Jet Mill Research Articles

Fluid-particle energy transfer in spiral jet milling

Spiral jet milling is a size reduction process driven by the fluid energy of high velocity gas jets. Inter-particle and particle-wall interactions are responsible for size reduction. The process is energy intensive, but inefficient. The underlying mechanisms for size reduction in the mill are also not very well understood. The optimum grinding conditions are still currently found by trial and error experimentation. In this work, the Discrete Element Method coupled with Computational Fluid Dynamics is used to investigate the effects of different parameters on the particle collisional behaviour in a spiral jet mill. These include the particle concentration in the grinding chamber, the particle size, and the fluid power input. We report on our work analysing the efficiency of energy transfer and how it can be improved by changing the milling conditions and particle properties.

Simulation of combined heterogeneous processes based on discrete models of the Boltzmann equation

A new approach to simulating combined heterogeneous processes of chemical technologies based on the Boltzmann kinetic equation has been proposed. Examples of using this approach to describe processes in a gas−solid heterogeneous system when combining processes of the movement, grinding, and classification of particles in a fluidized bed jet mill have been reported. The possibilities and advantages of applying discrete models of the Boltzmann equation to describe combined heterogeneous processes have been shown.

湿式ジェットミルによる二次元性ナノフィラーの薄片化における媒体粘度の影響

Wet-type jet milling (WJM) process was utilized to delaminate two kinds of two-dimensional (2D) nanofillers: hexagonal boron nitride (hBN) and graphite. Poly(dimethylsiloxane)s (PDMS) with different dynamic viscosities from 1 to 1,000 mm2/s were employed as process media in order to study the effect of medium viscosity on delamination behavior. Change in particle shape was followed by evaluating both particle width and thickness from image analysis of SEM images. Sedimentation behavior of the slurries was also studied. It was found delamination of 2D nanofillers was induced by WJM treatment in the low viscosity PDMS. On the contrary, the treatment in high viscosity PDMS was ineffective in delamination of 2D nanofillers. Significant increase of equilibrium sedimentation height was observed for hBN slurry treated in low viscosity PDMS. It is considered that both change in primary particle size/shape and aggregation structure contributes to the increase. In the case of graphite, increase of equilibrium sedimentation height was observed even in higher viscosity PDMS, suggesting the importance of aggregation structure.

Нелинейная модель измельчения смеси разнопрочных компонентов в струйной мельнице кипящего слоя

Нелинейная модель измельчения смеси разнопрочных компонентов в струйной мельнице кипящего слоя

HPLC METHOD DEVELOPMENT AND VALIDATION FOR QUANTITATION OF TRIGONELLINE FROM MIRABILIS JALAPA LINN. LEAVES AND ENHANCEMENT IN EXTRACTION YIELD FROM ULTRA FINE POWDER

Objective: Development and validation of a simple and reliable HPLC method for determination of an alkaloid, trigonelline, in the methanolic extract of Mirabilis jalapa Linn. leaves and comparing the extraction yields of trigonelline from micro powder and ultrafine powder.Methods: The quantitation of trigonelline was carried out on a Phenomenex (Luna 5 U RP C8 (2) column, 25 cm x 4.6 mm, i.d. 5 µm), using mobile phase comprising of distilled water containing HCl (pH adjusted to 3.5) and methanol in the volume ratio of 70:30, which was delivered at the flow rate of 0.5 ml per min, at 35 °C column temperature. The detection and quantitation of trigonelline were carried out using PDA detector at the wavelength λ=264 nm.Ultra-fine powder of Mirabilis jalapa Linn. was prepared using simple stepwise powdering method. The dried leaves of Mirabilis jalapa Linn. were ground using ice jacketed domestic mixer. This powder was sieved through a BSS 85 mesh sieve and considered as a micro powder. Further fine grinding was done by jet milling, followed by ball milling. This powder was considered as an ultra-fine powder.Results: The proposed HPLC method for quantitation of trigonelline from dried leaf powder of Mirabilis jalapa Linn. is rapid, simple, accurate and precise.Conclusion: The amount of trigonelline obtained using methanolic extracts of Mirabilis jalapa Linn. Ultra-fine powder and the micro powder was found to be 1.1103 mg/g and 0.7258 mg/g respectively.

Моделирование активационного измельчения частиц ромбической серы в дезинтеграторе

Based on the theoretical studies, complete picture of a mechanical processing of sulfur in the disintegrator is given. Kinematic and dynamic characteristics of elastic and inelastic collisions of particles of processed rhombic sulfur with rows of disintegrator fingers are calculated. Based on the analysis of the obtained dependency of the rotation frequency of the rotors offers, advices on selecting optimal conditions for activation milling of α-sulfur in the disintegrator are given. These results can be partially used in the processing of sulfur and in other types of shock grinding devices, in particular, jet mills.

The effect of nano-TiC addition on sintered Nd-Fe-B permanent magnets

This paper addresses the effect of nano-TiC addition on sintered Nd-Fe-B permanent magnets. TiC nanoparticles were added to sintered Nd-Fe-B magnets with a specific aim to improve the Curie temperature and thermal stability. A standard powder metallurgy route was adopted to prepare the magnets. It was found that introducing nano-TiC prior to jet milling was effective as the nanoparticles dispersed in the final alloy, concentcalcrating in the neodymium-rich phase of the magnets. Magnets with optimal properties were obtained with the addition of 1wt% TiC nanoparticles. The hysteresis loop for such magnets showed an improved shape and VSM analysis a coercivity value of 1188kA/m, a remanence value of 0.96T and a maximum energy product of 132kJ/m3. The maximum working point and the Curie temperature of the developed magnets were 373K and 623K respectively.

Application of three control banding tools to occupational health risk assessment of titanium dioxide manufacturing factory

Objective: To explore and validate suitable risk assessment methods for titanium dioxide though applying three risk assessment tools for nanomaterials based on the control banding (CB) approach. Methods: A factory manufacturing titanium dioxide in Jinan city, Shandong province, was assessed using a quantitative exposure method and qualitative risk assessment methods in September, 2014. A condensation particle counter equipment was used to monitor the number concentration of particles at packaging workshop and jet milling workshop. We employed three control banding tools, including CB nanotool, Stoffenmanager nano and the Guidance on working safely with nanomaterials and nanoproducts (GWSNN) to evaluate the two workshops, then compared the evaluation results. Results: The increases of particle concentrations were generated directly by packaging and jet milling processes, the number concentration from (3.52±1.46) ×10(4)/cm(3) to (14.70±8.86) ×10(4)/cm(3) at packaging workshop and from (0.97±0.25) ×10(4)/cm(3) to (1.26±0.35) ×10(4)/cm(3) at milling workshop (both P<0.05) . The number concentrations at packaging workshop were higher than those at jet milling workshop during both manufacturing and break times (both P<0.05) . The results of CB nanotool showed that the risk level of the packaging workshop was classified as high and the risk level of the jet milling workshop was classified asmedium. The results of Stoffenmanager nano showed that the risk level of the packaging workshop was classified as medium and the risk level of the jet milling workshop was classified as low. The results of GWSNN showed that the risk level of packaging workshop was classified as high and the risk level of jet milling workshop was classified as low. Conclusion: The results of evaluation based on the three control banding tools are related and aligned with the results of quantitative monitoring, so they are all suitable to perform occupational health risk assessment on industrial scale production of titanium dioxideto some extent.

Preparation and physicochemical characterization of spray-dried and jet-milled microparticles containing bosentan hydrate for dry powder inhalation aerosols.

The objectives of this study were to prepare bosentan hydrate (BST) microparticles as dry powder inhalations (DPIs) via spray drying and jet milling under various parameters, to comprehensively characterize the physicochemical properties of the BST hydrate microparticles, and to evaluate the aerosol dispersion performance and dissolution behavior as DPIs. The BST microparticles were successfully prepared for DPIs by spray drying from feeding solution concentrations of 1%, 3%, and 5% (w/v) and by jet milling at grinding pressures of 2, 3, and 4 MPa. The physicochemical properties of the spray-dried (SD) and jet-milled (JM) microparticles were determined via scanning electron microscopy, atomic force microscopy, dynamic light scattering particle size analysis, Karl Fischer titration, surface analysis, pycnometry, differential scanning calorimetry, powder X-ray diffraction, and Fourier transform infrared spectroscopy. The in vitro aerosol dispersion performance and drug dissolution behavior were evaluated using an Anderson cascade impactor and a Franz diffusion cell, respectively. The JM microparticles exhibited an irregular corrugated surface and a crystalline solid state, while the SD microparticles were spherical with a smooth surface and an amorphous solid state. Thus, the in vitro aerosol dispersion performance and dissolution behavior as DPIs were considerably different due to the differences in the physicochemical properties of the SD and JM microparticles. In particular, the highest grinding pressures under jet milling exhibited excellent aerosol dispersion performance with statistically higher values of 56.8%±2.0% of respirable fraction and 33.8%±2.3% of fine particle fraction and lower mass median aerodynamic diameter of 5.0±0.3 μm than the others (P<0.05, analysis of variance/Tukey). The drug dissolution mechanism was also affected by the physicochemical properties that determine the dissolution kinetics of the SD and JM microparticles, which were well fitted into the Higuchi and zero-order models, respectively.

Effect of microstructure on the breakage of tin bronze machining chips during pulverization via jet milling

In this study, jet milling was used to recycle tin bronze machining chips into powder. The main purpose of this study was to assess the effect of the microstructure of tin bronze machining chips on their breakage behavior. An experimental target jet mill was used to pulverize machining chips of three different tin bronze alloys containing 7wt%, 10wt%, and 12wt% of tin. Optical and electron microscopy, as well as sieve analysis, were used to follow the trend of pulverization. Each alloy exhibited a distinct rate of size reduction, particle size distribution, and fracture surface appearance. The results showed that the degree of pulverization substantially increased with increasing tin content. This behavior was attributed to the higher number of machining cracks as well as the increased volume fraction of brittle δ phase in the alloys with higher tin contents. The δ phase was observed to strongly influence the creation of machining cracks as well as the nucleation and propagation of cracks during jet milling. In addition, a direct relationship was observed between the mean δ-phase spacing and the mean size of the jet-milled product; i.e., a decrease in the δ-phase spacing resulted in smaller particles.

Injection molding of tungsten powder treated by jet mill with high powder loading: A solution for fabrication of dense tungsten component at relative low temperature

The greater demands on final product quality of powder metallurgy processing have led to an increased demand for metal powders with high quality. In this paper we report the successful preparation of tungsten powder with a near-spherical shape and surface morphology by jet milling process, with the disappearance of agglomeration and the improvement of dispersion, narrow particle size distribution of tungsten powder was achieved. The values of D10, D50 and D90 changed from 2.02μm, 3.67μm and 6.34μm to the original tungsten powder to 1.36μm, 2.13μm and 3.19μm for the treated tungsten powder, respectively. The process increases apparent density and tap density from 3.71g/cm3, 5.54g/cm3 to 5.71g/cm3, 8.47g/cm3. Due to the optimization of the powder characteristics, the powder loading of the feedstock was raised to 65vol% for the treated powder. The sintered samples of 65vol% powder loading is easy to get sinter densification with no cracks and has superior hardness and microstructure at a relative low temperature of 1900°C.

Batch grinding kinetics of scrap tire rubber particles in a fluidized-bed jet mill

Grinding plays an important role in achieving scrap tires recycling. The batch grinding kinetics of scrap tire rubber particles in a fluidized-bed jet mill was studied based on population balance modeling. The selection and breakage functions were obtained according to the first Kapur function. It is found that these two functions were affected by the operating parameters such as the inlet gas pressure, feed load and grinding temperature. The breakage behaviors of scrap tire rubber particles under different operating conditions in the jet mill were discussed. Furthermore, a cubic function was proposed to predict the relation between the Kapur function and the particle size. The model prediction agrees well with the experimental data obtained under various operational conditions.

Palmitoylethanolamide sub-micronization using fast precipitation followed by supercritical fluids extraction

Sub-micronization of palmitoylethanolamide (PEA) was successfully performed using fast precipitation coupled with supercritical fluid extraction. Different solvents were tested: acetone, ethyl acetate, isopropanol, dimethyl sulfoxide and ethanol; water was used as the antisolvent. PEA precipitated in all cases as crystals of hexagonal morphology. The best result in terms of control of dimension of the crystals was obtained using ethanol as solvent. Moreover, varying the concentration of PEA in the solution from 5 to 9mg/mL, it was observed an increase of crystal dimensions. The effect of other process parameters, such as the solvent/antisolvent ratio and the concentration of surfactant in the antisolvent phase, was investigated to better control the crystallization process. Micronized crystals with controlled and regular dimensions (about 1μm) and nanometric thickness (about 100nm) were obtained at the optimized process conditions. A mass reduction of PEA particles of about ten times was obtained with respect to jet milling micronized particles.The supercritical extraction process, performed at 120bar, 44°C and at a liquid to gas ratio of 0.05, allowed the selective extraction of ethanol from the water suspensions with a final solvent residue of 88ppm; i.e. well below the pharmacopeia limit. Particles characterization was also performed using X-ray diffraction, differential scanning calorimetry and Fourier transform infrared spectroscopy. PEA fast precipitated particles were characterized by a reduced degree of crystallinity with respect to unprocessed PEA.

Preparation of slab-shaped lactose carrier particles for dry powder inhalers by air jet milling

Dry powder inhalers are often formulated by attaching micronized drug particles onto carrier particles, which are generally lactose. In this study, commercially available lactose was air jet milled to produce unique slab-like coarse carrier particles, which have larger and rougher surfaces compared to other commercially available lactose. Two key processing factors, i.e., classifier speed and jet milling pressure, were systematically investigated. The largest fraction of slab-like particles in the resulting powder was obtained at a classifier speed of 3000 rpm. The slab-like coarse carrier particles are expected to exhibit superior performance than commercial lactose due to their unique surface properties.

Enyzyme-Immobilized Electrode Prepared Using Cellulose Nanofiber

Various procedures have been proposed for the preparation of enzyme-immobilized electrode, such as covalent attachment, cross-linking, hydrogel entrapment, polymer film entrapment, and the combination of two or more methods.Cellulose is a linear polysaccharide of glucose, which have significant high strength and stability due to strong intra- and inter-molecular hydrogen bonds within and among individual chains. Cellulose nanofiber (CNF) dispersion solution can be obtained by stripping down water insoluble cellulose fibers using procedures such as wet jet milling. In this study, CNF was applied for the immobilization of enzyme by entrapping it within CNF matrix. Glucose oxidase (GOx) was employed as the enzyme, and GOx-CNF immobilized electrodes were fabricated by simple repetitious drops of cellulose solution containing GOx on the surface of an electrode. The obtained electrode provided a glucose sensor with significantly high response speed and good linear relationship between glucose concentration and response current. Introduction of CNF films on GOx-CNF film successfully reduced the release of GOx from enzyme-immobilized electrode and glucose sensor with good long term stability was obtained.

Preparation Of High-performance Photocatalytic Core-shell Lamellar Nanostructures ZnO-(Si)-ZnO With high Specific Surface Area

A new preparation method of lamellar core-shell ZnO-(Si)-ZnO nanostructures with high specific surface area and high photocatalytic efficiency is presented in this article. This novel method is based on the application of controlled vacuum sublimation of the frozen liquid dispersion of silicon nanoparticles which were prepared by using the &quot;top-down&quot; process in cavitation Water Jet Mill disintegrator. The particle size of thus disintegrated silicon nanoparticles was measured by dynamic light scattering (DLS). Final product ZnO-(Si)-ZnO was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and amount of ZnO and Si was measured by energy dispersive x-ray spectroscopy (EDAX). Specific surface area was obtained from Brunauer-Emmett-Teller analysis (BET). The photocatalytic activity of ZnO-(Si)-ZnO nanostructure was verified by the decomposition of methylene blue (MB) solution. The Final nanomaterial shows a relatively high specific surface area of 134 m2/g and significantly higher photocatalytic activity compared to standard TiO2 (Degussa P25). Such procedure based on the controlled vacuum sublimation of frozen liquid of suitable metal salts could be a promising method for obtaining photocatalytic nanomaterials with higher specific surface area.

Influence of jet milling and particle size on the composition, physicochemical and mechanical properties of barley and rye flours

Finer barley and rye flours were produced by jet milling at two feed rates. The effect of reduced particle size on composition and several physicochemical and mechanical properties of all flours were evaluated. Moisture content decreased as the size of the granules decreased. Differences on ash and protein contents were observed. Jet milling increased the amount of damaged starch in both rye and barley flours. True density increased with decreased particle size whereas porosity and bulk density increased. The solvent retention capacity profile was also affected by jet milling. Barley was richer in phenolics and had greater antioxidant activity than rye. Regarding colour, both rye and barley flours when subjected to jet milling became brighter, whereas their yellowness was not altered significantly. The minimum gelation concentration for all flours was 16%w/v. Barley flour gels were stronger, firmer and more elastic than the rye ones.

The spiral jet mill cut size equation

Micronisation, or fine grinding, is a key unit operation for many industries, with the spiral jet mill being popular as it is robust and reliable. Within this paper an analytical derivation for spiral jet mill cut size as a function of micronisation settings, gas thermodynamic properties and empirically derived constants for the material and mill is presented for the first time. This has been corroborated by experimental evidence and previously reported data in the academic literature and provides an insight into the interaction between aerodynamic particle classification and fine grinding. A scale up methodology is proposed for a high value material by using a small scale mill to determine the material specific constants of the high value material and a cheaper surrogate material to determine mill specific constants at increased scale.

Combined viscoelastic and elastic wave dissipation mechanism at low velocity impact

The understanding of effects occurring during low velocity normal particle impact on a hard elastic plate is important for the description of different processes occurring during pneumatic conveying, in jet mills, mixers, or fluidized bed apparatuses. In this study, a suitable semi-empiric method is proposed to calculate the coefficient of restitution. This coefficient of restitution is modelled by means of combination of two different approaches. The first approach is based on dissipation of impact energy due to bending wave excitation in the plate described only by one inelasticity parameter. The second approach is based on viscoelastic mechanism of energy dissipation, represented by an additional viscoelastic damping coefficient. Thus, these two coefficients are responsible for bending and viscoelastic energy dissipation and are calculated independently from each other. The summarized energy dissipation is used to determine both material parameters and coefficients. A good agreement between calculated and measured coefficient of restitution was observed. In this way, the interaction between steel spheres impacting on glass plates with a thickness comparable to the diameter of the sphere was calculated as an example.

Impact of jet-milling and wet-polishing size reduction technologies on inhalation API particle properties

The main goal of this work is to investigate the physical and chemical properties of fluticasone propionate (FP), mometasone furoate (MF) and salmeterol xinafoate (SX) after being size-reduced by jet-milling (JM) and wet-polishing (WP) technologies. FP, MF and SX crystals were size-reduced by JM and WP until a volumetric median particle size (Dv50) of 2μm. Additionally, FP particles were also produced by WP to target a Dv50 of 3μm. The micronized APIs were analyzed by laser diffraction, scanning electron microscopy, modulated differential scanning calorimetry, X-ray powder diffraction, Karl-Fischer, dynamic vapour sorption, mercury intrusion, Brunauer-Emmet-Teller adsorption method and by gas chromatography. The FP and MF powders size-reduced by JM presented a higher specific surface area (SSA), rugosity, porosity and water content and lower skeletal density, bulk density and solvents content when compared to the WP powders. On the other hand, SX by JM powders presented lower SSA, rugosity and porosity and higher densities compared to the WP powders. FP size-reduced by WP to a Dv50 of 2 and 3μm showed identical physicochemical properties. The JM and WP technologies produced FP, MF and SX powders with a similar PSD suitable for inhalation delivery but with distinct physicochemical properties that were technology dependent. These singular attributes may impact the interfacial properties and therefore the final drug product behavior, indicating that additional characterization of micronized API might be recommended for establishing meaningful and performance-oriented specifications.