2013 Volume 53 Issue 10 Pages 1770-1778
A low coke rate operation in blast furnace is desired to decrease the carbon input and mitigate global warming problem. However, low coke rate operation tends to cause the gas permeability to deteriorate. The mixing of small-size coke (nut coke) including high reactivity coke in ore layer is considered to be a promising way to improve permeability and increase reaction efficiency in a blast furnace. Although adding a nut coke mixing to an ore layer is predicted to be empirically effective in low coke rate operation, there is little actual data on microscopic phenomena of each particle in the packed bed. In the present study, an Euler–Lagrange approach was introduced to precisely understand the influence of the packed bed structure on the reaction behavior of each particle in the three-dimensional particle arrangement.
It was observed that the heterogeneity on the reaction rate and temperature distribution was influenced by the particle arrangement. When high-reactivity coke was used at approximately 1273 K, although CO gas fraction increased, the gaseous phase temperature decreased due to the active solution loss reaction rate of the nut coke in the mixed layer. As a result, the ore reduction rate decreased. The contribution of high-reactivity coke to the ore reduction rate depends on the particle arrangement through the heat transfer and reaction heat. Accordingly, in the case of the mixed charge of the high reactivity nut coke in the ore layer, the design of the packed bed structure is important.