Note: Descriptions are shown in the official language in which they were submitted.
~E~HOD QF PRODUCI~G ME'~I~IC NICKEL
The prese~t invention rela-tes to plasma metallurgy~
and more particularl~, to a mebhod o~ prod~ci~ metallic
nickel~
~ he invention is readily applicable to t~e production
o* nickel which is made in the ~orm o~ pellets a~d i~ots
~or use in the iron-a~d-steel making industr~9 as well as
to the production of n~w alloys7 such as Mon~ metal, to be
used in the manufacture of engines, and ma~netic alloys for the
ele¢tronic indus~ry.
In view o~ an ever growing demand for less expe~sive
~rades of metallic nickel, as compared with appreciably ex-
pensi~e elec-trolytic and carbonyl nickel~ it is an imFerative
~or the producers o~ nickel to reduce its production cost.
One o~ the mos-t wid~ly used methods o~ producing înex-
pensive grades of metallic nickel comprises processing
nickel-bearing oxide material by way o~ its reductio~9
which is ef~ected by melting this material i~ a mi~ture with
a solid reduci~g age~t through -the usa of elec-tric current.
The above met~od consists i~ that a charge is prepared
Prom a ~ickel-bearing oxide ma-terial ? Por example, ~ickel
monoxide, and a solid reducing agent; such as petroleum
or pitch cokeq whereupon the charge is melted down under
the action of electris currentO In the process o~ melting,
-the oxygen o~ the ~ickel-bearing oxide material intera¢ts
with the solid reducing agent with the resultant -~ormation
o~ a metallic niGkel mel-t.
~ 'o effect decarbonization o~ metall~c nlckel, nickel
.. ~
monQxide is introduced into the melt o~ the ~o:rmerO There-
a~-ter, silicon is added lnto th~ melt o~ metalllc n~ ck~l
to ef~ect its deo~idation, ~he melt o~ me~allic nickel
is ~ur-ther subjected to desulphuriza-tlon~ which is e~eoted
through th~ use of calcium-con-taining materials~ such as
lime. The described method is per~ormed b~ means o~ ~ three-
phase electrio ~urnace similar to that used in the steel~
making practice. The product o~ reduction contains about
98% o~ metallic nickel (see, ~'or example~ a book '~etal-
lurgy o~ Copper~ Nickel a~ Cobalt", vol~ 2~ ppr122~126g
Metallurgia Publisher~g ~oscow~ 1977). The yield o~ ~ickel
obtained in accordance with the a~oredescribed technology
was 99-%~
Howevers the method re~erred to above su~ers ~rom a
seriou~ disadvantages~ namely: the production cost o~
metallic nickel is increased due to the necessîty o~ usi~g
a solid reducing agent; premixing an initial material with
the reducin~ agent; consuming an excessive amount o~ power
re~uired for the operations of decarbonization, deoxidation
a~d desulphurization; employing slag-forming materials and
d~o~idizing age~t.
In addition, the above method is disadvantageous in
that the iron and c obalt oxides contained in -the nickel-bearing
materlal are completel~ reduced, as a result o~ which iron
and oobal-t are transferred into the m~lt o~ metallic nickel
and thus bring down the content o~ -the la-tter in the melt.
s~
The above-mentioned disadvantages of the prior-art
process called for the necessity to develop a me-thod of pro¢es-
sing a nickel-bearing oxide material ~o be e~fected under
the action of a low-temperature plasma.
Thus a new method was developed according -to which
car~othermic reduction of a nickel-beari~g oxide material
is e~fected with the use o~ plasma~arG heating performed in
a plasma furnace equipped with an ingo-t mould / see a book
by YuoV4 Tsvetov~ S.A. Pa~filo~, entitled "Low-Tempera~e
Plasma';, Nauka Publishers, Moscow, 1980~ p.261/.
According to this met~od 9 a granula-ted charge with a
gra~ule size o~ 1-2 cm, composed of nickel monoxide, such
as fired converter matte with a particle size of 50 -to 100 ~m,
coke ~ines with a particle size o~ 63 to ~0~ ~m9 and a bi~der.
The charge -thu ~ repared is then fed in-to tke reactîon zone
of a chamber in an amount o~ 0.1 to 0.2 -times that o~ the
total weight of the charge delivered durin~ the first feed.
The chamber is evacua-ted to a pressure of 005 mm Hg, a~d
then treated with technical-grade argon. Thereafter~ the
charge i5 subjected to heating by means of argon-shielded
plasma arc. U~der the action of plasma arc, the charge
is melted do~n. In the process of mel-ting, the ox~gen
contained in tbe nickel-bearing oxids material reac-ts with
-the carbon o~ the solid reducing agerlt to result in the r~-
duction o~ nick:el to metal. ~he remainder amount OI the charge
mateirial is ~ed at regular int~r~als in small batches into
bhe melt o~ metallic nickel. The method in ques-tion is carri-
ed out with a pressure in the p:lasma plant being maintained
in the order of 1005 k~/cm20 A~-ter an ingot has been produ-
ced, the plant is deenergized alld the ingot is held in the
atmosphere of argon to permit its cooling~ ~he metallic
nickel produced in accordance with this method contains
abo~t 2 per cen-t of carbon and sulphur, the amou~t o:E which
corresponds to i-ts content in the ini-tial material in the
range ~rom 0.24 to 0~45 per cen-t.
~ he practioal value o~ the above process is somewhat
lowered by -the necessity to prepare granulated charge
and to use low-temperatuxe plasma ~or a si~gle purpose o~
heating r
In addition, to produce metallic nickel of a desired
quality~ the reduction o~ a nickel-bearing oxide material
should be effected with -the use o~ slag~forming, decarbonizing
and deoxidizl~g materials added into the mel-t o~ metallic
nickel as a solid reducing agent~ In o-ther ~Jords, the melting
process in a p~asma furnaGe during reduction o~ a nickel~
-bearing oxide material hardly dif~ers from -the processes
run in arc three-phase electric ~urnaces. ~hus 9 the method
in question has all the disadvantages i~herent in the
processes of reduc-tion melting carried ou~ in electric
furnacesv
Xt is an object o~ the prese~-t invention to reduce the
amoun-t o~ admix-tures in metallic nickel produced in accordance
~:~g~s~
wi-th a pgrometallurgical technique~
Another objec-t of the invention is to reduce -the amount
of losses o~ metallic nickel carried awa,y with slags by
lowering the am~;~unt o~ the latter.
Still ano-ther object o~ the lnvention is to bring
down the time re~uired ~or the produc-tion o~ me~allic nickel
by reducing the number o~ slag~formiDg operations and egclu-
di~ such operations as de~arbonizatlon and deoxidationO
Yet another object o~ the invention is to prevent
pollution o* the atmosphere by eliminating or substantially
reducing the amo~nt o~ carbon o~ide i~ the outgoing gases.
These and other obaects o~ the invention are accomplis-
hed by the provision o~ a method ~or produci~ metallic
~ickel from a nick~1-based oxide ~aterial, comprising pro-
ducing a plasma aet by passing a reducing gas through the
zone oP electric discharge; heating the nickel-based oxide
material by the plasma ~e-t to the melti~g tempera-ture o~
metallic ~ickel; in the process o~ heati~g, nickel o~ides
being reduced ~o metal, and iro~ and cobalt oxides contai~ed
in the nickel-bearing material bei~g partially reduced
in the presence of a reducing gas ~ed in an amount ranging
~rom about 1.2 to 1~75 times that of the reducing gas
required in accordance with stoichiometry, with the re~ul-
tant ~ormation of a melt of me-tallic nickel; subaecti~g
the m~lt o~ ~e-tallic nickel to desulphurization and then
e~fecti~g its :re:t`inement by removing there:~rom incomple-tely
reduced iron and cobalt o~ides as well as gases dissolved
inthe m~lt.
g
6~
~ hus, the me-thod OI -the inventi on permi-t s -the amolLnt
o:~ admixtures cont~ined in metallic nickel -to be reduced
by eliminati~g the necessity o~ using a solid reduci~g
agent, slag :~orming materials and d~o:~idizing aOents. As a
result, the amou~t o~ carbon o~de con-tained in the outgoiDg
gases i~ brought d~wn9 thereby preventi~g pollution of the
atmosphere and improvi~g health conditions at industrial
enterpri se s .
Employing a reducing g~s as the plasma-~orming agent
would enhance its reacti~ity with the resultant decrease
in the time re~uired ~or nickel oxides to be reduced to metal~
If the amount o~ the reduci~g gas used in th~ process
is less than 1.2 times ~hat o~ the reducing gas required
in accordance with stoichiometry, the metallic nickel -to be
produced will contain an excessive amount o~ oxygenO I~
however, the amount of this gas is more than 1.75 times that
requ~red in accordance with stoichiometryy -the metallic
nickel to b~ produced ~ill contain an e~cessive amou~ of
iron and cobalt which are red~lced ~rom the initial nickel-
-bearing oxid~ materialO ~he sele~ted lower and upper boundaries
in.the amount o:e the reduciDg gas required in accordance
with stoichiometry, ranging ~rom 1r2 to 1.75 times res-
pectively, ensure -the pxoduction o:E metallic ni¢k:el wi-th a
minimum co~tent o~ admix~ es, suah as iron and cobalt.
By using a reduc:ing gas in the pxocess9 lt i~ pos~ible to bring
down the aontenti o~ aarbon in m~talliG nickel, whereby the
quality o:f metal is improved and the process time is sub-
sta~-tially shortened b;T eliminating such -technological
operations a 5 decarboniza-tion o~ metallic nickel and its
subsequent deoxidation. In addit:ion" in the method o~ the
i~vention use is made OI hydroge-n of -the reducing gas ~or the
desulphurization OI metallic nic:kel, which enters in-to reac~
tio~ with sulphur, contained in the melt~ to Iorm vola-tile
compounds therewith~ In -this way sulphur is removed from
the melt and its content in the metallic nickel being pro-
duced is materially lowered~ As a result9 i-t becomes Ieasible
to cut down -the ~umber o~ operations ~ ~or e:~ample, such as
the production o:f slags for -the removal o:e sulphur 9 and
-thereby -to shorten the time of -the production process and
reduce losses OI metal wasted with slags~
'rhe raducir~; gas passed -through the zone of electric
discharge is pre~erably substituted by a neutral gas to
be used for re:Eining the melt o~ metallic nickel by removing
there.ïorm incompletely reduced iron and cobalt oxides
as wel~ as gases dissolved in the melt.
'rhis permits the hydrogen of -the reduci~g gas dissolved
in the melt o~ metallic cobalt -to be removed thereIrom.
In -the course o:E re:~ining, the tempe~ature OI the melt
of me-tallic nickel is pre~erably raised -to about 162i~C
with a view to obtaining quality metal when poured in ingot
mould 5 .
~ he invention will be :further lllustrated, by way
--8
o~ example o~ly, wi-th re~erenc~ to the accompanying drawing 9
wherein:
FIG. 1 is a longi-tudinal sectional view o~ a plasma
~eltin~ ~urnace with a ceramic crucible and a hearth electro-
de ~or carryl~g i~to e~ect the me-thod o~ the inventio~
~or producing metallic nickel.
The method of the i~en~ion is carried ou-t by means
o~ a plasma melti~g furnace l, such as sho~ in FI~
which comprises a ceramic crucible 2 closed b~ a refractory
-lined cover 3 having a gas outlet pipe 4. Fi-tted i~ the
central part of -the cover 3 is an opening 5 provided the-
rei~ to receive a plasma ~enerator 6 having its worklng
electrode connec~ed to the negative polarity o~ a power
source (not show~). The positlve polarit~ o~ the power
source is co~ected to an electlode 7 uhich is located
in the bottom ~f th~ crucible 2~ Formed in the side wall
of ~he crucible 2 is a tap hole 8 with a pouring lip 9.
The method c.~ the inventio~ is carried out as ~ollows.
A nio~el-bearinæ oxide material 10 i9 ~ed into t~e ceramio
crucibl~ 2. The material 10 i9 heated by a plasma jet 11 to
a nickel melting temperature pro~uced by ~he plasma generator
6. The plasma jet ll i9 produced by passing a reducing
gas~ such as hydrogen9 natural raw or conversion gas mixed
with a neutral gas, through the ~one o~ electric discharge.
The electric discharge is produced between the working elec-tro-
de o:~ the plasma generator 6 and the melt 12. 'rhe reduc-tion
5~9
of nic:kel oxide s to me-tal is eIfec-ted under the actio~
of a reducing gas with an enhanced reactivity~ which is ~ed
in an amolmt ranging from about 1.2 to 1075 times -that
of the reducing ~as re~uired in accordance with stoiehiometry~
Simultaneousl~ the melt of me-tallic cobalt is subjec-ted to
desulphuriza-tion, which is made possible due to the ~ormation
Gf hydrqgen sulphide discharged toge-ther with the outgGing
gases -through the uu-tle-t pipe 4~ A required -tempera-ture
in the range of 140~ to 1520C is maintained throughou-t
the reduction process by adausting the power capacity o~
the pla sma generator 6.
A~ter nickel oxides have bee~ reduced to metal and the
resultan~ melt s~bjected to desulphurization, the melt of
metallic nickel undergoes refiniDg operation i~ the course
o~ whlch the hydrogen dissolved in the melt is removed.
For this purpose, the reduci~g gas passed through the zone
of electric discharge is subs-tituted b~ a neutral gas~ suoh
as argon. During re~inlng, the temperature of the metallic
nia~el melt is raised to about 1620C, which is -the me-tal
tappi~g temperature~ In -this way i~ becomes possible -to en-
sure a hlgh quality of metal a~ter it is poured in ingot
moulds.
~ he invention will bs further illustrated by th~
following Examples.
Eæample 1
An initial nickel-bearing oxide material composed of
75.4% Ni~ 0.6~o C0~ 0.5% Fe~ 0~5% Cu, 0.01% S, 1.5% Al~ and
up to 1.5% Of oxides of other metals (Si, ~n, Mg, etc.) with
a si~e particle o~ up to 300~ m~ was subjected to reduction
in a plasma ~ur~ace of the type shown i~ ~IG~ 13 with the
power capacity o~ the plasma generator being 60 Kwt. A gas
miætu~e o~ argon a~d hydrogen9 ~ed wi-th a ratio o~ 1:1 in a ~lo~
rate o~ 10 nm3/h and in an amour~t o~ 1075 times that
o~ the reduci~g gas required in accordance with stoichio-
~etry~ was introduced -through the plasma generatorO r~he
temperature o~ the melt was maintained within the range
of 1400 to 1520C~ 'rhe xeduction process was not accompanied
b~ any spattering o~ metal, ~he completion o~ the reduction
process was dete~mined by an increase in the contents of
hydrogen in the outgoing gases, whereupon tke melt o~ metal-
lic cobalt was subjected to refining duri~ which the
gases (H2) and non-metallic inclusions (parts of the lining
and incompletely reduced o~ides of the initial material~
such as FeO9 MgO, etc.) were removed while a neutral gas~
such as argon, was fed through the plasma generator~
In -the course o~ the refini~g procoss 9 metallic nickel
w~s hea-ted to a -tempera~ure o~ 1600 -to 1620a, and then
poured into ingot moulds~
~ he resu~tant metal had the ~ollo~ing composition:
99.07% Ni~ 0.35~0 Co, 0.05yo ~e, 0~ 52~o Cu, 0.0015ya S~ and
0.005% C.
ample 2
An initial nickel-bearing material o~ the composition
and par-ticle size similar to ~tha~t o~ Example 1 was subjected
to reductio~ in a plasma furnace9 such as shown in FIG. l,
with the power capacity of the plasma generator being 75 Kwto
A gas mixture o~ argon9 carbon oxide and hydro~en (Ar-~CO~H2),
~sd in a ratio of 3:1:29 at a f]ow rate of 10 m3/h a~d -in
an amount o~ 1.2 -times that of the reducing Oas required
in accordance with stoichiometr~; was introduced -through
-the plasma generatox. The tempera-ture of the melt was
maintained within the range of 1460 to 1510C. ~he reduction
process was no-t accompanied by an~ spattering of me-tal.
~he completion of the reduction process was determined as
described in Example 1; whereupon the melt of metallic
nickel underwent refining operation duri~g which the gases
(H2) and nou-metallic inclusions (parts o~ the linin$ and
incompletely reduced oxides of the initial material, such
as FeOq CoO, ~gO, e-tc~) were removed from the melt while
a neutral gas, such as argon, was fed through the pla~ma
~enerator. In the course o~ r0fining, metallic nickel
was heated to a temperature o~ 16~0-1620C, a~ then was
poured into ingot moulds~
The resultant metal had the following composition-
99~01% ~i~ 0~38Yo cO~ 0005~0 Fe, 0.55% Cu) 00 002~o s~ 0.005% C.
~his inven-tion may be variously otherwise embodied
within the scope o~ the appended claims.
