Ridge iron ore mine Shandong Gold (referred Jinling Iron) is processed in contact with high-temperature hydrothermal account skarn polymetallic magnetite. The ore type is mainly magnetite, followed by skarn magnetite and imaginary hematite. Metallic minerals are mainly magnetite, followed pyrite (containing cobalt), yellow copper ore, pyrrhotite; gangue minerals pyroxene, followed by chlorite, phlogopite, vermiculite and a small amount of calcite .
1 Original process and problems
Jinling iron ore processing plant raw process: Sec crushing and screening process is a closed circuit, disposed before the finely divided pre-screening, the screen was magnetically pulley preselected throw waste, after the screening examination set finely divided, magnetic material through the sieve After the pulley is preselected, it will return to the fine crushing to form a closed circuit. After the grinding process is a closed-circuit grinding, the staged overflow will first be mixed and floated to separate the flotation, and the copper and cobalt will be recovered, and the mixed tailings will recover the iron through three-stage magnetic separation.
The main problems with the original process are:
(1) With the increase in the throughput, the ball mill can no longer guarantee the fineness required for the grinding production process.
(2) The working condition of the magnetic gathering machine is poor, and the grade of the iron concentrate is fluctuating greatly; the processing capacity of the CTB1024 magnetic separator is seriously insufficient, and the sorting effect is poor.
(3) The Auxiliary Equipment also has the problem of insufficient production capacity to varying degrees, which restricts the sorting effect of the production process.
2 Measures to improve the grade of iron concentrate
2.1 Improve the grinding mill fineness production practice and test shows that within a certain range, the grinding fineness increases by 1 percentage point, the iron concentrate grade increases by 0.08 percentage points. Due to the needs of enterprise development, the iron ore fines production capacity of the concentrator increased from 50,000 tons in 1997 to 675,000 tons in 2001, and the processing capacity of the ball mill increased from 28 tons to 38 tons.
2.1.1 Reducing the grain size of the mill The mill treatment capacity of the concentrator increased by 27% on the premise that there was no major change in the ore properties. Since 1998, Jinling Iron Mine has reduced the grinding grain size from 0 to 20 mm to 0 to 14 mm, which has achieved the goal of multi-grinding and grinding, improving grinding efficiency, reducing production cost and meeting the production process requirements.
2.1.2 The ores of the rational ore dressing plant are from the three sub-mines of Zhaokou, Houzhuang and Tieshan. The ore properties of each sub-mine are quite different, and there are obvious differences in grindability and selectivity. In order to stabilize the ore-bearing properties of the ball mill, the grinding amount of the three mining plants was strictly matched according to the production amount. When the mining of the three mining plants is uneven, a buffer storage yard is set up to ensure the ratio of the ore to the ore. [next]
 Through the above two measures, the grinding fineness of the ball mill is basically stable within the requirements of the production process (see Table 1), which creates conditions for the stable improvement of iron concentrate grade.
Table 1 Fineness of iron concentrate from 1998 to 2001 | ||||
Year / year | 1998 | 1999 | 2000 | 2001 |
Annual processing capacity / 10,000 t | 52.5 | 58 | 60.5 | 67.5 |
Taiwan processing capacity / t | 30 | 32 | 35 | 38 |
Ball mill feed size / mm | 0 to 20 | 0 to 18 | 0 to 16 | 0 to 14 |
Average fineness | 68 | 68 | 69 | 70 |
(-0.074mm content ) / % | ||||
2.2 Reforming the selection process to improve process conditions
2.2.1 The original magnetic separation process of the ore dressing plant is a selection of three sections and a sweeping selection, as shown in Figure 1. The processing capacity of the CTB1024 magnetic separation machine is 70-130t, while the processing time of the mill is 140t, which has greatly exceeded the processing capacity of its original design. Therefore, the CTB1024 magnetic separator can not meet the production requirements. The specific performance is as follows: the working space of the magnetic separator is not enough, the flushing water is insufficiently added, the working concentration is very high, and the suitable working concentration requirement of 25% to 35% cannot be achieved, which results in poor sorting effect and affects the iron concentrate. Quality; the operating conditions of the magnetic condenser are relatively complicated, the working conditions are extremely unstable, the sorting effect is poor, the product quality fluctuates greatly, and at the same time, the quality of the returned sweep concentrate is very low, which seriously affects the concentrate of the magnetizer. quality. [next]
In August 1998, Jinling Iron Mine changed the first and second magnetic separators to CTB1030 magnetic separator. The three-stage magnetic separation replaced the magnetic condenser with CTB1024 magnetic separator, and the sweeping operation was removed. In 2000, the three magnetic magnetic separator was changed to CTB1030 magnetic separator. The new process is shown in Figure 2. The CTB1030 magnetic separator meets the production requirements, improves the processing capacity of the magnetic separation process, reduces the working concentration of magnetic separation, and increases the number of magnetic tumbling times. The magnetic separator replaces the magnetic condenser to dredge the process and stabilize the quality of the iron concentrate. After the transformation, the magnetic separation process has reached 700,000 tons of concentrates per year. At the same time, new processes and new equipment have played a key role in improving iron concentrate grade and iron metal recovery. [next]
2.2.2 Reconstruction of iron concentrate filter From August 1998 to November 1999, four filters were modified to increase the magnetic wrap angle of the filter from 31° to 39°. After the magnetic filter is modified, the adsorption area is increased, and the unit processing capacity of the filter is increased by 25%, effectively solving the pressure brought by the increased processing capacity. At the same time, two sets of magnetic blocks are added along the circumferential direction, which increases the number of magnetic tumbling of the iron concentrate in the adsorption zone, which is beneficial to the cleaning of the gangue mixed in the magnetic mineral, further improving the grade of the iron concentrate.
2.3 Actively apply new equipment to improve equipment level
2.3.1 Application of CTDG1010N permanent magnet dry magnetic separator The original preselected throwing equipment is 1030mm×1045mm water-cooled electromagnetic magnetic pulley. The device has many shortcomings: (1) the magnetic field force and its depth of action are small, resulting in metal loss; (2) the magnetic system design is unreasonable, the waste rock is mixed in the middle of the magnetic ore, affecting the quality of the concentrate; (3) the structure is complex and faulty Frequent, affecting the normal production of the process. In August 1998, the original electromagnetic magnetic pulley was replaced by CTDG1010N permanent magnet dry magnetic separator. The CTDG1010N permanent magnet dry magnetic separator has a reasonable magnetic system design, high field strength and large magnetic field depth. After the transformation, magnetic tumbling occurs in the direction of circular motion, and 11520 tons of waste rock is thrown each year. At the same time, the iron grade of the milled ore is increased by 1-2%, which plays an important role in improving the grade of iron concentrate. [next]
2.3.2 Magnetic tailings pump modification The tailings pump of one magnetic and two magnetic magnetic separation operation was originally 8/6E-AH slurry pump, and its processing capacity was up to 400m 3 /h. After the ball mill processing capacity is increased, the lack of processing capacity of the slurry pump restricts the addition of the blown water of the magnetic separator, affecting the working concentration of one magnetic and two magnetic. In December 2000, the company invested 120,000 yuan to complete the transformation of the magnetic separation tailings pump and switched to the 200ZGB slurry pump. After the transformation, the tailings pump satisfies the production demand, and the one magnetic and two magnetic magnetic separators achieve the ideal working condition, optimizing the sorting effect of the magnetic separator. Moreover, the power consumption of the tailings pump is reduced by 40 kW, saving more than 300,000 kW.h per year.
3 Production indicators and economic benefits analysis <br> The application of the above measures has made the grade of iron concentrates increase year by year. In 2001, the qualified rate of iron fines powder delivery (concentration grade is not less than 65.50%) has reached 100%, and the average grade of departure is 66.37%. The comparison of iron concentrate indexes before and after the transformation is shown in Table 2.
Table 2 Comparison of iron concentrate indexes before and after transformation | |||||
Items | Transformation of the former | After transformation | |||
(1997) | 1998 | 1999 | 2000 | 2001 | |
Iron concentrate starting grade /% | 65.54 | 65.84 | 65.88 | 66.01 | 66.37 |
Iron concentrate production / 10,000 t | 46.5 | 52.5 | 58 | 60.5 | 67.5 |
It can be seen from Table 2 that from 1997 to 2001, while the iron concentrate production increased steadily, the grade of iron concentrate increased by 0.83 percentage points. According to the sales contract, for every 0.1 grades, the economic benefit will be 0.7 yuan, and the annual average increase will be more than 1.6 million yuan. 
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