PROCESS FOR THE PRODUCTION OF IRON ORE FINES AGGLOMERATE AND THE AGGLOMERATED PRODUCT

Abstract

The present invention relates to a process for the production of iron ore fines agglomerate, resistant to handling, transport, and contact with water. The process consists of mixing iron ore fines with sodium silicate, nanomaterials, catalyst, fluxes and plasticizer; adjusting the moisture of the mixture; agglomerating the mixture by pelletizing, briquetting or extrusion; performing curing at room temperature. The process does not require energy input for heat treatment and allows obtaining an agglomerated product with high physical and metallurgical performance to replace metallic load, including sinter, in reduction furnaces, without the emission of harmful gases such as CO.sub.2, dioxins, furans, and SO.sub.x.

Claims

1. Process for the production of iron ore fines agglomerate for metallic load replacement in reduction furnaces, characterized by comprising the following steps: a) mixing a nanomaterial and a catalyst to sodium silicate for preparing the binder mixture; b) mixing 1-5% of the binder mixture from step a) with 70-100% iron ore fines, 0-30% fines of fluxes and 0-5% plasticizer in intensive mixer; c) adjusting the moisture in such a way as to obtain the amount of 0-30% of water weight in the mixture; d) performing agglomeration by pelletizing, briquetting or extrusion; e) keeping the agglomerates at room temperature for 2-10 days for curing; wherein the following dosages are used: 0.05 to 2% by weight of nanomaterial relative to sodium silicate; and 0.05 to 5% by weight of catalyst relative to sodium silicate.

2. Process, according to claim 1, characterized in that it does not use fossil fuels, does not require energy input for heat treatment, and there are no emissions of CO.sub.2, dioxins, furans, and SO.sub.x.

3. Process, according to claim 1, characterized in that the nanomaterial used in step a) is selected from the group consisting of carbon nanotube, exfoliated graphite, functionalized micro-silicate, tubular nano-silica, tubular halloysite, carbon nanofiber, and graphene.

4. Process, according to claim 1, characterized in that the catalyst used in step a) is selected from the group consisting of sodium pyrophosphate, magnesium hydroxide, propylene carbonate, glycerin carbonate, calcium hydroxide, calcium oxide, glycerol triacetate, aluminum chloride, aluminum hydroxide, triacetin, diacetin, and metallic aluminum.

5. Process, according to claim 1, characterized in that the sodium silicate used in step a) has a SiO.sub.2/Na.sub.2O molar ratio from 1.8 to 4.5 and solids percentage from 36 to 48%.

6. Process, according to claim 1, characterized in that the iron ore fines used in step b) have granulometry less than 10 mm, iron content (Fe.sub.Total) from 30 to 68%, and are selected from the group consisting of sinter feed, pellet feed, and ultrafine iron ore tailings.

7. Process, according to claim 1, characterized in that the fluxes used in step b) are selected from the group consisting of calcium hydroxide, calcitic limestone, dolomitic limestone, calcined magnesite, serpentinite, talc, dunite, and olivine.

8. Process, according to claim 1, characterized in that the plasticizer used in step b) is selected from the group consisting of bentonite, corn starch, cassava starch, glycerin, and CMC (carboxymethyl cellulose).

9. Process, according to claim 1, characterized in that the mixing of step b) is carried out in an intensive mixer for 10 to 180 seconds.

10. Process, according to claim 1, characterized in that the curing of step e) is carried out in a covered place in the first 2 days until the briquettes reach sufficient water resistance to be exposed to weather and transportation.

11. Process, according to claim 1, characterized in that, in step e), drying can be carried out in a horizontal furnace for 10 to 30 minutes at a temperature of 100 to 550° C.

12. Iron ore fines agglomerate produced by the process as defined on claims 1 to 10 characterized by having chemical, physical and metallurgical qualities suitable for replacing metallic load in reduction furnaces.

13. Iron ore fines agglomerate according to claim 12, characterized by being resistant to handling, transport, water, and weathering.

14. Iron ore fines agglomerate, according to claim 12, characterized by having the a “pillow” type briquette shape whose dimensions are 20-40 mm×10-30 mm×5×20 mm.

15. Iron ore fines agglomerate, according to claim 12, characterized by having the shape of a spherical pellet whose diameter is 10-30 mm.

16. Iron ore fines agglomerate, according to claim 12, characterized by having a cylindrical shape of 5-30 mm in diameter and 5-30 mm in height after extrusion.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0045] The present invention is described in detail based on the respective figures:

[0046] FIG. 1 illustrates a simplified block diagram of the process for the production of agglomerates from iron ore fines.

[0047] FIG. 2 illustrates a graph showing the reduction of curing time at room temperature as a function of the use of catalyst.

[0048] FIG. 3 shows the granulometric distribution of the sinter feed sample used in the pilot test.

DETAILED DESCRIPTION OF THE INVENTION

[0049] Although the present invention may be susceptible to different embodiments, the preferred embodiments are shown in the Figures and in the following detailed discussion, with an understanding that the present description must be considered as an exemplification of the principles of the invention, and they are not intended to limit the present invention to what was hereby illustrated and described.

[0050] The subject matter of the present invention will be detailed hereafter by the way of example and not limitative, since the materials and methods hereby disclosed may comprise different details and procedures without escaping from the scope of the invention. Unless otherwise stated, all parts and percentages shown below are weight percentages.

[0051] The main approach of this invention is related to a process for the production of iron ore fines agglomerate comprising the following steps:

a) mixing a nanomaterial and a catalyst to sodium silicate for preparing the binder mixture;
b) mixing 1-5% of the binder mixture from step a) with 70-100% iron ore fines, 0-30% fines of fluxes and 0-5% plasticizer in intensive mixer;
c) adjusting the moisture in such a way to obtain the amount of 0-30% of water weight in the mixture;
d) performing the agglomeration by pelletizing, briquetting or extrusion;
e) keeping the agglomerates at room temperature for 2-10 days for curing;
wherein the following dosages are used:
0.05 to 2% by weight of nanomaterial relative to sodium silicate;
0.05 to 5% by weight of catalyst relative to sodium silicate.

[0052] The process for the production of agglomerate, represented by the block diagram of FIG. 1, preferably begins with the mixing and dispersion of the additives in sodium silicate, which is the binder agent applied in the process.

[0053] The sodium silicate used in the process has preferably the SiO.sub.2/Na.sub.2O molar ratio of from 1.8 to 4.5, 36 to 48% of solids, and the following composition: 5-14.6% of Na.sub.2O; 22-33.2% of SiO.sub.2; 54.0-73.0% of H.sub.2O.

[0054] As an additive to sodium silicate, there is the addition of nanomaterial under mechanical stirring, at a dosage of 0.05 to 2% by weight relative to the amount of sodium silicate used in the mixture. The nanomaterial is selected from the group consisting of: carbon nanotube, exfoliated graphite, functionalized microsilicate, tubular nano silica, tubular halloysite, carbon nanofiber, and graphene.

[0055] As a catalyst to accelerate the curing process at room temperature, sodium pyrophosphate, magnesium hydroxide, propylene carbonate, glycerin carbonate, calcium hydroxide, calcium oxide, glycerol triacetate, aluminum chloride, aluminum hydroxide, triacetin, diacetin, and metallic aluminum can be used. Under mechanical stirring, 0.05 to 5% by weight of catalyst relative to the amount of sodium silicate used in the mixture are added.

[0056] The second step of the process for the production of agglomerate consists on adding 1 to 5% of the agglomerating mixture (formed by sodium silicate, nanomaterial, and catalyst), to from 70 to 100% by weight of iron ore fines, 0 to 30% by weight of fluxes and 0 to 5% by weight of plasticizer. Mixing should preferably be carried out in an intensive mixer for 10-180 seconds.

[0057] The iron ore fines to be used in the process must have a particle size distribution of less than 10 mm, d.sub.90 between 1 and 8 mm, and maximum moisture of 25%. Sinter feed, pellet feed, and ultrafine iron ore tailing can be used, which, in the prior art, is disposed of in tailings dams. The preferred chemical composition of ore fines consists of 30 to 68% Fe.sub.Total, 0.5 to 15% SiO.sub.2, 0.1 to 5.0% Al.sub.2O.sub.3, 0.001 to 0.1% P, 0.1 to 2% Mn and 0.1 to 8% PPC (loss on ignition).

[0058] The fluxes used in the process for the production of agglomerates are selected from the group consisting of calcium hydroxide, calcitic limestone, dolomitic limestone, calcined magnesite, serpentinite, talc, dunite, and olivine.

[0059] The plasticizing agent used in the process for the production of agglomerate is selected from the group consisting of bentonite, corn starch, cassava starch, glycerin, and CMC (carboxymethyl cellulose).

[0060] The third step of the process for the production of agglomerate is to adjust the moisture by adding water in such a way that the mixture has optimal moisture (0 to 30%) for the subsequent agglomeration process.

[0061] The fourth step of the process for the production of agglomerate consists of carrying out agglomeration by pelletizing, briquetting, or extrusion.

[0062] If the agglomeration method by briquetting is chosen, the mixture should preferably contain moisture in the range of 2-10%. The briquetting can be carried out by means of press with rollers containing cavities appropriate for obtaining briquettes with the dimensions of 20-40 mm×10-30 mm×5-20 mm, and with the necessary pressure adjustment to obtain briquettes with bulk density between 2.5 to 3.5 g/cm.sup.3. Bulk density control is necessary to obtain briquettes with adequate porosity.

[0063] If the agglomeration method by pelletizing is chosen, the mixture should preferably contain moisture in the range of 8-11%. The pelletizing process can be carried out in a rotary disc or drum, forming spherical pellets with 10-30 mm in diameter.

[0064] If the agglomeration method by extrusion is chosen, the mixture should preferably contain moisture in the range of 10-30%. The extrusion process can be carried out on extruders which, preferably, allow the formation of cylindrical agglomerates of 530 mm in diameter and 5-30 mm in height.

[0065] The fifth step of the process for the production of agglomerate consists in curing at room temperature.

[0066] The use of catalysts to promote the hardening of sodium silicate is efficient in reducing the curing time from 15 days to 2 days, thereby allowing the transport and handling of the product in rainy conditions (bad weather). The catalyst promotes the formation of insoluble compounds and polymerization of sodium silicate, making the product more resistant to water in a shorter cure time, as shown in FIG. 2.

[0067] Complete curing at room temperature, which occurs from 2 to 10 days, allows the final moisture of the agglomerates to be less than 3%.

[0068] Optionally, if it is necessary that the agglomerates get resistance in the shortest possible time, it can be chosen to perform the drying in horizontal furnace for 10 to 30 minutes at a temperature of from 100 to 550° C. However, this option is not recommended because it is not considered an environmentally sustainable alternative.

[0069] The iron ore agglomerate obtained by means of the present invention is presented as an alternative to replace metallic load in reduction furnaces since it presents adequate chemical, physical and metallurgical quality, such as presented in Table 1, Table 2 and Table 3 as follows.

TABLE-US-00001 TABLE 1 Chemical quality of the agglomerates obtained by means of the process of the present invention Briquettes FeT (30-68%); SiO.sub.2 (0.5-15%); Al.sub.2O.sub.3 (0.1-5%); P (0.001 to 0.1%); Mn (0.1-2%); CaO (0-15%), MgO (0-5%); PPC (0.1 to 8%). Pellets FeT (30-68%); SiO.sub.2 (0.5-15%); Al.sub.2O.sub.3 (0.1-5%); P (0.001 to 0.1%); Mn (0.1-2%); CaO (0-15%), MgO (0-5%); PPC (0.1 to 8%). Extruded FeT (30-68%); SiO.sub.2 (0.5-15%); Al.sub.2O.sub.3 (0.1-5%); P (0.001 to 0.1%); Mn (0.1-2%); CaO (0-15%), MgO (0-5%); PPC (0.1 to 8%).

TABLE-US-00002 TABLE 2 Metallurgical quality of the agglomerates obtained by means of the process of the present invention Briquettes ISO 7215 reducibility: >60% ISO 4696-2 RDI: % −2.8 mm: <25% ISO 4698 swelling: <25% Pellets ISO 7215 reducibility: >60% ISO 4696-2 RDI: % −2.8 mm: <25% ISO 4698 swelling: <25% Extruded ISO 7215 reducibility: >60% ISO 4696-2 RDI: % −2.8 mm: <25% ISO 4698 swelling: <25%

TABLE-US-00003 TABLE 3 Physical quality of the agglomerates obtained by means of the process of the present invention Briquettes JIS M8711 ShatterTest: % +10 mm: >90% ISO 3271 Tumbler Test: % +6.3 mm: >85% ISO 3271 Abrasion: % −0.5 mm: <10% ISO 8371 Crackling: % −6.3 mm: <5% Shatter Test JIS M8711 *Weathering: % +10 mm: >80% Dry compressive strength: daN/briquette >200 Pellets JIS M8711 Shatter Test: % +10 mm: >90% ISO 3271 Tumbler Test: % +6.3 mm: >85% ISO 3271 Abrasion: % −0.5 mm: <15% ISO 8371 Crackling: % −6.3 mm: <5% JIS M8711 Shatter Test *Weathering: % +10 mm: >80% Dry compressive strength: daN/briquette >150 Extruded JIS M8711 Shatter Test: % +10 mm: >90% ISO 3271 Tumbler Test: % +6.3 mm: >85% ISO 3271 Abrasion: % −0.5 mm: <15% ISO 8371 Crackling: % −6.3 mm: <5% Shatter Test JIS M8711 *Weathering: % +10 mm: >80% *weathering: immersion into water for 1 hour.

Example

[0070] In order to evaluate the quality, characteristics, and performance of the agglomerates produced by means of the process described by the present invention, pilot scale tests were performed for the production of briquettes, using the sinter feed as iron ore fines.

[0071] The sinter feed used had moisture of less than 8% and d.sub.90 between 2 to 8 mm. The particle size distribution curve is shown in FIG. 3, wherein the sample used was found to be in the granulometric range evidenced by the hatched area. The tests were carried out in batches of 100 kg of sinter feed each.

[0072] The sodium silicate solution used presented a SiO.sub.2/Na.sub.2O molar ratio of 2.15, solids percentage of 47%, being composed by 14.6% Na.sub.2O, 31,4% SiO.sub.2, and 54% H.sub.2O. The solution presented true density of 1.57 g/cm.sup.3 and viscosity of 1175 cP at 25° C. Functionalized microsilicate was added at a dosage of 0.1% relative to the amount of sodium silicate used in the mixture. The calcium hydroxide catalyst was added at a dosage of 2.5%. Mechanical mixing was performed for 5 minutes to obtain the final binder mixture.

[0073] 3% of said binder mixture was added to 71.7% of sinter feed, 25% of fines of fluxes (calcitic limestone and serpentinite) and 0.3% of bentonite. Mixing was carried out in the Eirich intensive mixer for 120 seconds.

[0074] Briquettes were produced using a Komarek briquetting press, at 200 Bar, which allowed the formation of “pillow” type morphology briquettes, with dimensions of 25×20×15 mm and moisture <0.5%. Curing was carried out at room temperature for 5 days.

[0075] The quality of the briquettes was evaluated concerning physical, chemical, and metallurgical properties, according to procedures specified in standards for the evaluation of iron ores.

[0076] The compression strength was evaluated using dry briquettes in an automatic press with a ±5 daN sensitivity, to evaluate the compressive load that causes its breakdown. The same test was performed with briquettes after immersion in water for a period of 1 hour. The average result obtained for dry briquettes was >120 daN/briquettes in the largest area (25×20 mm), and for briquettes, after immersion, there was a 30% resistance drop.

[0077] The test for abrasion resistance and tumble indices was performed using 1.5 kg of dry briquettes subjected to 464 revolutions in a drum. At the end of the test, the mass was sifted in sieves with openings of 6.3 mm and 0.5 mm. The tumble indices (ISO 3271), which consists of the percentage of mass retained at 6.3 mm, was >85%. The abrasion indices (ISO 3271), which consists of the percentage of passing mass in 0.5 mm, was <15%.

[0078] The shatter strength test was performed with a 3 kg sample of dry briquettes subjected to four successive drops of three meters. At the end of the last drop, the mass was sifted using a sieve with a 10 mm opening. The Shatter Strength Index (Shatter—JIS M8711), which consists of the mass percentage greater than 10 mm, was >95%.

[0079] For determining the decrepitation index (DI), the test mass was rapidly heated from room temperature up to 700° C., maintained at this temperature and then air cooled until reaching room temperature. Sieving was carried out with a sieve containing 6.3 mm square openings. The Decrepitation Index, which consists of the mass percentage of the material with a size greater than 6.3 mm, was <5%.

[0080] The reducibility index (RI) of the briquettes has been evaluated according to ISO 7215, under conditions similar to the conditions that prevail in the blast furnace reduction zone. The average result obtained was >60%.

[0081] The low-temperature reduction-degradation test (RDI) was performed in accordance with ISO 4696-2, after reduction with CO and N gases under conditions similar to the low-temperature reduction-zone of the blast furnace. The average result was <15%.

[0082] Table 4 presents a comparison between the physical quality of the briquette produced by the process of the present invention in relation to other products such as sinter (obtained by means of the traditional sintering process), pellet (obtained by means of the traditional pelletizing process), and the commercial granules from Brazil and Australia. It is possible to prove that the briquette produced by means of the process of the present invention has high physical and metallurgical performance and, for this reason, it is considered as an alternative for substituting the metallic load of reduction furnaces with less environmental impact.

[0083] Note that, in Table 4, the “RDI” acronym refers to the degradation test under low-temperature reduction, “S” corresponds to the permeability index, “ΔPmax” corresponds to the maximum gas pressure drop, “T.sub.S200” corresponds to the dripping start temperature, “Td” corresponds to the softening end temperature, and “ΔT” refers to the temperature gradient corresponding to the softening and melting zone (Td−T.sub.S200).

TABLE-US-00004 TABLE 4 Comparison of the briquette quality parameters obtained by means of the process of the present invention Decrepita- Re- Fines of Tumble Abrasion tion RDI ducibility S ΔP max TS.sub.200 ΔT Td adherents % > 6.3 mm % < 0.5 mm % > 4.75 mm %-2.8 mm % kg*C/cm.sup.2 mmH.sub.20 ° C. ° C. ° C. % Vale BRIQUETTE 85 10 0.1 15 60 30 3000 1150 200 1350 0.5 Vale Sinter 65 NA NA 25 65 30 3000 1150 200 1350 NA Vale Pellet 90 6 0 5 60 100 5000 1100 300 1400 NA Vale Granulate 1 75 18 3 26 66 45 3247 1087 312 1427 2.8 Vale Granulated 2 79 15 2 15 58 41 3440 1104 250 1392 3 Vale Granulated 3 81 15 0.5 32 64 30 2363 1156 296 1457 2.02 Vale Granulated Average 78 16 2 24 63 38 3017 1116 286 1425 3 AUS Granulated 1 85 10 6 26 56 56 4897 1111 282 1406 3.89 AUS Granulated 2 85 8 3 19 70 44 4897 1128 269 1429 0.96 AUS Granulated 3 85 9 4 23 60 34 3676 1146 228 1418 2 AUS Granulated Average 85 9 4 23 62 45 4490 1128 260 1418 2

[0084] Thus, although only some embodiments of the present invention have been shown, it will be understood that various omissions, substitutions, and changes can be made by a skilled person, without departing from the spirit and scope of the present invention. The described embodiments should be considered in all aspects only as illustrative and not restrictive.

[0085] It is expressly provided that all combinations of the elements that perform the same function substantially in the same manner to achieve the same results are within the scope of the invention. Substitutions of elements from one described embodiment to another are also fully intended and contemplated.