Humidified sweep gas for dedusting process

Abstract

Methods and apparatus for separating polysilicon powder from a mixture of granular polysilicon and polysilicon powder are disclosed. The method includes tumbling the polysilicon material in a tumbling device while flowing humidified sweep gas through the tumbling device. Also disclosed are compositions including granulate polysilicon or polycrystalline silicon, in some examples, including a coating layer consisting essentially of water.

We claim: 
     
         1 . A composition comprising a composite particle of spheroidal shape comprising a core surrounded by a core coating layer, wherein:
 the core comprises polycrystalline silicon having a purity of at least 99.999 wt % and a chlorine content of less than 10 ppm by weight; and   the core coating layer is a film consisting essentially of water, wherein the layer is 5-100 Å thick,   
       wherein the composite particle is present in the composition in at least 99.9 wt % based on the total weight of the composition. 
     
     
         2 . The composition of  claim 1 , wherein the core has an average diameter of from 0.25 mm to 20 mm. 
     
     
         3 . The composition of  claim 1 , wherein the core has an average diameter of from 0.001 mm to less than 0.25 mm. 
     
     
         4 . The composition of  claim 1 , wherein the core has an average diameter of less than 50 μm. 
     
     
         5 . The composition of  claim 1 , where the core has a bimodal size distribution and comprises:
 (a) a first particle, wherein the core has an average diameter of from 0.25 mm to 20 mm; and   (b) a second particle, wherein the core has an average diameter of less than 50 μm,   wherein the first particle is present in at least 99.9 wt % of the total weight of the core and the second particle is present in an amount of less than 0.01 wt % of the total weight of the core.   
     
     
         6 . The composition of  claim 5 , wherein the first particle has a surface roughness Ra of less than 1 μm. 
     
     
         7 . The composition of  claim 1 , wherein the core is substantially devoid of attached fine-powdered polycrystalline silicon having an average particle size of less than 50 μm. 
     
     
         8 . The composition of  claim 1 , wherein the core coating layer comprises physisorbed water. 
     
     
         9 . A package for shipment or storage comprising:
 a wall having an inner surface that defines a cavity; and   a volume of the composition of  claim 1  contained within the cavity.   
     
     
         10 . The package of  claim 9 , wherein:
 the wall has an inner surface that faces the volume of granulate polysilicon composition; and   the wall is constructed of a non-contaminating material or the inner surface is coated with a protective layer of a non-contaminating material.   
     
     
         11 . The package of  claim 10 , wherein the non-contaminating material comprises elastomeric polyurethane or polyethylene.