Transient Accumulation Behavior of Fines in Packed Beds of Pulverized Coke Particles.

Hidaka, Nobuyuki; Matsumoto, Tsunekazu; Kusakabe, Katsuki; Morooka, Shigeharu

doi:10.1252/jcej.33.152

Cited by 21 publications

(22 citation statements)

References 12 publications

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“…The time required for steady flow may depend on the experimental condition. For example, Hidaka et al 7) report an extremely short time as 5-10 min compared with Figs. 3 and 4, which may be due to a larger initial void fraction (ε 0 = 0.51) and smaller diameter ratio λ than in the present work.…”

Section: Effect Of Particle Diameter Ratio On Permeability Of Fines Flowmentioning

confidence: 93%

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Permeation and Blockage of Fine Particles Transported by Updraft through a Packed Bed

2011

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The fines generated in iron making blast furnace bring about the unsteady or unstable gas/liquid permeability and solid motion. Fundamental experiment was carried out to investigate the inhomogeneous phenomena such as flow channel blockage by fine particles transferred by updraft through a fixed packed bed. The alumina sphere and coke were used for packed bed and fine particles transferred, respectively. Conclusion of this study is as follows. The principal factor controlling a criterion for the blockage is a particle diameter ratio of coke to alumina particle, and fines concentration is not a primary factor. Consideration on a hydraulic equivalent diameter of a regular packing model of spheres is effective to predict the critical diameter ratio and it resulted in good agreement with the experimentally determined. Locally blocked mass, that is, a cluster consisting of coarse alumina particles and fines through which gas is incapable of flowing is dispersed in the bed. The void fraction of packed bed being equivalent to the pressure drop, calculated from Ergun's equation, is considerably small compared with the initial value when the local blockage is in existence. Fraction of the local blockage calculated from the void fraction and static holdup of fines is 15-20% as far as the present experimental condition.

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Section: Effect Of Particle Diameter Ratio On Permeability Of Fines Flowmentioning

confidence: 93%

“…6) However, the steady flow defined as fines supplying rate is equal to fines discharging rate from packed bed, was chosen as the subject of those studies. Transient accumulation behavior of coke fines was also studied, 7) but limited to such a system as steady state could be secured.…”

Section: Introductionmentioning

confidence: 99%

Permeation and Blockage of Fine Particles Transported by Updraft through a Packed Bed

2011

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“…13,14) Other experimental investigations also include visual characteristics of the powder accumulation. 15,16) Theoretical models for the accumulation of the injected powders, based on visual observations of a blast furnace cold model cross section 16) or on experiments covering a wide range of conditions, [17][18][19] have also been developed. However, classically studies on deposition of aerosol filtration are concentrated mainly in the collection efficiency of fibrous and granular bed filters.…”

Section: Introductionmentioning

confidence: 99%

Mathematical Model of Over-micron and Nano-scale Powders Accumulation in a Coke Fixed-Bed Filter

et al. 2005

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The advances in Electric Arc Furnace (EAF) dust treatment have been slowed down by high treatment costs and the large amount of residue to be processed and disposed. A process of direct separation and recovery of iron and zinc is now under development, which adds environmental and economical perspectives to the EAF dust treatment process. In this process, a coke bed filter can be directly connected to an EAF, collecting metallic iron and slag components, whereas the gas containing zinc and lead vapors flows to a zinc condenser. It results in zero amount of dust liberated to the environment. A two dimensional, axisymmetric and steady state mathematical model describing a coke fixed-bed filter is developed. The model solves coupled equations for gas-powder flow and is specifically applied in the investigation of over-micron and nano-scale powders (similar to EAF dust particle size) collection behavior. The theoretical model results are compared with the cold model experimental results, in which both injection of glass (over-micron) and silica (nano-scale) powders are considered. Microscopic observations and analysis are performed in order to describe better the injected powder behavior through the filter. EAF dust samples morphology is characterized as agglomerates of small particles. Its particle size distribution is obtained by the combination of leaching treatment and image analysis. Calculated results show that the powders particle size distribution has a direct effect in the static hold up. The model has been validated by its enough agreement for static hold up and pressure drop with experimental data from cold model experiments.KEY WORDS: mathematical model; Electric Arc Furnace; dust treatment; environment; packed bed; filter.have advanced for more detailed investigations, e.g. including the effect of the temperature, 23) the presence of an electrified field, 24) or the effect of the aerosol deposition on the filtration. 25) A model equation adapted from the theory for a fibrous filter, describing the dust load distribution in a coke bed filter, has also been recently developed and tested. 26)The aim of this research is contribute to the development and improvement of the process of direct separation and recovery of iron and zinc, testing and analyzing its efficiency and effectiveness. The physical modeling of the packed bed filter had provided a series of experimental results about pressure drop and the powder collection. [27][28][29][30][31][32] In this work a mathematical model of a cold coke fixed-bed filter has been developed. This model is used to investigate the powder accumulation behavior and pressure drop with the injection of over-micron and nano-scale powders in a packed bed. The mathematical model developed here is expected to be the framework for simulation of a high-temperature coke fixedbed filter and further on to study different aspects of this process. Microscopic Observations and AnalysisDue to lack of information about aerosol collection in packed bed filters, including the theoretical ...

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“…For this method fundamental flow mechanisms need to be formulated. Powder motion in packed bed had researched by several research groups to clarify traveling velocity of powder, [13][14][15] interaction force between powder and packed particles, [16][17][18][19][20][21] distribution of powder hold up 19,[22][23][24][25] and powder deposition behavior, 26,27) and their results were applied to simulate powder behavior [28][29][30][31] in shaft furnace, blast furnace mid zone, and so on. However, the effects of deadman structure and powder properties on powder and gas flows in the lower part of the blast furnace has yet to be discussed.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation on Effects of Deadman Structure and Powder Properties on Gas and Powder Flows in Lower Part of Blast Furnace

et al. 2004

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Fig. 3. Calculated in-furnace distributions of standard condition. fraction of powder in the raceway zone decreases. In the deadman zone, liquid volume fraction decreases with going down because the liquid temperature increases mainly due to heat exchange with solid phase, and liquid viscosity decreases with this temperature rise, that results in higher liquid descending velocity.Regarding to the gas temperature, it shows the maximum around the raceway end zone due to the combustion of coke and pulverized coal. The high temperature region surrounded by 2 473 K isotherm shows almond nut shape. The gas temperature decreases with ascending in the furnace mainly due to heat exchange with solid phase. In the cohesive zone, exchanged heat from gas to solid is consumed as melting latent heat, cooling rate of gas phase gets quicker. In the stack region, central gas flow forms and cone shape temperature distribution is formed. In the wall region, gas temperature increases because increase in gas flow rate due to burden distribution and assumption of adiabatic wall.The evaluation parameters for this standard condition are follows. The penetration of high temperature gas at tuyere level and the maximum penetration are 2.86 and 3.50 m, respectively, and the height of maximum penetration is 3.28 m. Flow ratios of the gas and the powder phases are 45.1 and 72.7 %. The maximum powders volume fraction in the deadman is 0.096 %, and the average liquid temperature at tuyere level is 1 751 K. Effect of Deadman Coke DiameterFigure 4 compares gas temperature distributions calculated for various deadman coke diameter. The coke diameter is decreased from 40 (a) to 15 mm (d). The high temperature region surrounded by 2 473 K isotherm shrinks with decrease in deadman coke diameter. However, deformation of this region is small. This is considered that the deadman voidage for the smallest coke diameter case (15 mm) is still 0.445, and decrease in deadman permeability is small. The deadman cools with decrease in deadman coke diameter. The isotherm of 2 273 K encroached into the deadman region in smaller diameter cases, namely 20 and 15 mm. On the contrary, the deadman coke diameter has small effect on the temperature distribution in the upper half of the furnace is small. In Fig. 4(d), slightly higher temperature region appears in the central bottom region. This temperature increase is caused by numerical instability due to accumulation of powder in central bottom numerical grid. Although this phenomenon is observed in some other cases with low permeable deadman, it is confirmed that its effect on overall calculation results is small. Figure 5 shows the variations of evaluation parameters with deadman coke diameter extracted from calculated distributions of process variables. Both the maximum and tuyere-level penetrations of hot gas into deadman and maximum penetration height monotonically increases with increase in deadman coke diameter in accordance with variation of high-temperature region shape. The maximum volume fraction of powder p...

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Transient Accumulation Behavior of Fines in Packed Beds of Pulverized Coke Particles.

Cited by 21 publications

References 12 publications

Permeation and Blockage of Fine Particles Transported by Updraft through a Packed Bed

Permeation and Blockage of Fine Particles Transported by Updraft through a Packed Bed

Mathematical Model of Over-micron and Nano-scale Powders Accumulation in a Coke Fixed-Bed Filter

Numerical Investigation on Effects of Deadman Structure and Powder Properties on Gas and Powder Flows in Lower Part of Blast Furnace

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