EP0767290B1 - Process for operating a power plant - Google Patents

Description

Technical field

The present invention relates to a method of operation a power plant according to the preamble of claim 1.

State of the art

In a power plant, which consists of a gas turbine group, a downstream heat recovery steam generator and a subsequent steam circuit, it is advantageous to achieve a maximum efficiency to provide a supercritical steam process in the steam circuit.
Such a circuit has become known from CH-480 535. In this circuit, a mass flow of the gas turbine cycle medium is branched off and used recuperatively in the gas turbine for the purpose of optimal utilization of waste heat from the gas turbine group in the lower temperature range of the waste heat steam generator. Both the gas turbine and steam processes have sequential combustion. In the case of modern, preferably single-shaft, gas turbines, however, this configuration leads to an undesirable complication in terms of design.

The document EP-A1-588 392 discloses a combination system for generating electrical Electricity, which consists of a steam and a gas turbine. In detail there is this system from a combustion unit, an overheating unit, an economizer, a degassing unit various turbines and a humidification system. The Temperature in the economizer can be regulated in this way by varying the mass flow be that the temperature of the water is a few degrees below the evaporation temperature is set.

Presentation of the invention

The invention seeks to remedy this. The invention how it is characterized in the claims, the task lies based on a power plant of the type mentioned Type of heat absorption on the steam cycle side in the lower temperature range of the heat recovery steam generator to maximize this Connection with a single-shaft gas turbine.

The main advantages of the invention can be seen in that despite the simplest design, a better one Use of the exhaust gases from the last turbine down to 100 ° C and lower is accomplished by the steam cycle side Heat absorption within a first heat exchange stage in the lower temperature range of the heat recovery steam generator, commonly known as the economizer.

Advantageous and expedient developments of the inventive Task solutions are characterized in the other claims.

In the following, an embodiment will be made with reference to the drawings the invention explained in more detail. All for the immediate Understanding the invention does not require elements have been omitted. The flow direction of the media is indicated with arrows. The same elements are in the different Figures with the same reference numerals.

Brief description of the drawings

Fig. 1

eine Schaltung einer Kraftwerksanlage und

Fig. 2

ein H/T-Diagramm dieser Schaltung gemäss Fig. 1.

It shows:

Fig. 1

a circuit of a power plant and

Fig. 2

an H / T diagram of this circuit according to FIG. 1.

Ways of carrying out the invention, commercial usability

Fig. 1 shows a power plant, which consists of a gas turbine group I., one of the gas turbine group I. downstream heat recovery steam generator II., And one of these heat recovery steam generators II. Downstream steam cycle III. consists.

The present gas turbine group I. is on a sequential Combustion built up. The not visible in Fig. 1 Provision of the to operate the various combustion chambers necessary fuel can for example by using the gas turbine group cooperating coal gasification become. Of course it is also possible to fuel used from a primary network Respectively. Will supply a gaseous fuel provided for the operation of the gas turbine group via a pipeline, so the potential from the pressure and / or temperature difference between primary network and consumer network for the interests of the gas turbine group, or the circuit in general, be recuperated. The present gas turbine group, too can act as an autonomous unit consists of a compressor 1, a first combustion chamber connected downstream of the compressor 2, one downstream of this combustion chamber 2 Turbine 3, one of these turbine 3 downstream second Combustion chamber 4 and one downstream of this combustion chamber 4 second turbine 5. The named flow machines 1, 3, 5 have a uniform rotor shaft 39. This rotor shaft 39 itself is preferably not visible on two in the figure Bearings, which are on the top of the compressor 1 and are placed downstream of the second turbine 5. The Compressor 1 can, depending on the design, for example by the increase specific power in two or more not shown partial compressor can be divided. With one The constellation then becomes downstream of the first partial compressor and an intercooler upstream of the second partial compressor switched, in which the partially compressed air is cooled becomes. The intercooler, also not shown in this The heat generated is optimal, i.e. beneficial, in traced the process. The intake air 6 flows as compressed air 7 in a housing, not shown, which includes the compressor outlet and the first turbine 3. The first combustion chamber 2 is also in this housing housed, which preferably as a coherent annular combustion chamber is trained. Of course, the condensed Air 7 to the first combustion chamber 2 from a not shown Air storage system can be provided. The ring combustion chamber 2 has a number on the head, distributed over the circumference of burners not shown, which preferably are designed as a premix burner. In itself, here diffusion burners are also used. In the sense of Reduction of pollutant emissions from this combustion, However, it is particularly so when it comes to NOx emissions advantageous, an arrangement of premix burners according to EP-PS-0 321 809 to provide, the subject of the invention integral part of said publication Description is, in addition, that described there Method of supplying a fuel 12. What the arrangement the premix burner in the circumferential direction of the annular combustion chamber 2 As far as this is concerned, this can be different from the usual Configuration of same burners differ, and instead can use pre-mix burners of different sizes come. This is preferably done in such a way that between two large premix burners a small premix burner has the same configuration. The big premix burners, which perform the function of main burners have the small premix burners that are the pilot burners of this combustion chamber, with respect to those flowing through it Burner air, i.e. the compressed air from the Compressor 1, in a size ratio to each other, that is determined on a case-by-case basis. In the entire load range of the combustion chamber the pilot burners work as independent premix burners, whereby the air ratio remains almost constant. The Zuoder The main burner is switched off according to certain system-specific Requirements. Because the pilot burners as a whole Load range can be driven with an ideal mixture NOx emissions are very low even at partial load. At a Such a constellation comes the circulating streamlines in the Front area of the annular combustion chamber 2 very close to the vortex centers the pilot burner approached, making an ignition in itself is only possible with these pilot burners. When starting up is the amount of fuel supplied through the pilot burner is increased as far as until these are controlled, i.e. until the full amount of fuel is available. The configuration is chosen so that this point of the respective Load shedding conditions of the gas turbine group. The further one The main burner then increases the power. At the peak load of the gas turbine group there are also those Main burner fully controlled. Because of the pilot burners initiated configuration of "small" hot vortex centers between the "big" coolers from the main distillers Vortex centers also turn out to be extremely unstable lean operated main burners in the partial load range a very good burnout with low NOx emissions CO and UHC emissions achieved, i.e. the hot whorls of Pilot burners immediately penetrate the small swirls of the main burners on. Of course, the annular combustion chamber 2 consist of a number of individual tubular combustion chambers, which are also inclined, sometimes also helical, are arranged around the rotor axis. This ring combustion chamber 2, regardless of its design, will and can be geometric arranged so that they match the rotor length has virtually no influence. The hot gases 8 from this Annular combustion chamber 2 act on the immediately downstream one first turbine 3, whose caloric relaxing effect on the hot gases is deliberately kept to a minimum, i.e. this Turbine 3 is therefore not more than two rows of blades consist. With such a turbine 3 it will be necessary pressure equalization on the end faces for stabilization of the axial thrust. The partially relaxed in the turbine 3 Hot gases 9, which are directly in the second Combustion chamber 4 flow, have a for the reasons stated quite high temperature, preferably it is company-specific to be designed so that it is still around 1000 ° C. This second combustion chamber 4 essentially has the Shape of a coherent annular axial or quasi-axial Ring cylinder. This combustion chamber 4 can of course also from a number axially, quasi-axially or helically arranged and self-contained Combustion chambers exist. As for the configuration of the annular, Combustion chamber 4 consisting of a single combustion chamber, so these are annular in the circumferential direction and radially Cylinder several not shown in the figure Dispose of fuel lances. This combustion chamber 4 has none Burner on: The combustion of one in from the turbine 3 upcoming partially released hot gases 9 injected fuel 13 happens here by self-ignition, as far as of course the temperature level permits such an operating mode. outgoing that the combustion chamber 4 with a gaseous Fuel, for example natural gas, must be operated the outlet temperature of the partially relaxed hot gases 9 the turbine 3 still be very high, as set out above 1000 ° C, and of course also at part-load operation, which is a causal role in the design of this turbine 2 plays. To ensure operational reliability and high efficiency with a combustion chamber designed for self-ignition ensure it is extremely important that the flame front remains locally stable. For this purpose, in this Combustion chamber 4, preferably on the inner and outer wall in Scheduled circumferential direction, a number of not shown Elements provided, which preferably in the axial direction are placed upstream of the fuel lances. The The task of these elements is to create vortices which is a backflow zone, analogous to that in the already mentioned premix burners. Since this is Combustion chamber 4, due to the axial arrangement and the overall length, is a high-speed combustion chamber at which the average velocity of the working gases is greater 60 m / s, the vortex-generating elements must conform to the flow be formed. On the inflow side these preferably have a tetrahedral shape with inclined flow Areas exist. The vortex producing Elements can either be on the outer surface and / or on the Be placed inside. Of course, the vortex generating Elements also shifted axially to each other his. The downstream surface of the vortex generating Elements is essentially radial, so that from there a backflow zone is set. The auto ignition in the combustion chamber 4 must, however, also in the transient load ranges as well as in the part-load range of the gas turbine group remain, i.e. auxiliary measures must be provided be the auto-ignition in the combustion chamber 4 as well then ensure if there is a flexion of the temperature of the Adjust gases in the area of fuel injection should. To ensure safe ignition of the in the combustion chamber To ensure 4 injected gaseous fuel this a small amount of another fuel with one added lower ignition temperature. As an "auxiliary fuel" For example, fuel oil is very suitable here. The liquid Auxiliary fuel, injected accordingly, meets the Task to act as a kind of fuse, and enables also auto-ignition in the combustion chamber 4 when the partially relaxed hot gases 9 from the first turbine 3 a Temperature below the desired optimal level of Should be 1000 ° C. This precaution to ensure fuel oil Providing self-ignition proves of course, it is always particularly appropriate when the Gas turbine group is operated with a greatly reduced load. This arrangement also makes a decisive contribution to that the combustion chamber 4 have a minimal axial length can. The short overall length of the combustion chamber 4, the effect of vortex generating elements for flame stabilization as well The constant guarantee of autoignition are accordingly responsible for burning very quickly takes place, and the residence time of the fuel in the range of hot flame front remains minimal. An immediate combustion specific measurable effect from this affects the NOx emissions, which are minimized, that they are no longer an issue. This starting point also allows to clearly define the place of combustion, which results in optimized cooling of the structures this combustion chamber 4 precipitates. The combustion chamber 4 prepared hot gases 10 then apply a downstream second turbine 5. The thermodynamic parameters The gas turbine group can be designed so that the Exhaust gases 11 from the second turbine 5 still have so much calorific value Have potential so that one here using a heat recovery steam generator 15 shown steam generation stage II. And Steam cycle III. to operate. As in the description the ring combustion chamber 2 has been pointed out, this is geometrically arranged so that it matches the rotor length of the Gas turbine group has practically no influence. Furthermore it can be determined that the second between the outflow plane the first turbine 3 and the inflow level of the second turbine 5 running combustion chamber 4 has a minimum length. There further the expansion of the hot gases in the first turbine 3, for reasons stated, carried out over a few rows of blades, a gas turbine group can be provided whose Rotor shaft 39 is technically flawless due to its minimized length can be supported on two bearings. The power output the turbomachines are done via a compressor side coupled generator 15, which also serve as a starting motor can. After relaxation in the turbine 5, they still flow through with high calorific potential exhaust gases 11 a heat recovery steam generator 15, in which in heat exchange processes steam is generated in various ways, which then becomes the working medium of the downstream steam circuit. The calorically used exhaust gases then flow as Flue gases 38 outdoors.

Assuming that the exhaust gases 11, which are at G in the heat recovery steam generator 15 arrive, its operation continues is described below, with a better understanding of the Path of the flowing into the heat recovery steam generator 15 and from a pump 23 pumped feed water 34 is tracked, have a temperature of about 620 ° C, and under the condition a minimal temperature jump of 20 ° C for the heat transfer, these exhaust gases could only be useful up to 200 ° C be cooled. To fix this disadvantage here is between points A, namely the entrance of the feed water 34 in the heat recovery steam generator 15, and B, branch at the end treatment within an economist level 15a, the amount of the feed water 34 increased so far, in the example to 180%, that the cooling line (see Fig. 2, Pos 11/38) of the exhaust gases at point H, namely immediately before the branch B, as the resultant experiences a kink (see Fig. 2, item 41), which to is sufficient to 100 ° C. In connection with the percentage quantity The relation of the feed water is that 100% of the nominal water quantity fixed depending on that of the exhaust gases 11 offered energy stands.

The feed water 34, which has a temperature of about 60 ° C at a 300 bar, is in A in the heat recovery steam generator 15 initiated and is there to steam of about 540 ° C can be thermally upgraded. The one in the economizer 15a 300 ° C heated feed water is divided into two in point B. Split streams. The one, here larger, partial water flow of 100% in the following tube bundle 15b supercritical high pressure steam 27 thermally processed. Thereby the exhaust gases 11 between points G and H, which symbolize the effective distance of the said tube bundle 15b, the majority of the heat energy is removed. To a first expansion in a high pressure steam turbine 16 this steam 28 with the remaining energy between the Points D and E, which are the range of action of another Tube bundle 15c symbolized in the heat recovery steam generator 15, reheated and as medium pressure steam 29 of a medium pressure steam turbine 17 fed. The residual expansion of the exhaust steam 30 from the medium pressure steam turbine 17 then takes place in a low pressure steam turbine 18, which with another Generator 19 is coupled. It is also possible by coupling to the shaft 39, the power to the generator 14 transfer.

A smaller partial water flow 35 is in the area of point B branched off, and via a throttle element 25 of an evaporation bottle 26 supplied, the pressure level of the saturated steam pressure of Corresponds to 150-200 ° C. The resulting steam is 37 fed to the medium pressure steam turbine 17 at a suitable point. That only served as a heat transfer medium for evaporation still hot residual water 36 is passed through another control device 24 passed into a feed water tank and degasser 22 in which in addition to preheating the condensate Another steam 33 is developed, the low-pressure steam turbine 18 is supplied at a suitable point.

The finally relaxed steam 31a, 31b from this low pressure steam turbine 18 is in a water or air cooled Condenser 20 condenses. Through a downstream of this Condenser 20 acting condensate pump 21 becomes the condensate 32 in the feed water tank and degasser already mentioned 22 promoted from where the previously described cycle starts all over again.

For improved exergy use of the evaporation cascade described this can be done in more than two stages.

Of course, in order to achieve a good use of the exhaust gases 11 a separate one in the waste heat steam generator 15 Steam generating device are integrated, the steam either in the steam cycle III. headed, or in one separate expansion machine is being implemented. It but can also branch off a partial flow of the exhaust gases and in one separate waste heat boiler can be used. Instead of water in this case, preferably an ammonia / water mixture apply. But also other fluids, such as Freon, propane, etc. can be used. A certain one Improve the use of exhaust gases from the turbine up to a lower level can also be realized in that by an additional firing (not shown in the heat recovery steam generator) the temperature level at its entry increased becomes. However, this measure brings in terms of what can be achieved Efficiency no improvement with it.

Fig. 2 shows the H / T diagram, i.e. the course and the in Fig. 1 already recognized significant points of the feed water preheating and steam generation and steam reheating a supercritical steam turbine process. In the The following reference symbol list becomes the respective reference symbol circumscribed this figure. In addition to the statements under Fig. 1, which in connection with the Play this diagram, the following is added. The feed water is at A with, for example, 60 ° C 300 bar initiated, and it is supposed to F in steam of 540 ° C be thermally upgraded using gas turbine waste heat. to a first stage of expansion in the high pressure steam turbine, which leads up to 300 ° C, an intermediate overheating of D to E, also at 540 ° C. The solid line 40 shows the resulting course of heat absorption and Temperature. Assuming that the exhaust gases from the last Gas turbine have a temperature of 620 ° C, and below the condition of a minimum temperature jump of 20 ° C for the Heat transfer, these exhaust gases could reach point J, i.e. here, for example, can only be cooled to 200 ° C. In order to remedy this disadvantage, between points A and B increases the amount of feed water so far, in the example 180% that the cooling curve 11/38 of the exhaust gases in point H results in a kink as a resultant 41, and up to I, i.e. to is sufficient to 100 ° C. This additional feed water flow will removed at B and an evaporation cascade (see Fig. 1) so fed that the steam generated to the medium and low pressure part can be fed to the steam turbine like this also emerges from Fig. 1. The appreciation of the rest Points also emerge from the description of FIG. 1.

LIST OF REFERENCE NUMBERS

I.

Gas turbine group

II.

Steam generation stage

III.

Steam cycle

1

compressor

2

First combustion chamber

3

First turbine

4

Second combustion chamber

5

Second turbine

6

intake

7

Compressed air

8th

hot gases

9

Partial clamping hot gases

10

hot gases

11

exhaust

12

fuel

13

fuel

14

generator

15

heat recovery steam generator

15a

Economizer, in the lower temp. Area op. Heat exchange level

15b

Pipe bundle for supercritical high pressure steam

15c

Pipe bundle for reheated medium pressure steam

16

High pressure steam turbine

17

Medium pressure steam turbine

18

Low pressure steam turbine

19

generator

20

capacitor

21

feed pump

22

Feed water tank and degasser

23

feed pump

24

regulating element

25

regulating element

26

flashing cylinder

27

Supercritical high pressure steam

28

Expanded steam from 16th

29

Reheated medium pressure steam

30

Evaporation from 17 in 18

31a

Relaxed steam from 18

31b

Relaxed steam from 18

32

condensate

33

Steam from 22 in 18

34

feedwater

35

Small partial water flow

36

Hot residual water from 26 in 22

37

Steam from 26

38

fumes

39

rotor shaft

40

Supercritical steam generation curve

41

resultant

11/38

cooling curve

A

Feed water after 22

B

Tapping point for pressurized water to 26

B-C

Sum of B-F + D-E, overheating and intermediate overheating

D-E

Reheat in 15c

F

Place supercritical high pressure steam

G

Entry of exhaust gases in 15

H

Flue gas temperature at extraction point B

I

Exhaust gases from 15 = flue gases

J

Fictitious final flue gas value without withdrawal in B

FROM

Generally over 100%, in the example 180% water flow

B-F

100% water flow

Claims (6)

1. Method of operating a power station plant, essentially comprising a gas-turbine group (I), a waste-heat steam generator (15) arranged downstream of the gas-turbine group, and a steam cycle (III) arranged downstream of the waste-heat steam generator (15), the gas-turbine group (I) consisting of at least one compressor unit (I), at least one combustion chamber (2, 4), at least one turbine (3, 5) and at least one generator (14), the exhaust gases from the last turbine (5) flowing through the waste-heat steam generator (15), in which the generation of at least one steam portion for operating at least one steam turbine (16, 17, 18) of the steam cycle takes place, wherein a liquid quantity increased above 100% circulates in a heat-exchange stage (15a), operating in the low temperature range, of the waste-heat steam generator (15), wherein 100% defines that nominal water quantity which is in relationship to the energy offered by the exhaust gases (11), wherein the portion above 100% of this liquid quantity is diverted at the end of this heat-exchange stage (15a) and is evaporated in at least one pressure stage (26), wherein steam (37) arising herein is fed to a steam turbine (17) at a suitable point, wherein a still hot liquid quantity (36) from the pressure stage (26) is fed to a feed-water tank and deaerator (22), and wherein steam (33) arising herein is fed to a further steam turbine (18) at a suitable point.
2. Method according to Claim 1, characterized in that the gas-turbine group (I) is operated with sequential combustion.
3. Method according to Claim 1, characterized in that the 100% liquid quantity is processed in a heat-exchange stage (15b), directly following the heat-exchange stage (15a) in the low temperature range, to form supercritical steam (27), which is admitted to a further steam turbine (16), in that the steam (28) expanded in this steam turbine (16) is fed back into the waste-heat steam generator (15) in such a way that it is processed there in a further heat-exchange stage (15c) to form reheated steam (29), which is then admitted to a corresponding pressure stage of a steam turbine (17) arranged downstream.
4. Method according to Claim 1, characterized in that the feed-water tank and deaearator (22) is operated as the sole evaporation stage of the steam cycle (III).
5. Method according to Claim 1, characterized in that the portion above 100% of the liquid quantity is directed in a separate heat-exchange element in parallel with and/or in series with the heat-exchange stage (15a) in the low temperature range.
6. Method according to Claim 5, characterized in that the portion above 100% of the liquid quantity differs from the fluid expanding in the steam cycle (III), and in that its thermal energy resulting from the heat exchange is utilized in a separate machine.

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