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Effect of swelling clay dispersion type on fine coal flotation

Zhang Mingqing, Yu Wei, Cao Yijun, Xu Haiyu

Physicochemical Problems of Mineral Processing

2019

Vol. 55, iss. 2

380--388

The influence of bentonite dispersion on fine coal flotation was examined to better understand the role of swelling clay in the process of flotation. It was found that the coal flotation recovery was lower with uncontrolled dispersion of bentonite than with controlled dispersion. The detrimental effect was attributed to the increase in slime coating. In the uncontrolled dispersion, the dispersed bentonite platelets formed an extensive card-house structure. The three-dimensional networks increased the slurry viscosity, and caused significant coating of the coal particles, thereby inhibiting particle mobility and bubble-particle attachment. In the controlled dispersion, the bentonite mineral appeared as separate particles with low aspect ratios. The coal particles were partially coated, and the slurry viscosity was lower, resulting in higher flotation recovery. The findings in this study suggested that a practical solution to mitigate the negative impact of swelling clay on flotation would be to maintain high electrolyte levels in the wash water to inhibit clay swelling and dispersion.

Influence of controlled dispersion on rheology of swelling clay suspensions in the presence of coal flotation reagents

Zhang M., Cao Y., Chen Y., Yu W.

Physicochemical Problems of Mineral Processing

2017

Vol. 53, iss. 2

1148--1160

Swelling clay minerals, which are innately capable of dispersing into thin flakes in water, can significantly depress coal flotation. Some researchers partially attribute depression to pulp viscosity increments. This study sought to understand the role of swelling clay minerals in fine coal flotation, by investigating the rheological behavior of bentonite suspensions under controlled and uncontrolled dispersion conditions. The effect of collector, frother, and solution pH on rheological properties of the pulp was studied. Findings showed that at a natural pH, Newtonian flow properties were displayed when bentonite was directly added into a swelling suppressed solution containing calcium ions. The same process was repeated under uncontrolled conditions, and the suspensions transferred from Newtonian to non-Newtonian flows with pseudo-plastic characteristics, depending on the solid density. Further, pH value, methyl isobutyl carbinol (MIBC) and kerosene had the potential to alter the rheological behavior of controlled and uncontrolled systems, especially pH value in the uncontrolled system.