The Effect of Particle Size, pH, and Flocculant Dosage on the Gel Point, Effective Solid Stress, and Thickener Performance of a Coal-Washing Plant

Abstract

A common way to separate the solid from the liquid in high volumes is using thickeners. Since, the amount of water consumption in the mineral- and coal-processing plant is high, water management needs to optimize the input variables and thickener performance. In this study, the effect of particle size, pH, and flocculant dosage on the parameters (gel point and effective solid stress) of mathematical model for the sedimentation and thickening has been investigated. The gel point and effective solid stress was measured using different batch settling and batch centrifuge tests, respectively. The results showed that in the case of nonflocculated suspension, the gel point increased with lowering of pH, however, in the case of flocculated suspension the gel point decreased with lowering of pH. The gel point also increased with increasing flocculant dosage in certain pH values for the two flocculated and nonflocculated fractions. In the case of nonflocculated suspension, the gel points for d80 = 275 µm and d80 = 125 µm were equal at a certain pH value but in the case of the flocculated suspension the gel point for d80 = 275 µm was higher than that of d80 = 125 µm at a given pH value. Likewise, the results showed that effective solid stress decreased with increasing gel point and settling rate.