The feasibility of shaft‐level reducing gas injection has been widely investigated as a method to increase operational efficiency, enable higher oxygen‐enrichment operation, and minimize process CO 2 emissions. Computational fluid dynamics modeling is employed in this study to investigate the impacts of shaft injection gas composition on replacement ratios and furnace operation. An expansion to existing blast furnace CFD modeling techniques to simulate midshaft gas injection is described, and midshaft injection is simulated at a ∼3000 m 3 North American blast furnace. A reduced‐order model is developed to relate the momentum flux and mass flow rate of incoming reducing gas blends to the internal mass flux of the injected gas to predict midshaft gas distribution inside the furnace, and a range of midshaft CO‐H 2 gas blends were investigated to determine their influence on productivity and coke replacement. Modeling indicated the best performance with a gas blend of 70%H 2 –30%CO delivered through midshaft tuyeres located 4 m above the main tuyeres, providing a replacement ratio of 1.24 kg of coke per kg of injected gas. High CO or H 2 levels resulted in a reduction in replacement ratio at all injection rates.
Nielson et al. (Thu,) studied this question.