Flocculation Studies of Coal Tailings and the Development of a Settling Index

A parameter Settling Index (SI) has been proposed mathematically. The index was used to evaluate the performance of the flocculation studies of coal fines in the tailings collected from a coal preparation plant of India. Effect of the process parameters on the settling rate were investigated using anionic polyacrylamide as the flocculant at the following parameter levels: Pulp density: 6-12% solids (w/w); slurry pH: 4-10; and flocculant dosage: 6.5-26 g/t-solid. The optimum conditions for settling were obtained at the flocculant dosage of 19.5 gpt, pH 8, and pulp density of 8% solid (w/w) and showed a settling rate about 168 mm/min. At the optimum condition of settling rate, the density of settled slurry was 40.84% solid (w/w). The Settling Index was found to be a useful tool for analyzing the settling performance. An empirical model was developed using the experimental settling rate data with an R-2 value of .929.