Study on the Flow Characteristics of Desulfurization Ash Fine Particles in a Circulating Fluidized Bed

In view of the current status of catalytic cracking flue gas treatment, it is necessary to study the flow environment of desulfurization ash particles, which are a type of Geldart C particle, in a circulating fluidized bed (CFB) for semi-dry flue gas desulphurization using CFB technology. This study investigated the flow characteristics of desulphurization ash particles in a riser with an inner diameter of 70 mm and a height of 12.6 m, at a gas velocity of 4–7 m/s and a solids circulation rate of 15–45 kg/m2·s. The solids holdup in the axial distribution is relatively high near the bottom of the riser, and gradually decreases as the riser height increases, with a stable value from the middle to the top of the riser. In the radial distribution, the solids holdup of desulfurization ash particles is low in the center and high in the wall region. Within the above operating conditions, the solids holdup ranges from 0.008 to 0.025. The particle-based Archimedes number has a linear relationship with the solids holdup at all operating conditions.

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3D CPFD Simulation of Circulating Fluidized Bed Downer and Riser: Comparisons of Flow Structure and Solids Back-Mixing Behavior

Processes ◽

10.3390/pr8020161 ◽

2020 ◽

Vol 8 (2) ◽

pp. 161

Author(s):

Yancong Liu ◽

Yingya Wu ◽

Xiaogang Shi ◽

Chengxiu Wang ◽

Jinsen Gao ◽

...

Keyword(s):

Fluidized Bed ◽

Residence Time ◽

Circulating Fluidized Bed ◽

Operating Conditions ◽

Solids Holdup ◽

The Difference ◽

Large Clusters ◽

Small Clusters ◽

Cluster Behavior ◽

Back Mixing

The difference of gas-solids flow between a circulating fluidized bed (CFB) downer and riser was compared by computational particle fluid dynamics (CPFD) approach. The comparison was conducted under the same operating conditions. Simulation results demonstrated that the downer showed much more uniform solids holdup and solids velocity distribution compared with the riser. The radial non-uniformity index of the solids holdup in the riser was over 10 times than that in the downer. In addition, small clusters tended to be present in the whole downer, large clusters tended to be present near the wall in riser. It was found that the different cluster behavior is important in determining the different flow behaviors of solids in the downer and riser. While the particle residence time increased evenly along the downward direction in the downer, particles with both shorter and longer residence time were predicted in the whole riser. The nearly vertical cumulative residence time distribution (RTD) curve in the downer further demonstrated that the solids back-mixing in the downer is limited while that in the riser is severe. Solids turbulence in the downer was much weaker compared with the riser, while the large clusters formation near the wall in the riser would hinder solids transportation ability.

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Effect of Operating Conditions on the Efficiency of Circulating Fluidized Bed Flue Gas Desulphurization

Advances in Intelligent and Soft Computing - Proceedings of the 2011 International Conference on Informatics, Cybernetics, and Computer Engineering (ICCE2011) November 19–20, 2011, Melbourne, Australia ◽

10.1007/978-3-642-25194-8_54 ◽

2011 ◽

pp. 445-453

Author(s):

Shaohua Li ◽

Guixia Tang ◽

Hu Wang ◽

Hao Gao

Keyword(s):

Fluidized Bed ◽

Flue Gas ◽

Circulating Fluidized Bed ◽

Operating Conditions ◽

Flue Gas Desulphurization

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Different Exit Effects between a Combined Riser with Variable Exit Constraints and a Conventional Riser with Weak Exit Constraints

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.550-553.529 ◽

2012 ◽

Vol 550-553 ◽

pp. 529-533

Author(s):

De Wu Wang ◽

Meng Da Jia ◽

Shao Feng Zhang ◽

Chun Xi Lu

Keyword(s):

Fluidized Bed ◽

Particle Velocity ◽

Large Scale ◽

Operating Conditions ◽

Wall Region ◽

Cold Model ◽

Linear Distribution ◽

Cross Sectional ◽

Bed Height ◽

Solids Holdup

A large-scale cold model experimental setup of combined riser with variable constraint exit (CRVCE) was established. The axial and radial distributions of solids holdup and particle velocity, under different operating conditions, were investigated experimentally, and the results were compared with conventional riser (CR). Experimental results showed that, the exit restrictive effect of combined riser with variable constraint exit was weak when particle circulation flux and static bed height in upper fluidized bed were lower, while it turned to be strong when superficial gas velocity and static bed height in upper fluidized bed were higher. Under the same conditions, averaged cross-sectional solids holdup of CRVCE was characterized by C type distribution when article circulation flux was higher, while that of CR with weak constraint exit was characterized by linear distribution. In axial direction, averaged cross-sectional particle velocity of CRVCE changed in order: acceleration-constant-decrease velocity, while that of CR changed in another: acceleration-constant velocity. The maximum of local solids holdup value of CRVCE appeared at the dimensionless radius position r/R=0.7, while that of CR appeared in the wall region. Their local particle velocities were similar in the core region, while local particle velocity of CRVCE was lower than that of CR in the annular region.

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Hydrodynamic Flow Characteristics in an Internally Circulating Fluidized Bed Gasifier

Journal of Energy Resources Technology ◽

10.1115/1.4041092 ◽

2018 ◽

Vol 141 (3) ◽

Cited By ~ 1

Author(s):

J. P. Simanjuntak ◽

K. A. Al-attab ◽

Z. A. Zainal

Keyword(s):

Fluidized Bed ◽

Flow Rate ◽

Circulating Fluidized Bed ◽

Draft Tube ◽

Three Dimensional ◽

Flow Characteristics ◽

Hydrodynamic Flow ◽

Orifice Diameter ◽

Circulation Rate ◽

Cfd Models

In this paper, the hydrodynamic flow inside an internally circulating fluidized bed (ICFBG) was characterized using experimental and three-dimensional computational fluid dynamics (CFD) models. Eulerian-Eulerian model (EEM) incorporating the kinetic theory of granular flow was implemented in order to simulate the gas–solid flow. A full-scale plexiglass cold flow experimental model was built to verify simulation results prior to the fabrication of the gasifier. Six parameters were manipulated to achieve the optimum design geometry: fluidization flow rate of the draft tube (Qdt), aeration flow rate of the annulus (Qan), initial bed static height (Hbs), draft tube height (Hdt), draft tube diameter (Ddt), and orifice diameter (Dor). The investigated parameters showed strong effect on the particle flow characteristics in terms of the pressure difference (ΔP) and solid circulation rate (Gs). The predicted results by simulation for the optimum case were in close agreement with experimental measurements with about 5% deviation. The results show that the ICFBG operated stably with the maximum Gs value of 86.6 kg/h at Qdt of 350 LPM, Qan of 150 LPM, Hbs of 280 mm, Hdt of 320 mm, Ddt of 100 mm, and Dor of 20 mm.

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Effect of Various Parameters on the Solids Holdup in a Liquid-Solid Circulating Fluidized Bed

International Journal of Chemical Reactor Engineering ◽

10.2202/1542-6580.1581 ◽

2008 ◽

Vol 6 (1) ◽

Author(s):

Natarajan Palani ◽

Velraj Ramalingam ◽

Seeniraj R.V.

Keyword(s):

Experimental Data ◽

Fluidized Bed ◽

Flow Rate ◽

Liquid Flow ◽

Circulating Fluidized Bed ◽

Liquid Flow Rate ◽

Tap Water ◽

Solid Particles ◽

Circulation Rate ◽

Solids Holdup

A liquid-solid circulating fluidized bed (LSCFB) is operated at high liquid velocity, where particle entrainment is highly significant and between the conventional liquid fluidized bed and the dilute phase liquid transport regimes. In the present work, systematic experiments were carried out in a 0.094 m ID and 2.4 m height laboratory-scale liquid-solid circulating fluidized bed apparatus by using various solid particles and tap water as a fluidizing medium to study the hydrodynamics (axial solids holdup and solids circulation rate). The effects of operating parameters, i.e., primary liquid flow rate in the riser (jf), auxiliary liquid flow rate (ja), total liquid flow rate (jl), particle density (?s), particle diameter (dp) and solids feed pipe diameter (do) on the axial solids holdup distribution were analyzed from the experimental data. Finally, a correlation was developed from the experimental data to estimate average solid holdup in the riser, and it was compared with present experimental and available data in the literature. They agree well with a maximum root-mean-square deviation of 9.12 %.

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Behavior of Organic and Inorganic Micropollutants in Chlorine Spiked Sludge Incineration by a Circulating Fluidized Bed Furnace

17th International Conference on Fluidized Bed Combustion ◽

10.1115/fbc2003-105 ◽

2003 ◽

Author(s):

Giuseppe Mininni ◽

Dario Marani ◽

Camilla Maria Braguglia ◽

Ettore Guerriero ◽

Andrea Sbrilli

Keyword(s):

Fluidized Bed ◽

Flue Gas ◽

Circulating Fluidized Bed ◽

Combustion Process ◽

Operating Conditions ◽

Metal Enrichment ◽

Chlorinated Organic Compounds ◽

Sludge Incineration ◽

Before And After ◽

Afterburning Chamber

The effects of combustion and feeding conditions on Polycyclic Aromatic Hydrocarbons (PAH) and PCDD/F formation and appearance in the emissions at the stack during sludge incineration are discussed in this paper. Partitioning in the solid streams of Cd, Cr, Cu, Mn, Ni, Pb and Zn is also analyzed. Tests were performed on a demonstrative plant equipped with a fluidized bed furnace (FBF) using sewage sludge either as is or spiked with chlorinated organic compounds (tetrachloroethylene or a mixture of tetrachloroethylene, chlorobenzene and toluene) to study the chlorine effect on the presence of micropollutants in the different streams. Exhaust gases were sampled both before and after the treatment system (bag house and wet scrubber). In the untreated flue gas the highest values of PCDD/F and PAH were detected when the afterburning chamber was not in use or operating at low temperatures. Operation of the afterburning chamber at temperature higher than 850–900 °C was sufficient to keep organic micropollutants concentrations in the untreated flue gas at reasonably low levels. No significant correlation of the operating conditions with emissions at the stack was found. High copper concentration in the feed enhanced PCDD/F formation, with exception of tests carried out with high afterburning temperature. The homologue profile of PCDD/F and PAH depended on test conditions. Preferential accumulation of heavy metals in the filter ash with respect to cyclone ash was quantified in terms of an enrichment factor. Out of the seven metals considered, only Cd and Pb undergo significant enrichment in the filter ash. The enrichment increased with increasing chlorine content of the feed. In contrast, Cu, Cr, Mn, Ni, and Zn behaved as refractory (non-volatile) elements even at high chlorine dosage. In accordance with the widely accepted hypothesis that metal enrichment is due to metal vaporization in the combustion chamber and subsequent condensation onto the filter ash particles, a thermodynamic model of the combustion process was able to satisfactorily predict the different metal behavior and the effect of chlorine dosage on metal enrichment.

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