Sugeng Winardi

Effect of Particle Size on Simulation of Three-Dimensional Solid Dispersion in Stirred Tank

This work concerns the effect of particle size on three-dimensional solid dispersion in a baffled tank stirred with a disc turbine. The system studied consists of a cylindrical flat bottom four-baffled tank, 30 cm in diameter, with a six-blade disc turbine impeller, 10 cm in diameter, filled with water. Baffle width is 0.1-tank diameter and impeller clearance from tank bottom is 0.3-tank diameter. The height of liquid level in the tank is equal to tank diameter. The density of solid particle used is 2360 kg m −3 and the diameters are 87 μm, 50 μm and l0μm. Average solid concentration in the tank is 5% and 20% by volume. The impeller rotation speed is 13.3rps. In this work the three-dimensional solid concentration distribution was predicted using the Algebraic Slip Mixture model (ASM model) under FLUENT 1 5.1 facility. Standard k-ɛ turbulent model is used to model fluid flow field in the tank, and swirling radial jet model (SRJ model) approximates the velocity profile at the impeller tip. The simulation results are presented as concentration contour on r-z plane and r-θ plane in several positions in the tank for different average solid concentration and particle sizes. The solid concentration contour for 87 μm diameter solid and 5% average concentration shows that there is still a rather high solid concentration in the centre of the tank bottom, while in the liquid surface around the shaft the solid concentration is very low. This indicates the accumulation of solid particles in the centre of the tank bottom. For the other particle sizes the pattern of solid concentration distribution is similar. Below the impeller region the solid concentration near to the shaft is higher than the concentration far from the shaft. However, in the above impeller region the solid concentration near to the shaft is lower than the concentration far from the shaft. The distribution of the smaller particles is more uniform than the larger particles. Under the same rotation speed of 13.3 rps the distribution of l0 μ mon particles is almost uniform. The simulation result was verified using experimental data 2 . The simulation result agreed very well with experimental data up to average solid concentration, 20% by volume.

Modeling of and experiments on dust particle levitation in the sheath of a radio frequency plasma reactor

The equilibrium and trapping of dust particles in a plasma sheath are investigated, both experimentally and theoretically. A self-consistent sheath model including input power as one of the model parameters is proposed, to predict the equilibrium position of particle trap. The electron temperature and density are estimated from the observed current and power (I-P) characteristics using the sheath model developed. Direct comparisons are made between the measured equilibrium position and the predicted equilibrium position. The equilibrium position moves closer to the electrode with increasing rf power and particle size. The position is apparently related to the sheath thickness, which decreases with increasing rf power. The model can correctly predict the experimentally observed trend in the equilibrium position of particle trap. It is found that the particle charge becomes positive when the particle gets closer to the electrode, due to the dominant influence of ion currents to the particle surface.

Subcritical Water Extraction of Xanthone from Mangosteen (Garcinia Mangostana Linn) Pericarp

Subcritical water extraction of phenolic compounds from mangosteen pericarps was examined at temperatures of 120-180°C and pressures of 1-5 MPa using batch and semi-batch extractor. This method is a simple and environmentally friendly extraction method requiring no chemicals other than water. Under these conditions, there is possibility for the formation of phenolic compounds from mangosteen pericarps from decomposition of bounds between lignin, cellulose, and hemicellulose via autohydrolysis. In both of systems, the total phenolic content inclusive xanthone increased with increasing extraction temperature. In batch-system, the maximum yield of xanthone was 34 mg/g sample at 180°C and 3 MPa with 150 min reaction time. The total phenolic content could approach to 61 mg/g sample at 180°C and 3 MPa with 150 min extraction time. The results revealed that subcritical water extraction is applicable method for the isolation of polyphenolic compounds from other types of biomass and may lead to an advanced plant biomass components extraction technology.

Incorporation of Dust Particles into a Growing Film During Silicon Dioxide Deposition from a TEOS/O2 Plasma

The effects of gas flow rate on particle formation and film deposition during the preparation of silica thin film using a TEOS/O2 plasma were investigated. Particle formation and growth are suppressed with increasing gas flow rates. The film deposition rate increases with increasing gas flow rate, reaches a maximum value, and eventually decreases again. However, the uniformity of the film tends to degrade at high gas flow rates. At a high gas flow rate, some particles trapped in the sheath near the grounded electrode pass through the sheath to reach the substrate and are then embedded in the growing film. A self-consistent sheath model combined with particle force balance based on charge fluctuation was developed to explain these experimental findings qualitatively. The model reveals that charge fluctuation is a key factor for the particle to overcome the potential barrier of the negatively charged particles to pass through the sheath, eventually reaching the substrate. The model further shows that the probability of a particle being deposited on the substrate is higher for increased gas flow rates, which correctly predicts the experimentally observed trend.

Effect of turbulence modelling to predict combustion and nanoparticle production in the flame assisted spray dryer based on computational fluid dynamics

Flame assisted spray dryer are widely uses for large-scale production of nanoparticles because of it ability. Numerical approach is needed to predict combustion and particles production in scale up and optimization process due to difficulty in experimental observation and relatively high cost. Computational Fluid Dynamics (CFD) can provide the momentum, energy and mass transfer, so that CFD more efficient than experiment due to time and cost. Here, two turbulence models, k-e and Large Eddy Simulation were compared and applied in flame assisted spray dryer system. The energy sources for particle drying was obtained from combustion between LPG as fuel and air as oxidizer and carrier gas that modelled by non-premixed combustion in simulation. Silica particles was used to particle modelling from sol silica solution precursor. From the several comparison result, i.e. flame contour, temperature distribution and particle size distribution, Large Eddy Simulation turbulence model can provide the closest data to th...

Particle formation of hydroxyapatite precursor containing two components in a spray pyrolysis process

The particle formation mechanism of hydroxyapatite precursor containing two components, Ca(OOCCH3)2 and (NH4)2HPO4 with a ratio of Ca/P = 1.67, in a spray pyrolysis process has been studied by computational fluid dynamics (CFD) simulation on the transfer of heat and mass from droplets to the surrounding media. The focus included the evaporation of the solvent in the droplets, a second evaporation due to crust formation, the decomposition reaction of each component of the precursor, and a solid-state reaction that included the kinetic parameters of the precursor regarding its two components that formed the hydroxyapatite product. The rate of evaporation and the reacted fraction of the precursor both increased with temperature. The predicted average size of the hydroxyapatite particles agreed well with the experimental results. Therefore, the selected models were also suitable for predicting the average size of particles that contain two components in the precursor solution.

Effect of the flame temperature on the characteristics of zirconium oxide fine particle synthesized by flame assisted spray pyrolysis

Zirconium oxide fine particles were synthesized by flame assisted spray pyrolysis using zirconium chloride solution as precursor. Propane gas and air were used as a fuel and an oxidizer, respectively. The ratio of flow rate of oxidizer and fuel was maintained constant at 10:1 to ensure a complete combustion. Increasing fuel flow rate led to the increase of temperature distribution in the flame reactor. The intensity of XRD patterns increased with temperature and precursor concentration. Phase composition of zirconium oxide produced by this process consisted of monoclinic and tetragonal phases. The volume fraction of monoclinic phase of zirconium oxide increased with temperature and precursor concentration. The morphology particles observed by SEM resulted in spherical particles with size in the submicron range depending on the precursor concentration.

Effect of fuel rate and annealing process of LiFePO4 cathode material for Li-ion batteries synthesized by flame spray pyrolysis method

In this study the effect of fuel rate and annealing on particle formation of LiFePO4 as battery cathode using flame spray pyrolysis method was investigated numerically and experimentally. Numerical study was done using ANSYS FLUENT program. In experimentally, LiFePO4 was synthesized from inorganic aqueous solution followed by annealing. LPG was used as fuel and air was used as oxidizer and carrier gas. Annealing process attempted in inert atmosphere at 700°C for 240 min. Numerical result showed that the increase of fuel rate caused the increase of flame temperature. Microscopic observation using Scanning Electron Microscopy (SEM) revealed that all particles have sphere and polydisperse. Increasing fuel rate caused decreasing particle size and increasing particles crystallinity. This phenomenon attributed to the flame temperature. However, all produced particles still have more amorphous phase. Therefore, annealing needed to increase particles crystallinity. Fourier Transform Infrared (FTIR) analysis showe...

Diffusion Flame Synthesis of Hydroxyapatite Nanoparticles using Urea Assisted Precursor Solution

Hydroxyapatite (HA) or (Ca10(PO4)6(OH)2 has been widely used in orthopedics and dental applications for human bone implant and teeth filler due to their biocompatibility and osteoconductive properties. Fine to nanoparticles of HA with appropriate stoichiometry and purity are preferred because they enhance densification and bioactive properties. Here, we reported the synthesis of hydroxyapatite particles in a diffusion flame reactor. LPG mainly consisting of butane and propane was used as fuel and compressed air was used as oxidizer and carrier gas. The effects of urea adding into precursor on morphology and crystallinity of the generated particles were investigated. Scanning electron microscopy (SEM) and X‐ray diffraction (XRD) were used to observe particles morphology and crystallinity, respectively. Purity of the generated particles was analyzed quantitatively from XRD pattern using Rietveld method. Spherical shape of particles morphology was obtained for particles synthesized without urea added into pr...

Hexagonal hollow silica plate particles with high transmittance under ultraviolet-visible light

Creating hollow structures is one strategy for tuning the optical properties of materials. The current study aimed to increase the optical transmittance of silica (SiO2) particles. To this end, hexagonal-shaped hollow silica plate (HHSP) particles were synthesized from tetraethyl orthosilicate (TEOS) and zinc oxide (ZnO) template particles, using a microwave-assisted hydrothermal method. The size and shell thickness of the HHSP particles could be adjusted by using different TEOS/ZnO molar ratios and different ZnO template sizes, respectively. The optical transmittance of the HHSP particles depended on the shell thickness and particle size. The highest transmittance was 99% in the ultraviolet and visible region (300–800 nm) and was exhibited by HHSP particles with the thinnest shell thickness of 6.3 nm. This transmittance was higher than that exhibited by spherical hollow silica particles with a similar shell thickness. This suggested morphology-dependent transmittance for the semiconducting material. These preliminary results illustrate the promising features of the HHSP particles and suggest their potential application in future transparent devices.