In my previous article, I talked about transformation. I shall go deeper into understanding how transformation will make aluminium and sustainability go hand-in-hand.
The transformation will begin with processes about ores containing the target mineral phase and desired crystalline phases for the best response to process chemistry. It will be adopted to recover alumina by alkali digestion through the Bayer process. For this to be effective, one has to study the association of gibbsite with iron-bearing goethite and clay-type materials bearing reactive silica. The liberation of the phases needs to be analysed.
Segregation of ores to maximise the extraction efficiency of alumina will ask for the elimination of reactive silica, which hinders the best possible alkali utilisation in the refinery. What is natural is that ore with 3 to 4 per cent reactive silica will be unavoidable. Therefore, addressing this material will become a necessity.
To me, a disruptive change in the industry will require two solutions. One is beneficiation of ores to keep the reactive silica close to 2 per cent. Second, target alumina to iron oxide ratio of 3:1.
Solutions for both are available today and the industry will have to consider transformation to the same soon at scales to preserve the precious ores. Reactive silica reduction requires special scrubbing. However, the loss of alumina in the tailings will be addressed by special processing. This is where technology starts.
The question to be answered now is how much alumina can be retained in the system and the best possible utilisation of the tailings materials rendering the process economically viable and sustainable. I don’t think technology stops here. This is because of extra processing, rather it will try to find technical advantage of carrying out the mineralogical and chemical processing.
A compact well-integrated process addressing all aspects with optimum usage of alkali, enhanced recovery of alumina and an energy-efficient process will become next-level technology in my opinion. The industry will surely find this competitive and sustainable.