The aim of this work is to show that the equations developed by Sovova, based on the concept of broken and intact cells for describing the supercritical extraction curves from plants and vegetables, can be applied for the modelling of the supercritical CO2 extraction curves obtained with microalgae. Experimental and modelling results of supercritical carbon dioxide extraction of lipids from four different microalgae: Nannochloropsis oculata, Cylindrotheca closterium, Chlorella vulgaris and Spirulina platensis, are presented. The experimental setup is a laboratory scale apparatus which allows an accurate monitoring of the mass loss of the microalgae sample during the extraction. The experimental data were obtained at a pressure of 40 MPa, a temperature of 333 K and CO2 flow rates from 0.3 to 0.5 kg h(-1). The extraction experiments were performed on samples having undergone different pretreatments: (i) after harvesting and centrifugation, microalgae were dried either by freeze-drying or air flow drying) and (ii) they were ground and sieved at different particle sizes (particle diameters ranging from 160 to 1000 pm). The complete extraction of neutral lipids was performed leading to mass losses up to 30% depending on the samples and on the operating conditions. Extracts were mainly composed of triglycerides (more than 90 wt% of extracts). The mathematical model published in 2005 and the simplified equations of extraction curves (using the characteristic times characterizing each extraction step) published in 2012 by Sovova were chosen to fit the experimental data. Among the hypotheses proposed by Sovova, we considered that the flow pattern of supercritical CO2 in the extraction autoclave was plug flow and the extraction process was supposed to occur with negligible solute-matrix interactions. The adjustable parameters were calculated by minimizing the sum of least squares between experimental and calculated values of the extraction yield. Good agreement between the two models and our experimental measurements was obtained. The average absolute relative deviation ranges between 0.5 and 10.2%. (C) 2013 Elsevier B.V. All rights reserved.

The aim of this work is to show that the equations developed by Sovova, based on the concept of broken and intact cells for describing the supercritical extraction curves from plants and vegetables, can be applied for the modelling of the supercritical CO2 extraction curves obtained with microalgae. Experimental and modelling results of supercritical carbon dioxide extraction of lipids from four different microalgae: Nannochloropsis oculata, Cylindrotheca closterium, Chlorella vulgaris and Spirulina platensis, are presented. The experimental setup is a laboratory scale apparatus which allows an accurate monitoring of the mass loss of the microalgae sample during the extraction. The experimental data were obtained at a pressure of 40 MPa, a temperature of 333 K and CO2 flow rates from 0.3 to 0.5 kg h(-1). The extraction experiments were performed on samples having undergone different pretreatments: (i) after harvesting and centrifugation, microalgae were dried either by freeze-drying or air flow drying) and (ii) they were ground and sieved at different particle sizes (particle diameters ranging from 160 to 1000 pm). The complete extraction of neutral lipids was performed leading to mass losses up to 30% depending on the samples and on the operating conditions. Extracts were mainly composed of triglycerides (more than 90 wt% of extracts). The mathematical model published in 2005 and the simplified equations of extraction curves (using the characteristic times characterizing each extraction step) published in 2012 by Sovova were chosen to fit the experimental data. Among the hypotheses proposed by Sovova, we considered that the flow pattern of supercritical CO2 in the extraction autoclave was plug flow and the extraction process was supposed to occur with negligible solute-matrix interactions. The adjustable parameters were calculated by minimizing the sum of least squares between experimental and calculated values of the extraction yield. Good agreement between the two models and our experimental measurements was obtained. The average absolute relative deviation ranges between 0.5 and 10.2%. (C) 2013 Elsevier B.V. All rights reserved.

Single adsorption isotherms and differential enthalpies of adsorption of nitrogen were measured on a microporous-activated carbon at various temperatures. A new way for calculating the differential enthalpies of adsorption is presented, and the results obtained were compared to those obtained by the isosteric method derived from the equilibrium data using the Clausius-Clapeyron equation. The measurements were made thanks to a coupled thermostated calorimetric-manometric apparatus which can be operated for pressures up to 2.5 MPa and temperatures from 303 to 423 K. This article provides experimental data which can be used for the adjustment of interaction potential in computational simulations for supercritical adsorption.

The aim of this study is to apply the membrane bioreactor technology in an oxidation ditch in submerged conditions. This new wastewater filtration process will benefit rural areas (<5,000 population equivalent) subject to chronic water shortages by reusing this water for irrigation of green areas. For this purpose, the membranes developed without support are immersed in an aeration well and work in suction mode. The development of the membrane without support and more precisely the performance of spacers are approached by computational fluid dynamics in order to provide the best compromise between pressure drop/flow velocity and permeate flux. The numerical results on the layout and the membrane modules' geometry in the aeration well indicate that the optimal configuration is to install the membranes horizontally on three levels. Membranes should be connected to each other to a manifold providing a total membrane area of 18 m. Loss rate compared to the theoretical throughput is relatively low (less than 3%). Preliminary data obtained by modeling the lagoon provide access to its hydrodynamics, revealing that recirculation zones can be optimized by making changes in the operating conditions. The experimental validation of these results and taking into account the aeration in the numerical models are underway. =20

In order to assess and improve the quality of high pressure and temperature adsorption isotherms and differential enthalpies of adsorption on microporous and mesoporous materials, a specific thermostated device comprising a differential heat flow calorimeter coupled with a home-built manometric system has been built. The differential heat flow calorimeter is a Tian Calvet Setaram C80 model which can be operated isothermally, the manometric system is a stainless steel homemade apparatus. The thermostated coupled apparatus allows measurements for pressure up to 2.5 MPa and temperature from 303 to 423 K. Reliability and reproducibility were established by measuring adsorption isotherms on a benchmark sorbent (Filtrasorb F400). A detailed experimental study of the adsorption of pure carbon dioxide and methane has been made on activated carbons (Filtrasorb F400 and EcoSorb); a new procedure for determining the differential enthalpies of adsorption based on the stepwise method is also proposed. The error in the determination of the amount adsorbed is about 3.6%, and the error in the determination of the differential enthalpies of adsorption is 4%.