Experimental techniques

Louge, Michel Y.

doi:10.1007/978-94-009-0095-0_9

Cited by 22 publications

(3 citation statements)

References 128 publications

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“…(1) There are many different experimental techniques available for studying gas−solid systems, − each subject to limitations in terms of such factors as interference with local flow behavior, indistinct delineation of the measuring volume, time response, drift, and so forth.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of Gas-Fluidized Beds in Different Flow Regimes

Bai

Issangya

Grace

1999

Ind. Eng. Chem. Res.

123

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Hydrodynamic characteristics among different flow regimes of gas fluidized beds are compared on the basis of experiments with fluidized catalytic cracking particles in a 76.2 mm diameter riser. Pressure and local voidage fluctuations were analyzed using both statistical and chaotic tools. The standard deviations of local voidage fluctuations are much lower in a high-density circulating fluidized-bed riser than in the bubbling and turbulent flow regimes, even for identical local time-mean voidages. A chaotic time series analysis can distinguish flow structures of the various flow regimes. Bifractal structures, characterized by two Hurst exponents, two correlation dimensions, and two Kolmogorov entropies, characterize the motions of the dilute and emulsion phases in the bubbling and turbulent flow regimes. The two-phase structure becomes less distinguishable with increasing gas velocity, eventually disappearing on reaching dilute phase transport. However, for high solids concentrations, the bifractal character persists, suggesting that particles may travel in two different forms. Radial profiles of chaotic parameters are relatively flat in the bubbling and turbulent flow regimes, but significantly nonuniform in dense suspension upflow. Flow behavior in the high-density riser and in the dense bottom region of a low-density riser operated in the fast fluidization regime differ from the bubbling and turbulent flow regimes, even when compared where there are equal local voidages.

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Section: Introductionmentioning

confidence: 99%

Characteristics of Gas-Fluidized Beds in Different Flow Regimes

Bai

Issangya

Grace

1999

Ind. Eng. Chem. Res.

123

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“…For instance, low-frequency and time-averaged measurements of the static pressure drop across a vertical section of the bed have been used to calculate the expanded bed height in a bubbling fluidized bed or the density in a circulating fluidized bed as a function of the bed height (Louge, 1997;Gallucci et al, 2002;van der schaaf et al, 2002;sasic et al, 2007). in contrast, dynamic properties of the bed can be retrieved from high-frequency pressure fluctuation measurements (PFM) sampled at frequencies beyond 20 Hz (lim et al, 2009; van ommen et al, 2004c).…”

Section: Pressure Measurementmentioning

confidence: 99%

Measurement, monitoring and control of fluidized bed combustion and gasification

Rüdisüli

Schildhauer

Biollaz

et al. 2013

Fluidized Bed Technologies for Near-Zero Emission Combustion and Gasification

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“…Methods of estimating W s that use readily measured riser conditions, such as the pressure drop or gradient, have the advantage of relative simplicity making them attractive for high-temperature process conditions. One of the simplest methods of estimating W s in a riser is to measure the axial dynamic pressure gradient ( P a,na ′ ( z )) and gas velocity ( U ) in the nonacceleration section of a riser and to assume the particle slip velocity ( u sl ) may be obtained using the standard drag curve ( C ds ). ,,, This method will produce questionable results because the value of the single-particle drag coefficient ( C d ) in both the acceleration and nonacceleration sections of a riser has been shown to be affected by several properties of the flow including: the presence of other particles, relative turbulence intensity ( I R ), turbulence macroscale ( L e ) and spectrum, and particle deceleration/acceleration. − As a result, the modeling of the acceleration and non-acceleration sections of a riser does not reveal a general relation between C d and variables such as turbulence intensity and spectrum.…”

Section: Introductionmentioning

confidence: 99%

Determining the Solids Mass Flow Rate in a Gas–Solids Riser Using an Integral Momentum Balance

Paccione

2022

Ind. Eng. Chem. Res.

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Determining the solids mass flow rate (W s ) in a gas−solids riser often entails closing a one-dimensional, two-fluid model by relating the total wall friction (F w ) and the drag coefficient (C d ) to riser conditions. However, this requires relating these two parameters to several riser variables making it difficult to apply these relations generally. In this work, closure is obtained using a model for the conservation of linear momentum in the acceleration (entrance region) of a riser. The model relates the total forces imposed on the control volume to the change in linear momentum of the solids. Additional expressions are obtained from the model which provide a means for defining the boundary condition at the entrance to the control volume. The resulting model provides a means of determining the solids mass flow rate (W s ) from three readily measured and physically relevant riser operating parameters: the dynamic pressure drop across the acceleration section (ΔP a ), the normalized dynamic pressure gradient at the end of the acceleration section (P a ′(1)), and the superficial gas velocity (U) in a riser. The agreement between measured and model values ranges from very good to excellent with the average absolute deviation being <5% of the measured values.

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Experimental techniques

Cited by 22 publications

References 128 publications

Characteristics of Gas-Fluidized Beds in Different Flow Regimes

Characteristics of Gas-Fluidized Beds in Different Flow Regimes

Measurement, monitoring and control of fluidized bed combustion and gasification

Determining the Solids Mass Flow Rate in a Gas–Solids Riser Using an Integral Momentum Balance

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