High-temperature SCR regulated air system for gas turbine partial load efficiency and extended turndown

Abstract

This invention provides a conditioned air system for a selective catalytic reduction system that improves the partial load efficiency of a gas turbine engine and provides an expanded turndown capability. [Solution] A method is provided for increasing the efficiency of a gas turbine engine 10 or extending the turndown range when the output of the gas turbine engine 10 is reduced by a predetermined percentage. The method may include the steps of: closing some inlet guide vanes 95 to reduce the airflow to the compressor 15 of the gas turbine engine 10; turning on a standby or delay fan 100 of a regulated air system 75 of a selective catalytic reduction system 45 coupled to the gas turbine engine 10, such that the standby or delay fan 100 reduces the output of the gas turbine engine 10 by at least a portion of a predetermined percentage; and reopening the inlet guide vanes 95 to increase the airflow to the compressor 15.

Description

Technical Field

[0001] This application and the patents resulting therefrom generally relate to gas turbine engines, and more particularly to an air adjustment system for a selective catalytic reduction system that can improve part load efficiency and provide an extended turndown capacity.

Background Art

[0002] In the combustion process of a gas turbine engine, nitrogen oxides and other types of regulated emissions are generated. Specifically, the gas turbine emits high-temperature flue gas, which often contains unacceptable levels of nitrogen oxides. One solution for reducing the overall level of nitrogen oxide emissions is the use of a selective catalytic reduction ("SCR") system. Generally speaking, the SCR system adds a reducing agent, typically ammonia or urea, to the high-temperature combustion gas stream, and then passes the combustion gas stream through a catalyst bed so as to selectively absorb the nitrogen oxides and the reducing agent. The absorbed components undergo a chemical reaction on the catalyst surface, and the reaction products are desorbed. Specifically, the reactants react with the nitrogen oxides in the combustion gas stream to produce water and nitrogen.

[0003] The overall efficiency of the SCR system may at least partially depend on the temperature of the high-temperature combustion gas stream. Specifically, the efficient temperature range of the SCR system may be relatively narrow. Therefore, the high-temperature combustion gas stream generally should be cooled sufficiently before reaching the catalyst bed. Thus, the SCR system may use an air adjustment system to introduce ambient air or the like to lower the temperature of the high-temperature combustion gas stream before the flow reaches the catalyst.

[0004] Gas turbine engine operators seek the maximum power output and efficiency from the engine. Maximum power output and efficiency typically occur when operating at base load. During base load operation, the majority of the compressed air from the compressor section is burned, and the inlet guide vanes (IGVs) are fully open to allow the compressor to draw in the maximum amount of air from the surrounding environment. However, base load operation is not always feasible. Energy markets (such as the power grid) may not have sufficient demand for all the energy produced at base load. The power plant must either shut down or operate in a so-called “partial load” state (also referred to herein simply as “partial load”), where less energy is produced than the maximum amount. [Overview of the project]

[0005] Gas turbine engines typically need to maintain emissions compliance while generating power. A gas turbine engine operating at partial load may not be able to maintain emissions compliance across the entire partial load range. The turndown range can be considered the load range over which a gas turbine engine maintains emissions compliance. A wider turndown range allows operators to maintain emissions compliance, minimize fuel consumption, and avoid thermal transients associated with power plant shutdowns.

[0006] Accordingly, the present application and the resulting patents provide a method for increasing the efficiency of a gas turbine engine or extending the turndown range when the output of the gas turbine engine should be reduced by a predetermined percentage in partial load operation. The method may include the steps of: closing several inlet guide vanes to reduce the airflow to the compressor of the gas turbine engine; turning on a standby or delay fan of a regulating air system of a selective catalytic reduction system, wherein the standby or delay fan reduces the output of the gas turbine engine by at least a predetermined percentage; and reopening several inlet guide vanes to increase the airflow to the compressor.

[0007] This application and the resulting patent further provide a gas turbine engine. The gas turbine engine includes a compressor having several inlet guide vanes; a combustor fluid-coupled to the compressor; a turbine fluid-coupled to the combustor; and a selective catalytic reduction system located downstream of the turbine and fluid-coupled to the turbine, wherein the selective catalytic reduction system comprises one or more standby or delay fans. By turning on one or more standby or delayed fans, the inlet guide vanes can remain open or more open when the gas turbine engine is operating at partial load.

[0008] This application and the resulting patents further provide a method for increasing the efficiency of a gas turbine engine or extending its turndown range. The method includes the steps of reducing the output of a gas turbine engine by a predetermined percentage in partial load operation and turning on a standby or delayed fan of a regulated air system of a selective catalytic reduction system. The standby or delayed fan reduces the output of the gas turbine engine by at least a portion of the predetermined percentage.

[0009] These and other features and improvements of this application and the resulting patent will become apparent to those skilled in the art when the following detailed description is considered together with some drawings and the attached claims. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of a gas turbine engine, showing an example of a compressor, combustor, turbine, and selective catalytic reduction system. [Figure 2] This is a flowchart of exemplary method steps for using standby or delay fans in a regulated air system to increase the overall efficiency of a gas turbine at partial load or to extend the turndown range of a gas turbine engine. [Figure 3] This flowchart shows exemplary method steps for using standby or delay fans in a regulated air system to extend the turndown range of a gas turbine engine. [Modes for carrying out the invention]

[0011] Referring now to the drawings, similar reference numerals indicate similar elements across several figures, and Figure 1 shows a schematic diagram of a gas turbine engine 10 that may be used herein. The gas turbine engine 10 may include a compressor 15. The compressor 15 compresses an incoming flow of air 20. The compressor 15 delivers the compressed flow of air 20 to a combustor 25. The combustor 25 mixes the compressed flow of air 20 with a pressurized fuel flow 30 and ignites the mixture to create a flow of combustion gases 35. Although only a single combustor 25 is illustrated, the gas turbine engine 10 may include any number of combustors 25 positioned in a circumferential array or the like. The flow of combustion gases 35 is then delivered to a turbine 40 (e.g., an expansion turbine). The flow of combustion gases 35 drives the turbine 40 to generate mechanical work. The mechanical work generated in the turbine 40 drives the compressor 15 via a shaft coupled to an external load such as a generator.

[0012] The gas turbine engine 10 may use natural gas, various types of synthesis gas, liquid fuels, and / or other types of fuels, as well as blends thereof. The gas turbine engine 10 may be any one of several different gas turbine engines offered by GE Vernova in Greenville, South Carolina, including, but not limited to, 7 Series or 9 Series heavy-duty gas turbine engines. The gas turbine engine 10 may be part of a simple cycle power generation system or other types of power generation systems. The gas turbine engine 10 may have different configurations and may use other types of components. Other types of gas turbine engines may also be used herein. Multiple gas turbine engines, other types of turbines, and other types of power generation equipment may also be used together herein.

[0013] The gas turbine engine 10 may also include an SCR system 45. The SCR system 45 may be located downstream of the turbine 40. As described above, the SCR system 45 may contain a catalyst 50 to react with the combustion gas flow 35. The catalyst 50 may be of a conventional design or may be manufactured from a suitable carrier and active catalytic components. Various types of catalysts 50 may be used herein. The catalyst 50 may have any suitable size, shape, or configuration. The SCR system 45 may extend from the inlet 55 to a stack 60 or other type of exhaust pipe. An ammonia injection grid 65 may be located near the catalyst 50 to inject a reducing agent such as ammonia into the combustion gas flow 35. The ammonia injection grid 65 may communicate with an ammonia source 70. The ammonia injection grid 65 may communicate with the ammonia source 70 via an extensive piping system to provide a suitable ammonia distribution in the incoming combustion gas flow 35. The stack 60 or other type of exhaust pipe may be located downstream of the catalyst 50.

[0014] The SCR system 45 may also include a regulated air system 75. The regulated air system 75 may reduce the temperature of the combustion gas flow 35 by introducing ambient air 20, etc., before the flow 35 reaches the catalyst 50. The regulated air system 75 may include a regulated air grid 80 located near the inlet 55 of the SCR system 45 and upstream of the ammonia injection grid 65 and the catalyst 50. The regulated air grid 80 may communicate with a source of ambient air 20 via one or more regulated air fans 85 or other types of air transport devices. Each regulated air fan 85 may have a damper 88 at the fan inlet and / or outlet. The damper 88 may include valves, plates, and blades, etc., to regulate or stop the airflow through it as needed. The damper 88 may be closed until sufficient pressure and volume are ensured to spool up the regulated air fan 85 and prevent backflow through the regulated air fan 85.

[0015] The gas mixer 90 may be positioned downstream of the regulated air grid 80. The gas mixer 90 may also include a series of baffles, etc. The gas mixer 90 can mix the incoming combustion gas flow 35 with the ambient air 20 to achieve a suitable temperature distribution. The cooled flow can then flow through the ammonia injection grid 65 and the catalyst 50 and react with them. The SCR system 45 described herein is for illustrative purposes only. Many other types of SCR systems and components may be used herein.

[0016] The SCR system 45 generally has some redundancy with respect to the regulated air fan 85. The regulated air fan 85 may be configured as a 2×100% configuration, a 3×50% configuration, and a 4×33% configuration, etc., with at least one standby or delay fan 100. The exemplary system in Figure 1 shows a 4×50% configuration. In advanced gas turbine engines 10, the size of the fan motor may be greater than or equal to 1 megawatt. In a known 2×100% configuration, the standby or delay fan 100 may be about 6 megawatts or larger. Variable-size and speed motors and fans may also be used together as described herein. Motors and fans of different speeds may also be used. When a standby or delay fan 100 is turned on, the net power output of the gas turbine engine 10 decreases accordingly; that is, turning on a 5 megawatt standby or delay fan 100 reduces the net power output of the gas turbine engine 10 by 5 megawatts. If two or more standby or delay fans 100 are used simultaneously, parasitic losses increase accordingly. The standby or delay fan 100(s) may be provided with a damper 88 that functions as described above.

[0017] The compressor 15 may include several inlet guide vanes 95 positioned around its inlet. Generally speaking, the output (electrical or mechanical, etc.) of the gas turbine engine 10 is governed by the amount of mass flow entering the compressor 15. The mass flow may be considered as the product of the density and volumetric flow rate of the inlet air 20 entering the compressor 15. The amount of volumetric flow entering the compressor 15 may vary depending on the ambient temperature conditions and the angle of the inlet guide vanes 95. The angle of the inlet guide vanes 95 may determine the flow area at the inlet of the compressor 15. The angle of the inlet guide vanes 95 may be reduced to a minimum angle to limit the amount of turndown. At the minimum angle, a corresponding minimum volumetric flow rate is drawn into the compressor 15. Similarly, at the maximum angle, a corresponding maximum volumetric flow rate is drawn into the compressor 15.

[0018] Figure 2 shows a flowchart of exemplary method steps for using a standby or delay fan 100 to increase the overall efficiency of the gas turbine engine 10 in partial load operation or to extend the overall turndown range of the gas turbine engine 10. As described above, when the standby or delay fan 100 is turned on, the output of the gas turbine engine 10 is reduced accordingly by the energy consumed by the standby or delay fan 100. This output reduction allows the inlet guide vanes 95 to widen to improve the efficiency of the gas turbine engine 10 and, as a result, reduce fuel consumption. Alternatively, the output reduction may extend the turndown range of the gas turbine engine 10.

[0019] For example, the base load output of the gas turbine engine 10 may be 100 times, and each standby or delay fan 100 may be 5 times larger. In step 110, the gas turbine engine 10 may be moved to partial load operation. In other words, the overall power demand may be reduced by a predetermined percentage, for example, 5 percent, such that the output of the gas turbine engine should be reduced to 95 times. As a result, the angle of the inlet guide vane 95 must be reduced (moved to a more closed position) in step 115 to accommodate the partial load operation. In step 120, one of the standby or delay fans 100 may be turned on and spool-up may be initiated. Before turning on the standby or delay fan 100, the damper 88 on the standby or delay fan 100 may be closed. In step 130, the output of the gas turbine engine 10 is reduced by 5 times to power the standby or delay fan 100. In step 140, the angle of the inlet guide vane 95 may be increased (moved to a more open position) to achieve the same net output. Therefore, in step 150, the inlet guide vane 95 is returned to a more open position, as in base load operation, to achieve this same net output. In step 160, the standby or delay fan 100 may be fully spooled up. The damper 88, which may be closed before the standby or delay fan 100 is turned on, is maintained in the closed position during spool-up. In an optional step 170, once the standby or delay fan 100 is fully operational, the damper 88 on the standby or delay fan 100 may be opened. In an optional step 180, the dampers 88 on all or some of the regulating air fans 85 and the standby or delay fan 100 may be moved to a more closed position to achieve the same or somewhat higher overall regulating airflow as in base load operation. These steps may be at least partially reversed when the gas turbine engine 10 returns to base load operation.

[0020] Instead of using the damper 88 on the standby or delay fan 100, in an optional step 175, the airflow through it may be exhausted to the atmosphere or for other purposes instead of the SCR system 45. Similarly, the damper 88 on the standby or delay fan 100 may remain closed at all times in an optional step 185, in which case the method in Figure 2 may omit steps 170 and 180, and the flow through the standby or delay fan 100 may be exhausted to the atmosphere. If a predetermined percentage of partial load operation increases or otherwise changes, an additional standby or delay fan 100 may be turned on. Standby or delay fans 100 of different sizes or with variable speed or capacity may be used together to more precisely address a predetermined percentage of partial load operation.

[0021] Therefore, the use of standby or delay fans 100 increases the efficiency of the gas turbine engine 10 during partial load operation and extends the overall turndown range. Any number of standby or delay fans 100 may be used together depending on the desired degree of partial load operation. Furthermore, given that a standard SCR system requires redundancy in the conditioned air system, this overall efficiency improvement can be provided without additional capital investment.

[0022] In addition to the standby or delayed fan 100 of the regulated air system 75, other types of auxiliary and / or parasitic systems may also be in operation to reduce the overall output of the gas turbine engine 10. However, there are few other components that can be operated with a large auxiliary load and without causing any harm to the system.

[0023] FIG. 3 is a further flowchart showing exemplary method steps for expanding the turndown range of the gas turbine engine 10. At step 190, the gas turbine engine 10 transitions to a partial load operation. At step 200, the gas turbine engine 10 reaches a minimum partial load turndown. At step 210, standby or delayed fan(s) 100 are turned on. When the standby or delayed fan(s) 100 are turned on, at step 220, the output of the gas turbine engine 10 further decreases, and thus the turndown range is further expanded. These steps may be executed continuously or in parallel.

[0024] It is clear that the above relates only to specific embodiments of this application and the resulting patents. Those skilled in the art may make numerous changes and modifications herein without departing from the general spirit and scope of the invention defined by the following claims and their equivalents.

[0025] Further aspects of the invention are provided by the subject matter of the following clauses.

[0026] 1. A method for increasing the efficiency or expanding the turndown range of a gas turbine engine when the output of the gas turbine engine is to be reduced by a predetermined percentage in a partial load operation, the method comprising closing a plurality of inlet guide vanes to reduce the air flow to the compressor of the gas turbine engine; turning on a standby or delayed fan of an adjustment air system of a selective catalytic reduction system coupled to the gas turbine engine, wherein the standby or delayed fan reduces the output of the gas turbine engine by at least a portion of the predetermined percentage; and reopening the plurality of inlet guide vanes to increase the air flow to the compressor.

[0027] 2. The method according to any of the preceding clauses, further comprising the step of turning on an additional standby or delayed fan when the predetermined percentage increases.

[0028] 3. The method described in any of the preceding clauses, further comprising the step of turning on multiple standby or delayed fans.

[0029] 4. The method described in any of the preceding clauses, wherein the step of turning on multiple standby or delay fans includes turning on multiple standby or delay fans of different sizes.

[0030] 5. The method of any of the preceding clauses, wherein the step of turning on a standby or delayed fan includes turning on a variable-speed standby or delayed fan.

[0031] 6. The method of any of the preceding clauses, further comprising the step of closing the damper on the standby or delay fan before turning on the standby or delay fan.

[0032] 7. The method of any of the preceding clauses, further comprising the step of maintaining the damper in the closed position while the standby or delayed fan spools up.

[0033] 8. The method of any of the preceding clauses, further comprising the step of opening at least partially a damper on a standby or delay fan when the standby or delay fan spools up.

[0034] 9. The method of any of the preceding clauses, further comprising providing dampers on a plurality of regulated air fans, and further comprising the step of partially closing the dampers of the plurality of regulated air fans and standby or delay fans.

[0035] 10. The method of any of the preceding clauses, further comprising the step of turning off a standby or delayed fan when partial load operation is complete.

[0036] 11. A gas turbine engine comprising: a compressor having a plurality of inlet guide vanes; a combustor fluid-coupled to the compressor; a turbine fluid-coupled to the combustor; and a selective catalytic reduction system located downstream of the turbine and fluid-coupled to the turbine, wherein the selective catalytic reduction system comprises one or more standby or delay fans, wherein by turning on one or more standby or delay fans, the plurality of inlet guide vanes can remain in an open position when the gas turbine engine is operating at partial load.

[0037] 12. Any gas turbine engine described in the preceding clause in which one or more standby or delayed fans are part of the regulated air system.

[0038] 13. A gas turbine engine as described in any of the preceding clauses, wherein one or more standby or delayed fans are provided with dampers on one or more standby or delayed fans.

[0039] 14. One or more standby or delayed fans, including multiple fans of different sizes, in any of the gas turbine engines described in the preceding clause.

[0040] 15. A gas turbine engine as described in any of the preceding clauses, in which the open position includes at least a partially open position.

[0041] 16. A method for increasing the efficiency of a gas turbine engine or extending its turndown range, the method comprising: reducing the output of the gas turbine engine by a predetermined percentage in partial load operation; and turning on a standby or delay fan of a regulated air system of a selective catalytic reduction system, wherein the standby or delay fan reduces the output of the gas turbine engine by at least a portion of the predetermined percentage.

[0042] 17. The method of any of the preceding clauses, further comprising the step of maintaining a plurality of inlet guide vanes in at least a partially open position in order to maintain airflow to the compressor of a gas turbine engine when a standby or delay fan is turned on.

[0043] 18. The method of any of the preceding clauses, further comprising the step of closing a plurality of inlet guide vanes to reduce the airflow to the compressor of a gas turbine engine before a standby or delay fan is turned on.

[0044] 19. The method of any of the preceding clauses, further comprising the step of reopening multiple inlet guide vanes to increase airflow to the compressor once the standby or delayed fan is turned on.

[0045] 20. The method of any of the preceding clauses, further comprising the step of exhausting the air of a standby or delayed fan into the atmosphere. [Explanation of Symbols]

[0046] 10 Gas turbine engines 15 Compressor 20. Airflow, ambient air, inlet air 25 Combustor 30 Fuel flow 35. Combustion gas flow, combustion gas flow 40 Turbine 45 SCR System 50 Catalysts 55 Entrance 60 stacks 65 Ammonia injection grid 70 Ammonia sources 75 Adjustable Air System 80 Adjustable Air Grid 85 Adjustable Air Fan 88 Damper 90 Gas Mixer 95 Entrance guide vanes 100 standby or delayed fans 110 steps 115 steps 120 steps 130 steps 140 steps 150 steps 160 steps 170 Optional Steps 175 Optional Steps 180 Optional Steps 185 Optional Steps 190 steps 200 steps 210 steps 220 steps

Claims

1. A method for increasing the efficiency of a gas turbine engine (10) or expanding the turndown range when the output of the gas turbine engine (10) should be reduced by a predetermined percentage during partial load operation, In order to reduce the airflow to the compressor (15) of the gas turbine engine (10), the following is done: closing (115) a plurality of inlet guide vanes (95), Turning on (120) the standby or delay fan (100) of the conditioned air system (75) of the selective catalytic reduction system (45) coupled to the gas turbine engine (10), The standby or delayed fan (100) is turned on (120) to reduce the output of the gas turbine engine (10) by at least a portion of the predetermined percentage, To increase the airflow to the compressor (15), the plurality of inlet guide vanes (95) are reopened (140, 150), Methods that include...

2. The method according to claim 1, further comprising the step of turning on an additional standby or delay fan (100) when the predetermined percentage increases.

3. The method according to claim 1, further comprising the step of turning on a plurality of standby or delayed fans (100).

4. The method according to claim 3, wherein the step of turning on the plurality of standby or delay fans (100) includes turning on a plurality of standby or delay fans of different sizes.

5. The method according to claim 1, wherein the step of turning on a standby or delay fan (100) includes turning on a variable-speed standby or delay fan.

6. The method according to claim 1, further comprising the step of closing a damper (88) on the standby or delayed fan (100) before turning on the standby or delayed fan (100).

7. The method according to claim 6, further comprising the step of maintaining the damper (88) in a closed position while the standby or delayed fan (100) spools up.

8. The method according to claim 7, further comprising the step of at least partially opening the damper (88) on the standby or delayed fan (100) after the standby or delayed fan (100) has spooled up.

9. The method according to claim 8, further comprising providing dampers (88) on a plurality of regulated air fans (85), and further comprising the step of partially closing the dampers (88) of the plurality of regulated air fans (85) and the standby or delayed fan (100).

10. The method according to claim 1, further comprising the step of turning off the standby or delayed fan (100) when the partial load operation is completed.

11. The method according to claim 1, further comprising the step (175) of exhausting the air from the standby or delayed fan (100) to the atmosphere.

12. A gas turbine engine (10), A compressor (15) equipped with multiple inlet guide vanes (95), A combustor (25) is fluid-coupled to the compressor (15), A turbine (40) is fluid-coupled to the combustor (25), A selective catalytic reduction system (45) located downstream of the turbine (40) and fluid-coupled to the turbine (40), wherein the selective catalytic reduction system (45) comprises one or more standby or delay fans (100), Equipped with, By turning on one or more standby or delay fans (100), the gas turbine engine (10) can remain in the open position when the gas turbine engine (10) is operating at partial load.

13. The gas turbine engine (10) according to claim 12, wherein the one or more standby or delay fans (100) are part of a regulated air system (75).

14. The gas turbine engine (10) according to claim 12, wherein the one or more standby or delayed fans (100) are provided with dampers (88) on the one or more standby or delayed fans (100).

15. The gas turbine engine (10) according to claim 12, wherein the one or more standby or delayed fans (100) include a plurality of fans of different sizes.

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