GAS TURBINE EFFICIENCY AND POWER AUGMENTATION IMPROVEMENTS UTILIZING HEATED COMPRESSED AIR

Abstract

The present invention discloses a novel apparatus and methods for augmenting the power of a gas turbine engine, improving gas turbine engine operation, and reducing the response time necessary to meet changing demands of a power plant. Improvements in power augmentation and engine operation include systems and methods for preheating a steam injection system.

Claims

1. A system for preheating a power augmentation system of a power plant comprising: a gas turbine engine comprising a compressor coupled to a turbine by a shaft, the compressor and the turbine in fluid communication with one or more combustors; a heat recovery steam generator; steam injection piping connecting the gas turbine engine to the heat recovery steam generator, the steam injection piping comprising a steam injection valve and an isolation valve; and, an air vent and an air vent valve in communication with the steam injection piping; wherein the isolation valve and air vent valve are configured to selectively permit flow of air from the compressor, through the steam injection piping, and to the air vent, thereby preheating the steam injection piping.

2. The system of claim 1 further comprising a compressor discharge plenum for receiving compressed air from the compressor and with which one or more combustors are in fluid communication.

3. The system of claim 2, wherein the flow of air is taken from the compressor discharge plenum.

4. The system of claim 1, wherein the heat recovery steam generator utilizes heated exhaust from the gas turbine engine for the production of steam.

5. The system of claim 1, wherein the steam injection valve controls flow of steam from the heat recovery steam generator and to the steam injection piping.

6. The system of claim 1, wherein the isolation valve controls a flow of steam to the gas turbine engine and a flow of compressed air from the gas turbine engine.

7. The system of claim 1, wherein steam produced by the heat recovery steam generator is used in part by an external process.

8. A system for preheating a power augmentation system comprising: a gas turbine engine comprising a compressor coupled to a turbine by a shaft, the compressor and the turbine in fluid communication with one or more combustors; a heat recovery steam generator in selective fluid communication with the gas turbine engine; steam injection piping connecting the gas turbine engine to the heat recovery steam generator, the steam injection piping comprising a steam injection valve, a steam vent valve, a steam vent, and an isolation valve; an air vent and air vent valve in communication with the steam injection piping; and, an auxiliary source of compressed air comprising: a fueled engine coupled to a multi-stage compressor, the fueled engine configured to produce exhaust heat; a recuperator receiving compressed air from the multi-stage compressor and configured to heat the compressed air with the exhaust heat; and, an air injection valve located between the recuperator and the steam injection piping.

9. The system of claim 8 further comprising a compressor discharge plenum for receiving compressed air from the compressor and to which one or more combustors are in fluid communication.

10. The system of claim 9, wherein the flow of air is taken from the auxiliary source of compressed air.

11. The system of claim 8, wherein the heat recovery steam generator utilizes heated exhaust from the gas turbine engine for the production of steam.

12. The system of claim 8, wherein the steam injection valve controls flow of steam from the heat recovery steam generator and to the steam injection piping.

13. The system of claim 8, wherein upon opening of the air injection valve and the isolation valve, heated compressed air from the auxiliary source of compressed air passes through the steam injection piping to preheat the steam injection piping.

14. The system of claim 8, wherein upon the steam injection piping reaching a predetermined temperature, the air injection valve is closed and steam injection valve and steam vent valve are opened to permit steam from the heat recovery steam generator to flow into the gas turbine engine.

15. A system for preheating a power augmentation system comprising: a gas turbine engine comprising a compressor coupled to a turbine by a shaft, the compressor and the turbine in fluid communication with one or more combustors; a heat recovery steam generator in selective fluid communication with the gas turbine engine; steam injection piping connecting the gas turbine engine to the heat recovery steam generator, the steam injection piping comprising a steam injection valve, a steam vent valve, a steam vent, and an isolation valve; an air vent and air vent valve in communication with the steam injection piping; and, an auxiliary source of compressed air comprising: a fueled engine coupled to a multi-stage compressor, the fueled engine configured to produce exhaust heat; a recuperator receiving compressed air from the multi-stage compressor and configured to heat the compressed air with the exhaust heat; and, an air injection valve located between the recuperator and the steam injection piping; wherein, the air injection valve is configured to be closed and each of the steam injection valve and the steam vent valve are configured to be opened upon the steam injection piping reaching a predetermined temperature to permit steam from the heat recovery steam generator to flow into the gas turbine.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0017] The present invention is described in detail below with reference to the attached drawing figures, wherein:

[0018] FIG. 1 is a schematic drawing of a steam injection system on a gas turbine engine of the prior art.

[0019] FIG. 2 is a schematic drawing of an embodiment of the present invention where an air bleed system is added to a new or existing steam injection system on a gas turbine engine.

[0020] FIG. 3 is a flow diagram identifying a method of preheating a power augmentation system.

[0021] FIG. 4 is a schematic drawing of an embodiment of the present invention where a supplementary source of compressed air is used to preheat the steam injection lines.

[0022] FIG. 5 is a flow diagram identifying an alternate method for preheating a power augmentation system.

DETAILED DESCRIPTION

[0023] The present invention is disclosed in FIGS. 2-5. An aspect common to all embodiments of the present invention is an air vent valve 112 positioned near the source of the steam injection, typically very close to the steam injection valve 114. Before steam injection is initiated, the air vent valve 112 is opened to allow air to flow through the steam injection piping, towards the steam source, and discharged into the atmosphere 156. This allows the steam injection piping to be pre-heated to increase the speed that power augmentation with the steam injection system can be started. Various embodiments for heating the steam pipes are discussed herein.

[0024] Typically, steam injection takes at least thirty minutes to initiate and achieve a desired steam injection level. With the steam system pre-heated, the steam injection system can be brought to full flow in less than three minutes. This same air bleed system can be used to purge the steam injection lines when the steam injection process is finished. Typically when the steam injection process is turned off, it is ramped down slowly, many times at a much slower pace than the start-up process. The steam flow is ramped down, because if the steam process is suddenly stopped, the steam injection piping will be full of steam and this steam will turn into water when the steam cools down. Utilizing an air purge system as disclosed herein allows the steam injection to be stopped rapidly, as the steam can be purged from the air steam lines with a process similar to the pre-heat cycle.

[0025] An additional benefit of both the pre-heat and the post purge is that the reverse flow can purge out any foreign matter that might be obstructing the steam injection system. For example, on a General Electric Frame 7FA gas turbine engine, the steam injection system has known operating issues such as plugging of the steam injection system. In this system, the steam is supplied to the gas turbine through a six inch pipe, which is a manifold to fourteen distinct combustors through a three inch pipe. Inside each combustor can there is an annulus that is approximately one inch wide by 0.75 inches tall that supplies ten steam pegs that have five holes approximately 0.030 in diameter. If a foreign matter gets in the flow of steam, it will plug these small holes in the pegs. By purging air from these small holes, any foreign matter that might be caught in them can be flushed out to atmosphere or where ever the air vent is discharging the air.

[0026] Referring now to FIG. 2, a system for preheating a power augmentation system of a power plant is provided. The system 250 comprises a gas turbine engine 1 comprising a compressor 10 coupled to a turbine 16 by a shaft 6. The compressor 10 and turbine 16 are in fluid communication with one or more combustors 12. The system 250 also comprises a heat recovery steam generator 605, or HRSG. The HRSG 605 takes hot exhaust gases 22 from the turbine 16 and a water supply source (not shown) and generates a supply of steam 603.

[0027] The system 250 also comprises steam injection piping 601 connecting the gas turbine engine 1 to the HRSG 605. More specifically, the steam injection piping 601 comprises a steam injection valve 114 and an isolation valve 113. The system 250 also comprises an air vent 156 and air vent valve 112 that is in communication with the steam injection piping 601. As will be discussed further below, the isolation valve 113 and air vent valve 112 selectively permit the flow of compressed air from the compressor 10, and/or a compressor discharge plenum 14, through the steam injection piping 601 and to the air vent 156, thereby preheating the steam injection piping 601. The steam injection piping also includes a steam vent valve 116 for venting steam to the atmosphere through a steam vent 115 when steam is flowing.

[0028] It is important to note that the positions of the steam injection valve 114 and orientation of steam injection piping 601 is merely illustrative of an embodiment of the present invention. As such, it is envisioned that the steam injection valve 114 may be positioned closer to the HRSG 605. For example, in one embodiment is is envisioned that the steam injection piping 601 between the steam injection valve 114 and gas turbine engine 1 could be a couple hundred feet in length.

[0029] Steam 603 produced by the HRSG 605 can be used for multiple purposes. A portion of the steam 603 can be directed through steam injection piping 601, as discussed herein, for injection in the gas turbine engine 1. Alternatively, a portion of the steam 603 can be directed to an external process 602, such as for use in an adjacent manufacturing plant.

[0030] Referring now to FIG. 3, a method 300 of operating a gas turbine energy system is disclosed. In a step 302, a gas turbine engine is operated where the gas turbine engine has a compressor coupled to a turbine, and the compressor and turbine are in fluid communication with one or more combustors. A steam injection system is also in communication with the gas turbine engine where the gas turbine engine produces a heated exhaust utilized by the steam injection system for producing steam.

[0031] In a step 304, a supply of steam is generated by the heated exhaust from the gas turbine engine. Then, in a step 306, a portion of the air from the compressor, or compressor discharge plenum, is directed through at least a portion of the steam injection piping. As shown in FIG. 2, the steam injection piping utilizes an isolation valve adjacent the compressor and an air vent valve for permitting the flow of compressed air to pass from the compressor and through the steam injection piping. As a result of the flow of compressed air the temperature of the steam injection piping is increased and the piping is preheated.

[0032] In a step 308, a determination is made as to whether the steam injection piping temperature has reached an acceptable level. Generally speaking, for the Frame 7FA gas turbine engine discussed above, the steam injection piping is desired to reach approximately 500 degrees Fahrenheit. If the temperature of the steam injection piping has not reached the desired temperature, then compressed air continues to pass through the steam injection piping in order to raise the temperature of the steam injection piping. As discussed above, an isolation valve and air vent valve are opened to permit the flow of compressed air from the gas turbine engine to preheat the steam injection piping. Furthermore, once the determination is made in step 308 that the piping has reached an acceptable temperature, the air vent valve closes and steam injection valve opens, directing steam from the HRSG through the piping. Once the steam injection piping has reached its desired operating temperature, then in a step 310, the flow of air from the compressor to the piping is terminated and then in step 312, at least a portion of the steam supply is directed through the piping and into the gas turbine engine. It is understood that the use of steam and compressed air could overlap such that both fluids could be passing through the piping. Furthermore, it is possible that steam and air could be vented from the piping simultaneously.

[0033] Referring now to FIG. 4, an alternate system for preheating a power augmentation system is disclosed. The system disclosed in FIG. 4 provides an alternate source of compressed air for preheating the steam injection piping. More specifically, the system 450 comprises a gas turbine engine 1 comprising a compressor 10 coupled to a turbine 16 by a shaft 6. The compressor 10 and turbine 16 are in fluid communication with one or more combustors 12. The system 450 also comprises a heat recovery steam generator 605, or HRSG. The HRSG 605 takes hot exhaust gases 22 from the turbine 16 and a water supply source (not shown) and generates a supply of steam 603. As will be discussed below, the HRSG 605 is in selective fluid communication with the gas turbine engine 1.

[0034] The system 450 also comprises steam injection piping 601 connecting the gas turbine engine 1 to the HRSG 605. More specifically, the steam injection piping 601 comprises a steam injection valve 114, a steam vent valve 116, and an isolation valve 113. The system 250 also comprises an air vent 156 and air vent valve 112 that are in communication with the steam injection piping 601. As will be discussed further below, the isolation valve 113 and air vent valve 112 selectively permit the flow of compressed air to the steam injection piping 601, thereby preheating the steam injection piping. The steam injection piping 601 also includes a steam vent valve 116 for venting steam to the atmosphere through a steam vent 115.

[0035] It is important to note that, as with the system 250 in FIG. 2, the positions of the steam injection valve 114 and orientation of steam injection piping 601 is merely illustrative of an embodiment of the present invention. As such, it is envisioned that the steam injection valve 114 may be positioned closer to the HRSG 605. For example, in an embodiment of the present invention, steam injection piping 601 downstream of the steam injection valve 114 could be a couple hundred feet in length.

[0036] Steam 603 produced by the HRSG 605 can be used for multiple purposes. A portion of the steam 603 can be directed through steam injection piping 601, as discussed herein, for injection in the gas turbine engine 1. Alternatively, a portion of the steam 603 can be directed to an external process 602, such as for use in an adjacent manufacturing plant.

[0037] The system 450 also comprises an auxiliary source of compressed air. One such example is the TurboPHASE air injection system produced by PowerPHASE LLC of Jupiter, Fla. Such an auxiliary source of compressed air comprises a fueled engine 151 coupled to a multi-stage compressor 116. The fueled engine 151 takes ambient air 150 and fuel 124 and through its operation provides mechanical output in the form of power to drive the shaft which is coupled to compressor 116 as well as exhaust heat 152. The compressor 116 is a multi-stage intercooled compressor in which ambient air 115 is drawn into the compressor 116 and compressed to a higher pressure. After each stage of compression, the compressed air is cooled, thereby permitting further compression. After the air passes through the last stage of the intercooled compressor 116, the compressed air 117 passes into a recuperator 155. The recuperator 155 receives the compressed air 117 and exhaust heat 152 from the fueled engine 151. The temperature of the compressed air 117 increases as it passes through the recuperator 155 which is heated with the exhaust heat 152 to produce hot compressed air 118. The system 450 also comprises an air injection valve 111 located between the recuperator 155 and the steam injection piping 601. That is, upon opening of the air injection valve 111 and valve 116, heated compressed air from the auxiliary source of compressed air is directed into the steam injection piping 601. The auxiliary source of compressed air can be used to preheat the steam piping 601, inject air into the gas turbine 1, and also inject steam and air into the gas turbine.

[0038] Typically, the steam injection piping 601, which in this case is also an air injection means, is designed such that the pressure of the hot compressed air 118, or steam if it is being injected instead of air, is only about 5 to 10 psi higher than pressure in the gas turbine combustion discharge wrapper 14.

[0039] Referring now to FIG. 5, an alternate method 500 of operating a gas turbine energy system is provided. The method disclosed in FIG. 5 corresponds to the system disclosed in FIG. 4. More specifically, in a step 502, a gas turbine engine is operated where the gas turbine engine has a compressor coupled to a turbine, where the compressor and turbine are in fluid communication with one or more combustors. A steam injection system is also in communication with the gas turbine engine where the gas turbine engine produces a heated exhaust utilized by the steam injection system for producing steam.

[0040] In a step 504, a supply of steam is generated by heated exhaust from the gas turbine engine. Then, in a step 506, heated compressed air from an auxiliary compressor and heated engine is generated. As shown in FIG. 4, the steam injection piping utilizes an isolation valve adjacent the compressor, an air injection valve, and an air vent valve for permitting the flow of compressed air to pass from the auxiliary source of compressed air and through the steam injection piping. As a result of the flow of compressed air the temperature of the steam injection piping is increased and the piping is preheated.

[0041] In a step 508, the heated compressed air from the auxiliary source of compressed air produced by the fueled engine and intercooled compressor is directed into the steam injection piping. Then, in a step 510, a determination is made as to whether the steam injection piping temperature has reached an acceptable level. Generally speaking, for the Frame 7FA gas turbine engine discussed above, the steam injection piping is desired to reach approximately 500 degrees Fahrenheit. If the temperature of the steam injection piping has not reached the desired temperature, then compressed air continues to pass through the steam injection piping in order to raise the temperature of the steam injection piping, as discussed with respect to step 508. Once the steam injection piping has reached its desired operating temperature, then in a step 512, the flow of air from the compressor to the piping is terminated. Once the steam injection piping is at its desired temperature, then in step 514, at least a portion of the steam supply is directed through the piping and into the gas turbine engine. As discussed above, an air injection valve and air vent valve are opened to permit the flow of compressed air from the auxiliary source of compressed air to preheat the steam injection piping. Furthermore, once the determination is made in step 510 that the piping has reached an acceptable temperature, the air vent valve closes and steam injection valve opens, directing steam from the HRSG through the piping. It is understood that the use of steam and compressed air could overlap such that both fluids could be passing through the piping. Furthermore, it is possible that steam and air could be vented from the piping simultaneously.

[0042] Typical steam injection systems utilize steam that is in a highly superheated phase because of the potential temperature drop and concern for water formation. Also, high pressure steam injection systems promote even distribution of the steam throughout the gas turbine and steam nozzles are employed at the point of injection to accomplish this. Therefore the steam that is used is in a very high energy state, typically accomplished by using higher pressure steam, typically 100 to 150 psi higher than the pressure in the gas turbine compress discharge wrapper 114. With a combined air and steam injection system, the air 118 and steam 603 would be joined together and mix as they travel through the steam piping 601 and therefore, much lower quality steam can be used to accomplish the same level of power augmentation. Typically steam quality would be lowered by utilizing lower pressure steam source, and therefore, the steam would have been able to perform useful work in the steam turbine cycle before being extracted for injection, which improves the efficiency of the steam injection system.

[0043] While the invention has been described in what is known as presently the preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment but, on the contrary, is intended to cover various modifications and equivalent arrangements within the scope of the following claims. The present invention has been described in relation to particular embodiments, which are intended in all respects to be illustrative rather than restrictive.

[0044] From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects set forth above, together with other advantages which are obvious and inherent to the system and method. It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and within the scope of the claims.