A study of pressure fluctuations in a bubbling fluidized bed

Baskakov, A. P.; Tuponogov, V. G.; Filippovsky, N.F.

doi:10.1016/0032-5910(66)80003-7

Cited by 97 publications

(51 citation statements)

References 3 publications

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“…On the contrary, as shown in Fig. 6, the frequency of the simulated pressure drop for the bed without vibration coincides with the natural frequency of the bed esti mated with f n % (g/h 0 ) 1/2 /p = 4.3 Hz [36]. This natural frequency is still present in the vibrated fluidized bed since the amplitude of the 15 Hz pressure drop oscillations in Fig.…”

Section: Time Evolution Of Particle Volume Fraction and Pressure Dropmentioning

confidence: 55%

A novel methodology for simulating vibrated fluidized beds using two-fluid models

Acosta-Iborra

Hernández-Jiménez

Vega

et al. 2012

Chemical Engineering Journal

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Section: Time Evolution Of Particle Volume Fraction and Pressure Dropmentioning

confidence: 55%

A novel methodology for simulating vibrated fluidized beds using two-fluid models

Acosta-Iborra

Hernández-Jiménez

Vega

et al. 2012

Chemical Engineering Journal

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“…According to that, from the characteristic frequencies of the measured pressure fluctuation signals shown in Fig. 7, it can be observed that the energy of the spectra is distributed mainly below 10 Hz with a dominant frequency at 2.5 Hz, which correspond to the natural bed frequency (f bulk ¼2.5 Hz (Baskakov et al, 1986), for all operational conditions covered. Moreover, the dynamical features of the two flow conditions qualitatively described previously, from visual observation, are now explained by the spectra shown on Fig.…”

Section: Frequency Domain Analysismentioning

confidence: 78%

“…The resulting normalized COP function of pressure and E signals are shown in Fig. 10, where the contribution due to the bed mass oscillation, f bulk ¼2.5 Hz (Baskakov et al, 1986) is clearly distinguishable on the COP spectra for both pressure and E time series. Moreover, it is observed that for bubble regime, the second maximum detected by the COP estimated from the pressure fluctuation signals does not appear on the COP computed from E signals that shows a low coherence for the frequencies above 4 Hz.…”

Section: Cop/iop Analysismentioning

confidence: 99%

Can low frequency accelerometry replace pressure measurements for monitoring gas-solid fluidized beds?

Martín

Briongos

Aragón

et al. 2010

Chemical Engineering Science

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a b s t r a c tThis paper is addressed to introduce a methodology based on low frequency accelerometry that can be used for gas solid fluidized bed monitoring, and for dynamic diagnosis purposes. The proposed methodology consists on extracting the low frequency information encoded within an accelerometry signal, by means of the Hilbert transform method. The time and the frequency domain analysis show how this low frequency information is directly related to the conventional pressure fluctuation measurements, providing useful information on bulk and bubble dynamics. The cross correlation and the coherence function analysis between the pressure and the envelope process of the measured accelerometer signals ''E'', exhibit values approaching unity for frequencies ranging between 2 and 4 Hz. This reveals that pressure signals and accelerometry envelope are related processes. The results from the Coherent Output Power, COP, and the Incoherent Output Power, IOP, analysis confirms that both pressure and envelope time series exhibit the same global and local features open the possibility of using low frequency accelerometers instead of conventional pressure transducers for monitoring and for dynamic diagnosis purposes.

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“…The third source of compression waves is the eruption of bubbles at the surface of the bed. When the top of a bubble reaches the bed surface, the actual bed height decreases at that position, leading to a decrease in the pressure below the erupting bubble (Baskakov et al, 1986). d. Gas flow fluctuations.…”

Section: Origin Of Pressure Fluctuationsmentioning

confidence: 99%

Measuring the Gas-Solids Distribution in Fluidized Beds -- A Review

Ommen¹,

Mudde²

2008

International Journal of Chemical Reactor Engineering

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In gas-solid fluidized beds, the distribution of the particles typically varies both in time and space. Since the gas-solids distribution and its variation have a strong influence on the performance of a fluidized bed for a given process, it is very important to accurately measure the gas-solids or voidage distribution. This paper reviews techniques for measuring the voidage distribution in gas-solid fluidized beds, with a focus on the developments during the last ten years. We will treat subsequently direct visualisation, tomography, optical probes, capacitance probes, and pressure measurements.Dense gas-solids flows are typically opaque to visible light. This makes optical techniques only of limited use in dense gas-solids flow. However, direct visualization can be useful for very dilute systems, pseudo 2-D beds, and the outer layer of dense, 3-D systems. Tomography is frequently used to obtain the voidage distribution in a horizontal cross-section of the bed. Electric capacitance tomography is fast, but its spatial resolution is limited and image reconstruction is still troublesome. Although some steps forward have been made, research is continuing at this point. For nuclear (X-ray and gamma-ray) tomography, the image reconstruction is much easier and the spatial resolution better, but its temporal resolution is typically much lower. Therefore, research efforts for nuclear tomography are mainly aimed at increasing the measurement frequency. Optical probes determine the voidage as a function of time in a small measurement volume, either by the degree of reflection or by the degree of transmission of a light bundle. Capacitance probes determine the voidage as a function of time in a small measurement volume by measuring the dielectric permittivity of the gas-solids suspension in the measurement volume. Both optical and capacitance probe techniques are reasonably well-developed; the current research effort spent at improving them seems * We would like to thank M.O. Coppens, J. Nijenhuis, R.W.S Bohlken, and M.A. Wormsbecker for useful suggestions during preparation of this manuscript. limited, especially for capacitance probes. Time-averaged pressure measurements are commonly used to determine the average bed density and bed height. By sampling the local pressure at a sufficiently high frequency (typically in the order of 200 Hz), much more information can be obtained about the fluidized bed hydrodynamics. However, obtaining quantitative voidage data from pressure fluctuations measurement remains a difficult task; in-bed pressure fluctuation (and acoustic) measurements are mostly used to determine changes in the voidage dynamics and distribution.

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A study of pressure fluctuations in a bubbling fluidized bed

Cited by 97 publications

References 3 publications

A novel methodology for simulating vibrated fluidized beds using two-fluid models

A novel methodology for simulating vibrated fluidized beds using two-fluid models

Can low frequency accelerometry replace pressure measurements for monitoring gas-solid fluidized beds?

Measuring the Gas-Solids Distribution in Fluidized Beds -- A Review

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