Efficiency of coal washing process and Harrington desirability function

The technological efficiency of the coal washing process is traditionally assessed by the correlation between the practically achieved results of this coal washing at a coal dressing plant and the theoretically possible ones defined by the laboratory testing to define the coal washability. However, the laboratory assessment of coal washability is a labor-intensive process and cannot be used for on-line control. The article considers the possibility of introducing a performance evaluation indicator using parameters traditionally defined in operational control schemes. This indicator is based on the well-known function of qualitative process evaluation based on several parameters, i.e. the Harrington's desirability function. The proposed efficiency indicator was calculated based on the qualitative and quantitative parameters of washing thirty different coals using the conventional processing scheme. Evaluation of the proposed efficiency indicator was made by comparing it with the traditionally used efficiency indicators. The evaluation results showed that the proposed indicator is more informative, because it also allows to take into account the compliance of the ash content during washing with the specified parameter, as well as to evaluate the efficiency of the washing process more objectively than the traditionally used clean coal yield indicator. Within a given ash content of the clean coal there exists a correlation with the performance indicators recommended for assessment of the washing efficiency. Given the specific features of the desirability function, the indicator makes it possible to qualitatively assess the coal washing process and determine the optimal value..

A Study on Magnetic Separation Washability Mathematical Model of Pulverized Coal

To further understand the magnetic separation washability of pulverized coal, washability curve and mathematical model were done based on internal relations of curves. The model included non-magnetic substance accumulated curve, ash characteristic curve and magnetic susceptibility curve mathematical model. The theoretical separation indicators and the non-magnetic product yield among the adjacent sub-selections susceptibility can be found and determined from these. We also can make a quantitative assessment of the magnetic separation washability and predict the actual results. Results showed that simulation results and experiments results can tally well according to choose reasonable parameters. Evaluation criteria of magnetic separation washability of pulverized coal has yet to make a further investigation. These indicate as a powerful tool of studying magnetic separation washability of pulverized coal can not only be qualitative reasonably but also investigate quantitatively. Key words: pulverized coal; magnetic separation; washability; mathematical model