Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
il45147
REDt~CTION OF METALS
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The present inventlon relates to a method of
aluminothermic reduction of metals from their oxides or from
the ore. More specifically, the invention deals with
reducing these metals using iron free thermic boosters.
Aluminothermic reduction of metals has been performed
using iron oxides as heat boosters. This procedure always
produces an iron-containing compound as the product. For
example, in the aluminothermic reduction of columbium or
tantalum from their ores, there is produced FeCb and FeTa.
The iron oxides are necessary to provide sufficient heat of
reaction between the aluminum and oxygen to provide a molten
product whereby the slag and dross may be separated from the liquid
metal by differences in specific gravity, the slag or dross
beinq less dense than the molten metal. The iron oxide
heat boosters usually used are FeO, Fe203 and/or Fe304 and
FeCb and FeTa are produced for alloying applications. This
process, however, when used to produce columbium and tan-
talum for alloying wherein no iron is desired, requires a
further purification step to remove the iron from the FeCb
and FeTa which is produced~
In the past when pure columbium is desired free from
iron, a hydrogen fluoride dissolution or caustic fusion of
the ore was used. These processes, however, are more
expensive.
There is, therefore, a need for a process for pro-
ducing metals from their ore or oxide by aluminothermic
; reduction free of iron except for the iron occurring
naturally in the ore.
In accordance with the present invention it has been
found that metals such as Cb, Ta, Mn, V, and Cr can be
produced from their oxides or their ores by an alumino-
thermic reduction process wherein the product formed is
relatively free of iron. This is accomplished by using, as
heat boosters, one or more of CaS04, MnO2, S, SiO2, Ba(NO3)2,
Sr(NO3)2 and Ca(NO3)2.
While this invention is broadly concerned with a
method for producing metals of the group Cb, Ta, Mn, V and
Cr from their o~ides and ores by an aluminothermic reduction
process whereby the product produced is relatively free from
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iron, for purposes of illustration, the production of Cb from
its ore will be described in detail herein, but it is to be
understood that the other metals mentioned above can be
produced by a similar method.
With regard to upgraded Cb and/or Ta ores, the alumino-
thermic reduction thereof is performed in accordance with
this invention using as heat boosters at least one of CaS04,
MnO2, S, SiO2, Ba(N03)2, Sr(N03)2 and Ca(N03)2. By this pr~cess, Cb
is recovered without increasing the iron content of the
product. This process for producing relatively iron free
Cb is less expensive than prior art methods wherein hydrogen
fluoxide dissolution or caustic fusion of the ores are
required.
A particular advantage in using calcium sulphate as an
oxidizer in the reaction is its great stability, making it
much safer to handle when mixed with atomized aluminum
powder or other metal powders. Further, radioactive
elements such as U and Th are found in ores containing Cb
and Ta. This method of reduction separates the Cb and Ta
from the radionuclides by not reducing the radionuclides
to a metallic state but leaving them in the slag in a
combined and diluted state.
When using CaLN03)2 it is necessary, because of its
delinquenscent properties, to dry the material or to use it
in a controlled atmosphere or vacuum. It should further be
noted that SiO2 and MnO2 cause the slag to be more viscous
while CaS04 and Ba(N03)2 cause the slag to be less viscous.
It is, therefore, necessary to combine various amounts of
the above to achieve the slag viscosity desired.
~0 Using Ba(N03)2 as a booster it can react in various
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ways with aluminum powder always yielding BaO and A1203,
following some examples of possible reactions:
3Ba(N03)2 + lOAl = 3BaO + 5A1203 + 3N2
3Ba(N03)2 + 2Al = 3BaO ~ A1203 + 6N02
or with Cb2o5
3Cb205 + 3BalN03)2 + 20Al = 3BaO + lOA1203 + 6CbN
In reality a combination of these reactions takes
place along with reactions with the minor constituents of
the ore.
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The ignition temperature used for the above booster
ores mix is generally from about 200C to about 3000~C.
This temperature is controlled by the mi~ used and the ratio
boosters to ore. The boosters generally do not exceed about
75 ~ by weight of the mix. The boosters are usually present
in an amount to cause the reaction temperature to rise from
about 10C to about 1000C above the melting point of the
metal.
The following tests have been conducted using pyrochlore
ores from Canada and Brazil. Atomized Al powder and the
following oxides were also used: CaSO4, MnO2, Ba(NO3)2 and
a mix of CaSO4 and Sr(NO3)2.
Example 1
Using CaSO4 as an oxidizer and heat booster for the
reaction, the following mix was used:
5396 gms Pyrochlore Ore
2320 gms. Atomized Al
; 2320 gms. CaSO4 (Dry~
After blending 20 minutes, the mix was poured into an
Al tube and ignited at a~ove 2000C. The mix burned rapidly,
being completely burned in 50 seconds. The separation of
the metal and slag was clean with no tendency for the metal
and slag to adhere to each other. Recovery was in excess
of ga wt.%.
Metal Analysis
Cb 90.6%
S 2.08%
Al 4.4%
Fe 1.8%
Ti 0. 75%
Si 0. 1%
U 3.3 ppm
0 1.1%
Example 2
35 The following mix was used:
539~ gms. Pyrochlore Ore
2320 gms. Atomized Al
` 2226 gms. MnO2
The same mixing time and preparation as recited in
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Example l was used. The mix burned very rapidly, in about
15 seconds, and there was an excellent separation of the
slag and the metal, but the recovery was very low,
approximately 61~. It is not clear why the recovery was
so low because sufficient heat seemed to be generated.
As stated above, although the test was conducted with
Cb ore for the production of Cb, the concept ol this
invention is applicable to the extraction of any metal from
the ore which can be reduced by atomized Aluminum powder;
i.e., Mn from MnO, MnO2 and Mn2O3; V, Cr, Ta from oxide
or ore.
Exam~le 3
~sing Ba(NO3)2 as an oxidizer and heat booster the
following mix was blended 20 minutes in a V-cone blender:
5070 gms. Pyrochlore Ore
1465 gms. Atomized Aluminum Powder
6q6 gms. Ba(NO3~2
The blend was ignited and burned in 150 seconds pro-
ducing a metal derby and slag which was well separated.
Metal Analysis ~
Cb 88
O 1.3
Al 3.2
N 0.92
Fe 2.9
Ti 1.6
Si 0.18
Example 4
Using CaSO4 + Sr(NO3)2 as oxidizers and heat boosters
the following experiment was conducted:
- Blending for 20 minutes in a V-cone blender:
5070 gms. Pyrochlore Ore
1545 gms. Atomized Aluminum Powder
q70 gms. CaSO4 (Dry~
243 gms. Sr~NO3)2
This blend was poured into an Al tube surrounded on
all sides and the bottom by crushed slag. After igniting
at above 2000C the mix burned in 120 seconds. Separation
of the metal and slag was excellent with a Cb recovery of
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approximate ly ~1% .
Metal Analysis 96
Cb 88.4
Al 0. 5
Fe 3.3
o 1.6
N 0.6
Si 0.5
Ti 0 . 2 3
S 4.5
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