Fixed bed gasifier with temperature-homogenization layer
Patent Information
- Application Number
- EP2023712335
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-03-16
- Filing Date
- 2023-03-02
- Publication Date
- 2025-01-22
Smart Images
Figure 1.1
Abstract
Description
[0001] Fixed bed gasifier with temperature homogenization layer
[0002] Description
[0003] Technical area
[0004] The present disclosure relates to a fixed-bed gasifier for generating a product or synthesis gas from solid fuel, in particular from slag-forming fuel, comprising a gasifier vessel, in particular a cylindrical one. The gasifier vessel has a fuel supply for supplying a solid fuel, a gasification agent supply for supplying a gasification agent used to gasify the solid fuel contained in the vessel, and an outlet for removing slag, ash, and product gas produced during the gasification of the solid fuel.
[0005] In a fixed-bed gasifier, (loose) fuel, especially biomass, in a solid state (solid fuel), typically wood or coal, sewage sludge, but also biomass-like and other secondary fuels, as well as domestic waste / plastic fractions, is thermo-chemically converted into a combustible product or synthesis gas (fuel gas) with the aid of a gasification or oxidizing agent, especially air, oxygen, carbon dioxide, or steam. Through gasification in a fixed-bed gasifier, the solid fuel can be converted into a gaseous secondary fuel or product gas, which can be used, for example, in electricity generation or as a fuel (fuel gas), or as synthesis gas for chemical synthesis.
[0006] The fixed bed gasifier or gasifier vessel is divided vertically or axially into different, adjacent temperature zones. The temperature zone closest to the opening is a drying zone, in which the water contained in the solid fuel is evaporated at a drying temperature. Vertically below the drying zone there is a pyrolysis zone. In the pyrolysis zone the solid fuel is decomposed at a pyrolysis temperature. Vertically below the pyrolysis zone there is an oxidation zone. In the oxidation zone the carbon (C) and hydrogen (H) contained in the decomposed solid fuel are oxidized at an oxidation temperature to form carbon dioxide (CO2) and water (H2O) respectively. Vertically below the oxidation zone there is a reduction zone. In the reduction zone the carbon dioxide (CO2) and hydrogen (H) contained in the oxidation zone are oxidizedThe water (H2O) is reduced at a reduction temperature to form the combustible product or synthesis gas as a product of fixed-bed gasification. In the fixed-bed gasifier, the drying temperature is lower than the pyrolysis temperature, which in turn is lower than the oxidation temperature, which in turn is higher than the reduction temperature. Carbonaceous ash remains as a permanent component of the gasified solid fuel.
[0007] Furthermore, fixed-bed gasifiers can be used to gasify slag-forming fuels or biomass, especially biological residues, preferably waste, and more preferably sewage sludge, as fuel. The gasification of such slag-forming fuels, especially sewage sludge, serves the environmentally friendly disposal of these materials.
[0008] In fixed-bed gasification, particularly in cases where slag-forming fuels such as waste are used as the biomass to be gasified, the oxidation temperature varies / fluctuates depending on the material used. Although the oxidation temperature is maintained within a certain range, large temperature gradients occur in the gasification vessel, particularly during start-up and shut-down of the fixed-bed gasifier (when starting and stopping gasification). The temperature gradients (local temperature differences) occur primarily in the vertical or axial direction (along the longitudinal axis of the fixed-bed gasifier or gasification vessel), as well as in the circumferential and possibly also in the radial direction. For temperature gradients that are greater than a certain limit temperature gradient, the gasification vessel undergoes plastic and thus permanent deformation and must be exchanged or replaced after a short time. This is not economical.Heat-resistant materials such as concrete, fireclay, or ceramics lack thermal shock resistance to withstand the rapid and significant temperature changes (temporal temperature differences) in these relatively small systems. They break and crumble after a short period of time.
[0009] Accordingly, it is an object of the present disclosure to provide a fixed-bed gasifier that solves the problem described above. In particular, a fixed-bed gasifier is to be provided whose operation is economical in the long term. Preferably, a fixed-bed gasifier is to be provided in which large temperature gradients, particularly in the vertical and circumferential directions and, if appropriate, in the radial direction of the fixed-bed gasifier, are avoided.
[0010] The problem underlying the disclosure is solved by a fixed bed gasifier according to claim 1.
[0011] Accordingly, the present disclosure relates to a fixed-bed gasifier for generating a product or synthesis gas from solid fuels, in particular from slag-forming fuels, comprising a gasifier vessel, in particular a cylindrical one. The gasifier vessel has a fuel supply for supplying a solid fuel, one or more gasification agent supplies for supplying one or more gasification agents used to gasify the solid fuel contained in the vessel, and an outlet for removing slag, carbonaceous ash, and product and synthesis gas produced during the gasification of the solid fuel.At least a section of a container wall of the carburetor container, in particular of a carburetor insert in the carburetor container, is surrounded by a temperature homogenization layer whose thermal conductivity is (significantly) greater than the thermal conductivity of the container wall and which ensures a uniform temperature distribution in the container wall in the axial direction and circumferential direction of the carburetor container.
[0012] By attaching the temperature homogenization layer to the gasifier vessel, especially in the gasifier insert, where large temperature gradients of 450 K or even more can occur, the temperature is distributed evenly and homogeneously across the vessel wall. Since the temperature homogenization layer has a significantly higher thermal conductivity than the vessel wall, previously different temperature ranges in this temperature homogenization layer balance each other out. Thus, large temperature gradients of 450 K or even more are avoided. If temperature gradients still occur in the vessel wall at all, they are significantly smaller than 450 K, for example, a maximum of 200 K. Thus, thanks to the
[0013] The temperature homogenization layer prevents the vessel wall from warping or permanently plastically deforming, thus significantly extending the service life of the carburetor vessel, especially the carburetor insert. This process ensures long-term, economical use despite frequent start-up and shut-down of the carburetor.
[0014] When the fixed-bed gasifier heats up, the gasifier vessel, especially the gasifier insert, quickly reaches its operating temperature of approximately 700°C to approximately 900°C. Regardless of the operating mode of the disclosed fixed-bed gasifier, the temperature remains within the operating temperature range of approximately 700°C to approximately 900°C, even when the fixed-bed gasifier is stopped. Temperature peaks of 1000-1700°C can occur occasionally in the bed during this process.
[0015] Advantageous aspects of the present disclosure are the subject of the dependent claims and are explained in more detail below.
[0016] Advantageously, the thermal conductivity of the temperature homogenization layer is at least 3.8 times, preferably at least 9 times, more preferably at least 19 times, greater than the thermal conductivity of the container wall.
[0017] With such differences in thermal conductivity between the temperature homogenization layer and the container wall, it can be ensured that the temperature can be distributed sufficiently evenly across the container wall. In particular, it can be provided that the container wall forms an inner shell which, together with an outer shell spaced from the inner shell, in particular in the radial direction, encloses the temperature homogenization layer, and the thermal conductivity of the temperature homogenization layer is also greater than the thermal conductivity of the inner and outer shells. The inner and outer shells preferably form an annular channel in which the temperature homogenization layer is accommodated.
[0018] Temperatures of up to 1700°C can occur in a fixed-bed gasifier. The temperature homogenization layer can reach up to 1200°C. The melting point of the material forming the temperature homogenization layer may be reached during this process. To prevent the molten temperature homogenization layer from simply "flowing away," it is enclosed by the inner and outer shells and thus remains in the corresponding section of the vessel wall. Because the thermal conductivity of the inner and outer shells is lower than the thermal conductivity of the temperature homogenization layer, heat is not dissipated from the gasifier vessel. This is positive with regard to the energy balance of the fixed-bed gasifier and ensures that a high level of efficiency is maintained in the fixed-bed gasifier.
[0019] Due to the temperature homogenization layer, the inner and outer shell remain below their melting temperature, even though the temperatures in the bulk material may be above the melting temperature of the inner and outer shell material.
[0020] Preferably, an outer and inner shell is provided for the container wall or for the carburetor insert, the materials of which are to be selected so that their melting point is above the maximum temperatures reached in the temperature homogenization layer, in particular above 1200°C.
[0021] This prevents the container wall or the outer and inner shells of the carburetor insert from melting. In particular, it can be advantageous if the outer shell and inner shell are made of the same material. Furthermore, in view of the core concept of the present disclosure, it is very useful if the temperature homogenization layer is made of a different material than the container wall or the inner shell, and in particular also than the outer shell.
[0022] It is desirable that the temperature homogenization layer is made of a material that has a thermal conductivity of at least 190 W / mK.
[0023] If the temperature homogenization layer has such a high thermal conductivity, it can be ensured that the temperature can be distributed sufficiently evenly across the container wall. The higher the thermal conductivity of the temperature homogenization layer, the more even the temperature distribution in the container wall.
[0024] Furthermore, it is preferred that in the gasification vessel, the solid fuel is gasified in different temperature zones which are successive or adjacent to one another in the axial direction and which in particular have a drying zone, a pyrolysis zone, an oxidation zone and a reduction zone, and that the section of the vessel wall of the gasification vessel which is surrounded by the temperature homogenization layer extends at least (in the axial direction) over the area of the different temperature zones.
[0025] The greatest temperature gradients in the fixed-bed gasifier occur in the area of the different temperature zones within the gasification vessel. Accordingly, it is particularly useful to provide the temperature homogenization layer at this location or in this area. This is where the temperature homogenization layer has the greatest effect on the uniform temperature distribution in the fixed-bed gasifier. It is also conceivable for the vessel wall to be made of stainless steel or carbon steel, preferably stainless steel, and for the temperature homogenization layer to be made of copper, aluminum, silver, or alloys thereof, preferably copper.
[0026] If stainless steel or black steel is used for the vessel wall or the inner shell and preferably also for the outer shell and copper, aluminum, silver or alloys thereof for the temperature homogenization layer, it can be ensured that the thermal conductivity of the temperature homogenization layer is sufficiently greater than that of the vessel wall.
[0027] Stainless steel has a thermal conductivity of 21 W / mK, black steel a thermal conductivity of 50 W / mK, aluminum a thermal conductivity of 190 W / mK, copper a thermal conductivity of 400 W / mK and silver a thermal conductivity of 427 W / mK.
[0028] It is particularly advantageous if the inner and outer jackets are each made of stainless steel and the temperature homogenization layer is made of copper.
[0029] If stainless steel is used for the inner shell or the vessel wall, sufficient scale resistance of the inner shell or vessel wall can be ensured. Stainless steel has a higher scale resistance than black steel. High scale resistance is particularly crucial given the high maximum temperatures in a fixed-bed gasifier. Scale is the solid product formed at high temperatures when a metal reacts with its environment, particularly its gaseous environment. Scaling leads to the destruction of the metallic material. A metal's high scale resistance counteracts scaling of that metal. Furthermore, the copper in the temperature homogenization layer has such a positive effect on the stainless steel shell (inner and outer shell together) that, due to its particularly temperature-homogenizing effect, the stainless steel shell does not warp (which would occur with large temperature fluctuations or gradients).Compared to silver, copper is significantly cheaper, and its thermal conductivity is sufficient for the temperature-homogenizing effect of the temperature-homogenizing layer. While the thermal conductivity of aluminum is sufficient for the temperature-homogenizing effect of the temperature-homogenizing layer, that of copper is significantly better.
[0030] It is also advantageous if the carburetor insert (with temperature homogenization layer and outer jacket) is surrounded by a temperature insulation layer.
[0031] The temperature insulation layer reinforces the temperature homogenizing effect of the temperature homogenizing layer.
[0032] Furthermore, it is useful if the temperature insulation layer has a significantly lower thermal conductivity than the container wall, in particular a maximum thermal conductivity of 0.04 W / mK.
[0033] If the temperature insulation layer has a significantly lower thermal conductivity than the container wall and in particular than the outer casing, it prevents the heat generated in the carburetor container from being transferred to the environment.
[0034] It may be that a higher performance of the carburetor used is desired. The greater the desired performance of the fixed-bed gasifier, the larger the diameter, especially the inner diameter, of the carburetor vessel should be.
[0035] Due to this simple relationship, the performance of the fixed bed gasifier can be easily adjusted by adjusting the gasifier container diameter.
[0036] It can be provided that the thickness of the temperature insulation layer increases with increasing diameter, in particular inner diameter, of the section of the container wall of the carburetor container, in particular of the carburetor insert, which is surrounded by the temperature homogenization layer; and the thickness of the temperature insulation layer decreases with increasing thickness of the temperature homogenization layer.
[0037] In this way, it can be ensured that the temperature insulation layer always sufficiently insulates the carburetor container from the environment.
[0038] It is useful that, if the temperature homogenization layer is made of a material that has a thermal conductivity of at least 190 W / mK, preferably made of copper, with a diameter, in particular inner diameter, of the section of the container wall of the gasification container that is surrounded by the temperature homogenization layer of up to 600 mm, the thickness of the temperature homogenization layer is between 3 mm and 5 mm, in particular 5 mm, and with a diameter, in particular inner diameter, of the section of the container wall of the gasification container that is surrounded by the temperature homogenization layer of equal to or greater than 600 mm to 1000 mm, the thickness of the temperature homogenization layer is between 5 mm and 7 mm, in particular a maximum of 7 mm.
[0039] Such a selection of the thickness of the (copper) temperature homogenization layer depending on the diameter of the section of the vessel wall of the gasifier vessel that is surrounded by the temperature homogenization layer ensures that the temperature homogenizing effect of the (copper) temperature homogenization layer is ensured for each fixed bed gasifier size.
[0040] The following Table 1 shows the relationships between the diameter of the section of the gasification vessel wall surrounded by the temperature homogenization layer (simply referred to as section diameter), the thickness of the (copper) temperature homogenization layer (simply referred to as layer thickness) and the thickness of the temperature insulation layer (simply referred to as insulation thickness):
[0041] Table 1
[0042] It is also advisable if the container wall, which is particularly made of stainless steel, or the inner shell has a wall thickness of 3 mm to 4 mm.
[0043] A vessel wall of this material thickness can adequately withstand the mechanical forces resulting from slag formation in the oxidation zone. If the vessel wall is thicker than 4 mm, e.g., 5 mm or thicker, heat transfer to the temperature homogenization layer is poorer than with the preferred vessel wall thickness.
[0044] It is an advantageous aspect of the present disclosure that the gasifier vessel has a downcomer into which both the gasification agent supply and the fuel supply discharge, and a gasifier insert or combustion chamber insert formed separately from the downcomer, which insert has the outlet for removing slag and carbonaceous ash, as well as product and synthesis gas, and forms an inner shell, outer shell, and temperature homogenization layer. If the gasifier has a gasifier insert formed separately from the downcomer, the gasifier insert can be easily replaced independently of the remaining fixed-bed gasifier components. Furthermore, the combination of vessel wall or inner shell with temperature homogenization layer and preferably with outer shell is particularly easy to manufacture in the form of a gasifier insert.
[0045] Preferably, the carburetor insert and the drop shaft are thermally separated, so that temperature homogenization only needs to be ensured in the area or over the length of the carburetor insert.
[0046] It is useful if the carburettor insert is connected via a holder, which is in particular a stable insulating plate, directly, i.e. without an intermediate element, or indirectly, e.g. via the drop shaft, to a carburettor casing that at least partially surrounds the carburettor container.
[0047] Short description of the characters
[0048] Fig. 1 is a schematic longitudinal sectional view of a fixed bed gasifier;
[0049] Fig. 2 is a schematic longitudinal sectional view of a carburetor insert;
[0050] Fig. 3 is a schematic plan view of two rollers;
[0051] Fig. 4 is a schematic longitudinal sectional view of two rollers arranged side by side; and
[0052] Fig. 5 is a simplified schematic longitudinal sectional view of a fixed bed gasifier with more than two rollers.
[0053] Description of the aspects of the present disclosure Aspects of the present disclosure are described below based on the accompanying figures. The aspects presented are merely exemplary and may be combined with one another where technically feasible.
[0054] Fig. 1 is a schematic longitudinal sectional view of a fixed-bed gasifier F. The fixed-bed gasifier F described below is particularly suitable for the gasification of slag-forming solid fuels, in particular waste, e.g. sewage sludge. The fixed-bed gasifier F has a gasifier vessel VB. The gasifier vessel VB has, in its uppermost section viewed in the axial direction or height direction H, a fuel feed 1 as well as a main gasification agent feed 2a and a secondary gasification agent feed 2b. The (solid) fuel to be gasified, in particular slag-forming fuel, is fed to the gasifier vessel VB via the fuel feed 1. A gasification agent, such as air, oxygen, water vapor or carbon dioxide, is fed to the gasifier vessel VB of the fixed-bed gasifier F via the gasification agent feeds 2a, 2b.The gasification vessel VB has a chute 3, to the uppermost section of which, in a vertical direction H, the fuel supply 1 and the gasification agent supply lines 2a, 2b are connected. The chute 3 opens with its lowermost section into a, in particular, pressure-tight, gasification casing 4. The chute 3 is hollow-cylindrical.
[0055] The main gasification agent feed 2a is used in every operating mode of the fixed-bed gasifier F. The secondary gasification agent feed 2b is used when the system is operated with oxygen and water vapor / carbon dioxide. The pressure-tight gasifier shell 4 is essentially hollow-cylindrical. On its upper side (topmost side of the gasifier shell 4 in the vertical direction H), the gasifier shell 4 has an opening 5 through which the downcomer 3 is connected to the gasifier shell 4. The upper part of the fixed-bed gasifier F, i.e., the downcomer 3 with fuel feed 1 and main gasification agent feed 2a as well as secondary gasification agent feed 2b, forms a flange 5 and is flange-mounted to the gasifier shell 4.The flange connection between the upper part of the fixed bed gasifier F and the gasifier jacket 4 is sealed gas-tight to the environment so that no gas can escape from the fixed bed gasifier F between the upper part of the fixed bed gasifier F and the gasifier jacket 4.
[0056] In the gasification vessel VB, which extends into the gasification shell 4, successive, different temperature zones 6 to 9 are present within the gasification shell 4 in the height direction H. The uppermost temperature zone viewed in the height direction H of the fixed bed gasifier F is the drying zone 6. At a drying temperature of approximately 100°C, the water contained in the fuel is evaporated here. Below this is the pyrolysis zone 7, in which the fuel is decomposed at a pyrolysis temperature of up to 250°C. Below the pyrolysis zone 7 is the oxidation zone 8, in which the carbon and hydrogen present in the fuel are oxidized to carbon dioxide and water at an oxidation temperature of up to 1700°C (see above).Below oxidation zone 8 is reduction zone 9, the lowest section of the gasification vessel VB. In this zone, the carbon dioxide and water obtained in oxidation zone 6 are reduced at a reduction temperature between 600°C and 800°C. After reduction, the finished product, namely a product or synthesis gas, is obtained.
[0057] Carbonaceous ash and slag remain as solid residues from the gasification in temperature zones 6 to 9 in the fixed-bed gasifier F. These are discharged into the gasifier shell 4 via an outlet on the gasifier vessel VB (lowest section of the gasifier vessel VB in the vertical direction H), which is arranged within the gasifier shell 4. In order to remove these solid residues from the gasifier shell 4 and to guarantee homogeneous bed conditions in the gasifier shell 4, the solid residues are conveyed into an ash and gas outlet 11 by means of at least two counter-rotating rollers 10 (described in more detail with reference to Fig. 3 to Fig. 5), which are arranged in a lower section of the gasifier shell 4 (viewed in the vertical direction H). The gasifier shell 4 tapers conically towards the ash and gas outlet 11. The solid residues and the product gas obtained from the fixed bed gasifier F are removed via the ash and gas outlet 11.The section of the carburetor vessel VB in which temperature zones 6 to 9 are located is designed here as a carburetor insert 12 formed separately from the downcomer 3. The carburetor insert 12 is arranged within the carburetor casing 4 and extends in the vertical direction H. The carburetor insert 12, like the downcomer 3, has a hollow cylindrical shape. The diameter, in particular the inner diameter, of the carburetor insert 12 advantageously corresponds to the diameter, preferably the inner diameter, of the downcomer 3. The carburetor insert 12 limits the diameter of the temperature zones 6 to 9 to its own inner diameter.
[0058] The side of the carburetor insert 12 facing a central longitudinal axis M of the carburetor vessel VB, which forms at least a portion of the vessel wall of the carburetor vessel VB, is referred to as the inner shell 13. The inner shell 13 is advantageously made of stainless steel. Together with an outer shell 14, which is spaced parallel from the inner shell 13, the inner shell 13 encloses a temperature homogenization layer 15. The outer shell 14 is advantageously also made of (stable) stainless steel. In particular, copper is used as the temperature homogenization layer 15. The copper ensures that the temperature is optimally distributed homogeneously in the vertical direction H and in the circumferential direction of the carburetor vessel VB.
[0059] The carburetor insert 12, in particular its uppermost section in the vertical direction H, is connected to the downcomer 3, in particular to its lowermost section in the vertical direction H, by means of a holder 16. The holder 16 is a type of flange that is flange-mounted to the carburetor insert. An insulating plate can be attached as a seal for the two flanges. This insulating plate thermally insulates the carburetor insert 12 from the downcomer 3. Furthermore, a temperature-insulating layer 17 is provided between the outer casing 14 and the inner wall of the carburetor casing 4. The temperature-insulating layer 17 reinforces the temperature homogenization or even temperature distribution inherent in the carburetor insert 12 and thus reduces or even prevents temperature gradients within the carburetor container VB or the carburetor insert 12.The temperature insulation layer 17 is hollow cylindrical and surrounds the carburetor insert 12 from the outside.
[0060] Fig. 2 is a schematic longitudinal sectional view of the gasifier insert 12. It is clearly visible how the temperature homogenization layer 15 is enclosed or encompassed by the inner shell 13 and the outer shell 14. The temperature homogenization layer 15 can, under certain circumstances, melt or liquefy at very high temperatures (from approximately 1085°C for copper). Since temperatures of up to 1700°C occur in the fixed-bed gasifier F, the copper can melt. Enclosing the temperature homogenization layer 15 by the inner shell 13 and outer shell 14 prevents the temperature homogenization layer 15 from "flowing away."
[0061] Fig. 3 is a schematic plan view of two intermeshing rollers 10 arranged in the gasifier shell 4, particularly directly below the outlet of the gasifier vessel VB. With the help of the rollers 10, fine and coarse ash or slag particles are conveyed axially symmetrically and proportionally to a roller speed. The rollers 10 thus support trouble-free continuous operation of the fixed-bed gasifier F and good gas quality (little or no contaminated gas). The center distance between the two rollers 10 corresponds at least to the diameter of the gasifier insert 12.
[0062] The rollers 10 consist of a plurality of annular roller discs 18,
[0063] 19. The annular roller discs 18, 19 are arranged one behind the other along the roller's longitudinal axis W and are connected to each other in a rotationally fixed or integral manner. Roller discs 18 with a smooth outer circumference alternate with roller discs 19 with teeth distributed over their outer circumference.
[0064] 20. The roller discs 19 with teeth 20 are larger in diameter by the number of teeth 20 than the smooth roller discs 18. The smooth roller discs 18 of one roller 10 each contact the roller discs 19 with teeth 20 of the other roller 10 arranged next to it. In this way, the two adjacent rollers 10 clean each other. At least one tooth 20 meshes with the corresponding tooth 20 of the adjacent roller 10 in the longitudinal direction of the roller.
[0065] Fig. 4, like Fig. 1, shows a longitudinal sectional view of two intermeshing and counter-rotating rollers 10, which rotate relative to each other at the top (carburettor insert side) and thus form a roller pair. The arrow D in the respective roller 10 indicates their direction of rotation. It can be seen that the rollers 10 rotate relative to each other. In doing so, the rollers 10 rotate away from the outlet of the gasification vessel VB (see Fig. 1). The teeth 20 of the interacting rollers 10 of a roller pair engage and mesh with one another. As a result, the teeth 20 grasp and crush lumpy slag. The teeth 20 of a roller disk 19 differ in size and are divided into teeth 20 and smaller teeth 20, which are smaller than the teeth 20. The teeth 20 and the smaller teeth 20 alternate over the outer circumference of the respective roller disc 19.The rollers 10 are arranged and aligned with one another in such a way that a tooth 20 of one roller 10 meshes or interacts with a tooth 20 of the other roller 10 of the roller pair arranged next to it, and a smaller tooth 20 of one roller 10 meshes or interacts with a smaller tooth 20 of the other roller 10 of the roller pair arranged next to it. In particular, the longitudinal shaft axes W of the two adjacent rollers 10, 10 are parallel to one another. In addition, the teeth 20 on the roller disks 19 are arranged spirally or helically with respect to the respective roller longitudinal axis W. This ensures that only one pair of teeth 20 of the roller pair is in engagement at any one time. Advantageously, this minimizes the drive power for the rollers 10 and the load on a roller bearing.
[0066] Furthermore, the rollers 10 can reach very high temperatures, as the ash and slag they convey have temperatures of up to 1000°C. Cooling of the rollers 10 is therefore necessary. Accordingly, the rollers 10 are arranged on hollow shafts 21 for cooling. A coolant, in particular water or oil, flows through the hollow shafts 21 to cool the rollers 10. Thanks to this type of cooling, inexpensive or simple seals and bearings, in particular radial shaft seals, can be used in the fixed-bed gasifier F. Advantageously, the coolant flowing past the hot rollers 10 and thus heated can be used to dry the solid fuel. It is particularly useful to dry the solid fuel outside the fixed-bed gasifier F using the heat from the heated coolant.
[0067] The fixed bed gasifier F can be scaled taking into account the ratio of the roller center distance to the inner diameter of the gasifier insert 12.
[0068] Fig. 5 is a simplified schematic longitudinal sectional view of the fixed-bed gasifier F with four rollers 10 arranged side by side. For simplicity, only the gasifier insert 12 is shown here, as well as the temperature zones 6 to 9 occurring within the gasifier insert 12. Four rollers 10 are arranged below the gasifier insert 12 at a height in the vertical direction H. The center distance of the two outermost rollers 10 corresponds at least to the inner diameter of the gasifier insert 12. Each roller 10 rotates in the opposite direction to the roller(s) 10 arranged next to it. The outer rollers 10 and the inner rollers 10 arranged directly next to it each form a roller pair. In the event that more than one pair of rollers is provided in the fixed-bed gasifier F, the rollers 10 are smaller and have a greater distance from the oxidation zone 8 or from the reduction zone 9 than in comparison with a fixed-bed gasifier F which has only one pair of rollers.The rollers 10 of one roller pair rotate toward each other. The inner rollers 10 of the respective different roller pairs rotate away from each other. The rollers 10 are constructed as shown in Figures 3 and 4 and arranged such that the roller discs 18 without teeth of one roller are opposite the roller discs 19 with teeth of another (adjacent) counter-rotating roller, and vice versa.
[0069] I Fuel supply
[0070] 2a Main gasification agent supply
[0071] 2b Secondary gasification agent supply
[0072] 3 Drop shaft
[0073] 4 carburetor casing
[0074] 5 Opening
[0075] 6 drying zone
[0076] 7 Pyrolysis zone
[0077] 8 Oxidation zone
[0078] 9 Reduction zone
[0079] 10 rollers
[0080] II Ash and gas extraction
[0081] 12 Carburettor insert
[0082] 13 Inner jacket
[0083] 14 Outer jacket
[0084] 15 Temperature homogenization layer
[0085] 16 Bracket
[0086] 17 Temperature insulation layer
[0087] 18 smooth roller disc
[0088] 19 Roller disc with teeth
[0089] 20 teeth
[0090] 21 Hollow shaft
[0091] D Direction of rotation of roller
[0092] F fixed-bed gasifier
[0093] H Altitude direction
[0094] M center axis carburetor tank
[0095] R Radial direction
[0096] VB carburetor tank
[0097] W longitudinal axis of the roll
Claims
Claims 1. Fixed-bed gasifier (F) for producing product or synthesis gas from solid fuel, in particular from slag-forming fuel, comprising a gasifier container (VB), in particular a cylindrical one, which has: a fuel feed (1) for supplying a solid fuel, at least one gasification agent feed (2a, 2b) for supplying at least one gasification agent which serves to gasify the solid fuel located in the container (VB), and an outlet for removing slag and product and synthesis gas which are produced during the gasification of the solid fuel, characterized in that at least a section of a container wall of the gasifier container (VB) is surrounded by a temperature homogenization layer (15) which extends along the container wall,whose thermal conductivity is greater than that of the container wall and which ensures a uniform temperature distribution in the container wall in the axial and circumferential directions of the gasifier container (VB).
2. Fixed-bed gasifier (F) according to claim 1, characterized in that in the gasifier container (VB) the solid fuel is gasified in different axially successive temperature zones (6 to 9), which in particular have a drying zone (6), a pyrolysis zone (7), an oxidation zone (8) and a reduction zone (9), and the section of the container wall of the gasifier container (VB) which is surrounded by the temperature homogenization layer (15) extends at least over the area of the different temperature zones (6 to 9).
3. Fixed bed gasifier (F) according to claim 1 or 2, characterized in that the container wall is made of stainless steel or carbon steel, and the temperature homogenization layer (15) is made of a material having a thermal conductivity of at least 190 W / mK, preferably made of copper, aluminum, silver or alloys thereof.
4. Fixed bed gasifier (F) according to one of claims 1 to 3, characterized in that the container wall forms an inner shell (13) which, together with an outer shell (14) spaced apart from the inner shell (13), in particular in the radial direction, encloses the temperature homogenization layer (15) and the thermal conductivity of the temperature homogenization layer (15) is greater than the thermal conductivity of the inner and outer shell (13, 14).
5. Fixed bed carburetor (F) according to claim 4, characterized in that the inner jacket (13) and the outer jacket (14) are each made of stainless steel and the temperature homogenization layer (15) is made of copper.
6. Fixed bed gasifier (F) according to one of claims 1 to 5, characterized in that the temperature homogenization layer (15), but preferably the outer shell (14), is surrounded by a temperature insulation layer (17).
7. Fixed bed gasifier (F) according to claim 6, characterized in that the temperature insulation layer (17) has a significantly lower thermal conductivity than the container wall, in particular a maximum thermal conductivity of 0.04 W / mK.
8. Fixed-bed gasifier (F) according to one of claims 1 to 7, characterized in that the temperature homogenization layer is made of a material having a thermal conductivity of at least 190 W / mK, and for a diameter, in particular inner diameter, of the section of the container wall of the gasifier container (VB) surrounded by the temperature homogenization layer (15) of up to 600 mm, the thickness of the temperature homogenization layer (15) is between 3 mm and 5 mm, in particular 5 mm, and for a diameter, in particular inner diameter, of the section of the container wall of the gasifier container (VB) surrounded by the temperature homogenization layer (15) of 600 mm to 1000 mm, the thickness of the temperature homogenization layer (15) is between 5 mm and 7 mm.
9. Fixed bed gasifier (F) according to one of claims 1 to 8, characterized in that the gasifier container (VB) has a drop chute (3) into which both the fuel supply (1) and the at least one gasification agent supply (2) open, and a gasifier insert (12) designed separately and thermally separated from this, which has the outlet for removing slag and product and synthesis gas.