Fuel Gas Booster-Gas Turbine Integration for Energy Savings and Optimized Operational Performance

Abstract

A fuel gas booster-gas turbine integration for energy conservation and optimized operability is disclosed. The fuel gas booster-gas turbine integration comprises an integrated system including a reciprocating compressor-based fuel gas booster (10) and a gas turbine (11), wherein a gas turbine flow and pressure control system (15) and a fuel gas booster pressure and capacity control system (20) are synchronized to optimize fuel gas booster power consumption or fuel gas booster and gas turbine package power consumption, the gas turbine flow and pressure control system (15) including at least one gas turbine fuel gas input control valve (14), and the fuel gas booster control system (20) including a gas turbine fuel gas input control valve position controller associated with the at least one gas turbine fuel gas input control valve (14) and a fuel gas booster capacity controller associated with the reciprocating compressor-based fuel gas booster (10).

Description

[Technical Field]

[0001] The present disclosure relates to a thermodynamic system and method, and more particularly to an integrated system comprising a reciprocating compressor-based fuel gas booster and a gas turbine, in which fuel gas booster pressure and capacity control and gas turbine flow and pressure control are integrated to optimize the operation of the reciprocating compressor-based fuel gas booster. According to the embodiments disclosed herein, the reciprocating compressor-based fuel gas booster and gas turbine system are automatically synchronized to a minimum absorbed power operating point regardless of changes in ambient and fuel gas pressure, temperature, and composition. [Background technology]

[0002] Gas turbines require fuel gas at a certain pressure to combine it with compressed air before combustion. Typically, the gas pressure available from pipelines is not sufficient to deliver the pressure required by gas turbines. In practice, due to the increasingly higher gas pressures required for high-efficiency gas turbines and the increasing demand for natural gas, the gas pressure in the pipelines cannot be maintained at a sufficiently high value. This is especially true for recent generation gas turbines (which require fuel gas pressure values even exceeding 30 bar absolute), and also during peak demand periods, such as in summer or during the day, when the gas pressure in the pipelines gradually decreases and may even fluctuate.

[0003] To meet the gas turbine's gas flow requirements while adequately handling fluctuations in gas pressure from such pipelines, a fuel gas compressor must be interposed between the pipeline and the gas turbine. This fuel gas compressor is commonly called a fuel gas booster. The two variables most relevant to a fuel gas booster are suction gas pressure fluctuations and changes in turbine load.

[0004] U.S. Patent No. 6,948,919 (B2) discloses a fuel booster operable to compress combustible fuel, comprising a compressor housing, a compressor rotor, and a seal assembly coupled to the compressor housing. The fuel booster also includes a motor having a motor rotor and a motor stator. A variable frequency drive provides power to the motor to control the compressor output pressure and / or flow rate. During operation, one or more sensors monitor engine parameters (e.g., fuel pressure, fuel flow rate, power output, turbine outlet temperature, etc.). The rotational speed of the compressor motor is controlled to maintain the engine parameters at desired values. For example, one system monitors the fuel booster discharge pressure (fuel pressure) and varies the speed of the compressor motor to achieve the desired fuel pressure. If the pressure is too high, the speed of the compressor motor is reduced via the variable frequency drive. If the pressure is too low, the speed of the compressor motor is increased. In another configuration, the engine parameter is fuel flow rate measured by a fuel flow meter (not shown) located downstream of the fuel booster. If the flow rate exceeds the desired value, the variable frequency drive reduces the frequency of the power provided to the compressor motor, reducing the compressor motor speed and flow rate. If the flow rate is too low, the variable frequency drive increases the compressor motor speed, increasing the flow rate to the desired value. In yet another configuration, the turbine outlet temperature is measured directly or indirectly and the compressor motor speed is controlled to maintain the desired turbine outlet temperature. The above-described system controls the compressor output without the use of a traditional slide valve.

[0005] U.S. Patent No. 4,922,710(A) discloses an integrated boost compressor / gas turbine control system in which a fuel gas boost compressor boosts fuel gas pressure before supplying fuel gas to the gas turbine control valves, i.e., the stop / speed ratio or pressure control valve and the gas control or volumetric valve, which then provide the fuel gas to the gas turbine. According to this disclosure, the pressure drop through the gas turbine control valves, and therefore the boost power requirements, is minimized by driving these valves to a fully open position under normal operating conditions and using the valves in their normal control mode during other operating conditions, such as start-up and sudden load rejection. Thus, after start-up operations, system control is transitioned to minimum system pressure drop operation, utilizing boost compressor flow control to control the gas turbine fuel flow and therefore the gas turbine power output.

[0006] Although the above-described systems effectively control the operation of the gas turbine, they have significant limitations due to the power consumption of the fuel gas booster, which can amount to up to 10% of the total rated power of the gas turbine.

[0007] Furthermore, these limitations are also evident in the case of reciprocating compressor-based fuel gas boosters, which is the preferred type of compressor applied to fuel gas boosters in the typical size range (below 500 kW). In fact, reciprocating compressors allow lubricant-free operation, which is essential to avoid oil contamination of the combustion chamber, and very high compression efficiencies compared to competing rotary technologies (e.g., screw compressors).

[0008] Therefore, improved systems and methods for operating reciprocating compressor-based fuel gas boosters and gas turbines to address the absorption power challenges of current technology would be beneficial and welcome in the art. More generally, it would be desirable to provide methods and systems adapted to more effectively address the problems posed by the need to increase fuel gas pressure, while at the same time leading to significant energy and operating cost savings. Summary of the Invention

[0009] In one aspect, the subject matter disclosed herein is directed to a system that integrates fuel gas booster pressure and capacity control with gas turbine flow and pressure control to enable optimization of fuel gas booster and gas turbine package operation and power consumption or at a minimum when a reciprocating compressor based fuel gas booster is used.

[0010] In another aspect, the subject matter disclosed herein relates to a control principle that automatically synchronizes fuel reciprocating compressor based gas booster and gas turbine packages to a minimum absorbed power operating point despite changes in ambient and fuel gas pressure, temperature, and composition. [Brief explanation of the drawings]

[0011] A more complete understanding of the disclosed embodiments of the present invention and many of the attendant advantages thereof will be readily obtained by reference to the following detailed description when considered in conjunction with the accompanying drawings. [Figure 1] 1 illustrates a schematic diagram of an integrated system comprising a reciprocating compressor-based fuel gas booster and a gas turbine according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] According to one aspect, the present subject matter is directed to an integrated system comprising a reciprocating compressor-based fuel gas booster and a gas turbine, wherein fuel gas booster pressure and capacity control and gas turbine flow and pressure control are controlled to optimize operation of the reciprocating compressor-based fuel gas booster.

[0013] According to one embodiment, a reciprocating compressor-based fuel gas booster is integrally connected to the gas turbine casing, and the booster compressor increases the pressure and gas fuel, which is used to increase the internal energy and generate more power with less gas fuel flow.

[0014] According to one aspect, a fuel gas booster control system and a gas turbine control system are integrated to automatically synchronize a reciprocating compressor-based fuel gas booster and gas turbine package to a minimum absorbed power operating point regardless of changes in ambient and fuel gas pressure, temperature, and composition.

[0015] According to certain aspects, when the gas turbine control system sets the gas turbine control valve to a position other than fully open to optimize gas turbine operation, the fuel gas booster control system is operated to reduce capacity. As a result of the fuel gas booster reducing capacity, the fuel gas from the reciprocating compressor-based fuel gas booster has a lower pressure, which allows the gas turbine control system to set the gas turbine control valve to a fully open position and reduce the pressure drop through the gas turbine control valve.

[0016] According to one embodiment, the fuel gas booster is a reciprocating compressor-based fuel gas booster including multiple cylinders, each cylinder including at least one cylinder effect, and the fuel gas booster capacity is controlled by each cylinder effect being provided with a cylinder valve unloader that allows for efficient step control (e.g., a four-cylinder compressor with two effects per cylinder can be managed with a 12.5% capacity step adjustment).

[0017] According to one aspect, fuel gas booster capacity control can be achieved through additional variable clearance pockets that can manage capacity variations by increasing and decreasing individual cylinder clearance pockets with an actuator.

[0018] According to other aspects, other devices can be used to manage the compressor valves to manage efficient capacity control.

[0019] Alternatively, to manage the capacity of a reciprocating compressor-based fuel gas booster, the motor driving the compressor can be equipped with a variable speed system.

[0020] Other fuel gas booster pressure and capacity control devices can be used, but the technical and commercial viability of different solutions must be evaluated depending on the specific service of each individual reciprocating compressor-based fuel gas booster.

[0021] According to another aspect, the fuel gas booster control system is configured as a slow speed control system to minimize any interference with the gas turbine control system. As a result, the pressure drop through the gas turbine control valves, and therefore the boost power requirements, are minimized by driving these valves to a fully open position under normal operating conditions, while the gas turbine control valves are still used to regulate the operation of the gas turbine in a normal control mode.

[0022] According to one particular aspect, a gas turbine control valve is used to regulate gas turbine operation during start-up and sudden load rejection.

[0023] According to another aspect, optimizing reciprocating compressor-based fuel gas booster operation leads to significant energy and operating cost savings.

[0024] Reference will now be made in detail to the embodiments of the present disclosure, one or more examples of which are illustrated in the figures. Each example is provided by way of explanation of the disclosure, not as a limitation of the disclosure. Indeed, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. References throughout this specification to "one embodiment" or "one embodiment" or "some embodiments" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the disclosed subject matter. Thus, the appearances of the phrases "in one embodiment" or "in one embodiment" or "some embodiments" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0025] When presenting elements of various embodiments, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the element. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0026] Referring now to the drawings, FIG. 1 shows a schematic diagram of an exemplary integrated system including a reciprocating compressor-based fuel gas booster 10 and a gas turbine 11, a fuel gas delivery line 12 connecting the inlet of the reciprocating compressor-based fuel gas booster 10 to a fuel gas pipeline (not shown), and a compressed fuel gas line 13 connecting the outlet of the fuel gas booster 10 to the inlet of the gas turbine 11. A gas turbine control valve 14 is disposed on the compressed fuel gas line 13 to regulate the pressure and flow rate of the fuel gas at the gas turbine inlet. The gas turbine control valve 14 is operated by a gas turbine control system 15 through a gas turbine control system output line 16. An input to the gas turbine control system 15 includes a pressure indicator 17 disposed upstream of the gas turbine control valve 14 on the compressed fuel gas line 13 and connected to the gas turbine control system 15 through a pressure indicator line 18. An input to the gas turbine control system 15 also includes a gas turbine flow demand line 19.

[0027] There is also a fuel gas booster control system 20, the input to which comprises a gas turbine control valve position indicator line 21. The fuel gas booster control system 20 controls the capacity of the reciprocating compressor based fuel gas booster 10 by means of a particular pressure and capacity control device selected for a particular service from amongst, for example, a cylinder valve unloader for any of the cylinders of the reciprocating compressor, an additional variable clearance pocket that can manage capacity variations by increasing and decreasing the individual cylinder clearance pockets with an actuator, a reciprocating compressor inlet valve or a variable frequency drive motor 23 connected to the fuel gas booster control system 20 through a fuel gas booster control system output line 22.

[0028] The integrated system of the present invention operates as follows: The fuel gas booster control system 20 continuously detects the position of the gas turbine control valve 14. If the gas turbine control system 15 sets the gas turbine control valve 14 to a position other than fully open to optimize gas turbine operation, the fuel gas booster control system 20 reduces the capacity of the fuel gas booster through one of the capacity control devices selected for the particular service. After reducing the capacity of the reciprocating compressor-based fuel gas booster 10, the fuel gas from the reciprocating compressor-based fuel gas booster 10 has a lower pressure, which allows the gas turbine control system 15 to set the gas turbine control valve 14 to a fully open position and reduce the pressure drop through the gas turbine control valve 14. As a result, the power absorbed by the reciprocating compressor-based fuel gas booster 10 is reduced without reducing the operability of the gas turbine.

[0029] In particular, if the fuel gas pressure and / or flow rate from the reciprocating compressor-based fuel gas booster 10 is higher than the pressure and flow rate actually required by the gas turbine 11, for example, as a result of high ambient temperature or a reduced turbine load, the gas turbine control system 15 operates the gas turbine control valve 14 to a position other than fully open. Partial closure of the gas turbine control valve 14 causes a pressure drop of the fuel gas from the reciprocating compressor-based fuel gas booster 10 before it reaches the gas turbine inlet. This means that some of the fuel gas compression performed by the reciprocating compressor-based fuel gas booster 10 is lost, and from a different perspective, the reciprocating compressor-based fuel gas booster 10 operates to compress the fuel gas in excess of the pressure required by the gas turbine 11. At the same time, the reciprocating compressor-based fuel gas booster 10 is absorbing an excessive amount of power relative to its needs. According to the present disclosure, this amount of absorbed power is conserved by reducing the capacity of the reciprocating compressor-based fuel gas booster 10 by allowing it to compress the fuel gas to the pressure required by the gas turbine and then minimizing any possible pressure drop. In fact, within certain limits, reducing the pressure of the fuel gas at the inlet of the gas turbine 11 does not adversely affect the operability of the gas turbine 11, especially in the case of reduced load or high temperatures. Generally, fuel gas boosters are designed to function at 30 bar absolute, but can also function at lower pressures (down to about 26-27 bar absolute) when temperatures are high (typically in the summer) or load is low.

[0030] Importantly, in accordance with the present disclosure, because the fuel gas booster control system 20 is used as an additional control system to the gas turbine control system 15, care must be taken to avoid interference between the systems that could cause instability. In this regard, the fuel gas booster control system 20 is configured as a slow control system, while the gas turbine control system 15 is a fast control system. More specifically, the regulator of the fuel gas booster control system 20 is a proportional or proportional-integral regulator with a low proportional gain value. As a result, the operation and transient conditions of the gas turbine are still controlled by the gas turbine control system 15 without any interference from the fuel gas booster control system 20, while the fuel gas booster control system 20 is used only to regulate the capacity of the reciprocating compressor-based fuel gas booster 10.

[0031] In particular, the integration of the fuel gas booster control system 20 and the gas turbine control system 15 according to the present disclosure can be used to automatically synchronize a reciprocating compressor-based fuel gas booster and gas turbine package to a minimum absorbed power operating point.

[0032] Alternatively, the integration of the fuel gas booster control system 20 and the gas turbine control system 15 according to the present disclosure can be used to minimize the fuel gas booster absorbed power operating point.

[0033] In particular, the integration of the fuel gas booster control system 20 and gas turbine control system 15 according to the present disclosure can be used to reduce the settle-out pressure of the closed circuit in the thermodynamic system after the shutdown of a boosting device such as a compressor, to facilitate the start-up of the system.

[0034] According to a specific implementation of the integration of the fuel gas booster control system 20 and the gas turbine control system 15 of the present disclosure, two fuel gas boosters can be used, with the fuel gas boosters designed to provide lower pressure and flow than required by the gas turbine, even up to 50% of the pressure and flow required by the gas turbine. This configuration ensures increased availability and reliability in certain conditions without adversely affecting the system under normal operating conditions. For example, in the summer, the gas turbine can be operated at full load with reduced fuel gas pressure from the reciprocating compressor-based fuel gas booster, allowing only one of the redundant reciprocating compressor-based fuel gas boosters to be used while the other is undergoing maintenance.

[0035] Finally, the integration of the fuel gas booster control system 20 and gas turbine control system 15 according to the present disclosure allows for fuel gas booster power savings of up to 30% (location dependent), increased reliability and availability for minimum load operation of the reciprocating compressor based fuel gas booster in all conditions, and automatic tracking of ambient and fuel gas booster conditions.

[0036] While aspects of the present invention have been described in terms of various specific embodiments, it will be apparent to those skilled in the art that many modifications, changes, and omissions are possible without departing from the spirit and scope of the claims. Additionally, unless otherwise specified herein, the order or sequence of any process or method steps may be varied or rearranged according to alternative embodiments.

Claims

1. 1. An integrated system comprising: a reciprocating compressor-based fuel gas booster (10); and a gas turbine (11), wherein a gas turbine flow and pressure control system (15) and a fuel gas booster pressure and capacity control system (20) are synchronized to optimize fuel gas booster power consumption or fuel gas booster and gas turbine package power consumption, the gas turbine flow and pressure control system (15) including at least one gas turbine fuel gas input control valve (14), and the fuel gas booster pressure and capacity control system (20) including a gas turbine fuel gas input control valve position controller associated with the at least one gas turbine fuel gas input control valve (14), and a fuel gas booster capacity controller associated with the reciprocating compressor-based fuel gas booster (10).

2. 2. The system of claim 1, wherein the fuel gas booster capacity control device is selected from among a cylinder valve unloader associated with each cylinder effect of the reciprocating compressor-based fuel gas booster, an additional variable clearance pocket for each individual cylinder clearance pocket, a reciprocating compressor inlet valve, or a variable frequency drive motor.

3. 3. The system of claim 1 or 2, wherein the fuel gas booster pressure and capacity control system (20) is a low speed control system.

4. The system of claim 3, wherein the fuel gas booster pressure and capacity control system (20) is a proportional control system.

5. The system of claim 3, wherein the fuel gas booster pressure and capacity control system (20) is a proportional-integral control system.

6. The system of claim 1 , wherein the gas turbine flow and pressure control system (15) is a high speed control system.

7. The system of claim 1 , wherein the reciprocating compressor-based fuel gas booster (10) is integrally connected to a gas turbine casing.

8. The system of claim 1 comprising two reciprocating compressor-based fuel gas boosters.

9. The system of claim 8 , wherein each reciprocating compressor-based fuel gas booster is designed to provide at least the pressure and capacity required by the gas turbine.

10. 9. The system of claim 8, wherein each reciprocating compressor based fuel gas booster is designed to provide a lower pressure and capacity than required by the gas turbine, and wherein the overall pressure and capacity of the reciprocating compressor based fuel gas boosters is at least equal to the pressure and capacity required by the gas turbine.

11. 10. A method for controlling the operation of an integrated reciprocating compressor based fuel gas booster and gas turbine system according to claim 1, comprising: - controlling the position of a gas turbine fuel gas input control valve; If the position is not more open than a set point (depending on the gas turbine), - reducing the fuel gas booster capacity.

12. The method of claim 11 , wherein the step of reducing the fuel gas booster capacity is performed slowly.

13. When two reciprocating compressor based fuel gas boosters are used, if the required fuel gas pressure from the fuel gas booster is equal to or less than the pressure that can be provided by each of the two reciprocating compressor-based fuel gas boosters; 12. The method of claim 11, wherein only one reciprocating compressor based fuel gas booster is used.

14. 14. The method of claim 13, wherein only one reciprocating compressor based fuel gas booster is in use while the other is undergoing maintenance.

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