The column flotation studies were carried out using a 100 mm diameter by 2800 mm tall laboratory column, developed and designed by IMMT, Bhubaneswar. The schematic diagram of the experimental set up is shown in Fig. 1. Initially 20 kg of coal sample was conditioned with 0.5 kg/tonne of sodium silicate at 40% solids in a 200-litre capacity conditioner with mixing arrangement. Then 1000 cc/tonne of light diesel oil was added and further conditioned for 5 min. Additional water was added to reduce the solids concentration to 10% and then 150 cc/tonne of pine oil was added to the slurry. The slurry was fed by peristaltic pump at a required rate to the column. The required air rate was maintained by rotameter. The slurry flow rate of feed and tailings were monitored. The column was operated continuously for about 30 min to reach steady state, which was confirmed by constant flow of tailings and froth. The samples of both concentrate and tailings were collected simultaneously for a fixed time.