1

SIMULATION OF

IRON ORE REDUCTION IN A FIXED BED

J. Aguilar, R. Fuentes, R. Viramontes *

Universidad Autónoma de Nuevo León

Facultad de Ingeniería Mecánica y Eléctrica

Doctorado en Ingeniería de Materiales

A.P. 076 "F", Monterrey, N.L. 66450 México

*HYLSA, S.A. de C.V.

Departamento de Investigación y Desarrollo

A.P. 996, Monterrey, N.L. 64000, México

1. ABSTRACT

A simulation of direct reduction in a fixed bed process of

iron ore is presented. Simulation is done with a model which takes

into account bed characteristics, including reaction kinetics,

thermal effects, quality and flow of reducing gas. It is

considered that reactor is a cylinder with wall made of layers of

refractory and insulator, this reactor contains a bed of iron ore

pellets which will be reduced under a flow of reducing gas in

longitudinal direction (along cylinder).

Finite difference method is used to solve simplified

differential equations for description of heat transfer gas-

pellet, gas-refractory, refractory-insulator-environment, and heat

changes due to reaction inside reactor.

2

Simulator is fitted by using reducibility tests in laboratory

and runs in a pilot plant. It is found that due to process nature,

this process is carried out almost fully in transitory stage and

that is way this simulation is necessary.

2. INTRODUCTION

At present time, direct reduction process are calling

researchers [1,2,3,4,5] attention in world, whom are looking for

an efficient reduction process which includes advantages of direct

reduction together with smelter reduction in a blast furnace, this

process has been called "Smelter Reduction Process".

Taking into account that there are process developed until

commercialization, and world trend is still including direct

reduction as part of a new process, becomes important to study

this stage by using available tools.

One of most common low cost tools used for design and test of

new plant is simulation processes. In case of chemical processes

which are batch conducted, one of the most important knowledge is

time necessary to carried out such process, that is the aim of

this work, to determinate time necessary to reduce an iron ore bed

in contact with reducing gas and to obtain a desired reduction

degree (in this case to wustite) under given operation conditions.

Fixed bed scheme is more complex than moving bed, because of

the first one includes transitory state. In this paper is

presented a model which was developed to simulate transitory

condition, after this it is uncomplicated to pass to moving bed.

3

3. GENERAL DESCRIPTION OF A NEW REDUCTION PROCESS

In a general way, new reduction process consists of a smelter

unit charged with pre-reduced iron ore that is reduced to iron by

combustion of carbon and oxygen. Combustion products have enough

reducing potential to pre-reduce iron ore to wustite, that is way

the gases are passed through a reactor with a bed of iron ore

pellets which will be pre-reduced by direct reduction process and

charged to smelter unit.

With the goal of evaluate this process some researchers [6,7]

have ran tests on pilot plant, however this model only simulates

direct reduction part (pre-reduction).

4. DEVELOPMENT

It is assumed in this work that reactor is a cylinder with

compound wall made of refractory and insulator layers (Figure 1),

iron ore (pellet) is inside of cylinder and reducing gas is

passing through from top to bottom. Gas is flowing in

unidirectional way following z axe in a plate front (turbulent

flow).

Used equations are explained below:

4.1 Heat transfer

This concept corresponds to heat transfer between gas and

pellet, and gas and refractory-insulator system in wall and

environment. This section takes into account physic properties of

gas used by process.

4

Equations which handle heat transfer are:

a) Heat transfer from gas;

b) Heat transfer to pellets;

c) Heat transfer between insulator and refractory layers in

wall;

with heat transfer coefficients for a pellet bed;

M C)T - T( A H + )T- T( A H =

zT

gg

rgrgpgpgpg

∂∂

1

M C)T- T( A H =

tT

pp

pgpgpp

∂∂

2

)T - T( pra + )T- T( pra + T pra = tT

ma6ar5f4

r

∂∂

3

)T - T( pra + )T - T( pra + T pra = t

Tma3mr2f1

a

∂∂

4

)- (1 D a

)( = C

p

a1.40.3

p

a

3

1

ρρ

ρρ

5

5

and an auxiliary function for transitory stage in wall.

4.2 Kinetics of iron ore reduction

This aspect is very important because it is an element

inherent to process due to thermal profile and chemical gas

composition are strongly related, in other words, reduction

kinetics depends on temperature and gas composition, and these

depend again on reduction kinetics.

Reduction kinetics employed in this work includes three

oxidation stages of iron, in a simultaneous reduction process

where first reduction product, which corresponds to first oxide,

is reactive for next reaction for a homogeneous process.

Equations for this section are related to two reactions, the

first one is reduction by hydrogen, and second one is reduction by

carbon monoxide. Reduction from hematite to magnetite (Fe2O3 to

Fe3O4) is described as;

)G W( C = Hg

gg0.7

g1g µα 6

K 5a +

H1

1 = H

pg

gp 7

K)T - T( H = T

b

rgbgf ε 8

6

hydrogen contribution is governed by;

and;

Same procedure is used for CO (in equation (10) term H2

related with hydrogen pressure is exchanged by CO pressure).

From reduction from magnetite to wustite (Fe3O4 to FeO) and

from wustite to iron (FeO to Fe) expressions are very similar, but

in these cases thermodynamic constants for equilibrium are taken

into account, this constants are almost zero for reduction from

hematite to magnetite (that is why for hematite to magnetite is

independent of water pressure), besides it is necessary to take

into account the reagent amount given by reaction just before,

this consideration gives the following equation for magnetite to

wustite:

and for wustite to metallic iron;

R + R = tR

mmm

ch∂∂

9

)R - (1 H A = R m2gmm hh ρ 10

)Tp R

Qmh(- fmh = Amhexp 11

)R- R( K + 1

O)H K - H( A = R wm

w

2w2

gww

h

h

hh ρ 12

7

Reduction rate is handle in same way that reaction from

hematite to magnetite, and with CO contributions (same kind that

hydrogen ones) there are enough equations to know global reduction

degree. Thermal behavior is taken from heat of reaction of each

one of involved reaction, this contribution is added to heat

transfer section. Even when the objective of this work is centered

on wustite production, this model takes into account reduction

from iron ore to metallic iron because some times it is possible

to have conditions, which permits to reach metallic iron.

4.3 Kinetics of gas conversion

In this section equilibrium degree inside of bed is

considered, with this information it is possible to work with

thermodynamic equilibrium letting gases to complete reactions, or

as an opposite way, to inhibit gas reactions away of thermodynamic

equilibrium. With these capacities the model can reproduce any

experimental conditions and know how far from equilibrium the gas-

gas reactions are taking place.

4.4 Condensation and evaporation of water

This phenomenon must be considered especially in cases where

reducing gas composition is high in hydrogen and water is a

)R- R( K + 1

O)H K - H( A = R fw

f

2f2

gff

h

h

hhρ 13

8

reaction product. This is also very important because simulation

and actually the process starts from room temperature and water

vapor is condensing, when the iron ore bed reaches water

evaporation temperature water boils and modify the temperature

profile strongly. This phenomena is handling by taking into

account pressure inside reactor and pellet temperature, thus water

change its state from liquid to vapor and backward, water amount

in this changing process depends on evaporation kinetics and

obviously it can not be grater than energy provided by heat

transfer gas-pellet.

This part is also included in heat transfer section with heat

transfer terms in equations.

5. EQUATIONS RESOLUTION PRESENTED AS SIMULATION MODEL

Flow diagram in figure 2 shows the sections above described

linked with the aim to have a fully integrate simulator. Start

point is to have general initialization values, such as ore

properties, process parameters (temperature, composition and flow

of reducing gas), reactor characteristics (dimensions and physic

properties of refractory and isolator) and data related to iron

ore bed to be reduced.

Due to fixed bed is a batch process, thermal transitory state

is taking place while reduction (required time for reduction is

less than time for reach steady state) and this condition makes

necessary to evaluate and take into consideration thermal

parameters of refractory-insulator-environment [8].

9

In accordance with equations showed before, finite

differences method uses a loop in time which contains a loop along

z axe. Adjust of right parameters in model was done by runs in

laboratory and pilot plant. Simulation model reproduces

experimental runs with different conditions, thus it is already

validated.

6. EXPERIMENTAL

6.1 Experimental design for laboratory tests

Experimentation was conducted on a fixed mass of 500 gr. of

iron ore pellets with three different temperatures (750oC, 850oC

and 950oC) and three reducing gasses of different compositions

where employed, gas flow was 55 lts/min.

Experimental design for laboratory test is listed in tables I

through IV:

Table IDesign Matrix for reduction from

hematite to magnetite

Temperature oC

H2/H2O(1)

H2/H2O(2)

H2/H2O(3)

CO/CO2

(1)CO/CO2

(2)CO/CO2

(3)

750 0.1 0.37 0.64 0.1 0.28 0.47

850 0.1 0.22 0.34 0.1 0.22 0.36

950 0.1 0.15 0.20 0.1 0.19 0.29

Table IIDesign Matrix for reduction from

magnetite to wustite

10

Temperature oC

H2/H2O(1)

H2/H2O(2)

H2/H2O(3)

CO/CO2

(1)CO/CO2

(2)CO/CO2

(3)

750 0.70 0.40 0.22 0.51 0.39 0.31

850 1.41 1.09 0.90 1.05 1.16 1.28

950 2.18 1.84 1.60 1.63 1.97 2.28

Table IIIDesign Matrix for reduction from

wustite to iron

Temperature oC

H2/H2O(1)

H2/H2O(2)

H2/H2O(3)

CO/CO2

(1)CO/CO2

(2)CO/CO2

(3)

750 2.39 2.02 1.76 1.79 2.16 2.50

850 4.13 3.56 3.18 3.05 3.78 4.54

950 6.08 5.29 4.77 4.47 5.64 6.84

Table IVComplementary Matrix design

Temperature oC

H2/H2OFe2O3 toFe3O4

CO/CO2

Fe2O3 toFe3O4

H2/H2OFe3O4 toFeO

CO/CO2

Fe3O4 toFeO

H2/H2OFeO toFe

CO/CO2FeO toFe

650 0.69 2.00 ∞

800 0.23 0.21 1.21 1.11 ∞ ∞

950 0.10 0.14 0.89 1.29 ∞ ∞

6.2 Ore

Tested ore comes from the Alzada mine, located at the Mexican

State of Colima. The mean characteristics of this ore are given in

Table V.

11

Table VMean ore characteristics

PHYSICS

Granulation + 3/8" - 5/8" (0.95-1.58 cm)

Average diameter 1.27 cm

Density 4.222 gr/cm3

Apparent density 2.200 gr/cm3

CHEMICAL

Total Fe 66.5 %

Fe+2 0.65 %

Gangue 5.3 %

CaO 37 %

MgO 11 %

SiO2 38 %

Al2O3 14 %

6.3 Experimental devices and procedures

Experimental tests were conducted in a rector for

reducibility tests. The equipment includes an 18 Kw furnace,

reactors to conduct iron ore reduction and control it, and

instrumentation, as it is shown in Figure 3. This laboratory is

fully prepared to make comparative reducibility ore tests. It is

possible to change the temperature, gas flow, pressure and charge

to which the pellets are exposed to.

A bed of 500 gr. of dry ore pellet were placed inside a

12

reactor. This reactor consists in two concentric tubes in such a

way that the inlet gas pass between the internal wall of the

external tube and the external wall of the internal tube, and

leaves it through the ore bed placed inside of the internal tube

(Figure 4). The reactor has a thermocouple in contact with the top

of the ore bed and another on bottom for temperature controlling.

It is important to notice that this experimental device gives

information of an iron ore bed reduced in batch process, and

simulation of bed conditions is an aim of this work. Searching for

constants is the first application of simulation model. In order

to simplify search for constants, each reducing stage was

conducted independently (Tables I through IV) so there is just one

set of constants to seek in each stage.

A 10 lts/min flow of high purity nitrogen is passed through

the sample until the testing temperature is reached and stabile,

after this is done, the appropriate gas is injected and the weight

loss is registered.

The flow control is made by calibrated flowmeters and the gas

composition is checked by chromatography analysis. The water vapor

amount in gas is indirectly measured.

During the reduction the sample looses weight until all the

oxygen has been removed. In this kind of test, the sample is

heated by radiation and conduction. In order to simulate a real

bed, in a second part alumina pellets where placed on top and

bottom of the ore bed, while the reactor walls where covered with

an insulating wool. All these avoids the instability of the gas

13

flow entering into the bed, some results are presented in figures

5 through 9.

6.4 Experimental procedures for pilot plant tests

Pilot plant consist in a vertical steel cylindrical reactor

with wall covered of refractory and insulator layers, inlet gas

which passes through pellet bed, is at top and wasted gas leaves

reactor at bottom. There are several thermocouples and takes for

gas analysis along reactor. Reactor is fully instrumented with

central data acquisition and control for temperatures, pressures,

gas flows, gas compositions.

General characteristics of this reactor are shown in Table

VI, this information is provided to simulation model. Cages of ore

sated at same positions than thermocouples and test points for gas

analysis, these cages are recovered after tests for a chemical

analysis in order to have thermal and chemical data.

Preparation for test consists of charging reactor. Depending

on the kind of test it is possible to heat the ore bed with hot

nitrogen, air or a selected gas until it reach desired

temperature. If a reducing gas is used, then a reduction will

start too. Timing for tests in this work starts when gas is

getting in reactor, thus heating and reduction starts at same

time. Selected gases are shown in Table VII. Most used gas is

shown in column three.

Normal criteria to define the end of process is taking

temperature at bottom of bed, looking evolution of gas composition

14

or flows between inlet gas and outlet gas.

Table VIGeneral Data

Item Value

Density of refractory 2300 Kg/m3

Refractory's heat capacity 1178 J/Kg oC

Density of insulator 800 Kg/m3

Insulator's heat capacity 1154 J/Kg oC

Apparent density of bed 1900 Kg/m3

Density of a single pellet 4222.2 Kg/m3

Pellet's heat capacity 957.6 J/Kg oC

Reactor's diameter 0.914 m

Radius of a single pellet 6.35 x 10-3 m

Thickness of refractory 0.0762 m

Thickness of insulator 0.1016 m

Pellets' thermal conductivity 0.5 W / m oC

Refractory's thermal conductivity 1.441 W / m oC

Insulator's thermal conductivity 0.255 W / m oC

Refractory and insulator masses 1.749 & 0.956 m tons

Pellet mass 3.4 m tons

Height of bed 3.20 m

Table VIIChemical analysis of used gases for reduction

and operation temperatures

Temp. 950 oC 950 oC 900 oC 800 oC 800 oC

vol %

H2 23.12 14.8 24.14 27.14 48.80

15

CO 10.61 15.8 10.52 10.19 16.06

CO2 04.35 09.60 04.53 05.15 08.09

H2O 15.29 12.80 15.23 14.71 26.56

N2 46.60 46.00 45.57 42.77 00.27

CH4 < 0.01 01.00 < 0.01 0.034 0.123

10. RESULTS AND DISCUSSION

10.1 Simulator adjustment

Simulator is based on basic principles, which governs the

process behavior by using a set of functions and equations with

constants experimentally determined. First part of simulator

adjustment is to take constant values from those already published

[9,10,11,12,13,14,15,16] for heat transfer in beds, on the other

hand, reducibility tests at laboratory are used to determine

kinetic constants for iron ore reduction following those above

proposed.

With this set of parameters simulator is tested by

comparisons between model results with actual pilot plant data.

Constant values were adjusted until model reproduced experimental

results. Constants has a physical sense which not was changed

along adjusting, constants still having their sense and magnitude

order that represent. These constants are including effects that

are not described separately, such as Sherwood and Schmidt

numbers, which are related with bed and flow conditions for

convective transfer, and Knudsen diffusivity coefficient for

16

diffusion in a pellet. Model presented in this work is a

simplification, which reproduces experimental data and gives a

very straight criteria for determining the end of process.

One of the experimental runs is showed on Figure 10, which

presents thermal profile of reactor at the different thermocouples

position along z axe, and its evolution with time, it is possible

to see that temperature at the beginning of test is almost

constant around boiling temperature water, thus it is shown that

it is very important to consider condensation - boiling phenomena

inside model.

Heat transfer coefficients inside simulation model are moving

in order to achieve the same temperature profiles obtained at

pilot plant, and it is necessary to take into account that could

be interactions between phenomena which are not considered in

mathematical model, but they are, as it was pointed before,

included inside of constants. Boundary phenomena such as diffusion

of gas in the layer of reaction products and interaction of the

phase-boundary reaction with diffusion in the reacting layers are

in adjusted constants because there are many effects that can not

be evaluated in a single way (combined effects of the phase-

boundary reaction, gas flow, diffusion in reacting layers, and

diffusion in the end products reaction).

Kinetic constants were evaluated from reducibility tests and

cages located inside reactor in know places (same positions than

thermocouples). Kinetic reductions are strongly important because

it has influence on temperature profiles and gas conversion

17

kinetics.

Kinetics of reduction gas conversion was calculated from

analysis of samples of gas obtained along reactor at the same

positions than thermocouples, this kinetic was adjusted until

model gives the same results than chemical analysis. All of the

profiles (bed temperature, wall temperature, iron ore reduction

degree and chemical gas composition) were reproduced.

When constants satisfy all of these conditions then the

simulation model is complete and can be used, curves in Figure 11

were obtained using the simulator and the results are in good

agreement with actual data. With this model, next step is to

calculate reduction time, and with this information it is possible

to calculate specific consumption of gas for certain given

conditions, which helps to give an advice on operation conditions.

10.2 Simulator validation

Due to the objective of this work is oriented to make

predictions about reduction time, at this point, with specific

operation conditions, different than those used for model

adjustment, this simulator gives results which had been compared

with tests carried out in pilot plant and exhibits a good

agreement. Figure 12 shows a curve for reduction time as a

function of reducing gas flow at one given temperature and

composition, this curve was obtained by using the model, and

experimental data from runs are plotted. Notice that when gas flow

is not enough to compensate heat loss the time to finish reduction

18

is too long, and when gas flow is very high there is a kinetic

frontier imposed by process.

With this information and including the reducing gas

generation it is possible to get specific consumption.

Some adjusted parameters and functions are presented in Table

VIII through XI, gas properties, thermal and thermodynamic

constants are already published in several books and papers.

Previous work [17] with this kind of atmosphere shows that

reduction with carbon monoxide is about one fifth of hydrogen,

thus in this case water shift reaction outside pellet is

considered.

Table VIIIAdjusted parameters and functions

(Kinetics)

Parameters and functions Remarks

)T

6000(- 45 = Ap

mhexp

Kinetic constant for reductionfrom hematite to magnetite withhydrogen

19

)T

2600(- 0.36 = Ap

whexp

Kinetic constant for reductionfrom magnetite to wustite withhydrogen

)T

2600(- 0.18 = Ap

f hexp

Kinetic constant for reductionfrom wustite to metallic ironwith hydrogen

5A = A m

mh

c

Kinetic constant for reductionfrom hematite to magnetite withcarbon monoxide

5A = A w

wh

c

Kinetic constant for reductionfrom magnetite to wustite withcarbon monoxide

5A = A f

fh

c

Kinetic constant for reductionfrom wustite to metallic ironwith carbon monoxide

Table IXAdjusted parameters and functions

(Kinetics)

Parameters and functions Remarks

)R-(1 H A = R m2gmm hh ρ Reduction rate forhematite to magnetite withhydrogen

K+1)R-R( O)H K-H( A = R

w

wm2w2gwm

h

hhh ρReduction rate formagnetite to wustite withhydrogen

20

K+1)R-R( O)H K-H( A = R

f

fw2f2gff

h

hhhρ

Reduction rate for wustiteto metallic iron withhydrogen

)R-(1 CO A = R mgmm cc ρ Reduction rate forhematite to magnetite withcarbon monoxide

K+1)R-R( )CO K-(CO A = R

w

wm2wgww

c

ccc ρReduction rate formagnetite to wustite withcarbon monoxide

K+1)R-R( )CO K-(CO A = R

f

fw2fgff

c

cccρ

Reduction rate for wustiteto metallic iron withcarbon monoxide

Table XAdjusted parameters and functions

(Gas-gas reactions)

Parameters and functions Remarks

)T

9000(- 2 = p

expλApparent kinetic constant forwater shift reactionCO+H2O=CO2+H2

OHH CO K = CO

2

2shiftmequilibriu

CO calculated from equilibriumof water shift reaction

21

CO+COCO-CO = CO

mequilibriu

mequilibriumdegreeequilibriu-non

CO non equilibrium degree inaccordance with water shiftreaction

)T

12000(- 0.04 = p

expβApparent kinetic constant formethane reforming reactionCH4+H2O=3H2+CO

All of this reactions have a thermal contribution on system,

this contribution is integrated to mass and heat balance

equations.

Table XIAdjusted parameters and functions

(Gas-gas reactions)

Parameters and functions Remarks

K OHH CO P = CH

reforming2

32

2

4 mequilibriu

CH4 calculated from equilibriumof methane reforming reaction

CH+CHCH-CH = CH

44

44

4

mequilibriu

mequilibriu

mdegreeequilibriu-non

CH4 non equilibrium degree inaccordance with methanereforming reaction

22

CO C = GIP mdegreeequilibriu-non2

g1 λρCO coming from water shiftreaction

CH C = BETAP 4

2

g1 mdegreeequilibriu-nonβρ

CH4 coming from methanereforming reaction

11. CONCLUSION

When reproduction of experimental data is achieved, including

thermo-chemical profiles inside reactor and time to reduction, it

is possible to say that model is already validated and its results

are in this scope reliable. It is clear that simulator represents,

under different conditions, the general behavior of reactor.

With a model of simulation of this kind there is another

potential tool for reactors design, and a very important advance

in statistic experimental designs, besides, it is possible to make

a sensibility analysis of different process variables and

operational conditions.

Even when by adjusting model it is not possible to give

values for each phenomena in pellet and bed (i.e. diffusion

resistance), adjusted parameters gave good results about bed

behavior. Further studies will permit to determine the limitations

of this simulation model and if it is necessary to made

modifications.

23

Finite difference method gives the opportunity to pass

directly to moving bed by changing elements conditions and places.

This model gives a criteria to determinate the end of a batch

process, also gives information about specific consumption of

reducing gas, and the chance to modify and test different

atmospheres at different temperatures.

11. NOMENCLATURE

ais the pellet radius.

Amhis the kinetic term for reduction from hematite to magnetite

with hydrogen.

Amcis the kinetic term for reduction from hematite to magnetite

with carbon monoxide.

Afh and Awh

are kinetic terms for reduction from wustite to iron and from

magnetite to wustite respectively with hydrogen.

Afc and Awc

are kinetic terms for reduction from wustite to iron and from

magnetite to wustite respectively with carbon monoxide.

Ap and Ar

are respectively pellet area and refractory area.

Cg and Cp

are respectively heat capacities of gas and pellet.

COis carbon monoxide partial pressure.

Dis the reactor diameter.

Ggis the gas flow.

24

H2is hydrogen partial pressure.

H2Ois partial pressure of water vapor.

Hg and Hgp

are coefficients for heat transfer in the iron ore bed and gas-

pellet.

Kb and Kp

are coefficients for heat conduction in refractory and pellet.

Kwh, Kfh, Kwc and Kfc

are thermodynamic constants for reduction from magnetite to

wustite and wustite to metallic iron with hydrogen and with

carbon monoxide respectively.

Kshiftequilibrium constant for water shift reaction.

Kmethane

equilibrium constant for methane reforming reaction.

Kfh and Kwh

are thermodynamic equilibrium constant for reduction from wustite

to iron and from magnetite to wustite respectively, with

hydrogen.

Mg and Mp

are the masses of gas and pellet.

prai

are coefficients for heat transfer coefficient of refractory-

insulator-environment system.

Qmhrepresents activation energy for reduction from hematite to

magnetite with hydrogen.

25

Rm, Rmc and Rmh

are reduction degree for hematite to magnetite, reduction degree

due to carbon monoxide and hydrogen.

Rf and Rw

are reduction degrees of reaction from wustite to iron and from

magnetite to wustite.

Ta, Tg, Tf, Tm, Tp and Tr

are respectively temperatures of insulator, gas, system wall,

environment, pellet and refractory.

tis the time coordinate

Wgis the molecular weight of gas

zis the coordinate along reactor cylinder

αgis the heat conduction coefficient of gas

εbis the refractory thickness

ρais the apparent density of iron ore bed

ρpis the pellet density

μgis the gas viscosity.

ρgis reducing gas density.

ACKNOWLEDMENTS

J. A. gives the thanks to the CONACYT (National Science and

Technology Council) for its support along this work.

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26

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13-Seth (B.B.L), Ross (H.U.).- Application of a generalized rate

equation to the gaseous reduction of iron oxide. Canadian

Metallurgical Quarterly, v. 5, nº 4, p. 315-328

14-The making shaping and treating of steel 10th edition:

Association Of Iron And Steel Engineers, 1988

15-Fuentes (R.), Aguilar (J.) Núñez (C.), et al..- Heat transfer

and reduction to wustite of a bed of hematite pellets, Report

DIM/10/02-040 HYLSA, June, 1989.

16-Fuentes (R.), Aguilar (J.) Farías (L.).- Mathematical modelling

of the behavior of different gases for reduction from

hematite to wustite in the HYLSA pilot fixed bed plant,

Report DIM/01/06-073 HYLSA, November, 1989.

17-Fuentes (R.), Aguilar (J.).- Reduction from hematite to

wustite, Report DIM/01/04-22, November, 1988.

28

29

Figure 1.Scheme of a reactor of fixed bed reduction (TR-nrepresents thermocouple positions along reactor)

30

Figure 2.Flow diagram for the simulation of direct reductionprocess

31

Figure 3. Reducibility Laboratory

32

Figure 4. Reducibility reactor scheme

33

Figure 5. Experimental data reduction from hematite to magnetiteat 650oC with H2/H2O = 41/59

34

Figure 6. Experimental data reduction from magnetite to wustite at750oC with H2/H2O = 58/42

35

Figure 7. Experimental data reduction from wustite to metalliciron at 850oC with H2/H2O = 84/16

36

Figure 8. Reducibility test, 800oC, 55 liters/minute, (55% H2, 21%CO, 14% CO2, 10% N2)

37

Figure 9. Reducibility test, 950oC, 55 liters/minute (55% H2, 21%CO, 14% CO2, 10% N2)

38

Figure 10.Reduction test of pellet from hematite to wustite,charge of 4400 Kg.

39

Figure 11.Simulation of run showed in Figure 10

40

Figure 12.Reduction time against flow of reducing gas (samecomposition than figure 11)