(290a) CO2 Mineralisation Through Hydrometallurgical Leaching of Brown Coal Fly Ash

The use of an industry waste, brown coal fly ash collected from the Latrobe Valley, Victoria, Australia, has been tested for the post-combustion CO₂ capture through indirect minersalisation in acetic acid solution. After the optimum leaching, the majority of calcium and magnesium in fly ash were dissolved into the solution, the carbonation potential of which have been investigated intensively through the use of a continuously stirred high-pressure autoclave reactor and an advanced analytical protocol for the carbonation precipitate chracterisation. A large CO₂ capture capacity for fly ash under mild conditions has been confirmed. The CO₂ was fixed in both carbonate precipitates and water-soluble bicarbonate, and the conversion between these two species were achievable at approximately 60^oC and a CO₂ partial pressure above 3 bar. The kinetic analysis confirmed a fast reaction rate for the carbonation of the brown coal ash-driven acetic acid leachate at a global activation energy of 12.7 kJ/mol. It is much lower than that for natural minerals and is also very close to the potassium carbonate/Piperzine system. The CO₂ capture capacity of this system was also proven to reach maximum 264 kg CO₂/t which is comparable to the natural minerals tested in the literature. As the fly ash is a valueless waste and requires no comminution prior to use, the technology developed here is highly efficient and cost-effective, the resulting carbonate products of which are also invaluable for the use as additive to cement and in the paper and pulp industry.