KR101638286B1 - Supercritical CO2 generation system and method for controlling output thereof - Google Patents

Abstract

The present invention relates to a supercritical carbon dioxide power generation system and a method of controlling the output of the system, and more particularly, to a supercritical carbon dioxide power generation system and a method of controlling the output of the system. The system includes a cooler for cooling a working fluid, a compressor connected to a rear end of the cooler for compressing the working fluid, A turbine rotatably driven by the working fluid that has passed through the heater; and a generator connected to the turbine and driven to produce electric power, wherein the turbine has an output frequency corresponding to an output frequency of the generator And is controlled to have a rotation number.
According to the present invention, the use of the AC / DC converter is unnecessary because the number of revolutions of the turbine is constantly controlled by using the flow rate control device and the output control device, so that there is no restriction on the power generation output, and the power can be directly supplied to the grid. Further, there is a characteristic that the number of revolutions or the output of the turbine can be controlled in accordance with the characteristics of the generator.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supercritical carbon dioxide (CO2) generation system,

The present invention relates to a supercritical carbon dioxide power generation system and an output control method thereof, and more particularly, to a supercritical carbon dioxide power generation system capable of controlling a turbine revolution frequency or torque in accordance with a generator characteristic and an output control method thereof .

Internationally, there is an increasing need for efficient power generation. As the movement to reduce the generation of pollutants becomes more active, various efforts are being made to increase the production of electricity while reducing the generation of pollutants. As one of such efforts, research and development on a supercritical carbon dioxide power generation system using supercritical carbon dioxide as a working fluid has been activated as disclosed in Japanese Patent Application Laid-Open No. 145092/1989.

Since supercritical carbon dioxide has a gas-like viscosity at a density similar to that of a liquid state, it can minimize the power consumption required for compression and circulation of the fluid as well as miniaturization of the apparatus. At the same time, the critical point is 31.4 degrees Celsius, 72.8 atmospheres, and the critical point is much lower than the water at 373.95 degrees Celsius and 217.7 atmospheres, which is easy to handle. This supercritical carbon dioxide power generation system shows a net generation efficiency of about 45% when operating at 550 ° C. It can improve the power generation efficiency by more than 20% compared to the existing steam cycle power generation efficiency and reduce the turbo device to one tenth There are advantages.

However, in the conventional supercritical carbon dioxide power generation system, the centrifugal type turbine is used as the main turbine to generate the output of the power generation stage. The AC output is converted into DC without the flow control of the turbine inlet, It is used by switching to electric power.

However, as the production capacity of the supercritical carbon dioxide power generation system becomes larger, the AC / DC / AC converter occupies the largest portion of the entire power generation system, resulting in a reduction in efficiency.

Japanese Patent Laid-Open Publication No. 2012-145092 (published on Aug. 02, 2012)

It is an object of the present invention to provide a supercritical carbon dioxide power generation system capable of controlling the turbine revolution number or torque in accordance with generator characteristics and a method of controlling the output of the system.

The supercritical carbon dioxide power generation system of the present invention comprises a cooler for cooling a working fluid, a compressor connected to a rear end of the cooler for compressing the working fluid, a heater for heating the working fluid passed through the compressor, A turbine rotatably driven by the working fluid passing through the turbine, and a generator connected to the turbine and generating electric power, wherein the turbine is controlled to have a rotation speed corresponding to an output frequency of the generator A compressor circulation valve provided at the front end of the heater to be openable and closable, and a compressor bypass flow passage connecting the rear end and the front end of the compressor.

And a flow rate control device installed at a front end of the turbine and controlling a flow rate of the working fluid supplied to the turbine.

The flow rate control device controls the working fluid to bypass the turbine or increases the flow rate of the working fluid to the turbine as the number of rotations of the turbine increases or decreases from the number of rotations corresponding to the output frequency of the generator Feature.

The heater may include a first heater connected to a rear end of the compressor, and a second heater connected to a rear end of the first heater.

And a recuperator that is branched at a downstream end of the compressor (branch point A) and connected between the first heater and the second heater (branch point B).

The recuperator is connected to a rear end of the turbine and a front end of the cooler. The recuperator recovers heat from the working fluid passing through the turbine and recovers the working fluid passing through the compressor.

A turbine bypass flow path connecting the front end of the flow rate control device and the rear end of the turbine and bypassing a part or all of the working fluid flowing into the turbine and a turbine bypass flow path provided on the turbine bypass flow path, And may further include a turbine bypass valve.

And an output control unit provided between the turbine and the generator for controlling an output of the turbine according to an output frequency of the generator.

And the output control device reduces the rotational speed (rpm) of the turbine according to the output frequency of the generator.

The output control device lowers the output of the turbine and transfers the output to the generator when the rotational speed of the turbine is higher than the rotational speed corresponding to the output frequency of the generator.

The output control device is a torque converter.

Also, a method of controlling an output of a supercritical carbon dioxide power generation system of the present invention includes a working fluid supply step (S100) of supplying a working fluid into a supercritical carbon dioxide power generation system, (S300) in which the working fluid compressed in the compressing step (S200) is heated in a heater, and the working fluid passing through the heating step (S300) is supplied to the turbine (S400) for driving the turbine (S400), and a power generation step (S500) for generating power in the generator connected to the turbine. In the turbine driving step (S400), the turbine And is controlled to have a rotation number.

And an output control step (S450) of adjusting the output of the turbine to the output frequency of the generator after the driving the turbine (S400) and transmitting the adjusted output to the generator.

A first determining step S330 of determining whether the compressor is being driven before the turbine driving step S400 and a second determining step S350 of determining whether the turbine rotation speed is increased if the compressor is not initially driven ).

If it is determined that the compressor is initially being operated in the first determining step S330 or that the operating fluid is circulated by bypassing the turbine when it is determined that the number of rotations of the turbine is increased in the secondary determining step S350 And a turbine bypassing step (S370).

If it is determined that the number of revolutions of the turbine is not increased in the secondary determination step (S350), the turbine driving step (S400) is performed.

A supercritical carbon dioxide power generation system and an output control method thereof according to an embodiment of the present invention use a flow control device and an output control device to constantly control the number of revolutions of the turbine so that the use of an AC / And there is an advantage in that power can be directly supplied to the grid. Further, there is a characteristic that the number of revolutions or the output of the turbine can be controlled in accordance with the characteristics of the generator.

1 is a block diagram of a supercritical carbon dioxide power generation system having an output control apparatus according to an embodiment of the present invention;
2 is a flowchart illustrating an output control method of a supercritical carbon dioxide power generation system according to an embodiment of the present invention.

Hereinafter, a supercritical carbon dioxide power generation system and an output control method of the system according to an embodiment of the present invention will be described in detail with reference to the drawings.

First, the output control apparatus of the supercritical carbon dioxide power generation system will be described with reference to FIG.

A typical supercritical carbon dioxide power generation system uses a supercritical carbon dioxide as a working fluid, forming a closed cycle in which carbon dioxide used for power generation is not discharged to the outside.

Supercritical carbon dioxide working fluid (hereinafter referred to as working fluid) in the cycle is heated while passing through a compressor and then through a heat source such as a heater, and a sufficiently heated working fluid drives the turbine. The turbine is a variable-speed turbine in which the number of revolutions changes with the flow rate of the working fluid. The turbine is connected to the generator and the voltage converter, and is driven by the turbine to produce electric power. Turbines used in supercritical carbon dioxide power generation systems are variable turbines because they are difficult to design at constant speed due to their small size.

The working fluid used for the production of electric power is cooled through the heat exchanger, and the cooled working fluid is supplied to the compressor again to circulate in the cycle. A plurality of turbines or heat exchangers may be provided.

In the present invention, an output control device and method capable of controlling the output in accordance with the characteristics of the generator even when the turbine of the basic supercritical carbon dioxide power generation system operates as a constant speed turbine and the flow rate of the turbine front end is varied, .

A flow path through which a working fluid flows in the system is defined as a transport pipe, and a flow path separately branched from the transport pipe is defined as a separate name.

The term " supercritical carbon dioxide power generation system " according to various embodiments of the present invention is intended to encompass not only the system in which all of the working fluid flowing in the cycle is a supercritical state but also the supercritical state, System.

Also, in various embodiments of the present invention, carbon dioxide is used as the working fluid, wherein the term " carbon dioxide " refers to pure carbon dioxide in a chemical sense, carbon dioxide in a state of being somewhat impure and carbon dioxide in a general sense, As well as fluids in a mixed state.

1 is a block diagram illustrating a supercritical carbon dioxide power generation system having an output control apparatus according to an embodiment of the present invention.

As shown in FIG. 1, the supercritical carbon dioxide power generation system according to an embodiment of the present invention includes supercritical carbon dioxide as a working fluid and a working fluid supply device 100 for supplying a working fluid. A plurality of heaters 400 and 500 for heating a working fluid that has passed through the compressor 300 and a heater 300 for heating the working fluid, 400, and 500, and a turbine 600 driven by a high-temperature, high-pressure working fluid.

The supercritical carbon dioxide power generation system further includes a recuperator that further recovers the working fluid and a generator 610 coupled to the turbine 600 and a turbine 600 installed between the turbine 600 and the generator 610, And an output control device 630 for changing the torque according to the number of revolutions of the engine and transmitting the torque to the generator. Each of the components is connected by a transfer pipe 800 through which a working fluid flows.

The working fluid supply device 100 serves to supply the working fluid for driving the system into the cycle and can supply the working fluid in order to preserve the amount of the working fluid lost when the working fluid leaks in the cycle have.

The working fluid injected by the working fluid supply device 100 flows into the cooler 200 through the supply valve 110.

The cooler 200 cools the working fluid and the working fluid sufficiently cooled in the cooler 200 is supplied to the compressor 300 via the injection valve 210.

The compressor 300 compresses the working fluid to a high pressure. The working fluid compressed in the compressor 300 is transferred to the first heater 400, and a part of the working fluid is transferred to the recuperator 700. To this end, a branch passage 810 is provided, and a control valve 812 is provided on the branch passage 810 to open and close the branch passage 810.

A separate compressor turbine, a motor, or the like may be provided as a power source for driving the compressor 300.

The high-pressure working fluid that has passed through the compressor 300 flows into the first heater 400 and is heated first, then heated again through the second heater 500 to drive the turbine 600 Lt; / RTI >

The turbine 600 is driven by a high-temperature, high-pressure working fluid to generate electric power by driving a generator 610 coupled to the turbine 600. As the working fluid is expanded while passing through the turbine 600, the turbine 600 also functions as an expander. The working fluid drives the turbine 600 and is discharged in a low pressure state and sent to the recuperator 700.

The turbine 600 is a centrifugal type or an axial flow type turbine. A flow rate control device 650 is installed at a front end of the turbine 600 and an output control device 630 is connected to the turbine 600. Since the turbine 600 can not be driven at a rotational speed corresponding to the output frequency of the generator 610 when the flow rate at the inlet end of the turbine 600 is increased or decreased, Thereby controlling the flow rate of the working fluid.

The number of revolutions of the turbine 600 may vary depending on the increase / decrease of the load, the variation of the temperature and the pressure condition of the working fluid, the amount of churning of the turbine 600, or the amount of exhaust. The flow rate control device 650 controls the flow rate of the flow of the refrigerant into the turbine 600 corresponding to the change in the number of revolutions of the turbine 600.

During normal operation in which the turbine 600 is operated to have a speed corresponding to the output frequency of the generator 610, the number of revolutions of the turbine 600 depends on the frequency of the generator 610. Accordingly, the flow rate control device 650 controls the flow rate of the working fluid so that the rotational speed of the turbine 600 corresponds to the frequency of the generator 610.

That is, when the rotational speed of the turbine 600 increases more than the rotational frequency corresponding to the output frequency of the generator 610, the flow control device 650 partially blocks the working fluid flowing to the turbine 600, So that the number can be reduced again. A part of the working fluid which has not flowed into the turbine 600 is directly sent to the rear end of the turbine 600 so that it is transmitted to the recuperator 700 without going through the turbine 600. For this purpose, it is preferable that a turbine bypass valve 852 is provided on the turbine bypass flow passage 850 connecting the front end of the flow control device 650 and the rear end of the turbine 600 (this will be described later).

As the flow rate of the working fluid to the turbine 600 decreases, the speed of the turbine 600 decreases, so that the number of revolutions of the turbine 600 can be controlled not to exceed the number of revolutions corresponding to the output frequency of the generator 610 .

  The flow rate control device 650 controls the rotation of the turbine 600 by increasing the flow rate of the working fluid flowing to the turbine 600 when the number of rotations of the turbine 600 decreases from the number of rotations corresponding to the output frequency of the generator 610. [ So that the number can be maintained. To this end, the working fluid sent to the recuperator 700 through the compressor 300 must be introduced into the turbine 600. It is preferable that the working fluid further recuperated by the recuperator 700 is further introduced and the working fluid passing through the compressor 300 and the recuperator 700 is supplied to the first heater 400 and the second heater 500 and is mixed with the working fluid that has passed through the first heater 400.

As the flow rate of the working fluid to the turbine 600 increases, the speed of the turbine 600 increases, so that the number of rotations of the turbine 600 can be controlled not to decrease below the number of rotations corresponding to the output frequency of the generator 610 .

Taking the generator 610 having an output frequency of 60 Hz as an example, the generator 610 should always generate an AC voltage with an output frequency of 60 Hz constantly. For this purpose, the turbine 600 should be rotated at a constant rotation speed corresponding to the frequency, and the speed of the turbine 600 corresponding to 60 Hz, which is the output frequency of the generator 610, may correspond to 3600 rpm. In an embodiment of the present invention, the flow controller 650 controls the rotational speed of the turbine 600 to be constant as described above, and transmits the power to the generator 610, so that an AC voltage of 60 Hz can be produced. Accordingly, there is no need to use an AC / DC converter that occupies a large area, and there is an advantage that there is no restriction on the output of the power generation. In addition, since the generator 610 produces an AC voltage, it can directly supply power to the grid.

The output control device 630 can be applied when it is necessary to use the turbine 600 having a high-speed rpm inevitably on the supercritical carbon dioxide power generation system. The output control device 630 changes the rpm of the turbine 600 so that the turbine 600 has a specific rpm that matches the characteristics of the generator 610. [ That is, by adjusting the speed of the turbine 600 in accordance with the output frequency of the generator 610, the generator 610 can generate an AC voltage of a constant frequency.

For example, if the number of revolutions of the turbine 600 is tens of thousands of rpm and the output frequency of the generator 610 is 60 Hz, the number of revolutions of the turbine 600 corresponding to the output frequency of the generator 610 should be 3600 rpm.

However, since the number of revolutions of the turbine 600 is too high to match the output frequency of the generator 610, the output control device 630 can be used to reduce the number of revolutions of the turbine 600 and to deliver it to the generator 610 have.

The output control device 630 may be implemented as a kind of torque converter capable of adjusting the oil pressure. In this case, the output control device 630 adjusts the hydraulic pressure according to the number of revolutions of the turbine 600 to decelerate the number of revolutions of the turbine 600, so that the number of revolutions of the generator 610 is reduced to a value corresponding to the output frequency of the generator 610, . Therefore, the output control device 630 can provide the rotation speed corresponding to the output frequency of the generator 610 even if the transmission turbine having the high rotation speed is used.

Meanwhile, the supercritical carbon dioxide power generation system of the present invention further includes a bypass flow path bypassing the compressor 300 and the turbine 600.

The working fluid sent to the compressor 300 through the cooler 200 is sent to the first heater 400 and the compressor circulation valve 310 is installed at the front end of the first heater 400 for this purpose. However, the compressor circulation valve 310 may remain closed and bypass the working fluid back to the front end of the compressor 300.

The working fluid that has passed through the compressor 300 to circulate the working fluid until the working fluid warms up enough to drive the turbine 600 during the initial startup of the compressor 300, It can be bypassed to the front end. To this end, a compressor bypass flow passage 830 for connecting the rear end and the front end of the compressor 300 is provided and a compressor bypass flow passage 832 is provided on the compressor bypass flow passage 830 to open and close the compressor bypass flow passage 830 . The working fluid that has been passed through the compressor 300 a plurality of times can pass through the first heater 400 and the second heater 500 and circulate in the system without going through the turbine 600 until the working fluid is sufficiently warmed up have.

In addition, a turbine bypass flow path 850 for connecting the front end and the rear end of the turbine 600 may be provided to circulate the working fluid during the initial operation of the compressor 300 without passing through the turbine 600, even if the working fluid circulates in the system . To this end, a turbine bypass valve 852 is provided on the turbine bypass flow passage 850 to open and close the turbine bypass flow passage 850.

The working fluid that has escaped through the turbine bypass flow path without passing through the turbine 600 is sent to the recuperator to recover a part of the working fluid flowing into the recuperator 700 through the compressor 300, ). The working fluid recovered through the heat exchange in the recuperator 700 may flow into the branch point A between the first heater 400 and the second heater 500 and may be supplied to the second heater 500.

After the initial warm-up, the working fluid that has normally passed through the turbine 600 is also sent to the recuperator. It is more efficient to cool the working fluid flowing into the cooler 200 after the heat of the working fluid is used for the recovery of the working fluid passing through the compressor 300 than to cool the working fluid that is still hot, .

Although not described in the above-described embodiments, various control valves can be controlled by receiving signals through a separate controller for controlling opening and closing of the valves. The output control device of the supercritical carbon dioxide power generation system should be understood as a concept including both the above-described control valves, the flow control device, and the output control device including the controller.

The output control method of the supercritical carbon dioxide power generation system, which will be described below, will not be described as a separate control subject, but the controller is the control subject, and various control valves, flow control devices, and output control devices can be controlled by the controller. In addition, the controller may be provided integrally or separately with a part of the configuration in the power generation system, or may be provided outside the system to exchange control signals through wireless communication.

Next, the output control method of the supercritical carbon dioxide power generation system will be briefly described with reference to FIG.

2 is a flowchart illustrating an output control method of a supercritical carbon dioxide power generation system according to an embodiment of the present invention.

As shown in FIG. 2, first, the working fluid is supplied into the supercritical carbon dioxide power generation system (operating fluid supply step, S100). The working fluid is cooled through the cooler 200 and supplied to the compressor 300 to be compressed (compression step S200). The compressed working fluid is sufficiently heated through the first heater 400 and the second heater 500 (Heating step S300), and supplied to the turbine 600 to drive the turbine 600 (turbine driving step, S400). The generator 610 finally outputs an AC voltage having a preset output frequency (power generation step, S500).

The turbine 600 is controlled to rotate at a rotation number corresponding to the output frequency of the generator 610 in the turbine drive step S400 and the turbine 600 is controlled using the output control device 630 when the high- To be output to the generator 610 after the output of the generator 610 is adjusted according to the output frequency of the generator 610 (output control step S450). Alternatively, in the output control step S450, the rotational frequency of the turbine 600 may be adjusted according to the output frequency of the generator 610.

When the compressor 300 is initially driven or when the number of revolutions of the turbine 600 is increased during operation of the turbine 600, the working fluid may be circulated by bypassing the turbine 600 without being sent to the turbine 600 . To this end, a primary determination step (S330) of determining whether the compressor (300) is being driven before the turbine driving step (S400) and a first determining step (S330) of determining whether the number of rotations of the turbine (600) (Step S350).

If it is determined in the first determination step S330 that the compressor 300 is initially driven, the working fluid is circulated by bypassing the turbine 600 (bypassing the turbine, step S370), and in the secondary determination step S350, 600) is increased, the flow proceeds to the turbine bypass step S370. If it is determined that the number of revolutions of the turbine 600 is not increased in the secondary determination step S350, the turbine driving step S400 is performed.

As described above, the apparatus and method for controlling the output of the supercritical carbon dioxide power generation system of the present invention are characterized in that the use of the AC / DC converter is unnecessary by controlling the number of revolutions of the turbine by using the flow rate control device and the output control device, There is no restriction, and there is an advantage that power can be supplied directly to the grid. Further, there is a characteristic that the number of revolutions or the output of the turbine can be controlled in accordance with the characteristics of the generator.

One embodiment of the present invention described above and shown in the drawings should not be construed as limiting the technical spirit of the present invention. The scope of the present invention is limited only by the matters described in the claims, and those skilled in the art can improve and modify the technical spirit of the present invention in various forms. Accordingly, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

100: working fluid supply device 200: cooler
300: compressor 400: first heater
500: second heater 600: turbine
610: Generator 630: Output control device
650: Flow control device 700: Recuperator
800: Feed pipe 810:
830: Compressor bypass flow 850: Turbine bypass flow

Claims (16)

A cooler for cooling the working fluid,
A compressor connected to a rear end of the cooler for compressing the working fluid,
A heater for heating the working fluid passed through the compressor,
A turbine rotatably driven by the working fluid that has passed through the heater;
And a generator connected to the turbine and generating electric power,
Wherein the turbine is controlled to have a revolution number corresponding to an output frequency of the generator,
A compressor circulation valve provided at the front end of the heater so as to be openable and closable,
Further comprising a compressor bypass channel connecting the rear end and the front end of the compressor. The method according to claim 1,
Further comprising a flow rate control device installed at a front end of the turbine to control a flow rate of the working fluid supplied to the turbine. 3. The method of claim 2,
The flow control device controls the working fluid to bypass the turbine or increases the flow rate of the working fluid to the turbine as the turbine rotation speed increases or decreases from the rotation frequency corresponding to the output frequency of the generator A supercritical carbon dioxide power generation system characterized by. The method of claim 3,
Wherein the heater includes a first heater connected to a rear end of the compressor, and a second heater connected to a rear end of the first heater. 5. The method of claim 4,
Further comprising a recuperator branching at a downstream end of the compressor (branch point A) and connected between the first heater and the second heater (branch point B). 6. The method of claim 5,
Wherein the recuperator is connected to a rear end of the turbine and a front end of the cooler, and recovers heat from the working fluid passing through the turbine and recovers the working fluid passing through the compressor. The method of claim 3,
A turbine bypass flow path connecting the front end of the flow rate control device and the rear end of the turbine and bypassing a part or all of the working fluid flowing into the turbine and a turbine bypass flow path provided on the turbine bypass flow path, A turbine bypass valve, further comprising a supercritical carbon dioxide power generation system. The method according to claim 1,
Further comprising an output controller disposed between the turbine and the generator for controlling an output of the turbine according to an output frequency of the generator. 9. The method of claim 8,
Wherein the output control device reduces the rotational speed (rpm) of the turbine according to an output frequency of the generator. 9. The method of claim 8,
Wherein the output control device lowers the output of the turbine and transfers the output of the turbine to the generator when the rotational speed of the turbine is higher than the rotational speed corresponding to the output frequency of the generator. 11. The method of claim 10,
Wherein the output control device is a torque converter. 11. A method of controlling an output of a supercritical carbon dioxide power generation system having the configuration of any one of claims 1 to 11,
A working fluid supply step (SlOO) for supplying a working fluid into the supercritical carbon dioxide power generation system,
A compressing step (S200) in which the working fluid is cooled through a cooler and then supplied to a compressor and compressed;
A heating step (S300) in which the working fluid compressed in the compression step (S200) is heated in the heater,
A turbine driving step (S400) of supplying the working fluid through the heating step (S300) to the turbine to drive the turbine,
And a power generation step (S500) of generating power at a generator connected to the turbine,
Wherein the turbine is controlled to have a rotation speed corresponding to an output frequency of the generator in the driving the turbine (S400). 13. The method of claim 12,
Further comprising an output control step (S450) of adjusting the output of the turbine to an output frequency of the generator after the driving the turbine (S400) and transmitting the adjusted output to the generator (S450). 13. The method of claim 12,
A first determining step S330 of determining whether the compressor is being driven before the turbine driving step S400 and a second determining step S350 of determining whether the turbine rotation speed is increased if the compressor is not initially driven Further comprising the step of controlling the power of the supercritical carbon dioxide power generation system. 15. The method of claim 14,
If it is determined that the compressor is initially being operated in the first determining step S330 or that the operating fluid is circulated by bypassing the turbine when it is determined that the number of rotations of the turbine is increased in the secondary determining step S350 Further comprising a turbine bypass step (S370) for controlling the output of the supercritical carbon dioxide power generation system. 16. The method of claim 15,
Wherein the turbine driving step (S400) is performed when it is determined that the number of rotations of the turbine is not increased in the second determining step (S350).

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