Method and device for the production of synthesis gas for operating an internal combustion engine

Abstract

A method for producing synthesis gas for operating an internal combustion engine from an organic solid fuel decomposed into pyrolysis products in a pyrolysis reactor without an oxygen supply, includes feeding the pyrolysis products from a bottom of the pyrolysis reactor to a fluidized bed reactor. A synthesis gas produced in the fluidized bed reactor is withdrawn as product gas. The products gas is directly or indirectly fed to the internal combustion engine. The pyrolysis reactor is operated using at least one pyrolysis auger for conveying the solid fuel. The fluidized bed reactor is fluidized by supplying air at a rate above a minimal loosening rate of the bed material of the fluidized bed of the fluidized bed reactor.

Claims

1. A method for producing synthesis gas, for operating an internal combustion engine, from an organic solid fuel, the method comprising the steps of: conveying organic solid fuel to a pyrolysis reactor using a pyrolysis auger; decomposing the organic solid fuel into pyrolysis products in the pyrolysis reactor, without an oxygen supply; feeding the pyrolysis products from a bottom of the pyrolysis reactor to a fluidized bed reactor; producing a synthesis gas in the fluidized bed reactor; and withdrawing the synthesis gas from the fluidized bed reactor as product gas and directly or indirectly feeding the product gas to the internal combustion engine; wherein fluidized bed reactor is fluidized by supplying air at a rate above a minimal loosening rate of a bed material of a fluidized bed of the fluidized bed reactor; wherein the organic solid fuel comprises a biogenic waste material having an ash content of at least 20% of a solid mass of the organic solid fuel; and wherein the pyrolysis products formed in the pyrolysis reactor in the step of decomposing are pyrolysis oil, pyrolysis coke, and pyrolysis gas.

2. The method according to claim 1, wherein the biogenic waste material comprising the organic solid fuel has solid contents between 80% and 98% and includes one or more of the group consisting of: sewage sludge; paper pulp; and pomace.

3. The method according to claim 2, further including operating the fluidized bed reactor at an operating temperature ≦960° C.

4. The method according to claim 1, further including a step of externally heating the pyrolysis auger.

5. The method according to claim 4, wherein the step of externally heating the pyrolysis auger relies upon heated gas such as heated air.

6. The method according to claim 5, wherein the heated gas is the hot product gas from the fluidized bed reactor.

7. The method according to claim 5, wherein the step of externally heating the pyrolysis auger relies upon a thermolysis burner for further increasing the temperature of the heated gas.

8. The method according to claim, wherein the step of feeding includes feeding air into the fluidized bed reactor from the bottom or from an air flow that is characterized as sufficient to sustain a vortexing and cracking process in the fluidized bed reactor, and wherein said air is supplied at an air flow rate that is between 5% and 20% above a minimum loosening rate required for operating the fluidized bed reactor.

9. A device for producing synthesis gas, for operating an internal combustion engine, from an organic solid fuel, comprising: a pyrolysis auger for conveying organic solid fuel; a pyrolysis reactor for receiving the organic solid fuel from the pyrolysis auger and decomposing the organic solid fuel into pyrolysis products, without an oxygen supply; a fluidized bed reactor for receiving the pyrolysis products from a bottom of the pyrolysis reactor and producing a synthesis gas, therefrom; means for withdrawing the synthesis gas from the fluidized bed reactor as product gas, and directly or indirectly feeding the product gas to an internal combustion engine; wherein fluidized bed reactor is fluidized by supplying air at a rate above a minimal loosening rate of a bed material of a fluidized bed of the fluidized bed reactor; wherein the organic solid fuel comprises a biogenic waste material having an ash content of at least 20% of a solid mass of the organic solid fuel; wherein the pyrolysis products formed in the pyrolysis reactor are pyrolysis oil, pyrolysis coke, and pyrolysis gas; and wherein a cross-sectional area of a clear inner space of the fluidized bed reactor increases from a bottom toward a top of the fluidized bed reactor, at least in sections in a manner of an inverted cone.

10. The device for producing synthesis gas according to claim 9, wherein an opening is included in a side of the fluidized bed reactor for the gravitational discharge of ash accumulating during operation of the fluidized bed reactor.

11. The device for producing synthesis gas according to claim 10, wherein the opening at the end of the fluidized bed and at a beginning of a gas chamber, therein.

12. The device for producing synthesis gas according to claim 10, comprising a device for conveying initially cold air out of the fluidized bed reactor in counterflow to the discharged ash.

13. The device for producing synthesis gas according to claim 9, comprising a further device for feeding air into the fluidized bed reactor, on a side of the fluidized bed reactor, in a region between a fuel inlet and an ash discharge of the fluidized bed reactor, wherein the air that is fed is withdrawn as a bypass air flow from the air supply into the fluidized bed reactor, which takes place from the bottom for fluidization.

14. The device for producing synthesis gas according to claim 13, comprising an additional device for feeding air into the fluidized bed reactor, arranged (7) on the side, in the region above the ash discharge in a gas chamber of the fluidized bed reactor, which fed air is withdrawn as a bypass air flow from the air supply into the fluidized bed reactor.

15. The device for producing synthesis gas according to claim 9, comprising a device for cooling product gas removed from the fluidized bed reactor

16. The device for producing synthesis gas according to claim 15, wherein the device for cooling product gas removed from the fluidized bed reactor comprises one or more of the group consisting of: a Venturi scrubber; a device for aerosol deposition comprising a centrifugal scrubber; and a device for ammonia deposition comprising a spray scrubber, are present after a first cooling stage and a dust-removing device.

17. The device for producing synthesis gas according to claim 16, wherein the device for cooling product gas removed from the fluidized bed reactor comprises a Venturi scrubber, a device for aerosol deposition comprising a centrifugal scrubber and a device for ammonia deposition comprising a spray scrubber, arranged after a first cooling stage and a dust-removing device, and are connected in series.

18. The device for producing synthesis gas according to claim 1, comprising a device for removing any of the group consisting of mercury, hydrogen sulphide, and hydrocarbons from the product gas withdrawn from fluidized bed reactor, and wherein the device for removing operates based on adsorption or filtering, activated carbon filtering.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The invention is schematically depicted in the drawing and is described in greater detail regarding one exemplary embodiment.

[0043] FIG. 1 presents a schematic depiction of one embodiment of the device for carrying out the method according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0044] The following is a detailed description of example embodiments of the invention depicted in the accompanying drawings. The example embodiments are presented in such detail as to clearly communicate the invention and are designed to make such embodiments obvious to a person of ordinary skill in the art. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention, as defined by the appended claims.

[0045] FIG. 1 depicts a gasification device 1. This gasification device is used for implementing the method for producing synthesis gas for operating an internal combustion engine from an organic solid fuel, according to the invention. Fuel is fed to a fuel silo 3 by a fuel supply 2a. In this exemplary embodiment, sewage sludge in the form of sewage sludge pellets having 90% solid content is used as the fuel. A predefined quantity of calcium carbonate is added to the fuel in the fuel silo 3. Calcium carbonate is added in this case to subsequently primarily reduce sulfur in the gas phase.

[0046] The fuel, which has been preconfigured in this way, is subsequently introduced into a pyrolysis reactor 4. The pyrolysis reactor 4 comprises a pyrolysis auger 5, which is a twin auger in this case. The pyrolysis reactor 4 is held at a constant temperature by the infeed of heating gas. For this purpose, air is preheated in an air preheater 12 and is additionally heated up, as necessary, by a thermolysis burner 6, which is operated using sewage gas in this exemplary embodiment. The heating takes place in this case externally by the heating gas. Thus, an admixture of heating gas with pyrolysis educts and products is avoided. The pre-stage is preferably operated in a temperature window between 600-650° C. In the present embodiment, the pyrolysis process is carried out in an oxygen-free manner, and therefore this corresponds to a thermolysis. Pyrolysis gas, pyrolysis coke, and pyrolysis oil are formed as process products during the pyrolysis or thermolysis.

[0047] In one further method step, the process products from the pyrolysis reactor 4 are transferred to a fluidized bed reactor 7. A feed auger, which is not depicted in FIG. 1 greater detail, is provided in this exemplary embodiment. The pyrolysis products are introduced into the fluidized bed reactor 7 from the bottom by feed auger. A wind box 8 is disposed on the underside of the fluidized bed reactor 7. By this wind box 8, gasification air is fed from a gasification-air supply 2b to the fluidized bed reactor 7. The fluidized bed reactor 7 extends eccentrically and to expand conically upward in the region of a fluidized bed 9 that is forming. A gas chamber 10 adjoins the fluidized bed 9. In the sense of two bypasses, a portion of the gasification air is branched off from the branch leading to the wind box 8 and is fed, in part, in the region of the fluidized bed 9 and, in another part, in the region of the gas chamber 10.

[0048] Slightly above the fluidized bed 9 there is an ash discharge duct 11 which leads into an opening 11c located in a wall of the fluidized bed reactor 7. The ash discharge duct 11 has a slant, and therefore ash is gravitationally discharged out of the inner chamber of the fluidized bed reactor 7 via the ash discharge duct 11. From there, the ash passes through a cooling reactor 11a and enters an ash trap 11b. Ash is removed therefrom, as necessary, also as a substitute for activated carbon, and is used in filter devices 18a, 18b and 18c which are described in greater detail further below.

[0049] A portion of the gasification air withdrawn from the gasification-air supply 2b is conveyed into the fluidized bed reactor 7 in counterflow through the ash discharge duct 11. Thus, a recalcination of the ash takes place and heat is transferred from the hot ash to the initially cold gasification air.

[0050] The supply of gasification air is adjusted in such a way that the air supply is just sufficiently great enough for sustaining vortexing and cracking processes in the fluidized bed reactor 7. The air is supplied at a rate of approximately 10% above the minimum loosening rate required for operating the fluidized bed reactor 7. It is thereby ensured that the pyrolysis gas has good contact with the bed material of the fluidized bed. Furthermore, a catalytic cracking of the tar on the pyrolysis coke obtained in the process products of the pyrolysis reactor 4 takes place already in the fluidized bed 9.

[0051] As soon as the material flow forming in the fluidized bed reactor 7 reaches the opening 11c of the ash discharge duct 11, ash is gravitationally discharged from the material flow.

[0052] The operating temperature of the fluidized bed reactor 7 is regulated to ≦960° C. In alternative embodiments, the method provides aligning the operating temperature with the particular ash melting temperature of the solid fuel that is used. As soon as the material flow has reached the upper end of the fluidized bed reactor 7 or the gas chamber 10, the material flow emerges from the fluidized bed reactor 7 in the form of hot synthesis gas.

[0053] In subsequent steps, this synthesis gas is dedusted and purified, and the heat contained therein is recovered. For this purpose, the synthesis gas is initially conveyed to a dust-removing device 13. In this exemplary embodiment, the dust-removing device 13 is a cyclone separator for removing the predominant portion of fly ash still present therein. Next, the synthesis gas, which is still at approximately 800° C. in this phase, is conveyed over the heating gas preheater 12, which is used for preheating the heating gas of the pyrolysis reactor 4, as described above. The synthesis gas reemerges from the heating gas preheater 12 at a temperature of approximately 400° C. and is passed through a tubular filter 14 to a Venturi scrubber 15, by which the synthesis gas is further cooled and purified. Aerosols that have formed are subsequently separated out in a device for aerosol deposition 16, which is a centrifugal scrubber in this case. The synthesis gas is then routed to a device for ammonia deposition 17. In this case, the device for ammonia deposition 17 is designed as a spray scrubber.

[0054] In a final step, the synthesis gas, which has now already been precleaned, is freed of remaining impurities and pollutants. For this purpose, after emerging from the device for ammonia deposition 17, the synthesis gas is conveyed over a recuperator which is not depicted in greater detail in FIG. 1. The recuperator is used for preventing the formation of mist and, in general, for ensuring that the dew point is not reached. A portion of the heating-gas exhaust gas from the pyrolysis reactor 4 is used for heating the synthesis gas in recuperator.

[0055] The synthesis gas then sequentially reaches three filter devices 18a, 18b, 18c. In this exemplary embodiment, these filter devices 18a, 18b, 18c are activated-carbon filters and activated-carbon absorbers. A predefined portion of the activated carbon is replaced by sewage sludge ash, from the ash trap 11b, having been aligned with the dimension of the filter devices 18a, 18b, 18c and the required filter yields. Advantage is taken of the fact, in this case, that the sewage sludge ash is like activated carbon in that it has a high porosity and specific surface. In other words, the sewage sludge ash is at least partially reused as filter material.

[0056] The filter device 18a is used in this case for separating out any mercury remaining in the synthesis gas. The filter device 18b is used for separating out the hydrogen sulphide remaining in the synthesis gas. The final filter device 18c is used for separating out any hydrocarbon-containing pollutants that remain. The filter device 18c is therefore a policing filter.

[0057] The synthesis gas, which has been produced, dedusted and purified in this way, now has a quality which enables the requirements on a motor-related use to be met. Thus, the synthesis gas that is available at the filter device 18c or at a synthesis-gas outlet 2c adjoining said device can now be transferred, for example, to an internal combustion engine 19 for an energy-related use. For this purpose, the internal combustion engine 19 is designed as a gasoline engine having an attached generator and an attached device for utilizing waste heat in the sense of an energy-based co-generator. Thus, the originally supplied solid fuel, sewage sludge, is utilized comprehensively in an energy-related manner, electrically and thermally. Alternatively, the organic solid fuels may further comprise combinations of biogenic waste material, sewage sludge, paper pulp, pomace, husks, manure, shells or the like, for gasification into the synthesis gas, which is suitable for motor-related use by means of a gas turbine.

LIST OF REFERENCE NUMBERS

[0058] 1 gasification device [0059] 2a fuel supply [0060] 2b gasification-air supply [0061] 2c synthesis gas outlet [0062] 3 fuel silo [0063] 4 pyrolysis reactor [0064] 5 pyrolysis auger [0065] 6 thermolysis burner [0066] 7 fluidized bed reactor [0067] 8 wind box [0068] 9 fluidized bed [0069] 10 gas chamber [0070] 11 ash discharge duct [0071] 11a cooling reactor [0072] 11b ash trap [0073] 11c opening [0074] 12 heating-gas preheater [0075] 13 dust-removing device [0076] 14 tubular filter [0077] 15 Venturi scrubber [0078] 16 device for aerosol deposition [0079] 17 device for ammonia deposition [0080] 18a-c filter devices [0081] 19 internal combustion engine

[0082] As will be evident to persons skilled in the art, the foregoing detailed description and figures are presented as examples of the invention, and that variations are contemplated that do not depart from the fair scope of the teachings and descriptions set forth in this disclosure. The foregoing is not intended to limit what has been invented, except to the extent that the following claims so limit that.