To better understand the hydrodynamic behavior of an internally circulating fluidized bed,solids holdup in the down-comer(ε_(sD)),solids circulation rate(G_s) and gas bypassing fraction(from down-comer to riserγ_(DR),and from riser to down-comer γ_(RD)) were experimentally studied.The effects of gas velocities in the riser and in the down-comer(U_R and U_D),orifice diameter in the draft tube(d_(or)),and draft tube height(H_R) were investigated.Experimental results showed that increase of gas velocities led to increase in G_s and γ_(DR),and slight decrease in γ_(RD)-Larger orifice diameter on the draft tube led to higher ε_(sD),G_s and γ_(DR),but had insignificant influence on γ_(RD).With increasing draft tube height,both G_s and γ_(DR) first increased and then decreased,while γ_(RD) first decreased and then increased.Proposed correlations for predicting the hydrodynamic parameters agreed reasonably well with experimental values. To better understand the hydrodynamic behavior of an internally circulating fluidized bed, solids holdup in the down-comer (ε_ (sD)), solids circulation rate (G_s) and gas bypassing fraction (from down-comer to riserγ_ (DR) riser to down-comer γ_ (RD) were experimentally studied.The effects of gas velocities in the riser and in the down-comer (U_R and U_D), orifice diameter in the draft tube (d_ or), and draft tube (H_R) were investigated. Experimental results showed that increase of gas velocities led to increase in G_s and γ_ (DR), and slight decrease in γ_ (RD) -Larger orifice diameter on the draft tube led to higher ε_ (sD), G_s and γ_ (DR), but had insignificant influence on γ_ (RD) .With increasing draft tube height, both G_s and γ_ (DR) first increased and then decreased, while γ_ (RD) first decreased and then increased. Proposed correlations for predicting the hydrodynamic parameters agreed reasonably well with experimental values.