Jet Mill Research Articles

Вплив місця розташування елементу керування газовими потоками в ежекторному вузлі на характер течії потоку

This article is devoted to a numerical simulation of the flow in a jet mill ejector equipped with a gas flow control element. This element is a channel wherefrom an additional gas flow enters the accelerating tube of the ejector. The gas flows in the mill ejector are controlled using the energy of additional gas flows, thus increasing the velocity of the main flow at the outlet of the ejector accelerating tube and producing a protective layer around the tube walls to prevent their wear. At the same time, there is no substantiation for the choice of optimal control parameters, a methodology, or scientific methods for gas flow control in the ejector channels. The purpose of this work is to investigate the effect of the location of the gas flow control element on gas-dynamic ejector performance and the flow pattern in the ejector channels. A numerical study was carried out using the Ansys Fluent software package and the SST k-? turbulence model. In the course of the study, the pressure of the additional gas flow and the distance from the accelerating tube inlet to the energy carrier supply channel were varied. The angle of the additional gas flow was 20 ?. The numerical simulation gave flow patterns in the ejector as a function of the location of the gas flow control element. Streamlines of the additional gas flow were constructed. The article presents the average flow velocity at the accelerating tube outlet and the energy carrier flow rate as a function of the pressure of the additional flow of the energy carrier and the location of the gas flow control element and the maximum values of the average outlet velocity for given pressure ranges. The article substantiates the choice of the gas flow control parameters that maximize the velocity of the mixed flow at the accelerating tube outlet at a minimum gas flow rate. The results may be used in improving material processing technologies.

Efficient abrasive water jet milling for near-net-shape fabrication of difficult-to-cut materials

The utilization of materials with high strength to density ratio enables efficiency improvements and is therefore demanded for many applications, particularly in the aerospace and other mobility sectors. However, the machining of these typically difficult-to-cut materials poses a challenge for conventional manufacturing technologies due to the high tool wear. Abrasive water jet (AWJ) machining is a promising alternative manufacturing technology for machining difficult-to-cut materials, since the tool wear is low and material independent. However, AWJ machining is limited regarding the producible geometries when conducting cuts through a material. This limitation can be resolved with AWJ milling operations which on the other hand are time-consuming. To approach this challenge, an enhanced AWJ milling operation is presented and investigated in this paper with the aim to expand the producible geometries. This operation consists of two kerfs, inserted from different sides of the workpiece, which intersect at their kerf ground. Consequently, a piece of material is separated without the cut material being entirely chipped. Thus, the operation possesses a high aggregated material removal rate. The investigations presented in this paper show and evaluate the effects that occur during the milling of kerfs with variable depths on titanium aluminide TNM-B1. Furthermore, a method to compensate these effects is introduced and thus the producible geometries for effective AWJ milling could be enhanced.

The Evaluation of the Properties of the Collision-Plate-Type Jet Mill for Dry Recycling of MOX Powder

A collision plate type jet mill is assumed to be a promising pulverizer that can control the particle size for nuclear fuel fabrication. The collision plate type jet mill consists of two modules, a classifier and a pulverizer. Coarse component of powder is cycled in the equipment and finally pulverized into objective particle size. In this report, simulated crushed powders were classified and pulverized step by step, and particle size distribution were compared. The collision plate type jet mil can produce objective size particles with less overgrinding.

Influence of holdup on gas and particle flow patterns in a spiral jet mill

Particle size reduction in spiral jet mills is induced by high velocity gas jets, causing interparticle and particle wall collisions leading to breakage. Despite extensive research on the design and operational parameters, the underlying mechanics of size reduction is still poorly understood. Discrete Element Method and Computational Fluid Dynamics are used here to analyse particle and fluid motions. A fast shearing dense particle bed is formed on the wall, with a transition to lean phase towards the centre of the mill. This necessitates four-way coupling of fluid and particle interactions for analysis. It is shown that increasing the depth of the particle bed reduces the fluid phase tangential velocity in the proximity of the classifier, as momentum is exchanged with circulating particles. The energy dissipation through particle collisions occurs mainly along the bed surface and in front of the grinding jet nozzles.

The Effect of Fine Dispersed Slag Component on the Slag Portland Cement Properties

Cement compositions based on slag Portland cement and fine dispersed slag component are considered. It has been established that the introduction of 1-3% fine slag obtained as a result of ultrafine grinding in a jet mill into the slag Portland cement composition provides an increase in the strength and structural characteristics of cement stone from the first day of hardening, which is important for slag cements. To ensure the fine dispersed slag particles’ stabilization in the cement matrix, the cement compositions were sealed with water with the addition of a plasticizer on either sulfa-naphthalene formaldehyde or polycarboxylate substrates in an amount of 0.5% of the cement composite content. In the research course it was found that in the initial stages of hardening and grade age, the strength of the samples containing a fine dispersed slag component and a sulfa-naphthalene formaldehyde-based plasticizer increased by 20%. When the cement composition is mixed with water with a polycarboxylate-based plasticizer, an increase in strength in the initial period of hardening by 60% is noted, at the vintage age - by 30%. At the same time, the porosity of the samples based on slag Portland cement with the addition of fine dispersed slag and one of the plasticizers in the initial period was reduced by 16-21%, at the vintage age - by 33-35%.

Simultaneous attainment of particle dispersion and surface modification of Al2O3nanoparticles via wet–jet milling

The good dispersion and chemical modification of alumina (Al2O3) nanoparticles as filler were simultaneously performed by a wet–jet milling (WJM) process to disperse the nanoparticles effectively in the polymeric composite. The grafting densities of Al2O3nanoparticles silane–coupling modified by WJM increased from 0.73 to 1.84 molecules/nm2in hexyltriethoxysilane, and from 0.65 to 1.09 molecules/nm2in 3–glycidoxypropyltriethoxysilane. Furthermore, the Al2O3nanoparticles were dispersed to the primary particle size. In addition, the mechanical properties of the Al2O3/epoxy composite prepared by the in–situ mixing process were higher than those prepared by conventional dry mixing process. As results, the mechanical properties of the Al2O3/epoxy composite could be improved by optimizing the dispersion, chemical modification of the nanoparticles and mixing process of nanoparticles and polymer.

Modified heat-insulating binder using jet-grinded waste of expanded perlite sand

The direction of many leading states is aimed at the development of the Arctic, so the creation of new generation thermal insulation materials is given priority. The novelty of the paper is to identify the scientific patterns of the influence of binder composites based on Portland cement and waste of expanded pearlite sand during joint jet grinding on the hydration mechanism and the structure of the plaster mortar. The grinding of heat-insulating binders in ball, vibration and vortex jet mills was studied. The features of hydrated phase formation and hardening of modified binders were studied taking into account the chemical, structural and morphological features of perlite wastes. Besides, the microstructural, morphological and thermal properties of the hardened binders at 28 days of curing were determined. For the first time, the scientific data were obtained on the properties of modified heat-insulating binder and plaster mortars based on it, obtained by mechanochemical jet activation. The results indicate that the jet activation of the modified binder based on Portland cement, waste from the production of expanded perlite sand and superplasticizer, contributes to the improvement of the physicomechanical properties of 28-days hardened binder: the compressive strength of 84.2 MPa and density of 2100 kg/m3. Based on the developed modified binder, the effective heat-insulating plaster mortars with heat conductivity of 0.051–0.059 W/(m·°C), a density of 240–260 kg/m3 and a compressive strength of 1.3–1.43 MPa were obtained, which meets the requirements. Technological route for the production of low-density plaster thermal insulation mix was developed.

Cyclodextrin-based metal-organic frameworks for pulmonary delivery of curcumin with improved solubility and fine aerodynamic performance.

Pulmonary drug delivery has attracted considerable attention in recent years. However, it is still a major challenge to deliver poorly water-soluble drugs to lungs with good solubility and fine aerodynamic performance. In this study, curcumin was loaded into cyclodextrin-based metal-organic frameworks (CD-MOFs) for pulmonary delivery. Compared with micronized curcumin prepared by jet milling, curcumin-loaded CD-MOFs (Cur-CD-MOFs) exhibited excellent aerodynamic performance, which was attributed to the unique porous structure and lower density of CD-MOFs. The dissolution test showed that the drug release rate of Cur-CD-MOFs was much faster than that of micronized curcumin. The all-atom molecular dynamic simulation showed that curcumin molecules were loaded into the hydrophobic cavities of CD-MOFs or entered into the large hydrophilic cavities to form nanoclusters. The elevated wettability of Cur-CD-MOFs and the unique spatial distribution feature of curcumin in porous interior of CD-MOFs might be favorable for the improved dissolution rate. The DPPH radical scavenging test showed that Cur-CD-MOFs had prominent antioxidant activities. Therefore, CD-MOFs were expected to be promising carriers for pulmonary delivery of poorly water-soluble drugs.

Assessment of the parameter identifiability of population balance models for air jet mills

Air jet mills are ubiquitous breakage devices not only in the pharmaceutical industry, but also in food and the toner manufacturing industry. The popularity of air jet mills arises due to its self-classifying, non-contaminating, and non-degrading operation while also maintaining a narrow particle size distribution. A popular approach towards mathematically modelling comminution devices like the jet mill is the population balance model framework. Population balance model for breakage is a semi-empirical framework in which several parameters are estimated from the experimental data. In many cases the experimental data available is insufficient, or of bad quality to guarantee the estimation of unique parameters. Thus it is imperative to assess the identifiability of such models to ensure that the chosen model structure is identifiable, both structurally and practically. In this study, we analyse the identifiability of the population balance model developed for the air jet mill. The identifiability analysis is carried out on basis of in-silico data generated by assuming certain parameter values to represent the true process. Based on several scenarios tested with data containing variety of information, it is shown that the model is practically non-identifiable for the situations in which the particle size measurement is available only at the end of the milling. The model becomes identifiable once continuous time measurements are available. The same holds for a reduced model with only the five breakage parameters.

Fluidized Bed Jet Milling Process Optimized for Mass and Particle Size with a Fuzzy Logic Approach.

The milling process is a complex phenomenon dependent on various technological and material parameters. The development of a fluidized bed jet milling model is of high practical significance, since milling is utilized in many industries, and its complexity is still not sufficiently recognized. Therefore, this research aims to optimize fluidized bed jet milling with the use of fuzzy logic (FL) based approach as one of the primary artificial intelligence (AI) methods. The developed fuzzy logic model (FLMill) of the investigated process allows it to be described as a non-iterative procedure, over a wide range of operating conditions. Working air pressure, rotational speed of the classifier rotor, and time of conducting the test are considered as inputs, while mass and mean Sauter diameter of the product are defined as outputs. Several triangular and constant linguistic terms are used in the developed FLMill model, which was validated against the experimental data. The optimum working air pressure and the test’s conducting time are 500 kPa and 3000 s, respectively. The optimum rotational speed of the classifier is equal to 50 s−1, considering the mass of the grinding product, and 250 s−1 for the mean Sauter diameter of the product. Such operating parameters allow obtaining 243.3 g of grinding product with the mean Sauter diameter of 11 µm. The research proved that the use of fuzzy logic modeling as a computer-based technique of solving mechanical engineering problems allows effective optimization of the fluidized bed jet milling process.

Cryogenic grinding performance of scrap tire rubber by devulcanization treatment with ScCO2

The cryogenic grinding performance of scrap tire rubber modified by devulcanization treatment in supercritical carbon dioxide (ScCO2) was studied with a fluidized-bed jet mill. Scrap tire rubbers devulcanized with various concentrations of devulcanizing reagents were ground to analyze the effect of the degree of devulcanization on the particle size distribution of the ground product. Population balance modeling based on selection and breakage functions was adopted to explore the evolution rule of the particle sizes in the grinding process. The results of the cryogenic grinding experiment show that the devulcanization treatment can promote particle size reduction and lead to the transformation of the grinding mechanism from abrasion to cleavage or fracture. Furthermore, Kapur function fitted by the population balance modeling was proposed with a cubic polynomial, and the calculation results agreed well with the experimental data.

Development and demonstration of a semi-automatic system for the bulk production of lithium titanate (Li2TiO3) pebbles by solid state reaction process (SSRP)

Abstract Lithium titanate ( L i 2 T i O 3 ) has been selected as ceramic solid tritium breeding materials for the ITER Test Blanket Module (TBM) and also for DEMO reactor. Looking towards its future demand in large quantities, it is necessary to develop a system for bulk production of the lithium titanate pebbles. A semi-automatic system for the bulk production of lithium titanate (Li2TiO3) pebbles by Solid-State Reaction Process (SSRP) has been designed, developed and successfully demonstrated. Raw materials; viz. lithium carbonate ( L i 2 C O 3 ) and titanium dioxide ( T i O 2 ) were mixed in required stoichiometry and fed into the continuous rotary synthesizer. L i 2 T i O 3 powder was synthesized in a continuous rotary synthesizer at 10 kg/h production capacity. This synthesized powder was milled in air jet mill. Milled powder was fed into the extrusion-spheronization based automated granulation system and green, spherical L i 2 T i O 3 pebbles of were produced at the production rate of 25 kg/h. Green spherical pebbles were dried, classified and sintered It was found that the synthesized L i 2 T i O 3 was in monoclinic β- L i 2 T i O 3 phase according to JCPDS No. 33-0831 and the properties of the sintered Li2TiO3 pebbles were well within the desired values. The process and various process parameters are discussed in details in this paper.

Aggregate and Disaggregate Production Planning, Material Requirement, and Capacity Requirement in PT. XYZ

Good production planning which suitable for the company in fulfilling demand will increase amount of profits. PT. XYZ is a company which produce talc powder in lots of type, such as Globe 107 sterile, Globe 107 non-sterile, Globe 207 sterile, Globe 207 non-sterile, Globe 307 sterile, Globe 307 non-sterile, Globe 407 sterile, Globe 407 non- sterile, Globe 507 sterile, and Globe 507 is non-sterile. PT. XYZ problem is they can’t fulfil all of their demands. Data used in this research are demand data from August 2015 until July 2019, company’s cost component, and capacity of each machine used in the production process. The aim of this research is to project the next 12 months demands, determine the best lot sizing technique, and determine the capacity requirement for PT. XYZ. Based on the research, the best forecasting method is using artificial neural network, the best lot sizing technique is using AWW method with total cost Rp 2.310.465.513. The capacity problems in crusher and sterile machine are solved by implementing overtime, while in jet mill, sieve screening, and packaging can reduce their working shift.

Numerical and experimental investigation on the depressurization capacity of a new type of depressure-dominated jet mill bit

Efficient cuttings transport and improving rate of penetration (ROP) are two major challenges in horizontal drilling and extended reach drilling. A type of jet mill bit (JMB) may provide an opportunity to catch the two birds with one stone: not only enhancing cuttings transport efficiency but also improving ROP by depressuring at the bottom hole. In this paper, the JMB is further improved and a new type of depressure-dominated JMB is presented; meanwhile, the depressurization capacity of the depressure-dominated JMB is investigated by numerical simulation and experiment. The numerical study shows that low flow-rate ratio helps to enhance the depressurization capacity of the depressure-dominated JMB; for both depressurization and bottom hole cleaning concern, the flow-rate ratio is suggested to be set at approximately 1:1. With all other parameter values being constant, lower dimensionless nozzle-to-throat-area ratio may result in higher depressurization capacity and better bottom hole cleaning, and the optimal dimensionless nozzle-to-throat-area ratio is at approximately 0.15. Experiments also indicate that reducing the dimensionless flow-rate ratio may help to increase the depressurization capacity of the depressure-dominated JMB. This work provides drilling engineers with a promising tool to improve ROP.

Effects of jet milling on W–10 wt.%Cu composite powder for injection molding

Ultrafine W–10wt.%Cu powders synthesized by thermo-chemical method have a good sinterability compared with the mechanically mixed powers, which are suitable for powder injection molding (PIM). The deagglomeration, however, is necessary to improve the flowability of the ultrafine powder to obtain a PIM feedstock with high powder loading. Jet milling (JM) was employed in this study to reduce the strong agglomerations among the particles, which were subsequently used for PIM. Results showed that JM was a proper process to modify the ultrafine powders for mass production with negligible contamination. JM modified the powder characteristics, including agglomeration, size distribution, surface morphology, and tap density, which considerably improved the rheological properties of feedstock. With the increasing of powder fraction in the feedstock from 46vol.% to 52vol.%, the shrinkage of the parts during sintering reduced accordingly, which is favorable for dimensional stability. The resulted W–10wt.%Cu sintered composite has excellent physical properties, such as high thermal and electric conductivity, as well as low coefficient of thermal expansion, which can be attributed to its near full density and homogeneous microstructure.

Application of recycled carbon-fibre-reinforced polymers as reinforcement for epoxy foams

The ever-increasing demand for carbon fibre reinforced polymers (CFRP) and stringent environmental legislation have driven the research into recycling and reusing the CFRP waste. This paper presents a mechanical recycling process of CFRP and the application of the recyclates as reinforcement for epoxy foams. The CFRP was mechanically processed using a jet mill. Up to 10 wt% of the CFRP recyclates, without separation of fibre-rich portion and resin-rich portion, was added into epoxy foams. The compressive modulus and strength of the epoxy foams increased from 288 MPa and 7.0 MPa, respectively, to 1060 MPa and 22.8 MPa, respectively, accompanied with an increase in foam density from 0.37 g cm−3 to 0.68 g cm−3. Consequently, the specific compressive modulus and strength (normalised against density) increased from 789 MPa cm3 g−1 and 19.1 MPa cm3 g−1 for unreinforced foam to 1563 MPa cm3 g−1 and 33.5 MPa cm3 g−1 for CFRP recyclates reinforced foam, representing a 98% and 75% improvement, respectively. These results demonstrate that the CFRP recyclates have excellent reinforcing ability for epoxy foams.

Assessing stress conditions and impact velocities in fluidized bed opposed jet mills

Fluidized bed opposed jet mills are capable of meeting the continuously growing demand for contamination-free fine particles. In this type of jet mill, the solid material is entrained and accelerated by expanding gas jets that are focused onto a focal point inside a fluidized bed. The resulting particle collisions induce breakage. The process is affected by the relative particle velocities and the number of particle–particle collisions. Clearly, both quantities are distributed. However, to date, neither relative particle velocities nor collision frequencies in such units have been determined. The present work introduces an innovative method to assess the stressing conditions in jet mills experimentally. To this end, mixtures of glass and ductile metal microspheres were used, with the latter employed in small amounts. Inter-particle collisions between the aluminum and glass spheres lead to the formation of dents on the microparticles. The size and number of these dents are associated with the individual collision velocities and overall collision frequencies. The correlation between dent size and collision velocity was obtained from finite element calculations based on empirical data. The proposed approach was validated using particle image velocimetry during secondary gas injection into a fluidized bed reactor. In this case the effect of the distance between two opposed nozzles was examined. For a lab-scaled fluidized bed opposed jet mill the effects of gas pressure and hold-up were investigated. Relative particle velocities were found to be significantly lower than the gas velocities, while the number of contacts per particle was determined to be extremely high.

In vivo efficacy of a dry powder formulation of ciprofloxacin-copper complex in a chronic lung infection model of bioluminescent Pseudomonas aeruginosa

A significant limitation of locally delivered treatments for chronic pulmonary infections is often the short residence time within the airways. Ciprofloxacin (CIP), for example, undergoes rapid absorption from the airway lumen. Previously, we demonstrated that the complexation of CIP with copper (CIP-Cu) reduces its apparent epithelial permeability and pulmonary absorption rate without affecting antimicrobial activity against Pseudomonas aeruginosa grown planktonically or as biofilms. This study aimed to evaluate the in vivo efficacy of CIP-Cu, prepared as a dry powder, in a chronic lung infection model. The powders were prepared by jet milling (CIP-HCl) and by spray drying (CIP-Cu). A bioluminescent strain of P. aeruginosa (PAO1::p16Slux) was used to prepare bacteria-loaded agar beads that were inoculated intratracheally to rats. The dynamics of the infection were monitored using luminometry. The bacteria/beads ratio was optimized to allow the highest luminescence signal and animal survival for 8 days. The efficacy of the treatment was evaluated by luminometry in addition to the end-point (Day 8) where colony counting was performed after lung harvesting. Luminescent P. aeruginosa entrapped in agar beads were useful to monitor the spatial development of the chronic lung infection in rats. The rats were treated with the dry powders in a nose-only inhalation exposure system (NOIES). CIP-Cu and CIP-HCl powders showed similar aerodynamic properties and comparable CIP lung deposition. However, treatment with CIP-Cu significantly (p < 0.01) reduced by 4-log the number of CFU of P. aeruginosa per lung in the chronic infection model, whereas CIP-HCl effect was not different from the untreated control group.

Investigating the Possibility of Fabricating Pr2Fe14B/α-Fe Composite Materials by Oxidation of the Pr–Fe–B Alloy in a Fluidized-Bed Jet Mill

The results of studying the possibility of fabricating the Pr2Fe14B/α-Fe composite materials by oxidation of the Pr–Fe–B alloy in a fluidized-bed jet mill are presented. It is shown that the use of the standard powder metallurgy technology supplemented by oxidation of the Pr–Fe–B alloy in a fluidized-bed jet mill for rare-earth magnetically hard materials (MHMs) makes it possible to fabricate Pr2Fe14B/α-Fe composites with high magnetic characteristics. It is established that, when fabricating finely dispersed powders according to the proposed technology in the argon medium containing 0.2 vol % oxygen, residual magnetic induction (Br) occurs with an insignificant drop in the coercive force (jHc). This effect causes a 5% increase in the maximal energy product (BH)max. The almost complete oxidation of the highly praseodymium phase PrxFe occurs with a further increase in the oxygen concentration, which leads to an abrupt drop in the coercive force and, consequently, a decrease in (BH)max. The particles of the α-Fe phase formed due to the oxidation of the magnetic material are formed at the boundaries between the grains of the Pr2Fe14B phase. Herewith, the highest magnetic characteristics are implemented if the α-Fe particles are separated from the grains of the main magnetic phase by thin interlayers of nonmagnetic phases, which makes it possible to hold a high level of jHc for sintered MHM samples. Herewith, the optimal thickness of the α-Fe layers is 0.2–0.3 μm. The α-Fe layers formed with an oxygen content of 0.3 vol % turned out considerably thicker (from 0.8 to 1.1 μm), which leads to an almost 10% decrease in the coercive force of the samples and 3–7% decrease in other magnetic parameters (Br, (BH)max). Thus, when controlling the oxygen content in the working medium of the jet mill, we can vary the thickness of the interlayer of the forming α-Fe phase in the Pr2Fe14B/α-Fe composite material and control its magnetic parameters.

Ultrafine grinding of wheat flour: Effect of flour/starch granule profiles and particle size distribution on falling number and pasting properties.

In the present paper, the properties of different ultrafine flour samples, including particle size distribution, damaged starch content, falling number, and pasting properties, were examined. The results indicated that the particle size decreased significantly after jet milling, as the rotation speed and grinding time increased, and the damaged starch content significantly increased as the size of the flour/starch decreased; this is in contrast to the significant decrease in falling number. Significant differences in pasting temperature were observed between straight‐grade flour (68.6°C) and five ultrafine flour samples (from 86.3 to 87.9°C). We also observed significant increases in peak viscosity, trough, breakdown viscosity, final viscosity, and setback as the flour particle size decreased from 43.07 µm to 25.81 µm (D50). The same parameters significantly decreased as the flour particle size decreased from 25.81 µm to 10.15 µm (D50). Correlation analysis identified a significant negative correlation between flour particle size (D50) and damaged starch content and pasting temperature, while a significant positive correlation was found with the falling number values. The results of this work may have an important impact on the quality of processed foods.