A desulfurization system centrifugal oxidation fan device with self-power generation protection and magnetic suspension bearing

Abstract

The application discloses a desulfurization system centrifugal oxidation fan device with self-power generation protection and magnetic suspension bearing, relates to the technical field of flue gas desulfurization, and comprises a rotor kinetic energy recovery system containing a permanent magnet power generation winding and a super capacitor module integrated in a main shaft, which continuously generates power and stores energy during normal operation; a process state sensing and communication module is connected with a desulfurization DCS system and acquires parameters such as a desulfurization tower inlet in real time; an intelligent power-off protection strategy decision module calculates the above parameters, pregenerates a suspension protection strategy, a controlled landing strategy or a mixed strategy; a power-off detection and execution unit calls the pregenerated strategy when the power grid is powered off, controls a power supply switching unit and the rotor kinetic energy recovery system to execute corresponding suspension maintenance or controlled landing actions. The application realizes real-time quantitative matching of the power-off protection strategy and the desulfurization process state, and ensures reliable energy supply for power-off protection through full-time self-power generation and energy storage.

Description

Technical Field

[0001] This invention relates to the field of flue gas desulfurization technology, specifically to a centrifugal oxidation fan device for a desulfurization system with self-generating protection and magnetic levitation bearings. Background Technology

[0002] Magnetic levitation centrifugal oxidation fans are key equipment in wet desulfurization systems, oxidizing calcium sulfite into calcium sulfate by supplying oxidizing air into the desulfurization tower. The magnetic levitation bearings keep the rotor completely suspended during high-speed rotation, eliminating mechanical contact. However, since the levitation force of the magnetic levitation bearings depends on a continuous power supply, a power outage will cause the high-speed rotating rotor to lose its levitation support and fall onto the protective bearings, resulting in severe impact and wear, potentially leading to equipment damage. Therefore, power failure protection technology is the core guarantee for the safe operation of magnetic levitation fans.

[0003] In the prior art, invention patent publication number CN110417334A discloses a kinetic energy feedback voltage interruption protection system for a magnetic levitation bearing. After a power outage, the motor switches from motoring to generating mode, feeding back the kinetic energy of the rotor rotation as electrical energy to supply the displacement controller to maintain bearing levitation. Another invention patent publication number CN117072558B discloses an energy feedback device, method, and magnetic levitation system for a magnetic levitation bearing system, which switches between different paths based on changes in bearing voltage to extend the levitation working time after a power outage. A common feature of these solutions is that the power outage protection action is initiated only after a power grid outage occurs, and a fixed protection program is executed, independent of the actual operating conditions of the desulfurization system.

[0004] However, the process status of the desulfurization system is dynamic: under full-load operation and high inlet SO2 concentration, a shutdown of the oxidation blower for even a few minutes can lead to excessive SO2 emissions; while under low-load operation or during system start-up and shutdown, a short-term shutdown of the blower has a relatively small impact on desulfurization efficiency. Existing power-off protection schemes completely fail to detect process parameters reflecting the urgency of the desulfurization reaction, such as the SO2 concentration at the desulfurization tower inlet, slurry pH value, and the operating status of the slurry circulation pump. This results in a mismatch between protection actions and process requirements, failing to secure a longer suspension recovery time window during critical periods of the desulfurization reaction, and failing to prioritize equipment landing safety when the system can be temporarily shut down. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a centrifugal oxidation fan device for a desulfurization system with self-generating protection and magnetic levitation bearings. By sensing the desulfurization process parameters in real time and generating matching strategies for maintaining suspension or controlling landing in advance, and by using the permanent magnet power generation winding integrated into the main shaft to achieve all-time self-generated energy storage, it can dynamically select to extend suspension or achieve controlled soft landing according to the urgency of the desulfurization reaction when the power grid fails. This achieves quantitative matching between the protection strategy and process requirements and ensures independent and reliable energy supply for power failure protection.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a centrifugal oxidation fan device for a desulfurization system with self-generating protection and magnetic levitation bearings, the device comprising: The main body of the magnetic levitation centrifugal oxidation fan includes a main shaft, impeller, magnetic levitation bearing and high-speed motor; The rotor kinetic energy recovery system includes a permanent magnet power generation winding, a rectifier module and a supercapacitor module integrated into the main shaft. When the rotor rotates normally, the permanent magnet power generation winding generates induced electrical energy to charge the supercapacitor module, thus forming a self-generated energy storage system in the non-power-off state. The power switching unit has its input end connected to the mains power supply, the supercapacitor module and the kinetic energy feedback circuit, and its output end connected to the magnetic levitation bearing controller. The process status sensing and communication module connects to the desulfurization DCS system via industrial Ethernet to receive desulfurization process parameters, including SO2 concentration at the desulfurization tower inlet, slurry pH value, slurry circulation pump operating status, and desulfurization system operating mode. The intelligent power failure protection strategy decision module is connected to the process status sensing and communication module. When the power grid is supplying power normally, it generates and stores a power failure protection strategy in advance based on the desulfurization process parameters. The power failure protection strategy includes a suspension maintenance strategy for extending suspension and a landing control strategy for controlling deceleration. The power failure detection and execution unit calls a pre-generated power failure protection strategy when it detects a power failure in the power grid, and controls the power switching unit and the rotor kinetic energy recovery system to perform the corresponding levitation maintenance action or controlled landing action.

[0007] Furthermore, the intelligent power failure protection strategy decision module calculates the desulfurization reaction urgency index and system interruptibility index based on the SO2 concentration at the desulfurization tower inlet, the slurry pH value, the slurry circulation pump operating status, and the desulfurization system operating mode. When the desulfurization reaction urgency index is ≥70 and the system interruptibility index is ≤30, a suspension retention strategy is generated. When the desulfurization reaction urgency index is ≤40 and the system interruptibility index is ≥70, a controlled fall strategy is generated, thereby establishing a quantitative mapping relationship between the protection strategy and the real-time process status of the desulfurization system. The process status sensing and communication module also receives the liquid level of the desulfurization tower.

[0008] Furthermore, the intelligent power failure protection strategy decision module is also configured as follows: When the desulfurization reaction urgency index and the system interruptibility index do not meet the conditions for generating the suspension-maintaining strategy and the conditions for generating the fall-controlled strategy, a hybrid strategy is generated. The hybrid strategy involves first maintaining rotor levitation for 1.5s-2.5s. If power is not restored during the levitation period, the system switches to controlled deceleration and landing, thus balancing levitation maintenance and soft landing protection when the process is in the intermediate region.

[0009] Furthermore, the desulfurization reaction urgency index RUI is calculated using the following formula: In the formula, This refers to the SO2 concentration at the inlet of the desulfurization tower, expressed in mg / Nm³. To preset the upper limit of SO2 concentration, To preset the optimal pH value, The maximum allowable pH deviation; This is the operating status factor of the slurry circulation pump. It is set to 100 when all circulation pumps are running normally, 50 when some are running, and 0 when all are stopped. , , These are the weighting coefficients. , , .

[0010] Furthermore, the system interruptibility index SII is calculated using the following formula: In the formula, M is the quantitative value of the desulfurization system operation mode, which is 0 for full load operation, 30 for low load operation, 70 for start-up and shutdown, and 100 for maintenance. L is the liquid level in the desulfurization tower. The highest liquid level in the desulfurization tower is represented by H, which is the historical shutdown impact factor. If there has been a recent shutdown, take 0; otherwise, take 100. , , These are the weighting coefficients. , , .

[0011] Furthermore, the suspension maintenance strategy includes: a target suspension time of ≥3s, a kinetic energy recovery voltage set to 95%-100% of the rated value, and a supercapacitor module allowed to discharge to a depth of 80%, in order to maximize the rotor suspension time during the critical period of desulfurization reaction and gain a time window for power restoration or backup fan startup.

[0012] Furthermore, the controlled landing strategy includes: target hover time ≤ 1s, kinetic energy recovery voltage set to 60%-80% of the rated value, and priority use of supercapacitor module power for active deceleration control, so as to prioritize the controlled soft landing of the rotor under the condition that the desulfurization system can be shut down for a short time.

[0013] Furthermore, the rotor levitation time in the hybrid strategy is 1.5s-2.5s, and if the power grid is detected to be restored during the levitation period, the power failure protection is exited, thereby avoiding unnecessary landing procedures during instantaneous power grid fluctuations.

[0014] Furthermore, the permanent magnet power generation winding includes an annular permanent magnet embedded in the rotor shaft surface and an induction coil arranged on the stator side. The permanent magnet power generation winding shares a magnetic circuit with the electromagnetic coil of the magnetic levitation bearing, so as to achieve self-generated energy storage without increasing the axial dimension of the rotor.

[0015] Furthermore, the intelligent power-off protection strategy decision module is also configured to: when communication with the desulfurization DCS system is interrupted, adopt a preset fixed power-off protection strategy to replace the power-off protection strategy pre-generated according to the desulfurization process parameters, so as to ensure that the power-off protection function does not fail under communication failure conditions.

[0016] Compared with existing technologies, this centrifugal oxidation fan device for desulfurization systems, featuring self-generating protection and magnetic levitation bearings, has the following advantages: I. This invention acquires process parameters such as sulfur dioxide concentration at the desulfurization tower inlet, slurry pH value, slurry circulation pump operating status, and desulfurization system operating mode in real time. While the power grid is supplying power normally, a power outage protection strategy matching the urgency of the desulfurization reaction is pre-generated. This ensures that the selection of protection actions is no longer a fixed procedure disconnected from process requirements, but rather dynamically determined based on the real-time urgency of the desulfurization reaction and the system's interruptibility. When desulfurization is under high-load critical conditions, a suspension-maintaining strategy is implemented to maximize the rotor's suspension time, providing a window for power restoration and preventing sulfur dioxide emissions from exceeding standards due to oxidation air interruption. When desulfurization is under low load or during start-up / shutdown phases, a controlled landing strategy is implemented to prioritize a controlled soft landing of the rotor, reducing the risk of impact damage to the protective bearings. This achieves quantitative adaptation of the power outage protection strategy to the desulfurization process state, solving the problem of insufficient or excessive protection caused by mismatches between protection actions and process requirements in existing solutions. This significantly improves the operational reliability and process adaptability of the magnetic levitation centrifugal oxidation fan in wet desulfurization systems.

[0017] II. This invention integrates a permanent magnet power generation winding on the main shaft of a magnetic levitation centrifugal oxidation fan. During normal rotor rotation, this winding continuously generates induced electrical energy and charges the supercapacitor module, creating a self-generating energy storage circuit completely independent of the power grid. This energy storage method does not rely on activation after a power outage but continuously stores energy throughout the system's operation, ensuring the supercapacitor module is always fully charged and ready. In the event of a power outage, the supercapacitor module can immediately provide power, working in conjunction with the rotor kinetic energy feedback circuit to provide the necessary electrical energy for maintaining levitation or controlled descent of the magnetic levitation bearing. This eliminates the risk of protection failure due to insufficient energy storage during a power outage. Furthermore, the self-generating winding shares a magnetic circuit with the electromagnetic coil of the magnetic levitation bearing, achieving the above functions without increasing the rotor's axial dimensions, thus maintaining the compactness of the fan's structure. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0019] Figure 1 This is a block diagram of the device components of the present invention; Figure 2 A flowchart for generating the strategy of this invention; Figure 3 This is a flowchart illustrating the power-off protection process of the present invention. Detailed Implementation

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

[0021] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0022] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, the technical features involved in the different embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0023] This embodiment provides a centrifugal oxidation fan device for a desulfurization system with self-generating power protection and magnetic levitation bearings. By real-time sensing of the desulfurization process status, a power outage protection strategy adapted to the urgency of the desulfurization reaction is pre-generated before a power outage occurs. In the event of a power outage, this strategy achieves the dual protection objectives of extending the rotor levitation time or ensuring a safe landing of the rotor. The overall composition of the device is as follows: Figure 1 As shown, refer to Figure 1 The device includes a magnetic levitation centrifugal oxidation fan body, a rotor kinetic energy recovery system, a power switching unit, a process status sensing and communication module, an intelligent power failure protection strategy decision module, and a power failure detection and execution unit.

[0024] The magnetic levitation centrifugal oxidation fan body includes a main shaft, an impeller mounted at one end of the main shaft, magnetic levitation bearings for radial and axial support of the main shaft, and a high-speed motor driving the main shaft to rotate. The stator windings of the high-speed motor are powered by a frequency converter, and the rotor adopts a permanent magnet structure. The magnetic levitation bearings include radial and axial magnetic levitation bearings. Its controller receives the main shaft position signal detected by the displacement sensor and adjusts the current in the electromagnetic coil to keep the main shaft in a suspended state without mechanical contact. During normal operation, the levitation force of the magnetic levitation bearings depends entirely on the continuous power supply.

[0025] The rotor kinetic energy recovery system continuously converts and stores a portion of the rotor's kinetic energy into electrical energy during rotation, forming a self-generating energy storage system in non-power-out conditions. This system includes a permanent magnet generator winding integrated into the main shaft, a rectifier module, and a supercapacitor module. During normal rotor rotation, the permanent magnet generator winding generates an induced electromotive force due to the relative motion between the permanent magnets on the rotor and the stator-side induction coils. The output AC power is converted to DC power by the rectifier module and then charges the supercapacitor module. The supercapacitor module consists of multiple supercapacitor cells connected in series and parallel, possessing rapid charging and discharging capabilities and a long cycle life. During normal grid power supply, the supercapacitor module is continuously charged to a preset voltage, serving as an independent power source during power outage protection.

[0026] Specifically, the permanent magnet power generation winding uses a ring-shaped permanent magnet embedded in the rotor shaft surface, while induction coils are arranged on the stator side. This integration allows the permanent magnet power generation winding and the electromagnetic coils of the magnetic levitation bearing to share a portion of the magnetic circuit. That is, in the same axial region on the rotor shaft surface, there exists both a bias magnetic field for generating levitation force and an induction coil for power generation. The magnetic field provided by the ring-shaped permanent magnet is utilized by both the levitation coil and the power generation coil. When the rotor rotates, the rotating magnetic field generated by the ring-shaped permanent magnet induces an electromotive force in the power generation coil. Because the power generation winding and the levitation electromagnetic coil are structurally integrated and share axial space, the axial dimension of the rotor does not increase due to the addition of the power generation function. The rectifier module uses a three-phase bridge rectifier circuit to rectify the three-phase AC power output from the induction coil into DC power. The supercapacitor module is equipped with a voltage equalization protection circuit and a voltage monitoring circuit to ensure that the voltage of each individual capacitor is consistent and to prevent overcharging.

[0027] The power switching unit has multiple input terminals and at least one output terminal. Its input terminals are connected to the rectified DC bus of the mains power supply, the output terminal of the supercapacitor module, and the output terminal of the kinetic energy feedback circuit. The kinetic energy feedback circuit can switch the high-speed motor to generator mode after a power outage, utilizing the residual kinetic energy of the rotor to generate electrical energy. The output terminal of the power switching unit is connected to the magnetic levitation bearing controller to provide operating power to the magnetic levitation bearing. The power switching unit is internally composed of power semiconductor switching devices, such as low on-resistance MOSFETs or insulated-gate bipolar transistors, enabling microsecond-level power path switching. The switching control signal comes from the power outage detection and execution unit.

[0028] The process status sensing and communication module serves as the data interface between the unit and the external desulfurization distributed control system (DCS). This module communicates with the desulfurization DCS system in real time via industrial Ethernet protocols, such as PROFINET or Modbus TCP. The desulfurization process parameters received by the module from the DCS system include: sulfur dioxide concentration in the flue gas at the desulfurization tower inlet, pH value of the slurry inside the desulfurization tower, operating status signal of the slurry circulation pump, and operating mode signal of the desulfurization system. The operating mode signal indicates whether the system is currently operating at full load, low load, in a start-up / shutdown phase, or under maintenance. In addition, the module also receives the desulfurization tower liquid level signal. All received process parameters are continuously updated and transmitted to the intelligent power failure protection strategy decision module.

[0029] The intelligent power-down protection strategy decision module is the core computing unit of this device. It can be implemented by an independent embedded microcontroller, such as a microprocessor based on an ARM Cortex-M7 core, or by a programmable gate array (FPGA) combined with a soft-core processor. When the power grid is supplying power normally, this module calculates the desulfurization reaction urgency index and the system interruptibility index in real time based on the desulfurization process parameters obtained from the process status sensing and communication module. It then pre-generates a power-down protection strategy based on the combination of these two indices, storing the strategy type and corresponding control parameters in non-volatile memory for the power-down detection and execution unit to recall during a power outage. Since the strategy generation is completed before the power outage, no complex calculations are required at the moment of power failure, allowing for immediate execution of protection actions and shortening the response delay.

[0030] The workflow of the intelligent power failure protection strategy decision module is illustrated as follows: Figure 2 As shown, refer to Figure 2 After the system is powered on, the module enters a cyclic execution state. At the beginning of each operation cycle, it first obtains the latest desulfurization process parameters through the process status sensing and communication module, including the sulfur dioxide concentration at the desulfurization tower inlet, the slurry pH value, the slurry circulation pump operating status, the desulfurization system operating mode, and the desulfurization tower liquid level. Next, it checks whether the communication is normal. If communication with the DCS is interrupted, the currently acquired process data is discarded, and a preset fixed power-off protection strategy is adopted. This fixed strategy is a conservative hybrid strategy, that is, the rotor is first kept suspended for 2 seconds. If the power supply is not restored within 2 seconds, it switches to controlled deceleration and landing to ensure that the power-off protection function does not fail under the condition of communication failure, and to avoid equipment damage. If the communication is normal, exponential calculation is performed.

[0031] The Desulfurization Reaction Urgency Index (RUI) reflects the urgency of the impact of the current oxidation air interruption on desulfurization efficiency. This index is calculated according to formula (1): In the formula, The sulfur dioxide concentration at the inlet of the desulfurization tower is obtained in real time, in units of... ; This is a preset upper limit for sulfur dioxide concentration, which is determined based on the maximum concentration at the design inlet of the desulfurization system. For example, it can be taken as... ; The pH value of the desulfurization tower slurry is obtained in real time; The preset optimal pH value is usually between 5.2 and 5.8; This is the absolute value of the maximum allowable pH deviation, for example, it can be 1.0; The slurry circulation pump operating status factor is set to 100 when all slurry circulation pumps in the desulfurization system are operating normally, 50 when some pumps are operating and some are shut down, and 0 when all circulation pumps are shut down; weighting coefficient. , , .

[0032] The System Interruptionability Index (SII) reflects the extent to which the current desulfurization system allows for short-term shutdown of the oxidation blower. This index is calculated according to formula (2): In the formula, M is the quantified value of the desulfurization system operation mode. The quantification rules for the operation mode are: 0 for full load operation, 30 for low load operation, 70 for start-up and shutdown, and 100 for maintenance; L is the real-time liquid level of the desulfurization tower; The maximum liquid level designed for the desulfurization tower; H is the historical outage impact factor, determined based on whether the desulfurization system has experienced any unplanned outages recently. If, for example, within the past 72 hours, the desulfurization system has experienced an outage due to an interruption of oxidation air, then H is set to 0; if there are no recent outage records, then H is set to 100; weighting coefficients. , , .

[0033] Both indices are calculated using a normalization approach, ensuring the final values ​​fall within the range of 0 to 100, facilitating threshold comparisons. After calculation, the module will determine and generate corresponding strategies based on the indices.

[0034] When the desulfurization reaction urgency index RUI ≥ 70 and the system interruptibility index SII ≤ 30, it indicates that the oxidation reaction in the desulfurization tower is very active, the sulfur dioxide concentration is high, the slurry pH deviates from the optimal value, and the circulating pump is fully operational, the system is under high load and full power generation. If the oxidation air is interrupted, emissions will quickly exceed standards. At this time, a suspension maintenance strategy is generated. The control parameters for the suspension maintenance strategy are set as follows: the target suspension time is not less than... The kinetic energy recovery voltage is set to 95%-100% of its rated value, and the supercapacitor module is allowed to discharge to a depth of 80%. The goal of this strategy is to maximize the levitation time of the magnetic levitation rotor after a power outage, providing at least a 3-second window for grid power restoration or the start-up of the backup oxidation fan. Since ensuring the uninterrupted desulfurization reaction is paramount at this time, the strategy allows for deep discharge of the supercapacitor, even if it may affect some subsequent energy supply.

[0035] When the desulfurization reaction urgency index RUI ≤ 40 and the system interruptibility index SII ≥ 70, it indicates that the desulfurization system is in a low-load or start-up / shutdown phase, the slurry circulation pump may be partially shut down, and the process has a high tolerance for oxidation air interruption. At this time, a controlled landing strategy is generated. The control parameters for the controlled landing strategy are set as follows: target suspension time no greater than 1 second, kinetic energy recovery voltage set to 60%-80% of the rated value, and priority is given to using the power energy of the supercapacitor module for active deceleration control. The core objective of this strategy is not to maintain suspension after a power outage, but to use limited energy storage to apply a controllable electromagnetic braking torque to the high-speed rotating rotor, causing it to decelerate in a short time and reduce the speed to a low value before the protective bearing contacts, ultimately achieving a soft landing. Since the landing process requires energy for braking, suspension is maintained for only a very short time to ensure a smooth transition to the landing procedure.

[0036] When the desulfurization reaction urgency index and system interruptibility index do not meet the conditions for explicitly generating either a suspension-maintaining strategy or a controlled landing strategy, the system is in an intermediate transition state, and the module generates a hybrid strategy. The action sequence of the hybrid strategy is as follows: after a power outage, the rotor is first maintained in suspension for 1.5s to 2.5s, for example, preferably set to 2s; if the grid power supply is restored during the suspension maintenance period, the power outage protection is immediately exited, and normal suspension control is restored to avoid unnecessary landing procedures due to instantaneous grid fluctuations; if the power supply has not been restored by the end of the suspension maintenance time, the system switches to controlled deceleration landing, and subsequent actions are the same as the controlled landing logic in the controlled landing strategy. The hybrid strategy takes into account both suspension maintenance and soft landing requirements.

[0037] Each newly calculated power-down protection strategy type, along with its corresponding threshold, time, and voltage parameters, is stored in a shared register or dual-port random access memory accessible by the power-down detection and execution unit for high-speed retrieval during power-down.

[0038] The power failure detection and execution unit is responsible for monitoring the power grid status in real time and immediately executing pre-stored strategies when a power failure occurs. For example... Figure 3 As shown, this unit detects the AC or DC bus voltage of the input grid power supply through a voltage comparison circuit. When the voltage drops below 85% of the rated value and persists for more than 1 ms, it is determined to be a grid power outage event. Once a power outage is determined, the unit reads the pre-generated strategy identifier and control parameters from the storage area of ​​the intelligent power failure protection strategy decision module within microseconds, and then outputs a control signal according to the strategy type.

[0039] If the read strategy is a levitation-preserving strategy, the power failure detection and execution unit performs the following sequence of actions. First, the control power switching unit instantly switches the power source of the magnetic levitation bearing controller from the grid power supply to the supercapacitor module. Simultaneously, a command is issued to put the high-speed motor drive circuit into kinetic energy feedback generation mode. The electrical energy output from the motor windings is rectified by the feedback circuit and replenished to the power supply bus of the magnetic levitation bearing controller. The kinetic energy recovery voltage is set to 95%-100% of the rated value to ensure the stable voltage required for levitation. In this mode, the supercapacitor module provides the main power supply, but its voltage is allowed to continuously decrease until the depth of discharge reaches 80%. By coordinating the supercapacitor energy storage and rotor kinetic energy feedback, efforts are made to ensure that the rotor maintains complete levitation for at least 3 seconds. If the grid power supply is restored during this period, the power switching unit seamlessly switches back to grid power, the motor exits the feedback mode, and the system resumes normal operation. If the grid power supply has not been restored after 3 seconds, the supercapacitor's charge is nearly depleted, and the rotor speed decreases due to kinetic energy extraction. The magnetic levitation bearing will be unable to maintain levitation due to insufficient energy, and the rotor will begin to fall towards the protective bearing. However, since the rotor speed had already been reduced, the impact energy of the drop was significantly reduced compared to a direct high-speed drop.

[0040] If the read strategy is a controlled landing strategy, the action sequence is completely different. The power failure detection and execution unit will still briefly switch the power supply to the supercapacitor module, maintaining levitation for no more than 1 second. This brief levitation serves as a buffer for system state switching. Subsequently, the control power switching unit will primarily allocate the output of the supercapacitor module to the active deceleration control circuit. The active deceleration control applies an electromagnetic force opposite to the rotor's rotation direction through a portion of the coils of the magnetic levitation bearing or a dedicated braking winding, causing the rotor speed to decrease rapidly. The kinetic energy recovery voltage is set at 60%-80% of its rated value to limit the extraction of regenerative energy and prevent overcurrent in the coils due to excessive rotor deceleration. The supercapacitor's energy storage is used cautiously, mainly for powering the control circuits during braking and supplementing a small amount of braking energy. Throughout the landing process, the displacement sensor continuously monitors the rotor position. Once the rotor's radial displacement exceeds the safe range, the protective bearing will act as the final support to support the rotor. Since the rotor speed has been significantly reduced at this point, the impact force and wear on the protective bearing are minimal, achieving a controlled soft landing.

[0041] If the read strategy is a hybrid strategy, the power failure detection and execution unit first performs the same actions as the initial stage of the levitation maintenance strategy, that is, switching to a combination of supercapacitor and kinetic energy feedback to maintain levitation, with the levitation maintenance time set to 2 seconds. During this period, the power grid recovery detection circuit remains operational. If the power grid voltage is detected to return to normal within 2 seconds, the power failure procedure is exited, and normal operation is restored. If the power grid does not recover within 2 seconds, the system automatically switches to the controlled descent procedure, and subsequent actions are completely consistent with the controlled descent strategy.

[0042] To ensure the reliability of self-generated energy storage, the power output of the permanent magnet winding during normal rotor rotation is designed to be slightly higher than the sum of the standby power consumption of the magnetic levitation bearing controller and the power consumption of the strategy decision module, for example, 20%, to ensure a continuous net charging power supply to the supercapacitor module. During rotor acceleration from zero to rated speed, the output voltage of the permanent magnet winding increases with the rotational speed. A boost or buck voltage regulator circuit is provided after the rectifier module to ensure stable charging of the supercapacitor module when the rotational speed reaches more than 30% of the rated speed. During long-term operation, the supercapacitor module's voltage remains fully charged. Once a small leakage current loss is compensated, the module enters standby mode. This self-generated energy storage mechanism is completely independent of the power grid. Even if the power grid remains operational for an extended period, the supercapacitor still has energy reserves, completely avoiding the risk of protection failure due to the supercapacitor not being charged during a power outage.

[0043] Regarding the communication interface, the data refresh cycle between the process status sensing and communication module and the DCS system is set to 200ms, which is a typical value that balances data real-time performance and communication load. Sulfur dioxide concentration data at the desulfurization tower inlet comes from the continuous flue gas monitoring system, slurry pH value comes from the pH meter inside the tower, slurry circulation pump operating status is acquired through feedback contacts in the motor control center, and the desulfurization system operating mode is given by the DCS logic configuration. These signals have been filtered and converted to engineering units within the DCS and can be directly read via Ethernet.

[0044] The calculation cycle of the intelligent power-down protection strategy decision module is set to be the same as the data refresh cycle, i.e., a strategy update is performed every 200ms. When process parameters fluctuate slightly, the index value will change accordingly, but as long as it does not cross threshold boundaries such as 70, 40, and 30, the strategy type will not switch frequently. This is achieved by setting a small hysteresis interval near the threshold to avoid strategy oscillation. For example, when RUI fluctuates around 70, hysteresis comparison is used. Switching from the suspension-maintaining strategy to the non-suspension-maintaining strategy requires RUI to drop below 68, while switching back to the suspension-maintaining strategy requires RUI to rise above 72. This process ensures the stability of the control system.

[0045] It should also be noted that the magnetic levitation bearing in this device can be an active electromagnetic bearing, and its controller adopts a current control method based on a digital signal processor. Isolation measures are taken for both the power switching unit and the kinetic energy feedback circuit to prevent high-voltage feedback from interfering with the control circuit. The number of turns of the induction coil and the air gap of the magnetic circuit in the permanent magnet generator winding of the rotor kinetic energy recovery system are designed based on the rated speed and the required charging power. Specific design methods can be based on conventional motor design theory and will not be elaborated here.

[0046] The following three typical operating scenarios further illustrate the effectiveness of this device. These data are derived from power outage simulation tests conducted on-site at the desulfurization system under different operating conditions. During the tests, the power supply to the blower was disconnected to simulate a grid power outage, and the protection action process and related parameters were recorded.

[0047] In Scenario 1, under full-load high-sulfur conditions: the desulfurization system operates at full load, and the measured sulfur dioxide concentration at the desulfurization tower inlet is 1850 mg / Nm³. 3 The slurry pH was 5.1, all three slurry circulation pumps were operating, and the desulfurization tower level was 92% of its maximum. The system had not experienced any recent outages. The calculated desulfurization reaction urgency index (RUI) was 86, and the system interruptibility index (SII) was 12. The strategy decision module generated a suspension-maintaining strategy. During the simulated power outage, the power switching unit switched to supercapacitor module power within 0.3ms, and the motor switched to regenerative braking mode, with the kinetic energy recovery voltage stabilizing at 98% of its rated value. The rotor maintained complete suspension for 3.6s after the power outage, during which the maximum radial displacement monitored by the displacement sensor was only 6μm, far below the protective bearing clearance. Power was restored to the grid in 2.9s, and the system resumed normal operation. The sulfur dioxide concentration at the desulfurization tower outlet did not exceed the standard. No contact marks were found on the protective bearing.

[0048] In Scenario 2, during the low-load start-up and shutdown phase: the desulfurization system is operating at a low load and preparing to shut down, with an inlet sulfur dioxide concentration of 220 mg / Nm³. 3 The slurry pH was 5.8, only one slurry circulation pump was operating at low load, and the other pump was shut down. The desulfurization tower level was 60% of its maximum level, and the system had recently experienced a normal shutdown. Calculations yielded RUI=15 and SII=82, generating a controlled descent strategy. After simulating a power outage, the suspension lasted only 0.8 seconds before actively entering the braking descent procedure. The supercapacitor energy was primarily used to provide braking pulses, and the motor feedback voltage was limited to 72% of its rated value. Within approximately 4.2 seconds, the rotor speed decreased from the rated speed of 24000 r / min to 1200 r / min, after which the rotor contacted the protective bearing and came to a stop. During the descent, the maximum instantaneous impact force upon contact with the protective bearing was only about 11% of that under normal high-speed drop conditions, and the bearing temperature rise did not exceed 5K, resulting in no damage. Sulfur dioxide emissions remained unaffected throughout the entire process.

[0049] In Scenario 3, under medium load transition conditions: the desulfurization system is under medium load, with an inlet sulfur dioxide concentration of 1120 mg / Nm³. 3The slurry pH was 4.9, two circulating pumps were running and one was on standby, the desulfurization tower level was 78%, and the system had not been shut down recently. RUI=58 and SII=44 were calculated, a combination of values ​​in the middle range, generating a mixing strategy with a preset suspension time of 2 seconds. After simulating a power outage, suspension was maintained initially, and if the power grid was not restored, the system automatically switched to a controlled drop program at the end of 2 seconds. The rotor took (5.1) seconds to come to a complete stop after the power outage, with the protective bearing contact speed at 980 r / min, and the impact was slight. In the subsequent second test, the simulated power grid was restored 1.3 seconds after the power outage. The system immediately exited the power outage protection upon detecting the power grid restoration, the suspension state was not interrupted, and the fan continued to supply air normally, achieving a breakthrough against instantaneous voltage flashover.

[0050] The above embodiments clearly demonstrate that this device achieves a quantitative match between the power failure protection strategy of the centrifugal oxidation fan in the desulfurization system and the real-time process status. During the critical period of the desulfurization reaction, it can provide at least 3 seconds of suspension time for power restoration, minimizing the risk of decreased desulfurization efficiency and excessive emissions. Under conditions where the system allows for short shutdowns, it does not blindly pursue extended suspension but prioritizes a safe soft landing, protecting the magnetic levitation bearing system from impact damage. This adaptive protection mechanism overcomes the problem of existing solutions being out of sync with process requirements, effectively improving the reliability and availability of the magnetic levitation centrifugal oxidation fan in wet desulfurization applications. Simultaneously, the permanent magnet power generation winding integrated into the main shaft enables continuous self-generated energy storage in non-power failure states, ensuring that the supercapacitor module is always fully charged and ready, eliminating the uncertainty of dependence on grid status and providing fundamental energy security for full-condition coverage of power failure protection. The fixed strategy setting during communication interruptions further ensures that the device does not fail under abnormal operating conditions.

[0051] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A centrifugal oxidation fan device for a desulfurization system with self-generating protection and magnetic levitation bearings, characterized in that, The device comprises: The main body of the magnetic levitation centrifugal oxidation fan includes a main shaft, impeller, magnetic levitation bearing and high-speed motor; The rotor kinetic energy recovery system includes a permanent magnet power generation winding, a rectifier module, and a supercapacitor module integrated into the main shaft; The power switching unit has its input end connected to the mains power supply, the supercapacitor module and the kinetic energy feedback circuit, and its output end connected to the magnetic levitation bearing controller. The process status sensing and communication module connects to the desulfurization DCS system via industrial Ethernet to receive desulfurization process parameters, including SO2 concentration at the desulfurization tower inlet, slurry pH value, slurry circulation pump operating status, and desulfurization system operating mode. The intelligent power failure protection strategy decision module is connected to the process status sensing and communication module. When the power grid is supplying power normally, it generates and stores a power failure protection strategy in advance based on the desulfurization process parameters. The power failure protection strategy includes a suspension maintenance strategy for extending suspension and a landing control strategy for controlling deceleration and landing. The power failure detection and execution unit calls a pre-generated power failure protection strategy when it detects a power failure in the power grid, and controls the power switching unit and the rotor kinetic energy recovery system to perform the corresponding levitation maintenance action or controlled landing action.

2. The centrifugal oxidation fan device for a desulfurization system with self-generating protection and magnetic levitation bearing as described in claim 1, characterized in that, The intelligent power failure protection strategy decision module calculates the desulfurization reaction urgency index and system interruptibility index based on the SO2 concentration at the desulfurization tower inlet, the slurry pH value, the slurry circulation pump operating status, and the desulfurization system operating mode. When the desulfurization reaction urgency index is ≥70 and the system interruptibility index is ≤30, a suspension retention strategy is generated. When the desulfurization reaction urgency index is ≤40 and the system interruptibility index is ≥70, a controlled fall strategy is generated. The process status sensing and communication module also receives the desulfurization tower liquid level.

3. A centrifugal oxidation fan device for a desulfurization system with self-generating protection and magnetic levitation bearings as described in claim 2, characterized in that, The intelligent power failure protection strategy decision module is also configured to: When the desulfurization reaction urgency index and the system interruptibility index do not meet the conditions for generating the suspension-maintaining strategy and the conditions for generating the fall-controlled strategy, a hybrid strategy is generated. The hybrid strategy involves first maintaining rotor levitation for 1.5s-2.5s. If power is not restored during the levitation period, the system switches to controlled deceleration for landing.

4. A centrifugal oxidation fan device for a desulfurization system with self-generating protection and magnetic levitation bearings as described in claim 2, characterized in that, The desulfurization urgency index RUI is calculated using the following formula: In the formula, This refers to the SO2 concentration at the inlet of the desulfurization tower, expressed in mg / Nm³. To preset the upper limit of SO2 concentration, To preset the optimal pH value, The maximum allowable pH deviation; This is the operating status factor of the slurry circulation pump. It is set to 100 when all circulation pumps are running normally, 50 when some are running, and 0 when all are stopped. , , These are the weighting coefficients. , , .

5. A centrifugal oxidation fan device for a desulfurization system with self-generating protection and magnetic levitation bearings as described in claim 2, characterized in that, The System Interruptionability Index (SII) is calculated using the following formula: In the formula, M is the quantitative value of the desulfurization system operation mode, which is 0 for full load operation, 30 for low load operation, 70 for start-up and shutdown, and 100 for maintenance. L is the liquid level in the desulfurization tower. The highest liquid level in the desulfurization tower is represented by H, which is the historical shutdown impact factor. If there has been a recent shutdown, take 0; otherwise, take 100. , , These are the weighting coefficients. , , .

6. A centrifugal oxidation fan device for a desulfurization system with self-generating protection and magnetic levitation bearings as described in claim 1, characterized in that, The suspension maintenance strategy includes: target suspension time ≥ 3s, kinetic energy recovery voltage set to 95%-100% of the rated value, and supercapacitor module allowed discharge depth up to 80%.

7. A centrifugal oxidation fan device for a desulfurization system with self-generating protection and magnetic levitation bearings as described in claim 1, characterized in that, The controlled landing strategy includes: target hovering time ≤ 1s, kinetic energy recovery voltage set to 60%-80% of the rated value, and priority given to using supercapacitor module power for active deceleration control.

8. A centrifugal oxidation fan device for a desulfurization system with self-generating protection and magnetic levitation bearings as described in claim 3, characterized in that, The hybrid strategy maintains rotor levitation for 1.5s-2.5s, and if power grid restoration is detected during levitation, the power failure protection is deactivated.

9. A centrifugal oxidation fan device for a desulfurization system with self-generating protection and magnetic levitation bearings as described in claim 1, characterized in that, The permanent magnet power generation winding includes an annular permanent magnet embedded in the rotor shaft surface and an induction coil arranged on the stator side. The permanent magnet power generation winding and the electromagnetic coil of the magnetic levitation bearing share a magnetic circuit.

10. A centrifugal oxidation fan device for a desulfurization system with self-generating protection and magnetic levitation bearings as described in claim 1, characterized in that, The intelligent power failure protection strategy decision module is also configured to replace the power failure protection strategy pre-generated based on the desulfurization process parameters with a preset fixed power failure protection strategy when communication with the desulfurization DCS system is interrupted.

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