Geology Reference
In-Depth Information
The electrothermal process is used to produce ferromanganese. The ore is first
smelted with coke as a reducing agent in an electric furnace or in a blast furnace
to decrease its iron oxide content. The obtained high carbon ferromanganese may
contain between 30-80% of Mn whilst the slag is also rich (up to 30%) in manganese
oxide. This slag is then submerged in an electric arc furnace with silicon to produce
silico-manganese. If this molten silico-manganese is treated with liquid slag from
the first stage, relatively pure manganese metal (up to 98% Mn) can be attained
(IPPC, 2009).
Batelle-Columbus-Laboratories (1975) published data for the production of fer-
romanganese and suggested that the energy consumption during the mining and
concentration stage is 0.91 MJ/t of FeMn whilst the energy required for concen-
trated ore refining is 57.3 GJ/t FeMn.
In the process of obtaining electrolytic manganese, Morral et al. (1985), indicate
that the electricity consumption for one kilogram of manganese lies in the range of
39.6 to 43.2 GJ/t of pure manganese. On the other hand, Hancock (1984) proposed
the value of 15.5 GJ/t for manganese leaching, which is equal to that of the copper
obtaining process. In the compilation of Classen et al. (2007), Adelhardt and Saiger
(1999) report a total energy consumption in the mining and concentration stages
of 0.16 GJ/t of Mn and around 28.5 GJ/t in the smelting and refining processes.
8.11.3 Tungsten (Wolfram)
Wolframite (Fe;Mn)WO
4
and scheelite CaWO
4
are the two most common ores
from which tungsten is obtained. They are less than 1.5% rich in WO
3
and need
to be liberated from the gangue material. Once the ores are crushed and ground,
wolframite is concentrated by gravity and magnetic separation, whereas sheelite is
concentrated using gravimetric and floatation methods.
The chemical separation of tungsten essentially consists of converting the salts
into tungsten trioxide through alkaline treatment and then reducing it with hydro-
gen gas. If the metal powder is treated with black carbon, it produces tungsten
carbide (WC), which may be further cemented with cobalt to form hardmetal
14
.
Its hydrometallurgical process involves alkaline pressure leaching of the concen-
trated ore. This produces sodium tungstate and dissolves all the elements present
such as As;Sb;Bi;Pb and Co including Mo in the form of thiomolybdate which
can further be used for Mo production. Once purified, the sodium tungstate is
converted into ammonium tungstate by an ion exchange process and crystallised.
The resulting solid is then calcined in a rotary kiln to obtain tungsten oxides at
temperatures ranging from 400 to 800
o
C.
14
See http : ==education:jlab:org=itselemental=ele074:html. Accessed Sep. 2011, and
http : ==en:wikipedia:org=wiki=Tungsten. Accessed Sep. 2011.
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