AT507176B1 - METHOD AND DEVICE FOR PRODUCING AN NITROGEN ARM AND / OR NEAR NITROGEN-FREE GASES - Google Patents

Abstract

Disclosed is a method of producing a nitrogen-lean, or near-nitrogen-free gas by gasifying heterogeneous biogenic fuels, residues and / or plastics in a reactor comprising a gasification and a combustion zone, the reactor having a fluidized bed material continuously in a heated state is passed from the combustion zone into the gasification zone and from the gasification zone in the cooled state together with non-gasified residual fuel back into the combustion zone, characterized in that the fuel is introduced into the formed as a circulating fluidized bed gasification zone, wherein a part of the fluidized bed is designed as a moving bed , the fuel in the circulating fluidized bed of the gasification zone at Luftabschluss to form a product gas is at least partially degassed or gasified and the remaining or unreacted residual fuel together with the cooled Bettmate Rial over the moving bed is brought into the combustion zone, where the bed material fluidized to form a fast fluidized bed, reheated by combustion of the residual fuel and recycled to the circulating fluidized bed of the gasification zone. Furthermore, an apparatus for carrying out this method will be described.

Description

Description: The present invention relates to a method for producing a nitrogen-poor or nearly nitrogen-free gas by gasification of heterogeneous, biogenic fuels or mixtures of heterogeneous, biogenic fuels and plastics, and to an apparatus for carrying out this method.

It is known to gasify fuels at temperatures of about 800 degrees by the action of a controlled amount of air and optionally water vapor. This has the disadvantage that the fuel gas produced has a high nitrogen content, so that its calorific value is low.

It is also known from EP 302 849 AI, at a fluidized bed combustion to pyrolyze the fuel to be burned first, then to burn and finally initiate the pyrolysis gas in the combustion chamber and burn. This method does not lead to fuel gas production.

US 3,853,498 A discloses a process in which domestic waste is pyrolyzed in an inert atmosphere and the fuel is heated in a separate combustion zone. US 4 405 339 A proposes a fluidized bed apparatus comprising a zone for cracking fuel and a heating zone for heating the heat transfer medium by combustion of the residues from the cracking zone. The processes of the latter two patents lead to a product gas containing a too high proportion of hydrocarbons for our purposes.

EP 202 215 A2 discloses a combustion process in a fluidized bed furnace with internal circulation of the solid. However, no product gas is generated. GB 2 203 445 A proposes a process for the production of methane, in which the gasification takes place in a circulating fluidized bed.

AT 405 937 describes a process wherein, to produce a nitrogen-lean, or nearly nitrogen-free gas by gasification of heterogeneous, biogenic fuels and plastics, first the fuel to be gasified is brought into air-tight contact with the hot bed material of a fluidized bed combustion and thereby in the presence is at least partially degassed by steam and / or CO 2. The resulting residual fuel is fed to a fluidized bed (2) with circulating bed material and thereby burned, whereby the bed material is heated and is returned after its separation from the exhaust gas back into the vestibule (1). The gasification plant for carrying out the method is characterized in that it is formed in a housing of an internally circulating fluidized bed, wherein the antechamber (1) is used for the return of the hot bed material and is formed as a gasification space, while the actual fluidized bed (2) is formed as a combustion zone, being provided for the integration of the bed material in the fluidized bed (2) as well as in the return of the hot bed material in the vestibule (1) lock-like devices. In particular, the bed material is sand mixed with catalytic nickel and / or niobium compounds, thereby lowering the gasification temperature and controlling the gas composition particularly in the direction of reducing the CH 4 content.

However, the method described has shortcomings, which can be remedied by the subject invention.

In particular, the method described in AT 405 937 B has the disadvantage that the automatically adjusting temperatures in the gasification and combustion part can not be practically influenced. In practice, this means that the process is almost unusable, since the temperature in the gasification for the gas quality and in particular for the tar content of the product gas is crucial. The possibility of regulating the temperature to a desired value is therefore absolutely necessary.

[0009] In a first step to remedy this deficiency, recirculation of produced product gas for incineration into the combustion part has been provided in systems of the type described so far. However, this leads to loss of efficiency compared to the direct use of the solid fuel, since already the production of the product gas is associated with energy losses. Furthermore, the problem with the existing plants was that only little to no residual fuel could be transferred to the combustion zone, in particular when biomass was used, since the residual fuel in the stationary fluidized bed of the gasification zone of the prior art owes its comparatively low density to the combustion zone Surface of the fluidized bed so to speak sponge up and thus could not reach the provided at the bottom of the fluidized bed connection between gasification zone and combustion zone.

The object of the present invention is to avoid the disadvantages of the prior art and to provide a method and an apparatus in which the temperatures in the gasification and combustion part can be influenced.

According to the invention is therefore intended to produce a nitrogen or virtually nitrogen-free gas by gasification heterogeneous, biogenic fuels, residues and / or plastics in a reactor comprising a gasification and a combustion zone, the reactor having a fluidized bed material, which fed continuously in the heated state from the combustion zone into the gasification zone and from the gasification zone in the cooled state together with non-gasified residual fuel back into the combustion zone, to introduce the fuel into the gasification zone formed as a circulating fluidized bed, wherein a part of the fluidized bed is designed as a moving bed, the fuel in the circulating fluidized bed of the gasification zone in the absence of air at least partially to degas or gas to form a product gas and the remaining or unreacted residual fuel together with the cooled bed material on the W. bed to be spent in the combustion zone, where the bed material fluidized to form a fast fluidized bed, reheated by combustion of the residual fuel and recycled to the circulating fluidized bed of the gasification zone. In other words, the present invention thus provides that a portion of the fuel to be gasified is introduced directly into the combustion part together with the circulating bed material. This can be realized by suitable design measures in the gasification part, wherein the lower part of the carburetor is changed so that the amount of fuel flowing into the combustion chamber can be influenced by suitable combination of the feed point and the fluidization. Fluidization in two levels (e.g., as a two-stage supply of gasification agent) provides for the controlled transfer of the required amount of fuel to the combustion part and provides e.g. a circulating fluidized bed in the upper part of the gasification zone and a moving bed in the lower part of the gasification zone.

In addition, it is also advantageous if the circulating fluidized bed is provided in the gasification zone of the reactor by different fluidization rates over the cross section of the gasification zone of the reactor.

It is known that by deliberately different fluidization of a stationary (bubble-forming) fluidized bed to a bed material circulation within the fluidized bed. In this case, the bed material flows downwards in the low-fluidized area and upwards in the higher-fluidized area. This circulation can be made so strong - possibly the flow-conducting internals can be used to support the effect - that partially gasified fuel particles, which would otherwise float, are taken down to the bottom of the fluidized bed with the bed material flow directed downwards, thus creating the possibility of to transport these also in the combustion area.

Preferably, the product gas is freed of dust formed in the gasification zone, wherein the dust is transported as additional fuel via the moving bed in the combustion zone. In practice, the particle discharge from the gasification section has proven to be a major shortcoming. Even with normal wood chips, the fine fraction had to be partially screened out in order to be able to control the higher tar load associated with higher fines. The problem is that the residence time of the small fuel particles in the hot carburetor region is too short. The voriiegende invention provides for this purpose an internal Partikei-separator, whereby the fine Partikei so that in the hot Vergasungsteii bieiben and can be gassed reguiär without higher Anteiie to produce tar. On the other hand, the non-gasified Staubmateriai is then used as an additional fuel and spent on the moving bed in the combustion zone. For this purpose, the formation of the above-described circulating fluidized bed in the gasification section may be performed by introducing the separated and floating-liable dust into the downward flow of the circulation. In this way, it is transported to the transition together with fuel that has not yet been gassed, and finally into the combustion zone. This also ensures that fine ashes, which can only be discharged via the combustion section, are also located there.

The present invention further relates to a device for producing a nitrogen-poor, or virtually nitrogen-free gas by gasification of heterogeneous, biogenic fuels, residues and / or plastics in a reactor comprising a gasification zone and a combustion zone, wherein the reactor by an influx of Fiuidisierungsgas Fiuidungen Fiuidisiertes Bettmateriai which is fed in a heated state via a line continuously from the combustion zone in the gasification zone and in the cooled state via a line from the gasification zone together with non-gasified residual fuel back into the combustion zone, characterized in that the fuel over introducing a conduit into the gasification zone formed as a circulating fluidized bed, wherein a portion of the fluidized bed is laid out as the moving bed, the fuel in the circulating fluidized bed of the gasification zone being exhausted under air g. a product gas is at least partially degassed or gasified and the spent or unreacted residual fuel is transported together with the cooled Bettmateriai on the moving bed and via the line in the combustion zone, where the Bettmateriai fiuidisiert under Biidung a snowy Wirbeibettes by combustion of the Residual fuel is reheated and recycled via a line in the circulating Wirbeischicht in the gasification zone. As can be seen kiar for the device the same advantages as for the inventive method.

It is advantageous if the circulating fluidized bed in the gasification zone of the reactor by suitable internals, such as baffles, is provided. This embodiment is easy to accomplish, even existing systems can be easily converted to the inventive method.

It is also advantageous if additional inlet nozzles are provided for fluidizing gas for provid- ing the moving bed in the bottom region of the gasification zone of the reactor in the vicinity of the fuel supply and / or in environment or in the line from the gasification zone into the combustion zone. The adequate circulation of the bed material is an essential part of the functionality of the process. The transfer of the bed material from the gasification zone in the combustion zone is often done in practice via an inclined fluidized slide (here, the inclination angle of the slide is crucial), this is often a weak point in terms of material flow but also leakage of air into the gasification zone, which largely avoided must become. By suitable design of the inlet nozzles, by the pulse of the incoming gas actively supports the flow of solids from the gasifier zone into the combustion zone and counteracts the leakage, both requirements can be met much better.

According to the invention, a device is provided, wherein the gasification zone of the reactor on the outlet side has devices for separating dust formed in the gasification zone, wherein the separated dust is transported via a guide in the interior of the gasification zone in the circulating fluidized bed or in the moving bed. Again, the gieichen Vorteiie apply as for the corresponding inventive method for the special embodiment of the device.

As already mentioned, it is also advantageous if the devices for the separation of dust formed in the gasification zone are selected from the group comprising filtering separators, centrifugal separators and combinations thereof, and if metal or ceramic candle filters are used as filtering separators, which optionally are equipped with catalytically active for the Teerspaltung materials. The internal separators may, as stated, be made differently and may, for example, operate on a centrifugal basis (e.g., cyclones) or as filtering separators (e.g., metallic or ceramic candle filters). In the filtering separators, it is advisable to use catalytically active materials for the tar splitting, which enables a significant tar reduction at suitable temperatures. Thus, a combined particle and tar separation would be possible and it can downstream devices avoided and also the product gas can be cooled easily without having to fear a tar condensation.

Sand or catalytically active natural materials, preferably calcite, dolomite or olivine or mixtures thereof can be used as the bed material. Furthermore, nickel and / or zirconium compounds come into question.

In the following, the present invention will be explained in more detail with reference to the accompanying drawings. The illustrated schematic embodiments are to be understood as examples and are not intended to limit the invention in any way.

Figure 1 shows a schematic cross section through a fiction, contemporary design of a carburettor with internally circulating fluidized bed in the gasification, moving bed and fast fluidized bed in the combustion part and in addition an internal dust removal with recycling of the dust into the moving bed.

In Fig. 2 is a schematic cross section of an embodiment of a carburetor according to the invention shown with internally circulating fluidized bed in the gasification and combined fuel-dust recirculation in the chute and faster fluidized bed in the combustion part.

Figures 3a and 3b show examples of embodiments of the invention

Flow in the transition from the gasification part in the combustion part or optionally in the moving bed (Figure 3a hole bottom design in basic and elevation,

Fig. 3b nozzle for nozzle bottom design in basic and elevation).

The gasification reactor of FIG. 1 consists of a circulating fluidized bed (1) in the gasification region, a moving bed (2), in which here the fuel is introduced, a connecting line (3) (executed here as a connection slide) between the gasification zone and as rapid fluidized bed of formed combustion zone (4) and a further connecting line (5) with cyclone and siphon for returning heated bed material in the gasification zone. The fuel supply (6) takes place in the moving bed (2), which can be adjusted by suitable fluidization of the fuel input into the connecting chute (3). When increasing the fluidization via inflow devices (9) more fuel enters the circulating fluidized bed arranged above it (1), with reduction of the fluidization via the inflow devices (9), a larger proportion of fuel goes directly into the connecting chute (3) and thus into the combustion zone (4).

The fluidization of the gasification fluidized bed (1) is divided and can therefore be set differently. By higher fluidization via inflow devices (7) in the left part of the lower region of the gasification zone (1) and less fluidization via inflow devices in the right part (8), a circulation of the bed material sets in a clockwise direction. As a result of this circulation of bed material, particles which tend to float are carried downwards and can thus be transported via the connecting chute (3) and further into the combustion zone (4). To assist circulation in the gasification zone, internals (e.g., baffles 14) may also be installed. Via inflow devices (10), a fluidization in the connection chute (3), via inflow devices (11), the fast fluidized bed in the combustion zone (4) is provided and for the return line (5) with siphon, the gas supply can be adjusted independently of each other, that the desired circulation of bed material between the gasification zone (1) and combustion zone (4) results.

In the upper region of the gasification zone (1) of the gasification reactor according to the invention a particle separator (15) is shown, e.g. a candle filter with pulse cleaning. By means of this particle separator (15), a dust-free and tarry raw gas can be achieved even at higher fines in the fuel. The separated particles are introduced via a collecting line (16) directly into the connecting chute (3) and thus transferred into the combustion zone (4). This prevents unwanted accumulation of fine ash particles in the gasification zone. In the combustion zone (4), the fine particles are burned out and leave the reactor via the cyclone of the combustion zone as fly ash.

In Figure 2, another possible embodiment of the gasification reactor of the invention is shown schematically. In contrast to the embodiment in FIG. 1, the fuel feed (6) opens into the upward flow of solids of the circulating fluidized bed (1). As a result, the fuel to be gasified is transported upwards, partially gassed, but when arrived at the top, it is at least partially flushed into the moving moving bed (2) and transported down there, and flows into the connecting chute (3). This way, a higher proportion of the fuel passes into the combustion zone (4) and can be adjusted to the desired value by suitable adjustment of the fluidizations by inflow means (7, 8, 9). The moving bed (2) is simultaneously used to transport the fine particle stream coming from the internal separator (15) into the connecting chute (3) and further into the combustion zone (4).

Figure 3 shows embodiments according to the invention of arrival or inflow devices (13) of the embodiments of FIG. 1 or 2 for the chute (3) or optionally also for the moving bed (2). Fig. 3a shows a section of a perforated bottom, Fig. 3b, a nozzle for a nozzle bottom. Both have in common that the gas flowing into the reactor exerts an impulse on the bed material in its flow direction (traveling direction), which results in advantages for the circulation of the solids and in the reduction of leaks.

Claims (9)

claims Anspruch [en] A process for producing a nitrogen-poor gas by gasification of heterogeneous biogenic fuels, residues and / or plastics in a reactor comprising a gasification zone and a combustion zone, wherein the reactor comprises a fluidized bed material which is continuously heated in the combustion zone is fed into the gasification zone and from the gasification zone in the cooled state together with non-gasified residual fuel back into the combustion zone, characterized in that the fuel is introduced into the gasification zone formed as a circulating fluidized bed, wherein a part of the fluidized bed is designed as a moving bed, the fuel in the circulating fluidized bed of the gasification zone in the absence of air with the formation of a product gas at least partially ent-resp. is gasified and the remaining or unreacted residual fuel material is spent together with the cooled bed material on the moving bed in the combustion zone, where the bed material fluidized to form a fast fluidized bed, reheated by combustion of the residual fuel and recycled to the circulating fluidized bed of the gasification zone , 2. The method according to claim 1, characterized in that the circulating fluidized bed is provided in the gasification zone of the reactor by over the cross section of the gasification zone of the reactor different fluidization rates. 3. The method according to claim 1 or 2, characterized in that the product gas is freed of dust formed in the gasification zone, wherein the dust is transported as an additional fuel via the moving bed in the combustion zone. 4. A device for generating a nitrogen-poor, or nearly nitrogen-free gas by gasification heterogeneous, biogenic fuels, residues and / or plastics in a reactor comprising a gasification zone (1) and a combustion zone (4), wherein the reactor supply lines (7, 8, 9, 10, 11) for supplying a fluidizing gas for fluidizing the bed material, a conduit (5) for continuously guiding the bed material in a heated state from the combustion zone (4) into the gasification zone (1) and a conduit (3) for guiding the Bed material together with non-gasified residual fuel in the cooled state from the gasification zone (1) back into the combustion zone (4), characterized in that the device comprises a conduit (6) for introducing the fuel into the gasification zone (1) formed as a circulating fluidized bed, wherein in the conduit (3) inlet nozzles for the provision of a moving bed (2) are present. 5. Apparatus according to claim 3, characterized in that in the gasification zone (1) of the reactor suitable internals, such as baffles (14), are provided for provid- ing the circulating fluidized bed. 6. Apparatus according to claim 4 or 5, characterized in that in the bottom region of the gasification zone (1) of the reactor in the vicinity of the fuel supply (6) and / or in the environment or in the conduit (3) of the gasification zone (1) in the Combustion zone (4) additional inlet nozzles (9 or 13) for fluidizing gas to Provide the moving bed (2) are provided. 7. Device according to one of claims 4 to 6, characterized in that the gasification zone (1) of the reactor outlet side devices (15) for the separation of dust formed in the gasification zone, wherein the separated dust via a guide (16) inside the Gasification zone is spent in the circulating fluidized bed or in the moving bed (2). 8. The device according to claim 7, characterized in that the devices (15) are selected for the separation of dust formed in the gasification zone from the group comprising filtering separators, centrifugal separators and combinations thereof. 9. Apparatus according to claim 8, characterized in that metal or ceramic candle filters are used as filtering separators, which are optionally equipped with catalytically active for the Teerspaltung materials.