A device and method for avoiding tripping of a main pipe electric desalination system

Abstract

The application relates to a device and a method for avoiding tripping of a mother pipe electric desalting system, which comprises an EDI feed water tank, a water supply mother pipe, multiple sets of EDI devices, wherein each set of EDI device comprises EDI equipment, a constant-frequency feed water pump and a connecting branch pipe, the water supply mother pipe is communicated with the EDI feed water tank, one end of the connecting branch pipe is communicated with the water supply mother pipe, and the other end is communicated with the EDI equipment, a flow protection fixed value is arranged in the EDI equipment, the constant-frequency feed water pump is arranged on the connecting branch pipe, the constant-frequency feed water pump is in communication connection with the EDI equipment, and multiple sets of adjusting assemblies corresponding to the EDI devices are further arranged, each adjusting assembly is provided with an electric slow door and a frequency converter, the electric slow door is arranged on the connecting branch pipe, the frequency converter is arranged on the constant-frequency feed water pump, and the frequency converter is used for adjusting and controlling the actual flow value of the feed water in the connecting branch pipe to the flow protection fixed value; the flow of the feed water in the connecting branch pipe is gradually increased; the tripping problem of the EDI device in operation is avoided; the service life of the EDI device is prolonged, and meanwhile, the stability of system water production is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power plant desalination, in particular to a device and method for avoiding tripping of a power plant desalination system. BACKGROUND

[0002] It is a relatively mature technology for power plants to use an electric desalination device (EDI) to produce desalinated water. A power plant is generally equipped with two or more sets of EDI devices, and each set of EDI device is correspondingly provided with a fixed-frequency feed water pump. Since the feed water of the EDI device is supplied through a single feed water main pipe, in the actual operation process, the feed water of multiple fixed-frequency feed water pumps comes from the single feed water main pipe. When the EDI device needs to switch modes, for example, when one of the EDI devices needs to start other EDI devices at the same time during operation, the suddenly started EDI device will cause a temporary shortage of feed water in the main pipe,

[0003] which will instantaneously reduce the flow and pressure of the feed water entering the EDI device. Low flow and low pressure of the feed water will trigger the protection mechanism of the EDI device, and the EDI device will be tripped for protection.

[0004] The tripping of the EDI device is a non-normal operating condition, which has a great harm to the device itself and the operation of the entire system. In addition, a power plant will adjust the operating condition of the water production system according to the load condition of the generator unit, and the adjustment of the operating condition will inevitably lead to frequent mode switching of the EDI device, which will also cause frequent tripping of the EDI device. Frequent tripping will have a great impact on the service life of the EDI device. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the defect in the prior art that the sudden operation of other EDI devices during the production of desalinated water in a power plant based on a common main pipe causes the EDI device in operation to trip, thereby providing a device and method for avoiding tripping of a power plant desalination system.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A device for avoiding tripping of a power plant desalination system, comprising: an EDI feed water tank, a feed water main pipe, and multiple sets of EDI devices.

[0008] Each set of EDI device comprises an EDI device, a fixed-frequency feed water pump, and a connecting branch pipe. The feed water main pipe is in communication with the EDI feed water tank. One end of the connecting branch pipe is in communication with the feed water main pipe, and the other end is in communication with the EDI device. A flow protection set value is provided in the EDI device. The fixed-frequency feed water pump is provided on the connecting branch pipe. The fixed-frequency feed water pump is in communication connection with the EDI device.

[0009] Further comprising a plurality of sets of adjusting assemblies, which are arranged one-to-one with the EDI device, and each set of the adjusting assemblies comprises a slow electric door and a frequency converter, the slow electric door is arranged on the connecting branch pipe, and the frequency converter is arranged on the fixed-frequency water supply pump, and is used for regulating the actual flow value of the water supply in the connecting branch pipe to the flow protection fixed value.

[0010] Preferably, a central processing module is arranged in the EDI device, and the flow protection fixed value is set in the central processing module.

[0011] A detection unit is arranged on the fixed-frequency water supply pump corresponding to the EDI device, and the detection unit is in communication connection with the central processing module.

[0012] Preferably, the time for the frequency converter to control the fixed-frequency water supply pump from the initial power to the rated power is 10-15S.

[0013] Preferably, the time for the slow electric door to adjust from the fully closed state to the fully open state is 10-15S.

[0014] Preferably, a valve body assembly is further included, and the valve body assembly comprises a first valve body, a second valve body and a third valve body,

[0015] The first valve body, the second valve body and the third valve body are arranged on the connecting branch pipe, the first valve body is in communication with the outlet of the fixed-frequency water supply pump, the second valve body is in communication with the inlet of the fixed-frequency water supply pump, and the third valve body is located between the first valve body and the outlet of the fixed-frequency water supply pump.

[0016] The first valve body and the second valve body are both butterfly valves, and the third valve body comprises a check valve.

[0017] Preferably, the EDI device further has a water supply inlet, a pure water outlet, a concentrated water outlet and an extreme water outlet,

[0018] The water supply inlet is in communication with the water supply main pipe through the connecting branch pipe, the pure water outlet is in communication with a desalted water tank, the concentrated water outlet is in circulation communication with a reverse osmosis device, and the extreme water outlet is in communication with external air.

[0019] Preferably, the concentrated water outlet and the extreme water outlet are both provided with a flow measuring instrument and a pressure measuring instrument.

[0020] Preferably, a plurality of security filters are further included, and each of the security filters is arranged on the connecting branch pipe.

[0021] A method for avoiding tripping of a main pipe system electric desalination system, which is executed by using the tripping device described above, mainly comprises the following steps,

[0022] When a single EDI device is running, and multiple EDI devices need to be started simultaneously, the power of the corresponding fixed-frequency feedwater pump controlled by the frequency converter is slowly increased from the initial power to the rated power; at the same time, the corresponding electric slow door is controlled to adjust from the fully closed state to the fully open state in coordination with the power frequency modulation of the frequency converter, so that the actual flow value of the feedwater in the connecting branch slowly increases; until the actual flow is greater than or equal to the flow protection set value, the frequency converter controls the fixed-frequency feedwater pump to adjust to the rated power, and the electric slow door adjusts to the fully open state.

[0023] Compared with the prior art, the beneficial effects of the present application are:

[0024] The above technical solution provides a device and method for avoiding tripping of a mother pipe electric desalting system, which sets a frequency converter on the fixed-frequency feedwater pump to gradually increase the power of the fixed-frequency feedwater pump, and gradually increase the flow of feedwater in the connecting branch in coordination with the electric slow door; avoid the problem of insufficient feedwater in the water supply mother pipe caused by the EDI device running at rated power during the switching of the running mode of the EDI device, which causes the EDI device to trip; on the one hand, it prolongs the service life of the EDI device, and on the other hand, it ensures the stability of the water production of the electric desalting system; at the same time, based on the gradual adjustment of the frequency converter and the electric slow door, the tripping action of the EDI device can also be delayed to avoid damage to the EDI device caused by sudden tripping of the EDI device. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the specific embodiments or prior art of the present application, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative labor.

[0026] Figure 1 The overall structure of the mother pipe electric desalting system provided in the first embodiment of the present application is shown in the figure.

[0027] Explanation of reference signs:

[0028] 1, EDI feedwater tank; 11, water supply mother pipe;

[0029] 2, EDI device; 21, feed water inlet; 22, pure water outlet; 23, concentrated water outlet; 24, polar water outlet; 25, security filter; 26, connecting branch; 261, fixed frequency feed water pump; 262, first valve body; 263, second valve body; 264, third valve body; 265, local pressure gauge; 266, pressure measuring instrument; 267, flow measuring instrument;

[0030] 3, electric slow door; 31, frequency converter. DETAILED DESCRIPTION

[0031] The technical solutions of the present application will be described clearly and completely below in conjunction with the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0032] In the description of the present application, it should be noted that the orientations or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0033] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0034] The EDI water production system of the existing thermal power plant generally adopts the manifold system, and the feed water pump of the EDI device in the system mainly adopts the fixed frequency feed water pump 261; based on the several-use several-preparation principle of system design, two or more EDI devices are usually set in the EDI water production system; then when one EDI device is running, another EDI device or multiple EDI devices need to be started at the same time, due to the common use of the manifold, the pressure and flow of the feed water will be insufficient, which will trigger the protection mechanism of the pre-operated EDI device, causing the EDI device to trip.

[0035] Based on this, embodiments of the present invention provide a device to prevent the tripping of a mains-controlled electrostatic desalination system, such as... Figure 1 The system includes: an EDI water supply tank 1, a water supply header 11, and multiple EDI units. The EDI water supply tank 1 stores water containing impurities, the water supply header 11 transports the water, and the EDI units purify the water containing impurities for use in industrial manufacturing. Specifically, each EDI unit includes an EDI device 2, a fixed-frequency water supply pump 261, and a connecting branch pipe 26. The water in the EDI water supply tank 1 is discharged through the fixed-frequency water supply pump 261 and then discharged through the connecting branch pipe 26. The water supply is delivered to the EDI device 2 for purification; therefore, the water supply main pipe 11 is connected to the EDI water supply tank 1, one end of the connecting branch pipe 26 is connected to the water supply main pipe 11, and the other end is connected to the EDI device 2. The fixed frequency water supply pump 261 is installed on the connecting branch pipe 26 to control the output of the water supply; more specifically, the EDI device 2 is equipped with a flow protection setpoint. When the actual flow rate of the water supply is lower than the flow protection setpoint, the EDI device 2 will trigger the protection mechanism to trip the EDI device 2 for protection.

[0036] Specifically, the device also includes multiple sets of adjustment components, with the number of adjustment components corresponding one-to-one with the number of EDI devices; each set of adjustment components includes an electric slow-opening door 3 and a frequency converter 31; and

[0037] The frequency converter 31 is installed on the fixed-frequency water pump 261 to regulate the flow rate of the water supply in the connecting branch pipe 26 by adjusting the power of the fixed-frequency water pump 261. Since the frequency converter 31 has a minimum initial power for frequency conversion, such as 30 Hz, the frequency converter 31 alone cannot achieve the purpose of gradually changing the frequency of the water pump from the initial power to the rated power. Therefore, the regulating component also includes an electric slow-opening valve 3, which is installed on the connecting branch pipe 26 to control the output of water from the connecting branch pipe 26 to the EDI device 2. Then, by adjusting the power of the fixed-frequency water pump 261 in conjunction with the frequency converter 31, the actual flow rate of the water supply in the connecting branch pipe 26 is adjusted to the flow protection set value in the EDI device 2.

[0038] Specifically, the running power of the fixed-frequency feed water pump 261 is adjusted by the frequency converter 31, and the feed water flow in the connecting branch pipe 26 is gradually increased under the action of the electric slow-opening door 3; that is, the running power of the fixed-frequency feed water pump 261 starts to run from the initial power under the action of the frequency converter 31, and gradually increases to the rated power by frequency conversion, and correspondingly, the electric slow-opening door 3 is adjusted from the fully closed state to the fully open state by the frequency conversion adjustment of the frequency converter 31, so as to delay the judgment of the EDI equipment 2 to the flow protection set value signal; at this time, the flow of the feed water in the connecting branch pipe 26 also slowly increases as the power gradually increases; when the frequency converter 31 adjusts the fixed-frequency feed water pump 261 from the initial power to the rated power, and the electric slow-opening door 3 is adjusted to the fully open state, the actual flow value of the feed water in the connecting branch pipe 26 is equal to or greater than the flow protection value set in the EDI equipment 2.

[0039] By setting the frequency converter 31 on the fixed-frequency feed water pump 261, the running power of the fixed-frequency feed water pump 261 is gradually increased, and the feed water flow in the connecting branch pipe 26 is gradually increased under the cooperation of the electric slow-opening door 3; avoiding that the EDI device causes the feed water in the water supply main pipe 11 to be insufficient when the EDI equipment 2 is running at rated power during the switching process of the running mode, and then causing the EDI device to trip; on the one hand, the service life of the EDI device is prolonged, and on the other hand, the stability of the water production of the electric desalting system is ensured; at the same time, based on the gradual adjustment action of the frequency converter 31 and the electric slow-opening door 3, the tripping action of the EDI equipment 2 can also be delayed to avoid damage to the EDI equipment 2 caused by sudden tripping of the EDI device.

[0040] Specifically, the central processing module is arranged in the EDI equipment 2, and the flow protection set value is arranged in the central processing module; more specifically, the protection program is also arranged in the central processing module; that is, when the actual flow value is greater than or equal to the flow protection set value, the protection program does not start, and the EDI equipment 2 does not trip; when the actual flow value is less than the flow protection set value, the protection program is triggered, and the EDI equipment 2 is protected and tripped; further, the detection unit is also arranged on the fixed-frequency feed water pump 261, the detection unit is used to obtain the actual flow value of the feed water in the connecting branch pipe 26, and the detection unit is in communication connection with the central processing module, and is used to feed the detected actual flow value to the central processing module, so that the central processing module compares the detected actual flow value with the flow protection set value and then judges whether to trip, and the detection unit can be arranged on the fixed-frequency feed water pump 261 or the connecting branch pipe 26; preferably, in the actual operation process, the central processing module in the EDI equipment 2 is connected to the control panel or the upper computer in a wired or wireless manner, so that the staff can adjust the flow protection set value in the EDI equipment 2 according to the needs of different application scenes of the thermal power plant.

[0041] Preferably, the time for the frequency converter 31 to control the fixed-frequency feed water pump 261 from the initial frequency to the rated frequency is 10-15S; since the initial power of the frequency converter 31 is not zero, in order to better control the actual flow value of the feed water in the connecting branch pipe 26, the time for the electric slow-opening door 3 to adjust from the fully closed state to the fully open state is also 10-15S; then in the process of the step-by-step adjustment of the frequency converter 31 and the electric slow-opening door 3, the feed water flow in the connecting branch pipe 26 can be slowly increased from 0 until the flow protection setting value of the EDI device 2 is met; at the same time, based on the joint action of the frequency converter 31 and the electric slow-opening door 3, the time delay of the protection program triggered in the EDI device 2 can also be achieved, and the specific delay time is 1-3S; then when the regulation cannot directly avoid the tripping of the EDI device, the signal delay can also be used to reduce the damage caused by the sudden tripping to the EDI device.

[0042] Specifically, the valve body assembly further includes a first valve body 262, a second valve body 263 and a third valve body 264; the first valve body 262, the second valve body 263 and the third valve body 264 are all arranged on the connecting branch pipe 26; in order to facilitate the maintenance of the device assembly, the first valve body 262 is in communication with the outlet of the fixed-frequency feed water pump 261, and the second valve body 263 is in communication with the inlet of the fixed-frequency feed water pump 261; for example, when the fixed-frequency feed water pump 261 needs to be overhauled, the staff can operate the first valve body 262 and the second valve body 263 to cut off the EDI feed water tank 1 from the EDI device 2, so as to avoid the influence of the feed water flowing out on the overhauling work; in order to facilitate the adjustment of the staff, the first valve body 262 and the second valve body 263 are both butterfly valves; further, in order to avoid the backflow of the feed water in the connecting branch pipe 26 impacting the fixed-frequency feed water pump 261 when the EDI device 2 is stopped or tripped, the third valve body 264 is arranged between the first valve body 262 and the outlet of the fixed-frequency feed water pump 261, and the third valve body 264 includes a check valve.

[0043] Specifically, the EDI device 2 also has a feed water inlet 21, a pure water outlet 22, a concentrated water outlet 23 and an extreme water outlet 24; the feed water inlet 21 is in communication with the water supply main pipe 11 through the connecting branch pipe 26, so that the EDI feed water tank 1 can transport feed water to the feed water inlet 21 through the water supply main pipe 11 and the connecting branch pipe 26; the pure water outlet 22 is in communication with a desalted water tank, the concentrated water outlet 23 is in circulation with a reverse osmosis device, and the extreme water outlet 24 is in communication with the outside air; after the feed water is treated by the EDI device 2, three types of pure water, concentrated water and accumulated water are usually formed; the pure water is transported to the desalted water tank through the pure water outlet for production use, and the concentrated water is transported to the reverse osmosis device for circulation to perform the next round of purification treatment; since the extreme water contains chlorine, oxygen and hydrogen which cannot be used, the generated extreme water is discharged to the air.

[0044] In some cases, the actual pressure of the feed water detection auxiliary actual flow control of the feed water is added, and then the actual pressure value and the actual flow value of the feed water are used to improve the detection accuracy of the feed water in the connecting branch pipe 26, so as to avoid the jump of the EDI device; therefore, a pressure detector is arranged on the connecting branch pipe 26 or the fixed-frequency feed water pump 261, and the specific arrangement position is determined according to the actual demand, and in the embodiment, the on-site pressure gauge 265 is preferred; in addition, since the size of the feed water flow in the connecting pipe directly affects the formation of concentrated water and extreme water after the EDI equipment 2 is processed, and the flow and pressure of the concentrated water and the extreme water also trigger the protection mechanism of the EDI equipment 2, considering the design difficulty and the modification cost of the system, the detection data of the concentrated water and the extreme water are also used for adjustment; that is, the detection unit is arranged at the concentrated water outlet 23 and the extreme water outlet 24 respectively; and the detection unit includes the flow measuring instrument 267 and the pressure measuring instrument 266, and the flow measuring instrument 267 and the pressure measuring instrument 266 are arranged at the concentrated water outlet 23 and the extreme water outlet 24 respectively.

[0045] Further, when the monitoring position is adjusted to the concentrated water outlet 23 and the extreme water outlet 24, the staff needs to reset the flow protection set value and the pressure protection set value in the central control module of the EDI equipment 2 through the control panel or the upper computer, and the actual flow value and the actual pressure value of the concentrated water outlet 23 and the extreme water outlet 24 are obtained by the detection unit; if the actual flow value and the actual pressure value are both greater than or equal to the flow protection set value and the pressure protection set value, the EDI equipment 2 does not jump; if either the actual flow value or the actual pressure value is less than the flow protection set value or the pressure protection set value, the EDI equipment 2 jumps.

[0046] Further, since the feed water in the EDI feed water tank 1 contains a large amount of impurities, the system further includes a plurality of safety filters 25, which can improve the purity of the pure water generated by the feed water on the one hand, and can also avoid damage to the EDI equipment 2 caused by impurities when the system purifies the feed water, and each safety filter 25 is arranged on the connecting branch pipe 26; in order to ensure the filtering effect, the safety filter 25 is arranged between the electric slow-opening door 3 and the feed water inlet 21 of the EDI equipment 2.

[0047] The method for avoiding tripping of the mother pipe system of the electric desalting system is executed by using the tripping device, and mainly comprises the following steps: when multiple EDI devices need to be started to operate simultaneously during operation of a single EDI device, the corresponding fixed-frequency feed water pump 261 is controlled by the frequency converter 31, so that the power of the fixed-frequency feed water pump 261 is slowly increased from an initial power to a rated power (if the initial power of the frequency converter is 30 Hz and the rated power of the fixed-frequency feed water pump 261 is 60 Hz, then the frequency converter 31 is adjusted from the initial power of 30 Hz to the rated power of 60 Hz, and the adjustment is stopped); at the same time, the corresponding electric slow door 3 is adjusted from a fully closed state to a fully open state (i.e., the opening degree of the electric slow door is adjusted from 0 to 100%); wherein the time for the frequency converter 31 to control the power adjustment of the fixed-frequency feed water pump 261 is 10-15 S, and based on the initial power set by the frequency converter 31, in order to achieve the purpose of slowly increasing the feed water flow in the connecting branch pipe 26, the time for the electric slow door 3 to be adjusted from the fully closed state to the fully open state is the same as the adjustment time of the frequency converter 31, i.e., 10-15 S; so as to ensure that after the fixed-frequency feed water pump 261 is started, the flow of the feed water in the connecting branch pipe 26 is slowly increased from 0 until the flow protection set value in the central processing module of the EDI device 2 is met; and when the actual flow value of the feed water in the connecting branch pipe 26 is greater than or equal to the flow protection set value in the central processing module of the EDI device 2, the power of the fixed-frequency feed water pump 261 reaches the rated power, and the electric slow door 3 is in the fully open state; at this time, the EDI device 2 being operated and the newly operated EDI device 2 are normally operated, and there is no tripping phenomenon.

[0048] In addition, under the joint action of the frequency converter 31 and the electric slow door 3, the flow feedback signal received by the central processing module of the EDI device 2 can be delayed for 1-3 S; when the flow control of the feed water in the connecting branch pipe 26 cannot meet the flow protection set value in the central processing module, the delayed signal of the EDI device 2 can also avoid sudden tripping of the EDI device 2, so as to reduce damage to the internal components of the EDI device 2.

[0049] The above embodiments are only preferred embodiments of the present application, and cannot be used to limit the protection scope of the present application, and any non-essential changes and replacements made by those skilled in the art on the basis of the present application all belong to the protection scope of the present application.

Claims

1. A method for avoiding a trip of a common pipe electric deionization system, which is implemented by a device for avoiding a trip of a common pipe electric deionization system, characterized in that, The jump device comprises an EDI feed water tank, a feed water main pipe, and multiple sets of EDI devices; The feed water main pipe is in communication with the EDI feed water tank, one end of the connecting branch pipe is in communication with the feed water main pipe, and the other end is in communication with the EDI device, a flow protection set value is arranged in the EDI device, and the fixed-frequency feed water pump is arranged on the connecting branch pipe; the fixed-frequency feed water pump is in communication connection with the EDI device; The jump device further comprises multiple sets of adjusting assemblies, the adjusting assemblies are arranged in one-to-one correspondence with the EDI devices, each set of the adjusting assembly comprises an electric slow-opening door and a frequency converter, the electric slow-opening door is arranged on the connecting branch pipe, and the frequency converter is arranged on the fixed-frequency feed water pump and used to adjust the actual flow value of the feed water in the connecting branch pipe to the flow protection set value; The jump method mainly comprises the following steps: When multiple EDI devices need to be started to run simultaneously during the running of a single EDI device, the power of the corresponding fixed-frequency feed water pump is slowly increased from an initial power to a rated power by using the frequency converter; at the same time, the corresponding electric slow-opening door is controlled to be gradually adjusted from a completely closed state to a completely open state in cooperation with the power frequency adjustment of the frequency converter, so that the actual flow value of the feed water in the connecting branch pipe is slowly increased; until the actual flow value is greater than or equal to the flow protection set value, the fixed-frequency feed water pump is adjusted to the rated power by the frequency converter, and the electric slow-opening door is adjusted to the completely open state.

2. The method of claim 1, wherein the method further comprises: A central processing module is arranged in the EDI device, and the flow protection set value is set in the central processing module; A detection unit is arranged on the fixed-frequency feed water pump corresponding to the EDI device, and the detection unit is in communication connection with the central processing module.

3. The method of claim 1, wherein the method further comprises: The time for the frequency converter to control the fixed-frequency feed water pump to increase from the initial power to the rated power is 10-15 seconds.

4. The method of claim 1, wherein the method further comprises: The time for the electric slow-opening door to adjust from the completely closed state to the completely open state is 10-15 seconds.

5. The method of claim 1, wherein the method further comprises: The jump device further comprises a valve body assembly, and the valve body assembly comprises a first valve body, a second valve body and a third valve body, The first valve body, the second valve body and the third valve body are arranged on the connecting branch pipe, the first valve body is in communication with the outlet of the fixed-frequency feed water pump, the second valve body is in communication with the inlet of the fixed-frequency feed water pump, and the third valve body is located between the first valve body and the outlet of the fixed-frequency feed water pump; The first valve body and the second valve body are butterfly valves, and the third valve body comprises a check valve.

6. The method of claim 1, wherein the method further comprises: The EDI device further has a feed water inlet, a pure water outlet, a concentrated water outlet and an extreme water outlet, The feed water inlet is in communication with the feed water main pipe through the connecting branch pipe, the pure water outlet is in communication with a desalted water tank, and the concentrated water outlet is in circulation communication with a reverse osmosis device.

7. The method of claim 6, wherein the method further comprises: The concentrated water outlet and the extreme water outlet are respectively provided with a flow measuring instrument and a pressure measuring instrument.

8. The method of claim 1, wherein the method further comprises: The jump device further comprises multiple security filters, and each security filter is arranged on the connecting branch pipe.

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