Temperature variation characteristics in flocculation settlement of tailings and its mechanism
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Temperature variation characteristics in flocculation settlement of tailings and its mechanism Dao-lin Wang 1), Qin-li Zhang 1), Qiu-song Chen 1,3), Chong-chong Qi 1), Yan Feng 1), and Chong-chun Xiao 2) 1) School of Resources and Safety Engineering, Central South University, Changsha 410083, China 2) Feny Co., Ltd., Changsha 410083, China 3) Sinosteel Maanshan Institute of Mining Research Company Limited, Maanshan 243000, China (Received: 5 December 2019; revised: 13 January 2020; accepted: 16 February 2020)
Abstract: Rapid flocculation and settlement (FS) of mine tailings is significant for the improvement and development of the filling process, whereas the settlement velocity (SV) of tailings in FS has been recognized as a key parameter to evaluate the settlement effect. However, the influence of temperature on the SV and its mechanism have not been studied. FS experiments on tailings with various ambient temperatures were carried out. The SVs of tailings with a solid waste content of 10wt% and an anionic polyacrylamide content of 20 g·t−1 were measured at different temperatures. The SV presented an “N”-shaped variation curve as the temperature changed from 5 to 40°C. The mechanism of these results can be explained from the perspective of the electric double-layer repulsive force, molecular dynamics, and the polymer flocculation principle, as revealed from the scanning electron microscopy of floc particles. The findings will be beneficial in the design of tailings dewatering processes and save costs in the production of cemented paste backfill. Keywords: cemented paste backfill; tailing dewatering; flocculation settlement; temperature
1. Introduction The cemented paste backfill (CPB) has been widely used as a hardened composite material in most modern mines to decrease the environmental impact and future capital expenditures related to the tailing facility while guaranteeing the safety of mineworkers [1–2]. CPB is a paste mixture of fine process tailings, hydraulic binder, and water [3]. The CPB design encompasses flocculation and settlement (FS), CPB mix design, and CPB pipe transport processes. Meanwhile, FS play a significant role in dewatering mixes of fine process tailings with significant water content [4–8]. With the rapid development of ore-dressing technology in metal ore mining, the tailings directly produced by processing plants have become more fine-grained. The proportion of particles below 37 µm often reaches more than 50wt%, which seriously affects the sand settlement velocity (SV) and the solid content of overflow water in the tailings dewatering equipment [9]. The low SV in tailings FS leads to low efficiency and undesirable properties of CPB. To achieve rapid dewatering of mortar tailing, scholars have discussed various factors affecting FS, such as mortar concentration, flocculant consumption, and flocculant types.
For mines located in middle and high latitudes, the air temperature can change evidently in different sea
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