At present, the situation of China's mineral resources is severe, and the per capita possession of 45 major mineral resources is less than half of the world's per capita level. In order to realize the sustainable development of China's economy and society and to resolve the contradiction between economic growth and the relative shortage of mineral resources, in addition to strengthening the exploration, evaluation, planning, management, protection and outsourcing of mineral resources, we should also vigorously develop the associated mineral resources. Comprehensive utilization, implementation of the scientific development concept, and maximize the comprehensive utilization of mineral resources.

A phosphorus-containing magnetite iron ore genus Low Grade Low Grade magnetite - apatite ore, mainly magnetite useful minerals, apatite, with some typical. Due to the low phosphorus content, large beneficiation ratio, and limited by the process and technology, most of the local concentrators that have been built and invested in the production only use the magnetic separation process to recover the magnetite, and the useful minerals such as phosphorus. Magnetic separation tailings are discarded. Therefore, this type of ore is subjected to beneficiation test research to solve the technical problems, to achieve simultaneous recovery of iron and phosphorus, to maximize the recovery of valuable elements, and to have good economic, ecological and social benefits. On the one hand, it can reduce tailings emissions, improve the impact of tailings on the environment, and implement sustainable development strategies; on the other hand, it can reduce the comprehensive cost of mineral processing, increase revenue, improve enterprise efficiency and market competitiveness.

I. Research on ore process mineralogy

(1) Chemical composition of the ore sample

In order to understand the content of various elements in the ore and the form of iron, the chemical polymorphism analysis and iron phase analysis of the original ore samples were carried out. The results are shown in Tables 1 and 2.

Table 1 Multi-element analysis of raw ore chemistry (mass fraction) /%

Table 2 Iron phase analysis

It can be seen from the data in Table 1 and Table 2 that the iron grade in the ore sample is relatively low, only 15.30%, which belongs to low grade iron ore. The main component of the ore for beneficiation recovery is iron, and the comprehensive utilization component is P ₂ O ₅ . The alkalinity coefficient (MgO + CaO) / (SiO ₂ + A1 ₂ O ₃ ) is 0.39, which is an acidic ore. The slag-forming components that need to be removed by beneficiation are mainly SiO. The highest proportion of the ore samples are magnetic ores, followed by red (brown) iron ore and iron silicate. The weak magnetic separation process is used to recover iron. The maximum theoretical recovery of iron is 53.67%.

(2) Mineral composition of mineral samples and main mineral embedding characteristics

The main types of mine ore GNEISSIC apatite ore fines and titanium apatite magnetic, non-metallic minerals apatite, hornblende, feldspar, biotite, quartz, pyroxene, metal Minerals include magnetite, ilmenite, pyrrhotite, hematite, and pyrite.

The apatite has a relatively uniform particle size, generally 0.4-0.8 mm, maximum 0.72 mm, and content 6%-10%. The apatite is aligned along the ore and is evenly distributed, with hornblende, plagioclase, biotite, Magnetite and ilmenite are closely embedded, and some small crystals are wrapped by hornblende, plagioclase, magnetite and ilmenite.

The magnetite is in the form of granular particles with a particle size of 0.074 to 2.22 mm and a content of 7.0%. The distribution is uneven. Some are composed of ilmenite ore, and some are scattered in the ore, with ilmenite and horn. Amphibole and apatite are embedded, and the ilmenite is irregularly granular. The particle size is 0.074~3.774mm, the content is 7%, and the distribution is uneven. Some are composed of magnetite or strips, and some are sporadic ore. Among them, it is closely embedded with magnetite, and the ore is easy to be mined.

Hemp-like apatite ore: granitic crystal structure, hemp-like structure. The mineral composition is 30%-40% of the total amphibole and biotite, the total amount of plagioclase and quartz is 35%~45%, and the total amount of ilmenite and magnetite is 15% (where the ilmenite content is greater than magnetic Iron ore), apatite contains about 10%.

Titanium magnet phosphate ore: granitic crystal structure, ramie structure. The mineral composition mainly includes ilmenite and magnetite totaling 40% to 50%, pyroxene 20%, hornblende and biotite 20%, and apatite containing more than 10%. Apatite: white columnar crystal, the edges and corners are ablated to varying degrees. Its long axis is basically consistent with the direction of the film, and it is closely symbiotic with hornblende, biotite, plagioclase, pyroxene and titanomagnetite. A small number of apatite single crystals are encapsulated in hornblende, biotite, plagioclase, and titanomagnetite particles. The apatite has a relatively uniform particle size, generally 0.2 to 0.8 mm, the finest 0.08 mm, and the largest 3 mm. The apatite coated with other minerals has a particle size of 0.1 to 0.2 mm. According to the single mineral analysis of apatite, it is Buddha apatite.

Ilmenite: It is produced in the form of agglomerates or infestation in the form of irregular granules and magnetite. The ilmenite crystals are surrounded by fine hematite unmixed crystals, and hematite is oriented parallel in its particles. In the individual package has titanium magnetite ore fine brass particles. The ilmenite single crystal has a particle size of 0 to 0.8 m, a fine 0.1 mm, and an aggregate of 4 mm or more.

Magnetite: It is irregularly granulated and infiltrated together with ilmenite. Some magnetite edges are replaced by hematite. The particle size is generally 0.3 to 0.8 mm, the fineness is 0.07 mm, and the aggregate is 3 mm or more.

Pyrite: It is embedded in irregular granules between mineral granules, and is individually packed in irregular granules in ilmenite. The amount is less than 1% and the particle size is 0.02-0.07mm. The sample was observed under the naked eye as a yellowish brown.

Second, the test equipment and process

(1) Test main equipment

The main equipments of the test are: PE-60×100 jaw crusher , Ф200×75 double roll crusher , set sieve and vibrating screen machine, XMQ-240×90mln cone ball mill , volume 6.25L, CTB-Ф300×400 permanent magnet Cartridge magnetic separator, XCGS-type Ф50 magnetic separator, XFDl-63 0.75L single tank flotation machine.

(2) Process selection principle

According to the ore process mineralogical research results, combined with the domestic experience of the same type of ore production practice, the iron selection method uses magnetic separation method, the phosphorus selection method adopts the flotation method, and the sample is subjected to the sapphire process test. First, after the magnetic separation Flotation, flotation to mine is the magnetic separation of tailings; second, the first flotation after magnetic separation, flotation tailings as magnetic selection ore. The iron ore selection operation and the phosphorus selection operation of the two processes all adopt the same structure, that is, the iron selection adopts two-stage grinding. The stage selection. The fine screening self-circulation process (Fig. 1), the flotation adopts a coarse one sweep and two fine Process flow (Figure 2).

Figure l Iron selection process

Figure 2 Phosphorus selection process

Third, the first magnetic post-floating ore test research

In order to determine the appropriate particle size, magnetic field strength and other process parameters for each section of the grinding operation, four conditions of grinding grain size, primary magnetic field strength, final concentrate size, and selected magnetic field strength were tested.

The flotation test is based on the magnetic separation tailings as the flotation to the ore, and the five conditions of the flotation concentration, particle size, the amount of the crude collector, the amount of the crude inhibitor, and the amount of a selected inhibitor are tested. Based on the closed circuit process test.

(1) Magnetic separation condition test

1. Primary magnetic separation particle size condition test On-site ball mill discharge is selected into the ore, the fixed magnetic field strength is 200kA/m, and the particle size is tested. The results are shown in Table 3.

Table 3 Primary magnetic separation particle size condition test results

The results in Table 3 indicate that as the grinding size becomes finer, the concentrate yield gradually decreases, the grade of iron concentrate gradually increases, and the grade of tailings is the lowest at -0.074mm, which is 25%, and the recovery rate is the highest; 40% at -0.074mm When % is the highest, the recovery rate is the lowest. More than 98% of the phosphorus in the three kinds of grinding minerals entered the tailings. Considering the production practices of existing concentrating plants and the characteristics of magnet mineral embedding, the content of -0.074mm fraction was selected as 25% for the first grinding size.

2, a magnetic field strength test conditions fixed particle size -0.074mm grain content accounted for 25%, varying magnetic field strength test. The results are shown in Table 4.

Table 4 Results of a magnetic field strength test

The results in Table 4 indicate that when the recovery rate is close, the magnetic field strength is higher at 200 kA/m, so the magnetic field strength of the first-stage magnetic separation is preferably 200 kA/m.

3. The final concentrate particle size condition test According to the test results of one magnetic separation condition, the primary magnetic separation concentrate is used as the ore, the fixed magnetic field strength is 128kA/m, and the grinding grain size is tested. The test results are shown in Table 5.

Table 5 Results of final concentrate particle size conditions test

The results in Table 5 indicate that as the grinding size becomes finer, the concentrate grade is increased from 65.14% to 69.05%, and the operation recovery rate is reduced from 93.52% to 91.33%. Considering the improvement of production efficiency and the market price of iron concentrate powder, grinding The particle size is selected to be -0.074 mm and the fractional content is preferably 53%.

4. Selected magnetic field strength condition test Fixed particle size - 0.074mm grain content accounted for 53%, and the magnetic field strength was tested. The results are shown in Table 6.

Table 6 Selected magnetic field strength condition test results

It can be seen from Table 6 that in the case of low tailings grade, when the field strength is 128kA/m, the concentrate grade is higher and the concentrate grade fully meets the market demand, and the selected magnetic field strength is 128kA/m.

(2) Flotation condition test

1. Flotation phosphorus particle size conditions

The test feed is a primary magnetic separation test tailings, and the test flow is shown in Figure 2. The flotation operation concentration is 35%, and the phosphorus selection operation agent system: the amount of coarse selection adjuster is 1300g/t, the amount of inhibitor is 530g/t, the amount of collector is 900g/t, and the amount of one selected inhibitor is 180g/t. . The test results are shown in Table 7.

Table 7 Flotation particle size condition test results

From the test data of Table 7, it is seen that the concentrate grade and recovery rate are the highest when the ore size is -0.074mm, which accounts for 35%. According to the test results and with reference to other mine production technical indicators of the same type, the flotation feed size is determined to be -0.074mm, and the grain size is preferably 35%.

2. Flotation phosphorus concentration conditions

The test ore is a magnetic separation tailings with a particle size of -0.074 mm and a grade of 35% and a P ₂ O ₅ grade of 4.18%. The test flow is shown in Figure 3. The phosphorus selection operation agent system has a coarse selection agent dosage of 1300 g/t, an inhibitor dosage of 530 g/t, and a collector dosage of 900 g/t. The test results obtained under different working concentrations are shown in Table 8. From the test results in Table 8, when the working concentration is 35%, the grade and recovery rate of the phosphate concentrate are high, so it is most suitable to select 35% of the coarse selection concentration. The coarse selection operation maintains a higher slurry concentration, which helps to improve the recovery rate, flotation machine production capacity, and reduce the amount of chemicals and water consumption.

Figure 3 Flotation granularity test procedure

Table 8 Test results of flotation concentration conditions

From the test results in Table 8, when the working concentration is 35%, the grade and recovery rate of the phosphate concentrate are high, so it is most suitable to select 35% of the coarse selection concentration. The coarse selection operation maintains a higher slurry concentration, which helps to improve the recovery rate, flotation machine production capacity, and reduce the amount of chemicals and water consumption.

3, collector dosage test

The ore is a magnetic separation tailings with a particle size of -0.074 mm and a grade of 35% and a P ₂ O ₅ grade of 4.18%. The test procedure is shown in Figure 4. The other conditions are unchanged, and the amount of the coarse selection collector is changed. The test results are shown in Table 9.

Figure 4 Flotation concentration condition test procedure

Table 9 Test results of rough selection of collectors

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