FIELD OF INVENTION:
The present invention relates to a process and method of increasing the strength of
briquettes produced from wastes generated in iron and steel industry using ladle
furnace slag as binder.
BACKGROUND AND PRIOR ART TO THE INVENTION:
In an integrated iron and steel plant, a number of iron bearing by-products are
generated which are not suitable for further processing and are termed as “Wastes”
and disposed normally in landfill. Moreover these wastes are in fine form varying in
granulometry and cannot be directly recycled in their fine form. Therefore, these
need to be agglomerated.Agglomeration method of sintering, pelletizing and
briquetting are common practices in iron and steel industries for converting iron ore
fines, minerals and solid wastes into blocks and lumpy sizes for various metallurgical
uses. Depending upon the nature of the metallurgical fines and wastes, its
granulometry and rheology, Fe-content, associated minerals and oil contamination,
many process developments have been made for the production of briquettes by
both hot and cold methods.
The briquetting of the wastes is technically viable, economically attractive and
environmental safe way for reuse and recycling of the wastes from the iron and steel
industry. The briquettes contain iron - bearing wastes of the iron and steel
manufacturing process for the purpose of replacing iron ore hence, reduce the
depletion of the earth’s limited natural resources which is getting scarce.

Briquetting of waste materials as an aggregate for smelting furnaces of an iron
foundry, containing hydraulic binders in the form of MgO filter dust and limestone
dust is described by Thomas Bilke, Patent No. EP0861909 A1. Similarly, use of
cement and water as a binder in briquetting of iron containing dust from foundry
operations is reported by Manfred DrRosmann et al., in Patent No. DE19509366 A1.
Briquetting of mill scale, iron-ore fines, iron pellet fines using granulated blast
furnace slag cement and bentonite as binder is reported by Eugene A. Bogdan et al.,
Patent No. US5395441 A.Briquetting process having approximately 50% metallic
fines, 41% mill scale, 2% bentonite, 3% pitch residue, 2% burnt lime fines, and 2%
molasses is described by Robert R. Strange, Patent No. US4369062 A.
Use of hydrated high-alumina cement as the binder for briquetting iron ore fines,
sinter fines, BOF and EAF dusts, mill scale is reported by Jay Aota et al., Patent No.
US6676725 B2.Addition of small amount of bentonite enhanced the strengths of the
pellets at elevated temperature.
Briquetting iron oxide fines at lower temperatures with a binder, such as bituminous
coal, pitch, molassess, sulfite liquoror the fines can be briquetted at high
temperatures without a binder is described by Brisse Andre H et al., Patent No.
US3174846 A.
Mixture of cupola-furnace top-gas filter dust and small particle residue from
punching and cutting, which is pressed to form a briquettes and can subsequently
charge in cupola furnace for cast iron production and is described in Patent No. DE
44 16 699 A1. Cupola-furnace top-gas filter dust contains approximately 5% to 12%
sulphur and sulphur containing compounds which increases the viscosity of the melt
and hardness of the casting.

Slag-forming briquettes from filler dust and foundry sand using sulphite lye as a
binder is illustrated in Patent No. DE 43 08 294 A. The adverse effect of sulphur
compound upon the melt is mentionedabove; moreover the concentration of SO2
and SO3 increases in wastes gas.
Briquetting of iron containing steel-works dust in a rotary hearth furnace at 500oC in
an inert atmosphere, without the application of binder is described in Patent No. DE
37 32 351 A1.
Briquetting of filter dust from foundry industry using natural binders such as glucose
syrup, maize starch etc. is described in Patent No. DE 42 07 265 A1.
Briquetting of ferrous and non-ferrous ores using ordinary Portland cement as a
binder is reported in Patent No. Patent No. JP 80, 100, 940. The briquettes are
cured for 3 days at ambient temperature and then steam curing at 100° C followed
by drying at 100o to 500° C.
Briquetting of iron ores by using 5 to 15% basic slag as a binder is accounted in
Patent No. JP 60 33 319. The briquetting process involves hardening at 200o C and
then curing under steam for the development of strength.
Use of ordinary portland cement as a binder for iron ore briquetting is illustrated in
Patent No. 8135, 731. The process involves heat treatment for 1 day at 90o C and
then drying for 1 hour at 90o C. the briquettes attain strength of 256 Kg.
Cold bonded iron ore pellets by using mixture of chlorides salts and ordinary
Portland cement as activator is described in Patent No. USSR 730, 844.

Non-sintered iron ore pellets by using mixture of cement clinkers and limestone as a
binder is illustrated in Patent No. JP 7711103.
The setbacks of the aforesaid inventions are the use of various types ofexpensive
natural, organic or inorganic binding materials such as ordinary Portland cement,
bentonite, molasses, glucose syrup, maize starch, lime, tar, basic slag, earth
materials, chloride salts, sulphite lye, bituminous coal, pitch, blast furnace slag,
sulfite liquor, limestone, dolomite by both hot and cold methods which include
compacting under pressure,followed by curing at ambient temperature, under steam
at 90o to 150o C and then drying at atmospheric temperature or at 90o to 500o C in
furnace to achieve adequate strength. Furthermore, the presence of alkalis,
chlorides, sulphates in the binding materials not only addsimpurities to the melt but
also increases the concentration of SO2, SO3and various other hazardous gases in
waste gases. Hence, there is a need for a technically viable, economically attractive
and environmental safe way of agglomerating iron rich steel plant wastes which
overcomes the aforementioned limitations.
OBJECTS OF THE INVENTION
The main objective of the present invention is to develop a briquetting process for
iron and/ or carbonbearing wastes oxides by using ladle furnace slag as a binder.
Another objective of the invention is to develop briquettes suitable for charging into
a furnace which overcomethe drawbacks as aforementioned above.
Another object of the present invention is toproffer an briquetting process that
produce value added products from steel plant wastes more efficiently to meet the
objective of zero waste or green steel concepts.

One more object of the present invention is to proffer abriquetting process that
replaces the use of different types of binders that contains various impurities which
are deleterious for the metallurgical operations.
Still another object of the present invention is to proffer a briquetting process is to
reduce the depletion of earth’s limited natural resources produced by discharging
untreated waste.
Furthermore object of the present invention is to proffer a briquetting process that
accepts a wide variety of wastes that differ in granulometry to convert into a form
which gives improved mechanical and metallurgical properties.
SUMMARY OF THE INVENTION
Accordingly, this invention relates to development of briquetting composition with
ladle furnace slag as a binder. The typical binders used in briquetting operations are
ordinary Portland cement, bentonite, molasses, glucose syrup, maize starch, lime,
tar, basic slag, earth materials, chloride salts, sulphite lye, bituminous coal, pitch,
blast furnace slag, sulfite liquor, limestone and dolomite.A typical ladle furnace slag
comprises 25 - 60% by Wt. CaO, about 8 – 30% by Wt. of Al2O3 + SiO2, about 1 -
5% by Wt. of MgO.
This invention provides a process for briquetting of iron bearing metallurgical
dust/fines/sludge/mill scale/agglomerate wastesproduced in steel plants, mixed
together with sufficient amount of Ladle furnace slag as a binder, burnt lime fines
and water to form a homogenized moist mix. The moist mix is then compacted
under load to form briquettes of any preferred shape, preferably pillow shaped
bodies under high pressure in a roll type press. The amount of binder is optimized to
provide briquette with adequate mechanical strength to avoid excessive degradation
in handling at ordinary temperatures, and also to withstand temperatures and
conditions encountered in iron making and or steel making furnaces. The amount of
water is adjusted to provide a uniform shape and complete hydration to ensure

complete setting.The green briquettes thus formed are cured by moisture treatment
under humid atmospherefor 1 to 6 days and water spraying for the next 3 to 10
days and thereafter drying them under sunlight for next 1 to 4 days. The cured
briquettes are then fed into the furnace and heated to a temperature of around 500
oC, as such to increase the metallurgical strength of the briquettes by the formation
of hedenbergite phase and by the oxidation of wustite to hametite.These briquettes
can be used in any either Blast furnace or Rotary Hearth Furnace for iron making or
used in LD Convertor for Steel making.
DETAILED DESCRIPTION OF THE INVENTION
A process for briquetting of iron and or carbonbearing metallurgical dust/fines/
sludge/mill scale/agglomerate dust using ladle furnace slag as a binder comprises of
the following steps:
(a) Mixing of about 40% to about 80% metallurgical dust/fines/sludge/mill
scale/agglomerate dust having size less than 6 mm with about 10% to about
50% ladle furnace slag, optionally along with about 2% to about 4% of
hydrated burnt lime fines to form a homogenized dry mixture. Burnt lime
fines are added to provide green strength to the briquettes.
(b) Adding of about 4% to about 10% water to the dry mixture from step (a)
sufficient enough to fully hydrate ladle furnace slag binder and uniformly
mixing so as to form a homogenized moist mixture.
(c) Compacting the moist mixture from step (b) in a cylindrical mould under load
to form briquettes of any preferred shape, preferably pillow shaped
bodiesunder high pressure in a roll type press.
(d) The green briquettes from step (c) are then subjected to three different
stages of curing for 7 to 14 days.The green briquettes were covered with
polythene or humidified by spraying water or kept in a humid container/room
for the first 1 to 3 days to provide a humidified atmosphere. The humidified
briquettes were subsequently water cured for next 3 to 7 daysat ambient
atmosphere, followed by sun - dry curing for next 2 to 4 days.

(e) Heating of the cured briquettes from step (c) or (d) in a kiln to temperature
of about 300 to about 800 oC to further increase the metallurgical strength by
oxidation of wustite to hametite and by the formation of hedenbergite phase.
Application case study:
This example demonstrates strength enhancement of LD Sludge briquettes by
heat treatment. The chemistry of raw materials used in the experimentsis shown
in Table 1

The briquetting composition as per the current invention comprises LD sludge in the
range of 25 to 93 by weight % and Ladle furnace (LF) slag in the range of 5 to 50
weight %. The composition further comprises lime in the range of 2 to 10 weight%.
The LD sludge varies preferably in the range of 40 to 85 wt.%and weight
percentage is generally varied as per the granulometry/fineness of the waste oxide
fines. SimilarlyLadle Furnace slag composition varies preferably in the range of 12 to
18 wt.%.
Mix proportion was thoroughly mixed in a Muller mixer for 5 minutes to form a
homogeneous dry mix and the blend was mixed further with 10% water solution
containing 2% lime, until a uniform mixture was obtained which takes around 15
minutes. The mixture was then compressed in a roller press to form pillow shaped

briquettes.The briquettes thus produced are subject to three different stages of
curing. The specimens were covered with polythene for 3 days to provide a
humidified atmosphere. The cover was removed and the specimens were
subsequently water cured for next 7 days, followed by sun - dry curing for next 4
days.The cured briquettes were introduced in a kiln and heated to temperature of
400oC. Due to heating the wustite present in the briquettes get oxidized to hematite
and the formation of hedenbergite phase was observed which further enhances the
strength of the briquettes. The XRD analysis of the heat treated briquettes is shown
in Table 2.

The strength of the briquettes increased significantly when heated at 400 °C for 1
hour. Cold crushing strength, which is a measure of compressive loading, increased
from 42 kg/piece to 98 kg/piece. Similarly, tumbler index (+6.3 mm fraction), which
is a measure of impact and vibrational loading during transportation found to be
71.9 % when compared with LD lump iron ore with tumbler index of 74.5 % (shown
in Figure 1).

The increase in strength of briquettes could be attributed to the formation of
hematite and hedenbergite phases.
Initial phases in the briquette sample contained magnetite (12%), Wustite (13%),
Calcium catina silicate (6%), and andradite (68%). On heating at 400 °C for 1 hour,
these phases disappeared and hematite and hedenbergite phases formed.
Hedenbergite itself is a solid solution chain of augite and diopside.
Mechanism of strengthening due to formation of Hedenbergite and Hematite is
explained below:
Step 1: Mix consist of Initial phases in the briquette sample-
At initial step, a mixture of different phases like magnetite, Wustite, calcium catina
silicate, andradite etc. were found to be present in briquette sample(shown in Figure
2).
Step 2: Precipitation of hedenbergite and hematite nucleation
As the sample is heated in normal air atmosphere, Magnetite and Wustite start
getting oxidized and other phases start getting transformed to another phases
(shown in Figure 3)..
Step 3: Hedenbergite molecule chain growth and hematite grain growth
Size enlargement of hedenbergite solid solution chain and hematite grain growth
occurs. Henedenbergite monoclinic structure nucleates and grows in the vicinity of
already existing hedenbergite phase. Hedenbergitephases are bonded to each other
(shown in Figure 4)
Step 4: Interlocking of Hedenbergite and Hematite phases
Hedenbergite and hematite phase formation increases and then completes after
which they gets interlocked with each other to provide the strength of the briquettes
(shown in Figure 5).

Step 5: Precipitation of Hematite phase from hedenbergite and its bonding
with already existing hematite
Hedenbergite itself is a solid solution chain of augite and diopside. Augite on heating
in oxygen atmosphere with small amount of moisture converts into goethite by the
reaction.
Augite + water + oxygen = Kaolinite + Goethite + Solution
Also on heating at 400 degree Celsius, goethite converts to hematite
2FeO(OH) = Fe2O3 + H2O
Moisture for conversion of augite to goethite will be available from hydrated
moisture present in the cured briquettes. Since, briquettes were heated in air
atmosphere so oxygen also will be available for augite to goethite conversion
reaction.
Due to heating, goethite formed from augite will convert to hematite and will form
bonding with hematite which is already existing. This phenomenon increases the
strength of briquettes significantly (shown in Figure 6).
It is to be understood that the invention is not limited by the specific example and
embodiment described hereinabove, but includes such changes and modifications as
may be apparent to one skilled in the art upon reading the appended claims. The
invention of the current invention provides a mechanism to reuse recycle steel
wastes in an effective fashion. The process and composition of the briquettes
produced as per the current invention reduces the environmental hazard and at the
same time makes the whole steel making process further energy efficient.

WE CLAIM:
1. A process for briquetting of iron and or carbon bearing steel plant by
products, , the process comprising:
a) mixing iron and or carbon bearing steel plant by productshaving size less
than 6 mm with ladle furnace slag;
b) adding 4% to 10% water to the dry mixture from step (a) to fully hydrate
ladle furnace slag binder and uniformly mixing so as to form a
homogenized moist mixture;
c) compacting the moist mixture from step (b) in a roller press to form
briquettes of pillow shape under high pressure in a roll type press; and
d) heating the green briquettes from step (c) in a kiln to a temperature of
200 oC to 800 oC so as to precipitate hedenbergite phase and oxidation of
wustite to hematite.

2. The process as claimed in claim 1, wherein the iron and or carbon bearing
steel plant by productsis selected from the group consisting of metallurgical
dust, fine sludge, mill scale, agglomerate dust, ladle furnace slag and mixture
thereof.
3. The process as claimed in claim 1 further comprising the step of optionally
adding hydrated burnt lime fines to the iron and or carbon bearing steel plant
at step a) or step b).
4. The process as claimed in claim 1 further comprising the step of curing
briquettes from step (c).
5. The process as claimed in claim 4, wherein curing of the briquettes is done by
humidifying the briquettes for 1 to 3 days, followed by water curing for 3 to 7
days at ambient atmosphere, followed by sun - dry curing for 2 to 4 days.

6. The process as claimed in claim 2, wherein LD sludge varies in the range of
25 to 93 by weight %, preferably in the range of 40 to 85 wt.%.
7. The process as claimed in claim 1, wherein Ladle furnace (LF) slag varies in
the range of 5 to 50 weight %, preferably in the range of 12 to 18 wt.%.
8. The process as claimed in claim 3, wherein burnt lime varies in the range of 2
to 10 weight%.
9. The process as claimed in claim 1, wherein the briquettes were heated at step
d) in the range of temperature from 200 to 800 oC, preferably in the range of
200 to 400oC.
10. The process as claimed in claim 1, wherein hedenbergite phase varies in the
range 10 to 80 weight %, preferably in the range of 30 to 70 weight %.
11. The process as claimed in claim 7, wherein hematite phase varies in the
range 10 to 80 weight %, preferably in the range of 30 to 70 weight %.
12. A briquetting composition for steel making and blast furnace operations as
claimed in any of the preceding claims, the briquetting composition
comprises:
LD sludge in the range of 25 to 93 by weight %; and
Ladle furnace (LF) slag in the range of 5 to 50 weight %
Wherein hedenbergite phase of briquetting composition varies in the range 10
to 80 weight %, and hematite phase varies in the range 10 to 80 weight %.

13.The briquetting composition as claimed in claim 12, wherein hedenbergite
phase preferably varies in the range of 30 to 70 weight %.
14. The briquetting composition as claimed in claim 12, wherein hematite phase
varies preferably in the range of 30 to 70 weight %.
15.The briquetting composition as claimed in claim 12, wherein tumbler index of
the briquetting composition is in at least 71%.