Jet Mill Research Articles

Influence of optimal conditions of ultrasonic dispersion on the stability of suspensions of finely ground slags

The preparation in the jet mill of finely ground slag (FGS) from the waste of metallurgical production granulated blast-furnace slag, the obtaining of slag suspensions, and the behavior of FGS particles in an aqueous dispersion medium are considered in the paper. It was found that FGS particles in the suspension form micelles of two types with negative (micelle 1) and positive (micelle 2) charges of FGS surface. To increase the aggregative and sedimentation stability of FGS particles in suspensions, studies were carried out using ultrasonic dispersion. The results of investigations on the detection of optimal dispersion parameters for slag suspensions are presented. It was found that in the absence of temperature control, the process of coagulation of slag particles is accelerated and aggregative and sedimentation stability of suspensions of FGS is reduced. The slag particles in the suspension form aggregates that lead to a deterioration of the strength characteristics of the cement stone using suspensions of FGS. Optimal parameters of ultrasonic dispersion of slag suspensions are established: the frequency of ultrasonic vibrations is equal to 44 kHz; the dispersion temperature is 25 ± 2 °C; the dispersion time is 15 min. It was found that the application of ultrasonic dispersion to slag suspensions with the observance of dispersion conditions can increase the aggregative and sedimentation stability of FGS suspension by 2-3 times in comparison with the mechanical mixing of suspensions. The strength of samples with suspensions of FGS prepared using UST under the recommended dispersing conditions increased by 19 to 39% in the first day; for 28 days of hardening - by 19 - 36%, which allows using slag suspensions in the production of cement composite materials and concretes based on them.

Properties and microstructure of blackcurrant powders prepared using a new method of fluidized-bed jet milling and drying versus other drying methods

ABSTRACTThis study compared the bioactive, physical and microstructural properties of blackcurrant powders prepared by an innovative fluidized-bed jet milling and drying method (FBJD) with those obtained by freeze drying (FD), convective drying (CD) and spray drying (SD). Bioactives such as vitamin C and anthocyanins were measured by HPLC, while antioxidant activity and total content of polyphenols were measured spectrophotometrically. A scanning electron microscope was used to establish the microstructure of both fresh fruits and powders. Water activity, water-holding capacity, water solubility index and pH were also determined. Retention of total polyphenols and vitamin C in FBJD powders was 88% and 79%, respectively, and 80% for both polyphenols and vitamin C in FD powders. Taking the above into account the FBJD method was found to be comparable to the FD method and compared favorably against the commonly used CD and SD methods.

Ways of a two-phase flow control in the jet mill ejector channels

Ways of a two-phase flow control in the jet mill ejector channels

Effective Heat-Insulating Solutions

The paper presents the results of the study devoted tothe reduction of perlite wastesin size in a vortex jet mill, as well as their reduction features. The bonding compositions were obtained at various ratios of cement and perlitesand wastes in a vortex jet mill at different reduction modes. Peculiarities of reduction processes were studied and technological and physical-mechanical properties of obtained bonding compositions were defined. The electron microscopy made it possible to study microstructures of cement stones received from taggedPortland cement and bonding compositions in a vortex jet mill. It was established that the open pores of cement bonding compositions prepared using perlite aggregates are always filled with new growths at various stages of collective growth. The microstructure of bonding compositions has dense structure due to rationally selectedcontent, use of effective mineral aggregates, i.e. perlite wastes thus creating additional substrates for the formation of an internal microstructure of a composite, mechanochemical activation of raw mix allowing obtaining composites with prescribed properties.

Electrostatic separation for sustainable production of rapeseed oil cake protein concentrate: Effect of mechanical disruption on protein and lignocellulosic fiber separation

Rapeseed oil cake (ROC) is a biomass of particular interest for biorefinery and food activities, due to its high protein, lignin, polyphenol and fiber contents. An environmental separation process combining ultrafine milling and electrostatic separation was recently developed for proteo-lignocellulosic plant fractionation. Several of the parameters of the fractionation process (milling mode, electrode voltage, charge, particle size, etc.) can affect the efficiency of protein separation and extraction. We assessed the impact of three different mechanical modes of milling — ball milling, impact grinding and jet milling — on the electrostatic separation (ES) of lignin and protein from ROC biomass. The initial biomass and the ES fractions were characterized and correlations were identified between particle colors and sizes and their protein and fiber contents. Mechanical grinding had a significant impact on the surface properties of the particles, influencing their charge and the electrostatic separation of lignin and protein from biomass. The combination of impact grinding and electrostatic separation appear the most efficient and effective technologies for rapeseed oil cake protein concentrate.

A new method for simulation of comminution process in jet mills

Recently, a computational fluid dynamics–discrete element method (CFD–DEM) model of comminution in a jet mill (Datta and Rajamani [1]) is developed. The model is based on a method previously defined by Kalman et al. [2] in which empirical comminution functions (strength distribution, selection, breakage, and fatigue functions) are implemented. Consequently, an accurate simulation of the size-reduction process is achieved. However, this simulation requires an overlong running time that might prevent its use in practical cases. Therefore, in this paper, we present a new procedure to describe the comminution process in a jet mill that can be applied in any size-reduction system.The new procedure uses the same material functions that are applied to any particle in the mill. However, three additional machine functions are required in order to implement the breakage procedure: impact velocity, frequency distributions, and classification functions. These machine functions are derived from the CFD–DEM simulations of the jet mill, where particle breakage is ignored; accordingly, the running time is considerably reduced. Moreover, once these distributions are defined for a particular mill configuration as a function of particle size and air flow rate, simple and fast simulations can be performed for a variety of operating conditions. Results of the new simulation method are comparable with the jet mill experimental results.

Visualization of flow conditions inside spiral jet mills with different nozzle numbers– Analysis of unloaded and loaded mills and correlation with grinding performance

Plenty of operational and geometric parameters have effects on spiral jet milling. Changes in the parameters cause distinctions in the flow conditions inside the mill and thereby also lead to consequences regarding the milled product. A new type of experimental spiral jet mill apparatus with almost entire optical accessibility enables a very convenient variation of the operational and geometric parameters as well as the determination of the flow conditions inside the spiral jet mill via non-invasive optical methods. Particle Image Velocimetry (PIV) measurements with diethylhexyl sebacat (DEHS) tracer droplets as well as solid barium sulphate micro particles were carried out to investigate the flow conditions inside the spiral jet mill. The differences between the net milling gas velocity fields and the velocity fields of loaded spiral jet mills were exposed. With the mill being loaded, the comminution zone decreases in the horizontal direction as well as decreases and deflects in the vertical direction. Besides, the analysis of the velocity fields inside the mill apparatus showed that decreasing milling nozzle numbers lead to increasing velocities inside the spiral jet mill, even if the mass flow rate of the gas supply is kept constant and the nozzle jet velocity is limited to sonic velocity at choked flow. With decreasing milling nozzle numbers, broader comminution zones and increasing lengths of the milling jets were investigated. As a consequence, a better grinding efficiency was expected and also confirmed with decreasing milling nozzle number by grinding experiments, as the new type of experimental apparatus was constructed in a fully operative way concerning the grinding ability.

Complex permittivity, permeability, magnetic and microwave absorbing properties of Ni2+ substituted mechanically milled U-type hexaferrites

The polycrystalline samples of Ni2+ substituted U-type hexaferrite; (Ba0.7Bi0.2)4(Co1−xNix)2Fe36O60 (0.25 ≤ x ≤ 1.00, in steps of 0.25) were prepared through solid state reaction method. XRD patterns, fitted with Le Bail method, revealed the formation of U-type hexaferrite phase in as-prepared samples. Scanning electron micrograph (SEM) indicates the presence of plate-like hexagonal particles with average sizes of ∼1–4 μm. In order to reduce the grain sizes down to nanoscale, two stage high energy mechanical jet milling was performed on x = 0.75 composition sample. The jet milled hexaferrite exhibits relatively smaller grain sizes (∼20–50 nm), lower saturation magnetisation (Ms∼38.6 emu/g) and higher coercivity (Hc∼590.2 Oe) in comparison to unmilled sample of same composition (x = 0.75). The jet milled sample, with nanoscale hexaferrite particles, exhibits excellent reflection loss (RL) of −43.8 dB (99.99% MW absorption) at 11.3 GHz frequency. In addition, the jet milled sample displays a broad frequency bandwidth (∼8.6 GHz) for RL ≤ −10 dB (90% MW absorption), extending over ∼9.1–17.7 GHz frequency range.

Coercivity enhancement and grain refinement in Nd-Fe-B sintered magnets with pyrite doping by jet milling

In this paper, the methods to solve the uniformity problem of sulfur (S) element were studied in pyrite-doped Nd-Fe-B sintered magnets. With pyrite addition, the coercivity was enhanced, except for the magnets with pyrite doped by arc melting. Sulphur loss existed during the arc melting process. When pyrite doped by ball milling, the coercivity increased from 1236.3 kA/m to 1327.0 kA/m. The average grain size decreased from 9.10 µm to 7.9 µm. As a drawback, obvious sulfur clusters were formed. Jet milling was an effective way to achieve uniform distribution of S element. In the magnets with pyrite doped by jet milling, clear and continuous grain boundary phases were formed with smaller grain size. Correspondingly, the average grain size further decreased to 6.7 µm. A coercivity enhancement of 13.4% (1401.8 kA/m) was obtained with slightly decreasing in remanence and maximum magnetic energy product.

In vitro/vivo assessment of praziquantel nanocrystals: Formulation, characterization, and pharmacokinetics in beagle dogs

To investigate the impact of particle size on in vitro/vivo performance of praziquantel (PZQ), nanocrystals (NCs) and microcrystals (MCs) of PZQ were prepared using the methods of wet milling and jet milling, respectively. PZQ NCs and MCs were characterized with dynamic light scattering, laser particle size analyzer, transmission electron microscopy, differential scanning calorimetry, X-ray powder diffraction and fourier transform infrared spectroscopy. The average diameters of PZQ NCs and MCs were 364.4 nm and 3.7 µm, respectively. No change in crystalline form was observed. Dissolution tests were performed in two different media, where the cumulative dissolution and dissolution rate of NCs were significantly improved in comparison with those of MCs and KANGQING® in non-sink condition. Similarly, oral bioavailability of PZQ NCs in beagle dogs was 1.68 (P < 0.05) and 1.83 fold (P < 0.01) higher than that of MCs and KANGQING®. Considering the advantages of in vitro/vivo performance and facile preparation, PZQ NCs may have a great application in the treatment of schistosomiasis.

A new solution to enhance cuttings transport in mining drilling by using pulse jet mill technique

In horizontal drilling, the cuttings bed is frequently formed to result in severe problems such as backing pressure, binding of bottom hole assembly (BHA) and even sticking of tool. Practice and research show that the smaller particle size is, the more favorable to carry out from bottom of hole in extended reach well or horizontal well. This paper presented a new solution to enhance cuttings transport in mining drilling through a new type of bit called pulsed mill bit (PMB) by using pulse jet mill technique. It provides a promising solution to enhance the efficiencies of rock breaking and cuttings carrying for pulsed jet, sucking cuttings to decrease the chip hold down effect, and reducing cuttings’ diameter to eliminate cuttings bed. The design was supported by the calculation models of Helmholtz resonator natural frequency, optimal drilling fluid flow rate of resonator, drilling fluid flow velocity in forward jet channel, critical impact velocity of cuttings and minimum length of the accelerating cavity. Meanwhile, factors affecting optimal drilling fluid flow rate, critical impact velocity of cuttings and minimum length of accelerating cavity were investigated. Case study showed a good consistency between the calculation results and the related theories. It is concluded that optimal drilling fluid flow rate increases with the increase of inlet and outlet cavity’s diameter, and decreases with the increase of the diameter of the resonant cavity. Critical impact velocity of cuttings increases with the energy conversion factor (β) and ROP, while decreasing with the final size of the cuttings (dt). This effect is obvious when β<0.2, ROP <3.048 m h−1 and dt<0.3 mm. Minimum length of the accelerating cavity decreases with the increase of the resonator’s natural frequency and separation coefficient (α) of drilling fluid flow rate. This study provides a promising solution to remove cuttings bed in horizontal well.

A supersonic target jet mill based on the entrainment of annular supersonic flow.

Jet mill is an apparatus that produces superfine powder and is widely used in various industries. In this work, a new supersonic target jet mill based on aerodynamic theory is presented according to the flow field of a traditional jet mill. An annular supersonic flow produced by an annular converging-diverging nozzle is used to entrain the central particle flow by the shear mechanism in this new supersonic target jet mill. Then, the particle beam concentrating in the flow center impacts the target with high kinetic energy after the entrainment of the supersonic flow. An apparatus of the annular supersonic target jet mill was created to validate the theoretical design. Two types of experiments were implemented to estimate its performance. The validation experiments confirmed that the gas speed in the collision chamber was approximately 600 m/s and the supersonic flow could deliver a kinetic energy of approximately 180 J/s to the particles. The particle size reduction of boroncarbide (B4C) and silica (Si) in the collision tests showed that the accelerated particles concentrated in the supersonic flow center collided on the targets precisely with high collision energy.

Effect of jet milling on the physicochemical properties, pasting properties, and in vitro starch digestibility of germinated brown rice flour

Germinated brown rice (GBR) flours were prepared by hammer milling and jet milling. The effect of the milling on the physicochemical and pasting properties of the resultant flours were investigated. The jet milling of GBR resulted in flour with different particle sizes, which were air-classified into coarse and fine size fractions. As the particle size decreased, the amount of damaged starch increased. The WAI, WSI, and oil absorption of the jet-milled GBR flour was slightly lower than that of the hammer-milled flour. Increased α- and β-amylase activities were observed in the coarse fraction of the jet-milled GBR flour compared with the hammer-milled and jet-milled fine fractions. The RVA viscosity profiles of the fine fraction of the jet-milled GBR flour were significantly higher than those of the hammer-milled or the coarse fraction of the jet-milled GBR flour. Compared with the hammer-milled flour, jet milling increased in vitro starch hydrolysis.

Predicting breakage behavior and particle size of bronze and cast iron machining chips pulverized by jet milling

It has been proposed that the breakage behavior of particulate materials can be described by two material parameters fmat and Wmin. fmat describes the resistance of the material to fracture in impact pulverization and Wmin characterizes the specific energy which a particle can absorb without fracture. It is shown in this study that this concept can be used to quantify breakage behavior of bronze and cast iron chips in jet milling process and also to predict particle size of the jet milled product. Different tin bronze and cast iron chips with varying initial size were pulverized in a target plate jet mill with different velocity. fmat was found to be in the range of 0.06–0.09 and 0.18–0.25 for bronze and cast iron alloys, respectively. For the cast iron alloys fmat increased with increasing content of carbon and silicon. Similarly, for the bronze alloys, fmat increased with increasing tin content. An equation was developed to predict mean particle size of the jet milled chips as a function of the kinetic energy, initial chip size and material parameters. The experimental results of various alloys confirmed that the mean particle size after single and multiple impacts were accurately predicted.

Controlling the structure of arborescent carbon nanotube networks for advanced rubber composites

We propose a method for controlling the arborescent structure of long carbon nanotubes (CNTs) to harness their intrinsic properties in advanced rubber composites. Our method of structural control was based on a wet-jet mill to vary the shear forces (20–150 MPa) applied to aligned single-wall CNTs in solution. As the pressure of jet mill increased, the resulting suspended CNTs changed from agglomerates of bundled “trunk”-like structures to a CNT “mesh”-like structure with a high degree of disentanglement and absence of the “trunk”-like structures. The sizes of the CNT agglomerates became small and the number increased with the pressure of jet mill, indicating that smaller “mesh”-like CNT structures were formed with shortening of CNTs. This knowledge was used to increase the electrical conductivity of a CNT-rubber composite, highlighting the need to optimize the disentanglement state of the CNTs for application towards composite materials. Thus we successfully fabricated a CNT rubber with higher electrical conductivity (1.4 × 10−2 S/cm) by balancing the disentanglement and shortening of the CNTs at the jet mill pressure of 120 MPa. On the other hand, the higher pressure of 150 MPa resulted in the lowest conductivity (7.5 × 10−4 S/cm) due to more extensive shortening of CNTs.

Steam jet mill—a prospective solution to industrial exhaust steam and solid waste

Bulk industrial solid wastes occupy a lot of our resources and release large amounts of toxic and hazardous substances to the surrounding environment, demanding innovative strategies for grinding, classification, collection, and recycling for economically ultrafine powder. A new technology for grinding, classification, collection, and recycling solid waste is proposed, using the superheated steam produced from the industrial exhaust steam to disperse, grind, classify, and collect the industrial solid waste. A large-scale steam jet mill was designed to operate at an inlet steam temperature 230-300°C and an inlet pressure of 0.2-0.6MPa. A kind of industrial solid waste fluidized-bed combustion ashes was used to grinding tests at different steam temperatures and inlet pressures. The total process for grinding, classification, and collection is drying. Two kinds of particle sizes are obtained. One particle size is d50 = 4.785μm, and another particle size is d50 = 8.999μm. For particle size d50 = 8.999μm, the inlet temperature is 296°C and an inlet pressure is 0.54MPa for the grinding chamber. The steam flow is 21.7t/h. The yield of superfine powder is 73t/h. The power consumption is 3.76kWh/t. The obtained superfine powder meets the national standard S95 slag. On the basis of these results, a reproducible and sustainable industrial ecological protocol using steam produced by industrial exhaust heat coupled to solid waste recycling is proposed, providing an efficient, large-scale, low-cost, promising, and green method for both solid waste recovery and industrial exhaust heat reutilization.

Numerical simulation on the electric charge decay of micropowder prepared by jet milling/electrostatic dispersion

Preparation of micropowder by the combination of jet milling and electrostatic dispersion is an innovative method. By means of this method, it can achieve the dual goal of producing fine powders and maintaining the dispersiveness. While, the electric charge carried by particles will vanish gradually when refined powder is stored in air, which lead to that the dispersion effect of charged particles will weaken and even disappear. In this paper, a model of electric charge decay of charged particle in air is established, the influence of particle size, relative humidity of the atmosphere, relative permittivity and initial q/m i.e. charge to mass ratio of charged micropowder on the decay process are evaluated. In addition, the non-contact measuring experiment is designed to verify the simulation results as well. The results indicate that the q/m of charged particle decreases as exponential relationship with the storage time, the remained q/m and its decay rate of particle with smaller size is lower during the whole process. The decay rate of charged powder increases with the increase of relative humidity in air. Particles with higher relative permittivity has a lower decay rate of charge, and the decay rate of particles with larger initial charge to mass ratio would also be higher. The numerical results of the model could reveal the rules in electric charge decay process well in general.

Influence of Fluidized Bed Jet Milling on Structural and Functional Properties of Normal Maize Starch

Normal maize starch samples with moisture contents of 11.24%, 6.18%, and 1.5% are ground using a fluidized bed jet mill at classifier frequencies of 2400, 3000, 3600, and 4200 to produce micronized starch powder. The changes in structural and functional properties of the starch after jet milling process are studied. The particle size of starch significantly (p &lt; 0.05) decreases after jet milling and as the classifier frequency increases. Also, the bulk and tap density decreases; while the specific surface area increases and the flowability of the milled samples becomes quite poor as the classifier frequency increases. The microscopy analysis shows that the jet milling destroys the crystalline areas and promotes amorphous areas of starch granules. The micronized starch samples show a significant (p &lt; 0.05) increase in their water solubility, swelling power, water and fat holding capacities, and pasting temperature compared with native starch. However, a decrease in viscosity parameters of starch is found after jet milling and as classifier frequency increases. The initial moisture content of starch shows a slight effect on the functional properties of the micronized starch. The obtained results suggest that modified starch can be produced by fluidized bed jet milling.

超微粉分級機搭載 カウンタジェットミルAFG-CRS

超微粉分級機搭載 カウンタジェットミルAFG-CRS

Properties of flour films as affected by the flour's source and particle size

Wheat (W) and rye flour (R, R1 and R2) films were developed. The rye flours used differed in their particle size. R1 and R2 resulted from jet milling of the R flour at two different feed rates. The mean particle size of W, R, R1 and R2 flours was 173.87, 100.91, 54.59 and 35.66 μm, respectively. Glycerol was used as plasticizer at concentrations of 0.5, 0.7 and 1 g/g of flour. Films made from mixtures of flours (50:50 w/w) were also studied in the presence of 0.7 g glycerol/g of flour. Colour, moisture content, solubility, thickness, viscosity, microstructure and mechanical properties were assessed. In most cases the films were homogeneous. Film moisture content, thickness, opacity and mechanical properties were correlated to glycerol concentration. Particle size was found important for the mechanical properties. Wheat films were lighter ([L*] ≈ 49) and less opaque (135). For both single and composite films, moisture content varied from 24 to 35%, solubility from 43.5–58%, opacity from 135 to 371, thickness from 0.66–0.72 mm and mechanical strength from 0.68–1.7 MPa. All film-forming solutions exhibited shear thinning behaviour. Wheat flour dominated most of the studied properties in composite films. Rye films were more opaque, with relatively high solubility but greater mechanical strength.