To solve the plastic deformation problem occurred in central cylinder of cyclone separator in circulating fluidized bed(CFB) boiler

according to the force form of the central cylinder

an analytical model of the cylinder with simple support or clamped support on one end

free on the other end is established in this paper. The results show that

under the action of external pressure

large circumferential bending stress is formed in the central cylinder of the cyclone separator. When the stiffness of the exit tube is insufficient

the bending stress will directly lead to the instability of the cylinder. When the stiffness meets the requirements

the bending stress will cause the instability deformation or creep deformation of the central cylinder under external pressure due to long-time operation of the central cylinder at high temperature. This deformation has the characteristics of ellipse ormulti waveform of the instability deformation as the general external pressure cylinder. Measures like setting the stiffening ring to improve the stiffness of the central cylinder can be taken to avoid the instability deformation.