System for producing power using Brayton cycle

Abstract

A Brayton cycle operation system is disclosed that can increase efficiency and utilization rate by effectively driving a compressor and a pump by providing a pilot pump to reliably operate the Brayton cycle. The Brayton cycle operation system is characterized by including a controller, a Brayton cycle block that performs power generation according to the control of the controller, and a fluid supply block that supplies working fluid to the Brayton cycle block.

Description

Technology Field

[0001] The present invention relates to a power generation operation technology using a Brayton cycle, and more specifically, to a Brayton cycle operation system having a heater that can stably and easily operate the power generation cycle and increase the utilization rate and efficiency of the power generation cycle while protecting the power generation system by switching to a pump mode instead of a compressor for fluid compression when there is a high probability that the fluid of the power generation system contains a liquid phase. Background Technology

[0002] The Brayton cycle is a cycle that repeats the processes of compression, heating, expansion, and cooling without phase change, and gas turbines are a representative example of this cycle. When designing and / or operating such a Brayton cycle, lowering the low-temperature and low-pressure sections of the cycle can improve the output of the power generation system and increase efficiency.

[0003] Lowering the temperature and pressure in this way to expand the operating range presents a problem in that it increases the likelihood of the cycle entering the steam dome region. Among power generation technologies utilizing the Brayton cycle, supercritical CO2 power generation technology replaces the steam working fluid of conventional thermal power plants with carbon dioxide.

[0004] The advantages of this technology include the ability to reduce greenhouse gas emissions through improved efficiency compared to steam turbines, the capacity to reduce turbine size, and a wide range of applications, such as various heat sources (e.g., renewable energy, waste heat, nuclear power, thermal power) and power storage. Furthermore, this technology utilizes the Brayton cycle, which involves compression, heating, expansion, and cooling processes using carbon dioxide at temperatures and pressures higher than its critical point. A typical supercritical CO2 power generation system configuration (simple recuperated Brayton cycle) includes a compressor, cooler, recuperator, turbine, and heater.

[0005] In such a supercritical CO2 power generation system, to increase power generation efficiency and operate the system in a safe operating range, and simultaneously to inject fluid into the power generation system during initial startup, the system is operated by moving from the right side of the steam dome to the left side of the steam dome, while maintaining distance from the steam dome or critical point. To maintain distance from the steam dome or critical point, it is advantageous to operate the compressor at a high pressure during the initial injection or transient state.

[0006] However, if the compressor operating pressure is raised above the steady-state pressure during initial operation, including the injection of working fluid into the system, there are disadvantages such as increased costs, which make operation difficult and require raising the system design pressure.

[0007] Furthermore, there is a demand for additional safety devices, and concerns about damage still exist if the operating range deviates from the compressor's optimal range. Prior art literature

[0008] 1. Korean Published Patent No. 10-2021-0010067 The problem to be solved

[0009] The present invention is proposed to resolve the problems according to the background technology above, and aims to provide a Brayton cycle operating system having a heater that can increase efficiency and utilization rate by effectively driving the compressor and pump by equipping a pilot pump to reliably operate the Brayton cycle.

[0010] In addition, another objective of the present invention is to provide a Brayton cycle operating system and method that can stably operate in a transient state when entering a dangerous operating range, even during initial start-up or normal operation, so that the compressor can be operated in a stable range. means of solving the problem

[0011] To achieve the above-mentioned objectives, the present invention provides a Brayton cycle operation system equipped with a pilot pump to effectively drive the compressor and pump, thereby reliably operating the Brayton cycle and increasing efficiency and utilization rate.

[0012] The above Brayton cycle driving system is,

[0013] Controller;

[0014] A Brayton cycle block that performs power generation according to the control of the above controller; and

[0015] It is characterized by including a fluid supply block that supplies working fluid to the Brayton cycle block.

[0016] At this time, the Brayton cycle block is characterized by comprising: a first heater for primary heating of the working fluid; a compressor for producing a compressed working fluid by compressing the primary heated working fluid at high pressure; a recuperator for performing heat exchange with the compressed working fluid; a second heater for secondary heating of the heat-exchanged working fluid; a turbine for generating power through the expansion of the secondary heated working fluid; and a cooler for cooling the expanded working fluid.

[0017] In addition, the first heater is characterized by heating the working fluid to a constant temperature so that droplets do not form at the front of the compressor.

[0018] In addition, the Brayton cycle block is characterized by including a bypass valve that connects the upstream and downstream ends of the compressor to bypass the primary heated working fluid.

[0019] In addition, the first end is connected between the rear end of the cooler and the front end of the first heater, and a first valve block is disposed to control the flow of the cooled working fluid.

[0020] At this time, the Brayton cycle operating system is characterized by including a pilot pump connected to the other end of the first valve block to pump the cooled working fluid.

[0021] At this time, the first valve block is characterized by comprising: a first-1 valve, one end of which is connected to the rear end of the cooler; a first-2 valve, one end of which is connected to the rear end of the first-1 valve and the other end of which is connected to the front end of the first heater; and a first-3 valve, one end of which is connected to the middle of the first-1 valve and the first-2 valve and the other end of which is connected to the front end of the pilot pump.

[0022] In addition, it is characterized by having a second valve block disposed between the pilot pump, the fluid supply block, and the first valve block.

[0023] Additionally, the second valve block is characterized by comprising: a second-1 valve, one end of which is connected to the rear end of the pilot pump; a second-2 valve, one end of which is connected to the rear end of the second-1 valve and the other end of which is connected between the rear end of the cooler and the front end of the first valve block; and a second-3 valve, one end of which is connected to the rear end of the second-1 valve and the other end of which is connected to the fluid supply block.

[0024] Additionally, the fluid supply block is characterized by comprising: a storage tank for storing the working fluid; a transfer pump for transferring the working fluid; a vaporizer that vaporizes the working fluid to change it into a vaporized working fluid; and a buffer tank connected to the pilot pump to send the cooled working fluid or the vaporized working fluid back to the cooler.

[0025] In addition, when a pump mode is selected according to the preset operating conditions of the compressor, the first and second valves are closed or the front and rear ends of the compressor are closed when injecting the working fluid into the cycle block, and a certain amount of the working fluid stored in the storage tank is injected through the transfer pump, the vaporizer, and the buffer tank, and the operating conditions are characterized as operating conditions on the temperature-enthalpy (TS) diagram based on temperature and pressure conditions.

[0026] In addition, before the compressor is driven, the first-2 valve is closed, and the first-1 valve, the first-3 valve, the second-1 valve, and the second-2 valve are opened to circulate the working fluid, and when the preset conditional pressure of the compressor reaches a preset set pressure, the first-2 valve is opened and the second-1 valve and the second-2 valve are closed.

[0027] In addition, the invention is characterized by having a chiller placed upstream of the pilot pump to protect the pilot pump.

[0028] On the other hand, another embodiment of the present invention provides a Brayton cycle operation system characterized by comprising: a controller; a Brayton cycle block that performs power generation according to the control of the controller; a fluid supply block that supplies working fluid to the Brayton cycle block; and an option line that continues to supply the working fluid from the Brayton cycle block for power generation when a driving danger condition occurs in the compressor of the Brayton cycle block.

[0029] At this time, the Brayton cycle block is characterized by comprising: a first heater for primary heating of the working fluid; a compressor for producing a compressed working fluid by compressing the primary heated working fluid at high pressure; a recuperator for performing heat exchange with the compressed working fluid; a second heater for secondary heating of the heat-exchanged working fluid; a turbine for generating power through the expansion of the secondary heated working fluid; and a cooler for cooling the expanded working fluid.

[0030] In addition, the first end is connected between the rear end of the cooler and the front end of the first heater, and a first valve block is disposed to control the flow of the cooled working fluid.

[0031] At this time, the system includes a pilot pump connected to the other end of the first valve block to pump the cooled working fluid, wherein one end of the option line is connected to the pilot pump and the other end is connected to the double heater, and a line valve is installed on the option line.

[0032] In addition, a bypass valve and a shut-off valve are respectively positioned at the upstream and downstream ends of the compressor, and the bypass valve and the shut-off valve are both closed when the operating danger condition occurs.

[0033] On the other hand, another embodiment of the present invention provides a Brayton cycle operation method characterized by comprising: (a) a step in which a controller performs control; (b) a step in which a Brayton cycle block performs power generation according to the control of the controller; and (c) a step in which a fluid supply block supplies a working fluid to the Brayton cycle block.

[0034] On the other hand, another embodiment of the present invention provides a Brayton cycle operation method characterized by comprising: (a) a step in which a controller performs control; (b) a step in which a Brayton cycle block performs power generation according to the control of the controller; (c) a step in which a fluid supply block supplies a working fluid to the Brayton cycle block; (d) a step in which the controller determines whether a driving risk condition occurs in a compressor among the Brayton cycle blocks; and (e) a step in which the controller continues to supply the working fluid from the Brayton cycle block for power generation through an option line. Effects of the invention

[0035] According to the present invention, the compressor can be switched to a pump mode when entering an unstable region of the compressor drive point during initial startup and operation, thereby improving the efficiency, ease of operation, and stability of the compressor.

[0036] In addition, another advantage of the present invention is that by utilizing the pilot pump-option line during the initial system charging, the interior of the system can be easily and stably filled with fluid while safely protecting the compressor. Brief explanation of the drawing

[0037] FIG. 1 is a block diagram of a Brayton cycle operation system according to an embodiment of the present invention. FIG. 2 is a block diagram of a Brayton cycle operation system according to another embodiment of the present invention. Figure 3 shows the temperature-entropy of a typical supercritical CO2 Brayton cycle enter It is a leader. Figure 4 is a conceptual diagram of a general system maneuvering strategy in airframe area 1. Figure 5 is a conceptual diagram of a general system maneuvering strategy in airframe area 2. Figure 6 is a conceptual diagram of a system operation strategy in the liquid-vapor or liquid region. Figure 7 is the critical point and vapor dome diagram of carbon dioxide. FIG. 8 is a flowchart showing the Brayton cycle operation process according to an embodiment of the present invention. Specific details for implementing the invention

[0038] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the invention to specific embodiments, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0039] Similar reference numerals are used for similar components when describing each drawing. Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another.

[0040] For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and / or" includes a combination of a plurality of related described items or any of a plurality of related described items.

[0041] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains.

[0042] Terms such as those defined in commonly used dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0043] A Brayton cycle operation system and method according to an embodiment of the present invention will be described in detail below with reference to the attached drawings.

[0044] In one embodiment of the present invention, a supercritical CO2 power generation cycle is described as a representative cycle of the Brayton cycle.

[0045] Meanwhile, when designing a power generation system, it is important to ensure the compressor is operated safely by avoiding dangerous operating conditions that could cause problems. However, due to various factors, there may be instances where the compressor operates outside of stable conditions (the compressor operating range) during initial startup or operation.

[0046] To safely operate the system even in such adverse operating conditions, when there is a high probability that the fluid in the power generation system contains a liquid phase, it is necessary to switch from a compressor mode to a pump mode for fluid compression to protect the power generation system, operate the power generation cycle stably and easily, and increase the utilization rate and efficiency of the power generation cycle.

[0047] To operate a compressor safely, it is advisable to increase the temperature or pressure of the fluid entering the compressor inlet to keep it as far away as possible from the critical point, vapor dome, or liquid region. However, from the perspective of cycle efficiency or work, lowering the cycle's minimum temperature and pressure is advantageous for maximizing cycle performance.

[0048] Therefore, operating the compressor within a stable range while minimizing its temperature and pressure is a crucial factor in improving the work and efficiency of the power generation cycle.

[0049] Ultimately, because of the situation where the compressor must be operated near the critical point or steam dome, finding conditions such as temperature and pressure to ensure optimal operation of the compressor in a stable range, or switching to pump mode when moving out of the stable range to wait until the system moves to a stable operating range, or switching to pump mode for a certain period to implement the power generation cycle can help improve system utilization and efficiency, reduce costs, and ensure robust operation and control.

[0050] FIG. 1 is a block diagram of a Brayton cycle operation system (100) according to an embodiment of the present invention. Referring to FIG. 1, the Brayton cycle operation system (100) may be configured to include a controller (101), a Brayton cycle block (110) that performs power generation according to the control of the controller (101), a chiller (120) connected to the Brayton cycle block (110), a fluid supply block (102) that supplies fluid to the Brayton cycle block (110), etc.

[0051] A Brayton cycle block (110) has a Brayton cycle that undergoes compression, heating, expansion, and cooling processes. To this end, the Brayton cycle block (110) may be configured to include a first heater (112) that heats the working fluid first (a heater to prevent liquid generation at the compressor inlet and entry into the steam dome internal area, which may not operate as needed), a compressor (114) that compresses the first-heated working fluid to high pressure to produce compressed working fluid, a recuperator (115) in which heat exchange takes place between the compressed working fluid discharged from the compressor (114) and the working fluid that has passed through the turbine (117), a second heater (116) that heats the heat-exchanged working fluid secondarily, a turbine (117) that generates power through the expansion of the secondarily heated working fluid, and a cooler (118) that cools the expanded working fluid.

[0052] A valve block (111) is configured at the front end of the first heater (112). This valve block (111) functions to deliver the working fluid cooled by the cooler (118) to the first heater (112) or the chiller (120). To this end, the valve block (111) is composed of a first-1 valve (111-1) with one end connected to the rear end of the cooler (118), a first-2 valve (111-2) with one end connected to the other end of the first-1 valve (111-1) and the other end connected to the front end of the first heater (112), and a first-2 valve (111-3) with one end connected to the middle of the first-1 valve (111-1) and the first-2 valve (111-2) and the other end connected to the front end of the pilot pump (130).

[0053] In addition, a bypass valve (113) is provided to connect the front and rear ends of the compressor (114) to connect the working fluid from the first heater (112) to the double heater (115). When the compressor is out of the operating range, the bypass valve (113) is opened, and the compressor (114) is not driven, thereby protecting the compressor. In addition, When the working fluid is first injected into the system, the bypass valve (113) is opened when compressor operation is not required.

[0054] Meanwhile, a chiller (120) and a pilot pump (130) are sequentially connected to the valve block (111). The chiller (120) is positioned to protect the pilot pump (130). The chiller (120) is a device for lowering the temperature of the fluid, and it is generally advantageous for the pump to keep the temperature of the inlet fluid low for smooth operation.

[0055] Additionally, check valves (119-1, 119-2) are configured at the rear end of the double-heater (115) and the rear end of the cooler (118), respectively. The check valves (119-1, 119-2) are valves that prevent the working fluid from flowing in the opposite direction.

[0056] A valve block (141) is positioned at the rear end of the pilot pump (130). The valve block (141) consists of a second-1 valve (141-1) with one end connected to the rear end of the pilot pump (130), a second-2 valve (141-2) with one end connected to the rear end of the second-1 valve (141-2) and the other end connected between the rear end of the cooler (118) and the front end of the valve block (111), and a second-3 valve (141-3) with one end connected to the rear end of the second-1 valve (141-2) and the other end connected to the buffer tank (180). In particular, the rear end of the second-2 valve (141-2) is connected between the first-1 valve (111-1) and the check valve (119).

[0057] In the front end of the buffer tank (180), a vaporizer (170), a transfer pump (160), a storage tank (150), etc. are sequentially configured. That is, the fluid supply block (102) may be configured to include a storage tank (150) for storing working fluid, a transfer pump (160) for transferring the working fluid, a vaporizer (160) that vaporizes the working fluid to change it into a vaporized working fluid, and a buffer tank (180) connected to the pilot pump (130) to send the cooled working fluid or the vaporized working fluid back to the cooler (118).

[0058] A valve (192) and a check valve (191) are sequentially connected to the front end of the buffer tank (180). The valve (192) is connected between the double heater (115) and the cooler (118).

[0059] Referring to FIG. 1, in the case of one embodiment of the present invention, when system conditions (temperature, pressure) are formed on the left side of the steam dome (including liquid) or inside the steam dome, Brayton cycle initiation and operation using a pilot pump is performed. To elaborate, working fluid is filled into the loop through a transfer pump (160) and a buffer tank (180), and when a certain pressure is reached, the pilot pump (130) is driven to convert the inlet conditions of the compressor (114) to a stable region, thereby driving the compressor (114) to operate the power generation system.

[0060] At this time, the chiller (120) is driven to protect the pilot pump (130), or the liquid level of the buffer tank (180) is raised.

[0061] To protect the loop of the recycling system using the pilot pump (130), the valve (141-3) is opened toward the buffer tank (180) to create a circulating structure. When the recycling system using the pilot pump (130) is driven, after the discharge of the pilot pump (130), the pressure and temperature rise, so the inlet conditions of the compressor (114) move to a stable region. The stable region is a region that is far from the critical point, vapor dome, and liquid region on the TS diagram.

[0062] For the recycling system loop, the first-2 valve (111-2) is closed and the first-1 and first-3 valves (111-1, 111-3) are opened to recycle, and when appropriate conditions are met, the first-3 valve (111-3) is closed and the first-2 valve (111-2) is opened to drive the compressor (114). At this time, the pilot pump (130) is stopped.

[0063] Alternatively, when restarting the system, if it is difficult to use the compressor depending on the conditions within the loop, the pilot pump (130) is driven to the left of the steam dome, and the compressor (114) is driven when the inlet conditions of the compressor (114) change to a stable region.

[0064] Alternatively, working fluid is injected into the entire system loop. While injecting, when conditions at the inlet and outlet of the compressor (114) enter a stable region, the pilot pump (130) is stopped, the pump connection circuit (111-3, 120, 130) is closed, and the compressor connection circuit (111-1, 111-2, 114) is opened to help the power generation system start normally.

[0065] In addition, if compression is performed near a vapor dome, the working fluid of the compressor (114) may enter the vapor dome or temporarily move to a place with a significant change in density (liquid portion). In this case, there is a high possibility of adverse effects on the system including the compressor. However, according to one embodiment of the present invention, the mode is safely switched to a pump, and when entering a safe area, the system is switched to a compressor mode to ensure stable operation.

[0066] Referring to Fig. 1, the operation process is described as follows.

[0067] When injecting working fluid into the Brayton cycle block (110) for the first time (i.e., in the initial case), the 1-3 valve (111-3) and the 2-2 valve (141-2) are closed, and a certain amount of working fluid from the storage tank (150) is injected through the transfer pump (160) → vaporizer (170) → buffer tank (180). Then, before driving the compressor (114), the working fluid is circulated from ① → ③ → ④ → ⑤ with the 1-2 valve (111-2) closed to raise the pressure to the driving pressure of the compressor (114) required by the power generation system. Once the desired pressure is reached, the 1-2 valve (111-2) is opened, and the 1-2 and 2-2 valves (111-2, 141-2) are closed to bring the power generation system cycle to a normal state and enable operation.

[0068] At this time, the first heater (112) located at the downstream end of the first-2 valve (111-2) can serve to raise the temperature to a desired level without creating liquid droplets at the upstream end of the compressor (114). Meanwhile, the line (141-1, 141-3, 180) branching from the second-1 valve (141-1) to the buffer tank (180) is an auxiliary facility that circulates to the buffer tank to relieve sudden pressure rise when the pump is driven.

[0069] The valve (111-1 to 111-3, 113, 141-1 to 141-3), 192) is an electronic valve and is controlled by a controller (101). The controller (101) performs the function of controlling the components. To this end, the controller (101) may be configured to include a microprocessor, memory, power supply circuit, switching circuit, etc.

[0070] FIG. 2 is a block diagram of a Brayton cycle operation system (200) according to another embodiment of the present invention. Referring to FIG. 2, the Brayton cycle operation system (200) may be configured to include a controller (201), a Brayton cycle block (210) that performs power generation according to the control of the controller (201), a chiller (220) connected to the Brayton cycle block (210), a fluid supply block (202) that supplies working fluid to the Brayton cycle block (210), etc.

[0071] A Brayton cycle block (210) has a Brayton cycle that undergoes compression, heating, expansion, and cooling processes. To this end, the Brayton cycle block (210) may be configured to include a first heater (212) that heats the working fluid first, a compressor (214) that compresses the first-heated working fluid to high pressure to produce compressed working fluid, a recuperator (215) in which heat exchange occurs between the compressed working fluid discharged from the compressor (214) and the working fluid that has passed through the turbine (217), a second heater (216) that heats the heat-exchanged working fluid secondarily, a turbine (217) that generates power through the expansion of the secondarily heated working fluid, and a cooler (218) that cools the expanded working fluid.

[0072] A valve block (211) is configured at the front end of the first heater (212). This valve block (211) functions to deliver the working fluid cooled by the cooler (218) to the first heater (212) or the chiller (220). To this end, the valve block (211) is composed of a first-1 valve (211-1) with one end connected to the rear end of the cooler (218), a first-2 valve (211-2) with one end connected to the other end of the first-1 valve (211-1) and the other end connected to the front end of the first heater (212), and a first-2 valve (211-3) with one end connected to the middle of the first-1 valve (211-1) and the first-2 valve (211-2) and the other end connected to the front end of the pilot pump (230).

[0073] In addition, a bypass valve (213) is provided to connect the front and rear ends of the compressor (214) to connect the working fluid from the first heater (212) to the double heater (215).

[0074] Meanwhile, a chiller (220) and a pilot pump (230) are sequentially connected to the valve block (211). The chiller (220) is positioned to protect the pilot pump (230).

[0075] Additionally, check valves (219-1, 219-2) are configured at the rear end of the double-heater (215) and the rear end of the cooler (218), respectively. The check valves (219-1, 219-2) are valves that prevent the working fluid from flowing in the opposite direction.

[0076] A valve block (241) is positioned at the rear end of the pilot pump (230). The valve block (241) consists of a second-1 valve (241-1) with one end connected to the rear end of the pilot pump (230), a second-2 valve (241-2) with one end connected to the rear end of the second-1 valve (241-2) and the other end connected between the rear end of the cooler (218) and the front end of the valve block (211), and a second-3 valve (241-3) with one end connected to the rear end of the second-1 valve (241-2) and the other end connected to the buffer tank (280). In particular, the rear end of the second-2 valve (241-2) is connected between the first-1 valve (211-1) and the check valve (219).

[0077] In the front end of the buffer tank (280), a vaporizer (270), a transfer pump (260), a storage tank (250), etc. are sequentially configured. That is, the fluid supply block (202) may be configured to include a storage tank (250) for storing working fluid, a transfer pump (260) for transferring the working fluid, a vaporizer (260) that vaporizes the working fluid to change it into a vaporized working fluid, and a buffer tank (280) connected to the pilot pump (230) to send the cooled working fluid or the vaporized working fluid back to the cooler (218).

[0078] A valve (292) and a check valve (291) are sequentially connected to the front end of the buffer tank (280). The valve (292) is connected between the double heater (215) and the cooler (218).

[0079] The Brayton cycle operating system (200) illustrated in FIG. 2 is similar to the Brayton cycle operating system (100) illustrated in FIG. 1, but when a driving risk condition (or driving risk area) occurs in the compressor (214) during initial system charging or system operation, both the bypass valve (213) and the shut-off valve (214-1) placed at the front and rear ends of the compressor (214) are closed. Driving risk conditions include when the inlet condition of the compressor on the TS diagram enters the liquid area, when it is adjacent to the critical point and vapor dome, or when a droplet is formed at the compressor inlet.

[0080] At this time, the pilot pump (230) configures a thermodynamic cycle in place of the compressor (214) through the option line (206) to continuously operate (power generation) without stopping. Alternatively, during the initial charging of the system, the pilot pump (230) and the option line (206) can be utilized to easily and stably charge the fluid inside the system while safely protecting the compressor (214).

[0081] Referring to Fig. 2, the operation process is explained as follows.

[0082] When a dangerous operating zone of the system compressor (214) occurs during initial system charging or system operation, the front and rear ends of the compressor (214) are both closed by valves (213, 214-1), and the thermodynamic cycle is configured in place of the compressor (214) through the option line (206) from the pilot pump (230) so that operation (power generation) continues without stopping.

[0083] Alternatively, when initially charging the system, the pilot pump (230)-option line (206) can be utilized to easily and stably charge the working fluid inside the system while safely protecting the compressor (214).

[0084] Meanwhile, a line valve (231) is installed on the option line (206) to block or allow the inflow of working fluid from the pilot pump (230).

[0085] Figure 3 is a temperature-pressure diagram of a typical supercritical CO2 Brayton cycle. Referring to Figure 3, the vertical axis is temperature (T), the horizontal axis is enthalpy (S), and high pressure (P high ), low pressure (P low ...is indicated. Generally, compressors used in the Brayton cycle or the Oil & Gas industry are mostly operated in an area away from the steam dome during operation, so the inlet state of the compressor is gas.

[0086] However, in the case of a supercritical carbon dioxide Brayton cycle (or depending on the working fluid in the Brayton cycle), since the compressor's operating point is close to the vapor dome or liquid region, it is crucial to predict and execute stable compressor operation based on inlet region conditions (temperature, pressure, etc.).

[0087] FIG. 4 is a conceptual diagram of a general system start strategy in gas region 1. Referring to FIG. 4, when driving the compressor, the entire system loop is generally filled with working fluid starting from low pressure, and once a certain amount is filled, the compressor inlet state is sent from the rated value to the required value according to the compressor inlet temperature, inlet pressure, and pressure within the system loop. Generally, starting from the right side of the steam dome (410), the drive point (421) is sent from a point a certain distance away from the steam dome to start operation according to the Brayton cycle (420).

[0088] To elaborate, when operating the compressor, the working fluid is filled starting from the right side of the steam dome, passes through the top of the steam dome (410) (above the critical point), and moves to the normal state compressor operating point formed on the left side of the steam dome to operate the compressor.

[0089] FIG. 5 is a conceptual diagram of a general system operation strategy in gas region 2. Referring to FIG. 5, in order to increase efficiency and safely find the operating region, the system is safely distanced from the steam dome (510) or critical point (521), moved to the left side of the steam dome, and then lowered the pressure to start operation according to the Brayton cycle (520).

[0090] Although moving to the left side of the steam dome to lower the pressure improves system efficiency, it has disadvantages such as making operation difficult and increasing costs by requiring the internal pressure to be higher than the steady-state operating pressure, as well as raising the system design pressure.

[0091] To operate the compressor (114, 214) safely, it is preferable to increase the temperature or pressure of the working fluid entering the inlet of the compressor (114, 214) to keep it as far as possible from the critical point, vapor dome, or liquid region. However, from the perspective of cycle efficiency or work, lowering the minimum temperature and pressure of the cycle is advantageous for maximizing cycle performance.

[0092] Therefore, operating the compressor in a stable range while keeping the temperature and pressure of the compressor (114, 214) as low as possible is a very important factor in the power generation system.

[0093] Ultimately, because the compressor (114, 214) must be operated near the critical point, finding conditions such as temperature and pressure to ensure optimal operation of the compressor (114, 214) in a stable range, or switching to pump mode when moving out of the stable range to wait until the system stabilizes, or performing the function of switching to pump mode for a certain period of time can help improve system utilization and efficiency, reduce costs, and ensure robust operation and control.

[0094] Figure 6 is a conceptual diagram of a system start-up strategy when the state of the compressor inlet is in the liquid-vapor or liquid region during system operation, start-up, or restart. Referring to Figure 6, it is a diagram indicating a transition to compressor inlet conditions for safe compressor operation inside a vapor dome or in the liquid region.

[0095] That is, when using the pilot pump (130) according to one embodiment of the present invention, the system is initially filled with working fluid, and then the pressure is increased by the pilot pump (130) to enter the driving point (i.e., critical point) (621) of the compressor (114, 214), and operation according to the Brayton cycle (520) begins. In the throttling section of the compressor (114, 214), the fluid velocity becomes faster than at the inlet of the compressor, so the pressure is lower than at the inlet of the compressor, and thus it approaches the steam dome (610), which can threaten the stability of the compressor (114, 214). Therefore, a compressor operation device using a pilot pump can be utilized by predicting the dangerous operating area even in the throttling section of the compressor. The constriction zone is a section within a fluid system characterized by a rapid decrease in the cross-sectional area of ​​the flow path, resulting in increased fluid velocity and decreased pressure.

[0096] Check the factors that determine the compressor's operating conditions. Based on temperature and pressure conditions, appropriately select and use the pump mode and compressor mode on the TS diagram.

[0097] The focus is on presenting a methodology that enables stable transient operation when the compressor enters a dangerous operating region during initial startup or normal operation, so that the compressor can operate in a safe region. This can be utilized for the safe operation of the system and the compressor, and allows the system to be mechanically configured to return to a normal operating trajectory even when operating in a dangerous region during system operation.

[0098] FIG. 7 shows the critical point (700) and vapor dome diagram of carbon dioxide. Referring to FIG. 7, the critical point (73.8 bar, 31°C) and vapor dome diagram of CO2 can be seen. Near the critical point (700), the thermophysical properties of carbon dioxide change very rapidly. That is, it changes to any one of the supercritical region (710), sub-cooling (730), gas-liquid (720), or gas (730).

[0099] By reducing the compressibility at this critical point (700) position, the pressure of the working fluid is increased, and the energy required to reach the desired upper pressure is reduced, so the efficiency of the SCO2 cycle can be theoretically optimized near the critical point.

[0100] Slight changes in the cycle could easily cause the system to fall into a steam dome or high-density state region. Since small changes in ambient temperature affect the fluid state in the compressor, they can have a significant impact on the compressor's condition or the power generation cycle. For this reason, general designers recommend avoiding operation of the compressor near the critical point and instead using cycles with starting pressures or temperatures much higher than the critical point. However, operation at the critical point can dramatically improve cycle efficiency.

[0101] FIG. 8 is a flowchart showing the Brayton cycle operation process according to an embodiment of the present invention. Referring to FIG. 8, factors capable of determining the operating conditions of the compressor are checked (step S810).

[0102] Based on the temperature and pressure conditions, the pump mode and compressor mode are appropriately selected and used according to the operating conditions on the TS diagram (step S820). In addition, stable operating conditions of the compressor are set on the thermodynamic diagram, and a Brayton cycle starting and operating device using a pilot pump is utilized (steps S830, 840).

[0103] Since the supercritical state possesses both gaseous and liquid properties, the compressor inlet state can be assumed to be either liquid or gas. However, when compression is performed, if liquid components enter the compressor, it adversely affects the compressor's performance.

[0104] Therefore, it is useful to operate the compressor in steady-state compressor mode, and to use the pilot pump mode when the inlet region of the compressor momentarily changes to liquid during startup or operation. When determining the operating mode (compressor or pump), the most important thing is to accurately determine the inlet state of the compressor through temperature and pressure on the T (temperature) - S (entropy) diagram.

[0105] By automatically determining the compressor mode and pump mode based on the compressor status, stable operation of the power generation cycle can be ensured and system costs reduced. Additionally, in compressor mode, factors such as speed, Mach number, and noise may need to be considered in addition to temperature and pressure.

[0106] In a carbon dioxide power generation cycle, optimal system efficiency can be easily achieved if the compressor can be operated stably at low temperatures and pressures. However, operation in this region is very difficult and challenging because the thermophysical changes of carbon dioxide near the critical point are very rapid. In particular, the fluid may enter a two-phase dome (gas-liquid), resulting in the coexistence of liquid and gas.

[0107] In order to avoid the two-phase region and reduce the influence of the liquid, it is necessary to operate the compressor at a location far from the critical point and to control the temperature of the fluid at the compressor inlet. In one embodiment of the present invention, to protect the compressor, when the compressor moves out of the stable operating region, it is replaced by a pump to operate the cycle during initial startup or in a transient state.

[0108] Assuming that the enthalpy is constant when passing through the throttling section inside the compressor on the TS diagram, the inlet state of the compressor moves downward as shown in Fig. 7, and the compressor operation must be carried out in a safe area by keeping it as far as possible from the outside of the steam dome or the liquid region.

[0109] Additionally, the steps of the method or algorithm described in connection with the embodiments disclosed herein may be implemented in the form of program instructions that can be executed through various computer means, such as a microprocessor, a processor, a CPU (Central Processing Unit), etc., and recorded on a computer-readable medium. The computer-readable medium may include program (instruction) code, data files, data structures, etc., either alone or in combination.

[0110] The program (instruction) code recorded on the above medium may be those specifically designed and configured for the present invention, or those known and available to those skilled in the art of computer software. Examples of computer-readable recording media may include magnetic media such as hard disks, floppy disks, and magnetic tapes; optical recording media such as CD-ROMs, DVDs, and Blu-rays; and semiconductor memory devices specifically configured to store and execute program (instruction) code, such as ROMs, RAMs, and flash memory.

[0111] Here, examples of program (instruction) code include not only machine code, such as that generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter, etc. The aforementioned hardware device may be configured to operate as one or more software modules to perform the operation of the present invention, and vice versa. Explanation of the symbols

[0112] 100,200: Brayton cycle driving system 101,201: Controller 102,202: Fluid supply block 110,210: Brayton Cycle Block 111,211: 1st valve block 112,212: 1st heater 113,213: Bypass valve 114,214: Compressor 115,215: Double heat 116,216: 2nd heater 117,217: Turbine 118,218: Cooler 120,220: Chiller 130,230: Pilot pump 141,241: Second valve block 150,250: Storage tank 160,260: Transfer pump 170,270: Carburetor 180,280: Buffer tank 206: Option line 214-1: Shut-off valve

Claims

Claim 1 The apparatus comprises: a controller (101); a Brayton cycle block (110) that performs power generation according to the control of the controller (101); and a fluid supply block (102) that supplies a working fluid to the Brayton cycle block (110); wherein the Brayton cycle block (110) comprises: a first heater (112) that heats the working fluid first; a compressor (114) that compresses the first heated working fluid at high pressure to produce a compressed working fluid; a recuperator (115) that performs heat exchange with the compressed working fluid; a second heater (116) that heats the heat-exchanged working fluid secondarily; and a turbine (117) that performs power generation through the expansion of the second heated working fluid. and a cooler (118) for cooling the expanded working fluid; wherein a first valve block (111) is disposed with one end connected between the rear end of the cooler (118) and the front end of the first heater (112) and controls the flow of the cooled working fluid, and a pilot pump (130) connected to the other end of the first valve block (111) for pumping the cooled working fluid is included, wherein the first valve block (111) comprises: a first-1 valve (111-1) with one end connected to the rear end of the cooler (118); and a first-2 valve (111-2) with one end connected to the rear end of the first-1 valve (111-1) and the other end connected to the front end of the first heater (112); and a first-third valve (111-3) having one end connected to the middle of the first-first valve (111-1) and the first-second valve (111-2) and the other end connected to the front end of the pilot pump (130);A Brayton cycle operating system having a heater, comprising, wherein the first heater (112) prevents the working fluid from being exposed into the steam dome interior region, a second valve block (141) is disposed between the pilot pump (130), the fluid supply block (102), and the first valve block (111), and a chiller (120) is disposed upstream of the pilot pump (130) to protect the pilot pump (130).

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