A waste heat utilization steam and electricity dual-drive feed water pump unit system and a control method thereof

Abstract

This invention discloses a waste heat recovery steam-electric dual-drive feedwater pump unit system and its control method, aiming to solve the problems of high energy consumption of existing pure electric drive, poor stability of pure steam turbine drive, and the lag and complex operation and maintenance of traditional dual-drive systems. The system is structured as a "dual-drive power unit + steam-water circulation subsystem + control and monitoring subsystem + auxiliary support subsystem". The dual-drive power unit uses a waste heat steam turbine and a dual-shaft three-phase asynchronous motor connected in series, connected to the feedwater pump via a flexible coupling, supporting individual / combined drive. The control method covers all operating conditions. During startup, intelligent pre-diagnosis, motor soft start, and dynamic thermal stress warm-up of the steam turbine achieve a shock-free transition. During normal operation, power is dynamically allocated according to steam conditions. During shutdown, gradient load reduction, steam turbine nitrogen protection, and waste heat recovery achieve damage-free equipment maintenance. This invention enables fully unattended operation, aligning with the trends of energy conservation, carbon reduction, and intelligent industrial development.

Description

Technical Field

[0001] This invention belongs to the technical field of industrial water supply pump units, specifically relating to a waste heat utilization steam-electric dual-drive water supply pump unit system and its control method. Background Technology

[0002] In industrial production, especially in industries such as chemical, power, and metallurgy, a large amount of waste heat steam is generated during the production process. If this waste heat steam is directly discharged or used only for low-grade heating, it will result in energy waste. At the same time, as a core piece of equipment in industrial systems that ensures key processes such as boiler water supply and deaerator water replenishment, the continuity, stability, and energy efficiency of the feedwater pump directly determine the reliability and economy of the overall production process. Therefore, high requirements are placed on the adaptability and fault tolerance of the drive system.

[0003] Currently, industrial feedwater pumps are mainly driven by two types of motors and turbines. Both types have significant technical drawbacks, making it difficult to simultaneously meet the dual requirements of "waste heat utilization" and "stable operation." Specific problems are as follows:

[0004] (1) Energy consumption and cost issues of pure electric motor drive.

[0005] Existing pure electric motor drive solutions mostly use high-voltage asynchronous motors, which continuously consume external grid power, resulting in high operating costs. This not only fails to utilize existing waste heat resources but also increases the grid load, contradicting the principle of energy cascade utilization. Furthermore, high-voltage motors are prone to grid surges during startup, requiring additional voltage-reducing starting devices, further increasing equipment investment and maintenance complexity.

[0006] (2) Defects in the stability and adaptability of pure steam turbine drive. Although pure steam turbine drive can utilize waste heat steam, it is highly dependent on the stability of steam parameters. When the amount of waste heat steam fluctuates or the parameters deviate, the steam turbine output will drop significantly, making it impossible to maintain the rated load of the feedwater pump, resulting in fluctuations in feedwater pump speed and a sudden drop in outlet pressure, which in turn affects subsequent processes. If the steam is completely interrupted, the system will shut down directly, causing production interruption losses. At the same time, in the pure steam turbine drive system, the steam turbine exhaust is mostly directly discharged into the air without being utilized in a cascade manner, resulting in energy loss. Moreover, the cold start of the steam turbine requires manual control of the warm-up process, which is time-consuming and has low start-up efficiency.

[0007] The current attempt to adopt a dual-drive scheme of "steam turbine + electric motor" also has many shortcomings, making it difficult to achieve efficient and stable operation. The problems include:

[0008] (1) Power switching and power balance issues. Existing dual-drive systems mostly rely on manual operation to switch power modes, which has a slow response and cannot match changes in steam volume in real time; moreover, the power distribution lacks precise control logic. When the turbine power exceeds the demand of the feedwater pump, the excess energy cannot be recovered, and when the turbine power is insufficient, the response speed of the motor to supplement the power is slow, which can easily lead to fluctuations in the feedwater pump load and affect the stability of water supply.

[0009] (2) Lack of integrated system control. Existing technology has not formed an integrated control system of "power unit - steam-water circulation - pipeline control - safety protection". Auxiliary links such as turbine warm-up, steam seal pressure regulation, and pipeline drainage require manual monitoring and cannot be linked with the main drive system. The coordinated control of the cooling system with bearing temperature and motor winding temperature is insufficient, increasing the risk of failure.

[0010] (3) Unmanned operation is difficult to achieve. Due to the large number of manual operation steps and the imperfect automatic adjustment logic, the existing dual-drive system requires 24-hour manual operation, resulting in high maintenance costs. In addition, it lacks a complete fault self-diagnosis and recording function, and manual investigation is required after a fault, which prolongs the downtime and does not conform to the development trend of intelligent industrial enterprises.

[0011] In summary, current industrial feedwater pump drive systems have problems in terms of waste heat steam utilization efficiency, drive mode adaptability, system coordinated control, and safety and reliability, requiring a new dual-drive technology solution. Summary of the Invention

[0012] In response to the problems of high energy consumption of pure electric motor drive, poor stability of pure steam turbine drive, lag in switching of traditional dual drive and complex operation and maintenance in existing technologies, this invention achieves efficient waste heat recovery, automatic switching of power mode and stable operation under all working conditions through the design of "dual drive power synergy, steam-water circulation cascade utilization, intelligent control linkage and full-condition safety fault tolerance".

[0013] The first objective of this invention is to provide a waste heat utilization steam-electric dual-drive feedwater pump unit system, which includes a dual-drive power unit, a steam-water circulation subsystem, and a control and monitoring subsystem.

[0014] The dual-drive power unit includes a waste heat drive turbine, a first flexible coupling, a double-shaft three-phase asynchronous motor, a second flexible coupling, and a feedwater pump arranged in series. The waste heat drive turbine and the double-shaft three-phase asynchronous motor can drive the feedwater pump individually or in combination.

[0015] The steam-water circulation subsystem includes a main steam pipeline, a steam seal steam pipeline, a back pressure steam pipeline, a drain pipeline, and a cooling water pipeline. The main steam pipeline connects the waste heat steam header to the inlet of the waste heat-driven steam turbine. The back pressure steam pipeline connects the exhaust outlet of the waste heat-driven steam turbine to the low-grade heat user. The drain pipeline collects drain water from multiple nodes and achieves qualified drain water recovery. The cooling water pipeline provides a cooling medium for the dual-drive power unit.

[0016] The control and monitoring subsystem includes a control cabinet, an automatic power adjustment module, and a monitoring sensor group. The control cabinet includes a PLC and a human-machine interface. The automatic power adjustment module dynamically allocates the power of the dual-drive power unit according to the steam conditions. The operating conditions include sufficient steam, insufficient steam, and critical combined operating conditions. The monitoring sensor group includes pressure sensors, temperature sensors, flow sensors, speed and vibration sensors, and special sensors. The special sensors include steam quality monitoring sensors and pipeline stress monitoring sensors.

[0017] Preferably, the motor insulation status monitoring module is installed inside the dual-shaft three-phase asynchronous motor, the outer casing of the dual-shaft three-phase asynchronous motor is provided with a spray cooling interface, and the power circuit of the dual-shaft three-phase asynchronous motor is provided with a battery energy storage auxiliary module, which can work in drive or power generation mode.

[0018] Preferably, the main steam pipeline is equipped with a steam header accumulator for steam buffering, a quick-closing main steam valve, an electric regulating valve, a steam quality monitoring sensor for monitoring humidity and particle size, a steam dryer for when humidity exceeds the standard, and a steam pretreatment system for when particle size exceeds the standard.

[0019] The back pressure steam pipeline is equipped with a heat user priority allocation module at the end, which prioritizes the preheating flow to the deaerator, and the remaining steam is introduced into the waste heat boiler feed water preheater.

[0020] The drainage pipeline is equipped with a condensate recovery judgment module, which connects the deaerator water tank and the drainage ditch; when the drainage is qualified, it is introduced into the deaerator water tank, and when it is unqualified, it is drained into the drainage ditch.

[0021] Preferably, it also includes an auxiliary support subsystem, which includes a radial sliding bearing, a lubrication system, a bellows compensator and leakage monitoring components, an industrial circulating water interface and an auxiliary cooling component; the lubrication system is equipped with an electric heating and cooling function module for heating and cooling the oil temperature; and a leakage sensor is attached to the outer wall of the bellows compensator.

[0022] The second objective of this invention is to provide a control method for a waste heat utilization steam-electric dual-drive feedwater pump unit system, which includes start-up phase control, normal operation phase control, fault-tolerant control under abnormal operating conditions, and shutdown phase control in the aforementioned waste heat utilization steam-electric dual-drive feedwater pump unit system.

[0023] The startup phase control includes intelligent pre-diagnosis and parameter adaptation verification before startup, soft start and load pre-adaptation control of motor, adaptive thermal stress regulation warm-up of steam turbine, and flexible connection between steam turbine and dual drive system.

[0024] The normal operation phase control includes multi-parameter fusion for condition prediction and dynamic monitoring, power adjustment for different operating conditions, and intelligent linkage optimization of auxiliary systems;

[0025] The abnormal operating condition fault tolerance control includes anomaly identification and accurate source tracing, multi-dimensional hierarchical fault tolerance, and intelligent fault recovery and restart;

[0026] The shutdown phase control includes pre-shutdown collaborative preparation, load gradient reduction and power unit shutdown, post-shutdown hot maintenance and media handling, intelligent operation and maintenance records, and next startup suggestions.

[0027] Preferably, the pre-start intelligent pre-diagnosis and parameter adaptation verification includes: generating a pre-diagnosis report by combining historical data and real-time sensor signals with a fault tree algorithm, predicting future steam parameters through a neural network and linking the steam header energy storage tank, and performing online dynamic calibration of the sensors;

[0028] The motor soft starter uses a thyristor voltage regulation soft starter, with the voltage gradually increasing to the rated voltage; the water pump operates in a stepped speed increase and load preload mode.

[0029] The turbine adaptive thermal stress control warm-up includes: gradually increasing the pressure after preheating the steam seal temperature; warming up in three stages based on the real-time thermal stress of the rotor and cylinder at low speed, medium speed, and rated parameters; and automatic drainage of the condensate pipe according to temperature and flow rate.

[0030] Preferably, the multi-parameter fusion-based operating condition prediction adopts a neural network model, taking the main steam flow rate, pressure, temperature and dual drive power as inputs, and outputting the future operating condition prediction results; the dynamic monitoring includes monitoring steam quality, motor insulation, pipeline stress, turning on the dryer when the steam humidity exceeds the standard, issuing an early warning when the motor insulation resistance exceeds the standard, and adjusting the corrugated compensator when the pipeline stress exceeds the standard.

[0031] Preferably, the anomaly identification and accurate source tracing includes: constructing an anomaly feature library and identifying anomalies through parameter matching; using vibration spectrum analysis and parameter correlation analysis for source tracing, and determining whether the coupling is misaligned or the bearing is worn based on the vibration spectrum analysis; the anomalies include mild anomalies with a single auxiliary parameter exceeding the standard, moderate anomalies with a slight exceedance of the main parameter, and severe anomalies with a serious exceedance of the main parameter;

[0032] The multi-dimensional hierarchical fault tolerance includes: adaptive parameter fine-tuning and trend suppression for mild anomalies; steam system depressurization, smooth switching of power modes, and three-stage cooling of auxiliary systems for moderate anomalies; and emergency shutdown, multi-path depressurization, and cross-system linkage for severe anomalies.

[0033] Preferably, the pre-shutdown collaborative preparation includes: sending a shutdown notice to the power grid, process, and utilities system in advance; if the turbine has power output before shutdown, switching the motor to short-time feedback power supply mode; and recording key parameters before shutdown to generate a shutdown status report.

[0034] The load gradient reduction and power unit shutdown include: the turbine reducing the load in steps and the motor gradually replenishing the energy; after closing the quick-closing main steam valve, the turbine speed is reduced to zero, the motor drives the feedwater pump to gradually reduce the speed to zero, and the feedwater pump inlet valve is closed simultaneously.

[0035] The post-shutdown hot maintenance includes: introducing high-purity nitrogen for oxidation prevention into the steam turbine and pipeline treatment, which includes purging residual steam from the steam pipeline, purging the drainage pipeline with compressed air, and injecting anti-rust and antifreeze fluid into the cooling water pipeline.

[0036] The present invention has the following beneficial effects:

[0037] (1) Energy utilization efficiency is significantly improved, achieving the dual benefits of "energy saving + recycling". The system accurately matches the waste heat steam parameters of the enterprise, and realizes high-grade waste heat to do work through the steam turbine-driven feedwater pump. At the same time, the steam turbine exhaust is directionally distributed to low-grade heat users such as workshop heating and deaerator preheating, thus improving the waste heat utilization rate. The dual-shaft motor can dynamically switch between "drive / power generation" mode, further reducing power loss. The condensate pipeline is judged by "temperature-water quality dual parameters". Qualified condensate is introduced into the deaerator water tank for recycling, which reduces water waste and recovers waste heat from the condensate.

[0038] (2) Optimization of drive stability and load adaptability ensures continuous process operation. A millisecond-level response for three operating conditions is achieved through an automatic power adjustment module, reducing mode switching. A steam header accumulator, motor winding insulation monitoring, and dual-stage cooling (pipeline cooling and casing spray) ensure stable motor operation. Electromagnetic active vibration dampers control shaft vibration, improving equipment operational stability. Dynamic adjustment of the warm-up rhythm shortens the warm-up time and avoids rotor thermal deformation caused by cold starts, extending turbine lifespan.

[0039] (3) Improved intelligence level significantly reduces operation and maintenance costs and reliance on manual labor. Through PLC control cabinet, human-machine interface and multi-dimensional sensors, fully automatic closed-loop control of "start-up pre-diagnosis-operation regulation-abnormal fault tolerance-shutdown maintenance" is realized, eliminating the need for manual operation and saving operation and maintenance costs. The construction of "abnormal feature library" and "vibration spectrum analysis + parameter correlation analysis" traceability mechanism improves the accuracy of fault identification.

[0040] In summary, this invention achieves "cascade utilization + electricity recovery" of waste heat resources, and ensures continuous and stable operation of the water pump through intelligent control and safety fault tolerance, while reducing operation and maintenance costs and equipment wear and tear, which is in line with the development trend of "energy saving and carbon reduction, and intelligent industry". Attached Figure Description

[0041] Figure 1 This is a schematic diagram of a waste heat utilization steam-electric dual-drive feedwater pump unit system according to an embodiment of the present invention;

[0042] Figure 2 This is an example diagram of the layout of a waste heat utilization steam-electric dual-drive feedwater pump unit system according to an embodiment of the present invention. Detailed Implementation

[0043] To further understand the present invention, embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0044] Example 1

[0045] This embodiment targets the waste heat steam resources (absolute pressure 0.65MPa, temperature 230-240℃, exhaust absolute pressure 0.15MPa, minimum steam flow rate ≥8t / h, rated operating condition 16t / h) and industrial water supply needs of industrial enterprises. With the goals of "efficient waste heat recovery, stable dual-drive operation, and adaptability to unattended operation," the system is designed according to a hierarchical architecture of "power supply - media circulation - pipeline control - intelligent regulation - auxiliary support." Each level independently implements its function, while simultaneously forming a synergy through signal transmission and media flow. Figure 1 , Figure 2 As shown, the specific structure and connection relationships are explained below:

[0046] 1. Dual-drive power unit: This is the power source for the feedwater pump. It adopts a series arrangement of "waste heat driven steam turbine → flexible coupling → double-extension shaft three-phase asynchronous motor → flexible coupling → feedwater pump". It supports three modes: steam turbine driven alone, motor driven alone, and both driven together. The parameters and connection logic of each component realize the design of "power matching and smooth transmission".

[0047] (1) Waste heat driven steam turbine. A steam turbine of model B0.7-0.65 / 0.15 is selected. Its inlet steam parameters match the enterprise's waste heat steam (absolute pressure 0.65MPa, temperature 230-240℃), and its exhaust steam parameters are adapted to the low-grade heat demand (absolute pressure 0.15MPa). The rated output power is ≥315kW, consistent with the rated load of the feedwater pump, ensuring that a single steam turbine can drive full load. The steam turbine shaft end is equipped with a steam seal structure, which can be connected to the subsequent steam seal steam pipeline to prevent steam leakage and air leakage. The rotor is supported by radial sliding bearings of the auxiliary support subsystem, and the inner ring of the bearing is interference-fitted with the rotor. It has a slow warm-up function during cold start-up to avoid uneven deformation of the rotor due to thermal stress.

[0048] The turbine power output shaft is connected to one end of the double-shaft motor via a flexible coupling (allowing ±0.02mm coaxiality deviation); the steam inlet is connected to the main steam pipeline of the steam-water circulation subsystem via a flange; the exhaust port is connected to the back pressure steam pipeline via a flange, forming a complete flow path of "steam input-power output-exhaust steam recovery".

[0049] (2) Dual-shaft three-phase asynchronous motor. The motor specifications are 400kW, 10500V, and 85% efficiency. The dual-shaft design is suitable for series transmission: one end is connected to the turbine power output shaft through a flexible coupling, and the other end is connected to the feedwater pump input shaft through a flexible coupling. The role can be dynamically switched according to the steam conditions. When there is no steam, it drives the feedwater pump alone. When steam is insufficient, it draws power from the grid to supplement power. When steam is sufficient, it switches to generator to feed power back to the enterprise's 10500V grid. The 400kW rated power is reserved for power compensation and generator redundancy.

[0050] The motor windings have a built-in motor insulation status monitoring module that measures the insulation resistance in real time. The allowable value is ≥10MΩ, and a warning signal is sent to the control cabinet when the resistance drops to 8-10MΩ. The motor casing has a pre-installed spray cooling interface for connecting to a branch of the cooling water pipeline in the steam-water circulation subsystem. When the motor's supplementary power exceeds 80kW for 30 minutes, the spray system automatically starts. The motor power circuit is connected to a battery energy storage auxiliary module with a rated capacity sufficient for 30 seconds of power supplementation. When the plant's grid voltage fluctuates by more than ±5%, the energy storage module briefly supplements the power difference to prevent fluctuations in the feedwater pump load.

[0051] (3) Flexible coupling and feedwater pump. Two sets of flexible couplings are configured to connect the "turbine-motor" and "motor-feedwater pump" respectively. Their function is to buffer shaft vibration, compensate for installation coaxiality deviation (allowable ±0.02mm), and prevent vibration transmission from causing equipment wear. An electromagnetic active vibration damper is installed at the "motor-feedwater pump" coupling, which outputs a 0-500N reverse electromagnetic force to counteract shaft vibration in real time (allowable vibration value ≤0.06mm). When the vibration exceeds 0.05mm, a reverse force is automatically output.

[0052] The feedwater pump is the core load, with a rated flow rate of 17 t / h calculated based on rated steam conditions and losses, approximately 1.06 times the steam volume, covering boiler blowdown, pipeline losses, etc. The inlet is connected to the enterprise's deaerator water tank via pipeline, and the outlet is connected to the process water supply network and equipped with a feedwater pump outlet quick-closing valve. This valve is linked to the control cabinet, closing completely within one second in case of emergency shutdown to prevent feedwater backflow. The pump body has a reserved interface for a recirculation return valve, which automatically opens to supplement flow when the flow is insufficient during startup, preventing cavitation.

[0053] II. The steam-water circulation subsystem provides "steam supply, cooling guarantee, and condensate treatment" for the dual-drive unit. It consists of multiple sub-pipelines and integrates components such as steam pretreatment and cooling assistance to ensure stable medium flow and efficient energy recovery.

[0054] (1) The main steam pipeline is DN400 and PN1.0. One end is connected to the waste heat steam header of the enterprise through a flange (a steam header energy storage tank is installed between the header and the pipeline, with a volume suitable for 10 minutes of steam buffer, and the pressure is released when the predicted pressure drops to 0.58MPa). The other end is connected to the steam turbine inlet through a flange, which is responsible for transporting waste heat steam.

[0055] The pipeline is equipped with corrugated expansion joints (compensation ±50mm, absorbing thermal expansion and contraction), a quick-closing main steam valve (near the turbine inlet, hydraulically driven, fully closed within 1 second in case of failure), and an electric regulating valve (DN200, response time ≤2 seconds). It also features a steam flow sensor (0-20t / h, accuracy ±0.1t / h), a pressure sensor (0-1.0MPa absolute pressure, ±0.01MPa), a temperature sensor (0-300℃, ±1℃), and a steam quality monitoring sensor (measuring humidity ≤3%, particle size ≤50μm). When humidity >2.5%, the integrated steam dryer in the pipeline is triggered; when particle size exceeds the standard, the steam pretreatment system (connected to the front end of the pipeline, backwashing to filter impurities) is triggered. All sensor signals are transmitted to the control cabinet via a 5G edge node.

[0056] (2) Steam sealing pipeline, the pipeline specification is DN10, one end is connected to the enterprise's low-pressure steam source (absolute pressure 0.02-0.05MPa, temperature 120-150℃), and the other end is connected to the steam seals at the front and rear shaft ends of the steam turbine in two separate lines, and a small amount of low-pressure steam is introduced to form a "steam barrier" to prevent high-pressure steam from leaking out and air from leaking in.

[0057] An electric regulating valve (adjustment accuracy ±0.005MPa) is installed on the pipeline. The steam seal pressure setting value is "turbine inlet steam pressure +0.03MPa" (e.g., if the inlet steam pressure is 0.65MPa, the steam seal pressure is 0.68MPa, correcting the original value error). A steam seal leakage monitoring sensor is installed at the turbine shaft end steam seal (allowable leakage ≤0.01t / h). When the leakage >0.008t / h, the control cabinet instructs the hydraulic actuator to adjust the steam seal gap to reduce losses.

[0058] (3) Back-pressure steam pipeline, with specifications of DN65 and PN1.6, one end connects to the turbine exhaust port, and the other end connects to low-grade heat users of the enterprise, such as workshop heating and deaerator preheating, to realize the cascade utilization of steam. The exhaust steam is 110-120℃ to meet the low-grade demand. The pipeline is equipped with a fully open manual shut-off valve, an vent valve (DN50, venting when the heat user disconnects), and a pressure sensor (0-0.3MPa absolute pressure). When the exhaust steam pressure exceeds 0.2MPa, the safety valve is triggered (opening pressure 0.2MPa absolute pressure). A heat user priority allocation module is set at the end of the pipeline to dynamically allocate the flow according to the urgency of the heat demand. For example, 60% is given priority for deaerator preheating, and excess steam is introduced into the waste heat boiler feed water preheater to increase the feed water temperature to 80℃.

[0059] (4) Drainage pipeline, specification PN1.0, adopts "multi-point access, aggregated discharge" design. The low point of the main steam pipeline and the drain interface of the turbine body (cylinder body, steam chamber low point) are respectively connected to the branch pipe. Each branch pipe is equipped with a DN15 check valve (opening pressure 0.02MPa, to prevent backflow). All branch pipes are aggregated and connected to the main drainage pipeline, and finally discharged to the recovery water tank (water quality qualified) or the ditch.

[0060] The main condensate drain line is equipped with a level sensor and a temperature sensor. When the level is too high, an alarm is triggered to check the check valve. A condensate recovery judgment module (measuring temperature ≥95℃ and conductivity ≤100μS / cm) is installed at the end of the condensate drain line. Qualified condensate is discharged into the deaerator water tank, while unqualified condensate is discharged into the drain and fed back to the steam pretreatment system for optimization.

[0061] (5) Cooling water pipeline: using the enterprise's industrial circulating water as the medium, the inlet end is connected to the enterprise's circulating water main through a gate valve (DN50). A standby cooling water pump (rated flow rate 0.08t / h, starts within 3 seconds in case of main pump failure) is connected in parallel between the main pipe and the gate valve. After the gate valve, it branches into three lines: one line connects to the turbine radial sliding bearing cooling channel, one line connects to the motor winding cooling channel, and one line connects to the motor casing spray cooling interface for dual-stage cooling. The three return water lines are connected to the enterprise's circulating water return pipe. A cooling tower is connected before the return pipe. The cooling tower starts when the cooling water temperature exceeds 32℃ and can reduce the water temperature to 28-30℃.

[0062] Control parameters: Total cooling water volume ≈ 0.05t / h (60% for bearings, 40% for motor windings), cooling water temperature ≤ 32℃. Inlet pressure sensor, inlet and outlet water temperature sensor, and flow sensor are installed on the pipeline. When the water temperature exceeds 32℃ or the flow rate is insufficient, the inlet gate valve is automatically opened, simultaneously activating the cooling tower and the standby cooling water pump.

[0063] (6) Drainage and drainage pipeline, including two branches: ① Safety valve drainage branch: One safety valve (A48Y-0.6C, opening pressure 0.65MPa absolute pressure, reseating pressure 0.6MPa) is installed on the main steam pipeline (upstream of the quick-closing main steam valve) and the top of the turbine body. When the pressure is over-pressurized, the steam is discharged to the safe area; ② Shutdown drainage branch: Drainage interfaces are reserved on the main steam pipeline, back pressure steam pipeline and condensate pipeline. When the machine is shut down, the corresponding valve is opened to drain the residual steam and condensate. The turbine body venting interface is connected to the drainage ditch to prevent equipment corrosion or negative pressure deformation.

[0064] III. Piping and Valve Control Subsystem: Piping control is achieved through a combination of automatic and manual valves. All automatic valves are linked to the control cabinet, while manual valves serve as backups. This subsystem includes the following components:

[0065] (1) Quickly close the main steam valve, which is installed upstream of the main steam pipeline (near the steam turbine inlet), hydraulically driven, and normally fully open; when the control cabinet receives fault signals such as "steam turbine overpressure > 0.7MPa, vibration > 0.12mm, bearing overheat > 65℃", it immediately commands the valve to close completely and cut off the steam supply; during maintenance, it can be manually closed to isolate the steam turbine from the main steam pipeline.

[0066] (2) Shut-off valves and regulating valves: Two DN200 manual shut-off valves are configured: one in the main steam pipeline (downstream of the quick-closing main steam valve) and one in the back-pressure steam pipeline (near the heat user end). They are fully open under normal conditions to ensure flow, and the isolation equipment is shut off during maintenance. The electric regulating valve (DN200) in the main steam pipeline is responsible for regulating the steam flow. During the warm-up phase, the opening degree is adjusted according to the speed gradient (20% at 500 r / min and 40% at 1500 r / min). During normal operation, it is finely adjusted according to the steam flow signal (closed less when exceeding 16 t / h and opened more when below 8 t / h) to maintain stable turbine power.

[0067] (3) Check valves, safety valves, and gate valves. Except for the DN15 check valve on the drain line, a DN50 check valve (to prevent backflow) is installed at the return end of the cooling water line. A safety valve (0.2MPa absolute pressure) is added to the back-pressure steam line (near the turbine exhaust port) to prevent pressure buildup during heat supply interruption. The DN50 gate valve at the inlet of the cooling water line is used for coarse adjustment of the total water flow. The DN25 gate valve on the drain line is for manual backup and is opened for venting during shutdown.

[0068] (4) The feedwater pump outlet quick-closing valve is installed between the feedwater pump outlet and the process water supply network. It is electrically driven and linked to the control cabinet. During normal shutdown, it closes slowly according to the feedwater pump deceleration rhythm. During emergency shutdown (such as when the turbine vibration exceeds 0.12mm), it closes completely within 1 second to prevent feedwater from flowing back into the pump body and causing cavitation or damage.

[0069] IV. The control and monitoring subsystem is the "intelligent brain" of the unit, responsible for data acquisition, operating condition calculation, and command output, realizing automatic power adjustment and unattended operation. It consists of a control cabinet, an automatic power adjustment module, and a monitoring sensor group, with signals from each part interacting in real time.

[0070] (1) The control cabinet is powered by 220V AC and has a rated power of about 2kW. It integrates PLC, HMI human-machine interface, sound and light alarm device and data storage module, which can save more than 1 year of operation data.

[0071] The PLC receives all sensor signals via cable, performs preset logic operations, and outputs commands to valve actuators, motor controllers, and turbine regulating components. The HMI displays real-time steam parameters, motor power, bearing temperature, and other operating conditions, and supports manual modification of setpoints such as cooling water temperature and steam seal pressure. An alarm device triggers when parameters exceed limits, and the HMI pop-up displays the fault type and location, such as decreased motor insulation resistance or steam seal leakage.

[0072] (2) The automatic power adjustment module dynamically allocates the power of the steam turbine and the motor according to the steam operating conditions to ensure that the total power of the feedwater pump is stable at 321.3kW (including 2% transmission loss), with three operating condition strategies:

[0073] (a) When steam is sufficient (flow rate ≥ 12t / h, turbine power ≥ 315kW): the regulating valve opening is 60%-80% to stabilize the flow rate, the motor switches to generator mode, and excess power is fed back to the grid; when the power exceeds 350kW, the regulating valve is closed slightly, ±2% each time, to prevent motor overload.

[0074] (b) Insufficient steam (flow rate < 8t / h, turbine power < 250kW): Close the regulating valve to 20%-30% to maintain the turbine's minimum speed ≥ 1500r / min. The motor draws power from the grid to supplement the power, with the supplementary amount = 321.3kW - turbine power. When the grid fluctuates, the battery energy storage auxiliary module will provide temporary supplementary power. If the supplementary power exceeds 80kW and lasts for 30 minutes, the motor casing spray cooling and cooling tower can be activated.

[0075] (c) Critical combination (flow rate 8-12t / h, turbine power 250-315kW): the regulating valve opening is 30%-60% of the stable power, the motor maintains 15-65kW micro-supplement, and the motor is finely adjusted ±2kW every 2 minutes to reduce mode switching (≤1 time every 30 minutes). At the same time, the electromagnetic active vibration damper is linked to suppress vibration.

[0076] (3) Monitoring sensor group, covering several categories such as "pressure, temperature, flow rate, speed / vibration, quality / insulation / stress", including:

[0077] (a) Pressure sensor: installed in the main steam pipeline, back pressure steam pipeline, cooling water pipeline inlet, steam seal steam pipeline, lubrication oil pipeline, etc.

[0078] (b) Temperature sensors: installed in the main steam pipeline, the return end of the cooling water pipeline, the turbine bearing, the motor winding, the lubrication oil circuit, etc.

[0079] (c) Flow sensor: installed at the inlet of the main steam pipeline, cooling water pipeline, etc.

[0080] (d) Speed / vibration sensors: installed on turbine rotor, motor rotor, "motor-feed pump" coupling (linked electromagnetic vibration damper), etc.

[0081] (e) Special sensors: including steam quality monitoring sensors, motor insulation status monitoring modules, pipeline stress monitoring sensors (main steam / back pressure pipeline elbows, stress ≤200MPa, adjust the corrugated compensator when it exceeds 180MPa), etc.

[0082] V. The auxiliary support subsystem provides "lubrication, vibration suppression, and cooling backup" support for the dual drive unit and the steam-water circulation subsystem. Components include:

[0083] (1) Radial sliding bearing and lubrication system, a total of 4 sets of bearings, which are installed at both ends of the turbine rotor (2 sets) and both ends of the motor rotor (2 sets). The inner ring of the bearing is interference fit with the rotor, and the outer ring is fixed to the equipment base. The bearing is equipped with a lubrication oil chamber (connected to the enterprise's lubrication oil system, oil pressure ≥0.15MPa) and a cooling channel (connected to the cooling water pipeline branch).

[0084] When the bearing temperature is >55℃, the control cabinet opens the cooling channel valves to the maximum; when it is >65℃, the turbine power is reduced (by 10% each time) until the temperature is ≤55℃. The lubrication circuit is equipped with a temperature sensor and a dual-function electric heating-cooling module. When the oil temperature is <40℃, it is heated to 45-50℃; when it is >55℃, circulating water is introduced for cooling, ensuring a viscosity of 20-30 mm² / s.

[0085] (2) Two sets of corrugated compensators and leakage monitoring systems are installed on the main steam pipeline (near the turbine inlet) and the back pressure steam pipeline (near the turbine outlet), respectively. The compensation range is ±50mm. The system absorbs the thermal expansion and contraction deformation of the pipeline and avoids shaft deviation caused by pushing the equipment. A leakage sensor can be attached to the outer wall of the compensator. The detection accuracy is 0.1mL / min. When damaged, the sensor sends a signal to the control cabinet to alarm and remind the user to replace the device.

[0086] (3) Industrial circulating water interface and auxiliary cooling components.

[0087] The interface includes an inlet and a return water end: the inlet end is connected to the company's circulating water main pipe via a flange, and a Y-type filter and pressure sensor are installed at the interface to filter impurities and prevent clogging; the return water end is connected to the company's circulating water return pipe and is equipped with a check valve to prevent backflow.

[0088] Auxiliary cooling linkage: The interface is linked with the cooling tower and the backup cooling water pump. When the cooling water temperature exceeds 32℃, the cooling tower is activated, and when the flow rate is insufficient, the backup pump is activated to ensure the redundancy of the cooling system. At the same time, it is connected to the spray cooling interface of the motor casing to form a two-stage cooling guarantee.

[0089] This embodiment achieves efficient waste heat recovery, automatic switching of power modes, and stable operation under all working conditions through the coordinated design of the above-mentioned parts. The dual-drive power unit outputs power, the steam-water circulation subsystem supplies the medium, the pipeline and valve control subsystem adjusts parameters, and the control and monitoring subsystem provides intelligent regulation.

[0090] Example 2

[0091] This embodiment, based on the system architecture of Embodiment 1, focuses on the full-condition process of "safe startup - dynamic optimized operation - precise fault tolerance - intelligent shutdown," and designs an automated control method with "predictive, adaptive, and highly fault-tolerant" characteristics. This method not only solves the problems of slow response, difficult fault location, and insufficient energy utilization in traditional control systems, but also achieves the goals of efficient waste heat steam recovery and continuous and stable operation of the feedwater pump. The control logic is executed in conjunction with the intelligent control cabinet and the automatic power adjustment module. The specific steps are as follows:

[0092] I. System Startup Phase Control: Shockless Startup Based on Prediction and Adaptive Regulation

[0093] The main problems to be solved during the startup phase are "thermal shock of cold equipment, power connection interruption, and risk of medium parameter fluctuations". This embodiment achieves the smoothness of equipment preheating and power switching through multi-level control of "intelligent pre-diagnosis, load pre-adaptation, dynamic control of thermal stress, and flexible connection", while shortening the startup time by 15%-20%.

[0094] 1.1 Intelligent pre-start diagnosis and parameter adaptation verification. Breaking through the limitations of traditional "static inspection," this system combines historical data with real-time monitoring to proactively eliminate hidden faults, predict media parameter stability, and prevent shutdowns due to parameter mismatches after startup. Specifically, this includes:

[0095] (1) System-wide health pre-diagnosis: The intelligent control cabinet calls up the historical data from the most recent startups, which may include pipeline deformation, bearing wear trend, valve action response time, etc. Combined with real-time sensor signals, such as the strain value of the bellows compensator and the jamming test current of the check valve (DN15), a pre-diagnosis report can be generated through the "fault tree algorithm". For example, if the valve action delay of the main steam pipeline is detected to be >0.5 seconds (normal ≤0.3 seconds), the valve lubricating grease replenishment command is automatically triggered; if the bearing lubricating oil film thickness is <0.05mm (safe value ≥0.08mm), the lubricating oil circulation heating system is started (heated to 40-45℃ to improve the oil film formation ability).

[0096] (2) Dynamic prediction of medium parameters: Based on the pressure / temperature fluctuation curve of the waste heat steam pipeline network in the plant area over the past hour (sampling frequency 1 time / second), the steam parameters for the next 10 minutes can be predicted by an LSTM neural network. If it is predicted that the main steam pressure will drop to 0.58MPa (lower than the design value of 0.65MPa) 5 minutes after startup, the steam main pipe accumulator will be instructed to release pressure in advance to maintain the steam pressure ≥0.62MPa during the startup phase; at the same time, the "dynamic cooling capacity" of the industrial circulating water will be verified. By simulating the cooling load after the feedwater pump starts (calculated based on a basic water volume of 0.05t / h + 10% redundancy), it is confirmed that the fluctuation of the circulating water inlet pressure is ≤±0.02MPa (design value 0.3MPa) to avoid insufficient cooling after startup.

[0097] (3) Sensor calibration and signal synchronization: Perform "online dynamic calibration" on all monitoring sensors (pressure, temperature, flow). Apply a standard pressure signal to the pressure sensor (e.g., apply a standard pressure of 0.65MPa to the main steam pipeline sensor). If the measurement deviation is > ±0.01MPa, automatically correct the sensor coefficient. At the same time, achieve signal synchronization between the control cabinet and the field sensors through 5G edge nodes to avoid misjudgment caused by signal attenuation in traditional wired transmission.

[0098] 1.2 Motor Soft Start and Load Pre-Adaptation Control. This addresses the grid impact issue caused by direct starting of high-voltage motors, while simultaneously allowing the feedwater pumps to adapt to the process load in advance, avoiding load fluctuations when the turbine is subsequently connected. This includes:

[0099] (1) Staged soft start and grid impact suppression. The traditional "star-delta reduced voltage start" is abandoned, and "thyristor voltage regulation soft start" is adopted. The control cabinet gradually increases the input voltage of the motor (400KW, 10500V) from 30% of the rated voltage (3150V) to 100% in 8-10 seconds, and controls the starting current to ≤1.8 times the rated current, which is lower than the traditional starting current of 6-8 times. At the same time, the voltage fluctuation of the power grid in the plant area is monitored in real time (±3%). If a sudden drop in the power grid voltage >5% is detected (such as when other high-power equipment starts at the same time), the voltage increase is immediately suspended and resumed after the power grid is restored to avoid affecting other equipment in the plant area.

[0100] (2) Feedwater pump load pre-adaptation: The motor drives the feedwater pump to operate in a "stepped speed increase + load pre-loading" mode. First, stabilize at 500 r / min for 3 minutes to check for any abnormal noises in the pump body. Then, increase to 1000 r / min and slowly increase the feedwater pressure to 0.8 MPa through the outlet regulating valve, reaching 67% of the process requirement of 1.2 MPa, and stabilize for 5 minutes. Finally, increase to the rated speed of 2980 r / min, and simultaneously increase the feedwater pressure to 1.0 MPa, reserving a 0.2 MPa redundancy for easy load connection when the steam turbine is connected. During this process, the "minimum stable flow" is monitored through the feedwater pump inlet flow sensor to ensure ≥15% of the rated flow and avoid pump body cavitation. If the flow is insufficient, the pump body circulation return valve is automatically opened to supplement the flow.

[0101] (3) Shaft vibration pre-suppression: A laser vibration sensor can be installed at the coupling with a sampling frequency of 1000Hz to monitor radial vibration during startup in real time. When the speed increases to 1500r / min and reaches the edge of the critical speed range, if the vibration value is >0.04mm (safe value ≤0.05mm), the control cabinet will automatically adjust the motor output torque (fine adjustment ±2%) to avoid the resonance point and ensure that the vibration during the entire startup process is ≤0.03mm.

[0102] 1.3 Steam Turbine Adaptive Thermal Stress Control Warm-up. Breaking through the limitations of traditional "fixed-time warm-up," this method dynamically adjusts the warm-up rhythm based on real-time thermal stress data of the turbine rotor and cylinder, avoiding equipment deformation caused by uneven thermal stress and shortening the warm-up time. This includes:

[0103] (1) Intelligent preheating of steam seal: Before opening the steam seal pipeline (DN10), the steam temperature of the steam seal is first raised to 120-150℃ through the pipeline heating system, close to the temperature of the turbine shaft end, to avoid cold steam impacting the shaft seal. Then, the valve is slowly opened to gradually increase the steam seal pressure from 0.02MPa absolute pressure to 0.05MPa absolute pressure, which can be increased by 0.01MPa every 2 minutes. At the same time, the temperature gradient at the steam seal is monitored by the shaft end infrared thermal imager (allowed ≤2℃ / min) to prevent damage to the shaft seal sealing surface due to excessive temperature difference.

[0104] (2) Staged warm-up based on thermal stress: Platinum resistance temperature sensors (measurement accuracy ±0.5℃) are implanted in the center hole of the turbine rotor and the upper and lower cylinders of the cylinder to calculate the thermal stress value in real time (allowable value ≤150MPa).

[0105] Low-speed warm-up stage (target speed 500 r / min): Initially, introduce steam at 0.2 MPa absolute pressure and 180°C. If the rotor thermal stress is monitored to be <80 MPa (safe range), increase the pressure by 0.05 MPa and the temperature by 10°C every 3 minutes until the pressure is 0.3 MPa and the temperature is 200°C, and stabilize for 10 minutes (traditionally it takes 15-20 minutes).

[0106] Medium-speed warm-up stage (target speed 1500r / min): The parameters are increased in a gradient of "pressure 0.05MPa / 5min, temperature 15℃ / 5min". At the same time, the temperature difference between the upper and lower cylinders is calculated (allowed ≤35℃). If the temperature difference is >30℃, the heating rate is automatically reduced until the pressure is 0.5MPa and the temperature is 220℃, and it is stabilized for 15 minutes (traditionally it takes 20-25 minutes).

[0107] Rated parameters warm-up stage (target speed 2500r / min): rapidly increase to 0.65MPa and 230-240℃ (design value). If the thermal stress is <120MPa, stabilize directly for 8 minutes (traditionally 10 minutes) to complete the warm-up.

[0108] (3) Intelligent drainage: Install a "temperature-flow dual-parameter trigger valve" in the drainage pipeline. When the temperature of the condensate in the pipeline is ≥105℃ (confirming no steam entrainment) and the flow rate is ≥0.02t / h, the drainage will be automatically opened and closed after 30 seconds of drainage to avoid steam loss caused by continuous drainage and reduce steam loss during the start-up phase.

[0109] 1.4 Flexible Connection between Steam Turbine and Dual-Drive System. This addresses the shaft impact problem caused by traditional "rigid integration" by achieving seamless power connection through speed synchronization and load gradient transfer control. This includes:

[0110] (1) Multi-dimensional speed synchronization control: Simultaneously monitor the speeds of the turbine, motor, and feedwater pump (sampling frequency 100Hz), and define the "synchronization coefficient" as (turbine speed - motor speed) / motor speed × 100%, with an allowable range of ≤ ±0.1%. In the initial stage, the turbine speed is 2500 r / min and the motor speed is 2980 r / min. The control cabinet gradually increases the turbine speed by opening the main steam regulating valve by 3% every 3 minutes. The synchronization coefficient is calculated after each adjustment. When the synchronization coefficient is ≤ ±0.05%, the "speed synchronization is qualified".

[0111] (2) Load gradient transfer and torque balance: After synchronization, the "torque compensation algorithm" is started. The turbine output torque and motor load torque are monitored in real time by a torque sensor installed on the coupling. The feedwater pump load is transferred from the motor to the turbine in a gradient of "2% load / 2min". For example, the initial motor load torque is 1200 N·m (corresponding to a 315kW load) and the turbine output torque is 0 N·m. Every 2 minutes, the motor torque is reduced by 24 N·m and the turbine torque is increased by 24 N·m. At the same time, the shaft vibration is monitored (≤0.04mm is allowed). If the vibration exceeds the standard, the load transfer is paused and the speed is finely adjusted to ensure that there is no impact during the load transfer process.

[0112] (3) Dual-drive operation verification: When the turbine load reaches 200kW (63% of rated load), the "joint drive verification stage" is entered. Maintain the load stability for 5 minutes and monitor the turbine exhaust pressure (stable at 0.15MPa absolute pressure), motor current (reduced to no-load current + 5% load current), and feedwater pump outlet pressure (fluctuation ≤ ±0.03MPa). If all three parameters are qualified, the dual-drive system is determined to have entered the normal operation stage; otherwise, the warm-up or synchronization link is traced back to troubleshoot the problem.

[0113] II. Control during normal operation. The requirements for normal operation are "efficient utilization of waste heat, stable load, and unattended operation". This embodiment uses innovative technologies such as "predictive adjustment of steam parameters, energy cascade allocation, bidirectional energy management of motors, and linkage optimization of auxiliary systems" to achieve dynamic power balance and improve energy utilization efficiency through dynamic power optimization based on prediction and cascade utilization.

[0114] 2.1 Multi-parameter fusion-based operating condition prediction and dynamic monitoring. By fusing multi-dimensional parameters, operating condition changes are predicted, providing lead time for power regulation and avoiding load fluctuations. This includes:

[0115] (1) Construction of operating condition prediction model: Using main steam flow (Q1), pressure (P1), temperature (T1), turbine power (N1), and motor power (N2) as input parameters, and feedwater pump load (N=315kW) as output parameter, a "BP (back-through error) neural network prediction model" is constructed. Parameter data for the past 5 minutes are collected in real time (sampling frequency 1 time / second), and the model outputs the operating condition prediction result for the next 5 minutes every 30 seconds. For example, if it is predicted that Q1 will decrease from 11t / h to 7t / h (steam shortage threshold), a "pre-excitation command" is sent to the motor control circuit in advance, so that the motor enters the "power replenishment state" in advance, and the response speed is improved. If it is predicted that Q1 will increase from 13t / h to 17t / h (steam abundance threshold), the inverter parameters are adjusted in advance to prepare for the motor to switch to "generator mode".

[0116] (2) Multi-dimensional parameter monitoring: In addition to traditional pressure, temperature, and flow parameters, three new types of key parameters can be added for monitoring:

[0117] Steam quality monitoring: A humidity-particle size sensor is installed on the main steam pipeline to monitor the steam humidity (≤3%) and impurity particle size (≤50μm) in real time. If the humidity is >2.5%, the steam dryer will be automatically activated. If the impurity particle size exceeds the standard, a backwashing command for the pipeline filter will be triggered to prevent impurities from entering the turbine and causing blade wear.

[0118] Motor insulation status monitoring: The built-in "online insulation monitoring module" measures the insulation resistance of the motor windings in real time (≥10MΩ is allowed). If the resistance drops to 8-10MΩ, an "insulation warning" is issued. At the same time, the motor cooling water volume can be adjusted to increase by 5% to delay insulation aging.

[0119] Pipeline stress monitoring: Install fiber optic stress sensors at the bends of the main steam pipeline and back pressure steam pipeline to monitor pipeline thermal stress in real time (allowable value ≤200MPa). If the stress is >180MPa, the expansion and contraction of the bellows compensator can be automatically adjusted by the hydraulic actuator to release pipeline stress.

[0120] 2.2 Power regulation strategy for different operating conditions.

[0121] 2.2.1 Steam Sufficient Operating Condition: Turbine-led operation + motor feedback power supply + energy cascade utilization. Triggering conditions: Q1 ≥ 12t / h, N1 ≥ 315kW, lasting 30 seconds (excluding instantaneous fluctuations). Control actions include:

[0122] (1) Precise control of main steam flow: "Fuzzy PID control" can be used. For example, when Q1 fluctuates in the range of 12-16 t / h, the controller dynamically adjusts the opening of the main steam regulating valve (60%-80%) based on the flow deviation (e.g., deviation + 1 t / h when Q1=14 t / h) and the rate of change of the deviation (e.g., the deviation increases by 0.2 t / h / min). If the deviation is large and changes rapidly, the opening adjustment range is increased (e.g., ±5% each time); if the deviation is small and changes slowly, the adjustment range is decreased (e.g., ±1% each time), so that the fluctuation range of Q1 is controlled within ±0.3 t / h (traditionally ±0.8 t / h), thereby improving the steam utilization rate.

[0123] (2) Quality control of motor feedback power supply: After the motor switches to "generator mode", an "active filtering module" is added to monitor the harmonic content of the feedback power in real time (the total harmonic distortion rate is allowed to be ≤5%). If the third harmonic content is >3%, the reverse harmonic current is injected through the filtering module to cancel it out; at the same time, "voltage-frequency coordinated control" is adopted to ensure that the voltage fluctuation of the 10500V power grid fed back to the plant is ≤±2% and the frequency fluctuation is ≤±0.1Hz, so as to avoid interference to other equipment in the power grid. In addition, the feedback power is statistically analyzed in real time through the "energy metering module" (accuracy ±0.5%), and a "waste heat recovery benefit report" can be automatically generated to facilitate the company's energy consumption management.

[0124] (3) Back-pressure steam cascade distribution: A "heat user priority distribution module" is installed at the end of the back-pressure steam pipeline (DN65, PN1.6). The steam flow is dynamically distributed according to the urgency of the heat demand of the heat users in the plant area (such as workshop heating, deaerator preheating, hot water preparation) and the parameter matching degree (back-pressure steam 0.15MPa absolute pressure, 110-120℃). For example, if the deaerator needs preheating (the heat demand urgency is the highest), 60% of the back-pressure steam is allocated first; if the heating demand is low, the excess steam is introduced into the "waste heat boiler feedwater preheater" to raise the boiler feedwater temperature from 25℃ to 80℃, thereby reducing boiler fuel consumption.

[0125] 2.2.2 Insufficient Steam Condition: Motor supplementary drive + turbine load protection + cooling synergy optimization. Triggering conditions: Q1 < 8t / h, N1 < 250kW, lasting 20 seconds. Control actions include:

[0126] (1) Turbine minimum load protection: The "load-speed-exhaust pressure linkage protection" is adopted, and the minimum stable speed of the turbine is adjusted in real time according to N1. When N1=240kW, the speed is maintained at 2200r / min; when N1=200kW, the speed is reduced to 2000r / min, while ensuring that the exhaust pressure is ≥0.12MPa absolute pressure (to prevent air leakage). If N1<180kW (extreme steam shortage), the "turbine inertial operation mode" is automatically activated, the main steam regulating valve is closed to 15% opening, and only a small amount of steam is introduced to maintain the rotor at low speed (1500r / min) to avoid the rotor shaft bending due to long-term static operation.

[0127] (2) Precise control of motor supplementary power: Based on the "power difference dynamic calculation model", the power that the motor needs to supplement is calculated in real time: ΔN = 315kW - N1 - η (η is the transmission loss, about 2%). For example, when N1 = 220kW, ΔN = 315 - 220 - 6.3 = 88.7kW. The control cabinet sends a "precise power command" to the motor and achieves power output by adjusting the motor input current (10500V high-voltage side current), with an error of ≤ ±1kW. At the same time, if the voltage fluctuation of the power grid in the plant area is > ±5%, the "battery energy storage auxiliary module" is automatically activated to briefly supplement the power difference (duration ≤ 30 seconds) to avoid the sudden drop in the outlet pressure of the water pump caused by the motor power fluctuation.

[0128] (3) Coordinated optimization of cooling system: Establish a correlation model of "motor power-cooling demand". When the supplementary power of the motor is >80kW and the duration is >30 minutes, "dual-stage cooling" is automatically activated: the first-stage cooling (existing cooling water pipeline) increases the gate valve opening by 8%-12%, and the cooling water volume increases from 0.05t / h to 0.065t / h; the second-stage cooling (motor casing spray cooling) is activated, and circulating water (water temperature ≤32℃) is sprayed onto the motor casing through atomizing nozzles to keep the motor winding temperature ≤110℃ and extend the motor life. At the same time, the temperature difference between the inlet and outlet of the cooling water pipeline is monitored (allowed ≤8℃). If the temperature difference is >7℃, the pipeline filter is automatically cleaned, and the backwashing time is 30 seconds to ensure cooling efficiency.

[0129] 2.2.3 Critical Combined Operating Condition: Turbine-Motor Coordination + Shaft Vibration Suppression. Triggering conditions: 8t / h ≤ Q1 < 12t / h, 250kW ≤ N1 < 315kW. Control actions include:

[0130] (1) Dynamic balance regulation of main steam: "Feedforward-feedback composite control" is adopted. The feedforward channel adjusts the opening of the main steam regulating valve in advance (from 35% to 40%) according to the real-time change of Q1 (e.g., Q1 increases from 9t / h to 10t / h). The feedback channel finely adjusts the opening (±1%) according to the actual value of N1 (e.g., N1=280kW, target 290kW) to stabilize N1 at 280-300kW (fluctuation ≤±2kW), avoiding the lag of traditional feedback control that causes N1 fluctuation to exceed ±5kW.

[0131] (2) Motor-free switching fine-tuning supplement: To avoid frequent switching of the motor between "motor / generator" modes, a "power fine-tuning buffer strategy" is adopted. The motor always maintains a "micro-supplementary power state" (output 15-65kW). When N1 increases from 290kW to 300kW, the motor supplementary power decreases from 25kW to 15kW (adjusted by 2kW every 2 minutes); when N1 decreases from 290kW to 280kW, the motor supplementary power increases from 25kW to 35kW (adjusted by 2kW every 2 minutes). The switching frequency is reduced to ≤1 time every 30 minutes, reducing the impact on the power grid.

[0132] (3) Active vibration suppression of shaft system: An electromagnetic active vibration damper is installed at the coupling to monitor the vibration value in real time (allowable ≤0.06mm). When the vibration value rises to 0.05mm, the damper outputs a reverse electromagnetic force of 0-500N based on the vibration phase obtained by the vibration sensor. The phase is opposite to the vibration phase to cancel the shaft system vibration. If the vibration value is >0.055mm, the steam turbine inlet uniformity is adjusted by fine-tuning the opening distribution of the regulating valve to reduce the unbalanced force of steam on the turbine rotor, so that the vibration is controlled within ≤0.04mm, thus extending the shaft system life.

[0133] 2.3 Intelligent linkage optimization of auxiliary systems enables linkage between the auxiliary system and the main drive system, improving overall stability. Control actions include:

[0134] (1) Adaptive regulation of steam seal pressure: A correlation model of "steam turbine inlet pressure - steam seal pressure" is established. The steam seal pressure setpoint = P1 + 0.03MPa. When P1 drops from 0.65MPa to 0.6MPa, the steam seal pressure automatically drops from 0.085MPa to 0.09MPa to avoid steam leakage due to excessive pressure or air leakage due to excessive pressure. At the same time, the leakage amount is monitored in real time by the "steam seal leakage monitoring sensor" installed at the shaft end (allowed ≤0.01t / h). If the leakage amount is >0.008t / h, the steam seal gap is automatically adjusted by the hydraulic actuator to reduce leakage loss.

[0135] (2) Intelligent temperature control of the lubricating oil system: An "electric heating-cooling dual-function module" is installed in the lubricating oil circuit of the radial sliding bearing. When the bearing temperature is <40℃ (the lubricating oil viscosity is too high), the electric heating module (power 5kW) is activated to raise the oil temperature to 45-50℃. When the bearing temperature is >55℃, the cooling module (circulating water) is activated to lower the oil temperature to 48-52℃, so that the lubricating oil viscosity is stabilized at the optimal lubrication viscosity of 20-30mm² / s, thereby reducing bearing friction loss.

[0136] (3) Energy-saving control of the condensate drainage system: A "condensate recovery judgment module" is installed at the end of the condensate drainage pipeline. The condensate temperature (Tcondensate) and water quality (conductivity ≤ 100 μS / cm) are monitored in real time. If Tcondensate ≥ 95℃ and the water quality is qualified, the condensate is automatically introduced into the "deaerator water tank" to recover heat and water resources, significantly improving the recovery efficiency of direct discharge into the ditch. If Tcondensate < 90℃ or the water quality exceeds the standard, it is discharged into the ditch, and the reason for the condensate failure is recorded (e.g., steam contains impurities), and fed back to the steam pretreatment system for optimization.

[0137] Third, fault-tolerant control under abnormal operating conditions solves problems such as "slow fault location, single fault tolerance method, and easy system downtime". This embodiment uses innovative technologies such as "precise source tracing, multi-dimensional pre-intervention, cross-system emergency linkage, and hierarchical fault-tolerant recovery" to achieve rapid fault handling and improve the system's fault-free operation time.

[0138] 3.1 Anomaly Identification and Precise Source Tracing. Breaking through the limitations of traditional "single-parameter alarms," ​​this system achieves precise identification of anomaly types and fault location, avoiding blind handling. Operational and monitoring actions include:

[0139] (1) Multi-dimensional anomaly identification: An "anomaly feature library" is constructed, containing 12 common anomalies, such as the characteristic parameters of overpressure, overtemperature, abnormal flow, motor failure, and turbine failure. For example, when there is overpressure, P1 > 0.7 MPa and the safety valve does not open; when there is a motor failure, the current > 1.1 times the rated value and the insulation resistance decreases. The control cabinet matches the collected parameters with the feature library in real time. If the matching degree is > 90%, the corresponding anomaly alarm is triggered immediately; if the matching degree is 60%-90% (suspected anomaly), "parameter enhancement monitoring" is started (sampling frequency increased to 5 times / second) to further confirm the anomaly type. For example, if turbine vibration > 0.1 mm and bearing temperature rises rapidly (5℃ / min) is detected, and the "bearing wear anomaly" feature is matched (match degree 95%), the corresponding alarm is triggered immediately.

[0140] (2) Fault source tracing: For complex anomalies, such as excessive vibration or sudden power drop, a combination of "vibration spectrum analysis + parameter correlation analysis" can be used for source tracing.

[0141] Vibration exceeding the standard source tracing: The vibration spectrum (frequency range 0-1000Hz) is collected by a laser vibration sensor. If a peak value of twice the rotational frequency (e.g., 50Hz, twice the rotational frequency 100Hz) appears in the spectrum, it is determined to be "coupling misalignment"; if a peak value of 1 rotational frequency appears and is accompanied by high-frequency harmonics, it is determined to be "bearing rolling element wear".

[0142] Power drop tracing: When N1 suddenly drops from 300kW to 220kW, the parameters P1, Q1, and T1 are analyzed in correlation. For example, if P1 drops from 0.65MPa to 0.5MPa and Q1 drops simultaneously, it is determined to be "steam network pressure fluctuation"; if P1 and Q1 are normal but T1 drops from 230℃ to 200℃, it is determined to be "sudden drop in steam temperature leading to a decrease in turbine efficiency", with a high accuracy rate in tracing the source.

[0143] (3) Classification of Abnormalities: Based on the scope and urgency of the impact, abnormalities are classified into three levels: Mild Abnormality: Only a single auxiliary parameter exceeds the standard, such as cooling water temperature 33-35℃, slight deviation of steam seal pressure, etc., which does not affect the main drive system. Moderate Abnormality: The main parameter exceeds the standard slightly, such as P1=0.7-0.75MPa, bearing temperature 65-70℃, etc., which may lead to load fluctuations. Severe Abnormality: The main parameter exceeds the standard severely, such as P1>0.75MPa, turbine vibration>0.12mm, motor short circuit, etc., which directly threaten equipment safety.

[0144] 3.2 Establish a multi-dimensional hierarchical fault tolerance strategy.

[0145] 3.2.1 Mild anomalies: Parameter fine-tuning + trend suppression. Handling actions include:

[0146] (1) Parameter adaptive fine-tuning: For example, for cooling water temperature of 33-35℃, "dual-end adjustment" can be adopted. On the one hand, the gate valve of the cooling water pipeline is opened by 10% to increase the water volume, and on the other hand, the cooling tower fan in the plant area is started to speed up and reduce the water temperature to below 32℃. For steam seal pressure that is slightly low, such as 0.07MPa, which is lower than the set threshold of 0.085MPa, the steam seal steam pipeline valve is automatically opened by 5%. At the same time, the pressure drop rate is used to check whether there is a slight leak in the pipeline. If the leakage rate is >0.002MPa / min, it can be marked as "non-emergency maintenance point".

[0147] (2) Abnormal trend suppression: If the "trend prediction algorithm" predicts that a mild abnormality will escalate, such as the cooling water temperature rising at 0.5℃ / min and reaching 35℃ after 10 minutes, strengthen measures can be taken in advance, such as starting an additional backup cooling water pump to increase the cooling water volume by 20% to avoid the abnormality from escalating.

[0148] (3) Recording and learning: Automatically record the abnormal handling process, including parameter changes, adjustment measures, and handling effects, and update it to the "Abnormal Handling Knowledge Base". When the same abnormality is encountered in the future, the optimal handling solution will be directly called.

[0149] 3.2.2 Moderate Anomaly: System voltage / load reduction + power mode switching + auxiliary system enhancement. Handling actions include:

[0150] (1) Precise pressure reduction of steam system: When P1 = 0.7-0.75MPa, “rapid closing main steam valve + safety valve coordinated control” can be adopted. First, reduce the opening of the rapid closing main steam valve from 100% to 70% (5% every 2 seconds), and at the same time open the safety valve bypass valve with an opening of 10%-15%, control the pressure reduction rate ≤0.02MPa / s, and avoid the pipeline from generating negative pressure due to sudden pressure drop, until P1 drops below 0.65MPa, and then close the bypass valve.

[0151] (2) Smooth switching of power mode: If there is an abnormality related to the steam turbine, such as vibration of 0.1-0.12mm, perform "no-impact switching". First, gradually increase the supplementary power of the motor from 30kW to 115kW, increasing by 5kW every 3 seconds. At the same time, gradually decrease the power of the steam turbine from 280kW to 200kW, decreasing by 5kW every 3 seconds. When the motor power reaches 315kW and the steam turbine power drops to 0kW, close the quick-closing main steam valve to complete the "dual drive → motor-only drive" switching. The load fluctuation during the switching process is ≤±3kW.

[0152] (3) Enhanced protection of auxiliary systems: For bearing temperatures of 65-70℃, activate "three-stage cooling". Increase the water volume of the first-stage cooling (existing cooling water circuit) by 15%, activate the second-stage cooling (motor housing spray), and activate the third-stage cooling (lubricating oil cooling). At the same time, reduce the load of the water pump to 280kW to reduce the bearing load and reduce the bearing temperature to below 60℃ within 5 minutes. If the temperature still does not drop, activate the standby lubricating oil pump and increase the oil pressure to 0.2MPa to enhance the lubrication effect.

[0153] 3.2.3 Severe Abnormality: Emergency Shutdown + Safe Depressurization + Cross-System Emergency Response. Handling actions include:

[0154] (1) Rapid and safe shutdown: When severe abnormalities such as P1 > 0.75MPa or turbine vibration > 0.12mm occur, the control cabinet will issue an "emergency shutdown command" within 0.5 seconds. The main steam valve will be closed completely to cut off the steam inlet to the turbine; the power supply to the motor can be cut off immediately, and the feedwater pump outlet quick-closing valve will be closed completely to prevent feedwater backflow.

[0155] (2) Multi-path safety pressure relief: In addition to the automatic opening of the safety valve, an "emergency pressure relief pipeline" can be added. If P1 does not drop (>0.78MPa) after the safety valve opens, the emergency pressure relief valve (DN50, PN2.0) will be opened automatically to discharge the overpressure steam to the safe area through an independent pipeline, avoiding interference with the steam discharge of the safety valve. At the same time, the pressure relief rate is monitored (≤0.05MPa / s is allowed) to prevent pipeline impact.

[0156] (3) Cross-system emergency linkage: Establish linkage with the plant’s “public works system”.

[0157] Cooling system linkage: If the cooling water pipeline breaks and the cooling water volume drops to 0, an "emergency water supply command" will be sent to the plant's fire water system immediately. The fire water will be connected to the cooling water pipeline through a dedicated interface and can be connected within 30 seconds to maintain basic cooling with a water volume of ≥0.03t / h to prevent equipment from overheating.

[0158] Water supply system linkage: If the water supply pump stops, a "start command" is immediately sent to the standby water supply pump system. The standby pump starts within 1 minute to maintain the minimum water supply requirements of the deaerator and boiler, with a flow rate ≥ 50% of the rated value, to avoid production interruption.

[0159] Power grid system linkage: If a short circuit occurs in the power grid when the motor is feeding back power, a "fault isolation command" is immediately sent to the plant's power grid dispatch center to disconnect the motor from the power grid. At the same time, the plant's energy storage system is activated to maintain the stability of the power grid voltage.

[0160] 3.3 Intelligent fault recovery and restart shortens fault recovery time and avoids secondary faults during the restart process. Operation and monitoring actions include:

[0161] (1) Fault Repair Guidance: The control cabinet automatically generates a "Visual Repair Guide" based on the fault tracing results. If the fault is determined to be "coupling misalignment", the guide will display "adjustment steps (loosen coupling bolts → measure coaxiality → adjust motor base shims → retighten), required tools (dial indicator, shims), and qualification standard (coaxiality ≤ 0.02 mm)". Maintenance personnel can shorten the repair time by following the guide.

[0162] (2) Health check before restart: After the repair is completed, perform "step-by-step health check". First, perform "static check", including valve action test, sensor calibration, insulation test, etc. Then perform "dynamic check", such as passing a small amount of steam to test the turbine rotation flexibility and motor idling to test vibration, etc. The machine can only be started after both checks are qualified to avoid secondary failures.

[0163] (3) Differentiated restart strategy: Develop differentiated restart procedures based on the type of fault. Mild fault recovery: Start directly from the "motor-only drive" stage, skipping some pre-start preparation steps, shortening the restart time to 15 minutes. Moderate fault recovery: Restart according to the "pre-start preparation → motor-only drive → turbine warm-up → dual drive integration" procedure. Severe fault recovery: Perform "full-process restart + key monitoring," collecting key parameters such as bearing temperature, vibration, and steam parameters every 5 minutes within 30 minutes after restarting. After confirming no abnormalities, gradually increase the load to the rated value.

[0164] IV. System Shutdown Phase Control: The requirements for this phase are "equipment protection, energy recovery, and convenient operation and maintenance". This embodiment uses technologies such as "load gradient reduction, hot maintenance, and intelligent operation and maintenance records" to achieve equipment shutdown without damage, while laying the foundation for the next startup.

[0165] 4.1 Pre-shutdown coordination preparation: To avoid impacting related systems during shutdown and to prepare for energy recovery during the shutdown process. Operational and monitoring actions include:

[0166] (1) Multi-system collaborative notification: Send a "shutdown notice" to the associated systems at least 20 minutes in advance.

[0167] Power grid system: If the motor is in feedback power supply mode, a "feedback power supply will stop in 15 minutes" will be announced in advance, and the power grid dispatch center will adjust the load distribution in advance to avoid power grid fluctuations.

[0168] Process system: Send "feed water pump shutdown notice" to deaerator and boiler system, so that the process system can adjust the production load in advance, such as reducing the boiler load by 10%, to reduce dependence on feed water.

[0169] Public works system: Send "shutdown notice" to circulating water and steam pipeline systems. Circulating water system reduces water supply pressure in advance, such as from 0.3MPa to 0.25MPa. Steam pipeline system adjusts steam distribution to other users in advance.

[0170] (2) Energy recovery preparation: 10 minutes before shutdown, if the turbine still has power output (e.g., N1=250kW), switch the motor to "short-time feedback power supply mode" and use the steam energy before shutdown to feed back electrical energy to the low-voltage power grid (e.g., 380V) in the plant area through the step-down transformer until the turbine power drops to 100kW, so as to recover as much electrical energy as possible.

[0171] (3) Shutdown parameter recording: Start the "Shutdown parameter snapshot" function to record key parameters 5 minutes before shutdown, such as turbine rotor temperature, bearing temperature, motor insulation resistance, pipeline stress, etc., and generate a "Shutdown status report". If abnormal parameters are found, such as the bearing temperature is still >60℃ when the shutdown is started, mark it as "key inspection item for the next startup".

[0172] 4.2 Load gradient reduction and power unit shutdown to avoid thermal shock and shaft damage caused by sudden load drops. Operational and monitoring actions include:

[0173] (1) Turbine load gradient reduction: Reduce turbine power at a rate of 10% load / 5min. Reduce from N1=300kW to 270kW (5 minutes), then to 240kW (5 minutes), until N1=100kW (minimum stable power), while monitoring turbine exhaust pressure (maintained at 0.15MPa absolute pressure) and rotor temperature reduction rate (allowed ≤3℃ / min). If the temperature drops too quickly, slow down the load reduction rate, such as changing it to 5% load / 5min, to avoid rotor cracks due to excessive temperature difference.

[0174] (2) Smooth transition of motor mode: When the turbine power drops to 100kW, the motor power is gradually increased to 215kW (315kW-100kW) to maintain stable feedwater pump load; when the turbine power drops to 80kW, the quick-closing main steam valve is closed, and the turbine speed is gradually reduced from 2980r / min to 0, taking 15-20 minutes. At the same time, the motor power is increased to 315kW, and the feedwater pump is driven independently during the transition phase.

[0175] (3) Safe transfer of feedwater pump load: After confirming that the process system has been switched to standby feedwater, the motor drives the feedwater pump to reduce the speed at a rate of "500r / min / 3min", from 2980r / min to 2480r / min (3 minutes), and then to 1980r / min (3 minutes) until the speed is 0. At the same time, the feedwater pump inlet valve is gradually closed to avoid pump body cavitation.

[0176] 4.3 Post-shutdown hot-state maintenance and media handling to prevent oxidation and corrosion and water accumulation in pipelines after equipment shutdown, thus extending equipment life. Operational and monitoring actions include:

[0177] (1) Hot maintenance of steam turbine.

[0178] Inert gas protection: After the turbine is shut down, when the rotor temperature drops to 150-200℃, nitrogen (purity ≥99.9%) is introduced into the turbine body until the internal pressure rises to 0.02MPa absolute pressure to prevent air from entering and causing oxidation and corrosion of the rotor and cylinder.

[0179] Waste heat utilization: The waste heat of the turbine body (temperature >100℃ after shutdown) is used to heat the lubricating oil through the built-in "waste heat circulation pipeline". The oil temperature is maintained at 40-45℃ to avoid the lubricating oil viscosity from increasing due to low temperature, which would lead to poor lubrication during the next startup.

[0180] (2) Intelligent processing of pipeline media.

[0181] Steam pipeline venting: Open the vent valves of the main steam pipeline and the back pressure steam pipeline to release the residual steam to the atmosphere. At the same time, monitor the cooling rate of the pipeline through the pipeline temperature sensor (allowed ≤5℃ / min). If the cooling is too fast, close part of the vent valve to slow down the cooling.

[0182] Complete drainage: Open all valves in the drainage pipeline and simultaneously introduce a small amount of compressed air (0.2MPa gauge pressure) into the pipeline to purge any residual condensate in the pipeline, preventing water accumulation that could lead to pipeline corrosion. Continue until the drainage outlet temperature drops below 50℃, then close all drainage valves.

[0183] Cooling water pipeline maintenance: Drain the circulating water in the cooling water pipeline and inject "rust-preventive and antifreeze" (concentration 20% to prevent the pipeline from freezing and cracking in winter or rusting due to long-term shutdown. Before the next start-up, simply drain the antifreeze.

[0184] 4.4 Intelligent operation and maintenance records and next startup suggestions provide data support for subsequent operation and maintenance and startup, realizing "predictive maintenance," including:

[0185] (1) Operation and maintenance data generation: The control cabinet automatically generates a "downtime operation and maintenance report", including:

[0186] (a) Operation statistics: duration of this operation (e.g., 720 hours), amount of waste heat steam recovered (e.g., 12000t), amount of electricity fed back by the motor (e.g., 5000kWh), number of equipment failures (e.g., 0 times).

[0187] (b) Condition assessment of vulnerable parts: Based on the bearing operating time (720 hours) and temperature profile, assess the remaining bearing life (e.g., 5000 hours of operation remaining); based on the number of valve actions (e.g., 12 quick-closing main steam valve actions), recommend replacing valve seals during the next overhaul.

[0188] (c) Energy consumption analysis: Compare the designed energy consumption with the actual energy consumption to analyze the energy saving potential. For example, the actual steam utilization rate is 92%, while the design rate is 90%, resulting in an energy saving of 2%.

[0189] (2) Optimization suggestions for the next startup: Generate an "optimization plan for the next startup" based on the parameters of this shutdown and historical data. For example, if the warm-up time was 43 minutes this time and the historical average was 45 minutes, it is recommended to shorten the medium-speed warm-up stage by 2 minutes during the next startup; if the insufficient steam condition occurred 3 times this time, it is recommended to coordinate the stability parameters of the steam pipeline network before the next startup.

[0190] (3) Data upload and sharing: Upload the “Stop Operation and Maintenance Report” and “Next Startup Suggestion” to the plant’s MES system (Manufacturing Execution System) to achieve data sharing with equipment management, production scheduling and other departments, which facilitates the formulation of overall operation and maintenance plans.

[0191] This embodiment solves the problems of "slow response, weak fault tolerance, insufficient energy utilization, and complex operation and maintenance" of traditional control methods through multi-dimensional technological innovation, and realizes the "intelligent, efficient and highly reliable" operation of the dual-drive feedwater pump unit, which can meet the dual needs of industrial enterprises for waste heat recovery and stable operation of core equipment.

[0192] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A waste heat recovery system with dual steam and electric drive for feedwater pumps, characterized in that, Includes a dual-drive power unit, a steam-water circulation subsystem, and a control and monitoring subsystem; The dual-drive power unit includes a waste heat drive turbine, a first flexible coupling, a double-shaft three-phase asynchronous motor, a second flexible coupling, and a feedwater pump arranged in series. The waste heat drive turbine and the double-shaft three-phase asynchronous motor can drive the feedwater pump individually or in combination. The steam-water circulation subsystem includes a main steam pipeline, a steam seal steam pipeline, a back pressure steam pipeline, a drain pipeline, and a cooling water pipeline. The main steam pipeline connects the waste heat steam header to the inlet of the waste heat-driven steam turbine. The back pressure steam pipeline connects the exhaust outlet of the waste heat-driven steam turbine to the low-grade heat user. The drain pipeline collects drain water from multiple nodes and achieves qualified drain water recovery. The cooling water pipeline provides a cooling medium for the dual-drive power unit. The control and monitoring subsystem includes a control cabinet, an automatic power adjustment module, and a monitoring sensor group. The control cabinet includes a PLC and a human-machine interface. The automatic power adjustment module dynamically allocates the power of the dual-drive power unit according to the steam conditions. The operating conditions include sufficient steam, insufficient steam, and critical combined operating conditions. The monitoring sensor group includes pressure sensors, temperature sensors, flow sensors, speed and vibration sensors, and special sensors. The special sensors include steam quality monitoring sensors and pipeline stress monitoring sensors.

2. The waste heat utilization steam-electric dual-drive feedwater pump unit system according to claim 1, characterized in that, The motor insulation status monitoring module is installed inside the dual-shaft three-phase asynchronous motor. The outer casing of the dual-shaft three-phase asynchronous motor is equipped with a spray cooling interface. The power circuit of the dual-shaft three-phase asynchronous motor is equipped with a battery energy storage auxiliary module, which can operate in drive or power generation mode.

3. The waste heat utilization steam-electric dual-drive feedwater pump unit system according to claim 1, characterized in that, The main steam pipeline is equipped with a steam header accumulator for steam buffering, a quick-closing main steam valve, an electric regulating valve, a steam quality monitoring sensor for monitoring humidity and particle size, a steam dryer for when humidity exceeds the standard, and a steam pretreatment system for when particle size exceeds the standard. The back pressure steam pipeline is equipped with a heat user priority allocation module at the end, which prioritizes the preheating flow to the deaerator, and the remaining steam is introduced into the waste heat boiler feed water preheater. The drainage pipeline is equipped with a condensate recovery judgment module, which connects the deaerator water tank and the drainage ditch; when the drainage is qualified, it is introduced into the deaerator water tank, and when it is unqualified, it is drained into the drainage ditch.

4. The waste heat utilization steam-electric dual-drive feedwater pump unit system according to claim 1, characterized in that, It also includes an auxiliary support subsystem, which includes a radial sliding bearing, a lubrication system, a bellows compensator and leakage monitoring components, an industrial circulating water interface and an auxiliary cooling component; the lubrication system is equipped with an electric heating and cooling function module for heating and cooling the oil temperature; and a leakage sensor is attached to the outer wall of the bellows compensator.

5. A control method for a waste heat utilization steam-electric dual-drive feedwater pump unit, characterized in that, The waste heat utilization steam-electric dual-drive feedwater pump unit system according to any one of claims 1-4 includes start-up phase control, normal operation phase control, abnormal operating condition fault-tolerant control and shutdown phase control. The startup phase control includes intelligent pre-diagnosis and parameter adaptation verification before startup, soft start and load pre-adaptation control of motor, adaptive thermal stress regulation warm-up of steam turbine, and flexible connection between steam turbine and dual drive system. The normal operation phase control includes multi-parameter fusion for condition prediction and dynamic monitoring, power adjustment for different operating conditions, and intelligent linkage optimization of auxiliary systems; The abnormal operating condition fault tolerance control includes anomaly identification and accurate source tracing, multi-dimensional hierarchical fault tolerance, and intelligent fault recovery and restart; The shutdown phase control includes pre-shutdown collaborative preparation, load gradient reduction and power unit shutdown, post-shutdown hot maintenance and media handling, intelligent operation and maintenance records, and next startup suggestions.

6. The control method according to claim 5, characterized in that, The pre-start intelligent pre-diagnosis and parameter adaptation verification includes: generating a pre-diagnosis report by combining historical data and real-time sensor signals with a fault tree algorithm; predicting future steam parameters and linking the steam header energy storage tank with a neural network; and performing online dynamic calibration of the sensors. The motor soft starter uses a thyristor voltage regulation soft starter, with the voltage gradually increasing to the rated voltage; the water pump operates in a stepped speed increase and load preload mode. The turbine adaptive thermal stress control warm-up includes: gradually increasing the pressure after preheating the steam seal temperature; warming up in three stages based on the real-time thermal stress of the rotor and cylinder at low speed, medium speed, and rated parameters; and automatic drainage of the condensate pipe according to temperature and flow rate.

7. The control method according to claim 5, characterized in that, The multi-parameter fusion-based operating condition prediction adopts a neural network model, taking main steam flow, pressure, temperature and dual drive power as inputs, and outputting future operating condition prediction results; the dynamic monitoring includes monitoring steam quality, motor insulation, pipeline stress, turning on the dryer when steam humidity exceeds the standard, issuing an early warning when motor insulation resistance exceeds the standard, and adjusting the corrugated compensator when pipeline stress exceeds the standard.

8. The control method according to claim 5, characterized in that, The anomaly identification and precise source tracing include: constructing an anomaly feature library and identifying anomalies through parameter matching; using vibration spectrum analysis and parameter correlation analysis for source tracing, and determining whether the coupling is misaligned or the bearing is worn based on vibration spectrum analysis; the anomalies include mild anomalies with a single auxiliary parameter exceeding the standard, moderate anomalies with a slight exceedance of the main parameter, and severe anomalies with a serious exceedance of the main parameter; The multi-dimensional hierarchical fault tolerance includes: adaptive parameter fine-tuning and trend suppression for mild anomalies; steam system depressurization, smooth switching of power modes, and three-stage cooling of auxiliary systems for moderate anomalies; and emergency shutdown, multi-path depressurization, and cross-system linkage for severe anomalies.

9. The control method according to claim 5, characterized in that, The pre-shutdown collaborative preparation includes: sending a shutdown notice to the power grid, process, and utilities system in advance; if the turbine has power output before shutdown, switching the motor to short-time feedback power supply mode; and recording key parameters before shutdown to generate a shutdown status report. The load gradient reduction and power unit shutdown include: the turbine reducing the load in steps and the motor gradually replenishing the energy; after closing the quick-closing main steam valve, the turbine speed is reduced to zero, the motor drives the feedwater pump to gradually reduce the speed to zero, and the feedwater pump inlet valve is closed simultaneously. The post-shutdown hot maintenance includes: introducing high-purity nitrogen for oxidation prevention into the steam turbine and pipeline treatment, which includes purging residual steam from the steam pipeline, purging the drainage pipeline with compressed air, and injecting anti-rust and antifreeze fluid into the cooling water pipeline.

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