FIELD OF THE INVENTION
The present invention relates to the technology of making chrome concentrate micro
fines briquettes with different alternate binders to use it in submerged electric arc
furnace for ferrochrome production. More particularly, the invention relates to a process
of manufacturing High Strength Briguettes from Chrome concentrate micro fines.
BACKGROUND OF THE INVENTION
Chrome ore fines are generated during mining operation which cannot be directly
charged into submerged electric arc furnace due to adverse effect on gas permeability
leading to crust formation at the inner top surface of the furnace. Direct usage of
chromite ore fines and micro fines in the electric arc furnace will lead to entrainment of
the fines by the gas stream coming out of the furnace.
In the existing briquetting process, chromite ore fines (0 – 6mm) are conveyed through
a dryer to reduce the moisture content to 3 – 3.5 % and then mixed with binders in a
mixer. The binders used in briquetting process in general are hydrated lime and
molasses. Moisture present in the chromite ore is reduced for proper binding of
hydrated lime with chromite ore fines. Therefore chromite ore fines are dried in a dryer
through combustion of furnace oil. Drying process results in the loss of chromite ore due
the entrainment of fines with the flue gases from the dryer.
In the reference (Patent no. US005302341A),agglomeration of fines and ultrafine using
a binder called poly isocyanate based co – reactant and an amine catalyst are pressed
in a briquetting machine to form briquettes. These briquettes are cured in the heated
conveyor for 4 minutes to complete curing. Amount of binders is less than 1 %.
In another reference (Patent no. US2775566A), finely divided metal oxides are
agglomerated using the binders containing components like stearic acid in saponified
form, an alcohol – soluble, water – insoluble phenol formaldehyde resin, a water soluble

partially condensed urea formaldehyde resin with optimized proportion. The
agglomerated briquette is subjected to heat treatment at a temperature within the range
of 800 – 1500ºC.
Chrome concentrate micro fines due to its very fine particle size distribution requires
huge amount of binders like molasses to agglomerate it. Increased usage of molasses
may lead to increase in the sulphur content in the final ferrochrome alloy product.
Further, environment regulations from the government strictly restrict the particulate
matter in the surrounding atmosphere for ferroalloy production. This will force the
manufacturers to reduce the amount of fines generated from electric arc furnace and
look for alternate binders which can be used in minimum amount so as to be under
pollution norms.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a process of manufacturing High
Strength Briguettes from Chrome concentrate micro fines.
Another object of the invention is to propose a process of manufacturing High Strength
Briguettes from Chrome concentrate micro fines, in which alternate binders are used to
eliminate adverse effect of moisture content in the chrome concentrate micro fines.
SUMMARY OF THE INVENTION
According to the invention, the chromeconcentrate micro fines are agglomerated with
optimum usage of binders with a fixed amount of pressure in the briquetting machine at
the plant. Binders were selected such that the moisture present in the chrome
concentrate micro fines does not influence the final strength of the pillow shape
briquette. With the usage of the new binders, drying of the materials to remove moisture
is reduced so that fuel oil consumption in the drying process is minimized.

Chromite ore in the form of briquette are smelted and reduced in a submerged electric
arc furnace in presence of fluxes and coke at 1500-1600o C to produce ferrochrome.
Particle granulometry plays vital role in this process and fines are undesired in this
process.Micro fines are having fines with 85% less than 150 microns.The binders are
used for agglomeration of chrome concentrate micro fines.Chrome concentrate micro
fines and fines are generated after beneficiation of chromite orein the chrome ore
beneficiation plant.
In agglomerating the fines, binders are required to mix with them along with some
amount of water and the mixture is subjected to briquetting pressure in the moulds to
form a desired briquette. Therefore, we have selected the following binders for mixing
with chrome concentrate micro fines
1. Phenolic resin and
2. Resin binder with setting catalyst
Details of the binder
Phenolic resins are of two different types namely novolacs and resoles(The Chemical
Company). Novolacs are phenol-formaldehyde resins with molar ratio of formaldehyde
to phenol less than 1. The polymerization is brought to completion using acid–catalysis
such as oxalic acid, hydrochloride acid, or sulfonate acid. The molecular weights are in
the low thousands, corresponding to about 10 – 23 phenol units. Resoles is the resin
formed by the combination of formaldehyde and phenol by adding them in the ratio of
more than 1 (usually 1.5). They are usually used as bonding building materials.
Structure of the novolac resin is shown in the literature as follows1
Formaldehyde undergoes polymerization reaction with Phenol and exists in equilibrium
with methylene glycol and given as


The above monomers react to form one or two general type of resins.
3. NOVOLAC RESIN and
4. RESOL RESIN
Regarding the production process of NOVOLAC resin, with the excess ratio of phenol
and formaldehyde with acidic catalyst (Ethylene Glycol), 3 range of polymers are
possible described as below. Initial reaction is between methylene glycol and phenol.
The product from this reaction reacts further with another phenol molecule and
continues with splitting of water. The final resin will be of 3 types namely ortho-orhto,
ortho – para, and para – para depending of the positioning of OH molecule attachment
on the phenolic ring.
How the bonding works by Novolac resin and its catalyst
The novolac resin used in the experiment contains hexamethylene tetramine (HMTA) as
catalyst for setting of the resin. HMTA curesthe resin by further linking and polymerizing
the molecule to an infusible state. This results in strong bonding by forming three –
dimensional network of extreme molecular weight. Hence this aromatic phenolics
accounts for the cured material hardness and gives good strength to the agglomerate.
In the second type of experiment containing Novolac resin (both in solid and liquid form)
and HMTA (solid powder) in the liquid form is used as catalyst. In both the experiments,
HMTA acts as a catalyst and aids in setting of the agglomerate giving a good strength
after heating the agglomerate to a temperature of 423 K (150 oC).
Chrome concentrate micro fines were prepared after beneficiation of the chromite ore
that comes from run off mines. This beneficiated product contains less amount of
gangue material (consisting of SiO2 and Al2O3). Due to less amount of SiO2 the clay
type of nature is not expected from the chrome concentrate micro fines. Hence, the
surfaceof chrome concentrate is having poor binding property with the conventional
binders. So, these resins (Novolac) are explored to be used for the formation of
agglomerate.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows a schematic diagram of the mould that was used in the invention, for the
briquette preparation.
DETAIL DESCRIPTION OF THE INVENTION
As shown in figure , the mould for briquette preparation comprises a hollow cylinder to
press the mould mixture within the hollow space of bigger cylinder.
Experiment 1
200 g chrome concentrate micro fines, 2% lime, 2% molasses and 5% water are
thoroughly mixed and kept in briquette making mould. Hydraulic press is used to apply a
load of 5 tons on the mould to form cylindrical briquettes. These briquettes are then
heated to a temperature of 423 K (150 oC) for 30 min and then cured in atmosphere for
24 hours. After 24 hours of curing time, cold crushing strength (CCS) is done in a CCS
machine. Average strength of these briquettes is observed to be 332 kgf/briquette. This
is the basis for the next experiments with the identified 2 binders to compare with this
base strength.
Experiment 2
200 g chrome concentrate micro fines, 3.5 % novolac resin binder and 5.5% water are
thoroughly mixed and kept in briquette making mould. Hydraulic press is used to apply a
load of 5 tons on the mould to form cylindrical briquettes. These briquettes are then kept
in the furnace and heated to a temperature of 423 K(150 oC) for 30 min and then cured
inopen atmosphere for 24 hours. After 24 hours of curing time, these briquettes are
subjected to cold crushing strength (CCS) test to evaluate its compressive strength.
Average CCS of these briquettes is found to be 385 kgf/briquette which is considerably
higher than the desired strength (100 kgf/briquette) required in the plant.

Experiment 3
200 g chrome concentrate micro fines, 3% Novolac liquid, 0.45 % Novolac powder,
hexamine catalyst (0.3 %) and 5.5 % water are thoroughly mixed and kept in briquette
making mould. Hydraulic press is used to apply a load of 5 tons on the mould to form
cylindrical briquettes. These briquettes are heated to 423 K (150 oC) for 30 min and
then cured in open atmosphere for 24 hours. After 24 hours of curing time, these
briquettes are subjected to CCS and the average value of CCS is found to be 774
kgf/briquette. This is considerably higher than the desired strength of 332 kgf/briquette
evaluated in experiment 1. Hexamine catalyst used in this experiment will result in
faster setting of the mixture for faster agglomeration of the fines.
Presently used binder (molasses)is a co-product of the naturally available sugarcane.
Sugarcane is a seasonal crop and hence there will be uncertainty in the availability of
molasses. The alternate binders proposed in this patent will be available and they are
synthetic products and will be used in less quantity compared to molasses.
Diagram of Briquette mould
Following Figure shows the rough sketch of the mould that was used for the briquette
preparation. A small cylinder of 25 mm diameter, 70 mm length is made to press in the
hollow space of the hollow cylinder with the matching space for the small cylinder as
shown in Figure.. The whole arrangement is kept under hydraulic press and pressure is
applied on the top of the small cylinder to compress the material present in the hollow
portion of the big cylinder.

Prior Arts
Palowitz Francis S., Boardman, OH, US, US patent number US005302341A,
Continuous method for formation of briquettes contains less than 1% binder by weight
of the briquette, 1994
Crowley Henry L, US patent number US2775566A, Binder for agglomerating finely
divided materials, 1956
Economic times. (2016). Retrieved September 12, 2016, from
http://articles.economictimes.indiatimes.com/2016-03-15/news/71543379_1_blending-
targets-ethanol-blending-programme-ethanol-production
(1994). Patent No. US005302341A.
The Chemical Company. (n.d.). Retrieved August 23, 2016, from
https://www.thechemco.com/chemical/phenolic-resin/

WE CLAIM
1. A process for manufacturing High Strength Briquettes from Chrome concentrate, the
process comprising steps of:-
forming a mixture of chrome concentrate micro-fines with a liquid phenolic resin binder,
solid phenolic resin binder and water, in the ratio of 90-92 : 2.5-3.5 : 0.4-3.5 : 4-5 (all in
wt.%), the chrome concentrate micro fines having a size range of 85% less than 150
microns and chemical analysis of Cr2O3: 54-60, Fe2O3:12-19.5, Al2O3: 10-12, MgO: 10-11.5,
CaO- 0.03 (max), SiO2: 2.7-3.5 (all in wt.%) rest unavoidable impurities, and
subjecting the mixture to a briquetting press machine under a pressure of 10.5-12.5 N/mm2.
2. The process as claimed in claim 1, wherein a catalyst with 0.2-0.4 wt.% is added to said
mixture.
3. The process as claimed in claim 2, wherein the catalyst is hexamine.
4. The process as claimed in claim 1, wherein the phenolic resin binder comprises phenol 40-
50% by wt.
5. A chrome concentrate briquette comprising:
Cr2O3: 50-54, Fe2O3:17-18, Al2O3: 11.5-12, MgO: 9-10, CaO- 0.03 (max), SiO2: 3-3.5,
phenol: 1.30-1.89, formaldehyde: 1.30-1.89, water: 4-4.5 (all in wt.%) and a cold crushing
strength of 350-800 kgf /briquette rest unavoidable impurities.