Iron ore reserves are limited and the grade is low. The content of fly ash is more than 5%. Selecting iron rich micro beads from fly ash can also supplement some sources of iron ore. The quality of fly ash, such as fire resistance, can be improved by using iron tailings after iron separation, which can create conditions for other utilization ways. It can be seen that the quality of fly ash such as fire resistance has been improved, which can create conditions for other utilization ways. It can be seen that separating iron rich microsphere from fly ash is one of the economic utilization ways. In addition to a small amount of iron rich glass bodies dissolved in dense glass beads (the amount of iron content determines the different colors of iron rich glass beads, such as yellow, brown, red, black, etc.), most of the iron rich glass bodies in fly ash are composed of microscopic magnetite and hematite. The particle size of iron rich microsphere is less than 45 μ m, and the relative density is about 4.2. Its characteristics are low activity, magnetism, conductor, high strength and good fluidity, which can reach 15% of the total ash.
The separation of iron rich micro beads from fly ash by magnetic separation process is mainly based on mineral processing technology. The method is simple. However, due to the different ash discharge modes of power plants, magnetic separation process can be divided into dry magnetic separation and wet magnetic separation, among which the wet magnetic separation process is more mature.
1. Dry magnetic separation
Dry magnetic separation is mainly used for dry discharge of fly ash. Iron concentrate is selected on one side and tailings are discharged on the other side by magnetic separator. Because the material layer of dry magnetic separation is too thick, it is not easy to ｓｅｌｅｃｔ the magnet in the upper ash, and the recovery rate is low. At the same time, due to the adhesion of dust, the concentrate contains a lot of silicon aluminum particles, so that the grade of concentrate is not high. In addition, the equipment is difficult to seal and there is dust pollution. These are the aspects that need to be improved in dry magnetic separation.
2. Wet magnetic separation
The magnetic separator is installed under the wet dust collector, and the slurry flows into the magnetic separator naturally by using the ｄｒｏｐ. This is the primary magnetic separation. After the separation, the grade of iron rich microsphere is usually only 46% - 50%. Therefore, a cleaning process should be added, i.e. secondary magnetic separation, with a grade of 56% and SiO2 content below 16%.
Before roughing, in order to avoid sticking phenomenon caused by remanence, demagnetization ｏｒ flushing process should be used to clean the micro magnetic gangue and other impurities between iron particles. Only when the slurry after demagnetization ｏｒ flushing is sent to the cleaning process with mud pump, can the grade of iron rich microsphere be provided.