Fluidized bed reactor and process for producing polycrystalline silicon granules

In a fluidized bed reactor for producing polycrystalline silicon granules comprising a reactor head, a reactor tube and a reactor base, and additionally comprising a heating device, at least one base fluidizing gas supply nozzle and also at least one secondary reaction gas supply nozzle, a seed particle feeder, a polycrystalline silicon granule product withdrawal line, and also an off-gas removal appliance, the improvement comprising:

• providing high purity graphite seals to seal at least one of the base fluidizing gas nozzle, the at least one secondary reaction gas supply nozzle, or the polycrystalline silicon granule product withdrawal line, against the reactor base, or to seal the reactor tube against the reactor head and the reactor base, wherein the seals comprise chambered seals of graphite containing less than 500 ppmw of phosphorus, between inner and outer flanges of stainless steel.