Fernando Augusto Pedersen Voll

A Dynamic Two-Dimensional Model for Deep-Bed Drying of Mate Leaves (Ilex paraguariensis) in a Single-Pass/Single-Zone Conveyor-Belt Dryer

A fundamental model for deep-bed drying of mate leaves in a cross-flow, single-pass/single-zone conveyor-belt dryer is suggested. It involves a set of four partial differential equations obtained by solute mass and energy balances in the solid and fluid phase of the dryer. A set of experimental results of moisture content, absolute humidity, air temperature, and solid temperature available in the literature for deep-bed drying of corn and rough rice in batch dryers was preliminarily used to validate the model. To confirm the reliability of the model for current purposes, drying experiments were carried out at steady-state conditions by feeding 0.05 m, 0.10 m, and 0.15 m deep beds of mate leaves in a bench-scale conveyor-belt dryer at inlet average drying temperatures close to 39°C, 47°C, and 53°C. Air and solid temperature at the top of the beds and average moisture content were well-captured by the model. A good agreement between experimental and calculated open-loop transient responses of average moisture of mate leaves in the discharge of the dryer, in the presence of imposed disturbances in the speed of the conveyor, was also observed. In all cases, the dynamic model was solved numerically by the method of lines without involving any adjustable parameter.

Liquid-liquid Equilibrium in Systems Containing Olive Oil, Free Fatty Acids, Ethanol and Water

This paper reports experimental data and the thermodynamic modeling of the liquid-liquid equilibrium systems with triacylglycerols, free fatty acids (obtained from olive oil), ethanol and water. The experimental data were fitted using the UNIQUAC model, in which absolute deviation of 1.28 % and root mean square deviation of 2.10 % between experimental and calculated mass fraction of the components in each phase were obtained. The results from this study can be complementary to investigations of more complex liquid-liquid equilibrium of systems containing diacylglycerols and monoacylglcerols of olive oil in hydroalcoholic solutions, once such systems will mostly also contain triacylglycerols and free fatty acids on its composition. Diacylglycerols are obtained from different reaction processes and can be purified by liquid-liquid extraction at mild conditions of temperature and pressure, what justifies the experimental and theoretical approach made in this work.

Density, refractive index and viscosity as content monitoring tool of acylglycerols and fatty acid methyl esters in the transesterification of soybean oil

The growing interest in research and development for alternative biofuels has drawn special attention to biodiesel, a mixture of fatty acid methyl esters (FAMEs) that can be obtained by the transesterification reaction of triacylglycerols (TAGs) with a short chain alcohol. During transesterification reaction kinetic studies, it is important to monitor the levels of diacylglycerols (DAGs) and monoacylglycerols (MAGs), as well as those of TAGs and FAMEs. These contents are generally determined according to reference methods by GC-FID analysis. This technique is expensive and time consuming, not to mention that samples with higher TAG contents can be harmful to the chromatography column and accessories. In this context, this study aims to determine the composition of a quaternary system, in which virtually only the four compounds cited previously are present, using a single-step chemometrics analysis that uses mathematical modelling to correlate the composition with three physical properties (density, refractive index and viscosity) of the same sample, one at a time. Subsequently, a sample with an unknown composition has the same properties determined and then a system of equations composed of three equations (one for each physical property) with three unknowns are solved to determine the unknown samples composition. This method can be used as an initial screening method to determine both the TAG and FAME content in a sample, to be implemented prior to the performance of the GC analysis, because the results obtained in this study have shown that the approach proposed was able to determine mass fractions of quaternary systems with both a Mean Absolute Error (MAE) and Root Mean Square Deviation (RMSD) of less than 0.03.

Kinetics of Pressure Cycling Extraction of Solute from Leaves of Mate (Ilex paraguariensis) Dispersed in Water

A set of seven extraction experiments was performed to investigate the influence of pressure cycles on the kinetics of solute removal from leaves of mate dispersed in water. The mass ratio of liquid to dry solid (40), the temperature (32°C), and time of extraction (3600 s) were not varied. Five extraction runs were under cyclic pressurization (1 cycle = 300 s at 91.4 kPa + 300 s at 182.8 kPa) and stirring speeds (S) of 0, 150, 500, 1500, and 2000 rpm, while the two other ones were at constant pressure (182.8 kPa) and S close to 1500 and 2000 rpm. Based on seven pairs of parameters of a reliable second-order kinetic model (R2 ≥ 0.967), cyclic pressurization had no effect on equilibrium and kinetics of extraction (p > 0.05) when the role of convection on solute transfer was negligible (S ≥ 500 rpm). In the stirring speed range from 500 to 2000 rpm, the operation was controlled by diffusion (Bi  > 1.7 × 103), so a transient two-dimensional diffusion model was able to describe correctly the changes of solute concentration with time. Below 500 rpm, solute transfer was governed by a combination of diffusion and convection with the external resistance to mass transfer as a function of S (16 ≤ Bi ≤ 28).

Kinetics of Enzymatic Hydrolysis of Olive Oil in Batch and Fed-batch Systems

This work reports experimental data, kinetic modeling, and simulations of enzyme-catalyzed hydrolysis of olive oil. This reaction was performed in batch system and an ordered-sequential Bi Bi model was used to model the kinetic mechanism. A fed-batch system was proposed and experimental data were obtained and compared to the simulated values. The kinetic model used was able to correlate the experimental data, in which a satisfactory agreement between the experimental data and modeling results was obtained under different enzyme concentration and initial free water content. Therefore, the modeling allowed a better understanding of the reaction kinetics and affords a fed-batch simulation for this system. From the results obtained, it was observed that the fed-batch approach showed to be more advantageous when compared to the conventional batch system.