A method for low-carbon deep depletion of copper slag

Abstract

The invention discloses a method for low-carbon deep depletion of copper slag, which mainly comprises: directly introducing the molten copper slag produced by copper pyrometallurgy into a reduction depletion furnace and heating it to a specified temperature, then adding biomass carbon, slag-making agents (CaO, SiO 2 、Al 2 O 3 and B 2 O 3 ) add copper slag in a certain proportion, and keep it warm at a specified temperature for a certain period of time, so that the copper and iron oxides in the copper slag are fully reduced to metallic copper and iron to form a copper-iron alloy. The metal phase in the slag aggregates and settles and separates from the slag phase. The upper layer is slag, and the metal melt in the lower layer is discharged from the bottom of the reduction and depletion furnace to obtain a copper-iron alloy. This method uses biomass carbon as a reducing agent and realizes low-carbon and efficient recovery of copper and iron resources in copper slag by means of slag type regulation. Compared with the existing copper slag depletion technology, this method has lower copper content in the slag, shorter process, simpler operation, and less carbon emissions. The copper-iron alloy produced has broad application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for low-carbon deep depletion of copper slag. Background Art

[0002] Copper is one of the most common metals in human daily life and is widely used in construction, electricity, transportation and other related fields. In recent years, the global demand for copper has been strong, and copper production has increased year by year, reaching 28.5 million tons in 2019. At present, more than 80% of the world's copper products are produced by pyrometallurgical processes. Therefore, the production of copper slag is inevitable. Copper slag is one of the important by-products produced by the copper pyrometallurgical smelting process. According to statistics, for every ton of copper produced, about 2 to 3 tons of slag will be produced. Calculated based on the copper production in 2019, the copper content in the slag will be reduced by 80% by the depletion process compared with before depletion. The copper slag depletion technology will recover at least 100,000 tons of metallic copper, with significant economic benefits.

[0003] There are two methods for industrial copper slag depletion: ore dressing and pyrometallurgical depletion. Although the ore dressing method can achieve a higher copper recovery rate, the slag slow cooling cycle is long during the treatment process, the area occupied by the slow cooling site is high, and it will cause huge energy waste. The pyrometallurgical depletion method is to reduce the iron oxides in the slag by reducing agents, improve the slag fluidity, reduce the slag viscosity, and improve the sedimentation conditions of metal droplets, thereby reducing the copper content in the slag. However, the waste slag after pyrometallurgical depletion still contains more than 0.5% copper, and the copper content of the waste slag is still relatively high, which causes a great waste of copper resources. Therefore, the development of a new method for deep depletion of copper slag is of great significance to the sustainable development of the copper industry and the comprehensive utilization of resources.

[0004] Copper slag depletion usually involves the addition of reducing agents such as coal, coke, oil and natural gas to reduce the magnetic iron in the slag, reduce the viscosity of the copper slag, and increase the copper recovery rate. Fossil reducing agents are obviously no longer suitable for the development needs of the current "dual carbon" era. The renewability and wide sources of biomass energy make it an alternative energy source. The development and utilization of biomass energy can effectively alleviate ecological and economic problems. Since biomass contains a large amount of fixed carbon, it has strong reducing properties at high temperatures and can be used as a reducing agent to achieve the reduction of metal oxides. Biomass carbon is used as the only reducing agent in this patent.

[0005] The patent with publication number CN105671326B proposes a method for impoverishing copper slag by stirring and coordinating gas injection with sulfiding agent. The method injects the sulfiding agent into the molten slag through the carrier gas to impoverish the copper slag. The utilization rate of the sulfiding agent reaches more than 80%, which can effectively avoid the formation of foam slag, and the copper content in the slag can be reduced to 0.26%. The patent with publication number CN105779778A proposes a method for impoverishing copper slag. The method impoverishes the copper slag by eccentric mechanical stirring and injecting natural gas. The copper content in the impoverished slag can be reduced to 0.28%. Although the above two methods can recover the copper resources in the copper slag, the copper content in the impoverished slag is still more than 0.25%, and the high prices of sulfiding agent and natural gas will also lead to an increase in production costs. In addition, the above methods do not reasonably recycle the iron resources in the copper slag.

[0006] Copper loss in slag can generally be divided into two categories: mechanical entrainment and chemical dissolution. Conventional copper slag depletion processes mainly recover copper lost in the slag in the form of mechanical entrainment, and cannot recover chemically dissolved copper. Chemically dissolved copper is closely related to the slag type of copper slag. Therefore, to achieve deep depletion of copper slag, it is necessary to give priority to the reasonable regulation of the slag type of copper slag. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a method for low-carbon deep depletion of copper slag, which uses biomass carbon as a reducing agent and reduces the content of chemically dissolved copper in the slag by controlling the slag shape, thereby achieving deep depletion of copper slag and efficient recovery of copper and iron resources.

[0008] In order to achieve the above technical purpose, the present invention is implemented by the following technical scheme: a method for low-carbon deep depletion of copper slag, characterized in that it comprises the following steps:

[0009] S1: directly introducing the molten copper slag produced by copper pyrometallurgy into a reduction and depletion furnace and heating it to 1300-1500°C;

[0010] S2: adding biomass carbon and slag-making agent into copper slag in a certain proportion;

[0011] S3: Keep the temperature at a specified temperature for 60 to 120 minutes to fully reduce the copper and iron oxides in the copper slag to metallic copper and iron to form a copper-iron alloy;

[0012] S4: The metal phase in the slag is fully aggregated and settled, and then separated from the slag phase. The upper layer is molten slag, and the lower layer of molten metal is discharged from the bottom of the reduction and depletion furnace to obtain copper-iron alloy;

[0013] Preferably, the temperature of the molten copper slag in S1 is controlled at 1150-1250°C;

[0014] Preferably, the biomass carbon in S2 is 5-15% of the mass of the copper slag;

[0015] Preferably, the slag-forming agent in S2 includes but is not limited to: CaO, SiO 2 、Al 2 O 3 and B 2 O 3 ;

[0016] Preferably, the amount of CaO added to S2 is 20-40% of the mass of the copper slag; 2 The amount of addition is 15-45% of the copper slag mass, Al 2 O 3 The amount added is 10% to 30% of the copper slag mass; B 2 O 3 The amount added is 0-10% of the copper slag mass;

[0017] Preferably, the iron content in the slag in S4 is less than 15%, and the copper content in the slag is less than 0.15%;

[0018] Preferably, the copper-iron alloy obtained in S4 has a Cu content of 10-20% and a Fe content of 75-90%.

[0019] The beneficial effects of the present invention are:

[0020] 1) The present invention realizes deep depletion of copper slag by a slag type control method, thereby solving the problem that the existing copper slag depletion process is long and the copper content of the slag is still high after the copper slag is depleted;

[0021] 2) Add appropriate amount of flux to modify the copper slag, so that the copper slag type changes from the original FeO-SiO 2 Slag system transformed into CaO-Al 2 O 3 -SiO 2 Slag system improves the physical and chemical properties of slag and effectively reduces the chemical and physical loss of copper in the slag. The copper content in the slag after dilution is less than 0.15%, which is significantly lower than the copper slag dilution process and copper slag flotation process currently used in industrial production;

[0022] 3) The present invention uses biomass carbon as a reducing agent to replace the petrochemical reducing agent used in the traditional copper slag depletion process, thereby achieving low-carbon depletion of copper slag and promoting the green and sustainable development of copper slag depletion technology;

[0023] 4) Add a certain amount of B 2 O 3 , so that the physical and chemical properties of the slag are changed to be conducive to the aggregation and sedimentation of metal droplets, and the residue is vitrified, which can be used as building material or further prepared into microcrystalline glass, thus maximizing resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 11 is the XRD spectrum of the upper slag finally obtained in exemplary embodiments 1 to 3 of the present invention. DETAILED DESCRIPTION

[0025] In order to make a clear and complete description of the technical scheme and technical effects of the present invention, the following embodiments are described in detail;

[0026] The composition of the copper slag used in the examples of the present invention is shown in Table 1. The fixed carbon content of the biomass carbon used in the examples is 75-85%.

[0027] Table 1 Copper slag composition (mass percentage, %)

[0028] composition Cu S CaO MgO <![CDATA[SiO 2 ]]> <![CDATA[Al 2 THE 3 ]]> TFe content 4.49 0.53 0.86 0.61 21.04 2.57 44.91

[0029] Example 1

[0030] S1: Directly introduce the 1200℃ molten copper slag produced by copper pyrometallurgy into the reduction depletion furnace and heat it to 1450℃;

[0031] S2: 12% biomass carbon, 31% CaO, 15% SiO 2 、29%Al 2 O 3 and 0% B 2 O 3 After thorough mixing, add copper slag;

[0032] S3: Keep the temperature at 1450℃ for 90min to fully reduce the copper and iron oxides in the copper slag to metallic copper and iron to form a copper-iron alloy;

[0033] S4: The metal phase in the slag is fully aggregated and settled, and then separated from the slag phase. The upper layer is molten slag, and the lower layer of molten metal is discharged from the bottom of the reduction and depletion furnace to obtain copper-iron alloy;

[0034] The copper content in the upper layer slag in Example 1 is 0.11%, and the iron content is 10.64%. The alloy element composition is shown in Table 2. The copper content in the copper-iron alloy is 13.41%, and the iron content is 78.03%.

[0035] Table 2 Copper-iron alloy composition (mass percentage, %)

[0036] composition Cu Fe S Pb Al Si Ca other content% 13.41 78.03 2.00 0.70 0.20 0.20 0.10 5.36

[0037] Example 2

[0038] S1: Directly introduce the 1250℃ molten copper slag produced by copper pyrometallurgy into the reduction and depletion furnace and heat it to 1400℃;

[0039] S2: 10% biomass carbon, 31% CaO, 15% SiO 2、29%Al 2 O 3 and 0% B 2 O 3 After thorough mixing, add copper slag;

[0040] S3: Keep the temperature at 1400℃ for 90min to fully reduce the copper and iron oxides in the copper slag to metallic copper and iron to form a copper-iron alloy;

[0041] S4: The metal phase in the slag is fully aggregated and settled, and then separated from the slag phase. The upper layer is molten slag, and the lower layer of molten metal is discharged from the bottom of the reduction and depletion furnace to obtain copper-iron alloy;

[0042] The XRD results of the upper slag in Example 2 are as follows: Figure 1 As shown in Table 3, the copper content in the copper-iron alloy is 13.68% and the iron content is 69.50%.

[0043] Table 3 Copper-iron alloy composition (mass percentage, %)

[0044] composition Cu Fe S Pb Al Si Ca other content% 13.68 69.50 2.00 0.20 2.00 2.00 2.00 8.62

[0045] Example 3

[0046] S1: Directly introduce the 1250℃ molten copper slag produced by copper pyrometallurgy into the reduction and depletion furnace and heat it to 1400℃;

[0047] S2: 10% biomass carbon, 24% CaO, 40% SiO 2 、10%Al 2 O 3 and 7% B 2 O 3 After thorough mixing, add copper slag;

[0048] S3: Keep the temperature at 1400℃ for 90min to fully reduce the copper and iron oxides in the copper slag to metallic copper and iron to form a copper-iron alloy;

[0049] S4: The metal phase in the slag is fully aggregated and settled, and then separated from the slag phase. The upper layer is molten slag, and the lower layer of molten metal is discharged from the bottom of the reduction and depletion furnace to obtain copper-iron alloy;

[0050] The XRD results of the upper slag in Example 3 are as follows: Figure 1 As shown in Table 4, the copper content in the copper-iron alloy is 16.37% and the iron content is 79.21%.

[0051] Table 4 Copper-iron alloy composition (mass percentage, %)

[0052] composition Cu Fe S Pb Al Si Ca other content% 16.37 79.21 3.00 0.30 0.20 0.30 0.10 0.52

[0053] Example 4

[0054] S1: Directly introduce the 1200℃ molten copper slag produced by copper pyrometallurgy into the reduction depletion furnace and heat it to 1450℃;

[0055] S2: The copper slag contains 31% CaO, 15% SiO 2 、29%Al 2 O 3 and 0% B 2 O 3 After thorough mixing, add copper slag;

[0056] S3: adding 10%, 12%, and 15% of the biomass carbon by mass of the copper slag to the copper slag, numbered 1, 2, and 3 respectively;

[0057] S4: Keep the temperature at 1450°C for 90 minutes to fully reduce the copper and iron oxides in the copper slag to metallic copper and iron to form a copper-iron alloy;

[0058] S5: The metal phase in the slag is fully aggregated and settled, and then separated from the slag phase. The upper layer is molten slag, and the lower layer of molten metal is discharged from the bottom of the reduction and depletion furnace to obtain copper-iron alloy;

[0059] In Example 4, the copper content of the upper layer of slag of sample No. 1 is 0.11%, the copper content of the upper layer of slag of sample No. 2 is 0.12%, and the copper content of the upper layer of slag of sample No. 3 is 0.14%.

[0060] As can be seen from Example 4, the amount of biomass carbon added has little effect on the copper content in the slag. The main purpose of adding biomass carbon is to reduce the iron oxides in the slag and reduce the viscosity of the slag. The main reason for reducing the copper content in the slag is the effective regulation of the slag shape in this patent.

Claims

1. A method for deep low-carbon depletion of copper slag, characterized in that: The following steps are involved: S1: directly introducing the molten copper slag produced by copper pyrometallurgy into a reduction and depletion furnace and heating it to 1300-1500°C; S2: adding biomass carbon and slag-making agent into copper slag in a certain proportion; S3: Keep the temperature at a specified temperature for 60 to 120 minutes to fully reduce the copper and iron oxides in the copper slag to metallic copper and iron to form a copper-iron alloy; S4: The metal phase in the slag is fully aggregated and settled, and then separated from the slag phase. The upper layer is molten slag, and the lower layer of molten metal is discharged from the bottom of the reduction and depletion furnace to obtain copper-iron alloy; The temperature of the molten copper slag in S1 is controlled at 1150-1250°C; The biomass carbon in S2 is 10% of the mass of the copper slag; The slag-forming agents in S2 include but are not limited to: CaO, SiO2, Al2O3 and B2O3; The amount of CaO added to the S2 is 24% of the mass of the copper slag; the amount of SiO2 added is 40% of the mass of the copper slag; the amount of Al2O3 added is 10% of the mass of the copper slag; the amount of B2O3 added is 7% of the mass of the copper slag; The iron content in the slag of S4 is less than 15%, and the copper content in the slag is less than 0.15%; The copper-iron alloy obtained in S4 has a Cu content of 10-20% and a Fe content of 75-90%.

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