Investigating the efficiency of gravity and flotation methods in the processing of medium-grain and high-sulfur coals of Parvadeh Coal Processing Plant of Tabas

In the Tabas coal processing plant,, particles smaller than 0.5 mm are treated by column flotation and those from 0.5 to 22.5 mm are treated by a heavy media cyclone. In order to investigate the effectiveness of gravity and flotation methods for medium grain size, ash and sulfur reduction experiments were performed on three coal samples from Madanjoo, Negin and Takht-Zeitoun mines. The results showed that despite the higher ash content in smaller fractions, the efficiency of the flotation process in materials with a size range higher than 0.3 mm is lower than that in the finer-grain sizes. The comparison of the results of gravity and flotation tests showed that the processing of the fraction with the medium grain size range by gravity method leads to an increase in yield, and a decrease in the ash content and a decrease in the sulfur content for all three coal samples. The monitoring of the heavy media cyclone in the plant also showed that the separation-error and cut-point for particles smaller than 1.4 mm is more than those for larger particles, Results showed that the gravity separation had a higher efficiency in treating particles larger than 0.3 mm in the flotation, which could be attributed to the relative floatability of pyrite and their relative floatability in the presence of diesel fuel, and it is suggested to wash particles with a size range of 0.3 to 1.4 mm by another gravity separation system such as TBS, spiral or a combination of them.