The effect of spray drying parameters on drying of magnesium silicate hydroxide microspheres

Abstract

Magnesium hydroxide silicate (MSH), as an antiwear additive for lubricating oil, effectively solves the problem that conventional additives contain chlorine, phosphorus and sulfur, which are harmful to environment. However, it is ineffective to prepare MSH powder by traditional drying combined with mechanical ball milling. So the purpose of this study is to prepare smooth MSH microspheres with controllable particle size and moisture content by adjusting spray drying parameters based on hydrothermal synthetic MSH suspension. Results showed that the particle size of MSH microsphere was reduced from 5.5 ± 2.9 μm to 2.78 ± 1.37 μm, and the moisture content was reduced from 7.3% to 4.43% by decreasing solid-liquid ratios and rotating speed of peristaltic pump, or raising inlet temperature of hot air, flow rate of compressed gas and inlet air. In addition, due to the surface energy difference at the interface between liquid-gas and solid-gas during the drying process, nano flaky MSH continuously moved to the center of the droplet, and the capillary force generated by gaps between MSH nanosheets discharges the moisture in the wet core, so that the MSH nanosheets gather and finally form dense and smooth MSH microspheres.