FI66544C - FOERFARANDE FOER SELEKTIV FLOTATION AV NICKELSULFIDMALMER - Google Patents

Description

ι 66544

Method for selective foaming of nickel sulphide ores

The invention relates to the enrichment of complex nickel sulphide ores, whereby a high yield of nickel as a rich concentrate is achieved together with an improved rejection of magnetic pyrite.

In the Sudbury region of Canada, as in other parts of the world, nickel is found as a fine-grained complex of 10 ores with other precious metals such as copper, platinum group metals, and so on. The main minerals consist of pentlandite as a nickel sulfide mineral, copper pyrite, and magnetic pyrite, with magnetic pyrite (which itself contains only a minor portion of nickel as a solid solution) 15 present in a much larger amount than pentlandite. The ratio of magnetic pyrite to pentlandite may be, for example, about 5: 1. These ores and their treatment have been the subject of research for many years and much has been invented. For example, it is known that finely divided free pentlandite, a valuable mineral, tends to oxidize and does not foam once oxidized.

The methods used to enrich these complex ores, which include the separation of metals into nickel stream, copper stream, magnetic pyrite stream, and discarded side rock or aggregate, are trade-offs in which the recovery and degree of enrichment of the desired metals is balanced. Thus, in ore flotation, a practice has been adopted in which a nickel-copper co-concentrate is formed by discarding the magnetic pyrite and side rock, followed by further flotation to achieve a separation of nickel and copper. When the separation of nickel and copper is carried out, the copper-pyrite is foamed before the pentlandite. It is necessary to foam a large amount of magnetic pyrite to recover the slowly foaming fine pentlandite and medium particle dewes. Thus, significant amounts of magnetic pyrite remain in the nickel concentrate, with the result that the nickel concentrate is analyzed to contain about 11% 2,66544 nickel. In contrast, the resulting copper concentrate contains about 30% copper. The nickel concentrate still contains copper and the copper concentrate still contains nickel, which makes further processing in smelting more complicated. The magnetic stripe concentrate discarded from round 5 should contain as little nickel as possible.

The fact that the nickel concentrate currently obtained in order to maximize nickel recovery is of relatively poor quality means that the total sulfur content of the nickel-10 concentrate fed to the smelter is higher than desired in terms of operating costs, nickel production volume, nickel losses, cobalt losses and sulfur losses. For example, raising the grade of concentrate from about 11% to 17% nickel would reduce sulfur dioxide emissions by about 25%, which is a highly desirable result, and other economic benefits can be achieved. Although the provision of methods for treating nickel sulfide ore to obtain an improved quality nickel concentrate has long been recognized as important, no practical means have been found without the economic disadvantages.

Flotation is one of the most useful mineral enrichment techniques available to an engineer to concentrate valuable minerals in ores. Many special flotation techniques have been developed for the treatment of special ores, and a wide variety of chemicals have been used to provide a variety of advantageous results in the application of such techniques. For example, in 1933, S. Power Warren observed the depressing effect of cyanide ion on magnetic flux (Trans, Can. Inst. Of Min. And 30 Metal 1933, 186), but he did not exceed 100 g / t cyanide addition, presumably due to fear of depressing pentlandite. He was also able to foam pentlandite before copper pyrite, but this was allegedly due to the action of sodium pyrophosphate. Sodium cyanide in lime solution 35 has also been used in an apparently unsuccessful attempt to selectively depress the magnetic pyrite from pentlandite in Australian ores (Eltham and Tilyard, 3,665,444).

Australian Inst, of Min. and Metal Conference, Western Australia May 1973). It has been reported in the Soviet literature that cyanide is a non - selective depressant in the flotation of copper - nickel ores (Chem.

5 Abs. 54, 10701 f) and that the use of cationic collectors for foaming copper ore and pentlandite from magnetic fiber has yielded 13% nickel concentrates (Chem. Abs. 78, 149907). Sodium cyanide can be used as a depressant in a cycle adjusted to a pH of about 12 kal-10 wedge for pentlandite in the separation of copper and nickel.

Sodium carbonate is known to enhance the separation of pentlandite from magnetic pyrite in the treatment of certain Manitoba nickel sulfide ores. Despite varying and often divergent advice in this field, prior to the present invention, there was no way to separate pentlandite from magnetic pyrite by foaming in such a way as to obtain a high yield of pentlandite.

The invention relates to a process for recovering metals from nickel sulphide ores or concentrates containing pentlandite, copper ore, magnetic ore and side rock, the slurry preferably containing 20 to 45% by weight of solids by foaming an aqueous slurry of such ground ore or such concentrate.

The invention is characterized in that it comprises the following steps: the pH of the slurry is adjusted to 9-10, sufficient cyanide ions are added to depress the entire pentlandite content of the slurry, the slurry is prepared by aeration with stirring to foam nickel sulphide, a strong sulfide and the nickel sulfide is foamed and removed to obtain a nickel concentrate.

Flotation is carried out in the usual way by aerating the sludge.

35 Adjusting the pH of the slurry to about 10 It is recommended to do this by adding sodium carbonate during grinding of the slurry. If the pH is too low, 4,66544 will not succeed in foaming significant amounts of nickel sulfide mineral.

When the slurry contains, as is generally the case, pentlandite, copper ore, magnetic ore and side rock, the pentlandite is first foamed and removed, the copper ore 5 can then be foamed and, if desired, finally the magnetic ore, whereby the side stone is discarded. If re-grinding is necessary to release the minerals from each other, it is recommended that this grinding be performed in the presence of sodium carbonate at pH 10.

It is recommended to add cyanide ions as sodium cyanide, but if desired, potassium cyanide may be used instead and potassium carbonate may be used instead of sodium carbonate to adjust the pH.

It is important to add enough cyanide ions to depress all sulfide minerals in the slurry; if too little is added, the copper ore will immediately foam together with the pentlandite. However, large excess cyanide must be avoided as this results in slowly foaming pentlandite and increases the amount of nickel present in the copper concentrate.

It is recommended to control the addition of cyanide to the slurry and the subsequent selective foaming of the minerals in the feed using the oxidation-reduction potential. Oxidation-reduction potential, as used herein, refers to a voltage measurement obtained with a high impedance voltmeter using a metal working electrode such as a gold electrode in direct contact with the slurry and a reference electrode such as a saturated calomel electrode with a normal electrode plug and a normal porous plug. The saying oxidation-reduction potential does not mean that this is a thermodynamic, reversible potential of the sludge. Rather, it is a mixed potential that results from both the quality of the solution and the blinking contact of the surface of the working electrode 35 with the mineral particles.

Thus. to obtain at least about -390 mV (gold-impregnated Kalo melody electrode). The slurry is then prepared for some time, for example about 20 minutes, during which time the solids 10 are kept in suspension with vigorous stirring by aeration. During training, the oxidation-reduction potential of the sludge rises to about -330 mV. At this point, the addition of a sufficient amount of a strong sulfhydryl scavenger, such as potassium amyl xanthate, proportional to the purple quality of the slurry Nikke-15, initiates foaming of the pentlandite. The foaming of the pentlandite then continues until the end and the collector is added if necessary.-

Too small an amount of collector will result in very slow foaming of the pentlandite and too large an amount may reduce the nickel yield. A considerable amount of collector is required compared to the amounts used in conventional flotation methods and the amount is proportional to the nickel quality of the slurry. For example, a grade containing 1.7% nickel requires about 0.25 g of potassium amyl xanthate per kg of sludge solids, while a grade containing 10% nickel requires 1.5 g of collector per kg of sludge solids.

The copper ore and magnetic ore remain depressed as long as the oxidation-reduction potential of the slurry remains below about -245 mV. The potential can be increased to about -240 mV to initiate foaming of the copper ore by adding, for example, a metal salt that reacts with a cyanide ion such as nickel sulfate. The copper ore vaah-35 is then formed without an additional collector. The foaming of the magnetic flux depends on the amount of xanthate previously added, but usually does not start until the oxidation-reduction potential rises to about -200 mV.

6 66544

The temperature of the slurry during the process should be at least 6 ° C, but preferably not more than 30 ° C, otherwise the cyanide ion will be rapidly depleted, allowing the oxidation-reduction potential of the slurry to reach the point where foaming begins before pentlandite recovery is complete. . Satisfactory operation takes place at about 20 ° C.

The sludges to be treated preferably contain 20 to 45% by weight of solids.

An exemplary low-grade concentrate containing 1.18% copper, 1.74% nickel and 48.1% myrrotite by analysis was ground in sodium carbonate solution (pH 10.5 so that 13% by weight of the particles were above 38 .mu.m. This concentrate was The known slurry enrichment methods were ineffective in providing quality improvement without metal loss.The powdered slurry was diluted to a dry matter content of 30% and the pH of the slurry was readjusted to sodium carbonate 10. Sodium cyanide was added 1.4 g / kg 20 then for 10 minutes in a 3 L foam cell The slurry was aerated at this point for 10 minutes at 1 L / min of air to bring the oxidation-reduction potential to -330 mV. Potassium amyl xanthate was then added in an amount of 0.16 g / kg dry matter of the slurry. a. The slurry was prepared for 1 min. time and then foamed for 17 min by adding an additional 0.08 g / kg collector for 7 min. after flotation to produce nik-30 gel concentrate. The potential rose to -240 mV during the flotation of the nickel concentrate. The copper concentrate was removed in the next 6 min. flotation. The material balance shown in Table I was obtained.

·? / < '

Table I

7 66544

Analysis (%) Distribution (%)

Cu Ni Pn Ma Wt Cu Ni Pn Ma

Nickel - rich 4.3 10.9 29.8 24.1 10.2 38.7 64.8 83.7 4.8

Copper - rich 13.6 2.2 5.4 37.6 4.0 47.9 5.2 5.9 2.9

Magnetic pyrite / stone (enrichment 10 waste) 0.17 0.60 0.44 55.1 85.8 13.3 30.0 10.5 92.3

Bale quality 1.12 1.72 3.64 51.3 (calculated)

Note. Pentlandite (Pn) and magnetic pyrite (Ma) have been calculated assuming 0.8% nickel in magnetic pyrite and 35.9% nickel in pentlandite.

1 5

The results in Table I show that more than 92% of the magnetic pyrite contained in the original low-grade concentrate was discarded and that the discarded nickel was associated with the magnetic pyrite. The high rejection value of the magnetic pyrite meant that the sulfur load in the smelting furnace, which recovers 20 metals from this particular concentrate, was greatly reduced.

The effect of excess sodium cyanide on the retardation of pentlandite foaming and thus on the increase in the amount of nickel in the copper concentrate is shown in Table II. 25

The values are obtained by repeating the procedure just described but adding 1.8 g / kg sodium cyanide and 0.24 g / kg potassium amyl xanthate collector.

>; · <,: 'S> t - «.

Table II

6 6544

Analysis (%) Distribution (%)

Cu Ni Pn Ma Wt Cu Ni Pn Ma 5

Nickel-rich 4.13 12.8 35.1 22.1 10.5 33.5 60.1 71.1 5.0 Copper-rich 13.9 6.68 17.9 30.7 4.2 45.1 12.6 14.5 2.8 Magnetic pyrite / stone (enrichment 0.32 0.71 0.88 49.8 85.3 21.5 27.3 14.5 92.1 10 waste) Main quality 1.29 2.23 5, 18 46.1 (calculated)

The results of experiments similar to the example above, but without the use of sodium carbonate, illustrate the effect of pH. After grinding in tap water containing about 50 ppm of calcium ions, the pH was 7.9 and after the addition of sodium cyanide 9.6. The results showed increased pentlandite losses to tailings. However, high quality 20 concentrates were obtained. In another experiment, similar to the example above, but without sodium carbonate in grinding and using industrial water containing 500 ppm of calcium ions, more than 26% of the pentlandite was not foamed.

25 Similar experiments as in the example above, but using a correspondingly too small number of collectors, i. 0.18 g / kg and using an excess collector, i.e. 0.30 g / kg, showed very slow pentlandite foaming and slightly greater pentlandite losses to residues, while an excess collector gave a rather unexpected result with reduced nickel yield and effect on magnetic rejection rejection or enrichment waste was relatively small. The results are shown in Tables 3 and 4: λ: * :? ·

Table III

9,66544 (0.18 g / kg collector)

Analysis (%) Distribution (%) 5

Cu Ni Pn Ma Wt Cu Ni Pn Ma

Nickel rich 2.85 11.9 32.5 27.7 8.7 21.8 60.3 78.3 4.5

Copper concentrate 11.7 1.56 3.14 53.4 6.3 64.7 5.7 5.5 6.4

Magnetic pyrite / 1rt stone (enrichment 0.18 0.69 0.69 55.4 85.0 13.5 34.0 16.2 89.1 waste) Main quality 1.14 1.72 3.61 52.8 (calculated )

Table IV

^ (0.30 g / kg collector)

Analysis (%) Distribution (%)

Cu Ni Pn Ma WT Cu Ni Pn Ma

Nickel - rich 4.40 8.05 21.8 25.5 10.7 37.2 38.8 45.1 6.1 20

Copper concentrate 7.13 9.46 25.3 43.5 8.9 50.0 37.9 43.5 8.6

Magnetic pyrite / 0.20 0.65 0.73 47.8 80.4 12.8 23.4 11.5 85.4 stone (tailings) Main quality 1.27 2.23 5.18 45.1 (calculated) 25

The process of the invention can be used to treat a high grade material to produce a nickel concentrate containing 28% nickel, a copper concentrate containing 30% copper and a tailings waste which is subjected to a rip concentrate containing 1% nickel and 1% copper.

When concentrates of this quality are fed into the melting furnace, its sulfur load is significantly reduced compared to current practice, leading to a substantial reduction in sulfur dioxide emissions and other economic benefits.

Those skilled in the art will appreciate that other reagents may be used for known purposes in flotation as long as a combination of sodium or potassium carbonate and sodium or potassium cyanide is used. For example, known foams such as MIBC and DOW SA1263 can be used. However, no substitute has been found for cyanide ion.

Claims (8)

10 66544 A process for recovering metals from nickel sulphide ores or concentrates containing pentlandite, copper ore, magnetic ore and side rock, the slurry preferably containing 20 to 45% by weight of solids, by foaming an aqueous slurry of such ground ore or concentrate, characterized in that it comprises the following steps: the pH of the slurry is adjusted to 9-10, sufficient cyanide ions are added to depress the entire pentanite content of the slurry, the slurry is prepared by aeration with stirring to foam nickel sulfide, a strong sulfhydryl collector known per se is added to foam foamed and removed to obtain a nickel concentrate. Process according to Claim 1, characterized in that the pH of the slurry is adjusted to 9 to 10 by adding sodium carbonate during the grinding of the slurry. 20 Process according to Claim 2, characterized in that the amount of cyanide added is such that the oxidation-reduction potential of the slurry (measured using a gold electrode against a saturated calomel electrode) decreases to at least -390 mV. 25 A method according to claim 3, characterized in that the slurry is prepared to foam the pentlandite by stirring aeration to increase the oxidation-reduction potential of the slurry to -330 mV, the xanthate collector is added, the pentlandite is foamed and removed. Process according to Claim 4, characterized in that, after flotation of the pentlandite, the oxidation-reduction potential of the slurry is increased to -240 mV, the copper ore is foamed and removed. 35 11 6 6 5 4 4 Method according to Claim 5, characterized in that, after flotation of the copper ore, the oxidation-reduction potential of the slurry is increased to -200 mV, and the magnetic ore is foamed and removed. Process according to one of the preceding claims, characterized in that the collector is potassium amyl xanthate. Process according to one of the preceding claims, characterized in that the temperature of the slurry 10 is about 20 ° C. 12 66544