High-pressure-difference small-flow multi-stage feed water pump system suitable for chemical looping and control method

Abstract

The application provides a high-pressure-difference small-flow multi-stage feed water pump system and a control method suitable for chemical looping, the system comprising an inlet buffer pretreatment unit, a CLC feed water adaptive multi-stage centrifugal pump unit, an outlet pressure stabilizing water supply unit connected in sequence, and a minimum flow dynamic adjustment protection unit and a full working condition collaborative control unit electrically connected with each unit of the system; the control method comprises four core steps of system operation preparation, full working condition matching operation, minimum flow dynamic protection and pressure stabilizing water supply control. The application can realize stable water supply of the chemical looping combustion system under 30%THA~VWO full working condition without flow fluctuation, surge and cavitation, solves the problems of poor wide working condition adaptability, low operation efficiency and insufficient protection capability of the existing general pump type, the efficiency of the pump group under rated working condition is more than 55%, the average efficiency under full working condition is increased by more than 8%, and the pump group can be directly adapted to the engineering landing demand of the chemical looping combustion demonstration project.

Description

Technical Field

[0001] This invention relates to chemical loop combustion technology and auxiliary equipment technology for thermal power generation, and in particular to a high-pressure differential, low-flow multistage feedwater pump system suitable for chemical loop combustion. Background Technology

[0002] Chemical looping combustion (CLC) is a novel near-zero carbon emission combustion technology. It utilizes an oxygen carrier to circulate oxygen between the fuel reactor and the air reactor, avoiding direct contact between fuel and air. This allows for the direct production of high-concentration carbon dioxide without the need for additional carbon capture devices, achieving low-cost carbon enrichment. It is one of the core technological pathways for the low-carbon transformation of the coal-fired power generation industry. Currently, demonstration projects for CLC technology have entered the engineering implementation phase. The feedwater system is a core auxiliary system ensuring stable reactor temperature and pressure. It must meet the requirements of high temperature, high pressure differential, low flow rate, and wide load fluctuations, placing extremely high demands on the pump set's operational stability, hydraulic efficiency, and adaptability to varying operating conditions.

[0003] Currently, most feedwater pumps used in thermal power generation adopt general-purpose MD / MC type multistage centrifugal pumps. Their technical solutions are mainly divided into three categories: The first category is high-pressure multistage centrifugal pumps with single-condition hydraulic design. The hydraulic profiles of the impeller and guide vanes are designed only according to the rated THA condition. They can only adapt to the rated flow and head conditions and cannot meet the needs of wide load fluctuations. The second category is a simple variable frequency speed control scheme. The pump speed is adjusted only according to the single parameter of outlet pressure. The influence of medium temperature, density, and viscosity on large fluctuations in the unit load is not considered. It cannot adapt to the changes in hydraulic characteristics under variable conditions. The third category is a conventional minimum flow return scheme. Only a return pipeline with a fixed opening is set. There is no dynamic adjustment and protection function. The protection effect under low load conditions is poor. Currently, existing technical solutions suffer from the following core defects: 1. General-purpose multistage centrifugal pumps have poor adaptability to the wide operating conditions of chemical loop combustion projects. Designed only for a single rated operating condition, the operating point deviates significantly from the high-efficiency zone under varying load conditions (30% THA~VWO). At low flow rates, flow fluctuations, surges, and cavitation are prone to occur, failing to meet the core requirement of continuous and stable water supply for chemical loop combustion systems. 2. Existing control schemes have simple logic and do not consider the impact of significant fluctuations in medium temperature, density, and viscosity in the chemical loop combustion system relative to the unit load. This leads to drift in the pump's hydraulic characteristics, resulting in a rated efficiency of only about 50%, low average efficiency across all operating conditions, and high energy consumption. 3. Existing minimum flow protection schemes lack dynamic adjustment capabilities and cannot adjust the return flow based on real-time operating conditions. They exhibit poor anti-sloshing and anti-cavitation effects under low load conditions and lack coordinated linkage with pump speed and outlet pressure control, resulting in low system integration. 4. Existing MD-type multistage centrifugal pumps lack mature engineering performance in high-temperature, high-pressure, and low-flow conditions around 180℃, and their structural reliability is insufficient; the hydraulic characteristics of MC-type high-temperature pumps cannot adapt to the requirements of low flow and high pressure difference, resulting in high modification costs and making them unsuitable for the engineering implementation requirements of chemical loop combustion projects.

[0004] To date, no patents or mature technical solutions have been found for a water pump system that integrates full-condition hydraulic optimization, dynamic minimum flow protection, and full-condition collaborative control, specifically addressing the wide operating conditions, high pressure differential, and low flow rate requirements of chemical looping combustion projects. Summary of the Invention

[0005] The purpose of this invention is to provide a high-pressure differential, low-flow multistage feedwater pump system and control method suitable for chemical chain systems. By integrating a multistage centrifugal pump unit with full-condition three-dimensional flow optimization, a dynamic minimum flow protection unit, and full-condition collaborative control logic, it solves the core defects of existing general-purpose pumps, such as poor adaptability to wide operating conditions, low operating efficiency, and easy instability under low flow conditions. It achieves efficient, stable, and safe continuous water supply under all operating conditions from 30% THA to VWO, providing reliable core auxiliary machine support for the engineering implementation of near-zero carbon emission combustion technology in chemical chains.

[0006] According to one objective of the present invention, the present invention provides a high pressure differential low flow multistage feedwater pump system suitable for chemical chains, including an inlet buffer pretreatment unit, a CLC feedwater adaptable multistage centrifugal pump unit, a minimum flow dynamic adjustment protection unit, an outlet pressure stabilizing water supply unit, and a full-condition collaborative control unit. The inlet of the imported buffer pretreatment unit is connected to the deaerator outlet header of the chemical loop combustion system, and the outlet is connected to the inlet of the CLC feed water adapter multi-stage centrifugal pump unit. It is used to remove impurities and stabilize the pressure of the incoming water, and to collect the medium parameters of the incoming water in real time. The outlet of the CLC water supply adapter multi-stage centrifugal pump unit is connected to the inlet of the outlet pressure stabilizing water supply unit, which is used to gradually increase the pressure of the incoming water to meet the flow and head requirements of the chemical loop combustion system under all operating conditions from 30% THA to VWO. The inlet of the minimum flow dynamic adjustment protection unit is connected to the outlet main pipe of the CLC water supply adapter multi-stage centrifugal pump unit, and the outlet is connected to the return port of the inlet buffer pretreatment unit. It is used to dynamically adjust the return opening according to the real-time operating flow of the pump group to ensure the stability of the pump group operation. The outlet of the pressure-stabilizing water supply unit is connected to the water supply header of the chemical loop combustion system to eliminate water pressure fluctuations and stabilize the water supply pressure. The full-condition collaborative control unit is electrically connected to the inlet buffer pretreatment unit, the CLC water supply adapter multi-stage centrifugal pump unit, the minimum flow dynamic adjustment protection unit, and the outlet pressure stabilizing water supply unit, respectively. It is used to collect the operating parameters of the entire system and collaboratively control the pump speed, the opening of the reflux regulating valve, and the water supply pressure to match the water supply requirements of the chemical loop combustion system under all operating conditions.

[0007] Furthermore, the CLC water supply adapter multi-stage centrifugal pump unit is a 16-stage horizontal multi-stage centrifugal pump, including 16 impellers and guide vanes connected in series, a pump body, a drive motor, and a double-end-face high-temperature resistant mechanical seal; the impeller and the guide vane adopt a three-dimensional flow optimized profile for all working conditions, and the impeller is suitable for media temperatures ranging from 130 to 185°C; the double-end-face high-temperature resistant mechanical seal is suitable for high-temperature media ranging from 130 to 185°C.

[0008] Furthermore, the inlet buffer pretreatment unit includes an inlet filter and an inlet buffer tank connected in series along the water flow direction. The inlet buffer tank is equipped with an inlet pressure transmitter and an inlet temperature transmitter. The inlet filter is used to filter solid impurities in the medium, the inlet buffer tank is used to eliminate pressure fluctuations in the deaerator outlet water, and the inlet pressure transmitter and the inlet temperature transmitter are used to collect the inlet pressure and temperature parameters of the medium in real time and transmit them to the full-condition collaborative control unit.

[0009] Furthermore, the minimum flow dynamic adjustment protection unit includes a return pipeline, and a minimum flow regulating valve and a return check valve connected in series along the return direction on the return pipeline. A flow transmitter and a differential pressure transmitter are also installed on the return pipeline. The minimum flow regulating valve is an electric intelligent regulating valve with an adjustment accuracy of ≤±1%. The return check valve is used to prevent the inlet medium from flowing back through the return pipeline.

[0010] Furthermore, the outlet pressure stabilizing water supply unit includes an outlet pressure stabilizing tank, an outlet check valve, and an outlet electric gate valve connected in series along the water flow direction. The outlet pressure stabilizing tank is equipped with an outlet pressure transmitter. The outlet pressure stabilizing tank is used to eliminate pressure fluctuations in the pump set outlet water. The outlet check valve is used to prevent backflow of the medium in the chemical loop combustion system. The outlet electric gate valve is used for pipeline on / off control during pump set start-up, shutdown, and maintenance. The outlet pressure transmitter is used to collect outlet water pressure parameters in real time and transmit them to the full-condition collaborative control unit.

[0011] Furthermore, the all-condition collaborative control unit includes a PLC controller, a frequency converter, a signal acquisition module, and an actuator drive module; the input terminal of the signal acquisition module is electrically connected to all pressure, temperature, flow, differential pressure, and speed sensors in the system, and the output terminal is electrically connected to the input terminal of the PLC controller; the output terminal of the PLC controller is electrically connected to the frequency converter, the minimum flow regulating valve actuator, and the outlet electric gate valve actuator; the output terminal of the frequency converter is electrically connected to the drive motor of the CLC water supply adapter multi-stage centrifugal pump unit; the all-condition collaborative control unit can adjust the pump group operating speed range to 3064~3129 rpm, matching the water supply requirements of seven typical operating conditions of the chemical loop combustion system: VWO, THA, TRL, 75%THA, 50%THA, 40%THA, and 30%THA.

[0012] According to another objective of the present invention, the present invention provides a control method for a high-pressure differential, low-flow multistage feedwater pump system suitable for chemical loops, comprising the following steps: S1. System commissioning preparation: The deaerator effluent of the chemical loop combustion system enters the inlet buffer pretreatment unit. After impurity removal and pressure stabilization, it enters the CLC feedwater adapter multi-stage centrifugal pump unit. The full-condition collaborative control unit is powered on, collects real-time data from all sensors in the system, and completes the system self-test. S2. Full-condition matching operation: The full-condition collaborative control unit automatically calculates the optimal operating speed based on the current operating conditions of the chemical loop combustion unit through the built-in multi-condition matching algorithm, and adjusts the speed of the drive motor through the frequency converter to ensure that the outlet head and flow rate of the pump unit are precisely matched with the current operating conditions. At the same time, the hydraulic calculation model is corrected based on the real-time collected inlet medium temperature, density and viscosity parameters to avoid hydraulic characteristic drift caused by fluctuations in medium properties. S3. Minimum flow dynamic protection: Real-time monitoring of the pump unit's operating flow rate. When the operating flow rate is lower than the preset minimum stable flow rate threshold, the full-condition collaborative control unit automatically adjusts the opening of the minimum flow rate regulating valve and opens the return pipeline to ensure that the flow rate inside the pump is always higher than the minimum stable flow rate threshold, thus avoiding sloshing, surge, and cavitation under low flow conditions. S4. Pressure Stabilization and Water Supply Control: The pressure fluctuation of the pump set outlet water is eliminated by the outlet pressure stabilizing tank, the outlet water supply pressure is monitored in real time, the pump set speed is dynamically adjusted to ensure the stability of the water supply pressure of the chemical loop combustion system, and achieve stable water supply under all operating conditions from 30% THA to VWO.

[0013] Further, in step S2, the full-condition matching operation covers seven typical operating conditions of the chemical loop combustion unit, namely VWO, THA, TRL, 75%THA, 50%THA, 40%THA, and 30%THA, corresponding to the pump unit's operating speed range of 3064~3129 rpm; in step S2, the full-condition collaborative control unit incorporates a medium temperature-density-viscosity correction algorithm, based on a medium temperature of 136.8~181.9℃ and a density of 0.885~0.929 kg / dm³. 3 The viscosity fluctuates within the range of 0.17~0.22cSt, and the optimal operating speed is automatically corrected to ensure that the pump set operating efficiency is ≥55% under all operating conditions.

[0014] Furthermore, in step S3, the minimum stable flow threshold is 85% of the rated flow of the pump set. When the operating flow of the pump set is higher than the minimum stable flow threshold, the minimum flow regulating valve remains closed.

[0015] Furthermore, in step S4, the water supply pressure fluctuation of the chemical loop combustion system is controlled to be ≤±0.1MPa by dynamically adjusting the pump speed and the opening of the minimum flow regulating valve.

[0016] The technical solution of this invention constructs a dedicated feedwater pump system for chemical chain combustion, integrating pretreatment, pressurization, dynamic protection, pressure stabilization, and full-condition coordinated control. Addressing the core water supply needs of chemical chain combustion systems—high pressure differential, low flow rate, and wide load fluctuations—it achieves coordinated operation across the entire chain. Through the matching and connection of each unit, it stabilizes the influent conditions at the source, accurately adapts to variable load pressurization demands, dynamically prevents instability risks at low flow rates, and continuously stabilizes the water supply pressure. This completely solves the core pain points of existing general-purpose pumps, such as poor adaptability to wide operating conditions, easy operational instability, and disconnected control links. It can guarantee continuous and stable water supply under all operating conditions from 30% THA to VWO, providing reliable core auxiliary equipment support for the engineering implementation of chemical chain low-carbon technology. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a system process flow diagram according to an embodiment of the present invention; Figure 2 This is a logic block diagram of the control system of the all-condition collaborative control unit in an embodiment of the present invention; Figure 3 This is a schematic diagram of the impeller guide vane structure of the CLC water supply adapter multi-stage centrifugal pump unit according to an embodiment of the present invention.

[0019] In the diagram: 1. Inlet buffer pretreatment unit; 101. Inlet filter; 102. Inlet buffer tank; 103. Inlet pressure transmitter; 104. Inlet temperature transmitter; 2. CLC water supply adapter multi-stage centrifugal pump unit; 201. Impeller; 202. Guide vane; 3. Minimum flow rate dynamic adjustment and protection unit; 301. Return pipeline; 302. Minimum flow rate regulating valve; 303. Return check valve; 304. Flow transmitter; 305. Differential pressure transmitter; 4. Outlet pressure stabilizing water supply unit; 401. Outlet pressure stabilizing tank; 402. Outlet check valve; 403. Outlet electric gate valve; 404. Outlet pressure transmitter; 5. Full-condition collaborative control unit; 501. PLC controller; 502. Frequency converter; 503. Signal acquisition module; 504. Actuator drive module; 505. Touch screen; 6. Deaerator outlet main pipe; 7. Chemical loop feed main pipe; 8. Drive motor. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0022] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] Example 1 This embodiment describes a high-pressure differential, low-flow-rate multistage feedwater pump system suitable for chemical chain systems, the structure of which is as follows: Figure 1 As shown, it includes an inlet buffer pretreatment unit 1, a CLC water supply adapter multi-stage centrifugal pump unit 2, a minimum flow dynamic adjustment protection unit 3, an outlet pressure stabilizing water supply unit 4, and a full-condition collaborative control unit 5.

[0024] The inlet of the inlet buffer pretreatment unit 1 is connected to the deaerator outlet header 6 of the chemical loop combustion system, and the outlet is connected to the inlet of the CLC feedwater adapter multi-stage centrifugal pump unit 2. The inlet buffer pretreatment unit 1 includes an inlet filter 101 and an inlet buffer tank 102 connected in series along the water flow direction. An inlet pressure transmitter 103 and an inlet temperature transmitter 104 are installed on the inlet buffer tank 102. The inlet filter 101 uses a stainless steel filter screen with a precision of 50μm, which can effectively filter solid impurities in the medium and protect the subsequent impeller and mechanical seal from wear. The inlet buffer tank 102 has a design pressure of 2.0 MPa, a design temperature of 220℃, and an effective volume of 0.5 m³. 3It can effectively eliminate pressure fluctuations in the deaerator outlet water, stabilize the pump inlet pressure, and prevent cavitation caused by a sudden drop in inlet pressure; the inlet pressure transmitter 103 and the inlet temperature transmitter 104 collect the inlet pressure and temperature parameters of the medium in real time and transmit them to the full-condition collaborative control unit 5.

[0025] The outlet of the CLC water supply adapter multi-stage centrifugal pump unit 2 is connected to the inlet of the outlet pressure stabilizing water supply unit 4, and its structure is as follows: Figure 3 The image shows a 16-stage horizontal multistage centrifugal pump, comprising 16 impellers 201 and guide vanes 202 connected in series, a pump body, a drive motor 8, and a double-end-face high-temperature resistant mechanical seal. The impellers 201 and guide vanes 202 employ a three-dimensional flow optimization profile for all operating conditions. The flow field was optimized within the 30% THA~VWO range using CFD flow field simulation, effectively reducing eddies and hydraulic losses within the flow channel. The impeller 201 has a rated diameter of 225mm, a rated speed of 3129rpm, and a rated flow rate of 28.36m³ / h. 3 The rated head is 1275m, and the applicable medium temperature range is 130~185℃; the double-end high-temperature resistant mechanical seal adopts a cartridge structure with built-in cooling and flushing pipelines, and is suitable for high-temperature media of 130~185℃, which can meet the long-term continuous transportation requirements of high-temperature media in chemical loop combustion systems; the drive motor 8 adopts a variable frequency special high-voltage motor with a rated power of 160kW and an applicable speed adjustment range of 3064~3129rpm.

[0026] The inlet of the minimum flow dynamic adjustment protection unit 3 is connected to the outlet header of the CLC water supply adapter multi-stage centrifugal pump unit 2, and the outlet is connected to the return port of the inlet buffer tank 102. The minimum flow dynamic adjustment protection unit 3 includes a return pipeline 301, and a minimum flow regulating valve 302 and a return check valve 303 connected in series along the return direction on the return pipeline 301. A flow transmitter 304 and a differential pressure transmitter 305 are also installed on the return pipeline 301. Among them, the minimum flow regulating valve 302 is an electric intelligent regulating valve with a nominal pressure of 16MPa and a regulating accuracy of ≤±1%, which can realize precise regulation of the backflow flow; the backflow check valve 303 adopts a swing type high-pressure check valve with a nominal pressure of 16MPa, which can effectively prevent the inlet medium from backflowing through the backflow pipeline 301 and ensure the safe operation of the system; the flow transmitter 304 and the differential pressure transmitter 305 collect the operating flow and head data of the pump group in real time and transmit them to the full-condition collaborative control unit 5.

[0027] The outlet of the outlet pressure-stabilizing water supply unit 4 is connected to the chemical loop combustion system's chemical loop water supply header 7. It includes an outlet pressure-stabilizing tank 401, an outlet check valve 402, and an outlet electric gate valve 403, connected in series along the water flow direction. An outlet pressure transmitter 404 is installed on the outlet pressure-stabilizing tank 401. The outlet pressure-stabilizing tank 401 has a design pressure of 16 MPa, a design temperature of 220℃, and an effective volume of 0.3 m³, effectively eliminating pressure fluctuations in the pump unit's outlet water and stabilizing the water supply pressure of the chemical loop combustion system. The outlet check valve 402 is a swing-type high-pressure check valve with a nominal pressure of 16 MPa, effectively preventing backflow of the chemical loop combustion system's medium and damage to the pump unit. The outlet electric gate valve 403 is a flange-connected high-pressure electric gate valve with a nominal pressure of 16 MPa, used for pipeline on / off control during pump start-up, shutdown, and maintenance. The outlet pressure transmitter 404 collects the outlet water pressure parameters in real time and transmits them to the full-condition collaborative control unit 5.

[0028] The control system logic block diagram of the full-condition collaborative control unit 5 is as follows: Figure 2 As shown, the system includes a PLC controller 501, a frequency converter 502, a signal acquisition module 503, an actuator drive module 504, and a touch screen 505. The input terminals of the signal acquisition module 503 are electrically connected to the inlet pressure transmitter 103, the inlet temperature transmitter 104, the flow transmitter 304, the differential pressure transmitter 305, the outlet pressure transmitter 404, and the speed sensor of the drive motor 8, respectively. Its output terminal is electrically connected to the input terminal of the PLC controller 501. The output terminals of the PLC controller 501 are electrically connected to the frequency converter 502 and the actuator drive module 504, respectively. The output terminals of the actuator drive module 504 are electrically connected to the actuators of the minimum flow regulating valve 302 and the outlet electric gate valve 403, respectively. The output terminal of the frequency converter 502 is electrically connected to the drive motor 8. The touch screen 505 is communicatively connected to the PLC controller 501 and is used for system parameter setting, operating status monitoring, and fault alarm display.

[0029] The all-condition collaborative control unit 5 can adjust the pump unit's operating speed range from 3064 to 3129 rpm, matching the water supply requirements of seven typical operating conditions of chemical loop combustion systems: VWO, THA, TRL, 75% THA, 50% THA, 40% THA, and 30% THA. It has a built-in medium temperature-density-viscosity correction algorithm, which can correct the hydraulic calculation model based on real-time inlet medium parameters and automatically match the optimal operating speed. It can calculate the pump unit's operating efficiency and stability margin by monitoring the pump unit's inlet and outlet pressure, flow rate, and temperature online, ensuring that the pump unit is free from sloshing and cavitation under all operating conditions.

[0030] The system in this embodiment has an overall design pressure of 16MPa, a design temperature of 200℃, and a footprint of only 3870×1250×2280mm. It has a high degree of integration and can be directly adapted to the on-site installation and operation and maintenance needs of chemical looping combustion demonstration projects.

[0031] Example 2 This embodiment presents a full-condition control method for a high-pressure differential, low-flow-rate multi-stage feedwater pump applicable to chemical loop systems. Based on the feedwater pump system described in Embodiment 1, the method includes the following steps: S1. System commissioning preparation: Start the chemical loop combustion system. The deaerator effluent enters the inlet buffer pretreatment unit 1. After impurity removal by the inlet filter 101 and pressure stabilization treatment by the inlet buffer tank 102, it enters the CLC feedwater adapter multi-stage centrifugal pump unit 2. The full-condition collaborative control unit 5 is powered on. The real-time data of each sensor in the whole system is collected through the signal acquisition module 503. The system self-test is completed. After confirming that there are no faults in the system and the valve status is normal, it enters the standby operation state.

[0032] S2. Full-condition matching operation: The PLC controller 501 receives the current operating condition command sent by the DCS system of the chemical loop combustion unit, and automatically calculates the optimal operating speed under the current condition through the built-in multi-condition matching algorithm. The speed of the drive motor 8 is adjusted by the frequency converter 502 to ensure that the outlet head and flow rate of the pump unit are accurately matched with the current operating condition requirements. At the same time, based on the real-time medium temperature collected by the inlet temperature transmitter 104 and combined with the built-in medium temperature-density-viscosity correspondence table, the density and viscosity parameters of the current medium are obtained. The hydraulic calculation model is corrected by the medium temperature-density-viscosity correction algorithm, and the optimal operating speed is automatically adjusted to avoid hydraulic characteristic drift caused by fluctuations in medium properties, ensuring that the pump unit is always in the high-efficiency operating range.

[0033] In this step, the full-condition matching operation covers seven typical operating conditions of the chemical loop combustion unit: VWO, THA, TRL, 75%THA, 50%THA, 40%THA, and 30%THA, corresponding to pump unit operating speeds ranging from 3064 to 3129 rpm. The medium temperature-density-viscosity correction algorithm can adapt to medium temperatures of 136.8~181.9℃ and densities of 0.885~0.929 kg / dm³. 3 The viscosity fluctuates within a range of 0.17~0.22 cSt, ensuring that the pump set operating efficiency is ≥55% under all operating conditions.

[0034] S3. Minimum Flow Dynamic Protection: The flow rate of the pump unit is monitored in real time by the flow transmitter 304. The PLC controller 501 compares the real-time operating flow rate with the preset minimum stable flow rate threshold. In this embodiment, the minimum stable flow rate threshold is 85% of the rated flow rate of the pump unit, i.e., 24.11 m³ / h. When the real-time operating flow rate is lower than the minimum stable flow rate threshold, the PLC controller 501 automatically adjusts the opening of the minimum flow rate regulating valve 302 through the actuator drive module 504, opens the return pipeline 301, and returns part of the effluent to the inlet buffer tank 102 to ensure that the flow rate in the pump is always higher than the minimum stable flow rate threshold, avoiding sloshing, surge and cavitation under low flow conditions. When the real-time operating flow rate is higher than the minimum stable flow rate threshold, the PLC controller 501 controls the minimum flow rate regulating valve 302 to remain closed to reduce the return energy consumption.

[0035] S4. Pressure Stabilization and Water Supply Control: The pressure fluctuation of the pump set outlet water is eliminated by the outlet pressure stabilizing tank 401, and the outlet water supply pressure is monitored in real time by the outlet pressure transmitter 404. The PLC controller 501 compares the real-time water supply pressure with the set pressure value corresponding to the current working condition, calculates the pressure deviation, and dynamically adjusts the pump set speed and the opening of the minimum flow regulating valve 302 through the PID adjustment algorithm to control the water supply pressure fluctuation of the chemical loop combustion system to ≤±0.1MPa, so as to achieve stable water supply under all working conditions from 30%THA to VWO.

[0036] Example 3 This embodiment is a specific application of the control method described in Embodiment 2 under the rated operating conditions of a chemical looping combustion unit (THA). The specific steps are as follows: 1. Start the chemical loop combustion system. The deaerator outlet water parameters are: pressure 1.22 MPa, temperature 181.9℃, density 0.885 kg / dm³. 3 The viscosity is 0.17 cSt. The effluent enters the inlet buffer pretreatment unit 1, and after impurity removal by the inlet filter 101 and pressure stabilization by the inlet buffer tank 102, it enters the 16-stage MD 50-220 multi-stage centrifugal pump unit 2.

[0037] 2. After the full-condition collaborative control unit 5 completes its power-on self-test, it receives the THA rated operating condition command sent by the chemical loop combustion unit DCS system. The PLC controller 501 calculates the optimal operating speed as 3068 rpm through the multi-condition matching algorithm, and adjusts the speed of the drive motor 8 to 3068 rpm through the frequency converter 502.

[0038] 3. After the pump set is running stably, the output flow rate is 28.10 m³ / h. 3 The pump has a flow rate of 1222.4 m and an outlet pressure that is stable at 13 MPa.a. The water is delivered to the feedwater header of the chemical loop combustion system via the outlet pressure stabilizing tank 401, the outlet check valve 402, and the outlet electric gate valve 403.

[0039] 4. Under this operating condition, the pump set operating flow rate is higher than the minimum stable flow rate threshold, and the minimum flow regulating valve 302 remains closed; the PLC controller 501 corrects the hydraulic model in real time through the medium correction algorithm, the pump set operating efficiency reaches 55.2%, the water supply pressure fluctuation is ≤±0.05MPa, and the operation is stable.

[0040] Example 4 This embodiment is a specific application of the control method described in Embodiment 2 under low-load conditions of 30% THA in a chemical looping combustion unit. The specific steps are as follows: 1. When the load of the chemical loop combustion unit drops to 30% THA, the deaerator outlet water parameters are: pressure 0.51 MPa.a, temperature 136.8℃, density 0.929 kg / dm³, viscosity 0.22 cSt. This outlet water enters the inlet buffer pretreatment unit 1, and after impurity removal and pressure stabilization, it enters the multi-stage centrifugal pump unit 2.

[0041] 2. The PLC controller 501 receives the 30% THA condition command and, through its built-in medium correction algorithm, corrects the hydraulic calculation model based on the current medium parameters, automatically adjusting the speed of the drive motor 8 to 3074 rpm.

[0042] 3. Real-time monitoring showed that the pump unit's operating flow rate dropped to 26.90 m³ / h, which is lower than the minimum stable flow threshold. The PLC controller 501 automatically adjusted the opening of the minimum flow regulating valve 302 to 15% and opened the return pipeline 301 to return part of the effluent to the inlet buffer tank 102, ensuring that the flow rate inside the pump is stable above 24.11 m³ / h.

[0043] 4. After the pump set is running stably, the outlet pressure is stable at 12MPa.a, the water supply flow is stable, and there are no sloshing, surging, or cavitation phenomena. The water supply pressure fluctuation is ≤±0.08MPa, and the pump set operating efficiency is maintained above 55%, which fully meets the water supply needs under low load conditions.

[0044] In the above embodiments, compared with the rated efficiency of 50.1% of existing general-purpose pumps, the rated operating efficiency of the system of the present invention reaches 55.2%, the average efficiency under all operating conditions is increased by 9.2%, and the operating energy consumption is reduced by 32%. Within the full operating range of 30% THA to VWO, the pump set has no sloshing, no surge, and no cavitation, and the water supply pressure fluctuation is ≤ ±0.08MPa, which fully meets the water supply requirements of the chemical looping combustion project under all operating conditions.

[0045] Compared with the prior art, the present invention has the following advantages: 1. Significantly improved stability under all operating conditions. This invention, through the optimization of the impeller and guide vane hydraulic profiles under all operating conditions using a three-dimensional flow system, combined with a dynamic minimum flow protection unit, achieves pump unit operation without sloshing, surge, or cavitation within the entire operating range of 30% THA to VWO. It can fully meet the core requirements for continuous and stable operation of chemical loop combustion systems, and completely solves the pain points of poor adaptability of general-purpose pumps under wide operating conditions and easy instability under low flow conditions.

[0046] 2. Significantly improved operating efficiency and energy saving. This invention solves the problem of hydraulic characteristic drift caused by large fluctuations in the temperature, density, and viscosity of the medium in a chemical loop combustion system through a comprehensive control logic with a built-in medium property correction algorithm. The rated operating efficiency of the pump set is increased from 50.1% in the prior art to over 55%, the average efficiency under all operating conditions is increased by 8% to 10%, and the operating energy consumption is reduced by more than 30%, resulting in significant energy saving.

[0047] 3. High system integration and strong engineering practicality. This invention integrates the design of pressurization, buffering, stabilization, protection, and control units. The system occupies only 3870×1250×2280mm, which can perfectly adapt to the on-site installation conditions of chemical loop combustion demonstration projects, making installation and maintenance convenient. The pump body structure optimized for high temperature of 181.9℃, ultra-high head of 1275m, and low flow conditions solves the pain point of existing pump types lacking mature application performance in high-temperature conditions. It can be directly implemented in projects without additional modifications, significantly reducing project costs.

[0048] 4. Synergistic improvement in energy and carbon utilization efficiency. By ensuring a continuous and stable water supply to the chemical loop combustion system, this invention can effectively avoid unplanned system downtime caused by feedwater pump failure, while significantly reducing the energy consumption of auxiliary equipment. This indirectly improves the overall energy utilization efficiency and carbon emission reduction benefits of the chemical loop combustion system, contributing to the low-carbon transformation of the coal-fired power generation industry.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-pressure differential, low-flow-rate multistage feedwater pump system suitable for chemical loops, characterized in that, It includes an inlet buffer pretreatment unit, a CLC-adapted multi-stage centrifugal pump unit, a minimum flow dynamic adjustment and protection unit, an outlet pressure stabilizing water supply unit, and a full-condition collaborative control unit; The inlet of the imported buffer pretreatment unit is connected to the deaerator outlet header of the chemical loop combustion system, and the outlet is connected to the inlet of the CLC feed water adapter multi-stage centrifugal pump unit. It is used to remove impurities and stabilize the pressure of the incoming water, and to collect the medium parameters of the incoming water in real time. The outlet of the CLC water supply adapter multi-stage centrifugal pump unit is connected to the inlet of the outlet pressure stabilizing water supply unit, which is used to gradually increase the pressure of the incoming water to meet the flow and head requirements of the chemical loop combustion system under all operating conditions from 30% THA to VWO. The inlet of the minimum flow dynamic adjustment protection unit is connected to the outlet main pipe of the CLC water supply adapter multi-stage centrifugal pump unit, and the outlet is connected to the return port of the inlet buffer pretreatment unit. It is used to dynamically adjust the return opening according to the real-time operating flow of the pump group to ensure the stability of the pump group operation. The outlet of the pressure-stabilizing water supply unit is connected to the water supply header of the chemical loop combustion system to eliminate water pressure fluctuations and stabilize the water supply pressure. The full-condition collaborative control unit is electrically connected to the inlet buffer pretreatment unit, the CLC water supply adapter multi-stage centrifugal pump unit, the minimum flow dynamic adjustment protection unit, and the outlet pressure stabilizing water supply unit, respectively. It is used to collect the operating parameters of the entire system and collaboratively control the pump speed, the opening of the reflux regulating valve, and the water supply pressure to match the water supply requirements of the chemical loop combustion system under all operating conditions.

2. The high-pressure differential, low-flow-rate multistage feedwater pump system suitable for chemical loops according to claim 1, characterized in that, The CLC water supply adapter multistage centrifugal pump unit is a 16-stage horizontal multistage centrifugal pump, including 16 impellers and guide vanes connected in series, pump body, drive motor, and double-end-face high-temperature resistant mechanical seal; the impeller and guide vane adopt a three-dimensional flow optimized profile for all working conditions, and the impeller is suitable for media temperatures ranging from 130 to 185℃; the double-end-face high-temperature resistant mechanical seal is suitable for high-temperature media ranging from 130 to 185℃.

3. The high-pressure differential, low-flow-rate multistage feedwater pump system suitable for chemical loops according to claim 1, characterized in that, The inlet buffer pretreatment unit includes an inlet filter and an inlet buffer tank connected in series along the water flow direction. The inlet buffer tank is equipped with an inlet pressure transmitter and an inlet temperature transmitter. The inlet filter is used to filter solid impurities in the medium, and the inlet buffer tank is used to eliminate pressure fluctuations in the deaerator outlet water. The inlet pressure transmitter and the inlet temperature transmitter are used to collect the inlet pressure and temperature parameters of the medium in real time and transmit them to the full-condition collaborative control unit.

4. The high-pressure differential, low-flow-rate multistage feedwater pump system suitable for chemical loops according to claim 1, characterized in that, The minimum flow dynamic adjustment protection unit includes a return pipeline, and a minimum flow regulating valve and a return check valve connected in series along the return direction on the return pipeline. A flow transmitter and a differential pressure transmitter are also installed on the return pipeline. The minimum flow regulating valve is an electric intelligent regulating valve with an adjustment accuracy of ≤±1%. The return check valve is used to prevent the inlet medium from flowing back through the return pipeline.

5. The high-pressure differential, low-flow multistage feedwater pump system suitable for chemical loops according to claim 1, characterized in that, The outlet pressure stabilizing water supply unit includes an outlet pressure stabilizing tank, an outlet check valve, and an outlet electric gate valve connected in series along the water flow direction. An outlet pressure transmitter is installed on the outlet pressure stabilizing tank. The outlet pressure stabilizing tank is used to eliminate pressure fluctuations in the pump set outlet water. The outlet check valve is used to prevent backflow of the medium in the chemical loop combustion system. The outlet electric gate valve is used for pipeline on / off control during pump set start-up, shutdown, and maintenance. The outlet pressure transmitter is used to collect outlet water pressure parameters in real time and transmit them to the full-condition collaborative control unit.

6. The high-pressure differential, low-flow-rate multistage feedwater pump system suitable for chemical loops according to claim 1, characterized in that, The full-condition collaborative control unit includes a PLC controller, a frequency converter, a signal acquisition module, and an actuator drive module. The input terminals of the signal acquisition module are electrically connected to all pressure, temperature, flow, differential pressure, and speed sensors in the system, and the output terminal is electrically connected to the input terminal of the PLC controller. The output terminals of the PLC controller are electrically connected to the frequency converter, the minimum flow regulating valve actuator, and the outlet electric gate valve actuator. The output terminal of the frequency converter is electrically connected to the drive motor of the CLC water supply adapter multi-stage centrifugal pump unit. The full-condition collaborative control unit can adjust the pump unit's operating speed range from 3064 to 3129 rpm, matching the water supply requirements of seven typical operating conditions of the chemical loop combustion system: VWO, THA, TRL, 75% THA, 50% THA, 40% THA, and 30% THA.

7. A control method for a high-pressure differential, low-flow-rate multistage feedwater pump system suitable for chemical loops, based on any one of claims 1-6, characterized in that, Includes the following steps: S1. System commissioning preparation: The deaerator effluent of the chemical loop combustion system enters the inlet buffer pretreatment unit. After impurity removal and pressure stabilization, it enters the CLC feedwater adapter multi-stage centrifugal pump unit. The full-condition collaborative control unit is powered on, collects real-time data from all sensors in the system, and completes the system self-test. S2. Full-condition matching operation: The full-condition collaborative control unit automatically calculates the optimal operating speed based on the current operating conditions of the chemical loop combustion unit through the built-in multi-condition matching algorithm, and adjusts the speed of the drive motor through the frequency converter to ensure that the outlet head and flow rate of the pump unit are precisely matched with the current operating conditions. At the same time, the hydraulic calculation model is corrected based on the real-time collected inlet medium temperature, density and viscosity parameters to avoid hydraulic characteristic drift caused by fluctuations in medium properties. S3. Minimum flow dynamic protection: Real-time monitoring of the pump unit's operating flow rate. When the operating flow rate is lower than the preset minimum stable flow rate threshold, the full-condition collaborative control unit automatically adjusts the opening of the minimum flow rate regulating valve and opens the return pipeline to ensure that the flow rate inside the pump is always higher than the minimum stable flow rate threshold, thus avoiding sloshing, surge, and cavitation under low flow conditions. S4. Pressure Stabilization and Water Supply Control: The pressure fluctuation of the pump set outlet water is eliminated by the outlet pressure stabilizing tank, the outlet water supply pressure is monitored in real time, the pump set speed is dynamically adjusted to ensure the stability of the water supply pressure of the chemical loop combustion system, and achieve stable water supply under all operating conditions from 30% THA to VWO.

8. The control method for a high-pressure differential, low-flow-rate multistage feedwater pump system suitable for chemical loops, as described in claim 7, is characterized in that... In step S2, the full-condition matching operation covers seven typical operating conditions of the chemical loop combustion unit, namely VWO, THA, TRL, 75%THA, 50%THA, 40%THA, and 30%THA, with corresponding pump unit operating speed ranges of 3064~3129 rpm; in step S2, the full-condition collaborative control unit incorporates a medium temperature-density-viscosity correction algorithm, based on a medium temperature of 136.8~181.9℃ and a density of 0.885~0.929 kg / dm³. 3 The viscosity fluctuates within the range of 0.17~0.22cSt, and the optimal operating speed is automatically corrected to ensure that the pump set operating efficiency is ≥55% under all operating conditions.

9. The control method for a high-pressure differential, low-flow-rate multistage feedwater pump system suitable for chemical loops, as described in claim 7, is characterized in that... In step S3, the minimum stable flow threshold is 85% of the pump set's rated flow. When the pump set's operating flow is higher than the minimum stable flow threshold, the minimum flow regulating valve remains closed.

10. The control method for a high-pressure differential, low-flow-rate multistage feedwater pump system suitable for chemical loops, as described in claim 7, is characterized in that... In step S4, the water supply pressure fluctuation of the chemical loop combustion system is controlled to be ≤ ±0.1MPa by dynamically adjusting the pump speed and the opening of the minimum flow regulating valve.

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