Circulating fluidized bed boiler

The utility model belongs to the technical field of boilers, and particularly relates to a circulating fluidized bed boiler which comprises an air pipe, a limiting ring and a bell-shaped air cap head, the top end of the air pipe is designed to be open, a compression spring is arranged in the air pipe, a channel is formed in the outer wall of the air pipe in a penetrating mode, and the limiting ring is arranged in the channel. When the bell-shaped air cap head is installed, a fixing block arranged on the air cap head slides along the channel, so that after the air cap head enters an inner cavity of the air pipe, the air cap head is fixed to the air pipe, and the air pipe is fixed to the air pipe. The limiting ring is rotated to enable the limiting groove to be in contact with the top end of the fixing block so that the air cap head can be limited, the fixing block is limited by the limiting groove, so that the air cap head is difficult to jack up to fall off, the connection stability of the air pipe and the be