A new method of red mud recycling in the process of hot metal pretreatment

To realize a large-scale consumption of red mud in the steelmaking industry, a new recycling method was investigated through the pre-reduction roasting experiment and the slag-metal interaction experiment simulating the hot metal pretreatment process in the steelmaking industry. In virtue of the sensible heating of the hot metal and the reducibility of [C] and [Si], the iron could be separated and recovered from the pre-reduced red mud pellets into the hot metal directly with a recovery rate exceeding 75%. With the composition adjustment of the residual oxides in the pre-reduced red mud (PRRD) using CaO and Al2O3 or aluminium dross (AD), a slag having a low melting point (below 1300 °C) and a high sulfide capacity (lgCS = −2.3) was formed, and more than 94% of [S] in the hot metal could be removed into this slag through the slag-metal interaction. The desulfurization efficiency of the flux (PRRD-CaO–Al2O3; PRRD-CaO–AD) is approximate to the traditional desulfurizing flux (CaO–CaF2). The advantages of this method are summarized as the low energy cost and the slag valorization.

Desiliconisation and Dephosphorisation Behaviours of Various Oxygen Sources in Hot Metal Pre-Treatment

In order to obtain a better understanding of the efficiencies of desiliconisation and dephosphorisation reactions during hot metal pretreatment in an open ladle, a number of simulation experiments were carried out with various oxygen sources. Three types of solid oxygen materials (sintered return ore, scale briquette and fine mill scale) were carefully investigated as hot metal pre-treatment agents, evaluating their desiliconisation and dephosphorisation efficiencies. The method applied for supplying gaseous oxygen was also assessed. The comparison between top blowing and injection methods indicated that injected oxygen gas is more advantageous for desiliconisation, while top-blown oxygen gas is favourable for dephosphorisation. The obtained information on the characteristics of gaseous oxygen can be used for the optimisation of blowing patterns, in order to improve the efficiency of the hot metal pre-treatment.