CN104946903A - Method for recovering metal resource from zinc calcine through reduction roasting-leaching-zinc sinking - Google Patents

Abstract

The invention discloses a method for recovering metal resources by reducing roasting-leaching-precipitating zinc ferrite-containing materials. The high-iron zinc calcine containing zinc ferrite is reduced and roasted under CO atmosphere to decompose zinc ferrite into zinc oxide and iron oxide, and then the roasted product is alkaline leached with sodium hydroxide solution to obtain calcine containing less impurity ions Sodium zincate solution, iron, lead and silver, etc. enter the leaching slag for enrichment and recovery, realizing efficient separation of zinc and iron. The waste electrolyte in conventional zinc hydrometallurgy is used to neutralize the leaching solution to adjust zinc precipitation, and after precipitation, it is calcined in a muffle furnace to recover zinc resources in the form of active zinc oxide. The method of the invention avoids the complex iron-precipitating process in the conventional zinc hydrometallurgy process, has good separation effect of zinc and iron, and achieves the purpose of comprehensively recovering metal resources.

Description

A method for zinc calcine reduction roasting-leaching-precipitating zinc to recover metal resources

technical field

The invention belongs to the intersecting field of metallurgical engineering and environmental engineering, and mainly relates to a method for efficiently separating zinc and iron from a traditional zinc hydrosmelting process and recovering valuable metal resources.

Background technique

my country is a big country in zinc smelting, and its zinc output has always been among the top in the world. At present, more than 85% of zinc is produced by traditional roasting-leaching-purification-electrowinning wet process. Zinc ore is often associated with 8-15% Fe. During the oxidation roasting process of hydrometallurgy, this part of Fe inevitably reacts with zinc oxide in zinc calcine to form zinc ferrite with stable properties. Zinc ferrite is difficult to dissolve in conventional neutral leaching and acid leaching, resulting in a low recovery rate of zinc, and a large amount of leaching slag containing lead and silver is piled up, causing environmental pollution and loss of valuable metal resources.

At present, the methods of decomposing zinc ferrite to treat zinc-containing waste slag include fire method and wet method. Conventional pyrotechnics, such as rotary kiln volatilization method, add 40-50% reduced coke to the zinc-containing waste residue, and reduce zinc ferrite to zinc vapor at a high temperature of 1100°C-1300°C, and the zinc vapor is oxidized and collected to return to zinc Leaching section. The process has high energy consumption, high labor operation intensity, low recovery rate of zinc and serious environmental pollution. The generated rotary kiln slag is mainly a solid solution of carbon, iron, lead, silver and scattered metals, which is hard, difficult to grind, difficult to follow-up treatment, and a large amount of accumulation pollutes the environment. The wet treatment process is mainly high temperature and high acid leaching-iron precipitation process. Zinc ferrite is forcibly dissolved under high temperature and high acid conditions. The sinking iron process is complicated, the production cost is high, and the requirements for equipment are high. A large amount of sinking iron slag is also a waste of resources and a pollution to the environment. Therefore, how to improve the hydrometallurgy process to efficiently separate zinc and iron has become the key to the development of the zinc smelting industry.

Contents of the invention

The purpose of the present invention is to provide a method for recovering metal resources by reducing roasting-leaching-precipitating zinc ferrite-containing materials. The method of the invention avoids the complicated iron-precipitation process in the conventional zinc hydrometallurgy process, has good separation effect of leaching zinc and iron, and can efficiently and comprehensively recover valuable metal resources.

A method for recovering metal resources by reduction roasting-leaching-zinc-precipitation of zinc ferrite-containing materials, comprising the following steps: reduction roasting of zinc ferrite-containing materials, alkaline leaching of reduction roasting products, neutralization of the leaching solution and regulation of precipitation of zinc, iron, lead and silver Enriched in the slag for further recovery.

In the above method, the reducing agent for reduction roasting is coal powder, coal gas, natural gas, carbon monoxide or hydrogen; the roasting temperature is 600-850° C.; the roasting time is 30-90 minutes.

The alkali used in the alkaline leaching of the reduced roasted product in the above method includes: sodium hydroxide, ammonia water or a mixture of the two.

The amount of alkali added in the above method is such that zinc mainly exists in the form of zincate ZnO ₂ ^2- after alkaline leaching of the reduced product. 0.8-2 times the theoretical mass where all the zinc is leached in the form of sodium zincate is preferred.

In the above method, the leaching temperature is 60-85°C, the liquid-solid ratio is 6:1-10:1, and the leaching time is 20-60min.

In the above method, dilute sulfuric acid, zinc purification solution or zinc waste electrolyte is used to neutralize the leaching solution and adjust the zinc precipitation.

In the above method, the neutralization end point pH is controlled to be 7-10.

In the above method, the leach solution is neutralized to adjust the zinc precipitation reaction temperature to 20-45° C., and the reaction takes 10-30 minutes.

In the above method, the leaching solution is neutralized to adjust zinc precipitation, filtered, and then calcined at 250-300° C. for 1 hour to obtain active zinc oxide.

Concrete technological process of the present invention and process parameter are as follows:

1. Roasting

Roast the zinc ferrite-containing material in a weak reducing atmosphere. When the weak reducing atmosphere is CO, control the CO concentration to 4-10%, and the rest of the gas is nitrogen. The roasting temperature is 600-850°C, and the roasting time is 30-90 minutes. The possible chemical reactions of zinc ferrite in the process are as follows:

3ZnFe ₂ O ₄ +CO＝3ZnO+2Fe ₃ O ₄ +CO ₂

ZnFe ₂ O ₄ +CO=ZnO+2FeO+CO ₂

ZnFe ₂ O ₄ +FeO=ZnO+Fe ₃ O ₄

Fe ₃ O ₄ +CO=FeO+CO ₂

2. Leaching

Take out the roasted product, quench it with water, and then add solid sodium hydroxide to the ratio. The added mass of solid sodium hydroxide is 0.8-2 times of the theoretical mass in which all the zinc in the reduced product is leached in the form of sodium zincate, and the leaching temperature is 60-85 ℃, liquid-solid ratio 6-10:1, leaching time 20-60min. The chemical reactions that may occur during the leaching process are as follows:

ZnO+2NaOH+H ₂ O=Na ₂ [Zn(OH) ₄ ]

3. Precipitation

Mix and add neutralizing solution to the zinc-containing leaching solution, control the pH of the neutralization end point to 7-10, and the temperature to 20-45°C, filter after reacting for 10-30 minutes, and calcinate the precipitate at 250-300°C for 1 hour to obtain an active zinc oxide product .

The weakly reducing atmosphere can be coal powder, coal gas, natural gas, carbon monoxide or hydrogen.

The neutralizing solution can be dilute sulfuric acid, zinc purification solution or zinc waste electrolyte.

Compared with prior art, effect of the present invention is as follows:

The present invention adopts weak reducing gas CO for roasting, so that most of the zinc ferrite components in the high-iron zinc calcine are decomposed, and the leaching rate of valuable metals is improved; hot alkali leaching is used in the leaching process to realize efficient separation of zinc and iron, which is different from the currently commonly used Compared with the hot acid leaching-jarosite method, the iron leaching rate is greatly reduced, the complicated iron precipitation process is avoided, the process flow is shortened, and the leaching efficiency is improved; the neutralization solution required by the present invention can utilize the conventional zinc electrodeposition process The waste electrolyte produced in the process can neutralize the alkaline leaching solution of zinc, which can be combined with the conventional zinc electrowinning process to make full use of the waste electrolyte to recycle valuable metals; the zinc precipitate is mainly in the form of active zinc oxide after calcination Recycling zinc resources has high utilization value and good economic benefits.

Description of drawings

Fig. 1 is the XRD pattern of raw material zinc calcined sand;

Fig. 2 is the XRD figure of roasting product under different reducing roasting conditions in the embodiment;

Fig. 3 is the effect figure after alkali leaching of roasted product under different reducing roasting conditions in the embodiment;

Figure 4 is the XRD pattern of the zinc-precipitated product in the example after calcination.

Detailed ways

The drawings and specific embodiments are intended to further describe the present invention in detail, but not to limit the present invention.

Example

In the present embodiment, the method of zinc calcined reduction roasting-alkali leaching-precipitating zinc comprises the following steps:

(1) Dry the zinc-zinc calcined sand of a lead-zinc smelter and grind it until it passes through a 100-200-mesh sieve. The chemical phase analysis and XRD analysis of all elements and zinc of zinc calcine are shown in Table 1, 2 and Figure 1, respectively. It can be seen from the analysis that the zinc calcine mainly contains 53.5% Zn and 12.1% Fe, and the Fe mainly exists in the form of ferrite. The recovery of zinc in zinc ferrite is the key to improving the overall zinc recovery rate.

Table 1 Elemental analysis results of zinc calcine, wt%

Table 2 zinc phase analysis results, wt%

(2) Put the dry and fine zinc calcine into the reduction roasting furnace, use _N2 to clear the air in the furnace, raise the temperature of the reduction roasting furnace to 700-800 ° C, start adding CO gas, and control the CO concentration to 4-10% , and the rest is nitrogen; the reaction time is 30-90min. After the reaction time is over, quickly take out the sample and water-cool it to prevent the reduced calcine from regenerating zinc ferrite during the cooling process. The XRD comparison of roasted products obtained under different roasting conditions is shown in Figure 2. Comparing the phases before and after roasting, it can be seen that most of the zinc ferrite is decomposed after reduction roasting to obtain zinc oxide and iron oxide. Take the reduced calcined sand and mix it with NaOH solid. The added mass of NaOH is 0.8-2 times of the theoretical mass in which all the zinc in the reduced product is leached in the form of sodium zincate. Add a certain amount of warm water for leaching, and control the temperature at 30-60 ℃, liquid-solid ratio (7-10): 1, stirring and leaching at 400r/min for 15-30min, filtering after the reaction, and analyzing the zinc leaching rate in the leaching solution by titration, the experimental results are shown in Figure 3. It can be seen from Figure 3 that the zinc leaching rate of reduced calcine under the conditions of 4% CO concentration, 800°C and 45 minutes can reach 87.32%, while the iron leaching rate is only 0.13%. Compared with acid leaching under the same conditions, the zinc leaching rate can be guaranteed. At the same time, the iron leaching rate is greatly reduced. Add dropwise the simulated prepared zinc electrowinning waste electrolyte (H ₂ SO ₄ concentration 130-150g/L) into the alkaline immersion solution, stir at 300r/min at room temperature, and control the pH at 8-10 at the same time, and react 10- After 30 minutes, it was filtered, and the precipitate was calcined at 300° C. for 1 hour. The XRD pattern of the calcined product is shown in FIG. 4 . The zinc recovery rate can reach 92-93% through analysis and calculation. Compared with the existing technology, the complicated iron precipitation steps are avoided while the zinc recovery rate is ensured, the process flow is optimized, and zinc resources are mainly recovered in the form of zinc oxide.

Claims (10)

1. A method for reducing and roasting-leaching-zinc-precipitating zinc ferrite-containing material to recover metal resources, comprising the following steps: reducing and roasting the zinc-ferrite-containing material, alkaline leaching of the reduced-roasted product, neutralizing the leaching solution and adjusting the precipitation Zinc, iron, lead and silver are enriched in the slag for further recovery. 2. The method according to claim 1, characterized in that the reducing agent for reduction roasting is coal powder, coal gas, natural gas, carbon monoxide or hydrogen; the roasting temperature is 600-850° C.; the roasting time is 30-90 minutes. 3. The method according to claim 1, characterized in that the alkali used in the alkaline leaching of the reduced roasted product comprises sodium hydroxide, ammonia or a mixture of the two. 4. The method according to claim 1 or 3, characterized in that the zinc mainly exists in the form of zincate ZnO ₂ ^2- after alkaline leaching of the reduction roasted product. 5. The method according to claim 1 or 3, characterized in that the added quality of the alkali is 0.8-2 times of the theoretical quality that all zinc in the reduction product is leached with sodium zincate form. 6. The method according to claim 1 or 3, characterized in that the leaching temperature is 60-85°C, the liquid-solid ratio is 6:1-10:1, and the leaching time is 20-60min. 7. The method according to claim 1, characterized in that dilute sulfuric acid, zinc purification solution or zinc waste electrolyte is used for neutralizing the leaching solution and regulating zinc precipitation. 8. The method according to claim 1 or 7, characterized in that the neutralization terminal pH is controlled to be 7-10. 9. The method according to claim 1 or 7, characterized in that the leach solution is neutralized to adjust the zinc precipitation reaction temperature to 20-45° C., and the reaction takes 10-30 minutes. 10. The method according to claim 1, characterized in that the leaching solution is neutralized to adjust zinc precipitation, filtered, and then calcined at 250-300° C. for 1 hour to obtain active zinc oxide.