Experimental and modelling of supercritical oil extraction from rapeseeds and sunflower seeds

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 CO₂ 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.     

Effect of hydraulic retention time on a continuous biohydrogen production in a packed bed biofilm reactor with recirculation flow of the liquid phase

The present paper reports on results obtained from experiments carried out in a laboratory-scale anaerobic packed bed biofilm reactor (APBR), with recirculation of the liquid phase, for continuously biohydrogen production via dark fermentation. The reactor was filled with Kaldnes^® biofilm carrier and inoculated with an anaerobic mesophilic sludge from a urban wastewater treatment plant (WWTP). The APBR was operated at a temperature of 37 °C, without pH buffering. The effect of theoretical hydraulic retention time (HRT) from 1 to 5 h on hydrogen yield (HY), hydrogen production rate (HPR), substrate conversion and metabolic pathways was investigated. This study indicates the possibility of enhancing hydrogen production by using APBR with recirculation flow. Among respondents values of HRT the highest average values of HY (2.35 mol H₂/mol substrate) and HPR (0.085 L h^?1L^?1) have been obtained at HRT equal to 2 h.     

Separation of particles from hot gases using metallic foams

One of the most complicated tasks in the field of hot gas cleaning is the removal of particles from a complex mixture of degradation products formed during thermal treatment. A robust and completely reliable technology is still to be developed to achieve high efficiencies. In the past few years, significant improvements have been brought to gas cleaning technologies. Nevertheless, none of the existing processes has proved fully successful.The aim of this work is to perform the filtration of particles generated in fluidized bed gasification experiments using metallic foams. The gasified material used is dried sewage sludge. Nickel–chromium metallic foams are likely to have inherent properties that would make them suitable for use in structures where strength, high temperature-resistance and corrosion resistance are required. Moreover, metallic foams are characterized structurally by their cell topology, relative density, high porosity (? = 0.95) and cell size. In hot gas filtration, high temperature-resistance and low pressure drop to specific area ratio are essential characteristics. In the present work, several experimental operating conditions (heating time, temperature, washing method and metallic foam thickness) are investigated. The pressure drops in the metallic foams during filtration are calculated. The experimental results obtained are compared with numerical simulation results and a good agreement is obtained. The metallic foams are simulated from tomography results and a model is created.     

A Practical Method to Derive Sample Temperature during Nonisothermal Coupled Thermogravimetry Analysis and Differential Scanning Calorimetry Experiments

Nonisothermal thermogravimetry differential scanning calorimetry (TG‐DSC) mounting is intensively used for the determination of kinetic parameters and reaction heat along the chemical transformation of a solid. Nevertheless, when tests are performed with heating rates as high as those encountered in industrial processes, e.g., several tens of K min^–1, there is great uncertainty in the knowledge of the exact sample temperature. In this work, a method to derive a simple mathematical expression is proposed and fully described in order to calculate the real sample temperature throughout a temperature‐ramped test on a commercial apparatus. The furnace temperature and the heat flow signals were used, together with the crucible specific heat and the heating rate. A number of validation tests were performed to derive similar reaction rates for a reference. First‐order kinetic reactions were presented and reconciled over a large range of heating rates from 3 to 50 K min^–1.     

Measurements and correlations for gas liquid surface tension at high pressure and high temperature

Surface tension of water/nitrogen and water–phenol/nitrogen systems was successfully measured by the hanging drop method in a wide domain of temperature (from 100 to 300°C) and pressure (from 4 to 30MPa), conditions little explored in litterature. Results show that surface tension of water–phenol mixtures decreases as phenol mass fraction increases. This decrease is observed under saturated and unsaturated conditions and is more pronounced at low temperatures and does not seem to depend on pressure. The effect of saturation on surface tension in the water/nitrogen system has been correlated with water vapor pressure by using experimental points with a great accuracy. For the water–phenol/nitrogen system, experimental data obtained with different mass fraction of phenol were correlated using Macleod‐Sugden equation for mixtures. © 2018 American Institute of Chemical Engineers © 2018 American Institute of Chemical Engineers AIChE J, 64: 4110–4117, 2018     

Process optimisation using the combination of simulation and experimental design approach: Application to wet air oxidation

This study develops a coupling of energetic and experimental design approaches on a given configuration of wet air oxidation process (WAO), applied for wastewater containing a hard chemical oxygen demand (phenol for instance). Taking into account thermodynamic principles and process simulation, the calculation of minimum heat required by the process, exergetic efficiency and work balance is presented. Five parameters are considered: pressure (20-30 MPa); temperature (200-300 °C); chemical oxygen demand (23-143 g l⁻¹); air ratio (1.2-2) and temperature of exiting steam utilities (160-200 °C). Using the surface response method, it appears that initial chemical oxygen demand and temperature are the two parameters that mainly influence the result. With the modelling, good conditions for the functioning of the presented process are the following: pressure of 19.4 MPa, temperature of 283 °C, chemical oxygen demand of 54.9 g l⁻¹, air ratio of 1.7 and vapour temperature of 183 °C.     

Microstructure and properties of copper and aluminum alloy 3003 heavily worked by equal channel angular extrusion

A technique invented in the former Soviet Union and recently introduced in the United States, called equal channel angular extrusion (ECAE), produces intense and uniform deformation by simple shear and is applied to 25 × 25 × 152-mm billets of Cu 101 and Al 3003. Microcrystalline structures with a grain size of 0.2 to 0.4 μm are created during room-temperature multipass ECAE deformation for true strains lying in the range ε=2.31 to 9.24. Evidence shows that intense simple shear deformation promotes dynamic or continuous recrystallization by subgrain rotation. The effects of the number of extrusion passes and deformation route for Cu 101, and the deformation route after four passes for Al 3003, are studied. Increasing the number of ECAE passes in Cu 101 causes strength to reach saturation and grain refinement stabilization after four passes (true strain of 4.68), and subgrain misorientation to increase as the number of passes increases. For multipass ECAE with billet orientation constant (route A) or rotated 90 deg between all passes (route B), two levels of structures are created inside the original grains: shear bands (first level) and very fine subgrains (second level) within the shear bands. For a billet rotation of 180 deg between passes (route C), an unusual event is observed. At each even numbered pass, shear bands nearly disappear and only subgrains are present inside the original grains. Route B gives the highest strength, whereas route C produces a more equiaxed and stable microstructure. Subsequent static recrystallization increases the average grain size to 5 to 10 μm.     

Limiting the Pollutant Content in the Sewage Sludge Producer Gas through Staged Gasification

Sewage sludge gasification deals with the release of nitrogen and sulfur compounds, the main sources for pollutants during the final combustion. In order to handle these compounds, a staged gasification process is proposed. During the low‐temperature thermal treatment of the first stage, nitrogen and sulfur compounds are removed from the solid fuel. The second stage converts the remaining solid into combustible compounds through gasification reactions. The producer gas obtained during this stage is compared to the producer gas of a simple gasification. The presence of pollutant precursors was considerably diminished during the staged experiments. A successful staged gasification may eliminate the need for downstream cleanup and thus limit the energy consumption. This work proves that staged gasification may be the key to obtain energy from waste fuel, limiting the concerns about pollutants.     

Comparison Between Static and Dynamic Methods for Sorption Isotherm Measurements

Sorption isotherms of Microcrystalline Cellulose (MCC), pharmaceutical granules, PolyEtherBlocAmide (PEBA) membrane and sewage sludges were measured at various temperatures using three different experimental gravimetric methods: the saturated salt method, the Dynamic Vapor System (DVS) apparatus and a simultaneous gravimetric and calorimetric measurement techniques using a Setaram TGA-DSC111. A comparison between the salts method and DVS is proposed at ambient temperature for the MCC, the pharmaceutical granules and the PEBA membrane. The comparison between the static method and the DVS shows that the results are consistent as long as the apparent moisture content in the material is high. When the apparent diffusion coefficient becomes low, the difficulty to reach the thermodynamic equilibrium appears in the saturated salts method. Then, DVS and TGA-DSC apparatus were used to investigate the desorption isotherms for the MCC between the ambient temperature and 90°C. Finally, an application on biological products is proposed: the desorption isotherms for two sewage sludges coming from the same wastewater treatment plant were determined with the DVS and the TGA-DSC equipments at 45°C. The accuracy of the TGA-DSC is good as long as the apparent diffusion coefficient is above 10^-9 m²/s. When this threshold value is overstepped, the desorption isotherms are overestimated.