The coal industry remains an important energy sector component in many countries. Coal preparation produces large volumes of fine sludge that require efficient disposal and treatment before being discharged to external sludge ponds or reused. Low settling velocity and complex sludge structure make it difficult to settle them using traditional methods, leading to significant energy costs, loss of useful product (coal) and negative environmental impact. This article investigates the features of the settling processes of model suspensions of coal sludge with a concentration of 5 to 100 g/l. To create the model suspensions, we used the real sludge from a coal preparation plant after sieving on vibrating screens with a particle size of the solid phase of less than 20 µm, from 0 to 40 µm, and particles of 40–80 µm. The regularities of changes in the rate of sedimentation of the solid phase of suspensions without and with the addition of flocculants depending on the concentration of the solid phase and the content of fine fractions (less than 20 µm, less than 40 µm), as well as a polydisperse mixture of fine fractions (less than 40 µm) and granular particles of 40–80 µm in a ratio of 4:1 were established. The results obtained will help optimise the operation of sedimentation and dewatering facilities of the water-sludge circuit of concentrators, reduce the environmental risks of discharging fine fractions, increase resource efficiency and facilitate the transition to more sustainable production.