Abstract
Hydrodynamic properties in turbulent fluidized beds of three different sizes of coal (d p = 0.507, 0.987, 1.147 mm) have been determined from the pressure fluctuations in a 0.1 m-ID × 3.0 m high Plexiglas column. The transition velocity from the slugging to turbulent flow regimes can be determined from the statistical analysis of pressure fluctuations such as mean amplitude, standard deviation and skewness, the pressure wave velocity, and the bed expansion with gas velocity. The bed expansion in the slugging and turbulent flow regimes cannot be estimated from the two-phase theory. The voids rise velocity and the bed expansion ratio (H/H mf ) in the turbulent flow regime have been correlated with the relevant dimensionless and operating parameters\(\begin{gathered} V_t = 40.66Ar^{ - 0.280} \left[ {0.35\left( {gD_t } \right)^{1/2} } \right] - U_{mf} \hfill \\ \frac{H}{{H_{mf} }} = 1 + 10.805Ar^{ - 0.290} \left( {\frac{{U_g - U_{mf} }}{{V_t }}} \right)0.635 \hfill \\ \end{gathered} \)
The ransition velocity to the turbulent flow regime has been determined based on the slug breakdown caused by the inertial force of an upflowing maximum stable slug which overcomes the gravitational force induced by solid refluxing as:\(\operatorname{Re} _c = \left[ {\left( {33.7} \right)^2 + 0.0408Ar} \right]^{1/2} + 0.598Ar^{1/2} - 33.7\)
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Abbreviations
- Ar:
-
Archimedes number, d 3cp ρg(ρs-ρg)g/Μ2
- dp :
-
mean particle size, m
- dpi :
-
mean particle size in the i-th size interval, m
- ds :
-
slug size, m
- Dt :
-
column diameter, m
- Fr:
-
Froude number, ρgU 2s.max /(ρs-Pg)gdp
- g:
-
gravitational constant m/s2
- H:
-
expanded bed height, m
- H mf :
-
bed height at minimum fluidizing condition, m
- δ L:
-
distance between measuring points, m
- n:
-
Richardson-Zaki’s index
- δ P:
-
pressure drop, Pa
- Rec :
-
Reynolds number based on the transition velocity to turbulent flow regime, ρgdρUc/Μ
- Remf :
-
Reynolds number based on the minimum fluidizing gas velocity,ρgdpUmf/Μ
- Uc :
-
transition velocity from slugging to turbulent flow regimes, m/s
- Ucl :
-
terminal velocity of clusters, m/s
- Ug :
-
superficial gas velocity, m/s
- Umf :
-
minimum fluidizing gas velocity, m/s
- Us :
-
slug rise velocity, m/s
- Ut :
-
terminal velocity of an individual particle, m/s
- Vt :
-
voids rise velocity, m/s
- wi :
-
weight fraction of the i-th particle size
- ε:
-
bed voidage
- ε mf :
-
bed voidage at minimum fluidizing condition
- μ :
-
gas viscosity, Pa.s
- ρ g :
-
gas density, kg/m3
- ρ s :
-
particle density, kg/m3
- Σ :
-
standard deviation of particle size distribution, m
- av:
-
average
- c:
-
calculated
- m:
-
measured
- max:
-
maximum stable bubble
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Lee, G.S., Kim, S.D. Hydrodynamic properties of coal in turbulent fluidized beds. Korean J. Chem. Eng. 6, 338–346 (1989). https://doi.org/10.1007/BF02705223
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DOI: https://doi.org/10.1007/BF02705223