Fluidized bed reactor and process for producing polycrystalline silicon granules

A fluidized-bed reactor for producing granular polycrystalline silicon, comprising:

• a reactor vessel, and a reactor tube and a reactor bottom within the reactor vessel, wherein the reactor tube comprises a main element with a surface coating, and an intermediate jacket is present between an outer wall of the reactor tube and an inner wall of the reactor vessel, and further comprising a heating device, at least one fluidizing gas nozzle for introduction of a fluidizing gas and at least one reaction gas nozzle for introduction of reaction gas, a silicon seed particle feed for introducing silicon seed particles, an offtake conduit for granular polycrystalline silicon product and a reactor offgas discharge, wherein the main element of the reactor tube comprises a base material having an ash content of <2000 ppmw and the surface coating is a CVD coating which has a layer thickness of from 5 μm to 700 μm and comprises at least 99.995 % by weight of silicon carbide.