Fluidized-bed combustor

A fluidized-bed combustor for combusting combustible material containing incombustible material in a fluidized-bed furnace and comprising:

• a first diffuser plate disposed at a bottom of said fluidized-bed furnace and having a plurality of holes for supplying fluidizing gas with a relatively low fluidizing gas velocity;
• a second diffuser plate disposed at a bottom of said fluidized-bed furnace and having a plurality of holes for supplying fluidizing gas with a relatively high fluidizing gas velocity;
• a combustible material supply port disposed above said first diffuser plate for supplying combustible material into said fluidized-bed furnace;
• and
• an incombustible material discharge port for discharging the incombustible material out of said fluidized-bed furnace, said incombustible material discharge port being defined between said first diffuser plate and said second diffuser plate;
• a diffuser device for supplying fluidizing gas through said incombustible material discharge port into said fluidized-bed furnace;
• said first diffuser plate having a surface inclined downwardly toward said incombustible material discharge port and operable to supply fluidizing gas to fluidize a fluidized medium at a relatively low fluidizing speed and create a descending flow of the fluidized medium;
• and
• said second diffuser plate being operable to supply fluidizing gas to fluidize the fluidized medium at a relatively high fluidizing speed and create an upward flow of the fluidized medium.