Numerical study on coherent jet characteristics with bunch-type nozzle structure at various shrouding gas parameters

Abstract

During the electric arc furnace (EAF) steelmaking, the coherent lance is the core oxygen supply device for improving oxygen utilisation rate and the mixing efficiency of the molten bath. To further prolong the jet core length of the coherent lance installed on the furnace wall, a detachable coherent lance with a bunch-type nozzle structure is designed, and an attempt is made to use H₂ as the shrouded gas to reduce dependence on natural gas. For this purpose, a three-dimensional model is established in this paper to analyse the influences of different nozzle tip structures and shrouding gas conditions on the coherent jet characteristics. The simulation results show that, for different nozzle tip structures, the bunch-type design is more helpful in prolonging the jet core length. Increasing the hydrogen–oxygen input ratio helps the main oxygen jet maintain a large axial velocity and jet core length. However, when this ratio exceeds 20%, the increase in the input ratio has little effect on the jet velocity and jet core length. Compared with pure H₂ fuel, adding an appropriate amount of CH₄ to H₂ can rapidly increase both the axial velocity and the core length of the main oxygen jet. However, when the CH₄ in the mixture exceeds 40%, increasing the CH₄ ratio has a limited effect on the jet axial velocity and the jet core length. Compared with the 280-CH₄ supplement method, the axial velocity and jet core length of the primary oxygen jet are shortened by the 280-H₂ supplement method at the same volume flow rate, but prolonged by the 840-H₂ supplement method at the same mass calorific value.