CN101470094B - Method for measuring pH value of high-temperature high-pressure water solution - Google Patents

Abstract

The invention relates to a method for measuring the pH value of high temperature high pressure water solution, belonging to the measurement technology of pH value, for resolving the pH value measurement problem on the high temperature high pressure water solution of unknown components and concentration. The measurement method comprises: (1) measuring the potential E1 of a pH sensor in a standard solution 1 relative to a reference electrode; (2) measuring the potential E2 of a pH sensor in a standard pollution 2 relative to a reference electrode; (3) measuring the potential Ex of a pH sensor in an object solution relative to a reference electrode; (4) according to E1, E2, Ex, converting the potential measured by pH sensor in high temperature water into pH value. The measurement method onlyneeds the potentials of temperature, pressure, concentration and pH sensors in solution, to obtain the pH value of an unknown solution at current temperature and pressure. The measurement method can be test the pH value of the water solution whose temperature range is 25 to 300DEG C and solution concentration is lower than 1.0mol/Kg.

Description

A kind of measuring method of pH value of high-temperature high-pressure water solution

Technical field

The present invention relates to the measuring technique of pH value, be specially a kind of measuring method of pH value of high-temperature high-pressure water solution.

Background technology

High-temperature high-pressure water solution is a kind of heat-exchange fluid the most frequently used in the current nuclear reactor, also is the main media of overcritical water-cooled reactor of future generation and supercritical water oxidation wastewater treatment.The variation of temperature and pressure (particularly when temperature and pressure all above critical value time) can cause a lot of character of the WS, like all change (Fig. 1) such as ionic products of density, dielectric properties and water.Because the pH value of high-temperature high-pressure water solution is in close relations with the corrosion of the equipment and materials of in this environment, being on active service, so measure that pH value of aqueous solution receives much concern under the HTHP.

For concentration and the known high-temperature high-pressure water solution of composition, its pH value can obtain through Theoretical Calculation, can calculate the common pH value of aqueous solution of HTHP below 350 ℃ like the business software of GE company.Yet for composition and the unknown high-temperature high-pressure water solution of concentration, the method for Theoretical Calculation is restricted, and can only try to achieve through measurement.Up to now, more accurate pH value of water solution measurement all is the method that adopts electrochemical potential to measure.Glass electrode (indicator electrode) is with respect to the current potential of contrast electrode in the solution in order to measure for the principle of the pH meter measuring chamber warm water solution pH value that the laboratory is commonly used, and the measurement system is that thermodynamics is reversible, and Nernst equation capable of using converts potential value into the pH value of solution.Pyrosol pH value research the earliest starts from the seventies in last century, and the researchist utilizes the hydrogen concentration cell, has tested the pH value of lean solution under the high temperature.People utilize Pd-H again afterwards ₂The pH value of electrode test pyrosol.Because these electrodes all require research system can not contain oxidizing substance simultaneously, thereby limitation is not bigger by hydrogen reducing.Last century the eighties, after utilizing principle that pottery can transmit oxonium ion to develop yttria-stabilized zirconia (YSZ) thin film sensor to emerge, this novel sensor is applied to during pyrosol pH measures very soon.Practice shows that the YSZ thin film sensor is more satisfactory pyrosol pH survey sensor, and the principle of the pH value of its test HTHP solution can be used following primary element model representation:

Pt|Hg (l) | HgO (s) | YSZ| solution | (0.1mol/Kg) NaCl|AgCl|Ag

The reaction that takes place on the YSZ pH sensor is:

Can know that based on corresponding Nernst equation there are following relation in the current potential of YSZ pH sensor and the pH value of solution:

$E_{\mathrm{YSZ}}=E_{\mathrm{Hg}/\mathrm{HgO}}^0-\frac{\left(2.303\mathrm{RT}\right)}{F}\mathrm{pH}-\frac{\left(2.303\mathrm{RT}\right)}{2F}\log {\mathrm{\α}}_{H_{2}O}---\left(1\right)$

E wherein _YSZBe the absolute potential of YSZ pH sensor, E ⁰ _Hg/HgOBe the standard electrode potential (being the standard electrode potential of YSZ pH sensor) of Hg/HgO, R is the calibrating gas constant, and T is an absolute temperature, and F is Faraday constant (96485C), α _H2OBe the activity of water in the solution, pH is the pH value of solution.

E _YSZCan't measure, and its potential value E with respect to the Ag/AgCl contrast electrode can measure.Different with the normal temperature pH meter is, in the HTHP measurement system of reality, the electroactive element (Ag/AgCl) of Ag/AgCl contrast electrode places room temperature, and the high-temperature part of this active element and system links to each other through isothermal salt bridge not, causes hydrothermal solution to connect the existence of current potential.Also there is the isothermal liquid junction potential between reference solution (0.1mol/Kg NaCl) and solution to be measured simultaneously.The existence of these two kinds of current potentials makes that the potential value E that measures is non-equilibrium current potential, and high temperature pH measurement system is discontented with sufficient thermodynamics reversal condition, need proofread and correct (formula 2).

Updating formula 2 is developed by formula 1 and comes (the document that sees reference [1] D.S.Seneviratne; V.G.Papangelakis; X.Y.Zhou; At250 ℃ of relevant to of S.N.Lvov.Potentiometric pH measurements in acidic sulfate solutions pressure leaching.Hydrometallurgy, 2003,68,131-139):

${\mathrm{pH}}_1-{\mathrm{pH}}_2=-\mathrm{\α}\frac{(E_1-E_2)}{\frac{2.303\mathrm{RT}}{F}}-\frac{1}{2}\log \[\frac{{\mathrm{\α}}_{H2O}^1}{{\mathrm{\α}}_{H2O}^2}\]+\frac{(E_{d,1}-E_{d,2})}{\frac{2.303\mathrm{RT}}{F}}---\left(2\right)$

α is a correction coefficient in the formula, pH ₁For the pH value of standard solution 1, pH ₂For the pH value of standard solution 2, E ₁Be YSZ pH sensor measurement potential value with respect to the Ag/AgCl contrast electrode in standard solution 1, E ₂Be YSZ pH sensor measurement potential value with respect to the Ag/AgCl contrast electrode in standard solution 2, α ¹ _H2OBe the activity of water in the standard solution 1, α ² _H2OBe the activity of water in the standard solution 2, E _{D, 1}Be the isothermal liquid junction potential between standard solution 1 and the reference solution, E _{D, 2}Be the isothermal liquid junction potential between standard solution 2 and the reference solution.Because temperature, pressure, flow velocity and the reference solution of solution are constant when measuring, the hydrothermal solution in standard solution 1 and the standard solution 2 connects current potential and equates, so does not have hydrothermal solution to connect current potential in the formula 2.

At first select two groups of standard solution that concentration is different of composition of the same race in the trimming process, the pH value of calculating this two standard sets solution is (to the HCl-NaCl system with formula 3; To the NaOH-NaCl system with formula 4), water activity (formula 5) and isothermal liquid junction potential (formula 6), measure in the two standard sets solution YSZ pH sensor then respectively with respect to the potential value E of Ag/AgCl contrast electrode ₁And E ₂, at last aforementioned calculation result and measured value substitution formula 2 can be calculated correction coefficient alpha.

$\mathrm{pH}=-\log \[\frac{m_{\mathrm{HCl}}}{1-\frac{K_{\mathrm{HCl}}}{2K_{\mathrm{NaCl}}}\×(1-\sqrt{1+4K_{\mathrm{NaCl}}{{\mathrm{\γ}}^2}_{\±}{m}_{\mathrm{NaCl}}})}\]---\left(3\right)$

$\mathrm{pH}=-\log \frac{K_W}{\[\frac{m_{\mathrm{NaOH}}}{1-\frac{K_{\mathrm{NaOH}}}{2K_{\mathrm{NaCl}}}(1-\sqrt{1+4K_{\mathrm{NaCl}}{m}_{\mathrm{NaCl}}{\mathrm{\γ}}_{\±}^2})}\]{\mathrm{\γ}}_{\±}^2}---\left(4\right)$

$\ln {\mathrm{\α}}_{H2O}=-\frac{m_{\mathrm{tot}}{M}_W}{1000}\×$

$\{1-\frac{{Z_i}^2{A}_m}{B_m^3{a}^3{\left(\sqrt{I_m}\right)}^3}\[(1+B_{m}a\sqrt{I_m})-2\ln (1+B_{m}a\sqrt{I_m})-{(1+B_{m}a\sqrt{I_m})}^{-1}\]+\frac{1000}{m_{\mathrm{tot}}{M}_W}\lg (1+\frac{m_{\mathrm{tot}}{M}_W}{1000})\}---\left(5\right)$

$-E_d=\underset{i}{\mathrm{\Σ}}\frac{\mathrm{RT}}{{\mathrm{FZ}}_i}{\∫}_A^B{t}_{i}d\ln {\mathrm{\α}}_i---\left(6\right)$

After obtaining correction coefficient alpha, the relation of the current potential of solution and pH value is reduced to formula 7 (referring to document [1]):

${\mathrm{pH}}_x-p{H}_s=\mathrm{\α}\frac{E_x-E_s}{\frac{\mathrm{RT}}{F}\ln 10}---\left(7\right)$

PH wherein _xBe the pH value of unknown solution, pH _sBe the pH value of standard solution, E _xBe YSZ pH sensor measurement potential value with respect to the Ag/AgCl contrast electrode in unknown solution, E _sBe YSZ pH sensor measurement potential value with respect to the Ag/AgCl contrast electrode in standard solution.

In sum, under measuring HTHP, in the process of unknown solution pH value, relate to a large amount of numerous and diverse calculation of thermodynamics (like formula 2-7), need carry out accurate data computing and processing.

Document [2]: Chinese invention patent (patent No.: ZL02132544.8, Granted publication CN1216288C) discloses a kind of bypass supercritical water well-oxygenated environment pH value on-line testing method and specialized equipment thereof.It adopts the bypass working method, and a kind of standard solution is injected electrochemical cell through pH value sensor, and reference solution injects electrochemical cell through contrast electrode, records the current potential E of pH value sensor with respect to contrast electrode ₁Another kind of standard solution is injected electrochemical cell through pH value sensor, use with quadrat method and inject reference solution, record the current potential E of pH value sensor with respect to contrast electrode ₂Stopping criterion solution injects, and test solution is injected electrochemical cell; Constantly inject reference solution, gather pH value sensor simultaneously at the current potential E of test solution environment with respect to contrast electrode to contrast electrode _TestGet E ₁, E ₂, E _TestData get the pH of test solution by high temperature fluid pH value computing formula _TestValue.It is to test environment is noiseless, pollution-free, measuring accuracy is high, operating temperature range is wide.For improving the work efficiency of the YSZ pH sensor of developing early stage (document [2]); Realize the measurement quick and precisely of unknown solution pH value under the HTHP; Need a kind of pH value of high-temperature high-pressure water solution measuring method of exploitation, convenient, fast, the potential value with YSZ pH sensor measurement in the high-temperature high-pressure water solution converts the pH value into exactly.

Summary of the invention

The object of the present invention is to provide a kind of measuring method of pH value of high-temperature high-pressure water solution, convert the potential value of pH sensor measurement in the high-temperature water into the pH value, solve for the problems such as pH value measurement of composition with the high-temperature high-pressure water solution of concentration the unknown.

Technical scheme of the present invention is:

A kind of measuring method of pH value of high-temperature high-pressure water solution, operation as follows:

(1) standard solution 1:0.01mol/Kg NaOH+0.1mol/Kg NaCl is pumped in the autoclave; Flow velocity is 0.1-10ml/min; In temperature T=25 ℃-300 ℃ when being any pressure that is higher than more than the water saturation vapour pressure with pressure P, measuring pH sensor current potential with respect to contrast electrode in this solution is E ₁

(2) standard solution 2:0.1mol/Kg NaOH+0.1mol/Kg NaCl is pumped in the autoclave; Flow velocity is 0.1-10ml/min; In temperature T=25 ℃-300 ℃ when being any pressure that is higher than more than the water saturation vapour pressure with pressure P, measuring pH sensor current potential with respect to contrast electrode in this solution is E ₂

(3) solution to be measured is pumped in the autoclave, flow velocity is 0.1-10ml/min, and temperature T=25 ℃-300 ℃ and pressure are when being higher than the above any pressure of water saturation vapour pressure, to measure pH sensor current potential E with respect to contrast electrode in solution _x

(4) according to above-mentioned E ₁, E ₂, E _x, convert the potential value of pH sensor measurement in the high-temperature water into the pH value.

The measuring method of described pH value of high-temperature high-pressure water solution, to convert the process of pH value into following for the potential value of pH sensor measurement in the high-temperature water:

At first, input temp T, pressure P, choice criteria solution is imported two groups of concentration M then ₁And M ₂Standard solution, calculate under this temperature T and the pressure P, the density of two standard sets solution, association constant, specific inductive capacity, activity coefficient, water activity and pH value, main formulas for calculating respectively as follows:

(1) when temperature T, pressure P, the computing formula of density p:

$v(\mathrm{\π},\mathrm{\τ})\frac{P}{\mathrm{RT}}=\mathrm{\π}{\mathrm{\γ}}_{\mathrm{\π}}$

${\mathrm{\γ}}_{\mathrm{\π}}=\underset{i=1}{\overset{34}{\mathrm{\Σ}}}-n_i{I}_i{(7.1-\mathrm{\π})}^{I_i-1}{(\mathrm{\τ}-1.222)}^{J_i}$

Wherein $\mathrm{\ρ}=\frac{1}{v(\mathrm{\π},t)},$ π=P/P ^*, τ=T ^*/ T P ^*=16.53MPa, T ^*=1386K, γ _πThe derivant of expression dimensionless Gibbs free energy, R is calibrating gas constant 8.314J/Kmol

(2) association constant computing formula:

$\lg K_{\mathrm{NaCl}}=\mathrm{\ρ}(13.384-49.322\tilde{T})+{\mathrm{\ρ}}^2(-69.643+119.11\tilde{T})+{\mathrm{\ρ}}^3(19.292-61.348\tilde{T})$

$+(-27.161+42.031\tilde{T}-50.1231g\tilde{T})\left[\exp (-19.814\mathrm{\ρ}\tilde{T})-1\right]3.798+29.019\tilde{T}$

$+0.53671g\tilde{T}+\lg (83.144\mathrm{\ρ}/\tilde{T})$

$\lg K_{\mathrm{HCl}}=\mathrm{\ρ}(255.63-192.62\tilde{T})+{\mathrm{\ρ}}^2(-385.8+295\tilde{T})+{\mathrm{\ρ}}^3(162.46-135.2\tilde{T})$

$+42.16[\exp \left(-31.202\mathrm{\ρ}\tilde{T}\right)-1]+1.652+35.6\tilde{T}-0.2211g\tilde{T}-1.744$

$\lg K_{\mathrm{NaOH}}=\mathrm{\ρ}(148.07-106.94\tilde{T})+{\mathrm{\ρ}}^2(-149.28+96.13\tilde{T})+{\mathrm{\ρ}}^3(49.65-25.43\tilde{T})$

$+40.06[\exp (-29.051\mathrm{\ρ}\tilde{T})-1]-4.817+34.700\tilde{T}-0.2351g\tilde{T}+\lg (83.144\mathrm{\ρ}/\tilde{T})$

Wherein, K _NaCl, K _HCl, K _NaOHRepresent NaCl, HCl and NaOH association constant respectively; ρ is the density of water, the g/cm of unit ³, $\tilde{T}={10}^3/T,$ Here T is an absolute temperature, unit K;

(3) activity coefficient γ _iComputing formula:

The 3rd correction formula according to Debye-Hu&4&eckel limiting law:

${\mathrm{lg\γ}}_i=-\frac{A_m\sqrt{I_m}}{1+\stackrel{0}{B_{m}a\sqrt{I_m}}}+C{I}_m-\lg (1+\frac{m_{\mathrm{tot}}{M}_W}{1000})$

$A_m=\frac{1}{2.303}{\left(2\mathrm{\πL\ρ}\right)}^{\frac{1}{2}}{\left(\frac{e^2}{4\mathrm{\π}{\mathrm{\ϵ}}_0\mathrm{\ϵkT}}\right)}^{\frac{3}{2}}$

$B_m={\left(\frac{2\mathrm{\ρ}{e}^{2}L}{{\mathrm{\ϵ}}_0\mathrm{\ϵkT}}\right)}^{\frac{1}{2}}$

K-Boltzmann constant

ε ₀-permittivity of vacuum

The specific inductive capacity of ε-water

L-avogadros constant

The density of ρ-water

The electric weight of e-unit charge

m _TotThe molality sum of all solutes in the-solution

M _WThe molal weight of-water, the g/mol of unit

Know the density p and the DIELECTRIC CONSTANTS of water, can obtain A _mAnd B _m, C can use following experimental formula:

C＝1.06×10 ^-3×(T-298.15)-7.64×10 ^-6×(T-298.15) ²

Here T is an absolute temperature, unit K;

I _mBe ionic strength, $I_m=\frac{1}{2}\mathrm{\Σ}{m}_i{Z_i}^2,$ Z in the formula _iBe the valence mumber of ion i, m _iBe molality;

(4) pH value computing formula in the HCl-NaCl solution:

$\left[H^{+}\right]=\frac{m_{\mathrm{HCl}}}{1-\frac{K_{\mathrm{HCl}}}{2K_{\mathrm{NaCl}}}\×(1-\sqrt{1+4K_{\mathrm{NaCl}}{{\mathrm{\γ}}^2}_{\±}{m}_{\mathrm{NaCl}}})}$

PH value of solution=-log [H ⁺] γ _±, K wherein _HCl, K _NaClBe respectively the association constant of HCl and NaCl, m _HCl, m _NaClBe respectively the molality of HCl and NaCl, γ _±Be mean activity coefficient of ions;

Next, saturated solution density, solution viscosity, ion molar conductivity and two standard sets solution and the isothermal liquid junction potential E of reference solution under this temperature T and pressure P during accounting temperature T _{D, 1}And E _{D, 2}, main formulas for calculating is distinguished as follows:

(5) saturated liquid density p ₀

ρ ₀＝ρ _c(1+b ₁τ ^1/3+b ₂τ ^2/3+b ₃τ ^5/3+b ₄τ ^16/3+b ₅τ ^43/3+b ₆τ ^110/3)

In the following formula, $\mathrm{\τ}=1-\frac{T}{T_c},$ T _c=647.096K, ρ _c=322Kg/m ³

(6) computing formula of isothermal liquid junction potential

$-E_d=\underset{i}{\mathrm{\Σ}}\frac{\mathrm{RT}}{{\mathrm{FZ}}_i}{\∫}_A^B{t}_{i}d\ln {\mathrm{\α}}_i$

Wherein, E _dRepresent the isothermal liquid junction potential, A, B represent to connect mutually two phases on boundary, and A representes the reference solution phase among this paper: 0.1mol/Kg NaCl, B represent test solution phase: NaOH+NaCl, or HCl+NaCl, Z _iBe the valence mumber of ion i, t _iBe the transport number of ion i, α _iBe the activity coefficient of ion i, T representes the absolute temperature of solution, unit K; R is calibrating gas constant 8.314J/Kmol, and F is Faraday constant 96485C;

Obtain standard solution pH value and liquid junction potential according to aforementioned calculation, and the potential value E that the pH sensor records in the two standard sets solution under input temp T and the pressure P ₁And E ₂, can calculate correction coefficient alpha, computing formula is following:

${\mathrm{pH}}_1-{\mathrm{pH}}_2=-\mathrm{\α}\frac{(E_1-E_2)}{\frac{2.303\mathrm{RT}}{F}}-\frac{1}{2}\log \[\frac{{\mathrm{\α}}_{H2O}^1}{{\mathrm{\α}}_{H2O}^2}\]+\frac{(E_{d,1}-E_{d,2})}{\frac{2.303\mathrm{RT}}{F}}$

Wherein, pH ₁, pH ₂Be the pH value of two standard sets solution, E ₁, E ₂The potential value that records for pH sensor in the two standard sets solution, Be the water activity of two standard sets solution, E _{D, 1}, E _{D, 2}Represent the isothermal liquid junction potential between two standard sets solution and reference solution respectively, R is calibrating gas constant 8.314J/Kmol, and F is Faraday constant 96485C;

At last; The pH value of input standard solution and measurement current potential, and import under this temperature T and the pressure P measurement current potential Ex of pH sensor in the unknown solution to be measured, calculate the pH value of unknown solution to be measured; Export the pH value back of unknown solution to be measured and finish, computing formula is following:

${\mathrm{pH}}_x-p{H}_s=\mathrm{\α}\frac{E_x-E_s}{\frac{\mathrm{RT}}{F}\ln 10}$

Wherein

PH _xThe pH value of-unknown solution

PH _sThe pH value of-standard solution

E _xMeasurement potential value in the-unknown solution, the v of unit

E _sMeasurement potential value in the-standard solution, the v of unit

α-correction coefficient

R-calibrating gas constant 8.314J/Kmol

F-Faraday constant 96485C

T-absolute temperature, unit are K.

The measuring method of described pH value of high-temperature high-pressure water solution; After obtaining pH value of solution value to be measured; With the result of calculation contrast of result and Theoretical Calculation result and the commercial pH meter calculation of GE software, the pH value of confirmatory measurement and Theoretical Calculation result and commercial pH meter are calculated computed in software basically identical property as a result.

The invention has the beneficial effects as follows:

1, the invention provides a kind of can be with high-temperature high-pressure water solution (temperature range: 25 ℃-300 ℃; Pressure limit: greater than the water saturation vapour pressure; Solution concentration 1.0mol/Kg) in the potential value of YSZ pH sensor measurement convert the method for pH value into.Its major function is:

(1) can realize the calculating of the thermodynamic parameters such as density, viscosity, specific inductive capacity, mean activity coefficient, pH value, water activity and liquid junction potential of standard solution under known temperature and pressure;

(2) can proofread and correct the nonreversibility of YSZ pH sensor measurement;

(3) can be quickly and easily convert the potential value of pH sensor measurement in the high-temperature high-pressure water solution into the pH value;

(4) can carry out function and expand, the pH that carries out the supercritical water scope measures.

2, the present invention places the backstage to carry out a large amount of numerous and diverse calculation of thermodynamics; The user only needs parameters such as input temp, pressure, concentration just can obtain the thermodynamic data of standard solution under this temperature and pressure quickly and accurately, and the potential value that can conveniently YSZ pH sensor under the high-temperature high-pressure water solution be recorded converts the pH value of solution into.

3, the present invention is easy to use, and the user only needs input temp, pressure, concentration and the potential value of YSZ pH sensor in solution, just can obtain the pH value of unknown solution to be measured under Current Temperatures and pressure.

4, but the present invention's satisfied temperature scope is 25 ℃-300 ℃, and pressure limit is to be higher than the above any pressure (the pressure preferable range is 0.1-30MPa) of water saturation vapour pressure, and solution concentration is less than the testing requirement of the pH value of high-temperature high-pressure water solution of 1.0mol/Kg.And through expanding thermodynamic parameter, the pH that can carry out the supercritical water scope measures.

Description of drawings:

The density of water and ionic product are with variation of temperature figure under Fig. 1 constant pressure of the present invention.

Fig. 2 Software Operation surface chart of the present invention.

The measurement process flow diagram of Fig. 3 software of the present invention.

The NaOH of 150 ℃ of Fig. 4 the present invention, three kinds of concentration of 7MPa and NaCl mixed solution pH value.

Fig. 5 is the measurement mechanism structural representation of pH value of the present invention.

Among Fig. 5,1, the YSZpH sensor; 2, YSZpH sensor solution inlet; 3, contrast electrode; 4, reference solution inlet; 5, solution main-inlet; 6, taphole; 7, heating system; 8, cooling system.

Embodiment:

Embodiment 1

150 ℃, the NaOH of three kinds of concentration of 7MPa and the test of NaCl mixed solution pH value

1, standard solution 1 (0.01mol/KgNaOH+0.1mol/KgNaCl) pumps in the autoclave, and flow velocity is 1ml/min, and when temperature T=150 ℃ and pressure P=7MPa, measuring YSZ pH sensor current potential with respect to contrast electrode in this solution is E ₁=-0.03876v;

2, standard solution 2 (0.1mol/Kg NaOH+0.1mol/Kg NaCl) pumps in the autoclave, and flow velocity is 1ml/min, and when temperature T=150 ℃ and pressure P=7MPa, measuring YSZ pH sensor current potential with respect to contrast electrode in this solution is E ₂=-0.04775v;

3, with three kinds of solution to be measured (0.02mol/Kg NaOH+0.1mol/Kg NaCl; 0.08mol/KgNaOH+0.1mol/Kg NaCl; 0.3mol/Kg NaOH+0.1mol/Kg NaCl) (for making the pH measurement result unknown solution to be measured of imaginary three kinds of alkalescence of comparing with the commercial pH computed in software of Theoretical Calculation result and GE result) pumps in the autoclave successively; Flow velocity is 1ml/min; When temperature T=150 ℃ and pressure P=7MPa, measure YSZ pH sensor current potential E with respect to contrast electrode in solution respectively _1x=-0.04444v, E _2x=-0.04692v, E _3x=-0.04831v;

4, with temperature T=150 ℃; Pressure P=7MPa; The concentration value Input Software (Fig. 2) of standard solution 1 (0.01mol/Kg NaOH+0.1mol/Kg NaCl) and standard solution 2 (0.1mol/Kg NaOH+0.1mol/Kg NaCl) by calculating 1 key, obtains the pH value pH of standard solution ₁=9.44, pH ₂=10.42, water activity α ¹ _H2O=0.997, α ² _H2O=0.995;

5, the concentration 0.1mol/Kg of input reference solution by calculating 1 key, obtains liquid junction potential E again _{D, 1}=2.29mv, E _{D, 2}=14.5mv;

6, the potential value E that YSZ pH sensor records in two kinds of standard solution of input ₁And E ₂,, obtain correction coefficient alpha=-7.74 by calculating 2 keys;

7, import the potential value Ex that YSZ pH sensor records in the solution to be measured respectively, obtain three kinds of solution at 150 ℃, the pH during 7MPa is respectively 9.96,10.19 and 10.32.The result of calculation contrast of result and Theoretical Calculation result and the commercial pH meter calculation of GE software is shown that the pH value of measurement and Theoretical Calculation result and commercial pH meter are calculated computed in software basically identical (Fig. 4) as a result.

Embodiment 2

230 ℃, 28MPa, the test of 0.01mol/Kg HCl+0.1mol/Kg NaCl pH value of solution value

1, standard solution 1 (0.001mol/Kg HCl+0.1mol/Kg NaCl) pumps in the autoclave, and flow velocity is 1ml/min, and when temperature T=230 ℃ and pressure P=28MPa, measuring YSZ pH sensor current potential with respect to contrast electrode in this solution is E ₁=0.186v;

2, standard solution 2 (0.1mol/Kg HCl+0.1mol/Kg NaCl) pumps in the autoclave, and flow velocity is 1ml/min, and when temperature T=230 ℃ and pressure P=28MPa, measuring YSZ pH sensor current potential with respect to contrast electrode in this solution is E ₂=0.311v;

3, solution 0.01mol/Kg HCl+0.1mol/Kg NaCl to be measured (for making the pH measurement result unknown solution to be measured of imaginary acidity of comparing with the commercial pH computed in software of Theoretical Calculation result and GE result) pumps in the autoclave; Flow velocity is 1ml/min; When temperature T=230 ℃ and pressure P=28MPa, measure YSZ pH sensor current potential E with respect to contrast electrode in this solution _x=0.245v;

4, with temperature T=230 ℃, pressure P=28MPa, standard solution 1 (0.001mol/Kg HCl+0.1mol/Kg NaCl) and standard solution 2 (0.1mol/Kg HCl+0.1mol/Kg NaCl) Input Software (Fig. 2) by calculating 1 key, obtain the pH value of standard solution, pH ₁=3.21, pH ₂=1.26, water activity α ¹ _H2O=0.998, α ² _H2O=0.995;

5, the concentration 0.1mol/Kg of input reference solution by calculating 1 key, obtains liquid junction potential E again _{D, 1}=-0.217mv, E _{D, 2}=-13.2mv;

6, YSZ pH sensor records in two kinds of standard solution of input potential value E1 and E2 press the 2# calculation key, obtain correction coefficient alpha=1.46;

7, the potential value Ex that YSZ pH sensor records in the input solution to be measured obtains this solution at 230 ℃, the pH=2.22 during 28MPa.This result and Theoretical Calculation result contrast demonstration, the pH value of measurement and Theoretical Calculation result identical better (table 1).

The pH value of 230 ℃ of 28MPa0.01mol/KgHCl+0.1mol/KgNaCl solution of table 1

As shown in Figure 3, the measurement flow process of this software is:

At first, input temp T (unit K or ℃), pressure P (units MPa or psi), choice criteria solution is imported two groups of concentration M then ₁And M ₂(unit: standard solution mol/Kg), calculate under this temperature T and the pressure P: the density of two standard sets solution, association constant, specific inductive capacity, activity coefficient, water activity (α ¹ _H2OAnd α ² _H2O) and pH value (pH ₁And pH ₂), main formulas for calculating is following

1. when temperature T, pressure P, the computing formula of density p:

$v(\mathrm{\π},\mathrm{\τ})\frac{P}{\mathrm{RT}}=\mathrm{\π}{\mathrm{\γ}}_{\mathrm{\π}}---\left(8\right)$

${\mathrm{\γ}}_{\mathrm{\π}}=\underset{i=1}{\overset{34}{\mathrm{\Σ}}}-n_i{I}_i{(7.1-\mathrm{\π})}^{I_i-1}{(\mathrm{\τ}-1.222)}^{J_i}---\left(9\right)$

Wherein $\mathrm{\ρ}=\frac{1}{v(\mathrm{\π},t)},$ π=P/P ^*, τ=T ^*/ T P ^*=16.53MPa, T ^*=1386K, γ _πThe derivant of expression dimensionless Gibbs free energy), R is calibrating gas constant 8.314J/Kmol.n _i, I _i, J _iBe known number, can table look-up (document that sees reference [3] The Intemational Association for the Properties of Water andSteam.Lucerne, Switzerland.August2007).

2.NaCl, HCl and NaOH association constant computing formula:

$\lg K_{\mathrm{NaCl}}=\mathrm{\ρ}(13.384-49.322\tilde{T})+{\mathrm{\ρ}}^2(-69.643+119.11\tilde{T})+{\mathrm{\ρ}}^3(19.292-61.348\tilde{T})$

$+(-27.161+42.031\tilde{T}-50.1231g\tilde{T})[\exp (-19.814\mathrm{\ρ}\tilde{T})-1]-3.798+29.019\tilde{T}---\left(10\right)$

$+0.53671g\tilde{T}+\lg (83.144\mathrm{\ρ}/\tilde{T})$

$\lg K_{\mathrm{HCl}}=\mathrm{\ρ}(255.63-192.62\tilde{T})+{\mathrm{\ρ}}^2(-385.8+295\tilde{T})+{\mathrm{\ρ}}^3(162.46-135.2\tilde{T})$

(11)

$+42.16[\exp \left(-31.202\mathrm{\ρ}\tilde{T}\right)-1]+1.652+35.6\tilde{T}-0.2211g\tilde{T}-1.744$

$\lg K_{\mathrm{NaOH}}=\mathrm{\ρ}(148.07-106.94\tilde{T})+{\mathrm{\ρ}}^2(-149.28+96.13\tilde{T})+{\mathrm{\ρ}}^3(49.65-25.43T+40.06$

$[\exp (-29.051\mathrm{\ρ}\tilde{T})-1]-4.817+34.700\tilde{T}-0.2351g\tilde{T}+\lg (83.144\mathrm{\ρ}/\tilde{T})---\left(12\right)$

Wherein, K _NaCl, K _HCl, K _NaOHRepresent NaCl, HCl and NaOH association constant respectively, ρ is the density of water, the g/cm of unit ³, $\tilde{T}={10}^3/T$ (T is a kelvin degree here, unit K).

3. activity coefficient γ _iComputing formula:

The 3rd correction formula according to your limiting law of debye-shock:

${\mathrm{lg\γ}}_i=-\frac{A_m\sqrt{I_m}}{1+\stackrel{0}{B_{m}a\sqrt{I_m}}}+C{I}_m-\lg (1+\frac{m_{\mathrm{tot}}{M}_W}{1000})---\left(13\right)$

$A_m=\frac{1}{2.303}{\left(2\mathrm{\πL\ρ}\right)}^{\frac{1}{2}}{\left(\frac{e^2}{4\mathrm{\π}{\mathrm{\ϵ}}_0\mathrm{\ϵkT}}\right)}^{\frac{3}{2}}---\left(14\right)$

$B_m={\left(\frac{2\mathrm{\ρ}{e}^{2}L}{{\mathrm{\ϵ}}_0\mathrm{\ϵkT}}\right)}^{\frac{1}{2}}---\left(15\right)$

K-Boltzmann constant

ε ₀-permittivity of vacuum

The specific inductive capacity of ε-water

L-avogadros constant

The density of ρ-water

The electric weight of e-unit charge

m _TotThe molality sum of all solutes in the-expression solution

M _WThe molal weight of-expression water, the g/mol of unit

Know the density p and the DIELECTRIC CONSTANTS of water, can obtain A _mAnd B _m, C can use following experimental formula:

C＝1.06×10 ^-3×(T-298.15)-7.64×10 ^-6×(T-298.15) ² (16)

Here T is an absolute temperature, and unit is K;

I _mBe ionic strength, $I_m=\frac{1}{2}\mathrm{\Σ}{m}_i{Z_i}^2,$ Z in the formula _iBe the valence mumber of ion i, m _iBe molality.

4.HCl-NaCl pH value computing formula in the solution

$\left[H^{+}\right]=\frac{m_{\mathrm{HCl}}}{1-\frac{K_{\mathrm{HCl}}}{2K_{\mathrm{NaCl}}}\×(1-\sqrt{1+4K_{\mathrm{NaCl}}{{\mathrm{\γ}}^2}_{\±}{m}_{\mathrm{NaCl}}})}---\left(17\right)$

PH value of solution=-log [H ⁺] γ _±

Wherein, K _HCl, K _NaClBe respectively the association constant of HCl and NaCl, m _HCl, m _NaClBe respectively the molality of HCl and NaCl, γ _±Be mean activity coefficient of ions.

Next, saturated liquid density, solution viscosity, ion molar conductivity during accounting temperature T, and then calculate two standard sets solution and the isothermal liquid junction potential E of reference solution under this temperature T and pressure P _{D, 1}And E _{D, 2}, main formulas for calculating is distinguished as follows:

(1) saturated liquid density p ₀

ρ ₀＝ρ _c(1+b ₁τ ^1/3+b ₂τ ^2/3+b ₃τ ^5/3+b ₄τ ^16/3+b ₅τ ^43/3+b ₆T ^110/3) (18)

In the following formula $\mathrm{\τ}=1-\frac{T}{T_c},$ T _c=647.096K, ρ _c=322Kg/m ³, b1-b6 is a coefficient, and the document [4] that specifically sees reference (The International Association for the Properties of Water and Steam.St.Petersburg, Russia.Steptember1992)

(2) calculating of isothermal liquid junction potential

$-E_d=\underset{i}{\mathrm{\Σ}}\frac{\mathrm{RT}}{{\mathrm{FZ}}_i}{\∫}_A^B{t}_{i}d\ln {\mathrm{\α}}_i---\left(19\right)$

Wherein, E _dRepresent the isothermal liquid junction potential, A, B represent to connect mutually two phases on boundary, and A representes reference solution phase (0.1mol/Kg NaCl) among this paper, and B representes test solution phase (NaOH+NaCl, or HCl+NaCl), Z _iBe the charge number of ion i, t _iBe the transport number of ion i, α _iBe the activity coefficient of ion i, T representes the absolute temperature (unit K) of solution, and R is calibrating gas constant (8.314J/Kmol), and F is Faraday constant (96485C).

According to top standard solution pH value and the liquid junction potential of calculating, the potential value E that YSZ pH sensor records in the two standard sets solution under input temp T and the pressure P ₁And E ₂, calculate correction coefficient alpha.Computing formula is seen formula 2.

At last, input standard solution pH value and measure current potential is imported under this temperature T and the pressure P measurement current potential Ex of YSZ pH sensor in the unknown solution to be measured, calculates the pH value of unknown solution to be measured, the pH value end afterwards of exporting unknown solution to be measured.Computing formula is seen formula 7.

The main program statement of The whole calculations process is following:

(1) asks density program statement under known temperature and the pressure

Private?Sub?Commandl_Click()

DimT#

DimP#

Dim?N(34)As?Double

Dim?I(34)As?Double

Dim?J(34)AsDouble

Dim?Y(34)AsDouble

Dim?sum#

DimV#

Dimd#

N(1)＝0.14632971213167

N(2)＝-0.84548187169114

N(3)＝-3.756360367204

N(4)＝3.3855169168385

N(5)＝-0.95791963387872

N(6)＝0.15772038513228

N(7)＝-0.016616417199501

N(8)＝8.1214622983568E-04

N(9)＝2.8319080123804E-04

N(10)＝-6.0706301565874E-04

N(11)＝-0.018990068218419

N(12)＝-0.032529748770505

N(13)＝-0.021841717175414

N(14)＝-5.283835796993E-05

N(15)＝-4.7184321073267E-04

N(16)＝-3.0001780793026E-04

N(17)＝4.7661393906987E-05

N(18)＝-4.4141845330846E-06

N(19)＝-7.2694996297594E-16

N(20)＝-3.1679644845054E-05

N(21)＝-2.8270797985312E-06

N(22)＝-8.5205128120103E-10

N(23)＝-2.2425281908E-06

N(24)＝-6.5171222895601E-07

N(25)＝-1.4341729937924E-13

N(26)＝-4.0516996860117E-07

N(27)＝-1.2734301741641E-09

N(28)＝-1.7424871230634E-10

N(29)＝-6.8762131295531E-19

N(30)＝1.4478307828521E-20

N(31)＝2.6335781662795E-23

N(32)＝-1.1947622640071E-23

N(33)＝1.8228094581404E-24

N(34)＝-9.3537087292458E-26

I(1)＝0

I(2)＝0

I(3)＝0

I(4)＝0

I(5)＝0

I(6)＝0

I(7)＝0

I(8)＝0

I(9)＝1

I(10)＝1

I(11)＝1

I(12)＝1

I(13)＝1

I(14)＝1

I(15)＝2

I(16)＝2

I(17)＝2

I(18)＝2

I(19)＝2

I(20)＝3

I(21)＝3

I(22)＝3

I(23)＝4

I(24)＝4

I(25)＝4

I(26)＝5

I(27)＝8

I(28)＝8

I(29)＝21

I(30)＝23

I(31)＝29

I(32)＝30

I(33)＝31

I(34)＝32

J(1)＝-2

J(2)＝-1

J(3)＝0

J(4)＝1

J(5)＝2

J(6)＝3

J(7)＝4

J(8)＝5

J(9)＝-9

J(10)＝-7

J(11)＝-1

J(12)＝0

J(13)＝1

J(14)＝3

J(15)＝-3

J(16)＝0

J(17)＝1

J(18)＝3

J(19)＝17

J(20)＝-4

J(21)＝0

J(22)＝6

J(23)＝-5

J(24)＝-2

J(25)＝10

J(26)＝-8

J(27)＝-11

J(28)＝-6

J(29)＝-29

J(30)＝-31

J(31)＝-38

J(32)＝-39

J(33)＝-40

J(34)＝-41

T#＝Val(Text1.Text)

P#＝Val(Text2.Text)

sum＝0#

For?k＝1To34

Y(k)＝-N(k)*I(k)*((7.1-P/16.53)^(I(k)-1))*((1386/T)-1.222)^J(k)sum＝sum+Y(k)

Nextk

V＝(0.46151805*10^3)*T*sum/(16.53*10^6)

d＝1/V/1000

Text3.Text＝d

End?Sub

(2) ask the association constant of HCl, NaCl, NaOH under known temperature and the density

Private?Sub?Commandl_Click()

DimT# ' temperature

Dimd# ' density

The association constant of Dim K1# ' HCl

The association constant of Dim K2# ' NaCl

The association constant of Dim K3#NaOH

T#＝Val(Text1.Text)

d#＝Val(Text2.Text)

KI#＝10^(d*(255.63-192.62*1000/T)_

+(d^2)*(-385.8+295#*1000/T)+(d^3)*(162.46-135.2*1000/T)_

+42.16*(Exp(-31.202*d*1000/T)-1)_

+35.6*1000/T-(0.221*Log(1000/T)/Log(10))_

+1.652-1.744)

The association constant of ' HCl is calculated

K2#＝10^(d*(13.384-49.322*1000/T)_

+(d^2)*(-69.643+119.11*1000/T)_

+(d^3)*(19.292-61.348*1000/T)_

+(-27.161+42.031*1000/T-50.123*Log(1000/T)/Log(10))_

*(Exp(-19.814*d*1000/T)-1)_

-3.798+29.019*1000/T_

+(0.5367*Log(1000/T)/Log(10))_

+Log(83.144*d*T/1000)/Log(10))

The association constant of ' NaCl is calculated

K3#＝10^(d*(148.07-106.94*1000/T)_

+(d^2)*(-149.28+96.13*1000/T)_

+(d^3)*(49.65-25.43*1000/T)_

+40.06*(Exp(-29.051*d*1000/T)-1)_

-4.817+34.7*1000/T-(0.2351*Log(1000/T)/Log(10))_

+Log(83.144*d*T/1000)/Log(10))

The association constant of ' NaOH is calculated

Text3.Text＝K1

Text4.Text＝K2

Text5.Text＝K3

End?Sub

As shown in Figure 5, the measurement mechanism structure of pH value of the present invention is following:

YSZ pH sensor 1, contrast electrode 3 are installed respectively on the measurement mechanism main body, and YSZ pH sensor 1 links to each other with external electric chemical measurement instrument through its lead-in wire with contrast electrode 3.On the measurement mechanism main body, be provided with solution main-inlet 5, on each electrode, be provided with corresponding solution inlet (YSZpH sensor solution inlet 2 and reference solution inlet 4) simultaneously.Test solution gets into from solution main-inlet 5 and YSZpH sensor solution inlet 2, and reference solution gets into from reference solution inlet 4, and solution is regulated through the back pressure mediation valve, flows out from taphole 6.Peripheral hardware heating system on measurement mechanism main body and each electrode (with heating system 7 expressions), equal peripheral hardware cooling system on each electrode (with cooling system 8 expressions).

The measurement mechanism of above-mentioned pH value mainly is that after the corresponding pH value that calculates, the concrete course of work of its potential measurement is following through the potential value in the measurement solution:

(1) design temperature and pressure;

(2) pump into test solution from YSZpH sensor solution inlet 2 with solution main-inlet 5 with constant flow rate (0.1ml/min-10ml/min is adjustable continuously); When treating that system pressure reaches setting value; Pump into reference solution with constant flow rate (0.1ml/min-10ml/min is adjustable continuously) from reference solution inlet 4, solution flows out from taphole 6 after the backpressure regulation valve regulation;

(3) open 7 pairs of system heating of heating system;

(4) open chilled water simultaneously, utilize cooling system 8 cooling electrodes, guarantee that contrast electrode 3 and YSZpH sensor 1 are in room temperature away from an end of measurement mechanism main body;

(5) after temperature and pressure all reached setting value, (unit v) with respect to the potential value E of contrast electrode 3 to measure YSZ pH sensor 1;

(6) measure end.

Claims (3)

1. the measuring method of a pH value of high-temperature high-pressure water solution is characterized in that, as follows operation:

(1) standard solution 1:0.01mol/Kg NaOH+0.1mol/Kg NaCl is pumped in the autoclave; Flow velocity is 0.1-10ml/min; In temperature T=25 ℃-300 ℃ when being any pressure that is higher than more than the water saturation vapour pressure with pressure P, measuring pH sensor current potential with respect to contrast electrode in this solution is E ₁

(2) standard solution 2:0.1mol/KgNaOH+0.1mol/KgNaCl is pumped in the autoclave; Flow velocity is 0.1-10ml/min; In temperature T=25 ℃-300 ℃ when being any pressure that is higher than more than the water saturation vapour pressure with pressure P, measuring pH sensor current potential with respect to contrast electrode in this solution is E ₂

(3) solution to be measured is pumped in the autoclave, flow velocity is 0.1-10ml/min, and temperature T=25 ℃-300 ℃ and pressure are when being higher than the above any pressure of water saturation vapour pressure, to measure pH sensor current potential E with respect to contrast electrode in solution _x

(4) according to above-mentioned E ₁, E ₂, E _x, convert the potential value of pH sensor measurement in the high-temperature water into the pH value;

Said pH sensor is a yttria-stabilized zirconia pH sensor.

2. according to the measuring method of the described pH value of high-temperature high-pressure water solution of claim 1, it is characterized in that to convert the process of pH value into following for the potential value of pH sensor measurement in the high-temperature water:

At first, input temp T, pressure P, choice criteria solution is imported two groups of concentration M then ₁And M ₂Standard solution, calculate under this temperature T and the pressure P, the density of two standard sets solution, association constant, specific inductive capacity, activity coefficient, water activity and pH value, main formulas for calculating respectively as follows:

(1) when temperature T, pressure P, the computing formula of density p:

$v(\mathrm{\π},\mathrm{\τ})\frac{P}{\mathrm{RT}}={\mathrm{\π\γ}}_{\mathrm{\π}}$

${\mathrm{\γ}}_{\mathrm{\π}}=\underset{i=1}{\overset{34}{\mathrm{\Σ}}}-n_i{I}_i{(7.1-\mathrm{\π})}^{I_i-1}{(\mathrm{\τ}-1.222)}^{J_i}$

Wherein

π=P/P ^*, τ=T ^*/ T P ^*=16.53MPa, T ^*=1386K, γ _πThe derivant of expression dimensionless Gibbs free energy, R is calibrating gas constant 8.314J/Kmol

(2) association constant computing formula:

$\lg K_{\mathrm{NaOH}}=\mathrm{\ρ}(148.07-106.94\tilde{T})+{\mathrm{\ρ}}^2(-149.28+96.13\tilde{T})+{\mathrm{\ρ}}^3(49.65-25.43\tilde{T})$

$+40.06[\exp (-29.051\mathrm{\ρ}\tilde{T})-1]-4.817+34.700\tilde{T}-0.2351g\tilde{T}+\lg (83.144\mathrm{\ρ}/\tilde{T})$

Wherein, K _NaCl, K _HCl, K _NaOHRepresent NaCl, HCl and NaOH association constant respectively; ρ is the density of water, the g/cm of unit ³, Here T is an absolute temperature, unit K;

(3) activity coefficient γ _iComputing formula:

The 3rd correction formula according to Debye-Hu&4&eckel limiting law:

$\lg {\mathrm{\γ}}_i=-\frac{A_m\sqrt{I_m}}{1+B_{m}a\sqrt{I_m}}+{\mathrm{CI}}_m-\lg (1+\frac{m_{\mathrm{tot}}{M}_W}{1000})$

$A_m=\frac{1}{2.303}{\left(2\mathrm{\πL\ρ}\right)}^{\frac{1}{2}}{\left(\frac{e^2}{4\mathrm{\π}{\mathrm{\ϵ}}_0\mathrm{\ϵkT}}\right)}^{\frac{3}{2}}$

$B_m={\left(\frac{2\mathrm{\ρ}{e}^{2}L}{{\mathrm{\ϵ}}_0\mathrm{\ϵkT}}\right)}^{\frac{1}{2}}$

The k-Boltzmann constant

ε ₀-permittivity of vacuum

The specific inductive capacity of ε-water

The L-avogadros constant

The density of ρ-water

The electric weight of e-unit charge

m _TotThe molality sum of all solutes in the-solution

M _WThe molal weight of-water, the g/mol of unit

Know the density p and the DIELECTRIC CONSTANTS of water, can obtain A _mAnd B _m, C can use following experimental formula:

C＝1.06×10 ^-3×(T-298.15)-7.64×10 ^-6×(T-298.15) ²

Here T is an absolute temperature, unit K;

I _mBe ionic strength,

Z in the formula _iBe the valence mumber of ion i, m _iBe molality;

(4) pH value computing formula in the HCl-NaCl solution:

$\left[H^{+}\right]=\frac{m_{\mathrm{HCl}}}{1-\frac{K_{\mathrm{HCl}}}{2K_{\mathrm{NaCl}}}\×(1-\sqrt{1+4K_{\mathrm{NaCl}}{{\mathrm{\γ}}^2}_{\±}{m}_{\mathrm{NaCl}}})}$

PH value of solution=-log [H ⁺] γ _±, K wherein _HCl, K _NaClBe respectively the association constant of HCl and NaCl, m _HCl, m _NaClBe respectively the molality of HCl and NaCl, γ _±Be mean activity coefficient of ions;

Next, saturated solution density, solution viscosity, ion molar conductivity and two standard sets solution and the isothermal liquid junction potential E of reference solution under this temperature T and pressure P during accounting temperature T _{D, 1}And E _{D, 2}, main formulas for calculating is distinguished as follows:

(5) saturated liquid density p ₀

ρ ₀＝ρ _c(1+b ₁τ ^1/3+b ₂τ ^2/3+b ₃τ ^5/3+b ₄τ ^16/3+b ₅τ ^43/3+b ₆τ ^110/3)

In the following formula,

T _c=647.096K, ρ _c=322Kg/m ³

(6) computing formula of isothermal liquid junction potential

$-E_d=\underset{i}{\mathrm{\Σ}}\frac{\mathrm{RT}}{{\mathrm{FZ}}_i}{\∫}_A^B{t}_{i}d\ln {\mathrm{\α}}_i$

Wherein, E _dRepresent the isothermal liquid junction potential, A, B represent to connect mutually two phases on boundary, and A representes reference solution phase: 0.1mol/KgNaCl among this paper, and B representes test solution phase: NaOH+NaCl, or HCl+NaCl, Z _iBe the valence mumber of ion i, t _iBe the transport number of ion i, α _iBe the activity coefficient of ion i, T representes the absolute temperature of solution, unit K; R is calibrating gas constant 8.314J/Kmol, and F is Faraday constant 96485C;

Obtain standard solution pH value and liquid junction potential according to aforementioned calculation, and the potential value E that the pH sensor records in the two standard sets solution under input temp T and the pressure P ₁And E ₂, can calculate correction coefficient alpha, computing formula is following:

${\mathrm{pH}}_1-{\mathrm{pH}}_2=-\mathrm{\α}\frac{(E_1-E_2)}{\frac{2.303\mathrm{RT}}{F}}-\frac{1}{2}\log \left[\frac{{\mathrm{\α}}_{H2O}^1}{{\mathrm{\α}}_{H2O}^2}\right]+\frac{(E_{d,1}-E_{d,2})}{\frac{2.303\mathrm{RT}}{F}}$

Wherein, pH ₁, pH ₂Be the pH value of two standard sets solution, E ₁, E ₂The potential value that records for pH sensor in the two standard sets solution,

Be the water activity of two standard sets solution, E _{D, 1}, E _D.2Represent the isothermal liquid junction potential between two standard sets solution and reference solution respectively, R is calibrating gas constant 8.314J/Kmol, and F is Faraday constant 96485C;

At last; The pH value of input standard solution and measurement current potential, and import under this temperature T and the pressure P measurement current potential Ex of pH sensor in the unknown solution to be measured, calculate the pH value of unknown solution to be measured; Export the pH value back of unknown solution to be measured and finish, computing formula is following:

${\mathrm{pH}}_x-{\mathrm{pH}}_s=\mathrm{\α}\frac{E_x-E_s}{\frac{\mathrm{RT}}{F}\ln 10}$

Wherein

PH _xThe pH value of-unknown solution

PH _sThe pH value of-standard solution

E _xMeasurement potential value in the-unknown solution, the v of unit

E _sMeasurement potential value in the-standard solution, the v of unit

α-correction coefficient

R-calibrating gas constant 8.314J/Kmol

F-Faraday constant 96485C

T-absolute temperature, unit are K.

3. according to the measuring method of the described pH value of high-temperature high-pressure water solution of claim 2; It is characterized in that; After obtaining pH value of solution value to be measured; With the result of calculation contrast of result and Theoretical Calculation result and the commercial pH meter calculation of GE software, the pH value of confirmatory measurement and Theoretical Calculation result and commercial pH meter are calculated computed in software basically identical property as a result.

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