The flotation of LCC, MCC and HCC was conducted first in deionised water. Combustible recovery and ash recovery as a function
of flotation time are shown in Fig. 2. The flotation of HCC was verypoor with only 8% mass recovery at the end of flotation. The corresponding combustible recovery and ash recovery were 22% and 5%,
respectively. This is consistent with the observation in the plant
that the flotation of this high-clay-content coal is not effective with
existing flotation conditions. It seems that the high clay mineral
content caused high pulp viscosity inhibiting the mobility of bubbles and particles in the flotation cell and therefore limiting both
true flotation and gangue mineral entrainment. The flotation of
LCC was much better with 61% mass recovery at the end of flotation. The combustible recovery and ash recovery were 70% and
13%, respectively, in line with flotation results in the plant. The flotation of MCC was further increased with 72% combustible recovery and 14.5% ash recovery at the end of flotation.