Process for the recovery of nickel from nickeliferous lateritic ores

Claim 2

The process of claim 1, wherein such ore contains an iron content very much in excess of the nickel content, but the ferronickel produced contains at least 45 percent nickel by weight, with such nickel recovery constituting at least 90 percent of the nickel content of such ore.

Claim 3

The process of claim 1, wherein such charge is thus first heated at a temperature below 2,000* F. to effect such first reduction and subsequently heated to at least 2,600* F. to effect such further reduction and to melt such charge.

Claim 4

The process of claim 1, wherein such charge is preformed into compacts, and the individual identities of such compacts are preserved throughout such first heating stage and transfer to such subsequent heating stage.

Claim 5

The process of claim 5, wherein such compacts are formed of ground nickeliferous lateritic ore and ground solid particulate reducing agent, and such compacts are transferred in hot condition in a nonoxidizing atmosphere from such first heating stage to such subsequent heating stage.

Claim 6

The process of claim 6, wherein such solid particulate reducing agent is thus ground to two substantially different degrees of fineness, the more finely ground reducing agent component acting to prereduce such ore during such first lower temperature heating stage and the less finely ground reducing agent component acting further to reduce such ore during such second higher temperature heating stage.

Claim 7

The process of claim 5, wherein such first component is a high volatile coal and such second component is coke.

Claim 8

The process of claim 8, wherein approximately 90 percent of such coal by weight is about 200 mesh or finer and approximately 80 percent of such coke by weight is about 40 mesh or coarser.

Claim 9

The process of claim 5, wherein the total amount of reducing agent initially contained in such compacts is between about 0.5 percent and about 6 percent by weight of such compacts, and said compacts contain approximately 1 percent carbon by weight following such first heating stage and prior to such subsequent heating stage.

Claim 10

A process for the recovery of metallic nickel in the form of ferronickel which comprises preforming a charge of nickeliferous lateritic ore and uniformly admixed particulate carbonaceous reducing agent into compacts, said reducing agent comprising a first component capable of reacting readily with the nickel compounds and the iron compounds of such ore to reduce them at a relatively low temperature and a second component substantially unreactive with such compounds at such temperature but capable of subsequently reacting with nickel compounds and iron compounds present in the charge at a substantially higher temperature, passing such compacts through a shaft furnace to heat them to such relatively low temperature for a period of time sufficient to cause such first reducing agent component to reduce such iron compounds to ferrous oxide without production of metallic iron and without sticking together of such compacts and without disintegrating such compacts, and to reduce a substantial portion of such nickel compounds to metallic nickel, a substantial amount of such second component of such reducing agent surviving undestroyed in such compacts discharged from suCh furnace, and subsequently heating such compacts to such substantially higher temperature effective to react such second reducing agent component with the remaining nickel compounds to substantially complete the reduction of all such compounds to metallic nickel and to react such second reducing agent component with such ferrous oxide to reduce a sufficient portion of the latter to metallic iron to produce ferronickel containing a substantial amount of iron, and melting the charge.

Claim 11

The process of claim 11, wherein the ferronickel produced contains from about 20 percent to about 50 percent nickel by weight.

Claim 12

The process of claim 11, wherein such heating in such shaft furnace is at a temperature below 2,000* F., and such subsequent heating is performed in an electric furnace at a temperature of at least approximately 2,600* F. to melt such charge to produce ferronickel and slag, such heating in such shaft furnace and transfer to such electric furnace being effected under nonoxidizing conditions.

Claim 13

The process of claim 11, wherein the reaction of such first reducing agent component in such shaft furnace produces hydrogen and carbon monoxide which are removed from such furnace with the exit gas, cooled, mixed with primary burner gas, and recycled to the lower region of such furnace to ensure substantial equilibrium with the ferrous oxide in the partially reduced compacts in such region and to regulate the temperature of such gaseous mixture introduced to the shaft furnace.

Claim 14

The process of claim 11, wherein said compacts as discharged from such shaft furnace contain sufficient carbon, not substantially in excess of 1 percent by weight, to perform the specified further reduction of the charge in such subsequent heating stage.

Claim 15

The process of treating nickel ore which comprises intimately mixing such ore with a solid reductant, forming such mixture into compacts, heating such compacts at only a relatively low temperature in a first furnace only partially to reduce the nickel compounds and iron compounds of such ore without disintegrating such compacts, without producing a consequential amount of metallic iron, without causing such compacts to stick, and without entire consumption of such reductant, and subsequently heating such prereduced compacts in another furnace to a much higher temperature substantially to complete the reduction of the entire nickel content to metallic nickel and the reduction of a portion only of the iron content to metallic iron thereby to produce molten ferronickel.

Claim 16

The process of claim 16, wherein such reductant is particulate carbonaceous material, said ore contains nickel oxide and iron oxide and is finely ground, heating gases of a reducing nature are introduced into such first furnace to ensure substantial equilibrium with ferrous oxide in such partially reduced compacts, and such partially reduced compacts contain a small amount of carbon effective substantially to complete reduction of the nickel oxide to metallic nickel and to reduce a portion only of such ferrous oxide to metallic iron during such subsequent heating at such higher temperature, only sufficient metallic iron being thus produced to extract substantially the maximum amount of metallic nickel from such ore in the form of molten ferronickel, such metallic iron constituting not more than 80 percent of such ferronickel by weight.

Claim 17

The process of claim 17, wherein only sufficient ferrous oxide is thus reduced to metallic iron during such subsequent heating to produce molten ferronickel which is approximately one-half iron and one-half nickel by weight.

Claim 18

The process of extracting nickel from nickeliferous ores containing substantially more iron than nickel which comprises forming compacts of such ore with a solid reducing agent, preliminarily reducing such iron content to ferrous iron and a substantial amount of such nickel content to metallic nickel without disintegration of such cOmpacts while preserving a portion of such reducing agent therein only sufficient subsequently to complete reduction of substantially all such nickel content to metallic nickel and to reduce such ferrous oxide to produce a substantially equal weight of metallic iron, performing such subsequent reduction at a much higher temperature in a melting furnace, and melting such compacts to ferronickel and slag.

Claim 19

A process for the recovery of metallic nickel in the form of ferronickel from a refractory nickeliferous lateritic ore containing at least about 0.5 percent combined nickel by weight and a substantially greater amount of combined iron, comprising grinding such ore and intimately mixing the same with a solid particulate carbonaceous reducing agent, such reducing agent comprising a portion capable of reacting readily with the nickel compounds and the iron compounds of such ore to reduce them in a first heating stage at a temperature below 2,000* F. and a further portion capable of persisting through such first heating stage and of subsequently reducing the nickel and iron compounds then present at a substantially higher temperature of at least approximately 2,600* F., forming such mixture into compacts, passing such compacts through a shaft furnace to heat them to such first heating stage temperature for a period of time sufficient to reduce such combined iron to ferrous oxide without production of metallic iron and without sticking together of such compacts and without disintegrating such compacts and to reduce a substantial portion of such combined nickel to metallic nickel, introducing gases of a reducing nature to such shaft furnace to maintain substantial equilibrium with such ferrous oxide in such partially reduced compacts and prevent reoxidation thereof to ferric oxide, subsequently transferring such partially reduced compacts while still hot under nonoxidizing conditions to an electric melting furnace and there heating the same to a temperature of at least approximately 2,600* F. effective to reduce the remaining nickel compounds to substantially complete the reduction of all such compounds to metallic nickel and to reduce a portion only of such ferrous oxide to metallic iron, the amount of reducing agent persisting through such first heating stage being only sufficient thus to complete reduction of such nickel compounds and of a portion only of such iron compounds to produce a ferronickel containing at least about 20 percent nickel by weight, and melting the resultant ferronickel and slag.

Claim 20

The process of extracting nickel from nickeliferous lateritic ore which comprises grinding such ore, mixing the ground ore with a solid particulate carbonaceous reducing agent, forming compacts of such mixture, partially prereducing the nickel and iron compounds of such compacts at a temperature below 2,000* F. to produce a substantial amount of metallic nickel and to produce ferrous oxide without production of metallic iron and without complete destruction of such solid reducing agent, and thereafter heating such prereduced compacts at a much higher temperature effective to melt the same, such solid reducing agent content thereof being present in a predetermined amount effective substantially to complete the reduction of such nickel compounds to metallic nickel and to reduce a predetermined amount only of such ferrous oxide to metallic iron to produce molten ferronickel containing at least 20 percent nickel by weight.