Extended gas turbine process having an expander

Abstract

A power plant including a compressor, a combustion chamber and a turbine, and a compressor air line, which connects the compressor to the combustion chamber, a first heat exchanger connected into the compressor air line and into an exhaust line branching off the turbine. A first expander is arranged between the first heat exchanger and the combustion chamber in the compressor air line, and the first expander and the compressor are arranged on a common shaft.

Claims

1. A method for operating a power plant having a compressor, a combustion chamber and a turbine, the method comprising: choosing an outlet pressure of the compressor to be higher than a required turbine inlet pressure, preheating the compressor air in a heat exchanger before the compressor air is expanded prior to the combustion, wherein the compressor air is preheated in the heat exchanger with an exhaust gas of the power plant, and wherein the expansion of the compressor air prior to the combustion is utilized for driving the compressor.

2. The method as claimed in claim 1, wherein the compressor air is lowered by the expansion to a turbine pressure level and a maximum permissible temperature for the combustion chamber.

3. The method as claimed in claim 1, wherein waste heat from the exhaust gas and from a compressor intercooling is utilized for driving a chiller that utilizes the waste heat, for the purpose of improved intercooling of the compressor.

4. The method as claimed in claim 3, wherein water is heated in the heat exchange with the exhaust gas and compressed air and is then evaporated at least partially by a first flash evaporator, wherein the steam produced by the first flash evaporator is fed to a steam jet nozzle and the water produced is further cooled and fed to a second flash evaporator, in which the heated water is evaporated, the steam withdrawn by at least one steam jet nozzle for withdrawing the steam by suction, wherein the water cooled during the evaporation is fed to an inlet of at least part of the compressor intercooling.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be explained in greater detail by way of example with reference to the drawings, in which, schematically and not to scale:

(2) FIG. 1 shows an extended gas turbine process according to the prior art,

(3) FIG. 2 shows an extended gas turbine process having a first expander according to the invention,

(4) FIG. 3 shows an extended gas turbine process having single-stage low-pressure steam, a steam jet nozzle and an injection condenser,

(5) FIG. 4 shows an extended gas turbine process having a heat exchanger for a thermally driven chiller which is in a changed position compared to the exemplary embodiment of FIG. 3,

(6) FIG. 5 shows an extended gas turbine process having two-stage low-pressure steam and an injection condenser,

(7) FIG. 6 shows an extended gas turbine process having two-stage low-pressure steam and a low-pressure evaporator,

(8) FIG. 7 shows an extended gas turbine process as in FIG. 4 having a surface condenser instead of an injection condenser, and

(9) FIG. 8 shows an extended gas turbine process having a second expander.

DETAILED DESCRIPTION OF INVENTION

(10) FIG. 1 shows, schematically and by way of example, an extended gas turbine process according to the prior art. The power plant 1 comprises a compressor 2, a combustion chamber 3 and a turbine 4. A compressor air line 5 connects the compressor 2 to the combustion chamber 3. A first heat exchanger 7 is connected into the compressor air line 5 and into an exhaust line 6 which branches from the turbine 4. In FIG. 1, the first heat exchanger 7 comprises two heat exchanger modules 13, which are both arranged one behind the other in each case in the compressor air line 5 and the exhaust line 6, wherein a water injection 14 is arranged in the compressor air line 5 between the heat exchanger modules 13.

(11) The compressor 2 is a multi-stage intercooled compressor 2, in which second heat exchangers 10 are arranged as compressor intercooling 11 between the compressor stages 9.

(12) The compressor 2 further has taps 33 between the compressor stages 9, for cooling of the combustion chamber 3 and/or the turbine 4.

(13) Finally, the power plant 1 of FIG. 1 comprises a generator 34, which is connected to the turbine 4 via a transmission 35.

(14) FIG. 2 shows an extended gas turbine process having a first expander 8 according to the invention. The first expander 8 is arranged in the compressor air line 5 between the first heat exchanger 7 and the combustion chamber 3 and can be coupled with the compressor 2 via a common transmission 12.

(15) For better utilization of the heat generated on compression, the second heat exchangers 10 are connected into a district heating circuit 15. The provision of heat for the district heating circuit 15 takes place as follows. The cold return water stream from the district heating circuit 15 is divided. A first partial stream is fed to the second heat exchangers 10 for the intercooling 11 of the compressor 2, and a second partial stream is fed to a fifth heat exchanger 36, which is arranged in the exhaust line 6. After heating, the two partial streams are combined and fed to a sixth heat exchanger 37, which is likewise arranged in the exhaust line 6 upstream of the fifth heat exchanger 36 in the direction of flow of the exhaust gas. The stream of water, which is further heated there, is fed to the district heating circuit 15 again.

(16) If no district heating is required, the heat generated on compression is discharged to the environment, for example via Fin-Fan cooling or a cooling tower. For this purpose, a bypass line having a seventh heat exchanger 39 is provided in the power plant 1 of FIG. 2.

(17) FIG. 2 further shows a third heat exchanger 17 for preheating fuel, which third heat exchanger is arranged in the exhaust line 6 between the heat exchanger modules 13.

(18) Finally, a fourth heat exchanger 18 is also arranged in an air supply line 19 to the compressor 2 and connected into a cooling circuit 20 of the power plant 1.

(19) The embodiment of FIG. 3 comprises a thermally driven chiller 21, which is connected on its input side 22 via an eighth heat exchanger 42 to the exhaust line 6 and to a return line 24 of the compressor intercooling 11.

(20) A stream of water from the return line 24 of the compressor intercooling 11 is divided. A first partial stream passes through the heat exchanger 42 and takes up heat from the exhaust line 6. After heating, it is fed to a flash evaporator 29, wherein the steam that is produced is fed to the motive agent connection 43 of a steam jet nozzle 27, while water that remains is fed to a second partial stream of the water from the return line 24 of the compressor intercooling 11. This re-combined stream, after being cooled in the seventh heat exchanger 39, is divided again, wherein a first partial stream cools the air fed to the last compressor stage 9 and a second partial stream is fed to a flash evaporator 29. Steam that is produced is fed to a suction connection 30 of the steam jet nozzle 27, water that remains is fed to the inlet of the compressor intercooling 11, which supplies cooling water to all the other compressor stages 9 apart from the last compressor stage 9.

(21) The steam leaving the mixed stream outlet of the steam jet nozzle 27 is fed to an injection condenser 40 with injection cooling. The condensate that forms is mixed upstream of the seventh heat exchanger 39 with the stream of water coming from the compressor cooling 11. The water required for the injection condenser 40 is removed from the line downstream of the seventh heat exchanger 39.

(22) FIG. 4 shows an exemplary embodiment in which the heat exchanger 42, as compared with the exemplary embodiment of FIG. 3, is moved upwards, in terms of its arrangement in the exhaust line 6, between the heat exchanger modules 13. As a result of the higher exhaust gas temperature at that point in comparison with the embodiment of FIG. 3, a higher steam pressure level, and thus an increased efficiency of the thermally operated steam jet chiller, is possible. Furthermore, there is obtained a better part-load control behavior of the compressed air outlet temperature from the high-temperature recuperation by the intermediately connected external heat transfer.

(23) The cooling process does not necessarily have to be carried out with the steam jet. Absorption or adsorption processes are likewise possible.

(24) FIG. 5 shows an extended gas turbine process having two-stage low-pressure steam and an injection condenser. The chiller 21 thereby comprises two steam jet nozzles 27, the mixed stream outlets 28 of which are brought together, and which are connected together in such a manner that flash evaporators 29 are arranged upstream of the respective suction connections 30 of the steam jet nozzles 27, and a water outlet 31 of one flash evaporator 29 is connected to a water inlet 32 of the other flash evaporator 29. In this manner it is possible to achieve more pronounced cooling of the water for the compressor intercooling 11 than in the exemplary embodiment of FIG. 3.

(25) FIG. 6 shows a further variant, in which steam, at least in part, is not produced in a flash evaporator 29, but in which a low-pressure evaporator 44 is arranged in the exhaust line 6.

(26) Finally, FIG. 7 shows a surface condenser 41 as an alternative to the injection condenser 40 of FIG. 4. The surface condenser 41 would then, like the seventh heat exchanger 39, have to be supplied by external cooling.

(27) Finally, FIG. 8 shows an embodiment of the invention having a second expander, which is arranged on the same shaft 46 as the first expander 8 and is connected on the input side to the compressor air line 5 at a position downstream of the first expander 8 and opens on the output side into the exhaust line 6. The arrangement on one shaft 46 is not absolutely necessary. The second expander can also be seated on its own shaft, which is incorporated into the transmission.

(28) The connection of the expanders 8, 45 is designed as a series connection, that is to say the second expander 45 is connected not in parallel but in series downstream of the first expander 8.

(29) In addition, the second expander, like the first expander 8, is connected to the compressor 2 via a transmission.