The Equilibrium Constant of the Reaction Between Liquid Iron and Hydrogen Sulphide

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The

EQUILIBRIUM

CONSTANT

o f t h e r e a c t i o n b etw een

LIQUID

IRON

and

HYDROGEN

SULPHIDE«

ProQuest N um ber: 13849813

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uest ProQuest 13849813 Published by ProQuest LLC(2019). C opyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C o d e M icroform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 4 8 1 0 6 - 1346

T H E S I S

submitted to the

UNIVERSITY

HUGH

OF

GLASGOW

SKELLY,

B .S e .,

for the

DEGREE

QF

DOCTOR

OF

PHILOSOPHY -

CONTENTS. Page INTRODUCTION....................................................................................... PRINCIPLE

OF

1

M E T H O D ............................................................

12

APPARATUS............................................................................................. .

14

PRELIMINARY

INVESTIGATIONS............................................................ 26

EXPERIMENTAL

METHOD

...............................................................

33

EXPERIMENTAL

RESULTS

..................................................

44

DISCUSSION

OF

.

RESULTS...................................................................... 59

C O N C L U S IO N ..................................................................................................66 ACKNOWLEDGMENTS........................................................................................69 REFERENCES

...................................................................... 70

1. INTRODUCTION,

B a la n c e d R e a c tio n s and D e s u l p h u r i s a t io n i n th e B a sic O p en -H earth F u r n a c e . The r e a c t i o n s w h ic h b r i n g a b o u t t h e r e m o v a l o f i m p u r i t i e s fro m t h e b a t h o f m e t a l i n t h e b a s ic , o p e n - h e a r t h f u r n a c e h a v e b e e n e s t a b l i s h e d i n a q u a l i t a t i v e m anner.

The f o l l o w i n g e q u a t i o n s r e ­

p r e s e n t th e p r i n c i p a l r e a c tio n s in v o lv e d in th e p u r i f i c a t i o n o f t h e m o lten m e ta l: C +■ FeO

=

F e t CO

-

36 c a l s . --------------------(1 )

Mn ■+• FeO

=

Fe -h MnO

+

2 6 c a l s . --------------------(2 )

S i *f* 2FeO

=

2 F e +■ S i 0 2

+

65 c a l s . --------------------( 3 )

2P +* 5FeO

-

5 F e - h P2 0 5

B e s id e s t h e s e fu n d a m e n ta l r e a c t i o n s ,

+• 37 c a l s ----------------------( 4 )

second ary r e a c tio n s such as

t h e f o l l o w i n g may o c c u r : 5C •+• P 2 0 5

=

SCO +• 2P -

220

c a l s . --------------------(5 )

The d i f f e r e n t c o n s t i t u e n t s o f t h e s l a g a l s o I n t e r a c t a n d p r o d u c e com pounds w h ic h may h a v e a g r e a t i n f l u e n c e on t h e p r o c e s s o f p u r i ­ fic a tio n .

Thus t h e f o ll o w i n g r e a c t i o n i s p o s s i b l e : 4CaO -h P 2 0 5

=

4CaO .P 2 O5 -

The f o r m a t i o n o f t r i - c a l c i u m p ro d u c tio n o f th e t e t r a -

----------------------------------( 6 )

p h o sp h a te i s a l s o p o s s i b l e , and th e

or tri-c a lc iu m

p h o sp h a te w i l l p ro b a b ly

d e p e n d on t h e a m o u n t o f a v a i l a b l e l i m e i n t h e s l a g . th e im p u ritie s c o n s is ts th e n e s s e n tia lly

The r e m o v a l

of

in th e o x id a tio n o f tn e

c a r b o n , m a n g a n e s e , s i l i c o n , a n d p h o s p h o r u s by m eans o f i r o n o x i d e .

I t i s p ro b a b le t h a t th e f e r r o u s o x id e a ls o p la y s p art

an im p o rta n t

i n t h e r e m o v a l o f s u l p h u r f ro m t h e b a t h o f m o l t e n m e t a l .

The

c h i e f d e s u l p h u r i s i n g a g e n ts u se d a r e m anganese and lim e , and t h e i r a c t i o n s may b e r e p r e s e n t e d by t h e e q u a t i o n s :

Some

F eS

+-

GaO

FeS

+

Mn

= =

FeO

h-

MnS

CaS

———

---------— . - . . . - ( 7)

F e —-------------------------------------------------( 8)

o f t h e MnS f o r m e d by r e a c t i o n

( 8 ) r is e 's i n t o th e

s l a g w h ere i t

is o x id ise d as fo llo w s : 2MnS -h

202

=

2MnO -h 2 3 0 2 ----------------------------------------------- -(9)

The g r e a t e r t h e am ount o f l i m e a n d t h e s m a l l e r t h e am ount o f f e r ­ rous o x id e , th e f u r t h e r w i l l r e a c tio n to w ard s th e r i g h t .

(7 ) t e n d t o go t o c o m p l e t i o n

I n o t h e r w o r d s , t h e l a r g e r t h e r a t i o CaO/FeO,

t h e m ore s u l p h u r w i l l b e t r a n s f e r r e d fro m t h e s t e e l t o t h e s l a g . Lime a l s o c o m b in e s w i t h P 2 O5 t o fo rm 4 Ca 0 .P 2 0 5 , a n d t h e m ore lim e t h e r e i s t h e g r e a t e r w i l l b e t h e am ount o f c a l c i u m p h o s p h a t e p r o ­ duced.

The P 2 O5 r e s u l t s fro m t h e o x i d a t i o n of p h o s p h o r u s by FeO,

(e q u a tio n

(4) ) , a n d i f t h e r e i s a n e x c e s s o f l im e i n t h e s l a g ,

t h e n t h e P 2 O5 w i l l q u i c k l y co m b in e w i t h t h e l i m e t o f o rm 4 C aO .Po 0 5 . T h i s w i l l h a s t e n t h e o x i d a t i o n o f t h e p h o s p h o r u s a n d so t h e FeO c o n te n t o f th e S la g w i l l f a l l . ganese in th e b a th

(e q u a tio n

As t h e FeO a l s o o x i d i s e s t h e man­ ( 2 ) ) , t h e n t h e am ount of m a n g a n e s e

i n t h e b a t h w i l l i n c r e a s e d u e t o t h e d e c r e a s e i n t h e FeO c o n t e n t o f th e s la g .

T h u s , i t may b e s a i d t h a t t h e e f f e c t o f a d d i n g e x ­

c e s s l i m e t o t h e s l a g i s t o I n c r e a s e t h e am o un t o f m a n g a n e s e i n th e b a th .

T h is m anganese w i l l th e n p ro c e e d t o d e s u lp h u r i s e as

show n i n e q u a t i o n s

( 8 ) and ( 9 ) .

The t r a n s f e r e n c e o f s u l p h u r fro m

metal to slag thus depends on the ratio CaO/(FeO+-MhO)

1 ^

' **'

"

3 .'

'

!

J /V 7

'

..

The a c t i v e d e s u l p h u r i s i n g a g e n t t h e n seem s t o b e m a n g a n e s e '

/

'

w h ic h i s p r e s e n t e i t h e r a s a d i r e c t a d d i t i o n o r t h r o u g h t h e r e ­ d u c t i o n o f MnO fro m t h e s l a g .

The f e r r o u s o 'xide a l s o p l a y s a n

i m p o r ta n t p a r t i n t h e rem o v al o f s u lp h u r , b e c a u s e th e lo w er t h e FeO c o n t e n t o f t h e s l a g , t h e l e s s m a n g a n e s e w i l l b e o x i d i s e d a n d s o t h e r e w i l l b e m ore o f t h e l a t t e r a v a i l a b l e f o r d e s u l p h u r i s a t i o n . M o r e o v e r , when FeO i s a d d e d t o t h e b a t h i t p r o b a b l y r e a c t s w i t h t h e MnS t h u s : FeO

+•

MnS

=

F eS

+

MnO-------------;------------------------(1 0 )

The FeS w i l l r e m a i n d i s s o l v e d i n t h e m e t a l , b u t t h e MnO w i l l go t o t h e s l a g a n d so t h e m a n g a n e s e c o n t e n t o f t h e m e t a l w i l l d e c r e a s e , w ith a c o n se q u e n t d e c r e a s e in th e p ro c e s s o f d e s u lp h u r is a tio n . A l t h o u g h t h e r e a c t i o n s w h ic h b r i n g a b o u t t h e r e m o v a l o f im ­ p u ritie s

f ro m t h e m o l t e n m e t a l i n t h e b a s i c o p e n - h e a r t h p r o c e s s

h a v e b e e n q u a l i t a t i v e l y e s t a b l i s h e d , much w ork h a s y e t t o b e c a r r i e d o u t on t h e p h y s i c a l c h e m i c a l c h a r a c t e r i s t i c s o f t h e s e r e ­ a c tio n s.

A w i d e r a n d m ore a c c u r a t e k n o w le d g e o f t h e e q u i l i b r i u m

c o n s ta n ts o f th e b a la n c e d r e a c tio n s i s d e s ir a b l e , to g e th e r w ith t h e e f f e c t on t h e r e a c t i o n s o f v a r i o u s c o n t r o l l i n g f a c t o r s , s u c h as te m p e ra tu re and th e c o n s t i t u t i o n o f th e s la g . Me C an c el h a s p o i n t e d o u t t h a t d i f f e r e n t r e a c t i o n s w h ic h a r e i n t e r r e l a t e d h a v e a c h a r a c t e r i s t i c p r o p e r t y w h ic h c a n b e u s e d t o d e riv e v a lu e s f o r th e e q u ilib riu m c o n s ta n ts .

The f o l l o w i n g e x ­

a m p le i s a n i l l u s t r a t i o n o f MG C a n c e 's t e c h n i q u e . th re e e q u a tio n s:

C o n sid e r th e

4. FeO

+-

CO

s

Fe

2C0 2 -

2 CO

+

0 2 - -------------------------------- —

2Fe

+•

O g - - ----------------

2Fe0 I f e q u a tio n to

»

+■ COg-----------------------------------

(n ) 12)

(13)

(1 1 ) i s m u l t i p l i e d by tw o a n d a d d e d a l g e b r a i c a l l y

( 1 2 ) , th e n e q u a tio n

(1 3 ) w i l l r e s u l t .

w il l h o ld f o r th e e q u ilib riu m

A sim ila r re la tio n s h ip

c o n s t a n t s o f t h e s e r e a c t i o n s an d

th e re fo re ; K ia

-

K f x .K 12

w h e re Kpq, % 2 5 an