4,398,945 Process for producing a ferronickel alloy from nickel bearing laterites

Patent Number/Link:

United States. Patent [19]

Stephens, Jr.

[11]

[45]

4,398,945

Aug. 16, 1983

6 Oaims, 1 Drawing Figure

3,656,934 4/1972 Curlook 75/82

3,947,267 3/1976 d'Entiemont et at 75/130.5

3,999,981 12/1976 Brandstatter 75/84

4,053,301 10/197'7 Stephens, Jr 75/11

4,256,496 3/1981 Brandstatter 106/43

Primary Examinf!r-L. Dewayne Rutledge

Assistant Examiner-Christopher W. Brody

The object of the invention is to provide a process for

the recovery of iron and nickel from low iron content

laterite ores.

Said process comprises subjecting the ore to a carburizing

step in the presence of a reducing agent and carbon

supplying agent to convert the iron to iron carbide,

followed by smelting the residue or product of the carburizing

step to produce a ferronickel product.

An alternative embodiment is the recovery of the iron

and nickel from the product of the carburizing step by

magnetic separation.

[54] PROCESS FOR PRODUCING A

FERRONICKEL ALLOY FROM NICKEL

BEARING LATERITES

[7§] Inventor: Frank M. Stephens, Jr., 12225 W.

18th Dr., Lakewood, Colo. 80233

[2J] Appl. No.: 276,040

[22] Filed: Jun. 22, 1981

[51] Int. 0.3 C21C 5/52

[52] U.S. O 75/11; 75/26;

423/148

[58] Field of Search 75/11, 10 R, 26, 80,

75/82, 84; 423/138, 148

[56] References Cited

U.S. PATENT DOCUMENTS

2,473,795 6/1949 Hills et aI. 75/82

2,740,710 4/1956 Johannsen 75/133.5

3,077,396 2/1963 Moussoulos 75/31

3,502,461 3/1970 Guttier et aI. 75/10

3,503,735 3/1970 Beggs et aI. 75/31

3,634,064 111972 Vedensky 75/31

[57] ABSTRACf

ORE

H2 +CH 4 0R CO

--,

-,-- --,

GNETIC I

ATMENT I

____ ...J

"')

CARBIDE

CONVERSION

f---.;;';"'-

, ,_.-

ARC FURNACE Fe .J MA

MELTING ·Ni I TRE L __

HEATSLAG

FER RONICKEL

U.S. Patent Aug. 16, 1983 4,398,945

ORE

H2 +CH 4 OR CO

--,

I -,-- --,

GNETIC I

ATMENT I

____ -.J

CARBIDE

CONVERSION

f.--- --

r---

ARC FURNACE ..fe..J MA

MELTING Ni I TRE

L __

HEATSLAG

FERRONICKEL

4,398,945

0.7

5.J

4.3

WI. %

17.4

1.5

23.3

23.0

0.7

H20

AhO]

18.7

27.2

27.3

wt.%

MgO

Si02

MgO

Si02

EXAMPLE 2

A sample of the residue from Example 1 was separated

magnetically using a 15-gram sample as feed to a

Davis tube separator. The Davis tube products were

analyzed for iron as iron carbide and nickel and were

examined by mossbauer spectroscopy to determine the

mode ofoccurrence ofthe iron. The results showed that

a magnetic fraction can be separated and that its iron

assay will be about 45 percent and its nickel assay about

1.4 percent. This represents a significant grade improvement.

EXAMPLE 3

A lOO-gram charge of the residue or product of Example

1 was melted in a Deltech furnace. The product

had a melting temperature of about 1550· C. and upon

melting formed a metallic button and a slag cover.

The metallic button contained 79.9 percent iron and

2.95 percent nickel; whereras, the slag assayed 0.95

percent of iron and 0.005 percent nickel. This represents

a significant recovery of iron and over 99 percent of the

contained nickel in the metallic button.

The results show that a feasible and technically efficient

process has been developed based on the. partial

conversion of iron to iron carbide in low iron laterities

followed by smelting to produce ferronickel.

The iron oxide in the sample of nickel laterite was

converted to iron carbide in a laboratory 4-inch fluidized-

bed reactor. The unit was operated at a temperature

of 550· to 580· C. using gas compositions containing

63 to 69 percent hydrogen as the reducing agent, 10

to 20 percent methane and 12 to 16 percent CO (carbon

monoxide) as carbon supplying agents, and 3 to 12 percent

C02. The temperatures used are dictated by economy

with a preferred range being between about 500·

C. to 700· C. with the preferred upper limit about 700·

C. The above gases can be used within the ratios disclosed

in U.S. Pat. No. 4,053,301. The progress of the

conversion of Fe203 to Fe3C was monitored by submitting

samples of mossbauer and carbon analysis.

After twelve. hours of operation, the carbon content

of the bed material leveled offat 1.5 percent carbon and

the mossbauer analysis indicated that 50 percent of the

iron in the sample had been cOllverted to iron carbide

with the balance being present as iron silicates which

was not converted. This material was removed from the

fluidized-bed. reactor and was used as feed material for

30 testing the recovery therefrom of iron and nickel by

magnetic separation and by smelting. The fluidized bed

residue or product had the following analysis:

EXAMPLE 1

TECHNICAL FIELD

BACKGROUND ART

DISCLOSURE OF THE INVENTION

PROCESS F'OR PRODUCING A FERRONICKEL

ALLOY FROM NICKEL BEARING LATERITES··.

Twopyrometallurgical processes are currently in use 20

for the treatment of low iron laterite. In the rotary

kiln-arc furnace process the ore is mixed with coke,

preheated, and partially reduced in the rotary kiln and

the hot kiln product used as feed to an arc furncace

smelting step to produce ferronickel and slag. In the 25

other commercial process, the ore is melted in an arc

furnace arid then mixed with molten ferronickel and

molten ferrosilicon to yield an enriched ferronickel and

slag.

In accordance with the present invention, the nickel

and iron in nickel containing laterite ore are recovered

as a ferronickel product by first reducing and carburizing

the iron oxides to iron carbide in accordance with 35

the teaching of U.S. Pat. No. 4,053,301 with simultaneous

disruption of the ferrite structure of nickel ferrites,

followed by smelting the product in an electric

furnace to product the ferronickel product.

The improved process has the advantage that the 40

product from the carburizing step can be introduced

directly into the electric furnace for smelting to produce

the ferronickel product with high yields of nickel

without the addition of ferrosilicon. Further, the carbu- 45

rized product is magnetic, making possible the magnetic

recovery of iron carbide and nickel from the ore.

The invention relates to the· recovery of· iron and

nickel from laterites. It is difficult to economically recover

iron alone from low iron content laterites without

the simultaneous recovery of some other valuable 10

metal, such as, nickel in nickel containing laterites. It is

difficult to recover the nickel and iron simultaneously

because of the difficulty of disrupting the ferrite structure

of nickel ferrites. Further, a process is desirable for

the direct conversion to a ferronickel product of the 15

iron and nickel in nickel containing laterites, and without

the· use of ferrosilicon, as in· the prior art.

The nickel bearing laterite ore used in this example

had the following composition:

BRIEF DESCRIPTION OF THE DRAWINGS

The single FIGURE of the drawing is a flowsheet of 50

the process.

BEST MODE FOR CARRYING OUT THE

INVENTION

The disclosure of the carburizing process of U.S. Pat. 55

No. 4,053,301 is incorporated herein by reference, including

the use of a fluidized bed, the carburizing temperatures,

reducing and carburizing materials, ratios of

additives, and other critical factors.

THE TERM "laterite ore" as used herein includes all 60

nickel bearing laterite ores of various compositions. The

nickel bearing laterite ore used in the examples was

ground to a fine particle size, typically about - 200

mesh, but this is. not critical.

4~398,945 ..•

The conversion to carbide can be accomplished at

relatively low temperatures using gaseous reductant

produced from low rank fuels and the arc furnace operation

would involve only melting with no electrical

energy or secondary reductant involved for the reduc': 5

tion of nickel.

The results of Example 1 show that substantially all

of the iron present as iron oxides in the laterite ore can

be converted to iron carbide by the present process, but

the iron present as complex silicates cannot be so con- IO

verted, thus illustrating the unpredictability of ores

upon which the process is operative.

Because of the large excess of iron over nickel in most

laterities, it is generally not advisable to convert all of

the iron to ferronickel because the resulting iron-nickel 15

alloy produced in the melt step would have an unfavorably

iron to nickel ratio. The iron to nickel ratio in the

ferronickel alloy product. is controlled by converting

only a portion of the iron in the ore to iron carbide. 20

The invention is not restricted to use on ores or other

materials containing only nickel with iron but can be

used in similar fashion to recover other metals existing

with iron in ores and other materials which metals have

a melting point in excess of 750· C. and which alloy 25

with iron upon smelting. Examples of these other metals

recoverable by the process along with iron are cobalt,

chromium, manganese,' molybdenum, nickel, tungsten,

and vanadium. All of these metals alloy with iron in

steel making processes.

Also, the invention is not restricted to making' the

iron carbide in situ to make the final alloy product. The

iron carbide can be made or obtaind separately and

either part or all that is required added during the processing.

I claim:

1. A process for recovering a metal which has a melting

point in excess of about 750· C, and is'c:apable of

alloying with iron, in the form of an iron alloy from a

material containing iron and said metal, said process

comprising: .

(a) contacting said material with iron carbide, at least

some of said iron carbide being formed by converting

at least some of said iron in the material containing

iron to iron carbide in a fluidized bed in the

presence of a carbon-supplying material and a reducing

agent, and

(b) smelting the product of step (a) to produce the

alloy of said metal with iron

2. The process of claim 1 in which no additional

reducing agent is added to step (b).

3. The process of claim 1 in which said other metal is

selected from the group consisting of cobalt, chromium,

manganese, molybdenum, nickel, tungsten and vanadium.

4. The process of claim 3 in which said other metal is

nickel.

5. The process of claim 1 in which said material containing

iron and said metal is laterite ore.

6. A process for producing an alloy of iron and another

metal, said other metal having a melting point in

excess of about 750· C. and being capable of alloying

with iron, from an ore containing iron and said other

metal, comprising: .

(a) contacting said ore with iron carbide, at least sone

of said iron carbidge being formed by converting at

least some of said iron in said ore to iron carbide in

a fluidized bed in the presence of a carbon-supplying

material and a reducing agent, and

(b) smelting the product of step (a) to produce the

alloy of said metal with iron.

* * * * *