Addition Of Solid Particles Research Articles

An embolic gelling solution based on acrylic copolymers in ethanol for the treatment of arteriovenous malformations

We report the preparation of an embolic agent based on specific association of an acrylic copolymer with dedicated particles formulated in ethanol. The copolymers were synthesized by radical polymerization of tertiobutylacrylamide (tBA) and 2-hydroxypropyl methacrylate (HPMA). Influences of the monomers composition, molecular weight and copolymer concentration have been evaluated on an in vitro model. Introduction of tBA units improves significantly the occlusion properties but these properties are similar whatever the molecular weight of the copolymer. As observed by viscosity studies, it seems necessary to work with a relatively high polymer concentration (C > Ce) to form a cohesive embolus. Addition of solid particles composed by a crosslinked polymer of 2-hydroxyethyl methacrylate (HEMA) and N-trishydroxymethyl methacrylamide (TRIS) in the acrylic copolymer solution has allowed to obtain an embole having an enhanced cohesion and giving a more compact structure. An in vivo evaluation has been performed by injection of this embolic agent in intercostal arteries and renal artery of sheep. There was no fragmentation of the plug during and after injection and a complete arterial occlusion by a cohesive embole. The pathological examination confirmed that there was a complete arterial occlusion by the plug and that the dedicated particles were as expected embedded in the precipitate acrylic copolymer.

Characteristics of Flow and Heat Transfer in a Tube Bundle Evaporator with a Vapour–Liquid–Solid Flow

In this paper, a tube bundle experimental evaporator with a specific vapour–liquid–solid (V-L-S) flow boiling system with external natural circulating is established to imitate and investigate a typical three-phase flow and boiling heat-transfer characteristics in order to reveal the mechanism of this apparatus. It is shown that under the ranges of the experimental parameters tested, the average heat transfer film coefficient h fb increases with increasing of temperature difference between the inside surface of tube wall and the boiling fluid. Lowering holdup of the solid particles enhances the heat transfer process. Meanwhile, the average heat transfer film coefficient h in each tube was found to be quite different for different tubes. The addition of solid particles enlarges this difference. The circulating velocity in the tube in V-L-S flow boiling was found to increase with the increase of the overall driving force of heat transfer or temperature difference between the steam and the boiling fluid, and it is higher than that of the V-L flow boiling. Opposite is true for the pressure drop in the tube in V-L-S flow boiling. There is no obvious effect of circulating velocity but there is a clear distinction in the pressure drops when varying the solid holdups. These results may offer some useful data sets to design, scale-up of this type of evaporators.

Advanced Oxidation Processes in Azo Dye Wastewater Treatment

The chemical degradation of synthetic azo dyes color index (C.I.) Acid Orange 7, C.I. Direct Orange 39, and C.I. Mordant Yellow 10 has been studied by the following advanced oxidation processes: Fenton, Fenton-like, ozonation, peroxone without or with addition of solid particles, zeolites HY, and NH4ZSM5. Spectrophotometric (UV/visible light spectrum) and total organic carbon measurements were used for determination of process efficiency and reaction kinetics. The degradation rates are evaluated by determining their rate constants. The different hydroxyl radical generation processes were comparatively studied, and the most efficient experimental conditions for the degradation of organic azo dyes solutions were determined.

Fenton type processes for minimization of organic content in coloured wastewaters. Part II: Combination with zeolites

The addition of solid particles, namely synthetic zeolites NH 4ZSM5 and HY, was investigated in order to enhance the efficiency of AOPs for dye wastewater treatment. Experiments were conducted at the optimal operating parameters for each Fenton type process and studied coloured pollutants established in Part I of this study in order to find the optimal dose of applied zeolites and understand their role in the new combined AOPs. Degradation of the studied dyes, C.I. Reactive Blue 49 and C.I. Reactive Blue 137, was monitored by means of the UV/VIS, TOC and AOX analysis, thus determining decolourization and mineralization extents of model solutions. Organic content adsorbed onto applied zeolites after the treatment was scanned and characterized using FT-IR spectrophotometer. Applied AOPs in combination with zeolites were shown to be very successful in colour removal, >98%, similarly like Fenton type processes reported in Part I of this study, while improvements in the mineralization of the studied dyes depended on the type and the dose of zeolite, as well as on dye structure and the type of applied AOP.

Effects of Addition of Solid Particles on Thermal Characteristics in Hydrogen-Air Flame

From the view of environmental protection against the use of fossil fuels, a great number of efforts have been exerted to find an alternative energy source. Hydrogen may become an alternative. However, the only product species of the hydrogen flame is H 2 O, which emits only nonluminous radiation, so the radiation from a hydrogen flame is much smaller than that for a hydrocarbon flame. The authors designed and fabricated a laboratory-scale test furnace to study thermal characteristics of a hydrogen-air diffusion flame. In addition, the effects of addition of reacting as well as nonreacting solid particles were experimentally investigated. Among the total heat flux to the wall, about 75% was occupied by radiation while 25% was occupied by convection. When the aluminum oxide (Al 2 O 3 ) particles were added, the radiative heat flux was reduced due to heat blockage effects. On the other hand, the total heat flux was increased when the carbon particles were seeded, because the overall temperature increased. The effects of swirl and excess air ratio were also examined. Additionally, a numerical simulation was carried out to simulate a hydrogen-air diffusion flame and was compared with the experimental results.

Freeform fabrication by controlled droplet deposition of powder filled melts

A method of directly delivering highly filled hot-melt particulate suspensions using piezoelectric droplet generators is presented. Highly fluid suspensions of alumina in a mixture of long and short chain n-alkanes containing up to 40% by volume solids have been prepared. These fluids were subsequently used to deposit ceramic objects using a commercial ink-jet printer. These objects were then successfully sintered to near full density. The deposition mechanism is controlled by the propagation of acoustic waves in a droplet generating chamber. We have observed the change in resonance of this chamber with the introduction of particles into a fluid. A simple model is developed to explain these observations in terms of changes in the speed of sound of the fluid on the addition of solid particles in suspension.

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Heat transfer operations are very common in the process industry to transfer a huge amount of thermal energy, i.e., heat, from one fluid to another for different purposes. Many fluids are used as heat transfer fluid (HTF), in which water is the most common HTF due to its high specific heat, availability, and affordability. However, conventional HTFs, including water, have a lower thermal conductivity, which is the most critical thermophysical property, hence decreased heat transfer efficiency. The addition of solid particles of highly thermally conductive material, specifically at nano-size, i.e., nanoparticles NPs, result in nanofluid NF, which has evolved over the last two decades as efficient HTF and have been investigated in a wide range of applications. Among NPs, graphene (Gr) based materials have shown very high potential as NF due to the very high thermal conductivity up to 5,000 W/m.K, hence higher thermal conductivity NF. This work aims to thoroughly discuss the thermophysical properties of Gr-based NFs, including thermal conductivity, heat capacity, density, and viscosity. The discussion focus on the thermophysical properties as it is the ultimate determinator of the heat transfer characteristics of the HTF, such as the convective and the overall heat transfer coefficient as well as the heat transfer capacity of the NF. The discussion expands to the relative enhancement in such thermophysical properties reaching up to a 40% increase in thermal conductivity, as the most critical thermophysical property. The discussion shows that Gr-based NF has a much higher thermal conductivity relative to widely studied metal oxide NF and at much lower content, and lower density and viscosity increase, which is critical for determining the pumping power requirements. Critical challenges facing the application of Gr-based NFs such as cost, stability, increased density and viscosity, and environmental impacts are thoroughly discussed with mitigation recommendations given.

Linear instability of two-way coupled particle-laden jet

The two-way coupled particle-laden jet is studied numerically in order to understand how the addition of solid particles affects the stability of the jet. In contrast with the particle-laden mixing layer studied, the jet flow stability is complicated by a variable wave (or phase) velocity and an additional curvature parameter, i.e., the ratio of jet radius to shear layer thickness. Nevertheless, we have demonstrated that the following similar scenario holds for a particle-laden jet: the addition of particles can destabilize the flow at small particle Stokes number, while the stabilizing effect prevails for intermediate to large Stokes numbers. Both these competing effects scale approximately linearly with the particle mass loading. We also found that the addition of particles increases the wave velocity at high wave numbers but decreases the wave velocity at low wave numbers. The fact that the addition of particles can destabilize the gas flow in the absence of gravity has been shown to follow the previous speculation. Two general asymptotic relations proposed by Saffman have been confirmed numerically for the case of the particle-laden jet. Physically, the increase of effective inertia of the fluid–particle mixture causes a destabilization effect while the enhanced viscous dissipation around the particles gives a stabilization effect. Results for various mass loadings, Stokes numbers, and wave numbers show that for a given mass loading and wave number, there is an intermediate Stokes number that corresponds to a maximum flow stability. We have shown that this Stokes number is on the order of 1 and depends weakly on the wave number.

Two-way coupled particle-laden mixing layer. Part 1: Linear instability

The two-way coupled particle-laden mixing layer is studied numerically and theoretically in order to understand how the addition of solid particles affects the stability of the gas flow. Numerical simulations are undertaken to obtain results equivalent to solving the Orr–Sommerfeld equation of a dusty gas mixing layer first derived by Saffman. The growth rate of a viscous particle-laden mixing layer depends on the wavenumber, flow Reynolds number, Stokes number, and bulk particulate mass loading. Two asymptotic relations proposed by Saffman have been confirmed for the first time by numerical simulations. In addition to the stabilizing effect of particles on the gas flow at large Stokes number, a destabilizing influence at small Stokes number is also observed at finite flow Reynolds number. The fact that the addition of particles can destabilize the gas flow in the absence of gravity has been shown to follow the original speculation of Saffman. Physically, the increase of effective inertia of the fluid–particle mixture causes a destabilization effect, while the enhanced viscous dissipation around particles gives a stabilization effect. These qualitatively different effects have been shown to be directly related to the direction of interphase energy transfer. Results at arbitrary mass loading, Stokes number, and wavenumber show that for a given mass loading and wavenumber, there is an intermediate Stokes number which corresponds to a maximum flow stability. We have shown that this Stokes number is on the order of one, and depends on the wavenumber. An analytical model for predicting the growth rate in a viscous, particle-laden gas mixing layer is proposed and compared with the simulation results.

Toluene-insoluble fraction from thermal cracking of Athabasca gas oil: formation of a liquid-in-oil emulsion that wets hydrophobic dispersed solids

The formation of a toluene-insoluble (TI) fraction and its interaction with fine solids was studied by heating coker gas oil from Athabasca bitumen in a stirred batch reactor at 300–420°C and a total pressure of 13 MPa (from an initial hydrogen pressure of 7 MPa before heating) for 1 h. The TI solids were filtered from the product oil and analyzed by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectrometry, and elemental analysis. The micrographs indicated that the TI fraction formed a liquid-in-oil emulsion at reactor conditions, consisting of spheres of TI material suspended in gas oil. The spheres were soluble in quinoline, and therefore were not mesophase coke. The TI spheres gave very little physical interaction with 5 μm kaolin particles, but the addition of particles with non-polar surface groups (carbon black and asphaltene-coated clay) suppressed the formation of spheres. The addition of solid particles did not affect the total yield of TI significantly, based on carbon and sulfur analysis. These results suggested that the liquid TI fraction wetted and spread on non-polar surfaces, but not on polar surfaces.

Performance of an Entrained-Particle Heat Exchanger

An experimental investigation was carried out to determine the thermal performance of a heat exchanger operating with vertical upflow of a hot gas loaded with solid particles. Using particles having mean diameters (88-157 μm), the inlet gas velocity was varied from 1.5 to 13 m/s and the inlet temperature was varied from 100 to 600°C. This resulted in mixture densities of 2.0 to 30 kg/m3 for the gas-solid flow. The results showed that thermal performance improved with the addition of solid particles to the gas stream. At a given gas velocity, the gas-side coefficient could be increased by factors of 2 to 4 with the addition of solid particles. The exchanger performance was enhanced with increasing solid loading, decreasing particle size, and increasing gas temperature.

Growth of electrodeposited ?-manganese dioxide from a suspension bath

The addition of solid particles of manganese oxides to the electrolyte of a manganese dioxide production bath (suspension bath process=SBP) allows the anodic current density to be increased to values more than twice that used in the conventional EMD process. This is possible even with the use of titanium anodes which are sensitive to passivation if the current density exceeds critical values. Analysis of deposition conditions and properties of the SBP-EMD shows that the SBP-EMD resembles and EMD which has been deposited at very low current densities. These low current densities are realized by the adsorption of the suspended particles on the anode surface, thereby promoting dendritic crystal growth on the adsorbed particles and increasing the real anode surface by up to a factor of ten. This assumption is able to explain most of the properties found for the SBP-EMD, e.g. X-ray pattern, potential drop, hardness of the deposit, low specific surface area, low content of combined water and high electronic conductivity.

Improving solidification pattern of ESR ingots combined with energy savings

Most of the metallurgical effects resulting from electroslag remelting of metal may be divided into two groups, namely, the effects due to the slag/metal reactions taking place and the effects due to the special solidification conditions characteristic of this process. Solidification of ESR ingots takes place progressively as heat is removed from the liquid metal pool via the mold walls. By careful matching of the melting rate with the freezing rate, the desired shallow metal pool is attained, leading to the well known directional solidification pattern with consequent improvement in properties of the steel. The choice of power parameters is limited by a compromise between the need for a high melting rate for economic reasons (costs) which may tend to give a rather deep metal pool and the need for a shallow metal pool to obtain optimum metallurgical properties. In this process only a relatively small amount of the total energy input is actually utilized to melt down the metal. The major part of the energy is lost from the slag and metal pool to the water cooled mold.In this paper the results of numerical and experimental investigations are presented, setting out a simple method of saving energy and controlling the solidification pattern of the ingot. This method involves the addition of solid particles to the melt to utilize the surplus energy evolved in the central area of the slag bath.

Properties of bubble swarm in a slurry bubble column.

The effects of solid concentration and liquid viscosity on bubble properties such as bubble size and bubble rising velocity were measured with a dual-electroresistivity probe in a slurry bubble column of 0.15m diameter. The behavior of volume-surface mean bubble diameter, dvs, was analyzed. By addition of solid particles at small gas velocity, the bubble size distribution shifted to a large-size region and the bubble velocity distribution shifted to a large-velocity region. At the same time, the flow pattern changed from homogeneous flow to heterogeneous flow. The effect of solid particles on bubble size, however, became small as the particle diameter decreased or the liquid viscosity increased. The following equation was derived to estimate dvs. dvs=0.59(VD/eg)2/gwhere VD is the drift flux of gas, eg is the cross-sectionally averaged gas holdup and g is the gravitational acceleration.

Gas holdup and volumetric liquid-phase mass transfer coefficient in solid-suspended bubble column with draught tube.

The effects of column dimensions, gas velocity and properties of the liquid and the solid particles on the gas holdup eG and the volumetric liquid-phase mass transfer coefficient kLa in a solid suspended bubble column with a draught tube and a conical bottom were studied experimentally in a liquid-solid batch operation. The presence of suspended solid particles in the column reduces the values of eG and kLa, and their reduction due to the addition of solid particles to the column increases with increasing solid concentration and terminal velocity of a single particle. Based on these observations, empirical equations for eG and kLa are proposed which are applicable to columns with diameter of 0.1-0.3 m.

PART 2: The Influence of Solid Inclusions

AbstractSolids in the form of colour pigments are commonly added to tablet film coats for the purpose of identification. This work examines the effect of their addition on certain mechanical properties of the films. Films were cast from aqueous solutions of hydroxypropylmethylcellulose (HPMC) in which the solids had been dispersed. Titanium dioxide was added in concentrations of up to 40% in the dried film. Two grades (regular and high tinting) of the following aluminium lakes (Colorcon Limited) were also investigated: Brilliant Blue FCF, Erythrosine and Tartrazine. A tensile test was performed on the films using an Instron test machine. In general, the addition of solid particles reduced the tensile strength of the film, shortened the elongation at break and increased the elastic modulus, i.e. the films became more brittle. The influence of storage humidity on these properties is also reported.Changes in these fundamental properties are correlated with practical problems associated with the addition of s...

Gas holdup and volumetric liquid-phase mass transfer coefficient in solid-suspended bubble columns.

The effects of column dimensions, gas velocity and the properties of liquid and solid particles on the gas holdup eG and the volumetric liquid-phase mass transfer coefficient kLa in the solid-suspended bubble column of liquid-solid batch operation were studied experimentally. The presence of suspended solid particles in the bubble column reduces values of eG and kLa, and their reduction by an addition of solid particles to the column is high in the transition regime and low in the heterogeneous flow regime. Based on these observations, empirical equations for eG in transition flow and in heterogeneous flow, and an empirical equation for kLa a applicable to the above two flow regimes are proposed.

The influence of design and operating variables on the capacities of hydrocyclone classifiers

An extensive test programme has been conducted on 10.2-, 25.4- and 38.1-cm “Krebs” hydrocyclones in order to study the effects of some design and operating variables on their volume capacities. For a given pressure the capacity of a cyclone was found to rise sharply with the addition of solid particles to water until the solids content was about 15% by weight. Further increase in solids caused a decrease in throughput. The effect of vortex finder diameter on the throughput was found to be non-linear. A general equation which relates inlet and outlet diameters, operating pressure and feed solids content to the volume capacity is presented. This equation is independent of hydrocyclone diameter.

Friction in turbulent flow of solids‐gas systems

AbstractTwo‐phase solids‐in‐air flow was experimentally studied in a once‐through circular tube flow system using nominal 25μ and 50μ spherical glass beads. At mass flow ratios up to 1.6, the friction factor was found to be generally higher than that for air flow alone but considerably less than that for a single‐phase fluid having a density the same as that of the mixture.The pressure drop experienced by the 2 phase system of 25μ beads and air was found to show true drag reduction.A continuum mechanics analysis showed the viscous stresses and Reynolds stresses to be significantly affected by solid particle addition.

Heat transfer of gas-particle flow in a supersonic convergent-divergent nozzle

Heat flux, wall heat transfer coefficients, and wall pressures are determined for high velocity flow of gas-solid mixtures in a converging-diverging nozzle. Flow separation accompanied with oblique shock formation occurs in the diverging section of the nozzle. The shock strength is reduced upon the addition of solid particles. The wall pressure in the convergent section of the nozzle appears unaffected by the presence of solid particles. In the divergent section, however, the wall pressure is slightly lowered. At the maximum ratio of solid to air flow used in the experiments (3.7) increases in the heat transfer rate of up to 20 and 50 percent are obtained in the convergent and separated (divergent) regions of the nozzle, respectively. Slightly larger increases in the wall heat transfer coefficients are also obtained. It is concluded that the wall heat flux and heat transfer coefficients are influenced strongly by the presence of disturbances upstream of the nozzle inlet.