Graphite ore has good hydrophobicity, and is primarily enriched and purified by flotation. In order to obtain concentrate with high fixed carbon content, flotation generally requires one roughing, one scavenging and 2~10 cleaning operations. As there are many grinding and beneficiation times, a large amount of middlings will be produced in the process flow (the proportion of middlings is generally 50%~70%, or even more than 85%), so graphite middlings need to be treated to improve the recovery rate.
At present, the methods of graphite ore middling treatment include centralized middling return, sequential return, separate treatment and multiple treatment. Now let's learn about the middling treatment method of graphite ore.
Centralized return of middlings refers to centralized return of middlings in the process to an appropriate location. The centralized return of middlings also includes the centralized return of the first section, the centralized return of the second section or the centralized return of multiple sections, and the centralized return of the concentration and regrinding of middlings. The advantage of centralized return of middlings is to simplify the process, while the disadvantage is that when there are many middlings and the nature of middlings varies greatly, it will have a negative impact on flotation. If there are too many middlings, it is easy to cause large fluctuations in the flotation level, the fixed carbon content of tailings is easy to become higher, and the recovery rate of concentrate decreases.
(1) Centralized return process of graphite ore section I
The first stage centralized return of middlings is to return all middlings in the process to a certain operation. The return positions include rough separation, rough grinding, primary cleaning, etc. The specific return point depends on the nature of middlings. The centralized return of the first section of the middling mine is suitable for processing the surface graphite ore sand mainly of gneiss type, which is extremely effective for improving the fixed carbon content of the final concentrate. However, this process is not easy to control and the process fluctuates greatly. Generally, small concentrators can return in a centralized way.
(2) Sectional centralized return process of graphite ore
Sectional centralized return generally refers to the centralized return of middlings with low fixed carbon content to a certain operation, and then the combined return of middlings with high fixed carbon content to another operation. The return location of middlings can be determined according to the properties of middlings and fixed carbon content, which is conducive to improving the recovery rate and ensuring that the final concentrate has the same fixed carbon content.
Sequential return of graphite middling includes ordinary sequential return and interval sequential return of middling. Generally, the graphite ore with poor floatability and high recovery rate should be returned in sequence. The ordinary sequential return means that Zhongkuang returns to the previous operation in turn, while the alternate sequential return means that Zhongkuang does not return to the previous operation, but returns to the previous operation in the process. It is applicable to the situation where the floatability of graphite is poor, but the recovery rate should be strengthened. As there are few opportunities for middlings to be re selected, they will return in order, and the large scales will not be lost easily, so the recovery rate is high.
The sequential return of middling can greatly reduce the middling circulation, reduce the burden of roughing and scavenging operations, and is conducive to the improvement of mineral processing recovery. However, due to the orderly return of middlings, their chances of being sorted are correspondingly reduced. Due to the dilution of the front operation and the large number of middlings, it is easy to reduce the fixed carbon content of the final concentrate. However, if the intermediate ore contains less intergrowth and the pulp concentration is low, the method of sequential return is beneficial to improve the concentrate grade and recovery. In addition, when the middlings are returned in sequence, the water with people in the middlings can reduce the addition of fresh water in the flotation operation. Compared with other return methods, it reduces the burden of concentration and dehydration in the concentrator and increases the utilization rate of return water.
However, there are few opportunities for regrinding and re concentration of middlings after the middlings are returned in sequence, and the fixed carbon content is not improved much. Therefore, there are few process flows for complete sequential return at present, and they are generally used together with other middlings treatment methods.
The separate treatment of middlings is to combine the middlings for regrinding and re concentration separately. It refers to the direct tailing, separate regrinding and re concentration or direct re concentration of middlings according to the nature of different middlings. The separate treatment of middlings includes: direct tailing of extremely low-grade middlings, some middlings as low-grade concentrate products, centralized separate re concentration return process of middlings, and centralized re grinding and re concentration return process of middlings.
This method can reduce the circulating amount of middling, lighten the burden of roughing operation, reduce the tailings grade and improve the recovery rate of beneficiation. In addition, when the target mineral graphite of the middling ore is mostly associated with gangue minerals such as quartz in the form of graphite inclusion between the gangue mineral pores, or is wrapped and adsorbed by gangue minerals, separate regrinding and re concentration of the middling ore can further separate the graphite and gangue minerals, and effectively recover this part.
As the graphite beneficiation process is long, there are many middlings, and the nature of middlings varies greatly, it is reasonable to adopt multiple treatment methods to jointly treat the middlings, which is also a trend of graphite middlings treatment.
The multiple combined treatment processes of Sinopec include the combination of separate treatment and centralized return of Sinopec, the combination of separate treatment and partial sequential return of Sinopec, and the combination of centralized return and sequential return.
The specific process of the above graphite ore middling treatment shall be determined according to the specific process. It is recommended to conduct beneficiation test first, and customize the appropriate graphite ore beneficiation process and reasonable graphite ore beneficiation equipment based on the test results. In order to obtain the ideal rate of return on investment.
