Hi Friends,
In continuation to my earlier posts, I thought of sharing my views on beneficiation of Bauxite with the objective to optimum utilization of natural resources available with us. I am presenting here my views on the subject as outlined here under in subsequent paragraphs.
The mineral, Bauxite, is a rich
source of alumina for making aluminum. The aluminium metal and its alloys have
strong growth potential in international market for wide range of industrial
applications. Bauxite is also used in refractory, cement, absorbents, steel,
abrasives, rubber, plastic, cosmetics, paints, paper, polishes, glass, enamel
and ceramics.
Since bauxite is a mineral
occurring in earth’s crust, it has a number of impurities, like iron, silica,
titania, calcium, and small quantities of phosphorous, sulfur, zinc, magnesium
and various carbonate and silicate minerals. These impurities create quality
problems during processing thereby increase production costs. Therefore, the
removal of impurities to the extent possible economically is essential before
processing further for any application.
Most mines abroad subject their
run of mine ore (ROM) to the mineral dressing operation most suitable for their
material. Crushing the ROM, usually in hammer mills, is an operation practiced
worldwide. Depending on the bauxite, and the quality/grade required, the next
stages are screening, scrubbing and washing, magnetic separation and drying.
Magnetic separation is done to remove iron, however, is normally practiced in a
limited way to produce high value, special grade bauxites. At present, the
production of bauxite in most operative mines in India is not sufficiently high
as to warrant a capital-intensive beneficiation plant, which usually requires a
large capacity to be really economical. Hence, ore dressing efforts have been
mainly confined to removal of silica by manual and/or mechanized breaking,
crushing, manual sorting and dry screening.
Efforts towards research are
being emphasized in most bauxite producing countries to develop cheap and
innovative bauxite beneficiation processes. Many new methods of magnetic
separation are also being tried out. These include rare earth roll separators,
super conducting high gradient magnetic separators and open gradient,
non-cryogenic high gradient magnetic separators. Other methods being researched
include fluidized bed acid leaching, hydrogen assisted beneficiation and bio
leaching. However, despite decades of intensive studies, economical bauxite
beneficiation technology for removal of impurities satisfactorily is not
available as on date.
Research in India is along
international lines but still confined to the laboratory. The Indian Bureau of
Mines, Nagpur (IBM), the Jawaharlal Nehru Research Development and Design
Center, Nagpur (JNARDDC), and the Regional Research Laboratory, Bhubaneswar
(RRL), all claim to have laboratory scale processes that are ready to be up scaled
to pilot plant levels. The IBM has done numerous beneficiation tests, using
different methods, on various bauxites found in India. The RRL claims to have
developed a beneficiation process to produce non-metallurgical grade bauxite,
whereas the JNARDDC says it has processes for both metallurgical and
non-metallurgical grades.
As per the available published
literatures and analysis, the savings on raw ore cost brought by JNARDDC's
process through beneficiating metallurgical grade bauxite appears to be over
17% and that of non-metallurgical grade at least 19%. Bauxite users in India
have indicated that they are willing to pay between 10-50% higher for a
reduction in impurities by a similar amount. This would make the production and
marketing of beneficiated bauxite more profitable.
We will welcome your comments / remarks on the elaborated topic.
Regards.
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