Three-dimensional discrete element method simulation of the effect of bottom structure on solid flow in COREX shaft furnace
COREX is an industrially and commercially proven smelting reduction process. The shaft furnace (SF) for the pre-reduction of iron ore is one of the two major reactors of COREX. As one of the industrial systems using screw feeders, the burden descending behaviour in SF can be directly affected by the bottom structure such as the design of screw and associated charging container. In this work, a three-dimensional actual size model of COREX-3000 SF is established by means of the discrete element method. The effect of bottom structure, for example, the guiding cone and the design of screw, on solid flow is investigated. The results show that burdens are mainly drawn down from the first flight of the screw in the reference case, while the slow-moving particles located above the end of the screw. Placing a guiding cone and reducing the flight diameter of screw have a benefit for restraining the descending velocities in the central area of the SF and help to obtain a uniform flow pattern. An optimised case is also proposed. In the optimised case, a relatively uniform solid flow profile can be obtained and the uniformity of descending velocity along the radius is improved greatly. The findings of this work should be useful for the design, control and optimisation of the SF operation.
Keywords: COREX shaft furnace, Guiding cone, Screw design, Solid flow, DEM