Macroscopic Flow Structure of Solid Particles in Circulating Liquid-Solid Fluidized Bed Riser.

Kuramoto, Koji; Tanaka, Katsutoshi; Tsutsumi, Atsushi; Yoshida, Kunio; Chiba, Tadatoshi

doi:10.1252/jcej.31.258

Cited by 20 publications

(16 citation statements)

References 13 publications

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“…Hence correlations based on homogenous fluidization may not be readily applicable to the circulating fluidization regime because of difference in flow structure. These observations are similar to the reported literature [12,19].…”

Section: Variation Of Bed Voidage With Operating Conditionssupporting

confidence: 93%

“…In this arrangement, the solids feed pipe connecting the riser and downcomer makes an angle with the axis of the riser and the axis of the downcomer. In the second arrangement, the main liquid is sent through a porous plate distributor at the bottom of the riser and the other stream is sent through an L-Type valve connecting the riser and the downcomer [6,[19][20][21][22].…”

Section: Nomenclaturementioning

confidence: 99%

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Hydrodynamics of a liquid–solid circulating fluidized bed: Effect of dynamic leak

Vidyasagar

Krishnaiah

Sai

2008

Chemical Engineering Journal

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Section: Variation Of Bed Voidage With Operating Conditionssupporting

confidence: 93%

Section: Nomenclaturementioning

confidence: 99%

Hydrodynamics of a liquid–solid circulating fluidized bed: Effect of dynamic leak

Vidyasagar

Krishnaiah

Sai

2008

Chemical Engineering Journal

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“…Both the intermittency index and the bed voidage at a given radial position remain fairly constant along the riser. This confirms the uniform axial voidage distribution that has been observed elsewhere (Liang et al ., 1997;Kuramoto et al ., 1998;Zheng et al, 1999a). This result also shows that the axial particle movement (on microscale as well as macroscale) is uniform although nonuniformity (in both micro-and macro-scales) is present in the radial direction with more vigorous interaction at the wall region.…”

Section: Axial Flow Structurementioning

confidence: 99%

Microstructural aspects of the flow behaviour in a liquid—solids circulating fluidized bed

Zheng

Zhu

2000

Can J Chem Eng

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which is between the conventional liquid fluidization and the dilutephase liquid transport regime. They also characterized this regime with axial uniformity. This was later confirmed by several other researchers (Kuramoto et al., 1998;Zheng et al., 1999a) using different types of particles and various measurement techniques.With respect to the radial flow structure, Liang et al. (1 996) reported that the radial non-uniformity can be clearly recognized in the liquid-solids circulating fluidization regime using a conductivity probe.The solids concentration increases from the centre to the wall of the riser. Lately, Zheng et al. (1999b) confirmed the above radial structure by using a fibre-optic probe. At the same time, they pointed out that the radial flow structure is affected significantly by the operating conditions and particle properties. The radial non-uniformity is increased with increasing solids circulation rates but decreasing liquid velocity. At the same average solids holdup, lighter particle systems have a relatively more uniform radial flow structure. Furthermore, they showed that the radial non-uniformity is a unique characteristic of the liquid-solids circulating fluidization regime, which is different from the uniform radial flow structure observed in the conventional liquid-solids fluidization regime. However, the above conclusions are all for the time-average flow structure (the macroflow structure). Studies on the instantaneous flow structure (microflow structure) have not been reported.Knowledge of the microflow structure is important to the design and operation of the liquid-solids circulating fluidized bed reactors. For example, the radial distributions of mass and heat transfer behaviour are closely linked to the fluctuations of the local solids concentration. Liquid and particle residence time distributions also depend on the fluctuations as well as the time-average values of the concentration and velocity of particles and liquid in the riser. All these parameters are the key aspects which affect the design and scale-up of a LSCFB. To gain a better understanding of the local flow behaviour, it is important to examine the instantaneous flow behaviour in addition to the time-averaged flow behaviour. The probability density function can provide an overall picture of local voidage fluctuations and a more quantitative description is reflected in the standard deviation of the local solids holdup about its mean. In the gas-solids circulating fluidized beds, microflow structure has been studied by many researchers through recording time variations of gas and solids flow. For example, Schnitzlein and Weinstein (1988) characterized the flow structure using instantaneous pressure signals.~~ *Author to whom correspondetice may be addressed. E-mail address: zhu@uwo.ca I instantaneous and time-average suspension densities were determined in a 76 mm diameter by 3 m tall liquid-solids circulating fluidized bed riser using a fibre-optic probe. Attempts were made to qualify the microflow structure throu...

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“…To circumvent the problems of conventional liquid-solid fluidized beds, liquid-solid circulating fluidized beds have been proposed (Liang et al, 1996(Liang et al, , 1997Kuramoto et al, 1998Kuramoto et al, , 1999. It has been recognized that the liquid-solid circulating fluidized bed has several advantages, such as more effective contacting between phases and considerable reduction of back mixing of the liquid phase.…”

mentioning

confidence: 99%

Liquid Radial Dispersion in Liquid-solid Circulating Fluidized Beds with Viscous Liquid Medium

Song

Lee

et al. 2005

Chemical Engineering Communications

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Liquid dispersion in the radial direction was investigated in the riser of a viscous liquid-solid fluidized bed 0.102 m in diameter and 3.5 m in height. Pressure fluctuations in the riser were also measured and analyzed to examine the behavior of fluidized particles. Effects of liquid velocity (0.15-0.45 m=s), solid circulation rate (2-8 kg=m 2 s), particle size (1-3 mm), and liquid viscosity (0.96-38 mPas) on pressure fluctuations and the liquid radial dispersion coefficient were determined. The infinite space model was employed to obtain the radial dispersion coefficient from the radial concentration profiles of the tracer. The pressure fluctuations were analyzed by means of autocorrelation coefficient as well as power spectral density function. The dominant frequency obtained from the autocorrelation coefficient or power spectral density function of pressure fluctuations decreases with increasing liquid viscosity or liquid velocity, but it increases with increasing particle size. The liquid radial dispersion coefficient decreases with increasing liquid velocity or viscosity, but it increases as the solid circulation rate or particle size increases. The liquid radial dispersion coefficient is related closely to the resultant behavior of fluidized particles. The radial dispersion coefficient has been well correlated with operating variables in terms of dimensionless groups.

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Macroscopic Flow Structure of Solid Particles in Circulating Liquid-Solid Fluidized Bed Riser.

Cited by 20 publications

References 13 publications

Hydrodynamics of a liquid–solid circulating fluidized bed: Effect of dynamic leak

Hydrodynamics of a liquid–solid circulating fluidized bed: Effect of dynamic leak

Microstructural aspects of the flow behaviour in a liquid—solids circulating fluidized bed

Liquid Radial Dispersion in Liquid-solid Circulating Fluidized Beds with Viscous Liquid Medium

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