RESUMEN
The aim of this study was to obtain the relationship between ion interactions and the crystallization patterns of salt species in the lithium-rubidium-magnesium sulfate system at 298.2 K. The phase equilibria of the aqueous quaternary system Li+, Rb+, Mg2+//SO42--H2O were studied by the isothermal dissolution method at T = 298.2 K and p = 94.77 kPa. The density, refractive index, and composition of equilibrium solution were determined, on the basis of which solid-liquid phase diagrams and density/refractive index vs composition diagrams were drawn. The phase diagram consists of four quaternary invariant points and six crystallization regions, corresponding to the crystallization areas of single salts Rb2SO4, Li2SO4·H2O, and MgSO4·7H2O, as well as double salts 3Li2SO4·Rb2SO4·2H2O, Li2SO4·Rb2SO4, and Rb2SO4·MgSO4·6H2O. Notably, rubidium-containing double salts occupy more than 50% of the entire phase diagram area. The results indicate that the interactions between Li+ and Rb+ with coexisting Mg2+ and SO42- are complex, leading to the formation and precipitation of various lithium- and rubidium-bearing double salts, which hinder the effective concentrations of lithium and rubidium during the solar evaporation process in salt pans. Additionally, a multitemperature comparison of the solid-liquid phase diagrams at 273.2, 298.2, and 308.2 K reveals that temperature is also a significant factor influencing the solid-phase types and crystallization areas. For instance, the crystallization form of the double salt 3Li2SO4·Rb2SO4·2H2O changes to 3Li2SO4·Rb2SO4 at 308.2 K and the crystallization area of Li2SO4·Rb2SO4 gradually decreases, while the crystallization area of Rb2SO4·MgSO4·6H2O generally exhibits an increasing trend.
RESUMEN
Friction and wear behavior exists between hoisting ropes that are wound around the drums of a multi-layer winding hoist. It decreases the service life of ropes and threatens mine safety. In this research, a series of experiments were conducted using a self-made test rig to study the effects of the strand lay direction and crossing angle on the winding rope's tribological behavior. Results show that the friction coefficient in the steady-state period shows a decreasing tendency with an increase of the crossing angle in both cross directions, but the variation range is different under different cross directions. Using thermal imaging, the high temperature regions always distribute along the strand lay direction in the gap between adjacent strands, as the cross direction is the same with the strand lay direction (right cross contact). Additionally, the temperature rise in the steady-state increases with the increase of the crossing angle in both cross directions. The differences of the wear scar morphology are obvious under different cross directions, especially for the large crossing angle tests. In the case of right cross, the variation range of wear mass loss is larger than that in left cross. The damage that forms on the wear surface is mainly ploughing, pits, plastic deformation, and fatigue fracture. The major wear mechanisms are adhesive wear, and abrasive and fatigue wear.
RESUMEN
The impact behavior between the charge and lifter has significant effect to address the mill processing, and is affected by various factors including mill speed, mill filling, lifter height and media shape. To investigate the multi-body impact load behavior, a series of experiments and Discrete Element Method (DEM) simulations were performed on a laboratory-scale mill, in order to improve the grinding efficiency and prolong the life of the lifter. DEM simulation hitherto has been extensively applied as a leading tool to describe diverse issues in granular processes. The research results shown as follows: The semi-empirical power draw of Bond model in this paper does not apply very satisfactorily for the ball mills, while the power draw determined by DEM simulation show a good approximation for the measured power draw. Besides, the impact force on the lifter was affected by mill speed, grinding media filling, lifter height and iron ore particle. The maximum percent of the impact force between 600 and 1400 N is at 70-80% of critical speed. The impact force can be only above 1400 N at the grinding media filling of 20%, and the maximum percent of impact force between 200 and 1400 N is obtained at the grinding media filling of 20%. The percent of impact force ranging from 0 to 200 N decreases with the increase of lifter height. However, this perfect will increase above 200 N. The impact force will decrease when the iron ore particles are added. Additionally, for the 80% of critical speed, the measured power draw has a maximum value. Increasing the grinding media filling increases the power draw and increasing the lifter height does not lead to any variation in power draw.