(3) Adhesive sorting In the adhesion sorting, the air is mixed with the liquid in a dispersed state, and the gas is dissolved under the pressure generated by the liquid self-weight (this pressure can reach 600 kPa), and in the subsequent depressurization process. It is also precipitated to form bubbles, and the generated bubbles have highly expandable surfaces on which various kinds of hydrophobic substances and surface active substances are concentrated, and in the adhesion sorting, the load bubbles are brought to "water-atmosphere". The interface is not caused by the floating of air bubbles (in the case of conventional flotation), but by the flow of liquid. The velocity of this liquid flow is greater than that of the flotation machine (50 cm · sec -1 or more); at the same time, the relative motion between the bubble and the liquid flow is small.
Adhesive sorting process, according to process equipment characteristics, includes three forms: cascade sorting, depth sorting and surface sorting. As shown in Figure 11, the principle of sorting is the same.
A Cascade Adhesion Sorting Raw water falls to a specific plane of dispersed air while trapping air. As shown in Figure 11. The flow falls from a certain height onto the counterattack plane and the dissolution of the air is achieved by the pressure of the liquid stream which is inversely proportional to the square of the final velocity. After that, bubbles are formed on one side, and a combination of various substances is formed to form a complex, and then, by means of a special screen, it is brought to the water-atmosphere surface by a liquid flow velocity of 50 cm · sec -1 or more, and enters the sorting tank. . The substance that forms a combination with the air bubble and the substance that is lighter than the water are carried to the surface, and the liquid that moves at a low speed is discharged from the lower portion through the device. The material that enters the sorting tank during sorting is removed by means of an adhesive drum or other means (as shown in Figure 12).
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This process can be repeated 1 to 3 to 6 times, and there are single-stage, three-stage, and six-stage series sorting devices in the industry.
The cascade adhesion sorting device is suitable for the purification treatment of water containing petroleum oil and other hydrophobic dispersions with a lower total content, and the above substances can be reduced from 100 mg · l -1 to 5-8 mg · l - 1 , can also remove fine mud.
B Deep-adhesion flotation The use of boreholes or mines to recover oily or surface-active substances from water. In a hole or mine of a certain depth (for example, 65 meters), the water to be floated is introduced at a slightly upper part (for example, 61 meters), and is diffused by an air compressor through a drilling casing in the middle (for example, 63 meters). air. As shown in Figure 11b. At 404 to 606 kPa (6 to 4 atm), the air is dissolved in a large amount, and then the bubble starts to precipitate as the pressure drops during the rise of the water flow. The air bubble is about 0.05 mm in size and then expands rapidly. When it rises to the bubble-atmosphere interface, each liter of air can expand to a surface of 30 m2 . The water stream carries such a highly expandable bubble enriched with a hydrophobic substance and a surface active material and rises into the sorting tank.
Using deep adhesion sorting method, the removal rate of petroleum and oil is over 80%, and the content of hydrophobic substance is reduced from 10-40 mg · l -1 to 2.5-5 mg · l -1 . hydrophobized galena recovery of less than 0.07 mm up to 100%; freed of almost all water-insoluble organic matter, BOD 5 reduce 70 ~ 75%, with the depth of the water purification adhesion sorting results humic-containing .
The deep-adhesion flotation processing capacity is not limited and is proportional to the diameter of the mine. When the mine diameter is 9 meters and the separation tank is 100 meters, the treatment capacity of deep-adhesion flotation is 1×10 5 m 3 /h. .
C Surface Adhesion Flotation The basic principle of surface adhesion flotation is exactly the same as the first two. However, in order to adapt to the sorting of raw materials with higher suspended solid content, special equipment is used. For example, the Soviet Union has ПAC-6, ПAC-9, ПAC-12, ПAC-18, and other models. Suitable for separation with high concentration (>1000 mg?l-1) of hydrophobic suspended matter and sand and mud. When the content of petroleum products and oils is higher than 5000% 10000 mg · l -1 , the surface-adhesive sorting is used, and the recovery rate of the above substances is 98 to 99%. The content of ethers can be reduced from 1 (3200 to 19500 mg · l -1 to 80.6 to 121.5 mg · l -1 ) .   Â
D Adhesive sorting application and process Adhesive sorting is mainly used to recover or remove petroleum, oil, ether, phenol, organic matter, bacteria, hydrophobic minerals, etc. from water or pulp. It is used for purification of waste water, backwater or recovery of valuable components; purification of various industrial water, decontamination of reservoirs and rivers.
The biggest feature of the adhesion sorting is that the processing capacity is not limited, and the drilling, the old mine, etc. can be utilized, and only the corresponding adhesion sorting equipment and pumping station are needed. Low energy consumption and low cost.
Three different performance sorting equipments can be combined to purify any water and adapt to various purposes. 13 and 14 are examples of different adhesive sorting device combination processing flows.
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(IV) Operational factors of special flotation The operation factors of special flotation are generally the same as those of froth flotation, mainly including the concentration of surfactant, the concentration of auxiliary agent, the pH value of the medium, the basic variables such as ionic strength, temperature and viscosity. Operating variables such as air velocity, bubble size, bubble layer height, feed rate, and reflux ratio.
Surfactant Concentration The flotation process depends on the combination of the target and the active agent. Therefore, in principle, the degree of recovery of the target increases as the concentration of the surfactant increases until the CMC. The recovery rate of zinc and copper ion flotation has been found to increase with the increase of the concentration of sodium lauryl sulfate in a certain range; however, the recovery rate of precipitation flotation of zinc and copper is not sensitive to the concentration of surfactant, as long as Can produce a stable foam. It has been found both theoretically and practically that the lowest concentration of surfactant to ensure the desired foaming characteristics is most suitable for sorting. The shortness of proper foam life is one of the keys to effective sorting. Generally, the lower the surfactant concentration, the shorter the foam life.
Auxiliary agent concentration % The auxiliary agent is mainly used to adjust the particle size in the special flotation, activate the adsorption of the collector and promote the aggregation or adsorption of the solute. The auxiliary agent is added as a precipitant, an adsorbent, a medium regulator, and an auxiliary collector. The most commonly used adjuvant is iron sulfate, aluminum sulfate.
Solution pH The pH of the solution determines the size and sign of the charge on the various inorganic particles and determines the presence of the solute and agent. Therefore, the adsorption of the pH by the pH has an important effect on the degree of separation of the particles. In fact, the initial pH of the solution during flotation determines whether the method used will be ion flotation or precipitation flotation. As shown in Fig. 15, when pH < 8, Zn 2+ is ion flotation, and pH > 8 is precipitation flotation. Microbial flotation often occurs only in a specific pH range. For example, separation of E. coli with lauric acid and alcohol is best only at pH 4-8; sorting with lauric acid or dodecylamine The best when pH <8. [next]
The increase of ionic strength ionic strength promotes the adsorption of surfactant at the liquid-vapor interface, but reduces the CMC of the surfactant, and also affects the electric double layer structure of bubbles and particles, which increases the viscosity and surface tension of the medium, making it difficult to dissolve. The solubility of the compound is increased, and the like. These effects have different pros and cons for flotation, depending on the circumstances. For example, ionic strength promotes the flotation of nickel and cobalt by sulfide precipitation; there is no significant effect on the flotation of nickel and palladium by ion flotation, and precipitation flotation of zinc and copper; but the flotation of cesium by amine collector There are adverse effects.
Temperature The effect of temperature on special flotation is also complicated. Temperature affects the speed of chemical reaction, the adsorption of various components, the viscosity of the medium, and the particle size of the precipitate. Generally, when the temperature is raised, the effect between the surfactant and the target is favorable for the flotation of chemical adsorption, which is disadvantageous to the physical adsorber.
The size of the bubble and the speed of the air supply. The size of the bubble to the rising speed of the bubble (ie, the immersion time in the slurry), the detachment caused by the residual capillary pressure in the bubble after the bubble adheres to the ore, the adhesion area, the ore The probability of collision between the particles and the bubbles has a direct impact. The rate of rise of the bubble as a function of diameter is shown in Figure 16. As can be seen from the figure, the 20 micron bubble rises only a few millimeters per second, while the diameter of a few millimeters has a velocity 10 to 30 times greater. .
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