Investigation of the bed types and particle residence time in a staged fluidised bed

Kuo, H.P.; Cheng, Chung-Yu

doi:10.1016/j.powtec.2006.07.012

Cited by 11 publications

(3 citation statements)

References 25 publications

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“…4,5 AFM observations on Haliotis rufescens and Pinctada maxima (a giant oyster) have also shown that individual aragonite platelets consist of a large number of nanoparticles. 3,6,7 Interestingly, the aragonite nacre's platelets analysed in the works above cited do not show heavy {110} twinning, which was instead observed into other shell structures 8 and into acicular aragonite crystals forming the fibrous layer between the inner nacreous and outer calcite layers of Haliotis discus hannai and Omphalius rusticus. 4,5 Instead, simple aragonite crystals of inorganic origin are rare, as twinning about the 110 plane is nearly always present.…”

Section: Introductionmentioning

confidence: 98%

Surface structure, morphology and (110) twin of aragonite

2014

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In order to better understand the growth mechanisms involving the aragonite in both geological and biological systems, a detailed study of its surfaces was performed. By adopting a two dimensional slab model and performing empirical calculations, we determined the equilibrium geometry at 0K of the (100), (010), (001), (110), (101), (011), (111), (102), (012), (021), (112), (121), (122), (031) and (130) surfaces, both in anhydrous and hydrated conditions. Furthermore, the equilibrium geometry at 0K of the (110) twin boundary interface was also determined. The dry and solvated surface energies at 0K of the crystal faces were also calculated, as well as the (110) twinning energy at 0K, a key thermodynamical quantity for the determination of the equilibrium morphology of twins, and the estimation of their most probable mechanism of formation during growth. As concerns the (110) twin, the interface elastic energy was also evaluated. The solvated equilibrium shape (ES) of aragonite is drawn and compared to the dry one; a comparison with the previous dry and solvated ES calculated at 0K is also performed. Furthermore, the surface structure modifications due to the presence of water is discussed. Our calculations explain the high occurrence of twinned crystals in case of nucleation and growth in inorganic environments. On the contrary, in living organism the crystallization route, the crystal sizes and morphologies are deeply modified by the adhesion on organic substrates and adsorption of organic molecules.

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Section: Introductionmentioning

confidence: 98%

Surface structure, morphology and (110) twin of aragonite

2014

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“…Large block (110) twins have been observed in the nacre of P. maxima in a previous study. 39 Different from the nanotwins generally observed in mollusc shells, 42,43 the large block twins exhibit a straight twinning plane propagating across the whole tablet. Based on this observation, atom-byatom attachment was used to explain the formation mechanism of these block twins by referring to the classical recrystallization model.…”

Section: Resultsmentioning

confidence: 96%

Nanostructured individual nacre tablet: a subtle designed organic–inorganic composite

et al. 2015

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“…Two main types of segregation are usually observed: axial segregation in the direction parallel to the axis of rotation [11,12,13,20], and radial segregation in the direction normal to the axis of rotation [14,15,21,22,23,24]. A combination of the two types can lead to complex patterns in special cases [25]. When the rotating tumbler is thin enough, axial segregation is frustrated and only radial segregation is observed.…”

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Characterization of invariant patterns in a slowly rotated granular tumbler

Reyes

Pérez

Colonnello

et al. 2015

Physica A: Statistical Mechanics and its Applications

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h i g h l i g h t s• A simple geometric model explains the invariant patterns experimentally obtained.• The finite width of avalanches has quantifiable consequences. • There is a special filling area for which the invariant patterns are closer to a circle. • We have obtained an explicit expression for the contour of the invariant patterns. a b s t r a c tWe report experimental results of the pattern developed by a mixture of two types of grains in a triangular rotating tumbler operating in the avalanche regime. At the centroid of the triangular tumbler an invariant zone appears where the grains do not move relative to the tumbler. We characterize this invariant zone by its normalized area, A i , and its circularity index as a function of the normalized filling area A. We find a critical filling area so that only for A > A c invariant zones are obtained. These zones scale as A i ∼ (A − A c ) 2 near A c . We have obtained a maximum in the circularity index for A ≈ 0.8, for which the shape of the invariant zone is closer to a circular one. The experimental results are reproduced by a simple model which, based on the surface position, accounts for all the possible straight lines within the triangle that satisfy the condition of constant A. We have obtained an analytic expression for the contour of the invariant zone. Experimentally, we obtained a displacement in A c that we explain in terms of a finite width of the avalanche region. This displacement is needed only to correct the size of the invariant zone, not its shape.The physics of granular matter is an active field of research, the static and dynamic collective properties of a large number of grains are still under scrutiny [1,2]. A rotating tumbler filled with grains is an interesting model system: it has direct industrial analogs [3][4][5] and is simple enough for theory and numerical simulations [6][7][8]. Several regimes can be found in this type of system [9,10], the Froude number F r = ω 2 L/g being one of the important parameters to characterize the experimental situation. Here ω is the angular speed of rotation, L is a characteristic length of the tumbler and g is the acceleration of gravity. For small F r we are in an avalanche regime, where grain flow occurs during localized episodes of short duration compared to the period of rotation. By increasing ω we can go to a continuous flow regime. In the avalanche regime we typically find segregation, kinks and pattern formation. Two main types of segregation are usually observed: axial segregation * Corresponding author. Tel.: +58 212 9063541.E-mail address: lireyes@usb.ve (L. Reyes).

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Investigation of the bed types and particle residence time in a staged fluidised bed

Cited by 11 publications

References 25 publications

Surface structure, morphology and (110) twin of aragonite

Surface structure, morphology and (110) twin of aragonite

Nanostructured individual nacre tablet: a subtle designed organic–inorganic composite

Characterization of invariant patterns in a slowly rotated granular tumbler

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