CN113802149B - Method for extracting metallic iron from zinc kiln slag - Google Patents

Abstract

The invention discloses a method for extracting metallic iron from zinc kiln slag, which comprises the steps of taking zinc kiln slag and a graphite rod as a cathode electrode and an anode electrode respectively, inserting the zinc kiln slag and the graphite rod into a molten salt system formed by mixing and melting sodium chloride and potassium chloride in a protective gas atmosphere, carrying out molten salt constant-tank pressure electrolysis reaction, and finally cleaning and drying the cathode electrode to obtain the metallic iron. The method has the advantages of simple operation, concise flow, high recovery rate of the metallic iron, low energy consumption and less pollutant discharge, is suitable for industrial production, and solves the problems of low extraction rate and high extraction difficulty caused by complex zinc kiln slag system in the traditional process. The method is suitable for extracting the metallic iron from the zinc kiln slag.

Description

A method for extracting metallic iron from zinc kiln slag

technical field

The invention belongs to the technical field of metallurgical engineering and relates to zinc kiln slag, in particular to a method for extracting metallic iron from zinc kiln slag.

Background technique

Zinc kiln slag is the leaching slag (zinc tailings) produced by zinc ore hydrometallurgy, mixed with a certain amount of coke, and then reduced in a rotary kiln at high temperature to recover zinc, lead and other metals. At present, most of the zinc kiln slags in my country are piled up in smelters because they are not rationally utilized. As the country attaches great importance to environmental protection, this treatment method not only occupies a large amount of land resources, but also the heavy metals in the kiln slag are easy to migrate or seep into the ground with rainwater, and cause great damage to the environment. The main chemical components of zinc kiln slag are iron oxide, silicon dioxide, calcium oxide and aluminum oxide, etc. The main chemical components and contents are shown in the following table:

It can be seen that there is still a large amount of metallic iron in the zinc kiln slag.

At present, zinc kiln slag is usually sold to cement plants at a lower price for use as ingredients, resulting in low utilization efficiency due to non-recovery of valuable metals, which is a low value-added utilization. Due to the addition of coke or various reagents to extract metal zinc during the treatment of zinc tailings, the content of valuable metals in the generated zinc kiln slag is greatly reduced, and the zinc kiln slag system becomes more complicated. These factors Both have greatly increased the difficulty of recovering valuable metals from zinc kiln slag.

There are several ways to deal with zinc kiln slag in the traditional process:

(1) Mineral dressing method: the best process flow is flotation-magnetic separation-flotation full open circuit test, the recovery of Ag is better in this process, but the particle size requirements in the two flotation processes are different, Grinding must be done separately. Peng Wei et al. treated zinc kiln slag by flotation-magnetic separation process. Firstly, flotation was used to recover carbon preferentially, and then the tailings after flotation were recovered iron by magnetic separation. The results showed that the recovery of carbon and iron The rate reached 85.60% and 68.24% respectively, which has high economy, but it also needs to refine the grinding part, which will inevitably increase the operation process and cost;

(2) Reduction vulcanization method: adding a certain amount of reducing agent during reduction smelting can reduce the melting temperature of the obtained product (from the original 1600°C to 1250-1300°C), and separate the alloy powder into pure Fe and Ag after electrolysis and Ga anode slime. The collection of pure Fe obtained has great benefits, but the problem to be considered is the impact of the released flue gas SO ₂ pollution problem;

(3) Blast furnace smelting method: In the production process, the zinc kiln slag is mixed with a certain amount of coke and vulcanizing agent, and then put into the blast furnace for smelting, and finally three products of zinc oxide fume, slag and matte are obtained. This process only enriches and recycles the copper and zinc in the zinc slag, but the iron content in the zinc slag is high and has high utilization value, and it is not recycled;

(4) Melting chlorination volatilization method: This process has the advantages of self-heating and high enrichment rate of valuable elements in soot. The volatilization time of chlorination and the amount of chlorination agent used make the volatilization rate of lead, copper and germanium reach higher, respectively 96.79%, 97.36%, 82.71% and 91.78%, but the volatilization rate of zinc and copper is low, and the volatilization index of gallium not ideal. Moreover, there is also a major problem in this method, that is, the volatilization of chlorination has a greater impact on the corrosivity of equipment in the industrial production process;

(5) Melting pool smelting method: This method was developed in Australia and other countries and has many advantages, such as: energy saving, simple operation, and comprehensive recovery of valuable metals. Zhou Hongwu and others treated the zinc leaching slag of Zhuzhou smelter by molten pool smelting method. The research results showed that the recovery rate of silver by adding capture agent was as high as 90%, and the recovery rate of other valuable metals copper and zinc was more than 80%. The recovery rate reaches 90%, and there is good recovery, but because the number of times of sulfur reversion increases in the process, there is also the problem of SO ₂ pollution.

Contents of the invention

The object of the present invention aims to provide a method for extracting metallic iron from zinc kiln slag, to solve the waste problem of a large amount of metal resources caused by the low utilization rate of zinc kiln slag in the traditional technology, and to make full use of the valuable iron in zinc kiln slag Valence metal iron, increase the added value of zinc kiln slag.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A method for extracting metallic iron from zinc kiln slag, which comprises the following steps carried out in sequence:

S1. Get the zinc kiln slag material and fix it on the electrode rod as the cathode electrode; get the graphite rod and fix it on the electrode rod as the anode electrode;

S2. Mix sodium chloride and potassium chloride and heat to melt to obtain a molten salt system;

S3. In the atmosphere of protective gas, the cathode electrode and the anode electrode are respectively inserted into the molten salt system to form a reaction system, and carry out the piezoelectric reaction of the molten salt constant tank;

S4. After the electrolysis reaction is finished, cool the reaction system, take out the negative electrode, wash and dry in sequence to obtain metallic iron.

In step S1, the hardness of the zinc slag material is 5.5-10HB.

As another limitation, the zinc kiln slag material is the residue produced after the zinc tailings produced by the zinc ore after zinc smelting are reduced at high temperature and zinc and lead are recovered.

As a third limitation, in step S2, the molar ratio of sodium chloride to potassium chloride is 1:0.4-2.5;

The temperature after the heating is 160-240°C, and the holding time is 2-6h;

The heating rate is 3-8°C/min, the temperature after heating is 360-440°C, and the holding time is 12-24h.

As a fourth limitation, in step S3, the protective gas is argon or nitrogen;

The mass ratio of the negative electrode, the molten salt system and the positive electrode is 1:100-150:6-12;

The temperature of the electrolysis reaction is 750-950°C, the time is 8-12h, and the voltage is 2-3v.

As a fifth limitation, in step S4, the temperature after cooling is 15-35°C;

The cleaning is carried out in distilled water and ultrasonic waves successively;

The drying is drying at 100-150° C. for 30-70 minutes.

Owing to having adopted above-mentioned technical scheme, the technical progress that the present invention obtains compared with prior art is:

① The method for extracting metallic iron from zinc kiln slag provided by the present invention adopts the method of molten salt electro-deoxidation to recover metallic iron, which solves the problem of low extraction rate and difficulty in extraction due to the complex system of zinc kiln slag in the traditional process At the same time, it avoids the problems of serious environmental pollution and high reaction temperature caused by the addition of various reagents such as reducing agents or vulcanizing agents in the traditional process;

②The method for extracting metallic iron from zinc kiln slag provided by the present invention has simple operation, concise process and high recovery rate of metallic iron. , the temperature of the reaction system is low, which reduces energy consumption and conforms to the concept of green environmental protection;

③The method for extracting metallic iron from zinc kiln slag provided by the present invention uses sodium chloride and potassium chloride as the molten salt system, compared with the molten salt system aluminum chloride and calcium chloride in traditional electro-deoxidation, reduces While reducing the cost, the reaction rate is increased.

The invention is suitable for extracting metallic iron from zinc kiln slag.

Description of drawings

Below in conjunction with accompanying drawing and specific embodiment the present invention is described in further detail:

Fig. 1 is the molten salt phase diagram of KCl-NaCl molten salt system in the embodiment of the present invention 1;

Fig. 2 is the used electrolysis reaction schematic diagram of the embodiment of the present invention 1-6;

Figure 3 is the XRD spectrum of the product after electrolysis in Example 1 of the present invention.

Detailed ways

The present invention will be described in further detail below through specific embodiments, and it should be understood that the described embodiments are only used to explain the present invention, and do not limit the present invention.

Embodiment 1 A method for determining the amount of each component in the molten salt system

Prepare the following six groups of molten salt systems α ₁ -α ₆ respectively, and melt them separately, and measure the molten salt phase diagrams of the six groups of solids, as shown in Figure 1:

α ₁ : 1mol (58.5g) anhydrous sodium chloride;

α ₂ : 0.2mol (11.7g) anhydrous sodium chloride and 0.8mol (59.6g) anhydrous potassium chloride;

α ₃ : 0.4mol (23.4g) anhydrous sodium chloride and 0.6mol (44.7g) anhydrous potassium chloride;

α ₄ : 0.6mol (35.1g) anhydrous sodium chloride and 0.4mol (29.8g) anhydrous potassium chloride;

α ₅ :0.8mol (46.8g) anhydrous sodium chloride and 0.2mol (14.9g) anhydrous potassium chloride;

α ₆ :1mol (74.5g) anhydrous potassium chloride;

It can be seen from Figure 1 that when the molar ratio of sodium chloride to potassium chloride is 1:0.4-2.5, the state of the molten salt system reaches the optimum value, and the temperature of the molten salt system is kept at a low level, that is, 657-700 ℃.

Example 2 A method of extracting metallic iron from zinc kiln slag

The reaction principle of this embodiment is shown in Figure 2.

This embodiment includes the following steps carried out in sequence:

a. Take zinc kiln slag (that is, the leaching slag (zinc tailings) produced by zinc ore after hydrometallurgy is added with a certain amount of coke, and is reduced by high temperature in the rotary kiln to recover zinc, lead and other metals) , grind in a ball mill until the powder has a uniform particle size, take 10kg and compact it into a block under the condition of a pressure of 8MP, put it into a muffle furnace and sinter at a temperature of 700°C for 6h to enhance the hardness of the zinc kiln slag material, and prepare Zinc kiln slag material, spare; after testing, the hardness of zinc kiln slag material is 7.8HB;

b. Take 10000mol (585kg) of anhydrous sodium chloride and 10000mol (745kg) of anhydrous potassium chloride, grind them separately and mix them evenly. First, raise the temperature to 160°C and keep it warm for 4 hours. After removing the physically adsorbed water, use Continue to heat up to 360°C at a rate of 5°C/min and hold for 18 hours to remove chemically bound water to obtain a molten salt system;

c. Fix the zinc kiln slag material on the electrode rod as the cathode electrode; fix the 80kg graphite rod on the electrode rod as the anode electrode, and immerse the cathode electrode and the anode electrode in the molten salt system in an argon atmosphere, and open the DC stabilized power supply, adjust the electrolysis voltage to 2.3V, the temperature of the molten salt system is 800°C for electrolysis reaction, and the electrolysis time is 10h;

d. Cool the reaction system after the electrolysis reaction to 25°C, take out the negative electrode, wash it fully with distilled water first, then use ultrasonic cleaning to remove the residual molten salt in the cathode sheet, and then place it in a 120°C drying oven for drying After 50 minutes, 5.78kg of the reaction product was obtained, which was detected by XRD, and the detection results are shown in FIG. 3 .

It can be seen from Figure 2 that the main phase of the product after electrolysis is the metal Fe phase, followed by less FeO phase, and less Ca ₂ (Al ₂ O ₃ ) and Ti ₄ O ₇ . The experimental results show that the molten salt electro-deoxidation method can The elemental metal Fe was extracted from the zinc kiln slag, and the XRD analysis showed that the content of Fe in the electrolysis product was 86.75%.

Embodiment 3-7 extracts the method for metallic iron from zinc kiln slag

Embodiments 3-7 are respectively a method for extracting metallic iron from zinc kiln slag, they are all realized according to the reaction principle shown in Figure 2, and their steps are basically the same as in Example 1, the difference is only in the process The parameters are different, see Table 1 for details:

Claims (3)

1. a method for extracting metallic iron from zinc kiln slag, which is characterized by comprising the following steps in sequence:

s1, fixing a zinc kiln slag material on an electrode rod to serve as a cathode electrode, and fixing a graphite rod on the electrode rod to serve as an anode electrode;

the zinc kiln slag material is residues generated after zinc tailings generated after zinc ore zinc smelting are subjected to high-temperature reduction and zinc and lead recovery;

s2, mixing sodium chloride and potassium chloride, wherein the molar ratio of the sodium chloride to the potassium chloride is 1:0.4-2.5, heating to 160-240 ℃ and preserving heat for 2-6h; then heating to 360-440 ℃ at a heating rate of 3-8 ℃/min for 12-24 hours to obtain a molten salt system;

s3, in the atmosphere of protective gas, respectively inserting a cathode electrode and an anode electrode into a molten salt system to form a reaction system, and carrying out molten salt constant-tank pressure electrolysis reaction;

the protective gas is argon or nitrogen;

the mass ratio of the cathode electrode to the molten salt system to the anode electrode is 1:100-150:6-12;

the electrolysis reaction temperature is 750-950 ℃, the time is 8-12h, and the voltage is 2-3v;

s4, after the electrolytic reaction is finished, cooling the reaction system, taking out the cathode electrode, and sequentially cleaning and drying to obtain the metal iron.

2. A method for extracting metallic iron from zinc kiln slag as defined in claim 1, wherein, in step S1,

the hardness of the zinc kiln slag material is 5.5-10HB.

3. A process for extracting metallic iron from zinc kiln slag according to claim 1 or 2, characterized in that,

in the step S4, the temperature after cooling is 15-35 ℃;

the cleaning is to sequentially wash in distilled water and ultrasonic waves;

the drying is carried out at 100-150 ℃ for 30-70min.

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