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Carbothermic Reduction of MoO3 for Direct Alloying Process
JOURNALOFIRON ANDSTEELRESEARCH,INTERNATIONAL２ ０ １ ３,２ ０( １ ０):５ １ Ｇ ５ ６
Ca r bo t he rmi cRe du c t i ono fMoO３f o rDi r e c tAl l o i ngPr o c e s s y ZHU Hang Ｇ Ｇ bang, YANG Ha i Ｇ s en, LUO L i n Ｇ yu, LIZheng gen
( t r a lI r onandS t e e lRe s e a r chI ns t i t u t e,Be i i ng１０００８１,Ch i na) Depa r tmen to fMe t a l l u r i c a lTe chno l ogy,Cen j g Ab s t r a c t:Th et h e rmodyn ami c so fMo ＧOＧCa ndCa ＧMo ＧOＧCs s t emswa ss t ud i e di no r d e rt ound e r s t a ndt h ec a r bo t h e rmi c y r educ t i ono fmo l r i ox i de,andk i ne t i cs t ud i e swe r ea l s oc a r r i edou tbyme anso ft he rmog r av ime t r i cana l s i s ybdenumt y unde ra r tmo sphe r ewi t hahe a t i ngr a t eo f１０ ℃/mi n．Subs e t l e a c t i onp r oduc t sa tva r i oust empe r a t u r e s gona quen y,r ( ) we r ei den t i f i edbyXＧ r ayd i f f r a c t i on XRD andt her e su l t sc on f i rmedt hep r e v i oust he rmodynami c sana l s i s．Me an Ｇ y wh i l e,i twa sf oundt ha ti n t e rmed i a t ep r oduc t sMoO２andCaMoO４appe a r edi nt hep r o c e s so fc a r bo t he rmi cr educ t i on o fMoO３ wi t ho rwi t hou tCaO,wh i chwe r esubs e u e n t l e d u c e dt o M oo rm o l b d e n u mc a r b i d e ． A ne x e r i m e n t a l l q yr y p y de t e rmi nedr e a c t i onme chan i sm wa sp r opo s edandd i s cus s ed．Ther educ t i onr e a c t i ono f MoO３ wi t hc a r bonc ou l dbe d i v i dedi n t otwos t age s．Thef i r s ts t agei nc l ude st hed i r e c tr e a c t i onbe twe enMoO３andc a r bonandt hec a r bonga s i f i c a Ｇ t i onr e a c t i on．Thes e c onds t agei st hega s Ｇ s o l i dr e a c t i onbe twe enCOand MoO２ ,andt hed i f f us i ono fga s e st hr ough t hesu r f a c eo fMoO２ de t e rmi ne st heove r a l lr e a c t i onr a t e．Thea c t i va t i onene r i e so ft he mi x t u r e swi t ho rwi t hou t g /mo CaO we r ee s t ima t edt obe５６ ６and５２ ９kJ l,r e spe c t i ve l ． y Ke r d s:c a r bo t he rmi cr educ t i on;mo l r i ox i de;s t ab i l i z i ng;c a l c i umox i de ybdenumt ywo
Fe r r omo l l l oyi s wi de l edi nt he ybdenum a y us r oduc t i ono fs t e e l sc on t a i n i ng mo l I nr e Ｇ p ybdenum． c en tye a r s,me t a l l u r i s t sa r e t r i n t ou s em o l b d e Ｇ g y g y num ox i dec onc en t r a t e sa st heagen ti ns t e e lmak i ng [ ] r o c e s s１－２ ,s i nc ed i r e c ta l l oy i ngbyus eo f mo l Ｇ p yb denumox i dec onc en t r a t e sha sc l e a re c onomi csupe r i Ｇ o r i t l i dec onc en t r a t e s me l ti n y and mo ybdenum ox s t e e lba t hr ap i d l ompa r edwi t hf e r r omo l yc ybdenum． Thema i npr ob l emf o rd i r e c ta l l oy i ngwi t h mo l Ｇ ybde numox i de si st hesub l ima t i ono fmo l r i ox Ｇ ybdenumt i de,wh i chl e adst oal ow y i e l do f Moi nt hes t e e l Ｇ mak i ngp r oc e s s． Seve r a li nve s t i t i onshavebe enr e Ｇ ga r t edt ha ta l ka l i sanda l ka l i nee a r t hox i de sa swe l l po a sc a rbona t e sc anr e s t r a i nt h ee v a r a t i ono fmo l e Ｇ po ybd [ ] numt r i ox i d e,s u c ha s,CaO,MgO,CaCO３,e t c３－４ , a ndt her e a s oni st h ef o rma t i ono fmo l a t e sa ta bou t ybd ６００ ℃ wh i chi sf a rbe l owc l e a revapo r a t i onpo i n to f mo l r i ox i de．The s e mo l t e sa r es t ab l e ybdenumt ybda a ts t e e lmak i ng t empe r a t u r e and c an be e a s i l e Ｇ yr duc edbyr e l evan tr educ t an ti ns t e e lmak i ngp r o c e s s． I nt hep a s t,v a r i ou s me t hod st or e du c e mo l e Ｇ ybd , , numt r i ox i d ewe r ep r opo s e ds u c ha s hyd r og e nr e du c Ｇ [ ] [ ] t i on５－６ ,me t a l l o t h e rmi cr e du c t i on７－９ a ndc a r bo t h e r Ｇ [ ] mi cr e du c t i on１０ ．Tho s eme t hod sa r ec ommon l dop t e d ya
t op r oduc e mo l rf e r r omo l r ybdenum o ybdenum．Fo d i r e c ta l l oy i ngi ne l e c t r i ca r cf urna c e( EAF),mo Ｇ l i deconc en t r a t e s mi xed wi t hc a rbono r ybdenum ox s i l i conme t a lands c r aps t e e lwe r el oc a t edi nf urna c e bo t t om．Mo l e num ox i d e swe r ep r e Ｇ r e du c e da st emＧ ybd e r a t u r er o s e,bu tmo s timpo r t an t l l Ｇ p y,mo ybdenumox i de sc anber educ ede f f e c t i ve l t he re l e Ｇ y by many o men t si nl i i ds t e e la f t e rt hes c r aps t e e lme l t i ng． qu The pur eo ft he p r e s en ts t udyi st o ga i n pos mo r eunde r s t and i ngo ft hec a rbo t he rmi cr educ t i ono f MoO３ ,ande f f e c to fCaOonr e s t r a i n i ngevapo r a t i on o fMoO３i sa l sod i s cus s ed．
１ Th e rmodynami c s
The ma i n componen t so f mo l i de ybdenum ox conc en t r a t ea r eMoO３and MoO２ ．MoO３c anbee a s i Ｇ [ ] l educ edt oMoO２ byc a rbona t５００－６００ ℃ １１ be Ｇ yr c aus eo fi t sh i c t i v i t e a c t i onc anbewr i t Ｇ gha y．Ther : t ena sf o l l ows ( ２MoO３ ＋C＝２MoO２ ＋CO２( １) g) Cons equen t l her educ t i ono fMoO３ byc a rbon y,t si ntwos t eps,r educ t i ono fMoO３t o MoO２ ,f o r goe , t hef i r s ts t ep andr educ t i ono fMoO２t o Moo rmo Ｇ l a rb i de,f o rt hes e conds t ep． ybdenumc
Founda t i onI t em: I t em Spons o r edbySc i enc eandTe chno l ogyAch i evemen tSpe c i a lFounda t i ono fJ i angsuPr ov i nc eo fCh i na ( BA２０１０１３９) B i o r aphy: ZHU Hang Ｇ １９８４—),Ma l e,Do c t o r; E Ｇma i l:hangyu_zhu＠a l i c om; Re c e i v e dDa t e:Ap r i l２６,２０１２ yu( yun g
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J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２０
I nt hepr e s enc eo fCaO,t hechemi c a lc omb i na Ｇ t i onbe twe enMoO３andCaOo c cu r sa tal owt empe r Ｇ a t u r e,s imi l a r l ot heh i c t i v i t f MoO３ , y duet gha yo andt her e a c t i onc anbewr i t t ena sf o l l ows: ( MoO３ ＋CaO＝CaMoO４ ２)
Equ i l i br i umr e l a t i onsi nt hec a rbo t he rmi cr educ Ｇ t i ono fMoO３ wi t ho rwi t hou tCaOa r ec omp l ex,due t ot heva r i ousr e a c t i onpa t hsandal a r ro f genumbe r educ t i onp r oduc t si n Ca ＧMo ＧOＧCs t em．Thef o l Ｇ ys l owi ngt he rmodynami cana l i s wa sc a r r i edou tby ys [ ] us i ngr e l evan tt he rmodynami cda t a１２ ．
１ １ Mo ＧOＧCs s t em y I ti swe l la c c ep t edt ha tc a rbo t he rmi cr educ t i on o f me t a lox i de si nc l ude stwopa r t s:i nd i r e c tr educ Ｇ t i onandt hec a rbon ga s i f i c a t i onr e a c t i on．Chemi c a l : r e a c t i onequa t i onsa r er ep r e s en t eda sf o l l ows ( MO＋CO( ３) g)＝M＋CO２( g) ( CO２( ４) g)＋C＝２CO( g)
whe r eMOi s me t a lox i deand Mi sr educ t i onp r od Ｇ uc t．CO２ ex i s t sa sani n t e rmed i a t ep r oduc t．Ca rbon c onsumedt hei nd i r e c tr educ t i onp r oduc t( CO２ )and ( ) t henwa st r ans f o rmedt or educ t an t CO ．Gene r a l l y, t hema i nr educ i ngagen twa sCOi nt hep r o c e s so fr e Ｇ [ ] duc t i ono fme t a lox i de sabove７００ ℃ １３ ． [ ] Fr om Mo ＧCb i na r s ed i ag r am １４ ,t hes t ab l e ypha r educ t i onspe c i e si nMoO２ＧCs t ema r eMo,Mo２C, ys MoC,r e spe c t i ve l hec a rbo t he rmi cr educ t i on y,andt o fMoO２shou l dp r o c e edbyt hef o l l owi ngr e a c t i ons: ( MoO２ ＋２CO( ５) g)＝Mo＋２CO２( g) ) / / ( ) ( MoO２ ＋３CO( ＝１ ２ M o C＋５ ２ C O ６) g ２ ２ g ( ) ( ) ( MoO２ ＋４CO g ＝MoC＋３CO２ g ７) ( Mo＋CO( ８) g)＝１/２Mo２C＋１/２CO２( g) ( ) ( ) ( Mo２C＋２CO g ＝２MoC＋CO２ g ９)
F i １ Pr e domi nanc e Ｇ a r e ad i a r amf o r g g c a r bo t h e rmi cr e du c t i ono fMoO２
s imu l t an e ou se i l i b r i um po i n tamong MoO２, Mo２C, qu , and Moi s１０６０ ℃ andi tc anbes e ent ha tMocou l d bep r oduc edove r１０６０ ℃ unde rc e r t a i nCOr a t i o． １ ２ Ca ＧMo ＧOＧCs s t em y As imi l a rd i ag r amf o rc a rbo t he rmi cr educ t i ono f CaMoO４i sshowni nF i ２．Ther e l evan tr e a c t i ons g a r ep l o t t ed: CaMoO４ ＋３CO( １０) g)＝Mo＋CaO＋３CO２( g) ( ) / CaMoO４ ＋４CO( ＝１ ２ M o C＋C a O＋ g ２ ( ７/２CO２( １１) g) CaMoO４ ＋５CO( １２) g)＝MoC＋CaO＋４CO２( g) ( , L i ket he Mo ＧOＧCs s t e m M o Cc o u l db e r o Ｇ y p ２
duc edi nt het empe r a t ur er angeo f８２０t o１２００ ℃ a t ０ １ MPa,andCaMoO４ c anb er educ edt o Moabove １２００ ℃． I nt h i ss t udy,expe r imen t shavebe enc a r r i ed ou tt or e s e a r cht hec a rbo t he rmi cr educ t i ono fMoO３ wi t ho rwi t hou tCaO．
andt hec a rbonga s i f i c a t i onr e a c t i onr e f e r r edt or e a c Ｇ t i on ( ４)． Thep r e domi n a n c e Ｇ a r e ad i a r amo fc a r bo t h e rmi cr e Ｇ g du c t i ono fMoO２i ss howni nF i １,a ndt h ee i l i b r i um g qu COr a t i of o rt hec a rbonga s i f i c a t i onr e a c t i oni sa l s o , i n c l ud e di nt h ef i r e wh e r e PCO ＋PCO２ ＝０ １ MPa gu wa sc on s i d e r e da ndt h ea c t i v i t fc a r boni se a lt o１． yo qu Thus,a t０ １ MPa,t her i to ft h i sl i nei st her e Ｇ gh , , duc t i onr eg i on andi nt h i sa r e a MoO２ c anber e Ｇ duc edt o Moo rmo l a rb i debyCO．Att he ybdenumc F i ２ Pr e domi nanc e Ｇ a r e ad i a r amf o r g g s amet ime,c a rbonex i s t si nt hel e f tr eg i onwh i chi s c a r bo t h e rmi cr e du c t i ono fCaMoO４ t heox i da t i onz one．F i １showst ha ts imu l t aneous g equ i l i br i um among MoO２ ,C,and MoC o c cu r sa t ２ Ex e r imen t a l p ６００ ℃ ,wh i ch me anst ha t MoO２ c anber educ edby c a rbonove rt h i st empe r a t u r et o MoCon l nana r Ｇ ２ yi １ Ma t e r i a l s r owr eg i on ( ６００－６５０ ℃ )．Ove r６５０ ℃ ,t her educ Ｇ Mo l e numt r i ox i d e,c a l c i umox i d eanda c t i v a t e d ybd t i onpr oduc twi l lbeMo２Cwh i chi smo r es t ab l e．The c a r bon we r eus eda sr aw ma t e r i a l s．Ca l c i um ox i de
I s sue１０ Ca r bo t he rmi cReduc t i ono fMoO３f o rDi r e c tAl l oy i ngPr o c e s s
r s( １５０μm,９９％ )we r ep r ehe a t eda t９００ ℃ powde f o r１２ht or emover e s i dua lH２OandCaCO３ ．Mo l Ｇ yb ( denumt r i ox i de s pa r t i c l es i z e －１５０and ＋１０６μm, ９９％ )we r ed r i eda t２００ ℃f o rabou t１２h．Ac t i va t ed c a rbon (－７５and４８μm,f i xedc a rbon９２ １％ ,pu r i Ｇ ) t i rt han９９ ５％ we r eus eda sr educ i ngagen t． yh ghe The s epowde r s we r eana l t i c a l l r eandsupp l i ed y ypu byS i nopha rm Chemi c a lRe agen tBe i i ngCo ,Lt d． j Samp l e mi x t u r e swe r ep r epa r edbyt ho r ough l y mi x i ngi na mo r t a r．Mo l r i ox i deanda c t i Ｇ ybdenumt , va t edc a rbonwe r emi xeda tmo l a rr a t i oo f１∶３ and t hemo l a rr a t i oo f MoO３ ∶CaO∶C wa s１∶１∶３． Thecompos i t i ono fmi x t u r e sandf i na lma s sl o s si n t hep r e s en ts t udya r eshowni nTab l e１．
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F i ３ Ma s schang e sf o rr e du c t i ono f g MoO３ wi t ho rwi t hou tCaO
Cand CaO＋ MoO３ ＋C mi x t ur e si na r tmos Ｇ gona r ea tt hehe a t i ngr a t eo f１０ ℃/mi na r ep r e s en t ed． phe I tc anbeobs e r vedt ha tt empe r a t ur eha save r i Ｇ ys g w MoO３/ wCaO/ wC/ Mi x t ur e F i na lma s s No n i f i c an ti n f l uenc eont her e a c t i on． /mg /％ ma s s l o s s ％ ％ ％ F o rC a O＋ M o O t h e r ei sas l i tde c r e a s ei n gh ３, １ ７２ ２８ － ８ ２ ９ ７ m a s s l o s s i nt h e t e m e r a t u r er a n eo f７ ５ ０t o９ ０ ０ ℃ p g ２ ８０ － ２０ １３ ２ ３４ ８ duet osub l ima t i on o f MoO３ wh i ch wa sunr e a c t ed ３ ６１ ２４ １５ １１ ４ ２８ ５ wi t hCaO． Fo rbo t h mi x t u r e so fMoO３ ＋CandCaO＋ MoO３ ＋C,t her e du c t i ongo e si nt h r e es t e swi t ht he p ２ ２ Expe r ime n t a lpr o c e du r e ( ) s ames t a r t i ngt emp e r a t u r ef o rt hef i r s ts t e I n p ５００℃ ． I s o t he rma le xp e r ime n t swe r ec a r r i e dou ti nac on Ｇ t hec a s eo fMoO３ ＋C mi x t ur e,t hef i r s ts t epc anbe v e n t i on a lMoS i u r n a c e．Thes amp l e mi x t u r e s we r e i ２f n f e r r edt ot hep r oc e s so fMoO３r educ edt oMoO２ by l a c edi nac o rundum c ruc i b l eandt henl owe r edt o c p a rbon．Ther e su l t sa r ei nag r e emen twi t ho t he ri n Ｇ t hec ons t an tt empe r a t u r er eg i ono ft hef u rna c e． Pu r i Ｇ ve s t i t i onswh i chr epo r t edt ha t MoO２ wa st hei n Ｇ ga f i edn i t r ogenwa sus edi nt hef u rna c et ubet oensu r e t e rmed i a t ep r oduc ti nt he p r oc e s so fr educ t i on o f [ , / １０] ani ne r ta tmo sphe r e andt hef l owr a t ewa s５L mi n． MoO３ byc a rbon ．Thes e conds t epi st hesub l ima Ｇ Tempe r a t ur eo fe a ch r e a c t i on wa s me a su r ed by t i ono fMoO３ co r r e spond i ngt oTGcur veo fCaO＋ me anso fap l a t i num rhod i umt he rmo c oup l el o c a t ed MoO３ ．Thet h i rds t ep s t a r t sabove９００ ℃ ,wh i ch us tbe l ow t hec o rundum c ruc i b l e wh i chc on t a i ned j wa sa t t r i bu t edt ot her educ t i ono f MoO２ t o Moo r t hes amp l e．Att heendo fe a chexpe r imen t,XＧ r ay mo l a rb i de． ybdenumc d i f f r a c t i onme a su r emen t( PANa l t i c a l,X′Pe r tPr o) I y nt hec a s eo fCaO＋MoO３ ＋C mi x t u r e,t hef i r s t wa st akent oi den t i f her educ t i onp r oduc t sa tr oom twos yt t age sa r es imi l a rt ot her e a c t i ono f MoO３ ＋C． t empe r a t ur eus i ngCuKαr ad i a t i on． Theobv i ousd i f f e r enc ei si ns t ep ３,f o rl e s s ma s s ( ) Th et h e rmo r a v i m e t r i c T G e x e r i m e n t sw e r e e r Ｇ g p p l os si nt heen t i r er educ t i onp r oc e s s．Th i si sa t t r i bu Ｇ f o rme di nat h e rmo r a v ime t r i ca n a l s i sb a l a n c e( HENVＧ t g y edt ot her e a c t i ono fCaOandMoO３ ．Thef o rma t i on /２)w EN HCT Ｇ １ i t ht h ea c c u r a c f±０ ０ ０ ０１ mg．Al u Ｇ o yo fCaMoO４ s t ab i l i z e s MoO３ and p r even t ssub l ima Ｇ mi nac ruc i b l e so f５mmi ni nn e rd i ame t e ra nd４mmi n t i ono fMoO３ ． h e i twe r eu s e d．Th eTGa n a l s e swe r ec a r r i e dou ti n gh y Ara tmo s r ea ndt h ef l owr a t ewa s４０ mL/mi n．The ３ phe ２ XRDana l s i s y s amp l e swe r ehe a t edi nanon Ｇ i s o t he rma lmodef r om １)CaO＋MoO３ r oomt empe r a t u r eupt o１２００ ℃ a tahe a t i ngr a t eo f Ther e a c t eds amp l e swe r eana l z edbyXRDand y １０ ℃/mi n．The ma s s change s we r er e c o r ded by t hed i f f r a c t i onpa t t e rnsob t a i nedf o rs amp l e sr e a c t ed c ompu t e rpe rs e c ondi nt hep r o c e s so fr e a c t i on． a t７００and９００ ℃ a r eshowni nF i ４．Th i sf i e g gur Tab l e１ Compo s i t i ono fmi x t u r e sandf i na lma s s l o s sa tah e a t i ngr a t eo f１０ ℃/mi n
３ Re s u l t sandDi s c u s s i on
３ １ TGana l s i s y I nF i ３,t h ema s sl o s s e so fCaO＋MoO３,MoO３＋ g
c l e a r l he p r e s enc eo fCaMoO４ ands t r ong y showst aksf o rCaMoO４a t７００ ℃ a swe l la s９００ ℃．The s e pe f i nd i ngsi nd i c a t et ha tt het empe r a t ur eo ff o rma t i on o fCaMoO４ wa sl owe rt hant ha to fe v a r a t i ono fpu r e po
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J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２０
F i ４ X Ｇ r a i f f r a c t i onpa t t e rn sf o rCaOＧMoO３ mi x t u r e s g yd r e a c t e da td i f f e r en tt emp e r a t u r e sf o r３０mi n
MoO３andt hef o rma t i onr a t ewa sh i rt hanevapo Ｇ ghe r a t i onr a t e．Theabove Ｇmen t i onedana l s i sc o n f i r m s y ( t h ep r e v e n t ab l ee f f e c tons ub l ima t i ono fMoO３ s h a r l p y e v a r a t eabo v e７９５℃)byCaO． Thes t a r t i ngt empe r Ｇ po a t u r eo ff o rma t i ono fCaMoO４ obs e r vedbyt hecu r Ｇ r en texpe r imen t si sa l s oi ngoodag r e emen twi t ht ha t [ ] r epo r t edi nl i t e r a t u r e１５ wh i chi s６１０ ℃． ２)MoO３ ＋C Mi x t u r e so f MoO３ a ndCa tv a r i ou st emp e r a t u r e s we r ea l soana l z edby XRD．Ther e su l t sa r eshown y i nF i ５．At８００ ℃ ,s t r ongpe aksf o rMoO３ ,MoO２ g and Mo２C we r ei den t i f i ed．The ma o rspe c i e s we r e j MoO２ andpa r t l r e a c t ed MoO３ ．Thef o rma t i ono f yun MoO２ wa sde t e c t eda si n t e rmed i a t espe c i e sf o rt he r educ t i ono f MoO３ t o Moo r Mo２C．Mo r eove r,a t １０００ ℃ ,Mo２Candami no rpa r to fun r e a c t edMoO２ and MoO３ we r ei den t i f i edandt hema o rspe c i e swa s j r educ t i onp r oduc t Mo２C．Mo r eamoun to f Mo wa s de t e c t eda t１２００ ℃ c ompa r edwi t ht ho s ep r oduc t sa t , l owe rt empe r a t u r e．At１２００ ℃ MoO３ and MoO２ we r eno tde t e c t ed,pr obab l oh i c t i v i t f yduet gha yo MoO３ andt hef a s tr educ t i onr a t eo fMoO２t o Moo r Mo２C． ３)CaO＋MoO３ ＋C I nt hec a s eo fCaO＋ MoO３ ＋C,t her e a c t i on , r oduc t sa r eshowni nF i ６．At８００ ℃ CaMoO４ p g wa sde t e c t edt hes amea smi x t u r e so fCaO＋ MoO３ ． Me anwh i l e,t hepe aksf o r MoO２ ,Mo２C,un r e a c t ed , MoO３ andCaO we r eobs e r ved．Thema i nr educ t i on r oduc t so fCaO＋MoO３ ＋Ca t１０００ ℃ we r e Mo２C p c ompa r edwi t h Moa t１２００ ℃ ,andt ha twa si na c Ｇ c o r danc ewi t hp r ev i oust he rmodynami c sans l i s． I t ys c an be s e en t ha t CaO r e s t r a i ned vo l a t i l i z a t i on o f MoO３ e f f e c t i ve l her educ t i on p r oduc t s we r e y andt t hes amea sMoO３ ＋C;s imu l t aneous l s yCaMoO４ wa t hei n t e rmed i a t epr oduc t．
F i ５ X Ｇ r a i f f r a c t i onpa t t e rn sf o rMoO３ＧC mi x t u r e s g yd r e a c t e da tv a r i ou st emp e r a t u r e sf o r３０mi n
F i ６ X Ｇ r a i f f r a c t i onpa t t e rn sf o rCaOＧMoO３ＧC mi x t u r e s g yd r e a c t e da tv a r i ou st emp e r a t u r e sf o r３０mi n
I s sue１０ Ca r bo t he rmi cReduc t i ono fMoO３f o rDi r e c tAl l oy i ngPr o c e s s
５５
wi t hc a rbondependsont her e a c t i ono fCO２ wi t hso l Ｇ i dc a rbon．I t me anst ha tt her e a c t i ono fCO２ wi t h Dur i ngt hepa s tye a r s,anumbe ro fs t ud i e shave so l i dc a rbonde t e rmi ne st heove r a l lr e a c t i onr a t e． Bu t be enc a r r i ed ou tont hec a rbo t he rmi cr educ t i on o f a th i he rt empe r a t ur e,t her e a c t i ono fCO２ wi t hc a r Ｇ g [ ] me t a lox i de s１６－１９ ．Seve r a l me chan i smshave be en boni sr a t he rqu i ck,soi ti simpos s i b l et ha tt h i sc a r Ｇ r opos edt oexp l a i nt hei n t e r a c t i on o f me t a lox i de bonga p s i f i c a t i onr e a c t i oncon t r o l st heove r a l lr educ Ｇ andc a rbonwi t ht hef o rma t i ono fs o l i dme t a lo rme t Ｇ t i onr a t e．Ther egene r a t edCOsuppo r t st hecon t i nu Ｇ a lc a rb i de,bu ts omeappa r en tc on t r ad i c t i onsi nt he a t i ono ft her educ t i ono fMoO２ ．Thus,i ti sdeduc ed expe r imen t a lr e su l t shavel edt oanumbe ro fd i f f e r Ｇ t ha tt hed i f f u s i ono fg a s e st h r ought hes u r f a c eo fMoO２ en ti n t e r r e t a t i onso ft her e a c t i on me chan i sm． p i st her a t ede t e rmi n i ngs t epi nt hes e conds t ep． I nt h i spape r,abou tt her educ t i ono fMoO３ by Thec a rbo t he rmi cr educ t i onda t awe r er e co rded c a rbon,t he r ea r es omed i f f e r enc e sf r omt hep r ev i ous bycompu t e r,andt heba s i cexp r e s s i onf o rt hei n t e Ｇ s t ud i e sont hec a rbo t he rmi cr educ t i ono f me t a lox Ｇ g r a lme t hodso fana l i so ft he rmoana l t i c a lcur ve s ys y [ ] i de s．Unde rt he Ara tmo sphe r e,t her educ t i on o f a sp r opos edby Coa t s ＧRed f e rn２０ f o rnon Ｇ i so t he rma l MoO３byc a rbonwa sc a r r i edou ta tabove７９５ ℃ ,t h e s t ud i e si sg i venbyEqn ( １３)． éê me l t i ngpo i n to fmo l e numt r i ox i d e,a nd MoO３ wi l l ybd g( α) AR æç ２RT ö÷ ùúú E ê ( ç ÷ － l n ＝ l n １３) １－ ２ êê sub l imesha r l t sme l t i ngpo i n t． p yabovei E çè T E ÷ø úúû RT ëβ Ba s ed on t he t he rma lana l i sr e su l t s,t he whe ys r eg( α)i saf unc t i ono fα,wh i chi st hef r a c t i on who l er educ t i onpr o c e s sc anbede s c r i beda sf o l l ows: r e a c t ed,andA ,E ,R ,βandT a r er e spe c t i ve l t y he １)Att hebeg i nn i ng,MoO３i sr educ edt oMoO２ , r e Ｇ exponen t i a lf a c t o ro f Ar rhen i us equa t i on t he p byc a rbon,andt her e a c t i onp r o c e edsa tt hesu r f a c e a c t i va t i onene r hega scons t an t,t hehe a t i ngr a t e gy,t o fe a ch MoO３r e su l t i ngi nt hef o rma t i ono fc ohe r en t andt heabso l u t et empe r a t ur e．Thef r a c t i onr e a c t edi s MoO２l aye rbe twe en MoO３ andc a rbon．Thef o l l owＧ g : i vena sf o l l ows i ng two p r o c e s s e st ake p l a c es imu l t aneous l h e y:t ( /( W ０ －Wt) W ０ －Wf) α＝ ( １４) f i r s ton ei sd i f f u s i ono foxyg e ni onf r om MoO３ＧMoO２ r ei n i t i a lma s s,ma s sa tt ime whe r eW ０ ,WtandWfa i n t e r f a c et owa r ds MoO２ i n t e r f a c e,andt hes e c ond tandt hef i na lma s s,r e spe c t i ve l y． onei st her e a c t i ono ft h i soxygenwi t hf r e ec a rbona t Fo rt heg e n e r a lc hemi c a lr e a c t i on,１－２RT/E ≈１, t he MoO２ＧCi n t e r f a c e．Th i ss t epi st hes o l i d pha s e t / ) , ( A R E i sc o n s t a n tf o rag i v e nr e a c Ｇ ha ti st os a l n y β bounda r e a c t i onbe twe en MoO３ andc a rbonpa r t i Ｇ t yr , [ ( ) / i ona tac on s t an the a t i ngr a t et hep l o t so fl ng α c l e s,andt her e a c t i onr a t edependsonbo t hpa r t i c l e s T２]ve r sus１/T shou l dbeal i ne a rr e l a t i onsh i p,and s i z eandr e l a t i vep r opo r t i ono ft hes o l i dr e a c t an t s． t hes l opeo ft hel i neg i ve st hea c t i va t i onene r gyE ． ２)Ast her educ t i onp r og r e s s e s,t hepa r t i c l es i z e Thea c t i v a t i one n e r fbo t hr e a c t i on swe r ec a l c u Ｇ gyo o fMoO２i nc r e a s e s,andt hec on t a c t i nga r e abe twe en l /T２]v a t e d,andt hep l o t so fl n[ α) s１/T a r es hown g( MoO３andc a rbonpa r t i c l ede c r e a s e s．Thes o l i dpha s e i /mo nF i ７．Thea c t i v a t i one n e r f５２ ９k J lwa s g gyE o bounda r e a c t i onbe twe en MoO３ andc a rbonpa r t i Ｇ ob yr /mo t a i n e di nt her e a c t i onwi t hou tCaOand５６ ６k J l c l e si snol onge rt hema i np r o c e s s．Thec a rbonga s i Ｇ wi t hCaO． Ba s edont hea r t, i tappe a r si nsup Ｇ gumen f i c a t i onr e a c t i onandt her educ t i ono f MoO２ by CO be c omet hema i nr e a c t i onp r o c e s s． I ns t an t aneousr e Ｇ a c t i ono fMoO２ andCOa tt he MoO２ su r f a c er e su l t s i nt hef o rma t i ono ft h i nc ohe r en tMo２Co r Mol aye r ont hesur f a c eo fMoO２ pa r t i c l e． Duet ot hesub l ima t i oncha r a c t e r i s t i co f MoO３ andi t sh i c t i v i t tt hef i r s ts t ep,t hema s sd i f f u Ｇ gha ya s i onandchemi c a lr e a c t i onbe twe en MoO３ andc a r Ｇ bona r enol onge rt her a t ede t e rmi n i ngs t epi nt he who l er e a c t i on．Att hes e c onds t age,t he po s s i b l e r a t ede t e rmi n i ngs t epsa r et hef o l l owi ngtwopa r t s: １)t hechemi c a lr e a c t i onbe twe en MoO２ andCO;２)
４ Re du c t i onKi n e t i c s
t hed i f f us i ono fga s e st hr ought hesu r f a c eo fMoO２ ． Ther e a c t i ono fCO２ wi t hc a rboni sve r l owbe l ow ys ; , １０００ ℃ me anwh i l et her educ t i ono fme t a lox i de s
F i ７ Ar rh en i u sp l o tf o rr e du c t i ono fMoO３ by g c a r bonwi t ho rwi t hou tCaO
５６
J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２０
r to ft hed i f f us i ono fga s e st hr ought hesu r f a c eo f po MoO２ a sr a t ec on t r o l l i ngs t ep． Ther e su l t so ft he p r e s en ti nve s t i t i on have ga demons t r a t edf e a s i b i l i t fd i r e c ta l l oy i ngbyus eo f yo mo l b d e n u mo x i d e c o n c e n t r a t e s ． M o O c a nb e s t a b i Ｇ y ３ l i z edby mi x i ng w i t hCaO,a ndf o rt h i sr e a s on,a dd i ng CaOa sr aw ma t e r i a li sane f f e c t i vewayt oimp r ove Moy i e l d．Fo rd i r e c ta l l oy i ngbyus eo fmo l ybdenum ox i deconc en t r a t e si nEAFo ri nduc t i onf u rna c e,be Ｇ f o r es t a r t i ngsme l t i ng,mo l i dec onc en Ｇ ybdenum ox t r a t e s mi xed wi t h powde r edc a rbonandl ime we r e l o c a t edi nf urna c ebo t t om,andt hens c r aps t e e land o t he ra l l oy i ng ma t e r i a l swe r eaddedi n t ot hef u rna c e． Ast empe r a t u r er o s e mo l i de s we r er e Ｇ ybdenum ox duc edt omo l rmo l a rb i de．Af t e r ybdenumo ybdenumc t hes c r aps t e e lme l t i ng,mo l a rb i deo rpa r t ybdenumc o fun r educ edmo l i de sc anber educ ede f Ｇ ybdenumox f e c t i ve l t he re l emen t si nl i i ds t e e l． yby manyo qu Howeve r,t he s es t ud i e sf o cusons o l i dr e a c t i on, and on l an be app l i ed t op r e r educ t i on i nt he yc r o c e s so ft empe r a t u r er i s i ng．Fu r t he rs t ud i e sa r e p ne ededt ode t e rmi net hebehav i o ro f MoO３i nl i i d qu s t e e lo rs l ag．
５ Conc l u s i on s
The rmodyn ami c so fCaO＋ MoO３,MoO３ ＋Ca nd CaO＋MoO３ ＋C mi x t u r e swa ss t ud i ed,r e spe c t i ve l y． , Ther e su l t sshowedt ha t wi t ht hedeve l opmen to f r educ t i on,MoO２andCaMoO４appe a r eda st hei n t e r Ｇ med i a t e sandt hef i na lr educ t i onp r oduc t swe r e Mo o r mo l a rb i de．Mi x t u r e so fCaO＋ MoO３ ybdenum c a r euns t ab l eandc ou l dr e a c tt of o rm CaMoO４ be f o r e t heevapo r a t i ono fMoO３ ．Fr omt he s ef i nd i ngs,i ti s c onc l udedt ha tt her educ t i ono fMoO３ wi t hc a rboni n t hep r e s enc eo fCaO p r obab l e su l t si nah i i e l d yr ghy o fMoi ns t e e lmak i ngp r o c e s s． Re a c t i on me chan i sm wa sp r opo s ed and d i s Ｇ cus s edba s edont het he rmog r av ime t r r imen t． yexpe Ther educ t i onr e a c t i ono fMoO３ wi t hc a rbongoe si n Ｇ t otwos t age s．Thef i r s ts t agei nc l ude st hed i r e c tr e Ｇ a c t i on be twe en MoO３ and c a rbon andt hec a rbon s i f i c a t i onr e a c t i on．Thes e c onds t agei st hega s Ｇ s o l Ｇ ga , i dr e a c t i onbe twe enCOandMoO２ andt hed i f f us i on o fga s e st hr ought hesu r f a c eo fMoO２i st her a t ede Ｇ t e rmi n i ngs t ept hr ought heove r a l lr e a c t i on． I nt he c a s eo fCaO＋MoO３ ＋C,t her e a c t i on me chan i smi s s imi l a rt ot her educ t i ono f MoO３ wi t hc a rbon．The on l i f f e r enc ei st hei n t e rmed i a t eCaMoO４ ．Thea c Ｇ yd t i va t i onene r i e so ft he mi x t u r e s wi t ho r wi t hou t g /mo CaO we r ee s t ima t edt obe５６ ６and５２ ９ kJ l, r e spe c t i ve l y．
Re f e r enc e s:
[ １] Ku l i shVP,Go l ov i nLP,B i r l oy i ngo fS t e e lWi t h yukS N．Al Mo l en t r a t e[ J]．Me t a l l ur i s t,１９７３,１６( ６):３９９． ybdenum Conc g [ ２] ChychkoA,TengL,Se e t ha r amanS．MoO３ Evapo r a t i onS t ud Ｇ i e sFr om B i na r t emsTowa r dsCho i c eo fMoPr e cur s o r si n ySys EAF [ J]． S t e e lRe s e a r chI n t e r na t i ona l,２０１０,８１( ９):７８４． [ ３] Sabur iT,Mur a t aH,Suzuk iT,e ta l．OxygenP l a smaI n t e r a c Ｇ t i on sWi t h Mo l e num:Fo rma t i ono fVo l a t i l e Mo l e num Ox Ｇ ybd ybd i d e s[ J]． J ou r n a lo fP l a smaa ndFu s i onRe s e a r c h,２００２,７８( １):３． [ ４] Ki rk ＧOt hme r．Enc l oped i ao fChemi c a lTe chno l ogy [M]． ５ t h yc ed．New Yo rk:Wi l ey Ｇ I n t e r s c i enc e,２００７． [ ５] Kennedy MJ,BevanSC．A Ki ne t i cS t udyo ft heReduc t i ono f Mo l i ox i deby Hyd r ogen [ J]．J our na lo ft heLe s s ybdenum Tr Common Me t a l s,１９７４,３６( １):２３． [ ６] Schu lmeye r W V,Or t ne rH M．Me chan i smso ft he Hyd r ogen Reduc t i ono fMo l i de s[ J]． I n t e r na t i ona lJ our na lo f ybdenum Ox Re f r a c t o r t a l sandHa r d Ma t e r i a l s,２００２,２０( ４):２６１． y Me [ ７] Gup t aC K,J enaP K．Reduc t i ono fMo l i ox i deby ybdenum Tr Al umi num [ J]． J our na lo ft heLe s sCommon Me t a l s,１９６８,１４ ( １):１４８． [ ８] Ki r shenbaum A D,Be a r de l lAJ．The rma lAna l i so ft heRe Ｇ ys a c t i on o f Mo l i ox i de Wi t h Va r i ous Me t a l s[ J]． ybdenum Tr The rmo ch imi c aAc t a,１９７２,４( ３):２３９． [ ９] J amsh i d iK,Abd i z adehH,Hana iK．Me t a l l o t he rmi cReduc t i on o fMoO３ Thr ough Mak i ng Ni ＧMo Al l oysbyt heESR Me t hod [ J]． I n t e r na t i ona lJ our na lo fRe f r a c t o r t a l sandHa r dMa t e Ｇ yMe r i a l s,２００４,２２( ６):２４３． [ １０] Chaudhur r e eSK,Va i dyaV N,e ta l．Ki ne t i c sand yS,Muke j Me chan i smo fCa r bo t he rmi cReduc t i ono fMoO３t oMo２C [ J]． J our na lo fAl l oysandCompounds,１９９７,２６１( １):１０５． [ １１] Manukyan K,Ayd i nyan S,Agha anyan A,e ta l．Re a c t i on j Pa t hwayi nt heMoO３＋Mg＋CRe a c t i veMi x t ur e s[ J]． I n t e r Ｇ na t i ona lJ our na lo f Re f r a c t o r t a l sand Ha r d Ma t e r i a l s, y Me ２０１２,３１:２８． [ １６ t hed． １２] Spe i tJG．Lange ′ sHandbooko fChemi s t r gh y [M]． New Yo rk:McGr awＧHi l l,２００５． [ １３] RaoY K,El ＧRaha i byS K．Di r e c tReduc t i ono fLe adSu l f i de Wi t hCa r bonand L ime:Ef f e c to fCa t a l t s:Pa r tⅠExpe r i Ｇ ys men t a l[ J]．Me t a l l ur i c a land Ma t e r i a l sTr ans a c t i ons,１９８５, g １６B( ３):４６５． [ １４] Ma s s a l sk iT B．B i na r l oyPha s eDi agr ams [M]．２nded． yAl , Oh i o:TheMa t e r i a l sI n f o rma t i onSo c i e t y １９９６． [ １５] Yanushkev i chT M,Zhukov i t sk i iV M．Pha s eDi ag r am o ft he Mo l i ox i de ＧCa l c i um Ox i de Sys t em [ J]．Zhur na l ybdenum Tr Neo r i che sko iKh imi i,１９７３,１８( ８):２２３４ ( i nRus s i an)． gan [ １６] Na i r ne rN A． Sme l t i ngReduc t i ono fI lmen i t eby yang Ma,Wa Ca r boni n Mo l t enP i r on [ J]．Canad i an Me t a l l ur i c a lQua r Ｇ gI g t e r l ３):１６５． y,１９９９,３８( [ １７] RaoY K,ChuangY K．A Phys i c o ＧChemi c a lMode lf o rRe a c Ｇ t i onsBe twe enPa r t i cu l a t eSo l i ds Oc cur r i ng Thr ough Ga s eous I n t e rmed i a t e s—I I．Gene r a lSo l u t i ons [ J]．Chemi c a lEng i ne e r Ｇ i ngSc i enc e,１９７４,２９( ９):１９３３． [ １８] RaoY K．TheKi ne t i c so fReduc t i ono fHema t i t ebyCa r bon [ J]．Me t a l l ur i c a land Ma t e r i a l sTr ans a c t i ons,１９７１,２B( ５): g
１４３９． [ １９] HongL,Sohn H Y,Sano M．Ki ne t i c so fCa r bo t he rmi cRe Ｇ duc t i ono fMagne s i aandZ i ncOx i debyThe rmog r av ime t r i c Ana l i sTe chn i J]．Sc and i nav i anJ our na lo f Me t a l l ur ys que [ gy, ２００３,３２( ３):１７１． [ ２０] Vya z ovk i nS,Wi tC A．Mode l ＧFr e eand Mode l ＧF i t t i ngAp Ｇ gh r oa che st oKi ne t i cAna l i so fI s o t he rma landNon i s o t he rma l p ys Da t a[ J]．The rmo ch imi c aAc t a,１９９９,３４０( １):５３．
JOURNALOFIRON ANDSTEELRESEARCH,INTERNATIONAL２ ０ １ ３,２ ０( １ ０):５ １ Ｇ ５ ６
Ca r bo t he rmi cRe du c t i ono fMoO３f o rDi r e c tAl l o i ngPr o c e s s y ZHU Hang Ｇ Ｇ bang, YANG Ha i Ｇ s en, LUO L i n Ｇ yu, LIZheng gen
( t r a lI r onandS t e e lRe s e a r chI ns t i t u t e,Be i i ng１０００８１,Ch i na) Depa r tmen to fMe t a l l u r i c a lTe chno l ogy,Cen j g Ab s t r a c t:Th et h e rmodyn ami c so fMo ＧOＧCa ndCa ＧMo ＧOＧCs s t emswa ss t ud i e di no r d e rt ound e r s t a ndt h ec a r bo t h e rmi c y r educ t i ono fmo l r i ox i de,andk i ne t i cs t ud i e swe r ea l s oc a r r i edou tbyme anso ft he rmog r av ime t r i cana l s i s ybdenumt y unde ra r tmo sphe r ewi t hahe a t i ngr a t eo f１０ ℃/mi n．Subs e t l e a c t i onp r oduc t sa tva r i oust empe r a t u r e s gona quen y,r ( ) we r ei den t i f i edbyXＧ r ayd i f f r a c t i on XRD andt her e su l t sc on f i rmedt hep r e v i oust he rmodynami c sana l s i s．Me an Ｇ y wh i l e,i twa sf oundt ha ti n t e rmed i a t ep r oduc t sMoO２andCaMoO４appe a r edi nt hep r o c e s so fc a r bo t he rmi cr educ t i on o fMoO３ wi t ho rwi t hou tCaO,wh i chwe r esubs e u e n t l e d u c e dt o M oo rm o l b d e n u mc a r b i d e ． A ne x e r i m e n t a l l q yr y p y de t e rmi nedr e a c t i onme chan i sm wa sp r opo s edandd i s cus s ed．Ther educ t i onr e a c t i ono f MoO３ wi t hc a r bonc ou l dbe d i v i dedi n t otwos t age s．Thef i r s ts t agei nc l ude st hed i r e c tr e a c t i onbe twe enMoO３andc a r bonandt hec a r bonga s i f i c a Ｇ t i onr e a c t i on．Thes e c onds t agei st hega s Ｇ s o l i dr e a c t i onbe twe enCOand MoO２ ,andt hed i f f us i ono fga s e st hr ough t hesu r f a c eo fMoO２ de t e rmi ne st heove r a l lr e a c t i onr a t e．Thea c t i va t i onene r i e so ft he mi x t u r e swi t ho rwi t hou t g /mo CaO we r ee s t ima t edt obe５６ ６and５２ ９kJ l,r e spe c t i ve l ． y Ke r d s:c a r bo t he rmi cr educ t i on;mo l r i ox i de;s t ab i l i z i ng;c a l c i umox i de ybdenumt ywo
Fe r r omo l l l oyi s wi de l edi nt he ybdenum a y us r oduc t i ono fs t e e l sc on t a i n i ng mo l I nr e Ｇ p ybdenum． c en tye a r s,me t a l l u r i s t sa r e t r i n t ou s em o l b d e Ｇ g y g y num ox i dec onc en t r a t e sa st heagen ti ns t e e lmak i ng [ ] r o c e s s１－２ ,s i nc ed i r e c ta l l oy i ngbyus eo f mo l Ｇ p yb denumox i dec onc en t r a t e sha sc l e a re c onomi csupe r i Ｇ o r i t l i dec onc en t r a t e s me l ti n y and mo ybdenum ox s t e e lba t hr ap i d l ompa r edwi t hf e r r omo l yc ybdenum． Thema i npr ob l emf o rd i r e c ta l l oy i ngwi t h mo l Ｇ ybde numox i de si st hesub l ima t i ono fmo l r i ox Ｇ ybdenumt i de,wh i chl e adst oal ow y i e l do f Moi nt hes t e e l Ｇ mak i ngp r oc e s s． Seve r a li nve s t i t i onshavebe enr e Ｇ ga r t edt ha ta l ka l i sanda l ka l i nee a r t hox i de sa swe l l po a sc a rbona t e sc anr e s t r a i nt h ee v a r a t i ono fmo l e Ｇ po ybd [ ] numt r i ox i d e,s u c ha s,CaO,MgO,CaCO３,e t c３－４ , a ndt her e a s oni st h ef o rma t i ono fmo l a t e sa ta bou t ybd ６００ ℃ wh i chi sf a rbe l owc l e a revapo r a t i onpo i n to f mo l r i ox i de．The s e mo l t e sa r es t ab l e ybdenumt ybda a ts t e e lmak i ng t empe r a t u r e and c an be e a s i l e Ｇ yr duc edbyr e l evan tr educ t an ti ns t e e lmak i ngp r o c e s s． I nt hep a s t,v a r i ou s me t hod st or e du c e mo l e Ｇ ybd , , numt r i ox i d ewe r ep r opo s e ds u c ha s hyd r og e nr e du c Ｇ [ ] [ ] t i on５－６ ,me t a l l o t h e rmi cr e du c t i on７－９ a ndc a r bo t h e r Ｇ [ ] mi cr e du c t i on１０ ．Tho s eme t hod sa r ec ommon l dop t e d ya
t op r oduc e mo l rf e r r omo l r ybdenum o ybdenum．Fo d i r e c ta l l oy i ngi ne l e c t r i ca r cf urna c e( EAF),mo Ｇ l i deconc en t r a t e s mi xed wi t hc a rbono r ybdenum ox s i l i conme t a lands c r aps t e e lwe r el oc a t edi nf urna c e bo t t om．Mo l e num ox i d e swe r ep r e Ｇ r e du c e da st emＧ ybd e r a t u r er o s e,bu tmo s timpo r t an t l l Ｇ p y,mo ybdenumox i de sc anber educ ede f f e c t i ve l t he re l e Ｇ y by many o men t si nl i i ds t e e la f t e rt hes c r aps t e e lme l t i ng． qu The pur eo ft he p r e s en ts t udyi st o ga i n pos mo r eunde r s t and i ngo ft hec a rbo t he rmi cr educ t i ono f MoO３ ,ande f f e c to fCaOonr e s t r a i n i ngevapo r a t i on o fMoO３i sa l sod i s cus s ed．
１ Th e rmodynami c s
The ma i n componen t so f mo l i de ybdenum ox conc en t r a t ea r eMoO３and MoO２ ．MoO３c anbee a s i Ｇ [ ] l educ edt oMoO２ byc a rbona t５００－６００ ℃ １１ be Ｇ yr c aus eo fi t sh i c t i v i t e a c t i onc anbewr i t Ｇ gha y．Ther : t ena sf o l l ows ( ２MoO３ ＋C＝２MoO２ ＋CO２( １) g) Cons equen t l her educ t i ono fMoO３ byc a rbon y,t si ntwos t eps,r educ t i ono fMoO３t o MoO２ ,f o r goe , t hef i r s ts t ep andr educ t i ono fMoO２t o Moo rmo Ｇ l a rb i de,f o rt hes e conds t ep． ybdenumc
Founda t i onI t em: I t em Spons o r edbySc i enc eandTe chno l ogyAch i evemen tSpe c i a lFounda t i ono fJ i angsuPr ov i nc eo fCh i na ( BA２０１０１３９) B i o r aphy: ZHU Hang Ｇ １９８４—),Ma l e,Do c t o r; E Ｇma i l:hangyu_zhu＠a l i c om; Re c e i v e dDa t e:Ap r i l２６,２０１２ yu( yun g
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J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２０
I nt hepr e s enc eo fCaO,t hechemi c a lc omb i na Ｇ t i onbe twe enMoO３andCaOo c cu r sa tal owt empe r Ｇ a t u r e,s imi l a r l ot heh i c t i v i t f MoO３ , y duet gha yo andt her e a c t i onc anbewr i t t ena sf o l l ows: ( MoO３ ＋CaO＝CaMoO４ ２)
Equ i l i br i umr e l a t i onsi nt hec a rbo t he rmi cr educ Ｇ t i ono fMoO３ wi t ho rwi t hou tCaOa r ec omp l ex,due t ot heva r i ousr e a c t i onpa t hsandal a r ro f genumbe r educ t i onp r oduc t si n Ca ＧMo ＧOＧCs t em．Thef o l Ｇ ys l owi ngt he rmodynami cana l i s wa sc a r r i edou tby ys [ ] us i ngr e l evan tt he rmodynami cda t a１２ ．
１ １ Mo ＧOＧCs s t em y I ti swe l la c c ep t edt ha tc a rbo t he rmi cr educ t i on o f me t a lox i de si nc l ude stwopa r t s:i nd i r e c tr educ Ｇ t i onandt hec a rbon ga s i f i c a t i onr e a c t i on．Chemi c a l : r e a c t i onequa t i onsa r er ep r e s en t eda sf o l l ows ( MO＋CO( ３) g)＝M＋CO２( g) ( CO２( ４) g)＋C＝２CO( g)
whe r eMOi s me t a lox i deand Mi sr educ t i onp r od Ｇ uc t．CO２ ex i s t sa sani n t e rmed i a t ep r oduc t．Ca rbon c onsumedt hei nd i r e c tr educ t i onp r oduc t( CO２ )and ( ) t henwa st r ans f o rmedt or educ t an t CO ．Gene r a l l y, t hema i nr educ i ngagen twa sCOi nt hep r o c e s so fr e Ｇ [ ] duc t i ono fme t a lox i de sabove７００ ℃ １３ ． [ ] Fr om Mo ＧCb i na r s ed i ag r am １４ ,t hes t ab l e ypha r educ t i onspe c i e si nMoO２ＧCs t ema r eMo,Mo２C, ys MoC,r e spe c t i ve l hec a rbo t he rmi cr educ t i on y,andt o fMoO２shou l dp r o c e edbyt hef o l l owi ngr e a c t i ons: ( MoO２ ＋２CO( ５) g)＝Mo＋２CO２( g) ) / / ( ) ( MoO２ ＋３CO( ＝１ ２ M o C＋５ ２ C O ６) g ２ ２ g ( ) ( ) ( MoO２ ＋４CO g ＝MoC＋３CO２ g ７) ( Mo＋CO( ８) g)＝１/２Mo２C＋１/２CO２( g) ( ) ( ) ( Mo２C＋２CO g ＝２MoC＋CO２ g ９)
F i １ Pr e domi nanc e Ｇ a r e ad i a r amf o r g g c a r bo t h e rmi cr e du c t i ono fMoO２
s imu l t an e ou se i l i b r i um po i n tamong MoO２, Mo２C, qu , and Moi s１０６０ ℃ andi tc anbes e ent ha tMocou l d bep r oduc edove r１０６０ ℃ unde rc e r t a i nCOr a t i o． １ ２ Ca ＧMo ＧOＧCs s t em y As imi l a rd i ag r amf o rc a rbo t he rmi cr educ t i ono f CaMoO４i sshowni nF i ２．Ther e l evan tr e a c t i ons g a r ep l o t t ed: CaMoO４ ＋３CO( １０) g)＝Mo＋CaO＋３CO２( g) ( ) / CaMoO４ ＋４CO( ＝１ ２ M o C＋C a O＋ g ２ ( ７/２CO２( １１) g) CaMoO４ ＋５CO( １２) g)＝MoC＋CaO＋４CO２( g) ( , L i ket he Mo ＧOＧCs s t e m M o Cc o u l db e r o Ｇ y p ２
duc edi nt het empe r a t ur er angeo f８２０t o１２００ ℃ a t ０ １ MPa,andCaMoO４ c anb er educ edt o Moabove １２００ ℃． I nt h i ss t udy,expe r imen t shavebe enc a r r i ed ou tt or e s e a r cht hec a rbo t he rmi cr educ t i ono fMoO３ wi t ho rwi t hou tCaO．
andt hec a rbonga s i f i c a t i onr e a c t i onr e f e r r edt or e a c Ｇ t i on ( ４)． Thep r e domi n a n c e Ｇ a r e ad i a r amo fc a r bo t h e rmi cr e Ｇ g du c t i ono fMoO２i ss howni nF i １,a ndt h ee i l i b r i um g qu COr a t i of o rt hec a rbonga s i f i c a t i onr e a c t i oni sa l s o , i n c l ud e di nt h ef i r e wh e r e PCO ＋PCO２ ＝０ １ MPa gu wa sc on s i d e r e da ndt h ea c t i v i t fc a r boni se a lt o１． yo qu Thus,a t０ １ MPa,t her i to ft h i sl i nei st her e Ｇ gh , , duc t i onr eg i on andi nt h i sa r e a MoO２ c anber e Ｇ duc edt o Moo rmo l a rb i debyCO．Att he ybdenumc F i ２ Pr e domi nanc e Ｇ a r e ad i a r amf o r g g s amet ime,c a rbonex i s t si nt hel e f tr eg i onwh i chi s c a r bo t h e rmi cr e du c t i ono fCaMoO４ t heox i da t i onz one．F i １showst ha ts imu l t aneous g equ i l i br i um among MoO２ ,C,and MoC o c cu r sa t ２ Ex e r imen t a l p ６００ ℃ ,wh i ch me anst ha t MoO２ c anber educ edby c a rbonove rt h i st empe r a t u r et o MoCon l nana r Ｇ ２ yi １ Ma t e r i a l s r owr eg i on ( ６００－６５０ ℃ )．Ove r６５０ ℃ ,t her educ Ｇ Mo l e numt r i ox i d e,c a l c i umox i d eanda c t i v a t e d ybd t i onpr oduc twi l lbeMo２Cwh i chi smo r es t ab l e．The c a r bon we r eus eda sr aw ma t e r i a l s．Ca l c i um ox i de
I s sue１０ Ca r bo t he rmi cReduc t i ono fMoO３f o rDi r e c tAl l oy i ngPr o c e s s
r s( １５０μm,９９％ )we r ep r ehe a t eda t９００ ℃ powde f o r１２ht or emover e s i dua lH２OandCaCO３ ．Mo l Ｇ yb ( denumt r i ox i de s pa r t i c l es i z e －１５０and ＋１０６μm, ９９％ )we r ed r i eda t２００ ℃f o rabou t１２h．Ac t i va t ed c a rbon (－７５and４８μm,f i xedc a rbon９２ １％ ,pu r i Ｇ ) t i rt han９９ ５％ we r eus eda sr educ i ngagen t． yh ghe The s epowde r s we r eana l t i c a l l r eandsupp l i ed y ypu byS i nopha rm Chemi c a lRe agen tBe i i ngCo ,Lt d． j Samp l e mi x t u r e swe r ep r epa r edbyt ho r ough l y mi x i ngi na mo r t a r．Mo l r i ox i deanda c t i Ｇ ybdenumt , va t edc a rbonwe r emi xeda tmo l a rr a t i oo f１∶３ and t hemo l a rr a t i oo f MoO３ ∶CaO∶C wa s１∶１∶３． Thecompos i t i ono fmi x t u r e sandf i na lma s sl o s si n t hep r e s en ts t udya r eshowni nTab l e１．
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F i ３ Ma s schang e sf o rr e du c t i ono f g MoO３ wi t ho rwi t hou tCaO
Cand CaO＋ MoO３ ＋C mi x t ur e si na r tmos Ｇ gona r ea tt hehe a t i ngr a t eo f１０ ℃/mi na r ep r e s en t ed． phe I tc anbeobs e r vedt ha tt empe r a t ur eha save r i Ｇ ys g w MoO３/ wCaO/ wC/ Mi x t ur e F i na lma s s No n i f i c an ti n f l uenc eont her e a c t i on． /mg /％ ma s s l o s s ％ ％ ％ F o rC a O＋ M o O t h e r ei sas l i tde c r e a s ei n gh ３, １ ７２ ２８ － ８ ２ ９ ７ m a s s l o s s i nt h e t e m e r a t u r er a n eo f７ ５ ０t o９ ０ ０ ℃ p g ２ ８０ － ２０ １３ ２ ３４ ８ duet osub l ima t i on o f MoO３ wh i ch wa sunr e a c t ed ３ ６１ ２４ １５ １１ ４ ２８ ５ wi t hCaO． Fo rbo t h mi x t u r e so fMoO３ ＋CandCaO＋ MoO３ ＋C,t her e du c t i ongo e si nt h r e es t e swi t ht he p ２ ２ Expe r ime n t a lpr o c e du r e ( ) s ames t a r t i ngt emp e r a t u r ef o rt hef i r s ts t e I n p ５００℃ ． I s o t he rma le xp e r ime n t swe r ec a r r i e dou ti nac on Ｇ t hec a s eo fMoO３ ＋C mi x t ur e,t hef i r s ts t epc anbe v e n t i on a lMoS i u r n a c e．Thes amp l e mi x t u r e s we r e i ２f n f e r r edt ot hep r oc e s so fMoO３r educ edt oMoO２ by l a c edi nac o rundum c ruc i b l eandt henl owe r edt o c p a rbon．Ther e su l t sa r ei nag r e emen twi t ho t he ri n Ｇ t hec ons t an tt empe r a t u r er eg i ono ft hef u rna c e． Pu r i Ｇ ve s t i t i onswh i chr epo r t edt ha t MoO２ wa st hei n Ｇ ga f i edn i t r ogenwa sus edi nt hef u rna c et ubet oensu r e t e rmed i a t ep r oduc ti nt he p r oc e s so fr educ t i on o f [ , / １０] ani ne r ta tmo sphe r e andt hef l owr a t ewa s５L mi n． MoO３ byc a rbon ．Thes e conds t epi st hesub l ima Ｇ Tempe r a t ur eo fe a ch r e a c t i on wa s me a su r ed by t i ono fMoO３ co r r e spond i ngt oTGcur veo fCaO＋ me anso fap l a t i num rhod i umt he rmo c oup l el o c a t ed MoO３ ．Thet h i rds t ep s t a r t sabove９００ ℃ ,wh i ch us tbe l ow t hec o rundum c ruc i b l e wh i chc on t a i ned j wa sa t t r i bu t edt ot her educ t i ono f MoO２ t o Moo r t hes amp l e．Att heendo fe a chexpe r imen t,XＧ r ay mo l a rb i de． ybdenumc d i f f r a c t i onme a su r emen t( PANa l t i c a l,X′Pe r tPr o) I y nt hec a s eo fCaO＋MoO３ ＋C mi x t u r e,t hef i r s t wa st akent oi den t i f her educ t i onp r oduc t sa tr oom twos yt t age sa r es imi l a rt ot her e a c t i ono f MoO３ ＋C． t empe r a t ur eus i ngCuKαr ad i a t i on． Theobv i ousd i f f e r enc ei si ns t ep ３,f o rl e s s ma s s ( ) Th et h e rmo r a v i m e t r i c T G e x e r i m e n t sw e r e e r Ｇ g p p l os si nt heen t i r er educ t i onp r oc e s s．Th i si sa t t r i bu Ｇ f o rme di nat h e rmo r a v ime t r i ca n a l s i sb a l a n c e( HENVＧ t g y edt ot her e a c t i ono fCaOandMoO３ ．Thef o rma t i on /２)w EN HCT Ｇ １ i t ht h ea c c u r a c f±０ ０ ０ ０１ mg．Al u Ｇ o yo fCaMoO４ s t ab i l i z e s MoO３ and p r even t ssub l ima Ｇ mi nac ruc i b l e so f５mmi ni nn e rd i ame t e ra nd４mmi n t i ono fMoO３ ． h e i twe r eu s e d．Th eTGa n a l s e swe r ec a r r i e dou ti n gh y Ara tmo s r ea ndt h ef l owr a t ewa s４０ mL/mi n．The ３ phe ２ XRDana l s i s y s amp l e swe r ehe a t edi nanon Ｇ i s o t he rma lmodef r om １)CaO＋MoO３ r oomt empe r a t u r eupt o１２００ ℃ a tahe a t i ngr a t eo f Ther e a c t eds amp l e swe r eana l z edbyXRDand y １０ ℃/mi n．The ma s s change s we r er e c o r ded by t hed i f f r a c t i onpa t t e rnsob t a i nedf o rs amp l e sr e a c t ed c ompu t e rpe rs e c ondi nt hep r o c e s so fr e a c t i on． a t７００and９００ ℃ a r eshowni nF i ４．Th i sf i e g gur Tab l e１ Compo s i t i ono fmi x t u r e sandf i na lma s s l o s sa tah e a t i ngr a t eo f１０ ℃/mi n
３ Re s u l t sandDi s c u s s i on
３ １ TGana l s i s y I nF i ３,t h ema s sl o s s e so fCaO＋MoO３,MoO３＋ g
c l e a r l he p r e s enc eo fCaMoO４ ands t r ong y showst aksf o rCaMoO４a t７００ ℃ a swe l la s９００ ℃．The s e pe f i nd i ngsi nd i c a t et ha tt het empe r a t ur eo ff o rma t i on o fCaMoO４ wa sl owe rt hant ha to fe v a r a t i ono fpu r e po
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J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２０
F i ４ X Ｇ r a i f f r a c t i onpa t t e rn sf o rCaOＧMoO３ mi x t u r e s g yd r e a c t e da td i f f e r en tt emp e r a t u r e sf o r３０mi n
MoO３andt hef o rma t i onr a t ewa sh i rt hanevapo Ｇ ghe r a t i onr a t e．Theabove Ｇmen t i onedana l s i sc o n f i r m s y ( t h ep r e v e n t ab l ee f f e c tons ub l ima t i ono fMoO３ s h a r l p y e v a r a t eabo v e７９５℃)byCaO． Thes t a r t i ngt empe r Ｇ po a t u r eo ff o rma t i ono fCaMoO４ obs e r vedbyt hecu r Ｇ r en texpe r imen t si sa l s oi ngoodag r e emen twi t ht ha t [ ] r epo r t edi nl i t e r a t u r e１５ wh i chi s６１０ ℃． ２)MoO３ ＋C Mi x t u r e so f MoO３ a ndCa tv a r i ou st emp e r a t u r e s we r ea l soana l z edby XRD．Ther e su l t sa r eshown y i nF i ５．At８００ ℃ ,s t r ongpe aksf o rMoO３ ,MoO２ g and Mo２C we r ei den t i f i ed．The ma o rspe c i e s we r e j MoO２ andpa r t l r e a c t ed MoO３ ．Thef o rma t i ono f yun MoO２ wa sde t e c t eda si n t e rmed i a t espe c i e sf o rt he r educ t i ono f MoO３ t o Moo r Mo２C．Mo r eove r,a t １０００ ℃ ,Mo２Candami no rpa r to fun r e a c t edMoO２ and MoO３ we r ei den t i f i edandt hema o rspe c i e swa s j r educ t i onp r oduc t Mo２C．Mo r eamoun to f Mo wa s de t e c t eda t１２００ ℃ c ompa r edwi t ht ho s ep r oduc t sa t , l owe rt empe r a t u r e．At１２００ ℃ MoO３ and MoO２ we r eno tde t e c t ed,pr obab l oh i c t i v i t f yduet gha yo MoO３ andt hef a s tr educ t i onr a t eo fMoO２t o Moo r Mo２C． ３)CaO＋MoO３ ＋C I nt hec a s eo fCaO＋ MoO３ ＋C,t her e a c t i on , r oduc t sa r eshowni nF i ６．At８００ ℃ CaMoO４ p g wa sde t e c t edt hes amea smi x t u r e so fCaO＋ MoO３ ． Me anwh i l e,t hepe aksf o r MoO２ ,Mo２C,un r e a c t ed , MoO３ andCaO we r eobs e r ved．Thema i nr educ t i on r oduc t so fCaO＋MoO３ ＋Ca t１０００ ℃ we r e Mo２C p c ompa r edwi t h Moa t１２００ ℃ ,andt ha twa si na c Ｇ c o r danc ewi t hp r ev i oust he rmodynami c sans l i s． I t ys c an be s e en t ha t CaO r e s t r a i ned vo l a t i l i z a t i on o f MoO３ e f f e c t i ve l her educ t i on p r oduc t s we r e y andt t hes amea sMoO３ ＋C;s imu l t aneous l s yCaMoO４ wa t hei n t e rmed i a t epr oduc t．
F i ５ X Ｇ r a i f f r a c t i onpa t t e rn sf o rMoO３ＧC mi x t u r e s g yd r e a c t e da tv a r i ou st emp e r a t u r e sf o r３０mi n
F i ６ X Ｇ r a i f f r a c t i onpa t t e rn sf o rCaOＧMoO３ＧC mi x t u r e s g yd r e a c t e da tv a r i ou st emp e r a t u r e sf o r３０mi n
I s sue１０ Ca r bo t he rmi cReduc t i ono fMoO３f o rDi r e c tAl l oy i ngPr o c e s s
５５
wi t hc a rbondependsont her e a c t i ono fCO２ wi t hso l Ｇ i dc a rbon．I t me anst ha tt her e a c t i ono fCO２ wi t h Dur i ngt hepa s tye a r s,anumbe ro fs t ud i e shave so l i dc a rbonde t e rmi ne st heove r a l lr e a c t i onr a t e． Bu t be enc a r r i ed ou tont hec a rbo t he rmi cr educ t i on o f a th i he rt empe r a t ur e,t her e a c t i ono fCO２ wi t hc a r Ｇ g [ ] me t a lox i de s１６－１９ ．Seve r a l me chan i smshave be en boni sr a t he rqu i ck,soi ti simpos s i b l et ha tt h i sc a r Ｇ r opos edt oexp l a i nt hei n t e r a c t i on o f me t a lox i de bonga p s i f i c a t i onr e a c t i oncon t r o l st heove r a l lr educ Ｇ andc a rbonwi t ht hef o rma t i ono fs o l i dme t a lo rme t Ｇ t i onr a t e．Ther egene r a t edCOsuppo r t st hecon t i nu Ｇ a lc a rb i de,bu ts omeappa r en tc on t r ad i c t i onsi nt he a t i ono ft her educ t i ono fMoO２ ．Thus,i ti sdeduc ed expe r imen t a lr e su l t shavel edt oanumbe ro fd i f f e r Ｇ t ha tt hed i f f u s i ono fg a s e st h r ought hes u r f a c eo fMoO２ en ti n t e r r e t a t i onso ft her e a c t i on me chan i sm． p i st her a t ede t e rmi n i ngs t epi nt hes e conds t ep． I nt h i spape r,abou tt her educ t i ono fMoO３ by Thec a rbo t he rmi cr educ t i onda t awe r er e co rded c a rbon,t he r ea r es omed i f f e r enc e sf r omt hep r ev i ous bycompu t e r,andt heba s i cexp r e s s i onf o rt hei n t e Ｇ s t ud i e sont hec a rbo t he rmi cr educ t i ono f me t a lox Ｇ g r a lme t hodso fana l i so ft he rmoana l t i c a lcur ve s ys y [ ] i de s．Unde rt he Ara tmo sphe r e,t her educ t i on o f a sp r opos edby Coa t s ＧRed f e rn２０ f o rnon Ｇ i so t he rma l MoO３byc a rbonwa sc a r r i edou ta tabove７９５ ℃ ,t h e s t ud i e si sg i venbyEqn ( １３)． éê me l t i ngpo i n to fmo l e numt r i ox i d e,a nd MoO３ wi l l ybd g( α) AR æç ２RT ö÷ ùúú E ê ( ç ÷ － l n ＝ l n １３) １－ ２ êê sub l imesha r l t sme l t i ngpo i n t． p yabovei E çè T E ÷ø úúû RT ëβ Ba s ed on t he t he rma lana l i sr e su l t s,t he whe ys r eg( α)i saf unc t i ono fα,wh i chi st hef r a c t i on who l er educ t i onpr o c e s sc anbede s c r i beda sf o l l ows: r e a c t ed,andA ,E ,R ,βandT a r er e spe c t i ve l t y he １)Att hebeg i nn i ng,MoO３i sr educ edt oMoO２ , r e Ｇ exponen t i a lf a c t o ro f Ar rhen i us equa t i on t he p byc a rbon,andt her e a c t i onp r o c e edsa tt hesu r f a c e a c t i va t i onene r hega scons t an t,t hehe a t i ngr a t e gy,t o fe a ch MoO３r e su l t i ngi nt hef o rma t i ono fc ohe r en t andt heabso l u t et empe r a t ur e．Thef r a c t i onr e a c t edi s MoO２l aye rbe twe en MoO３ andc a rbon．Thef o l l owＧ g : i vena sf o l l ows i ng two p r o c e s s e st ake p l a c es imu l t aneous l h e y:t ( /( W ０ －Wt) W ０ －Wf) α＝ ( １４) f i r s ton ei sd i f f u s i ono foxyg e ni onf r om MoO３ＧMoO２ r ei n i t i a lma s s,ma s sa tt ime whe r eW ０ ,WtandWfa i n t e r f a c et owa r ds MoO２ i n t e r f a c e,andt hes e c ond tandt hef i na lma s s,r e spe c t i ve l y． onei st her e a c t i ono ft h i soxygenwi t hf r e ec a rbona t Fo rt heg e n e r a lc hemi c a lr e a c t i on,１－２RT/E ≈１, t he MoO２ＧCi n t e r f a c e．Th i ss t epi st hes o l i d pha s e t / ) , ( A R E i sc o n s t a n tf o rag i v e nr e a c Ｇ ha ti st os a l n y β bounda r e a c t i onbe twe en MoO３ andc a rbonpa r t i Ｇ t yr , [ ( ) / i ona tac on s t an the a t i ngr a t et hep l o t so fl ng α c l e s,andt her e a c t i onr a t edependsonbo t hpa r t i c l e s T２]ve r sus１/T shou l dbeal i ne a rr e l a t i onsh i p,and s i z eandr e l a t i vep r opo r t i ono ft hes o l i dr e a c t an t s． t hes l opeo ft hel i neg i ve st hea c t i va t i onene r gyE ． ２)Ast her educ t i onp r og r e s s e s,t hepa r t i c l es i z e Thea c t i v a t i one n e r fbo t hr e a c t i on swe r ec a l c u Ｇ gyo o fMoO２i nc r e a s e s,andt hec on t a c t i nga r e abe twe en l /T２]v a t e d,andt hep l o t so fl n[ α) s１/T a r es hown g( MoO３andc a rbonpa r t i c l ede c r e a s e s．Thes o l i dpha s e i /mo nF i ７．Thea c t i v a t i one n e r f５２ ９k J lwa s g gyE o bounda r e a c t i onbe twe en MoO３ andc a rbonpa r t i Ｇ ob yr /mo t a i n e di nt her e a c t i onwi t hou tCaOand５６ ６k J l c l e si snol onge rt hema i np r o c e s s．Thec a rbonga s i Ｇ wi t hCaO． Ba s edont hea r t, i tappe a r si nsup Ｇ gumen f i c a t i onr e a c t i onandt her educ t i ono f MoO２ by CO be c omet hema i nr e a c t i onp r o c e s s． I ns t an t aneousr e Ｇ a c t i ono fMoO２ andCOa tt he MoO２ su r f a c er e su l t s i nt hef o rma t i ono ft h i nc ohe r en tMo２Co r Mol aye r ont hesur f a c eo fMoO２ pa r t i c l e． Duet ot hesub l ima t i oncha r a c t e r i s t i co f MoO３ andi t sh i c t i v i t tt hef i r s ts t ep,t hema s sd i f f u Ｇ gha ya s i onandchemi c a lr e a c t i onbe twe en MoO３ andc a r Ｇ bona r enol onge rt her a t ede t e rmi n i ngs t epi nt he who l er e a c t i on．Att hes e c onds t age,t he po s s i b l e r a t ede t e rmi n i ngs t epsa r et hef o l l owi ngtwopa r t s: １)t hechemi c a lr e a c t i onbe twe en MoO２ andCO;２)
４ Re du c t i onKi n e t i c s
t hed i f f us i ono fga s e st hr ought hesu r f a c eo fMoO２ ． Ther e a c t i ono fCO２ wi t hc a rboni sve r l owbe l ow ys ; , １０００ ℃ me anwh i l et her educ t i ono fme t a lox i de s
F i ７ Ar rh en i u sp l o tf o rr e du c t i ono fMoO３ by g c a r bonwi t ho rwi t hou tCaO
５６
J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l Vo l ２０
r to ft hed i f f us i ono fga s e st hr ought hesu r f a c eo f po MoO２ a sr a t ec on t r o l l i ngs t ep． Ther e su l t so ft he p r e s en ti nve s t i t i on have ga demons t r a t edf e a s i b i l i t fd i r e c ta l l oy i ngbyus eo f yo mo l b d e n u mo x i d e c o n c e n t r a t e s ． M o O c a nb e s t a b i Ｇ y ３ l i z edby mi x i ng w i t hCaO,a ndf o rt h i sr e a s on,a dd i ng CaOa sr aw ma t e r i a li sane f f e c t i vewayt oimp r ove Moy i e l d．Fo rd i r e c ta l l oy i ngbyus eo fmo l ybdenum ox i deconc en t r a t e si nEAFo ri nduc t i onf u rna c e,be Ｇ f o r es t a r t i ngsme l t i ng,mo l i dec onc en Ｇ ybdenum ox t r a t e s mi xed wi t h powde r edc a rbonandl ime we r e l o c a t edi nf urna c ebo t t om,andt hens c r aps t e e land o t he ra l l oy i ng ma t e r i a l swe r eaddedi n t ot hef u rna c e． Ast empe r a t u r er o s e mo l i de s we r er e Ｇ ybdenum ox duc edt omo l rmo l a rb i de．Af t e r ybdenumo ybdenumc t hes c r aps t e e lme l t i ng,mo l a rb i deo rpa r t ybdenumc o fun r educ edmo l i de sc anber educ ede f Ｇ ybdenumox f e c t i ve l t he re l emen t si nl i i ds t e e l． yby manyo qu Howeve r,t he s es t ud i e sf o cusons o l i dr e a c t i on, and on l an be app l i ed t op r e r educ t i on i nt he yc r o c e s so ft empe r a t u r er i s i ng．Fu r t he rs t ud i e sa r e p ne ededt ode t e rmi net hebehav i o ro f MoO３i nl i i d qu s t e e lo rs l ag．
５ Conc l u s i on s
The rmodyn ami c so fCaO＋ MoO３,MoO３ ＋Ca nd CaO＋MoO３ ＋C mi x t u r e swa ss t ud i ed,r e spe c t i ve l y． , Ther e su l t sshowedt ha t wi t ht hedeve l opmen to f r educ t i on,MoO２andCaMoO４appe a r eda st hei n t e r Ｇ med i a t e sandt hef i na lr educ t i onp r oduc t swe r e Mo o r mo l a rb i de．Mi x t u r e so fCaO＋ MoO３ ybdenum c a r euns t ab l eandc ou l dr e a c tt of o rm CaMoO４ be f o r e t heevapo r a t i ono fMoO３ ．Fr omt he s ef i nd i ngs,i ti s c onc l udedt ha tt her educ t i ono fMoO３ wi t hc a rboni n t hep r e s enc eo fCaO p r obab l e su l t si nah i i e l d yr ghy o fMoi ns t e e lmak i ngp r o c e s s． Re a c t i on me chan i sm wa sp r opo s ed and d i s Ｇ cus s edba s edont het he rmog r av ime t r r imen t． yexpe Ther educ t i onr e a c t i ono fMoO３ wi t hc a rbongoe si n Ｇ t otwos t age s．Thef i r s ts t agei nc l ude st hed i r e c tr e Ｇ a c t i on be twe en MoO３ and c a rbon andt hec a rbon s i f i c a t i onr e a c t i on．Thes e c onds t agei st hega s Ｇ s o l Ｇ ga , i dr e a c t i onbe twe enCOandMoO２ andt hed i f f us i on o fga s e st hr ought hesu r f a c eo fMoO２i st her a t ede Ｇ t e rmi n i ngs t ept hr ought heove r a l lr e a c t i on． I nt he c a s eo fCaO＋MoO３ ＋C,t her e a c t i on me chan i smi s s imi l a rt ot her educ t i ono f MoO３ wi t hc a rbon．The on l i f f e r enc ei st hei n t e rmed i a t eCaMoO４ ．Thea c Ｇ yd t i va t i onene r i e so ft he mi x t u r e s wi t ho r wi t hou t g /mo CaO we r ee s t ima t edt obe５６ ６and５２ ９ kJ l, r e spe c t i ve l y．
Re f e r enc e s:
[ １] Ku l i shVP,Go l ov i nLP,B i r l oy i ngo fS t e e lWi t h yukS N．Al Mo l en t r a t e[ J]．Me t a l l ur i s t,１９７３,１６( ６):３９９． ybdenum Conc g [ ２] ChychkoA,TengL,Se e t ha r amanS．MoO３ Evapo r a t i onS t ud Ｇ i e sFr om B i na r t emsTowa r dsCho i c eo fMoPr e cur s o r si n ySys EAF [ J]． S t e e lRe s e a r chI n t e r na t i ona l,２０１０,８１( ９):７８４． [ ３] Sabur iT,Mur a t aH,Suzuk iT,e ta l．OxygenP l a smaI n t e r a c Ｇ t i on sWi t h Mo l e num:Fo rma t i ono fVo l a t i l e Mo l e num Ox Ｇ ybd ybd i d e s[ J]． J ou r n a lo fP l a smaa ndFu s i onRe s e a r c h,２００２,７８( １):３． [ ４] Ki rk ＧOt hme r．Enc l oped i ao fChemi c a lTe chno l ogy [M]． ５ t h yc ed．New Yo rk:Wi l ey Ｇ I n t e r s c i enc e,２００７． [ ５] Kennedy MJ,BevanSC．A Ki ne t i cS t udyo ft heReduc t i ono f Mo l i ox i deby Hyd r ogen [ J]．J our na lo ft heLe s s ybdenum Tr Common Me t a l s,１９７４,３６( １):２３． [ ６] Schu lmeye r W V,Or t ne rH M．Me chan i smso ft he Hyd r ogen Reduc t i ono fMo l i de s[ J]． I n t e r na t i ona lJ our na lo f ybdenum Ox Re f r a c t o r t a l sandHa r d Ma t e r i a l s,２００２,２０( ４):２６１． y Me [ ７] Gup t aC K,J enaP K．Reduc t i ono fMo l i ox i deby ybdenum Tr Al umi num [ J]． J our na lo ft heLe s sCommon Me t a l s,１９６８,１４ ( １):１４８． [ ８] Ki r shenbaum A D,Be a r de l lAJ．The rma lAna l i so ft heRe Ｇ ys a c t i on o f Mo l i ox i de Wi t h Va r i ous Me t a l s[ J]． ybdenum Tr The rmo ch imi c aAc t a,１９７２,４( ３):２３９． [ ９] J amsh i d iK,Abd i z adehH,Hana iK．Me t a l l o t he rmi cReduc t i on o fMoO３ Thr ough Mak i ng Ni ＧMo Al l oysbyt heESR Me t hod [ J]． I n t e r na t i ona lJ our na lo fRe f r a c t o r t a l sandHa r dMa t e Ｇ yMe r i a l s,２００４,２２( ６):２４３． [ １０] Chaudhur r e eSK,Va i dyaV N,e ta l．Ki ne t i c sand yS,Muke j Me chan i smo fCa r bo t he rmi cReduc t i ono fMoO３t oMo２C [ J]． J our na lo fAl l oysandCompounds,１９９７,２６１( １):１０５． [ １１] Manukyan K,Ayd i nyan S,Agha anyan A,e ta l．Re a c t i on j Pa t hwayi nt heMoO３＋Mg＋CRe a c t i veMi x t ur e s[ J]． I n t e r Ｇ na t i ona lJ our na lo f Re f r a c t o r t a l sand Ha r d Ma t e r i a l s, y Me ２０１２,３１:２８． [ １６ t hed． １２] Spe i tJG．Lange ′ sHandbooko fChemi s t r gh y [M]． New Yo rk:McGr awＧHi l l,２００５． [ １３] RaoY K,El ＧRaha i byS K．Di r e c tReduc t i ono fLe adSu l f i de Wi t hCa r bonand L ime:Ef f e c to fCa t a l t s:Pa r tⅠExpe r i Ｇ ys men t a l[ J]．Me t a l l ur i c a land Ma t e r i a l sTr ans a c t i ons,１９８５, g １６B( ３):４６５． [ １４] Ma s s a l sk iT B．B i na r l oyPha s eDi agr ams [M]．２nded． yAl , Oh i o:TheMa t e r i a l sI n f o rma t i onSo c i e t y １９９６． [ １５] Yanushkev i chT M,Zhukov i t sk i iV M．Pha s eDi ag r am o ft he Mo l i ox i de ＧCa l c i um Ox i de Sys t em [ J]．Zhur na l ybdenum Tr Neo r i che sko iKh imi i,１９７３,１８( ８):２２３４ ( i nRus s i an)． gan [ １６] Na i r ne rN A． Sme l t i ngReduc t i ono fI lmen i t eby yang Ma,Wa Ca r boni n Mo l t enP i r on [ J]．Canad i an Me t a l l ur i c a lQua r Ｇ gI g t e r l ３):１６５． y,１９９９,３８( [ １７] RaoY K,ChuangY K．A Phys i c o ＧChemi c a lMode lf o rRe a c Ｇ t i onsBe twe enPa r t i cu l a t eSo l i ds Oc cur r i ng Thr ough Ga s eous I n t e rmed i a t e s—I I．Gene r a lSo l u t i ons [ J]．Chemi c a lEng i ne e r Ｇ i ngSc i enc e,１９７４,２９( ９):１９３３． [ １８] RaoY K．TheKi ne t i c so fReduc t i ono fHema t i t ebyCa r bon [ J]．Me t a l l ur i c a land Ma t e r i a l sTr ans a c t i ons,１９７１,２B( ５): g
１４３９． [ １９] HongL,Sohn H Y,Sano M．Ki ne t i c so fCa r bo t he rmi cRe Ｇ duc t i ono fMagne s i aandZ i ncOx i debyThe rmog r av ime t r i c Ana l i sTe chn i J]．Sc and i nav i anJ our na lo f Me t a l l ur ys que [ gy, ２００３,３２( ３):１７１． [ ２０] Vya z ovk i nS,Wi tC A．Mode l ＧFr e eand Mode l ＧF i t t i ngAp Ｇ gh r oa che st oKi ne t i cAna l i so fI s o t he rma landNon i s o t he rma l p ys Da t a[ J]．The rmo ch imi c aAc t a,１９９９,３４０( １):５３．