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Particle suspension in air-agitated pachuca tanks: Investigation of hysteresis and a novel split air injection technique

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Abstract

Particle suspension is an important parameter in the design of an energy-efficient Pachuca tank. The objectives of the present investigation are to (1) establish the phenomenon of hysteresis, (2) examine the effect of a novel split air injection technique on the critical velocity for particle suspension, and (3) determine the optimum state of suspension in full center column (FCC) Pachuca tanks. Extensive investigations have been carried out in three laboratory-scale Pachuca tanks with a maximum slurry density of 25 wt pct solids. Results that have a bearing on the design of energy-efficient Pachuca tanks have emerged. The magnitude of hysteresis in FCC Pachuca tanks is of the order of 20 pct, which is about 10 times less than in bubble columns. Split air injection, with 30 pct air injected into the annulus from the top and 70 pct air injected into the draft tube from the bottom, lowers the critical air velocity for particle suspension by 37 pct, with respect to bottom-blown Pachuca tanks.

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Abbreviations

d p :

particle diameter (m)

D t :

tank diameter (m)

D d :

draft tube diameter (m)

D n :

air inlet nozzle diameter (m)

H t :

tank height (m)

U c :

critical superficial air velocity for particle suspension (m/s)

U g :

superficial air velocity (m/s)

ΔU cs :

hysteresis for complete suspension (m/s)

ΔU os :

hysteresis for complete onset of suspension (i.e., complete settling) (m/s)

U c4(0 pct):

U c4 for 100 pct bottom air injection (m/s)

U c4(30 pct):

U c4 for 30 pct top-70 pct bottom split air injection (m/s)

cs :

complete suspension

os :

onset of suspension

1:

onset of settling with respect to maintaining suspension

2:

complete settling with respect to maintaining suspension

3:

onset of suspension with respect to generating suspension

4:

complete suspension with respect to generating suspension

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Authors and Affiliations

  1. the Department of Materials and Metallurgical Engineering, Indian Institute of Technology, 208 016, Kanpur, India

    S. P. Mehrotra (Professor) & R. Shekhar (Associate Professor)

Authors
  1. S. P. Mehrotra
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  2. R. Shekhar
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Mehrotra, S.P., Shekhar, R. Particle suspension in air-agitated pachuca tanks: Investigation of hysteresis and a novel split air injection technique. Metall Mater Trans B 32, 223–231 (2001). https://doi.org/10.1007/s11663-001-0045-3

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  • DOI: https://doi.org/10.1007/s11663-001-0045-3

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