Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Estimation and Measurement for pH of High Pressure and High Temperature Sour Environments
Akihiro MIYASAKAKozo DENPOHiroyuki OGAWA
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1988 Volume 74 Issue 10 Pages 2033-2040

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Abstract

A new technique for estimating the pH of concentrated aqueous solutions in equilibrium with high pressure H2S and CO2 at elevated temperature was proposed. Based on the thermodynamic investigation for solution properties, the following equation was obtained.
pH=-logγH + {(K1, HKH, HPH2S2±H2S)1/2 + (K1, CKH, CPCO22±CO2)1/2}
The physico-chemical parameters in the equation were calculated by PBILC (Principle of Balance of Identical Like Charges) proposed by COBBLE et al. or assumed to be identical with those for HCl + NaCl aqueous solutions. The calculation of the pH of high temperature and high pressure sour environments was enabled by using this equation.
A Nb-doped TiO2 semiconductor electrode of n-type was well applied to measure the pH of the environments and underwent no interference with NaCl, H2S and CO2. The measured pH values agreed well with those estimated by the newly proposed technique at the temperature up to 473 K and at partial pressures of H2S and CO2 up to 4 MPa. It was ascertained by pH measurements for HCl + NaCl aqueous solutions at elevated temperatures that the assumption made for physicochemical parameters in the pH estimation was valid.

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© The Iron and Steel Institute of Japan
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