Low-temperature smelting process for electrolytic anode slime

Abstract

The invention discloses a low-temperature smelting process for electrolytic anode slime. The low-temperature smelting process comprises the steps of freezing pretreatment, wet ball-milling refining, smelting and mixing, medium-temperature smelting, metal recovery and the like. According to the method, the crystal structure of the anode slime is embrittled through freezing pretreatment, wet ball milling refining and medium-temperature reduction smelting are combined, and efficient recycling of valuable metal such as silver and lead is achieved at the temperature of 700-850 DEG C. And compared with a traditional process, the energy consumption is reduced by 30%-50%, the metal recovery rate is increased to 90% or above, the smoke emission is reduced by 50% or above, and the method is suitable for industrial continuous production.

Description

Technical Field

[0001] The present invention relates to the technical field of non-ferrous metal smelting and resource recycling, and in particular to a low-temperature smelting process for electrolytic anode mud. The process is based on the coordinated freezing pretreatment and medium-temperature reduction smelting of the electrolytic anode mud, and is suitable for efficiently recovering valuable metals from electrolytic anode mud containing metals such as lead, silver, antimony, and copper, and is particularly suitable for the green and low-carbon treatment of copper electrolytic anode mud. Background Art

[0002] Electrolytic anode mud is a byproduct of the metal electrolytic refining process, rich in valuable metals such as silver (Ag), lead (Pb), antimony (Sb), and copper (Cu). Traditional processing technology mainly uses high-temperature smelting (>1000°C), and representative technologies include:

[0003] (1) Pyrometallurgical smelting-electrolysis (e.g., CN102534223A): Metals are separated by high-temperature melting, but the energy consumption is as high as 1200-1500 kWh / ton of raw materials, and flue gas containing heavy metal dust (PbO, As2O3, etc.) is generated, requiring a complex flue gas purification system.

[0004] (2) Wet leaching-extraction method (such as CN104611517A): Use strong acid to leach metals. Although the temperature is relatively low, a large amount of acid-containing wastewater is produced, and the recovery rate of silver and lead is less than 80%.

[0005] The existing electrolytic anode mud treatment process mainly has the following problems:

[0006] (1) High energy consumption: High-temperature smelting requires a large amount of fuel or electricity, and the processing cost per ton of raw materials exceeds 5,000 yuan (data source: "Economic Analysis of Non-ferrous Metal Smelting Technology", 2021).

[0007] (2) Serious pollution: The high-temperature process releases SO2, heavy metal vapor and dust, and the cost of environmental protection treatment accounts for more than 30% of the total investment.

[0008] (3) Low recovery rate: The recovery rates of silver and lead fluctuate between 75% and 85%, while the recovery rate of antimony is less than 70% due to serious volatilization losses.

[0009] Therefore, there is an urgent need to develop a low-temperature, closed, short-process smelting process that can reduce energy consumption while increasing metal recovery rates and reducing pollution. Summary of the Invention

[0010] In response to the above technical problems, the present invention provides a low-temperature smelting process for electrolytic anode mud. Through the synergistic technology of "freeze embrittlement-mechanical refinement-medium-temperature reduction smelting", the following goals are achieved: smelting temperature ≤ 850°C, energy consumption reduced by ≥ 30%; silver and lead recovery rates ≥ 90%, antimony recovery rate ≥ 85%; smoke dust emissions reduced by ≥ 50%, without the need for a complex exhaust gas treatment system.

[0011] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0012] A low-temperature smelting process for electrolytic anode mud comprises the following steps:

[0013] S1. Freezing pretreatment: The electrolytic anode mud is placed in an environment of -30℃ to -3℃ and frozen for 10 to 60 minutes. The water and bound water in the electrolytic anode mud form ice crystals at low temperatures, which expand and destroy the metal sulfide / oxide lattice, thereby improving the subsequent crushing efficiency.

[0014] S2. Wet ball milling: The electrolytic anode mud after the freezing treatment in step S1 is wet ball milled for 1 to 3 hours to prepare anode mud fine powder;

[0015] S3. Smelting mixture: mixing the anode mud fine powder with a reducing agent and a slag forming agent to obtain a mixture, wherein the amount of the reducing agent is 10% to 30% by mass of the anode mud fine powder, and the amount of the slag forming agent is 10% to 50% by mass of the anode mud fine powder;

[0016] S4 medium temperature melting: The mixture obtained in step S3 is placed in a closed medium frequency induction furnace, the melting temperature is 700~850 ℃, the holding time is 30~60 minutes, and the reaction path is:

[0017] PbS+C→Pb+CO↑+S↑ (ΔH=-120kJ / mol).

[0018] S5. Metal recovery: separation of metal ingots from glassy slag.

[0019] Furthermore, in step S1, the freezing temperature is preferably -30°C to -5°C, more preferably -25°C to -15°C, and the freezing time is preferably 30 to 45 minutes.

[0020] Furthermore, in step S1, the freezing temperature is controlled by a low-temperature freezing device, preferably a screw conveyor low-temperature cabinet, which can be adjusted to -40°C.

[0021] Furthermore, in step S2, the ball milling speed is 150-250 rpm, more preferably 180-220 rpm, and the ball milling water-to-material ratio is 1:1-2; the particle size of the fine powder is controlled to be ≤100 mesh, and the specific surface area is increased by 3-5 times through wet ball milling, thereby enhancing the reduction reaction kinetics.

[0022] Furthermore, in step S3, the amount of the reducing agent is preferably 15% to 25% of the mass of the anode mud fine powder, and the amount of the slag forming agent is preferably 20% to 40% of the mass of the anode mud fine powder.

[0023] Furthermore, in step S3, the reducing agent is preferably coke powder, whose fixed carbon content is ≥85%; the slag-forming agent is preferably silica powder, whose SiO2 content is ≥95%; the coke provides a reducing atmosphere (CO), and the silica and the metal oxides generate low-melting-point silicate slag (melting point ≤1000°C), exerting a synergistic effect.

[0024] Furthermore, in step S4, the frequency of the closed medium frequency induction furnace is 1000-2500 Hz; and the smelting temperature is preferably 750-800°C.

[0025] Furthermore, in step S4, the smelting flue gas is condensed to recover elemental sulfur.

[0026] Furthermore, in step S5, the separation method is gravity sedimentation-water quenching method, and the purity of the metal ingot is Ag ≥ 95%, and Pb ≥ 90%.

[0027] Furthermore, the electrolytic anode mud includes copper electrolytic anode mud, lead electrolytic anode mud, silver electrolytic anode mud and other electrolytic anode muds.

[0028] The beneficial effects of the present invention are:

[0029] (1) Significantly reduce energy consumption: the process temperature is controlled at 700-850℃ (traditional process requires >1000℃), and the comprehensive energy consumption is reduced by 35%-45%; freezing pretreatment (-30--3℃) destroys the crystal structure of the anode mud, reducing ball milling time and energy consumption; silica slagging agent cooperates with coke reducing agent to reduce the melting point of slag and shorten the smelting time.

[0030] (2) High and stable metal recovery rate: Freezing-ball milling synergistically increases the specific surface area (2.8-3.2 m2 / g), strengthens the reduction reaction kinetics, and the closed medium-frequency electric furnace reduces metal volatilization losses. The silver and lead recovery rates are ≥90%, and the antimony recovery rate is ≥85%.

[0031] (3) Outstanding environmental friendliness: dust concentration ≤ 20 mg / m3 (GB 25467-2010 limit 30 mg / m3); heavy metal (such as Ni, Co) content ≤ 0.1 mg / m3 (GB 31574-2015 standard); glassy slag is highly chemically inert, and the toxic leaching concentration is far lower than the national standard (TCLP method detects Pb leaching < 1 mg / L); at the same time, it replaces the traditional acid leaching process to avoid the generation of acidic wastewater.

[0032] (4) Significant cost advantages: The processing cost per ton of raw materials is reduced by about 40% (the fuel + environmental protection cost of traditional processes accounts for >50%); the purity of metal ingots is ≥95% and can be directly used for refining or alloy preparation. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited thereto.

[0034] Example 1: Copper electrolysis anode mud treatment

[0035] (1) Raw materials: 5 kg of copper electrolytic anode mud (composition: Ag 8.2 wt%, Pb 25.6 wt%, Sb 4.1 wt%, Cu 3.5 wt%);

[0036] (2) Freezing treatment: Freezing at -25°C for 45 minutes, the ice crystals expand and the volume of the raw material increases by 12%;

[0037] (3) Ball milling: water-to-material ratio 1.5:1, wet milling at 200 rpm for 2 hours, sieve through 100 mesh, the specific surface area of the obtained copper electrolysis anode mud fine powder reaches 2.8 m2 / g;

[0038] (4) Mixing: Add 1.2 kg of coke powder (24% of the mass of the copper electrolysis anode mud fine powder) and 1.8 kg of silica powder (36% of the mass of the copper electrolysis anode mud fine powder) and mix well.

[0039] (5) Melting: Keep the temperature at 750℃ in a closed medium frequency induction furnace for 50 minutes. The slag has good fluidity (viscosity ≤ 5 Pa·s).

[0040] (6) Separation of metal ingots and slag.

[0041] The energy consumption comparison between Example 1 and the existing process is shown in Table 1.

[0042] Table 1 Comparison of energy consumption between Example 1 and conventional high temperature smelting process

[0043]

[0044]

[0045] As can be seen from Table 1, the energy consumption of the present invention is reduced by about 42% compared with the traditional process.

[0046] At the same time, the experimental results show that the recovery rates of metal ingots are: Ag recovery rate 93.3%, Pb recovery rate 95.7%, and Sb recovery rate 87.5%.

[0047] Flue gas composition: CO2 accounts for >95%, SO2 is not detected (because sulfur is condensed and recovered as elemental S), and the dust concentration in the flue gas is ≤20mg / m3 (GB 25467-2010 meets the standard).

[0048] Slag toxicity: tested by TCLP (Toxicity Characteristic Leaching Procedure), the leaching concentration of Pb and As is less than 1 mg / L (GB5085.3-2007 limit is 5 mg / L).

[0049] Example 2: Treatment of lead electrolysis anode mud

[0050] (1) Raw materials: 5 kg of lead electrolysis anode mud (composition: Ag 6.5 wt%, Pb 38 wt%, Sb 8 wt%);

[0051] (2) Freezing treatment: Freeze at -20°C for 50 minutes;

[0052] (3) Ball milling: water-to-material ratio 1:1, wet milling at 180 rpm for 2.5 hours to obtain lead electrolysis anode mud fine powder;

[0053] (4) Mixing material: 1.0 kg of coke powder (20% of the mass of lead electrolysis anode mud fine powder), 2.0 kg of silica powder (40% of the mass of lead electrolysis anode mud fine powder);

[0054] (5) Melting: Keep the temperature at 780℃ in a closed medium frequency induction furnace for 50 minutes. The slag has good fluidity (viscosity ≤ 5 Pa·s);

[0055] (6) Separation of metal ingots and slag.

[0056] Experimental results:

[0057] Metal recovery: Ag 91.2%, Pb 93.8%, Sb 87.3%;

[0058] Environmental protection indicators: Flue gas dust concentration ≤ 20mg / m3 (GB 25467-2010 standard).

[0059] Example 3: Silver electrolysis anode mud treatment

[0060] (1) Raw materials: 5 kg of silver electrolytic anode mud (composition: Ag 15.2 wt%, Pb 9.8 wt%, Sb 4.5 wt%, Cu 1.5 wt%);

[0061] (2) Freezing treatment: Freezing at -28°C for 40 minutes, the ice crystals expand and the volume of the raw material increases by 10%;

[0062] (3) Ball milling: water-to-material ratio 1.2:1, wet milling at 220 rpm for 1.8 hours, sieve through 120 mesh, the obtained fine powder has a specific surface area of 3.2 m2 / g;

[0063] (4) Mixing: Add 0.75 kg of coke powder (15% of the mass of the silver electrolysis anode mud fine powder) and 1.25 kg of silica powder (25% of the mass of the silver electrolysis anode mud fine powder) and mix well;

[0064] (5) Melting: Keep the temperature at 760℃ for 55 minutes in a closed medium frequency induction furnace, and the slag viscosity should be ≤4.5Pa·s;

[0065] (6) Metal recovery: Separate the metal ingots and slag after cooling.

[0066] Experimental results:

[0067] Metal recovery rate: Ag 96.5%, Pb 92.7%, Sb 88.1%;

[0068] Environmental protection indicators: Flue gas dust concentration ≤18mg / m3 (GB 25467-2010 standard).

[0069] From the above examples, it can be seen that the process of the present invention is universally applicable to various types of electrolytic anode mud, such as copper, lead, and silver:

[0070] (1) Low temperature and high efficiency: The melting temperature is controlled at 700-800℃, and energy consumption is reduced by 35%-45%;

[0071] (2) High recovery rate: the recovery rate of main metals such as Ag and Pb is ≥90%, and the recovery rate of metals such as Sb is ≥85%;

[0072] (3) Green and environmentally friendly: Flue gas, dust and heavy metal emissions are far below national standards, and the glassy properties of slag avoid secondary pollution.

Claims

1. A low-temperature smelting process for electrolytic anode mud, characterized in that: The steps include: S1. Freezing pretreatment: Place the electrolytic anode mud in an environment of -30℃ to -3℃ and freeze for 10 to 60 minutes; S2. Wet ball milling: The electrolytic anode mud after the freezing treatment in step S1 is wet ball milled for 1 to 3 hours to prepare anode mud fine powder; S3. Smelting mixture: mixing the anode mud fine powder with a reducing agent and a slag forming agent to obtain a mixture, wherein the amount of the reducing agent is 10% to 30% by mass of the anode mud fine powder, and the amount of the slag forming agent is 10% to 50% by mass of the anode mud fine powder; S4 medium temperature melting: The mixture obtained in step S3 is placed in a closed medium frequency induction furnace, the melting temperature is 700 to 850 ℃, and the holding time is 30 to 60 minutes; S5. Metal recovery: separation of metal ingots from glassy slag.

2. The low-temperature smelting process of electrolytic anode mud according to claim 1, characterized in that: In step S1, the freezing temperature is -25°C to -10°C, and the freezing time is 30 to 45 minutes.

3. The low-temperature smelting process of electrolytic anode mud according to claim 1, characterized in that: In step S1, the freezing temperature is controlled by a low-temperature freezing device.

4. The low-temperature smelting process for electrolytic anode mud according to claim 1, characterized in that: In step S2, the ball milling speed is 150-250 rpm, the ball milling water-to-material ratio is 1:1-2, and the particle size of the fine powder is controlled to be ≤100 mesh.

5. The low-temperature smelting process of electrolytic anode mud according to claim 1, characterized in that: In step S3, the amount of the reducing agent is 15% to 25% of the mass of the anode mud fine powder, and the amount of the slagging agent is 20% to 40% of the mass of the anode mud fine powder.

6. The low-temperature smelting process of electrolytic anode mud according to claim 1, characterized in that: In step S3, the reducing agent is coke powder, and its fixed carbon content is ≥85%; the slag-forming agent is silica powder, and its SiO2 content is ≥95%.

7. The low-temperature smelting process of electrolytic anode mud according to claim 1, characterized in that: In step S4, the frequency of the closed medium frequency induction furnace is 1000-2500 Hz; the smelting temperature is 750-800°C.

8. The low-temperature smelting process of electrolytic anode mud according to claim 1, characterized in that: In step S4, the smelting flue gas is condensed to recover elemental sulfur.

9. The low-temperature smelting process of electrolytic anode mud according to claim 1, characterized in that: In step S5, the separation method is gravity sedimentation-water quenching method, and the purity of the metal ingot is Ag≥95%, and Pb≥90%.

10. The low-temperature smelting process for electrolytic anode slime according to any one of claims 1 to 9, characterized in that: The electrolytic anode mud is selected from copper electrolytic anode mud, lead electrolytic anode mud or silver electrolytic anode mud.

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