Process and apparatus for cleavage of fuels by thermal breakdown by means of partial oxidation

Abstract

The invention relates to a process for cleavage of fuels by thermal breakdown of the fuel to give fuel gas and charcoal within a reactor (3) that extends in a longitudinal direction (L) from an entry section (7) of the reactor (3) to an exit section (9) of the reactor (3), characterized by the process steps of: a. feeding the fuel into the entry section (7) of the reactor (3), with formation of a gas space (16) above a bed of the supplied fuel in the reactor (3), b. conveying the bed of fuel within the reactor (3) from the entry section (7) of the reactor (3) to the exit section (9) of the reactor (3) by means of a mechanical conveying device (15), c. cleaving the solid fuel by thermal breakdown by partial gasification by means of partial oxidation, d. sucking fuel gas out of the gas space (16) at a suction site (27) in the reactor (3) into a recirculation system (25), e. feeding the fuel gas from the recirculation system (25) back into the gas space (16) at a feed point (37) in the reactor (3) which is at a distance from the suction site (27) in the reactor (3), and f. discharging the at least partly broken-down fuel from the reactor (3) in the exit section (9).

Description

Title: Method and device for splitting fuels by thermal decomposition using partial oxidation Description

[0001] The invention relates to a method and a device for splitting, in particular, moist fuels by thermal decomposition of the fuel into gaseous components (hereinafter referred to as "fuel gas") and a solid, carbon-containing product (hereinafter referred to as "coal") within a moving-bed reactor, as well as the optionally desired further treatment of the produced fuel gas into synthesis gas or flue gas and of the produced coal into activated carbon or ash. The method and device serve both in the sense of pyrolysis for the effective production of coal and in the sense of gasification for the effective production of fuel gas.

[0002] To split solid fuels into fuel gas and coal, the fuel to be split is thermally decomposed at high temperatures, preferably between approximately 300°C and approximately 750°C. To control the process temperatures and prevent the resulting products (fuel gas and coal) from completely oxidizing, this thermal decomposition takes place in an oxygen-free or at least oxygen-poor atmosphere. The composition of the resulting gaseous products consists of a variety of chemical compounds and depends on the fuels used and the process conditions. Typical compounds are CO, CO2, H2, H2O, CH4, C2H4, as well as a variety of other low-molecular-weight organic compounds, as well as higher-molecular-weight oils and tars, and coal.

[0003] According to the current state of the art, this decomposition takes place either in allothermal or autothermal reactors, or in hybrids of these two basic process variants. The allothermal process variant is characterized by the fact that the temperature required for the process is introduced into the reactor by external heat input (typically using the reactor wall as the heat transfer surface). In contrast, in the autothermal process, the required heat energy is generated in the reactor itself. This occurs through partial combustion (partial oxidation). In this process, a portion of the fuel and / or combustible gases is oxidized or burned within the reactor by adding comparatively small amounts of oxidant.

[0004] An example of a plant for splitting solid fuels using allothermal reactor chambers is disclosed in patent EP 1 943 461 B1. There, the fuel gas produced from the solid fuel in the two cylindrical, parallel-operating allothermal reactor chambers is combusted with air in an external combustion chamber. The hot flue gas is then directed around the two allothermal reactor chambers, thus heating them. To improve heat transfer, the walls of the reactor chambers are equipped with flow baffles and attachments. Coal exits the reactor chambers as another product.

[0005] An example of the autothermal decomposition of solid fuels in a multi-stage gasification process for woody biomass is disclosed in patent DE 1 807 988 B4, which describes the process control of the autothermally operated degassing stage for the decomposition of solid fuels. In this case, a bed of wood chips, preferably consisting of wood chips, is stirred by means of a stirring device in a horizontal, cylindrical reactor, and simultaneously, air or oxygen is injected from the underside of the horizontal reactor in such a way that The exothermic oxidation reactions maintain a desired process temperature of approximately 500 °C. Fuel gas and coal leave the degassing reactor as products.

[0006] As explained in DE 198 07 988 B4, the major advantage of autothermal processing is that it avoids the transfer of large amounts of heat at a high temperature through the reactor wall, as is necessary in allothermal processing. Autothermal processing is therefore significantly less complex in terms of equipment, has a higher power density, and is therefore significantly more economical.

[0007] This thesis is also underscored by the numerous unsuccessful multi-stage gasification projects with allothermal process stages for economic and technical reasons. Among other problems, the required heat transfer was generally not achieved.

[0008] In contrast, it should be noted that multi-stage gasification processes using autothermal degassing stages, as described in DE 10 2007 012 452 B4, have achieved sustained market success.

[0009] However, the autothermal process steps implemented so far for splitting solid fuels into fuel gas and coal all have one technical drawback: the injection of the oxidant for the autothermal process takes place directly into the coal bed. This can be seen, for example, in patent DE 198 07 988 B4. Although the homogeneous oxidation reaction between fuel gas and oxidant proceeds significantly faster and preferentially than is the case for the heterogeneous oxidation reaction between the solid coal and the oxidant, the direct injection of the The introduction of an oxidizer into the coal bed leads to excessive coal consumption. This occurs because there is insufficient fuel gas in the coal bed, and therefore any locally present excess oxidizer oxidizes the coal. If the process aims to produce the largest possible quantities of coal, this process is therefore unsuitable.

[0010] EP 3 858 952 A1 proposes introducing an oxidizing agent into the gas chamber above the fuel bed via a plurality of nozzles distributed along the length of the reactor, thereby creating a desired temperature profile. While this process makes it possible to carbonize moist fuels with a water content of up to 40%, the throughput and carbonization efficiency, or rather the yield of coal, are correspondingly lower for such moist fuels. According to the current state of the art, fuels with a water content of more than 40% must be dried beforehand.

[0011] Other known carbonization processes and reactors are only suitable for fuels with a water content of up to 25% or 30%, requiring the use of an upstream dryer to reduce the water content of the fuel to below 25% or 30% before the carbonization process. However, an upstream dryer is expensive to purchase and operate, requires a lot of space, and is difficult to obtain approval due to dust and odor emissions.

[0012] The present invention is therefore based on the problem of more efficiently autothermally splitting moist fuels with up to 45% water content in a very compact and simply constructed apparatus and thereby producing coal with a higher carbonization efficiency. efficiency without having to dry the fuel in an upstream dryer.

[0013] This problem is solved by the features listed in the patent claims. Preferred embodiments of the invention can be found in the subclaims, the description, and the figures.

[0014] According to a first aspect of the present invention, a method is provided for splitting fuels by thermal decomposition of the fuel into fuel gas and coal within a reactor extending in a longitudinal direction from an inlet section of the reactor to an outlet section of the reactor, characterized by the method steps: a) feeding the fuel into the inlet section of the reactor, wherein a gas space is formed above a fuel bed in the reactor above the supplied fuel, b) conveying the fuel bed within the reactor from the inlet section of the reactor to the outlet section of the reactor by means of a mechanical conveying device, c) splitting the solid fuel by thermal decomposition through partial gasification by means of partial oxidation, d) extracting fuel gas from the gas space at an extraction point of the reactor into a recirculation system,e) feeding oxidant into at least a portion of the extracted fuel gas in the recirculation system, f) returning the fuel gas from the recirculation system to the gas space at a reactor feed point remote from the reactor extraction point, and g) discharging the at least partially decomposed fuel from the reactor in the outlet section.

[0015] The process according to the invention enables more efficient autothermal decomposition of fuels with up to 45% water content, thereby producing coal with a higher carbonization efficiency without having to first dry the fuel in an upstream dryer. By recirculating at least a portion of the fuel gas, the required evaporation enthalpy can be provided from a portion of the chemical energy contained in the recirculated fuel gas. This prevents the reactor from cooling excessively due to evaporation, even with very moist fuels, but rather keeps the thermal decomposition running at substoichiometric rates. Ambient air is preferably used as the oxidant.

[0016] Optionally, oxidant can be fed into at least a portion of the extracted fuel gas in the recirculation system. This can occur at one or more points in the recirculation system, as required. By feeding in oxidant, a portion of the extracted fuel gas ignites automatically, provided its temperature is above the auto-ignition temperature. The auto-ignition of a portion of the extracted fuel gas increases the temperature of the extracted fuel gas, thus preventing the temperature of the extracted fuel gas in the recirculation system from falling below the auto-ignition temperature. The feed of oxidant can be metered and, if necessary, controlled by temperature measurement, so that only enough oxidant is fed in to ensure that the temperature of the extracted fuel gas in the recirculation system remains a certain degree above the auto-ignition temperature.The smaller the portion of the fuel gas that reacts with the oxidant in the recirculation system, the greater the calorific value of the fuel gas that is returned to the reactor and can be diverted from the recirculation system into a fuel gas chamber.

[0017] Optionally, the reactor's exhaust point can be located in the reactor's inlet section, and the reactor's feed point in the reactor's outlet section. This is advantageous for several reasons. First, the water vapor content in the reactor's inlet section is particularly high. The exhaust in the inlet section creates a potentially advantageous fuel gas flow in the reactor opposite to the flow direction of the fuel bed.

[0018] Alternatively, the reactor's exhaust point can be located in the reactor's outlet section, and the reactor's feed point can be located in the reactor's inlet section. Optionally, the recirculation system can reverse the flow direction of the fuel gas through the recirculation system as needed, so that the exhaust point becomes the feed point, and vice versa.

[0019] Optionally, the extracted fuel gas can be dedusted in a dedusting system, with dedusting taking place using gravity, centrifugal force, and / or a filter in a separator. This is useful so that a portion of the fuel gas can be fed to a downstream fuel gas chamber for useful heat extraction with as little dust as possible.

[0020] Oxidizing agent is preferably fed into the extracted fuel gas in the recirculation system before the temperature of the extracted fuel gas in the recirculation system falls below the autoignition temperature of the extracted fuel gas, in order to at least partially ignite and thus heat it by the injected oxidizing agent. For this purpose, the fuel gas can be kept at a minimum temperature in the reactor at the extraction point that is sufficient to ensure that the fuel gas in the recirculation system does not fall below the autoignition temperature of the extracted fuel gas until the oxidizing agent is fed in. sucked-in fuel gas cools down. There is then no need to heat the fuel gas in the recirculation system upstream of the oxidant feed. Depending on the length and design of the recirculation system, oxidant can be fed in at several points in the recirculation system. As soon as the fuel gas, which has a temperature above the auto-ignition temperature, comes into contact with the fed-in oxidant, it ignites automatically and releases corresponding thermal energy. It is therefore advisable to feed the oxidant to the fuel gas in the recirculation system close to the feed point so that as much of the released thermal energy of the recirculated, ignited fuel gas as possible is used for thermal decomposition in the reactor. To monitor the temperature in the recirculation system, the recirculation system preferably has one or more temperature sensors.It is advantageous to measure the temperature downstream of each oxidant inlet to be able to regulate or control the oxidant flow based on the temperature measurement. It is also possible to check and control that the temperature does not exceed certain safety limits due to the oxidant inlet.

[0021] Optionally, oxidant can be introduced into the gas space above the fuel bed via a plurality of valve-controlled nozzles distributed in the longitudinal direction of the reactor, and a mass flow of oxidant introduced via the valve-controlled nozzles can be controlled in such a way that a specific, desired process temperature profile is established within the reactor in the longitudinal direction from the inlet section of the reactor to the outlet section of the reactor. The nozzles are valve-controlled in that a valve assigned to each nozzle regulates the mass flow of oxidant through the nozzle as a function of a temperature measurement value, wherein the temperature measurement value is provided by a temperature sensor assigned to each nozzle. The respective temperature sensor measures the temperature in the reactor in the area where the associated nozzle The desired process temperature profile does not have to be constant along the length of the reactor. Since the fuel bed becomes drier in the conveying direction, a higher temperature may be desired in the inlet section than in the outlet section. Accordingly, the mass flow of oxidant through the nozzles at the inlet section can be higher than the mass flow of oxidant through the nozzles at the outlet section.

[0022] Optionally, the oxidant can be preheated to increase efficiency. This can be useful to prevent the fuel gas from cooling below its autoignition temperature due to the addition of oxidant. Heating can be achieved by routing the oxidant lines along the outside of the reactor and / or a fuel gas chamber in such a way that, through thermal coupling, the waste heat from the reactor and / or the fuel gas chamber is used to preheat the oxidant. A further advantage of preheating the oxidant before it is fed in is that less oxidant is required and correspondingly less fuel gas has to be oxidized to maintain the temperature. The calorific value of the ultimately produced fuel gas is correspondingly higher.

[0023] Optionally, a portion of the extracted fuel gas can be diverted to a fuel gas chamber, preferably after the extracted fuel gas has been dedusted. The fuel gas chamber can be used for heat recovery to maximize the chemical energy contained in the diverted fuel gas. Utilizing the waste heat from the fuel gas chamber to preheat the oxidant is particularly useful.

[0024] According to a second aspect of the present invention, an apparatus is provided for splitting fuels by thermal decomposition of the fuel into fuel gas and coal within a reactor which extends in a longitudinal direction from an inlet section of the reactor for supplying fuel into the reactor to an outlet section of the reactor for removing the at least partially decomposed fuel from the reactor, wherein the reactor has a mechanical conveying device for conveying a fuel bed within the reactor from the inlet section to the outlet section, wherein the reactor forms a gas space for the fuel gas above the conveyed fuel bed, characterized in that the device has a recirculation system which is designed to suck fuel gas out of the gas space at a suction point of the reactor and then to feed the fuel gas back into the gas space at a feed point of the reactor which is remote from the suction point of the reactor.

[0025] Optionally, the recirculation system may be configured to feed oxidizing agent into at least a portion of the extracted fuel gas in the recirculation system.

[0026] Optionally, the reactor's exhaust point can be located in the reactor's inlet section and the reactor's feed point can be located in the reactor's outlet section.

[0027] Optionally, the recirculation system may comprise a dust removal device for removing dust from the extracted fuel gas by means of gravity, centrifugal force and / or a filter in a separator.

[0028] Optionally, the recirculation system may have at least one temperature sensor to check whether the extracted fuel gas has a temperature above the autoignition temperature of the extracted fuel gas, in particular after the oxidant is fed in, in order to be able to regulate or control the feed of oxidant based on the temperature measured by the temperature sensor. The position of the temperature sensor in the recirculation system is therefore preferably downstream shortly after an oxidant feed.

[0029] Optionally, the recirculation system can be configured to feed in oxidizing agent depending on the temperature measured by the at least one temperature sensor and thereby keep the temperature of the extracted fuel gas in the recirculation system above the autoignition temperature.

[0030] Optionally, the device can have a plurality of valve-controlled nozzles distributed in the longitudinal direction of the reactor and arranged above the fuel bed for introducing oxidant into the gas space, wherein a mass flow of oxidant introduced via the valve-controlled nozzles can be regulated such that a specific, desired process temperature profile is established within the reactor in the longitudinal direction from the inlet section of the reactor to the outlet section of the reactor.

[0031] Optionally, the reactor may be a first of at least two reactors, wherein a second of the at least two reactors is connected downstream of the first reactor and extends from an inlet section of the second reactor to an outlet section of the second reactor, wherein the second reactor also has a mechanical conveying device for conveying a fuel bed within the second reactor from the inlet section of the second reactor to the outlet section of the second reactor, wherein the inlet section of the second reactor is connected to the outlet section of the first reactor, so that the fuel at least partially decomposed in the first reactor can be fed to the second reactor and coal can be discharged in the outlet section of the second reactor.

[0032] Optionally, the device can have a dust recirculation system, wherein the recirculation system comprises a dust removal device for removing dust from the extracted fuel gas by means of gravity, centrifugal force and / or a filter in a separator, wherein the dust recirculation system is connected between the dust removal device and the inlet section of the second reactor to supply separated dust to the second reactor for further thermal decomposition. This is particularly useful for completely carbonizing the separated dust in the second reactor.

[0033] Optionally, the second reactor can have a plurality of valve-controlled nozzles distributed in the longitudinal direction of the second reactor and arranged above the fuel bed of the second reactor for introducing oxidant into the gas space of the second reactor, wherein a mass flow of oxidant introduced into the second reactor via the valve-controlled nozzles can be regulated such that a specific, desired process temperature profile is established within the second reactor in the longitudinal direction from the inlet section of the second reactor to the outlet section of the second reactor. The desired temperature profile in the second reactor can differ from the desired temperature profile. The second reactor, in which the fuel has already partially decomposed and is less moist, can, for example, be operated hotter or cooler than the first reactor in order to achieve a specific quality or quantity of coal to be discharged.

[0034] Optionally, the second reactor can be arranged parallel to the first reactor below the first reactor, with the conveying direction of the mechanical conveying device in the second reactor being opposite to the conveying direction of the mechanical conveying device in the first reactor. This allows for a particularly compact design of the device and good thermal coupling between the two reactors.

[0035] Optionally, the reactors can be operated in a temperature range of 500 - 900 °C, preferably in a temperature Temperature range of 620 - 800 °C. Generally, throughput increases with increasing temperature. On the other hand, the achievable coal yield per fuel decreases at high temperatures. It has been shown that a process temperature profile of 720 °C - 750 °C in a central section of the reactors located approximately midway between the respective inlet and outlet sections achieves good results. In the respective outlet section, a higher average process temperature profile, for example, 770 °C - 800 °C, can be advantageous.

[0036] Exemplary embodiments of the invention are explained below with reference to drawings. They show: Figure 1 is a schematic representation of a first part of an advantageous embodiment of a device according to the invention, with reference to which the method steps according to the invention are explained; and Figure 2 is a schematic representation of a second part of the embodiment according to Fig. 1.

[0037] Figure 1 shows a schematic representation of an apparatus 1 according to the invention for carrying out the method according to the invention for decomposing, in particular, moist fuels by thermal decomposition by means of partial oxidation. The method is of course also applicable to dry fuels, but has particular advantages in the decomposition of relatively moist fuels. The apparatus 1 here has a first reactor 3 and a second reactor 5 connected downstream of the first reactor 3. The first reactor 3 extends from an inlet section 7, where, for example, moist fuel is fed to the reactor 3, along a longitudinal direction L to an outlet section 9, where at least partially decomposed fuel material falls from the first reactor 3 into the second reactor 5. The fuel is fed to the reactor 3 via a rotary valve 11 and a conveyor screw 13, so that the fuel forms a fuel bed on a conveyor device 15 in the inlet section 7 of the first reactor 3. The conveyor device 15, for example in the form of a conveyor screw located in the first reactor 3, transports the fuel bed in the longitudinal direction L to the outlet section 9. Above the fuel bed, the first reactor 3 forms a gas space 16 in which fuel gas is formed during thermal decomposition.

[0038] The second reactor 5 also has a conveying device 17, whereby the conveying direction in the second reactor 5 is opposite to the conveying direction in the first reactor 3. Alternatively, the conveying direction in the second reactor 5 can coincide with the conveying direction in the first reactor 3. The inlet section 1 of the second reactor 5 is therefore arranged below the outlet section 9 of the first reactor 3. The second reactor 5 is here approximately as long as the first reactor 3 and extends parallel to the first reactor 3 below the first reactor 3. Alternatively, the second reactor 5 can be longer or, preferably, shorter than the first reactor 3. At the outlet section 21 of the second reactor 5, coal is then discharged via a rotary valve 23. The two reactors 3, 5 can be surrounded by a common thermal insulation or heat insulation in order to minimize overall heat loss to the outside.The fuel gas produced in the second (lower) reactor 5 can flow upwards, opposite to the fuel bed, from the inlet section 19 of the second reactor 5 into the gas space 16 in the outlet section 9 of the first reactor 3. The gas space in the second (lower) reactor 5 can be designed correspondingly smaller than the gas space 16 in the first (upper) reactor 3.

[0039] According to the invention, the device 1 comprises a recirculation system 25 (the lines of which are shown in dashed lines in Fig. 1), with which fuel gas is extracted from the gas space 16 of the first reactor 3 at an extraction point 27. In the illustrated embodiment, the extraction point 27 is located in the inlet section 7 of the first reactor 3. The recirculation system 25 comprises a recirculation fan 29, which controls the flow in the recirculation system 25. The recirculation system 25 further comprises a dedusting device 31 in the form of a separator. A portion of the dedusted fuel gas is diverted to a fuel gas chamber 33 shown in Fig. 2. Oxidizing agent in the form of air is fed into another part of the dedusted fuel gas at an ignition point 35a of the recirculation system 25, whereby a part of the fuel gas is automatically ignited and then fed back to the gas space 16 of the first reactor 3 at a feed point 37.The feed point 37 is located here in the outlet section 9 of the first reactor 3. This creates a fuel gas flow in the gas chamber 16 opposite to the conveying direction of the fuel bed. A further ignition point 35b is provided upstream of the dedusting device 31, where oxidant is fed into the recirculation system 25 via a valve 45 to prevent the temperature of the extracted fuel gas in the recirculation system 25 from falling below the autoignition temperature of the fuel gas. This can be checked by means of a temperature sensor 38 arranged downstream of the ignition point 35b, and the valve 45 can be controlled depending on the temperature measurement of the temperature sensor 38. Only as little oxidant as possible should be fed in, but as much as necessary to maintain the temperature.

[0040] If the recirculated fuel gas has a temperature above the autoignition temperature of the fuel gas at the respective ignition point 35a, b, it ignites itself when the oxidant is fed in. The temperature can be controlled by a temperature sensor located in the recirculation ion system 25 downstream of the respective ignition point 35a, b. By recirculating the fuel gas, the vaporization enthalpy required for the relatively high water content in the fuel is obtained from the fuel gas. To start the recirculation process, a starting aid 39 in the form of a controlled ignitable liquid gas supply is provided to supply a combustible gas to the ignition point 35a of the recirculation system 25 and ignite it to the first reactor 3 at the supply point. As soon as the fuel gas circulates at autoignition temperature in the recirculation system 25, the recirculation process is maintained solely by the respective feed of the oxidizing agent at the ignition points 35a, b, so that the starting aid 39 is no longer required.

[0041] The air used as the oxidizing agent is extracted from the ambient air 43 by means of a primary air blower 41 and fed to the recirculation system 25 at the ignition points 35a, b via controllable valves 45. Furthermore, the primary air blower 41 supplies a plurality of nozzles 47 distributed along the length of the two reactors 3, 5, which are designed to introduce oxidizing agent from above into the respective reactor 3, 5. The nozzles 47 are each valve-controlled, with the mass flow of oxidizing agent through the respective nozzle 47 being regulated by an associated temperature-controlled valve 49 as a function of a temperature measured in the region of the respective nozzle 47 by an associated temperature sensor 51. This allows a desired temperature profile to be set along the length of the respective reactor 3, 5, which does not have to be constant along the length of the reactor 3, 5.The higher the respective mass flow of oxidant, the higher the temperature in the area of ​​the respective nozzle 47. This is because the thermal decomposition as a whole takes place substoichiometrically, ie in the respective reactor 3, 5 there is always a lack of oxidant or an excess of fuel gas, which. never burns completely in reactor 3, 5. With the addition of oxidant, the autothermal decomposition is therefore specifically fueled locally in the respective reactor 3, 5.

[0042] In the embodiment shown, the dust separated in the dedusting device 31 is fed to the inlet section 19 of the second (lower) reactor 5 via a rotary valve 53 and a conveyor screw 55 so that the separated dust can be completely carbonized in the second reactor 5.

[0043] During the process, the reactors 3, 5 and the recirculation system 25 are fed with the fuel gas produced from the fuel, i.e., mainly gaseous hydrocarbons and water vapor, and the oxidant. The reactors 3, 5 and the recirculation system 25 should, if possible, have a pressure slightly below the ambient air pressure to prevent gas from escaping, for example, at the rotary valves 11, 23. To achieve this, a portion of the fuel gas is diverted from the recirculation system 25; this portion is slightly larger than the sum of the fuel gas currently produced in the reactors 3, 5 and the supplied oxidant, creating a slight negative pressure.

[0044] Fig. 2 shows how the branched portion of the fuel gas is directed into the fuel gas chamber 33, where ambient air 43 is directed into the fuel gas chamber 33 by means of a secondary air blower 57 for the most complete combustion of the fuel gas. In a waste heat boiler 59, the heat generated in the fuel gas chamber 33, which is discharged with the exhaust gas 61 from the fuel gas chamber 33, is used for other purposes by means of a useful heat extraction 63. A speed-controlled exhaust fan 65 determines the mass flow of exhaust gas 61 from the device 1. The speed of the exhaust fan 65 is preferably dependent on a value in the first or second reactor. The exhaust gas pressure is regulated by the pressure measured in the reactors 3, 5 and / or in the recirculation system 25 by at least one pressure sensor 67. The exhaust fan 65 thus ensures the desired slight negative pressure in the reactors 3, 5 and the recirculation system 25. For this purpose, at least one pressure sensor 67 is preferably arranged at the outlet section 9 of the first reactor 3 in order to regulate the speed of the exhaust fan 65 according to the pressure measured there. Optionally, as shown in Fig. 2, a portion of the exhaust gas can be fed again to the combustion gas chamber 33 via an exhaust gas recirculation fan 69 in order to reduce nitrogen oxide emissions. Completely burnt exhaust gas, which also contains the entire water vapor load from the fuel moisture, then escapes in a chimney 71. List of reference symbols I Device 3 first reactor 5 second reactor 7 Inlet section of the first reactor 9 Exit section of the first reactor II Rotary valve 13 Conveyor screw 15 Conveyor system in the first reactor 16 Gas room 17 Conveyor system in the second reactor 1 Inlet section of the second reactor 21 Exit section of the second reactor 23 Rotary valve 25 Recirculation system 27 Extraction point 29 Recirculation fan 31 Dust extraction system 33 Fuel gas chamber 35a, b Inflammation site 37 Feed point 38 temperature sensors 39 Jump start 41 Primary air blower 43 Ambient air 45 valve 47 nozzles 49 Valve 51 Temperature sensor 53 Rotary valve 55 screw conveyor 57 Secondary air blower 59 waste heat boilers 61 exhaust 63 Useful heat extraction 65 Extraction fan 67 Pressure sensor 69 exhaust gas recirculation blower 71 fireplace L longitudinal direction

Claims

Claims 1. A method for splitting fuels by thermal decomposition of the fuel into fuel gas and coal within a reactor (3) which extends in a longitudinal direction (L) from an inlet section (7) of the reactor (3) to an outlet section (9) of the reactor (3), characterized by the method steps: a. feeding the fuel into the inlet section (7) of the reactor (3), wherein a gas space (16) is formed above a fuel bed in the reactor (3) above the fed fuel, b. conveying the fuel bed within the reactor (3) from the inlet section (7) of the reactor (3) to the outlet section (9) of the reactor (3) by means of a mechanical conveying device (15), c. splitting the solid fuel by thermal decomposition by partial gasification by means of partial oxidation, d. Suction of fuel gas from the gas space (16) at a suction point (27) of the reactor (3) into a recirculation system (25), e.Returning the fuel gas from the recirculation system (25) into the gas space (16) at a feed point (37) of the reactor (3) remote from the extraction point (27) of the reactor (3), and f. Expelling the at least partially decomposed fuel from the reactor (3) in the outlet section (9).

2. The method according to claim 1, wherein oxidizing agent is fed into at least a portion of the extracted fuel gas in the recirculation system (25).

3. The method according to claim 1 or 2, wherein the suction point (27) of the reactor (3) is located in the inlet section (7) of the reactor (3) and the feed point (37) of the reactor (3) is located in the outlet section (9) of the reactor (3).

4. Method according to one of the preceding claims, wherein the extracted fuel gas is dedusted in a dedusting device (31), wherein the dedusting takes place by means of gravity, centrifugal force and / or a filter in a separator.

5. Method according to one of the preceding claims, wherein the fuel gas is kept at a temperature in the recirculation system (25) above the autoignition temperature of the extracted fuel gas, preferably by feeding in oxidizing agent.

6. The method according to any one of the preceding claims, wherein oxidizing agent is introduced into the gas space (16) above the fuel bed via a plurality of valve-controlled nozzles (47) distributed in the longitudinal direction (L) of the reactor (3), and a mass flow of oxidizing agent introduced via the valve-controlled nozzles (47) is controlled in such a way that a specific, desired process temperature profile is established within the reactor (3) in the longitudinal direction (L) from the inlet section (7) of the reactor (3) to the outlet section (9) of the reactor (3).

7. The method according to any one of the preceding claims, wherein the oxidizing agent is preheated before the preheated oxidizing agent is fed into the recirculation system (25) and / or the reactor (3).

8. Method according to one of the preceding claims, further comprising a step of branching off a portion of the extracted fuel gas from the recirculation system (25) to a fuel gas chamber (33), preferably after dedusting the extracted fuel gas.

9. The method according to claim 8, wherein the portion of the extracted fuel gas is branched off by means of a speed-controlled extraction fan (65), wherein a speed of the extraction fan (65) is regulated as a function of a pressure measured in the reactor (3) and / or in the recirculation system (25) by at least one pressure sensor (67).

10. Device (1) for splitting fuels by thermal decomposition of the fuel into fuel gas and coal within a reactor (3), which extends in a longitudinal direction (L) from an inlet section (7) of the reactor (3) for supplying fuel into the reactor (3) to an outlet section (9) of the reactor (3) for removing the at least partially decomposed fuel from the reactor (3), wherein the reactor (3) has a mechanical conveying device (15) for conveying a fuel bed within the reactor (3) from the inlet section (7) to the outlet section (9), wherein the reactor (3) forms a gas space (16) for the fuel gas above the conveyed fuel bed, characterized in that the device has a recirculation system (25) which is designed toTo extract fuel gas from the gas space (16) at an extraction point (27) of the reactor (3) and then to feed the fuel gas back into the gas space (16) at a feed point (37) of the reactor (3) remote from the extraction point (27) of the reactor (3). 1 1. Device (1 ) according to claim 10, wherein the recirculation system (25) is arranged to feed oxidizing agent into at least a part of the extracted fuel gas in the recirculation system (25).

12. Device (1) according to claim 10 or 11, wherein the suction point (27) of the reactor (3) is located in the inlet section (7) of the reactor (3) and the feed point (37) of the reactor (3) is located in the outlet section (9) of the reactor (3).

13. Device (1) according to one of claims 10 to 12, wherein the recirculation system (25) has a dedusting device (31) for dedusting the extracted fuel gas by means of gravity, centrifugal force and / or a filter in a separator.

14. Device (1) according to one of claims 10 to 13, wherein the recirculation system (25) has at least one temperature sensor (38) to check whether the extracted fuel gas in the recirculation system (25) has a temperature above the autoignition temperature of the extracted fuel gas.

15. Device (1) according to claim 14, wherein the recirculation system (25) is configured to feed in oxidizing agent as a function of the temperature measured by the at least one temperature sensor (38) and thereby to keep the temperature of the extracted fuel gas in the recirculation system (25) above the autoignition temperature.

16. Device (1) according to one of claims 10 to 15, with a plurality of valve-controlled nozzles distributed in the longitudinal direction (L) of the reactor (3) and arranged above the fuel bed. sen (47) for introducing oxidizing agent into the gas space (16), wherein a mass flow of oxidizing agent introduced via the valve-controlled nozzles (47) is controllable in such a way that a specific, desired process temperature profile is established within the reactor (3) in the longitudinal direction (L) from the inlet section (7) of the reactor (3) to the outlet section (9) of the reactor (3).

17. Device (1) according to one of claims 10 to 16, wherein the reactor (3) is a first of at least two reactors (3, 5), wherein a second (5) of the at least two reactors (3, 5) is connected downstream of the first reactor (3) and extends from an inlet section (19) of the second reactor (5) to an outlet section (21) of the second reactor (5), wherein the second reactor (5) also has a mechanical conveying device (17) for conveying a fuel bed within the second reactor (5) from the inlet section (19) of the second reactor (5) to the outlet section (21) of the second reactor (5), wherein the inlet section (19) of the second reactor (5) is connected to the outlet section (9) of the first reactor (3),so that the fuel at least partially decomposed in the first reactor (3) can be fed from the outlet section (9) of the first reactor (3) to the inlet section (19) of the second reactor (5) and coal can be discharged in the outlet section (21) of the second reactor (5).

18. Device (1) according to claim 17, further comprising a dust return, wherein the recirculation system (25) comprises a dust removal device (31) for removing dust from the extracted fuel gas by means of gravity, centrifugal force and / or a filter in a separator, wherein the dust return is connected between the dust removal device (31) and the inlet section (19) of the second reactor (5) in order to return the separated dust to the inlet inlet section (19) of the second reactor (5) for further thermal decomposition. 1 . Device according to claim 17 or 18, wherein the second reactor (5) has a plurality of valve-controlled nozzles (47) distributed in the longitudinal direction (L) of the second reactor (5) and arranged above the fuel bed of the second reactor (5) for introducing oxidizing agent into the gas space of the second reactor (5), wherein a mass flow of oxidizing agent introduced via the valve-controlled nozzles (47) is controllable such that a specific, desired process temperature profile is established within the second reactor (5) in the longitudinal direction (L) from the inlet section (19) of the second reactor (5) to the outlet section (21) of the second reactor (5).

20. Device (1) according to one of claims 14 to 16, wherein the second reactor (5) is arranged parallel to the first reactor (3) below the first reactor (3), wherein the conveying direction of the mechanical conveying device (17) in the second reactor (5) is opposite to the conveying direction of the mechanical conveying device (15) in the first reactor (3).

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