KR20190070610A - Supercritical CO2 generating system and method for operating thereof - Google Patents

Abstract

The present invention relates to a supercritical carbon dioxide power generation system and an operation method thereof. According to the present invention, the supercritical carbon dioxide power generation system comprises: a supply pump for supplying working fluid to a pump inlet port in a main cycle of a supercritical carbon dioxide power generation system; a supply pipe connected to the pump inlet port of the main cycle in the supply pump and through which the working fluid flows; and a recirculation line branching out of the supply pipe and recirculated to the supply pump. The working fluid of a predetermined minimum flow rate from the supply pipe is extracted and recycled to the supply pump through the recirculation line.

Description

Supercritical CO2 generation system and method of operating the same

The present invention relates to a supercritical carbon dioxide power generation system and a method of operating the same, and more particularly, to a supercritical carbon dioxide power generation system capable of preventing overheating and breakage of a working fluid supply pump and a method of operating the same.

Internationally, there is an increasing need for efficient power generation. As the movement to reduce pollutant production becomes more active, various efforts are being made to increase the production of electricity while reducing the generation of pollutants. Research and development of a supercritical CO2 generation system using supercritical carbon dioxide as a working fluid is being promoted.

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. The supercritical carbon dioxide power generation system has a net generation efficiency of about 45% when operated at a temperature of 550 ° C. and has an advantage of improving the generation efficiency of the steam cycle by 20% or more and reducing the turbo device.

Generally, a supercritical carbon dioxide power generation system forms a closed cycle that does not discharge the carbon dioxide used for power generation, and uses supercritical carbon dioxide as a working fluid.

The supercritical carbon dioxide working fluid is stored in a separate storage tank and supplied to the supercritical carbon dioxide power generation system by a feed pump. An example of such a working fluid filling system is disclosed in U.S. Patent No. 8281593.

Further, Korean Patent Laid-Open Publication No. 2015-7028161 discloses a charge pump system having a pump for supplying a working fluid and a start-up pump in a power generation cycle without a separate supply system.

However, the working fluid filling system disclosed in the above-mentioned prior art has a problem in that when there is no separate flow rate control structure and the flow rate of the working fluid below the minimum flow rate continues, the supply pump is overheated or broken. Therefore, there is a need for a method that can prevent overheating and breakage of the operating fluid supply pump.

US Patent No. 8281593 (Registration date October 10, 2012)

An object of the present invention is to provide a supercritical carbon dioxide power generation system capable of preventing overheating and breakage of a working fluid supply pump and a method of operating the same.

The supercritical carbon dioxide power generation system of the present invention and its operation method include a supply pump for supplying the working fluid to a pump inlet end in a main cycle of a supercritical carbon dioxide power generation system, And a recirculation line branched from the supply pipe and recirculated to the supply pump, wherein a predetermined minimum flow rate of the working fluid is added from the supply pipe and recirculated through the recirculation line to the supply pump .

Characterized in that it further comprises a storage tank for storing working fluid, said recirculation line being branched from said supply line and connected to said storage tank, said minimum flow rate of working fluid being recycled to said feed pump via said storage tank .

A first control valve installed in the supply pipe to control a flow rate of the working fluid supplied to the main cycle and a second control valve provided on the recirculation line for controlling a flow rate of the working fluid supplied from the supply pipe to the storage tank, And a control valve.

And a flow meter installed at a discharge end of the supply pump for measuring a flow rate of the working fluid.

And the recirculation line is branched between the flowmeter and the first control valve.

Wherein the first control valve is a pressure control valve (PCV), which is a pressure control valve for regulating the pressure difference between the front and rear ends, or a level control valve, which is a level control valve for controlling a flow rate level of the working fluid, And the valve is provided with a flow control valve (FCV), which is a flow control valve for controlling the flow rate of the working fluid.

When the main cycle is started, the first control valve is closed and the second control valve is partially opened to supply the working fluid of the minimum flow rate to the supply pump.

And the opening degree of the first control valve and the second control valve is controlled by determining the required flow rate of the working fluid required in the main cycle after supplying the working fluid with the minimum flow rate to the supply pump.

When the required flow rate of the working fluid required in the main cycle is equal to or greater than a set value, the second control valve is closed and the first control valve is opened, and if the required flow rate is less than the set value, And a part of the second control valve is opened.

The first control valve is closed during operation of the main cycle, and when the overheating of the supply pump occurs, the second control valve is opened to control the minimum flow amount of the working fluid to be supplied to the supply pump .

The present invention also relates to a supercritical carbon dioxide power generation system comprising a supply pump for supplying the working fluid to a heat exchanger or a recuperator in a main cycle of a supercritical carbon dioxide power generation system, 1 supply line, a start-up pump for supplying the working fluid to the heat exchanger or the recuperator at the start of the main cycle, and a start-up pump connected to the heat exchanger or the recuperator, A first circulation line and a second circulation line branched from the first supply line and the second supply line respectively and recirculated to the start-up pump and the supply pump, And a second supply line for supplying a predetermined flow volume of the working fluid from the second supply line, And is recirculated to the start-up pump and the supply pump through the first circulation line and the second circulation line, and a method of operating the system.

The first circulation line and the second circulation line are connected to a condenser for cooling the working fluid so that the minimum flow rate of the working fluid is recirculated to the supply pump via the condenser.

And a first control valve and a second control valve respectively installed in the first circulation line and the second circulation line for controlling the flow rate of the working fluid branched to the first circulation line and the second circulation line.

The first circulation line and the second circulation line being installed after the branch point at which the first circulation line and the second circulation line are branched to control the flow rate of the working fluid in the first supply line and the second supply line, The first valve and the second valve.

And a flow meter installed at a discharge end of the supply pump and the start-up pump to measure a flow rate of the working fluid.

The first control valve and the second control valve are provided as a flow control valve (FCV) which controls a flow rate of the working fluid.

The second valve is closed and the first control valve and the second control valve are partially opened to supply the working fluid of the minimum flow rate to the start-up pump and the supply pump at the start of the main cycle .

And controlling the opening degree of the first control valve and the second control valve by determining the required flow rate of the working fluid required in the main cycle after supplying the working fluid with the minimum flow rate to the start-up pump and the supply pump .

When the required flow rate of the working fluid required in the main cycle is equal to or greater than a set value, the first control valve and the second control valve are closed and the first valve is opened, And the valve and the second control valve are partly opened.

The second valve is closed while the main cycle is in operation and the second control valve is opened when the start-up pump is overheated, so that the minimum flow amount of the working fluid is supplied to the start-up pump do.

The supercritical carbon dioxide power generation system and its operation method according to an embodiment of the present invention include a structure for controlling the flow rate and a separate flow path for stably supplying the minimum flow rate, .

1 is a schematic diagram showing a working fluid supply system of a supercritical carbon dioxide power generation system according to an embodiment of the present invention,
2 is a graph showing the discharge amount and temperature relationship of the working fluid supply pump,
3 is a graph showing the operation line of a general working fluid supply pump,
4 is a graph showing the operation line of the working fluid supply pump of the present invention,
FIG. 5 is a flowchart showing an operation method at the start of a supercritical carbon dioxide power generation system to which the working fluid supply device of FIG. 1 is applied,
FIG. 6 is a flowchart showing an operation method of a supercritical carbon dioxide power generation system to which the working fluid supply device of FIG. 1 is applied,
FIG. 7 is a schematic diagram illustrating a supercritical carbon dioxide power generation system according to an embodiment of the present invention. FIG.
FIG. 8 is a flowchart showing an operation method at the start of a supercritical carbon dioxide power generation system to which the working fluid supply device of FIG. 7 is applied,
FIG. 9 is a flowchart showing an operation method of a supercritical carbon dioxide power generation system to which the working fluid supply device of FIG. 7 is applied,
10 is a schematic diagram showing an example of a supercritical carbon dioxide power generation system according to another embodiment of the present invention.

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

Generally, a supercritical carbon dioxide power generation system forms a closed cycle that does not discharge the carbon dioxide used for power generation, and uses supercritical carbon dioxide as a working fluid.

The supercritical carbon dioxide power generation system can be used not only in a single power generation system but also in a hybrid power generation system with a thermal power generation system since the working fluid is carbon dioxide in a supercritical state and exhaust gas discharged from a thermal power plant can be used. The working fluid of the supercritical carbon dioxide power generation system may separate carbon dioxide from the exhaust gas and supply the carbon dioxide separately.

The supercritical carbon dioxide in the cycle passes through a compressor and then is heated while passing through a heat source such as a heater to generate a high-temperature high-pressure working fluid to drive the turbine. The turbine is connected to a generator or a pump, which drives the pump using a turbine connected to the pump and generating power by the turbine connected to the generator. The working fluid passing through the turbine is cooled as it passes 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.

A supercritical carbon dioxide power generation system according to various embodiments of the present invention includes not only a system in which all of the working fluid flowing in a cycle is in a supercritical state but also a system in which a majority of the working fluid is supercritical and the rest is subcritical It is used as a meaning.

Also, in various embodiments of the present invention, carbon dioxide is used as the working fluid, wherein carbon dioxide refers to pure carbon dioxide in the chemical sense, carbon dioxide in a state where the impurities are somewhat contained in general terms, and carbon dioxide in which at least one fluid is mixed Is used to mean a fluid in a state where the fluid is in a state of being fluidized.

1 is a schematic diagram showing a working fluid supply system of a supercritical carbon dioxide power generation system according to an embodiment of the present invention.

As shown in FIG. 1, a working fluid supply system of a supercritical carbon dioxide power generation system according to an embodiment of the present invention supplies a working fluid into a supercritical carbon dioxide power generation system. This system aims at stable control of the supply pump, which will be described later.

The supplied working fluid is compressed and heated while circulating in a closed loop cycle (hereinafter referred to as " main cycle ") of the power generation system to drive the turbine to produce electric energy. The working fluid after turbine operation is cooled through heat exchange and circulated in the cycle.

The supply system of the working fluid includes a storage tank 100 for storing the working fluid, a supply pump 200 for supplying working fluid into the cycle, and a plurality of valves and a flow meter 600. In addition, a mass control tank (Mass Control Tank) or a heat engine (Heat Engine) may be additionally provided.

It is to be understood that each configuration of the present invention is connected by a transfer pipe through which the working fluid flows, and that the working fluid flows along the transfer pipe even if not specifically mentioned. However, in the case where a plurality of components are integrated, it is to be understood that the working fluid flows along the conveying pipe, as a matter of course, since there will be a part or region which actually functions as a conveying pipe in the integrated structure.

The storage tank 100 stores a working fluid and is a tank having a buffer function. A buffer tank having a buffer function or a capacitor having a buffer function by changing the shape of the capacitor. The storage tank 100 is connected to a discharge line 310 for transferring the working fluid discharged from the mass control tank or the heat engine 300 and a supply line 110 for transferring the working fluid to the supply pump 200. The discharge line 310 is provided with a valve for opening and closing the discharge line 310.

The supply pump 200 is provided with a supply pipe 210 for supplying the working fluid to the main cycle and the first control valve 400 is installed on the supply pipe 210. A flow meter 600 is installed adjacent to the discharge end of the feed pump 200 and a recirculation line 230 is branched between the flow meter 600 and the first control valve 400, And the front end of the storage tank 100 are connected to each other. A second control valve 500 is installed on the recirculation line 230 and the second control valve 500 is controlled based on the measurement result measured by the flow meter 600.

The first control valve 400 may be a pressure control valve (PCV), which is a pressure control valve for presetting the pressure required on the main cycle and following the set pressure. That is, when the working fluid pressure of the line supplied to the pump from the rear end of the condenser of the main cycle is less than a specific value, the first control valve 400, which is a PCV, may be opened to further supply the working fluid. On the contrary, when the pressure of the working fluid in the line supplied to the pump from the rear end of the condenser of the main cycle is excessively high (in the case of the set value or more), the first control valve 400 may be closed to stop the supply of the working fluid.

 Alternatively, the first control valve 400 may be provided with a level control valve (LCV), which is a level control valve for controlling the buffer level of the working fluid (buffer level). That is, it is possible to install a buffer capable of maintaining the flow rate of the condenser downstream of the main cycle. However, the buffer level is too low to cause cavitation or surge in the pump. At this time, if the buffer level is too low to protect the pump, the first control valve may be opened to supply the working fluid so that the buffer level is higher than a certain level. If the buffer level above a certain level is maintained, the first control valve may be closed to stop further supply of working fluid.

The second control valve 500 may be provided with a flow control valve (FCV), which is a flow control valve for regulating the flow rate of the working fluid.

When the first control valve 400 is a pressure control valve, it is controlled according to the pressure required at the input of the supply pump 200, and when the first control valve 400 is a level control valve, It is controlled according to the level of the fluid. Since the second control valve 500 is a flow control valve, it is controlled according to the minimum recirculation flow rate of the working fluid recirculated to the feed pump 200.

The flow meter 600 is installed at a discharge end (rear end) of the feed pump 200 to measure a minimum flow rate of a working fluid (FIT), and it is an orifice type, a venture type, (ultra-sonic) type and the like. If the working fluid flow rate at the downstream end of the feed pump 200 is less than the set value, the flow rate from the feed pipe 210 to the recirculation line 230 is increased so that the working fluid above the set value can be supplied to the feed pump 200 The flow rate corresponding to the set value is defined as the minimum flow rate). At this time, it is preferable that the second control valve 500 is controlled so that the working fluid circulated to the recycle line 230 can be increased without stopping supply of the working fluid to the pump inlet end of the main cycle. That is, the second control valve 500 is controlled so that the minimum flow rate of the working fluid can be supplied to the recycle line 230 without being fully opened. However, when the working fluid supply to the main cycle is not required, the first control valve 400 may be closed and the second control valve 500 may be completely opened.

The mass control tank or the heat engine 300 may be connected to an auxiliary feed pipe () so that a small amount of high-pressure working fluid can be supplied when an emergency occurs. The auxiliary transfer pipe () can be connected to the supply pipe 210 and supplied with a part of the working fluid from the supply pump 200.

In the working fluid supply apparatus of the present invention having the above-described configuration, the operation of the supply pump will be described in more detail (the reference numerals of the respective constructions will be referred to Fig. 1).

FIG. 2 is a graph showing the discharge amount and temperature relationship of the working fluid supply pump, FIG. 3 is a graph showing the operating line of a general working fluid supply pump, FIG. 4 is a graph showing the operating line of the working fluid supply pump of the present invention to be.

2, when the flow rate of the working fluid supplied to the feed pump 200 is too small as compared with the design value, the temperature of the feed pump rises due to an increase in the internal friction of the feed pump 200 Shaded section). In other words, if the flow rate of the working fluid is too small, the pump will overheat because it can not sufficiently remove the frictional heat generated by rotating the stator and rotor of the pump. The pump overheat causes the working fluid to rise in temperature, and when the working fluid is heated above 31 degrees Celsius, it becomes supercritical and the volume increases about 50 times. Since the sudden increase in the volume of the working fluid causes fatal damage to the pump, the working fluid in the pump needs to prevent the pump from overheating to maintain the liquid phase.

For example, when the flow rate of 50 m 3 / h or less flows into the feed pump designed to have a discharge rate of 250 m 3 / h, the temperature in the pump increases sharply. Therefore, problems due to overheating may occur.

As shown in Fig. 3, it is generally possible to define a region (the shaded region in Fig. 3) in which the flow rate of the working fluid required in the power generation system is within 30% of the design value of the working fluid supply pump, as the pump overheating operation region .

When the pump overheats, the pump trips or trips by the pump's own protection logic. If the pump is suddenly stopped, the working fluid is not supplied to the external heat exchanger, and the external heat exchanger is also overheated. When the external heat exchanger is overheated, the heat exchange tube is broken and the reliability of the power generation system is drastically reduced. It is necessary to prevent the reliability degradation of the power generation system because it is very important for the operation of the power generation system. In addition, if the pump overheat occurs continuously, the pump also breaks, so that the pump needs to be replaced.

Therefore, as shown in FIG. 4, it is necessary to control so that the working fluid having the minimum flow rate or more flows stably in the pump overheating operation region in order to prevent overheating of the pump and thereby damage thereof. To this end, the first control valve 400 and the second control valve 500, the flow meter 600, and the recirculation line 230 are provided to control the flow rate of the working fluid recirculated to the feed pump 200 will be.

In the working fluid supply device of the supercritical carbon dioxide power generation system according to an embodiment of the present invention having the above-described configuration, a method of preventing overheat of the supply pump will be described in order ).

FIG. 5 is a flowchart showing an operation method of the supercritical carbon dioxide power generation system to which the working fluid supply device of FIG. 1 is applied, and FIG. 6 is a flowchart of a method of operating the supercritical carbon dioxide power generation system of FIG. Fig.

At the start-up of the supercritical carbon dioxide power generation system, the working fluid must be supplied into the main cycle and at least the working fluid flow rate should be supplied to prevent the overheating of the supply pump 200.

5, the first control valve 400 is fully opened, and the second control valve 500 is partially controlled to be opened (first step, S1). The second control valve 500 is partly opened to supply the working fluid to the supplying pump 200 at a minimum flow rate to prevent overheating of the supplying pump 200 and to supply the working fluid to the main circulation (Step 2, S2).

Then, the required flow rate of the power generation system is determined (third step, S3). 4), the second control valve 500 of the recirculation line 230 may be connected to the second control valve 500. In this case, So that the working fluid is supplied only to the main cycle (Steps 4-1 and S4-1).

On the contrary, when the required flow rate of the power generation system is small (the set value by the experiment can be determined, for example, it may correspond to 30% or less of the range shown in FIG. 4) The second control valve 500 is opened (step 4-2, step S4-2). According to this process, stable start control and overheating of the supply pump 200 can be prevented (S5, S5).

As shown in FIG. 6, since the supercritical carbon dioxide power generation system does not need to supply additional working fluid to the supercritical carbon dioxide power generation system, the first control valve 400 is completely closed (first step, S10) . If a problem occurs in the working fluid supply system and a less amount of working fluid circulates in the supply pump 200 than the minimum flow rate, overheating of the supply pump 200 may occur (second step, S20).

In more detail, the ideal supercritical carbon dioxide power generation system allows continuous operation without the need for additional working fluid. However, in actual supercritical carbon dioxide power generation systems, some working fluid must be continuously supplied in the working fluid supply system because of the leakage of the working fluid generated in the turbo apparatus and the change of the total working fluid flow rate due to changes in the outside temperature. If too little flow is continuously supplied, the pump will overheat.

 Or the pulsating flow rate of the working fluid can be supplied irregularly to the supply pump 200 continuously. This causes the feed pump to fail, and the pump startup speed makes it impossible to immediately supply the working fluid. In order to solve this problem, it is preferable to continuously flow the minimum flow rate through the second control valve 500 and to supply immediate CO2 without damaging the feed pump as necessary.

Accordingly, the second control valve 500 is opened to prevent the supply pump 200 from overheating, and the second control valve 500 is opened so that the flow rate of the working fluid can be maintained at the minimum flow rate, And controls the opening degree of the control valve 500 (third step, S30).

When the problem of the working fluid supply system is solved, the first control valve 400 is adjusted to prepare the driving of the supply pump 200 in the open standby state (fourth step, S40) , The working fluid can be supplied again to the main cycle without a sudden stop (Step 5, S50).

In the foregoing, a working fluid supply apparatus for a supercritical carbon dioxide power generation system according to an embodiment of the present invention has been described. Hereinafter, a working fluid supply apparatus according to another embodiment of the present invention will be described.

7 is a schematic diagram showing a supercritical carbon dioxide power generation system according to another embodiment of the present invention.

7, the supercritical carbon dioxide power generation system according to another embodiment of the present invention includes a turbo pump 100 'for supplying a working fluid and a starter pump 100 for driving the starter pump 100' And a flow meter 500 '. The present system aims at stable control (overheating prevention) of the turbo pump 100 'and the start-up pump 100.

The rear end of the turbo pump 100 'is connected to the first supply line A to the heat exchanger or recuperator of the main cycle and to the first circulation line A' branched from the first supply line A toward the condenser 400 ' (C). The rear end of the start-up pump 100 is connected to the second supply line B toward the heat exchanger 300 'or the recuperator 200' of the main cycle and the condenser 400 ' The second circulation line D is branched. A first valve V1 for opening and closing the line is provided after the branch point of the first circulation line C and a second valve V2 is provided for opening and closing the line after the branch point of the second circulation line D.

A flow meter 500 'is installed on the first supply line A and the second supply line B which are the rear ends of the turbo pump 100' and the start-up pump 100, respectively. A first control valve 400 and a second control valve 700 'are provided on the first circulation line C and the second circulation line D, respectively. The first supply line A and the second supply line B merge after the branch point where the first circulation line C and the second circulation line D branch off and are connected to the heat exchanger 300 ' 200 '). The working fluid moving through the first circulation line C and the second circulation line D joins the working fluid circulating line coming from the recuperator 200 'and circulated to the capacitor 400'.

In this embodiment, the flow meter 500 'is the same as the embodiment of FIG. 1, and the first control valve 600' and the second control valve 700 'are the same as the first control valve The flow control valve can be provided as a flow control valve (the same configuration is not described in detail).

In the working fluid supply device of the supercritical carbon dioxide power generation system according to an embodiment of the present invention having the above-described configuration, a method of preventing overheating of the supply pump will be described in order ).

FIG. 8 is a flowchart showing an operation method of the supercritical carbon dioxide power generation system to which the working fluid supply device of FIG. 7 is applied, and FIG. 9 is a flowchart of the operation method of the supercritical carbon dioxide power generation system to which the working fluid supply device of FIG. Fig.

At the start-up of the supercritical carbon dioxide power generation system, a minimum flow rate or more of the operating fluid flow rate must be supplied to supply the working fluid into the main cycle and to prevent overheating of the start-up pump 100 and the turbo pump 100 ' .

8, the second valve V2 is completely closed, and the first control valve 600 'and the second control valve 700' are partially opened (first step, S1 '). . The first control valve 600 'and the second control valve 700' are partially opened to supply the minimum flow rate of working fluid to the first circulation line C and the second circulation line D (second step, S2 '). This working fluid is circulated through the condenser to the start-up pump 100 and the turbo pump 100 ', thereby preventing overheating of the start-up pump 100 and the turbo pump 100'. At the same time, since the first valve (V1) for supplying the working fluid into the main cycle is not closed, the working fluid can be supplied to the main cycle.

Then, the required flow rate of the power generation system is determined (third step, S3 '). When the required flow rate of the power generation system is sufficiently large (the set value by the experiment can be determined, for example, it may correspond to 30% or more of the intervals in FIG. 4), the first circulation line C and the second circulation line The first control valve 600 'and the second control valve 700' of the control valve D are completely closed to allow the working fluid to be supplied only to the main cycle (steps 4-1 and S4-1 ').

Conversely, when the required flow rate of the power generation system is small (the set value by the experiment can be determined, for example, it may correspond to a period of 30% or less of FIG. 4), the first circulation line C and the second circulation line The first control valve 600 'and the second control valve 700' are opened (Steps 4-2 and S4-2 ') so that a minimum flow rate of the working fluid can be supplied to the first control valve 600'. According to this process, stable start control and overheating of the turbo pump 100 'can be prevented (step S5, S5').

As shown in FIG. 9, during operation of the supercritical carbon dioxide power generation system, there is no need to additionally supply the working fluid to the supercritical carbon dioxide power generation system, so that the second valve V2 is completely closed (first step, S10 '). . If a problem occurs in the power generation system during operation of the start-up pump 100 and a smaller amount of working fluid than the minimum flow rate is circulated to the start-up pump 100, overheating of the start-up pump 100 may occur Step S20 ').

In this case, in order to prevent the start-up pump 100 from overheating, the second control valve 700 'is opened, and the flow rate of the working fluid is maintained at the minimum flow rate or the flow rate of the working fluid is circulated to the start-up pump 100 (Third step, S30 ') so that the second control valve 700' is opened.

When the problem of the power generation system is solved, the start-up pump 100 is prepared to be driven (step 4, step S40 ') by adjusting the second valve V2 so that the start-up pump 100 is overheated or damaged, The fluid can be supplied again to the main cycle (step 5, S50 ').

The start-up pump 100 is required only at start-up and shut-down, but the flow rate of the start-up pump 100 to the start- Irregularities may occur or the operation may be continued for a certain time or less with a minimum flow rate. In this case, problems such as overheating, breakage, and sudden stop of the start-up pump 100 may occur. In particular, in the case of a combined-cycle power plant requiring a daily start-up / daily shut-down, the start-up pump 100 operates one to two times each day. If the start-up pump 100 is not prepared for driving, It can not survive and can be destroyed. Therefore, the contrast between the fourth and fifth steps as described above is required.

Meanwhile, supercritical carbon dioxide power generation system and its operation method can be operated as a system using LNG cold heat.

10 is a schematic diagram showing an example of a supercritical carbon dioxide power generation system according to another embodiment of the present invention.

As shown in Fig. 10, the power generation system is constructed so as to connect the LNG terminal c with the supercritical carbon dioxide power generation system (b) supplied with the working fluid from the working fluid supply system (a) for storing and supplying the working fluid .

In this case, the working fluid is supplied from the storage tank 100 of the working fluid supply system () to the condenser 400 'of the supercritical carbon dioxide power generation system (), and the remaining system configuration is the same as the embodiment of FIGS. 1 and 7 .

The condenser 400 'can perform heat exchange with the working fluid by air-cooling or water-cooling. In this embodiment, the system is configured to perform heat exchange in the condenser 400' using the LNG cold.

The LNG terminal (c) is a part of the LNG system and has a storage tank 10 for storing LNG (liquefied natural gas) having a temperature of minus 165 degrees to minus 150 degrees (the temperatures described below are all degrees Celsius) And an LNG heat exchanger 30 for supplying heat to the LNG system in the form of NG (natural gas, in the range of -50 to -10 degrees Celsius) by heat exchange with the LNG. The LNG terminal (c) can be defined as a cold / hot operating condition since the LNG is phase-changed into a gas phase in the range of -50 degrees to -10 degrees.

The LNG heat exchanger 30 phase-changes the LNG to NG via an antifreeze having an operating temperature in the range of minus 162 degrees to 30 degrees. This antifreeze is supplied to the refrigerant for the condenser () of the supercritical carbon dioxide power generation system .

Under the LNG cooling and operating conditions, the condenser () of the supercritical carbon dioxide power generation system is operated at minus 40 degrees, so that the turbo pump () and the start-up pump () can be operated in a liquid state. Since the operating fluid supply system and the supercritical carbon dioxide power generation system described with reference to Figs. 1 and 7 are applied, the supply pump, the turbo pump, and the start-up pump are controlled so as not to operate at the minimum flow rate, So that a smooth operation state can be maintained.

Without the pump control mechanism of the present invention, each pump can be operated below the minimum flow rate, there is a risk of overheating, and the pump operating temperature can rise to more than 31 degrees Celsius. In this case, the working fluid becomes a supercritical state and the volume increases by about 50 times, which causes fatal damage to the pump. Therefore, in order to solve such a problem, the system configuration of FIG. 10 is provided.

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: Storage tank 200: Feed pump
210: feed pipe 230: recirculation line
300: Mass control tank or heat engine
400: first control valve 500: second control valve
600: Flow Meter

Claims (20)

A supply pump for supplying the working fluid to the pump inlet end in the main cycle of the supercritical carbon dioxide power generation system,
A supply pipe connected to the pump inlet end of the main cycle in the supply pump and through which the working fluid flows,
And a recirculation line branched from the supply pipe and recirculated to the supply pump,
Wherein the predetermined minimum flow amount of the working fluid is added from the supply pipe and recirculated to the supply pump through the recirculation line. The method according to claim 1,
Further comprising a storage tank for storing a working fluid,
Wherein the recirculation line is branched from the supply pipe and connected to the storage tank, and the minimum flow rate of the working fluid is recirculated to the supply pump through the storage tank, and a method of operating the same. 3. The method of claim 2,
A first control valve installed in the supply pipe to control a flow rate of the working fluid supplied to the main cycle and a second control valve provided on the recirculation line for controlling a flow rate of the working fluid supplied from the supply pipe to the storage tank, A supercritical carbon dioxide power generation system, and a method of operating the same. The method of claim 3,
Further comprising a flow meter installed at a discharge end of the supply pump for measuring a flow rate of the working fluid, and a method of operating the supercritical carbon dioxide power generation system. 5. The method of claim 4,
Wherein the recirculation line is branched between the flow meter and the first control valve, and a method of operating the same. 6. The method of claim 5,
Wherein the first control valve is a pressure control valve (PCV), which is a pressure control valve for regulating the pressure difference between the front and rear ends, or a level control valve, which is a level control valve for controlling a flow rate level of the working fluid, Wherein the valve is provided with a flow control valve (FCV), which is a flow control valve for controlling the flow rate of the working fluid, and a method of operating the same. The method according to claim 6,
Wherein the first control valve is closed and the second control valve is partially opened to allow the working fluid to be supplied to the supply pump at the minimum flow rate at the start of the main cycle and the supercritical carbon dioxide generation system Operating method. 8. The method of claim 7,
And controls the opening degree of the first control valve and the second control valve by determining the required flow rate of the working fluid required in the main cycle after supplying the working fluid with the minimum flow rate to the supply pump. Critical carbon dioxide power generation system and method of operation thereof. 9. The method of claim 8,
When the required flow rate of the working fluid required in the main cycle is equal to or greater than a set value, the second control valve is closed and the first control valve is opened, and if the required flow rate is less than the set value, And the second control valve is partially opened, and a method of operating the same. The method according to claim 6,
Wherein the first control valve is closed during operation of the main cycle and the second control valve is opened when overheating of the supply pump occurs so that the minimum flow amount of the working fluid is supplied to the supply pump Supercritical carbon dioxide power generation system and method of operation thereof. A supply pump for supplying the working fluid to the heat exchanger or the recuperator in the main cycle of the supercritical carbon dioxide power generation system,
A first supply line connected to the heat exchanger or the recuperator from the supply pump to flow the working fluid,
A start-up pump for supplying the working fluid to the heat exchanger or the recuperator when the main cycle is started,
A second supply line connected to the heat exchanger or the recuperator from the start-up pump to flow the working fluid,
A first circulation line and a second circulation line branched from the first supply line and the second supply line and recirculated to the start-up pump and the supply pump, respectively,
Wherein a predetermined minimum flow rate of the working fluid from the first supply line and the second supply line is added and recirculated to the start-up pump and the supply pump through the first circulation line and the second circulation line Supercritical carbon dioxide power generation system and method of operation thereof.
12. The method of claim 11,
Wherein the first circulation line and the second circulation line are connected to a condenser for cooling the working fluid so that the minimum flow rate of the working fluid is recirculated to the feed pump through the condenser and the supercritical carbon dioxide generating system Operating method. 13. The method of claim 12,
Further comprising a first control valve and a second control valve respectively installed in the first circulation line and the second circulation line for controlling the flow rate of the working fluid branched to the first circulation line and the second circulation line, Carbon dioxide power generation system and its driving method. 14. The method of claim 13,
The first circulation line and the second circulation line being installed after the branch point at which the first circulation line and the second circulation line are branched to control the flow rate of the working fluid in the first supply line and the second supply line, Further comprising a first valve and a second valve for performing the operation of the supercritical carbon dioxide generation system. 15. The method of claim 14,
Further comprising a flow meter installed at a discharge end of the feed pump and the start-up pump to measure a flow rate of the working fluid, and a method of operating the supercritical carbon dioxide power generation system. 16. The method of claim 15,
Wherein the first control valve and the second control valve are provided as a flow control valve (FCV), which is a flow control valve for controlling the flow rate of the working fluid, and a method of operating the supercritical carbon dioxide generating system. 17. The method of claim 16,
The second valve is closed and the first control valve and the second control valve are partially opened to supply the working fluid of the minimum flow rate to the start-up pump and the supply pump at the start of the main cycle And a method of operating the same. 18. The method of claim 17,
And controlling the opening degree of the first control valve and the second control valve by determining the required flow rate of the working fluid required in the main cycle after supplying the working fluid with the minimum flow rate to the start-up pump and the supply pump Characterized by a supercritical carbon dioxide power generation system and its operating method. 19. The method of claim 18,
When the required flow rate of the working fluid required in the main cycle is equal to or greater than a set value, the first control valve and the second control valve are closed and the first valve is opened, Wherein the valve and the second control valve are partly opened, and a method of operating the same. 17. The method of claim 16,
The second valve is closed while the main cycle is in operation and the second control valve is opened when the start-up pump is overheated, so that the minimum flow amount of the working fluid is supplied to the start-up pump Supercritical carbon dioxide power generation system and its operation method.

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