Experimental study on recovery of iron minerals from laterite nickel ore acid leaching residue

I. Introduction

The world's nickel ore resources are extremely limited. Nickel-containing minerals mainly include nickel oxide ore and nickel sulfide ore. Nickel oxide accounts for 60% to 70% of nickel reserves in the world, and nickel sulfide accounts for 30% to 40%. Nickel sulfide nickel ore reserves of 87%, 13% nickel oxide, of which up to Gansu Jinchuan, accounting for 68.5% of total reserves of nickel ore, is a rare high-grade nickel sulphide deposits in the world. In recent years, with the rapid development of industry, the demand for nickel in the world has risen sharply, the price of nickel has risen sharply, and nickel resources have become increasingly exhausted. People have focused on research and development of low-grade, complex red earth nickel ore. The hydrometallurgy of laterite nickel ore has a long history. The recovery of iron minerals from leaching slag can reduce the environmental pollution of leachate and effectively utilize mineral resources. It is of great practical significance to study the leachate. The iron minerals recovered from a laterite nickel ore acid leaching residue studied in this paper have a wide representativeness. The roasting magnetic separation method is used to indicate the research direction for the treatment of leaching slag containing fine red and limonite. All the test ore samples were crushed to less than 2 mm, and the mixture was prepared for testing.

Second, the nature of the ore

(1) Multi-element chemical analysis (see Table 1)

Table 1 Multi-element chemical analysis of acid leaching residue (%)

From Table 1, multi-element analysis results can be seen, Leach Residue recyclable main component is iron in an amount of 42.17%, but further mineral enrichment; main impurity is silicon dioxide content of 11.87%, the content of harmful elements P Low, S content is high, up to 2.96%, which needs to be removed by mineral processing. Burning up to 14.91%.

(II) Analysis of mineral phase

1. Phase analysis

Table 2 lists the results of phase analysis of acid leaching slag. The analysis shows that the content of iron silicate minerals which are not easily recovered in ore is 0.65%. The content of red and limonite in iron minerals is as high as 97.57% due to the low content. Other iron minerals are less.

Table 2 Analysis results of acid phase leaching iron phase (%)

2. The state of occurrence of major minerals

Leach Residue of main minerals iron minerals, metal sulfides and non-metallic mineral composition, wherein the iron minerals are mainly hematite, goethite, magnetite, chrome ore, iron oxide, chromium, iron, titanium iron, diaspore; metal sulfides mainly pyrite, copper mines, pentlandite; non-metallic minerals are quartz, serpentine.

Iron mineral is the main mineral in acid leaching slag, its content is about 90%, iron mineral particle size is uneven, large particle size is 0.5mm, and most of the particle size is about 2um and less than 1um, and small The gangue and the metal sulfide are mixed together and interwoven into a gel to cement the leaching slag into a block.

The metal sulfide particles are fine, all of which are single mineral particles dispersed in iron oxide. The particle size is relatively uniform. Chalcopyrite and pentlandite are mostly granules of 2 to 4 um. The fine particle size of pyrite is about 3 um, and the larger particle size is about 1 mm.

Quartz is mainly semi-self-shaped - self-shaped crystal, single particle dispersion; serpentine semi-self-shaped - irregular strip shape, single particle dispersion state. Quartz is the main non-metallic mineral with a relatively high content and a small amount of serpentine.

(3) Particle size determination

Table 3 shows the results of water-separation measurement of the acid leaching residue ore. The results of water analysis show that the grain size of the acid leaching slag ore is very fine, less than 11.3um accounts for 77.11% of the total acid leaching ore, the iron mineral distribution rate is 87.9%, and the main iron minerals are distributed in this grain size; At this level, the content is 46.97%, and the acid leaching slag is basically muddy fine particles.

Based on the above analysis of the ore properties, the red earth nickel ore acid leaching slag used in this test has a very fine particle size, and the content below 11.3 um reaches 77.11%. The iron minerals and metal sulfide ore and gangue are mixed with very fine grain size. The gelled material is cemented into lumps, and the iron minerals are mainly red and limonite. The ore contains high sulfur. The non-magnetic iron minerals are so fine, and they are explored by strong magnetic separation and flotation. The test is difficult to achieve, and the method of roasting magnetic separation is finally determined.

Third, roasting magnetic separation

The roasting equipment used in the roasting magnetic separation test is a SK22212 tubular electric furnace, and the sorting equipment is an XCGS-73 magnetic separator. Siderite ore because little content, red iron minerals limonite based, so a reductive calcination firing process, the reducing agent is coal power, chemical analysis shown in Table 4. All calcination conditions of the acid leaching calcination test are shown in Table 5. The roasting magnetic separation test adopts the single factor test method. The magnetic field strength of all magnetic separation tube tests is set at 1200 Oe, and all the calcined ore are ground to 75 um or less for sorting.

(1) Conditional test

1, temperature test

The temperature condition test was carried out under the conditions of a fixed calcination time of 40 min, a coal blending ratio of 3%, and a magnetic separation magnetic field strength of 1200 Oe. Table 6 shows the results of roasting magnetic separation; Figure 1 shows the concentrate and recovery index of roasting magnetic separation at different temperatures.

From the test results in Table 6 and the corresponding relationship in Figure 1, it can be seen that the concentrate grade and recovery rate are ideal when the calcination temperature is 800 °C, and the concentrate grade drops sharply after the temperature rises again. Therefore, it is preferred to select a baking temperature of 800 °C.

2, roasting time condition test

The time condition test was carried out under the conditions of a fixed coal blending ratio of 3%, a magnetic separation magnetic field strength of 1200 Oe, and a selected calcination temperature of 800 °C. Table 7 shows the results of calcination magnetic separation; Figure 2 is a graph showing the relationship between calcination time and magnetic separation concentrate and recovery.

The test results in Table 7 and the corresponding relationship in Figure 2 show that the concentrate grade and recovery rate are ideal when the calcination time is 45 min. After the calcination time is increased, the concentrate grade drops sharply. Therefore, the concentrate grade and recovery rate are better when the baking time is 45 min.

3, reducing agent dosage condition test

The reducing agent dosage condition test was carried out at a fixed temperature of 800 ° C, a magnetic separation magnetic field strength of 1200 Oe, and a selected firing time of 45 min. Table 8 shows the results of roasting magnetic separation; Figure 3 is a graph showing the relationship between the amount of reducing agent and magnetic separation concentrate and recovery.

It can be seen from the test results in Table 8 and the corresponding relationship in Figure 3. When the amount of reducing agent is 2%, the concentrate grade and recovery rate are ideal, and the dosage is increased again, and the recovery rate begins to decrease. Therefore, the condition that the reducing agent is used in an amount of 2% is preferable.

4, magnetic field strength condition test

In the field strength test, the fixed calcination temperature was 800 ° C, the roasting time was 45 min, and the coal blending ratio was 2%. Different field strength tests were selected. The test results are shown in Table 9. From the test results of Table 9, it can be seen that the magnetic field strength is 1200 Oe, and the result is good.

(2) Roasting magnetic separation stability test

In the stability test, the fixed calcination temperature was 800 ° C, the calcination time was 45 min, the coal blending ratio was 2%, and the magnetic field strength was 1200 Oe. The batch test was repeated. The average results are shown in Table 10. When the ore grade is 40.96%, the index of calcined ore grade is 50.26%. The concentrate grade calculated by magnetic separation operation is 57.09% and the recovery rate is 89.36%.

Fourth, product analysis

Table 11 lists the results of multi-element analysis of magnetically selected concentrates.

According to the results of Table 11 and the multi-element analysis of the acid-leaching slag ore, the Ig decreased from 14.91% to 0.72%, and the S decreased from 2.96% to 0.280%. The reduction was large, indicating that the roasting effect was obvious, and most of the sulfide ore was calcined by roasting. The selection can be eliminated; the effect of SiO2 decreasing from 11.87% to 8.40% is not obvious, because the content of SiO ₂ in the ore -11.3um grade is higher, reaching 46.97%, which is difficult to dissociate from iron ore, which not only affects the concentrate. The iron grade is improved, and the grade of tailings remains high. Al ₂ O ₃ , CaO, MgO, K ₂ O, Na ₂ O, etc. did not change much, and BaO changed from 1.96% to 0.05%. In order to further improve the concentrate grade, the anti-flotation exploration test of the magnetic separation concentrate has a poor effect, and the purpose of separating the ferrosilicon is not achieved at the existing particle size.

V. Conclusion

(1) The original ore of the laterite nickel ore acid leaching slag has a fine particle size, and the content of the grade below 11.3 um is as high as 77.11%. The iron distribution rate of this grade is 87.9%, and the silicon distribution rate is 46.97%. The muddy phenomenon is serious.

(2) The useful iron minerals in the acid leach residue are mainly red and limonite, accounting for 97.57% of the total iron minerals. Iron mineral is the main mineral in acid leaching slag, the content is about 90%, the iron mineral particle size is uneven, the large particle size is 0.5mm, and most of the particle size is about 2um and less than 1um, with small veins. The stone and the metal sulfide are mixed together and interwoven into a gel to cement the leaching slag into a block.

(3) The acid leaching slag ore has a high sulfur content of up to 2.96%, which is the main harmful element. The higher impurity SiO2 reaches 11.87% and the burning loss is 14.91%. The acid leaching residue was subjected to roasting magnetic separation test. When the ore grade was 40.96%, the magnetic separation tube concentrate grade reached 57.09%, the recovery rate based on the original ore was 81.48%, and the S drop in the concentrate was 0.3% or less.

(4) Industrial roasting generally treats mineral materials, while acid leachables are powdery and fine-grained materials. The gas permeability during roasting is not good, and the particles are easily adhered to the furnace wall, thereby causing difficulty in feeding and discharging. The extraction of useful minerals from acid leaching slag can solve the environmental pollution of acid leaching slag and make full use of limited resources. If it can be applied in industry, the prospect of iron selection is relatively large.

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