Theoretical background

A new, CO² free process for production of the critical raw material silicon (“SisAl”, see figure 1a and b), using secondary materials, has been developed to large laboratory/small pilot scale and patented by NTNU under the umbrella of the Norwegian centre “CRI Metal Production”. The process produces both silicon and a valuable slag as outputs.
Figure 1a: Illustration of the SisAl process
Figure 1b: Illustration of the production of HPA from the slag utilizing CO² looping

NTNU coordinates a H2020 project SisAl Pilot starting in 2020 in which ELKEM, Mytilineos, SiQAl, NTUA and BNW, are partners. In this project, focus is mainly placed on large scale demonstration of the part of the SisAl process producing silicon (the aluminothermic step), using various raw materials, with secondary focus on processes to bring the resulting slag into valuable products.

NTNU and ELKEM received Fast Track funding from EIT RM in 2019 which has been used to perform two pilot tests (300 kg scale) of the aluminothermic step of the SisAl process at Elkem’s pilot station in Norway, bringing the process to >TRL5, made an extensive market analysis directed at HPA in batteries and made a dissemination and communication strategy for the current application.

Mytilineos, NTUA and NTNU are partners in the SPIRE project ENSUREAL, where focus lies on extraction of alumina (Al²) from Bauxite without production of Bauxite Residue (“BR or Red Mud”) by re-implementing the Pedersen process (in industrial operation in Norway until the 1970´s, hence at TRL9) where production takes place by leaching a slag very similar to that produced by the SisAl process. Through the project, new hydrometallurgical methods for more efficient extraction of HPA have been developed and a hydrometallurgical demonstration plant built in Greece (co-funded by other H2020 projects such as SCALE).


SiQAl is an SME which has received booster funding from the EIT RM for a proof of concept study on the co-production of solar grade silicon (SoG-Si) and 4N+ purity Al²O³ (HPA) for high-tech applications. Through the project, aluminothermic reduction in combination with new hydrometallurgical methods for extraction of high purity Al²O³ have been developed to TRL 4. Seen together, the overall process for making HPA from slag for the cluster Mytilineos, SiQAl, NTUA and Enalos are at TRL5.

CALEF together with ENEA, Walter Tosto, Sandvik, have developed CO² looping technology with slags as absorbent material in the H2020 project ASCENT, developing a number of demo loops (ZECOMIX and VALCHIRIA) to be used in the current project. With the advances in FeCeAl materials and overlay welding of high temperature compound vessels from H2020 project NEXTOWER, it becomes possible to develop the full CO² looping demo from a current TRL5, which will be pursued as a mobile unit easy to plug-in in SisAl to boost environmental performance.

SisAl Slag Valorisation will integrate elements of the above described project technologies and background IPs into a cohesive project aimed at targeted development of the products (HPA and Si) for dedicated markets such as battery separators for HPA and the technologies (SisAl and mobile CO² looping reactor for high CO² concentration gas streams) ready for market introduction and implementation both in- and outside Europe.