A low copper loss two-sided blown bath smelting process

Abstract

The application discloses a low copper loss double-side blown bath smelting method and belongs to the technical field of copper pyrogenic smelting. The method constructs a vertical oxygen potential gradient in the same smelting furnace: 70%-85% of oxygen-rich air is blown into the tuyere at the lower part of the furnace body to form a strong oxidation smelting zone; and a reducing medium such as natural gas or pulverized coal is sprayed into the slag layer at the upper part of the furnace body to form a weak reduction clarification zone. The amount of the reducing medium sprayed is dynamically adjusted by on-line monitoring of the CO content in the flue gas or the Fe3O4 content in the slag, and the Fe3O4 content in the slag is controlled to be 3%-6%. The method efficiently reduces Fe3O4 in the slag into FeO, significantly reduces the viscosity of the molten slag, and improves the slag-ice-copper separation condition, so that the copper content in the discarded slag is stably reduced from more than 1.8% in the conventional method to less than 1.3%, and the metal recovery rate is improved. Meanwhile, the method realizes integration of smelting and tempering, simplifies the process, reduces energy consumption, and enhances the adaptability to complex raw materials.

Description

Technical Field

[0001] This invention belongs to the field of copper pyrometallurgical technology, specifically relating to a double-sided blowing pool smelting method with low copper loss. Background Technology

[0002] In the high-oxygen double-sided blowing pool smelting process, there is a core contradiction between the operation of strengthening the oxidizing atmosphere to improve production efficiency and the good slag-metal separation conditions required for low metal loss. The strong oxidizing atmosphere easily leads to slag over-oxidation, generating a large amount of high-melting-point magnetic iron oxide (Fe3O4), which increases the viscosity of the slag and reduces its fluidity. This severely hinders the settling and aggregation of matte droplets, ultimately resulting in a high copper content in the waste slag, reducing metal recovery rate and economic benefits.

[0003] To address the aforementioned problems, existing technologies typically seek solutions from different angles, such as raw material control, process intensification, or back-end treatment, but all have limitations. For example, patent CN102994775A focuses on strictly controlling the content of impurities such as lead and zinc in the raw materials fed into the furnace, aiming to solve the problem of flue blockage. However, this method is a front-end static control and cannot cope with the dynamic peroxidation reaction inside the slag during the smelting process. Patent CN103014369A intensifies the smelting process by blowing highly oxygen-enriched air into the furnace from both sides, but this may further aggravate the oxidation of the molten pool and is not conducive to inhibiting the formation of Fe3O4. This technical solution usually requires the slag to be discharged into a separate depletion electric furnace for subsequent treatment, which is complex and increases equipment investment and energy consumption. In addition, there are methods that set up dedicated furnaces outside the smelting process to reduce and deplete the slag, which belong to "end-of-pipe treatment" and fail to achieve the integration of smelting and slag quality control.

[0004] Therefore, there is an urgent need for a new method that can effectively coordinate the contradictions between oxidation smelting and reduction clarification in a single smelting furnace, based on the process mechanism. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention provides a low-copper-loss double-sided blowing pool smelting method. The method is characterized by constructing and maintaining a vertical oxygen potential gradient within the molten pool in the same double-sided blowing pool furnace. This gradient consists of a lower strong oxidation smelting zone and an upper weak reduction clarification zone. Specifically, the method includes the following steps:

[0006] a) By blowing oxygen-enriched air with an oxygen concentration of 70%-85% into the lower part of the molten pool through the double-sided main air inlets located at the lower part of the side wall of the molten pool, the strong oxidation smelting zone is formed.

[0007] b) By using a reducing medium injection device located above the main air outlet and opening into the slag layer of the molten pool, a reducing medium is injected into the slag layer to form the weak reduction clarification zone in the upper part of the molten pool.

[0008] c) Monitor the CO content in the flue gas discharged from the smelting furnace online, and / or periodically detect the Fe3O4 content in the slag layer of the molten pool;

[0009] d) Based on the CO content and / or Fe3O4 content obtained from step c), dynamically adjust the injection amount of the reducing medium so that the Fe3O4 content in the slag in the weakly reducing clarification zone is controlled within the range of 3%–6%.

[0010] Furthermore, the reducing medium is one or more of natural gas, liquefied petroleum gas, pulverized coal, and coke powder.

[0011] Furthermore, in step d), the CO content in the flue gas is controlled within the range of 0.5% to 1.5% by adjusting the injection amount of the reducing medium.

[0012] Furthermore, the total amount of the injected reducing medium accounts for 3%–10% of the total fuel consumption.

[0013] Furthermore, the melting temperature in the strong oxidation melting zone is controlled at 1250-1280℃.

[0014] Furthermore, the blowing pressure of the oxygen-enriched air blown in through the main air inlet is 110-130 kPa.

[0015] Furthermore, the nozzle of the reducing medium blowing device is located in the middle or lower part of the slag layer in the molten pool.

[0016] Furthermore, the reducing medium is injected into the slag layer of the molten pool via a dedicated spray gun using a pneumatic delivery method.

[0017] Furthermore, after being tempered in the weak reduction clarification zone, the copper content of the discarded slag is reduced to below 1.3%.

[0018] The technical solution of the present invention has the following beneficial effects:

[0019] (1) Significantly reduces copper content in waste slag and improves metal recovery rate. By constructing a weak reduction clarification zone in the upper part of the molten pool, the high-valence iron oxide (Fe3O4) in the slag is effectively reduced to low-valence iron oxide (FeO), which greatly reduces the viscosity of the molten slag and improves the slag-gold separation conditions. After implementing this invention, the copper content in waste slag can be stably reduced from the conventional 1.8% to below 1.3%, significantly improving the copper recovery rate and resulting in huge economic benefits.

[0020] (2) Simplify the process flow and reduce energy consumption and investment. The present invention realizes the integration of efficient smelting and slag reduction and conditioning in a single smelting furnace. Unlike existing technologies, it does not require the configuration of large post-processing equipment such as independent lean electric furnaces. This simplifies the production process, saves equipment investment and land area, and reduces heat loss and energy consumption caused by slag transfer and secondary treatment.

[0021] (3) Improve process stability and intelligence. By injecting a reducing agent into the upper slag layer, not only is the slag fluidity improved, which is conducive to the stable and smooth operation of production, but a closed-loop feedback control loop based on the CO content in the flue gas or the Fe3O4 content in the slag is also established. This dynamic control method allows the oxygen potential of the molten pool to be precisely and in real time controlled within the ideal range, thereby improving the intelligence level and anti-interference ability of the entire smelting process.

[0022] (4) Expanding the adaptability of raw materials. Since this method can actively regulate the oxygen potential in the upper part of the molten pool, it effectively inhibits and eliminates the problem of slag over-oxidation. Therefore, it has a stronger adaptability to processing complex copper concentrate raw materials with low sulfur content that are prone to slag over-oxidation, thus expanding the range of raw material selection. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the double-sided blown-melt pool smelting furnace of the present invention.

[0024] Explanation of the attached diagram labels: 1-1, Strong oxidizing smelting zone; 1-2, Weak reducing clarification zone; 2, Double-sided main air inlet; 3, Reducing medium injection device; 4, Flue; 5, Siphon well; 6, Slag outlet. Detailed Implementation

[0025] The low-copper-loss double-sided blown pool smelting method of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0026] The core of the method provided by this invention lies in improving the traditional double-sided blowing pool smelting furnace. Within the molten pool of the same furnace chamber, a bottom-up oxygen potential gradient environment is actively constructed and maintained through a spatially separated gas supply design. Specifically, as... Figure 1As shown, the existing double-sided main air inlets 2 are used on the lower sidewall of the molten pool to blow in high-concentration oxygen-enriched air, forming a zone of intense bubbling and strong oxidation reaction, namely the strong oxidation smelting zone 1-1. In this zone, copper concentrate, flux, and other furnace materials are rapidly melted, and iron and sulfur undergo intense oxidation to produce matte (Cu2S-FeS) and primary slag, releasing a large amount of heat of reaction. The smelting temperature is typically controlled between 1250℃ and 1280℃. The concentration of the injected oxygen-enriched air is preferably 70% to 85%, and the blast pressure is 110 kPa to 130 kPa to ensure sufficient oxidation intensity and molten pool agitation.

[0027] The key innovation of this invention lies in the addition of one or more reducing medium injection devices 3 (e.g., water-cooled spray guns) on the side wall of the furnace body above the double-sided main tuyeres 2. The injection nozzles of these devices penetrate deep into the slag layer of the molten pool, preferably located in the middle or lower-middle part of the slag layer. Through these devices, a reducing medium is quantitatively injected into the high-temperature slag layer. The reducing medium can be one or more of natural gas, liquefied petroleum gas, pulverized coal, or coke powder. The injected reducing medium undergoes cracking, gasification, or incomplete combustion in the high-temperature (1200℃) slag layer, producing reducing gases such as CO and H2. This creates a weakly reducing clarifying zone 1-2 in the upper part of the molten pool, especially near the slag-matte interface, where the oxygen potential is significantly lower than that of the lower smelting zone.

[0028] Within this weakly reducing clarifying zone, two key processes primarily occur: First, chemical conditioning, where reducing gases partially reduce excess magnetic iron oxide (Fe3O4) from the lower strongly oxidizing zone, dissolved in the slag or suspended in solid form, to ferrous oxide (FeO). The basic reaction is: Fe3O4 (slag) + CO / H2 → FeO (slag). This reaction significantly reduces the viscosity, surface tension, and density of the molten slag. Second, physical promotion, where the weakly reducing atmosphere protects the surface of the matte droplets rising to this zone from excessive oxidation, facilitating the growth of small matte droplets through collision and aggregation. The synergistic effect of these two processes greatly optimizes the settling and separation kinetics of matte droplets in the slag phase.

[0029] To achieve precise and stable control of the oxygen potential gradient, this invention introduces a dynamic feedback adjustment system. A preferred control method involves installing an online flue gas analyzer at the outlet of flue gas 4 of the smelting furnace to monitor the CO concentration in the flue gas in real time. The control system (not shown in the figure) automatically adjusts the supply flow rate of the reducing medium injection device 3 according to the set target CO concentration range (e.g., 0.5%–1.5%). Another equivalent or supplementary control method is to periodically (e.g., every 2–4 hours) obtain slag samples from the slag outlet or through a dedicated sampler, analyze their Fe3O4 content, and use this data to manually or automatically adjust the injection amount of the reducing medium. The ultimate goal of the control is to stabilize the Fe3O4 content in the slag of the weakly reducing clarifying zone within the optimized range of 3% to 6%. Typically, a significant effect can be achieved when the total amount of injected reducing medium accounts for 3% to 10% of the total fuel consumption (including any possible replenishment of coal or coke) throughout the entire smelting process.

[0030] Through the above process, the slag with good fluidity after tempering and the aggregated matte are efficiently separated. The matte is discharged continuously or intermittently through siphon well 5 and enters the next blowing process; while the slag with significantly reduced copper content is smoothly discharged from slag outlet 6 and becomes the final waste slag. The high-temperature flue gas rich in SO2 enters the waste heat recovery and acid production system through flue 4.

[0031] Example 1

[0032] A factory processes conventional copper concentrate containing 25% copper. Two natural gas lances are symmetrically installed in the middle of the slag layer of a double-blown smelting furnace (approximately 1.2 meters from the lower main tuyeres). 78% oxygen-enriched air is blown into the lower main tuyeres at a pressure of 120 kPa, controlling the molten pool temperature at 1260℃. The CO concentration is monitored by an online flue gas analyzer, and the natural gas injection rate is automatically controlled to maintain the CO concentration between 0.8% and 1.2%. After stable operation, the slag fluidity significantly improved, the Fe3O4 content in the slag decreased from approximately 12% in the traditional process (without the natural gas lances) to 5.2%, and the average copper content in the discarded slag decreased from 1.82% to 1.08%.

[0033] Example 2

[0034] This method processes a complex copper concentrate of the high magnetite type that is prone to peroxidation. The oxygen concentration in the lower part is adjusted to 75%. Pulverized coal is selected as the reducing medium and injected into the lower part of the slag layer via a pneumatic conveying and injection system. Samples are taken every 4 hours to analyze the Fe3O4 content in the slag, and the pulverized coal injection rate is manually adjusted to control the Fe3O4 content in the slag between 5.5% and 6.0%. After implementation, the copper content in the waste slag is stabilized below 1.25%, and because the pulverized coal is partially burned for heating, the total fuel consumption is reduced by approximately 3% compared to traditional methods.

[0035] Comparative Example

[0036] Under the same equipment, raw materials, and lower blast conditions as in Example 1, the natural gas lance was shut off and the system was run for 24 hours (simulating the conventional process). The Fe3O4 content in the slag rebounded to 12.1%, the slag became more viscous, and the average copper content in the discarded slag during this period was 1.79%. This comparison directly demonstrates the necessity and effectiveness of constructing a weakly reducing clarification zone in reducing copper loss.

[0037] The above description is a preferred embodiment of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A double-sided blown pool smelting method with low copper loss, characterized in that, Within the same double-sided blown pool smelting furnace, a vertical oxygen potential gradient is constructed and maintained in the molten pool, consisting of a strongly oxidizing smelting zone at the bottom and a weakly reducing clarifying zone at the top. This specifically includes the following steps: a) By blowing oxygen-enriched air with an oxygen concentration of 70%-85% into the lower part of the molten pool through the double-sided main air inlets located at the lower part of the side wall of the molten pool, the strong oxidation smelting zone is formed. b) By using a reducing medium injection device located above the main air outlet and opening into the slag layer of the molten pool, a reducing medium is injected into the slag layer to form the weak reduction clarification zone in the upper part of the molten pool. c) Monitor the CO content in the flue gas discharged from the smelting furnace online, and / or periodically detect the Fe3O4 content in the slag layer of the molten pool; d) Based on the CO content and / or Fe3O4 content obtained from step c), dynamically adjust the injection amount of the reducing medium so that the Fe3O4 content in the slag in the weakly reducing clarification zone is controlled within the range of 3%–6%.

2. The low copper loss double-sided blown pool smelting method according to claim 1, characterized in that, The reducing medium is one or more of natural gas, liquefied petroleum gas, pulverized coal, and coke powder.

3. The low copper loss double-sided blown pool smelting method according to claim 1, characterized in that, In step d), the CO content in the flue gas is controlled within the range of 0.5% to 1.5% by adjusting the injection amount of the reducing medium.

4. The low copper loss double-sided blown pool smelting method according to claim 1, characterized in that, The total amount of the injected reducing medium accounts for 3%–10% of the total fuel consumption.

5. The low copper loss double-sided blown pool smelting method according to claim 1, characterized in that, The smelting temperature in the strong oxidation smelting zone is controlled at 1250-1280℃.

6. The low copper loss double-sided blown pool smelting method according to claim 1, characterized in that, The blowing pressure of oxygen-enriched air blown in through the main air inlet is 110-130 kPa.

7. The low copper loss double-sided blown pool smelting method according to claim 1, characterized in that, The nozzle of the reducing medium blowing device is located in the middle or lower part of the slag layer in the molten pool.

8. The low copper loss double-sided blown pool smelting method according to claim 1, characterized in that, The reducing medium is injected into the slag layer of the molten pool via a special spray gun using a pneumatic delivery method.

9. The low copper loss double-sided blown pool smelting method according to any one of claims 1 to 8, characterized in that, After being quenched and tempered in the weak reduction clarification zone, the copper content of the discarded slag is reduced to below 1.3%.

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