XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1991
CFD simulations reveal consistent trends in bed height
versus fluidisation rate across all particle sizes. Initially, no
noticeable bed expansion is observed until the fluidisation
rate reaches a minimum threshold. Subsequently, the bed
expands, particularly for smaller particles, with escalat-
ing turbulence becoming evident as the fluidisation rate
increases. However, for coarser particles (600 and 700 µm),
the bed appears to achieve a state of minimum fluidisation,
aligning well with the experimental findings.
Figure 4 presents a comparison of the bed differential
pressure at various fluidisation rates. It is evident that the
bed differential pressure rises with increasing flowrate until
the bed attains a state of minimum fluidisation and stabi-
lizes. During minimum fluidisation, the differential pres-
sure across a particulate bed equals the effective bed weight,
and subsequent increases in flowrate have no further impact
as the bed expands to facilitate fluid passages (Sutherland
et al., 1963). Notably, for smaller particles, the differential
pressure is higher compared to coarser particles, indicating
the influence of particle size on bed hydrodynamics. The
pressure values predicted by CFD simulations for larger
particles exhibit reasonable agreement with the experimen-
tal data. It is acknowledged that a bed comprising multiple
particle sizes may exhibit different characteristics than one
containing mono-sized particles, providing an avenue for
exploration in future studies.
Effect of Particle Size on the Bed Hydrodynamics
Figure 5 illustrates the impact of particle size and flowrate
on fluidised bed hydrodynamics. CFD simulations reveal
that bed expansion increases with decreasing particle size
(Figure 5a). Additionally, the bed expands linearly with
increasing flowrate. Coarser particles (700 and 600 µm)
exhibit the lowest bed expansion, reaching a maximum
height of 15.7 cm. In contrast, for smaller particles (450
and 350 µm), bed expansion initiates with increasing flow-
rate, accelerates beyond the minimum fluidisation velocity,
and stabilizes at a height of approximately 20.0 cm. This
observation aligns with findings in other published litera-
ture (Peng et al., 2021).
In fluidised beds, the passage of fluid through a par-
ticulate bed induces a pressure drop, attributed to frictional
loss and inertia. The lowest time-averaged bed differential
pressure (approximately 2000 Pa) is noted for larger diam-
eter particles, whereas the highest is observed for smaller
particles, resulting in nearly double the pressure for the
latter compared to the larger size groups (Figure 5b).
Interestingly, higher flowrates do not appear to exert a sig-
nificant influence on the bed pressure drop. This finding
aligns with similar observations reported in the literature
regarding the measurement of bed pressure drop in flui-
dised beds (Islam &Nguyen, 2021 Peng et al., 2022).
This bed behaviour is attributed to the properties of
solid particles, where both density and diameter signifi-
cantly impact fluidisation velocity (Rao et al., 2010 Tang,
Liu, &Li, 2016). Heavier and larger particles possess higher
Figure 4. Comparison of numerically predicted bed pressure vs fluidisation rate with experimental results
CFD simulations reveal consistent trends in bed height
versus fluidisation rate across all particle sizes. Initially, no
noticeable bed expansion is observed until the fluidisation
rate reaches a minimum threshold. Subsequently, the bed
expands, particularly for smaller particles, with escalat-
ing turbulence becoming evident as the fluidisation rate
increases. However, for coarser particles (600 and 700 µm),
the bed appears to achieve a state of minimum fluidisation,
aligning well with the experimental findings.
Figure 4 presents a comparison of the bed differential
pressure at various fluidisation rates. It is evident that the
bed differential pressure rises with increasing flowrate until
the bed attains a state of minimum fluidisation and stabi-
lizes. During minimum fluidisation, the differential pres-
sure across a particulate bed equals the effective bed weight,
and subsequent increases in flowrate have no further impact
as the bed expands to facilitate fluid passages (Sutherland
et al., 1963). Notably, for smaller particles, the differential
pressure is higher compared to coarser particles, indicating
the influence of particle size on bed hydrodynamics. The
pressure values predicted by CFD simulations for larger
particles exhibit reasonable agreement with the experimen-
tal data. It is acknowledged that a bed comprising multiple
particle sizes may exhibit different characteristics than one
containing mono-sized particles, providing an avenue for
exploration in future studies.
Effect of Particle Size on the Bed Hydrodynamics
Figure 5 illustrates the impact of particle size and flowrate
on fluidised bed hydrodynamics. CFD simulations reveal
that bed expansion increases with decreasing particle size
(Figure 5a). Additionally, the bed expands linearly with
increasing flowrate. Coarser particles (700 and 600 µm)
exhibit the lowest bed expansion, reaching a maximum
height of 15.7 cm. In contrast, for smaller particles (450
and 350 µm), bed expansion initiates with increasing flow-
rate, accelerates beyond the minimum fluidisation velocity,
and stabilizes at a height of approximately 20.0 cm. This
observation aligns with findings in other published litera-
ture (Peng et al., 2021).
In fluidised beds, the passage of fluid through a par-
ticulate bed induces a pressure drop, attributed to frictional
loss and inertia. The lowest time-averaged bed differential
pressure (approximately 2000 Pa) is noted for larger diam-
eter particles, whereas the highest is observed for smaller
particles, resulting in nearly double the pressure for the
latter compared to the larger size groups (Figure 5b).
Interestingly, higher flowrates do not appear to exert a sig-
nificant influence on the bed pressure drop. This finding
aligns with similar observations reported in the literature
regarding the measurement of bed pressure drop in flui-
dised beds (Islam &Nguyen, 2021 Peng et al., 2022).
This bed behaviour is attributed to the properties of
solid particles, where both density and diameter signifi-
cantly impact fluidisation velocity (Rao et al., 2010 Tang,
Liu, &Li, 2016). Heavier and larger particles possess higher
Figure 4. Comparison of numerically predicted bed pressure vs fluidisation rate with experimental results