The higher the drying temperature and the smaller the particles of sludge, the shorter time be needed to dry to a certain moisture content and the higher drying rate in constant rate drying stage.

In this paper, the method for determining the drying rate curves of sodium molybdate under constant drying conditions was given.

The falling-rate drying kinetic equation of droplets proposed by Marshall s deduced once again, and the result shows that the Marshall's equation is still an equation for constant-rate drying process.