Influence of Screw Design on Burden Descending Velocity and Particle Segregation in COREX Shaft Furnace

COREX shaft furnace (SF) is an industrial system that employs screw feeders; thus, the burden descending velocity and particle segregation in the SF can be directly affected by the design of screw. A three-dimensional actual size model of COREX-3000 SF was established using the discrete element method. Four types of burdens, including pellet, ore, flux and coke, were considered in this model. With this consideration, the effect of screw design on solid flow was investigated. Results showed that, in the base case, burdens fell primarily down from the first flight of the screw. The burden descending velocities were nearly uniform in the peripheral direction and decreased along the radial direction. In addition, the normalized particle size increased in the center area and decreased in the wall area. Reducing the flight diameter of screw benefited an even flow pattern and restrained the rolling tendency of burden from the edge to center areas. An optimized case was also proposed, in which a uniform solid flow profile could be obtained and the evenness of descending velocity along the radius could be greatly improved.