improving manganese utilization in the production of manganese ferroalloys

ISSN 0967�0912, Steel in Translation, 2013, Vol. 43, No. 7, pp. 424–428. © Allerton Press, Inc., 2013.Original Russian Text © V.Ya. Dashevskii, Yu.S. Yusfin, A.A. Aleksandrov, L.I. Leont’ev, G.S. Podgorodetskii, V.I. Gubanov, 2013, published in “Izvestiya VUZ. Chernaya Metallurgiya,”2013, No. 7, pp. 32–37.

424

In the smelting of manganese ferroalloys, much ofthe manganese is lost with the tailings slag. The fur�nace smelting of manganese with silicon is character�ized by Mn losses that may be as much as 40% [1]. Theextraction of manganese is no more than 60–65%,since manganese is irreversibly lost with the tailingsslag and also with the volatiles. In this process, the pro�duction of 1 t of metallic manganese is accompaniedby the formation of 3.5–4.0 t of slag containing up to20–22% MnO [2]. To increase the utilization of man�ganese, we need effective means of removing manga�nese from the slag.

The tailings slag from the furnace smelting of man�ganese with silicon contains 13–16 wt % Mn, 0.003–0.005 wt % P, 27–29 wt % SiO2, 43–46 wt % CaO, 2–4 wt % Al2O3, 2–4 wt % MgO, 0.1–0.2 wt % FeO, and0.1–0.2 wt % S [1, 2]. In view of the high Mn contentin the slag and the very low phosphorus content, it maybe regarded as a promising source of manganese. Onepossible approach to extracting manganese from suchslag is its reduction with metallic melts containing ele�ments whose oxygen affinity is higher than that ofmanganese. In that case, metallic manganese may beextracted from the slag.

The melts of iron, high�carbon ferromanganese,and ferrosilicomanganese are best suited to suchreduction. These melts contain carbon and silicon,which have an oxygen affinity higher than that of man�ganese and so are promising reducing agents. How�ever, the carbon and silicon in the melts is alreadybound to iron and manganese and hence will havereducing properties less pronounced than those of the

pure elements. Therefore, to establish whether thecarbon and silicon present in the selected melts arecapable of reducing manganese from the slag, weundertake thermodynamic analysis and experimentalverification.

The reduction of manganese in the tailings slag byelement R, whose oxygen affinity is higher than that ofmanganese, may be described in the form

(1)

where fi is the activity coefficient; the contents of thecomponents are expressed in wt %.

The liquid metal discharged from the furnace in theproduction of hot metal, high�carbon ferromanga�nese, or ferrosilicomanganese is at 1500–1550°C. Theslag from the furnace smelting of manganese with sili�con is liquid at those temperatures [1]. Since the slagmelts as a result of heat from the molten metal, thisheat is disregarded in the subsequent thermodynamiccalculations.

When using hot metal, we may write the corre�sponding form of Eq. (1)

(MnO) + [C]1%(Fe) = [Mn]1%(Fe + CO(g) (1a)

n MnO( ) li( ) m R[ ]1%+

= n Mn[ ] RmOn( ) so li g, ,( );+

K 1( )

%Mn[ ]fMn( )naRmOn

aMnO %R[ ]fR( )m��,=

Improving Manganese Utilization in the Production of Manganese Ferroalloys

V. Ya. Dashevskiia, Yu. S. Yusfina, A. A. Aleksandrovb, L. I. Leont’eva, G. S. Podgorodetskiia, and V. I. Gubanovc

aMoscow Institute of Steel and AlloysbBaikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences

cKosogorsk Metallurgical PlantReceived June 3, 2013

Abstract—To extract manganese from the tailings slag produced in the furnace smelting of manganese withsilicon, a possible approach is to reduce the slag by means of melts of iron, high�carbon ferromanganese, orferrosilicomanganese. Thermodynamic analysis of this process is undertaken. The reaction of these meltswith the slag is also studied experimentally. It is found that the reduction of manganese from such slag by car�bon from hot metal is promising for practical purposes. Hence, the overall extraction of manganese may beincreased if the tailings slag from furnace smelting of manganese is used to alloy hot metal with manganese.

Keywords: manganese, slag, hot metal, carbon, manganese extraction

DOI: 10.3103/S0967091213070036

STEEL IN TRANSLATION Vol. 43 No. 7 2013

IMPROVING MANGANESE UTILIZATION 425

as the sum of reactions

(2)

(3)

(4)

(5)

Here is the activity coefficient of oxygen in meltat infinite dilution; Mi is the molecular mass.

The Gibbs energy in Eq. (1a) is calculated as

For iron�based solutions, = 1.44 and =0.538 [4]. On average, hot metal contains 4% C. Inthat case, γC = 3.3 [5].

At 1773 K

= 250760 J/mol, = –267289 J/mol,

= –62286 J/mol, = –27639 J/mol.

Hence, = –51176 J/mol. We see that thereduction of manganese from manganese�productionslag by the carbon in hot metal is a viable process.

When using high�carbon ferromanganese, we maywrite the corresponding form of Eq. (1)

(MnO) + [C]1%(Mn) = Mn(li) + CO(g) (1b)

as the sum of Eqs. (2) and (3) and the reaction

(6)

The Gibbs energy in Eq. (1b) is calculated as

For manganese�based solutions

= –1.5966 + 1.0735 × 10–3T [6],

at 1773 K, = 0.307. The mean carbon content forthe ferromanganese is 6% C, and so γC = 2.3 [5].

At 1773 K

= 250760 J/mol, = –267289 J/mol,

= –33191 J/mol.

MnO so( ) Mn li( ) 1/2O2 g( ),+=

ΔG 2( )° 406873 88.05T, J/mol [3];+=

C so( ) 1/2O2 g( )+ CO g( ),=

ΔG 3( )° 114598 86.12T, J/mol [3];––=

Mn li( ) Mn[ ]1%(Fe),=

ΔG 4( )° RT

γMn Fe( )° MFe

100MMn

��⎝ ⎠⎛ ⎞ ;ln=

C so( ) C[ ]1%(Fe),=

ΔG 5( )° RT

γC Fe( )° MFe

100MC

��⎝ ⎠⎛ ⎞ln .=

γi Fe( )°

ΔG 1( )° ΔG 2( )

° ΔG 3( )° ΔG 4( )

° ΔG 5( )° .–+ +=

γMn° γC°

ΔG 2( )° ΔG 3( )

°

ΔG 4( )° ΔG 5( )

°

ΔG 1a( )

°

C so( ) C[ ]1%(Mn),=

ΔG 6( )° RT

γC Mn( )° MMn

100MC

��⎝ ⎠⎛ ⎞ .ln=

ΔG 1b( )° ΔG 2( )

° ΔG 3( )° ΔG 6( )

° .–+=

γC°

γC°

ΔG 2( )° ΔG 3( )

°

ΔG 6( )°

Hence, = 16 662 J/mol. We see that the reduc�tion of manganese from manganese�production slagby the carbon in high�carbon ferromanganese is not aviable process.

When using ferrosilicomanganese, we may writethe corresponding form of Eq. (1)

2(MnO) + [Si]1%(Si–Mn) = Mn(li) + (SiO2) (1c)

as the sum of Eq. (2) and the reactions

(7)

(8)

The Gibbs energy in Eq. (1c) is calculated as

For manganese�based solutions [7]

Hence, at 1773 K, = 2.518 × 10–5. Ferrosilicoman�ganese contains 18% Si, on average. Therefore, γSi =0.0127 [7].

At 1773 K

= 250760 J/mol, = –597112 J/mol,

= –124730 J/mol.

Hence, = 29074 J/mol. We see that the reduc�tion of manganese from manganese�production slagby the carbon in ferrosilicomanganese is not a viableprocess.

The reaction between slag from the furnace smelt�ing of manganese with silicon and the three melts ofinterest here—iron, high�carbon ferromanganese,and ferrosilicomanganese—is now studied experi�mentally.

We use an induction furnace connected to a 12�kWCEIA Power Cube 180/50 high�frequency generator.A weighed portion of metal (~400 g) is melted in acorundum crucible and its temperature is raised to1500°C. A portion of slag is spread over the moltenmetal. The slag melts and remains in contact with themetal. Metal samples are taken after the initial meltingof the metal and then at 5�min intervals after introduc�ing the slag.

ΔG 1b( )°

Si O2 g( )+ SiO2,=

ΔG 7( )° 949709 198.87T, J/mol [3];+–=

Si li( ) Si[ ]1%(Si–Mn),=

ΔG 8( )° RT

γSi Si–Mn( )° MSi–Mn

100MSi

��⎝ ⎠⎛ ⎞ln .=

ΔG 1c( )° 2ΔG 2( )

° ΔG 7( )° ΔG 8( )

° .–+=

γSi°ln 13206/T–=

– 7693.6/T 1.242–( ) 1+exp[ ]ln .

γSi°

ΔG 2( )° ΔG 7( )

°

ΔG 8( )°

ΔG 1c( )°

426


DASHEVSKII et al.

REACTION OF SLAG WITH HOT METAL

The initial hot�metal composition is as follows:3.25 wt % C, 0.26 wt % Mn, 0.41 wt % Si, 0.11 wt % S.

The composition of the tailings slag is as follows:15.7 wt % Mn, 0.2 wt % FeO, 0.005 wt % P, 27.9 wt %SiO2, 45.4 wt % CaO, 3.5 wt % Al2O3, 3.3 wt % MgO,0.19 wt % S.

We consider four melts: the slag content is 5% ofthe hot�metal mass (20 g) in melts 1 and 2, 3% (12 g)in melt 3, and 10% (40 g) in melt 4. The results areshown in Table 1 and in figure (a). As is evident, themanganese content in the melt increases over time,thanks to the reaction of manganese oxide in the slagwith carbon from the hot metal (Table 1, figure (a)).Correspondingly, the carbon content in the metaldeclines (Table 1, figure (b)), partly on account ofreaction with atmospheric oxygen. The manganesecontent in the hot metal increases increase in theadded slag: when the slag amounts to 10% of the metalmass, the manganese content in the melt increasesalmost fivefold. Calculations show that, on treatingthe hot metal with slag from the furnace smelting ofmanganese with silicon, 60–75% of the manganese inthe slag is removed, and hence the overall utilization ofthe manganese is improved (Table 2).

Thus, in smelting hot metal, the consumption ofmanganese�bearing raw materials may be reduced(or eliminated), and the required Mn content in thehot metal (0.5–1.5% or more) may be provided byadding slag from the furnace smelting of manganesewith silicon.

Note that, in the presence of the slag, the sulfurcontent in hot metal is reduced by 30–45%, depend�ing on the quantity of slag (Table 1, figure (c)). Sincethe initial slag contains 0.19% S, it is interesting tostudy how the desulfurization occurs. Two routes arepossible: by reaction of calcium oxide CaO (45.4% ofthe slag) with sulfur in the hot metal, to form calciumsulfide CaS in the slag; or by the reaction of manga�nese from the slag with sulfur dissolved in the hotmetal, to form manganese sulfide MnS, which passesto the slag

[S] + (CaO) → (CaS);[S] + [Mn] → (MnS).

To resolve this issue, we conduct experiments onthe desulfurization of iron melt containing sulfur butno carbon in the presence of slag from the furnacesmelting of manganese with silicon. In the experi�ments, a weighed portion of carbonyl iron (400 g) ismelted in a corundum crucible and heated to 1600°C.A weighed portion of Fe–S alloy (22.5% S) is depos�

Table 1. Variation in Mn, C, and S content in the hot metal, %

MeltSample 1 Sample 2 Sample 3 Sample 4

Mn C S Mn C S Mn C S Mn C S

1 0.26 3.25 0.11 0.58 3.07 0.076 0.70 2.87 0.077 0.82 2.72 0.0772 0.26 3.25 0.11 0.75 3.10 0.082 0.79 2.95 0.078 0.81 2.74 0.0823 0.26 3.25 0.11 0.51 3.13 0.092 0.56 2.99 0.087 0.61 2.85 0.0874 0.26 3.25 0.11 1.0 3.23 0.061 1.1 3.13 0.056 1.2 3.02 0.059

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

1

2

3

4

Mn

, w

t %

(a)

3.6

3.4

3.2

3.0

2.8

2.6

1 2

3

4

C,

wt

%

(b)

0.14

0.12

0.10

0.08

0.06

0.04

1

23

4

S,

wt

%

(c)

0 5 10 15t, min

Manganese (a), carbon (b), and sulfur (c) content in hotmetal as a function of the holding time in contact with slagfrom manganese production, for melts 1–4.


IMPROVING MANGANESE UTILIZATION 427

ited on the melt surface, so as to obtain ~0.1% S in themelt. After holding for 5 min, the initial sample istaken. Then slag from the furnace smelting of manga�nese with silicon is deposited on the melt surface in afixed quantity (20 g, or 5% of the metal mass), andsamples are taken after 5, 10, and 15 min. Table 3 pre�sents the experimental results.

As we see, if iron melt containing 0.09–0.15% S istreated with slag from manganese production, the sul�fur content is not reduced, despite the high content ofcalcium oxide in the slag (45.4% CaO). This is obvi�ously because the slag already contains sulfur (0.19% S).Hence, in the treatment of hot metal with slag frommanganese production, desulfurization evidentlyoccurs because of the formation of manganese sulfide,which passes to the slag. The degree of desulfurizationdepends both on the manganese content in the meltand on the carbon content, since carbon not onlyreduces manganese from the slag but also significantlyincreases the activity of sulfur in iron�based melts

( = 6.24 [4]), thereby facilitating more completedesulfurization.εS Fe( )

C

Thus, the experimental results are in completeagreement with the thermodynamic analysis. In thepresence of hot metal, significant quantities of manga�nese are extracted from slag produced in the furnacesmelting of manganese with silicon. Hence, the overallutilization of the manganese is improved.

On that basis, we have developed and patented amethod for the alloying of hot metal with manganese[8]. In the method, hot metal from the blast furnace isdischarged to a ladle that already contains tailings slagfrom the furnace smelting of manganese with silicon.The quantity of slag is calculated on the basis of therequired manganese content in the hot metal. Corre�spondingly, manganese�bearing ore is completely orpartially removed from the batch used in smelting thehot metal.

REACTION OF SLAG WITH MOLTEN HIGH�CARBON FERROMANGANESE

The initial ferromanganese composition is as follows:16.3 wt % Fe, 6.36 wt % C, 1.09 wt % Si, 0.01 wt % S,0.12 wt % P. We consider three melts. The methodemployed is as in the previous case. The slag content is5% of the hot�metal mass (20 g). The results are shownin Table 4.

As is evident, the content of manganese, carbon,and silicon in the melt remains practically unchangedover time. Hence, there is no reaction of carbon andsilicon from the melt with manganese oxide in the slag.The results are in good agreement with the thermody�namic analysis.

REACTION OF SLAG WITH MOLTEN FERROSILICOMANGANESE

The initial ferrosilicomanganese composition is asfollows: 73.8 wt % Mn, 30.3 wt % Si, 1.05 wt % C,0.32 wt % P. We consider three melts. The methodemployed is as in the previous case. The slag content is5% of the hot�metal mass (20 g). The results are shownin Table 5.

As is evident, the content of manganese, carbon,and silicon in the melt remains practically unchangedover time. Hence, there is no reaction of carbon andsilicon from the melt with manganese oxide in the slag.

Table 2. Reduction of manganese from slag by the carbonin hot metal

Melt Quantity of Mn in added slag, g

Transfer of Mn to hot metal, g

Degree of Mn reduction from

slag, %

1 3.14 2.24 71.34

2 3.14 2.20 70.06

3 1.88 1.40 74.31

4 6.28 3.76 59.87

Table 3. Sulfur content in hot metal, %

Melt Sample 1 Sample 2 Sample 3 Sample 4

1 0.09 0.09 0.09 0.10

2 0.15 0.15 0.15 0.14

3 0.13 0.13 0.13 0.13

Table 4. Variation in Mn, C, and S content in ferromanganese, %


Mn C Si Mn C Si Mn C Si Mn C Si

1 75.61 6.28 1.06 75.69 6.28 1.09 73.81 6.21 1.02 73.31 6.31 1.07

2 76.39 6.27 1.12 74.52 6.39 1.01 72.38 6.30 0.72 70.06 6.40 0.64

3 74.06 6.44 0.92 73.41 6.49 1.08 73.53 6.47 1.00 72.91 6.50 0.88

428


DASHEVSKII et al.

The results are in good agreement with the thermody�namic analysis.

CONCLUSIONS

Thermodynamic analysis of the extraction of man�ganese from tailings slag obtained in the furnacesmelting of manganese with silicon shows that thisprocess is well developed in the presence of hot metal.Carbon in the hot metal reduces the manganese oxidein the slag. In the case of high�carbon ferromanganeseand ferrosilicomanganese, despite their high contentof carbon and silicon, there is no extraction of manga�nese from the slag.

Experiments confirm the reduction of manganesefrom the slag in the presence of hot metal. Hence, theoverall utilization of the manganese in the initial ore isimproved if the slag obtained from the furnace smelt�ing of manganese with silicon is used to alloy hot metalwith manganese. By this means, the consumption ofmanganese�bearing raw materials may be reduced(or eliminated). The proposed method is covered by aRussian patent.

Experiments also confirm that high�carbon ferro�manganese and ferrosilicomanganese do not permitextraction of manganese from the slag in the same way.

REFERENCES

1. Gasik, M.I., Metallurgiya margantsa (Metallurgy ofManganese), Moscow: Metallurgiya, 1992.

2. Lyakishev, N.P., Gasik, M.I., and Dashevskii, V.Ya.,Metallurgiya ferrosplavov (Metallurgy of Ferroalloys),Moscow: Ucheba, 2006, vol. 1.

3. Kulikov, I.S., Raskislenie splavov (Reduction of Alloys),Moscow: Metallurgiya, 1975.

4. Steelmaking Data Sourcebook, New York: Gordon &Breach, 1988.

5. Katsnelson, A.M., Dashevskiy, V.Ya., and Kashin, V.I.,Steel Res., 1993, vol. 64, no. 4, pp. 197–202.

6. Dashevskii, V.Ya., Metally, 2007, no. 6, pp. 13–17.

7. Dashevskii, V.Ya., Katsnel’son, A.M., Krylov, A.S.,et al., Thermodynamic properties of manganese–phosphorus and manganese–silicon alloys, Teoriya ipraktika metallurgii margantsa (Theoretical and Practi�cal Aspects of the Metallurgy of Manganese), Moscow:Nauka, 1990, pp. 9–18.

8. Dashevskii, V.Ya., Yusfin, Yu.S., Aleksandrov, A.A., et al.,Russian patent application 2011123752/02(033136), 2012.

Translated by Bernard Gilbert

Table 5. Variation in Si and Mn content in ferrosilicomanganese, %


Si Mn Si Mn Si Mn Si Mn

1 21.2 74.8 20.7 72.8 20.3 73.9 19.6 75.0

2 19.6 73.6 19.4 72.3 21.1 75.4 21.1 74.2

3 21.8 73.2 20.0 74.4 19.2 76.8 19.5 73.6

improving manganese utilization in the production of manganese ferroalloys

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