The Quality Control System of Sintering Plant at Kashima Steel Works

CONTROL AND MODELLING IN EXTRACTION METALLURGY

Copyright (c) IFAC Automation in Mining, Mineral and Metal Processing, Helsinki , Finland, 1983

THE QUALITY CONTROL SYSTEM OF SINTERING PLANT AT KASHIMA STEEL WORKS O. Arai*, A. Yamamoto*, T. Joko**, K. Inada*** and S. Yumoto**** *Instrumentation and Control Engineering Section, Kashima Steel Works, Sumitomo Metal Industries, Ltd., Ibarakz; 314 Japan **Iron-making Control Sectl'on, Kashima Steel Works, Sumitomo Metal Industries, Ltd., Ibaraki, 314 Japan ***Instrumentation and Control Technology Department, Central Research Laboratory, Sumitomo Metal Industries, Ltd., Hyogo, 660 Japan ****System Planning Department, Kahima Steel Works, Sumitomo Metal Industries, Ltd., Ibaraki, 314 Japan

Abstract In recent years, the quality control of sintered ore has become more and more important for stable operation of modern blast furnaces where the sinter ratio of feedstock material exceeds 50%. The quality control system of sintering plant has been developed by SMI (Sumitomo Metal Industries, Ltd.), which consists of the measurement systems of free carbon and FeO content in raw mat erials , the control system of particle distribution of crushed coke and the FeO content in sintered ore. It's well known that the conventional batch sampling method has such limitations for quality control of sintered ore as its poor sampling frequency and time lag before result is acquired. In the past several years, SMI has developed the sensors and control system of sintered ore with satisfactory results. Our research in those several years, the following result s are attained. (1) There is close relation between indices of RDI (Reduction and Dis integration Index) and TI (Tumbler Index) of sintered products and the ratio of smaller particle size of crushed coke than 1 mm. (2) FeO con tent of products is con tr ollable by regulating the coke ratio in relation to the FeO content of raw materials and products. (3) FeO content can be controlled more accurate ly by regulating the coke ratio in which the effect of free carbon content of raw materials is corrected. From those facts, the following measurement systems are developed. (1) Continuous FeO measurement meter for raw materials ----- The principle

of FeO measurement meter cons i sts in inductance change of detecting coil by the FeO content of raw materials. (2) Continuous FeO measurement meter for sintered products. (3) Particle distribution measurement system of c rush ed coke ----- This system uses an optical pattern recogni tion method. (4) Free carbon content measurement system of raw materials ----- This system estimates the total carbon consumption by calcu lating the data of flue gas vol ume and components. The recent operation has obtained the changing the desired value of RDI from 40% to 42% as a result of the improvemen t of con trol accuracy, so the FeO and Si0 content of products can be cut down more than 0.7% which bring 2 about much cost-down of products. Keywords Sintering plant; RDI; TI; Magnetite Me ter; Sintered Products; Raw Materials; Coke Breeze Particle Size Distribution; Free carbon content; Quality Control.

347

348

O. Arai et al .

INTRODUCTION The Sys t em adopted in the sin t ering plant a t Kashima is the DDC (Direct Digital Control) system which performs a series of process controls, from the raw materials weighing control to the burn through point control. That system has attained much improvement of the quality of sintered products and saveenergy by means of decreasing the coke rat io and the dispersion of RDI and basisity . One of the reasons of the stable operation of blast furnaces is well known to charge the high quality sintered products. Recently, moreover, operating conditions of blast furnaces are desired to make better and much more flexible, which make advanced quality control of sintered products necessary such as the quality indices of RDI, TI and basisity are measurable and controllable continuously. Under those backgrounds, SMI has developed quality measurement sensors and control system with satisfactory results. This paper presents an outline, with the results, of the quality measurement sensors and control system. EFFECTS OF CONVENTIONAL DDC SYSTEM In 1977 DDC system was developed, it's control systems are shown in Fig.l. The control models of this system were constructed based on the research made in the past several years at our central research laboratory and the analytical results of the micro-computer based data logging of sintering plant for about two years. Table 1 shows the process control items of DDC . The DDC system has brought us many effects shown in Table 2 . There installs an automatic calibration sub s ystem of Constant Feed \
where L

self inductance of iron core solenoid coil )le = effective permeability of iron core d diameter of solenoid coil 1 length of solenoid coil N turn of solenoid coil K Nagaoka's factor Y filling up rate of sintered products in solenoid coil FeO content in sintered products Feo Lo self inductance of coreless solenoid coil =

FeO content in sintered products is measured and calculated by the self inductance of solenoid coil which is filled up of sintered products . Self inductance is changeable not only FeO content but also filling up rate of solenoid coil mainly . So, in case of batch sampling and measurement system, samples are had to classify in proper particle size, but this method is not practical for having some of weak points written before . The indispensable conditions of Magnetite meter for quality control as our regards are listed below. (1) (2) (3) (4)

FeO content can be measured continuously. Filling up rate can be constant . Sampling system should be simple. Specimen should be sampled at the representative part of sintered products

Thus, optimum sampling and measurement system has been developed shown in Fig . 4. Fig . S shows the relation between Magnetite meter and FeO-chemical analysis. Fig . 6 shows the relation between FeO and RDI in sintered products. Those facts can be possible to control RDI of sintered products by using the Magnetite meter for the input value of feedback control system. This feedback control system has been effected to decrease the long-rangedispersion of RDI remarkably. But, there has been a limitation to control more accurately and quickly as it's long time delay, also two hours from raw materials feeders to the exit of the cooler. So, the next step system was designed consisting of the two control sub-systems written below. (1) Feedforward control system by which using the measurement of FeO content in raw materials. (2) Feedback control system by which using the measurement of FeO in sintered pro ducts. We call Magnetite meters for raw materials and sintered products as R-Magnetite meter and S- Magnetite meter. EFFECTS OF CONTINUOUS FeO MEASUREMENT METER FOR RAW MATERIALS R-Magnetite meter can't be consist of similar system of S- Magnetite meter as the raw materials contain much moisture .

The Quality Control System of Sintering Plant So, R-Magnetite meter should be designed to measure the raw materials' FeO content of the outside of detecting coil shown in Fig.7. The key point of development was how to improve the sensitivity of R-Magnetite meter. Vortex current loss caused by the protector -- austenite type stainless steel tube -could be cut small be thinning the thickness and cutting off the protector of useless part of strength. Sensitivity could be improved by cutting small of vortex current loss and increasing the turn of solenoid coil and stabilizing the amplifier characteristics depending on temperature-change. Specifications of both Magnetite meters are shown in Table 4 and Fig.8 shows the relation between R-Magnetite meter and FeOchemical analysis. Fig.9 shows the correspondence between Rand S-Magnetite meters in the sintering plant operation. Output values of both Magnetite meters are so similar that FeO content in sintered products can be controllable by feedforward and feedback control. So, the control test of FeO content was carried out shown in Fig. 10. Results of control actions are written below. (1) When decreasing the mixing percentage of high FeO content raw material from 4% to 0%, also both Magnetite meters' indications decrease. Calculated FeO change is 0.84% (based on the relation shown in Fig.8) and measured FeO change is 0.8%. (2) When increasing the mixing percentage of high FeO content raw material from 0% to 4% and decreasing the mixing percentage of coke breeze from 3.32% to 3.22%, R-Magnetite meter's indication increases, but S-Magne tite meter's indication doesn't change. Those facts have proved that FeO content in sintered products can be controlled by regulating the FeO and coke breeze contents in raw materials. There is a last improvement point in RMagnetite meter that the indication drift caused by the mixing of various types of FeO content materials. Magnetite meter's characteristics for various kinds of FeO content materials is shown in Fig.ll. EFFECTS OF PARTICLE SIZE MEASUREMENT SYSTEM OF CRUSHED COKE It has been cleared that the FeO content in sintered products can be controlled by regulating the FeO and coke breeze contents in raw materials written before. Moreover, we have yielded the facts by laboratory experiment and operation analysis of sintering plant written below. There are close relations between FeO, TI and coke content, and when operating the

349

same coke content, TI and RDI are dependent on coke breeze particle size distribution. The development of continuous type of particle size distribution measurement system was carried out based on the optical type experimental system reported previously. The development items for practical application are listed below. (1) Sampling system for optimum dryness control. (2) Optimum control of sampling volume to keep at constant rate of falling volume and thickness. (3) Optimum regulation between focus length of the camera and lower, upper range of measurable particle size. (4) Threshold level tuning method for image processing of proper particle size. (5) Control method of particle size distribution. The yielded development results are shown in Fig.12-Fig.15 and Table 5. (1) Configuration diagram of particle size distribution control is shown in Fig.12. (2) Particle size distribution measurement system is shown in Table 5. (3) Threshold level tuning method is shown in Fig. 14. (4) Particle size distribution measurement result is shown in Fig. 13. (5) The relation between charging volume for Rod Mill and particle size disbribution is shown in Fig. 15. RDI and TI have been stabilized by making use of particle distribution control system based on the relations shown in Fig.16 and Fig. 17. EFFECTS OF FREE CARBON CONTENT MEASUREMENT SYSTEM OF RAH MATERIALS The quality improvement of sintered products can be executed under making use of R- and S-Magnetite meter, and particle size distribution measurement system for coke breeze. But there has been a residual unknown change of FeO content in sintered products, which can't be presumed based on the informations of the known input data of FeO and Carbon contents in raw materials and operating conditions of sintering plant. Our raw materials are so consist of various kinds of materials, such as fine crushed ore and blast furnace dust and converter slug and so on, that the unmeasurable carbon input in raw materials except for the coke breeze make probably change the FeO content in sintered products. So, the total input carbon content has been presumed to depend on the principle written below. Fig.18 shows the principle of the presumption method of total carbon content in raw materials, and the calculation formula is shown in Formula (4). C=G(C0 +3!2CO-lOO(1-N /79»!22.4 x M (4) 2 2 where CO = CO percentage in main flue gas 2 2 of sintering plant

O. Arai et al.

350

co

CO percentage in main flue gas of sintering plant NZ percentage in main flue gas of slntering plant main flue gas (Nmtminute) total material charge (kg/minute)

Precise calculation process is shown in Appendix 1. Operating results are shown in Fig.19. There has been cleared that the FeO content in sintered products is stabilized by regulating the coke breeze content based on the relation between FeO (FeO in sintered products - FeO-in raw materials) and the total carbon presumption in raw materials shown in Fig.20. So, the dispersion of RDI is decreased shown in Fig.2l. CONCLUSION 1. Quality control sensors for sintering

plant have been developed written below (1) S-Magnetite meter (continuous FeO measurement meter for sintered products) (2) R-Magnetite meter (continuous FeO measurement meter for raw materials) (3) Measurement system for coke breeze particle size distribution . (4) The presumption system for total carbon content in raw materials. 2. The quality indices of RDI and TI in sintered products can be controlled fairly stable by making use of those sensors. 3. Objective RDI can be increased possible from 40% to 42%, moreover, improvement of blast furnace operation having been carried out at the same period make possible to cut down the FeO and Si0 2 contents about 0.7% (there are close relations between RDI, TI and FeO, Si0 2 contents in sintered products). So, the hot metal making cost is saved by 0.3%. REFERENCES 1. G Meunier: Metallurgical Reports C.N.R.M.

No.9, December 1966 2. Kawasaki Steel Corporation: No.52 Instrumentation Comittee of ISIJ, 1972 3. J. LUCKERS, G. MEUNIER: "Regulation automatique continue de la qualite d'un agglomere sur une bande industrielle", International Congree of Automation in Iron and Steel Horks, 1970

Appendix 1 Presumption of Free Carbon Content 1. Data from Exhaust Gas Composition (CO), (C02), (02) % Exhaust Gas Volume G Nm 3 /min.

i) Presumption of N2 Composition in Exhaust Gas (NZ) = 100 - {(CO)+(COZ)+(OZ)} (1) ii) Presumption of Exhaust Gas Volume from N2 Balance Exhaust Gas Volume/Air Volume (2) = K = 79/(N2) Z.Supposition of Reaction i) Carbonate Resolution MeC03 ) MeO + C02 ii) Carbon Combustion C + 1/202---> CO C + 0Z~C02 iii) Ore Reduction 3Fe203~2Fe304 + 1/202

(3)

(4 ) (5) (6)

3.Gas Balance i) Input Air Volume 100 (NZ) in 79 (7) (02) in = 21 (8) ii) Output Exhaust Gas Volume 100*K (9) (N2) out = 79 (02) out = 100*K'''(02) /100 = K"(02) (10) (COZ)out= K*(C02)= (C02)C+(C02)R (ll) (CO) out = K*(CO) = (CO)C (lZ) where (CO)R is COZ from Carbonate Resolution(3), (COZ)C is COZ from Carbon Combustion (4) and (CO)C is CO from Carbon Combustion (5), from Oz Balance (OZ) out can be expressed (OZ) out = (02) - (C02)C - 1/2(CO)C (13) and Increase of Gas Volume is 100*(K - 1) = (C02)R + 1/2(CO)C (14) from equation (1)~(14), we get (CO)C = K*(CO) in (15 ) (C02)R 100*(K - 1) - 1/2K*(CO) (16 ) (C02)C = (C02) out - (C02)R = K*(COZ)+1/2K*(CO)-100*{K-l) (17) (02)R = (02) - (02)out= (C02)+1/2(CO)C = K"(C02) +K1'(CO)-100*(K-l) (18) from equation (15)~(17), GCCO, GCCOZ and GR C0 2 can be expressed as GCCO =G*(CO)/lOO (Nm 3 /min.) (19) GCC02=G*{(COZ)+1/2(CO)-100*(1-1/K)}/100 (20) GR C02 =G*{100*(1-1/K)-1/2(CO)}/100 (21) where G is Exhaust Gas Volume (Nm 3 /min.) OUTPUT

INPUT

CO [rom Free Carbon

Carbon ill Dust

4. T. SHIRAIWA, Y. SAKAMOTO et.al .: "CONTINUOUS MEASUREMENT OF THE PARTICLE SIZE DISTRIBUTION OF RAW MATERIALS", Proceedings of the lMEKO MOSKOW, 1981

Sintering Coke

C02 from Free Carbon

Nachine

r-----~/ Catbonctte MeeO]

iii)

r-----.:'~~ --Loss

Presumptive of Free Carbon C in Raw Materials can be expressed as C (G CCD+GC C0 2)*12/22.4M G*{( C02)+3/2(CO)-100*(1-1/K)}/22.4M (ZZ)

G CO C

G CO, C

G CO, R

351

Th e Quality Control System of Sint e ring Pl a nt

r------------ - ------------- - l------ --...-_-_-_--....L_---.

....--_---.JfL...-_-_--....,- --- - - -- - - - -- --- -...-----..... :=1"-_---, Feeding control of sinter feed and

Moi sture

coke breeze etc.

of raw material

flit:: I :

~

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Level cont rol

Den city control

Burning control

Damper control

Burn ing through

of raw material

of raw material

of furnace

of wind

pOint

______ ,

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TABLE 1 Control

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. Data

Preparation

of

Reports

~

Process Monitoring

:

feed

addifion control

TABL E 2

3. Level control

Effec ts of

of

hot metal1s

0 .063

0 .046

metal's

value of Si content In hOt metal blost

furnace

making

Man power savlflg for weigher calibration

slug

I

! I

~

Sensors for Qual ity Control

FeO

R - Magnetite meter

FeO content in

content In

Item

sintered row

products

materials breeze

materials

Specifica tion of

magnetite

me ter

DOG

Dispe rsion of basisity

meta l

I

Free carboo content presumption in ro w

0 .040

in hot

I

I

Carbon con te nt presumption system

0.055

slug

I

at Kashima steel works.

S - Magnetite meter

BefOfe Installation After Ins1110tioo

Man power saving for repon

I I

Crushed coke (before Rod Mill) and coke (offer Rod Mill) pa n icle size distribution

sintered products

Reduction of coke ra tio of

I I

I

Particle size distribution measurement syst em

Dispersion of bos isi ty in

Objective

I I

Measured

TABLE 4

in hot

I

Doe Effects

Item

SI content

I

I

I

· C. RT · Data logging . · Dai ly and monthly reports . · Automatic calibration of C. F. W. and belt weighers . · etc.

control

6. Burn through point control

Oisperslon of

I I I

fo r control

I Material

,

,

I

I I

VHl ~ _____ J

TABLE 3

2. Moisture

iI

:,

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Others

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Process cont rol back up

Objective va lue of basisity

I

lL _ _ __________ ____________________ _ ___ ____ _ _ _ _____________ __ _

4. Permeability Control

. On-line data transmission

in

,

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Name

acquisition

: :

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DD C

Computer

I I I

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( Si nte ring Process Control System)

COOlputer for management

I

: I

system of sintering plant

Items of

I I I I

r--:~~=~~~~-_-_-_-_-~J I , ,I

I

Fig. 1 Control

I

I I

I

Neutron probe Level meter Flow meter Cylinder Permeability measure of raw material at charge side Thickness mea sure of raw material at charge side Orif ice Thermocouple for furna ce The r mocouple f or waste ga s at wi nd box Permeability measure at wind box

I

,

Detector

I. 2. 3. 4. 5. 6. 7 8. 9. 10.

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cont rol

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boxes

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1.25

0 .044

0 .032

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045 L25kg/H -M Ton 1440 Mon hour J

120 tv1on -hour

Fa, ,aw materia ls

Item Diameter Detecting

coil

Length Turn

Frequency Current

Fa, sintered products

105 "

105 "

2001

200L

3000turn

300 Hz Under I OmA

IOOOtur n 1000Hz Under I 0 mA

O. Ar ai et al.

352

Coke and Row ROD

Mill

Sintering Machine

Materials Mixing

RDI T! FeO

Cooler

Coke breeze Particle size Distribution

GCi Gpi Hi GMi :

+

Controller Process Measurement system Control Model

Fe O, RDI, Tl Chemical Analysis

(T!, RDI, FeO) Desire d

FeO (RDI , TU

Objective Free Carbon Obj ective co ke particle size dist ribution

Desired RDI and Tl

Fig.2 Quality Control Configuration Flow

of

Sintering

Plant

Oscill a tor 44

o

* ~

o

cC

~ Q)

0 J!1 c

·in

s . 53

0

S 56 3

0

0

0

OOo~ O 0 o o

32

40 FeO In

Output ~

and block diagram

•

0

o

Fig.6

7.5

o

et:

FeO and filling up rate

Principle

0

Sensitivity

Measuring objects -Filling up in the solenoid coilalso contain FeO component Inductance

0

Zero point

Detecting Coi I

Adjuster

Fig.3

o CfJO o

Detector

Automatic Constant Voltage Uni t

0

dO o

E 40 E

of

Magnetite - meter

slnrered

50 products

FeO in sintered v.s. RDI

products

8

6 .5

.'.,. :

5.5

Screen

•

c 0

4.5

If 3.5 2.0

3.0

Magnetite

Fig5

4 .0 Meter

5.0

6.0

Va lue (%)

Magnetite meter value in sintered products

_ - - L _ L - - =_ _

GL + 200

v.s. FeO Fig 4

Construction of magnetite meter products

for sintered

The Quality Control System of Sin t ering Plant

353

6

Pipe for Protection (SUS 304)

~~~~~~-- ----- ITronSducer t ·-n--iTI Recorder

4 4 Output of Magnetite

Fig.7

Flg.8

Construc ti on of magnetite meter for raw materials

s - Magnetite

j

:" ,

" '\

Meter

( %)

Relationship between output of magnetite meter and FeO in raw ma terial s

meter

... ....

.,'

S - Magnet ite meter

.. I..' ', ~. \.: ...~ ,

...

.... :.

... .-.;

10' !

'".

~ I Hr

9' !

5' ,

Fig.9

3' ,

4' ,

Correspondence between S - and R - Magnetite meters

Fig 10

Cont rol te st of

FeO

conte nt

30 r------,r-----~----~

•• 2 3

~ !!'. 0

~

Dot No. I

.,

5

Ore Romerol Iron Sand PF. Peru Dried Oust Cake SF Corolrake

6 7 B

Sinfer Ore M .B R Converter Slug

9

Dust Pelle • BF Dust

2 . 4

20

4

~ s 0

~

•5

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IOD

50

100

Fig II

Value of hand sc reen ing

--+-

Valu e of porticle

dlsfr ibut ion system

~

size measurement

.c

0>

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o Our pur of Magnetite

--0--

80

2

5

Accumulotive

150

8

15 20

particle

size

distribut io n (m/m)

Meler

Measuring

Fig. 13

Relationship between ou tput of magnetite meter and FeO In materials

T I and ROl ConTrol

Obj ective

Objec :l ve

depe nd on co ke

TI

Re sult of particle

RDI

breeze distribullon*

*

Ref er to Fig 16 &. 17

value

Feeding Weighl

Object ive

Control UM

Cha ring Weight

Feed Feed coke siz e

for word and bac k control of breez partIcle distr ibution

Crushed co ke parti cle size dis tribution

Coke breeze particle sIze dis tribution -\~

Mea suremenT system of particle siz e distribution

Co ke breeze par ticle size di st ribution

Coke breeze

Fig. 12

Configuration diagram control

of particle size distribution

size

distributi on

O. Arai et a'l.

354

Brightness of the background

~ View of the Field

Improved le ve l

threshold

*

Threshold le vel (General moth od )

Mistaken to be particle Darkness region

Threshold

Fig. 14

Our Method

Particle

Geveral Method

metho d

tuning

level

Principle

Item

Parlicle size c an be calcu lated by re ckoning numbers of darkness image elements

Measuri ng range (diameter)

0.5-30 mm

O.I-lOmm

Freguency of image processing

3s

3s

Objective Moisture of coke

Under 3%

Under 3%

400

400

Numbers of image processin for distribution calculation

E~5r-------------------'

..s~

o Charging

size

Principle and Specifications of particle distribution measurement system

TABLE 5

78 ·

•• • •• ••• ••••

weight : 30 - 45 T/ H

•• • •• • • • •

76 -

"

74

•

•

;:

72

• • •

70

20

10

44

Fig.15

Crushed

D

.~

conveyor

_______ J Gas Composition

iCOI ,iCO,I ,(O, 1 Carr ie·r Gas Process Compute r

C ' G [CO + 3/ 2 CO - 100 ----------.------ --- , - _x_(_I '_N_I_7_9_1_1 1_2_2_A_ M_ _-.l

Fig.IS

56

52 size

under

60

I mm (%)

Flg.16 Relation between T 1 and coke breeze particle si ze

Character istics of Rod Mi"

(

48

Coke breeze porticle

Average particle Diameter (m/m) (Ch arge to the Rod Mill)

D

Printer

---- --

Presumption of Free Ca rbon in Raw Material s

Sca le

The Quality Control System of Sintering Plant

../

42

~

E E

'"

~.

38

•••• •• /

34

•

1;;

•

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C ::l

355

30

• ••• •••• • •

a 0::

26 48

44

52

56

particle size under

Coke breeze

60

I mm

(%)

Fig.17 Relation between RDI and coke breeze particle size 12

I

16 5 / 22 20

0

4

4

8

12

16 5 / 23 20

4

2.7

Presumptive

2.6

Content of

2 .5 Free Corbon (0;.)

2.4

Coke Content 3.0 (0;.) in Row Materials 2.9 Operation Guidance FeO

in

..

4.5 Sintered Products (0;.)

4.0 3.5 42

RDI

40

under

3mm

38

(%)

36

Fig. 19 '81 May

.,

0.6

~

'b

June

• • • • • • •• • • • • ••• • • ••• • • ••

0.8

0.4

,f
•

0.2

-

30

~ ~

u

~

~

'aO/II 'all TES T

20

0

, .:: ~

5.0

0' ~

10

~

0

a:

•

'0

24

'§ Q> a. Cl) i5

4 .0

c

0

•• 22

Results of Test

26

28

of Test

Presumpfive Free carbon COnTent in Row Materials (%)

(BL NO) 12 13 14 15

*6 FeO = (FeO in sintered products ) - (FeO in Raw Materials)

Fig 20 Presumptive Free Carbon Content in Raw Materials V.S llFeO

9

Fig.21

10

Results

'81 11 12 I

16 17

' - - - - - - - ', '-------'

2

345

of Dispersion (fV) of

7

6

R Dr