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A radiation-heated fluidized-bed reactor and a process for producing high-purity polycrystalline silicon by using this reactor are provided. In this reactor, a heater device (14) is a radiation source for thermal radiation which is arranged outside the inner reactor tube and as a cylinder around the

A radiation-heated fluidized-bed reactor and a process for producing high-purity polycrystalline silicon by using this reactor are provided. In this reactor, a heater device (14) is a radiation source for thermal radiation which is arranged outside the inner reactor tube and as a cylinder around the heater zone, without being in direct contact with the inner reactor tube. The inner reactor tube is designed in such a manner that it uses thermal radiation to heat the silicon particles in the heating zone to a temperature which is such that the reaction temperature is established in the reaction zone.

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What is claimed is: 1. A fluidized-bed reactor (1) comprising: a) a pressure-supporting enclosure (2); b) an inner reactor tube (3) within said enclosure ( 2) and made from a material which exhibits high transmission for thermal radiation; c) an inlet (4) at a top of said enclosure (2) for silicon

What is claimed is: 1. A fluidized-bed reactor (1) comprising: a) a pressure-supporting enclosure (2); b) an inner reactor tube (3) within said enclosure ( 2) and made from a material which exhibits high transmission for thermal radiation; c) an inlet (4) at a top of said enclosure (2) for silicon particles (5); d) an inlet device (6) for supplying a reaction gas (7) which contains a silicon compound in gas or vapor form, the inlet device (6) being of tubular design and dividing the fluidized bed into zones consisting of a heating zone (17) and a separate reaction zone (18) situated above the heating zone, wherein the inlet device is positioned so that the reaction gas supplied by the inlet device does not enter the heating zone; e) a gas-distribution device (8) at a bottom of said enclosure (2) for feeding a fluidizing gas (9) into the heating zone; f) an outlet (10) at the top of said enclosure ( 2) for reaction gas which has not fully reacted, fluidizing gas and products of reaction (11) which are in gas or vapor form and collect above a fluidized-bed surface (19); g) an outlet (12) at the bottom of said enclosure ( 2) for a product (13); h) a heater device (14); i) an energy supply (15) for the heater device ( 14); and wherein the heater device (14) is a radiation source for thermal radiation which is arranged outside the inner reactor tube and as a cylinder around the heating zone (17), without being in direct contact with the inner reactor tube, and is designed in such a manner that it uses thermal radiation to heat the silicon particles in the heating zone to a temperature which is such that the reaction temperature is established in the reaction zone (18). 2. The fluidized-bed reactor as claimed in claim 1, wherein a space between said inner reactor tube (3) and said pressure-supporting enclosure (2) is provided with thermal insulation ( 16). 3. The fluidized-bed reactor as claimed in claim 1, wherein the heater device is formed over a large area around the entire heating zone and thus forms a cylindrical radiation source. 4. The fluidized-bed reactor as claimed in claim 1, wherein the heater device emits thermal radiation with a wavelength of from 0.4 μm to 900 μm. 5. The fluidized-bed reactor as claimed in claim 4, wherein the heater device emits thermal radiation with a wavelength of from 0.4 μm to 300 μm. 6. The fluidized-bed reactor as claimed in claim 1, wherein the heater device is selected from the group consisting of a heater element made from doped silicon, a heater element made from graphite, a heater element made from silicon carbide, a quartz tube radiator, a ceramic radiator and a wire radiator. 7. The fluidized-bed reactor as claimed in claim 1, wherein all components of the reactor which come into contact with product are selected from the group consisting of an inert material and a component coated with an inert material. 8. A fluidized-bed reactor (1) comprising: (a) a pressure supporting enclosure (2); (b) an inner reactor tube (3) within said enclosure (2) and made from a material which exhibits high transmission for thermal radiation; (c) an inlet (4) at a top of said enclosure (2) for silicon particles (5) (d) an inlet device (6) for supplying a reaction gas (7) which contains a silicon compound in gas or vapor form, the inlet device (6) being of tubular design and dividing the fluidized bed into a heating zone (17) and a reaction zone ( 18) situated above the heating zone; (e) a gas-distribution device (8) at a bottom of said enclosure (2) for feeding a fluidizing gas (9) into the heating zone; (f) an outlet (10) at the top of said enclosure ( 2) for reaction gas which has not fully reacted, fluidizing gas and products of reaction (11) which are in gas or vapor form and collect above a fluidized-bed surface (19); (g) an outlet (12) at the bottom of said enclosure ( 2) for a product (13); (h) a heater device (14); (i) an energy supply (15) for the heater device ( 14); and wherein the heater device (14) is a radiation source for thermal radiation which is arranged outside the inner reactor tube and as a cylinder around the heating zone (17), without being in direct contact with the inner reactor tube, and is designed in such a manner that it uses thermal radiation to heat the silicon particles in the heating zone to a temperature which is such that the reaction temperature is established in the reaction zone (18) and wherein the heater device is a tube with meandering slots made from graphite with a SiC surface coating which is arranged in the reactor, standing on or hanging from electrode terminals.