DEM-CFDに基づく水素富化直接還元プロセスの熱物質移動解析

抄録

Hydrogen utilization in a direct reduction shaft furnace is a promising technology for carbon neutrality. On the other hand, some kind of heat compensation appears to be necessary, because the temperature in the furnace decreases and the reduction degree stagnates due to hydrogen enrichment. Therefore, a tool which can quantitatively evaluate the efficiency of heat compensation from a kinetic viewpoint considering detailed heat and mass transfer is useful for operational design. Based on the above, a numerical simulation model based on DEM-CFD was developed for the direct reduction process, and the following findings were obtained.

(1) A numerical analysis simulating a model plant confirmed that the calculation accuracy of the developed model is sufficiently high. The gas composition varies greatly depending on the degree of achievement of shift equilibrium.

(2) A numerical analysis of a commercial plant revealed the distribution with low temperature and low reduction degree in the radial center of the furnace. Hydrogen enrichment lowers the temperature and expands the region with a low reduction degree.

(3) As a technique for thermal compensation for hydrogen enrichment, it was found that increasing the inlet gas temperature increases the reduction degree exponentially.

(4) DEM-CFD can be a useful approach, since operational design considering powder phenomena, as represented by reduction degradation and clustering, appears to be necessary.