In the coal mud flotation process, the factors affecting their buoyancy is extremely complex, both containing floating characteristic slime itself, and also that affect the flotation process a variety of process conditions. In order to obtain better technical indicators, in addition to the use of collectors and foaming agents, the flotation can also be combined with suitable adjusting agents when necessary. It is an auxiliary flotation that controls the interaction between minerals and collectors. Agents, the regulators that may be used in coal preparation are mainly medium pH adjusters and inhibitors.
First, the medium pH adjuster
1. The role of medium pH adjuster
The pH value has a great influence on the floatability of coal and mineral impurities. All kinds of flotation agents can reach the highest efficiency and the minimum amount only within a certain pH range. In addition, the pH adjuster plays an important role in eliminating the harmful effects of ions in the water, adjusting the dispersion and flocculation of the fine mud.
(1) Adjusting the pH of coal slurry
The interaction between the surface of the coal particles and the non-polar oil collector is physical adsorption. The surface electrical properties of the coal particles determine whether the non-polar oil can adsorb to it, and the pH value of the coal slurry (ie pH) directly affects the coal. The surface electrical properties, that is, the pH determines whether the oil collector can be effectively adsorbed on the coal particles. All kinds of mineral flotation have the best pH range. The slime can only have the best floatability in neutral or weakly alkaline coal slurry, so when the coal slurry is acidic (very few in China) Phenomenon), you should consider adding a medium pH adjuster to adjust the pH of the coal slurry.
(2) Elimination of harmful components
When slime flotation pyrite sulfur removal, can theoretically employ sulfur positive float coal flotation suppression, suppression sulfur coal may also be anti-floating flotation, it is the key inhibitor. Because the floatability of pyrite is good, the collector for collecting coal can also collect pyrite. When using conventional floating coal to suppress sulfur and positive flotation, not only the amount of inhibitor is high, but also the cost is high. And the effect is not too significant. In order to remove more pyrite, two stages of reverse flotation are generally used for desulfurization: the first stage is conventional flotation, the clean coal is floated, but the sulfur content is higher; the second stage is the reverse flotation of clean coal. Inhibition of clean coal, floating pyrite. The collector used in the reverse flotation is xanthate. When the pH is less than 6, the xanthate is easy to collect pyrite. The regulator is sulfuric acid, and the pH of the coal slurry is adjusted to less than 6.
(3) Adjusting the dispersion and condensation of fine mud
There are a lot of clay- like fine muds in the coal flotation. They form a cover on the surface of the coal particles, which reduces the yield of flotation clean coal and increases the ash. By changing the pH value of the coal slurry to control the coverage of the fine mud on the surface of the coal particles, most of the pH adjusting agents used in the actual application are dispersing agents or coagulants of fine mud.
2. The nature and type of medium pH modifier
(1) Alkaline regulator
Commonly used are lime and sodium carbonate.
(2) Acidity regulator
Commonly used is sulfuric acid.
Second, the inhibitor
There are two main types of minerals affecting the floating coal selection index: argillaceous minerals and sulfide minerals. The former includes kaolin , hydromica , chlorite, Montmorillonite, shale shale, etc., the latter is mainly pyrite, white iron ore. These minerals are embedded in fine or fine particles. If the monomer is not completely dissociated, it is difficult to separate. When the particle size is too fine, the dissociation is good, but the selectivity is lowered. Mud minerals are easily muddy. When the content is high, the flotation process is disturbed, which seriously affects the sorting operation. In addition, the floatability of sulfide minerals is similar to that of coal, and the carbon pollution of its composition and structure makes it The buoyancy is closer to coal, affecting the quality of clean coal. Therefore, if necessary, a good flotation agent or process should be used to inhibit the minerals in the coal.
Inhibitor action
1. In order to improve the hydrophilicity of the mineral surface in coal, weaken its adsorption capacity to the collector, and increase the difference in floatability with coal, a hydrophilic film can be formed on the surface of the mineral to inhibit its floatability. Prevents the interaction of the collector with the inhibited mineral. The stronger the hydrophilic membrane, the stronger the inhibition.
The hydrophilic film formed by the inhibitor on the mineral surface has the following forms:
(1) forming a poorly soluble hydrophilic compound film on the surface of the mineral;
(2) forming a colloidal adsorption film on the surface of the mineral;
(3) Forming an ion-adsorbing film on the surface of the mineral.
2. Types and properties of inhibitors
Common inhibitors lime, sodium hexametaphosphate, starch and dextrin, sodium sulfide, and the like xanthate.
There are many types and effects of inhibitors, and the same regulator can have different effects under different conditions, and sometimes two or more effects can be simultaneously performed. In actual flotation, the type of modifier is usually divided according to its main role.
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