
Presentation of industrial uptake-controlled conditioning of silicon by ROSI
Presentation of ROSI and its role in ICARUS
ROSI SAS is a French start-up, which offers a complete solution to recycle and revalorize several industrial waste streams during the PV production value chain, including liquid additives from wafer sawing process, high purity Silicon from kerf loss, and reconditioned Silicon granules from FBR Silicon fines. Since its foundation in November 2017, ROSI has been supported by SATT (Technology Transfer Acceleration Companies), BPI/French Tech in France, by EIT InnoEnergy and European Innovation Council in Europe, as well as international industrial companies like Itochu Corporation from Japan, to continue developing its disruptive technology to render PV production value chain a truly circular economy.
ROSI is a company that enables a truly sustainable solar industry. Our team is dedicated to making the PV industry a model of circularity and reducing its environmental footprint not only during deployment but also during manufacturing. ROSI brings innovative technologies targeting at transforming the whole industry: competitive, scalable and sustainable. We aim to change the industry in cooperation with all partners who are fighting towards the same direction: less impact, more value.
In the ICARUS project, ROSI is responsible for Pilot C: Enabling industrial uptake-controlled conditioning of silicon. The 2 main objectives of the pilot are:
– Development of a pilot integrated line with a feeding system, a melting unit and a conditioning unit
– Integration of purification process for light elements such as oxygen and carbon
Presentation of purification of Silicon developed during the ICARUS project
Silicon is in the form of micro-metric powder in the kerf loss, which implies several difficulties to be re-integrated into the PV production value chain. The apparent density of silicon powder is less than 15% of that of silicon bulk, which renders the filling factor for any batch-wise process, such as filling of a recrystallization furnace, very low. The dust hazard of the micro-metric powder in an industrial environment is another security concern. Therefore, a well-controlled and protected continuous feeding process into the conditioning unit is a must for industrial efficiency and safety.
ROSI solution
To reach the targeted industrial scale silicon production and purification defined by ICARUS, ROSI has elaborated a detailed plan of upscaling based on its laboratory process and prototype, which consisted of a detailed PDF (process flow diagram) and an overall integration plan. Continuous process optimization has also been carried out to optimize the design and construction.
A dedicated machine was developed within the frame of ICARUS project to transform “kerf” silicon waste into high-purity silicon that can be reintegrated into the photovoltaic silicon production chain. This recycled silicon avoids the extraction of natural resources to obtain new raw materials. It also embodies much lower carbon footprint in the silicon than conventional means.
Promising results from ICARUS so far
SiO2 deoxidation & fusion: Road towards 4N
Concentration of the impurities for pretreated kerf and recycled silicon granules using ROSI process.
From 4N to 6N purity
A proof of concept has been performed by ROSI and IPG on an ingot of 8kg of recycled silicon. A further purification route has been designed to bring the silicon from 4N to 6N, which consists of directional purification, which allows a significant reduction of metal content in the so-obtained ingot. The following picture shows such an ingot with its purity above 5,5N, with the remaining 0,5N coming from Boron impurity.
Next steps
In order to further reduce the last impurities such as Boron, additional technologies can be applied during the ingot pulling process, such as an additional electro-magnetic field. On-going work is moving towards higher purity than 6N in the final ingot.