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The hetero-salt, a solid waste, is generated due to the simultaneous crystallization and agglomeration of two or more salts in the evaporative crystallization of multi-salt solution. However, the waste can be transformed into resource if the different crystalline particles can be separated effectively. In this study, NaCl and Na 2 SO 4 were taken as examples and mixed in the solution. It was found that the agglomeration of the crystals occurred both in the drying and crystallization stage. But the crystals could be independent at certain concentration and evaporation time. Meanwhile, the morphological characteristics of NaCl and Na 2 SO 4 crystals were quite different. Therefore, a lab-scale overflow device was prepared to separate the mixed crystals. The results showed that it was possible to separate the two kinds of crystals in simultaneous crystallization effectively. The purity of recovered NaCl was up to 97.58% at a flow velocity of 0.04 m/s. [Display omitted] • Simultaneous crystallization of NaCl and Na 2 SO 4 was studied in the NaCl-Na 2 SO 4 -H 2 O system. • The agglomeration of NaCl and Na 2 SO 4 crystals makes it difficult to separate the two crystals. • The crystals could be isolated under certain conditions during simultaneous crystallization. • The overflow device could separate the two crystals of NaCl and Na 2 SO 4 effectively. [ABSTRACT FROM AUTHOR]

To investigate the effect of surfactants in compound solution on the wetting-agglomeration properties of the bituminous coal dust, this paper selected anionic surfactants SDS, SDBS and non-ionic surfactants APG0810 and PPG400 for compounding with agglomerated solutions 0.05 wt% XTG (xanthan gum). The sink test, surface tension test, viscosity test, fourier transform infrared spectroscopy(FTIR) and scanning electron microscope(SEM) were used to investigate the wettability and agglomeration of the four compound solutions and analyze the agglomeration wetting mechanism. The results show that SDBS has the most obvious improvement in the wettability of compound solution. The surface tension of SDBS + 0.05 wt% XTG is 28.98 mN/m after CMC value and sinking rate will reach 14.29 mg/s with 0.6 wt% SDBS in compound solution; Furthermore, FTIR results showed that surface hydroxyl content of bituminous coal dust treated by 0.2 wt% SDBS + 0.05 wt% XTG solutions has increased 26.3% than that treated by 0.05 wt% XTG, which promoted the adsorption of xanthan gum molecules on the coal surface. The presence of surfactants decreases the viscosity and surface tension of compound solution, and xanthan gum–surfactants interaction will promote bituminous coal dust agglomeration effect. This agglomeration mechanism is mainly reflected in the distribution mechanism and bituminous coal dust can form to large agglomerates under this action. [Display omitted] • Influence mechanism of surfactants in compound solution on viscosity is analyzed. • Wetting-agglomeration properties of coal dust by composite reagent are studied. • The distribution mechanism about coal dust agglomeration has been found. • The formed process of distribution mechanism has been described. [ABSTRACT FROM AUTHOR]

Agglomerates are a large cluster of primary particles, which may result in the flaws of the final ceramics. Stereolithography suspensions could pose challenges to identify their coarse agglomerates without modifications to their properties; the suspensions are mostly high turbid and viscous in some cases. Any modifications, such as dilution, can alter the actual degree of agglomeration. In this study, a means to characterize the degree of dispersion was developed using the automated fineness of grind gauge. The fineness of grind gauge was visualized to determine the nature of the trapped agglomerates and their distribution. The resulted agglomerate size distribution was treated mathematically as a power law distribution in a selected region. The power law function was found to describe the degree of dispersion of suspensions, which was associated with the coarse agglomerate distribution behavior. Unlabelled Image • Identified the degree of dispersion of stereolithography suspensions. • Defined the power law coefficients of the agglomerate size distribution. • Provided a correlation between coarse agglomerate and power law exponent. [ABSTRACT FROM AUTHOR]

The impact of agglomerates on solid surfaces occurs inevitably during the processing of granular materials. In this work, numerical simulations of the surface impact of wet agglomerates are carried out by introducing liquid bridge interactions into a soft-sphere DEM model, and the instantaneous impact behaviors are discussed quantitatively at the single particle scale. Results indicate that the impact process usually includes four stages, i.e., compression, expansion, fragmentation, and re-agglomeration. The expanding radius is found to follow an exponential-law with time, and the number of fragments follows a power-law with impact velocity. Due to liquid bridge interactions, chain-like structures are observed beyond the impact, similar to those formed during the impact of dense suspension droplets. Moreover, the impact behaviors can be generally classified into four groups with respect to impact velocity, i.e., minor compression without splashing, severe compression with minor splashing, severe splashing with minor fragmentation, and severe fragmentation. Unlabelled Image • Surface impacts of wet agglomerates are quantitatively investigated using DEM. • Impact dynamics including compression, expansion and fragmentation are discussed. • Re-agglomeration is observed at the late stage of the impact of wet agglomerates. • Four categories of impact behavior are identified with respect to impact velocity. [ABSTRACT FROM AUTHOR]

Cold, binder-free tableting experiments under controlled pressure (0-450 MPa), water addition (0-10 wt.%) and pH (4, 11) were performed on powder of pyrolusite ore concentrates, refined hausmannite, bentonite, kaolinite, as well as blends of those materials. It has been shown that increased pressure was beneficial for agglomeration of oxide materials, but pressure > 250 MPa triggered an elastic recovery in the clay minerals. Water addition up to 4 wt.% improved tabletability, increasing diametral resistance and reducing elastic recovery and fines generation. Amounts above 6 wt.% decreased diametral resistance. The presence of layered-structure minerals (such as montmorillonite, kaolinite, lithiophorite) appeared to be key to determine the agglomeration potential of a sample. This study also showed that tableting provides good performances for recycling industrial manganese oxide fines by obtaining industrial-grade resistance for tablets made with an 80/20 pyrolusite concentrate/hausmannite blends and 4 wt.% H 2 O. Unlabelled Image • Tableting presents an alternative recycling process for Mn processing fines. • Mn refining and laterite ore fines can be recycled at 20/80 wt.% with 4 wt.% H 2 O. • Soft, plastic material with high specific surface area is key for good tableting. • Lithiophorite acts as natural binder in tableting due to its layered structure. • Prediction of fines tableting behavior requires a deep understanding of materials. [ABSTRACT FROM AUTHOR]

Hydrophobic agglomeration of rhodochrosite fines in aqueous suspensions with sodium oleate has been investigated through wettability measurement, optical microscopy observation, laser-based particle size detection, micro-flotation test, zeta potential measurement in this work. The experimental results indicated that the hydrophobicity of rhodochrosite was a dominant factor for the hydrophobic agglomeration. And a higher sodium oleate concentration could contribute to bigger agglomeration particle size and more regular agglomerates. The increased apparent particle size of minerals through hydrophobic agglomeration interaction was conducive to the micro-flotation recovery improvement of rhodochrosite fines in spite of a simultaneous increase in the negative zeta potential of rhodochrosite, meaning that the chemical adsorption was the primary reason between sodium oleate and rhodochrosite. Furtherly, the data calculated from extended DLVO theory was also convinced that hydrophobic interaction between the particles increased much more strongly than electrostatic repulsion from the adsorption of sodium oleate. Schematic diagram of rhodochrosite hydrophobic agglomeration induced by NaOL. Unlabelled Image • Morphology changes of rhodochrosite agglomerates were investigated. • Correlate agglomeration with hydrophobicity, flotability and surface charge. • Sodium oleate could chemically adsorb on the surface of rhodochrosite. • Extended DLVO theory demonstrated the interaction energy between particles. [ABSTRACT FROM AUTHOR]

Controlled agglomeration during spray drying offers several advantages for both powder manufacturers and consumers, and thus it is commonly implemented by industry. The implementation, however is largely based on experience, given the scarcity of comprehensive prediction tools. A resource-efficient approach to numerically treat agglomerates and yet provide an indication of their structures is desired to perform realistic simulations without the need for high-performance computing. In this work, a new numerical model for the treatment of coalescence and agglomeration was implemented and evaluated at two distinct scales with significantly different particle number densities within a Eulerian-Lagrangian CFD framework. The model could accurately predict the trends in the final particle size distributions and distinguish realistic agglomerate structures occurring under different conditions. Challenges were encountered as a result of how the underlying collision detection routine handles high particle number density. Several strategies are proposed to overcome these challenges. This work constitutes significant progress towards achieving an efficient prediction tool to estimate final powder properties and will prove useful in performing large-scale simulations to design and control agglomeration. Unlabelled Image • A rigorous modelling approach was developed for agglomeration in spray drying. • The proposed model was found to be resource efficient and yet useful and informative. • Coalescence and agglomeration of particles were distinguished via penetration depth. • Surface area reduction coined as a parameter indicated agglomerate compactness. • Experimental data obtained from lab- and large-scale dryer supported the assessment. [ABSTRACT FROM AUTHOR]

Heat transfer behaviors in a pulsed fluidized bed are numerically investigated by means of a combined approach of computational fluid dynamics (CFD) and discrete element method (DEM). The effect of pulsation flow on bed heat transfer characteristics is evaluated. It is found that the pulsed gas flow leads to an intense oscillating flow behavior in the bed, enhancing the the cooling rate of hot particles. Three kinds of heat transfer mechanisms are examined. The results reveal that the particle-fluid convection is dominated. Meanwhile, heat transfer mechanisms in a polydisperse system are also discussed. It is observed that the addition of fine particles promotes the total particle-fluid convection and the fluctuating degree with time becomes evident. Unlabelled Image • Heat transfer in a pulsed fluidized bed is investigated by the CFD-DEM. • Effect of pulsation frequency on heat transfer is evaluated. • Gas-particle and particle-particle heat transfer with pulsed flow are examined. • Heat transfer mechanisms in a polydisperse system are analyzed. [ABSTRACT FROM AUTHOR]

Crystallization is one of the most important unit operations for production of active pharmaceutical ingredients (API) in pharmaceutical industry. This work studied the impact of solvent chemical composition on fesoterodine fumarate dissolution in 2-butanone/cyclohexane mixtures and seeded cooling crystallization, combining population balance equation (PBE) modelling with experiments. Thermodynamics, transport phenomena and kinetics of nucleation, crystal growth, agglomeration, and dissolution were taken into account, two in-line process analytical technologies (PAT) – attenuated total reflectance Fourier-transform infrared spectroscopy (ATR–FTIR) and focused beam reflectance measurement (FBRM) – were used for monitoring seeded experiments, and non-linear regression analysis was applied for parameter estimation. Cyclohexane not only decreased solute saturated solubility, but increased rates of all mechanisms. Model validation by temperature cycling showed a good agreement between results and simulations which opens up possibilities for further engineered optimization and control. Combined cooling & antisolvent crystallization (CCAC) experiment revealed a complex antisolvent impact on particle dynamics. Unlabelled Image • Addition of cyclohexane impacts both solubility and crystallization kinetics. • Fesoterodine fumarate solubility surface modelled by linear interpolation. • Rates of crystallization mechanisms and dissolution increase to different extent. • Larger particles are formed by increasing the amount of cyclohexane. • Simulations show that the impact of antisolvent on kinetics should not be neglected. [ABSTRACT FROM AUTHOR]

One of the key challenges that the pharmaceutical industry is trying to address is to maintain particle properties across the entire purification and isolation process. This research focuses on the effect of slurry properties, wash solvent, filtration and washing mechanisms on API agglomeration/granulation during the processes of downstream isolation and the impact on the physical properties of the product. In this investigation, each isolation step was analysed to identify factors that have the potential to affect the final product qualities using a multivariate statistical design of experiments approach. The factors which were most detrimental in increasing particle agglomeration, were found to be the particle size of the input material, the quantity and identity of wash solvent and the drying mode. Low boiling point aliphatic hydrocarbons are shown to be desirable final wash solvents to reduce the extent and strength of agglomerates and to produce free flowing powder/readily disrupted agglomerates. Unlabelled Image • Filtration, washing and drying parameters impact the isolated product quality. • Particle size, agglomeration extent and mechanical properties are affected. • Guidance is provided on API isolation strategy to minimize agglomeration. • The effect of sedimentation prior to filtration was investigated. • 1H NMR used to monitor cake washing efficiency. [ABSTRACT FROM AUTHOR]

Contamination due to dry snow smoke adhesion is an evident danger for sensor blinding on future autonomous driving cars under winter road conditions. This paper examines at what velocities ice particles and agglomerates, representing dry snow, adhere to surfaces of various materials. Contact models for normal direction, tangential sliding, and tangential rolling that account for the adhesive interaction of spherical particles due to Van der Waals forces are used in the study. Three different scenarios of impacts are presented i) single particle impact, ii) small agglomerate impacts, and iii) large agglomerate impacts. It is shown that by increasing the number of particles in an agglomerate, the velocity at which the agglomerate sticks to the impact wall increases, i.e. the agglomerate is more likely to stick to a surface. It is also shown how material properties influence the tendency of dry road snow to adhere to a surface. Unlabelled Image • The critical sticking velocity for ice particles and agglomerates are predicted. • Collisions of agglomerates onto different wall materials are investigated. • Critical radius for rolling and sliding of adhesive particles are defined. • Simulations show considered amount of energy loss due to tangential interactions. [ABSTRACT FROM AUTHOR]

Fine particles (<3 mm) are important, environmentally hazardous wastes of the mining and metallurgical industries that still contain valuable metals. Agglomeration, mainly using binders, is a common process to safely recycle those materials. This study aims at mastering cold agglomeration through understanding natural binder properties of the material. For the first time, a comprehensive physico-chemical characterization was performed on 13 samples from a manganese processing chain including ore fines. The main parameters to predict the agglomeration potential of the materials used in the present study are the presence of layer- and/or tunnel-structured phases along with the particle and grain size distribution, hardness and shapes, and particle surface charges. The Gabon ore fines show the best agglomeration potential. The soft, layer-structured plastic minerals (clays, lithiophorite) present naturally coat the hard grains (pyrolusite, cryptomelane) forming particles with enhanced binding potential. Blending these ore fines with low agglomeration potential dusts avoids binder use in the agglomeration process. Image 1 • Dusts properties highly depends on their production process. • Ore fines have complex particle shapes and mineralogy, unlike refining dusts. • Ore fines show higher interaction potential due to their mineralogy and morphology. [ABSTRACT FROM AUTHOR]

The properties of nucleating and growing struvite crystals are important aspects to pellet agglomeration and growth mechanisms in fluidized bed reactors (FBR). A new approach, using a laser to sense crystals of approximately 650 nm, was used to measure the induction time of nucleating struvite. The ability of the laser to indicate an approximate size ensured the presence of crystals in solution for zeta potential (ζ) measurements. This is the first study where ζ was measured for nucleating and growing struvite crystals, and it was not negative like aged crystals; it changed over time as the solution conditions changed, generally started positive and became more negative as precipitation proceeded. The time where ζ≈ 0 can be related to supersaturation ratio (SSR) and optimal agglomeration locations within FBR systems. SSR values between 2 and 6 are recommended to reduce ζ values for extended periods and to improve struvite FBR agglomeration processes. Image 1 • A new laser method has been used in sensing induction times of struvite. • Aged struvite zeta potentials are negative as reported in literature. • The zeta potential of nucleating struvite changes as the reaction proceeds. • Low initial SSRs produce smaller zeta potentials for extended periods. • SSRs between 2 and 6 are recommended to improve FBR agglomeration processes. [ABSTRACT FROM AUTHOR]

Many researchers have considered air quality degradation due to the emission of fine particles from industrialized and urban areas during recent decades. Recently, the European Parliament has had concerns about ensuring a healthy human environment. Therefore, the experimental and theoretical investigations of the dynamics of fine particulate matter are for determining efficient monitoring and cleaning air from industrially generated air pollutants. These investigations also imply the use of alternate methods that stimulate fine particle agglomeration. One of the methods is the use of acoustics. Many experimental investigations of particles with a diameter between 1 and 10 μm have proven that the use of acoustic agglomeration increases the particle size. Then, conventional air filters can be used to collect the larger particles. This process improves the collection efficiency of the particles. Particulate agglomeration chamber consisting of an acoustic field generator and an inner part was created for the test particles of diesel engines (range from 0.3 to 10 μm). Modeling of its elements was performed using Comsol multifunctional software. This sound pressure level is enough [1] to lead the acoustic agglomeration process of particles in the measurable range from 0.3 to 10 μm. The sound pressure level reach this value (130–140 dB) at the acoustic agglomeration zone. Additionally, the theoretical evaluation of the agglomeration time of two sub-micron particles enabled the estimation of efficient agglomeration of particles with sizes between 0.3 and 10 μm during the measurement period. A starting value of 136 dB of sound pressure level (SPL) was created in the experimental chamber with the turbulence condition, where SPL values were measured by using the Bruel&Kjaer measurement system "Type 9727" with hydrophone 8104. The observation concentrations of diesel engine exhaust particles in the experimental chamber with and without acoustic influence were performed using Particle Concentration Analyzer 4 APC ErgoTouch Pro 2. The results of experimental research shows that the acoustic agglomeration effect formed the proper conditions for the agglomeration of particles of all diameters (0.3, 0.5, 1.0, 3.0, 5.0 and 10 μm). Image 1 • The IC (internal combustion) engine exhaust particle emissions are considered. • An acoustic generator for the agglomeration of particles was created and validated. • Acoustic agglomeration produces about 140 dB of sound pressure at 24 kHz frequency. • The agglomeration of particles (0.3–10 μm) approved by experimental studies. [ABSTRACT FROM AUTHOR]

The effect of polar and nonpolar liquid process control agents (PCA) on properties of metal rich Al/CuO thermites prepared by Arrested Reactive Milling was studied. Acetonitrile and hexane, and their mixtures were used as PCA. Milling in nonpolar hexane results in fully dense, micron-sized composite particles of 100 nm-scale CuO inclusions in an Al matrix. Using polar acetonitrile results in a mixture of nano-sized, largely unagglomerated Al and CuO particles. Porous composites, agglomerated to different degrees, formed in hexane-acetonitrile mixtures. In particular, micron-sized porous spherical composite particles formed in a mixture with 25% acetonitrile. Such spherical composites may result from interaction of suspended powder particles with stressed droplets of a Pickering emulsion forming when immiscible liquids serve as PCA. Despite dramatic changes in the powder morphology, all composites were reactive. Systematic differences, discussed in the text, were observed in their ignition temperatures and oxidation kinetics. Image 1 • Energetic composite materials prepared by arrested reactive milling. • Novel use of immiscible solvents as process control agents. • Resulting emulsion determine properties of produced composite particles. [ABSTRACT FROM AUTHOR]

In this study, the effect of kerosene and sodium oleate (NaOL) on inducing hydrophobic agglomeration flotation of fine cassiterite was investigated through the micro-flotation tests, particle size distribution and morphological analysis, zeta potential and contact angle measurements. The results indicated that adding kerosene before NaOL could obtain a higher recovery than adding NaOL before kerosene. The agglomerates induced by adding kerosene before NaOL was dense and regular in structure with larger particle size distribution and stronger surface hydrophobicity, which jointly contributed to its higher flotation recovery. Furtherly, the extended DLVO theory calculation was carried out to explain the agglomeration behaviour of fine cassiterite under different reagents. The results convinced that under the reaction of NaOL before kerosene or kerosene before NaOL, hydrophobic interaction and sufficient kinetic energy input were necessary to form agglomerates, and the attraction effect between cassiterite particles under the reaction of kerosene before NaOL was the strongest. [Display omitted] • Hydrophobic agglomeration flotation of fine cassiterite was investigated. • Agglomerates induced by adding kerosene before NaOL were favorable for flotation. • Extended DLVO theory revealed the agglomeration behaviour of fine cassiterite. • Hydrophobic interaction and energy input were necessary for agglomeration. [ABSTRACT FROM AUTHOR]

In the incineration process, agglomeration is caused by the combustion of wastes containing adhesion materials such as alkalis and earth alkalis. Alkali oxides not only have a low melting point but also can react with Si to form low-melting-point eutectics. Most of the researches focused on the inlet materials, however, the properties of sand bed materials are also playing an important role on defluidization process. A comprehensive analysis of sand compositions on the prediction of defluidization tendency is carried out. Variation of sand properties before and after fluidized bed operation is estimated by XRF characterization, and the effect of particle size distribution is also in consideration. Experimental results indicated that defluidization time decreases with the increasing particle size of all sand sources. Higher temperature promotes agglomeration/defluidization. According to the agglomeration indices calculation, indicator Al + Ca + Mg/(Na + K + Fe) can be used to estimate the defluidization tendency before fluidized bed operation for particle sizes below 770 μm. In contrast, for a particle size of 920 μm, Al + Ca + Mg + Fe /(Na + K) can be utilized to qualitatively characterize the defluidization time. On the other hand, the Support Vector Regression (SVR) model was the best model for predicting the defluidization time (R2 of 93.40% and MSE of 3470). Causal analysis shows particle size, K 2 O, and Na 2 O were the top three most important factors that affect the particle agglomeration. The results are helpful to the evaluation of the agglomeration tendency of sand bed materials before using fluidized bed waste incineration agglomeration in terms of qualitative analysis and quantitative analysis. [Display omitted] • Sand bed compositions have effect on the agglomeration behavior. • Agglomeration indices qualitatively evaluate the defluidization time (DFT). • Machine learning were used to quantitatively predict the DFT. • Support Vector Regression model was the best model for predicting the DFT. [ABSTRACT FROM AUTHOR]

The hydrodynamics of flotation machines can significantly impact the flotation performance of fine minerals, however, those of fluidized bed flotation columns with binary particles remain poorly understood. This paper investigated the hydrodynamics of fluidized bed flotation columns such as bed pressure drop, minimum fluidization velocity, bed expansion ratio, and gas holdup. The effect of liquid velocity, gas velocity, and particle size on hydrodynamics was discussed. The hydrodynamics of fluidized beds with binary particles was compared with that of unitary particles. Results showed that the hydrodynamics of the fluidized bed with binary particles lay between the fluidized bed with large and small particles as influenced by the combination of large and small particles. A fluidized bed flotation column with binary particles demonstrates great potential in changing hydrodynamics. [Display omitted] • An investigation of the fluidization process in a fluidized bed with binary particles. • The gas holdup in the freeboard zone and the fluidized zone was studied. • Gas introduction facilitates fluidized bed formation. • The hydrodynamics of the bed are affected by both small and large particles. • Binary particles can aid in regulating the hydrodynamics of the bed. [ABSTRACT FROM AUTHOR]

Anthropogenic climate change is amongst the greatest of challenges to human civilization. A key area that will play a large role in mitigating its effects are clean fossil fuel applications. Clean coal combustion can be achieved with an oxygen-fired pressurized fluidized bed combustor incorporating carbon capture and storage. In relation to pressurized fluidization processes, understanding the influence of pressure on fluidized bed hydrodynamics and, in turn, their effect on parameters including fuel residence time is essential. For the combustor under consideration here, a fraction of the heat exchanger boiler tubes are submerged in the fluidized bed such that the effect of the horizontal tube bundle on the fuel residence time is of great importance. The main focus of the present work was to evaluate the impact of gas velocity, pressure, presence or absence of a horizontal tube bundle and fuel feed rate on the average fuel residence time in a dense gas-solid fluidized bed. Experiments were conducted under cold flow conditions in a pressurized fluidized bed with an inner diameter of 0.15 m. The fluidization material was large glass beads (1.0 mm in diameter) while fuel particles were simulated with smaller glass beads (64 and 83 μm in Sauter mean diameter) that were susceptible to entrainment. Operating pressures and superficial gas velocities were maintained between 101.3 and 1200 kPa and 1.5 and 3.2 U mf, respectively. To simulate continuous fuel injection, experiments were conducted with the fuel surrogate particles being continuously fed to the fluidized bed of large particles over a desired period of time. Downstream, entrained particles were captured to determine the average entrainment rate and average mass of fuel particles inside the fluidized bed at steady state, which yielded the average fuel residence time. The combination of elevated pressure with the tube bundle present was found to have the most influential impact when compared to base conditions of atmospheric pressure and with no tube bundle present. It was found to enhance gas bubble break up and reduce the average gas bubble size substantially. In turn, this increased the average residence time of 83 μm particles by nearly three-fold in comparison to the case of atmospheric pressure with no tube bundle present. The effect of gas velocity on particle residence time was not found to be statistically significant under the range tested. Similarly, the effect of increasing fuel feed rate by 50% had no statistically significant impact. Unlabelled Image • Studied particle residence time in a pressurized fluid bed with in-bed heat exchanger tubes. • Fine particles were continuously fed to the fluid bed of large particles. • Evaluated the impact of gas velocity, pressure, and presence of a horizontal tube bundle. • The combination of elevated pressure with the tube bundle present had the most impact. • Average particle residence time increased by nearly threefold at pressure and with tube bundle. [ABSTRACT FROM AUTHOR]

Wurster coater was utilized for coating glass beads with HPMC/PEG. The effects of design and operating parameters on the coating process were evaluated. It was found that the pressure drop decreases when spraying the coating solution into the bed, indicating that spraying prevents the particles from flowing easily in the draft tube. Moreover, it was observed that the minimum spouting velocity increases during the coating process. The results indicated that increasing the entrainment zone height and decreasing the distributor hole pitch increase the coating yield, while the draft tube height did not have a significant influence on the coating yield. These findings were confirmed by thermogravimetric analysis (TGA). The degree of agglomeration intensifies when increasing the entrainment zone height, increasing draft tube height and decreasing the distributor hole pitch. Finally, scanning electron microscopy and energy dispersive X-ray spectroscopy analyses confirmed deposition of the coating material on the surface of particles. Unlabelled Image • HPMC/PEG film coating of the pellets in a Wuster coating process. • Entrainment zone height, draft tube height and distributor hole pitch were studied. • Stability of Wurster coating process were studied using pressure drop measurements. • Both hydrodynamic and interparticle forces govern hydrodynamic of the Wurster coater. • Operating and system design parameters affect coating yield and agglomeration degree. [ABSTRACT FROM AUTHOR]

Abstract Both the chemical and turbulent agglomeration are promising pretreatment technologies for promoting the removal of fine particles. However, single chemical and turbulent agglomeration both have some shortcomings in improving the agglomeration of fine particles. Based on the combination of chemical and turbulent agglomeration, different coupling modes of chemical and turbulent agglomeration were proposed and investigated to get the most effective mode in this study. In order to compare the effect of the two coupling modes, the particle agglomeration effect and removal performance by ESP under different agglomeration conditions were studied respectively. The results showed that chemical-turbulent agglomeration had more advantages over turbulent-chemical agglomeration. Furthermore, the interaction mechanism of chemical-turbulent agglomeration was explored by analyzing the motions of chemical droplets and particles in turbulent agglomerator and the promoting effect of chemical agglomeration on turbulent agglomeration. The calculation results showed that in the process of chemical-turbulent agglomeration, the turbulent agglomeration improved the effect of chemical agglomeration by affecting the motion trajectories of droplets and particles, and the chemical agglomeration improved the probability of particles collision in turbulent agglomeration by enlarging the particle size before turbulent agglomeration, which made chemical-turbulent agglomeration more effective than turbulent-chemical agglomeration. Graphical abstract Unlabelled Image Highlights • Different coupling modes of chemical and turbulent agglomeration were proposed. • The chemical-turbulent agglomeration was proved to be the best coupling mode. • The turbulent agglomeration led to different motion trajectories of droplets and fine particles. • Chemical agglomeration improved the probability of particles collision in turbulent agglomeration. [ABSTRACT FROM AUTHOR]

Abstract The work described in this paper employs large eddy simulation and a discrete element method to study turbulent particle-laden channel flows at low concentrations (particle volume fraction 10−4–10−5), including particle dispersion, collision and agglomeration. Conventional understanding of such flows is that particle interactions are negligible, this work however demonstrates that such interactions are common at large Stokes numbers in turbulent flow. The particle-particle interaction model is based on the Hertz-Mindlin approach with Johnson-Kendall-Roberts cohesion to allow the simulation of cohesive forces in a dry air flow. The influence of different flow Reynolds numbers, and therefore the impact of fluid turbulence, on agglomeration behaviour is investigated. The agglomeration rate is found to be strongly influenced by the flow Reynolds number, with most of the particle-particle interactions taking place at locations close to the channel walls, aided by the higher turbulence levels and concentration of particles in these regions. Graphical abstract Unlabelled Image Highlights • Turbulent structure of the flow dominates motion creating particle interactions • Agglomeration increase with Reynolds number at low surface energy • Process of particle agglomeration was seen to be enhanced in two separate regions [ABSTRACT FROM AUTHOR]

Abstract With the rapid depletion of relatively simple iron ores that can be readily beneficiated, agglomeration magnetic separation has been increasingly applied for recovery of fine iron minerals. In this study, the effects of stirring speed, pH, and flocculant dosage on the recovery of fine hematite are investigated by floc-magnetic separation experiments in the presence of carboxymethyl starch (CMS). The experimental results show that the recovery of fine hematite is improved in the presence of CMS in the high-intensity magnetic separation (HIMS) with sufficient kinetic energy input and appropriate pulp pH value. Compared to the conventional HIMS, the concentrate recovery has increased by 7.03 percentage point in the presence of CMS under optimal conditions. Furthermore, the mechanism of the interaction between CMS and fine hematite is investigated through scanning electron microscopy, energy dispersive spectroscopy, and zeta potential and infrared spectrum measurements. The results of SEM-EDS and optical microscope tests indicate that CMS can adsorb on the surface of hematite, but not on the quartz surface. The results of the zeta potential and FTIR measurement illustrate that electrostatic adsorption and hydrogen bond adsorption exist between hematite and CMS, but barely found between quartz and CMS. Therefore, the selective agglomeration of fine hematite particles is formed by the polymer bridging effect of CMS in the pulp. Subsequently, the collecting efficiency of fine hematite particles is improved in the HIMS. The model of selective flocculation of fine hematite is proposed and attributed to two processes: the sensitisation process and the collision process. While the former process is the selective adsorption of CMS on the surface of fine hematite particles through hydrogen bonds, the later process is the polymer-bridging flocculation performance with sufficient kinetic energy input at an appropriate pulp pH value. Graphical abstract Unlabelled Image Highlights • Carboxymethyl starch has selective flocculation effect on fine-grained hematite. • The main factors affecting the selective aggregation of hematite particles have been investigated. • The recovery of fine hematite can be enhanced on magnetic separation with the presence of CMS. • Electrostatic adsorption and hydrogen bond adsorption existed between hematite and carboxymethyl starch. [ABSTRACT FROM AUTHOR]

Abstract The inorganic coating of Al 2 O 3 was introduced on nanoparticles to weaken their tendency of agglomeration in electroless plating bath. The influence of the coating on interaction energy and interaction forces between the coated particles was evaluated in this study. The Al 2 O 3 -coated diamond particles were prepared by the heterogeneous nucleation process. The attractive interaction and repulsive interaction between the coated particles in electroless nickel (EN) solution were calculated by the classical DLVO theory. Sedimentation tests were conducted to verify the modelling. The calculation predictions are well in agreement with the experimental results. The Al 2 O 3 coating could reduce van der Waals attraction by enlarging the surface separation distance of diamond particles, and could increase electrical double layer repulsion by increasing the surface potentials in EN solution. Consequently, it could weaken the net attractive interaction, whose net attractive force decreased from −3.77×10−2N/m between bare particles to −1.12×10−2N/m between the coated ones, a reduction by 70%, at the separation distance of 1 κ −1. The coated diamond particles in EN solution show a slower settling rate than bare ones. The Al 2 O 3 coating contributes to the high dispersability of the coated particles under the agitation condition. Graphical abstract Unlabelled Image Highlights • Al 2 O 3 -coated diamond particles are successfully prepared. • Al 2 O 3 coating reduces van der Waals energy of diamond in electroless solution. • Coated diamond particles show an increased zeta potential in electroless solution. • Al 2 O 3 coating remarkably reduce net attractive force of diamond particles. [ABSTRACT FROM AUTHOR]

Abstract This paper presents the results of experimental studies on desulfurization of high sulfur Indian coal by oil agglomeration using linseed oil. During experimental studies, various operating parameters like effect of pH, particle size, pulp density, agglomeration time, agitation rate and linseed oil dose were studied to find their impact on clean coal properties like sulfur reduction ratio (S/So), ash reduction ratio (A/Ao) and gross calorific value (GCV) ratio (GCV/GCVo). Experimental results showed that raw coal with 5.52% sulfur, 13.47% ash and GCV of 7038 kcal/kg can be beneficiated to produce clean coal with 2.18% sulfur along with 5.32% ash and 7769 kcal/kg GCV. Physico-chemical characterizations of raw and clean coal samples were carried out by using Field Emission Scanning Electron Microscope (FESEM), Fourier Transformation Infrared (FTIR) and Petrographic analysis to appraise the product quality. Microscopic analysis using FESEM confirmed the formation of agglomerates and reduction of mineral matters from coal structure. Petrographic analysis further confirms the increases in vitrinite, inertinite and liptinite from 68.62 to 73.61%, 12.45 to 14.07% and 3.25 to 4.27% respectively in the clean coal along with reduction of pyritic sulfur (from 9.37 to 3.87%) and mineral matter (from 6.31 to 4.18%). FTIR results infers the reduction of sulfur, oxygen rich hydrocarbons and minerals along with increase of carbon, hydrogen rich hydrocarbons in the clean coal. Graphical abstract Unlabelled Image Highlights • Influence of Linseed oil in agglomeration process on high sulfur coal was studied. • Maximum desulphurization of high sulfur coal was observed at 15 min agglomeration time. • Maximum deashing of high sulfur coal was observed at 19 μm particle size. • The increase of calorific value is inversely proportional to ash content. • The increase of hydrophobicity of coal in agglomeration process decrease their ash and sulfur content. [ABSTRACT FROM AUTHOR]

Abstract Spherical agglomerated crystals of ascorbic acid (AA) have been prepared with a trace of polyvinylpyrrolidone (PVP) by a spherical agglomeration method. The process of spherical crystallization has been monitored online with a particle vision and measurement (PVM) probe. The effect of PVP on the metastable zone width of ascorbic acid in aqueous solutions has been characterized by a laser method. Hydrogen bonding interactions between AA and PVP have been identified by Fourier-transform infrared spectroscopy and 1H nuclear magnetic resonance. Differential scanning calorimetry and powder X-ray diffraction measurements have shown that the prepared spherical crystals still exhibited a crystallin nature. The micromeritic properties, namely flowability, packability, and compressibility, were significantly improved compared to those of the pure drug crystals. In this study, we have explored the mechanism of the spherical crystallization process in the presence of the polymer, and the beneficial effect of the polymer on the micromeritic properties of crystals of ascorbic acid. Graphical abstract Unlabelled Image Highlights • Spherical agglomerated crystals of AA with superior micromeritic properties have been prepared with PVP. • The metastable zone width of AA in aqueous solution is significantly expanded by the addition of PVP. • Hydrogen bonding interactions between AA and PVP have been found in the prepared crystals. [ABSTRACT FROM AUTHOR]

Abstract An effective technique for fine particle removal using the combined effect of acoustic field and seed nuclei was presented. The key operation parameters, such as sound pressure level, initial particle number concentration, seed nuclei and particle properties on the agglomeration and capture performance of fine particles were investigated experimentally. The results showed that the separation of fine particle was improved efficiently with the combined external fields. Fine particle removal efficiencies increased by 25% with the combined effect of acoustic field and droplets at a SPL of 153 dB. Removal efficiency increased with the seed nuclei size. The value increased from 20% to 50% as the seed particle size increased from 10 to 30 μm, but removal efficiency showed few changes when seed particle size was larger than 30 μm. Particle removal efficiency correlated well with the initial particle number concentration in the combined effect fields. The removal efficiency with the combined effect of acoustic field and droplets was much higher than those with the combined effect of acoustic field and solid seed particles in high particle loading. Fine particle removal was significantly impacted by the particle wettability, when the combined effect of acoustic field and droplets was used. The removal efficiency of MWI particles was improved by 20% with the combined effect of acoustic field and droplets, comparing to the removal efficiency of BC particles. Fine particle removal efficiency can be highly improved with the combined external fields, especially in low acoustic intensity. Graphical abstract Unlabelled Image Highlights • Interaction of fine particles and seed nuclei with acoustic activity was presented. • The agglomeration properties of fine particles are changed by different seed nuclei. • Fine particle removal efficiency is highly improved with AFSD for good wettability particles. • Removal efficiency with AFSD is much higher than the value with AFSP in high particle loading. • Combined effects contribute to improve fine particle removal efficiency in low acoustic intensity. [ABSTRACT FROM AUTHOR]

In this work, particle circulation and separation of binary solids were investigated in a novel fluidized bed system, constructed with two sections connected through a slit. One side contains a vigorously fluidized bed with an inclined distributor for biomass pyrolysis, while the other provides for a gentle fluidized bed for particle separation. Particle exchange through the slit was observed and analyzed by PIV to explain the driving force transporting particles between sections. An inclined distributor facilitated smooth transportation of particles to the gentle bed where the lower-density char was effectively removed from the denser bed materials. Particle transportation, and therefore, particle separation, depended on the gas flow rate into the lower end of the inclined distributor plate and was sensitively affected by the location of the slit. The driving forces of particle transport through a slit were, the instantaneous local pressure difference induced by babbles and also hydraulic head difference. [Display omitted] • Two-coupling fluidized bed via a slit is developed for a char-particle removal. • Particle exchange through a slit is analyzed by PIV methods to explain the mechanism. • The inclined gas distributor indicates good performance for particles exchange via a slit. • Driving forces of particle movement are induced by bubbles and the hydraulic head difference. [ABSTRACT FROM AUTHOR]

The deposition efficiency of metal based additive manufacturing processes, particularly with directed energy deposition (DED) equipment which requires powder feedstock, is often <50%. While reuse of the remaining powder is common in industry, the precise effects on build quality resulting from possible morphological, microstructural, and chemical changes in the powder remain poorly understood. In this study, the reuse of 316L stainless steel powder in the Laser Engineered Net Shaping (LENS®) machine was investigated through multiple deposition cycles. Particular attention was paid to the influence of reusing powder on: particle morphology, flowability, agglomeration, chemical composition and microstructure, via scanning electron microscopy, particle size analysis and mechanical testing of deposited parts from select reuse cycles. Results show that, for the range of parameters studied in this investigation, the physical properties of powder particles vary over multiple deposition cycles without significantly effecting the build quality of deposited parts. [ABSTRACT FROM AUTHOR]

Nano- and submicron particles typically exist in the form of agglomerates. The shear flow, a common local flow, plays an important role in the breakage and restructuring of agglomerates. In this work, the discrete element method (DEM) with a cohesive contact model is used to simulate the dynamic evolution of agglomerates under shear flow. The results show that the size and structure of agglomerates at a steady state are the results of competition among the shear gradient of the flow field, the surface energy and the initial structure of the agglomerates. Based on the variation of the radius of gyration ( R g ) and fractal dimension ( D f ) of agglomerates with time, the following three stages can be distinguished: (a) a stage dominated by stretch and breakage, (b) a stage dominated by agglomeration and densification, and (c) a stage characterized by the steady size and structure of agglomerates. With increasing shear gradient, the agglomerate fragments at the steady stage become smaller, more compact and more uniform. When the shear gradient is high, increasing the surface energy can result in larger fragments with a more compact structure. However, when the shear gradient is low, increasing the surface energy does not lead to larger fragments. The effect of initial structure on the stable size and structure of fragments disappears gradually with the increase in shear gradient. The detailed simulation results can improve the understanding and control of the size and structure of agglomerates in practical devices. [ABSTRACT FROM AUTHOR]

In this paper, five types of horizontal single-pitch screw conveyors with modified geometry, with three different lengths (400, 600 and 800 mm) were investigated for transport and auxiliary mixing action of two materials: natural zeolite and quartz aggregate (sand) with particle sizes 3, 4 and 5 mm. The geometry of the screw transporter is changed by welding three additional helices oriented in the same or the opposite direction from screw cutting edges, enabling the premixing of materials, during the transport. The proper mixing of the observed materials provides an adequate disposition of zeolite particles within the composite and prevents agglomeration and interference with cement hydration. Zeolite application as a binder in a building material is a possible solution to environmental pollution problems caused by cement production. The influences of screw length, particle diameter, the studied geometry variations of screw design, on the mixing performances of the screw conveyor-mixer during material transport were explored. All investigations were performed experimentally and numerically, by using Discrete Element Method (DEM). The experimental results and the results of the DEM investigation were used for the development of mathematical models for the prediction of mixing quality, which are presented in the form of second order polynomial and artificial neural network model. [ABSTRACT FROM AUTHOR]

Spherical crystallization can be an important technological step in the production of a solid form active agent. By the production of spherical crystals, direct compression tablet making can be applied to the powder material. This method makes the tableting process quicker, shorter and more economical with reduced amounts of additives and a reduced number of technological steps. This way, the granulation method can be avoided, which is also advantageous for a moisture sensitive drug. In this paper, we presented Focused Beam Reflectance Measurement (FBRM) studies applied in the case of the non-typical spherical crystallization methods of the active pharmaceutical ingredient ambroxol hydrochloride. Spherical agglomeration and controlled cooling crystallization methods were carried out based on our previous studies regarding these methods and the crystal formation processes were investigated with FBRM probe. Critical agglomeration periods and other mechanisms, such as the breakage of the agglomerates and the precipitation of small particles, were investigated. Chord length values were observed continuously and samples were taken out in certain points of the crystallization. Particle size analysis was carried out in each case to obtain information on the particle size enlargement caused by the crystallization methods. With the application of light microscopic analysis, aspect ratio and roundness values were also determined to obtain pieces of information on the sphericity-changes of the particles throughout the crystallization and large improvements were presented either for these parameters (aspect ratio from ~ 1.7 to ~ 1.3; roundness from ~ 2.4 to ~ 1.5) and the mean particle size (from ~13 μm to 120–400 μm). Among others, it was revealed that after the spherical agglomeration method (SA), mostly crystal agglomerates were formed, while slow cooling crystallization with alternating temperature profile (ATP) yielded larger and probably harder individual crystals. [ABSTRACT FROM AUTHOR]

Phyllantus niruri Linn or stonebreaker plant has recently received increasing interest for use as a pharmaceutical drug form. However, modernization by means of quality control and standardization of medicinal herbal plants applications as pharmaceutical drug forms is critical for international acceptance. Therefore, using a spouted bed, the coating process of stonebreaker granules was modeled to understand the critical parameters influencing coating efficiency, particle growth and agglomeration index. A 2 3 factorial experimental design using atomization pressure, feed flow rate and inlet temperature was implemented. Results revealed coating efficiencies ranging from 40% to 93%, mean particle growths of 9.7% and agglomeration indexes, which is an undesirable result, close to 0%. Initially models revealed that low temperatures/low coating flow rate or high temperatures/high coating flow rate provided more efficient coating. Further analysis proved that is relative humidity, a scalable variable, the most critical parameter on process efficiency. [ABSTRACT FROM AUTHOR]

Fine particles from industrial processes are significantly harmful to people's health and atmospheric environment. However, a number of fine particles are discharged into the air due to the low removal efficiency in traditional precipitators. A novel pretreatment process using the chemical and turbulent agglomeration for fine particles agglomeration was forward. In this study, a pilot-scale containing a chemical agglomeration chamber and a turbulent device connected to an Electric precipitator (ESP) unit has been built to investigate the novel pretreatment effect. Results seem to show that the diameter of particles increases significantly in the pretreatment device, which has a significant positive effect on improving the ESP removal efficiency. The application of turbulent agglomeration leads to the efficiency of PM 2.5 increasing from 75.5% to 79.6%, meanwhile, the application of chemical and turbulent agglomeration makes PM 2.5 removal efficiency go up to 83.1%. The important factors to agglomeration efficiency were also investigated, furthermore, according to the SEM images and experimental results, the agglomeration models in pretreatment devices were put forward. Finally, combining experimental results and agglomeration modes the coupling of two technologies overcome the disadvantages of each technology, and significantly improve the PM 2.5 removal efficiency of ESP. [ABSTRACT FROM AUTHOR]

An experimental system composed of microscopic visualization and high-speed photography was developed to observe the relative motion and agglomeration characteristics between fine particles and a large glass particle directly. The large glass particle was fixed in the middle of a rectangular flow channel, fine particles were generated by burning sandalwoods in a buffer tank. The observations showed that fine particles flowed over the large glass particle when they were uncharged. When the large particle and fine particles carried charge of different polarities, an obvious attraction between them was observed. When the large particle and fine particles carried charge of the same polarity, the fine particles showed two kinds of motion characteristics, depending on the charge number they carried. When fine particles carried a small number of charge, they still attracted each other. In contrast, fine particles carrying a large number of charge led to repelling. The induced dipole force was taken into consideration to explain the observed phenomenon. A simulation of the movements of the fine particles considering the combined effects of the induced dipole force, the Coulomb force, the drag force and the electric field force was carried out. The simulation results matched the experimental results well. [ABSTRACT FROM AUTHOR]

The aim of this work is to follow the agglomeration mechanism of an in situ Fluid Bed Melt Granulation (FBMG) by means of machine learning with Artificial Neural Network (ANN) modelling. Scanning Electron Microscopy (SEM) was used as a complementary tool with particle size analysis to evaluate the effect of the material properties on the quality attributes of the final granules and provide further insight into the growth mechanisms. The experiments were performed using lactose monohydrate as model filler and two grades of polyethylene glycol (PEG 2000 and 6000) as meltable binders in different contents and in different size fractions, respectively. A multilayer perceptron neural network was developed using MATLAB neural network toolbox and the evaluated quality attributes of the final granules were used as a database for the development and selection of the optimal architecture of the ANN model. The Garson equation was used to quantify the relative importance of each independent variable and thus it was established that the particle size had the highest impact on the granule properties. The distribution and immersion granule growth mechanisms were determined to occur for low and high binder particle size, respectively, as confirmed by the SEM pictures, and the response surfaces helped determine the optimal design space of the process and the optimal FBMG conditions. [ABSTRACT FROM AUTHOR]

Comminution involves the reduction of materials to the required sizes, from coarser to finer. The population balance method (PBM) is the most frequently used approach to obtain the particle size distribution (PSD) of materials. To numerically obtain the PSD, a semi-empirical approach known as the size-mass balance equation is commonly employed. The existing technique to determine the parameters in the size-mass balance equation is cumbersome as PSD for early grinding times of different feed sizes must be obtained experimentally. Therefore, a new technique using only a limited data to determine the parameters is introduced and examined. In general, the strong capability of the presently proposed technique is evidenced through successfully capturing of the existing experimental PSD. The advantages of using this technique are that only two experimental PSD of any grinding time are needed to predict the PSD using the size-mass balance equation and without the restriction of input from an early grinding time. This study also proposes to use the cumulative PSD rates as an indicator for the limit of particle size reduction of the materials. It is suggested that the grinding of materials should stop before there is a pivotal change in the initial slopes, i.e., before the difference of the cumulative PSD rates between each initial slopes is found to change sign, or when the difference of the cumulative PSD rates is close to 0% in order to prevent agglomeration or over-grinding. The grinding time fulfilling this criterion is considered as optimal. [ABSTRACT FROM AUTHOR]

The discrete element method (DEM) is used to simulate two types of mixing processes (radial mixing and axial mixing) of particles with and without cohesive interparticle forces in a two-dimensional (2D) fluidized bed. By using the Ashton index, the mixing degree is quantified and the differences between the mixing characteristics of particles with and without cohesive interparticle forces are compared. The cohesive interparticle forces, which impair bubble behaviors, can apparently weaken the mixing process and prolong the mixing time. This effect increases with increasing cohesive interparticle force. Radial mixing, which is mainly dependent on the convective mixing caused by bubbles, is relatively sensitive to cohesive interparticle force and shows a long mixing time, while axial mixing, which is mainly induced by the bubble wake, is less sensitive to cohesive interparticle force and presents a fast mixing process. Finally, to weaken the effect of cohesive interparticle force, an uneven air distribution is introduced, which greatly improves the mixing process by changing the bubble movement. This method may be helpful for the reduction of particle agglomeration in high-temperature fluidized beds. [ABSTRACT FROM AUTHOR]

Particle design via spherical agglomeration is a size enlargement technique used in various bulk and fine chemical industries, with recent interest extending into pharmaceuticals, in which an immiscible bridging liquid is added to agglomerate crystals prior to deliquoring. Spherical agglomeration has the potential to dramatically simplify downstream processing, and improves the handling of difficult, needle-shaped crystals. This review consolidates the understanding of the controlling process parameters, identifies the rate processes that control agglomerate attributes, and examines the modelling approaches taken in the literature to optimise the design of such systems. The most important controlling parameters are solvent system composition (requiring knowledge of the ternary phase diagram) and bridging liquid to solid ratio (BSR). Agglomerate size is a highly non-linear function of BSR with many literature systems showing qualitatively similar behaviour. However, there is no method to predict the optimum BSR. Other important process parameters are temperature, constituent particle properties, agitation rate and batch/residence time. Each parameter can have significant effects on the final agglomerate properties including agglomerate size, porosity, strength and dissolution profile. The rate processes in spherical agglomeration are analogous to those in wet granulation. A general classification of rate processes is proposed in this review including nucleation by distribution or immersion, consolidation, coalescence, layered growth and breakage. While many papers give proof of concept examples of spherical agglomeration for specific systems, only a few have focused explicitly on mechanistic understanding. There is significant scope for further work to quantify the effect of both process parameters and formulation properties on these rate processes. Recent developments in on-line monitoring using process analytical technologies (PAT) should enable these studies. Using the mechanistic understanding, population balance models can be developed to include kernels for each of the relevant rate processes. Such models should be powerful tools of process optimisation and model driven design with reduced experiments at all scales. [ABSTRACT FROM AUTHOR]

As the major constituent of air pollution, inhalable particles, especially the fine particles are inflicting great harm on human health due to their small particle size and absorption of hazardous components on them. However, the current conventional devices used for removing these particles suffer from low removal efficiency. Acoustic agglomeration is considered as a very effective pre-treatment technique for removing fine particles. Fine particles can agglomerate and grow to form large particles in the sound field, which can be easily removed by conventional particle removing devices. In this paper, the acoustic agglomeration and fragmentation of three different kinds of particles with different size distributions were experimentally studied. The fragmentation of agglomerates was calculated using the agglomerates forces. It was found that the particle size distribution and the volume fraction of fine particles affected the agglomeration efficiency. For unimodal particles having a narrow size range, higher the sound pressure level (SPL), greater was the agglomeration efficiency. However, there existed the optimal SPLs at 115 dB and 120 dB with 25% and 55% agglomeration efficiency (respectively) for bimodal particles with a wide size range. A desirable agglomeration could only be obtained in a narrow SPL range, while the agglomeration efficiency decreased significantly over the range due to the fragmentation of agglomerates. The fragments of agglomerates started to agglomerate again, though the new agglomerates were smaller than the previous agglomerates obtained at higher SPL. The spraying of water droplets can improve the agglomeration efficiency while avoiding the fragmentation of agglomerates for the bimodal particles with a wide particle size range. [ABSTRACT FROM AUTHOR]

An acoustic agglomeration process, in which high-intensity sound is used to agglomerate particles in aerosols, can be simulated using the discrete element model (DEM). However, the conventional DEM is very time-consuming due to the large difference between the various time scales involved in the modeling. In this paper, a multiple-time-step algorithm is used to speed up the 3D DEM simulation of aerosol acoustic agglomeration, which reduces the computational time by more than one order of magnitude, comparing with the conventional DEM. When the computational domain contains N particles, the computational complexity of the improved DEM simulation is of the order of O ( N ), by restricting the acoustic wake effect in certain ranges and performing contact detection based on a search grid. The DEM simulation model has been validated by: 1) the analytical solution for the oscillation motion of an isolated particle in a sound field, 2) the experimental result of the agglomeration trajectories of two particles under the mutual effect of acoustic wakes, and 3) the experimental results of acoustic agglomeration of coal-fired fly ash particles. It is found that the agglomeration efficiency obtained from DEM simulation is in good agreement with the experimental results at moderate sound pressure levels, while the simulation overestimates the agglomeration efficiency at a high sound pressure level of 149 dB, due to the breakage of aggregates in the experiment. [ABSTRACT FROM AUTHOR]

In a fluidized bed spray granulation, a particle-particle adhesion by a liquid bridge, which shows dynamic motion due to moving particles, is the most fundamental phenomenon. Therefore, understanding of the particle-particle adhesion by such a dynamic liquid bridge is very important to elucidate mechanisms of particle agglomeration phenomenon in the wet granulation. In this study, the particle-particle adhesion phenomenon at the individual particle scale was analyzed using a direct numerical simulation. Collision of two particles mediated by binder droplets on a particle surface was simulated. In particular, the effect of droplet size under constant total liquid volume on adhesiveness of two colliding particles was investigated. In the present simulation, multiple liquid bridges were simultaneously formed, and these liquid bridges coalesced into single liquid bridge. The simulation results exhibited that the adhesiveness of particles increased with a decrease in the droplet diameter under a constant total liquid volume. In an initial stage of the particle growth in a fluidized bed spray granulation, the tendency of the calculations was consistent with experimental results. We revealed that the capillary pressure force and shapes of the liquid bridge are key factors for particle-particle adhesion at different droplet sizes under constant total liquid volume. [ABSTRACT FROM AUTHOR]

A population balance model is developed for the growth of pre-formed agglomerates in a fluidized bed with several agglomeration mechanisms considered. Primary agglomeration takes place when dry particles collide with the wet surface of the original agglomerate. Secondary agglomeration occurs either by wet particles colliding with the dry surface of agglomerates, or by liquid migration to the top layer of an agglomerate and subsequent collisions with dry particles. The properties of the liquid binder determine the dominant mechanism. The new agglomeration model for high- and low-viscosity liquid binders is implemented in ANSYS FLUENT commercial software. Model predictions agree reasonably well with available experimental results without altering the previously published parameters of the sub-models employed. It is found that the viscosity of the liquid binder and surface asperities play notable roles in the agglomeration. Surface asperities are especially important when asperity heights are of the same order as the thickness of the liquid film. [ABSTRACT FROM AUTHOR]

This work presents a systematic experimental study of continuous spray fluidized bed (SFB) layering granulation with external product separation. In layering granulation processes the product particle morphology is controlled by the drying conditions during operation. But varying drying conditions during continuous SFB layering granulation have a significant influence on process stability. High fluidizing gas inlet temperature, high fluidizing gas mass flow rate and low spray mass flow rate, resulting in intense drying conditions, led to stable steady state operation. An equilibrium between seed particle production, particle growth and product discharge was established. In contrast, low fluidizing gas inlet temperature, low fluidizing gas mass flow rate and high spray mass flow rates, resulting in moderate drying conditions, led to self-sustained oscillations of the particle size distribution (PSD) in the fluidized bed. The oscillations in PSD where partly transmitted to the PSD of the product, but they were limited by the mesh widths of the sieves, which were used for external separation. For the cases with an oscillatory steady state, equilibrium between seed particle formation, particle growth and product discharge could not be achieved due to temporarily excessive seed particle formation. [ABSTRACT FROM AUTHOR]

Discrete particles with the moisture in a rotating system tend to form themselves as lumped mass granules of different sizes. This paper depicts the agglomeration of the particles using batch and continuous system through the mathematical modeling. The liquid bridge formation, coalescence and breakage are essential steps in the agglomeration process of continuous system. The combination of two effects, namely, binder viscosity and surface tension will govern the bridge formation. In case of batch system of granulation, a regime map of granulation behaviour has been developed for the particulate system of sago powder-water mixer. This regime map predicts the granule growth behaviour and it is possible to assist in designing and controlling the granulation systems. In these processes, mass of the granules varies continuously with respect to time. According to the conditions of coalescence and breakage behaviour, the agglomeration is maximum during three to six minutes of granulation due to the maximum percentage of granule breakage. After six minutes the granule breakage and growth is gradually reduced and after 10 min there is no granule growth due to minimum or no breakage. The number of granule breakage increases with the Stokes deformation number. [ABSTRACT FROM AUTHOR]

Control of agglomeration, i.e. the cementation of two or more single crystals by crystal growth, is crucial in crystallization processes. Especially undesired agglomeration may lead to broaden crystal size distributions (CSDs) and mother liquor inclusions reduce the purity. To reach product specifications and avoid loss of batches gassing crystallization could be one way to control agglomeration degree of final product. Hence, in this study the effect of gassing process parameters to reduce the number of agglomerates within the CSD of adipic acid is systematically investigated using Design of Experiments (DoE). For quantification of agglomeration the overall agglomeration degree (Ag) and the agglomeration degree distribution (AgD) are determined using an image analysis tool. The AgD describes the relative frequency of agglomerates within each particle fraction of the CSD. Both in combination allow distinguishing between two populations, namely single crystals and agglomerates. The results show that gassing crystallization is a promising method to get crystalline products with a reduced number of agglomerates, which affects the width of the CSD. Moreover, a higher reproducibility of product batches than for cooling crystallization without gassing is achieved. [ABSTRACT FROM AUTHOR]

The granulation of ammonium chloride (AC) fertilizer has been investigated in a laboratory scale based on the pan granulator at ambient temperature. Significant improvement of granulation efficiency of AC was achieved by using polyaluminium chloride (PAC) as solid binder and urea as granulation additive. Highly charged cations by PAC hydrolysis could reduce the electrostatic force of AC, resulting in efficient particle agglomeration. Analyzing the surface structure and characteristics of the PAC and AC granules revealed their interactions, which lead to the formation of aggregate nucleus. Furthermore, PAC contained a larger number of active groups, which served as bridges to form particle-polymer-particle complex, and facilitated the growth of particle. Meanwhile, urea and AC could react with each other to form stable inclusion complex which also had pronounced effect on the increase of granulation rate for AC. [ABSTRACT FROM AUTHOR]

Agglomeration of fine particles in fluid flows is important for many processes in powder handling or production. In order to accurately perform numerical calculations of such processes models are needed which realistically describe particle agglomeration. For applications in the frame of an Euler/Lagrange approach such a model was developed which allows predicting the agglomerate structure and its behaviour in the point-particle approximation. The detection of collisions between primary particles or particles and agglomerates is realised by the stochastic collision model. The collision point on the particle or agglomerate surface is generated by accounting for the impact efficiency. The developed structure model is based on storing location vectors from the reference primary particle to all other particles collected in the agglomerate which is still treated as point-mass. Thereby the structure and porosity of the agglomerate is known and an equivalent agglomerate diameter (e.g. gyration diameter) is obtained. With this information the fluid dynamic forces acting on the agglomerates can be predicted correctly as well as the appropriate collision cross-section is used in the collision modelling. For testing the novel agglomerate structure model, fine particle agglomeration in homogeneous isotropic turbulence is calculated considering different properties of the primary particles or droplets. In the case of dry solid particles the van der Waals adhesion force is considered and based on an energy balance the possibility of particle sticking or rebound is calculated. Moreover, high viscous droplets are considered as primary particles, a situation also found in spray dying. For such cases the penetration of two primary particles or a primary particle and a stochastically selected primary particle within an agglomerate is modelled. The structure of the agglomerates produced under these different situations and for mono- and poly-sized primary particles are analysed and compared, using for example gyration diameter, porosity of convex hull and fractal dimension. These results demonstrate that the developed novel agglomerate structure model is applicable in the frame of an Euler/Lagrange approach and provides appropriate results. [ABSTRACT FROM AUTHOR]

Discrete Element Method (DEM) simulations are a promising approach to accurately predict agglomeration and deposition of micron-sized adhesive particles. However, the mechanistic models in DEM combined with high particle stiffness for most common materials require time step sizes in the order of nanoseconds, which makes DEM simulations impractical for more complex applications. In this study, analytically derived guidelines on how to reduce computational time by using a reduced particle stiffness are given. The guidelines are validated by comparing simulations of particles with and without reduced particle stiffness to experimental data. Then two well-defined test cases are investigated to show the applicability of the guidelines. When introducing a reduced particle stiffness in DEM simulations by reducing the effective Young's modulus from E to E mod , the surface energy density γ in the adhesive Johnson-Kendall-Roberts (JKR) model by Johnson et al. [1] should be modified as γ mod = γ ( E mod / E ) 2/5 . Using this relation, the stick/rebound threshold remains the same but the collision process takes place over a longer time period, which allows for a higher time step size. When rolling motion is important, the commonly used adhesive rolling resistance torque model proposed by Dominik and Tielens [2,3] , Krijt et al. [4] can be used by modifying the contact radius ratio ( a / a 0 ) 3/2 to ( a mod / a 0,mod ) 3/2 , while keeping the other terms unaltered in the description of the rolling resistance torque M r,mod = −4 F C ( a / a 0 ) 3/2 ξ . Furthermore, as the particle stiffness is reduced from E to E mod , the time period for collisions (or oscillations when particles stick upon impact) Δ t col is found to vary as Δ t col,mod = Δ t col ( E / E mod ) 2/5 . As the collision duration and the collision time step size are directly related, this criterion can be used to estimate how much the time step size can be changed when a reduced particle stiffness is introduced. Introducing particles with a reduced particle stiffness has some limitations when strong external forces are acting to break-up formed agglomerates or re-entrain particles deposited on a surface out into the free stream. Therefore, care should be taken in flows with high local shear to make sure that an external force, such as a fluid drag force, acting to separate agglomerated particles, is several orders of magnitude lower than the critical force required to separate particles. [ABSTRACT FROM AUTHOR]

A study is reported that examines computations of turbulent particle agglomeration with one-way and two-way phase coupling for cases with small overall particle concentration. The fluid flow was computed using a direct numerical computation using the point-force approximation for particle-induced body force, and a soft-sphere, adhesive discrete-element method was used to simulate the particulate transport and agglomerate formation. Computations were performed with different values of the Stokes number and the adhesion parameter. A variety of measures were used to examine both the effect of particle agglomeration on the fluid turbulence and the structure and flow field within the particle agglomerates. It was found that agglomeration has little influence on the attenuation of turbulence by the particles, at least in the range of Stokes numbers examined in the paper. Computations with two-way coupling generated agglomerates that were larger and contained more particles than those for one-way coupling. The agglomerate structure for both one-way and two-way coupling cases had a fractal structure with a similar value of the fractal dimension. As the agglomerate size increased, the fluid motion inside the agglomerates was found to become increasingly correlated to the agglomerate velocity, acting to decrease the relative velocity and shear stress of the inner particles within the agglomerate. [ABSTRACT FROM AUTHOR]