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Particle motion in CFB cyclones as observed By positron emission particle tracking / Chian W. Chan in Industrial & engineering chemistry research, Vol. 48 N°1 (Janvier 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N°1 (Janvier 2009) . - P. 253-261 Titre : Particle motion in CFB cyclones as observed By positron emission particle tracking Type de document : texte imprimé Auteurs : Chian W. Chan, Editeur scientifique ; Jonathan P. K. Seville, Editeur scientifique ; Xianfeng Fan, Editeur scientifique Année de publication : 2009 Article en page(s) : P. 253-261 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Circulating  fluidized  CFB  Cyclones Résumé : Circulating fluidized bed (CFB) cyclones operate at high solids loadings. The paper presents, for the first time, particle trajectories within a cyclone obtained by positron emission particle tracking (PEPT), as a function of the solids loading (Cs). The pressure drop across a cyclone is a strong function of the solids loading. The objective of this work was to explain this behavior by direct observation of the particle movement. Cyclones normally operate in a stable particle movement mode, always with a spiral motion in the cylindrical part of the cyclone, followed by either a continued spiral in the cone (at low Cs) or by a much denser solids flow near the cone wall at higher Cs values. Data are used to obtain the tangential and axial velocity components of a tracer particle, the residence time of the particles in the cyclone, the thickness of the boundary layer in the cylindrical section of the cyclone, and the thickness of the dense wall layer in the conical section. This downward moving layer reduces the effective “free” cross section of the cyclone, thus increasing the air velocity and the pressure drop (ΔP), especially for small cyclones, as in the present research. This effect will be negligible for larger cyclones, where the influence of solids film thickness is less important, when compared to cyclone diameter, and ΔP values are expected to remain almost constant with increases in the solids loading. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800213g [article] Particle motion in CFB cyclones as observed By positron emission particle tracking [texte imprimé] / Chian W. Chan, Editeur scientifique ; Jonathan P. K. Seville, Editeur scientifique ; Xianfeng Fan, Editeur scientifique . - 2009 . - P. 253-261. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N°1 (Janvier 2009) . - P. 253-261 Mots-clés : Circulating  fluidized  CFB  Cyclones Résumé : Circulating fluidized bed (CFB) cyclones operate at high solids loadings. The paper presents, for the first time, particle trajectories within a cyclone obtained by positron emission particle tracking (PEPT), as a function of the solids loading (Cs). The pressure drop across a cyclone is a strong function of the solids loading. The objective of this work was to explain this behavior by direct observation of the particle movement. Cyclones normally operate in a stable particle movement mode, always with a spiral motion in the cylindrical part of the cyclone, followed by either a continued spiral in the cone (at low Cs) or by a much denser solids flow near the cone wall at higher Cs values. Data are used to obtain the tangential and axial velocity components of a tracer particle, the residence time of the particles in the cyclone, the thickness of the boundary layer in the cylindrical section of the cyclone, and the thickness of the dense wall layer in the conical section. This downward moving layer reduces the effective “free” cross section of the cyclone, thus increasing the air velocity and the pressure drop (ΔP), especially for small cyclones, as in the present research. This effect will be negligible for larger cyclones, where the influence of solids film thickness is less important, when compared to cyclone diameter, and ΔP values are expected to remain almost constant with increases in the solids loading. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800213g