Experimental study of high pressure phase equilibrium of (CO2 + NO2/N2O4) mixtures

Experimental bubble pressure, as well as liquid density of (CO2 + NO2/N2O4) mixtures are reported at temperatures ranging from (298 to 328.45) K. Experiments were carried out using a SITEC high-pressure variable volume cell. Transition pressures were obtained by the synthetic method and liquid density was deduced from measurement of the cell volume. Correlation of experimental results was carried out without considering chemical equilibrium of NO2/N2O4 system. (Liquid + vapour) equilibrium was found to be accurately modelled using the Peng–Robinson equation of state with classical quadratic mixing rules and with a binary interaction coefficient kij equal to zero. Nevertheless, modelling of liquid density values was unsatisfactory with this approach

Dust emission by powder handling: Influence of the hopper outlet on the dust plume

Dust generation in solids handling involving free fall of bulk materials and impacts on a stockpile can cause many problems in industry and be a great danger for operators health. This paper describes an experimental set up to characterize the dust plume formed in free fall of powders from a hopper and investigates the influence of various outlet geometries on the dust plume. For this purpose an image analysis technique was developed to quantify the characteristics of the dust plume

Supercritical carbon dioxide : an efficient tool for the production of ultra-fine particles for the food and pharmaceutical industries

International audienceThe agro-food, pharmaceutical, cosmetics and detergent industries are among the greatest users of particulate solids, or powders. It is hardly necessary, therefore, to expound their industrial importance. However, there is still plenty of room for development, as their generation, their formulation and the control of their usage properties are yet to be fully mastered.In the domain of particle formation, there are traditionally two main ways of obtaining divided solids, depending on whether the base material is in the solid or liquid state: crushing, milling, comminution belong to the former category while crystallisation, precipitation, spray-drying and atomization belong to the latter. Obtaining powders by processes using supercritical fluids is a third route, which has undergone significant development during the last decade. By using pressure as an operating parameter, these processes lead to the production of fine and monodisperse powders. There exist three families of processes (RESS, SAS and PGSS) according to the way in which the FSC - generally CO2 - is used.•In the RESS process, CO2 is the solvent and it is the fall of density related to a rapid depressurisation which promotes the nucleation of the solute. Although it is easy to implement, this process is however limited by the relatively tight spectrum of CO2-solvent properties. •In the SAS process, CO2 is used as a non (or anti)-solvent and it is the reciprocal dissolution of an organic solution and the supercritical fluid which causes precipitation. The great versatility of SAS remains its principal advantage. •Lastly, in the PGSS process, the dissolution of CO2 into an organic solution or a molten polymer, is followed by an abrupt depressurisation in which the dissolved gas acts as an aerosol generator helping the particle formation. This process is particularly advisable for polymer coating applications.In this paper, two examples of application of these processes are described.A high-value foodstuff, cocoa butter has been crystallised in a specific polymorph. The particles produced can be used to improve tempering, a key-stage in the chocolate manufacturing process. Secondly, a hypocholesterolemic drug, eflucimibe, has been processed. A new process using three different steps has allowed a significant improvement in dissolution rate and oral bioavailability

Modelling solid solubilities in SC-CO2 and cosolvent : development of enhanced density-based models

International audienceThe solubility of a solid of pharmaceutical interest in supercritical carbon dioxide, with or without cosolvent has been measured by means of a novel apparatus. This solubility data has been correlated by means of several density–based semi–empirical models, which have been extended and modified to be applicable to mixtures with cosolvent

La génération de solides divisés par voie supercritique : principes de base, considérations sur l'état d'avancement des recherches

National audienceOn se propose ici de faire le point sur la génération de solides divisés par voie supercritique : les principes de base des différents types de procédés existants sont donnés. On fait également le point sur l'état d'avancement des connaissances sur ces procédés. L'exemple de leur application dans le domaine pharmaceutique est abordé

Development of an improved falling ball viscometer for high-pressure measurements with supercritical CO₂

International audienceThis study presents the development of an improved technique for viscosity measurements under high pressure. The apparatus is based on the principle of the falling ball viscometer, implemented in a high-pressure autoclave fitted with visualisation windows. The originality here is that the balls fall through a tube open at both ends with a diameter slightly greater than that of the balls, allowing a simplified modelling and numerical simulation. A numerical approach has been used for viscosity determination. Calculations have been made with COMSOL Multiphysics® with the laminar Navier–Stokes model for Newtonian mixtures. It includes the specific hydrodynamic effects without the need for a calibration fluid. However, validation experiments were carried out at atmospheric pressure with dimethylsulfoxide (DMSO) at 298, 308 and 318 K and with cocoa butter at 313 and 353 K, with values of viscosity in the range from 1.4 to 45.4 mPa s. Comparative measurements with literature data have been conducted with cocoa butter saturated with carbon dioxide at 313 and 353 K and for pressures ranging from 0.1 to 25 MPa. At 313 K, viscosity varies from 45.4 mPa s to 3.1 mPa s while at 353 K it varies from 12.4 to 1.9 mPa s. For both isotherms tested, within the range 0–15 MPa, the higher the CO2 dissolution in the cocoa butter, the lower the viscosity. However, this decrease in viscosity is more pronounced at the lowest temperature. Above 15 MPa the CO2 dissolution effect on viscosity becomes insignificant, i.e. within the experimental error, due to a counter effect linked with the high hydrostatic pressure. Furthermore, the limits of use of this method have been determined. This technique is revealed as reliable and can therefore be used with other binary systems

Fast pyrolysis of contaminated biomass: The chemical and thermodynamic description of the intermediate liquid compound

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Use of ress and sas processes for powder generation of an active substance

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High pressure phase equilibrum behaviour of naphthalene in supercritical co2 experimental results and calculation with the peng-robinson equation of state

International audiencePhase equilibrium calculations involving a pure solid component are presented. The fluid phases are modelled using the Peng-Robinson's equation of state (EoS) using two different mixing rules for the covolume of mixing: the classical linear mixing rule and the van der Waals or quadratic mixing rule with a binary interaction parameter. The pure solid chemical potential used in the model does not require the value of the sublimation pressure-it is based on the measurements made with a differential scanning calorimeter of the melting point of the solid. This model has been used for estimating the solubility of naphthalene in carbon dioxide (CO2). Experimental results have been obtained with an original apparatus, based on an open-circuit analytical method. These high accuracy measurements of the solubility of naphthalene in CO2 up to the supercritical region have been compared with the predicted values. The binary interaction parameters have been optimised using a parametric identification method. With these parameters a phase diagram of the binary mixture naphthalene-CO2 is calculated

Etude de la cristallisation d'une nouvelle molécule à efficacité cardiotonique dans un mélange liquide ionique-eau

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