An on-line monitoring system and method for chloride ions in desulfurization slurry

Abstract

The present invention discloses an on-line monitoring system and method for chloride ions in desulfurization slurry, including a slurry inlet pipeline, a slurry inlet flow regulating valve, a slurry pretreatment device, a measurement flow-through cell, a chloride ion electrode, a transmitter and a controller; the slurry inlet pipeline is communicated with the inlet on the bottom side of the slurry pretreatment device through the slurry inlet flow regulating valve, the water outlet on the side of the slurry pretreatment device is communicated with the inlet of the measurement flow-through cell, the chloride ion electrode is inserted into the measurement flow-through cell, a stirrer is arranged in the measurement flow-through cell, and the chloride ion electrode is connected with the transmitter and the controller. This system and method can realize the on-line monitoring of the chloride ion content in desulfurization slurry, and the measurement accuracy is relatively high.

Description

Technical Field

[0001] The invention belongs to the field of water quality monitoring in power generation technology, and relates to an on-line monitoring system and method for chloride ions in desulfurization slurry. Background Art

[0002] In the wet desulfurization system of a power plant, the chloride ion content in the desulfurization slurry is one of the main monitoring and control indicators during the operation of the desulfurization system. In the limestone-gypsum wet flue gas desulfurization process, too high chloride ion content in the desulfurization slurry will cause problems such as corrosion of desulfurization system equipment, low desulfurization efficiency, and poor gypsum quality. In order to maintain the normal operation of the system, the chloride ion content in the slurry needs to meet certain requirements, and the chloride ion concentration in the slurry generally remains at 20000 mg / L. When the measured value is too low, the problem of excessive chloride ions cannot be detected, which will cause corrosion of desulfurization equipment and related equipment; when the measured value is too high, the actual control value will be too low, which will greatly increase the dosage of limestone slurry, increase the operation cost of desulfurization equipment, increase the discharge amount of desulfurization wastewater, and increase the operation burden and cost of zero-emission equipment. Therefore, accurate monitoring of the chloride ion content is of great significance for the safe and economic operation of the desulfurization system.

[0003] At present, there are the following problems in measuring the chloride ion content in desulfurization slurry:

[0004] 1) The chloride ions in the desulfurization slurry are mainly measured by the manual analysis method through regular sampling by laboratory technicians every day. The manual analysis method is not only cumbersome in operation, greatly increasing the workload of staff, but also limited by the analysis level of staff in terms of measurement accuracy, and it is difficult to guarantee.

[0005] 2) Due to the complex composition of the desulfurization slurry and the presence of a large amount of suspended matter and sludge, it has a great impact on the measurement accuracy and service life of the instrument.

[0006] 3) The desulfurization slurry has a complex composition, containing F - , S 2- , Br - etc., which will interfere with the chloride ion measurement and affect the accuracy of chloride ion measurement.

[0007] Therefore, there is currently no instrument suitable for on-line monitoring of chloride ions in desulfurization slurry. Summary of the Invention

[0008] The purpose of the invention is to overcome the above-mentioned shortcomings of the prior art, and provide an on-line monitoring system and method for chloride ions in desulfurization slurry, which can realize on-line monitoring of the chloride ion content in desulfurization slurry and has relatively high measurement accuracy.

[0009] To achieve the above object, the on-line chlorine ion monitoring system for desulfurization slurry of the present invention comprises a slurry inlet pipe, a slurry inlet flow regulating valve, a slurry pretreatment device, a measurement flow cell, a chlorine ion electrode, a transmitter and a controller;

[0010] The slurry inlet pipe is communicated with the inlet on the bottom side of the slurry pretreatment device through the slurry inlet flow regulating valve. The water outlet on the side of the slurry pretreatment device is communicated with the inlet of the measurement flow cell. The chlorine ion electrode is inserted into the measurement flow cell. A stirrer is arranged in the measurement flow cell. The chlorine ion electrode is connected with the transmitter and the controller.

[0011] It further comprises a measurement flow cell inlet diverter valve and a measurement flow cell inlet valve. The outlet of the slurry pretreatment device is communicated with the inlets of the measurement flow cell inlet diverter valve and the measurement flow cell inlet valve. The outlet of the measurement flow cell inlet valve is communicated with the inlet of the measurement flow cell.

[0012] It further comprises a chlorine ion standard solution tank and a chlorine ion standard solution metering pump. The outlet of the chlorine ion standard solution tank is communicated with the measurement flow cell through the chlorine ion standard solution metering pump.

[0013] It further comprises a high-purity water tank and a high-purity water metering pump. The outlet of the high-purity water tank is communicated with the measurement flow cell through the high-purity water metering pump. The outlet of the flushing water tank is communicated with the measurement flow cell through a flushing water pump.

[0014] The water outlet on the top of the slurry pretreatment device is communicated with the measurement flow cell through a supernatant metering pump.

[0015] A filter screen is installed inside the slurry pretreatment device. A bottom drain valve is arranged at the bottom drain outlet of the slurry pretreatment device. The water outlets on the side and the top of the slurry pretreatment device are located above the filter screen. The inlet of the slurry pretreatment device is located below the filter screen.

[0016] The bottom drain outlet of the measurement flow cell is communicated with a measurement flow cell bottom drain valve.

[0017] The water outlet on the side of the measurement flow cell is communicated with a flow cell water outlet valve.

[0018] The on-line chlorine ion monitoring system and method for desulfurization slurry of the present invention comprises the following steps:

[0019] The desulfurization slurry enters the slurry pretreatment device through the slurry inlet flow regulating valve for solid-liquid separation. The separated clear liquid enters the measurement flow cell. The chlorine ion content in the measurement flow cell is measured by the chlorine ion electrode, and the chlorine ion measurement value is displayed through the transmitter and the controller, so as to realize the on-line measurement of the desulfurization slurry.

[0020] The on-line chlorine ion monitoring system and method for desulfurization slurry of the present invention comprises the following steps:

[0021] 1) The clear liquid after solid-liquid separation of the slurry by the slurry pretreatment equipment enters the measurement flow cell, and the chloride ion content of the solution in the measurement flow cell is measured by a chloride ion electrode as calibration point 1. After the data is stable, record its potential value as E1 and the chloride ion concentration as C1;

[0022] 2) Flush the measurement flow cell. After the cleaning is completed, send 10 mL of the clear liquid after solid-liquid separation to the measurement flow cell, and then inject pure water into the measurement flow cell to dilute the clear liquid to 100 mL. Measure the diluted solution by a chloride ion electrode as calibration point 2. After the data is stable, record its potential value as E2 and the chloride ion concentration as C2;

[0023] 3) Add 10 mL of a chloride ion standard solution with a concentration of 100 g / L to the measurement flow cell, and measure the solution by a chloride ion electrode as calibration point 3. After the data is stable, record its potential value as E3 and the chloride ion concentration as C3;

[0024] Calculate the calibrated electrode potential E, and calculate the calibrated chloride ion content according to the calibrated electrode potential E, where,

[0025] E1 - E2 = -k·lg(C1 / C2) = -k

[0026] E2 - E3 = -k·lg(C2 / C3)

[0027] C3 = (100C2 + 10×100000) / 110

[0028] E2 = E0’ - k·lg(C2 / 35000)

[0029] E = E0’ - k·lg(C Cl / 35000).

[0030] The present invention has the following beneficial effects:

[0031] For the on-line monitoring system and method of chloride ions in desulfurization slurry of the present invention, in the normal measurement state, the desulfurization slurry first enters the slurry pretreatment equipment for solid-liquid separation of the slurry, and the clear liquid enters the measurement flow cell and is measured by a chloride ion electrode to realize on-line monitoring of the chloride ion content in the desulfurization slurry; when calibration is required, the clear liquid is diluted and concentrated, and the measurement value of the original clear liquid is calibrated according to the measurement values of the diluted and concentrated solutions, so as to realize automatic calibration of the on-line monitoring system of chloride ions in desulfurization slurry and improve the measurement accuracy. Brief Description of the Drawings

[0032] Figure 1 It is a schematic structural diagram of the present invention;

[0033] Figure 2 It is the flow chart of Embodiment 3.

[0034] Among them, 1 is the slurry inlet flow regulating valve, 2 is the slurry pretreatment equipment, 3 is the supernatant metering pump, 4 is the filter screen, 5 is the bottom drain valve of the pretreatment equipment, 6 is the measuring flow cell inlet shunt valve, 7 is the measuring flow cell inlet valve, 8 is the measuring flow cell, 9 is the chloride ion electrode, 10 is the stirrer, 11 is the bottom drain valve of the measuring flow cell, 12 is the flow cell outlet valve, 13 is the chloride standard solution metering pump, 14 is the high-purity water metering pump, 15 is the flushing water pump, 16 is the chloride standard solution tank, 17 is the high-purity water tank, 18 is the flushing water tank, and 19 is the transmitter and controller; Detailed implementation manners

[0035] In order to enable those skilled in the art to better understand the solution 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 accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments, and are not intended to limit the scope of the present invention disclosure. In addition, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts disclosed in the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the scope of protection of the present invention.

[0036] The structural schematic diagrams according to the disclosed embodiments of the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and for the purpose of clear expression, some details are enlarged and some details may be omitted. The shapes of various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are only exemplary. In practice, there may be deviations due to manufacturing tolerances or technical limitations, and those skilled in the art can design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0037] Embodiment 1

[0038] Refer to Figure 1 , the on-line chloride ion monitoring system for desulfurization slurry of the present invention includes a slurry inlet pipeline, a slurry inlet flow regulating valve 1, a slurry pretreatment equipment 2, a supernatant metering pump 3, a filter screen 4, a bottom drain valve 5 of the pretreatment equipment, a measuring flow cell inlet shunt valve 6, a measuring flow cell inlet valve 7, a measuring flow cell 8, a chloride ion electrode 9, a stirrer 10, a bottom drain valve 11 of the measuring flow cell, a flow cell outlet valve 12, a chloride standard solution metering pump 13, a high-purity water metering pump 14, a flushing water pump 15, a chloride standard solution tank 16, a high-purity water tank 17, a flushing water tank 18, and a transmitter and controller 19;

[0039] The slurry inlet pipe is connected to the inlet on the bottom side of the slurry pretreatment device 2 through the slurry inlet flow regulating valve 1. The water outlet on the side of the slurry pretreatment device 2 is connected to the inlet of the measuring flow cell inlet shunt valve 6 and the inlet of the measuring flow cell inlet valve 7. The outlet of the measuring flow cell inlet valve 7 is connected to the inlet of the measuring flow cell 8.

[0040] The chloride ion electrode 9 is connected to the transmitter and controller 19. The transmitter and controller 19 is connected to the control ends of the supernatant metering pump 3, the measuring flow cell inlet shunt valve 6, the measuring flow cell inlet valve 7, the stirrer 10, the measuring flow cell bottom drain valve 11, the flow cell outlet valve 12, the chloride standard solution metering pump 13, the high-purity water metering pump 14 and the flushing water pump 15.

[0041] The outlet of the chloride standard solution tank 16 is connected to the measuring flow cell 8 through the chloride standard solution metering pump 13.

[0042] The outlet of the high-purity water tank 17 is connected to the measuring flow cell 8 through the high-purity water metering pump 14. The outlet of the flushing water tank 18 is connected to the measuring flow cell 8 through the flushing water pump 15.

[0043] The water outlet at the top of the slurry pretreatment device 2 is connected to the measuring flow cell 8 through the supernatant metering pump 3.

[0044] A filter screen 4 is installed inside the slurry pretreatment device 2 to separate solid and liquid of the desulfurization slurry. A bottom drain valve is provided at the bottom drain port of the slurry pretreatment device 2. The concentrated slurry is discharged through the bottom drain valve 5 of the pretreatment device. Among them, the water outlet on the side and the water outlet at the top of the slurry pretreatment device 2 are located above the filter screen 4, and the inlet of the slurry pretreatment device 2 is located below the filter screen 4.

[0045] The slurry inlet flow regulating valve 1, the measuring flow cell inlet shunt valve 6, the measuring flow cell inlet valve 7, the measuring flow cell bottom drain valve 11 and the flow cell outlet valve 12 are all solenoid valves.

[0046] The supernatant metering pump 3, the chloride standard solution metering pump 13, the high-purity water metering pump 14, the flushing water pump 15 and the stirrer 10 are all driven by stepping motors.

[0047] The transmitter and controller 19 integrates system control and numerical display, and the instrument has an automatic temperature compensation function.

[0048] The chloride ion electrode 9 is inserted into the measuring flow cell 8. A stirrer 10 is arranged in the measuring flow cell 8. The bottom drain port of the measuring flow cell 8 is communicated with the measuring flow cell bottom drain valve 11. The water outlet on the side of the measuring flow cell 8 is connected to the flow cell outlet valve 12.

[0049] Example 2

[0050] The on-line monitoring system and method for chloride ions in desulfurization slurry of the present invention include the following steps:

[0051] Open the slurry inlet flow regulating valve 1, the measuring flow cell inlet valve 7 and the flow cell outlet valve 12, and close the drain valve 11 at the bottom of the measuring flow cell. The desulfurization slurry enters the slurry pretreatment equipment 2 through the slurry inlet flow regulating valve 1 for solid-liquid separation. The clear liquid enters the measuring flow cell 8 through the measuring flow cell inlet valve 7. The chloride ion content in the measuring flow cell 8 is measured by the chloride ion electrode 9, and the chloride ion measurement value is displayed through the transmitter and controller 19. The measured slurry is discharged through the flow cell outlet valve 12 to realize the on-line measurement of the desulfurization slurry.

[0052] Example 3

[0053] Reference Figure 2 , the on-line monitoring system and method for chloride ions in desulfurization slurry of the present invention include the following steps:

[0054] 1) Open the slurry inlet flow regulating valve 1, the measuring flow cell inlet valve 7 and the flow cell outlet valve 12, and close the drain valve 11 at the bottom of the measuring flow cell. The clear liquid after solid-liquid separation of the slurry by the slurry pretreatment equipment 2 enters the measuring flow cell 8 through the measuring flow cell inlet valve 7. The chloride ion content in the measuring flow cell 8 is measured by the chloride ion electrode 9 as calibration point 1. After the data is stable, record its potential value as E1 and the chloride ion concentration as C1;

[0055] 2) Open the slurry inlet flow regulating valve 1 and the measuring flow cell inlet shunt valve 6, close the measuring flow cell inlet valve 7 and the flow cell outlet valve 12, open the drain valve 11 at the bottom of the measuring flow cell, and turn on the flushing water pump 15 to flush the measuring flow cell 8. After the cleaning is completed, close the drain valve 11 at the bottom of the measuring flow cell, turn on the supernatant metering pump 3, extract 10 mL of clear liquid through the supernatant metering pump 3 and send it to the measuring flow cell 8, turn on the high-purity water metering pump 14, and at the same time turn on the stirrer 10 to dilute the clear liquid in the measuring flow cell 8 to 100 mL. Measure the diluted solution as calibration point 2. After the data is stable, record its potential value as E2 and the chloride ion concentration as C2;

[0056] 3) Turn on the chloride standard solution metering pump 13, add 10 mL of chloride standard solution with a concentration of 100 g / L to the measuring flow cell 8, measure the solution by the chloride ion electrode 9 as calibration point 3. After the data is stable, record its potential value as E3 and the chloride ion concentration as C3 to complete the automatic calibration;

[0057] 4) After the automatic calibration is completed, open the drain valve 11 at the bottom of the measurement flow cell, turn on the flushing water pump 15, and clean the measurement flow cell 8. After the cleaning is completed, automatically enter the measurement mode.

[0058] 5) The calculation formula is:

[0059] E1 - E2 = -k·lg(C1 / C2) = -k

[0060] E2 - E3 = -k·lg(C2 / C3)

[0061] C3 = (100C2 + 10×100000) / 110

[0062] E2 = E0’ - k·lg(C2 / 35000)

[0063] Obtain the values of k and E0’, and according to the formula: E = E0’ - k·lg(C Cl / 35000), calculate the calibrated chloride ion content from the calibrated electrode potential value E.

[0064] Table 1 shows the chloride ion content in different desulfurization slurries measured according to the calibration method and measurement method of the present invention, and the comparison with the measurement values by the manual titration method.

[0065] Table 1

[0066]

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: still can modify the specific implementation manners of the present invention or make equivalent replacements, and any modification or equivalent replacement without departing from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. An on-line monitoring method for chloride ions in desulfurization slurry, characterized in that, It includes the following steps: 1) First, the clear liquid after solid-liquid separation of the slurry by the slurry pretreatment equipment enters the measurement flow cell. The chloride ion content of the solution in the measurement flow cell is measured by a chloride ion electrode as calibration point 1. After the data is stable, record its potential value as E1 and the chloride ion concentration as C1; 2) Clean the measurement flow cell. After cleaning the measurement flow cell, then send 10 mL of the clear liquid after solid-liquid separation to the measurement flow cell, and then inject pure water into the measurement flow cell to dilute the clear liquid to 100 mL. Measure the diluted solution by a chloride ion electrode as calibration point 2. After the data is stable, record its potential value as E2 and the chloride ion concentration as C2. Among them, the potential value E2 is the recorded value; the chloride ion concentration C2 is the chloride ion content in the current water sample. The chloride ion concentration C2 of calibration point 2 is the result of diluting the water sample of calibration point 1 by 10 times, that is, the concentration of chloride ions C1 is 10 times the concentration of chloride ions C2, C1 = 10×C2, then C1 / C2 = 10, and formula (1) can be written as E1 - E2 = -k×lg(C1 / C2) = -k×lg(10) = -k. The k value can be calculated through formula (1), and the k calculated through formula (1) is used as the reference value for subsequent substitution; 3) Add 10 mL of chloride ion standard solution with a concentration of 100 g / L to the measurement flow cell, and measure the solution by a chloride ion electrode as calibration point 3. After the data is stable, record its potential value as E3 and the chloride ion concentration as C3. Among them, the potential value E3 is the recorded value; the chloride ion concentration C3 is the chloride ion content in the current water sample. Then, C2, C3, E2, and E3 satisfy the following formula (2) that is E2 - E3 = -k·lg(C2 / C3) and formula (3) that is C3 = (100C2 + 10×100000) / 110. In formula (2) E2 - E3 = -k·lg(C2 / C3) and formula (3) C3 = (100C2 + 10×100000) / 110, there are only two unknowns C2 and C3, and E2 and E3 are both recorded values, that is, E2 and E3 are known quantities. k can be calculated through formula (1). Formula (2) and formula (3) form a system of binary linear equations with two unknowns C2 and C3. The specific values of C2 and C3 can be calculated through this system of equations; 4) Then calculate the value of E0’ through formula (4) that is E2 = E0’ - [k·lg(C2 / 35000)]; the meaning of formula (4) that is E2 = E0’ - [k·lg(C2 / 35000)] is E0’ minus k·lg(C2 / 35000). Among them, E2 is a known quantity, k is calculated through formula (1), and C2 is obtained through the system of binary linear equations with two unknowns C2 and C3 formed by formula (2) and formula (3). Therefore, in formula (4) E2 = E0’ - [k·lg(C2 / 35000)], only E0’ is an unknown quantity, and the value of E0’ can be obtained through calculation; 5) Then calculate the value of C through formula (5), i.e., E = E0’ - [k·lg(C Cl / 35000)]. The meaning of formula (5), i.e., E = E0’ - [k·lg(C Cl / 35000)], is E0’ minus k·lg(C Cl / 35000). The values of E0’ and k are both obtained through calculations using formulas (1) to (4). By the measured E value of the current water sample, the chloride ion content of the current water sample, i.e., C Cl / 35000), can be calculated through formula (5), i.e., E = E0’ - [k·lg(C Cl / 35000)]. Cl .

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