FLUIDIZED BED REACTOR

A fluidized bed reactor including in its lower part a furnace section having a bed of fluidized solid particles, the furnace section being delimited by side walls such as external side walls (22, 24) and/or partition walls (34, 36) and a bottom grid (28', 28"), and a supplying device for introducing gas, e.g. secondary air, into the furnace section at a level above the bottom grid, the supplying device including a gas source chamber (38"), an opening (48) in at least one of the side walls at a level above the bottom grid, and a conduit (42, 44) having a first end connected to the opening and a second end (52) connected to the gas source chamber. The conduit includes a solid flow seal preventing solid particles from flowing backwards from the furnace section into the conduit in a manner preventing or noticeably decreasing introduction of gas from the gas source chamber to the furnace section.