Mechanisms of Collision and Coagulation between Fine Particles in Fluid

Shoji, Tetsuya; Kikuchi, Atsushi

doi:10.2355/tetsutohagane1955.78.4_527

Cited by 73 publications

(45 citation statements)

References 26 publications

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“…2) To optimize these processes, computer simulations concerning the evolution and removal behavior of alumina inclusions in molten steel are of great assistance, [3][4][5][6][7][8][9][10][11][12][13] as is basic research about the nucleation and growth of deoxidation products. [14][15][16][17][18][19][20][21][22][23] The coagulation coefficient of alumina particles strongly affects the collision growth rate of alumina clusters larger than 1 μm; however, as the reported values for the coefficient vary widely between 0.03 and 0.7, [3][4][5][6][7][8][9][10][11][12][13] it is still difficult to interpret the experimental results, although the Brownian motion, the van der Waals force and other forces related to fluid dynamics were taken into consideration. We think that the coagulation behavior must also depend on the liquidcapillary force of a very small amount of liquid iron oxide bridging the solid alumina particles and working as a "binder" because of its good wettability, in addition to the abovementioned forces.…”

Section: Introductionmentioning

confidence: 99%

Influence of Unstable Non-equilibrium Liquid Iron Oxide on Clustering of Alumina Particles in Steel

et al. 2013

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Alumina clusters extracted from molten steel and from a cast slab at our plant were analyzed by SEM and TEM. It was found that a small amount of liquid FeO could accelerate the clustering of alumina inclusions in aluminum-killed steel because of the strong liquid-capillary negative pressure of liquid FeO. The sources of the FeO are most likely oxygen contamination from ferroalloy additives, residual steel adhering to the refractory surfaces of ladles and vessels, and air entrainment.

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Section: Introductionmentioning

confidence: 99%

Influence of Unstable Non-equilibrium Liquid Iron Oxide on Clustering of Alumina Particles in Steel

et al. 2013

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“…The coalescence among inclusions in liquid steel occurs in the metallurgical reactor due to Brownian collisions, 14) Stoke collisions, 7) and turbulent collisions. 15) The collision rates for these collision modes are …”

Section: Collision Mechanismmentioning

confidence: 99%

Collision and Coalescence of Alumina Particles in the Vertical Bending Continuous Caster.

Lei

Wang

et al. 2002

ISIJ International

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The three-dimensional fluid flow in a vertical bending continuous caster was numerically studied. Three dimensionless collision numbers were introduced to analyze the inclusion collision mechanism. The analysis showed that turbulent collisions were the major factor causing inclusions to collide with each other in the continuous caster. Stokes collisions had a minor effect and Brownian collisions were negligible. A mathematical model was then developed to study the inclusion collisions in the continuous caster. The mathematical model considered the inclusion mass transfer and expressed the radius and population of new inclusions after coalescence relative to the mass and population conservation. Since the motion of clustershaped inclusions differs from that of spherical inclusions, the inclusion physical parameters were modified. The results showed that the inclusions congregated approximately one fourth of the face width from the slab edge so that the characteristic radius distribution of the inclusions had a 'W' shape, while the inclusion concentration and number density had an inverse 'W' shape in the longitudinal direction. More inclusions were trapped near the inner arc and they had larger characteristic radii than those near the outer arc. The concentration and inclusion number density decreased with the distance from the free surface, but the inclusion radius increased.

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“…[1][2][3][4][5][6][7] The physical mechanism of the agglomeration and cluster formation was also reported by using the direct observation. 8) The collision and the agglomeration mainly occur not at the solidifying front and its vicinity but in the bulk flow.…”

Section: Introductionmentioning

confidence: 99%

Model Experiment of Particle Engulfment into the Solidifying Shell under Fluid Flow

2004

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A model experiment was performed to investigate movement of inclusions near the solid wall and engulfment into the solidifying front. Polystyrene particles (100 mm in diameter) were suspended in flowing melts (water, 20 mass% NaCl aqueous solution and succinonitrile). As the average flow velocity increased, number of the particles reaching the vicinity of the solid wall increased whereas the average stationary time of the particles near the wall decreased. Number of the particles engulfed into the solidifying shell deceased with increasing the flow velocity. Moreover, addition of 3 mass% acetone clearly reduced number of the engulfed particles. In this study, the stationary time and the capture time were introduced to consider the engulfment. The particle engulfment was qualitatively explained by considering changes of the stationary time and the capture time. According to the observation, probability of the engulfment for the particles reaching the solidifying front was 0.01 at most. Only the particles of which the stationary time was much longer than the average value were engulfed. The present study indicated that the particle engulfment under the melt flow should be considered as a probabilistic process.KEY WORDS: inclusion; engulfment; melt flow; solidifying front.ing. 23,24) A model experiment using water was also performed to analyze behavior of non-metallic inclusions near the solidified shell under the fluid flow. 25) According to the water model experiment, 25) the main factor avoiding the nonmetallic inclusion entrapment is the force given by the horizontal flow. The Saffman force was recognized when the particles removed from the solidifying shell. Moreover, effects of the surface roughness and the flow direction with respect to the rising/sedimentation velocity on the inclusion entrapment were also reported. [26][27][28] The immiscible particles that are denser than the liquid phase tended to concentrate near the wall, whereas the immiscible particles that were less dense than the liquid tended to migrate away from the wall. 28) However, it is not still understood how the immiscible particles reach the solidifying front under the turbulent flow and are engulfed into the solidifying front. Furthermore, it is of interest to consider a phenomenological model which systematically links the controllable parameters such as flow velocity and alloy concentration with the engulfment of the particles into the solidifying front.In this study, movement of the polystyrene particles near the solid wall under melt flow is observed in water, 20 mass% NaCl aqueous solution and succinonitrile (an organic material). Simple parameters related to the particle movement near the solidifying front are introduced to explain effect of the melt flow and the solute addition on the particle engulfment. Based on the experimental results, the particle engulfment into the solidifying front is discussed by using the parameters. Figure 1 shows an experimental cell in which the particle movement near the solid wall is observed under ...

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Mechanisms of Collision and Coagulation between Fine Particles in Fluid

Cited by 73 publications

References 26 publications

Influence of Unstable Non-equilibrium Liquid Iron Oxide on Clustering of Alumina Particles in Steel

Influence of Unstable Non-equilibrium Liquid Iron Oxide on Clustering of Alumina Particles in Steel

Collision and Coalescence of Alumina Particles in the Vertical Bending Continuous Caster.

Model Experiment of Particle Engulfment into the Solidifying Shell under Fluid Flow

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