Fluidized bed reactor and method for producing granular polysilicon

Patent metadata

Field	Value
Publication number	US-2016236940-A1
Application number	US-201414888594-A
Country	US
Kind code	A1
Filing date	Apr 15, 2014
Priority date	May 2, 2013
Publication date	Aug 18, 2016
Grant date	—

Abstract

Granular polysilicon is produced in a fluidized-bed reactor by fluidizing silicon particles by means of a gas flow in a fluidized bed heated to a temperature of 850-1100° C., adding a silicon-containing reaction gas by means of a nozzle and depositing of silicon on the silicon particles, wherein, in at least 56% of an axially symmetric region around a nozzle opening of the nozzle,
the reaction gas concentration is greater than 75% of the maximum concentration of the reaction gas (10 to 50 mol %),
the fluidized-bed temperature is greater than 95% of the fluidized-bed temperature outside the axially symmetric region (850-1100° C.) and
the solids concentration is greater than 85% of the solids concentration at the edge of the fluidized bed (55 to 90% by volume).

First claim

1 .- 9 . (canceled)

10 . 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×m 2 ), a specific hydrogen volumetric stream is 800-4000 Nm 3 (STP)/h×m 2 ), a specific bed weight of the fluidized bed is 800-2000 kg/m 2 , a specific seed particle metering rate is 8-25 kg/(h×m 2 ) and a specific reactor heating power is 800-3000 kW/m 2 , 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 L G reaction gas concentration is equal to 75% of the maximum concentration of the reaction gas, and
an L T temperature is equal to 95% of the fluidized-bed temperature outside the jet region, and
an L 1−∈ 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 h T of nozzle opening from respective points of intersection of the isolines for temperature L T and solids concentration L 1−∈ 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 L G with the line of axial spacing=2h T ; and
a maximum axially symmetric region=r×2h T .

11 . The method of claim 10 , wherein a plurality of reaction gas nozzles are present and a spacing y between a reactor wall and a closest spaced reaction gas nozzle satisfies the relationship 1.5r<y<2.5r.

12 . The method of claim 11 , wherein a spacing x of two adjacent reaction gas nozzles satisfies the relationship: 2r<x<3.2r.

13 . The method of claim 10 , wherein the isolines L G reaction gas concentration equal to 75% of the maximum concentration of the reaction gas, L T temperature equal to 95% of the fluidized-bed temperature outside the jet region, and L 1−∈ solids concentration equal to 85% of the solids concentration at the edge of the fluidized bed, are determined by fluidizing silicon particles by means of a gas flow containing nitrogen in a fluidized bed instead of a hydrogen gas flow, adding a gas mixture containing nitrogen and containing helium as a tracer gas, instead of adding trichlorosilane, which characterizes the spread of the reaction gas of at least one nozzle in the measurement and measuring solids concentration, tracer gas concentration and temperature distribution in the axially symmetric region of the at least one nozzle by means of measuring probes which are mounted in the reactor interior, and after determination of the axially symmetric region, producing granular polysilicon.

14 . The method of claim 10 , wherein particles which have grown in diameter by deposition are removed from the reactor and fresh silicon particles are continuously added.

15 . A fluidized-bed reactor for producing granular polysilicon by the method of claim 10 , comprising a container having an inner reactor tube for a fluidized bed of granular polysilicon and a reactor bottom, a heating device for heating the fluidized bed in the inner reactor tube, at least one bottom gas nozzle for feeding fluidizing gas, and at least one reaction gas nozzle for feeding reaction gas, a reactor off-gas outlet comprising an off-gas conduit in which a gas chromatograph is situated, at least one pyrometer for determining the fluidized-bed temperature, a silicon particle feeder, a take-off conduit for removing granular polysilicon product, wherein a spacing y between a reactor wall and a closest spaced reaction gas nozzle satisfies the relationship 1.5r<y<2.5r, wherein r is the maximum radius of an axially symmetric region around a nozzle opening, where r is determined as follows:
determination of isolines in a jet region:
an L G reaction gas concentration equal to 75% of the maximum concentration of the reaction gas,
an L T temperature equal to 95% of the fluidized-bed temperature outside the jet region,
an L 1−∈ solids concentration equal to 85% of the solids concentration at the edge of the fluidized bed;
the isolines in the jet region are plotted, where in the y direction, the axial spacing from the nozzle opening and, in the x direction, the radial spacing from the nozzle opening are plotted;
the minimum axial spacing h T of the nozzle opening from the respective points of intersection of the isolines for temperature L T and solids concentration L 1−∈ with the line of radial spacing=0 is determined;
wherein the maximum radius r of the axially symmetric region is defined as a radial spacing of the nozzle opening from a point of intersection of the isoline L G with the line of axial spacing=2h T .

16 . The fluidized-bed reactor of claim 15 , wherein the fluidized-bed reactor comprises a plurality of reaction gas nozzles and a spacing x of two adjacent reaction gas nozzles satisfies the following relationship: 2r<x<3.2r.

17 . The fluidized-bed reactor of claim 15 , wherein a control section is situated between the gas chromatograph and the polysilicon particle feeder appliance, and the control section adjusts a polysilicon particle feed based on chromatographic determined concentration of components in a reactor off-gas.

18 . The fluidized-bed reactor of claim 16 , wherein a control section is situated between the gas chromatograph and the polysilicon particle feeder appliance, and the control section adjusts a polysilicon particle feed based on chromatographic determined concentration of components in a reactor off-gas.

19 . The fluidized-bed reactor of claim 16 , wherein a control section is situated between the gas chromatograph and the heating device, and the control section adjusts power to the heating device based on chromatographic determined concentrations of components in a reactor off-gas.

19 . The fluidized-bed reactor of claim 17 , wherein a control section is situated between the gas chromatograph and the heating device, and the control section adjusts power to the heating device based on chromatographic determined concentrations of components in a reactor off-gas.

20 . The fluidized-bed reactor of claim 16 , wherein a control section is situated between the gas chromatograph and the heating device, and the control section adjusts power to the heating device based on chromatographic determined concentrations of components in a reactor off-gas.

Assignees

• Wacker Chemie Ag

Inventors

• Weckesser Dirk
• Hertlein Harald

Classifications

• B01J2208/00017

  Controlling the temperature · CPC title

• B01J8/1872

  Details of the fluidised bed reactor (B01J8/1836 takes precedence) · CPC title

• C01B33/03 Primary

  by decomposition of silicon halides or halosilanes or reduction thereof with hydrogen as the only reducing agent · CPC title

• B01J2208/065

  Heating or cooling the reactor · CPC title

• B01J2208/00761

  Discharging · CPC title