Cold-pressed solid agglomerate for the production of iron-nickel alloys, manufacturing process of the same, and, production process of an iron-nickel alloy

Abstract

The present invention relates to a cold-pressed solid agglomerate for producing iron-nickel alloys, the manufacturing process thereof, and a process for producing iron-nickel alloys. The present invention features a cold-pressed solid agglomerate with the following mass proportions: 80 to 95% by mass of laterite ore; 3 to 10% by mass of at least one binder; and 2 to 10% by mass of a carbon source. The agglomerate manufacturing process comprises the steps of (i) mixing the laterite ore with at least one binder and a carbon source; and (ii) cold pressing the mixture to form the agglomerate. The process of producing an iron-nickel alloy comprises the steps of (i) mixing the laterite ore with at least one binder and a carbon source; (ii) cold pressing the mixture to form an agglomerate; (iii) pre-reducing the solid agglomerate in a furnace with a controlled atmosphere; and (iv) melting the pre-reduced solid agglomerate in a furnace with a controlled atmosphere.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to iron-nickel alloys. More specifically, the present invention relates to a process for producing an iron-nickel alloy from a cold-pressed solid agglomerate.BACKGROUNDS OF THE INVENTION

[0002] The cold agglomeration process is a method used to compact fine materials (powder or granules), forming briquettes without the need to apply heat. This technique is used in industry to transform mineral-metallurgical raw materials into high-density briquettes, which can be easier to handle, store and transport.

[0003] Briquettes, or solid agglomerates, are a viable and sustainable option for providing the necessary metallic filler in the production of metal alloys, contributing to obtaining high-quality alloys and reducing material waste. They can be used as raw material in metallurgical furnaces for the production of alloys, and can be manufactured from various materials, depending on their application, such as: scrap metal, coal, coke fines or iron ore.

[0004] Nickel laterite ore is typically formed from limonite, garnierite, and sometimes from a magnesium silicate. This ore comes from the weathering of ultramafic or ultrabasic rocks, where nickel, due to its Ni 2+< ion, is able to replace Fe 2+< and Mg 2+< ions in the crystal lattice of these minerals.

[0005] Within the laterite ore there are zones with different concentrations of nickel, depending on the depth and climatic conditions of the environment in which they are found. These zones are classified as: limonite zone, intermediate zone and saprolite zone, the latter being the deepest and with the highest concentration of the metal, exceeding 3% of the total mass value.

[0006] Most of the nickel produced in the world comes from pyrometallurgical routes, and one of them is the production of iron-nickel by the RKEF (Rotary Kill Electric Furnace) process, used to treat saprolite-type laterite ore. Due to the high iron content and low nickel content in limonite fractions, this ore is not used as raw material for the process, as it would produce an alloy with a low content of the metal.

[0007] Nickel has a high carbothermic reduction capacity, that is, in the presence of carbon it is reduced more easily than iron oxide, for example. Accordingly, when making self-reducing mixtures with different levels of carbon, there will be less Fe formation, an increase in the FeO content in the slag, and greater incorporation of nickel into the alloy. The reduction reactions of nickel oxide by solid carbon are shown below:         NiO + C = Ni + CO (1)         2NiO + C = 2Ni + CO 2 (2)

[0008] The relative proportion of the products CO and CO 2 depends on the equilibrium of the system. Thus, reactions (1) and (2) occur simultaneously, indicating that NiO reacts with C to form Ni, CO and CO 2 .

[0009] Document CN102758092A describes a method for producing nickel iron by comprehensively utilizing low-grade lateritic nickel ore. The method comprises the following steps: after roasting, crushing, screening and grinding the raw lateritic nickel ore, adding coke powder or coal powder, proportionally mixing with a binding agent, carrying out cold pressing on the mixture to obtain a block, and curing the cold-pressed block to enhance the strength; and proportionally adding the lateritic nickel ore cold-pressed block with a certain strength and coke into a shaft furnace, and meanwhile, blowing hot air and oxygen into the shaft furnace.

[0010] Document BR102021018716 describes a cold-pressed solid agglomerate that uses an organic binder, the cold-pressed solid agglomerate containing a mixture that, in turn, comprises at least one main compound and at least one organic binder, wherein the at least one organic binder is obtained by the chemical reaction of starch under controlled pH through at least one alkali in aqueous medium and at room temperature. Furthermore, document BR102021018716 discloses a process for producing a cold-pressed solid agglomerate, comprising the steps of (i) mixing at least one main compound with at least one organic binder and (ii) cold-pressing the mixture to form an agglomerate, in which the at least one organic binder is obtained by the chemical reaction of starch under controlled pH through at least one alkali in aqueous medium and at room temperature.

[0011] Document US20170211166A1 describes a method for producing pellets by which, when nickel oxide ore is being pelletized and smelted to produce ferronickel, which is an iron-nickel alloy, it is possible to allow the smelting reaction to proceed effectively. A method for producing pellets is for producing pellets which are used in producing iron-nickel alloy and which are produced by mixing raw materials including nickel oxide ore and agglomerating the resulting mixture, wherein the method comprises: a mixing step for mixing at least nickel oxide ore, a carbonaceous reducing agent, and iron oxide to generate a mixture; and a pellet formation step for agglomerating the resulting mixture and forming pellets. In the mixing step, the mixture is generated such that the total weight of nickel and iron accounts for 30 wt % or more of the total weight of the pellets formed.

[0012] The existing iron-nickel alloy production processes on the market generally do not employ pre-reduced solid agglomerates in their process, nor do they consider catalytic elements in the agglomerate mixture. In addition, the combination of used raw materials, as well as the types of furnaces employed in the melting of the raw material, do not generate good efficiency in the production process as a whole.

[0013] The invention proposed herein solves the problems of the above-described state of the art in a simple and efficient way.SUMMARY OF THE INVENTION

[0014] The present invention has as its first objective to provide a cold-pressed solid agglomerate for the production of iron-nickel alloys and a manufacturing process thereof employing laterite ore and a carbon source in its composition.

[0015] The present invention has as its second objective to provide a process for the production of an iron-nickel alloy from a cold-pressed solid agglomerate that utilizes an efficient combination of the composition of the solid agglomerate, the type of furnace used, and the pre-reduction and melting steps of the raw material.

[0016] In order to achieve the above-described objectives, the present invention provides a cold-pressed solid agglomerate for the production of iron-nickel alloys comprising 80 to 95% by mass of laterite ore, 3 to 10% by mass of at least one binder, and 2 to 10% by mass of a carbon source.

[0017] The present invention further provides a process for manufacturing a cold-pressed solid agglomerate for the production of iron-nickel alloys, the process comprising the steps of (i) mixing 80 to 95% by mass of laterite ore, 3 to 10% by mass of at least one binder, and 2 to 10% by mass of a carbon source; and (ii) cold pressing the laterite ore, the at least one binder and the carbon source to form a solid agglomerate.

[0018] Finally, the present invention provides a process for producing an iron-nickel alloy from a cold-pressed solid agglomerate, the process comprising the steps of (i) mixing 80 to 95% by mass of laterite ore, 3 to 10% by mass of at least one binder, and 2 to 10% by mass of a carbon source; (ii) cold pressing the laterite ore, the at least one binder and the carbon source to form a solid agglomerate; (iii) pre-reducing the solid agglomerate in a furnace with a controlled atmosphere; and (iv) melting the pre-reduced solid agglomerate in a furnace with a controlled atmosphere.BRIEF DESCRIPTION OF THE FIGURES

[0019] The detailed description presented below refers to the attached figures and their respective reference numbers. Figure 1 shows an Ellingham diagram with the incorporation of nickel through the C / Fe ratio, as used in the present invention. Figure 2 shows the result of the agglomerate manufacturing process and a flowchart of the iron-nickel alloy production process of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Preliminarily, it should be emphasized that the following description will be based on a preferred embodiment of the invention. As will become apparent to any technician skilled on the subject, however, the invention is not limited to this particular embodiment.

[0021] The cold agglomeration process is a method used to compact fine materials (powder or granules), forming briquettes without the need to apply heat. It should be emphasized that the particle size for briquetting must be below 6.3 mm.

[0022] The present invention provides a cold-pressed solid agglomerate for the production of iron-nickel alloys. The cold-pressed solid agglomerate of the present invention comprises a mixture which, in turn, comprises the following proportions by mass: 80 to 95% by mass of laterite ore; 3 to 10% by mass of at least one binder; 2 to 10% by mass of a carbon source.

[0023] The carbon source is used in order to maximize the incorporation of nickel into the alloy, in which the carbon source is at least one of: charcoal, coal, anthracite coal, or other carbon sources. The higher incorporation of nickel can be explained by means of the C / Fe ratio of this mineral, as can be seen in the Ellingham diagram shown in Figure 1.

[0024] More preferably, the used laterite ore belongs to the saprolite zone, as it has a high nickel content when compared to other mineral zones.

[0025] Preferably, the at least one binder can be: starch or bentonite. More preferably, the at least one binder can be replaced by 4.5% to 6% organic starch, by using the reagents in the following mass proportions: Water: 83 to 87.5%; Starch: 12 to 16%; Sodium Hydroxide: 0.5 to 1%.

[0026] The present invention provides a manufacturing process for a cold-pressed solid agglomerate for the production of iron-nickel alloys. The manufacturing process for the cold-pressed solid agglomerate according to the present invention comprises the steps of (i) mixing laterite ore with at least one binder and a carbon source; and (ii) cold pressing the mixture to form an agglomerate.

[0027] The mixing step of the manufacturing process of the present invention comprises a mixture which, in turn, comprises the following mass proportions: 80 to 95% by mass of laterite ore; 3 to 10% by mass of at least one binder; 2 to 10% by mass of a carbon source.

[0028] Preferably, the manufacturing process for the cold-pressed solid agglomerate of the present invention comprises a drying step of the laterite ore, prior to the step of cold pressing the mixture, so that the laterite ore reaches a maximum moisture content of 10%.

[0029] Preferably, the manufacturing process of the cold-pressed solid agglomerate of the present invention comprises a step of separating the laterite ore with a 5 mm sieve before the drying step, in order to perform the granulometric adjustment of the raw material.

[0030] Preferably, after the pressing step, the manufacturing process of the cold-pressed solid agglomerate of the present invention comprises a step of drying the solid agglomerate at a temperature of 100 to 120 °C for 3 to 5 hours.

[0031] The present invention further provides a process for producing an iron-nickel alloy from a cold-pressed solid agglomerate. The process for producing an iron-nickel alloy from a cold-pressed solid agglomerate, according to the present invention, comprises the steps of (i) mixing the laterite ore with at least one binder and a carbon source; (ii) cold pressing the mixture to form a solid agglomerate; (iii) pre-reducing the solid agglomerate in a furnace with a controlled atmosphere; and (iv) melting the pre-reduced solid agglomerate in a furnace with a controlled atmosphere.

[0032] The step of mixing the laterite ore with at least one binder and a carbon source of the iron-nickel alloy production process of the present invention comprises a mixture which, in turn, comprises the following mass proportions: 80 to 95% by mass of laterite ore; 3 to 10% by mass of at least one binder; 2 to 10% by mass of a carbon source.

[0033] Preferably, the iron-nickel alloy production process according to the present invention comprises a step of drying the laterite ore before the step of cold pressing the mixture, so that the laterite ore reaches up to 10% moisture.

[0034] Additionally, before the cold pressing step of the laterite ore, the at least one binder, and the carbon source to form a solid agglomerate, the production process of an iron-nickel alloy of the present invention preferably comprises a step of separating the laterite ore with a 5 mm sieve before the drying step, in order to perform the granulometric adjustment of the raw material.

[0035] Preferably, after the pressing step, the manufacturing process of the cold-pressed solid agglomerate of the present invention comprises a step of drying the solid agglomerate at a temperature of 100 to 120 °C for 3 to 5 hours.

[0036] Preferably, the step of pre-reducing the solid agglomerate in a controlled atmosphere furnace of the present invention comprises pre-reducing the solid agglomerate in a furnace with an oxidizing-reducing atmosphere, such as an induction furnace, at a temperature between 1000 °C and 1200 °C for 25 to 70 min. More preferably, the pre-reducing step is carried out between 1000 °C and 1100 °C for 55 to 70 min or between 1100 °C and 1200 °C for 25 to 40 min.

[0037] Optionally, the step of pre-reducing the solid agglomerate in a controlled atmosphere furnace of the present invention may occur in a rotary kiln, of the RK (Rotary Kiln) type, at a temperature of 1050 °C to 1450 °C for 30 to 60 min.

[0038] Preferably, a temperature of 1200 °C is recommended because it is high enough to initiate the carbothermic reduction reaction of nickel in the solid agglomerate, but not so high as to cause problems with the melting of the solid agglomerates, or with excessive wear of the furnace. In addition, the temperature of 1200 °C is capable of achieving an efficient reduction rate for most applications. In turn, the temperature of 1050 °C is recommended in some cases in which the reduction speed is not so critical or when the furnace used is not capable of reaching higher temperatures. The reduction at 1050 °C requires a longer reaction time, but may be more suitable for some processes.

[0039] The step of melting the pre-reduced solid agglomerate in a controlled atmosphere furnace of the present invention comprises carrying out the melting at a temperature starting from 1400 °C. The optimum melting temperature is 1450 °C, where the incorporation contents of iron and nickel are higher.

[0040] Optionally, the pre-reducing and melting steps of the pre-reduced solid agglomerate can be carried out in the same batch in an induction furnace at higher temperatures, from 1450 °C to 1500 °C. In this way, one step is carried out subsequently to the other in the same induction furnace, reducing production time.

[0041] In order to test the quality of the solid agglomerates and the iron-nickel alloy produced from the same, three formulations were carried out for the composition of the cold-pressed solid agglomerates for the production of iron-nickel alloys, which are presented in Table 1 below: Table 1 MaterialRecipe 1Recipe 2Recipe 3Saprolite Ore89.63%88.05%86.50%Carbon Source (Charcoal)3.37%4.97%6.52%Bentonite5.51%5.49%5.49%Starch1.49%1.49%1.49%

[0042] Table 2 below shows the results obtained for the reduction of saprolite ore and the iron-nickel ratio (Fe / Ni) of the alloy. Table 2 Melting temperature °CMelting time (min)Fe incorporationNi incorporationFe / NiC / Fe 0.20 - recipe 314503055%90%9.4C / Fe 0.15 - recipe 214503045%90%7.7C / Fe 0.10 - recipe 114503030%90%5.1

[0043] Melting tests show that to increase the nickel content in pig iron, the iron incorporation in the alloy must be decreased. The C / O ratio of the solid agglomerate must be reduced to decrease the degree of metallization. When the metallization is low, the iron incorporation is reduced and the nickel content is increased. To improve the iron incorporation, the basicity of the solid agglomerate must be increased. According to the tests, to increase the incorporation of nickel in the alloy, the amount of reducing agent in the solid agglomerate must be decreased until it is sufficient to reduce only the nickel and not the iron, for example, Table 3, where the "optimal" content of reducing agent in the agglomerate was 8%, thus decreasing the incorporation of iron in the alloy.

[0044] The tests show that the nickel content in the alloy is inversely related to the carbon content of the solid agglomerate due to the lower incorporation of iron. The lower the incorporation of iron, the higher the incorporation of nickel. To increase the incorporation of iron, the basicity must be adjusted from 0.6 to 1.0.

[0045] Table 3 below shows the results obtained relating the percentage of nickel in the alloy to the carbon content of the agglomerate. Table 3 Reducing agent content in the solid agglomerate %Melting temperature (°C)Melting time (min)Basicity% Fe in the alloyFe incorporation% Ni in the alloyNi incorporation161450300.693.5894.341.7294.36101450300.692.3063.022.5396.5881450300.690.9853.173.0398.3861450300.687.3830.475.1095.7141450300.688.109.093.8891.4461450301.091.4628.825.4692.58

[0046] Table 4 below shows the results obtained relating the degree of metallization to the reducing agent content in the agglomerate. Table 4 Reducing agent in the solid agglomerate Total C / Fe (including coal outside the solid agglomerate reducing environment) Pre-reduction °C Pre-reduction min Fe τ % Fe M % Metallization % %C / Fe160.2620.55010506056.6545.1679.72120.2060.25610506053.9730.2656.07100.1720.22210506055.9125.8246.1880.1370.18710506055.5620.4336.7760.1030.15310506053.8213.2624.6440.0690.11910506053.585.7210.68

[0047] Tests showed that melting, when occurring inside the induction furnace, produces slag containing the unreduced constituents: SiO 2 , FeO, SiO 2 and MgO, and the iron-nickel alloy contains between 20% and 40% nickel. It is worth highlighting that, in the end, the alloy obtained can undergo refining and purification processes of phosphorus and sulfur before being sent to special steel production units.

[0048] Numerous variations falling within the scope of protection of the present application are permitted. In this way, it is reinforced that the present invention is not limited to the particular configurations / embodiments described above.

Claims

1. A cold-pressed solid agglomerate for the production of iron-nickel alloys, characterized in that it comprises: 80 to 95% by mass of laterite ore, wherein the laterite ore is an ore originating from the saprolite zone; 3 to 10% by mass of at least one binder; 2 to 10% by mass of a carbon source.

2. The agglomerate according to claim 1, characterized in that at least one binder is at least one of: starch; bentonite.

3. A manufacturing process for a cold-pressed solid agglomerate for the production of iron-nickel alloys, characterized in that it comprises the steps of: mixing 80 to 95% by mass of laterite ore, 3 to 10% by mass of at least one binder, and 2 to 10% by mass of a carbon source, wherein the laterite ore is an ore originating from the saprolite zone; and cold pressing the laterite ore, the at least one binder, and the carbon source to form a solid agglomerate.

4. The process according to claim 3, characterized in that it further comprises a step of drying the laterite ore to 10% moisture content before the mixing step.

5. The process according to claim 4, characterized in that it further comprises a step of separating the laterite ore with a 5 mm sieve before the drying step.

6. The process according to any one of claims 3 to 5, characterized in that it further comprises a step of drying the solid agglomerate after the cold pressing step of the mixture.

7. The process according to any one of claims 3 to 6, characterized in that it comprises, after the pressing step, an additional step of drying the solid agglomerate at a temperature of 100 to 120 °C for 3 to 5 hours.

8. A process for producing an iron-nickel alloy from a cold-pressed solid agglomerate, characterized in that it comprises the steps of: mixing 80 to 95% by mass of laterite ore, 3 to 10% by mass of at least one binder, and 2 to 10% by mass of a carbon source, wherein the laterite ore is an ore originating from the saprolite zone; and cold pressing the laterite ore, the at least one binder and the carbon source to form a solid agglomerate; pre-reducing the solid agglomerate in a furnace with a controlled atmosphere; and melting the pre-reduced solid agglomerate in a furnace with a controlled atmosphere.

9. The process according to claim 8, characterized in that the step of pre-reducing the solid agglomerate in a furnace with a controlled atmosphere is carried out in an induction furnace or in a rotary kiln RK.

10. The process according to claim 8 or 9, characterized in that the step of pre-reducing the solid agglomerate in a furnace with a controlled atmosphere is carried out at a temperature between 1000 °C and 1450 °C for 25 to 70 min.

11. The process according to any of claims 8 to 10, characterized in that the step of melting the pre-reduced solid agglomerate is carried out at a temperature greater than or equal to 1400 °C.

12. The process according to claim 8, characterized in that the steps of pre-reducing and melting the pre-reduced solid agglomerate are carried out in the same batch in an induction furnace at temperatures of 1450 °C to 1500 °C.

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