Abstract
Due to continuous improvements in the beneficiation process, the size of tailings has decreased. In many mines, more than 50% of the total tailings are finer than 74 μm. Ultrafine tailings exhibit a slow settling velocity and uneven settling, which pose new challenges to the safety and stability of tailings dams. In this paper, ultrafine iron tailings from the Makeng Iron Mine in Longyan City, Fujian Province, were used as the research object. A four-factor, three-level orthogonal test method was used to study the sedimentation characteristics of ultrafine tailings with four common curing agent materials, including polyacrylamide, polyaluminum chloride, polyaluminum sulfate, and polyferric sulfate. The results show that when the pulp concentration is 30%, the polyacrylamide is cationic and the molecular weight is 10 million, the optimal content of the flocculant is 3‰, the optimum dose of the polyaluminum chloride with a content of 28 is 0.1‰, the optimum dose of polyaluminum sulfate is 1‰, and the optimum dose of polymeric ferric sulfate is 1‰. When the flocculant is mixed according to the proportion of 2‰ polyacrylamide, 0.05‰ polyaluminum chloride, 1‰ polyaluminum sulfate, and 1.0‰ polyferric sulfate, the sedimentation speed of the ultrafine tailings is fast, and the supernatant liquid is clear. The results of multivariate nonlinear regression analysis of the sedimentation curve show that the primary and secondary factors affecting sedimentation are polyacrylamide > polyaluminum sulfate > polyaluminum chloride > polyferric sulfate. When the optimal ratio is applied, the cohesion (c) of ultrafine tailings increases from 27 kPa to 68.75 kPa and the internal friction angle (φ) increases from 25.53° to 27.53°, which shows that the shear strength improves and the stability of the tailings dam increases. The economic analysis of the composite flocculant with the optimal ratio shows that the flocculant with the optimal proportion has an obvious economic advantage over polyacrylamide alone.
Highlights
China is a major producer of mined materials and possesses some of the richest mineral resources, reserves, and production in the world [1]
With the continuous development and utilization of mineral resources, the grade of mined ores is declining annually. e minerals are in a complex state; the high-grade, easy-to-separate rich mineral resources are becoming gradually depleted; and the mineral concentration of deposits has gradually decreased
All of these factors lead to the need for more ore. us, the separation and enrichment of useful minerals by grinding to fine or even ultrafine particle size levels [2] has promise
Summary
China is a major producer of mined materials and possesses some of the richest mineral resources, reserves, and production in the world [1]. E minerals are in a complex state; the high-grade, easy-to-separate rich mineral resources are becoming gradually depleted; and the mineral concentration of deposits has gradually decreased All of these factors lead to the need for more ore. Wang et al [15] performed a flocculation sedimentation test on the influence of the type of flocculant, the concentration of pulp, and the addition amount of different chemicals on the sedimentation velocity and confirmed the effect of highmolecular-weight flocculant on accelerating particle sedimentation. Wang et al [16] used the ultrafine tailings of a mine to investigate the three experimental factors of slurry concentration, flocculant unit consumption, and flocculant concentration and studied the influence of different factors on sedimentation velocity and concentration. This paper selected curing agent materials comprising polyacrylamide, polyaluminum chloride, polyferric sulfate, and polyaluminum sulfate, which are effective flocculants for the sedimentation of ultrafine tailings slurries. e optimum types and optimal dose of each of these materials were investigated separately. en, the synergistic effect of the above four flocculants was investigated using a four-factor and three-level orthogonal experiment, and most of the four flocculants behaved better in combination. e tailings floc using the optimal ratio of flocculant was subjected to a direct shear test and permeation test to analyze the changes in mechanical properties
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