silicon for the chemical and solar industry XIII

Technical Solution

The proposed technology concept utilizes in-house developed process steps along

with inert gas atomization technology.

The wet and thermal steps will not be disclosed herein but the atomization process

step brings distinct advantages including improved handling from uniform particle

shape and size; increased reaction rate due to evenly distributed intermetallic phases

formation of binary, ternary and even multicomponent silicides at the grain boundaries

(some beneficial to the MCS reaction).

Of the many benefits of atomized silicon to the polysilicon process

, one of the main

ones is the ability of doping the material with a selected catalyst that can aid in the

reaction kinetics of both the Direct Chlorination and Hydrochlorination processes. The

cooling rate of silicon, when atomized, is on the order of 10

– 10

K/second which

prohibits metallic impurities in the silicon from quickly segregating, as can easily

happen in traditional casting of silicon and slow cooling of ingots. Additionally, the

physically restricted shape of the particle creates barriers to segregation from one

particle to another. Rapid cooling of the silicon during atomization also creates surface

points on the particle at which the intermetallic phases are present. When low

temperature catalysts are used, these “last to freeze” elements tend to also be present on

the surface.

Figure 5 Comparison of grinded MG silicon versus recycling MG silicon wastes

Uniform size and shape, flowability, lower segregation of impurities, usage of fine grain feedstock, low

surface area, catalyst addition, etc.