In the flotation process, the use of a collector can increase the hydrophobicity of the surface of the coal particles. At this time, if there is a good-quality bubble adhering to the coal particles in the coal slurry, the sorting can be effectively achieved. We know that bubbles in pure water are extremely unstable. When they come into contact with each other, they immediately merge and form a large bubble. When they rise to the surface of the water, they are immediately destroyed. Bubbles of this nature are unable to achieve froth flotation. There are three reasons for the bursting of bubbles: First, when the bubbles collide with each other, the water layer between the bubbles is thinned by the bubbles themselves until they disappear, so that the bubbles merge with each other. Second, at the moment when the bubble rises to the liquid surface, the gas-liquid interface at the upper part of the bubble communicates with the inner layer of the fluid. Under the pressure of the interface between the two phases and the gravity of the liquid itself, the water is squeezed downward and the water layer changes. Thin, until it disappears, so the gas escapes from the water. Third, when the water layer is very thin, the evaporation rate of water plays a significant role, causing the bubble to rupture. First, the role of foaming agent The foaming agent itself does not generate bubbles. After adding a foaming agent to the aerated coal slurry, it can disperse the airflow into a large number of small bubbles of suitable diameter and stability, and the bubbles adhere to the hydrophobic coal particles to achieve mineralization and rise to the liquid surface. A foam layer is formed. Why does the foaming agent have such a effect? ​​Because the foaming agent is a heteropolar molecule whose polar group is hydrophilic and strongly attracts water molecules, so it faces the water layer, and the non-polar group is in the air or bubbles. Inside. Thus, the foaming agent achieves directional adsorption and alignment of the monolayer at the gas-liquid interface (see Fig. 2). The main role of the foaming agent is as follows: 1, control bubble size Depending on the chemical composition of the blowing agent, they are surface active substances. The term "surface active material" refers to a substance that reduces the surface tension of the gas-liquid interface. After adding a foaming agent to the coal slurry, the surface tension of the gas-liquid interface is lowered. Therefore, under the same amount of aeration, more gas-liquid interfaces, that is, a large number of small diameter bubbles can be produced to meet the needs of froth flotation. Tests have shown that when no foaming agent is added to the coal slurry, the average diameter of the bubbles is about 3-5 mm. After the foaming agent is added, the diameter of the bubbles can be reduced to 0.5-1 mm. Figure 2 Adsorption and alignment of foamer molecules at the gas-liquid interface 2, maintain bubble stability The foaming agent forms a hydration layer on the surface of the bubble, and its polar group attracts water molecules, slowing down the flow of water downward from the upper portion of the bubble, and the rupture time is delayed when the bubble rises to the liquid surface. The foaming agent molecules aligned on the surface of the bubble can also reduce the evaporation rate of water and prolong the life of the bubble. In this way, the stability of the bubble is maintained. 3. Slow down the bubble merger The foaming agent molecules adsorbed on the bubbles have a polar group facing the water and attracting water molecules to form a hydration layer. When the two bubbles are close to each other, the hydration layer acts as a hindrance (see Fig. 3). Moreover, the mutual exclusion of the polar-based isoelectrics of the blowing agent also slows the merger of the bubbles. Figure 3 Schematic diagram of foaming agent to slow down the bubble 4, increase the elasticity of bubbles In the flotation machine, the bubble is subjected to various external forces and is always deformed. This requires the bubble to have a certain elasticity and can be quickly restored to its original state. That is, after the foaming agent is adsorbed at the gas-liquid interface, the ability to resist deformation is enhanced. If the bubble deformation caused by the external force is not large, the bubble does not rupture, which is equivalent to increasing the elasticity of the bubble (ie, the mechanical strength of the bubble). 5. Extend the residence time of bubbles in coal slurry There are two reasons why a foaming agent can reduce the speed of bubble rise and fall: (1) Under the action of the foaming agent, the bubbles are spherical and are not easily deformed, and the movement resistance of the balls in the water is large. (2) The air charged into the flotation machine is dispersed into many small-diameter bubbles due to the action of the foaming agent. Small bubbles rise and fall at a much slower rate than large bubbles. This prolongs the residence time of the bubbles in the coal slurry, so that the probability of contact between the coal particles and the bubbles increases, which promotes mineralization and speeds up the sorting speed. Second, the type and performance of commonly used foaming agents Foaming agents can be divided into three categories according to their sources: natural, industrial by-products and synthetic products. 1. Natural foaming agent This type of foaming agent is a product directly distilled and processed from forest trees. Due to the limited resources of forest products, natural foaming agents are less used in coal preparation plants. 2. Industrial by-product foaming agent Such foaming agents are commonly used in coal preparation plants in China. (1) GF flotation agent It is made of butanol and octanol as raw materials and then processed by special processing. It has a reddish brown oily liquid and it has certain catching performance. Because GF flotation agent has strong foaming performance, small dosage and good selectivity, it is widely used as a foaming agent in coal preparation plants in China. Make full use of various industrial by-products and carry out effective processing as a foaming agent. This is an important way to develop and develop flotation agents, with high economic and social benefits. (2) fusel alcohol The source is wider, and it is also a foaming agent that is used more in coal preparation plants. A by-product of the production of alcohol by fermentation, the main component of which is a mixture of propanol, butanol and pentanol. The density of such a sterol is about 0.8 g/cm3, and the yellow transparent liquid produces a fragile foam with good selectivity. In addition, chemical plant by-products such as carbon monoxide and hydrogen for methanol synthesis also have such a by-product. 3, synthetic foaming agent This type of foaming agent is a chemical product specially produced according to the characteristics of the floated minerals. (1) Ether alcohol foaming agent Such foaming agents are novel foaming agents synthesized from petrochemical products, such as methyl ether alcohol, ethyl ether alcohol, butyl ether alcohol and the like. The ethyl ether alcohol produced in China is formed by the polymerization of ethoxypropane and ethanol under caustic soda, also known as ether alcohol oil. Such foaming agents can be artificially synthesized in strict accordance with the number of oxypropanes and the carbon chain length of the alcohol, and the foaming properties can also be pre-designed. The foaming ability increases as the number of oxypropylene groups and the number of carbon atoms in the hydrocarbon chain of the alcohol increases, and at the same time, the trapping performance increases and the selectivity decreases. The foaming agent has high water solubility, compact foam structure, no stickiness, good selectivity, easy defoaming, and low dosage, and can generate a large number of small bubbles of less than 0.2 mm which are favorable for flotation, but the price is expensive. (2) Ether foaming agent This type of foaming agent is a new type of foaming agent. The domestic oil is of this type and its composition is triethoxybutane. This type of foaming agent is also called butyl ether oil. The main raw material is a by-product of the process of synthesizing polyvinyl alcohol, and the source is wide. Industrial No. 4 oil contains a small amount of resin impurities, which is orange-yellow and has a fruity aroma. The No. 4 oil has a low price, and the foaming ability is stronger than that of the No. 2 oil. The amount used is only half of the No. 2 oil, and the generated foam is brittle. This type of foaming agent decomposes and oxidizes quickly in tailings water, losing harmful effects. Synthetic foaming agents have many advantages and are an important way to develop and develop flotation agents. Ultrasonic Aroma Humidifier,Aroma Diffuser Humidifier,Led Aroma Diffuser,Aroma Diffuser And Humidifier Guangzhou Chiyang Scent Technology Co., Ltd. , https://www.gzdiffuserscent.com