Abstract: A fluidized bed apparatus having a gas distribution plate containing a plurality of tuyeres, which tuyeres provide a uniform gas flow from the gas chamber of the apparatus to the reactor chamber of the apparatus and prevents particulate matter of the fluidized bed from backsifting from the fluid bed chamber through the gas distribution plate to the gas chamber. The tuyeres are secured in openings in the gas distribution plate and comprise a porous plate and preferably a perforated plate superposed within a flanged two-component structure which two components are screwed together or otherwise secured together to form the tuyere.