Blast Furnace Operation with 100% Extruded Briquettes Charge

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Industrial stiff vacuum extrusion briquettes (BREX) producing line can efficiently provide for the small-scale blast furnace (BF) operation with 100% briquetted charge. Physical and metallurgical properties of the BREX are being investigated. A new effect of the non-linear strengthening of the BREX bonded with the combined Portland cement and Bentonite binder is described. Application of this combined binder results in the local maximum of the cold compressive strength of the BREX on third day of strengthening. Hot strength mechanism of the BREX is explained and was found to be related with creation of the metallized shell on their surface, sintering of the iron-containing particles and further creation of the metallicc phase surrounded by the silicates and ferrites. The addition of the iron ore fines to the BREX composition can improve their sintering during reduction thus helping to keep the integrity of the agglomerates. Results of the industrial operation of the small-scale BF with BREX are analyzed. The consumption of coke in the BF at 100% of BREX does not exceed 500 kg/t compared with 680 kg/t for the smelting without BREX.

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ISIJ International, Vol. 55 (2015), No. 1, pp. 175–182

# Blast Furnace Operation with 100% Extruded Briquettes Charge

Aitber BIZHANOV, 1)* Ivan KURUNOV, 2) Yogesh DALMIA, 3) Bhagiratha MISHRA 3) and Srishti MISHRA 4)

1) J. C. Steele & Sons, Inc., 710 South Mulberry Street, Statesville, NC 28677 USA. 2) Novolipetsk Steel (NLMK), pl.
Metallurgov 2, 398040, Lipetsk, Russia. 3) Suraj Products Ltd., 770017, Sundargarh, Orissa, India.
4) IGIT, 759146 Sarang, Dhenkanal, Odisha.

( _Received on September 2, 2014; accepted on October 20, 2014_ )

Industrial stiff vacuum extrusion briquettes (BREX) producing line can efficiently provide for the smallscale blast furnace (BF) operation with 100% briquetted charge. Physical and metallurgical properties of
the BREX are being investigated. A new effect of the non-linear strengthening of the BREX bonded with
the combined Portland cement and Bentonite binder is described. Application of this combined binder
results in the local maximum of the cold compressive strength of the BREX on third day of strengthening.
Hot strength mechanism of the BREX is explained and was found to be related with creation of the metallized shell on their surface, sintering of the iron-containing particles and further creation of the metallicc
phase surrounded by the silicates and ferrites. The addition of the iron ore fines to the BREX composition
can improve their sintering during reduction thus helping to keep the integrity of the agglomerates.
Results of the industrial operation of the small-scale BF with BREX are analyzed. The consumption of coke
in the BF at 100% of BREX does not exceed 500 kg/t compared with 680 kg/t for the smelting without
BREX.

KEY WORDS: extrusion briquette (BREX); stiff vacuum extrusion; small-scale blast furnace; coke rate; hot
strength.

1. Introduction

For many years almost all major metallurgical plants in
the world have accumulated millions of tons of blast furnace
(BF) and steelmaking sludge, containing a significant
amount of zinc oxides. The main method of such wastes
recycling is their utilization at the sintering plant as the
charge component for production of the sinter in quantities
limited by the allowed zinc income to the blast furnace. The
economic efficiency of this technology is provided by the
partial replacement of the concentrate by the cheap sludge.
However, the addition of such sludge in the sintering charge
has a negative impact on the stability and quality of the sinter. More promising and environmentally friendly way of
recycling of the sludge is their briquetting and subsequent
use of briquettes in the BF. Thus, in addition to the improving of the stability and sinter’s quality, carbon of the BF
sludge in the briquettes is used as the reducing agent, whereas in the sinter process it almost does not work. A new concept in the BF sludge recycling includes the manufacture of
briquettes from a mixture of sludge with iron ore concentrate and their utilization as the charge component of the
blast furnace. The sludge is being removed from the sintering charge and the zinc incomes to the blast furnaces with
briquettes do not exceed the established limits. The economic efficiency of this recycling technology is provided by the
replacing of the expensive merchandise pellets, reduction of

the coke consumption by smelting of the carbon-containing
briquettes and by the improvement of the sinter quality after
the sludge removal from the charge of sinter plant.

At the beginning of the 20’s of the last century the briquetting technology – the only agglomeration technology
available at that time - has been widely used for the agglomeration of the iron ore fines and waste. For example, briquettes share in the charge of BF plant “West” in the Calbe
(Germany) reached 30–40%, and in the low-shaft BF plant
Maxhütte (Germany) -100%. These briquettes were made
from iron ore fines, coke and limestone dust. 1) In the BF
plant of the Kuvshinovskyi metallurgical plant (Russia) the
share of the briquettes in the charge was as high as 25%.
Briquettes in amounts up to 100 thousand tons per year were
used in the BF of the Kerch and Taganrog metallurgical
plants (Russia). 2) However, with the advent and development of high-productive iron ore and concentrates sintering
method briquetting was not able to compete with this new
technology due to the low capacity of the briquetting equipment.

briquettes from a mixture of sludge with iron ore concen- At present time the agglomeration of the anthropogenic
trate and their utilization as the charge component of the and natural iron containing substances by cold briquetting
blast furnace. The sludge is being removed from the sinter- with the mineral or organic binders is obtaining increasing
ing charge and the zinc incomes to the blast furnaces with application in BF production. Three basic briquetting techbriquettes do not exceed the established limits. The econom- nologies are being applied – roller-pressing, vibropressing
ic efficiency of this recycling technology is provided by the and the stiff vacuum extrusion. Application of the stiff vacreplacing of the expensive merchandise pellets, reduction of uum extrusion for the agglomeration of fine ores and dis
perse metallurgical wastes has been mastered in the early

- Corresponding author: E-mail: abizhanov@jcsteele.com 21th century by the J. C. Steele&Sons, Inc. (USA). This
DOI: http://dx.doi.org/10.2355/isijinternational.55.175 modern technology comprises pushing of the homogeneous

ISIJ International, Vol. 55 (2015), No. 1

wet (moisture contents 12–16%) mix of the substances
under the pressure of 3.0–3.5 Mpa through the die holes
under the vacuum in the working chamber of the extruder.
In 2012 the term BREX (briquettes of extrusion) has been
introduced to distinguish these kinds of agglomerates from
traditional briquettes. 3) The capacity of the industrial stiff
extruders of J. C. Steele ranges from 15 to 115 tons per hour.
The self-cost for the production of one ton of the BREX varies
from 2 to 10 USD depending on the extrusion line capacity.

The first application of the auger extrusion for agglomeration of ore and metallurgical wastes took place in the 90ies of the 20th century when the industrial stiff extrusion
briquetting line with the capacity of 20 tons per hour of the
sludge and flue dust briquettes was commissioned at the
Bethlehem Steel company (USA). 4) These briquettes were
melted in blast furnaces. The line was in operation till 1996
up to the cessation of main production.

2. Industrial Stiff Extrusion Briquetting Line

In April 2011 the industrial stiff extrusion line based on
the Steele 25 Extruder for the production of the sludge, BF
dust and iron ore fines briquettes for the small-scale BF was
commissioned in Rourkela (West Bengali, India). 5) The
capacity of this line is 20 tons per hour, or an average 6 000
tons per month with two shifts per day working schedule
and 20 working days per month, which fully meets the
requirements of the BF in agglomerated charge.

Stiff Extrusion relies on heavy duty augers to create high
pressures for forging materials through forming dies. As the
materials are pressed through the augers and dies under high
pressure and shear there is a lot of particle breakdown that
occurs within the material mass. The particle breakdown
that occurs is unique to the Stiff Extrusion process and the
affect is to produce a particle size distribution that improves
the “extrudability” of the material. This high pressure and
shear has the added benefit of intensively mixing the materials to a high degree of homogeneity. The most unique
aspect to Stiff Extrusion is the use of vacuum. The combination of high auger pressure and vacuum de-airing results
in a tougher agglomerated product, even in the green state,
that can withstand multiple handling operations. The stiff
extrusion process typically requires less binders and additives.

This step involves subjecting the material to an intense
vacuum prior to extrusion in order to remove all of the compressible air from the material before it is compressed under
high pressure. The end result is a much stronger and more
durable agglomerated product. This feature is not expensive
although the effect adds great benefit. It should be noted that
the application of vacuum requires specialized vacuum sealing mixers - Pug Sealers. The volumetric dosing is applied
for the charge components and is being implemented by the
automatic loader, which creates the stockpile of the charge
mix (but the cement), taking each single component from
separate stockpiles located at the open air areas. Charge mix
is also being fed to the hopper of the briquetting line by
loader where from it goes through the homogenizing mixers
to the extruder.

The blended material is loaded into a Steele 88E Even
Feeder at the start of the process. Output from the feeder

Fig. 1. Stiff extrusion under the vacuum process diagram.

goes into the primary mixer, a Steele Model 25A Pug Sealer.
These “Pug Sealer” mixers have a high pressure screw section which intensively mixes the materials. A second 25A
Pug Sealer is next in line. This machine sits on top of the
extruder and not only mixes intensively but also seals for
vacuum ( Fig. 1 ).

The mix enters the vacuum chamber being partially
agglomerated and due to the presence of a high vacuum
inside the chamber and removal of the air and moisture
these agglomerates immediately crumbles to isolated particles that drop down at the blades of the extruder’s auger.
The vacuum is maintained throughout the working volume
of the extruder. The application of the vacuum has its result
in the lower content of the binder required for the BREX to
achieve the design level of the mechanical strength when
compared with the traditional briquetting technologies. For
BF applications the average amount of Portland cement is
less than 6–8% of the BREX mass against 10–12% usually
required for the vibropressing technology.

A model 25B Vacuum Extruder completes the process by
pressing the material mixture through the extrusion dies
under high pressure and vacuum. The green BREX from the
extruder are directed into a covered stockpile where they
cure of at least 3 days. Due to the high pressure of the extrusion and the mixture’s deairing in the vacuum the green
BREX at the exit of the extruder dies have a dense structure,
high initial strength and plasticity. This allows the transportation and the stockpiling of the BREX for strengthening
without any fines generation. The general layout of the
industrial extrusion agglomeration line is given in Fig. 2 .

2.1. Raw Materials
The main components of the brex are – steel-making (LD;
Linz-Donau process sludge) and BF dust, iron ore fines. The
binder and plasticizer are the Portland cement (OPC53) and
the Bentonite. Phase compositions of these substances are
given in Table 1 .

Chemical composition of the BREX is given in Table 2 .
Grains sizes of these component’s particles are as follows: iron ore fines - 80–82% of particles smaller than 1
mm; BF dust – 75-7% of particles smaller than 0.149 mm;
LD sludge – 43-47% of particles smaller than 0.149 mm.
For Portland cement the typical particles surface area is larger than 4 000 cm 2 /g. Bentonite particles – up to 75–90%
smaller than 0.074 mm. Chemical composition of the binder
and plasticizer are given in Table 3 .

ISIJ International, Vol. 55 (2015), No. 1

Fig. 2. General layout of the industrial extrusion agglomeration line with capacity of 20 tons per hour for blast furnace.

Table 1. Phase composition of the BREX components.

BREX component Main phases Minor phases

Goethite, Gibbsite,
Iron ore fine Hematite
Kaolin, Pyroxene

Magnetite, Hematite,
Blsat furnace dust
Graphite

Wustite, Quartz,
Dicalcium aluminate

LD sludge Magnetite, Wuestite Wollastonite, calcite

Table 2. Chemical composition of the BREX components.

%

BREX
Fe2O3/FeO SiO2 CaO MgO Al2O3 TiO2 C Fetotal
components

Iron ore
78.5 5.6          -          - 5.4 0.8          - 53.5
fines

Blast furnace
51.5 6.3 4.9 0.2 5.1          - 30.5 35.6
dust

LD sludge 87.5 0.6 9.5 1.2 0.3 - - 64.0

Table 3. Chemical composition of the binder (Portland cement)
and plasticizer (Bentonite).

%

Elements Portland cement OPC53 Bentonite

CaO 63.2 0.8

SiO2 20.5 58.4

Al2O3 4.5 12.6

Fe2O3 4.2 10.6

MgO 2.1 0.3

K2O + Na2O 0.6 4.4

SO3 2.6

LOI 1.5 9.4

2.2. BREX Physical Properties and Cold Compressive
Strength
We have selected the BREX of the following composition
for the cold compressive strength (CCS) testing: 47.2% LD
sludge, 28.3% BF dust, 18.9% iron ore fines, 4.7% Portland
cement and 0.9% Bentonite. Chemical composition of the

Fig. 3. Distribution of the pores with the sizes larger than 100 μm.

BREX after curing: Fetotal-43–48%; CaO 11–13%; SiO2 7.2–
7.7%; Al2O3 -4.30–5.9%; MgO 2.9–3.9%; LOI (hydrated
water + carbon) 11–11.9%, (СаО/SiO2) = 1.4. Distribution
of these main components inside the BREX body was discovered to be very uniform. Their concentrations in the
“core” and in the “shell” of the BREX were as follows (%):
Fetotal-45.11 and 45.25; CaO-12.59 and 12.96; SiO2-7.68 and
7.26; Al2O3-5.16 and 5.01; MgO 3.53 and 3.70. Cement and
Bentonite were blended in the dry state manually (Portland
cement is 75% and Bentonite is 25%) and added to the mixture before the Pug Sealer. This combined binder’s share in
the BREX varies from 6 to 8%. For the chosen BREX samples we have measured daily: CCS, apparent density and
porosity. Compressive strength was measured on a “Tonipact 3000” (Germany) in accordance with the standard DIN
51067. Cylindrical samples sizes for testing were: diameter
32.6 mm and height 60 mm. Density was measured using
scales Metler (USA).

Apparent porosity was measured according to DIN
51056. We have also applied X-ray computed high resolution computed tomography system Phoenix V|tome|X S 240
(General Electric, USA) in order to investigate the macro
pores with the sizes larger than 100 μm. Figure 3 shows this

ISIJ International, Vol. 55 (2015), No. 1

Table 4. Values of physical properties of the BREX during
strengthening.

Strengthening
duration, days

Apparent
porosity,%

Density,

Density, Cold compressive

g/cm 3 strength, kg/cm 2

strength, kg/cm 2

1 31.5 2.42 24

2 25.4 2.66 45

3 32 2.43 63

4 27 2.44 52

5 27.2 2.45 56

6 26.2 2.45 57

7 26.8 2.46 59

8     -     - 75

9     -     - 80

Fig. 4. Porosity and cold compressive strength during strengthening.

distribution to be sufficiently uniform thus promoting for
the reducibility.

The measurement results for the apparent porosity and
CCS are listed in Table 4 and illustrated by Fig. 4 .

The strengthening curve has a local maximum on day
three followed by the day of the strength loss and then by
its final growth. The BREX compressive strength value on
the day three is about 84% of its value after a week of
strengthening. Almost the same is the character of the apparent porosity change except the very first day of the strengthening. Reduction of the porosity value is obviously connected
with the Bentonite swelling leading to the filling of the pore
space.

Samples of the BREX kept their integrity during the compressive and tensile splitting tests on the third day of curing
exhibiting the viscous-plastic behavior. Despite the almost
complete development of cracks during the splitting test on
the third day of curing both halves of the BREX continued
to be coupled. Compressive and tensile splitting tests on the
day seven showed complete loss of the viscous-plastic
destruction.

Such effect of the non-monotonic strengthening of briquette on the cement binder with the presence of local maximum of the strength accompanied by the viscous-plastic
destruction under the external load has not been previously
experienced and has not been described in the literature. In
the described phenomenon the significant is the fact that the
cement-bentonite composite binder changed the behavior of
the BREX reducing the probability of its brittle fracture.

Fig. 5. Needle-like particles of cement (Ettringit) in the BREX surrounded by the bentonite flakes. SEM image (magnification
10 000).

In our view, this BREX behavior is due to the properties
of the cement-bentonite binder and is the result of creation
of the coagulation structure in the cement-bentonite-water
system leading to modifications of the properties of the
binder. The driving force of the creation of such structures
is the attraction of the negatively charged particles of bentonite to positively charged particles of Portland cement,
leading to very rapid mutual coagulation of particles and to
the formation of the structure, with the weighed particles of
cement. Hydrating cement particles are being gradually covered by impermeable shells of the flake type particles of
bentonite. The amount of adsorbed bentonite particles is
proportional to the activity of cement. In the process of
hydration the cement particles increase in volume, which
leads to the tension and disrupt the integrity of bentonite
membrane and to water penetration inside the cement particles, leading to their further hydration and to the increased
adsorption of bentonite. Gradually this coagulation structure
will collapse as a result of coagulating action of calcium
ions and will be replaced by a structure of hardening cement
stone. The remains of this structure can be illustrated by Fig.
5 obtained by the Scanning Electronic Microscopy (SEM)
with the help of AURIGA ® CrossBeam ® workstation (Carl
Zeiss) combined with the energy dispersing spectrometer
INCA X-Max. Reduced strength, observed on the third day
after the peak, can be explained by the destruction of structures. Further increase in strength is fully controlled by the
cement hydration.

The effect we found can have the practical value,
comprised in the possibility to utilise the BREX on cementbentonite binder as a component of the charge of metallurgical furnaces on the third day of drying under natural
conditions, thus leading to the significant reduction of the
required storage size of finished BREX.

Another distinctive feature of the BREX is that they have
a considerable length at the exit from the extruder’s die. Following transportation via conveyors and subsequent reloading and stacking, the final length of the extrusion product is,
usually, not more than two-to-three times its diameter. The
mechanism of this fragmentation has been explained by
Bizhanov _et al._ 6) and is related with the bending of the elon

ISIJ International, Vol. 55 (2015), No. 1

Table 5. Iron ore and BREX metallization and reducibility comparison.

Temperature,

°C

Femet
(Iron ore/BREX), %

Fetotal
(Iron ore/BREX), %

Metallization
(Iron ore/BREX), %

Reducibility
(Iron ore/BREX), %

1 000 2.16/14.20 67.48/60.50 3.20/23.50 35/48

1100 12.69/20.96 69.52/61.70 18.25/33.97 52/62

1 200 17.65/30.36 70.25/63.70 25.10/47.66 61/72

1 300 30.33/44.74 73.3/65.60 41.30/68.20 65/80

1 400 53.75/47.04 80.79/67.46 66.53/69.70 82/88

1 500 84.25/79.22 90.40/80.87 93.20/97.95 93/99

gated BREX under their own weight at the exit of the
extruder’s die leading to the formation of the zones of stress
concentration. Finite element simulation process of fragmentation of the elongated BREX was made with the use of
Simulia Abaqus software system. Maximum stress zones
and the areas of the fracture initiation have been identified.
In case when the fixed length of the BREX will be required
these extruders are usually equipped with the cutters.

3. BREX Reducibility and Hot Strength Mechanism

In order to better understand the behavior of the BREX
in BF we have compared their reducibility with that of the
iron ore. For this purpose we have used the following testing
procedure. A hollow alumina tube having length 1 000 mm,
outside diameter 85 mm and inside diameter 75 mm makes
the test chamber. Weights of the BREX and iron ore samples
were taken before and after their smelting at 1 300°C for 30
minutes. BREX and iron ore samples are placed in graphite
crucible inside of alumina crucible covered by coke breeze
having size 1–5 mm throughout the diameter engulfing the
graphite crucible completely. Thickness of the coke breeze
layer is 25 mm. Then it is blocked by perforated plug from
both sides and is covered by the insulation. Water-cooled
metallic clamps are fitted in both sides of alumina tube. Vacuum pump is connected in one of the clamp along with air
supply connected with flow meter. Before staring the heating, the inside chamber of the alumina tube is evacuated up
to 0.5 mbar. The furnace was switched on with a heating rate
of 10°C/minute and when the temperature reached 800°C air
supply was started at a rate of 10 liters /minute till the completion of the test. Both BREX and iron ore samples were
fired from 1 000°C to 1 500°C for 2 hours in step of 100°C.

Reducibility was calculated based on the oxygen loss calculations. Metallic Fe and metallization degree were evaluated.
Total and metallic Fe contents, metallization and reducibility
values of iron ore and BREX samples are given in Table 5 .

It follows from these data that the BREX shows better
metallization and reducibility in comparison with the iron
ore fines which also means that they will show also better
values when compared with the lumpy ore since the reducibility of the iron ore depends strongly on the lump size. 7)

The reason for this is evidently related with the presence of
the carbon in the BF sludge which promotes for better carbothermic reduction due to the close contact of the iron
oxides and the carbon. This carbon is represented mainly by
the coke breeze. Another reason for the BREX good reducibility is related with the dynamics of changes of porosity

Cold BREX 25.8 2.60

500 33.66 2.67

1 000 37.36 2.81 9.6

1100 37.28 2.61 12.5

1 200 46.87 2.56 78.5

1 300 29.71 3.08 80.1

1 400 22.6 3.19 85.4

*– not cured BREX

Table 7. The phase composition of the BREX at different temperatures.

Phase (mass share,%)/temperature, °C 950 1 000 1 300 1 400

Hematite (Fe2O3) 22.1 18.6 n/o 4.2

Magnetite (Fe3O4) 47.0 49.2 2.3 16.6

Wustite (FeO) 10.7 3.4 24.8 34.5

α-Fe n/o n/o 31.2 12.0

Gehlenite (Ca2Al2SiO7) 3.8 5.4 16.0 11.9

Larnite (β-Ca2SiO4) 16.4 23.4 17.1 15.2

Calcium ferrite (CaFe2O4) n/o n/o n/o 2.6

Dicalcium ferrite (Ca2Fe2O5) n/o n/o 8.7 3.1

Quartz (SiO2) n/o n/o n/o n/o

Calcite (CaCO3) n/o n/o n/o n/o

during heating

Table 6 shows how the not cured BREX apparent porosity, density and reducibility vary with the temperature of the
firing under the reduction atmosphere. The porosity values
remain at sufficiently high level up to 1 200–1 300°C which
strongly contributes to the BREX reducibility.

The phase composition of the BREX samples fired during
2 hours at different temperatures has been determined by
ARL 9900 XRF series with integrated XRD capability
(Japan). The results are given in Table 7 .

Using these date we have investigated the mechanism of
the hot strengthening of the BREX under the reduction
atmosphere. The specially prepared samples of the BREX
reduced during 2 hours at different temperatures were analyzed with the help of the Leica DFC300 FX Digital Color
Camera. Figure 6 shows different stages of the BREX

Table 6. BREX * properties at different temperatures.

BREX
temperature, °C

Apparent
porosity %

Density
(gm/c 3 )

Reducibility

ISIJ International, Vol. 55 (2015), No. 1

Fig. 6. Optical microscopy of the BREX strengthening during heating under the reduction atmosphere. 1-950°C; 21 000°C; 3-1 100°C, BREX shell region; 4-1 300°C; 5-1 300°C (another view); 6-1 400°C. Magnification 200.

strengthening (magnification 200).

It follows from these photos that the sintering of the
grains starts at T = 1 000°C. At T = 1100°C the crust is
being formed by sintered grains on the surface of the BREX.
This helps to strengthen the shell of the BREX and to support the BREX. Inside the BREX the further sintering is taking place at T = 1 300°C. We can witness at this temperature
that iron ore grains reduce faster than those of the LD sludge
and BF dust due to the higher activity of the “virgin” substance in comparison with the substances which had already
underwent high temperature treatment. 8) The concentration
of the Gehlenite (sorosilicate) increases whereas the concentration of the island silicate Larnite decreases at this temperature. These both silicates are known to exhibit good
binding properties at the presence of free CaO and MgO
which are present in the LD sludge and in the BF dust. 9) All

these substances create a new binder which supports the
BREX at high temperatures during its reduction and metallization. Worth to mention that the presence of the Larnite
and Gehlenite has been discovered during the investigation
of the reduction behavior of cold-bonded briquettes under
simulated BF conditions. 9) The detailed investigation of the
role of these silicates in the BREX strengthening will
follow.

At T = 1 400°C one can see the structure of the metal surrounded by the silicates and ferrites. This mechanism coincides generally with the mechanism of the strengthening of
the vibropressed briquettes described by Kurunov _et al_ . 10)

Thus the metallization of the surface layer of the agglomerated product helps to keep the integrity during its reduction
with the creation of the metallic phase supported by the silicates and ferrites matrix.

ISIJ International, Vol. 55 (2015), No. 1

4. Results and Discussions

Based on the above mentioned results of the investigations it has been decided to try to achieve maximum possible
share of the BREX in the charge of the industrial small-scale
BF with the volume equal to 45 m 3 (useful volume 40.01
m 3 ). The BF is equipped with: skip hoist with the skip volume of 0.5 m 3, double-cone charging device, and hydraulic
equipment for notch service, hot blast stoves and two-stage
dry gas-cleaning system (dust collector and seven modules
of the bag filters). BF has eight air tuyeres and one iron
notch. The furnace is cooled by external watering. Produced
cast iron is immediately poured by the casting machine and
slag is granulated. Cast iron and granulated slag are being
shipped to the customers by trucks.

With the two shifts working schedule the extrusion line
produces 200 tons of BREX per day (12 castings per day).
A required amount of the washing BREX made of the manganese ore fines (–3 mm size) with 5% of Portland cement
as the binder are also produced according to the operation
schedule. The BREX in amount of 100–135 tons per day are
being melted in the Blast Furnace.

The operation has started in the May 2011 with 10% of
the BREX in the charge. Then this share has been gradually
increasing. When working on the charge consisting of 80%
of the BREX and 20% of iron ore, the coke consumption
decreased by 150 kg/t of cast iron (22%) in the result of the
decrease of the carbon content in the BREX and by the withdrawal of the charge of raw fluxes. Lowering of the BF performance by 15% while switching to the new charge with
BREX was mainly due to lower iron content in this charge
by 7.2% compared to the charge consisting of the iron ore
and raw fluxes. Further increase of the BREX share in the
charge was not possible because of the excessive increase in
basicity of slags caused by the high basicity of the BREX
in the result of the LD sludge presence.

During the development of the BF regimes with this new
type of briquetted charge we had to go to the new lower level of the stockline in the furnace due to the difficulties
encountered in the dry gas cleaning system. Gradual
increase in the share of the BREX in BF charge resulted in
a lowering of the temperature of the furnace top gas and
increased its moisture content. As a result the bag filters get
clogged with the wetted dust and their regeneration by the
reverse pressure pulses has not reached the positive effect.
Stockline lowering helped to increase the furnace top gas
temperature and the bag filters sticking stopped. Lowering
of the stockline virtually had no impact on the performance
of BF mainly due to the iron oxides of the BREX are being
reduced by the dispersed carbon contained in them. At the
same time it has been decided to increase the iron ore fines
share in the BREX from 9.45% up to 18.9% which has also
contributed to the better BF performance due to the mentioned above better sintering and higher value of the activity
of the “virgin” iron ore substance when compared with the
sludge and dust which already have undergone high-temperature processing once.

For more than 2.5 years the BF has worked successfully
with the charge containing 80% of the BREX and is now
(August 2014) for already ten months this BF works with
the 100% briquetted charge.

Successful practice of the BREX utilization as the primary, and then the only component of the BF charge became
possible due to their good metallurgical properties corresponding with the requirements of the ironmaking throughout the life cycle of the BREX from the moment they exit
the extruder’s die and till the formation of cast iron in the
blast furnace. Indeed, on the way from the extruder to stockpile and then to the ready goods warehouse the BREX do
not generate fines. Negligible amount of fines can only be
generated during the BREX loading by the fork-lift trucks.
This allows to avoid the fines screening before the charging
the BREX to the BF without any damages for blast furnace.
Skips with the BREX do not contain any fines and their
pouring from the bunker to skip and from skip to charging
device of BF is not accompanied by the dust generation.

In the BF when lowering from the top the BREX do not
collapse and preserve its integrity up to the softening and
further melting in cohesion zone. The results of the wide set
of the high-temperature testing of the BREX of different
composition in reducing atmosphere confirm this conclusion. 11) All the BREX when heated at a speed of 500°С/h up
to 1150°С and a half-hour excerpt at that temperature and
then cooled in an inert atmosphere kept its shape °С.

The BF operation parameters with different shares of the
BREX in the charge are given in Table 8 .

Table 8. BF operation parameters.

Blast furnace operation
parameters

Consumption, kg/t:

100%
iron ore

80%
BREX

100%
BREX

iron ore 1 500 372 372

BREX - 1 425 1 960

Limestone 150 -

dolomite 144 - 29

scrap 132 -

Quartzite - - 13

washing Mn ore BREX - 19 75

Coke 680 530 490

Iron content in the fluxed
57.6 50.4 45.5
charge*,%

Furnace capacity, t/m 3 в сут. 1.9 1.62 2.0

Blast temperature, °С 925 900 1 000

Tuyere pressure, kg/cm 2 0.5 0.34–0.38 0.38–0.42

Pig iron chemistry, %:

Si 1.0–1.8 1.0–1.5 0.8–1.1

Mn 0.2 0.4–0.5 0.7–0.8

C 3.8–4.0 3.75–3.90 3.80–3.95

S 0.050–0.060 0.038–0.050 0.038–0.042

Pig iron temperature, °С 1 380–1 440 1 400–1 450 1 410–1 450

Slag chemistry, %:

CaO 34.86 33.12 38–39

SiO2 31.98 30.23 30.0–32.0

Al2O3 23.87 17.98 16.0–18.8

MgO 9.46 9.48 8.0–9.5

FeO 1.01 1.26 0.6–1.15

*–without СО2 and fluxes

ISIJ International, Vol. 55 (2015), No. 1

As it is seen, despite the high specific heat loss, due to
the small size of the blast furnace, and low blast temperature, the consumption of coke in the BF at 100% of BREX
does not exceed 500 kg/t, which corresponds to the modern
high-efficiency furnaces with iron content of 58–59% in
charge with a temperature of 1 200°С and with the blast
overpressure of gas on furnace top equal to180–250 kPa.
This is the consequence of the self-reducing nature of the
BREX (due to the presence of carbon in BF dust) and of
their basicity, providing the necessary basicity of BF slag.
The latter allowed eliminating use of the limestone. Additions of the quartzite and dolomite were applied in order to
adjust the slag basicity and magnesia content in the slag. As
a result the coke consumption for the 100% of the BREX in
the charge has fallen on about 200 kg/t compared to the
100% rich iron ore charge operation of blast furnace. It can
also be seen that Si content in pig iron has approached the
level typical for large blast furnaces. The total self-cost of
the BREX is less than 11 USD for one ton (including all
expenses and the binder cost) which helps to this BF to
operate with positive economic efficiency.

5. Conclusions

From the results of more than three years of the industrial
cats iron production by the small-scale BF with the BREX
as the major and an exclusive charge component it follows
that:

(1) Stiff vacuum extrusion provides for the metallurgical properties of the BREX which meet the requirements of
the BF process with a lower level of the binder content compared with traditional briquetting technologies.

(2) BREX have sufficient mechanical strength to with

stand the transportation and further handling, including
stockpiling and further feeding to the BF without generation
of the fines.

(3) Application of the combination of the Portland
cement and the Bentonite can lead to the local maximum of
the BREX mechanical strength on third day of its curing.

(4) BREX have sufficient porosity to ensure their good
reducibility.

(5) Strengthening of the BREX during their heating
under the reduction conditions comprises the creation of the
metallized shell on their surface, sintering of the ironcontaining particles and further creation of the metallicс
phase surrounded by the silicates and ferrites.

(6) BREX can be used as the major or exclusive charge
component of the small scale blast furnaces sufficiently
improving their economic attractiveness.

REFERENCES

1) B. M. Ravich: Briquetting in Ferrous and Non-Ferrous Metallurgy,
Metallurgy, Moscow, (1975), 232.
2) A. G. Astakhov, A. I. Machkovskyi, A. I. Nikitin, N. V. Fedorovskyi:
Handbook of Sinter Plant Worker, Tekhnika, Kyiv, (1964), 448.
3) A. M. Bizhanov: BREX, Trademark Certificate No. 498006, (2013).
4) R. B. Steele: Proc. of 23rd Biennial Conf., IBA, USA, (1993), 205.
5) Y. K. Dalmia, I. F. Kurunov, R. B. Steele and A. M. Bizhanov: _Met-_
_allurgist_, (2012), No. 3, 39.
6) A. M. Bizhanov, I. F. Kurunov, N. M. Durov, D. V. Nushtaev and S.
A. Ryzhov: _Metallurgist_, 56 (2012), 489.
7) O. A. Esin and P. V. Geld: Physical Chemistry of Pyrometallurgic
Processes, Part 1, Mettallurgisdat, Moscow, (1962), 671.
8) Ya. E. Geguzin: Physics of Sintering, Nauka, Moscow, (1967).
9) A. Kempainen, M. Iljana, E.-P. Heikkinen, T. Paananen, O. Mattila
and T. Fabritius: _ISIJ Int._, 54 (2014), 1539.
10) I. F. Kurunov, T. Ya. Malysheva and O. G. Bolshakova: _Metallurgist_,
(2007), No. 10, 41.
11) I. F. Kurunov, A. M. Bizhanov, D. N. Tikhonov and N. R. Mansurova:
_Metallurgist_, (2012), No. 6, 44.

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