The flooding characteristics of hydrofoil impeller were systematically investigated in a two-and three-phase 383 mm i.d. stirred tank operated on air

water and spherical glass beads. The volumetric solid concentration

C

s

was varied from 0 to 25%. And the superficial gas velocity

U

g

was at the range of 0-0.096 m·s

-1

. A fast and objective method for identifying flooding point

N

F

is developed based on the statistical analysis of the pressure fluctuation signals. It is found

the effect of solid concentration on the flooding point

N

F

depends on the gas velocity. At the lower gas velocity (

U

g

=0.010 m·s

-1

)

the solid concentration has only a minor effect. However

it displays a very significant effect on the flooding point

N

F

at the medium and high gas velocity. The flooding point

N

F

linearly increases with the gas velocity

U

g

at lower solid concentration (

C

s

=0

10%). When

C

s

=20%

the behavior of

N

F

versus

U

g

becomes more complex. The correlations of the flooding characteristics in the slurry stirred tank are proposed by considering the solid concentration effect.