OJSC “NOVOLIPETSK STEEL” ENVIRONMENTAL ASPECT OF INDUSTRIAL TECHNOLOGIES FOR RECYCLING OF FE- AND ZN-CONTAINING SLUDGE AND DUST Speaker: Ivan Kurunov – Doctor of Technical Sciences 2011

The production of one ton of steel requires spending almost 20 GJ of energy and is accopmpanied by the emission of 1.7 t of СО2 into the atmosphere. In addition 20-25 kg of sludges and dust are generated, containing up to 60% of iron in the form of oxides and up to 2.5% of zink. In blast furnace iron production 5-15 kg of sludges is generated, where, apart from iron and carbon (25-30%), up to 1.5% of zink is contained. The recycling of this technologically generated raw material will be a solution to one of the most important environmental and economical tasks.

We reviewed four industrial process routes for recycling of iron and zink containing sludges and dusts with the obtaining of iron as a final product and commodity output with high content of zink. For all the routes СО2 through out emission was calculated at the recycling of BOF and BF iron and zink containing sludges for iron producer of an integrated type in the amount of 600 thousand t/y. The first stage for all these technologies is usually a pelletizing of the sludges by the method of hard extrusion which makes able to obtain sturdy cylindrical briquettes 20-30 mm in diameter and 40-80 mm in length.

Melting briquettes in a blast furnace (DK Recycling process)

Metallization of briquettes in a ring chamber furnace with rotating floor (Fastmet, Rediron) and the use of the received DRI in blast furnace process

Metallization of briquettes by Waeltz process and the use of the resulting DRI in blast furnace process

Melting of briquettes in OxyCup cupola

The method for calculation of through out consumption of fuel and emission of СО2 Consumption of fuel and oxygen in blast furnace process for different variants was evaluated by computer simulation model with the application of a balance mathematical model of a blast furnace process, constructed with the use the operational line of A. Rist. The fuel consumption in OxyCup process was assumed according to the published data. At the calculation of through out consumption of fuel and emission of СО2 the following fuel consumption figures were taken into account: coke production, sinter production, pellets calcination, production of DRI out of sludges, oxygen production, iron production in a blast furnace, ironmaking in a cupola.

Consumption of carbon and emission of СО2 in ironmaking according to the variants, kg/t Points of carbon consumption, kg/t of hot metal Blast furnace burden components Process OXYCUP Sinter and pellet Briquettes and pellets DRI (Fastmet), sinter, pellets DRI (Waeltz) Sinter Production output 65 – 14 Pellet production 2,5 15 13 Production DRI * 71 393 Briquette composition 108 262,5 DRI composition 4,5 Coke** 315 277 285 263 Natural gas 56 28 50 Oxygen content in the blast*** 11,5 9 39 Carbon consumed 451,0 428,0 446,5 768,5 564,5 Emission of СО2 1654 1569 1674 2818 2070 * Heating up to 1300 °С, direct iron reduction, overall heat losses. **Less carbon, which was transfered into iron. *** Assuming 1787 kkal/m3 О2 or С/m3 О2.

CONCLUSION Of all industrially used technologies for recycling of iron and zink containing sludges and dusts the minimum fuel consumption per ton of iron, made using them, and the minimum СО2 emission is provided by: the blast furnace process recycling of briquettes from these sludges and blast furnace processing of DRI which was produced by metallization of such briquettes by Fastmet or Rediron processes. Through out emission of СО2 in OXYCUP process and in BF process with the use of DRI, produced by Waeltz process, 1.3 and 1.8 times higher, than during the melting of the briquettes in the blast furnace.

Thank you for your attention!