Process For the Improvement of Copper Leaching Processes Using Calcium Chloride

Abstract

A process to significantly improve the copper chemical leaching process for primary and secondary minerals, using calcium chloride including the agglomeration, curing, and leaching with a high content of chloride, iron and copper stages. The mineral is then washed with a low concentration of copper and a high concentration of acid, where the impregnated copper is extracted from the pit and wherein a recirculated solution is used in the agglomeration stage.

Claims

1. A process to significantly decrease the leaching times of primary and secondary crushed copper minerals with a particle size between 80% under 12 mm to 80% under 3 mm wherein it is used to leach copper sulphurated minerals having a primary and/or secondary copper mineralization as chalcopyrite, bornite and covellite, wherein the process comprises: a first agglomeration process in which the agglomeration solution is a combination of sea water, saline or another type of water with recirculated solution; a second curing process in the pit after the prior agglomeration process in which the mix of sea water, saline or another type of water, calcium chloride, sulphuric acid and recirculated solution is fed at temperatures higher than 30° C. and lower than 60° C.; a third leaching process in the pit containing recirculated solution after the prior curing process in which the recirculated solution for irrigation of the stack gets in at a temperature higher than 30° C. and lower than 60° C.; a fourth washing process with refinement solution after the prior leaching process in the pit, wherein the refinement solution for irrigation of the previously treated pit with recirculated solution and previously heated at temperatures higher than 30° C., after going through the solvent extraction process also enters the stack as refinement solution at a temperature higher than 30° C. and lower than 60° C.

2. A process according to claim 1, wherein during the first agglomeration process the agglomeration solution is added at a rate of 1 to 40 L/ton of dry mineral with recirculated solution, added to the agglomeration drum at a rate of 25.0 to 100.0 L/ton of dry mineral and sulphuric acid between 50-80% of the total according the consumption obtained from laboratory procedures.

3. A process according to claim 1, wherein during the first agglomeration process the recirculated solution is at a temperature higher than 30° C. and lower than 60° C.

4. A process according to claim 1, wherein during the first agglomeration process the recirculated solution has a total copper concentration of 0.2 to 5.0 [g/L].

5. A process according to claim 1, wherein during the first agglomeration process the recirculated solution has a ferrous ion concentration of 1.0 to 10.0 [g/L].

6. A process according to claim 1, wherein during the first agglomeration process the recirculated solution has a ferric ion concentration of 1.0 to 10.0 [g/L].

7. A process according to claim 1, wherein during the first agglomeration process the recirculated solution has a sulphuric acid concentration of 2.0 to 10.0 [g/L].

8. A process according to claim 1, wherein during the first agglomeration process the recirculated solution has a chloride ion concentration of 30.0 to 130.0 [g/L].

9. A process according to claim 1, wherein during the first agglomeration process the resulting agglomerate has a humidity between 6 to 12% when exiting the agglomeration drum depending on the material composition.

10. A process according to claim 1, wherein during the second curing process in stack the mix of sea water, saline or another type of water, calcium chloride, sulphuric acid and recirculated solution fed at temperatures higher than 30° C. forms a solution reaching maximum values of temperature of 70 to 85° C. depending of the material composition.

11. A process according to claim 1, wherein during the second process the solution reach ion chloride concentrations of 140 to 365 g/L and ensure the cuprous ion stability in solution in boundary layer.

12. A process according to claim 1, wherein during the second curing process in pits, energy is added as heat by means of water jackets, electric heaters, hot air, solar radiation, or another method allowing to keep the temperature of the mineral in a range over 30° C. and under 60° C.

13. A process according to claim 1, wherein during the second curing process in pits the curing period is higher than 3 days and preferably higher than 7 days.

14. A process according to claim 1, whererin during the third process recirculated solution is heated at a temperature higher than 30° C. and lower than 60° C. by heat exchange with the PLS solution at the exit of the stack.

15. A process according to claim 1, wherein during the third leaching process in pits, the irrigation effective period for secondary sulphurs is less than 80 days and for primary sulphurs is less than 300 days.

16. A process according to claim 1, wherein during the fourth washing process, the irrigation refinement solution in stacks is heated at a temperature higher than 30° C. and lower than 60° C. by a heat exchange (6) operating with the rich solution at the exit of the pit (12).

17. Use of the process according to claim 1 to significantly reduce the leaching times of primary and secondary crushed copper minerals with a particle size between 80% under 12 mm to 80% under 3 mm, wherein said process it is useful to leach copper sulphurated minerals having primary and/or secondary mineralization of copper such as chalcopyrite, bornite and covellite.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0024] FIG. 1 shows the process industrially used by Minera Michilla (prior art).

[0025] FIG. 2 shows the process of the invention, using intermediate solution in the agglomerate, and temperature in the curing, leaching and washing.

[0026] FIG. 3 shows a graphic of the effect of the copper extraction for chalcopyrite mineral according to the temperature with a total copper content (CuT) in the mineral of 0.632%.

[0027] FIG. 4 shows a graphic of the effect of the copper extraction for chalcopyrite mineral with temperature and a total copper content (CuT) in the mineral of 0.36%.

[0028] FIG. 5 show a graphic of the effect in the copper extraction for primary sulphurs by adding recirculated solution to the agglomeration.

[0029] FIG. 6 show a leaching column with a water jacket to perform the leaching experiment with temperature of the chalcopyrite minerals.

DETAILED DESCRIPTION OF THE INVENTION

[0030] As shown in FIG. 2, a process using calcium chloride or primary and secondary crushed copper minerals with a particle size from about 80% under 12 mm to about 80% under 3 mm is described. The selection of the particle size is a function between the recovery goal and the cost of crushing. The new process presented herein, uses recirculated solution obtained from the resulting solutions from leaching (3) and washing (4) which are extracted from a pool (14). This process has four novel process allowing improvements in the copper recovery:

[0031] Addition of recirculated solution in the agglomeration process (1)—This process considers adding during the agglomeration stage (1) the recirculated solution, which is carried through a line (13) for this purpose, using primary and secondary copper minerals. This process has two advantages: The first one, is that the recirculated solution already has the chemical agents needed for the dissolution of the sulphurated copper species (Fe.sup.3+, Fe.sup.2+, Cu.sup.2+ y Cl.sup.−) which implies a kinetic advantage in the curing stage, as the copper and ferric ion needed are delivered to start the leaching reactions of the primary and secondary copper mineral.

[0032] The second advantage is that the recirculated solution has a higher concentration of chloride ion (30 to 130 g/L) compared to the 21 g/L from sea water, which implies that for the same amount of agglomeration solution the contribution of chloride ion is higher, which is needed for the ferric ion regeneration reactions. The agglomeration solution is a combination of sea water, saline or another type of water, or leaching solution added at a rate of 1 to 40 L/ton of dry mineral with recirculated solution added to the agglomeration drum, at a rate of 25 to 100 L/ton of dry mineral and the addition of sulphuric acid according to the consumption obtained in laboratory processes, typically between a 50 to 80% of the total. The recirculated solution contains a total copper concentration of 0.2 to 5.0 g/L, a ferrous ion concentration of 1.0 to 10 g/L, a ferric ion concentration of 1.0 to 10.0 g/L, and a sulfuric acid concentration of 2.0 to 10.0 g/L.

[0033] The resulting agglomerate has a humidity between 6 and 12% when exiting the agglomeration drum (1), depending on the mineral characteristics. Additionally, in the agglomeration process the recirculated solution is at a temperature higher than 30° C. and lower than 60° C.

[0034] Addition of heat (10) to the primary sulphur mineral and/or the solution in the curing stage (2) with a temperature higher than 30° C. and lower than 60° C.—After the agglomeration process, the mix of sea water, saline or another type of water, calcium chloride, sulphuric acid and recirculated solution fed at higher temperatures than 30° C. form a solution reaching maximum temperature values of 70° C. to 85° C. depending on the material composition. The formed solution reaches chloride ion concentrations of 140 to 365 g/L and ensures the stability of the cuprous ion in solution in boundary layer.

[0035] This step is performed by heating the bed (10) and/or the solution according the methods available in the market, such as water jackets, electric heaters, hot air, solar radiation or any other method that allows to maintain a mineral temperature higher than 30° C. and lower than 60° C. The curing time is higher than 3 days and preferably higher than 7 days.

[0036] Addition of heat to the mineral (11) or heating of the solutions (5) in the leaching stage (3) in stacks with solution containing recirculated solution at a higher temperature than 30° C. and lower than 60° C.—After the previous curing process, follows this process, which with the addition of calcium chloride (CaCl.sub.2) during the agglomeration (1) is efficient for the leaching of primary and secondary copper minerals. A form to significantly increase the copper extraction with high contents of chalcopyrite is by adding heat to the system.

[0037] In this case, heat is added to the mineral by heating the leaching solutions (5) and/or adding hot air (11). This, in addition to the leaching of pyrite, would generate enough heat to increase the chalcopyrite leaching speed. The heat produced in this stage is due to an exothermic reaction during the leaching of the pyrite. The amount of heat generated depends of the mineralogical composition of the ore. The recirculated solution for irrigation of the stack, gets in at a temperature higher than 30° C. and lower than 60° C., heated by heat exchange (5) with the rich solution (PLS) at the exit of the stack, transported by pipes (7). The irrigation effective period for secondary sulphurs is lower than 80 days and for primary sulphurs, lower than 300 days.

[0038] Washed of stacks with refinement solution from the prior leaching in pit process—The irrigation refinement solution for the pit previously treated with recirculated solution and previously heated at temperatures higher than 30° C. and lower than 60° C., after passing through the solvent extraction process also enters the pit (4) as refinement solution at a temperature higher than 30° C. and lower than 60° C., heated by heat exchange (6) operating with the PLS solution at the pit exit (12) transported by pipes (8). The refinement solution for this process is extracted from a refinement solution pool (15) at the exit of the solvent extraction exit.

EXAMPLES

Experimental Stage (I)

[0039] These experimental test were performed in leaching columns (1), (see FIG. 6) one meter tall, with a tubular shape, where the mineral with 0.632% of total copper content, with a 95% content of chalcopyrite is heated, obtaining the following results with a crushed sample 100% under 12 mm:

TABLE-US-00001 TABLE 1 Copper recovery with and without temperature with CuT = 0.632%. Leaching CuT = 0.632% Leaching CuT = 0.632% without CuT with CuT temperature Extraction temperature extraction Time (accumulated) Time (Accumulated) [days] [%] [days] [%] 0 0.0 0 0.0 1 1.6 1 15.1 2 2.4 2 16.5 3 2.6 3 17.8 4 2.8 4 18.3 5 2.9 5 18.5 6 3.1 6 19.4 12 4.1 12 25.2 19 5.2 19 30.7 26 6.2 26 34.4 33 7.1 33 35.6 39 7.9 39 40.0 48 8.9 48 42.3 54 9.6 54 44.1 61 8.4 61 45.6 68 9.1 68 45.5 75 9.7 75 47.6 82 10.3 82 50.3 89 10.8 89 51.8 96 11.3 96 52.0 103 11.8 103 53.1 110 12.2 110 54.7 117 12.6 117 55.3 124 13.0 124 59.1 131 13.3 131 57.0 138 13.7 138 57.2 145 14.0 145 58.2 152 14.3 152 57.9 159 14.5 159 62.0 166 14.8 166 61.0 173 15.0 173 60.2 180 15.2 180 60.4 187 15.4 187 60.4 194 24.1 194 72.4 201 28.7 201 75.3 205 28.8 205 75.4
This data corresponds to the graphic in FIG. 3.

[0040] A second experience was performed contributing heat to the leaching column, this time using a mineral with 0.36% of CuT, with chalcopyrite contents over 90%, obtaining the following values for crushed samples 100% under 12 mm:

TABLE-US-00002 TABLE 2 Results of the leaching process using temperature. Leaching with CuT = 0.36% temperature CuT extraction Time Accum. of Cu Ext. Days [%] 0 0 60 35.65 124 45.5 166 50.1
This data corresponds to the graphic in FIG. 4.

[0041] According to these results, it can be appreciated that a higher recovery is obtained using temperature in the leaching process indicated.

[0042] The final recovery depends mainly of the copper release and the CaCl.sub.2 effect on the agglomerate quality allows treating in rolls of pressure up to less than 2 mm.

Experimental Stage (II)

[0043] The experimental results simulating the agglomeration and curing stages show that the minerals to which ILS (recirculated solution) was incorporated, have a better copper extraction, which means downstream (leaching process with solution) an improvement in the copper extraction kinetics, i.e., the same amount of copper can be obtained in less time.

[0044] FIG. 5 shows scanning experiments where different concentrations were used in the curing stage, which were performed to a mineral coming from Estefania mine from Minera Michilla, with a total amount of copper of 1.69% and soluble copper of 0.69%. Additionally, it can be observed in FIG. 5 that in the case of the process without ILS (recirculated solution), a 34% or total copper recovery was obtained. However, when the extraction was performed in the agglomeration process, the copper recovery increased with the addition of a 50% of ILS solution (recirculated solution) or with a 75% of ILS solution (recirculated solution), wherein a total copper recovery of 40% and 46% was obtained, respectively.

[0045] Minerals were agglomerated with the following dose of compounds:

TABLE-US-00003 TABLE 3 dose of the compounds for the agglomeration Agglomeration ILS Sol. (recirculated H.sub.2SO.sub.4 CaCl.sub.2 H.sub.2O solution) CURED Target 25 [kg/t] 4 [kg/t] 65 [L/t] 0 [L/t] 10 DAYS 50% of water 25 [kg/t] 4 [kg/t] 32.5 [L/t] 32.5 [L/t] replaced with ILS (recirculated solution) 75% of 25 [kg/t] 4 [kg/t] 16.25 [L/t] 48.75 [L/t] water replaced with ILS (recirculated solution)
The re-circulated leaching solution used has the following characteristics:

TABLE-US-00004 TABLE 4 dose of the compounds in the ILS (recirculated solution) Compound Dosage Cu.sup.2+ 0.5 to 4 [g/L]   Fe.sup.2+ 2 to 5 [g/L] Fe3+ 2 to 5 [g/L] H.sub.2SO.sub.4 2 to 6 [g/L] Cl.sup.− 70 to 80 [g/L]