Development of new burden for blast furnace operation with ... and Steel 2 Secured...

11

Development of new burden for blast furnace operationfor blast furnace operation

with low carbon consumption

Kenichi HiguchiNippon Steel & Sumitomo Metal

IEAGHG/IETS Iron & Steel Industry CCUS & Process Integration Workshop, Kenichi Higuchi, 6th Nov. 2013

© 2013 NIPPON STEEL & SUMITOMO METAL CORPORATION All Rights Reserved.

6th Nov. 2013 EAGHG/IETS Iron & Steel Industry

CCUS & Process Integration Workshop

22Outline

1. Purpose and background

RCA, Reactive Coke Agglomerate

RCAReactive Coke Agglomerate

1. Purpose and background2. Laboratory tests

1) Influence of carbon content of burden2) Estimation of reaction beginning temperature

3. Plant trial of RCA4. Commercialization of RCA

Iron oxide Coke

C + CO2 = 2CO

FeO + CO = Fe + CO2

Close arrangement



4. Commercialization of RCA5. Conclusion

33Purpose and backgroundTwo possible approaches to reduce carbon consumption of blast furnace.・ A to B; Increasing shaft efficiency. → Limitation ・ B to C; Lowering the Carbon consumption ・ B to C; Lowering the temperature of thermal reserve zone (Fe/FeO equilibrium).

Carbon consumption

Temperature of thermal reserve zone is controlled namely by gasification rate of carbon.



New agglomerates both with high reducibility and with high gasification of carbon have been designed.

Fig. Explanation of approach for decreasing carbon consumption of blast furnace by using RIST diagram*.

* M. Naito et al. : Proc. of 3rd ICSTI, Düsseldorf, VDEh, (2003), 539.

44

Development of new burden for blast furnace operation with low carbon consumption

Principle of designing new burden

Composite agglomerate

Ore

RCAReactive Coke AgglomerateRCA

Close arrangement of coke and iron oxide results in high reactivity

Conventional layer structure

Half thickness

Homogeneously mixed

Small coke mixed New burden

・Decrease of distance between coke and ores ・Increase of contacting surface area

Ferro-coke

coke Iron oxide Coke

C + CO2 = 2CO

FeO + CO = Fe + CO2

Close arrangement



Close arrangement of coke and iron oxide results in high reactivity

Decrease of temperature of thermal reserve zone

Low carbon consumption of blast furnace

55

1 kgf/cm2Load

Influence of carbon content of burden

Cement-bonded, carbon composite agglomerate (CCA), containing different carbon content (T.C =0～23%) were manufactured.

2. Laboratory tests

1 kgf/cm2

Coke

Sinter

CCA

Sinter

Al2O3 balls

Load

Gas

Graphite

10-15mm, 100 g

10-15mm, 200 g

10-15mm, 200 g

400 600 800

1000 1200

Tem

pera

ture

(℃

)

1℃/min5℃/min900℃

1000℃

23%) were manufactured.

Manufacturing condition of CCA’s is , Cement 10%, curing time 2 days in 50℃, 12 days in room temperature.



0 200 400

0 50 100 150 200 250

Tem

pera

ture

(℃

)

Time(min)

0 10 20 30 40 50

0 50 100 150 200 250

Gas

com

posi

tion

(%)

Time (min)

CO2/(CO+CO2) 0.56 0.30

CO

CO2

15℃/min

balance N2

Fig. Test procedure of reduction test under load.

66Result of laboratory test

CCA had higher reduction degree thanfired pellet. High carbon content of CCA resulted

in higher reduction degree. 90% of60

80

100 R

educ

tion

degr

ee (%

)

CCA

Fired pellet

in higher reduction degree. 90% ofreduction degree was attained by CCAwith carbon content above 10%. Further high carbon content of CCA

resulted in higher reduction degree ofmixed sinter due to higher reductiongas potential formed by carbon in CCA.

40 0 10 20 30

Red

uctio

n de

gree

(%)

T.C content in pellet (mass%)

CCA

50

60

70

Red

uctio

n de

gree

(%)

Sinter at upper layerSinter at lower layer

C = 20%

Carbon composite agglomerate



Fig. Influence of carbon content of CCA on reduction degree of materials at 1100℃.

40 0 10 20 30

Red

uctio

n de

gree

(%)

T.C content of CCA (mass%)

Sinter at lower layerCharged materials total

Carbon composite agglomerate containing high carbon content, C=20%

→ RCA, Reactive Coke Agglomerate

77Microstructure of CCA’s after reaction

Carbon composite agglomerate containing high carbon content, C=20%


Sinter Fired pellet

Fig. Microstructures of CCA’s after reaction up to 1100℃.White: Metal (M) , pale gray :Wustite (W), dark gray: residual




White: Metal (M) , pale gray :Wustite (W), dark gray: residual carbonaceous materials(C), black : void

Many small white particles, representing metal, were observed in CCA with high carbon content (see CCA 2, 3, 4). CCA 4 contained residual carbonaceous materials. Less metal formation

would lead loss of strength after reaction.

88Plant trial

Plant trials of manufacturing and using in blast furnacewere performed at Oita works in 2007.RCA was manufactured in dust treatment factory

equipped by pan-pelletizer and cured for 2 weeks inyard-piling.

Table. Result of RCA production.

yard-piling.Quality and quantity of RCA were enough as blast

furnace burden.

Total production t 21000

Crushing strength (average) kg/piece 114.8

Crushing strength (minimum） kg/piece 100.2Total carbon % 21.3



Total carbon % 21.3Total Fe % 36.6

Mean size mm 13.6

99

Table. Comparison of basic properties of plant manufactured RCA with those of other conventional burden materials.

Result of plant trial ; manufacturing

RCA FiredPellet A

FiredPellet B

Lump oreA

Lump oreB

SinterPellet A Pellet B A B

MS (mm) 13.6 14.3 14.0 23.2 23.3 21.1

TI (+10mm%)97.4

(99.4) 94.1 95.6 87.4 82.5 70.2

AI (-0.5mm%) 2.0 (0.1) 1.8 4.4

JIS-RI (%) 97.6 73.3 71.2 43.9 70.3 63.0



Basic properties of RCA were enough as blast furnace burden andcomparable with those of other conventional burden materials.

RDI (%) 2.7 6.7 6.6 8.6 41.2 35.7

(evaluated in wet state)

1010

Using ratio of RCA was increased in stepwise up to 54 kg/tHM.

Result of plant trial ; Oita No.2 BFBF volume 5775 m3

Charging device Bell

The number of tuyere 42

Period of RCA use 80 days

9000

10000

11000

12000

13000

2/6 2/16 2/26 3/8 3/18 3/28 4/7 4/17 4/27

0

10

20

30

40

50

60

2/6 2/16 2/26 3/8 3/18 3/28 4/7 4/17 4/27

Production

(t/d)

RCA

(kg/tHM)

84

86

88

90

SLC

(kg/tHM)

As RCA using ratio was increased, gas utilization was improved. Solution loss carbon was decreased accordingly.

Raw value of reducing

54 kg/tHM



80

82

84

2/6 2/16 2/26 3/8 3/18 3/28 4/7 4/17 4/27

(kg/tHM)

460

470

480

490

500

2/6 2/16 2/26 3/8 3/18 3/28 4/7 4/17 4/27

CR+PCR

(kg/tHM)

Raw value of reducing agent rate (CR+PCR) was deceased by 25 kg/tHM.25 kg/tHM

1111

10

12

Dep

th f

rom

charg

ed s

urf

ace

（m

)

Without RCA

Result of plant trial ; Oita No.2 BF

14

16

18

20

Dep

th f

rom

charg

ed s

urf

ace

With RCA(54kg/tHM)

Without RCA

Temperature of thermal reserve zone was lowered.

83℃



20

0 200 400 600 800 1000

Temperature （℃）

Fig. Changes in temperature profile with using RCA measured by vertical probe during test.

1212Changes in input carbon of blast furnace

-2

-1

0

Corr

ecte

d input

carb

on（kgC/tH

M）

Decrease of temperature of thermal reserve zone (℃)

83

Decrease of input carbon (kgC/tHM) 4.0

0.36

-5

-4

-3

0 3 6 9 12Consumption of RCA　（kgC/tHM）

Corr

ecte

d input

carb

on

Decrease of input carbon (kgC/tHM) 4.0

( kgC/tHM／▲10℃TRZ) 0.5(kgC/tHM／ + 1 kgC /tHM) 0.36

Fig. Relationship between consumption of RCA and corrected input carbon* .



Input carbon was decreased with using RCA in a linear fashion.It was estimated that corrected input carbon was decreased by 0.36 kgC / tHM

if we input 1 kgC / tHM from RCA.

of RCA and corrected input carbon* .* calculated by heat and mass balance based on the Rist model.

1313

1) RCA, Reactive Coke Agglomerate, containing 20 %carbon has been developed as a new burden for blastfurnace. Beside its high reactivity, RCA promotesreduction of mixed sinter.

5. Conclusion

reduction of mixed sinter.2) Reaction beginning temperature of carbon in RCA was

lower than that of conventional coke and along thetheoretical lower limit. Thus, RCA is effective burden tolower the temperature of thermal reserve zone.

3) Facility of manufacturing RCA has been installed at Oitaworks in 2011. Since then, smooth production of RCAhas been established. RCA has contributed low RAR,



has been established. RCA has contributed low RAR,low input carbon, operation of blast furnace at Oitaworks.

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