An iron ore sedimentary metamorphic iron deposit. The iron mineral is mainly magnetite, and the gangue is mainly quartz . The original ore is crushed, two sections of closed-circuit grinding and two sections of magnetic separation are selected, and a magnetic separation concentrate containing 61% to 62.5% of iron can be obtained. Reverse flotation is one of the effective ways to improve the grade of magnetic separation concentrate.
The magnetic separation concentrate has a particle size of 83.5 to 86.5% to 200 mesh. It can be seen from the preliminary exploratory test that the magnetic separation concentrate can obtain 69-70% high-quality concentrate with a rough selection, and the rough-selected foam product contains 32% to 37% of iron. After two sweeps, The foam product contained iron to 28 to 30 Vo, but the final tailings could not be obtained. Microscopic examination of the foam product revealed that 26% of the ore particles were present in the continuous body, and 87% of the biomass had a particle size of less than 200 mesh. The effect of re-grinding the foam product for flotation was not good. However, after re-grinding for magnetic separation, a portion of the ore containing 41% to 46.6% of iron may be obtained, and the tailings having a yield of 7% to 9% and containing 8.7% to 10.2% of iron may be discarded. Therefore, the re-election of magnetic separation concentrates uses a flotation-magnetic separation process.
The reverse flotation test on magnetic separation concentrates, hematite and limonite in several mines revealed that:
1. Reverse flotation requires fine grinding of ore. Generally, the flotation size of the ore is in the range of 85% to 95%-200. The finer the particle size, the higher the grade of concentrate. For quartz particles of +0.06 mm, it is often impossible to float because of insufficient cation activation or insufficient amount of collector , and residual in the tank affects the quality of the concentrate. If the mineral monomer dissociation is not good, there may be a phenomenon that the concentrate grade is low and the tailings grade is high, and the tailings (foam product) is difficult to reduce the iron content after several sweeps.
2. Commonly used anion collectors are fatty acids and their soaps. Tests have shown that unsaturated fatty acids and naphthenic acids capture quartz better than saturated fatty acids. Therefore, Tal oil, crude sulfate soap and alkali residue are often used as collectors in tests or production.
3. The activator of quartz is calcium oxide or calcium chloride, and the suitable pH of calcium ion activated quartz is=11.5. The pH value of the pulp is too low (%26lt; 11), the inhibition of iron minerals and the activation of quartz are not good, and the grade of concentrate is low and the grade of tailings is high. The pulp pH is too high (%26gt; 12), quartz and iron minerals are suppressed together, and the obtained iron concentrate grade is low.
4, anti-floating mineral slurry pH adjusting agent mainly is sodium hydroxide. Sometimes a mixture of calcium oxide (i.e., an activator and a pH adjuster for the slurry) and sodium carbonate may be used. The suitable ratio is 14:1. However, calcium oxide or sodium carbonate cannot be used alone as a pH adjuster. When calcium oxide is used alone, calcium ions react with the collector to form a precipitate, and under the condition that the amount of the collector is doubled, no mineralized foam can be formed. When sodium carbonate is used alone, the iron mineral cannot be completely inhibited, and the sorting effect is poor.
5. The main inhibitor of iron minerals is starch. At present, sulfite pulp waste liquid and chlorinated lignin have been used as substitutes in industrial tests, but the amount of general chemicals is relatively large.
6. The dosing sequence of the reverse flotation is sequentially added according to the medium adjusting agent-inhibitor-activator-collector, and the activator may be added to the ball mill together with the medium adjusting agent. However, the collector cannot be added to the flotation slurry prior to the inhibitor and activator, otherwise the inhibition of the iron mineral and the activation of the quartz will be invalidated.
7. The temperature of the flotation slurry is between 15 and 30 °C, and the impact on the flotation index is relatively small. Generally, increasing the temperature of the slurry can improve the quality of the concentrate and the recovery rate will decrease accordingly.
The advantage of reverse flotation of anionic collector is that under most conditions, pre-desilting is not required before flotation; the change of iron mineral composition in ore has little effect on flotation index; the reverse flotation of ore containing iron silicate The grade of concentrate obtained is higher than that of concentrate obtained by positive flotation; the hardness of float water and the temperature of slurry have little effect on flotation index. The main disadvantage is that the reverse flotation of the anion collector needs to be carried out in the strong alkaline pulp, the consumption of alkali is large, the flotation tailings water needs to be treated; the anti-flotation agent system is more complicated; in hematite or limonite In the case of reverse flotation, the total amount of medicament is generally 2 to 3 times more than that of positive flotation.
The application range of reverse flotation of the reverse flotation cation collector for flotation of quartz and silicate gangue by cationic collector is the same as that of anionic collector reverse flotation.
The reverse flotation of hematite cation collector is a hematite quartzite . The main useful minerals are hematite and a small amount of limonite and magnetite. The gangue is mainly quartz. The particle size of iron minerals and quartz is very fine. Generally, the monomer crystal grains are 0.04 to 0.2 mm, and the 0.02 to 0.1 mm grain size accounts for 80%. The flotation test of hematite with a cationic collector revealed:
1. The fatty amine is hardly soluble in water. It should be formulated into an ammonium acetate or amine hydrochloride salt before use, and then formulated into an aqueous solution of an amine salt.
2. The degree of dissociation of the amine salt in the solution and the adsorption amount of the amine ion on the quartz surface increase with the increase of the pH value of the slurry (7-10). Therefore, the flotation of the amine collector is generally carried out in a weakly basic medium in which sodium carbonate is used as a regulator. Calcium oxide is also used as a medium regulator.
3. The amine cation easily reacts with various anions to form a precipitate, which weakens or loses the effect of the collector. Therefore, when using a cationic collector to float quartz, a nonionic high-molecular compound is commonly used as an inhibitor of iron minerals, such as caustic starch, hydroxyethyl cellulose, and the like.
4. The adsorption of amine cations on the surface of quartz is weak, and it is easy to desorb during the dilution process and mixing of the slurry. In order to ensure the floating of quartz, the collector needs to be added separately in each operation of flotation.
5. The effect of flotation slurry temperature and water quality on flotation indicators is relatively small.
The advantage of reverse flotation of cation collector flotation quartz is that the amount of the agent is small, the sorting effect is good, and the flotation can be carried out in seawater or hard water at normal temperature. The main disadvantage is that the collector is expensive and requires starch as an inhibitor.
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