Abstract: A COREX-3000 shaft furnace model was established based on discrete element method to compare the drawdown uniformity coefficient， drawdown pattern and distribution of descending velocity between Baosteel screw and the newly designed screw by means of simulating. The results show that the drawdown uniformity coefficients of Baosteel screw from pitch 1 to pitch 5 are small and the peak 0.36 appears at pitch 4. However， the drawdown uniformity coefficients of the newly designed screw are close to 1 in all the burden drawdown area. From the macroscopic aspect， the drawdown patterns of the new screw along the whole height of shaft furnace are more uniform than that of Baosteel screw. Below the gas slots， the distribution of descending velocity along the radius of the shaft furnace with the new screw are more uniform than that with Baosteel screw. Above the gas slots， the effect of screw structure on burden descending velocity is small， and the drawdown patterns is more like plug flow.

Key words: COREX shaft furnace, discrete element methods, flow patterns, screw design, burden descending velocity