Magnetite ore dressing plant saves energy and reduces consumption

First, the status quo

In the treatment of various types of ore beneficiation plant, the largest number of magnetic iron ore concentrator, the total output of the greatest. Although the scale of the iron ore plant is very different, the largest annual treatment of 14 million tons, the minimum scale of 30,000 tons, but the difference in process flow is not large, so many technological transformation measures can be used in large, medium and small selection plants. At present, the energy consumption of the concentrator is about 90%, and the unit cost of ore dressing accounts for more than 50% of the total unit cost of the concentrator. According to statistics, the largest electricity consumption of the concentrator is the grinding process, which accounts for more than 50% of the power consumption of the whole plant; the tailing pump transportation process accounts for more than 20% of the power consumption of the whole plant; the crushing process accounts for 10% of the power consumption of the whole plant. the above.

The crushing, grinding and tailings transportation are important links in the beneficiation process. There are many reasons for the high power consumption of crushing mills. For example, there are a large amount of waste rock mixed in the ore mining, which increases the crushing and grinding processing volume; the crushing and grinding process has no selectivity and the crushing ratio is large; the mill The power consumption of the movement of the self, the lining and the grinding medium; the size of the grinding product is large; the classification efficiency is low, the cycle load of the mill is increased; the tailings concentration is low, and the like. This determines that the way to reduce the power consumption of crushing, grinding and tailings transportation must also adopt comprehensive technical measures to achieve the desired results.

Second, the way to save energy and reduce consumption

1. Using ultra-fine crushing equipment to optimize the crushing process system

The cone crusher produced by foreign companies such as Sandvik and Metso can reduce the particle size of the final crushed product by an average of 5 to 8 mm, which creates conditions for improving the grinding efficiency of the mill and increasing the processing time of the mill. However , due to the high cost of the imported cone crusher , many beneficiaries are discouraged. At present, the domestically produced high-efficiency cone crusher is also emerging in the field of crushing. Due to its relatively low price, it can be applied in many large and medium-sized factories. High-efficiency energy-saving crushing equipment not only has low power consumption, but also has a deeper effect on the crushing process due to its smaller product size. If the number of working sections is reduced, the closed circuit is simplified to an open circuit, which can reduce the number of equipment, save infrastructure investment, and reduce operating costs.

2, more broken less grinding, reduce the size of grinding ore

The crushing and grinding is the two stages of the crushing operation, and the crushed product is fed into the grinding operation. The material is broken by the crushing and impact of the crushing equipment; while the grinding is caused by the centrifugal force and the friction force, so that the ore is continuously crushed by impact, extrusion, shearing and grinding. The rate of change of energy with particle size reduction in the conventional crushing range is small, while the energy in the grinding range increases sharply with the decrease of particle size. The low energy consumption of crushing than grinding is a recognized concept in the mineral processing industry. Therefore, the particle size of the crushed final product (ie, grinding ore) is minimized, which is called “more broken and less grinding”. This principle has been adopted by most of the selected factories, and the design of the new plant is generally considered. The technical transformation of the old plant also reduces the grain size of the mill as one of the main contents. At present, the grain size of the large and medium-sized plants is controlled below 15mm, and the effect of reducing the particle size of the grinding mill is remarkable.

However, there are not many concentrating plants with a maximum particle size of less than 10 mm, mainly because the performance of traditional fine crushing equipment determines that the product is difficult to be finely crushed. If the product size is not properly reduced, the crushing capacity is reduced and the crusher is accelerated or even damaged. Therefore, to further reduce the grain size, it is necessary to select a new type of fine crushing equipment.

3, set dry pre-selection operations, improve the grade of grinding ore

Dry pre-selection operations are now widely used in large, medium and small magnetite ore dressing plants. Most of the magnetic rollers (magnetic pulleys) used are permanent magnet magnetic systems, and a few are electromagnetic magnetic systems. The magnetic field strength of the permanent magnet magnetic system is generally 150-250 KA/m. In recent years, with the application of high-efficiency permanent magnet materials, the magnetic field strength can reach 350-400 KA/m.

The magnetic pulley has a wide range of particle size and processing capacity. The concentrator adopting the self-grinding mill adopts a large magnetic pulley to pre-select the ore entering the self-grinding machine. The maximum particle size is generally 300-350mm, and is dried after being crushed. The upper limit of the particle size of the magnetic separation is generally controlled to be no more than 100 mm; the pre-selection of the fine ore before entering the mill can be as high as 400 tons. Pre-selection of magnetic pulley can greatly save energy, reduce consumption and increase production. Especially when the mixed rate of waste rock is high, its effect will be even greater, and 20% to 50% of raw ore can be discarded.

4. Strengthen grading and improve grading efficiency

Over-grinding is one of the main causes of energy loss in grinding, which leads to the cause of over-grinding and removing the grinding machine itself. The main reason is that the classification efficiency is low, so that the qualified grain size cannot be separated in time. At present, most of the concentrating plants in China use spiral classifiers, which have low classification efficiency. Therefore, a considerable amount of qualified product particles are mixed in the sand returning sand, resulting in a large number of qualified product particle size returning to the mill and grinding, which not only affects the output but also increases the mineral over-grinding. Power consumption. At present, new classification equipment such as hydraulic cone classifier, high frequency vibrating fine screen, linear vibrating fine screen, swirl fine screen, vertical cylinder screen and double vortex hydrocyclone have appeared, both inside and outside, and the application of two-stage classification process , created conditions for the strengthening of grading operations in China. The coarse-grain classification is replaced by a fine sieve instead of a spiral classifier; the fine-grain classification is mainly hydro-swirl, and the hydraulic conical classifier or high-frequency fine sieve, cyclone fine sieve and vertical cylinder sieve are secondary Segment classification. However, it is necessary to quickly solve the problems of the structure, parameters, materials and automatic control of the hydrocyclone to maintain the stability of its process indicators.

5, using the stage grinding phase selection process, try to choose the tail when the coarse grain

The grade of magnetite ore in China is generally low. The embedding granularity of gangue in ore is often larger than the embedding granularity of magnetite. In the process of ore pulverization, the first is to dissociate the gangue, and to dissociate the gangue early. When the particles are selected, it is possible to avoid wasting energy and materials due to the involvement of the gangue in grinding or gangue over-grinding. Therefore, the use of stage grinding can achieve energy saving. Practice has proved that the lower the grade of raw ore, the more significant the economic benefits of using stage grinding. In particular, the process of “super coarse grinding and large particle magnetic separation and tailing” is adopted, that is, the process of magnetic separation to remove tailings when grinding to 1 to 5 mm, and has outstanding energy saving, consumption reduction and yield increasing effects.

6. Select new grinding machine, grinding medium and liner

1) The plant's equipment is developing in the direction of large-scale operation and automation of the operation process; while the small-scale selection plant is innovating in terms of the type of grinding machine bearing and the method of returning sand. The small mill with specifications below Ø1500~3000mm adopts rolling bearing instead of sliding bearing, which can save energy by 30%~50%. If there is a selection plant to improve the structure of the sand returning sander on the basis of the original equipment, the sand returning to the sand, and entering the mill together with the raw ore to save the scoop head, not only save energy, reduce impact, extend the drum feeder And gear life, but also improve the operating rate, the mill is easy to start, energy saving and production increase effect.

2) In the case of rough grinding, a spherical medium is often used, and the fine grinding generally adopts a columnar or tapered grinding section. The material, microstructure and shape of the grinding media are important factors influencing the mill. Now there is new type bainite steel ball, low-chromium alloy cast ball, troostite high chromium alloy cast iron ball polyols, have a high strength, impact toughness, wear resistance, crushing rate and so on.

3) The advantages and disadvantages of the structure and material of the mill liner directly affect the power consumption of the grinding. Currently metal ore dressing plant of high-manganese steel ball is still mainly steel consumption is as large as 0. 25 kg / t problems; large power consumption, consumption per ton of ore milled 8 ~ 20 kWh electrical energy, about beneficiation The total power consumption of the plant is more than 50%; the service life is short, 6 to 8 months in a ball mill, and 12 to 18 months in the second section; heavy weight; high noise; poor resistance to chemical corrosion of pulp in wet grinding . In recent years, the successful development of rubber linings, rounded square linings and magnetic linings has achieved significant energy savings in ball mill applications.

Rubber linings have unique elasticity and outstanding corrosion resistance. It can be deformed when impacted, with high life, light weight and remarkable power saving effect. Generally, the power consumption can be reduced by 10% to 15%.

Rounded square linings, ie, angled spiral linings, because the linings are arranged at a certain angle along the mill, the material in the cylinder forms a perpendicular shearing plane with the axis of the mill, creating additional shear on the material. The effect is to significantly reduce power consumption.

The metal magnetic lining plate is closely attached to the barrel of the ball mill by magnetic force. The surface of the metal magnetic lining adsorbs the ground steel ball and the magnetic material with different particle sizes to form a rolling protective layer of 20-50 mm thick, which has a corrugated effect on the grinding ore. The fine-grained easy-to-magnetize material is stably consolidated at the bottom layer, which can effectively eliminate the wear of the liner. It is characterized by a long service life and is 6 to 8 times higher than that of a high manganese lining. The thin thickness, light weight and low steel consumption can reduce the mechanical and electrical consumption of the ball mill by 6% to 7%. The advent of magnetic linings is a major breakthrough in the history of ball mill linings.

7. Reforming grinding control

Using automatic detection instrument, detecting mill audio, mill power and classifier current, analyzing mill working condition, using fuzzy algorithm and fuzzy reasoning, optimizing mill grading control model, realizing automatic control of ball mill feeding and automatic control of grinding concentration The automatic control of the graded overflow granularity fully utilizes the grinding and classification efficiency, reduces or eliminates the swelling and idling time of the ball mill, reduces the loss of the steel ball and the lining, reduces the production cost, and has remarkable economic effects.

8. The magnetic artery magnetic separator is matched with the fine sieve to improve the concentrate grade and output.

9, tailings transportation

The tailings transportation of the ore dressing is another major energy consumption. Since the tailings must be transported to the tailings dam in time, the slurry pump must be operated 24 hours a day. Due to the low emission concentration (15% to 16%), the energy consumption of tailings transportation is large and the operating expenses are high. In the case that the pump station, pipeline and lift are fixed, it is easy to use the frequency converter to change the speed of the unit, change the parameters of the pump impeller, etc. to renovate the old pump and realize the high concentration or constant concentration through the frequency conversion tailing pump. Conveying can greatly save energy.

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