Co-combustion of semicoke and coal in an industry ironmaking blast furnace: Lab experiments, model study and plant tests

Low-rank coals can be upgraded to semicoke, and potentially used to partly replace expensive metallurgical coals in pulverised coal injection (PCI) in ironmaking blast furnaces (BFs). In this paper, an integrated research of "lab experiments - model study - plant test" is used to study the feasibility of injecting semicoke in BFs. First, lab experiments are conducted to characterise the metallurgical properties of semicoke. Secondly, a three-dimensional CFD model is developed to study in-furnace phenomena related to two PCI operations: single injection of semicoke and co-combustion of PCI coal and semi-coke under full-scale BF conditions. The simulation results indicate that the semicoke shows similar combustion profiles with the PCI coal, confirming the feasibility of using semicoke in BFs. Moreover, the co-combustion of semicoke and PCI coal with the blending ratios of 0-40% is studied, as a result, the optimal blending ratio of semicoke, 30%, is recommended. Then, plant tests of semicoke combustion of blending ratio 0-20% are conducted. It is indicated that ironmaking indexes remain stable largely, confirming the practical feasibility of semicoke co-injection operation. The study provides a combined view of co-injecting PCI coal and semicoke in terms of fundamental combustion profiles and plant performance in a commercial BF.