FI64297B - FOERFARANDE FOER SEPARATION AV KOPPARKIS PENTLANDIT OCH MAGNETKIS GENOM FLOTATION - Google Patents

Description

I · * § & »*] M fl1) MOON> UTUSJULKA! SU C Λ? Q Π L J 11 UTLAGG N I NGSSKRI FT 0 ^ /. 7 (C (45) Pc exam syjnr.cUy 10 11 1933

Patent ceddelat, (51) Ky.ik.1 / Int.a? B 03 D 1/02 FINLAND —FI NLAND <H) Patent application - Patent patentök 793 ^ + 32 (22) HakemlspIlvS - Ansöknlngjdag 01.11.79 (23) Initial cloud - Glltlghetsdag 01.11.79 (41)

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* (44) Date of first issue - after 07 ft-2

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(32) (33) (31) Privilege claimed — Begird priorltet 04. ± 2. "jQ

Canada (CA) 317321 (71) Inco Limited, 1 First Canadian Place, Toronto, Ontario, Canada (CA) (72) Cordon Edward Agar, Etobicoke, Ontario, William Bruce Kipkie,

Mississauga, Ontario, Peter Frederic Wells, Oakville, Ontario,

Canada (CA) (jh) Oy Kolster Ab (tk) Method for the separation of copper ore, pentlandite and magnetic ore by foaming - Forfarande för separation av kopparkis, pentLandit och magnetkis genom flotation

The present invention relates to an ore beneficiation and in particular to a flotation process for separating copper, nickel and iron sulfide minerals.

Sulfide copper-nickel mines (which usually contain varying amounts of copper ore and pentlandite) are complicated by the fact that a certain amount of magnetic ore is usually present in addition to non-ferrous sulfides. Typically, such ores are co-foamed to remove a substantial amount of side rock from them, and the resulting co-concentrate is then treated to separate the nickel and copper sulfides. In carrying out this separation, it is desirable to be able to produce a copper-rich concentrate with a copper to nickel ratio of 30: 1 or more. Although in practice it is not always possible to achieve such a good separation, it is desirable to carry out the separation in such a way that as much of the 2 64297 copper as possible is recovered in the copper-rich concentrate. To date, the best known method for producing a copper concentrate has involved flotation carried out at a slightly elevated temperature in the presence of lime and sodium cyanide. Under these conditions, the depression of both the pentlandite and the magnetic pyrite results in the formation of a copper-rich foam product and a tailings product in which most of the magnetic pyrite remains, with only a small amount of nickel.

It is an object of the present invention to provide a process which makes it possible to obtain three separate products which contain, respectively, most of the copper ore present in the feed ore, most of the pentlandite present in the feed and most of the magnetic ore.

Unless otherwise stated, all percentages in this specification and claims refer to percentages by weight.

In the process of the invention, the sulfide ore containing copper, nickel and iron is co-foamed using xanthate as a collector to obtain a concentrate containing copper flux, pentlandite and magnetic pyrite, and the concentrate is treated with a second flotation treatment to separate the copper pyrite therefrom. This second flotation treatment includes the following steps: I. Treat the aqueous slurry of the co-concentrate with lime to raise the pH of the slurry to at least 12, II. introducing an oxidizing gas stream into the slurry to reduce its residual xanthate content, III. subjecting the slurry to a primary flotation treatment to separate a first flotation product containing primarily copper ore and magnetic ore from a first landing product containing mainly pentlandite and forming a high quality nickel concentrate.

IV. Treating the first flotation product with a cyanide salt to settle the magnetic pyrite and preparing the cyanidized first flotation product long enough to ensure subsequent rapid and substantially complete foaming of the copper ore. contains mainly magnetic pyrite and forms a low quality nickel concentrate, VI. subjecting the second foam product to purification flotation to separate the final foam product comprising the high quality copper concentrate from the third settling product, and VII. recirculating the third settling product to place it in the cyanide addition and training step (IV).

The success of the process according to the invention is based on the surprising consideration that subjecting an aqueous slurry to gas oxidation, for example by simply aeration, not only causes pentlandite to settle but also activates the magnetic pyrite in the next primary flotation step. Aeration should be carried out under very temporal conditions and should preferably be continued until the xanthate level _ 6 is reduced to a maximum of 10 x 10 mol / l. The observed effect of sludge pre-aeration is astonishing given the findings of their previous investigators in studying the effect of pre-aeration on subsequent flotation of copper minerals.

To the best of our knowledge, no previous pre-aeration study has concerned the separation of copper ore from pentlandite. However, pre-aeration has been proposed as a means to improve copper flotation and to aid in the separation of copper ore from sulfur ore. Thus, for example, U.S. Patent No. 3,456,792 describes a process in which aeration of a slurry containing copper or pyrite is believed to reduce pyrite and allow it to be separated. Magnetic pyrite could be expected to behave in the same way as sulfur pyrite when it comes to the effect of aeration on it. Such a finding is indeed made in “The Role of Oxygen in the Xanthate Flotation of Galena,

Pyrite and Chalcopyrite ", I.B. Klymowsky and P. Salman, CIM Transactions, Vol. LXXIII, pp. 147 ... 152, 1970, where the authors write:

Aeration primarily causes sulfur pyrite and magnetic pyrite minerals associated with copper pyrite to settle and therefore quality improves.

However, it has now been found that when applied to the types of co-concentrates of the type 4 64297 to which the present invention relates, i. containing copper ore, pentlandite and magnetic ore, aeration carried out under very temporal conditions presses only the pentlandite present, leaving the magnetic ore easily flotated with copper ore, allowing the production of a high quality nickel concentrate in the primary flotation stage. In fact, it has been found that aeration generally improves the foaming of copper ore, especially in a highly sulfide environment such as that prevailing in the practice of the present invention. Thus, when, as is generally preferred, a thickener is used at the beginning of the flotation circuit, the oxygen demand of the slurry is such that the dissolved oxygen becomes consumed and the oxidation-reduction potential is found to become very negative. Under such oxidation-reduction conditions, the copper ore did not foam easily, however, after aeration of the thickened slurry, the foaming of the copper ore was found to be rapid and substantially complete.

The co-concentrate feed to the process of the invention is typically in the form of a slurry having a solids density of 30-35% and such a slurry density is suitable for performing various flotation operations in the process of the invention. Thus, the initial pH adjustment can be accomplished with a thickener, which increases the slurry density to about 60-70% solids. The use of such a thickener, although by no means essential to the operation of the process of the invention, is not preferred for a number of reasons. First, the addition of lime to the feed slurry causes some of the xanthate to be released and therefore to be removed along with the water removed during the thickening operation. Second, reducing the volume of the sludge makes it possible to use smaller vessels to aerate the sludge.

Aeration oxidizes the xanthate present in the feed as a result of the co-flotation to which the slurry was subjected. Whatever the exact role of the oxidizing gas, it has been found that measuring the xanthate concentration in the slurry provides a reliable guide to the recommended aeration end point.

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Although aeration can be accomplished by spraying pure oxygen into the slurry, it is by no means necessary to rely on pure oxygen, but air is used for convenience and economy. Attempts have been made to achieve similar results by using chemical oxidants to oxidize xanthate or by using charcoal to adsorb xanthate, but the desired three-way separation of copper ore, pentlandite, and magnetic ore has not been achieved without the use of gas oxidation.

The foamable product from the primary flotation is essentially a copper-magnetic-magnetic fiber mixture. In order to cause the magnetic pyrite to settle, cyanide, preferably in the form of sodium cyanide, is added in an amount corresponding to at least about 0.3 g / kg, e.g. 0.3 to 0.5 g / kg by weight of the concentrate to be treated. After the addition of cyanide to the slurry, a pretreatment treatment is required to ensure that the copper ore does not settle due to cyanidization but becomes rapidly and completely floating in the subsequent flotation. The training may be performed at ambient temperature and generally comprises an equivalent charge residence time of at least 5 minutes. In the process according to the invention, it is particularly advantageous that the different flotation operations or the treatment of the sludge between them do not require raising the temperature of the sludge above the ambient temperature.

The trained slurry is then subjected to a secondary flotation operation to obtain a settling product containing most of the feed from the magnetic pyrite. The foam product is purified to yield the final foam product, which contains a large proportion of copper ore, but little of the pentlandite and magnetic ore previously associated with it. Purification is usually carried out as a multi-stage countercurrent operation, i. as a flotation operation in which the foam product from each stage is fed to the next stage, while the settling product from each stage is recycled to the previous stage.

The process according to the invention will now be described in more detail with reference to the accompanying drawings.

Figure 1 schematically shows a flow chart of a process for treating a co-concentrate in accordance with the present invention.

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Figure 2 is a graph illustrating the effect of different additions of lime and sodium cyanide on the efficiency of the process of Figure 1.

A series of tests were performed as described in Figure 1. The feed was freshly prepared powdered product containing copper ore, pentlandite and magnetic ore and was obtained by foaming using a xanthate collector. It was first thickened to a solids slurry density of 65% and subjected to lime addition (11), during which sufficient lime was added to form a lime titration of 0.7 to 0.9 g per kg of solution. This ensured a pH above 12. The alkaline slurry was then subjected to oxidation 12 by blowing air through it for two hours. At the end of this oxidation period, the residual level of xanthate had fallen below 10 x 10 6 mol / l.

During this aeration, considerable foaming tended to occur due to the presence of a blowing agent in the slurry. However, it was found that the mixture, which was strong enough to produce a vortex, provided sufficient foaming control during the oxidation process.

The oxidation slurry was then diluted to a solids density of 30-35% and passed to primary flotation 13. The feed rate for this flotation operation corresponded to about 10 kg of solids per minute and the equivalent charge residence time of 10 minutes. The foam product from the primary flotation was combined with the settling product from the purification flotation 17 and the resulting slurry was passed to the cyanide addition station 14, followed by coaching. Cyanidization 14 involved the addition of 0.6 g of sodium cyanide per kg of concentrate feed. Training 15 consisted of keeping at room temperature the residence time of the equivalent batch for at least 5 minutes.

The trained slurry was then fed to a secondary flotation 16 where most of the magnetic pyrite becomes discarded as a settling product. Flotation was performed with an equivalent charge residence time of 12 minutes. The foam product from step 16 was mixed with the settling product from repurification step 18 and fed to purification flotation 17 with an equivalent charge residence time of 8 minutes. The foam product from this operation was fed to repurification flotation 18, where the batch had an equivalent residence time of 5 minutes, and a high quality copper concentrate was produced as the foam product li 7 64297.

Table 1 shows the results when the process described above was used to treat the feed with the analysis of: Cu 11.5%, Ni 11.9%, Fe 35.2%, S 32.9% and the rest of the side rock.

table 1

Product Composition% Distribution% _Cu_Ni__Fe_Weight Cu Ni Fe

Input 11.5 11.9 35.2 100 100 100 100

Cu concentrate 32.1 0.33 31.2 34.2 95.6 0.9 30.9

High quality Ni concentrate 0.21 30.2 28.6 31.2 0.6 79.3 25.4

Low quality Ni concentrate 1.28 6.8 45.1 34.7 3.9 19.8 44.4 When using a feed concentrate whose analysis was:

Cu 12.6%, Ni 9.9%, Fe 37.1%, S 33.6% and the rest of the side rock, the results shown in Table 2 were obtained.

Table 2

Product Composition% Distribution%

Cu Ni Fe Weight Cu Ni Fe

Input 12.6 9 ~ 9 3 7.1 100 lQQ lOQ LÖÖ

Cu concentrate 30.0 0.44 32.0 40.3 96.3 1.7 34.8

High quality Ni concentrate 0.29 29.5 30.3 27.9 0.5 83.2 22.8

Low Quality Ni Concentrate 1.37 4.7 49.5 31.8 3.1 15.1 42.4 To provide a numerical factor to evaluate the success of the process, we have used measured numerical values for a freely chosen recovery and separation factor (RSF). which reflects both the amount of copper recovery from the copper concentrate and the quality of the copper concentrate. RSF is defined as follows: RSF = c where A is the weight of copper in the copper concentrate; B is the weight of nickel in the copper concentrate and C is the weight of copper in the feed.

An ideal copper-nickel separation process would give an RSF of one. The RSF values calculated from the results in Tables 1 and 2 are 0.916 and 0.906, respectively. Such high RSF values are not achievable with previously known separation processes. However, RSF values are not the only criteria by which the process must be judged. An equally valuable and hitherto unattainable result is the production of a nickel concentrate with a nickel content of about 30% by weight and containing about 80% of all the nickel in the feed concentrate. In fact, the results in Tables 1 and 2 show an almost complete separation of the three minerals, copper-pyrite, pentlandite, and magnetic pyrite. Thus, determined from the results in Table 1 and the sulfur analysis of the different products, the mineral distribution was calculated as shown in Table 3.

Table 3

Product Distribution%

Copper Pyrite Pentlandite Magnetic Pyrite

Input 100 100 100

Cu concentrate 95.5 0.9 5.8

Of high quality

Ni concentrate 0.6 79.3 6.0

Low Quality

Ni concentrate 3.9 19.3 88.2

In order to determine the preferred process conditions described above, the use of different amounts of lime and cyanide was investigated. In each case, the RSF value was calculated from the measured results, and a mathematical model was developed from the numerical values to determine the dependence of the RSF values on the addition of lime and cyanide. Figure 2 shows a series of curves obtained from a mathematical model representing RSF values of 0.84, 0.86, 0.88, 0.90, and 0.92. Figure 2 also shows individual scores that represent empirically determined RSF values. From these curves it can be seen that an optimal RSF value of 0.92 can be achieved with a lime addition of 1.05 g / kg and a sodium cyanide addition of 0.37 g / kg. For practical reasons, including the ease of filtration of the nickel concentrate produced, it is not advisable to use just as much lime. Accordingly, if a preferred lime addition of about 0.9 g / kg is used, a cyanide addition of about 0.38 g / kg is required to obtain an RSF of at least 0.90. The amounts of lime and cyanide added do not appear to have a significant effect on the recovery of high quality nickel concentrate or the quality of the concentrate.

Excellent results in Tables 1 and 2 were obtained using a process that included aeration carried out continuously in three tanks with an average total residence time of 2 hours. An attempt to achieve a similar separation using chemical oxidation gave the results shown in Table 4. In this case, the procedure was similar to that explained above except that the two-hour aeration was replaced by the addition of 1 to 2 g of sodium hypochlorite per kilogram of feed concentrate to be treated.

Table 4

Product Composition% Distribution%

Cu Ni Fe Weight Cu Ni Fe

Feed 13.9 lli4 35.2 100 100 100 100

Cu concentrate 24.6 0.87 35.5 55.8 98.8 4.3 56.3

High quality Ni concentrate 0.43 26.7 32.7 18.8 Q, 6 44.0 17.5

Low Quality

Ni concentrate 0.33 23.2 36.2 25.4 0.6 51.7 26.1

The results in Table 4 show an RSF of 0.844, which, although inferior to the results in Tables 1 and 2, nevertheless represents a satisfactory copper-nickel separation. However, the failure of this comparative test is clearly demonstrated by the fact that less than half of the nickel content is recovered in the so-called as a high-quality nickel concentrate with a slightly better quality than the so-called with low quality nickel concentrate.

The results of other attempts to replace aeration are shown in Table 5. Four tests using essentially identical feed concentrate are described. Test A was performed in accordance with the present invention and was in fact performed as described above in connection with Tables 1 to 3. Tests B, C, and D were performed in an almost identical manner except that the addition of a chemical oxidant or adsorbent was used instead of aeration to remove unwanted xanthate. In each case, an amount of hypochlorite, peroxide or charcoal corresponding to 1 g of concentrate per kilogram of concentrate was added.

Table 5

Test A Test-i B Test C Test D η,. +. +. Κωτ, (using (using (using _Na0cl> »2 ° 2> charcoal)

Feed Composition Cu 11.5 11.3 11.1 11.6 mus% Ni 8.95 8.91 8.89 8.84

Fri 37.9 37.6 38.6 38.3

Copper Composition Cu 25.4 21.8 23.9 30.7 Consensus% Ni 0.709 0.927 0.755 0.490 Wire Fe 33.2 35.8 35.0 30.1

Jakaan- wt 43.4 49.4 44.0 35.0 nuclear Cu 95.9 94.8 94.7 93.0% Ni 3.40 5.10 3.70 1.90

Fe 38.0 47.0 39.8 27.5

High Composition Cu 0.12 Q, 21 Q, 21 0.15 Quality% Ni 29.8 25.5 25.5 25.4

Distribution Fe 29'6 32'Q 33 '° 33ί1 ^ 0nr ma% wt 24.7 18.7 24.9 24.0

Cu 0.30 0.30 0.50 0.30 raauru Ni 82.3 53.4 71.4 68.9

Fe- 19.3 · 15.9 21.3 2Q, 7

Low Composition Cu 1.40 1.72 1.72 1.90 Quality% Ni 4.01 11.6 7.08 6.28 Ni-Fe 50.7 43.7 48.2 48.4

Distribution wt 31.9 32.0 31.2 41.0 A ma% Cu 3.90 4.90 4.80 6.70

Ni 14.3 41.5 24.8 29.1 ______________ 42.6 37.1 ___ 39.0_51.7 FSF 0.85 0.79 0.83 0.87 u 64297

Although ESF values indicate that acceptable copper-nickel separation was achieved by using hydrogen peroxide or charcoal instead of air, data on the superiority of aeration from high quality nickel concentrate. It is found that aeration produced a nickel content of 29.8% in this concentrate compared to 25.4 and 25.5% in other tests. In addition, the distribution of nickel in this high quality concentrate was significantly lower, 53.4 to 71.4%, in comparative tests than the value of 82.3% obtained when aeration was used.

Thus, it is found that only when appropriate amounts of lime and cyanide are used and recourse is made to pre-aeration, the following valuable results can be obtained: I) high quality copper concentrate; II) a large copper recovery of copper concentrate; III) high quality nickel concentrate; and IV) high nickel recovery to a high quality nickel concentrate.

Claims (6)

A process for separating copper coffin, penteandite and magnetic coffin by co-flotation of a sulphide ore containing copper, nickel and iron using a xanthate as collector reagent to obtain a co-concentrate containing copper coffin, pentlandite and magnetic coffin and then by further flotation, characterized therefrom , the further flotation comprises the following steps: I) a sludge in water of the concentrate is treated with lime to raise the pH of the sludge to a value of at least 12; is subjected to a primary flotation to separate a first float product containing substantially copper canopy and magnetic box from a first sink product which contains substantially pentlandite and forms the high-grade nickel concentrate; IV) the first float product is treated with a cyanide salt to press the magnetic coffin and the cyanide first float product are conditioned for a time sufficient to ensure that in the next step the copper coffin is flotated rapidly and substantially completely; V) the conditioned first float product is subjected to a second flotation to separate a second float product containing essentially copper coffin from a second sink product. VI), the second float product is subjected to a purification flotation to separate a final float product from a third sink product, and VII) the third sink product is recirculated to undergo - discard the same cyanide addition and conditioning in step (IV). Process according to Claim 1, characterized in that the step (II) comprises aeration of the sludge for a time sufficient to ensure that the residual xanthate content of the sludge does not exceed 10 x 10 mol / l. 11