l .. PRINCIPLESOF BLASTFURNACE IR6NMAKING .Co1pyright 1981 AnilK.Biswas FirstIndianedition .1984 All rightsReserved: Nopartof thispublication may bereproduced,stored inaretrievalsystemortransmitted' inanyformor bymeans:electronic;electrostatic,mechanical photocopying,magne.tictape,orotherwise without, the prior written permission of SB1APUBLICATIONSCALCUTTA Libraryof CongressCatalogCardNo.80.65943 ISBN0-949917-08-7 (Flexicover) (StudentsEdition) Published bySBAPUBLICATIONS 1/1,Meredith Street, PostBox13315,Calcutta 700 072 and PrintedbytheRekhaPrintersPvtLtd A102/1OkhlaIndustiiaLArea,- PhaseII-NEWDELHlll0020. 1 'i lJ J.k, . .1 \. )____J...'. (. ;:,I ':1 .... : \]:. :f. J\. .. ,;rr-. .. (\1.-. jJ Jof thechemicalheat,i.e.,unusedCO,isindirectlyThe blastis introducedaboyethe bottom .of thefurnacethrough tuyeres. whereastheburdenmaterial'sarechargedfrom- the .topwiththehelpof . skip carsor sometimesby conveyerbelts.'.....Asectionof theblastfurnaceisshowninFig.1. L The_ cylindrical top . portion (thewalt armouredfor. protection of refractory brick lining against. falling hardburden mate:dals)iscalledthe throatand below that the stack orshaftextendswithincreasingdiameteruptothecylindricalbellyor . bosh-parallel.Thereafter,the diameterdecreasesintheportion; knownas bosh;,which_oonnectswiththebottom-mostportion,thehearth,where . moltenmetalandslag/_ .. Theopeningatthetopisprovidedwithadoublebellorother:new systems(e.g.,orbell'"lesstop)forchargingtheburden which has to traveldownwardsformoteor fess,. about 25 .metresinorder toprovide theascendinggasestheopportunitytogiveup itssensibleheataswell asto. enableitsreducingComponent, CO(and .H1i)topre-reducethe 'iron oxides (indirectreduction).Fromtheopening,the .throat extendsvertically downwardsforacoupleof metresormore; thereafter,thestackextends downwards .toanextentof about3/5of thet'otalheight,itsincreasing diameter Jacilitatitl"gauniformflowof thethermallyexpandinggasesand burden materials. The cylindrical bellyhasthe largest diameter in thefur-nace and, normally,thefusionandconsequent contractionof theslag and metal start inregion.The boshhasthe shapeof. an invertedtruncated eone,thebasemergiD:gwiththebellyandthe.topwiththetopofthe. The blast is through a series ofequidistant water-coole(i tuyeresaroundthe hearthperipheryabout40-60 embelow: itsuppef rim atapressureof1.5-2.5atm.gaugetoovercametheresistanceofthe materialsinside. theItentersthehearthc;ttavelocityof 150-300 nils;. .Thefurnaceprofile,i.e.,theshapeanddimensionof eachindividual .. poriion (e.g., 'theheights, diametersandangleswith. thehorizon),dt=w a::u.,_ wBlii a:: a:::;) ......

.2: a:: 0 a::-IIJO :z:z 1--I _FeO +CO= Fe+ COz + UN,REDUC.EDFeO I I. I.. __j_L_- ----- .!.:.-- ____t_-------DIRECTREDUCTION ANDMELTINGZONE,SLAG ANOIRON '.. - . Fe900 hf-bgOO 10.2 whereQ>900isthethermalrequirementperTHMabove900C.As the flamet_emperatureand,therefore,hfincreaseswith theblast tempera- ture _itis_apparentthatCt. willdecrease. correspondingly.AsCtbecomes less,.the_.tuyeregas generatedandhencethethermalcapacityof thegas. at 900C per THM entering the upper zonewillbe less.SiJlcethe thermal requirement intheupperzoneremains..constant,thetop gastemperaturewillfall.As' forexample;if Q