Jet Mill Research Articles

Investigation of the Effect of Mechanical Activation of Powder Components on the Properties of Polyimide Composites

This study presents the results of an analysis of the influence of joint mechanical activation of a polyimide matrix and tungsten (IV) oxide (WO2) on the mechanical properties of their composites. Mechanical activation of the powder components of the matrix and the filler is performed in a vortex jet mill. The ultimate tensile strength, tensile modulus and relative elongation at break of the composites are all investigated. When using mechanical activation, an increase in tensile strength of 9% is observed with a content of 30 wt.% WO2 filler and of 12% with a content of 70 wt.% WO2 filler compared to composites in which the joint mechanical activation of components is not used. Using scanning electron microscopy, it is shown that the use of mechanical activation by dispersing in a jet-vortex mill made it possible to achieve a uniform distribution of highly dispersed filler based on tungsten dioxide in a polyimide matrix.

Selective laser melting of CP-Ti to overcome the low cost and high performance trade-off

In this study, commercially pure titanium (CP-Ti) parts were successfully fabricated by selective laser melting (SLM) using cost-effective hydride-dehydride (HDH) Ti powders for the first time modified by jet milling. Jet milling effectively improves the particle-shape sphericity, suppresses the impurity pick-up, and produces localized plastic deformation. The flowability of the jet-milled powders is tremendously improved to 29.7 s/50 g that satisfies the SLM processing well, while the oxygen content only increases by 0.02 wt.% (the raw oxygen level: 0.15 wt.%). The oxide layer in the powder surface is determined with the thickness of ∼8 nm and TiO being the predominant phase before and after jet milling. The SLM-made (SLMed) CP-Ti achieves dominant martensitic α’ phase with the fracture tensile strength up to 731.5 ± 5.7 MPa and elongation of 20.5 ± 1.1%, comparable with those using expensive atomized powders. Contrary to the conventional metallurgical mechanism for Ti which suffers the cost-performance dilemma, this work presents SLMed CP-Ti with excellent synergy of strength and ductility while using the cost-affordable HDH Ti powders.

Effects of different drying and milling methods on the physicochemical properties and phenolic content of hawthorn fruit powders

This study aims to obtain the physicochemical properties of hawthorn fruit powder produced using different methods. Two drying methods, hot-air drying and freeze-drying, and three grinding methods, mortar grinding, shear pulverization, and jet milling, were applied to obtain the hawthorn fruit powders. The physicochemical properties of the six powders were compared using scanning electron microscopy, X-ray diffraction (XRD) analysis, and differential scanning calorimetry. The phenolic content analyses were performed using EIS-MS2 high-pressure liquid chromatography. The results showed that freeze-drying and shear pulverization yielded higher content of cyanidin-3-galactoside content. Freeze-drying and jet milling were the most effective for reduction of the hawthorn fruit powder particle size (D50 value 27.81 μm); a higher water solubility index; higher phenolic content, such as chlorogenic acid and hyperoside; and a more natural color, all of which made the powder better for application in functional foods. Different drying and grinding methods did not change the crystal structure of the hawthorn fruit powder fiber. As a result, the superfine grinding of hawthorn fruit powders could be a promising process in manufacturing instant and convenient foods, as well as active pharmaceutical ingredients. Practical applications Superfine grinding is a new technology that can yield powder with excellent surface properties. Ultrafine powder has unique physical and chemical properties, such as good solubility, dispersion, adsorption, and chemical activity, and is an ideal means of food processing. Hot-air drying in combination with jet milling can significantly improve the fluidity of the powder. However, freeze-drying in combination with jet milling results in a higher water solubility index (WSI), procyanidin B2, and chlorogenic acid content, and a more uniform and nonseparable mixture. Freeze-dried powders have smaller particle sizes and larger specific surface areas than hot-air-dried powders. The superfine grinding of hawthorn fruit powders could be a promising process in manufacturing instant and convenient foods, as well as active the pharmaceutical ingredients.

An investigation on optimum grinding system and conditions for steel plant ARP by-product α-Fe2O3 for pigment industry

After some other processes, α-Fe2O3 red powder particles -by-product of regeneration of spent pickling liquor in ARP in iron and steel industry- should be ground up to pigment grade to convert it to a value added product, red iron oxide pigment. In this study, grinding tests on α-Fe2O3 red powder were performed using four different types of laboratory-scale mills, namely the vibrating cup mill, vertical ball mill, planetary ball mill, and fluidized bed jet mill. The particle structure of the α-Fe2O3 was investigated by SEM, while its chemical composition was determined by ICP-OES, density, LOI, humidity, Cl content etc. were determined by laboratory tests. Particle size distribution and surface area value of each ground sample was determined using the laser diffraction method. Targeted particle size distribution ranges could only be achieved with the jet mill. Other mills encountered caking and adhesion problem with α- Fe2O3. It was assessed that the adhesion to the inner walls of the grinding chamber and the caking effect were both caused by the humidity content of the material. The grinding yield of the material was found to increase with increased jet mill grinding air pressure (0.8, 3.2 and 7 bars).

Physical properties and sensory evaluation of bread containing micronized whole wheat flour

The aim of this study was to evaluate the potential use of micronized whole wheat flours in breadmaking. The micronization process was achieved by a jet mill and flours (JF) of particle size, ranged from 17 to 84 μm, were used. According to the particle size of the JF, the amount of water added to dough changed and ranged from 77 to 84% as it was calculated in farinograph experiments. JF breads had higher bread yield, firmer crumb, higher elasticity, lower porosity and darker bread color compared to control whole wheat bread. Overall a lower particle size of JF resulted in a close structure of bread. According to sensory evaluation, difference among samples was difficult to perceive. During storage JF bread presented lower limiting firmness potential. After all, there is evidence that jet milled flour determined bread physical characteristics and further storage stability.

Разработка системы автоматического управления струйным измельчением на основе экспериментальных данных

Актуальность тематики данной работы определяется необходимостью снижения энергоемкости тонкого измельчения путем управления процессом, что предлагается осуществлять на основе результатов акустического мониторинга. В работе предложена система автоматического управления по критерию максимальной производительности, учитывающая особенности процесса. Описана функциональная и создана структурная схема измельчительной установки замкнутого цикла измельчения. Для описания процесса подачи материала используется модель бункера с учетом изменения площади его выходного отверстия. Процесс измельчения в рабочей зоне измельчения рассматривается как изменение концентрации материала в камере. При моделировании потока материала в классификаторе учитываются пульсации циркуляционной нагрузки в замкнутом цикле измельчения. Разработанная схема системы автоматического управления включает два уровня управления и описание объекта управления. Полученные результаты позволят качественно улучшить управление процессом измельчения.

Investigation of particle dynamics and classification mechanism in a spiral jet mill through computational fluid dynamics and discrete element methods

Predicting the outcome of jet-milling based on the knowledge of process parameters and starting material properties is a task still far from being accomplished. Given the technical difficulties in measuring thermodynamics, flow properties and particle statistics directly in the mills, modelling and simulations constitute alternative tools to gain insight in the process physics and many papers have been recently published on the subject. An ideal predictive simulation tool should combine the correct description of non-isothermal, compressible, high Mach number fluid flow, the correct particle-fluid and particle-particle interactions and the correct fracture mechanics of particle upon collisions but it is not currently available. In this paper we present our coupled CFD-DEM simulation results; while comparing them with the recent modelling and experimental works we will review the current understating of the jet-mill physics and particle classification. Subsequently we analyze the missing elements and the bottlenecks currently limiting the simulation technique as well as the possible ways to circumvent them towards a quantitative, predictive simulation of jet-milling.

Effects of Process Gas Pressure and Type on Oxygen Content in Sintered Titanium Produced using Jet-Milled Titanium Hydride Powders

Titanium hydride powders are increasingly being used to produce titanium components via powder metallurgy processes due to their improvements in densification over titanium metal powders. Since the oxygen content plays a significant role in the mechanical properties of titanium alloys, understanding how powder preparation techniques, such as milling, affect the final oxygen content is key. In this work, titanium hydride powders were milled through jet milling using air, nitrogen, and argon gas at various processing pressures. The oxygen content in the sintered powders is shown to be mostly dependent on the specific surface area, which is mainly affected by the grinding pressure. The type of gas used was also found to have an effect on the oxygen content, but the dependence was small.

Development of an Excipient-Free Peptide Dry Powder Inhalation for the Treatment of Pulmonary Fibrosis.

The caveolin scaffolding domain peptide (CSP) is being developed for the therapeutic intervention of a lethal lung disease, idiopathic pulmonary fibrosis. While direct respiratory delivery of CSP7 (a 7-mer fragment of CSP) is considered an effective route, proper formulation and processing of the peptide are required. First, air-jet milling technology was performed in order to micronize the neat peptide powder. Next, the fine particles were subjected to a stability study with physical and chemical characterizations. In addition, the in vivo efficacy of processed CSP7 powder was evaluated in an animal model of lung fibrosis. The results revealed that, with jet milling, the particle size of CSP7 was reduced to a mass median aerodynamic diameter of 1.58 ± 0.1 μm and 93.3 ± 3.3% fine particle fraction, optimal for deep lung delivery. A statistically significant reduction of collagen was observed in diseased lung tissues of mice that received CSP7 powder for inhalation. The particles remained chemically and physically stable after micronization and during storage. This work demonstrated that jet milling is effective in the manufacturing of a stable, excipient-free CSP7 inhalation powder for the treatment of pulmonary fibrosis.

Characteristics of Bread Made of Various Substitution Ratios of Bran Pulverized by Hammer Mill or Jet Mill.

The physicochemical and antioxidant properties of dough and bread were measured in wheat flours substituted with two types of bran (HMB: bran pulverized by a hammer mill and JMB: bran pulverized by a jet mill) at various ratios (0%, 5%, 10%, 15%, 20%, and 25%) of substitution. The particle size of hammer mill bran (HMB) (119.71 µm) was larger than that of jet mill bran (JMB) (25.78 µm). Wheat flours substituted with HMB contained more total dietary fiber than those with JMB. A significant increase of water absorption and dough development time in Mixolab® analysis was observed depending on the level of HMB or JMB substitution. The breads made with HMB or JMB (5% or 10%) showed a higher specific volume and lower crumb hardness than the control bread. However, breads made with ≥15% HMB or JMB had a decreased specific volume and increased crumb hardness. Overall, breads made with wheat flour substituted with 5%–10% HMB or JMB were of a higher bread quality and had more antioxidant properties.

Theoretical aspects of energy consumption acoustic evaluation at the jet grinding

The objective of this work was to develop an acoustic method for evaluating energy consumption during the jet mill operation on the basis of the new generalized physical laws of material dispersion at it destruction. Theoretical explanation is given to the problem of energy consumption diminish in the mode of fine grinding. Dependences between the product dispersion and critical energy density in the course of destruction are described. The acoustic-emissive parameters of dispersion of the samples loaded by compression and results of acoustic estimation of the jet grinding are considered. Interrelation between the gas-jet mill performance and parameters impacting on the energy consumption are analyzed. Grounds are given for using a criterion of extremal control of the working process for maintaining maximal performance. An acoustic size effect of dispersion is formulated by the analogy with dynamic size effect of destruction (DSE). A new approach to evaluation of energy consumed by the jet mill is developed from positions of unity of nature and mechanism of the loaded body destruction with community of manifestation of physical laws of acoustic emission and effects of new surface formation on the destroyed particles. Leading role in the methodology of energy consumption evaluation is given to the coefficient gN (J/imp) of transformation of the consumed energy into acoustic radiation at optimal mode of the mill operations (at maximum performance), which is calculated as a ratio of the reduced work (energy) to the acoustic signal counts in the grinding zone. Current energy consumption ЕDt (J) for period Dt (s) of work is calculated with taking into account coefficient gN (J/imp) and average (for the interval Dt) acoustic activity (imp/s). It is possible to maintain minimum energy consumption at the jet grinding by the snap-acting control of jets loading up to the level of the measured acoustic activity in the grinding zone, at which a “conditionally permanent” value of coefficient gN can be achieved. The results of acoustic evaluation of effective surface energy at optimal grinding mode correspond to the range of estimation gs in the regularity of the DSE destruction. This fact confirms validity of the dispersion theory (including the acoustic size effect) use for evaluating current energy consumption in the course of the jet mill operation.

Mathematical model of glass crushing in the jet mill

Environmental management and environmental protection require waste recycling and industrial circulation of substances that does not violate the ecological balance and will be beneficial for the national economy. Thus, the development of a non-waste technology for glass production, research on recycling, industrial glass production waste and optimization of technological regimes for glass production waste processing are promising for manufacturing marketable products.

A numerical study on particle behaviors of fluid flow in pulverizer

Abstract In the case of the developed countries, pulveriser systems exhibit a high level of sophistication, but competitive pressures threaten family farm units and rural communities. Also, the improvement of the added values of existing products has been concentrated. Until now, high-speed rotary milling machine which be capable of producing 20 kg/h of materials containing a large amount of fat without heat denaturation of about 20μm or less has not yet been commercialized in the world. There are two air stream mill techniques such as the jet and high-speed rotary mill methods among the air stream-type pulverizing method in the world markets. However, the high-speed rotary mill method is known as the only method of crushing the raw materials not only soybeans, but also coffee. In order to optimise the pulverised fluid flow, many aspects need to be taken into account. The objective of this paper is concentrated on a technique that can be finely pulverized to submicron size while maintaining the composition and nutrition without heat denaturation. First, a FEA (Finite Element Analysis) that the optimal number of revolution as input parameter is obtained through the impulse analysis to minimize the thermal denaturation has been carried out. Second, the optimum inlet velocity for producing particles less than 20μm is derived by checking the particle size distributions which employed particle behaviour analysis. Finally, the relationship between the flow and the kinetic characteristics of particles generated by crushing of soybeans for the development of high-speed rotary milling machine using the developed FEA models has been discussed

ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ СТРУМИННОГО ПОДРІБНЕННЯ НА ОСНОВІ АКУСТИЧНОГО МОНІТОРИНГУ ПРОЦЕСУ

Мета. Метою роботи є розробка шляхів підвищення ефективності струминного подрібнення на основі встановлення зв’язку продуктивності млина та якості продукту з характеристиками акустичних сигналів.Методика. Оптимізація процесу струминного подрібнення виконувалась з використанням аналізу акустичних сигналів робочих зон струминного млина. Для побудови залежностей технологічних і акустичних параметрів було використано статистичний аналіз експериментальних даних.Результати. Дослідження підтвердили залежність параметрів акустичних сигналів робочих зон від режиму подрібнення. Встановлено, що зміни максимальної і середньої амплітуди акустичних сигналів робочої зони в процесі подрібнення мають чітко виражений коливальний характер, що пов’язано зі зміною циркуляційного навантаження в робочій зоні. Показано, що відносна продуктивність млина, нормована рівнем завантаження камери подрібнення, змінюється в процесі подрібнення за квадратичним законом. В той же час, зміна максимальної і середньої амплітуди акустичних сигналів робочої зони в процесі подрібнення описується поліномом 4 порядку, при цьому величина середньої амплітуди акустичних сигналів робочої зони подрібнення в сталому режимі процесу є квадратичною функцією від відносної продуктивності за рівнем завантаження. Показано, що амплітуда акустичних сигналів характерної частоти, записаних в зоні за класифікатором, прямо пропорційна крупності часток готового продукту, що транспортується.Наукова новизна. Вперше науково обґрунтовано і експериментально підтверджено, що продуктивність струминного млина за рівнем завантаження матеріалом змінюється в процесі подрібнення за квадратичним законом. А залежність амплітуд акустичних сигналів зони подрібнення від відносної продуктивності носить поліноміальний характер.Практична цінність. Встановлення нових залежностей характеристик акустичних сигналів від технологічних параметрів дозволить підвищить ефективність струминного подрібнення на основі результатів акустичного моніторингу. Контроль продуктивності млина та якості продукції за величиною середньої амплітуди акустичних сигналів в робочих зонах установки дасть змогу знизити витрати енергії в технологічних процесах подрібнення для одержання тонкого і надтонкого матеріалу.

Preparation of a new high-performance calcium-based desulfurizer using a steam jet mill

Dry flue gas desulfurization is an increasingly attractive technique in SO2 emission control. However, the low efficiency in dry desulphurization is the bottleneck of this technology. To find a high-performance desulfurizer is an urgent task. This research utilized a steam jet mill digestion to prepare a desulfurizer at steam temperature of 220 ℃ and pressure of 0.45 MPa, and compared this product with the conventional digestion desulfurizer. Our results show that the digestion in steam jet mill can transform all the calcium oxide into calcium hydroxide. The calcium hydroxide had good fluidity and with honeycomb morphological characteristics. The experiments of dry flue gas desulfurization demonstrated that under the relative humidity of 15, 30 and 45%, the total dead times were 340, 640 and 720 min, the working time for keeping a 100% desulfurization efficiency were 120, 420 and 580 min, and the total sulfur fixation were 124.05, 274.58 and 332.09 mg. Compared with the desulfurizer by conventional dry digestion, the desulfurizer prepared in this research had a significantly superior performance. This experiment provides a new method for high-performance desulfurizer via quicklime digestion, which is an important step in pushing forward the application of dry flue gas desulfurization.

Investigation of the possibility of Pr<sub>2</sub>Fe<sub>14</sub>B/α-Fe composite obtaining by Pr–Fe–B alloy oxidation in a fluidized bed jet mill

Investigation of the possibility of Pr<sub>2</sub>Fe<sub>14</sub>B/α-Fe composite obtaining by Pr–Fe–B alloy oxidation in a fluidized bed jet mill

High-Sulfur-Content Graphene-Based Composite through Ethanol Evaporation for High-Energy Lithium-Sulfur Battery.

Lithium-sulfur batteries are the most promising candidates for next-generation energy storage devices owing to their high theoretical specific capacity of 1675 mAh g-1 and high theoretical energy density of approximately 3500 Wh kg-1 . However, the lack of cathode active materials with appropriate electrical conductivities and stability coupled with an inexpensive and industrially compatible production process has so far hindered the development of practical devices. Here, a facile preparation pathway is reported for the production of a sulfur-carbon composite active material by drying a mixture of highly conductive few-layer graphene (FLG) flakes (produced by exploiting an innovative wet jet milling process with a yield of ≈100 % and production capability of ≈23.5 g h-1 ) with elemental sulfur, using ethanol as an environmentally friendly solvent. The designed sulfur-FLG composite shows excellent electrochemical results. The assembled lithium-sulfur battery exhibits a stable rate capability up to a current rate of 2C, a coulombic efficiency approaching 100 % for 300 cycles at the current rate of C/4 (420 mA g-1 ), and a long cycle life up to 500 cycles delivering around 600 mAh g-1 at 2C (3350 mA g-1 ).

Tailoring Physical and Sensory Properties of Tofu by the Addition of Jet-Milled, Superfine, Defatted Soybean Flour.

The use of defatted soybean flour (DSF) in food as a source of dietary fiber has been limited due to its rough texture and bitter taste. Our previous work indicates that superfine DSF prepared by jet milling could overcome these problems, as it positively affected physical and sensory properties. Therefore, differently sized DSFs were incorporated in tofu, and their impacts on physical and sensory properties were investigated in this study. Coarse DSF (Dv50 = 341.0 µm), fine DSF (Dv50 = 105.3 µm), and superfine DSF (Dv50 = 5.1 µm) were prepared by conventional sifting and jet milling. Tofu was made with a 5% addition of differently sized DSFs and without DSF (control tofu). The quality of tofu was evaluated by scanning electron microscopy, color measurement, texture profile analysis, and quantitative descriptive analysis. The tofu made with coarse and fine DSF showed negative changes in its physical and organoleptic qualities, such as reduced yields, a less pure color, a harder texture, and a rougher mouthfeel. However, the tofu made with superfine DSF showed only minimal changes in its qualities compared to the control. Therefore, superfine DSF is a promising fiber supplement that does not change the physical and sensory properties in the making of high-quality tofu.

Metal-coated Sm2Fe17N3 magnet powders with an oxide-free direct metal-metal interface

We successfully prepared Sm2Fe17N3 magnet powders uniformly coated with non-magnetic metals without oxides in the interface between the magnet phase and the coating layer. The whole process from powder preparation by jet milling to coating was undertaken in a low-oxygen atmosphere. Powder coating was investigated using two different dry thin-film preparation methods, arc-plasma deposition (APD) and DC magnetron sputtering. The powder was continuously stirred during coating in order to ensure the uniformity of the coating layer. Scanning electron microscopy with energy dispersive X-ray spectrometry (EDS) and X-ray photoelectron spectroscopy demonstrated that an arc-plasma deposited Zn layer on Sm2Fe17N3 powder had nearly 100% coverage and an oxide-free direct metal-metal interface with the underlying magnet phase. The effects of metal-coatings and coating methods on the coercivity of the magnet powder were evaluated with Zn, Ti, and Al as the coating materials and with APD and DC magnetron sputtering as the coating methods. With all three coating metals, the sputter-coated Sm2Fe17N3 powders showed higher coercivity than the raw powders. The APD powders had lower coercivity than the sputter-coated powders, and in the case of Ti, coercivity was even lower than that of the raw powder. Transmission electron microscopy with EDS and nano-beam electron diffraction suggested that the high energy particles deposited by APD damaged the magnetic phase. This study demonstrated that nanometer-thick coatings of non-magnetic metals without oxides in the interface with the magnet phase have the effect of enhancing the coercivity of Sm2Fe17N3 powders, provided the proper coating method is selected.

Particle size controllable jet milling technology for efficiently recycling titanium-bearing blast furnace slag: Numerical simulation and industrial test

Abstract Large amounts of titanium-bearing blast furnace slag have been dumped in China, resulting in serious environmental contamination and a waste of precious titanium resource. At present, a process for recovering titanium from titanium-bearing blast furnace slag has been developed. Unfortunately, current size reduction techniques fail to meet the material size requirements. In this paper, a particle size controllable jet milling technology was proposed based on the idea of one-time collision between the particle and the target. To better control the breakage size, computational fluid dynamics was used to model the new jet mill giving a detailed understanding of the mechanisms. Simulated results showed that the acceleration region of the low velocity fluid was located inside the ejected stream. The velocity at which the fluid hits the target was relatively uniform. It indicated that the new jet mill was advantageous for obtaining a pulverized product having a narrower particle size distribution. Experimental results showed that the excessive size reduction was effectively reduced. The average mass fraction of the particles with the particle size of 150 μm was 8.2%, meeting the requirement for titanium recycling from titanium-bearing blast furnace slag in industry. This study provides a feasible method for reducing particle size to a desired distribution to promote resource sustainable utilization and pollution reduction in an environmentally friendly way.