research article conversion of mill scale waste into...

Research ArticleConversion of Mill Scale Waste into Valuable Products viaCarbothermic Reduction

Mamdouh Eissa Azza Ahmed and Mohamed El-Fawkhry

Steel Technology Department (STD) Central Metallurgical RampD Institute (CMRDI) PO Box 87 Helwan Cairo 11421 Egypt

Correspondence should be addressed to Mohamed El-Fawkhry abdrabu1979kamalyahoocom

Received 1 June 2015 Accepted 30 August 2015

Academic Editor Brij Kumar Dhindaw

Copyright copy 2015 Mamdouh Eissa et alThis is an open access article distributed under theCreative CommonsAttribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Mill scale is one of waste materials which is produced as a result of hot rolling of steel in all steel companies On the other handmill scale is considered a rich iron source with minimum impurities This work aims at conversion of mill scale by adjustingsmelting processes to produce different valuable products The smelting processes were carried out using carbothermic reductionin a submerged arc furnace Two carbonaceous reducing agents and different fluxing materials have been used to adapt optimumsmelting process condition A maximum iron recovery of 83 was obtained by using graphite compared with 76 obtained byusing coke Low sulphur content (le002wt S) can be attained by using graphite as a reducing agent in amount that equals orexceeds the stoichiometric molar ratio By using coke the highest degree of desulfurization of 978 and much lower content ofsulphur in the castable metal (00028wt S) were obtained by controlling the type and quantity of the flux The results reveal thatmill scale waste can be converted into valuable products such as high purity iron as alternative to Sorelmetal used in ductile ironproduction low carbon steel and free cutting steel

1 Introduction

The management of wastes generated by hot metal and steelhas become an important issue due to ever-tightening envi-ronment regulations Furthermore the depletion of iron oresnecessitates extensive research work to reuse the secondaryraw materials produced as a by-product in steel companiesand considered as waste materials

During hot rolling of steel iron oxides formon the surfaceof the metal as scales The scale is accumulated as wastematerial in all steel companies In an integrated steel plantportion of mill scale the large size one was recycled insintering plants [1] But a study on recycling mill scale of steelin the sintering process showed that the sinter productivitydecreased with the increase in mill scale addition due to adecrease in sinter bed permeability [2]

In the past years steelmakers used this mill scale asoxidizer in conventional electric arc furnace steelmakingprocess However the modern electric arc furnaces areequipped with oxygen lancing system to enhance meltingand oxidation processes with higher efficiency thanmill scalepractice [3] A small portion of mill scale has been used by

cement plants However the mill scale does not uniformlyblend with the other feed stock materials due to its higherdensity than any of the blend components and thus causes agreater variation in the blend of the kiln feed [4] At the sametime the amount of mill scale used by cement plants as a rawmaterial in the manufacturing of clinker is still rather little

A study on laboratory scale was made to use millscale waste to prepare iron powder The authors used COfollowed by H

2as a reducing gas When the reduction was

carried out by carbon monoxide the maximum iron content(9840wtFe) in the iron powder was obtained at 1050∘Cfor 180min A reduction annealing under hydrogen makesit possible to decrease carbon and oxygen contents of thereduced iron powder up to acceptable values 023 and 028respectively [5] A recent study was made of the reduction ofmill scale to sponge iron using coke at different temperaturesand times Sponge iron was successfully produced for reusein electric furnaces as part of the metallic charge or as a rawmaterial in the production of iron-based powder metallurgyparts [6]

Unfortunately no technology has been implementedin mass to recover and use such materials [7] In some

Hindawi Publishing CorporationJournal of MetallurgyVolume 2015 Article ID 926028 9 pageshttpdxdoiorg1011552015926028

2 Journal of Metallurgy

steel manufacturing companies the bulk of mill scale wastewas dumped in landfills and resulted in leaching of somepercentages of heavy metals into soil and groundwater thusthreatening the environment The continuous demand formore landfills and bad effect on the environment highlightthe need for more effective methods of productive utilizationof mill scale

In this studymill scale waste produced in steel companieswas recycled to produce valuable products by suitable smelt-ing process using submerged arc furnace and carbonaceousreducing agent The reductant and fluxing materials wereoptimized to obtain different valuable products

2 Experimental

Mill scales generated in the hot rolling step of steel producedby electric arc furnace EAF together with reducing agent andfluxing material were used as raw materials Sieve analysischemical composition and XRD examination of mill scalewere carried out Reducing agents (crushed coke and crushedbroken graphite electrode waste) and fluxing materials (CaOCaF2 CaSi Al

2O3 and Na

2CO3) chemical compositions

were determinedThe chemical composition was determinedusing X-ray fluorescence XRF (Philips PW 1410 X-ray spec-trometer with PW 1390 channel control) Phase analysis wasobserved using X-ray diffractometer XRD Bruker AXS D8Advance Germany

Different series of experimental runs were carried outusing 5 kg of mill scale The first and second series werecarried out to investigate the effect of the type and the amountof reducing agent at constant weight (500 gm) of calciumoxide and calcium fluoride with the weight ratio 4 1 Thethird series was designed to investigate the effect of differentfluxing materials on decreasing the sulfur content of thecastable metal by coke reduction

The third series was subdivided into three subseries asfollows

(1) Fluxing material in the form of calcium oxide andcalcium fluoride (weight ratio 4 1) was added in thefurnace with the charge in increment amount from 0to 750 gm

(2) Fluxing material (250 gm) in the form of calciumoxide and calcium fluoride (weight ratio 4 1) wasadded in the furnace with the charge and a mixtureof 250 gm of another type of the fluxing material wasadded in a metallic mold

(3) Fluxing material (500 gm) in the form of calciumoxide and calcium fluoride (weight ratio 4 1) wasadded in the furnace with the charge and a mixtureof 250 gm of another fluxing material was added in ametallic mold

Different fluxing materials were investigated CaSi Na2CO3

CaO-CaF2-Al2O3 and CaO-CaF

2-FeSi-C The fluxing addi-

tion in the mold was carried out during tapping to enhancethe contact area between slag and metal

For each experimental run the amount of the reducingagent required for 5 Kg mill scale was calculated according to

the material balance In the third series constant amount ofcoke was used (15 of the stoichiometric molar ratio)

The smelting experimental runs were carried out in apilot plant submerged electric arc furnace The furnace walland bottom were rammed with a thick magnesite layer Forselecting the voltage and current suitable for carrying outsmooth melting of the charge preliminary experiments werecarried out It was found that the best current for melting thecharge has 480A and 35V

To carry out the experimental runs the components ofthe charge mill scale reducing agent and flux materialswere hand mix together The furnace was preheated to about1000∘C for 30 minutes After all of the main charge hadbeen completely melted the molten metal and slag wereleft for 30 minutes with the current switch on to ensurethe maximum degree of reduction and complete settling ofthe molten metal into the slag The maximum temperatureachieved in the furnace was about 1700∘C The product wascast into metallic moulds where the metal covered by theslag was left to cool to room temperature The castable metalof every experimental run was weighed and representativesamples were then taken for chemical compositions usingspectrographic analysis (Spectro Analytical Instruments)

3 Result and Discussion

During this investigation different parameters affect thereduction of mill scale and quality of castable metal wasstudied These parameters include the type and amount ofreducing agent the type and amount of fluxing material andthe technology of fluxing material addition Two techniquesof addition were investigated In the first one all amountof fluxing material was added in the furnace In the secondtechnique a portion of fluxing material was added in thefurnace while another portion was added in the mold duringtapping

The sieve analysis of mill scale is given in Table 1 and itschemical composition is shown in Table 2 It is clear fromTable 2 that the mill scale contains mainly iron oxides and asmall amount of SiO

2andMnOThe other oxides are present

in minor amounts At the same time the results of XRDexamination of mill scale showed the presence of iron in theform of hematite (Fe

2O3) magnetite (Fe

3O4) and wustite

(FeO) Figure 1 The reductants (coke and graphite) chemicalcompositions are given in Table 3 In addition the chemicalcomposition of coke ash is given in Table 4

4 Effect of the Reducing Agent

Coke or graphite was used as a reducing agent The amountof reducing agent was increased from 07 up to 17 fromthe calculated stoichiometric molar value Stoichiometricmolar ratios of CO higher than 1 were used to compensatethe carbon consumed in reducing of reducible oxides suchas MnO and SiO

2 Figure 2 shows the effect of carbon

stoichiometric molar ratio (C-SR) on iron recovery Fromthe figure the iron recovery increases as the amount ofreductant increases up to about 15 of stoichiometric molarratio This result agrees with the result of Camci et al [1]

Journal of Metallurgy 3

Table 1 Sieves analysis of EAF mill scale

Volume fraction(mm) minus01 +01

minus025+025minus05

+05minus1

+1minus2

+2minus3

+3minus4

+4minus47 +47

Wt 41 148 190 78 208 10 207 38 80

Table 2 Chemical compositions wt of EAF mill scale

FeTotal Fe2O3

SiO2

Al2O3

K2O CaO MnO TiO

2MgO Na

2O P

2O5

CuO Cr2O3

S LOI6755 965 068 016 0012 013 1022 0013 010 004 0074 04 014 0013 11

Table 3 Reducing materials chemical compositions wt

Cfixed S Ash VM MoistureCoke 826 07 135 14 18Graphite 995 01 04

Table 4 Chemical compositions wt of coke ash

SiO2Al2O3

Fe2O3

CaO MgO MnO TiO2

S P462 3285 154 3 025 065 1 012 0028

Above this amount the increasing of the reductant amountleads to decrease of the iron recoveryThismay be due to over-reductant amount The improper utilization of reductantcan be understood in the light of the iron oxide reductionreactions As indicated fromXRD analysis the constituents ofmill scale were Fe

2O3 Fe3O4 and FeO phases The possible

reduction of these oxides is

Fe119898O119899+ (119899 minus 119898)CO 997888rarr 119898FeO + (119899 minus 119898)CO

2 (1)

Fe119898O119899+ 119899C 997888rarr 119898Fe + 119899CO (2)

Reaction (1) is called indirect reaction while reaction (2)is called direct reaction When the temperature was 800ndash1000∘C the reaction at the surface of the reductant wassuitable to make themill scale reduction and the ldquoBoudouardreactionrdquo in (3) to run simultaneously As a result the CO

2gas

formed by reduction of mill scale reacted with carbon to givethe reaction

C + CO2997888rarr 2CO

Δ119866∘(Jmole) = 14837025 minus 462737119879

(3)

It seems that over-reductant amount encourages theldquoBoudouard reactionrdquo to occur which retarded the directreduction of mill scale reaction (2)

Also by comparing the maximum iron recovery it canbe noticed that the maximum iron recovery obtained whenusing coke (76) was lower than when using graphite (83)This can be attributed besides the effect of over-reductant tothe ash constituents in the coke According to the literature[5] the coke ash components such as silica alumina andsilicates alter the reduction equilibrium

The increase of the iron recovery was reflected on theweight of the castable metal Thus the weight of the castablemetal increased with increasing the amount of the reductant

a

a

a wustiteb magnetitec hematite

b

a b ac b

b ac c b

30 40 50 60 70 80 90

2120579

0

2

4

6

8

10

Lin

(cou

nts)

12

14

16

Figure 1 XRD on mill scale of steel produced in EAF

GraphiteCoke

07 08 09 1 11 12 13 14 15 16 17 1806Stoichiometric carbon molar ratio

0

10

20

30

40

50

60

70

80

90

Iron

reco

very

()

Figure 2 Influence of the amount of reducing agent on ironrecovery

The reductant type and amount do not only affect themetal weight and iron recovery but also affect the chemi-cal composition of the castable metal So the relationshipbetween the amount and type of the reductantwith theweightchemical composition of the castable metal C S P Mn andSi was studied


GraphiteCoke

07 08 09 1 11 12 13 14 15 16 17 18060

05

1

15

2

25

3

35

4

45

[C] (

wt

)

Stoichiometric carbon molar ratio

Figure 3 Influence of the amount of reducing agent on metalcarbon content

The change of final metal carbon content with the stoi-chiometric carbon molar ratio at different reductant agentscan be revealed from Figure 3 The carbon content of themetal increases with increase of reductant amount Butafter reaching a maximum value the metal carbon contentdecreases This behavior can be explained in the light of dis-solution and removal of carbon from the iron The carbon isdissolved into iron through the following reactions

Cs 997888rarr Cin metal Δ119866∘(Jmole) = 22594 minus 4228119879 (4)

2COg 997888rarr Cin metal + CO2

Δ119866∘(Jmole) = minus14837025 + 462737119879

(5)

while it can be removed from the iron through the followingreactions

Oin metal + Cin metal 997888rarr COg

Δ119866∘(Jmole) = minus18319 minus 41369119879

(6)

CO2+ Cin metal 997888rarr 2COg

Δ119866∘(Jmole) = 14837025 minus 462737119879

(7)

At low stoichiometric carbon molar ratio up to 12 the reac-tion rate of the dissolution was faster than the rate of theremoval and this trend increased by increasing stoichiometriccarbon molar ratioThis results in increasing the final carboncontent of the castable metal On the other hand decreasingthe metal carbon content after reaching the maximum con-tent resulted from increasing the reaction rate of the carbon(reactions (6)-(7)) especially that of Bodouard reaction asit is discussed before Furthermore it is noticed that at thesame stoichiometric carbon molar ratio the metal carboncontent when using coke was less than metal carbon contentwhen using graphiteThis behavior could be attributed to thehigher reactivity of the coke (01ndash05 times 10minus4 Sminus1) than that ofthe graphite (003 times 10minus4 Sminus1) [8] which means that the rates

GraphiteCoke

0

005

01

015

02

025

[S] (

wt

)

108 0907 11 12 13 14 15 1606


Figure 4 Influence of the amount of reducing agent on metalsulphur content

CokeGraphite


0

0005

001

0015

002

0025[P

] (w

t)

Figure 5 Influence of the amount of reducing agent on metalphosphorous content

of gasification reactions (6) and (7) are faster for coke thangraphite

The relationship between sulphur and phosphorous con-tents of the metal and stoichiometric carbon molar ratio isshown in Figures 4 and 5 respectively It is clear fromFigure 4that the sulphur content of the metal decreases by increas-ing the reducing agent amount (graphite or coke) On thecontrary the phosphorus had the opposite behavior as itincreased by increasing the amount of reducing agent Figure5

The sulphur and phosphorous behavior could beexplained in terms of slag condition Dephosphorization anddesulfurization of hot metal are known to proceed underdifferent conditionsThemost popular method of desulphur-ization is removal of sulphur frommetal to the basic reducing


slag while the most popular dephosphorization is removalof phosphorous from metal to the basic oxidizing slag asindicated from the following chemical equations [9ndash11]

[S] + (CaO) = (CaS) + [O] (8)

The equilibrium constant 119870S of the reaction is

119870S =119886[O] lowast 119886(CaS)

119886[S] lowast 119886(CaO)

(9)

where 119886[O] and 119886[S] are activities of oxygen and sulphur in

the liquid metal 119886(CaS) and 119886(CaO) are activities of CaS and

CaO in the slag

2 [P] + 5 (FeO) + 3 (CaO) = (3CaO sdot P2O5) + 5Fe (10)

The equilibrium constant 119870P of the reaction is

119870P =119886(3CaOsdotP

2O5)

119886[P]2lowast 119886(CaO)3lowast 119886(FeO)5 (11)

where 119886[P] is activity of phosphorus in the liquid metal

119886(3CaOsdotP

2O5) 119886(CaO) and 119886(FeO) are activities of (3CaOsdotP2O5)

CaO and FeO in the slagThese series of experiments have nearly constant slag

basicity because constant weight of fluxing material wasadded So the behavior of sulphur and phosphorus atdifferent reducing agent was related to the effect of the slagiron oxide content Increase of the reducing agent amountleads to decreasing slag iron oxide content and increasingmetal carbon content The activity of the oxygen in the meltis directly proportional to the slag iron oxide content [12]Therefore low activity of oxygen in the metal is expectedleading to appropriate conditions for the removal of thesulphur and desulphurization of the metal as it is indi-cated from (8) On the contrary these conditions encouragerephosphorization process and consequently the phosphoruscontent in themetal increases as the reducing agent increasesas it is indicated from (11)

On the other hand the metal sulphur and phosphorouscontent produced when using graphite is less than coke atthe same stoichiometric carbon molar ratio This could beattributed to the lower sulphur and phosphorous contents ofgraphite compared with coke

Also it can be observed that at different type and amountof the reductant the metal phosphorous content is low andin the range of the iron and steel making Therefore thephosphorous content of the castable metal does not representany problem

Figure 6 illustrates the relationship between the amountof the reductant and the silicon and manganese contents ofthe metal As expected both the silicon and manganese con-tents of the castable metal increase with increasing amount ofthe reductant The coke ash contains SiO

2and MnO At the

same stoichiometric carbon it is expected that the silicon andmanganese contents of themetal produced by coke reductionare higher than that obtained by graphite reduction But theresults showed the opposite behavior to the expected oneThis result can be explained in the light of the effect of the

0

02

04

06

08

1

12

06 07 08 09 1 11 12 13 14 15 16 17 18

[Si]

[Mn]

(wt

)


[Si] using coke[Si] using graphite

[Mn] using coke[Mn] using graphite

Figure 6 Influence of the amount of reducing agent on Mn and Sicontent of the metal

slag FeO content on the reduction of the manganese andsilicon oxides As it is revealed in Figure 2 the iron recoveryobtained when using graphite was greater than that obtainedby coke This indicates that the FeO content of the slag whenusing graphite is less than that obtained when using cokeThe reduction of the oxides increases with decreasing FeOcontent of the slag subsequently the transfer of the siliconand manganese to the metal increases

Also the sharp increase in the silicon content after 15of stoichiometric carbon molar ratio can be noticed Thistrend results from the fact that the reducing ability of SiO

2

by carbon is less than that of MnO as it is indicated from freeenergy of reactions (12) and (13)

(SiO2) + 2 [C] = [Si] + 2CO

Δ119866∘(Jmole) = 611302 minus 33647119879

(12)

(MnO) + [C] = [Mn] + CO

Δ119866∘(Jmole) = 219521 minus 14668119879

(13)

Thus when most of MnO was reduced the reduction rate ofSiO2increases leading to sharp increase of the metal silicon

contentVariations of chemical composition of castablemetal with

coke and graphite at different amounts of the reductant aregiven in Tables 5 and 6 respectively These results show thatvaluable products can be achieved by controlling the type andamount of the reductant such as

(1) low carbon steel containing 017 wtC 005wt Sand 001 wt P (steel number 10)

(2) low carbon high sulphur steel which can be usedas free cutting steel by adding the adjusting Mn attapping (steel numbers 1 and 2)


0

20

40

60

80

0 1000750500250(CaO + CaF2) fluxing mixture (gm)

120575[S][S

o]

()

(a)

0 1000750500250000002004006008010012

[S]

(wt

)

(CaO + CaF2) fluxing mixture (gm)

(b)

Figure 7 Variation of sulphur content and desulfurization degree of the metal with respect to CaO-CaF2fluxing mixture amount added in

the furnace

Table 5 Mill scale experimental runs (reducing agent coke)

Heat number Stoichiometric carbon Chemical composition of produced metal wtC Si Mn S P

1 09 002 0001 0032 0199 00052 10 032 0004 0127 0210 00153 11 180 0005 0171 0191 00184 12 181 0008 0122 0151 00155 13 304 0020 0211 0165 00226 15 384 0079 0337 0053 00157 16 313 0664 0495 0067 00168 17 374 0969 0675 0021 0015

(3) high purity high carbon iron with chemical com-position (38 wtC 028wtMn 0015 wt S and001 wtP) suitable as an alternative of Sorelmetal tobe used for the ductile iron production (steel number14)

(4) iron high carbon (38 wt) and low phosphorus(0015 wt) but containing high sulphur (0053wt)(steel number 6) it can be used as an alternative ofSorelmetal after reducing the sulfur content by usingsuitable fluxing agent with higher desulphurizingpower

5 Effect of Fluxing Materials

The preceding results demonstrate the success of the car-bothermic reduction for mill scale by either coke or graphitein producing different grades of iron and steel with lowphosphorus contents (le002wtP) Low-sulphur content(lt002wt S) can be also attained by using graphite asa reducing agent in amount that equals or exceeds thestoichiometric molar ratio On the other hand metal withhigher sulphur content was produced when using coke asreducing agent Producing low-sulphur metal (le002wt S)necessitates using higher amount of coke that equals orexceeds 17 of stoichiometric molar ratio

Different technologies and fluxing materials were usedto decrease the sulphur content in castable metal from millscale reduced by coke To investigate the fluxing materialseffect the third series of experiments was carried out Two

techniques of addition were investigated In the first one allamount of fluxing material was added in the furnace In thesecond technique a portion of fluxing material was addedin the furnace while another portion was added in the moldduring tapping The variations of fluxing materials for thisseries and the chemical composition of the castable metalsare given in Table 7

The achieved results of subseries 31 of the third series areplotted in Figure 7 where the variation of sulphur contentof the metal and desulphurization degree are plotted withrespect to the variation of the quantity of a mixture of CaOandCaF

2(weight ratio 4 1)The desulphurization degreewas

calculated as follows

120575[S][S119900]=([S119900] minus [S

119894])

[S119900] (14)

where [S119894] is sulphur content of castable metal in run 119894 and

[S119900] is sulphur content of castable metal in reference run

(without fluxing addition)In the reference run without flux addition the sulphur

content of the castable metal was high (0128wt S) Desul-phurization degree of 586 was attained by adding 500 gmof CaO and CaF

2mixture with charge in the furnace but the

sulphur content of the castable metal was still considerablyhigh (0053wt S) However higher desulphurization degreeof 873 was attained when adding 750 gm of CaO and CaF

2

mixture resulting in a decrease of the sulphur content of themetal to be 00162wt


Table 6 Mill scale experimental runs (reducing agent graphite)


9 07 0014 00009 0033 00835 0000310 08 0167 00009 0048 00498 0010311 09 233 00015 0198 00322 0001512 10 298 00454 0353 00143 0016913 11 336 00038 0347 00100 0010914 12 379 00294 0283 00151 0010915 13 380 01620 0471 00104 0010516 15 379 02450 0464 00109 00117

Table 7 Experimental series according to variation of the flux materials and chemical composition of the castable metal (using coke asreducing agent)

Series Fluxing materials gm Chemical analysis of produced metal wtWith charge (CaO)-(CaF

2) In mould C Si Mn S P

31mdash mdash 346 0356 0217 0128 00241

(400)-(100) mdash 384 0079 0437 0053 00153(600)-(150) mdash 365 0725 0649 00162 00216

32

(200)-(50)(CaO)-(CaF

2)

(200)-(50)(80)-(20)

337 0300 026 0118 00181

(200)-(50) (CaSi)(250) 349 111 0549 0060 00211

(200)-(50)(CaO)-(CaF

2)-(FeSi)-(C)

(157)-(31)-(31)-(31)(625)-(125)-(125)-(125)

342 0679 057 0085 00185

(200)-(50)(CaO)-(CaF

2)-(Al2O3)

(38)-(137)-(75)(15)-(55)-(30)

366 0502 0524 0103 00234

(200)-(50) (Na2CO3)

(250) 359 0601 0493 0109 00238

33

(400)-(100)(CaO)-(CaF

2)

(200)-(50)(80)-(20)

362 0855 0604 00107 00229

(400)-(100) (CaSi)(250) 361 192 060 00028 00199

(400)-(100)(CaO)-(CaF

2)-(FeSi)-(C)

(157)-(31)-(31)-(31)(625)-(125)-(125)-(125)

359 0973 0650 00174 00241

The results of subseries 32 are presented in Figure 8where the variation of sulphur content of themetal and desul-phurization degree are plotted versus the different fluxingmaterials It was clear that CaSi was the most effective desul-phurized agent among the different fluxing materials usedin this investigation However the highest desulphurizationdegree was only 531 and sulphur content of the castablemetal was still considerably high (0060 S)

On the other hand Figure 9 illustrates that increasingthe amount of CaO-CaF

2mixture (weight ratio 4 1) in the

furnace to 500 gm and adding another 250 gm of this mixturein the mold gives higher degree of desulfurization of 916and lower content of sulphur in the metal (00107wt S)

Much higher degree of desulfurization of 978 and muchlower content of sulphur in the castable metal (00028wt-)were obtained when adding 250 gm of CaSi in the moldinstead of CaO-CaF

2mixture

The effect of the type and amount of the flux on themetal sulfur content could be attributed to its effect on theslag basicity Figure 10 illustrates the relation between themetal sulphur content and slag basicity It was clear from thisfigure that the metal sulphur content decreases by increasingthe slag basicity It can be also noticed that at the sameslag basicity the dotted line (fluxing material includes CaSi)represents lower sulphur content comparing to the solid line(fluxing material does not include CaSi) This behavior could


0102030405060

1 2 3 4 5

120575[S][S

o]

(a)

000002004006008010012

[S]

(wt

)

1 2 3 4 5(b)

Figure 8 Variation of (a) sulphur content and (b) desulfurization degree of the metal using 250 gm of CaO-CaF2(4 1) in the furnace and

adding 250 gm of different types of flux in the mold (1) CaO + CaF2 (2) Na

2CO3 (3) CaO + CaF

2+ Al2O3 (4) CaO + CaF

2+ FeSi + C and

(5) CaSi

0

20

40

60

80

100

1 2 3 4

120575[S][S

o]

(a)

000001002003004005

[S]

(wt

)

1 2 3 4(b)

Figure 9 Variation of (a) sulphur content and (b) desulfurization degree of the metal using 500 gm of CaO-CaF2(4 1) in the furnace with

adding 250 gm of different fluxing type in the mold (1) zero (2) CaO + CaF2+ FeSi-C and (3) CaO + CaF

2(4) CaSi

Without using CaSiUsing CaSi

0

002

004

006

008

01

012

[S]

(wt

)

1 2 3 4 50

(CaO + MgO)(SiO2 + Al2O3)

Figure 10 Variation of metal sulphur content with slag basicity

be attributed to the powerful effect of CaSi as deoxidizingagent results in low activity of oxygen in the melt leadingto appropriate conditions for the removal of the sulphur anddesulphurization of the metal [13]

6 Conclusions

Carbothermic reduction of mill scale waste produced insteelmaking process using two carbonaceous reducing agents

(graphite or coke) and different fluxing materials in sub-merged arc furnace reveal the following conclusions

(1) The iron recovery increases as the amount of reduc-tant increases up to about 15 of stoichiometric molarratio Above this amount the increasing of the reduc-tant amount leads to decrease of the iron recovery

(2) The maximum iron recovery obtained by using coke(76) is lower than by using graphite (83)

(3) The carbon silicon and manganese contents of thecastable metal increase by increasing the reductantamount At the same stoichiometric carbon molarratio the metal carbon silicon and manganese con-tents when using coke were less than that attainedwhen using graphite

(4) At different type and amount of the reductant themetal phosphorous content was low and in the rangeof the iron and steel making

(5) Low-sulphur content (le002wt S) can be attainedby using graphite as a reducing agent in amount thatequals or exceeds the stoichiometric molar ratio Onthe other handmetal with higher sulphur contentwasproduced when using coke as reducing agent Pro-ducing low-sulphur metal (le002wt S) necessitatesusing higher amount of coke that equals or exceeds 17of stoichiometric molar ratio

(6) The highest degree of desulfurization of 978 andmuch lower content of sulphur in the castable metal


(00028wt S) are obtained by controlling the typeand quantity of the flux

(7) By controlling the type and amount of the reductantand using a suitable fluxing material mill scale wasteproduced in steelmaking process can be convertedinto valuable products such as high purity iron asalternative to Sorelmetal used in ductile iron produc-tion low carbon steel and free cutting steels

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] L Camci S Aydin and C Arslan ldquoReduction of iron oxide insolid wastes generated by steelworksrdquo Turkish Journal of Engi-neering and Environmental Sciences vol 26 pp 37ndash44 2002

[2] T Umadevi A Brahmacharyulu P Karthik P C MahapatraM Prabhu and M Ranjan ldquoRecycling of steel plant mill scalevia iron ore sintering plantrdquo Ironmaking and Steelmaking vol39 no 3 pp 222ndash227 2012

[3] R Farahat M Eissa G Megahed and A Baraka ldquoReduction ofmill scale generated by steel processingrdquo Steel Grips vol 8 pp88ndash92 2010

[4] R D Young and D Norris ldquoProcess for using mill scale incement clinker productionrdquo US Patent no 6709510B1 2004

[5] O Benchiheub S Mechachti S Serrai and M G KhalifaldquoElaboration of iron powder frommill scalerdquo Journal of Materi-als and Environmental Science vol 1 no 4 pp 267ndash276 2010

[6] M I Martın F A Lopez and J M Torralba ldquoProduction ofsponge iron powder by reduction of rolling mill scalerdquo Iron-making amp Steelmaking vol 39 no 3 pp 155ndash162 2012

[7] S Cho and J Lee ldquoMetal recovery from stainless steel mill scaleby microwave heatingrdquoMetals and Materials International vol14 no 2 pp 193ndash196 2008

[8] R C Gupta Theory and Laboratory Experiments in FerrousMetallurgy Prentice Hall New Delhi India 2010

[9] KMori HWada and R D Pehlke ldquoSimultaneous desulfuriza-tion and dephosphorization reactions of molten iron by sodaash treatmentrdquo Metallurgical Transactions B vol 16 no 2 pp303ndash312 1985

[10] G Li T Hamano and F Tsukihashi ldquoThe effect of Na2O and

Al2O3on dephosphorization of molten steel by high basicity

MgO saturated CaO-FeO x-SiO2slagrdquo ISIJ International vol

45 no 1 pp 12ndash18 2005[11] T Nagai Y Tanaka and M Maeda ldquoThermodynamic mea-

surement of di-calcium phosphaterdquoMetallurgical andMaterialsTransactions B vol 42 no 4 pp 685ndash691 2011

[12] MM Eissa K A El-FawakhryW Tayor H El-Faramawy andA M Ahmed ldquoFerrous oxide activity in FeO-TiO

2-CaO-Al

2O3

systemrdquo ISIJ International vol 36 no 5 pp 512ndash516 1996[13] K Mineura I Takahashi and K Tanaka ldquoDeoxidation and

desulfurization of pressurized liquid high nitrogen stainlesssteels with calciumrdquo ISIJ International vol 30 no 3 pp 192ndash198 1990

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


steel manufacturing companies the bulk of mill scale wastewas dumped in landfills and resulted in leaching of somepercentages of heavy metals into soil and groundwater thusthreatening the environment The continuous demand formore landfills and bad effect on the environment highlightthe need for more effective methods of productive utilizationof mill scale

In this studymill scale waste produced in steel companieswas recycled to produce valuable products by suitable smelt-ing process using submerged arc furnace and carbonaceousreducing agent The reductant and fluxing materials wereoptimized to obtain different valuable products

2 Experimental

Mill scales generated in the hot rolling step of steel producedby electric arc furnace EAF together with reducing agent andfluxing material were used as raw materials Sieve analysischemical composition and XRD examination of mill scalewere carried out Reducing agents (crushed coke and crushedbroken graphite electrode waste) and fluxing materials (CaOCaF2 CaSi Al

2O3 and Na

2CO3) chemical compositions

were determinedThe chemical composition was determinedusing X-ray fluorescence XRF (Philips PW 1410 X-ray spec-trometer with PW 1390 channel control) Phase analysis wasobserved using X-ray diffractometer XRD Bruker AXS D8Advance Germany

Different series of experimental runs were carried outusing 5 kg of mill scale The first and second series werecarried out to investigate the effect of the type and the amountof reducing agent at constant weight (500 gm) of calciumoxide and calcium fluoride with the weight ratio 4 1 Thethird series was designed to investigate the effect of differentfluxing materials on decreasing the sulfur content of thecastable metal by coke reduction

The third series was subdivided into three subseries asfollows

(1) Fluxing material in the form of calcium oxide andcalcium fluoride (weight ratio 4 1) was added in thefurnace with the charge in increment amount from 0to 750 gm

(2) Fluxing material (250 gm) in the form of calciumoxide and calcium fluoride (weight ratio 4 1) wasadded in the furnace with the charge and a mixtureof 250 gm of another type of the fluxing material wasadded in a metallic mold

(3) Fluxing material (500 gm) in the form of calciumoxide and calcium fluoride (weight ratio 4 1) wasadded in the furnace with the charge and a mixtureof 250 gm of another fluxing material was added in ametallic mold

Different fluxing materials were investigated CaSi Na2CO3

CaO-CaF2-Al2O3 and CaO-CaF

2-FeSi-C The fluxing addi-

tion in the mold was carried out during tapping to enhancethe contact area between slag and metal

For each experimental run the amount of the reducingagent required for 5 Kg mill scale was calculated according to

the material balance In the third series constant amount ofcoke was used (15 of the stoichiometric molar ratio)

The smelting experimental runs were carried out in apilot plant submerged electric arc furnace The furnace walland bottom were rammed with a thick magnesite layer Forselecting the voltage and current suitable for carrying outsmooth melting of the charge preliminary experiments werecarried out It was found that the best current for melting thecharge has 480A and 35V

To carry out the experimental runs the components ofthe charge mill scale reducing agent and flux materialswere hand mix together The furnace was preheated to about1000∘C for 30 minutes After all of the main charge hadbeen completely melted the molten metal and slag wereleft for 30 minutes with the current switch on to ensurethe maximum degree of reduction and complete settling ofthe molten metal into the slag The maximum temperatureachieved in the furnace was about 1700∘C The product wascast into metallic moulds where the metal covered by theslag was left to cool to room temperature The castable metalof every experimental run was weighed and representativesamples were then taken for chemical compositions usingspectrographic analysis (Spectro Analytical Instruments)

3 Result and Discussion

During this investigation different parameters affect thereduction of mill scale and quality of castable metal wasstudied These parameters include the type and amount ofreducing agent the type and amount of fluxing material andthe technology of fluxing material addition Two techniquesof addition were investigated In the first one all amountof fluxing material was added in the furnace In the secondtechnique a portion of fluxing material was added in thefurnace while another portion was added in the mold duringtapping

The sieve analysis of mill scale is given in Table 1 and itschemical composition is shown in Table 2 It is clear fromTable 2 that the mill scale contains mainly iron oxides and asmall amount of SiO

2andMnOThe other oxides are present

in minor amounts At the same time the results of XRDexamination of mill scale showed the presence of iron in theform of hematite (Fe

2O3) magnetite (Fe

3O4) and wustite

(FeO) Figure 1 The reductants (coke and graphite) chemicalcompositions are given in Table 3 In addition the chemicalcomposition of coke ash is given in Table 4

4 Effect of the Reducing Agent

Coke or graphite was used as a reducing agent The amountof reducing agent was increased from 07 up to 17 fromthe calculated stoichiometric molar value Stoichiometricmolar ratios of CO higher than 1 were used to compensatethe carbon consumed in reducing of reducible oxides suchas MnO and SiO

2 Figure 2 shows the effect of carbon

stoichiometric molar ratio (C-SR) on iron recovery Fromthe figure the iron recovery increases as the amount ofreductant increases up to about 15 of stoichiometric molarratio This result agrees with the result of Camci et al [1]




minus025+025minus05

+05minus1

+1minus2

+2minus3

+3minus4

+4minus47 +47

Wt 41 148 190 78 208 10 207 38 80


FeTotal Fe2O3

SiO2

Al2O3

K2O CaO MnO TiO

2MgO Na

2O P

2O5

CuO Cr2O3

S LOI6755 965 068 016 0012 013 1022 0013 010 004 0074 04 014 0013 11




SiO2Al2O3

Fe2O3

CaO MgO MnO TiO2

S P462 3285 154 3 025 065 1 012 0028





2 (1)

Fe119898O119899+ 119899C 997888rarr 119898Fe + 119899CO (2)


2gas



Δ119866∘(Jmole) = 14837025 minus 462737119879

(3)




a

a


b

a b ac b

b ac c b

30 40 50 60 70 80 90

2120579

0

2

4

6

8

10

Lin

(cou

nts)

12

14

16


GraphiteCoke


0

10

20

30

40

50

60

70

80

90

Iron

reco

very

()




GraphiteCoke

07 08 09 1 11 12 13 14 15 16 17 18060

05

1

15

2

25

3

35

4

45

[C] (

wt

)






Δ119866∘(Jmole) = minus14837025 + 462737119879

(5)




(6)


Δ119866∘(Jmole) = 14837025 minus 462737119879

(7)


GraphiteCoke

0

005

01

015

02

025

[S] (

wt

)

108 0907 11 12 13 14 15 1606



CokeGraphite


0

0005

001

0015

002

0025[P

] (w

t)







[S] + (CaO) = (CaS) + [O] (8)


119870S =119886[O] lowast 119886(CaS)

119886[S] lowast 119886(CaO)

(9)



CaO in the slag



119870P =119886(3CaOsdotP

2O5)



119886(3CaOsdotP







2and MnO At the


0

02

04

06

08

1

12

06 07 08 09 1 11 12 13 14 15 16 17 18

[Si]

[Mn]

(wt

)







2


(SiO2) + 2 [C] = [Si] + 2CO

Δ119866∘(Jmole) = 611302 minus 33647119879

(12)

(MnO) + [C] = [Mn] + CO

Δ119866∘(Jmole) = 219521 minus 14668119879

(13)







0

20

40

60

80


120575[S][S

o]

()

(a)

0 1000750500250000002004006008010012

[S]

(wt

)


(b)


the furnace



1 09 002 0001 0032 0199 00052 10 032 0004 0127 0210 00153 11 180 0005 0171 0191 00184 12 181 0008 0122 0151 00155 13 304 0020 0211 0165 00226 15 384 0079 0337 0053 00157 16 313 0664 0495 0067 00168 17 374 0969 0675 0021 0015










120575[S][S119900]=([S119900] minus [S

119894])

[S119900] (14)







2





9 07 0014 00009 0033 00835 0000310 08 0167 00009 0048 00498 0010311 09 233 00015 0198 00322 0001512 10 298 00454 0353 00143 0016913 11 336 00038 0347 00100 0010914 12 379 00294 0283 00151 0010915 13 380 01620 0471 00104 0010516 15 379 02450 0464 00109 00117




31mdash mdash 346 0356 0217 0128 00241

(400)-(100) mdash 384 0079 0437 0053 00153(600)-(150) mdash 365 0725 0649 00162 00216

32

(200)-(50)(CaO)-(CaF

2)

(200)-(50)(80)-(20)

337 0300 026 0118 00181

(200)-(50) (CaSi)(250) 349 111 0549 0060 00211

(200)-(50)(CaO)-(CaF

2)-(FeSi)-(C)

(157)-(31)-(31)-(31)(625)-(125)-(125)-(125)

342 0679 057 0085 00185

(200)-(50)(CaO)-(CaF

2)-(Al2O3)

(38)-(137)-(75)(15)-(55)-(30)

366 0502 0524 0103 00234

(200)-(50) (Na2CO3)

(250) 359 0601 0493 0109 00238

33

(400)-(100)(CaO)-(CaF

2)

(200)-(50)(80)-(20)

362 0855 0604 00107 00229

(400)-(100) (CaSi)(250) 361 192 060 00028 00199

(400)-(100)(CaO)-(CaF

2)-(FeSi)-(C)

(157)-(31)-(31)-(31)(625)-(125)-(125)-(125)

359 0973 0650 00174 00241






2mixture



0102030405060

1 2 3 4 5

120575[S][S

o]

(a)

000002004006008010012

[S]

(wt

)

1 2 3 4 5(b)



2CO3 (3) CaO + CaF


2+ FeSi + C and

(5) CaSi

0

20

40

60

80

100

1 2 3 4

120575[S][S

o]

(a)

000001002003004005

[S]

(wt

)

1 2 3 4(b)



2(4) CaSi


0

002

004

006

008

01

012

[S]

(wt

)

1 2 3 4 50




6 Conclusions














References
















2-CaO-Al

2O3










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






minus025+025minus05

+05minus1

+1minus2

+2minus3

+3minus4

+4minus47 +47

Wt 41 148 190 78 208 10 207 38 80


FeTotal Fe2O3

SiO2

Al2O3

K2O CaO MnO TiO

2MgO Na

2O P

2O5

CuO Cr2O3

S LOI6755 965 068 016 0012 013 1022 0013 010 004 0074 04 014 0013 11




SiO2Al2O3

Fe2O3

CaO MgO MnO TiO2

S P462 3285 154 3 025 065 1 012 0028





2 (1)

Fe119898O119899+ 119899C 997888rarr 119898Fe + 119899CO (2)


2gas



Δ119866∘(Jmole) = 14837025 minus 462737119879

(3)




a

a


b

a b ac b

b ac c b

30 40 50 60 70 80 90

2120579

0

2

4

6

8

10

Lin

(cou

nts)

12

14

16


GraphiteCoke


0

10

20

30

40

50

60

70

80

90

Iron

reco

very

()




GraphiteCoke

07 08 09 1 11 12 13 14 15 16 17 18060

05

1

15

2

25

3

35

4

45

[C] (

wt

)






Δ119866∘(Jmole) = minus14837025 + 462737119879

(5)




(6)


Δ119866∘(Jmole) = 14837025 minus 462737119879

(7)


GraphiteCoke

0

005

01

015

02

025

[S] (

wt

)

108 0907 11 12 13 14 15 1606



CokeGraphite


0

0005

001

0015

002

0025[P

] (w

t)







[S] + (CaO) = (CaS) + [O] (8)


119870S =119886[O] lowast 119886(CaS)

119886[S] lowast 119886(CaO)

(9)



CaO in the slag



119870P =119886(3CaOsdotP

2O5)



119886(3CaOsdotP







2and MnO At the


0

02

04

06

08

1

12

06 07 08 09 1 11 12 13 14 15 16 17 18

[Si]

[Mn]

(wt

)







2


(SiO2) + 2 [C] = [Si] + 2CO

Δ119866∘(Jmole) = 611302 minus 33647119879

(12)

(MnO) + [C] = [Mn] + CO

Δ119866∘(Jmole) = 219521 minus 14668119879

(13)







0

20

40

60

80


120575[S][S

o]

()

(a)

0 1000750500250000002004006008010012

[S]

(wt

)


(b)


the furnace



1 09 002 0001 0032 0199 00052 10 032 0004 0127 0210 00153 11 180 0005 0171 0191 00184 12 181 0008 0122 0151 00155 13 304 0020 0211 0165 00226 15 384 0079 0337 0053 00157 16 313 0664 0495 0067 00168 17 374 0969 0675 0021 0015










120575[S][S119900]=([S119900] minus [S

119894])

[S119900] (14)







2





9 07 0014 00009 0033 00835 0000310 08 0167 00009 0048 00498 0010311 09 233 00015 0198 00322 0001512 10 298 00454 0353 00143 0016913 11 336 00038 0347 00100 0010914 12 379 00294 0283 00151 0010915 13 380 01620 0471 00104 0010516 15 379 02450 0464 00109 00117




31mdash mdash 346 0356 0217 0128 00241

(400)-(100) mdash 384 0079 0437 0053 00153(600)-(150) mdash 365 0725 0649 00162 00216

32

(200)-(50)(CaO)-(CaF

2)

(200)-(50)(80)-(20)

337 0300 026 0118 00181

(200)-(50) (CaSi)(250) 349 111 0549 0060 00211

(200)-(50)(CaO)-(CaF

2)-(FeSi)-(C)

(157)-(31)-(31)-(31)(625)-(125)-(125)-(125)

342 0679 057 0085 00185

(200)-(50)(CaO)-(CaF

2)-(Al2O3)

(38)-(137)-(75)(15)-(55)-(30)

366 0502 0524 0103 00234

(200)-(50) (Na2CO3)

(250) 359 0601 0493 0109 00238

33

(400)-(100)(CaO)-(CaF

2)

(200)-(50)(80)-(20)

362 0855 0604 00107 00229

(400)-(100) (CaSi)(250) 361 192 060 00028 00199

(400)-(100)(CaO)-(CaF

2)-(FeSi)-(C)

(157)-(31)-(31)-(31)(625)-(125)-(125)-(125)

359 0973 0650 00174 00241






2mixture



0102030405060

1 2 3 4 5

120575[S][S

o]

(a)

000002004006008010012

[S]

(wt

)

1 2 3 4 5(b)



2CO3 (3) CaO + CaF


2+ FeSi + C and

(5) CaSi

0

20

40

60

80

100

1 2 3 4

120575[S][S

o]

(a)

000001002003004005

[S]

(wt

)

1 2 3 4(b)



2(4) CaSi


0

002

004

006

008

01

012

[S]

(wt

)

1 2 3 4 50




6 Conclusions














References
















2-CaO-Al

2O3










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




GraphiteCoke

07 08 09 1 11 12 13 14 15 16 17 18060

05

1

15

2

25

3

35

4

45

[C] (

wt

)






Δ119866∘(Jmole) = minus14837025 + 462737119879

(5)




(6)


Δ119866∘(Jmole) = 14837025 minus 462737119879

(7)


GraphiteCoke

0

005

01

015

02

025

[S] (

wt

)

108 0907 11 12 13 14 15 1606



CokeGraphite


0

0005

001

0015

002

0025[P

] (w

t)







[S] + (CaO) = (CaS) + [O] (8)


119870S =119886[O] lowast 119886(CaS)

119886[S] lowast 119886(CaO)

(9)



CaO in the slag



119870P =119886(3CaOsdotP

2O5)



119886(3CaOsdotP







2and MnO At the


0

02

04

06

08

1

12

06 07 08 09 1 11 12 13 14 15 16 17 18

[Si]

[Mn]

(wt

)







2


(SiO2) + 2 [C] = [Si] + 2CO

Δ119866∘(Jmole) = 611302 minus 33647119879

(12)

(MnO) + [C] = [Mn] + CO

Δ119866∘(Jmole) = 219521 minus 14668119879

(13)







0

20

40

60

80


120575[S][S

o]

()

(a)

0 1000750500250000002004006008010012

[S]

(wt

)


(b)


the furnace



1 09 002 0001 0032 0199 00052 10 032 0004 0127 0210 00153 11 180 0005 0171 0191 00184 12 181 0008 0122 0151 00155 13 304 0020 0211 0165 00226 15 384 0079 0337 0053 00157 16 313 0664 0495 0067 00168 17 374 0969 0675 0021 0015










120575[S][S119900]=([S119900] minus [S

119894])

[S119900] (14)







2





9 07 0014 00009 0033 00835 0000310 08 0167 00009 0048 00498 0010311 09 233 00015 0198 00322 0001512 10 298 00454 0353 00143 0016913 11 336 00038 0347 00100 0010914 12 379 00294 0283 00151 0010915 13 380 01620 0471 00104 0010516 15 379 02450 0464 00109 00117




31mdash mdash 346 0356 0217 0128 00241

(400)-(100) mdash 384 0079 0437 0053 00153(600)-(150) mdash 365 0725 0649 00162 00216

32

(200)-(50)(CaO)-(CaF

2)

(200)-(50)(80)-(20)

337 0300 026 0118 00181

(200)-(50) (CaSi)(250) 349 111 0549 0060 00211

(200)-(50)(CaO)-(CaF

2)-(FeSi)-(C)

(157)-(31)-(31)-(31)(625)-(125)-(125)-(125)

342 0679 057 0085 00185

(200)-(50)(CaO)-(CaF

2)-(Al2O3)

(38)-(137)-(75)(15)-(55)-(30)

366 0502 0524 0103 00234

(200)-(50) (Na2CO3)

(250) 359 0601 0493 0109 00238

33

(400)-(100)(CaO)-(CaF

2)

(200)-(50)(80)-(20)

362 0855 0604 00107 00229

(400)-(100) (CaSi)(250) 361 192 060 00028 00199

(400)-(100)(CaO)-(CaF

2)-(FeSi)-(C)

(157)-(31)-(31)-(31)(625)-(125)-(125)-(125)

359 0973 0650 00174 00241






2mixture



0102030405060

1 2 3 4 5

120575[S][S

o]

(a)

000002004006008010012

[S]

(wt

)

1 2 3 4 5(b)



2CO3 (3) CaO + CaF


2+ FeSi + C and

(5) CaSi

0

20

40

60

80

100

1 2 3 4

120575[S][S

o]

(a)

000001002003004005

[S]

(wt

)

1 2 3 4(b)



2(4) CaSi


0

002

004

006

008

01

012

[S]

(wt

)

1 2 3 4 50




6 Conclusions














References
















2-CaO-Al

2O3










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





[S] + (CaO) = (CaS) + [O] (8)


119870S =119886[O] lowast 119886(CaS)

119886[S] lowast 119886(CaO)

(9)



CaO in the slag



119870P =119886(3CaOsdotP

2O5)



119886(3CaOsdotP







2and MnO At the


0

02

04

06

08

1

12

06 07 08 09 1 11 12 13 14 15 16 17 18

[Si]

[Mn]

(wt

)







2


(SiO2) + 2 [C] = [Si] + 2CO

Δ119866∘(Jmole) = 611302 minus 33647119879

(12)

(MnO) + [C] = [Mn] + CO

Δ119866∘(Jmole) = 219521 minus 14668119879

(13)







0

20

40

60

80


120575[S][S

o]

()

(a)

0 1000750500250000002004006008010012

[S]

(wt

)


(b)


the furnace



1 09 002 0001 0032 0199 00052 10 032 0004 0127 0210 00153 11 180 0005 0171 0191 00184 12 181 0008 0122 0151 00155 13 304 0020 0211 0165 00226 15 384 0079 0337 0053 00157 16 313 0664 0495 0067 00168 17 374 0969 0675 0021 0015










120575[S][S119900]=([S119900] minus [S

119894])

[S119900] (14)







2





9 07 0014 00009 0033 00835 0000310 08 0167 00009 0048 00498 0010311 09 233 00015 0198 00322 0001512 10 298 00454 0353 00143 0016913 11 336 00038 0347 00100 0010914 12 379 00294 0283 00151 0010915 13 380 01620 0471 00104 0010516 15 379 02450 0464 00109 00117




31mdash mdash 346 0356 0217 0128 00241

(400)-(100) mdash 384 0079 0437 0053 00153(600)-(150) mdash 365 0725 0649 00162 00216

32

(200)-(50)(CaO)-(CaF

2)

(200)-(50)(80)-(20)

337 0300 026 0118 00181

(200)-(50) (CaSi)(250) 349 111 0549 0060 00211

(200)-(50)(CaO)-(CaF

2)-(FeSi)-(C)

(157)-(31)-(31)-(31)(625)-(125)-(125)-(125)

342 0679 057 0085 00185

(200)-(50)(CaO)-(CaF

2)-(Al2O3)

(38)-(137)-(75)(15)-(55)-(30)

366 0502 0524 0103 00234

(200)-(50) (Na2CO3)

(250) 359 0601 0493 0109 00238

33

(400)-(100)(CaO)-(CaF

2)

(200)-(50)(80)-(20)

362 0855 0604 00107 00229

(400)-(100) (CaSi)(250) 361 192 060 00028 00199

(400)-(100)(CaO)-(CaF

2)-(FeSi)-(C)

(157)-(31)-(31)-(31)(625)-(125)-(125)-(125)

359 0973 0650 00174 00241






2mixture



0102030405060

1 2 3 4 5

120575[S][S

o]

(a)

000002004006008010012

[S]

(wt

)

1 2 3 4 5(b)



2CO3 (3) CaO + CaF


2+ FeSi + C and

(5) CaSi

0

20

40

60

80

100

1 2 3 4

120575[S][S

o]

(a)

000001002003004005

[S]

(wt

)

1 2 3 4(b)



2(4) CaSi


0

002

004

006

008

01

012

[S]

(wt

)

1 2 3 4 50




6 Conclusions














References
















2-CaO-Al

2O3










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

20

40

60

80


120575[S][S

o]

()

(a)

0 1000750500250000002004006008010012

[S]

(wt

)


(b)


the furnace



1 09 002 0001 0032 0199 00052 10 032 0004 0127 0210 00153 11 180 0005 0171 0191 00184 12 181 0008 0122 0151 00155 13 304 0020 0211 0165 00226 15 384 0079 0337 0053 00157 16 313 0664 0495 0067 00168 17 374 0969 0675 0021 0015










120575[S][S119900]=([S119900] minus [S

119894])

[S119900] (14)







2





9 07 0014 00009 0033 00835 0000310 08 0167 00009 0048 00498 0010311 09 233 00015 0198 00322 0001512 10 298 00454 0353 00143 0016913 11 336 00038 0347 00100 0010914 12 379 00294 0283 00151 0010915 13 380 01620 0471 00104 0010516 15 379 02450 0464 00109 00117




31mdash mdash 346 0356 0217 0128 00241

(400)-(100) mdash 384 0079 0437 0053 00153(600)-(150) mdash 365 0725 0649 00162 00216

32

(200)-(50)(CaO)-(CaF

2)

(200)-(50)(80)-(20)

337 0300 026 0118 00181

(200)-(50) (CaSi)(250) 349 111 0549 0060 00211

(200)-(50)(CaO)-(CaF

2)-(FeSi)-(C)

(157)-(31)-(31)-(31)(625)-(125)-(125)-(125)

342 0679 057 0085 00185

(200)-(50)(CaO)-(CaF

2)-(Al2O3)

(38)-(137)-(75)(15)-(55)-(30)

366 0502 0524 0103 00234

(200)-(50) (Na2CO3)

(250) 359 0601 0493 0109 00238

33

(400)-(100)(CaO)-(CaF

2)

(200)-(50)(80)-(20)

362 0855 0604 00107 00229

(400)-(100) (CaSi)(250) 361 192 060 00028 00199

(400)-(100)(CaO)-(CaF

2)-(FeSi)-(C)

(157)-(31)-(31)-(31)(625)-(125)-(125)-(125)

359 0973 0650 00174 00241






2mixture



0102030405060

1 2 3 4 5

120575[S][S

o]

(a)

000002004006008010012

[S]

(wt

)

1 2 3 4 5(b)



2CO3 (3) CaO + CaF


2+ FeSi + C and

(5) CaSi

0

20

40

60

80

100

1 2 3 4

120575[S][S

o]

(a)

000001002003004005

[S]

(wt

)

1 2 3 4(b)



2(4) CaSi


0

002

004

006

008

01

012

[S]

(wt

)

1 2 3 4 50




6 Conclusions














References
















2-CaO-Al

2O3










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






9 07 0014 00009 0033 00835 0000310 08 0167 00009 0048 00498 0010311 09 233 00015 0198 00322 0001512 10 298 00454 0353 00143 0016913 11 336 00038 0347 00100 0010914 12 379 00294 0283 00151 0010915 13 380 01620 0471 00104 0010516 15 379 02450 0464 00109 00117




31mdash mdash 346 0356 0217 0128 00241

(400)-(100) mdash 384 0079 0437 0053 00153(600)-(150) mdash 365 0725 0649 00162 00216

32

(200)-(50)(CaO)-(CaF

2)

(200)-(50)(80)-(20)

337 0300 026 0118 00181

(200)-(50) (CaSi)(250) 349 111 0549 0060 00211

(200)-(50)(CaO)-(CaF

2)-(FeSi)-(C)

(157)-(31)-(31)-(31)(625)-(125)-(125)-(125)

342 0679 057 0085 00185

(200)-(50)(CaO)-(CaF

2)-(Al2O3)

(38)-(137)-(75)(15)-(55)-(30)

366 0502 0524 0103 00234

(200)-(50) (Na2CO3)

(250) 359 0601 0493 0109 00238

33

(400)-(100)(CaO)-(CaF

2)

(200)-(50)(80)-(20)

362 0855 0604 00107 00229

(400)-(100) (CaSi)(250) 361 192 060 00028 00199

(400)-(100)(CaO)-(CaF

2)-(FeSi)-(C)

(157)-(31)-(31)-(31)(625)-(125)-(125)-(125)

359 0973 0650 00174 00241






2mixture



0102030405060

1 2 3 4 5

120575[S][S

o]

(a)

000002004006008010012

[S]

(wt

)

1 2 3 4 5(b)



2CO3 (3) CaO + CaF


2+ FeSi + C and

(5) CaSi

0

20

40

60

80

100

1 2 3 4

120575[S][S

o]

(a)

000001002003004005

[S]

(wt

)

1 2 3 4(b)



2(4) CaSi


0

002

004

006

008

01

012

[S]

(wt

)

1 2 3 4 50




6 Conclusions














References
















2-CaO-Al

2O3










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0102030405060

1 2 3 4 5

120575[S][S

o]

(a)

000002004006008010012

[S]

(wt

)

1 2 3 4 5(b)



2CO3 (3) CaO + CaF


2+ FeSi + C and

(5) CaSi

0

20

40

60

80

100

1 2 3 4

120575[S][S

o]

(a)

000001002003004005

[S]

(wt

)

1 2 3 4(b)



2(4) CaSi


0

002

004

006

008

01

012

[S]

(wt

)

1 2 3 4 50




6 Conclusions














References
















2-CaO-Al

2O3










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials








References
















2-CaO-Al

2O3










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



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