Low-temperature vacuum drying device for high-salinity wastewater

Abstract

The utility model belongs to the technical field of wastewater treatment, and particularly relates to a low-temperature vacuum drying device for high-salinity wastewater, which comprises a feeding component and a discharging component, the feeding component comprises a first feeding tank and a second feeding tank which are arranged side by side, and a liquid inlet valve is mounted at the bottom between the first feeding tank and the second feeding tank; the second feeding tank is communicated with the low-temperature evaporation tank body through a feeding pipeline, the low-temperature evaporation tank body is connected with a vacuum pump, and a first feeding valve is mounted on the feeding pipeline; the discharging assembly comprises a spiral discharging machine, a discharging tank and a storage tank, and a first discharging valve is installed on a feeding port of the spiral discharging machine; a second discharge valve is mounted between the discharge tank and the storage tank; the first discharging valve and the second discharging valve are arranged in an interlocking mode. According to the device, a negative-pressure self-suction two-stage feeding mode and a closed two-section discharging mode are adopted, frequent conversion of the low-temperature vacuum evaporation tank body under vacuum and normal pressure is avoided, and mechanical abrasion and operation cost are reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of wastewater treatment, and in particular relates to a low-temperature vacuum drying device for treating high-salt wastewater. Background Art

[0002] Wastewater generated during industrial production that has a total salt content of 1% or more is called high-salinity wastewater. This type of wastewater usually contains high concentrations of inorganic ions (such as Cl - 、SO4 2- 、Na + and Ca 2+ Due to its poor biodegradability, high-salinity wastewater is extremely difficult to treat, and an efficient and reliable method is needed to further reduce the amount of high-salinity wastewater.

[0003] Low-temperature vacuum drying technology has the characteristics of low energy consumption and strong applicability. It is currently an effective means of treating high-salt wastewater. This technology can evaporate the water in the wastewater at a relatively low temperature, realize the separation of brine and the resource utilization of wastewater. Existing low-temperature vacuum drying equipment mainly includes paddle dryers and belt dryers. Among them, paddle dryers are widely used in wastewater reduction treatment due to their advantages such as large heat transfer area, small footprint and high loading coefficient.

[0004] The paddle dryer mainly includes a low-temperature evaporation tank, an inlet and outlet port set at both ends of the low-temperature evaporation tank, and a condenser for condensing the steam generated during the evaporation of high-salt wastewater. Its working principle is to first evacuate the low-temperature evaporation tank, then introduce the high-salt wastewater into the low-temperature evaporation tank for low-temperature evaporation, and the water vapor enters the condenser and condenses into water before being discharged in compliance with the standards; the remaining material is discharged from the outlet after drying. However, when discharging, it is necessary to restore the normal pressure in the low-temperature evaporation tank before discharging, which requires frequent vacuum pumping and release operations, which not only increases energy consumption, but also causes the low-temperature evaporation tank to frequently switch between normal pressure and vacuum states, resulting in mechanical wear of the equipment structure, especially the frequent wear of key components such as vacuum pumps in frequent vacuum adjustments, which directly shortens the service life of the equipment. In addition, during the discharging process, the vacuum environment is destroyed and the equipment is in a shutdown state; after feeding, it is necessary to re-vacuum, which increases the wastewater treatment time and reduces the operating efficiency of the equipment. Utility Model Content

[0005] The purpose of the utility model is to provide a low-temperature vacuum drying device for high-salt wastewater in order to solve the above-mentioned problem.

[0006] The technical solution of this utility model is as follows:

[0007] A low-temperature vacuum drying device for high-salinity wastewater, comprising a feed assembly and a discharge assembly, wherein the feed assembly comprises a first feed tank and a second feed tank arranged side by side, and a liquid inlet valve is installed at the bottom between the first feed tank and the second feed tank; the second feed tank is connected to a low-temperature evaporation tank body through a feed pipeline, the low-temperature evaporation tank body is connected to a vacuum pump, and a first feed valve is installed on the feed pipeline;

[0008] The discharging assembly includes a spiral discharging machine, a discharging tank and a storage tank. The feed port of the spiral discharging machine is connected to the low-temperature evaporation tank body, and a first discharging valve is installed on the feed port; a second discharging valve is installed between the discharging tank and the storage tank; the first discharging valve and the second discharging valve are interlocked.

[0009] According to a further solution, the second feed tank is connected with a first vacuum gauge for detecting the internal vacuum degree thereof, and the feed pipeline is installed with a first liquid flow meter; the output ends of the first vacuum gauge and the first liquid flow meter are both connected to a controller, and the output end of the controller is respectively connected to the liquid inlet valve and the first feed valve to control their opening or closing actions.

[0010] In a further solution, the first feed tank is connected to an external pipeline, and a second liquid flow meter and a second feed valve are installed on the external pipeline to control the feed amount.

[0011] In a further solution, the input ends of the spiral discharging machine and the first discharging valve are both connected to a controller to control them to work synchronously;

[0012] A second vacuum gauge is installed on the discharge tank to detect the vacuum degree.

[0013] In a further embodiment, the aspect ratio of the low-temperature evaporation tank is 2 to 3:1.

[0014] According to a further solution, a sensor is installed at the feed port of the spiral discharging machine, the output end of the sensor is connected to the controller, the output end of the controller is respectively connected to the first discharging valve and the second discharging valve, and a contactor is connected between the controller and the second discharging valve; when the controller drives the first discharging valve to open, the second discharging valve is closed; when the controller drives the first discharging valve to close, the second discharging valve is opened.

[0015] In a further solution, the inner cavity of the low-temperature evaporation tank body is provided with a central transmission shaft along the length direction, and multiple stirring shafts are installed on the outer periphery of the central transmission shaft, and the multiple stirring shafts are arranged in an equidistant and staggered manner; a scraper is installed at the end of the stirring shaft, and a spoiler blade is installed in the middle section of the stirring shaft.

[0016] In a further solution, the scrapers and spoiler blades are arranged crosswise with the stirring shaft, and the scrapers and spoiler blades on the same stirring shaft are arranged in an eight-shaped shape.

[0017] In a further solution, the central transmission shaft is connected to a servo motor to drive the central transmission shaft to rotate.

[0018] In a further solution, the width of the scraper and the spoiler blade is 8 to 12 cm and the length is 10 to 15 cm; the horizontal distance between the centers of two adjacent groups of scrapers is not less than 1 / 10 of the length of the low-temperature evaporation tank body and not more than 1 / 8 of the length of the low-temperature evaporation tank body; the vertical distance between the centers of the scraper and the spoiler blade is not less than 1 / 8 of the diameter of the low-temperature evaporation tank body and not more than 3 / 8 of the diameter of the low-temperature evaporation tank body.

[0019] The utility model has the following beneficial effects:

[0020] In the utility model, when the first feed tank is feeding, the first feed valve installed on the feed pipeline between the second feed tank and the low-temperature evaporation tank body is in an open state, and the liquid inlet valve between the first feed tank and the second feed tank is closed. The vacuum pump evacuates the low-temperature evaporation tank body to make the second feed tank negative pressure; when a certain negative pressure is reached, the liquid inlet valve is opened, and the high-salt wastewater in the first feed tank enters the second feed tank through the liquid inlet valve; at the same time, the high-salt wastewater enters the low-temperature evaporation tank body through the feed pipeline under the action of negative pressure. At the same time, the feed amount is calculated by the first liquid flow meter. When the feed amount reaches the preset value, the first feed valve is closed, and the high-salt wastewater in the second feed tank stops entering the low-temperature evaporation tank body.

[0021] In addition, the feed port of the spiral discharge machine in the discharge assembly of the utility model is equipped with a first discharge valve, and a second discharge valve is installed between the discharge tank and the storage tank; and the first discharge valve and the second discharge valve are interlocked. That is, when the first discharge valve is opened, the second discharge valve is closed, and when the first discharge valve is closed, the second discharge valve is opened. Thereby, the vacuum degree in the discharge tank is ensured, and then the vacuum degree of the low-temperature evaporation tank body is ensured, so that it is in a vacuum state throughout the entire working process, and there is no need for frequent vacuum pumping and releasing operations, which reduces energy consumption. Therefore, the low-temperature vacuum drying device of the present application will not destroy its internal vacuum environment during the discharge process, so that it can operate continuously and realize non-stop drying of multiple batches of high-salt wastewater.

[0022] Therefore, the utility model adopts negative pressure self-priming two-stage feeding (from the first feeding tank to the second feeding tank, and then to the low-temperature evaporation tank body) and a closed two-stage discharging method (the first discharging valve is installed at the feeding port of the spiral discharging machine, and the second discharging valve is installed between the discharging tank and the storage tank, and the first discharging valve and the second discharging valve are interlocked), that is, during the feeding and discharging process, the feeding assembly and the discharging assembly will not enter the entire device. When the low-temperature vacuum tank body is working, the feeding assembly and the discharging assembly are both in a pressure-maintaining state, avoiding the reduction of the system vacuum degree of the device during the multi-batch operation process, reducing the mechanical wear of the device and the loss of key components such as the vacuum pump. It also avoids the frequent conversion of the low-temperature vacuum evaporation device under vacuum and normal pressure, reducing mechanical wear and operating costs.

[0023] The low-temperature vacuum drying device in the utility model can operate continuously to realize non-stop drying of multiple batches of high-salt wastewater. During the entire drying process, material can be fed again after the discharge is completed, without the need to frequently pump and release the vacuum of the device, thus avoiding the loss of time and cost caused by interrupted operation, and improving the overall processing efficiency and the continuity of the device operation.

[0024] The scrapers and spoiler blades used in the low-temperature vacuum tank of the utility model are arranged in an equidistant and staggered manner, which can prevent the accumulation of salt and crystals on the inner wall of the device, reduce scaling, enhance the heat conduction efficiency of the low-temperature vacuum drying tank, improve the turbulence effect of high-salt wastewater, and enhance the drying ability of the low-temperature vacuum evaporation tank for high-salt wastewater.

[0025] In the utility model, the scraper and the spoiler blades are arranged crosswise and obliquely with the stirring shaft, and the two are arranged in an eight-shaped shape, and the size and spacing of the scraper and the spoiler blades are set according to the size of the low-temperature vacuum tank body, so that the working area inside the low-temperature evaporation tank body can be fully covered; and the reasonable spacing between the scraper and the spoiler blades can increase the turbulence effect inside the high-salt wastewater in the early and middle stages during the drying process, reduce the evaporation time of the high-salt wastewater, and improve the evaporation efficiency of the high-salt wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of the utility model;

[0027] Figure 2 This is a right view of the interior of the low-temperature evaporation tank of the utility model;

[0028] Figure 3 It is a structural schematic diagram of the stirring blade in the utility model;

[0029] Figure 4 It is a structural schematic diagram of the discharging assembly in the utility model;

[0030] Figure 5 It is a structural schematic diagram of the feeding component in the utility model.

[0031] The following are the descriptions of the reference numerals:

[0032] 1. Low-temperature evaporation tank; 11. Central transmission shaft; 12. Stirring shaft; 1201. Scraper; 1202. Turbine blade; 13. Servo motor;

[0033] 2. Feed assembly; 21. Feed pipeline; 2101. First liquid flow meter; 2102. First feed valve; 22. Feed tank; 2201. First feed tank; 2202. Second feed tank; 2203. Liquid inlet valve; 2204. First vacuum gauge; 23. External pipeline; 2301. Second liquid flow meter; 2302. Second feed valve;

[0034] 3. Discharging assembly; 31. Screw discharging machine; 32. First discharging valve; 33. Second vacuum gauge; 34. Discharging tank; 35. Second discharging valve; 36. Storage tank. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the utility model clearer, the technical solution of the utility model will be described in detail below. The described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other implementation methods obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0036] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present utility model, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0037] See also Figure 1-5 As shown, this embodiment provides a low-temperature vacuum drying device for high-salt wastewater, including a low-temperature evaporation tank body 1, a feed assembly 2 and a discharge assembly 3, wherein the feed assembly 2 and the discharge assembly 3 are arranged at both ends of the low-temperature evaporation tank body 1; one end of the feed assembly 2 is connected to an external pipeline 23 for communicating with external high-salt wastewater to realize system feeding; the other end of the feed assembly 2 is connected to the low-temperature evaporation tank body 1 through a feed pipeline 21.

[0038] like Figure 5As shown, the feed assembly 2 includes a feed tank 22, and the feed tank 22 adopts a two-stage structure, specifically a first feed tank 2201 and a second feed tank 2202 arranged side by side, the bottom of the first feed tank 2201 and the second feed tank 2202 are connected through a liquid inlet, and a liquid inlet valve 2203 is installed on the liquid inlet; the discharge port of the second feed tank 2202 is connected to the feed port of the low-temperature evaporation tank body 1 through a feed pipeline 21, and the low-temperature evaporation tank body 1 is connected to a vacuum pump (not shown in the figure) to evacuate the low-temperature evaporation tank body 1; the feed pipeline 21 is installed with a first feed valve 2102;

[0039] When the vacuum inside the low-temperature evaporation tank body 1 reaches a certain level, such as -50 to -60 KPa, the liquid inlet valve 2203 is opened, and the high-salt wastewater in the first feed tank 2201 enters the second feed tank 2202, and then enters the low-temperature evaporation tank body 1 through the feed pipeline 21 under the action of negative pressure for treatment.

[0040] like Figure 4 As shown, the discharge assembly 3 includes a spiral discharge machine 31, a discharge tank 34 and a storage tank 36. The spiral discharge machine 31 is a closed type, and its feed port is connected to the low-temperature evaporation tank body 1. A first discharge valve 32 is installed on the feed port; a second discharge valve 35 is installed between the discharge tank 34 and the storage tank 36; the first discharge valve 32 and the second discharge valve 35 are interlocked.

[0041] In this embodiment, the spiral discharging machine 31 and the first discharging valve 32 are both opened and closed synchronously, and can be opened or closed simultaneously manually, and can also be automatically controlled by a controller, that is, the input ends of the spiral discharging machine 31 and the first discharging valve 32 are connected to the controller to realize the control of their synchronous operation; wherein the first discharging valve 32 is selected as a solenoid valve, and the first discharging valve 32 and the spiral discharging machine 31 are connected in parallel at the output end of the controller, and the controller automatically controls their opening and closing.

[0042] In this embodiment, the controller may be any conventional controller in the art, as long as it can receive signals and output control signals.

[0043] Specifically, the second feed tank 2202 is connected with a first vacuum gauge 2204 for detecting the internal vacuum degree thereof, and the feed pipeline 21 is installed with a first liquid flow meter 2101; the output ends of the first vacuum gauge 2204 and the first liquid flow meter 2101 are both connected to a controller, and the output ends of the controller are respectively connected to the liquid inlet valve 2203 and the first feed valve 2102 and control their opening or closing actions. The first feed tank 2201 is connected to an external pipeline 23, and the external pipeline 23 is installed with a second liquid flow meter 2301 and a second feed valve 2302, which are used to control the feed amount of the feed tank 22. In order to prevent external air from entering the device, at the beginning, the liquid inlet valve 2203 is closed and the first feed valve 2102 is open. When the low-temperature tank body is evacuated, the second feed tank body and the low-temperature vacuum tank body are connected, and the vacuum degree detected by the first vacuum gauge 2204 is the vacuum degree inside the low-temperature vacuum tank body. The feed amount of the first feed tank 2201 is controlled by the second liquid flow meter 2301, and the first vacuum meter 2204 controls the opening and closing of the liquid inlet valve 2203 and the vacuum state of the second feed tank 2202 before feeding. When the first vacuum meter 2204 shows that the vacuum degree reaches -50 to -60 KPa, the liquid inlet valve 2203 is opened, and the high-salt wastewater in the first feed tank 2201 enters the second feed tank 2202 through the liquid inlet valve 2203; at the same time, the high-salt wastewater enters the low-temperature evaporation tank body 1 through the feed pipeline 21 under the action of negative pressure, and the feed amount is calculated by the first liquid flow meter 2101. When the feed amount reaches the preset value, the first feed valve 2102 is closed, and the high-salt wastewater in the second feed tank stops entering the low-temperature evaporation tank body 1.

[0044] In this embodiment, the liquid inlet valve 2203 and the first material inlet valve 2102 are both solenoid valves, and their actions can be controlled by a controller.

[0045] In this embodiment, the first discharge valve 32 and the second discharge valve 35 are interlocked, that is, when the first discharge valve 32 is opened, the second discharge valve 35 is closed, and when the first discharge valve 32 is closed, the second discharge valve 35 is opened. This ensures the vacuum degree in the discharge tank, and then ensures the vacuum degree of the low-temperature evaporation tank body 1, so that it is in a vacuum state throughout the entire working process, and does not require frequent vacuum pumping and release operations, thereby reducing energy consumption. Therefore, the low-temperature vacuum drying device of the present application will not destroy its internal vacuum environment during the discharge process, so that it can operate continuously and realize non-stop drying of multiple batches of high-salinity wastewater.

[0046] Specifically, the feed port of the spiral discharger 31 is equipped with a sensor, the output end of the sensor is connected to the controller, the output end of the controller is respectively connected to the first discharge valve 32 and the second discharge valve 35, and a contactor is connected between the controller and the second discharge valve 35; in a specific embodiment, the contactor is a normally closed contact connected in series between the controller and the second discharge valve 35, and the coil is connected in series between the controller and the first discharge valve 32. When the controller receives the signal from the sensor that the dry material has reached the feed port, the first discharge valve 32 is driven to open, and the second discharge valve 35 is closed, and the material enters the discharge tank 34; when the dry material falls into the discharge tank 34, the controller does not receive the sensor signal, and the first discharge valve 32 is driven to close, and the second discharge valve 35 is opened. The material in the discharge tank 34 falls into the storage tank 36 located below under the action of gravity for collection. The interlocking arrangement of the first discharge valve 32 and the second discharge valve 35 can ensure the vacuum degree in the discharge tank, and further ensure the vacuum degree of the low-temperature evaporation tank body 1. A second vacuum gauge 33 is installed on the discharge tank 34 to detect the change of the terminal vacuum degree during discharge and operation.

[0047] After the first discharge valve 32 is closed, the feed assembly 2 enters the next feeding cycle. During the discharge process, the system vacuum degree remains relatively stable, thereby achieving continuous evaporation of high-salt wastewater.

[0048] In another specific embodiment, a second liquid flow meter 2301 and a second feed valve 2302 are installed on the external pipe 23 connected to the first feed tank 2201 to control the feed amount of the first feed tank 2201 .

[0049] In order to further improve the drying effect of high-salt wastewater, in practice, as a preferred embodiment, the length-to-diameter ratio of the low-temperature evaporation tank body 1 is 2 to 3:1. Selecting a low-temperature evaporation tank body with a reasonable length-to-diameter ratio can avoid uneven heating and improve the utilization efficiency of the heat source in the process of achieving high-efficiency evaporation of high-salt wastewater.

[0050] like Figure 1 , 2 As shown, the inner cavity of the low-temperature evaporation tank body 1 is provided with a central transmission shaft 11 along the length direction, and multiple stirring shafts 12 are installed on the periphery of the central transmission shaft 11, and the multiple stirring shafts 12 are arranged in an equidistant and staggered manner; a scraper 1201 is installed at the end of the stirring shaft 12, and a spoiler blade 1202 is installed in the middle of the stirring shaft 12. The central transmission shaft 11 is connected to a servo motor 13, which drives the central transmission shaft to rotate to stir the liquid and increase the turbulence effect of the high-salinity wastewater. The high-salinity wastewater in the tank body is continuously stirred by the scraper and the spoiler blades to achieve rapid evaporation of the wastewater.

[0051] Specifically, Figure 3As shown, the scraper 1201 and the spoiler blade 1202 are arranged crosswise with the stirring shaft 12, and the scraper 1201 and the spoiler blade 1202 on the same stirring shaft 12 are arranged in an eight-shaped shape, that is, the length direction of the scraper 1201 and the spoiler blade 1202 are consistent with the length direction of the low-temperature evaporation tank body 1 and are at an angle of 30° to the axial direction of the central transmission shaft 11. That is, when viewed from the same direction on the same stirring shaft 12, the scraper 1201 is inclined at an angle of 30° toward the center, and the spoiler blade 1202 is inclined at an angle of 30° toward the outer wall.

[0052] In order to improve efficiency, the width of the scraper 1201 and the spoiler blade 1202 is 8 to 12 cm and the length is 10 to 15 cm; the horizontal distance between the centers of two adjacent groups of scrapers 1201 is not less than 1 / 10 of the length of the low-temperature evaporation tank body 1 and not more than 1 / 8 of the length of the low-temperature evaporation tank body 1; the vertical distance between the centers of the scraper 1201 and the spoiler blade 1202 is not less than 1 / 8 of the diameter of the low-temperature evaporation tank body 1 and not more than 3 / 8 of the diameter of the low-temperature evaporation tank body 1.

[0053] That is, in this embodiment, the sizes of the scraper and the spoiler blades are set according to the size of the low-temperature vacuum tank body, so that three sets of stirring shafts 12 can be used in the low-temperature evaporation tank body of this embodiment, that is, the working area inside the low-temperature evaporation tank body 1 can be fully covered; and the reasonable spacing between the scraper and the spoiler blades can increase the turbulence effect inside the high-salt wastewater in the early and middle stages during the drying process, reduce the evaporation time of the high-salt wastewater, and improve the evaporation efficiency of the high-salt wastewater.

[0054] The above is a schematic description of the present invention and its implementation methods, which is not restrictive and is only one of the implementation methods of the present invention, and is not actually limited to this. Therefore, if ordinary technicians in this field are inspired by it and design structural methods and embodiments similar to the technical solution without creativity without departing from the purpose of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A low-temperature vacuum drying device for high-salinity wastewater, comprising a feed component (2) and a discharge component (3), characterized in that: The feed assembly (2) comprises a first feed tank (2201) and a second feed tank (2202) arranged side by side, and a liquid inlet valve (2203) is installed at the bottom between the first feed tank (2201) and the second feed tank (2202); the second feed tank (2202) is connected to the low-temperature evaporation tank body (1) through a feed pipeline (21), the low-temperature evaporation tank body (1) is connected to a vacuum pump, and a first feed valve (2102) is installed on the feed pipeline (21); The discharge assembly (3) comprises a spiral discharge machine (31), a discharge tank (34) and a storage tank (36); a feed port of the spiral discharge machine (31) is in communication with the low-temperature evaporation tank body (1); a first discharge valve (32) is installed on the feed port; a second discharge valve (35) is installed between the discharge tank (34) and the storage tank (36); the first discharge valve (32) and the second discharge valve (35) are interlocked.

2. The low-temperature vacuum drying device according to claim 1, characterized in that: The second feed tank (2202) is connected to a first vacuum gauge (2204) for detecting the vacuum degree inside the second feed tank (2202), and the feed pipeline (21) is installed with a first liquid flow meter (2101); the output ends of the first vacuum gauge (2204) and the first liquid flow meter (2101) are both connected to a controller, and the output end of the controller is respectively connected to the liquid inlet valve (2203) and the first feed valve (2102) to control their opening or closing actions.

3. The low-temperature vacuum drying device according to claim 1, characterized in that: The first feed tank (2201) is connected to an external pipeline (23), and a second liquid flow meter (2301) and a second feed valve (2302) are installed on the external pipeline (23) for controlling the feed amount.

4. The low-temperature vacuum drying device according to claim 1, characterized in that: The input ends of the spiral discharge machine (31) and the first discharge valve (32) are both connected to a controller to control them to work synchronously; The discharge tank (34) is provided with a second vacuum gauge (33) for detecting the vacuum degree.

5. The low-temperature vacuum drying device according to claim 1, characterized in that: The low-temperature evaporation tank (1) has an aspect ratio of 2 to 3:

1.

6. The low-temperature vacuum drying device according to claim 1, characterized in that: The feed port of the spiral discharge machine (31) is equipped with a sensor, the output end of the sensor is connected to a controller, the output end of the controller is respectively connected to a first discharge valve (32) and a second discharge valve (35), and a contactor is connected between the controller and the second discharge valve (35); when the controller drives the first discharge valve (32) to open, the second discharge valve (35) is closed; when the controller drives the first discharge valve (32) to close, the second discharge valve (35) is opened.

7. The low-temperature vacuum drying device according to claim 1, characterized in that: The inner cavity of the low-temperature evaporation tank (1) is provided with a central transmission shaft (11) along the length direction; a plurality of stirring shafts (12) are installed on the outer periphery of the central transmission shaft (11); the plurality of stirring shafts (12) are arranged in an equidistant and staggered manner; a scraper (1201) is installed at the end of the stirring shaft (12); and a spoiler blade (1202) is installed in the middle section of the stirring shaft (12).

8. The low-temperature vacuum drying device according to claim 7, characterized in that: The scraper (1201) and the spoiler blade (1202) are both arranged crosswise with the stirring shaft (12); the scraper (1201) and the spoiler blade (1202) on the same stirring shaft (12) are arranged in an eight-shaped shape.

9. The low-temperature vacuum drying device according to claim 7, characterized in that: The central transmission shaft (11) is connected to a servo motor (13).

10. The low-temperature vacuum drying device according to claim 7, characterized in that: The width of the scraper (1201) and the spoiler blade (1202) is 8 to 12 cm, and the length is 10 to 15 cm; the horizontal distance between the centers of two adjacent groups of scrapers (1201) is not less than 1 / 10 of the length of the low-temperature evaporation tank (1) and not more than 1 / 8 of the length of the low-temperature evaporation tank (1); and the vertical distance between the centers of the scraper (1201) and the spoiler blade (1202) is not less than 1 / 8 of the diameter of the low-temperature evaporation tank (1) and not more than 3 / 8 of the diameter of the low-temperature evaporation tank (1).

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