The troublesome problems occurred in four years from putting an imported title boiler into operation are presented

and retrofit of its components

such as fluidizing air pipes

cooling water pipes

cooling water tank

secondary air fan

primary air fan

non-metallic expansion joints on feed-back leg of cyclonic-separater

fly ash recirculating system

upper opening of secondary air

bottom ash cooler etc.

is described. It is considered to have definite value for reference in design and operation of CFB boilers.