Iron ore concentration process with grinding circuit, dry desliming and dry or mixed (dry and wet) concentration

Abstract

The present invention discloses an advantageous and effective process for the concentration of iron ores, which can be fully dry or mixed, part of the process being dry, part wet. The invention thereby improves process efficiency as a whole by increasing recovery of concentrators and increasing the useful life of the mines.

Claims

1. An iron ore concentration process with grinding circuit, dry desliming and dry concentration, wherein the process comprises the steps of: a) crushing an iron ore; b) dry grinding of the iron ore crushed in step a); c) dry desliming of the iron ore grinded in step b); and d) magnetically separating the iron ore deslimed in step c), resulting in a concentrate iron product and a reject that is separated, wherein step c) is performed by pneumatic classifiers, with a cut of 90%<37 m, wherein step d) is performed by magnetic drums using a combination of first and second intensity magnetic fields followed by a magnetic roll separator having a third intensity magnetic field and a gradient, wherein the third intensity magnetic field is higher than the second intensity magnetic field, and the second intensity magnetic field is higher than the first intensity magnetic field, and wherein the process is a fully dry concentration process.

2. The iron ore concentration process according to claim 1 wherein the process is applied for concentration of iron ores with one stage of grinding, including ores with coarse liberation sizes.

3. The iron ore concentration process according to claim 1, wherein the process is applied for concentration of iron ores with two stages of grinding and regrinding, including for ores with fine liberation sizes.

4. The iron ore concentration process according to claim 1, further comprising obtaining slimes and tailings, and disposing said slimes and tailings in stacks.

5. The iron ore concentration process according to claim 1, wherein the concentrate iron product has up to 68% iron.

6. The iron ore concentration process according to claim 1, wherein step c) is performed by pneumatic classifiers, with a cut of 90%<5 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a flowchart for concentration of iron ores with one stage of grinding, usually used for ores with coarse liberation sizes known from the state of the art.

(2) FIG. 2 shows a flowchart for concentration of ores with two stages of grinding, usually used for ores with fine liberation sizes known from the state of the art.

(3) FIG. 3 shows a mixed flowchart (dry and wet) for concentration of ores with one stage of grinding, usually used for ores with coarse liberation sizes according to the present invention.

(4) FIG. 4 shows a mixed flowchart (dry and wet) for concentration of iron ores with two stages of grinding, usually used for ores with fine liberation sizes according to the present invention.

(5) FIG. 5 shows a flowchart for dry concentration of iron ores with one stage of grinding, usually used for ores with coarse liberation sizes according to the present invention.

(6) FIG. 6 shows a flowchart for dry concentration of iron ores with two stages of grinding, usually used for ores with fine liberation sizes according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(7) In light of the above described results observed, the present invention describes an advantageous and effective process for the concentration of iron ores, which can be fully dry or mixed, part of the process being dry, part wet, thereby enhancing the process efficiency as a whole by increasing recovery of concentrators and increasing the useful life of the mines.

(8) The following detailed description does not intend to, in any way, limit the scope, applicability or configuration of the invention. More specifically, the following description provides the necessary understanding for implementing the exemplary embodiments. When using the teachings provided herein, those skilled in the art will recognize suitable alternatives that can be used, without extrapolating the scope of the present invention.

(9) The present invention is directed to an ore concentration process, embodiments of which are shown in FIGS. 3 to 6.

(10) The process of the present invention comprises the following steps:

(11) TABLE-US-00001 For a fully dry process For a mixed (dry and wet) process a) Crushing an ore; a) Crushing an ore; b) Dry grinding of the ore crushed b) Dry grinding of the ore crushed in in step a); step a); c) Dry desliming of the ore milled c) Dry desliming of the ore milled in in step b); step b); d) Magnetic separation of the ore d) Adding water to the ore deslimed deslimed in step c), resulting in a in step c) concentrate product and a reject e) Flotation, resulting in a reject that is separated that is separated; f) Filtration, obtaining a concentrated product

(12) The terms grinding and milling may be used interchangeably. Grinding or milling is designed to break a solid material into smaller pieces.

(13) According to preferred embodiments of the present invention, the slimes originating from desliming are dry produced by pneumatic classifiers, with a cut that may be between about 90%<37 m and about 90%<5 m. In the mixed process, tailings from flotation should be filtered and mixed to the dry sludge for placement into piles. The water from filtering the tailings is recirculated in the concentration.

(14) The first concentration stage shown in FIGS. 3 and 4 can be replaced by wet high intensity magnetic separation.

(15) Alternatively to wet concentration, a fully dry concentration process is presented in FIGS. 5 and 6, in which concentration is performed firstly by magnetic drums using a combination of low and medium intensity magnetic field and afterwards by high gradient-high intensity magnetic roll separators.

(16) The need for desliming in the process of concentration by flotation is well known. However, the ultrafines also adversely affect the dry magnetic concentration. As a result of the stage of dry desliming, the process according to the present invention has an advantage in relation to the conventional path of dry concentration, where there is no desliming. An example is shown in Tables 1 and 2 below.

(17) TABLE-US-00002 TABLE 1 Results of magnetic concentration of deslimed sample. Stage Flow Mass (g) Fe SiO.sub.2 1.sup.st stage medium intensity Feed 7820.6 42.98 36.35 magnetic drum Concentrate 1 3164.3 67.49 2.78 Tail 1 4656.3 28.63 58.41 2.sup.nd stage medium intensity Concentrate 2 703.6 67.41 2.96 magnetic drum Tail 2 3952.7 20.44 69.43 3.sup.rd stage high gradient high Concentrate 3 2043.9 37.68 43.39 intensity magnetic roll Tail 3 1908.8 1.98 97.31 4.sup.th stage high intensity roll Concentrate 4 1054.4 64.14 6.80 Tail 4 989.5 10.63 81.34 Final Concentrate 4922.3 66.76 3.67 Final Tail 2898.3 4.93 91.86 Mass yield (%) 61.54 Metallurgical recovery (%) 95.59 Gaudin's selectivity index 18.41

(18) TABLE-US-00003 TABLE 2 Results of magnetic concentration of non-deslimed sample. Stage Flow Mass (g) Fe SiO.sub.2 1.sup.st stage medium intensity Feed 8833.3 42.00 37.80 magnetic drum Concentrate 1 2372.2 59.28 12.72 Tail 1 6461.1 38.08 44.04 2.sup.nd stage medium intensity Concentrate 2 2031.8 60.87 10.66 magnetic drum Tail 2 340.4 52.89 22.77 3.sup.rd stage high gradient high Concentrate 3 62.3 60.97 10.83 intensity magnetic roll Tail 3 6398.8 35.47 47.45 Final Concentrate 2094.1 60.87 10.67 Final Tailing 6739.2 36.35 46.20 Mass yield (%) 23.04 Metallurgical recovery (%) 33.99 Gaudin's selectivity index 2.69

(19) Table 1 shows that with the stage of desliming it was possible to obtain a concentrate with 66.76% Fe and tailings with just 4.93% Fe. However, the same sample that was not deslimed generated a concentrate with Fe content of 60.87%, which does not meet market specifications and tailings with 36.35% Fe, which causes a major loss of useful mineral.

(20) The advantages obtained with the process of the present invention: Disposal of coarse and ultrafine tails in stacks reducing the environmentally impacted areas in comparison with the large areas needed for the wet process inherent to the dam arrangement form. Enhanced processing efficiency as a whole increasing recovery of concentrators and whereby increasing the useful life of the mines. Enhanced quality of the generated concentrate, which has a higher Fe content and lower SiO.sub.2 content compared to the conventional process.