Method for intensifying trapping and recycling of valuable metal in olivine type iron-rich non-ferrous metal smelting slag

Abstract

The invention discloses a method for intensifying capture and recovery of valuable metals in olivine type iron-rich non-ferrous metal smelting slag, which comprises the following steps: proportioning olivine type iron-rich non-ferrous metal smelting slag with strontium carbonate, manganese carbonate and calcium carbonate additives, carrying out oxygen-rich roasting, and carrying out cooling, ore grinding and magnetic separation on the obtained roasted product to obtain the valuable metals in the olivine type iron-rich non-ferrous metal smelting slag. The valuable metal enriched product can be used as an important raw material for nonferrous metallurgy. The method is particularly suitable for enrichment and separation of valuable metals nickel, cobalt, copper and zinc wrapped in the complex olivine type non-ferrous metal smelting slag.

Description

Technical Field

[0001] This invention belongs to the field of combined beneficiation and upgrading of smelting slag, specifically relating to a method for enhancing the capture and recovery of valuable metals in olivine-type iron-rich non-ferrous metal smelting slag. Background Technology

[0002] Research on large-scale utilization technologies for copper / nickel slag metallurgical solid waste aligns with my country's major national strategic needs for the green transformation and development of its resource industries and the comprehensive improvement of solid waste resource utilization. Copper slag is an iron-rich solid waste generated during pyrometallurgical copper smelting, possessing a complex phase composition. my country's annual copper slag emissions exceed 20 million tons. China is a major producer of nickel slag. Currently, the comprehensive utilization rate of nickel slag is only about 10%, with most nickel slag being stockpiled and disposed of, posing a persistent environmental risk to the industry. The National Economic and Social Development Plan clearly states the goal of "significantly improving the comprehensive utilization rate of newly generated bulk solid waste and orderly reducing existing bulk solid waste." Therefore, research on large-scale utilization technologies for copper / nickel slag is of great significance.

[0003] The matte smelting of copper, nickel, and cobalt sulfide concentrates is an oxidative smelting process. In production, the physicochemical properties of copper, nickel, and cobalt—their affinity for sulfur being similar to that of iron, while their affinity for oxygen is far less than that of iron—are utilized. During matte smelting at varying degrees of oxidation, iron sulfides are continuously oxidized into oxides, which are then removed by slag formation with gangue. The behavior of iron is one of the core metallurgical processes in sulfide ore matte smelting, primarily involving the formation, transformation, and distribution of iron sulfides and oxides between matte (copper matte / nickel) and slag, directly affecting metal recovery and process efficiency. Iron mainly exists as FeS (ferrous sulfide) in matte smelting. Iron sulfides in the raw materials (such as FeS2) decompose or oxidize at high temperatures. FeS is preferentially oxidized to FeO; when the oxygen content is high, FeO further oxidizes to Fe3O4 (ferric oxide). This oxidation reaction releases a large amount of heat, maintaining the high temperature required for smelting. Iron oxides react with added flux (such as SiO2) to form slag. FeO combines with SiO2 to form fir olivine (2FeO·SiO2), which constitutes the main component of iron silicate slag. The slag composition is usually 30%~40% SiO2, 38%~50% FeO, and 8%~10% CaO, with the SiO2 content needing to be close to saturation (35%~40%) to reduce slag viscosity and promote the separation of matte and slag. Due to the characteristics and efficiency of the smelting process, nickel slag contains 30%~40% iron, as well as trace amounts of non-ferrous metals such as nickel, cobalt, and copper. The main iron-containing phase is the fir olivine phase, which is encapsulated by a glassy phase, resulting in a relatively dense structure, making comprehensive utilization difficult and with low utilization rate. The main components of copper slag are iron and its oxides, copper, silicon dioxide, aluminum oxide, and calcium oxide, as well as associated elements such as zinc, lead, cobalt, and nickel, and small amounts of precious metals such as gold and silver. Copper exists mainly as sulfides, oxides, and metals, while iron exists mainly as silicates (such as iron olivine Fe2SiO4) and magnetite (Fe3O4).

[0004] Domestic and international scholars have conducted extensive and fruitful research on the comprehensive utilization technology of copper / nickel slag solid waste. The resource utilization of nickel slag mainly focuses on the separation and recovery of valuable metals, including physical beneficiation, direct reduction, smelting reduction, smelting oxidation-grinding, and wet leaching processes. High-temperature reduction / oxidation-grinding technology based on the control of iron mineral phases and magnetism can efficiently achieve iron separation and enrichment, with an iron recovery rate exceeding 80%. However, the high-temperature reduction process of copper / nickel slag requires the addition of calcium flux to disrupt the olivine structure, generating a large amount of secondary smelting slag that requires further treatment. Furthermore, the magnetite phase and particle size in the smelting oxidation process need precise control to meet the mineralogical requirements of subsequent efficient grinding separation (insufficient oxidation, over-oxidation, and small particle size all adversely affect separation and are detrimental to stable production). The wet leaching process has advantages such as simple process, flexibility and high leaching efficiency of multiple components such as iron, nickel, cobalt and copper. However, the olivine structure is dense, the acid consumption during leaching is large, and a large amount of waste acid and wastewater are generated that need to be treated harmlessly. Moreover, the co-leaching of multiple metals inevitably makes it difficult to separate multiple components in subsequent unit operations such as hydrolysis, precipitation, extraction and ion exchange.

[0005] In summary, copper / nickel slag is rich in valuable metals such as iron, copper, nickel, cobalt, and zinc, and has high comprehensive utilization value. Currently, technologies such as physical sorting, carbothermal reduction, and hydrometallurgy can effectively recover these valuable metals, but they face challenges such as low separation efficiency and secondary pollution. Addressing the difficulties in reconstructing the ferroolitic structure and recovering valuable metals from copper / nickel slag, constructing a suitable trapping carrier based on the geochemical affinity of elements is an effective way to efficiently separate valuable metals. Therefore, developing methods to enhance the trapping and recovery of valuable metals in olivine-type iron-rich non-ferrous metal smelting slags based on the characteristics of the smelting and processing process is of great significance. Summary of the Invention

[0006] To address the challenges of reconstructing the structure of fir olivine and recovering valuable metals from copper / nickel slag, this invention aims to provide a method for enhancing the capture and recovery of valuable metals in olivine-type iron-rich non-ferrous metal smelting slag. This method involves batching, intensified oxidative roasting, and regulation of the fir olivine phase reconstruction into composite iron oxides. These composite iron oxides possess numerous tetraoctahedral structures, providing a favorable structural basis for the enrichment of valuable metals such as copper, nickel, cobalt, and zinc. By controlling the magnetic properties of the composite iron oxides, and then employing crushing, grinding, and magnetic separation methods, efficient separation of valuable metals can be achieved. This method has a wide range of applicable raw materials, can handle complex and difficult-to-benefit fir olivine-type smelting slag, and features a simple process, environmental friendliness, and low cost.

[0007] To achieve the above-mentioned technical objectives, the present invention provides the following technical solution: A method for enhancing the capture and recovery of valuable metals in olivine-type iron-rich non-ferrous metal smelting slag involves batching the olivine-type iron-rich non-ferrous metal smelting slag with strontium carbonate, manganese carbonate, and calcium carbonate additives, followed by oxygen-enriched roasting. The roasted product is then cooled, ground, and magnetically separated to obtain a valuable metal-enriched product. The batching of the olivine-type iron-rich non-ferrous metal smelting slag with strontium carbonate, manganese carbonate, and calcium carbonate satisfies the following mass ratios: valuable metal (one or more of copper, zinc, cobalt, and nickel) + strontium + manganese to iron is (0.10~0.35):1; strontium to manganese is (0.05~0.35):1; CaO to SiO2 is (0.2~1.0):1; and the iron content in the smelting slag ranges from 15% to 55%.

[0008] The olivine-type iron-rich non-ferrous metal smelting slag includes one or more of copper slag, nickel slag, and cobalt slag.

[0009] The SrCO3, MnCO3, and CaCO3 contents in the strontium carbonate, manganese carbonate, and calcium carbonate additives are not less than 85 wt%.

[0010] The particle size of the mixture obtained after batching is 200 mesh, with the mass ratio of fine particles being 100%.

[0011] The roasting refers to roasting at 1150~1200℃ for 10~30 minutes, followed by roasting at 1250℃~1280℃ for 10~25 minutes, and the oxygen volume content in the roasting atmosphere during roasting is not less than 25%.

[0012] The roasted agglomerates are cooled by air cooling or in-furnace cooling.

[0013] The grinding fineness of the cooled agglomerates is 100% by mass of 200 mesh and 15% to 25% by mass of 300 mesh.

[0014] The magnetic field strength in the magnetic separation process is 200~650 Gauss.

[0015] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows: This invention leverages the characteristic that key metallic elements in geochemical mineralization processes tend to accumulate in certain special crystal structures with extraordinary enrichment. Through batching and enhanced oxidative roasting, the phase reconstruction of fir olivine is controlled to form composite iron oxides, utilizing the abundant tetrahedral / octahedral interstitial structures to trap valuable metals. By controlling the occupancy of bulk ferromagnetic atoms in the composite oxide crystal structure, the magnetic properties of the oxide carrier are controlled, providing the physical conditions for magnetic separation. Furthermore, controlled cooling transforms the complex silicate glass phase generated during roasting. Finally, selective grinding technology is employed to achieve efficient monomer dissociation of the composite oxide carrier, providing favorable mineralogical conditions for this efficient monomer dissociation.

[0016] Ferrolivine-type copper / nickel slag often exhibits a low melting point in reduction systems, with valuable metals such as copper, zinc, cobalt, and nickel being encapsulated by olivine, making recovery difficult. Furthermore, the strong chemical bond between ferrous oxide and oxides in ferolivine makes reduction and dissociation challenging. This invention employs a strongly oxidizing atmosphere for roasting olivine-type copper / nickel slag. During roasting, the low-melting-point liquid phase transforms into a high-melting-point oxide framework structure, with a small amount of liquid phase remaining within the solid framework. This facilitates the gas-liquid-solid three-phase reaction system, promoting the enrichment of valuable metals through reaction with iron oxides. Moreover, the strongly oxidizing atmosphere roasting method of this invention results in lower energy consumption and carbon emissions compared to carbothermal reduction techniques that require large amounts of carbonaceous reducing agents. The constructed valuable metal composite oxide carrier is easily dissociated and sorted, and the process is simple and low-cost. Detailed Implementation

[0017] The present invention will be further explained and illustrated below with reference to specific embodiments. These embodiments are only for better understanding of the present invention and are not intended to limit the scope of protection of the present invention. In the following embodiments and comparative examples, the content of SrCO3, MnCO3, and CaCO3 in the strontium carbonate, manganese carbonate, and calcium carbonate additives is not less than 85 wt%.

[0018] Example 1 Finely ground copper pyrometallurgical slag containing 0.82 wt% copper, 2.14 wt% zinc, 25 wt% silica, and 46 wt% ferrous oxide was mixed with analytical grade strontium carbonate, manganese carbonate, and calcium carbonate additives. The mixture met the following requirements: the mass ratio of copper, zinc, manganese, and strontium to iron was 0.35:1; the mass ratio of strontium to manganese was 0.35:1; and the mass ratio of CaO to SiO2 was 0.2:1. The particle size of the mixture was 200 mesh, with fine particles accounting for 100% by mass. A tubular furnace was used as the roasting equipment. The mixture was roasted at 1150℃ for 30 min, followed by roasting at 1280℃ for 10 min. During the roasting process, air and oxygen were introduced through a gas configuration system, and the oxygen volume content in the roasting furnace atmosphere was 25%. The resulting roasted agglomerates were allowed to cool naturally to room temperature in air. The cooled agglomerates were then ground using a ball mill, with the grinding fineness controlled to be 100% by mass of 200 mesh and 25% by mass of 300 mesh or finer particles. The finely ground roasted product was then separated using a magnetic separator with a magnetic field strength of 650 Gauss, yielding a magnetic concentrate with a copper grade of 2.1% and a recovery rate of 94.2%, a zinc grade of 4.2% and a recovery rate of 95.5%, and an iron grade of 39% and a recovery rate of 92.3%.

[0019] Example 2 Finely ground nickel pyrometallurgical slag with a nickel content of 0.78 wt%, cobalt content of 0.62 wt%, silicon dioxide content of 32 wt%, and ferrous oxide content of 51 wt% was mixed with strontium carbonate, manganese carbonate, and calcium carbonate additives. The mixture met the following requirements: the mass ratio of nickel + cobalt + manganese + strontium to iron was 0.15:1; the mass ratio of strontium to manganese was 0.25:1; and the mass ratio of CaO to SiO2 was 1.0:1. The particle size of the mixture was 200 mesh, with fine particles accounting for 100% by mass. A tubular furnace was used as the roasting equipment. The mixture was roasted at 1200℃ for 10 min, and then the temperature was increased to 1250℃ and roasted for 25 min. During the roasting process, air and oxygen were introduced through a gas configuration system, and the oxygen volume ratio in the roasting furnace atmosphere was 28%. The resulting roasted agglomerates were allowed to cool naturally to room temperature in air. The cooled agglomerates were then ground using a ball mill, with the grinding fineness controlled to be 100% by mass of 200 mesh and 15% by mass of 300 mesh. The finely ground roasted product was then separated using a magnetic separator with a magnetic field strength of 200 Gauss, yielding a magnetic concentrate with a nickel grade of 2.2% and a recovery rate of 92.3%, a cobalt grade of 1.7% and a recovery rate of 93.7%, and an iron grade of 42% and a recovery rate of 91.4%.

[0020] Comparative Example 1 The ingredients in this comparative example are not within the preferred range.

[0021] Finely ground copper pyrometallurgical slag with a copper content of 0.92 wt%, zinc content of 1.89 wt%, silica content of 27 wt%, and ferrous oxide content of 37 wt% was mixed with strontium carbonate, manganese carbonate, and calcium carbonate additives. The mixture met the following requirements: the mass ratio of copper + zinc + manganese + strontium to iron was 0.05:1; the mass ratio of strontium to manganese was 0.3:1; and the mass ratio of CaO to SiO2 was 0.05:1. The particle size of the mixture was 200 mesh, with fine particles accounting for 100% by mass. A tubular furnace was used as the roasting equipment. The mixture was roasted at 1175℃ for 20 min, and then the temperature was increased to 1275℃ and roasted for another 20 min. During the roasting process, air and oxygen were introduced through a gas configuration system, and the oxygen volume ratio in the roasting furnace atmosphere was 28%. The resulting roasted agglomerates were allowed to cool naturally to room temperature in air. The cooled agglomerates were then ground using a ball mill, with the grinding fineness controlled to be 100% by mass of 200 mesh and 20% by mass of 300 mesh. The finely ground roasted product was then separated using a magnetic separator with a magnetic field strength of 350 Gauss, yielding a magnetic concentrate with a nickel grade of 1.0% and a recovery rate of only 74.2%, a cobalt grade of 2.4% and a recovery rate of 75.1%, and an iron grade of 30.2% and a recovery rate of 71.5%.

[0022] Comparative Example 2 In this comparative example, the roasting temperature and atmosphere are not within the preferred range.

[0023] Finely ground nickel pyrometallurgical slag with a nickel content of 0.69 wt%, cobalt content of 0.81 wt%, silicon dioxide content of 34 wt%, and ferrous oxide content of 52 wt% was mixed with strontium carbonate, manganese carbonate, and calcium carbonate additives. The mixture met the following requirements: the mass ratio of nickel + cobalt + manganese + strontium to iron was 0.25:1; the mass ratio of strontium to manganese was 0.25:1; and the mass ratio of CaO to SiO2 was 0.50:1. The particle size of the mixture was 200 mesh, with fine particles accounting for 100% by mass. A tubular furnace was used as the roasting equipment. The mixture was roasted at 950℃ for 25 min, and then the temperature was raised to 1180℃ and roasted for another 25 min. During the roasting process, air and nitrogen were introduced through a gas configuration system, and the oxygen volume ratio in the roasting furnace atmosphere was 16%. The resulting roasted agglomerates were allowed to cool naturally to room temperature in air. The cooled agglomerates were then ground using a ball mill, with the grinding fineness controlled to be 100% by mass of 200 mesh and 20% by mass of 300 mesh. The finely ground roasted product was then separated using a magnetic separator with a magnetic field strength of 300 Gauss, yielding magnetic concentrates with a nickel grade of 1.4% and a recovery rate of only 63.6%, a cobalt grade of 1.8% and a recovery rate of 64.2%, and an iron grade of 41.3% and a recovery rate of 67.5%.

[0024] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the specific implementation of the present invention and not to limit it. Those skilled in the art should understand that any equivalent substitutions or obvious modifications made to the implementation of the present invention without changing its performance or use, without departing from the spirit of the present invention, should be covered within the scope of protection claimed by the present invention.

Claims

1. A method for enhancing the capture and recovery of valuable metals in olivine-type iron-rich non-ferrous metal smelting slag, characterized in that: Olivine-type iron-rich non-ferrous metal smelting slag is mixed with strontium carbonate, manganese carbonate, and calcium carbonate additives, and then roasted in an oxygen-enriched environment. The roasted product is cooled, ground, and magnetically separated to obtain a valuable metal enriched product. The olivine-type iron-rich non-ferrous metal smelting slag mixed with strontium carbonate, manganese carbonate, and calcium carbonate meets the following requirements: the mass ratio of valuable metal + strontium + manganese to iron is (0.10~0.35):1; the mass ratio of strontium to manganese is (0.05~0.35):1; the mass ratio of CaO to SiO2 is (0.2~1.0):1; the mass range of iron in the smelting slag is 15%~55%; and the valuable metals refer to one or more of copper, zinc, cobalt, and nickel.

2. The method for capturing and recovering valuable metals in enhanced olivine-type iron-rich non-ferrous metal smelting slag according to claim 1, characterized in that: Olivine-type iron-rich non-ferrous metal smelting slag is one or more of copper slag, nickel slag, and cobalt slag.

3. The method for capturing and recovering valuable metals in enhanced olivine-type iron-rich non-ferrous metal smelting slag according to claim 1, characterized in that: The SrCO3, MnCO3, and CaCO3 contents in the strontium carbonate, manganese carbonate, and calcium carbonate additives are not less than 85 wt%.

4. The method for capturing and recovering valuable metals in enhanced olivine-type iron-rich non-ferrous metal smelting slag according to claim 1, characterized in that: The particle size of the mixture obtained after batching is 200 mesh, with the mass ratio of fine particles being 100%.

5. The method for capturing and recovering valuable metals in enhanced olivine-type iron-rich non-ferrous metal smelting slag according to claim 1, characterized in that: The roasting refers to roasting at 1150~1200℃ for 10~30 minutes, followed by roasting at 1250℃~1280℃ for 10~25 minutes, and the oxygen volume content in the roasting atmosphere during roasting is not less than 25%.

6. The method for capturing and recovering valuable metals in enhanced olivine-type iron-rich non-ferrous metal smelting slag according to claim 1, characterized in that: The cooling method is either air cooling or furnace cooling.

7. The method for capturing and recovering valuable metals in enhanced olivine-type iron-rich non-ferrous metal smelting slag according to claim 1, characterized in that: The grinding process refers to grinding to a point where the mass percentage of fine particles at 200 mesh is 100%, and the mass percentage of fine particles at 300 mesh is 15% to 25%.

8. The method for capturing and recovering valuable metals in enhanced olivine-type iron-rich non-ferrous metal smelting slag according to claim 1, characterized in that: The magnetic field strength during the magnetic separation process is 200~650 Gauss.