Points for discussion about issues regarding flotation efficiency

With an aim to going deeper into the discussion on points concerning evaluation of flotation performance, the following related study and analysis are made specifically on the academic viewpoints put forward in the article “Analysis of flotation efficiency evaluation method” published on bimonthly periodical Coal Preparation Technology(No.4, 2021): calculation of coal preparation plant′s screening efficiency, hydraulic classification efficiency, flotation perfect index, and dewatering efficiency using Hancock separation efficiency formula; necessary explanatory notes on the organic efficiency of concentrate and flotation perfect index, two key indicators as specified in the international standard “MT/T 180—1988 Coal Preparation Plant Flotation Performance Evaluation Method”; and analysis on the number of groups of samples divided according to ash content, and the method for making flotation experiment, as specified in the industry standard “Analysis of flotation efficiency evaluation method”. In addition to the above-going work, the flotation efficiency of Xipang plant is calculated using Hancock formula. Owing to the objective fact that the slime contains materials with an ash either greater or smaller than the boundary ash which is derived through graphical calculation, the calculation on flotation efficiency is made based on the flotation concentrate and tailings, respectively. As indicated by study results, when screening efficiency, hydraulic classification efficiency, flotation efficiency and dewatering efficiency are calculated using Hancock formula, the calculated result will remain unchanged no matter what product is taken as the basis for making the calculation; despite the fact that the phenomenon of “misplacement of material” occurring in flotation process is not considered as a factor in defining the flotation perfect index, and the latter is caused hence to have certain “limitations” for use as a criterion, yet, for flotation of the fine coal having the identical properties, the flotation efficiency should be evaluated with the focus on the differences between the examined indices, rather than the magnitudes of absolute values; the method for making flotation experiment as stipulated in the article “Analysis of flotation efficiency evaluation method” offers a new train of thoughts for the evaluation of flotation performance in the future. Nevertheless, for avoiding the presence of two adjacent groups having only minor difference in ash, or in case that the sampled coal is not good in quality, the number of groups should be reduced; when the flotation efficiency is calculated based on the concept of separation efficiency calculating method proposed by Hancock, an identical calculation result can be obtained irrespective of whether the flotation concentrate or the tailings is taken as the calculation basis. The rigor and strictness of Hancock formula is well verified by the analysis work described above. It is proposed that in flotation of the fine coal having identical properties, there should be a clear understanding of the meaning of the term flotation perfect index defined in this case; and while maintaining the accuracy of the flotation experiment, the number of groups of product samples divided according to ash content be reduced in experiment. It is held that the “flotation efficiency” as an indicator of flotation performance can reflect in a quantitative manner the correctly placed and misplaced materials of both low-ash and high-ash fine coal, and it is also suitable for use as an indicator for making crosswise comparisons of flotation performances in flotation of fine coal with varying properties.