Turbine pump and liquid ring pump series combination system and control method thereof

Abstract

The invention provides a turbine pump and liquid ring pump series combination system and a control method thereof. Comprising a turbine pump, a condenser, a liquid ring pump, a heat exchanger, a steam-water separator, a control cabinet, a first variable frequency motor, a second variable frequency motor, a first pressure transmitter, a second pressure transmitter, a third pressure transmitter, a first temperature transmitter, a second temperature transmitter, a liquid level transmitter, a first electric control switch valve, a second electric control switch valve and a first electric control regulating valve. And a second electric control regulating valve and other components and related pipelines. By the adoption of the system formed by connecting the turbine pump (the front-stage pump) and the liquid ring pump (the rear-stage pump) in series and the control method of the system and monitoring the feature points of the front-stage pump and the rear-stage pump, the working conditions of the front-stage pump and the rear-stage pump can be adjusted in time, the phenomena of surge, stall, cavitation and the like are avoided, and therefore the energy consumption of the system is reduced, and the stability of the system is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of vacuum pumps, and in particular relates to a series combination system of a turbine pump and a liquid ring pump and a control method thereof. Background Art

[0002] Currently, common turbine vacuum pump (hereinafter referred to as "turbo pump") systems consist of a single turbine pump or multiple turbine pumps connected in series and associated equipment. Systems consisting of a single turbine pump and associated equipment have a narrow air volume adjustment range, making it difficult to meet the vacuuming needs of large and medium-sized equipment. Systems consisting of multiple turbine pumps connected in series and associated equipment, while offering a wider air volume adjustment range, will still experience a malfunction in a single turbine pump, impacting the operation of the entire system. Furthermore, since turbine pumps are dry pumps, they often employ a multi-stage impeller structure. During operation, the rotor within the pump body rotates at high speed, generating heat within the fan due to friction caused by the high-speed rotor operation and also due to compression. This heat accumulation can easily cause internal pump parts to expand and become stuck. In particular, systems composed of multiple turbine pumps, due to their high speeds, heat rises as the gas passes through the foreline pump, causing it to expand and impact the flow of gas from downstream pumps. This results in excessive gas volume within the system and a failure to automatically adjust the volume. This can lead to surge, stall, and increased noise, resulting in a sharp decline in system performance. Furthermore, excessive gas volume can easily lead to problems such as motor overload.

[0003] It should also be noted that in addition to systems consisting of multiple turbine pumps and supporting equipment connected in series, common vacuum systems also include other combinations, such as systems consisting of multiple liquid ring vacuum pumps (hereinafter referred to as liquid ring pumps) and supporting equipment connected in series, and systems consisting of Roots vacuum pumps (hereinafter referred to as Roots pumps) and liquid ring pumps and supporting equipment connected in series. While systems consisting of multiple liquid ring pumps and supporting equipment connected in series offer greater vacuuming capabilities than systems consisting of a single liquid ring pump and supporting equipment, they also suffer from reduced overall system energy efficiency and higher power consumption due to the cumulative energy losses from multiple stages of compression. In particular, systems containing multiple liquid ring pumps in series can significantly increase operating costs in high-pressure or high-flow scenarios. Systems consisting of both Roots and liquid ring pumps connected in series and supporting equipment, while combining the advantages of both types of vacuum pumps, are less energy-efficient. In particular, due to the small clearance between the rotors of Roots vacuum pumps, the rotors can easily seize due to heat expansion during operation, placing high thermal expansion requirements on the rotor material, meaning that the thermal expansion coefficient should be as low as possible. In addition, the rotor material should also meet many other process requirements such as strong corrosion resistance and high structural strength. This makes the configuration of the rotor material not flexible, resulting in poor overall corrosion resistance of the system, and it is easy for oil sticking or jamming to occur inside during actual operation. Summary of the Invention

[0004] The purpose of the present invention is to provide a vacuum pump system with stable operation, low energy consumption, more flexible material selection, strong corrosion resistance and not easy to get oily or stuck inside, so as to overcome the above-mentioned defects of the prior art.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A turbine pump and liquid ring pump series combination system, comprising a turbine pump, a condenser, a liquid ring pump, a heat exchanger, a steam-water separator, a control cabinet, a first variable frequency motor, a second variable frequency motor, a first pressure transmitter, a second pressure transmitter, a third pressure transmitter, a first temperature transmitter, a second temperature transmitter, a liquid level transmitter, a first electrically controlled on-off valve, a second electrically controlled on-off valve, and a first electrically controlled regulating valve;

[0007] The first variable frequency motor is connected to the turbine pump shaft, and the second variable frequency motor is connected to the liquid ring pump shaft; the control cabinet is communicatively connected to the first variable frequency motor, the second variable frequency motor, the first pressure transmitter, the second pressure transmitter, the third pressure transmitter, the first temperature transmitter, the second temperature transmitter, the liquid level transmitter, the first electronically controlled on-off valve, the second electronically controlled on-off valve, and the first electronically controlled regulating valve;

[0008] The air inlet of the turbine pump is connected to the system's main air inlet pipeline, and the first pressure transmitter is arranged on the system's main air inlet pipeline; the air outlet of the turbine pump is connected to the air inlet of the condenser through the condenser's air inlet pipeline, and the second pressure transmitter is arranged on the condenser's air inlet pipeline;

[0009] The air outlet of the condenser is connected to the air inlet of the liquid ring pump through the liquid ring pump air inlet pipeline. The first temperature transmitter and the third pressure transmitter are arranged on the liquid ring pump air inlet pipeline. The first electronically controlled regulating valve is arranged on the pipeline connected to the water inlet of the condenser.

[0010] The air outlet of the liquid ring pump is connected to the air inlet of the steam-water separator through the liquid ring pump exhaust pipeline, and the exhaust port of the steam-water separator is connected to the main exhaust pipeline of the system; the liquid replenishment port of the steam-water separator is connected to the liquid replenishment pipeline, and the discharge port of the steam-water separator is connected to the discharge pipeline; the return water port of the steam-water separator is connected to the front section of the liquid ring pump water replenishment pipeline, the middle section of the liquid ring pump water replenishment pipeline is arranged inside the heat exchanger, and the rear section of the liquid ring pump water replenishment pipeline is connected to the water replenishment port of the liquid ring pump; the second temperature transmitter is arranged on the side of the rear section of the liquid ring pump water replenishment pipeline; the liquid level transmitter is arranged on one side of the steam-water separator.

[0011] On the basis of the above technical solutions, the present invention may add the following technical means to better or more specifically solve the technical problems to be solved by the present invention:

[0012] It also includes a second electronically controlled regulating valve, which is installed on a pipeline connecting the system's main air intake pipeline and the system's main exhaust pipeline. The second electronically controlled regulating valve is communicatively connected to the control cabinet.

[0013] Furthermore, it also includes a check valve, which is installed on the air inlet pipeline of the liquid ring pump, or installed at the connection point between the exhaust port of the steam-water separator and the main exhaust pipeline of the system.

[0014] Furthermore, the turbine pump is a turbine pump with a spray device.

[0015] Furthermore, the number of the turbine pumps is two or more, and the two or more turbine pumps are connected in series through pipelines. The turbine pump at the front end is connected to the total air intake pipeline of the system, and the turbine pump at the rear end is connected to the air intake pipeline of the condenser.

[0016] With the above technical solution as the material and technical means, the present invention further provides a control method for a system of a turbine pump and a liquid ring pump connected in series, comprising the following steps:

[0017] Step 1: Start the system, and the gas is pumped into the turbine pump through the system's main air inlet pipeline;

[0018] Step 2: After passing through the turbine pump, the gas enters the condenser along the condenser inlet pipe, and after being cooled by the condenser, enters the liquid ring pump along the liquid ring pump inlet pipe;

[0019] Step 3: After the gas passes through the liquid ring pump, it enters the steam-water separator along the liquid ring pump exhaust pipeline and is separated into working fluid and pure gas in the steam-water separator. The separated pure gas is discharged from the system along the system total exhaust pipeline, and the separated working fluid is returned to the liquid ring pump along the liquid ring pump water supply pipeline and after being cooled by the heat exchanger, the working fluid is replenished to the liquid ring pump.

[0020] Furthermore, after the system is turned on, the liquid ring pump is started first and the P A The set value for the system to start the turbine pump. A ≥P 25 When the liquid ring pump is working normally, the system will automatically start the turbine pump. 25 Indicates the vacuum degree measured by the third pressure transmitter.

[0021] Furthermore, the control cabinet calculates the saturated vapor pressure corresponding to the temperature of the gas entering the liquid ring pump and the gas volume entering the liquid ring pump. The calculation formula for the saturated vapor pressure is as follows:

[0022] Pt=1000*10^(5.11564-1687.537 / (230.17+C2));

[0023] Where, C2 represents the temperature of the gas inhaled by the liquid ring pump in °C, and the unit of the saturated vapor pressure Pt is hPa;

[0024] The calculation formula for the gas volume entering the liquid ring pump is as follows:

[0025]

[0026] Where, Qt represents the gas volume entering the liquid ring pump when the water temperature is t °C, and the unit is m 3 / min; P I represents the suction pressure of the liquid ring pump, and the unit is Torr; P t represents the saturated vapor pressure when the water temperature is t °C, and the unit is Torr; P 15 represents the saturated vapor pressure when the water temperature is 15 °C, and the unit is Torr.

[0027] Furthermore, when P4 ≤ P 25 ≤ P1, it indicates that the liquid ring pump is working normally;

[0028] When P 25 < P4 < P l it indicates that the vacuum degree of the liquid ring pump is too high; in this case, the control cabinet controls the second variable-frequency motor to gradually reduce the rotational speed of the liquid ring pump; if the rotational speed of the liquid ring pump is reduced to the lowest rotational speed, the first electric control valve is already closed, and the liquid ring pump still cannot avoid the limit working condition within the set time (this set time is generally defaulted to 3 minutes), then the system alarms;

[0029] When P l < P 25 < P4, it indicates that the saturated vapor pressure is too high; in this case, the control cabinet automatically monitors the value of the second temperature transmitter, and if the temperature is too high, the system automatically alarms that the water temperature is abnormal;

[0030] When P4 < P l < P 25 it indicates that the gas volume of the liquid ring pump is too small and the generated vacuum degree is not enough. In this case, the control cabinet automatically increases the water supply of the cooling water for the condenser by increasing the opening degree of the first electric control valve; after increasing the water supply of the cooling water for the condenser, if the liquid ring pump still cannot return to the normal working condition, the control cabinet controls the rotational speed of the second variable-frequency motor to gradually increase. Within the set time after the rotational speed of the second variable-frequency motor increases to the highest rotational speed of the liquid ring pump (this set time is defaulted to 5 minutes), if the liquid ring pump still cannot return to the normal working condition, then the system automatically alarms;

[0031] Where, P1 represents the lowest pressure during the operation of the liquid ring pump, P4 represents the highest pressure during the operation of the liquid ring pump, and P 25 represents the vacuum degree measured by the third pressure transmitter.

[0032] Further, the control cabinet monitors the operation of the turbine pump and the first variable-frequency motor through the values displayed on the pressure gauges of the first pressure transmitter and the second pressure transmitter. When it indicates that the first variable-frequency motor is overloaded. In the formula, P2 is the value displayed on the pressure gauge of the first pressure transmitter (the vacuum degree actually measured by the first pressure transmitter), and P5 is the value displayed on the pressure gauge of the second pressure transmitter (the vacuum degree actually measured by the second pressure transmitter); in the case of the first variable-frequency motor being overloaded, the control cabinet controls the first variable-frequency motor to reduce its frequency.

[0033] Further, it is set that P2 < PMAX + 0.5, where PMAX is the limit pressure that the turbine pump unit can obtain, and 0.5 is the protection value.

[0034] Compared with the prior art, the main beneficial effects of the present invention are as follows:

[0035] By adopting a system composed of a turbine pump (front-stage pump) in series with a liquid ring pump (rear-stage pump) and its control method, as well as monitoring the characteristic points of the front and rear-stage pumps, the present invention can timely adjust the operating conditions of the front and rear-stage pumps, avoid phenomena such as surging, stalling, and cavitation, thereby reducing the system energy consumption and significantly improving the stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a schematic structural diagram of Embodiment 1 of the present invention.

[0037] In the figure:

[0038] 1 - system total intake pipeline; 2 - first pressure transmitter;

[0039] 3 - turbine pump; 4 - first variable-frequency motor;

[0040] 5 - second pressure transmitter; 6 - condenser intake pipeline;

[0041] 7 - condenser; 8 - liquid ring pump intake pipeline

[0042] 9 - liquid ring pump; 10 - second variable-frequency motor;

[0043] 11 - liquid ring pump exhaust pipeline; 12 - liquid ring pump water supply pipeline;

[0044] 13 - heat exchanger; 14 - steam-water separator;

[0045] 15 - first electric control switch valve; 16 - drain pipeline;

[0046] 17 - liquid level transmitter; 18 - second electric control switch valve;

[0047] 19 - water supply pipeline; 20 - system total exhaust pipeline;

[0048] 21——first temperature transmitter; 22——second temperature transmitter;

[0049] 23 - check valve; 24 - first electronically controlled regulating valve;

[0050] 25——the third pressure transmitter; 26——the second electronically controlled regulating valve

[0051] 27——Control cabinet. DETAILED DESCRIPTION

[0052] In order to facilitate those skilled in the art to fully understand the technical solution of the present invention, an embodiment of the present invention is described below with reference to the accompanying drawings.

[0053] like Figure 1 As shown, a turbine pump and liquid ring pump series combination system (hereinafter referred to as the system) includes a turbine pump 3, a condenser 7, a liquid ring pump 9, a heat exchanger 13, a steam-water separator 14, a control cabinet 27 (the control cabinet is also called an electric control cabinet), a first variable frequency motor 4, a second variable frequency motor 10, a first pressure transmitter 2, a second pressure transmitter 5, a third pressure transmitter 25, a first temperature transmitter 21, a second temperature transmitter 22, a liquid level transmitter 17, a first electrically controlled on-off valve 15, a second electrically controlled on-off valve 18, a first electrically controlled regulating valve 24, and a second electrically controlled regulating valve 26.

[0054] The first variable frequency motor 4 is connected to the turbine pump 3 shaft (the first variable frequency motor 4 is used to drive the turbine pump 3); the second variable frequency motor 10 is connected to the liquid ring pump 9 shaft (the second variable frequency motor 10 is used to drive the liquid ring pump 9); the control cabinet 27 is communicatively connected to the first variable frequency motor 4, the second variable frequency motor 10, the first pressure transmitter 2, the second pressure transmitter 5, the third pressure transmitter 25, the first temperature transmitter 21, the second temperature transmitter 22, the liquid level transmitter 17, the first electrically controlled switching valve 15, the second electrically controlled switching valve 18, the first electrically controlled regulating valve 24, and the second electrically controlled regulating valve 26.

[0055] The air inlet of the turbine pump 3 is connected to the system's main air inlet pipeline 1, and the first pressure transmitter 2 is arranged on the system's main air inlet pipeline 1; the air outlet of the turbine pump 3 is connected to the air inlet of the condenser 7 through the condenser air inlet pipeline 6, and the second pressure transmitter 5 is arranged on the condenser air inlet pipeline 6.

[0056] The gas outlet of the condenser 7 is connected to the gas inlet of the liquid ring pump 9 through the liquid ring pump inlet pipeline 8. The first temperature transmitter 21 and the third pressure transmitter 25 are arranged on the liquid ring pump inlet pipeline 8. The liquid ring pump inlet pipeline 8 is also provided with a check valve 23. It should be noted that the present invention can also be provided with a check valve at the connection between the exhaust port of the steam-water separator 14 and the system main exhaust pipeline 20.

[0057] The air outlet of the liquid ring pump 9 is connected to the air inlet of the steam-water separator 14 through the liquid ring pump exhaust pipeline 11, the exhaust port of the steam-water separator 14 is connected to the system total exhaust pipeline 20, the rehydration port of the steam-water separator 14 is connected to the rehydration pipeline 19, and the discharge port of the steam-water separator 14 is connected to the discharge pipeline 16; the return water port of the steam-water separator 14 is connected to the front section of the liquid ring pump water supply pipeline 12, the middle section of the liquid ring pump water supply pipeline 12 is arranged inside the heat exchanger 13, and the rear section of the liquid ring pump water supply pipeline 12 is connected to the water supply port of the liquid ring pump 9; the second temperature transmitter 22 is arranged on the side of the rear section of the liquid ring pump water supply pipeline 12; the liquid level transmitter 17 is arranged on one side of the steam-water separator 14.

[0058] The first electrically controlled regulating valve 24 is installed on a pipeline (condensate pipeline) connected to the water inlet of the condenser 7; the second electrically controlled regulating valve 26 is installed on a pipeline connecting the system's main air intake pipeline 1 with the system's main exhaust pipeline 20. It should be noted that in this embodiment, a pipeline connecting the system's main air intake pipeline 1 and the system's main exhaust pipeline 20 is provided, and the second electrically controlled regulating valve 26 is installed on this pipeline. The purpose is to control the opening and closing of the second electrically controlled regulating valve 26 according to the actual needs during system operation, thereby directing the gas originally discharged through the system's main exhaust pipeline 20 into the system's main air intake pipeline 1 and into the turbine pump 3, thereby achieving a reflux effect.

[0059] In this embodiment, a turbine pump 3 is provided in the system. However, when the present invention is actually implemented, multiple (two or more) turbine pumps connected in series can also be provided according to the actual needs of different working conditions. The performance and specifications of each turbine pump can be the same or different. Multiple turbine pumps are connected in series in sequence through pipelines. The turbine pump at the front end is connected to the system's total air intake pipeline 1, and the turbine pump at the tail end (the last turbine pump) is connected to the condenser air intake pipeline 6. The gas discharged from the last turbine pump is processed by the condenser 7 and enters the liquid ring pump 9 as the subsequent pump. In addition, as a preferred embodiment, the present invention can select a turbine pump with a spray device. The turbine pump with a spray device can further shrink and condense the gas after entering the impeller, thereby indirectly improving the suction capacity of the system.

[0060] The structural features of Example 1 of the present invention are described above in conjunction with the accompanying drawings. The control method and working principle thereof are further described below.

[0061] The operation process of this embodiment is automatically controlled by the control cabinet 27, which not only saves manpower, but also makes the control more convenient and accurate, the range of control over abnormal working conditions is wider, and the system is more stable. Its main working steps are:

[0062] In step 1, the system is started. Gas (referring to water-containing gas outside the system) is pumped through the system's main air intake line 1 to the turbine pump 3. While the system is executing step 1, the control cabinet 27 monitors the pressures of the gas being drawn in and discharged from the turbine pump 9 via the first and second pressure transmitters 2 and 5, respectively.

[0063] In step 2, after the gas passes through the turbine pump 1, it enters the condenser 7 along the condenser air inlet pipe 6. After cooling treatment in the condenser 7, it enters the liquid ring pump 9 along the liquid ring pump air inlet pipe 8. When the system executes step 2, the control cabinet 27 can monitor the temperature and pressure of the gas sucked into the liquid ring pump 7 through the third pressure transmitter 25 and the first temperature transmitter 21.

[0064] In step 3, after the gas passes through the liquid ring pump 9, it enters the steam-water separator 14 along the liquid ring pump exhaust pipe 11 and is separated into working fluid and pure gas in the steam-water separator. The separated pure gas is discharged from the system along the system main exhaust pipe 20, and the separated working fluid is returned to the liquid ring pump 9 along the liquid ring pump water supply pipe 12 and after being cooled by the heat exchanger 13, the working fluid is replenished to the liquid ring pump 9. When the system executes step 3, the control cabinet 27 can monitor the temperature of the working fluid through the second temperature transmitter 22.

[0065] The structural features and main working steps of an embodiment of the present invention are described above. The following further introduces five issues related to the control method and working principle of this embodiment.

[0066] 1. Calculation of saturated vapor pressure of liquid ring pump working fluid

[0067] When the system executes the above steps, the control cabinet 27 can calculate the saturated vapor pressure and cavitation range of the liquid ring pump working fluid through the temperature of the liquid ring pump working fluid monitored by the second temperature transmitter 22, the gas temperature monitored by the first temperature transmitter 21, and the gas pressure monitored by the third pressure transmitter 25, and adjust the working conditions according to the calculation results. Taking the working fluid as water and the water temperature C = 15 ° C as an example, the calculation formula for the saturated vapor pressure of the liquid ring pump working fluid is as follows:

[0068] P=1000*10^(5.11564-1687.537 / (230.17+C));

[0069] Where P is the saturated vapor pressure of the working fluid at the corresponding water temperature, in hPa (hectopascals)

[0070] Substituting the water temperature C = 15°C into the above formula yields: Pw = 17.0808hPa, or Pw = 1.70808kPa (kilopascals). Pw represents the saturated vapor pressure of the working fluid calculated using the above formula. The theoretical minimum vacuum pressure of a liquid ring pump is the saturated vapor pressure of the working fluid, while the actual minimum vacuum pressure is higher than the saturated vapor pressure at that water temperature.

[0071] 2. About system startup and shutdown

[0072] After the system is turned on, the liquid ring pump 9 will be started first. For example, if the saturated vapor pressure of the working fluid is 1.70808 kPa, the vacuum limit obtained by the liquid ring pump is about 3.3 kPa. Taking into account the influence of factors such as gas reflux, plus the empirical coefficient of 2 kPa, the control cabinet 27 calculates 5.3 kPa as the set value P for the system to start the turbine pump 3. A At the same time, the control cabinet 27 will monitor the value displayed by the pressure gauge of the third pressure transmitter 25 in real time (the vacuum degree actually measured by the third pressure transmitter 25) P 25 , when P A ≥P 25 , it indicates that the liquid ring pump 9 is working normally and the system will automatically start the turbine pump 3.

[0073] After the system starts the liquid ring pump 9, set the time T (default 5 minutes) when P A <P 25 , the control cabinet 27 will control the first variable frequency motor 4 (turbine pump motor) to increase the speed. After the speed reaches the limit speed of the turbine pump 3 for a period of time (the default time T is 5 minutes), if P A <P 25 , indicating that the system or liquid ring pump is abnormal, for example, there may be a system leak, instrument failure and other problems, and the system automatically alarms. After the system automatically alarms, the on-site operator will handle it as appropriate based on the specific content of the alarm (the same below).

[0074] It is worth noting that after the system is shut down, the pressure difference between the vacuum in the system and the external atmospheric pressure will cause the working fluid to flow back to the liquid ring pump, thereby damaging the liquid ring pump. In order to prevent this situation from occurring, the present invention provides a check valve 23 in the system (in this embodiment, the check valve 23 is installed on the liquid ring pump air inlet pipe 8 in front of the air inlet of the liquid ring pump 7. When the present invention is actually implemented, the check valve can also be installed at the place where the exhaust port of the steam-water separator 14 is connected to the system's main exhaust pipe 20). Through the check valve 23, the present invention can effectively prevent the working fluid from flowing back to the liquid ring pump due to the pressure difference between the inside and outside of the system. Therefore, when the system needs to be shut down, the turbine pump 3 and the liquid ring pump 9 can be turned off at the same time.

[0075] 3. Regarding the control of the turbine pump 3 and the first variable frequency motor 4.

[0076] To protect the system, the control cabinet 27 monitors the operating conditions of the turbine pump 1 through the pressure transmitters before and after the turbine pump 3, that is, through the first pressure transmitter 2 and the second pressure transmitter 5. Specifically, the control cabinet 27 monitors the operation of the turbine pump 1 through the values shown on the pressure gauges of the first pressure transmitter 2 and the second pressure transmitter 5. The limit pressure difference before and after the turbine pump is generally 1:3. However, in order to make the system more stable, the present invention sets the maximum pressure difference before and after the turbine pump 3 to 1:2. Then when it indicates that the first variable-frequency motor 4 (turbine pump motor) is overloaded. Here, P2 is the value shown on the pressure gauge of the first pressure transmitter 2 (the vacuum degree actually measured by the first pressure transmitter 2), and P5 is the value shown on the pressure gauge of the second pressure transmitter 5 (the vacuum degree actually measured by the second pressure transmitter 5). In the case of the first variable-frequency motor 4 being overloaded, the control cabinet 27 reduces the frequency of the first variable-frequency motor 4.

[0077] To ensure the stable operation of the turbine pump 3, the present invention sets P2 < PMAX + 0.5, where PMAX is the limit pressure that the turbine pump unit can obtain, and 0.5 is a protection value (which can be adjusted according to the working conditions). If the value of P2 is too high (for example, P2 ≥ PMAX + 0.5), the turbine pump 3 is prone to surging. To avoid the occurrence of this phenomenon, the turbine pump 3 can be restored to the normal working condition by reducing the intake air volume and vacuum degree of the turbine pump 3. For this purpose, the control cabinet 27 first controls the first variable-frequency motor 4 to reduce the frequency, reducing the pressure difference and air volume of the turbine pump.

[0078] If the turbine pump 3 cannot be restored to the normal working condition after the first variable-frequency motor 4 reduces the frequency, the control cabinet 27 controls the opening degree of the second electric control valve 26 to control the intake air volume of the turbine pump 3, reducing the pressure difference between the intake and exhaust ports of the turbine pump 3, so as to restore the turbine from the limit working condition to the normal working condition and avoid damage to the turbine pump 3 and the first variable-frequency motor 4.

[0079] If the above steps cannot restore the turbine pump 3 to the normal working condition, the system automatically alarms.

[0080] When the vacuum degree P2 actually measured by the first pressure transmitter 2 is less than the preset value, the control cabinet 27 controls the first variable-frequency motor 4 to gradually increase the speed. If P2 still cannot return to the normal vacuum degree after increasing the speed to the maximum value of this variable-frequency motor for a period of time, the system automatically alarms.

[0081] IV. Control of the liquid ring pump 9 and the second variable-frequency motor 10

[0082] After the gas is discharged from the exhaust port of the turbine pump 3, it flows along the liquid ring pump inlet pipe 8 and enters the liquid ring pump 9 after cooling treatment by the condenser 7. During this process, the control cabinet 27 monitors the working condition of the liquid ring pump 9 through the third pressure transmitter 25, the first temperature transmitter 21 and the second temperature transmitter 22.

[0083] The calculation formula for the saturated vapor pressure corresponding to the temperature of the gas entering the liquid ring pump 9 is as follows:

[0084] Pt=1000*10^(5.11564-1687.537 / (230.17+C2));

[0085] Where C2 represents the temperature of the gas sucked by the liquid ring pump 9 in °C, and the unit of saturated vapor pressure Pt is hPa;

[0086] The calculation formula for the gas volume entering the liquid ring pump 9 is as follows:

[0087]

[0088] Where Qt represents the gas volume (m 3 / min), for example, when the water temperature is 15℃, use Q 15 Indicates the gas volume corresponding to the temperature (m 3 / min), P I Indicates the suction pressure of the liquid ring pump 9 (Torr), P t Indicates the saturated vapor pressure (Torr) when the water temperature is t℃, P 15 Indicates the saturated vapor pressure (Torr) when the water temperature is 15°C

[0089] According to the above formula, the control cabinet 27 can control the gas volume of the liquid ring pump 9 by adjusting the water supply amount of the condenser 14 and the speed of the liquid ring pump 9.

[0090] For example: under the working conditions of 15℃ water and saturated vapor pressure of 1.7056kPa, the minimum pressure P when the liquid ring pump 9 is working l =i*Pa, i is the empirical coefficient (0.8 in this embodiment), and P is calculated l =4.24. When the technical solution of the present invention is actually implemented, i can be adjusted according to the working conditions.

[0091] In this embodiment, the maximum pressure P4 of the liquid ring pump 9 during operation is Pt*i2+1, where i2 is an empirical coefficient (1.9 in this embodiment). When the technical solution of the present invention is actually implemented, i2 can be adjusted according to the working conditions.

[0092] When P4≤P 25 When ≤P1, the liquid ring pump 9 works normally and is in normal working condition. At this time, there is no need to adjust the system.25 It represents the measured vacuum degree of the third pressure transmitter 25, and P1 represents the lowest pressure during the operation of the liquid ring pump 9.

[0093] When P 25 < P4 < P l it indicates that the vacuum degree of the liquid ring pump 9 is too high. In this case, the control cabinet 27 gradually reduces the rotational speed of the liquid ring pump 9 by controlling the second variable-frequency motor 10. After the rotational speed of the liquid ring pump 9 is reduced to the lowest rotational speed, the first electronically controlled regulating valve 24 (condenser water supply valve) is gradually closed under the control of the control cabinet 27, and the intake air volume of the liquid ring pump 9 is controlled by controlling the temperature of the inhaled gas. If the second variable-frequency motor 10 cannot be further reduced in frequency, that is, the rotational speed of the liquid ring pump 9 is reduced to the lowest rotational speed, the first electronically controlled regulating valve 24 has been closed, and the limit working condition of the liquid ring pump still cannot be avoided within the set time (default 3 min), the system will alarm, thereby avoiding cavitation of the liquid ring pump, affecting the normal operation of the system, and causing damage to the liquid ring pump and the motor.

[0094] When P l < P 25 < P4, it indicates that the saturated vapor pressure is too high at this time. The control cabinet 27 automatically monitors the value of the second temperature transmitter 22. If the temperature is too high, the system will automatically alarm for abnormal water temperature. If the temperature is normal, it indicates that it is an abnormality caused by other factors such as instrument abnormality, etc. Generally speaking, when the saturated vapor pressure is too high and the temperature displayed by the second temperature transmitter 22 is normal, the possibility of instrument abnormality is relatively high.

[0095] When P4 < P l < P 25 at this time, the gas volume of the liquid ring pump 9 is too small, and the generated vacuum degree is insufficient. In this case, the control cabinet 27 automatically increases the cooling water supply volume of the condenser 7 by increasing the opening degree of the first electronically controlled regulating valve 24. After increasing the cooling water supply volume of the condenser 7, if the liquid ring pump 9 still cannot return to the normal working condition, the control cabinet 27 gradually increases the rotational speed of the second variable-frequency motor 10. If the liquid ring pump 9 still cannot return to the normal working condition within a certain time (default 5 min) after the rotational speed of the second variable-frequency motor 10 is increased to the highest rotational speed of the liquid ring pump 9, the system will automatically alarm.

[0096] V. Control of the steam-water separator 14

[0097] The control cabinet 7 judges the liquid level of the steam-water separator 14 according to the liquid level transmitter 17. When the liquid level is too high, the first electronically controlled switch valve 15 is opened to discharge the excess working fluid out of the system. When the liquid level is too low, the second electronically controlled switch valve 18 is opened to replenish the working fluid in the steam-water separator to the preset value.

[0098] It should also be noted that although the control method introduced above is for a system consisting of a turbine pump and a liquid ring pump connected in series, in terms of the control principle involved in the control method, the principle of the above control method is no different from the principle of the control method for a system consisting of multiple turbine pumps and a liquid ring pump connected in series in sequence.

Claims

1. A turbine pump and liquid ring pump series combination system, characterized by: It includes a turbine pump, a condenser, a liquid ring pump, a heat exchanger, a steam-water separator, a control cabinet, a first variable frequency motor, a second variable frequency motor, a first pressure transmitter, a second pressure transmitter, a third pressure transmitter, a first temperature transmitter, a second temperature transmitter, a liquid level transmitter, a first electric-controlled on-off valve, a second electric-controlled on-off valve, and a first electric-controlled regulating valve; The first variable frequency motor is connected to the turbine pump shaft, and the second variable frequency motor is connected to the liquid ring pump shaft; the control cabinet is communicatively connected to the first variable frequency motor, the second variable frequency motor, the first pressure transmitter, the second pressure transmitter, the third pressure transmitter, the first temperature transmitter, the second temperature transmitter, the liquid level transmitter, the first electronically controlled on-off valve, the second electronically controlled on-off valve, and the first electronically controlled regulating valve; The air inlet of the turbine pump is connected to the system's main air inlet pipeline, and the first pressure transmitter is arranged on the system's main air inlet pipeline; the air outlet of the turbine pump is connected to the air inlet of the condenser through the condenser's air inlet pipeline, and the second pressure transmitter is arranged on the condenser's air inlet pipeline; The air outlet of the condenser is connected to the air inlet of the liquid ring pump through the liquid ring pump air inlet pipeline. The first temperature transmitter and the third pressure transmitter are arranged on the liquid ring pump air inlet pipeline. The first electronically controlled regulating valve is arranged on the pipeline connected to the water inlet of the condenser. The air outlet of the liquid ring pump is connected to the air inlet of the steam-water separator through the liquid ring pump exhaust pipeline, and the exhaust port of the steam-water separator is connected to the main exhaust pipeline of the system; the liquid replenishment port of the steam-water separator is connected to the liquid replenishment pipeline, and the discharge port of the steam-water separator is connected to the discharge pipeline; the return water port of the steam-water separator is connected to the front section of the liquid ring pump water replenishment pipeline, the middle section of the liquid ring pump water replenishment pipeline is arranged inside the heat exchanger, and the rear section of the liquid ring pump water replenishment pipeline is connected to the water replenishment port of the liquid ring pump; the second temperature transmitter is arranged on the side of the rear section of the liquid ring pump water replenishment pipeline; the liquid level transmitter is arranged on one side of the steam-water separator.

2. The turbine pump and liquid ring pump series combination system according to claim 1, characterized in that: It also includes a second electronically controlled regulating valve, which is installed on a pipeline connecting the system's main air intake pipeline and the system's main exhaust pipeline. The second electronically controlled regulating valve is communicatively connected to the control cabinet.

3. The turbine pump and liquid ring pump series combination system according to claim 1, characterized in that: It also includes a check valve, which is installed on the air inlet pipeline of the liquid ring pump, or installed at the connection point between the exhaust port of the steam-water separator and the main exhaust pipeline of the system.

4. The turbine pump and liquid ring pump series combination system according to claim 1, characterized in that: The turbine pump is a turbine pump with a spray device.

5. The turbine pump and liquid ring pump series combination system according to claim 1, characterized in that: The number of the turbine pumps is two or more, and the two or more turbine pumps are connected in series through pipelines. The turbine pump at the front end is connected to the total air intake pipeline of the system, and the turbine pump at the rear end is connected to the air intake pipeline of the condenser.

6. A control method for a turbine pump and a liquid ring pump series combination system according to any one of claims 1 to 5, characterized in that: The steps include: Step 1: Start the system, and the gas is pumped into the turbine pump through the system's main air inlet pipeline; Step 2: After passing through the turbine pump, the gas enters the condenser along the condenser inlet pipe, and after being cooled by the condenser, enters the liquid ring pump along the liquid ring pump inlet pipe; Step 3: After the gas passes through the liquid ring pump, it enters the steam-water separator along the liquid ring pump exhaust pipeline and is separated into working fluid and pure gas in the steam-water separator. The separated pure gas is discharged from the system along the system total exhaust pipeline, and the separated working fluid is returned to the liquid ring pump along the liquid ring pump water supply pipeline and after being cooled by the heat exchanger, the working fluid is replenished to the liquid ring pump.

7. The control method for a turbine pump and liquid ring pump series combination system according to claim 6, characterized in that: After the system is turned on, start the liquid ring pump first and A The set value for the system to start the turbine pump. A ≥P 25 When the system automatically starts the turbine pump, P 25 Indicates the vacuum degree measured by the third pressure transmitter.

8. The control method for a turbine pump and a liquid ring pump series combination system according to claim 7, characterized in that: The control cabinet calculates the saturated vapor pressure corresponding to the temperature of the gas entering the liquid ring pump and the amount of gas entering the liquid ring pump. The calculation formula for the saturated vapor pressure is as follows: Pt=1000*10^(5.11564-1687.537 / (230.17+C2)); Where, C2 represents the gas temperature sucked by the liquid ring pump, and the unit of saturated vapor pressure Pt is hPa; The calculation formula for the gas volume entering the liquid ring pump is as follows: Where Qt represents the gas volume entering the liquid ring pump when the water temperature is t℃, and the unit is m 3 / min; P I Indicates the suction pressure of the liquid ring pump, the unit is Torr; P t Indicates the saturated vapor pressure when the water temperature is t℃, the unit is Torr; P 15 Indicates the saturated vapor pressure when the water temperature is 15°C, in Torr.

9. The control method for a turbine pump and a liquid ring pump series combination system according to claim 8, characterized in that: When P4≤P 25 ≤P1, indicating that the liquid ring pump is operating normally; When P 25 <P4<P l When the vacuum level of the liquid ring pump is too high, the control cabinet controls the second variable frequency motor to gradually reduce the speed of the liquid ring pump. If the speed of the liquid ring pump is reduced to the minimum speed, the first electronically controlled regulating valve is closed, and the extreme working condition of the liquid ring pump cannot be avoided within the set time, the system will alarm. When P l <P 25 <When P4, it indicates that the saturated vapor pressure is too high; in this case, the control cabinet automatically monitors the value of the second temperature transmitter. If the temperature is too high, the system will automatically alarm that the water temperature is abnormal; When P4 <P l <P 25 When the pressure drops below 0.15, it indicates that the gas volume of the liquid ring pump is too small and the vacuum degree generated is insufficient. In this case, the control cabinet automatically increases the cooling water supply to the condenser by increasing the opening of the first electronically controlled regulating valve. After increasing the cooling water supply to the condenser, if the liquid ring pump still cannot return to normal working condition, the control cabinet controls the speed of the second frequency conversion motor to increase gradually. Within the set time after the speed of the second frequency conversion motor increases to the maximum speed of the liquid ring pump, if the liquid ring pump still cannot return to normal working condition, the system automatically alarms. In the formula, P1 represents the lowest pressure when the liquid ring pump is working, P4 represents the highest pressure when the liquid ring pump is working, and P 25 Indicates the vacuum degree measured by the third pressure transmitter.

10. The control method for a turbine pump and a liquid ring pump series combination system according to claim 6, characterized in that: The control cabinet monitors the operation of the turbine pump and the first variable frequency motor through the pressure gauges of the first pressure transmitter and the second pressure transmitter. When , it means that the first variable frequency motor is overloaded. In the formula, P2 is the vacuum degree measured by the first pressure transmitter 2, and P5 is the vacuum degree measured by the second pressure transmitter. When the first variable frequency motor is overloaded, the control cabinet controls the first variable frequency motor to reduce its frequency.

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