Production Of Fine Powders Research Articles

Droplet drying and whey protein denaturation in pulsed gas flow - A modeling study

Pulse combustion drying is a novel advanced drying technique that uses pulsating gas flow generated by intermittent combustion. The technique has been used for fine powder production from various materials, including heat sensitive materials such as foods and pharmaceuticals. In this study, denaturation of whey protein isolate (WPI) during drying in pulsated gas flow is investigated numerically. A mathematical model has been developed by coupling a single droplet drying model with a kinetic model of whey protein denaturation, both validated experimentally. To understand the influence of operating conditions on process dynamics and product properties, variations of initial droplet size, initial solid content, gas temperature, pulsation frequency, and gas velocity components are simulated. It is found that small droplets undergo drying and denaturation faster, and stay longer in the drying chamber. The influence of initial solid content is complex and depends on other variables. Gas pulsation has been shown to enhance drying with small reduction in final product activity. It also reduces the discrepancies in product quality and energy consumption in case of different initial droplet size distributions. The influence of frequency and velocity amplitude weakens at higher magnitudes of the same. Average flow velocity has a negligible effect on the properties of dried product, but it determines the droplet residence time. For WPI it is better to dry slowly at moderate temperatures than to dry faster at high temperatures, to prevent too much denaturation. It is also shown that employing pulsation is a better strategy than increasing temperature to enhance the drying process while preserving product quality. • Whey protein denaturation during droplet drying in pulsating flow is modelled. • Denaturation is faster at higher temperature, stronger pulsation, and smaller droplet size. • Small droplets stay longer in drying chamber, getting more dried and denatured. • Pulsation reduces quality differences due to different initial droplet size distributions. • Product quality is retained better by pulsating flow than by increasing temperature.

Attrition of CaO-based adsorbent in a laboratory-scale fluidized system

The attrition behavior of CaO-based adsorbent particles was systematically studied in a laboratory-scale fluidized device. Five operational and design parameters were investigated in terms of attrition. Fine powder production, attrition rate and particle size statistics were experimentally analyzed to explore the attrition characteristics of the particles. The results revealed that longer time aggravated the breakage, and larger particles possessed the better attrition resistance. Higher gas velocity promoted the attrition rate. Larger orifice number and orifice diameter reduced the degree of attrition. Linear fitting was used to analyze the relation between the mass of fine powder and other parameters. A mathematical model-R=0.67×109⋅D−0.848⋅U3.136⋅nor−0.950⋅dor−1.196 was established on the basis of experimental results to combine the effects of the various parameters. The model could be used to describe, simulate and predict the fluidized attrition phenomenon of particles.

Matrix model of the grinding process of cement clinker in the ball mill

In the article attention is paid to improving the efficiency of production of fine powders, in particular Portland cement clinker. The questions of Portland cement clinker grinding in closed circuit ball mills. Noted that the main task of modeling the grinding process is predicting the granulometric composition of the finished product taking into account constructive and technological parameters used ball mill and separator. It is shown that the most complete and informative characterization of the grinding process in a ball mill is a grinding matrix taking into account the transformation of grain composition inside the mill drum. Shows how the relative mass fraction of the particles of crushed material, get to corresponding fraction. Noted, that the actual task of reconstruction of the matrix of grinding on the experimental data obtained in the real operating installations. On the basis of experimental data obtained on industrial installations, using matrix method to determine the kinetics of the grinding process in closed circuit ball mills. The calculation method of the conversion of the grain composition of the crushed material along the mill drum developed. Taking into account the proposed approach can be optimized processing methods to improve the manufacturing process of Portland cement clinker.

Chromium Extraction via Chemical Processing of Fe-Cr Alloys Fine Powder with High Carbon Content

Ferrous alloys are important raw materials for special steel production. In this context, alloys from the Fe-Cr system, with typical Cr weight fraction ranging from 0.45 to 0.95, are prominent, particularly for the stainless steel industry. During the process in which these alloys are obtained, there is considerable production of fine powder, which could be reused after suitable chemical treatment, for example, through coupling pyrometallurgical and hydrometallurgical processes. In the present study, the extraction of chromium from fine powder generated during the production of a Fe-Cr alloy with high C content was investigated. Roasting reactions were performed at 1073 K, 1173 K, and 1273 K (800 °C, 900 °C, and 1000 °C) with 300 pct (w/w) excess NaOH in an oxidizing atmosphere (air), followed by solubilization in deionized water, selective precipitation, and subsequent calcination at 1173 K (900 °C) in order to convert the obtained chromium hydroxide to Cr2O3. The maximum achieved Cr recovery was around 86 pct, suggesting that the proposed chemical route was satisfactory regarding the extraction of the chromium initially present. Moreover, after X-ray diffraction analysis, the final produced oxide has proven to be pure Cr2O3 with a mean crystallite size of 200 nm.

Milling of magnesium powders without additives

Abstract Mechanical milling of ductile metals and alloys into fine powders is difficult to achieve due to particle agglomeration. Even though cryogenic milling and/or wet milling can lead to substantial reduction of particle size, the production of fine powders from ductile metals and alloys is a difficult process. The current study deals with the milling of Mg and examines alternative processing methods that would yield an efficient size reduction. Two methods were studied; milling with MgH 2 addition, and milling the powders pre-deformed by equal channel angular pressing (ECAP). The study showed that both methods are successful in preventing particle agglomeration resulting in a significant reduction in particle size. Equal channel angular pressing has the advantage that could be applied to all metals and alloys whereas milling with hydride could only be applied to metals forming their own hydride. It is concluded that, of the two methods, milling with hydride addition is a more effective method of size reduction.

History of the pharmaceutical use of pumice

Abstract Pumice has been used as an abrasive with medical applications for over 2000 years. Introduced into traditional Chinese medicine in the mid-eighteenth century, it has been employed as part of a decoction (tea) in combination with a range of herbs and other geopharmaceuticals (including amber, cinnabar, mica and the bones of fossil vertebrates) in the treatment of gall bladder cancer, urinary conditions, dry and hacking coughs, and anxiety disorders. Pumice has had a relatively stable literary history in Western medicine. ‘Spuma maris’ (sea foam) has been a source of some confusion in classical literature, a situation exacerbated by some medieval revisionist texts. In a medical context, the term most commonly refers to pumice. Pumice has been employed since classical times in preparations acting as dentifrices, cleansers for ulcers (particularly of the skin and cornea), cicatrizing agents to help wounds scar efficiently, an active ingredient in eye ointments and powders in both farriery and human medicine, sneeze-inducing powders, and abrasives for removing body hair and assisting in the production of fine powders of resistant pharmaceutical ingredients.

Highly tuned gas atomization for controlled preparation of coarse powder

AbstractWhile close‐coupled gas atomization has been demonstrated for highly controlled production of fine powders in many alloy systems, defense applications for Mg powder demand that such an atomization system also be capable of producing a narrow standard deviation for coarse Mg powders. To develop this capability, a series of 5 gas atomization experiments were conducted with Al, as a less hazardous surrogate for Mg, over a range of a very low atomization gas pressures. The optimum result produced an average particle diameter of about 460 μm with a standard deviation of 1.53 using Ar atomization gas, sufficiently close to the 500 μm target size. These experiments achieved the process uniformity needed for this narrow standard deviation by stabilizing melt filming with an expanded discrete jet, close‐coupled atomization nozzle and a slotted trumpet bell pour tube. Initial analysis of the size results indicated that decreased atomization gas velocity, acting within the acceleration wave model, was the key controlling variable in this low‐pressure regime. No consistent influence of gas/melt mass flow ratio was detected in the data. Experimental observation of the atomization spray images also indicated that a practical lower limit to atomization gas pressure is about 69 kPa for achieving atomization process uniformity with the method of this study.

916 燃焼技術を利用した微粒子製造プロセスの開発(FM-1 燃焼による材料微粒子合成)

916 燃焼技術を利用した微粒子製造プロセスの開発(FM-1 燃焼による材料微粒子合成)

B301 Development of fine powder production process using combustion technology(Combustion-9)

B301 Development of fine powder production process using combustion technology(Combustion-9)

Investigation on metal powder production efficiency of new convergent divergent nozzle in close coupled gas atomisation

In the present study, a new designed close coupled annular slit type nozzle is discussed for the most efficient powder production and the availability of the finest particle size. Pure tin powder was produced by using nitrogen gas at the Dumlupinar gas atomisation unit. It was found that the finest particle size with the highest efficiency was obtained at the atomising pressure where the maximum aspiration pressure is formed. Above a certain gas/melt flow ratio, the resultant particle sizes cannot be considerably reduced by further increasing atomising pressure. At that point, the applied nozzle system reaches a capacity limit, which also marks the point of the most economic work for the production of fine powders with that system. The main achievement of the nozzle discussed in the present study is that the most efficient powder product is accomplished at relatively low atomisg gas pressures.

Melt film formation and disintegration during novel atomization process

Hybrid atomization is a new powder-making method and can produce economically very fine, clean, spherical tin alloy powders with average particle size about 10μm and narrow size distributions. The key concept of hybrid atomization is to control the liquid film formation on disk for fine powder production. Low-pressure gas atomization was utilized to promote the formation of a very thin stable liquid film before centrifugal breakup and give a better preparation for the final disintegration of melts. Besides the breakup ability of the rotating atomizer, the characteristics of liquid film on rotating disk affect the atomization mechanism and results remarkably. The main disintegration mode of melt is the breakup type of liquid film, which depends on the film instability and the atomization ability of the rotating disk. On the other hand, the mean powder size relates closely to the film thickness. The powder size distribution is mainly controlled by the atomization mode and the stability, flow type of liquid film on the rotating disk. A very thin, stable liquid film with long ligaments and a small pitch in LF mode results in very fine uniform tin alloy powders.

Improvements to close coupled gas atomisation nozzle for fine powder production

In the present study, a new close coupled annular slit type nozzle was designed and constructed to produce metal powders in order to investigate the improvement of efficiency of fine powder production. The atomisation runs for the present study were performed with a small scale close coupled gas atomisation system designed and constructed at the Mechanical Engineering Department of Dumlupinar University. Pure tin powders were produced using nitrogen gas. The effects of the atomisation gas pressure on the backpressure and powder size have been discussed. The present atomisation runs showed that particle size decreased as atomising gas pressure increased. The particle size was reduced from 55·4 to 12·9 μm with increasing pressure from 0·9 to 3·1 MPa. The mass median particle sizes decreased continuously from 55 μm at a G/M of 0·22 to 12·9 μm at a G/M of 1·36 with increasing G/M ratio. Above a certain G/M, the resultant particle sizes cannot be considerably reduced by further increasing atomising pressure.

High Efficient Metal Powder Production by Gas Atomisation Process

The most important parameter for production of fine powders efficiently is the velocity of the atomizing gas. This can be achieved by increasing the pressure, but this way will not be economic. For that reason, to achieve supersonic velocities different nozzle designs are used in close coupled configuration for an efficient atomization. In this study, a new laval type nozzle was designed and manufactured. Using this nozzle tin powder was produced in close coupled system by using nitrogen gas at different operating conditions. The results showed that the increasing the gas pressure up to 1.47 MPa reduced the mean powder size down to 11.39 microns with a gas/melt mass flow rate ratio of 2.0. Powders are spherical in shape and have smooth surfaces.

Co-precipitation of carotenoids and bio-polymers with the supercritical anti-solvent process

Carotenoids are widely used as natural colorants in food or pharmaceutical industries. In some industrial formulations, these carotenoids are mixed with bio-polymers, to improve the stability of the carotenoid, its dissolution rate in water, and to make the dosage and the handling of the product easier. The supercritical anti-solvent (SAS) process is specially suitable for the production of fine powders of these mixtures, as it yields solvent-free products with a reduced thermal degradation or oxidation of the carotenoids. In this work, the application of the SAS process to the precipitation of β-carotene or lutein with poly-ethylene glycol (PEG) has been studied. The influence of different process parameters, including the operating pressure and temperature, the polymer/carotenoid concentration ratio, and the CO 2 flowrate have been studied experimentally. Additionally, a phase equilibrium model of these systems based in the perturbed hard-sphere-chain equation of state (PHSC EoS) has been developed. This model is helpful for the analysis of the experimental results. In particular, this model predicts the apparition of a liquid–liquid immiscibility region at moderate temperatures due to the co-solvent effect of CO 2 on PEG. This explains the difficulties found in the precipitation experiments performed at these conditions. The existence of this phase behavior has been corroborated by performing batch gas anti-solvent (GAS) precipitation experiments in a windowed vessel.

Hydrogen pulverization of refractory metals, alloys and intermetallics

Hydrogen-induced pulverization allows the production of fine powders with high purity and low cost in refractory metals, alloys, and intermetallics. In this paper, their hydrogen pulverization behavior has been investigated in order to further utilize hydrogen pulverization as a new powder fabrication process. Hydrogen pulverization was examined by the following three methods: (i) hydrogenation in an arc-melting chamber for NbCr2 and Ta2Ni alloys; (ii) measurement of hydrogen absorption-desorption curves in a Sieverts-type apparatus for Nb3Al alloys; and (iii) heat treatment in a hydrogen furnace for pure Ta. Two-phase alloys of NbCr2/Nbss, Nb3Al/Nbss, Nb3Al/Nb2Al, Ta2Ni/Tass and Tass/Ta2H (Nbss and Tass denote Nb and Ta solid solutions, respectively) are pulverized by absorbing a large amount of hydrogen. It is suggested that cracking leading to pulverization is initiated at brittle intermetallic regions or hydrides, which are fractured by lattice expansion of Nbss or Tass due to hydrogen absorption.

Use of prefilm nozzle for fine powder production : S. Sheikhaliev, S. Lagutkin. (NPI-MIFI - Uralnetramm, Sverdlovsk, Russia.)

Use of prefilm nozzle for fine powder production : S. Sheikhaliev, S. Lagutkin. (NPI-MIFI - Uralnetramm, Sverdlovsk, Russia.)

Centrifugal pneumatic atomization for production of fine powders

Centrifugal pneumatic atomization for production of fine powders

Application of mist pyrolysis method to preparation of Ni/ZrO 2 anode catalyst for SOFC type reactor

The ultrasonic mist pyrolysis method (mist method), a novel technique for the production of fine powders, is applied to the preparation of cermet anodes for solid oxide fuel cell (SOFC) reactors. This method is very useful for the fixation of micron-scale metal-oxide cermet powders on the YSZ substrate. The powders are spherical, well dispersed and homogeneous. The oxidation of methane was studied in a SOFC reactor with Ni/ZrO 2 anodes. The Ni/ZrO 2 cermet prepared by the mist method was selective for the oxidative coupling of methane (OCM), while the Ni/ZrO 2 cermet prepared by the ordinary paste method was active for CO and CO 2 formation. Although the supported amount of the mist anode was 100 times less than the supported amount of the paste one, both anodes showed similar total yields. The variations in activity and selectivity may be due to the different morphologies resulting from the two preparation methods.

Production of fine powder from silk by radiation

Silk fine powder was prepared directly from silk fibers irradiated with an accelerated electron beam (EB). Irradiated silk fibers were well pulverized only by physical crushing using a ball mill without any chemical pretreatment. Silk fibroin fibers were irradiated at ambient temperature in the dose range of 250–1 000 kGy. Although unirradiated silk fibers were not pulverized at all, irradiated fibers were easily pulverized and showed a high conversion efficiency from fiber to powder at high irradiation doses. The presence of oxygen in the irradiation atmosphere enhanced pulverization of the silk fibers. The electron microscopic observation showed that the minimum particle size of silk powder obtained from fibers irradiated at 1 000 kGy in oxygen was less than 10 μm. It was found that fibroin powder obtained in this work dissolved remarkably in water, thought unirradiated fibroin fibers were insoluble even in hot water. The soluble fraction was about 60% of fibroin powder for 1 000 kGy irradiation in oxygen.

Production of fine powder from silk by radiation

Production of fine powder from silk by radiation