Solids flow diagram of a CFB riser using Geldart B-type powders

Mahmoudi, Shiva; Chan, Chian W.; Brems, Anke; Seville, Jonathan; Baeyens, Jan

doi:10.1016/j.partic.2011.09.002

Cited by 37 publications

(25 citation statements)

References 68 publications

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“…The comparison of all experimental data, with (6), is illustrated in Figure 5(a). The literature data on choking conditions are scarce outside the experimental data that lead to the establishment of the empirical equations of (1)-(4).…”

Section: Resultsmentioning

confidence: 99%

“…Having established a correlation for Ch in terms of gas and solids properties, the "work" diagram of Mahmoudi et al [5,6] can be adapted, as illustrated in Figure 6. Clearly, the occurring choking regime is specifically important at high values of G and/or low values of ( − TR ).…”

Section: Resultsmentioning

confidence: 99%

“…Bi and Fan [10] Ch √ = 21.6( The objective of the present research hence considered (i) the delineation of the choking phenomenon in different riser geometries and using different A-type powders, (ii) the comparison of experimental results with the empirical predictions of (1)-(4), and finally (iii) the adaptation of the proposed operation diagram of Mahmoudi et al [5,6] to include the ( , ) region subject to choking.…”

Section: Literature Correlations To Predict Choking Velocitiesmentioning

confidence: 99%

“…First approaches to develop a "work map" of the riser operation were presented by, for example, Grace [1], Yerushalmi and Avidan [2], and Bai et al [3]. It was further developed by Chan et al [4] and Mahmoudi et al [5,6] for both Geldart A-and B-type powders: the operating gas velocity ( ) and the solids circulation flux ( ) jointly delineate different regimes, called, respectively, dilute riser flow (DRF), core-annulus flow (CAF) (possibly with a turbulent fluidized bed at the bottom of the riser (TFBB)), and dense riser upflow (DRU). For a given powder and its associated transport velocity, TR , the combination of and will determine the flow regime encountered.…”

Section: Introductionmentioning

confidence: 99%

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Choking Affects the Operation Diagram of a CFB Riser

Zhang

Degrève

Baeyens

et al. 2014

Journal of Powder Technology

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Experiments in 3 different CFB risers have confirmed that common riser operations can be hampered in a well-defined (U, G) range where choking occurs. Geldart A-type powders were investigated. Experimental results of the choking velocity were empirically correlated, being about 30% lower than predicted by the correlation of Bi and Fan, but largely exceeding other predictions. Introducing the findings into the operation diagram presented by Mahmoudi et al. adds a region where stable riser operation is impossible. The adapted diagram enables CFB designers to better delineate the operating characteristics.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Literature Correlations To Predict Choking Velocitiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Choking Affects the Operation Diagram of a CFB Riser

Zhang

Degrève

Baeyens

et al. 2014

Journal of Powder Technology

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“…The voidage tends to distribute more at the riser bottom for the large particles in comparison to smaller particles. It has been shown that most particles are mainly found near the wall of the riser in the freeboard area [40]. Solid particles separated by the cyclone were injected into the riser with a small amount of aeration which diluted the particles near the wall.…”

Section: Effect Of Superficial Gas Velocity On Bed Voidagementioning

confidence: 99%

Hydrodynamic experiments on a small-scale circulating fluidized bed reactor at elevated operating pressure, and under an O2/CO2 environment

et al. 2017

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Pressurized circulating fluidized bed technology is a potentially promising development for clean coal technologies. The current work explores the hydrodynamics of a small-scale circulating fluidized bed at elevated operating pressures ranging from 0.10 to 0.25 MPa. The initial experiments were performed at atmospheric pressure with air and O 2 /CO 2 environments as the fluidization gas to simulate the hydrodynamics in a circulating fluidized bed. A comparison between the effects of air and O 2 /CO 2 mixtures on the hydrodynamics was outlined in this paper for particles of 160 μm diameter. A small but distinct effect on axial voidage was observed due to the change in gas density in the dense zone of the bed at lower gas velocity, while only minimal differences were noticed at higher gas velocities. The hydrodynamic parameters such as pressure drop and axial voidage profile along the height were reported at two different bed inventories (0.5 and 0.75 kg) for three mean particle sizes of 160, 302, and 427 μm and three superficial gas velocities. It was observed that the operating pressure had a significant effect on the hydrodynamic parameters of bed pressure drop and axial bed voidage profiles. The effect of solids loading resulted in an exponential change in pressure drop profile at atmospheric pressure as well as at elevated pressure. The experimental results on hydrodynamic parameters are in reasonable agreement with published observations in the literature.

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Working diagrams to identify the operating range of a bubbling fluidized bed reactor for the CO₂ methanation

Martin-del-Campo

Kopyscinski

2020

Can J Chem Eng

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Fluidized bed reactors for the catalytic CO 2 methanation is a promising concept within the power-togas (methane) process. Due to the intermittency of renewable electricity generation and thus hydrogen production, the subsequent methanation reactor should also be able to operate at lower feed flow rates, while maintaining fluidized bed conditions. Bubbling fluidized bed reactors offer the required flexibility as shown with the new type of working diagrams. These working diagrams visualize a decision window for (a) determining the reactor diameter and (b) operating the fluidized bed reactor with a turndown ratio of 0.5-1.1. Reducing the turndown ratio (ie, inlet flow rate) could lead to defluidization, thus increasing temperature or reducing the pressure are alternatives to maintain fluidization conditions. The former method is not desired, as a temperature increase would significantly reduce the CH 4 yield due to thermodynamic constraints and therefore reduce the overall efficiency. An industrial CO 2 methanation reactor, for example, that is designed for 10 bara (1 bara = 100 kPa) and 340 C with a total inlet flow rate of 5000 m 3 N Á h −1 (H 2 /CO 2 = 4) can be operated at a turndown ratio of 0.5 (2500 m 3 N Á h −1) at the same temperature and the same u 0 /u mf ratio by reducing the pressure to 5 bara with only a slight decrease in the CO 2 equilibrium conversion from 96.7% to 94.6%.

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Solids flow diagram of a CFB riser using Geldart B-type powders

Cited by 37 publications

References 68 publications

Choking Affects the Operation Diagram of a CFB Riser

Choking Affects the Operation Diagram of a CFB Riser

Hydrodynamic experiments on a small-scale circulating fluidized bed reactor at elevated operating pressure, and under an O2/CO2 environment

Working diagrams to identify the operating range of a bubbling fluidized bed reactor for the CO₂ methanation

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Solids flow diagram of a CFB riser using Geldart B-type powders

Cited by 37 publications

References 68 publications

Choking Affects the Operation Diagram of a CFB Riser

Choking Affects the Operation Diagram of a CFB Riser

Hydrodynamic experiments on a small-scale circulating fluidized bed reactor at elevated operating pressure, and under an O2/CO2 environment

Working diagrams to identify the operating range of a bubbling fluidized bed reactor for the CO2 methanation

Contact Info

Product

Resources

About

Working diagrams to identify the operating range of a bubbling fluidized bed reactor for the CO₂ methanation