Smelting Oxidation Desulfurization of Copper Slags

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J O U R N A L OF IRON A N D S T E E L R E S E A R C H , I N T E R N A T I O N A L . 2012, 1 9 0 2 ) : 14-20

Smelting Oxidation Desulfurization of Copper Slags LI L e i ,

HUJian-hang,

W A N G Hua

( E n g i n e e r i n g Research Center of Metallurgical E n e r g y Conservation and E m i s s i o n R e d u c t i o n of Ministry of E d u c a t i o n , F a c u l t y of Metallurgical and E n e r g y E n g i n e e r i n g , K u n m i n g U n i v e r s i t y of Science and T e c h n o l o g y , K u n m i n g 6 5 0 0 9 3 , Y u n n a n , China) Abstract: A c c o r d i n g to the m e c h a n i s m of sulfur removal easily t h r o u g h o x i d a t i o n , the p r o c e s s of smelting oxidation desulfurization of copper s l a g s is s t u d i e d , w h i c h supplies a n e w thinking for obtaining the m o l t e n iron of l o w e r sulfur content by s m e l t i n g reduction of copper s l a g s . Special attention is g i v e n to the effects of the holding t e m p e r a t u r e , the holding time and C a F , CaO addition a m o u n t s o n the desulfurization rate of copper slags. T h e results indicate that 2

the rate of copper s l a g s s m e l t i n g oxidation desulfurization d e p e n d s o n the m a t t e m a s s transfer rate t h r o u g h the slag phase. After the oxidation t r e a t m e n t , sulfur of copper s l a g s can be removed as S O 2 efficiently.

A m o u n t of C a

2 +

of

copper s l a g s affects the desulfurization rate g r e a t l y , and the slag desulfurization rate is reduced b y adding a certain amount of C a F and CaO. Compared w i t h C a F 2 , CaO is negative to s l a g s sulfur removal w i t h equal C a 2

2 +

addition.

U n d e r the air f l o w of 0. 3 L ' / m i n , the sulfur content of copper s l a g s can be reduced to 0. 0 0 4 6 7 % in the condition of the holding time of 3 m i n and the holding temperature of 1 5 0 0 °C. T h e sulfur content of m o l t e n iron is reduced to 0. 0 0 0 8 % in the s m e l t i n g reduction of treated s l a g s , and the problem of high sulfur content of m o l t e n iron obtained by s m e l t i n g reduction w i t h copper slag h a s been s u c c e s s i v e l y solved. Key w o r d s : copper s l a g ; s m e l t i n g oxidation desulfurization; additive; gas-liquid reaction

Copper slags are silicates melted by smelting copper b u r d e n and fuels, which contain the main sim­ ple oxides of S i 0 , F e O , CaO, A 1 0 and MgO™ , etc. F e O of 5 1 . 4 3 % is well w o r t h recycling. 2

Z

3

[ 2 ]

R e c e n t l y , t h r e e m e t h o d s for recycling iron from copper slags have been s t u d i e d : high t e m p e r a t u r e oxidation-room temperature crushing magnetic selection process - , multistage grinding-mineral process - ~ and direct smelting reduction process. There are two defects existing in the high t e m p e r a t u r e oxidation-room tem­ p e r a t u r e crushing magnetic selection p r o c e s s ; 1

3]

1

4

5]

1) F o r the reason t h a t slags melting point and viscosity are increased at the end of the oxidation re­ action caused by large a m o u n t of magnetite precipi­ t a t i o n , the oxidation reaction occurrence and the magnetite phase aggregation g r o w t h are prevented and the iron recovery rate of copper slags is reduced; 2) The process is complicated with the material used as ironmaking after the crushing magnetic selection. Because t h e magnetite content of copper slags is

as low as 2 0 % — 30 X - - , the main ferric-containing phase ferrosilicate enters tailings in multistage grinding-mineral p r o c e s s , which causes the iron r e ­ covery rate low ( a b o u t 6 0 % ) . LI L e i , et a l uti­ lize direct smelting reduction to enhance the iron re­ covery rate from copper s l a g s , but the results show that the sulfur content of molten iron is high causing the generated iron worthless. Using the secondary refining - - to realize the sulfur removal, the process energy consumption is large. 1

4

1

m

1

7-8

1

Based on the a b o v e , smelting oxidation-reduc­ tion process is firstly submitted to generate molten iron of low sulfur content from copper slags. Effects of the holding t e m p e r a t u r e , the holding t i m e , the addi­ tive sorts and a m o u n t s on copper slags desulfuriza­ tion rate are investigated.

1 1.1

Experimental Experimental reagents T h e chemical composition of copper slags used

Foundation Item Item Sponsored by National Natural Science Foundation of China (50906035, 51204082) :

Biography LI Lei( 1 9 8 6 — ) , Male, Doctor; :

E-mail: [email protected];

Corresponding Author: H U Jian-hang(1976—), Male, Professor;

[6]

Received Date: August 1 , 2 0 1 1

E-mail: [email protected]

S m e l t i n g O x i d a t i o n Desulfurization of Copper S l a g s

Issue 12

15

is presented in T a b l e 1. It s h o w s t h a t iron content of

slags are 2FeO · S i 0

the copper slag is 38. 5 5 % , which is well w o r t h to

have proposed t h a t the main sulfur phases of copper

be reclaimed. But t h e sulfur content is 0. 5 2 % .

To

and F e 0 .

2

3

slags are F e S and C u S 2

[ 9

1 1 ]

.

4

Some researchers

" O t h e r s " ( T a b l e 1) is

characterize t h e copper slag phase components clearly,

mainly composed of Ο (existing as F e O , F e 0

the original copper slag are reprocessed.

C u 0 etc. ) ,

3

T h e y are

2

Pb ( 2 . 0 6 6 5 % )

4

and

and Zn ( 1 . 8 3 8 3 % )

remelted in t h e furnace firstly and then cooled slowly

e t c , effects of which on sulfur removal are insignifi­

in N . Fig. 1 indicates that the main phases of copper

cant due to their components or low contents.

2

Table 1

Chemical composition of copper slags

Component

Fe

CaO

Si0

Contents

38.55

2. 77

34.08

1200 r

•

Fe Si0 2

A Fe 0 3

A1 0

2

2

3

3. 90

(mass percent, %)

MgO

Cu

S

Others

1. 14

1.06

0. 52

17. 98

Fl 4



I

4

valve j Relief valve / Furnace cover 1

Control cabinet -Thermocouple • MoSi? heating staff i^A^Os furnace tube !>A1 0 gas piping -^Reactor 2

20

60

40

pad block

20/(°) Fig. 2 Fig. 1

2

atmosphere after being melted

the container is cooled d o w n under N velocity of 0. 1 L/min. 2

Experimental set-up and procedure T h e main furnace used is a crucible furnace with

a m a x i m u m operating t e m p e r a t u r e of 1 600 'C with a p r o g r a m m a b l e E u r o t h e r m 2416

fit

temperature

controller. T h e furnace is heated w i t h six vertical MoSi

2

Experimental device

X R D pattern of copper slags cooled with

furnace in N

1. 2

3

Tire-resistant

elements secured around t h e furnace

work

tube. T h e reactor is m a d e of M g - A l spinel.

1.3

Characterization T h e chemical composition of copper slags is an­

alyzed by chemical analysis.

T h e sulfur content of

t h e treated copper slags and molten iron is analyzed with Inductive Coupling Plasma Emission Spectro­ graph ICP-ΙΟΟΟΠ produced by J a p a n Shimazu Com­

T h e air flow rate is fixed at 0. 3 L / m i n in all ex­

pany. Rigaku D / m a x - 3 B X-ray diffraction ( X R D ) is

periments'- - . Effects of t h e holding t e m p e r a t u r e and

applied to investigate the phase composition of cop­

the holding time on the desulfurization rates of cop­

per slags.

per slags are researched firstly, and t h e holding t e m ­

( 1 0 0 ) with a step of 8° and a time per step of 1 min.

3

1

perature is varied from 1500 to 1600

'C and t h e

holding time from 0 to 10 min. T h e n t h e ( C a F

2

to

copper slags) and ( C a O to copper slags) m a s s ratio of w=0,

5. 3 % , 6. 7 % , 9. 2 % and 11. 1 % are con­

sidered to elucidate t h e effects of additive a m o u n t s and s o r t s on desulfurization rates. Before being load­ ed into t h e furnace, t h e additives and copper slags are mixed firstly. After t h e materials being filled in­ to the r e a c t o r , t h e container with its content is heat­ ed to t h e envisaged t r e a t m e n t t e m p e r a t u r e under N

z

velocity

2

of

0. 1

L/min

in

the

experiments.

N

changed into 0 , A 1 0 gas piping (Fig. 2) is inserted 2

2

3

into the molten pool to realize t h e sulfur oxidative removal from copper slags. At the end of the treatment,

2 2.1

Spectra is registered b e t w e e n 5 and 80

Results and Discussion Relation of copper slags desulfurization rate

with holding temperature Effects of t h e holding t e m p e r a t u r e varying from 1 500 to 1600°C on copper slags desulfurization rate are studied in the first series of experiments. Copper slags smelting oxidation desulfurization is gas-liquid reaction, possible reaction process of which can be illustrated as t h e following e q u a t i o n s : Cu S+|-0 -f-;ySi0 =Cu 0 · ySi0 +S0 2

FeS-

2

2

2

2

-0 +xSi0 =FeO · xSi0 +S0 2

2

2

2

2

(1) (2)

Journal of Iron and Steel R e s e a r c h ,

16

International

Vol. 19

It consists of five steps as follows: 1) 0 diffusion from t h e main g a s body to t h e gas-liquid interface. 2) FeS and C u S diffusion from the main slag body to the gas-liquid interface.

on t h e oxygen transfer rate when Eqn. ( 8 ) is grati­ fied, and t h e n it depends on t h e F e S transfer rate

3) F e O , C u 0 and S O production by the oxidation reaction of 0 , FeS and Cu S at the gas-liquid interface.

Cls w h e n / ? = ! .

2

Po,

with C . < F

S

2

z

2

2

2

2

ko,

5) S 0 diffusion into t h e gas phase. T h e oxidization rates of F e S , C u S , t h e silicatization rates of F e O , C u 0 and t h e S 0 diffusion into gas rate are fast at copper slags molten state, meaning steps ( 3 ) , ( 4 ) , and ( 5 ) are not rate limited l i n k s , causing t h e rate limited links possibly to be step ( 1 ) or step ( 2 ) . 2

2

2

2

T h e oxygen transfer rate J o t h r o u g h t h e gas 2

phase is proportional t o t h e 0

2

mass transfer coeffi­

cient ko and t h e driving pressure difference (·Ρο ~~ z

2

Ρ ο ) , is defined by Eqn. ( 3 ) : ko,

(3)

w h e r e , R is t h e mole gas c o n s t a n t ; Τ is t h e ambient temperature; P

is t h e oxygen partial pressure of

0Z

the main gas body.

T h e oxygen interface

partial

p r e s s u r e Pq in Eqn. ( 3 ) is equal to 0 because t h e in­ 2

terface reaction rate is fast. T h e oxygen transfer rate at this point is t e r m e d a s J„ =^Po 2

:

(4)

2

Based on t h e Fick first l a w , t h e F e S transfer r a t e JF s t h r o u g h molten slags is determined using the following relation: e

Fs e

(C -C * ) (5) where, £ is t h e mass transfer coefficient of F e S ; CF„S is t h e F e S concentration of molten s l a g s ; Cpes is t h e interfacial concentration of F e S . A s m e n t i o n e d a b o v e , Cpes is also equal to 0. T h e n / e s can be changed to Eqn. ( 6 ) , F e S

F

e S

F e S

(6)

=

e

β is defined as t h e ratio of t h e oxygen and F e S transfer hr a t e , ko, 1 (7) RT

CfcS

In Eqn. ( 7 ) , if /?
W i t h t h e F e S mass transfer coefficient k of 9. 6 Χ 1 ( Γ c m / s at 1 300 ' C , £ . s diffusion through copper slags is calculated of 1. 11 X 10"" c m / s at 1 500 °C by an equation of D = D e ~ , w h e r e , D is the diffusion coefficient of F e S , D is t h e frequency factor of F e S , and Q is diffusion activation energy of FeS. T h e n t h e critical concentration C s is obtained to be 2. 7 % by inserting t h e oxygen pressure P ( 2 1 . 2 7 k P a ) , mass transfer coefficient k ( 0 . 6 4 c m / s ) , copper slag density ( 2 . 7 Χ 10 k g / m ) and the F e S transfer rate coefficient k $ into Eqn. ( 9 ) at a t e m p e r a t u r e of 1 500 "C. It is higher t h a n F e S con­ tent of copper s l a g s , because t h e F e S content should be lower t h a n 1. 43 % owing to t h e relatively low sulfur content ( 0 . 5 2 % ) of copper slags. T h e oxida­ tion of F e S depends on its mass transfer r a t e , so does t h e oxidation reaction of C u S . FeS

5

2

RT

z

Q / R T

0

0

Fe

0

Qi

z

3

3

Fe

2

For t h e reason that t e m p e r a t u r e increase aug­ m e n t s t h e F e S and C u S mass transfer r a t e , t h e slag sulfur content after t r e a t m e n t is decreased from 0 . 0 0 4 6 7 % to 0 . 0 0 4 3 2 % slowly w h e n t h e holding t e m p e r a t u r e is increased from 1500 to 1575 °C at t h e holding time of 3 min ( F i g . 3 ) . W h e n t h e holding t e m p e r a t u r e is increased to 1 600 °C , t h e slag sulfur content is decreased to 0. 0 0 0 5 % sharply. T h e reason may be t h a t t h e slag viscosity is reduced rapidly at a higher t e m p e r a t u r e of 1 600 "C , which enhances t h e mass transfer rate of F e 0 and sulfur phases greatly. T h e n t h e sulfur is removed rapidly by the oxidation of 2

3

4

0.009

• 3 min • 5 0.007 • * 8

i

Β 0.005 ο g 0.003 8P

55

^ 0

(8)

T h e desulfurization rate of copper slags depends

[ 1 2 ]

K

1

1500 C-FeS^-*

(9)

RT

F

JVeS ^ F s C F e S

Po,

2

2

J FeS ~k

copper slags is defined as t h e critical concentration

2

4) FeO · x S i 0 and C u 0 · v S i 0 diffusion into the slag phase produced by t h e complex reaction forms of F e O , C u 0 and S i 0 .

T h e F e S concentration of

RT

2

Fig. 3

1 535 "C

\ ^

1

1520 1540 1560 1580 Holding temperature/t

1 600

Effect of holding temperature on slag oxidation treatment

S m e l t i n g Oxidation Desulfurization of Copper S l a g s

Issue 12

the inherent and new generated F e 0 of copper slags. The possible reactions considered a r e 3

4

:

3(FeO) + l / 2 0 = F e 0 (10) 3Fe O +FeS=10(FeO)+SO (g) (11) 3Fe 0 + C u S = 9 ( F e O ) + C u 0 + S 0 ( g ) (12) When the holding time is prolonged to 5 and 8 min, the slag sulfur content is firstly decreased slowly with t e m p e r a t u r e increased from 1 500 to 1 535 °C , then elevated sharply as the holding t e m p e r a t u r e is increased to 1 575 °C , at last reduced to a lower level with t e m p e r a t u r e increased to 1 600 "C (Fig. 3 ) . T h e melting slag surface tension is increased w i t h the holding t e m p e r a t u r e of 1 535 *C , resulting in the di­ ameter of S 0 bubble reduction. According to u = dlg(.pi—p )/12, the velocity of S 0 bubble ascend­ ing t h r o u g h the molten slag is decreased, w h e r e , u is the rising velocity of S 0 b u b b l e , d is t h e equiva­ lent diameter of S 0 b u b b l e , pi is the density of mol­ ten s l a g s , g is the gravitational constant and p is the density of S 0 b u b b l e . T h e n it causes S 0 to be oxi­ dized by the p u m p e d air and reacted with CaO form­ ing CaS0 - - which is immobilized in t h e slag. T h e direct decomposition of C a S 0 at t h e test t e m p e r a ­ ture is not feasible for AG of its ( C a S 0 ) decompo­ sition is above 0 according to T a b l e 2 , but S i 0 ex­ isting in the original slags urges it to happen by de­ creasing the activity of CaO generated [ E q n . ( 1 4 ) ] . After C a S 0 is decomposed, S 0 can be immobilized in copper slags as C a S 0 again [ E q n . ( 1 5 ) ] . T h e closed circulation of S 0 generation and immobiliza­ tion is formed in the slag ( S 0 ) — » - ( C a S 0 ) , causing the sulfur content to be increased slightly as t e m p e r ­ ature is increased from 1 500 to 1 575 "C. 2

3

3

4

4

3

2

4

2

2

2

2

t

2

2

c

2

g

2

1

13

2

17

is little; w h e n the holding time is prolonged to 5 and 8 m i n , the slag sulfur content is increased with tem­ perature rising from 1 535 to 1 575 "C; as the tempera­ ture is 1600 °C, the energy consumption is huge t h o u g h t h e slag sulfur content is reduced sharply. At l a s t , the holding t e m p e r a t u r e is fixed at 1 500 °C. 2. 2 Relation of copper slags desulfurization rate with holding time In the second series of e x p e r i m e n t s , effects of the holding time varying from 0 to 10 min on copper slags desulfurization rates are studied with the hold­ ing t e m p e r a t u r e of 1 500 'C. It is inferred from Fig. 4 that the slag sulfur content is firstly reduced and then increased slightly when the holding time is prolonged from 5 to 10 min. W i t h the holding time for 0 m i n , the slag sulfur content is decreased from 0. 5 2 % to 0. 0 4 9 % , the reason for which may be ascribed to the desulfurization reactions between F e 0 and sul­ fur phases. 3

4

1

4

4

9

4

2

4

2

4

2

2

4

4 6 Holding time/min Fig. 4

2CaS0 =2CaO-|-2S0 +0 4

2

(13)

2

2CaS0 + 2 S i 0 = 2 S 0 (g) + 2 C a S i 0 + 0 4

2

2

3

2

(g) (14)

2S0 +0 +2CaO=2CaS0 (15) W h e n the t e m p e r a t u r e is increased to 1 600 "C , the decomposition of C a S 0 plays a major role resul­ ting the slag sulfur content after treatment is reduced sharply. 2

2

4

4

A s mentioned a b o v e , the slag sulfur content is reduced w h e n t e m p e r a t u r e is increased from 1 500 to 1575 °C w i t h the holding time for 3 min, but the range

Effect of holding time on slag sulfur content after

oxidation treatment under holding temperature of 1 5 0 0 C

W h e n the holding time is prolonged to 1, 2 and 3 m i n , the slag sulfur content is decreased signifi­ cantly to 0.019 3 % , 0 . 0 0 8 0 6 % and 0 . 0 0 4 6 7 % re­ spectively because of the strong oxidation of the pumped air. H o w e v e r , when the holding time is prolonged f u r t h e r , the quantity of magnetite F e 0 is increased. A s a r e s u l t , the slag viscosity is im­ proved and the rate of the S 0 bubble ascending t h r o u g h the molten slag is decreased. T h e n one part of S 0 has been oxidized and immobilized in the slag as C a S 0 [ E q n . ( 1 5 ) ] before it escapes from the mol­ ten slag interface. So the slag sulfur content is in­ creased slightly from 0. 004 3 1 % to 0. 005 2 1 % with the holding time prolonged from 5 to 10 min. 3

4

2

2

Table 2

Value of AG" at different temperatures of C a S 0

4

direct decomposition and decomposition participated by S i 0 T/C

1 500

1525

1550

2

1575

1600

72. 477

61.227

50. 000

38. 794

27.610

- 2 6 . 196

— 28. 907

- 3 1 . 615

- 3 4 . 319

- 3 7 . 019

4

T o increase t h e desulfurization rate of copper s l a g s , the holding time is fixed for 3 min with the

Journal of Iron and Steel R e s e a r c h ; International

18 ·

holding t e m p e r a t u r e of 1 500 "C.

Vol. 19

ficient of S ~ is decreased greatly with C a F addition a m o u n t s increased, owing to C a generated from C a F bounding S " and forming weak electron pair (CaS) , which results in the decreasing of desulfu­ rization rate. T h e other one is t h a t the amount of C a is increased with C a F addition amounts enhanced according to the ion theory h y p o t h e s i s , for which more S 0 can be immobilized in the slag as illustrated in the following equations-. 2

2

2 +

2.3 Relation of copper slags desulfurization rate with additives A s mentioned a b o v e , the oxidation rates of F e S and C u S depend on their m a s s transfer rates. Effects of C a O , C a F addition a m o u n t s on the desul­ furization rates of copper slags are studied for the reason t h a t t h e slag viscosity and surface tension af­ fect the m a s s transfer rate coefficient g r e a t l y . 2. 3. 1 Effects of amount of CaF on copper slags desulfurization rate 2

2

[ H ]

2

W i t h C a F addition a m o u n t s increasing from 0 to 1 1 % , Fig. 5 shows that the hematite ( F e 0 ) content of copper slags is increased. It indicates that the components of the molten slag m a s s transfer rates are enhanced with the increasing of C a F addi­ 2

2

3

2

tion amounts'[15-17] But Fig. 6 s h o w s that the sulfur contents are improved when the CaF addition amounts are increased, and there may be two kinds of mecha­ nisms for t h i s . T h e first one is t h a t the activity coef2

1200

•Fe 0 *Fe 0

1000

JI:

2

3

3

4

2 +

2

2

CaF =Ca

2 +

2

+2F^

(16)

0 =2[0] S "+2[0] = S0 +2e^

(17) (18)

2

2

2

[0] + Ca +O ^+S0 =CaS0 (19) T h e regular p a t t e r n of copper slags sulfur desul­ furization rate with the holding time of 5 min is stud­ ied to determine the mechanism. 2 +

z

2

4

Fig. 7 shows that the sulfur contents are increased significantly when the holding time is prolonged from 3 to 5 min, indicating that the reason for the sulfur con­ tent improvement with CaF addition amount increase cannot be the first one. If n o t , the sulfur contents of copper slags after t r e a t m e n t should be reduced when the holding time is prolonged, for the reason t h a t the standard gibbs free energy A,G of CaS oxidation reaction is equal to —316 480 J / m o l lower than 0 ac­ cording to Eqn. ( 2 0 ) , meaning sulfur can be removed by the oxidation of C a S : 2

e

m

Τ

800

^

C a F 2 addition

600 400

C a S + y 0 = =CaO+S0 2

200

2

(20) - 4 5 3 710 + 77. AT J / m o l [18] S 0 immobilization with CaO is found to be r e ­ sponsible for the sulfur accumulation in the slag dur­ ing the oxidation t r e a t m e n t . W h e n the holding time is prolonged, the quantity of hematite F e 0 is in­ creased, as a result of which the slag viscosity is im­ proved and the rate of S 0 bubble ascending t h r o u g h the molten slag is decreased. Then one part of S 0 has A,GJL =

No additive 0

2

20

40

60

100

win Fig. 5

2

2

X R D patterns of treated copper slags with

1 1 % C a F addition and n o additive under 2

holding time of 3 m i n at 1 5 0 0 °C

2

3

2

2

0.018

4 8 CaF addition amount/%

12

2

Fig. 6

CaF addition amount/%

Effect of C a F amounts on slag sulfur

2

2

content after oxidation treatment under holding time of 3 m i n at 1 5 0 0 °C

Fig. 7

Effect of C a F amounts on slag sulfur content after 2

oxidation treatment under holding temperature of 1 5 0 0 °C

Issue 12

S m e l t i n g Oxidation Desulfurization of Copper S l a g s

been oxidized and immobilized in the slag as C a S 0 [Eqn. ( 1 5 ) ] before they escape from the molten slag interface. 4

2. 3. 2 Effects desulfurization

of amounts rate

of CaO on copper

slags

2 +

z +

2

Fig. 8 s h o w s the slag sulfur content after oxidiz­ ation with CaO addition is higher t h a n t h a t with C a F addition as equal C a addition. T h i s effect is explained by the fact t h a t C a F can reduce the viscos­ ity of copper slags more obviously t h a n CaO which promotes the desulfurization reaction; in addition CaO activity is decreased by the formation of eutectoids - - between C a F and CaO which decreases its fixation effect of S 0 . 2 +

2

2

13

circulation of S 0 generation and immobilization is formed in the slag; ( S 0 ) - * • ( C a S 0 ) . When the tem­ perature is increased to 1600 *C , sulfur content of slags is reduced sharply caused by rate of decomposi­ tion of C a S 0 higher t h a n S 0 immobilization. 2) Reactions between F e 0 and FeS, C u S hap­ pened as copper slags are melt, causing the slag sulfur content decrease with t h e holding time for 0 min. 3) T h e desulfurization rate of copper slags is de­ creased with C a F , CaO addition, because of the im­ mobilization of C a to S 0 ; C a F has a better per­ formance t h a n t h a t of CaO in desulfurization with equal C a quantity in oxidation t r e a t m e n t process. 2

2

4

4

According to the above analysis, a m o u n t of C a of copper slags affects the desulfurization rate greatly. W i t h the same C a addition amount as C a F , effects of a m o u n t s of CaO on the slag desulfu­ rization rate are studied.

1

19

1

4

2

2

2 +

2

2

2+

References: [I]

Shen H , Forssberg E. An Overview of Recovery of Metals

[2]

ZHU Zu-ze, HE Jia-qi. Modern Copper Metallurgy [ M ] . Bei­

From Slags [ J ] . Waste Management, 2003, 2 3 ( 1 0 )

:

933.

jing: Science Press, 2003 (in Chinese).

2

2

2

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