UMG-Si Production

About 10 kWhr/kg, and 10 kg/hr at 100kW process scale. [1]. Heated by induction, with graphite crucible as susceptor (starts the melt)

Process Step	Description	Typical Temp (°C)	Energy (kWh/kg Si)	Notes (100 kW scale effects)
Feedstock Selection & Blending	Crushing, sorting, magnetic separation, blending of MG-Si	Ambient	0.05–0.15	Mostly mechanical energy; minor relative contribution
Primary Melting & Slag Refining	Melt MG-Si (~1414°C), add CaO/SiO2 slag, impurity oxidation & partitioning	1450–1550	3.5–6.0	Dominant energy load; small furnaces have high radiant/convective losses
Gas Refining / Vacuum Refining	Removal of B, P via O2, H2O, H2, or vacuum evaporation	1500–1600	1.5–3.0	Inefficient gas utilization at small scale; vacuum pumps add parasitic load
Directional Solidification	Controlled solidification to segregate impurities (top cut removal)	1400 → 1200	2.0–4.0	Long cycle times → major heat loss; poor insulation penalizes small systems
Crushing, Classification, QC	Break ingot, remove impurity-rich zones, size grading, analysis	Ambient	0.2–0.5	Includes mechanical comminution and some analytical overhead
Optional Repeat Refining Passes	Re-melt and re-solidify for higher purity	1450–1550	2.0–5.0	Highly variable; depends on target purity (solar vs near-electronic grade)
Total (single pass, no repeats)	—	—	7.25–13.65	Typical practical range for small-scale UMG-Si
Total (with 1 repeat pass)	—	—	10–18+	Required for higher purity (approaching SoG-Si)