Mathematical Modelling of Sticking Phenomena in COREX Reduction Shaft by CFD-DEM Method

Abstract

Liquid iron for steel production is produced mainly in a conventional blast furnace (BF). New iron-making processes have been introduced in the last two decades because of environmental concerns. One such process is COREX smelting technology, which can operate, at least in theory, without any need for coking-coal, significantly reducing CO2 emissions and production costs of liquid iron. However, the complicated gas-solid flow inside the reduction shaft (RS) of COREX gives rise to operational difficulties such as sticking of particles at high temperature. Understanding the flow patterns in RS would enhance the ability to control them, resulting in an improved overall process quality. To understand multiphase flow in the RS, mathematical modelling has been employed here, coupling discrete element method (DEM) with computational fluid dynamics (CFD). Using this CFD-DEM approach, gas-solid flow and heat transfer phenomena were investigated at microscopic level. The results indicate that gas inlet velocity has an insignificant effect on solid flow pattern due to small gas-solid interaction forces. The model was able to describe heat transfer inside the RS, and a new burden distribution arrangement was proposed, with some improvement in heat transfer in the central part of the furnace. While future analysis and investigation should deal with more realistic properties, these results confirm that mathematical modelling, in particular CFD-DEM, is an effective tool for describing complicated phenomena inside the RS. The findings of this study should be useful for control and optimization of the RS operation.