Comminution process of iron ore or iron ore products at natural moisture

Abstract

This invention relates to a process of comminution of iron ore or iron ore products (pellet feed, sinter feed, etc.) at natural moisture without the need to add water or to include a drying step in the process, that is technically and economically feasible. The comminution process of this invention uses at least one piece of equipment selected from the group consisting of roller press (HPGR), vertical roller mill (VRM), roller crusher (RC) and high acceleration screen of at least 10G.

Claims

1. A process for comminuting an iron ore at natural moisture or an iron ore product at natural moisture, comprising: milling with a vertical roller mill comprising a rotatable turntable and rollers arranged thereon with the iron ore at natural moisture or the iron ore product at natural moisture being comminuted therebetween, and pressing with a high-pressure grinding rolls roller press comprising a pair of oppositely rotating rollers supported on a rigid frame the iron ore at natural moisture or the iron ore product at natural moisture, wherein the process includes the vertical roller mill followed by the high-pressure grinding rolls roller press in series, and wherein a moisture content of the iron ore at natural moisture or the iron ore product at natural moisture is not adjusted prior to milling.

2. The process according to claim 1, further comprising screening in a high-acceleration screen of at least 10G, wherein the process includes the high-pressure grinding rolls roller press with the screening performed in the high-acceleration screen of at least 10G in a closed circuit.

3. The process according to claim 1, further comprising screening in a high-acceleration screen of at least 10G, wherein the process includes the vertical roller mill with the screening performed in the high-acceleration screen of at least 10G in a closed circuit.

4. The process according to claim 1, further comprising screening in a high-acceleration screen of at least 10G, wherein the process includes the vertical roller mill, then the high-pressure grinding rolls roller press, followed by the screening in the high-acceleration screen of at least 10G in closed circuit.

5. The process according to claim 1, further comprising screening in a high-acceleration screen of at least 10G, wherein the process includes the screening in the high-acceleration screen of at least 10G followed by the high-pressure grinding rolls roller press.

6. The process according to claim 1, wherein the iron ore at natural moisture is from a run-of-mine and the iron ore product at natural moisture is pellet feed or sinter feed.

7. The process according to claim 1, wherein the iron ore at natural moisture or the iron ore product at natural moisture has up to 12% moisture by weight.

8. The process according to claim 1, wherein a final comminution product has a particle size of less than 16 mm.

9. The process according to claim 1, wherein a final comminution product has a particle size of less than 8 mm.

10. The process according to claim 1, wherein a final comminution product has a particle size of less than 0.074 mm.

11. The process according to claim 1, wherein grinding on the high-pressure grinding rolls roller press or the vertical roller mill is carried out in up to three steps.

12. The process according to claim 1, further comprising screening with a high-acceleration screen of at least 10G.

Description

DESCRIPTION OF THE FIGURES

(1) The detailed description given below refers to the attached figures, which:

(2) FIG. 1 illustrates a wet iron ore beneficiation process (ROM), according to the state of the art;

(3) FIG. 2 illustrates a wet process of beneficiation of iron ore products (pellet feed, sinter feed, among others), according to the state of the art;

(4) FIG. 3 illustrates a dry raw iron ore beneficiation process (ROM) according to the state of the art;

(5) FIG. 4 illustrates a dry process of beneficiation of iron ore products (pellet feed, sinter feed, among others), according to the state of the art;

(6) FIG. 5 illustrates the process of beneficiation of raw iron ore or iron ore products at natural moisture, according to this invention;

(7) FIG. 6 shows the nine processing routes of this invention.

DETAILED DESCRIPTION OF THE INVENTION

(8) The following detailed description is in no way intended to limit the scope, applicability or configuration of the invention. More precisely, the following description provides the understanding necessary for the implementation of exemplary embodiments. Using the teachings herein, those skilled in the art will recognize convenient alternatives that may be used without extrapolating the scope of this invention.

(9) As will be obvious to any person skilled in the art, the invention is directed to comminution in the iron ore beneficiation process, without addressing any other steps such as concentration, for example. However, the invention is not limited to such particular embodiments.

(10) FIG. 1 shows a state-of-the-art process of wet iron ore beneficiation (ROM) containing the crushing 101, screening 102, grinding 103 and concentration 104 steps. Crushing step 101 may be performed in various stages (e.g. primary crushing to quaternary crushing), being carried out in closed circuit with screening step 102, which may be performed, for example, on vibrating screens. Grinding step 103 requires the addition of a significant volume of water. The ore concentration step 104 can be performed by gravitational, magnetic, flotation methods, etc.

(11) FIG. 2 shows a state-of-the-art process for beneficiation of wet iron ore products (pellet feed, sinter feed, etc.), where the comminution circuit contains a first grinding step 201, a filtration step 202 due to high moisture of the material, and a second grinding step 203. After comminution, the material goes through pelletizing step 204 to obtain the desired final product, which in this case is iron ore pellets.

(12) FIG. 3 shows a state-of-the-art process of dry iron ore beneficiation (ROM) containing crushing 301, screening 302, drying 303, grinding 304 and concentration 305 steps. Crushing step 301 may be performed in various stages (e.g. primary crushing to quaternary crushing), being carried out in closed circuit with screening step 302, which may be performed, for example, on vibrating screens. Drying 303 may occur within the grinding equipment itself by means of hot air flow from burners and blowers. Concentration 305 can be performed by gravitational, magnetic, electrostatic methods, etc.

(13) FIG. 4 shows a state-of-the-art process for dry iron ore product beneficiation (pellet feed, sinter feed, among others), where the comminution circuit contains a drying step 401, a first grinding step 402 and a second grinding step 403. After comminution, the material goes through pelletizing step 404 to obtain the desired final product, which in this case is iron ore pellets.

(14) The following description will address (9) nine possible comminution routes of this invention. Routes apply for two iron ore source possibilities: 1) a first source of material coming directly from the mine (ROM), and 2) a second source of iron ore products already processed at the beneficiation plant (pellet feed, sinter feed, etc.) before entering this invention's process.

(15) This invention, illustrated in a simplified manner by FIG. 5, is a beneficiation process whose comminution circuit 501 is fully performed at natural moisture, either from a material coming directly from the mine (ROM) with up to 12% moisture by weight, or already processed iron ore products (pellet feed, sinter feed, etc.), also with up to 12% moisture. After comminution 501, the final product may be the comminuted iron ore itself, or concentration 502, pelletizing 503 or sintering 504 stages may be carried out according to the desired final product.

(16) The 9 (nine) processing routes of the present invention are illustrated in detail in FIG. 6 and consist of: Route 1: The comminution circuit 501, at natural moisture, occurs first in a roller press (HPGR) in up to three steps and is later reprocessed in a vertical roll mill (VRM) in up to three steps in series; Route 2: The comminution circuit 501, at natural moisture, occurs first in a vertical roller mill (VRM) in up to three steps, and then is reprocessed in a roller press (HPGR) in up to three steps in series; Route 3: Comminution circuit 501, at natural moisture, occurs in a roller press (HPGR) and is coupled in a closed circuit with a high acceleration screen (at least 10G) where the coarse product (retained material) will be directed back to the roller press (HPGR) and fine product (passing material) is the final comminution product; Route 4: Comminution circuit 501, at natural moisture, occurs in a vertical roller mill (VRM) and is coupled in a closed circuit with a high acceleration screen (at least 10G), where the coarse product (retained material) will be redirected to the vertical roller mill (VRM) and the fine product (passing material) is the final comminution product; Route 5: Comminution circuit 501, at natural moisture, starts at the roller press (HPGR), the material goes on to be processed in a vertical roll mill (VRM) and is then classified into a high acceleration screen (of at least 10G), where the coarse product (retained material) returns to the roller press (HPGR), closing the circuit, and the fine product (passing material) is the final comminution product; Route 6: Comminution circuit 501, at natural moisture, starts at the vertical roller mill (VRM), the material goes on to be processed in a roller press (HPGR) and is then classified into a high acceleration screen (of at least 10G), where the coarse product (retained material) returns to the vertical roller mill (VRM), closing the circuit, and the fine product (passing material) is the final comminution product; Route 7: In comminution circuit 501, at natural moisture, the material is classified by the high acceleration screen (of at least 10G), and its fine product (passing material) is processed by the roller press (HPGR) or vertical mill (VRM) in up to three steps. The product of the latter consists of the fine product, which is the final product of comminution; and coarse material (retained material) is also considered a product as it is traded in this way (sinter feed); Route 8: Comminution circuit 501, at natural moisture, occurs in a roll crusher (RC) and can be performed in several steps in a comminution series using equipment with double rollers or more; and Route 9: The comminution circuit 501, at natural moisture, starts at the roller crusher (RC), and can occur in several steps in a comminution series using equipment with double rolls or more, and is then classified in a high acceleration screen (of at least 10G), where the coarse product (retained material) returns to the roller crusher (RC), closing the circuit, and the fine product (passing material) consists of the final product.

(17) Tests have shown that the present invention produces different particle size products of less than 16 mm, particle size of less than 8 mm, particle size with up to 99.8% passing material in the 1 mm mesh and between 60% to 85% passing material in the 0.074 mm mesh.

Example 1

(18) Pilot scale high-acceleration screen testing was performed using iron ore with about 50% passing material at 1 mm, 11% moisture and very high loss on ignition (LOI) (about 10%), which is characteristic of a cohesive material that is difficult to screen at natural moisture. The undersize recovery of the 1.0 mm mesh ranged from 35% to 41%, consistent with the amount of fines the sample had, which shows the efficiency of natural moisture screening even for such a cohesive material. Tables 1a, 1b and 1c show the chemical analysis, the particle size distribution of the tested sample and the undersize and oversize partition obtained in the pilot tests, as well as the mass balance of the test.

(19) TABLE-US-00001 TABLE 1a Chemical analysis Chemical analysis (%) Fe SiO.sub.2 P Al.sub.2O.sub.3 Mn TiO.sub.2 CaO MgO LOI 57.0 6.23 0.196 1.610 0.263 0.104 0.023 0.112 9.99

(20) TABLE-US-00002 TABLE 2b Particle size distribution of tests with high acceleration screen Test 1 Test 2 Mesh Particle Size Distribution (%) Particle Size Distribution (%) (mm) Feed Undersize Oversize Feed Undersize Oversize 40,000 100.00 100.00 100.00 100.00 100.00 100.00 31,500 98.04 100.00 96.69 98.38 100.00 97.50 25,000 96.38 100.00 93.89 97.79 100.00 96.59 19,000 92.17 100.00 86.79 95.07 100.00 92.40 16,000 90.09 100.00 83.27 92.63 100.00 88.64 12,500 86.11 100.00 76.57 88.87 100.00 82.84 10,000 82.59 100.00 70.62 85.43 100.00 77.54 8,000 79.09 100.00 64.72 82.21 100.00 72.57 6,300 75.60 100.00 58.83 78.23 100.00 66.44 2,400 57.07 99.27 28.05 57.64 99.50 34.97 1,000 48.37 88.05 21.09 47.01 86.52 25.62 840 47.30 85.75 20.86 45.75 83.34 25.40 710 45.93 82.71 20.64 44.22 79.48 25.12 500 43.42 77.12 20.25 41.58 72.67 24.74 210 37.50 64.55 18.90 35.58 58.24 23.31 150 34.83 59.25 18.04 33.11 53.11 22.28 106 32.20 54.09 17.14 31.06 49.34 21.17 74 31.54 52.92 16.84 29.16 44.80 20.69 45 26.16 43.86 14.00 24.90 38.04 17.78 37 23.77 39.36 13.05 23.32 35.60 16.66 25 18.69 30.06 10.87 19.70 30.13 14.05 15 12.93 19.95 8.10 15.00 23.15 10.59 10 9.40 14.00 6.24 11.72 18.26 8.17

(21) TABLE-US-00003 TABLE 3c Mass balance of tests with high acceleration screen. Flow % Mass Flow % Mass Test 1 Feed 100.00 Test 2 Feed 100.00 Undersize 40.70 Undersize 35.10 Oversize 59.30 Oversize 64.90

Example 2

(22) Tests were performed on the HPGR and the test results are presented in table 2. After two processing runs in the same equipment, it was possible to obtain 56% of material retained in a 0.074 mm mesh. This highlights the high reduction ratio of fine particles.

(23) TABLE-US-00004 TABLE 4 Particle size distribution of the HPGR tests. Press feed 1st run 2nd run % % % % % Size Individual Accumulated % Individual % % Individual Accumulated % (mm) Retained Retained Passing Retained Retained Passing Retained Retained Passing 3.360 0.39 0.39 99.61 0.02 0.02 99.98 0.01 0.01 99.99 1.000 38.53 38.92 61.08 21.16 21.18 78.82 13.72 13.72 86.28 0.710 4.68 43.60 56.40 5.75 26.93 73.07 4.57 18.29 81.71 0.500 5.13 48.73 51.27 5.55 32.47 67.53 4.59 22.88 77.12 0.420 1.89 50.62 49.38 2.65 35.12 64.88 2.40 25.28 74.72 0.300 5.71 56.33 43.67 6.32 41.45 58.55 6.96 32.24 67.76 0.210 4.18 60.51 39.49 5.00 46.45 53.55 5.37 37.61 62.39 0.150 6.02 66.53 33.47 7.42 53.86 46.14 7.48 45.09 54.91 0.074 7.06 73.59 26.41 9.77 63.63 36.37 11.42 56.50 43.50 0.045 4.33 77.93 22.07 6.18 69.81 30.19 7.30 63.81 36.19 bypass 22.07 100.00 0.00 30.19 100.00 0.00 36.19 100.00 0.00

Example 3

(24) Tests were performed in a vertical roller mill (VRM) and the results are presented in table 3. The tests were performed under high and low pressure conditions, 500 psi and 300 psi respectively, and under both conditions it was possible to reduce the material above 1 mm, which shows the good reduction ratio of particles in thicker fractions.

(25) TABLE-US-00005 TABLE 5 Particle size distribution of tests with vertical roller mill. Size High Pressure-1 run Low Pressure-2 runs (mm) Feed Product Feed Product 9.525 100.00 100.00 100.00 100.00 6.350 98.72 100.00 100.00 100.00 4.750 96.82 100.00 100.00 100.00 3.350 95.92 100.00 99.90 100.00 2.360 94.80 99.89 99.90 100.00 1.700 94.08 99.78 99.40 99.90 1.180 93.35 99.44 98.70 99.70 0.850 92.79 98.65 94.60 98.80 0.600 92.29 97.75 96.60 97.90 0.425 91.34 96.86 95.80 97.00 0.300 90.89 96.07 95.00 96.10 0.212 89.83 95.12 94.10 95.30 0.150 86.26 93.04 92.10 94.10 0.106 78.99 88.43 89.20 91.90 0.090 71.90 80.97 85.40 89.40 0.075 63.91 76.59 80.70 85.00 0.045 33.41 55.81 56.20 63.90

Example 4

(26) Pilot tests were performed using a roller crusher (RC) with iron ore with about 43% retained in 1 mm and the results are presented in table 4, showing that it is possible to reduce the material above 1 mm and provide a high generation of fine particles (less than 0.075 mm) Tests have shown that the roller crusher is efficient in reducing size for various initial particle sizes.

(27) TABLE-US-00006 TABLE 4 Particle size distribution of roller crusher tests. Size 1 2 4 5 6 (mm) Feed Run Runs Runs Runs Runs 1.00 43.68 13.34 3.88 0.36 0.2 0.12 0.500 56.86 25.92 15.39 6.09 3.99 2.00 0.150 79.93 45.12 33.00 28.70 25.43 21.71 0.106 84.40 50.21 37.41 35.75 32.36 28.81 0.075 88.47 53.73 40.31 41.29 37.78 33.25 0.045 56.79 42.70 46.40 42.32 35.99

(28) Numerous variations on the scope of protection of this application are permitted. Thus, it is emphasized that the present invention is not limited to the particular configurations/embodiments described above.