Flotation tailings - intensification of the dewatering process by the aluminium prehydrolysed coagulants

Abstract

Most mineral-separation processes involve the use of substantial quantities of water and a larger portion of it ends up in a tailings stream. Typically, sedimentation and filtration are used to dewater the coal product. Large amount of dilute suspension has to be treated. The main driving force for coal tailing treatment is the elimination of unsustainable disposal of fine coal tailings in large tailings dams. Coagulation/Flocculation is usually a necessary pre-treatment step in dewatering streams containing significant quantities of very fine particles. The effectiveness of the coagulation/flocculation step may determine the performance and, ultimately, the capacity of the dewatering system. The objective of dewatering processes is often to obtain clear water with low percentage of solids.

The article presents the results of possibility of intensification of dewatering of the flotation tailing streams from coal preparation Paskov mine (Czech Republic). The results imply that the selected aluminium pre-hydrolysed coagulants (aluminium chlorohydrate - FLOKOR1.2A, FLOKOR D15, polyaluminium chloride - PAX-18) are convenient in dewatering process of tailing slurries and are practicable for further tests and use in industry. It is possible to achieve effective dewatering in short time. Optimal doses of all coagulants do not worsen the conditions in the process water for its hypothetic re-use. Experiments were conducted in temperature interval from 5 degrees C to 20 degrees C. Standard jar tests were performed to evaluate coagulation efficiencies. Different mixing conditions were evaluated. Relation between tailings and addition of coagulant was characterized by zeta-potential. Turbidity, pH values and residual concentrations of aluminium were measured.