Sedimentary Calcareous Phosphate Rock Ore Dressing Process Example

I. Intermediate test of Hejiayan phosphate ore dressing

Hejiayan phosphate mine in Lueyang Shaanxi Province. Between 1965 and 1975, the mine was subjected to laboratory tests of the flotation method and roasting method and intermediate tests of the roasting method.

The phosphate rock in this area is layered in the lower part of the Devonian strata and is a sedimentary calcareous phosphate rock ore. The ore body is divided into east and west sections, and the average content is P ₂ O ₅ 21%.

The natural types of ore are divided into two types: strip-like gray phosphorus rock and false-like clastic lime rock. It is a cryptocrystalline and false-twisted structure, a plate-like structure and a massive structure. Useful mineral is phosphate rock, apatite; gangue minerals are dolomite, calcite, quartz, sericite, carbonaceous, argillaceous pyrite and the like.

The collophanite is mostly a cryptocrystalline structure, and most of the banded aggregates are present in the ore, sometimes filled with cement between the false granules and the debris.

Dolomite is granular or striped, often associated with calcite, and contains muddy, charcoal and so on.

Calcite often appears as a separate band, and it also has fine vein filling in the late fissures.

According to the x-ray diffraction pattern, it is found that the ore is mainly composed of fluoroapatite and dolomite; the secondary phase α-quartz and a small amount of calcite. The theoretical content of the monomeric phosphorus mineral P ₂ O ₅ is 41% to 42%.

The chemical composition of the ore is listed in Table 1.

Table 1 Chemical composition of ore (%)

On this basis, an intermediate test of roasting method with a daily processing capacity of about 5 tons of raw ore was carried out, and the process equipment connection diagram is shown in Fig. 1. The process is described as follows:

The ore with a particle size of 12 to 0 or 25 to 0 mm is loaded into a weighing barrel and transported to the hopper by the carriage, and is fed into the tail of the rotary kiln by a belt feeding and measuring machine. The material is in countercurrent contact with the high temperature furnace gas (the fuel is light diesel oil) in the kiln and stays in the kiln for 100 to 140 minutes. After roasting, the product is discharged into the underground discharge bucket, sent to the storage bucket by the trolley, and then sent to the horizontal double-axis digester through the belt measuring machine. PCT rotameter was digested with water by a water header tank to the inclined screw conveyor from the center, and flows in a countercurrent direction to the roasted ore digested biaxially digester (mean: magnesium oxide clinker calcination of calcium oxide The process of turning into a hydroxide), the generated milk is discharged from the overflow and finally to the tailings pond. The phosphate concentrate is transported to the yard by cart. The high-temperature furnace gas that escapes from the kiln tail is vented after being cooled by multiple stages of dust removal.

Fig.1 Contact of the experimental equipment in the enrichment process of the Hejiayan phosphate rock roasting method

1-feeding hopper; 2-belt feeding measuring machine; 3-feeding pipe; 4-smoking box; 5-ф600×9000 rotary kiln; 6-underground discharging device; 7-clinker truck; 8-clinker storage bucket 9-belt feeding machine; 10-tail paddle; 11-horizontal biaxial digester (L×h=3000×305mm); 12-sand pump; 13-slanting screw conveyor (ф200×3200mm); - hot water measurement and metering; 15 - hot water high level water tank; 16 - side dust collector; 17 - tornado dust collector; 18 - impact type cooling washer; 19 - jet type absorber;

20-foam absorption tower; 21-centrifugal exhaust fan

The main equipment rotary kiln has a feeding end inner diameter of 0.6m, a length of 9m, an inner diameter of the discharge end of 0.75m and a length of 5m. The total length is 14m. The effective volume is 4.79m ³ . The bottom of the horizontal biaxial digester is curved, and the agitating twin shafts each have 38 blades of 30° with the shaft.

The preferential conditions for each assignment are:

Calcination: The ore grade contains P ₂ O ₅ 20.31% and particle size 25~0mm. The calcination temperature is 1050 to 1100 ° C, and the calcination time is 138 to 105 min. The calcined furnace has a residual amount of 0.3 to 0.6%.

Digestion: ore temperature 300±50°C, water temperature 50～60°C. The digestion time is 5-10 min, and the liquid-solid ratio during digestion is 5:1 to 3:1.

According to the above conditions, the phosphorus concentrate contains P ₂ O _{5 of} more than 31% and MgO of less than 2.5%; the recovery rate of the raw ore is greater than 90%, and the recovery rate of the calcined ore is greater than 95%. The decalcification rate is greater than 80%.

The whole system material balance is shown in Figure 2 in terms of 1000 kg of raw ore.

Fig.2 Hejiayan phosphate rock roasting method

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The main raw materials and power consumption per ton of raw ore are: heavy oil 0.05t, water 10m ³ , electricity 15°, steam 0.22t. Enrichment (dressing) than :1.47.

2. Intermediate test of ore dressing in Yingping section of Yanfu Phosphorus Mine

The Yanfu Phosphorus Mine is located in the two counties of Qiang and Fuquan in Miao and Buyi Autonomous Prefectures of southern Anhui. It is a large-scale high-quality marine sedimentary phosphorite deposit in China. Since 1976, the laboratory tests and intermediate tests of flotation and roasting of phosphate rock in different mining areas, ore sections and ore layers have been carried out, and good results have been obtained.

The mine is located in the Doushantuo Formation at the bottom of the Upper Sinian. The outcrop starts from the Yuhua area in the north and reaches the Gaoping area in the Fuquan area. It is about 17.5km long and has an area of ​​58km ² . According to the geological and geographical features of the distribution of the ore layer, it is divided into two major mining areas, Baiyan and Gaoping, with a total of nine ore sections. The Yingping section contains an average of about 29% P ₂ O ₅ .

The industrial significance of the Yingping section is the “b” layer ore, and the outcrop of the ore body is 2700-3000m long. From bottom to top, it can be divided into three natural types: gravel-like dolomitic phosphorite, clumpy dolomitic phosphorite and compact massive phosphate rock. Direct roof dolomite, dolomite siliceous or siliceous rocks; floor phosphorus-containing silicalite or silicalite agglomerates, all mine ore segments containing an average of P ₂ O ₅ 29.09%, and generally containing iodide (about 0.006 %~0.011%, average 0.0076%), iodine mainly occurs in dense massive phosphate rock.

The mineral composition of ore is: 70% of phosphorus minerals, 21% of carbonate minerals (dolomite), followed by 3% of quartz, 4% of hydromica and charcoal, and 1% of iron.

Phosphorus minerals are mainly “phosphorite mines” and belong to the fluorocarbon apatite series. Generally crystalline, less impurities are mixed in. The colloidal phosphate ore is round, elliptical, etc., and often adsorbs some charcoal and iron. The cement of the colloidal phosphate rock is carbonate, which is generally in contact with the substrate. Followed by cryptocrystalline apatite, mostly in the form of fine particle aggregates.

Carbonate minerals generally exist in the form of granular individuals or aggregates, and the particle size varies, and the particles are often mixed with charcoal.

Quartz is generally a crumb-like individual, scattered in phosphorus minerals or carbonates.

The chemical composition of the ore is beneficial to Table 2.

Table 2 Ore chemical components

For the ore in the Yingping section, laboratory experiments have been carried out with the reverse flotation method using sulfuric acid as an inhibitor and the conventional roasting-digestion-grading method. When the former is used, a comprehensive concentrate containing P ₂ O ₅ 29.31% and MgO 4.41% may be obtained, and a comprehensive concentrate containing P ₂ O ₅ 35.3% and MgO 1.59% is obtained, and the recovery rate is 94.18%; when the latter is used, the same composition may be used. For the ore, a phosphorus concentrate containing 37.43% of P ₂ O ₅ and 1.23% of MgO was obtained, and the recovery rate was 96.89%. The iodine can be recovered from the furnace gas, and the total recovery of iodine is about 70%.

On this basis, a reverse flotation method with a daily treatment of 1.5 tons of ore and an intermediate test of 3 to 5 tons of roasting were carried out. They are briefly described as follows:

Single reverse flotation intermediate test

The process and main equipment of the single reverse flotation intermediate test are shown in Figure 3. The flotation process conditions are listed in Table 3. The number and quality flow of the backwater test (return water content of 36.88% of the total water consumption) obtained under this condition are shown in Fig. 4.

Figure 3 Contact of the intermediate test equipment of the single reverse flotation method in Yingping Mine Section of Yanfu Phosphorus Mine

1-feeding machine; 2-ф600×600 ball mill ; 3-ф200×1650 classifier;

4-30 liter mixing drum; 5-12 liter ring-type flotation machine; 6-Ñ„ 750 concentrator; 7-vertical sand pump

Fig. 4 Intermediate test number and quality flow of single reverse flotation method in Yingping Mine Section of Yanfu Phosphorus Mine

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Table 3 Flotation process conditions

The backwater quality analysis was carried out on May 13-14, 1984. The results were (mg/L): H ₃ PO ₄ 330-350, Ca ^{2 +} 1034 to 1205, Mg ^{2 +} 194-263, P ₂ O _{5 liquid phase} 224 ~ 226, solid content 729 ~ 955, pH value 4.70 ~ 5.20.

The main chemical components of the phosphate concentrates (concentrate 1 and concentrate 2) and tailings (carbonate) obtained in accordance with Figure 4 are listed in Table 4.

Table 4 Main chemical composition of phosphate concentrate and tailings

Intermediate test of roasting-digestion-classification method (also recovering iodine)

The principle process of the roasting-digestion-classification method. Shown in Figure 5. Its process equipment contact diagram is shown in Figure 6. The simple process is: crushing the ore to 10~0mm, feeding it into the rotary kiln through the disc, and roasting at the calcination temperature of 1050 °C and the residence time of the material in the kiln for 80-100 min. Digested in a double digester in the bedroom, the digestion time is 3 to 5 minutes, and the liquid-solid ratio during digestion is 1:1. It is then graded using a biaxial scrub grader to obtain the final phosphate concentrate and lime milk. The furnace gas is sent for iodine recovery; the lime milk is carbonized or discharged as tailings, or magnesium bicarbonate is prepared.

Figure 5 Process principle of roasting method

Figure 6 Contact of the intermediate test equipment for roasting method (and recovery of iodine) in Yingping Mine Section of Yanfu Phosphorus Mine

1-original mine; 2-bucket hoist; 3-mine, disc feeder;

4-ф450×8000 rotary kiln; 5-ф136×2000 horizontal double-stirred digester; 6-ф136×2400 double-axis scrubber; 7-cyclone dust collector; 8-ф200-4000 spray tower; 9-ф200×5000 Sieve tray tower; 10-water circulation pump compressor; 11-ф250×5750 carbonization tower; 12-concentrator; 13-drum filter; 14-cooler; 15-acid pump; 16-iodine tank; 17-vortex Pump

Due to the different fuels used, the quality of the obtained phosphate concentrate is different, but it has no effect on the iodine recovery process. With a light diesel fuel, grade phosphate concentrate containing _{P 2 O 5 37.48%, MgO} 1.27%, the recovery rate 95.14%; coal as a fuel, a phosphorus-containing concentrate grade of _{P 2 O 5 35.87%, MgO} 2.31%, the recovery The rate is 95.77%. The quality of the phosphate concentrate is reduced due to the mixing of unburned coal powder and ash. Taking light diesel as fuel as an example, the material balance results of the roasting-digestion-grading process are listed in Table 5. The main chemical components of the obtained phosphate concentrate and tailings (lime milk) are shown in Table 6.

Table 5 Material balance in the roasting-digestion-grading process

Table 6 Main chemical components of phosphorus concentrate and tailings (lime milk)

The principle flow of the iodine recovery process is shown in Figure 7. The results of stable operation test show that the actual absorption rate of iodine can reach 83.24% with light diesel oil, and only 74.55% with pulverized coal. The reason why the latter is lower is because iodine is adsorbed by soot that is partially activated by activated carbon and is incompletely burned.

Figure 7 Process flow for extracting iodine from absorbent

When the concentration of the absorbing liquid is low (concentration is less than 1 g/L), the material balance of iodine recovery using oil as fuel is shown in Fig. 8. When the purity of refined iodine was 99.5% or more, the final total recovery of iodine was 68.92%. In addition, when the concentration of the absorbing liquid is high (greater than 10 g/L), the total recovery of iodine can be increased by about 5%, and the process can be simplified, but the dust collecting efficiency in the roasting process is required to be high.

Figure 8 When using light diesel oil as fuel, from a low concentration (concentration is less than 1g / L)

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Material balance of iodine extracted by absorption liquid

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