I. Introduction

Yunnan phosphorus-rich ore reserves which ranks first, predict the amount of resources of 18.3 billion t, wherein P ₂ O ₅ content of between 15% to 25%, is in the low grade. At present, the province has proven reserves of about 6 billion tons, and about 80% of them are P ₂ O ₅ <25% medium and low grade ore.

The Dianchi area is the main development zone of phosphate ore in Yunnan Province. It has concentrated more than a dozen large phosphate mines. Among them, the three major mines of Kunyang, Haikou and Jinning, which have been and will be mass-produced, have formed the current Yunnan phosphate mine. The main base of production. However, most of the reserves held therein are medium and low grade phosphate rock.

Such abundant phosphorus resources, due to the problems of mineral processing technology and economic benefits, have not been used for a long time, so it is necessary to develop research on the mineral processing technology of low-grade phosphate ore .

During the "Sixth Five-Year Plan" and "Seventh Five-Year Plan" period, the state has invested considerable research funds, and has done a lot of research on the beneficiation of collo-phosphorus ore. Many achievements have been made, but these results should be promoted in Yunnan Province, especially in Dianchi Lake. There are two major problems in the utilization: First, the environmental protection requirements in the Dianchi area are strict. It is obvious that it is necessary to mine a large amount of phosphate rock, and it is obviously not feasible to use a large amount of flotation reagents in the Dianchi Lake. The second is to use the whole flotation method for mineral processing, high drug consumption and cost. Large, poor economic returns, and no competition with the mainland. In view of the above reasons, the Provincial Science and Technology Commission decided to organize the “Eighth Five-Year Plan” to find out whether it is possible to find a flotation-free method, or to use a re-election method, or a heavy-floating joint process to reduce the amount of flotation selected as much as possible. Contaminated or low-pollution agents, effective and economical, beneficiation process routes accepted by environmental protection in Dianchi Lake, development and utilization of low-grade phosphate ore in three major mining areas, so that P ₂ O ₅ content and impurity content in phosphate concentrates can reach National acid standard second class mine standard.

Second, the conclusion of the process mineralogical research

According to the study of process mineralogy, the main target mineral of the three mining areas is colloidal phosphate, which is a mechanical mixture of apatite aggregates with ultrafine particles and extremely fine gangue minerals; Qualitative, cryptocrystalline, ultra-microscopic apatite microcrystalline aggregates, the structure of which is mostly granular, agglomerate or crumb-like, while quartz , mica and other siliceous gangue, with powder sand, particles The form is matrix or embedded in the colloidal phosphate ore; the Kunyang and Hairi Phosphate ores also contain carbonate gangue, such as calcite , dolomite, etc., which are irregularly cemented in the collophanite or The star point is embedded in the phosphate rock. The phosphate rock and gangue of the three mining areas are all unevenly embedded in fine particles. When the particle size is 0.1mm, the monomer can be dissociated by 80%, but some monomers are also dissociated at 0.45mm. .

As for the type of gangue, the main gangue of Jinning Mine is quartz, followed by silicate gangue such as mica, and the re-election selectivity index is calculated according to their specific gravity. Although it is difficult to select, some of the coarse-grained phosphate rock can be recycled by high-efficiency re-election equipment , and the fine combination of the size of the inlay and the gangue can only be used for flotation. The gangue minerals of Kunyang and Haikou phosphate mines are mainly dolomite, followed by siliceous, the difference in specific gravity between dolomite and apatite is small, and the re-election selectivity index is calculated. It is extremely difficult to select, and the dolomite inlay is fine in size and complex in structure. Therefore, it is extremely difficult to remove MgO by re-election. It can obtain P ₂ O ₅ >28% concentrate, but it contains MgO>1.5%. ~2.8%, can only rely on flotation to achieve the task of reducing Mgo. It is recommended that the beneficiation adopt a heavy-floating combined process.

Third, the re-election optional test

In order to further confirm the conclusions of the process mineralogy research, the heavy liquid separation test and the shaker selection test of each sample were carried out from 15 to 0.074 mm. Obviously, the re-election index of Jinning phosphate mine is the best, when the weight ratio of heavy liquid At 2.85, a concentrate of 27.78% of P ₂ O ₅ grade can be obtained with a recovery rate of 42.9%. If the particle size is further reduced to -1 mm, the concentrate grade can be increased to over 28% and the recovery rate is 40%. The bed selection test, when the selected particle size is -0.28mm plus time, the concentrate with a grade of 29.12% and a recovery rate of 40.48% can be obtained. The Kunyang Phosphate Mine has a grade of 28.38% and a recovery rate of 44.62% of phosphate concentrate at a specific gravity of 2195. However, MgO is >115% to 218%. When the particle size is -0115mm, P can be obtained after bed selection. ₂ O ₅ 28.68%, recovering 42187% of phosphate concentrate, but wherein MgO>1.5% to 2.8%. The Haikou Phosphorus Mine is similar. When the ore is ground to -0.28mm, the bed can be selected to obtain 28.63% of the grade and the recovery rate is 41.33% of the phosphate concentrate, but the MgO is >1.5% to 2.8%. The re-election optionality test confirmed the conclusion of the process mineralogical research, the single re-election recovery rate is low, and it is desirable to use the heavy-floating combination to minimize the flotation input.

Fourth, the key to achieving heavy-floating union

The selection of phosphate ore has several characteristics: the processing capacity of raw ore is large, the yield of concentrate is high, and the difference in specific gravity between phosphate rock and gangue is small. Therefore, in order to realize the key of heavy-floating combination, efficient sorting equipment must be available. The re-election equipment researched by the test-water medium cyclone; flotation equipment -dwarf column flotation tank, etc., all have the characteristics of high sorting efficiency, large processing capacity, simple and stable operation, and low price. The water medium cyclone is different from the ordinary cyclone, and has a short bottom cone and a large cone angle. The diameter of the overflow tube has a deep insertion depth: after the slurry is pressed in, the slurry vortex flow formed by the centrifugal force in the simplified body is used. The self-dielectric layer of the conical zone is sorted, and the light and fine particles cannot pass through the high-density dielectric layer and move upward along the inner spiral through the overflow pipe, while the coarse and heavy particles pass through the dielectric layer and are excluded from the grit. Mine, thus completing the entire sorting process. Therefore, in addition to the centrifugal force sorting effect of the ordinary cyclone, it also has the sorting action of heavy medium in the large cone angle region, which is advantageous for recovering the collophanite which has a small difference in specific gravity from the gangue mineral.

The water medium cyclone mainly recovers the phosphate rock of +0.037mm. Taking Jinning as an example, when the particle size is -0.28mm, the grade of phosphorus in +0.037mm can reach 25.95%, which is about 4% higher than the original grade. It can reach more than 28% after one sorting, which is conducive to the re-election of the recovered concentrate. The gangue of Jinning Mine is mainly siliceous, which is easy to re-separate and separate from the other two mines. The controlled ore pressure is 115~2kg/cm ² , and the primary rough concentrate can reach the standard, and the recovery rate is over 40%. Its processing capacity is large, the water-flow cyclone treatment of <75mm can reach 400-1000kg/h·table, the equipment only weighs 9kg, no power, stable operation.

The short column flotation cell is a highly efficient flotation device that has successfully developed the characteristics of the Australian Jameson flotation column. It achieves mineralized particles in full contact with air and produces a uniform mineralized layer of bubbles, enabling minerals to It is fully harvested and has great advantages for the flotation of phosphate ore with high concentrate yield. <1000mm×400mm short column flotation tank treatment capacity can reach 1000kg/h·set, the enrichment ratio is high, and a coarse sweep can obtain more than 30% of concentrate, and the working efficiency is 70%.

These two high-efficiency equipments are the key to achieving a heavy-floating combined process.

5. Good prospects for heavy-floating alliances

The heavy-floating combined process has achieved good results in dealing with low-grade phosphate ore in Dianchi area, especially Jinning ore. The process flow of <75mm water medium cyclone + <1000mm×400mm dwarf column flotation cell is adopted. The concentrate with a yield of 63172%, a grade of 28137% and a recovery rate of 83150% can be obtained. The concentrate contains only 0135% of MgO, and other elements are qualified. The mass quality flow is shown in Fig. 1.

Figure 1 Heavy-floating joint quantity quality process

It has obvious advantages over full flotation:

1. The grinding fineness is -10228mm, and the full flotation must be ground to -01074mm, accounting for more than 90%, thus avoiding the difficult problem of flotation foam sticking and filtering and drying operations caused by easy grinding of phosphate rock. .

2. The consumption of the heavy-floating process is significantly lower than that of the full flotation. It only needs 3187kg/t, which is reduced by 6147kg/t (see Table 1). With the return rate of 70%, the drug consumption can be further reduced and the dressing can be reduced. Cost, improve economic efficiency.

3, the process is simple, the operation is stable, the retry of small test and expansion test is good (see Table 1)

Table 1 Comparison of test results of total flotation and heavy-floating combined process

(4) All kinds of equipments are self-contained. It is seen from the results of the recovery of the heavy-grained concentrates (see Table 2) that the re-selection of the aqueous medium cyclone mainly recovers the -0.037mm colloidal phosphate ore and the short column flotation The tank mainly recovers -0.037mm phosphate rock, which ultimately makes the total recovery rate more than 80%.

Table 2 % of test results of expanded test and granular concentrate recovery rate

(5) The recovery rate of re-selected concentrate is higher than flotation, accounting for 51.79% of the total concentrate recovery rate, which is very beneficial to the treatment of the final product and greatly reduces the cost of mineral processing.

(6) According to the water quality analysis results of Jing tailings (see Table 3), except for the suspension of tailings water, the others are all qualified, and 70% of the water return rate in the process can save the drug consumption and reduce the tail water. Emissions are good for the environment.

Table 3 Product water quality analysis results mg/L

(7) The test used to treat the grade ore in Jinning Mine by the full re-election process. The grade of the selected material was increased from 21% to 24%. The crude medium cyclone was obtained by rough selection only, and the yield was 54.53%, and the grade was 28.74. %, a concentrate with a recovery rate of 70%, indicating that the grade ore in the full re-election process is achievable.

The enrichment rules of the heavy-floating combined process of Haikou and Kunyang phosphate mines are similar to those of Jinning, and they have also achieved good indicators; the concentrate yield of Kunyang phosphate mine is 70.96%; the grade P ₂ O ₅ 28.14% (including MgO 1185%), The concentrate recovery rate is 81.96%. The yield of concentrate in Haikou Phosphate Mine is 64.86%; the grade of P ₂ O _{5 is} 28.87% (including MgO 1.97%), and the recovery rate of concentrate is 84.69%. However, in order to reduce the addition of more phosphoric acid to the MgO in the concentrate by double reverse flotation, the phosphate in the tail water exceeds the standard, and the flotation is further optimized, and the combination of heavy and floating is feasible.

Conclusion

In summary, the heavy-floating combined process can deal with low-grade phosphate ore in Dianchi Lake more economically and rationally. It is superior to single-floating flotation and provides good mining and utilization of many of the same types of phosphate rock in Yunnan Province. Prospects. Efficient heavy and flotation equipment is the key to realize the heavy-floating combined process, and will have strong vitality after further industrialization.

With the increasing requirements of the country for the quality of phosphate concentrates and the increasingly strict environmental protection in the Dianchi area, it is necessary to study high-efficiency, low-pollution beneficiation routes to deal with low-grade phosphate ore.

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