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Jorge MadiasConsultantmetallonA Review of the Production of Ferromanganese in Blast Furnace

1ContentFacts and figuresRaw materialsBlast furnace design & operationComparison with SAFConclusions

2Facts and figuresHigh C FeMn world production 5 Mtpy50% production in China (both BF and SAF)Including SiMn smelters, some 600 companies are located in China, with a large excess of installed capacityProduction of High C FeMn in blast furnaces is concentrated in China, Russia, Ukraine, Poland and Japan

3Facts and figuresBlast furnaces were widely used in developed countries, up to the end of World War IIUsually, integrated plants destined their smaller blast furnace for High C FeMnTop gas in the FeMn blast furnace entrained excessive fines, so, hot blast air came from the other furnacesSAFs replaced blast furnaces (smaller coke rate, longer refractory life, no need of hot blast, reuse of MnO-rich slag for FeSiMn)

4Facts and figuresRussia and China: abundance of low Mn ores could has been a driver for keeping the blast furnaces runningJapan, the decision of building a FeMn blast furnace was taken during the second oil crisis, to replace two SAFsSince then, those plants have been improving raw materials preparation, equipment and operating practice, and new, more modern plants have been built

5Raw materialsMn OreBlast furnaces are more forgiving than SAFs regarding raw material quality. It is possible to consume efficiently Mn ores with a minimum of 28% MnMn ore is composed by manganese oxides (MnO2, Mn2O3, Mn3O4), accompanied by iron oxide, silica and other oxidesCarbonates have been processed, at least in Russia and China

6Raw materialsMn OreMn/Fe ratio>7.5:1 (iron oxide is fully reduced in the furnace, taking part in the ferroalloy)P: as in iron BF, all charged P reports to the alloy

Mn ore producers: Brazil, Gabon, Australia, Russia

Mn (%)Fe (%)Al2O3 (%)Al2O3+SiO2 (%)As (%)P (%)Cu+Pb+Zn (%)48 min.6 max.7 max.11 max.0.18 max.0.19 mx.0.30 max.

7Raw materialsMn Ore preparation at Azul Mine, Brazil: grinding & screening; lumps & sinter feed

8Raw materialsMnO sinterIn Russia and China, low Mn ore (30%) with high content of fines, calls for sinteringSinter charge in some Chinese FeMn BFs:

Improvements with sinter increase:PlantXinyuSaoxinYangkuanBayiGuilinXinyangLangfangWujingAverageSinter %66.17.839.248.763.134.541.231.240.5Sinter (%)60708090100Coke (kg/t)21962145208320752064Fluxes (kg/t)1158978604526355Slag (kg/t)26842631248424732465Productivity (t/m3.day)0.4650.4920.5090.5140.537

9Raw materialsReductantsCoke (20 60 mm), produced in by-products or in non-recovery/heat-recovery batteriesNo reports about other reductants used in SAFs (charcoal, pet coke)Although suggested in literature, no reports on PCI, except for an experimental shaft furnace in JapanOil injection in the Japanese blast furnace (100 kg/t)

10Raw materialsFluxesSlag chemistry control is requiredfor the slag to flow through tap hole and runnersfor not having high MnOfor desulphurizationfor Na2O / K2O absorption Limestone and dolomite for basicity controlWhen possible, part of the fluxes are introduced through sinter or after calcining

11Raw materialsFluxesChinaFirst, use of calcined lime (Yanggang)Then, dolomite through sinter plant (Xinggang)Finally, most plants tended to charge a high basicity (1.7), high MgO sinter, and calcined lime in the furnace, simultaneously

12Blast furnaceUsually within the range on MBF (