The ore dressing methods of fluorite mines in China include hand selection, gravity (jig) ore dressing and flotation.
(1) Hand selection, re-election
The hand selection is mainly used for fluorite ore with very clear boundary between fluorite and gangue, easy removal of waste rock, and easy identification of different grades of ore. It is the most convenient and economical method of mineral processing.
Gravity (Jig) beneficiation mainly selects particle ore with higher ore grade and particle size of 6~20mm. Gravity beneficiation has the advantages of simple structure, convenient operation and remarkable efficiency.
(2) Fluorite flotation
The main problem with fluorite flotation is the separation of gangue minerals such as quartz , calcite and barite .
1) Fluorite-containing fluorite ore
Generally , the sulphide ore is first floated with a xanthate collector , and if necessary, activated by sodium sulfide, and then fatty acid is added to obtain fluorite. Sometimes, in the fluorite flotation operation, a small amount of cyanide is added to suppress residual sulfide ore. To ensure the quality of fluorite concentrate.
2) Fluorite ore containing barite calcite
Usually first with oleic acid as collector, float fluorite, aluminum salt plus a small amount of fluorite can be activated. Adding dextrin inhibits barite and calcite while activating fluorite. Water glass also has a similar effect when used in small amounts.
The use of baking gum to inhibit calcite and barite proves that for more complex fluorite containing more calcite, limestone, dolomite, etc., it is good to suppress the gangue mineral with baking glue and lignosulfonate. .
3) Sorting of fluorite and quartz
Use fatty acid as a collector, use water glass as gangue inhibitor, flotation fluorite, and adjust the pH of the slurry to 8~9 with sodium carbonate.
The amount of water glass should be controlled well. When it is small, it will activate fluorite, and excessive fluorite will be inhibited. For less water glass, but also to enhance the inhibition of gangue quartz, often added multivalent heavy metal cations (Al3 +, Fe2 +) and alum, and aluminum sulfate;
The addition of Cr3+, Zn2+ ions also have an effect, these ions not only inhibit quartz, but also the calcite.
In addition, in order to obtain high-quality low-silicon fluorite concentrate, it is necessary to control the fineness of grinding and the concentration of flotation pulp (the concentration of pulp in selected operations should be low), temperature, composition and dosage.
4) Sorting of fluorite and barite
It is common to mix fluorite and barite, and then separate them. The eucalyptus is used as a collector and the water glass is used as an inhibitor. For the separation of mixed concentrates, the following two methods can be used:
1) inhibition of barite with dextrin iron salts or tannin, and oleic acid float fluorite.
2) Flotation of barite with hydrocarbyl sulfate, leaving the fluorite concentrate in the tank.
The results show that the separation of fluorite and barite, first floating fluorite or first floating barite can get better results.
2. Mineral processing technology
1) Process research on particle size control:
Grinding particle size selection
Dry and wet grinding
Stage grinding process
2) pH value of pulp:
“All-alkali processâ€: Fully alkaline (pH=9.0) flotation
“Alkaline-acid processâ€: Alkaline (pH=9.0) rough selection, weakly acidic (pH=6.0)
“Full acid processâ€: full weak acid (pH=6.0) flotation
3) Middle mine treatment
Medium mine return and centralized return
Medium mine treatment
4) Concentrate re-grinding and throwing tailings
Crude concentrate regrind
Featured tail
1) Process research on grain size control
1 Fluorite ore with quartz as the main gangue has a common law, that is, rough roughing requires proper coarse grinding;
2 Some people in Japan compared the effects of dry grinding and wet grinding on fluorite flotation. It was found that dry grinding has special effects, and the concentrate grade and recovery rate are higher than wet grinding because of the dry grinding of fluorite. The crystal is converted from a semiconductor N-type to a P-type, and is more easily captured by oleic acid.
3 Using the stage grinding and floating process, good indicators can be obtained, and the stage grinding and early disposal of tailings can reduce the pulverization of fluorite.
2) Test results of pulp pH value n open circuit test n program concentrate index (%)
1 alkali-acid process
Yield 49.87; grade 98.27; recovery 76.66
2 total alkali process
Yield 26.08; grade 98.69; recovery 40.26
3 full acid process
Yield 52.10; grade 97.08; recovery 79.11
Closed-circuit test results of two schemes
Program concentrate index (%):
1 alkali-acid process
Yield 57.20; grade 98.59;
Recovery rate 88.21; beneficiation efficiency 31.01
2 total alkali process
Yield 58.10; grade 97.37;
Recovery rate 88.49; beneficiation efficiency 30.39
3) Middle mine treatment
1 Chinese mine returns in sequence
The monomer dissociation is good, the ore is easy to be selected, and the process and process arrangement is simple.
2 Central mine returns
Difficult to choose ore, high grade of concentrate; high process layout, need to concentrate and dehydrate the mine.
3 medium mine treatment
Medium ore re-grinding or separate treatment
The middle ore has many births and returns to affect the concentrate grade.
Return to the coarse concentrate and re-grind or set the mine to re-grind
4) coarse concentrate regrind and selected tails
1 coarse concentrate regrind
For unevenly embedded ore and lean ore, the regrind process of coarse concentrate has a significant impact on improving concentrate grade and recovery rate.
Rough grinding → rough selection → coarse concentrate regrind → selection
Advantages: less equipment investment, two-stage grinding machine
Disadvantages: The dewatering of the mine is difficult (foam), the concentration is low, the grinding efficiency is low, and the management is difficult.
2 Selected tailings
The first selection of tailings is discarded as the final tailings, which is conducive to improving the concentrate grade and improving flotation conditions.
3. Factors affecting fluorite flotation
1) pH of the pulp
The pH value of the slurry has a great influence on the flotation of fluorite. When using oleic acid as the collector, the pH value is 8~11, the floatability is good, and the recovery rate can reach 80~90%; When the pH is 6, the floatability is also good.
For different types of fluorite ore, the floatability of gangue minerals is also affected by the pH value, which affects the sorting effect. For example, when using oleic acid as a collector, the pH is 8~9.5. Both the stone and the calcite have good floatability.
2) Temperature of the slurry
Fluorite is usually floated with a carboxylic acid collector. Due to the high freezing point of the carboxylic acid, the slurry temperature has a significant effect on the flotation process. In a certain temperature range, the temperature increases, the solubility of the carboxylic acid in the pulp increases, and it is easy to disperse, thereby facilitating the full utilization of the collecting performance. The use of oleic acid in production is generally heated to 30 °C.
3) Flotation granularity
Coarse-grade fluorite, high flotation selectivity, high grade and low recovery rate;
Medium-grade fluorite, high grade and recovery rate in flotation;
Fine-grained fluorite, flotation concentrate grade and recovery rate are low.
4) Water quality
When fluorite is collected by oleic acid, due to the presence of Ca2+ and Mg2+ ions in the water, studies have shown that the presence of Mg2+ can seriously interfere with the flotation of fluorite and significantly reduce the flotation effect, so the flotation fluorite needs to be softened beforehand.
Add sodium carbonate to soften the water.
5) Flotation agent
1 collector
The collector may be used as a collector of fluorite, such as hydrocarbyl sulfate, alkylsulfonated succinamine, sodium oleate sulfonate, and other sulfonates and amines;
2 inhibitor
Water glass is the most commonly used inhibitor for fluorite flotation. In order to improve the selective inhibition ability of water glass, water glass and soluble salts are combined into a combination inhibitor, or sulfuric acid is formulated into an acidic water glass in a certain ratio.
Soviet Union patent describes a fluorite calcite separated organic inhibitor, than sodium Silicate, aluminum sulfate and sodium hexametaphosphate phosphate good effect.
H1010 of Guangdong Nonferrous Metal Research Institute is a mixed regulator composed of acid, alkali and synergist, which can effectively separate fluorite from calcite and quartz.
NL, NS and NO3 inhibitors composed of water glass, aluminum sulfate, sodium sulfate and carboxymethyl cellulose are used for fluorite flotation in Shizhuyuan, and the effect is good.
4. Other technical measures
(1) Branch flotation should be used in the fluorite flotation process
In order to adapt to the high-quality concentrate production and strengthen the effect of low-grade raw ore sorting, the branch flotation process has been adopted abroad. The research on fluorite ore has proved that the index of the branch flotation process (concentrate contains CaF295.8%, the recovery rate is 97.6 %) superior to direct flotation (concentrate containing CaF289%, recovery rate 97.8%).
(2) Fatty acid collectors are still the main agents for flotation fluorite. Therefore, how to improve its selectivity and ability to capture is still a way to strengthen fluorite flotation. The following measures are often used:
1) Strengthen mechanical agitation;
2) increase the temperature of the pulp;
3) oleic acid oil and coal mix (1: 1);
4) Saponify oleic acid with an excess of soda (1:0.28), or emulsifie oleic acid with a small amount of sodium carbonate (1:0.05);
5) Alkyl sulfate is used as a Dispersing agent for the fat soap liquid.
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