To provide a circulated fluidized furnace capable of reducing unburnt combustible content included in a furnace gas by properly bringing the secondary air, improving desulfurization rate, smoothing the circulation of a fluid medium, and achieving stable operation of the furnace.
In this circulated fluidized furnace 20 wherein a fluid bed 17 is formed on a furnace bottom for burning sludge 32 while mixing it with the fluid medium by the primary air 31 introduced from a bottom part of a riser 11, and a free board 18 is formed at an upper part of the fluidized bed 17 to circulate the fluid medium by the secondary air 31 introduced from a secondary air blowout nozzle 20, a taper restriction part 25 is formed in a state that its diameter is reduced downward from an upper position of the secondary air blowout nozzle 20, a riser diameter D0 of a height position of the secondary air blowout nozzle 20 is smaller than a riser diameter D of an upper part with respect to the restriction part 25, and a riser lower space is smaller than a riser upper space to increase a void tower speed at the lower part of the riser.
YOSHIDA SUEO
SASAYA SHIRO
KUROYAMA KAZUHIRO
Hisamaru Hanada
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