Wall-to-bed heat transfer in a circulating fluidized bed for the reduction of iron ore particles

Hahn, Yoon‐Bong; Im, Yu-Bin

doi:10.1007/s11663-997-0045-z

Cited by 5 publications

(9 citation statements)

References 26 publications

(59 reference statements)

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“…And it has been observed in practice especially for fine iron oxide particles. [18][19][20][21] Hence, it is assumed that the mass transfer resistance of gases from the bulk to the surface can be neglected. Thurnhofer 18) conducted microscopical analyses of polished sections of reduced iron ore fines and observed that a high amount of pores were spread through the entire fine.…”

Section: )mentioning

confidence: 99%

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Simulation Study on Performance of Z-path Moving-fluidized Bed for Gaseous Reduction of Iron Ore Fines

2012

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Performance of the Z-path moving-fluidized bed reactor for gaseous reduction of iron ore fines was numerically investigated. The proposed mathematical model was developed by analyzing the gas-solid transport phenomena and chemical reactions in the reactor. The model was solved by a new solving approach -integration of FLUENT package (V6.3) and PHOENICS (V3.3). Numerical simulation results of cold state were compared with the experimental data and the simulation results including pressure drop per perforated plate, gas flow pattern and solid flow pattern agreed well with the experimental ones. The developed CFD model then conducted some hot state predictions of gaseous reduction of iron ore fines using reformed COG gas and purified COREX export gas in this reactor. Results indicate that under hot state, the performance of the reactor depends on the reducing gas supplied. Pressure drop per perforated plate decreases one by one from the bottom plate to the top plate and some improvements are needed for the perforated plate arrangement in the reactor. For ore fines gaseous reduction, the reactor displays a high utilization efficiency of gas sensible heat and gas reduction potential. The Z-path moving fluidized bed has the advantage that it realizes a gradient utilization of heat and reduction potential of the gas in iron ore fines reduction with a comparatively simple structure. In the cases simulated, the top two plates play a role of preheating the ore fines and the bottom three plates reducing the ore fines. For operation control, the reactor with three inclined perforated plates is reasonable and preheating ore fine may be carried out by other means.

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Section: )mentioning

confidence: 99%

“…So pore diffusion is not limiting the reduction. Based on these assumptions and observations, Hahn,19,20) Thurnhofer,…”

Section: )mentioning

confidence: 99%

Simulation Study on Performance of Z-path Moving-fluidized Bed for Gaseous Reduction of Iron Ore Fines

2012

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“…Equation [13] indicates that the fines have smaller residence times than the coarse because of larger K(d pi ) values for the fines. In the extreme, for fine particles, where K(d pi )…”

Section: Residence Time Distributionmentioning

confidence: 99%

“…Recently, Hahn et al [11,12,13] bed (CFB) for prereduction of iron ores. Their model incorporates hydrodynamics, reduction kinetics, and heat and mass transfer.…”

Section: Introductionmentioning

confidence: 99%

“…[11,12] They also developed a wall-tobed heat transfer model to describe the heat transfer occurring in the CFB based on the core-annulus type flow structure and the wall emulsion layer growing downward along the surface. [13] However, for the reduction of iron ore particles in a bubbling bed, especially in the two stages of the twin-fluidized bed (TFB) system, little work has been done in terms of mathematical modeling. Considerable size degradation of iron ore particles has been reported in both types of fluidized bed systems.…”

Section: Introductionmentioning

confidence: 99%

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Mathematical modeling of the reduction process of iron ore particles in two stages of twin-fluidized beds connected in series

Hahn

Chang

1998

Metall Mater Trans B

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A mathematical model is presented to describe the reduction process of iron ore particles in two stages of twin-fluidized beds (TFBs) connected in series: prereduction and final reduction stages. Main features of the model are the inclusion of particle degradation phenomenon to account for its effect on reduction of iron oxides and reduction kinetics for multiparticles having a wide size distribution. It was found that about 90 pct of overall particle degradation occurs in the prereduction stage mainly due to thermal stress and volume expansion. The reduction degree of particles larger than 1 mm decreased fast with increasing particle size in both the prereduction and final reduction stages. However, the particles sized between 0.2 and 1 mm showed mild increase in reduction degree, and steep increase for the fines smaller than 0.2 mm. The reduction degree was also gradually decreased with increasing the gas oxidation degree of feed gas in both the prereduction and final reduction stages. It was found that to obtain a desired reduction degree, it is of great importance to control the bed temperature in stage I rather than in stage II. The optimum range of residence time was 15 to 20 minutes in the prereduction stage and 30 to 35 minutes in the final reduction stage.

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Density Functional Theory Study on the Carbon-Adhering Reaction on Fe3O4(111) Surface

Zhong

Zou

et al. 2015

Metall Mater Trans B

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The density functional theory (DFT) has been employed to investigate the carbon-adhering reaction on Fe 3 O 4 (111) surface, which consists of two steps: (1) the adsorption of CO onto the Fe 3 O 4 (111) surface and (2) the second CO seizes an O atom from CO, which adsorbed on the surface, to form a CO 2 molecule and the C atom left behind adheres onto the Fe 3 O 4 (111) surface. At step 1, there are five stable configurations of CO adsorbed onto Fe oct2 -terminated Fe 3 O 4 (111) surface and four stable formations of CO adsorbed onto the Fe tet1 -terminated Fe 3 O 4 (111) surface. The top configurations of these two surfaces are most stable. Moreover, a density of the state (DOS) analysis is used to investigate the bonding mechanism of CO adsorbed onto these two surfaces. The results reveal the new C-O bonds generation on two surfaces, which is important and necessary for the formation of a CO 2 molecule. Besides, the transition states (TS) are searched to analyze the energy barrier in the process of CO 2 desorption from two surfaces. The result indicates that the oxidation reaction of adsorbed CO molecule and surface O atom is feasible. For step 2, the result shows that the carbon-adhering reaction occurs only on the top site of Fe oct2 atom and the magnetite plays a catalytic role in the carbonadhering reaction process.

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Wall-to-bed heat transfer in a circulating fluidized bed for the reduction of iron ore particles

Cited by 5 publications

References 26 publications

Simulation Study on Performance of Z-path Moving-fluidized Bed for Gaseous Reduction of Iron Ore Fines

Simulation Study on Performance of Z-path Moving-fluidized Bed for Gaseous Reduction of Iron Ore Fines

Mathematical modeling of the reduction process of iron ore particles in two stages of twin-fluidized beds connected in series

Density Functional Theory Study on the Carbon-Adhering Reaction on Fe3O4(111) Surface

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