co with cao and part of caso 4 serving as catalysts exhaust gases free from no x flow from the lower fluidized bed portion 11 into the upper fluidized bed portion 13 through the gas distribution holes 24 of the partition device 12 as described elsewhere combustion air is charged into the upper fluidized bed 13 from the main blower 20 through the valve 18 the header 27 the distribution pipes 26 and the nozzles 25 so that the unburned gases in the exhaust gases from the lower fluidized bed 11 are burned completely while they are passing through the upper fluidized bed 13 and the freeboard 14 so 2 and so 3 which are produced and remain in the upper fluidized bed 13 react with fluidized particles m of lime stone s and are converted into caso 3 and caso 4 which remain in the upper fluidized bed 13 as the bed or fluidized particles m together with cao which has not been reacted fluidized or bed particles m drop into the lower fluidized bed 11 as described above and become the bed or fluidized particles thereof the bed or fluidized particles in the lower fluidized bed 11 are discharged through the discharge pipe or chute 22 to the exterior of the reactor 8 thus the lower and upper fluidized beds 11 and 13 may be maintained at predetermined levels or depths exhaust gases free from no x and so x flow into the cyclone 21 where unburned particles and ash are.