Due to the different geological age and mineralization coal components contained, in the case of flotation separation is also different. Specific to the selection of flotation agent, the flotation agent with significant effect on slime should be selected by means of trial and verification. In principle, consider the following aspects: (1) The flotation agent is selected according to the nature of the suspended coal slurry, and the selected flotation agent has stable performance, and can obtain the best process index and technical and economic effects, so that the flotation cost is reduced to a minimum. (2) The flotation agent is rich in source, non-toxic, tasteless and does not pollute the environment. (3) The foam is easy to defoam to facilitate transport and filtration dehydration. Second, the selection of flotation agent It depends mainly on the nature of the slime and the type and amount of mineral impurities it contains. When flotation is easy to select coal, the flotation agent's floating ability can be lower, but when the surface is poorly hydrophobic, it is necessary to use a flotation agent with high floating ability. For the high ash content of more fine clay slime, flotation agent should be chosen with good selectivity, we need to add an inhibitor or dispersant, if necessary, to effectively reduce the content of pyrite in the coal. Selection of collector 1. The collector of coal slime flotation is mainly non-polar hydrocarbon oil. The oil has different varieties, the molecular weight of hydrocarbon is different, and the flotation effect is also different. The low molecular weight oil is easy to spread on the surface of the coal particles, but the oil film is unstable and can penetrate into the pores of the coal, so that the flotation agent consumption is increased. The most widely used collectors in the industry are kerosene and light diesel oil, but because of the different processing methods of petroleum raw materials, they are also kerosene or light diesel oil, and their chemical compositions are different, thus having different collection capacities and selectivity. For example, straight-run kerosene and cracked kerosene, hydrogenated kerosene, straight-run light diesel oil and cracked light diesel oil have different flotation effects. Some oils have lower capture capacity and higher selectivity, while others have the opposite. The oil with different freezing points has different flotation effects. Coal is an extremely complex compound and any single component non-polar hydrocarbon oil will not be the best collector. In order to improve the performance of the flotation agent, the best collection performance for coal, a mixture of aromatic hydrocarbons and alkane components should be the best collector. Foaming agent selection 2. There are many kinds of foaming agents, and the chemical composition is very different, so they have different chemical properties. A foaming agent having a higher proportion of polar groups has higher hydrophilicity and lower foaming property, and a foaming agent having a higher proportion of non-polar groups has higher surface activity. The choice of blowing agent depends on the amount of high ash fines contained in the slime and the aeration of the flotation machine. For coal slime with high ash content and fine mud content, it is not advisable to use a foaming agent with high foaming rate, small bubble diameter and long service life. Instead, a foaming agent with a slightly larger bubble diameter, brittleness and less long life should be used. In order to increase the secondary enrichment, the high ash fine mud is mechanically entrained by the foam gas floc to improve the selectivity of flotation. In the flotation of high-slurry coal slurry, it is preferred to use a foaming agent with a high foaming rate, a small bubble diameter and a long life to help the particles adhere to the bubbles. For a flotation machine with a large amount of coal slurry aeration, a foaming agent with a high foaming rate should be used. When selecting a foaming agent, it should also be noted that the foaming agent used should be insensitive to changes in the pH of the coal slurry and does not interact with mineral salt ions in the solution. When the salt ion content of the coal slurry is high, the use of an ionic foaming agent should be avoided. Adjustment agent selection 3. In the flotation of coal slime, generally only two flotation agents are used, one is a collector which improves the hydrophobicity of the surface of the coal particles, and the other is a foaming agent. The regulator is not used much in the coal flotation, but with the further improvement of the coal quality requirements, the use of the regulator may be given a certain degree of attention. As the coal slurry pH adjuster, lime, sodium carbonate, hydrochloric acid or the like can be used. The adjusting agent is used in order to make the coal slurry have a suitable acidity and alkalinity, for example, pine oil, kerosene, etc. are preferably used in alkaline coal slurry. The existing conventional floating coal preparation technical conditions can not remove pyrite sulfur, and in many cases, the sulfur content in the flotation clean coal is higher than the sulfur content in the feed, that is, pyrite particles and coal. The pellets float together and are enriched in the clean coal. In order to suppress the pyrite which is naturally hydrophobic, the regulators which can be used are lime, sodium carbonate and the like. Lime, salt, aluminum chloride, etc. can be used to remove the fine mud to the fine coal pollution. Because the fine mud content in the coal slurry is high, it can adsorb on the surface of the coal particles, increase the clean coal ash, and also increase The hydrophilicity of the surface of the coal particles reduces the yield of the clean coal. The choice of flotation agent is influenced by many factors. The more common requirement for slime flotation is to clearly understand which flotation agent is used to achieve the best flotation effect. Third, the new flotation agent selection steps It has been proven that the use of a mixed collector containing multiple components is more effective than a single hydrocarbon oil. Therefore, in recent years, countries around the world have used synthetic by-products such as chemical by-products to replace petroleum product collectors such as kerosene and diesel to reduce costs and improve selectivity and clean coal yield. The selection of high-efficiency flotation agent is a major part of the work of coal preparation technology, and a positive and cautious scientific attitude should be adopted. To do this, follow these steps: (1) To fully understand and analyze the chemical composition and characteristics of the new flotation agent, to find out the theoretical basis and the basic conditions suitable for selection. (2) There must be relevant identification of the environmental and labor protection departments to prove that it will not cause environmental pollution and affect human health. (3) Technical appraisal of industrial tests successfully tested in some coal preparation plants. (4) A laboratory flotation test in comparison with a conventional flotation agent is carried out, and optimum addition conditions are preferred. (5) Conduct an industrial test for about half a month. The reasons for using the longer test are as follows: 1 The operator has a process of adapting and mastering the performance of the new flotation agent. 2 The conditions of the laboratory test are not the same as the industrial production conditions, so the addition amount and proportion of the new flotation agent need to be further adjusted. 3 The quality of flotation clean coal and tail coal, the effect of foam transport and dewatering, and the clarification of tail coal water need to be assessed with a certain time limit. The problems that may occur in the production of new flotation agents also need a certain time limit to fully display them. The new flotation agent is generally in the form of a series to meet different coal quality requirements. In practical applications, it is often formulated into a series of products according to the different coal quality and flotation conditions.
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First, the principle of selection of flotation agent