In flotation line practice, in order to overcome the deterioration of fine mud in the flotation process and eliminate the harmful effects of fine mud, the following measures are often adopted.
① When there is not much fine mud, the dispersant is added to reduce its influence
Generally, sodium silicate and sodium hexametaphosphate can be added. The dispersant is a pure electrolyte, whose function is to increase the electric potential on the surface of fine mud. When fine slimes are close to each other, they repel each other due to the same electrical properties, so that the slime plays a role in dispersion and prevents nonselective agglomeration of fine slimes.
The method of adding dispersing agents is relatively simple and suitable for the case with less mud. However, this method still can not fundamentally solve the disadvantages of poor selectivity and a large dosage of reagent caused by fine mud, so it is often necessary to strengthen the cleaning operation in production practice.
② The slime shall be removed in advance before flotation
There are two methods of pre desliming: flotation desliming and mechanical desliming. Flotation desliming is to float out part of the slime with a small amount of foaming agent and collector, and then carry out coarse-grained flotation. Mechanical desliming is to use a classifier (such as hydrocyclone) to remove some fine mud before flotation. Generally, the particle size of desliming is 10.20 microns. The desliming particle size is mainly determined by the performance of classification equipment. After desliming, the effect of coarse particle flotation can also be improved. The main problem is that the fine mud is difficult to treat. If the content of useful minerals in the fine mud is very small, it can be discarded. However, the grade of useful minerals in the fine mud is often similar to that of raw ore. if it is discarded, the metal in the fine mud will be lost.
③ Silt separation
Process requirements for separate flotation of fine mud:
a. A longer flotation time should be used. According to the data, the flotation time of particles smaller than 10 microns is as long as 40-60 minutes;
b. High concentration pulp mixing (up to 60% – 70% pulp concentration), low concentration flotation (generally below 20%);
c. Sectional administration, increase the amount of collector and reduce the amount of foaming agent;
d. Large air volume and small bubbles weaken the rising pulp flow
In actual flotation line production, it is difficult to meet the above process requirements of fine mud flotation, so the indexes of fine mud flotation are not high. Although the above method for treating fine mud is adopted in production, it does not solve the special process of fine mud flotation. From the current research trend, there are two ways to improve the flotation speed of fine mud: one is to increase the particle size of fine mud flotation; The second is to reduce the particle size of flotation bubbles.