This dataset models the Czochralski process for the production of monocrystalline silicon blocks.
The following description of the production process is based on an older literature reference (Hagedorn & Hellriegel 1992) and has not been updated for this dataset.
The purified silicon and recycled silicon parts are broken down to a size of 0.1 to 7.5 cm. In an acid bath with nitric acid, hydrogen fluoride and acetic acid the surface is purified and SiO2 is removed. The following reactions take place:
3 Si + 4 HNO3 -> 3 SiO2 + 4 NO + 2 H2O
SiO2 + 6HF -> H2SiF6 + 2 H2O
The waste gases of the process (e.g. NOx, HF, acetic acid- and nitric acid) are treated in a gas cleaner before they are released. Information about possible releases is not available. Effluents are discharged directly and have been assessed with older literature data. Deionised water is used for cleaning and acetone is used for final drying. The cleaned silicon parts are melted in a crucible and a seed crystal is first dipped into the melt. Then the seed is slowly withdrawn vertically to the melt surface whereby the liquid crystallises at the seed. The pulling is done under argon inert gas stream. In order to reduce the argon consumption, a pressure of 5 to 50 mbar is required.
Reference:
Jungbluth N., Stucki M, and Frischknecht R. (2009) Photovoltaics. In Dones, R. (Ed.) et al., Sachbilanzen von Energiesystemen: Grundlagen für den ökologischen Vergleich von Energiesystemen und den Einbezug von Energiesystemen in Ökobilanzen für die Schweiz. ecoinvent report No. 6-XII, Swiss Centre for Life Cycle Inventories, Dübendorf, CH, 2009.
G. Hagedorn, „Kumulierter Energieaufwand von Photovoltaik- and Windkraftanlagen“, IfE-Schriftenreihe, Heft Nr. 25, 1. Auflage, TU München, Technischer Verlag Resch KG, 1992