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

Wengfu phosphate mine in south urn Miao, Buyi Autonomous Prefecture in Weng'an, Fuquan counties territory, China is a large marine chemical deposition of high-quality phosphate rock deposits. 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.

Ore mineral composition: phosphate was 70%, mineral carbonates (dolomite) 21%, followed by 3% quartz, mica and carbon muddy water, 4% total iron mass was 1%.

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 1.

Table 1 Ore chemical composition

project	P 2 O 5	CaO	MgO	CO 2	Acid not Soluble	SiO 2	Loss on ignition	Fe 2 O 3	Al 2 O 3		F	I	Na 2 O
content(%)	30.20	46.33	3.72	9.57	3.74	3.39	10.46	0.79	0.29	0.19	2.63	0.0073	0.33

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 1. The flotation process conditions are listed in Table 2. 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. 2.

Fig.1 Contact of intermediate test equipment for single reverse flotation method in Yingping 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. 2 Intermediate test number and quality flow of single reverse flotation method in Yingping section of Yanfu Phosphorus Mine

Table 2 Flotation process conditions

Process conditions		Job name
		Stirring tank	Rough selection of the second slot	Rough selection of the third slot	First selection	Second selection	Third selection	Middle mine re-election	total
Flotation drug Dosage (kg/t)	Oxidized paraffin soap	0.40	0.25	0.10	0.40	0.10	-	0.10	1.35
	sulfuric acid	-	-	-	6.00	2.00	0.50	3.00	11.50
Floating mineral slurry temperature (℃)		22.5	22.5	22.5	23.00	23.00	23.00	23.00	-
Flotation slurry pH		8.5 to 8.6	8.5 to 8.6	8.5 to 8.6	5.15~5.4	4.90	4.75~4.85	4.70~4.50	-
Flotation slurry concentration (%)		23.77	23.77	23.77	11.61	8.93	8.86	13.45	-

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 Fig. 2 are listed in Table 3.

Table 3 Main chemical composition of phosphate concentrate and tailings

product name	Component name
	P 2 O 5		CaO	MgO	CO 2	Acid insoluble matter	SiO 2	Loss on ignition
	Volumetric method	Gravimetric method
	content(%)
Concentrate 1	35.20	34.97	50.01	1.35	4.81	4.04	3.84	5.28
Concentrate 2	34.55	34.03	49.07	1.73	4.79	4.09	3.42	5.85
Tailings (carbonate)	-	11.47	36.26	13.46	32.00	1.66	1.42	32.11
product name	Component name
	F		Cl	I	Fe 2 O 3	Al 2 O 3	K 2 O	Na 2 O
	content(%)
Concentrate 1	3.10	0.33	0.99	0.0098	0.38	0.09	0.07	0.40
Concentrate 2	3.05	0.93	0.99	0.0053	0.65	0.26	0.09	0.40
Tailings (carbonate)	0.98	1.45	0.015	0.00066	0.70	0.53	0.16	0.18

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

The principle process of the roasting-digestion-classification method. Shown in Figure 3. Its process equipment contact diagram is shown in Figure 4. 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 3 Roasting principle process

Figure 4 Contact of the intermediate test equipment for the 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-classification process are listed in Table 4. The main chemical components of the obtained phosphate concentrate and tailings (lime milk) are shown in Table 5.

Table 4 Material balance in the roasting-digestion-grading process

project	Job name
	Ore preparation	Roasting			digestion			Grading
	product
	Raw ore	Roasting Vector	Iodine residue	Spin dust	Roasting ore	Before digestion	After digestion	Tailings (lime milk)	Iodine concentrate 2
Weight (kg)	1000.00	98.20	0.50	3.50	897.80	897.80	915.80 1	144.60	771.20
P 2 O 5 content (%)	30.38	-	27.48	24.04	33.73	33.73	33.07	9.55	37.48
Recovery rate (P 2 O 5 %)	100.00	-	0.04	0.27	99.69	99.69	99.69	4.55	95.14

Note: 1 After digestion, the ore absorbs 18 kg; 2 phosphorus concentrate contains MgO 1.27%.

Table 5 Main chemical components of phosphorus concentrate and tailings (lime milk)

product name	Component name
	P 2 O 5		CaO	Active CaO	MgO	CO 2	Loss on ignition	Acid insoluble matter	SiO 2
	Gravimetric method	Volumetric method
Phosphate concentrate	37.52	37.65	51.81	0.77	1.14	0.85	1.07	4.40	3.90
Tailings (lime milk)	9.31	9.82	43.88	23.07	20.07	5.45	-	4.21	3.69
product name	Component name
	Al 2 O 3		Fe 2 O 3	F		I	Na 2 O	K 2 O
Phosphate concentrate	0.25		0.37	3.47	0.42	0.0012	0.26	0.06
Tailings (lime milk)	0.58		0.80	1.00	0.46	0.0015	0.28	0.07

The principle flow of the iodine recovery process is shown in Figure 6. 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 6 Process flow for extracting iodine from absorbent

The material balance of iodine recovery with oil as fuel when the concentration of the absorbing liquid is low (concentration is less than 1 g/L) is shown in Fig. 7. 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 7 When using light diesel oil as fuel, from a low concentration (concentration is less than 1g / L)

Material balance of iodine extracted by absorption liquid

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