NOVELTY - Purifying low-purity metallurgical grade silicon having metal contaminants and obtaining higher-purity solid polycrystalline silicon involves: (A) containing a melt of low-purity grade silicon in mold (10) having insulated bottom wall (10a), insulated side walls (10b), and open top (10c); (B) solidifying the melt; (C) controlling a rate of the unidirectional solidification; (D) stopping the unidirectional solidification when the melt has partially solidified; and (E) creating an opening in the exterior shell of ingot to outflow impurity-enriched liquid silicon.    USE - For purifying low-purity metallurgical grade silicon containing metal contaminants, to obtain higher-purity solid polycrystalline silicon (claimed) for photovoltaic applications such as photovoltaic cells, solar cells.    ADVANTAGE - The process produces solar grade silicon directly from metallurgical grade silicon on a large-scale basis; provides a top portion of higher-purity solid polycrystalline silicon containing at least 90% less metal contaminants of Al, As, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, K, La, Mg, Mn, Mo, Na, Ni, Pb, Sb, Sc, Sn, Sr, Ti, V, Zn, and Zr, than the low-purity metallurgical grade silicon; removes more than 50% of phosphorus and makes the method very interesting for the production of Solar Grade silicon from Metallurgic Grade silicon; provides higher-purity solid polycrystalline silicon containing at least 45% less phosphorus and at least 10% less boron than the low-purity metallurgical grade silicon; and provides impurity-enriched liquid silicon containing less than 60 parts per million (ppm) of carbon and less than 20 ppm of oxygen and is a low carbon and low oxygen grade of silicon.    DETAILED DESCRIPTION - Purifying low-purity metallurgical grade silicon, containing at least one of aluminum (Al), arsenic (As), barium (Ba), bismuth (Bi), calcium (Ca), cadmium (Cd), iron (Fe), cobalt (Co), chromium (Cr), copper (Cu), lanthanum (La), magnesium (Mg), manganese (Mn), molybdenum (Mo), sodium (Na), nickel (Ni), phosphorus (P), lead (Pb), antimony (Sb), scandium (Sc), tin (Sn), strontium (Sr), titanium (Ti), vanadium (V), zinc (Zn), zirconium (Zr), or boron (B), and obtaining a higher-purity solid polycrystalline silicon, involves:    (A) containing a melt of low-purity metallurgical grade silicon in a mold (10) having an insulated bottom wall (10a), insulated side walls (10b), and an open top (10c);    (B) solidifying the melt by unidirectional solidification from the open top towards the insulated bottom wall of the mold while electromagnetically stirring the melt;    (C) controlling a rate of the unidirectional solidification;    (D) stopping the unidirectional solidification when the melt has partially solidified to produce an ingot having an exterior shell comprising the higher-purity solid polycrystalline silicon and a center comprising an impurity-enriched liquid silicon (11); and    (E) creating an opening in the exterior shell of the ingot to outflow the impurity-enriched liquid silicon and leave the exterior shell comprising the higher-purity solid polycrystalline silicon thereby obtaining the higher-purity solid polycrystalline silicon.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of a mould containing a melt of low-purity silicon.    Mould (10)    Insulated bottom wall (10a)    Insulated side walls (10b)    Open top (10c)    Liquid silicon (11)    Electromagnetic stirrer (14)