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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; 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.

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.

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.

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.

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.

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.

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.