Single-step production of high-purity silicon demonstrated
By Mary Page Bailey |
Achieving silicon of acceptable purity for solar-energy applications typically requires several purification steps. Now, a new process has been demonstrated that can produce high-purity Si from low-quality quartz in a single step. The PureVap technology from PyroGenesis Canada Inc. (Montreal, Que.; www.pyrogenesis.com) utilizes a powerful vacuum-arc furnace, combining the carbothermic reduction of silicon and purification into one process, explains Pierre Carabin, chief technology officer for PyroGenesis Canada.
Traditional arc furnaces produce relatively low-purity Si, around 98.5% purity, requiring subsequent purification. Inside the PureVap furnace, low-quality (97.5%) quartz and a carbon source are exposed to heat from a plasma arc, creating CO2 and Si. The vacuum-arc furnace allows for the vaporization of contaminants, including boron and sulfur. By manipulating the metallic vapors’ partial pressures, the contaminants are removed.
In 2016, following successful demonstration of the PureVap process at the laboratory scale, PyroGenesis announced a contract worth over $6 million with Canadian mining company HPQ Silicon Resources, Inc. to develop a pilot plant to produce 200 metric tons per year…