Mass transfer coefficient and the characteristics of coated apples in osmotic dehydrating

In a dynamic osmotic dehydration from 0 to 180 min, the influence of different edible coating materials such as Low-Methoxyl Pectinate (LMP), Carboxyl-Methyl Cellulose (CMC), Corn Starch, and an osmotic sucrose solution with two concentration of 50% and 60% (w/w) on apple rings and their physical characteristics were studied, which included: moisture loss (ML), solid gain (SG), ML/SG ratio, effective diffusivity of solute and water (D_es, D_ew). The qualitative characteristics such as: firmness of the texture or shear stress (SS), and Browning index (BI) were also tested. Using Fick's first and second laws, the effective diffusion coefficient of water and solute were calculated. Osmosed apples in solution with 60% sucrose concentration, showed higher ML/SG ratio than other samples and, apples coated with 2% CMC and osmodehydrated in 60% sucrose, showed not only higher ML/SG ratio but higher diffusivity coefficient as well. The results showed that in comparison with non-coated samples, coating process can cause to improve the textural structure of the apple rings. By increasing the concentration of osmotic solutions, the Browning index (BI) of both coated and uncoated samples decreased.     

Mathematical modeling of moisture and solute diffusion in the cylindrical green bean during osmotic dehydration in salt solution

In this study, mass transfer during osmotic dehydration of cylindrical cut green beans in salt solution was investigated. The osmotic solution concentrations used were 10%, 20% and 26.5% (w/w) NaCl, osmotic solution temperatures used were 30 °C, 40 °C and 50 °C, the solution-to-green bean mass ratio was more than 20:1 (w/w) and the process duration varied from 0 to 6 hr. A two-parameter mathematical model developed by Azuara et al. (1992) was used for describing the mass transfer in osmotic dehydration of green bean samples and estimation of the final equilibrium moisture loss and solid gain. Effective radial diffusivity of moisture as well as solute was estimated using the analytical solution of Fick's second law of diffusion in the cylindrical coordinates. For above conditions of osmotic dehydration, moisture and salt effective diffusivities were found to be in the range of 1.776 × 10⁻¹⁰-2.707 × 10⁻¹⁰ m²/s and 1.126 × 10⁻¹⁰-1.667 × 10⁻¹⁰ m²/s, respectively. Moisture and solute distributions as a function of time and location in the radial direction were plotted by using the estimated equilibrium moisture and solute concentrations and also moisture and solute diffusivities.     

Ultrasound-assisted osmotic process on quality of microwave vacuum drying sweet potato

The effects of pretreatment before microwave vacuum drying (MVD) on texture, color, expansion, rehydration, drying rate, microstructure, sensory evaluation, and other properties of sweet potato were investigated in this study. The pretreatment consisted in five processing conditions, using blanching; osmotic dehydration at 35°Brix of sucrose (OD); ultrasound in distilled water (US); ultrasound in distilled water before osmotic dehydration (US?+?OD), and ultrasound-assisted osmotic dehydration (USOD). Pretreatments of sweet potato before MVD have shown success in reducing drying time with US treatment relatively more effective regarding drying time than other treatments. Compared with other treatments, US showed the highest rehydration ratio values. The osmotic group pretreatment exhibited a pronounced effect on water loss and solid gain, improved the color, aroma, and taste of dried sweet potato, whereas sucrose impregnation resulted in a hard texture observed with OD sample. USOD samples had a higher expansion ratio, lower hardness and color difference values, appeared less cell damaged, and recorded better overall quality than the other samples. There was a slight difference between USOD and US?+?OD samples. Combining osmotic dehydration with ultrasound as a pretreatment can significantly accelerate the heat transfer rate, reducing the dried time accordingly and increasing energy efficiency.     

PTA溶剂脱水系统中PX组分的影响及调控

对二甲苯(PX)组分对精对苯二甲酸(PTA)装置溶剂脱水系统的共沸精馏塔操作有较大的影响,容易在共沸精馏塔内富集。当共沸精馏塔操作条件控制不合理时,PX难以从系统内拔除,影响共沸精馏分离效果。本文对溶剂脱水系统PX组分的影响规律进行了分析和优化,通过模拟计算,获得了PX在共沸精馏塔中的分布规律;研究了抽出板温度对PX抽出浓度的影响,确定了合适的实现PX组分有效拔除的温度范围,为溶剂脱水系统的优化操作提供了指导。     

Drying of Wheat Based on the Non-Equilibrium Thermodynamics: A Numerical Study

A new mathematical model to describe simultaneous heat and mass (liquid and vapor) transfer and shrinkage during drying of capillary-porous bodies with particular reference to prolate spheroid solid is presented. As an application, the methodology was used to predict drying of soft red winter wheat (Arthur). The mathematical model was based on the nonequilibrium thermodynamics considering variable transport coefficients and convective boundary conditions at the surface of the solid. All the partial differential equations presented in the model have been written in prolate spheroidal coordinates and solved numerically by a finite-volume method using implicit fully formulation. Results of the drying and heating kinetics and moisture content and temperature distributions in a wheat kernel during drying process are presented and analyzed. The methodology allows verification of the heat, liquid, and vapor fluxes, taking into account the thermal and hydrical gradients inside the grain.     

Influence of Mn doping on electrical conductivity of lead free BaZrTiO3 perovskite ceramic

Mn doped barium zirconate titanate lead free ceramic with formula BaZr_.045(Mn_xTi_1-x) _.955 O₃ for x?=?0.00, 0.01, 0.02 and 0.03 has been prepared by solid-state reaction method. The single phase tetragonal structure was confirmed by X-ray diffraction (XRD) pattern using Rietveld refinement. Scanning electron microscopy (SEM) shows an inhomogeneous distribution of randomly oriented grains with some voids. Electrical conductivity of Mn doped BZT ceramics was studied using impedance analyzer in the temperature range 493K–673K over wide frequency window. The dispersion behaviour in electrical conductivity obeys Jonscher's double power law for Mn free compound, while it follows single power law for Mn doped compositions. Various parameters viz. dc conductivity (σ_dc), pre-exponential factor (A), frequency exponent (s) and activation energy (E_a) have been estimated by the theoretical fitting of experimental data. The reciprocal temperature dependence of dc conductivity follows the Arrhenius law and specifies thermally activated conduction mechanism. The obtained value of activation energy (E_a) evidences the conduction mechanism is induced by the migration of oxygen vacancies and oxide ions. All samples shows Negative temperature coefficient of resistance (NTCR) and hence exhibit semiconducting behaviour. The environmental friendly lead free ceramic can be exploit to design advanced materials and suitable for the fuel cell electrolyte/electrode applications.     

Influence of magnetic field and gravity on the morphology of zinc fractal electrodeposits

We present a comprehensive study of growth of zinc fractal electrodeposits in a flat electrochemical cell considering the effects of applied voltage, electrode shape and thickness, ion concentration and applied magnetic field for both concentric and parallel electrode geometries. The effect of gravity is also considered in vertical cells. ‘Phase diagrams’ set out the variety of morphologies achievable at different voltages and concentrations for both electrode geometries. Electron microscope analysis indicates that the deposits are built from individual micron-sized crystallites. The system is modelled numerically using a number of modifications to the diffusion-limited aggregation (DLA) model to introduce migration and convection. Experimentally observed morphologies are reproduced numerically for horizontal and vertical, concentric and parallel electrode cells. Each occupied numerical site represents not an individual atom, but the point of nucleation and growth of an individual zinc crystallite containing ∼10¹⁰ atoms.     

Experimental and numerical studies on the effects of pressure release rate on number density of bubbles and bubble growth in a polymeric foaming process

A simulation of simultaneous bubble nucleation and growth was performed for a batch physical foaming process of polypropylene (PP)/CO₂ system under finite pressure release rate. In the batch physical foaming process, CO₂ gas is dissolved in a polymer matrix under pressure. Then, the dissolved CO₂ in the polymer matrix becomes supersaturated when the pressure is released. A certain degree of supersaturation produces CO₂ bubbles in the polymer matrix. Bubbles are expanded by diffusion of the dissolved CO₂ into the bubbles. The pressure release rate is one of the control factors determining number density of bubbles and bubble growth rate.To study the effect of pressure release rate on foaming, this paper developed a simple kinetic model for the creation and expansion of bubbles based on the model of Flumerfelt's group, established in 1996 [Shafi, M.A., Lee, J.G., Flumerfelt, R.W., 1996. Prediction of cellular structure in free expansion polymer foam processing. Polymer Engineering and Science 36, 1950-1959]. It was revised according to the kinetic experimental data on the creation and expansion of bubbles under a finite pressure release rate. The model involved a bubble nucleation rate equation for bubble creation and a set of bubble growth rate equations for bubble expansion. The calculated results of the number density of bubbles and bubble growth rate agreed well with experimental results. The number density of bubbles increased with an increase in the pressure release rate. Simulation results indicated that the maximum bubble nucleation rate is determined by the balance between the pressure release rate and the consumption rate of the physical foaming agent by the growing bubbles. The bubble growth rate also increased with an increase in the pressure release rate. Viscosity-controlled and diffusion-controlled periods exist between the bubble nucleation and coalescence periods.     

Waste water treatment using reverse osmosis: real osmotic pressure and chemical functionality as influencing parameters on the retention of carboxylic acids in multi-component systems

The influence of chemical functionality in carboxylic acids and osmotic pressure of multi-component solutions on the retention in the reverse osmosis process are discussed. Therefore formic-, acetic-, propionic-, glycolic-, acrylic- and methoxyacetic acid (target substances) were combined with one or two other carboxylic acids (active substances), chosen out of a pool of 16. All investigations were carried out with an aromatic polyamide membrane and the operating conditions were kept constant. Although the combination of all effects is extremely complex, the experiments showed that the influence on the retention of a substance equate as an outcome of molecular mass, acidity, functionality and spatial requirement. The influence of functionality in the active substances could be further divided into an additional carboxylic group, double bond and aromaticity. The calculation of the osmotic pressure demonstrated that there was no observable difference between the real and ideal one when the solution contained the same number of components. Therefore it can be concluded that in this study the osmotic pressure has no influence on the retention of the target substance.     

Design and construction of an equipment for the determination of solubility of gases in liquids

This article presents the design and construction of a new isochoric saturation apparatus for the determination of gas solubility in liquids based on the gas drop pressure method. The major improvement of this design is the separation between the solubility and the gas cells. With this separation, the change of pressure and temperature inside the system is minimum when the gas gets in contact with the liquid and it allows degassing the liquid in an easy way. The performance of the equipment was evaluated measuring the solubility of argon and nitrogen in pure water at 283.15, 288.15, 293.15, and 298.15 K. The gas solubility was calculated according to the Henry's law. The results obtained and the comparison with literature values show that the equipment provides an accurate and precise method for determination of gas solubility in water. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3105–3109, 2017     

Effects of brown coal quality and process parameters on the hydroliquefaction of brown coal

During the development of the HVB process the influence of different parameters on the process have been investigated. In this Paper the influence of the properties of the brown coal on the process is reported. It is shown that: (1) the petrographical composition of Rhenish brown coal has virtually no effect on the HVB process; (2) the problems of sedimentation caused by the ash composition of the brown coal can be overcome by a particular thermal pretreatment of the coal; and (3) the moisture content of the brown coal is of minor importance for the technical realization of the HVB process.     

Influence of process parameters on breakage kinetics and grinding limit at the nanoscale

In long‐term milling experiments, in a stirred media mill, a grinding limit where no further particle breakage occurs was identified. During mechanical stressing of the particles, defects are generated in the crystalline lattice, which allows real fracture of nanoparticles. Below a critical size, defects cannot be stored or generated in the crystallites and the overall limit of grinding is reached. This limit is strongly influenced by material properties and hardly affected by most of the process conditions. However, the breakage kinetics strongly depend on the process parameters and suspension conditions as long as the grinding limit is not reached. Based on these findings, two mechanisms of nanoparticle breakage are proposed. Proper choice of process parameters saves not only up to 90% of the energy input to reach the grinding limit but also leads to a higher product quality in terms of crystallinity and less milling bead wear. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Influence of process parameters on the electrical properties of offset printed conductive polymer layers

We report on results of investigating the material–process interaction for the case of offset printed conductive polymers. We interpret the characteristic branched morphology of printed layers of Poly(3,4-ethylenedioxythiophene) doped with Poly(4–styrenesulfonate) in terms of the phenomenon of “viscous fingering”. A comprehensive study of the relevant process parameters reveals that the conductivity of the printed layers results from an interplay between the characteristic wavelength of the fingered structure and the deposited amount of material. Furthermore, optimization of the process parameters allows for significant reduction of the sheet resistance for about 1 order of magnitude to 0.5 kΩ.     

Influence of operation parameters on the separation of mixtures by pervaporation and vapor permeation with inorganic membranes. Part 1: Dehydration of solvents

The separation performance of two different commercially available tubular inorganic membranes was studied for solvent dehydration. The separation layers consisted of A-type zeolite and microporous silica. The membrane characteristics were determined as function of operating conditions such as feed composition, temperature, and permeate pressure in pervaporation and vapor permeation. Among different membranes of the same batch, flux and selectivity were reproducible within 10%. The partial flux of water as the preferentially permeating component increases linearly with the water vapor pressure difference between feed and permeate and depends only marginally (viscosity influence) upon the properties of the organic component. The flux of the organic (retained) component is low and can best be described by assuming a substance and membrane specific permeance (flux over partial pressure difference) that is independent of composition. At very low water concentration in the feed one would expect a strong increase in permeability of the retained component through non-zeolite pores and larger silica pores as predicted by pure component measurements. However, this effect was not observed in mixtures within the concentration range studied here. A temperature rise improves flux rates exponentially while selectivity remains high. Thus, higher module cost in comparison to polymeric membranes can be compensated by reduced membrane area if a higher operating temperature can be chosen. Flux and selectivity decline as a function of permeate pressure with decreasing driving force. In vapor permeation with inorganic membranes superheating of the vaporous feed improves their performance while for polymeric materials a steep flux decline is observed. High flux and selectivity are obtained in the separation of water from alcohols. The normalized flux values of the A-type zeolite membrane are roughly 10 kg/m² h bar with a mixture selectivity of 2000 for methanol, 4000 for ethanol and 8000 for n-butanol. The average permeance of the amorphous silica membrane lies above 12 kg/m² h bar with mixture selectivity of 50 for methanol, 500 for ethanol and 2000 for n-butanol. The separation mechanism is mainly based on adsorption and diffusion enhanced by shape selectivity and size exclusion in some cases. The transport characteristics could be described with a simple transport model based on normalized permeate fluxes. With regard to the operation stability of the membranes, no deterioration of the performance was observed for the A-type zeolite in solvent dehydration or in separation of water from reaction mixtures. The silica membrane showed an initial conditioning effect involving a rearrangement of Si-OH groups with an increase in selectivity and decrease in flux of about 30%. After a few hours the performance stabilized and remained constant during further operation.     

On the Influence of Permeability and Young's Modulus on the Dehydration of a Strongly Shrinkable Two-Phase Porous Medium: A Model Sensibility Analysis and the Development of a Contact Mechanics Measurement Setup

A model that describes the mass transfer in a two-phase shrinkable porous media by using a classic Darcy law for the fluid relative to solid transfer has been recently developed by Cáceres et al.^[ 1-2 Cáceres , G. ; Bruneau , D. ; Jomaa , W. Two-phase shrinking porous media drying: A modeling approach including liquid pressure gradients effects . Drying Technology 2007 , 25 , 1927 – 1934 . Cáceres , G. Modeling the drying of a saturated shrinkable porous medium: Taking into account the liquid pressure. Ph.D. Thesis, University of Bordeaux, France, 2006 (in French).   ^] This model describes the coupling between the fluid pressure and the solid structure deformation tensor by using the Terzaghi stress tensor decomposition for the media and elastic constitutive law for the solid structure.^{[ 3} Terzaghi , K. Theoretical Soil Mechanics ; John Wiley & Sons : New York , 1943 .[Crossref] , [Google Scholar] ^]

The aim of this article is to point out the sensitivity of this model relative to the two main physical parameters that govern the coupled mass transfer and stress level in a strongly shrinkable porous medium, namely, permeability and the Young's modulus. An experimental setup that makes possible the simultaneous measurement of those two parameters as well as the Poisson ratio is developed in agreement with the recent theoretical suggestions of Lin et al. The experimental evolution of these quantities versus the moisture content is discussed for an agar gel.     

Influence of seasonal conditions on the composition and quality parameters of monovarietal virgin olive oils

The aim of this work was to determine the effect of the climatological conditions of the olive crop season on the composition of monovarietal virgin olive oils obtained from the Arbequina cultivar with special emphasis on the phenolic fraction, its percent distribution, and related oil quality parameters such as oxidative stability and bitter index. The main differences were due to freeze injuries caused by low temperatures in December 2001. The levels of chlorophylls and carotenoids in olive oil or pulp from frost-damaged olive trees were lower as a consequence of faster ripening. The olive oil extracted from frost-damaged olive pulp had lower contents of secoiridoid and especially lower levels of 3,4-DHPEA-EDA (the dialdehydic form of elenolic acid linked to hydroxytyrosol). In the following crop seasons, a significant increase in phenolic compounds, especially in secoiridoid derivatives such as 3,4-DHPEA-EDA, was observed. This increase may be due to the fact that olive trees that suffered frost damage in December 2001 were more sensitive to stress caused by the water deficit during summer in the subsequent crop seasons, which is usual in this olive-growing region. Moreover, important correlation coefficients were observed between the main secoiridoid derivative compound (3,4-DHPEA-EDA) and oxidative stability and the bitter index.     

Influence of drying conditions on the moisture diffusion and fluidization quality during multi-stage fluidized bed drying of bovine intestine for pet food

In order to establish the influence of the drying air characteristics on the drying performance and fluidization quality of bovine intestine for pet food, several drying tests have been carried out in a laboratory scale heat pump assisted fluid bed dryer. Bovine intestine samples were heat pump fluidized bed dried at atmospheric pressure and at temperatures below and above the materials freezing points, equipped with a continuous monitoring system. The investigation of the drying characteristics have been conducted in the temperature range ?10 to 25 °C and the airflow in the range 1.5–2.5 m/s. Some experiments were conducted as single temperature drying experiments and others as two stage drying experiments employing two temperatures. An Arrhenius-type equation was used to interpret the influence of the drying air temperature on the effective diffusivity, calculated with the method of slopes in terms of energy activation, and this was found to be sensitive to the temperature. The effective diffusion coefficient of moisture transfer was determined by the Fickian method using uni-dimensional moisture movement in both moisture, removal by evaporation and combined sublimation and evaporation. Correlations expressing the effective moisture diffusivity and drying temperature are reported.Bovine particles were characterized according to the Geldart classification and the minimum fluidization velocity was calculated using the Ergun Equation and generalized equation for all drying conditions at the beginning and end of the trials. Walli's model was used to categorize stability of the fluidization at the beginning and end of the drying for each trial. The determined Walli's values were positive at the beginning and end of all trials indicating stable fluidization at the beginning and end for each drying condition.     

Influence of preparation parameters on the CHT curing diagrams of MUF polycondensation resins

Lignocellulosic substrates such as wood have been found to have a marked modifying influence on both lower‐temperature and higher‐temperature zones of TTT and CHT diagrams during hardening of formaldehyde‐based polycondensates. While the modifying influence of the substrate has been described, the modifying influence of some of the most important manufacturing parameters of the resins on the CHT diagram, not having been previously investigated, are explored here and clear trends are shown. In the case of melamine–urea–formaldehyde (MUF) resins for wood adhesives, the molar ratio (M+U):F appear to be the dominant parameter influencing the relative position of gel and vitrification curves in relation to each other. The ratio of melamine to urea does not appear to have any effect on the relative position of the curve, lacking any clear trend, at least at the higher (M+U) molar ratio of 1:1.9 used for this series of resins. In the case presented for the first time, the influence of resin manufacturing parameters on CHT curing diagrams was studied in combination with the modifications introduced by the substrate. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2821–2825, 2001     

Influence of process parameters on the hydrothermal decomposition and oxidation of glucose in sub- and supercritical water

Supercritical water oxidation (SCWO) of wet waste biomass for energy recovery could be an advantageous alternative to conventional combustion with preceding drying. Therefore the reactions of glucose as a model substance for cellulosic biomass were investigated in sub- and supercritical water. The results of hydrothermal and oxidative experiments carried out in a continuous high-pressure plant with a feed solution of 0.2-1.2% (g g⁻¹) glucose at 24-34 MPa, 250-480 °C and residence times of 2-35 s are presented. In the presence of a stoichiometric oxygen concentration (for total oxidation to carbon dioxide and water) glucose decomposes already at subcritical temperatures readily to carbon monoxide and low molecular liquid substances, chiefly organic acids like e.g. acetic acid and glycolic acid. In turn these are in general more stable and react only slowly with oxygen. The effect of temperature, residence time, pressure, reactant concentration and addition of zinc sulfate on the conversion and the yields of reaction products was demonstrated. Already at 350 °C (24 MPa and 30 s) 99% of the glucose are converted. With increasing temperature the production of CO₂ increases. However, even at 480 °C (34 MPa and 4 s) significant amounts of CO are formed and the reaction of glucose to CO₂ and H₂O is not complete. Higher temperatures or greatly longer residence times are needed for a total combustion of the glucose.     

Influence of ozone treatment on change of structural-chemical parameters of coal vitrinites and their reactivity during the thermal liquefaction process

The treatment of the coal organic matter by ozone is shown by means of the chemical analysis and IR-spectroscopy to result in the redistribution of oxygen atoms in the functional groups. Based on the X-ray diffraction data, it has been shown that the change of the macromolecular organization of the coal organic matter under ozonization is due to the transformation of an amorphous phase, i.e. the formation of crystal associates in it, resulting from packing the plane aromatic fragments after their substituents have been separated. The kinetic analysis of the thermal liquefaction process of ozonized coal in tetralin under non-isothermal conditions indicates that successive liquefaction of the coal organic substance activated by ozone and a certain part of the non-activated coal does occur. The amounts of the coal organic matter activated by ozone and effective activation energy values of the thermal liquefaction process have been estimated.