The SELISI project aims to develop processes for recycling powder from sawing silicon bricks. The objective is to achieve various qualities of recycled material for recovery in different industrial sectors such as Li-ion batteries, silicon-based ceramics and photovoltaics.
In the photovoltaic industry, the cutting of silicon bricks into wafers generates more than 35% material loss in the form of fine powders. This material, which is highly contaminated with metallic and light elements (oxygen and carbon levels greater than 1% by mass), is characterised by a centred grain size (1-10 µm) and low density (about 0.5 g.cm-3).
The solution developed for the photovoltaic application consists of two steps: a chemical treatment followed by segregation by directional solidification. It addresses various scientific and technical issues related to the high carbon and oxygen contamination and the density of the material to be recycled. The CEA teams at INES have precisely provided a proof of concept for the solution proposed for the segregation step, by carrying out a pilot-scale demonstration, i.e. a G2 ingot weighing around 50 kg. The reuse of purified silicon in the photovoltaic chain has been demonstrated by the production of a monolike ingot of G2 size.
SELISI (2018-2020), an European project funded by KIC Raw Materials (https://eitrawmaterials.eu/), has brought together together two manufacturers in the field in addition to the CEA laboratories at INES: RESITEC (Norway), a specialist in the chemical treatment of silicon powders, and ECM Greentech (France), a manufacturer of directional solidification furnaces