Papers by Keyword: Granulation

Abstract: The electrolysis of granular matte is a new alternative method for processing sulphide copper materials with the production of cathode copper and the conversion of sulfur to the elemental state. For the first time were established the regularities for the Cu_2-xS – Fe_x+1S granules distribution by the size classes of obtained granulations for the Cu - Fe - S melt at temperatures of 1200, 1250, 1300 and 1350 °C. The maximum amount of Cu_2-xS – Fe_x+1S material of size class 5.0 + 2.5, -2.5 + 1.6 and-1.6 + 1.0 mm, which corresponds to the conditions of following electrochemical processing and estimated as 72.5%, was obtained by granulation of the melt at 1200 °C. The granulometric characteristics of Cu_2-xS – Fe_x+1S granules were estimated. With an increase in the overheating temperature of the Cu - Fe - S melt, granules with a large value of the average diameter were obtained, also the root-mean-square deviation of the particle size from the average value increases and the degree of polydispersity of the granules decreases. The duration of cooling for Cu_2-xS – Fe_x+1S granules from the melt temperatures at 1200, 1250, 1300 and 1350 °C was calculated. In the entire considered temperature range, the particle cooling time is much longer than the spheroidization time, which contributes to the formation of spherical particles.

Abstract: This study was conducted as a part of a research to assess the influence of the volumetric properties of geopolymer artificial aggregates made of fly ash to the performance of asphalt mixture to be used in pavement layers. This paper presents the parameters adopted during the production of geopolymer artificial aggregates which may affect the volumetric properties and the structure of the aggregates. The investigated volumetric properties included specific gravity and water absorption. In the experiment laboratory, two variables were utilized for producing the artificial aggregates, which might affect the considered volumetric properties. Those variables are pan-granulator slopes and alkaline ratios (the ratios of Sodium Silicate to Sodium Hydroxide). The pan-granulator slopes were set at 3 different angles, i.e. 45^o, 50^o, and 55^o. The selected alkaline ratios were 1.5, 2.0, 2.5, and 3.0. The test results indicated that the best volumetric properties were obtained at a slope of 50^o and alkaline ratio of 2.5. The bulk specific gravity values at the best volumetric properties were found to be: 1) oven dry at 1.9 grams/cm³; 2) saturated surface dry (SSD) at 2.0 grams/cm³, and 3) apparent at 2.1 grams/cm³ with 6% water absorption. In addition, the interfacial transition zone and microstructure aggregates were examined by using Scanning Electron Microscope (SEM). In this study, it was found that there were effects of Na₂SiO₃/ NaOH ratios and the granulation method on the volumetric properties.

Abstract: The present work investigates the effects of microwave-assisted annealing on the granulation and photocatalytic performance of anodic TiO₂ nanotubes. The results indicate that although microwave-assisted heating can transform the amorphous TiO₂ nanotubes into completely anatase one within 5min, it brings the collapse and granulation of TiO₂ nanotubes, which weaken their photocatalytic activity. Meanwhile, the detachment and evolution of F^- rich layer to a layer of TiO₂ membrane with rounding-off surface, and the stripping of TiO₂ nanotube bottom from its body are also observed.

Abstract: This article offers a qualitatively new approach for production fused welding fluxes granules, based on the use of a plasma arc and the Ural region raw materials that have a particularly low content of harmful impurities. The processes of fused welding flux granules forming from the Ural region mineral raw materials under the impact of a highly concentrated energy source have been studied. A new fused welding flux for submerged arc welding is produced by plasma electric arc granulation, and has required shape and fractional, chemical and phase composition of the particles. This research presents experimental and theoretical studies of interaction processes of fine-dispersed batch from mineral raw materials with a highly concentrated energy source, aimed at obtaining new information about the basic patterns of the formation, structure and composition of resulting granules of functional materials, such as welding fused fluxes.

Abstract: The article outlines the main principles of granulation technology for fused welding flux using highly concentrated heat sources (e.g. plasma arc). Modern plasma equipment and methods of its use for producing new welding materials (plasma-granulated welding flux) from mineral raw materials and synthetic mineral alloys are described. The developed technology makes it possible to produce granulated flux in a wide range of fractional composition (from 0.2 to 3 mm). Studies have focused on the influence of granulation regimes (plasmatron moving speed, current, voltage, arc length) on formation process and the morphology of welding flux particles. Mineral raw materials used for granulation were igneous rocks (basalt, hornblendite) and synthetic mineral alloys. The results obtained during experiments on the use of highly concentrated heat sources for granulation of a fused welding flux confirm the feasibility and prospects of this technology. Typical equipment for air-plasma cutting is used, and no new complex technological equipment is required, therefore it eliminates large material and labor costs.

Abstract: The research and description of modern methods and procedure of welding flux manufacture are presented. The technology of welding fused flux production by influencing on the composition of mineral raw materials furnace burden (from 0,5 mic up to 0,20 mm) with electric arc (diameter graphite electrodes 6-18 mm, current from 200 up to 600 A) is proposed to be significantly reducing the labor input as well as dustiness during the operation and transport and improves mechanical properties (granules strength of 16-19 N/mm²) and surface condition of flux granules. The equipment for the granulation does not require large melting furnace and powerful transformers, fuel gas, coke or oil, i.e. welding flux is easy to manufacture.

Abstract: Self-lubrication composites containing second phase particles incorporated into the volume of the material appears to be a promising solution for controlling friction and wear in modern systems. The objective of this work was the development of steels with low friction coefficient using granulated powders through a precursor (SiC), which generate carbon nodules in a ferrous matrix. The studied alloy composition was Fe+0,6C+3SiC using 2 wt.% of EVA as binder. In this study, the influence of the average size of the iron particles and silicon carbide (SiC) in the microstructure, mechanical and tribological properties was evaluated. The powders were first mixed in a "Y" type mixer, granulated drum, compressed and sintered in plasma in a single thermal cycle assuring binder extraction and sintering of components. The achieved results were close to those of alloys of the same composition produced via powder injection molding (PIM) but with processing time and cost close to those of conventional powder metallurgy (PM). Materials with yield strength of 250 MPa, durability of 2800 Nm and 0.11 friction coefficient were obtained.

Abstract: The granulation process is a unit operation with broad application in the fertilizer industry. The granular fertilizer has a better physical appearance, facility of agricultural application and elimination of fugitive dust in the production and bagging units. Phosphogypsum is a residue from the production of phosphate fertilizers. It known that for every 1 t of phosphate fertilizer produced, about 4 t of phosphogypsum are obtained, causing problems in storage and risks to the environment. Such problems may be minimized by granulating the waste phosphogypsum and using it in agriculture. This work aims at the construction of a laboratory-scale rotating disk granulator with a pre-established combination of reagents to promote granulation of the waste from phosphate fertilizer production. For construction of the equipment a theoretical study was performed in order to establish the principal variables influencing the granulation technique and the dimensions required for building the granulator. The equipment attained the expected results and the disc speed (22 to 250 rpm) and disc inclination (0 to 90 degrees) can be manipulated. In this paper three binders used were: Manioc starch, carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA), each at three different concentrations. The tests were conducted using a rotating disk granulator and hardness tests on a universal mechanical testing machine. The figures of merit used in this study were percentage particle size, hardness and sphericity of the granules obtained. With the analysis of the data, it can be concluded that the granulation process was adequate, considering the settings employed.

Abstract: In fertilizers industries the granulation is an essential operation to form pellets with good quality. The granular product has improved handling, hardness, solubility, resistance to segregation and meets requirements such as the size, shape and particle size distribution through appropriate manipulation of the process variables. There are several types of granulators, however, this work is intended to study a granulator known as rotating disk, which promotes agitation of the particles by rotating around its axis. Although these devices are used industrially, cannot be found in the literature many details about the fluid dynamics in these operations. To study the fluid dynamics behavior of these particles on a rotation disk was analyzed the variables: rotation axis and filling degree. It was verified the existence of flow regimes which depends on these variables: rolling, cascading and centrifugation. Also, it was evaluated the dynamic angle of repose, that characterizes the rolling regime. This work aimed to obtain results of fluid dynamics that describe the behavior of solids flowing in a rotating disk. Thus, to meet the objectives of this work, simulations was carried out through the techniques of Computational Fluid Dynamics (CFD) and Discrete Element (DEM) to evaluate different parameter values: restitution coefficient (η), friction coefficient (μ) and the coefficient of elasticity (k) of the linear model "spring-dashpot" to find a good set of parameters that characterizes this system.

Abstract: This work focuses on clay ceramic hollow spheres (CCHS) preparation using Liepa clay and sacrificial template method in a lab scale device and testing of their properties. Water retention and compression strength were investigated in order to found out if obtained CCHS can be used as an additive for improving soil resilience.The synthesis and characterization of CCHS using expanded polystyrene spheres (EPS) as sacrificial template is presented. CCHS were fired at five different temperatures and their compressive strength, water retention, bulk density, material density, water absorption, phase composition, surface morphology, porosity using hydrostaticweighing and BET nitrogen adsorption methods, were determined.Study of clay ceramic hollow sphere structure and surface morphology revealed that all samples have spherical shape. These spheres have several pronounced protrusions from the granulation process. Clay ceramic hollow spheres have porosity rate of 21 - 36% and a water absorption rate of 15 -33%. The highest rate of porosity and water absorption was observed for hollow spheres fired at 1050°C.The increase of clayceramic hollow spheresfiringtemperature led to decrease of specific surface area-thehighestvaluewas observed at950°C and the lowest at 1150°C. The bulk density increased at 1150°C.Mechanicalstrength test of ceramic hollowspheres(HS)revealedthat with the increase of scorchingtemperature the compression strength of the spheres increasedas well.The sphere hollowshadpractically globular shape with the averagewallthickness of0,6 mm, whichcomprises10-13% ofthe outer diameter.The obtained clay ceramic hollow spheres are proposed as water retention agent.