Method for producing low-nickel molten iron in blast furnace by sintering high-alkalinity sintered ore from laterite-nickel ore

Abstract

The invention provides a method for producing low-nickel molten iron in a blast furnace by firing high-alkalinity sinter from laterite-nickel ore, which comprises the following steps: step 1, controlling the content of Al2O3 in blast furnace slag to be lower than 26% as a target value, and increasing the binary alkalinity control value of the laterite-nickel ore sinter to 1.55-1.75; step 2, mixing and granulating: mixing the dehydrated laterite-nickel ore with materials containing quicklime powder, fine powder, cold-rolled oxide skin, sintered return mine, fuel and pickling mud according to the material ratio of the mixture to prepare small balls; step 3, sintering: mixing and granulating the raw materials, and then, distributing the raw materials on a sintering trolley for sintering to obtain high-alkalinity laterite-nickel ore sintered ore; 4, blast furnace ore blending is conducted, specifically, the proportion of high-alkalinity laterite-nickel ore sintered ore in a furnace burden structure is 87-92%, and the proportion of high-silicon briquette ore in the furnace burden structure is 8-13%; and 5, the high-alkalinity laterite-nickel ore sintered ore and the high-silicon briquette ore are mixed into a blast furnace according to the furnace burden structure in the step 4, and low-nickel molten iron is smelted.

Description

Technical Field

[0001] This invention relates to the field of pyrometallurgical smelting of laterite nickel ore, specifically to a method for producing high-basicity sinter from laterite nickel ore for use in blast furnaces to produce low-nickel molten iron. Background Technology

[0002] With the increasing depletion of nickel sulfide ore resources and the consumption of large quantities of high-nickel-content laterite nickel ore, low-nickel, high-iron limonite-type laterite nickel ore has become the main source of raw materials for stainless steel products. In recent years, the sintering-blast furnace process for smelting low-nickel, high-iron limonite-type laterite nickel ore has been widely used in China. Compared with traditional stainless steel smelting processes, the sintering-blast furnace process for smelting laterite nickel ore has advantages such as low energy consumption, mature technology, and low cost.

[0003] Lateritic nickel ore of the limonite type (Fe: 46-51%, Ni: 0.8-1.1%, SiO2: 3-8%, Al2O3: 3-9%, MgO: 1-4%) is characterized by high physical and crystalline water content, low iron grade, numerous high-melting-point minerals, and high loss on ignition. During sintering, it suffers from significant bed shrinkage, uneven permeability, and low heat transfer efficiency. Currently, domestic stainless steel enterprises generally control the binary basicity of lateritic nickel ore sintering between 1.00 and 1.40. Within this basicity range, the main binder phases are fir olivine, magnesium-calcium olivine, and diopside, which have poor consolidation strength, resulting in low sinter yield, high return rate, poor drum strength, and high fuel consumption. The poor physical properties and low iron grade of lateritic nickel ore sinter lead to large slag volume and low blast furnace air volume during blast furnace smelting, causing the blast furnace softening zone to shift upwards, resulting in poor permeability of the charge column and low gas utilization. Due to the poor quality of sintered ore, the entire industry utilizes 600m³ volume ore. 3 The following small blast furnaces smelt laterite nickel ore, but have low blast furnace utilization and high fuel consumption.

[0004] In summary, the existing technology has the following problems: poor quality of laterite nickel ore sinter, low utilization coefficient of small blast furnaces, and high fuel consumption. Summary of the Invention

[0005] This invention provides a method for producing high-basicity sinter from laterite nickel ore for use in blast furnaces to produce low-nickel pig iron, thereby solving the problems of poor quality of laterite nickel ore sinter, low utilization coefficient of small blast furnaces, and high fuel consumption.

[0006] Therefore, this invention proposes a method for calcining laterite nickel ore into high-basicity sinter for use in blast furnace production of low-nickel pig iron, the method comprising:

[0007] Step 1: Sintering batch preparation, with the Al2O3 content in blast furnace slag controlled below 26% as the target value, and the binary basicity of laterite nickel ore sinter controlled to 1.55-1.75 to promote the formation of liquid phase and composite calcium ferrite during the sintering process;

[0008] Step 2: Mixing and granulation. The dehydrated laterite nickel ore is mixed with materials including quicklime powder, concentrate, cold-rolled oxide scale, sintered return ore, fuel, and pickling mud according to the material ratio of the mixture and then made into small balls.

[0009] Step 3: Sintering. After the raw materials are mixed and granulated, they are placed on a sintering trolley for sintering to obtain high-alkalinity laterite nickel ore sinter.

[0010] Step 4: Blast furnace ore blending. The proportion of high-alkalinity laterite nickel ore sinter in the furnace charge structure is 87-92%, and the proportion of high-silicon lump ore is 8-13%.

[0011] Step 5: Smelting low-nickel pig iron in a blast furnace. High-alkalinity laterite nickel ore sinter and high-silicon lump ore are blended into the blast furnace according to the furnace charge structure in Step 4 to smelt low-nickel pig iron.

[0012] This invention significantly improves the physical properties of sinter by stabilizing and controlling the SiO2 content in limonite-type lateritic nickel ore sinter and increasing the binary basicity to 1.50–1.70, thereby promoting the formation of more liquid phase and composite calcium ferrite and improving the strength of the binder phase. The average drum index of the sinter increased from 53.11% to 60.33%, with a maximum drum index of 72%; the external return rate decreased from 22.96% to 20.53%; and the proportion of -10mm particles decreased from 40.07% to 32.75%. The blast furnace adopted a burden structure of high-basicity lateritic nickel ore combined with high-silicon lump ore, increasing the lump ore ratio by 6%, increasing the overall iron grade of the ore fed into the furnace by 0.5%, improving the permeability of the burden column, increasing the blast furnace gas utilization rate from 32% to 36%, and decreasing the fuel ratio by approximately 20 kg / t; the average daily output of molten iron increased from 1172.61 t to 1192.44 t. Detailed Implementation

[0013] To provide a clearer understanding of the technical features, objectives, and effects of this invention, the invention is now described.

[0014] This invention stabilizes the SiO2 content in the laterite nickel ore sintering mixture, increases the binary basicity of the sinter, and appropriately increases the CaO content to obtain a sufficient liquid phase. Furthermore, it promotes the formation of composite calcium ferrite. The dense interwoven structure formed by the composite calcium ferrite and fir olivine enhances the strength of the binder phase, thereby improving the physical and metallurgical properties of the sinter. Improved sinter quality contributes to enhanced technical and economic indicators of the blast furnace. The blast furnace used in this invention is a 320m³ blast furnace. 3 Blast furnaces can provide production data references for feasibility studies of smelting low-nickel iron in medium and large blast furnaces.

[0015] This invention provides a method for preparing high-basicity sinter from limonite-type lateritic nickel ore for blast furnace smelting of low-nickel pig iron. The binary basicity of the lateritic nickel ore sinter is increased to 1.55–1.75, promoting the formation of the liquid phase and composite calcium ferrite during sintering, improving the consolidation strength of the binder phase, and enhancing the physical properties of the sinter. Simultaneously, the blast furnace adopts a charge structure suitable for high-basicity lateritic nickel ore sinter, improving charge permeability, enhancing furnace stability, fully releasing blast furnace capacity, and reducing fuel consumption. This invention is achieved through the following steps:

[0016] Step 1: Sintering Batching Calculation. Based on the requirements of blast furnace smelting for sinter, determine the proportions of the sintering mixture. Using an Al2O3 content in the blast furnace slag below 26% as the target value, select three different varieties of laterite nickel ore for blending according to a certain ratio of high-alumina to low-alumina ore. Simultaneously calculate the proportions of quicklime powder, concentrate, cold-rolled oxide scale, sinter return ore, fuel, and other materials to ensure that the mass ratios of each component in the mixture meet the following conditions:

[0017] R2 = 1.55~1.75, the binary basicity of sintered ore is adjusted by increasing or decreasing the proportion of quicklime powder.

[0018] SiO2 (content) = 5.60–6.20%,

[0019] Al2O3 / SiO2 = 0.8–1.0

[0020] MgO / Al2O3 = 0.40–0.60.

[0021] Step 2: Mixing and granulation. The dehydrated laterite nickel ore (moisture content 24-27%) is mixed with quicklime powder, concentrate, cold-rolled oxide scale, sintered return ore, fuel, pickling mud and other materials according to the proportions calculated for ore blending, and then made into small balls.

[0022] The proportions of each material in the mixture are as follows: quicklime powder: 4.5%–5.5%, laterite nickel ore: 60%–65%, iron concentrate: 5%–7%, cold-rolled oxide scale: 1%–2%, sintered return ore: 15%–25%, fuel: 6.5%–8.5%, and pickling mud: 1%–2%.

[0023] Use a vibrating screen to remove particles larger than 20mm from the dried laterite nickel ore.

[0024] The moisture content of the mixture should be controlled at 15-18%.

[0025] Step 3: Sintering. After the raw materials are mixed and granulated, they are placed on a sintering trolley for sintering. The thickness of the base material is 30-40 mm, and the thickness of the material layer is 700-900 mm. The key control parameters of the sintering process are as follows.

[0026] Ignition temperature: 1100±50℃

[0027] Sintering endpoint temperature: 300~450℃

[0028] Sintering negative pressure: 8~14kPa

[0029] FeO content in sintered ore: 19–22%

[0030] Binary basicity of sintered ore: 1.55~1.75.

[0031] Step Four: Blast Furnace Ore Blending. To obtain a suitable blast furnace slag system, this invention develops a burden structure consisting of high-silica lump ore (SiO2 content 12-20%) and high-basicity lateritic nickel ore sinter. Based on meeting the steelmaking production requirements with low-nickel molten iron composition, the ratio of high-silica lump ore to sinter is adjusted to maximize the overall iron grade of the ore fed into the furnace. The proportion of lateritic nickel ore sinter in the burden structure is 87-92%, and the proportion of high-silica lump ore is 8-13%. The blast furnace slag system requirements are as follows.

[0032] Slag R2 = 0.90~1.0,

[0033] (MgO) (content) = 8-11%,

[0034] (Al2O3) (content) = 22-27%.

[0035] Step 5: Blast furnace smelting of low-nickel pig iron. High-basicity laterite nickel ore sinter and high-silicon lump ore are blended and fed into the blast furnace according to the above-mentioned charge structure to smelt low-nickel pig iron with a nickel content of 1.20–1.30% and a chromium content of 3.50–4.30%. This invention provides a blast furnace operation system suitable for smelting high-basicity laterite nickel ore sinter, and the main operation process control parameters are as follows.

[0036] [Si] (content) = 0.70–1.40%,

[0037] [S] (content) = 0.050~0.110%,

[0038] The physical heat of molten iron is 1480–1550℃.

[0039] Blower kinetic energy = 65-80 kJ / s

[0040] The theoretical combustion temperature at the air vent is 2350–2450℃.

[0041] Oxygen enrichment rate = 3-5%,

[0042] This invention adopts a single-ring ore charging mode, which focuses on developing edge airflow, appropriately loosens the center, maintains long-term furnace conditions, and improves the permeability of the blast furnace charge column.

[0043] The process for producing high-alkalinity limonite-type laterite nickel ore sinter for blast furnace smelting of low-nickel molten iron has been applied in the applicant's actual production and has achieved significant results. Specific examples are shown in Table 1.

[0044] Table 1 Examples and Comparative Examples of Using Laterite Nickel Ore Sinter for Blast Furnace Smelting of Low-Nickel Pig Metal

[0045]

[0046]

[0047] As shown in the table, by stabilizing the SiO2 content in limonite-type lateritic nickel ore sinter and increasing the binary basicity to 1.50–1.70, more liquid phase and complex calcium ferrite formation are promoted, improving the strength of the binder phase and significantly improving the physical properties of the sinter. The average drum index of the sinter increased from 52.69% to 60.54%; the external return rate decreased from 22.96% to 20.59%; and the proportion of -10mm particle size decreased from 39.86% to 32.75%. The blast furnace adopted a burden structure of high-basicity lateritic nickel ore combined with high-silicon lump ore, increasing the lump ore ratio by 6%, increasing the overall iron grade of the ore fed into the furnace by 0.5%, improving the permeability of the burden column, increasing the blast furnace gas utilization rate from 32% to 36%, and decreasing the fuel ratio by approximately 20 kg / t; the average daily output of molten iron increased from 1172.61 t to 1193.33 t.

[0048] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. The various components of the present invention can be combined with each other without conflict. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for producing high-basicity sinter from laterite nickel ore for use in blast furnaces to produce low-nickel pig iron, characterized in that, The method for producing high-alkalinity sinter from laterite nickel ore for use in blast furnaces to produce low-nickel pig iron includes: Step 1: Sintering batch preparation, with the Al2O3 content in blast furnace slag controlled below 26% as the target value, and the binary basicity of laterite nickel ore sinter controlled to 1.55-1.75 to promote the formation of liquid phase and composite calcium ferrite during the sintering process; Step 2: Mixing and granulation. The dehydrated laterite nickel ore is mixed with materials including quicklime powder, concentrate, cold-rolled oxide scale, sintered return ore, fuel, and pickling mud according to the material ratio of the mixture and then made into small balls. Step 3: Sintering. After the raw materials are mixed and granulated, they are placed on a sintering trolley for sintering to obtain high-alkalinity laterite nickel ore sinter. Step 4: Blast furnace ore blending. The proportion of high-alkalinity laterite nickel ore sinter in the furnace charge structure is 87-92%, and the proportion of high-silicon lump ore is 8-13%. Step 5: Smelting low-nickel pig iron in a blast furnace. High-alkalinity laterite nickel ore sinter and high-silicon lump ore are blended into the blast furnace according to the furnace charge structure in Step 4 to smelt low-nickel pig iron.

2. The method for producing high-basicity sinter from laterite nickel ore as described in claim 1, used in a blast furnace to produce low-nickel pig iron, characterized in that... In step one, the binary basicity of the sinter is adjusted by increasing or decreasing the proportion of quicklime powder in the sintering batch.

3. The method for producing high-basicity sinter from laterite nickel ore as described in claim 1, used in a blast furnace to produce low-nickel pig iron, characterized in that... In step one, the sintering materials must meet the following conditions: SiO2=5.60~6.20%, Al2O3 / SiO2=0.8~1.0, MgO / Al2O3=0.40~0.

60.

4. The method for producing high-basicity sinter from laterite nickel ore as described in claim 1, used in a blast furnace to produce low-nickel pig iron, characterized in that... In step two, the material ratio of the mixture is as follows: quicklime powder: 4.5% to 5.5%, laterite nickel ore: 60% to 65%, iron concentrate: 5% to 7%, cold-rolled oxide scale: 1% to 2%, sintered return ore: 15% to 25%, fuel: 6.5% to 8.5%, and pickling mud: 1% to 2%.

5. The method for producing high-basicity sinter from laterite nickel ore as described in claim 1, used in a blast furnace to produce low-nickel pig iron, characterized in that... In step two, a vibrating screen is used to remove particles larger than 20mm from the dried laterite nickel ore.

6. The method for producing high-basicity sinter from laterite nickel ore as described in claim 1, used in a blast furnace to produce low-nickel pig iron, characterized in that... In step two, the moisture content of the mixture is controlled at 15-18%.

7. The method for producing high-basicity sinter from laterite nickel ore as described in claim 1, used in a blast furnace to produce low-nickel pig iron, characterized in that... In step three, the thickness of the base material is 30-40mm, and the thickness of the material layer is 700-900mm.

8. The method for producing high-basicity sinter from laterite nickel ore as described in claim 1, used in a blast furnace to produce low-nickel pig iron, characterized in that... In step three, the key control parameters for the sintering process are as follows: ignition temperature: 1100±50℃, sintering endpoint temperature: 300~450℃, sintering negative pressure: 8~14kPa, Fe0 content of sintered ore: 19~22%, binary basicity of sintered ore: 1.55~1.

75.

9. The method for producing high-basicity sinter from laterite nickel ore as described in claim 1, used in a blast furnace to produce low-nickel pig iron, characterized in that... In step four, the requirements for the blast furnace slag system are as follows: slag R2 = 0.90~1.0, MgO content: 8~11%, Al2O3 content: 22~27%.

10. The method for producing high-basicity sinter from laterite nickel ore as described in claim 1, used in a blast furnace to produce low-nickel pig iron, characterized in that... In step five, the process control parameters are as follows: Si content: 0.70~1.40%, S content: 0.050~0.110%, physical heat of molten iron: 1480~1550℃, blast kinetic energy: 65~80kJ / s, theoretical combustion temperature at the tuyeres: 2350~2450℃, and oxygen enrichment rate: 3~5%.

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