Pulverization Process Research Articles

Pulverization of oxide powders utilizing thermal treatment in ammonia-based atmosphere

A new pulverization process utilizing thermal treatment in controlled atmosphere was developed. The samples, including SrTiO3 single crystals, TiO2 single crystals and BaTiO3 ceramic, were pulverized into nano-sized powder by heating in gas stream containing air and ammonia (NH3) at high temperature. Although the detailed mechanism for this pulverization process is still unclear but it is evident that thermal treatment in NH3 based atmosphere containing small fraction of air (5–10%) causes not sintering but pulverization. Efficient synthesis of an oxynitride compound, LaTiO2N, was demonstrated by using nano-sized La2Ti2O7 precursor prepared by utilizing this new powder preparation process.

Pulverization of end-of-life tires by ultra-high pressure water jet process

Abstract Crumb rubber (CR), as a final product from end-of-life tires through size reduction process, has proved an appropriate end product for accumulated discard waste tires all around the world. Unlike pre-existing pulverization methods, such as ambient or cryogenic grinding and solid-state shear extrusion, an entire cool pulverization process utilizing ultra-high pressure water jet (UHPWJ) was proposed in this paper. Pulverization experiments under various processing parameters were designed and conducted. The particle size distributions of produced CR were obtained using laser particle analyzer. Microscopic morphologies of CR and rubber fracture surface were observed under scanning electron microscopy. The crosslink density and gel fraction of produced CR were experimentally determined. Influence of four main processing parameters as pump pressure, transverse velocity, standoff distance and impacting angle was discussed in detail, and the most suitable processing parameters were recommended. The results show that the particle size distribution of produced CR with UHPWJ is between 45 μm and 200 μm, and the surface of CR is coarse and porous. High compressive shear effect and erosion are the main mechanisms in UHPWJ pulverization. Besides, the produced CR has already been partly devulcanized after UHPWJ pulverization, and polymer degradation occurred in the meanwhile.

Effect of Recycled Rubber Particles and Silica on Tensile and Tear Properties of Natural Rubber Composites

Application of scrap rubber and worn out tires in natural rubber compounds has been studied. The scrap rubber can, however, be recycled and compounded with natural rubber and thus can be generated as a rubber composite. In this work, recycled rubber particles (RRP) were prepared using pulverization process. Then, RRP was blended with natural rubber and silica compounds, and it was synthesized by two- roll mill and hydraulic press at specified operating conditions. The samples ranging from 0 to 40 phr of RRP loaded with silica were used as constant filler. The mechanical properties and morphological analysis were carried out. The results showed that tensile strength and elongation at break gradually decreased with increasing RRP loading in natural rubber and silica compounds. Tensile modulus went down at 10 phr of RRP and then showed an increasing trend. Hardness increased up to 30 phr of RRP and tear strength increased up to 20 phr of RRP. A comparative study was also carried out with virgin natural rubber vulcanizates. The incorporation of RRP and silica up to 20 phr in natural rubber did not lower the performance of rubber articles. Morphological studies revealed that better filler dispersion, interfacial adhesion, and cross link density could increase the tensile and tear strengths. DOI: http://dx.doi.org/10.5755/j01.ms.22.2.7330

Synthesis of nanostructured Ho(Ni0.5Fe0.5)3 compound via ball-milling

The morphology and magnetic properties of the crystalline and ball-milled Ho(Ni0.5Fe0.5)3 intermetallic compounds are studied. The presence of PuNi3 type of crystal structure was confirmed in crystalline as well as powdered samples. The emergence of a partly amorphous phase was confirmed at the end of the pulverization process. The use of the ball-milling method for various grinding time is reflected in the fabrication of nanostructured flakes, with a thickness of less than 100nm. Prolonged milling favors an assemblage of as-prepared nanopowder. The increase of pulverization time leads to the reduction in crystallites sizes confirmed by a variety of complementary measurement methods. Moreover, the increase in comminution duration results in the enhancement of the coercivity (HC), non-linear dependence of remanence (Mr) and emergence of Mr./MS ratio to values higher than 0.5. A quantitative analysis of XPS spectra shows an increase of Fe concentration versus sputtering which is in coincidence with magnetic measurements.

Fractal and Pyrolysis Characteristics of Ultra-fine Pulverized Coal Particles

A new method for optimizing ultra-fine pulverization and abating reactive condition of coal liquefaction is investigated. The single fractal and multifractal approaches are applied to analyze the fractal size dimensions of coal samples at various points within 25 h during the ultra-fine pulverizing process. Pyrolysis and infrared spectrum analyses of the samples are carried out and first expressed with the fractal size dimension of smaller particles by a bi-fractal law. It is shown that the fractal size dimension values of smaller particles are ranged from 1.715 to 1.909 and the minimum is 1.715 at 7 h. The breaking of partial chemical bonds and high pyrolysis reactivity have been demonstrated. Finally, the fractal size dimension is proposed as a promising parameter of the combined reactor of both coal ultra-fine pulverization and liquefaction.

폐 PCBs의 미분쇄 공정 적용에 따른 유가금속 분포 특성 및 금속 침출 향상에 관한 연구

The main objective of this study is to recovery valuable metals with metal particle size distributions in waste cell phone PCBs(Printed Circuit Boards) by means of pulverization and nitric acid process. The particle size classifier also was evaluated by specific metal contents. The PCBs were pulverized by a fine pulverizer. The particle sizes were classified by 5 different sizes which were PcS1(0.2 mm below), PcS2(0.20~0.51 mm), PcS3(0.51~1.09 mm), PcS4(1.09~2.00 mm) and PcS5(2.00 mm above). Non-magnetic metals in the grinding particles were separated by a hand magnetic. And then, Cu, Co and Ni were separated by 3M nitric acid. Particle diameter of PCBs were 0.388~0.402 mm after the fine pulverizer. The sorting coefficient were 0.403~0.481. The highest metal content in PcS1. And the bigger particle diameter, the lower the valuable metals exist. The recovery rate of the valuable metals increases in smaller particle diameter with same leaching conditions. For further work, it could improve to recovery of the valuable metals effectively by means of individual treatment, multistage leaching and different leaching solvents.

Optimization of a lignite-fired open pulverizing system boiler process based on variations in the drying agent composition

This paper evaluates three lignite-fired OPSB (open pulverizing system boiler) processes, named OPSB-A, OPSB-B and OPSB-C, corresponding to three options of drying agents used for the pulverizing systems. OPSB-B is similar to our previous work [18] on drying agent composition. Performances of the three OPSBs were calculated and compared with a 600 MW lignite-fired boiler as the reference. The results showed that the coal savings of OPSB-A and OPSB-C were 5.41% and 4.06% in comparison with the reference boiler, whereas for OPSB-B, the savings was 2.57%. Accordingly, emissions of each OPSB could be reduced in proportion to the coal savings. Among the three OPSBs, OPSB-C showed the best performance of water recovery from mill-exhausts because it had the highest mill-exhaust water dew point of 73.2 °C, whereas the exhaust dew points of OPSB-A and OPSB-B were 63.9 °C and 70.9 °C, respectively. Both OPSB-C and OPSB-B are beneficial for achieving a high mill-exhaust humidity ratio, which facilitates water recovery from the mill-exhaust, and a low oxygen content in mill-exhaust, which improves the operating safety of the pulverizing systems, whereas OPSB-A is relatively inferior in these respects. The OPSB-C process is recommended for engineering applications because of its favorable overall performances.

Estimation of Production and Energy Consumption in Woody Biomass Pulverization Using a Multiple Tube Vibration Mill

The evaluation of the scale-up potential of woody biomass pulverization using a newly developed multiple tube vibration mill (MTVM) was performed. The pulverization ability of a large MTVM was estimated based on the results of a laboratory-scale pulverization experiment. The pulverization pot arrangement was investigated, and the optimum pulverization conditions for woody biomass in MTVM were calculated in terms of the yield of wood powder and energy consumption. The pulverization performance of MTVM was compared to that of a conventional single tube vibration mill, where MTVM is shown to have higher productivity for a given energy consumption, and has the ability of producing high yields with larger pot sizes. Applying the stage grinding method, low-crystallinity wood powder (crystallinity index of cellulose <10%) can be produced around 1.2 t/h with an energy consumption of 1.0 GJ/t-product with an industrial-scale MTVM. The total energy consumption in the woody biomass pulverization process including coarse, middle, and fine grindings is 1.48 GJ/t-product.

석탄 분쇄기용 유성감속기 케이싱의 거동에 관한 유한요소해석

In this study, the structural analysis and the modal analysis are conducted to investigate the stress level, the deformation characteristics and the natural modes of the casing of a planetary gear reducer for a 800kW grade pulverizer mill. The casing is subjected to the load, 2800 kN, from the lump coals in the pulverizing process. Because of the symmetry, the half portion of the reducer casing is modeled for the stress analysis. But the full model is used to find out the eigenvalues and natural modes for the modal analysis. The contact conditions are applied between the thrust pad bearing and the adjacent contacting parts. The results shows that the casing structure has the sufficient strength and stiffness to support the load under consideration. ANSYS version 15 is employed to perform the numerical study.

Numerical and experimental analysis of pulverized coal mill classifier performance in the Soma B Power Plant

Coal particle separation in a classifier after the pulverization process in power plants (PP) is very important to obtain the desired level of coal fineness while reducing unburned carbon losses and slagging potential. In this study, flow inside of the coal mill classifier of Soma B PP suffering from low boiler efficiency due to high unburned carbon loss was numerically analyzed with respect to its initial flow measurements and isokinetic coal samples at the exit of the classifier as a base case. In the numerical analyses, a Eulerian/Lagrangian approach and a Reynolds stress turbulence model (RSTM) were applied. To increase coal separation efficiency, four different designs were numerically analyzed and the results were compared to the results of the base case by accounting for the total mass flow rate to the burners and coal size distribution at the outlet of the classifier. Among them design D-21 was chosen and applied to the PP mill classifier. Finally, this design was tested in a PP with different inner plate adjustments, and there was good agreement between the numerical and experimental results with a maximum difference of 2.5% for the individual coal size distributions and a cumulative maximum difference of 5% for the total coal size distributions. The assumption of a decreasing regrind outlet of coal flow rate by plate adjustment in the classifier for D-21 appears to be sufficient to increase total coal flow rate to the burners. In the tests, operating the mill at lower load conditions resulted in a finer coal size distribution at the outlet.

In-Situ Characterization of Si-Based Electrodes By Dilatometry and Acoustic Emission

The replacement of carbon by silicon as active material in negative electrodes of Li-ion batteries is very attractive since the gravimetric and volumetric capacities of silicon are much higher than those of carbon. However, silicon suffers from huge volume variation (up to ~300% versus 10% for C) upon cycling. This leads to the electrode pulverization inducing electrical disconnections in addition to cause an instability of the solid electrolyte interface (SEI), resulting in poor cycle life and coulombic efficiency. A precise evaluation of the volume variation and cracking processes is thus crucial to develop more efficient Si-based electrodes. For that purpose, in the present study, the volume change of Si-based anodes during cycling is monitored by in situ dilatometry. In addition, in situ acoustic emission (AE) measurements are performed to study the electrode pulverization process with cycling. For a better identification of the origin of the different populations of detected AE signals, a detailed study of their energetic and temporal characteristics (amplitude, rise time, frequency...) is conducted. The influence of the cycling conditions (discharge capacity, cycle number, C-rate), electrode formulation (Si particle size…) and processing (calendar pressure) and electrolyte composition on the electrode volume variation and cracking is highlighted and correlated to its electrochemical performance.

Experimental and Numerical Study of a Combined Blast and Ballistic Protection

The work presented in this paper concerns a project on the optimization of protections subjected to explosions (IED’s threat). Explosions generate two types of threats for a protective structure: blast and impact of fragments. Perforating and non-perforating impact tests were performed in our laboratory with steel spherical projectiles impacting a target based on Kevlar® textile layers and a crushable material, Crushmat®. These tests required to develop a specific experimental test setup in order to contain the composite protective structure and to be able to measure the relevant parameters. The experiments allow us to determine the ballistic performance and basic parameters of the protection, and to validate finite element numerical models (LS-DYNA) resulting in a performant prediction tool. The approach used for the simulation consists in the representation of the full textile architecture with solid elements. Therefore, the textile material is explicitly represented in the model in order to have a good representation of the physical phenomena occurring during impact. For the crushable material, a representation using SPH was chosen in order to take the granular behaviour of this material into account. Good results are obtained with such models. However, these models are very complicated and computing time consuming. The geometry has to be well adapted and symmetry has to be exploited. On the other hand, representation of a granular material with SPH does not take into account some characteristics of this material during impact, such as the pulverisation process of the granular material. Solutions to take these phenomena into account in the model are proposed.

Recycling Polyurethane Materials: A Comparison of Polyol from Glycolysis with Micronized Polyurethane Powder in Particleboard Applications

Three different types of recycled polyurethane (PUR) material, two in powder form from a pulverizing process (one < 50 µm and one < 250 µm) and one in polyol form from a glycolysis process, were used as substitutes for polymeric methylene diphenyl diisocyanate (pMDI) resin at 5%, 15%, and 30% ratio, respectively, to replace the pMDI resin for particleboard manufacturing at 8% resin loading. The reactions between pMDI resin and recycled PUR powder and polyol were investigated with Fourier transform infrared (FT-IR) spectroscopy. It was found that 5% substitution of pMDI with recycled PU powder of < 50 µm resulted in significantly higher panel internal bonding (IB) strength than pure pMDI resin, which also tended to increase panel modulus of rupture (MOR), and modulus of elasticity (MOE). Polyol did not show advantages over PUR powder in particleboard application. Increasing the size of recycled PUR powder from < 50 µm to < 250 µm decreased the panel IB, which also tended to decrease MOR and MOE. Recycling PUR materials in either powder or polyol form in particleboard manufacturing did not improve panel thickness swelling, but did appear to improve panel water absorption.

Development of a Model to Predict the Shear Force of a Horizontal Mechanical Digester

A model to predict the shearing/crushing force of an existing horizontal mechanical digester used for pulverization/digestion or maceration of date palm fruit was developed in the study. The model accurately predicted the shearing force used in digestion of fruit with model simulation done using Matlab 7.9 (R2009b). The results obtained showed a linear relationship between shearing force and angular velocity of implements/beater arms which are components of the digester that did the shearing of fruit mesocarp. It was also observed from results obtained that the higher the magnitude of angular velocity of shearing implement the higher the magnitude of shearing force of the digester. An angular velocity of 15.71 rads-1 yielded a shear force of 400.00 kN with an angular velocity of 34.56 rads-1 yielding a shear force of 880.00 kN. It was reported by the literary world that high magnitude of shear force is more efficient in pulverization process than shear force of low magnitude.

Development of Highly Efficient Saving Processes of Rare Earth in R-T-B Permanent Magnet

In this study, cost reduction of manufacturing R (Nd, Pr, and Dy) –T (Fe, Co)-B permanent magnets was investigated. An efficient direct melting recycle of R-T-B magnet scraps and multiple methods for saving Dy were focused. In the former, Decarburization and deoxidation of R-T-B magnet scraps were developed as a pre-treatment technique for conventional induction melting. The decarburized scraps 0.001mass% carbon or less was subsequently deoxidized by calciothermic reduction. The recycled scraps can be used as low cost alloying elements by re-melting. In the latter, the casting conditions for R-T-B alloy with small admixture of Ga and the improved pulverization process of R-T-B magnet alloy were developed. Microstructure of R-T-B magnet alloy with small admixture Ga was optimized by controlling cooling rate during solidification, and its average crystalline size was to be 5μm. In order to obtain finer R-T-B magnet alloy powder preferable to the coercive force, conditions of hydrogen decrepitation (HD) prior to pulverization were optimized. Specific surface area of the HD magnet alloy was increased with decreasing temperature and hydrogen pressure, and its grindability was verified by Jet milling.

Evaluation of Mean Crystallite Size on Magnetic Powder by Scanning Electron Microscopy and Synchrotron Diffractometry

This paper presents the results of investigations carried out with Pr-based magnetic powders. The magnetically hard powders were produced from homogenised alloys using a high temperature hydrogen pulverization process. Alloys and powders were investigated by scanning electron microscopy and by energy dispersive X-ray analysis. Mean crystallite size of the pulverized material was estimated using synchrotron powder diffractometry and the Scherrer method. A comparison between these two investigation techniques has been carried out. The effects of copper on the properties of the magnetic powders have been studied. It has been shown that the addition of this alloying element had a marked effect on the microstructure of the powders.

Morphological Stability of Sn Electrode for Electrochemical Conversion of CO2

The morphological stability of 100 nm Sn particles as the electrode for electrochemical reduction of CO2 was studied in a full electrochemical cell at room temperature and pressure. A degradation of selectivity towards CO2 reduction, accompanied by the pulverization of Sn particles was observed during long-term measurements. During the pulverization process, the size of Sn particles decreased from ~ 100 nm to ~ 3 nm in approximately 60-hour operation. The Faradaic efficiency towards the formation of formate decreased from ~90% to ~56%. On the contrary, the Faradaic efficiency for H2 evolution increased during the measurement. The degradation of the selectivity towards CO2 reduction is primarily attributed to the decrease of the potential atthe cathode.

Electrochemical properties of Cu2S with ether-based electrolyte in Li-ion batteries

Investigation of Cu2S as cathode in lithium cells with ether-based electrolytes shows a discharge voltage plateau at 1.7 and 2.25V in the first cycle which slowly evolve, respectively, to 1.74 and 1.94V in the following cycles. This transition process has been analyzed by ex situ X-ray diffraction, scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). The discharged products are identified as Li2S and elemental copper, and the charged product is Cu1.96S, all of which are crystalline during cycling. SEM reveals a pulverization process of particles during the phase transition and the EIS shows a significant reduction in charge transfer resistance after charges. The Cu2S electrodes exhibit a relatively stable discharge capacity of around 250mAhg−1 at rates of C/10, C/5, and C/2 after a capacity decline in the first cycle. Coulombic efficiency starts to decrease in early cycles as the rate increases. The poor cyclability and low Coulombic efficiency at high rates like 1C rate indicate the transition process is limited at high rates due to the large particle size.

Novel, synergistic composites of polypropylene and rice husk ash: Sustainable resource hybrids prepared by solid-state shear pulverization

Rice husk ash (RHA) is an agrowaste byproduct resulting from the incineration of rice husks for power production; white RHA is ∼90 wt% or more silica, which makes it a potentially sustainable and inexpensive substitute for commercial (less “green”) silica filler. Past research on polypropylene (PP)-RHA hybrids made by melt processing has yielded modest increments in Young's modulus, reduced yield strength, and drastic reductions in elongation at break relative to neat PP. Using the industrially scalable solid-state shear pulverization (SSSP) process, PP-RHA hybrids are made with 4–38 wt% RHA. As determined by microscopy and other methods, composites made by SSSP have much better RHA dispersion than composites reported in the literature made by twin-screw extrusion. The superior dispersion leads to major enhancements in tensile modulus (up to 100% increases relative to neat PP) while maintaining the yield strength of neat PP and remarkably high values of elongation at break (e.g., 520% at 19 wt% RHA), far higher than composites made by melt processing. The properties of hybrids made by SSSP are competitive with and in some cases superior to those of PP hybrids made with commercial silica. The PP-RHA hybrids also exhibit major increases in hardness, approaching that of polycarbonate in the case of a 38 wt% RHA hybrid. The 38 wt% RHA hybrid exhibits solid-like rheology at low frequency. Nevertheless, all PP-RHA hybrids made by SSSP exhibit viscosities at moderate to high shear rates that are little changed from that of neat PP. POLYM. COMPOS., 34:1211–1221, 2013. © 2013 Society of Plastics Engineers

Combustion synthesis of TiFe-based hydrogen storage alloy from titanium oxide and iron

In this paper, we describe the combustion synthesis of a TiFe-based hydrogen storage alloy from Fe and TiO2 using metallic calcium as the reducing agent and heat source. The effects of hydrogen on the combustion ignition temperature and the hydrogenation properties of the products were examined. In the experiments, Fe, TiO2, and Ca were mixed with a molar ratio of 1:1:4 and heated in a hydrogen atmosphere until the ignition due to the hydrogenation of calcium. For comparison, the same experiment was performed in an argon atmosphere. The ignition and maximum temperatures in the hydrogen atmosphere were drastically lower than those in the argon atmosphere. According to X-ray diffraction (XRD) analyses, all the peaks of the product combustion-synthesized in a hydrogen atmosphere were due to the TiFe phase, although some peaks of the product synthesized in argon indicated the existence of the TiO phase in addition to the TiFe phase. The product synthesized in hydrogen demonstrated a hydrogen storage capacity of 1.39 mass%, which is equal to that achieved using pure TiFe reagent. Moreover, a fine powdered product was obtained without any pulverization processes. This method creates an innovative production route for TiFe.