RU2368894C1 - Method for calibration of ionomers and device for its realisation - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: invention may be used in heat and nuclear power stations for measurements of ion concentrations in water of high purity of condensate type and feed water of power unit. In device for calibration of ionomers, according to invention, initial working medium is cleaned at ion-exchange filter 1 of mixed action for preparation of high purity water (HPW). Via the first conductometric detector 11 of reference conductormetre 10 and switch of flow 2, having several (for instance, four) fixed positions, HPW is supplied to one (depending on type of calibrated ionomer) of channels 3, 4, 5 or 6, where electrolyte is dosed in it (for instance, barium sulfate, silver chloride, acetic acid, ammonia). Further solution via the second flow switch 7 is supplied to anti-ion-exchanging filter 8 or to cation-exchanging filter 9, saturated by controlled ion, or to the second conductometric detector 12 of reference conductometre 10 and further to flow detector 14 of calibrated ionomer 13. Results of measurements of temperature, specific electric conductivity and concentration are sent to personal computer 15. Reference value of calibrated ion concentration is calculated, with which readings of calibrated ionomer are compared and, if required, corrected. Also method for calibration of ionomers is suggested.

EFFECT: expansion of functional resources of ionomers with flow detector due to possibility of calibration of ionomers of any type with simultaneous increase of calibration accuracy.

4 cl, 3 dwg

Description

The invention relates to methods for calibrating ionomers with a flow sensor and can be applied at thermal and nuclear power plants when measuring ion concentrations in high-purity water such as condensate and feed water of a power unit.

A known method of verification of conductometric analyzers of liquids, performed using installations of type UPS-1 or UPPK-2. The method consists in passing NaCl standard solutions through a conductometric fluid analyzer, the minimum concentration of which is not less than 7.5 g / l (0.128 mol / l), which is 5-6 orders of magnitude higher than real salt concentrations in the working environment of the power unit [GOST 8.354 -85 GSI. Conductometric fluid analyzers. Verification Method].

The closest known technical solution is a method for calibrating pH meters, which consists in dosing ammonia with a concentration varying 1.5-2.0 times, then passing the resulting solution through cation exchange resin in H-form, measure the specific electrical conductivity and temperature of the initial and H-cated samples of the working medium, the measurement results are processed on a computer using a system of equations characterizing the ionic equilibrium in the initial sample and H-cated, the pH value is calculated, comparing they are fed with the measured pH value and the calculated pH value is established on a pH meter in a working environment [RF patent No. 2244294, publ. 01/10/2005].

The disadvantages of this method are the inaccuracy and unreliability of the calibration of devices, which is associated with the presence in the calibration solution of NaCl and H ₂ CO ₃ , the concentrations of which are unknown. Without these values, the calculation contains the uncertainty of the pH value. In the prototype method for the concentration of Cl, an assumption of constancy ^is made, H ₂ CO _{3 is} not taken into account, on the basis of which it can be concluded that the negative effect of H ₂ CO ₃ noted in the said patent is not specified by the proposed calculation either. In addition, at least 11 tabular (literary) quantities are used in the calculation: equilibrium constants of electrolytic dissociation and values of the equivalent electrical conductivity of individual ions and input data (indicators of automated chemical control devices). The accuracy of measurements of the ionization constants of monobasic acids and bases ranges from 0.5-10%. The calculations for this patent include 4 such constants. Therefore, the relative error of the calculated values can be 40% without taking into account the errors of the automated chemical control devices (ACC) and conductivity meter used in the calibration process. The calculated pH values of ammonia solutions indicated in the materials for the specified patent (table 1 of the prototype), in our calculation, are pH = 9.57 (in the prototype - 9.26) and pH = 9.82 (in the prototype - 9.61) , which is 0.31 and 0.21 different from the reference pH values that should be used when calibrating the pH meter. In addition, calibration of pH meters involves the use of at least two calibration solutions, the pH of which should differ as much as possible from each other. The use of ammonia solutions allows you to actually have one calibration solution (pH according to the specified patent in the range of 9.25-9.61). We also note that the calculation of the equilibrium according to 13 equations requires significant computer resources.

Closest to the claimed device of the known technical solutions is a device for determining the microconcentration of chloride ions in high purity water [A.S. No. 1079047, publ. 06/10/1999] containing ion-exchange filters, a mode switch connected hydraulically through a mixed-action ion-exchange filter to a calibration unit made in the form of a second ion-exchange filter, a flow switch, a flow divider with parallel channels, at least one of which is filled sparingly soluble salt, dissociating with the formation of chloride ions, and the third ion-exchange filter.

The disadvantage of this device is that the actual concentration of chloride ions is not determined. The authors calculate this value, knowing the solubility product of the sparingly soluble salt, and use it to calibrate the chloride meter. For AgCl at 25 ° С, the concentration in the saturated solution is 1.33 · 10 ^-5 g-ion / l, which meets the requirements for the operation of ionomers used in thermal and nuclear power plants to measure ion concentrations in high-purity water such as condensate and nutrient water unit. However, the practically obtained concentration of AgCl in the stream of pure water is not theoretically possible for a saturated solution. In our conditions, it amounted to 25% of the calculated from solubility. Without additional measurements, the concentration of chloride ions remains unknown, so the calibration of the chloride meter in the stream using the specified known device is not entirely satisfactory.

The proposed inventions solve the problem of expanding the functionality of ionomers with a flow sensor due to the possibility of calibrating any type of ionomers while improving the accuracy of calibration.

The specified technical result is achieved by the fact that in a method comprising dosing an electrolyte of various concentrations, measuring the electrical conductivity and temperature, calculating the concentration of the ion being determined, comparing the calculated value with the measured one and setting the calculated concentration value on the calibrated ionomer, according to the invention, the initial working medium is purified using ion exchange mixed-action filter to high purity water (VHF) and create the required reference medium by dosing electro ita comprising controlled depending on the ion type ionomer calibrated at a concentration that differs by 1-3 orders of magnitude. Dosing of the electrolyte is carried out by passing VHF first through one of the parallel-connected calibration channels containing sparingly soluble salts and dialyzers, and then through an ion-exchange filter saturated by a controlled ion.

The calculation equation for calculating the electrolyte concentration has the following form:

C = 1000 κ / λ,

where κ is the electrical conductivity of the electrolyte solution (SEC), S / m,

λ is the equivalent electrical conductivity of the medium under the measurement conditions, Cm · m ² / g-eq;

λ = λ _K + λ _A ,

λ _K and λ _A - ultimate mobility (or equivalent electrical conductivity) of the cation and anion.

The relative error in determining the UEP by the conductometer-salimeter MARK-602 according to the passport data is 2%. In the data reference tables, for the values of the equivalent electrical conductivity of individual ions, at least three characters are given. Therefore, the relative error in determining X can be estimated at 1%. In this case, the expected relative error in determining the concentration is estimated at 3%.

To achieve the specified technical result and solve the problem, a device with a calibrated ionomer, an ion-exchange filter (IOF) of mixed action, a flow switch connected to calibration channels, some of which are filled with sparingly soluble salt, and a cation-exchange filter, a reference conductometer with two flow conductivity sensors and a PC, which is connected to a reference conductometer and calibrated ionomer, a second flow switch and an anion exchange filter, and dialyzers are additionally placed in two channels for calibration, with the first conductometric sensor located between the ion exchange filter and the first flow switch, the second flow switch connected to calibration channels, anion exchange and cation exchange filters saturated by the monitored ion, and the second conductometric sensor which is connected hydraulically to a calibrated ionomer sensor.

The presence in the device of channels in which the dialyzers are located extends the range of concentrations of controlled hydrogen ions, which increases the accuracy of pH meter calibration, since in the acidic region you can choose a pH value of about 5.5, and in the alkaline region, a pH value of about 8.5. The change in the concentration of hydrogen ions is 3 orders of magnitude. The presence of cation exchange and anion exchange filters saturated with a controlled ion in the device makes it possible to calibrate any type of ionomer: pH meter, pCl meter, pNa meter, etc.

The invention is illustrated by drawings, which depict:

figure 1 - schematic diagram of the calibration of the ionomer;

figure 2 - the dynamics of changes in the measured pH, reference pH _calculation and conductivity at the output of the calibration device flow analyzers pH high purity water (when the temperature of the water drift in the calibration conditions from 20.3 to 20.8 ° C and flow rate from 0.9 to 1.4 dm ³ / h). The average value of the measured pH is 9.37, the standard deviation is 0.01; the average value of the calculated pH is 9.11, the standard deviation is 0.02. 1, 2- pH; 3 - UEP; 1 - experiment, 2 - calculation;

figure 3 - the dynamics of changes in the measured pH, reference pH _calculation and conductivity at the output of the calibration device flow analyzers pH high purity water (when the drift of the temperature of the aqueous medium in the conditions of calibration from 21 to 24 ° and flow rate variation from 1.3 to 1 8 dm ³ / h). The average value of the measured pH is 9.25, the standard deviation is 0.04; the average value of the calculated pH is 9.26, the standard deviation is 0.02. 1, 2 - pH; 3 - UEP; 1 - experiment, 2 - calculation.

The proposed method is carried out in the following sequence. High purity water is prepared; for this, standard sample preparation devices and ion-exchange filters of mixed action are used. A reference medium is created by dosing in VHF electrolyte of various concentrations, differing by 1-3 orders of magnitude. For this, the VHF through the first sensor of the reference conductivity meter and the first flow switch is fed into the calibration channels containing sparingly soluble salts and dialyzers. The VHF stream dissolves sparingly soluble salts (BaSO ₄ , AgCl) or acetic acid (ammonia) in the channel. The resulting solution is then passed through a second flow switch through an anion exchange or cation exchange filter saturated with a controlled ion, and fed to the second sensor of the reference conductivity meter or fed directly to the second sensor, bypassing the IOF. After the second sensor of the conductometer, the resulting standard solution is supplied to the calibrated ionomer sensor hydraulically connected to it. Measure the temperature and electrical conductivity of the VHF and the reference solution with a reference automatic conductivity meter and the concentration of the ion with a calibrated ionomer. Using the measured values, a reference value of the ion concentration is calculated using a PC, according to which the calibration is carried out, the calculated value is compared with the measured one and the calculated value is set on the calibrated ionomer.

The proposed device contains a series-connected (from the input side of the analyzed water) mixed-ion filter 1, a flow switch 2, a calibration channel 3 filled with an insoluble salt of barium sulfate, a calibration channel 4 filled with an insoluble silver chloride salt, a calibration channel 5 containing a dialyzer made in the form of a silicone tube placed in acetic acid and a calibration channel 6 containing a dialyzer made in the form of a silicone tube placed in ammonia , a second flow switch 7, a cation exchange filter 8 and an anion exchange filter 9 saturated by the monitored ion, a reference conductometer 10 with the first 11 and second 12 flow conductivity sensors, respectively, a calibrated ionomer 13 with a flow sensor 14 and PC 15.

The device operates as follows. The analyzed water with a flow rate of 0.6-1.8 dm ³ / h sequentially enters the ion-exchange filter 1 of mixed action to obtain water of high purity. Then, through the first conductivity sensor 11 of the reference conductometer 10 and the flow switch 2, which has several (for example, four) fixed positions, the HFV enters one (depending on the type of calibrated ionomer) from channels 3, 4, 5 or 6, where it is dosed an electrolyte (e.g., barium sulfate, silver chloride, acetic acid, ammonia). Then, the solution through the second flow switch 7 enters the anion exchange filter 8 or the cation exchange filter 9 saturated by the monitored ion, or to the second conductivity sensor 12 of the reference conductivity meter 10 and then to the flow sensor 14 of the calibrated ionomer 13. Temperature, electrical conductivity and concentration measurements recorded through the digital outputs of the measuring instruments in the PC file 15. In accordance with the calculation equation calculates the reference value of the concentration of the calibrated ion with which m compared readings calibrated ionomer and, if necessary, corrected.

Example

Calibration under bench conditions of an EV-74 ionomer with an ESL-63-07 glass electrode and an EVL-1M3.1 silver-silver electrode in a standard cell with limited contact with the atmosphere through which the solution to be evaluated was carried out as follows. A number of pH _{measurements were} recorded in a PC file through the digital output of the device, showing and recording the “Technograph 160”. The reference pH _{calculation was} calculated based on the ratios indicated above, using reference data on the thermodynamic constants and properties of substances used in the ion generator circuit. A number of UEP values of the solution being measured, measured with a MARK-602 conductometer-salimeter, were also recorded in the PC file using the Technograph 160.

The steps for calibrating a pH meter with a channel containing barium sulfate and anion exchange resin AB-17 × 8hs in OH form are shown in FIG. 2 (before adjustment) and in FIG. 3 (after adjustment). The reference solution used to calculate the pH _calculation was a solution of Ba (OH) ₂ .

Other examples of calibrating the pH meter and pCl meter (chloride meter) and the results of measurements and calculations are shown in table 1.

Table 1 The results of a comparative assessment of the measurement error during calibration of the flow sensor of the pH and pCl measurement channel. Channel for ionomer calibration Dosage substance Calibrated Instrument Reference value pX ^* ΔpX standard deviation Sparingly soluble salt BaSO ₄ , then anion exchange resin pH meter 9.26 0.02 AgCl, then cation exchange resin pCl meter 5.95 0.09 AgCl, then cation exchange resin pCl meter 5.5 0.10 With dialyzer Acetic acid pH meter 5.51 0.01 Ammonia pH meter 8.69 0.008

^* pX = -lg [X]

These results indicate that the proposed method allows you to calibrate pH meters with an error of not more than 0.02 pH units, while the calibration method for buffer solutions is 0.05 pH units. The chloridomer can be calibrated to work with solutions containing chloride ion with a concentration of (40-110) μg / dm ³ and an absolute error of not more than 15 μg / dm ³ .

This method and device, in comparison with the known ones, allows more accurate calibration of ionomers with a flow sensor, which measure the concentration of ions in high-purity water under power unit conditions, due to the uniqueness of the composition of the created reference medium and accurate calculation of the concentration of the electrolyte containing the controlled ion.

Claims (4)

1. A method for calibrating ionomers with a flow sensor, including dosing an electrolyte of various concentrations, measuring the electrical conductivity and temperature, calculating the concentration of the ion being determined, comparing the calculated value with the measured one and setting the calculated concentration value on the calibrated ionomer, characterized in that the initial working medium is purified to water high purity and an electrolyte is dosed into it containing a controlled ion with concentrations differing by 1-3 orders of magnitude, for which water of high purity first let through a calibration channel containing a sparingly soluble salt or dialyzer, and then through an ion-exchange filter saturated with a controlled ion. 2. A device for calibrating ionomers with a flow sensor, containing a calibrated ionomer, a mixed-ion filter, a flow switch connected to parallel channels for calibration, some of which are filled with sparingly soluble salt, and a cation-exchange filter, characterized in that a reference conductometer is additionally introduced into it with two flow conductivity sensors and a PC, which is connected to a reference conductometer and calibrated ionomer, a second flow switch and anion-exchange phi two, and in the other two channels for calibration, dialyzers are additionally placed, with the first conductometric sensor located between the ion exchange filter and the first flow switch, the second flow switch connected to the calibration channels and through the anion exchange and cation exchange filters saturated with a controlled ion, with the second conductometric sensor, or directly with the second conductometric sensor, which is connected hydraulically to the sensor calibrated ionomer. 3. The device according to claim 2, characterized in that the channels contain barium sulfate and silver chloride as sparingly soluble salts. 4. The device according to claim 2, characterized in that the dialyzers are made in the form of a silicone tube placed in acetic acid or ammonia.

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