Roots vacuum pump and screw vacuum pump series system

Abstract

The utility model provides a kind of Roots vacuum pump and screw vacuum pump series system, including Roots vacuum pump, screw vacuum pump, condenser, first motor, second motor, water storage tank, electric cabinet, first electric control switch valve, second electric control switch valve, third electric control switch valve, electric control three-way valve, liquid level transmitter, pressure transmitter, first check valve and relevant pipeline;First motor is connected with Roots vacuum pump shaft, and second motor is connected with screw vacuum pump shaft;Liquid level transmitter is arranged at the side of water storage tank;Electric cabinet is respectively connected with first motor, second motor, first electric control switch valve, second electric control switch valve, third electric control switch valve, electric control three-way valve, liquid level transmitter, pressure transmitter communication connection.By using Roots vacuum pump and screw vacuum pump in series, the utility model not only can improve the vacuum degree of system and the stability of work and the efficiency of system vacuum extraction, but also can ensure normal work of work object while reducing system energy consumption.

Description

Technical Field

[0001] This utility model belongs to the field of vacuum pump technology, and specifically relates to a series system of a Roots vacuum pump and a screw vacuum pump. Background Technology

[0002] In enterprises requiring condensers, such as thermal power plants, chemical plants, and smelters, vacuum pump units are typically used to evacuate the condenser to improve power generation efficiency or solve other technical problems. Existing vacuum pump units, such as those consisting of two or more screw vacuum pumps or two or more liquid ring vacuum pumps, can quickly create a vacuum in the condenser and are technologically mature, thus enjoying widespread application. However, existing vacuum pump units also have some technical shortcomings, mainly in the following three aspects:

[0003] (1) Using the same set of units to form and maintain vacuum results in high energy consumption of the units.

[0004] (2) Cavitation is prone to occur during the vacuuming process, and the impeller is easily damaged when cavitation occurs.

[0005] (3) Disadvantages include low ultimate vacuum and vacuum degree that is easily affected by water temperature. Summary of the Invention

[0006] The purpose of this invention is to rapidly evacuate the condenser and maintain its high vacuum level while reducing the energy consumption of the vacuum pump unit, mitigating the impact of water temperature on the vacuum level, reducing cavitation during the evacuation process, and extending the service life of the impeller, thereby overcoming the shortcomings of the prior art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A series connection system of a Roots vacuum pump and a screw vacuum pump includes a Roots vacuum pump, a screw vacuum pump, a condenser, a first motor, a second motor, a water tank, an electrical control cabinet, a first electrically controlled switching valve, a second electrically controlled switching valve, a third electrically controlled switching valve, an electrically controlled three-way valve, a level transmitter, a pressure transmitter, and a first check valve. The first motor is connected to the shaft of the Roots vacuum pump, and the second motor is connected to the shaft of the screw vacuum pump. The level transmitter is located on one side of the water tank. The electrical control cabinet is communicatively connected to the first motor, the second motor, the first electrically controlled switching valve, the second electrically controlled switching valve, the third electrically controlled switching valve, the electrically controlled three-way valve, the level transmitter, and the pressure transmitter.

[0009] The inlet of the Roots vacuum pump is connected to the outlet of the condenser, which is the working object, through a first pipeline. The pressure transmitter and the first check valve are installed on the first pipeline. The outlet of the Roots vacuum pump is connected to the inlet of the condenser through a second pipeline. The outlet of the condenser is connected to the inlet of the screw vacuum pump through a third pipeline. The outlet of the screw vacuum pump is connected to the atmosphere outside the system through a fourth pipeline.

[0010] The first electrically controlled switch valve is located on the eighth pipeline, with its inlet connected to the condensate outlet of the condenser and its outlet connected to the inlet of the water storage tank. The second electrically controlled switch valve is located on the drain pipeline, with the outlet of the water storage tank connected to the outside of the system via the drain pipeline. The third electrically controlled switch valve is located on the fifth pipeline, with its inlet connected to the first pipeline and its outlet connected to the third pipeline. An electrically controlled three-way valve is located at the junction of the sixth and seventh pipelines, dividing the sixth pipeline into upper and lower sections. The upper valve of the electrically controlled three-way valve is connected to the second pipeline via the upper section of the sixth pipeline, and the lower valve is connected to the air inlet of the water storage tank via the lower section of the sixth pipeline. The side valve of the electrically controlled three-way valve is connected to the outside atmosphere via the seventh pipeline.

[0011] The above-described technical solution is the basic technical solution for solving the technical problem of this utility model. Based on this basic technical solution, this utility model may add the following technical means, or add the following technical means while discarding certain technical means in the basic technical solution, in order to better or more specifically solve the technical problem to be solved by this utility model:

[0012] The Roots vacuum pump is an air-cooled Roots vacuum pump.

[0013] Furthermore, the fifth pipeline and the third electrically controlled switch valve are discarded, and a liquid ring vacuum pump and a third motor are installed separately; the third motor is shaft-connected to the liquid ring vacuum pump and is communicatively connected to the electrical control cabinet; the air inlet of the liquid ring vacuum pump is connected to the first pipeline through the ninth pipeline, and a second check valve is installed on the ninth pipeline; the air outlet of the liquid ring vacuum pump is connected to the tenth pipeline, and the tenth pipeline is connected to the atmosphere outside the system after converging with the fourth pipeline.

[0014] Furthermore, the tenth pipeline is directly connected to the external atmosphere. This means that the tenth pipeline and the fourth pipeline do not intersect; rather, each is independently connected to the external atmosphere.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects:

[0016] First, by using a Roots vacuum pump in series with a screw vacuum pump, this invention not only improves the system's vacuum level, operational stability, and vacuuming efficiency, but also ensures the normal operation of the condenser, the object of the work, while reducing system energy consumption.

[0017] Third, by replacing the ordinary Roots vacuum pump with an air-cooled Roots vacuum pump as the backing pump, this invention can directly start the backing pump without relying on the pre-vacuuming of the screw pump, thereby reducing the system's vacuuming time and enabling the system to reach the vacuum maintenance stage more quickly.

[0018] Third, by using the liquid ring vacuum pump and its supporting equipment and pipelines, this utility model can further improve the system's vacuuming capability and is better suited for large and medium-sized enterprises. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of this utility model;

[0020] Figure 2 Yes Figure 1 A schematic diagram showing the structure with the pipelines marked individually.

[0021] Figure 3 This is a structural schematic diagram of Embodiment 2 of the present invention;

[0022] Figure 4 Yes Figure 3 A structural diagram showing the pipelines marked individually.

[0023] In the picture:

[0024] 1 – Roots vacuum pump; 2 – Screw vacuum pump;

[0025] 3 – Condenser; 4 – First motor;

[0026] 5 – Second motor; 6 – Water storage tank;

[0027] 7—Electrical control cabinet; 8—First electrically controlled switch valve;

[0028] 9 – Second electrically controlled switching valve; 10 – Third electrically controlled switching valve;

[0029] 11—Electrically controlled three-way valve; 12—Level transmitter;

[0030] 13—Pressure transmitter; 14—First check valve;

[0031] 15 – Second check valve; 16 – Liquid ring vacuum pump;

[0032] 17 – Third motor; 18 – First pipeline;

[0033] 19 – Second pipeline; 20 – Third pipeline;

[0034] 21 – Fourth pipeline; 22 – Fifth pipeline;

[0035] 23 – Sixth pipe; 24 – Seventh pipe;

[0036] 25 – Eighth pipeline; 26 – Ninth pipeline;

[0037] 27 – Tenth pipe; 28 – Drainage pipe;

[0038] 29—Condenser. Detailed Implementation

[0039] To facilitate a full understanding of the technical solution of this utility model by those skilled in the art, two embodiments of this utility model are described below in conjunction with the accompanying drawings. Figure 1 This is a structural schematic diagram of Embodiment 1 of the present invention. Figure 2 Yes Figure 1 A structural diagram showing the pipelines marked individually. Figure 1 and Figure 2 The technical content illustrated is exactly the same; the only difference between the two is: Figure 1 The various devices in Example 1 were labeled, but the piping between the devices was not labeled. Figure 2 The piping between the various devices in Example 1 is specifically marked. This separate marking method for the accompanying drawings is used to avoid the drawing's effectiveness being affected by too many reference numerals and their leaders. Similarly, Figure 3 and Figure 4 The technical content illustrated is exactly the same; the only difference between the two is: Figure 3 The various devices in Example 2 were labeled, and Figure 4 The piping between the devices in this embodiment is specifically marked. Example 1

[0040] like Figure 1 and combined Figure 2As shown, a series system of a Roots vacuum pump and a screw vacuum pump (hereinafter referred to as the system) includes a Roots vacuum pump 1, a screw vacuum pump 2, a condenser 3 (in the figure, the two arrows above the condenser 3 indicate the inlet and outlet directions of the coolant, respectively), a first motor 4, a second motor 5, a water tank 6 (also called a condensate tank), an electrical control cabinet 7 (also called a control cabinet), a first electrically controlled switch valve 8 (also called a condensate electrically controlled valve), a second electrically controlled switch valve 9 (also called a drain pipe electrically controlled valve), a third electrically controlled switch valve 10, an electrically controlled three-way valve 11, a level transmitter 12, a pressure transmitter 13, and a first check valve 14; the first motor 4 is connected to the shaft of the Roots vacuum pump 1, and the second motor 5 is connected to the shaft of the screw vacuum pump 2; the level transmitter 1... 2 is located on one side of the water storage tank 6; the electrical control cabinet 7 is connected to the first motor 4, the second motor 5, the first electrically controlled switch valve 8, the second electrically controlled switch valve 9, the third electrically controlled switch valve 10, the electrically controlled three-way valve 11, the level transmitter 12, and the pressure transmitter 13 respectively.

[0041] The inlet of the Roots vacuum pump 1 is connected to the outlet of the condenser 29 (the condenser 29 is the working object of this utility model; in the figure, the arrows on the left and right sides of the condenser 29 indicate the direction of coolant entry and exit, respectively, and the arrow above the condenser 29 indicates the direction of steam exiting the turbine entry) through the first pipeline 18. The pressure transmitter 13 and the first check valve 14 are installed on the first pipeline 18 (the function of the pressure transmitter 13 is to monitor the system vacuum level, and the function of the first check valve 14 is to ensure that the steam entering the first pipeline 18 can only flow in one direction). The outlet of the Roots vacuum pump 1 is connected to the inlet of the condenser 3 through the second pipeline 19. The outlet of the condenser 3 is connected to the inlet of the screw vacuum pump 2 through the third pipeline 20. The outlet of the screw vacuum pump 2 is connected to the atmosphere outside the system through the fourth pipeline 21.

[0042] The first electrically controlled switch valve 8 is installed on the eighth pipe 25, with its inlet end connected to the condensate outlet of the condenser 3 and its outlet end connected to the inlet of the water storage tank 6; the second electrically controlled switch valve 9 is installed on the drain pipe 28, with the outlet of the water storage tank 6 connected to the outside of the system via the drain pipe 28; the third electrically controlled switch valve 10 is installed on the fifth pipe 22, with its inlet end connected to the first pipe 18 and its outlet end connected to the third pipe 20; the electrically controlled three-way valve 11 is installed on... At the intersection of the sixth pipeline 23 and the seventh pipeline 24, the sixth pipeline 23 is divided into upper and lower sections; the upper valve of the electrically controlled three-way valve 11 is connected to the second pipeline 19 through the upper section of the sixth pipeline 23, and the lower valve of the electrically controlled three-way valve 11 is connected to the air inlet of the water storage tank 6 through the lower section of the sixth pipeline 23. The side valve of the electrically controlled three-way valve 11 (in the figure, the side valve is located on the left side of the electrically controlled three-way valve 11; in actual implementation of this utility model, the position of the side valve can be adjusted according to the site conditions) is connected to the atmosphere outside the system through the seventh pipeline 24.

[0043] The structural features of Embodiment 1 of this utility model have been described above with reference to the accompanying drawings. The working principle will be further explained below:

[0044] When it is necessary to evacuate the condenser 29, under the control of the electrical control cabinet 7, the upper and lower valves of the electrically controlled three-way valve 11 are opened, so that the upper and lower sections of the sixth pipeline 23 are connected. At the same time, the side valve of the electrically controlled three-way valve 11 is closed, so that the seventh pipeline 24 is closed; the first electrically controlled switch valve 8 is opened, so that the eighth pipeline 25 is connected; the second electrically controlled switch valve 9 is closed, so that the drain pipeline 28 is closed.

[0045] Then, the third electrically controlled switch valve 10 is opened, and the system first starts the screw vacuum pump 2. The screw vacuum pump 2 continuously reduces the system vacuum level through the fifth pipeline 22. The electrical control cabinet 7 monitors the system vacuum level through the pressure transmitter 13. When the system vacuum level reaches the preset value, the electrical control cabinet 7 controls the Roots vacuum pump 1 to start, and then closes the third electrically controlled switch valve 10. At this time, the Roots vacuum pump 1 and the screw vacuum pump 2 operate in series to maintain the vacuum level of the condenser 1.

[0046] During system operation, condenser 3 continuously produces condensate (condensate is the product of heat exchange between steam and coolant within condenser 3). Under the influence of gravity, the condensate is injected into the water storage tank 6 through the eighth pipe 25. When the condensate collected in the water storage tank 6 reaches the preset value (upper limit value) of the level transmitter 12, the electrical control cabinet 7 issues a command based on the electrical signal received from the level transmitter 12 to close the upper valve of the electrically controlled three-way valve 11 and open the side and lower valves of the electrically controlled three-way valve 11, thereby disconnecting the upper and lower sections of the sixth pipe 23 and connecting the lower section of the sixth pipe 23 with the seventh pipe 24. Simultaneously, the first electrically controlled switch valve 8 is closed, disconnecting the eighth pipe 25. At this time, the water storage tank 6 is connected to the atmosphere outside the system through the lower section of the sixth pipe 23 and the seventh pipe 24. At the same time, the electrical control cabinet 7 issues an instruction to open the second electrical control switch valve 9, so that the condensate in the water storage tank 6 is discharged out of the system along the drain pipe 28.

[0047] When the condensate level in the water storage tank 6 drops to the preset value (lower limit) of the level transmitter 12, it indicates that the condensate in the water storage tank 6 is almost empty. In this situation, the electrical control cabinet 7 issues a command to switch the electrically controlled three-way valve 11 to a state where the upper and lower valves are open and the side valve is closed, thus disconnecting the lower section of the sixth pipeline 23 and the seventh pipeline 24 (meaning the passage between the water storage tank 6 and the external atmosphere is closed), and reconnecting the upper and lower sections of the sixth pipeline 23, thereby making the air pressure in the water storage tank 6 the same as the system air pressure, resulting in a negative pressure. At this time, the first electrically controlled switch valve 8 opens, and the water storage tank 6 continues to collect the condensate generated by the condenser 3 during operation.

[0048] It should be noted that in Embodiment 1, the Roots vacuum pump 1 constitutes the backing pump of the system, and the screw vacuum pump 2 constitutes the backing pump. Since no gas compression occurs within the pump chamber of the Roots vacuum pump 1 during operation, and specifically, the two figure-eight rotors of the Roots vacuum pump 1 maintain a certain gap with the pump chamber, and a pair of synchronously counter-rotating high-precision gears ensure that the two rotors do not contact each other and maintain a certain gap when rotating within the pump chamber (one rotation of the rotor within the pump chamber completes one intake and exhaust process), it is not sensitive to water vapor in the pumped gas and can provide strong pumping capacity. Therefore, it serves as the backing pump in this embodiment. The screw vacuum pump 2 achieves a high vacuum level, but its vacuuming efficiency is relatively low. This embodiment uses the Roots vacuum pump 1 and the screw vacuum pump 2 in series, which not only improves the system's vacuuming efficiency but also enhances the system's vacuum level and operational stability, thereby reducing system energy consumption while ensuring the normal operation of the condenser.

[0049] It should also be noted that while a standard Roots vacuum pump can be used as the backing pump in this embodiment, a gas-cooled Roots vacuum pump can be used instead of the standard Roots vacuum pump as a preferred embodiment. Using a gas-cooled Roots vacuum pump instead of a standard Roots vacuum pump as the backing pump eliminates the need for pre-vacuuming with a screw pump, allowing the backing pump to start directly and reducing the system's evacuation time, thus enabling the system to reach the vacuum maintenance stage more quickly. Example 2

[0050] The basic structure of Example 2 is the same as that of Example 1. The differences between the two are as follows:

[0051] First, such as Figure 3 and combined Figure 4 As shown, in Embodiment 2, a liquid ring vacuum pump 16 and a third motor 17 are also configured. The third motor 17 is shaft-connected to the liquid ring vacuum pump 16, and the electrical control cabinet 7 is communicatively connected to the third motor 17. The inlet of the liquid ring vacuum pump 16 is connected to the first pipeline 18 through the ninth pipeline 26. A second check valve 15 is provided on the ninth pipeline 26 (the function of the second check valve 15 is to ensure that the steam entering the ninth pipeline 26 from the first pipeline 18 can only flow in one direction). The outlet of the liquid ring vacuum pump 16 is connected to the tenth pipeline 27, and the tenth pipeline 27 is connected to the atmosphere outside the system after converging with the fourth pipeline 21.

[0052] Second, Figure 3 , Figure 4 and Figure 1 , Figure 2 As can be seen from the comparison, Example 2 does not have a fifth pipeline 22, and correspondingly, it does not have a third electrically controlled switch valve 10 installed on the fifth pipeline 22. In other words, Example 2 is not simply an addition of a liquid ring vacuum pump 16, a third motor 17, a ninth pipeline 26, a tenth pipeline 27, and a second check valve 15 to Example 1, but rather a combination of additions and subtractions.

[0053] Furthermore, the basic working principle of Embodiment 2 is the same as that of Embodiment 1. Both use the Roots vacuum pump 1 as the backing pump and the screw vacuum pump 2 as the backing pump. The main difference is that, due to the inclusion of the liquid ring vacuum pump 16 and its matching third motor 17, Embodiment 2 has a stronger vacuuming capacity and is more suitable for large and medium-sized enterprises. Large and medium-sized enterprises, such as large and medium-sized power plants, use condensers that are too large. Relying solely on a Roots vacuum pump to evacuate the condenser would take too long. In such cases, the technical solution of Embodiment 2 is preferred. The liquid ring vacuum pump 16 is started first to evacuate the condenser. Because the liquid ring vacuum pump has a larger power, it can evacuate the condenser more quickly. After the liquid ring vacuum pump 16 is started, the system vacuum gradually decreases. According to the electrical signal from the pressure transmitter 13, when the system vacuum decreases to a preset value, the electrical control cabinet 7 issues a command to stop the third motor 17, thereby shutting down the liquid ring vacuum pump 16. At this point, the system switches to the system working mode of Roots vacuum pump 1 and screw vacuum pump 2 connected in series to maintain the system vacuum level. Since the system of Roots vacuum pump 1 and screw vacuum pump 2 connected in series has low power consumption and can maintain a high vacuum level, the system power consumption can be greatly reduced in the vacuum maintenance stage.

[0054] It should also be noted that, in the actual implementation of the technical solution of this embodiment, for operating conditions where the condenser exhaust gas is polluted and therefore needs to be treated before being discharged outside the system, the solution of connecting the tenth pipe 27 and the fourth pipe 21 to the atmosphere outside the system should be preferred. This solution essentially integrates the exhaust ends of the tenth pipe 27 and the fourth pipe 21 into a single pipe, thus facilitating the control and treatment of the condenser exhaust gas. For operating conditions where the condenser exhaust gas is unpolluted and can be directly discharged outside the system without treatment, this embodiment can also adopt a solution where the tenth pipe 27 is directly connected to the atmosphere outside the system. In essence, the tenth pipe 27 and the fourth pipe 21 are directly connected to the atmosphere outside the system, without needing to integrate the exhaust ends of the tenth pipe 27 and the fourth pipe 21 into a single pipe.

Claims

1. A series connection system of a Roots vacuum pump and a screw vacuum pump, characterized in that: It includes a Roots vacuum pump, a screw vacuum pump, a condenser, a first motor, a second motor, a water storage tank, an electrical control cabinet, a first electrically controlled switch valve, a second electrically controlled switch valve, a third electrically controlled switch valve, an electrically controlled three-way valve, a level transmitter, a pressure transmitter, and a first check valve; the first motor is connected to the shaft of the Roots vacuum pump, and the second motor is connected to the shaft of the screw vacuum pump; the level transmitter is located on one side of the water storage tank; the electrical control cabinet is communicatively connected to the first motor, the second motor, the first electrically controlled switch valve, the second electrically controlled switch valve, the third electrically controlled switch valve, the electrically controlled three-way valve, the level transmitter, and the pressure transmitter. The inlet of the Roots vacuum pump is connected to the outlet of the condenser, which is the working object, through a first pipeline. The pressure transmitter and the first check valve are installed on the first pipeline. The outlet of the Roots vacuum pump is connected to the inlet of the condenser through a second pipeline. The outlet of the condenser is connected to the inlet of the screw vacuum pump through a third pipeline. The outlet of the screw vacuum pump is connected to the atmosphere outside the system through a fourth pipeline. The first electrically controlled switch valve is located on the eighth pipeline, with its inlet connected to the condensate outlet of the condenser and its outlet connected to the inlet of the water storage tank. The second electrically controlled switch valve is located on the drain pipeline, with the outlet of the water storage tank connected to the outside of the system via the drain pipeline. The third electrically controlled switch valve is located on the fifth pipeline, with its inlet connected to the first pipeline and its outlet connected to the third pipeline. An electrically controlled three-way valve is located at the junction of the sixth and seventh pipelines, dividing the sixth pipeline into upper and lower sections. The upper valve of the electrically controlled three-way valve is connected to the second pipeline via the upper section of the sixth pipeline, and the lower valve is connected to the air inlet of the water storage tank via the lower section of the sixth pipeline. The side valve of the electrically controlled three-way valve is connected to the outside atmosphere via the seventh pipeline.

2. The Roots vacuum pump and screw vacuum pump series system as described in claim 1, characterized in that: The Roots vacuum pump is an air-cooled Roots vacuum pump.

3. The Roots vacuum pump and screw vacuum pump series system as described in claim 1, characterized in that: The fifth pipeline and the third electrically controlled switch valve are discarded, and a liquid ring vacuum pump and a third motor are installed separately. The third motor is shaft-connected to the liquid ring vacuum pump and is communicatively connected to the electrical control cabinet. The inlet of the liquid ring vacuum pump is connected to the first pipeline through the ninth pipeline, and a second check valve is installed on the ninth pipeline. The outlet of the liquid ring vacuum pump is connected to the tenth pipeline, and the tenth pipeline is connected to the atmosphere outside the system after converging with the fourth pipeline.

4. The Roots vacuum pump and screw vacuum pump series system as described in claim 3, characterized in that: The tenth pipeline is directly connected to the external atmosphere.

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