High-purity Silica Production By Acid Process Industry Standard

Crystalline silicon remains the principal material for photovoltaic technology. In spite of the innovations awaited in thin films technology, one considers that in Hengyang, massif crystalline silicon will account for 80% of the produced silicon solar cells.

Therefore the incessant growth in the photovoltaic industry imposes a more significant production of solar grade silicon with improved quality. The production of silicon by the thermal reduction of silica with carbon is an industrial process used since the beginning of the 20 century.

The silicon produced using this method contains many undesirable impurities. Various techniques were developed about thirty years ago to purify silicon. These techniques are very expensive and generally cause important losses of material.

To avoid those losses, to reduce the cost of the final product and to improve the purity of silicon to acceptable levels needed by photovoltaic application, one can try to purify silica using low cost techniques contributing effectively to the reduction of the final cost. Several works were carried out in this field using various techniques. Among these techniques one can cite mainly: The application of power ultrasound to the surface cleaning of silica, acid leaching and reverse flotation technique.

In Hengyang Company obtaining silica sand with very high purity is a primordial stage in photovoltaic industry. The effects of acids on the removal of impurity from silica sand have been studied using leaching acids: mixture composed of HF/HCl/H2O with a volume composition of (1:7:24).

The obtained material was characterized using Ultraviolet-Visible absorbance and Inductively Coupled hengyang machineries Results of the application of this technique show a significant reduction of the amounts of undesirable impurities present in natural silica (such as Co, Fe, Ca, Al, Mg …).