Design And Fabrication Of Iron Ore Sintering Machine
1. 1
DESIGN & FABRICATION OF IRON ORE
SINTERING MACHINE
A Project Report
Submitted by
ALBIN KURIACHAN CHERIAN (090250121028)
SIDDHARTH RATHOD (100253121009)
In fulfillment for the award of the degree
of
BACHELOR OF ENGINEERING
In
Department of B.E. in Metallurgy Engineering
Indus Institute of Technology & Engineering, Ahmedabad
Gujarat Technological University, Ahmedabad
May 2013
2. 2
Indus Institute of Technology and Engineering, Ahmedabad
Department of B.E. in Metallurgy Engineering
2013
CERTIFICATE
Date: 23/05/2013
This is to certify that the dissertation entitled “ Design and Fabrication
Of Iron Ore Sintering Machine ” has been carried out by Albin K.
Cherian & Siddharth Rathod under my guidance in fulfillment of the
degree of Bachelor of Engineering in Department of B.E. in Metallurgy
Engineering (7th
Semester/8th
Semester) of Gujarat Technological
University, Ahmedabad during the academic year 2012-13.
Guides:
INTERNAL
Mr. D.K. Chauhan
Mr. Shashi Tandon
Head of The Department
Prof. D. K. Basa
3. 3
ACKNOWLEDGEMENT
We feel profound pleasure in bringing out this project report for which
we have to go from pillar to post to make it a reality. This project work
reflects contributions of many people with whom we had long discussions
and without which it would not have been possible. We must first of all,
express our heartiest gratitude to respected Mr. D.K. Chauhan, Mr. Shashi
Tandon for providing us all guidance to get an insight about the project,
“Design And Fabrication Of Iron Ore Sintering Machine”. We are sure
that their experience and the valuable guidelines will help us completing this
project successfully. Also, we wish to receive their guidance for the
upcoming part of the project as well.
We feel greatly honored to mention the invaluable Contribution and timely
co-operation extended to us by the staff members of our department and
especially we are grateful to the most worthy advices given by Mr. D. K.
Basa (H.O.D.) that would help us in the future also.
Albin K. Cherian(090250121028)
Siddharth Rathod (100253121009)
4. 4
Abstract
The sintering process converts fine-sized raw materials, including iron, coke breeze,
limestone, mill scale and flue dust, into an agglomerated product, sinter of suitable size
for charging into the blast furnace. The raw materials are something mixed with water to
provide a cohesive matrix, and then placed on a continuous, travelling grate called the
after which the combustion is self supporting and it provides sufficient heat 1200 –
1300o
C, to cause surface melting and agglomeration of the mix. On the underside of the
sinter strand is a series of windboxes that draw combusted air down through the material
bed into a common duct, leading to a gas cleaning device.
The fused sinter is discharged at the end of the sinter strand, where it is crushed and
screened. Undersize sinter is recycled to the mixing mill and back to the strand. The
remaining sinter product is cooled in open air or in a circular cooler with water sprays or
mechanical fans. The cooled sinter is crushed and sreened for a final time, then the fines
are recycled, and the product is sent to be charged to the blast furnaces. Generally, 1 Mg
of raw materials, including water and fuel, are required to produce 0.9 Mg of product
sinter.
PROBLEM SUMMARY
To make working model of sintering machine in metallurgical engineering
department laboratory for experimental studies.
Materials used in fabrication of sintering machine are :-
Cylindrical container with conical end for charging sintering raw materials.
Grit for supporting the charge.
Gas burner for igniting the sinter charge.
Arrangement for regulating flow of combustion air.
Blower for suction of products of combustion.
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LIST OF TABLES
NO. Table Description Page No.
Table 3.5.1 Details of Sinter Strands
provided in early years in
Indian Steel Plants
16
Table 3.8 Indian Sintering Plants
And their Performance
29
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LIST OF FIGURES
No. Figures Description Page No.
1. Dwight – Llyod
Sintering Machine
17
2. Spark Plasma Sintering
Machine
20
3. Selective Laser Sintering
Machine
23
4. Gas Fired Sintering
Machine
26
5. Design of Iron Sintering
Machine
36 to 40
6. Dimensions of sintering
machine
41 to 46
7. Cylindrical Container 48
8. Manometer 49
9. Grid with Gasket 50
10. Dust collector 51
11. Blower 52
12. Seamless pipe 53
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TABLE OF CONTENTS
Acknowledgment …………………………………………………. ….. ..3
Abstract ………………………………………………………………….4
List of Tables……………………………………………………………..5
List of Figures ……………………………………………………………6
Table of Contents…………………………………………………………7
Chapter :1 Introduction to Project
1.1 Sintering Process……………………………………………..9
1.2 Advantages……………………………………………………10
Chapter: 2 Detail Description of Sintering process…………………..11
Chapter: 3 Literature Survey
3.1 Principle of Sintering process……………………………….13
3.2 Process Variables…………………………………………….14
3.3 Function of sintering process………………………………..14
3.4 Advantages …………………………………………………...14
3.5 Types Of Sintering machine…………………………………15
3.6 Sinter Quality…………………………………………………27
3.7 Mechanism of sintering………………………………………28
3.8 Efficiency of sintering Machine……………………………..29
3.9 Control of sintering process…………………………………30
3.10 Principle of sinter making machine……………………….31
3.11 Economics of sintering……………………………………...32
3.12 Recent trends in sintering practice………………………..33
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3.13 Sintering of iron ore fines in india…………………………34
3.14 Steps in making Iron ore sinter……………………………35
Chapter: 4 Implementation of the project work
4.1 Design Of The Iron Ore Sintering Machine………………37
4.2 Dimesions of Iron Ore Sintering Machine………………...41
4.3 Raw Materials & Equipments……………………………...47
4.4 Process Parameters…………………………………………47
4.5 Fabrication…………………………………………………..47
4.6 Plan Of Work……………………………………………….54
4.7 Scope of future work………………………………………..55
4.8 Conclusion…………………………………………………...56
References………………………………………………………………57
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Chapter : 1
Introduction To Project
1.1 Sintering Process:
Sintering of iron ore was developed as a means to utilize the iron ore fines which
otherwise cannot be directly charged into the Blast Furnace. The function of the Sinter
Plant is to supply the blast furnaces with sinter, combination of blended ores, fluxes and
coke, which is partially ‘cooked’ or sintered. In this form, the materials combine
efficiently in the blast furnace and allow for more consistent and controllable iron
manufacture.
Common methods of burden preparation related to the performance improvements of iron
making (blast furnaces & direct reduction process)
The merits of sintering process are listed below in comparsion to iron ore pellets:
i. The sintering process uses cheap coke breeze as fuel while pellets need
expensive oil for firing.
ii. It is possible to agglomerate finer ore particles by sintering process
without any ore grinding step as needed by pelletising technique. It may be
recalled that grinding iron ore grinding step as needed by pelletising
technique. It may be recalled that grinding iron ore is very expensive
process.
The iron ore particles from 10mm to 3mm are accepted directly for
sintering. The particles smaller than 0.5mm are nodulised to 3 – 4 mm size
and then sintered.
iii. The limestone and dolomite can be added during sinter making to increase
the basicity (CaO/SiO2) up to 3 whereas addition of lime during pellet
making is not possible due to formation of low melting calcium ferrite
which renders pellet firing difficult.
iv. Calcination of limestone occurs during sintering process with coke breeze
as cheap energy source. This offers saving of expensive metallurgical coke
in the blast furnace.
v. The good reducibility of iron ore sinter promotes its use.
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vi. The large voidage in sinter offers good bed permeability in the furnace.
vii. The chemistry of iron ore sinter can be adjusted as per need.
viii. Sintering process can accept a variety of solid waste for recycling which is
the need of the day in the light of environmental considerations.
The major advantages of using sinter in BFs are
Use of iron ore fines, coke breeze, metallurgical wastes, lime, dolomite for hot
metal production.
Better reducibility and other high temperature properties.
Increased BF productivity due to higher softening temperature and lower
softening melting temperature range.
Improved quality of hot metal.
Reduction in coke rate in blast furnaces.
1.2 ADVANTAGES OF SINTERING PROCESS
Allows making complex geometries.
Ultilization of iron ore fines, mill scale and coke breeze.
High Precision.
Stability in large scale production process.
Good strength and stability.
Cost economy in comparsion with aaglomeration process.
Improvements and efficiency can be gained from higher softening
temperature and narrower softening in the melting zone, which increases the
volume of the granular zone and shrinks the width of the cohesive zone. A
lower silica content and higher hot metal temperature contributes to more
sulphur removal.
11. 11
Chapter : 2
DETAIL DESCRIPTION OF SINTERING PROCESS
The principal feed materials for sintering are fine untreated ores (8–10 mm) and ore
concentrates, as well as fuel (coke breeze and anthracite breeze up to 3 mm), flux
(limestone and dolomite up to 3 mm), and in some cases fine wastes (flue dust, scale, and
others). The end product is sinter cake. Over 95 percent of the sinter is used in ferrous
metallurgy; sinter is used in aluminum production, nickel production, and lead production
in nonferrous metallurgy.
The sintering process includes preparation of the charge, including proportioning or
batching the individual components, mixing, moistening, and pelletizing; sintering a
prepared charge on sintering machines; and processing the hot sintered cake by
fragmentation, screening to remove lumps up to 5–10 mm, cooling up to 100°C and
sorting. Sintering is closely coordinated with the operation of process machinery
preparing raw materials for sintering. This relationship places a premium on stabilization
of the principal input parameters of the process (blending and proportioning of materials,
chemical composition, moisture content, and so on), which opens up avenues for
comprehensive automation of the sintering process.
Sintering is carried out at sintering plants, which include stockpiles for blending and
storing reserves of charge materials, receiving hoppers, departments for comminution of
coke and limestone (also for calcining limestone), a charge preparation department, a
sintering department, and a department for processing the finished sinter cake.
Sintering machines are the basic process equipment in the sintering process. Conveyor-
type sintering machines featuring an endless train of grate-bottomed sinter buggies
(pallets) in motion are widely used. The buggy passes under the feeder, which lays down
a bed of charge of 250–400 mm on the pallet and then passes under the ignition furnace,
where the solid fuel contained in the surface zone of the sinter bed is ignited. The exhaust
12. 12
fan draws air downward through the bed (80–100 m3
/min per square meter of sintering
area); the combustion zone (15–20 mm) progresses downward through the bed at a speed
of 20–40 mm/min. Much of the charge melts at temperatures of 1200–1500°C, in the
combustion zone of the solid fuel. As the combustion zone progresses downward, the
semi-molten mass in the upper portion of the bed cools to form sinter cake. Gases
emanating from the combustion zone dry out and heat the lower portions of the sinter bed,
from which hygroscopic and hydrate water, carbon dioxide gas, and other volatiles are
driven off, as well as sulfur, arsenic, and other harmful impurities.
Many countries, including Russia, France and Germany, have underground deposits of
iron ore in dust from (blue dust). Such iron ore cannot be directly charged in a blast
furnace . In the early 20th
century, sinter technology was developed for converting ore
fines into lumpy material chargeable in blast furnace. Sinter technology took 30 years to
gain acceptance in the iron- making domain, but now plays an important role. Initially
developed to generate steel, it is now a means of using metallurgical waste generated in
steel plants to enhance blast furnace operation and reducing waste.
13. 13
CHAPTER: 3
LITERATURE SURVEY
3.1 Principle Of Sintering Process
In iron – ore sintering, essence is carried out by putting mixture of iron bearing
fines mixed with solid fuel on a permable grate.
Since coke breeze is available as a otherwise wasted product in an intergrated iron
and steel plant.
Its universally incorporated as a solid fuel in the sinter mix.
The top layer of this sinter bed is heated to the sintering temperature 12000
–
13000
C by a gas or oil burners and air is drawn downwards, through the grate,
with the help of blowers connected from underwater to the grade.
The narrow combustion zone developed initially at the top layer travels through
the bed, raising temperature of the bed, layer by layer to the sintering level.
The cold blast drawn through the bed cools the already sintered layer and thereby
get itself heated. The heat of the blast is utilized in drying and preheating the
lower layer in bed.
Therefore combustion advances, each layer gets dried and preheated by the heat
transferred from the upper combustion zone. Much of the heat in the gases is
absorb by the lower portion of the bed.
Sinter coke is then tipped from the grate in the hot condition or after particle
cooling.
Its broken, screened and cooled to produced desired fraction. The undersize is
recycled.
This process is known as down – draught since the air blast is draw through the
sinter-bed downwards.
In the first decade of the present century dwight and llyod in mexio developed the
continuous sintering for ferrous and Non- metal.
So it was adopted for iron ore sintering
Today Dwight – Lloyed - for only large scale machine for both ferrous and non-
metal.
14. 14
3.2 Process variables:
The variables of the sintering process are broadly as follow:
1. Bed permability as decided by the particle by the particle size and shape.
2. Thickness of the bed.
3. Volume of air blast drawn through sintering.
4. Rate of blast drawn through the sinter bed.
5. Amount and type of carbonates present in the charge.
6. Amount of moisture in the charge.
7. Amount and quaility of solid fuel in the charge.
8. Nature of ore fines. E.g. chemical composition.
9. Non-uniformity in the bed composition.
3.3 Role of Sinter Plant
The function of the Sinter Plant is to supply the blast furnaces with sinter, combination of
blended ores, fluxes and coke, which is partially ‘cooked’ or sintered. In this form, the
materials combine efficiently in the blast furnace and allow for more consistent and
controllable iron manufacture.
3.4 Advantages of using Sinters in the blast furnace
There are certain advantages of using sinters as opposed to using other materials
which include recycling the fines and other waste products, to include flue dust,
mill scale, lime dust and sludge. Processing sinter helps eliminate raw flux, which
is a binding material used to agglomerate materials, which saves the heating
material, coke, and improves furnace productivity.
Improvements and efficiency can be gained from higher softening temperature
and narrower softening in the melting zone, which increases the volume of the
granular zone and shrinks.
15. 15
3.5 TYPES OF SINTERING MACHINES:
1. Dwight – Lloyed Sintering Machine
2. Spark Plasma Sintering Machine
3. Selective Laser Sintering Machine
4. Gas Fired Sintering Machine
3.5.1 Dwight – Lloyed Sintering Machine:
of iron ore fines is now universally carried out on travelling machine
running on a continuous basis.
In 1958 large machine in operation was 3.7m in width, 223 m2
area,
production 800t/day.
Rigt now, the largest machine are use in japan and is nearly 8m width ,
500m2
, 24000t/day.
The Dwight-Llyod sintering machine is essentially an endless bend of pellets
moving over rails.
Stretched across and over two huge pulleys, oe which is driven by a motor
through a reduction gear system.
The rotating machine are loaded at one end of the machine and top layer is
ignited as it immediately comes under a fixed ignition hood.
As pellets moves the ignited portion comes over series of stationary wind-
boxes connected an exhaust blower.
Sintering of charge is completed by the time the pellets travels over nearly
the whole useful length of machine.
The sintered cake does out at the other end when the pellets turn upside
down.
The coke is broken, screened and the oversize is cooled.
The undersize is usually 9mm, is returned to machine for re-sintering whereas
the oversize after rescreening goes to the blast furnace as charge.
The exhaust gases from the windboxes are let off into the atmosphere through
a chimney after dust extraction.
16. 16
Table 3.5.1.Details of Sinter Strands provided in early years in Indian Steel Plants
Bhilai Durgapur Rourkela TISCO Bokaro
No. Of Strands 4 2 2 2 2(1.7Mt)
2(in
second
stage)
Width 2 2.5 2.5 2 4
Working length, m 25 57 50 30 63
Working area, m2
50 142.5 125 60 252
Annual prod. Capacity
, Mt
2 2.1 1.2 1.26 4.2
Depth of bed mm 300 300 300 300 350
Area of cooling
section m2
- - - - 60
The important parts of the machine and its accessories that make the complete
sinter plant are as follows:
1. Storage bins, mixers, feeder, etc.
2. Charge leveler.
3. Ignition hood
4. Band of pallets and rails for its movement.
5. Drive mechanism.
6. Sinter breaker, screen, cooler, etc.
7. Spillage collector.
8. Windboxes, dust extractor , exhaust fan , chemistry, etc.
18. 18
3.5.2 Spark Plasma Sintering Machine:
Spark plasma sintering (SPS), also known as field assisted sintering
technique (FAST) or pulsed electric current sintering (PECS), is
a sintering technique.
Spark plasma sintering (SPS) is a form of sintering where both external pressure
and an electric field are applied simultaneously to enhance the densification of the
metallic/ceramic powder compacts. This densification uses lower temperatures
and shorter amount of time than typical sintering. The theory behind it is that there
is a high-temperature or high-energy plasma that is generated between the gaps of
the powder materials; materials can be metals, inter-metallic, ceramics,
composites and polymers. Using a DC pulse as the electrical current, spark
plasma, spark impact pressure, joule heating, and an electrical field diffusion
effect would be created.
Certain ceramic materials have low density, chemical inertness, high strength,
hardness and temperature capability; nanocrystalline ceramics have even greater
strength and higher superplasticity.
Many microcrystalline ceramics that were treated and had gained facture
toughness lost their strength and hardness, with this many have created ceramic
composites to offset the deterioration while increasing strength and hardness to
that of nanocrystalline materials. Through various experiments it has been found
that in order to design the mechanical properties of new material, controlling the
grain size and its distribution, amount of distribution and other is pinnacle.
The main characteristic of Spark Plasma Sintering is that the pulsed DC
current directly passes through the graphite die, as well as the powder compact, in
case of conductive samples. Therefore, the heat is generated internally, in contrast
to the conventional hot pressing, where the heat is provided by external heating
elements. This facilitates a very high heating or cooling rate (up to 1000 K/min),
hence the sintering process generally is very fast (within a few minutes). The
general speed of the process ensures it has the potential of densifying powders
with nanosize or nanostructure while avoiding coarsening which accompanies
standard densification routes. Whether plasma is generated has not been
confirmed yet, especially when non-conductive ceramic powders are compacted.
19. 19
It has, however, been experimentally verified that densification is enhanced by the
use of a current or field.
Spark Plasma Sintering as a Useful Technique to the Nanostructuration of Piezo-
Ferroelectric Materials
Benefits of Spark Plasma Sintering Machine:
Reduced sintering time.
Good grain to grain bounding.
Clean grain boundaries.
Initial activation of powders by pulsed voltage.
Resistance under sintering pressure.
Principle of Spark Plasma Sintering Machine:
The SPS process features a very high thermal efficiency because of the direct
heating of the sintering graphite in old and stacked powder materials by the large
spark pulse current. It can easily consolidate a homogeneous, high-quality sintered
compact because of the uniform heating, surface purification and activation made
possible by dispersing the spark points.
Examples of Spark Plasma Sintering applications:
High-temperature short-period SPS sintering is expected to provide almost all
ceramic materials with new characteristics and sintered effects which are different
from those obtained by the HP and HIP processes. The ceramic materials which
can be sintered at high density include oxides such as A1203, mullite, Zr02, MgO,
Hf02 and SO2, carbides such as Sic, B4C, TaC and Tic, borides such as TiB2 and
HfB2 and nitrides such as Si3N4, TaN, TiN and AIN.
21. 21
3.5.3 Selective Laser Sintering Machine:
Selective Laser Sintering was developed and patented by Dr. Carl Deckard at the
University of Texas at Austin in the mid-1980s, under sponsorship of DARPA. A
similar process was patented without being commercialized by R.F. Housholder in
1979.
Selective laser sintering (SLS) is an additive manufacturing technique that uses a
high power laser (for example, a carbon dioxide laser) to fuse small particles of
plastic, metal (direct metal laser sintering), ceramic, or glass powders into a mass
that has a desired 3-dimensional shape. The laser selectively fuses powdered
material by scanning cross-sections generated from a 3-D digital description of the
part (for example from a CAD file or scan data) on the surface of a powder bed.
After each cross-section is scanned, the powder bed is lowered by one layer
thickness, a new layer of material is applied on top, and the process is repeated
until the part is completed.
Because finished part density depends on peak laser power, rather than laser
duration, a SLS machine typically uses a pulsed laser. The SLS machine preheats
the bulk powder material in the powder bed somewhat below its melting point, to
make it easier for the laser to raise the temperature of the selected regions the rest
of the way to the melting point.
Some Selective Laser Sintering machines use single-component powder, such as
direct metal laser sintering. However, most Selective Laser Sintering machines
use two-component powders, typically either coated powder or a powder mixture.
In single-component powders, the laser melts only the outer surface of the
particles (surface melting), fusing the solid non-melted cores to each other and to
the previous layer.
22. 22
Compared with other methods of additive manufacturing, Selective Laser
Sintering can produce parts from a relatively wide range of commercially
available powder materials. These include polymers such as nylon, (neat, glass-
filled, or with other fillers) or polystyrene, metals including steel, titanium, alloy
mixtures, and composites and green sand. The physical process can be full
melting, partial melting, or liquid-phase sintering. Depending on the material, up
to 100% density can be achieved with material properties comparable to those
from conventional manufacturing methods. In many cases large numbers of parts
can be packed within the powder bed, allowing very high productivity.
Selective Laser Sintering is performed by machines called Selective Laser
Sintering systems. Selective Laser Sintering technology is in wide use around the
world due to its ability to easily make very complex geometries directly from
digital CAD data. While it began as a way to build prototype parts early in the
design cycle, it is increasingly being used in limited-run manufacturing to produce
end-use parts. One less expected and rapidly growing application of Selective
Laser Sintering is its use in art.
Unlike some other additive manufacturing processes, such as stereolithography
(SLA) and fused deposition modeling (FDM), SLS does not require support
structures due to the fact that the part being constructed is surrounded by
unsintered powder at all times.
24. 24
The STL file of your 3D CAD data is entered into the Sinter station system. A thin
layer of powdered SLS material is then spread across the build platform by a roller
mechanism. Using data from the STL file, a CO2 laser selectively draws a cross
section of the object on the layer of powder. As the laser draws the cross section,
it selectively 'sinters' (heats and fuses) the powder creating a solid mass that
represents one cross section of the part. Once a cross section is completed the
build platform lowers by 0.1mm layer thickness and a new layer of powder is
spread. The system continually spreads and sinters layer after layer until the object
is complete. Once the build is completed, the part is removed from the machine
and the unsintered, loose powder is simply brushed away leaving a fully
functional nylon model, ready to send to the customer.
Selective laser sintering Applications:
1. Rapid Manufacturing:
Aerospace Hardware
UAS, UAV, UVG, UGV Hardware
Medical and Healthcare
Electronics; packing , connectors
Homeland Security
Military Hardware
2. Rapid Prototypes:
Functional proof of concept prototypes
Design Evaluation Models (Form, Fit & Function)
Product Performance & Technique
Engineering Design Verification
Wind – Tunnel Test Models
3. Tooling and Patterns:
Rapid tooling ( concept development & bridge tools)
Injection Mold Inserts
Tooling and manufacturing estimating visual aid
25. 25
3.5.4 Gas Fired Sintering Machine:
Gas Fired furnaces T max. 900 – 1400c
For the temperature range between 900 to 1400 c
Thermoconcept supplies different furnaces individually designed to meet the
specific requirements:
1. Furnace system for temperature up to 1400 c
2. Various furnace types ( Chamber Furnaces, bogie hearth furnaces, hood
furnaces, driving hood furnaces)
3. Superb firing results.
4. Low power consumption due to special multilayer refractory linning with
best insulation properties.
5. Burner systems with large performance range, specially designed to match
the furnace.
6. Automatic control of burner atmosphere.
7. Start – up furnace at low temperature with high temperature uniformity
and without sudden temperature changes.
8. Optimal temperature distribution by means of multi- zone control and
special flue gas routing system.
9. Cutting- edge control and regulation system with optimal process control
for fully – automatic system operation, perfectly matching the needs of
users.
10. Minimal maintenance required.
27. 27
3.6 SINTER QUALITY:
To increase the size of ore fines to a level acceptable to the B.F.
To form a strong agglomerate with high bulk reducibility.
To remove volatile like CO2 from carbonates, from hydroxide or S from sulphide
ore fines along with their agglomeration.
To incorporate flux in the burden.
Three different types of sinter are being produced depending upon the extent of
addition of flux in the mix and these are
a. Acid Sinter
b. Fluxed Sinter
c. Super – Fluxed Sinter
a. Acid sinter:
The sinter mix does not contain flux at all.
Flux is added in the furnace separately.
The properties of this type is fast and most modern practice produce
self- fluxing or super – fluxed sinter.
b. Fluxed sinter:
The amount of flux added in the mix in such that the basicity of the
mix equal to that of the slag to be produced in the furnace.
Separate addition of flux would be red only in proportion to the
amount of natural lumpy ore charged in the furnace.
c. Super – fluxed sinter:
The entire amount of flux required to be otherwise charged in the
furnace, when run of 100% natural ore charged is added is added in the
mix.
The basicity of the mix would be obviously more than that of the slag
in the furnace.
Since a part of charge would either be natural lumpy ore or sinter of
lower basicity than that of normal Blast furnace slag.
No separate flux is required if super – fluxed sinter is used.
28. 28
3.7 MECHANISM OF SINTERING:
Each layer below the ignited top layer undergoes changes in the order as follow
Wet Ore – Drying – Calcining – Pre-heating – Combustion – Cooling .
The same order of changes take place on a moving bed.
Chemical composition changes gradually across various zone
The Proportion of ferrous iron is more in the zone of calcination combustion but it
decrease on cooling.
Two types of bond may be formed during sintering.
Diffusion or Recrystallization or Solid State Bond:
It’s formed due to recrystallization of the parent-phase at the point of
contact of two particles in the solid state.
Glass or slag bond:
It’s formed due to formation of low melting slag and glass at the point of
content depending upon the mineral constitution, flux addition etc.
The sinter can have three constitutents :
Mineral without any change
Change of physical structure without chemical change.
Secondary constituent due to reaction between two or more of the original
constituents.
More slag bonding means stronger sinter but less reducibility.
More diffusion bonding means more reducibility but less strength.
The best practice is to sinter at lower temperature and at rapid rate as to form
enough slag bond but not much of recrystallization.
29. 29
3.8 Efficiency Of Sintering Machines
The efficiency of sintering machine can be assessed in terms of the following parameters:
1. Productivity in tonnes of useful sinter per square meter of the working area per
hour. Bigger is the figure, more efficiency is the unit.
2. Effective suction as determined by the effectiveness of leak proof seals measured
in terms of length of seals per square meter working area. Smaller is the length
better is the efficiency.
3. The quantity of air drawn through the bed per unit time. The higher is the value
better is the efficiency.
The data from Indian plants may be worthwhile to be examined here in this
regard. These are given in Table
Table 3.8
Indian Sintering Plants And their Performance
No.
Steel
Plants
Rated
Capacity
Mt/year
Sintering
Area m2
*
No. of
strands
Suction
Bed
Bed height
mm
Sinter
production
t/m2
/hr
%
sinter
in B.F.,
burden
1 Bokaro 4.94
252/312 *
3
1350 350 1.20
70
2 Bhilai 4.18 75*4 1100 300 1.28
60
3 Rourkela 1.80 125*2 900 527 1.00
45
4 Durgapur 1.50
140*2 and
180*1
945 400 0.92
35
5 Tata Steel 2.54
75*2 and
192*1
1000 and
1328
340
600
1.06
65
6 VSP 2.45 312 1250 400 1.20
70
30. 30
3.9 Control Of Sintering Process
The operation of a sintering machine can be controlled by proper adjustments of
the following operational variables:
1. Fuel content for heat input
2. Ignition intensity
3. Moisture content of mix to control its permeability
4. Machine speed to obtain complete ‘burn through’
5. Percent Returns
6. Bed height
For an idel operation these parameters are fixed and the operator must, as far as possible,
ensure maximum consistency (i.e. minimum of departure from the standard conditions) in
plant operation so that sinter of desired properties would be automatically obtained.
31. 31
3.10 Principle Of Sinter Making Machine.
The iron ore sinters are made in the sintering machine. These machines are designed for
different capacities, ranging from a few kilograms per batch in pot sintering (laboratory
use) to a few hundred tons/hour in Dwight Lloyed Sintering Unit (industrial use).
However, the principle of working remains the same.
The basic components of the equipment are:
a) A fixed grate (pot unit) or travelling grate (industrial unit)
b) Air suction device
c) A combustion initiating device.
32. 32
3.11 Economics Of Sintering
Typical figures indicating capital cost of setting up of sinter plant are shown below:
% of total cost
Civil work
Foundation 10
Buildings 23
Electricals 15
Sinter machine (including controls) 16
Sinter cooler 7
Blower, apron etc. 7
Raw material handling equipments 10
Gas main, bunkers, etc. (Plate work) 7
Miscellaneous 5
Total 100
The operating cost – breakdown is typically as follows:
Wages 30%
Repair maintainance, supplies,utilities,etc. 50%
Transportations and general services 5%
Fixed expenses 15%
Total 100
33. 33
3.12 Recent Trends in Sintering Practice
Couple of decades ago when furnace oil was cheaper than coke it was extensively used to
replace coke. Emphasis was then to produce sinter with maximum cold strength as
measured by shatter and tumbler test indices. Now the scenario is changed and coke and
coal are being used in blast furnaces. Now the sinter is aimed to be better reducible .
Sintering with low heat input can lead to these objectives:
1. Better reducibility
2. Less slag volume
3. Good high temperature properties like softening and melting characteristics.
4. Optimum strength and RDI
These have resulted in charges in sintering practices as follows:
1. Use of magnesium silicate mineral as flux in sinter – mix.
2. Use of quick – lime as flux in sinter – mix to improve upon the bondings.
3. Increase in depth of sinter bed from usual 350 – 400 mm to 600 – 650 mm. This
has resulted in much higher productivity and decreased coke rate by about 5 – 10
kg/t sinter. This has been actually been achieved at Tata Steel.
4. Deeper bed logically leads to adoption of double layer sintering, i.e. different coke
percentages in the two layers higher in the top and lower in the bottom. This saves
coke breeze rate by about 4 kg/t sinter and reduced blast rate by about 0.5 Nm3
/t
sinter.
5. Oxygen enrichment of the igniting fuel gas and extending the ignition area by
about 10% more by extending the ignition hood length. This gives better
productivity and better shatter strength.
6. Nearly 50% of the heat required in sintering is discharged in the open atmosphere
as waste heat. Sintering process consumes nearly 10% of the total energy required
in an integrated steel plant. Heat recovery systems have been developed by the
Kokura Steel Works of sumitomo Metal Industries, Japan.
7. For low production of sinter china has development an alteranative to standard
sintering machine. It is known as ‘ Step – by – Step Box Sintering Machines. Its
capital cost is half that of the standard machine.
34. 34
3.13 Sintering Of Iron Ore Fines In India
The cost of hot metal is one of the key factors that influences the economy of steel
production in an hot metal based integrated steel plant. Cost of hot metal is influenced by
the quality of coke and the quality of iron ore in the form of lumps.
Besides the iron content and strength, the alumina content of the ore decides the quality of
ore. Fortunately by proper washing treatment it is possible to reduce the alumina content
of the ore lumps to below 2 % as against the maximum 1% all over the world. This is the
best that can be done under Indian conditions, as far as the lumpy fraction of the ore is
concerned.
Alumina content of the burden makes the slag more refractory and this problem has to be
tackled by increasing the basicity and/or addition of MgO. All this tend to increase the
slag volume along with its attendant problems like decreased productivity and increased
coke rate, and high operating temperature leading to high silicon content in the hot metal.
The adverse role of alumina in the burden need no extra emphasis.
The adverse role of alumina in the sinter on its strength and reduction - degradation
properties (RDI) has now been conclusively proved. Any increase in alumina content of
the sinter beyond 2% alumina decreases the sinter strength as determined by the tumbler
test and similarly it increase the reduction – degradation index, and as a result coke rate
goes up. For maintaining the same RDI , basicity of the sinter has to be increased. For
better blast furnace performance the stack zone should be as extended as possible with the
softening and melting zone confined to as narrow a zone as possible in the lower part.
This is possible only if the RDI is low i.e. alumina content is low, particularly at low
basicities. Lower slag volume i.e. lower bascities can be obtained only by restricting the
sinter content of the burden under Indian conditions. Alternatively the sinter alumina
should be reduced by prior benefication of the classified fines of iron ore to preferably
lower than 2% alumina content. This is being adopted at the Tata Steel for the first time in
India to improve upon the sinter quality and thereby to have more than 70% sinter in the
burden for efficient blast furnace operation.
35. 35
3.14 Steps in Making Iron Ore Sinter
The main steps during sinter making are:
1. Raw material preparation
2. Mixing
3. Feeding
4. Combustion
5. Sintering
6. Sinter cooling/screening
These steps are described briefly in the following lines.
1. Raw material preparation
The sinter process can use a variety of material generated as waste. The main
components of raw material are:
i. Iron ore (~ 10mm) fines with minimum quantity of particles below
0.150mm (~ 100 mesh)
ii. Coke breeze (~ 3mm)as fuel
iii. Flux (limestone, dolomite, etc.) (~3mm)
iv. Waste fines (flue, dust, sludge,etc.) as micro – nodule of 3 – 4mm.
As the ingredients are stored in separate bins and they are weighed in the required
proportion before mixing.
2. Mixing
The various ingredients are fed to a mixing drum with water and rotated. After
mixing the sinter mix, it may be further rotated in another drum to agglomerate for
better bed permeability.
3. Feeding
The wet sinter mix is fed on the hearth layer. The bed height is regulated by a
leveling bar.
4. Combustion
When the green mix reaches below the ignition hood, it is exposed to burner flame
and also suction from bottom located wind box. The coke breeze on the top layer
gets ignited.
5. Sintering
Once the top layer is ignited, the sintering begins. As the grate advances, the
suction of air makes the combustion front move downwards. The progress of
sintering on a moving bed with sintering time starting from ignition hood. The
topmost layer of friable sinter as it does not get sufficient time to fuse and get
stronger due to cooling by the incoming air. The next layer consist of strong
sintered iron ore. The combustion zone is plastic due to heat and is just beginning
36. 36
to sinter. Below the combustion zone lies a calcination and dry zone of iron ore
created by flowing hot gases. The thickness of various zones vary on the grate at
different locations. Near the ignition hood, the thickness of green sinter is more
whereas the strong sinter zone thickness is more before discharge end. The speed
of the grate is so adjusted that the sintering is complete before it reaches the
discharge end.
6. Sinter cooling/screening
At the end of the grate, the rotating hammer breaks down the discharged sinter
into smaller size. This is screened, cooled and used according to size. The -
15+10mm size sinter is used as hearth layer whereas +15mm size is used for the
blast furnaces.
47. 47
4.3 Raw Materials and Eqiupments used in Fabrication are as follows:
1. Mild Steel Sheet (MS:IS:2062)
2. Burner
3. Gaskets (20 mesh – 30mesh)
4. Manometer
5. Thermocouple
6. Dust Catcher
7. Blower attached with motor (Single Phase)
4.4 PROCESS PARAMETERS
1. Pressure
2. Gas Velocity
3. Bed Height
4. Size distribution of the material
5. Temperature
6. Nature of the ore fines
4.5 Fabrication
1.Burner:
There will be an oil fired burner with vaccum blower which will be used for
heating so with sufficient heat the heating will be carried out.
48. 48
2 .Cylindrical container
MS.IS:2062 Cylindrical container having a diameter of 170mm, length of 350mm
and thickness of 4.9mm will be used for the sintering process. The container
having tilting ends on the pipe so that tilting of the sinter product can be carried
out easily.
Fig.16
49. 49
3.Manometer
The manometer will be attached on the side of the seamless pipe so that it can
check the air pressure usually limited to measuring pressures near to atmospheric.
Normally, the will be attached with elbow pipe and to the seamless pipe so that
appropriate pressure can be checked accurately.
Fig: 17
50. 50
4.Grid with Gasket
The grid and gasket will be placed at the below the cylindrical container and
gasket will be of 30 mesh in size will be attached with the grid on which sintering
process will be carried out.
Fig:18
51. 51
5.Dust Collector
The dust collector will be a cylindrical. The dimension of the cylinder will be 300
length and a thickness of 6 mm of the cylinder. One end of the pipe is connected
from the upward and other is connected from the front of the collector.
Dust collectors are used in many processes to either recover valuable granular
solid or powder from process streams, or to remove granular solid pollutants from
exhaust gases prior to venting to the atmosphere. Dust collection is an online
process for collecting any process-generated dust from the source point on a
continuous basis. Dust collectors may be of single unit construction, or a
collection of devices used to separate particulate matter from the process air. They
are often used as an air pollution control device to maintain or improve air quality.
Fig:19
Mist collectors remove particulate matter in the form of fine liquid droplets from
the air. They are often used for the collection of metal working fluids, and coolant
or oil mists. Mist collectors are often used to improve or maintain the quality of
air in the workplace environment.
Fume and smoke collectors are used to remove sub micrometre size particulate
from the air. They effectively reduce or eliminate particulate matter and gas
streams from many industrial processes
52. 52
Important parameters in specifying dust collectors include airflow the velocity of
the air stream created by the vacuum producer; system power, the power of the
system motor, usually specified in horsepower; storage capacity for dust and
particles, and minimum particle size filtered by the unit. Other considerations
when choosing a dust collection system include the temperature, moisture content,
and the possibility of combustion of the dust being collected.
5. Seamless Pipe with attached motor and Blower
The seamless pipe with attached motor and blower will be used so that suction of
the hot air and fumes will be carried out easily.
Fig:20
53. 53
• The blower will be attached at the end pipe with motor so that suction can be
carried out.
• The motor which is to be attached will be three phase motor which will having a
blower and a Single phase motor .
54. 54
4.6 PLAN OF WORK
1. Since design and fabrication of iron ore sintering process involves proper
understanding and to have desired strength and quality of sinter,Keeping this in
mind suitable process and materials are selected for the laboratory scale sintering
machine.
2. Initial trials are conducted without charging of materials to ensure proper working
of the all parts and assembly machine.
3. After successful working of all parts of the machine, trial is conducted with charge
materials.
4. Then sintering parameters are established to obtain desired strength and
reducibility of the sinter.
• Materials used in fabrication of sintering machine are :-
1. Cylindrical container with conical end for charging sintering raw materials.
2. Grit for supporting the charge.
3. Gas burner for igniting the sinter charge.
4. Blower for suction of products of combustion.
5. Arrangement for pressure/ Suction measurement.
• In case of need suitable modifications will be carried out.
• Then trial runs will be conducted to observe proper working.
• Then trial charges are loaded and performance is observed.
• The literature survey and material selection:100% work completed.
• Desgin of the machine: 100% work completed
• Fabrication: completed.
55. 55
4.7 Scope of future work
1. Due to difficulties encountered during fabrication work, the actual design has been
modified slightly by the fabricator.
2. The actual sintering process trials will be done in the modified fabrication
equipment.
3. Depending upon the nature of sinter obtained then the equipment can be modified
further.
4. The location of thermocouple will have to been changed.
56. 56
CONCLUSION
A laboratory scale sintering machine for developmental studies.
It will need the important aspect of agglomeration process.
57. 57
REFERENCES
An Intoduction to Modern Iron Making , Khanna Publications, Chapter 7,
Page No. 95
http://en.wikipedia.org/wiki/Sintering
http://encyclopedia2.thefreedictionary.com/Sintering
xa.yimg.com/.../SUMITOMO%2BREVIEW-Spark-Plasma-Sintering....
www.csc.com.tw/csc_e/pd/prs02.html
http://en.wikipedia.org/wiki/Selective_laser_sintering
http://en.wikipedia.org/wiki/Spark_plasma_sintering
www.waset.org/journals/ijcie/v6/v6-34.pdf
www.doiserbia.nb.rs/ft.aspx?id=0350-820X0901035B
http://en.wikipedia.org/wiki/gas_fired_sintering
