u03bcm a sphericity of 0 55 and a degree of roughness of 0 74 the sharp edged particles were discharged from the reactor with the off gas stream owing to the superficial gas velocity in the expansion head of the fluidized bed reactor of 0 4 m s and continuously removed the silicon containing deposit in the off gas heat exchanger the gas velocity in the liebig tube was 70 m s the off gas heat exchanger cooled the off gas from 700 u00b0 c to 100 u00b0 c the device used for carrying out the method is explained hereinafter with reference to fig1 and 2 the fluidized bed reactor consists of a reactor vessel 1 into which an inner reactor tube 2 is inserted between the inner wall of the reactor and the outer wall of the inner tube is situated an intermediate space 3 in the interior of the reactor tube there is situated the fluidized bed 4 with the polysilicon granules the fluidized bed is heated by means of a heating device 5 as feed gases the fluidizing gas 7 and the reaction gas mixture 6 are fed to the reactor the gas feed proceeds in this case in a specific manner via nozzles the fluidizing gas 7 is fed via bottom gas nozzles 19 and the reaction gas mixture is fed via what are termed secondary gas nozzles reaction gas nozzles 20 the height of the secondary gas nozzles can differ from the height of the bottom gas nozzles in the.