Processing of converter slurry by coking with coal

Abstract

Processing of the industrial waste formed at steel plants is of great importance. In the converter production of steel, 12–25 kg of fine dust is formed in the production of 1 t of steel, depending on the composition of the raw materials, the furnace design, and the smelting conditions. Wet cleaning of the waste gases converts the dust into a slurry containing 46–50% Fe2O3. It is difficult to process such slurry because of its high water content, the small particle size, and the presence of zinc oxides. Standard dehydration technology is complex. It is also associated with thermal drying, which poses an explosion risk, while briquetting or granulation does not resolve the problem posed by the presence of zinc oxides and is complicated by a lack of acceptable binders. Researchers at Siberian State Industrial University have developed complex conditioning of iron-bearing slurry by nonthermal adsorptive dehydration and subsequent thermochemical agglomeration, with simultaneous reduction of the iron and zinc oxides. Adsorptive dehydration to a moisture content of 2‒3% is possible by contact with porous lignite semicoke produced by Termokoks technology. Then the lignite semicoke is pneumatically separated and sent for use in energy systems, while the iron-bearing product is mixed with GZh or Zh coal and sent for thermooxidative coking in a furnace of special design (an annular furnace with a rotating hearth), where large and strong pieces of ferrocoke are obtained at 1050–1100°C. The ferrocoke contains 55–60% of the iron-bearing product. The oxides of iron and zinc are almost completely reduced. The zinc passes to the vapor phase and is removed with the combustion products of the volatile coking components. On cooling to 850°C, the zinc vapor condenses. The ferrocoke obtained is suitable for blastfurnace use, thereby reducing the consumption of sinter and coke. The heat obtained on cooling the ferrocoke and the energy of the combustion products after the deposition of zinc are utilized in a gas-turbine system.