EP0229835B1

EP0229835B1 - Process for the selective separation of a copper molybdenum ore

Info

Publication number: EP0229835B1
Application number: EP86905004A
Authority: EP
Inventors: Alfredo P. Vargas; Nathaniel Arbiter
Original assignee: PHLOTEC SERVICES Inc
Current assignee: PHLOTEC SERVICES Inc
Priority date: 1985-07-09
Filing date: 1986-07-09
Publication date: 1993-06-16
Anticipated expiration: 2006-07-09
Also published as: JPS63500577A; ATE90592T1; FI870999A0; FI870999A7; EP0229835A1; WO1987000088A1; EP0229835A4; AU6191386A; DE3688591T2; AU5684090A; FI80835B; AU629646B2; BR8606758A; FI80835C; DE3688591D1

Abstract

A process for separation of the mineral components of a copper/molybdenum sulfide ore by flotation including (a) crushing and grinding the ore to liberate the minerals; (b) in a primary flotation circuit, adding a molybdenum collector selected from the group of hydrocarbon oils, and a frother; (c) floating a primary (molybdenum) concentrate in the primary circuit in the absence of a copper collector; (d) directing the primary molybdenum concentrate to an upgrading separation circuit to produce a final molybdenum concentrate; and (e) directing the non-float of the primary circuit to a secondary scavenger circuit for recovery of copper and additional molybdenum with addition of a copper collector, the process being conducted at a natural pH essentially determined by the ore composition and the quality of the water used to form the pulp, without addition of substantial amounts of alkaline or acid pH modifiers sufficient to change the pH.

Description

The present invention relates to an improved process for the selective separation of the components of a copper molybdenum (Mo-Cu) ore by flotation. More particularly, the present invention relates to a process for such separation conducted at a natural pH (i.e. without addition of alkalies (such as lime) or acids in amounts sufficient to substantially modify the pH) and without the addition of a copper collector in the primary flotation circuit, which leads to the recovery of a primary Mo-Cu concentrate.
In conventional flotation systems for copper ores with recoverable molybdenum by-product values, the ore is first crushed and ground with lime usually added to depress pyrite. The ore is then treated in a primary flotation circuit after copper collector and frother have been added. The copper rougher concentrate thus obtained contains most of the copper and a substantial portion of the molybdenum. This rougher copper concentrate is then subjected to several stages of cleaner flotation (usually after a regrind operation) to produce a finished copper concentrate. This concentrate contains substantially all of the molybdenite (MoS₂) recovered in the rougher circuit. The copper concentrate is then treated in a series of separation steps designed to separate the molybdenite, a by-product in many copper ores, as a high-purity concentrate.
A major problem with this system is that lime which is invariably used, may depress a portion of the molybdenum, causing a decrease in the obtainable recovery of MoS₂ mineral.
Another major problem with the conventional system is that it requires molybdenum recovery from a copper concentrate with a high reagent content. Because of this, the separation of molybdenum from the copper minerals is especially difficult. A complex secondary separation system is necessary, which is costly, requires a high level of copper depressants, and may cause lowering of molybdenum recovery.
[ In US-A-2316743 there is disclosed a process for the recovery of molybdenite by a primary froth flotation using a three component collector comprising at least one higher aliphatic alcohol having six to ten carbon atoms (the frother), a hydrocarbon of the paraffin series and a hydrocarbon of the terpene series, wherein the alcohol content of the frother collector is substantially 40%.
In US-A-3426896 there is disclosed a process for the separation of metallic ores containing molybdenum, copper and iron minerals, in which new molybdenum/copper collectors using isothiouronium salts are used.
In US-A-4515688 there is disclosed a process for the separation of the components of an ore by sequential flotation of a pulp of the ore and water at its natural pH using the addition of sulphide ions and cyanide ions to depress and inhibit flotation of pyrites and other base metal sulphides which it is not desired to collect.]
One object of the present invention is to provide a process for the separation by flotation of the components of a copper ore (with molybdenum as a by-product) by flotation. This process affords a convenient, inexpensive, and efficient method of molybdenum recovery at an acceptable grade.
Another object of this invention is to provide a process for such separation, which can be conducted at a natural pH and avoids use of lime and other pH modifiers.
Another object of this invention is to provide a process for such separation which avoids use of substantial amounts of depressant for copper minerals.
Another object of this invention is to provide a process for such separation that avoids use of a copper collector in the primary flotation circuit.
Another object of this invention is to achieve the recovery in the primary flotation circuit of a concentrate substantially enriched in molybdenum which, because of its enhanced molybdenum content, can be further separated into a molybdenum concentrate with less reagents and in a substantially smaller number of cleaning stages, and which affords substantially enhanced recovery of the molybdenum mineral initially contained in the ore. The copper content of this primary flotation circuit, after the cleaning stages, can be diverted to the copper circuits. Hence, the overall copper recovery of the system is not jeopardized.
According to the present invention there is provided a process for the separation of mineral components of an ore containing base metal sulphides, including copper and molybdenum sulphides, and pyrites, which process comprises the steps of:
grinding the ore to liberate the minerals and to form a pulp of water and the ore;
adding to the pulp a hydrocarbon oil molybdenum collector and a frother;
floating a primary molybdenum concentrate from the pulp in a primary flotation circuit;
directing the primary molybdenum concentrate away for further treatment to produce a final molybdenum concentrate; and
treating the non-floating components of the primary flotation circuit for recovery of copper and molybdenum,
characterized in that the process further comprises the step of subjecting the pulp to aeration prior to the flotation of the primary molybdenum concentrate, which flotation is carried out at the natural pH of the pulp being essentially determined by the water used and the composition of the ore, without the addition of alkaline or acid pH modifiers.
Further features of the process are set out in the dependent claims.
These and other features of this invention will be apparent to one of ordinary skill in the art in light of the following description, accompanying claims and appended drawings in which:

Fig. 1 is a flowsheet of a copper-molybdenum ore separation scheme by flotation in accordance with the present invention; and
Fig. 2 is a water-balance flowsheet for a copper-molybdenum flotation process, as it is typically practiced in the Southwestern United States where water is in short supply.

In accordance with the present invention, copper ore with associated molybdenum contents, from a mine is crushed and ground to the required particle size to form the flotation feed and ore pulp.
Preflotation conditioning of the ore may be conducted during or after the wet grinding stage and is completed before the first flotation stage. Preconditioning is marked as 1 in Fig. 1. According to the present invention, apart from the required aeration, the only preconditioning that may be necessary at this stage would require addition of very small amounts of redox agents, such as sodium sulphide hydrogen peroxide, etc. Combined contributions from ore mineralization, degree of surface oxidation and water chemistry (unless modified) can result in varying degrees of copper and iron sulphide mineral recovery along with the molybdenite, in the primary molybdenum rougher stage. Preflotation conditioning of the ore, by aeration and optionally also with specific reagents, conducted during or after the grinding stage, is necessary to prevent or minimize this recovery of copper and iron sulphides. The additional specific reagents used may be of reducing characteristics, such as hypochlorites or peroxides. The amount of preconditioning required is that just sufficient to prevent or minimize the aforesaid recovery of copper and iron sulphides along with the molybdenite during the primary molybdenite flotation stage. In other words, the amount of the optional redox reagent and the extent of aeration, is preferably just sufficient to prevent or minimize copper sulphide and pyrite flotation, i.e. to depress their natural flotability, without affecting molybdenite flotation, and does not affect the pH. In the vast majority of the cases, no lime or other pH modifiers are added (or, if added, lime is in extremely small amounts compared with the conventional lime circuits and only for protective alkalinity, i.e. to prevent equipment corrosion).
No copper collector is added in the primary molybdenite flotation circuit. However, a small amount of a hydrocarbon oil is added as a MoS₂ (moly)-collector, at 2 in Fig. 1, along with a frother.
Suitable hydrocarbon oils include vapour oil, diesel oil, fuel oil, etc. Preferably, the hydrocarbon will contain as little wax fraction as possible.
The primary flotation circuit produces a rougher molybdenum concentrate containing some copper and a non-float.
This concentrate, which is substantially enriched in MoS₂ (moly)as compared to conventional circuits, is then reground if necessary and directed to cleaner stages which lead to the production of a final molybdenum concentrate. The cleaner stage simplification and cost savings achieved by the present invention are also substantial.
The non-float of the primary circuit is directed to a copper flotation circuit. The non-float contains some of the copper and the remaining non-floating minerals. Copper collector is added at 3 in Fig. 1.
Whether an oxidation/reduction agent is added or not (either before primary flotation at 1, or before the scavenger flotation at 4 in Fig. 1) depends in large measure on the natural oxidation/reduction conditions of the ore and the water used in the flotation process.
The copper rougher concentrate is typically directed to regrind and cleaner operations, resulting in production of a final copper concentrate, a final tailings product, and possibly a secondary molybdenum concentrate. This latter concentrate, when produced, represents a small proportion of the total moly content of the original ore, because, of the efficiency of the present primary flotation circuit in recovering molybdenite. This secondary molybdenum concentrate may be recycled to the primary molybdenum circuit, or to the molybdenum cleaner circuit, depending on the molybdenum assay.
Further separation of the scavenger concentrate may require addition of a small amount of an oxidation/reduction agent sufficient to minimize pyrite flotation.
The process of the present invention does not need to employ cyanide.
Aeration is advantageously used instead of (or in addition to) a redox additive to control the redox potential of the pulp. Aeration can be used at 1 in the primary flotation circuit, or at 4 in the first scavenger circuit.
Advantages of the present process include simplification of the flotation scheme and savings in all reagents, including those resulting from the omission of lime and the minimal -- if any -- addition of a redox agent, and also in frother and collector consumption.
Other advantages stem from the improvement in moly recovery and/or grade.
Suitable molybdenum-copper ores for practice of the present process include copper-molybdenum sulphide ores which contain chalcopyrite and chalcocite.
The present process is particularly suited for ore separation in plants where the water is recycled. In fact, the present process can be advantageously introduced in separation plants where a major portion of the water is reclaimed as illustrated in Fig. 2 (Prior Art). This is so because the addition of reagents (including collector and redox reagent, if any) is so minimal that they do not accumulate in the reclaimed water. In Fig. 2 approximately 60% of the water in the system is reclaimed after flotation of a rougher concentrate, 4. Additional water is reclaimed from the non-float scavenger circuit, 2. All reclaimed water is combined at 3. The term GPT means U.S. Gallons Per Short Ton of Ore Processed.
The invention is further illustrated below by reference to specific examples. However, the scope of the present invention is not limited to these examples.

Example 1

Ore: 500 g of copper-moly ore from Chino Mines Division, Kennecott Copper Company containing mostly chalcopyrite.
Water: 350 ml process H₂O (from stage 1 of Fig. 2).

After grinding (for 6 min.) Na₂S was added to the pulp (the equivalent of 50g/ton of ore) in a conditioning step (1 min.). The pulp was aerated for about 2 minutes with mixing and then the air was turned off. Fuel oil, 2 drops, was added to the pulp together with 6 drops of metal-iso-buutyl-carbinol (MIBC), a frother. After flotation of the rougher concentrate (3 min.), 2 drops of 2694, a copper collector were added in a conditioning stage (2 min.) and the first scavenger concentrate was floated (4 min.). Subsequently, one more drop of the copper collector was added (2 min.) and the second scavenger concentrate was floated. The electrochemical potential was measured and found to be +40 in the first conditioning stage, during aeration, and in the rougher concentrate flotation step, and +50 in the first scavenger flotation step. The pH was 7.5 during aeration, 7.8 during conditioning, 8.0 during flotation of the primary concentrate and 8.2 during flotation of the secondary concentrate. The results were as follows:

Product	Weight	Analysis		Distribution
		Mo	Cu	Mo	Cu
Rougher Conc.	2.7	0.338	17.75	60.75	34.10
1-Scavenger Conc.	3.62	0.032	18.06	9.59	57.89
Primary Conc.	5.79	0.147	17.94	70.35	91.99
Non-float	94.21	0.0038	0.096	29.65	8.01
Calculated Head	100.00	0.121	1.129

Example 2

Ore: 500 g of the same copper-moly ore as in Example 1.
Water: 350 ml Process H₂O (from stage 1 of Fig. 2).

The ore was ground for 6 min. and only frother (2 drops of MIBC) was added. Fuel oil (6 drops) was added in a first conditioning stage (1 min.) and the pulp was aerated for two min. No sodium sulphide or other redox reagent was added. The rougher concentrate was floated (3 min.) and the non-float was conditioned (2 min.) with the addition of 2 drops of copper collector. The first scavenger concentrate was floated (4 min.) and the non-float was conditioned for 2 minutes with 1 additional drop of copper collector (2694) after which the second scavenger concentrate was floated. The results were as follows:

Product	Weight	Analysis		Distribution
		Mo	Cu	Mo	Cu
Rougher Conc.	0.72	0.878	8.11	54.36	5.13
1-Scavenger Conc.	3.88	0.036	24.42	12.01	83.29
Primary Conc.	4.60	0.168	21.87	66.37	88.43
Non-float	95.40	0.0041	0.138	33.63	11.57
Calculated Head	100.00	0.0116	1.137

Claims

A process for the separation of mineral components of an ore containing base metal sulphides, including copper and molybdenum sulphides, and pyrites, which process comprises the steps of:
grinding the ore to liberate the minerals and to form a pulp of water and the ore;
adding to the pulp a hydrocarbon oil molybdenum collector and a frother;
floating a primary molybdenum concentrate from the pulp in a primary flotation circuit;
directing the primary molybdenum concentrate away for further treatment to produce a final molybdenum concentrate; and
treating the non-floating components of the primary flotation circuit for recovery of copper and molybdenum,
characterized in that the process further comprises the step of subjecting the pulp to aeration prior to the flotation of the primary molybdenum concentrate which, flotation is carried out at the natural pH of the pulp being essentially determined by the water used and the composition of the ore, without the addition of alkaline or acid pH modifiers.
A process according to claim 1, wherein the aeration is carried out during or after grinding of the ore.
A process according to claim 1 or 2, wherein the aeration is carried out before or after addition of the molybdenum collector and frother.
A process according to claim 1, 2 or 3, which further comprises the step of adding an oxidizing or reduction agent (redox reagent) to the pulp.
A process according to claim 4, wherein the addition is carried out during or after grinding of the ore.
A process according to claim 4 or 5, wherein the addition of redox reagent is carried out before or after the addition of the molybdenum collector and frother.
A process according to claim 1, 2 or 3, wherein the flotation of the primary molybdenum concentrate is carried out at the natural redox potential of the pulp.
A process according to any preceding claim, wherein the molybdenum collector and frother are added during grinding.
A process according to any preceding claim, wherein the further treatment of the primary molybdenum concentrate is carried out in an upgrading separation circuit.
A process according to any preceding claim, which further comprises the addition of an oxidizing or reducing agent to the primary molybdenum concentrate during its further treatment in an amount sufficient to at least minimize the flotation of copper and iron sulphides.
A process according to any preceding claim, wherein the treatment of the non-floating components of the primary flotation circuit includes directing the non-floating components of the primary flotation circuit to a secondary flotation circuit for recovery of copper and additional molybdenum.
A process according to claim 11, wherein the treatment of the non-floating components of the primary flotation circuit comprises floating a copper containing concentrate, and obtaining additional molybdenum and a final copper concentrate therefrom.
A process according to any preceding claim, which further comprises the addition of an oxidizing or reducing agent during the treatment of the non-floating component.
A process according to any preceding claim, which further comprises the addition of a collector during the treatment of the non-floating components of the primary flotation circuit.
A process according to claim 14, in which the collector is a copper collector.
A process according to any preceding claim, in which the treatment of the non-floating components of the primary flotation circuit comprising subjecting those components to aeration.
A process according to any preceding claim, wherein the treatment of the non-floating components of the primary flotation circuit is carried out at the natural pH of the non-floating components being essentially determined by the water used and the composition of the non-floating components, without addition of alkaline or acid pH modifiers.
A process according to any one of claims 4 to 6, 9 or 13, wherein the oxidising or reducing agent is sulphide ion.
A process according to claim 18, wherein the oxidising or reducing agent is added in an amount ranging between 0 and 5 g/ton of ore.