Many customers with mineral processing needs are not very familiar with middling product. Fodamon engineers explain that in the flotation process, the cleaned tailings or swept foam products are generally called middling product. Generally, the grade of middling ore is lower than that of concentrate but higher than that of raw ore, and its floatability is also lower than that of concentrate but higher than that of tailings. For the treatment of middlings, first analyze the situation of intergrowth in middlings, study the floatability of middlings and requirements for concentrate quality, and then determine the treatment method of middlings. Whether the middling treatment method is appropriate or not is very important to improve the beneficiation index. The following four common methods are used.
(1) Return the middling to the appropriate place in the front of flotation. If the useful minerals of the middling have been basically separated, return it to the appropriate place in the front of flotation. There are two methods.
① Sequential return is shown in Figure 6-27. Sequential return means that the middlings obtained from later operations return to the previous operation in turn. When the floatability of useful minerals is poor, in order to reduce the metal loss of return and re concentration and ensure the recovery rate, the number of re concentration of middlings should be reduced. It is better to use sequential return for middlings treatment.
② Centralized return is shown in Figure 6-28, that is, all middlings are combined and returned to the front of flotation for proper operation. The floatability of middlings is good, and centralized return of middlings is appropriate when the requirements for concentrate quality are high. As the middling ore has been cleaned for many times, the concentrate quality can be improved most.
(2) When there are many intergrowths of middlings returning to grinding classification cycle, it is better to return to grinding classification cycle, as shown in Fig. 6-29.
If the middling contains some mineral particles separated from the intergrowth and some monomer, they can be returned to the classification operation. In order to increase the mechanical scrubbing of the middling surface, they can also be returned to the grinding machine.
(3) If the middling is treated separately, the nature of the middling is more complex, such as complex inlaying, the floatability is greatly different from that of the raw ore, and there is more slime, if the middling is returned to the original flotation cycle, the whole flotation process will be deteriorated. In this case, middlings should be treated separately, as shown in Figure 6-30.
(4) If the above methods can not achieve good results in processing middlings by other methods, chemical methods can be considered for processing, but experimental research work should be carried out for middlings. According to the test results, comprehensive technical and economic indicators should be compared for the schemes used, and the scheme that is technically reasonable and economically cost-effective should be adopted. In addition, it can also consider whether it is possible to sell low-grade concentrates without further treatment.
In a word, in the flotation process, the middling treatment method should be carefully studied and a reasonable scheme should be selected, which is of great significance for improving the beneficiation index. In general, the middling should be returned to the operation with similar grade. If the middling concentration is too low or the drug content is too large. So as to affect the normality of the near return operation, it is necessary to return after dehydration and drug removal.