Industrial test of smelting reduction for manganese ore in converter

The smelting reduction of manganese ore in the converter has been reported in China since the 1990s, and some steel enterprises have successively carried out industrial tests of this technology. However, the recovery ratio of Mn in manganese ore is low and fluctuates greatly due to various reasons such as inadequate hot-metal pretreatment, the poor bottom blowing effect of the converter furnace, and unreasonable positioning of the smelting end point. The smelting reduction of manganese ore has not been successfully applied in converter steelmaking and failed to benefit steel enterprises. In this study, the thermodynamic parameters of manganese ore melting reduction were discussed to improve the recovery ratio and yield of manganese and find a way to directly use manganese ore in a converter. The industrial test was carried out in a 200 t converter at a steel mill. Results showed that the efficient and stable ‘tri-de’ (dephosphorization/desulphurization/desiliconization) hot-metal pretreatment was the basic premise for the success of manganese ore smelting reduction. The theoretical calculation revealed that when the content of MnO in slag is 5%–10% and the terminal content of [C] is 0.13%–0.36%, the end-point of [Mn] in molten steel can be controlled above 0.3%. For an improved recovery ratio of Mn in manganese, the industrial test mainly adopted the smelting operation of double-slag operation to ensure that the amount of slag and iron oxide in the slag was reduced as much as possible under low phosphorus content in molten iron in the early stage. Under the existing process control conditions, the industrial test results showed a manganese yield of more than 40% and an average value of 51.40% when the added amount of manganese ore was under 10 kg·t−1. For an excellent manganese yield, the total amount of manganese smelting reduction slag must be strictly controlled from 40 kg·t−1 to 60 kg·t−1, and the amount of lime must be 10–15 kg·t–1. This work provides an important reference for the development and direct application of manganese ore in the converter.