WO2014026832A1

WO2014026832A1 - Gas and steam turbine system comprising a cooling tower

Info

Publication number: WO2014026832A1
Application number: PCT/EP2013/065576
Authority: WO
Inventors: Uwe Juretzek
Original assignee: Siemens Aktiengesellschaft
Priority date: 2012-08-14
Filing date: 2013-07-24
Publication date: 2014-02-20
Also published as: DE102012214444A1

Abstract

The invention relates to a gas and steam turbine system (1) comprising an exhaust heat producer (11) and a cooling tower (21), wherein an exhaust gas pipe (26) connects the exhaust heat producer (11) to the cooling tower (21). The invention further relates to a method for operating such a gas and steam turbine system.

Description

description

The invention relates to a gas and steam turbine plant with a cooling tower and relates to the introduction of exhaust gases into the cooling tower. The invention further relates to a method for operating such a gas and steam turbine plant. For water-steam cycle power plants, a condenser is part of the configuration. This must be cooled accordingly and the heat absorbed must be released to the environment. This is often done by cooling towers. In general, it can be used in wet, hybrid and dry cooling towers (i.e., with and / or without evaporative cooling) and in natural draft and forced air

Cooling towers can be distinguished. Which cooling principle (dry, wet, hybrid, etc.) is used depends essentially on the site conditions. In general, in most climatic zones with wet cooling towers, on average, lower cooling water temperatures or

Achieve condenser pressures and thus an improved power plant efficiency. In that regard, they are the generally preferred type of cooling tower, unless other reasons, such as e.g. the unavailability or limited availability of additional cooling tower water for the use of dry or hybrid cooling systems.

Natural draft cooling towers represent the cheapest of all cooling tower variants in terms of operating costs, since they have no electrical and maintenance requirements for fans, the train is generated "naturally" only by the difference in density between warm air inside the cooling tower and colder ambient air is low, is to produce this "chimney effect" a correspondingly large height of

Cooling tower required, which in Naturzugkühltürmen the required Invest compared to other cooling tower variants is highest. This leaves the application of this cooling As a rule, tower construction is reserved only for large fossil-fired steam power plants and nuclear power plants, which are to be operated in base load.

In other types of power plants, such as gas and steam power plants, the required draft is usually generated "forcibly" by sucking or pushing fans, thus reducing the overall height radically and cooling the tower as a so-called cell cooling tower, resulting in a significant reduction of the necessary Invests but also to a significant increase in the power plant's own needs and thus the ongoing operating costs.

Compared with the forced-ventilated versions, the natural draft cooling tower offers a number of other advantages:

- The large height between air inlet and outlet of the cooling tower reliably prevents each

Recirculation of hot air, which would result in a reduction in performance,

the extensive absence of moving parts leads to high reliability and low maintenance,

- because of hot air outlet at a higher altitude, the immediate environment is spared swath influences,

- If several cooling towers are to be built at the same location, they can be built closer to each other, which reduces the space requirement and

- There are fewer soundproofing measures necessary because fans are omitted as a sound source.

A problem with wet cooling towers (regardless of how the train is produced) is the occurrence of cooling tower swells in the prevailing weather conditions, which can prevent their use depending on site conditions.

One possibility the advantages of both cooling tower variants

(Natural draft and forced ventilated cell cooling tower) to use and compensate for the respective disadvantages, at least partially, The round cooling tower represents a compromise between reducing the height by using fans driven by motors and a reduction of the own demand by the natural train, which can not be ignored due to the average height

The cooling tower variant has already been used in gas and steam turbine plants and has thus demonstrated its competitiveness in comparison to pure forced-ventilated cell cooling towers.

If freedom from swells was required, a dry or hybrid cooling system has been used in the past, with a corresponding cost increase and deterioration of efficiency and performance.

An enhancement of the natural draft can be achieved, for example, by additionally heating the cooling tower exhaust air by means of exhaust gas, as described in US Pat. No. 3,965,672. In gas and steam power plants (consisting of gas turbine,

Waste heat boiler and steam turbine) without district heating economizer in the waste heat boiler, the waste gas leaves the waste heat boiler with a minimum temperature of approx. 80 ° C. Depending on the circuit configuration, sulfur content in the exhaust gas, etc., the exhaust gas temperature can also reach much higher values of up to 160 ° C.

Under ISO environmental conditions, e.g. At an exhaust gas temperature of 80 ° C, the same Archimedean buoyancy with an effective cooling tower height reduced by about 25%

(Height above the air inlet). If exhaust gas with a temperature of 160 ° C is introduced into the cooling tower, the necessary effective cooling tower height is reduced by about half.

The disadvantage of this measure, however, is that at higher sulfur contents in the exhaust gas special materials or coatings for the cooling tower must be selected. _Λ

The object of the invention is to provide a gas and steam turbine plant with improved recooling and a corresponding method.

According to the invention this object is achieved by the device according to claim 1 and the method according to claim 10. Advantageous developments of the invention are defined in the respective dependent claims. In a gas and steam turbine plant, comprising a heat recovery steam generator and a cooling tower, an exhaust line connects the heat recovery steam generator with the cooling tower and means for

Drying of exhaust gas is provided prior to its introduction into the cooling tower during drying, the sulfur dioxide (S0 ₂ ) contained in the exhaust gas can be "washed out" with the water and therefore no special materials or coatings for the cooling tower must be selected.

In an advantageous embodiment, the exhaust pipe is designed so that the previously discharged without further use to the environment hot exhaust gas from the heat recovery steam generator in a region between a heat exchange zone for water to be cooled and cooling tower air and an upper end of the cooling tower in the cooling tower can be introduced.

In the case of wet cooling, "heat exchange zone" means the area in which water to be cooled is sprayed into the air and trickled over with filler particles, thus removing heat of evaporation In dry cooling, heat is transferred via convection heat exchanger to the air ,

It is expedient for the exhaust gas line to open into a device for distributing and mixing the exhaust gas with already heated cooling tower air. In this way, the natural draft is enhanced by the additional warming up. In an advantageous embodiment, the device is a distribution grate with a plurality of exhaust ports, which are directed substantially to the upper end of the cooling tower out and from which the exhaust gas exits and then mixes with the passing cooling tower air.

It is expedient if droplet catchers are arranged in the cooling tower and the exhaust gas between the drip and the upper end of the cooling tower can be introduced into the cooling tower.

In an advantageous embodiment, the device for drying exhaust gas in the cooling tower (above the drip) is arranged and includes a heat exchanger, which is connected on the primary side in the exhaust pipe and the secondary side by a cooling tower exhaust air mass flow can be cooled. In this case, the much larger cooling tower exhaust air mass flow cools the heat exchanger wall far enough that it comes locally to the dew point underrun and the resulting condensate can be removed. By this predrying of the exhaust gas and the heating of the cooling tower exhaust air swathing can be avoided at the cooling tower outlet. Disadvantage of this solution is the increasing pressure loss in the cooling tower, which in turn would result in an increase in the necessary height. It is expedient if the heat exchanger is arranged between the device for distribution and mixing of the flue gas with already heated cooling tower air and the drip catcher. In a further alternative advantageous embodiment, the device for drying exhaust gas prior to introduction into the cooling tower comprises a heat exchanger which is connected on the primary side into the exhaust pipe and on the secondary side into at least a partial flow of the already heated cooling water return from the condenser to the cooling tower. The dew point is only fallen below locally on the heat exchanger wall, since the heat transfer is determined by the water side, the exhaust gas itself is only slightly cooled. Again, join Although pressure drops on, but these do not beat on the required cooling tower height, but only lead to slight power plant efficiency losses, which are far below those of an alternative hybrid or dry cooling system in terms of cost and are overcompensated anyway by the reduced own use of Naturzugkühlturmes. A side effect of the exhaust gas drying is that a certain amount of liquid is recovered from the exhaust gas and thus helps to cover the water demand of the power plant. Also accumulating sulfuric acid may possibly be reused.

In still another advantageous embodiment of an exhaust gas drying the heat exchanger described in the preceding paragraph is not flowed through by a partial mass flow of the already heated cooling water, but by cold condensate from the Kondensatorhotwell. For this purpose, the heat exchanger is connected on the secondary side in the cold condensate stream. This possibility exists when the condensate is sufficiently cold to keep the heat exchanger wall temperature over the entire heat exchange surface so far below the acid dew point that sufficient drying takes place. The advantage would be that in this way the necessary condensate preheater surface in the heat recovery steam generator would be reduced, since the condensate already enters the condensate preheater of the heat recovery steam generator at a higher temperature.

Basically, the dew point can be helpful at higher sulfur levels in the exhaust gas, since with dew point undershoot the S0 ₂ contained in the exhaust gas is "washed out" and therefore no special materials or coatings for the cooling tower must be selected.

Based on the method, the object is achieved by a method for operating a combined cycle power plant, comprising a heat recovery steam generator and a cooling tower, in which hot exhaust gas from the heat recovery steam generator in the cooling tower is introduced and the exhaust gas is dried before being introduced into the cooling tower.

As already stated in the device, it is expedient if the hot exhaust gas is introduced into the cooling tower between a heat exchange zone for water to be cooled and cooling tower air and an upper end of the cooling tower.

It may be advantageous to cool the exhaust gas in heat exchange with cooling tower air so far that locally a Abgastaupunkt the exhaust gas is fallen below on a heat exchanger wall.

Alternatively, it may be advantageous to cool the exhaust gas in heat exchange with a partial flow of the already heated Kühlwasserrücklau- fes from the condenser to the cooling tower so far that an exhaust dew point of the exhaust gas is fallen below at a heat exchanger wall locally.

Finally, it may be advantageous to cool a heat exchanger wall of a heat exchanger by means of a condensate flow so far that an exhaust dew point is locally undershot.

The essence of the invention lies in the use of a device for drying the exhaust gas before it is introduced into the cooling tower (it is irrelevant how the train is generated or whether it is a dry / hybrid / wet cooling tower).

With the use of a device for drying the exhaust gas can be achieved depending on environmental conditions and fuel in addition to the reduction of sulfur problems especially freedom from swirling at the cooling tower outlet even under unfavorable conditions and then one of the conditions for using a more advantageous wet cooling system instead of a dry / hybrid cooling system can be created (comparatively lower costs and higher efficiency / performance).

By increasing the temperature of the total exhaust air mass flow is usually the dew point below the Cooling tower exit and the associated cooling tower swath formation avoided. The relatively humid exhaust gas from the boiler (humid, in particular, when natural gas is used as fuel) accounts for only a comparatively small proportion of approx. 15% of the total exhaust air mass flow and therefore generally lacks weight.

Another advantage is the dilution of the exhaust gas with cooling tower exhaust air. Thus legally permissible emissions, whose visibility can however lead to questions from the population (eg N0 ₂ ), can be diluted to such an extent that you no longer notice them.

The invention will be explained in more detail by way of example with reference to three drawings. Shown schematically and not to scale:

1 shows a gas and steam turbine plant according to the invention with waste gas drying outside the cooling tower by means of cooling water return from the condenser to the cooling tower,

Figure 2 shows a gas and steam turbine plant according to the invention with waste gas drying outside of the cooling tower by means of condensate and

FIG. 3 shows a gas and steam turbine plant according to the invention with exhaust gas drying within the cooling tower.

1 shows a gas and steam turbine plant 1. The gas turbine 2 comprises a turbine 3 with coupled air compressor 4 with compressor intake air line 5 and a turbine 3 upstream combustion chamber 6, which is connected to a compressed air line 7 of the compressor 4. A

Fuel line 8 opens into the combustion chamber 6. The turbine 3 and the air compressor 4 and a generator 9 sit in the embodiment of Figure 1 on a common shaft 10th The hot and pressurized combustion gases from the combustion chamber 6 are supplied to the turbine 3 and there relaxed under the power of work. An exhaust gas line 12 is connected to the heat recovery steam generator 11 for supplying working medium or exhaust gas expanded in the turbine 3 into the waste heat steam generator 11. In the waste heat steam generator 11, the hot exhaust gas releases part of its heat to the superheater, evaporator and preheater of the individual pressure stages of the water-steam cycle 13 of the steam turbine plant 14.

In the steam turbine plant 14, the steam is supplied to a steam generating and superheating the steam turbine 15, which is coupled via a shaft 16 to a generator 17, for relaxation and performing mechanical work.

Regardless of the described embodiment, the invention is suitable both for single and for multi-shaft systems.

The expanded steam is liquefied in the condenser 18, and the condensate is fed via a condensate pump 19 to the heat recovery steam generator 11 again. The liquefaction of the vapor in the condenser 18 takes place in the heat exchange with cooling water.

The cooling water in turn is sprayed in the present example, a wet cooling in the air 20 in the cooling tower 21 and trickled over cooling tower internals 22. Evaporation removes heat from the cooling water and humidifies the air. The cooling water is also cooled by contact with the air by convection. This warms the air, reducing the density of the air and increasing its buoyancy. At the mist eliminator 23, water droplets entrained by the draft are separated and thus returned to the cooled water mass flow falling into the cooling tower cup 24. The cooled water is then in turn promoted by means of pump 25 to the condenser 18. _χ

According to the invention, the cooled exhaust gas leaves the heat recovery steam generator 11 via the exhaust pipe 26 in the direction of the cooling tower 21 and there in a region between a heat exchange zone 27 for water to be cooled and cooling tower air and an upper end 28 of the cooling tower 21 via a device 29th for distributing and mixing the exhaust gas with already heated cooling tower air, for example, a distribution grille 30 with a plurality of exhaust ports 31, which are directed substantially to the upper end 28 of the cooling tower 21, introduced into the cooling tower 21.

FIG. 1 also shows an exhaust gas drying 32 in the exhaust gas line 26 outside the cooling tower 21 and before the exhaust gas is introduced into the cooling tower 21. The heat exchanger 33 of the exhaust gas drying 32 is cooled with a partial amount of the already heated cooling water return from the condenser 18 to the cooling tower 21. Based on the subset of the cooling water mass flow, this is controlled by the valves 34 and 35, al- ternatively, the entire return of the secondary cooling water system can be passed through the heat exchanger 33 unregulated

FIG. 2 shows a detail of FIG. 1 with modified exhaust gas drying. In the example of FIG. 2, the exhaust gas cooling takes place by means of cold condensate, which is conducted via the condensate pump 19 to the heat exchanger 33. A condensate amount control is not provided differently than in the embodiment of Figure 1. The entire available condensate mass flow is passed through the heat exchanger 33.

FIG. 3 shows an alternative exhaust gas drying system 36 in the cooling tower 21, in which a heat exchanger 37 is arranged in the cooling tower 21 above the droplet catcher 23 for local undershooting of the exhaust gas dew point. The cooling tower exhaust air mass flow, which is substantially larger than that of the flue gas, cools the wall of the heat exchanger 37 to such an extent that it is exposed to the dew point. is coming. The resulting condensate is removed (not shown).

Claims

Gas and steam turbine plant (1) comprising a heat recovery steam generator (11) and a cooling tower (21), wherein an exhaust pipe (26) connects the heat recovery steam generator (11) to the cooling tower (21), characterized in that means (32, 36) is provided for drying exhaust gas before its introduction into the cooling tower (21).

The combined cycle power plant (1) according to claim 1, wherein the exhaust pipe (26) is configured such that exhaust gas from the heat recovery steam generator (11) is disposed between a heat exchange zone (27) for water to be cooled and cooling tower air (20) and an upper one End (28) of the cooling tower (21) in the cooling tower (21) can be introduced.

Gas and steam turbine plant (1) according to one of the claims

1 or 2, wherein the exhaust pipe (26) in a device (29) for distribution and mixing of the exhaust gas with already heated cooling tower air (20) opens.

A gas and steam turbine plant (1) according to claim 3, wherein the means (29) is a distribution grate (30) having a plurality of exhaust ports (31) directed generally toward the top end (28) of the cooling tower (21).

Gas and steam turbine plant (1) according to one of the claims

2 to 4, wherein drip (23) in the cooling tower (21) are arranged and the exhaust gas between drip (21) and upper end (28) of the cooling tower (21) in the cooling tower (21) can be introduced.

Gas and steam turbine plant (1) according to one of the preceding claims, wherein the device (36) for drying exhaust gas in the cooling tower (21) is arranged and a heat exchanger (37), the primary side in the Ab- Gas line (26) is connected and the secondary side by cooling tower air (20) is coolable.

7. Gas and steam turbine plant (1) according to claims 3 and 6, wherein the heat exchanger (37) between the means (29) for distributing and mixing the flue gas with already heated cooling tower air and the drip traps (23) is arranged. 8. Gas and steam turbine plant (1) according to one of claims 1 to 5, wherein the means (32) for drying exhaust gas comprises a heat exchanger (33), the primary side in the exhaust pipe (26) and the secondary side in at least a partial flow of an already heated Kühlwasserrücklau- fes from the condenser (18) to the cooling tower (21) is connected.

9. Gas and steam turbine plant (1) according to one of claims 1 to 5, wherein the means (32) for drying exhaust gas comprises a heat exchanger (33), the primary side in the exhaust pipe (26) and the secondary side in a cold condensate stream is switched.

10.Verfahren for operating a gas and steam turbine plant (1) comprising a heat recovery steam generator (11) and a

Cooling tower (21), in which hot exhaust gas from the heat recovery steam generator (11) is introduced into the cooling tower (21), characterized in that the exhaust gas is dried before being introduced into the cooling tower (21).

11.The method of claim 10, wherein the hot exhaust gas between a heat exchange zone (27) for water to be cooled and cooling tower air (20) and an upper end (28) of the cooling tower (21) is introduced into the cooling tower (21).

12.Verfahren according to any one of claims 10 or 11, wherein a heat exchanger wall of a heat exchanger (37) by means of Cooling tower air (20) is cooled down so far that an exhaust dew point is locally undercut. Method according to one of claims 10 or 11, wherein a heat exchanger wall of a heat exchanger (33) by means of a partial flow of an already heated cooling water return from a condenser (18) to the cooling tower (21) is cooled so far that a Abgastaupunkt locally falls below. Method according to one of claims 10 or 11, wherein a heat exchanger wall of a heat exchanger (33) is cooled by means of a condensate flow so far that a Abgastaupunkt locally falls below.