scholarly journals The Effect of Very Cohesive Ultra-Fine Particles in Mixtures on Compression, Consolidation, and Fluidization

Processes ◽  
2019 ◽  
Vol 7 (7) ◽  
pp. 439
Author(s):  
Abbas Kamranian Marnani ◽  
Andreas Bück ◽  
Sergiy Antonyuk ◽  
Berend van Wachem ◽  
Dominique Thévenin ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Binary Mixture ◽  
Packing Density ◽  
Fine Particles ◽  
Bulk Material ◽  
Applied Pressure ◽  
Gas Velocity ◽  
History Effect ◽  
Ultra Fine Particles ◽  
Linear Manner

This paper focuses on the effect of ultra-fine ( d < 10 µm) powders in mixtures with fine ( d < 100 µm) bulk material on compression processes and also evaluates the re-fluidization behavior of the compressed bed (history effect). Achieving this goal, different mixtures of fine and ultra-fine Ground-Carbonate-Calcium were compressed at three pressure levels. The results show that by increasing the applied pressure, the compressibility decreases due to change in compaction regime. Subsequently, for the higher pressure, the slope of packing density versus applied stress curves is noticeably different. However, this slope does not depend on the size distribution of mixtures, but on the type of material. Comparing fluidization and re-fluidization curves (bed pressure drop vs. gas velocity) shows an increase in the maximum bed pressure drop ( Δ P p e a k ) for re-fluidization. By increasing the portion of ultra-fine particles in the binary mixture, Δ P p e a k increases in a non-linear manner. Furthermore, the incipient fluidization point moves to a higher gas velocity. After compression, the peak of the bed pressure drop in the re-fluidization test happens at a lower gas velocity than in the initial fluidization test. Thus, the slope of the loading curve is much larger for re-fluidization. The opposite is observed for the unloading curves.

Experimental Investigation of Fine Particles Classification Properties in Gas-Solid Multilevel Particular Fluidization Tower

2013 ◽  
Vol 803 ◽  
pp. 300-307
Author(s):  
Hui Yang ◽  
Dong Yu Wan ◽  
Chang Qing Cao
Keyword(s):  
Pressure Drop ◽  
Quartz Sand ◽  
Fine Particles ◽  
Solid Phase ◽  
Sand Particle ◽  
Gas Velocity ◽  
Experimental Conditions ◽  
Cross Sectional ◽  
Superficial Gas Velocity ◽  
Rectangular Body

The fine particles classification properties in a gas-solid multilevel particular fluidization tower (MPFT) with the rectangular body of 2.4 m in height and 0.032 m2in cross sectional area, five tower plates of 0.39 m in length and 0.08 m in width and 0.005 m in thickness were investigated using two different properties particles, talc particle and quarts sand particle, as solid phase and air as gas phase. It was found from the experimental results that the pressure drop increases with increasing superficial gas velocity. And the spread of pressure drop was gradually decreased from top to bottom in the tower. The grade efficiency for talc powder particle (dp= 10 μm) attained 78.78% and d95 reached 12.84 μm atUg= 0.122 m/s. Meanwhile, for quartz sand particle (dp= 10 μm), the grade efficiency attained 92.80% and d95 reached 12.58 μm atUg= 0.139 m/s. The grade efficiency for the two different properties particles both increases with decreasing feed rate at these experimental conditions in this work. The particle size distribution range of overflow particle increases a little with increasing circulating gas velocity. The grade efficiency for quartz sand particle (dp= 10 μm) dropped from 92.56% to 82.70% with increasing different regurgitant rates from 0 to 12.5 kg/h.

scholarly journals The Effect of the Presence of Very Cohesive Geldart C Ultra-Fine Particles on the Fluidization of Geldart A Fine Particle Beds

Processes ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 35 ◽  
Author(s):  
Abbas Kamranian Marnani ◽  
Andreas Bück ◽  
Sergiy Antonyuk ◽  
Berend van Wachem ◽  
Dominique Thévenin ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Fine Particles ◽  
Mean Values ◽  
Fine Powders ◽  
Group A ◽  
Total Mixture ◽  
The Subject ◽  
Materials Used ◽  
Ultra Fine Particles ◽  
Particle Beds

The effect of the presence of ultra-fines (d < 10 μm) on the fluidization of a bed containing fine particles (d < 100 μm), is the subject of this paper. Practically, it can happen due to breakage or surface abrasion of the fine particles in some processes which totally changes the size distribution and also fluidization behaviour. The materials used in this study are both ground calcium carbonate (GCC); fine is CALCIT MVT 100 (Geldart’s group A) and ultra-fine is CALCIT MX 10 (group C). The experimental results for different binary mixtures of these materials (ultra-fines have 30%, 50%, or 68% of the total mixture weight) show that the physical properties of the mixtures are close to those of pure ultra-fine powders. Using mean values of the bed pressure drop calculated from several independent repetitions, the fluidization behaviour of different mixtures are compared and discussed. The fluidization behaviour of the mixtures is non-reproducible and includes cracking, channelling and agglomeration (like for pure ultra-fine powders). Increasing the portion of ultra-fine materials in the mixture causes a delay in starting partial fluidization, an increase in the bed pressure drop as well as a delay in reaching the peak point.

Minimum Fluidization Velocity of Fine Particles

2008 ◽  
Vol 591-593 ◽  
pp. 335-340 ◽  
Author(s):  
Cássia Regina Cardoso ◽  
Carlos Henrique Ataíde ◽  
J.M. Abreu
Keyword(s):  
Pressure Drop ◽  
Fine Particles ◽  
Zinc Powder ◽  
Gas Velocity ◽  
Minimum Fluidization Velocity ◽  
Fluidization Velocity ◽  
Glass Spheres ◽  
Minimum Fluidization ◽  
Industrial Unit ◽  
Superficial Gas Velocity

The minimum fluidization velocity is an important parameter in the design and operation of an industrial unit of fluidization. In the present work the minimum fluidization velocities of fine particles were obtained through two experimental methodologies. The first one is the classic procedure to determine that parameter analyzing the diagram of medium pressure drop in the bed in function of the superficial gas velocity, during the defluidization of the bed. And the second is the technique of identifying the minimum fluidization velocity interpreting the behavior of the normalized standard deviation of the pressure drop in the bed. A cylindrical bed of transparent acrylic was used in the process and the used particles were glass spheres, FCC and zinc powder. To compare the precision of the two methodologies some equations that predict the minimum fluidization velocity were used.

Studies of copper selenide ultrafine particles by newly developed gas evaporation method

1990 ◽  
Vol 48 (4) ◽  
pp. 306-307
Author(s):  
Chihiro Kaito ◽  
Yoshio Saito
Keyword(s):  
Crystal Structure ◽  
Ultrafine Particles ◽  
Fine Particles ◽  
Production Method ◽  
Atmospheric Temperature ◽  
Copper Selenide ◽  
Quartz Boat ◽  
Selenium Vapor ◽  
Ar Gas ◽  
Ultra Fine Particles

The direct evaporation of metallic oxides or sulfides does not always given the same compounds with starting material, i.e. decomposition took place. Since the controll of the sulfur or selenium vapors was difficult, a similar production method for oxide particles could not be used for preparation of such compounds in spite of increasing interest in the fields of material science, astrophysics and mineralogy. In the present paper, copper metal was evaporated from a molybdenum silicide heater which was proposed by us to produce the ultra-fine particles in reactive gas as shown schematically in Figure 1. Typical smoke by this method in Ar gas at a pressure of 13 kPa is shown in Figure 2. Since the temperature at a location of a few mm below the heater, maintained at 1400° C , were a few hundred degrees centigrade, the selenium powder in a quartz boat was evaporated at atmospheric temperature just below the heater. The copper vapor that evaporated from the heater was mixed with the stream of selenium vapor,and selenide was formed near the boat. If then condensed by rapid cooling due to the collision with inert gas, thus forming smoke similar to that from the metallic sulfide formation. Particles were collected and studied by a Hitachi H-800 electron microscope.Figure 3 shows typical EM images of the produced copper selenide particles. The morphology was different by the crystal structure, i.e. round shaped plate (CuSe;hexagona1 a=0.39,C=l.723 nm) ,definite shaped p1 ate(Cu5Se4;Orthorhombic;a=0.8227 , b=1.1982 , c=0.641 nm) and a tetrahedron(Cu1.8Se; cubic a=0.5739 nm). In the case of compound ultrafine particles there have been no observation for the particles of the tetrahedron shape. Since the crystal structure of Cu1.8Se is the anti-f1uorite structure, there has no polarity.

scholarly journals New Maskless Film Making Method Using Ultra Fine Particles.

Materia Japan ◽  
1995 ◽  
Vol 34 (4) ◽  
pp. 455-460 ◽  
Author(s):  
Eiji Fuchita ◽  
Masaaki Oda ◽  
Chikara Hayashi
Keyword(s):  
Fine Particles ◽  
Ultra Fine Particles ◽  
Film Making

Ultrafeine Partikel im Abgas von Humankremationsanlagen/Ultra-fine particles in the flue gas of human crematories

Gefahrstoffe ◽  
2020 ◽  
Vol 80 (01-02) ◽  
pp. 19-24 ◽  
Author(s):  
M. Köhler ◽  
A. Ohle ◽  
M. Beckmann ◽  
S. Steinau ◽  
F. Tettich ◽  
...  
Keyword(s):  
Flue Gas ◽  
Fine Particles ◽  
Ultra Fine Particles

Der Anteil an Kremationen (Feuerbestattungen) nimmt in Deutschland seit Jahren zu und umfasst bereits mehr als 65 % aller Bestattungen. Grenzwerte für die Emissionen von Feinstaub oder die Anzahl ultrafeiner Partikel (UFP) existieren nicht und bisher sind auch keine systematischen Untersuchungen bekannt, welche Partikelemissionen in Krematorien auftreten. Daher kann zum aktuellen Zeitpunkt nicht beurteilt werden, ob es sich bei Krematorien um nennenswerte Feinstaubquellen handelt. Um diese Lücke zu schließen, wurden die reingasseitigen UFP-Konzentrationen in zehn Krematorien unterschiedlichen Bau- bzw. Modernisierungsjahres und mit verschiedenen Abgasreinigungstechnologien gemessen. Über die Kremationsdauer gemittelte UFP-Konzentrationen zwischen 1,19 · 10³ und 4,26 · 107 cm–3 wurden erfasst. Die höchsten Konzentrationen zeigten sich bei Anlagen mit Flugstromverfahren, deren Filtereinheiten unmittelbar vor der nächsten Revision standen. Bei Anlagen gleichen Typs mit gewarteten Filtereinheiten lag die mittlere UFP-Konzentration zwei Größenordnungen darunter.

Vaporization and Ultra-Fine Particle Generation during the Plasma Spraying Process

1997 ◽  
Author(s):  
K.A. Gross ◽  
P. Fauchais ◽  
M. Vardelle ◽  
J. Tikkanen ◽  
J. Keskinen
Keyword(s):  
Fine Particles ◽  
High Concentration ◽  
Thermal Spray Process ◽  
Particle Generation ◽  
Spray Process ◽  
Ultra Fine Particle ◽  
Fast Cooling ◽  
Ultra Fine Particles ◽  
Plasma Spraying Process ◽  
Very High

Abstract The thermal spray process melts powder at very high temperatures and propels the molten material to the substrate to produce a coherent deposit. This heating produces a certain amount of vaporization of the feedstock. Upon exiting the plasma plume the fast cooling conditions lead to condensation of the vapor. An electrical low pressure impactor was used to monitor the concentration of ultra-fine particles at various radial and axial distances. Metal, namely iron powder, showed very high concentration levels which increase with distance. Ultra-fine particles from ZrO2-8Y2O3 reached a peak concentration at 6 cm. Use of an air barrier during spraying decreases the population of ultra-fine particles facilitating the production of a stronger coating.

scholarly journals Welding, Bonding, Brazing. Part II. Titanium Brazing with Ultra Fine Particles.

Shinku ◽  
1996 ◽  
Vol 39 (6) ◽  
pp. 302-305
Author(s):  
Seiichirou KASHU ◽  
Yasuo MIHARA ◽  
Chikara HAYASHI
Keyword(s):  
Fine Particles ◽  
Ultra Fine Particles
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