A method for recovering cobalt from organic cobalt residue of zinc hydrometallurgy

Abstract

The present application relates to a kind of methods for recovering cobalt from organic cobalt residue of zinc hydrometallurgy, belong to the field of metallurgical solid waste comprehensive recovery.The organic cobalt residue is added into pyrolysis furnace, and low-temperature pyrolysis is carried out on the organic cobalt residue by using natural gas combustion external heating to generate pyrolysis residue and pyrolysis flue gas, and natural gas combustion is converted into low-temperature harmless heating tail gas;The pyrolysis flue gas is introduced into the combustion furnace to ignite, and the pyrolysis flue gas is used for self-heating combustion to degrade organic matter to generate high-temperature tail gas of combustion furnace, and the high-temperature tail gas of combustion furnace is returned to the pyrolysis furnace to replace the external heating of natural gas combustion to carry out low-temperature pyrolysis on the organic cobalt residue, at the same time, the high-temperature tail gas of combustion furnace is converted into low-temperature harmless heating tail gas;Industrial water is added to the pyrolysis residue for slurry, and zinc is transferred to the solution by stirring and leaching at a temperature of 50-70 DEG C for 1-3h, and low-zinc-content cobalt concentrate is obtained by solid-liquid separation.The present application has good zinc and cobalt separation effect, and can solve the problems of poor operation environment, roasting or pyrolysis flue gas pollution of organic purification cobalt residue direct pickling.

Description

Technical Field

[0001] This invention relates to a method for recovering cobalt from organic cobalt slag in wet zinc smelting, belonging to the field of metallurgical solid waste disposal technology. Background Technology

[0002] Hydrometallurgical zinc smelting enterprises use sodium formaldehyde sulfoxylate, a novel organic reagent, as a cobalt removal agent to purify zinc sulfate solutions. The resulting organically purified cobalt slag is primarily processed using a combination of direct acid washing, roasting (or pyrolysis), and reductive leaching to decompose organic matter and recover cobalt. Acid washing of the organically purified cobalt slag achieves effective separation of zinc and cobalt. High-temperature roasting decomposes the stable cobalt chelates formed by the organic cobalt removal agent and cobalt ions, while the organic matter is burned, and cobalt metal is enriched into soluble compounds. Reductive leaching is then used to recover the cobalt after roasting. However, the organically purified cobalt slag has a pungent odor, the acid washing process creates a poor operating environment, and it is easily decomposed by heat, producing mixed gases such as sulfur and amines, which are difficult to recover comprehensively. The roasting process also generates a large amount of foul-smelling gases, causing environmental pollution. Therefore, the industrial-scale application of comprehensive recycling and utilization of organically purified cobalt slag is limited, and most enterprises currently store it awaiting processing.

[0003] How to comprehensively develop and utilize the organically purified cobalt slag produced by organic cobalt removal agents in the hydrometallurgical zinc smelting industry, effectively solve the environmental pollution caused by the organically purified cobalt slag, and comprehensively recover the valuable metals contained therein, is a key technical problem that the industry urgently needs to solve. Summary of the Invention

[0004] To address the problems of poor operating environment and high flue gas pollution from roasting or pyrolysis when treating cobalt slag from organic purification in wet zinc smelting using direct acid washing-roasting (or pyrolysis) processes, this invention proposes a method for recovering cobalt from organic cobalt slag in wet zinc smelting. This method employs low-temperature pyrolysis of cobalt slag, flue gas degradation and waste heat utilization, and water leaching to remove zinc and prepare cobalt concentrate. This method has low energy consumption, no pollution, and good separation effect between zinc and cobalt.

[0005] This invention employs a low-temperature pyrolysis-flue gas degradation and waste heat utilization-water washing zinc removal process to treat organic purified cobalt slag and prepare cobalt concentrate. Through a multi-furnace combined harmless treatment technology, the organic cobalt slag is pyrolyzed at low temperature in the pyrolysis furnace using the heat from the combustion of its own organic matter. A small amount of natural gas is used in the combustion furnace to ignite the pyrolysis flue gas and degrade the organic matter. The combustion exhaust gas is returned to the pyrolysis furnace for low-temperature pyrolysis of the organic purified cobalt slag. This method solves the problems of poor operating environment and high pollution from roasting or pyrolysis flue gas associated with direct acid washing of organic purified cobalt slag. The method of this invention has low energy consumption, no pollution, and good separation effect between zinc and cobalt.

[0006] A method for recovering cobalt from organocobalt slag in wet zinc smelting includes the following steps: (1) Organic cobalt slag is added to a pyrolysis furnace and the organic cobalt slag is pyrolyzed at low temperature by external heating with natural gas combustion to generate pyrolysis slag and pyrolysis flue gas; (2) The pyrolysis flue gas is introduced into the combustion furnace for ignition. The pyrolysis flue gas uses self-heating combustion to degrade organic matter and generate high-temperature tail gas from the combustion furnace. The high-temperature tail gas from the combustion furnace is returned to the pyrolysis furnace to replace the external heating of natural gas combustion for low-temperature pyrolysis of organic cobalt slag. At the same time, the high-temperature tail gas from the combustion furnace is converted into low-temperature harmless heating tail gas. (3) Add industrial water to the pyrolysis residue to make a slurry, stir and leach at 50~70℃ for 1~3h to transfer zinc into the solution, and then separate the solid and liquid to obtain cobalt concentrate with low zinc content.

[0007] Preferably, the temperature of the low-temperature pyrolysis in step (1) is 400~450℃ and the pyrolysis time is 1~3h.

[0008] Preferably, the combustion temperature in step (2) is 1100~1300℃, and the high-temperature exhaust gas temperature of the combustion furnace is 800~1000℃.

[0009] Preferably, in step (3), the liquid-to-solid ratio of industrial water to pyrolysis residue is 5-10:1 (mL:g).

[0010] The beneficial effects of this invention are: (1) The invention of low-temperature pyrolysis of organic matter + high-temperature degradation and harmlessness of flue gas: the organic salts of cobalt in the organic purification slag of wet zinc smelting are mainly (C6H 12 The high-temperature calcination or oxidative roasting process (CoN2S4) typically involves oxidizing and burning organic matter at temperatures above 600℃, producing a large amount of "rotten-smelling" gases. Furthermore, the oxidation of organic matter releases a certain amount of nitrogen oxides, making it difficult to meet environmental protection requirements and resulting in emissions that fail to meet standards. This invention employs an oxygen-free low-temperature pyrolysis technology below 450℃ to decompose organic chelates into solids such as CoS, Co2S3, and ZnSO4, as well as N2 and carbon-containing organic gases. This process does not alter the physical characteristics of the organic matter, does not introduce new pollutants, and produces no nitrogen oxides. The pyrolysis flue gas is then subjected to high-temperature combustion degradation, achieving harmless and pollution-free flue gas treatment. (2) The material of the present invention generates heat by itself and has low energy consumption: the pyrolysis flue gas generated by the low-temperature pyrolysis of organic cobalt slag is burned at high temperature. The combustion process makes full use of the characteristics of the C-containing organic gas in the pyrolysis flue gas being flammable and releasing a large amount of heat. After the initial ignition with a small amount of natural gas, there is no need to supply natural gas or other fuels. At the same time, the combustion tail gas is used for the low-temperature pyrolysis of organic cobalt slag to realize the material generating heat by itself and supplying heat without the need for energy supply.

[0011] (3) The zinc-cobalt separation process of the present invention is simple, clean and efficient: The main phases in the organically purified cobalt slag are zinc sulfate hexahydrate, basic ferric sulfate, cadmium sulfate hexahydrate, cobalt sulfate hexahydrate and organic salts of cobalt. Direct acid washing and pre-leaching of zinc from organically purified cobalt slag results in a poor operating environment and low zinc removal rate due to the influence of organic matter; roasting or calcination is carried out in an oxidizing atmosphere, and the slag (cobalt concentrate) produced mainly contains cobalt phases of CoSO4, CoO and a small amount of Co3O4, while the zinc phase is mainly ZnO and a small amount of ZnSO4. Since the leaching behavior of the main phase sulfates is similar, zinc and cobalt are leached simultaneously in the subsequent leaching process of cobalt concentrate, making it difficult to achieve effective separation of zinc and cobalt in cobalt concentrate. The leaching solution has high zinc content and low cobalt content, making cobalt separation and enrichment difficult. The cobalt-containing phase in the pyrolysis residue obtained by low-temperature pyrolysis of this invention is mainly CoS and a small amount of Co2S3, while the zinc-containing phase is mainly ZnSO4 and a small amount of ZnS. The leaching thermodynamic conditions of the cobalt phase and the zinc phase in the pyrolysis residue are completely different. Zinc can be effectively leached from the pyrolysis residue by water washing, realizing the separation of zinc and cobalt, thereby obtaining a cobalt concentrate with a significantly reduced zinc content, which is beneficial to the subsequent leaching of cobalt concentrate and the separation and enrichment of cobalt in the leachate. Detailed Implementation

[0012] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0013] The organic cobalt slag in this embodiment of the invention is sodium formic acid leaching and zinc removal slag, and its main components (mass percentage) are: Co 5.12%, Zn 5.03%, S 31.68%, C 15.71%, N 11.35%.

[0014] Example 1: A method for recovering cobalt from organocobalt slag in wet zinc smelting, the specific steps of which are as follows: (1) Organic cobalt slag is added to a pyrolysis furnace and heated by natural gas combustion. The organic cobalt slag is pyrolyzed at a low temperature of 450℃ for 1 hour to generate pyrolysis slag and pyrolysis flue gas. (2) The pyrolysis flue gas is introduced into the combustion furnace and ignited by natural gas. The pyrolysis flue gas uses self-heating combustion to degrade organic matter and generate high-temperature tail gas from the combustion furnace. The combustion temperature is controlled at 1200~1300℃ and the high-temperature tail gas temperature is 900~1000℃. The high-temperature tail gas from the combustion furnace can be returned to the pyrolysis furnace to replace the external heating of natural gas combustion for low-temperature pyrolysis of organic cobalt slag. (3) Add industrial water to the pyrolysis residue to make a slurry. The liquid-solid ratio of the industrial water to the pyrolysis residue is 5:1 mL:g. Stir and leach at 50°C for 3 hours to transfer zinc into the solution. Solid-liquid separation is then performed to obtain cobalt concentrate with low zinc content. In this embodiment, the cobalt recovery rate reached 98.27%; the cobalt concentrate contained 1.25 wt% zinc and 10.36 wt% cobalt.

[0015] Example 2: A method for recovering cobalt from organocobalt slag in wet zinc smelting, the specific steps of which are as follows: (1) Organic cobalt slag is added to the pyrolysis furnace and heated by the high-temperature tail gas of the combustion furnace in Example 1. At a temperature of 400°C, the organic cobalt slag is pyrolyzed at low temperature for 3 hours to generate pyrolysis slag and pyrolysis flue gas. The high-temperature tail gas of the combustion furnace is converted into low-temperature harmless heating tail gas. (2) The pyrolysis flue gas is introduced into the combustion furnace for ignition. The pyrolysis flue gas utilizes self-heating combustion to degrade organic matter and generate high-temperature tail gas from the combustion furnace. The combustion temperature is controlled at 1100~1200℃, and the high-temperature tail gas temperature is 800~900℃. The high-temperature tail gas from the combustion furnace can be returned to the pyrolysis furnace to replace the external heating of natural gas combustion for low-temperature pyrolysis of organic cobalt slag. (3) Add industrial water to the pyrolysis residue to make a slurry. The liquid-solid ratio of the industrial water to the pyrolysis residue is 10:1 mL:g. Stir and leach at 70°C for 1 hour to transfer zinc into the solution. Solid-liquid separation is then performed to obtain cobalt concentrate with low zinc content. In this embodiment, the cobalt recovery rate reached 98.92%; the cobalt concentrate contained 0.73 wt% zinc and 10.51 wt% cobalt.

[0016] Example 3: A method for recovering cobalt from organocobalt slag in wet zinc smelting, the specific steps of which are as follows: (1) Organic cobalt slag is added to the pyrolysis furnace and heated by the high-temperature tail gas of the combustion furnace in Example 2. At a temperature of 420°C, the organic cobalt slag is pyrolyzed at low temperature for 2 hours to generate pyrolysis slag and pyrolysis flue gas. The high-temperature tail gas of the combustion furnace is converted into low-temperature harmless heating tail gas. (2) The pyrolysis flue gas is introduced into the combustion furnace for ignition. The pyrolysis flue gas utilizes self-heating combustion to degrade organic matter and generate high-temperature tail gas from the combustion furnace. The combustion temperature is controlled at 1150~1250℃, and the high-temperature tail gas temperature is 850~950℃. The high-temperature tail gas from the combustion furnace can be returned to the pyrolysis furnace to replace the external heating of natural gas combustion for low-temperature pyrolysis of organic cobalt slag. (3) Add industrial water to the pyrolysis residue to make a slurry. The liquid-solid ratio of the industrial water to the pyrolysis residue is 8:1 mL:g. Stir and leach at 60°C for 2 hours to transfer zinc into the solution. Solid-liquid separation is then performed to obtain cobalt concentrate with low zinc content. In this embodiment, the cobalt recovery rate reached 97.69%; the cobalt concentrate contained 0.86 wt% zinc and 10.45 wt% cobalt.

[0017] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for recovering cobalt from organocobalt slag in wet zinc smelting, characterized in that, The specific steps are as follows: (1) Organic cobalt slag is added to a pyrolysis furnace and the organic cobalt slag is pyrolyzed at low temperature by external heating with natural gas combustion to generate pyrolysis slag and pyrolysis flue gas; (2) The pyrolysis flue gas is introduced into the combustion furnace for ignition. The pyrolysis flue gas uses self-heating combustion to degrade organic matter and generate high-temperature tail gas from the combustion furnace. The high-temperature tail gas from the combustion furnace is returned to the pyrolysis furnace to replace the external heating of natural gas combustion for low-temperature pyrolysis of organic cobalt slag. At the same time, the high-temperature tail gas from the combustion furnace is converted into low-temperature harmless heating tail gas. (3) Add industrial water to the pyrolysis residue to make a slurry, stir and leach at 50~70℃ for 1~3h to transfer zinc into the solution, and then separate the solid and liquid to obtain cobalt concentrate with low zinc content.

2. The method for recovering cobalt from organocobalt slag in hydrometallurgical zinc refining according to claim 1, characterized in that: Step (1) The temperature for low-temperature pyrolysis is 400~450℃, and the pyrolysis time is 1~3h.

3. The method for recovering cobalt from organocobalt slag in hydrometallurgical zinc refining according to claim 1, characterized in that: Step (2) The combustion temperature is 1100~1300℃, and the high temperature of the exhaust gas from the combustion furnace is 800~1000℃.

4. The method for recovering cobalt from organocobalt slag in hydrometallurgical zinc refining according to claim 1, characterized in that: Step (3) The liquid-solid ratio of industrial water to pyrolysis residue is 5~10:1 mL:g.