Power plant desulfurization wastewater system lime adjustment triple box pH value control system and method

Abstract

The application discloses a lime-adjusting triple-box pH value control system and method for a power plant desulfurization wastewater system. When the equipment is in operation, the water inflow of a neutralization tank is monitored by a DCS control system to keep the pH value in the tank stable, and then the frequency of a lime milk delivery pump is controlled to control the amount of lime powder added into a lime milk preparation tank. When the lime milk delivery pump adjusts the frequency, the frequency of a screw weighing conveyor should also be changed accordingly to maintain the relative stability of the lime milk concentration in the lime milk preparation tank. By adjusting the frequencies of the screw weighing conveyor and the lime milk delivery pump and changing the amount of lime powder, the addition amount of lime milk is adjusted, the purpose of adjusting the lime addition amount with the pH value is achieved, and the problem that the frequent start and stop of the existing addition pump can affect the service life of the equipment and reduce the risk of lime milk pipeline blockage is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power plant wastewater treatment, and relates to a lime adjustment triple tank pH value control system and method for a power plant desulfurization wastewater system. BACKGROUND

[0002] At present, the common process of the power plant desulfurization wastewater system is that the wastewater is preliminarily precipitated and separated in a pre-sedimentation tank, the upper wastewater is sent into a buffer tank by a wastewater lifting pump, and then into a triple tank including a neutralization tank, a reaction tank and a flocculation tank. The desulfurization wastewater is fully mixed with added lime in the neutralization tank to adjust the pH value, remove most of the hardness and a small amount of heavy metal ions. In the reaction tank, organic sulfur is added to remove most of the heavy metal ions, and then the heavy metal ions further generate flocculation with a coagulant. In the flocculation tank, a coagulant aid is added to form larger alum flowers and other flocculation. The wastewater is separated and clarified in a thickening and clarifying tank, and then the clear water is sent into a discharge tank and reused by a wastewater discharge pump. The sludge generated in the pre-sedimentation tank, the triple tank and the thickening and clarifying tank is periodically discharged and compressed into mud cakes by a sludge removal machine.

[0003] Since the water quantity and water quality are in a constant change process, the lime milk dosing also needs to be adjusted in time to ensure that the pH value in the neutralization tank is within a suitable range. The conventional processes mainly include: 1. The pH value is adjusted by changing the start-stop state of the lime milk delivery pump. The frequent start-stop of the dosing pump can affect the service life of the equipment. At the same time, since the lime milk pipeline needs to be flushed immediately after shutdown to prevent the lime milk from remaining in the pipeline and causing pollution, the frequent start-stop operation increases the risk of pollution. 2. The screw weighing conveyor is controlled by frequency conversion, and the lime milk delivery pump is a power frequency pump. The frequency of the screw weighing conveyor is changed to adjust the lime powder dosing amount, but there is a long delay. 3. The screw weighing conveyor is controlled by power frequency, and the lime milk delivery pump is controlled by frequency conversion. The frequency of the lime milk delivery pump can be changed to adjust the lime milk dosing amount, but since the output of the screw weighing conveyor cannot be changed, the frequency of the lime milk delivery pump can only adjust the lime milk dosing amount for a short time. From a long-term point of view, the concentration of the lime milk in the lime milk preparation tank gradually decreases or increases, which cannot meet the requirement of adjusting the pH value in the neutralization tank. SUMMARY

[0004] In view of the problems in the prior art, the present application provides a lime adjustment triple box pH value control system and method for a power plant desulfurization wastewater system, which adjusts the frequency of a lime milk delivery pump to change the amount of lime powder, thereby adjusting the amount of lime milk added, achieving the purpose of adjusting the amount of lime added according to the pH value, and solving the problem that the frequent start and stop of the existing dosing pump can affect the service life of the equipment and reduce the risk of pollution and blockage of the lime milk pipeline.

[0005] The present application is realized by the following technical solutions:

[0006] A lime adjustment triple box pH value control method for a power plant desulfurization wastewater system, comprising:

[0007] When the equipment is in operation, the water inflow of the neutralization tank is monitored by the DCS control system to keep the pH value in the neutralization tank stable, and then the frequency of the lime milk delivery pump is adjusted to control the amount of lime powder added into the lime milk preparation tank; when the adjustment frequency of the lime milk delivery pump changes, the frequency of the screw weighing conveyor should also change accordingly to maintain the relative stability of the lime milk concentration in the lime milk preparation tank.

[0008] When the pH value in the neutralization tank is less than the preset value, the frequency of the lime milk delivery pump is increased to increase the amount of lime powder entering the lime milk preparation tank; if it is greater than the preset value, the frequency of the lime milk delivery pump is reduced to reduce the amount of lime powder entering the lime milk preparation tank.

[0009] Preferably, by monitoring the water inflow of the neutralization tank, the adjustment calculation method of the frequency of the lime milk delivery pump is:

[0010] f1=A×Q×50÷(PS×ρ)

[0011] In the formula: Q is the water inflow of the neutralization tank, with a unit of m 3 / h; A is the amount of lime powder required to be added per liter of wastewater, with a unit of g / L; PS is the output of the lime milk delivery pump, with a unit of m 3 / h; ρ represents the concentration of lime milk in the lime milk preparation tank 13 per unit volume, with a unit of kg / m 3 ; f1 is the frequency of the lime milk delivery pump, with a unit of Hz;

[0012] Preferably, the frequency adjustment change relationship between the screw weighing conveyor and the lime milk delivery pump is:

[0013] fS=fL×c

[0014] In the formula: fS is the frequency change amount of the lime milk delivery pump, with a unit of Hz; fL is the frequency change amount of the screw weighing conveyor, and c represents the frequency ratio of the screw weighing conveyor and the lime milk delivery pump when they are in normal operation, which can be obtained through field test.

[0015] A lime adjustment triple box pH value control system of a power plant desulfurization wastewater system, comprising,

[0016] A lime milk storage unit, a wastewater pre-sedimentation unit, a neutralization and cleaning unit and a DCS control system; the neutralization and cleaning unit comprises a neutralization tank;

[0017] The lime milk storage unit comprises a lime powder bin, a screw weighing conveyor and a lime milk preparation tank; the outlet of the lime powder bin is connected with the screw weighing conveyor, and the conveying end of the screw weighing conveyor is connected with the lime milk preparation tank;

[0018] The wastewater pre-sedimentation unit is connected with the neutralization tank through a pipeline; the lime milk preparation tank is connected with the neutralization tank through a pipeline; a neutralization tank water inflow meter is installed on the inlet pipeline of the neutralization tank, and a neutralization tank pH meter is installed in the neutralization tank; and the DCS control system is used for remote monitoring and control of each device.

[0019] Preferably, the wastewater pre-sedimentation unit comprises a pre-sedimentation tank, a buffer tank and a wastewater lifting pump;

[0020] The pre-sedimentation tank is connected with the buffer tank through a pipeline, the inlet pipeline of the wastewater lifting pump is deep into the buffer tank, and the outlet of the wastewater lifting pump is connected with the neutralization tank through a pipeline.

[0021] Preferably, the neutralization and cleaning unit further comprises a reaction tank, a flocculation tank and a concentration and clarification tank;

[0022] The neutralization tank is connected with the reaction tank, the flocculation tank and the concentration and clarification tank through pipelines in sequence; a neutralization tank stirrer is arranged in the neutralization tank, a reaction tank stirrer is installed in the reaction tank, and a flocculation tank stirrer is installed in the flocculation tank.

[0023] Preferably, the wastewater discharge unit is further comprised, and the wastewater discharge unit comprises a wastewater discharge tank and a wastewater discharge pump; the outlet of the concentration and clarification tank is connected with the wastewater discharge tank through a pipeline, and the inlet pipeline of the wastewater discharge pump is deep into the wastewater discharge tank.

[0024] Preferably, a lime milk preparation tank liquid level meter and a lime milk preparation tank stirrer are arranged in the lime milk preparation tank; and a lime milk preparation tank water supplement valve is arranged on the inlet pipeline of the lime milk preparation tank.

[0025] Preferably, a lime milk preparation tank water outlet valve and a lime milk conveying pump are arranged on the outlet pipeline of the lime milk preparation tank; a lime milk conveying pump water outlet valve is arranged at the outlet of the lime milk conveying pump; and a lime milk flushing water valve is arranged on the bypass pipeline between the lime milk preparation tank water outlet valve and the lime milk conveying pump.

[0026] Compared with the prior art, the present application has the following beneficial technical effects:

[0027] The present invention provides a pH control method for a lime adjustment triple tank in a power plant desulfurization wastewater system. Based on the monitoring and operation of multiple devices within the dosing unit by a DCS control system, the pH value is adjusted by adjusting the device frequency and remotely switching automatic valves, thereby varying the lime milk dosage. This method eliminates the need for manual operation. When the water flow rate into the neutralization tank changes, the frequency of the lime milk delivery pump is adjusted accordingly to adjust the lime milk dosage. When the pH value in the neutralization tank fluctuates, the frequency of the lime milk delivery pump is adjusted accordingly to adjust the lime milk dosage. When the frequency of the lime milk delivery pump changes, the frequency of the screw weighing conveyor is adjusted accordingly to ensure that the concentration of the lime milk in the lime milk preparation box does not decrease or increase due to the increase or decrease in the frequency of the lime milk delivery pump. This method can not only ensure continuous dosing, but also solve the equipment safety risks and pipeline blockage risks brought about by adjusting the pH value by starting and stopping the lime milk delivery pump. Secondly, it solves the problem of long delay in adjusting the dosage when the screw weighing conveyor is frequency conversion controlled and the lime milk delivery pump is an industrial frequency pump. Thirdly, it solves the problem of the concentration of lime milk in the lime milk preparation box cannot be stabilized over a long period of time when the screw weighing conveyor is industrial frequency controlled and the lime milk delivery pump is frequency conversion controlled.

[0028] The present invention provides a lime dosing control system for a desulfurization wastewater system. This control system adjusts the frequency of a spiral weighing conveyor and a lime milk delivery pump to change the amount of lime powder, thereby adjusting the lime milk dosage. This achieves the goal of adjusting lime dosage with pH. The DCS control system monitors and operates multiple devices within the dosing system. By adjusting the device frequency and remotely opening and closing automatic valves, the lime milk dosage is adjusted to achieve pH adjustment without manual operation. By installing a water inlet flowmeter on the inlet pipe of the neutralization tank, the frequency of the spiral weighing conveyor and the lime milk delivery pump is adjusted accordingly when the neutralization tank inlet flow rate changes, thereby adjusting the amount of lime powder and thus adjusting the amount of lime milk dosage. By installing a neutralization tank pH meter in the neutralization tank, the frequency of the spiral weighing conveyor and the lime milk delivery pump is adjusted accordingly when the neutralization tank pH value fluctuates, thereby adjusting the amount of lime powder and thus adjusting the amount of lime milk dosage. This method ensures continuous dosing, solves the equipment safety risks and pipeline blockage risks brought about by adjusting the pH value by starting and stopping the lime milk delivery pump, can accurately control the dosage, and improve the dosing efficiency; solves the impact and safety risks brought about by starting and stopping the lime milk delivery pump, avoids the problem of unqualified final water quality due to changes in water volume and water quality fluctuations, can accurately control the dosage, and improve the dosing efficiency;

[0029] Further, the screw weighing conveyor can adjust the output by frequency conversion, and then adjust the amount of lime powder. The lime powder conveyed by the screw weighing conveyor enters a lime milk preparation tank. An industrial water pipeline is connected to a lime milk preparation tank water supplement valve through a pipeline. The liquid level in the lime milk preparation tank is monitored through a lime milk preparation tank liquid level meter. When the liquid level reaches a set low liquid level, the lime milk preparation tank water supplement valve is opened, and industrial water is automatically supplemented into the lime milk preparation tank. When the liquid level reaches a set high liquid level, the lime milk preparation tank water supplement valve is closed, and the water supplement is stopped. The lime milk preparation tank mixer operates to ensure that the lime powder added into the lime milk preparation tank is fully mixed to form uniform lime milk without precipitation, so that the lime milk can be automatically produced according to the demand, and the lime milk addition amount is adjusted.

[0030] Further, when the lime milk addition equipment is shut down, the lime milk flushing water valve is automatically controlled to be opened through the DCS control system, and the lime milk in the pipeline and the pump is flushed clean by using industrial water, so that the risk of pollution and blockage caused by frequent start-stop operation of the addition pump is reduced.

[0031] Further, when the frequency of the lime milk conveying pump changes, the DCS control system controls the frequency of the screw weighing conveyor to change correspondingly according to a certain proportional coefficient, so that the problem that the concentration of the lime milk in the lime milk preparation tank changes when the frequency of the lime milk conveying pump changes but the frequency of the screw weighing conveyor remains unchanged is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The principle diagram of the lime addition control system for the desulfurization wastewater system;

[0033] In the figure: lime powder bin 11, screw weighing conveyor 12, lime milk preparation tank 13, lime milk preparation tank mixer 14, lime milk preparation tank liquid level meter 15, lime milk preparation tank water supplement valve 16, lime milk preparation tank water outlet valve 21, lime milk conveying pump 22, lime milk conveying pump water outlet valve 23, lime milk flushing water valve 24, pre-sedimentation tank 31, buffer tank 32, wastewater lifting pump 33, neutralization tank water inlet flow meter 41, neutralization tank 42, neutralization tank mixer 43, reaction tank 44, reaction tank mixer 45, flocculation tank 46, flocculation tank mixer 47, neutralization tank pH meter 48, concentration and clarification tank 49, wastewater discharge tank 51, wastewater discharge pump 52, DCS control system 61. DETAILED DESCRIPTION

[0034] The application will be further described in detail below in combination with specific embodiments, which are an explanation of the application rather than a limitation.

[0035] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0036] A method for controlling the pH value of a lime adjustment triplex tank in a power plant desulfurization wastewater system, such as Figure 1 As shown, it includes a lime powder silo 11, a screw weighing conveyor 12, a lime milk preparation tank 13, a lime milk preparation tank mixer 14, a lime milk preparation tank level gauge 15, a lime milk preparation tank water supply valve 16, a lime milk preparation tank outlet valve 21, a lime milk delivery pump 22, a lime milk delivery pump outlet valve 23, a lime milk flushing water valve 24, a pre-sedimentation tank 31, a buffer water tank 32, a wastewater lift pump 33, a neutralization tank inlet flowmeter 41, a neutralization tank 42, a neutralization tank mixer 43, a reaction tank 44, a reaction tank mixer 45, a flocculation tank 46, a flocculation tank mixer 47, a neutralization tank pH meter 48, a concentration and clarification tank 49, a wastewater discharge tank 51, a wastewater discharge pump 52, and a DCS control system 61.

[0037] The DCS control system 61 is connected to the screw weighing conveyor 12, the lime milk preparation tank mixer 14, the lime milk preparation tank level gauge 15, the lime milk preparation tank water supply valve 16, the lime milk preparation tank outlet valve 21, the lime milk delivery pump 22, the lime milk delivery pump outlet valve 23, the lime milk flushing water valve 24, the wastewater lift pump 33, the neutralization tank inlet flowmeter 41, the neutralization tank mixer 43, the reaction tank mixer 45, the flocculation tank mixer 47, the neutralization tank pH meter 48, and the wastewater discharge pump 52. Through the DCS control system 61, the status of the above equipment can be remotely monitored, valves can be opened and closed, and pumps can be started and stopped. By monitoring the changes in the neutralization tank inlet flowmeter and the neutralization tank pH meter, the DCS control system adjusts the amount of lime powder by changing the frequency of the screw weighing conveyor in the lime milk preparation system, thereby achieving the purpose of adjusting the pH value by changing the lime milk concentration. It solves the impact and safety risks caused by the start-stop method of the lime milk delivery pump, avoids the problem of unqualified final water quality due to changes in water volume and water quality fluctuations, and can accurately control the dosage and improve the dosing efficiency;

[0038] The pre-sedimentation tank 31 is connected to the buffer water tank 32 through a pipeline. The inlet pipe of the wastewater lifting pump 33 extends deep into the buffer water tank 32. The outlet of the wastewater lifting pump 33 is connected to the neutralization box 42 through a pipeline. A neutralization box water inlet flowmeter 41 is installed on the pipeline.

[0039] After entering neutralization tank 42, the wastewater is thoroughly mixed and reacted with lime milk in neutralization tank agitator 43. The pH value is monitored using a neutralization tank pH meter 48 installed inside neutralization tank 42. The pH-adjusted wastewater then enters reaction tank 44, where it is thoroughly mixed and reacted with organic sulfur and coagulant in reaction tank agitator 45 to remove heavy metals and form flocs. The effluent from reaction tank 44 enters flocculation tank 46, where it is thoroughly mixed and reacted with coagulant aid in flocculation tank agitator 47 to form larger flocs, facilitating subsequent separation and sedimentation.

[0040] The outlet water of the flocculation box 46 is connected to the concentration and clarification tank 49 through a pipeline, and the outlet water of the concentration and clarification tank 49 is connected to the wastewater discharge tank 51 through a pipeline. The inlet pipe of the wastewater discharge pump 52 penetrates into the wastewater discharge tank. The outlet water of the flocculation box 46 enters the concentration and clarification tank 49, where it is separated. Large flocs such as alum flowers are precipitated, and the clean water enters the wastewater discharge tank 51 from the upper part through the outlet pipe and is finally reused by the wastewater discharge pump 52.

[0041] The outlet of the lime powder silo 11 is connected to a screw weighing conveyor 12, which can adjust its output and, in turn, the amount of lime powder, through frequency conversion. The lime powder transported by this conveyor enters the lime milk preparation tank 13. The industrial water pipeline is connected to the lime milk preparation tank water supply valve 16 via a pipeline. A level gauge 15 is installed inside the lime milk preparation tank 13 and monitors the liquid level inside. When the liquid level reaches the set low level, the lime milk preparation tank water supply valve 16 opens, automatically replenishing the lime milk preparation tank 13 with industrial water. When the liquid level reaches the set high level, the lime milk preparation tank water supply valve 16 closes, stopping water supply. The lime milk preparation tank mixer 14 operates to ensure that the lime powder is thoroughly mixed after being added to the lime milk preparation tank 13, forming a uniform lime milk without precipitation.

[0042] When the lime milk dosing equipment is in operation, the lime milk preparation tank outlet valve 21 is open, the lime milk delivery pump outlet valve 23 is open, and the lime milk delivery pump 22 is started to add lime milk to the triple tank to adjust the pH. When the lime milk dosing equipment is shut down, the screw weighing conveyor 12, the lime milk preparation tank mixer 14, and the lime milk delivery pump 22 should be shut down first. Then, the pipelines should be flushed to prevent any residual lime milk from clogging them. Close the lime milk preparation tank outlet valve 21, keep the lime milk delivery pump outlet valve 23 open, open the lime milk flushing valve 24, and flush the lime milk from the pipelines and pump with industrial water. Finally, close the lime milk flushing valve 24 and the lime milk delivery pump outlet valve 23.

[0043] When the device is running, the DCS control system 61 monitors the flow of the neutralization tank water flow meter 41 to reduce the flow, in order to ensure that the pH value is not changed, at this time the lime milk dosage should be reduced accordingly, the DCS control system 61 reduces the frequency of the lime milk delivery pump 22 to reduce the amount of lime milk added to the neutralization tank 42. Conversely, the DCS control system 61 monitors the flow of the neutralization tank water flow meter 41 to increase the flow, then increase the frequency of the lime milk delivery pump 22 to increase the amount of lime milk added to the neutralization tank 42. Q(m 3 / h) represents the water flow of the neutralization tank water flow meter 41, A(g / L) represents the amount of lime powder required per liter of wastewater, PS(m 3 / h) represents the output of the lime milk delivery pump 22, and p(kg / m 3 ) represents the concentration of lime milk in the lime milk preparation tank 13 per unit volume, and f1(Hz) represents the frequency of the lime milk delivery pump 22. There is a relationship between f1 and the above parameters, where A can be obtained from a small test or field test according to the situation of each site device and the quality of the wastewater:

[0044] f1=A×Q×50÷(PS×p)

[0045] By adjusting the lime milk dosage in the above manner, the flow change can be quickly responded to, and the problem of pH value adjustment delay can be avoided. However, if the frequency of the lime milk delivery pump 22 is adjusted for a long time without adjusting the frequency of the screw weighing conveyor 12, the concentration of lime milk in the lime milk preparation tank 13 will gradually thicken or dilute, p(kg / m 3 ) cannot maintain a relatively stable value, and the ability to adjust the pH value will gradually decrease or even cannot meet the requirements of pH value adjustment. Therefore, when the frequency of the lime milk delivery pump 22 changes, the frequency of the screw weighing conveyor 12 needs to be changed accordingly, so that the concentration of lime milk in the lime milk preparation tank 13 is maintained within a relatively stable range. When the frequency of the lime milk delivery pump 22 changes, the DCS control system 61 controls the frequency of the screw weighing conveyor 12 to change accordingly according to a certain proportional coefficient, fS(Hz) represents the frequency change of the lime milk delivery pump 22, fL(Hz) represents the frequency change of the screw weighing conveyor 12, and the proportional coefficient between them is represented by c, which can be obtained by field test. Then fS and fL have the following relationship:

[0046] fS=fL×c

[0047] When running, the DCS control system 61 monitors the pH value of the neutralization tank pH meter 48, and if the pH value is less than 9.0, the amount of lime milk to be added should be increased accordingly in order to increase the pH value. The DCS control system 61 increases the amount of lime milk added to the neutralization tank 42 by increasing the frequency of the screw weighing conveyor 12. Conversely, if the DCS control system 61 monitors the pH value of the neutralization tank pH meter 48, and if the pH value is greater than 9.5, the frequency of the screw weighing conveyor 12 is reduced to reduce the amount of lime milk added to the neutralization tank 42.

[0048] If the frequency of the lime milk delivery pump 22 is increased by 5 Hz, the frequency of the screw weighing conveyor 12 is correspondingly increased by 5 c (Hz), thereby avoiding the problem that the concentration of lime milk in the lime milk preparation tank 13 changes when the frequency of the lime milk delivery pump 22 changes but the frequency of the screw weighing conveyor 12 remains unchanged.

[0049] It should be noted that when an element is referred to as being "on" another element, it can be directly on the other element or intervening elements can also be present. In addition, when an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements can also be present. When an element is referred to as being "positioned on" another element, it can be directly on the other element or intervening elements can also be present.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this description, the singular forms "a", "an" and "the" include plural references unless the context clearly dictates otherwise. The term "and / or" includes any and all combinations of one or more of the associated listed items.

[0051] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application in any form. Any person skilled in the art can easily implement the present application according to the drawings and the above description. However, any equivalent changes, modifications and evolutions made by those skilled in the art without departing from the technical solution of the present application, using the technical content disclosed above, are equivalent embodiments of the present application. Meanwhile, any equivalent changes, modifications and evolutions made by those skilled in the art without departing from the technical solution of the present application, using the technical content disclosed above, are equivalent embodiments of the present application.

Claims

1. A method for controlling the pH value of a lime adjustment triple tank in a power plant desulfurization wastewater system, characterized in that: include: When the equipment is in operation, the water inlet flow of the neutralization tank (42) is monitored by the DCS control system (61) to maintain the pH value in the neutralization tank (42) stable, thereby controlling and adjusting the frequency of the lime milk delivery pump (22) to control the amount of lime powder added to the lime milk preparation tank (13); when the frequency of the lime milk delivery pump (22) is changed, the frequency of the screw weighing conveyor (12) should also be changed accordingly to maintain the relative stability of the lime milk concentration in the lime milk preparation tank (13); The changing relationship between the screw weighing conveyor (12) and the lime milk delivery pump (22) is: fS=fL×c Where: fS is the frequency change of the lime milk delivery pump, in Hz; fL is the frequency change of the screw weighing conveyor, and c is the frequency ratio of the screw weighing conveyor and the lime milk delivery pump during normal operation. c can be obtained through field tests.

2. The method for controlling pH value of a lime adjustment triple tank in a power plant desulfurization wastewater system according to claim 1, characterized in that: By monitoring the water flow rate of the neutralization tank (42), the frequency adjustment calculation method of the lime milk delivery pump (22) is: f1=A×Q×50÷(PS×ρ) Where: Q is the water flow rate of the neutralization box, unit is m 3 / h; A is the amount of lime powder to be added per liter of wastewater, in g / L; PS is the output of the lime milk delivery pump, in m 3 / h; ρ represents the concentration of lime milk per unit volume in the lime milk preparation tank, in kg / m 3 ; f1 is the frequency of the lime milk delivery pump, in Hz.

3. The method for controlling pH value of a lime adjustment triple tank in a power plant desulfurization wastewater system according to claim 2, characterized in that: When the pH value in the neutralization tank (42) is less than a preset value, the frequency of the lime milk delivery pump (22) is controlled to increase, thereby increasing the amount of lime powder entering the lime milk preparation tank (13); if the pH value is greater than the preset value, the frequency of the lime milk delivery pump (22) is controlled to decrease, thereby reducing the amount of lime powder entering the lime milk preparation tank (13).

4. A pH value control system for a lime adjustment triple tank in a power plant desulfurization wastewater system, based on the pH value control method for a lime adjustment triple tank in a power plant desulfurization wastewater system according to any one of claims 1 to 3, characterized in that: include, A lime milk storage unit, a wastewater pre-precipitation unit, a neutralization and cleaning unit and a DCS control system (61); the neutralization and cleaning unit includes a neutralization tank (42); The lime milk storage unit comprises a lime powder silo (11), a screw weighing conveyor (12) and a lime milk preparation box (13); the outlet of the lime powder silo (11) is connected to the screw weighing conveyor (12), and the conveying end of the screw weighing conveyor (12) is connected to the lime milk preparation box (13); The wastewater pre-precipitation unit is connected to the neutralization tank (42) through a pipeline; the lime milk preparation tank (13) is connected to the neutralization tank (42) through a pipeline; a neutralization tank water inlet flow meter (41) is installed on the inlet pipeline of the neutralization tank (42), and a neutralization tank pH meter (48) is installed in the neutralization tank (42); the DCS control system (61) is used for remote monitoring and control of various devices.

5. A power plant desulfurization wastewater system lime adjustment triple tank pH value control system according to claim 4, characterized in that: The wastewater pre-precipitation unit includes a pre-precipitation tank (31), a buffer water tank (32) and a wastewater lifting pump (33); The pre-sedimentation tank (31) is connected to the buffer water tank (32) via a pipeline, the inlet pipeline of the wastewater lifting pump (33) is deep into the buffer water tank (32), and the outlet of the wastewater lifting pump (33) is connected to the neutralization tank (42) via a pipeline.

6. A power plant desulfurization wastewater system lime adjustment triple tank pH value control system according to claim 4, characterized in that: The neutralization and cleaning unit further includes a reaction tank (44), a flocculation tank (46) and a concentration and clarification tank (49); The neutralization tank (42) is connected to the reaction tank (44), the flocculation tank (46) and the concentration and clarification tank (49) in sequence through pipelines; the neutralization tank (42) is provided with a neutralization tank stirrer (43), the reaction tank (44) is provided with a reaction tank stirrer (45), and the flocculation tank (46) is provided with a flocculation tank stirrer (47).

7. A power plant desulfurization wastewater system lime adjustment triple tank pH value control system according to claim 6, characterized in that: It also includes a wastewater discharge unit, which includes a wastewater discharge tank (51) and a wastewater discharge pump (52); the outlet of the concentration and clarification tank (49) is connected to the wastewater discharge tank (51) through a pipeline, and the inlet pipeline of the wastewater discharge pump (52) is deep into the wastewater discharge tank (51).

8. The pH value control system of a lime adjustment triple tank in a power plant desulfurization wastewater system according to claim 5, characterized in that: The lime milk preparation tank (13) is provided with a lime milk preparation tank level gauge (15) and a lime milk preparation tank mixer (14); and a lime milk preparation tank water supply valve (16) is provided on the inlet pipe of the lime milk preparation tank (13).

9. The pH value control system of a lime adjustment triple tank in a power plant desulfurization wastewater system according to claim 5, characterized in that: A lime milk preparation tank outlet valve (21) and a lime milk delivery pump (22) are provided on the outlet pipe of the lime milk preparation tank (13); a lime milk delivery pump outlet valve (23) is provided at the outlet of the lime milk delivery pump (22); and a lime milk flushing water valve (24) is provided on the bypass pipe between the lime milk preparation tank outlet valve (21) and the lime milk delivery pump (22).

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