Low-emission gas turbine plant for peak load, and method

Abstract

The invention relates to a plant comprising at least: a gas turbine; a generator; a chimney (16) into which the hot exhaust gas from the gas turbine can be directed; a catalytic converter section (39) in the chimney (16), wherein nozzles (36) are arranged upstream of the catalytic converter section (39) and can inject a liquid in order to reduce the temperature of the hot exhaust gas from the gas turbine; optionally, a steam turbine and a heat recovery steam generator (HRSG).

Description

[0001] Low-emission gas turbine plant for peak load and process

[0002] The invention relates to a low-emission plant with a gas turbine (GT) that can also be operated at peak loads (peaker), and to a method.

[0003] Due to the tightened requirements of politics and the market regarding further increasing the flexibility of gas turbines or combined cycle power plants as well as regarding the storage of electrical energy, reducing fuel consumption, increasing the flexibility of conventional power plants as a support for renewable energy producers and emissions, especially of NO X , product serfs such as peaker gas turbines and hydrogen burning gas turbines were developed without limiting starts of the gas turbines without significant waiting times and delays when starting up the GT.

[0004] Over time, modern gas turbines will gradually be converted from gas, especially natural gas, to hydrogen as the new fuel. The initial plan is to use a mixture of 60% gas and 40% hydrogen by volume. The hydrogen, H2, will be produced through water electrolysis as part of the nationwide transition to renewable energies, with the electricity coming primarily from wind turbines or photovoltaic systems.

[0005] A gas turbine, whether powered by gas or hydrogen, generally produces relatively low-pollutant exhaust gases within its normal, permissible operating range. However, since the 78% nitrogen in the fresh air is partially converted to thermal nitrogen oxides at the high combustion chamber temperatures (> 1470 K), it produces a certain amount of NO. Xin the form of NO and NO2. In addition, the maximum daily / monthly and annual average values ​​have been significantly tightened under the latest legislation, which now fall below 10 mg nitrogen per m 3 Hydrogen operation could also result in higher primary nitrogen oxide levels, which could be higher and exceed the current emission limits.

[0006] Generally, denitrification (DeNOx) is used. As the name suggests, the catalytic denitrification (SCR) process used in this case for gas turbines is a lower-temperature process, typically 570K - 800K, in which the exhaust gases flow through a solid honeycomb or plate catalyst. The peaker gas turbine can also be operated without the otherwise conventional heat recovery steam generator (HRSG), meaning its exhaust gas is still at temperatures of 830K - 900K.

[0007] It is therefore an object of the invention to solve the above-mentioned problem.

[0008] The object is achieved by a system according to claim 1 and a method according to claim 9.

[0009] The subclaims list further advantageous measures which can be combined with each other as desired to achieve further advantages.

[0010] For SCR operation, the exhaust gas must be cooled to a tolerable temperature, either with additional "cold" ambient air or by injecting fully demineralized water (water variant), or a combination of both. Using the colder ambient air would result in a significant increase in the total volume flow (exhaust gas + ambient air) of 30% to 35%.

[0011] The water variant according to the invention utilizes the evaporation enthalpy (2300 kJ / kg) to reduce the cooling rate of the medium. Injecting 28-30 kg / s of water will be sufficient to reduce the gas turbine's exhaust temperature from approximately 91°C to below 800°C.

[0012] Preferably, an aqueous solution as ammonia water NH4OH, or chemically bound as urea H2N-CO-NH2, is used.

[0013] The invention provides for the effective influencing and regulating of the exhaust gas temperature of the gas turbine in gas turbine power plants so that the gas turbine can be operated in its optimal operating range, even if the exhaust parameters of the gas turbine change due to further developments.

[0014] When using an SCR, water is preferably injected into the exhaust duct upstream of the catalytic converter before entering the SCR in order to lower the exhaust gas temperature or adapt it to the current operating condition. The manipulated variable for this new control system is the water mass flow that is injected into the exhaust duct or chimney of the gas turbine. This manipulated variable can be used to adjust the controlled variable (temperature in the exhaust duct / if applicable upstream of the SCR / emissions) very quickly and effectively. By integrating this manipulated variable into the block control level, gas turbines are thermally decoupled across large parts or almost the entire operating range, regardless of SCR and emissions requirements. This means that current service life, control and operational restrictions no longer apply and are no longer applicable.

[0015] For this water injection, several nozzles must be installed in the exhaust duct, exhaust diffuser, or chimney. These are preferably positioned either after the gas turbine's outlet diffuser or, if necessary, before the SCR.

[0016] The nozzles are preferably installed so that they inject along the circumference of the exhaust duct / exhaust diffuser into the center of the exhaust duct.

[0017] The nozzles are supplied with water by connecting them from the water tank via so-called booster pumps. For this purpose, an additional pump and control valve system is installed for the water supply.

[0018] Other variants of the arrangement of the nozzles are conceivable.

[0019] The distance between the injection point and the SCR is determined in the design phase under aspects of the evaporation capacity of the water and mixing with hot exhaust gas under the aspect of a minimum temperature streak.

[0020] For this injection of water or ammonia water NH4OH or urea H2N-CO-NH2, several combinations of nozzles are installed in the exhaust duct or exhaust diffuser. These are arranged either downstream of the gas turbine outlet diffuser or upstream of the SCR. The nozzles are installed so that they inject, in particular, from the periphery of the exhaust duct / exhaust diffuser into the center of the exhaust diffuser. The nozzles are supplied with water or ammonia water NH4OH or urea H2N-CO-NH2 by connecting them from a water tank via so-called booster pumps and from ammonia water NH4OH or urea H2N-CO-NH2 storage tank. For this purpose, an additional pump and control valve unit is installed for the water supply or ammonia water NH4OH or urea H2N-CO-NH2 supply. Water can also be used to dilute ammonia water (NH4OH) or urea (H2N-CO-NH2). Dilution can even take place in combination nozzles.

[0021] The idea is to enable the operation of a gas turbine plant in a low-emission, legally permitted, yet energy-optimized zone through the permitted, effective, and life-saving use of SCR technology. On the other hand, this makes efficient operation of the gas turbine possible in the first place. To achieve this, the combustion temperature is lowered, which also significantly reduces the increase in CO in the exhaust gas.

[0022] The better, cost-effective and fast cooling of the exhaust gas as well as optional parallel injection of the SCR reactants such as ammonia water NH4OH or urea H2N-CO-NH2 are used here.

[0023] Further increases in the efficiency of the gas turbine are also possible with regard to emissions-compliant operation.

[0024] The further increases in exhaust gas temperature behind the gas turbine will result in tightening of the operating restrictions on the lifetime of the SCR, which can, however, be solved with this development.

[0025] In particular, the parallel combined injection of the SCR reactants will sustainably reduce secondary emissions. No separate measures for the provision of any reactants or coolants will be necessary.

[0026] The following advantages can be mentioned:

[0027] • Enabling the efficient operation of modern gas turbines as peakers, without fear of an unauthorized increase in NOx emissions in the exhaust gas and parallel use of environmentally friendly H2 as fuel

[0028] • Increased availability of the system is achieved

[0029] • Increased flexibility of the power plant, including rapid changes in gas turbine output

[0030] • By controlling the water injection and / or ammonia water NH4OH or urea H2N-CO-NH2, and integrating this control into the block line, the GT and catalyst operation modes are decoupled from each other over a very wide power range. This allows the entire plant to be operated more optimised and flexibly. The advantages of the gas turbine can be almost fully exploited.

[0031] • The operator has more control options to quickly and effectively control the desired parameters with the help of the existing control technology, even with complicated physical processes (start-up)

[0032] • Thanks to the controlled intervention of water injection at all conceivable loads, the exhaust gas temperature of the GT does not necessarily have to be lowered in order not to jeopardize the SCR's service life. If the exhaust gas temperature remains constant, or can even be increased, CO emissions also remain within the specified limits. The advantage of this operating mode would not only be a reduction in CO emissions, but also the possibility of operating the plant at low partial loads with a high combustion temperature, thus enabling flexible response and significant fuel savings.

[0033] • By controlling the water injection, the gas turbine exhaust temperature can be adjusted to the limitations of the catalyst at high ambient temperatures. This allows the gas turbine to continue operating in its optimal range without a reduction in power and efficiency.

[0034] • The combination of controlled water injection enables the installation of GT developments with regard to increased firing temperature, since the catalyst limits no longer represent a restriction.

[0035] • Suitable for retrofitting or conversion

[0036] • Sustainable reduction of plant technology, operating costs and space through the combined injection of water as exhaust gas cooling medium and ammonia water NH4OH or urea H2N-CO-NH2 as reactant for SCR

[0037] • The combination of controlled combined water injection and ammonia water NH4OH or urea H2N-CO-NH2 enables the implementation of enhanced GT systems with increased firing temperatures, as catalyst limits no longer represent a constraint and can be flexibly adapted over a wider range of operation. Figure 1 shows a first system, Figure 2 a second system, Figure 3 a gas turbine with an exhaust duct, and Figure 4 an exhaust duct with nozzles.

[0038] The figures and the description represent only embodiments of the invention.

[0039] Figure 1 schematically shows a plant 1 with a single gas turbine 4 (or gas turbines) driving a generator 7 (or more). An HRSG for this gas turbine 4 is not present.

[0040] Such a gas turbine 4, as shown in Figure 3, has a compressor 20 through which air is sucked in and compressed, mixed with the fuel in a combustion zone 21, and burned, and discharged into the hot gas section 22. The hot exhaust gases from the hot gas section 22 flow out through the chimney or exhaust duct 16.

[0041] Figure 2 shows a combined cycle power plant 11 which, in addition to the at least one gas turbine 4 - according to Figure 3 - has a waste heat boiler (HRSG) 10, the steam generated by which can operate at least one steam turbine 13.

[0042] According to the invention, the combined cycle power plant 11 can also be operated without at least one steam turbine 13.

[0043] Figure 4 shows a chimney or exhaust duct 16 of a plant according to Figure 1, 2 or 3. The hot exhaust gas 43 of the gas turbine 4 flows first in a horizontal direction into a chimney 16 which then extends vertically and at the end of which a catalyst section 39 is arranged.

[0044] At the turning point of the chimney 16, deflection elements 25 are preferably provided for the flow of the hot exhaust gas there.

[0045] According to the invention, liquid can then be introduced into the exhaust stream. This is done through nozzles 36 in the exhaust duct 16. The nozzles 36 are connected to a liquid supply line 28, through which water is preferably supplied.

[0046] Preferably, an emergency water tank 31 is provided which is connected to the liquid supply line 28 and can supply the liquid or water to the nozzles 36 via the liquid supply 28 in the event of irregularities in the liquid supply.

[0047] Optionally, the reducing agent, preferably ammonia, is fed into the liquid supply 28 or elsewhere, preferably from a reservoir 33, to the nozzles 36 and allowed to flow out.

[0048] 28 separate nozzles and separate supply lines can also be used for the reducing or reacting agent from the liquid supply line.

Claims

Claims 1. Plant (1, 11) comprising at least one gas turbine (4), one generator (7), one exhaust gas duct (16) into which the hot exhaust gas of the gas turbine (4) can be conducted, a catalyst section (39) in the exhaust gas duct (16), wherein nozzles (36) are arranged in the exhaust gas duct (16) upstream of the catalyst section (39) and can inject a liquid in order to be able to reduce the temperature of the hot exhaust gas of the gas turbine (4), optionally a steam turbine (13) and waste heat boiler (10).

2. System according to claim 1, wherein the nozzles (36) are installed in such a way that they can inject a liquid, in particular water, from the circumference into the center of the exhaust gas duct (16).

3. System according to one or both of claims 1 or 2, which has a liquid supply line (28), in particular water, into the exhaust gas duct (16) for the nozzles (36).

4. System according to one or more of claims 1, 2 or 3, comprising an emergency water tank (31) connected to the liquid supply line (28).

5. Plant according to one or more of claims 1, 2, 3 or 4, which has a feed line of a reactant, in particular ammonia, into the liquid feed line (28), and in particular has a reservoir (33) of ammonia.

6. Plant according to one or more of claims 1, 2, 3 or 4, which has a supply line of a reactant, in particular ammonia, for nozzles in the exhaust gas duct (16).

7. System according to one or more of the preceding claims, wherein the exhaust gas duct (16) has deflection elements (25) at the beginning of the vertical part.

8. Plant according to one or more of the preceding claims, which also comprises a waste heat boiler (10) and at least one steam turbine (13).

9. System according to one or more of the preceding claims, which has a catalyst section (39) at the end of the exhaust duct (16).

10. Method for operating a plant (1, 11) which has at least one gas turbine (4) with an exhaust gas duct (16), in which a liquid, in particular water, is injected into the exhaust gas duct (16) during operation of the gas turbine (4) in order to reduce the temperature of the hot exhaust gas of the gas turbine (4).

11. Method according to claim 10, wherein the plant (11) is a gas and steam turbine plant, wherein in particular only the gas turbine (4) is operated.

12. The method according to claim 10, wherein the plant (1) has and is operated with at least one gas turbine or only one gas turbine (4).

13. Method according to one or two of claims 10, 11 or 12, in which a reactant, in particular ammonia, is injected into the exhaust gas duct (16).

14. Method according to one or more of claims 13, in which a reactant, in particular ammonia, is injected into the exhaust gas duct (16) via nozzles (36) of a liquid feed line (28).

15. Method according to one or more of claims 13, in which a reactant, in particular ammonia, is injected into the exhaust gas duct (16) separately from the liquid supply line (28).

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