One-stage rotary kiln separation process

Stone of Guangdong, Lu copper mine is a deep oxidation of refractory copper, copper grades of up to 1.3 to 2.5%. Since 1964, the relevant scientific research and design units have been compared in various schemes. The separation-flotation method has the advantages of simple process, high grade of concentrate and high recovery rate. It was designed in 1966 and put into trial production in 1970.

The direct selection of refractory copper oxide ore is a new process. There is no practical experience in foreign countries. At the initial stage of production, many problems were encountered, such as low processing capacity, abnormal equipment operation, low concentrate grade and recovery rate, and very unstable production. After several years of hard work and repeated improvement, the key to the separation process and equipment of the direct heating rotary kiln was basically solved, and a good separation effect was obtained initially, which basically reached the level of production.

First, the nature of the ore

The mine belongs to the quartz diorite porphyry and the limestone limestone in contact with the skarn copper deposit. The ore is earthy and has a deep oxidation. Due to the secondary enrichment in the diagenetic stage, the copper liquid and the oxides of silicon, iron and aluminum form a combined copper oxide during the diffusion process of the copper liquid, covering the surface and sandwiching the malachite type ore. The copper-bearing minerals are mainly malachite, with a small amount of blue copper ore, chrysocolla and water cholesterium. Iron ore is mainly limonite, followed by magnetite and hematite. In addition to iron clay , gangues include quartz, mica , garnet , amphibole, serpentine, chlorite and calcite . The content of iron clay in the ore is very high, -200 mesh is as high as 48%, ore is 27.1%, and the ore is about 300 mm. The original mineral composition is listed in Tables 1 and 2.

Table 1 Raw mineral chemical composition

Table 2 Phase analysis and physical properties

The ore is seriously polluted by fine mud, and the copper binding rate is high. Generally speaking, the high ore grade is combined with the corresponding increase of copper. According to the results of phase analysis, combined copper accounts for 5~40% of total copper, free copper oxide accounts for 50~80%, and copper sulfide accounts for 9~20%.

Second, isolation - flotation process

In the flotation process (Fig. 1 and Fig. 2), the solid line indicates the process used before March 1975, and the flotation machine can select more than 40% of the refined ore grade.

Figure 1 Schematic diagram of the main equipment of the segregation system

1—combustion chamber; 2—stainless steel radial heat exchanger; 3—common steel honeycomb heat exchanger; 4—single tube vortex dust collector; 5—multiple tube vortex dust collector; 6—exhaust fan; Dust cooling tower; 8 - water film dust collector; 9 - plastic chimney; 10 - sealed disc feeder; 11 - belt scale

Figure 2 Segregation - flotation process

The size of the isolated rotary kiln is 3.6 meters in diameter and 50 meters in length. The kiln head part (2 meters) is made of 20 mm thick heat-resistant stainless steel plate and the other is 22~28 mm thick 18MnCu steel plate. Kiln lining of 200 mm (the low temperature section 150 millimeters) thick alumina brick, and 6 m from the kiln in the kiln Fangxiang An gold metal heat exchanger, the inclination of the kiln was 15.2 m 3% kiln JZS101 three-phase asynchronous commutator variable speed motor (N=15~25 kW, n=350 rev/min) is driven, and there is an auxiliary drive system with standby power supply. Under normal conditions, the kiln speed is 1.48~0.493 rev / Minute.

III. Segregation - Process parameters and results of flotation

Separation technical conditions: the original ore contains copper grade 2~3%, particle size-4 mm, moisture about 5%, additive ratio: coal 3.5~4%, salt 1.8~2%. Separation temperature: heavy oil combustion flue gas into the kiln temperature 1150 ~ 1250 ° C; kiln head temperature 880 ~ 950 ° C, isolation rotary kiln speed 0.66 ~ 0.75 rev / min.

Grinding and floating technical conditions: grinding overflow fineness 75~80%-200 mesh, grading concentration 30%, flotation concentration 24~28%, Dinghuang drug 1.2 company/ton, 25 ^# black drug 0.15 kg/ton, 2 ^#æ²¹0.5 kg / ton, water glass 0.1 kg / ton.

Segregation - Flotation results:

Isolation kiln throughput 19.36 tons of dry ore

Burning rate (heavy oil) 4%

Smoke rate 25.68%

Two-stage dry dust collection rate 86.99%

Two-stage wet dust collection rate 98.39%

Recovery rate of volatile copper chloride 72.71%

Wet dust contains copper and water soluble copper loss 3.8%

Isolation kiln operation rate 70%

Concentrate grade (one selection of flotation column) 25% or more

Tailings grade 0.5~0.7%

Segregation - flotation yield 77% or so

Fourth, the main measures to solve the problem of isolation process and equipment

(1) In order to meet the requirements of segregation in the thermal system, it is necessary to have a suitable separation temperature and maintain an atmosphere suitable for segregation in the kiln (neutral or weakly reducing).

(2) The combustion chamber was reformed in order to improve the combustion conditions of heavy oil and prevent the flame from entering the kiln to continue burning and causing sintering of the charge.

1. The volume of the combustion chamber is increased from 22 m ³ to 33 m ³ to reduce the thermal strength of the space.

2. Change the nozzle position from the original front to the side to extend the flame path.

3. Change the single nozzle (1000 kg / ton) to multiple nozzles (4 × 25 kg / ton).

(3) The kiln head is exchanged with a 2 m heat-resistant stainless steel cylinder, and the glass cloth is used to telescopically connect the movable grinding block, and the water-free cooling sealing device.

(4) Exhaust fans with a volume of 10 ⁵ m ³ /h and a pressure of 9810 Pa ( ¹⁰³ mm water column).

(5) In order to solve the anti-corrosion problem, the 1 ^# kiln dust collecting cooling tower flue gas inlet short pipe and the lower part of the tower are all lined with epoxy resin lining graphite plate, 3 ^# kiln is made of granite and epoxy resin mortar building turbulent collecting tower, titanium and graphite plate substrate inlet short tube.

(6) In order to simplify the dust collection system and improve the operating conditions, the dry dust collection equipment is increased by 10 meters, so that the dry dust is automatically returned to the kiln. At the same time, the separation batching and feeding were all modified to the disc feeder, and a self-made belt scale and necessary measuring instruments were installed.

(7) Reconstructing the pulverized coal system, using chain mill to crush, and wind-grading to produce coal for segregation, to solve the problem of insufficient coal production, poor quality, mixed coal in coal, and coal blending in mine.