WO2013038001A1

WO2013038001A1 - Device and method for converting a solid fuel

Info

Publication number: WO2013038001A1
Application number: PCT/EP2012/068216
Authority: WO
Inventors: Thomas Steer
Original assignee: H S Reformer Gmbh
Priority date: 2011-09-16
Filing date: 2012-09-17
Publication date: 2013-03-21
Also published as: EP2756179A1; DE102011113623A1

Abstract

For coupling the gas turbine process to the indirect gasification of solid fuels, particularly by means of steam, and to avoid the use of heat pipes (26) that must be operated using dangerous liquid alkali-metals, a second combustion chamber (25) is provided which is located outside the combustion chamber (6) of the steam turbine and whose heat can be kept to a low temperature level thus allowing the remaining processes to be made available with non-dangerous means.

Description

DEVICE AND METHOD FOR CONVERSION

A SOLID FUEL

I. Field of application The invention relates to a solid-fuel-fired gas turbine.

II. Technical Background Numerous processes for the conversion of chemically bound energy into mechanical or electrical energy are known in thermodynamics. One differentiates thereby processes, with which each fuel can be used, of those, which are reserved for only a few (nobler) fuels. The processes, which are reserved for only a few fuels, usually have a much higher process efficiency, so that there is always a desire to make these processes accessible even to less noble fuels.

For example, the Clausius-Rankine process (steam-power process) belongs to the category where combustion in a steam generator can use any fuel, while a joule process (gas turbine process) only reserves liquid or gaseous fuels is. Gas turbines are work machines in which cold air is compressed in a compressor, then heated in a combustion chamber by combustion of combustibles and finally expanded in a turbine. Since the relaxation of the gas takes place at a much higher temperature than the compression, mechanical work is released in this process. The use of solid fuels always fails because of the problem that the combustion of solid always produces ash particles that are present in the flue gas. Gas turbines do not tolerate dust-like particles. There are therefore numerous attempts to remove the dust particles before entering the gas turbine. Ultimately, however, all these methods lead to a significant loss of efficiency of the Joule process.

In US Pat. No. 4,212,652, it is possible for the first time to represent a Joule process with the aid of allogenic gasification of carbonaceous feedstocks with steam, which achieves the same magnitude of efficiency with solid (non-noble) fuels as with gaseous (noble) fuels. However, the process has so far not found commercial uses, which is probably due to problems in providing the surfaces or temperature differences required for heat transfer.

A further development is the application DE 10 2004 033 348 A1, in which the heat input is to take place via heat pipes. Here, the heat required for the allothermal gasification is decoupled from the combustion chamber of a gas turbine and coupled by means of heat pipe systems in an allothermal gasification chamber. The synthesis gas produced in the al- lothermal gasifier is fed to the gas turbine after gas cleaning of the combustion chamber. The heat required for heating the gasification chamber is according to the 1. The main theorem of thermodynamics as additional heat contained in the synthesis gas and is thus conducted in a short cycle back to the carburetor. The second part of the heat contained in the synthesis gas corresponds to the chemically bound energy of the fuel and is present in the synthesis gas predominantly as chemically bound heat, to a lesser extent as latent or sensible heat. This heat is used in the gas turbine completely for heating the compressed air, so that the process with the same Efficiency proceeds as with the use of precious energy sources such as natural gas.

However, the process is designed very complex due to the extraction of heat from the combustion chamber of the gas turbine and the coupling in an allothermal carburetor. The heat transfer from the combustion chamber into the carburettor takes place by means of heat pipes, in which liquid alkali metals in metallic form as heat transfer medium are required at the required temperature range. These media always carry a latent risk of leakage, leading to highly exothermic reactions with the formation of highly corrosive alkali oxides or alkali hydroxides.

III. DESCRIPTION OF THE INVENTION a) Technical Problem

It is therefore the object of the invention to maintain the efficiency potentials of the novel process and at the same time to minimize or completely avoid the dangers of the alkali metals.

b) Solution to the Problem This object is solved by the features of claims 1 and 9. Advantageous embodiments will be apparent from the dependent claims.

By in a second, separate from the combustion chamber of the gas turbine combustion chamber compressed fresh air and a fuel burned together, usually burned under pressure, and the heat from this combustion of the second combustion chamber is the allothermal Verga- sungsprozess provided , is due to the lower temperature level of combustion in the second combustion chamber compared to Temperature levels in the combustion chamber of the gas turbine, even with the use of heat pipes, the risk of leakage of liquid alkali metals not given because they are not needed because of the lower temperature levels but other, safer heat transfer medium can be used for this purpose.

In this case, the fresh air for this second combustion chamber can be treated separately, so compressed, and also be relaxed again afterwards. The fuel used is preferably part of the product gas generated in the gasification chamber, but any other fuel may be used.

Preferably, however, in a first embodiment according to the invention, a first partial flow of compressed for the gas turbine process fresh air before the combustion chamber of the gas turbine (under certain circumstances, only after this combustion chamber) withdrawn and fed to the second combustion chamber. This saves the effort of a separate preparation. This partial flow of the compressed fresh air can be additionally recompressed prior to introduction into the second combustion chamber to compensate for pressure losses, which is preferably done by means of a jet pump, which can be operated for example by means of a portion of the steam, anyway for introducing the required heat and / or fluidizing the fluidized bed in the gasification chamber is required for the solid fuel.

The combustion heat generated in the second combustion chamber can be used for the process in different ways:

The one solution is that this second combustion chamber is a separate combustion chamber, which is thus used exclusively for the combustion of the air introduced there with the fuel introduced there. This has the advantage that the processes in these separate firing can be controlled very accurately independent of other processes.

From this second, separate Brennkannnner now on the one hand heat can be coupled out and fed to the gasification chamber using heat pipes, for which preferably the second combustion chamber should not be located too far away from the gasification chamber, but as close as possible. Furthermore, the combustion gases escaping from this second combustion chamber contain a great deal of heat. These fuel gases are therefore returned to the gas turbine process by being preferably introduced from the combustion chamber of the gas turbine in the expander as the fuel gases. Another possibility is to first mix the combustion gases from the second combustion chamber with a portion of the product gas and to supply them to the first combustion chamber of the gas turbine process. Also, a supply in the gasification chamber as a fluidizing agent - or mixed with product gas as a fuel - is conceivable. Another solution is that the gasification chamber itself is used as the second combustion chamber.

Then, the compressed fresh air for the second combustion chamber, so for example, the branched off from the compressed fresh air for the gas turbine process substream, the gasification chamber, in particular the local fluidized bed, fed and there with a part of the introduced there solid fuel and / or with a part of the Gasification chamber recirculated product gas burned. The advantage is that the structural complexity is reduced because no separate combustion chamber is needed. The further advantage is that the heat generated during the combustion is already in the gasification chamber, and not be transported there first got to.

The disadvantage is that this combustion takes place within the gasification chamber and can not be controlled and regulated separately from it.

A heat transfer is only necessary within the gasification chamber, but is there usually fulfilled by the existing fluidized bed as a heat transfer medium:

Thus, the circulating fluidized bed may be exothermic in an area where combustion primarily occurs, and endothermic in another area where primarily the solid fuel gasification takes place. However, a heat exchange between these two areas is quasi automatically given by the circulation of the fluidized bed.

The treatment of the steam required as a hybridization agent for the gasification chamber can also be usefully integrated into the overall process:

The exhaust gases escaping the expander, such as the turbine, of the gas turbine process still contain a lot of heat, which can be used. On the one hand, this can be used to heat the compressed air for the gas turbine process, which increases its efficiency. On the other hand, this can cause the vaporization of the water and / or heating of the already generated steam for the gasification process.

Since these two heating processes occur at different temperature levels, it makes sense to use the exhaust gases from the expander first for heating the compressed air and only then at the then slightly lower temperature level for evaporating the water or heating the already generated steam. To carry out the method, therefore, a device is needed which comprises, in addition to a gas turbine with compressor, combustion chamber and expander, a gasification chamber for gasifying a solid fuel, the latter preferably being operated by means of a fluidized bed, and the raw gas produced there is preferably combined via a gas scrubber. Further, in addition to the combustion chamber of the gas turbine, a second combustion chamber is needed, which may be present separately or for which the gasification chamber can be used. In the former case, a heat-conductive connection is preferably necessary in the form of heat pipes between this separate second combustion chamber and the gasification chamber.

Preferably, a heat exchanger is also provided for heating the compressed fresh air for the gas turbine and a heat exchanger for evaporating water for generating the fluidizing steam, which are preferably both operated with the exhaust gases of the expander from the gas turbine.

c) embodiments

Embodiments according to the invention are described in more detail below by way of example. Show it:

Figure 1: a first embodiment according to the invention, and

Figure 2: a second embodiment according to the invention. In the figure 1, the gasification chamber 27 is shown in the upper right, in the lower region of which there is a circulating fluidized bed 43, which is fluidized by water vapor 21 supplied from below. The solid fuel supplied via the fuel supply 28 to the gasification chamber 27 becomes in the gasification chamber 27 - usually under pressure - largely gasified, possibly also burned to a part, in which case the heat of combustion gasification of the rest of the solid fuel benefits, and thus the generation of the raw gas 29, which after cleaning in a gas scrubber 30 as a product gas 31 is available.

Since this gasification process takes place allothermally, in addition to the solid fuel, even if it partially burns in the gasification chamber 27, heat must still be supplied, which takes place via the fluidizing vapor 21 and partly via heat pipes 26.

In the central region of FIG. 1, the gas turbine consisting of the first combustion chamber 6 and the turbine 10 acting as an expander is shown. In the combustion chamber 6 of the gas turbine, a diverted partial flow 7 of the product gas 31 is burned together with compressed air in a compressor 1 2, which is additionally heated in a heat exchanger 12. The fuel gases 8 of the second combustion chamber 25 are supplied to the turbine 9. A partial stream 4 of the compressed and warmed up fresh air 3 is recompressed in a steel pump 23 and this recompressed fresh air 24 is supplied to a second separate combustion chamber 25 in which a partial stream 32 of the product gas of 31 is burned together with this recompressed fresh air 24. The excess 34 of the product gas 31 is then available for further use. The resulting heat of combustion is supplied in part via the heat pipes 26 of the fluidized bed 43 in the gasification chamber 27, and fed in part in the form of discharged from the separate second combustion chamber 25 fuel gases 35 of the turbine 10.

The vapor 21 required for fluidizing the fluidized bed 43 in the gasification chamber 27 is generated by evaporation of water in the heat exchanger 13, and fed directly to the fluidized bed 43 in a substream 21, in another partial flow 22 initially used to operate the steel pump 23.

The air compressed by the compressor 2 2 is further heated in a heat exchanger 12, wherein both the heat exchanger 12 and the heat exchanger 13 are operated by means of heat from the exhaust gases of the turbine 10, the first from the output 1 1 of the turbine 10 to the heat exchanger 12 and are then passed through the heat exchanger 13 before being released into the environment.

The solution according to FIG. 2 differs from that of FIG. 1 in that there is no separate second combustion chamber 25 here, but rather the partial stream 4 of the compressed and heated air 3 branched off in front of the combustion chamber 6 of the gas turbine - in turn recompressed for compensation of pressure losses by means of the jet pump 23 - the fluidized bed 43 is supplied in the gasification chamber 27, which in this case acts as a second combustion chamber.

The compressed air 24 reacts there with the solid fuel and thereby generates heat which accelerates the gasification process in the gasification chamber 27 and / or reacts with product gas 41 or raw gas 29 recirculated into the fluidized bed 43 of the gasification chamber 27, if such recirculation occurs at the gasification chamber 27 is provided. This causes an increased yield of product gas 31 which, as in the first embodiment, is supplied to the first combustion chamber 6 of the gas turbine in a partial stream 7 and the remainder - optionally after branching off the recirculated product gas 41 - as surplus 34 is available for further use. LIST OF REFERENCE NUMBERS

compressor

compressed fresh air

warmed up compressed fresh air

Partial flow fresh air

first combustion chamber

Partial stream product gas

fuel gas

Feeder turbine

turbine

output turbine

heat exchangers

Partial steam

steel pump

recompressed fresh air second combustion chamber

Heatpipe

gasification chamber

Fuel supply

raw gas

gas scrubber

product gas

Surplus-product gas

fuel gas

recirculated product gas

steam

fluidized bed

Claims

1. A process for the conversion of chemically bound in a solid fuel energy into a more easily usable form of energy, with

a joule process or gas turbine process in which fresh air in a compressor (1) is compressed, then burned in a first combustion chamber (6) with a liquid or gaseous fuel and the fuel gases (8) in an expander, in particular a turbine ( 10), relax and provide mechanical energy,

an allothermal gasification process for a solid fuel, in which a combustible product gas (31) is produced in a gasification chamber (27),

wherein at least a partial stream (7) of the product gas (31) produced during the gasification is used as fuel for the combustion in the first combustion chamber (6),

characterized in that

- compressed fresh air (24) fed to a second combustion chamber and is burned with a fuel,

the heat from the combustion in the second combustion chamber is provided to the allothermal gasification process.

2. The method according to claim 1,

characterized in that

a partial flow (4) of the compressed fresh air (2, 3) for the gas turbine process before or after the first combustion chamber (6) withdrawn and the second combustion chamber is supplied.

3. The method according to claim 2,

characterized in that

the partial flow (4) of the compressed fresh air is recompressed, in particular by means of a steel pump (23) which is operated in particular with a partial flow (22) of the gasification chamber (27) supplied water vapor.

(Separate second combustion chamber) 4. The method according to any one of the preceding claims,

characterized in that

the partial flow (4) of the compressed fresh air in the second, separate combustion chamber (25) is burnt with a partial flow (7) of the product gas (31),

- The fuel gases (35) from the second combustion chamber (25) are supplied to the gas turbine process before the expander, or

the fuel gases (35) from the second combustion chamber (25) mixed with at least a portion of the product gas (31) are supplied to the first combustion chamber (6) of the gas turbine process.

5. The method according to any one of the preceding claims,

characterized in that

the heat from the combustion in the second, separate combustion chamber (25) is supplied to the al- lothermal gasification process via heat pipes (26) or heat pipe heat exchanger systems.

(Second combustion chamber = gasification chamber)

6. The method according to any one of the preceding claims,

characterized in that

the partial flow (4) of the compressed fresh air of the gasification chamber (27) is supplied as a second combustion chamber and there with a part the solid fuel and / or the product gas (41) recirculated into the gasification chamber (27) is burned,

the heat produced during the combustion is used to promote the gasification of the remaining solid fuel.

7. The method according to any one of the preceding claims,

characterized in that

in the gasification chamber (27) of the solid fuel in a fluidized bed (43) is guided, and

- The bed material of the fluidized bed (43) acts as a heat transfer medium from an exothermic combustion region in an endothermic gasification within the fluidized bed.

8. The method according to any one of the preceding claims,

characterized in that

the exhaust gas from the expander, in particular from the turbine (10), for heating the compressed air (2) in a heat exchanger (12) and / or for vaporizing the water in a heat exchanger (13) of the steam required for the gasification chamber (27) (21) is used.

9. An apparatus for converting chemically bonded energy in a solid fuel into a more easily usable form of energy, with

a gas turbine, is compressed in the fresh air in a compressor (1), then burned in a first combustion chamber (6) with a liquid or gaseous fuel and the fuel gases (8) in an expander, in particular a turbine (10) relaxed be and provide mechanical energy,

a gasification chamber (27) in which a solid fuel is gasified with the introduction of heat to produce a product gas (31), - wherein a partial stream (7) of the product gas (31) produced during the gasification is used as fuel for the combustion of the first combustion chamber (6 ) is supplied,

characterized in that a second combustion chamber is present in which compressed fresh air is burned with a fuel,

the second combustion chamber is connected via heat pipes (26) to the gasification chamber (27) and / or a line for the combustion gases (35) from the second combustion chamber to the gas turbine.

10. Apparatus according to claim 9,

characterized in that

the second combustion chamber is a separate combustion chamber (25).

11. Apparatus according to claim 9 or 10,

characterized in that

the second combustion chamber is the gasification chamber (27).

12. Device according to one of claims 9 to 11,

characterized in that

in the gasification chamber (27) a fluidized bed (43) is present.

13. Device according to one of claims 9 to 12,

characterized in that

the particular circulating fluidized bed (43) comprises an exothermic combustion zone and an endothermic gasification zone and, in particular in the cyclone of the fluidized bed (43), the two areas merge into one another or adjoin one another.

14. Device according to one of claims 9 to 13,

characterized in that

a heat exchanger (12) for heating the compressed fresh air (2) and / or a heat exchanger (13) for evaporating water are present and flow through in succession from the exhaust gases of the turbine (10).