GOALI: Recycling and Purification of Silicon from Solar Grade Silicon (SoG-Si) Wastes using Electromagnetic Field

Missouri University Of Science And Technology, Rolla MO

Investigators

Abstract

This Grant Opportunity for Academic Liaison with Industry (GOALI) award provides funding for a study to recycle and purify silicon from solar grade silicon waste using an electromagnetic field. During the sawing process used to produce silicon wafers more than half of the ingot enters the waste stream as silicon powder, along with silicon carbide particles, iron powders and glycol oil. The challenge is to recover the silicon powder and separate it from the similar sized but undesirable silicon carbide particles. It has been hypothesized that the nonconductive particles and less-conductive impurity phases suspended in the conductive liquid metal will be forced to move in the opposite direction of the applied electromagnetic force, thus enabling separation and recovery. Experimental work will investigate the effect of various process variables and theoretical studies will explore the separation of non-metallic particles from molten silicon under an electromagnetic field. The combined activities will contribute to an understanding of the solidification and crystallization process of the recycled solar grade silicon with the potential to further purify the material. Solar cell device demonstration activities are included in the plan. Solar cells are an attractive technology for renewable, non-polluting power generation and high purity silicon is the material of choice for these devices. Recovery of at least some of the silicon waste would offset a portion of the present day annual cost of wasted material which is estimated to exceed $5B. This novel process has the potential to lower the cost of solar cells through improved material yield and lessen the environmental impact through reduced carbon dioxide emissions.