Showing papers on "Jet mill published in 2002"

Production of Starch with Very Low Protein Content from Soft and Hard Wheat Flours by Jet Milling and Air Classification

Abstract: Jet milling is a fluid energy impact-milling technique generally used for the ultrafine reduction of higher value materials. The efficiency of jet milling combined with air classification appears very efficient to separate starch from other wheat flour aggregate components and to produce wheat starch with very low residual protein content. Indeed, residual protein content of the starch-rich fraction can be reduced to <2% db with a series of successive grinding and air classification operations. Lipid and pentosan contents were also reduced in the starch-rich fraction. Nevertheless, jet milling cannot eliminate grinding differences observed between different types of wheat. Wheat hardness continues to have an effect on milling and classification yields and on the composition of air classification fractions. To obtain starch-rich fraction with only 2% protein content, hard wheat flour required a series of at least five grinding steps, whereas only three steps are necessary for soft wheat flour. Und...

DEM Simulation of Particle Comminutionin Jet Milling

Abstract: A combined discrete element method (DEM) and CFD numerical model was developed to simulate particle comminution in a jet mill. The DEM was used to simulate the motion of the particles in the gas flow. For this, the compressible Reynolds Averaged Navier-Stokes (RANS) equations were used to describe the gas flow field inside a given size's jet mill. Ghadiri's models for breakage and chipping were implemented in the simulation to define the reduction of the particle's size during jet milling. The size distributions of the particles after grinding were obtained numerically. The prediction of the numerical simulation for the median particle size d 50 after grinding was qualitative compared with experimental results for the different operating conditions (i.e., feed rate, angle of grinding nozzles, volumetric rate of grinding air, etc.). The comparison shows good agreement with the experimental observation. The results shows that the feed rate, angle of feeding nozzle, and feeding air's flow rate have more infl...

Ultrafine grinding using a fluidized bed opposed jet mill: effects of feed load and rotational speed of classifier wheel on particle shape.

Abstract: Circularity, aspect ratio, modelx, and pellips were employed to study the effects of process parameters, namely varying feed loads and rotational speeds of the classifier wheel, of the fluidized bed opposed jet mill on the shape of the micronized particles produced. The Shapiro–Wilk statistical test showed that 80.0% of the shape distributions of the four descriptors were not normal. Therefore, the Kruskal–Wallis test, which is a nonparametric statistical test, was employed to analyze the data. Micronized particles were more spherical and less elongated, as indicated respectively by higher median circularity and lower median modelx values when compared to unmilled lactose. These descriptors were able to indicate that the particles had been micronized. When feed loads of 250 and 350 g were used, increasing the rotational speed of the classifier wheel was found to bring about a decrease in span values of all the shape descriptors, indicating that the micronized particles were more uniform in shape. ...

Raw feed feeding device of jet mill

Abstract: A particle feed apparatus is combined with a jet mill and has a particle feeder for feeding particles to an air injector that injects particles together with particle carrying air into the jet mill. The particle feed apparatus is a closed structure isolated from the environment. The use of the closed particle feed apparatus prevents the backflow of dust-loaded air that occurs in a milling system formed by combining a jet mill and an open particle feed apparatus. The use of the closed particle feed apparatus improves the working environment, enhances the milling ability of the jet mill and facilitates operations.

α-ALUMINA FOR CORDIERITE CERAMIC, METHOD OF PRODUCING THE SAME, AND STRUCTURE OF CORDIERITE CERAMIC USING THE α-ALUMINA

Abstract: PROBLEM TO BE SOLVED: To provide α-alumina usable for producing cordierite ceramics having a low coefficient of thermal expansion and high thermal shock resistance and exhibiting small variance in characteristics, and to provide a method of producing the α-alumina and a structure of the cordierite ceramics using the α-alumina SOLUTION: The α-alumina for the cordierite ceramics having a secondary particle size of 40 to 70 μm, a primary particle size of 15 to 30 μm and a BET specific surface area of 05 to 15 m 2 /g is pulverized by means of a jet mill The pulverized α-alumina comprises alumina particles of ≤3 μm in an amount of ≤30 mass % and alumina particles of ≤15 μm in an amount of ≥75 mass % in relation to a particle size distribution profile of the α-alumina, and has a mean particle size of 4 to 10 μm and a +90 μm sieve residue of ≤50 ppm by mass COPYRIGHT: (C)2003,JPO

Engineering Model of Friction of Gas‐Solids Flow in a Jet Mill Nozzle

Abstract: In this study we develop a model for estimating particle friction against the wall of a jet mill nozzle. The computation is reduced to a definition of conventional force acting on particles in a polydispersed stream. It is assumed that energy losses due to friction are caused by multiple particle collisions against the nozzle walls. The proposed model is oriented to calculating jet mill nozzles and is much simpler than previously applied methods. A parametric study of the proposed model was carried out and the effect of particle friction on particle and gas velocities was derived.

Particle feed apparatus for jet mill

Abstract: A particle feed apparatus is combined with a jet mill and has a particle feeder for feeding particles to an air injector that injects particles together with particle carrying air into the jet mill. The particle feed apparatus is a closed structure isolated from the environment. The use of the closed particle feed apparatus prevents the backflow of dust-loaded air that occurs in a milling system formed by combining a jet mill and an open particle feed apparatus. The use of the closed particle feed apparatus improves the working environment, enhances the milling ability of the jet mill and facilitates operations.

Designing a Jet Mill Nozzle of Maximum Efficiency

Abstract: A method of calculation for an accelerating jet mill nozzle profile which provides a maximum kinetic energy for solid particles at the nozzle outlet, is developed. The gas-solid flow in the nozzle is described by a well-known one-dimensional model. The effect of both solid loading and particle size on the optimal nozzle profile, as well as on the main flow parameters is studied. Distribution of particle velocities in the computed optimal nozzle is compared to that in a conical convergent-divergent nozzle of the same length. Computations demonstrated that optimized nozzles are profitable for fairly low solid loadings. The kinetic energy of solids at the optimized nozzle outlet is about 50% higher than that in a conical nozzle if the solid/gas mass flow ratio equals unity.

Fluidized bed type opposed jet mill

Abstract: PROBLEM TO BE SOLVED: To provide a fluid bed type opposed jet mill the constituent devices of which are easily accessible by an operator and accordingly, which is capable of simply and completely being cleaned without requiring much labor by modifying a conventional similar jet mill provided with a grinding vessel, a plurality of opposed jet nozzles, a classifier, a supporting and driving device, a material charging device and a very fine material conveyance section. SOLUTION: In this jet mill, a classifying wheel and a supporting and driving device are integrally formed into one constituent unit and the constituent unit is attachably and detachably connected to a grinding vessel and also, can be moved relatively to the grinding vessel with a kinematic device so that the classifying wheel is passed through a very fine material conveyance section and upwardly separated from the grinding vessel, however, the very fine material conveyance section is still retained in the connected state to the grinding vessel.

Cover gap adjustment device, and jet mill

Abstract: PROBLEM TO BE SOLVED: To provide an opposed-jet impact type jet mill having a cover gap (the gap between the lower end face of a classification rotor of a cover of the mill and the opening of a pulverized and classified powder conveyance means of a main body of the mill) adjustment device, which is capable of being used for pulverization, classification, etc., of a powder and easily performing adjustment of the above gap and also by which a pulverized and classified powder hardly contaminated with impurities can be obtained. SOLUTION: This mill is provided with: a cover 20 having a classification rotor 4 which is used for classifying a raw material powder pulverized with high-pressure gas streams opposed to each other and connected to a main body of the cover 20 in a upwardly and downwardly movable manner and provided at its lower end with a flat face 4f perpendicular to a rotary shaft 4b and also with an exposed flat face 4a that is positioned outside the main body of the cover 20 so as to be opposite and parallel to the face 4f; a pulverizer main body 10 having within it, a powder conveyance means 5 which is provided with an opening 5a that is formed opposite and parallel to the face 4f and used for introducing the powder classified with the rotor 4, and intended for conveying the power introduced through the opening 5a; and a displacement measurement means 30 for measuring the distance between the means 30 itself and the exposed flat face 4a and determining the difference of the measured distance from an initially set distance.

원보 : Ursodeoxycholic acid 의 무정형 초미립자제제들의 CCI4 유도 간손상 생쥐에 대한 보호 효과

Abstract: The particle size of medicinal materials is an important physical property that affects the pharmaceutical behaviors such as dissolution, chemical stability, and bioavailability of solid dosage forms. The size reduction of raw medicinal powder is needed to formulate insoluble drugs or slightly soluble medicines and to improve the pharmaceutical properties such as the solubility, the pharmaceutical mixing, and the dispersion. The objective of the present study is to evaluate physiological activity of amorphous and nano-particle preparations of insoluble drug, ursodeoxycholic acid (UDCA), which were made by three types of fine grinding mills. The change of physical properties of ground UDCA was conformed by Mastersiger microplus and X-ray diffraction. We have investigated hepatoprotective effects of the nano-particle preparations of UDCA by planetary mill, vibration rod mill and jet mill in CCl_4-induced oxidatively injured mouse liver. The results showed that nano-particle preparations of UDCA all decreased reactive oxygen sepecies generation and lipid peroxidation in CCl_4-induced oxidative stress mice. Among them, nano-particle preparations by vibration rod mill and jet mill showed more significantly hepatoprotective effects compared to intact UDCA and planetary millground UDCA. These results suggest that ground UDCA with vibration rod mill and jet mill shows a high amorphous state and the improved dissolution.