COMBINED MODEL "AC" - Computer Application in the Steel Industry: Control of Basic Ox

COMBINED MODEL "AC"

EXPERIMENTAL

(INSTALLATION) MODEL "C"

(PILOT)

Figure 6.

Source: [8]

Another way t o develop a mathematical model i s t o conduct a s t u d y of a p i l o t technology ( s e e C i n F i g u r e 6 ) . The s t u d y can be conducted i n s p e c i a l p i l o t u n i t s o r i n i n s t a l l a t i o n s , w i t h a view t o i d e n t i f y i n g s e p a r a t e p r o c e s s e s i n t h e technology, t o d e s i g n i n g a new t e c h n o l o g y , e t c . The r e s u l t s of t h e s e i n - v e s t i g a t i o n s can be used f o r developing t h e mathematical model on an e x p e r i m e n t a l b a s i s .

The advantages and d i s a d v a n t a g e s of a n a l y t i c a l and e x p e r i - mental approaches a r e w e l l known. Applying a combination of b o t h t y p e s of models i s even more advantageous ( s e e AB, A C , ABC i n F i g u r e 6 ) . These combined models use c l a s s i c a l laws and e x p e r i m e n t a l d a t a ( e . g . , c o e f f i c i e n t s and e q u a t i o n s ) , and a r e most widely used i n t e c h n o l o g i c a l f i e l d s .

T a b l e 3 shows some f e a t u r e s of model development f o r d i f - f e r e n t p u r p o s e s . A number of f a c t o r s must be c o n s i d e r e d when s t u d y i n g t h e system from a modeling v i e w p o i n t . For i d e n t i f y i n g o p e r a t i o n a l (management and c o n t r o l ) and r e s e a r c h problems, d a t a e x i s t on t h e t e c h n o l o g i c a l system t h a t can be used f o r model development. As f o r t h e development of models f o r d e s i g n i n g

Table 3 [81. Problems formulation

Problems Operational Control and Management Steps Special features of the study of the system under modeling Method of developing mathematical model

Research Model's size/complexity Computer Solution Data availability

Design Possible or necessary accuracy

Improvement of indices in technology in operation by means of operational control and management Knowledge and data avail- able. Implementation of special methods of study: experimental statistical, etc.

-

Analytical - Experimental - Combined Limited Universal On-line Necessary comparative data available

1

High Improvement of indices of up-to-date technology by means of research and development Knowledge and data avail- able. Implementation of special methods of study: experimental, statistical, etc. - Analytical

-

Experimental - Combined Any complexity

1

Possible comparative data available

Off -Line

Design of ad- vanced (new) technology

I

^Not

enough know- ledge and data about the exist- ing system

-

Analytical - Combined Any complexity Off -line Difficult

-

no comparative data Low

new t e c h n o l o g i e s , t h e r e i s o f t e n some d e l a y o r t h e model d e - s c r i p t i o n i s n o t p r e c i s e owing t o a l a c k o f r e a l d a t a . I n t h e l a t t e r c a s e , p r e v i o u s e x p e r i e n c e c o u l d b e u s e d o r a n a n a l o g t e c h n o l o g i c a l s y s t e m c o u l d b e s t u d i e d . N e v e r t h e l e s s , t h e r e may s t i l l b e i n s u f f i c i e n t i n f o r m a t i o n f o r d e v e l o p i n g t h e v e r i f y -

i n g d e s i g n m o d e l s s i n c e d a t a a r e n e e d e d f o r a p p l y i n g t h e s t a t i s - t i c a l method t o t h e d e v e l o p m e n t o f t h e s e m o d e l s .

O p e r a t i o n a l m o d e l s s h o u l d b e s o l v e d on l i n e i n a c c o r d a n c e w i t h t h e t e c h n o l o g i c a l c y c l e and h a v e a h i g h a c c u r a c y l e v e l ; t h e l a t t e r d e t e r m i n e s t h e p r o p e r t i e s o f models s u c h a s l i m i t e d s i z e , and u n i v e r s a l c o m p u t e r i m p l e m e n t a t i o n .

I n d i s c u s s i n g model d e v e l o p m e n t and d a t a s e l e c t i o n w i t h r e s p e c t t o c o m p u t e r a p p l i c a t i o n i n BOFs, it i s n e c e s s a r y t o stress t h a t o n e o f t h e e l e m e n t s o f a s y s t e m s a p p r o a c h s h o u l d b e c o n c e r n e d w i t h p r o b l e m o r i e n t a t i o n f o r a l l p r o c e c u r e s and t e c h n i q u e s .

The s t u d y o f a s i m u l a t e d s y s t e m i n c l u d e s i d e n t i f y i n g t h e main i n p u t and o u t p u t p a r a m e t e r s , g r o u p i n g t h e s i m i l a r p r o c e s s e s , and d i v i d i n g t h e s y s t e m i n t o s e v e r a l e l e m e n t a r y s u b s y s t e m s (see F i g u r e 7 ) . The BOF t e c h n o l o g y c a n a l s o b e c o n s i d e r e d a c o m p l e t e e n t i t y . I n t h i s c a s e t h e c o n n e c t i o n between i n p u t and o u t p u t p a r a m e t e r s c a n b e f o u n d w i t h o u t t a k i n g i n t o c o n s i d e r a t i o n t h e e l e m e n t a r y s u b p r o c e s s e s .

SLAG FORMATION3

I

t

HEATING AND ^I ¹

SOLUBILITY

-

A SOLID ADDITIVES4 6,(t)

Parameters

P

Uo,i

.

oxygen and fuel rate Gi : metal flow

Xme : carbon concentration @,(t) : reaction constant

MODELS FOR OFF-LINE COMPUTER APPLICATION

O X Y G E N ,

[x,li = CARBON CONCENTRATION ^STEEL

Parameters

Uoxi : oxygen and fuel rate Om(t): reaction constant

Xme : carbon concentration : time

Gi : metal flow

Fig~ln* t i . SolrnT: [Ill

TIME. hr

PRODUCTIVITY

6:

^=- ^{15 T/hr}

Figure 9.

Sour(:(:: [81

F o r t h i s p u r p o s e t h e model c a n be s o l v e d o f f - l i n e , and c a n h a v e a n y c o m p l e x i t y ; p r o c e s s d a t a c a n b e made a v a i l a b l e f o r model a d a p t a t i o n ; s o l u t i o n t i m e i s u n l i m i t e d ; demand f o r model a c c u r a c y i s n o t h i g h . T a k i n g t h e s e c o n s t r a i n t s i n t o c o n s i d e r - a t i o n , t h e combined e x p e r i m e n t a l and a n a l y t i c a l a p p r o a c h c a n b e u s e d t o d e v e l o p t h e m a t h e m a t i c a l model (see AB i n F i g u r e 6 ) . F i g u r e 10 shows t h e scheme o f t h e m o d e l .

MASS BALANCE Z G = 0 ISSUE OF STEEL HL@ Ui(t)* b

r,

t

CHEMICAL KINETIC

I I

E 4-

- [xme]

(f) = ~e~~ [Xmel(t) X [Xol (f) HEAT TRANSFER - SOLUTION

GP.

dGj(t) b Ti

7 +

Gj(t) = G; HEAT BALANCE A +

-

U(t) : oxygen throughput

I

ZQi=O Om(t)

i

HL : lance position I I input parameters G! : weight of additional agents Xme(t) : metal composition G; : charge composition initial Om(t) : temperature output parameters 0,(0) : temperature of pig iron qSt : metal yield Figure 10. Source: [8]

The model is a system of 48 linear and nonlinear equations including 13 differential equations. Two types of computers have been used for solving this model: an analog computer for the structural identification of the preliminary model, and a universal computer for detailed simulation of different types of technology.

Figure 1 1 shows one result of this investigation. The modern trend in BOF technology is to increase the specific oxygen consumption from 2 to 6-7 m3/t/min in order to increase

NUMBERS B Y CURVE - O X Y G E N VALUE, m 3 / mint t

Figure 1 1 .

p r o d u c t i v i t y . T h i s i n c r e a s e h a s a number o f c o n s e q u e n c e s ; f o r e x a m p l e , by i n c r e a s i n g t h e oxygen c o n s u m p t i o n t h e m e t a l s r e a c h t h e e n d - p o i n t t e m p e r a t u r e a t a much f a s t e r r a t e t h a n t h e c a r b o n c o n c e n t r a t i o n . The c a r b u r i z a t i o n r a t e may r e a c h 0 . 6 0 p e r c e n t p e r m i n u t e . T h e s e d a t a a r e v e r y i m p o r t a n t f o r c o n s t r u c t i n g a n e x h a u s t s y s t e m .

The i n f l u e n c e o f d i f f e r e n t p a r a m e t e r s o n t h e m e t a l y i e l d h a s a l s o b e e n i n v e s t i g a t e d . F i g u r e 12 shows t h e i n f l u e n c e o f t h e f r a c t i o n o f s c r a p i n t h e c h a r g e ; t h e maximum y i e l d i s ob- t a i n e d w i t h a b o u t 25 p e r c e n t s c r a p i n t h e c h a r g e .

FRACTION OF SCRAP IN CHARGE (%)

Computer a p p l i c a t i o n and m o d e l i n g a l l o w s o n e t o s t u d y t h e m a c r o p r o c e s s e s a n d t h e m i c r o p h y s i c a l - c h e m i c a l p r o c e s s e s o f BOFs.

F o r t h i s p u r p o s e , a d e t a i l e d model i n c l u d i n g a b o u t 50 l i n e a r and n o n l i n e a r d i f f e r e n t i a l e q u a t i o n s was d e v e l o p e d on a n a n a l y t i c a l b a s i s . The p r a c t i c a l d a t a h a v e b e e n u s e d f o r v e r i f y i n g t h e model.

F i g u r e 1 3 shows t h e d y n a m i c s o f c a r b o n o x i d a t i o n , h e a t i n g a n d s c r a p s o l u t i o n u s i n g d i f f e r e n t oxygen t h r o u g h p u t s a n d t h e f r a c t i o n o f s c r a p i n t h e c h a r g e . F i g u r e 14 shows t h e f r a c t i o n of d i r e c t d e c a r b u r i z a t i o n ( i n t h e r e a c t i o n C

+

0 = CO) i n t o t a l d e c a r b u r i z a t i o n . T h i s t y p e o f i n f o r m a t i o n i s v e r y d i f f i c u l t t o o b t a i n f r o m o t h e r m e t h o d s ( e . g . e x p e r i m e n t a l ) .

OXYGEN THROUGHPUT, a-2.1 m3/t min b-5.0 c-7.0 WEIGHT OF 1-30.0 SCRAP IN CHARGE, I 2.35.0 (FOR 131 BOFl 3-40.0 MELTING POINTS 0 5 10 15 20 25 time, mon OXYGENTHROUGHPUT, a-2.1 m3/t min b-5.0 c -7.0 WEIGHT OF SCRAP IN CHARGE, t (FOR 1301 BOFI Figure 13. Figure 14.

MODELS FOR ON-LINE COMPUTER APPLICATION

t o t h e p r o d u c t i v i t y of t h e CCM. T h i s i s p o s s i b l e t o a c h i e v e by

VARIANT ii (m=3, n=4)

H E A D O F F I C E

T h e r e a r e s e v e r a l c h a r a c t e r i s t i c s o f t h e s y s t e m w o r t h n o t i n g

i n s t a l l a t i o n p e r m i l l i o n t o n s o f s t e e l p r o d u c e d a n n u a l l y . T a b l e 4 g i v e s t h e s e i n d i c e s f o r d i f f e r e n t r e g i o n s a n d c o u n t r i e s .

T a b l e 4 . C o s t o f c o m p u t e r i n s t a l ' l a t i o n p e r m i l l i o n t o n s o f s t e e l ( i n 1000 US $ 1 [ l o ] .

Western Europe USA

Japan

The J a p a n e s e s t e e l i n d u s t r y h a s a much h i g h e r l e v e l o f c o m p u t e r - i z a t i o n a s compared t o t h a t o f W e s t e r n E u r o p e and t h e USA f o r a number o f r e a s o n s t h a t a r e c o n n e c t e d w i t h s p e c i a l f e a t u r e s o f t h e d e v e l o p m e n t o f t h i s i n d u s t r y i n J a p a n a n d o f t h e J a p a n e s e economy a s a w h o l e .

The IIASA s t u d y r e v e a l e d t h a t a c o m p l e t e l y i n t e g r a t e d com- p u t e r - b a s e d management s y s t e m , d e s i g n e d p a r t l y and d e v e l o p e d j o i n t l y w i t h new s t e e l p l a n t s , e x i s t s o n l y i n J a p a n .

CONCLUSIONS

Computer a p p l i c a t i o n i n BOFs i m p r o v e s t h e o p e r a t i o n a l con- t r o l and t h e r e s e a r c h a n d d e v e l o p m e n t o f t h e e x i s t i n g t e c h n o l o g y , and a i d s i n t h e d e s i g n o f a new t e c h n o l o g y b a s e d o n BOFs. The s y s t e m s a p p r o a c h i n v o l v e s f o r m u l a t i n g t h e o b j e c t i v e s and a p p l y - i n g c o m p u t e r s f o r model d e v e l o p m e n t , d a t a s e l e c t i o n , e t c . The c o n s i d e r a t i o n o f which m o d e l s may b e u s e d f o r o t h e r p u r p o s e s d e p e n d s g r e a t l y o n t h e o b j e c t i v e s a c h i e v e d .

The t a s k o f d e v e l o p i n g i n t e g r a t e d c o m p u t e r b a s e d c o n t r o l and management s y s t e m s , i n c l u d i n g BOF c o n t r o l s u b s y s t e m s , h a s b e e n s o l v e d o n l y t o a v e r y l i m i t e d d e g r e e . Most o f t h e s t e e l f i r m s h a v e a n e q u a l l e v e l o f c o m p u t e r i z a t i o n r e p r e s e n t e d i n t e r m s o f a c o r e memory c a p a c i t y i n b y t e p e r e m p l o y e e .

REFERENCES

[ I ] S t a h l e i s e n - K a l e n d e r 1 9 7 6 , V e r l a g S t a h l e i s e n M . B . H . , D u s s e l d o r f , 1976.

[ 2 ] L e f k o w i t z , I . and A . C h e l i u s t k i n , e d s . , I n t e g r a t e d S y s t e m s C o n t r o l i n t h e S t e e l I n d u s t r y , CP-76-13, I n t e r n a t i o n a l I n s t i t u t e f o r A p p l i e d S y s t e m s A n a l y s i s , L a x e n b u r g , A u s t r i a , 1976.

[3] McManus, G.J., Research Roulette Isn't for US Steel, I r o n Age, February 28 (1 977)

.

[4] Ito, K., Impact of Environmental Constraints in the Steel Industry, in [21.

[5] Warren, K., W o r l d S t e e l : A n E c o n o m i c G e o g r a p h y , Crane- Russak E Co. Inc., New York, 1975.

[61 P r o c e e d i n g s o f t h e I n t e r n a t i o n a l M e e t i n g o n I r o n a n d S t e e l

M a k i n g , 1976, Brussels/~~sseldorf, Volume Tb, Centre de

Recherches Metallurgigues, Brussels, 1976.

[7] Surguchov, G.D., E. Derkatschov, and G. Massalow, The Possibility of Controlling the LD Process on the Basis of a Dynamic Model, B e r g u n d ~ u t t e n m a n n i s c h e M o n a t s h e f t e , 7 (1973) (in German).

[81 Surguchov, G.D., I n d u s t r i a l T e c h n o l o g y : P r o b l e m O r i e n t e d

A p p r o a c h , RM-76-77, International Institute for Applied

Systems Analysis, Laxenburg, Austria, 1976.

[91 Zimin, I., and G. Surguchev, S h o r t - T e r m P l a n n i n g o f a n I n t e g r a t e d I n d u s t r i a l C o m p l e x , RM-75-13, International Institute for Applied Systems Analysis, Laxenburg, Austria.

[lo] Gohlke R., and E. Bykoff, Data Processing Systems in the Steel Industry, I r o n a n d S t e e l I n t e r n a t i o n a l ,

2,

2 (1976), 113-120.

D i s c u s s i o n

MATHEMATICAL MODELS AND CONTROL SYSTEMS I N BASIC O X Y G E N FURNACES

#

process phase

I

model start

desired steel analysis

desired analysis

Figure 3. The models as a block diagram.

desired temperature real analysis

real temperature

*

old adaptation

coefficients ^b

reblowing oxygen

cooling scrap b

steel weight

I I

AD AP

steel weight calculated steel

analysis ^b

desired analysis

real analysis cold

hot and liquid LEG

1

alloying materials b

new adaptation

coefficients ^#

alloying materials desired analysis

LEG hot and liquid

alloying materials ^b

Figure 4. The models as a block diagram.

adaptation coefficients desired values

real values ^b LEG

Table 1 . Coefficients of thermal conductivity.

inside Wall Thickness (cm) outside Figure 5. LD - Converter, cooling down from the steady state; wall thickness = 400 mm.

I . , _ , ,_ ,

, . ,

^{, , ,}. _ _ , ,

0 10 2 0 30 4 0 50

inside Wall Thickness (cm) outside

Figure 6. LD - Converter. cooling down from the steady state; wall thickness = 500 mm.

0 10 20 30 40 50 60

inside Wall Thickness (cm) outside

Figure 7. LD - Converter, cooling down from the steady state; wall thickness = 600 mm.

0 10 20 30 40 50 60 70

inside Wall Thickness (cm)

outside

Figure 8. LD - Convcrtc%r. cooling down l'ronl thc stvady statr.: wall il\ic.L~~c*.;h = 700 mu\.

Wall thickness

(mm)

-

Inside ₇₀₀

600 500

400

.

time (h)

Figure 9. Cooling down from the steady state: LD-Converter.

Time (h)

Figurt: 10. Cooling down from the steady state: heat flow through the vessel wall.

H e a t i n g A f t e r a S t o p of .48 Hours

The i n i t i a l c o n d i t i o n i s t h e f i n a l s t a t e c a l c u l a t e d a b o v e . The h e a t i n g i s performed u p t o a d e t e r m i n e d v e s s e l i n s i d e w a l l t e m p e r a t u r e of 1400 OC. The t e m p e r a t u r e g r a d i e n t s a r e p l o t t e d i n F i g u r e s 11 t o 14. Heat f l o w d e n s i t y and amount o f h e a t a r e shown i n F i g u r e s 15 and 1 6 .

A t t h e b e g i n n i n g of t h e h e a t i n g p r o c e s s t h e e n e r g y i s s t o r e d i n t h e c o n v e r t e r w a l l ; when t h e s t e a d y s t a t e i s r e a c h e d , i . e . a f t e r 24 h f o r a w a l l t h i c k n e s s of 400 mm, c o n s t a n t h e a t e m i s s i o n t a k e s p l a c e .

Of c o u r s e , a l l p o s s i b l e c a s e s c a n b e s i m u l a t e d w i t h t h i s program, e . g . o t h e r w a l l t e m p e r a t u r e s , h e a t i n g u p a f t e r a s t o p o f v a r i o u s d u r a t i o n s , o t h e r v e s s e l d i m e n s i o n s , e t c .

Now we i n c o r p o r a t e t h e r e s u l t s d i s c u s s e d above i n v a r i o u s ways i n t o t h e p r o c e s s models. E q u a t i o n s ( 1 ) t o ( 3 ) show a s i m p l e example.

,

r a d i a t i o n c o n s t a n t s ;

,

mean number o f h e a t s p e r v e s s e l campaign;

,

a c t u a l number o f h e a t s i n t h e v e s s e l campaign;

4

, , , , , , , , , . , , , , , , , , . , , , . . . ; , , , , , , , , , ; , , , , , , , , , ; , ,

0 5 10 15 20 25 30 35 40

inside Wall Thickness (em) outside

Figure 11. LD-Converter. heating up after a stop of 4 8 hours, wall thickness = 400 mm

l ' ' ~ ' ' ' l ' ' l ' ' l " " l ' l ' l l ' " ' ' ' l l r " ' l r l ' l

0 10 20 30 40 50

inside Wall Thickness (em) uutside

Figure 12. 1.1)-Convcrtcr. heating up aftcr a stop of 4 8 hours; wall thickness = 500 mm.

inside Wall Thickness (cm) outside Figure 13. LD-Converter, heating up after a stop of 48 hours; wall thickness = 600 nlm.

, , ,

.

, , , , , , , , , , , , , ,

0 10 20 30 40 50 60 70

inside Wall Thickness (cm) outside

Figure 14. L,D-(:onvrrter, heating up aStc:r a stop of 48 hours; wall 1hic.krlc:ss = 700 IIIIII.

10°kJ 140-

1 O6 kcal

C 100-

J= Heat storage in the wall

'C 20 ⁷⁰⁰₆₀₀^mm_mm

0 6 12 18 24 30 36 42 48

Time (h)

Figure 15. Heating up after a stop o f 4 8 hours: LD-Converter.

Wall

1 Thickness

(mm)

400 500 600 700

0 0 6 12 18 24 30 36 42 48

Time (h)

Figure 16. Heating up after a stop of 4 8 hours: heat flow through the vessel wall.

,

w a l l t h i c k n e s s a t t h e end of a campaign a s a p e r c e n t -

time (s)

Figure 17. Melting of a 150 mm thick scrap plate: temperature distribution.

8000-

6000-

-

m Y

4000-

2000-

0 500 1000 1500 T("C)

Figure 19. Specific heat capacit).

,

0 500 1000 1500 time (s)

Figure 21. Melting o f a scrap wheel o f diameter: 3 0 0 mm: temperature distribution.

outside radius (cm) middle

Figurc. 22. Mrlting o f a scrap wht:r.l o f diameter: 3 0 0 m m : temperature distribution.

Beginning Conditions

0 5 10 15

time, t (min)

Figure 23. Melting of a scrap plate.

1 woOc

F

Conditions ^Beginning

10 --

0 10 2 0

time, t (min) Figure 24. Melting o f a scrap wtit,el.

F o r t h e f i r s t s i x d a y s o f t h e t e s t , t h e a d a p t a t i o n model was n o t u s e d , b e c a u s e we wanted t o c o n t r o l t h e s t a b i l i t y of t h e model: i t was o n l y u s e d f o r t h e l a s t t h r e e d a y s . The p r o c e s s model c a l c u l a t e d t h e q u a n t i t i e s o f h o t i r o n , s c r a p , o r e , and

l i m e t o i n s e r t , w h i l e t h e v e s s e l crew f i x e d t h e s e q u a n t i t i e s by t h e i r own methods w i t h o u t c o n s i d e r i n g t h e computed v a l u e s . The model c a l c u l a t e d f o r t h e s e i n p u t s t h e p r o b a b l e t e m p e r a t u r e ob- t a i n e d i f t h e amount o f oxygen c a l c u l a t e d from t h e model was blown. The s t a n d a r d d e v i a t i o n s o f t h e s e v e r a l d a y s w e r e c a l c u - l a t e d a s f o l l o w s :

x

⁼

-

_n1

C

^AT,

The r e s u l t s a r e shown i n F i g u r e 2 5 . The s i m i l a r b e h a v i o r o f t h e s t a n d a r d d e v i a t i o n c u r v e s o f t e m p e r a t u r e a r e p r o b a b l y

day

Figure 2 5 . Temperatnrr standard deviation comparison: model and hand.

caused by measurement errors (hot iron analysis, hot iron temperature), unknown scrap composition, etc. Unless these measurement errors can be reduced, greater efforts in trying t o improve the accuracy of the process models will not give better results.

D i s c u s s i o n

H e a t l o s s f r o m t h e v e s s e l s i s v e r y i m p o r t a n t f r o m t h e c o n t r o l a n d i n v e s t i g a t i o n s p o i n t s o f v i e w . S e v e r a l i s s u e s w e r e r a i s e d a b o u t t h e d e c r e a s e i n t e m p e r a t u r e d u r i n g t h e t i m e t h e c o n v e r t e r i s i n o p e r a t i v e . I t was p o i n t e d o u t t h a t t h e model d i s c u s s e d i n t h e p r e v i o u s p a p e r t a k e s i n t o c o n s i d e r a t i o n a number o f f a c t o r s t h a t a f f e c t t h e t e m p e r a t u r e b e h a v i o r o f t h e c o n v e r t e r when i n o p e r a t i v e . The m o s t i m p o r t a n t f a c t o r i n f l u e n c i n g t e m p e r - a t u r e d e c r e a s e i s t h e w a l l t h i c k n e s s w h i c h , f o r e x a m p l e , c a n v a r y f r o m 4 0 t o 7 0 c m .

D i s c u s s i o n a l s o c e n t e r e d o n f a c t o r s a f f e c t i n g t h e e n d - p o i n t t e m p e r a t u r e . I t was p o i n t e d o u t t h a t , f r o m Mannesmann's c a l c u - l a t i o n , t h e m o s t i m p o r t a n t f a c t o r i s t h e amount o f s i l i c o n , t h e s e c o n d m o s t i m p o r t a n t i s t h a t o f c a r b o n , and t h e t h i r d i s t h a t o f s c r a p . The c a l c u l a t i o n s by B r i t i s h S t e e l C o r p o r a t i o n (BSC) show t h a t t h e m o s t i m p o r t a n t f a c t o r i s t h e e r r o r i n s i l i c o n a n a l y s i s , t h e s e c o n d t h a t i n c a g b o n a n a l y s i s and t h e t h i r d t h a t o f t h e h o t m e t a l w e i g h t . F o r VOEST-Alpine, t h e m o s t i m p o r t a n t f a c t o r i s a n a l y s i s and t h e s e c o n d i s h o t m e t a l t e m p e r a t u r e . The e n d - p o i n t e r r o r d e p e n d s o n t h e s t a n d a r d d e v i a t i o n o f t h e i n p u t f a c t o r s .

A n o t h e r i m p o r t a n t i s s u e d i s c u s s e d was t h e c h o i c e o f a r e p r e - s e n t a t i v e p o i n t f o r t e m p e r a t u r e m e a s u r e m e n t o f h o t m e l t e d s c r a p . Non-melted s c r a p makes t h i s t e m p e r a t u r e m e a s u r e m e n t d i f f i c u l t . Boundary c o n d i t i o n s a r e a r e a l p r o b l e m f o r s c r a p m e t a l s t u d i e s . F i g u r e s 1 9 and 2 0 i n t h e p a p e r by Weniger p r e s e n t s p e c i f i c h e a t c a p a c i t y and amount o f c o n v e c t i o n t o b e u s e d f o r t h e c a l c u l a t i o n . O t h e r b o u n d a r y c o n d i t i o n s c o n c e r n e d s c r a p c o n f i g u r a t i o n . F o r e x a m p l e , w i t h a t h i c k n e s s o f 1 5 c m , s c r a p c o u l d m e l t i n 1 5 min.

The model makes i t p o s s i b l e t o c a l c u l a t e t h e l a r g e s t s c r a p d i m e n s i o n s t h a t c a n b e m e l t e d w i t h i n t h e s h o r t b l o w i n g t i m e a s s o c i a t e d w i t h a h i g h oxygen blow. I t was p o i n t e d o u t t h a t t h e model c a l c u l a t i o n o f s c r a p m e l t i n g made i t p o s s i b l e t o c o r r e c t t h e m e a s u r e d t e m p e r a t u r e , however m e a s u r e d ; t h i s i s o f g r e a t p r a c t i c a l i m p o r t a n c e .

The Dynamic C o n t r o l o f B a s i c Oxygen F u r n a c e s

m e a s u r e m e n t o f t h e c a r b o n c o n t e n t and t e m p e r a t u r e w i t h a s e n s o r l o w e r e d i n t o t h e b a t h d u r i n g t h e c o u r s e o f b l o w i n g , t h e amount o f o x y g e n blown i n and o f i r o n o r e c h a r g e d c a n b e a d j u s t e d s o a s t o a t t a i n f i n a l c o n d i t i o n s o f t h e b a t h w i t h i n t h e aimed r a n g e T h i s s y s t e m i s more o r l e s s a n a l o g o u s t o t h a t o f a moon r o c k e t l a u n c h e d f r o m t h e E a r t h ( c o r r e s p o n d i n g t o t h e f i r s t b a t h ) whose c o u r s e i s a d j u s t e d f r o m k n o w l e d g e of i t s e x a c t p o s i t i o n when it a p p r o a c h e s t h e moon ( c o r r e s p o n d i n g t o t h e b a t h c o n d i t i o n a t t h e end o f b l o w i n g ) .

c u a ~ range

almed range ,/-

I I I 1 aimed

I l n l t l a l s t a g e

carbon content

Yigurr. 1. 1'rinc:iplr o f dynamic control.

THE TECHNIQUES TO BE DEVELOPED

The BOF dynamic c o n t r o l s y s t e m c o m p r i s e s f o u r i t e m s :

-

A t e c h n i q u e t o m e a s u r e r e p r e s e n t a t i v e v a l u e s , - A h i g h l y a c c u r a t e s e n s o r ,

-

R e l i a b l e s u b l a n c e e q u i p m e n t ( t o t r a n s m i t t h e s i g n a l f r o m t h e s e n s o r t o t h e c o m p u t e r ) , and

-

A good dynamic c o n t r o l m o d e l .

A T e c h n i q u e t o Measure R e p r e s e n t a t i v e V a l u e s

couple used in the sensor is maintained at a high level, i.e. - 0

to +1 OC at 1 6 0 0 OC. The solidification curve obtained by the

sensor is much affected by the construction of the sensor and so a number of sensors have been tested. A cross-section of our sensor, and curves recorded during blowing are shown in Figure 3.

Figure 2. The temperature and carbon distributions and the measuring point.

Table 1 . Measurement accuracies required of the sensor.

1 .O$ o r above Measurement Range

(Carbon C o n t e n t i n Molten S t e e l )

bout 0.5% +0.02%

Accuracy o f E l e c t r o m o t i v e

F o r c e A c c u r a c y o f

Carbon C o n t e n t

Accuracy o f S o l i d i f i c a t i o n

T e m p e r a t u r e

0.1% o r u n d e r +0.01% - ^+I- ^OC

I

^50.01^mv

(1) Cross section of NSC type sensor

Protective tube up to measuring point Sampling case

Solidification temperature sensor

Compensation conductor t o upper sublance

Degassing port -Molten steel

charging port Sample chamber

C e m e n t

* 2

Molten steel temperature sensor

Protective cap up t o measuring p o i n t 2

(2) Example of recorded curves during blowing

Cross section of sample

Carbon

(solidification temperature)

A

connected

Figure 3. NSC type sensor for CQT.

The S u b l a n c e E q u i p m e n t

Skull remover

I I -

Figurc 4. SuLlancr systertr (swirrg type).

T a b l e 2. P a r t i c u l a r s of t h e s u b l a n c e e q u i p m e n t .

BLOIVING CONTROL PATTERN U1.0lV START PUSH RL'TTOY

1

I AIMED C 5 LXM. 2.70- 1 2.1m- 2.m-

LANCE HEIGHT PATTERN 2.100- MATERIAL CHARGING PATTERN ORE ICO~TISUOCS C!I~IICINCI A,, /

(AIMED c r 0.m~) llOT METAL. TELIPERATURE I

t

I W I AUTOIATIC CONTRO1.S)

t

= AI\lE.D CARBON ANDTEM13ERATURE 2 I.ANCE IlElGHT M*TCRIA1' DYSAhlIC CONTROL .ACTIOSS U,FLOW CONTROL. COsTROI, \YI:IGI~I~C CARRIED OUT .AUTO>I.ATICAI.I.Y (BLOCK - I ) CHARGlYC COHTROI. RY COMPUTER

7

CALCULATED

f

% OXYGtX VOLUME L 4 < z 3 9 rn 6 I SUB MATERIAL WEIGHT E E < 3 u 9 HUT METAL WEIGtlT (BLOCK - 4 1 SCRAP lYFlCUT DYNAMIC CONTROL ( CALCULATIOS AND AUTOMATIC COXTROLI

1 2.603- 2.4rn- I . . . . . . . . -. . . . . (BLOCK - 3 r--- ' MEASURING TIME ... 2.m)Nm1 BEFORE AIMED 0, VOI.L'YE Q.\'AC ASALYSIS I DECIRBL'R12ATIOX YODEL TEIIPERATURI RlSlYG NODEL I I - - VOLUME BASED I

/

REcoRos OF DECARDCRIZATIO~ RATE

-

ON COOLANT BLOW OFF . i KAOI 025 D,

)L:PA~R~

EFFICIENCY 2UA06030 D, I I L I OXYGES YOLCME AT BIOW OFF COOLAXT AYOCYT FOR NECESSARY DxYcEn YULUHL ASD IHS22130 0, I CAN RE ORTAISED. OYYA\IIC COSTROI. USE COOLANT WUCHT ARE DISYLAYED.

I

ZJS06028 0, I CAI RE ORTIIIED CHAlCE OF CARBOY AID TEUYERATURE ARE cALcuL.!rEo AND DISPLAYED L---d OX CRT AT EVXRY i mDS THOSEDISAYICCOSTROL RFCORDSOFTHF PAST SEVERAL HEATS AIL DISPLAYED OX CRT TEMI'ERATURE RlSlSG RATE AUIUSTLIEST AS0 DLURBURIZATIOS PATTERS SELECTIOY CIS BE WXE. Figure 5. Flow diagram of dynamic control.

OPERATIONAL PERFORMANCE

0 . 5 p e r c e n t . A s shown i n F i g u r e 7 , t h e r a t e o f a c h i e v i n g s u c c e s s -

0 L O W L C 1 a M ~ d d l c l C l W L X H i s h l C l

cl T 0 l . l

1977

1 5 6 7 8 9 1 0 1 1 1 2 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 2 3

M O N T H

Figure 7 . Progress of dynamic control at Kimitsu works.

T a b l e 5 shows t h e i m p r o v e m e n t s i n o p e r a t i o n a l p e r f o r m a n c e b r o u g h t a b o u t b y CQT a t t h e No. 2 BOF o f Nagoya Works. The re- b l o w i n g r a t e i s d u e o n l y t o d e v i a t i o n s i n c a r b o n c o n t e n t a n d t e m p e r a t u r e a t t h e e n d p o i n t .

The f o l l o w i n g b e n e f i t s w e r e o b t a i n e d a s a r e s u l t o f t h e s e marked i m p r o v e m e n t s i n o p e r a t i o n a l p e r f o r m a n c e o f t h e p l a n t : M a t e r i a l s Merits

-

R e d u c t i o n i n c o n s u m p t i o n o f f u r n a c e r e f r a c t o r i e s b e c a u s e o f t h e r e d u c e d s a m p l i n g t i m e a n d r e b l o w i n g a n d o v e r b l o w i n g r a t e : 2.87 k g / t d 1 . 7 8 k g / t .

-

R e d u c t i o n i n c o n s u m p t i o n o f d e o x i d i z e r b e c a u s e o f t h e re- d u c e d amount o f oxygen i n s t e e l ( c o n s u m p t i o n o f a l u m i n u m ) . Low-carbon a l u m i n u m - k i l l e d s t e e l : 2.57 k g / t d 1 . 8 5 k g / t . A l - S i k i l l e c l s t e e l f o r h e a v y p l a t e : 0 . 9 3 k g / t + . 7 4 k g / t .

-

Improvement i n i r o n y i e l d b e c a u s e o f t h e r e d u c e d r e b l o w i n g r a t e a n d o v e r b l o w i n g r a t e : 9 7 . 5 d 9 8 . 0 9 6 .

T a b l e 5 . Improvements i n o p e r a t i o n a l p e r f o r m a n c e

T a b l e 6 . I n s t a l l e d a n d p l a n n e d s u b l a n c e e q u i p m e n t i n

Our a t t a i n m e n t o f s u c c e s s f u l h e a t s i s now o n l y a l i t t l e o v e r 9 0 % . A l l o u r e n g i n e e r s c o n c e r n e d w i t h s t e e l m a k i n g w i l l c o n t i n u e e x e r t i n g t h e i r u t m o s t e f f o r t s f o r making t h e r a t e o f a c h i e v i n g s u c c e s s f u l h e a t s a s n e a r 1 0 0 % a s p o s s i b l e .

D i s c u s s i o n

Dynamic O p e r a t i o n o f t h e LD P r o c e s s :

a r e i n s t a l l e d . Our s t u d i e s f o r p r o c e s s a u t o m a t i o n i n t h i s p l a n t have two main f e a t u r e s . We examined t h e c o n t r i b u t i o n of w a s t e g a s a n a l y s i s t o t h e m e t a l l u r g i c a l l y b a s e d p r o c e s s d e s c r i p t i o n and t o t h e r e s u l t i n g p r o c e s s c o n t r o l ; and we f o c u s e d on t h e end p o i n t o f blowing i n o r d e r t o r e a c h a b e t t e r a c c u r a c y of h i t .

I n t h e f i r s t p a r t o f o u r i n v e s t i g a t i o n [ I ] , t h e m e l t h i s t o r y and e s p e c i a l l y t h e s l a g h i s t o r y a s deduced from w a s t e g a s measure- ment was r e p r e s e n t e d . The b a s i s o f such a r e p r e s e n t a t i o n i s t h e c o n t i n u o u s oxygen b a l a n c e ; t h e r e s u l t i s t h e oxygen f l o w e n t e r - i n g o r l e a v i n g t h e s l a g . These r e s u l t s , d e r i v e d p u r e l y from measurements, c a n b e r e f i n e d by m e t a l l u r g i c a l a s s u m p t i o n s i n s u c h a way t h a t a l l t h e r e l e v a n t v a r i a b l e s of t h e s l a g h i s t o r y c a n b e r e p r e s e n t e d . F i g u r e 1 shows t h e c o u r s e o f t h e s l a g i n t h e q u a s i t e r n a r y s y s t e m .

0 10 20 30 40 50 60

(FeO)' in %

-

2...14 = 2nd ... 14th minute of blow

Figure 1. Error in thr description of the slag course.

The a c c u r a c y o f t h i s r e p r e s e n t a t i o n i s i m p o r t a n t i f it i s t o b e u s e d a s t h e s t a r t i n g p o i n t f o r p r o c e s s c o n t r o l . F i g u r e 1 t h e r e f o r e a l s o shows t h e i n a c c u r a c y o f t h e s l a g d i a g r a m a s e s t a b l i s h e d by e r r o r c a l c u l a t i o n . It c o m p r i s e s :

E r r o r r a n g e 11: Due t o m e t r o l o g y and t h e m e t a l l u r g i c a l model (BOF s h o p 1 ) ;

E r r o r r a n g e I : Assuming t h e b e s t c o n c e i v a b l e m e t r o l o g y and no model e r r o r .

C l e a r l y t h e i n a c c u r a c y o f t h e r e p r e s e n t a t i o n i s s t i l l c o n s i d e r - a b l e i n t h e most f a v o r a b l e h y p o t h e t i c a l c a s e ( e r r o r r a n g e I ) , and i s t o o g r e a t t o p e r m i t p r o c e s s c o n t r o l i n t e r m s of c o n f i r m e d m e t a l l u r g i c a l t a r g e t r a t e s . F i g u r e 2 , showing t h e i s o - s l a g l i n e s

[ 2 ] f o r p h o s p h o r o u s , i l l u s t r a t e s how n a r r o w t h e r a n g e i s i n s l a g g i n g c o n t r o l . The i n a c c u r a c y o f t h e m e a s u r e m e n t s by f a r e x c e e d s t h i s r a n g e .

Figure 2. Phosphorus ~lagging in the (CaO)' - (Si02)' . (FeO)' System.

A p a r t f r o m t h e oxygen b a l a n c e , w a s t e g a s a n a l y s i s t r a n s m i t s o t h e r p r o c e s s i n f o r m a t i o n , s u c h a s t h e d e c a r b u r i z a t i o n r a t e . H e r e t o o , e x t e n s i v e a t t e m p t s h a v e b e e n made t o d e v e l o p c o n t r o l a l g o - r i t h m s o r e s t a b l i s h p r o c e s s c o n t r o l s . The r e l a t i o n s h i p t o t h e p r o c e s s c a n , however, b e e s t a b l i s h e d o n l y e m p i r i c a l l y by many ob- s e r v a t i o n s . Such m e t h o d s h a v e no c a u s a l r e l a t i o n s h i p d e r i v a b l e f r o m t h e o r y .

I n t h e a r e a o f low c a r b o n c o n t e n t , h o w e v e r , s u c h a r e l a t i o n - s h i p c a n q u i t e w e l l b e shown. T h i s i s b e c a u s e , a s t h e p r o c e s s a p p r o a c h e s e q u i l i b r i u m , it t a k e s a p a t h t h a t c a n b e d e s c r i b e d i n t e r m s o f r e a c t i o n k i n e t i c s . T h i s i s s e e n i n t h e well-known re- l a t i o n b e t w e e n c a r b o n a n d d e c a r b u r i z a t i o n r a t e w h i c h , a f t e r e x p e r i - m e n t a l v a l i d a t i o n , i s o f t e n u s e d f o r c a r b o n e n d - p o i n t e v a l u a t i o n .

I n t h e s e c o n d p a r t o f o u r i n v e s t i g a t i o n s [ 3 ] w e t r i e d t o d e - r i v e t h i s r e l a t i o n from r e a c t i o n k i n e t i c s s o a s t o become more i n d e p e n d e n t o f c h a n g i n g r e a c t i o n p a r a m e t e r s . T h i s a p p r o a c h , i n w h i c h t h e p r o c e s s c o u r s e was d e s c r i b e d e s s e n t i a l l y by means o f t h e i n t e r m e d i a t e f o r m a t i o n o f FeO i n t h e f o c u s r e s u l t e d i n a v e r y u s e f u l m a t h e m a t i c a l r e l a t i o n b e t w e e n t h e b a t h c a r b o n a n d t h e d e - c a r b u r i z a t i o n r a t e . T h i s r e l a t i o n - - a n d t h e i n t e g r a l d e r i v e d f r o m i t , w h i c h shows t h e c a r b o n o x i d a t i o n l o s s c u r v e - - l e d t o a new d i s - p l a y o f t h e end p o i n t . With t h i s method t h e r e s i d u a l b l o w i n g t i m e (tblow) i s c o n t i n u o u s l y d e t e r m i n e d by c o m p u t e r , a s shown i n F i g u r e 3 . The r e s i d u a l b l o w i n g t i m e , w h i c h r e s u l t s f r o m t h e m e a s u r e d d e - c a r b u r i z a t i o n r a t e , t h e t a r g e t c a r b o n v a l u e , and t h e l a g t i m e o f t h e w a s t e g a s m e a s u r e m e n t , i s d i s p l a y e d o n a g r a p h i c d e v i c e . T h i s f o r m o f d i s p l a y h a s t h e f o l l o w i n g a d v a n t a g e . I f t h e p r o c e s s r u n s i n a c c o r d a n c e w i t h t h e p r e s e t r e a c t i o n p a r a m e t e r s , a 45O

s t r a i g h t l i n e i s d i s p l a y e d , g i v e n a p p r o p r i a t e p a p e r s p e e d . I f , however, t h e p r o c e s s t a k e s a n u n i n t e n d e d c o u r s e , t h e s h a p e of t h e g r a p h w i l l show i t . I n t h i s c a s e a l o w e r a c c u r a c y o f h i t may b e e x p e c t e d

.

-

kg C / dt- -time-

t blow = ttarget -tbath- lag t i m e

Figlrc: 3. (:arbon end-point control ("Countdown").

B e f o r e t h e e n d - p o i n t method was t e s t e d , a s t a t i c model had been i n o p e r a t i o n i n oxygen s t e e l p l a n t I f o r same t i m e . T h i s model, which i s based on c h e m i c o - p h y s i c a l e q u a t i o n s , h a s t h e t a s k o f c a l c u l a t i n g c h a r g e s , a d d i t i o n s and q u a n t i t y o f oxygen t o b e blown. I n t r o d u c t i o n o f t h e dynamic e n d - p o i n t method c a u s e d a n o v e r l a p of t h e two t e c h n i q u e s : f o r t h e blower g o e s by e i t h e r t h e r e s i d u a l blowing t i m e o r t h e oxygen q u a n t i t y t o b e blown.

A p o s s i b l e s o l u t i o n o f t h i s problem i s t o combine t h e two methods w i t h t h e u n d e r l y i n g i d e a o f improving t h e r e s u l t s by l i n k i n g two measurements. The p r e s u p p o s i t i o n f o r improvement, however, i s t h a t w h i l e t h e measurements d i f f e r i n method t h e y a r e c o m p a r a b l e i n t h e i r a c c u r a c y . T h i s i s t h e c a s e w i t h t h e dynamic and t h e s t a t i c methods, which b a s i c a l l y a r e m e r e l y ways of m e a s u r i n g c a r b o n and t e m p e r a t u r e ( s e e F i g u r e 4 ) . I f o n e blow o n l y by t h e dynamic method, a c c u r a c i e s o f h i t would b e a s on t h e l e f t s i d e o f t h e f i g u r e ; i f by t h e s t a t i c method, a s on t h e r i g h t .

d target - in O C 26 -

-

temperature hitting rate 22 -

20 - 18 - 16 - 14

-

10 -coefficient of combination- 6'('target

-

'actual' in % 10.' 0 10 2 0 3 0 4 0 5060 7 0 8 0 90100%

carbon hitting rate 3

-

0 1 0 2 0 3 0 4 0 5060 7080 90100%

dyn. mod.-coefficient of combination-stat. mod.

Figure 4. Combination of the dynamic and the static control systems.

A s c a n b e s e e n , t h e b e s t r e s u l t s a r e o b t a i n e d i f t h e two m e t h o d s

residual blowing time for

-

temperature

seconds

I ---

a) coincident end poinb b ) carbon end point ahead c) temperature end point ahead

Figure 5 . End-point display for temperature and carbon.

i m p r o v e s r e s u l t s . The d i f f i c u l t y h e r e i s t h a t t h i s c o m b i n a t i o n c a n n o t b e r e p r e s e n t e d i n m a t h e m a t i c a l terms. T h i s c a n b e com- p e n s a t e d t o some e x t e n t by n a r r o w i n g t h e l a t i t u d e o f t h e b l o w e r f o r d e p a r t i n g f r o m t h e i n s t r u m e n t i n d i c a t i o n s . The e f f i c i e n c y o f t h i s c o m b i n a t i o n m u s t b e c h e c k e d by c o n t i n u o u s s t a t i s t i c a l e v a l u a t i o n .

The s e c o n d r e a s o n i s t h a t we w a n t t o e n a b l e t h e b l o w e r t o g u i d e t h e p r o c e s s b e t t e r by g i v i n g him a s much i n f o r m a t i o n a s p o s s i b l e . The f i n a l r e s p o n s i b i l i t y , a n d t h u s i n v o l v e m e n t w i t h t h e p r o c e s s , s h o u l d b e l e f t t o him, h o w e v e r , a l s o w i t h a v i e w t o c o n t i n u o u s improvement o f t h e t e c h n i q u e s u s e d .

SUMMARY

W a s t e g a s m e a s u r e m e n t d e l i v e r s i m p o r t a n t p r o c e s s i n f o r m a t i o n f o r t h e LD method. F o r m e t a l l u r g i c a l l y b a s e d p r o c e s s c o n t r o l , h o w e v e r , t h i s i n f o r m a t i o n i s n o t s u f f i c i e n t l y a c c u r a t e . T h i s i s i n c o n t r a s t t o d e t e r m i n a t i o n o f t h e e n d p o i n t , w h e r e t h e r e s u l t s o f t h e d y n a m i c method d e v e l o p e d v i a w a s t e g a s m e a s u r e m e n t a r e good. They may b e f u r t h e r i m p r o v e d by c o m b i n i n g t h e d y n a m i c a n d t h e s t a t i c m e t h o d s . The i d e a u n d e r l y i n g t h i s l i n k a g e i s t o com- b i n e m e a s u r e m e n t s o f u n e q u a l p r e c i s i o n .

REFERENCES

[ I ] Dorr, W., and W. Lanzer, S t a h l und E i s e n

93

( 1 9 7 3 ) , 8 7 6 - 8 8 4 . [ 2 ] Bardenheuer, F., internal paper, Mannesmann-Forschungs-

institut GmbH, Duisburg.

[ 3 1 Dorr, W., W. Lanzer, E. Weiler, and H. Trenkler, S t a h l und E i s e n

94

( 1 9 7 4 ) , 3 8 1 - 3 8 6 .

D i s c u s s i o n

S e v e r a l p o i n t s w e r e r a i s e d a b o u t BOF o p e r a t i o n s a n d c o m p u t e r s y s t e m s , w i t h a v i e w t o u n d e r s t a n d i n g t h e f u n c t i o n s o f t h e s y s t e m more f u l l y . I t was s t a t e d t h a t Mannesmann p r o d u c e d s t e e l w i t h a c a r b o n c o n t e n t o f 0 . 2 0 - 0 . 5 p e r c e n t . W h i l e t h e r e a r e no p r o b l e m s w i t h s u l f u r , p h o s p h o r u s p r e s e n t s p r o b l e m s . Thus Mannesmann u s e s t h e i n f o r m a t i o n o n t h e c o n v e r t e r s o u n d , which i s a good i n d i c a t o r of t h e s l a g c o n s i s t e n c y a v a i l a b l e f o r t h e o p e r a t o r o n d i s p l a y .

C a l c u l a t i o n s f o r t h e dynamic model o n t h e w a s t e g a s a n a l y s i s a n d f o r t h e s t a t i c c h a r g e c a l c u l a t i o n model b e g i n a f t e r a c e r t a i n amount o f oxygen b l o w i n g . The d e c a r b o n i z a t i o n r a t e m u s t b e b e l o w a c e r t a i n l e v e l . I n t h e l a s t two m i n u t e s o f b l o w i n g , t h e o x y g e n f l o w r a t e a n d t h e l a n c e p o s i t i o n a r e a t t h e same l e v e l s . The combined r e s u l t s o f t h e c a l c u l a t i o n s f o r t h e s t a t i c a n d t h e dynamic m o d e l s a r e a v a i l a b l e t o t h e o p e r a t o r a t t h e e n d o f blow- i n g , t h u s g i v i n g improved a c c u r a c y .

One p a r t i c i p a n t p o i n t e d o u t t h a t a c c u r a c y of w a s t e g a s a n a l y s i s was n o t s u f f i c i e n t . Even t h e u s e o f mass s p e c t r o m e t e r s d o e s n o t make i t p o s s i b l e t o c o n t r o l t h e d e c a r b o n i z a t i o n p r o c e s s . A c o m b i n a t i o n o f t h i s i n f o r m a t i o n w i t h t h e s t a t i c model i m p r o v e s t h e f i n a l r e s u l t s . T h e r e i s , however, no dynamic i n f o r m a t i o n a b o u t t h e t e m p e r a t u r e .

The man-computer i n t e r f a c e was a l s o d i s c u s s e d . I t was p o i n t e d o u t t h a t t h e Mannesmann a p p r o a c h was t o n o t e n t r u s t t h e c o m p u t e r w i t h a l l c o n t r o l f u n c t i o n s , and t o k e e p t h e o p e r a t o r i n f o r m e d a b o u t t h e p r o c e s s , making i t p o s s i b l e f o r him t o make d e c i s i o n s i n a p a r t i c u l a r a r e a . To k e e p t h e o p e r a t o r i n f o r m e d a b o u t t h e d e c a r b o n i z a t i o n r a t e , s o u n d a n d t i m e o f b l o w i n g a r e u s e d . The f i n a l d e c i s i o n l i e s w i t h t h e o p e r a t o r .

P r o c e s s C o n t r o l Computer S y s t e m s f o r B a s i c Oxygen S t e e l m a k i n q :

r a i s e t h e p o t e n t i a l c a p a c i t y o f t h e A p p l e b y F r o d i n g h a m p l a n t f u r t h e r t o 6 M t p e r annum. A p l a n o f t h e BOS s h o p i s g i v e n i n F i g u r e 1 and t h e m a t e r i a l s f l o w i n r e l a t i o n t o t h i s i s g i v e n i n F i g u r e 2 . Key o p e r a t i n g d a t a f o r t h e p l a n t a r e g i v e n i n T a b l e 1 .

Restoppering stations Transfer to wntinuour cart plant

Scrap yard

Figrrc* 1. Plarl o f BOP shop al Applt.by -Frodit~ghan~.

T a b l e 1 . Key o p e r a t i n g d a t a f o r Appleby F r o d i n g h a m .

ROUTE

MANUAL MANUAL

INPUT INPUT

MANUAL

I N T "

TELETYPES

/q/q

+

VESSEL CONTROL

HOT

METAL TEEMING

INFORMATION

ZL

BLOWING ADDITIONS - INPUT

OPERATIONS CRT OPERATIONS MANUAL

INPUT

MANUAL MANUAL

INPUT INPUT

SCRAP STEEL

ANALYSIS

MANUAL MANUAL

INPUT INPUT

Figurr 3. Key rnar~nirlg arras for cotnputer prorrss control.

Alarm

~

Scanning

....

Preparation

V e s s e l S c h e d u l e

F o l l o w i n g t h e end of p o u r i n g t h e h o t m e t a l t r a n s f e r l a d l e

t e e m i n g w e i g h t s

a r e a l l e n t e r e d m a n u a l l y . The computer s u b s e q u e n t l y c a l c u l a t e s t h e y i e l d d a t a a n d o t h e r management i n f o r m a t i o n .

The o n l y d a t a r e c o r d e d by t h e computer o f t h e s t e e l c o n t i n - u o u s l y c a s t i s t h e s t e e l t e m p e r a t u r e i n t h e t e e m i n g l a d l e . Development o f P r o c e s s C o n t r o l F a c i l i t i e s

G e n e r a l

--

The c o n t r o l p e r f o r m a n c e a c h i e v e d a t S c u n t h o r p e , a s s e s s e d i n t e r m s o f t h e p r o p o r t i o n of b l o w s t h a t a r e c o r r e c t a t f i r s t t u r n down, i s between 4 0 and 6 0 p e r c e n t . The l e v e l o f s u c c e s s a c h i e v e d i s u s u a l l y d e t e r m i n e d by a c o m b i n a t i o n o f t h e q u a l i t y o f t h e i n f o r m a t i o n r e l a y e d t o t h e o p e r a t o r , and t h e c o n t r o l a c t i o n t a k e n by t h e o p e r a t o r i n r e s p o n s e t o t h e i n f o r m a t i o n p r o - v i d e d . Too o f t e n , u n f o r t u n a t e l y , t h e o p e r a t o r i s a s k e d t o com- p e n s a t e f o r u n d e t e c t e d v a r i a b i l i t y i n t h e raw m a t e r i a l s w i t h r e l a t i v e l y l i t t l e g u i d a n c e . A t t e m p t s h a v e been made t h e r e f o r e a t t h e n e a r b y Normanby P a r k BOS P l a n t , which r e c e n t l y h a s a l s o b e e n f i t t e d w i t h a F e r r a n t i Argus 5 0 0 computer t o e v a l u a t e t h e b e n e f i t s t o b e g a i n e d from a d e c a r b u r i z a t i o n r a t e d i s p l a y , w i t h a s u g g e s t e d g u i d e p a t h , and a n a u d i o m e t r i c m o n i t o r o f t h e s l a g d e v e l o p m e n t p a t t e r n , w h i l e c o n f o r m i n g s t r i c t l y t o t h e s t a t i c c h a r g e c a l c u l a t i o n r e q u i r e m e n t s .

C o n c u r r e n t d e v e l o p m e n t a t t h e Appleby Frodingham p l a n t o f t h e B e t h l e h e m s e c o n d a r y i a n c e s y s t e m s h o u l d a l l o w t h e e v e n t u a l m e r g i n g a t t h i s p l a n t of a p r o c e s s c o n t r o l s y s t e m c o m p r i s i n g

-

a c o m p u t e r b a s e d h e a t a n d mass b a l a n c e ( " s t a t i c " ) m o d e l ,

-

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

Equipment

W a s t e Gas A n a l y s i s : A fast responding but reliable waste gas sampling and analysis system requiring minimum maintenance was set as a first priority in the development of in-process control. The general arrangement and critical transit times at Normanby Park are shown in Figure 5.

Figure 5. Waste gas analysis measurements and transit times at Normarlby Park.

The water-cooled gas sampling probe is set into the upper hood and is designed to withstand temperatures up to 1500 OC.

Subsequently the hot gases are filtered in four stages before infrared analysis for CO and C02 and a paramagnetic analysis for 02. In the current trials program, a mass spectrometer operates in parallel with these analyzers for comparative evaluation.

After a period of training for the instrument maintenance personnel, the availability of data from the equipment rapidly climbed to greater than 90 percent, and as experience is gained

it is confidently expected that reliable data will be available to the vessel operator at all times.

A u d i o m e t e r : The optimum s i t i n g o f t h e a u d i o m e t e r f o r s l a g

individual rail weighbridges during loading so that the crane

P r o p o s e d P r o d u c t i o n F a c i l i t y Changes

With account being taken of the above, an examination of

The new f e r r o - a l l o y s l a d l e a d d i t i o n s w e i g h i n g s y s t e m , con-

P l a n t Mannina

BOS P l a n t P r o c e s s C o n t r o l Computer System

Heat data

Blow No.

Analysis & Wt.

Hot Metal

Calc. Blowing

Additions

H

Bath Temp.

& Carbon

Corructive Additions

Metal & Slag Analysis

Additions

Teeming Details

Pit Analyses

-7

Analysis

r n

Pit Analyses

u

Oxygen Vol.

Lime Wts.

Removal Rate

Oxygen and

t Analyses

Fe Si 1 Al Anthracite

Figures 10. O u t p u t s from tltc, rno(1t.l in rrlation l o p l a r ~ t ac:tivitic:s during a n d aft1.r thr: heat.

Management I n f o r m a t i o n R e p o r t s : The s y s t e m w i l l p r o v i d e p r i n t o u t s o f " h e a t e v e n t " a n d " a l a r m l o g s " , a " h e a t summary", a n d a " w e e k l y p e r f o r m a n c e summary". I n a d d i t i o n , it w i l l p r o - v i d e f a c i l i t i e s f o r t h e s t o r a g e o f s e l e c t e d d a t a o n t h e l a s t

1 0 0 0 h e a t s w i t h t h e a b i l i t y t o p e r f o r m s t a t i s t i c a l a n a l y s i s o f t h i s d a t a .

SUMMARY

A b r i e f d e s c r i p t i o n o f t h e BSC S c u n t h o r p e and Lackenby s t e e l m a k i n g and p r o c e s s c o n t r o l f a c i l i t i e s and p l a n n e d improve- m e n t s h a s b e e n g i v e n . The d e v e l o p m e n t s a t Lackenby h a v e b e e n

i n f l u e n c e d by e x p e r i e n c e and r e s e a r c h work d o n e b o t h a t Scun- t h o r p e a n d Lackenby BOS P l a n t s . The m a j o r o b j e c t i v e s o f t h e new p r o c e s s c o n t r o l s y s t e m a t Lackenby a r e improved c o n t r o l o f t h e s t e e l m a k i n g p r o c e s s w h i l e p r o d u c i n g s t e e l a t i n c r e a s e d r a t e s w i t h t h e u s e o f improved o p e r a t o r i n f o r m a t i o n and i n - b l o w g u i d a n c e s y s t e m s .

D i s c u s s i o n

The A p p l i c a t i o n o f Computer T e c h n i q u e t o P r o c e s s C o n t r o l o f

-

D i g i t a l and a n a l o g i n d i c a t o r s .

- -

b r o c e s s C o n t r o l Computer s y s t e m

1

P i g I r o n C o o l i n g Medium P i g I r o n

F i n a l P r o d u c t

A l l o y s

C h a r g i n g R e p o r t

1

C e n t r a l Computer

I,'igur~: 1. (:ornputt.r ~(,chr~iquc: ant1 equiprnclit I'or Ihr ^process

~ : o n t r o l syslcrn ol' lhtb sleel p l a n l .

The end-point determination of the charge, i.e. the end

0 . 4 p e r c e n t a n d t h e l i m e s a v e d by t h e e c o n o m i e s was 5 p e r c e n t . T h e s e r e s u l t s mean t h a t t h e p l a n t r e d e e m s t h e c o s t o f t h e c o m p u t e r - i z a t i o n w i t h i n 2 . 3 y e a r s .

D i s c u s s i o n

The d i s c u s s i o n c e n t e r e d on p r o c e s s t e c h n o l o g y and o r g a n i z a - t i o n i n t h e s t e e l i n d u s t r y . I t was p o i n t e d o u t t h a t i n t h e German D e m o c r a t i c R e p u b l i c , b a s i c o x y g e n f u r n a c e s (BOFs) a r e n o t u s e d ; t h e i r u s e i n s t e e l p l a n t s may b e i n c l u d e d i n t h e n e x t F i v e - Y e a r P l a n .

By means o f t h e b o t t o m - b l o w i n g p r o c e s s , a b o u t 6 0 0 , 0 0 0 t o f s t e e l a r e p r o d u c e d a n n u a l l y ; p h o s p h o r u s - r i c h p i g i r o n i s a l s o p r o c e s s e d u s i n g t h i s t e c h n i q u e . Oxygen and d i e s e l f u e l u s e d a s c o o l a n t s a r e i n j e c t e d s i m u l t a n e o u s l y . T h e r e a r e no p r o b l e m s w i t h s l a g f o r m a t i o n and p h o s p h o r u s r e m o v a l . I n c r u d e s t e e l t h e r e i s less t h a n . O 1 p e r c e n t p h o s p h o r u s .

A t t e n t i o n t h e n f o c u s e d o n t h e o r g a n i z a t i o n o f i n t e g r a t e d s y s t e m s i n s t e e l p l a n t s i n t h e GDR. I t was s t a t e d t h a t t h e s e c t o r i a l s y s t e m i s p a r t l y i n o p e r a t i o n f o r t h e s t e e l i n d u s t r y . S e v e r a l s t e e l p l a n t s h a v e i m p l e m e n t e d a c e n t r a l c o m p u t e r s y s t e m f o r p l a n n i n g , s c h e d u l i n g , s t o c k c o n t r o l , a n d t h e l i k e .

A d a p t a t i o n Methods i n I n v e s t i g a t i o n s , M o n i t o r i n g , And C o n t r o l o f t h e Oxygen C o n v e r t e r P r o c e s s Yu.A. V a s i l e v s k y , R.A. S i m s a r i y a n , and B . I . C h e r n o v

The o x y g e n c o n v e r t e r i s a p r o m i s i n g p r o c e s s whose d e v e l o p m e n t i s l i m i t e d c h i e f l y by t h e d e g r e e o f c o n t r o l p o s s i b l e . The c h i e f r e a s o n p r e v e n t i n g t h e d e v e l o p m e n t o f a p e r f e c t c o n t r o l s y s t e m i s t h e c o n t i n u a l c h a n g e c a u s e d b o t h by r e a c t i o n s i n t h e c o n v e r t e r a n d by t h e f r e q u e n t d e v e l o p m e n t s o f t h e p r o c e s s . S t a b i l i z a t i o n o f t h e r a w m a t e r i a l a n d b l o w i n g modes d o e s n o t e l i m i n a t e t h i s p r o b l e m ; f u r t h e r m o r e , no s t a b l e s t a t i s t i c a l v a r i a b l e s seem t o e x i s t t h a t c o u l d b e u s e d t o d e s c r i b e t h e p r o c e s s .

The c o n t i n u a l c h a n g e p r e v e n t s s u f f i c i e n t a p r i o r i d a t a ( a c c u r a t e s t a t i s t i c a l c h a r a c t e r i s t i c s o f t h e v a r i a b l e s and t h e n o i s e ) f r o m b e i n g o b t a i n e d f o r a m o n i t o r i n g a n d c o n t r o l s y s t e m ; b u t a d a p t a t i o n m e t h o d s [ 1 , 2 ] seem t o b e u s e f u l i n s t u d y i n g , i n o n i t o r i n g , a n d c o n t r o l l i n g t h e p r o c e s s .

P r o b l e m s s o l v e d by a d a p t a t i o n m e t h o d s h a v e b e e n f o r m u l a t e d [ 1 , 2 1 a s p r o b l e m s i n e s t i m a t i n g t h e p a r a m e t e r s w i t h a v i e w t o m i n i m i z i n g c e r t a i n l o s s f u n c t i o n s .

I n a g e n e r a l c a s e , t h e l o s s f u n c t i o n c a n b e r e p r e s e n t e d a s

w h e r e p ( x ) i s t h e d i s t r i b u t i o n d e n s i t y o f t h e random q u a n t i t y x and Q ( x , c ) a c e r t a i n f u n c t i o n o f x - a n d t h e v e c t o r

2

[ I ] .

One o f t h e a p r i o r i d a t a l a c k i n g i s p ( x ) . The a d a p t i v e a p p r o a c h t o t h e m i n i m i z a t i o n o f J ( 2 ) y i e l d s a r e c u r r e n c e a l g o r i t h m f o r e s t i m a t i n g t h e p a r a m e t e r v e c t o r

c :

The s h o r t a g e o f a p r i o r i d a t a i f t h e f o r m p ( x ) i s o f f s e t by t h e c u r r e n t d a t a c o n t a i n e d i n x [ n ] . The a l g o r i t h m ( 2 ) e n s u r e s a s y m p t o t i c c o n v e r g e n c e t o t h e v a l u e w h i c h m i n i m i z e s t h e l o s s f u n c t i o n s ( 1 ) i f t h e c o n v e r g e n c e c o n d i t i o n s o f [ I ] a r e m e t .

The c h o i c e o f t h e f u n c t i o n Q ( - 1 i s i n most c a s e s d i c t a t e d by t h e o b j e c t i v e f o r w h i c h t h e p a r a m e t e r s a r e e s t i m a t e d . The

c h o i c e h a s n o t b e e n f o r m a l i z e d b u t i f p ( x ) i s known t o b e l o n g t o a c e r t a i n c l a s s P t h e n t h e c h o i c e o f Q ( - ) c a n i n d e e d b e f o r m a l i z e d . M i n i m i z i n g o n t h e c l a s s P t h e F i s h e r i n f o r m a t i o n I ( p ) t h e " w o r s t v a l u e " f o r t h e g i v e n c l a s s P d i s t r i b u t i o n p* ( x

1 s)

i s f o u n d , which g i v e s t h e l o w e r bound f o r t h e e s t i m a t e v a r i a n c e i n t h e Kramer-Rao i n e q u a l i t y . One s h o u l d assume [3]

t h a t

T h i s a p p r o a c h r e s u l t s i n t h e s o - c a l l e d r o b u s t a l g o r i t h m s [Ql. C o n s e q u e n t l y , a d a p t a t i o n m e t h o d s a r e a s t a n d a r d way t o o b t a i n a l g o r i t h m s f o r t h e i n v e s t i g a t i o n o f r e a l - t i m e ( s t a t i s t i c a l d a t a p r o c e s s i n g , d e s i g n a n d a n a l y s i s o f m a t h e m a t i c a l m o d e l s , e x p e r i m e n t d e s i g n , e t c . )

,

a u t o m a t i c m o n i t o r i n g ( q u a n t i z a t i o n o f d a t a r e d u c t i o n ) , and c o n t r o l .

The m u l t i p u r p o s e a d a p t a t i o n a l g o r i t h m s a r e c o n v e n i e n t f o r t h e d e v e l o p m e n t o f program p a c k a g e s and make t h e s o f t w a r e e a s i l y r e s t r u c t u r a b l e and e x t e n s i b l e . B e c a u s e t h e y a r e i t e r a t i v e , t h e y c a n b e c o n v e n i e n t l y u s e d f o r d e s i g n i n g r e a l - t i m e d a t a p r o c e s s i n g p r o g r a m s and t h e y a r e f a i r l y i n s e n s i t i v e t o c o m p u t a t i o n , i n p a r t i c u l a r , r o u n d i n g e r r o r s .

The b a s i c d i f f i c u l t i e s i n a p p l y i n g a d a p t a t i o n o r a n y o t h e r m a t h e m a t i c a l methods a r e c h i e f l y i n t h e problem s t a t e m e n t , t h e c h o i c e o f v a r i a b l e s and methods t o m e a s u r e them, and i n t h e c h o i c e o f t h e l o s s f u n c t i o n and t h e v e c t o r o f a d j u s t i b l e param- e t e r s . A n o t h e r d i f f i c u l t y i s t h e n e e d f o r a n e a s i l y o p e r a b l e c o n t r o l s y s t e m .

T a b l e 1 p r e s e n t s a d a p t a t i o n a l g o r i t h m s u s e d i n s o l v i n g s p e c i f i c p r o b l e m s of oxygen c o n v e r t e r p r o c e s s c o n t r o l . Two e x a m p l e s w i l l be u s e d f o r i l l u s t r a t i o n .

M e a s u r i n g t h e L e v e l o f t h e S l a g M e t a l i n t h e F u r n a c e

The sound i n t e n s i t y p d u r i n g t h e m e l t i n g i s known t o depend on t h e d i f f e r e n c e Hf-n between t h e s l a g m e t a l l e v e l i n t h e f u r n a c e and t h e c u t o f f o f t h e t u y e r e n o z z l e [5]

.

T h i s d e p e n d e n c e c a n b e modeled a s a p i e c e w i s e l i n e a r f u n c t i o n :

Name and Notation 1. Moment estimates: n, step number y[nl, factor that satisfies convergence condition, x[nl, value of a random quantity, mK. moment of the ~th order 2. Estimate of a -quantile: d, confidence probability, q, a-quantile. 3. Histogram plotting: A. the jth decomposition Lterval, 6, size of decomposition intervals, g., histogram parameters. 4. Estimating the parameters of a piecewise-linear model : Y [nl , value at the nth Step associated with that of the argument x[nl.

+ (a 1 -a. 1-1) xi - x.

6. Obtaining a random value with specified characteristics: xIn1, value of a random quantity with arbitrary character- istics, y [nl , value of a random quantity with desired characteristics. 7. Automatic classification: u [nl = u [n-11 - r. [nl Fii (x[nl,

'ill

[n-11, u2 [n-11 13 1 I a[n] = uialn-11 - ua[nl lh [nl

-

hj) 1 Y n

Application orecasting the decarbur- zation rate; investiga- ion of the decarburiza- ion rate as a function f temperature in the eaction zone. eta1 oxidation meter nalysis; investigation f input-output models. ecarburization rate plot hape analysis: analysis f factors influencing he rolling performance.

w h e r e p a n d a i a r e t h e X - l i n e a n d Y - l i n e , r e s p e c t i v e l y , o f i

t h e i t h a p p r o x i m a t i o n u n i t ;

1 , w i t h pi < p ( t ) pi+,

Oi = { 0, w i t h pi

2

p ( t ) o r Pi+l < p ( t )

.

The p a r a m e t e r s a of t h i s f u n c t i o n v a r y w i d e l y i n t h e c o u r s e i

o f m e l t i n g a n d t o o b t a i n a c c u r a t e v a l u e s of H f - n t h e y need b e u p d a t e d . F o r t h i s p u r p o s e a d a p t a t i o n a l g o r i t h m s o f t h e f o r m

( 2 ) a r e u s e d [ 6 ] :

w h e r e ~ ( t ) i s t h e e r r o r i n c o m p u t i n g t h e d e s i r e d f u n c t i o n . The v a l u e s of a i a r e d e t e r m i n e d and u p d a t e d w h i l e t h e t u y e r e moves u p and down; 6 p ( t ) i s t h e v a r i a t i o n o f t h e n o i s e i n t e n s i t y w i t h t h e t u y e r e p o s i t i o n .

The c r u c i b l e l e v e l i s t h e sum o f H and t h e t u y e r e l e v e l . f - n

A d a p t a t i o n a l g o r i t h m s e n s u r e a n a c c u r a c y s u f f i c i e n t f o r p r a c t i c a . p u r p o s e s . The o p e r a t o r m a t c h e s t h e m e t e r a n d c a n u p d a t e i t s i n p u t - o u t p u t c h a r a c t e r i s t i c by moving t h e t u y e r e u p and down.

2

i n t h e C o u r s e o f Blowing

I t h a s b e e n f o u n d 171 t h a t s t a r t i n g a t a c e r t a i n t i m e , t h e oxygen c o n t e n t i n t h e c r u c i b l e i s d e s c r i b e d w e l l by t h e d i f f e r e n - t i a l e q u a t i o n

The c a r b o n c o n t e n t C c a n b e f o u n d f r o m

The unknown p a r a m e t e r s Co and K o f e q u a t i o n ( 8 ) a r e d e t e r m i n e d t h r o u g h c h a n g e s i n t h e d e c a r b u r i z e d r a t e vc =

--

d t

The p r o c e s s of c o n t i n u e d c h a n g e c a l l s f o r r e a d j u s t m e n t o f t h e p a r a m e t e r s ^K and C d u r i n g t h e c o u r s e o f t h e m e l t . The

p a r a m e t e r s a r e e s t i m a t e d a n d r e s t r u c t u r e d by u s i n g a n a l g o r i t h m o f t y p e ( 2 ) from t h e c u r r e n t v a l u e s o f vc i n e a c h m e l t :

a [ n ] = a [ n - 1 ]

-

^{Y i} [ n ] ( I n v e [ n l

-

a[n-11

-

B[n-11 n )

where B = - K a n d a = I n

KC^) ,

n a r e d i s c r e t e t i m e s o f t , a n d v [ n ] a r e d i s c r e t e v a l u e s o f vc _C

.

S i m i l a r a d a p t a t i o n a l g o r i t h m s d e t e r m i n e t h e t i m e a t which E q u a t i o n ( 7 ) s t a r t s t o h o l d f o r e a c h m e l t f r o m c u r r e n t v a l u e s o f v .

The a l g o r i t h m s w e r e t e s t e d i n t h e C h e l y a b i n s k and W e s t - S i b e r i a n Works. The t r a n s i e n t p e r i o d o f p a r a m e t e r a d j u s t m e n t was found t o depend on t h e c h o i c e of i n i t i a l v a l u e s and d i d n o t e x c e e d s e v e n t o t e n m e l t s w i t h z e r o i n i t i a l v a l u e s . C o n t i n u o u s p a r a m e t e r u p d a t i n g from t h e c u r r e n t v a l u e s o f vc r e s u l t s i n a c a l c u l a t e d c a r b o n c o n t e n t which d o e s n o t d i f f e r from t h e a c t u a l v a l u e by more t h a n 0 . 0 2 p e r c e n t ( t h e l i q u i d u s t e m p e r a t u r e b e i n g t h e i n d i c a t o r ) .

The a d a p t a t i o n a p p r o a c h seems p r o m i s i n g i n p r o c e s s e s o t h e r t h a n oxygen c o n v e r t e r s and s i g n i f i c a n t l y f a c i l i t a t e s t h e s y s t e m s a p p r o a c h i n i n v e s t i g a t i o n , m o n i t o r i n g , and c o n t r o l .

111 T z y p k i n , Y . Z . , A d a p t a t i o n a n d L e a r n i n g i n A u t o m a t i c C o n t r o l S y s t e m s , Nauka, Moscow, 1968 ( i n R u s s i a n ) .

[ 2 ) T z y p k i n , Y. Z., F o u n d a t i o n s o f L e a r n i n g S y s t e m s T h e o r y , Nauka, Moscow, 1970 ( i n R u s s i a n )

.

[3] Tzypkin, Y.Z. Optimization in Uncertainty Conditions, DAN, 228, 6 (1 976)

,

1306-1309 (in Russian)

.

-

[4] Polyak, B.T., and Y.Z. Tzypkin, Identification Stability of Noisy Signals, in I d e n t i f i c a t i o n a n d E v a l u a t i o n o f S y s t e m P a r a m e t e r E s t i m a t i o n , Vol. 1, preprints of the IVth IFAC Symposium, Tbilissi, pp. 190-213 (in Russian).

[ 5 ] Kolasin, S.M., and W. I. Jawoisky, Izvestia Wusow, M e t a l l u r g i a ,

No. 9 (1968).

[61 Vasilevsky, Yu.A. and A.D. Kalygina, Adaptive Bath Level Meter for Oxygen Converters, P r i b o r i i S y s t e m i U p r a v l e n i a , No. 2 (1977).

[7] Philippov, S.I., T h e T h e o r y o f D e c a r b u r i z a t i o n in S t e e l M e t a l l u r g y , Mezhdunarodnaia Kniga, Moscow, 1956 (in Russian).

D i s c u s s i o n

A t t e n t i o n f o c u s e d o n two m a i n p r o b l e m s : a d a p t a t i o n t e c h - n i q u e s o f m o d e l s , a n d t h e i r i m p l e m e n t a t i o n f o r c o n t r o l o f b a s i c o x y g e n f u r n a c e s (BOFs)

.

B e c a u s e o f t h e c h a n g i n g c h a r a c t e r i s t i c s o f t h e BOF p r o c e s s e - g . , d u r i n g t h e h e a t p e r i o d s a n d d u r i n g t h e l i f e o f t h e c o n - v e r t e r , a d a p t a t i o n i s e s s e n t i a l f o r BOF c o n t r o l . F o r e x a m p l e , t h e u s e o f o n l y o n e s t a n d a r d c u r v e f o r a p e r i o d o f 100 h e a t s w i t h o u t a d a p t a t i o n may r e s u l t i n a n e r r o r i n m e a s u r i n g t h e l a n c e p o s i t i o n t h a t c o u l d b e a s g r e a t a s 4 m. The s o u n d i n t e n s i t y o f t h e f r e q u e n c y o f 700 t o 900 Hz i s u s e d a s i n p u t i n f o r m a t i o n . T h i s s t a n d a r d c u r v e may b e u s e d f o r l a n c e p o s i t i o n c o n t r o l . The l a n c e may move d u r i n g t h e b l o w i n g p e r i o d , a n d t h e s p e c i a l d i s p l a y w i l l t h e n show t h e o p e r a t o r how much a d a p t a t i o n i s n e e d e d . The o p e r a t o r i s a b l e t o c h a n g e t h e l a n c e p o s i t i o n v e r y q u i c k l y i n s u c h a way t h a t t h e p o s i t i o n o f t h e b a t h r e m a i n s t h e s a m e . The c u r v e c a l i b r a t i o n i s d o n e o n t h e b a s i s o f c h a n g e s i n t h e s o u n d i n t e n s i t y . The new c a l i b r a t e d c u r v e i s u s e d f o r t h e l a n c e p o s i t i o n c o n t r o l i n t h e n e x t h e a t . T h i s s y s t e m h a s b e e n u s e d o n a 130 t c o n v e r t e r . The i m p l e m e n t a t i o n o f t h e s y s t e m m a k e s it p o s s i b l e t o p r e v e n t s l o p p i n g a n d t o i n c r e a s e t h e m e t a l y i e l d by u p t o 0 . 4 p e r c e n t . T h i s method h a s a l s o b e e n t e s t e d f o r 50 t o 300 t c o n v e r t e r s .

A n o t h e r s u b j e c t d i s c u s s e d was c a r b o n e n d - p o i n t c o n t r o l . I n t h i s c a s e , m o d e l a d a p t a t i o n b e g i n s f i v e m i n u t e s b e f o r e t h e assumed e n d - b l o w i n g t i m e f o r a 130 t c o n v e r t e r , and t h r e e m i n u t e s b e f o r e f o r a 350 t c o n v e r t e r . The i m p l e m e n t a t i o n o f t h e m o d e l h a s r e - s u l t e d i n s t a n d a r d d e v i a t i o n f o r t h e e n d p o i n t o f 0 . 0 2 p e r c e n t ; b e f o r e m o d e l i m p l e m e n t a t i o n , i t was 0 . 0 4 p e r c e n t .

O t h e r p r o b l e m a r e a s r e c e i v i n g a t t e n t i o n w e r e t e m p e r a t u r e m e a s u r e m e n t i n t h e r e a c t i o n z o n e and v i b r a t i o n m e a s u r e . A s t o t h e f o r m e r , t h e m e a s u r e m e n t , w h i c h was o r g a n i z e d t h r o u g h t h e o x y g e n l a n c e , was 2000 t o 2100 OC. The m o s t d i f f i c u l t p r o b l e m w i t h r e s p e c t t o v i b r a t i o n m e a s u r e i s t o d e t e r m i n e t h e p o i n t f o r t h e s e n s o r s t a t e m e n t .

Economic A s p e c t s o f Computer A p p l i c a t i o n I n B a s i c Oxygen F u r n a c e s

L . Surguchova

Computer a p p l i c a t i o n i n b a s i c oxygen f u r n a c e s (BOFs) n a t u r a l l y means a d d i t i o n a l i n v e s t m e n t and it i s i m p o r t a n t t o c a l c u l a t e t h e e f f i c i e n c y o f t h i s . I n t h i s p a p e r w e c o n s i d e r a b a s i c methodology f o r t h i s c a l c u l a t i o n which c a n b e u s e d f o r c a l c u l a t i n g t h e e f f i - c i e n c y o f b o t h p l a n n e d a n d o p e r a t i o n a l computer s y s t e m s .

I t i s g e n e r a l l y known t h a t computer a p p l i c a t i o n i n BOFs makes p o s s i b l e a r e d u c t i o n i n t h e number of c a r b o n and t e m p e r - a t u r e r e b l o w s and o v e r b l o w h e a t s - - i n o t h e r w o r d s , it i n c r e a s e s t h e number o f h e a t s p r o d u c e d f o r a g i v e n v a l u e o f t h e o u t p u t p a r a m e t e r s . T h i s c h a n g e s t h e number o f techno-economic i n d e x e s f o r t h e BOF p r o c e s s a n a l y z e d by t h e methodology ( d e c r e a s i n g t h e b l o w - t i m e , t h e t a p - t o - t a p c y c l e , t h e f e r r o - a l l o y c o n s u m p t i o n , w a s t e m a t e r i a l s , e t c . ) and l e a d s t o a n i n c r e a s e i n m e t a l y i e l d , t h e l i f e - s p a n o f t h e r e f r a c t o r y l i n i n g , e t c . (see F i g u r e 1 ⁾

.

T h i s i n t u r n l e a d s t o a c h a n g e i n t h e c o s t s of m a i n t e n a n c e , raw m a t e r i a l s , a d d i t i v e s , e t c .

The o t h e r i m p o r t a n t c o n s e q u e n c e n e c e s s a r y f o r c o n s i d e r - a t i o n when c a l c u l a t i n g t h e economics o f computer a p p l i c a t i o n i s t h e c h a n g e o f c a p i t a l i n v e s t m e n t i n a d j o i n i n g economic s e c t o r s

( F i g u r e 1 )

.

The i n c r e a s e i n t h e m e t a l y i e l d i s p o s s i b l y t h e main s o u r c e o f e f f i c i e n c y . The m e t a l y i e l d d e p e n d s on t h e s c r a p r a t i o i n t h e c h a r g e , t h e t e m p e r a t u r e o f t h e m e t a l s , t h e c a r b o n c o n c e n t r a - t i o n a t t h e end p o i n t , t h e blowing t i m e , e t c . T a b l e 1 shows a s a n example t h e dependency o f w a s t e on t h e e n d - p o i n t t e m p e r a t u r e f o r p i p e s t e e l . T h e r e i s a n o p t i m a l e n d - p o i n t t e m p e r a t u r e f o r m i n i m a l w a s t e .

T a b l e 1 .

End-Point Temperature

of Steel ( O C ) 1570 1580 1590 1600 1610 1620 1630 1640 1650 Waste ( 5 )

1

^1.7 ^1.2 ^0.7 ^0.6 ^0.7 ^0.2 ^0.3 ^1.8 ^2.6

Figure 1. General diagram of calculation of efficiency of computer application in BOFs.

More p r e c i s e e n d - p o i n t c o n t r o l l e a d s t o a r e d u c t i o n i n t h e

T a b l e 2 . Some r e s u l t s o f c o m p u t e r a p p l i c a t i o n i n BOFs.

Discussion

The participants underscored the difficulties encountered in eliminating small changes in the parameters because of com- puter application, as for example, changing the metallic yield 0.05 percent. One participant mentioned a case study in which a special test period was selected, say 200 to 300 heats with a computer, and the same number without a computer. Several different parameters were considered for five different plants.

Occasionally, it was found that change occurred because of computer application.

It was stated that improvement of the indexes is more impor- tant than cost. Cost-benefit analysis is the optimal method for presenting a good picture of computer application. There are very few published results about the efficiency of systems;

results are available for some steel plants in Japan. The de- velopment of techniques mentioned in these reports appears feasible.

Attention then focused on the use of computers for improving the results of poor versus good management. Each plant has its own considerations and management system, and the evaluation of improvements must take these factors into consideration. It may be possible that a good manager can control the converter better than a computer.

INTEGRATED SYSTEMS I N LARGE STEEL PLANTS

Integrated Computer Control System for the Steelmaking Plant at the Mizushima Works

Y. Iida and M. Ogawa

INTRODUCTION

Mizushima Works, with an annual raw steel production capac- ity of 12 million metric tons, is the second integrated steel- work of the Kawasaki Steel Corporation. It produces plates, hot- rolled sheets and strip, cold-rolled sheets and strip, wide-flange beams, steel bars, wire rods, steel castings, and forgings as finished products as well as materials for pipe and tubes to be shipped for a pipe making plant of the company.

Two steelmaking shops are in operation at Mizushima Works.

No. 1 steelmaking shop was started in 1967, and No. 2 shop in 1970. Table 1 lists some of the major equipments and facilities at both steelmaking shops.

Table 1. Selected equipment and facilities at Mizushima steelworking shops.

No. 1 Steelmaking Shop: 3 BOFs ( e a c h w i t h a nominal c a p a c i t y of 180 t )

1 R-H t y p e vacuum d e g a s s i n g equipment

Im Dokument Computer Application in the Steel Industry: Control of Basic Oxygen Furnaces and Integrated Management Systems in Large Plants (Seite 25-176)