A low-energy evaporation and crystallization control system for ferric phosphate wastewater

Abstract

This invention relates to the field of evaporation crystallization control technology, and particularly to a low-energy evaporation crystallization control system for iron phosphate wastewater. The system includes: a preheating module, an evaporation concentration module, a steam circulation module, a steam detection module, a salt separation and recovery module, and a low-energy control module. The preheating module preheats the wastewater. The evaporation concentration module achieves graded evaporation of water and concentration of the liquid through multi-stage evaporation units connected in series. The steam circulation module integrates a steam compressor and a steam ejector, and can intelligently switch the dominant equipment according to system requirements, achieving dual-mode operation of mechanical compression and thermal compression. The steam detection module analyzes the compressor's rotation shadow and vibration waveform, and the ejector's audio waveform to determine the equipment status in real time. The salt separation and recovery module continuously separates ammonium sulfate and monoammonium phosphate and recovers the crystals, and recovers the condensate for preheating. The low-energy control module dynamically adjusts the operating mode and steam parameters to achieve energy-saving optimization and stable control throughout the entire process.

Description

Technical Field

[0001] This invention relates to the field of evaporation and crystallization control technology, and in particular to a low-energy evaporation and crystallization control system for iron phosphate wastewater. Background Technology

[0002] In the field of ferric phosphate wastewater treatment, traditional evaporation crystallization technology mainly relies on a single-mode energy recovery system. Among them, multi-effect evaporation (MEE) and mechanical vapor recompression (MVR) are two of the most common existing technologies.

[0003] Multi-effect evaporation systems (MVRs) typically consist of three or four evaporators connected in series. Their working principle utilizes the secondary steam generated in the preceding effects as a heat source for the subsequent effects. By progressively reducing the operating pressure of each effect, the boiling point of the wastewater decreases sequentially at the corresponding effect, thus achieving multiple utilizations of steam thermal energy. Mechanical vapor recompression (MVR) technology, on the other hand, uses a centrifugal steam compressor to compress all the secondary steam generated by the evaporator, increasing its temperature and pressure before returning it as a heat source for the evaporator. This process only requires the introduction of live steam during system startup; during normal operation, the compressor is primarily driven by electricity to maintain the cycle, theoretically significantly reducing dependence on external live steam. However, MVR systems place extremely high demands on the performance of the steam compressor, resulting in high electricity costs. When treating easily scaling and corrosive ferric phosphate wastewater, scaling and corrosion easily occur on the compressor impeller and heat exchange surfaces, leading to decreased system efficiency and increased maintenance frequency and costs. Summary of the Invention

[0004] To address this issue, the present invention provides a low-energy evaporation and crystallization control system for iron phosphate wastewater, which overcomes the problem that existing equipment cannot perform adaptive operation and switching, and that complex operating conditions can easily affect evaporation efficiency, thereby leading to a reduction in the final salt recovery efficiency and product quality.

[0005] To achieve the above objectives, the present invention provides a low-energy evaporation and crystallization control system for ferric phosphate wastewater, comprising:

[0006] The preheating module is used to preheat the ferric phosphate wastewater solution with condensate and is connected to the solution inlet of the evaporation and concentration module.

[0007] An evaporation and concentration module includes several evaporation and concentration units connected in series. Each evaporation and concentration unit includes a heater and an evaporator, which are used to realize the evaporation of water in wastewater and the output of concentrated liquid through multi-stage steam heat exchange. Its liquid outlet is connected to the inlet of the salt recovery module.

[0008] The steam circulation module includes a steam compressor and a steam ejector. The main equipment is selected according to the steam inlet temperature of the evaporation and concentration module. The steam compressor is used to compress secondary steam and return it to the heater for recycling. The steam ejector is used to mix secondary steam with high-pressure steam to form a mixed heat source.

[0009] The steam detection module is used to detect the rotation shadow information and vibration amplitude of the steam compressor and construct a time-domain waveform diagram of the vibration amplitude, detect the audio amplitude of the steam ejector and construct a time-domain waveform diagram of the audio amplitude, and determine the existence of inefficient crystallization waveform segments based on the fluctuation discrete parameters corresponding to each time-domain waveform image.

[0010] The salt separation and recovery module is used to separate and collect ammonium sulfate crystals and monoammonium phosphate crystals, condense the steam discharged from the evaporation and concentration module into condensate, and store a portion of the condensate for the preheating operation of the preheating module.

[0011] The low-energy control module is used to adjust the low-energy circulation control mode during the evaporation and crystallization process according to the judgment result of the existence determination, and to obtain the rotation shadow information to determine whether to switch the main equipment, or directly switch the main equipment and adjust the steam input parameters of the circulation evaporation and concentration module.

[0012] As a preferred technical solution for the low-energy evaporation and crystallization control system for iron phosphate wastewater, the ammonium sulfate separation unit is provided with a first thickener, a first centrifuge, and a first semi-automatic packaging machine in sequence along the material flow direction. The inlet of the first thickener receives the concentrated liquid output from the evaporation and concentration module, and the outlet of the first centrifuge is connected to the inlet of the first semi-automatic packaging machine.

[0013] The ammonium phosphate separation unit includes a cooling crystallizer, a second thickener, a second centrifuge, and a second semi-automatic packaging machine. The inlet of the cooling crystallizer receives the mother liquor output from the ammonium sulfate separation unit. The inlet of the second thickener is connected to the outlet of the cooling crystallizer, and the outlet of the second centrifuge is connected to the inlet of the second semi-automatic packaging machine.

[0014] In this module, the units of the salt separation and recovery module are directly connected by pipelines, without the intervention of intermediate storage containers, and the material is processed in a continuous flow manner to complete the salt separation process.

[0015] As a preferred technical solution for a low-energy evaporation and crystallization control system for iron phosphate wastewater, the steam circulation module determines the main equipment based on the steam inlet temperature of the first evaporation and concentration unit in the evaporation and concentration module.

[0016] Based on the determination result that the steam inlet temperature is greater than or equal to the preset circulation temperature, the main device is determined to be a steam ejector;

[0017] Based on the determination that the steam inlet temperature is less than the preset circulation temperature, the main equipment is determined to be a steam compressor.

[0018] As a preferred technical solution for the low-energy evaporation and crystallization control system for iron phosphate wastewater, the steam detection module periodically acquires the peak values ​​of image generation parameters in the time-domain waveform diagrams of each amplitude of the main equipment, calculates the average value and standard deviation of the peak values ​​of the image generation parameters, and determines the fluctuation discrete parameters of the main equipment based on the ratio of the standard deviation to the average value.

[0019] The parameters for generating the audio amplitude time-domain waveform diagram are the audio amplitude of the steam ejector and the parameters for generating the vibration amplitude time-domain waveform diagram are the vibration amplitude of the steam compressor.

[0020] As a preferred technical solution for a low-energy evaporation and crystallization control system for iron phosphate wastewater, the steam detection module determines whether there is an inefficient crystallization waveform segment in the current dominant equipment based on the fluctuation discrete parameter, including:

[0021] Based on the determination result that the fluctuation discrete parameter is greater than or equal to the standard discrete parameter of the corresponding main equipment, it is determined that there is an inefficient crystallization waveform segment.

[0022] Based on the determination result that the fluctuation discrete parameter is less than the standard discrete parameter of the corresponding dominant device, it is determined that there is no inefficient crystallization waveform segment.

[0023] As a preferred technical solution for a low-energy evaporation and crystallization control system for iron phosphate wastewater, the low-energy control module adjusts the low-energy circulation control mode during the evaporation and crystallization process based on the judgment result of the existence determination, including:

[0024] Based on the determination that the inefficient crystallization waveform segment does not exist, it is determined that the low-power cyclic control mode will not be adjusted.

[0025] Based on the determination of the existence of the inefficient crystallization waveform segment, a corresponding low-power cyclic control mode is selected based on the current dominant equipment, wherein,

[0026] In response to the fact that the current dominant device is a steam compressor, a decision is made based on the rotation shadow information whether to switch the dominant device;

[0027] In response to the current dominant device being a steam ejector, the dominant device is directly switched and the steam input parameters of the circulating evaporation and concentration module are adjusted.

[0028] As a preferred technical solution for a low-energy evaporation and crystallization control system for iron phosphate wastewater, the low-energy control module determines whether to switch the dominant equipment based on the rotational shadow information, including:

[0029] The low-energy control module determines that the main device needs to be switched to a steam ejector based on the judgment result that the rotation shadow information does not meet the normal rotation shadow conditions.

[0030] The normal rotational shadow condition is that both the width and depth of the rotational shadow are within the corresponding standard range.

[0031] As a preferred technical solution for the low-energy evaporation and crystallization control system for iron phosphate wastewater, the low-energy control module responds to the direct switching of the main equipment by adjusting the steam input parameters of the steam circulation module to match the working range of the main equipment.

[0032] The evaporation and concentration module comprises three evaporation and concentration units connected in series.

[0033] Compared with existing technologies, the beneficial effects of this invention are as follows: the system automatically selects the high-temperature section of the main equipment to activate TVR mode based on the initial steam inlet temperature of the evaporation and concentration unit, utilizing the mixture of high-pressure new steam and secondary steam to form a heat source, reducing the external steam demand; in the low-temperature section, it switches to MVR mode, using the compressor to compress and heat the secondary steam for recycling, avoiding heat energy waste; the system monitors the equipment status in real time through vibration amplitude, audio amplitude, and rotation shadow parameters; when the compressor impeller fouling or dynamic imbalance risk exceeds the standard, it triggers a switch to the ejector based on the standard range of radar rotation shadow width and depth; when the ejector flow field becomes unstable, it directly switches modes and simultaneously adjusts operating parameters to ensure precise matching of heat energy supply and demand. This invention achieves efficient utilization and dynamic balance of heat energy through dual-dimensional intelligent switching, saving energy compared to traditional fixed-mode systems, while reducing the risk of equipment overheating, mechanical wear, and unplanned downtime.

[0034] In particular, in this invention, the dominant equipment is automatically selected based on the steam inlet temperature of the first evaporation and concentration unit, which realizes the efficient utilization of thermal energy in a cascade manner. Temperature threshold control also avoids the risk of equipment overheating. At the same time, combined with a dynamic steam temperature adjustment strategy, the thermal energy supply and demand balance of the evaporation, concentration and salt recovery modules is ensured, ultimately achieving the effects of low energy consumption, high stability and long equipment life.

[0035] In particular, this invention periodically monitors the time-domain waveform parameters of the vibration amplitude of the steam compressor and the audio amplitude of the steam ejector, and compares the fluctuating discrete parameters with standard discrete parameters to achieve accurate diagnosis of the operating status of the main equipment. When the vibration / audio fluctuation discrete parameters exceed the threshold, it determines that there is an inefficient crystallization waveform segment, thereby triggering predictive maintenance or mode switching. This mechanism not only achieves early warning of equipment failure through impeller dynamic balance monitoring and flow field acoustic characteristic analysis, avoiding efficiency decline and energy consumption increase caused by scaling, wear, or flow field instability, but also adapts to different equipment characteristics through independent determination of dual parameters, ensuring stable and efficient operation of the core power unit, ultimately achieving the comprehensive beneficial effects of improving system reliability, extending equipment life, reducing maintenance costs, and optimizing energy consumption.

[0036] In particular, this invention achieves dynamic low-energy control of the evaporation crystallization process through intelligent detection of inefficient crystallization waveform segments and coordinated optimization of the response strategy of the dominant equipment. When an inefficient crystallization waveform segment is detected, the system executes a differentiated control strategy based on the type of the current dominant equipment: for the steam compressor, a secondary verification mechanism using rotational shadow information is employed to accurately identify the risk of impeller scaling or dynamic imbalance, avoiding erroneous switching; for the steam ejector, mode switching is directly triggered and steam temperature, pressure, and flow parameters are adjusted synchronously to ensure the balance of heat supply and demand and safe operation of the equipment after the TVR / MVR mode switch. This invention not only reduces ineffective energy consumption but also improves the system's anti-interference capability and operational stability through equipment-level fault isolation and parameter adaptive matching, ultimately achieving multiple beneficial effects such as energy saving and consumption reduction, extended equipment life, reduced unplanned downtime, and optimized salt separation efficiency.

[0037] In particular, this invention uses linear frequency modulated continuous wave radar to monitor the width and depth of the impeller rotation shadow of the steam compressor in real time. By combining historical data confidence intervals to set normal condition thresholds, it achieves accurate equipment status diagnosis and intelligent response. When the rotation shadow is abnormal, it automatically switches to steam ejector mode to avoid efficiency decay and equipment damage caused by impeller scaling and dynamic imbalance. When the status is normal, it dynamically optimizes the secondary steam temperature based on fluctuating discrete parameters. By reducing droplet carryover, suppressing salt precipitation and liquid hammer risks, it improves compression efficiency and prevents the vicious cycle of efficiency decline and energy consumption increase caused by scaling. This invention not only achieves early warning and fault isolation of impeller status through non-contact radar technology, but also ensures safe equipment operation through temperature parameter co-optimization, ultimately achieving the effects of energy saving and consumption reduction, extending equipment life, reducing unplanned downtime, and improving salt separation quality. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the low-energy evaporation and crystallization control system for ferric phosphate wastewater according to an embodiment of the present invention.

[0039] Figure 2This is a schematic diagram of the structure of the salt recovery module according to an embodiment of the present invention;

[0040] Figure 3 The logic diagram for adjusting the low-consumption circulation control method during the evaporation and crystallization process in an embodiment of the present invention is shown. Detailed Implementation

[0041] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0042] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0043] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0044] Furthermore, it should be noted that, in the description of this invention, 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 according to the specific circumstances.

[0045] Please see Figure 1 As shown, this is a schematic diagram of the structure of the low-energy evaporation and crystallization control system for ferric phosphate wastewater according to an embodiment of the present invention. The present invention provides a low-energy evaporation and crystallization control system for ferric phosphate wastewater, comprising:

[0046] The preheating module is used to preheat the ferric phosphate wastewater solution with condensate and is connected to the solution inlet of the evaporation and concentration module.

[0047] An evaporation and concentration module includes several evaporation and concentration units connected in series. Each evaporation and concentration unit includes a heater and an evaporator, which are used to realize the evaporation of water in wastewater and the output of concentrated liquid through multi-stage steam heat exchange. Its liquid outlet is connected to the inlet of the salt recovery module.

[0048] The steam circulation module includes a steam compressor and a steam ejector. The main equipment is selected according to the steam inlet temperature of the evaporation and concentration module. The steam compressor is used to compress secondary steam and return it to the heater for recycling. The steam ejector is used to mix secondary steam with high-pressure steam to form a mixed heat source.

[0049] The steam detection module is used to detect the rotation shadow information and vibration amplitude of the steam compressor and construct a time-domain waveform diagram of the vibration amplitude, detect the audio amplitude of the steam ejector and construct a time-domain waveform diagram of the audio amplitude, and determine the existence of inefficient crystallization waveform segments based on the fluctuation discrete parameters corresponding to each time-domain waveform image.

[0050] The salt separation and recovery module is used to separate and collect ammonium sulfate crystals and monoammonium phosphate crystals, condense the steam discharged from the evaporation and concentration module into condensate, and store a portion of the condensate for the preheating operation of the preheating module.

[0051] The low-energy control module is used to adjust the low-energy circulation control mode during the evaporation and crystallization process according to the judgment result of the existence determination, and to obtain the rotation shadow information to determine whether to switch the main equipment, or directly switch the main equipment and adjust the steam input parameters of the circulation evaporation and concentration module.

[0052] This invention automatically selects the high-temperature section of the main equipment to activate TVR mode based on the initial steam inlet temperature of the evaporation and concentration unit. This mode utilizes the mixture of high-pressure fresh steam and secondary steam to form a heat source, reducing the demand for external steam. In the low-temperature section, it switches to MVR mode, where the secondary steam is compressed and heated by the compressor for recycling, avoiding heat energy waste. The equipment status is monitored in real time through vibration amplitude, audio amplitude, and rotation shadow parameters. When the compressor impeller is fouled or the risk of dynamic imbalance exceeds the standard, the system determines the switch to the ejector based on the standard range of radar rotation shadow width and depth. When the ejector flow field becomes unstable, the system directly switches modes and adjusts operating parameters simultaneously to ensure precise matching of heat energy supply and demand. This invention achieves efficient utilization and dynamic balance of heat energy through dual-dimensional intelligent switching, saving energy compared to traditional fixed-mode systems, while reducing the risk of equipment overheating, mechanical wear, and unplanned downtime.

[0053] Please see Figure 2 As shown, it is a structural schematic diagram of the salt separation and recovery module of an embodiment of the present invention. The salt separation and recovery module includes an ammonium sulfate salt separation unit and an ammonium phosphate salt separation unit.

[0054] The ammonium sulfate separation unit is provided with a first thickener, a first centrifuge and a first semi-automatic packaging machine in sequence along the material flow direction. The inlet of the first thickener receives the concentrated liquid output from the evaporation and concentration module, and the outlet of the first centrifuge is connected to the inlet of the first semi-automatic packaging machine.

[0055] The ammonium phosphate separation unit includes a cooling crystallizer, a second thickener, a second centrifuge, and a second semi-automatic packaging machine. The inlet of the cooling crystallizer receives the mother liquor output from the ammonium sulfate separation unit. The inlet of the second thickener is connected to the outlet of the cooling crystallizer, and the outlet of the second centrifuge is connected to the inlet of the second semi-automatic packaging machine.

[0056] In this module, the units of the salt separation and recovery module are directly connected by pipelines, without the intervention of intermediate storage containers, and the material is processed in a continuous flow manner to complete the salt separation process.

[0057] In practice, the concentrated liquid output from the evaporation and concentration module enters the first thickener, where gravity sedimentation achieves initial separation of ammonium sulfate crystals from the mother liquor. The concentrated slurry after initial separation is transported to the first centrifuge for secondary solid-liquid separation. The separated ammonium sulfate crystals are compressed into solid products by the first semi-automatic packaging machine. The mother liquor discharged from the centrifuge is directly transported through pipelines to the ammonium phosphate separation unit, retaining the monoammonium phosphate precursor components in the mother liquor.

[0058] The mother liquor discharged from the ammonium sulfate desalination unit enters the cooling crystallizer, where it is cooled to the crystallization temperature range of monoammonium phosphate, promoting the precipitation of monoammonium phosphate crystals. The slurry containing crystals is conveyed to the second thickener for secondary sedimentation and concentration. The concentrated slurry then enters the second centrifuge to complete solid-liquid separation. The separated monoammonium phosphate crystals are formed into solid products by the second semi-automatic packaging machine. The tail liquid discharged from the centrifuge is either discharged through pipelines into the system or sent to the subsequent wastewater treatment unit.

[0059] In the first thickener, ammonium sulfate crystals settle, and the supernatant is a mother liquor containing monoammonium phosphate precursor. After cooling in a cooling crystallizer, monoammonium phosphate crystals precipitate, forming a solid-liquid mixture. This slurry is further concentrated in the second thickener, and the supernatant is a suspension containing trace amounts of crystals. The concentrated slurry output from the second thickener is separated by a second centrifuge to obtain solid monoammonium phosphate product and a salt-containing tailings. The final products are solid ammonium sulfate and solid monoammonium phosphate, and the tailings are wastewater containing trace amounts of sodium sulfate and phosphate. The selection of the above equipment is not specifically limited.

[0060] Specifically, the steam circulation module determines the main equipment based on the steam inlet temperature of the first evaporation and concentration unit in the evaporation and concentration module;

[0061] Based on the determination result that the steam inlet temperature is greater than or equal to the preset circulation temperature, the main device is determined to be a steam ejector;

[0062] Based on the determination that the steam inlet temperature is less than the preset circulation temperature, the main equipment is determined to be a steam compressor.

[0063] During implementation, the preset circulation temperature is 100–115°C. The MVR mode is a steam compressor-dominated circulation mode, and the TVR mode is a steam ejector-dominated circulation mode.

[0064] Understandably, in MVR mode, the secondary steam generated by the evaporator is only 60-90°C. It must first pass through the steam compressor to increase its pressure and temperature synchronously before it can be sent back to the first-effect heater. Therefore, the steam temperature entering the heater is raised to about 100-110°C. In contrast, in TVR mode, the primary steam sent from the boiler is 0.35-0.6 MPa and 140-160°C. After mixing with some of the secondary steam in the ejector, its temperature is higher than that of the secondary steam. When the mixed steam enters the first-effect heater, its temperature usually reaches 115-125°C. Therefore, there will be a significant temperature difference of 5-15°C at the same heater inlet between the two modes.

[0065] In this invention, the dominant equipment is automatically selected based on the steam inlet temperature of the first evaporation and concentration unit, achieving efficient utilization of thermal energy in a cascade manner. Temperature threshold control also avoids the risk of equipment overheating. In addition, combined with a dynamic steam temperature adjustment strategy, the thermal energy supply and demand balance of the evaporation, concentration and salt recovery modules is ensured, ultimately achieving the effects of low energy consumption, high stability and long equipment life.

[0066] Please see Figure 3 As shown, it is a logic diagram of the low-consumption cycle control mode in the evaporation and crystallization process according to an embodiment of the present invention. The steam detection module periodically acquires the peak values ​​of the image generation parameters in the time domain waveform diagram of each amplitude of the main equipment, and calculates the average value and standard deviation of the peak values ​​of the image generation parameters. The fluctuation discrete parameters of the main equipment are determined according to the ratio of the standard deviation to the average value.

[0067] The parameters for generating the audio amplitude time-domain waveform diagram are the audio amplitude of the steam ejector and the parameters for generating the vibration amplitude time-domain waveform diagram are the vibration amplitude of the steam compressor.

[0068] In practice, the time interval corresponding to the time-domain waveform images is 1 hour. This is understandable because the steam compressor, as the core of the MVR mode, is prone to high-frequency vibration or localized overheating due to thermal stress and lubrication failure in its high-speed rotating components such as impellers and bearings. Hourly monitoring can capture early signs of failure and prevent equipment failure caused by bearing wear and gear fatigue. For example, when the bearing temperature exceeds 80°C, the lubricating oil viscosity decreases, significantly increasing the risk of lubrication failure, requiring immediate shutdown and maintenance.

[0069] Analyzing at hourly intervals can help deal with sudden failures, enable emergency shutdown protection, prevent catastrophic damage to equipment, avoid unnecessary waste of raw materials due to subsequent production inefficiencies, and reduce energy consumption of other equipment.

[0070] Specifically, the steam detection module determines whether there is an inefficient crystallization waveform segment in the current dominant equipment based on the fluctuation discrete parameter, including:

[0071] Based on the determination result that the fluctuation discrete parameter is greater than or equal to the standard discrete parameter of the corresponding main equipment, it is determined that there is an inefficient crystallization waveform segment.

[0072] Based on the determination result that the fluctuation discrete parameter is less than the standard discrete parameter of the corresponding dominant device, it is determined that there is no inefficient crystallization waveform segment.

[0073] In practice, the standard discrete parameters include audio standard discrete parameters and vibration standard discrete parameters, while the wave discrete parameters include vibration wave discrete parameters and audio wave discrete parameters.

[0074] The vibration standard discrete parameter is set specifically for steam compressors. As a high-speed rotating machine, the operating state of a steam compressor is closely related to the dynamic balance of its impeller. When fouling, wear, or dynamic imbalance occurs on the impeller, the impeller's mass distribution changes, generating periodically varying centrifugal forces under high-speed rotation. This physical change is directly and sensitively reflected in the vibration signal of the machine body. The fluctuation discrete parameter of the vibration time-domain waveform image is used to quantify the degree of deviation of this vibration signal from stability, in order to determine the impeller state within the steam compressor. An increase in this parameter clearly indicates that impeller fouling has led to uneven mass distribution, or that mechanical wear has occurred in rotating components such as bearings, resulting in increased overall machine vibration, decreased operational stability, and consequently, reduced compression efficiency and increased energy consumption.

[0075] The vibration standard discrete parameter is determined based on the average value of the vibration fluctuation discrete parameter in the historical data of the steam compressor under normal operating conditions.

[0076] The audio standard discrete parameters are set for steam ejectors. A steam ejector is a static device with no moving parts. Its core function is to generate a high-speed steam jet through a Laval nozzle to create negative pressure. Its operating state is mainly determined by the stability of the internal flow field. When the nozzle changes shape due to fouling or changes size due to wear, it disrupts the stable flow of steam, producing phenomena such as eddies and surges. These abnormalities in fluid dynamics cannot be effectively captured by vibration, but they directly alter the acoustic characteristics emitted during equipment operation. The normally smooth steam sound becomes sharp, intermittent, or muffled. By constructing a time-domain waveform of the audio signal and calculating its fluctuation discrete parameters, the degree of disturbance in these acoustic characteristics can be precisely quantified. An increase in this parameter clearly indicates instability in the internal flow field of the ejector, decreased nozzle efficiency, or blockage, leading to a reduction in its ejection mixing efficiency and an inability to provide a stable and sufficient amount of heat source steam to the system.

[0077] The audio standard discrete parameters are determined based on the average value of the audio fluctuation discrete parameters in historical data of the steam ejector under normal operating conditions.

[0078] Understandably, setting two independent standard discrete parameters essentially means setting judgment parameters best suited to the fault characteristics of two different types of equipment. By determining these two key parameters, the system can achieve comprehensive, accurate, and early diagnosis of the operating status of the core power unit, thereby providing reliable data support for timely predictive maintenance and energy efficiency optimization.

[0079] In this invention, the time-domain waveform parameters of the vibration amplitude of the steam compressor and the audio amplitude of the steam ejector are periodically monitored. Based on a comparison of standard discrete parameters with fluctuating discrete parameters, precise diagnosis of the operating status of the main equipment is achieved. When the vibration / audio fluctuation discrete parameters exceed a threshold, an inefficient crystallization waveform segment is identified, triggering predictive maintenance or mode switching. This mechanism not only achieves early warning of equipment failure through impeller dynamic balance monitoring and flow field acoustic characteristic analysis, avoiding efficiency decline and energy consumption increase caused by scaling, wear, or flow field instability, but also adapts to different equipment characteristics through independent dual-parameter determination, ensuring stable and efficient operation of the core power unit. Ultimately, it achieves a comprehensive beneficial effect of improving system reliability, extending equipment life, reducing maintenance costs, and optimizing energy consumption.

[0080] Specifically, the low-energy consumption control module adjusts the low-energy consumption cycle control mode during the evaporation and crystallization process according to the judgment result of the existence determination, including:

[0081] Based on the determination that the inefficient crystallization waveform segment does not exist, it is determined that the low-power cyclic control mode will not be adjusted.

[0082] Based on the determination of the existence of the inefficient crystallization waveform segment, a corresponding low-power cyclic control mode is selected based on the current dominant equipment, wherein,

[0083] In response to the fact that the current dominant device is a steam compressor, a decision is made based on the rotation shadow information whether to switch the dominant device;

[0084] In response to the current dominant device being a steam ejector, the dominant device is directly switched and the steam input parameters of the circulating evaporation and concentration module are adjusted.

[0085] During implementation, the low-energy control module switches the steam circulation path between MVR and TVR modes, adjusts the on / off of the steam compressor and steam ejector inlet pipes through control valves, and adaptively coordinates the operating parameters of each device after the mode switch to ensure that the system stably achieves wastewater treatment and desalination functions in MVR or TVR modes.

[0086] In this invention, dynamic low-energy control of the evaporation crystallization process is achieved through intelligent detection of inefficient crystallization waveform segments and coordinated optimization of the response strategy of the dominant equipment. When an inefficient crystallization waveform segment is detected, the system executes a differentiated control strategy based on the type of the current dominant equipment: for the steam compressor, a secondary verification mechanism using rotational shadow information is employed to accurately identify the risk of impeller scaling or dynamic imbalance, avoiding erroneous switching; for the steam ejector, mode switching is directly triggered and steam temperature, pressure, and flow parameters are adjusted synchronously to ensure the balance of heat supply and demand and safe operation of the equipment after the TVR / MVR mode switch. This invention not only reduces ineffective energy consumption but also improves the system's anti-interference capability and operational stability through equipment-level fault isolation and parameter adaptive matching, ultimately achieving multiple beneficial effects such as energy saving and consumption reduction, extended equipment life, reduced unplanned downtime, and optimized salt separation efficiency.

[0087] Specifically, the low-energy control module determines that the dominant device needs to be switched to a steam ejector based on the judgment result that the rotation shadow information does not meet the normal rotation shadow conditions.

[0088] The normal rotational shadow condition is that both the width and depth of the rotational shadow are within the corresponding standard range.

[0089] In practice, rotational shadow information is acquired using a linear frequency modulated continuous wave radar. The radar transmits a continuous wave with a linearly varying frequency, and the instantaneous distance to the target is accurately determined by calculating the frequency difference between the transmitted and received echoes. For a rotating impeller, it can continuously measure the distance between the radar probe and the tip of each blade. This results in a precise distance waveform that varies over time. Each trough corresponds to the point where the blade tip is closest to the probe, and each waveform represents the rotational shadow cast by one blade—that is, the rotational shadow information.

[0090] The rotational shadow width is obtained by the duration of the radar echo pulse, and it is mainly affected by the effective reflective area when the blade tip passes through the radar beam cross section. Impeller fouling leads to the accumulation of material at the blade edges, increasing its effective reflective area and thus significantly increasing the pulse width.

[0091] The rotational shadow depth is reflected by the amplitude or intensity of the radar echo pulse, primarily indicating the integrity and alignment of the blade tip reflector. Damage, curling, or severe contamination of the blade can weaken the reflected signal, causing a decrease in pulse depth and / or amplitude, or abnormal fluctuations.

[0092] The width and depth standard intervals are based on the confidence intervals of the shadow width and shadow depth intervals corresponding to the steam compressor operation when no abnormalities were found in historical working data.

[0093] If the rotation shadow information meets the normal rotation shadow conditions, the low-energy control module increases the temperature of the secondary steam. The increase is determined based on the difference between the fluctuating discrete parameter and the standard discrete parameter and the current temperature of the secondary steam, and the increased secondary steam will not damage the equipment.

[0094] Increasing the steam temperature, moving it away from saturation, allows tiny droplets suspended in the steam to evaporate rapidly into a gaseous state, reducing the number and size of droplets at the source. The increased temperature ensures that the droplets evaporate before impacting the blades, or evaporate immediately after impact, leaving no time for salt precipitation.

[0095] Understandably, if the imported secondary steam carries droplets, it will cause liquid hammer, severely damaging the impeller. This leads to scale buildup on the impeller, affecting dynamic balance and causing violent vibration. Blade notches or curling reduce the steam flow area and change the angle of attack, resulting in increased leakage within the compressor and a decrease in isentropic efficiency. Under the same evaporation load, the required motor current increases, energy consumption rises sharply, and reduced efficiency means insufficient compression temperature rise. The steam temperature of the first-effect heater is 3-8°C lower than the design value, resulting in reduced evaporation. The system is forced to operate at a reduced load, and in severe cases, the triple-effect gradient cannot be maintained, the discharge density decreases, the ammonium sulfate crystals become finer, and insufficient evaporation leads to prolonged residence time of the concentrate, increased supersaturation, and accelerated scale buildup on the inner wall of the heating tubes. At the same time, the reduced secondary steam volume increases the steam ejector inlet pressure and decreases the ejector ratio, trapping the system in a vicious cycle of increasing blockage and increasing rotation, eventually leading to a complete shutdown for cleaning. In addition, impeller imbalance causes coaxial vibration. Long-term vibration can cause the high-speed bearing raceway to peel off and the dry gas seal graphite ring to break, increasing maintenance costs from replacing the impeller to replacing the entire impeller, bearing, and seal set.

[0096] The radar probe continuously emits microwaves into the rotating impeller through a waveguide window and receives the echoes. Each blade tip generates a strong echo signal as it passes by, forming a periodic pulse on the range-time graph; this pulse is the radar shadow of the blade. If the depth, width, and period of all pulses are highly consistent, it indicates that the steam compressor blades are functioning normally. Conversely, if the blades become thickened due to fouling, the duration of the tip shadow on the radar, i.e., the pulse width, will increase. Changes in blade shape will also alter the pulse shape.

[0097] In this invention, the width and depth of the impeller rotation shadow of a steam compressor are monitored in real time using linear frequency modulated continuous wave radar. A normal condition threshold is set based on the confidence interval of historical data, enabling precise diagnosis and intelligent response of the equipment status. When the rotation shadow is abnormal, the system automatically switches to steam ejector mode to avoid efficiency degradation and equipment damage caused by impeller scaling and dynamic imbalance. When the status is normal, the secondary steam temperature is dynamically optimized based on fluctuating discrete parameters. This reduces droplet carryover, suppresses salt precipitation and liquid hammer risks, improves compression efficiency, and prevents the vicious cycle of efficiency decline and energy consumption increase caused by scaling. This invention not only achieves early warning and fault isolation of impeller status through non-contact radar technology but also ensures safe equipment operation through coordinated optimization of temperature parameters, ultimately achieving energy saving, extended equipment life, reduced unplanned downtime, and improved salt separation quality.

[0098] Specifically, the low-energy control module responds to the direct switching of the dominant device by adjusting the steam input parameters of the steam circulation module to match the operating range of the dominant device.

[0099] In implementation, the condensate generated by the preheating module is introduced through a control valve group. It mixes with high-temperature steam at the evaporator heater inlet, utilizing the flash evaporation effect to rapidly reduce the steam temperature to below 110°C, preventing overheating of the compressor inlet. A temperature sensor monitors the compressor inlet steam temperature in real time and sends a feedback signal to the low-energy control module. If the temperature still exceeds 100°C, the opening of the compressor bypass valve is adjusted to divert some steam to the condenser for cooling before reinjecting it into the system, forming a closed-loop cooling circuit.

[0100] Specifically, the evaporation and concentration module comprises three evaporation and concentration units connected in series.

[0101] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A low energy consumption evaporation crystallization control system for iron phosphate wastewater, comprising a preheating module and an evaporation concentration module comprising a plurality of evaporation concentration units, characterized in that, include: The steam circulation module includes a steam compressor and a steam ejector. The main equipment is selected according to the steam inlet temperature of the evaporation and concentration module. The steam compressor is used to compress secondary steam and return it to the heater for recycling. The steam ejector is used to mix secondary steam with high-pressure steam to form a mixed heat source. The steam detection module is used to detect the rotation shadow information and vibration amplitude of the steam compressor and construct a time-domain waveform diagram of the vibration amplitude, detect the audio amplitude of the steam ejector and construct a time-domain waveform diagram of the audio amplitude, and determine the existence of inefficient crystallization waveform segments based on the fluctuation discrete parameters corresponding to each time-domain waveform image. The salt separation and recovery module is used to separate and collect ammonium sulfate crystals and monoammonium phosphate crystals, condense the steam discharged from the evaporation and concentration module into condensate, and store a portion of the condensate for the preheating operation of the preheating module. The low-energy control module is used to adjust the low-energy cycle control mode during the evaporation and crystallization process according to the judgment result of the existence determination; to determine not to adjust the low-energy cycle control mode according to the judgment result of the absence of the inefficient crystallization waveform segment; and to determine to select the corresponding low-energy cycle control mode based on the current dominant equipment according to the judgment result of the presence of the inefficient crystallization waveform segment. Specifically, if the current dominant device is a steam compressor, the system determines whether to switch the dominant device based on the rotation shadow information; if the current dominant device is a steam ejector, the system directly switches the dominant device and adjusts the steam input parameters of the circulating evaporation and concentration module. Furthermore, based on the determination result that the rotational shadow information does not meet the normal rotational shadow conditions, it is determined that the dominant device needs to be switched to a steam ejector. The normal rotational shadow conditions are that the width and depth of the rotational shadow are both within the corresponding standard range.

2. The low energy consumption evaporation crystallization control system for iron phosphate wastewater according to claim 1, characterized in that, The salt separation and recovery module includes an ammonium sulfate salt separation unit and an ammonium phosphate salt separation unit; The ammonium sulfate separation unit is provided with a first thickener, a first centrifuge and a first semi-automatic packaging machine in sequence along the material flow direction. The inlet of the first thickener receives the concentrated liquid output from the evaporation and concentration module, and the outlet of the first centrifuge is connected to the inlet of the first semi-automatic packaging machine. The ammonium phosphate separation unit includes a cooling crystallizer, a second thickener, a second centrifuge, and a second semi-automatic packaging machine. The inlet of the cooling crystallizer receives the mother liquor output from the ammonium sulfate separation unit, the inlet of the second thickener is connected to the outlet of the cooling crystallizer, and the outlet of the second centrifuge is connected to the inlet of the second semi-automatic packaging machine. In this module, the units are directly connected by pipes, without the intervention of intermediate storage containers, and the material is processed in a continuous flow manner to complete the salt separation process.

3. The low energy consumption evaporation crystallization control system for iron phosphate wastewater according to claim 1, characterized in that, The steam circulation module determines the main equipment based on the steam inlet temperature of the first evaporation and concentration unit in the evaporation and concentration module; Based on the determination result that the steam inlet temperature is greater than or equal to the preset circulation temperature, the main device is determined to be a steam ejector; Based on the determination that the steam inlet temperature is less than the preset circulation temperature, the main equipment is determined to be a steam compressor.

4. The low energy consumption evaporation crystallization control system for iron phosphate wastewater according to claim 3, characterized in that, The steam detection module periodically acquires a peak value of an image generation parameter in each amplitude-time waveform graph of the leading device, calculates an average value and a standard deviation of the peak value of the image generation parameter, and determines a fluctuation dispersion parameter of the leading device according to a ratio of the standard deviation to the average value. The generation parameter of the audio amplitude-time waveform graph is an audio amplitude of the steam ejector, and the generation parameter of the vibration amplitude-time waveform graph is a vibration amplitude of the steam compressor.

5. The low energy consumption evaporation crystallization control system for iron phosphate wastewater according to claim 4, characterized in that, The steam detection module determines whether there is an inefficient crystallization waveform segment in the current leading device according to the fluctuation dispersion parameter, including: determining that there is an inefficient crystallization waveform segment according to a result that the fluctuation dispersion parameter is greater than or equal to a standard dispersion parameter of the corresponding leading device; determining that there is no inefficient crystallization waveform segment according to a result that the fluctuation dispersion parameter is less than the standard dispersion parameter of the corresponding leading device.

6. The low energy consumption evaporation crystallization control system for iron phosphate wastewater according to claim 5, characterized in that, The low-energy-consumption control module adjusts a steam input parameter of the steam circulation module to a working interval matching the leading device in response to the direct switching of the leading device.

7. The low energy consumption evaporation crystallization control system for iron phosphate wastewater according to claim 1, characterized in that, The evaporation and concentration module includes three evaporation and concentration units connected in series.

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