The development of environmental-friendly process for strategic metal extraction, limiting organic solvent use and effluent production, appears to be quite a challenging purpose. Production of pure molybdenum using supercritical CO2 extraction process, from sulfuric solution obtained by ore or used catalyst leaching, has been evaluated. Two organic ligands, trioctylamine and 2-ethylhexyl 2-ethylhexylphosphonic acid, were studied to extract Mo as metal complexes solubilized in supercritical CO2. Extraction with trioctylamine revealed to be non-efficient due to a lack of Mo-trioctylamine complex solubility in CO2, even if extraction selectivity of molybdenum versus iron impurity was interesting. On the contrary, extraction with 2-ethylhexyl 2-ethylhexylphosphonic acid leads to high Mo collection efficiency (up to 90% in 7 h). However, no selectivity was observed between molybdenum and zirconium. The selectivity of 2-ethylhexyl 2-ethylhexylphosphonic acid towards molybdenum in presence of iron was better but clearly decreased in presence of zirconium. (C) 2016 Elsevier B.V. All rights reserved.

This paper deals with formal modelling of Petri nets including shared resources. These phenomena appear widely in the production management context, for the modelling of manufacturing cells. But, they usually cannot be formally represented in dioid algebraic structures based on sets of scalars. In this paper, we design a method to describe such a phenomenon in a dioid of intervals. In fact, the resource-sharing problem is turned into a time uncertainty problem, regarding the access to the shared resource. In this new problem, time uncertainties are bounded and can be described by intervals. Both bounds of the behaviours of the studied production systems can be manipulated in the scope of the Zmacr max dioid, even though the original systems are not Zmacr max linear by essence.

Distributed systems consist of an interconnection of two or more subsystems. Control of such systems is structured by two or more controllers, each receiving an observation stream from a local subsystem and providing an input to the local subsystem. Coordinated distributed systems are defined for linear systems, for Gaussian systems, and for discrete-event systems and an algebraic-geometric characterization is provided. Coordination control of distributed systems requires a specific control synthesis procedure which is presented. Distributed control with communication between controllers is formulated and discussed.

The feasibility of extracting uranium from natural ores has been studied, using supercritical CO2 and either commercial extractants (PC88A, Cyanex 301 (R)) or an amidophosphonate molecule (named DEHCNPB). The impact of the process parameters has been evaluated. The uranium extraction yield was optimal at the lowest temperature (40 degrees C) and highest pressure (25 MPa) tested here. For a given CO2 flow rate, a compromise should be established between the amounts of extractant, acid and oxidant used. Uranium was successfully extracted directly from natural ore using DEHCNPB with a good selectivity over metal impurities such as iron, titanium and vanadium and yields up to 97%. Moreover, using Fe-2(SO4)(3) as an oxidant allows to minimize the water usage of the process. The mechanism of extraction using supercritical CO2 has been elucidated thanks to electrospray ionization mass spectrometry. (C) 2017 Elsevier B.V. All rights reserved.

The supercritical oil extraction from oleaginous seeds (sunflower and rapeseeds) is presented here through experimental and modelling results. The experimental setup allows an accurate following of the mass of the oil extracted and to derive the experimental influences of pressure, temperature and supercritical CO(2) flowrate on the extraction curves. These parameters are very sensitive and highlight the necessity of precise optimisation of experimental conditions. In order to complete the behaviour of supercritical fluids extraction, an improved modelling is proposed. The modelling basic equations are based on others modelling published previously. In this work, the determination of several parameters comes from correlations and the other constants are fitted with all the experimental results. Thus the modelling is more representative and predictive as other ones. The modelling results present a good agreement with the experimental results, and hence it can be used for the dimensioning of some extraction autoclaves. (C) 2011 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Among the industrial effluents presenting constraints to traditional biological treatments, those from textile industries are of particular concern. Wet air oxidation is an effective process that significantly increases biodegradability of the treated effluent. In this study, the advantage of this process was tested for the treatment of acid orange 7, a dye molecule used as a model textile effluent. Different experimental conditions of temperature (200 to 300 degrees C) and duration of treatment were used to determine its degradation yield during the wet air oxidation process, at a total pressure of 30MPa. All these conditions led to complete degradation of acid orange 7, but residual Total Organic Carbon always remained. Oxidation byproducts were identified by the means of GC and HPLC analyses. Acetic acid remains the major compound not oxidized. These experiments resulted in the proposal of a reaction scheme associated with kinetic constants. Finally, the optimal conditions for the improvement of the biodegradability of the effluent were determined. This wet air oxidation process could then be coupled with a biological treatment to obtain an overall degradation meeting the criteria for release into the environment.

An experimental design has been built in order to study the influence of different parameters on the oil extraction yield for two types of seeds (rape and sunflower) using supercritical CO(2): pressure (15-45 MPa), temperature (35-75 degrees C), CO(2) flow rate (8-19 kg h(-1)) and extraction duration (20-120 min). Extraction yields are between 0.3% and 89.8%, indicating that the experimental design covers a large range of results. Acidic and phosphorus contents in the oil and protein content in the residual cake have been done. The results indicate that pressure and extraction duration are the most influencing parameters together with temperature in the case of rape seeds. Thermodynamic effects (solubility) and kinetic effects (mass transfer depending on the seeds) have been evidenced. The selectivity of pure supercritical CO(2) has been shown: any phospholipid is extracted. In addition to selectivity, another interest of the process is the purity of the products recovered, totally free from organic solvent. (c) 2008 Elsevier Ltd. All rights reserved.

This work is dedicated to an accurate evaluation of thermodynamic and kinetics aspects of phenol degradation using wet air oxidation process. Phenol is a well known polluting molecule and therefore it is important having data of its behaviour during this process. A view cell is used for the experimental study, with an internal volume of 150 mL, able to reach pressures up to 30 MPa and temperatures up to 350 degrees C. Concerning the thermodynamic phase equilibria, experimental and modelling results are obtained for different binary systems (water/nitrogen, water/air) and ternary system (water/nitrogen/phenol). The best model is the Predictive Soave Redlich Kwong one. This information is necessary to predict the composition of the gas phase during the process. It is also important for an implementation in a process simulation. The second part is dedicated to kinetics evaluation of the degradation of phenol. Different compounds have been detected using GC coupled with a MS. A kinetic scheme is deduced, taking into account the evolution of phenol, hydroquinones, catechol, resorcinol and acetic acid. The kinetic parameters are calculated for this scheme. These data are important to evaluate the evolution of the concentration of the different polluting molecules during the process. A simplified kinetic scheme, which can be easily implemented in a process simulation, is also determined for the direct degradation of phenol into H(2)O and CO(2). The Arrhenius law data obtained for the phenol disappearance are the following: k = 1.8 x 10(6) +/- 3.9 x 10(5) M(-1) s(-1) (pre-exponential factor) and E(a) = 77 +/- 8 kJ mol(-1) (activation energy). (C) 2011 Elsevier Ltd. All rights reserved.

Diffusion coefficient is an important property in chemical industry and precise measurements can be achieved by electrochemical techniques. Study of ferrocene diffusion was carried out in 1-hexyl-3-methyl imidazolium hexafluorophosphate-dense CO(2) ([C(6)MIM][PF(6)-CO(2)])biphasic system using microelectrode technique. Diffusion coefficients were determined by cyclic voltammetry and Randles-Sevcik relationship in the temperature and pressure ranging from 303.15 to 333.15 K and 1-10 MPa, respectively. Computed phase simulations were also used. Two-phase system was determined whatever experimental conditions and composition tested. Volumes of heavy and light phase were estimated as well. Both electroanalytical and computed studies showed that [C(6)MIM][PF(6)]-CO(2) biphasic system containing initial molar fraction of CO(2) up to 0.9 can be used without decrease in diffusion coefficient values. The order of magnitude of these diffusion coefficients of ferrocene in greener aprotic media is about 10(-6) m(2) s(-1). Theoretical analysis of ferrocene mass transport was also carried out using Sutherland formula and viscosity model based on Eyring's absolute rate theory. Dramatic decrease in [C(6)MIM][PF(6)]-CO(2) mixture viscosity with x(CO(2)) was estimated by calculations. (C) 2011 Elsevier B.V. All rights reserved.

Wet air oxidation process (WAO) is used for wastewater treatment, especially when it contains high chemical oxygen demand. With non-catalytic processes, temperatures between 200 and 350 degrees C and pressures between 15 and 30 MPa are generally applied. A method, based on the coupling of simulations and experimental design, is used to compare and optimize two reactors (adiabatic and isotherm), their volume being equal and fixed. The interest of an experimental design approach is to plan simulation and to present results in immediate response surface. Four parameters have been selected; temperature, pressure, chemical oxygen demand, air ratio. After achieving the 25 simulations of the "numerical design", mass and energy balances were analysed through two energetic values integrated as the design responses: exergetic efficiency and minimum heat required by the process for the functioning. The surface response methodology determines which are the most influencing parameters on design responses. It also shows that temperature of reaction and air ratio are the most influencing parameters. At least elements to calculate the cost of the plant, for both reactors are given. Both reactors allow to get complete degradation of pollutants, but strategy of investment and control are opposite. (C) 2011 Elsevier Ltd. All rights reserved.

Many recrystallization processes in supercritical medium utilize CO(2) as antisolvent. This work presents two introduction devices based on the principle of the supercritical antisolvent process: the impinging jets and the concentric tube antisolvent reactor. Those two processes are very simple to develop and allow improving the mixing between the two phases. Some experiments have been conducted for the impinging jets using L-polylactic acid at 10 MPa and 308 K giving spherical particles with average diameter varying from 1.4 to 2.3 mu m. For the concentric tube antisolvent reactor, griseofulvin was tested at 10 MPa and temperatures between 308 and 323 K providing needles with lengths between 25 and 50 mu m. These results combined with previous ones allow comparing these introduction devices with the classical supercritical antisolvent (SAS) process, demonstrating the following improvements: (i) reduction of particle size, (ii) increase in initial solute concentration, and (iii) process intensification.