Magnesite beneficiation is mainly based on heavy media and hot beneficiation. With the advancement of science and technology and the increase in the requirements for the quality of concentrates, flotation and chemical beneficiation have become important methods for the purification of magnesite.
Flotation is one of the main methods for processing magnesite. For gangue minerals such as talc, quartz and other silicate minerals, flotation is usually carried out under the natural pH of pulp, and amine cation collectors are added. And foaming agent can achieve good results, improve the purity of magnesite to 95% to 97%
The beneficiation process is:
①Crushing and screening: raw ore with a particle size of less than 200mm is crushed to 10 ～ 0mm by a two-stage closed-circuit process consisting of a jaw crusher, a roll crusher and a vibrating screen, and used as a ball mill for ore feeding;
② Grinding classification: －10mm ore is ground through a section of closed-circuit grinding, and it is ground to –200 mesh, 70%, and enters flotation operation;
③Flotation: The flotation process consists of reverse flotation (one coarse and one sweep) and positive flotation (one coarse and one fine). The former selects all tailings, and the latter obtains magnesium concentrate and medium ore.
Light burning: The magnesite is calcined at a temperature of 750 to 1,100 ° C and is called "light burning", and its product is called light burning magnesium powder. Because the loss of magnesite is generally about 50%, by light burning, the MgO content in the ore can be almost doubled. In this sense, light burning is the most effective MgO enrichment method. In addition, light burning is also a preparatory operation for magnesite hot separation and some heavy separation. Light-burned magnesium has high activity and is an ideal raw material for producing high-density magnesia.
Hot separation method: The difference in thermal properties between magnesite and talc is used to cause the density difference and hardness difference between the two after calcination, and then the mineral is separated by selective crushing and simple screening or classification. The flotation process is simple and low cost.
Erhaicheng magnesite is purified by the reflection kiln light burning-hot separation method. The test ore is a Haicheng first-class ore with a grain size of 50 to 200 mm. The reflection kiln is 7.8m3, light burning temperature is 750 ~ 1100 ° C, and the residence time is 2h. The lightly burned ore is sieved into two parts -5mm and + 5mm. －5mm part is then finely selected in a 4R suspension roller mill. The purpose of -120 is high-purity light-burned magnesium powder. Merging of +120 mesh and +5 mm into commercial light-burned magnesium. High-purity light-burned magnesium powder is then compacted and re-fired to form high-purity magnesia.
In addition to the above-mentioned flotation method, light-burning method, and thermal separation method, barite magnesite beneficiation method includes gravity separation method, electric separation method, radiation beneficiation method, magnetic seed separation method, and the like. These latter methods are not widely used in China.