Silicon Kerf Waste Recycling: Recovering Sawing Dust from Wastewater

… more less Silicon kerf recycling tries to win back the dust lost when ingots are sawn. The sawing sludge holds very fine silicon powder mixed with water-based coolant, diamond grit and bits of metal from the wire. Filters, spinners and dryers split the powder from the liquid. The water can often be cleaned and reused in the saw. The hard part is the silicon itself. Each grain is tiny, so much of its surface has turned to silicon dioxide. Metal and carbon traces are mixed in too. Remelting this powder back to solar grade is hard and costly, so most of it goes to lower-grade uses. These include alloys for steel and aluminum, and research on silicon for battery anodes. When no buyer exists, the dried sludge goes to landfill as industrial waste. Fine silicon is mostly inert in soil, but it is wasted value. It also carries all the energy that was spent refining it. Wet silicon powder can slowly give off hydrogen gas, so stored sludge needs venting. Recycling the powder closes part of the silicon loop and lowers the carbon cost of each wafer. After this Concept you can judge a claim that a factory recycles its silicon waste by asking what grade the recovered silicon reaches.