Agglomeration Experiments Research Articles

The role of interfacial nanobubbles in the flotation performance of microfine particles

The enhanced role of Interfacial nanobubbles (INBs) in microfine particles flotation is still unclear. In this study, the microfine particles with different sizes were functionalized to obtain different wettability. The temperature difference method was employed to produce the nanobubbles water. Atomic force microscopy (AFM) was utilized to investigate the formation of INBs. A temperature-controlled flotation system was devised to investigate the flotation performance of microfine particles in the presence and absence of INBs. Agglomeration experiments and attachment time tests were conducted to elucidate the enhanced effects of INBs on flotation from the perspectives of particle-particle and bubble-particle interactions. The results showed that both the number and size of INBs increased with the increase of surface hydrophobicity and level of air saturation in water. In the temperature-controlled flotation system, the flotation recovery and flotation rate of microfine particles were improved significantly in nanobubbles water compared to that in normal water. The optimal flotation result of −38 μm strongly hydrophobic particles was obtained in nanobubbles water at 25 ℃. The enhanced impact of INBs on flotation was more pronounced for more hydrophobic particles. The increase in the apparent size of particles and reduction in particle-bubble attachment time facilitated by INBs contributed to the flotation performance of microfine particles. This study underscores the pivotal effect of INBs on the flotation of microfine particles through enhancing particle-particle and bubble-particle interactions.

Fundamental drying and agglomeration experiments with bio-fraction and refuse derived fuel for the development of pyrolysis reactor feed.

The EU's circular economy concept necessitates increasing the recycling ratio of municipal solid wastes. There are many existing mechanical-biological processing plants in Hungary for the preparation of residual municipal solid wastes (RMSWs). The two most important products of these plants are the bio-fraction and the refuse derived fuel (RDF). Currently, there are problems with both of these material streams in Hungary, since most of the bio-fraction is still landfilled, and the local thermal utilisation of the RDF has not been implemented yet. The high moisture content of the produced bio-fraction and RDF causes difficulties for the downstream operations; therefore, there is recent engineering interest in drying and agglomeration of these materials. The authors have carried out systematic and parallel drying and briquetting experimental series to study the effect of the material, material composition, mass (volume or surface) of the material, particle size distribution and pre-treatment with a cutting mill on drying intensity in a 1 m3 oven and their effect on briquettability by a laboratory briquette press. The initial slope of the relative moisture loss as function of time was determined. Process engineering design methods of convective hot air-drying can be further developed taking into account the research results. Results can be used for the design of the feed of a pyrolysis reactor once reactor experiments have provided the optimal feed requirements.

Oil Agglomeration in Zonguldak Bituminous Coal Dust: The Role of Inorganic Materials

In the present study, the effect of various The oil agglomeration method is of great importance for high recovery and low cost in capitalizing our energy resources that create environmental problems due to fineness of particle size or our low quality, oxidized coal resources with large reserves. Inorganic pretreatment materials, the ratio of bridging liquid, agglomeration time and mixing speed on the agglomeration recovery in the beneficiation of Zonguldak coal with low ash content (2.23%) through oil agglomeration. In the experiments, kerosene was used as the bridging liquid and NaCl, FeCl2, Fe2(SO4)3, Al2(SO4)3 were used as inorganic pretreatment materials. In the agglomeration experiments in which inorganic pretreatment materials and kerosene were used together, the maximum recovery was determined in the condition where the kerosene concentration was 15%, the mixing speed was 800 rpm and the agglomeration time was 10 min. It was found that, the recovery under suitable conditions was 71.5% in the agglomeration experiments conducted with only kerosene, whereas it was in varying rates between 76.5% and 81.6% in experiments where pretreatment materials and kerosene were used together. Among the inorganic pretreatment materials, when used together with kerosene, the best recovery was obtained with the use of 50 mg/L Fe2(SO4)3. The agglomeration recovery obtained in the experiments conducted with only kerosene under optimum conditions was reached when the agglomeration time was 5 min in the experiments in which the inorganic pretreatment materials and kerosene were used together.

The use of petroleum derivative mixtures as bridging liquid for oil agglomeration of lignite coal

ABSTRACT The aim of the present study was to investigate the use of mixtures of petroleum derivatives as bridging liquids for oil agglomeration of Sivas/Gemerek lignite coal. The study investigated the effect of various physical process parameters, such as type and dosage of bridging liquid, pulp pH, pulp density, agglomeration time, and coal particle size. Oil agglomeration experiments were evaluated along with yield, organic matter recovery and ash rejection values. The optimum conditions for agglomeration were found as follows: adding engine oil (0w-30) as a bridging liquid at a dosage of 30%, maintaining a pulp pH of 2, using a pulp density of 3.6% w/w, agglomerating for 25 minutes, and using coal particles with a size of −500 µm. Under these optimum oil agglomeration conditions, a yield of 85.4%, an organic matter recovery of 94.1% and an ash rejection of 51.6% were obtained. Under the optimum oil agglomeration conditions achieved, the ash content of the Sivas/Gemerek lignite coal was reduced from 19.1% to 15.5% level.

Design of spherical agglomeration via salt-induced liquid–liquid phase separation

In this study, a novel strategy for spherical agglomeration via salt-induced liquid–liquid phase separation (SI–SA) was developed. SI–SA technology achieves phase separation in the miscible binary anti-solvent crystallization system by adding certain amounts of salts, avoiding the use of toxic bridging liquids. Water–organic solvent–salt systems that induced phase separation were selected using phase separation experiments. The wetting performance of the organic solvent was estimated by droplet experiments, and organic solvents with stronger wettability for crystals than water would be selected for further verification. Spherical agglomeration experiments were designed based on the ternary phase diagrams of these selected systems. Water–organic solvent–salt systems of benzoic acid were selected, starting with six organic solvents and four salts. A total number of 16 water–organic solvents–salt systems were effectively predicted using the SI–SA strategy. The in-situ process analysis tool indicated that the formation of spherical particles of benzoic acid underwent a process of crystallization, phase separation, wetting, two-step agglomeration, and consolidation. The stirring rate and mass ratio of salt to final crystals were found to be important for controlling the morphology and particle size of the spherical crystals. The spherical particles of aspirin and salicylic acid were successfully predicted in different systems via SI–SA technology, demonstrating the universality and potential usage of SI–SA technology in industry.

ENRICHMENT OF SİVAS/GEMEREK LIGNITE COAL BY OIL AGGLOMERATION USING DIFFERENT VEGETABLE OILS

The aim of this study was to investigate the use of various vegetable oils (almond oil, hazelnut oil, poppy oil, soybean (soya) oil, sunflower oil) for Sivas/Gemerek (in Turkey) lignite coal by oil agglomeration. The study examined the effect of bridging liquid type and dosage on oil agglomeration. Vegetable oil dosages of 2%, 5%, 10% and 20% were investigated in oil agglomeration experiments. The agglomeration of lignite coal with these bridging liquids was evaluated based on yield, combustible recovery and ash rejection. The agglomeration performances of these vegetable oils were compared. The highest ash rejection (70.30%) was observed by using soybean (soya) at 20% of the bridging liquid dosage. The yield and combustible recovery of lignite coal were achieved 36.46% yield and 38.05% combustible recovery in this soybean (soya) oil dosage, respectively. The lignite coal ash content was reduced from 19.08% to 15.54% under these optimum conditions.

Experimental Study on the Agglomeration of Oily Fine Particles by Sound Wave

Oily fine particles are an important air pollutant in industrial environments. Workers exposed to oil mist for a long time face great health risks. Particle growth pretreatment is a technical principle to increase particle size and improve purification efficiency. Acoustic waves are commonly used to acheive particle growth, and a large number of acoustic wave agglomeration experiments have been carried out on non-oil fog. However, studies on oily particles are few. On the basis of previous studies on acoustic agglomeration of non-oily particles, this experiment designed a set of experimental equipment to compare the agglomeration effect of oily and non-oily particles. It was found that the agglomeration effect ratio of oily and non-oily particles to φ1oiliness/φ1non-oily particles was greater than 1. Therefore, the agglomeration effect of oily particles under stationary acoustic waves was more obvious. Results clearly show that oily particles have a higher agglomeration ability. In this study, a traditional ventilation and purification technology was expanded to include sound agglomeration technology into the pretreatment stage of purification and dust removal, thereby demonstrating feasibility of improved purification efficiency of an oily fine particle purification system, and laying a foundation for engineering applications.

Effect of Impeller and Gas Stirring on Agglomeration Behavior of Polydisperse Fine Particles in Liquid

Agglomeration, coalescence and flotation of non-metallic inclusions in steel melt are effective for obtaining “clean steel.” In this study, the agglomeration and breakup behaviors of particles with a primary particle size distribution (hereinafter, polydisperse particles) in a liquid under impeller and gas stirring were compared by numerical calculations and model experiments. The particle-size-grouping (PSG) method in the numerical agglomeration model of particles was combined with a breakup term of agglomeration due to bubble bursting at the free surface. Polydisperse and monodisperse polymethylmethacrylate (PMMA) particles were used in the agglomeration experiments. The agglomeration rate of the polydisperse particles under impeller stirring was increased by an increasing energy input rate, whereas the agglomeration rate under gas stirring decreased under this condition due to the larger contribution of the breakup of agglomerated particles during bubble bursting in gas stirring. At the same energy input rate, agglomeration of polydisperse particles was larger under impeller stirring than under gas stirring. The agglomeration rate of polydisperse particles was larger than that of monodisperse particles under both impeller and gas stirring at the same energy input rate. The computational temporal changes in the total number of particles were in good agreement with the experimental results. This means that the difference in the agglomeration behaviors observed in impeller and gas stirring can be explained by the turbulent coagulation and subsequent agglomerated particle breakup in gas stirring. The computational temporal change in the number of each group approximately agreed with the experimental change in both impeller and gas stirring.

Selective and ultrafast agglomeration of chalcopyrite by a water in oil emulsion binder

A high internal phase water in oil emulsion has been used as the binder in a novel agglomeration process for achieving selective and ultrafast recovery of hydrophobic particles. For the first time, the novel agglomeration was applied to the selective recovery of chalcopyrite particles from a model feed formed from equal portions of high grade chalcopyrite (27.5 wt% Cu grade) and pure silica, with Sauter mean diameter of the chalcopyrite of 11.0 µm. While very high copper recovery was achievable when sufficient binder was added, the selectivity was found to depend on the solution chemistry. The separation performance achieved in a period of 7 s of agglomeration was found to be very strong for a pH of 8.5, 9.0, and 9.5, but very poor at a pH of 10.5. Interestingly, this pH dependence was not observed in froth flotation experiments. Further, the aging of the model feed had an impact on the agglomeration but not on the flotation. These effects were attributed to the emulsifier, SMO, being released from the binder used in the agglomeration experiments.

Interaction between strong sound waves and cloud droplets: Cloud chamber experiment

Acoustic agglomeration refers to the group effect of micro-particle groups in a strong sound field, which promotes relative motion among the particles, leading to the rapid agglomeration of the particle groups. The existing theoretical and experimental research on acoustic agglomeration is focused on solid particles such as soot particles and aerosols, and the acoustic agglomeration of micron-scale cloud droplets has not been intensively investigated. In this study, a cloud with an average particle size of ~10 μm is generated in a cloud chamber at room temperature, and a series of acoustic agglomeration experiments of cloud droplets under the action of sound waves with a frequency and sound pressure level (SPL) of 35–100 Hz and 112–122 dB, respectively, are conducted to examine the impact law of the sound waves with different frequencies and SPLs on the cloud droplet size spectrum. At a constant sound frequency, the agglomeration effect of the cloud droplets is more pronounced under the action of sound waves with a higher SPL. Under a constant SPL, the agglomeration effect is the most notable when the sound frequency ranges from 50 to 65 Hz. The threshold SPL for the effective agglomeration ranges from 114 to 121 dB when the sound frequency is 35–100 Hz, and the threshold SPL gradually increases with the sound frequency. The findings can clarify the effect of the sound waves in promoting cloud condensation and provide guidance to develop atmospheric intervention technologies based on strong sound waves.

Agglomeration and Characterization of Nickel Concentrate (MHP) Pellets for Ferronickel Production

Mixed hydroxide precipitate (MHP) is a nickel intermediate product that has economical benefits to downstream leaching of lateritic marginal ores. Usually, this product is subsequently processed and refined to produce nickel by hydrometallurgy, but an alternative route can be made integrating hydrometallurgy and pyrometallurgy. Assessing the overall consumption of ferroalloys to obtain stainless steel, as an increasing practice performed in China, the synergy of nickel extraction from laterites by leaching and precipitation as MHP with the production of MHP agglomerates applied as raw material to furnaces of ferronickel production is a very attractive practice. This work aims to further the technological development of an agglomerated product feasible to hydro-pyro integration. The agglomeration experiments were performed by traditional pelletizing (firing the pellets) and cold bonded pelletizing (aging the pellets by appropriate stocking). Appropriate compositions were prepared with MHP, additives and binders for each of these routes. A specific study of binder composition was made to find an adequate melting point. The produced pellets were tested to prove their properties by crushing strength tests. The standardization applied to iron ore was followed. The best result of crushing strength was 98.52 daN/pellet. The agglomerates with approved crushing strength for use in electric furnaces were smelted to produce alloys containing nickel; the agglomerates were characterized by scanning electron microscopy. The alloy obtained was metallic ferronickel with sulphide precipitates. Therefore, MHP pellets can be precursors of nickel alloys, which have to be refined to obtain the desirable composition.

Effect of three different binders and pellet feed on granulation behaviour of sintering mixtures

ABSTRACT Cold agglomeration experiments were made in order to investigate the effect of three binders with different chemical composition (sodium polyacrylamide, cellulose derivate and a specific Brazilian mineral coal) and the addition of pellet feed in the sintering mixture, on the efficiency of granulation, evaluated by the mean particle size of the agglomerate and microstructure of the micro pellets. The binder that produced the highest mean particle size was used in new cold agglomeration experiments in order to indirectly evaluate the mechanical strength of the agglomerate. The experiments showed that only the cellulose derivate binder was capable of producing agglomerates with equal or greater mean particle size when compared with the base test for practically all performed tests, regarding the values of d 50 and Sauter mean diameter, besides promoting the increase on the adhering layer thickness and stability of the nuclei-adhering layer interface of the micro pellets.

Monte Carlo modeling of binder‐Less spray agglomeration in fluidized beds

Fluidized bed spray agglomeration is used in the industry to increase the particle size and to improve several properties, for example, bulk density, flowability, and dissolution behavior of particulate products. Usually, a binder liquid is sprayed on a particle bed. If amorphous materials are used, spraying of pure water may cause agglomeration due to glass transition at wet spots on the particle surface. As no process models covering binder‐less spray agglomeration currently exist, a model based on a Monte Carlo method is presented. In this method, the process is described by events and processes on the single particle scale. Additionally, agglomeration experiments in a lab‐scale fluidized bed using three different maltodextrins are presented. For each experiment, a simulation was performed. The simulation results are compared with the obtained experimental data. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3582–3594, 2018

Chemical agglomeration properties of fine particles immersed in solutions and the reduction in fine particle emission by adding emulsion polymers

To reduce the fine particle concentration in coal-fired flue gas, an emulsion agglomeration agent with excellent atomization performance and low viscosity was applied in a chemical agglomeration experiment. The chemical agglomeration properties of an emulsion polymer and a water-soluble polymer on fine particles were compared and investigated experimentally in this study. In addition, the relationship between the mass concentration and solution viscosity was explored, and the atomization performances of a two-fluid nozzle were also studied. The results showed that when the mass concentration of the agglomeration agent increased, the fly ash particles in the solution became larger; moreover, the final agglomerate diameter and the solution viscosity were related to the polymer molecular weight. According to the phase Doppler anemometry (PDA) experimental results, the median diameter (D50) of the agglomeration solution droplets increased as the mass concentration increased, and the atomization property of the emulsion polymer solution was evidently superior to that of the water-soluble polymer solution. In the experimental facility, chemical agglomeration experiments using four kinds of agglomeration agent were carried out, and they proved that the removal efficiency of fine particles was inversely proportional to the median diameter of the atomized solution droplets. Emulsion polymers can greatly enlarge fine particles and reduce the concentration of the fine particles. The removal efficiency of number concentration was improved by 20–25%.

Experimental analysis of the hydrodynamics, flow pattern and wet agglomeration in rotor-stator vortex separators

The effect of the stator geometry, cavity gap and fluid volume on the turbulent aggregation, hydrodynamics and flow pattern in rotor-stator vortex reactors have been investigated using a digital 2D Particle Image Velocimetry (PIV) and visual observation. The results of the study showed a more uniform distribution of the quantified flow parameters—velocity profile and vorticity map in the continuous reactor when compared to the batch reactor. In addition, a high velocity recirculating jet which creates a diverging flow as the jet hits the reactor wall was observed in the batch reactor creating two distinct vortex structures (core and marginal vortex). Frictional losses across the cavity account for much of the difference between the theoretically computed and measured values of the hydrodynamic parameters. The stream pattern obtained from the PIV analysis unexpectedly shows a fairly good correlation with the flow pattern created from the digital video recordings of the pellet motion during the wet agglomeration experiments.

Structure diagram of binary Lennard-Jones clusters.

We analyze the structure diagram for binary clusters of Lennard-Jones particles by means of a global optimization approach for a large range of cluster sizes, compositions, and interaction energies and present a publicly accessible database of 180 000 minimal energy structures (http://softmattertheory.lu/clusters.html). We identify a variety of structures such as core-shell clusters, Janus clusters, and clusters in which the minority species is located at the vertices of icosahedra. Such clusters can be synthesized from nanoparticles in agglomeration experiments and used as building blocks in colloidal molecules or crystals. We discuss the factors that determine the formation of clusters with specific structures.

Oil aggregated behavior for coal recovery and combustion characteristics of their aggregates from different grade coals

Large amounts of waste fi ne coals are very diffi cult to be treated due to the presence of ash and inorganic sulphur compounds. In order to use waste fi ne coal effi ciently, a retrieval technique is necessary for the recovery of combustible contents of coal from fi ne waste coals. Nowadays, a fl otation process has been used for the treatment, but it is impractical for developing countries due to its higher costs. Therefore, oil agglomeration process has been used to deal with these problems. In this study, the factors affecting the coal cleaning effi ciency of the oil agglomeration process were investigated with the element contents and chemical structure of three different grade coals. Chemical contents in three different grade coals were determined by proximate and ultimate analyses and the differences in chemical structure of carbonaceous contents of different grade coals were investigated by a Fourier transform-infrared spectrometry. In free coals or their mixed samples, the ratio of ash and carbonaceous contents were maintained to make it homogeneous. From the results of oil agglomeration experiments, it was concluded that the characteristics of agglomerate and the coal cleaning effi ciency of oil agglomeration were not only infl uenced by the type of oils but also by the oxygen contents and the aromatic and aliphatic chemical structures in different grade coals. The oxygenic functional groups of carbonaceous contents in coal samples prevented oil from attaching the carbonaceous surface and form the bulky aggregate. This depressed the combustible matter recovery, but this was resolved by changing the oil types. Oxygen contents in oils such as vegetable oil played a role in bridging material to the oxygenic functional groups of carbonaceous contents in coal samples. Meanwhile, it was observed that aromatic functional groups in carbonaceous contents interacted badly with the aliphatic functional groups in oil due to the resonance inspection of delocalized π electrons. Comparatively carbonaceous contents consisting of more aliphatic series or graphite-reinforced structures were tended to form aggregates easily. Even when different types of coals were used in the oil agglomeration, it was possible to achieve a better effi ciency by taking these factors into account. Moreover, by thermogravimetric-derivative thermogravimetric (TG-DTG) analyses, it was found that the combustion characteristics of carbonaceous contents were improved due to oil attachment.

Characterization of Glass Beads Surface Modified with Ionic Surfactants

Knowledge of the wetting characteristic of mineral surfaces is very important in enhancing the efficiency of separation of valuable minerals from gangue using froth flotation or oil agglomeration. In this paper a capillary rise technique was used to characterize the glass beads surface modified with cationic surfactant. The glass microspheres were used as model particles with a spherical shape and smooth surface to eliminate the roughness effect. The value of the contact angle for water was found to be 21.5 for unmodified beads, and 61.8, 89.7, 68.4 for 0.1, 1.0, 10 mg/gsolid of CTAB, and 39.8, 68.6, 87.9 for 0.1, 1.0, 10 mg/gsolid of DDAHCl, respectively. Data revealed that the adsorption of surfactant onto glass beads decreased the value of the electron donor component, γ-, which defines the hydrophobicity of the surface. Also, the property of the surface was investigated by flotation and oil agglomeration experiments. It was observed that particles with low value of contact angle for water and high for 1-bromonaphthalene and low value of γ- were floated with a recovery equal to 91.1 and 83.1% for CTAB and DDAHCl, respectively, and effectively agglomerated. This indicates that the capillary rise method can be successfully used to predict the wetting properties of solid particles in mineral processing.

Product design based on discrete particle modeling of a fluidized bed granulator

Fluidized bed agglomeration is a process commonly used to construct powdered food or pharmaceutical products to improve their instant properties. This works analyzes the influence of a wide range of operating parameters (i.e., fluidization air flow rate, temperature, and liquid injection rate) on growth rate, process stability, and product particle structure. Different granulator configurations (i.e., top spray, Wurster coater, spouted bed) are compared using identical process parameters. The impacts of both process variables and granulator geometry on the fluidization regime, the particle and collision dynamics, and the resulting product structure and corresponding properties are studied in detailed simulations using a discrete particle model (DPM) and lab-scale agglomeration experiments with amorphous dextrose syrup (DE21). The combination of numerical and experimental results allows to correlate the kinetics of micro-scale particle interactions and the final product properties (i.e., agglomerate structure and strength). In conclusion, detailed DPM simulations are proven as a valuable tool for knowledge-based product design.

Agglomeration and size distribution of debris in DEFOR-A experiments with Bi2O3–WO3 corium simulant melt

Flooding of lower drywell has been adopted as a cornerstone of severe accident management strategy in Nordic type Boiling Water Reactors (BWR). It is assumed that the melt ejected into a deep pool of water will fragment, quench and form a porous debris bed coolable by natural circulation. If debris bed is not coolable, then dryout and possibly re-melting of the debris can occur. Melt attack on the containment basemat can threaten containment integrity. Agglomeration of melt debris and formation of solid “cake” regions provide a negative impact on coolability of the porous debris bed. In this work we present results of experimental investigation on the fraction of agglomerated debris obtained in the process of hot binary oxidic melt pouring into a pool of water. The Debris Bed Formation and Agglomeration (DEFOR-A) experiments provide data about the effects of the pool depth and water subcooling, melt jet diameter, and initial melt superheat on the fraction of agglomerated debris. The data presents first systematic study of the debris agglomeration phenomena and facilitates understanding of underlying physics which is necessary for development and validation of computational codes to enable prediction of the debris bed coolability in different scenarios of melt release.