Description

TECHNICAL FIELD [0001] The present disclosure concerns a turbomachinery plant to maximize the power generated by an electrical reversible machine.

[0002] Particularly, the present disclosure concerns the structure of the turbomachin ery plant comprising a gas turbine module, a compressor (called process compressor) and a variable frequency drive electric unit, the latter comprising in turn an electrical reversible machine, wherein such structure is designed and conceived to increase the resistant torque of the electrical reversible machine and decrease the resistant torque of the compressor in such a way that the power absorbed by the compressor is as low as possible and the power generated by the electrical reversible machine is maximized.

[0003] More particularly, the structure of such plant is designed and conceived for a mechanical drive hybrid gas turbine.

BACKGROUND ART

[0004] The gas turbine hybridization concept is applicable to mechanical drive appli cation on new units or as upgrade on existing trains. It leverages the wide range capa bility synergy that a gas turbine in combination with a variable frequency drive electric unit can offer. The variable frequency drive electric unit comprises an electrical re versible machine and a VFD control panel for the electrical reversible machine.

[0005] The electrical reversible machine can supply power to a gas turbine so as to work as helper device for the gas turbine or can absorb power from the gas turbine so as to work as a generator to produce power. [0006] When the electrical reversible machine works as a generator and it is necessary to generate the maximum power, the resistant torque of the electrical reversible ma chine is increased automatically by the VFD control panel of the electrical reversible machine until the speed of the compressor (i.e. a process compressor) decreases to a minimum value substantially equally to the 50% of the speed nominal value of the compressor (and then also of the electrical reversible machine connected to the com pressor). Such minimum value represents a balance point where the electrical reversi ble machine generates the maximum power and the compressor absorbs the “minimum power”.

[0007] However, although the speed of the compressor is decreased and the amount of power absorbed by the compressor is considered minimal, the value of such amount of power is still a significant value and is substantially equal to the 10% of the nominal value of the power absorbed by the compressor itself.

[0008] As a result, the amount of power absorbed by the compressor affects the max imum power that can be generated by the electrical reversible machine. Indeed, if the power supplied by the gas turbine is equal to the sum of the power absorbed by the compressor and the power generated by the electrical reversible machine, the greater the power absorbed by the compressor, the lower the power generated by the electrical reversible machine.

[0009] Accordingly, a turbomachinery plant conceived to maximize the power gener ated by an electrical reversible machine and to minimize the power absorbed by the compressor is welcomed in the technology of turbomachinery, particularly when a me chanical drive gas turbine is used in the turbomachinery plant.

SUMMARY

[0010] In one aspect, the subject matter disclosed herein is directed to a turbomachin ery plant comprising a variable frequency drive electric unit and a compressor, con nected to the electrical reversible machine, an antisurge circuit, as well as a suction unit and a collection unit.

[0011] The variable frequency drive electric unit comprises an electrical reversible machine capable of supplying power.

[0012] The compressor is connected to the electrical reversible machine.

[0013] A first line connects a suction unit to the compressor and a second line connects the compressor to the gas collection unit. A first isolating valve is arranged on the first line and a second isolating valve is arranged on the second line.

[0014] The antisurge circuit comprises a third line, connecting the first line to the second line and an antisurge valve is arranged on the third line.

[0015] The turbomachinery comprises a gas depressurizing compressor with an inlet and an outlet, wherein the gas depressurizing compressor is configured to suck an amount of gas through the inlet, to decrease the pressure of the amount of gas and to eject the amount of gas through the outlet. A fourth line connects the second line to the inlet of the gas depressurizing compressor and a first on/off valve is arranged on the fourth line movable between an open state to allow the passage of an amount of gas toward the gas depressurizing compressor and a closed state to prevent the passage of an amount of gas toward the gas depressurizing compressor.

[0016] A central control unit is connected to the first and second isolating valves, the antisurge valve, the first on/off valve and is configured to close the first isolating valve and the second isolating valve and to open the antisurge valve so that an amount of gas flows substantially only in the antisurge circuit, and to open the first on/off valve and to activate the gas depressurizing compressor, so that an amount of gas sucked by the gas depressurizing compressor moves from the antisurge circuit to the gas depressur izing compressor, the compressor rotates encountering less resistance and absorbing less power and the power generated by the electrical reversible machine is maximized.

[0017] In another aspect of the invention, the antisurge circuit can comprise a cooler device and the central control unit is connected to the cooler device and is configured to activate the cooler device. The cooler device can be configured and sized to dissipate a predetermined quantity of heat when the compressor is in use.

[0018] In another aspect of the invention, the turbomachinery plant comprises a first control valve arranged on a sixth line connecting the first line to the third line and movable between an open state to allow the passage of an amount of gas from the suction unit to the compressor, and a closed state to prevent the passage of an amount of gas from the suction unit to the compressor, as well as a second control valve ar ranged on a seventh line connecting the outlet of the gas depressurizing compressor to the second line and movable between an open state to allow the passage of an amount of gas from the compressor to the collection unit and a closed state to prevent the passage of an amount of gas from the compressor to the collection unit.

A measurement and control temperature device is connected to the third line between the cooler device and the inlet of the compressor and is configured to measure and control a temperature value referred to the amount of gas in the antisurge circuit.

The central control unit is connected to the first control valve and the second control valve and to the first measurement and control temperature device and to storage means and is configured to: store in the storage means a predetermined temperature value, acquire the temperature value from a measurement and control temperature de vice, and adjust the opening of the first control valve and the opening of the second control valve, when the temperature value measured by the measurement and control temperature device is greater than the predetermined temperature value, in such a way that a first amount of gas having a first temperature enters the antisurge circuit through the first control valve and a second amount of gas having a second temperature exits the antisurge circuit, enters the gas depressurizing compressor, exits the gas depres surizing compressor and reaches the second line through the second control valve. The second amount of gas is equal to the first amount of gas and the second temperature is greater than the first temperature.

[0019] The present invention is also directed to a method for maximizing the power generated by an electrical reversible machine of a turbomachinery plant. In particular, the method comprises the following steps: closing the first isolating valve and the sec ond isolating valve and opening the antisurge valve, so that an amount of gas flows substantially only in the antisurge circuit, and opening the first on/off valve and acti vating the gas depressurizing compressor, so that an amount of gas sucked by the gas depressurizing compressor moves from the antisurge circuit to the gas depressurizing compressor, the compressor rotates encountering less resistance and absorbing less power and the power generated by the electrical reversible machine is maximized.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

Fig. 1 illustrates a schematic view of a turbomachinery plant according to a first embodiment;

Fig. 2 illustrates a schematic view of the turbomachinery plant according to a second embodiment;

Fig. 3 illustrates a flow chart of a method for maximizing the power generated by an electrical reversible machine by reducing the power absorbed by a compressor connected to the electrical reversible machine.

DETAILED DESCRIPTION OF EMBODIMENTS

[0021] In the field of power production, a turbomachinery plant comprises in combi nation a gas turbine, a compressor (called process compressor) and an electrical re versible machine capable of supplying power so as to work as helper device of the gas turbine or absorbing power so as to work as generator. The present disclosure is di rected to the case when the electrical reversible machine works as a generator to pro duce the maximum power required by the needs. Since the compressor absorbs a cer tain amount of power also when its speed reaches the minimum value, it is necessary to reduce this amount of power as much as possible to maximize the power generated by the electrical reversible machine.

[0022] The present subject matter is thus directed to a turbomachinery plant config ured to maximize the power generated by the electrical reversible machine by consid erably reducing the power absorbed by the compressor connected to the electrical re versible machine. The power absorbed by the compressor is reduced by about an order of magnitude compared to the power absorbed by a compressor in a turbomachinery plant of known type.

[0023] Particularly, the structure of the turbomachinery plant is designed and con ceived to substantially create a “vacuum condition” for the compressor so that the compressor absorbs less power because encounters less resistance. In this way, it is possible to maximize the power generated by the electrical reversible machine. [0024] As a result of such condition, it is possible to increase the number of revolu tions of the electrical reversible machine, so that the capability of the electrical reversi ble machine to supply power is increased.

[0025] Reference is now made to the drawings and particularly to Figure 1 that shows a first embodiment of the turbomachinery plant according to the invention.

[0026] The turbomachinery plant comprises a gas turbine module 10 comprising a gas turbine 1, a variable frequency drive electric unit 2 comprising an electrical reversible machine 21 capable of supplying power and a compressor 3 (called process compres sor), connected to the electrical reversible machine 21 and the gas turbine module 10.

In particular, the compressor 3 has an inlet 31 and an outlet 32.

Furthermore, a suction unit SU is connected to the inlet 31 of the compressor 3 by means of a first line LI and a collection unit CU is connected to the outlet 32 of the compressor 3 by means of a second line L2.

The turbomachinery plant comprises a first isolating valve SV1 arranged on the first line LI and a second isolating valve SV2 arranged on the second line L2, as well as an antisurge circuit AC comprising a third line L3 connecting the first line LI to the sec ond line L2 and an antisurge valve AV arranged on the third line L3.

The first isolating valve SV1 is movable between an open state, wherein it allows the passage of an amount of gas from the suction unit SU to the compressor 3, and a closed state, wherein it prevents the passage of an amount of gas from the suction unit SU to the compressor 3.

The second isolating valve SV2 is movable between an open state, wherein it allows the passage of an amount of gas from the compressor 3 to the collection unit CU, and a closed state, wherein it prevents the passage of an amount of gas from the compressor 3 to the collection unit CU.

[0027] In particular, the turbomachinery plant comprises:

- a gas depressurizing compressor 5 having an inlet 51 and an outlet 52 and configured to suck an amount of gas through the inlet 51, to decrease the pressure of the amount of gas and to eject the amount of gas through the outlet 52;

- a fourth line L4 connecting the second line L2 to the inlet 51 of the gas depressurizing compressor 5, so that the gas depressurizing compressor 5 is connected to the antisurge circuit AC;

- a first on/off valve VI arranged on the fourth line L4 and movable between an open state, so as to allow the passage of an amount of gas toward the gas depressurizing compressor 5, and a closed state, so as to prevent the passage of an amount of gas toward the gas depressurizing compressor 5.

Furthermore, the turbomachinery plant comprises a central control unit 7, connected to the first isolating valve SV1 and the second isolating SV2, the antisurge valve AV and the first on/off valve VI, and is configured to: close the first isolating valve SV1 and the second isolating valve SV2 and open the antisurge valve AV, so that an amount of gas flows substantially only in the antisurge circuit AC, and open the first on/off valve V 1 and activate the gas depressurizing compressor 5, so that an amount of gas that sucked by the gas depressurizing compressor 5 moves from the antisurge circuit AC to the gas depressurizing compressor 5 and the compressor 3 ro tates encountering less resistance and absorbing less power and the power generated by the electrical reversible machine 21 is maximized.

Advantageously, the number of revolutions of the electrical reversible machine 21 can be increased so that the electrical reversible machine 21 can supply more power than an electrical reversible machine of a turbomachinery plant of known type.

[0028] The control central unit 7 can be a programmable controller that may be im plemented by a microprocessor or a PLC along with an I/O module.

[0029] The gas sucked by the gas depressurizing compressor 5 is ejected on a fifth line L5 having a first end connected to the outlet 52 of the gas depressurizing compressor 5. In the embodiment being disclosed, the second end of the fifth line L5, opposite to the first end, is connected to the first line LI. Therefore, the amount of gas ejected from the gas depressurizing compressor 5 tends to return toward the suction unit SU. [0030] However, it is not necessary that the outlet 52 of the gas depressurizing com pressor 5 is connected to the first line LI. For example, the gas ejected from the gas depressurizing compressor 5 could be dispersed in the environment or directed to an other part of the turbomachinery plant, for example to a vent header or to a gas treat ment system.

[0031] With reference to the gas depressurizing compressor 5, the gas depressurizing compressor 5 is provided with adjusting means to adjust the flow rate of the gas de pressurizing compressor itself.

[0032] As shown in Figure 1, the central control unit 7 can be connected to the gas depressurizing compressor 5 and configured to control the adjusting means of the gas depressurizing compressor 5 so that the gas depressurizing compressor 5 absorbs as little power as possible.

[0033] Particularly, such adjusting means can comprise at least one valve (preferably two valves) arranged on one or more respective cylinders included in the gas depres surizing compressor 5 and the central control unit 7 is configured to control the flow rate of the gas depressurizing compressor 5 by adjusting the opening of the valve.

[0034] Furthermore, alternatively or in combination with the one or more valves ar ranged on respective cylinders, such adjusting means can comprise an electric device, for example a VFD electric motor, or mechanical device, for example a variable speed ratio gear box, to change the number of revolutions per minute of the gas depressuriz ing compressor 5 and the central control unit 7 is configured to control the flow rate of the gas depressurizing compressor by increasing/decreasing the number of revolu tions per minute through the electric device or the mechanical device.

[0035] In the first embodiment being disclosed, the gas depressurizing compressor 5 is a volumetric machine.

[0036] Furthermore, as shown in Figure 1, the antisurge circuit AC can comprise a cooler device 4 to cool the gas flowing in the third line L3 of the antisurge circuit AC. The cooler device 4 is provided with ventilation means 41 comprising one or more blades.

[0037] The central control unit 7 is connected to the cooler device 4 and configured to activate the cooler device 4.

[0038] Particularly, the central control unit 7 is configured to adjust the speed of the blades by means of a motor included in the cooler device 4, wherein the motor is con nected to the ventilation means 41.

[0039] The motor can be a multipole motor comprising one or more pole couples or a VFD electric motor.

[0040] Alternatively, the central control unit 7 can be configured to adjust the speed of the blades by changing over time a value associated to the pitch angle of the blades by means of an hydraulic or electric or pneumatic or electro-mechanical actuator in cluded in the cooler device 4. In the first embodiment being disclosed, the actuator is an electric actuator.

[0041] The cooler device 4 can be configured and sized depending on the needs, i.e. depending on the quantity of heat to be dissipated when the compressor 3 is in use.

[0042] Thus, the cooler device 4 is configured to dissipate a predetermined quantity of heat when the compressor 3 is in use.

[0043] Figure 2 shows a second embodiment of the turbomachinery plant.

[0044] In the second embodiment, differently from the first embodiment, the tur bomachinery plant further comprises:

- a sixth line L6 connecting the first line LI to the third line L3;

- a first control valve FV 1 arranged on the sixth line L6;

- a seventh line L7 connecting the outlet 52 of the gas depressurizing compressor 5 to the second line L2,

- a second control valve FV2 arranged on the seventh line L7;

- a measurement and control temperature device D1 configured to measure and control a temperature value referred to the amount of gas in the antisurge circuit AC.

[0045] The first control valve F V 1 is movable between an open state, wherein it allows the passage of an amount of gas from the suction unit SU to the antisurge circuit AC, and a closed state, wherein it prevents the passage of an amount of gas from the suction unit SU to the antisurge circuit AC.

The second control valve FV2 is movable between an open state, wherein it allows the passage of an amount of gas from the gas depressurizing compressor 5 to the second line L2, and a closed state, wherein it prevents the passage of an amount of gas from the gas depressurizing compressor 5 to the second line L2.

According to the respective opening of each control valve FV1, FV2, the respective gas flow rate at the valve outlet can vary.

The measurement and control temperature device D1 is connected to the third line L3 between the cooler device 4 and the inlet 31 of the compressor 3.

[0046] Furthermore, the turbomachinery plant comprises storage means 8 (such as a memory) for storing data and the central control unit 7 is connected to the first control valve FV1, the second control valve FV2, the measurement and control temperature device Dl, the storage means 8, and configured to: store in the storage means 8 a predetermined temperature value; acquire the temperature value from the measurement and control temperature de vice Dl, and adjust the opening of the first control valve FV1 and the opening of the second control valve FV2, when the temperature value measured by the measurement and control temperature device Dl is greater than the predetermined temperature value, in such a way that an amount of gas with a first temperature enters the antisurge circuit AC through the first control valve F V 1 and a second amount of gas having a second temperature exits the antisurge circuit AC, enters the gas depressurizing compressor 5, exits the gas depressurizing compressor 5 and reaches the second line L2 through the second control valve FV2, wherein the second amount of gas is equal to the first amount of gas and the second temperature is greater than the first temperature.

[0047] In other words, an amount of hot gas exits from the antisurge circuit AC and the same amount of fresh gas enters the antisurge circuit AC. [0048] In the embodiment being disclosed, the central control unit 7 comprises the storage means 8. However, the storage means 8 can be outside the central control unit 7 without departing from the scope of the invention.

[0049] To improve the control of the opening of the first control valve FV1 and the second control valve FV2 based on the gas temperature value, it is possible to control the gas pressure to verify that the gas pressure value is equal to a predetermined gas pressure value.

[0050] To this end, the turbomachinery plant further comprises a measurement and control pressure device D2 configured to measure and control a pressure value referred to the gas in the antisurge circuit AC, and the central control unit 7 is connected to the measurement and control pressure device D2 and configured to: store in the storage means 8 a predetermined pressure value; acquire the pressure value from the measurement and control pressure device D2; verify that the pressure value measured by the measurement and control pressure device D2 is equal to the predetermined pressure value, and if the pressure value is not equal to the predetermined pressure value, adjust the opening of the first control valve FV1 and the opening of the second control valve

FV2 so that the pressure value of the gas in the antisurge circuit AC tends to be equal to the predetermined pressure value.

[0051] The measurement and control pressure device D2 is connected to the third line L3 of the antirsurge circuit AC between the cooler device 4 and the inlet 31 of the compressor 3. However, the measurement and control pressure device D2 can be con nected to the third line L3 between the outlet 32 of the compressor 3 and the cooler device 4, without departing from the scope of the invention.

[0052] In the second embodiment, a second on/off valve V2 is arranged on the fifth line L5. Such a second on/off valve V2 is movable between an open state, so as to allow an amount of gas (i.e. the second amount of gas having a second temperature) ejected from the gas depressurizing compressor 5 to flow in the fifth line L5, and a closed state, so as to prevent an amount of gas (i.e. the second amount of gas having a second temperature) ejected from the gas depressurizing compressor from flowing in the fifth line L5, and the central control unit 8 is connected to the second on/off valve V2 and configured to close the second on/off valve V2 when adjusting the opening of the first control valve FV1 and the opening of the second control valve FV2 and open the second on/off valve V2 when the antisurge circuit AC is to be emptied.

[0053] In the second embodiment being disclosed, as already said for the first embod iment, the second end of the fifth line L5 is connected to the first line LI. Therefore, the second on/off valve V2 allows an amount of gas ejected from the gas depressuriz ing compressor 5 to reach the first line LI, when the second on/off valve V2 is in the open state, and prevents an amount of gas ejected from the gas depressurizing com pressor 5 from reaching the first line LI, when the second on/off valve V2 is in the closed state.

[0054] With reference to each embodiment above disclosed, the compressor 3 is ar ranged between the gas turbine 10 of the gas turbine module 1 and the variable fre quency drive unit 2, and the compressor 3 is preferably connected to the gas turbine 10 by means of a self synchronizing clutch 13.

[0055] A method for maximizing the power generated by an electrical reversible ma chine of a turbomachinery plant above disclosed, comprising the following steps: closing 101 the first isolating valve SV1 and the second isolating valve SV2 and open ing 102 the antisurge valve AV, so that an amount of gas flows substantially only in the antisurge circuit AC, and opening 103 the first on/off valve VI and activating 104 the gas depressurizing com pressor 5, so that an amount of gas sucked by the gas depressurizing compressor 5 moves from the antisurge circuit AC to the gas depressurizing compressor 5, the com pressor 3 rotates encountering less resistance and absorbing less power and the power generated by the electrical reversible machine 21 is maximized.

[0056] An advantage of the present technical solution is to maximize the power gen erated by an electrical reversible machine 2, when the latter works as a generator to produce power. With the same overall power of the gas turbine 1, the power absorbed by the compressor 3 is less than a power absorbed by a compressor included in a tur bomachinery plant of known type and then the power generated by the electrical re versible machine 2 is maximized. Furthermore, as a result, it is possible to increase the number of revolutions of the electrical reversible machine 2 so as to increase the ca pability of the electrical reversible machine to supply power.

[0057] Furthermore, a second advantage, due to the fact that the number of revolutions of the electrical reversible machine is increased, is that also the number of revolutions of the gas turbine can increase and then the rotation speed of the gas turbine can be increased, so that the gas turbine has an enhanced efficiency. In fact, the gas turbine efficiency is improved of a value in percentage terms between 2% and 4%

[0058] A third advantage is that it is possible to maximize the power generated by an electrical reversible machine by means of a technical solution having a low manufac turing cost with respect to the advantage that can be obtained. Therefore, the operating expenditure and capital expenditure for this technical solution are reduced with respect to a turbomachinery plant of known type.

[0059] Another advantage is given by the possibility to use a mechanical drive hybrid gas turbine.

[0060] While aspects of the invention have been described in terms of various specific embodiments, it will be apparent to those of ordinary skill in the art that many modi fications, changes, and omissions are possible without departing form the spirt and scope of the claims. In addition, unless specified otherwise herein, the order or se quence of any process or method steps may be varied or re-sequenced according to alternative embodiments.

[0061] Reference has been made in detail to embodiments of the disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the disclosure, not limitation of the disclosure. In fact, 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 disclo sure. Reference throughout the specification to "one embodiment" or "an embodiment" or “some embodiments” means that the particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrase "in one embodi ment" or "in an embodiment" or "in some embodiments" in various places throughout the specification is not necessarily referring to the same embodiment(s). Further, the particular features, structures or characteristics may be combined in any suitable man ner in one or more embodiments.

[0062] When elements of various embodiments are introduced, 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.