Assessment of shaft gas injection technology for blast furnace ironmaking

Shaft injection of reducing gas into ironmaking blast furnaces (BF) helps mitigate BF carbon footprint. However, its effectiveness relies on the interaction between shaft-injected gas (SIG) and other phases. This paper numerically studies shaft gas injection operations based on a 380-m³ industrial BF. A recently developed three-dimensional process model has been adopted to do so. This model is extended to track SIG and hearth-generated gas (HGG), define SIG penetration, and quantify the respective contributions of the two gases to BF performance. After validation, the model is applied to study the effects of three variables related to SIG penetration into the particle bed: SIG flow rate, shaft tuyere number, and horizontal cavity depth. The detailed analysis of flow and thermochemical behaviors shows that increasing the SIG flow rate increases the gas penetration and indirect reduction rate by SIG and lifts the cohesive zone. However, it impedes the indirect reduction reaction by HGG and increases the bed pressure. These effects collectively identify an optimum SIG flow rate. In addition, as the shaft tuyere number or horizontal cavity changes, the SIG penetration zone size changes oppositely in radial and circumferential directions, leading to similar total penetration zone sizes. Consequently, these two variables can limitedly improve BF performance, especially compared with the effect of SIG flow rate. The results suggest that the model offers convenience for exploring the shaft gas injection technology.