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We studied the effect of temperature gradients within a packed bed on the SuperCritical (SC) CO2 extraction of oil from pelletized cranberry seeds. Temperature gradients were imposed on the extractor by using different temperatures for the SC-CO2 flow and the extractor vessel wall in heating and cooling experiments (60 and 40 °C, and viceversa) for oilseed pellets and glass beads at 48 MPa. A two-phase heat transfer model and a linear-driving-force mass transfer model described temperature profiles and oil extraction curves. Overall, temperatures in the packed bed were more affected by the vessel wall than the SC-CO2 inlet condition. Extraction curves for heating and cooling experiments were between the isothermal extraction curves for 40 and 60 °C, being affected by the vessel wall temperature in the solubility-controlled period of the extraction and approaching each other after 1-h of dynamic extraction. Both heat and mass transfer models allowed a satisfactory prediction of such a behavior and represent a step forward in the prediction of SC-CO2 oil extraction course.

The effect of the main process variables affecting the supercritical CO 2 extraction of oil from seeds (namely grape seeds) was investigated, both experimentally and through modeling. The dependency of the extraction kinetics on the variables more tested in the literature (pressure, temperature, particle size and solvent flow rate) was confirmed, and original trends were obtained for the less investigated variables, such as the bed porosity ɛ and the extractor diameter to length ratio ( D / L ). The extraction kinetics did not depend on ɛ for 0.23 ≤ ɛ ≤ 0.41, while a further decrease in ɛ lowered the extraction rate, likely due to the occurrence of channeling. The effect of a variable D / L ratio was studied letting constant the ratio of substrate mass to CO 2 mass flow rate: the lower was D / L , the lower the specific CO 2 consumption. Through modeling, the values of internal and external mass transfer parameters were calculated and critically discussed on the basis of well-known literature correlations.

The objective of this study was to evaluate the feasibility of supercritical oil extraction from Jatropha curcas L (JCL). The influence of the operating conditions on oil yield, free fatty acid content of JCL oil, and oil quality was examined, which included pressure, temperature, particle size, and percentage of hull. The conditions for the fractionation of fatty acid were selected to obtain good-quality oil for biodiesel production. Finally, an experiment was conducted under different conditions in which the greatest amount of free fatty acids (FFA) (26.3 wt.%) was extracted during the first fractions and then the pressure was increased to achieve good oil removal (91 wt.% oil yield) performance with low content of free fatty acids (1 wt.%). This study has a promising role to fill as a more cost-effective processing technology, and it is not necessary to carry out a degumming, esterification and dehydration in the oil of the last fractions. Furthermore, all the phorbol ester was removed from the oil by conducting a supercritical extraction using CO 2 .

The current study focuses on the recovery of grape seed oil by supercritical CO2 extraction. Grape seeds from six grape cultivars were extracted in two subsequent harvesting years, and the resulting oils were characterized for the relative amount of: (a) lipid classes; (b) lipid acyl chains; and (c) tocopherols and tocotrienols. Comparative extractions were performed by utilizing n-hexane as solvent and by mechanical pressure. A well-established modeling approach was applied to evaluate the mass transfer parameters affecting the kinetics of supercritical CO2 extraction: with these parameters, process scale-up can be addressed. The results reported in this study testify the potentiality of grape seed oil as a source of unsaturated fatty acids and tocols. Moreover, they offer a clear picture of the similarities and differences among oils from different grape cultivars and obtained through different extraction techniques.

The aim of this work is to model the supercritical water gasification (SCWG) of methanol by means of a detailed kinetics model based on elementary reactions. The challenge consists in modeling SCWG by using existing models developed for combustion or supercritical water oxidation (SCWO) and adjusting their initial conditions to make them suitable for SCWG. To this purpose, three models (GRI-Mech 3.0, Brock and Savage and Webley and Tester) were selected, implemented in MatLab ® and run. Webley and Tester's model seems to describe quite well methanol conversion as a function of time. On the other hand, some mechanisms, like water–gas shift and methanation, are not correctly predicted. The main reaction pathways are identified and outlined.

This paper analyses the effects on the extraction kinetics of a solvent flow which is non-uniform in the extraction column bed cross-section. When modeling the extraction kinetics of a solute from a solid matter (for instance of oil from seeds), the solvent motion is normally assumed as consisting in plug flow, eventually corrected by the axial dispersion coefficient. Some experimental evidence put into question this simplified description. We have shown to which extent the effects of a non-uniform extraction bed permeability reflect on the extraction kinetics: in particular conditions, these effects could be even more significant than the effects due to the mass transport resistances governing the extraction of the solute out from the matrix.

In this work, an extraction model capable of predicting the supercritical extraction process of seed oil is presented. The model bridges the ‘broken and intact cells’ and the ‘shrinking-core’ models available in the literature: as the former, the proposed model takes into account the seed structure with the presence of oil-bearing cells; as the latter, it assumes that the particles progressively exhaust their oil content from the outside to the inside, with a core shrinking during the process. The internal mass transport coefficient is described with three alternative models: the discrete and the semi-continuous models are superior to the continuous one which undervalues the same coefficient. By means of a supercritical extractioncolumn model and utilizing several experimental data of supercritical grape-seed oil extraction, the value of the internal mass transport coefficient of a single layer of oil-bearing cell has been calculated: its value is roughly the same for all the experimental cases analyzed (average value: 5 × 10 −8 m/s), verifying the reliability of the proposed model.

The paper is devoted to modeling seed oil supercritical extraction introducing the novelty of considering the granulometric distribution of the substrate to be extracted. Reference is done to a model which, as the others available in the literature, simplifies the milled seed particles as having a unique representative average dimension, the Sauter mean diameter. At first, the new developed model and the reference model were compared on reference test cases for the prediction of the kinetics of extraction. Then the new model was utilized with experimental granulometric distributions of milled grape seeds and with the relevant experimental extraction data and it was tested also for what concerns the calculation of the effective diffusivity of the oil into the seed matrix. The results obtained show that adopting the Sauter mean diameter instead of the real particle diameters is a consistent simplification where the particle granulometric distribution presents small variance (error of a few percentages). In any case the new model predicts slightly better that the reference one and significant differences occur when calculating the internal mass transfer coefficient.

This paper focuses on supercritical CO 2 extraction of grape seed oil which has been analyzed both experimentally and theoretically. Extractions on crushed seeds at pressures varying in the range 280–550 bar and at a fixed temperature of 313 K were performed. From the initial linear portion of the experimental curves oil solubility data in the supercritical solvent have been obtained. By modeling the complete curves, the transport parameters regulating the oil mass transfer inside the seed particles have been calculated: the internal transport coefficient and the effective diffusivity. Three different extraction baskets (0.1, 0.2 and 0.5 l) have been utilized: the differences in the extraction curves have been modeled and explained in terms of the different void volume of the apparatus for the various baskets. A procedure to obtain consistent solubility data when dealing with extractor vessel with non-negligible void volume has been described.

In this paper, a typical analysis of the effect of model uncertainties on predictions is extended to a supercritical extraction process for an extractor feed by vegetable seeds and utilizing supercritical CO2 as solvent. The sensitivity analysis reveals that two parameters are particularly important for the extraction process modeling: the particle diameter and the internal mass transfer coefficient. Therefore, a deeper analysis of the sensitivity of these two parameters has been performed: the sensitivity depends on the length of the process. In the supercritical extraction process, two successive phases can be considered: the former is controlled by the solubility of the oil in the supercritical solvent, and it is therefore almost completely insensitive; the second phase, on the contrary, is mainly controlled by internal transport phenomena and it is very sensitive to the above mentioned parameters. The effect of changing some operative conditions is also investigated, underlining how the solvent flow rate and the seed milling affect the extraction process. From these results, an extraction procedure is proposed that would reduce the solvent consumption without resorting to the connection in series of several extractors.