15 Days Industrial Training Report
On Blast Furnace-V Plant (21.12.2022-06.01.2023)
Submitted to: R.S Kaushal
General Manager, BF-V
Rourkela Steel Plant
Submitted By: Dhritiman Debnath
College Name: Jadavpur University, Kolkata
Branch: Metallurgical and Material Engineering
Semester: 3rd Year 2nd Sem (6th Sem)
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ACKNOWLEDGEMENT
It is a matter of great pleasure and privilege for me to present this
report of 15 days Industrial Training in BF-V. Through this report, I
would like to thank numerous people whose consistent support and
guidance is a pillar in the architecture of this report.
To begin with, my sincere thanks to R.K Kaushal, General Manager of
Blast Furnace V for extending cooperation to enable me to get
acquainted with the various activities of their department.
I would like to express my sincere thanks towards members of the
Blast Furnace- V for helping me and making me get a deep knowledge
about various activities of Blast Furnace.
Dhritiman Debnath
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BLAST FURNACE
Blast Furnace is a counter current heat & mass exchanger, in which the burden (solid
raw materials like Iron ore, Sinter, Coke & additives / fluxes) is charged from top of the
furnace & hot blast is sent through the bottom via tuyeres. The heats transferred
through the ascending Hot gasses to the descending burden & oxygen from the burden
to the gasses. In the countercurrent process, the iron ore & reducing agents (Coke,
Coal) are transformed to hot metal & slag, formed from the gangue of the iron ore, sinter
& the ash of coke. The liquid hot metal & slag do not mix due to their density difference
and remain separated from each other with the slag floating on top of the denser iron.
The liquid iron & slag are separated in the cast house during casting. The other product
from the blast furnace is dust laden blast furnace gas, which is further cleaned in the
gas cleaning plant and is used as a fuel all over the plant and Granulated slag which is
formed from Hot slag by water cooling at Slag granulation plant. BF#5 in RSP was
commissioned with the technology assistance from M/S DC & M/S TPL.
The main sections supporting the furnaces are:
1. High line Stock House & charging section.
2. Furnace proper and cast house
3. Hot Blast Stoves
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4. Gas Cleaning plant
5. Cast House slag Granulation plant / External slag granulation plant
6. Pig Casting machine
7. Fleet of Hot metal ladles (80 T, 140 T & 350 T Torpedo) & slag pots.
8. Ladle repair Shop, Slag dump and clay preparation unit, Torpedo ladle repair shop.
9. Workshop.
10. Pulverized Coal Injection system
11. Top Pressure Recovery Turbine
The raw materials required for production of hot metal are Iron ore, Pellet, Sinter, Coke
& Fluxes ( LD Slag & Quartzite).Apart from these solid raw materials, it also requires air
and oxygen for burning of coke, water for cooling the refractory lining of the furnace and
equipment of furnaces. Iron ore supplied from RMHP, Sinter from Sintering Plant (I, II &
III), Coke from Coke Ovens . The hot metal which is basic raw material for steel making
is supplied to steel melting shops I & II of RSP. In case SMS is unable to accept hot
metal, the same is poured in Pig Casting Machine – 1 & Pig Casting Machine – 2 to
convert to solid pigs.
Raw Material Sources for Blast Furnace Iron Ore :
● RMHP(Barsuan / Kalta / Meghataburu / Kiriburu / Gua /Bolani / Chiria)
● Sinter : Sinter Plant – I, II & III
● Coke : Coke Ovens (Coals from Dugda, Bhojdih, Kargali,Rajarappa& imported
coal)
● Quartzite : Purchased
● LD Slag : SMS through MRD Nut Coke : Through Sinter in BF#1 & 4 & Internal
generation in BF # 5
● Pig Iron Chips : PCM through MRD
● PCI Coal : Raw Coal Purchased
Stock House
Stock house has 28 bunkers. Stock is prepared in the stock house and sent up
conveyors to the furnace top in batches. The furnace bell-less top has two lock-hoppers
with 70 m3 capacity each. A single batch of stock is discharged into a lock-hopper. A
nominal batch size of 27 to 58 m3 will provide a burden layer thickness of about 38 to
80 cm in the throat of the furnace. The bell-less top lock-hopper door is closed and the
hopper pressure is equalized with the furnace, so the batch can be discharged into the
furnace distribution equipment, The lock-hoppers alternate being filled and discharged.
Usually discharging a lock-hopper signals the start of sending the next batch of material
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for that lockhopper This occurs while the other lock-hopper is already filled and ready to
discharge. Two batches of stock are called a charge. A charge always consists of a
batch of coke followed by a layered batch of ore, miscellaneous material and nut coke.
For reference purposes the timing of the filling operation with an 80 cm ore layer and
fuel injection with pulverized coal will be discussed. The coke layer with this sample
burden is about 50 cm. A batch feeds onto the main stock house conveyor in about 111
second for coke and 177 seconds for an ore batch. The time difference is due the larger
batch size for the ore and misc. materials. The belt speed of the Main Charging
Conveyor (1CG01) is 1.78 m/sec. The belt width is 1600 mm and the belt has 35 degree
idlers. The carrying capacity is limited by volume for coke and by weight for ore. The
travel time from the furthest material bin in the stock house to the lock-hopper is 328
seconds for ore and 295 seconds for coke. The difference is due to bin location. One
weight hopper of coke can provide a typical coke batch of 36 m3. A median case of four
weigh hoppers of ore with miscellaneous and nut coke weigh hopper additions can
make up a typical ore charge of 58 m3. The weight hopper-feeders are tuned to
discharge a batch in 95 seconds.
FURNACE
There are three Blast Furnaces with combined installed capacity of 4.5 MT of hot metal
which was upgraded during the 2005,2013 & 2017 of hot metal per annum. Some of the
technical information about the three furnaces are listed below. The blast furnace is a
vertical shaft type furnace where reduction & melting of descending charge material
takes place due to the heat and ascending gasses produced due to combustion of coal
& coke by hot air blown through the tuyeres. The furnaces are fully refractory lined, the
bottom hearth to bosh with carbon blocks & their after with fire clay bricks whose %
Al2O3 goes on decreasing from bosh to shaft.
Major sections of the furnace proper are:
1. Top Charging Equipments
2. Cooling system
3. Hot Blast Stoves
4. Cast house & cast house Slag Granulation Plant
5. Pulverized coal injection plant
Reactions in the Blast Furnace
Upper Stack Zone
● Reduction of oxides
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3Fe2O3 + CO = 2 Fe2O3 + CO2
Fe3O4 + CO = 2 FeO + CO2
FeO + CO = Fe + CO2
● Decomposition of Hydrates
CO + H2O = CO2 + H2
● Decomposition of Carbonates
Middle Stack Zone
● Direct / Indirect reduction
FeO + CO=Fe + CO2
CO2 + C=2 CO
FeO + C=Fe + CO
Lower Stack Zone
● Calcination of lime
● Reduction of reduced iron
● Reduction of Silica / MnO2
● Formation / melting of slag
Combustion Zone
● Burning & combustion of coke & complete reduction of iron oxide.
C + CO2 = CO2 + 94450 Cal (Direct Reduction)
CO2 + C = 2CO – 41000 Cal (Solution loss reaction)
Raceway
● Coke & Hydrocarbons are oxidized
● Large evolution of heat.
Charging equipment for BF # 5 :
To dump the material into the furnace, the lower seal valve opens and then the lower
material gate is opened. The material is dumped through a rotating chute, which can
dump material at any position of the furnace and can complete the dumping in a
variable number of rotations so that desired burden distribution is achieved. The whole
BLT system is hydraulically operated & PLC controlled. Besides achieving perfect
burden distribution, BLT ensures very good gas sealing at the furnace top so that the
furnace can be operated at a high top pressure.
Cooling System ( BF # 5):
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The blast furnace cooling system is of major importance as it protects the shell and the
lining of the blast furnace against overheating. The blast furnace is equipped with an “on
furnace cooling system". known as the primary cooling system. The primary system is a
closed circuit system This system transfers heat from the blast furnace lining and
equipment via cooling elements to the cooling water. The Daneli corus design has
Copper Plates coolers & Staves coolers at Upper stack of the furnaces for cooling.
BF#5 has jacket cooling for its hearth cooling. Thermal energy from the primary cooling
system is transferred to the secondary cooling system with plate heat exchangers .
From the secondary cooling water system the heat is transferred to the surrounding
environment with cooling towers. Cooling water to the cooling elements must be
maintained at all times, as even if the blast furnace is shut down the heat load still can
be significant. This must be done to prevent possible local boiling in the cooling
elements that could lead to a loss of cooling to sections of the furnace. If this is not
done, the result may be severe damage to the furnace equipment and lining. As soon
as any cooling flow is reduced to 80% of the set point, the blast furnace production
should be reduced or the blast furnace should be shut down to reduce the heat load as
soon as possible. The primary and secondary cooling systems are equipped with
backup diesel pumps. The primary system is also equipped with a gravity fed
emergency water system should the diesels not start. These systems are used in the
event of power failure or when interruptions in the normal cooling water supply occur.
These systems are not intended as a 100% operational back-up, but as a back-up
which is available to provide at least a minimum cooling water flow maintained at all
times to allow the furnace to be shutdown in case the correct flow cannot be achieved.
Hot Blast Stoves & Associated System
The function of Hot Blast Stoves is to preheat the air blast before its admission into the
furnace through tuyeres. Each furnace is provided with 3 hot blast stoves which are tall
cylindrical shell with dome shaped top for BF # 4 & mushroom dome shape for BF # 1 &
5. Each stove consists of two parts namely combustion chamber & checker brick work.
The combustion chamber is lined with fire clay brick & checker bricks are Alumina
bricks. BF gas is burnt in the combustion chamber and the sensible heat of the flue
gasses heat up the checker bricks while passing through them from top towards bottom.
The period of heating is called “On Gas” & normally a stove remains on gas for 1 hour
30 minutes at a stretch for BF 1 & 5. After heating, a cold blast, supplied from turbo
blowers of CPP–I passed through the checker works from the bottom and the air got
heated up by taking sensible heat from the checkers. The period of blast heating is
called the “On Blast” condition of the stove. The blast period is usually for 1 hour for BF
# 5. The hot blast stoves are provided with several attachments such as burners to burn
the premixed air and BF gas in the combustion chamber. Different valves are provided
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for controlling the BF gas, combustion air, waste gas, cold blast and hot blast to or from
the stoves. The hot blast from stoves passes through insulating refractory bricks lined
pipes (hot blast main, bustle main & tuyeres stocks) and then injected through tuyeres
into the furnaces. The entire operation & control of stoves & hot blast is made from a
control room adjacent to the stove.
● Process description of BF # 5 Stove
The hot blast required for the blast furnace operation is generated in a system of
three regenerative heat exchangers. In this system these heat exchangers are
called stoves, These stoves are operated in a cyclic mode in order to be able to
produce a constant temperature and volume of hot blast. With three stoves the
system is operated in cyclic manner, where one stove is "on blast"(producing hot
blast) while the other two are “on gas” (being regenerated/fired), During the time
that the stove changes from “on blast" to “on gas” and vice versa only one stove
is on gas. During the regeneration phase the heat is accumulated in refractory
material.
The stove is a steel pressure vessel in which the following parts can be
discerned:
- Ceramic burner
- Combustion chamber
- Parabolic dome
- Checker chamber
- Checker support
CAST HOUSE
BF#5 has two cast houses for this Blast Furnace, designated as NORTH Cast house
and SOUTH cast house
The design of the cast houses is governed by the following parameters :
● Hot metal production
Normal 7294 thm / day
Maximum 8320 thm / day
● Slag Production
Normal 2456 T/Day
Maximum 2580 T/Day
● Slag rate 290 – 310 Kg/THM
● Tap holes 4 Nos.
● Tapping per day 10 – 12 Nos
● Tapping time per tap 1.5 – 2.5 hours
● Duration of slag flow 60 – 100 Minutes
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● Dry slag pits 4 Nos.
● Iron flow rate
Average 5 T/min
Normal range 4 – 6 T/min
Peak (< 3 min) 10 T/min
● Iron Temperature 1450 – 1500 0 C
● Slag flow rate
Average 5 T/min
Normal range 4 – 6 T/min
Peak (< 3 min) 12 T/min Slag
● Temperature 1500 – 1550 0 C
Cast House Slag Granulation Plant
In the granulation plant, the molten slag from the slag runner is delivered to the
Granulating Chute where water is injected through the Spray Head at a pressure of 230
kPa. The design and construction of the Spray Head ensures an intensive controlled
heat exchange between water and molten slag, thus producing high quality granulate.
The granulation process starts with 2000 cubic meters per hour (m3/hr) of water being
delivered to the Spray Head. Water is pumped from the Pump Basin by the granulation
pump to the Spray Head. The water level in the Pump basing is monitored by a level
transmitter which allows the PCSto control the level in the tank by signaling a control
valve to add make-up water as required. Up to600 cubic meters per hour (ms/hr) of
make-up will be required at maximum slag flow rates. An alarm is sounded to alert the
operator in case the water level in the Pump Basin exceeds the “high-level overflow" set
point or falls below the “low-low" level setpoint. The Granulation Pump is only permitted
to operate when the water level is above the “low-low" level set point. The granulation
water supply is secured through an elevated “Emergency Water Storage Tank".The tank
has a capacity of 80 m3 which will be delivered at a rate of 480 cubic meters per
hour(m3/hr). This protects the granulation tank for approximately ten (10) minutes,
during which time slag can be diverted to the slag pits.
Gas Cleaning Plant (GCP)
BF gas is subjected to successive cleaning in dust catcher (by changing the direction of
the flow of the gas), gas washer(washing with water sprays), whereby dust content is
reduced to the extent of 4 to 5 mg/Nm3.
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BF # 5 GCP and High Top Pressure
The raw gas leaves the blast furnace via the uptakes and is conveyed to the gas
cleaning facility via the downcomer and dust catcher. The gas cleaning plant consists of
a pre-scrubber, RS-scrubber and a vertical demister located downstream from the dust
catcher. The Scrubber performs gas cleaning by a two-stage process in two distinct
sections: the Pre-Scrubber (Stage 1) and RS Scrubber (Stage 2). The gas stream
enters the Pre-Scrubber where a series of water sprays cool and remove “airborne”
solids carried by the gas stream. The Pre-Scrubber water is injected via nine (9) spray
nozzles arranged to provide symmetrical hollow cone spray patterns. The resulting
slurry is discharged from the Pre-Scrubber via a level control system into a clarifier. The
gas stream exits the Pre-Scrubber through three (3) circular ducts, known as RS Tubes
and into the RS-Scrubber where final gas cleaning is performed. Three (3) independent
water sprays, combine with the gas upstream of the cone shaped, annular gapped
pressure control devices known as RS elements. In addition to the cleaning function,
these RS elements are used to control the furnace top pressure. The resulting slurry is
discharged from the RS Scrubber via an independent level control system into a
clarifier. The “clean” gas exits the RS Scrubber through the clean gas main and into the
Vertical demister. The Vertical demister utilizes fixed directional vanes to create a
spinning action in the gas stream. Free moisture is collected as a result of the
centrifugal forces produced by the spinning action. Entrained moisture collected within
the Demister is drained into the clarifier. Clean gas exits the Demister for use in the
stoves via the TRT. The scrubber’s three (3) movable cones are actuated by hydraulic
cylinders to accommodate variations in the gas flow and also control the top gas
pressure. The hydraulic power unit and associated pumps are located in the Hydraulic
Room located at ground level adjacent to the scrubber vessel.
Pig Casting Machine (PCM-1)
There are two machines. Each machine has two strands of chains fitted with small steel
mold rotating on sprockets. Hot metal is poured into the lime coated molds & cast as
solid pigs.PCM is provided with 2 EOT cranes for pouring metal, 1 crane for cleaning
and material handling and 1 magnet crane for loading / unloading pigs into
wagons.PCM handles 80 T capacity hot metal ladles only. Ladle cleaning, repairing &
heating is also done in PCM bay.
Pig Casting Machine (PCM-2)
There is one machine. This machine has two strands of chains fitted with small steel
molds rotating on sprockets. Hot metal is poured into the lime coated molds & cast as
solid pigs. PCM is provided with 1 crane for cleaning and material handling and 2
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magnet cranes for loading / unloading pigs into wagons. PCM handles 350T capacity
hot metal ladles only( Torpedo).
Ladle Repair Shops
There are two Ladle Repair Shops, where small and big ladles are repaired, cleaned
and relined. These are used for transportation of Hot Metal.
Torpedo ladle Repair Shop
Torpedo ladles are repaired, cleaned and relined.
Clay Preparation Unit
Tap hole clay, Mud gun clay and tar mass, which are needed for various jobs like tap
hole making, mud gun filling, spout making and trough / runner making, are prepared in
this unit by mixing ingredients like coke breeze, coal powder, fine clay, plastic clay,
refractory grog, coal tar pitch, sulphite lye and water.
Slag Granulation Plant ( External)
For every ton of Hot Metal produced in our Blast Furnaces, about 400 kg of slag is
generated as an industrial waste. The Slag in granulated form is used as excellent raw
material for the manufacture of cement. The granulated slag when used in the
manufacture of cement replaces the main ingredient clinker up to 50-60%. This results
in significant cost reduction in the cement industry and also results in marked
conservation of limestone, a basic raw material for both the industries.
Pulverized Coal Injection (PCI) System for BF#5
The Pulverized Coal Injection System (PCI) can be summarized as follows a) The
Pulverized Coal is fed from the Fine Coal Silo to the Feed Tanks, which is part of a
batch process where the Feed Tanks are either Filling, Pressurizing, Holding, Feeding,
or Depressurizing in order to provide a continuous flow of Pulverized Coal into the
Transport Line.
b) The single stream of Pulverized Coal in the Transport Line leaving the Feed Tank is
combined with Transport Gas in the Mixing Tee to convey the coal to the proximity of the
Blast Furnace.
c) The single stream of Coal/Transport Gas mixture feeds the Distributor, where the
single stream is distributed equally to each of the Injection Lines, which transport the
coal to the individual Tuyere.
The PCI System can be divided into the following main parts
● Pulverized Coal Storage and Injection system
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● Pulverized Coal Transport and Distribution system
● Utilities