Control method for the operation of a fluidized bed gasifier and fluidized bed reactor

Description

[0001] The present invention relates to a control method for the operation of a fluidized bed gasifier and a correspondingly designed device in the form of a fluidized bed reactor.

[0002] GB 673 648 A concerns the gasification of powdered carbon-containing material.

[0003] EP 1 666 567 A1 describes a gasification reactor with a frustoconical and cylindrical section and means for targeted gas supply.

[0004] EP 1 201 731 A1 discloses a process for gasification with dust separation and optimized process control.

[0005] WO 2005 / 040439 A1 concerns a device made of nickel-based alloy for corrosive high-temperature applications.

[0006] DE 36 17 802 A1 describes a method for loosening solids in a return line of a gasification reactor.

[0007] From DE 10 2007 012 452 A1, a method and a device for the gasification of organic substances in a fluidized bed are known. Fluidized bed gasification describes a staged gasification process in which, after pyrolysis or carbonization of a carbon-containing material, the resulting coke is gasified as completely as possible together with a pyrolysis gas in a fluidized bed reactor to produce a so-called product gas. This fluidized bed reactor comprises a cone-shaped section adjoining an inlet, which widens in a frustoconical shape and transitions into a cylindrical section with an outlet at one end. This body contains a fixed bed, formed from coke from the preceding pyrolysis process, which is suspended in the flow of a gasification agent. This coke is supplied by the appropriate introduction and metering of a gasification agent, such as...Air, held in suspension in an elevated position and continuously converted or gasified into a product gas.

[0008] In a fluidized bed reactor operating at equilibrium, precisely the amount of gasifying agent is introduced to maintain a constant quantity of coke in the reactor. The reduction of coke through the continuous conversion of coke to product gas and the addition of new bio-coke particles are thus balanced. However, due to the typically inhomogeneous composition of the supplied biomass, as well as measurement tolerances in biomass feed and gasifying agent dosing, this equilibrium is practically impossible to achieve and maintain consistently over long periods. Therefore, the fluidized bed reactor must be operated intermittently, with a build-up and reduction phase. This build-up and reduction phase is controlled by adjusting the gasifying agent dosage and monitored via a level measurement in the gasifier.These changes are not possible within the ongoing process without almost constant monitoring and intervention by trained supervisory personnel. With reference to the figures in the attached drawing, the processes during the assembly and disassembly operation of a known fluidized bed gasifier will now be briefly described. Description of the construction operation:

[0009] During the start-up phase, more coke enters the fluidized bed reactor than is currently being mined. As indicated by an arrow in Figure 3 of the accompanying drawing, this increases the amount of gasification coke in the reactor. A section of the fluidized bed reactor, in Figure 3The area, characterized by dense hatching, is constantly being replaced with fresh material, with excess material from this zone being incorporated upwards into the fluidized bed. The fill level in the reactor thus continuously rises, as indicated by the further hatching and the arrow. To prevent the fluidized bed reactor from overflowing, a sensor at its upper end measures the fill level. Description of the mining operation:

[0010] During mining operations, less coke enters the fluidized bed reactor than is mined, see Figure 4This is achieved by limiting the coke input and / or increasing the use of gasification agent. In any case, the amount of gasification coke in the reactor, and thus the thickness of the lubricated bed, continuously decreases. The layer of continuous degradation of the lubricated bed, indicated by dense hatching, is therefore typically reduced from the bottom up in the lubricated bed reactor. However, a characteristic particle size distribution also develops within the coke particles suspended in the lubricated bed reactor: Particles entering from the bottom are generally much larger than particles at the top of the lubricated bed. Therefore, as the overall thickness of the lubricated bed decreases from the bottom up during the degradation process, coke particles with a larger grain diameter are primarily converted into coke particles with a smaller grain diameter.Consequently, the fluidized bed progressively loses porosity and permeability to the produced gas. This reduced permeability results in an increased pressure drop, causing the fluidized bed to migrate upwards without significantly affecting the fill level measured from above in the fluidized bed reactor, as the bed is depleted from the bottom. Such a displaced area is found in... Figure 4 indicated as a hatched additional layer.

[0011] If this degradation effect reaches a critical level, the fluidized bed collapses and transitions into a fluidized bed. Besides comparatively lower efficiency, fluidized bed gasifiers are known to have other negative effects, such as the associated fouling of downstream components by adhering organic degradation products, particularly tar formed in the fluidized bed. If this instability persists for a certain period, it cannot be reversed by switching to a new build-up mode. The fluidized bed must be rebuilt, requiring a lengthy reactor shutdown.

[0012] The point at which a switch from an expansion to a dismantling operation is therefore generally easier to identify and has less serious consequences than the cessation of a mining operation. However, for the most efficient long-term operation possible, switchovers in both directions are necessary. Currently, the necessary decisions are typically made by specially trained monitoring and technical personnel.

[0013] The object of the present invention is to provide a control method and a correspondingly designed device for operating a floating bed gasifier, which ensures reliable and safe long-term operation of a system described above with significantly reduced requirements for monitoring and trained interventions by monitoring personnel.

[0014] This problem is solved by the features of a method according to claim 1 and a device according to the features of claim 10.

[0015] The invention is based on the understanding that the most stable operation possible of the aforementioned fluidized bed reactor requires operation in build-up mode. In this mode, a high material conversion rate with a high gas yield is achieved through the addition of gasifying agent. However, to prevent the fluidized bed from continuously increasing in thickness, it is necessary to also selectively reduce the fluidized bed. To prevent a reduction in the efficiency of the gasification process, or even a collapse of the fluidized bed or an irreversible transition to fluidized bed gasification, the invention, unlike a known control method, does not involve intervention at the reactor inlet by limiting the coke input and / or increasing the use of gasifying agent. Instead, it has been found that gasifying agent can be introduced directly into the fluidized bed for a targeted reduction, which is also easily controllable.

[0016] Accordingly, a method according to the invention is characterized in that a supporting layer of the flotation bed in the flotation bed reactor is constantly operated in a build-up mode and, in a temporally overlapping manner, a dismantling of the flotation bed is carried out by introducing additional gasification agent.

[0017] Advantageous further developments are the subject of the respective dependent claims. A key further development of the invention is the introduction of a distinction between a so-called "load-bearing" part of the flotation bed and a "non-load-bearing" part of the flotation bed, or corresponding layers, which exhibit a partially gradual transition. The load-bearing layer of the flotation bed is characterized by a continuous increase in new, and therefore comparatively coarse-grained, bio-coke, while the non-load-bearing layer consists predominantly of small-grained, largely converted coke granules.

[0018] According to the invention, during operation of the device in setup mode, additional gasifying agent is introduced into the non-load-bearing layer of the flotation bed. This process is carried out using at least one nozzle or lance. In a further development of the invention, lances are used which project into a cylindrical part of the reactor by a length of approximately 10 cm to preferably more than 20 cm, with the additional benefit of significantly minimizing local heating occurring on an adjacent wall of the reactor during injection. The diameter of the reactor in this area can be, for example, approximately 1.5 m or more.

[0019] Particularly advantageous is that these lances are covered during operation by a coke bed or a thickness of the non-load-bearing layer of the molten bed sufficient to ensure the most complete possible conversion of the additionally introduced gasifying agent into product gas. Even without additional injection, the temperatures in this area of ​​the reactor are already around 600°C, i.e., above the auto-ignition temperature of the coke. Therefore, if additional gasifying agent is injected at this point, it reacts immediately with the coke and gasifies it. The injection must therefore take place within the molten bed and thus directly into the coke.The bed above the injection point must be sufficiently high to ensure extensive, ideally complete, conversion of the introduced gasifying agent. This prevents the gasifying agent from reacting with the product gas, thus avoiding a reduction in efficiency and effectively increasing the plant's product gas output. These parameters can be determined and adjusted, for example, during a learning process in a given plant during initial commissioning.

[0020] It is preferred that the additionally introduced gasification agent be distributed among two to approximately 15 lances, preferably about six lances, which in one embodiment of the invention are arranged equidistantly across a circular cross-sectional plane. The lances are advantageously used individually and, in particular, at time intervals to inject the additional gasification agent into the non-load-bearing layer of the suspended bed. This prevents a locally excessive degradation of the non-load-bearing layer of the suspended bed and also limits local heating within the non-load-bearing layer of the suspended bed. Particularly preferably, directly adjacent lances are essentially skipped during a continuous change in the injection of the additional gasification agent in order to ensure the most uniform possible distribution.The uniform degradation of the non-load-bearing layer of the levee bed prevents direct local overheating. With a homogeneous distribution of additional degradation of the non-load-bearing layer of the levee bed, a substantially constant input of additional gasification agent results in a consistent additional yield of product gas.

[0021] Due to the continuous formation of the suspended bed in the supporting layer, the reactor can be operated at maximum capacity relative to the amount of biomass processed or introduced, as maximum permeability of the suspended layer to product gas is consistently ensured. The inventive method described above not only stabilizes continuous operation but also increases the overall plant's effective performance.

[0022] Due to the continuous build-up of the supporting layer, its gas permeability remains largely constant at high values. Instabilities in the bed, even leading to a transition to a fluidized bed, are largely prevented, especially during the bed dismantling process described below. Furthermore, the injection of additional gasifying agent through targeted dismantling in the non-supporting layer increases the conversion of small-grained coke particles into product gas. This further increases the gas yield and thus the overall plant output with only minor structural modifications.

[0023] The key parameter in biomass gasification is the lambda value, or air-fuel ratio, which in gasification plants is typically between approximately 0.3 and 0.4. The lambda value depends on the gasifying agent used, which can be air, oxygen, steam, or even water mist. In a typical embodiment of the invention, such plants are operated within a lambda range of approximately 0.31 to 0.36, where a lambda value of approximately 0.31 characterizes a classic build-up operation and a lambda value of approximately 0.36 a classic decomposition operation. In normal operation with the additional injection of gasifying agent, the lambda value below the suspended bed, i.e., at the reactor inlet, is kept constant at approximately 0.31. The additional injection of gasifying agent in the non-load-bearing layer is varied within a lambda range of approximately 0.00 to 0.05 during control.

[0024] The decision to switch between build-up and decomposition phases in a fluidized bed reactor, specifically in its non-load-bearing layer, by the controlled introduction of additional gasifying agent, is based on a level measurement within the fluidized bed reactor. A sensor or level sensor is provided for this purpose. This level measurement is preferably performed using a radar sensor, one or more rotary paddle switches, or a combination of a radar sensor and at least one rotary paddle switch. Once the level reaches a certain threshold, the rotary paddle switch can be locked, independently confirming a measurement from the radar sensor, thus initiating a controlled decomposition of the fluidized bed in the non-load-bearing section.In the suspended bed reactor, at least two rotary paddle switches, preferably located at different heights in the area of ​​the non-load-bearing layer, are provided for averaging signals for regulating the fill level.

[0025] There are various ways to determine the ideal packing height above the lances, depending on the design, the number of lances, and the reactor's dimensions and power class. The design must ensure that the gasification agent is fully converted. Injecting the gas above the flotation bed would only result in partial combustion of the product gas, without the desired additional gasification reactions occurring within the coke bed. All relevant gasification reactions require the presence of solid carbon, which is present here in the form of the coke grains in the non-load-bearing layer. However, due to the flow direction of the product gas, this carbon cannot be reached by the additionally injected gasification agent.

[0026] Due to the direct contact of the gasification agent with coke, temperatures exceeding 1000°C can occur locally in the injection area, leading to localized slagging depending on the biomass used. To counteract this effect, the temperature can be reduced, depending on the biomass used, by adding, for example, steam, water mist, water-enriched gasification agent, or by recirculating reaction temperature-reducing, possibly inert, gases such as exhaust gas from the gas engine or already produced product gas through the lances into the bed. While an admixture to the gasification agent is not strictly necessary, it is advantageous, at least with regard to temperature limitation.

[0027] A second possibility is the intermittent timing of the injection via the lances, which can be used as an alternative or additional to the aforementioned local temperature reduction, particularly through the addition of additives. Furthermore, spatial and / or temporal diversification of the injection also offers a way to locally limit heating. In this case, one lance is operated for only a short time and then switched to the next lance, for example, with a uniform arrangement of, say, seven lances distributed around the circumference. Spatial separation of the local heating can also be achieved by skipping immediately adjacent lances, i.e., switching from the first to the third lance, and so on, while maintaining essentially the same injection quantity.

[0028] Further features and advantages of embodiments of the invention are explained in more detail below with reference to an exemplary embodiment in comparison to a known device, using the drawing as an illustration. The drawing shows, in schematic representation: Figure 1a: a sectional view of a reduction unit according to an embodiment of the invention; Figure 1b: a temperature profile within the reduction unit of Figure 1a Figure 1c: a detail from Figure 1a Figure 2: a sectional view of a prior art device for the fluidized bed gasification of biomass; Figure 3: a sketch of the fluidized bed structure in the reduction unit; and Figure 4: analogous to the representation of Figure 3 A sketch illustrating the dismantling of the floating bed in the reduction unit.

[0029] Across the various illustrations, the same designations and reference symbols are always used for identical elements and process steps.

[0030] The sketch of Figure 2 Figure 1 shows a device 1 for the fluidized bed gasification of a carbon-containing material or biomass, known from DE 10 2007 012 452 A1, to which full reference is hereby made, as a complete system in a sectional view. The entire process path is shown here, from the feeding of a biomass B into a pyrolysis unit 2 with gas nozzles 3, from there via an oxidation unit or transport section 4 with nozzle unit 5 to the exit of a product gas P from a reduction unit 6 with nozzle unit 7 for the introduction and metering of gasification agent V.

[0031] As indicated by the dotted line in Figure 2The following discussion will focus only on the reduction unit 6 as a fluidized bed reactor: The reduction unit 6 comprises, following the nozzle unit 7, a first section 8 that widens in an approximately frustoconical shape and leads into a cylindrical section 9. This cylindrical section then tapers into a frustoconical section 10, which terminates in an outlet 11 for product gas P. A normal fill level of the reduction unit 6, with a bed of coke fragments in the form of a suspended layer 12 (shown here hatched), is in Figure 2 hinted at.

[0032] The fundamentally different states of construction and dismantling operations were already described at the outset, with reference to the illustrations of the Figures 3 and 4described. Even if an approximate fill level of the suspended layer 12 in the reduction unit 6 can be measured via a level sensor 13 on the now truncated cone-shaped section 10, for reasons of redundancy here by a combination of radar sensor and at least two rotary paddle switches set up at different heights in the area of ​​the non-load-bearing layer 16, and thus an overflow during a build-up operation can be ruled out relatively reliably, every switch to a reduction operation via the nozzle unit for the introduction and metering of gasification agent V into the reduction unit 6 entails at least the production risks described at the beginning and associated with longer downtimes due to the threat of instability of the suspended layer 12.To create a control method and a correspondingly designed device for operating a fluidized bed gasifier that ensures reliable and safe long-term operation of the aforementioned system with significantly reduced monitoring requirements and the need for trained intervention by monitoring personnel, an exemplary embodiment of an improved control method and an adapted device are described below. A key basis is the understanding that the fluidized bed 12 can be divided into a load-bearing layer 15 and a non-load-bearing layer 16. The transition between these layers is generally gradual and can extend over a considerable distance. However, the properties of these layers 15 and 16 within the fluidized bed can be considered reliable. Figure 1a The respective areas marked on the map apply.

[0033] Furthermore, the applicant has recognized that the non-load-bearing layer 16 can be selectively removed separately to reduce the thickness of the suspended bed 12. This is shown in the figure of Figure 1a It is provided that additional gasification agent Vz is introduced into the non-load-bearing layer 16 of the suspended bed 12 in the suspended bed reactor or the reduction unit 6.

[0034] In parallel, the load-bearing layer 15 of the fluidized bed 12 in the reduction unit 6 is continuously operated in build-up mode by means of a corresponding control of the nozzle unit 7. Simultaneously, the fluidized bed 12 is reduced by introducing additional gasification agent Vz into the non-load-bearing layer 16. This prevents overflow or overfilling with coke fragments, even with the overall increased turnover of the expanded fluidized bed reactor 6.

[0035] According to the above description, the following will be carried out in accordance with Figure 1aan injection of additional gasification agent Vz in the upper third of the reactor and ideally in the cylindrical part 9 of the reactor 6. This ensures that the injection into the coke bed always reliably occurs into the non-load-bearing part 16 of the suspended bed 12.

[0036] The illustration of Figure 1bFigure 6 shows a qualitative temperature profile T over the height of the extended fluidized bed reactor 6. During normal operation with additional injection of gasifying agent Vz, a lambda value of approximately 0.31 is maintained below the fluidized bed 12. The additional injection of gasifying agent Vz in the non-supporting layer 16 is varied within a lambda range of approximately 0.00 to 0.05. Accordingly, from the position of the nozzle unit 7, the temperature T rises sharply to nearly constant values ​​of approximately 1,000°C due to the metered injection of gasifying agent Vz. It only drops significantly to values ​​greater than approximately 600°C once the lower edge of the continuously rebuilding supportive layer 15 is reached. Over the remaining part of the first section 8, which widens in an approximately frustoconical shape, up to its junction with the cylinder section 9, the temperature T drops to values ​​around 600°C.This brings us to a section of the non-load-bearing layer 16 into which additional gasification agent Vz is introduced. The temperature T then rises almost instantaneously to values ​​of approximately 1,000°C, before cooling down again to approximately 600°C over a short distance h of coke cover until we leave the non-load-bearing layer 16.

[0037] Figure 1c displays a detail Figure 1awith details of the injection of additional gasification agent Vz into the non-load-bearing layer 16 in the area of ​​cylinder section 9. Accordingly, a pipe section designed as a lance 17 projects a length L of more than approximately 20 cm and a diameter d of approximately 25 mm into the cylinder section 9, which has a diameter of more than approximately 1.5 m, and thus into the coke of the non-load-bearing layer 16. As described above, the temperature T here is still approximately 600°C and thus significantly above the auto-ignition temperature of coke. The injection of additional gasification agent Vz leads to an immediate reaction and gasification of the surrounding coke. A product gas P, already flowing through the non-load-bearing layer 16 at a velocity v, pushes a hot reaction zone 18 in its direction of flow. Even if the reaction zone 18 reaches temperatures of approximately 1.When 000 °C is reached, coke has such good thermal insulation that a distance L of the conversion zone 18 from a wall of the cylinder section 9 is already sufficient to prevent any significant heating here.

[0038] Since injection above the flotation bed 12 or its non-load-bearing part 16 would only lead to partial combustion of the desired product gas P due to the lack of solid carbon or coke, without any significant additional gasification reactions, a sufficiently thick cover layer above the lance 17 must also be ensured. A cover layer thickness h is sufficient when the injected additional gasifying agent Vz has been essentially completely converted into product gas P. This can be measured, so that a corresponding cover height h of the lances 17 with coke from the non-load-bearing part 16 of the flotation bed 12 can be adjusted.

[0039] Another provision concerns the most homogeneous, even, and uniform possible degradation of the non-load-bearing layer 16 by injecting additional gasification agent Vz. For this purpose, in the illustrated embodiment, not only the [missing information] are required. Figure 1a Instead of the two lances 17 indicated, six lances 17 are provided, arranged equidistantly around the circumference of the cylinder section 9. These lances can, in principle, be operated simultaneously. However, due to the possibility of high local temperatures, this can lead to clumping or slagging of the coke in the area of ​​the respective conversion zones 18 over a longer period. This slagging can subsequently impair operation.

[0040] To counteract this, the lances 17 are intermittently supplied with an additionally injected gasifying agent Vz, i.e. .The system switches from one actively injecting lance 17 to the next. Furthermore, lances 17 injected with additional gasifying agent Vz are not directly adjacent to one another, preventing the formation of large areas of deposits or coke clumps in the non-load-bearing layer 16. For example, the first, third, and fifth lances 17 can inject additional gasifying agent Vz consecutively or simultaneously, followed after a short injection process by the second, fourth, and sixth lances 17, and so on.

[0041] Alternatively, the temperature in reaction zone 18 can be reduced by adding water vapor or even water droplets in the form of mist to the additionally injected gasification agent Vz. Besides varying the lambda value, those skilled in the art are aware of other ways to lower the temperature in reaction zone 18, including the addition of inert exhaust gases from the thermal conversion of the product gas P into the additionally injected gasification agent Vz. Reference symbol list

[0042] 1 Device 2 Pyrolysis unit 3 Gas nozzles 4 Oxidation unit / Transport section / Transport unit 5 Nozzle unit 6 Reduction unit / Fluidized bed reactor 7 Nozzle unit for introducing and dosing gasification agent V into the reduction unit 6 8 First section of the reduction unit, widening approximately in a frustoconical shape 6 9 Cylindrical section of the reduction unit 6 10 Section 10 of the reduction unit, tapering in a frustoconical shape 6 11 Outlet of the reduction unit 6 12 Coke granules in the form of a fluidized bed 13 Level sensor 14 15 Load-bearing layer 16 Non-load-bearing layer 17 Lance 18 Hot reaction zone in the non-load-bearing layer 16 B Biomass P Product gas d Diameter h Thickness / Height of the lance cover 17 L Length of a lance 17 in the suspended layer 12 V Gasification agent V Additional gasification agent v Flow velocity of the product gas P in the non-supporting layer 16

Claims

1. A regulating method for operating a floating bed gasifier in which carbonized biomass or coke is kept in suspension in the inflow of a gasification agent (V) as a bed (12) and converted into a product gas (P), in that a hollow body is used as the gasifier, which comprises a region (8) adjoining an inlet with a nozzle unit (7) and widening approximately in the shape of a truncated cone, which transitions into a cylinder section (9) that is provided with an outlet (11) at the end, wherein a fixed bed (12) is formed in this hollow body, which fixed bed is held in suspension in the inflow of gasification agent (V) and is formed from coke from a preceding pyrolysis process, characterized in that a supporting layer (15) of the fixed bed held in suspension is operated in the floating bed reactor (6) with a non-supporting layer (16) lying thereabove constantly in a build-up mode and, for this purpose, a reduction of the floating bed (12) takes place in a temporally overlapping manner, wherein additional gasification agent (Vz) is introduced during the build-up mode by means of injection nozzles which project into the non-supporting layer (16) of the floating bed (12), wherein the injection of the additional gasification agent (Vz) is carried out in dependence on a level control with the measurement of the filling level in the floating bed reactor (6).

2. The regulating method according to the preceding claim, characterized in that an additional gasification agent (Vz) is introduced into a non-supporting layer (16) of the floating bed (12) into the floating bed reactor (6) during operation of the floating bed reactor (6) in the build-up mode.

3. The regulating method according to the preceding claim, characterized in that the introduction of an additional gasification agent (Vz) is carried out using at least one nozzle and / or lance (17) projecting into the floating bed reactor (6).

4. The regulating method according to the preceding claim, characterized in that, during operation, the lances (17) are covered by a coke heap or a thickness (h) of the non-supporting layer (16) of the floating bed (12) sufficient to ensure the most complete possible conversion of the additionally introduced gasification agent (Vz) into a product gas (P).

5. The regulating method according to the preceding claim, characterized in that the thickness (h) is determined as a parameter in the course of a learning process in a respective plant in the course of the initial commissioning and is preferably set on the basis of a determination of a conversion of the additionally introduced gasification agent (Vz) that is as complete as possible.

6. The regulating method according to one of the preceding claims, characterized in that the lances (17) are used individually and particularly at time intervals for injecting the additional gasification agent (Vz) into the non-supporting layer (16) of the floating bed (12).

7. The regulating method according to one of the preceding claims, characterized in that the level control is carried out using a level sensor (13) designed as a radar sensor, as a rotary paddle switch or as a combination of a radar sensor and at least one rotary paddle switch.

8. The regulating method according to one of the preceding claims, characterized in that water vapor or even water droplets in the form of mist and / or inert waste gases from the thermal conversion of the product gas (P) are added to the additionally injected gasification agent (Vz).

9. The regulating method according to one of the preceding claims, characterized in that, in a normal operating mode with additional injection of a gasification agent (Vz), a lambda value below the floating bed (12) is maintained at approximately 0.31 and the additional injection of a gasification agent (Vz) in the non-supporting layer (16) is varied in a lambda window of approximately 0.00 to approximately 0.05.

10. A floating bed reactor (6) which as a hollow body comprises a region (8) which adjoins an inlet with a nozzle unit (7), widens approximately in the shape of a truncated cone and transitions into a cylinder section (9) provided with an outlet (11) at the end, said hollow body containing a fixed bed (12) which is held in suspension in the feed stream of the gasification agent (V) and has a supporting layer (15) and a non-supporting layer (16) located above it, wherein the bed (12) is formed from coke from a preceding pyrolysis process, characterized in that means for injecting an additional gasifying agent (Vz) are provided on said floating bed reactor (6), which means are provided in the upper third of the reactor and / or in the cylinder section (9) and project into the non-supporting part (16) of the floating bed (12), and a level sensor (13) for measuring a filling level of the floating layer (12) in the reduction unit (6) is provided for level control.

11. The floating bed reactor according to the preceding claim, characterized in that the means are configured as nozzles or lances (17).

12. The floating bed reactor according to one of the two preceding claims, characterized in that the means are arranged in the cylindrical part (9) of the hollow body of the reactor (6).

13. The floating bed reactor according to any one of the preceding claims 10 to 12, characterized in that the means are tubes which project by a length (1) of about 10 cm into the one cylindrical part (9) of the reactor (6) and 2 to about 15 lances (17), preferably about 6 lances (17) are provided, which are preferably arranged equidistantly distributed over a circular cross-sectional plane.

14. The floating bed reactor according to any one of the preceding claims 10 to 13, characterized in that the level sensor (13) is configured as a radar sensor, as a rotary paddle switch or as a combination of a radar sensor and at least one rotary paddle switch.

15. The floating bed reactor according to the preceding claim, characterized in that more than two rotary paddle switches set at different levels in the region of the non-supporting layer (16) are provided for controlling the filling level.