A system and method for detecting failure of pH electrode for low conductivity water in power plants

Abstract

The invention discloses a failure inspection system and method for low-conductivity water pH electrode in a power plant, comprising a standard pH meter, an online pH meter, an adjustable micro pump, a standard solution bottle and a deionized water pipeline; a dynamic online inspection method is adopted; the slopes of the secondary instrument of the standard pH meter and the secondary instrument of the online pH meter are both set to 100% or 59.16mV / pH, so that the performance of the online pH electrode is compared with the performance of the standard pH electrode under the same conditions. An ammonia solution with a set concentration in the standard solution bottle is added to the deionized water through an adjustable micro pump, and the power of the adjustable micro pump is adjusted multiple times to obtain a plurality of low-conductivity water samples with different pH values, and the range formed by these pH values ​​is greater than the pH value control range of the online water sample, so that the water sample passes through the standard pH meter electrode and the online pH meter electrode at the same time, and the electrode errors of the online pH electrode under different water samples are calculated respectively, and if there is a set of error absolute values ​​greater than 0.05, it can be determined that the online pH electrode is in a failure state.

Description

Technical Field

[0001] The invention relates to the field of online chemical instrument measurement and calibration of a water vapor circulation system in a power plant, and in particular to a failure detection system and method for a pH electrode of low conductivity water in a power plant. Background Art

[0002] pH is an important monitoring indicator of the water vapor quality of the power plant water vapor system. In order to prevent the corrosion of steel and copper in the water vapor system of the generator set in the thermal power plant, the water pH value is usually adjusted by adding ammonia. For different operating conditions, the pH value is basically between 8.3 and 9.6. In other words, the pH value of low conductivity water in the power plant has a certain control range. Its accurate measurement is of great significance to the chemical supervision and control of the power plant and the safe and economical operation of the unit. The pH electrode has a certain service life. The electrode performance of the pH electrode is effective within the service life, and the pH meter can accurately and timely measure the pH value of the water sample.

[0003] The conventional method to check the performance failure of pH electrode is to calibrate the pH meter with pH standard buffer solution (4.00, 6.86 and 9.18). If the electrode slope is lower than 90% or lower than 53.24mV / pH, it is considered that the performance of the pH electrode has declined and the electrode is judged to be in a failed state. This method determines that the service life of the electrode will not exceed one year.

[0004] In actual work, it is found that the service life of low conductivity water pH electrodes often exceeds one year. The electrode can still measure the pH value of low conductivity water in a timely and accurate manner, but the conventional method is used to test the performance of the pH electrode, and the result is a failure state. Therefore, the conventional inspection method cannot accurately and effectively detect whether the low conductivity water pH electrode that has exceeded the prescribed use time is in a failure state, shortening the service life of the electrode. Low conductivity water pH electrodes generally have a high purchase cost, resulting in unnecessary waste and increased production and labor costs.

[0005] In view of the above problems, it is necessary to design a failure detection system and method for low conductivity water pH electrode in power plants to accurately and effectively detect the performance status of low conductivity water pH electrode and determine whether the electrode is in a failure state. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a failure detection system and method for low conductivity water pH electrode in a power plant. The system and method adopt a dynamic online detection method to compare the performance of the online pH electrode with that of a standard pH electrode, accurately and effectively detect the performance of the low conductivity water pH electrode, and then determine whether the low conductivity water pH electrode is in a failure state.

[0007] The present invention is achieved through the following technical solutions:

[0008] A power plant low conductivity water pH electrode failure inspection system, comprising a standard pH meter, an online pH meter, an adjustable micro pump, a standard solution bottle and a deionized water pipeline;

[0009] The water inlets of the standard pH meter and the online pH meter are connected to the outlet of the desalted water pipeline through a tee, the inlet of the desalted water pipeline is connected to a desalted water source, the outlet of the adjustable micro pump is connected to the desalted water pipeline through a branch pipeline, and the inlet of the adjustable micro pump is connected to a standard solution bottle, and the standard solution bottle is filled with ammonia solution of a set concentration.

[0010] Preferably, the standard pH meter includes a standard secondary instrument and a standard pH electrode connected thereto, and the online pH meter includes an online secondary instrument and an online pH electrode connected thereto, and the standard pH electrode and the online pH electrode are respectively connected to two outlets of the tee.

[0011] Preferably, the standard pH electrode and the online pH electrode are respectively arranged in two circulation cells, and the inlet of the circulation cell is connected to the outlet of the tee.

[0012] Preferably, a liquid discharge port is provided at the upper portion of the circulation pool.

[0013] A method for detecting a failure of a low conductivity water pH electrode in a power plant comprises the following steps:

[0014] Step 1, mixing deionized water and an ammonia solution of a set concentration to form a low conductivity water sample, and passing it through a standard pH meter and an online pH meter at the same time;

[0015] Step 2, adjusting the pH value of the low conductivity water sample so that the measured value of the standard pH meter is the preset value, and adjusting the measured value of the online pH meter to be the same as the measured value of the standard pH meter;

[0016] Step 3, adjusting the pH value of the low conductivity water sample, and obtaining the measured value of the standard pH meter and the measured value of the online pH meter;

[0017] Step 4, repeating step 3, obtaining the measured values ​​of the standard pH meter and the measured values ​​of the online pH meter after adjusting the pH value of the low conductivity water sample multiple times;

[0018] Step 5, determining the electrode error of the online pH electrode of the online pH meter corresponding to each low conductivity water sample obtained by adjustment;

[0019] Step 6: Determine the performance status of the online pH electrode according to the electrode error of the online pH electrode of the online pH meter.

[0020] Preferably, the method for adjusting the pH value of the low conductivity water sample in step 2 and step 3 is to control the flow rate of the ammonia solution injected into the demineralized water pipeline by an adjustable micro pump to adjust the pH value of the low conductivity water sample.

[0021] Preferably, the preset value in step 2 is the middle value of the pH value control range of the online water sample.

[0022] Preferably, the pH value range formed by the pH value of the low conductivity water sample after multiple adjustments in step 4 is greater than the control range of the pH value of the online water sample.

[0023] Preferably, the calculation method of the electrode error of the online pH electrode in step 5 is as follows:

[0024] δ Gi =S ii -B Zi

[0025] Among them, S ii is the indication of the secondary instrument of the online pH meter after adjusting the pH value of the low conductivity water sample for the i-th time, B Zi It is the indication of the secondary instrument of the standard pH meter after adjusting the pH value of the low conductivity water sample for the i-th time.

[0026] Preferably, in step 6, when the absolute value of the electrode error of the online pH electrode is greater than a set value, the online pH electrode is in a failure state.

[0027] Compared with the prior art, the present invention has the following beneficial technical effects:

[0028] The invention discloses a method for detecting failure of a low-conductivity water pH electrode in a power plant. The method adopts a dynamic online detection mode. The slopes of the online secondary instrument and the standard secondary instrument are set to the optimal range, so that the performance of the online pH electrode is compared with that of the standard pH electrode under the same conditions. An ammonia solution of a set concentration in a standard solution bottle is added to the demineralized water by an adjustable micro pump. The power of the adjustable micro pump is adjusted multiple times to obtain a plurality of low-conductivity water samples with different pH values. The range formed by these pH values ​​is greater than the pH value control range of the online water sample. These low-conductivity water samples are simultaneously passed through a standard pH meter electrode circulation pool and an online pH electrode circulation pool. The electrode errors of the online pH electrode under different water samples are calculated respectively. If a set of error absolute values ​​is greater than 0.05, it can be determined that the online pH electrode is in a failed state. The method can quickly and accurately detect the pH electrode in long service, thereby reducing production and labor costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the inspection system of the present invention.

[0030] In the figure, 1. standard secondary instrument, 2. standard pH electrode, 3. standard pH electrode circulation cell, 4. online secondary instrument, 5. online pH electrode, 6. online pH electrode circulation cell, 7. adjustable micro pump, 8. standard solution bottle. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below in conjunction with the accompanying drawings, which are intended to explain the present invention rather than to limit it.

[0032] See also Figure 1 A low conductivity water pH electrode failure inspection system for a power plant includes a standard pH meter, an online pH meter, an adjustable micro pump 5, a standard solution bottle 6 and a deionized water pipeline; the standard pH meter includes a standard secondary instrument 1 and a standard pH electrode 2, and the online pH meter includes an online secondary instrument 4 and an online pH electrode 5.

[0033] The standard secondary instrument 1 is connected to the standard pH electrode 2 through a cable, and the online secondary instrument 4 is connected to the online pH electrode 5 through a cable. The standard pH electrode 2 and the online pH electrode 5 are respectively arranged in the standard pH electrode circulation pool 3 and the online pH electrode circulation pool 6. The standard pH electrode circulation pool 3 and the online pH electrode circulation pool 6 are both provided with drainage ports. The outlet of the deionized water pipeline is respectively connected to the standard pH electrode circulation pool 3 and the online pH electrode circulation pool 6 through a tee. The standard solution bottle 8 is perfused with an ammonia solution of a set concentration. The standard solution bottle 8 is connected to the deionized water pipeline through a branch pipeline. An adjustable micro pump 7 is arranged on the branch pipeline. The deionized water and the ammonia solution are mixed to form a low conductivity water sample, which is injected into the standard pH electrode circulation pool 3 and the online pH electrode circulation pool 6.

[0034] A method for detecting failure of a pH electrode for low conductivity water in a power plant, comprising the following steps:

[0035] Step 1: Pour an ammonia solution of a set concentration into the standard solution bottle 8.

[0036] Step 2: Set the slopes of the standard secondary instrument 1 and the online secondary instrument 4 to the optimal range.

[0037] For example, the optimal range of the slope is 90%-120% or 53.24 mV / pH-70.99 mV / pH, and preferably, the slope is set to 100% or 59.16 mV / pH.

[0038] Step 3: inject deionized water into the flow cells of the standard pH electrode flow cell 3 and the online pH electrode flow cell 6 at the same time.

[0039] Step 4, turn on the adjustable micro pump 7 to mix the ammonia solution and the desalted water to form a low conductivity water sample and inject it into the circulation pool, adjust the power of the adjustable micro pump 7, make the indication of the standard secondary instrument 1 the middle value of the pH value control range of the online water sample, and maintain the power of the adjustable micro pump 7, that is, the indication of the standard secondary instrument 1 is stable.

[0040] In this step, the flow rate of the ammonia solution is controlled so that the pH value of the low conductivity water sample injected into the circulation pool is the same as the middle value of the control range of the pH value of the online water sample, such as the water sample at the deaerator inlet or the generator cooling water sample.

[0041] Step 5: Adjust the indication of the online secondary instrument 4 so that the indication of the online secondary instrument 4 is the same as the indication of the standard secondary instrument 1 in step 4.

[0042] Step 6: Adjust the power of the adjustable micro pump 7 to change the pH value of the low conductivity water sample entering the circulation pool. After the instrument indication value stabilizes, obtain the measurement data of the group, which includes the indication value B of the adjusted standard secondary instrument 1. Zi and the indication S of the online secondary instrument 4 ii .

[0043] Step 7, adjust the power of the adjustable micro pump 7 and repeat step 6 to obtain multiple groups of measurement data.

[0044] The power of the adjustable micro pump 7 is adjusted so that the pH indication of the low conductivity water sample entering the circulation pool is a predetermined value. The pH value of the low conductivity water sample adjusted each time is different, and the pH value range formed by multiple predetermined values ​​is larger than the control range of the pH value of the online water sample. That is to say, the indication range formed by multiple indications of the standard secondary instrument 1 is larger than the control range of the pH value of the online water sample. For example, the control range of the pH value of the deaerator inlet water sample is 9.2-9.6, and the pH value range formed by multiple indications is 8-10.

[0045] Step 8: According to the multiple groups of measurement data obtained in step 7, the electrode errors of the online pH electrodes corresponding to the low conductivity water samples with different pH values ​​are calculated respectively.

[0046] Specifically, according to step 6, n groups of measurement values ​​are obtained, and the electrode error δ of the online pH electrode corresponding to the low conductivity water samples with different pH values ​​is calculated according to the following formula: Gi .

[0047] δ Gi =S ii -B Zi

[0048] Among them, i is the i-th group of measurements, S ii is the indication of the online secondary instrument of the i-th group of low conductivity water samples, B Zi is the indication of the standard secondary instrument for the i-th group of low conductivity water samples.

[0049] Step 8: When the absolute value of the electrode error of any group is greater than the set value, the online pH electrode 5 is in a failure state.

[0050] Specifically, if the absolute value of a group of electrode errors is greater than 0.05, it can be determined that the online pH electrode 5 is in a failed state.

[0051] Example 1

[0052] Take the inspection of the pH electrode at the inlet of a power plant deaerator as an example. The pH electrode at the inlet of the deaerator has been used for 10 years. The pH value control range of the water sample at the inlet of the deaerator is 9.20-9.60, and the middle point of the control range is 9.40. The inspection results are shown in Table 1.

[0053] Table 1 Deaerator inlet pH electrode inspection

[0054] <![CDATA[Indicated value B of the standard secondary instrument Z > <![CDATA[Indicated value S of on-line secondary instrument i > <![CDATA[Electrode error δ G > 8.50 8.52 0.02 9.00 9.01 0.01 9.20 9.20 0 9.30 9.31 0.01 9.40 9.40 0 9.50 9.50 0 9.60 9.60 0 10.00 10.01 0.01

[0055] From the test results, it can be seen that the pH electrode that has been used for 10 years still has good linearity and has the same performance as the standard pH electrode. The electrode has not failed and can continue to be used.

[0056] Example 2

[0057] Take the inspection of the pH electrode of the generator cooling water of a power plant as an example. The pH electrode of the generator cooling water has been used for 5 years. The pH value control range of the generator cooling water sample is 8.30-8.70, and the middle point of the control range is 8.50. The inspection results are shown in Table 2.

[0058] Table 2 Generator cooling water pH electrode inspection

[0059] <![CDATA[Indicated value B of the standard secondary instrument Z > <![CDATA[The indicated value S of the on-line secondary instrument i > <![CDATA[Electrode error δ G > 8.00 8.01 0.01 8.30 8.31 0.01 8.40 8.40 0 8.50 8.50 0 8.60 8.60 0 8.70 9.70 0 9.00 9.01 0.01 9.50 10.01 0.01

[0060] From the test results, it can be seen that the pH electrode that has been used for 5 years still has good linearity and has the same performance as the standard pH electrode. The electrode has not failed and can still be used.

[0061] The present invention discloses a power plant low conductivity water pH electrode failure inspection system and method, which adopts a dynamic online inspection method, and the slopes of the online secondary instrument and the standard secondary instrument are both set to 100% or 59.16mV / pH, so that the performance of the standard pH electrode is compared with the performance of the online pH electrode under the same conditions. An adjustable micro pump is used to add an ammonia solution of a set concentration in a standard solution bottle to demineralized water, and the power of the adjustable micro pump is adjusted multiple times to obtain a plurality of low conductivity water samples with different pH values, and the range formed by these pH values ​​is greater than the pH value control range of the online water sample, so that the water sample passes through the standard pH meter electrode and the online pH meter electrode at the same time, and the errors of the online pH electrode under different water samples are calculated respectively. If a set of error absolute values ​​is greater than 0.05, it can be determined that the online pH electrode is failed.

[0062] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for detecting failure of pH electrode in low conductivity water of power plant, characterized in that: The pH electrode failure inspection method is applied to a low-conductivity water pH electrode failure inspection system in a power plant, the system comprising a standard pH meter, an online pH meter, an adjustable micro pump (7), a standard solution bottle (8) and a deionized water pipeline; The water inlets of the standard pH meter and the online pH meter are connected to the outlet of the desalted water pipeline through a tee, the inlet of the desalted water pipeline is connected to a desalted water source, the outlet of the adjustable micro pump (7) is connected to the desalted water pipeline through a branch pipeline, and the inlet of the adjustable micro pump (7) is connected to a standard solution bottle (8), and the standard solution bottle (8) is filled with an ammonia solution of a set concentration; The standard pH meter comprises a standard secondary instrument (1) and a standard pH electrode (2) connected thereto, and the online pH meter comprises an online secondary instrument (4) and an online pH electrode (5) connected thereto, and the standard pH electrode (2) and the online pH electrode (5) are respectively connected to two outlets of the tee; The standard pH electrode (2) and the online pH electrode (5) are respectively arranged in two circulation pools, and the inlet of the circulation pool is connected to the outlet of the tee; The inspection method of the pH electrode failure inspection system comprises the following steps: Step 1: Set the slopes of the standard secondary instrument and the online pH meter to the optimal range, where the optimal range of the slope is 90%-120%; The demineralized water and the ammonia solution of set concentration are mixed to form a low conductivity water sample, and the sample is passed through a standard pH meter and an online pH meter at the same time; Step 2, adjusting the pH value of the low conductivity water sample so that the measured value of the standard pH meter is the preset value, and adjusting the measured value of the online pH meter to be the same as the measured value of the standard pH meter; The preset value is the middle value of the pH value control range of the online water sample; Step 3, adjusting the pH value of the low conductivity water sample, and obtaining the measured value of the standard pH meter and the measured value of the online pH meter; Step 4, repeating step 3, obtaining the measured values ​​of the standard pH meter and the measured values ​​of the online pH meter after adjusting the pH value of the low conductivity water sample multiple times; The pH value range formed by the pH value of the low conductivity water sample after multiple adjustments is larger than the control range of the pH value of the online water sample; Step 5, determining the electrode error of the online pH electrode of the online pH meter corresponding to each low conductivity water sample obtained by adjustment; The calculation method of the electrode error of the online pH electrode is as follows: in, For the i After adjusting the pH value of the low conductivity water sample for the first time, the secondary instrument indication of the online pH meter is For the i After the pH value of the low conductivity water sample is adjusted for the first time, the secondary instrument indication of the standard pH meter; Step 6: Determine the performance status of the online pH electrode according to the electrode error of the online pH electrode of the online pH meter.

2. A method for detecting failure of a low conductivity water pH electrode in a power plant according to claim 1, characterized in that: A liquid discharge port is arranged on the upper part of the circulation pool.

3. A method for detecting failure of a low conductivity water pH electrode in a power plant according to claim 1, characterized in that: The method for adjusting the pH value of the low conductivity water sample in step 2 and step 3 is to control the flow rate of the ammonia solution injected into the demineralized water pipeline by an adjustable micro pump (7) to adjust the pH value of the low conductivity water sample.

4. A method for detecting failure of a low conductivity water pH electrode in a power plant according to claim 1, characterized in that: In step 6, when the absolute value of the electrode error of the online pH electrode is greater than the set value, the online pH electrode is in a failure state.

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