Energy-saving vacuum pump system of dry large differential roots vacuum pump based on full bearing seal

Abstract

The application discloses an energy-saving vacuum pump system of a dry-type Roots vacuum pump with large pressure difference based on full-bearing sealing, which is formed by connecting a Roots vacuum pump with large pressure difference and high temperature and capable of bearing large pressure difference and high temperature with a front-stage pump in series, and the Roots vacuum pump is sealed by full bearings, a dry-type vacuum cavity is formed, internal emulsification erosion caused by saturated water vapor is prevented, condensed water is prevented from expelling vacuum lubricating oil, and the bearing and impeller mechanism of the Roots vacuum pump can be kept in effective operation for a long time. The application is suitable for power plant condensers and other occasions using large liquid ring vacuum pumps, steam-type vacuum pumps, centrifugal vacuum pumps, water flushing vacuum pumps and other low-efficiency vacuum pumps, and the energy-saving and emission-reducing effects are achieved. The so-called large pressure difference refers to that the Roots vacuum pump can operate under the inlet pressure of 5000 to 30000 Pa all day long under the condenser vacuum maintaining condition, can bear the pressure difference of 5000 to 10000 Pa or more, and can bear the temperature of 130 DEG C or more.

Description

TECHNICAL FIELD

[0001] The present application relates to a vacuum pump system, in particular, an energy-saving vacuum pump system based on a full-bearing sealed dry large differential Roots vacuum pump. BACKGROUND

[0002] In thermal power plants, the condenser vacuum has a great impact on the coal consumption of power generation. For example, for a 300-330 MW pump set, if the vacuum degree is increased by 1 KPa, the corresponding coal consumption of power generation will decrease by 2.6 g / kWh. The vacuum extraction equipment commonly used in power plants at present is a water jet vacuum pump, a water ring / liquid ring pump, or a steam vacuum pump. The performance of these water-based vacuum pumps is highly related to environmental factors such as water temperature or pressure, so the efficiency is low and difficult to control. In order to maintain the overall vacuum efficiency, multiple vacuum pumps are often used, which greatly increases the energy consumption. In order to reduce the energy consumption of the condenser vacuum pump, the following methods are currently mainly used:

[0003] 1. Installing a refrigeration device to reduce the temperature of the working fluid. However, since the power plant mainly uses a loop water, the temperature of the loop water will rise in summer and the working fluid temperature cannot be effectively reduced. If refrigeration equipment is used to produce chilled water, the energy consumption will be even greater.

[0004] 2. Replacing the original single-stage water ring pump with a more efficient two-stage water ring pump. However, the energy-saving ratio of this method is only about 20% to 30%, and the energy-saving efficiency is limited.

[0005] 3. Installing an atmospheric ejector to eliminate the limitation of the vacuum pump's extreme suction pressure on the improvement of the condenser pressure. However, this method will reduce the air extraction amount and increase the power consumption.

[0006] 4. Using a gas-cooled Roots pump with a liquid ring pump energy-saving vacuum device, but this method requires that part of the mixed gas that has been removed is cooled by a large heat exchanger and then partially returned to the gas-cooled Roots pump to cool the pump body, which reduces the overall efficiency. In addition, the gas-cooled Roots pump is large in size, heavy in weight, high in power consumption, and high in maintenance cost, which is not conducive to system configuration and operation efficiency. Moreover, in addition to low efficiency, this application also causes a large proportion of bearing and vacuum oil failure due to the lack of full-bearing sealing technology.

[0007] 5. Using a water-cooled Roots pump with many stages (5-7 stages). However, the evaporation of water caused by water entering the Roots pump will reduce the actual air extraction efficiency of the Roots pump, and too many stages of the Roots pump will complicate the system, so it is not seen in practical application.

[0008] 6. Systems using ordinary Roots pumps are not fully sealed because they employ labyrinth or ring seals, which cannot completely seal the bearings and vacuum oil tank. Furthermore, ordinary Roots pumps operate at pressure differentials below 5000 Pa and cannot withstand large pressure differentials (several thousand Pa to 30,000 Pa). Therefore, in power plant applications, water vapor can easily seep in, causing vacuum oil emulsification or leakage, leading to bearing failure or seizing due to overheating and deformation, rendering the system unusable.

[0009] Therefore, this invention aims to propose a novel energy-saving vacuum pump system based on a dry, high-differential-pressure Roots vacuum pump with full bearing seals, in order to overcome the aforementioned deficiencies in the prior art. Summary of the Invention

[0010] Therefore, the purpose of this invention is to solve the problems in the prior art mentioned above. This invention proposes an energy-saving vacuum pump system based on a dry, high-differential-pressure Roots vacuum pump with full bearing seal.

[0011] To achieve the above-mentioned purpose, the application provides a kind of energy-saving vacuum pump system based on full bearing seal dry large differential Roots vacuum pump, including an input valve (9), it is a vacuum inlet pneumatic shut-off valve, for receiving the mixed gas of saturated water vapor and non-condensable air from power plant condenser, and the mixed gas is input to the device of next stage;A first Roots vacuum pump (1) is connected to the input valve (9), the first Roots vacuum pump (1) is used to receive the mixed gas from the input valve (9) and is compressed to the device of next stage after being output to the outside;A second Roots vacuum pump (2) is connected to the first Roots vacuum pump (1), for further compression of the mixed gas output from the first Roots vacuum pump (1), and the compressed mixed gas is output to the device of next stage;Wherein the first Roots vacuum pump (1) and the second Roots vacuum pump (2) all include a shell with inlet and outlet, the shell forms a vacuum cavity and two bearing chambers located on both sides of the vacuum cavity;The vacuum cavity is communicated with the inlet and the outlet;There is a drive shaft in the shell, which penetrates the vacuum cavity and the two bearing chambers, and one end of the drive shaft penetrates the outer side wall of the shell, there is an impeller in the vacuum cavity, which is installed on the drive shaft, the mixed gas input from outside enters the vacuum cavity, and the mixed gas is compressed by the rotation of the impeller;Wherein the two inner side walls between the vacuum cavity and the two adjacent bearing chambers and the outer side wall of the shell are provided with bearings, and the drive shaft penetrates each bearing and is supported by each bearing;Wherein each bearing and the drive shaft form a full-sealed structure, so that the vacuum cavity and the two bearing chambers are completely isolated from each other, so that the liquid outside the shell or the two bearing chambers cannot penetrate into the vacuum cavity, and the mixed gas in the vacuum cavity cannot enter the bearing chamber;The inlet of the second Roots vacuum pump (2) is connected to the outlet of the first Roots vacuum pump (1);And wherein the first Roots vacuum pump (1) and the second Roots vacuum pump (2) are all structures that can withstand large pressure difference, so-called large pressure difference refers to that the first Roots vacuum pump (1) and the second Roots vacuum pump (2) can operate under 5000 to 30000 Pa inlet pressure under the condenser vacuum maintenance condition, and can withstand pressure difference above 5000 Pa.Further, it further includes: a third Roots vacuum pump (3), the third Roots vacuum pump (3) is the same as the first Roots vacuum pump (1), the inlet of the third Roots vacuum pump (3) is connected to the outlet of the second Roots vacuum pump (2), the third Roots vacuum pump (3) is used to further compress the mixed gas output from the second Roots vacuum pump (2), and the compressed mixed gas is output to the device of next stage.

[0012] Further, the first Roots vacuum pump (1) and the second Roots vacuum pump (2) are all high-temperature-resistant structures, so-called high-temperature-resistant refers to that the first Roots vacuum pump (1) and the second Roots vacuum pump (2) can withstand temperature above 130 DEG C when operating.

[0013] Further, a heat exchanger (6) is connected between the outlet of the second Roots vacuum pump (2) and the inlet of the third Roots vacuum pump (3) to cool the mixed gas output by the second Roots vacuum pump (2).

[0014] Further, a backing pump (4) is connected to the outlet of the second Roots vacuum pump (2) to further compress the mixed gas output by the second Roots vacuum pump (2) and output the compressed mixed gas; and a gas-water separator (5) is connected to the backing pump (4) to separate the mixed gas output by the backing pump (4) into gas and liquid, and output the separated gas and liquid.

[0015] Further, a backing pump (4) is connected to the outlet of the third Roots vacuum pump (3) to further compress the mixed gas output by the third Roots vacuum pump (3) and output the compressed mixed gas; and a gas-water separator (5) is connected to the backing pump (4) to separate the mixed gas output by the backing pump (4) into gas and liquid, and output the separated gas and liquid.

[0016] Further, the Roots vacuum pumps are integrated.

[0017] Further, the first Roots vacuum pump (1) and the second Roots vacuum pump (2) further comprise a variable frequency motor to drive the corresponding driving shaft to drive the corresponding impeller to compress the mixed gas in the corresponding vacuum cavity.

[0018] Further, the first Roots vacuum pump (1) further comprises an inlet vacuum pressure sensor (11) at the inlet thereof and an outlet end temperature sensor (15) at the outlet thereof. The second Roots vacuum pump (2) further comprises an outlet end pressure sensor (12) and an outlet end temperature sensor (15) at the outlet thereof. The system integrates and analyzes the pressure values detected by the inlet vacuum pressure sensor (11) and the outlet end pressure sensor (12) and the temperature feedback values detected by the outlet end temperature sensors (15) of the first Roots vacuum pump (1) and the second Roots vacuum pump (2), and then transmits a control signal to the variable frequency motors of the first Roots vacuum pump (1) and the second Roots vacuum pump (2) to adjust the rotation speeds of the variable frequency motors.

[0019] The present application has the following advantages:

[0020] The energy-saving vacuum pump system based on the dry-type large-pressure-difference Roots vacuum pump with full-bearing seal is provided in the present application, which uses one or more levels of full-bearing seal, can bear large pressure difference and high temperature, and is connected with the front-stage pump to form a multi-level structure. The Roots vacuum pump of the present application uses full-bearing seal, so that a full-dry vacuum cavity can be formed, internal emulsification erosion caused by saturated water vapor can be prevented, oil stains in the bearing box can be prevented from being brought into the vacuum cavity due to pressure fluctuation, or condensed water in the oil tank is condensed, and then the vacuum lubricating oil is expelled into the vacuum cavity, and the like, so that the bearing and impeller mechanisms of the Roots vacuum pump can be maintained in effective operation for a long time. Therefore, the present application is suitable for power plant condensers or other occasions using large liquid ring vacuum pumps, steam-type vacuum pumps, centrifugal vacuum pumps, water flushing vacuum pumps and other low-efficiency vacuum pumps, and can achieve the effect of energy saving and emission reduction. The present application also uses PLC and variable frequency motor control to achieve intelligent frequency conversion, so that data can be continuously and instantaneously collected, and the rotation speed of each vacuum pump can be automatically or manually adjusted according to the experience of the power plant, seasonal changes, generator load changes, and working conditions of each pump in the pump set, so as to optimize the safe operation of the system and achieve the purpose of energy saving. For some large condensers of large power plants, when the vacuum degree is high or the air extraction amount is particularly large, three-level Roots vacuum pumps can be used to meet the operation requirements.

[0021] The features and advantages of the present application can be further understood from the following description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A schematic block diagram showing the combination of elements of the first embodiment of the present application;

[0023] Figure 2 A cross-sectional schematic view showing the first Roots vacuum pump of the present application;

[0024] Figure 3 A schematic block diagram showing the combination of elements of the second embodiment of the present application;

[0025] Figure 4 A schematic structural view showing the third embodiment of the present application;

[0026] Figure 5 A side view showing Figure 4 ;

[0027] Figure 6 Another side view showing Figure 4 ;

[0028] Figure 7 A schematic block diagram showing the combination of elements of the third embodiment of the present application.

[0029] BRIEF DESCRIPTION OF DRAWINGS

[0030] 1: First Roots vacuum pump; 11: Inlet vacuum pressure sensor; 12: Outlet pressure sensor; 14: Inlet temperature sensor; 15: Outlet temperature sensor; 18: Drive mechanism; 181: Variable frequency motor; 2: Second Roots vacuum pump; 20: Temperature sensor; 21: Pneumatic valve; 3: Third Roots vacuum pump; 31: Housing; 311: Inlet; 312: Outlet; 313: Inner wall; 314: Inner wall; 315: Outer wall; 32: Vacuum chamber; 33: Bearing chamber; 34: Drive shaft; 35: Impeller; 36: Bearing; 4: Backing pump; 401: Input end; 5: Gas-liquid separator; 501: Input end; 6: Heat exchanger; 7: Circulating liquid heat exchanger; 9: Input valve. Detailed Implementation

[0031] The following is a detailed description of a preferred embodiment of the present invention, in conjunction with the accompanying drawings, regarding its structural composition, effects, and advantages.

[0032] Please refer to Figures 1 to 7 As shown, this invention presents an energy-saving vacuum pump system based on a dry, high-pressure-difference Roots vacuum pump with a full bearing seal. The invention uses a Roots vacuum pump with a specific structure, which achieves a dry vacuum chamber structure using a full bearing seal and has the ability to withstand large pressure differences and high temperatures.

[0033] Figure 1 This illustrates a first embodiment of the invention, which primarily utilizes a first Roots vacuum pump 1 and a backing pump 4. This example includes the following components:

[0034] An input valve 9, which is a vacuum inlet pneumatic shut-off valve, is used to receive a mixture of saturated steam and non-condensable air from the power plant condenser and input the mixture to the next stage device.

[0035] A first Roots vacuum pump 1 is connected to the input valve 9. The first Roots vacuum pump 1 is used to receive the mixed gas from the input valve 9, compress it, and output it to the next stage device.

[0036] like Figure 2As shown, the first Roots vacuum pump 1 includes a housing 31 having an inlet 311 and an outlet 312. A vacuum chamber 32 and two bearing chambers 33 located on either side of the vacuum chamber 32 are formed inside the housing 31. The vacuum chamber 32 connects the inlet 311 and the outlet 312. A drive shaft 34 is located inside the housing 31, passing through the vacuum chamber 32 and the two bearing chambers 33. One end of the drive shaft 34 extends through an outer side wall 315 of the housing 31. An impeller 35 is located inside the vacuum chamber 32, mounted on the drive shaft 34. The externally input mixed gas enters the vacuum chamber 32, and the mixed gas is compressed by the rotation of the impeller 35. The vacuum chamber 32 is connected to the adjacent two bearing chambers 311 and the outlet 312. Bearings 36 are provided on the two inner sidewalls 313 and 314 between the bearing chambers 33 and the outer sidewall 315 of the outer casing 31. The drive shaft 34 passes through each bearing 36 and is supported by each bearing 36. Each bearing 36 and the drive shaft 34 form a fully sealed structure, completely isolating the vacuum chamber 32 from the two bearing chambers 33. This prevents liquids from the outside of the outer casing 31 or the two bearing chambers 33 from seeping into the vacuum chamber 32, and also prevents the mixed gas inside the vacuum chamber 32 from entering the bearing chamber 33. Therefore, during operation, the vacuum chamber 32 of the first Roots vacuum pump 1 will only contain the original air and the input mixed gas, without any other impurities. Furthermore, liquids such as lubricating oil inside the bearing chambers 33 will not leak out of the outer casing 31.

[0037] The present invention uses a fully sealed structure, rather than a semi-sealed form such as a labyrinth or sealing ring, so the present invention can completely isolate the vacuum chamber 32, bearing chamber 33 and related drive mechanism (such as gear) from the liquid, so as to prevent problems related to the emulsification or discharge of water vapor.

[0038] The first Roots vacuum pump 1 is designed to withstand large pressure differentials. Large pressure differentials mean that the first Roots vacuum pump 1 can operate around the clock at inlet pressures of 5000 to 30000 Pa under condenser vacuum maintenance conditions, and can withstand pressure differentials of 5000 to 10000 Pa or more. Existing Roots pumps generally cannot withstand these operating conditions.

[0039] The first Roots vacuum pump 1 has a high-temperature resistant structure. The so-called high-temperature resistant means that the first Roots vacuum pump 1 can withstand temperatures above 130°C during operation, and the gas temperature in the vacuum chamber 32 of the first Roots vacuum pump 1 can reach 200°C during operation.

[0040] The first Roots vacuum pump 1 also includes a drive mechanism 18 for driving the impeller 35 within the vacuum chamber 32. The drive mechanism 18 includes a drive shaft 34 and a variable frequency motor 181. The variable frequency motor 181 drives the drive shaft 34 to drive the impeller 35, thereby driving the mixed gas within the vacuum chamber 32 to perform gas compression. The variable frequency motor 181 is a variable frequency motor, whose speed can be adjusted according to the frequency of the input power.

[0041] A backing pump 4, with its input end 401 connected to the outlet 312 of the first Roots vacuum pump 1, receives the mixed gas output from the first Roots vacuum pump 1 and compresses and mixes it to form a gas-water mixture. The backing pump 4 can be a single-stage or two-stage liquid ring pump, a gas jet pump, a screw pump, or other types of Roots pumps. The input end 401 of the backing pump 4 has a suction inlet temperature sensor 14 for measuring the temperature of the input end 401 and transmitting the measured value outwards.

[0042] A gas-liquid separator 5 has its input terminal 501 connected to the pre-pump 4. The gas-liquid mixture from the pre-pump 4 is input into the gas-liquid separator 5 for gas-liquid separation, and the separated gas and liquid are discharged separately. The gas-liquid separator 5 includes a temperature sensor 20 for measuring the water temperature of the gas-liquid separator 5 and transmitting the measured value.

[0043] When the fore-pump 4 is a liquid ring pump, the liquid separated by the gas-liquid separator 5 is cooled by a circulating liquid heat exchanger 7 before being returned to the fore-pump 4. A pneumatic valve 21 is installed at the connection point between the fore-pump 4 and the circulating liquid heat exchanger 7 to control the flow rate of the separated liquid from the gas-liquid separator 5 into the fore-pump 4. When the system needs to start or stop, or in case of a malfunction, controlling the opening and closing of the pneumatic valve 21 prevents excessive liquid from the gas-liquid separator 5 from entering the fore-pump 4, avoiding problems such as backflow or flooding during system shutdown.

[0044] Figure 3 This illustrates a second embodiment of the invention, in which a second Roots vacuum pump 2 is connected in series with the outlet 312 of the first Roots vacuum pump 1 in the first embodiment, and then connected in series with the backing pump 4. This embodiment is applicable to general power plant condensers. In this example, elements identical to those in the above embodiments are represented by the same symbols and have the same function; their details will not be repeated. This example also includes:

[0045] A second Roots vacuum pump 2 has the same structure as the first Roots vacuum pump 1. The inlet 311 of the second Roots vacuum pump 2 is connected in series with the outlet 312 of the first Roots vacuum pump 1. The second Roots vacuum pump 2 is used to further compress the mixed gas output from the first Roots vacuum pump 1 and output the compressed mixed gas to the next stage device.

[0046] The backing pump 4 is connected in series with the outlet 312 of the second Roots vacuum pump 2. The backing pump 4 is used to further compress the mixed gas output from the second Roots vacuum pump 2 before outputting it.

[0047] The present invention also includes a pressure and temperature feedback control mechanism, which enables the system to achieve higher efficiency. The first Roots vacuum pump 1 includes an inlet vacuum pressure sensor 11 located at its inlet 311 and an outlet temperature sensor 15 located at its outlet 312. The second Roots vacuum pump 2 includes an outlet pressure sensor 12 and an outlet temperature sensor 15 located at its outlet 312. Based on the pressure values ​​detected by the inlet vacuum pressure sensor 11 and the outlet pressure sensor 12, and the temperature feedback values ​​detected by the outlet temperature sensors 15 of the first and second Roots vacuum pumps, the system integrates and analyzes these values ​​and then transmits control signals to the variable frequency motors 181 of the first and second Roots vacuum pumps to adjust the speed of each variable frequency motor 181, so that the entire system achieves optimal efficiency and safe operation.

[0048] Figures 4 to 7 This invention illustrates a third embodiment where a third Roots vacuum pump 3 is connected in series with the outlet 312 of the second Roots vacuum pump 2 in the second embodiment, and then connected in series with the backing pump 4. This example is mainly applicable to situations with high condenser leakage rates in large power plants (e.g., 1000MW and above), or in the case of air-cooled condensers. In this example, components identical to those in the above embodiments are represented by the same symbols and have the same functions; their details will not be repeated. This example also includes:

[0049] A third Roots vacuum pump 3 has the same structure as the first Roots vacuum pump 1. The inlet 311 of the third Roots vacuum pump 3 is connected in series to the outlet 312 of the second Roots vacuum pump 2. The third Roots vacuum pump 3 is used to further compress the mixed gas output from the second Roots vacuum pump 2 and output the compressed mixed gas to the next stage device.

[0050] The backing pump 4 is connected in series with the outlet 312 of the third Roots vacuum pump 3. The backing pump 4 is used to further compress the mixed gas output from the third Roots vacuum pump 3 before outputting it.

[0051] A heat exchanger 6 is connected in series between the outlet 312 of the second Roots vacuum pump 2 and the inlet 311 of the third Roots vacuum pump 3 to cool the mixed gas output by the second Roots vacuum pump 2.

[0052] In the second and third embodiments described above, the first Roots vacuum pump 1, the second Roots vacuum pump 2, or the first Roots vacuum pump 1, the second Roots vacuum pump 2, and the third Roots vacuum pump 3 can be integrated into a single unit, meaning all the Roots vacuum pumps are integrated into a single structure. Alternatively, each of the first Roots vacuum pump 1, the second Roots vacuum pump 2, and the third Roots vacuum pump 3 can be an independent, separate unit.

[0053] In the third embodiment of the present invention, a pressure and temperature feedback control mechanism can also be used. The third Roots vacuum pump 2 further includes an outlet pressure sensor 12 and an outlet temperature sensor 15 located at its outlet 312. Based on the pressure values ​​detected by the inlet vacuum pressure sensor 11 and the outlet pressure sensor 12, and the temperature feedback values ​​detected by the outlet temperature sensors 15 of the first, second, and third Roots vacuum pumps 1 and 3, the system integrates and analyzes these values ​​before transmitting control signals to the variable frequency motors 181 of the first, second, and third Roots vacuum pumps 1 and 3, respectively, to adjust the speed of each variable frequency motor 181, thereby achieving optimal efficiency and safe operation of the entire system.

[0054] The advantages of this invention lie in its use of a single-stage or multi-stage Roots vacuum pump with full bearing seals, capable of withstanding large pressure differentials and high temperatures. This pump is connected in series with a backing pump to form a multi-stage structure. The Roots vacuum pump of this invention uses full bearing seals, thus forming a completely dry vacuum chamber. This prevents internal emulsification and erosion caused by saturated water vapor, eliminates the possibility of oil contamination in the bearing housing being carried into the vacuum chamber due to pressure fluctuations, and prevents condensation of water in the oil tank, which could then displace vacuum lubricating oil into the vacuum chamber. This ensures that the bearings and impellers of the Roots vacuum pump can maintain effective operation for a long time. Therefore, this invention is suitable for power plant condensers or other applications using low-efficiency vacuum pumps such as large liquid ring vacuum pumps, steam vacuum pumps, centrifugal vacuum pumps, and water-flushing vacuum pumps, achieving energy saving and emission reduction. This invention also utilizes PLC and variable frequency motor control to achieve intelligent frequency conversion. Based on power plant experience, seasonal changes, generator load changes, and the operating status of each pump in the pump group, it continuously and instantly collects data and automatically or manually adjusts the speed of each vacuum pump to optimize the safe operation of the system while achieving energy saving. For large condensers in some large power plants, where the vacuum level is high or the pumping volume is particularly large, a three-stage Roots vacuum pump can be used to meet the operational requirements.

[0055] This invention utilizes a Roots vacuum pump with the highest operating efficiency to perform one or more stages of compression on the mixed gas before it enters the power-intensive direct-vent to the atmosphere backing pump, significantly reducing the volume of the mixed gas. Then, a backing pump with a power output far less than that of a traditional large water ring pump, steam pump, or centrifugal pump discharges the reduced-volume mixed gas to the atmosphere or other pipelines, thereby significantly reducing system power consumption. It also substantially reduces the large emissions generated when using liquid, steam, or water backing pumps.

[0056] The structure of this invention can reduce energy consumption by 65% ​​to 85% compared to traditional large water ring pumps, steam pumps, and centrifugal pumps under the same customer operating conditions. Compared to using a Roots air-cooled pump equipped with a liquid ring pump vacuum device, it can also improve energy saving by 25% to 35%, and its footprint is only one-quarter of that of a large water ring pump group or 70% of that of an air-cooled Roots pump group, making it the structure with the lowest power consumption and smallest footprint among various competing technologies. Furthermore, since the vacuum degree of a multi-stage Roots vacuum pump is mainly determined by the Roots vacuum pump itself, it is minimally affected by temperature. Even with a high leakage rate in the original vacuum system, it has the potential to improve the vacuum degree of the condenser. Therefore, the system of this invention is more suitable for use in the vacuum system of condensers in thermal power plants. In addition, the architecture of this invention has the advantage of small component size, and its annual maintenance and cost are significantly lower than those of large liquid ring pump systems; due to the protection of full bearing seals, its failure rate is significantly lower than that of air-cooled Roots pumps.

[0057] The above detailed description is a specific description of a feasible embodiment of the present invention, but the embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the spirit of the present invention should be included in the patent scope of the present invention.

Claims

1. An energy-saving vacuum pump system based on a dry-type high-differential-pressure Roots vacuum pump with full bearing seal, characterized in that, include: An input valve (9) is a vacuum inlet pneumatic shut-off valve used to receive a mixture of saturated steam and non-condensable air from the power plant condenser and input the mixture to the next stage device. A first Roots vacuum pump (1) is connected to the input valve (9). The first Roots vacuum pump (1) is used to receive the mixed gas from the input valve (9) and compress it before outputting it to the next stage device. A second Roots vacuum pump (2) is connected to the first Roots vacuum pump (1) for further compressing the mixed gas output from the first Roots vacuum pump (1) and outputting the compressed mixed gas to the next stage device. Both the first Roots vacuum pump (1) and the second Roots vacuum pump (2) include a housing with an inlet and an outlet. A vacuum chamber and two bearing chambers located on both sides of the vacuum chamber are formed inside the housing. The vacuum chamber is connected to the inlet and the outlet. A drive shaft is located inside the housing, passing through the vacuum chamber and the two bearing chambers. One end of the drive shaft extends out of an outer wall of the housing. An impeller is located inside the vacuum chamber and is mounted on the drive shaft. The mixed gas input from the outside enters the vacuum chamber and is compressed by the rotation of the impeller. Bearings are provided on the two inner walls between the vacuum chamber and the two adjacent bearing chambers and on the outer wall of the housing. The drive shaft passes through each bearing and is supported by each bearing. Each bearing and the drive shaft form a fully sealed structure. The vacuum chamber and the two bearing chambers are completely isolated from each other, so that liquid outside the housing or the two bearing chambers cannot penetrate into the vacuum chamber, and the mixed gas in the vacuum chamber cannot enter the bearing chamber. The inlet of the second Roots vacuum pump (2) is connected in series to the outlet of the first Roots vacuum pump (1); and Both the first Roots vacuum pump (1) and the second Roots vacuum pump (2) are structures capable of withstanding large pressure differences. The so-called large pressure difference means that the first Roots vacuum pump (1) and the second Roots vacuum pump (2) can operate at an inlet pressure of 5,000 to 30,000 Pa around the clock under the condition of maintaining condenser vacuum, and can withstand a pressure difference of more than 5,000 Pa.

2. The energy-saving vacuum pump system according to claim 1, characterized in that, Also includes: A third Roots vacuum pump (3) is the same as the first Roots vacuum pump (1). The inlet of the third Roots vacuum pump (3) is connected in series with the outlet of the second Roots vacuum pump (2). The third Roots vacuum pump (3) is used to further compress the mixed gas output from the second Roots vacuum pump (2) and output the compressed mixed gas to the next stage device.

3. The energy-saving vacuum pump system according to claim 1, characterized in that, Both the first Roots vacuum pump (1) and the second Roots vacuum pump (2) are high-temperature resistant structures. The so-called high-temperature resistant means that the first Roots vacuum pump (1) and the second Roots vacuum pump (2) can withstand temperatures above 130°C during operation.

4. The energy-saving vacuum pump system according to claim 2, characterized in that, A heat exchanger (6) is connected in series between the outlet of the second Roots vacuum pump (2) and the inlet of the third Roots vacuum pump (3) to cool the mixed gas output by the second Roots vacuum pump (2).

5. The energy-saving vacuum pump system according to claim 1, characterized in that, Also includes: A backing pump (4), connected in series with the outlet of the second Roots vacuum pump (2), the backing pump (4) being used to further compress the mixed gas output from the second Roots vacuum pump (2) before outputting it; and A gas-liquid separator (5) is connected to the pre-pump (4). The gas-liquid separator (5) is used to separate the mixed gas output from the pre-pump (4) into gas and liquid, wherein the separated gas and liquid are discharged to the outside.

6. The energy-saving vacuum pump system according to claim 2, characterized in that, Also includes: A backing pump (4), connected in series with the outlet of the third Roots vacuum pump (3), the backing pump (4) being used to further compress the mixed gas output from the third Roots vacuum pump (3) before outputting it; and A gas-liquid separator (5) is connected to the pre-pump (4). The gas-liquid separator (5) is used to separate the mixed gas output from the pre-pump (4) into gas and liquid, wherein the separated gas and liquid are discharged to the outside.

7. The energy-saving vacuum pump system according to claim 1 or 2, characterized in that, Each Roots vacuum pump forms an integrated structure.

8. The energy-saving vacuum pump system according to claim 1, characterized in that, The first Roots vacuum pump (1) and the second Roots vacuum pump (2) also include a frequency converter motor for driving the corresponding drive shaft to drive the corresponding impeller and drive the mixed gas in the corresponding vacuum chamber to perform gas compression.

9. The energy-saving vacuum pump system according to claim 8, characterized in that, The first Roots vacuum pump (1) also includes an inlet vacuum pressure sensor (11) located at its inlet and an outlet temperature sensor (15) located at its outlet; the second Roots vacuum pump (2) also includes an outlet pressure sensor (12) and an outlet temperature sensor (15) located at its outlet; the system integrates and analyzes the pressure values ​​detected by the inlet vacuum pressure sensor (11) and the outlet pressure sensor (12) and the temperature feedback values ​​detected by the outlet temperature sensor (15) of the first Roots vacuum pump (1) and the second Roots vacuum pump (2) and transmits control signals to the variable frequency motors of the first Roots vacuum pump (1) and the second Roots vacuum pump (2) to adjust the speed of each variable frequency motor.

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