Powder transport behavior in RH degasser with powder injection through up snorkel: a transient numerical model

A transient numerical model was established to predict the dispersion, distribution, and circulation behavior of the powder injected through the up snorkel in a Ruhrstahl-Heraeus (RH) degasser. The effects of the powder diameter, the lifting gas flow rate, and the powder injection rate on the powder transport were investigated. Local powder concentration was measured by a cold model. The results showed that the predicted powder concentration agreed well with the measured. The powder injection process is divided into three periods, named dispersion period, aggregation and circulation period, and dynamically stable period according to the powder transport behavior. The powder diameter has a great effect on the particle dispersion. When the particles size changes from 30 to 500 mu m, the powder dispersion characteristic index changes from 0.110 to 0.741, and the ladle top zone powder mass ratio changes from 0.118 to 0.685. The powder circulation mass flow rate increases to 101.0 kg min(-1) (150 mu m) and then decreases to 46.6 kg min(-1) (500 mu m). Powders with a diameter of more than 220 mu m can change the steel flow mode in the RH degasser. Increasing the lifting gas flow could slightly improve the powder dispersion. Variation in the powder injection rate has almost no effect on the powder dispersion.