Arjan Ciftja

Solar Silicon Refining: Inclusions, Settling, Filtration, Wetting Arjan Ciftja

The main objective of the present work is the removal of inclusions from silicon scrap and metallurgical grade silicon. To reach this goal, two various routes are investigated. First, settling of SiC particles from molten silicon followed by directional solidification is reported in this book. Then, removal of SiC and Si3N4 inclusions in silicon scrap by filtration with foam filters and wettabilities of silicon on graphite materials are studied. To supply the increasing needs of the PV industry it is necessary to produce a low cost silicon feedstock. The high carbon content of the metallurgical grade silicon in the form of SiC particles, needs to be removed before the silicon could be used as a feedstock to PV industry. The difference in density between the particles and the melt gives the SiC particles a relatively high settling velocity leading to a high removal efficiency. However, higher removal efficiencies are required. Filtration with foam filters appears to be very efficient and the removal efficiency for a 30 ppi SiC filter is more than 99%. A new filtration model named branch model is developed in this work.