Centrifugal fan exhaust system

Abstract

This invention provides a centrifugal fan exhaust system for treating gaseous effluents in a carrier evaporation process. The system includes a centrifugal fan unit and a monitoring component. The centrifugal fan unit includes a main body and a duct, through which the gas treated by the main body is discharged. The monitoring component includes a droplet size monitoring unit and a control unit. The main body and the control unit are communicatively connected. The droplet size monitoring unit is located in the duct and is communicatively connected to the control unit. When the signal sent by the droplet size monitoring unit reaches a warning value, the control unit generates a control signal and sends it to the main body to shut down the main body or adjust its operating parameters.

Description

Technical Field

[0001] This invention relates to the field of centrifugal fan exhaust technology, and more specifically to a centrifugal fan exhaust system. Background Technology

[0002] Centrifugal fan exhaust systems are widely used in carrier evaporation processes to treat gaseous effluents and ensure safe discharge. Existing conventional exhaust systems are mostly passive structures, possessing only basic air supply and exhaust functions. They cannot monitor the droplet size in the effluent online, nor can they automatically adjust the fan operation based on particle size, making it difficult to meet the high-precision and high-safety requirements of process emissions.

[0003] In actual operation, due to the lack of droplet size monitoring and closed-loop control mechanisms, existing systems often experience problems such as excessive droplet size and uncontrolled discharge of entrained materials. Furthermore, they cannot adjust fan parameters or provide shutdown protection in a timely manner under abnormal conditions, which not only affects process stability but also has defects such as high operating energy consumption, poor adaptability, and insufficient safety redundancy.

[0004] Based on this, the inventors of this application propose a centrifugal fan exhaust system in order to solve one or more of the above-mentioned technical problems. Summary of the Invention

[0005] The present invention solves the above-mentioned technical problems through the following technical solution: This invention provides a centrifugal fan exhaust system for treating process gaseous effluents in a carrier evaporation process. The system includes a centrifugal fan unit and a monitoring component. The centrifugal fan unit includes a main body and a duct, and the gas treated by the main body is discharged through the duct. The monitoring component includes a droplet size monitoring unit and a control unit. The main body is communicatively connected to the control unit. The droplet size monitoring unit is located in the air duct and is communicatively connected to the control unit. The control unit is used to generate a control signal and send it to the main body when the signal sent by the droplet size monitoring unit reaches the warning value, so as to shut down the main body or adjust the operating parameters.

[0006] According to one embodiment of the present invention, at least one viewing window is provided on the air duct, and each viewing window extends along the axial direction of the air duct; A bracket is also provided on one side of the duct, and the droplet size monitoring unit is installed on the bracket. The droplet size monitoring unit slides with the bracket along the axial direction of the duct.

[0007] According to one embodiment of the present invention, the support is provided with a slide rail, and one side of the droplet size monitoring unit is provided with a groove that slides in cooperation with the slide rail; or, The support has a groove, and the droplet size monitoring unit has a slide rail that slides in conjunction with the groove.

[0008] According to one embodiment of the present invention, the number of viewing windows is at least two, and the at least two viewing windows are arranged at intervals at the target monitoring point of the air duct; wherein, the target monitoring point includes at least the bending area of ​​the air duct and the connection area of ​​the air duct.

[0009] According to one embodiment of the present invention, the number of droplet size monitoring units is one; or, one droplet size monitoring unit is provided on the outer side of each viewing window.

[0010] According to one embodiment of the present invention, the control unit includes a programmable logic controller and a frequency converter; The programmable logic controller is used to receive the droplet size signal and determine whether the warning value has been reached, and the frequency converter is used to adjust the motor speed of the main body.

[0011] According to one embodiment of the present invention, it further includes a fresh air pretreatment system, wherein the programmable logic controller is signal-connected to the fresh air pretreatment system; The programmable logic controller is used to receive the air humidity signal delivered by the fresh air pretreatment system.

[0012] According to one embodiment of the present invention, the control algorithm employed by the programmable logic controller is as follows: ; Where u(t) is the control output signal used to adjust the motor speed of the centrifugal fan unit; e(τ) is the error between the droplet size value and the real-time droplet median size measurement value; Proportional gain coefficient; Integral gain coefficient; τ is the differential gain coefficient; t is the time variable; τ is the integral time variable.

[0013] According to one embodiment of the present invention, both the body and the duct are made of corrosion-resistant material; The corrosion-resistant material is austenitic stainless steel.

[0014] According to one embodiment of the present invention, the body includes a volute and an impeller, and an arc-sprayed alloy coating is further provided on the outer side of the volute and the impeller.

[0015] The positive and progressive effects of this invention are as follows: The centrifugal fan exhaust system of this invention integrates droplet size monitoring and closed-loop control unit into the centrifugal fan exhaust system. It can monitor the droplet state of process gaseous effluent in real time and automatically adjust the fan operating parameters or perform shutdown when the droplet size reaches the warning value. This effectively achieves precise control of droplet size, improves emission safety and process stability, avoids excessive emissions, and ensures continuous and reliable operation of the carrier evaporation process. Attached Figure Description

[0016] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, wherein: Figure 1 This is a schematic diagram of the centrifugal fan exhaust system of the present invention.

[0017] 1. Centrifugal fan unit; 11. Body; 12. Duct; 121. Viewing window; 13. Bracket; 14. Slide rail; 15. Slide groove; 16. Volute; 17. Impeller; 2. Monitoring components; 21. Droplet size monitoring unit; 211. Transmitter; 212. Receiver; 22. Control unit; 221. Programmable logic controller; 222. Frequency converter; 3. Fresh air pretreatment system. Detailed Implementation

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this application. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0019] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not specifically singular and may include plural forms. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0020] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0021] In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms 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, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0022] Existing centrifugal fan exhaust systems for carrier evaporation processes suffer from drawbacks such as the inability to monitor droplet size online, the inability to automatically adjust operating parameters, and the lack of early warning and protection mechanisms. Therefore, this application proposes a centrifugal fan exhaust system to address the aforementioned problems encountered by traditional centrifugal fan exhaust systems.

[0023] Please refer to the details. Figure 1 The centrifugal fan exhaust system proposed in this application includes a centrifugal fan unit 1 and a monitoring component 2. The centrifugal fan unit 1 is used to treat the process gaseous effluent generated by the loaded evaporation process, and to break up, disperse, and control the liquid droplets entrained in the effluent to a qualified particle size before safely discharging them. The centrifugal fan unit 1 specifically includes a body 11 and a duct 12. The gas treated by the body 11 is discharged to the outside through the duct 12.

[0024] The monitoring component 2 includes a droplet size monitoring unit 21 and a control unit 22. The main body 11 is communicatively connected to the control unit 22. The droplet size monitoring unit 21 is located in the air duct 12 and is communicatively connected to the control unit 22. The control unit 22 is used to generate a control signal and send it to the main body 11 when the signal sent by the droplet size monitoring unit 21 reaches the warning value, so that the main body 11 can be shut down or its operating parameters adjusted.

[0025] This application, by setting a droplet size monitoring unit 21 on the duct 12, can acquire the droplet size status of the process gas effluent in real time, and automatically adjust the fan operating parameters or directly shut down the duct 12 when the droplet size reaches the warning value. This allows for proactive control and effective monitoring of the process gas emission process, thereby effectively avoiding excessive droplet size emissions and improving the safety and stability of the carrier evaporation process.

[0026] Please continue to refer to Figure 1 At least one viewing window 121 is provided on the duct 12, and each viewing window 121 extends along the axial direction of the duct 12; a bracket 13 is also provided on one side of the duct 12, and a droplet size monitoring unit 21 is installed on the bracket 13, and the droplet size monitoring unit slides in cooperation with the bracket 13 along the axial direction of the duct 12.

[0027] A viewing window 121 extending axially is provided on the duct 12 to provide visibility for the droplet size monitoring unit 21. The droplet size monitoring unit 21 can complete the monitoring without extending into the inside of the duct 12, thereby reducing the difficulty of arranging the droplet size monitoring unit 21 and without damaging the flow channel structure inside the duct 12.

[0028] The droplet size monitoring unit 21 is slidably mounted on the bracket 13 to continuously scan and monitor the droplet size at different axial positions within the duct 12, thereby expanding the monitoring range, improving the comprehensiveness and accuracy of the particle size data, and ensuring more reliable control basis.

[0029] In one embodiment, the support 13 is provided with a slide rail 14, the length of which extends in the same direction as the axial direction of the duct 12. The droplet size monitoring unit 21 is provided with a groove 15 on one side that slides with the slide rail 14. Through the cooperation between the slide rail 14 and the groove 15, the droplet size monitoring unit 21 and the support 13 can be slidably coupled.

[0030] In some other embodiments, a groove 15 may be provided on the support 13, and a slide rail 14 that slides in cooperation with the groove 15 may be provided on the droplet size monitoring unit 21.

[0031] The sliding method between the support 13 and the droplet size monitoring unit 21 can be either of the two methods mentioned above, and no limitation is made here.

[0032] Optionally, one end of the bracket 13 can be erected on the ground, and the droplet size monitoring unit 21 can be installed on the top of the bracket 13 and arranged near the viewing window 121 of the duct 12. Alternatively, the bracket 13 can also be installed on a fixed structure on one side of the duct 12, such as a side wall, for support. The installation position of the bracket 13 is only an example and is not limited.

[0033] As for the slide rail 14 and the slide groove 15, the cross-sectional shape of both the slide rail 14 and the slide groove 15 can be T-shaped along their length extension direction, which can ensure the stability of their relative movement and prevent them from separating during movement.

[0034] It should be noted that the operator can manually slide the droplet size monitoring unit 21 relative to the bracket 13 to the target position. Alternatively, a motor can be installed on the bracket 13, and a linear guide rail can be installed at the motor output end. One end of the droplet size monitoring unit 21 can be matched with the linear guide rail, and the position of the droplet size monitoring unit 21 relative to the bracket 13 can be adjusted by motor drive.

[0035] The movement state of the droplet size monitoring unit 21 can be either manual or automatic, and no limitation is made here.

[0036] In one embodiment, the number of viewing windows 121 is at least two, and the at least two viewing windows 121 are arranged at intervals at the target monitoring points of the air duct 12; wherein, the target monitoring points include at least the bending area of ​​the air duct 12 and the connection area of ​​the air duct 12.

[0037] By setting up viewing windows 121 at key locations such as the bends and connections of the duct 12 where droplets are likely to accumulate or airflow disturbances occur, particle size information at points prone to exceeding standards can be captured in a targeted manner, improving the sensitivity of anomaly identification, making system control more targeted, and further ensuring emission safety.

[0038] The bending area refers to the curved section of duct 12 where the flow direction changes; this area is prone to airflow eddies and droplet accumulation. The connection area refers to the joints where duct sections 12 meet, including flange connections, plug connections, and welded connections; this area is prone to abrupt changes in cross-section, airflow disturbances, and droplet adhesion. By installing viewing windows at these key locations, particle size information at points prone to exceeding standards can be accurately captured, improving the sensitivity of anomaly identification and the targeted nature of control, further ensuring emission safety.

[0039] For the droplet size monitoring unit 21, a single droplet size monitoring unit 21 can correspond to multiple viewing windows 121. Thus, the droplet size monitoring unit 21 can move relative to the support 13 to different positions of the viewing windows 121 for monitoring, thereby saving costs.

[0040] Alternatively, the droplet size monitoring unit 21 can be made to correspond one-to-one with the viewing window 121, thereby improving the synchronization and accuracy of the position detection of each viewing window 121.

[0041] That is, the number of droplet size monitoring units 21 and viewing windows 121 can be flexibly selected according to the accuracy and cost requirements under different working conditions, and no limitation is made here.

[0042] Please continue to refer to Figure 1 The droplet size monitoring unit 21 can be a laser scattering particle size analyzer. The laser scattering particle size analyzer can move and scan along the axial direction of the air duct 12 by relative sliding with the support 13, so as to measure the droplet size at different positions of the air duct cross section.

[0043] It should be noted that the laser scattering particle size analyzer operates on the principle of light scattering. It uses a parallel laser beam emitted by the transmitter 211 to irradiate droplet particles in the airflow, causing the droplets to produce characteristic scattered light. The receiver then collects the scattered signals and calculates the droplet size and distribution data.

[0044] The laser scattering particle size analyzer has a transmitter 211 and a receiver 212. Therefore, two observation windows 121 on the duct 12 can be set radially along the duct 12, or an arc-shaped observation window 121 can be set around the outer periphery of the duct 12. The specific setting method is not limited here.

[0045] Figure 1 The diagram shows two observation windows 121, with the transmitter 211 and receiver 212 respectively positioned outside the observation windows 121 for particle size monitoring. Figure 1 This is merely an example and does not limit the way the bracket 13 and the observation window 121 are set.

[0046] Optionally, the transmitter 211 and receiver 212 can be mounted on one bracket 13 or on two separate brackets 13, which is not limited here. Both the transmitter 211 and receiver 212 can slide relative to the bracket 13 to facilitate adjustment of their measurement positions.

[0047] To ensure scanning accuracy, the viewing window can be made of quartz glass with anti-reflective coating on both sides, and an automatic dust removal device (not shown) is installed on the outside of the viewing window. The automatic dust removal device cleans the glass surface through a friction mechanism driven by a motor.

[0048] In one embodiment, the control unit 22 includes a programmable logic controller 221 and a frequency converter 222; the programmable logic controller 221 is used to receive the droplet size signal and determine whether the warning value has been reached, and the frequency converter 222 is used to adjust the motor speed of the body 11.

[0049] Specifically, the programmable logic controller 221 is configured to dynamically adjust the output frequency of the frequency converter 222 based on a droplet size warning value using a closed-loop control algorithm (hereinafter referred to as the PID algorithm). For example, the warning value can be 5 μm, and a warning value of 4.5 μm can also be set. When the median droplet size monitored in real time reaches 4.5 μm or is close to the upper limit of 5 μm, a control signal can be generated and sent to the main body 11. The main body 11 adjusts the motor speed to reduce the droplet size value, so as to ensure that no droplets of 5 μm or larger appear.

[0050] Optionally, the centrifugal fan exhaust system also includes a fresh air pretreatment system 3, and a programmable logic controller 221 is connected to the fresh air pretreatment system 3 via a signal connection; the programmable logic controller 221 is used to receive the air humidity signal delivered by the fresh air pretreatment system 3 as a feedforward compensation input.

[0051] In other words, the feedforward input is combined with the droplet size error signal through a weighting function to generate a composite control signal. This composite control signal is processed by the programmable logic controller 221 and then output to the frequency converter 222 to adjust the fan speed. The weighting function is set based on the correlation between air humidity and droplet evaporation efficiency, allowing for advance adjustment of the centrifugal fan unit 1's operating parameters when inlet air parameters fluctuate. This feedforward compensation mechanism runs in parallel with the PID control algorithm described below, applying control action in advance without waiting for error feedback, thereby improving system response speed and control stability.

[0052] Specifically, the programmable logic controller 221 executes a proportional-integral-derivative (PID) control algorithm. The control output of the PID algorithm is defined by a mathematical formula, which is: ; in, This represents the control output signal used to adjust the motor speed of centrifugal fan unit 1. The control output signal u(t) is converted into a 4-20 mA analog signal and output to the frequency converter 222. The frequency converter 222 adjusts the motor speed according to this signal. This represents the error between the droplet size setpoint and the real-time droplet median size measurement. The error e(τ) is calculated by sampling the droplet median size data in real time, and the sampling frequency is synchronized with the measurement frequency of the laser scattering particle size analyzer. This represents the proportional gain coefficient, used to amplify the instantaneous value of the error. The range of values ​​is determined based on the system response speed; This represents the integral gain coefficient, used to eliminate the cumulative effect of errors. The range of values ​​is determined based on the error elimination capability; The differential gain coefficient is used to predict the trend of error changes. The range of values ​​is determined based on system stability requirements; Represents a time variable. This represents the time variable for integration.

[0053] The proportional gain coefficient, integral gain coefficient, and differential gain coefficient are determined through system identification and debugging to ensure that the droplet size error converges to 0. The real-time median droplet size measurement is the median value of the droplet population size distribution detected in real time by the droplet size monitoring unit, which is used to objectively characterize the overall droplet size in the current airflow.

[0054] Furthermore, the droplet size warning value in the proportional-integral-derivative control algorithm is set to 4.5μm, and the control upper limit is 5μm. When the real-time measured value is ≥4.5μm, the PID algorithm immediately triggers speed regulation until the droplet size drops back to below 4.5μm, ensuring that there are no droplets of 5μm or larger throughout the process.

[0055] The mathematical formulas are discretized in the programmable logic controller 221, and the backward difference method is used for numerical integration and differentiation calculations. That is, the mathematical formulas are implemented in discretized form in the programmable logic controller 221. The backward difference method transforms continuous integration and differentiation operations into discrete numerical calculations suitable for digital controller operation, so that the control algorithm can run stably and in real time in the programmable logic controller 221.

[0056] In one embodiment, both the body 11 and the duct 12 are made of corrosion-resistant material; the corrosion-resistant material is austenitic stainless steel.

[0057] The body 11 and the duct 12 are made of austenitic stainless steel, a corrosion-resistant material that can withstand the long-term effects of corrosive media in the carrier evaporation process. This reduces component corrosion and extends the service life of the system, thereby improving the reliability of the equipment under harsh conditions.

[0058] Furthermore, the body 11 includes a volute 16 and an impeller 17, and the outer sides of the volute 16 and the impeller 17 are also provided with an arc-sprayed alloy coating.

[0059] An arc-sprayed alloy coating is added to the surfaces of the volute 16 and impeller 17, which further improves the corrosion resistance and surface smoothness of key rotating parts, reduces airflow resistance and media erosion, and enhances the operating efficiency and energy-saving effect of the fan while increasing durability.

[0060] Furthermore, the main body 1 also includes a fixed flow guide structure (not shown in the figure), which includes a volute tongue and a guide plate, with the guide plate having a horizontal angle of 35°. The fixed flow guide structure adopts a smooth streamlined design with a large radius of curvature. All flow guide components are integrally formed or fixedly connected to the volute 16 and impeller 17, with no moving or adjustable parts. Moreover, the flow channel surface of the fixed flow guide structure is made of the same corrosion-resistant material as the volute 16 and impeller 17, and undergoes the same surface treatment process.

[0061] This application uses corrosion-resistant materials to make the volute 16, impeller 17, and fixed flow guide structure of the centrifugal fan unit 1, and applies an arc-sprayed alloy coating that matches the base material to the flow channel surface. At the same time, the surface roughness of the flow channel is controlled and the internal welds are ground and polished. This can effectively adapt to the corrosive conditions of the process medium. The durability of key components is improved from both material selection and surface treatment, avoiding equipment damage caused by medium erosion. This can improve the system's adaptability to operating conditions and its service life.

[0062] In summary, the centrifugal fan exhaust system proposed in this application has at least the following advantages: By setting a droplet size monitoring unit 21 downstream of the duct 12 and combining it with PID closed-loop control, the emission particle size can be monitored in real time and precisely controlled. When the particle size is close to exceeding the standard, the fan speed can be automatically adjusted or the fan can be stopped, effectively avoiding the emission of large-diameter droplets.

[0063] Meanwhile, the system adopts corrosion-resistant materials and surface coating design, which is suitable for the corrosive working conditions of carrier evaporation process, extends the service life of the equipment, and achieves safe and controllable emissions, stable and reliable operation, energy efficiency and easy maintenance. It can well meet the stringent requirements of nuclear power carrier evaporation process for the treatment of gaseous effluents.

[0064] Similarly, it should be noted that, in order to simplify the description of the present application and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of the embodiments of the present application sometimes combines multiple features into a single embodiment, drawing, or description thereof. However, this disclosure method does not imply that the subject matter of the application requires more features than those mentioned in the claims. In fact, the embodiments contain fewer features than all the features of the single embodiments disclosed above.

[0065] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are modified in some examples with the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of scope in some embodiments of this application are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

[0066] Although this application has been described with reference to specific embodiments, those skilled in the art should recognize that the above embodiments are only used to illustrate this application, and various equivalent changes or substitutions can be made without departing from the spirit of this application. Therefore, any changes or modifications to the above embodiments within the essential spirit of this application will fall within the scope of the claims of this application.

Claims

1. A centrifugal fan exhaust system, characterized in that, The exhaust system is used to treat the gaseous effluent from the carrier evaporation process, and the system includes a centrifugal fan unit and a monitoring component. The centrifugal fan unit includes a main body and a duct, and the gas treated by the main body is discharged through the duct. The monitoring component includes a droplet size monitoring unit and a control unit. The main body is communicatively connected to the control unit. The droplet size monitoring unit is located in the air duct and is communicatively connected to the control unit. The control unit is used to generate a control signal and send it to the main body when the signal sent by the droplet size monitoring unit reaches the warning value, so as to shut down the main body or adjust the operating parameters.

2. The centrifugal fan exhaust system according to claim 1, characterized in that, At least one viewing window is provided on the air duct, and each viewing window extends along the axial direction of the air duct. A bracket is also provided on one side of the duct, and the droplet size monitoring unit is installed on the bracket. The droplet size monitoring unit slides with the bracket along the axial direction of the duct.

3. The centrifugal fan exhaust system according to claim 2, characterized in that, The support is equipped with a slide rail, and one side of the droplet size monitoring unit is provided with a groove that slides in conjunction with the slide rail; or... The support has a groove, and the droplet size monitoring unit has a slide rail that slides in conjunction with the groove.

4. The centrifugal fan exhaust system according to claim 2, characterized in that, The number of viewing windows is at least two, and the at least two viewing windows are arranged at intervals at the target monitoring points of the air duct; wherein, the target monitoring points include at least the bending area of ​​the air duct and the connection area of ​​the air duct.

5. The centrifugal fan exhaust system according to claim 4, characterized in that, The number of droplet size monitoring units is one; or, one droplet size monitoring unit is provided on the outer side of each of the viewing windows.

6. The centrifugal fan exhaust system according to claim 1, characterized in that, The control unit includes a programmable logic controller and a frequency converter; The programmable logic controller is used to receive the droplet size signal and determine whether the warning value has been reached, and the frequency converter is used to adjust the motor speed of the main body.

7. The centrifugal fan exhaust system according to claim 6, characterized in that, It also includes a fresh air pretreatment system, and the programmable logic controller is signal-connected to the fresh air pretreatment system; The programmable logic controller is used to receive the air humidity signal delivered by the fresh air pretreatment system.

8. The centrifugal fan exhaust system according to claim 7, characterized in that, The control algorithm used by the programmable logic controller is as follows: ； Where u(t) is the control output signal used to adjust the motor speed of the centrifugal fan unit; e(τ) is the error between the droplet size value and the real-time droplet median size measurement value; Proportional gain coefficient; Integral gain coefficient; τ is the differential gain coefficient; t is the time variable; τ is the integral time variable.

9. The centrifugal fan exhaust system according to claim 1, characterized in that, Both the main body and the air duct are made of corrosion-resistant materials; The corrosion-resistant material is austenitic stainless steel.

10. The centrifugal fan exhaust system according to claim 9, characterized in that, The main body includes a volute and an impeller, and the outer sides of the volute and the impeller are also provided with an arc-sprayed alloy coating.

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