The Role of Cohesion in the Formation of a Raceway of a Blast Furnace

Blast-furnaces (BFs) are the workhorses of the modern steel making industry. The annual output of the steel-industry amounts to 1.9 Gt, which releases around 650 Mt CO₂ or 7% of the global annual emissions. The modern BF process makes use of lateral injection of a mixture of pulverized coal and hot air by circular tubes at high velocity, which results in turbulent flow and the formation of a void region, called raceway. Understanding raceway formation is of great importance for the BF performance, including the process efficiency as well as the emission reduction.

The raceway is often characterized by the morphology and dimensions. However these characteristics are extremely difficult to obtained experimentally under actual process conditions. Thus, numerical modelling using computational fluid dynamics (CFD) is an alternative. The contribution of this work is the consideration of cohesive particle-particle interaction in the CFD model to investigate its impact on the raceway formation. The modelled cohesive forces correspond with particle agglomeration (sintering). Simulations are performed using the CFD-DEM approach with incorporation of a simplified JKR model accounting for particle cohesive forces. Following verification with literature data the model was used to quantify the effects of cohesive particle-particle interaction and raceway characteristics, where we observed increased bed resistance of ca. 5%. This resulted in a collapse of the raceway at lower blast velocity. At higher blast velocity fluidization and gas leakage was suppressed, resulting in more uniform flow conditions.