Control of the flow of operating liquid into a liquid ring pump

Abstract

A control system comprising: a suction line (28); a discharge line (30); an operating liquid line (32); a liquid ring pump (10) coupled to the suction, discharge, and operating liquid lines; a regulating device configured to control flow of operating liquid into the liquid ring pump (10); a pressure sensor (22) configured to measure pressure of input fluid to the liquid ring pump (10) via the suction line (28); a first temperature sensor (24) configured to measure temperature of discharge fluid output by the liquid ring pump (10) via the discharge line (30); a second temperature sensor (26) configured to measure temperature of operating liquid received by the liquid ring pump (10) via the operating liquid line (32); and a controller (20) configured to: control the one or more regulating devices using the sensor measurements.

Description

Technical Field

[0001] This invention relates to the control of the flow of operating liquids, such as water, entering a liquid ring pump. Background Technology

[0002] Liquid ring pumps are a known type of pump that commonly serves commercially as vacuum pumps and gas compressors. A liquid ring pump typically includes a housing having a chamber, a shaft extending into the chamber, an impeller mounted to the shaft, and a drive system, such as a motor, operatively connected to the shaft to drive it. The impeller and shaft are eccentrically positioned within the liquid ring pump's chamber.

[0003] During operation, the chamber is partially filled with an operating fluid (also known as a service fluid). As the drive system drives the shaft and impeller, a liquid ring forms on the inner wall of the chamber, providing a seal that isolates separate volumes between adjacent impeller blades. The impeller and shaft are eccentrically positioned relative to the liquid ring, which results in a periodic change in the volume enclosed between adjacent impeller blades and the liquid ring.

[0004] In the portion of the chamber where the liquid ring is further away from the shaft, there is a larger volume between adjacent impeller blades, resulting in lower pressure. This allows the portion where the liquid ring is further away from the shaft to act as the intake zone. In the portion of the chamber where the liquid ring is closer to the shaft, there is a smaller volume between adjacent impeller blades, resulting in higher pressure. This allows the portion where the liquid ring is closer to the shaft to act as the exhaust zone.

[0005] Examples of liquid ring pumps include single-stage liquid ring pumps and multi-stage liquid ring pumps. A single-stage liquid ring pump involves using only a single chamber and impeller. A multi-stage liquid ring pump (e.g., two-stage) involves using multiple chambers and impellers connected in series. Summary of the Invention

[0006] The suction capacity of a liquid ring vacuum pump can be affected by adjusting the temperature of the operating fluid used in the pump. For example, at high vacuum levels, higher pump efficiency is often achieved by lowering the operating fluid temperature. Typically, when water is used as the operating fluid, a lower temperature operating fluid is supplied by providing an open operating fluid loop in which the heated operating fluid from the pump is discharged and replaced by cold, fresh operating fluid. Therefore, liquid ring pumps can consume a considerable amount of fresh water.

[0007] The inventors have realized that it is desirable to control the operating liquid temperature and / or pressure of a liquid ring pump in a manner that minimizes power consumption. Such control often advantageously reduces the operating cost of the liquid ring pump.

[0008] The inventors have further realized the need for control of liquid ring pumps in a manner that prevents or combats cavitation. Cavitation is often a significant cause of wear and failure in some liquid ring pumps, especially those operating under low-pressure / high-vacuum conditions. Such control advantageously tends to reduce or eliminate wear caused by cavitation.

[0009] In a first aspect, a control system is provided, comprising: a suction line; a discharge line; an operating liquid line; a liquid ring pump including a suction input coupled to the suction line, a discharge output coupled to the discharge line, and a liquid input coupled to the operating liquid line; one or more regulating devices configured to control the flow of operating liquid into the liquid ring pump; a pressure sensor configured to measure the pressure of the input fluid received by the liquid ring pump via the suction line; a first temperature sensor configured to measure the temperature of the discharge fluid output by the liquid ring pump via the discharge line; and a second temperature sensor configured to measure the temperature of the discharge fluid received by the liquid ring pump via the operating liquid line. The operating liquid temperature; and a controller configured to: determine or estimate the vapor pressure of the operating liquid in the liquid ring pump using the temperature measurement of the discharged fluid; perform a first comparison, which is a comparison between a measured pressure of the input fluid and a function of the determined or estimated vapor pressure; control the one or more regulating devices to increase the flow rate of the operating liquid into the liquid ring pump in response to the first comparison satisfying one or more criteria; perform a second comparison, which is a comparison between a temperature measurement of the discharged fluid and a function of the temperature measurement of the operating liquid, in response to the first comparison not satisfying the one or more criteria; and control the one or more regulating devices based on the second comparison. This control system advantageously often enables intelligent handling of variable and uncertain load conditions that would otherwise lead to the shutdown of the pumping system, while achieving improved water and energy savings.

[0010] The vapor pressure of the operating liquid can be determined as follows:

[0011]

[0012] Where: A is a constant value; m is a constant value; T n It is a constant value; and T1 is the temperature measurement of the discharged fluid.

[0013] The first comparison may include determining the difference between a measured pressure of the input fluid and a function of a determined or estimated vapor pressure. The one or more criteria may include a criterion that the difference between the measured pressure of the input fluid and a function of the determined or estimated vapor pressure is less than or equal to a first threshold. The first threshold may be zero.

[0014] The controller can be configured to control the one or more regulating devices to increase the flow rate of the operating liquid into the liquid ring pump to a maximum flow rate in response to the first comparison satisfying the one or more criteria.

[0015] The second comparison may include determining the difference between the temperature measurement of the discharged fluid and the temperature measurement of the operating liquid. The controller may be configured to control the one or more regulating devices to increase the flow rate of the operating liquid into the liquid ring pump in response to the difference between the temperature measurement of the discharged fluid and the temperature measurement of the operating liquid being higher than a second threshold. The controller may be configured to control the one or more regulating devices to decrease the flow rate of the operating liquid into the liquid ring pump in response to the difference between the temperature measurement of the discharged fluid and the temperature measurement of the operating liquid being lower than a second threshold. The controller may be configured to control the one or more regulating devices to maintain the current flow rate of the operating liquid into the liquid ring pump in response to the difference between the temperature measurement of the discharged fluid and the temperature measurement of the operating liquid being equal to a second threshold. The second threshold may be variable, for example, selectable by a user. For wet processes (i.e., wet pumping processes), the second threshold may be set equal to a first value. For dry processes (i.e., dry pumping processes), the second threshold may be set equal to a second value. The first value may be different from the second value.

[0016] The controller may be a controller selected from the group of controllers consisting of the following: proportional controller, integral controller, derivative controller, proportional-integral controller, proportional-integral-derivative controller, proportional-derivative controller, and fuzzy logic controller.

[0017] The one or more regulating devices may include one or more devices selected from the group of devices consisting of: pumps, centrifugal pumps, valves, proportional valves.

[0018] In another aspect, a method for controlling a system is provided, the system comprising: an intake line; an exhaust line; an operating liquid line; a liquid ring pump including an intake input coupled to the intake line, an exhaust output coupled to the exhaust line, and a liquid input coupled to the operating liquid line; one or more regulating devices configured to control the flow of operating liquid into the liquid ring pump; a pressure sensor; a first temperature sensor; and a second temperature sensor. The method includes: measuring the pressure of an input fluid received by the liquid ring pump via the suction line using the pressure sensor; determining or estimating the vapor pressure of the operating liquid in the liquid ring pump using a temperature measurement of the discharge fluid; performing a first comparison, the first comparison being a comparison between a measured pressure of the input fluid and a function of the determined or estimated vapor pressure; controlling the one or more regulating devices to increase the flow rate of the operating liquid into the liquid ring pump in response to the first comparison satisfying one or more criteria; measuring the temperature of the discharge fluid output by the liquid ring pump via the discharge line using the first temperature sensor; measuring the temperature of the operating liquid received by the liquid ring pump via the operating liquid line using the second temperature sensor; performing a second comparison, the second comparison being a comparison between a temperature measurement of the discharge fluid and a function of the temperature measurement of the operating liquid in response to the first comparison not satisfying the one or more criteria; and controlling the one or more regulating devices based on the second comparison. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a vacuum system (not to scale);

[0020] Figure 2 This is a schematic diagram of a liquid ring pump (not to scale);

[0021] Figure 3 It is a process flow diagram illustrating certain steps of the control process implemented by a vacuum system; and

[0022] Figure 4 It is shown in Figure 3 A process flow diagram of certain steps implemented during the control process. Detailed Implementation

[0023] Figure 1 This is a schematic diagram (not to scale) showing vacuum system 2. Vacuum system 2 is coupled to facility 4 such that, in operation, vacuum system 2 establishes a vacuum or low-pressure environment at facility 4 by evacuating gas (e.g., air) from facility 4.

[0024] In this embodiment, the vacuum system 2 includes a check valve 6, a liquid ring pump 10, a motor 12, a separator 14, a pump system 16, a controller 20, a pressure sensor 22, a first temperature sensor 24, and a second temperature sensor 26.

[0025] Facility 4 is connected to the inlet of liquid ring pump 10 via suction or vacuum line or pipe 28.

[0026] Check valve 6 is installed on suction line 28. Check valve 6 is installed between facility 4 and liquid ring pump 10.

[0027] The check valve 6 is configured to allow fluid (e.g., a gas such as air) to flow from facility 4 to liquid ring pump 10, and to prevent or stop the flow of fluid in the opposite direction, i.e., from liquid ring pump 10 to facility 4.

[0028] In this embodiment, the liquid ring pump 10 is a single-stage liquid ring pump.

[0029] The gas inlet of the liquid ring pump 10 is connected to the suction line 28. The gas outlet of the liquid ring pump 10 is connected to the discharge line or conduit 30. The liquid ring pump 10 is coupled to the pump system 16 via a first operating liquid line 32. The liquid ring pump 10 is configured to receive operating liquid from the pump system 16 via the first operating liquid line 32. The liquid ring pump 10 is driven by a motor 12.

[0030] Figure 2 This is a schematic diagram (not to scale) of the cross-section of an example liquid ring pump 10. In the description Figure 2 Following the liquid ring pump 10 shown below, the rest of the vacuum system 2 will be described in more detail later.

[0031] Figure 2 The liquid ring pump 10 illustrated includes a housing 100 defining a generally cylindrical chamber 102, a shaft 104 extending into the chamber 102, and an impeller 106 fixedly mounted to the shaft 104. The gas inlet 108 of the liquid ring pump 10 (coupled to a suction line 28) is fluidly connected to the air inlet of the chamber 102. The gas outlet of the liquid ring pump 10 (… Figure 2 (Not shown) The gas output is fluidly connected to chamber 102.

[0032] During operation of the liquid ring pump 10, operating liquid is received in chamber 102 via a first operating liquid conduit 32. Furthermore, motor 12 rotates shaft 104, causing impeller 106 to rotate within chamber 102. As impeller 106 rotates, the operating liquid (not shown) in chamber 102 is pressed against the wall of chamber 102, forming a liquid ring that seals and isolates a separate volume between adjacent impeller blades. Meanwhile, gas (such as air) is drawn into chamber 102 via gas inlet 108 and the inlet of chamber 102 from suction line 28. This gas flows into the volume formed between adjacent blades of impeller 106. Rotation of impeller 106 causes the size of said volume to decrease. As the gas contained within this volume moves from the inlet of chamber 102 to the gas outlet of chamber 102, the rotation of impeller 106 compresses the gas, and the compressed gas exits chamber 102 at the gas outlet. The compressed gas leaving chamber 102 then exits the liquid ring pump via the gas outlet and discharge line 30.

[0033] Now return to the original Figure 1 As described, discharge line 30 is coupled between the gas outlet of liquid ring pump 10 and the inlet of separator 14. Separator 14 is connected to liquid ring pump 10 via discharge line 30 such that discharged fluid (i.e., compressed gas, which may include water droplets and / or vapor) is received by separator 14.

[0034] The separator 14 is configured to separate the discharge fluid received from the liquid ring pump 10 into gas (e.g., air) and operating liquid.

[0035] The gas separated from the received discharge fluid is discharged from the separator 14 and the vacuum system 2 via the system outlet pipe 34.

[0036] The separator 14 includes an operating liquid outlet through which the operating fluid separated from the received discharge fluid is output from the separator 14 and the vacuum system 2 via a discharge or venting pipe 36.

[0037] In this embodiment, the pump system 16 includes a pump (e.g., a centrifugal pump) and a motor configured to drive the pump. The pump system 16 is configured to pump operating liquid from an operating liquid source 38 via a second operating liquid conduit 40 and to pump the operating liquid to a liquid ring pump via a first operating liquid conduit 32.

[0038] The operating liquid source 38 can be any suitable operating liquid source. For example, in an embodiment where the operating liquid is water, the operating liquid source 38 can be a tap water supply system, a river, a lake, a water storage tank, etc.

[0039] Controller 20 may include one or more processors. In this embodiment, controller 20 includes a variable frequency drive (VFD) 42. VFD 42 is configured to control the speed of the motor of pump system 16. (See below for reference.) Figure 3 and Figure 4 In more detail, controller 20 is configured to receive sensor measurements from sensors 22-26. Controller 20 is further configured to process some or all of these sensor measurements and, based on this sensor data processing, control the operation of pump system 16 via VFD 42.

[0040] Controller 20 is connected to pump system 16 via its VFD 42 and via a first connection 44, such that control signals for controlling pump system 16 can be sent from controller 20 to the motor of pump system 16. First connection 44 can be any suitable type of connection, including but not limited to wired or fiber optic or wireless connections. Pump system 16 is configured to operate according to control signals received therefrom controller 20. (See below for further details.) Figure 3 and Figure 4 The controller 20 controls the pump system 16 in more detail.

[0041] Pressure sensor 22 is coupled to the suction line 28 between facility 4 and check valve 6. Pressure sensor 22 is configured to measure the pressure of the gas flowing in suction line 28, i.e., the pressure of the gas pumped from facility 4 by the action of liquid ring pump 10. Pressure sensor 22 can be any suitable type of pressure sensor. Pressure sensor 22 is connected to controller 20 via a second connection 46, such that the measurement value obtained by pressure sensor 22 is transmitted from pressure sensor 22 to controller 20. Second connection 46 can be any suitable type of connection, including but not limited to wired or fiber optic or wireless connections.

[0042] A first temperature sensor 24 is coupled to a discharge line 30 between the liquid ring pump 10 and the separator 14. The first temperature sensor 24 is configured to measure the temperature of the fluid discharged from the liquid ring pump 10 flowing in the discharge line 30, i.e., the temperature of the air-water mixture pumped by the liquid ring pump 10 to the separator 14. The first temperature sensor 24 can be any suitable type of temperature sensor. The first temperature sensor 24 is connected to the controller 20 via a third connection 48, such that the measured value obtained by the first temperature sensor 24 is transmitted from the first temperature sensor 24 to the controller 20. The third connection 48 can be any suitable type of connection, including but not limited to wired or fiber optic or wireless connections.

[0043] A second temperature sensor 26 is coupled to a first operating liquid conduit 32 between the heat exchanger 18 and the liquid ring pump 10. The second temperature sensor 26 is configured to measure the temperature of the operating liquid flowing into (i.e., pumped by the pump system 16) the liquid ring pump 10 via the first operating liquid conduit 32. The second temperature sensor 26 can be any suitable type of temperature sensor. The second temperature sensor 26 is connected to the controller 20 via a fourth connection 50, such that the measured value obtained by the second temperature sensor 26 is transmitted from the second temperature sensor 26 to the controller 20. The fourth connection 50 can be any suitable type of connection, including but not limited to wired or fiber optic or wireless connections.

[0044] Therefore, an embodiment of vacuum system 2 is provided.

[0045] The means including controller 20 for implementing the above arrangement and carrying out the method steps described below can be provided by configuring or adapting any suitable means (e.g., one or more computers or other processing means or processors) and / or providing additional modules. The means may include a computer, computer network, or one or more processors for implementing instructions and using data, including instructions and data in the form of one or more computer programs stored in or on a machine-readable storage medium (such as computer memory, computer disk, ROM, PROM, etc., or any combination of these or other storage media).

[0046] Now refer to Figure 3 and Figure 4 An embodiment describing a control process that can be implemented by vacuum system 2 is provided. It should be noted that details may be omitted. Figure 3 and Figure 4 The flowchart illustrates and describes some of the process steps below, or they can be presented and described below. Figure 3 and Figure 4 The process steps shown are performed in different orders. Furthermore, although all process steps have been depicted as discrete time-sequence steps for convenience and ease of understanding, some process steps may actually be performed simultaneously or at least overlap in time to some extent.

[0047] refer to Figure 3 and Figure 4 The described process often enables intelligent handling of variable and uncertain load conditions that would otherwise lead to system shutdown, while simultaneously achieving improved water and energy conservation.

[0048] Figure 3 This is a process flow diagram illustrating some steps of an embodiment of the control process implemented by the vacuum system 2 during operation. Figure 3 The process can be regarded as an "anti-cavitation control" process.

[0049] In step s2, the first temperature sensor 24 measures a first temperature T1. The first temperature T1 is the temperature of the fluid discharged from the liquid ring pump 10 flowing in the discharge line 30, that is, the temperature of the air-water mixture pumped to the separator 14 by the liquid ring pump 10. The measured value of the first temperature T1 is sent from the first temperature sensor 24 to the controller 20 via the third connection 48.

[0050] In step s4, the controller 20 uses the measured first temperature T1 to determine or estimate the vapor pressure of the operating liquid in the liquid ring pump 10. In this embodiment, the operating liquid is water, and therefore, the controller determines the vapor pressure of water for the first temperature T1, which will be referred to below as "water vapor pressure P". wv In this embodiment, the water vapor pressure P is determined using approximate formulas, particularly the Antoine equation. wv Water vapor pressure P wv It was identified as:

[0051]

[0052] Where: A is a constant value, for example, A can be between approximately 6.1 and 6.2, for example A = 6.116441;

[0053] m is a constant value; for example, m can be between approximately 7.5 and 7.6, such as m = 7.591306.

[0054] T n It is a constant temperature value (in Kelvin), for example, T. n It can be between approximately 240 and 241 Kelvin, for example, T. n =240.7263K; and

[0055] T1 is the first temperature measured.

[0056] In some embodiments, parameters A, m, and T n One or more of these are defined for the liquid used in the liquid ring pump and / or may have values ​​different from those given above.

[0057] In step s6, the controller 20 applies the determined water vapor pressure P wv An offset value is added to determine the updated pressure value. Therefore, in this embodiment, the updated pressure value P is determined as:

[0058] P = P wv +P offset

[0059] Where: P offset It is the offset value.

[0060] Offset value P offset This can be considered a safety margin. Offset value P offset This can be any suitable pressure value, including but not limited to values ​​between 1 mbar and 10 mbar, such as 1 mbar, 2 mbar, 3 mbar, 4 mbar, 5 mbar, 6 mbar, 7 mbar, 8 mbar, 9 mbar, or 10 mbar. In some embodiments, the offset value P is omitted. offset .

[0061] In step s8, pressure sensor 22 measures a first pressure P1, which is the pressure of the gas flowing in the suction line 28, i.e., the pressure of the gas pumped from facility 4 by the liquid ring pump 10. The measured value of the first pressure P1 is sent by pressure sensor 22 to controller 20 via second connection 46.

[0062] In step s10, the controller 20 compares the measured first pressure P1 with the determined updated pressure value P. Specifically, in this embodiment, the controller 20 determines the error value as the difference between the measured first pressure P1 and the determined updated pressure value P. Therefore, the error value ΔP can be calculated as:

[0063] ΔP=P1-P

[0064] In step s12, the controller 20 compares the determined error value ΔP with a first threshold. The first threshold may be, for example, zero (0).

[0065] If in step s12, the controller determines that the error value ΔP is less than or equal to the first threshold, that is, if ΔP≤0, then the method proceeds to s14.

[0066] However, if in step s12 the controller determines that the error value ΔP is greater than the first threshold, the method proceeds to s18. Step s18 will be described in more detail later.

[0067] In step s14, in response to determining that the error value ΔP is less than or equal to the first threshold, the controller 20 adjusts the control variable v(t) to increase the error value ΔP.

[0068] In this embodiment, the control variable v(t) is the operating speed of the motor of the pump system 16. The controller 20 can adjust the control variable v(t) to cause an increase in the error value ΔP by adjusting or changing the control variable v(t) in a manner that would lead to an increase in the operating speed of the motor of the pump system 16.

[0069] An increase in the operating speed of the motor in pump system 16 will often cause pumping system 16 to pump more operating liquid into liquid ring pump 10. This can increase the pressure within liquid ring pump 10, and thus increase the initial pressure P1.

[0070] This increase in the operating speed of the motor in pump system 16 will often cause pumping system 16 to pump more relatively cold operating fluid into liquid ring pump 10 (within a given time), which will often result in a decrease in the temperature of the operating fluid in liquid ring pump 10 (and also a decrease in T1). This will often result in a decrease in the evaporation pressure of the operating liquid in liquid ring pump 10.

[0071] Therefore, the controller 20 can adjust the operating speed of the motor of the pumping system 16 to cause an increase in the error value ΔP.

[0072] In some embodiments, in step s14, in response to determining that the error value ΔP is less than or equal to a first threshold, the controller 20 adjusts the control variable v(t) to increase the operating speed of the motor of the pump system 16 to its maximum speed.

[0073] In this embodiment, controller 20 is a proportional-integral (PI) controller. Therefore, controller 20 can apply corrections / adjustments to the control variable v(t) based on, for example, the proportional and integral terms of the error value ΔP. The adjusted value of the control variable v(t) can be determined as a weighted sum of the control terms (i.e., the proportional and integral parameters determined by controller 20).

[0074] In step s16, the controller 20 uses the adjusted control variable v(t) to control the motor of the pump system 16.

[0075] Specifically, controller 20 generates a control signal for the motor of pump system 16 based on the adjusted control variable v(t) determined in step s14. This control signal is then sent from controller 20 to the motor of pump system 16 via first connection 44. The motor of pump system 16 operates according to the received control signal. In particular, in this embodiment, increasing the speed of the motor of pump system 16 results in an increase in the flow rate of the operating liquid entering liquid ring pump 10. This tends to lead to an increase in the error value ΔP.

[0076] Increasing the error value ΔP means increasing the first pressure P1 and the water vapor pressure P. wv The difference between them. The pressure of the gas pumped in the liquid ring pump 10 is removed from the water vapor pressure P. wv This often reduces the likelihood of cavitation caused by inlet gas in the liquid ring pump 10.

[0077] After step s16, repeat Figure 3 The process, for example, continues until vacuum system 2 is shut down. Figure 3 The process can be carried out continuously, or more preferably continuously during the operation of vacuum system 2.

[0078] Now, returning to the case where, in step s12, controller 20 determines that the error value ΔP is greater than the first threshold, the method proceeds to s18.

[0079] In step s18, implementation Figure 4 The control process.

[0080] Figure 4 This shows the vacuum system 2 in Figure 3 The process flowchart shows some steps of the control process implemented at step s18.

[0081] In step s20, the first temperature sensor 24 measures a first temperature T1. The first temperature T1 is the temperature of the fluid discharged from the liquid ring pump 10 flowing in the discharge line 30, that is, the temperature of the air-water mixture pumped to the separator 14 by the liquid ring pump 10. The measured value of the first temperature T1 is sent from the first temperature sensor 24 to the controller 20 via the third connection 48.

[0082] In step s22, the second temperature sensor 26 measures the second temperature T2. The second temperature T2 is the temperature of the operating liquid received by the liquid ring pump 10 via the first operating liquid conduit 32. The measured value of the second temperature T2 is sent from the second temperature sensor 26 to the controller 20 via the fourth connection 50.

[0083] In step s24, the controller 20 determines the temperature difference as the difference between the measured first temperature T1 and the measured second temperature T2. Therefore, in this embodiment, the temperature difference ΔT is calculated as:

[0084] ΔT=T1-T2

[0085] In step s26, controller 20 operates to reduce or minimize the temperature difference ΔT by adjusting the control variable v2(t).

[0086] In some embodiments, the controller 20 attempts to make the temperature difference ΔT equal to a second threshold, or to cause the temperature difference ΔT to be within a first threshold range (e.g., a first threshold plus / minus a constant). The second threshold can be any suitable value, such as 1°C, 1.5°C, 2°C, 2.5°C, or 3°C. The second threshold can be determined by testing, for example, to determine a threshold associated with high or optimal liquid ring pump efficiency. The second threshold can depend on the size or power of the liquid ring pump 10.

[0087] In some embodiments, the second threshold is a variable, such as one that can be changed by the user of system 2. For example, the second threshold can be set by the user based on the pumped fluid, the desired operation of the system, etc. For wet processes, the second threshold can be set equal to the first value. For dry processes, the second threshold is set equal to a second value (different from the first value).

[0088] The term "wet process" can be used to refer to processes such as pumping processes, where the process gas pumped by a liquid ring pump system contains a significant amount of vapor (e.g., the percentage of vapor in the process gas is higher than the threshold percentage composition of vapor). In wet processes, the process gas may contain some liquid. In wet processes, the temperature of the process gas is typically high, e.g., above a threshold temperature. Examples of wet processes include, but are not limited to, power plant pumping processes, steam pumping from turbines, and tire vulcanization processes.

[0089] The term "dry process" can be used to refer to processes such as pumping processes, where the process gas pumped by a liquid ring pump system does not contain a significant amount of vapor (e.g., the percentage of vapor in the process gas is below the threshold percentage composition of vapor). In a dry process, the process gas does not contain liquid. In a dry process, the temperature of the process gas is often lower than in other dry processes, for example, below the threshold temperature. Examples of dry processes include, but are not limited to, supplying a vacuum to a facility (e.g., by pumping air) for cleaning or maintenance.

[0090] In this embodiment, controller 20 is a proportional-integral (PI) controller. Therefore, controller 20 applies corrections / adjustments to the control variable v(t) based on the proportional and integral terms of the temperature difference ΔT. The adjusted value of the control variable v(t) can be determined as a weighted sum of the control terms (i.e., the proportional and integral parameters determined by controller 20).

[0091] In this embodiment, if the temperature difference ΔT is too high, for example, ΔT is higher than a threshold such as the second threshold mentioned above, the controller 20 increases the control variable v(t). As described above, increasing the control variable v(t) corresponds to the accelerator pump system 16.

[0092] Similarly, if the temperature difference ΔT is too low, for example, ΔT is below a threshold such as the second threshold mentioned above, then the controller 20 decreases the control variable v(t). Decreasing the control variable v(t) corresponds to slowing down the pump system 16.

[0093] In this embodiment, if the temperature difference ΔT equals the second threshold, the controller 20 maintains the control variable v(t). This corresponds to maintaining the current speed of the motor of the pump system 16.

[0094] In step s28, controller 20 controls (using VFD) pump system 16 using the adjusted control variable v(t).

[0095] Specifically, controller 20 generates a control signal for the motor of pump system 16 based on the adjusted control variable v(t) determined in step s8. This control signal is then sent from controller 20 to pump system 16 via second connection 44. Pump system 16 operates according to the received control signal.

[0096] Therefore, if the temperature difference ΔT is too high, the pump system 16 accelerates according to the increased control variable v(t). This increases the flow rate of the relatively cold operating liquid entering the liquid ring pump 10. This often results in a decrease in the first temperature T1 measured by the first temperature sensor 24, thereby reducing the temperature difference ΔT.

[0097] Similarly, if the temperature difference ΔT is too low, the pump system 16 slows down according to the reduced control variable v(t). This reduces the flow rate of the relatively cold operating liquid entering the liquid ring pump 10. This often results in an increase in the first temperature T1 measured by the first temperature sensor 24, thereby increasing the temperature difference ΔT.

[0098] After step s28, repeat Figure 4 The process, for example, continues until vacuum system 2 is shut down. Figure 4 The process can be carried out continuously, or more preferably continuously during the operation of vacuum system 2.

[0099] Therefore, an embodiment of a control process implemented by the vacuum system 2 is provided. This control process includes a control loop feedback mechanism in which continuous modulation control of the pump system 16 is implemented.

[0100] Advantageously, the above-described system and the first control process enable control of the operating liquid temperature in the liquid ring pump.

[0101] The aforementioned systems and control processes often advantageously achieve improved performance and efficiency of liquid ring pumps.

[0102] The aforementioned systems and control processes advantageously tend to reduce the likelihood of the operating fluid overloading the liquid ring pump. Furthermore, they tend to reduce the likelihood and / or severity of hydraulic shocks (also known as "water hammer"). This tends to reduce damage to the liquid ring pump. Advantageously, the aforementioned systems and first control processes tend to provide reduced or minimized operating fluid consumption. The operating fluid is often recirculated within the aforementioned systems and first control processes. This tends to reduce the operating costs of the liquid ring pump.

[0103] The aforementioned systems and control processes advantageously and often reduce the likelihood and / or severity of cavitation in liquid ring pumps.

[0104] Advantageously, if the heat load of the above system is low, the pump system will tend to slow down. Therefore, energy consumption tends to be reduced.

[0105] Advantageously, the aforementioned systems and control processes often enable control of the fluid temperature and pressure within the liquid ring pump.

[0106] The aforementioned systems and control processes advantageously often result in improved reliability of liquid ring pumps.

[0107] The aforementioned systems and control processes advantageously tend to reduce the likelihood and / or severity of cavitation in liquid ring pumps. For example, cavitation can occur in liquid ring pumps because the inlet pressure (i.e., the pressure of the gas from the suction line) is at or below the vapor pressure of the operating liquid. The aforementioned control processes advantageously tend to adjust the pressure within the liquid ring pump to move it away from the vapor pressure of the operating liquid, thereby reducing the likelihood of cavitation. Therefore, damage to the liquid ring pump caused by cavitation is often reduced or eliminated.

[0108] In the above embodiments, the vacuum system includes the above-referenced... Figure 1 The components described. Specifically, the vacuum system includes a check valve, a liquid ring pump, a motor, a separator, a pumping system, a controller, a pressure sensor, first and second temperature sensors, and connections therebetween. However, in other embodiments, the vacuum system includes other components in lieu of or in addition to those described above. Moreover, in other embodiments, some or all of the components of the vacuum system may be connected together in a suitable manner different from that described above. In some embodiments, multiple liquid ring pumps may be implemented.

[0109] In some embodiments, heating and / or cooling devices may be arranged to heat and / or cool the operating fluid entering the liquid ring pump. For example, heating and / or cooling devices may be coupled to a first operating fluid conduit 32 and configured to heat and / or cool the operating fluid therein.

[0110] In the above embodiments, the separator outputs the separated operating liquid and separated gas from the system via corresponding output pipes. However, in other embodiments, the separated operating liquid and / or separated gas are not output from the system. For example, in some embodiments, the operating liquid is recirculated from the separator back to the liquid ring pump. Recirculation of the operating liquid advantageously tends to reduce operating costs and water consumption. In some embodiments, the separator may be omitted.

[0111] In the above embodiments, the liquid ring pump is a single-stage liquid ring pump. However, in other embodiments, the liquid ring pump is a different type of liquid ring pump, such as a multi-stage liquid ring pump.

[0112] In the above embodiments, the operating liquid is water. However, in other embodiments, the operating liquid is a different type of operating liquid.

[0113] In the above embodiments, the controller is a PI controller. However, in other embodiments, the controller is a different type of controller, such as a proportional (P) controller, an integral (I) controller, a derivative (D) controller, a proportional-derivative (PD) controller, a proportional-integral-derivative (PID) controller, or a fuzzy logic controller.

[0114] In the above embodiments, a single controller controls the operation of multiple system components (e.g., motors). However, in other embodiments, multiple controllers may be used, each controlling a corresponding subset of the component group. For example, in some embodiments, each motor may have a dedicated controller.

[0115] In the above embodiments, the temperature difference is determined as ΔT = T1 - T2. However, in other embodiments, the temperature difference is determined in a different manner, for example, using different appropriate formulas. For example, the temperature difference can be a different function of the first temperature T1 and / or the second temperature T2. For example, weights can be applied to the measured temperatures T1 and T2.

[0116] In the above embodiments, the Antoine equation is used to express the water vapor pressure P. wv Estimated as However, in other embodiments, the water vapor pressure is estimated in different appropriate ways, such as using different approximations, including the August-Roche-Magnus (or Magnus-Tetens or Magnus) equation, the Tetens equation, the Buck equation, or the Goff-Gratch equation. In some embodiments, the water vapor pressure Pwv is determined as

[0117] In the above embodiments, the error value ΔP is determined as ΔP = P1 - P. However, in other embodiments, the error value is determined in a different manner, for example, using different appropriate formulas. For example, the error value may be a different function of the first pressure P1 and / or the first temperature T1. In some embodiments, weights may be applied to the measured pressure P1 and / or the updated pressure value P.

[0118] In the above embodiments, the motor of the pumping system is controlled to regulate or adjust the flow of the operating fluid into the liquid ring pump. However, in other embodiments, one or more different types of regulating devices are implemented instead of the pumping system or in addition to the pumping system. The controller can be configured to control the operation of one or more regulating devices. For example, in some embodiments, the pumping system may be omitted, and one or more valves may be present along the operating fluid lines 32, 40 to control the flow of the operating fluid therethrough. In some embodiments, the pumping system is replaced by a proportional valve controlled by the controller. The proportional valve can be controlled in the same manner as the pumping system, as referenced earlier above. Figure 3 and Figure 4Described in more detail, the valve is opened to increase the flow of operating fluid into the liquid ring pump, and closed to reduce the flow of operating fluid into the liquid ring pump. In some embodiments, in step s14, in response to determining that an error value ΔP is less than or equal to a first threshold, the controller controls the one or more valves (e.g., one or more proportional valves) to open to their maximum extent. The use of one or more valves (e.g., one or more proportional valves) is often useful in embodiments where the supply of operating fluid from the operating fluid source has sufficient pressure to bring the operating fluid received by the liquid ring pump to the desired pressure. In some embodiments, both the pumping system and the valve system are implemented to regulate the flow of operating fluid to the liquid ring pump.

[0119] Advantageously, the system is configured such that neither the maximum centrifugal pump speed nor the maximum proportional valve opening causes overload of the liquid ring pump.

[0120] Figure Labels

[0121] 2-Vacuum System

[0122] 4- Facilities

[0123] 6-Check valve

[0124] 10-Liquid Ring Pump

[0125] 12-motor

[0126] 14-Separator

[0127] 16-Pump System

[0128] 20-Controller

[0129] 22-Pressure Sensor

[0130] 24-First Temperature Sensor

[0131] 26-Second Temperature Sensor

[0132] 28-Suction Line

[0133] 30-Discharge pipeline

[0134] 32-First Operating Liquid Pipeline

[0135] 34-System Outlet Pipeline

[0136] 36-Drainage pipe

[0137] 38-Operating Liquid Source

[0138] 40-Second Operating Liquid Pipeline

[0139] 42-Variable Frequency Drive

[0140] 44-First Connection

[0141] 46-Second Connection

[0142] 48-Third Connection

[0143] 50-Fourth Connection

[0144] 100-Shell

[0145] Room 102

[0146] 104-axis

[0147] 106-Impeller

[0148] 108-Gas Inlet

[0149] s2-s28-Method Steps

Claims

1. A control system comprising: Inhalation line; Discharge pipeline; Operate liquid lines; A liquid ring pump, the liquid ring pump including a suction input coupled to the suction line, a discharge output coupled to the discharge line, and a liquid input coupled to the operating liquid line; One or more regulating devices, the one or more regulating devices being configured to control the flow of operating liquid into the liquid ring pump; A pressure sensor configured to measure the pressure of the input fluid received by the liquid ring pump via the suction line; A first temperature sensor is configured to measure the temperature of the discharged fluid output by the liquid ring pump via the discharge line; A second temperature sensor is configured to measure the temperature of the operating liquid received by the liquid ring pump via the operating liquid line; as well as The controller is configured to: Using the temperature measurement of the discharged fluid, determine or estimate the vapor pressure of the operating liquid in the liquid ring pump; A first comparison is performed, which is a comparison between a measured pressure of the input fluid as a function of a determined or estimated vapor pressure. In response to the first comparison satisfying one or more criteria, the one or more regulating devices are controlled to increase the flow rate of the operating fluid into the liquid ring pump; In response to the first comparison not meeting one or more criteria, a second comparison is performed, which is a comparison between the temperature measurement of the discharged fluid as a function of the temperature measurement of the operating liquid; as well as The one or more regulating devices are controlled based on the second comparison.

2. The control system according to claim 1, wherein the vapor pressure of the operating liquid is determined as: in: A is a constant value; m is a constant value; T n It is a constant value; and T1 is the temperature measurement of the discharged fluid.

3. The control system according to claim 1 or 2, wherein the first comparison includes determining the difference between a measured pressure of the input fluid and a function of a determined or estimated vapor pressure.

4. The control system of claim 3, wherein the one or more criteria include a criterion that the difference between the measured pressure of the input fluid and a function of the determined or estimated vapor pressure is less than or equal to a first threshold.

5. The control system according to claim 4, wherein the first threshold is zero.

6. The control system according to any one of claims 1 to 5, wherein the controller is configured to control the one or more regulating devices to increase the flow rate of the operating liquid into the liquid ring pump to a maximum flow rate in response to the first comparison satisfying the one or more criteria.

7. The control system according to any one of claims 1 to 6, wherein the second comparison includes determining the difference between the temperature measurement of the discharged fluid and the temperature measurement of the operating liquid.

8. The control system of claim 7, wherein the controller is configured to control the one or more regulating devices to increase the flow rate of the operating liquid into the liquid ring pump in response to the difference between the temperature measurement of the discharged fluid and the temperature measurement of the operating liquid being higher than a second threshold.

9. The control system of claim 7 or 8, wherein the controller is configured to control the one or more regulating devices to reduce the flow rate of the operating liquid into the liquid ring pump in response to the difference between the temperature measurement of the discharged fluid and the temperature measurement of the operating liquid being less than a second threshold.

10. The control system according to any one of claims 7 to 9, wherein the controller is configured to control the one or more regulating devices to maintain the current flow rate of the operating liquid into the liquid ring pump in response to the difference between the temperature measurement of the discharged fluid and the temperature measurement of the operating liquid being equal to a second threshold.

11. The control system according to any one of claims 8 to 10, wherein the second threshold is variable.

12. The control system according to any one of claims 8 to 10, wherein for a wet process, the second threshold is set to be equal to a first value, and for a dry process, the second threshold is set to be equal to a second value, wherein the first value is different from the second value.

13. The control system according to any one of claims 1 to 12, wherein the controller is a controller selected from the group of controllers consisting of: proportional controller, integral controller, derivative controller, proportional-integral controller, proportional-integral-derivative controller, proportional-derivative controller, and fuzzy logic controller.

14. The control system according to any one of claims 1 to 13, wherein one or more regulating devices comprise one or more devices selected from the group consisting of: pumps, centrifugal pumps, valves, proportional valves.

15. A method for controlling a system, the system comprising: Inhalation line; Discharge lines; operating liquid lines; A liquid ring pump, the liquid ring pump including a suction input coupled to the suction line, a discharge output coupled to the discharge line, and a liquid input coupled to the operating liquid line; One or more regulating devices, the one or more regulating devices being configured to control the flow of operating liquid into the liquid ring pump; Pressure sensor; First temperature sensor; The method includes: and a second temperature sensor. The pressure of the input fluid received by the liquid ring pump via the suction line is measured by the pressure sensor; Using the temperature measurement of the discharged fluid, determine or estimate the vapor pressure of the operating liquid in the liquid ring pump; A first comparison is performed, which is a comparison between a measured pressure of the input fluid as a function of a determined or estimated vapor pressure. In response to the first comparison satisfying one or more criteria, the one or more regulating devices are controlled to increase the flow rate of the operating fluid into the liquid ring pump; The temperature of the discharged fluid output by the liquid ring pump via the discharge line is measured by the first temperature sensor; The temperature of the operating liquid received by the liquid ring pump via the operating liquid line is measured by the second temperature sensor; In response to the first comparison not meeting one or more criteria, a second comparison is performed, the second comparison being a comparison between the temperature measurement of the discharged fluid as a function of the temperature measurement of the operating liquid; and The one or more regulating devices are controlled based on the second comparison.

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