Citronella essential oil has more than eighty components, of which the most important ones are citronellal, geranial and limonene. They are present at high concentrations in the oil and are responsible for the repellent properties of the oil. The oil was extracted using supercritical carbon dioxide due to the high selectivity of the solvent. The operational conditions studied varied from 313.15 to 353.15 K for the temperature and the applied pressures were 6.2, 10.0, 15.0 and 180.0 MPa. Better values of efficiency of the extracted oil were obtained at higher pressure conditions. At constant temperature, the amount of extracted oil increased when the pressure increased, but the opposite occurred when the temperature increased at constant pressure. The composition of the essential oil was complex, although there were several main components in the oil and some waxes were presented in the extracted oils above 10.0 MPa. The results were modeled using a mathematical model in a predictive way, reproducing the extraction curves over the maximum time of the process.

Supercritical CO2 extraction of macadamia nut oil was carried out in a flow apparatus at the following operational conditions: pressures of 10, 15 and 18 MPa; and temperatures of 313 and 353K; a volumetric flow of 1.64 x 10-7 m³.s-1 was used for one hour in each experiment. The efficiency of the extraction process showed to be low. The behaviors of the extraction curves were very similar at all temperatures and the best efficiency value was obtained at 10 MPa. Chromatographic analysis demonstrated the ability of supercritical CO2 to remove some of the main components of the oil: myristic (C14:0), palmitic (C16:0), oleic (C18:1) and linoleic (C18:2) acids, and that higher pressures favoured the removal of lighter components. The extraction process was represented by a simple model based on Langmuir Isotherm, showing a good data fitting.

Supercritical CO2 extraction of the pigments from Bixa orellana seeds was carried out in a flow apparatus at a pressure of 200 bar and a temperature of 40 ºC at two fluid flow rates (0.67g/min and 1.12g/min). The efficiency of the extraction was low (only about 1% of the pigment was extracted). The increase in flow rate led to a decrease in pigment recovery. A large increase in recovery (from 1% to 45%) was achieved using supercritical carbon dioxide with 5 mol % ethanol as extraction fluid at pressures of 200 and 300 bar and temperatures of 40 and 60 ºC. Although the increase in temperature and pressure led to an increase in recovery, the changes in flow rate did not seem to affect it. Furthermore, two plug flow models were applied to describe the supercritical extraction of the pigments from annatto seeds. Mass transfer coefficients were determined and compared well with those obtained by other researchers with similar models for the supercritical extraction of solutes from plant materials.

The objective of this work was the scientific development of concentration of vitamin E from deodorizer distillate of soybean oil (DDSO) using supercritical CO2. Vitamins and sterols rare produced synthetically, but recently the interest in their extraction from natural sources has increased. Therefore, the motivation behind this work was to concentrate the tocopherols from deodorizer distillate of soybean oil, thereby increasing the value of this by-product, rich in fatty acids, sterols, tocopherols and squalene. The experimental step and the simulation of the process were done in a semi-batch mode using supercritical carbon dioxide. The operational conditions studied were temperatures of 40, 60 and 80ºC and pressures from 90 to 350 bar. The best results for concentration factor and efficiency and pressures were achieved in a continuous process where the operational variables were optimized.

This paper presents the utilization of a stochastic global optimization method for the problem of parameter estimation in thermodynamic models. The method is based on an adaptation of the simulated annealing method to continuous variables. The proposed approach is applied to a vapor-solid equilibrium with supercritical carbon dioxide as solvent. Numerical results indicate that the simulated annealing method calculated a set of parameter values associated with considerably smaller errors as compared with a traditional method of local optimization.

Process simulation involves the evaluation of output variables by the specification of input variables and process parameters. However, in a real process, input data and parameters cannot be known without uncertainty. This fact may limit the utilization of simulation results to predict plant behavior. In order to achieve a more realistic analysis, the procedure of stochastic simulation can be conducted. This technique is based on a large set of simulation runs where input variables and parameters are randomly selected according to adequate probability density functions. The objective of this work is to illustrate the application of a stochastic simulation procedure to the process of fractionation of orange essential oil, using supercritical carbon dioxide in a multistage extraction column. Analysis of the proposed example demonstrates the importance of the stochastic simulation to develop more reliable designs and operating conditions for a supercritical fluid extraction process.

The synthesis and analysis of heat exchanger networks are issues of great industrial interest due to the possibilities of decreasing plant costs, through the reduction of the utilities consumption and/or the number of equipments, in a grassroot design or retrofitting an existent network. The present paper explores a new design algorithm based on the Total Annual Cost (TAC) optimization for a thermal equipment, with mean tubeside and shellside flow velocities constraints, studying also the influence of pumping cost in the network’s final cost.