Spherical Pellets Research Articles

Modeling breakage by impact of fragments of fired iron ore pellets

As soon as fired iron ore pellets suffer their first breakage event, fragments are created. During handling from the pelletizing plant to the steelmaker furnace, several stages of handling occur, so that if a well-formed and nearly spherical pellet breaks early in the handling chain, its fragments may also end up undergoing breakage. This is particularly important if one wishes to predict breakage during all handling stages. Unfortunately, no study in the past analyzed breakage of fragments of fired iron ore pellets, which will likely differ in comparison to the nearly spherical pellets owing to the irregular shapes of fragments. This work investigates breakage of fragments of iron ore pellets by impact using a pneumatic gun device, investigating the effect of fragment history and impact velocity on the breakage probability, the generation of fines by surface breakage as well as the fragment size distribution from body breakage. Results show that fragments are more amenable to surface breakage than well-formed pellets and also that their strength increases as fragment sizes reduce.

Utilization of Pharmaceutical Technology Methods for the Development of Innovative Porous Metasilicate Pellets with a Very High Specific Surface Area for Chemical Warfare Agents Detection.

Pharmaceutical technology offers various dosage forms that can be applied interdisciplinary. One of them are spherical pellets which could be utilized as a carrier in emerging second-generation detection tubes. This detection system requires carriers with high specific surface area (SSA), which should allow better adsorption of toxic substances and detection reagents. In this study, a magnesium aluminometasilicate with high SSA was utilized along with various concentrations of volatile substances (menthol, camphor and ammonium bicarbonate) to increase further the carrier SSA after their sublimation. The samples were evaluated in terms of physicochemical parameters, their morphology was assessed by scanning electron microscopy, and the Brunauer–Emmett–Teller (BET) method was utilized to measure SSA. The samples were then impregnated with a detection reagent o-phenylenediamine-pyronine and tested with diphosgene. Only samples prepared using menthol or camphor were found to show red fluorescence under the UV light in addition to the eye-visible red-violet color. This allowed the detection of diphosgene/phosgene at a concentration of only 0.1 mg/m3 in the air for samples M20.0 and C20.0 with their SSA higher than 115 m2/g, thus exceeding the sensitivity of the first-generation DT-12 detection tube.

RETRACTED: Study on the Removal Efficiency and Mechanism of Tetracycline in Water Using Biochar and Magnetic Biochar

In this study, a new type of sludge-derived biochar material with high tetracycline removal efficiency, named magnetic Fe3O4 biochar, was accomplished by KOH activated and loaded with magnetic Fe3O4. The particles with spherical pellets observed by SEM, as well as the XRD patterns, indicated that magnetic Fe3O4 nanoparticles were successfully loaded onto the biochar. We studied the adsorption effects and mechanisms of the following three different adsorption materials for tetracycline: biochar (BC), magnetic Fe3O4, and magnetic biochar (MBC), and the loading conditions and reusability of the materials were also considered. The adsorption effects were as follows: Fe3O4 (94.3%) > MBC (88.3%) > BC (65.7%), and the ratio of biochar to ferric salt was 0.2:1; the removal effect reached the best result. Under an acidic condition, the adsorption capacity of all the materials reached the maximum, and the adsorption of tetracycline in water, by three adsorbents, involves chemical adsorption as the leading process and physical adsorption as the auxiliary process. Various characterizations indicated the removal of tetracycline, including pore filling, electrostatic interaction, hydrogen bond action, and cationic-π action. Complex bridging is a unique adsorption mechanism of magnetic Fe3O4 and magnetic biochar. In addition, the magnetic biochar also possesses π–π bond interaction. The magnetic materials can still maintain a certain amount of adsorption capacity on tetracycline after five cycles. This study proved that the magnetic sludge-based biochar are ideal adsorbents for the removal of tetracycline from water, as well as an effective route for the reclamation of waste sludge.

The Potential Use of Raw Iron Ore in Fischer-Tropsch Synthesis

Fischer-Tropsch (FT) synthesis has been studied in the literature as a greener pathway to cleaner and sustainable hydrocarbons production. However, the cost to upscale laboratory FT formulations to pilot scale is significantly expensive. This work proposes a cheaper and scalable low-temperature FT modified iron ore catalyst that is mechanically suited for fixed bed reactors. The mechanical strength reported in this investigation was three times more than commercial alumina spherical pellets and, therefore, suitable for pilot scale scenarios. A manufacturing cost analysis of iron ore was estimated to be US$38.45/kg using the CatCost model, and the conventionally prepared iron catalyst was US$71.44/kg using the same model. The manufacturing cost estimations of modified iron ore were found to be 46% cheaper than a conventional commercial iron catalyst. The catalytic performance of the modified iron ore catalyst showed a CO conversion of 72.1% ±4.24, with WGS and C5+ selectivity 48.6% ±1.96 and 83.2% ± 5.24, respectively. These findings were comparable (both in CO conversion and product selectivity) to the ones reported by other researchers.

A Visual Tour of Carbon Export by Sinking Particles.

To better quantify the ocean's biological carbon pump, we resolved the diversity of sinking particles that transport carbon into the ocean's interior, their contribution to carbon export, and their attenuation with depth. Sinking particles collected in sediment trap gel layers from four distinct ocean ecosystems were imaged, measured, and classified. The size and identity of particles was used to model their contribution to particulate organic carbon (POC) flux. Measured POC fluxes were reasonably predicted by particle images. Nine particle types were identified, and most of the compositional variability was driven by the relative contribution of aggregates, long cylindrical fecal pellets, and salp fecal pellets. While particle composition varied across locations and seasons, the entire range of compositions was measured at a single well‐observed location in the subarctic North Pacific over one month, across 500 m of depth. The magnitude of POC flux was not consistently associated with a dominant particle class, but particle classes did influence flux attenuation. Long fecal pellets attenuated most rapidly with depth whereas certain other classes attenuated little or not at all with depth. Small particles (<100 μm) consistently contributed ∼5% to total POC flux in samples with higher magnitude fluxes. The relative importance of these small particle classes (spherical mini pellets, short oval fecal pellets, and dense detritus) increased in low flux environments (up to 46% of total POC flux). Imaging approaches that resolve large variations in particle composition across ocean basins, depth, and time will help to better parameterize biological carbon pump models.

Optimization of the Nutrient Medium for Flammulina velutipes Submerged Biomass Production and Micromorphology of Its Mycelium

Based on the assessment of the trophic needs of basidiomycete Flammulina velutipes and the optimization of the composition of the nutrient medium using design of experimental approach, the yield of the submerged biomass of the fungus was increased to 41 g/L, the duration of the cultivation process was reduced to 5 days. For this purpose, the 24 full factorial design, the Box–Wilson steep ascent method and the construction of the response surface were used. Using the method of scanning electron microscopy, it was shown that the studied F. velutipes strain grew in the form of small spherical pellets with a diameter of 1–2 mm on an optimized medium. The surface of the pellets was loose; the inner part was filled with hyphae tightly adjacent to each other. The center of the pellets had no cavity. F. velutipes pellets were formed by septate hyphae with clamp connections. The micromorphological characteristics of the submerged F. velutipes mycelium ensured a high diffusion of nutrients and oxygen into the pellets and their maximum filling of the volume of the culture medium.

Optimization of catalyst pellet structures and operation conditions for CO methanation

A fundamental understanding of the effects of catalyst pellet structures and operation conditions on catalytic performance is crucial for the reactions limited by diffusion mass transfer. In this work, a numerical investigation has been carried out to understand the effect of catalyst pellet shapes (sphere, cylinder, trilobe and tetralobe) on the reaction-diffusion behaviors of CO methanation. The results reveal that the poly-lobe pellets with larger external specific surface area have shorter diffusion path, and thus result in higher effectiveness factors and CO conversion rates in comparison with the spherical and cylindrical pellets. The effects of operating conditions and pore structures on the trilobular catalyst pellet with high performance are further probed. Though lower temperature can contribute to larger effectiveness factors of pellets, it also brings about lower reaction rates, and pressure has little impact on the effectiveness factors of the pellets. The increase in porosity can reduce the pellet internal diffusion limitations effectively and there exists an optimal porosity for the methanation reaction. Finally, the height of the trilobular pellet is optimized under the given geometric volume, and the results demonstrate that the higher the trilobular catalyst, the better the reaction performance within the allowable mechanical strength range.

Experimental study on the competing effect of ceramic pellets on premixed methane-air flame propagation in a duct

It is urgent to explore effective suppression methods for gas fires and explosions to ensure the safe utilizations of combustible gases in industrial processes. In this work, experiments are performed to study the effect of spherical ceramic pellets on premixed methane-air flame propagation in a closed duct. High-speed schlieren photography and pressure transducers are used to record the flame propagation and pressure transient, respectively. Behaviors of the flame propagating through a section of the duct filled with ceramic pellets in mixtures at different equivalence ratios are scrutinized. Three different diameters of pellets are considered in the experiments. The result shows that the flame can be quenched in the case with a smaller pellet diameter (3 mm) for a wide range of equivalence ratios from fuel-lean to fuel-rich mixture. For larger pellet diameter (5 or 10 mm), flame extinction occurs in fuel-rich mixtures (e.g. Φ = 1.1, 1.2). For the cases of flame surviving through the pellets bed, the pellets show a significant influence on the flame structure and behavior. The flame propagation depends on the porosity and the mean void diameter of the porous media in the pellets bed. Small void diameter is beneficial to flame quenching, while large porosity can accelerate the flame propagation. The pressure dynamics evolution is closely related to the interaction of flame with the pellets, and it depends on whether the flame quenches in the pellets bed. Overall, d = 3 mm ceramic pellets display the best suppression effect on flame propagation and pressure buildup in this study. The results of this study are of great significance to guide the safety design of spherical suppression materials in engineering applications for process safety researchers and engineers.

Spatial characteristics of luminous hydrocarbon pellet clouds in the large helical device

This study analyzes the dependences of the size of the luminous region of hydrocarbon pellet cloud on the ablation rate, as well as on the ambient plasma electron density and temperature. The data were obtained in a series of experiments where spherical solid polystyrene pellets with a diameter of ≈900 μm at a speed of ≈450 m s−1 were injected into hydrogen plasma of the large helical device. The ambient plasma with an electron temperature of 0.5–1.5 keV and a density of (1–7) × 1019 m−3 was maintained by injection of neutral atom beams with total the heating power of 3–14 MW. A scaling law was derived for determining the transverse size of the cloud’s luminous region from the known values of the pellet’s current radius as well as the values of the density and temperature of the ambient plasma at the place of image acquisition. The interdependencies between various dimensions of the luminous region obtained in the line spectrum are established. The presence of such dependences makes it possible to describe the dimensions of the luminous region comprehensively by means of the scaling law for its transverse size.

Demonstration of Advanced Data Mining Tools for Optimization of Pellets Employing Modified Extrusion-pelletization Technique

Background: The multi particulate drug delivery system is preferred due to its numerous advantages but the batch to batch consistency and to achieve desired physical properties are the major challenges in the formulation of such dosage form. Objective: The objective of the present study was to explore the concept of quality by design for the development of galantamine HBr controlled release pellets using a modified palletization technique. Methods: Compritol 888 and Ethocel were chosen as hydrophobic release retardants, while Avicel was chosen as pelletization aid. A compatibility study was conducted between the drug and excipients. Drug loaded extrudes were prepared by using a mixture of isopropyl alcohol, and dichloromethane. Before converting the wet extrudes into pellets, pregelatinized starch was sprinkled on them to improve the physical properties of the pellets. The pellets were characterized for size, shape, and flow. The critical evaluation parameter was the drug dissolution pattern in distilled water. The dissolution data were treated with advanced data mining techniques. The in-vivo profile was predicted employing pharmacokinetic parameters of the drug and in-vitro drug release data of optimized batch pellets. Results: The failure mode and effect analysis revealed that the amount of Compritol 888 ATO and Ethocel were the most critical formulation parameters. The results of FTIR and DSC revealed compatibility between the drug and the excipients. The spherical pellets exhibited good flow. The drug dissolution studies of the batches, prepared according to the central composite design, revealed modified drug release. Multiple regression analysis and analysis of variance were performed to identify statistically significant factors. Contour plots demonstrated the impact of the amount of Compritol 888 and ethyl cellulose. The Design-Expert software was used to identify optimized formulation. The predicted in-vivo plasma concentration-time profile revealed the modified drug release up to 12h. Conclusions: Compritol and Ethocel were able to retard the drug release up to 12 hrs in distilled water. The innovative finding of this study is the use of a dry binder (pregelatinized starch) to improve the characteristics of pellets. Other dry binders are expected to show a similar effect. The newer processing technique can be of use in the industry.

Direct-drive target designs as energetic particle sources for the Laser MégaJoule facility

This work aims to analyse the possibility of directly driven imploding spherical targets in order to create a source of energetic particles (neutrons, protons, alphas, tritium and 3He ions) for the Laser MégaJoule facility. D3He gas-filled spherical SiO2 glass pellets, irradiated by an absorbed laser intensity of 1014 W cm−2 or 1015 W cm−2 have been considered. Depending on the absorbed laser intensity and the amount of the ablated glass layer two distinct regimes have been identified: a massive pusher and an exploding pusher. Both regimes are analysed in terms of hydrodynamics and fast particle spectra. Energetic particle time-resolved spectra are calculated and used to infer ionic temperatures and total areal densities. A parametric study has been performed by varying the shell thickness and target inner radius for both laser absorbed intensities.

Remediation of oxalate in a homogeneous granulation process in the frame of crystallization

Oxalate is a common contaminant found in industrial wastewater particularly in bauxite refining industries. Crystallization in fluidized-bed processes have been established to be effective toward eliminating the problems associated to sludge disposal. In this study, the effects of oxalate removal in a simulated wastewater were investigated at varying initial oxalate concentration (150 mg/L to 450 mg/L), oxalate to calcium molar ratio (1:2 to 2:1), influent flow rate (0.6 L/h to 1.9 L/h) and pH (4.5 to 8.5) through an unseeded crystallization setup. A homogeneous granulation process in a fluidized-bed reactor was continuously operated for 110 h. The final crystal products were characterized using the scanning electron microscopy and X-ray diffraction analyses. Results showed that the ideal operating conditions for oxalate granulation were at 300 mg/L initial oxalate concentration, 1:1 molar ratio, 0.9 L/h influent flow rate and pH 6.5. These conditions have led to high efficiencies of granulation and total oxalate removal of 94.6% and 96.0%, respectively. For crystal characterization, more than 0.149 mm were formed at a cumulative mass of 67.4% to 67.7%. Furthermore, the results obtained from the characterization of the granule products confirmed the development of spherical pellet shaped calcium oxalate monohydrate crystals.

Influence of material properties on voidage of numerically generated random packed beds

Numerical studies on random packed beds require information on pellet arrangement. Often, the packing structure is taken for granted and not given much attention. This study presents an investigation of the influence of bed height 17<H/d<164, pellet insertion height 40d,200d and material properties such as friction 0⩽μ⩽1.1 and restitution 0.1⩽e⩽0.9 on the resulting voidage of beds of spheres in cylindrical containers with diameter aspect ratios of 5.6⩽D/d⩽8.41, numerically generated using LIGGGHTS® and Blender™. The results reveal a wide range of obtained arrangements from loose to dense packings, emphasising the importance of parameter settings in numerical packing generation as the bed structure may have a significant influence, particularly on fluid flow and heat transfer. Though limited to spherical pellets, it is anticipated that the observed trends hold for other pellet and wall geometries.

Simulation of absorption processes in nanoparticle catalysts

AbstractIn this contribution, we present a novel modeling approach for mass transport problems that connects the microscale with the macroscale. It is based on a proper investigation of the diffusion process in the catalytic pellets from which, after semi‐analytic considerations, a source term for the macroscopic advection‐diffusion process can be identified. For the special case of a spherical catalyst pellet, the parabolic partial differential equation at the microscale can be reduced to a single ordinary differential equation in time through the proposed semi‐analytic approach. After the presentation of our model, we show results for its calibration against the macroscopic response of a mass transport experiment. Based thereon, the effective diffusion parameters of the catalyst pellet can be identified. Furthermore, we test the model's robustness by applying significant noise to virtual experimental datasets.

Conductivity Of Series Mechanism For Spherical Pellets (Kser) In Fixed Bed Reactor At High Pressure

Conductivity Of Series Mechanism For Spherical Pellets (Kser) In Fixed Bed Reactor At High Pressure

The Effect of Packing Material Properties on Tars Removal by Plasma Catalysis

Plasma catalysis has been utilized in many environmental applications for removal of various hydrocarbons including tars. The aim of this work was to study the tars removal process by atmospheric pressure DBD non-thermal plasma generated in combination with packing materials of various composition and catalytic activity (TiO2, Pt/γAl2O3, BaTiO3, γAl2O3, ZrO2, glass beads), dielectric constant (5–4000), shape (spherical and cylindrical pellets and beads), size (3–5 mm in diameter, 3–8 mm in length), and specific surface area (37–150 m2/g). Naphthalene was chosen as a model tar compound. The experiments were performed at a temperature of 100 °C and a naphthalene initial concentration of approx. 3000 ppm, i.e., under conditions that are usually less favorable to achieve high removal efficiencies. For a given specific input energy of 320 J/L, naphthalene removal efficiency followed a sequence: TiO2 &gt; Pt/γAl2O3 &gt; ZrO2 &gt; γAl2O3 &gt; glass beads &gt; BaTiO3 &gt; plasma only. The efficiency increased with the increasing specific surface area of a given packing material, while its shape and size were also found to be important. By-products of naphthalene decomposition were analyzed by means of FTIR spectrometry and surface of packing materials by SEM analysis.

Quantitative DEM simulation of pellet and sinter particles using rolling friction estimated from image analysis

We characterize pellet and sinter particles used in the blast furnace in terms of DEM simulation parameters. By designing an innovative rotating tumbler setup whose length can be adjusted, we measure the dynamic angle of repose at six different rotation speeds for two different tumbler lengths. DEM simulations are performed in identical geometry by identifying the key simulation parameters which significantly affect the simulation results. Most of these parameters are directly measured using laboratory experiments. Using a novel image analysis based approach, we measure rolling friction for nearly spherical pellet particles and highly irregular shape sinter particles. Using these measured values of the rolling friction in DEM simulations, we obtain a very good agreement between experimental and simulation data without any calibration. The methodology presented here can be used for estimating rolling friction of non-spherical particles for usage in DEM simulations of bulk solids along with other DEM parameters.

MANUFACTURE OF SPHERICAL GRANULES OF ISOSORBIDE DINITRATE WITH MODIFIED RELEASE

Objective: This study was aimed to obtain spherical matrix pellets of isosorbide dinitrate with different dissolution kinetics to create a multidosage medicinal form with controlled release of the active substance. Material and Method: Spherical matrix granules were obtained by extrusion-spherinization and coated with different amounts of polymer shell. Dissolution profiles of the obtained spheroids were compared with reference drug tablets. Result and Discussion: The results showed that the combination of spherical granules provides an isosorbide dinitrate release profile similar to the dissolution of Cardicet Retard tablets. The target dissolution profile is achieved using a combination of uncoated spherical granules and spheroids with a 10% film coating. The similarity coefficient (f2) is 73.6.

Single step fabrication of spherical CaO pellets via novel agar-assisted moulding technique for high-temperature CO2 capture

CaO sorbents have received extensive attentions in the field of high-temperature CO2 removal due to its outstanding characters of low cost, fast sorption kinetics and high theoretical capacity. Granulating CaO powder into spherical pellets is requisite prior to its commercial application for post-combustion CO2 capture. This work proposed a facile agar-assisted moulding technique for the pelletization of CaO sorbents inspired from the strong coagulability and hydrophobicity of agar powder. In addition, finding efficient calcium precursors to produce CaO sorbents is also crucial to their CO2 sorption performance. Hence, two novel organometallic precursors, i.e., calcium laurate and calcium myristate, were employed in the current work. The obtained CaO sorbents exhibited a high degree of sphericility and uniform sizes of 3–4 mm. Besides, these sorbent pellets presented good CO2 sorption performance. In particular, the pellets using calcium laurate as precursor showed impressive performance, including high sorption rate and carbonation conversion (up to 0.92). The excellent performance was attributed to the rich porosity and porous structures of this sorbent. Such characters were believed to be brought by the burning of agar and organometallic precursors at high temperatures, which resulted in the quick release of large volumes of gases in a short time and, thus, led to the formation of porous structures. In addition, the burning out of the well dispersed agar powder in the sorbent pellet also left abundant pores in situ in the pellets. Generally, the good performance of the prepared CaO pellets demonstrates the effectiveness of the agar-assisted moulding technique for the sorbent granulation and the suitability of calcium laurate as calcium precursor.

Viscoelastic Resistance of the Surface Layer of Steel Products to Shock Attack of a Spherical Pellet

The results of experimental studies of a separate contact dynamic interaction of a spherical non-deformable pellet with a plastic flat metal surface at different angles of attack (20° ≤ α ≤ 90°) at high speeds (v ≈ 100m/s) are presented. A method is described for determining the nature of the viscoelastic resistance of a surface layer attacked by a pellet during contact displacement along the normal to the surface and rigid plastic resistance during tangential displacement, which can be used to establish the processing regimes of products by a mass flow of abrasive particles, in particular, shot-blasting cleaning. The results of comparing the obtained and known theoretical data with each other and with experimental studies are presented.