Utilization of grinding aids in oil shale milling

Grinding aids (GAs) effectively reduce the energy requirements of the grinding process and improve grinding productivity. Two GAs (sodium silicate and triethanolamine (TEA)) were selected and their mechanisms of action were explored. The effect of the different grinding parameters on oil shale grinding efficiency was determined. The adsorption characteristics of the GAs were investigated using scanning electron microscopy (SEM), pulp viscosity, surface potential, and Fourier transform infra-red spectroscopy (FTIR). The results indicate that compared to grinding without GAs, the addition of sodium silicate and triethanolamine (TEA), increases the yield of −0.075 mm particles by −2.97% and 14.05%, respectively. The optimal grinding parameters were determined for a pulp concentration 40%, a steel ball weight ratio of Φ32 mm: Φ25 mm: Φ22 mm: Φ18 mm (50:24:17:9), and a grinding time of 20 min. The flotation test results indicate that compared to sodium silicate, TEA is the more suitable GA. The addition of sodium silicate reduced the sharp edges of the particles, increased the pulp viscosity and reduced the surface potential. It was not conducive to pulp dispersion. Conversely, TEA reduced the pulp viscosity and increased the surface potential, which enhanced the repulsive force between the particles, increasing the particle spacing, and the dispersion of the pulp. Sodium silicate and TEA both formed hydrogen bonds or chemical bonds on the surface of the mineral particles, strengthened the steric-hinderance effect, and enhanced the repulsive force between the particles.