Kinetic Model Research on Drying Characteristics of Composite Green Pellet in Rotary Hearth Furnace

Abstract

The drying process of green pellet is the intermediate link of direct reduction in rotary hearth furnace, which can reduce energy consumption, prevent green pellet from bursting during drying and reduce pulverization rate. In this study, the effects on the drying rate of raw metallurgical dusts pellet at a hot air flow rate of 1 m/s and drying temperatures of 211°C, 254°C, 282°C and 314°C was investigated to clarify the drying characteristics of the green pellet. The results show that there were accelerated drying stage, constant drying stage and deceleration drying stage in the drying process of green pellet. The drying temperature had a significant effect on the dehydration rate during the drying process. The effective diffusion coefficient increased with the increase of drying temperature, and the activation energy of the whole drying process was 10.4 kJ/mol. Then the drying fitting models of Page (III), Lewis, Wang and Singh, and Weibull are used to describe the drying kinetics of green pellet. The fitting results show that the green pellet drying process is consistent with the Page (III) and Weibull models. Finally, the Weibull model was selected to compare the experimental values with the fitted values and the results indicate that the fitting model can well describe the actual drying process.