Technology

Greening the Clean-Tech Supply Chain

With SiQAL and our partners, we are implementing a novel process that transforms industrial wastes from the Aluminum industry into high-purity materials for tech applications. The process uniquely valorizes the grey energy contained in aluminum drosses. For the first time, this allows an up-cycling of this well specified waste to new materials of high-purity and quality.
SiQAl’s core technology is based on an aluminothermic reduction of silicon dioxide. In this metallurgical process an aluminum source is molten with Calciumoxide (CaO) and silicon dioxide (SiO2). At high temperatures, aluminum oxidizes to aluminum oxide dissolved in the calcium slag, which results in a calcium aluminate phase. At the same time, the silicon dioxide is reduced to metallic silicon that floats atop the calcium aluminate.

The three input materials are
– Aluminum metal: the process is uniquely capable of absorbing alloyed and partly oxidized materials while recovery alloying elements such as Silicon, Titanium, Magnesium etc. An example of such a material is aluminum dross, of which large volumes are generated in the production of primary aluminum. In fact, up to one million tons of aluminum dross are generated every year and either burnt-off or lost to low value applications.
– Silicon dioxide: depending on the purity targets, this can be either high-purity quartz sands, quartzite rocks or even recycling glass.
– Calciumoxide: this material is widely available and may be treated for high purity if needed. In fact, Calciumoxide is recovered from the calcium aluminate product to operate in a closed loop. This makes the process waste free.

The products of the pyrometallurgical step:

  • Calcium aluminate: this material of is composed of 60% Al2O3 and 40% CaO. It is of high-purity, because impurities from the input materials are extracted to the metallic silicon phase. Because it is very reactive, it is readily post-processed hydrometallurgically. This recovers the CaO and upgrades the Al2O3 to high purity alumina (HPA). HPA is the feedstock for synthetic sapphire crystals used in LEDs. It is used in variety of other applications in the tech-industry.
  • Silicon: the process produces Silicon without the CO2 footprint typically associated with it. Due to the process it is up to 500x purer in critical elements like boron and phosphorous, two dopants abundant in traditional metallurgical grade silicon. It is therefore predestined for further upgrading, e.g. for uses in photovoltaics.