Method for the production of solar grade silicon
OwnerHarsharn Tathgarinventor
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Abstract
The present invention relates to a method for the preparation of solar grade silicon comprising crystallization of large high purity silicon crystals in a hyper eutectic binary or ternary alloy containing silicon, or a refined silicon melt, wherein small silicon crystals are added to the melt and the resulting large silicon crystals are separated from the melt. The separation may be performed by centrifugation or filtration.
Claims10
A semi-continuous process for the formation, separation and melting of large and pure silicon crystals of a size of 1-5 mm, wherein a prepurified binary or ternary hypereutectic alloy containing Si melt is transferred to a furnace having a temperature gradient from top to bottom, small and pure silicon crystals of a size of 100-200 μm are then added to the melt in the furnace and grow due to the temperature difference until the melt in the furnace reaches eutectic composition, whereupon the melt is transported from the furnace and brought to the hypereutectic state, is then returned to the furnace and the process is repeated until an amount of large (1-5 mm) Si crystals has been formed.
An apparatus for the preparation of solar grade silicon, the apparatus comprising:
- a first furnace;
- and
- a second furnace connected to the first furnace;
- wherein the apparatus is arranged to allow a binary or ternary hypereutectic alloy containing silicon melt to be made in the first furnace and transferred to the second furnace;
- wherein the second furnace is arranged to have a temperature gradient with a higher temperature at the top of the furnace and a lower temperature at the bottom of the furnace and is arranged to be fed with pure silicon crystals of a size of 100-200 μm which grow in the melt to form larger (1-5 mm) silicon crystals;
- and wherein the apparatus is arranged to pump melt from the second furnace to the first furnace through a ceramic filter when the melt in the second furnace reaches eutectic composition.
Dependencies are inferred from the claim text.