Properties of iron bearing materials under simulated blast furnace indirect reduction conditions Part 3 Reducibility

摘要

A laboratory furnace was built to study thebehaviour of materials in the shaft region of a blast furnace .Inthis paper the reducibility of two sinters ,two lump ores ,and arange of fluxed pellets was studied under a number of simulatedblast furnace wall and centre conditions ,i.e. vertical temperatureand gas composition profiles .Reducibility values obtained wereconsistently much lower than equivalent values obtained by thepopular JIS standard test .In addition ,the ranking of thematerials was different to that obtained using the standardtest .For the standard test the reducibility of porous hematitelump ores was lower than the values obtained for sinters andsignificantly lower than the values obtained for fluxedpellets .However ,under blast furnace simulated conditions thereducibility of lump ores was generally as good as ,if not betterthan ,values obtained for the fluxed pellets .The causes of thisdiscrepancy are :(I)hematite reduces at lower temperaturescomparison with the bonding phases present in the sinters andpellets,e.g.silicoferrite of calcium and aluminium (SFCA)andmagnetite ,and (ii)reduction occurs before the fine pores presentin the ore coalesce and decrease the available intraparticle surfacearea ,which occurs in the JIS test .In particular ,the study alsoshowed that ,for lump ore ,reducibility is a function of particlesize ,suggesting that lump ores charged into a blast furnaceshould be of smaller size than pellets or sinters .Finally ,the studyhighlighted the important role of carbon dioxide ,which is notincluded in standard test gas mixes ,in suppressing reduction.