Flowable chips and methods for the preparation and use of same, and apparatus for use in the methods
A method for recharging a crucible with polycrystalline silicon comprises adding flowable chips to a crucible used in a Czochralski-type process. Flowable chips are polycrystalline silicon particles made from polycrystalline silicon prepared by a chemical vapor deposition process, and flowable chips have a controlled particle size distribution, generally nonspherical morphology, low levels of bulk impurities, and low levels of surface impurities. Flowable chips can be added to the crucible using conventional feeder equipment, such as vibration feeder systems and canister feeder systems.
1. A method comprising:
a) comminuting polycrystalline silicon rods,
b) sorting the product of step a) using a step deck classifier to obtain a controlled particle size distribution, and
c) removing impurities from the product of step a), step b), or both;
wherein the step deck classifier comprises:
i) a first deck comprising
a) an inlet end of the first deck to a grooved region,
b) the grooved region beginning at or near the inlet end of the first deck, where
each groove comprises crests and troughs, and
c) an outlet end of the first deck, where
the outlet end of the first deck is angled such that the crests of the grooves extend out further over a first gap between the first deck and a final deck than the troughs of the grooves, and
ii) the final deck positioned downstream of the first gap and below the first deck, the final deck comprising
a) an inlet end of the final deck,
b) a grooved region beginning at or near the inlet end of the final deck, where
each groove comprises crests and troughs, and
c) an outlet end of the final deck,
iii) a collection container under the first gap for collecting articles that fall through the first gap, and
iv) an oversize collection container under the outlet for collecting articles that do not fall through the first gap.
2. The method of claim 1 , where step a) is carried out by a method comprising using a jaw crusher.
3. The method of claim 1 , where step c) is carried out by a method comprising exposing the product of step b) to a magnetic field.
4. The method of claim 1 , where step c) is carried out by a method comprising surface cleaning the product of step b).
5. Flowable chips prepared by the method of claim 1 .
6. An apparatus comprising:
I) a vibratory motor assembly, and
II) a step deck classifier mounted to the vibratory motor assembly, where
the step deck classifier comprises
i) a first deck comprising
a) an inlet end of the first deck to a grooved region,
b) the grooved region beginning at or near the inlet end of the first deck, where
each groove comprises crests and troughs, and
c) an outlet end of the first deck, where
the outlet end of the first deck is angled such that the crests of the grooves extend out further over a first gap between the first deck and a final deck than the troughs of the grooves, and
ii) the final deck positioned downstream of the first gap and below the first deck, the final deck comprising
a) an inlet end of the final deck,
b) a grooved region beginning at or near the inlet end of the final deck, where
each groove comprises crests and troughs, and
c) an outlet end of the final deck,
iii) a collection container under the first gap for collecting articles that fall through the first gap, and
iv) an oversize collection container under the outlet for collecting articles that do not fall through the first gap.
7. The apparatus of claim 6 , further comprising an additional deck between the first deck and the final deck, where the additional deck comprises
a) an inlet end of the additional deck,
b) a grooved region beginning at or near the inlet end of the additional deck, where
each groove comprises crests and troughs, and
c) an outlet end of the additional deck, where
the outlet end of the additional deck is angled such that the crests of the grooves extend out further over an additional gap at the outlet end of the additional deck than the troughs of the grooves.
8. The apparatus of claim 6 , further comprising a weigh scale under iii) the collection container.
9. The apparatus of claim 6 , where the step deck classifier further comprises a dust removing system located upstream of the first gap.
10. The apparatus of claim 6 , where the articles are polycrystalline silicon pieces.