1

EFFECT OF MOISTURE CONTENT ON

TURNDOWN TEMPERATURE AT LD#1

SUMMER INTERNSHIP 2017

PRESENTED BY:

Keerthik Mohanan

Kevin George

Under the auspice of

Mr. Amarnath Mukherjee, Sr. Manager PSM,LD1

Mr. Abhinav Singhvi, Manger PSM,LD 1

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DECLARATION

I Keerthik Mohanan student of Mahatma Gandhi University Id No 14002956

hereby declare that the internship Report is submitted by me in partial
fulfilment of the requirement for the award of the degree of Bachelor of
Technology

Place: Jamshedpur

Date: 11-08-2017
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CONTENTS
1) Acknowledgement
2) The TATA group
3) TATA steel
4) Plant layout
5) Importance of steel
6) Overview of the BOS process
7) BOF structure side
8) Hot metal
9) Oxygen Lance technology
10) Basic operation
11) Importance of slagin LD
12) Iron ore addition
13) Blow practices
14) Turndown conditions
15) Blowing control and turndown
16) Turndown control
17) Correction of temperature and analyses
18) Reblow
19) The automation model
20) Problem facing in LD1
21) Cause and effect diagram
22) Aim
23) Sample study and moisture testing
24) Calculation work
25) Heat Comparison of wet and dry iron ore
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Acknowledgement

Great success can only be attained when we have the shoulders of colossus to
stand over and look yonder. At Tata Steel we met people who have excelled in
their respective fields. They have proved time and again that they are the ones
who are shaping the present and future of this great institution. Holding our
hands, they have guided us through this endeavour, morphing and shaping the
technical as well as operational aspect of our outlook

Mr Amarnath Mukherjee, Sr Manger primary steel making, LD#1 our guide who
gave us his precious time; shared with us his insight and experiences,
appreciated us and inspired us throughout our stay we thank him profusely for
being a wonderful mentor.

Mr. Zachariah Chacko our co-guide is acknowledged for being our pillar of
strength and our motivator who made us dream big and channelled our efforts
in the right direction

Mr Abhinav Singhvi, who constantly oversaw our proceedings and who left no
stone unturned to make our experience at Tata Steel wonderful.

Sincere thanks to SNTI team for making all the arrangement and safety
training.

I would like to thank my own College, AMAL JYOTHI COLLEGE OF ENGINEERING

and Department of Metallurgy for giving us an opportunity to do an internship
at TATA Steel

Special thanks to all the operators at PSM, LD1, who contributed selflessly in
making us understand the whole working of the vessel and control room.

A special thanks to everyone at TATA Steel who touched our lives in the due
course and made us feel at home. We are proud to visit this beautiful city of
Jamshedpur

Keerthik Mohanan

Kevin George
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The TATA Group

The TATA Group: A Legacy of Trust

TATA is India’s largest and most diversified business conglomerate with more
than 100 operating companies spread over 85 countries in six different
continents, employing 350,000 people, TATA companies share five core values-

 Integrity
 Understanding
 Excellence
 Unity
 Responsibility

Each TATA company agrees to the TATA code of conduct by signing the TATA
Brand Equity and Business Promotion Agreement with TATA Sons Ltd. This
ensures adherence to the TATA ethos and value system. Adherence to ethics
and excellence and the commitment towards serving communities have been
at the core of TATA’s unblemished growth and sustenance for over 140 years.
This heritage evokes trust and goodwill among consumers, employees,
shareholders and the larger community. Today, the TATA name is a unique
asset representing ‘Leadership with Trust’. This legacy has earned the
admiration of the group’s stakeholders in a manner few business houses can
ever hope to match.

The business operations currently encompass seven business sectors namely:

 Engineering
 Materials
 Services
 Energy
 Customer products,
 Communications and IT,
 Chemicals
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The major companies in the group of TATA include:

 TATA Steel
 TATA Motors
 TCS
 TATA Power
 TATA Chemicals
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TATA Steel
Established in 1907, TATA Steel is more than 100 years old company and is
among the top ten Global Steel companies. It is now one of the world’s most
geographically-diversified steel producers, with operations in 26 countries and
a commercial presence in over 50 countries.

The TATA Steel Group, with a turnover of US$ 22.8 billion in FY’ 10, has over
80,500 employees across five continents and is a Fortune 500 company.

TATA Steel’s vision is to be the world’s steel industry benchmark through the
excellence of its people, its innovative approach and overall conduct.
Underpinning this vision is a performance culture committed to aspiration
targets, safety and social responsibility, continuous improvement, openness
and transparency.

TATA Steel’s larger production facilities include those in India, the UK, the
Netherlands, Thailand, Singapore, China and Australia. Operating companies
within the group include TATA Steel Limited (India), TATA Steel Europe Limited
(formerly Corus), Natsteel, and TATA Steel Thailand (formerly Millennium
Steel).

TATA Steel has believed that the principle for mutual benefit- between
countries, corporations, customers, employees and communities- is the most
effective route to profitable and sustainable growth.

TATA Steel limited is a multinational steel company headquartered in Mumbai,

India and subsidiary of TATA group. It is the tenth largest steel producing
company in the world with an annual steel crude capacity of 23.88 million
tonnes(FY 17), and the second largest steel company in India(measured by
domestic production) with an annual capacity of 9.7 million tonnes after SAIL.

Tata Steel’s largest plant is located in Jamshedpur, Jharkhand, with its recent
acquisitions; the company has become a multinational with operations in
various countries. The company is listed on Bombay Stock exchange and
National Stock Exchange of India and employs about 80,500 people.

Tata Steels products include:

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 Cold/hot rolled coils and sheets

 Billets
 seamless bars(RCS, RDS & Gothic bars)
 forged rounds
 rolled & forged rings
 tubes & bearings

In an attempt to ‘ decommoditise’ steel, the company has introduced brands

like:

 Tata Steelium (the world’s first branded cold rolled steel)

 Tata Shaktee (galvanazed corrugated sheets)
 Tata Tiscon (rebars)
 Tata Bearings
 Tata Agrico (Hand tools and implements)
 Tata Wiron (galvanized wire products)
 Tata Pipes (Pipes for construction)
 Tata Structura (Contemporary construction Materials)

Apart from these product brands, the company also hass its folds a service
brsand called ‘STEEL JUNCTION”
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The Process Flow at TATA Steel

Vision

Its vision is to be the global steel industry benchmark for value creation and
corporate citizenship.

Tata Steel achieves its vision through :

 Its People

By fostering teamwork, nurturing talent, enhancing leadership capability and

acting with pace, pride and passion.

 Its Offer

By becoming the supplier of choice, delivering premier products and services

and creating value for its customers.

 Its Innovative Approach

By developing cutting edge solutions in technology, processes and products.

 Its Conduct

By providing a safe workplace, respecting the environment, caring for

communities and demonstrating high ethical standards.
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AWARDS AND ACHIEVEMENTS

 Tata Steel was awarded the ‘ 2015 World’s Most Ethical Company’
award under the Metals Category by the Ethisphere Institute. This was
the third time that Tata Steel won this award.
 The Ministry of Steel awarded Tata Steel the Prime Minister’s Trophy for
‘ Best Performing Integrated Steel Plant’ in the year 2010-11, thus
making it the eighth time that it received this award since the trophies
institution in 1992-93.
 In 2015, Tata Steel’s Climate disclosure received highest rating of 100 %
CDLI (Climate Disclosure Leadership Index) score.
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PLANT LAYOUT
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IMPORTANCE OF STEEL

Steel has had a major influence in our lives. The cars we drive, the buildings we
work in, the homes in which we live and countless other facets in between.
Steel is used in our electricity-power-line towers, natural-gas pipelines,
machine tools, military weapons-the list is endless.

Steel has earned a place in our homes in protecting our families, making our
lives convenient, its benefits are undoubtedly clear.

Steel is by far the most important, multifunctional and the most adaptable of
materials. The development of mankind would have been impossible but for
steel. The backbone of developed economies was laid on the strength and
inherent uses of the steel.

The characteristics of steel are:

 Hot and cold formable

 Weldable
 Suitable machinability
 Hard, tough and wear resistant
 Corrosion resistant
 Heat resistant and Resistance to deformation at high temperatures.

Steel compared to other materials of its type has low production costs. The
energy required for extracting from ore is about 25% of what is needed for
extracting Aluminium. Steel is environment friendly as it can be recycled. 5.6%
of element iron is present in Earth’s crust, representing a secure raw material
base.

Steel production is 20 times higher as compared to production of all non-

ferrous metals.

The steel industry has developed new technologies and has strived hard to
make the world’s strongest and most versatile material even better. There are
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altogether about 2000 grades of steel developed of which 1500 grades are high
grade steels. There is still immense potential for developing new grades of
steel with varying properties.

Steel has changed our world like no other substance. New high performance
steel allows a jet pilot to reach new heights, a surgeon to perform a delicate
operation. It is the solid rocket booster casings that allow shuttle astronauts to
explore new frontiers and the roller coaster ridden by a child. Each piece of
steel we make is engineered to fit precise specifications. It is an industry where
product quantity is measured by the millions of tons, but quality is measured
by the millionth of an inch.

The same utmost precision applies to the processes employed throughout

today’s steel plant. Tata Steel is truly a high-tech industry, with automation
and advanced technologies driving the way it does its business. Some of the
most advanced technologies available today are utilised throughout the steel
making process, which enables the industry to maximise the efficiency while
minimising the environmental footprint.
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OVERVIEW OF BOF PROCESS AT LD1

Oxygen steelmaking has become the dominant method of producing steel

from blast furnace hot metal. Although the use of gaseous oxygen (rather than
air) as the for agent for refining molten and scrap mixture to produce steel by
pneumatic processes received the attention of numerous investigator from
Bessemer onward, it was not until after World War ll that commercial success
was attained.

The primary raw materials for the BOP are 85-90% liquid hot metal from the
blast furnace and the balance is steel scrap. These are charged into the Basic
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Oxygen Furnace (BOF) vessel. Oxygen (>99.5% pure) is "blown" into the BOF at
supersonic velocities(1.5 times to that of speed of sound) and oxygen per
blow is around 7200 NM3. It oxidizes the carbon and silicon contained in the
hot metal liberating great quantities of heat which melts the scrap.Total Argon
of 25 Nm3 is purged from the bottom of the furnace for perfect stirring and to
maintain homogeneity throughout the bath during the process The post
combustion of carbon monoxide as it exits the vessel also transmits heat back
to the bath.

The product of the BOS is molten steel with a specified chemical anlaysis at
1590°C-1650°C. From here it may undergo further refining in a secondary
refining process or be sent directly to the continuous caster where it is
solidified into semi finished shapes: blooms, billets, or slabs.

Basic refers to the magnesia (MgO) refractory lining which wears through
contact with hot, basic slags. These slags are required to remove phosphorus
and sulfur from the molten charge
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BOF- THE STRUCTURAL SIDE

An operating BOF,consists of the vessel and its refractory lining, vessel

protective slag shields, the trunnion ring, a vessel suspension system
supporting the vessel within the trunnion ring, trunnion pins and support
bearings, and the oxygen lance. It consists of a spherical bottom, cylindrical
body and conical top with a tap hole in between the conical and cylindrical
portion.

The BOF vessel consists of the vessel shell, made of a bottom, a cylindrical
center shell (barrel), and a top cone; reinforcing component
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to the cone, such as a lip ring and top ring; auxiliary center shell and top cone
flanges for bolted-on top cones; auxiliary removable bottoms for bottom reline
access, or for individual bottom reline of bottom-blown vessels; and a taphole.
This list is not intended to be either restrictive or comprehensive, e.g., top
cone flanges are not universal.

BOF vessels can be one of the general classifications presented in. These are
top-blown vessels, in which the oxygen is injected above the hot metal bath by
means of a retractable lance; top-blown vessels, in combination with bottom
stirring, the latter usually by introducing metered amounts of inert gas at
specific locations under the hot metal bath—the introduction of the inert gas is
either through porous plugs or tuyeres; bottom-blown vessels, in which the
oxygen is injected under the molten metal bath through tuyeres arranged in
the bottom of the vessel, and usually carrying pulverized additives; bottom-
blown vessels utilizing a calculated source of heat energy provided by
hydrocarbon fuel, in a very similar arrangement as the bottom blown vessel;
and combination-blown vessels, in which the oxygen is introduced under the
bath through tuyeres in the bottom of the vessel, as well as above the bath
through a lance—the oxygen blown through the bottom usually carries
pulverized additives.

The Vessel Bottom: It is influenced by the process and the weight balance
required to optimize the tilt drive system. The common shape is torispherical.
For processes requiring the introduction of gases from thebottom of the vessel
(through tuyeres), the shape of the bottom tends to be flatter than those
which have only top blowing. Also, because some bottom stirring/blowing
processes pose more of a burden on the bottom refractory, the bottom is
designed to be interchangeable to enhance relining. For example, in the OBM
(Q-BOP) process, the refractory lining in the bottom of the vessel wears more
than twice as fast as that in the rest of the vessel. Therefore, the bottomis
replaced at mid-campaign. This also allows for the maintenance of the tuyeres.
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HOTMETAL

Hot metal is liquid iron from the blast furnace saturated with up to 4.3%
carbon and containing 1% or less silicon, Si. It is transported to the BOF shop
either in torpedo cars or ladles. The hotmetal chemistry depends on how
theblast furnace isoperated and what burden (iron bearing)materials are
charged to it. The trend today is to run at high productivity with low slag
volumes and fuel rates, leading to lower silicon and higher sulphur levels in
hot metals. If BOF slag is recycle, P and Mn level rise sharply since they report
almost 100 % to the hot metal. The sulphur level from the blast furnace can be
0.05 % but an efficient hot metal desulfurizing facility ahead of the BOF will
reduce this to blow 0.1%.AS mentioned above the most common
desullphuring reagents lime, calcium carbide and magnesium – used alone or
in combination are injected into the hot metal through a lance .the sulphur
containing compound report to the slag; however, unless the sulphur rich slsg
is skimmed before the hot metal is poured in to the BOF, the sulfur actually
charged will above the level expected from the hot metal analysis.
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OXYGEN LANCE TECHNOLOGY

In modern steelmaking production, a water-cooled lance is used as the

refining tool by injecting a high velocity stream of oxygen onto a molten
bath. The velocity or momentum of the oxygen jet results in the penetration of
the slag and metal to promote oxidation reactions over a relatively small area.
The jet velocity and penetration characteristics are functions of the nozzle
design. This section will discuss the design and operation of water-cooled
oxygen lances as they apply to modern steelmaking practices in the BOF.

Oxidation Reactions

The primary reason for blowing oxygen into steel is to remove carbon to
endpoint specifications. The principle reaction which results from theoxygen
lancing is the removal of carbon from the bath as CO. This is an exothermic
reaction which adds heat to the system. A small amount of CO2 is also
produced, but 90% or more is usually CO. As will be discussed later, the
burning of this CO inside the furnace by reacting with oxygen is called post-
combustion. Other elements such as Si, Mn, and P are also oxidized and are
absorbed in the slag layer. These reactions are also exothermic, further
contributing to the required heat to melt scrap and raise the steel bath to the
necessary temperature. The oxidation of the silicon is particularly important
because it occurs early in the oxygen blow and the resultant silica combines
with the addedlime to form the molten slag. Table below presents the
oxidation reactions during the steelmaking process.
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Supersonic Jet Theory

Nozzles are designed for a certain oxygen flow rate, usually measured in scfm
(Nm3/min), resulting in a certain exit velocity (Mach number), with the
required jet profile and force to penetrate the slag layer and react with the
steel bath in the dimple area.

Supersonic jets are produced with convergent/divergent nozzles, Figure below.

A reservoir of stagnant oxygen is maintained at pressure, Po. The oxygen
accelerates in the converging section up to sonic velocity, Mach = 1, in the
cylindrical throat zone. The oxygen then expands in the diverging section. The
expansion decreases the temperature, density, and pressure of the oxygen and
the velocity increases to supersonic levels, Mach > 1.

As the oxygen jet exits into the furnace, at a pressure P°, it spreads and decays.
A supersonic core remains for a certain distance from the nozzle. Supersonic
jets spread at an angle of approximately12°.

Proper nozzle design and operation are necessary both to efficiently produce
the desired steelmaking reactions and to maximize lance life. If a nozzle is
overblown, which means that the oxygenjet is not fully expanded at the time it
exits the nozzle, shock waves will develop as the jetexpands outside of the
nozzle. Useful energy is lost in these shock waves, and an overblown jet will
impact the steel bath with less force than an ideally expanded jet.

Nozzles are underblown when the jet expands to a pressure equal to the
surrounding pressure and then stops expanding before it exists the nozzle. In
this case, the oxygen flow separates from the internal nozzle surface. Hot gases
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from the steel vessel then burn back or erode the nozzle exit area. This erosion
not only decreases the lance life, but also results in a loss of jet force, leading
to a soft blowing condition. Overblowing and underblowing conditions are
demonstrated in figure below

This figure displays the major components of the BOF oxygen lance. These
include oxygen inlet fittings, the oxygen outlet (lance tip), which is made of a
high thermal conductivity cast copper design with precisely machined nozzles
to achieve the desired flow rate and jet parameters. Cooling water is essential
in these lances to keep them from burning up in the vessel. The lance barrel is
a series of concentric pipes, an outer pipe,an intermediate pipe and the central
pipe for theoxygen. Lances must be designed to compensate for thermal
expansion and contraction. The outer barrel/pipe of the lance is exposed to the
high temperatures in the furnace. As its temperature increase it expands and
the overall lance construction internally is constructed with O-ring seals and
various joints, but can accommodate the thermal expansion and contraction
while in service. The lance also has a stress-free design and it must be built
with mill duty construction quality to be able to withstand the normal steel mill
operating conditions.
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BASIC OPERATION

Once the hot metal temperature and chemical analaysis of the blast furnace
hot metal are known, a computer charge models determine the optimum
proportions of scrap and hot metal, flux additions, lance height and oxygen
blowing time.

A "heat" begins when the BOF vessel is tilted about 45 degrees towards the
charging aisle and scrap charge (about 10 to 15% of the heat weight) is
dumped from a charging box into the mouth of the cylindrical BOF.

The hot metal is immediately poured directly onto the scrap from a transfer
ladle. Fumes and kish (graphite flakes from the carbon saturated hot metal)
are emitted from the vessel's mouth and collected by the pollution control
system. Charging takes 3-4 minutes.

Then the vessel is rotated back to the vertical position and lime/dolomite
fluxes are dropped onto the charge from overhead bins while the lance is
lowered to a few feet above the bottom of the vessel. The lance is water-
cooled with a multi-hole copper tip(convergence-divergence Laval shaped
nozzle). Through this lance,oxygen of greater than 99.5% purity is blown into
the mix. If the oxygen is lower in purity, nitrogen pick up starts.

As blowing begins, an ear-piercing shriek is heard. This is soon muffled as

silicon from the hot metal is oxidized forming silica, SiO2, which reacts with
the basic fluxes to form a gassy molten slag that envelops the lance. The gas
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is primarily carbon monoxide (CO) from the carbon in the hot metal. The rate
of gas evolution is many times the volume of the vessel and it is common to
see slag slopping over the lip of the vessel, especially if the slag is too viscous.
Blowing continues for a predetermined time based on the metallic charge
chemistry and the melt specification. This is typically 15 to 20 minutes, and
the lance is generally preprogrammed to move to different heights during the
blowing period.

The lance is then raised so that the

vessel can be turned down towards the
charging aisle for sampling and
temperature tests. Furthermore, below
0.2% C, the highly exothermic oxidation
of iron takes place to a variabledegree
along with decarburization. The "drop"
in the flame at the mouth of the vessel
signals low carbon.

In some shops, sublances provide a

temperature-carbon check about two
minutes before the scheduled end of the blow. This information permits an "in
course" correction during the final two minutes and better turn-down
performance. However, operation of sublances is costly, and the required
information is not always obtained due to malfunctioning of the sensors.

Once the heat is ready for tapping and the preheated ladle is positioned in the
ladle car under the furnace, the vessel is tilted towards the tapping aisle, and
steel emerges from the taphole in the upper "cone" section of the vessel. To
minimize slag carryover into the ladle at the end of tapping, various "slag
stoppers" have been designed. These work in conjunction with melter's
eyeballs, which remain the dominant control device. Slag in the ladle results in
phosphorus reversion, retarded desulfurization, and possibly "dirty steel".
Ladle additives are available to reduce the iron oxide level in the slag but
nothing can be done to alter the phosphorus.
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IMPORTANCE OF SLAG IN THE LD PROCESS

Slag has in the LD-process various functions and roles.Primarily, it is

spontaneously formed by the non-volatileoxides resulting in the

oxidation of hot metal minorconstituents and iron (SiO2, MnO, P2O5, TiO2,
VOx, and FeO). In order to flux the impurity oxides to form a lowmelting, fluid
slag, lime and sometimes dolomite (a mixture of CaO and MgO) and, if
necessary, fluorspar (CaF2) are charged into the converter. Secondly, molten
slag is areaction environment for impurity elimination like desulphurization
and dephosphorization, although ladle treatments have diminished the
importance of the LD process in this respect. Slag, when forming an emulsion
with carbon monoxide and metal droplets—slag foaming—obviously plays
some role in post-combustion of primary carbon monoxide to carbon dioxide,
and affects the radiation heat transfer from the ‘hot spot’ formed in the
oxygen jet-iron melt impingement cavity, levelling out the temperature
distribution in the furnace. Foaming slag obviously also decreases dust
generation rate by absorbing some fraction of dust. From the slag formation
point of view, there are two limiting blowing practices:

1. Soft blowing with high lance position without inert gas bottom stirring,
characterized by low iron bath mixing intensity, and
2. Hard blowing with ‘low lance’ and bottom stirring (in combined blown
converters), characterized by more intensive iron bath mixing and
deeper interaction of oxygen jet with the bath.

In the firstcase the interaction of the oxygen jet with the iron bath
is‘superficial’, mass transfer from the bath interior is slowdue to weak mixing,
and iron is in the first place oxidized and slagged.
In the second case interaction between theoxygen jet and the bath, as well as
mass transfer from thebath interior to the superficial layers, is more intensive
andthe minor elements of the bath are in the first placeoxidized. The effects of
blowing practice i.e. soft blowingversus hard blowing, can be summarized as
follows:

• soft blowing increases the slag formation rate

• results in higher FeO content in slag (as well as raises oxygen super -
saturation in the metal)
• favours slag foaming
• promotes dephosphorization at least at a high carbon level
 26

• increases the oxidation rate of Mn, V, Ti etc.

• increases refractory wear
• raises the risk of slag slopping out of the furnace.

Formation of the Slag: Slag formation starts with the dissolution of oxygen in
iron melt and simultaneous oxidation of iron and minor bath constituents in
the oxygen jet impact zone. As the bathtemperature in the impact zone is very
high, over 2000°C, iron can dissolve a great amount of oxygen (up to 1 wt%).
Iron oxide forms and the primary oxidation zone and high oxygen iron
penetrate the bath and meet ‘fresh’ iron melt with higher contents of carbon
and other minor bath constituents oxidizing them. Part of the primary reaction
products are splashed into the slag and furnace atmosphere. Iron oxide and
other

nonvolatile oxidation products (SiO2,MnO, P2O5, TiO2, VOx etc.) mix with
existing slag and more lime (doloma) is dissolved into the molten slag. Slag is,
accordingly, formed by a complex chain of reactions. The overall slag forming
can be presented by the following set of reactions.

These reactions are followed by secondary oxidation-reduction reactions,

especially by decarburization takingplace on the surface of metal droplets
circulating in the slag.
 27

In the start-up period of a converter blow, when the bath temperature is low,
slag might be saturated by dicalcium silicate, but with theprogress of hot metal
oxidation the slag composition departs from the dicalcium silicate ‘nose’
returning in the later stage of the blow back to it and passing it to the
tricalcium silicate saturation or even lime saturation range (see Figure 3). The
evaluation of the slag path passing the high temperature liquidus surfaces such
as the dicalcium silicate nose or liquidus surfaces of the tricalcium silicate or
lime and corresponding precipitation of solid phases from the melt, is
somewhat obscured by the fact that slags are multicomponent phases and the
slag temperatures have been reported to exceed, even by several hundred
degrees, the average temperature of the iron bath.
 28

THE ADDITION OF IRON ORE

IRON ORE ADDITION

Depends on Increases in Will affect
1) Si content 1) HM weight 1) Turndown
2) Scrap added 2) HM Temperature temperature
3)HM temperature 3) Si content 2) Turndown P
4) Dolomite addition 3) Slag condition
5) Vessel condition (viscosity)

Scrap, slag and iron ore addition are made to the furnace for a variety of
reasons

 To adjust the liquid the metal temperature

 To adjust the liquid metal composition
 To change the slag composition and thereby its properties

An optimum addition of iron ore is essential because:

If the addition is more than required, a heavy cooling can take place. one ton
of extra iron ore reduces the temp by 30 deg c

 Slag fe can increase leading to liquid slag

 Iron ore may not go in to the metal

If the addition are less than required, the temp may shoot up and go much
above the aim temp leading to the vessel damage

 The chance of rephos increases after the steel is made and from the
carrying over slag phos can again go in to the metal
 Slag Fe decreases and thick slag can be found
 29

BLOW PRACTICE

 The blow practice depend upon following parameter

 Initial vessel condition (initial temp)
 Retain slag (slag wash)
 Hot metal temp and composition
 Lime ,ore and raw dolomite addition
 Number of TBMs open (stirring)
 Lace height and lance moment
 Bath ;height control to adjust blow and slag formation
 Hard blow make the slag dry and cause phosphorus reversal.
 Two soft blow will increase Fe content in slag.

AT LD #1 the operators follow a basic procedure during the blow as mention as

under:

 Lance hood and skirt is checked for any water leakage

 The model is run by the controller giving remaining slag, aim temp.
 Then the “PREP” button and Blow start button is pressed after
checking all the inter locks.
 Then the ignition switch is pressed which starts the timer and oxygen
counting.
 Now the skirt is lowered for :
 Positivepressure at the vessel mouth.
 To stop excessive ingress of air
 All lime and dolomite added with in first 3 min.
 Now the both slopping and drying condition of slag can be watch
which there basically governed by the sound by the vessel makes.
 Lance height and venture is maintained and adjusted automatically
 Iron ore is added as per the model or previous heat experienced.
Higher addition may lead to slopping.
 The blow is then terminated
 The vessel is purged for 30 sec for homogenisation .
 The sample and temp is taken.
 The slag is analysed by controller based on its thickness .
 Some slag is retained for next heat and for slag coating
 30

TURNDOWN CONDITIONS

TURNDOWN TEMPERATURE WITHIN A GIVEN RANGE (1640 – 1680 deg

C)

GOOD
TURNDOWN
OPTIMUM BASICITY GOOD AMOUNT OF
REQUIRES
(3 – 3.4) SLAG Fe (15-18%)

PHOSPHOUS REMOVAL

DEPHOSPHORISATION

 Out of all these, removal of phosphorus from the steel is of prime

importance and should be done with care so as to avoid rephos from the
slag to the steel
 Best condition from the phosphorus removal from the liquid steel from
a thermodynamic view point can be summarised as a highly basic, lime –
rich slag.
 A satisfactorily high level of oxidation of iron .(if it is much more than
Ca0 wt % will decrease)
 2 p+5feo=p2o5=5fe
 Lower possible temp
 The lowest possible amount of undissolved free lime in slag. (this is
because of low kinetics)

END POINT CARBON ABD TEMPERATURE CONTROLL

 31

Following parameter are employed to evaluate the efficency of end point

carbon and temp control:

 Hit rate: report as %heats where the heat point C & T are within
specified tolerance bands.
 Standard deviation; from the aim value of C&T.
 Percentage of reblows requireds to arrive at aimed end points (non
reblows is ideal)
 32

REACTION IN THE VESSEL

OXYGEN PICK UP BY THE METAL:

O2 (g)=2O

(FeO)=Fe + o

Fe2O3 =2FeO + O

Co2(g) = Co(g) + O

Oxidation of element in metal:

C + O =Co(g)

Fe + O =(FeO)

Si +2O =Si

Mn +O=(MnO)

2P+5O=(P2O5)

OXIDATION OF COMPOUND IN THE SLAG

2(FeO)+1/2O 2(g)=(Fe2O3)

2(FeO)+CO 2(g)=Fe2O3)+CO

FLUX REACTION

MgO(s)=(MgO)

CaO(s)=(CaO)

GAS REACTION

CO(g)+1/2o2(g)=CO2
33
 34

BLOWING CONTROL AND TURNDOWN

The primary objective of refining or blowing control is to oxidise the metalloid

impurities in the charge and to form a basic slag as rapidly as possible in order
to protect the lining and to permit adequate sulphur and phosphorus removal.
the control of the refining cycle can be attained by proper combination of
lance practice , flux practice and oxygen flow rate. It is essential to develop a
refining strategy which form an early basic slag and maximises carbon removal
rates without adversely affecting the lime solution and sulphur and
phosphorus removal and which minimise slopping and ejection from the vessel
during the blow. Last but most important,the temp at turndown should be
optimum.

TURNDOWN CONTROL

The time required between first turndown and start tap is an important factor
in overall productivity of a BOF shop. Heat require for large correction for temp
or analysis will significantly productivity last decay has seen mean very
development aimed at improving turndown or end point control .

The control of end point condition should start with a good static charge
control practice which requires both good thermodynamic model and close
attendance to the accuracy of the input to the model in turn of weight ,temp
and chemical analysis of the charge materials. Every effect should me to
employ a consistence scrap charge on all heats in term of the relative amount
of each type of scrap. A well standardised blowing and flux addition practice
should to be used on each type of heat in order to reduce the heat to heat
variability in decarburisation and slag development kinetics consistent
application of the above criteria will performance of each of the dynamic end
point methods
 35

CORRECTION OF TEMPERATURE AND ANALYSES

IN TATA Steel correction of temperature is done by adding scrap to hot metal.

Scrap addition is done as per the hot metal availability, that is we consider 5
ton hot metal we add 10 ton of scrap it. The maximum scrap addition will be
up to 20ton (limited the size of the scrap charging chute/pan and
thermodynamic heat balancing)

If the slag is thick as is the case with the use of large percentage of dolomite
lime or where the FeO is low , as high carbon heat, the limestone chips are less
effective. Occasionally even iron ore will land on top of every thick slag and
remain there without reaction.

The furnace may be rocked to promote a more rapid reaction with the coolant.
Reblowing with the lance raised can shape up the slag, and accelerate cooling
with limestone when slag are very thick.

The use of limestone and particularly iron ore for cooling can result in further
bath decarburisation particularly on higher carbon heats.

When coolant scrap is added the slag is usually penetrated readily and the
temperature drop obtained is more predictable. However, when large
amounts of scrap are used, sufficient time must be allowed for the scrap to
melt before the heat is tapped

REBLOW

If the bath temperature is too cold (less than 1630 deg C) the heat will
normally be reblown immediately without waiting for the analysis of the
turndown sample. Some shop do not even sample the bath if it is cold and
requires a reblow for temperature .for a 200 ton BOF heat approximately
15000 SCF of re blow oxygen will raise the bath temperature by 30⁰F

If the turndown bath analysis for carbon, sulphur, phosphorus or manganese is

above the tapping specification for the scheduled grade, corrective reblows
 36

can normally be used to reduce the analysis to the required specification. The
following reblow practice are used for these corrections

Type of reblow Lance height Vessel addition

For temperature Low None
For carbon reduction Low None
For manganese High None
reduction
For phosphorus High Iron ore
reduction
For sulphur reduction High Lime and fluorspar
 37

THE AUTOMATION MODEL

The static model used in BOF is based on pre-set calculation which are based
on the input mechanism of parameter data, its processing in accordance with a
well defined chemistry and the overall material and heat balance process.

The BOF model used at LD#1 is a static model and takes into account various
parameters/ variables for calculating the addition require for each single blow.
The relationship between various parameters are customised and set in
accordance with pre-existing literature.

MODEL WORKS IN FOLLOWING FASHION

INPUT OF DATA FROM THE SYSTEM

PROCESSING IT IN ACCORDANCE WITH CHEMICAL AND HEAT BALANCE

EQUATION

PRECDICTING AN OUTPUT ON THE BASIS OF THE INPUT DATA

 38

INPUTS TO STATIC BOF MODEL AT LD

ORE
HOT METAL SCRAP RETAINED
LIME
ANALYSIS SLAG
LIMESTONE
DOLOMITE
OXYGEN

HOT METAL
WEIGHT CAST NO
BOF MODEL
RET STEEL
GRADE

HOT METAL AIM CONVERTER NO

TEMPERATURE ANALYSIS LADLE NO
AIMWt PAN NO
AIM Temp BATH HEIGHT
BLOWER

OUTPUT TO STATIC MODEL AT LD 1

PREDICTED
VALUE PREDICTED VALUES
STEEL ANALYSIS
1.ORE
2.LIME
3.LIMESTONE
4.DOLOMITE
5.OXYGEN

BOF model

PREDICTED VALUES

EOB SLAG ANALYSIS

 39

STATIC MODELS CAN BE USED TO CALCULATE

a. Optimum charge mix,

b. Requirement of addition during blowing
c. Total oxygen required.
d. Time of blow.

THEY CANNOT PREDICT

a. blowing parameters like oxygen flow rate .

b. lance height or bath height.
c. Any parameter as a function of time.

The soundness of the prediction depends on several factors

a. Accuracy charge control mode.

b. Accuracy of input to the computer system.
c. Consistency of steelmaking practices.
d. Reliability of computersystem and its use.
 40

For making such estimate dynamic models a required. The presented model
can be used for semi dynamic control taking the help of sub lance
measurements. However by their very nature static models are not able to
predict many variation as mentioned above.

Dynamic model contains all the feature of static models and in addition having
terms for reaction kinetic and process dynamic. The possible approaches
include the following.

 Instantaneou sequilibria amongst the reacting phase may be assumed

and the process can be treated as being thermodynamically reversible.
 Reaction are assumed to be mass transfer control.
 After SI oxidation, the major reaction are those of iron and carbon.in
the case of fully dynamic control ,exit gas will be help.
 41

FLAWS IN THE PRESENT AUTOMATION MODEL

 The BOF model fails if all the input are not given; although the
main inputs are HM temp, weight, scrap, and si.
 The retained slag input is some fixed value of 0,2,5and 10 tons
,etc and cannot be altered as per requirements.
 Although the model take care of history but still feedback given
that can be improved.
 Operators deviate greatly from the models.
 The model is unable to rectify these changes as it mostly follow
strict theoretical calculation.
 42

PROBLEMS FACED IN LD 1

 Fast productivity and slow demand

 Over capacity in steel
 Market distortion
 Sticking of ore
 Slurry formation
 Non uniform discharge of lump formation
 Delay in shooting time
 Problems in steel making in rainy season
In rainy season the raw materials such as lime, iron ore, scrap, dolomite
contain moisture presence which affect steel making.

WET RAW MATERIAL

LIME may be used for sulphur and phosphorus removal at this stage as well.
Most importantly, quicklime is typically added to the mixture in the
steelmaking furnace after the beginning of the oxygen “blow” where it reacts
with impurities (primarily silica and phosphorus) to form a slag which is later
removed.lime plays a key role in fine tuning steel chemistry, lowering oxygen
content, removal of impurities such as sulphur and reduction in inclusions
trapped by the basic slag.

Lime is used in these secondary processes, Ladle Metallurgical Furnace, (LMF)

and Vacuum Degassing. moisture content in the lime make loss on ignition
which will lead to higher lime consumption

CaO+H2OCaOH2+HEAT

IRON ORE:- Iron ores are rocks and minerals from which metallic iron can be
economically extracted. The ores are usually rich in iron oxides and vary in
 43

colour from dark grey, bright yellow, or deep purple to rusty red. The iron itself
is usually found in the form of magnetite (Fe. 3O. 4, 72.4% Fe), hematite
(Fe2O3)when iron ore having moisture content is used, temperature
malfunction will carry out in the vessel feeder jamming is another problem
facing with moisture content

Dolomiteis an anhydrous carbonate mineral composed

of calcium magnesium carbonate, ideally CaMg(CO3)2. The term is also used
for a sedimentary carbonate rock composed mostly of the mineral dolomite.
An alternative name sometimes used for the dolomitic rock type is dolostone.
Dolomite having moisture content will have a problem that temperature
malfunction will take place in the vessel

SCRAP:- Scrap consists of recyclable materials left over from product

manufacturing and consumption, such as parts of vehicles, building supplies,
and surplus materials. Unlike waste, scrap has monetary value, especially
recovered metals, and non-metallic materials are also recovered for recycling
when we use wet scrap for steel making it will leave to explosion
 44

AIM OF THE PROJECT

Effect of moisture content on turndown temperature

The study and analysis of moisture present in ironore and dolomite.

SAMPLE STUDY AND MOISTURE TESTING

IN TATA steel moisture presence is noted by the normal method of moisture

testing. RAC lab 3 is mentioned for the operation. the given samples are
weighted and heated in furnace which having a heat range of 150-200 deg c
for 15- 30 min. after that the heated sample is taken out and weighted again
and now we can find the moisture content by substracting by intial weight and
final weight

Moisture % =( intial weight- final weight) *100

RESULT OF SAMPLE TESTING

SAMPLES MOISTURE OF IRON MOISTURE OF

ORE DOLOMITE
SAMPLE-1 4.75% 2.86%
SAMPLE-2 5.56% 2.62%
SAMPLE-3 3.25% 2.32%
SAMPLE-4 3.0% 1.9%
SAMPLE-5 4.28% 2.44%

Average moisture percentage of iron ore =5%

We have found that moisture percentage of dolomite is very small so we

neglected the moisture percentage of dolomite
 45

IRON ORE HAVING 5% MOISTURE

Calculation of corresponding drop in temperature of steel due to the
additional presence of moisture in Fe2O3 added during the blow

Tonnage of FeO =10.577

%H2O in FeO =5%

Tonnage of liquid steel in the vessel =160

Temperature of Flue gas at Vessel mouth during blowing =650⁰C

Room temperature =30⁰C

Specific heat of water= 4.185 J/g/K

Specific heat of steam (approx. from 100deg C to 650 deg C) = 2.675

Specific heat capacity of liquid steel at 1600deg C =0.82

Latent heat of vapourisation =2257

Tonnage of H2O in FeO =0.52885

Heat required to heat H2O from room temp to 100 deg c =154.9266075

Heat required to convert H2O to H2O at 100degc =1193.61445

Heat required to heat steam from 100deg c to 650 degC=778.0705625

Total heat extracted by moisture in FeO=2126.61162

Corresponding drop in temperature of liquid steel at 1600⁰c = 16⁰c

 46

EFFECT ON STEEL MAKING (∆H +∆H(MOISTURE))

3Fe2O3 + CO(g) 2Fe3O4 +CO2 (S) ---------------------------------------------1

Fe2O4 + CO(g)3FeO (s)+CO2(g) ---------------------------------------------2

FeO(S)FeO(SLAG) ---------------------------------------------------------------3

When we add 10 ton Fe2O3 heat is extracted

1) Raise in temp
2) Enthalpy change

If we add 10 ton dry Feo3 what is absolute temp drop in liquid steel

160ton * Cp *[Xa – 1637] = 1+2

If we add 10 ton moist Fe2O3 what is the absolute temp drop in liquid steel

160 ton * Cp * [Xb – 1637] = 1 + 2 + (Mw*Cp*∆t) + (Mw *latent heat) +

(Mw* Cp*(600-100))

3Fe2o3 + CO Fe3O4 + CO2

2Fe3O4 +2CO  6 FeO +3CO 2

3Fe2O3 + 3CO  6FeO +3CO 2

Fe2O3 +CO 2FeO + CO2

By mole fraction method we can say that enthalpy formation

Fe2O3 = 814.1

CO = 114.4

2FeO =2* 263.7

 47

CO2 =395.3 KJ/mol

Therefore we say that the equation,

Fe2O3 + CO  2FeO + CO 2

=5.8 KJ/mol

1 mol Fe2O3= 56 * 2 + 16 * 3

=160

1 tonne of Fe2O3 = 36,250 KJ/tonne

FeO(S)FeO(SLAG )

FeO(S)FeO(l)

By mole fraction we can say that enthalpy formation

FeO(S) =263.7

FeO(l )=225.6

Per mole of FeO= 38.1kj/mol

FeO =56+16 =72 gm

Per ton of FeO = 38.1*2/0.000072

=1058333KJ

FeO FeO SLAG

Per ton at Fe2O3 HEAT extracted

=1*Cp fe2o3 [1637-3] +1* [1058333+36250]KJ

=1*0.8864*1000[1637-30] +[1094583]

=1424444.8+1094583

=2519027.8KJ

For 10 ton Fe2O3

 48

Q =25190278KJ

Original temp of steel =T⁰s

160*1000*0.82*(TS-1637)=25190278

T⁰s = 1637+192

For 9.5Fe2O3+0.5H2O

Q Fe 2O3=2519027.8*9.5=23730764kj

For 0.5ton of H20

Q H2O=2010600 KJ (the predetermine value of heat extracted by the moisture

in FeO)

TOTAL Q=25941364

(T⁰S=1637+197.7 ⁰c)

Drop in temperature of 160t of liquid steel for addition of 10t Iron ore
with different moisture content
200
199
Temparture drop, deg C

198
197
196
195
194
193
192
191
0% 1% 2% 3% 4% 5% 6% 7%
Moisture in Iron Ore, %
 49

KEY LEARNING OUTCOMES

The internship has provided good learning outcomes which included

 Practical understanding of corporate environment

 Importance of punctuality and time management
 Enhanced inter personal skills and learnt how to deal with seniors and
colleagues
 Learnt team work
 Learnt the working operation
 Learnt basic process carry out
 Try to find effect of moisture