FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (See Section 10; rule 13)
TITLE OF THE INVENTION
COAL BRIQUETTE AND A METHOD FOR COLD BRIQUETTING OF COAL FINES USING A POLYMERIC ORGANIC BINDER
APPLICANT
Essar Steel India Limited, an Indian Company
Having its office at
27 KM Surat Hazira Road,
Hazira 394 270, Dist. Surat,
Gujarat, India.
PREAMBLE OF INVENTION The following specification particularly describes the invention and the manner in
which it is performed.

FIELD OF THE INVENTION
This invention relates to the method of cold briquetting of coal fines using polymer based organic binder and is particularly applicable to charge the briquettes in the melter-gasifier of Corex iron making furnace. More particularly the present invention relates to briquette which is produced from mixture of two or more types of fine coal by using poly vinyl group of adhesives and water.
BACKGROUND OF THE INVENTION
The Corex process of iron making uses certain types of non-coking coal as the principal source of energy and reducing agent. Coal lumps in the size range of 6.3 mm to 50 mm are charged in the melter-gasifier to generate heat and reducing gas for the furnace. The reducing gas is passed to the reduction shaft for reduction of iron ore. Non coking coals owing to their poor strength generate 35-45 % fines during loading/unloading/handling on its way to the actual feeding point. These fines are screened out and stored in the yard for selling at subsidized rates or used in thermal power plants. To avoid losses incurred in disposing the fines for sub-standard uses, a process of briquetting the coal fines has been invented.
It is known that processes like corex or other smelting reduction iron making processes have advantages in terms of fuel availability in that instead of coke, coal is used as a fuel. However, as for a fuel, when the coal is fine coal having particle size of 6.3 mm or less, it fails to undergo complete combustion in the melter gasifier of a corex furnace and is trapped in a dust collector in an excessive amount, the thermal balance of the process is lost, thereby causing various problems with the process. Therefore use of such fine coal should be limited in the iron making process.
However, coals currently used are generally lumps and the fines can neither be used completely for injection nor for coke making owing to their non coking nature. Corex process involves use of 800 - 900 kg coal per tonne of hot metal production along with 80 - 150 kg of coke. Coal is first screened to +6.3 mm in the yard and the fines are separated.

The coal is then passed into a coal drying plant where the moisture is removed and dried coal is sent to the stock house.
Coal is then charged into the smelter gasifier at a temperature of around 900-1000 degrees centigrade, where it observes thermal shock. Along with thermal shock there is mechanical stress due to charging of partially reduced iron ore pellets from the vertical reduction shaft present at the top. The coal gets converted into coal char and remains in the form of char bed. The char is then exposed to carbon dioxide attack as pure oxygen is blown from the tuyeres located below. The oxygen reacting with carbon present in char forms carbon monoxide first, this carbon monoxide reacts either with oxygen of iron ore or further gets oxidized by oxygen from tuyeres to form carbon dioxide. The carbon dioxide reacts with carbon of the char to form carbon monoxide again. Along with all these char reactivity properties, the char is continuously subjected to mechanical stress hence the char should also have some strength after reaction. The coal char keeps on burning and gets consumed but it has to maintain a minimum specific size above the tuyere level to allow the oxygen and other gases to pass through the char bed. A large amount of fines in the char bed would reduce the gas flow / wind rate leading to several process related problems. Finally in front of tuyeres the char should completely burn out and the ash, hence formed should go to slag and finally get drained out. To maintain sufficient permeability in the char bed, some amount of coke is charged that comes down along with iron ore pellets from the reduction shaft.
Thus, it is desirable to obtain a method of making a briquette by agglomerating fine coal in an appropriate way so that it meets all the high temperature requirements of the furnace similar or superior to lump coal. The quality of the briquettes if attained as per the specification of corex then it can also replace the coke and lead to monitory savings.
However, as to the state of the art so far, no successful technology to make fine coals into briquettes applicable to the corex and similar iron making processes have been found meeting all the high temperature properties along with room temperature strength. Many methods have been disclosed for making briquettes using mixture of fine coal, molasses and inorganic binder with curing of 2-3 days or in oven at 200-300° C for 1 hour to increase strength of briquettes. In this case the efficiency of curing is poor and high

temperature properties are not achieved limiting the percentage replacement of coal in the furnace. Similar methods using binders like lime, bentonite, starch, tar, pitch and various organic and inorganic materials have been tried to get high temperature properties that exists in the prior art.
SUMMARY OF THE INVENTION
A coal briquette comprising polymer based organic binder either alone or in combination thereof to provide the high temperature strength as well as room temperature requirements for metallurgical applications. The polymer based organic binder is selected from the group consisting of poly vinyl alcohol, polyvinyl acetate) and the like. The polymer based organic binder is a poly vinyl alcohol and vinyl acetate monomer either alone or in combination thereof.
The polymer based organic binder with 23% to 25% solid content is formed as an emulsion by radical polymerization by mixing poly vinyl alcohol of 2 to 10% and vinyl acetate monomer is of 5 to 50%.
The briquette has thermal stability more than 90% and thermo mechanical stability more than 40%. At least 30 % of coal is of the category of 3-5 FSI and the ambient temperature of the binder is maintained at 20-40°C till briquetted to retain its cohesive and adhesive properties.
The briquettes are sealed so that during impact in the green stage the briquettes do not break from center line. The compressive forces are uniformly provided to avoid squeezing of the moisture and binder from corners to center to further avoid the concentration difference leading to excessive expansion during curing and cracking of the briquettes.
At higher temperature poly vinyl acetate (PVAC) / poly vinyl alcohol (PVA) decomposes and it leads to the formation of polyenes which further undergoes cross-linking and aromatization to form highly thermally stable and infusible materials which is optionally catalyzed by the different metal oxides present in coal to provide protection to the coal from instantaneous degradation on heating.

A method of making coal briquettes comprising the steps of
a. Crushing of coal fines of size between -3mm to +3mm/ FSI between 1-2 in a hammer
crusher and crushed in a hammer crusher;
b. blending in a blender in a fixed ratio based on their individual FSI with a minimum 30%
of coal with FSI of 3-5 and the rest can be lower than that;
c. drying or optionally adjusting for moisture, based on the moisture content of the blend
after blending;
d. passing the blend under a double belt magnetic separator before being charged into the
mixer to separate any metallic object (foreign material) present in the coal fines to avoid
damage of the briquetting dye and jamming the system and hampering production;.
e. mixing of binder with water in 1:1 ratio by a homogenization pump;
f. adding a controlled amount of binder in the range of 3-10% in the mixer and adjusting
the feed rate through a control valve by maintaining the temperature of the mix at ambient
temperature and pH to retain binder's cohesive and adhesive properties;
g. mixing the above mix with coal fines and kneading to obtain coal briquettes with a
predetermined amount of moisture and binder to form a green mix;
h. providing the mix to briquetter with specifically designed pockets to charge the green
mix in to the briquetting hopper to form briquette;
i. curing the green briquettes in the band dryer at temperature between 60 to 120°C for 3 to
6 hours and then passes through a cooler for reducing the temperature down to ambient
temperature to drain out all entrapped moisture from them and obtain coal briquettes with
thermal stability more than 90% and thermo mechanical stability more than 40%;
the cured briquettes from the briquetting plant are ready for loading in corex furnace
BRIEF DESCRIPTION OF DRAWINGS
Figure - 1 shows the process of briquette making.
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to the method of cold briquetting of coal fines using polymer based organic binder and is particularly applicable to charge the briquettes in the melter-gasifier of Corex iron making furnace. The application can extend to other high temperature reactors, where the briquettes need to have adequate strength at high temperature. Organic

polymers are used for briquetting coal fines at ambient temperature under application of pressure. The process is so designed to satisfy the room temperature as well as high temperature strength requirements for metallurgical applications like Corex.
More particularly the present invention relates to briquette which is produced from mixture of two or more types of fine coal by using poly vinyl group of adhesives and water. The polymeric binder encapsulates the fine particles of coal and binds them owing to their adhesive and cohesive properties, once cured. The binder penetrates the porous coal and forms inter locking between the particles, once the moisture is removed by curing, the room temperature strength is achieved and briquettes can be easily transported without generating too much fines. Since the briquettes prepared according to the invention have superior physical strength along with superior high temperature properties, it is applicable to a smelting reduction iron making process like corex.
The present invention provides a process of manufacturing of briquettes. The basic requirement for converting coal fines into briquettes is suitable binder that would provide sufficient cold strength and resist breakage at high temperature under carbon dioxide environment. To check these conditions standard tests for coals are slightly modified based on experience to suit corex application for coal briquettes. For high temperature properties four basic requirement and their test procedure is as below.
1. Thermal stability
2. Thermo mechanical stability
3. Char reactivity index
4. Char strength after reaction.
Thermal stability test:
Sized coal briquettes of 1 kg is charged in a furnace at 1000 degrees in nitrogen environment and kept for 1 hr. The briquettes gets converted into char which are cooled in air and taken in a 10 mm screen. The percentage of briquettes retained on the 10 mm screen is considered as thermal stability index.
Thermo mechanical stability test

The char of+10 mm in a fixed quantity is taken in an I-drum and rotated for 25 minutes. After rotation it is again taken in a 10 mm screen. The percentage of briquettes retained on the 10 mm screen is considered as thermo mechanical stability index.
Char reactivity test
500 gm of sized char is taken in the size range of 19 to 21 mm and charged in a cylindrical furnace and heated to 1100 degrees under carbon dioxide environment for 1 hr. The material is then taken out and cooled and the percentage weight loss obtained after reaction is considered as char reactivity index.
Char strength after reaction test
The char after reaction of+10 mm in a fixed quantity is taken in an I drum and rotated for 25 minutes. After rotation it is taken in a 3.5 mm screen. The percentage of briquettes retained on the 3.5 mm screen is considered as char strength after reaction. Thus the Coal briquettes to be used in corex should be made with the aim to meet the high temperature properties, list of such properties along with specification for corex is shown in table 1, along with these some other room temperature properties are also required, as the briquettes should resist the mechanical stresses while it is being transported from the briquetting plant to the smelter gasifier of corex furnace. The cold strength specification for corex is shown in table II.

Properties Thermal Stability Thermo-
mechanical
stability Char reactivity index Char strength after reaction
Specification Min 70 % Min 20 % Max 55 % Min 35 %
Table I-High temperature properties required for coal briquettes For cold strength two basic tests are done and again the methods are modified based on
experience on corex application.
1. Cold crushing strength
2. Shatter strength
Cold crushing strength test
In this test coal briquettes after complete curing are taken in a CCS tester with flat bottom plate and flat top ram. Constant load is applied till the briquettes break. At a time 3 -7

briquette pieces are taken based on consistency. The maximum load achieved before breaking is considered as cold crushing strength.
Shatter strength
In this test 20 kg of coal briquettes after complete curing are charged in the shatter box at a height of 5 meters. The material is released at a time from the bottom door of the shatter box through a pipe under free fall on a 10 mm thick steel plate. This procedure is again repeated for three more time and the entire material is screen on a 20 mm screen and the percentage of material retained is considered as the shatter index.

Properties Cold Crushing strength Shatter strength
Specification Min 55 Min 70
Table II - Cold strength properties requirement for coal briquettes
The high temperature strength also depends on the type of coal in the coal fine mixture, it is necessary for one of the coal to have FSI between 1-2 so that at high temperature it shows some softening and fuses with nearby coals having FSI <1. Point to be noted that at high temperature the fusion or bonding between the coal particles will only take place when the binder does not leave any residue after evaporation like ash in case of molasses, starch, tar, etc. Here the typical characteristic of polymer binder comes into picture which leaves the carbon backbone behind after evaporating or burning at high temperature that allows coal particles to easily fuse with each other. In many cases it is clearly observed that, with reduction in binder % the high temperature properties improves but the room temperature strength deteriorates hence an optimum binder percentage is maintained. The following example will further illustrate certain aspects and embodiments of the invention in detail and not intended to limit the scope of the invention.
Example 1
Coal fines briquetting was done using poly vinyl alcohol and poly vinyl acetate binder. Binder was prepared using 2 - 10 % poly vinyl alcohol and 5-50 % vinyl acetate monomer to form poly vinyl acetate emulsion by radical polymerization. The binder hence formed with about 23-25 % solid content was used for briquetting of coal fines.

In this experiment the effect of coal fines size and percentage moisture is studied. The variation of these two parameters affects the high temperature properties of the briquettes. When the fines are more thermo mechanical stability is good but Char strength after reaction is lowered. Moisture improves the thermal stability but reduces the thermo mechanical stability. Hence optimization of these parameters is must to obtain briquettes with satisfactory high temperature properties.
Three types of coal from Australia and South Africa were used. A, B & C.
The composition of green mix is as per the attached table along with high temperature test results

Coal
A% Coal B% Coal
C% Size
3-6.3
mm
% Size
0-3
mm
% % Moisture % Binder Thermal Stability Thermo
mechanical stability CRI CSR
40 40 20 10 90 10 5 95.6 64.92 44.5 33.21
40 40 20 20 80 10 5 91.91 52.06 49 31.86
40 40 20 30 70 10 5 95.56 42.23 45 36.95
40 40 20 40 60 10 5 95.56 54.33 43 49.02
40 40 20 10 90 12 5 96.17 51.92 45.5 31.19
40 40 20 20 80 12 5 96.04 42.29 43.6 31.13
40 40 20 30 70 12 5 96.25 49.75 40.5 36.80
40 40 20 40 60 12 5 95.54 47.26 40 38.55
CRI: Coke Reactivity index, CSR: Coke Strength after reaction, RSI: Relative strength
index
Process of briquetting
Bituminous coal is used in the briquetting process with FSI of less than 2. Various blends of coals can be used based on availability with a minimum of 30 % coal having FSI 1-2. The complete process is divided into three main steps or processes.
1. Material preparation.
2. Mixing and briquetting.
3. Curing.
Material preparation

Different types of coals are first individually screened for -3mm size and the +3 mm fines are crushed in a hammer crusher and then blended in a fixed ratio based on their individual FSI. A minimum of 30 % of coal should be of the category of 3-5 FSI and rest can be lower than that. The blend is then either dried or adjusted for moisture based on its moisture content after blending. The blend then passes under a double belt magnetic separator before being charged into the mixer.
The binder on the second hand is mixed with water in 1:1 ratio using a homogenization pump. A controlled amount of binder in the range of 3-10 % is added in the mixer adjusting the feed rate through a control valve. The temperature and pH of the mix is monitored and in case of any fluctuation the process is stopped and rectified. Samples of water and binder are checked for their quality in the laboratory. The temperature of the binder is continuously measure as any fluctuation due to high agitation rate can increase the temperature and change the property of the binder. Binder has to be strictly maintained at ambient temperature (20-40°C) until briquetted to retain its cohesive and adhesive properties.
Mixing and briquetting
In the mixer the coal fines blend under goes shoveling and kneading action and a mixer of binder and water is sprayed from fine nozzles from the top. The material gets mixed till it reaches the exit of the mixer and is called the green mix. Mixing phenomenon is very critical; the spray of binder when falls on the moist coal initially forms small granules, the layer of fine coal below the top surface then starts the growth. The shoveling action breaks the granules or pellet shaped balls and allows dry fines to come in contact and again agglomerate. The kneading action helps homogenizing the mixing process as unlike mixing of solid binders with coal fines here there are high chances of non uniform concentration of the binder in the mix due to granule formation. The core of the granules generally contains high binder content and they need to break and form again. The green mix should not be held for more than 30 minutes else excessive mixing may lead to heating and evaporation of moisture. Retention time of material in the mixture is adjusted by speed of rotation or angle of the drum or screw conveyor rpm. The green mix is then charged in the receiving hopper of a roller briquetting press.

The briquetting takes place in a pneumatic press with pressure control and force feeder. The rolling pressure requirement is in the range of 100 - 700 kg/cm2. The roll rpm to be maintained at minimum based on the diameter of the roll. The force feeder has to be operated at 80 bar hydraulic pressure ensuring that all the pockets of the briquetting press are filled completely. The briquettes are released on a chain conveyor from which the fines are recycled back to the hopper and prime briquettes are moved to the curing station. In this process the shape of the briquette is very important as it controls the compressive force that falls on the briquettes. The force applied along the cross-section of the briquette should be uniform to avoid breakage due to impact after curing. If the compressive forces are not uniform then it may squeeze moisture + binder from corners to center and during curing this concentration difference may lead to excessive expansion and later cracking of the briquettes. Extra force may lead to crushing of the coal fines during briquetting inside the die. The cursing will generate new surface which do not have any contact with the binder, this will lead to reduction in strength and crack can easily propagate upon impact. The shape also facilitates ease of release of the sticky briquettes just after they are formed, from the die wall. The edges of the briquettes to be sealed so that during impact in the green stage the briquettes do not break from center line.
Curing
Curing of the briquette is possible either under sunlight for 48 hrs or forced curing at 60-120 degree for 3-6 hrs. In the briquetting plant, there is curing section that contains, band driers and coolers. The green briquettes passes through the metallic conveyors of the band drier at a temperature of 60 -120 degrees for 3-6 hours based on the production and quality requirements. The band drier runs either on electric heating or gas/oil burners with a temperature controller and suction fans. The temperature in the drier is slowly increased from Room temperature to a desired set point. The slow heating will allow moisture to evaporate from the briquettes more easily than sudden expansion that can lead to cracking. The network of polymer binder around the coal fines have a unique characteristics that the water molecules present in the polymer chain breaks and comes out of the system leaving a porous network much before the moisture in the coal evaporates. This porous network becomes a critical path for the moisture of coal to come out without exerting extra pressure on the coal wall. Due to the above mentioned phenomenon drying takes place

from centre to surface in 3-6 hours without cracking. Any type of tensile force generated within the briquette is absorbed by the elastic property of the polymer.
Once the briquettes are dried they are passed though a cooler and the temperature is brought down to room temperature. The cooling leads to release of any remaining moisture entrapped in the core of the briquettes. As the core is still hot while surface is cooled to room temperature by blowing air, due to density difference breathing takes place and remaining moisture if any comes out from the core. The dried and cured briquettes are then sent to final screen belt and weight feeder to the collecting hopper. From there it is discharged for charging in corex smelter gasifier.
Binder
Binders play an important role in coal briquetting. Briquetting using binder is the best solution to minimize energy loss and pollution. Among different types of binders, organic binders have several advantages. They bind effectively coal particles and don't make the coal briquettes brittle. They don't cause smoke or corrosive gases. They do not increase in the content (%) of ash or clinker during burning. In this case the organic polymeric binders are much superior to inorganic binders. The several organic and polymeric binders used in coal briquetting are: starch, molasses, poly(vinyl acetate), carboxyl methyl cellulose, tar, pitch, crude oil, sulphide liquors etc.
Among the different polymeric binders, poly vinyl acetate (PVAC) has several advantages over other polymeric/organic binders. PVAC is very easy to prepare via radical polymerization, as it is relatively cheaper. PVAC is usually combined with poly vinyl alcohol (PVA). PVA and PVAC have good interaction with the coals because coal has different metal oxides as major constituents. It is usually prepared via free radical polymerization in emulsion as well as in solution. Vinyl acetate monomer is easily polymerized using PVA by alcoholysis.
The binder used for this application is organic in nature. The basic constituents are from the poly vinyl group of organic chemicals. These polymers have good adhesive and cohesive properties; they provide sufficient cold strength to the briquettes. At high temperature the polymer evaporate leaving the carbon back bone behind which is very

stable at high temperature. At this time the coal char is formed and the particle gets fused to each other as they are not encapsulated by any binder. As the layer of binder keeps on evaporating the coal keeps of converting into char and starts fusing with one another. This thing does not happen in inorganic binder as the inorganic materials does not evaporate and acts as hindrance to the char pieces for fusing with each other.
At room temperature, the binder first encapsulates the coal fines and due to its high adhesive and cohesive nature binds the fines together once compacted in the briquetting press. When it is heated, the moisture evaporates and the binder is water based and once the moisture is driven out the polymer attains its maximum room temperature strength. The percentage of binder is maintained depending on the strength required in the briquettes.
PVAC/PVA resins form clear and hard films which have good weather resistance and withstand water, grease and petroleum fuels. The binder has a mixture of PVAC & PVA. The binder has good compatibility with the coal. Because it has important interactions between the numerous metal oxide (like Si02, A1203, Fe203, CaO etc.) in the coal and the -OH as well as acetate (-OCOCH3) groups in the binder. The binder forms a thin coating over the coal grains. It has been confirmed by Scanning Electron Microscope analysis. On heating at higher temperature the binder melts at higher temperature. This temperature lies in between the melting or softening of the binder and softening of the coal as it commences to cake. In the furnace the briquette does not get heated thoroughly at the same time. As the binder near the surface of the briquette melts and passes out as a gas, the binder in the next interior layer of the briquette takes its place and so on. In this way briquette is held together until the coal at its surface softens and cakes. When this happens the briquette commences to regain its strength and with many coals soon become stronger than when placed in the fire.
At higher temperature PVAC/PVA decomposes and it leads to the formation of polyenes. These polyenes undergo cross-linking and aromatization to form highly thermally stable and infusible materials. This may be catalyzed by the different metal oxides present in coal. This infusible layer also gives some kind of protection to the coal from instantaneous

degradation on heating. The above mentioned phenomenon if responsible for high temperature properties attained by the briquettes made through the present invention.
Figure 1 shows the process of briquette making as follows:
1. Coal fines of one or more types that are generated during transportation of coal and handling in the yard before it enters the furnace is screened. These fines are blended together and sent through belt conveyor (1) to the coal receiving bin (2) of a briquetting plant.
2. Coal bin (2) holds dry coal fines of size less than 6.3 mm that cannot be charged in (specifically) a corex melter gasifier. The bin has a weigh feeder at its exit and a screw dozer to supply measured quantity of fines to the briquetting unit.
3. The coal fines passes through a magnetic separator (3) where any metallic object (foreign material) if present in the coal fines gets separated. This is very important as the metallic objects can damage the briquetting dye and can also jam the system hampering production.
4. The coal fines after magnetic separation (3) enters a hammer crusher (4). The crusher (4) converts all fines into less than 3 mm size and the load on the crusher is reduced by providing 3 mm screens that initially removes all fines less than 3 mm and then starts crushing 3 - 6.3 mm fraction.
5. The mixer (5) is a horizontal cylindrical system with high speed rotation arms and screws that ploughs and kneads the coal to mix it properly with a controlled amount of moisture and binder.
6. Once the material is mixed with binder within no time it is taken to the briquetting unit though a bucket elevator (6). There are similar elevators to recycle fines generated from green briquettes also.

7. Briquetter (7) has two rolls with specifically designed pockets either round or pillow shaped. The green mix is charged in to the briquetting hopper and the screw feeder forces the material to fill all the pockets of the rotating rolls. The briquetting rolls provide compressive force on the green mix and converts them into green briquettes. The briquettes fall on chain conveyors and all fines generated are separated and recycled.
8. The green briquettes are handled with care before it enters the band dryer (8) for curing. The band dryer (8) is a series of metallic belt conveyor with opening from bottom for movement of hot air about 60-120 °C. The briquettes remain in the dryer for about 3-6 hours.
9. After drying, it enters the rotary cooler (9) where cold air is passed to bring the briquettes to room temperature and drain out all entrapped moisture from them.
10. The air coming out of both the dryer and cooler may contain some dust. The exit air is taken into bag filters for cleaning and all dust generated is recycled back to the coal bin (2).
11. Blowers (14) are installed to provide air that is "heated either electrically or using fuels burners before entering the dryer (9).
12. At the end the cured briquettes comes out of the briquetting plant and are ready for use in corex furnace.
The Part Designation is as follows:
1 - Belt Conveyor
2 - Coal Bin
3 - Magnetic Separator
4 - Hammer Crusher
5 - Mixer
6 - Bucket Fly
7 - Briquetter
8 - Band dryer

9 - Rotary Cooler
10 - Bag Filter
11 - Heating Chamber
12 - Delivery section of cured briquettes
13 - Rotary valve
14 - Turbo Blower
15 - Turbo Blower
16 - Belt Conveyor
17 - Belt Conveyor
18 - Belt Conveyor
19 - Metal Scrap
20 - Water
21 - Binder
22 - Coal
The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

WE CLAIM
1. A coal briquette comprising polymer based organic binder either alone or in combination thereof to provide the high temperature strength as well as room temperature requirements for metallurgical applications.
2. The coal briquette as claimed in claim 1, wherein the polymer based organic binder is selected from the group consisting of poly vinyl alcohol, polyvinyl acetate) and the like.
3. The coal briquette as claimed in claim 2, wherein the polymer based organic binder is poly vinyl alcohol and vinyl acetate monomer either alone or in combination thereof.
4. The coal briquette as claimed in claim 1 wherein the polymer based organic binder with 23% to 25% solid content is formed as an emulsion by radical polymerization by mixing poly vinyl alcohol of 2 to 10% and vinyl acetate monomer is of 5 to 50%.
5. The coal briquette as claimed in claim 1, wherein the briquette has thermal stability more than 90%, thermo mechanical stability more than 40%, minimum char strength after reaction (CSR) 35% and maximum char reactivity index (CRI) 55%.
6. The coal briquette as claimed in claim 1, wherein at least 30 % of coal is of the category of 3-5 FSI and the ambient temperature of the binder is maintained at 20-40°C till briquetted to retain its cohesive and adhesive properties.
7. The coal briquette as claimed in claim 1, wherein the edges of the briquettes are sealed so that during impact in the green stage the briquettes do not break from center line.
8. The coal briquette as claimed in claim 1, wherein compressive forces are uniformly provided to avoid squeezing of the moisture and binder from corners to center to

further avoid the concentration difference leading to excessive expansion during curing and cracking of the briquettes.
9. The coal briquette as claimed in claim 1, wherein at higher temperature poly vinyl acetate (PVAC) / poly vinyl alcohol (PVA) decomposes and it leads to the formation of polyenes which further undergoes cross-linking and aromatization to form highly thermally stable and infusible materials which is optionally catalyzed by the different metal oxides present in coal to provide protection to the coal from instantaneous degradation on heating.
10. A method of making coal briquettes comprising the steps of
a. crushing of coal fines of size between -3mm lo +3mm/ FSI between 1-2 in a
hammer crusher and crushed in a hammer crusher;
b. blending in a blender in a fixed ratio based on their individual FSI with a
minimum 30% of coal with FSI of 3-5 and the rest can be lower than that;
c. drying or optionally adjusting for moisture, based on the moisture content of the
blend after blending;
d. passing the blend under a double belt magnetic separator before being charged
into the mixer to separate any metallic object (foreign material) present in the
coal fines to avoid damage of the briquetting dye and jamming the system and
hampering production;.
e. mixing of binder with water in 1:1 ratio by a homogenization pump;
f. adding a controlled amount of binder in the range of 3-10% in the mixer and
adjusting the feed rate through a control valve by maintaining the temperature of
the mix at ambient temperature and pH to retain binder's cohesive and adhesive
properties;
g. mixing the above mix with coal fines and kneading to obtain coal briquettes
with a predetermined amount of moisture and binder to form a green mix;
h. providing the mix to briquetter with specifically designed pockets to charge the green mix in to the briquetting hopper to form briquette;
i. curing the green briquettes in the band dryer at temperature between 60 to 120°C for 3 to 6 hours and then passes through a cooler for reducing the temperature down to ambient temperature to drain out all entrapped moisture

from them and obtain coal briquettes with thermal stability more than 90% and thermo mechanical stability more than 40%; j. the cured briquettes from the briquetting plant are ready for loading in corex furnace