KIER hot gos desulfurization system consisting of a reactor of a transport mode, a regenerator of a fluidized bed mode, two loopseals, and two gas streams was tested for the stable operation of circulating solids between two reactors. Pressures in a circulation loop at various conditions were measured in a cold mode(a 0.03 m I.D. riser and a 0.075m I.D. fluidized bed) with particles of mean diameter of 87×10^-6 m and the bulk and particle density of 1,900 and 3,300 kg/m³ respectively. The voidages and mixture densities of gas-solid at various sections were analyzed from differential pressures data. The continuous circulation of solids was confirmed by the single closed loop of pressure balance curves. The loopseal took a role of preventing the gas of a reactor from flowing to another reactor.