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Optimum temperatures for carbon deposition duringintegrated coal pyrolysis –tar decomposition (CVIironmaking)

Rochim B. Cahyono , Naoto Yasuda, Takahiro Nomura,Tomohiro Akiyama

Center for Advanced Research of Energy & Materials,Hokkaido University, JAPAN

Kuala Lumpur, Dec 12-14, 2013

1



2

Ironmaking industry

[1] World Steel Association, 2011. Steel statistical yearbook 2011.; [2] The Japan Iron and Steel federation. ; [3] http://1ms.net/chevrolet-camaro-indianapolis-500-pace-car-221845.html; [4] http://atlazcrew-world.blogspot.jp/2012/04/my-dream-jalur-lintas-nusantara.html; [5] http://www.ipact.com/solutions/blast-furnace-applications/

Raw materials : Coal (HG) = 690 kg/ton-pig ironIron ore (HG) = 1390 kg/ton-pig iron

Consumes around 5% of the total world energy[=24 EJ]Energy recovery : 25.3 % of input energyCO2 emission: 1519 kg-CO 2/ton-pig iron

Years

P i g i r o n p r o d u c

t i o n ,

1 0 3 M t

World pig iron production

Pig iron



7

Dehydration process

(a)

Micropore

Macropore

Mesopore

Removing H2O during dehydration processcreated porous ore with layer by layer structureThe micropore/mesopore was predominat in thedehydrated ore



A higher temperature resulted in a

large reduction degree because ofindirect reduction of CO and fastreduction rate.FeO was found at hightemperature; this is consistent withthe phase diagram.

30 40 50 60 70 802θ [degree]

I n t e n s i t y [ a . u ]

400 oC

500 oC

600 oC

700 oC

800 oC

Dehydrated ore

Fe2O3 Fe3O4 FeOH ore; pyro lysis temp : 800 oC

(b)

0

0.2

0.4

0.6

0.8

1

400 500 600 700 800 900 1000Tar decomposition temp [ oC]

Fe

Fe3O4

FeO P C

O

P C O

+ P C

O 2 [ - ]

Fe2O3

H ore; pyrolysis temp : 800 oC

(a)

2

243

24332

COFeCOFeO

CO3FeOCOOFe

;COO2FeCOO3Fe

Tar decomposition

9



0

20

40

60

0 5 10 15

P o r e s i z e

d i s t r i b u t i o n

[ 1 0 - 6 m

3 / n m / k g ]

Pore size [nm]

DH

400600

800

: Dehydrated ore (DH)

: Tar decomposition at 400o

C: Tar decomposition at 600 oC

: Tar decomposition at 800 oC

H ore;

Pyrolysis temp: 800 oC

86.7

21.9 20.32.8

DH 400 600 800

BET surfacearea [m 2/g]

Tar decomposition temp [ oC]

3.15

3.89

1.94

400 600 800

Carbon deposition [%mass]

Tar decomposition temp [ oC]

Tar decomposition

10

Smallest carbon depositionbut largest deceasing ofsurface are and poredistribution, why??

The amount of carbon deposition should beproportional with the decreasing of surfacearea and pore size distribution.The melting point of the iron ore (Fe 2O 3) was1733 K(=1460 oC)

Sintering process

[14] HSC chemistry 7.0; [15] Canovaa, IC. et.al. Materials Research Vol. 2, No. 3, (1999) 211-217



-0.16

-0.14

-0.12-0.10

-0.08

-0.06

-0.04

-0.02

0.00

0.02

100 300 500 700 900 1100 1300

W e i g h t c

h a n g e r a t i o =

[ - ]

Temperature [ oC]

.Carbonized ore - Lignite

∆ W W o

Heating rate = 50 oC/minAtmosphere = Argon (500

NmL/min )

Reagent Fe 3O4 + coke

COFeCFeO;COFeO3COFe 43

Reactivity of CVI ore

~nm

The nano-scale contact between iron ore and carbon enhances thecontacting area and results in the increasing of reaction rate

Iron ore

Carbon

11

Iron oreCoke (carbon)

~cm

[16] http://webs.purduecal.edu/civs/research/educationtraining/virtual-blast-furnace/



Reactivity of CVI ore

The carbonized ore was also useful and effective in the reduction reaction whichwas indicated by decreasing of carbon content during reduction reactionThe XRD result confirmed that the reduction reaction was started at 750 - 900 oC

Reduction of Fe 3O 4 to FeO was started

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Reactivity of CVI oreTransforming of iron compound in each experiment steps

The final product of CVI ore can be sent directly to blast furnace and

sintering machine

30 40 50 60 70 80

I n

t e n s

i t y [

a . u

]

2θ [degree]

Fe2O3 FeOFeOOH FeFe3O4

Original ore

Dehydrated oreat 450 oC

Carbonizationat 600 oC

Reduction a t900 oC

OHOFeOH2FeO 232

24332

243232

COOFe2COO3Fe

OHO2FeHO3Fe

COFeCFeO

CO3FeOCOFe 43

Tar decomposition

Direct reduction at

13



Conclusions

The highest deposited carbon was obtained at tar decomposition

temperature of 600o

C. At elevated temperature, the amount of deposited carbon decreased dueto carbon gasification.

At tar decomposition temperature of 800 oC, the FeO was found but thesintering phenomena was startedThe deposited carbon within iron ore showed promising candidate as goodreducing agent due to higher reactivity and lower reduction temperature.The reactivity of carbon-deposited ore increased because carbondeposited within iron pores and caused nanoscale contact between theiron ore and carbon.

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