To provide a method and system for preventing unburnt components from scattering in a pressure fluidized bed boiler, in which the operability of plant is improved significantly.

Run-of-mine coal A in a run-of-mine coal banker 1 and run-of- mine coal B, having high coking property in a run-of-mine coal banker 2, are crushed separately by means of a crusher 3. Mixture of crushed run-of-mine coals A, B is fed to a kneader 5, where it is stirred along with a specified quantity of water and limestone to produce CWP containing prescribed moisture. The CWP is fed to a pressure fluidized bed boiler 6 and burnt. Since specified quantities of coals are fed separately to the crusher 3, the CWP can be mixed with the coal B having high coking property at a constant ratio. Since the coal B is susceptible to condensation during combustion, it acts as a binder with respect to the coal A. Since fine particles are condensed in the fluidized bed, they are hardly scattered. Furthermore, unburnt components are prevented from scattering because the mass of CWP is less likely to be broken by the coal B having high coking property when a plant is started.