Nano-enabled agglomerates and compact:Design aspects of challenges

Nanoscale medicine confers passive and active targeting potential.The development of nanomedicine is however met with processing,handling and administration hurdles.Excessive solid nanoparticle aggregation and caking result in lowproduct yield,poor particle flowability and inefficient drug administration.These are overcome by converting the nanoparticles into a microscale dosage form via agglomeration or compaction techniques.Agglomeration and compaction nonetheless predispose the nanoparticles to risks of losing their nanogeometry,surface composition or chemistry being altered and negating biological performance.This study reviews risk factors faced during agglomeration and compaction that could result in these changes to nanoparticles.The potential risk factors pertain to materials choice in nanoparticle and microscale dosage form development,and their interplay effects with process temperature,physical forces and environmental stresses.To render the physicochemical and biological behaviour of the nanoparticles unaffected by agglomeration or compaction,modes to modulate the interplay effects of material and formulation with processing and environment variables are discussed.

Experimental Research on Enhanced Cyclone Separation of Acoustic Agglomerated Particles

To test the particles solidity and to verify the separating efficiency at normal atmospheric temperature, the experimental research was made on the enhanced cyclone separation of acoustic agglomerated fly ash particles. The separating efficiency has increased by 3%-4% in a sound field with 150 dB pressure level compared with that obtained without acoustic wave processing. The enhanced cyclone separation test study for acoustic agglomerated particles has provided a technical basis for pressurized fluid bed combustion(PFBC) application.

Effect of jet milling on micro-strain behavior and rupture behavior of agglomerates of ultrafine WC powders

The Williamson-Hall and uniaxial compression methods were used to study the variations of the micro-strain and stress-strain relations in WC powders after jet milling and ball milling, respectively. The rupture behavior of agglomerates in WC powders was investigated. Meanwhile, the as-obtained WC powders treated by different milling methods were used to fabricate WC-10%Co cemented carbides, followed by the performance assessment of cemented carbides. The results show that the micro-strain of the jet-milled WC powders decreases significantly compared with that of the ball-milled WC powders, and that the cemented carbides prepared by jet-milled WC powders exhibit excellent properties with a transverse-rupture strength of 4260 MPa, due to the elimination of agglomerates and the reduction of lattice strain.

Aggregation and fragmentation of agglomerates in a fluidized bed of mixed nanoparticles by adding FCC coarse particles

In this study, the influence of fluid cracking catalyst(FCC) on the fluidization behavior of ZnO-CuO binary nanoparticles was systematically investigated by varying FCC size. High-speed camera was employed to analyze the collision and fragmentation process of agglomerates with adding FCC coarse particles. It can be found from photographs by the camera that fluidization performance improved by the agglomerate variation that is bound to be shaped a compact and spherical structure. Furthermore, the result of agglomeration composition analysis showed that uniform mixing of nanoparticles remarkably affected the fluidization behavior of ZnO-CuO binary system. Finally, the improvement of fluidization performance can be justified by the analysis of inter-cohesive force between the two agglomerates with sharp reduction of the newly-formed agglomerates.

Improved CFD modeling of full dissolution of alumina particles in aluminum electrolysis cells considering agglomerate formation

The full alumina dissolution process in aluminum electrolysis cells was investigated using an improved computational fluid dynamics(CFD)model based on the previous researches by consideration of agglomerate formation.The results show that the total mass of alumina agglomerate and its maximum size are mainly dependent on the feeding amount and increase with increasing it.Higher superheat can effectively inhibit the agglomerate formation and thus promote the full alumina dissolution behavior.The full alumina dissolution process mainly includes a fast stage and a slow stage,with an average dissolution rate of 17.24 kg/min and 1.53 kg/min,respectively.About 50%(mass percentage)of the total alumina particles,almost all of which are the well-dispersed alumina fine grains,dissolve within the fast dissolution stage of about 10 s.The maximum values of the average dissolution rate and final percentage of the cumulative dissolved alumina mass are obtained with a feeding amount of 1.8 kg for a superheat of 12℃.The formation of the alumina agglomerates and slow dissolution characteristics play a dominant role in the full dissolution of alumina particles.

The effect of agglomerate on micro-structural evolution in solid-state sintering

Discrete element method （DEM） is used in the present paper to simulate the microstructural evolution of a planar layer of copper particles during sintering. Formation of agglomerates and the effect of their rearrangement on densification are mainly focused on. Comparing to the existing experimental observations, we find that agglomerate can form spontaneously in sintering and its rearrangement could accelerate the densification of compacts. Snapshots of numerical simulations agree qualitatively well with experimental observations. The method could be readily extended to investigate the effect of agglomerate on sintering in a three- dimensional model, which should be very useful for understanding the evolution of microstructure of sintering systems.

Particle Size Distribution,Powder Agglomerates and Their Effects on Sinterability of Ultrafine Alumina Powders

An intensive study of the particle size distribution of four commercial ultrafine alumina powders to obtain information about the powder agglomeration and relate them to the compactibility and the sinterability has been made.

Numerical study on the hydrodynamics of agglomerates at intermediate Reynolds numbers

The flow pattern and hydrodynamics of a heterogeneous permeable agglomerate in a uniform upward flow at intermediate Reynolds numbers(1–40)are analyzed from three-dimensional(3 D)computational fluid dynamics simulations.Different from the homogeneous or stepwise-varying permeability models used in previous papers,a continuously radially varying permeability model is used in the present study.The effects of two dimensionless parameters,the Reynolds number and the permeability ratio,on the flow field and the hydrodynamics were investigated in detail.The results reveal that unlike the solid sphere,a small recirculating wake initially forms inside the agglomerate.The critical Reynolds number for the formation of the recirculating wake is lower than that of the solid sphere and it decreases with the increase of permeability ratio.A correlation of drag coefficient as a function of the Reynolds number and permeability ratio is proposed.Comparisons of drag coefficients obtained by different permeability models show that at intermediate Reynolds numbers(1–40),the effect of radially varying permeability on the drag coefficient must be considered.

Quantifying growth and breakage of agglomerates in fluid-particle flow using discrete particle method

The cohesive solids in liquid flows are featured by the dynamic growth and breakage of agglomerates, and the difficulties in the development, design and optimization of these systems are related to this significant feature.In this paper, discrete particle method is used to simulate a solid–liquid flow system including millions of cohesive particles, the growth rate and breakage rate of agglomerates are then systematically investigated. It was found that the most probable size of the agglomerates is determined by the balance of growth and breakage of the agglomerates the cross point of the lines of growth rate and breakage rate as a function of the particle numbers in an agglomerate, marks the most stable agglomerate size. The finding here provides a feasible way to quantify the dynamic behaviors of growth and breakage of agglomerates, and therefore offers the possibility of quantifying the effects of agglomerates on the hydrodynamics of fluid flows with cohesive particles.

STUDY ON AUTOMATIC IN-LINE MEASUREMENT OF FeO CONTENT IN AGGLOMERATE

In this paper, the mechanism of physical method for measuring the FeO content in agglomerate replacing the chemical method is proposed after studying the electromagnetic property of the agglomerate. The microcomputer-measuring system for FeO content is provided. Attention is also paid to introducing the working principle of the H-type compensation sensor and the processing method of the measured data. This system has been successfully applied in practice to in-line measure the FeO content.

A Study on the Density of Agglomerates Prepared from Cork Wastes

The density of black regranulate (BR) of cork and of black agglomerate (BA) and composite agglomerate (CA) prepared fromsuch a waste by different methods was investigated. The preparation of the agglomerates was undertaken by controlling thespecimen thickness for BA and the particle size for BR and the binder dosage for CA. The mass changes produced in theoven-drying treatment at 376.15 K of the agglomerates and in their subsequent stabilization under ambient conditions werealso analyzed. The density was determined by standard methods. For BR, the bulk density first decreased and then increasedwith decreasing particle size. It was much lower than the apparent density of the agglomeration products of cork. Although toa lesser extent, the density was also lower for BA than for CA. It was higher for the smaller thickness specimens of BA. In thecase of CA, the density followed the same variation trends as for BR. Furthermore it increased significantly with the increasein resin dosage. This resulted in a noticeable increase in the weight loss during the oven-drying and in a significant decreasein the degree of moisture adsorption during the stabilization period of the agglomerate.

Moisture Distribution of Heterogeneous Agglomerates in Fluidized Bed

Agglomerates formed in the fluidized bed were studied in this paper using the TEB atomization nozzle. The multi-sieving method was adopted to distinguish the size of original particles, nucleation agglomerates, coherence agglomerates, and paste agglomerates in order to successfully identify the different growth stages and select the region for coexistence of most stable heterogeneous agglomerates as the research object. A multi-channel conductance electrical circuit experimental device was developed in this study to measure the conductance signal, which was found to have a liner relationship with the moisture content inside the fluidized bed. By adjusting the sieve mesh openings to achieve the layered isolation of heterogeneous agglomerates, the conductance signal recovered slowly as a result of the agglomerates' fracture during the continuous fluidization process, so that particles and agglomerates moisture distribution measurements could be implemented. The device was used to measure the particles and agglomerates moisture distribution state in the heterogeneous coexistence region, when they were injected with liquid mass within the range of w i=2.8 kg to 4.4 kg. The results indicated that with the increase of liquid mass flow, the moisture content of coherence agglomerates also increased, but the moisture content of nucleation agglomerates was decreased, and that of the original particles was maintained at a relatively low level. When the experimental injection amount reached 4.4 kg, the moisture contained in coherence agglomerates could amount to 87.3%, accounting for a big percentage of moisture in the fluidized bed.

Study of Alkali Metal Corrosion on Heating Surfaces and Bed Material Agglomerate in Biomass-fired Fluidized Bed Boiler

The bed material agglomeration and heating surface high-temperature Corrosion Problems of biomass-fired boiler in South China were studied in this work. The inner and outer surfaces of the corrosion sample were investigated by scanning electron microscope (SEM) with Bruker EDX and XRD. Results showed that the outer side of the corrosion sample was mainly composed of alkali chloride deposited ash, sulphide and a small amount of eutectoid;while the inner side of the corrosion sample was still mainly made up of the composition of SUS316, but added with alkali metal, oxygen, chlorine and sulphur elements, appearing as the corrosion products and eutectoid. It was thought that alkali chloride deposit and the reaction with pipe metal to generate low melting point eutectoid on the outer surfaces, or the corrosion reaction through the alkali metal sulphatization process was the main reasons leading to the damage of metal surface oxide film. Chlorine plays a role as haptoreaction in the corrosion process, and transports metal material as the form of chloride from the inner side to the outer side of the pipe surfaces by diffusion, accelerating the corrosion process. Meanwhile, the slag was studied by scanning electron microscope (SEM) with Bruker EDX, and the transformation process of slage was computationally analyzed by FACTSAGE. Results showed that the amount of alkali metal in the agglomerates was little, however, caused a great impact on severe agglomerates. The increase of temperature enhanced the conversion process of alkali metal to molten oxide, especially when the temperature was higher than760℃, the amount of molten product increased sharply. Thus, the temperature control of fluidized bed plays an important role in solving the problem of alkali metal agglomerates;it also reliefs the volatile of alkali metal into gas phase, benefiting the control of heating surface corrosion.

Relationship between attachment probability and surface energy in adhesion process of gold particles to oil-carbon agglomerates

Based on the theoretical analyses, the adhesion process of fine gold particles to oil-carbon agglomerates in a dynamic system was quantitatively investigated in terms of the relationship between the attachment probability and the surface energy. The proposed way to establish this relationship is to firstly theoretically derive the formula to （evaluate） the surface energy change of the system by analyzing the adhesion process of a gold particle on an oil-carbon agglomerate in a mathematic and thermodynamic way. The obtained formula of the maximum energy change of unit surface area is, (Δw′max=12σhw（cos θ-1）,) which involves two measurable elements: interfacial tension and contact angle. In a well-quantified system, based on the related model it is also possible to calculate the complicated concept, namely, the attachment probability by transferring other measurable indices. In this way, after some adhesion experiments and measurements of relevant parameters, the empirical relationship between the attachment probability and the surface energy change was established in an exponential function, Pa=Aexp(-ΔGsurf/k).

New Technology “Flotation to Form Agglomerates and Magnetic Separation” Allows Great Breakthrough for World Low-Grade Light Rare Earth Ores

Rare earth resources are relatively scarce worldwide, but their global consumption is increasing year-by-year. At present, China has about 36% of the global rare earth reserves, but provides 90% of the world＇s supply, which has generally met world demand and promoted the development of the world economy. In order to continuously and stably supply rare earths to international markets, the Chinese Government has financially supported the Institute of Multipurpose Utilization of Mineral Resources within the China Geological Survey to study the utilization of low-grade rare earth ores. Following many years of experimental research, the project has developed a new technology entitled ＂Flotation to Form Agglomerates and then Magnetic Separation＂, which will bring a technological revolution to the world＇s light rare earth ore dressing.

The Effect of Bridging Liquid Surface Tension and Specific Surface Area on Strength Factor of Coal Agglomerates

The aim of this research is to determine the effect of bridging liquid surface tension and specific surface area on strength factor of coal agglomerates. The production of coal agglomerates of the range 15-27.51 mm was achieved. The crushing strength of the agglomerates was determined for good handling of fine （coal-liquid mixture） to improve fugitive dust control, decrease in transportation losses, reduce risk of coal freezing, lower risk of spontaneous combustion, etc. in iron and steel industries, railway corporations and coal corporations. Kerosene （paraffin oil） was used as a binder and the agglomerated coal oil mixture was pelletized using balling technique （disc）. Mechanical and physical tests like compressive strength test, etc. were carried out. The relationship between the bridging liquid surface tension and specific surface area on strength factor of coal agglomerates showed that there is considerable variation in these parameters in the coal powder systems.

Agglomerate control in the complexing sol-gel process

Nanometer ZrO2 - 8% Y2O3 (mole fraction, % ) powders were prepared by the EDTA (ethylenediaminetetraacetic acid) sol-gel process. Effects of the addition of ethylene glycol on agglomerate control was investigated. The results showed that because of the replacement of hydrogen bonds with ethylene glycol in the polymerized gel, gel stabilization and homogeneity were improved and close approach of gel particles was prevented, which led to reduction of hard agglomerates to some extent. Calcined at 4OO t for 2 h and 700 C for 2 h, the powders had a specific surface area of 35 m2/g, average particle size of 28 nm, and median particle size (d50) of 0. 44um with very sharp distribution, mostly being soft agglomerates.

Modelling the formation and dissolution behavior of alumina agglomerate in the cryolite

The presence of alumina agglomerates seriously affects the current efficiency of the aluminum electrolysis process.Clarify the dynamic dissolution process of agglomerates is essential to improve the current efficiency of aluminum electrolysis.A mathematical model is proposed to describe the different phenomena from the formation until complete dissolution of agglomerates.Considering permeation and solidification processes of cryolite,a semi-analytical mathematical model is developed to formulate the formation,melting and dissolution processes of agglomerates,and the time duration for each stage is deduced.Porosity and heat mass transfer of agglomerates are explored based on the packing theory and mechanism of heat mass transfer in wet porous media.Dimensionless approach is applied to investigate the main factors affecting the dissolution stages and porosity of agglomerates.The results show that the superheat has a great influence on the formation and melting stage,the diameter of agglomerates can reach 14.93 mm for 200 particles agglomerated.The density decreases with the increase of agglomerated particle number,which varies in the range of 2.27-2.28 g/cm^(3).The average dissolution rate of agglomerates is about 1.83×10^(-5)-2.95×10^(-5) kg/s within the range of alumina concentration in this study.

Optimization of product characteristics of porous carbon agglomerates using a design of experiments in fluidized bed agglomeration

Spraying parameters during particle agglomeration processes can affect the agglomeration kinetics and particle growth.This study was conducted to better understand the influence of the spraying parameters in a fluidized bed wet agglomeration process,and the influence on the stability characteristics of carbon tablets.A formulation based on fine carbon and peroxide powder,as well as carboxymethyl cellulose as a binder,was used to produce agglomerates in a first production step.Thereafter in a second production step carbon tablets with a high porosity were molded for the customer goods industry.The optimization of the compressive strength of these carbon tablets was the goal of the trials.Carbon agglomerates were produced with a laboratory scale granulator called“ProCell”and were compressed with a five-cavity mechanical press.The screening of the agglomeration process parameters and their influence on the agglomerates quality,as well as the performance characteristics of the carbon tablets,were investigated using a multilevel factorial design.The experimental runs were done by varying atomized air pressure and feed rate of the fluid.This was determined by the design model.The findings of the statistical trials showed that low atomized air pressure and a low feed rate lead to a higher tablet compressive strength.

Transient flameout process of boron-magnesium agglomerates during combustion in oxygen-rich atmospheres

In this study,boron–magnesium agglomerates with varying mass ratios were prepared by drying a micron-sized boron–magnesium mixed suspension,and the combustion process of these agglomerates under different oxygen-rich concentrations were investigated using a laser ignition system.The test results showed that when the mass fraction of magnesium powder in boron-magnesium agglomerates exceeded a certain threshold(between 2%and 5%),flame extinction and reignition occurred after a significant reduction in the agglomerate volume during combustion.This process is referred to as the transient flameout process,which is affected by the magnesium content of the agglomerate and the oxygen concentration in the ambient atmosphere.An increase in the magnesium content or oxygen concentration makes this phenomenon more pronounced.During weakening of the flame intensity,a dark film gradually covered the particle surfaces.X-ray diffraction and elemental analyses of the cross-section and outer surface of the condensed combustion product suggested that the dark film is primarily composed of Mg-B-O ternary oxides.This film prevents direct contact between boron and oxygen,thereby inhibiting surface and gas-phase reactions and leading to the occurrence of the transient flameout phenomenon.