Índice de refracción e impedancia eléctrica en función de la temperatura de aceites de semillas de uva (Vitis vinifera, Vitis labrusca) extraídos mediante Soxhlet y prensado mecánico

In this report, the temperature dependence of the refractive index and electric impedance of vegetable oil grape seeds extracted from Vitis vinifera (v. Cabernet) and Vitis labrusca (v. Bordo) are investigated by means of experimental techniques. The seeds were collected from wineries located in two cities in the south of Brazil. In both extraction methods, the seeds were dried at 40.0 °C and at 80.0 °C, respectively, before the oil extraction. From optical microscopy and refractometry results, one can see that the grape seed oil extracted by mechanical pressing shows a linear dependence between the refractive index and temperature and has no birefringent residues. From the fitting of the EIS (Electrical Impedance Spectroscopy) data, an equivalent electric circuit composed of a parallel RC in series with a resistor is proposed. The circuit model is in good agreement with the experimental data and provides the electrical permittivity of the vegetable oils investigated.Se investiga mediante técnicas experimentales la dependencia del índice de refracción y la impedancia eléctrica de aceites vegetales extraídos de semillas de uva Vitis vinifera (v. Cabernet) y Vitis labrusca (v. Bordo). Las semillas fueron recolectadas de bodegas situadas en dos ciudades al sur de Brasil. Antes de la extracción del aceite, mediante dos métodos de extracción, las semillas fueron secadas a 40,0 °C y 80,0 °C. De los resultados de refractometria y microscopía óptica, se comprueba que el aceite de semilla de uva extraída por prensado mecánico obedece a una relación lineal del índice de refracción con la temperatura y no presentan resíduos birrefringentes. Con los datos de impedancia eléctrica, se propone un circuito eléctrico equivalente formado por una resistencia y un condensador en paralelo, a su vez ligado a otra resistencia en serie. El modelo de circuito tiene una alta correlación con los datos experimentales y permite obtener la constante dieléctrica de los aceites vegetales investigados

Modeling Heavy Metal Sorption Kinetics Using Fractional Calculus

Heavy metals are commonly regarded as environmentally aggressive and hazardous to human health. Among the different metals, lead plays an important economic role due to its large use in the automotive industry, being an essential component of batteries. Different approaches have been reported in the literature aimed at lead removal, and among them a very successful one considers the use of water hyacinths for sorption-based operation. The modeling of the metal sorption kinetics is a fundamental step towards in-depth studies and proper separation equipment design and optimization. Fractional calculus represents a novel approach and a growing research field for process modeling, which is based on the successful use of derivatives of arbitrary order. This paper reports the modeling of the kinetics of lead sorption by water hyacinths (Eichhornia crassipes) using a fractional calculus. A general procedure on error analysis is also employed to prove the actual fractional nature of the proposed model by the use of parametric variance analysis, which was carried out using two different approaches (with the complete Hessian matrix and with a simplified Hessian matrix). The joint parameter confidence regions were generated, allowing to successfully show the fractional nature of the model and the sorption process

MgO and Nb2O5 oxides used as supports for Ru-based catalysts for the methane steam reforming reaction

A comparative analysis of Ru catalysts for low temperature (400–750 °C) methane steam reforming reaction has been performed on magnesia, niobic acid and niobia supports. Ru from chloride or nitrosyl nitrate precursors was deposited by incipient wetness impregnation method on supports calcined in different ways. All of the MgO-supported catalysts were calcined at 400 °C while the niobia-based catalysts underwent different calcinations regimes. The catalytic activity towards the methane steam reforming reaction was assessed in a fixed bed quartz reactor with an overall flow rate of 100 Ncm3 min–1 (weight space velocity WSV of 33 Ncm3 min–1 gcat–1 and steam-to-carbon S/C ratio equal to 4). All of the catalysts showed comparable results, especially the magnesia- and the niobic acid-supported catalysts resulted in high activity at 700 °C, whereas a few of the niobia-supported catalysts achieved complete CH4 conversion. The best performing catalysts were characterized by BET, CO chemisorption, XRD, XPS and SEM analyses

Circular Economics in Agricultural Waste Biomass Management

The present study deals with the reuse of agro-industrial waste with a specific focus on biochar (processed plant biomass or biochar) consisting of organic and inorganic waste biomass subjected to thermochemical processes. The objective of this work is to carry out a systematic review of the literature according to the Methodi Ordinatio methodology and select a bibliographic portfolio of high relevance to this study that makes it possible to present the concepts, applications and interest on the part of companies in including biochar in their processes, as well as addressing the environmental impacts linked to incorrect waste disposal. In this sense, biochar presents an interesting potential solution from both a waste management and environmental point of view. The current challenge is studies that prove economic viability

Active Control System Applied to Vibration Level Control in High-Speed Elevators

This work presents an active control system applied to vibration level reduction in high-performance vertical transport, aiming at improving the passengers’ comfort in high-speed elevators. The control system design includes the use of a Proportional Integral Derivative (PID) control. Three strategies were proposed in order to achieve a 90% reduction in the vibration amplitudes: (I) the consecutive reduction of 90% of the displacements, (II) the consecutive reduction of 90% of the velocity, and (III) the consecutive reduction of 90% of the acceleration. The presentation of these three proposals allows their application for the use of different sensors. The performance of each strategy was evaluated through mathematical modeling and numerical simulations of a vertical transport with 4 degrees of freedom, submitted to excitations arising from rail deformations. Vibration and comfort levels in the cabin were numerically analyzed, taking into account ISO 2631 and BS 6841 standards for elevator lateral acceleration level and comfort level felt by passengers. Numerical simulations showed that the force required to reduce the vibration levels is practically the same for the three proposed strategies. However, strategy (III) – the successive reduction of 90% of acceleration – proved to be more efficient at improving passengers’ comfort level when compared to the other two strategies