Some of the most commonly used processes for HPA production include alkoxide process, thermal decomposition process, choline hydrolysis process, and modified Bayer process
. Prominent product types offered in the HPA market are 4N HPA--99.99%, 5N HPA--99.999%, and 6N HPA-- 99.9999%.
Digestion refers to the first of four successive stages outlined within the Bayer process
, through which alumina is derived from bauxite ore.
On the project progress, EGA said commissioning of the four major sections of Al Taweelah alumina refinery is being completed in a carefully planned order, with the final stages of the Bayer process
ready for production first.
The chain for producing aluminum from bauxite to primary aluminum includes refining using the Bayer process
. One of the main waste products of the Bayer process
is the fly ash collected from the cyclone overflow of the fluidized bed boilers at operational conditions of 900[degrees]C of temperature and 120 kPa of pressure.
Natural Bayer red mud is a bauxite residue generated from the Bayer process
(a wet process) for alumina production, which presents the color of reddish brown.
* The Bayer process
: A common way to produce alumina, which extracts aluminum hydroxide (alumina) from bauxite as raw material, by utilizing sodium hydroxide (caustic soda).
Known as the Bayer process
, the ore is washed with heated sodium hydroxide, then subsequently cooled and treated with carbon dioxide, which yields alumina ([Al.sub.2][O.sub.3]), the penultimate step of making aluminum metal.
These include the formation of anionic polyacrylamide through hydrolysis, (17) the synthesis of sulfomethylated derivatives from the reaction of polyacrylamide with formaldehyde and sodium bisulfate, (18) the formation of aminomethylated polyacrylamide from the reaction of polyacrylamide with formaldehyde and dimethylamine (Mannich reaction), (19) and the generation of various derivatives by transamidation reactions including hydroxamated polyacrylamides used as a flocculant in the Bayer process
For metal grade bauxite the aluminum content should be more than 40% and for chemical grade it may above 60% while most Bayer process
plants use bauxite having alumina content greater than 40% however all the technical factors from mining to marketing are to be considered .
The available alumina and reactive silica results quoted are unbeneficiated, and based on low temperature caustic digest analysis (143AC), to simulate extraction by the Bayer process
. Drilling will continue to define the extent of mineralisation, with a further upgrade expected during the latter half of 2013.