Everton Fernando Zanoelo

Dyeing of polyethylene terephthalate fibers with a disperse dye in supercritical carbon dioxide

A 24 factorial design of experiments complemented with a central point was performed to examine the influence of operating factors on color strength and color fastness of polyethylene terephthalate (PET) fibers dyed with the Disperse Orange 30 dye in supercritical CO2. The effects of temperature, pressure, dyeing time and mass ratio between the dye and PET introduced in the dyeing chamber (α ratio) were considered. An additional set of kinetic results of color strength was obtained at the optimum condition in terms of pressure at the already presented temperatures and α ratios. A significant statistical effect of all the investigated factors on the color was observed, but except for the temperature, the influence of the same variables on wash fastness was negligible (p < 0.05). The color results expressed in terms of K/S from 2.4 to 21.8 revealed that the use of supercritical CO2 as a solvent for the dye is a rapid and reliable alternative procedure for dyeing of PET fibers with the Disperse Orange 30 dye. The results of wash fastness currently obtained (i.e. 4.69 ± 0.18) support the use of ScCO2.

Thin-Layer Drying of Mate Leaves (Ilex paraguariensis) in a Conveyor-Belt Dryer: A Semi-Automatic Control Strategy Based on a Dynamic Model

A feedback strategy of drying control of mate leaves in a thin-layer conveyor-belt dryer was experimentally evaluated. Moisture content in the discharge of the continuous dryer was controlled by manually adjusting the speed of the moving belt between 3.7 × 10−4 and 15.2 × 10−4 m s−1 for approximately 7200 s in 120 s time steps. The sets of PID controller parameters and manipulated conveyor velocities were computed with a dynamic drying model at conditions identical to those found in the closed-loop experiments. The model is represented by a system of two partial differential equations built by energy and solute mass balances in the solid phase of the dryer. A large set of experimental drying curves and temperature of mate leaves as a function of drying time, in the temperature range from 55 to 130°C, confirmed the reliability of the considered model. Experimental closed-loop responses of discharge moisture content in the presence of disturbances in the feed moisture content (≈ 0.5 − 1.7 dry basis) and variations in set-point (≈ 0.1 − 1.0 dry basis) validated the suggested control scheme.

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.

Removal of clomazone herbicide from a synthetic effluent by electrocoagulation

The aim of this work was to investigate the kinetics of removal of clomazone herbicide from an aqueous solution by electrocoagulation. The experiments were performed in a cylindrical batch reactor with six aluminum electrodes in monopolar mode, arranged in series and connected to a digital DC power. The aqueous solution (tap water + clomazone) with initial pH close to 7.9 was always treated at ambient temperature (≈20 °C) and atmospheric pressure for 5,400 s. For a confidence level of 95% the rate constant of electrocoagulation and the efficiency of removal of clomazone at equilibrium were 2.1 × 10(-3) ± 0.5 × 10(-3) s(-1) and 97.7 ± 2.2%, respectively. The final chemical oxygen demand was 88% lower than that measured initially, while turbidity and apparent color were totally removed from the synthetic solution at a rate close to that of formation of aluminum hydroxides. Some reaction intermediates, such as benzonitrile-2-chloro and 2-chloro-hex-2,4-diene-1,6-dioic-acid determined by gas chromatography mass spectrometry (GC-MS) analysis, explain the ratio of equilibrium to initial total organic carbon approximately between 0.6 and 0.8 at a probability of 95%.

Predicted Nitric Oxide Emission from an Ethanol/Gasoline HCCI Engine

The main aim of this study is to investigate theoretically the formation of nitric oxide (NO) in a homogeneous charge compression ignition (HCCI) engine fueled with blends of ethanol and synthetic gasoline (RON25, RON50, RON75). A detailed kinetic mechanism involving 1086 chemical species and 4754 elementary reactions taking place in a HCCI engine modeled as an adiabatic single-zone reactor was applied to simulate the emission of the investigated pollutant. A close agreement between experimental and calculated results of ignition delay, species concentrations in ideal reactors, and laminar flame velocities of pure ethanol, n-heptane and iso-octane confirmed the reliability of the kinetic model. An analogous comparison, but considering a set of data (NO formation, temperature, and pressure) obtained in a single-cylinder HCCI engine operated with different mixtures of primary reference fuels (n-heptane and iso-octane) over the equivalence ratio range from approximately 0.15 to 0.4, revealed the consistency of the adiabatic single-zone model. Despite the low to moderate content of NO typically observed in the exhausts from HCCI engines, a further decrease of this pollutant was still revealed at all the considered simulating conditions when the percentage of ethanol in the fuel (synthetic gasoline) was increased. However, the extent of NO reduction was more evident for blends involving up to approximately 20% of ethanol (<E20) and synthetic gasolines with low octane number (<RON50). From a practical point-of-view, this finding reveals that the injection of a small volume of ethanol to gasoline (<20%) could be an alternative procedure to reduce the rates of exhaust gas recirculation applied to control the HCCI operation, making it a promising strategy to have a conciliation between low NO and moderate UHC and CO emissions in gasoline HCCI.

An Experimental Investigation of Flammability Limits and Autoignition Temperatures of Petrofuels and Biofuels in a Tubular Burner

A set of experiments to determine the flammability limits of pure and binary blends of fuels was carried out in a combustion tube operated at atmospheric pressure. The lowest and highest volumetric fraction of vapor fuels that allowed flame propagation when the air/fuel mixture was submitted to a high voltage spark with energy higher than the minimum ignition energy defined the lower and upper flammability limit, respectively. The obtained experimental results for liquefied petroleum gas (LPG), acetone, ethylic alcohol, gasoline, diesel, and bioethanol are in close agreement with results reported in the literature. Diagrams of flammability limits of mixtures of gasoline/bioethanol and diesel/biodiesel were found within the range of composition of standard commercial blends of these fuels available for market in Brazil. The autoignition temperature and the influence of temperature on flammability limits of pure ethanol and a commercial mixture with 4% of biodiesel and 96% of diesel were experimentally determined.

Mechanisms of heat and mass transfer during drying of mate (Ilex paraguariensis) twigs

ABSTRACT Experimental results of surface temperature and moisture content of twigs of mate were obtained in a conveyor-belt dryer operated batchwise. The first response was determined with an infrared sensor, while the second was by conventional gravimetry. A set of 0.04-m-long cylindrical twigs classified manually into three different subgroups on the basis of their diameters (3.5 × 10−3, 6.5 × 10−3, and 10 × 10−3 m) were used in the experiments. Drying always took place in a chamber fed with a thin single layer of material 0.5 m in length and 0.05 m wide. The fresh twigs without leaves at ambient temperature (≈27.2 ± 2.6°C) and with an initial moisture content close to 0.8 ± 0.1 were dried at three different average air temperatures (65.5, 80.2, and 83.8°C) for 7200 s. A full set of nine (31 × 31) drying experiments were performed by varying the examined factors (particle diameter and drying temperature) at three levels. The low estimated Biot numbers (<0.55) indicate that convection plays a much more important role than conduction in heat transfer. Because of this and since heating was much faster than drying, the Newton’s law of cooling alone was successfully applied to describe the increase of particle temperature with time. From a similar analysis involving a convective mass transfer coefficient calculated with the Chilton-Colburn analogy emerged high-mass-transfer Biot numbers (≈5.37 × 103 − 3.65 × 105) that reveal drying of twigs is governed by diffusion. In fact, the equation that represents the Fick’s second law of diffusion in a long cylinder (one-dimensional transfer), solved analytically and coupled to the model of heat transfer, was able to describe the kinetics of drying of mate twigs.

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).

Photo-fenton and UV photo degradation of naphthalene with zero- and two-valent iron in the presence of persulfate

Abstract An initial set of 12 kinetic experiments was carried out to remove naphthalene from an aqueous effluent by photo-Fenton involving Fe0 and Fe2+ at two different concentrations of H2O2 (150 and 300 mg L−1) and three different pHs (3, 5, and 7) (22×31 experiments). The rate constants (k) for the reaction of naphthalene degradation by involving Fe2+ as reactant were in general higher than those with Fe0, but the use of Fe2+ increased the concentration of naphthalene at equilibrium (Ce) when compared with the same response obtained with Fe0 at analogous conditions. A second set of twelve kinetic experiments of photo-Fenton degradation was also performed with persulfate as additive at the conditions already reported, but at a constant concentration of H2O2 of 150 mg L−1 (21×31 experiments with NaCl +21×31 experiments without NaCl). In almost all the runs in which only the source of iron was varied, k from the kinetic data involving Fe2+ was higher than that involving Fe0, but no difference was observed in terms of Ce that was always zero. The addition of persulfate to treat the effluent either containing or not containing salt enhanced the chemical kinetics, and shifted the equilibrium toward the full removal of naphthalene. A final set of nine experiments of UV photo degradation of naphthalene by involving persulfate without iron, with Fe0 and Fe2+ in the pH range from 3 to 7 (32 experiments) mainly showed that the use of H2O2 may be avoided to remove rapidly and completely naphthalene from wastewater.

Soft-sensor models to estimate the efficiency of H2S removal from an oil refinery stream of nonphenolic sour water

ABSTRACT A large set of results of concentration of hydrogen sulfide in the feed and bottom product streams of a sour water stripper found in a typical oil refinery was experimentally obtained. The readings of H2S concentrations were at several different operating conditions in terms of the main process variables that classically have significant effects on the efficiency of H2S removal (E). In particular, the considered factors were the mass flow rate, and temperature of sour water fed into the stripper, the mass flow rate of external steam injected into the reboiler, the difference between the temperature of the product stream leaving and entering the reboiler, and the difference of pressure at the two ends of the tower. Three different soft-sensor models were suggested to describe the observed variation in E from 63 to 97%, namely, an equilibrium, statistical and an artificial neural network model. The best of them was the neural network one with three input variables, four neurons in the one-hidden layer, and a hyperbolic tangent function for both the output and one-hidden layers. The mean absolute relative deviation between measured and calculated E by involving this model was only approximately 2.5% with negligible tendency for the residuals. It confirms the reliability of this approach as a tool to inferential estimation of the efficiency of removal of H2S from the sour water by stripping.