A γ-ray detection system for 3-D particle tracking in multiphase reactors

Larachi, Faı̈çal; Kennedy, G.; Chaouki, Jamal

doi:10.1016/0168-9002(94)91343-9

Cited by 119 publications

(87 citation statements)

References 15 publications

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“…Lin et al (1985) improved the signal processing scheme, utilizing the redundancy of signals to increase accuracy by reducing the influence of intrinsic noise due to the quantized nature of gamma emission. The Radioactive Particle Tracking (RPT) technique developed by Larachi et al (1994) was in principle similar to that of Lin et al (1985), but it yielded improved Na I NaI NaI NaI Figure 2 -Arrangement of the detectors around the CFB riser.…”

Section: Measurement Of Solids Velocities In Cfbmentioning

confidence: 98%

Position and velocity of a large particle in a gas/solid riser using the radioactive particle tracking technique

1999

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The flow behavior of the solids phase in the fully developed region of a laboratory-scale circulating fluidized bed riser was studied using an assembly of sixteen NaI detectors to determine the position of a 500 pm radioactive particle, 100 timeds. The particle location was inferred from the number of y-rays recorded by the assembly. The knowledge of the instantaneous positions enabled the determination of the instantaneous and mean velocity fields. Tests were conducted in a 0.082 m diameter, 7 m tall riser using 150 p silica sand particles. Data were obtained at a gas superficial velocity of 4 m/s and solids mass fluxes from 23 to 75 kg/m2.s. Radial profiles of axial particle velocity showed that the solids velocity decreased with increasing solids circulation rates. Correspondingly, turbulent particle velocities and solids dispersion coefficient in the longitudinal direction were found to decrease as the solids circulation rate increased. The crosssectional area where, on average, solids downflow took place, increased with increasing solids circulation rate.On a etudie le comportement en koulement de la phase des solides dans la region pleinement developpee d'une colonne montante a lit fluidise circulant a I'echelle de laboratoire en utilisant un assemblage de seize detecteurs NaI afin de determiner la position d'une particule radioactive de 500 pm, a une frhuence de 100 foids. La localisation de la particule a ete estimee a partir du nombre de rayons y et la connaissance des positions instantanees a permis de determiner les champs de vitesse instantane et moyen. Nous avons utilid une colonne de laboratoire montante de 0,082 m de diametre et 7 m de hauteur avec des particules de sable de d i c e de 150 p. Des donnees ont ete obtenues a une vitesse de gaz superficielle de 4 m/s et a des taux de circulation de solides de 23 a 75 kg/m2.s. Des profils radiaux de la vitesse axiale des particules montrent que la vitesse des solides diminue avec I'augmentation des taux de circulation des solides. De la mBme maniere, on a trouve que les vitesses de particules turbulentes et le coefficient de dispersion des solides dans la direction longitudinale diminuaient avec I'augmentation du taux de circulation des solides. La region transversale a la paroi oh, en moyenne, se produit I'ecoulement de solides descendant, augmente avec la circulation des solides. Quantification of the flow patterns and backmixing is essential for proper design and scale-up of CFB risers. Existing models often suffer from a lack of pertinent experimental data for model validation. The gadsolid flow in the CFB riser is characterized by a strong heterogeneity. Yet, experimental investigations have demonstrated that the solids distribution is nonhomogeneous, in both axial and radial directions in the CFB riser. For example, the nonhomogeneous character of the solids distribution in the axial direction was attributed to the acceleration of particles entering with low velocities at the bottom of the riser. Harris et al. (1994) and Grace (1996) have also sh...

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Section: Measurement Of Solids Velocities In Cfbmentioning

confidence: 98%

Position and velocity of a large particle in a gas/solid riser using the radioactive particle tracking technique

1999

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“…In a previous work (Larachi et al, 1994), the following theoretical expression was used for expressing the recorded photopeak counts (Tsoulfanidis, 1983): According to Equation (1) the response of the detector in terms of photopeak counts is directly proportional to the activity of the source at very low activities of the source (C ª TAnfe where Anfet << 1) and approaches a constant at very high activities of the source (C ª T/t where Anfet >> 1). This expression describes a non-paralysable system and can be understood in terms of pulse pileup.…”

Section: Theorymentioning

confidence: 99%

Decreasing the Sampling Time Interval in Radioactive Particle Tracking

2003

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The study of the movement of solids in multiphase reactors using radioactive particle tracking is currently limited to fairly modest particle velocities because of count‐rate limitations of the detection system. In this work, this restriction was overcome by increasing the activity of the radioactive tracer, by decreasing the sampling time interval and by modifying the particle tracking software to recognize which detectors were saturated and to use only the data from the remaining unsaturated detectors. Higher tracer activity resulted in lower standard deviation of the calculated tracer coordinates.

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“…In this work, the framework established by Beam et al has been modified to include the presence of the reactor walls, and the two or three phase mixture in the reactor. A similar implementation of the Monte Carlo approach has been demonstrated to be successful by Larachi et al (1994).…”

Section: Mathematical Descriptionmentioning

confidence: 99%

Novel techniques for slurry bubble column hydrodynamics

Duduković¹

1999

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A γ-ray detection system for 3-D particle tracking in multiphase reactors

Cited by 119 publications

References 15 publications

Position and velocity of a large particle in a gas/solid riser using the radioactive particle tracking technique

Position and velocity of a large particle in a gas/solid riser using the radioactive particle tracking technique

Decreasing the Sampling Time Interval in Radioactive Particle Tracking

Novel techniques for slurry bubble column hydrodynamics

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