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Патент USA US2409429

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‘oct 15, 1946.
Filed Newe 14, 1941
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Patented Oct. 15, 1946
Daniel Gardner, New York, N. Y., assignor to
Virginia Metal Industries, Inc., a corporation
of West Virginia
Application November 14, 1941, Serial No. 419,222
7 Claims. (ci. 23;-56)
This invention is a novel process of treating
process. All are elements of passive character;
iron ores containing chromium and related ox
that is, the metals can be in the passive state,
ides; and pertains to the recovery from the ores,
becoming active only through the catalytic ac
or other raw materials, of the iron content and
tion of hydrogen ions, which is true of very few
other metals. Each of the metals is paramag
netic, as are also certain oxides thereof, facili
nese, cobalt and nickel when present, separately
tating magnetic separation. Their industrial ox
from the gangue and from each other.
ides are separable by leaching. Their industrial
This application is related to, and to a certain
point may follow, copending application No. 10 oxides can exist combined in the form of spinels,
corresponding to the common spinel, magnesium
415,890, filed October 211, 1940, patented July 11,
aluminate MgO'AlzOz, or to the abstract formula
1944, No. 2,353,613, which discloses the beneficia
MO-XzOa, wherein M may be Fe, Ni, Co or Mn
tion of iron ores, with the elimination of the
and X may be Fe, Cr or Mn; knowledge of which
gangue therefrom, and takes account of the prob
illuminates the structures of certain minerals and
able presence in the raw material of one or more
15 indicates the formulas of the ore compounds. As
of the five related metals chromium, manganese,
another similarity the five metals can form alums,
iron, cobaltV and nickel, or rather compounds
or double salts of the formula:
thereof, especially the oxides; and proposes the
recovery of all of these which may be present;
MZSOfMg ( S04) @24H20
which live metals for convenience may be termed 20
the series metals, being the metals of series 4
Certain portions of the disclosure of the `co
, of the periodic table falling under the higher
pending application may conveniently be first
groups VI and VII and VIII.
described because employed or partly followed
The general object of the present invention
in the present case. In the raw material or ore
is to provide an improved process for separating 25 the series metals may appear as follows, enumer
from the iron compounds the compounds of the
ated in the order of their atomic numbers:
other metals, and for the separate recovery of
each of these, in an industrially practicable man
or in combination with ferrous oxide FeOf as
ner; so that, with the growing importance of
-chromite FeO - CrzOa.
the respective non-ferrous metals, their recovery 30 Manganese.--As manganous oxide MnO or other
may have a value to compensate largely or wholly
oxide-for the process costs, thereby to convert an other
Iron.-As ferrie oxide or hematite FezOs, or as '
wise unproñtable iron ore to one profitable to be
ferrous oxide FeO, or in chromite as stated above.
worked, and at the same time affording iron free
Cobalt-_As cobaltous oxide CoO.
_ l
of the other metals.
A further object is to aiïord recovery as com 35 Nickel-As nickelous oxide NiO.
In thus referring to the oxides it is intended
plete as possible of each of the valuable metals.
Another object is to permit the elimination of ' to include the corresponding' hydroxides Cr(OH).3
and Mn(OI-I)2 and Fe(OH)3 and Fe<OHl2 and
the gangue by treatment at such a low tempera
Co(OH)2 and Ni(OH)2, Without further men
ture that the values are recoverable with mini 40 tion,
as possibly contained in the original ore.
mum diiiiculty and expense; the process being
Other elements present, as magnesium, cal
rather chemical than metallurgical.
cium or silicon are automatically eliminated with
A particular object is to afford an improved
gangue; while phosphorus and sulphur com
and more profitable method of separation and
pounds may be disposed of with the gangue or in
recovery of the aforesaid five series metals than
the gases.
that disclosed in said copending application.
In the accompanying drawing is illustrated a
Other objects and advantages will be .explained
flowsheet of one illustrative example or embodi
or appear in the hereinafter described process
ment of the present invention.
and the several examples thereof.
The close relationship of the five series metals 50 In' the copending case and preferably her'ein,
the raw material, ñnely crushed and ground, is
herein dealt with may be further shown as fol
intimately mixed with a solid carbon material
lows: Their atomic numbers are adjacent, being
and a basic hydroxide; or the mixing may pre
Nos. 24, 25, 26, 27 and 28. Each metal .has va
cede the grinding. The mixture is then heat
lences of 2 and 3, while Cr and Mn have also
higher valences, including 6, made use of in this 55 treated, as in a rotary kiln, for a period suffi
cientto complete the conversions to be effected.
The temperature is to be relatively low for a kiln
operation, and is distinctively different from met
allurgical smelting temperatures. This low heat
The kiln is of course sealed against air
While still excluding contact with air the kiln
discharge is next quenched by abrupt cooling, as
avoids softening and agglomeration so that the
in a water bath, preferably having a substantial
powdery condition of the mixture is retained;
proportion or saturation of a basic hydroxide or
but is preferably above about 450°, to ensure the
lime hydrate dissolved in it.
conversion reactions. The low temperature also
The converted mixture contains, besides the
minimizes the retention of the ore impurities
gangue materials of lighter specific gravity, the
with the values. The centigrade system is herein 10 heavier values, the oxides of the series metals,
used for temperatures.
iron, chromium, etc. Notably there will be fer
The carbon, in the form of coke, coal, etc., pref
roso-ferric oxide FeaO4 and/or its hydroxide,
erably lt°c coke, is a solid reducing agent, con
which is soluble in concentrated sulphuric or
verting the higher oxides present to lower oxides,
other acids as acetic, oxalic or tartaric; chrcmic
e. g. FezOs to FeO and these combining into
oxide CrzOs and/or its hydroxide, soluble in ex
Fes04 or magnetite; and similarly with Minox
cess of caustic soda NaOH solution; manganous
oxide MnO or manganosic oxide MnzOi and/or
and MnO, forming Mn3O4. The other metal ox
their hydroxides, soluble in ammonium salt solu
ides are not necessarily converted, e. g. the chro
tions; NiO and/or its hydroxide, soluble in arn
mium may remain as CrzOs, or its hydroxide
monium hydroxide; and CoO and/or its hydrox
ide, soluble in ammonium salts, and in acids, as
The basic hydrate is preferably calcium hy
acetic or tartaric. Now the gangue can be largely
droxide Ca(Ol-I)2, although the barium or stron
removed hydraulically, by gravity separation,
tium hydroxide may be employed.
being of lighter density and able to be flowed
Ca(OH)2 the kiln temperature should be between
away from the heavier values. There results a
about 450° and 525°, the latter being safely below
converted and enriched mixture ready for further
the point at which Ca(OH)2 yields its water of
treatments, which, in the copending case com
constitution and becomes lime CaO. By using
prise selective dissolvings, leachings, precipitat
Ba(OH)2 the temperature may be carried up to
ings, washings and dryings, not herein -followed
about 750° if desirable. In the presence of steam
the temperature may somewhat exceed the said 30 and therefore unnecessary to describe; although
certain of the steps may usefully be used in a
water yield point. The function of the basic
different manner in the present case.
hydroxide is important, as it reacts at the low
temperature with any silicon or aluminum com
pounds present such as silica SiOz and alumina
A general characteristic of the copending and
present applications may be described as follows.
A1203, and converts the metal silicates and alu
minates to oxides, thus to withdraw them from
undesirable combination with the iron; also it
The customary smelting in a blast furnace of the
some silicates and aluminates to oxides. It en
gages or absorbs silica, for example as comprised
in Such compounds as FeO~SiO2~ It does all this
other metals etc. These advantages are of espe
cial value when the gangue is only of a minor
or low proportion of the entire ore.
entire contents of the original ore is herein dis
pensed with, and the gangue portion is prelim
inarily eliminated, or largely so. This is done
tends further to promote the reduction reactions.
at low heat so that the materials need not be
It should be included somewhat in excess as ex
plained in the copending case thus to insure re 40 softened or fused, and they retain their powdery
or crushed condition, ensuring effective reactions
action with all silica and alumina present.
and avoiding slagging of the gangue and resulting
The basic hydroxide, e. g. calcium or barium
difficulties. Only the enriched values need go te
hydroxide, affords important functions in the
the smelting stage, and indeed these in separated
process. It takes part in converting the trouble
lwith the iron compound free of the
4 condition,
while operating at a relatively low temperature,
Example A
below that of softening of the ore, and below that
of water-loss from the hydroxide. For example, 50 In its ñrst embodiment or example the present
calcium hydroxide, a basic compound, retains its
invention commences with the quenched and en
Water of constitution up to about 580” (barium
riched mix containing the desired oxides of the
hydroxide to 750°), and the presence 'of :such
five series metals, preferably CrzOs, and MnO or
water component is important to the function
MnsOi, and FesO4 and CoO and'NiO; or the cor
ing of the agent, it being found that unslaked
responding hydroxides. Unless it be desired to
lime or calcium oxide CaO will not act similarly.
have the chromium (and manganese) separate
In the presence of the basic or calcium hydroxide,
away from the other values, after quenching, as
particularly with steam present, `and at the low
described in Example B, it may be caused to re
temperatures mentioned, the silica present in any
main with the other values. This is done by the
form in the ore tends desirably to enter into com
bination and to form calcium silicate CaSiOs,
which is a compound of light specific gravity and
later easily separable from the values of the ore.
Moreover when once formed, calcium silicate is
a stable compound with a high heat of formation,
described use of steam and carbon in the kiln
reactions, which causes the chromic oxide to take
the hydrated form Cr(OI-I)3 and this stays with
the other values FesO4 and MnaOi or Mn<Ol-l>z
f and CO(OH)2 and' Ni(OH)z when effecting the
preliminary removal of the gangue in the quench
ing vessel or following separator. After washing
separates the silica. Similar statements are ap
the mixture of the values the present invention
plicable to alumina in the ore, it becoming con
proceeds as follows.
verted to calcium aluminate; and corresponding
In a second furnace or kiln are performed sec
observations apply if calcium hydroxide be re 70 ond stage reactions at the somewhat higher tem
placed by barium or analogous basic hydroxide.
perature of about 550°, or within the range 500°
The kiln atmosphere must be non-oxidizing and
to 800°. The enriched mixture of oxides is first
may be reducing. Steam is a preferred atmos
mixed with a basic hydroxide or lime hydrate,
phere, but a volatile hydrocarbon gas may be
but the first-stage carbon is omitted. The atmos
used, as methane; or other gases as H or CO or
about 375 cal. The hydroxide thus potentially
phere now is to -be oxidizing and preferably con
sists of superheated steam mixed with air. With
ample steam in the atmosphere the hydroxide
desired separations. In some cases magnetic
separation steps may be of auxiliary value. The
ammonia vehicle is recoverable in gaseous form,
available for repeated use. After all the sepa
Ca(OH) 2 resists loss of its water of constitution to
these higher temperatures. These reactions may 5 `rations are completed conventional metallurgical
terminate ‘by cold quenching as before.
steps may be employed to convert the separated
By this hot treatment the chromic hydroxide
compound of each metal to the metallic form
(after losing its water of constitution) is rapidly
or to another desired compound or alloy.
oxidized and then converted to calcium chromate,
The various steps may in most part be per
while the manganese oxide is similarly converted
formed in continuous process, and the ore may
to calcium manganate, thus:
be passed from the crusher to a mixing point
and thence by infeed into a furnace chamber
with progressive advance, as in a downslanting
rotary kiln, which discharges to a quenching ves
These reactions are selective, since `the iron, 15 sel with which may be associated conveying, sep
cobalt and nickel do not undergo corresponding
arating and other apparatus elements, as of
transformation, and the separation out of the
known descriptions.
chromium and manganese values has thus been
begun. As the chromate and manganate (or
Example B
permanganate) are water-soluble, they may be 20
By a simpliñed process, using but one kiln or
taken up by the quenching water and thus sepa
furnace, the chromium and manganese values
rated from the other values and gangue.
may be conditioned to enter into solution in the
Now CaMnO4 changes or dissociates at about
quenching water and thus be separated in this
190° while CaCrO4 remains stable until about
way from the iron, cobalt and nickel compounds,
600°, although its hydrate` loses its two molecules
as well as from the gangue; and, after the gangue
of water at about 200°.
>is eliminated the last three metals are separable
By a suitable vehicle and procedure the chro
from each other, as in the manner previously de
scribed. This short cut process may proceedV as
mium and manganese can now be mutually sep
arated. An excellent solvent or vehicle is glyc
erol (glycerine), but alcohol and ether also dis
solve calcium chromate and will serve.
Into and through the hot reaction chamber or
kiln are passed the crushed ore and other agents,
ing glycerol, this boils at about 290°. It may be
for hot treatment and quenching. A basic hy
mixed with the quenching water in which the
droxide is included in mixture with the ore, but
two salts are dissolved. By heating up gradu
ally this solution, upon passing about 190° at 35 no carbon. To increase thermal conductivity
an agent such as calcium chloride is added. To
which calcium manganate dissociates, there oc
curs the precipitation of manganous hydroxide
Mn(OH)2, which may be continued to comple
tion, While the chromate alone remains dissolved
in the glycerol. Thus these two values are sepa
rated out of the five-metal mixture, and sepa
rated from each other.
From the glycerol solution of calcium chromate
the chromium may be recovered in different 1
ways. One `way is to employ a soluble lead salt,
for example the acetate, as an agent reactive to
precipitate the chromium as PbCrOa, from
which the metal is readily obtainable by known
improve porosity of the mix an agent such as
brick fragments or powder is preferred, diato
maceous earth, or a hygroscopic clay. The
materials may be briquetted before infeed
40 to the kiln.
The atmosphere is preferably of superheated
steam mixed with air, and therefore oxidizing.
The temperature, which should be indirectly pro
duced, may run between about 500° and 800°.
Following a duration of heating sufficient for the
reactions the mixture is then quenched.
Since the heating is in the presence of air,
methods. For example this salt may be reduced
followed by quenching, -the chromic oxide CrzOs
to Cr(O‘H)3 by distilling off the glycerol, and the 50 becomes converted to calcium chromate CaCrO4,
hydroxide then can be reduced by ethyl alcohol
which may first be without its water of crystalli
and then carbon; or by tartaric or hydrochloric
acid or sulphuretted hydrogen. The glycerol is
not impaired and is recoverable with practically
no loss and ready for repeated use.
Another mode of separating from each other
the chromium and manganese compounds is as
follows. First reduce them to their hydroxides,
, zation, but eventually acquire it. Likewise the
manganese oxides become the manganate
These calcium salts, the chromate
and permanganate C'a(MnO4)z, being water sol
CHOI-D3 and Mn(O:H)2. Then treat the mix
uble are rapidly taken up by the quenching bath,
ture with NaOH in excess, which acts to dissolve 60 and thus separated from the gangue and from
the chromium but not the manganese hydroxide;
the other values. The gangue is thus eliminated.
for which KOH also would serve but is uneco
The chromium and manganese oxides, by this
._ ,
process, are restrained from forming spinels or
The three remaining values, after the de
aluminates, and indeed the chromite part of the
scribed removal of the chromium and manganese 65 original ore becomes split in the furnace into
hydroxides, may be‘treated as follows. First,
the separate oxides of `iron and chromium, thus
leach the three-metal mixture with an ammonia
to insure conversion of the latter to chromate
solution, preferably with NHiCl added, which
and therefore solubility.
dissolves out the cobaltous and nickelous hydrox
The bath water is then treated by suitable
ides C0(OH)2 and NH01-D2, leaving the iron 70 agents to recover therefrom the chromium and
compound or magnetite FesOu isolated. Next,
manganese compounds, while separating these
treat the ammonia solution with sodium hydrox
>from each other, as in the manner already in
ide NaOH, which acts to precipitate the nickelous
dicated. In whatever form the other metals
oxide as the hydroxide, leaving the cobaltous
remain they may be treated to appropriate sepa
hydroxide in the solution; thus completing the 75 ration and conversions.
Further explanations
In one aspect the invention may be summed up
as involving the use at an early stage of the basic
hydroxide, es Ca(OH)2, to handle the compounds
containing silicon or aluminum and so to carry
these elements into the gangue, thus enriching
thev raw material values before smelting; also the
use of the same agent to convert certain of the
values, chromium and manganese, to soluble
salts, but not the others, thus giving easy initial
separation of these two, and facilitating com
plete separation of the respective values from
each other before smelting operations. In an
other aspect the process comprises mixing with
the finely divided ore material the basic hydrox
ide in excess, but no carbon, heating to 500° to
800° in a steam-air atmosphere, thus removing
silicon from compounds of the values and oxi
dizing the values, and also converting the chro
mium and manganese oxides to chromates and
manganates as calcium permanganate which
upon quenching may be dissolved out for their
separation from the other values.
It should finally be mentioned that vanadium,
element No. 23, in series ll, is to some extent or
degree amenable to the treatments hereinabove
disclosed for elements Nos. 24 to 28. Like the
others vanadium has, besides valences 2 and 3, a
higher valence, namely, 5. It also is a passive
element, as are the others, and as are molybde
num, ruthenium and tungsten, in other series.
And it has a similar tendency to oxidize, More
over its oxide, such as V205 is susceptible to con
version to calcium metavanadate Ca(VO3)2, in
parallel to the conversion of chromium and man
ganese, and this product teo is water-soluble and
dissolved into solution and thus separated from
the gangue and the insoluble iron compound.
2. The process as in claim 1 and wherein the
chromium compound is thereafter precipitated
from solution for reduction to metal form, and
the gangue is eliminated from the solids leaving
the Fe304 in enriched condition for reduction to
3. rthe process of separating chromium and
manganese xides from a mixture containing also
insoluble oxides of iron and of one or more of the
series metals of the group consisting of cobalt and
nickel, comprising treating the mixture with cal
cium hydroxide to convert the chromium and
manganese constituents only to soluble salts,
namely to a calcium chromate and calcium per
manganate, and then dissolving out such salts,
leaving the other values in solid form; and then
heating to above about 190° C. the separated so
lution of calcium chromate and calcium per
manganate thereby to convert the latter and pre
cipitate it as manganese hydroxide.
4. The process of treating metal oxide mix
tures in iinely divided form containing oxides of
iron and of chromium for the separate recovery
of such metals or values free from the gangue;
said process comprising the steps of mixing cal
cium hydroxide into the iinely divided material,
and subjecting the mixture in an oxidizing at
mosphere and in the substantial absence of car
bon, to a reaction temperature between about
500° C. and 300° C., and for a duration suñicient
to ensure the conversion of the chromium oxides
present to the soluble calcium chromate; followed
f by quenching oi the mixture in an aqueous bath,
and causing the converted chromium values to be
dissolved into solution and thus separated from
thus readily removable from the iron compounds.
the other values and gangue.
Therefore in a broad aspect the present invention
is applicable to this additional element of the
fourth periodic series. Vanadium however rarely
appears in the same iron ores with these other
series metals; and besides it has very individual
5. The process of treating iron ores containing
also oxides of other metals including a chromium
characteristics and requires special consideration
and steps in adapting the invention to iron ores
Having thus described examples of a novel
process for treating iron ores containing chro
mium and related oxides, embodying the prin
ciples of the present invention, it should be stated
that the process so disclosed may be variously
modified in regard to the character of the several
steps, and their order, the nature of the agents
employed, and such matters as temperature and
duration, without departing from the principles
involved, wherefore it is not intended to limit the
invention to the details disclosed except so far
as is set forth in the appended claims.
What is claimed is:
l. rI‘he process oi treating metal oxide mixtures
in finely divided form containing iron and chro
mium oxides for the- separate recovery of such
iro-n and chromium values free from the gangue;
said process comprising the steps of mixing cal
cium hydroxide into the ñnely divided material
and subjecting the mixture in a non-oxidizing
atmosphere, to an oxidizing temperature above
about 500° C. but insufficiently high for substan
tial loss from the calcium hydroxide of its water
of constitution, and for a duration sufficient to
ensure the substantial conversion of the iron ox
ides to Fea04 and the chromium oxides to a water
soluble calcium chromate; followed by quench
ing of the mixture in an aqueous vehicle, and
oxide, for the separate recovery of such iron and
other metals or values substantially free from
the gangue; said process comprising the follow
ingV steps: in a first reaction stage mixing the
ore with calcium hydroxide and a solid carbon
reducing agent, and in a non-oxidizing atmos
phere heating the mixture to a temperature above
about 450° C. but below the softening point of the
mixture, followed by quenching, whereby the iron
content is converted to ferroso-ferric oxide and
the chromium to chromic oxide or hydroxide and
the other metals similarly to recoverable oxides;
and in a second reaction stage mixing with the
recovered products of the iirst stage calcium
hydroxide and subjecting the carbon-free mix
ture in an oxidizing atmosphere, to a reaction
temperature between about 500° C. and 800° C.,
thereby to bring about the conversion of the
chromic oxide present to a soluble chromate; fol
lowed by quenching of the mixture in an aqueous
bath; and causing the converted chromium values
to be dissolved into solution and thus separated
from the other values and gangue.
6. The process of treating iron ores containing
also oxides of other metals including chromium
and manganese oxides, for the separate recovery
of such iron and other metals or values substan
tially free from the gangue; said process compris
ing the following steps: in a íirst reaction stage
mixing the ore with calcium hydroxide and a
solid carbon reducing agent, and in a non-oxidiz
ing atmosphere heating the mixture to a tem
perature above about 450° C. but below the soften
ing point of the mixture, followed by quenching,
causing the converted chromium compound to be 75 whereby the iron content is converted to ferroso
ferric oxide and the chromium to chromic oxide
or hydroxide and the other metals similarly to
about 450° C. and the softening point of the mix
recoverabie oxides; and in a second reaction
stage mixing with the products of the first stage
calcium hydroxide, and subjecting the carbon
free mixture in an oxidizing atmosphere, to a re
action temperature between about 500° and 800°
C., thereby to bring about the conversion of the
chromium and manganese oxides present to a
ture, followed by quenching, whereby the iron
content is converted to FeaO4 and the chromium
to Cr(OH)s and the manganese to Mn(OH)2 or
MnaO‘i; and in a second reaction stage, the said
products of the ñrst stage being in mixture with
Ca(OH)2, subjecting the carbon-fre@ mixture in
an oxidizing atmosphere, to a reaction tempera
ture between about 500° C. and 800° C., thereby
soluble chromate and permanganate respectively; 10 to bring about the ultimate conversion of such
followed by quenching of the mixture in an aque
ous bath; and causing the converted chromium
and manganese values to be dissolved into solu
tion and thus separated from the othei` values
and gangue.
oxides of chromium and manganese present to
soluble calcium salts of such metals respectively;
followed by quenching of the mixture in an aque
ous bath; and causing the converted chromium
15 and manganese values to be dissolved into water
7. The process of recovering from iron ores
solution and thus separated from the other values
containing iron oxides also oxides of other metals
and gangue; followed by separating the resulting
including chromium and manganese, of such iron
solution of chromium and manganese values and
and other metals substantially free` from the
then heating it to a temperature’ to convert and
gangue; said process comprising the following 20 precipitate the manganese content as insoluble
steps: in a first reaction stage mixing the ground
hydroxide, thus separating it from the chromium
ore with Ca(OH)2 and a solid carbon reducing
agent, and then in a non-oxidizing atmosphere
heating the mixture to a temperature between
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