Scientific and practical fundamentals of cokeless production of siliceous ferroalloys

Abstract

Application of mineral carbon as carbonaceous reducing agents instead of coke for siliceous ferroalloys smelting is one of perspective ways of high efficient production of them. Results of industrial tests of expensive coke substitution by long-flame and brown coals during smelting of power-intensive ФС75 ferrosilicon presented. Tests were carried out at three ferroalloys plants of Russia and Kazakhstan. The following coals were used: long-flame coals of Shubarkol’skoe deposit (Kazakhstan), brown coals of Kajchasky open-pit mine (Kuzbass) and Majkyubenskoye deposit (Kazakhstan). The coals have Аd ash content at the level of 3–11%, high indices of reaction ability and specific electrical resistance, increased yield of volatile substances (Vdaf = 42–46%) and content of reducing components (CO, H2) up to 180–215 m3 /t (comparing with 11 m3 /t in coke). At the plant “A” the industrial tests resulted in coke substitution by 88–99% with the mixture, kg/charge: 20 – coal Б, 165–190 – coal Д and 35–60 – wood chips. Satisfactory technical and economic indices of ФС75 ferrosilicon production reached. Because of the volatile substances high yield of Д and Б coals (Vdaf = 44–46 %), an increased temperature of emitted gases (up to 240–270 °С) under the hood observed and at the gascleaning system (up to 160–170 °С). At the plant “B” during ФС75 smelting, the long-flame coal was used constantly to substitute the coke by 84%. At the plant “C”, Kazakhstan, a technological possibility of complete (100%) coke substitution by long flame coal determined. To transfer to cokeless production of siliceous ferroalloys with application of low metamorphized coals of Д and Б grades it is necessary to make considerable changes in existing mode of ferroalloys furnaces running to provide high technical and economic indices of the production. Another variant means construction of new furnaces, adapted to increased temperature of emitted gases, forming at the coals pyrolysis with high yield of volatile substances.