khetri tank house modern is at ion

8/14/2019 Khetri Tank House Modern is at Ion

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K H E T R ITA N K H O U S E M O D E R N I Z AT I O N

S O M E T E C H N I C A LA N DE C O N O M I C A S P E C T S

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H i n d u s t a n C o p p e r L i m i t e dK h e t r i C o p p e r C o m p l e x

K h e t r i N a g e r - 3 3 3 5 0 4 ,( I n d i a )

A b s t r a c tThe paper o u t l i n e s th e ex i s t i n g f a c i l i t i e s and worki ng p r a c t i c e s

at the Khe tri e l e c t r o - r e f i n e r y of Hindustan Copper Limited. Planshave boon drawn up to mechanize sonic key ope cations to improve thoqu al i t y .o f ca thodes and the working environment as v;e 11 as economizethe re fi ne ry ope rat io ns . The economic an al ys is fo r dete rmin ingvarious optimum operational parameters under conditions existing inInd ia have als o been o u t l i n e d . The impact of capaci ty u t i l i s a t i o n andmechanizat ion under d i fferent se ts of condi t ions on opera t ional cos tshave been highlighted.

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KHETRI TANK HOUSE MODERNIZATIONh

SOME TECHNICAL AND ECONOMIC ASPECTS

BY

P. BALACHANDRANM . J. ALAM

G. L. BHOTOA

PAPER PRESENTED AT SYMPOSIUM SPONSORED BY THETMS COPPER, NICKEL, PRECIOUS METALS AND ELECTROLYTIC

PROCESSES COMMITTEES HELD AT THE TMS 116TH ANNUAL

MEETING IN DENVER, COLORADO,FEBRUARY 24-26, 1987..


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Introduction

H i n d u s t a n C o p p er L t d . , a G o ve r nm e n t o f I n d i a E n t e r p r i s e ,i s t h e s o l oproducer of copper in In d ia . The company has two undergroundm i n i n g / meta l lu rgi cal uni t s s i tua ted in t t i e eastern and western pa,rts ofthe country and an open-cast mine s i tua ted i n the central p a r t .

The u n i t s i t u a t e dComplex (KCC), hase lec t ro ly t ic g rade

c o n c e n t r a t o r , s m e l t e r

sec tor, ca l led the Khetri Copperproduce 31,000 m e t r i c tqns off a c i l i t i e s c o n s i s t of [ n i n e s ,

acid / f e r t i l i ze r p lan t s , The

in the westernfaci l i t i es toc o p p e r . T h e

r e f i n e r y a nds m e l t e r u t i l i z e s t h e f l a s h f u r n a c e , c o n v e r t e r a n d a n o d e f u r n a c e r o u t e f o rp r o d u c i n g a n o d e c o p p e r . T h e e l e c t r o l y t i c r e f i n e r y , o p e r a t i n g a t ac o n v e n t i o n a l c u r r e n t d e n s i t y p r o d u c e s c o p p e r a t 8 0 - 8 5 5 ! o f t h e r a t e dc a p a c i t y . T h e m e t a l l u r g i c a l c o m p l e x e s w o r ew e r e c o m m i s s i o n e d d u r i n gt t icy e a r 1 9 7 4 . I n o r d e r t o i n c r e a s e t h e p r o d u c t i o n o f c o p p e r i n t h e c o u n t r y ,t h e c o n c e n t r a t e s w h i c h a r e a v a i l a b l e f r o mt h e n e w m i n e l o c a t e d a tM a l a n j k h a n d iti t h e s t a t e o f K a d h y a P r a d e s h , a r e a l s o p r o p o s e d t o b es m e l t e da t K C C . B oLI) s m e l t e r a n d r e f i n e r yu n i t s a r c g o i n g t h r o u g hm a j o r 'm o d if i c a t i o n s t o i m p r o v e o p e r at i o n s t o a c c o m m o d a t e t h ei n c r e a s e dp r o d u c t i o n . A s a p a r t o f t h i s m o d e r n i z a t i o n s c h e m et h e f a c i l i t i e s a t the?e l e c t r o l y t i c p l a n t a r e e x p e c t e d t o b em e c h a n i z e d . I t i s a l s o p r o p o s e d t os e t u p a n e l e c t r o l y t e r e g e n e r a t i o n a n d p u r i f i c a t i o n p l a n t . I nt h i s , p a p e ra n a t t e m p t h a s b e e nm a d e t o a n a l y z e . t h e t e c h n i c a l a n d e c o n o m i c a s p e c t s o f

t h e T a n k H o u s e o p e r a t i o n , e s p e c i a l l y a s i t r e l a t e s t o m e c h a n i z i n g t h ee e l 1 o p e r a t i o n . C o s t c u r v e s h a v eb e e n d e v e l o p e d t o o b t a i n a b e t t e ru n d e r s t a n d i n g o f t h e i m p a c t o f v a r i o u s t e c h n i c a l p a r a m e t e r s o n t h eo p e r a t i n g e x p e n s e s .

D e s c r i p t i o no f t h e e x i s t i n g i n s t a i l a t i o n

T h e e x i s t i n g i n s t a l l a t i o n c o n s i s t s o f 4 4 0 c e l l s o f w h i c h 4 4 c e l l s a r es t r i p p e r c e l l s . T h r e e i n d e p e n d e n t e l e c t r o l y t e c i r c u i t s a r e u s e d t os u p p l y h o t , c o n d i t i o n e d , f i 1 1 n r e d e l e c t r o l y t e , o n e c i r c u i t i s u s e d f o rt h e s t r i p p e r e e l 1 s a n d t w o io r t h e c o m m e r c i a l c e l l s . T e n c o i i u n e r c i a lc e l l s , d i s t r i b u t e d e q u a l l y o v e r t h e e l e c t r o l y t i c p l a n t h a v e b e e n

".ing i n s o l u b l e a n o d e s . T h e y a r e u t i l i z e d t or i n t h e e l e c t r o l y t e . T h e c e l l s t h e m s e l v e s

i l c e l l s t o f a c i l i t a t e e l e c t r i c a l i s o l a t i o nc e l l s a r e c o n s t r u c t e d u s i n g 1 0 0 m. m t h i c kl e a d l i n e r s . T h e i r d i m e n s i o n s a r e3 . 6 m (

x 1 . 6 0 m ( h e i g h t ) . T h e c e l l s h a v e a d r a i n i n gm o v a l a n d s l i m e c o l l e c t i o n . T h e s l i m eI s s e n ti i n t h e s e p a r a t e b u i l d i n g f o r f i l t r a t i o n . T h e; a \ - c m a d e o fP V Cl i n e s w i t h Fill',

converted to c o n t r o l c e l l scontrol the build-up of C O J

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are a s s e m b l e d i n g r o u p s o ffor cel l operat ions. Theconcre te and 43! an t imon ia llength ) x 0.93m ( width ) xc i r c u i t f o r e l e c t r o l y t e rto the f i H e r press loca t ielectrolyte and s l ime pip;

The Tank House is divided i n t o three adjoining bays, two bays of atthe end are 2 4 , 2 5 m wide and a central one i s 1.1.5 m w id e. The two endbays accommodate the e lec t ro ly te cells and the central bay accommodatesthe e q u i p m e n t for heat , i n g , pumping and condi t i o n ing of the e l e c t r o l y t e ,as given in Figure 1.

The pr od uc ti on bays are se rv ic ed by th re e 12 tonne EOT Cranes , Thec e n t r a l boy i s p r o v M ' dwi th one 5 tonno EOT Crane for maintenance o f

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t h e e q u i p m e n t . T h e o p e r a t i n g d a t a o f t h e r e f i n e r y a r es h o w n i na p p e n d i x 1 .

Lin.1 c a s t I n th e s m e l t e r o n an a n o d e c a s t i n gw h e e l , ut h i c k n e s s i s m a n u a l l y c o n t r o lle d r e s u l t i n g i n w i d e v a r i a t i o n s i n a n o d ew e i g h t . U se o f su c h a n o d e s a d v e r s e l y a f f e c t s t h e s t e a d y o p e r a t i o n s i n t h eo l o c t r o l y tf c p l a n t . I t a l s o liar, a n i m p a c t o n m a t e r i a l s h a n d ] J n yo p e r a t i o n s . H e n c e i t lias b e e n d e c i d e d t o i n t r o d u c e a u t o m a t i c w e i g h tc o n t r o l f o r a n o d e s d u r i n g c a s t i n g a n d t o s u p p l y a n o d e s o f u n i f o r mw e i g h tt o the e l e c t r o l y t i c p l a n t .

S i n e e n o l e a d o r o t h e r h e a v y m e t a l s a r e p r e s e n t i n t h e K C C a n o d e s ,s l i m e s p r o d u c e d i n t h e e l e c t r o l y t e h a s a t e n d e n c y t of l o a t . S e t t l i n g a n df i l t r a t i o n s y s t e m s o r i g i n a l l y e n v i s a g e d b y t h e c o n s u l t a n t s p r o v e di n a d e q u a t e t o d e a l w i t h t h e s i t u a t i o n a t a h i g h l e v e l o f c a p a c i t yu t i l i z a t i o n . C o n s e q u e n t l y t h e s l i m e f i l t r a t i o n s y s t e m , t h e e l e c t r o l y t ef i l t r a t i o n s y s t e m a n d e l e c t r o l y t e m a k e - u p s y s t e m we r e m o d i f i e d t o s u p p l yc l e a r e l e c t r o l y t e t o t h e e l e c t r o l y t e C i r c u i t s b y u s i n g a S c h o o l e rf i l t e r .

T h e m a t e r i a l h a n d l i n g i n t h e e l e c t r o l y t i c p l a n t i s m a n u a li n n a t u r e .A n o d e s r e c e i v e d f r o m S m e l t e r a r e d r e s s e d a n d s p a c e d m a n u a l l y o nr a c k s , A1 2 t o n n e E O T c r a n e l i f t s t h e a n o d e s i n h o o k i n g d e v i c e s a n d c h a r g e s t h e m

i n t o t h e e e l 1 . C o p p e r s h i m s a r e u s e d u n d e r t h e a n o d e l u g t o e n s u r ep r o p e r v e r t i c a l a l i g n m e n t . T h e s t a r t i n g s h e e t s a r e m a n u a l l y s t r i p p e d f r o mc o p p e r m o t h e r b l a n k s a n d a r ec o n v e y e d t o t h e m a i n r i v e t i n g p r e s s b y m e a n so f e h a n d d r i v e n t r o i i c y . T h e r i v e t e d s h e e t s a r e then s t r a i g h t e n e dt h r o u g h a p a i r o f r o l l s w h i c h a l s o r i d g e d i z e s t h e s h e e t s . T h e r o u n dc u r r e n t c a r r y i n g b a r i s p l a c e d i n t h e lo o p m a n u a l l y a n dt f i e s h e e t s a r em a n u a l l y t r a n s f e r r e d o n s t o r a g er a c ' ;. S t a r t i n g s h e e t s a r e t r a n s f e r r e d b yE O T C r a n e a n d t h e n c h a r g e d a g a i nn . . . al ly b e t w e e n t h e a n o d e s i n t h e c e l l .C e l l s a r e f i l l e d w i t h e l e c t r o l y t e a n d t h e e l e c t r i c a l c i r c u i t i s s w i t c h e do n b y r e m o v i n g t h e i s o l a t i n g s h u n t .

P r o p o s e d M e c h a n i z a t i o n / K o d e r n i z a t i o n

T h e s e o p e r a t i o n s a r e \ - ? r y l a b o r i n t e n s i v e a n d n e e d

h i g h l y s k i l l e d o p e r a t o r s . O p e r a t o r s a n d s u p e r v i s o r s w e r e l e a v i n g ,c a u s i n g o c c a s i o n a l h i g h l a b o r t u r n o v e r a n d p o s i n g a p r o b l e m i nm a i n t a i n i n g a h i g h s t a n d a r d o f o p e r a t i o n s . M o r e o v e r ,t h e c o s t o f l a b o rh a s m o r e t h a n d o u b l e d f o r t h e p a s t f i v e y e a r s a n d t h i s t r e n d i s l i k e l y t oc o n t i n u e i n t o t h e f u t u r e . T h e c o s t o f f u e l a n d e l e c t r i c i t y h as i n c r e a s e dt h r e e t i m e s o v e r t h e p a s t f e wy o a r s , H e n c e , i t h a s b e c o m e v e r y n e c e s s a r yt o i n t r o d u c e m e c h a n i z a t i o n I ni.ho e l e c t r o l y t i c p l a n t i n o r d e r t o i ; e d u c ec o s t s a n d i m p r o v e t h e o p e r a t i n g e f f i c i e n c y a n d p r o d u c t i v i t y . I t w a s f e l ta t t h e o u t s e t t h a t s o m e o f t he o p e r a t i o n s o f t h e e x i s t i n g p l a n t o r en e c e s s a r y t o b e s t r e n g t h e n e d ' m o d if i e d t o i m p r o v e t h e m a t e r i a1 h a n d l I n ga n d th e p l a n t o p e r a t i o n . T h e p r o p o s e d sy s t e m d e a l s w i t ht h e a r e l a t i v e l y ,l ow c u r r e n t e f f i c i e n c y , t h e h i g h r a t e o f a n o d e s c r a p g e n e r a t i o n , t h eh i g hl e v e l o f f l o a t i n g s l i m e s i n t h e e l e c t r o l y t e a n d t h e h i g h l y l a b o r

i t . I n o r d e r t o i m p r o v e t h e o p e r a t i n go f t h e u n i t t h e f o l l o w i n g f a c i 1 i t i e s a r e

l o d i f i c a t i o n i n s o m e a r e a s o f o p e r a t i o n a r e

i n t e n s i v e h a n d l i n g e q u i p se f f i c i e n c y a n d p r o d u c t i v ep r o p o s e d t o b e a d d e d a n dp l a n n e d .

1 . A n o d em i l l i n g a n d s p a c i n g m a c h i n e2 . A u t o m a t i c s t a r t i n g s h e e t p r e p a r a t i o n m a c h i n e3 . C a t h o d e w a s h i n gm a c h i n e4 . M i s t s e p a r a t o r s L o i m p r o v e t h e v e n t i l a t i o n sy s t e m


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M i l l i - v o l t r e c o r d e r s f o r e a c h c e l l t o i m p r o v e s h o r t c i r c u i tdetectionM o d i f i c a t i o n s i n e l e c t r o l y t e a n d s l i m e c i r c u i t s t o r e du c e t h el e v e l o f f l o a t i n g s l i m e s i n t i i e e l e c t r o l y t eS e t t i n g u p o f a n e l e c t r o l y t e p u r i f iCd' . i on p l a n t f o r p u r i f i c a t i o no f e l e c t r o l y t e and r e - c i r c u l a t i o n o f b lack a c i d t o t h ee l e c t r o l y t e c i r c u i t w i t h a d d i t i o n a l f a c i l i t y f o r r e c o v e r y o fc r u d e n i c k e l s ut f a t e .M e c h a n i z e d s y s t e m f o r a d d i t i o n o f r e a g e n t s .

T h e s e m e a s u r e s h a v e b e e n p l ann e d f o r i m p l e m e n t a t i o na f t e r a d e t a i l e da n a l y s i s o f t h e p r o b l e m s f a c e di n t h e d a y - 1o-da.y o p e r a t i o n s o n t h e s h o pf l o o r . T h e f o l l o w i n g t a b l e g i v e s t h e e x p e c t e d b e n e f i t s o f t h em o d e r n i z a t i o n c o m p a r e dw i t h t h e e x i s t i n g p l a n t o p e r a t i o n .

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A n e c o n om i c a n a l y s i s o f a l l t h i m p o r t a n t paramete rs ass i s t s thedecis ion maker ( i . e . , tho Project Planner or the ttpumtittt] Munayor) inc l i o o s i r u j among th e m o s t c o s t e f f e c t i v e a l t e r n a t i v e s .

;,;;: Th e e c o n o m ic a n a l y s i s h as b e en ba s e d o n t h e h i s t o r i c a l c o s t d a t a oft h e e x i s t i n g t an k h o u s e . A n a n a l y s i s o f t h e o p e r a t i n g c o s t fo r the p a s tfew years a t KCC R e f i n e r y i n d i c a t e s t h a t 4 0 - 5 0 % o f t h e t o t a l c o s t o fp r o d u c t i o n a m o u nt s t o l o n g t e r m f i x e d c o s t s , They i n c l u d e d e p r e c i a t i o n ,a l l o c a t e d f i n a n c i n g c h a rg e s a nd a l l o c a t e d c o s t o f s e r v i c e s . Out of theb a l a n c e 4 0 -6 0 S o f t h e c o s t s , p o w e r a l o n e a c c o u n t s f o r th e 3'j.i. T h i s i sbecause power is a v e r y e x p a n s i v e c o m m o d i t y and at KCC t h e p r i c e i n c r e a s ep e r u n i t h as buut i tour to ] d o v e r t h e l a s t b y u j r s . A;> (.lie p l a n t s i\\\;l o c a t e d i n a p o w e r c le f i c iL area , c a p t i v e iji ' i iut ' i) L i o n of p o w e r i s b e i n gr e s o r t e d t o a n d t h e c o s t o f g e n e r a t i n g a n a d d i t i o n a l u n i t of power

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amounts to Rs, 1.75 per KW/hr, The other major cost Hems arc manpower,spares and stores nnri operating s u p p l i e s . However, these costs do notf l i c t u d e t h e c o s t s u f c a r r yl r J t h e s m ' L aI l o c k e d u p i n p r o c e s sn s w e i1 3 sthe cost of anode scrap r e m e l t i n y , but include allocated costs aridoverheads which are beyond the control of the Project Planner grOperating Manager.

In analyzing the impact of operating parameters on cost, the conceptof relevant cost has been adopted. Sunk costs which have already beenincurred at the time of making the decision have not been considered.Future cash costs l i k e i nt er es t on metal locked up, cost of mat eri als andenergy which are partially or fully amendable for control by the Project orOperat ing Manager have been taken i nto account. The fu tu re impact of sunkcosts like interest on capital already employed have not been accounted foras they have no influence on tlie decision at hand, The results of thesecalculations on a few critical parameters are discussed in this section.

Current density

Current density is the most important parameter in any copperre fi ne ry. In conventional ref in eri es ( l i k e KCC), the cu rre nt den sit y isnta In tained between 180-240 amps/st) .01. Increased' cur ren t den si tyincreases po la ri za ti on and f i n a l l y causes anode pa ss iv ati on . In thecont ex t of the KCC re fi ne ry , however, it is possi ble to operate at f a i r l yhigh levels of current density cfue to lower value of impurities' in

anodes ,1ltG power consumption i ncrcases wi th the current densi ty as the

production increases i n proportion to the current where as the powerconsumption increases by the square of the current even if a linear

voltage current relationship is assumed. Polarization and otherresistances themselves increase with current density and this increase "inpower consumption is even much larger.

A higher current densi ty .At a higher current density there isand formation of a spongy deposi t

On tlie other hand a hi gher

capital costs as the output

also requires better operational . c o n t r o l ,tendency for excessive nodulationa

w i t h t h e r e s u l t i n g c a t h o d e q u a l i t yc u r r e n t d e n s i t y r e d u c e s .' t h e

c e l l i n c r e a s e s . T h env es tmen t and cap i tal c o s t s as th e o u t p u t pe r c e l l i n c r e a s e s . T h eo p t i m u m c u r r e n t d e n s i t y d e p e n d s n o t o n l y o n t h e c a p i t a l c o s t , t h e c o s t o fp o w e r and l abor b ut also on the ski 11 a n d d i l i g e n c e o f t h e o p e r a t o r s .To r a n e x i s t i n g r e f i n e r y c a p i t a l c o s t is a s u n k c o s t and i s no tr e l e v a n t . I n c r e a s e s i n [.reduction a r c r e l e v a n t a n d h a v e t o b e

p o w e r and l abor b u t a l soTo r a n e x i s t i n g r e f i n e r yr e l e v a n t . I n c r e a s e s i nc o n s i d e r e d .

If th e c u r r e n t d e n s i ty i n an o p e r a t i n g r e f i n e r y l i k e K C C i si n c r e a s e d wi thou t a n y i m p r o v e m e n t s i n the o p e r a t i o n , 1 i k e b e t t e r s h o r tc i r c u i t d e t e c t i o n , o r L e t t e r e l e c t r o l y t e c i r c u l a t i o n , t h e c u r r e n te f f i c i e n c y i s 1 i k e l y to -'ateriorate wi th a s s o c i a t e d p r o b l e m s w h i c h m a yb e c o m e c o u n t e r - p r o d u c t i : < . . A n e c o n o m i c a n a l y s i s o f t h e K C C R e f i n e r yind ica tes tha t the o p t i n m i i s r e a c h e d a t a r o u n d 2 1 0 A m p s / s q . m . i . e l , a ta p r o d u c t i o n l e v el o f 3 0 5 0 H T o f c a t h o d e s p e r m o n t h . A s t h e a v a i l a b i l i t yo f a n o d e s i s b e l o w t h is l e v e l t h e t a n k h o u s e i s p r e s e n t l y b e i n g o p e r a t e da t a cu r r en t dens i ty o f 195 A m p s / s q . m . M o r e o v e r , as t h e e l e c t r o l y t er e g e n e r a t i o n c e l l s i n tank h o u s e a r e b e i n g s e r v i c e d b y t h e s a m e r e c t i f i e ri t i s n o t p o s s i b l e t o iticrease t h e c u r r e n t d e n s i t y t o t h e o p t i m u m . W h i l ec a l c u l a t i n g t h e r e l e v a n t c o s t , t h e co s t o f p o w e r , m a n p o w e r , o p e r a t i ngm a t e r i a l s , spa res and the i n t e r es t on the m e t o ! l ocked has b e e n ' takeni n t o a c c o u n t . T h e d - U a i s g i v e n i n F i g u r e ' I . T h i s g r a p h i s c o m p a r a t i v e

358


8/13

i n n a t u r e a n d t h e c o s t o f e x i s t i n g o p e r a t i o n si s t a k e n a s 1 0 0 . T h ey - a x i s i s b a s i c a l l y t h e r a t i o b e t w e e n t h ep r o j e c t e dc o s t a n d t h e s t a n d a r dc o s t e x p r e s s e d a s ap e r c e n t a g e .

I m p a c t o f M a t e r i a l H a n d l i n g

T h i s i s a n i m p o r t a n t s e c t i o n o f T a n k H o u s e f r o m t h e c o s tp o i n t o f

v i e w s i n c e m o s t o f t h e m a n p o w e r i s u s e df o r m a t e r i a l s h a n d l i n g . A si n d i c a t e d e a r l i e r , i t i s p o s s i b l e t o i n s u l a t e t h e e f f i c i e n c y o f c e l lo p e r a t i o n s f r o m t he m a n u a l s k i l l o f w o r k e r s1 W i n t r o d u c i n gm e c h a n i z a t i o n .C o n s e q u e n t l y , c o n s i d e r a b l e s c o p e e x i s t s i n i m p r o v i n g o p e r a t i o n a le f f i c i e n c y a n dp r o d u c t i v i t y .

W1 tl i mochanized ma te ri al hand] i ng,operations are expected to primarily take

1. Manpower requirement is reduced2 . Current efficiencies improve by .

1 1 5 T

t h el a c e :

f o l l o w i n g c h a n g e s i n '

ao

o

o

4*M

s

10 5

10 0

With mechanisation

Withoutraeohanigation

'2785" Mr5S15 MT

ooo Monthly output in MT.

Pior-2

"3500"

;r* '" '*"

!

: 1

I

I1"-

ill

-:

(Ii

V,

\

:

359


9/13

i it

the>% with

Increases morecompared to n not)

3 . C e l l n v a i l a b i l i t i e s i n c r e a s e b y5 - 1 0 ?1 . As tinotius and CitUtodos are uniform and s t r a igh t

between the anode and cathode can be reduced by [consequent saving in power

5, As a result of the above factors the outputin re la t ion to the c u r r e n l . rlcur, il.y n ;median i zcti opera I ion

6 , The chemical q u a l i t y of catliode improves (the impact of thiscost cannot be evaluated)

7, The cur re nt fl ow in alm ost al l the anodes and cathod es intank house would be uniform with v er y l i t t l e v a r i a t i o n i ncatliode weights as compared to manual operation

The effect of the above on the cost of operation is also given inF ig ur e 2 . It can be seen from th e f igure that the cos t of opera t ions arehig hly sens i t iv e to the lev els of product i on a ' f ter mechanizat ion ascompared to the manual o p e ra t io n . Thi s is because the co st s a s soc ia t edw i t h the cap i t a l expend i tu re i . e . , fu tu re deprec ia t ion and in t e re s t oninvestment ( roughly 6%) have to be incl ud ed in the co st . The net r e s u l tis that i r tho re f ine ry is operated below 90$ of the production capac I tyth e mechanization would not be e c o n o m i c a l . On the other hand expandingth e tank house by adding a few more operating cells w i l l reduce the costand make the mechanization more v i a b l e .

Cathode Weight

Once a current dens i ty has been determined the next major parameterwhich af fe c ts the cost is the cathode w ei gh t, Changes in the cathodeweight in an opera t ing ref inery have p r i m a r i l y the f o l l o w i n g costi m p l i c a t i o n s :

1, Increased cathode we ight decreases the s t a r t i n g sheetrequirementand reduces the material handling i n v o l v e d wi th anodes

Z. Increas ed cathode weigh t in t ur n incre ases the anode w eig ht thuslocking up more work-in-progress and hence higher working capitalcos ts

3. Increas ed cathode w e i g h ' resul ts in a decreased scrap melting,load as the cathode dep ; i . ; i t is more in proportion to the anodescrap generated

Due to the above three i sasons., i n order to compare the costbehavior of the va r ious pa ra in; ! ers and i t s s e n s i t i v i t y on c o s t , cathodeweight can be taken as the independent variable to study costs. However,due to practical problems the cathode weight cannot be Immediate lyincreas ed in an e x is ti n g tank i iouse. Parameters l i k e i n t e r f a c e c o r r o s i o na t th e loops and control of deposi t ion a t the loops are some of thev a r i a b l e s w h i c h ' a r e p rocess l i mi t a t i on s . S i mi l a r l y fo r a manual ma te r i a lhandling system (as ex i s t ing at KCC) the capacity of the operatingpersonnel to unload th e heavier cathodes manually also becomes ac o n s t r a i n t . However, prog ress ive incr eases i n cathode weight

over a period of time would help in reducing costs.

It.'

1 1 - 360


10/13

Crops of cathodes per anode cycle

In copper el ec tr o- re f i ning normally two crops of cathodes areobtained for one s e t of anodes charged ( i . e . , two crop o p e r a t i o n ) . Insome othe r conventional refi neries three crops of cathodes are obtainedfo r one s e t of anodes charged ( i . e . , t h r e e crop o p e r a t i o n ) . A majordeparture from this pract ice has been introduced successfully at OnahamaNo. 3 tank house where a one cathode crop/anode crop method has been

p r a c t i c e d . The eva lua t ion of the three a l t e rna t ives i s qui't e re levan tfor a re fi ne ry planning for mechani zat ion and hence a cost analysis isnecessary for this purpose.

180

170

I G o

3 150a

jjj 130o5 120

n6 100 -

90

80

2

3

60 7r> 80

C a t h o d e w e i g h t

Fig-3: Effect .f cathode weight onhandling costs & startingshoot costs for 1,2 & 3of cathodo/anode cycle.

The re lev an t cost s under con sid era tio n for an al ys is are the cost of manpower and s ta r t in g she e t s , in te re s t on work-in-progress employed andcost of remelt ing anode sc ra p. Figure 3-6 give the re le va nt co st s forcopper re fi ni ng in a conventi onal tank house. The ex is ti ng cost (a t 80 Kgof.cathode weight with 2 cycle operation) is taken as standardthe above figures.

. I t c a n b e s e e n f r o m F i g u r e 3 t h a t t h e c o s t o f m a t e r i a l h a n d l i n g a n ds t a r t i n g s h e e t p r e p a r a t i o n ( w i t hm a n u a l h a n d l i n g ) i s h i g h e s t f o r a o n ec r o p o p e r a t i o n . T h e c o s t d e c r e a s e sw i t h c a t h o d e w e i g h t d u e t o r e a s o n sm e n t i o n e de a r l i e r . T h e t h r e e c r o p o p e r a t i o n h a sm i n i m u m c o s t s d u e t o t h el o w e r a n o d e h a n d l i n g c o s tp e r c r o p .


11/13

The Figure 4 gives the cost of in process copper locked-up in' thec e l l s . Increased cathode weights increase th is f i g u r e . However, the oneco UKKIC crofi/itumfo eye lo oj iotMtion has .i t;l


12/13

Cost Ratie/MT of cathodeCost Ratlo/MT of cathode


13/13

. . I

il

The total relevant costs of processing are given in Figure 6, for a opec rop , I.wo eni]> .mil I h r e i1 crop i t pp tMt .i o n ,; l i d in he S M M I I nnu l it e fftjW|rt h a t t he cos t o f a t h ree c rop op e r a t io n i s a l m o s t I n d i f f e r e n t t o caLhii

khetri tank house modern is at ion

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