A method for improving the nickel grade of ferronickel products through pyrometallurgical smelting of laterite ore

Abstract

The application discloses a method for improving the nickel grade of ferronickel products in the pyrometallurgy of laterite nickel-iron, wherein carbon with a particle size of 20-30 mm is added to the laterite before roasting; and carbon with a particle size of 20-30 mm is added to the calcine obtained after roasting the laterite. Through twice carbon addition, the carbon addition amount of the two times of carbon addition is accurately controlled, the Si content of the ferronickel product is accurately controlled to be 0.8-1.0 wt%, the Fe content is 77-80 wt%, and the Ni content is correspondingly increased by 3-5%. The Fe content of the slag is 7-10 wt%. Although twice carbon addition is needed, the total amount of carbon addition is much lower than the amount of one-time carbon addition in the prior art. The method accurately selects the reduction at different stages, greatly reduces the amount of reducing agent, reduces the Fe and Si grades in the ferronickel, correspondingly increases the Ni grade, and settles the ferronickel sales according to the Ni point. The increase of the Ni grade of the unit product also greatly reduces the production cost of the unit product.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metallurgical industry, and particularly relates to a method for improving the nickel grade of products in the fire smelting of laterite nickel-iron. BACKGROUND

[0002] The RKEF nickel-iron process is a new fire smelting technology of nickel-iron in recent years. The wet laterite ore with a surface moisture content of 30-35% in the raw material stack is dewatered to a surface moisture content of about 20% by a drying kiln after being proportioned by a shovel loader and an excavator, and then the dry laterite ore is proportioned with a reducing agent and then enters a rotary kiln for further dewatering, roasting and pre-reducing. The high-temperature calcine produced is added into a furnace top bin, and the hot calcine is added into an electric furnace through a feeding pipe for further heating, reducing and melting, to produce flue gas containing a high content of CO and a melt. The melt forms coarse nickel-iron alloy and slag due to the difference in density. The electric furnace flue gas is used as part of the fuel of the rotary kiln after being cooled and dedusted. The electric furnace slag is intermittently discharged through a slag discharge port and flows into a dry slag field through a slag chute. The molten nickel-iron is periodically discharged through a nickel-iron discharge port and is cast into nickel-iron blocks through a nickel-iron chute.

[0003] According to the reduction properties and reduction capacities of the oxides in the laterite ore, NiO>CoO>Fe2O3>FeO>SiO2>CaO. The reaction temperature of NiO is 450 DEG C, and the reduction of NiO is basically completed in the rotary kiln. The reaction temperature of Fe2O3 is 550 DEG C, and most of the reduction of Fe2O3 starts in the rotary kiln. The reaction temperature of FeO is 750 DEG C, and a small part of the reduction of FeO is completed in the rotary kiln and most of the reduction is completed in the electric furnace. The reaction temperature of SiO2 is 1637 DEG C, and the region with the reaction condition is only in the polar circle region. To improve the nickel grade of the products, the grade of non-nickel elements in the nickel-iron products needs to be reduced, mainly the grade of iron and silicon. However, when the silicon content in the nickel-iron is lower than 0.8%, the nickel-iron discharge process is severely splashed, the flue gas volume is large, and the production operation is difficult. SUMMARY

[0004] In view of the problems in the prior art, the present application provides a method for improving the nickel grade of nickel-iron products in the fire smelting of laterite nickel-iron. The method controls the carbon addition amount of the two times of carbon proportioning accurately, and controls the silicon content in the nickel-iron in the lower limit range of 0.8-1%. Although the method needs to proportion carbon twice, the total amount of the carbon proportioning is much lower than the amount of the carbon proportioning in the prior art. The method accurately selects the reduction at different stages, greatly reduces the amount of the reducing agent, reduces the grade of iron and silicon in the nickel-iron, and correspondingly improves the nickel grade. The nickel-iron is sold according to the nickel points, the unit product nickel grade is improved, and the unit product production cost is also greatly reduced. The present application specifically includes the following contents:

[0005] A method for improving the nickel grade of ferronickel product in a ferronickel pyrometallurgical process of laterite, the ferronickel pyrometallurgical process of laterite comprising: roasting laterite to obtain calcine; electric furnace smelting the calcine to obtain ferronickel product and slag, further comprising:

[0006] (1) primary carbon addition: before roasting the laterite, adding carbon with a particle size of 20-30 mm to the laterite, the amount of added carbon meeting the carbon requirement for reducing more than 98% of NiO, more than 80% of Fe2O3, and 20-30% of FeO in the subsequent roasting;

[0007] (2) secondary carbon addition: adding carbon with a particle size of 20-30 mm to the calcine obtained after roasting the laterite, the amount of added carbon meeting the carbon requirement for reducing SiO2 within the electrode core circle and the silicon content of the ferronickel product being 0.8-1.0% in the subsequent electric furnace smelting.

[0008] Preferably, the laterite contains 1.8-2.5 wt% of nickel and 77-85 wt% of iron.

[0009] Preferably, the amount of carbon added in the primary carbon addition is 2-3 wt% of the mass of the laterite.

[0010] Preferably, the amount of carbon added in the secondary carbon addition is 0.5-1 wt% of the mass of the calcine.

[0011] Preferably, the carbon added in (1) and (2) is semicoke particles containing 82-86 wt% of fixed carbon.

[0012] Preferably, the ferronickel product contains 0.8-1.0 wt% of silicon, 77-80 wt% of iron, and 15-18 wt% of nickel, and the slag contains 7-10 wt% of iron.

[0013] The beneficial effects of the present application are:

[0014] (1) The method disclosed in the present application adds carbon with a particle size of 20-30 mm to the laterite before roasting the laterite, the amount of added carbon meeting the carbon requirement for reducing more than 98% of NiO, more than 80% of Fe2O3, and 20-30% of FeO in the subsequent roasting; adds carbon with a particle size of 20-30 mm to the calcine obtained after roasting the laterite, the amount of added carbon meeting the carbon requirement for reducing SiO2 within the electrode core circle and the silicon content of the ferronickel product being 0.8-1.0% in the subsequent electric furnace smelting. Through secondary carbon addition, the amount of carbon added in the two carbon additions can be precisely controlled, so that the silicon content of the ferronickel product is precisely controlled to be 0.8-1.0 wt%, the iron content is precisely controlled to be 77-80 wt%, the nickel content is precisely controlled to be 15-18 wt%, and the slag contains 7-10 wt% of iron.

[0015] (2) Although the method disclosed in this invention requires two carbon mixing processes, the total amount of carbon mixing is much lower than the amount of carbon mixing in one process in the prior art. This method makes precise selective reduction at different stages, which greatly reduces the amount of reducing agent used, while reducing the iron and silicon grades in ferronickel and correspondingly increasing the nickel grade. Ferronickel is sold based on nickel points, and the increase in the nickel grade of the unit product also greatly reduces the production cost of the unit product. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the process flow of the method disclosed in this invention. Detailed Implementation

[0017] The following is in conjunction with the appendix Figure 1 The present invention will be described in detail below with reference to specific embodiments. The embodiments shown below are not intended to limit the scope of the invention as described in the claims. Furthermore, the complete contents of the configurations shown in the embodiments below are not limited to those necessary for the solution of the invention as described in the claims.

[0018] Example 1

[0019] Reference Appendix Figure 1 The arrows in the diagram indicate the direction of material flow. A method for improving the nickel grade of ferro-nickel products through pyrometallurgical smelting of laterite ore includes: roasting the laterite ore in a rotary kiln to obtain roasted sand; and smelting the roasted sand in an electric furnace to obtain ferro-nickel products and slag. The laterite ore contains 1.8 wt% nickel and 77 wt% iron.

[0020] (1) Primary carbon addition: The dry laterite ore is added to the batching process after drying in the drying kiln. This is mainly to meet the reducing agent requirements for nickel reduction in the rotary kiln and most of the iron reduction in the electric furnace. Before the laterite ore enters the rotary kiln for roasting, semi-coke particles with a particle size of 25mm are added to the laterite ore. The semi-coke particles contain 84wt% carbon. The amount of carbon added is sufficient to meet the carbon requirements for the subsequent roasting process to reduce more than 98% of NiO, more than 80% of Fe2O3, and 20-30% of FeO. Specifically, the amount of carbon added in the primary carbon addition is 2wt% of the mass of the laterite ore.

[0021] (2) Secondary carbon addition: Secondary carbon addition is carried out in the two central chambers of the furnace top chamber. 25mm semi-coke particles are added to the roasted sand obtained after roasting the laterite ore. The addition is controlled uniformly by a slanted funnel bar valve. The main purpose is to reduce silicon within the electrode core. The semi-coke particles contain 84wt% carbon. The amount of carbon added meets the requirements for reducing SiO2 within the electrode core during subsequent electric furnace smelting and for achieving a silicon content of 0.8% in the nickel-iron product. Specifically, the amount of carbon added in the secondary carbon addition is 0.5wt% of the roasted sand mass.

[0022] The nickel-iron product obtained in this embodiment contains 0.8 wt% Si, 77 wt% iron, and 18 wt% nickel, while the slag contains 10 wt% iron.

[0023] Example 2

[0024] A method for improving the nickel grade of ferronickel-nickel products through pyrometallurgical smelting of laterite ore, the pyrometallurgical process comprising: roasting the laterite ore to obtain roasted ore; and smelting the roasted ore in an electric furnace to obtain ferronickel-nickel products and slag. The laterite ore contains 2.2 wt% nickel and 85 wt% iron.

[0025] (1) Primary carbon addition: Before roasting the laterite ore, 25mm semi-coke particles are added to the laterite ore. The semi-coke particles contain 84wt% carbon. The amount of carbon added is sufficient to meet the carbon requirements for the subsequent roasting process to reduce more than 98% of NiO, more than 80% of Fe2O3, and 30% of FeO. Specifically, the amount of carbon added in the primary carbon addition is 3wt% of the mass of the laterite ore.

[0026] (2) Secondary carbon addition: Add semi-coke particles with a particle size of 25mm to the roasted sand obtained after roasting laterite ore. The semi-coke particles contain 84wt% carbon. The amount of carbon added is sufficient to complete the reduction of SiO2 in the electrode center circle during subsequent electric furnace smelting and to ensure that the silicon content of the nickel-iron product is 1.0%. Specifically, the amount of carbon added in the secondary carbon addition is 1wt% of the mass of the roasted sand.

[0027] The nickel-iron product obtained in this embodiment has a Si content of 1.0 wt%, an iron content of 80 wt%, and a nickel content of 18%, while the slag has an iron content of 10 wt%.

[0028] Example 3

[0029] A method for improving the nickel grade of ferronickel-nickel products through pyrometallurgical smelting of laterite ore, the pyrometallurgical process comprising: roasting the laterite ore to obtain roasted ore; and smelting the roasted ore in an electric furnace to obtain ferronickel-nickel products and slag. The laterite ore contains 1.8 wt% nickel and 85 wt% iron.

[0030] (1) Primary carbon addition: Before roasting the laterite ore, 25mm semi-coke particles are added to the laterite ore. The semi-coke particles contain 84wt% carbon. The amount of carbon added is sufficient to meet the carbon requirements for the subsequent roasting process to reduce more than 99% of NiO, more than 85% of Fe2O3, and 23% of FeO. Specifically, the amount of carbon added in the primary carbon addition is 2wt% of the mass of the laterite ore.

[0031] (2) Secondary carbon addition: Add semi-coke particles with a particle size of 23 mm to the roasted sand obtained after roasting laterite ore. The semi-coke particles contain 84 wt% carbon. The amount of carbon added is sufficient to complete the reduction of SiO2 in the electrode center circle during subsequent electric furnace smelting and to ensure that the silicon content of the nickel-iron product is 0.85%. Specifically, the amount of carbon added in the secondary carbon addition is 0.5 wt% of the mass of the roasted sand.

[0032] The nickel-iron product obtained in this embodiment has a Si content of 0.8 wt%, an iron content of 80 wt%, and a nickel content of 13%, while the slag has an iron content of 10 wt%.

[0033] Example 4

[0034] A method for improving the nickel grade of ferronickel-nickel products through pyrometallurgical smelting of laterite ore, the pyrometallurgical process comprising: roasting the laterite ore to obtain roasted ore; and smelting the roasted ore in an electric furnace to obtain ferronickel-nickel products and slag. The laterite ore contains 2.5 wt% nickel and 77 wt% iron.

[0035] (1) Primary carbon addition: Before roasting the laterite ore, 25mm semi-coke particles are added to the laterite ore. The semi-coke particles contain 84wt% carbon. The amount of carbon added is sufficient to meet the carbon requirements for the subsequent roasting process to reduce more than 98.5% of NiO, more than 88% of Fe2O3, and 25% of FeO. Specifically, the amount of carbon added in the primary carbon addition is 2wt% of the mass of the laterite ore.

[0036] (2) Secondary carbon addition: 25mm semi-coke particles are added to the roasted sand obtained after roasting laterite ore. The semi-coke particles contain 85wt% carbon. The amount of carbon added is sufficient to complete the reduction of SiO2 in the electrode center circle during subsequent electric furnace smelting and to ensure that the silicon content of the nickel-iron product is 0.9%. Specifically, the amount of carbon added in the secondary carbon addition is 0.5wt% of the mass of the roasted sand.

[0037] The nickel-iron product obtained in this embodiment contains 0.8 wt% Si, 77 wt% iron, and 18% nickel, while the slag contains 9 wt% iron.

[0038] Example 5

[0039] A method for improving the nickel grade of ferronickel products through pyrometallurgical smelting of laterite ore, the pyrometallurgical process comprising: roasting the laterite ore to obtain roasted ore; and smelting the roasted ore in an electric furnace to obtain ferronickel products and slag. The laterite ore contains 2.0 wt% nickel and 82 wt% iron.

[0040] (1) Primary carbon addition: Before roasting the laterite ore, 28mm semi-coke particles are added to the laterite ore. The semi-coke particles contain 85wt% carbon. The amount of carbon added is sufficient to meet the carbon requirements for the subsequent roasting process to reduce more than 98% of NiO, more than 83% of Fe2O3, and 28% of FeO. Specifically, the amount of carbon added in the primary carbon addition is 2.5wt% of the mass of the laterite ore.

[0041] (2) Secondary carbon addition: Add semi-coke particles with a particle size of 28 mm to the roasted sand obtained after roasting laterite ore. The semi-coke particles contain 85 wt% carbon. The amount of carbon added is sufficient to complete the reduction of SiO2 in the electrode center circle during subsequent electric furnace smelting and to ensure that the silicon content of the nickel-iron product is 0.95%. Specifically, the amount of carbon added in the secondary carbon addition is 0.75 wt% of the mass of the roasted sand.

[0042] The nickel-iron product obtained in this embodiment has a Si content of 0.95 wt%, an iron content of 79.5 wt%, and a nickel content of 16%, while the slag has an iron content of 7.5 wt%.

[0043] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A process for improving the nickel grade of ferronickel product from a lateritic nickel ferronickel pyrometallurgical process, the lateritic nickel ferronickel pyrometallurgical process comprising: roasting the laterite ore to obtain calcine; electric furnace smelting the calcine to obtain ferronickel product and slag, characterized in further comprising: (1) primary carbon addition: before roasting the laterite ore, carbon with particle size of 20-30 mm is added into the laterite ore, the amount of the added carbon satisfies the carbon amount required for reducing more than 98% of NiO, more than 80% of Fe2O3, and 20-30% of FeO in the subsequent roasting, and the amount of the carbon added in the primary carbon addition is 2-3 wt% of the mass of the laterite ore; (2) secondary carbon addition: carbon with particle size of 20-30 mm is added into the calcine obtained after roasting the laterite ore, the amount of the added carbon satisfies the carbon amount required for reducing SiO2 within the electrode core circle and for the silicon content of the ferronickel product to be 0.8-1.0% in the subsequent electric furnace smelting, and the amount of the carbon added in the secondary carbon addition is 0.5-1 wt% of the mass of the calcine.

2. A process for improving the nickel grade of ferronickel product from red mud nickel laterite pyrometallurgical smelting according to claim 1, characterized in that, The laterite ore contains 1.8-2.5 wt% of nickel and 77-85 wt% of iron.

3. The process for nickel laterite nickel-iron pyrometallurgical smelting for increasing the nickel grade of the nickel-iron product according to any one of claims 1-2, characterized in that, The carbon added in the (1) and (2) is low-volatile metallurgical coke particle with fixed carbon content of 82-86 wt%.

4. The process according to any one of claims 1 to 2 for improving the nickel grade of the ferronickel product of the pyrometallurgical smelting of laterites, characterized in that, The ferronickel product contains 0.8-1.0 wt% of Si, 77-80 wt% of Fe, and 15-18 wt% of Ni, and the slag contains 7-10 wt% of Fe. The ferronickel product contains 0.8-1.0 wt% of Si, 77-80 wt% of Fe, and 15-18 wt% of Ni, and the slag contains 7-10 wt% of Fe.

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