Head Loss Investigations Inside 90° Pipe Bend for Conveying Of Fine Coal–Water Slurry Suspension

The present study investigates head loss for flow of coal–water slurry inside 90° pipe bend. The experiments were conducted with slurries of different solid concentrations, varying from 31.4 to 60.8% (by weight). Pulverized coal samples with particle sizes of less than 53 µm were used to prepare the slurry. During experimentation, average flow velocity was kept in the range of 2–5 m/s. Extensive rheological experimentation was performed to analyze the flow characteristics of coal–water slurry with and without the addition of additive namely sulfonic acid. Sulfonic acid was mixed with coal–water slurry in proportions of 1–4% (by weight) at higher concentrations (i.e., 60.8%). Coal–water slurry showed Newtonian behavior at low concentrations of 30%; above, it shows pseudoplastic behavior. The head loss across the pipe bend increases as the solid concentration of slurry increases and decreases as the proportion of an additive increases. Losses occurring in bend curves were given in terms of bend loss coefficient. The bend loss coefficient decreased as flow velocity increased and increased as solid concentration increased. The present study also highlights the role that solid concentration plays with regard to settling velocity of coal–water slurry. A trend of decreasing settling velocity was observed while the solid concentration (by weight) of the slurry was increased.