During the flotation process, there are many factors affecting the flotation effect, including ore properties (such as mineral composition, particle size distribution, shape, mineral floatability), flotation environment (agent dosage, slurry concentration, temperature, flotation time) and The characteristics of the flotation machine, etc. The characteristics of the flotation machine include structural characteristics (slot structure and impeller structure), agitation characteristics (impeller speed and impeller line speed), bubble characteristics (bubble size, aeration volume, air holding capacity), foam layer properties (foam layer thickness) , foam stability) and so on. The essence of the flotation machine affects the essence of the flotation process is the dynamic process of the three-phase flow of solid, liquid and gas in the flotation process. The flotation process of ore particles can be divided into three basic processes in terms of kinetics: collision of ore particles with bubbles, adhesion of ore particles to bubbles, and loss of ore particles from bubbles. In the flotation process, the primary condition is the collision and adhesion of the ore particles with the bubbles, and the ore-bubble aggregate rises in the flotation cell to form a mineralized foam. At the same time, the aggregate will experience a shedding-exchange process of shedding and re-crash attachment.
Flotation is the process of interaction between ore particles and bubbles. The ore particles and bubbles are two key factors in the process of action. The ore particles are fixed by ore, and the bubbles are forced into the mechanical agitation flotation machine by the impeller. The turbulent action of the slurry is formed and evenly distributed in the flotation cell. The size of the bubble is related to the structure of the flotation machine, the amount of inflation, the rotational speed (degree of turbulence), etc. Under normal circumstances, the bubble size will increase as the flotation machine increases, as the speed of the flotation machine increases. Large and reduced. At the same time, the structure of the flotation tank also has a great influence on the bubble, including the shape of the impeller, the distance from the impeller to the bottom of the flotation tank, the shape of the flotation tank and the depth of the flotation tank, which will affect the size of the bubble to varying degrees. And the consumption, as well as the contact probability of bubbles and ore particles, thus affecting the entire flotation process.
By improvement of laboratory flotation machine Type XFD-63, were systematically investigated the influence depth, and an amount of pneumatic flotation machine speed and other performance parameters of the flotation tank of the anti-flotation of bauxite.
First, the test
(a) sample
The bauxite ore sample used in the test is a comprehensive sample of several bauxite deposits in Henan Province. The main mineral ore is an aluminum diaspore, gangue mineral kaolinite, illite and pyrophyllite, Besides, it contains a small amount of goethite and hematite and the like. The ratio of aluminum to silicon in the ore is 6.20, and the chemical composition of the ore is shown in Table 1.
Table 1 Multi-element analysis of raw ore (mass fraction) /%
Al 2 O 3 | SiO 2 | Fe 2 O 3 | TiO 2 | CaO | MgO | K 2 O | Na 2 O | S |
65.92 | 10.62 | 4.93 | 3.04 | 0.58 | 0.31 | 1.10 | 0.39 | 0.08 |
(2) Test equipment and pharmacy
The flotation machine used in the test was improved by XFD-63 laboratory single-slot flotation machine. The overall height of the flotation machine reached 900mm, and the length of the flotation shaft was increased to 300mm, which can be used for different tank depth tests. After improvement, the maximum depth of the flotation cell can reach 254mm. The flotation machine is connected to an air compressor to ensure the stability of the air volume during the whole flotation process, and the glass rotor flow meter is used to measure the air volume. A frequency converter is installed on the flotation machine to control the rotation speed of the flotation machine. The impeller diameter is 0.06m, and the rotation speed can be arbitrarily adjusted between 0 and 3000r/min. The flotation machine and supporting equipment used in the test are shown in Figure 1.
The flotation reagent used in the test was a regulator Na 2 CO 3 (analytical grade), a collector 1231 (dodecyltrimethylammonium chloride, industrial product, produced in Nanjing), and a foaming agent MIBC (methyl). Isobutyl methanol, industrial product, produced from Zhuzhou).
(3) Test methods
The experiment focused on the influence of the flotation machine's aeration volume, rotation speed and flotation tank depth on the bauxite reverse flotation index. No pre-desilting was carried out in the test. Na 2 CO 3 was added as a modifier during the grinding process. After grinding, 1231 and MIBC were directly added for reverse flotation. The flotation reagent system and operating conditions of all the tests were consistent. The concentrate and tailings products obtained from the test were separately filtered, dried and weighed. The Al 2 O 3 and SiO 2 contents in each product were analyzed to calculate the concentrate aluminum-to-silicon ratio and the Al 2 O 3 recovery. The flotation process and the pharmaceutical system used in the test are shown in Figure 2.
The test used a single factor method to examine the effects of various performance parameters. According to the test results, the performance parameters of the best flotation index are selected as the optimized values ​​of the next test, the next parameter is tested, and the optimal performance parameters of the flotation machine are finally determined.
Second, test results and analysis
(1) The influence of the aeration volume of the flotation machine
The flotation machine's aeration amount mainly affects the bubble characteristics. Under certain drug system and speed conditions, as the flotation machine increases the air volume, the air dispersion in the flotation tank increases. When the amount of inflation reaches a certain level, the density of the air increases, and the degree of dispersion starts to decrease again, forming a large bubble. Under the condition of the flotation machine speed of 2200r/min and the flotation groove depth of 144mm, the influence of the aeration amount on the reverse flotation index was investigated. The test results are shown in Table 2.
Table 2 Effect of flotation machine aeration on reverse flotation
Flotation machine inflation setting / (L·h -1 ) | Concentrate aluminum to silicon ratio | Al 2 O 3 recovery rate /% |
100 | 8.62 | 7079 |
150 | 8.81 | 73.63 |
200 | 9.14 | 74.09 |
250 | 9.27 | 73.61 |
300 | 8.91 | 75.58 |
The results in Table 2 show that as the aeration increases, the air dispersion in the flotation cell increases correspondingly, the number of bubbles increases, the amount of foam increases, the floating rate of the silicon-containing mineral increases, and the quality of the reverse flotation concentrate gradually increases. The recovery rate of Al 2 O 3 is basically unchanged.
When the aeration amount exceeds 250 L/h, the bubble size in the flotation cell becomes larger, and the air dispersion begins to decrease, which is manifested as a decrease in the quality of the reverse flotation concentrate. A suitable amount of inflation is in the range of 200 to 250 L/h.
(2) Influence of the speed of the flotation machine
The speed of the flotation machine has a certain influence on the collision and falling probability of the ore particles and bubbles. When the rotation speed is too low, the turbulent flow in the flotation tank is poor, and the coarse particles with high grade are ineffective, which affects the flotation quality. At the same time, when the rotation speed is too low, the gas will directly rise through the impeller to the liquid surface, and a gas flooding phenomenon occurs. Therefore, the rotation speed of the flotation machine must reach the critical rotation speed required for the dispersed gas.
Under the condition that the flotation machine has a gas filling capacity of 200L/h and the flotation tank depth is 144mm, the influence of the flotation machine speed on the reverse flotation index is investigated. The test results are shown in Table 3.
Table 3 Effect of flotation machine speed on reverse flotation
Flotation machine stirring speed / (r·min -1 ) | Concentrate aluminum to silicon ratio | Al 2 O 3 recovery rate /% |
1500 | 7.92 | 81.05 |
1800 | 8.28 | 81.36 |
1900 | 9.04 | 74.18 |
2000 | 9.98 | 71.94 |
2100 | 9.73 | 72.41 |
2200 | 10.19 | 73.07 |
2400 | 9.53 | 71.35 |
The results in Table 3 show that as the speed of the flotation machine increases, the average speed and pulsation speed increase correspondingly, and the degree of turbulence in the flotation tank increases, which is beneficial to the reverse flotation of bauxite, which is reflected in the reverse flotation concentrate. The ratio of aluminum to silicon is gradually increased, and the recovery rate of Al 2 O 3 is gradually decreasing. When the flotation machine speed reached 2000r/min, the recovery ratio of concentrate aluminum to silicon and Al 2 O 3 reached a relatively stable value of 9.98 and 71.9%, respectively. When the rotation speed of the flotation machine is too high (more than 2200r/min), the inertial force of the ore particles falling off the bubble increases, which is not conducive to the mineralization of the bubbles, resulting in an excessively high flow rate of the influent flow, which destroys the sorting environment of the reverse flotation. , affecting the sorting index, the concentrate aluminum-silicon ratio and Al 2 O 3 recovery rate have begun to decline. It can be seen that the suitable flotation machine speed is 2000-2200r/min.
(3) Influence of flotation groove depth
The depth of the flotation cell is an important factor affecting the mass flow rate per unit section. From a kinetic point of view, the concentrate grade and recovery rate depend on the mass flow rate of the target mineral and gangue minerals. Increasing the target mineral or reducing the mass flow rate of the gangue minerals can increase the concentrate grade or recovery rate.
When the flotation machine speed is controlled to 2200r/min and the aeration volume is 200L/h, when the flotation reagent system and flotation operating conditions are constant, the ratio of flotation tank depth to reverse flotation concentrate aluminum-silicon ratio and recovery rate is investigated. The relationship is shown in Table 4.
Table 4 Effect of Flotation Tank Depth on Reverse Flotation Effect
Flotation groove depth / mm | Concentrate aluminum to silicon ratio | Al 2 O 3 recovery rate /% |
131 | 8.50 | 73.42 |
144 | 8.44 | 74.55 |
159 | 8.34 | 76.80 |
177 | 8.39 | 77.99 |
The results in Table 4 show that as the depth of the flotation cell increases, the air consumption in the tank decreases, the bubble rise distance increases, and the collision probability between the bubble and the ore and the ore particles increases, which is conducive to improving the concentrate grade and recovery. rate. At the same time, increasing the depth of the tank, it is easy to form a relatively stable foam zone and a long separation zone during the flotation process, which is conducive to improving the quality and recovery rate of the concentrate. When the depth of the flotation cell is increased from 131mm to 177mm, the recovery rate of concentrate Al 2 O 3 increases from 73.42% to 77.99% when the ratio of refined aluminum to silicon is close. This result indicates that the bauxite reverse flotation should use a deep tank flotation machine.
Third, the conclusion
The effects of performance parameters such as flotation machine's aeration volume, rotation speed and tank depth on the bauxite reverse flotation index were investigated, and the following basic rules were obtained:
(1) As the flotation machine increases the air volume, the air dispersion increases, and the reverse flotation index increases. When the flotation machine reaches a certain value, the air dispersion begins to decrease again, the bubble size becomes larger, and the reverse flotation index Getting worse. The optimal aeration volume of the flotation machine during bauxite reverse flotation is 200-250L/h.
(2) The speed of the flotation machine has a certain influence on the probability of colliding and falling off of the ore particles and bubbles. The rotation speed is too low, the coarse particle flotation effect is poor, and the gas cannot be dispersed, and the gas flooding phenomenon occurs; the rotation speed is too high, the falling inertia force increases, and the sorting environment is destroyed. The optimum speed of the flotation machine during bauxite reverse flotation is 2000~2200r/min.
(3) Increasing the depth of the flotation tank, reducing the air consumption, increasing the probability of colloidal-bubble collision, and easily forming a relatively stable foam zone and a longer separation zone, which is conducive to improving the quality and recovery rate of the reverse flotation concentrate. When the depth of the flotation cell increases from 131mm to 177mm, the recovery rate of concentrate Al 2 O 3 increases from 73.42% to 77.99% when the ratio of refined aluminum to silicon is similar.
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