China's iron ore resources are not ideal, mostly poor miscellaneous ore and composite ore, with an average grade of only 32.67%.
Large-scale deposits only account for 5%, and the recoverable reserves are low. For example, among the developed 1079 iron ore areas, less than 20% of the low-grade ores amount to tens of tons, and the Zhangjiakou-Chengde area alone has 5.5 billion tons.
First, the technical idea of comprehensive utilization of ultra-low grade iron ore development
Facing the huge demand for iron concentrate and the reality that China's iron ore resources are poor, fine and miscellaneous, comprehensive development and utilization of ultra-low grade iron ore,
It is an important way to contribute to the development of China iron and steel industry. Treating this kind of ore by conventional process has high unit power consumption, high unit water consumption and poor economic benefit.
According to the characteristics of ultra-low grade iron ore, on the basis of small-scale experiments, we have carried out "pre-screening of raw ore-improving coarse crushing ratio-multi-stage selective dry separation and pre-throwing"
Study on the new comprehensive utilization technology of "stage grinding, intensified classification and magnetic separation" This new technology has the remarkable characteristics of more waste, high separation efficiency, energy saving and consumption reduction.
It is especially suitable for grinding magnetic iron ore with large capacity, low grade and fine ore.
See figure 1 for the principle flow chart of ultra-low grade iron ore dressing process.
2. Technical characteristics of development and comprehensive utilization of ultra-low grade iron ore
1. Strengthen pre-screening.
Before the raw ore enters the first crusher, the newly developed new ZSG 1642 high-efficiency and energy-saving vibrating screening feeder is used to replace the traditional heavy plate feeder.
The machine adopts medium frequency, medium amplitude and large inclination technology, and has two functions of feeding ore and screening, which strengthens the pre-screening effect. Pre-screening-loom products in raw ore,
Improve the production capacity of crushing system by more than 20%.
The structure and appearance of ZSG 1642 high-efficiency and energy-saving vibrating screening feeder are shown in Figure 2, and the main technical parameters are shown in Table 1.
Table l
Main technical parameters of ZSG 1642 high-efficiency and energy-saving vibrating screening feeder
The production capacity is150-340m3/h.
The maximum exciting force is 2x75KN.
The vibration frequency is 960 times/minute.
The amplitude is 3.5㎜.
Vibration motor power 2x5.5KW
Chute size (length× width) 4200mm× 1600mm.
The inclination angle of the chute is 65438 05 degrees.
The vibration direction angle is 60 degrees.
The maximum feed block size is 750㎜.
Screening particle size < 100 ㎜.
Compared with the traditional thick plate feeder, ZSG 1642 high-efficiency and energy-saving vibrating screen feeder not only has the advantages of reliable operation, but also has a simple structure.
The equipment investment and operation cost are low, and the energy-saving effect is good. Compared with the vibrating ore drawing machine, it not only has the characteristics that the ore drawing machine increases the ore fluidity by means of strong vibration equipment on the basis of gravity ore drawing,
But also can be transported in a short distance, the uniformity of feeding is better, and the particle size of the transported materials is large. Compared with foreign similar products, the performance has reached the advanced level of similar products in the world.
The purchasing cost and consumable parts consumption are extremely low.
2. Improve the crushing ratio of coarse crushing section and distribute the crushing load of each section reasonably.
For the crushing system with a daily capacity of 8000 tons, the coarse crushing rate is improved. Reducing the particle size of medium and fine particles,
The use of small medium and fine crushing equipment can greatly reduce equipment investment, capital construction and operating costs.
See Table 2 for the comparison of equipment configuration between traditional crushing process and new crushing process.
The data in the table show that the crushing ratios of coarse crushing, medium crushing and fine crushing in the new crushing process are 5.1:3.751.91,respectively, while those in the traditional crushing process are 3.06: 3.57: 3.5.
The total power of crushing equipment in the new crushing process is 575KW, which is lower than 700KW in the traditional crushing process 125KW.
. The new crushing process equipment configuration can improve the crushing ratio of coarse crushing and reduce the crushing grade of medium crushing and fine crushing.
The purpose of reasonable distribution of crushing load in each section. The design of crushing process achieves the purpose of increasing crushing capacity and saving energy and reducing consumption.
3.PD90 120 external moving collar crusher has a large crushing ratio, which is an iron ore coarse crushing equipment.
External-driven pendulum crusher is a new generation of high-efficiency, energy-saving, environmental-friendly and low-wear crushing equipment developed by General Research Institute of Mining and Metallurgy, with 1 invention patents and 3 utility model patents.
The machine has novel design, unique structure, large crushing ratio, large production capacity, small product granularity, long lining life, energy-saving equipment and low noise.
Less dust and other notable features. This technology has been successfully applied to several nonferrous metal mines. According to the characteristics of iron ore (large capacity and continuous operation of equipment) for the first time,
On the original basis, the mechanism parameters were adjusted and improved, and the doomsday crushing of large-capacity iron ore was successful. See Figure 3 for the structural diagram and Table 3 for the main technical parameters.
The experimental and production data show that the processing capacity is large, the daily production capacity is 8000t, the highest is 9926t, the crushing ratio is large, the incoming particle size is -765mm, the minimum crushing particle size is 1000mm, the coarse crushing product particle size is-150 mm, the medium and fine crushing particle size is reduced, and the smaller medium and fine crushing equipment is adopted, which greatly reduces the equipment investment cost and infrastructure. Due to the ideal motion trajectory of the movable jaw, the wear of the lining plate is significantly reduced, and the equipment has been put into operation for one year without replacing the lining plate. The equipment runs for 24 hours for a long time, which is stable, safe and reliable.
4. Multi-stage selective dry separation and pre-disposal of wastes
Three-stage selective dry cleaning and pre-throwing are carried out by using magnetic pulley and new dry magnetic separator.
Magnetic pulleys are selected in the primary and secondary coarse crushing circuits, which are mainly used to throw away the waste rocks mixed in the mining process. The separation principle of magnetic pulley is that magnetic iron is attracted to the surface of magnetic pulley by magnetic force, and non-magnetic objects are thrown away from magnetic pulley under the action of centrifugal inertia, thus achieving the purpose of magnetic separation. Primary waste discharge:-150mm ore is discharged after coarse crushing and passes through nakano high-intensity magnetic pulley.
Scraping by CT 12 10, two-stage scraping operation: scraping the finely divided 150㎜ ore through the strong magnetic pulley in the middle field.
The new rotating magnetic field "CCXGY-8 14 dry pre-separator for fine magnetite" is used to discard broken gangue and further improve the grade of raw ore.
When the selected mineral particles are very fine and the water content is high, the inclusion of magnetic and nonmagnetic substances is serious, and it is difficult to improve the iron grade.
CCXGY dry magnetic separator has a unique structure, which can form a rotating magnetic field, so that coarse and fine strong magnetic minerals are not only attracted by the magnetic force on the surface of the magnetic separator,
At the same time, the magnetic material bounces over the surface of the sorting drum for many times, and the non-magnetic material mixed in it is thrown into the tailings, which not only ensures that the magnetic material is not lost, but also ensures that it is fully discarded.
The schematic diagram of CCXGY-8 14 fine dry pre-separator is shown in Figure 4, and the main technical parameters are shown in Table 4.
Through three-stage selective pre-throwing waste, a large number of waste rocks and unusable tailings separated after crushing are thrown out as soon as possible, which greatly improves the grade of iron separation. The effect of dry separation is remarkable, and the pre-throwing rate reaches 68%.
The grade of raw ore increased from 13% to 25.8%, and the recovery rate of magnetic iron reached 94.90%. The raw ore processing capacity of the concentrator is calculated at 800 t/d, and after dry grinding and pre-selection,
Only about 2400 t of ore enters the grinding-magnetic separation operation every day, which greatly reduces the transportation cost of waste rock and the grinding cost with the largest energy consumption in concentrator.
5. Sorting in strengthening stage and grinding stage
In the case of rough grinding, more than 60% of tailings are thrown away, which creates good conditions for regrinding. The grinding and magnetic separation workshop of concentrator adopts two-stage grinding and magnetic separation process. φ2700 is selected for initial grinding.
X2700 ball mill and φ 2000 spiral classifier form a closed circuit. After a rough magnetic separation, most of the tailings are discarded. The regrinding of coarse concentrate is 2700x2700.
The ball mill and φ500 cyclone set form a closed cycle, which not only has high classification efficiency and good classification effect,
It creates conditions for improving the grade of iron concentrate. Compared with the traditional closed circuit composed of grinding and fine screen, it is stable and convenient to operate and has high classification efficiency. Especially for the large-capacity concentrator, the floor space is small.
The equipment investment is low and the production operation is reliable.
Three. Implementation effect
The new comprehensive utilization technology of "enhanced pre-screening-coarse crushing with large crushing ratio-repeated dry separation and discarding-staged grinding and staged magnetic separation" was successfully adopted to develop ultra-low grade iron ore.
The new process has the remarkable characteristics of more waste, high separation efficiency, energy saving and consumption reduction, and is especially suitable for grinding large-capacity, low-grade and multi-fine ore.
1. The processing capacity of raw ore in the concentrator reaches 8000t/d on average, with a maximum of 9926t/d, with a large crushing ratio, a feed granularity of -765mm and a maximum crushing fragmentation of.
1000mm, and the particle size of coarse crushed products is-150 mm.
2. After repeated tailing, the pre-tailing rate reached 68%, the grade of raw ore increased to 25.8%, and the recovery rate of magnetic iron reached 94.90%.
. The raw ore processing capacity of the concentrator is 8000t/d, and only about 2500t of ore enters the grinding-magnetic separation operation after dry grinding and pre-selection.
The transportation cost of waste rock and the grinding cost with the largest energy consumption in concentrator are greatly reduced.
3. Stage grinding and stage separation, in the case of coarse grinding, more than 60% of tailings are thrown away, creating good conditions for regrinding. The final grade of iron concentrate reached 66%.
Above, the total iron recovery rate is 49.55%, and the magnetic iron recovery rate is 93.93%.
4. The processing cost per ton of raw ore is 18.99 yuan, and the processing cost per ton of iron concentrate is 194.6 yuan. According to the daily processing of 8,000 tons of raw ore, the price of iron concentrate is calculated in 500 yuan.
The annual economic benefit is 765,438+0,565,438+0.3 million yuan.
The comprehensive utilization technology of ultra-low grade iron ore is the integration of the latest independent innovation equipment and technology in China, which realizes the large-scale and low-cost development and utilization of ultra-low grade iron ore.