EP2377911B1 - Method and device for creating fuel gas from a solid fuel - Google Patents

Description

State of the art

The invention relates to a method and apparatus for producing fuel gas from a solid fuel in a shaft gasifier, which is designed as a fixed-bed gasifier.

For the production of fuel gas from a solid fuel multistage gasification processes are known, with which the problem of tar load to be met ( DE 198 46 805 A1 and DE 44 04 673 C2 ). In these methods, a fuel gas is generated in a pyrolysis stage, which contains a high tar load. In a downstream oxidation stage, the tar load together with the fuel gas by a high-temperature oxidation at a temperature of well above 1000 deg. C either thermally cracked and / or oxidized. In general, the oxidation state is operated with air or oxygen. In this case, temperatures above the ash melting point of the fuel used are achieved. The process is generally substoichiometric. The exhaust gas from the oxidation stage is then subjected to a reduction reaction with in-house produced coke (eg charcoal), whereby the combustion products (CO2 and H2O) with the coke to the combustible gas components CO and H2 react. In this case, a large part of the heat energy contained in the exhaust gas is consumed. The generated combustible gas is intended for use in internal combustion engines and gas turbines.

However, if, as in the known processes, the gas stream from the pyrolysis stage is passed through the oxidation stage and air or oxygen is used as the oxidizing agent, very high temperatures are required to destroy the tar constituents (> 1300 ° C.). Since the process proceeds clearly substoichiometric, the destruction is based more on a thermal splitting than on an oxidation. At the same time result within the oxidation stage due to high dust loading of the pyrolysis gases procedural difficulties with the handling of the forming liquid slag, which also partially discharged with the gas stream and enters the reduction zone and hardens there. Also, the following reduction stage must be constructively designed for the high temperature level of the incoming gas stream.

At the same time the addition of a correspondingly large amount of combustion air (or oxygen) is required to heat the entire amount of gas from the pyrolysis. This results in a considerable demand for reducing carbon, which is usually generated internally in the process, but must also be transported to the reduction stage and there the required reaction space must be made available. The transport of the Reduktionskokses can take place both in the gas stream, as in the in DE 198 46 805 A1 disclosed method, as well as separated from the gas flow in dedicated conveyors, as in DE 44 04 673 C2 disclosed. The transport in external conveyors is technically complex and subject to heat losses. The coke must not be coarse and may require mechanical pretreatment. This process is considerably more difficult due to mineral or metallic foreign bodies contained in the coke. Because of the required comminution of the coke, a fixed bed design of the reduction stage is only suitable to a limited extent, while a fluidized reduction stage requires a greater outlay.

Out FR 979542 For example, a gasifier is known in which solids are gasified in a boiler to fuel gas and the fuel gas is passed through a filter assembly before it is led out of the gasifier through an outlet opening. The filter assembly is in direct contact with the boiler wall towards the boiler.

Another way for the reducing coke from the pyrolysis stage to the reduction stage is the cyclic transport through the oxidation stage, as in DE 198 46 805 A1 disclosed. Because of the occurring short-term temperature fluctuations, this approach can lead to instabilities in the operation of the oxidation state.

The raw gas produced in carburetors has a more or less large amount of dust. The load is essentially dependent on the design of the carburettor, the starting materials and the mode of operation. Fixed bed gasifiers often have raw gas dust loadings of 2 - 8 g / Nm <3>. The raw gas dust loadings of fluidized bed gasifiers are even higher.

Due to the high dust load, gasification raw gases are to be dedusted for further use. The target values for clean gas dust loading are dependent on the requirements of the gas utilization facilities. In practice, for example, for applications with heat engines clean gas dust loads of up to 50 mg / NM <3> is required. The target values for this application are 5 mg / Nm <3>.

For the dedusting of the raw gas, the well-known methods such. Cyclone, electrostatic filters, fabric filters, hot gas filtration, scrubbers, etc. to disposal. The target values of 5 mg / Nm <3> required above can be achieved, for example, with fabric filters or hot gas filters. When using fabric filters, the dust-laden raw gas is initially at the typical temperature range of the filter materials 80 - 250 deg. C to pre-cool. In terms of process technology, the dust load proves to be a hindrance.

On the other hand, the use of hot gas filtration is particularly advantageous, since here, without intermediate cooling in the typical temperature range of the raw gas of 400 to 800 ° C. C common filter elements, such as e.g. Filter candles made of glass fiber, sintered metal or ceramic, can be used. These elements are arranged in corresponding independent filter apparatuses. In addition to the fact that a separate and for the operating temperature range appropriately designed filter apparatus is needed, the problem of discharging the filter ash deposited in the filter is to be solved. In particular, the high operating temperatures and other requirements serving for explosion protection lead to cost-intensive designs.

Summary of the invention

The object of the present invention is to provide a method and an apparatus for the simple and economic production of low-tar and dust-free fuel gas by multi-stage gasification of solid fuels. The procedure is process-technically stable and has improved operating parameters. The fuel gas produced is intended for use in heat engines.

Object of the present invention is also to provide measures for the dedusting of raw gas from a gasification plant, which takes place by the integration of the hot gas filtration in the carburetor in a manner that neither a separate filter housing nor an independent discharge of the filter ash is required.

The invention as characterized in the claims provides a method of producing fuel gas from a solid fuel, comprising the steps of: supplying the fuel into a pit gasifier formed as a descending fixed bed reactor; Degassing of the fuel in a degassing zone of the shaft gasifier by autothermal partial gasification with air supply from the outside; Supplying the pyrolysis gas thus obtained from the degassing zone into an oxidation stage located within the shaft and separated from the degassing zone, in which partial oxidation and thermal cracking of the raw gas take place with addition of an oxidizing agent; and reduction of the exhaust gas from the oxidation stage in a reduction zone downstream of the oxidation zone through the coke formed in the degassing zone with heat extraction to a fuel gas, wherein the Reduktionskoks from the degassing zone is bypassing the oxidation stage of the reduction zone fed directly.

A further feature of the method according to the invention is that the gas produced is filtered before it leaves the shaft. The filtering is carried out by arranged in front of the outlet opening filter cartridges, which are exposed to time-dependent or differential pressure controlled a pressure surge cleaning.

The process according to the invention has the advantage that the oxidation stage is charged with a low-pyrolysis gas and can be operated at a comparatively low oxidation temperature and thus also permits a low gas inlet temperature into the reduction stage, requires little reducing coke and allows easy transport of the uncut reducing coke from the degassing zone the reduction zone allows. The integrated into the gas generation filtering of the raw gas increases the freedom from dust of the clean gas.

The invention also consists in a device for producing fuel gas from a solid fuel in a shaft gasifier, which is designed as a descending fixed bed reactor. As characterized in the claims, the device comprises a central oxidation chamber arranged in the fixed bed reactor, which is separated from the degassing zone and to which the pyrolysis gas produced in the degassing zone is supplied. The oxidation chamber is connected to an oxidant supply line via which the oxidation chamber is supplied with an oxidizing agent, under the action of which partial oxidation and thermal cracking of the pyrolysis gas take place. Below the oxidation chamber, a reduction zone is arranged, which receives the exhaust gas from the oxidation chamber and which is supplied to the resulting in the pyrolysis gas production Reduktionskoks from the degassing zone directly and bypassing the oxidation chamber. In the reduction zone, a reduction of the exhaust gas from the oxidation chamber by the supplied reducing coke with heat removal takes place to a fuel gas.

Integrated into the shaft carburettor is a filter arrangement which is arranged inside the shaft in front of a gas outlet opening. The filter assembly comprises filter cartridges, which are arranged substantially horizontally or vertically in front of the gas outlet opening and which are exposed via jet pulse nozzles, the time-dependent or differential pressure controlled by a pressure surge cleaning.

Description of the drawings

• Figur 1: eine schematische Darstellung einer Vorrichtung gemäss der Erfindung anhand der die erfindungsgemässen Verfahrensschritte erläutert werden;
• Figur 2: als weiteres Ausführungsbeispiel der Erfindung einen Schachtvergaser mit einer zusätzlichen Vergasungszone;
• Figur 3: ein weiteres Ausführungsbeispiel der Erfindung, das einen Schachtvergaser mit einer integrierten Staubfilteranordnung umfasst;
• Figur 4: einen Schnitt nach Linie A - A in Figur 3;
• Figur 5: ein weiteres Ausführungsbeispiel der Erfindung, das einen Schachtvergaser mit einer abgewandelten Staubfilteranordnung umfasst; und
• Figur 6: ein schematische Darstellung eines Schachtvergasers, der nach dem Doppelfeuerverfahren arbeitet und in dem erfindungsgemäss eine Staubfilteranordnung integriert ist.

Hereinafter, embodiments of the invention are explained with reference to drawings. Show it:

• FIG. 1 a schematic representation of a device according to the invention with reference to the inventive method steps are explained;
• FIG. 2 as a further embodiment of the invention, a shaft gasifier with an additional gasification zone;
• FIG. 3 a further embodiment of the invention, comprising a shaft gasifier with an integrated dust filter assembly;
• FIG. 4 : a section along line A - A in FIG. 3 ;
• FIG. 5 a further embodiment of the invention, comprising a shaft carburetor with a modified dust filter assembly; and
• FIG. 6 : A schematic representation of a shaft gasifier, which operates according to the double fire method and integrated in the present invention, a dust filter assembly is.

Detailed description of the embodiments

The FIG. 1 shows a schematic representation of a shaft carburetor, which is designed as a descending fixed-bed gasifier 1, which has an upright cylindrical shaft 2. The fixed bed gasifier 1 is fed via a lock system 3 fuel from above.

This may be coal, wood or other woody biomasses. The supplied fuel is crushed into pieces or chips. The level of the shaft with fuel 4 is monitored by a level indicator 5. At the periphery of the shaft 2 there is a nozzle system, which may comprise at least one or more nozzle planes, which comprises a plurality of distributed over the circumference of the shaft 2 nozzles 6, which are fed via a ring channel 7 with fresh air. The annular channel 7 is supplied with an air stream 8 via an inlet connection 9, so that a partial flow of the air required for an autothermal partial gasification of the fuel is introduced into the shaft 2 through each of the nozzles. In the autothermal gasification process energy is obtained by partial combustion under air supply.

In the fuel bed, partial evolution of heat causes heat to develop which, as a result, causes degassing of the fuel 4 in a degassing zone 10 for a given residence time. The pyrolysis gas formed here in the degassing zone 10 is rich in long-chain hydrocarbons and water vapor, which essentially results from the water content of the fuel 4 and the decomposition products of the degassing reaction. The fixed-bed gasifier 1 has an oxidation stage separate from the degassing zone 10, in which a partial oxidation and a thermal cracking of the raw gas takes place with the addition of an oxidizing agent. The oxidation stage is formed by an oxidation chamber 12, which is preferably arranged centrally in the carburettor shaft 2. The oxidation chamber 12 has a cylindrical housing 13, which is arranged concentrically to the longitudinal axis 14 of the shaft and which is bounded above by a conical part 15 and which is open at the bottom. In the illustrated embodiment, the supply air duct 16 passes through the cover 17 of the shaft 2 and extends concentrically to the longitudinal axis 14 of the shaft 2. However, it can also be arranged laterally outside the longitudinal axis or in the radial direction and parallel to this run. In the upper part of the oxidation chamber 12 radial openings 18 are arranged, which are distributed over the circumference of the housing 13.

Due to the local pressure and flow conditions in the oxidation chamber 12 passes through the openings 18 under the action of an oxidizing agent in the form of supply air via the supply air duct 16 21 takes place in the oxidation chamber 12 is a stoichiometric combustion of the pyrolysis gas 20 thermal cracking and partial oxidation destroys the long-chain hydrocarbons, and an exhaust gas 22 is produced which has only a low calorific value. The exhaust gas 22 passes from the downwardly open oxidation chamber 12 in a lying below the oxidation chamber 12 reduction zone 23 in which a bed of reducing coke 24 is that forms a bulk cone 25 in the region of the downwardly open oxidation chamber 12.

The reducing coke 24 is generated in the space between the oxidation chamber 12 and the wall of the carburettor shaft 2 during the degassing of the fuel 4. Due to the central arrangement of the oxidation chamber 12 in the shaft 2 and the cylindrical housing 13 of the oxidation chamber 12 an annular space between the housing 13 and the shaft wall is formed, which is referred to herein as the annular gap 26 and the reducing coke 24 over the circumference of the annular gap 26th distributed to the reduction zone 23 is supplied. In this case, the reducing coke 24 can slip into the reduction zone 23 to replace the used reducing coke without the need for a mechanical conveying device. By reducing coke 24, the exhaust gas 22 is reduced in the reduction zone 23 under heat removal to fuel gas.

The reduction zone 23 is delimited by a grate which is designed as a movable grate and in particular as a rotary grate 28 and by means of which the ash produced during the reduction process is separated from the reduction zone 23 and disposed of via an exit opening 29. To drive the rotary grate 28 is an electric gear motor 30. The shaft 2 is closed at the bottom by a bottom plate 31 and rests on columns, of which FIG. 1 only the columns 32 and 33 are shown. The motor 30 is mounted below the bottom plate 31 on the columns or on the bottom plate and connected by a shaft 34 with the rotary grate 28.

By a height-adjustable arrangement of the rotary grate 28, the height extent of the reduction zone 23 can be changed, which is an optimization of the method in terms of ash quality, pressure loss in the reduction zone 23 and adaptation to fuel properties is advantageous. For this purpose, the shaft 34 is arranged axially displaceable in the output shaft of the electric geared motor 30 designed as a hollow shaft and can be fixed in the respectively selected position against a further displacement by adjusting rings, not shown. The height of the reduction zone 23 is dependent on a number of factors such as fuel ash content, particulate matter, gas generator load and coke reactivity.

In the illustrated embodiment, the oxidation chamber 12 is arranged in the cylindrical shaft 2 concentric with its longitudinal axis 14. The supply air duct 16 opens centrally from above into the oxidation chamber 12 and is extended in the direction of the center thereof, whereby a uniform combustion of the pyrolysis gas 20 supplied from the degassing zone 10 is promoted. Alternatively, to achieve a uniform combustion process within the oxidation chamber of the supply air duct 16 may be provided at its outlet opening with a mixing chamber in which the pyrolysis gas 20 and the supply air 21 are intimately mixed. The annular gap 26 filled with reducing coke 24 forms a flow resistance for the pyrolysis gas 20 produced in the degassing zone 10. Due to the flow resistance for the pyrolysis gas 20 prevailing in this coke charge, this preferably flows through the openings 18 arranged in the upper region into the oxidation chamber 12, which pure gas space has only a negligible flow resistance.

When using a plurality of superimposed nozzle planes 6 for the supply of the air stream 8 in the degassing zone 10, a flow through the annular gap 26 with pyrolysis gas 20 is also prevented by the inflowing through the lower nozzle levels supply air 8 generates a very low tarry fuel gas and thus a flow-related barrier represents for the pyrolysis gas formed in the region of the uppermost nozzle level. The very low tar content of the fuel gas formed in the region of the lower nozzle levels is due to the fact that here already degassed fuel is present in the form of the reducing coke 24 and thus no tar is released.

The fuel gas 35 collected in the space 45 below the grate 28 is sucked downwards or laterally out of the reduction zone 23, depending on the dedusting concept used. At the in FIG. 1 illustrated embodiment, the removal of the fuel gas 35 takes place laterally through an arranged in the wall of the shaft 2 in the lower part of the outlet opening 36. The fuel gas is after his Removal from the reduction zone 23 cooled and cleaned according to the requirements of use in heat engines.

Further embodiments of the invention

Notwithstanding the embodiment described above, the oxidation chamber 12 can also be operated with a significantly lowered oxidation temperature. This is always useful when using ash-rich fuels with low ash melting points required for the thermal destruction of long-chain hydrocarbons oxidation temperatures of 1000 deg. C or above are not permitted due to the danger of slagging. In this case, the intended for the oxidation stage combustion air or the pyrolysis gas stream 20 steam is added. Instead or in addition, in both cases flue gas from the heat engine or other combustion plants can be mixed. By a selective admixture of flue gas (equal to exhaust gas), the combustion temperatures are lowered. This process corresponds to the exhaust gas recirculation of internal combustion engines to reduce NOx emissions. Furthermore, the water vapor content in the gas increases, which also has a destructive effect on the tar. The admixture increases the mass flow in the oxidation chamber and thereby lowers the oxidation temperature with otherwise constant material flows.

The desired destruction of the long-chain hydrocarbons can be achieved if the amount of water vapor and / or flue gas admixed is determined such that even at stoichiometric ratios the oxidation temperature which is permissible to prevent the slagging is no longer exceeded. The hydrocarbons are then oxidized at considerably lower temperatures to carbon dioxide and water vapor. For this process to take place in a short time, slightly superstoichiometric ratios can also be set, resulting in combustion with excess oxygen. This is fast and increases the reaction rate, which can lead to smaller sizes of apparatus. Furthermore, the additionally introduced water vapor and / or the additionally introduced flue gas causes destruction of the tar constituents even at substoichiometric ratios, so that the oxidation temperature can be reduced at high partial pressures of water vapor.

To increase the efficiency of the degasification zone 10, the fixed-bed gasifier 1 is equipped with more than one nozzle plane with nozzles 6 for introducing the gasification air. In the embodiment of FIG. 1 two nozzle levels are provided, each of which receives an air stream 8 is supplied. In addition to in conjunction with FIG. 1 This has the advantage that the performance of the fixed-bed gasifier 1, the degassing temperature and the residence time of the fuel 4 in the degassing zone 10 can be increased. In addition, the nozzle levels 6 can be charged with different mixtures of air, water vapor and flue gases from the heat engine. The enrichment of the air stream 8 with steam and / or flue gas causes a reduction of the combustion temperatures in the degassing zone 10 and allows the control of these combustion temperatures. Where the gasification air 8 passes through the nozzles 6 in the bed, very high temperatures that can quite cause schlackungsprobleme arise. This can be counteracted by adding steam, whereby a temperature reduction can be achieved. In this way, slagging in the degassing zone 10 can be prevented.

As a further embodiment of the inventive device shows FIG. 2 a shaft carburetor based on FIG. 1 described type, which is equipped with an additional gasification zone. The manhole carburetor of FIG. 1 corresponding components have in FIG. 2 the same reference numerals. As with the device of FIG. 1 points the shaft carburetor of FIG. 2 a degassing zone 10, which is supplied via an inlet port 9 air, a central oxidation chamber 12 with a supply air duct 16 and a reduction zone 23.

In the area below the reduction zone 23, a further gasification zone 40 is provided, which is also referred to herein as Restkoksvergasungszone and which is operated with additional air as a countercurrent gasifier. The additional air is supplied as under-air 41 via an inlet port 42, which is arranged below a movable grate 43. The grate 43 is like the grate 28 of FIG. 1 designed as a rotating grate and is driven by an electric geared motor 44. Instead of using air 41, flue gas and / or water vapor can also be supplied for lowering and controlling the reaction temperatures. The generated raw gas is collected in an annular gas collecting space 45, which is arranged at the level of the reduction zone 23 and is formed by a cylindrical wall 46 and a cover 47. The gas collection chamber 45 is open at the bottom and is only through the bulk cone 48 of Reduction coke limited. The raw gas 50 collected in the gas collecting space 45 is sucked off via a nozzle 51 arranged on the circumference of the shaft 2. An advantage of in FIG. 2 illustrated device is that the separated with the grate 43 and disposed of via an outlet 49 ash contains only very small amounts of carbon.

A further embodiment of the device according to the invention is shown in FIG FIGS. 3 and 4 , The in FIG. 3 Shaft carburetor shown corresponds to that of FIG. 1 and additionally has an integration of the dedusting of the raw gas into the raw gas collecting space. Dedusting takes place through a filter arrangement 55, which is arranged below the grate 28 in a correspondingly enlarged raw gas collecting space 54 in front of the gas outlet opening 36. The filter arrangement 55 comprises filter cartridges 56 which are known per se and which are aligned transversely to the longitudinal axis 14 of the shaft, preferably horizontally, and are fastened to a filter plate 57 which separates a clean gas collecting space 58 from the raw gas collecting space 54. On the filter plate 57 opposite side, the filter cartridges 56 are held by a support plate 59. The filter cartridges 56 are arranged one above the other in front of the gas outlet opening 36, as shown in the sectional view of FIG. 4 seen. Under the action of the voltage applied to the gas outlet opening 36 vacuum, the raw gas is passed through the filter cartridges 56, wherein the dust contained in the raw gas is deposited on the filter cartridges 56. The separated dust collects together with the grate ash in the region 60 at the bottom of the shaft 2 and is discharged through the outlet opening 29.

The cleaning of the building up on the filter cartridges 56 filter cake is done according to the prior art time or differential pressure controlled by means of pressure surge cleaning (jet pulses). For this purpose, the filter cartridges are fed via jet-pulse nozzles 61 compressed gas pulses for cleaning the filter cartridges. In the shaft carburetor of FIG. 3 a jet-pulse nozzle 61 is arranged for each filter candle 56, of which in FIG. 3 only one is shown. The jet pulse nozzles 61 are fed in the prior art with compressed inert gas (nitrogen or carbon dioxide) or with compressed natural gas (clean gas).

When using the illustrated filter assembly 55 in a gasifier with raw gas temperatures, which are safe above the autoignition temperature of the raw gas, advantageously compressed ambient air can be used instead of inert gas or gas for the feed of the jet pulse nozzles 61. The introduced thereby Oxygen immediately after flowing out of the jet pulse nozzles 61 reacts with the surrounding gasification gas by partially oxidizing it. Thus, there is no danger of the formation of an explosive gas / air mixture.

In FIG. 5 is a modification of the gasification apparatus according to FIG. 2 represented, which is equipped with an integrated dedusting of the raw gas produced. When shaft carburetor 64 of FIG. 5 Dedusting is done by a filter assembly 65 which is arranged on the circumference of the carburettor. The filter assembly 65 includes hot gas filter cartridges 67, which are aligned substantially parallel to the longitudinal axis 14 of the shaft. The shaft carburetor 64 has an enlarged Rohgassammelraum 54, including the carburettor shaft is formed in two parts. A downwardly open upper carburetor chute 68 projects into an enlarged outer chute 69 which forms the lower part of the carburettor shaft. Between the upper carburetor shaft 68 and the outer shaft 69 is an annular gap 70, the upper end of which is connected by a flange 71 to the upper carburetor shaft 68. A gas outlet opening 72 is arranged at the upper end of the annular gap 70 in the outer shaft 69. Below the gas outlet opening 72 is located in the annular gap 70, a filter plate 78, in which the filter cartridges 67 are mounted and which separates a clean gas collection chamber 73 from the raw gas collection chamber 54. The filter cartridges 67 protrude in the annular gap 70 substantially parallel to the common longitudinal axis 14 of the wells 68 and 69 down. By a negative pressure, the raw gas from the Rohgassammelraum 54 via the filter cartridges 67 to the clean gas collection chamber 73 and forwarded via the gas outlet opening 72. In this case, the dust deposited on the filter candles falls within the scope of the cleaning described below as a filter cake on the bulk cone 74 of the Reduktionskokses 75. In this way, the filter dust enters the further gasification zone for the residual coke. The strongly carbonaceous filter dust is then largely gassed into ashes as part of the progressing gasification of the residual coke and discharged together with the grate ash via the outlet port 77.

Also in this arrangement, the cleaning of the filter cartridges 67 by compressed gas pulses, which are supplied via jet-pulse nozzles 76 takes place. The jet-pulse nozzles 76 are arranged in the flange 71 in association with the filter cartridges 67. The pressure gas supplied through the nozzles 76 corresponds to that previously in connection with FIG FIG. 3 described.

The integration of dedusting into a shaft gasifier is not limited to shaft carburetor with an oxidation stage separate from the degasification zone in the form of a central oxidation chamber, but may also be applied to shaft carburetors of other types such as e.g. at carburetors, which work after the so-called double fire procedure.

A double firing type carburetor 80 is shown in FIG FIG. 6 shown schematically. This carburetor corresponds in its outer structure of the shaft carburetor of FIG. 2 but without a separate from the degassing zone oxidation state in the form of a central oxidation chamber. The supply air to the carburetor 80 is usually referred to with upper air and lower air and is in FIG. 6 represented by the air feeds 81 and 82. As a result, two fire / Glutzonen form. The integrated dedusting is achieved in the carburetor 80 by a filter assembly 83 which is arranged on the circumference of a correspondingly enlarged Rohgassammelraum 84. The filter assembly 83 contains hot gas filter cartridges 86, which are arranged substantially parallel to the longitudinal axis of the carburetor 80. The enlargement of the Rohgassammelraums 84 and the arrangement of the filter cartridges 86 corresponds to that in conjunction with FIG. 5 described embodiment.

The filter cartridges 86 are arranged in an annular gap between a downwardly open shaft 90 and an outer shaft 91 comprising this shaft and lie in the flow direction in front of a gas outlet opening 92 which is located at the upper end of the annular gap. The filter cartridges 86 are mounted in a filter plate 87 which separates a clean gas collecting space 85 from the raw gas collecting space 84. The cleaning of the filter cartridges 86 is again carried out by compressed gas pulses via jet-pulse nozzles 93, which are arranged in a connection flange 94 of the outer shaft to the downwardly open shaft above the filter cartridges 86 are supplied. The compressed gas supplied through the nozzles 93 is the same as that previously described in connection with FIG FIG. 3 described. As with the device after FIG. 5 During operation of the carburettor 80, the dust deposited on the filter cartridges precipitates as filter cake onto a pour cone 94 of the reduction coke 95. In this way, the filter dust passes into the further gasification zone for the residual coke. The highly carbonaceous filter dust is then largely gassed into ashes in the context of progressing gasification of the coke and discharged together with the grate ash on the outlet port 96.

While the invention has been described in terms of preferred embodiments, variations of these embodiments and other embodiments may be practiced without departing from the scope of the invention as defined by the claims.

Claims (12)

1. Device for creating fuel gas from a solid fuel in a gasifier (80) which is configured as a top-down fixed-bed gasifier and has a gas outlet opening in the lower part of a gasifier shaft, characterised in that a filter arrangement (83) which has a plurality of filter cartridges (86) is arranged in a raw gas collecting space inside the gasifier shaft (81) upstream of a gas outlet opening (92).
2. Device according to claim 1, characterized by jet pulse nozzles (93) which are designed to feed compressed gas pulses to the filter cartridges (86) in order to clean the filter cartridges.
3. Device according to claim 1, characterized in that the filter cartridges are installed transversely to the longitudinal axis of the gasifier shaft in rows one above the other in a filter plate.
4. Device according to claim 1, characterised in that the filter cartridges (86) are installed parallel to the longitudinal axis of the gasifier shaft at the periphery of the raw gas collecting space (84) in a filter plate (87) which separates the raw gas collecting space (84) from a clean gas collecting space (85).
5. Device according to claim 1, characterised in that the gasifier (80) is designed to operate according to the double-fire method and has two fire/glow zones, between which the gas outlet opening (92) is located, and in that the filter arrangement is arranged in the raw gas collecting space (84) upstream of the gas outlet opening (92) in the direction of flow.
6. Device according to claim 1, characterised in that the filter cartridges are arranged in an annular gap between a downwardly open shaft (90) and an outer shaft (91) surrounding said shaft, and in that the gas outlet opening (92) is located at the upper end of the annular gap.
7. Device according to claim 6, characterised in that jet pulse nozzles (93) are arranged above the filter cartridges (86) in a connection flange (94) of the outer shaft which connects the latter to the downwardly open shaft (55), the compressed gas pulses of which jet pulse nozzles can be fed to the filter cartridges for cleaning purposes.
8. Device according to any of the preceding claims, characterised in that

   - the oxidation chamber (12) has radial openings (18) for feeding to the oxidation chamber the pyrolysis gas (20) created in the degasification zone (10), and

   - a further degasification zone (40) is connected to the reduction zone (23) in order to largely gasify the fine residual coke from the reduction zone (23) by feeding further gasification agents (41) into the gasification zone (40), which is operated as a counter-current gasifier.
9. Method for creating fuel gas from a solid fuel in a shaft gasifier (1), characterised by the steps:

   a) feeding the fuel into the shaft gasifier (1), which is configured as a top-down fixed-bed reactor;

   b) degasifying the fuel in a degasification zone (10) of the shaft gasifier by autothermal partial gasification with air being fed from outside;

   c) feeding the resulting pyrolysis gas (20) from the degasification zone (10) into an oxidation stage (12) which is located inside the shaft and is separate from the degasification zone and in which the raw gas is partially oxidized and thermally cracked by the addition of an oxidizing agent; and

   d) reducing the waste gas from the oxidation stage (12) in a reduction zone (23) downstream of the oxidation stage by means of the coke formed in the degasification zone, while withdrawing heat, so as to form a fuel gas (35),

   characterised in that, before leaving the shaft (2), the gas created is faltered thorough filter cartridges (56, 67) arranged upstream of the outlet opening (36, 72) .
10. Method according to claim 9, characterised in that the filtering takes place in the region upstream of an outlet opening (36, 72).
11. Method according to claim 9, Characterised in that filter cartridges (56, 67) are fed compressed gas pulses by jet pulse nozzles in order to clean the filter cartridges.
12. Method according to claim 9, characterised in that

    - the reduction coke (24) created in the degasifica'tian zone (10) is fed to the reduction zone (13), bypassing the oxidation stage (12), and

    - steam is mixed with the feed air (21) that is fed to the oxidation stage (12), and/or

    - flue gas from a heat engine which is operated with the fuel gas (35) is mixed with the feed air (21) that is fed to the oxidation stage (12), and/or

    - steam and/or flue gas from a heat engine is mixed with the air stream (8) that is fed to the degasification zone (10).

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