Influence of process parameters on impurity level in ferrochrome production-An industrial-scale analysis

Ferrochromium production is a highly energy-intensive process, consuming between 3000 and 4000 kWh for producing one ton of ferrochrome alloy. The alloy produced contains chromium, iron as a principal constituent and silicon and carbon as an impurity. Minor quantity of silicon is desirable to aid in the fluidity of the alloy while smelting chromite ore. Still, at a higher level, it not only deports as the impurity in alloy but also causes a considerable drain of energy. Also, the excess of carbon in alloy causes problem during final carbon adjustment during steelmaking. An exhaustive understanding of different process parameters affecting impurity intake in the alloy can significantly reduce impurity and hence, energy consumption. The gained knowledge can be further utilized to control the process better and achieve the alloy of the desired composition. Several sets of industrial data were obtained and analyzed to understand the process. Different parameters, such as coke rate, power input, input silicon and average moisture on the composition and recovery of ferrochrome, were studied. From the study, it was concluded that a high grade of feed material with input Si <13 Wt.%, a coke rate of 380–390 kg/t of alloy and power input in the range of 3067–3200 kWh/t of alloy can result in an alloy with Si <2 Wt.%. Operating under the given power range is also observed to reduce the Cr₂O₃ loss to the slag.