Study on static and dynamic flocculation settlement characteristics of fine tailings slurry and influence of flocculant on strength of fine tailings backfill

In order to study the static and dynamic flocculation settlement characteristics of fine total tailings and the influence law of flocculant on the mechanical properties of fine tailings backfill, the experimental research on the flocculation settlement and mechanical properties of fine total tailings was carried out in the laboratory. The static flocculation settlement test of fine total tailings was carried out by orthogonal test scheme, and the influence law of the full-tail mortar concentration (FTMC), flocculant unit consumption (FUC) and flocculant solution concentration (FSC) on the concentration of underflow and sedimentation rate was analyzed, and the best static flocculation settlement parameters were obtained. Secondly, the dynamic flocculation test was carried out on the basis of static flocculation settlement parameters to reveal the influence law of dynamic flocculation settlement on underflow concentration. Finally, the compressive strength of fine tailings backfill under different flocculant unit consumption were tested, and the microscopic evolution of backfill was investigated by scanning electron microscopy. The results show that: Anionic flocculant has better flocculation effect than non-ionic flocculant, so anionic flocculant can be preferred as flocculant for flocculation settlement of fine full tailings. The flocculation settlement process of fine tailings slurry can be divided into four regions: clarification region, settlement region, transition region and compression region. The influence degree of the three factors on settling velocity and underflow concentration is full-tail mortar concentration > flocculant unit consumption > flocculant solution concentration, and full-tail mortar concentration and flocculant unit consumption are significant influencing factors on settling velocity and underflow concentration. The flocculation settlement parameters of fine full tailings slurry are not only affected by single factor, but also by the interaction between factors. The optimal static flocculation sedimentation parameters are as follows: the full tailings slurry concentration is 20 %, the flocculant unit consumption is 10 g/t and the flocculant solution concentration is 0.3 %. The dynamic flocculation settlement can greatly increase the underflow concentration, and the underflow concentration increases with the residence time, but there is no significant change in the underflow concentration when the residence time exceeds 5 h. The compressive strength of fine tailings backfill decreases with the increase of flocculant unit consumption, and the microscopic test results show that the increase of flocculant unit consumption will weaken the compactness of the microstructure of the backfill, which leads to the decrease of the compressive strength of the backfill.