Use of Divalent Calcium and Magnesium Ions on Solid-Liquid Seperation of Fine Coal Tailings

Abstract

Solid-liquid separation of fine coal tailings is one of the most important problems of coal processing plants. In the concept of this paper, the solid-liquid separation of fine coal tailings collected from Manisa Soma Imbat A.S. Coal Processing Plant in Turkey was studied using divalent calcium and magnesium ions in absence and presence of SNF-923 flocculant. The results indicated that the settling rate of the tailing sample increased to 1.4 cm/min and 1.0 cm/min 10 min at 1x10(-1) M and 1x10(-2) M CaCl2 and MgCl2, respectively. The use of flocculant in the absence or presence of 1 x10(-1) M CaCl2 showed no effect on the settlement rate. However, the turbidity of the residual solution decreased to 8 NTU in the presence of 1x10(-1) M CaCl2 while it was 343 when SNF-923 used alone. The floc size analyses of the sample showed that the use of 150 g/t SNF-923 with 1 x10(-1) M CaCl2 or MgCl2 increased the floc size to 104 and 120 mu m, respectively (9% volume) while the particle size of the original sample was 104 mu m (5.7% volume). Furthermore, the particle size of the flocs increased to 363 mu m (9.1% volume) when 150 g/t SNF-923 used alone. These results clearly indicated that the use of divalent ions along with the flocculant improved considerably the settling process.