Hydrodynamics and flow regimes in turbulent bed contactor with non‐Newtonian liquids

The flow regimes normally encountered in a turbulent bed contactor (TBC) are static, partially fluidised, completely fluidised and flooding regimes. Experiments were conducted in a TBC operating in Type I mode to identify the flow regimes with non‐Newtonian liquid. Flow regime transition velocities were obtained from the pressure drop and bed expansion measurements at various operating and geometric variables. The variables include apparent viscosity of the liquid, gas and liquid velocities, size and density of the particles, and static bed height. The effect of the above variables on delineation of flow regime transition was studied. Based on the experimental data, correlations were proposed for predicting the transition velocity from one regime to the other. The influence of the variables on regime transition velocities is more or less similar to that observed for Newtonian liquids. © 2011 Canadian Society for Chemical Engineering     

Hydrodynamics of turbulent bed contactor: Flooding aspects

Experimental data on flooding characteristics were obtained in a Turbulent Bed Contactor (TBC). The flooding conditions and the mechanism of flooding in a single stage TBC have been analyzed for light and dense particles in order to obtain useful correlations that are easier to comprehend. The proposed correlations predict all the combinations of flooding velocities over a large range of variables.     

Modified gas‐perturbed liquid model (GPLM) for minimum fluidization velocity in a two‐phase inverse fluidized bed reactor with Newtonian and non‐Newtonian systems

In the present investigation minimum fluidization velocity, U_mf, in a two‐phase inverse fluidized bed reactor is determined using low‐density polyethylene and polypropylene particles of different diameters (4,6 and 8 mm) by measuring pressure drop. In a glycerol system U_mf decreased gradually with increase in viscosity up to a value of 6.11 mPa s (60%) and on further increase there was a slight increase in U_mf. In the case of the glycerol system the U_mf was found to be higher when compared to water. In the non‐Newtonian system (carboxymethylcellulose), U_mf decreased with increase in concentration in the range of the present study. The U_mf was found to be lower when compared to water as liquid phase. The modified gas‐perturbed liquid model was used to predict the minimum fluidization liquid velocity (U_lmf) for Newtonian and non‐Newtonian systems. Copyright © 2006 Society of Chemical Industry     

气-固微型流化床压降特性及最小流化速度的实验研究

在内径3～20 mm的4个气-固微型流化床中,分别考察了A类和B类两种类型颗粒的流化特性,同时研究了床几何结构、操作条件、物相性质等各因素对其最小流化速度的影响.结果 表明,气-固微型流化床中的床层压降特性与颗粒类型密切相关,不同的流动状态下两种类型颗粒的流动特性存在显著地差异.在固定床阶段,与B类颗粒相比,A类颗粒与...     

Prediction of minimum velocity and minimum bed pressure drop for gas-solid fluidization in conical conduits

Experimental investigations have been carried out for spherical and non-spherical particles using beds comprised of single-sized particles and mixtures in the size and particle density ranges of 439 to 1524 μm and 1303 to 4948 kg/m³, respectively. Five conical fluidizers with varying apex angles of 8.86, 14.77, 19.60, 32.0 and 43.2 degrees were used. Experimental values of minimum velocity and bed pressure drop with air as the fluidizing medium have been compared with their respective values obtained from different models available in the literature. Deviations for each chosen model have been presented.     

Intelligent fitting of minimum spout‐fluidised velocity in spout‐fluidised bed

The experiments were carried on to study the minimum spout‐fluidised velocity in the spout‐fluidised bed. It was found that the minimum spout‐fluidised velocity increased with the rise of static bed height, spout nozzle diameter, particle density, particle diameter, fluidised gas velocity but decreased with the rise of carrier gas density. Based on the experiments, least square support vector machine (LS‐SVM) was established to predict the minimum spout‐fluidised velocity, and adaptive genetic algorithm and cross‐validation algorithm were used to determine the parameters in LS‐SVM. The prediction performance of LS‐SVM is better than that of the empirical correlations and neural network.     

Local hydrodynamic parameters of bubble column reactors operating with non‐Newtonian liquids: Experiments and models development

The effects of liquid phase rheology on the local hydrodynamics of bubble column reactors operating with non‐Newtonian liquids are investigated. Local bubble properties, including bubble frequency, bubble chord length, and bubble rise velocity, are measured by placing two in‐house made optical fiber probes at various locations within a bubble column reactor operating with different non‐Newtonian liquids. It was found that the presence of elasticity can noticeably increase the bubble frequency but decreases the bubble chord length and its rise velocity. The radial profiles of bubble frequency, bubble chord length, and bubble rise velocity are shown to be relatively flat at low superficial gas velocity while they become parabolic at high superficial gas velocity. Moreover, the bubble size and gas holdup are correlated with respect to dimensionless groups by considering the ratio between dynamic moduli of viscoelastic liquids. The novel proposed correlations are capable of predicting the experimental data of bubble size and gas holdup within a mean absolute percentage error of 9.3% and 10%, respectively. © 2015 American Institute of Chemical Engineers AIChE J, 62: 1382–1396, 2016     

Pressure drop and mixing behaviour of non‐Newtonian fluids in a static mixing unit

Static or motionless mixers have received wide application in chemical and allied industries due to their low cost and high efficiency. The pressure drop and mixing behaviour of such mixers have been widely studied. However, the available information for non‐Newtonian fluids is scanty. The results of pressure drop and mixing studies conducted with a locally made motionless mixer (MALAVIYA mixer) and four non‐Newtonian fluids—aq. CMC, PVA, and PEG solutions are reported in this article. The new mixer causes less pressure drop compared to some of the commercial mixers. Mixing behaviour of the unit is more closer to plug flow and a two‐parameter model correlates the dispersion data.     

Pressure drop for single and two‐phase flow of non‐newtonian liquids in helical coils

New experimental results on pressure loss for the single and two‐phase gas‐liquid flow with non‐Newtonian liquids in helical coils are reported. For a constant value of the curvature ratio, the value of the helix angle of the coils is varied from 2.56° to 9.37°. For single phase flow, the effect of helix angle on pressure loss is found to be negligible in laminar flow regime but pressure loss increases with the increasing value of helix angle in turbulent flow conditions. On the other hand, for the two‐phase flow, the well‐known Lockhart‐Martinelli method correlates the present results for all values of helix angle (2.56‐9.37°) satisfactorily under turbulent/laminar and turbulent/turbulent conditions over the following ranges of variables as: 0.57 ≤ n′ ≤ 1; Re′ < 4000; Re_l < 4000; Re_g < 8000; 8 ≤ x ≤ 1000 and 0.2 ≤ De′ ≤ 1000.     

Correlations for critical fluidization velocity and maximum bed pressure drop for heterogeneous binary mixture of irregular particles in gas–solid tapered fluidized beds

The tapered fluidized bed is a remedial measure for certain drawbacks of the gas–solid system, by the fact that a velocity gradient exists along the axial direction of the bed with increase in cross-sectional area. To study the dynamic characteristics of heterogeneous binary mixture of irregular particles, several experiments have been carried out with varying tapered angles and composition of the mixtures with various particles. The tapered angle of the bed has been found to affect the characteristics of the bed. Models based on dimensional analysis have been proposed to predict the critical fluidization velocity and maximum bed pressure drop for gas–solid tapered fluidized beds. Experimental values of critical fluidization velocity and maximum bed pressure drop compare well with that predicted by the proposed models and the average absolute errors are well within 15%.     

CO2 abatement in oscillating packed‐bed scrubbers: Hydrodynamics and reaction performances for marine applications

Gas‐liquid flow dynamics and CO₂‐monoethanolamine absorption performances of an oscillating countercurrent packed bed were analyzed by means of a transient 3D nonisothermal two‐fluid flow model with a goal to understand the behavior of scrubbing units on‐board floating production, storage and offloading platforms. Gas‐liquid flow deviation from axial symmetry was significant at larger vessel inclinations prompting noticeable liquid accumulation in the column lowermost area. Conversely, in static vertical and slightly inclined columns only a reduced fraction of the liquid was subject to transverse segregation. Externally‐generated column oscillations brought about complex secondary flows in radial and tangential directions resulting in oscillatory patterns with amplitude and propagation frequency affected by the packed bed oscillations. CO₂ abatement in inclined and asymmetrically oscillating columns suffered perceptible deviations with respect to vertical configuration while symmetrically oscillating columns gave rise to CO₂ performances oscillating around the steady‐state solutions of the vertical column. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1064–1076, 2017     

Prediction of two‐phase pressure drop and liquid holdup in co‐current gas–liquid downflow of air–Newtonian systems through packed beds

The dependency of pressure drop and liquid holdup on phase velocities, geometry of the column and packing materials as well as on the physical properties have been analyzed. Our experimental data (825 data points obtained using four liquid systems and three different particles) along with those of the available literature (776 data point from five different sources) were used for the analysis. The applicability and the limitations of the literature correlations were evaluated using the available data. Based on the analysis, new correlations for the estimation of pressure drop and liquid holdup, valid for low and high interaction regimes have been developed using the available data, with a wide range of variables. Copyright © 2005 Society of Chemical Industry     

Prediction of critical fluidization velocity and maximum bed pressure drop for binary mixture of regular particles in gas–solid tapered fluidized beds

The problems associated with conventional (cylindrical) fluidized beds, viz., fluidization of wider size range of particles, entrainment of particles and limitation of fluidization velocity could be overcome by using tapered fluidized beds. Limited work has been carried out to study the hydrodynamics of single materials with uniform size particles in tapered beds. In the present work, an attempt has been made to study the hydrodynamic characteristics of binary mixtures of homogeneous and heterogeneous regular particles (glass bead and sago) in tapered fluidized beds having different tapered angles. Correlations have been developed for critical fluidization velocity and maximum bed pressure drop for gas–solid tapered fluidized beds for binary mixtures of regular particles. Model predictions were compared with experimental data, which were in good agreement.     

The investigation of novel non‐metallocene catalysts with phenoxy‐imine ligands for ethylene (co‐)polymerization

Phthaldialdehyde and phthaldiketone were treated with substituted phenols of 2‐amino‐4‐methylphenol, 2‐amino‐5‐methylphenol and 2‐amino‐4‐t‐butylphenol, respectively, and then treated with transition metal halides of TiCl₄, ZrCl₄ and YCl₃. A series of novel non‐metallocene catalysts (1–12) with phenoxy‐imine ligands was obtained. The structures and properties of the catalysts were characterized by ¹H NMR and elemental analysis. The catalysts (1–12) were used to promote ethylene (co‐)polymerization after activation by methylaluminoxane. The effects of the structures and center atoms (Ti, Zr and Y) of these catalysts, polymerization temperature, Al/M (M = Ti, Zr and Y) molar ratio, concentration of the catalysts and solvents on the polymerization performance were investigated. The results showed that the catalysts were favorable for ethylene homopolymerization and copolymerization of ethylene with 1‐hexene. Catalyst 10 is most favorable for catalyzing ethylene homopolymerization and copolymerization of ethylene with 1‐hexene, with catalytic activity up to 2.93 × 10⁶ gPE (mol Y)^?1 h^?1 for polyethylene (PE) and 2.96 × 10⁶ gPE (mol Y)^?1 h^?1 for copolymerization of ethylene with 1‐hexene under the following conditions: polymerization temperature 50 °C, Al/Y molar ratio 300, concentration of catalyst 1.0 × 10^?4 L^?1 and toluene as solvent. The structures and properties of the polymers obtained were characterized by Fourier transform infrared spectroscopy, ¹³C NMR, wide‐angle X‐ray diffraction, gel permeation chromatography and DSC. The results indicated that the obtained PE catalyzed by 4 had the highest melting point of 134.8 °C and the highest weight‐average molecular weight of 7.48 × 10⁵ g mol^?1. The copolymer catalyzed by 4 had the highest incorporation of 1‐hexene, up to 5.26 mol%, into the copolymer chain. © 2012 Society of Chemical Industry     

Synthesis and properties of non‐cytotoxic poly(l‐malic acid acetate‐co‐l‐lysine ester)s with thermo‐sensitivity as hydrophobic drug nanocarrier

In this investigation, a group of poly(l ‐malic acid acetate‐co‐l ‐lysine ester)s (PMALs) with excellent thermo‐sensitivity and non‐cytotoxicity were prepared by an optimized synthetic route from natural l ‐malic acid and l ‐lysine. The structure and properties of PMALs including monomers were systematically characterized by FTIR, ¹H NMR, UV, gel permeation chromatograph, scanning electron microscope, contact angle measurement, cell counting kit assess (CCK‐8), and confocal laser scanning microscopy (CLSM). Three PMALs show a reversible lower critical solution temperature of 8–36 °C depending on their chemical structure. The contact angle measurement revealed a considerable discrepancy in the hydrophilicity/hydrophobicity of PMALs and further influence on their thermo‐sensitivity. The viability of HeLa cells exposed to 0.2–100 μg/mL PMALs solution was found to be in a range 80–103% after 24, 48, and 72 h of incubation, indicating no cytotoxicity. Moreover, a spherical nanocarrier with core‐shell structure was facilely fabricated via the thermo‐sensitivity of PMALs and hydrophobicity of drug. CLSM observations manifested that the hydrophobic‐curcumin‐enwrapped nanocarriers can clearly internalize into the cellular inside. The sustained release of curcumin from nanocarriers in vitro provided a possibility of depressing fast hydrolytic degradation at physiological pH or other side‐effects. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45984.