply device.This allows the temperature in the thermal treatment device 12 to be controlled precisely and easily, even with fluctuating calorific value of the substitute fuel. Additionally, a second fuel supply device can be provided to, for example, supply fuel at two locations within the thermal treatment device 12, thereby maintaining a more constant temperature along its length or, if necessary, increasing it. Likewise, a third fuel supply device or even further fuel supply devices can be provided.

[0045] From the storage device 50, another part of the pyrolyzed and ground material is brought into an auxiliary combustion device 60, which ensures sufficiently high temperatures at the inlet of the combustion chamber 20 and thus enables good combustion of the substitute fuel.

[0046] Fig. 2 Figure 1 shows a second exemplary embodiment, which, in addition to the gas flows shown in the first exemplary embodiment, has the additional gas flows depicted. The gas used in the product cooler 14 to cool the product is fed from the product cooler to the combustion chamber 20. This returns the heat to the process. The gas can be, for example, air. However, enriched oxygen, for example with at least 50%, preferably at least 90% oxygen, can also be used. A different gas is required for the reduction device 13, since reducing components of the gas are needed here, not oxygen.Therefore, this reducing gas, which is for example synthesis gas and thus has in particular hydrogen and carbon monoxide as reducing components, can be used in the cooling device 30 to cool the combustible solid discharged from the fuel clamp 20 and thus preheated before being supplied to the reduction device 13.

[0047] In Fig. 3 A third exemplary embodiment of the system according to the invention is shown. This embodiment does not have a reduction device 13, so that the gas flow and the material flow from the preheater 11 are guided in counterflow through the thermal treatment device 12 and the product cooler 14. The gas supplied to the combustion chamber 20 is preheated in the cooling device 30. Reference sign

[0048] 11 Preheater 12 Thermal treatment device 13 Reduction device 14 Product cooler 20 Combustion chamber 30 Cooling device 40 Mill 50 Storage device 60 Auxiliary combustion device

Claims

1. Method for operating a plant, wherein the plant is used for the thermal treatment of a mineral substance, wherein the plant comprises a thermal treatment device (12), wherein the plant comprises a combustion chamber (20), wherein the combustion chamber (20) is connected to the thermal treatment device (12) for the transfer of combustion gases, wherein the combustion chamber (20) has a solid discharge, wherein the thermal treatment device (12) has a combustion area, wherein the combustion area is connected to a fuel supply device, wherein the combustion chamber (20) is designed to produce a not completely burnt solid residue, wherein the incomplete combustion produces a solid that is dry on the one hand and has a high calorific value on the other, wherein the solid discharge of the combustion chamber (20) is connected to a comminution device, wherein the comminution device is connected to the fuel supply device, characterised in that only substitute fuels are used as fuel for the plant and the substitute fuel is fed to the combustion chamber (20), whereby a not completely burned solid residue is produced from the substitute fuel, whereby the incomplete combustion produces a solid material which is dry on the one hand and has a high calorific value on the other.

2. Method according to claim 1, characterised in that the combustion of the substitute fuel is controlled in such a way that the incompletely burned solid residue, as a combustible solid, has a carbon content of at least 30% by weight, preferably at least 50% by weight, and particularly preferably at least 70% by weight.

3. Method according to one of claims 1 to 2, characterised in that only incompletely burned solid residue is fed to the combustion area as fuel.

4. Method according to one of the preceding claims, characterised in that combustion in the combustion chamber (20) is carried out under oxidising conditions.

5. Method according to one of the preceding claims, characterised in that the discharged combustible solid is comminuted to an airborne particle size.

6. Method according to one of the preceding claims, characterised in that the gas supply to the combustion chamber (20) is regulated in such a way that the oxygen content in the combustion gases is between 1% and 5%.

7. Method according to one of the preceding claims, characterised in that the proportion of the discharged combustible solid is adjusted via the feed quantity and dwell time of the fuel in the combustion chamber (20).

8. Method according to one of the preceding claims, characterised in that the comminuted combustible solid material is fed to the thermal treatment device (12) with a gas stream for combustion.

9. Method according to one of the preceding claims, characterised in that the comminuted combustible solid is fed to the combustion chamber (20).

10. Method according to one of claims 1 to 8, characterised in that the comminuted combustible solid is fed to the reduction device (13).

11. Method according to one of the preceding claims, characterised in that the solid discharge of the combustion chamber (20) is connected to a cooling device (30), wherein the cooling device (30) is designed to cool the combustible solid discharged from the combustion chamber (20), wherein the cooling device (30) is connected to a comminution device.

12. Method according to one of the preceding claims, characterised in that the cooling device (30) comprises gas cooling.

13. Method according to claim 12, characterised in that the cooling device (30) has a connection to the combustion chamber (20) for transferring the preheated air.

14. Method according to claim 12, characterised in that the plant has a reduction device (13) connected downstream of the thermal treatment device (12), wherein the cooling device (30) has a connection to the reduction device (13) for transferring the preheated gas.

15. Method according to one of the preceding claims, characterised in that the cooling device (30) has a water injection.

16. Method according to one of the preceding claims, characterised in that the cooling device (30) comprises a heat exchange medium, wherein the cooling device (30) comprises a separating element for separating the heat exchange medium and the discharged combustible solid.

17. Method according to one of the preceding claims, characterised in that the plant comprises a fluidised bed calciner, wherein the combustion zone is arranged in or on the fluidised bed calciner.