There are a variety of different industrial methods for producing HPA, including hydrolysis of aluminum alkoxide, thermal decomposition of ammoniumalum, thermal decomposition of ammonium aluminum carbonate hydroxide (AACH), underwater spark discharge with aluminum, vapor-phase oxidation and the like.
The most common process used by major producers is the hydrolysis of aluminum alkoxide. In this process, high purity aluminum alkoxide is synthesised from aluminum metal and alcohol, and hydrated alumina is produced by hydrolysis of alkoxide. HPA is then obtained by calcination.
This means that most current HPA producers are using an expensive and highly processed feedstock material such as aluminum metal to produce HPA quality product.
Altech is one of the first companies in the world that publicly report producing 4N directly for an ore feedstock, such as kaolin or aluminous clay.
The main advantage of this strategy is that Altech is utilising its low-cost, low-impurity kaolin feedstock, which has already been purified and processed by natural weathering processes over many millions of years.
As a result, the direct ore feed contains very low levels of impurities including iron, titanium, sodium, calcium, potassium and magnesium. The main impurity is insoluble silica, which can be easily filtered out during the processing, leaving the soluble alumina.
Altech’s high purity alumina (HPA) process is a hydrochloric acid leach (HCL) process with effective acid recovery.
- simple recovery of acid
- natural low-impurity ore feedstock
- calcination to alpha HPA
- micronisation to product requirement
The main advantage of this processing technology is the simple recovery of acid, which is re-used at the front-end of the process, thereby reducing operating costs.
The HCL process is a conventional, proven and robust chemical process that has existed since the early 1980’s.
The process was tailored to and highly supported by Altech’s aluminous clay deposit. The raw material contains low levels of impurities and high alumina content. This high-quality feedstock facilitates the production of a very pure alumina product, offering the Company a competitive advantage amongst the global HPA space.
Altech’s process allows a very tight control over product characteristics such as purity, size, crystal structure.
As an emerging producer of HPA, Altech will contribute in meeting the forecast HPA deficit as well as providing increased choice and flexibility for its buyers.