1998-mineng

8/12/2019 1998-MinEng

http://slidepdf.com/reader/full/1998-mineng 1/11

Pergamon

0892-6875 98)00031-4

Minerals Engineering V o l . I 1 , N o . 6 , p p . 4 8 9 - 4 9 9 , 1 9 9 8

© 1 9 9 8 Pu b l i sh e d b y E l s e v i e r Sc i e n c e L t dA l l r i g h t s r e s e r v e d . P r i n t e d i n G r e a t Br i t a i n

0 8 9 2 - - 6 8 7 5 / 9 8 1 9 .0 0 + 0 .0 0

A R E A L T I M E V I SU A L S E N S O R F O R

S U P E R V I S I O N O F F L O T A T I O N C E L L S

A . C I P R I A N O M . G U A R I N I R . V I D A L A . S O T O

C. SEPI3LVEDA D. M ER Y and H. BRISElqO

F acu l ty o f Eng inee r ing Ca tho l i c U n ive r s i ty o f Ch il e P O B ox 306

S an t i ago 22 Ch i le . E-mai l : ac ip r ian@ ing .puc .c l

(Received 2 September 1997; accepted 26 January 1998)

A B S T R A C T

This pap er describes an expert system fo r the supervision o f f lo ta tion p lants based on

AC EF LOT , a real t ime analyzer o f the characteris tics o f the f ro th that is form ed on the

surface o f f lo ta t ion cell s. The AC EF LO T analyzer is based on image processing and

me asu res severa l phy sical variables of the froth, including colorimetric, geom etric and

dyn am ic information. On the othe r hand, the expert system detects abn orm al operation

states and suggests corrective actions, supporting operators on the supervision and

contro l of the f lotation plant. © 1998 Pub lished by Elsevier Science Ltd. All rightsreserved

K e y w o r d s

M inera l process ing; f lo ta t ion f ro ths ; f lo ta t ion bubbles ; on- l ine analys is ; exper t sys tem s

I N T R O D U C ~ O N

S uperv i s ion a nd con t ro l o f f lo ta t ion p lan t s i s gene ra l ly accompl i s hed t ak ing in accou n t the in fo rm at ion

s upp l i ed by ex per t ope ra to r s w ho ob s e rve the f ro th and bubb les p roduced on the s u r f ace o f f lo ta tion ce il s

and r ec om m end ac t ions s uch as va ry ing l eve l s and mod i fy ing r eagen t s [1] .

The ava i l ab i l i ty o f low cos t and pow er fu l compu te r s toge the r w i th h igh pe r fo rmance f r ame g rabber s and

CC D indus t r ia l g r ade cameras a l low the u s e o f a r t if i c ia l v i s ion to s uppor t p lan t ope ra to r s in the i r ta s k o f

s uperv i s ing and co n t ro l l ing the f lo ta t ion p roces s p rov id ing them upda ted in fo rm at ion abou t the s t a te o f the

ce l l s and s ys tema t iz ing the r eas on ing mad e by exper ts .

Th i s w ork des c ribes f i rs t A C EF L O T an ana lyze r tha t meas u res the co lo r numb er s i ze s hape dens i ty

s peed and s t ab i li ty o f the bubb les p roduced on the s u r f ace o f a flo ta tion ce l l and s econd ly an exper t s y s tem

bas ed on A CE F L O T tha t de tec t s abnormal ope ra tion st a te s and p ropos es co r rec t ive ac tions s uch as

chang ing l eve l s e t po in t s o r mo d i fy ing the dos e o f r eagen ts .

Presented at Minerals Engineering 97, Santiago.Chile July-August 1997

489

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4 9 0 A C i p r i a n o e t a l

T H E A C E F L O T A N A L Y Z E R

e s c r i p t i o n

A CE FL O T i s a n a r t i f i c i a l v i s i o n b a s e d i n s t r u me n t d e v e l o p e d t o s u p p o r t p l a n t o p e r a t o r s i n t h e s u p e r v i s i o n

a n d c o n t r o l o f m i n e r a l f l o t a ti o n p r o c e s s . I t d e t e r mi n e s t h e c o l or , n u mb e r , s i ze , s h a p e , d e n s i ty , s p e e d a n d

s t a b i l i t y o f t h e f r o t h b u b b l e s a t t h e s u r f a c e o f a f l o t a t i o n c e l l . T h e i ma g e c o l o r i s d e f i n e d a s t h e me a n

i n t e n s i ty v a l u e o f e a c h o f t h e re d , g r e e n a n d b l u e RG B) i ma g e c o mp o n e n t s . T h e s i z e o f t h e b u b b l e s is

d e f i n e d a n d c o m p u t e d a s t h e a v e r a g e o f th e a r e a i n c m 2 o f a l l t h e b u b b l e s a p p e a r i n g i n t h e f r a m e c a p t u r e d

b y t h e C C D c a m e r a . T h e s h a p e o f th e b u b b l e s is d e fi n e d a nd c o m p u t e d a s th e m e a n r a ti o b e t w e e n t h e m i n o r

a n d m a j o r a x i s o f e a c h b u b b l e i n t h e ima g e , a n d f i n a ll y , t h e d e n s it y i s c o mp u t e d a s t h e n u m b e r o f b u b b l e s

p e r c m 2 i n t h e i ma g e .

A C E F L O T a l s o d e t e r mi n e s t h e ma g n i t u d e o f t h e s p e e d a n d th e mo v i n g d i r e c ti o n o f th e b u b b l e s , a s w e l l a s

t h e f r o t h s ta b i l it y , w h i c h i s a me a s u r e me n t o f th e r a te o f b u b b l e e x p l o s i o n s . A d d i t i o n a l ly , A CE FL O T k e e p s

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

H a r d w a r e s t r u c t u r e

Fi g u r e 1 s h o w s a s c h e ma t i c v i e w o f t h e h a r d w a r e s t r u c t u r e o f A C E F L O T . I t c o n s is t s o f :

T h r e e v i d e o a c q u i s i t i o n s u b s y s t e ms

O n e c o m m u n i c a t i o n s u b s y s t e m

O n e p r o c e s s i n g s u b s y s t e m

C o n t r o l/

': Processing

Subsystem

' . . . . . . . . . . . I . . . . . . . . . . . . . . .

I F I D e r O p t lc ~ i C o m m u n i c a t io n

cquisition I V i e o I ] i S u b s y s t e m

Subsystem { M u l t i p le x e r

. . . . . . . . . . . ' . 7 f . l : f ' 1 7 1 : 1 . . . . . . . . , . . . . . . . .

l C C D C o lo r 1 ~ 2 0

F i g. l A C E F L O T h a r d w a re .

E a c h v i d e o a c q u i s i t i o n s u b s y s t e m i s e n c l o s e d i n a h a r d s t e e l w a t e r a n d d u s t p r o o f c a s e , w h i c h h o u s e s a n

i n d u s t r i a l g r a d e c o l o r CCD c a me r a , a n A C/ D C p o w e r s u p p l y a n d f o u r s p e c i a l f l u o r e s c e n t l a mp s w i t h f l a t

c o l o r s p e c t r u m f o r i l l u mi n a t i n g t h e f r o t h s u r fa c e . T h e i ma g e c a p t u r e d b y e a c h c a m e r a i s t r a n s mi t t e d t h r o u g h

a d o u b l e i n s u l a t e d c o a x i a l c a b l e , t o t h e c o mmu n i c a t i o n s u b s y s t e m.

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Visual senso r for supervision of flotation cells 491

T h e c o m m u n i c a t i o n s u b s y s t e m i s c o m p o s e d o f a n a n a l o g v i d e o m u l t i p l e x e r , a f i b e r o p t i c l i n k f o r v i d e o

t r a n s m i s s i o n a n d a t w i s t e d p a i r c a b l e u s e d f o r c a m e r a s e l e c ti o n . T h e o p t i c a l f i b e r l i n k c o n s i s ts o f a n

e l e c t r i c a l / o p t i c a l c o n v e r t e r , t h e o p t i c a l f i b e r a n d a n o p t i c a l / e l e c t r i c a l c o n v e r t e r . T h e v i d e o s i g n a l i s

t r a n s mi t t e d f r o m t h e mu l t i p l e x e r o u t p u t t o t h e p r o c e s s i n g s u b s y s t e m t h r o u g h t h e f i b e r o p t i c l i n k .

T h e p r o c e s s i n g s u b s y s t e m c o n s is t s o f a n 1 0 0 M H z . P e n t i u m b a s e d P C w i th 3 2 M B o f R A M , a 1 .0 G B h a r d

d i s k , a 1 7 SV G A m o n i t o r a n d a c o l o r f r a me g r a b b e r b o a r d th a t a l l o w s t o d i s p l a y re a l ti me v i d e o i n t h e

mo n i t o r . Be c a u s e t h e f i b e r o p t i c l i n k t r a n s mi t s o n l y o n e v i d e o s i g n a l a t a t i me , t h e p r o c e s s i n g s u b s y s t e m

s e l e c t s t h e v i d e o s o u r c e , u s i n g a t w i s t e d p a i r c a b l e c o n n e c t e d t o a n RS- 2 3 2 p o r t w h i c h s e n d s a s i g n a l t o t h e

v i d e o a n a l o g mu l t i p l e x e r . A v i d e o f r a me i s c a p t u r e d a n d d i g i t i z e d i n t o me mo r y b y t h e f r a me g r a b b e r . T h e

c o m p u t e r p r o c e s s e s t h e i ma g e , d i s p l a y s t h e r e s u l ts o n t h e s c re e n o f th e c o m p u t e r a n d s t o r e s t h e m i n to t h e

h a r d d i s k .

pera t io n in t er f a ce

T h e A C E F L O T a n a l y z e r w a s d e v e l o p e d in C + + t o o pe r a t e u n d e r th e M i c r o s o f t W i n d o w s ® 3 .1 e n v i r o n m e n t

i n o r d e r t o p r o v i d e a f r i e n d l y i n t e r f a c e w i t h s e l e c t i o n me n u s , g r a p h i c b u t t o n s a n d o n l i n e e x p l a n a t i o n o f

f u n c t i o n s . F i g u r e 2 s h o w s a g e n e r a l v i e w o f th e u s e r i n te r f a c e s c re e n , w h i c h h a s t h r e e s e p a r a t e a n d

iden t i f i ab le a reas .

F i g . 2 A CE FL O T o p e r a t i o n i n t e r f a c e .

T h e f i rs t o n e , o n t h e t o p o f th e s c r e e n , a l l o w s t h e u s e r t o in t e r a c t w i t h t h e i n s t r u me n t u s i n g m e n u s a n d i c o n

i d e n t i fi e d b u t t o n s, w h i c h m a k e p o s s i b l e t o a c c e s s a n d a c t iv a t e d i v e r s e f u n c t i o n s o f A C E F L O T . Se v e r a l

p o s s i b i l i ti e s a r e a v a i l a b l e , s u c h a s c h o o s i n g o n e o f t h e f l o ta t i o n c e ll s , s h o w i n g t h e v i d e o i n r e a l t ime ,

f r e e z i n g a n i ma g e , p r o c e s s i n g t h e f r o z e n f r a me , d i s p l a y i n g a n d s t o r i n g t h e r e s u l t s , e t c .

T h e s e c o n d a r e a o n t h e l e f t o f t h e s c r e e n , c a l l e d p r o c e s s i n g a r e a , s h o w s t h e c u r r e n t f r a me u n d e r p r o c e s s .

T h e d i s p l a y r e f l e c t s t h e c h a n g e s g e n e r a t e d t h r o u g h t h e a p p l i c a t i o n o f t h e i ma g e p r o c e s s i n g a l g o r i t h ms

n e e d e d t o e x t r a c t t h e r e q u i r e d i n f o r ma t i o n f r o m t h e i ma g e .

T h e t h i r d s c r e e n a r e a , c a l le d i n f o r m a t i o n a r e a , h a s t h r e e s e c t io n s , o n e f o r e a c h f l o t a t io n c e l l. F i g u r e 3 s h o w s

a d e t a il e d v i e w p r e s e n t i n g t h e i n f o r ma t i o n c o r r e s p o n d i n g t o c e ll 1 . T h e w i n d o w d i s p l a y s t h e r e a l t i me i ma g e

o f t h is c e l l a n d s h o w s a l l t h e me a s u r e m e n t s , s u c h a s c o l o r , n u mb e r , s i z e , s h a p e a n d d e n s i t y o f th e b u b b l e s

as wel l as the ve loc i ty and s t ab i l i ty o f the f ro th .

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492 A. Cipriano t a l

T h e A C E F L O T o p e r a t io n i n te r f a ce a l s o d i s p la y s g r a p h s s h o w i n g t r e n d s in t i m e o f t h e m e a s u r e d v a r i a b le s ,

w h i c h a r e o b t a i n e d f r o m a u t o m a t i c a l l y r e c o r d e d h a rd d i s k h i s t o r ic d a ta . It i s a l s o p o s s i b l e t o d i s p l a y i m a g e

h i s t o g r a m s a n d to s h o w r e s u l ts f r o m t h e ex p e r t s y s t e m . A s a n e x a m p l e F i g u r e 4 p r e s e n t s a d e t a i l e d v i e w

s h o w i n g t h e h i s t o g r a m o f t h e s h a p e o f t h e b u b b le s a s w e l l a s t h e R G B v a r i a t i o n s t r e n d s ) d u r i n g th e la s t

2 0 m i n u t e s f o r a g i v e n c e l l .

N ~ e c ¢ ~ e a c t a ~ c e l l , ~ B u b b l e s , ~ n a t t y

~ o u n d m t h e l ~ s t

i n c a s e m e n t

N , ~ a b ~ I o f ' b u b b l e s J

fot~ ltd t r l Lhe ta~t , . S p ee d ~ t h e ~ o t ~

m e e s ~ e m e n ~

I m F t ~ ¢ h ~ t n ~ I t ~

i ~ A e e a c a ~ e t e e l b y ~ ~ b b l e s

exp ressed ss ~ ' lh e to t.d ~ e s

D a t e c u , m o f t h ~ f l e s h

t m + g e

~ : ' , , M e ~ n v ~ e o f t h e R O Ba e c o l r o h e

I ~ : ~ n e d ~ e d ~ , . . • c o m p ~ . a e n t ~ 0 t e t h e l ~ s t a n d i z e d , , M e e n v a l u e o t t h e

~rasge ~ - - ~ t ra e te ~ " ~ ' b u ~ e st r n ~ e

• M e ~ m v ~ u e o f t h e b r l g n tn e s s . M e ~ ¢ ~ , r , d l ~ . o f t h e

c ~ t ~ e 1 4 ~ ~ l z ~ d t t l~ ~ t ~' e ¢11 clJl ~ lt'y" ,:~ ~ l b b / e ~

F r s m ~ u ~ t h t h e m e r e. . M e s h " ¢ ~L~ o f t h e ~ x e l

~ t ~ t n e s o f t h e I ~ t s t ~ l ' ~ l l z e d~rasge co~eto d b y • an ~ le

b ~b ~ l e

F i g .3 I n f o r m a t i o n w i n d o w o f a s i n g l e c e ll .

~o.~+ . .. .. .. .. .. .. .. .. . r . .. .. .. . ~ . . . . . . I

. . . . . . i . . . .

, - i . . . .. . . .. . . . .. . . .. . . i . . . .. . . .. : . . . . . . . .. . . . iJ

+ ~ 1 ~ : ~ J ~ . ; ; . i ' . . . . . ~ . l g . ,

~ U i ~ J ' d ~ i i l : , ~ ~ ~ U T " ~ c ~ , . ~ . ~ B . ~ , ~

~ ' < ~ ' ~ ~ * : ~ . ~ ~ . ~ , , ~ , . ~ , .. . . . . . .. . . . . . . .. . ~ . ~ . . . . . . . . ~ . . . . . . . . . . . . .. . . . . . . . . . .

o n

Horo ~OM) ~ , - - . ~ + . . . . . . . . . . . . . . . . . . . . . . . . . .

T o d o s l o s C o l o r e s ~ + ~o+ • + : + +

+ + + - + + +~ + ~ : , + + , + + , +~ + ~ + ,

] . i . . . .+ v +++ ::: + + ;+++++ ;? + +++ ~++~++++++ +

~ o m e d l u +++++++++:':+++ +~ ++++ ::+~ o . . . . . . . . . . . . . . . . . . . . . . .

+ + + : i + + + + + , ~ , + + + + + + + + + + + + + i , + + + . . . . . . ~ . , , . ~ : ; , . . . ~ . . . . . . . . . . . ++

+ + 7 + + + + ~ ; + + ; : + : + + + ++ + + ++~+ '- + : + + + % i : 1 ~ + - I : + + ++ + ++ + +++ + + + + + + + + + + + ++ + + i+ + + + ++ ++ + + :+ ++++,~+++++#:++:+++ + , : + + : + + + + ++ ; + + ; + + + + + + l + _ . l+

F i g . 4 H i s t o g r a m a n d t r e n d g r a p h .

T h r o u g h t h e in t e r f a c e , th e u s e r c a n c o n f i g u r e d i f fe r e n t o p e r a ti n g o p t i o n s o f t h e i n s t r u m e n t , s u c h a s

c o m m u n i c a t i o n p o r t c o n f i g u r a t i o n , s e l e c t i o n o f d ig i ta l f il te r s , s e l e c t i o n o f a u t o m a t i c o r m a n u a l p r o c e s s i n g ,

a n d t h e p r o c e s s i n g i t se l f . R u n n i n g i n a P e n t i u m b a s e d c o m p u t e r , t h e s o f t w a r e c a n p r o c e s s a n d e x t ra c t a ll

t h e re q u ir e d m e a s u r e m e n t s f r o m o n e i m a g e i n a b o u t o n e m i n u t e . A w h o l e s y s t e m , i n c l u d i n g t h r ee c a m e r a s ,

c a n a n a l y z e o n e c e l l e v e r y t h r e e m i n u t e s .

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Visual sensor for supervisionof flotation cells 493

lgorithms

T o m e a s u r e t h e f r o t h c o l o r , t h e s o f tw a r e c o m p u t e s t h e a v e r a g e v a l u e o f t h e t h re e R G B ) c o l o r c o m p o n e n t s

o f each p i xe l , u s i ng t he i n fo rm at i on g i ven by t he f r am e g rabber [2 ] .

T o d e t e r m i n e t h e n u m b e r , s i z e , sh a p e a n d d e n s i t y o f th e b u b b l e s, A C E F L O T l o c a l iz e s t h e c e n t e r o f th e

b u b b l e s b y r e c o g n i z i n g t h e s h i n ie s t z o n e s o f t h e i m a g e , a n d t h e e d g e s o f t h e b u b b l e s b y r e c o g n i z i n g t h e

da rkes t zo nes [3 ]. The da rkes t zon es a re de t e rm i ned by s ea rch i ng t he po i n ts w i t h t he l owes t i n tens i t y i n 12

rad i a l d i r ec t i ons s t a r t i ng f rom t he cen t e r o f t he bubb l e .

F i g u r e 5 s h o w s a n i m a g e w i t h d e t e c t e d b u b b l e c e n t e rs a n d e d g e s . O n c e b u b b l e c e n t e r s a n d e d g e s a r e

de t ec t ed i t i s pos s i b l e t o com pu t e t he a rea , pe r i m e t e r , d i am et e r and c i r cu l a r i t y o f t he bubb l es .

F i g .5 Edge and cen t e r de t ec t i on .

Th e f ro t h v e l oc i t y and s t ab i l i ty i s eva l ua t ed t h rough t he p roces s i ng o f cons ec u t i ve i m ages , a t a r a t e o f 20

f r a m e s p e r s e c o n d . T h e s p e e d i s c o m p u t e d d e t e r m i n in g t h e m o v e m e n t o f t h e f r o th f r o m o n e f r a m e t o t h e

n e x t . T h e s t a b il it y i s e s ti m a t e d c o m p a r i n g t w o c o n s e c u t i v e im a g e f r a m e s , a n d e v a l u a t in g a m e a s u r e m e n t

o f t h e r a t e o f c h a n g e i n t h e a p p e a r a n c e [ 4 ] . F i g u r e 6 s h o w s a n i m a g e w i t h c o m p u t e d v e l o c i t y v e c t o r s

s u p e r i m p o s e d .

¢

:

F i g .6 Vec t o r s r ep res en t i ng t he m ovem en t o f t he f ro t h s u r face .

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4 9 4 A . C i p r i a n o e t a l .

T H X P R T S Y S T M

xpert sys tem s tructure

Th e ana l y s i s o f the cap t u red i m ages t oge t he r w i t h t he in fo rm at i on p rov i de d by expe r t f l o ta t i on t echn i c i an

a l l ow ed u s t o des i gn a know l edge bas e s t ruc t u red i n ru l e s t ha t de t e rm i nes t he ope ra t i on s t a t e o f each

f l o t a ti on ce l l u s i ng t he f ro t h co l o r ve l oc i t y and s tab i l it y i n fo rm at i on t oge t he r w i th t he m e as u rem en t s o f

b u b b l e s i z e s h a p e a n d d e n s i t y o b t a i n e d b y A C E F L O T .

F i gu re 7 s ho ws a b l ock d i ag ram o f t he exper t s y s t em s truc t u re . As s how n t he cha rac t e r i za t i on o f t he ce l l

p e r f o r m a n c e i s a c h i e v e d t h r o u g h t h e a n a l ys i s o f th e f r o t h c o lo r t h e g e o m e t r i c i n f o r m a t i o n o f th e b u b b l e s

a n d t h e f r o t h d y n a m i c s .

Dig a a l i ze d I ra ~ ge s P ~ oc e s s e cl I ra a ge s

C o l o r A n a l y s i s ] D y n m a t e A n a l y s t s

B l a c k , yellow, l~ht .10tue, Sl ow lest, stable, unstnble,g~ay,etc qmat, u ~ o u l e n t ate

D e t e c l ao n o f o p e r a t a o n s t a te s

- Light froth I - P .cntic r o t h

- He a vy t ro th ~ - Ope n t ro th- W atered roth . e tc

P o s s i b l e e ,a ~. Ta e o f l h e o p e r a t l o n s t a t e a l e s t a b l i n - h e d

A c t i o n s i ~ on l e r o c o r r e c t t h e a b n o m a a l s i t u a t ], o n r e s u g g e s t e d

Ge ome tm Ana lys i s

rtMl, large ubbles , e tc .

F i g .7 Exper t s y s t em s t ruc t u re .

Th e co l o r ana l y s i s des c r i bes t he f ro t h a s b lack ye l l ow l i gh t-b l ue e t c . The geo m e t r i c ana l y s i s de f i nes t he

bubb l es a s s m a l l l a rge e t c . The dyna m i c ana l y s is de t e rm i nes t he f ro t h s peed s t ab i li t y t u rbu l ence e t c .

d i s t i ngu i s h i ng cas es s uc h as s l ow o r fa s t f ro t h s t ab l e o r uns t ab le f ro t h qu i e t o r t u rbu l en t f ro th e t c .

F r o t h c h a r a c t e r i z a t i o n is a c c o m p l i s h e d t h r o u g h t h e p r o c e s s i n g o f I f T h e n ru l e s i n wh i ch t he m ea s u red

var i ab l es a r e checked aga i n s t p ro -es t ab l i s hed t h res ho l d l eve l s .

On ce t he f ro t h is cha rac t e r i zed t he exper t s y s t em de t e rm i nes wh i ch ope ra t i on s ta t e de f i ned i n t he know l edge

bas e f it s t o t he s t ud i ed ce ll . Th i s is a l s o ach i eved t h rough t he p roces s i ng o f I f T h e n ru les .

I f t he i den t i f i ed s t a t e co r res ponds t o abno rm al ope ra t i on t he exper t s y s t em s ea rches i n a t ab l e t he pos s i bk

caus es wh i ch can be an i nadeq ua t e dos e o f r eagen t s f ro t h con t am i na t i on wi t h ex t e rna l agen t s s uch a:

pe t ro l eu m o i l de t e rgen t s e t c . o r an i nadequa t e c l a s s if i ca t ion i n t he p rev i ous com m i nu t i on p roces s .

Th en t he e xpe r t s y s t em s ugges t s pos s i b l e co r rec t i ve ac t i ons t ha t t he p lan t ope ra t o r s hou l d fo l l ow i n o rde

t o s o l v e th e p r o b l e m f o r e x a m p l e a d j u st in g t h e d o s e o f re a g e n ts o p e n i n g th e c e l l c a p o r r e d u c in g t h e w a t e

s upp l y .

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Visual senso r for supervision of flotation cells 495

O p e r a t i o n i n t e r f a c e

T h e i n f o r m a t i o n p r o v i d e d b y t h e e x p e r t s y s t e m is p r e se n t e d i n a w i n d o w w i th i n t he A C E F L O T o p e r a t io n

i n t e r f a c e . T h i s w i n d o w d i s p l a y s t h e f r o t h s t a t e , t h e p o s s i b l e c a u s e s o f a b n o r ma l o p e r a t i o n s t a t e s a n d t h e

s u g g e s t e d c o r r e c t i v e a c t io n s . I f t h e i d e nt i fi e d s t a t e n e e d s a n a l a r m t h e e x p e r t s y s t e m m a k e s t h e c o m p u t e r

b e e p .

F i g u r e 8 s h o w s a d i s p l a y c o r r e s p o n d i n g t o ce l l 1 i n w h i c h t h e s t a te e x c e s s o f l i me h a s b e e n d e t e c t e d .

F i g . 8 E x p e r t s y s t e m i n t e r f a c e .

P r o g r a m m i n g s t ru c t u re

T h e e x p e r t s y s t e m u s e s f o u r t e x t f i le s f o r i ts o p e r a t i o n . I n t h e f i rs t o n e , var iab le .exp t h e f o r t y t w o v a r i a b l e s

m e a s u r e d b y A C E F L O T , a n d l is t ed o n T a b l e 1, a r e d ef in e d.

T A B L E V a r i a bl e s m e a s u r e d b y A C E F L O T a n d u se d b y t h e e x p er t s y s te m

V 0 0

V 0 1

V 0 2

V 0 3

V 0 4

V 0 5

V 0 6

v 7

V 0 8

V 0 9

V 1 0

V I I

V 1 2

V 1 3

V 1 4

V 1 5

V 1 6

V 1 7

V 1 8

V 1 9

V 2 0

V a r i a b l e s

N u m b e r o f b ub b l e s

Bu b b l e d e n s i t y

A r e a c o v e r e d b y f r o t h

M i n i m u m a r e a

M a x i m u m a r e a

M e a n a r e a

A r e a s t a n d a r d d e v i a t i o n

M i n i m u m p e r i m e t e rM a x i m u m p e ri m e te r

M e a n p e r i m e t e r

Pe r i me t e r s t a n d a r d d e v i a t i o n

M i n i m u m d i a m e t e r

M a x i m u m d ia m e te r

M e a n d i a m e t e r

D i a me t e r s t a n d a r d d e v i a t i o n

M i n i m u m c i r c u l a r i t y

M a x i m u m c i r c u l a r i t y

Me a n c i r c u l a r i t y

C i r c u l a r i t y s t a n d a r d d e v i a t i o n

R e d m i n i m u m v a l u e

R e d m a x i m u m v a lu e

V 2 1 R e d m e a n v a l u e

V 2 2 Re d s t a n d a r d d e v i a t i o n

V 2 3 G r e e n m i n i m u m v a lu e

V 2 4 G r e e n m a x i m u m v a lu e

V 2 5 G r e e n m e a n v a l u e

V 2 6 G r e e n s t a n d a r d d e v i a t i o n

V 2 7 B l u e m i n i m u m v a lu e

V 2 8 B l u e m a x i m u m v a lu eV 2 9 B l u e m e a n v a l u e

V 3 0 B l u e s t a n d a r d d e v i a t i o n

V 3 1 G r a y m i n i m u m v a lu e

V 3 2 G r a y m a x i m u m v a lu e

V 3 3 G r a y m e a n v a l u e

V 3 4 G r a y s t a n d a r d d e v i a t i o n

V 3 5 V e l o c i t y

V 3 6 D i s p l a c e m e n t a n g l e

V37 Stab i l i ty

V 3 8 M e a n d i a m e t e r c h a n g e

V 3 9 A n g l e c h a n g e

V 4 0 A r e a c o v e r e d c h a n g e

V 4 1 Br i g h t n e s s

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496 A. Cipriano et al

T h e n , i n o r d e r t o d e t e r m i n e w h i c h o f th e t w e n t y n i n e c h a r a c t e r i s t i c s s t o r e d i n c a r a c t e r e x p f i l e t h e s t u d i e d

f r o th p r e s e n t s , t h e e x p e r t s y s t e m c o m p a r e s t h e m e a s u r e d v a r i a b l e s t o f o rt y t w o c o n s t a n t s d e f i n e d i n

c o n s t a n t e x p f il e . T h e c h a r a c t e r i s t ic s a n d t h e i r c o r r e s p o n d i n g r u l e s a r e l is t e d o n T a b l e 2 . F o r e x a m p l e , r u l e

C OO s t a t es t h a t i f t h e g r a y m e a n v a l u e V 3 3 i s b e t w e e n K 0 0 = 0 a n d K 0 1 = 2 5 , t h e n t h e f r o t h is b l a c k . I t i s

i m p o r t a n t t o n o t e th a t th e c o n s t a n t s a re l a b e l e d f r o m K 0 0 t o K 4 9 . H o w e v e r , c o n s t a n t s K 0 4 , K 0 5 a n d

K 1 8 - K 2 3 a r e a c t u a l l y n o t b e i n g u s e d . T h e y a r e a v a i l a b l e f o r s p e c i f ic r e q u i r e m e n t s o f e a c h p l a n t a n d c a n

b e d e f i n e d b y t h e u s e r .

T A B L E C h a r a c t e ri s ti c s o f t h e f r o th i d en t if ie d b y A C E F L O T

C h a r a c t e r i s t i c C o r r e s p o n d i n gu l e C h a r a c t e r i s t i c C o r re sp o n di n gule

COO Black froth K00<=V33<=K01 C15 Very fast froth K35<=V35

C01 Yellow froth K06<=V21<=K07 C16 Very unstable froth V37<=K36K08<=V25<=K09

K 10<=V 29<=K 11

C 02 L ig ht-b lu e f r o t h K I 2 < = V 2 1 < = K 1 3 C 17 U n s ta b le r o t h K 3 6 < V 3 7 < = K 3 7

K 14<=V25<=K 15K 16<=V29<=K17

C03 Gray froth K02<V33<=K03 C18 ' Stable froth K38<=V37<K 39

C04 Very opaque froth V41<=K24 C19 Very stable froth K39<=V37

C05 Opaque froth K24<V41<=K25 C20 Very quiet froth V39<=K40

C06 Brilliant froth K26<=V41<K 27 C21 Quiet froth K40<V39<=K41

C07 V ery br il li an t f ro th K 27<=V41 C22 Tur bulen t r o t h K 4 2< =V 39 <K 43

C08 Very small bubb le V I 3<=K28 C23 Very turbulent froth K43<'--V39

C09 Small bubble K28<VI3<=K 29 C24 Very discharged tank V40<=K44

C 10 Large bubble K30<=V 13<K31 C25 Disch arged ank K 44 <V 40 <- -K 45

C 11 V ery lar ge bubble K 31 <=V 13 C26 Char g ed ank K 4 6< =V 40 < K 47

C12 Very slow froth V35<=K32 C27 Very charged tank K47<=V40

C13 Slow froth K32<V35<=K33 C28 Stable size K48<= V38<=K49C14 Fast froth K34<=V35<K35

F i n a l l y t h e t h i r t e e n o p e r a t i o n s t a te s t h a t t h e e x p e r t s y s t e m i d e n t i fi e s a re d e f i n e d i n r e g l a e x p f i l e u s i n g t h e

f r o t h c h a r a c t e r i s t ic s m e n t i o n e d a b o v e . T h e s e s t a te s a n d t h e i r c o r r e s p o n d i n g d e s c r i p t i o n s a r e l is t e d o n T a b l e

3 . F o r e x a m p l e , r u l e R 0 0 s t a te s t h a t i f t h e f ro t h i s b l a c k , v e r y fa s t a n d u n s t a b l e , t h e n i t s c o r r e s p o n d i n g

o p e r a t i o n s t a t e i s " l i g h t f r o t h " .

F i g u r e s 9 t o 1 2 p r e s e n t i m a g e s i l l u s t r a ti n g s o m e d e t e c t e d o p e r a t i o n s ta t e s. T h e u p p e r l e f t c o m e r o f F i g u r e

9 p r e s e n t s a s m a l l n u m b e r o f b u b b l e s , w h i c h i n d i c a t e s t h a t t h e o p e r a t i o n s t a te i s " o p e n f r o th " . F i g u r e 1 0

p r e s e n t s a l i g h t - b l u e a n d o p a q u e f r o t h w i t h v e r y s m a l l b u b b l e s , w h i c h c o r r e s p o n d s t o " d e m i n e r a l i z e d f r o th " .

F r o t h o f F i g u r e 1 1 i s y e l l o w , b r i l l i a n t a n d c o n t a i n s v e r y s m a l l b u b b l e s , w h i c h c o r r e s p o n d s t o " p y r i t i c f ro t h " .

F i n a l l y , b u b b l e s o f F i g u r e 1 2 a r e v e r y l a rg e a n d t h e f ro t h is b l a c k , w h i c h c o r r e s p o n d s t o " f ro t h c o n t a m i n a t e d

w i t h o i l " .

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Visual sensor for supervision of f lotat ion cel ls

T A B L E 3 O p e r a t i o n s t a t e s i d e n t i f i e d b y t h e e x p e r t s y s t e m

4 9 7

N ° O p e r a t i o n s t a t e

R Ligh t f ro th

R01 Heavy f ro th

R02 Wate red f ro th

R03 Pyri tic froth

R 4

R 5

R 6

R 0 7

R08

R 9

C h a r a c t e r i s t i c s

Black, very fast and unstable froth: C00 A ND C15 AN D C I7.

Yellow and slow froth, small bubbles: C01 AND C13 A ND C09.

Light-blue, fast a nd very unstable froth, small bubbles:

C 0 2 A N D C 1 4 A N D C 1 6 A N D C 0 9 .

Yellow, brilliant, slow an d very stable froth, ve ry small bubbles:

C01 AND C06 AN D C13 AND C19 AND C08 .

Op en froth: absence ofb ub - Unstable f ro th dischatg¢~t ank and stable s ize: C17 AN D C25 AN D C28.

b les over pa r t o f the su rface

Deminemlized froth Light-blne and opaque froth, very small bubbles: C02 AN D C05 AN D CO8.

Fro th con taminated wi th Very stable f ro th and small bubb les : C l 9 AN DC 09.

sulphurie acid

Froth contaminated with oi l Black froth and very large bubbles: CO0 AN D C l 1.

Machine obstruc t ion iFast and turbulent froth: CI 4 AND C22.

Excess o f l im e :Yellow and very slow froth, small bubbles: C01 AN D C12 AN D C09.

Yellow froth, discharged tan k, stable size and small bubbles:

C 1 A N D C 2 5 AND C28 AN D C09 .

Gray and very bri l liant froth, very large bubbles:

C03 AND C07 AN D CI 1 .

R 1 0 L a c k o f l i m e

RI 1 Lack of col lector

R I 2 N o r m a l froth None o f the above o pera t ion s ta tes .

r •

r . ? /

F i g . 9 O p e n f r o t h .

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498 A Cipr iano e t a l

F i g 1 0 D em i n e r a l i z ed f r o t h

Fig 11 Pyr i t i c f ro th

II

a ~ .

•

e

F i g 1 2 F r o t h co n t am i n a t ed w i t h o i l

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Visual sensor for supervision of flotation cells 499

F I N L R E M R K S

The already described expert system has been installed recently in one of the concentration plants of the

great copper mining in Chile, in which an industrial version of ACEFLOT supervises three flotation rougher

ceils, each one every three minutes. Currently we are working on the experimental validation of the

knowledge base and on the evaluation of the benefits provided by ACEFLOT and the expert system. Once

the knowledge base of the expert system be evaluated, we will investigate its application to scavenger and

cleaner cells.

ACKNOWLEDGMENT

The authors would like to thank the support provided by CODELCO E1 Teniente Division, DICTUC S.A.,

FONTEC, project ACEFLOT: A Real Time Analyzer of the Dynamic Characteristics of Froth for Mineral

Flotation Plants, and FONDEF, project Technological Transfer of ACEFLOT and SISCO.

.

3.

.

R E F E R E N C E S

Zavala, E., P6rez, R., Mufioz, C. Cipriano, A., Heuristic and model predictive control strategies

for a simulated flotation circuit. In Preprints of the 8th IFAC International Symposium on

Automation in Mining Mineral and Metal Processing Sun City, August 29-31, 1995, pp. 59-64.

Pratt, W., Digital image processing Wiley Sons, 1991.

Guarini, M., Cipriano, A., Soto, A. Guesalaga, A., Using image processing techniques to

evaluate the quality of mineral flotation process. In Proceedings of the 6th International Conferenceon Signal Processing Applications and Technology B oston, October 24-25, 1995, pp. 1227-1231.

Cipriano, A., Guarini, M., Soto, A., Brisefio, H. Mery, D., Expert supervision of flotation cells

using digital image processing. In Proceedings of the 20th International Mineral ProcessingCongress Aachen, September 21-26, 1997, pp. 281-292.

Corres ponden ce on papers publ ished in Minerals Engineering is invited, preferably by e-

mail to min. eng@n etmat ters .co.u k, or by Fax to +44-(0) 1326-318352

1998-mineng

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