Example of high nickel (copper) antimony refining process in Xinjiang Fukang Smelter

1.1 Chemical composition of high nickel bismuth and preparation of raw materials before leaching

The high nickel ruthenium that is selectively leached with sulfuric acid requires a lower sulfur content to facilitate the dissolution of nickel. This high nickel matte mainly composed of copper-nickel alloy, Ni ₃ S ₂ and CuS into three-phase level. Nickel is mainly present in the alloy phase and the Ni ₃ S ₂ phase, copper is present in the Cu ₂ S phase and the alloy phase, and iron and cobalt are present in the alloy phase. After the high-nickel crucible is blown, the water is usually quenched into a pellet by quenching in water, and then finely pulverized by a ball mill to be selectively leached by sulfuric acid.

The raw materials of Fukang Smelter are from the water-quenched metallized high-nickel niobium produced by Kalatongke Nickel Mine. After grinding, grading, dewatering and filtering by two-stage ball mill in the grinding and immersing workshop, the particle size is -0.045mm95% or more. A high nickel niobium filter cake containing 8% to 10% water. Its chemical composition is shown in Table 1. The chemical phase analysis of nickel cobalt is shown in Table 2.

Table 1 Chemical composition of high nickel sulfur in Fukang smelter

Table 2 Phase composition of nickel-cobalt contained in high-nickel sulfur in Yukang Smelter

The production practice shows that the nickel leaching rate of the alloy phase and the sulfide phase in high nickel bismuth is about 95.3%, and the leaching rate of cobalt is only 43.6%. If the reduction measures are taken in the converter, the leaching rate of cobalt can be greatly improved. And increase the leaching rate of nickel.

1.2 Main chemical reactions in the high nickel leaching process

The nickel and cobalt in the high nickel niobium are selectively leached with a sulfuric acid solution to suppress copper and precious metals in the leach residue. The leaching is generally composed of two or more steps of atmospheric pressure leaching and pressure leaching. The metal Ni in the normal pressure leaching section is completely dissolved, Ni ₃ S _{2 is} partially dissolved, and Cu ₂ S is not dissolved.

Ni+H ₂ SO ₄ =NiSO ₄ +H ₂

Ni+H ₂ SO ₄ +1/2O ₂ =NiSO ₄ +H ₂ O

Co+H ₂ SO ₄ +1/2O ₂ =CoSO ₄ +H ₂ O

The copper in the alloy phase is oxidized and reacts with Ni ₃ S ₂ under blasting air during leaching:

2Cu+1/2O ₂ =Cu ₂ O

Cu ₂ O+H ₂ SO ₄ =CuSO ₄ +H ₂ O+Cu

2Ni ₃ S ₂ +2Cu ²⁺ +1/2O ₂ =4NiS+2Ni ²⁺ +Cu ₂ O

Under pressure leaching, the following chemical reactions occur under oxidative conditions:

Cu ₂ S+H ₂ SO ₄ +1/2O ₂ =CuS+CuSO ₄ +H ₂ O

Ni ₃ S ₂ +H ₂ SO ₄ +Cu ₂ O=NiSO ₄ +2Cu+H ₂ O

NiS+CuSO ₄ =NiSO ₄ +CuS

Most of Ni and Co in the high-nickel lanthanum were leached into the solution (Ni leaching rate 94%, Co59%), and most of Cu remained in the slag in the form of CuS and Cu2S.

1.3 Production practice of high-nickel bismuth two-stage countercurrent sulfuric acid selective leaching

The high-nickel niobium was ball milled and filtered by the agricultural density. The filter cake was stirred and slurryed in two φ2500mm×3000mm pulping tanks with pressurized leaching solution and anolyte. The pulp was pumped to six φ2500mm×3000mm series leaching tanks. In the middle, the air is blasted for atmospheric pressure leaching, and the leached slurry is flowed to a φ6000 mm No. 1 thickener for liquid-solid separation. The overflow is an atmospheric pressure leaching solution, and the suspended matter is removed by pressure filtration through a plate and frame filter press, and then the cobalt removal process is sent to the nickel electrolysis workshop as a product liquid. The atmospheric pressure leaching end point until almost all of the sulfuric acid in the solution is neutralized, the end point pH = 5.5 to 6.3, and almost all of the Cu and Fe in the solution are hydrolyzed and precipitated into the slag.

In the atmospheric leaching stage, an appropriate amount of cesium carbonate is added. BaCO ₃ reacts with the sulfate solution to form insoluble isomorphous BaSO ₄ and PbSO ₄ , and coprecipitation of barium sulfate with lead sulfate also removes traces of lead from the solution.

The dense underflow after atmospheric leaching is subjected to a second stage pressure leaching with an anolyte (containing about 50 g/L of H ₂ SO ₄ ). The underflow was first slurried in an intermediate pulping tank of φ 2200 mm × 2000 mm. The slurry is pumped into the autoclave by a high pressure diaphragm pump for pressure leaching. The autoclave was mechanically agitated. The pressure leaching temperature was about 150 ° C and the pressure was 0.8 MPa.

After the pressure leaching, the slurry of the kettle is cooled by a vacuum from the evaporator, the gas is vented after defoaming, and the slurry is flowed to a No. 2 thickener for liquid-solid separation. After the bottom stream is filtered and washed by an automatic centrifuge, the obtained filter residue is a leaching final slag, and its composition (%) is Cu60-70, Ni4-5, S20-22, and is used as a raw material for extracting copper and precious metals.

In the pressure leaching, almost all of Ni, Co, and Fe were leached, and part of the copper was also leached, but most of the copper was poured into the slag. Pressure leaching overflow component (g/L): ～90Ni, ～2Cu, ～10H ₂ SO ₄ . After the pressure leaching, the liquid returns to normal pressure leaching.

The principle process of high nickel (copper) bismuth refining process in Fukang Smelter is shown in Figure 1. The technical conditions and main product components of the leaching process of the process are listed in Table 10-4.

High nickel bismuth is obtained by atmospheric pressure leaching to obtain a nickel sulphate solution containing less than 0.01 g/L of copper and iron, and the leaching slag is subjected to pressure leaching to deeply leaching the nickel-cobalt alloy phase and the sulfide phase, and the copper in the raw material, Almost all of iron, precious metals and sulfur remain in the final slag (copper slag) containing 4% to 5% of nickel, which facilitates the extraction of copper and precious metals by fire or wet methods.

The main feature of the process is that the pressurized acid leaching adopts continuous hot pressing leaching to control the air supply amount of the pressure autoclave, which not only ensures sufficient leaching rate, but also inhibits copper leaching, and realizes copper nickel at the same time of pressurized acid leaching. Separation. The production practice of the Fukang smelter shows that as long as the leaching conditions, such as kettle pressure, kettle temperature, air volume, copper content in the liquid return, and pH value at the end of the pressure leaching, are controlled, nickel can be realized in industrial production. The higher leaching rate, while suppressing most of the copper in the leaching slag, ensures that the process can be achieved by using only one piece of black nickel to remove the cobalt in the process, thus simplifying the process.

Figure 1 High-nickel (copper) bismuth refining process principle process of Fukang Smelter

Table 3 Technical conditions and results of selective leaching of high nickel bismuth sulphate in Fukang Smelter

1.4 Factors affecting the leaching process [next]

The main factors affecting the high nickel leaching process are: high nickel bismuth composition, grinding strontium composition, grinding particle size, stirring strength, blasting air volume and leaching temperature.

(1) High nickel bismuth composition

The nickel dissolution of high nickel bismuth is mainly determined by the sulphur content of high nickel bismuth. For high nickel bismuth with Ni:Cu>2, the dissolution rate of nickel decreases with the increase of sulphur content, but the Ni/Cu ratio continues to increase. The effect of nickel on the Ni:Cu<2 high nickel niobium (when the amount of S is contained) increases as the copper content increases. The effect of high nickel bismuth composition on nickel leaching rate is shown in Fig. 2.

(2) High nickel niobium grain size

The effect of grinding particle size on the leaching rate of high nickel niobium is mainly due to the fact that grinding can separate different minerals. The high nickel niobium particle size has a large influence on the reaction rate. The finer the high nickel honing, the larger the specific surface area of ​​the ore particles, and the faster the reaction proceeds, as shown in Figure 3. It can be seen from the figure that when the high nickel niobium fine particle size is -200 mesh to +270 mesh, the leaching reaction can be completed within 1.5 hours; when the particle size is -60 to +80 mesh, it takes 2.7 hours to complete; and the particle size is -5 At +9 mesh, nickel is not completely leached even for 6 hours.

Figure 2 Nickel leaching rate and nickel-copper of high nickel content with different sulfur content

Fig. 3 Effect of grinding particle size on nickel leaching speed

Particle size: 1-5 to 9 mesh; 2-60 to 80 mesh; 3-200 to 270 mesh

(3) Stirring

Stirring has a large effect on the reaction rate, because the agitation ensures good contact between the O2 in the air and the leachate and the high nickel niobium solid particles. For this reason, usually, in addition to the air agitator in each dipping tank, the slurry is stirred. In addition, a mechanical agitator was installed in the first leaching tank to which powdered high nickel ruthenium was added.

(4) The amount of air in the air

The amount of air blasted has a large influence on the reaction speed. Figure 4 shows the relationship between the leaching time in high nickel bismuth and the amount of air blasted. The relationship can also be expressed by:

Where Y-nickel leaching time, h;

x - the amount of air that is bubbled into the solution, L / h;

k, b-constant, related to temperature, leaching tank size, solution concentration, etc.

(5) Leaching temperature

The effect of leaching temperature on the leaching speed is multi-faceted. Increasing the leaching temperature can increase the diffusion coefficient of the material, thereby accelerating the leaching speed. As the leaching temperature increases, the solubility of the solution-soluble substance in the high nickel bismuth in the solution is large, and the leaching time can also be accelerated. FIG. 5 shows the relationship between the leaching time and the leaching temperature. As can be seen from the figure, increasing the leaching temperature can significantly increase the reaction rate. For example, at 80 ° C, the reaction time required for leaching is only 25% of the time required to reach the same degree of leaching at 30 ° C.

Figure 4 Relationship between leaching and the amount of air in the blast

Figure 5 Relationship between leaching time and leaching temperature

1.5 Technical progress of the selective leaching of sulfuric acid from Outokumpu, Finland

The Hajjaltar Nickel Refinery in Outokumpu, Finland, was the first (in 1960) plant with selective leaching of sulfuric acid and was introduced to nickel refineries in countries such as South Africa, Zimbabwe and Brazil.

The original high nickel niobium of Hajvarta Nickel Refinery has a particle size of 0.5-3.0 mm, containing (%) Ni 60-65, Cu 22-25, S 6-7, Fe about 0.5, and Co 0.7-1.0. The metal phase accounts for 66%, Ni ₂ S ₂ accounts for 18%, Cu ₂ S accounts for 15%, and impurities are about 1%. The effect of the leaching parameters on the leaching process is shown in Figure 6.

The leaching process is leached by three-stage atmospheric pressure countercurrent, so that the Ni and Co leaching rates are 98% and 97%, respectively. The relevant data is shown in Table 4.

In view of the advantages of sulfuric acid selective leaching method and the significant increase of nickel-copper ratio in raw materials, the plant revolutionized the old process in 1995. The new process features atmospheric pressure, pressure leaching, nickel electrowinning and hydrogen reduction. Cobalt and hydrogen reduction cobalt powder. The new process principle process is shown in Figure 7.

Table 4 Raw leaching process data of Hajjarta nickel refinery

Figure 7 Hajaralta nickel refining process