1.2 MT/YEAR PELLET PLANT
Field of the Invention
The present invention concerns development of core area of Pellet
Plant for carrying out induration and process gas recirculation for
pelletising of iron ore fines. In particular, the invention relates to
indigenous development of technology, basic and detailed engineering of
core area of Travelling grate type 1.2 Mt/Yr capacity pellet plant i.e.
induration and process gas recirculation system for performing various
heat treatment processes of drying, preheating, firing and cooling of
pellets.
Background of the Invention
Pelletising is the process of rolling of moist iron ore fines (less than
100 mesh size) with binder and additives into green balls and then dried,
pre-heated and fired to produce hardened pellets. Various steps of
pelletisation consist of additives storage and grinding, mixing, balling,
induration, process gas recirculation and pellet screening.
Availability of lump ore for blast furnaces and direct reduction
plants is becoming difficult nowadays and expensive too. On the other
hand, large amount of iron ore fines (including ultra fines) are being
generated at different mine heads during mining. Utilization of these fines
has become a great challenge for the iron and steel industry. Keeping in
view this fact, many entrepreneurs have either set up, or are inclined to
set up, pellet plants of capacity 1.0 to 1.2 Mt/yr in India in addition to
large sized pellet plants depending upon the requirement.

All the large capacity pellet plants installed in India are based on
travelling grate process and for which technology, basic engineering and
major process equipment have been procured from foreign technology
providers. Further, the other pellet plants having capacity varying from
0.3 Mt/yr to 1.2 Mt/yr) have been installed mostly based on grate-kiln
technology (process and equipment type being different from travelling
grate process) and were also supplied by foreign technology providers.
Currently, therefore, installation of pellet plants in India is
dependent on know-how and technology of foreign technology providers.
As a part of know-how and proprietary design, technology providers
never divulge information regarding design basis / basic sizing calculation
and manufacturing drawings of induration and process gas recirculation
area.
In order to eliminate dependency on foreign technology suppliers
and with a vision of "Make in India", work has been taken up to
develop indigenous technology and design for the core area of
pelletisation process i.e. Induration and Process Gas Recirculation
System.
Prior Art
Indian Patent Application No. 2454/CHE/2010 ("2454") titled
"Moving Car Furnace for Iron Ore Peptization Process" by Sree
Rayalseema Green Steloy Limited discloses a straight grate pelletization
process, the technology and proprietary equipment design whereof is
owned by few foreign technology providers. Although the present MECON
invention is also straight grate pelletising process, however, with a view
to eliminate dependency on foreign technology suppliers, complete know-

how and design has been developed for the core area of pelletisation
process i.e. induration and process gas recirculation system. While 2454
does not specify any equipment parameters for a particular production
capacity, the MECON invention design development is for 1.2 MT/yr Pellet
Plant and it specifies various equipment parameters for achieving the
rated capacity. While 2454 is silent about the basic and detailed design
and engineering development of the equipment (propriety in nature) and
process gas recirculation system including process gas ducting and fan
sizing, indurating hood, the parameters of propriety equipment
(indurating machine, hood and process duct work), process fans has
already been finalized based on the basic and detailed engineering
development in respect of the present MECON invention. Further, detailed
engineering and development of equipment manufacturing drawings are
in progress based on the basic design and engineering already carried
out. While 2454 is also silent about the design of indurating hoods and
furnace, the profile of the indurating hood and hoods in other zones were
designed by MECON based on the required gas to flow at desired velocity
and to ensure flow of the hot process gas from cooling zone to the
preheating zone on direct recuperation method. Further, burners are
envisaged on either sides in preheating and firing zones. These are
required for maintaining the desired temperature profile across the hood
based the quality of the raw materials. While the 2454 moving car has
uniform speed, the MECON process is envisaged with variable speed
pallet car drive to full fill the requirement of varied quality of input raw
materials. While the 2454 pallet car is made of perforated plates at the
bottom, the MECON pallet car is equipped with heat resistant replaceable
type grate bar which will give much better life.
Indian Patent Application No. 24/MUM/2013 titled "A Method for
Producing Iron Ore Pellet with Improved Quality and Increased

Production and A System Thereof" by JSW Steel Limited relates to a
operating methodology in an existing plant for production of iron ore
pellet with improved production rate and quality by optimizing the
indurating machine firing temperature and damper opening of process
fans at higher pellet bed height. The present MECON invention is a
development of know-how, basic design and engineering of core area of
pellet plant i.e. induration and process gas recirculation for 1.2 Mt/yr
production capacity of iron ore pellet plant.
Indian Patent Application No. 6040/CHENP/2010 titled "Method for
Producing Iron Ore Pellet" by Kabushiki Kaisha Kobe Seiko Sho (Kobe
Steel, Ltd.) discloses a method for producing iron ore pellet in accordance
with a grate kiln system, the method comprising sequentially heating an
iron ore pellet in a drying chamber, a dehydration chamber, and a
preheating chamber while the iron ore pellet is being moved with a
travelling grate and subsequently firing the iron ore.pellet with a rotary
kiln including kiln burner and cooling the pellets in annular cooler. The
present MECON method for producing iron ore pellet is in accordance
with straight grate system which involves drying, heating and cooling of
pellet in a indurating machine in place of three separate equipment as
required for grate kiln system.
Indian Patent Application No. 1884/DELNP/2003 titled "An
Apparatus and Method for Recycling Dust and Sludge Containing Iron in
Iron Making Process Using Coal and Fine Ore" by POSCO discloses a
process of producing molten pig iron or hot metal by a system having
preheating furnace, a pre-reduction furnace and a final reduction furnace
and a melter classifier having a char bed by using raw materials as fine
iron ore (generally of about 10 mm size). According to the present
MECON invention, the process for production pellet is by rolling of moist

iron ore fines (less than 100 mesh size) with binder and additives into
green balls and then dried, pre-heated and fired in indurating machine.
Under this, development work has been carried out to acquire know-how,
basic design and engineering of core area of pellet plant i.e. induration
and process gas recirculation for 1.2 Mt/yr iron ore pellet plant.
Indian Patent Application No. 6421/CHENP/2008 titled "Method and
Apparatus for Producing Direct Reduction Iron" by HYL Technologies, S.A.
DE C.V. is aimed to the direct reduction of iron oxide particles to produce
direct reduced iron (DRI), also known in the industry as sponge iron.
More specifically, the present invention is directed to improvements in the
methods and equipment employed for recycling cooling gas to the cooling
zone of the direct reduction reactor. According to the present MECON
invention, the process for production pellet is by rolling of moist iron ore
fines (less than 100 mesh size) with binder and additives into green balls
and then dried, pre-heated and fired in indurating machine which is
entirely different from both the process and end product point of view.
Indian Patent Application No. 2081/MUM/2011 titled "Gas Based
Direct Reduction Process for Producing Sponge Iron" by Ispat Industries
Limited discloses a process for production of sponge iron through gas
based process utilizing decreased percentage of pellet ore and increased
percentage of lump ore to reduced overall cost of the raw material
without compromising the quality of the product. The MECON process
deals with production of iron ore pellet by rolling of moist iron ore fines
(less than 100 mesh size) with binder and additives into green balls and
then dried, pre-heated and fired in indurating machine which is also
entirely different from both the process and end product point of view.
Indian Patent Application No. 3361/MUM/2012 titled "Partially-

Reduced Iron Producing Method and Partially-Reduced Iron Producing
Apparatus" by Mitsubishi-Hitachi Metals Machinery, Inc. discloses a
process involves production of partially reduced iron from iron ore pellets
(already produced) in a suitable endless grate packed with carbon
material. The partially reduced iron is produced by thermal reduction of
the packed bed pellets. THE MECON process for production pellet is by
rolling of moist iron ore fines (less than 100 mesh size) with binder The
MECON process is for production iron ore pellet which a raw material for
the production of partially reduced iron.
Indian Patent Application No. 1190/KOL/2012 titled "A Process for
the Production of Highly Metalized Directly Reduced Iron (DRI) from
Waste Iron Ore Fines" by Tata Steel Limited discloses a process for the
production of highly metaiized directly reduced iron (DRI) by waste iron
ore as raw materials. The process involves grinding, green ball formation,
removing the moisture content, mixing with ground waste carbonaceous
materials and reduction, heating and cooling in reducing environment to
avoid re-oxidation. The MECON process for producing pellet is by rolling
of moist iron ore fines (less than 100 mesh size) with binder and
additives into green bails and then dried, pre-heated and fired in
indurating machine which is entirely different from both the process and
end product point of view.
Indian Patent Application No. 53/KOL/2013 titled "Improved
Process for Preparation of Pellet-Sinter Composition Agglomerate (P-SCA)
of Iron Oxide Fines for Use in Blast Furnace" by Tata Steel Limited
discloses a process for producing P-SCA (Pellet Sinter Composite
Agglomerate) by (i) making green pellets from micro-fines /waste iron
oxides( i.e. LDS/ mill scale) and bentonite (ii) mixing with sinter mix (iii)
and making sinter through conventional sintering process with an aim in

improvement in physical properties. The MECON process and product are
entirely different from peptization process for which know-how, basic
design and engineering have been developed by MECON.
Indian Patent Application No. 1413/KOL/2011 titled "A System for
Continuous Production of Sponge Iron from Iron Ore Pellets / Briquettes
and a Method of Producing the Same" by Mayur Electro Ceramics Pvt.
Ltd. discloses a method for continuous production of sponge iron (DRI)
by tunnel kiln technology from iron ore fines (<10mm) in the form of
green pellets or pellets/briquettes or pellets or composite pellets along
with reductant such as coal or coke fines and limestone. The MECON
process for production pellet is by rolling.of moist iron ore fines (less than
100 mesh size) with binder and additives into green balls and then dried,
pre-heated and fired in indurating machine which is entirely different
from both the process and end product point of view.
Summary of the Invention
The present invention covers development of technology, basic and
detail design of Induration and Process Gas Recirculation System of Pellet
Plant including basic sizing calculation of equipment and preparation of
manufacturing drawings of relevant process equipment and technological
structures.
This area broadly consists of the following:
i. Indurating machine
ii. Indurating hood
iii. Process gas ducting and fan sizing.

The objective is attained by a induration and process gas
recirculation system for performing various heat treatment processes of
drying, preheating, firing and cooling of pellets.
Accordingly, the present invention provides indigenous technology
of core area of Travelling grate type 1.2 Mt/Yr capacity pellet plant which
consist induration and process gas recirculation system for pellet
production comprising: indurating machine, indurating hood, process gas
ducting and process fans, based on the achievable grate factor and total
induration time for Indian iron ores, for performing various heat
treatment processes of drying, preheating, firing and cooling of pellets.
Indurating machine consists of pallet car, sealing system, sealing track,
moving track, sprocket, drive system, scrapper system and chutes, and
other necessary systems.
Brief Description of the Accompanying Drawings
The invention is explained in more detail hereinafter with reference
to drawings of exemplary embodiments. In the figures,
a) Figure I - Process Gas Flow Diagram
b) Figure IA - View of Indurating machine with hood and furnace
c) Figure IB - Process gas re-circulation duct work arrangement
d) Figure II - Pallet Car
Detailed Description of the Invention

The process route involved in pelletization are mixing, balling,
induration and process gas handling, pellet screening for use in Blast
Furnace / Direct Reduction of Iron processes. Induration and process gas
handling are the core areas of pelletization which involve heat treatment
process like drying, pre-heating, indurating and cooling. In order to
perform various heat treatment process, the overall length of indurating
machine is divided into various zones and covered with specially designed
hood and furnace which is fixed on indurating machine operating floor
and the pallet cars are passed through the hood at variable speed as per
process requirement.
The design development was taken up at MECON Limited based on
the achievable grate factor and total induration time for Indian iron ores.
Various equipment involved for indurated pellet production are indurating
machine, indurating hood, process gas ducting and process fans. Design
development of these equipment and various process and equipment
parameters have been finalized suiting Indian iron ore characteristics
which however can accommodate varied quality of ore with the in-built
design cushion provided.
The basic parameters arrived at after process calculation for indurating
machine and hood are as follows:
i. Indurating Machine:



Indurating machine consist of various equipment i.e. pallet car,
sealing system, sealing track, moving track, sprocket, drive system,
scrapper system, chutes etc. Indurating machine is an endless chain of
pallet cars which moves on track with pellets. One of the critical
component of indurating machine is pallet car which is of width of 2900
mm and length 1000 mm. Figure II may please be referred in this
regard. The equipment is so designed that the air moves through pallet
car bed during heat hardening operation of green pellets.
Process gas re-circulation is described as follows:
The ambient air is blown through cooling zone by cooling air fan to
cool down the heated pellets to below 100 deg.C. A portion of hot air
above cooling zone gets delivered to updraft drying zone to dry the green
pellet by up-draft drying air fan. Hot air below firing zone used to dry the
pellet in downdraft drying zone with the help of a Wind box recuperation
fan. Hot exhaust gas below preheating zone and downdraft drying zone
gets vented through chimney via ESPs by Windbox exhaust fan. Hood
exhaust fan sucks air above updraft drying zone to vent it to air via ESPs

and chimney. Process gas flow is depicted in Figure I, which is further
elaborated in Figures IA and IB.
Based on the cooling air requirement and requirement of hot air at
various zones (UDDZ, DDDZ, PH, Firing, Cooling), the profile of the
indurating hood has been designed so that it can handle required volume
of gas to flow at desired velocity and ensure flow of the hot process gas
from cooling zone to the preheating and firing zone on direct recuperation
method. The profile of hood in other zones has also been designed based
on the volume of gas being handled.
Process gas ducting design has been carried out to ensure
availability of required volume of hot air at various zones and burners at
optimum speed. Process fan operating parameters have been finalized at
different operating conditions after (i) requirement of air at various
temperature and pressure at different zones, hood are calculated, (ii)
process ductwork routing and its design are over. Five process fans
envisaged for induration process to circulate air are as follows:
1. Cooling air fan
2. Up-draft drying air fan
3. Wind box recuperation fan
4. Wind box exhaust fan
5. Hood exhaust fan
Benefits
In addition to the benefits of pellet plants with travelling grate
technology, the following major benefits are foreseen from this
indigenous design development:

This indigenous development will reduce considerably dependency
on foreign technology provider for making availability of the technology
for supply of critical process equipment.
Further, with availability of design of critical process equipment, the
same can be manufactured in India.
The process parameters and equipment design are such that it can
accommodate varied quality of raw materials.
Pallet car, being the critical equipment, is designed to have longer
life of operation.
The specially designed hood and duct work ensures smooth flow of
process gas and minimum pressure loss resulting from optimum fan
parameters.
Indurating machine has been envisaged with variable speed drive
to cater retention time requirement at various zones depending upon
quality of raw materials and moisture.

WE CLAIM :
1. Travelling grate type 1.2 Mt/Yr capacity pellet plant comprising:
indurating machine, indurating hood, process gas ducting and process
fans, based on the achievable grate factor and total induration time for
Indian iron ores, for performing various heat treatment processes of
drying, preheating, firing and cooling of pellets.
2. A pellet plant as claimed in claim 1, wherein said indurating
machine consisting of pallet car, sealing system, sealing track, moving
track, sprocket, drive system, scrapper system and chutes.
3. A pellet plant as claimed in claim 1, wherein the profile of
indurating hood in various zones is designed based on the volume of gas.
4. A pellet plant as claimed in claim 1 or 2, wherein the indurating
machine comprises an endless chain of pallet cars which moves on track
with pellets.
5. A pellet plant as claimed in claim 4, wherein said pallet car has a
width of 2900 mm and length of 1000 mm.
6. A pellet plant as claimed in claims 1 to 5, wherein the equipment is
so designed that the air moves through pallet car bed during heat
hardening operation of green pellets.
7. A pellet plant as claimed in any preceding claim, wherein, for
performing various heat treatment processes, the overall length of

indurating machine is divided into various zones and covered with
specially designed hood and furnace which are fixed on indurating
machine operating floor.
8. A pellet plant as claimed in any preceding claim, wherein the pallet
cars are passed through the hood at variable speed as per process
requirement.
9. A pellet plant as claimed in any preceding claim, wherein, after
process calculation, the basic parameters of the indurating machine
include effective length 67m, effective area 194m2, pallet car width 2.9m,
pallet car length 1.0 m, side wall height 400mm, 17 windboxes, drying
zone length 15m, heating zone (pre-heating and firing) length 32m and
cooling zone length 20m, the individual zone length being adjustable
based on raw material condition while keeping the overall zone length
same.
10. A pellet plant as claimed in any preceding claim, wherein the
indurating machine is such that the process gas ducting design ensures
availability of desired volume of hot air at the various zones and burners
at optimum speed.
11. A pellet plant as claimed in any preceding claim, wherein the
process fan operating parameters are determined at different operating
conditions after (a) requirement of air at various temperature and
pressure at different zones, hood are calculated, (b) process ductwork
routing and its design are completed.
12. A pellet plant as claimed in any preceding claim, wherein five
process fans are envisaged for the induration process for circulating air.

13. A pellet plant as claimed in any preceding claim, wherein said five
process fans are cooling air fan, up-draft drying air fan, wind box
recuperation fan, wind box exhaust fan and hood exhaust fan.
14. A pellet plant as claimed in any preceding claim, wherein varied
quality of raw materials can be accommodated in the indurating machine.
15. A pellet plant as claimed in any preceding claim, wherein the pallet
cars are designed to have longer life of operation.
16. A pellet plant as claimed in any preceding claim, wherein the
specially designed hood and duct work of the indurating machine ensures
smooth flow of process gas and minimum pressure loss resulting from
optimum fan parameters.
17. A pellet plant as claimed in any preceding claim, wherein the
indurating machine comprises variable speed drive to cater to retention
time requirement at various zones depending upon quality of raw
materials and moisture.