The distribution of bed density in an air dense medium fluidized bed with single and binary mixtures of Geldart B and/or D particles

Self Cite

Effective density for the separation of immersed objects which determines the performance of coal dry beneficiation is of primary importance for Gas−Solid Fluidized Bed Coal Beneficiator (GSFBCB) applications. Of all factors affecting the effective density, fluidization hydrodynamics and properties of medium particles and immersed objects play the dominant roles. By correlating all available experimental data found in the literature, a general correlation has been developed for the first time to predict the effective density for immersed object separation in fluidized beds, ρ sep = 0.95ρ bed + 1.88ρ drag , where ρ bed is the fluidized bed density, and ρ drag is the effective bed density contributed by fluidization hydrodynamics. This correlation could accurately predict the effective density for various immersed objects in fluidized beds with single or binary particle systems in existing experimental results. With wide applicability and great accuracy, the proposed correlation not only provides an efficient way for the design and operation of the GSFBCB for coal dry beneficiation but also is applicable for iron and copper ore pretreatment, agricultural crop cleaning, municipal solid waste classification, etc.

Section: Theorymentioning

confidence: 99%

“…Otherwise, V sub is less than V. For the prediction of fluidized bed density (ρ bed ), a general correlation has been proposed in earlier work 21 and is shown as…”

Section: Theorymentioning

confidence: 99%

Characterization of the Effective Density for the Separation of Immersed Objects in the Gas–Solid Fluidized Bed Coal Beneficiator

Zhu

2023

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“…The air dense medium fluidized bed (ADMFB) is a branch of the gas–solid bubbling fluidized bed. The technology is mainly used for coal beneficiation, relying on the prominent advantage of a relatively stable bed density distribution. − With the global expansion of water scarcity, the dry separation method has attracted more and more attention, especially in China, India, Turkey, etc. − During the separation process, ADMFB can effectively separate clean coal and gangue due to the density difference. , Upward air flow suspends medium particles to form a fluid-like separation bed with a certain density ρ bed . Ideally, coal with lower density ρ coal floats to the top zone and gangue with higher density ρ gangue sinks to the bottom .…”

Section: Introductionmentioning

confidence: 99%

“…4−6 During the separation process, ADMFB can effectively separate clean coal and gangue due to the density difference. 7,8 Upward air flow suspends medium particles to form a fluid-like separation bed with a certain density ρ bed . Ideally, coal with lower density ρ coal floats to the top zone and gangue with higher density ρ gangue sinks to the bottom.…”

Section: Introductionmentioning

confidence: 99%

Axial Periodic Structures of the Expansion Process in a Gas–Solid Separation Fluidized Bed

Zhang

Zhou

Dong

et al. 2023

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The air dense medium fluidized bed (ADMFB), belonging to the bubbling fluidization regime, plays a critical role in dry coal beneficiation. The separation density of ADMFB depends on the understanding of bed density. Beyond the uniform hypothesis, a nonuniform hypothesis was assumed in which the bed density distribution has axial sinusoidal structures. Based on the force balance model, contact stress is responsible for the axial sinusoidal distribution. Experimentally, the fitting results of the axial sinusoidal distribution during the expansion process were presented in which the values of adj. R 2 are from 0.72 to 0.95. Through frequency domain analysis, a low frequency of 0.03 Hz defined as the global horizontal disturbance frequency is also the reason for the sinusoidal distribution. By analogy, the insect-population model could characterize the particle concentration model perfectly. Finally, the flow structure based on the above analysis was described to indicate its influence on coal separation.

“…The expansion rate of the emulsion phase is low, and to reduce the bed density, the proportion of the bubble phase needs to be increased accordingly. , However, if the proportion of the bubble phase is too large, then the bubbles are continuously merged and grown during the rising process, and the bed density fluctuates greatly, which is also not suitable for coal separation. Therefore, Dong et al introduced pulsating airflow into fluidized beds to form a pulsed gas–solid separation fluidized bed. , According to previous studies, pulsed fluidized beds can effectively inhibit the merger of bubbles, improving the fluidized quality of particles and optimizing a separation accuracy of −6 mm coal. − …”

Section: Introductionmentioning

confidence: 99%

Prediction of Bed Density in a Pulsed Gas–Solid Fluidized Bed

Zhou

Yang

et al. 2021

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Pulsed fluidized beds can reduce bubble generation and improve coal separation accuracy. The reasonable regulation and prediction of bed density are essential to improve the separation accuracy. However, existing bed density correlations are not applicable to pulsed fluidized beds because the pulsating energy affects the behavior of particles and bubbles, and the wake is also a key factor affecting the bed density. This work proposed a novel method of predicting bed density combined with gas–solid distribution theory. When compared with experimental results, the error of this prediction correlation was less than 10%. The distribution characteristics and change trends of the bed density under different operating conditions were also analyzed. This work offers a theoretical foundation for effective separation of coal with pulsed gas–solid fluidized beds.