Process for producing polycrystalline silicon granulate

A method of producing polycrystalline silicon granulate comprising:

• providing a reactor having a reactor tube with a fluidized bed region therein, the fluidized bed region being fluidized by a gas flow of a gas and heated by a heating apparatus;
• continuously supplying seed particles and a feed gas to the fluidized bed region, the feed gas including hydrogen, and silane and/or halosilane;
• determining a fluidized bed temperature (TWS) based on an offgas stream temperature (Toffgas,WS) represented by formula (12):
• T
• WS
• =
• T
• offgas
• ,
• WS
• =
• H
• .
• 22
• m
• .
• 22
• ,
• offgas
• ,
• WS
• *
• c
• p
• ,
• 22
• (
• 12
• )
• wherein, {dot over (m)}22,offgas,WS is an offgas mass flow from the fluidized bed region and {dot over (H)}22 is an enthalpy of the offgas mass flow from the fluidized bed ({dot over (m)}22,offgas,WS), and the enthalpy ({dot over (H)}22) of the offgas mass flow from the fluidized bed is represented by formula (10):
• {dot over (H)}22={dot over (H)}16−{dot over (H)}18−Q24−ΔRH23+Q20+{dot over (H)}21 (10),
• wherein, {dot over (H)}16 is an enthalpy of a feed gas stream ({dot over (m)}16,feed gas), {dot over (H)}18 is an enthalpy of a product stream {dot over (m)}18,Product, Q24 is energy removal from the reactor in the fluidized bed region, ΔRH23 is a reaction enthalpy, Q20 is a heating output of the heating apparatus, {dot over (H)}21 is an enthalpy of a seed particle stream into the fluidized bed region ({dot over (m)}21,KP,WS), and/or formula (11):
• {dot over (H)}22=−{dot over (H)}21+{dot over (H)}17−{dot over (H)}19−Q25 (11);
• wherein, {dot over (H)}17 is an enthalpy of the seed particle stream into the reactor ({dot over (m)}17,KP,Reactor), H19 is an enthalpy of an offgas stream from the reactor (m19,offgas, Reactor), H21 is an enthalpy of a seed particle stream into the fluidized bed region (m21,KP,wS), and Q25 is energy removal from the reactor in a region above the fluidized bed;
• and
• controlling the heating output (Q20) of the heating apparatus such that the fluidized bed temperature (TWS) is 700° C. to 1200° C., the heating output (Q20) being 0.5 to 3 KW per kilogram of silicon in the reactor tube;
• and
• wherein, elemental silicon is deposited on the seed particles to form a polycrystalline silicon granulate product that is discharged from the reactor as the product stream.