CA1095260A - Nickel sulfide benefication process - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A process for recovering nickel concentrates from nickel containing sulfide ores, nickeliferous pyrrhotites or, for example, mixtures of pentlandite and pyrrhotite, wherein the process feed, either an initial ore or concentrate, is upgraded by segregation roasting in an autogenous atmosphere at temperatures within the range of 1550°F to 1850°F, the process feed being mixed with one of the chloridizing compound additives CaO + NaCl, CaCo3 + NaCl, or Ca(OH)2 + NaCl, and a carbonaceous reductant such as coke or coal. The resulting calcine is beneficiated by conventional methods and a concentrate of substantially higher nickel content than the starting material is obtained at a very high rate of recovery.

Description

1 This invention relates to the beneficiation of nickel bearing ores or concentrates and particularly to an improved, highly efficient process for recovering nickel from sulfide ores and concentrates. Nickel, one of the most important alloying metals available, possesses qualities that are highly desirable to the alloyed metals, such as corrosion resistance, strength, and hardness to ferrous alloys and electric conductivity and magnetism to ferrous and to nonferrous alloys. Its properties, together with an attractive appearance, make nickel suitable for such diverse applications as coinage, tableware, custom jewelry, electroplating, and in alloys that are used in corrosive or in high temperature environments.
Nickel is produced from both oxide and sulfide ores.
The most important ores used for the recovery of nickel are the nickel bearing sulfide ores, such as the important deposits that are worked in the Sudbury District of Ontario and the Moak Lake Selling Lakes area of Manitoba, Canada. Canada is the largest producer of this ore. Most of the important deposits of su1fide nickel ores con~ain three principal sulfide minerals, pyrrhotite,

2~ pentlandite and chalcopyrite. Pyrrhotite which is essentially a mono-sulfide of iron is generally the most abundant sulfide mineral in these deposits. Pyrrhotite contains atoms of iron and sulfur in almost equal numbers but usually has slightly less iron than the 1:1 ratio, so that its formula is writt~n Fe(n l)Sn.
The value o "n" varies in pyrrhotites from different localities, the composition ranging from FeS to about Fe7S8. Much of the pyrrhotite is magnetic~ However, pyrrhotite having an iron to sulfur ratio close to 1:1 is nonmagnetic. Pentlandi-~e with the general composition tFe, Ni)gS8 is the principal nickel mineral in these sulfide nickel ores. In some Canadian deposits the ratio of pyrrhotite to pentlandlte may be in the order of from - 1 - ' ,~( ,, ~5;2~1D
1 2 to over 5 parts of pyrrhotite to one part of pentlandite.
Generally, the principal copper mineral is chalcopyrite (CuFeS2).
There may be other minor nic]cel and copper sulfide minerals presen-t as well as the iron sulfide pyrite. Some of these ores may also contain small amounts of precious metals, such as silver, gold and the platinum group metals. Pyrrhoti~e in such sulfide nickel ores generally contains significant amounts of nickel, often of the order from 0.75 to 1.00 percent and may con-tain small amounts o cobalt. This nickel may be present in the crystal structure of the pyrrhotite or as inclusions of pentlan-dite within the grains of the pyrrhotite. In either form, the nickel cannot be liberated by ordinary methods of beneficiation.
In some ore as much as 25 percent of the to*al nickel may occur in the pyrrhotite crystals and some nickeliferous pyrrhotite may assay over one percen-t nickel. With such sub-stantial nickel values thus available, it is essential to provide improved methods of concentration of the nickel values.
These sulfide deposits are mined and worked not only to recover their nickel content but also the copper, and they may be treated so that cobalt and precious metals may be recovered.
Also, these ores are sometimes processed to recover the iron as a saleable product. The sulfide minerals in these nickel ores are associated with worthless rockforming minerals. These ores generally have to be beneficiated to separate the valuable minerals from the worthless gangue to obtain concentrates that can ~e further treated to recover nickel, copper and other saleable products. The concentrates may be smelted to produce mattes which are refined to obtain saleable nickel and copper products.
Alternatively, the concentrates may be leached and the leached solutions treated to recover the metal or other salaable products.

1 The fact that most pyrrho-tites are magnetic permits the magnetic pyrrhotite to be separated from the other nonmagnetic sulfides and the nonmagnetic rock~forming minerals. In some plants, a magnetic separation is used to recover a pyrrhotite concentrate.
It is also desirable to provide nickel contairling sulfide ore beneficiation processes for effecting better metal recovery and at lower costs while also minimizing air and water ;
pollution.
1~ Accordingly, it is an object of this invention to provide an improved process for the beneficlation of nickel containing sulfide ores~ ;
It is another object of this invention to provide an improved process utilizing segretation roasting for recovering nickel from sulfide ores.
It is another object of this invention to provide an improved process for effecting better metal recovery from nickel bearing sulfide ores which is lower in cost and lower in water and air pollution effects.
It is a further object of this invention to provide an improved process for recovering nickel rom pyrrhotite ores.
It is a still further object of this invention to provide an improved process for the beneficiation of nickel bearing sulfide ores which ,s effective for both high and low ~-grade ores.
Briefly in carrying out the objects of my invention in one aspect thereof, by way of example, a nickel containing sulfide ore comprising a mixture of pentlandite and pyrrhotite is ground and classified and a concentrate then is obtained by flotation. This concentrate is briquetted with a mixture of 1 lime, coke and sodiu-m chloride and the briquetted mixture is then calcin~d a-t a tempera-ture of 1700F in an au-togenous atmosphere for one hour. The resulting calcine is then benefi-ciated by magnetic separation or flota-tion to recover an upgraded nickel concentrate.
In another aspect, the inven-tion provides a process for recovering from sul:Eide ore a concentrate o:E a metal in the group of metals consisting of nicke]., cobal-t and mixtures of nickel and cobal-t which comprises: mixing the ore with a carbonaceous material and an efective quantity o~ a reagent selected from the group consisting of sodium chloride and calcium oxide, sodium chloride and calcium carbonate, and sodium chloride and calcium hydroxide, roasting the ore and reagent mixture at a tempera-ture within the range o:E 1550F to 1850F in an autogenous atmosphere, cooling the roasted mixture, and beneficiating the roasted mixture to recover the metal values.
In still another aspect, the inven-tion further p.rovides a process for recovering nickel concentrat.es from sulfide ore which comprises: comminuting and sizing the ore, mixing the ore 20 with a carbonaceous material and an efEective quantity of a reagent selected from the group consisting of sodium chloride and calcium oxide, sodium chloride and calcium carbonate, and sodium chloride and calcium hydroxide, roastiny the mixture of ore and reagent at a tempe:rature within the .ranges oE 1550F to 1850F, cooling and comminuting the roasted mixture, and con-centratiny the mixture to produce nickel concentrates.
The Eeatures oE novelty which characterize my invention are pointed out in the appended claims~ My invention itselt, however~ -cogether with further objects and advantages thereo~
will best be unders-toodfrom the following description taken in ~ .~

6~1 1 co~nection wi-th th~ accompanyin~ drawing, the single Eigure of which is a flow shee-t illustra-ting a process of my invention Conventional processes Eor the beneficiation treatmen-t of nickel bearinc; sulfide ores have employed roasting of the ore which removes a substantial portion of the sulfur as sul~ur dioxide or have employed hydrometallurgical methods which may genera-te hydrogen sulflcle. The presence of these gases now re~uires further considera-tion for the purpose of compliance with present day regulations in regard to air and water pollution.
The present invention resulted from studies and a series of tests of segregation roasting of nickel containing sulfide ores in a neutral atmosphere during which I investigated the use of the lime-salt reagent disclosed in my United States Patent No. 3,7~5,039 assigned to the same assignee and relating to the segregation roasting of laterite ores. These investigationr, included tests oE various reagents and oE di~ferent quantities oE the reagents and of coke, and also included a consideration o~ converting the nickel sulfide to a soluble sulfate with subsequent recovery through leaching and precipitation. Tests 20 were made using sodium chloride and diEEerent propor-tions oE
lime or othar calcium compound, and it was fou d that siqniEicant " ~

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; - 4a -~, 1 differences in the final recovery of nickel resulted from changes in the ratios and quantities of salt and lime or other calcium compound.
Referring now to the drawing, the flow sheet indicates a process embodying the invention wherein the oriyinal sulfide ore is treated by a conventional process, preferably comminution and sizing followed by concentration which may be by flotation or other conventional process to produce firs~ a concentrate containing copper, next a concentrate containing nickel~ and then a concentrate containing nickeliferous pyrrhotiteO The tailings having been removed, this last concentrate is then mixed with a carbonaceous reductant, which may be coal or coke, sodium chloride and a calcium compound; this mixture is pelletized or briquetted, and then subjected to roasting in an autogenous atmosphere at temperatures in the range of 1550F to 1850~.
Alternatively, the concentrate and additives may be supplied directly to the roasting stage withou-t pelletiæing or briquetting r a flow direction selector and bypass around the pelleti~ing stage being indicated -for this purpose.
i 20 For some ores the flotation step may be omitted and ,~ :
~; the comminuted ore be mixed with the additives directly; a bypass and 10w selector are indicated for this purpose.
After roasting, the resulting ore mixture is ~uenched and yround and classified, the coaxse product from the classifier ., .
'; being returned to the grinder. The fines are then beneficiated by a conventional process which, for example, may be magnetic separation or Elotation to produce the final concentrate, the middlings, if present, from the magnetic separator or other beneficiation process being returned and mixed with the furnace 3~ input. The final product o-f the process is a high-grade nickel ..
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1 concentrate with nickel recovery which may range up to 99 percent of the nickel content of the roasted ore mixture.
Tests conducted in accordance with this process have established that CaCo3 ~ NaCl, CaO ~ NaCl, and Ca(OH)2 + NaCl all react well. My tests have indicated that for the ores or concentrates or process feeds the sodium chloride should be in a quantity of from 5 to 15 percent of the weight of the ore or concentrate in the mixture, and that the coke should be in the range of 1 to 10 percent o the weight of the ore or concentrate. The calcium compound should be added in amounts of between 10 and 150 percent of the weight of the ore. The amounts of the calcium compound required are related to the sulfur content of the ore or concentrate to provide for absorbing sulfur for purposes of pollution control.
By way of example, and not by way of limitation, a number of tests were conducted by briquetting a mixture o~ ore, lime, salt and coke and calcining this mixture at a temperature of 1700~ in an autogenous atmosphere. The ore used as the ,, process feed was flotation concentrate produced ~rom nickel ~O bearing sulfide ores. The calcines were then cooled and ground to about 95 percent minus 100 mesh on the United S~ates Standard Scale. The following three tests are illustrative o the best recovery results obtained in this series o tests:
E AMPLE NO. 1 A mix o flotation concentrates and additives was prepared in the following pxoportions:
Percent Flotation Concentrates71.7 CaO 1~.7 NaCl 6.6 Coke 5 0 3~ Total 100~0 ;~ - 6 -::

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1 The mix was then briquetted and treated as sta-ted above and the resulting calcine was beneficiated by wet magnetic separa-tion with the following results:
PercentPercentPercent Nickel Weight Nickel Distribution .
Head 100.00 4.25 100.0 Conc. 30.0 13.90 98.2 Tail 70.0 0.11 1.8 EXAMPLE NO. 2 A mix of ore and additives was prepared in the 10 following proportions:
~ Percent .~ Ore 55.6 CaO 38.0 ,, NaCl 4.8 Coke 1~6 ;: Total100.0 I The calcine resulting ~rom this mix was beneficiatea , ~
by wet magnetic separation with the following results:
PercentPercentPercent Nickel WeighkNickel Distribution ~;~ Heaa 100.0 2.29 100.0 Conc. 13.5 12.50 97.5 Tail 86.5 0.07 2.5 EXAMP.I,E NO. 3 A mix of flotation concentrates and additives was ; prepared in the following proportions:
; Percent .,, ~ .
Concentrates 78.7 I CaO 16.0 :~ NaCl 4.0 Coke 1.3 . ~0 Total100.0 , ~ 7 --1 The calcine resulting from this mix was benaiciated by wet magnetic separation with the following results.

Percent PercentPercent Nickel W~ NickelDistribution Head 100.0 4.90 100.0 Conc. 37.9 11.80 99.2 Tail 62.1 0.07 0.8 These three tests indicate that very high nickel recovery may be realized from the process of this invention and that the relative amounts of lime, sodium chloride and coke may be varied over a substan~ial range. Further, it is indicated that the amounts of the coke, salt and lime may be selected with a view to increased economy.
Subsequent tests have proved that calcium hydroxide and calcium carbonate or a mix~ure of both are effective and ,;,.... .
- can be substituted for lime in the process of the invention.
All references to "mesh" in this specification are to mesh sizes on the United States Standard Scale.
, By way of example, the three tests tabulated below were ; made each with identical additions of sodium chloride and coka to a raw sulfide ore and indicate high recovery when calcium carbonate and calcium hydroxide are substitu~ed for the lime.
For each of these examples, a mix of natural raw ore crushed and sized to pass approximately a 10 mesh sieve and additives was prepared in the following proportions:

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1 EXAMPLE NO.4 EXAMPLE NO.5 EXAMPLE NO.6 grams grams grams -~ Raw Sulflde ore (minus 10 mesh) 100 100 100 Calcium Carbonate CaCO3 100 0 0 Calcium hydroxide 0 74 0 ; Ca(OH) Calcium oxide CaO 0 0 56 Salt NaCl ` 30 30 30 Coke 3 3 3 Each of these mixtuxes of ore and additives was cal-cined at approximately 1750F in an autogenous atmosphere r and after cooling, the calcine was ground to pass approximately a 200 mesh sieve. ~he ground calcine was subjected to two maynetic separa-tions. The magnetic concentrate was firs~ removed on a permanent drum magnet and the middling was removed next usin~ an electro-magnet of higher intensity than the drum magnet. The results ~ of this bene~ication were as follows:
,'EXAMPLE NO. 4 EXAMPLE NO. 5 Percent Percent Percent Percent ; Product Nickel Nickel Nickel Nickel ~9 Distribution Distribution '~ Heads 1. 27 100 ~ 0 lr 26 100~ 0 ~ Magnetic ,-; Concentrates 19~50 71~3 18~60 76~0 , Middlings 1~ 20 7 ~ 3 0 ~ 72 5 ~ g Tails 0.3121.4 0. 2718 ~1 ~XAMPLE NO r 6 Percent Percent Product Nickel Nickel Distribution Heads 1. 26100 ~ 0 Magnetic 16.4077~8 Concentrates Middlings1.48lQ.0 Tails 0.1812.2 ~;

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1 Calcium hydroxide, calcium carbonate or calcium oxide when used in substantial amounts all act to prevent the escape of sulfur dioxide -to the atmosphere and thus may be an important consideration in view of the present concern over air pollutionO
Calcium carbonate because of its lower cost may be ~he preerred reagent when economy is a controlling factor~
The following two tests were made with the same raw ; sulfide ore as was used in Example 4 above. Example 7 was made with the ore ground to essentially all passing a 10 mesh sieve as in Example 4 above. Example 8 was made with the same ore ground to essentially all passing a 200 mesh sieve. These examples illustrate the advantage of using the finely ground ore - ~ in the feed mixture.
Examples No. 7 and No. ~
A mixture of raw sulfide ore and additives was pre-pared in the following proportions:
EXAMPLE NO. 7 EXAMæLE ~O. 8 grams grams Raw Sulfide Ore - minus 10 mesh 100 20 Raw Sulfide Ore - minus 200 mesh 100 Calcium Carbonate, CaCO3 100 100 Salt, NaCl 30 30 Coke 3 3 Each mixture of ore and additives was calcined at approximately 1750F in an autogenous atmosphere, and afker cooling, the calcines were ground to pass approximately a 200 mesh sieve.
Each ground calcine was subjected to two magnetic separations~
The magnetic concentrate was first removed on a permanent drum magnet and the middling was removed using an electro-magnet ; 3Q of higher intensity than the drum magnet.

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1 The results of these tests were as follows:
``: EXAMPLE NO~ 7 EXAMPL:E~ NO. 8 PercenE Ferc'e-nt-Nickel Percent ~ercen~E~ ckel ProductNickel Distr~ibution Nickel Distribution Heads1.28 lOOoO 1.28 100.0 ; Magnet.ic Concentrate 19.50 71.5 16.90 75.3 Middlings 1.20 7.3 1.59 10.6 Tails 0.31 21~2 0.21 14.1 ~; Studies with the optical microscope of -the magnetic con-centrates obtained from the calcines produced by this process ~,. revealed ~hat these magnetic concen-tra~es consisted in la.rge ` 10 part of metallic grains. ~ number of elec~ron micro probe f analyses on individual metallic grains indicated tha~ -these metallic grains consisted of an iron-nickel phase. In tests '~ where only a small amount of coke was used as a reducing agent in the xoas-ting step of the process, electron micro probe . analyses showed the grains studied to contain from 39.9 to :. 62.6 percent nickel. In tests where a larger amount of coke was used as a reducing agent in the roasting process, electron probe analyse,s showed the grains studied to contain from 9.1 `' to 20.9 percent nickel. Electron micro probe analyses o~ the ; metallic ~rains in ihe magne~ic concentrate showed copper present in the iron-nickel phase in amounts ranging from 0.5 percent to

4.~ percent.
A series of beneficiation tests on several sieve sizes of calcine tends to prove that the concentrate forms a hard core around the coke particles which resists comminution while the barren reject decrepitates into very fine particles. This differential in hardness is great enough to permit some concentration by sizing alone. Table I of the screen analysis test indicates this characteristic showing that the finer screen ':: 30 product contains a greater percentage of the nickel than the coarser fractions.

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1 The -test of Table I was performed on ~resh flotation - concentrate ~rom nickel bearing sulfide ores ground to 100 percent minus 150 mesh on the United States Standard Scale.
The ratios of the constituents of the mix were as follows:
500 grams concentrate ,~ 500 grams CaO

`'a 50 grams NaCl ~ 10 grams Coke `~ This mix was calcined for one hour at 1650F în an autogenous atmosphere, then cooled and stage ground to pass 100 mesh followed by high intensity magnetic separation. Low intensity magnetic separation would have resulted in higher '` grade nickel concentrate, but for this test itwas desired to provide a larger volume for each screen si2e.
For economic reasons, it is usually desirable that the -raw feed be subjected to flotation for the removal of a copper sulfide concentrate and to discard any barren gangue. Such procedure is reco~nended in rnost instances, and particularly where it is desirable to produce a product of low copper content.
20 However, the experimental data presented below shows that pre-, ~ concentration is not necessarily a prerequisite for successful j ~
concentration of nickel by roast segregation. In ~he followingtests a feed material, a raw sulfide ore, was crushed to pass 10 mesh and blended in a mixture consisting of 47.2 percent ore, 47.2 percent CaO, 4.7 percent NaCl and 0.9 percent coke. I'his mixture was calcined at 1750E~ without pelletizing and the calcine ; was ground to pass lSO mesh for magnetic separation giving the following results:
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EXAMPLE N0. 9 ~;~ Percent NiPercent Rec.
Head 0.98 100.0 Conc. 7.80 91.0 Tail 0.10 9.0 EXaMPLE N0. 10 Percent NiPercent Rec.
Head 0.75 100.0 Conc. 6.90 9208 ~ lQ Tail 0.06 7.2 ;~ EXAMPLE N0 11 ;~ Percent NiPercent Rec.
Head 0.58 100.0 Conc. 4.25 86.~
Tail 0.0~ 13~7 In some other applications of the process, i-t may be advantageous to remove a magnetic concentrate from the raw feed before segregation. When magnetic pyrrhotite is present, a magnetic concentrate may be removed ahead of the flotation process.
In addition to the magnetic concentrate, this type of operation also may produce a nonmagnetic iron flotation concentrate. Thus a magnetic concentrate may be removea from a bulk sulfide flotation concentrate or from the iron float concentrate produced at some mills. However, whether the pyrrhotite concentra~e is magnetic or not has no apparent beaxing on the present segregation process, this probably being clue to the destruction of the magnetic property upon heating to 660F. The above three Examples Nos. 9, 10 and 11 were conducted on process feed containing a mixture of magnetic and nonmagnetic pyrrhotite, but the following two examples were performed on a magnetic concentrate which comprises ' `.f' .: ~ .. :

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1 a mix of 46.5 percent ore, 46.5 percent CaO, ~.0 percenk NaCl and 1.0 percent Coke.
EXAMPLE NO. 12 _EXAMPLE NO 13 Percent Ni Percent Rec.Percent Ni Percent Rec.
Head 0.50 100.0 3.76 100.0 Conc. 2.44 86.8 13.18 94.2 Tail 0.08 13.2 0.30 5.8 The foregoing examples serve to indicate a range of process feed and additives and the resulting recoveries. These tests are ` 10 presented by way of example and not as the best results available with the process.
The following tests were conducted to compare the results obtained with the same ore and additives but with coke in Example No. 14 and coal in Example No. 15.
EXAMPLE NO. 14 Percent Wt. Percent Ni Percent Rec~
Calc.Head100~0 1.28 100.0 Magnetics 5.'7 16.90 75.3 ;
;~` Middlings 8.7 1.59 10.6 20 Nonmagnetics85.80.21 14.1 EXAMPLE NO. 15 , Percent Wt. Percent Ni. Percent Rec.
Caic. Head100.0 1.22 100.0 Magnetics6.8 13.90 77.3 Middlings15.0 0.70 8.6 Nonmagnetics78.2 0.22 14.1 In both the above tests 100 grams of ore crushed to pass 10 mesh were mixed with 100 grams of CaCO3 and 30 grams of NaCl. In Example No. 14, three grams of petroleum coke were used, ~. ~
and in Example No. 15, three grams of bituminous coal. Both mixes :

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1 ~ere firecl at 950C, and the calcine was ground to pass 200 mesh, and then processed first on a permanent magnet where the "magnetics"
were recoverecl, and then in a high-intensity electromagnet where the "middlings" were made. These tests show that coke and coal are both acceptable as the reductant in the process.
The tests using the process of this invention indicate that cobalt can be recovered effectively as wall as nickel and a part o~ the copper present in the ore may also be recovered.
Other metals, such as gold and silver, may volatilize during the chloridi~ing roast, and these latter might be recovered from the waste gases by passing the gases through water and absorbing them and than recovering the values from the water solution.
The following test was made to illustrate the character of the product that results from using a feed of low copper content. By way of example, a nickel bearing sulfide ore con-taining a substantial percentage of pyrrhotite with minor percentages of pendlandite and chalcopyrite was ground and classified and then subjected to a flotation beneficiation whereby a copper concentrate rich iII chalcopyrite was removed. Following 2~ removal of the copper concentrate, the ore was then subjected to further beneficiation by flotation to remove gangue. In this particular tes~, a separate concentrate enriched in pendlandite ; and one enriched in pyrrhotite were recovered. ~ mixture of the pendlandite concentrate and the pyrrhotlte con~entrate was used as a feed material. In practice, it would be expedient in most instances to produce one concentrate enriched in both pendlandite and pyrrhotite and use this as a feed material in place of making separate concentrates and recombining them as in this example. The proportions of feed and additives in the mixture - 3~ to be calcined are shown as follows:

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EXAMPLE NO. 16 Grams Feed - a mixture of pendlandite and pyrrhotite flotation concen-trates 200 Calcium carbonate (CaCO3) 200 Sodium chloride (NaCl) 40 Petroleum coke - essentially all passing 48 mesh and essentially all retained on a 80 mesh sieve 4 The test procedure was as follows:

The mixture oE feed and additives was first briquetted and then calcined at approximately 950C ~1740F) ~or one hour in an autogenous atmosphere and after cooling to ambient temperature the calcines were ground wet so that essentially all passed a 400 mesh screen. The grourld calcine was then subjected to a .
low intensity magnetic separation. The results of this test were as follows:

Percent Percent Percent Percent Percent Percent Nickel Iron Cobalt Copper Calcium Silicone (Ni) (Fe) (Co) (Cu)Oxide (SiO2) (CaO) .. . .. .. ..
Head 1.30 33.6 0.12 0.5021.8 6.8 ;~ Tail 0.14 ~1.5 0.04 0.3630.8 8.9 : ~ 0 Concentrate 22.40 66.0 0.76 0.724.8 0.7 Recovery-Percent89.8 12.1 70.4 56.0 - Rejection-Percen-t ~2.4 97.2 ~` The true density of the magnetic concentrate as determined by a pycnometer was 6.52 g/ccO The high density determined on this product and the high percentage of nickel and iron shown by the assay data indicate that the iron and nickel are essentially in the metallic -Eorm. The test f~lrther shows that there is effective recovery of cobalt in the magnetic concentrate. The product from this test shows a ratio of nickel to copper over thixty to one.
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1 In all of the above examples, the reco~ery o~ the metal is based upon the calcine. Tests have indicated that there is little, or no loss oE nickel by volatilization during the roasting operation and that the recoveries of nickel indicated for the calcine closely approximate recovery from the feed material.
This invention provides a highly efrective process for recovering nickel from sulfide ores, both low grade and high grade; it further effects a high recovery of nickel and at the same time makes possible the control and minimizing of the discharge of air and water polluting substances.
The concentrate of this process may be of sufficiently high nickel content that it can be used directly as a nickel alloying additive; for instance in the production of nickel containing steel and cast iron including but not limited to nic~el-chrome stainless steels and heat resisting Ni/Cr alloys.
Where the concentrate of the invention is to be ~lsed in a product where copper is objectionable, it is desirable to use a feed of low copper content. Alternatively, the concentrate may be further processed in a smelting or refining process to 20 produce higher purity nickel metal products and to recover other metal values in the concentrate made b~ this process. The invention makes it possible to obtain a concentrate of substanti-; all~ higher nickel content than the starting material and at a v~ry high rate of recovery.
While the invention has been described in connection withspecific tests and preferred aspects, various other applications and modiEications will occur to those skilled in the art. There-fore, I do not desire that m~ invention be limited to the parti-cular modification described, and I intend by the accompanying 30 claims to cover all modifications and variations which fall within the spirit and scope of my invention.

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Claims (30)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The process for recovering from sulfide ore a concentrate of a metal in the group of metals consisting of nickel, cobalt and mixtures of nickel and cobalt which comprises:
mixing the ore with a carbonaceous material and an effective quantity of a reagent selected from the group consisting of sodium chloride and calcium oxide, sodium chloride and calcium carbonate, and sodium chloride and calcium hydroxide, roasting the ore and reagent mixture at a temperature within the range of 1550°F to 1850°F in an autogenous atmosphere, cooling the roasted mixture, and beneficiating the roasted mixture to recover the metal values.

2. The process of claim 1 wherein the carbonaceous material has a weight in the range of 1 to 10 percent of the weight of the ore, the sodium chloride has a weight in the range of 5 to 10 percent of the weight of the ore, and the calcium oxide, carbonate, or hydroxide has a weight in the range of 10 to 150 per-cent of the weight of the ore.

3. The process of claim 1 wherein the carbonaceous material is coke.

4. The process of claim 1 wherein the carbonaceous material is coal.

5. The process of claim 3 wherein the metal is nickel and the coke has a weight of from 1.3 to 5.0 percent of the weight of the ore mixture, the sodium chloride has a weight of from

Claim 5 continued:
4.0 to 6.6 percent of the weight of the ore mixture, and the calcium compound is lime and has a weight of from 16.0 to 38.0 percent of the weight of the ore mixture.

6. The process of claim 1 wherein the beneficiation of the roasted mixture is effected by grinding followed by magnetic separation.

7. The process of claim 2 wherein the selected calcium compound is in excess of the amount for reaction with the sodium chloride during the roasting of the mixture, and including the step of utilizing the excess amount of the calcium compound for combination with sulfur compounds during roasting.

8. The process of claim 1 including the step of comminuting and sizing the ore before mixing it with the carbonaceous material and reagent.

g. The process of claim 1 including the steps of comminuting, sizing and concentrating the ore before mixing it with the carbonace-ous material and reagent.

10. The process of claim 1 wherein the step of beneficiating the roasted mixture comprises quenching and comminuting the mixture and thereafter concentrating the mixture.

11. The process of claim 10 wherein the step of quenching and comminuting the mixture makes fines and coarse product and including the step of returning the coarse product to the comminuting stage.

12. The process of claim 10 wherein middlings and tailings are produced during the concentration of the mixture and including the step of returning the middlings to the roasting stage.

13. The process of claim 12 wherein the concentration is effected by magnetic separation.

14. The process of claim 1 wherein said ore is copper bearing and including the initial step of beneficiating the ore by flotation to produce a copper concentrate and gangue, and removing the copper concentrate and the gangue before mixing the ore with the carbonaceous material and reagent.

15. A process for recovering nickel concentrates from sulfide ore which comprises:
comminuting and sizing the ore, mixing the ore with a carbonaceous material and an effective quantity of a reagent selected from the group consisting of sodium chloride and calcium oxide, sodium chloride and calcium carbonate, and sodium chloride and calcium hydroxide, roasting the mixture of ore and reagent at a temperature within the ranges of 1550 F to 1850 F, cooling and comminuting the roasted mixture, and concentrating the mixture to produce nickel concentrates.

16. The process of claim 15 wherein the comminuting of the roasted mixture makes fines and coarse product and including the step of returning the coarse product to the comminuting stage.

21 The process of claim 15 including the step of concentra-ting the comminuted ore and removing a nickel concentrate before mixing the ore with the reagent.

18. The process of claim 17 wherein the comminuting of the roasted mixture makes fines and coarse product and including the step of returning the coarse product to the comminuting stage.

19. The process of claim 15 including the step of concentra-ting the ore and removing a nickel concentrate and tailings before mixing the balance of the ore with the reagent, and wherein the balance of the ore is pyrrhotite.

20. The process of claim 19 wherein the comminuting of the roasted ore makes fines and coarse product and including the step of returning the coarse product to the comminuting stage.

21. The process of claim 15 wherein the step of concentrating said mixture makes tailings and middlings and including the step of returning the middlings to the roasting stage.

22. The process of claim 21 wherein the comminuting of the roasted ore makes fines and coarse product and including the step of returning the coarse product to the comminuting stage.

23. The process of claim 15 wherein the carbonaceous material has a weight in the range of 1 to 10 percent of the weight of the ore, the sodium chloride has a weight of 5 to 10 percent of the weight of the ore, and the calcium oxide, hydroxide, or carbonate has a weight in the range of 10 to 150 percent of the weight of the ore.

22 The process of claim 15 including the step of concentra-ting the ore before mixing with the carbonaceous material or reagent and wherein the carbonaceous material is coke having a weight within the range of from 1.3 to 5.0 percent of the weight of the mixture, the sodium chloride has a weight within the range of from 4.0 to 6.6 percent of the weight of the mixture, and the calcium oxide, hydroxide or carbonate has a weight within the range of from 16.0 to 38.0 percent of the weight of the mixture.

25. The process of claim 15 wherein the ore is copper bearing and including the step of beneficiating the ore by flotation to produce a copper concentrate and gangue and removing the copper concentrate and gangue before mixing the ore with the carbonaceous material and reagent.

26. The process of claim 25 wherein the removal of the copper concentrate is effected in a first flotation stage and including a second flotation stage for removing the gangue after the removal of the copper concentrate by said first stage.

27. The process of claim 25 including the step of also removing a nickel concentrate before the roasting stage.

28. The process of claim 25 wherein the ore contains chalcopyrite and the copper concentrate is rich in chalcopyrite.

29. The process of claim 28 wherein the removal of the copper concentrate is effected in a first flotation stage and including a second flotation stage for removing the gangue after removal of the copper concentrate by said first stage.

30, The process of claim 25 including the step of also removinq a nickel concentrate before the roasting stage.