FIELD OF THE INVENTION

The present invention relates in general to blast furnace plants for producing molten pig
iron, and in particular to an improved blast furnace plant for producing high quality hot
metal to be fed into the Basic Oxygen Furnace (BOF) converter (in particular to steel
making unit of 2.5 MTPA capacity) to maximize its effect on the BOF operation and improve
the crude steel quality while being user friendly and environment friendly. The invention
discloses the operation of such a blast furnace as well.
This complete specification is being filed in pursuance of provisional application no.
201631040211 filed on 24th November 2016 which is incorporated in its entirety in this
specification.
BACKGROUND AND PRIOR ART
A blast furnace is a gas-liquid-solid countercurrent chemical reactor whose main objective is
to produce pig iron, which is then converted into steel by reducing its carbon content.
The blast furnace is conventionally supplied with solid materials, mainly sinter, pellets, iron
ore and carbonaceous material, generally coke, charged into its upper part, called throat of
the blast furnace. The liquids consisting of pig iron and slag are tapped from the crucible in
the bottom of the blast furnace.
The iron-containing burden (sinter, pellets and iron ore) is converted to pig iron
conventionally by reducing the iron oxides with a reducing gas (containing CO, H2 and N2 in
particular), which is formed by combustion of the carbonaceous material in the tuyeres
located in the lower part of the blast furnace, where air, preheated to a temperature of
between 1000 and 13000C, called hot blast, is injected.
This process of converting the iron-containing burden takes place in two distinct zones of
the apparatus, separated by an intermediate zone called a thermal reserve zone. The latter
is characterized by an interruption of the heat exchange associated with the fact that the
gas and the solids are practically at the same temperature, called the reserve zone

temperature. This also causes an interruption of the chemical reactions between gases and
solids, thus defining a chemical reserve zone.
The two zones where the iron-containing materials are converted are:
- The lower part of the apparatus, called the production zone, which sets the energy
requirements of the blast furnace and serves to carry out the conversion of the iron
oxides from the wustite state to iron metal. It also serves to heat and melt the
materials from the reserve zone temperature to the final pig iron temperature;
- The upper part of the apparatus, called the preparation zone, which acts as a
recuperator of the thermal and chemical potential of the gas. It serves to heat the
materials from the ambient temperature to the reserve zone temperature and to
carry out the reduction of the iron oxides charged (hematite and magnetite) to the
wustite state.
To increase productivity and reduce cost, auxiliary fuels are also injected into the
tuyeres, such as pulverized coal fuel oil, natural gas or other fuels, combined with
oxygen which enriches the hot blast.
The gases recovered in the upper part of the blast furnace, called top gases, mainly
consist of CO, CO2, H2 and N2 in proportions of about 22%, 22%, 3% and 53%,
respectively. These gases are generally used as fuel in other parts of the plant. Blast
furnaces are therefore large producers of CO2.
In the blast furnace process, iron ore/ prepared burden and reducing agents (coke, coal) are
transformed into hot metal and slag is formed from the gangue of iron ore burden and the
ash of coke and coal. Ore and coke (burden) are charged in discrete layers through top of
the furnace. Hot metal and slag are separated from each other in cast house. Blast Furnace
Slag is a raw material component for production of slag cement.
A blast furnace is designed for a fixed hot metal production target in a day. Accordingly,
sizing of the blast furnace is finalized, which is indicated by its useful volume (from throat to
tap hole). In the present instance useful volume of BF is 4,250 m3 (working volume {WV}
3,621 m3) with target production of 8,500 tons per day (tpd) at productivity of 2.3t/ m3 WV/
day.

General industry consensus indicates that the blast furnace iron making technology will
continue to govern unless some other commercially viable alternative is proven to match
the scale of economies available in the blast furnace route. Among all iron making
processes to date, the blast furnace process is the largest in terms of unit production,
lowest in energy consumption, the highest in efficiency and delivers the best pig iron
quality. Use of larger size blast furnaces (volume > 4,000 m3) has become a worldwide
trend. There are quite a large number of Blast Furnaces that are upcoming/being
commissioned in India. The basic arguments for such large size Blast Furnaces are lower
cost of production per unit tonnage and lower fuel rates and these are matching with the
hot metal input demand of BOF (Basic Oxygen Furnace) converters. Lower land
requirement (reduced footprint for specific hot metal production) and less manpower
deployment is an added advantage. Low silicon and low sulphur hot metal is an essential
pre-requisite for BOF (Basic Oxygen Furnace) converter which is adequately met by large
blast furnaces.
Presently, all the large Blast Furnaces operating/ under construction in India are equipped
with technologies matching with global benchmarks as well as with an eye towards Indian
raw material conditions and operational practices.
The size of the blast furnace selected is apposite with the future need of adding large BF
production modules in India in course of prospective expansion plan of steel industry.
Iron making has come of age with increased consciousness amongst operators to meet the
requirements of competitive iron making at reduced cost with “green technologies”. The
need of the hour is to adopt cutting edge innovative technologies to achieve cost reduction
method, improve specific consumption of raw materials, increase energy efficiency and
improve quality, yield and productivity, increased automation, adopting ergonomic practices
with a focus on environmental aspect.
However, the blast furnaces of the prior art have room for further reducing the cost of
production and be made more user friendly as well as environment friendly. The present
invention seeks to overcome these drawbacks of the prior art.

OBJECTS OF THE INVENTION
The primary object of the invention is to provide an improved blast furnace plant which
produces hot metal in significantly higher quantity making the cost of production less, is
user friendly as well as environment friendly.
Another object of the present invention is to provide an improved blast furnace plant to
make low silicon, low sulphur and low phosphorus hot metal to meet the continuous
requirement of hot metal of steel making unit of an integrated steel plant.
Another object of the invention is to provide an improved blast furnace plant to make high
quality hot metal with lowest amount of impurities.
A further object of the invention is to provide an improved blast furnace plant having high
thermal efficiency.
Yet another object of the invention is to provide an improved blast furnace plant which is
capable of smooth ore reduction during the production of steel.
Another object of the invention is to provide optimum permeability for the flow of gas inside
the blast furnace.
How the foregoing objects are achieved will be clear from the following description. In this
context it is clarified that the description provided is non-limiting and is only by way of
explanation.
SUMMARY OF THE INVENTION
An improved blast furnace plant comprises of a blast furnace having high top pressure to
ensure better permeability, longer gas-solid reaction time and better fuel rate. It has a high
hot blast temperature with provision of O2 enrichment for smooth auxiliary fuel injection
such as pulverised coal injection. A plurality of hot stoves is provided with ceramic burner
with stabilizer for vigorous intermixing of air and gas for complete combustion. The stoves
have mushroom dome allowing independent growth of stove wall and dome. The plant has
twin cast houses with double tap holes per cast house. A stock house and a tangential

cyclone are also provided. The blast furnace has a plurality of tuyeres, a top pressure
recovery turbine, waste heat recovery system, a plurality of variable voltage variable
frequency (VVVF) drives and a cooling system comprising of soft water closed circuit cooling
tuyeres, tuyere cooler, stave coolers and under-hearth cooling.
The SG iron stave coolers are provided in the hearth zone and copper stave coolers
in the bosh, belly and lower stack regions of the blast furnace in the said cooling
system.
The instruments provided in the SG iron cooler portion of the blast furnace are
Temperature Thermocouple, Temperature Thermocouple (Duplex), Skin Flow
Temperature Thermocouple, Pressure Tapping and Stave Body Thermocouple.
The instruments provided in the copper stave cooler portion of the blast furnace are
Temperature Thermocouple and Stave Body Thermocouple.
Each SG iron/copper stave cooler has four inlet and four outlet cooling pipes in
tuyere zone, the bosh, belly, lower and upper stack regions being provided with
better corner cooling and with the possibility of zone wise heat load calculation.
Computer/PLC based state-of-art instrumentation and control system is provided for
sensing sufficient levels of temperature across the blast furnace profile for better
monitoring of life of refractory and coolers and multi-layer pressure measurements
for calculation of pressure drop across the furnace.
The tangential cyclone is devoid of moving mechanical equipments and is provided
with pressure transmitters, temperature elements, level sensors and purging
arrangements along with dust evacuation mechanism.
The mushroom dome of the hot blast stove removes dome refractory load from stove
refractory wall and ensures independent movement of stove wall refractory. The
dome is selected with special emphasis on creep resistance and provided with special
tongue and groove in three dimensions to ensure proper locking of dome structure.
The top pressure recovery turbine has a capacity of approximately 16 MW.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The nature and scope of the present invention will be better understood from the
accompanying drawings, which are by way of illustration of a preferred embodiment and not
by way of any sort of limitation. In the accompanying drawings:-
Figure 1 shows the general layout of the improved blast furnace plant of the present
invention.
Figure 2 shows the plan view of the blast furnace and the cast house.
Figure 3 shows the plan view of the blast furnace and the hot stove.
Figure 4 shows the general arrangement of cast house.
Figure 5A shows the general arrangement of blast furnace.
Figure 5B shows the plan view of the blast furnace.
Figure 5C shows the detail “A” of figure 5A.
Figure 5D shows the enlarged portion of hearth, Bosh and lower part of Stack.
Figure 5E shows the upper part of the Stack and throat.
Figure 6A shows a typical cross section of main trough along the line I-I of figure 2.
Figure 6B shows a typical cross section of slag runner and iron runner along the line J-J of
figure 2.
Figure 6C shows a typical cross section of drain runner along the line K-K of figure 2.
Figure 7A shows a general arrangement view of the tangential cyclone of the blast furnace.
Figure 7B shows the plan view of the tangential cyclone shown in figure 7A.

Figure 8 is the elevation view showing the connection between the hot stove and the blast
furnace.
Figure 9A is the elevation view of hot stove of the blast furnace.
Figure 9B is the cross sectional view along the line L-L of figure 9A.
Figure 9C is the plan view of the hot stove.
Figure 10A shows the orientation of various instruments of S.G. iron stave cooler portion of
the blast furnace.
Figure 10B shows a typical view of the thermocouple arrangement of S.G. iron stave cooler
portion of the blast furnace.
Figure 11A shows the orientation of various instrument of the copper stave cooler portion of
the blast furnace.
Figure 11B shows a typical view of the suspension pin with thermocouple arrangement of
Copper stave cooler portion of the blast furnace.
Figure 12A shows the orientation of various instruments at the spheroidal graphite (SG) iron
stave cooler portion of tuyere of the blast furnace.
Figure 12B shows the orientation of various instruments at the SG iron stave cooler part of
the other portion of the blast furnace.
DETAILED DESCRIPTION OF THE INVENTION
Having described the main features of the invention above, a detailed and non-limiting
description of a preferred embodiment of the invention will be given in the following
paragraphs with reference to the accompanying drawings.

In all the figures, like reference numerals represent like features. Further, the shape, size
and number of the devices shown are by way of example only and it is within the scope of
the present invention to change their shape, size and number without departing from the
basic principle of the invention.
Further, when in the following it is referred to “top”, “bottom”, “upward”, “downward”,
“above” or “below”, “right hand side”, “left hand side” and similar terms , this is strictly
referring to an orientation with reference to the apparatus , where the base of the
apparatus is horizontal and is at the bottom portion of the figures. The number of
components shown is exemplary and not restrictive and it is within the scope of the
invention to vary the shape and size of the apparatus as well as the number of its
components, without departing from the principle of the present invention.
All through the specification, the technical terms and abbreviations are to be interpreted in
the broadest sense of the respective terms, and include all similar items in the field known
by other terms, as may be clear to persons skilled in art. Restriction or limitation if any
referred to in the specification, is solely by way of example and understanding the present
invention.
The blast furnace according to the present invention is designed to produce high quality hot
metal with lowest amount of impurities, high thermal efficiency, smooth ore reduction and
optimum permeability for the flow of gas inside the blast furnace.
The major design/operating parameters of the blast furnace according to the present
invention are outlined below. These features enable the blast furnace meet the intended
target.
High Blast Furnace Top Pressure
High blast furnace top pressure is a pre-requisite of high productivity and high efficiency
blast furnace operation. High top pressure ensures better permeability, longer gas-solid
reaction time and better fuel rate. Beside increase in productivity level and decrease in fuel
rate, high top pressure also enables incorporation of top energy recovery turbine, which
makes the plant more energy efficient.

High Hot Blast Temperature
This is another important parameter for high productivity blast furnace operation which also
enables reduction in fuel rate. Higher hot blast temperature along with provision of O2
enrichment ensures smooth auxiliary fuel injection such as pulverised coal injection (PCI).
Blast Furnace Top Charging Equipment
Considering the precise burden distribution control required for operation of large capacity
blast furnace coupled with high top pressure operation, bell-less design has been found
most appropriate and has been adopted worldwide.
Blast Furnace Refractory and Cooling System
The selection of Blast Furnace refractory and cooling system has considerations for high
productivity and longer campaign life. In consideration of high productivity and long
campaign life requirement, use of copper staves along with compatible high spalling
resistance and high conductive refractory materials is most suited and adopted worldwide.
Stock House Configuration and Charging System
Considering the various burden mixes being used world over, provision is made for 70 to
80% sinter in burden, 10% to 30% of pellets in burden and remaining iron ore lump.
Besides the above, ferrous burden requirements, coke charging is done in 2 to 3 fractions
(8-35, 35-60 and 60-80) with nut coke charging facility.
Stock house screen/feeder capacities are selected such that inter changeability of day bins
between sinter/pellet/lump is possible.
Raw Material Quality
Consistency in characteristics of input raw materials is of paramount importance for smooth
operation of large blast furnaces. Considering the typical Indian raw material quality/
characteristics, an approach is required for suggesting the input material quality to be

maintained consistently.
Auxiliary Fuel Injection (Pulverised Coal Injection - PCI)
In line with the achieved pulverised coal injection rates in large blast furnaces, pulverised
coal injection capable of injecting avg. 200 kg/thm is provided.
As stated earlier, the improved blast furnace according to the present invention has been
provided with several new and inventive features. A non-limiting list of these features is as
under:
a) Suitable for long campaign life of Blast Furnace ~ 15 to 20 years
b) High level of productivity > 2.0 t/ m3 Working Volume(WV)/day
c) Closed circuit water cooling for efficient and contamination free cooling and less
make-up water requirement
d) High top pressure operation (2.0 atg to 2.5 atg)
e) Straight line hot blast temperature of ~ 1,200 °C
f) Pulverised coal injection (PCI) levels of > 150 kg/ thm (Design 200 kg/ thm)
g) Installation of Top Recovery Turbine (TRT) - 16 MW for 4,250 m3 BF
h) 100 % slag granulation with continuous de-watering facilities
i) Advanced charging practices and high levels of automation
j) Maximum use of prepared burden, centre coke charging, two fraction sinter charging,
base blending and the like
k) Extensive use of Variable Voltage Variable Frequency (VVVF) drives

l) Compulsory de-fuming and de-dusting facilities for maintaining ergonomic work
environment
The improved Blast Furnace according to the present invention has the specifications as
given in Table 1 below. However, the invention is equally applicable to Blast Furnaces
having other specifications as well.


Operational characteristics:
Table 2 below gives the estimated technological operating parameters based on the
prevailing raw material condition.



It may be clearly understood that the above figures are illustrative in nature and may vary
in actual performance of the invention.

We now refer to the accompanying drawings.
Blast Furnace (BF) Profile:
Reference is made to figure 1 to figure 5C.
Figure 1 shows the general layout of the Blast Furnace Plant (BF). Figure 2 shows the plan
view of the blast furnace (BF) and the cast house (CA). Figure 3 shows the plan view of the
blast furnace (BF) and the hot stove (SV). Figure 5A shows the general arrangement of the
blast furnace. Figure 5B shows the plan view of the blast furnace. Figure 5C shows the
detail “A” of figure 5A.
The profile of the blast furnace (BF) has been so made that it is capable of maintaining the
required productivity even with reasonable variations in raw material characteristics. The
bosh angle is so selected that the optimum permeability is achieved with the available coke.
High bog depth is maintained for steady thermal state of hearth and smoother cast. This
also ensures floating dead man which in turn eliminates peripheral erosion of hearth pad
and occurrence of elephant foot phenomenon. This ensures long and trouble free hearth life
and stable hearth pad-wall junction.
Adequate number of tuyeres is provided for better blast distribution and formation of
overlapped raceway to ensure continuous ring of void age creation for smoother burden
descent.
a) REFRACTORY DETAILS OF HEARTH, Bosh and Lower Stack Portion
We now refer to Fig. 5D.
The refractory material of the Hearth is selected from the following:
i)Alumina Castable (1’)
ii) Carbon Castable (2’)
iii) Graphite (3’)
iv)Micropore Carbon (4’)
v)Super Micropore Carbon (5’)
vi) Ceramic Cup (Corundum Sialon Bonded) (6’)
vii) Silicon carbide sialon bonded (7’)

viii) Alumina Injectable Mix (8’)
ix) Standard Carbon (9’)
x) Silicon Carbide Nitride Bonded Pre-Shaped Bricks (10’)
xi) Super duty bricks (15’)
xii) Mullite (16’)
xiii) Corundum Castable (17’)
The refractory material of the Bosh is selected from the following:
i) High Alumina Gunning Mix (11’)
The refractory material of the lower stack portion is selected from the following:
i) Carbon Ramming (12’)
b) REFRACTORY DETAILS OF THE UPPER STACK PORTION
We now refer to Fig. 5E.
i) Silicon Carbide sialon Bonded Insert Bricks (13’)
c) REFRACTORY DETAILS OF THE THROAT
i) High Alumina Co-Resistant Gunning Mix (14’)
Blast Furnace Stack Height:
Selection of stack height is an important criterion which depends on several variables,
primarily on the burden characteristics/composition and ratio. Optimum furnace stack
height is maintained (indirect reduction zone) resulting in better gas utilization and hence,
low coke rate.
Blast Furnace Cooling System:
Figure 10A shows the orientation of various instruments of SG Iron Stave cooler portion of
the Blast furnace. Figure 10B shows the typical view of a thermocouple of SG Iron Stave
cooler portion of the blast furnace. Figure 11A shows the orientation of various instrument
of copper stave cooler portion of the blast furnace. Figure 11B shows a typical view of the
thermocouple of the copper stave cooler portion of the blast furnace. Figure 12A shows the
orientation of various instruments at the cast iron stave cooler portion of tuyere of the blast

furnace. Figure 12B shows the orientation of various instruments at the cast iron stave
cooler portion of the other portion of the blast furnace.
Soft water closed circuit cooling system is provided for tuyere, tuyere cooler, stave coolers
and under-hearth cooling system.
Latest design of SG iron/copper stave coolers are adopted, each having four inlet and four
outlet cooling pipes in tuyere zone, bosh, belly, lower and upper stack region having better
corner cooling and providing possibility of zone wise heat load calculation. Cast SG iron
stave coolers are provided in the hearth zone. Bosh, belly and lower stack regions are
provided with copper stave coolers.
Various instruments are provided in the S.G Iron cooler portion in the blast furnace namely
Temperature Thermocouple (Simplex) (TTS), Temperature Thermocouple (Duplex) (TTD),
Skin Flow Temperature Thermocouple (Simplex) (SFT), Pressure Tapping (PT) and Stave
Body Thermocouple (SBT) {best shown in figure 10A}
Various instruments in the copper stave cooler portion in the blast furnace namely
Temperature Thermocouple (Simplex) (TTS) and Stave Body Thermocouple (SBT) {best
shown in figure 11A}
The Temperature Thermocouple (Simplex) (TTS) provided in the cast iron cooler portion in
the blast furnace is best shown in figure 12A.
The Temperature Thermocouple (Dimplex) (TTD) provided in the cast iron cooler portion in
the blast furnace is best shown in figure 12B.
Special manufacturing techniques adopted in the stave coolers ensure following expected
performance level of the coolers:
Heat load for Hearth and Tuyere zone
• Continuous operation 15 kW/m2
• Peak loads: 30 kW/m2

Heat load for bosh belly and lower stack
• Continuous operation 50 kW/m2
• Peak loads: 80 kW/m2
EXAMPLE :
Result of a sample calculation in the maximum heat load reaction zone is given below:
4250 m3 Blast Furnace – Heat Load calculation in the area of bosh, Belly and Lower stack
The heat load on the wall of the Blast Furnace is mainly attributed to two factors:
1. Heat load due to the air blast inside the Blast Furnace
2. Heat load due to heat transfer through burden material.
The outcome of the result is shown in table 3 below: -

Convection heat transfer between gas flow and skull (hf1)=230 W/m2/deg C
Radiation heat transfer between burden (coke + ore) to slag skull (hf2) =353 W/m2/deg C
Heat load at Bosh Belly and Lower stack = hf1 (Tf-Ts) + hf2(Tb-Ts)

= 55 KW/m2
Heat load for upper stack
• Continuous operation 30 kW/m2
• Peak loads: 50 kW/m2
Possibility of Charging Lower Fraction of Coke:
The improved blast furnace allows charging of +8 to 35 mm nut coke in addition to normal
charging of 35 to 80 mm coke and centre coke of +60 to 80 mm.
The charging of nut coke results in decrease of production cost and increased permeability
of ore burden by ~ 10 % which results in lower pressure drop and as such better gas
utilisation.
Blast Furnace Instrumentation and Control:
State-of-art instrumentation and control system is provided, which is based on
computer/PLC and has following features:
a. Sufficient levels of temperature sensing across BF profile. This results in better
monitoring of life of refractory and coolers.
b. Multi layer pressure measurements and calculation of pressure drop across the
furnace.
Stoves (SV) and Hot Blast Supply System:
Figure 8 is the elevation view showing the connection between the stove and the blast
furnace.
Figure 9A is the elevation view of the hot blast stove (SV). Figure 9B is the cross sectional
view of the stove along the line L-L of figure 9A. Figure 9C is the plan view of the hot stove
(SV).

The highlights of the hot blast stoves are as below:
a. Ceramic burner with stabilizer for vigorous intermixing of air and gas for complete
combustion.
b. Mushroom dome allowing independent growth of stove wall and dome.
c. Silica bricks for upper portion of stoves and upper checker work ensuring cleaner
checker holes.
d. Metallic shoes provided on top of grids to prevent checker breakage and provide
additional stability by restricting lateral movement.
e. Straight line hot blast temperature of 1,100-1,150°C with use of BF gas only with
preheated combustion air and BF gas.
f. Thermally compensated main hot blast and tuyere stock provided with bellow for
zero leakage.
Cast House (CA) and Cast House Runner Design:
We now refer to figures 2, 6A, 6B and 6C.
Figure 2 shows the general arrangement view of the cast house (CA). Figure 6A shows the
cross sectional view of the main trough. Figure 6B shows the cross sectional view of the slag
runner and iron runner. Figure 6C shows the cross sectional view of drain runner.
The blast furnace is provided with twin cast houses with double tap holes per cast house
(CA). Cast house runner system is adapted for better hot metal and slag separation. Slag
runner has been provided with optimum slope for better slag and hot metal separation. The
main iron trough is of adequate length and non-drainable type with forced air cooling
system.

Cyclone (CY)
Figure 7A shows general arrangement view of the tangential cyclone (CY). Figure 7B shows
the plan view of the tangential cyclone (CY).
The special features to effectively address the operational issues are:
• Improved efficiency (դ > 85 %) over dust catcher, thus reducing the load on
scrubber/venturi and enabling achieve better overall efficiency of gas the
cleaning system as a whole. Provision of dust separation by creating ‘vortex
motion’ offers significant advantage over the traditional ‘change in momentum
principle’.
• Absence of moving mechanical equipments makes the design operator-friendly
and eliminates frequent furnace shutdowns for its maintenance purpose.
• Cyclone (CY), which is the primary dust cleaning system, is an integral part of
the furnace operation. It not only takes care of potentially hazardous BF gas, but
also makes it usable (utilizing the calorific value and sensible heat) by separating
the dust content in tandem with GCP. Any breakdown of the same immediately
disrupts the operation cycle and in turn translates to monetary loss to plant.
Robust design with elimination of moving parts associated with the proposal
leads to minimize such losses
• Necessary instruments (pressure transmitters, temperature elements, level
sensors and purging arrangements) along with dust evacuation mechanism have
been provided and calibrated to assist the normal operation and emergency
measures.
Benefits of the New Design:
a) Design of Blast Furnace Proper (Smelter)
Currently, all basic metal extraction metallurgical process is burdened with ever
reducing quality of raw materials as well as operation with fluctuating compositions.

A blast furnace is not an exception. To cope up with such complexities which put
immense pressure on the operator, the basic smelter (BF proper) is made adequately
capable of handling raw material fluctuations and concurrent heat flux variations.
The Blast Furnace productivity has been kept at a modest figure of 2.31t/m3 WV/day
(based on assumed raw material standards).
To ensure sufficient inbuilt design robustness, the entire design has been carried out
considering a production level of 8,500 - 9,000 tpd along with adequacy of all
supporting auxiliary facilities.
b) Hot Blast Stoves
In order to build state-of-the-art hot blast stove system, the stoves (SV) have been
developed with emphasis on following three major considerations to ensure high
temperature and higher campaign life of stoves:
• Construction of stove proper with refractory and mechanical stability.
• Selection of suitable refractory materials for high temperature.
• Provision of close stove control.
The main features for hot blast stoves (SV) are as follows:
• Adoption of mushroom dome to achieve removal of dome refractory load from
stove refractory wall and to ensure independent movement of stove wall
refractory.
• The refractory of dome is selected with special emphasis on creep resistance and
provided with special tongue and groove in three dimensions to ensure proper
locking of dome structure.

• The refractory of the stove wall is designed in segment basis on panel design
with expansion joint in between and interconnected special shaped bricks for
overall stability.
• Refractory quality for various zones of hot blast stove has been selected keeping
eye on temperature profile of the hot blast stove. Silica bricks, having
tremendous advantage of no expansion above 600°C are selected for upper part
of stove walls.
• Measurement of interface temperature of silica and other refractory material
ensures stable refractory construction in spite of temperature fluctuation during
stove operation.
• The checker bricks have been specially constructed with high heating surface
area for efficient heat transfer and high hot blast temperature. The checker hole
size is selected to cater to gas cleanliness up to 10 mg/Nm3 level without any
blockage of checker holes. Silica checkers are considered for the top part of
checker work to avoid choking of checker holes. Silica also offers a glassy
surface to avoid sticking of dust particles.
• The stove shell and dome shell are lined with gunning castables to maintain the
shell temperature at relatively lower point, thus minimizing SOx/NOx cracking. It
also reduces radiation loss and thereby improves the efficiency of hot blast stove
• High capacity ceramic burner with stabilizer focusing on optimum burner angle is
provided to achieve vigorous intermixing of gas and air to ensure complete
combustion with minimum excess oxygen and no unburnt CO. Besides this,
optimum velocity of combustion product is maintained in combustion zone and
checker hole for better heat transfer.
• Provision has been made in the layout for accommodating a waste gas pre-
heater system. The gas and combustion air is designed to be pre-heated at
190°C to achieve high hot blast temperature.
• The hot blast stove control focuses on two key points of control:

a) Achieving dome temperature by regulating gas and air flow.
b) Once the desired dome temperature is achieved, shifting the control point
to waste gas temperature and maintaining it at designed level.
c) Monitoring of CO and O2 content in waste gas for integrating the input in
Level-2 for fine tuning the stove combustion process to achieve minimum
excess oxygen for highest combustion product temperature.
d) Energy Saving Devices
• Top Pressure Recovery Turbine - To use the pressure energy of top gas, Top
Recovery Turbine (TRT) of approx 16 MW capacity has been provided.
• Waste Heat Recovery System (WHRS) - Waste heat recovery system has been
provided for efficient utilisation of thermal energy of the flue gas coming out of
stoves. Similarly, waste gas of stoves is used in PCI system. Pre-heating of fuel
and combustion air through WHRS increases the burning efficiency and thus a
higher hot blast temperature can be achieved with reduction in consumption of
fuel.
• VVVF Drives - VVVF drives have been provided in areas like charging conveyor,
collecting conveyors, elevator, de-dusting system, ID fan in PCI etc., where the
load varies, to reduce the overall consumption of electrical energy.
e) Cast House (CA)
The improved blast furnace incorporates state-of-the-art cast house (CA) having flat
floor. All the runners are under sunk with removable covers. Separate set of
equipments have been provided for each trough, taking care about improving the
ambience of cast house and ease of man-machine movement.
The slag-and-iron runners are as short in length as possible to get rid of many basic

operational problems.
The height of the cast house is adequate for ease of movement of the Torpedo Ladle
Car below cast house.
f) Stock House (ST)
The prime objective of the stock house is to cater to the blast furnace burden
requirement (both quantitively and size distribution for charging burden) and
primarily matching with BLT cyclogram and burden descent in the furnace.
This facility has also been provided with following features, making the stock house
a more desirable facility for streamlined and trouble-free furnace operation:
• Adequate redundancy (for coke, iron bearing materials and additives) has been
envisaged, considering the non-availability/outage of feeders/screens/weigh
hoppers due to breakdown.
• Interchangeability explored with sinter, lump ore and pellets and between
surface coke and centre coke has also been ensured while making capacity
selection of equipment.
• Use of small sinter, 5-10 mm size (34 % of total sinter requirement), nut coke
(8-35 mm size - 20 kg/ THM) and centre coke (> 60 mm size - 20 % of total
coke requirement) charging facility has been incorporated in the material flow
scheme. It is not only in agreement with optimisation of resources, but at the
same time provides vital help towards operational control (central or peripheral
working) of a blast furnace, especially the larger ones.
• Width of the return fines conveyor belt has been kept on higher side to cope up
with Indian raw materials and large fines fractions.
• Capacity selection of equipment has been guided by clear depiction of charging
cycles of different materials by charging cyclogram, which also establishes the
above margins/cushions.

• All the parameters of furnace operations (all coke, normal ratings and max.
production) have been considered while deciding the parameters for the blast
furnace facility. Additional capacity cushion of min. 130 % force filling has also
been kept to meet the increased BF demands (during peak production on
specific demand of hot metal) and lowered equipment efficiency during its life.
The present invention has been described with reference to some drawings and a preferred
embodiment purely for the sake of understanding and not by way of any limitation and the
present invention includes all legitimate developments within the scope of what has been
described herein before and claimed in the appended claims.

We claim:

1. An improved blast furnace plant comprising of a blast furnace (BF) having high top
pressure to ensure better permeability, longer gas-solid reaction time and better fuel
rate and high hot blast temperature with provision of O2 enrichment for smooth
auxiliary fuel injection such as pulverised coal injection (PCI), a plurality of hot
stoves (SV) being provided with ceramic burner with stabilizer for vigorous
intermixing of air and gas for complete combustion and mushroom dome allowing
independent growth of stove wall and dome, twin cast houses with double tap holes
per cast house (CA), a stock house (ST) and a tangential cyclone (CY), the blast
furnace (BF) having a plurality of tuyeres, a top pressure recovery turbine, waste
heat recovery system, a plurality of variable voltage variable frequency (VVVF)
drives and a cooling system comprising of soft water closed-circuit cooling tuyeres,
tuyere cooler, stave coolers and under-hearth cooling.
2. The improved blast furnace plant as claimed in claim 1, wherein said stave coolers of
the cooling system comprise of SG iron stave coolers which are provided in the
hearth zone and copper stave coolers which are provided in the bosh, belly and lower
stack regions of the blast furnace (BF).
3. The improved blast furnace plant as claimed in claims 1 and 2, wherein the
instruments provided in the SG iron cooler portion of the blast furnace are
Temperature Thermocouple (TTS), Temperature Thermocouple (Duplex) (TTD), Skin
Flow Temperature Thermocouple (SFT), Pressure Tapping (PT) and Stave Body
Thermocouple (SBT).
4. The improved blast furnace plant as claimed in claims 1 and 2, wherein the
instruments provided in the copper stave cooler portion of the blast furnace are
Temperature Thermocouple (TTS) and Stave Body Thermocouple (SBT).
5. The improved blast furnace plant as claimed in claims 1 and 2, wherein each SG
iron/copper stave cooler has four inlet and four outlet cooling pipes in tuyere zone,
the bosh, belly, lower and upper stack regions being provided with better corner
cooling and with the possibility of zone wise heat load calculation.

6. The improved blast furnace plant as claimed in claim 1, wherein computer/PLC based
state-of-art instrumentation and control system is provided for sensing sufficient
levels of temperature across the blast furnae profile for better monitoring of life of
refractory and coolers and multi-layer pressure measurements for calculation of
pressure drop across the furnace.
7. The improved blast furnace plant as claimed in claim 1, wherein said tangential
cyclone (CY) is devoid of moving mechanical equipments and is provided with
pressure transmitters, temperature elements, level sensors and purging
arrangements along with dust evacuation mechanism.
8. The improved blast furnace plant as claimed in claim 1, wherein the mushroom dome
of said hot blast stoves (SV) is adapted to remove dome refractory load from stove
refractory wall and ensure independent movement of stove wall refractory, the dome
being selected with special emphasis on creep resistance and provided with special
tongue and groove in three dimensions to ensure proper locking of dome structure.
9. The improved blast furnace plant as claimed in claim 1, wherein said top pressure
recovery turbine has a capacity of approximately 16 MW.