Method for utilising vapours and vapour utilisation system

Abstract

The invention relates to a method for utilising vapours (B) which are obtained during the drying of a solid material (KS), preferably a sludge (KS), wherein the vapours (B) are introduced into a flue gas (R) which is obtained during combustion of a fuel (TS) in a combustion system (4, 8), and wherein the vapours (B) to be introduced into the flue gas (R) are heated to a vapour introduction temperature (BT4) of more than 350 °C. The invention further relates to a vapour utilisation system (9) for utilising vapours (B) which are produced during the drying of a solid material (KS), and to a utilisation plant (100), preferably a sludge utilisation plant (100), having such a vapour utilisation system (9).

Description

[0001] The invention relates to a method for utilizing vapors, wherein the vapors are introduced into a flue gas obtained during the combustion of a fuel in a combustion system. Furthermore, the invention relates to a vapor utilization system and a utilization plant.

[0002] Vapours are gases and / or air saturated with water vapor that are produced during the drying of solids. For example, vapours are produced during the drying of sewage sludge or industrial sludge.

[0003] The utilization or disposal of vapors is often complex and costly. In commercially available processes, vapors are frequently passed through condensers and condensed, whereby the released energy can, in the best case, be used at least partially for a district heating network. The resulting vapor condensate is then usually fed (back) into a wastewater treatment plant or disposed of there. However, plants that utilize vapors in the manner described above must have a wastewater treatment plant and / or a district heating network. Thus, the question of vapor utilization is often a crucial point in the (planned) implementation of a project, especially if the resulting vapor condensate cannot be disposed of / used on-site and must be transported to a recycling facility at great expense.

[0004] One utilization option of the type mentioned above is described, for example, in EP 3 275 845 A1. In the process described there, (ammonia-containing) vapors from sewage sludge drying are introduced or injected both into the fluidized bed and into the flue gas of a fluidized bed incinerator in which the dried sewage sludge is incinerated. The disadvantage of this process is that, at a vapor introduction temperature of preferably 300 °C to 320 °C, the vapors can only be utilized in relatively small quantities / volumes, as otherwise the temperature in the incineration plant would be reduced too far. In order to nevertheless utilize the entire amount of vapor generated, the plant described therein requires a multi-stage system that requires several (at least two) vapor introduction devices into the combustion system, which makes the process more complex.EP 0 883 778 B1 discloses a method and a corresponding device for the utilization of vapors. These vapors arise during the drying of sewage sludge. The vapors are introduced into a flue gas obtained from the combustion of the sewage sludge in a combustion system. The vapors are heated before being introduced into the flue gas.

[0005] It is an object of the present invention to provide an improved process for vapor utilization, as well as a vapor utilization system for the utilization of vapors and a utilization plant, in particular a sewage sludge utilization plant, with which the above-mentioned disadvantages are avoided.

[0006] This object is achieved by a method for utilizing vapors according to patent claim 1, a device for utilizing vapors according to patent claim 13, and a utilization plant according to patent claim 15.

[0007] In the process according to the invention for utilizing vapors or drying vapors obtained during the drying of a solid, as mentioned at the beginning, the vapors are introduced into a flue gas obtained during the combustion of a fuel in a combustion system.

[0008] As mentioned, the solid is preferably sewage sludge. However, in principle, any solid or sludge that produces vapors during drying is suitable for the process. The term "flue gas" refers here—as usual—to a dispersion of solid and / or liquid suspended particles in a gas obtained from the combustion of a fuel.

[0009] Within the scope of the invention, the fuel is preferably a solid fuel, but liquid and / or gaseous fuels can also be used, in particular a mixture of fuels. For example, coal, natural gas, or preferably other materials suitable for thermal utilization could be used. However, as in the previously mentioned prior art, the dried solid or sludge itself, i.e., a dry sludge obtained from the solid or sludge, in particular sewage sludge, during drying, is most preferably used as the fuel.

[0010] However, unlike the previously described prior art process, according to the invention the vapors are now heated to a vapor introduction temperature of at least 500 °C for introduction into the flue gas, ie the process is carried out in a considerably higher vapor introduction temperature range than in the prior art, as will be explained later.

[0011] For the purposes of this invention, the "vapor introduction temperature" refers to the temperature of the vapors during and / or shortly before their introduction into the flue gas. More detailed explanations of the vapor introduction temperature will follow later.

[0012] Surprisingly, it has been shown that, depending on the specific design and process control, the vapors can be fed into an incineration plant with up to 100% residue-free vapor introduction temperatures of more than 350 °C, without significantly lowering the flue gas temperature. This is of great importance from a process engineering perspective, as the flue gas should typically be heated to a (flue gas) temperature of at least 850 °C (for 2 seconds) to sufficiently reduce the pollutant load in the flue gas. Vapors heated to more than 350 °C can be introduced directly into the flue gas.

[0013] Since the vapor utilization process according to the invention allows for complete utilization of the vapors and no condensates are produced, which would later have to be disposed of at great expense via external treatment plants, sewage treatment plants, or similar disposal methods, the process according to the invention can also be used in plants that neither have a sewage treatment plant nor are connected to a district heating network. The vapor utilization process according to the invention can be used considerably more flexibly than previously known processes.

[0014] In particular, an incineration system such as a sewage sludge mono-incineration plant can operate without wastewater if the resulting vapors are fully utilized. Such wastewater-free operation allows for site-independent operation, meaning that a sewage treatment plant is not necessarily required to be located in the immediate vicinity of the incineration plant in order to operate it.

[0015] Due to the higher vapor introduction temperature, introducing vapor into the flue gas at a suitable point is sufficient. This means that—unlike the aforementioned prior art—no multi-stage system is required to introduce the vapor into the combustion system at different points. The system according to the invention is relatively cost-effective overall.

[0016] A vapor utilization system according to the invention for utilizing vapors obtained during the drying of a solid initially comprises a combustion system for combusting a fuel. Within the scope of the invention, a combustion system comprises a plant for combusting or utilizing a fuel, wherein the combustion system can preferably be a fluidized-bed combustion plant, a grate furnace, or a rotary kiln.

[0017] Furthermore, the vapor utilization system comprises a vapor introduction device for introducing the vapors into the flue gas produced during the combustion of the fuel. Within the scope of the invention, a vapor introduction device can comprise at least one vapor line system and, if appropriate, at least one nozzle connected thereto in the combustion system for introducing the vapors into the flue gas, wherein the vapors are preferably introduced entirely into the flue gas.

[0018] In addition, the vapor utilization system comprises a vapor heating device to heat the vapors to a vapor introduction temperature of at least 500 °C before or before they are introduced into the flue gas.

[0019] Within the scope of the invention, a vapor heating device comprises at least one heat exchanger, wherein the heat exchangers are preferably arranged in multiple stages. More detailed explanations of possible designs of such heat exchangers, as well as possible heating media, will be described in more detail later. The vapor heating device can, for example, be part of the vapor introduction device, in which—as will be shown later with examples—heat exchangers or the like are interposed in the vapor line system.

[0020] Advantageously, in the process and device according to the invention, or the vapor utilization system for vapor utilization, the (thermal) energy required to heat the vapors is utilized from the same system to which the vapors are ultimately fed. Thus, a large portion of the energy can be recovered through a "heat transfer system." The heat transfer system is implemented—as explained in detail later—by at least one, but preferably several, heat exchangers connected in series and / or in parallel.

[0021] A recycling plant or sludge recycling plant according to the invention comprises at least one dryer for the solids and a vapor recycling system according to the invention as described above. The dryer can be connected to the vapor introduction device of the vapor recycling system in order to remove the vapors from the dryer and recycle them as described above. The recycling plant is preferably a sewage sludge recycling plant, and the dryer is accordingly preferably a sewage sludge dryer.

[0022] Preferably, the dryer, in particular the sewage sludge dryer, is also connected to a fuel feed device of the combustion system of the vapor utilization system via a transport system for the dried (sewage) sludge (dry sludge), for example conveyor belts or the like, so that the dry sludge can be used as fuel to generate energy in the form of heat and, if suitable turbines are available, also electrical energy. Particularly preferably, at least a portion of the energy generated in the combustion system can be used to dry the solids or sludge, in particular sewage sludge, in the dryer or sewage sludge dryer. For example, process heat generated in the combustion system could be fed back to the dryer, preferably the sewage sludge dryer.

[0023] Further, particularly advantageous embodiments and developments of the invention emerge from the dependent claims and the following description, wherein the independent claims of one claim category can also be developed analogously to the dependent claims and embodiments of another claim category and, in particular, individual features of different embodiments or variants can be combined to form new embodiments or variants.

[0024] As mentioned, the invention requires a vapor introduction temperature of at least 500 °C. However, the vapor introduction temperature is preferably at least 600 °C. At higher temperatures, larger quantities of vapor can be introduced into the flue gas at once without lowering its temperature too drastically.

[0025] On the other hand, the vapor introduction temperature is preferably at most 900 °C, preferably at most 800 °C, and particularly preferably at most 700 °C. These temperatures can be achieved, for example, by utilizing the energy of the flue gas used to heat the vapor without external energy - as will be explained in more detail later.

[0026] In a particularly preferred variant, the vapors are introduced into the flue gas at a vapor introduction temperature in the range of 600 °C to 700 °C.

[0027] This vapor injection temperature range is particularly preferred in mono-combustion plants, i.e., in combustion systems that burn or utilize only one fuel, and particularly preferred in a mono-combustion plant that, as described above, uses only dried sludge, particularly sewage sludge, as fuel. This temperature range is particularly suitable if, as mentioned above, the recycling plant or sewage sludge recycling plant is to be used completely autonomously and all sludge, particularly sewage sludge, and the resulting vapors are to be fully utilized.

[0028] In principle, however, the vapors could also be partially recycled in another thermal recovery plant using other fuels. In this case, lower vapor injection temperatures of more than 350 °C, e.g., at least 360 °C, and no more than 600 °C, might be preferable. This is advisable if the thermal recovery plant is located nearby.

[0029] Preferably, the vapors are introduced into the flue gas at a flue gas temperature of at least 900 °C and / or at most 950 °C, wherein the flue gas temperature is the temperature that the flue gas has on average in the spatial area in which the vapors are fed.

[0030] The vapors are preferably introduced into the flue gas in such a way that the flue gas (still) has a (mixed gas) temperature of at least 850°C after the vapors have been introduced. In a particularly preferred embodiment, this mixed gas temperature of at least 850°C is maintained for at least 2 seconds. The mixed gas temperature is preferably a maximum of 900°C. The mixed gas temperature is the temperature of the flue gas immediately after the vapors have been added to the flue gas.

[0031] In principle, it would be possible to introduce the vapours into the flue gas at any point in the flue gas outlet. However, in order to achieve the longest possible residence time of the vapours mixed with the

[0032] To achieve flue gases at a certain temperature, the vapors are preferably introduced directly into the flue gas in a combustion chamber of the combustion system.

[0033] Preferably, the vapors are introduced into the flue gas only after at least partial combustion of the fuel, i.e. the vapors are preferably introduced above the actual fire.

[0034] Where exactly the vapors are introduced into the combustion chamber depends on the combustion system used: If a fluidized bed furnace is used for the combustion system, as is preferred, the vapors are preferably fed into the fluidized bed (combustion) in a free space (commonly referred to as the "freeboard"). The freeboard is the open area above the actual fluidized bed, into which the fuel is fed. This area is filled with flue gas, which is then directed upwards via the flue gas outlet into the next pass. In many cases, this freeboard also contains a secondary air supply to the flue gas to burn off any residual particles in the flue gas as much as possible.

[0035] If, for example, a grate furnace or a rotary kiln is used for the combustion system, the vapors are preferably introduced into the flue gas in the combustion chamber in the area of at least one secondary air supply.

[0036] As already mentioned above, the vapors can preferably be heated to the desired vapor introduction temperature by means of thermal energy obtained from the at least partial combustion of the fuel in the combustion system.

[0037] The vapors can preferably be heated in a vapor heating system, which—as already mentioned at the beginning—can be constructed in several stages, i.e., can include several downstream heat exchangers. In this multi-stage system, the vapors are gradually heated to increasing temperatures in various stages arranged one after the other in terms of the vapor transport path. This will be explained in more detail later using examples.

[0038] The vapor heating device preferably has at least one heat exchanger (for example, as the "final stage" in a multi-stage heat exchanger system), which ultimately heats the vapors (which may have already been preheated in other stages) to the desired vapor introduction temperature of at least 500 °C. This final stage can also comprise several sub-stages.

[0039] In a preferred embodiment, the vapors are heated at least partially, particularly preferably completely or exclusively, by means of the flue gas of the combustion system.

[0040] In this case, when vapors are utilized, the (thermal) energy required to heat them is used from the same system to which the vapors are ultimately fed. Thus, as mentioned above, a large portion of the energy can be recovered through a heat transfer system, which can be implemented, for example, with one, but preferably several, heat exchangers.

[0041] In a preferred variant, the flue gas into which the vapors have been introduced can be used to heat the vapors still to be introduced into the flue gas to the vapor introduction temperature. This means that the flue gas mixed with the vapors is used to heat the vapors still to be introduced.

[0042] There are various options for the concrete implementation of using the flue gas energy to heat the vapors: The heating of the vapors to the desired vapor introduction temperature can preferably be carried out at least partially directly using flue gas from the combustion system, for example, in a direct heat exchanger between the flue gas and vapor media. Accordingly, the vapor heating device particularly preferably comprises at least one heat exchanger (for example, the "final stage" in a multi-stage heat exchanger system) in which the flue gas is used directly to heat the vapors to the desired vapor introduction temperature.

[0043] The vapors can be heated to the desired vapor introduction temperature by means of the flue gas at a flue gas temperature of at least 400 °C and / or at most 980 °C.

[0044] In another embodiment, the vapors are heated using flue gas from the combustion system, at least partially indirectly, via an "exchange medium" as the heating medium. Here, the exchange medium is heated, for example, by flue gas in a first heat exchanger, thus receiving thermal energy, and then releases the thermal energy back to the vapors in a second heat exchanger. Examples of exchange media that can be used are water, steam, thermal oils, or gases. Steam is preferably used as the exchange medium. The exchange medium is preferably heated using flue gas to a desired heating temperature with a flue gas temperature of at least 400°C and / or at most 980°C.

[0045] The heating of the vapors and / or the exchange medium by flue gas can take place at least partially outside the combustion chamber, particularly preferably in a flue gas outlet. This means that the above-mentioned heat exchangers can, for example, be arranged at various locations in the flue gas outlet of the combustion system.

[0046] Additionally or alternatively, the vapors can also be heated, at least partially, directly in the combustion chamber of an incineration plant. In this design variant, at least a type of "heat exchanger" of the vapor heating device could be arranged directly in the combustion chamber of an incineration plant. If this is the case, this is preferably the aforementioned "final stage" in a multi-stage system, which ultimately heats the vapors to the vapor feed temperature.

[0047] The invention is explained in more detail below with reference to the accompanying figures using exemplary embodiments. In the various figures, identical components are provided with identical reference numerals. The figures are generally not to scale. They schematically show: Figure 1 a block diagram of a sewage sludge treatment plant with a vapor utilization system according to a first embodiment of the invention with a fluidized bed combustion system, Figure 2 a block diagram of a sewage sludge treatment plant with a vapor utilization system according to a second embodiment of the invention with a grate combustion system, Figure 3 a block diagram of an embodiment of a vapor preheater arrangement of a sewage sludge treatment plant according to the Figure 1 or 2 .

[0048] Figure 1shows a first embodiment of a sewage sludge utilization plant 100 with a vapor utilization system 9 according to the invention.

[0049] The sewage sludge utilization plant 100 here comprises a sewage treatment plant 2, which has a sewage sludge dryer 1 in which the recovered sewage sludge CS is dried. This drying process produces dry sludge TS (dried sewage sludge) and vapor B. This can be a conventional sewage sludge dryer 1. Various possible designs of such a sewage sludge dryer 1 and the associated drying processes are known to those skilled in the art, so no further explanation is required here.

[0050] It should be noted again at this point that use of the invention in a sewage sludge recycling plant is only a particularly preferred use and that use is also possible for the recycling of other solids to be dried. In particular, it is not necessary for the sewage treatment plant 2 itself to be part of the recycling plant or sewage sludge recycling plant 100, especially since no vapor condensate is produced in the sewage sludge recycling plant that would have to be disposed of in the sewage treatment plant. Thus, the sewage treatment plant 2 could, for example, be located at a spatial distance from the recycling plant 100, and the sewage sludge to be dried (or another solid to be dried) is delivered to the recycling plant or sewage sludge recycling plant 100, e.g., by transport vehicles, and fed there to the dryer 1.

[0051] In the illustrated embodiment, the dry sludge TS is processed as in Figure 1schematically indicated, via a suitable transport system, for example comprising several conveyor belts or the like, as fuel TS to a combustion system 4, in this preferred embodiment a fluidized bed combustion system 4.

[0052] In such a fluidized-bed combustion system 4, a mixture of sand and fuel TS (the fluidized bed W) is typically kept suspended in a fluidized state in a lower region of the combustion chamber 7 of the fluidized-bed combustion system 4 during operation by gas introduction via a nozzle base. The fuel TS is combusted, and the sand can circulate. Temperatures of 800 °C to 1000 °C typically arise in the fluidized bed W.

[0053] The structure and functioning of such a fluidized bed furnace or fluidized bed combustion system 4 are known to the person skilled in the art and therefore do not need to be explained in detail here either.

[0054] The combustion system 4, as usual, has a start-up burner 5 to bring the fluidized bed W to a sufficiently high temperature level. The fuel TS is introduced into this fluidized bed W at a high temperature by a feeding device 6, here a throw-away feeder 6, and then burned in the fluidized bed W.

[0055] The vapor utilization system 9 has a vapor introduction device 18 with a vapor line 17 suitably connected to the sewage sludge dryer 1. Via this vapor line 17, the vapors B are sucked in by a blower 11 of the vapor utilization system 9.

[0056] Subsequently, the vapors B are then heated in a vapor heating device 14 of the vapor utilization system 9 from an initial vapor temperature B T1 to a vapor introduction temperature B T4. This vapor heating device 14 comprises, as explained below, various heat exchangers 12, 12a, 12b, 13.

[0057] The vapors B are first heated in a vapor preheater arrangement 12 of the vapor heating device 14 from an initial vapor temperature B T1 of, for example, approximately 100 °C to an intermediate vapor temperature B T3 of, for example, approximately 200 °C.

[0058] Subsequently, the aforementioned vapors B are heated in a vapor introduction heater 13 (as a "final stage" 13) of the vapor heating device from the intermediate vapor temperature B T3 to a vapor introduction temperature B T4. This vapor introduction heater 13 or the final stage 13 is designed such that the vapors B reach a vapor introduction temperature B T4 of more than 350 °C, preferably a higher temperature, for example, of at least 600 °C.

[0059] In an optional variant, at least a portion of the vapors B can also be introduced directly from the vapor preheater arrangement 12 via a bypass 15 with an intermediate vapor temperature of B T3 into the flue gas R of a combustion system 4. This bypass of the vapor introduction heater 13 is controllable by a valve 16. Such a variant can be advantageous in vapor utilization systems 9 in which the vapor introduction temperature is to be regulated very precisely to a setpoint, since this is possible by adjusting the mixing ratio of the vapors B from the vapor preheater arrangement 12 and the vapors that have passed through the final stage 13. For this purpose, suitable temperature sensors can be arranged in the lines, and the temperature signals are fed to a control device (not shown), which in turn controls the valve 16.

[0060] In addition, a valve (not shown) could also be assigned to the final stage 13 in order to control the amount of vapor that is introduced into the flue gas from the final stage 13.

[0061] In particular, the vapors B can be introduced into the flue gas if required, for example temporarily, also with a (lower) vapor temperature, in extreme cases only with the intermediate vapor temperature B T3 , if the final stage is completely bypassed.

[0062] The vapors B heated to the desired vapor introduction temperature B T4 are fed as described in Figure 1 shown directly into the flue gas R in the "freeboard" 3 of the combustion chamber 7 of the fluidized bed combustion system 4.

[0063] The flue gas R, which is about 870 °C hot, is, as in Figure 1As shown, the flue gas is discharged from the combustion chamber 7 in the usual manner through a smoke outlet 19 adjoining the top of the combustion chamber 7 and (here in a first pass) passed over a first heating surface 21 to reduce the flue gas temperature. Behind this first heating surface 21, the flue gas temperature is approximately 800 °C.

[0064] This heating surface 21 is a heat exchanger 21 in which process steam generated in the plant itself is superheated by the flue gas R. This process steam can, for example, be fed in the usual way to a turbine (e.g., a high-pressure turbine) to generate electricity. Furthermore, at least a portion of this process steam can also be used as an exchange medium H to preheat the vapors B, as will be explained below.

[0065] Subsequently, the flue gas R is used to heat the vapors B directly in the vapor introduction heater 13 (i.e., the final stage 13) in a direct heat exchanger between the flue gas and vapor media to the desired very high vapor introduction temperature B T4. Downstream of this vapor introduction heater 13, the flue gas temperature is still approximately 600 °C.

[0066] Subsequently, the flue gas R is cooled again by a downstream heating surface 22. This heating surface 22 can also be a heat exchanger 22, which can also be used to superheat the process steam generated in the plant itself. This superheated process steam can, for example, then first be fed to the aforementioned heat exchanger 21 for further superheating. Depending on the temperature, it can also be fed directly to a turbine to generate electricity. Furthermore, at least a portion of this process steam can also be used as an exchange medium H to preheat the vapors B.

[0067] This second heating surface 22 is in turn followed by an evaporator 23, in which the above-mentioned process steam is generated from feedwater, and then, further downstream of the flue gas duct 19, an economizer 24 is connected, with the economizer 24 acting as a feedwater preheater for the evaporator 23. Downstream of the economizer 24, the flue gas temperature is then only approximately 130 °C to 200 °C.

[0068] In the process explained above, the temperature of the flue gas R is reduced by various heat exchangers 21, 13, 22, 23, 24 until the flue gas R can finally be cleaned in a flue gas cleaning system 25.

[0069] A heat exchanger 26 can be connected downstream to further reduce the temperature of the flue gas R, whereby the thermal energy contained in the flue gas R can be used in a heat sink 27, for example, for district heating. The flue gas R is finally sucked into a chimney 29 by a fan 28 and ultimately leaves the vapor utilization system 9.

[0070] In this embodiment, as mentioned, the thermal energy for the initial heating or preheating of the vapors in the vapor preheater arrangement 12 can be provided by an exchange medium H in the form of the process steam generated by means of the flue gas R in the evaporator 23 and superheated in further heat exchangers 21, 22.

[0071] The vapor preheater arrangement 12 is preferably constructed in several stages. A simple schematic example of this is shown in Figure 3 shown.

[0072] The heating of vapors B takes place in a first heat exchanger 12a (first preheating stage) from an initial vapor temperature B T1 of approximately 100 °C to a first intermediate vapor temperature B T2 of approximately 130 °C. As exchange medium H, for example, the process steam generated by the flue gas R, as mentioned above, can be used (steam inlets and outlets are in Figure 3 (not shown). The process steam may well have already been used in a turbine to generate electrical energy. For example, a portion of the medium-pressure steam generated downstream of the high-pressure turbine could be used, which could then be fed back into a low-pressure turbine.

[0073] In a subsequent second heat exchanger 12b, the vapors are then heated from this first intermediate vapor temperature B T2 to a second, higher intermediate vapor temperature B T3 of approximately 200 °C. In this second heat exchanger 12b, medium-pressure steam, for example, can be used as the exchange medium H. For example, this can be the superheated steam from the heat exchanger 21 located at the front in the flue gas exhaust path.

[0074] In principle, however, there are a variety of possibilities for using the superheated process steam H generated by the flue gas R to preheat the vapors B. As already mentioned, a suitable combination with other uses of the process steam, such as turbines, is also possible. The optimal connection or arrangement may depend on the specific on-site conditions.

[0075] In this respect, it should be pointed out once again that Figure 1 shows only one example of such a process diagram.

[0076] Figure 2 shows as an alternative to the embodiment from Figure 1 another embodiment of a vapor utilization system 9. In contrast to Figure 1 The dry sludge TS is burned as fuel TS here in a grate combustion system 8 and not in a fluidized bed combustion system. In such a grate combustion system 8, the fuel TS is burned on a combustion grate arranged at the bottom of the combustion chamber 33. However, the basic structure and operation of such a grate combustion system 8 are known to those skilled in the art and therefore do not need to be explained in detail here.

[0077] The grate firing combustion system 8 has, as usual, a fuel feed 31 (or charging device 31) above the grate, as well as a support burner 32. The support burner 32 serves to initiate the combustion start-up process. Autothermal combustion of the dry sludge TS is subsequently provided, meaning that no external energy supply is required for further combustion of the dry sludge TS.

[0078] Here, too, the vapors B are introduced into the combustion chamber 33 of the grate firing combustion system 8 at a specific vapor introduction temperature B T4 of more than 350 °C, but preferably at least 600 °C. The introduction takes place in the area of the auxiliary burners 32.

[0079] The remaining structure of the sewage sludge treatment plant 100 is the same as that of the Figure 1 All further process steps are analogous to those shown in Figure 1described procedural steps.

[0080] In all of the above-mentioned embodiments, it is advantageously possible to dispose of all dried sewage sludge (KS) or dry sludge (TS) produced, as well as all vapors (B) generated during drying, without residue, so that no vapor condensate is produced. The desired residence time of the flue gas (R) of at least 2 s in a temperature range of at least 850 °C is easily maintained. Essentially, all energy is generated by the system itself, and surplus energy can be used for other systems, for example, to drive turbines and / or for district heating networks. In particular, the energy can also be used to operate the sewage treatment plant.

[0081] Finally, it should be noted once again that the previously described methods for vapor disposal and the vapor utilization systems described are merely exemplary embodiments that can be modified in a variety of ways by those skilled in the art without departing from the scope of the invention. For example, the components shown in the respective exemplary embodiments, such as the number of heat exchangers used in vapor heating and / or the heating media or exchange media used in a vapor heating device, are interchangeable and / or combinable with one another as desired. Likewise, additional (optionally controllable) valves could be arranged at various locations and / or there could be more fans than those shown there, or the valves and / or fans could be arranged at other locations, to name just a few examples.Furthermore, the use of the indefinite articles "ein" or "eine" does not exclude the possibility that the characteristics in question may be present multiple times. List of reference symbols

[0082] 1 Dryer / sewage sludge dryer 2 Wastewater treatment plant 3 Free space / "Freeboard" 4 Fluidized bed combustion system 5 Start-up burner 6 Feeding device 7 Combustion chamber 8 Grate combustion system 9 Vapour utilization system 11 Blower 12 Vapour preheater assembly / heat exchanger assembly 12a First vapour preheater / heat exchanger 12b Second vapour preheater / heat exchanger 13 Vapour introduction heater / final stage 14 Vapour heating device 15 Bypass 16 Valve 17 Vapour line 18 Vapour introduction device 19 Flue outlet 21 First heating surface / heat exchanger 22 Second heating surface / heat exchanger 23 Evaporator 24 Economiser 25 Flue gas cleaning system 26 Heat exchanger 27 Heat sink 28 Blower 29 Stack 31 Feeding device 32 Support burner 33 Combustion chamber 100 Utilization plant / sewage sludge utilization plant B Vapours B T1 Initial vapour temperature B T2 First intermediate vapour temperature B T3 Second intermediate vapour temperature B T4 Vapour introduction temperature H Exchange medium / heating medium KS Sewage sludge RFlue gas TS Dry sludge W Fluidized bed

Claims

1. Method for the utilization of vapours (B) obtained during the drying of a solid (KS), preferably a sewage sludge (KS), - wherein the vapours (B) are introduced into a flue gas (R) which is obtained during combustion of a fuel (TS) in a combustion system (4, 8), and - wherein the vapours (B) are heated to a vapour introduction temperature (BT4) of at least 500 °C for introduction into the flue gas (R).

2. Method according to claim 1, wherein the vapour introduction temperature (BT4) is at least 600 °C.

3. Method according to claim 1 or 2, wherein the vapour introduction temperature (BT4) is at most 900 °C, preferably at most 800 °C, and particularly preferably at most 700 °C.

4. Method according to one of the preceding claims, wherein the vapours (B) are introduced into the flue gas (R) at a flue gas temperature of at least 900 °C and / or at most 950 °C.

5. Method according to one of the preceding claims, wherein the vapours (B) are introduced into the flue gas (R) in such a way that the flue gas (R) has a temperature of at least 850 °C after the introduction of the vapours (B).

6. Method according to one of the preceding claims, wherein the vapours (B) are introduced into the flue gas (R) in a combustion chamber (7) of the combustion system (4, 8).

7. Method according to one of the preceding claims, wherein the vapours (B) are introduced into the flue gas (R) in a region of a free board (3) above a fluidized bed (W) and / or in a region of a secondary air feed.

8. Method according to one of the preceding claims, wherein the vapours (B) are heated to a vapour introduction temperature (BT4) by means of thermal energy obtained from the combustion of the fuel (TS) in the combustion system (4, 8) before the introduction into the flue gas (R), wherein the heating of the vapours (B) preferably takes place at least partially by means of flue gas (R) of the combustion system (4, 8).

9. Method according to claim 8, wherein the heating of the vapours (B) takes place at least partially directly by means of flue gas (R) of the combustion system (4, 8).

10. Method according to claim 8 or 9, wherein the heating of the vapours (B) by means of flue gas (R) of the combustion system (4, 8) takes place at least partially indirectly via an exchange medium (H).

11. Method according to claim 8 or 10, wherein the heating of the vapours to the vapour introduction temperature (BT4) and / or the exchange medium (H) to a heating temperature takes place by means of flue gas (R) with a flue gas temperature of at most 980 °C.

12. Method according to one of the preceding claims, wherein the heating of the vapours (B) and / or the exchange medium (H) takes place at least partially outside the combustion chamber (7) of the combustion system (4, 8).

13. Vapour utilization system (9) for the utilization of vapours (B) which are obtained during the drying of a solid (KS), preferably a sewage sludge (KS), with - a combustion system (4, 8) for the combustion of a fuel (TS), - a vapour introduction device (18) arranged to introduce the vapours (B) into a flue gas (R) produced during the combustion of the fuel (TS), and - a vapour heating device (14) arranged to heat the vapours (B) for introduction into the flue gas (R) to a vapour introduction temperature (BT4) of at least 500 °C.

14. Vapour utilization system (9) according to claim 13, wherein the vapour heating device (14) comprises at least one heat exchanger (13) in which the flue gas (R) is directly used to heat the vapours (B) to the desired vapour introduction temperature (BT4).

15. Utilization plant (100), preferably sewage sludge utilization plant (100), with a dryer (1), preferably a sewage sludge dryer (1), and with a vapour utilization system (9) according to claim 13 or 14.

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