Fluidized bed furnace and waste treatment method

A fluidized bed furnace for heating waste to extract a combustible gas from the waste, comprising:

• fluidizable particles making up a fluidized bed to heat the waste;
• a furnace body having a bottom wall supporting the fluidizable particles from therebelow, and a sidewall standing upwardly from the bottom wall, wherein the bottom wall has a non-combustible substance discharge port provided at a position offset from a center position of the bottom wall in a specific direction to discharge non-combustible substances in the waste together with a part of the fluidizable particles, and an upper surface of the bottom wall is inclined to become lower toward the non-combustible substance discharge port so as to cause the non-combustible substances to fall on the upper surface of the bottom wall toward the non-combustible substance discharge port;
• a gas supply section for blowing a fluidizing gas from the bottom wall of the furnace body toward the fluidizable particles to fluidize the fluidizable particles;
• a waste supply section for supplying waste from a supply-side portion of the sidewall located on a side opposite to the non-combustible substance discharge port across the center position of the bottom wall, to a region on the fluidized bed adjacent to the supply-side sidewall portion, thereby causing the waste on the fluidized bed to be moved toward the non-combustible substance discharge port;
• and
• a sand circulation device for returning the fluidizable particles discharged from the non-combustible substance discharge port, to the fluidized bed from the side of the waste supply section to circulate the fluidizable particles, thereby forming a flow of the fluidizable particles directed from the supply-side sidewall portion located on the side opposite to the non-combustible substance discharge port, to the non-combustible substance discharge port,
• wherein:
• the gas supply section is adapted to blow the fluidizing gas from around the non-combustible substance discharge port to form a first fluidization region where the fluidizable particles are moved in a convection-like pattern and mixed with the waste to gasify the waste, while blowing the fluidizing gas between the first fluidization region and the waste supply section at a flow velocity less than that of the fluidizing gas to be blown in the first fluidization region, to form a second fluidization region having a degree of fluidization of the fluidizable particles lower than that in the first fluidization region;
• and
• the waste supply section is adapted to supply waste from the supply-side sidewall portion to the fluidized bed to cause the waste to be accumulated on the second fluidization region while causing the accumulated waste to be moved into the first fluidization region step-by-step.