SisAl Pilot - project meeting in Galicia - June 2022
The SisAl pilot partners gathered in Santiago de Compostela for the M24 progress meeting, hosted by CITMaga, at the Faculty of Maths, Partners discussed the results achieved so far in all the project work packages and planned key actions to be implemented in the next period.
Gabriella Tranell, SisAl Pilot coordinator, TV interview at FUNDICIONES REY premises (Spain)
In June 2022, the project coordinator Gabriella Tranell from NTNU was interviewed on TV at FUNDICIONES REY premises, in Spain. The whole project consortium was there to perform a progress meeting in Galicia.
SisAl Pilot MSc student: interview with Nishan Simkhada
Meet one of the MSc students contributing to the SisAl Pilot Project. Nishan Simkhada is conducting experiments to test the sustainable SisAl process for silicon production through aluminothermic reactions in the lab. Nishan is part of NTNU’s team.
Harald Philipson interview, NTNU
Meet one of SisAl Pilot’s PhD students Harald Philipson and get to know more about the project and his contribution to the demonstration of the far more environmental, sustainable, and economic process of producing silicon “the SisAl process” as compared to today’s carbothermic Submerged Arc Furnace (SAF) process. Harald is part of NTNU’s team.
The slag product
In addition to silicon, the SisAl process produces a calcium-aluminate slag with a high alumina content. The slag can either be sold to the steel industry as is, or it can be treated further. Some of the slag from the pilot at Elkem is crushed and sent to NTUA for hydrometallurgical processing. The slag is then separated into calcium oxide and alumina.The alumina can be used for a variety of applications, e.g primary production of high purity aluminium.
The Silicon product
The silicon product produced during the pilot experiments at Elkem is a silicon-aluminium alloy. The alloy itself is of interest to the partners in the aluminium industry: Fundiciones Rey SL and Hydro. The silicon can be refined to make metallurgical grade silicon, which is of interest for Elkem, Wacker and DOW. At Silicor materials, further refinements can be done to reach solar grade silicon.
At Elkem’s pilot site in Kristiansand, an IRB 7600-500/2,55 Industrial Robot is used for handling the moulds with hot metal. The robot carefully moves the moulds around, leaving empty moulds below the furnace for further tapping. The robot can also empty the moulds when they are sufficiently cooled down.
In this new video shot during the SisAl Pilot tests campaign implemented at Elkem premises, we can see the furnace during pouring. The furnace is tilted manually with a lever regulating the hydraulics of the oven. The liquid silicon alloy and the calcium-aluminate slag are respectively poured into small graphite moulds in batches of about 100 kg.
Samples are taken continuously to study the reduction of silica with aluminium to form silicon. The samples can be taken by using a small sampling cup, or by inserting a cold graphite rod into the melt. Metal and slag will solidify at the rod, and can be knocked off afterwards.
Charging and Stirring
During the SisAl Pilot pilot trials at Elkem, three different charging strategies are used. Two of them starts of by heating the SiO-CaO-slag, and then adding the aluminium. Then one can either stir the materials with rotor stirring or with a gas lance. ITMATI is modelling the different stirring alternatives at Elkem. The last charging strategy is co-charging. Here, the different raw materials are charged simultaneously.
The furnace at Elkem technology pilot department is a 600 kW induction furnace with a graphite crucible with a capacity of 235 litres. During the pilot runs, the furnace was operated at 1500-1750 C, at 110-190 kW. In the furnace, the silica reacts with aluminium through aluminothermic reduction, producing silicon metal and an alumina-rich slag.
The raw materials
The raw materials used in the pilot are aluminium, silica and calcium oxide. The aluminium sources are shavings, dross and blocks, supplied by Hydro. A slag containing 50/50 CaO and SiO2 is used as raw material for silica and calcium oxide. Pure, fine silica sand from Erisma is also used, mixed with calcium oxide powder to make an artificial slag.
SisAl Pilot at Elkem Technology Pilot Department
Elkem Technology Pilot Department will conduct the first large-scale aluminothermic experiments, with 22 pilot experiments, in Kristiansand in Norway. Different raw material mixes will be run to target different Si and slag products. Charging, tapping and phase separation will be investigated along with refractory interaction and temperature behaviour.