Vacuum unit

Abstract

The utility model belongs to the technical field of vacuum pumps. The problem that when an existing vacuum unit pumps condensable media, production efficiency, applicability and reliability cannot be considered at the same time is solved. The vacuum unit comprises a first roots pump, a second roots pump and a screw pump, the front end of the first roots pump is sequentially connected with a cooling separation tank and a first cooler from back to front, a second cooler is connected between the first roots pump and the second roots pump, and a third cooler is connected between the second roots pump and the screw pump. The cooling separation tank, the second cooler and the third cooler are all connected with first liquid storage tanks through automatic stop valves, the first liquid storage tanks are all connected with vacuum breaking valves, and the rear end of the screw pump is sequentially connected with a second liquid storage tank and a fourth cooler from back to front; and the second liquid storage tank and each first liquid storage tank are respectively connected with a liquid level meter and a liquid discharge valve. The device has the advantages that the production efficiency, the applicability and the reliability of equipment can be improved when the vacuum unit pumps condensable media.

Description

Technical Field

[0001] This utility model belongs to the field of vacuum pump technology and relates to a vacuum unit. Background Technology

[0002] A vacuum unit is a combination of equipment used to generate, improve, and maintain a vacuum environment. Vacuum units are widely used in the chemical industry because they can provide a high degree of vacuum, which enables effective separation of media. For example, Chinese patent literature discloses a device for separating and purifying polythiols (application number: 201620291978.2).

[0003] In existing vacuum units, when pumping condensable media, the medium liquefies as the pressure gradually increases beyond its saturated vapor pressure. This liquefaction accumulates at the lowest point of the pipeline or in the interstage recovery tank, requiring timely removal to prevent disruption to normal production and safety hazards. Common solutions include: 1. Designing a large recovery tank to meet the storage needs of condensate within a production cycle, but this results in excessive equipment footprint and high investment costs; 2. Shutting down the unit when condensate reaches a certain level, then draining the condensate, and resuming production only after the condensate is drained, but this significantly impacts production efficiency; 3. Designing the recovery tank at least 10 meters above the lowest point of the unit's pipeline, utilizing liquid level and gravity to achieve drainage without cavitation, but this is easily limited by the on-site installation environment; 4. Designing a negative pressure drainage pump, but the negative pressure pump itself is limited by exhaust leakage, shaft seals, and liquid seals, making it impossible to drain condensate in a high vacuum environment. In summary, the existing practices make it impossible for vacuum units to simultaneously achieve production efficiency, applicability, and reliability when pumping condensable media. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems in existing technologies by proposing a vacuum unit. The technical problem this invention aims to solve is how to improve the production efficiency, applicability, and reliability of the vacuum unit when pumping condensable media.

[0005] The objective of this utility model can be achieved through the following technical solutions:

[0006] A vacuum unit includes a first Roots pump, a second Roots pump, and a screw pump connected in sequence. The first Roots pump has a cooling separation tank and a first cooler with an air inlet connected sequentially from rear to front at its front end. A second cooler is connected between the first and second Roots pumps. A third cooler is connected between the second Roots pump and the screw pump. Each of the cooling separation tank, the second cooler, and the third cooler is connected to a first liquid storage tank via an automatic shut-off valve. Each first liquid storage tank is equipped with a vent valve. The screw pump has a second liquid storage tank and a fourth cooler with an exhaust port connected sequentially from rear to front at its rear end. A level gauge and a drain valve are also connected to each of the second and first liquid storage tanks.

[0007] This vacuum unit isolates each first liquid storage tank from the vacuum system by installing an automatic shut-off valve at the inlet of each tank. The level gauge on each tank directly reflects the liquid level. When the level reaches the set height, operators can puncture and drain the liquid using the puncture and drain valves on each tank. Simultaneously, the exhaust pressure of the fourth cooler is atmospheric pressure, so puncture is not required when draining the second liquid storage tank connected to the fourth cooler. This allows the vacuum unit to continuously drain liquid without shutting down, regardless of site elevation or the amount of condensate. It also reduces the scouring and corrosive effects of condensable media entering the pump's working chamber, thereby improving the unit's production efficiency, applicability, and reliability when pumping condensable media.

[0008] In the aforementioned vacuum unit, the unit further includes a PLC controller. The first Roots pump, the second Roots pump, the screw pump, the level gauge, the automatic shut-off valve, the venting valve, and the drain valve are all signal-connected to the PLC controller. The PLC controller controls the opening and closing of the automatic shut-off valve, the venting valve, and the drain valve located on the same first storage tank as the level gauge, or the opening and closing of the drain valve located on the same second storage tank as the level gauge, based on the signal from the level gauge. The level gauge detects the liquid level in each of the first and second storage tanks and feeds the detection signal back to the PLC controller. The PLC controller then controls the corresponding automatic shut-off valve, venting valve, and drain valve to perform corresponding actions, thereby achieving automatic discharge of liquid from each of the first and second storage tanks.

[0009] In one type of vacuum unit described above, a check valve and a solenoid valve for controlling the on / off state are connected in sequence between the second cooler and the screw pump. The check valve prevents backflow of the medium, while the solenoid valve controls the gas flow, ensuring the stability and accuracy of the vacuum level. Specifically, the solenoid valve can control the on / off state of the gas in the vacuum system, thereby achieving control over parameters such as vacuum level, pressure, and flow rate.

[0010] In the aforementioned vacuum unit, explosion-proof motors are connected to the first Roots pump, the second Roots pump, and the screw pump. An explosion-proof pressure transmitter is connected between the cooling separation tank and the first Roots pump. The explosion-proof pressure transmitter can monitor the pressure of the vacuum unit in real time and convert it into a corresponding electrical signal output, which is then fed back to the PLC controller. The PLC controller determines whether the pressure of the vacuum unit exceeds the set pressure threshold based on the received signal. If an abnormality is detected, it can promptly shut off all control power supplies and control signals to the explosion-proof motors to ensure the safety of the vacuum unit.

[0011] In one of the aforementioned vacuum units, an over-temperature protection transmitter is also connected to the screw pump. The over-temperature protection transmitter can monitor the temperature of the vacuum unit in real time and convert it into a corresponding electrical signal output, which is then fed back to the PLC controller. The PLC controller determines whether the temperature of the vacuum unit exceeds the set temperature threshold based on the received signal. If an abnormality is detected, it can promptly shut off all control power supplies to ensure the safety of the vacuum unit.

[0012] Compared with existing technologies, the advantages of this vacuum unit are: it can achieve continuous liquid discharge without stopping the machine, and is not limited by site elevation or the amount of condensate. It reduces the scouring and corrosive effects of condensable media entering the pump working chamber, thereby improving the production efficiency, applicability and reliability of the vacuum unit when pumping condensable media. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of this vacuum unit.

[0014] In the diagram, 1. First Roots pump; 2. Second Roots pump; 3. Screw pump; 4. Cooling separator; 5. First cooler; 5a. Air inlet; 6. Second cooler; 7. Third cooler; 8. Automatic shut-off valve; 9. First liquid storage tank; 10. Air vent valve; 11. Second liquid storage tank; 12. Fourth cooler; 12a. Exhaust port; 13. Level gauge; 14. Drain valve; 15. PLC controller; 16. Check valve; 17. Solenoid valve; 18. Explosion-proof motor; 19. Explosion-proof pressure transmitter; 20. Over-temperature protection transmitter. Detailed Implementation

[0015] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0016] A vacuum unit, as described above Figure 1The system includes a first Roots pump 1, a second Roots pump 2, and a screw pump 3 connected in sequence. The front end of the first Roots pump 1 is connected from back to front to a cooling separation tank 4 and a first cooler 5 with an air inlet 5a. A second cooler 6 is connected between the first Roots pump 1 and the second Roots pump 2. A third cooler 7 is connected between the second Roots pump 2 and the screw pump 3. The cooling separation tank 4, the second cooler 6, and the third cooler 7 are all connected to a first liquid storage tank 9 via an automatic shut-off valve 8. Each of the first liquid storage tanks 9 is connected to a vent valve 10. The rear end of the screw pump 3 is connected from back to front to a second liquid storage tank 11 and a fourth cooler 12 with an exhaust port 12a. The second liquid storage tank 11 and each of the first liquid storage tanks 9 are also connected to a level gauge 13 and a drain valve 14.

[0017] Furthermore, this vacuum unit also includes a PLC controller 15. The first Roots pump 1, the second Roots pump 2, the screw pump 3, the level gauge 13, the automatic shut-off valve 8, the venting valve 10, and the drain valve 14 are all signal-connected to the PLC controller 15. The PLC controller 15 controls the opening and closing of the automatic shut-off valve 8, the venting valve 10, and the drain valve 14 located on the same first storage tank 9 as the level gauge 13, or the opening and closing of the drain valve 14 located on the same second storage tank 11 as the level gauge 13, according to the signal from the level gauge 13.

[0018] Furthermore, a check valve 16 and a solenoid valve 17 for controlling the on / off state are sequentially connected between the second cooler 6 and the screw pump 3; an explosion-proof motor 18 is connected to the first Roots pump 1, the second Roots pump 2 and the screw pump 3; an explosion-proof pressure transmitter 19 is connected between the cooling separation tank 4 and the first Roots pump 1; and an over-temperature protection transmitter 20 is also connected to the screw pump 3.

[0019] The working principle of this vacuum unit is explained below:

[0020] The first Roots pump 1, the second Roots pump 2, the screw pump 3, the level gauge 13, the automatic shut-off valve 8, the venting valve 10, and the drain valve 14 of this vacuum unit are all signal-connected to the PLC controller 15. The PLC controller 15 sends control signals to each motor of the first Roots pump 1, the second Roots pump 2, and the screw pump 3, putting the vacuum unit into operation. When the liquid level in the first storage tank 9 reaches a set height, the level gauge 13 on the first storage tank 9 sends a high-level signal to the PLC controller 15. The PLC controller 15 then controls the automatic shut-off valve 8 on the first storage tank 9 to close, isolating the first storage tank 9 from the vacuum system. Next, the PLC controller 15 controls the venting valve 10 on the first storage tank 9 to open for venting. After venting, the PLC controller 15 then controls the drain valve 14 on the first storage tank 9 to open for normal operation. After the liquid is drained, the level gauge 13 on the first liquid storage tank 9 sends a low level signal to the PLC controller 15. The PLC controller 15 controls the drain valve 14 and the vent valve 10 on the first liquid storage tank 9 to close, and controls the automatic shut-off valve 8 on the first liquid storage tank 9 to open, so that the first liquid storage tank 9 is connected back to the vacuum system to continue receiving condensate. Before entering the second Roots pump 2, the unliquefied medium is compressed and pressurized by a first stage. When it enters the second cooler 6, some of the medium will liquefy after cooling under this pressure. The first liquid storage tank 9 connected to the second cooler 6 repeats the above process to automatically drain the liquid, reducing the amount of liquid medium entering the second Roots pump 2 and reducing the scouring and corrosion of the pump by the liquid medium. Similarly, the automatic draining process and principle of the first liquid storage tank 9 connected to the third cooler 7 are the same as above, reducing the amount of liquid medium entering the screw pump 3 and reducing the scouring and corrosion of the pump by the liquid medium.

[0021] The pressure at the exhaust port 12a of the fourth cooler 12 is atmospheric pressure, so the second liquid storage tank 11 connected to the fourth cooler 12 does not need to be punctured. When the liquid level in the second liquid storage tank 11 reaches the set height, the level gauge 13 on the second liquid storage tank 11 sends a high-level signal to the PLC controller 15. The PLC controller 15 controls the solenoid valve 17 to close, thus isolating the second liquid storage tank 11 from the vacuum system. Then, the PLC controller 15 controls the drain valve 14 on the second liquid storage tank 11 to open for draining. After draining, the level gauge 13 on the second liquid storage tank 11 sends a low-level signal to the PLC controller 15. The PLC controller 15 controls the drain valve 14 on the second liquid storage tank 11 to close and controls the solenoid valve 17 to open, so that the second liquid storage tank 11 is connected back to the vacuum system to continue receiving condensate. By setting the fourth cooler 13 at the end of the vacuum unit, the condensation and recovery of exhaust gas can be increased, maximizing the recovery of condensable solvent media, improving economic efficiency, reducing waste gas emissions, and being clean and environmentally friendly.

[0022] The specific embodiments described herein are merely illustrative examples illustrating the spirit of this utility model. Those skilled in the art to which this utility model pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of this utility model or exceeding the scope defined by the appended claims.

Claims

1. A vacuum unit, comprising a first Roots pump (1), a second Roots pump (2), and a screw pump (3) connected in sequence, characterized in that, The front end of the first Roots pump (1) is connected from back to front to a cooling separation tank (4) and a first cooler (5) with an air inlet (5a). A second cooler (6) is connected between the first Roots pump (1) and the second Roots pump (2). A third cooler (7) is connected between the second Roots pump (2) and the screw pump (3). The cooling separation tank (4), the second cooler (6), and the third cooler (7) are all connected to a first liquid storage tank (9) via an automatic shut-off valve (8). A venting valve (10) is connected to each of the first liquid storage tanks (9). The rear end of the screw pump (3) is connected from back to front to a second liquid storage tank (11) and a fourth cooler (12) with an exhaust port (12a). A level gauge (13) and a drain valve (14) are also connected to the second liquid storage tank (11) and each of the first liquid storage tanks (9).

2. A vacuum unit according to claim 1, characterized in that, This vacuum unit also includes a PLC controller (15). The first Roots pump (1), the second Roots pump (2), the screw pump (3), the level gauge (13), the automatic shut-off valve (8), the venting valve (10), and the drain valve (14) are all connected to the PLC controller (15) by signal. The PLC controller (15) controls the opening and closing of the automatic shut-off valve (8), the venting valve (10), and the drain valve (14) located on the same first liquid storage tank (9) as the level gauge (13) or the drain valve (14) located on the same second liquid storage tank (11) as the level gauge (13) according to the signal from the level gauge (13).

3. A vacuum unit according to claim 1 or 2, characterized in that, A check valve (16) and a solenoid valve (17) for controlling the on / off state are connected in sequence between the second cooler (6) and the screw pump (3).

4. A vacuum unit according to claim 1 or 2, characterized in that, An explosion-proof motor (18) is connected to the first Roots pump (1), the second Roots pump (2) and the screw pump (3), and an explosion-proof pressure transmitter (19) is connected between the cooling separation tank (4) and the first Roots pump (1).

5. A vacuum unit according to claim 4, characterized in that, The screw pump (3) is also connected to an over-temperature protection transmitter (20).

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