Composite alkali modifier for strengthening copper slag recycling and use method thereof

Abstract

The invention relates to the technical field of copper slag resource utilization, in particular to a composite alkali modifier for strengthening copper slag resource utilization and a using method thereof.The using method includes the steps that CaO and MgO are mixed to form the composite alkali modifier; weighing a compound alkali modifier to enable the compound alkali modifier to have a certain relationship with the SiO2 content in the copper slag; uniformly mixing the composite alkali modifier with the copper slag to obtain modified copper slag; the modified copper slag is heated to be in a molten state, and molten slag is obtained; the molten slag is subjected to heat preservation, oxidizing gas is continuously blown into the molten slag for oxidation, and reconstructed slag is obtained; cooling the reconstructed slag to room temperature to obtain cooled slag; and the cooling slag is crushed and then subjected to magnetic separation, the obtained magnetic substance is magnetite, and the obtained non-magnetic substance is silicate. After the copper slag is modified by the compound alkali composed of CaO and MgO, the copper slag is oxidized in a molten state, Fe components in the slag are enriched into magnetic magnetite, hematite is not generated, efficient enrichment of the iron components in the copper slag is achieved, and a foundation is laid for reduction and recycling of the copper slag.

Description

Technical Field

[0001] The present invention relates to the technical field of copper slag resource utilization, and in particular to a composite alkali modifier for enhancing copper slag resource utilization and a method for using the same. Background Art

[0002] As a byproduct of the pyrometallurgical copper smelting process, copper slag production increases with decreasing copper concentrate grade. Currently, every ton of blister copper produced produces approximately 2.2 tons of copper slag. Reportedly, my country produces approximately 20 million tons of copper slag annually, with a cumulative stockpile of approximately 200 million tons. This massive accumulation of copper slag not only occupies land and idles resources, but also requires the payment of corresponding environmental taxes and presents a range of potential environmental risks.

[0003] In recent years, China has placed significant emphasis on the comprehensive utilization of copper slag, issuing a series of policy documents requiring a 73% utilization rate by 2025. These policies have garnered increased attention for the comprehensive utilization of copper slag. Consequently, exploring new avenues for the comprehensive utilization of copper slag, a typical bulk industrial solid waste, is urgent.

[0004] Copper slag contains approximately 40% total iron, making it a potential alternative to iron ore. Since the iron in copper slag occurs primarily in the form of fayalite (Fe2SiO4) and a small amount of magnetite (Fe3O4), conventional direct crushing and magnetic separation methods can only recover a small amount of strongly magnetic magnetite, but are unable to process the weakly magnetic fayalite. Therefore, the key to comprehensive copper slag utilization lies in iron-silicon separation. Therefore, the mainstream approach to copper slag iron-silicon separation is to modify the copper slag with quicklime (CaO), then convert the Fe2SiO4 in the slag into reduced iron or magnetite through reduction or oxidation, and finally recover the iron component through magnetic separation.

[0005] Chinese patent CN101638704A discloses a method for obtaining reduced iron by reducing a mixture of a carbonaceous reducing agent, calcium oxide, and calcium carbonate at high temperature. However, the method does not describe the mineral composition of the non-magnetic fraction after magnetic separation. According to the examples, the total amount of carbonaceous reducing agent and calcium oxide exceeds the amount of copper slag, and the total amount of secondary slag must be quite large.

[0006] Chinese patent CN200610098601 discloses a method for separating iron and copper from copper smelting slag. The method involves injecting an oxidizing gas into a mixture of calcium oxide and copper slag at 1300°C. After oxidation for a specified period, the mixture is cooled to room temperature at a rate of 1°C / min. Magnetite is then recovered through crushing and magnetic separation. However, this process requires controlling the oxygen partial pressure, which presents challenges in practical operation. Furthermore, the occurrence form of the non-ferrous components is not mentioned.

[0007] Chinese patent CN116987897A discloses a method for enhancing the separation of iron from iron-rich copper slag using magnesium slag. This method uses reduced magnesium slag produced by the Pidgeon process as a copper slag modifier. The modified effects of Ca(OH)2 and MgO in the calcareous magnesium slag oxidize the Fe2SiO4 in the copper slag to MgFe2O4 in an air and oxygen atmosphere, thereby enriching and recovering the iron component in the copper slag. However, relatively few locations have both copper and magnesium enterprises, resulting in certain geographical restrictions.

[0008] Chinese patent CN109880999B uses calcium oxide and magnesium oxide as composite additives for copper slag, controlling the mass ratio of CaO to SiO2 to 1.8-2.1 and the mass ratio of Fe2O3 to MgO to 3.6-5.3. The mixture is then heated to 1200-1500°C in an air atmosphere and calcined at a constant temperature for 10-20 minutes. After calcination, the calcined system is slowly cooled by 100-300°C to allow the magnesia-iron spinel grains to grow. The mixture is then rapidly cooled to room temperature, ground, and magnetically separated to obtain an iron concentrate consisting of magnetite and magnesium ferrite. The tailings are dicalcium silicate. However, based on the data provided in the patent, it is estimated that the total amount of calcium oxide and magnesium oxide added is about half of that of the copper slag, resulting in a significant increase in the total amount of secondary slag. At the same time, the melting point of dicalcium silicate, which is enriched with calcium, magnesium and silicon, is as high as 2130℃, far exceeding the 1597℃ of magnetite. Therefore, dicalcium silicate will be generated from the system at the same time as magnetite, worsening the oxidation and mass transfer conditions of the system, which is not conducive to the enrichment of iron components in copper slag.

[0009] Chinese patent CN106916958A discloses a method for modifying copper slag and reducing it to obtain reduced iron using a composite additive consisting of 40-50% quicklime, 10-15% manganese monoxide, 10-15% pyrite, 5-15% chalcopyrite and 10-20% iron oxide. It is obvious that the composite additive is too complicated and requires the addition of pyrite and chalcopyrite, which has obvious geographical restrictions. The addition of iron oxide will also increase costs.

[0010] However, the CaO modification-reduction method for enriching iron components in copper slag requires the addition of excessive reducing agents and produces a large amount of tailings, emitting large amounts of greenhouse gases such as CO and CO₂. The resulting foamy slag makes process control difficult, and the reduced iron particles in the product, with a particle size of less than 50 μm, are not conducive to the dissociation and recovery of iron components. Impurity elements such as copper, lead, and zinc in the slag are reduced along with the Fe element and then converted into iron concentrate, making it unsuitable for smelting ordinary steel grades and only suitable for smelting some specialty steels. Therefore, from the perspectives of economics and applicability, this method is not the first choice for the comprehensive utilization of copper slag in the context of dual carbon.

[0011] The research on the enrichment of iron components in copper slag by CaO modification-oxidation method also has the following problems: 1) The magnetite generated by CaO modified copper slag is easily further oxidized to hematite (Fe2O3) in an oxidizing atmosphere, resulting in the coexistence of the two in the reconstructed slag. The Fe component in the non-magnetic hematite cannot be recovered by magnetic separation, which is not conducive to the enrichment and recovery of the Fe component. Although researchers have explored from many aspects such as CaO content, oxygen partial pressure (air, O2, 1vol%O2+99vol%N2 and water vapor), temperature, etc., the problem of magnetite overoxidation still exists. The above problems have not been effectively solved; 2) After CaO modification of copper slag, non-ferrous components are enriched into high-melting-point CaSiO3 or Ca2SiO4, which will crystallize and grow from the melt simultaneously with the magnetite enriched with iron components, resulting in a sharp increase in the viscosity of the system, a deterioration in the mass transfer environment of [O], and a decrease in the iron recovery rate; 3) A large amount of CaO needs to be added during the recovery of iron components in copper slag, resulting in a large amount of secondary slag; 4) There are also studies that use Na2CO3, Na2O, Al, B2O3, etc. as modifiers for the recovery of Fe components in copper slag, but they have the significant disadvantage of poor economic efficiency.

[0012] In view of this, the present invention proposes to use a composite alkali composed of calcium oxide and magnesium oxide as a modifier for copper slag, and realize the modification of copper slag by composite alkali by controlling the mass ratio of CaO and MgO in the composite alkali modifier (m(CaO) / m(MgO)), the total amount of CaO and MgO and the ratio of the amount of SiO2 in the copper slag ([m(CaO)+m(MgO)] / m(SiO2)); then the modified copper slag is oxidized and reconstructed in the molten state, and the magnetite enriched with the Fe component in the slag crystallizes and grows independently from the melt, while Si, Mg and Ca are mainly reconstructed into low-melting-point silicates and solidified during the cooling process of the furnace, thereby enhancing the iron-silicon separation of the copper slag and helping the resource utilization of the copper slag. Summary of the Invention

[0013] The object of the present invention is to provide a composite alkali modifier for enhancing the resource utilization of copper slag and a method for using the same, so as to solve the problems raised in the above background technology.

[0014] To achieve the above object, the present invention provides the following technical solution: a composite alkali modifier for enhancing the resource utilization of copper slag and a method for using the same, comprising the following steps: Step S1, weighing CaO and MgO respectively and uniformly mixing them in a certain proportion to form a composite alkali modifier; Step S2, weighing a certain amount of composite alkali modifier so that it has a certain relationship with the amount of SiO2 in the copper slag; Step S3, uniformly mixing the composite alkali modifier with copper slag of a certain particle size to obtain modified copper slag; Step S4, uniformly heating the modified copper slag to a certain temperature in an air atmosphere to make it molten, thereby obtaining molten slag; Step S5: The molten slag is kept warm for a certain period of time, and an oxidizing gas with a certain flow rate and pressure is continuously blown into the molten slag for oxidation to obtain reconstructed slag; Step S6: Cooling the reconstructed slag to room temperature in a certain cooling manner to obtain cooled slag; Step S7: After the cooled slag is crushed to a certain particle size, magnetic separation is performed under a certain magnetic field strength to obtain magnetite as the magnetic material and silicate as the non-magnetic material.

[0015] Preferably, the ratio in step S1 is a mass ratio of CaO to MgO m(CaO) / m(MgO)=8:1~0.125:1.

[0016] Preferably, the uniform mixing in steps S1 and S3 can be achieved by one or more of stirring mixing (mechanical stirrer mixing, air flow stirring mixing), grinding mixing (ball mill mixing), vibration mixing (vibration screen mixing), etc.

[0017] Preferably, the CaO and MgO in step S1 can be replaced or combined with raw materials or solid wastes such as dolomite, magnesium slag, carbide slag, magnesite, high-magnesium phosphate tailings, and high-magnesium saponification waste residue in equal amounts.

[0018] Preferably, the relationship in step S2 is [m(CaO)+m(MgO)] / m(SiO2)=0~2.5.

[0019] Preferably, the particle size in step S3 refers to the copper slag being crushed to below 200 mesh, specifically -74 μm.

[0020] Preferably, the temperature in step S4 is 1350-1450°C.

[0021] Preferably, the time in S5 is 0.5-1.5 h, the oxidizing gas can be compressed air or industrial oxygen, the flow rate is 100-1500 L / min, and the pressure is 0.1-1.5 MPa.

[0022] Preferably, the cooling method in step S6 can be one or more of water quenching, air cooling, air cooling or slow cooling.

[0023] Preferably, the particle size in step S7 is -200 mesh, and the magnetic field strength is a magnetic induction intensity ≤ 200 mT.

[0024] Compared with the prior art, the present invention has the following beneficial effects: The composite alkali modifier for enhancing the resource utilization of copper slag and the use method thereof: the composite alkali modifier composed of CaO and MgO is cheap and easily available, and can be replaced or combined with raw materials or solid wastes such as dolomite, magnesium slag, carbide slag, magnesite, high-magnesium phosphate tailings, and high-magnesium saponification waste slag. After the copper slag is modified by the composite alkali modifier composed of CaO and MgO, it is oxidized in a molten state, and the Fe component in the slag is enriched into magnetic magnetite without generating hematite, thereby achieving efficient enrichment of the iron component in the copper slag and laying a foundation for the reduction and resource utilization of the copper slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 A flow chart of a composite alkali modifier for enhancing copper slag resource utilization and its use method; Figure 2 This is a SEM image of the cooled slag in Example 1; Figure 3 The XRD spectra of the cooled slag in Example 1 and Example 2 are shown; Figure 4 This is a high-temperature laser confocal microscope image of the composite alkali-modified copper slag in Example 1; Figure 5 This is the SEM image of the cooled slag in Example 2; Figure 6 These are the respective conditions and morphology of magnetite in Example 2. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0028] See also Figures 1-6 , Example 1: The copper slag used in the present invention is the slowly cooled copper slag from pyrometallurgical copper smelting, and its chemical composition is shown in Table 1.

[0029] Table 1 Chemical composition of copper slag used in the examples (%)

[0030] Based on the chemical composition of the copper slag used in the embodiment shown in Table 1, this embodiment mainly introduces a composite modifier for enhancing the resource utilization of copper slag and its use method. The steps include: Step S1, respectively weighing 4.66 g of calcium oxide and 2.33 g of magnesium oxide and uniformly mixing them in a planetary ball mill to obtain a composite base modifier; Step S2, uniformly mixing the composite alkali modifier and 50 g of copper slag with a particle size of less than 74 μm in a planetary ball mill to obtain a modified copper slag with [m(CaO)+m(MgO)] / m(SiO2)=0.47; Step S3, the modified copper slag is placed in a corundum crucible and placed in a heating zone of a horizontal tube furnace, and uniformly heated to 1400° C. at a heating rate of 5° C. / min in an air atmosphere to obtain molten slag; Step S4: The molten slag is kept warm for 0.5 h, and compressed air is continuously blown into the slag at a rate of 300 mL / min for oxidation to obtain reconstructed slag; Step S5, cooling the reconstructed slag to room temperature along with the furnace to obtain cooled slag; Step S6: The cooled slag is crushed with a sealed laboratory crusher and then passed through a 200-mesh sieve, and magnetically separated in a magnetic separator at a magnetic field strength of 200 mT. The magnetic portion, magnetite I, is dried and crushed again, passed through a 300-mesh sieve, and magnetically separated in a magnetic separator at a magnetic field strength of 180 mT to obtain magnetite II and silicate II. The non-magnetic portion, silicate I and silicate II, are dried and crushed, passed through a 400-mesh sieve, and magnetically separated in a magnetic separator at a magnetic field strength of 180 mT to obtain magnetite III and silicate III. Magnetite II and magnetite III together constitute the recovered magnetite fine powder.

[0031] From the SEM image of this embodiment ( Figure 2 ) It can be seen that the iron and silicon in the cooling slag are present in a complementary form, indicating that the separation effect of the two is good; the element distribution of calcium and silicon is highly overlapped, indicating that the occurrence forms of the two are almost the same. Combined with the XRD spectrum of the cooling slag ( Figure 3 ) It can be seen that Figure 2 The particles in the middle are magnetite, the light grey base is common pyroxene (Ca(Mg,Fe)Si2O6), and the dark grey base is diopside (CaMgSi2O6). It is worth noting that the phase identification ( Figure 3 The iron-bearing phase in the results is mainly magnetite (Fe3O4), and no hematite (Fe2O3) is found, indicating that the iron in the copper slag has mainly migrated and enriched in magnetite (Fe3O4). Figure 4The laser confocal microscopy images shown show that at 1400°C, only one regular particle crystallized. Combined with the XRD pattern and mineral properties, this particle is magnetite. Silicates only solidify in large quantities from the liquid phase when the temperature is lowered to 1017°C. This demonstrates that the constant reaction temperature of 1400°C allows for the independent crystallization and growth of magnetite, while silicates only solidify at lower temperatures. The crystallization temperature, where the iron- and silicon-containing phases are larger, facilitates the separation of iron and silicon in the copper slag.

[0032] As shown in Table 2, the magnetic separation yield obtained in this example is 57.18%, the total iron grade of the magnetite recovered is 65.16%, and the iron recovery rate is 90.61%. Compared with the direct crushing and magnetic separation of copper slag, the mineral processing indicators are significantly improved.

[0033] Table 2 Magnetic separation index table of iron-rich copper slag, Example 1 and Example 2

[0034] Example 2: Based on the chemical composition of the copper slag used in the embodiment shown in Table 1, this embodiment mainly introduces a composite modifier for enhancing the resource utilization of copper slag and a method for using the same.

[0035] Step S1, weighing 8.68 g of calcium oxide and 8.68 g of magnesium oxide respectively and uniformly mixing them in a planetary ball mill to obtain a composite base modifier; Step S2, uniformly mixing the composite alkali modifier and 50 g of copper slag with a particle size of less than 74 μm in a planetary ball mill to obtain a modified copper slag with [m(CaO)+m(MgO)] / m(SiO2)=1.17; Step S3, the modified copper slag is placed in a corundum crucible and placed in the heating zone of a horizontal tube furnace. After replacing the atmosphere of the tube furnace with 500 mL / min of high-purity argon gas for 1 hour, the modified copper slag is uniformly heated to 1450° C. at a heating rate of 10° C. / min in the high-purity argon atmosphere to obtain molten slag; Step S4: The molten slag is kept warm for 1 hour, and oxygen is continuously blown into the slag at a rate of 500 mL / min for oxidation to obtain reconstructed slag; Step S5, cooling the reconstructed slag to room temperature along with the furnace to obtain cooled slag; Step S6: The cooled slag is crushed with a sealed laboratory crusher and then passed through a 200-mesh sieve, and magnetically separated in a magnetic separator at a magnetic field strength of 200 mT. The magnetic portion, magnetite I, is dried and crushed again, passed through a 300-mesh sieve, and magnetically separated in a magnetic separator at a magnetic field strength of 180 mT to obtain magnetite II and silicate II. The non-magnetic portion, silicate I and silicate II, are dried and crushed, passed through a 400-mesh sieve, and magnetically separated in a magnetic separator at a magnetic field strength of 180 mT to obtain magnetite III and silicate III. Magnetite II and magnetite III together constitute the recovered magnetite fine powder.

[0036] From the SEM image of this embodiment ( Figure 5 ) It can be seen that the separation effect of iron and silicon in the cooling slag is good, and the distribution of calcium and silicon is almost the same, indicating that the occurrence forms of the two are also the same. Combined with the XRD spectrum of the cooling slag ( Figure 3 ) It can be seen that Figure 5 The particles in the slag are magnetite, the dark gray base is common pyroxene (Ca(Mg,Fe)Si2O6), and the gaps between them are filled with calcite (Ca2MgSi2O7). At the same time, no hematite (Fe2O3) is found in the XRD spectrum, indicating that the iron in the copper slag is mainly enriched in magnetite (Fe3O4). The distribution and morphology of magnetite in the cooling slag are shown in Figure 2. Figure 6 .

[0037] As shown in Table 2, the magnetic separation yield obtained in this example is 54.63%, the total iron grade of the magnetite recovered is 67.93%, and the iron recovery rate is 90.25%. Compared with the direct crushing and magnetic separation of copper slag, the mineral processing indicators are significantly improved.

[0038] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0039] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A composite alkali modifier for enhancing copper slag resource utilization and a method for using the same, characterized in that: The following steps are involved: Step S1, weighing CaO and MgO respectively and uniformly mixing them in a certain proportion to form a composite alkali modifier; Step S2, weighing a certain amount of composite alkali modifier so that it has a certain relationship with the amount of SiO2 in the copper slag; Step S3, uniformly mixing the composite alkali modifier with copper slag of a certain particle size to obtain modified copper slag; Step S4, uniformly heating the modified copper slag to a certain temperature in an air atmosphere to make it molten, thereby obtaining molten slag; Step S5: The molten slag is kept warm for a certain period of time, and an oxidizing gas with a certain flow rate and pressure is continuously blown into the molten slag for oxidation to obtain reconstructed slag; Step S6: Cooling the reconstructed slag to room temperature in a certain cooling manner to obtain cooled slag; Step S7: After the cooled slag is crushed to a certain particle size, magnetic separation is performed under a certain magnetic field strength to obtain magnetite as the magnetic material and silicate as the non-magnetic material.

2. The composite alkali modifier for enhancing copper slag resource utilization and the method for using the same according to claim 1, characterized in that: The certain ratio in step S1 is a mass ratio of CaO to MgO m(CaO) / m(MgO)=8:1~0.125:

1.

3. The composite alkali modifier for enhancing copper slag resource utilization and the method for using the same according to claim 1, characterized in that: The uniform mixing in steps S1 and S3 can be achieved by one or more of the following methods: mechanical stirrer mixing, air flow stirring mixing, ball mill mixing, vibration screen mixing, etc.

4. The composite alkali modifier for enhancing copper slag resource utilization and the method for using the same according to claim 1, characterized in that: The CaO and MgO in step S1 can be replaced or combined with raw materials or solid wastes such as dolomite, magnesium slag, carbide slag, magnesite, high-magnesium phosphate tailings, and high-magnesium saponification waste residue in equal amounts.

5. The composite alkali modifier for enhancing copper slag resource utilization and the method for using the same according to claim 1, characterized in that: The relationship in step S2 is [m(CaO)+m(MgO)] / m(SiO2)=0~2.

5.

6. The composite alkali modifier for enhancing copper slag resource utilization and the method for using the same according to claim 1, characterized in that: The particle size in step S3 refers to the copper slag being crushed to below 200 mesh, specifically -74 μm.

7. The composite alkali modifier for enhancing copper slag resource utilization and the method for using the same according to claim 1, characterized in that: The temperature in step S4 is 1350-1450°C.

8. The composite alkali modifier for enhancing copper slag resource utilization and the method for using the same according to claim 1, characterized in that: The time in S5 is 0.5-1.5 h, the oxidizing gas can be compressed air or industrial oxygen, the flow rate is 100-1500 L / min, and the pressure is 0.1-1.5 MPa.

9. The composite alkali modifier for enhancing copper slag resource utilization and the method for using the same according to claim 1, characterized in that: The cooling method in step S6 can be one or more of water quenching, air cooling, air cooling or slow cooling.

10. The composite alkali modifier for enhancing copper slag resource utilization and the use method thereof according to claim 1, characterized in that: The particle size in step S7 is -200 mesh, and the magnetic field strength is a magnetic induction intensity ≤ 200 mT.

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