As part of the global efforts for renewable energy development, carbon dioxide solubility measurements were provided for the geothermal industry. Solubility is obtained at high pressures (6−40 MPa), in aqueous phases reproducing the exploited geothermal resources, through sodium chloride (NaCl) and calcium chloride (CaCl 2 ) synthetic brines (1.2 mol NaCl•kg H 2 O −1 and 0.2 mol CaCl 2 •kg H 2 O −1 ), at 333.15 and 453.15 K. Both mixed-salt and single-salt brines were analyzed to produce original results. A new stirred reactor, with variable volume, was conceived to maintain gas−liquid equilibria, while solubility measurements were performed by titration, with a relative uncertainty of 0.028. The experimental methods were validated with solubility analyses in pure water, at 333.15 K, and in sodium chloride and calcium chloride single-salt brines (1 mol•kg H 2 O −1 ), at 323.15 K. Then, 20 original data were obtained and compared to PHREEQC (pitzer.dat) calculation results. The measurements highlight that carbon dioxide solubility decreases when the aqueous phase salinity increases. This salting-out effect increases to about 23%, when observed in the analyzed mixed-salt brines at 333.15 K, and it is mostly caused by sodium chloride in these fluids. However, one can notice that calcium chloride in these brines promotes part of the phenomenon too.

The sequestration of carbon dioxide fumes from oxyfuel combustion is used to reduce significantly the carbon dioxide emissions from coal‐fired power plants. Impurities like nitric oxide, present in the fumes, can cause technical difficulties during the capture, the treatment, the transport, and the storage steps of the CO2 fumes. The purpose of this study is to better understand the oxidation of nitric oxide under pressure in the presence of carbon dioxide and in the experimental condition of flue gas treatment. This reaction is known to be a third‐order reaction, two order in nitric oxide and first order in oxygen. To examine the effect of the temperature, the pressure and the volume fraction of oxygen on the rate constant of oxidation, k1, an autoclave is used. The first experiment studies the influence of the temperature between 288 and 323 K. The results found are in the form of an Arrhenius‐type equation: k1 = 810 exp(620/T) and are in agreement with the literature. Carbon dioxide does not seem to have an influence on the rate constant, whereas our experimental measurements indicate an influence of the volume fraction of oxygen. The rate constant decreases when the oxygen volume fraction increases by up to 10%. Then the rate constant remains constant. This observation allows us to conclude that the mechanism involving the mechanism with a dimer of NO as an intermediate is more likely to be the mechanism involved in the nitric oxide oxidation in our experimental conditions: high pressure and ambient temperature. The rate constant k2, k–2, and k3 were also estimated in these conditions.

New experimental data for cosolubility of carbon dioxide, nitric oxide, and nitrogen dioxide produced from the reaction in situ between nitric oxide and dioxygen in pure water at 298.15 K and up to 3 MPa are presented in this work. These data are essential to develop and validate thermodynamic models for CO2 and other gases capture and storage processes. In this work, measurements of carbon and nitrogen oxide solubilities in water are achieved; the liquid phase composition at the thermodynamic equilibrium was determined by analytical methods (ion chromatography), pH-metric titration, and a static synthetic method, and the gaseous phase composition was determined by two infrared spectrometers. The experimental apparatus and the analytical procedure were validated by studying the CO2 + water systems and comparing the experimental measurements with the literature data. On the other hand, the measurements of NO2 + water systems are original and do not exist in the literature. In order to study the behavior of the nitrogen dioxide in water, a suitable reaction mechanism was carefully chosen to predict the composition of the different nitrogen species (NO, NO2, N2O3, N2O4, HNO2, H+, NO2 –, HNO3, and NO3 –.) in the aqueous medium at 298.15 K. Then, a Henry constant for the studied nitric oxide systems was calculated. Some difficulties have been encountered in the stabilization of the nitrogen dioxide partial pressure due to its metastable conditions; therefore, data related to the Henry constant of this compound will not be reported.

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