Mixing Of Binary Mixtures Research Articles

CFD-DEM mixing of rod-like and spherical particles in fluidized beds

Understanding the behavior of particle mixing in fluidized beds is crucial for enhancing process design. This article focuses on investigating the effect of key parameters, such as volume fraction of spherical particles, length of rod-like particles, and aspect ratio of rod-like particles, on the mixing of binary mixtures containing spherical and rod-like particles. The study employs a computational approach which couples the computational fluid dynamics and discrete element method (CFD-DEM) to explore mixing behavior of particles. Non-spherical particles are modeled using the multi-sphere method. A combination of qualitative and quantitative approaches is employed to assess the mixing performance, including visual examination of the fluidized bed and calculation of the subdomain-based mixing index. It was shown that an increase in rod-like particle length, aspect ratio, and volume fraction of rod-like particles weaken the mixing. Furthermore, the quality of mixing is directly influenced by bubble size and particle granular temperature. This study offers valuable insights into the mixing behavior of rod-like and spherical particles, contributing to the design and optimization of binary fluidization processes.

CFD study of binary mixture mixing/segregation of supercritical carbon dioxide fluidized bed

Mixing of binary mixture with small-sized particles component (SC) and large-sized particles component (LC) is simulated using unequal granular temperature-based kinetic theory (UGT-KT) in supercritical carbon dioxide fluid (S-CO2) fluidized bed. Synergy angle is applied to identify the tendency of mixing/segregation of SC and LC binary mixture according to the axial distribution of component volume fractions along bed height of S-CO2 fluidized bed. Three different regions, including segregation (SE) near the bed bottom, transition (TR) near the bed top and dense (DE) between the SE and TR regions along bed height, are discriminated. Large synergy angle reveals the tendency for the SC and LC particles to segregate. Small synergy angles occur with fluidizing velocity and temperature. Defluidization occurred at certain pressure ratio p/pcr of 1.22–1.62, leading to a large synergy angle in S-CO2 fluidized bed.

Numerical study of hydrodynamics with surface heat transfer in a bubbling fluidized-bed reactor applied to fast pyrolysis of rice husk

The present study investigates the hydrodynamics and heat transfer phenomena that occur during the biomass fast pyrolysis process. A numerical approach that combines a two-dimensional Eulerian multi-fluid model and the kinetic theory of granular flow has been applied to simulate the gas-solid flow in a bubbling fluidized-bed reactor. In this study, rice husk and quartz sand with specified properties were used as biomass and inert material, respectively. Our model was first validated the feasibility using previous findings, then an extensive parametric study was conducted to determine the effects of the major variables, especially the size of rice husk particles, on the flow distribution and the heat transfer between the phases. The concept of standard deviation attributed to the dispersion of solid volume fraction was used to calculate the intensity of segregation. The simulated results indicated that the mixing of binary mixture was strongly affected by different sizes of rice husk particles. The heat transfer occurring inside the fluidized bed was described by the distribution of solids temperature, the variation of surface heat flux and heat transfer coefficient. Both heat transfer quantities were observed to be dominant in the dense bed regions as they strongly depend on the solids concentration in the fluidized bed. The increasing inlet gas velocity promoted the mixing of solid particles, thus resulted in the effective heat transfer from wall to particles and between the particles.

X-ray structural studies on microscopic mixing in binary mixtures of dimethyl sulphoxide with acetonitrile and N,N-dimethylformamide

The liquid structures of binary acetonitrile (AN)–dimethyl sulphoxide (DMSO) and N,N-dimethylformamide (DMF)–DMSO mixtures were investigated by the X-ray scattering method. Comparison of the X-ray scattering data of AN–DMSO liquid mixtures with those of neat AN and DMSO revealed that the intermolecular AN–DMSO interactions are practically not detected; that is, the X-ray scattering data of the liquid mixtures are well reproduced by summing up those of neat AN and DMSO weighted by their mole fractions. The same applies for DMF–DMSO mixtures. Thus, each component solvent molecule independently forms self-assembled clusters in the liquid mixtures, the structures of which are the same as those in the neat liquids. The clusters are mixed to form macroscopically homogeneous liquid mixtures. The thermodynamic quantities on mixing process for the AN–DMSO, DMF–DMSO and AN–DMF systems in the literature are well elucidated on the basis of the microscopic structure of the liquid mixtures.

Pressure drop and pressure fluctuations in spouted beds with binary mixtures of particles

When handling fine particles in spouted beds, addition of coarse particles has shown improved spouting stability than single particle systems. However, segregation may still occur because of insufficient mixing in binary mixtures, which will adversely influence the process performance. Therefore, in this study, analysis of pressure drop and its fluctuation signals were for the first time used to understand mechanisms of flow regime transitions in spouted beds with binary mixtures. The results showed that the typical varying sequence of pressure drop can be observed for spouted bed with binary mixtures and the peak pressure drop is related to the mixing degree of particles, which is mainly influenced by the inter-particle forces between fine particles and their counterpart coarse ones. The statistic characteristics of pressure drop time series, i.e., average value, standard deviation and probability distributions, were found to vary for different flow regimes. Therefore, they could be used for the characterization of these flow regimes. The spouting stability of binary mixtures can be reflected by power spectrum analysis; the influences of particles size and density difference on spouting stability were discussed through power spectral analysis.

N-Acyl Chain in Ceramide and Sphingomyelin Determines Their Mixing Behavior, Phase State, and Surface Topography in Langmuir Films.

Sphingolipids are membrane lipids composed by a long chain aminediol base, usually sphingosine, with a N-linked fatty acyl chain whose quality depends on the membrane type. The effect of length and unsaturation of the N-acyl chain on the mixing behavior of different sphingolipids has scarcely been studied, and in this work this issue is addressed employing Langmuir monolayers at the air-water interface, in order to assess the surface mixing in binary mixtures of different species of sphingomyelins and ceramides. The dependence on the monolayer composition of the mean molecular area, perpendicular dipole moment, domain segregation, and surface topography, as well as the film elasticity and optical thickness were studied. The results indicate that composition-dependent favorable interactions among sphingomyelin and ceramide occur as a consequence of complementary lateral packing and increased acyl chain ordering; the phase state of the components appears as a major factor determining miscibility among sphingomyelins and ceramides even in cases where the lipids have a considerable hydrocarbon chain length mismatch.

CFD modeling the hydrodynamics of binary particle mixtures in bubbling fluidized beds: Effect of wall boundary condition

The hydrodynamics of binary particle mixtures differing in size and density in low gas velocity bubbling fluidized beds were simulated by a multi-fluid Eulerian model incorporating the kinetic theory of granular flow. Parametric studies of the particle–wall restitution coefficient and specularity coefficient were performed to investigate the influence of wall boundary condition on the predicted segregation and mixing behavior in terms of jetsam concentration and velocity distribution. The predicted axial and radial concentration distributions were compared with available experimental data. The results demonstrate that the particle–wall restitution coefficient only plays a minor role in predicting the segregation and mixing of binary particle mixtures in bubbling fluidized beds. For the segregation process, the predicted segregation is significantly affected by the specularity coefficient. No segregation can be predicted for small specularity coefficients, while for the mixing process, the predicted jetsam concentration distributions are almost unaffected by the specularity coefficient, although the jetsam velocity distributions are significantly influenced. The predicted segregation behavior of binary particle mixtures is significantly affected by the specularity coefficient. No segregation can be predicted for small specularity coefficients. ► We used multi-fluid model to simulate segregation and mixing of binary mixtures. ► We investigated the effect of wall boundary condition on hydrodynamics. ► Particle–wall restitution coefficient plays a minor role. ► Specularity coefficient affects segregation behavior and unaffects mixing behavior. ► Small specularity coefficient cannot predict segregation behavior.

Evaluation of Excess Gibbs Energy of Mixing in Binary Mixtures of Di-Isobutyl Ketone (Dibk) and Nonpolar Solvents

Excess Gibbs energy of mixing in binary mixture of Di-isobutyl ketone (DIBK) in nonpolar solvents namely n-heptane, p-xylene, cyclohexane, dioxane, benzene and tetra-chloromethane have been evaluated at 303°K. The results indicate that (ΔGAB)maxima is in the order, n-heptane > p-xylene > cyclohexane > benzene > dioxane > tetra-chloromethane.

Influence of Molecular Structure on the Ideality of Mixing in Micelles Formed in Binary Mixtures of Surface-Active Drugs

The influence of the structure of the hydrophobic group on the ideality of mixing in binary mixtures of surface active molecules has been investigated using combinations of amphiphilic penicillins. Critical concentrations (cc) of the binary mixtures of these anionic surfactants were determined by conductivity measurements as a function of the composition. The nonideality of mixing was evaluated using a regular solution approximation and expressed in terms of the interaction parameter, β. Mixing in micelles formed in binary mixtures of the structurally similar penicillins cloxacillin, dicloxacillin, and flucloxacillin was ideal (β = 0). In contrast, the combination of either cloxacillin or dicloxacillin with the penicillin nafcillin produced mixed micelles in which the mixing deviated from ideality (β = +0.1 to +0.2). The positive values of β for these systems indicated negative synergism between components of the mixtures that may be a consequence of the marked structural differences between the hydrophobic groups of these drugs. The composition of the mixed micelles was derived from the cc data by application of a theoretical treatment based on excess thermodynamic quantities.

Evaluation of Excess Gibbs Energy of Mixing in Extremely Dilute in Nonpolar Solvents Solutions of TRI-N-Butyl Phosphate

The excess gibbs energy of mixing in binary mixtures of TBP in nonpolar solvents viz. bcnzene, carbon disulphide, cyclohexane, n-heptane, n–hexane, p–xylene, tetrachloromethane at temperature 303°K is studied. The excess free energy of mixing (AGA8) is in the order, n–hexane < n–heptane < benzene < cyclohexane < p–xylene < CCI4 < CS2. The results corroborate the findings obtained through evaluation of the excess correlation Factor.

Evaluation of Excess Free Energy of Mixing in Binary Mixture of Polar-Nonpolar Liquids Using Dielectric Probe-an Experimental Assessment of the Efficiency of Proposed Equation

Excess free energy of mixing ΔFtotal ΔFAB in the binary mixtures of long chain alchols and amines in nonpolor solvent carbon tetrachloride have been calculated with the help of our proposed equation. The novelty of our equation is that it involves separate estimation of excess free energy of mixing due to interaction between polar-polar molecules, polar-induced nonpolar molecules and induced nonpolar molecules and a picture of molecular interaction in these mixtures has been elicited with the help of these parameters.

The intermolecular interactions in binaries

The recapitulation of systematical investigations of excess enthalpy of mixing in binary mixtures: pyridine base +n-alkane or some of arenes is presented. On the base of experimental results as well as model calculations (PFP, ERAS) the discussion of intermolecular interactions in pyridine bases is given.

Volumes of mixing of ternary alkane mixtures with branched chain components

Measurements at 25 °C are reported for the volumes of mixing of binary mixtures of n-dodecane + 2 methyl pentane and of ternary mixtures created by mixing an equimolar mixture of (n-decane + n-tetradecane) with each of the isomers of hexane. The results are compared with the work of Hamam etal. for binary mixtures of n-dodecane with the hexane isomers and shown to be in accord with the principle of congruence within the limits of experimental accuracy of the measurements.

Excess Enthalpies of Binary Solvent Mixtures of γ-Butyrolactone with Hexan-1-ol, Heptan-1-ol, Octan-1-ol and Decan-1-ol

Abstract The excess enthalpies of four alcohols with γ-butyrolactone were determined at 25°C, by a Parr 1451 solution Calorimeter. All the four systems showed endothermic behaviour. The results are explained on the basis of a steric effect on interaction. Enthalpies of mixing of binary mixtures do provide valuable insight into molecular interactions.

Excess Volumes of Binary Mixtures of γ-Butyrolactone with Some Aliphatic and Isomeric Alcohols

Abstract Excess volume data on mixing for binary mixtures of γ-Butyrolactone with propan-1-ol, butan-1-ol, pentan-1-ol, hexan-1-ol, propan-2-ol, 2 methyl propan-1-ol, 3 methyl butan-1-ol, have been determined at 303.15 K. The VE values are negative over the whole range of composition in mixtures containing propan-1-ol, propan-2-ol, butan-1-ol, 2 methyl propan-1-ol, and 3 methyl butan-1-ol. In pentan-1-ol, however, VE is negative at lower molefractions and positive at higher molefractions, whereas in hexan-1-ol the value of VE are positive throughout the entire concentration range, which indicates significant interaction between γ-butyrolactone and the aliphatic and isomeric groups. These values are attributed to weak complex formation and predominating de-association of associated liquids by γ-butyrolactone. The results are ascribed to interactions between unlike molecules.

Excess heat of mixing of binary mixtures of pyridine withn-alkanes at 313.15 K

The molar excess enthalpies of binary mixtures of pyridine with C6–C9n-alkanes have been measured at 313.15 K in the entire composition range. The measuredHE values were compared with those calculated by means of the Prigogine-Flory-Patterson theory and by the ERAS method.

Heats of mixing of binary mixtures of pyridine base with n-alkane

Heats of mixing of 2,4-lutidine and 2,4,6-collidine with n-alkanes were measured at 293.15 K using an isothermal dilution calorimeter. Experimental results were fitted with a Redlich–Kister polynomial. Experimental data and coefficients for the Redlich–Kister polynomials are reported.

Excess Volumes of Trichloroethylene with Some Aliphatic and Alicyclic Ketones at 303.15K and 313.15K

Abstract Excess volumes on mixing for binary mixtures of trichloroethylene with aliphatic ketones and alicyclic ketones have been determined dilatometrically. The VE data are reported over the complete mole fraction range at 303.15K amd 313.15K. Aliphatic ketones include methylethylketone, methylpropylketone, diethylketone and alicyclic ketones are cyclopentanone and cyclohexanone The measured VE values are negative over the entire composition range. Temperature effect is also studied for all the binary systems. The observed values are interpreted in terms of (i) formation of hydrogen bond and (ii) dipole-induced dipole interactions between the dipole of the ketone and trichloroethylene.

Heats of mixing of binary mixtures of 1,1,2,2-tetrachloroethane with 1-alcohols

Enthalpies d'exces H E de melange du tetrachloro-1,1,2,2 ethane dans le butanol-1 pentanol-1, hexanol-1 et heptanol-1