Purpouse:
The plant is designed for production of granular polycrystalline solar-grade silicon with the granule size of up to 1 mm. The continuous production of granular polycrystalline silicon in a fluidized bed reactor can be accomplished after prior optimization of operating conditions.
Short description and main performance characteristics; и основные технико-экономические показатели, advantageous over existing analogues:
The principle of plant operation is to fluidized of fine-dispersed silicon seed particles and to obtain deposition of silicon from monosilane on the surface of these particles.
For this purpose, the initial quantity of silicon fine-dispersed seed particles with prescribed size distribution is downloaded in the reactor. Degassing and nitrogen blowing of reactor and gas pipe lines is performed to remove oxygen and water marks from the system. In the beginning of attaining the prescribed temperature level in the reactor, nitrogen is supplied through a gas-distribution grate in its bottom to fluidized layer of seed particle. Nitrogen is gradually replace by hydrogen during this process of fluidized layer heating.
Monosilane-hydrogen mixture is fed into the reactor after attaining the operation temperature in the fluidized bed. Chemical vapor deposition of silicon proceeds at the surface of seed particles. Seed particle gain their size during silicon deposition and granules of polycrystalline silicon are formed. Large granules of polycrystalline silicon (of prescribed size) go down to the bottom of reactor and then are removed from the reactor by means of output device. To compensate reduction of the mass of fluidized layer and to provide continuous process in the reactor, the appropriate amount of new seed particles is fed into the reactor by means of charging device.
The main advantages of developed method are the following:
– High production rate;
– Comparatively simple equipment and possibility of continuous automated process;
– Low specific energy consumption comparatively to conventional multi-rod (Siemens) reactors;
– Low prime cost of the product in comparison with Siemens method.

Degree of method readiness:
Bench-scale fluidized-bed apparatus (photo); mathematical models allowing optimization of the process in the fluidized-be reactor and transition to the industrial scale; input (benchmark) design data for pilot-industrial plant.

Technical parameters of the fluidized-bed reactor
Output up to                                                          3 kg/h
Monosilane flow rate                                         2500 l/h
Hydrogen flow rate                                         18000 l/h
Inert gas flow rate                                          18000 l/h
Inner diameter of working zone of the reactor      150 mm
Temperature of fluidized bed up to                      850 °С
Power of the outer resistance-type heater up to     25 kW
Initial size of silicon seed particles from   0.25 to 0.30 mm
Size of discharged silicon particles up to                 1 mm

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