Gas turbine fuel systems

Abstract

The present disclosure is entitled "Gas Turbine Fuel System." In one embodiment, the present disclosure provides a gas turbine system comprising: a first pump that supplies distillate fuel to a combustor; a second pump that supplies fuel oil to the combustor; a fuel selection unit that controls the flow of the first distillate fuel and the second fuel oil to the combustor; and a controller that receives feedback from a sensor and, in response to the feedback from the sensor, controls the fuel selection unit to start the gas turbine system on the fuel oil.

Description

Background Art

[0001] The subject matter disclosed herein relates to gas turbines.

[0002] Gas turbines generate power by burning a mixture of air and fuel. This combustion generates exhaust gas that flows through a turbine containing a rotor. As the exhaust gas flows through the turbine, it contacts the turbine blades on the rotor. The rotor rotates in response to the force of the exhaust gas on the turbine blades. This rotation of the rotor, in turn, rotates a shaft coupled to the rotor. The shaft is coupled to a generator, which converts the shaft's mechanical energy into electrical energy.

[0003] Gas turbines can burn a variety of fuels, including diesel, fuel oil, and syngas. Some fuels may be more expensive than others. These cheaper fuels can be used during steady-state operation of the gas turbine. However, these cheaper fuels (such as fuel oil) cannot be used during startup or shutdown of the gas turbine because they cause coking and / or wax accumulation in the fuel lines after shutdown. Therefore, startup fuel, such as diesel, is used to start the gas turbine. The startup fuel is used to bring the gas turbine to full speed through partial load. After loading the gas turbine, the fuel source becomes the steady-state fuel used during steady-state operation. During shutdown, the steady-state fuel can be purged to prevent coking and wax accumulation in the fuel lines. Unfortunately, startup fuel is typically more expensive than steady-state fuel. Over time, each gas turbine startup increases the operating cost of the power plant. Summary of the Invention

[0004] The following summarizes certain embodiments that are comparable in scope to the initially claimed invention. These embodiments are not intended to limit the scope of the claimed invention, but rather, these embodiments are intended only to provide a brief overview of possible forms of the invention. In fact, the present invention may include various forms that may be similar or different from the embodiments set forth below.

[0005] In one embodiment, the present disclosure provides a gas turbine system comprising: a first pump that supplies distillate fuel to a burner; a second pump that supplies fuel oil to the burner; a fuel selection unit that controls the flow of the first distillate fuel and the second fuel oil to the burner; and a controller that receives feedback from a sensor and controls the fuel selection unit in response to the feedback from the sensor to start the gas turbine system on the fuel oil.

[0006] In another embodiment, the present disclosure provides a system comprising a controller that receives feedback from one or more sensors. In response to the feedback from the one or more sensors, the controller controls a fuel selection unit that controls a first fraction fuel flow and a second fuel oil flow to a gas turbine system to start the gas turbine system on the fuel oil. The fuel oil is substantially composed of carbon chains greater than C 20 of hydrocarbon molecules.

[0007] In another embodiment, the present disclosure provides a method for starting a gas turbine using fuel oil. The method includes receiving a signal to start a gas turbine system. The method also detects the fuel used in a previous shutdown of the gas turbine. The method starts the gas turbine system using the fuel oil in response to detecting the distillate fuel used in the previous shutdown. The fuel oil is substantially composed of carbon chains greater than C 20 of hydrocarbon molecules. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] These and other features, aspects, and advantages of the present invention will be better understood when the following detailed description is read with reference to the accompanying drawings, in which like characters represent like parts throughout, and in which:

[0009] Figure 1 is a schematic diagram of a turbine system according to one embodiment; and

[0010] Figure 2 A method for starting a gas turbine system according to one embodiment is provided. DETAILED DESCRIPTION

[0011] One or more specific embodiments of the present invention will be described below. In order to provide a concise description of these embodiments, not all features of an actual implementation may be described in the specification. It should be understood that in the development of any such actual implementation, as in any engineering or design project, many implementation-specific decisions must be made to achieve the developer's specific goals, such as complying with system-related and business-related constraints, which may vary from implementation to implementation. In addition, it should be understood that such development work may be complex and time-consuming, but it is still a routine task for ordinary technicians who benefit from this disclosure to design, fabricate and manufacture.

[0012] When introducing elements of various embodiments of the present invention, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0013] As mentioned above, gas turbines can burn a variety of fuels, including diesel, fuel oil, and syngas. For example, gas turbines can be designed to accommodate liquid and / or gaseous fuels. To operate a gas turbine economically, the cheapest fuel can be used. Unfortunately, cheap fuels can have undesirable effects on the gas turbine. For example, fuel oil can coke or produce wax accumulation in the fuel lines. Incomplete combustion of fuel oil can also produce excessive soot in the gas turbine. Therefore, different fuels can be used during different operating cycles. For example, during startup, a first fuel (e.g., startup fuel) can be used to start the gas turbine. The first fuel can be diesel or some other distillate fuel that will not coke or produce excessive soot in the fuel lines when the gas turbine is ramped up to steady-state operation. Once the gas turbine is at full speed or full speed at partial load (e.g., 30% load), a second fuel (e.g., steady-state fuel) can be used. After operating the gas turbine with the second fuel, the first fuel can be reintroduced to purge the gas turbine of the second fuel before shutting down the gas turbine. Thus, purging the gas turbine of the second fuel prior to shutdown may prevent coking and / or wax accumulation in the fuel lines.

[0014] Unfortunately, typical startup fuels (e.g., distillate fuels) can be more expensive than the fuel used during steady-state operation of a gas turbine. Consequently, the cost of starting and shutting down a gas turbine can increase the cost of operating the gas turbine. Consequently, the cost of operating multiple gas turbines in a power plant can increase when these gas turbines are turned on and off depending on power generation needs. Embodiments described below include gas turbine startup systems and methods that enable the startup of gas turbines using fuel oil or other less expensive fuels. By relying on fuel oil to start gas turbines, gas turbine operators can reduce overall operating costs.

[0015] Figure 1 is a schematic diagram of an embodiment of a turbine system 8 having a gas turbine fuel system 10 that enables the use of fuel oil (i.e., a carbon chain of C 20 or larger hydrocarbon molecules) to start the turbine system. The turbine system 8 (e.g., a dual-fuel turbine system) can use different types of liquid fuels to drive the turbine system 8. For example, the turbine system 8 can use distillate fuels (i.e., diesel, carbon chains less than C 20 hydrocarbon molecules) and fuel oil (i.e., carbon chains are C 20or larger hydrocarbon molecules). As depicted, a fuel nozzle 12 (e.g., a multi-tube fuel nozzle) draws fuel through a fuel line 14. The fuel line 14 may receive fuel from a distillate fuel tank or source 16 and a fuel oil tank or source 18. In the combustor, the liquid fuel is mixed with an oxidant (such as air, oxygen, oxygen-enriched air, air with a reduced oxygen content, or any combination thereof). Although the following discussion refers to the oxidant as air, any suitable oxidant may be used with the disclosed embodiments. It should be understood that the term fuel oil in this application refers to a fuel having a carbon chain of C 20 or larger hydrocarbon molecules, and the term distillate fuel refers to fuels with carbon chains less than C 20 hydrocarbon molecules (such as diesel).

[0016] The turbine system 8 may include one or more fuel nozzles 12 located inside a plurality of combustors 20. The fuel-air mixture is burned in a chamber within each of the plurality of combustors 20, thereby producing hot pressurized exhaust gas. The plurality of combustors 20 direct the exhaust gas through a turbine 22 toward an exhaust outlet 24. As the exhaust gas passes through the turbine 22, the gas drives the turbine blades to rotate a shaft 26 along the axis of the turbine system 8. As shown, the shaft 26 may be connected to various components of the turbine system 8, including a compressor 28. The compressor 28 also includes blades coupled to the shaft 26. As the shaft 26 rotates, the blades within the compressor 28 also rotate, thereby compressing air from an air inlet 30 through the compressor 28 and compressing the air into the fuel nozzles 12 and / or the plurality of combustors 20. The shaft 26 may also be connected to a load 32 (such as a generator in a power plant). The load 32 may include any suitable device capable of being powered by the rotational output of the turbine system 8.

[0017] To supply fuel to the fuel nozzles 12, the gas turbine fuel system 10 includes a distillate fuel (i.e., a fuel with a carbon chain less than C 20 The fuel system 10 also includes one or more pumps 34 that pump fuel oil (e.g., hydrocarbon molecules) from the distillate fuel tank 16 to the fuel selection unit 36. The fuel system 10 also includes one or more pumps 38 that pump fuel oil to the fuel selection unit 36. Because fuel oil can have a high viscosity and can coke or form wax in the fuel lines, the fuel system 10 includes one or more heaters 40 that heat the fuel oil to prevent and / or reduce wax formation and / or coking in the fuel lines. In other words, heating the fuel oil can facilitate the movement of the fuel oil through one or more fuel lines (e.g., fuel line 14).

[0018] For example, the fuel selection unit 36 may include one or more valves (e.g., three-way valves) that control the flow of distillate fuel and fuel oil to the fuel nozzle 12. The operation of the fuel selection unit 36 is controlled by signals from a controller 42. The controller 42 includes one or more processors 44 (such as the microprocessor shown) and one or more memory devices 46. The controller 42 may also include one or more storage devices and / or other suitable components. The processor 44 may be used to execute software, such as software for controlling the opening and closing of one or more valves in the fuel selection unit 36.

[0019] Processor 44 may include multiple microprocessors, one or more "general purpose" microprocessors, one or more special purpose microprocessors, and / or one or more application specific integrated circuits (ASICS), or some combination thereof. For example, processor 44 may include one or more reduced instruction set (RISC) processors.

[0020] Memory device 46 may include volatile memory (such as random access memory (RAM)) and / or non-volatile memory (such as read-only memory (ROM)). Memory device 46 may store a variety of information and may be used for a variety of purposes. For example, memory device 46 may store processor-executable instructions (e.g., firmware or software) for execution by processor 44. Storage devices (e.g., non-volatile memory) may include ROM, flash memory, a hard drive, or any other suitable optical, magnetic, or solid-state storage medium, or a combination thereof. Storage devices may store data, instructions, and any other suitable data.

[0021] As mentioned above, fuel costs vary. Therefore, the cheapest fuel, such as fuel oil (i.e., a fuel with a carbon chain greater than C 20 The fuel system 10 enables the turbine system 8 to begin operating on fuel oil, which can reduce the costs associated with operating the turbine system 8. During a typical shutdown of the turbine system 8, the controller 42 directs the fuel selection unit 36 to open and directs the distillate fuel through the fuel selection unit 36, through the fuel line 14, and into the fuel nozzles 12. The distillate fuel then enters the combustor 20, where it is burned while the turbine system 8 is shut down. By purging the fuel oil from the fuel in the fuel selection unit 36, the fuel line 14, the fuel nozzles 12, etc., the fuel oil is prevented from coking, forming wax, and / or forming excessive soot during the shutdown period and during the period between the shutdown of the turbine system 8 and the next restart. As a result, the distillate fuel will remain within the fuel selection unit 36 and the fuel line 14, and thus maintain an open flow path to the fuel nozzles 12 until the next restart of the turbine system 8.

[0022] This unused distillate fuel can then be used to ignite the turbine system 8 during the next restart. However, rather than continuing to use distillate fuel throughout the entire restart and initial loading, the fuel system 10 enables a quick transition to fuel oil. For example, a typical restart uses distillate fuel to increase the rotational speed of the gas turbine to approximately 100%, and then partially loads the turbine system 8 (e.g., to approximately 30%). In contrast, the fuel system 10 uses distillate fuel in the fuel line 14 (i.e., distillate fuel remaining from the previous shutdown) to ignite the turbine system 8, and then uses fuel oil to bring the gas turbine system 8 to approximately 100% rotational speed and final loading. As a result, less distillate fuel is used during the restart of the turbine system 8, which can reduce operating costs.

[0023] However, to restart turbine system 8 using fuel oil, the fuel oil must be pressurized above a threshold pressure and / or heated above a threshold temperature. If not pressurized and heated, the fuel oil may prevent turbine system 8 from restarting. Therefore, fuel system 10 may include one or more sensors that provide feedback regarding the properties of the fuel oil and / or other properties of turbine system 8. For example, fuel system 10 may include one or more temperature sensors 48 and one or more pressure sensors 50, each of which measures the temperature of the fuel oil to determine if it is above a corresponding threshold, and measures the pressure of fuel line 14 to ensure that the distillate fuel pressure is above a corresponding threshold, which enables restarting turbine system 8 with fuel oil. Temperature sensors 48 may be placed at various locations along the flow path between non-distillate tank 18 and combustor 20. For example, temperature sensors 48 may be coupled to heater 40, fuel selection unit 36, fuel line 14, and / or fuel nozzle 12 to detect the temperature of the fuel oil. Similarly, pressure sensors 50 may be placed at various locations along the flow path between fuel selection unit 36 and combustor 20. For example, a pressure sensor 50 may be coupled to the fuel selection unit 36, the fuel line 14, and / or the fuel nozzle 12 to detect the pressure of the fuel oil. In some embodiments, the fuel system 10 may also include an atomization pressure sensor 52 to detect whether the fuel oil is sufficiently atomized for combustion. These sensors 48, 50, and 52 are coupled to the controller 42, enabling the controller 42 to restart the turbine system 8 with fuel oil by controlling the pump 38, the heater 40, and the fuel selection unit 36.

[0024] Figure 2is an embodiment of a method 70 for starting a turbine system. At step 72, method 70 begins by receiving a signal to start the turbine system. Then, at step 74, method 70 determines whether the turbine system was previously shut down using distillate fuel. As described above, the turbine system uses the remaining distillate fuel in fuel line 14 to ignite the turbine system. If the turbine system was not shut down using distillate fuel, then at step 76, method 70 starts the turbine system using distillate fuel. If the turbine system was previously shut down using distillate fuel, then at step 78, method 70 determines whether the fuel pressure is greater than a threshold pressure. For example, controller 42 may receive feedback from pressure sensor 50 indicating that the pressure in fuel line 14 is insufficient (e.g., less than 25 PSIG) to maintain combustion in the turbine system. If the fuel oil pressure is less than the threshold, then at step 76, method 70 starts the turbine system using distillate fuel. If the fuel oil pressure is greater than the threshold, then at step 80, method 70 determines whether the fuel oil temperature is greater than a threshold temperature. For example, controller 42 may receive feedback from temperature sensor 48 indicating that the temperature of the fuel oil is insufficient (eg, less than 100 F) to maintain combustion in the turbine system. If the temperature of the fuel oil is less than a threshold, method 70 starts the turbine system on distillate fuel at step 76 .

[0025] If the turbine system was previously shut down using distillate fuel, the pressure in the fuel line 14 is above a threshold pressure, and the fuel oil is above a threshold temperature, then at step 82, method 70 continues by releasing the fuel oil. That is, the controller 42 signals the fuel selection unit 36 to release the fuel oil to the fuel nozzle 12. Then, at step 84, method 70 turns on the turbine system. When the turbine system is turned on, the remaining distillate fuel is ignited, thereby beginning combustion in the combustor 20. As the distillate fuel burns, exhaust gas flows through the turbine 22, thereby increasing the speed of the turbine 22 and, therefore, the rotation of the shaft 26. The turbine system continues to burn the remaining distillate fuel until the fuel oil reaches the fuel nozzle 12. The turbine system will then burn the fuel oil to increase the rotational speed of the turbine system, and then burn the fuel oil due to the turbine system loading (e.g., increasing electrical output). In some embodiments, at step 86, method 70 may determine whether the atomizing air pressure is greater than a threshold level. By monitoring the air atomizing pressure, method 70 may determine whether the fuel oil is sufficiently atomized for combustion. More specifically, a sufficient percentage of the fuel oil will be combusted in the combustor 20. If the atomization pressure is less than the threshold, then at step 88, the method 70 may stop the turbine system or switch to using distillate fuel. For example, the controller 42 signals the fuel selection unit 36 to stop the flow of fuel oil while releasing the distillate fuel for combustion. If the atomization pressure is greater than the threshold, then at step 90, the method 70 continues to start the turbine system using the fuel oil. That is, the speed of the turbine 22 is increased, and once the turbine reaches a steady-state speed, the load is increased.

[0026] The technical effects of the present invention include a gas turbine fuel system that enables a turbine system to be powered by fuel oil (i.e., a fuel oil having a carbon chain of C 20 That is, the gas turbine fuel system enables the turbine system to reach operating speed before loading by using fuel oil.

[0027] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any combined methods. The patentable scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. If such other examples have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims, such other examples are intended to be within the scope of the claims.

Claims

1. A gas turbine system (8), comprising: a first pump (34) configured to supply distillate fuel to the burner (20); a second pump (38) configured to supply fuel oil to the burner (20); a fuel selection unit (36) configured to control a flow of a first fraction fuel and a second fuel oil to the burner (20); and a controller (42) configured to receive feedback from sensors (48, 50, 52); Characterized in that the controller (42) is further configured to: determining whether the gas turbine system was previously shut down using distillate fuel; controlling the first pump (34), the second pump (38), and the fuel selection unit (36) in response to the feedback from the sensors (48, 50, 52) to start the gas turbine system (8) on the fuel oil if the gas turbine system was previously shut down on distillate fuel and if the feedback indicates that the pressure of the fuel oil is greater than a threshold pressure and the temperature of the fuel oil is greater than a threshold temperature; and The gas turbine system (8) is started on distillate fuel if the gas turbine system has not been previously shut down on distillate fuel or if the feedback indicates that the pressure of the fuel oil is less than a threshold pressure or the temperature of the fuel oil is less than a threshold temperature.

2. The system of claim 1, comprising a heater (40) configured to heat the fuel oil prior to combustion in the burner (20).

3. The system of claim 1, wherein the sensors (48, 50, 52) include a pressure sensor (50) configured to detect the pressure of the fuel oil in a fuel line (14).

4. The system of claim 1, wherein the sensor (48, 50, 52) comprises a temperature sensor (48) configured to detect a temperature of the fuel oil.

5. The system of claim 1, wherein the sensors (48, 50, 52) include an air atomization pressure sensor (52) configured to detect air atomization pressure.

6. The system of claim 1, wherein the distillate fuel comprises a carbon chain equal to or less than C 20 of hydrocarbon molecules.

7. The system of claim 1, wherein the fuel oil comprises a carbon chain greater than C 20 of hydrocarbon molecules.

8. A method for starting a gas turbine system (8) by means of fuel oil, the gas turbine system (8) comprising: A first pump (34) configured to supply distillate fuel to a burner (20); a second pump (38) configured to supply fuel oil to the burner (20); a fuel selection unit (36) configured to control a first distillate fuel flow and a second fuel oil flow to the burner (20); the method comprising: receiving a signal to start the gas turbine system (8); and receiving feedback from sensors (48, 50, 52); The method is characterized in that it further comprises: determining whether the gas turbine system was previously shut down using distillate fuel; If the gas turbine system was previously shut down on distillate fuel and if the feedback indicates that the pressure of the fuel oil is greater than a threshold pressure and the temperature of the fuel oil is greater than a threshold temperature, controlling the first pump (34), the second pump (38), and the fuel selection unit (36) in response to the feedback from the sensors (48, 50, 52) to start the gas turbine system (8) on the fuel oil, wherein the fuel oil is composed of carbon chains greater than C 20 The hydrocarbon molecular composition of The gas turbine system (8) is started on the distillate fuel if the gas turbine system has not been previously shut down on the distillate fuel or if the feedback indicates that the pressure of the fuel oil is less than a threshold pressure or the temperature of the fuel oil is less than a threshold temperature.

9. The method according to claim 8, wherein The sensors (48, 50, 52) include a pressure sensor (50), and wherein the method includes receiving a signal from the pressure sensor (50), wherein the pressure sensor (50) is configured to detect a pressure of the fuel oil in a fuel line (14), wherein in response to the pressure exceeding a threshold pressure, the method activates the gas turbine system (8) on the fuel oil, and wherein in response to the pressure being less than the threshold pressure, the method activates the gas turbine system (8) on the distillate fuel.

10. The method according to claim 9, wherein the distillate fuel is composed of carbon chains equal to or less than C 20 of hydrocarbon molecules.

11. The method according to claim 8, wherein The sensors (48, 50, 52) include a temperature sensor (48), and wherein the method includes receiving a signal from the temperature sensor (48), wherein the temperature sensor (48) is configured to detect a temperature of the fuel oil, wherein in response to the temperature exceeding a threshold temperature, the method activates the gas turbine system (8) on the fuel oil, and wherein in response to the temperature being less than the threshold temperature, the method activates the gas turbine system (8) on the distillate fuel.

12. The method according to claim 8, wherein The sensors (48, 50, 52) include an air atomization pressure sensor (52), and wherein the method includes receiving a signal from the air atomization pressure sensor (52), wherein the air atomization pressure sensor (52) is configured to detect an air atomization pressure, wherein in response to the air atomization pressure exceeding a threshold air atomization pressure, the method starts the gas turbine system (8) on the fuel oil, and wherein in response to the air atomization pressure being less than the threshold air atomization pressure, the method stops operation of the gas turbine system (8) or switches to the distillate fuel.

13. The method of claim 8, wherein starting the gas turbine system (8) on the fuel oil comprises increasing the speed of the gas turbine system (8) from a first rotational speed to a second rotational speed, wherein the gas turbine system (8) cannot be loaded at the first rotational speed but can be loaded at the second rotational speed.

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