CN210595353U

CN210595353U - Waste liquid recovery device

Info

Publication number: CN210595353U
Application number: CN202020419976.3U
Authority: CN
Inventors: 刘俊麟; 范永强
Original assignee: BASF Coatings Guangdong Co Ltd
Current assignee: BASF Coatings Guangdong Co Ltd
Priority date: 2020-03-27
Filing date: 2020-03-27
Publication date: 2020-05-22
Anticipated expiration: 2030-03-27

Abstract

A waste liquid recovery device comprises an evaporation tank, a condenser, a storage tank, a pressure regulating part and a vacuum generating part, wherein the pressure regulating part is connected with a nitrogen source pipeline and used for conveying nitrogen with regulated pressure to the evaporation tank through a pipeline; the evaporation tank is used for evaporating waste liquid and conveying steam to the condenser through a pipeline; the condenser condenses the vapor into a separation solvent and delivers the separation solvent to the storage tank; the storage tank is also connected with the vacuum generating part. The utility model discloses a position design of pressure regulating portion and vacuum generation portion has ensured safety in production to production efficiency has been improved.

Description

Waste liquid recovery device

Technical Field

The utility model relates to a waste liquid treatment device especially relates to a waste liquid recovery device.

Background

In the industrial production process, waste liquid is generated, wherein the waste liquid often contains industrial production raw materials, intermediate products, byproducts and the like, and often contains toxic and harmful substances, and the environmental pollution can be caused by random emission. The waste liquid often contains recyclable components, so that the waste liquid is effectively treated and separated, and the production cost of enterprises can be saved. The treatment method of the industrial waste liquid includes a physical treatment method, a chemical treatment method, a biological treatment method and the like. In the chemical industry, an organic solvent is generally used as a cleaning agent, and a waste liquid obtained after cleaning is substantially a mixture of the solvent and a solute. When the boiling point difference between the solvent and the solute is large, the purpose of separating the solvent and the solute can be achieved by adopting a distillation method. Traditional waste liquid evaporation and separation equipment has contained evaporating pot, condenser and collection device. The utility model CN209668987U discloses a waste water treatment equipment, through set up waste water recovery unit, separator, concentrate recovery unit, recycled water recovery unit, distillation plant, condensing equipment in the frame, reached and let it get back to and reuse in the cleaning equipment to reusable washing liquid and water, furthest's reduction waste liquid measure, it has easy and simple to handle, the cost of manufacture is low, energy-concerving and environment-protective technological effect. Utility model CN203677975U discloses a vacuum system of vacuum distillation, vacuumize through the vacuum pump, make the vacuum tank form certain vacuum, provide required vacuum for the vacuum distillation, reached the whole recycle of the material in the vacuum system tail gas, reduced the technological effect of the loss of vacuum distillation in-process material. The above patent technology connects the vacuum generator directly to the distillation system to lower the boiling point of each component in the waste liquid. However, the waste liquid is continuously supplemented into the distillation tank, air is difficult to avoid being brought into the distillation tank, and the vacuum generator can reduce the air in the distillation tank to a certain extent and reduce the possibility of explosion in the distillation tank. However, the air and the exhaust gas are simultaneously extracted and cannot be randomly released into the air, and the extracted air and the exhaust gas can still form explosive gas in the next processing device.

Therefore, a new waste liquid recycling device is needed to solve the above technical problems.

SUMMERY OF THE UTILITY MODEL

For solving the problem that retort, vacuum tank or other gaseous collection device can form explosive gas among traditional waste liquid recovery device, the utility model provides a waste liquid treatment device with fill nitrogen device to reach safety in production and improve production efficiency's purpose. The purpose of the utility model is realized by adopting the following technical scheme:

a waste liquid recovery device comprises an evaporation tank, a condenser, a storage tank, a pressure regulating part and a vacuum generating part, wherein the pressure regulating part is connected with a nitrogen source pipeline and used for conveying nitrogen with regulated pressure to the evaporation tank through a pipeline; the evaporation tank is used for evaporating waste liquid and conveying steam to the condenser through a pipeline; the condenser condenses the vapor into a separation solvent and delivers the separation solvent to the storage tank; the storage tank is also connected with the vacuum generating part.

Further, the pressure regulating part comprises a first pressure regulating valve, and the nitrogen gas source is a high-pressure nitrogen gas source; and nitrogen output by the high-pressure nitrogen source is reduced in pressure by the first pressure regulating valve and is input into the evaporating pot.

The pressure regulating part further comprises a second pressure regulating valve, the first pressure regulating valve and the second pressure regulating valve are connected in series, and nitrogen output by the high-pressure nitrogen source is input into the evaporating pot after being reduced in pressure by the first pressure regulating valve and the second pressure regulating valve in sequence.

Furthermore, the pressure regulating part also comprises a first pressure transmitter, a first exhaust pneumatic valve, an air transmission pneumatic valve and a controller; the first pressure transmitter is adapted to detect the first or second pressure regulating valve outlet; the nitrogen gas with the pressure measured by the pressure transmitter enters the evaporating pot through a main pipeline provided with a gas transmission pneumatic valve or is exhausted outside through a branch pipeline provided with the first exhaust pneumatic valve; the controller is in signal connection with the first pressure transmitter, the first exhaust pneumatic valve and the gas transmission pneumatic valve; when the measured value of the first pressure transmitter is higher than a first preset value, the first exhaust pneumatic valve is opened and the gas transmission pneumatic valve is closed; and when the measured value of the first pressure transmitter is lower than a first preset value, the gas transmission pneumatic valve is opened and the first exhaust pneumatic valve is closed.

Furthermore, the pressure regulating part also comprises a first pressure transmitter, an electric three-way valve and a controller; the first pressure transmitter is adapted to detect the first or second pressure regulating valve outlet; an outlet of the first pressure regulating valve or an outlet of the second pressure regulating valve is connected with a first port pipeline of the electric three-way valve, a second port of the electric three-way valve is connected with an air inlet pipeline of the evaporation tank, and a third port of the electric three-way valve is suitable for discharging nitrogen to the outside; the controller is in signal connection with the first pressure transmitter and the electric three-way valve; when the measured value of the first pressure transmitter is higher than a first preset value, the first port and the third port are communicated, and the first port and the second port are cut off; and when the measured value of the first pressure transmitter is lower than a first preset value, the first port and the second port are communicated, and the first port and the third port are cut off.

Further, the first preset value is less than or equal to 0.2 bar.

Further, the vacuum generating part comprises a vacuum generator, an inlet of the vacuum generator is connected with a high-pressure air source, and a sucker of the vacuum generator is connected with an air pumping port of the storage tank.

Further, the vacuum generating part also comprises a second pressure transmitter, a second discharge pneumatic valve and an air inlet valve; the gas of the high-pressure gas source enters the vacuum generator through the air inlet valve and is discharged through the second discharge pneumatic valve; and the second pressure transmitter is used for detecting the pressure of the inlet front end pipeline of the vacuum generator, and when the measured value of the second pressure transmitter is smaller than a second preset value, the air inlet valve and the second discharge pneumatic valve are closed.

Further, the second preset value is 4 bar.

Further, the vacuum generating part further comprises an air suction filter, and the pipeline between the air suction port and the vacuum generator is also connected with the air suction filter.

The utility model provides a waste liquid recovery device with a nitrogen charging device, wherein a pressure regulating part is connected with a nitrogen source pipeline and transmits nitrogen with regulated pressure to an evaporation tank through a pipeline; the evaporating pot is connected with the condenser and the storage tank, and the vacuum generating part is connected with the storage tank at the tail end. According to the connecting structure, nitrogen continuously replaces the gas in the evaporating tank, the condenser and the storage tank, most of the gas in the structure is expected to be nitrogen, and the gas in the structure is prevented from forming explosive gas; in addition, because the extracted gas mainly comprises nitrogen, the gas component is mainly nitrogen in the next step of treating the waste gas, and explosive gas cannot be formed, thereby systematically ensuring safety. In addition, the vacuum generating part is connected with the tail end, so that the whole medium air pressure of the evaporating pot, the condenser and the storage tank is lower, and the boiling point of the waste liquid solvent in the evaporating pot is reduced; on the other hand, the suction force of the vacuum generating part is also utilized, so that the steam flows rapidly along the direction of the condenser, and the production efficiency is improved; furthermore, the vacuum degree in the storage tank can be guaranteed, and the solvent in the storage tank is prevented from being deteriorated due to the reaction with the gas in the air.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the principles of the invention.

FIG. 1 is a schematic view of a waste liquid recovery apparatus according to the present invention;

FIG. 2 is a detailed view of the pressure regulating part of FIG. 1;

FIG. 3 is another detailed view of the pressure regulating section of FIG. 1;

FIG. 4 is a detailed schematic view of the tank of FIG. 1;

fig. 5 is a detailed schematic view of the vacuum generating part of fig. 1.

1. A pressure regulating part; 11. a first pressure regulating valve; 12. a second pressure regulating valve; 13. a first pressure transmitter; 14. a first exhaust valve; 15. a gas transmission pneumatic valve; 16. a pressure regulating switch valve; 17. an electric three-way valve; 171. a first port; 172. a second port; 173. a third port; 2. an evaporator tank; 21. an air inlet; 3. a condenser; 4. a storage tank; 41. a storage tank feed inlet; 42. a tank outlet valve; 43. an air extraction opening; 44. a vacuum degree measuring instrument; 45. a high level tuning fork; 5. a vacuum generating section; 51. a vacuum generator; 52. a second pressure transmitter; 53. a second discharge pneumatic valve; 54. an air intake valve; 55. an intake filter; 56. an inlet valve; 57. a flexible hose.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are for purposes of illustration only and are not to be construed as limitations of the invention. It should be noted that, for convenience of description, only the parts related to the present invention are shown in the drawings.

In the present invention, the embodiments and the features of the embodiments may be combined with each other without conflict. The present invention will be described in detail with reference to the accompanying drawings in conjunction with embodiments.

Referring to the attached drawing 1, the utility model provides a washing waste liquid recovery unit with fill nitrogen device, including transfer splenium 1, evaporating pot 2, condenser 3, storage tank 4 and vacuum generation portion 5.

The pressure regulating part 1 is connected with a nitrogen source pipeline, and nitrogen with regulated pressure is conveyed to the evaporating pot 2 through a pipeline. The gas source can be a low-pressure nitrogen gas source or a high-pressure nitrogen gas source. When the gas source is a low-pressure nitrogen gas source, the pressure regulating part 1 is provided with a compressor to regulate the gas pressure. The high-pressure nitrogen gas source is a nitrogen gas source which provides gas pressure not less than 1 bar. The evaporator 2 is used for evaporating waste liquid and conveying steam to the condenser 3 through a pipeline. The condenser 3 condenses the vapor into a separation solvent, and delivers the separation solvent to the storage tank 4. After the device is started, the nitrogen continuously replaces the gas in the evaporating pot 2, the condenser 3 and the storage tank 4, and most of the gas in the structure is expected to be the nitrogen, so that the gas in the structure is prevented from forming explosive gas. Further, the exhaust gas is required to be treated to discharge the gas from the evaporation tank 2, the condenser 3, and the storage tank 4, and there is still a possibility that the exhaust gas constitutes an explosive gas. After the nitrogen is filled, the extracted gas is mainly nitrogen, and in the next step of treating the waste gas, the gas component is mainly nitrogen, so that explosive gas cannot be formed, and the safety is systematically ensured.

The vacuum generating part 5 is also connected to the storage tank 4. The vacuum generator 5 continuously removes gas from the accumulator 4 so that the accumulator 4, the condenser 3, and the evaporator 2 are all kept at a certain vacuum level. From the Clausius equation: when the pressure is reduced, the boiling point is lowered, thereby reducing the energy consumption of the evaporation tank 2. On the other hand, the vacuum generating part 5 is arranged at the storage tank at the tail end of the system, a large pressure gradient is generated between the evaporating pot 2 and the storage tank 4, the flow of steam in the evaporating pot 2 to the condenser 3 is accelerated, and the production efficiency is further improved. In addition, vacuum storage is required after the solvent is collected to prevent the solvent from deteriorating due to contact with air. The technical scheme of the utility model, at the in-process of separation and purification solvent, just directly ensured storage tank 4's vacuum, improved separation solvent's quality.

Referring to fig. 2, a detailed structure of the pressure adjusting part 1 is shown. The pressure regulating part 1 comprises a first pressure regulating valve 11, and the nitrogen gas source is a high-pressure nitrogen gas source. And nitrogen output by the high-pressure nitrogen source is input into the evaporation tank 2 after being subjected to pressure reduction by the first pressure regulating valve 11. Since the main purpose of the nitrogen gas entering the evaporation tank 2 is to replace the gas in the evaporation tank 2, and the evaporation tank 2 needs to ensure a certain vacuum degree, if the pressure of the input nitrogen gas is too high, unnecessary loss of nitrogen gas will be caused, and mutual energy loss of the vacuum generation part 5 will also be caused. Therefore, the nitrogen gas pressure needs to be adjusted to an appropriate pressure value. Said suitable pressure value is less than 0.2 bar. When the pressure of the nitrogen gas source is at a lower position, if the air pressure of the high-pressure nitrogen gas source is 1bar, the pressure regulating requirement can be met by adopting a single pressure regulating valve. The second pressure regulating valve 12 needs to be added if the pressure of the high-pressure nitrogen gas source is large. The first pressure regulating valve 11 and the second pressure regulating valve 12 are connected in series, and nitrogen output by the high-pressure nitrogen source is input into the evaporation tank 2 after being subjected to pressure reduction through the first pressure regulating valve 11 and the second pressure regulating valve 12 in sequence. The first pressure regulating valve 11 can reduce the pressure of nitrogen to below 2bar, and then the second pressure regulating valve 12 can reduce the pressure to below 0.2 bar.

Considering the situation that the pressure of the high-pressure air source is too high or the first pressure regulating valve 11 and the second pressure regulating valve 12 fail, the pressure of the output nitrogen is caused to be more than 0.2 bar. Therefore, a detection device and an automatic control system are required to ensure the pressure of the gas to be supplied to the evaporation tank 2. Referring to fig. 2, a first embodiment of the pressure regulating section 1 is disclosed.

The pressure regulating part 1 further comprises a first pressure transmitter 13, a first exhaust pneumatic valve 14, a gas transmission pneumatic valve 15 and a controller. In the case of only the first pressure regulating valve 11, the first pressure transmitter 13 should be provided at the outlet of the first pressure regulating valve 11 for detecting the outlet pressure of the first pressure regulating valve 11. When there is a second pressure regulating valve 12 or a plurality of pressure regulating valves in series, a first pressure transmitter 13 should be provided at the outlet of the pressure regulating valve at the very end of the gas flow path to detect the gas pressure that is finally passed into the evaporation tank 2. The nitrogen gas whose pressure is measured by the first pressure transmitter 13 enters the evaporation tank 2 through a main pipeline provided with a gas transmission pneumatic valve 15. While a branch line with a first bleed air valve 14 is provided on the main line. The controller is in signal connection with the first pressure transmitter 13, the first exhaust pneumatic valve 14 and the gas transmission pneumatic valve 15. The first pressure transmitter 13 transmits the detected measurement value to the controller, which compares the measurement value with a preset first preset value, and when the measurement value is higher than the first preset value, the first exhaust valve 14 is opened and the pneumatic valve 15 is closed to exhaust the nitrogen gas from the first exhaust valve 14 to the outside. When the measured value is lower than a first preset value, the gas transmission pneumatic valve 15 is opened and the gas exhaust pneumatic valve is closed, and at the moment, nitrogen enters the evaporation tank 2 along the main pipeline.

Referring to fig. 3, another embodiment of the pressure regulating section 1 is disclosed. The pressure regulating part 1 comprises a first pressure transmitter 13, an electric three-way valve 17 and a controller.

The first port 171 of the electric three-way valve 17 is used for receiving nitrogen gas with pressure measured by the pressure transmitter; the second port 172 of the electric three-way valve 17 is connected to the gas inlet 21 of the evaporation tank 2 through a pipe, and the third port 173 of the electric three-way valve 17 is adapted to discharge nitrogen gas to the outside. The controller is in signal connection with the first pressure transmitter 13 and the electric three-way valve 17. When the measured value of the first pressure transmitter 13 is higher than a first preset value, the first port 171 and the third port 173 are communicated, and the first port 171 and the second port 172 are cut off; when the measured value of the first pressure transmitter 13 is lower than a first preset value, the first port 171 and the second port 172 are communicated and the first port 171 and the third port 173 are cut off.

The first preset value described in the above embodiment is less than or equal to 0.2 bar.

In order to facilitate the connection between the pressure regulating part 1 and the air source and have better maintainability, the foremost end of the pipeline of the pressure regulating part 1 is also provided with a pressure regulating part switch valve 16 for controlling the high-pressure nitrogen to enter the pressure regulating part 1.

Referring to fig. 4, a detailed structure of the reservoir 4 is shown. The storage tank 4 comprises a storage tank feeding hole 41, a storage tank discharging hole and an air pumping hole 43. The storage tank feed inlet 41 is connected with the condenser 3 through a pipeline and used for receiving the solvent condensed by the condenser 3, and the storage tank discharge outlet is connected with a storage tank outlet valve 42 and used for providing the purified solvent. The pumping port 43 is connected to the vacuum generating section 5 through a pipe. The storage tank further comprises a vacuum degree measuring instrument 44 for detecting the vacuum degree of the storage tank and a high liquid level tuning fork 45 arranged at the upper end of the storage tank. The high level tuning fork 45 is used to sense the level of the extracted solvent in the tank and signal when the detection position of the high level tuning fork 45 is reached to indicate that the tank is full.

Vacuum generating part 5 can utilize the mode that the vacuum pump bled air to obtain the vacuum, the utility model provides an adopt the mode of vacuum generator 51 evacuation to reduce cost. The vacuum generator 51 uses the relationship between the pressure and the flow rate of the fluid in the bernoulli principle, so that the high-pressure gas passes through the vacuum generator 51 at a high speed, thereby generating a suction force at the suction cup of the vacuum generator 51 to vacuumize the storage tank. Referring to fig. 5, a detailed structure of the vacuum generating part 5 is shown. The vacuum generating part 5 comprises a vacuum generator 51, the inlet of the vacuum generator 51 is connected with a high-pressure air source, and the suction cup of the vacuum generator 51 is connected with the pumping hole 43 of the storage tank. The high pressure gas source is adapted to provide high pressure gas at a pressure above 4 bar.

Since the pressure is smaller as the flow rate of the fluid is larger, it is necessary to secure a high flow rate of the fluid passing through the vacuum generator 51, but on the other hand, if the flow rate of the fluid passing through the vacuum generator 51 is too high, it is also disadvantageous to substantially replace the gas in the evaporation tank, and it is also wasteful of energy, so that after the storage tank reaches a certain vacuum degree, a pressure maintaining measure should be taken, and after the vacuum degree of the vacuum tank is reduced, the compressed gas source should be turned on. The utility model discloses in vacuum generation portion 5 sets up second pressure transmitter 52, second and discharges pneumatic valve 53 and air admission valve 54. The second pressure transmitter 52, the second exhaust pneumatic valve 53 and the air intake valve 54 are in signal connection with the controller.

The gas of the high-pressure gas source enters the vacuum generator 51 through the air inlet valve 54 and is discharged through the second discharge pneumatic valve 53; the second pressure transmitter 52 is used for detecting the pressure of the inlet front end pipeline of the vacuum generator 51. When the pressure value measured by second pressure transmitter 52 becomes lower, it is explained that the gas flow rate at the measurement point by second pressure transmitter 52 is faster at this time. Since the cross-sectional area of the pipe is constant, when the gas flow rate at the measurement point of the second pressure transmitter 52 is high, the amount of fluid passing through the measurement point per unit time is large, the suction force generated by the vacuum generator 51 is high, and at this time, the pressure maintaining function can be activated. I.e. the measured value of said second pressure transmitter 52 received by the controller is less than the second preset value, said air inlet valve 54 and second exhaust pneumatic valve 53 are closed to stop the evacuation of the tank and at the same time stop the nitrogen filling. The second preset value is 4 bar. In order to prevent mechanical impurities in the storage tank from entering the vacuum generator 51 during vacuum pumping and causing blockage of the vacuum generator 51, the vacuum generating part 5 further comprises a suction filter 55, and the suction filter 55 is connected to the pipeline between the suction port 43 and the vacuum generator 51. In order to facilitate the connection of the vacuum generating part 5 to an external high pressure air source, the air inlet valve 54 is connected to an inlet valve 56 through a flexible hose 57, and the inlet valve 56 is used for connecting to a high pressure air source.

In the description herein, reference to the description of the terms "one embodiment/mode," "some embodiments/modes," "example," "specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment/mode or example is included in at least one embodiment/mode or example of the application. In this specification, the schematic representations of the terms used above are not necessarily intended to be the same embodiment/mode or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments/modes or examples. Furthermore, the various embodiments/aspects or examples and features of the various embodiments/aspects or examples described in this specification can be combined and combined by one skilled in the art without conflicting therewith.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present application, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

It will be understood by those skilled in the art that the foregoing embodiments are provided for clarity of description only, and are not intended to limit the scope of the invention. Other variations or modifications to the above described embodiments will be apparent to those skilled in the art and are within the scope of the invention.

Claims

1. A waste liquid recovery device comprises an evaporation tank, a condenser and a storage tank; the method is characterized in that: the device also comprises a pressure regulating part and a vacuum generating part, wherein the pressure regulating part is connected with a nitrogen source pipeline and used for conveying the nitrogen with the regulated pressure to the evaporating pot through a pipeline;

the evaporation tank is used for evaporating waste liquid and conveying steam to the condenser through a pipeline;

the condenser condenses the vapor into a separation solvent and delivers the separation solvent to the storage tank;

the storage tank is also connected with the vacuum generating part.

2. A waste liquid recovery device as claimed in claim 1, wherein: the pressure regulating part comprises a first pressure regulating valve, and the nitrogen gas source is a high-pressure nitrogen gas source; and nitrogen output by the high-pressure nitrogen source is reduced in pressure by the first pressure regulating valve and is input into the evaporating pot.

3. A waste liquid recovery device as claimed in claim 2, wherein: the pressure regulating part further comprises a second pressure regulating valve, the first pressure regulating valve and the second pressure regulating valve are connected in series, and nitrogen output by the high-pressure nitrogen source is input into the evaporating pot after being reduced in pressure by the first pressure regulating valve and the second pressure regulating valve in sequence.

4. A waste liquid recovery device as claimed in claim 3, wherein: the pressure regulating part also comprises a first pressure transmitter, a first exhaust pneumatic valve, an air transmission pneumatic valve and a controller; the first pressure transmitter is adapted to detect the first or second pressure regulating valve outlet; the nitrogen gas with the pressure measured by the pressure transmitter enters the evaporating pot through a main pipeline provided with a gas transmission pneumatic valve or is exhausted outside through a branch pipeline provided with the first exhaust pneumatic valve; the controller is in signal connection with the first pressure transmitter, the first exhaust pneumatic valve and the gas transmission pneumatic valve; when the measured value of the first pressure transmitter is higher than a first preset value, the first exhaust pneumatic valve is opened and the gas transmission pneumatic valve is closed; and when the measured value of the first pressure transmitter is lower than a first preset value, the gas transmission pneumatic valve is opened and the first exhaust pneumatic valve is closed.

5. A waste liquid recovery device as claimed in claim 3, wherein: the pressure regulating part also comprises a first pressure transmitter, an electric three-way valve and a controller; the first pressure transmitter is adapted to detect the first or second pressure regulating valve outlet; an outlet of the first pressure regulating valve or an outlet of the second pressure regulating valve is connected with a first port pipeline of the electric three-way valve, a second port of the electric three-way valve is connected with an air inlet pipeline of the evaporation tank, and a third port of the electric three-way valve is suitable for discharging nitrogen to the outside; the controller is in signal connection with the first pressure transmitter and the electric three-way valve; when the measured value of the first pressure transmitter is higher than a first preset value, the first port and the third port are communicated, and the first port and the second port are cut off; and when the measured value of the first pressure transmitter is lower than a first preset value, the first port and the second port are communicated, and the first port and the third port are cut off.

6. A waste liquid recovery apparatus as claimed in any one of claims 4 to 5, wherein: the first preset value is less than or equal to 0.2 bar.

7. A waste liquid recovery apparatus as claimed in any one of claims 1 to 5, wherein: the vacuum generating part comprises a vacuum generator, an inlet of the vacuum generator is connected with a high-pressure air source, and a sucker of the vacuum generator is connected with an air pumping hole of the storage tank.

8. The waste liquid recovery apparatus according to claim 7, wherein: the vacuum generating part also comprises a second pressure transmitter, a second discharge pneumatic valve and an air inlet valve; the gas of the high-pressure gas source enters the vacuum generator through the air inlet valve and is discharged through the second discharge pneumatic valve; and the second pressure transmitter is used for detecting the pressure of the inlet front end pipeline of the vacuum generator, and when the measured value of the second pressure transmitter is smaller than a second preset value, the air inlet valve and the second discharge pneumatic valve are closed.

9. A waste liquid recovery device as claimed in claim 8, wherein: the second preset value is 4 bar.

10. The waste liquid recovery apparatus according to claim 7, wherein: the vacuum generating part further comprises an air suction filter, and the pipeline between the air suction port and the vacuum generator is further connected with the air suction filter.