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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)...

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...

International audience; The last few years have seen the proliferation of anaerobic digestion plants to produce biomethane. Oxygen (O2) traces added to biogas during the desulfurization process are co-injected in the gas network and can be stored in Underground Gas Storage (UGS). However, there are no data available for the undesirable effects of O2 on these anoxic environments, especially on deep aquifers. In addition to mineral alteration, O2 can have an impact on the anaerobic autochthonous microbial life. In our study, the storage conditions of an UGS aquifer were reproduced in a high-pressure reactor and bio-geo-chemical interactions between the aqueous, gas and solid phases were studied. Sulfate was depleted from the liquid phase for three consecutive times during the first 130 days of incubation reproducing the storage conditions (36 °C, 60 bar, methane with 1% CO2). Sulfate-reducers, such as Desulfovibrionaceae, were identified from the high-pressure system. Simulations with PHREEQC were used to determine the thermodynamic equilibrium to confirm any gas consumption. CO2 quantities decreased in the gas phase, suggesting its use as carbon source by microbial life. Benzene and toluene, hydrocarbons found in traces and known to be biodegradable in storages, were monitored and a decrease of toluene was revealed and associated to the Peptococcaceae family. Afterwards, O2 was added as 1% of the gas phase, corresponding to the maximum quantity found in biomethane after desulfurization process. Re-oxidation of sulfide to sulfate was observed along with the end of sulfate reducing activity and toluene biodegradation and the disappearance of most of the community. H2 surprisingly appeared and accumulated as soon as hydrogenotrophic sulfate-reducers decreased. H2 would be produced via the necromass fermentation accomplished by microorganisms able to resist the oxic conditions of 4.42·10-4 mol.Kgw-1 of O2. The solid phase composed essentially of quartz, presented no remarkable changes.

Geothermal energy has been a subject of great interest since the 1990s in the Upper Rhine Graben (URG), where the first European Enhanced Geothermal System (EGS) pilot site has been developed, in Soultz-sous-Forêts (SsF), France. Several studies have already been conducted on scales occurring at the reinjection side at the geothermal plants located in the URG. It has been observed that the composition of the scales changes as chemical treatment is applied to inhibit metal sulfate. The purpose of this study was to model the scaling phenomenon occurring in the surface pipes and the heat exchangers at the SsF geothermal plant. PhreeqC, a geochemical modelling software, was used to reproduce the scaling observations in the geothermal plant during exploitation. A suitable database was chosen based on the availability of chemical elements, minerals, and gas. A thermodynamic model and a kinetic model were proposed for modelling the scaling phenomenon. The thermodynamic model gave insight on possible minerals precipitated while the kinetic model, after modifying the initial rates equation, produced results that were close to the expected scale composition at the SsF geothermal plant. Additional laboratory studies on the kinetics of the scales are proposed to complement the current model.

International audience; Experimental CO2 solubility data in brine at high temperatures and pressures are important for CO2 capture and storage (CCS) applications. Many data have been acquired in single-salt aqueous solutions such as NaCl, CaCl2, and Na2SO4. CO2 solubility data in aqueous solutions containing MgCl2 are extremely scarce. In this work, new experimental data of CO2 solubility in MgCl2 solutions were acquired. Thirty-three experimental points of CO2 solubility have been reported in an original range of pressure (1.5 to 20 MPa), temperature (323.15, 373.15, and 423.15 K), and salinity (1, 3, and 5 mol/kg). Measurements were made using the potentiometric titration method. Results show that the CO2 solubility increases with the evolution of pressure and decreases with the evolution of MgCl2 concentrations. A discussion about the salting-out effect on MgCl2 solutions is made, and a comparison is proposed on the same effect in aqueous systems containing calcium chloride.

International audience; This article contributes to the development of a thermodynamic model for simulating CO2 solubility in pure water and aqueous brines under different conditions of temperature, pressure and ionic strength. The modeling activity-fugacity (γ-φ) approach allows calculating CO2 solubility, based on the Pitzer electrolyte theory for activity coefficient and Peng-Robinson's equation of state for fugacity. The present work proposes a new set of Pitzer interaction parameters through the set of CO2 solubility data in saline systems such as CO2-H2O-NaCl and CO2-H2O-Na2SO4. The determined model is capable of covering a wide T − P − I range (273.15–473.15 K, 0.1–40 MPa and 0–6 mol/kg). Average absolute deviation of CO2 solubility is about 5% compared to a large number of experimental data available (more than 700 data analyzed). New experimental solubility data for the CO2-H2O-NaCl-Na2SO4 system were also acquired in this study (303.15–423.15 K, 1.5–20 MPa and 0–6 mol/kg) to test the model's capacity: it is able to describe the CO2 solubility in aqueous salt mixtures without any further optimizations of interaction parameters.

International audience; Around the world, several dozen deep sedimentary aquifers are being used for storage of natural gas. Ad hoc studies of the microbial ecology of some of them have suggested that sulfate reducing and methanogenic microorganisms play a key role in how these aquifers' communities function. Here, we investigate the influence of gas storage on these two metabolic groups by using high-throughput sequencing and show the importance of sulfate-reducing Desulfotomaculum and a new monophyletic methanogenic group. Aquifer microbial diversity was significantly related to the geological level. The distance to the stored natural gas affects the ratio of sulfate-reducing Firmicutes to deltaproteobacteria. In only one aquifer, the methanogenic archaea dominate the sulfate-reducers. This aquifer was used to store town gas (containing at least 50% H2 ) around 50 years ago. The observed decrease of sulfates in this aquifer could be related to stimulation of subsurface sulfate-reducers. These results suggest that the composition of the microbial communities is impacted by decades old transient gas storage activity. The tremendous stability of these gas-impacted deep subsurface microbial ecosystems suggests that in situ biotic methanation projects in geological reservoirs may be sustainable over time.

International audience; A large part of Li production comes from the exploitation of saline lakes and salars. Industrial processes for Li recovery from such resources have to deal with highly saline waters. It is therefore necessary to develop the knowledge of Li chemistry adapted to these contexts. The present work aims to present a new set of Pitzer interaction parameters able to describe the chemical behavior of the H-Li-Na-K-Ca-Mg-Cl-H2O system up to salt solubility, at 25 °C. In a previous work, the model was limited to the H-Li-Na-K-Cl-H2O system. It is extended here by including Ca and Mg, taking into account recently revised parameters allowing the thermal properties of the binary CaCl2-H2O and MgCl2-H2O systems to be represented. The consistent extension of the thermodynamic database was made possible by the study of the binary CaCl2-H2O system up to the supersaturated metastable region and of nine ternary systems, namely X-Ca-Cl, X-Mg-Cl and Ca-Mg-Cl (where X = H, Li, Na, K). The model was finally tested on five quaternary systems.

International audience; The composition of the captured CO 2 mixture may considerably vary both qualitatively and quantitatively depending on the sources, the selected technologies for purification... Many other compounds could be co-captured at various concentration levels and their potential co-storage along with CO 2 could be considered. Since these compounds may change the behavior of the CO 2 rich mixture, operators of the whole CCTS chain therefore wait for Jerome Corvisier et al. / Energy Procedia 114 (2017) 3322-3334 3323 clear recommendations in terms of admissible concentration levels for the various co-injected impurities while regulators need tools allowing them to formulate these recommendations. The SIGARRR project aims at conducting precise geochemical simulations to model the long-term behavior of co-injected gases within CO 2 storage sites based on a combination of experimental and numerical approaches, to ensure the reliability of numerical simulations. Within this context and the recent improvements in both processes and geochemical codes, this paper presents the water solubility precise calculations for CO 2 and most of the potential impurities N 2 , O 2 , Ar, CO, H 2 S, SO 2 , CH 4 , H 2 and the brine solubility relatively accurate geochemical simulations for CO 2 , N 2 , O 2 and CH 4 as well.

Compared to conventional extractive techniques, bacterial assisted leaching, also called “biomining” is an eco-friendly technology that provides improved metal/solid separations. These separations are enhanced by the synergistic activities of astonishingly diverse groups of microorganisms, which lead to an extraction process with low energy consumption, low capital investment and low impact on the environment. Recently, biomining has received great attention in a variety of niche areas, especially in the mineral industries and solid industrial waste materials (e.g. galvanic sludge, sewage sludge, fly ash, electronic waste, spent petrochemical catalysts, medical waste, spent batteries, waste slag) where the metals values are low, or where the presence of certain elements would lead to smelter damage, or where environmental considerations favor biological treatments options. It allows the recovery of metal from low-grade sulfide ores and concentrates that cannot be processed economically by conventional techniques, as well as the production of concentrated metal salt solutions, which could be recycled. Bacterial assisted leaching processes are based on the ability of certain microorganisms to solubilize/or expose the metals contained in the ores and concentrates by direct oxidation, or through indirect chemical oxidation instigated by the corrosive metabolic by-products generated by an electrochemical option, or a combination of both of these. The valuable metals in solution can be recovered using conventional hydrometallurgical techniques. If the material of interest constitutes part of or is in the pre-treated residue then it can be further processed for metal recovery. The majority of microorganisms involved in bacterial assisted leaching processes are chemolithotrophs. Carbon dioxide (CO 2 ) and oxygen (O 2 ) are essential nutrients that are used by microorganisms for their growth, maintenance, metabolite production, and survival. This literature review aims to provide a fundamental understanding of the various mechanisms involved in microbial leaching of sulfide minerals and provide a brief look at the various factors affecting this process. Special attention is focused on the mass transfer rates in the gas phase and how they exert a pivotal role in microbially assisted leaching of sulfide minerals. Also reviewed are the major parameters that can affect gas phase mass transfer, with particular emphasis on how it is related to the efficiency of bacterial assisted leaching.

Summary The study of the phase equilibria of CO2 in aqueous solutions containing electrolytes is extremely relevant for several areas such as environment, oil and water production, or geothermal energy. With regard to the environment, CO2 capture and storage (CCS) in deep saline aquifers has been widely studied, as a strong potential for mitigating the global imbalance linked to greenhouse gas emissions. CO2 storage in deep aquifers is seen as the most promising geological storage techniques due to the large quantity and spreading of the reservoirs worldwide.

Summary As part of the global efforts for renewable energies development, CO₂ 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 NaCl and CaCl₂ synthetic brines (1.2 mol NaCl/kg H₂O and 0.2 mol CaCl₂/kg H₂O), at 333.15 and 453.15 K. This work is encouraged by the lack of literature measurements on CO₂ solubility at these experimental conditions. Both mixed-salts and single-salt brines are analysed for the production of original results. A new stirred reactor, with variable volume, was conceived to maintain gas-liquid equilibria, while solubility measurements were performed by titration. The experimental methods were validated with measures in pure water, at 333.15 K, as well as in NaCl and CaCl₂ single-salt brines (1 mol.kg H₂O), at 323.15 K. Then, twenty original measures were produced with their uncertainty, and compared to Phreeqc (Pitzer.dat) calculation results. The measurements highlight that CO₂ solubility decreases when the aqueous phase salinity increases. Finally, a discussion is proposed to determine if this salting-out effect is influenced mostly by the NaCl or the CaCl₂, when observed in the mixed-salts brines at 333.15 K.

International audience; The geological storage of carbon dioxide CO2 in deep saline aquifers hasbeen gaining interest to reduce greenhouse gas emissions. Thus, the number of studiesfocusing on the solubility of CO2 in brines at high temperature and high pressure hasbeen increasing in the last decades, but information remains scarce particularly at highsalt molality. In this work, an analytical method was developed for experimentalmeasurement of CO2 solubility in sodium sulfate (Na2SO4) solutions (1 and 2 mol/kg)at high pressures (1.5−20 MPa) and temperatures (303.15, 323.15, 373.15, and 423.15K). Forty-eight experimental points of CO2 solubility are reported here. Solubility hasbeen shown to increase with pressure evolution and decrease with temperature andNa2SO4 concentrations evolution. A discussion is proposed about the salting-out effectin Na2SO4 solutions, and a comparison is made with the same effect in aqueous systemscontaining sodium chloride (NaCl) and calcium chloride (CaCl2).

International audience; Experimental CO 2 solubility data in brine at high pressures and high temperatures are needed in different technologies such as carbon dioxide storage or geothermal process. A lot of data have been acquired in single-salt solutions, whereas data for mixed-salt solutions remain scarce. In this study, new carbon dioxide solubility data in salt solutions have been measured. Two synthetic brines have been studied at 323, 373, and 423 K from 1 to 20 MPa. The brine 1 is composed of a mixture of NaCl and CaCl 2 and the brine 2 is made from a mixture of NaCl, CaCl 2 , and KCl. Measurements have been carried out by conductimetric titration. In this study, 6 isotherms presenting 48 new solubility data have been reported. These results have been obtained in an original range of temperature, pressure, and salinity. In these conditions of temperature and pressure, we verified that an increase of the temperature or the salinity involves a decrease of the CO 2 solubility. On the other hand, an increase of the pressure implies an increase of the CO 2 solubility. Then, the obtained results were compared with the values calculated using PhreeSCALE and PSUCO2 models. The comparison between experimental and calculated values revealed a good agreement.

A new production process to obtain magnesium-enriched salt from natural mineral water is described. The main purpose of this study was to develop a reproducible process for the production of salt of known and fixed compositions without the addition of chemicals. The first step involved the prediction of the evaporite sequence from the studied spring water composition. This simulation was accomplished with a numerical model previously developed by our team. From the theoretical evaporite sequence of the salt water, the specifications of the pilot could then be established and analytical devices were chosen: chromatographic modules for measuring concentrations and an electronic densimeter to monitor the density of the solution. Later, the experimental study of these tools was performed: operating principle, protocol, repeatability. Finally, the new experimental laboratory scale apparatus was validated.

International audience

The performance of a heat-driven vapor absorption chiller with various alkane mixtures as working pairs was studied. A Thermodynamic analysis showed that under specified operating conditions and with a generator temperature below 130 °C, temperature achievable with a simple flat plate collector when solar energy is expected as the driving heat source, the application of some of the proposed alkane mixtures is not feasible. Simulations using ASPEN Plus flow sheeting program are then done with the selected working pairs. All simulations were done specifying the Peng-Robinson equation of state as the property method. A parametric study was carried out allowing the investigation of the generator temperature effect on the system performance and the comparison between performances released with each working pair. Results revealed that a water-cooled absorption machine using the C3H8/n-C9H20 pair as working fluid releases the best performances from a heat driving temperature level of about 100 °C.

International audience; This paper is concerned with the analysis and the simulation of a heat-driven absorption-diffusion cooling machine which can operate with low-grade heat sources. The simplified configuration of the heat-powered absorption-diffusion refrigerating machine considered in this study is based on the Platen-Munters single pressure refrigerators principle [Platen B.C.V. and Munters C.G. (1928) Refrigerator, US Patent 1, 685-764J. Three working fluids are used, nonane as an absorbent, propane as a refrigerant and hydrogen as the inert auxiliary gas. The designed cooling capacity of the machine is 1 kW which is suitable for a domestic use for refrigeration purposes. We restricted the maximum temperature of the driving heat supplied to the generator to 130 °C, a temperature achievable with evacuated-tube solar collectors. The simulations are carried out using a commercially available flow sheeting software with the PengRobinson equation of state as property prediction method. In this paper, we analyze the heat and mass transfer characteristics in all relevant machine components (absorber, condenser, generator and solution heat exchangers). The simulations results allow determining the values of different parameters of the systems such as the refrigerant and the solvent temperatures in various points of the machine, the liquid and the vapor flow rates and compositions. The system performances were parametrically analyzed using the flow sheeting software. Performance characteristics were determined for a wide range of operating conditions allowing investigating and evaluating the effect of various design parameters.

ACL; International audience; In the framework of the efforts of the scientific community developed for the reduction of CO2 emissions, the geological storage of CO2 in deep saline aquifers is under focus. An increase of salinity decreases the potential of CO2 solubilization into the water. In salty waters, the salinity is not only due to NaCl but also to others ions and in particular Ca and Mg. Experimental solubility data of CO2 in calcium chloride solution available in the literature at conditions relevant to carbon storage are particularly scarce. In this work, a new analytical method was developed for experimental measurement of CO2 solubility in calcium chloride solutions (1, 3, and 6 mol/kg) at high pressures (5-20 MPa) and temperatures (323.15, 373.15, and 423.15 K). This method is based on conductometric titration coupled with classical pH titration. The conductimetry shows sharper curves than the pH titration allowing a higher precision. Thirty-six new experimental data are reported in this paper. These data presented an experimental average uncertainty of 2.1% with the ANOVA calculation method based on repeatability and reproducibility experiments. The CO2 solubility in CaCl2 solutions is noticeable lower than in NaCl solution increasing the salting out effect. Considering our previous work on NaCl solutions and this paper for CaCl2 solutions, estimations of the real quantity of CO2 that may be dissolved in saline aquifers can be made with a significantly better precision.

New experimental solubility data for carbon dioxide in pure water and in aqueous solution containing sodium hydroxide in the temperature range (293.15 to 393.15) K and pressures up to 5 MPa are presented in this work. A new experimental apparatus based on an equilibrium cell with a constant volume allowing the measurement of carbon dioxide solubility is presented. The liquid phase composition at the thermodynamic equilibrium is determined by an analytical method (ion chromatography) and a static synthetic method. The CO2 + water system is used to validate the experimental apparatus; therefore data obtained are compared with literature data.

The aim of this work is to investigate the field of gasification of aqueous biomass in supercritical water. In order to achieve this analysis, a mathematical model (based on thermodynamical equilibrium assumption) is built. This model allows not only the computation of the solid, liquid and gas phases produced in a process composed of a gasification reactor and a separator unit, but also the computation of the energy requirements or yields in these specific units. The composition of these three phases is computed in terms of fractions of CH 4 , H 2 , H 2 O, CO, CO 2 , H 2 S, NH 3 , C 6 H 5 OH, CH 3 COOH, CH 3 CHO, C (s) and minerals. The model also predicts the lower heating value of the gas leaving the process. The main problem that is encountered in the derivation of this mathematical model is the estimation of the activities of the chemical species present in the mixture as well as the enthalpy of this mixture. In this work, these evaluations are performed using Peng–Robinson equation of state. Results of the model are presented in the frame of gasification of vinasse, which is an aqueous residue from the alcohol production industry. It is shown that some specific conditions exist where it is not necessary to yield energy to the reactor to convert the incoming biomass into a gas for which the lower heating value can reach 5 MJ/kg with a gasification efficiency of 85%.

The aim of this work is to give insights into the gasification of aqueous biomass in supercritical water. More precisely, a mathematical model based on the thermodynamical equilibrium assumption is derived in this study. This model allows the computation of the solid, liquid and gas phases produced in a process composed of a gasification reactor and a separator. The composition of these three phases is computed in terms of fractions of CH4, H2, H2O, CO, CO2, H2S, NH3, C6H5OH, CH3COOH, CH3CHO, C(s) and minerals. In the reactor, this composition is computed according to the derivation of balance equations on atoms and to the derivation of equations translating chemical equilibrium between species. Because of the specific conditions prevailing in this device (above the critical point of pure water), the computation of the activity of chemical species in the reacting media is performed using Peng–Robinson equation of state. The modelling of the separator is performed using mass balances as well as equations translating physical equilibrium of species between liquid and gaseous phases. The numerical predictions of this mathematical model are compared to experimental results obtained in the case of gasification of methanol and glucose in supercritical water. The gasification of sewage sludge is also investigated in this study.

The occurrence of sulfur deposits in natural gas transmission facilities has recently been observed. Only modeling approaches of this subject are available and suggest desublimation of sulfur as the mechanism responsible for the deposit. Quantification of the sulfur deposit is the first step to an experimental study of the phenomenon. The solid present on polluted pieces is recovered by solving it in a toluene bath. Thus, experimental data concerning sulfur solubility in toluene are necessary for the deposit quantification. The analytical method developed in this work is based on the chemical reaction between elemental sulfur and triphenylphosphine to produce triphenylphosphine sulfide. Gas chromatography (GC) coupled with a flame photometric detector (FPD) in phosphorus mode allows sulfur quantification indirectly. This analysis method is used for determining the solubility of sulfur in toluene under atmospheric pressure and temperature ranging from (267.15 to 313.15) K.

Hydrogenation experiments of 2-butyne-1,4-diol, catalysed by carbon-supported palladium, have been performed in a batch reactor using high pressurised carbon dioxide as reaction solvent. Carbon dioxide pressure was kept to a constant value of 18 MPa. The influence of the hydrogen pressure, varying from 0.2 to 0.8 MPa, on the conversion rate was investigated. Under these conditions, the reactive media is monophasic. Finally, we fitted our experimental results with a simple reaction kinetic model.

Due to increasingly strict environmental constraints, a new class of secondary refrigerants is needed. The use of ice slurries as secondary refrigerants is a very promising technology. In order to design cold distribution plants efficiently, one must know how to predict the thermodynamic properties of the mixtures. Existing models are based on correlations with numerous parameters. The aim of this study is to establish consistent thermodynamic models that require a minimum of parameters in order to determine the composition and the enthalpy of ice slurries. A model based on excess Gibbs energy is proposed. Comparisons between experimental and calculated values confirm the capacity of the model to describe simultaneously the phase behavior and the enthalpy of the ice slurry with the same set of parameters.

In a previous work [P. Cezac, J.-P. Serin, J. Mercadier, G. Mouton, Modelling solubility of solid sulphur in natural gas, Chem. Eng. J. 133 (1–3) (2007) 283–291], we established a model able to estimate the solubility of a solid in a supercritical fluid. For this kind of systems, the description of the phase equilibrium is a key point. In this work, a new expression of solid fugacity is established and compared with previous expressions. For sulphur precipitation in supercritical natural gas application, the three approaches to characterize the solid fugacity lead to similar qualitative description of the system behaviour. However, a sensitive analysis demonstrated that the choice of the fugacity expression influences the calculated amount of sulphur plugging.

Deposition of elemental sulphur in natural gas transmission line systems has been reported on only in recent times. The most common location is immediately downstream of a point of significant pressure reduction. A necessary step to eliminate solid sulphur deposition is to understand the deposit mechanism. Two mechanisms appear possible: condensate formation and desublimation of sulphur vapours. To study the plausible paths of solid sulphur formation, we established a thermodynamic model. The constitutive equations are classically the chemical and physical equilibriums, partial mass balances and energy balance. We chose the Peng Robinson equation of state to describe the phase behaviour. Mixing rules are conventional: quadratic for a and linear for b with one binary interaction coefficient. Desublimation seems to be the most plausible mechanism to explain the solid sulphur formation. Pressure reduction implies temperature reduction, which reinforces solid formation. A solution to minimize the solid sulphur deposition seems to be heating the gas stream immediately before pressure reduction.

ACL; International audience; Interest in CO2 solubility in brine at high pressure and high temperature has grown in the last few decades. Solubility data are especially important in petroleum geology, carbon capture and geological storage, and geothermal reservoir engineering. Nevertheless, for the CO2 + NaCl + H2O system there are fewer solubility data available in literature, particularly at high salt molality. A high-pressure experimental device was designed to perform measurements for carbon dioxide solubility in a complex aqueous solution. The apparatus was first validated from experiment on the CO2-pure water system at 323.15 K by comparison with literature data. Thirty-six new experimental solubility data point were obtained in the pressure range between 5 and 20 MPa at three temperatures (323.15, 373.15, and 423.15 K) and at three molalities of NaCl (1, 3, and 6 moles per kilogram of water). Solubility measurements were obtained by potentiometric titration after sample trapping in a sodium hydroxide solution. The experimental solubility data generated in this work were consistent with literature data, and four original isotherms were obtained at high salinity. \textcopyright 2016 American Chemical Society.

The thermal and volumetric properties of complex aqueous solutions are described according to the Pitzer equation, explicitly taking into account the speciation in the aqueous solutions. The thermal properties are the apparent relative molar enthalpy ( L ? ) and the apparent molar heat capacity ( C p , ? ). The volumetric property is the apparent molar volume ( V ? ). Equations describing these properties are obtained from the temperature or pressure derivatives of the excess Gibbs energy and make it possible to calculate the dilution enthalpy ( ? H D ), the heat capacity ( c p ) and the density (?) of aqueous solutions up to high concentrations. Their implementation in PHREEQC V.3 (Parkhurst and Appelo, 2013) is described and has led to a new numerical tool, called PhreeSCALE. It was tested first, using a set of parameters (specific interaction parameters and standard properties) from the literature for two binary systems (Na2SO4-H2O and MgSO4-H2O), for the quaternary K-Na-Cl-SO4 system (heat capacity only) and for the Na-K-Ca-Mg-Cl-SO4-HCO3 system (density only). The results obtained with PhreeSCALE are in agreement with the literature data when the same standard solution heat capacity ( C p 0 ) and volume (V0) values are used. For further applications of this improved computation tool, these standard solution properties were calculated independently, using the Helgeson-Kirkham-Flowers (HKF) equations. By using this kind of approach, most of the Pitzer interaction parameters coming from literature become obsolete since they are not coherent with the standard properties calculated according to the HKF formalism. Consequently a new set of interaction parameters must be determined. This approach was successfully applied to the Na2SO4-H2O and MgSO4-H2O binary systems, providing a new set of optimized interaction parameters, consistent with the standard solution properties derived from the HKF equations. We described the apparent properties of saline solutions with the Pitzer formalism.We implemented these calculations in the Phreeqc geochemical calculation code.PhreeSCALE is tested on several systems.We used PhreeSCALE to revise the interaction parameters for these two systems.

The purpose of this work is to propose a model able to estimate the solubility of sulphur in natural gas transmission and distribution networks. Thus, we developed a model to predict the equilibrium solubility of elemental sulphur in natural gas containing low amount of H 2 S, at pressure and temperature ranges lower than those encountered in production conditions. We established a reactive flash model. The constitutive equations are classically the chemical and physical equilibriums and partial mass balances. We chose the Peng–Robinson equation of state to describe the phase behaviour coupled with the van der Waals one-fluid mixing rules with one binary interaction coefficient. This approach needed critical parameters for each component. We determined the set of critical parameters for S 8 specie from three thermodynamic intrinsic properties including the description of sulphur dissociation reactions. Binary interaction parameters between CH 4 , CO 2 , H 2 S and sulphur are obtained by optimisation from binary and ternary solubility data. Comparisons with experimental values of solid sulphur solubility show that the model is able to describe the sulphur solubility in synthetic natural gases. The application of our model to different natural gases indicated that under transport conditions sulphur solubility is less than 0.005 mg per normal cubic meter.

This paper presents a new set of Pitzer ion interaction model parameters for the binary NaOH–H2O system for concentrations up to over 30 mol·kg−1 and temperatures ranging from 273.15 to 523.15 K. Assuming that the electrolyte is only partially dissociated, the model requires the adjustment of (i) the three classical binary interaction parameters β (0), β (1) and C ϕ , (ii) the equilibrium constant of formation of the aqueous complex NaOH0(aq), and iii) one binary (λ NaOH/NaOH) and one ternary (\( \zeta_{{{\text{NaOH}}/{\text{Na}}^{ + } /{\text{OH}}^{-} }} \)) interaction parameter. This approach, which provides much better results than the approach of treating NaOH as a fully dissociated electrolyte, was chosen to extend the description of the system to high temperatures and high concentrations. The temperature functions of the solubility products of anhydrous NaOH(cr) and five hydrated salts, NaOH·nH2O(cr) (where n = 1, 2, 3.11, 3.5, 4α), were determined. In order to evaluate the quality of the new set of parameters, several tests were run on various properties using various literature data. These include the boiling point elevation in the NaOH–H2O system and the phase diagrams of the two ternary systems NaOH–NaCl–H2O and NaOH–LiOH–H2O. Interaction parameters for the two related binary systems NaCl–H2O and LiOH–H2O were taken from previous studies. To ensure consistency, four new mixing parameters were revised (\( \zeta_{{{\text{Na}}^{ + } /{\text{Cl}}^{-} /{\text{NaOH}}}} \) and \( \varPsi_{{{\text{Cl}}^{-} /{\text{OH}}^{-} /{\text{Na}}^{ + } }} \) for the ternary system NaOH–NaCl–H2O and \( \lambda_{{{\text{Li}}^{ + } /{\text{NaOH}}}} \) and \( \varPsi_{{{\text{OH}}^{ - } /{\text{Na}}^{ + } /{\text{Li}}^{ + } }} \) for the ternary system NaOH–LiOH–H2O). Consistent with Pitzer’s equations, our new set of parameters can be used to satisfactorily describe the quaternary Na+–Li+–Cl−–OH−–H2O system to very high concentrations and temperatures.

The geothermal waters exploitation infrastructures in Chott El Fejjej (Tunisia) are constantly being damaged by a scaling phenomenon. Experimental work has been carried out on a new kind of decarbonation reactor: the open double partition reactor (RODP), which may be used in the construction of a new plant at the site of Chott El Fejjej. The objective of this paper is to propose a model, which may contribute to the design and optimisation of the process of decarbonation. Our model is based on the thermodynamic laws, which describe the physical and chemical phenomena occurring in an electrolytic three-phase continuous reactor. However, due to electrostatic forces, these kinds of systems cannot be successfully described by the concept of an ideal solution. Indeed, the calculation of activity coefficients is required. So, by using a group contribution method to calculate the activity coefficient, the model remains user-friendly. The non-linear system obtained is solved by using Newton–Raphson’s method. Confrontation with experimental results shows that the model correctly describes the ODP reactor.

Aqueous solutions are involved in many processes. Modelling is now becoming a necessary tool for processes simulation or optimisation. In this paper, the model is based on a thermodynamic description of the electrolytic system. The mathematical formulation includes: chemical or ionic equilibriums, physical equilibriums, between the solid phases that might be present, mass balances and an electroneutrality equation. Due to the electrostatic forces, these kinds of systems cannot be successfully described by the concept of an ideal solution. The calculation of activity coefficients is required. However, choosing a group contribution method to calculate the activity coefficient conserves user friendliness. The non-linear system obtained is solved by using Newton Raphson's method. The model is validated on several examples with concentrations of salts being up to saturation.

The dewatering of residual sludges is a current problem due to the huge production of this waste. Activated sludges are generally hard to dewater, and the design and the control of the separation operations are often quite difficult. In order to better understand this problem, pertinent indices are needed. The knowledge of how water is distributed within activated sludge is an interesting approach. Current literature dealing with this topic is, however, relatively difficult to apply. This work presents a review of the problem of moisture distribution classification and measurement within activated sludge. The main techniques used for this analysis are compared and discussed in detail. The estimation of the water binding energy is also extremely commented upon. Finally, the paper discusses the utility of this type of analysis to examine the conditioning and dewatering of activated sludge.

RESUME Le garnissage d'une colonne d'absorption reactive est assimile a un milieu poreux. Ainsi la modelisation des phenomenes de transports reactifs est basee sur une methode d'homogeneisation par prise de moyenne volumique, technique originale pour le domaine. Le modele est applique a l'absorption du dioxyde de carbone (CO2) dans une solution aqueuse d'hydroxyde de sodium (NaOH). Dans ce cas, les reactions sont supposees instantanement equilibrees. Les simulations instationnaires fournissent des informations locales sur le procede tel que les champs de vitesse, de pression, de concentration et de temperature au sein du milieu.

International audience; When capturing CO2, the collected gas mixture can vary considerably both qualitatively and quantitatively, based on the CO2 origin, the capture process and the industrial sector. Co-injected with CO2, these impurities might be an issue in case of leakage but may also impact the subsurface storage. Operators of the whole CCS chain are therefore waiting for recommendations in terms of admissible concentrations while regulators are waiting for tools allowing them to formulate these recommendations. The SIGARRR project aims at proposing accurate reactive-transport simulations to model the long-term behavior of CO2 and its coinjected gases within storage sites focusing on the reactivity with reservoirs and the possible inferences on the environment. The paper presents first numerical results on water-gas equilibriums in agreement with experiments.

The bioleaching of a cobaltiferous pyrite was carried out at 20% solids in a continuous laboratory-scale unit composed of four stirred reactors arranged in cascade. The gas balance method was used in order to follow the O 2 and CO 2 consumptions throughout the experiment. The dissolved oxygen concentration below which oxygen availability was limiting was 1.2 mg. l −1 . In the absence of oxygen limiting conditions, the pyrite oxidation was not directly linked to the bacterial growth metabolism. However, the quantity of biomass formed in the first steps of bioleaching influenced the overall efficiency of cobalt recovery. It was found that high agitation rates could affect bacterial productivity. The use of ammonium rather than urea improved the bioleaching efficiency by favouring bacterial attachment to the solid substrate. The oxygen requirements for pyrite oxidation were estimated on average to be 0. 89 kg of O 2 per kg of pyrite oxidised. The study was also used to evaluate the organic matter distribution and to propose a mathematical model of the bioleaching process. This model, which was calibrated with experimental data, demonstrated a good level of efficiency in its prediction of cobalt recovery for different cascade configurations.

In this paper, a model is developed in order to determine the melting thermogram of a binary mixture, presenting a solid solution. Considering the case of an ideal solution, whose enthalpy function is analytically derived, we highlight the large differences existing between the thermogram and the derivative of the enthalpy function. The influence of the heating rates and the mass of the sample are analyzed for different concentrations. Finally, in the case of a thermodynamical equilibrium, we describe how to construct the phase diagram of the solution (liquidus and solidus temperatures, total latent heat).

This study concerns the performance of a hydrogen-oxygen fuel cell with an immobilized alkaline electrolyte, intended for use in space applications. After optimization of the hydrogen flow rate allowing the precise removal of the water produced by the overall reaction of the cell, the question of electrolyte transfer at the cathode is approached. During long-term operation of the cell, the reaction brings about the accumulation of OH− ions in the reaction zone and the expulsion of electrolyte into the oxygen compartment, known as the weeping effect. It is shown that this phenomenon can be avoided by dampening the oxygen at the cell inlet. The moisture level is a critical factor and optimization studies are also necessary if the performance of the cell is to be maintained.