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

Abstract

The invention relates to a facility for thermally treating a mineral substance, wherein the facility has a device for a thermal treatment 12, and the facility has a combustion chamber 20. The combustion chamber 20 is connected to the device for a thermal treatment 12 in order to transfer the combustion gases, the combustion chamber 20 has a solids discharge, and the device for a thermal treatment 12 has a fuel supply device. The invention is characterized in that the solids discharge of the combustion chamber 20 is connected to a comminuting device, and the comminuting device is connected to the fuel supply device.

Description

[0001] Exclusive use of substitute fuels for the thermal treatment of mineral substances, in particular clays

[0002] The invention relates to 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, aluminum 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 the production of cement, whereby completely alternative fuels can be used and no additional fossil fuels are necessary.

[0003] The use of substitute fuels to reduce CCH emissions is well known and now widespread in many areas. However, substitute fuels often have fluctuating properties, particularly their calorific values. Furthermore, some fuels have a high moisture content, meaning they are often not self-ignitable. Furthermore, the varying moisture content leads to different energy requirements for the evaporation of the water, which also affects the temperature. Furthermore, the particle size of substitute fuels also varies. Smaller particles burn faster and can more easily burn completely, while larger particles burn more slowly and may not burn completely. Therefore, the particle size also influences the temperature.Therefore, plants fired with refuse-derived fuels often use auxiliary burners for rapidly adjustable fossil fuels to compensate for fluctuations in calorific value (here and in the following, calorific value refers to all of the aforementioned factors influencing temperature together) and the resulting temperature fluctuations. Furthermore, for 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 thermal treatment site. The input of fossil fuels is easier to meter and disperse, resulting in more homogeneous distribution and better interaction with the materials being treated. Gas or coal dust are preferred for this purpose. Thus, today often only 60 to 80% of the fuel is used in the form of refuse-derived fuel, while 20 to 40% is still fossil fuels.

[0004] 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 wherein a carbonization of the biomass takes place in a reactor.

[0005] WO 2012 / 056178 A2 describes a plant for the production of cement clinker. In addition to refuse-derived fuels, a portion of refined fuels is used in the process, with coal and petroleum coke being listed as refined fuels.

[0006] WO 2008 / 120 109 A1 discloses a process and a plant for producing cement clinker.

[0007] The object of the invention is to provide a device that enables the exclusive use of substitute fuels and thus makes it possible to completely dispense with fossil fuels.

[0008] This object is achieved by the system having the features specified in claim 1 and by the method having the features specified in claim 9. Advantageous further developments emerge from the subclaims, the following description, and the drawings.

[0009] The plant according to the invention serves for the thermal treatment of a mineral substance. An example of such a thermal treatment can be, for example and in particular, the thermal treatment of clay and clay-like materials to produce pozzolanic substances. The plant comprises a thermal treatment device. This can be referred to as an activator. For example and in particular, this can be designed as an entrained-flow calciner. Typically, a preheater is arranged upstream of the thermal treatment device. The preheater often consists of a cascade of cocurrent heat exchangers with a separation cyclone. Furthermore, optionally a reduction device for color optimization of the product and usually at least one product cooler for returning the heat to the process are arranged downstream of the thermal treatment device. The product cooler can also be designed in several stages. The plant comprises a combustion chamber.A 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 in the combustion chamber. The combustion chamber also has a solids discharge. Solid residues that are not converted into gaseous products during combustion are discharged via the solids discharge. The solids are preferably discharged by being thrown via a chute and a subsequent discharge device, but can also be done directly mechanically, for example with a screw or a slide. The solids can also be discharged pneumatically or by fluidizing with the help of a gas stream. The thermal treatment device has at least one combustion zone. A combustion zone can be located within the actual thermal treatment, for example in an entrained flow calciner.The advantage is that the heat is then generated directly at the location where it is also consumed by the thermal treatment of the material. The combustion zone can, however, also be arranged in a separate heating device, for example in order to supply preheated gas to a device, for example the combustion chamber. In the sense of the invention, the combustion zone is therefore not only 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, thus maintaining combustion in the combustion zone. The device for thermal treatment can also have two or more combustion zones and thus two or more fuel supply devices, in particular at different locations.A fuel is fed directly to the thermal treatment device via the fuel feed device. The thermal treatment device can, for example, have a reaction zone and a treatment zone. In this case, the fuel is fed into the reaction zone through the fuel feed device. This allows the temperature in the treatment zone to be kept more constant, since thermal treatment, especially in the reaction zone, usually extracts energy from the gas stream, thereby cooling it. It also allows the temperature inside the thermal treatment device to be controlled more precisely and quickly. Nowadays, substitute fuels are often used in the combustion chamber; these have a fluctuating calorific value (including moisture content, particle size, and other influencing factors), which leads to temperature fluctuations.In order to compensate for these, for example, coal dust is introduced directly into the thermal treatment device in order to specifically compensate for the fluctuations and thus control the temperature in a targeted manner, in particular to keep it constant.

[0010] According to the invention, the combustion chamber is designed to produce an incompletely burnt solid residue. The aim is for the fuel fed to the combustion chamber to be only partially burnt. This creates an incompletely burnt solid residue, which in turn can be combusted as a combustible solid elsewhere in the plant. The advantage of this is that low-quality fuels such as substitute fuels, which in the case of biomass, for example, can have a high moisture content, can be easily converted in the combustion chamber. These substitute fuels are therefore comparatively demanding in terms of their ignitability and the duration of combustion required for safe conversion. The only 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 locations where the safe combustion of alternative fuels is not possible and where, for example, coal dust has previously been used as fuel. The solids discharge from the combustion chamber is connected to a comminution device. The combustible solid (or solid containing calorific value) discharged from the combustion chamber, which in particular contains high-calorific and partially pyrolyzed components, is thus crushed. The solid discharged from the combustion chamber is crushed in the comminution device. Without prior cooling, the use of a crusher for comminution is preferred. This combustible solid, in turn, represents a thermally usable, processed combustible solid that can be used in a similar way to coal dust.Therefore, the shredding device is connected directly or, preferably, indirectly via a storage device to the fuel supply device. This makes it possible to completely eliminate fossil fuels. The high-calorie fuel required for this is thus produced in 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.

[0011] A grinder or crusher can be used as the comminution device. Since the partially pyrolyzed material is often very brittle and porous, sufficient comminution can often be achieved with a crusher in a technically very simple manner.

[0012] In a further embodiment of the invention, the solids discharge from the combustion chamber is connected to a cooling device. The combustible solid (or calorific solid) discharged from the combustion chamber, which in particular contains calorific and partially pyrolyzed components, is thus cooled. Cooling prevents unwanted oxidation, for example, with the oxygen in the air. The cooling device is thus 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.

[0013] 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 comminuted, in particular ground, combustible solid to be added at a specific time and thus enables targeted control, particularly with regard to the temperature in the thermal treatment device. This also makes it possible to react specifically to fluctuations in the calorific value of the substitute fuel introduced into the combustion chamber. Furthermore, if there is a surplus of comminuted, in particular ground, combustible solid, this can also be easily used for other purposes, for example, by feeding it to another system. 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 when not only the fuel supply device but also other devices are supplied with the shredded combustible solid. This embodiment is particularly preferred when, for example, another device is a power generation unit, which can easily be operated with fluctuating loads. In this case, any surplus is fed directly into the power generation unit, so that the plant always has exactly the required amount of shredded, combustible solid available, and no surplus is produced, since this is always converted directly in the power generation unit.

[0014] In a further embodiment of the invention, the cooling device comprises a gas cooling system. Cooling with an oxygen-containing gas has the advantage that the gas heated there can be easily integrated into other processes and thus the energy can easily be 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. Likewise, a gas with a reduced oxygen content, for example only 5 to 10%, can be used. This gas can, for example, originate from the overall process itself. The advantage of the reduced oxygen content is that unwanted oxidation of the combustible solid to be cooled can be avoided.

[0015] In an alternative embodiment, a gaseous reducing agent is used instead of the oxygen-containing gas for cooling the partially pyrolyzed fuel. This gaseous reducing agent can, for example, be fed to a reduction device for color optimization.

[0016] In a further embodiment, the plant comprises at least one reduction device downstream of the thermal treatment device. In the reduction device, iron compounds contained in the product, for example, are reduced to Fe 111to Fe" by means of a gaseous reducing agent, which causes a color adjustment from red towards black of the product. 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, the cooling gas used can be, for example, hydrocarbon-containing, hydrogen-containing gases and / or CO or mixtures of these gases as well as mixtures of these gases, in particular with inert gases such as nitrogen or carbon dioxide, which are used as gaseous reducing agent in the downstream reduction device.

[0017] In a further embodiment of the invention, the cooling device has a water injection system. This allows for very rapid cooling. The steam generated is preferably used in further processes to utilize the energy.

[0018] In a further embodiment of the invention, the cooling device comprises a heat exchange medium. The cooling device has a separating element for separating the heat exchange medium and the discharged combustible solid. For example, the heat exchange medium can flow through a tube jacket, and the combustible solid discharged from the combustion chamber is conveyed inside the tube, for example by means of a screw. The advantage of this embodiment is that this can occur with a significant reduction in air access, 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.

[0019] In a further embodiment of the invention, the combustion chamber has a transport device for the fuel. A transport device allows the residence time of the fuel in the combustion chamber to be specifically adjusted. Examples of such transport devices in combustion chambers include separately movable strip elements, a circulating conveyor belt made of chain elements, or pusher elements or screw conveyors. Alternatively, the transport devices can also be operated pneumatically or by fluidizing. For example, a fluidizing gas can be supplied from below, preferably with a flow direction along the conveying direction.

[0020] In a further embodiment of the invention, the plant comprises an auxiliary combustion device. The auxiliary combustion device is connected to the combustion chamber for transferring hot combustion gases. This can be used, for example, during start-up to bring the combustion chamber to a starting temperature. Similarly, additional firing can also be carried out during normal operation, for example, to ensure a sufficiently high ignition temperature, for example, with moist refuse-derived fuels. The auxiliary combustion device is connected to the comminution device. This can be done directly or via a storage device. This feeds the crushed combustible solid to the auxiliary combustion device.

[0021] In a further embodiment of the invention, the plant comprises an entrained-flow calciner. The combustion zone is arranged in or on the entrained-flow calciner. In particular, the combustion zone is located in the lower third of the entrained-flow calciner. Two or more fuel supply devices can also be provided to the lower third of the entrained-flow calciner in order to achieve the most uniform heat generation possible, parallel to the thermal conversion, as a heat sink, and thus to achieve the most constant temperature possible across the reaction zone.

[0022] In a further aspect, the invention relates to a method for operating a plant according to the invention. Only substitute fuels are used as fuel for the plant. The substitute fuel is fed to the combustion chamber. By using the crushed, in particular ground, combustible solid discharged from the combustion chamber as an additional fuel, the use of fossil fuels can be dispensed with and exclusively substitute fuels can be used. If the substitute fuels come from renewable sources, for example biomass including wood, the combustion is CO2-neutral. Since no or very little CO2 is released from the clays, the process represents an opportunity to further reduce the climate impact in this highly relevant sector of the cement industry. A partially burnt solid residue is produced from the substitute fuel.This incompletely burned solid residue represents a combustible solid, which usually has a higher calorific value than the substitute fuel and, above all, better ignitability. Furthermore, this combustible solid is easily made airworthy and, unlike substitute fuels, can therefore easily be used in other locations where substitute fuels cannot be burned or cannot be safely burned.

[0023] When a substitute fuel is burned in the combustion chamber, combustible gases are typically released. These are fed to the thermal treatment device along with the fuel gases heated in the combustion chamber, where they can continue to burn. This is advantageous because the area into which the fuel gases are fed requires heat, such as for thermal conversion; otherwise, the fuel gases would not be fed there.

[0024] In a further embodiment of the invention, the combustion of the substitute fuel is conducted in such a way that the incompletely burnt solid residue, as a combustible solid, has a carbon content of at least 30 wt.%, preferably at least 50 wt.%, particularly preferably at least 70 wt.%. This creates a combustible solid whose properties enable a similarly broad application as coal dust today. This, in particular, enables combustion in entrained stream.

[0025] In a further embodiment of the invention, only incompletely burnt solid residue is fed into the combustion chamber as fuel. Thus, valuable primary fuels such as gas, oil, or coal are completely eliminated.

[0026] In a further embodiment of the invention, the combustible solid is measured, for example, using NIR spectroscopy. 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. 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 a residual oxygen content. The goal is stoichiometric or slightly superstoichiometric combustion of the fuel used, with a portion of the substitute fuel pyrolyzing, i.e., essentially carbonizing. This carbon content of the combustible solid can then be excellently reused as fuel in the process after grinding.

[0027] In a further embodiment of the invention, clay, artificial or natural rocks, for example and in particular made of silicon dioxide, alumina, limestone, iron oxide, and alkaline substances, as well as aluminum- and / or silicon-containing residues from metal processing, the ceramics, and / or the paper industry, are used as the mineral substance. Clay is particularly preferred as the mineral substance.

[0028] In a further embodiment of the invention, biomass, preferably wood or a wood product, is used as substitute fuel.

[0029] In a further embodiment of the invention, the discharged combustible solid is ground to a particle size suitable for airborne transport. For the purposes of the invention, particles smaller than 500 pm, preferably smaller than 250 pm, and most preferably smaller than 100 pm are considered airborne. This makes it easy to incorporate them into the process later. At the same time, it allows for the continued use of these solids in existing plants, for example, in appropriate combustion devices or conveying units, for example, for coal dust.

[0030] In a further embodiment of the invention, the ground and cooled combustible solid is stored temporarily. This interim storage allows for targeted control of the process, particularly to precisely control the temperature. This can also help compensate for fluctuations in the calorific value of the substitute fuel. In addition, an auxiliary combustion device can be operated from the interim storage using the combustible solid, for example, in order to set a sufficiently high temperature for combustion of the substitute fuel before or at the inlet of the combustion chamber. Intermediate storage also makes it possible to divide the material flows differently between the different uses, thus allowing for more flexible responses. Furthermore, an existing, temporarily stored combustible solid can be used for subsequent start-up processes.

[0031] 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 and under standard conditions. This enables clean combustion. Furthermore, further combustion in the downstream thermal treatment device is also possible, since sufficient oxygen is still available.

[0032] In a further embodiment of the invention, the proportion of discharged combustible solid 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, and size, and thus combustion behavior, targeted control of the residence time is advantageous. Controlling this via the proportion of discharged combustible solid, for example, via the mass of the discharged combustible solid, represents a simple and targeted option without requiring precise knowledge of the combustion processes inside the combustion chamber itself. Furthermore, this ensures that there is always a sufficient amount of comminuted, especially ground, combustible solid available as additional fuel. This decoupling offers the advantage of consistent operation of the thermal treatment facility.

[0033] 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%, particularly preferably at least 95%. As a result, the exhaust air at the end of the entire process mainly comprises water and carbon dioxide. As a result, the carbon dioxide is relatively easy to separate and can be reused or stored to further minimize CO2 emissions and thus easily compensate for other CO2 emissions from other processes. In a further embodiment of the invention, the comminuted, in particular ground, combustible solid is fed to the thermal treatment device with a gas stream for combustion.

[0034] In a further embodiment of the invention, the comminuted, particularly ground, combustible solid is fed into the combustion chamber. This occurs, in particular, in an auxiliary combustion device, which ensures that a sufficient ignition temperature is generated 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.

[0035] 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 byproduct, the amount of combustible solid discharged is changed.

[0036] In a further embodiment of the invention, the comminuted combustible solid is fed to the reduction device. Here, the comminuted combustible solid can be used to generate a reducing atmosphere.

[0037] The system according to the invention is explained in more detail below using an embodiment shown in the drawings.

[0038] Fig. 1 first exemplary embodiment

[0039] Fig. 2 second exemplary embodiment

[0040] Fig. 3 Third exemplary embodiment Fig. 1 shows a first exemplary embodiment of the plant according to the invention, with the aid of which the method according to the invention will be explained. The material flow of the mineral substance to be thermally treated, for example and in particular a clay, is introduced into the preheater 11, preheated and, in a preheated state, reaches the device for thermal treatment 12. For example, an entrained-flow 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. The material flow then reaches a reduction device 13, where, in a reducing atmosphere containing, for example, hydrocarbons, hydrogen and / or carbon monoxide, color-imparting components, for example Fe 111, to less colored substances, for example Fe". The finished product, which is used, for example, in the cement industry, is then cooled in a product cooler 14.

[0041] In order to provide the energy required for the thermal treatment device 12, the system has a combustion chamber 20. A substitute fuel, for example biomass, is fed to the combustion chamber 20 and partially combusted there. However, a portion of the substitute fuel pyrolyzes only in the combustion chamber 20. The proportion of combustion and pyrolysis can be adjusted, in particular, via the feed quantity of substitute fuel and / or the transport or residence time of the substitute fuel through the combustion chamber 20. The shorter the residence time in the combustion chamber 20, the higher the proportion of pyrolyzed material will be, to a first approximation. The hot combustion gases are fed directly 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. This cools the pyrolyzed material very quickly, thus quickly preventing unwanted further 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 60. From the storage device 60, a portion of the pyrolyzed, cooled, and ground material is introduced into the thermal treatment device 12 via a fuel supply device.This allows the temperature in the thermal treatment device 12 to be controlled in a targeted and simple manner, even with a fluctuating calorific value of the substitute fuel. Additionally, a second fuel supply device can also be provided, for example, to supply fuel to two locations in the thermal treatment device 12 and thus keep the temperature more constant over the length of the thermal treatment device 12 or, if necessary, increase it. Likewise, a third fuel supply device or even further fuel supply devices can be provided.

[0042] Another part of the pyrolyzed and ground material is brought from the storage device 60 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.

[0043] Fig. 2 shows a second exemplary embodiment, which, in addition to the first exemplary embodiment, has additional gas flows shown. The gas used in the product cooler 14 to cool the product is guided from the product cooler to the combustion chamber 20. This returns the heat to the process. The gas is, for example, air. However, the gas can also be enriched oxygen, for example with at least 50%, preferably at least 90% oxygen. However, a different gas is required for the reduction device 13, since not oxygen but reducing components of the gas are required here.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 combustion clamp 20 and thus fed to the reduction device 13 in a preheated state.

[0044] Fig. 3 shows a third exemplary embodiment of the plant according to the invention. This does not have a reduction device 13, so that the gas flow and the material flow from the preheater 11 are conducted in countercurrent 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 numeral

[0045] 11 preheaters

[0046] 12 Device for thermal treatment

[0047] 13 Reduction device

[0048] 14 Product cooler 20 Combustion chamber

[0049] 30 Cooling device

[0050] 40 Mill

[0051] 50 storage device

[0052] 60 auxiliary combustion device

Claims

Patent claims 1. Plant for the thermal treatment of a mineral substance, the plant comprising a device for thermal treatment (12), the plant comprising a combustion chamber (20), the combustion chamber (20) being connected to the device for thermal treatment (12) for transferring the combustion gases, the combustion chamber (20) having a solids discharge, the device for thermal treatment (12) having a combustion region, the combustion region being connected to a fuel supply device, characterized in that the combustion chamber (20) is designed to produce an incompletely burnt-out solid residue, the solids discharge of the combustion chamber (20) being connected to a comminution device, the comminution device being connected to the fuel supply device.

2. Plant according to claim 1, characterized in that the solids discharge of the combustion chamber (20) is connected to a cooling device (30), wherein the cooling device (30) is designed to cool the combustible solids discharged from the combustion chamber (20), wherein the cooling device (30) is connected to a comminution device.

3. Plant according to one of claims 1 to 2, characterized in that the cooling device (30) has a gas cooling.

4. Plant according to claim 3, characterized in that the cooling device (30) has a connection to the combustion chamber (20) for transferring the preheated air.

5. Plant according to claim 3, characterized in that the plant has a reduction device (13) connected downstream of the device for thermal treatment (12), wherein the cooling device (30) has a connection to the reduction device (13) for transferring the preheated gas.

6. Plant according to one of claims 1 to 2, characterized in that the cooling device (30) has a water injection.

7. Plant according to one of claims 1 to 2, characterized in that the cooling device (30) has a heat exchange medium, wherein the cooling device (30) has a separating element for separating the heat exchange medium and the discharged combustible solid.

8. Plant according to one of the preceding claims, characterized in that the plant comprises an entrained-flow calciner, wherein the combustion region is arranged in or on the entrained-flow calciner.

9. A method for operating a plant according to one of the preceding claims, characterized in that only substitute fuels are used as fuel for the plant and wherein the substitute fuel is fed to the combustion chamber (20), wherein an incompletely burnt solid residue is produced from the substitute fuel.

10. A method according to claim 9, characterized in that the combustion of the substitute fuel is carried out in such a way that the incompletely burnt solid residue as a combustible solid has a carbon content of at least 30 wt.%, preferably of at least 50 wt.%, particularly preferably of at least 70 wt.%, carbon.

11. Method according to one of claims 9 to 10, characterized in that only incompletely burnt solid residue is supplied to the combustion area as fuel.

12. Method according to one of claims 9 to 11, characterized in that the combustion in the combustion chamber (20) is carried out under oxidizing conditions.

13. A method according to any one of claims 9 to 12, characterized in that the discharged combustible solid is comminuted to a particle size suitable for airborne use.

14. Method according to one of claims 9 to 13, characterized in that the gas supply to the combustion chamber (20) is regulated such that the oxygen content in the combustion gases is between 1% and 5%.

15. Method according to one of claims 9 to 14, characterized in that the proportion of the discharged combustible solid is adjusted via the feed quantity and residence time of the fuel in the combustion chamber (20).

16. Method according to one of claims 9 to 15, characterized in that the comminuted combustible solid is fed to the thermal treatment device (12) with a gas stream for combustion.

17. Method according to one of claims 9 to 16, characterized in that the comminuted combustible solid is fed to the combustion chamber (20).

18. Method according to one of claims 9 to 16, characterized in that the comminuted combustible solid is fed to the reduction device (13).