Numerical analysis of the carbon-containing pellet direct reduction process with central heat transfer enhancement

摘要

Pellet heat transfer has always been one of the biggest limiting factors in its direct reduction process in the rotary hearth furnace (RHF). Therefore, strengthening its heat transfer process is very important for productivity in RHF. In this study, a coupling model of the carbon-containing pellet reduction process considering porosity and chemical heat variation with intermediate media in its center was established. With the pellet radius R_0 = 11mm, the influence of the intermediate spherical medium radius r_0, the offset position of the spherical medium ξ, and the materials used on the overall pellet reduction process were analyzed. The results showed that the presence of a spherical medium in the pellet center can increase the temperature inside the pellet, leading to it being more advantageous for reduction of the pellet. With the increase of the medium radius r_0, it becomes more favorable for the pellet reduction process, as the spherical medium is more efficient for heat conduction. With the increase of the offset value ξ, the spherical medium acting as heat-conducting material can allow the heat transferred to the pellet inside faster, which is also more favorable to the reduction process. In addition, when the spherical medium has a smaller effective volume heat capacity pC_p and a larger thermal conductivity k, it is more favorable for the pellet reduction process too. These results can serve as a reference for optimum pellet design in RHF.