This is a new type of grading equipment developed abroad. It is said that the complex fluidization grading is the latest technology in the world of mineral grading, and it is also the third generation of advanced and reliable grading equipment in the world after spiral classifiers and hydrocyclones.
The design concept of the compound fluidization classifier originated in 1988 and was developed by several graduates of the mineral processing engineering graduated from the Achen University of Technology in the Federal Republic of Germany (also translated into the Asian University of Technology). The purpose is to adapt to the trend of large-scale international mineral processing equipment. The advantages of high classification efficiency, fine hierarchical granularity, high classification accuracy, and large processing capacity are concentrated on one device.
The compound fluidized classifier obtained German and European patents in 1991 and 1992 respectively. The first equipment was put into use in Germany in 1991. At present, about 60 sets of equipment are in operation around the world, and the application fields are constantly expanding. Figure 1 shows the appearance of a duplex fluidization classifier.
Structure and principle: The basic structure of the aFx complex fluidization classifier is that the upper part is cylindrical and the lower part is conical. Efficient grading is accomplished in the middle coarse-grained grading chamber and in the annular grading chamber surrounding it, using ascending water and fluidized bed techniques. The slurry is fed vertically from the middle of the coarse-grained classification chamber to the distribution tray at the bottom of the coarse-grained classification chamber via a special pipe. The rising water flows into the coarse-grained classification chamber through the annular gap between the distribution tray and the coarse-grained inner wall, and a turbulent zone is formed in the lower portion of the coarse-grained classification chamber to achieve coarse-grain classification. The coarse-grained mineral settles according to the process requirements, and enters the coarse-grain discharge port located at the middle of the bottom of the coarse-grained classification chamber through the annular gap. The medium-grain product enters the annular medium-grading chamber in an overflow manner. The medium-grain classification chamber uses a fluidized bed technique to classify medium- and fine-grained products. The rising water is evenly distributed throughout the middle of the middle classifying chamber through a special fluidized bed water supply net installed at the bottom of the middle classifying chamber to ensure a uniform and stable laminar fluidized bed for accurate classification. The fine-grained mineral enters and exits in an annular overflow tank surrounding the middle-grain classification chamber. The medium-grain mineral settles to the bottom of the middle-grain classification chamber and is discharged through a valve uniformly distributed in the circumferential direction.
The opening and closing and discharge speeds of all discharge valves in both the coarse and medium grain classification chambers are controlled and adjusted by online measurement of pulp density. According to the on-site fluid loading, the particle size of coarse, medium and fine-grained minerals (ie, coarse-grained classification chamber grit, medium-grain classification chamber grit and final overflow product) can be adjusted by changing the height of the fluidized bed and the amount of rising water. . In addition, the concentration and flow distribution of each graded product can also be adjusted automatically within a certain set value according to the process requirements.
According to the parameters such as ore size, mineral density and slurry concentration, different and adjustable rising water quantities are used, and the fluidized bed water supply network at the bottom of the middle grain classification chamber with different structures is selected to adjust the pressure difference between the fluidized bed and the water supply network. To ensure uniform fluidization and precise grading of mineral particles.
The basic structure and working principle of the compound fluidization classifier are shown in Figure 2.
Specifications and models: from small laboratories to large industrial equipment, there are various specifications and models of AFX composite fluidization classifier, solid processing capacity is generally 10~1000t/h, solid content (concentration) is generally 10%~ 75%, the slurry processing capacity is 20~2500m3/h, and the upper limit of the ore size is generally 8mm.
The table below lists the main equipment parameters for several common sizes and models of the duplex fluidization classifier. The optimal parameters of each concentrating plant site can be realized by optimizing the operation of the equipment according to the nature of the ore and the size of the product.
Characteristics: After more than ten years of production practice, the complex fluidized classifier has novel ideas, unique design, reasonable structure, economical and practical, all adopt automatic control and strong adaptability. The machine is highly efficient in separation and multi-purpose, and can perform three kinds of particle size classification to obtain three kinds of products. For modern mineral processing technology for mineral grading and harmonious grinding grading process, it provides a new concept of grading equipment, which generally has the following characteristics:
(1) High classification efficiency and superior index. In particular, the classification process of the fine particle classification chamber is performed in a laminar flow state. The hydrocyclone has a great influence on the classification efficiency due to the inevitable equal drop factor, but has little effect on the AFX composite flow layer hydraulic classifier.
(2) The processing capacity is large. The pulp processing capacity is up to 2500m3/h, the solid amount can reach 1000t/h, and one AFX compound fluidized classifier can replace many other grading equipment.
(3) The entire operation process including water supply and discharge is fully implemented with automatic control and process indicators, and the product particle size composition is stable. The control system has strong adaptability to the characteristics of the ore feeding and parameters (such as flow, concentration, particle size, etc.), and it is sensitive and timely adjusted to ensure the calibration of the grading indicators.
(4) Strong adaptability. Under the premise of not changing the volume of the slurry, the ore treatment volume can fluctuate within the range of about 30% without affecting the classification efficiency, which is an advantage that other classification and screening equipment cannot match.
figure 1 Â figure 2 Â table
(5) The concentration of the grit product in the coarse and medium-grain classification chambers can be maintained at 65% or more as needed. Furthermore, further concentration adjustments can be made according to subsequent grinding requirements, which is one of the obvious advantages compared to hydrocyclone. In order to achieve higher classification efficiency, the hydrocyclone should avoid the coarse particles entering the overflow. At this time, the discharge of the grit chamber must form an umbrella shape, so the concentration of the grit of the hydrocyclone must be very low. [next]
(6) One machine is multi-purpose, one equipment completes two-stage classification operation, and three kinds of products are generated, and the classification process of coarse and fine particles is relatively independent, which can be separately adjusted and optimized, and the slurry can be directly fed without pretreatment. The connection with the subsequent process is simple, and the auxiliary processes such as concentration and deliming can be eliminated or simplified, and the corresponding various supporting equipments are provided, which brings many technological advantages to the concentrating plant. This is also beyond the reach of hydrocyclones or screening equipment. For example, a double fluidized classifier can replace the multi-stage grading equipment such as double-helix classifier and fine sieve after the first and second stages of grinding, which can greatly improve the maintenance efficiency of the two sections while greatly reducing the maintenance workload of the equipment. It embodies the principle of simplifying the process of modern concentrator, large-scale equipment, centralization of equipment, and minimizing the number of equipment.
(7) Unlike other grading and screening equipment, the use of a double fluidized classifier retains the possibility of flexible and efficient response and adjustment at any time based on changes in the nature of the ore, without the need to reinvest. For example, to reduce the graded particle size from 100 μm to 75 μm, it is only necessary to adjust the fluid parameters. If the original screening equipment is used, the concentrator must immediately invest in a new screen, or even reduce the amount of processing at the same time in order to maintain the desired classification efficiency. If the hydrocyclone was used, the hydrocyclone will immediately be forced to deviate from the optimum working point, and a new nozzle combination and re-adjustment of the operating parameters must be used. In addition, it is necessary to change the operating parameters of the feed pump. Even so, it is difficult to avoid deviation from its optimum working point. If the granular online detection system is configured, the above advantages of the complex fluidization classifier will be more prominent, because "R needs to modify the set value in the control program.
(8) Since the entire equipment does not have any other moving parts except the grit product discharge valve, the running power consumption is very low. For the same reason, there is no noise during operation and the on-site working environment is improved.
(9) Small wear. The grit valve, which is the only moving part, has excellent wear resistance and low cost. Occasional replacement can also be done quickly. The bottom of the medium-grain classification chamber is the fluidized bed water supply network, which is also the top plate of the rising water tank. It is made of high-quality stainless steel and special design structure, which not only ensures the formation of a uniform and stable fluidized bed, but also makes the rising water form below the pulp layer. ~3mm buffer water film, the slurry is lifted and not in direct contact with the fluidized bed water supply mesh surface, thereby effectively protecting the fluidized bed water supply mesh surface from abrasion. As long as the rising water does not contain solid particles while the equipment is running, and the maximum water pressure is ensured by the detection system, the life of the fluidized bed at the bottom of the medium-grading chamber is almost unlimited.
(10) In addition to the obvious technical advantages, the biggest advantage of the complex fluidization classifier is its unparalleled economic indicators. The combination of high grading efficiency, large processing capacity, low floor space and complex grading advanced technology minimizes capital investment and operating costs. Due to the advantages of less wear and low power consumption, the complex fluidized classifier has a lower operating cost than other equipments except for less investment.
Application examples of compound fluidization classifiers in foreign countries:
In July 2002, 1 Allflux fluidized double grader put into operation in South Africa, a concentrator, replacing the original two series of grading equipment, magnetic iron ore fine grinding after grading process to be successful.
The model of the equipment is AFX-1500, the ore processing capacity is 280t/h, the ore density is 4500kg/m 3 , the pulp density is 1370kg/m 3 , and the pulp concentration is 35%. The maximum grain size of the ore is 850 μm, the P 80 is 140 μm, and the -45 μm is 20% to 35%.
The ore is first pre-classified in a coarse-grained classification chamber at a classification size of 212 μm, and then entered into a fine-grain classification chamber to complete a classification of 45 μm. The sanding products of the two classification chambers of the thickness have a mixing density of 2400 kg/m 3 and a solid content of 75%. The overflow concentration was 7% and pumped into the sedimentation tank for dehydration.
Process specifications exceeded expectations. The particle size of the classified product completely meets the requirement of 45 μm for P95, and the recovery rate of the -45 μm particles into the overflow product is as high as 74% to 92%. In addition, the advantages of simple process, stable operation, and extremely low production and maintenance costs also bring a series of additional benefits.
In 2003, three Allflux1000 sions iron ore in South Africa put into operation for hematite grading, each processing capacity of 180t / h. The ore size is 0~2mm, graded at 300μm and 74μm, the classification efficiency is up to 75%, the operation is reliable, and the index is stable.
From November 2004 to January 2005, the industrial test of the compound fluidization classifier was carried out at the Shantoushan Iron Mine of Benxi Iron and Steel Co., Ltd., and satisfactory technical indicators were obtained, which has high promotion value and application prospect.
The results of the industrial test of the AFX compound fluidized classifier at the Shantoushan Iron Ore Concentrator of Benxi Iron and Steel Co., Ltd. show that when the treatment capacity is 26~35t/h, the content of -74μm of coarse, medium and fine grain products is 6.09%. 11.82%, 82.73%, got an almost complete classification. The mass efficiency and quantity efficiency of the fine-grained products are as high as 74.38% and 87.66%, and the classification efficiency is 2.2 times that of the spiral classifier, 1.8 times that of the hydrocyclone, and 1.3 times that of the vibrating fine sieve. The classification efficiency of AFX complex fluidization classifier is analyzed from the distribution rate index. When the distribution rate is 50% and the particle size is 90μm, the slope of the distribution curve is steep, which not only indicates that the classification efficiency is high, but also indicates the classification with 90μm as the boundary granularity. The behavior is very accurate, and particles larger than dso enter the coarse product, less than d50. The particles enter the fine-grained product and the classification behavior is very accurate and reliable. The particle size difference between the three products of AFX compound fluidization classifier is very obvious. The classification limit between each particle size is very accurate. The coarse grain size is very coarse and the fine grain size is very fine. The medium-grain product has a particularly uniform particle size, and it contains neither fine-grained particles nor over-sized particles. This uniform medium-grained product constitutes another major feature of the complex fluidized classification. In particular, it should be noted that the dissociation degree of the medium-grain product monomer is as high as 92.50%, and a part of the qualified grade iron concentrate can be selected by the weak magnetic field sorting. For the classification process of the double fluidization classifier, a completely different process flow from the spiral classifier and the hydrocyclone can be used to reduce the amount of grinding and over-grinding, which not only saves energy and reduces consumption, but also produces coarse particles. Grade high quality iron concentrate.
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