Fluidized bed reactor and method for producing granular polysilicon

A method for producing granular polysilicon in a fluidized-bed reactor, comprises fluidizing silicon seed particles by a hydrogen gas flow in a fluidized bed which is heated to a temperature of 850-1100° C., adding trichlorosilane as a silicon-containing reaction gas by means of at least one nozzle, wherein a local gas velocity at an outlet of the at least one nozzle is 0.5 to 200 m/s, and depositing silicon on the silicon seed particles, wherein, relative to the reactor cross sectional area, a specific mass stream of trichlorosilane is 1600-5500 kg/(h×m2), a specific hydrogen volumetric stream is 800-4000 Nm3(STP)/h×m2), a specific bed weight of the fluidized bed is 800-2000 kg/m2, a specific seed particle metering rate is 8-25 kg/(h×m2) and a specific reactor heating power is 800-3000 kW/m2, and wherein the mass stream of trichlorosilane, the hydrogen volumetric stream and the reactor heating power are selected such that in at least 56% of an axially symmetric region around a nozzle opening of the at least one nozzle;

• the reaction gas concentration is greater than 75% of a maximum concentration of the reaction gas of 10 to 50 mol %,
• the fluidized-bed temperature is greater than 95% of a maximum fluidized-bed temperature of 850 to 1100° C.;
• and
• the solids concentration is greater than 85% of a maximum solids concentration of the fluidized bed of 55 to 90% by volume;
• wherein the axially symmetric region around a nozzle opening is determined as follows:
• determining isolines in a jet region, wherein an LG reaction gas concentration is equal to 75% of the maximum concentration of the reaction gas, and
• an LT temperature is equal to 95% of the fluidized-bed temperature outside the jet region, and
• an L1−∈ solids concentration is equal to 85% of the solids concentration at the edge of the fluidized bed;
• plotting a representation of the isolines in the jet region, where in the y direction, the axial spacing from the nozzle opening and, and in the x direction, the radial spacing from the nozzle opening are plotted;
• determining a minimum axial spacing hT of nozzle opening from respective points of intersection of the isolines for temperature LT and solids concentration L1−∈ with the line of radial spacing=0;
• defining a maximum radius r of the axially symmetric region as a radial spacing of the nozzle opening from a point of intersection of the isoline LG with the line of axial spacing=2hT;
• and
• a maximum axially symmetric region=r×2hT.