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 Î±-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 the table below.
Table The chemical composition of ore (%)
Mineral sample batch
Particle size (mm)
P 2 O 5
Fe 2 O 3
Al 2 O 3
Acid insoluble matter
Loss on ignition
Note: 1 is now burning at 950 Â° C, and then analyzed.
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-Ñ„600Ã—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 (LÃ—h=3000Ã—305mm); 12-sand pump; 13-slanting screw conveyor (Ñ„200Ã—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 30Â° 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 Â° 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 300Â±50Â°C, water temperature 50ï½ž60Â°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 original 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 15Â°, steam 0.22t. Enrichment (dressing)
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