The flow behaviors in the downer of a large-scale triple-bed circulating fluidized bed (TBCFB) gasifier cold model, which is composed of a downer (Phi 0.1 m x 6.5 m), a bubbling fluidized bed (BFB, 0.75 x 0.27 x 3.4 m(3)), a riser (Phi 0.1 m x 16.6 m) and a gas-sealing bed (GSB, Phi 0.158 m x 5 m), were investigated. Sand particles with a density of 2600 kg/m(3) and an average particle size of 128 mu m were used as bed materials. Solids mass fluxes were in the range 113-524 kg/m(2) s. Average solids holdup in the developed region of the downer increased with increasing solids mass flux. The gas seal between the riser and the downer had a large effect on the solids holdup distribution in the downer. Compared with the solids holdup in the riser, a relatively low solids holdup was formed in the downer even at high solids loadings. A pressure balance model was set up to predict the solids mass flux for this TBCFB system. It was found that the static bed height in the GSB had a great effect on the solids mass flux. The possibilities of achieving a high density solids holdup in a downer were discussed. (C) 2011 Elsevier Ltd. All rights reserved.