FIELD OF INVENTION
The present invention relates to the "Improvement of coke quality by
developing an innovative blend design with optimum amount of
organo-refined coal". More specifically, the relates to a method for
increasing strength of coke by developing a blend design using
organo-refined coal and coking coal.
BACKGROUND OF THE INVENTION
Coal blending is technique used for years to obtain a coal blend of
desired properties from one or more individual coals. In coke making,
it is important to have certain minimum properties of the coal that
goes into the coke ovens to obtain satisfactory coke strength, coke
stability, and other desired properties.
Metallurgical coke used in blast furnaces should have high coke
strength as indicated by hardness and stability. With time, the demand
of high quality coals having high coke strength has increased multi-
fold. The high quality coking coals generally have an optimum
percentage of volatiles in the coal, a high fluidity and a relatively low
percentage of inert components. Decreasing supply of high quality
metallurgical coals has led various research organizations to explore
the ways of achieving high strength coke using lower quality coals.
Blending coals of different quality has been practiced in industry to

utilize low quality coking coals with high/medium quality coking coals
and to achieve desired coke strength.
In the coke industry, blends of coals of differing ranks are commonly
used to obtain the proper coal characteristics needed to produce high
quality coke. Further, desired characteristics of coke depend upon
operating parameters and carbonization technology used in different
set-ups. Once desired characteristics of coke are identified then,
suitable blends need to be formulated with proper selection of
constituent coals so as to have optimum coal blend properties such as
ash in the range of 12-15 weight % and volatile matter in the range of
20-25 weight %.
Organo-refining is the method in which organic part of the coal
extracted out with the organic solvent. The organo-refining process
has been patented by Tata Steel (US20100307054 Al, US8262751
B2). The organo-refining process can be used to upgrade the quality of
low grade coal like thermal, washery rejects and middlings, run of
mine coal etc. Use of organo-refined coal in a blend can help improving
the quality of coke and also reduces the proportion of hard coking coal
in the coal blend.
OBJECTS OF THE INVENTION
The object of this invention is to propose a method for improving coke

quality using organo-refined coal.
Another object of this invention is to develop a blend design to
accommodate maximum amount of organo-refined coal in the blend to
achieve the desired coke quality.
Another object of this invention is to propose a blend design which can
accommodate organo-refined coal extracted from low grade feed coals
like thermal, tailings etc.
Still another object of this invention is to reduce the amount of hard
coking coal in the coal blend.
SUMMARY OF THE INVENTION
In the present invention, organo-refined coal extracted from low grade
coal is used in the stamp charging blend to produce high quality coke.
A blend design is developed to achieve the desired properties in terms
of coke strength. The developed blend design not only helps in
maintaining the coke quality but also helps in improving its strength
when used in optimum percentage in the coal blend. As the organo-
refined coal shows high swelling behavior, it has a positive interaction
effect when used along with semi-soft or less fluidic coal in a coal
blend.
The organo-refined coals are bitumen type in nature, having low

mineral matter and high swelling capabilities. Hence, coal blends are
designed in a way so as to incorporate more of the less fluidic coal and
replace the expensive prime hard coking coal.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
Figure 1 - shows a micrograph of organo-refined coal
Figure 2 - shows coal strength after reaction (CSR) of different blend
design.
DETAILED DESCRIPTION OF THE INVENTION
Blend design as per the current invention includes:
5-20 weight percentage of an organo-refined coal having ash content
(dry basis) in the range of 9 -10 weight %, volatile matter (dry basis)
in the range of 30-34 weight%, and Crucible Swelling Number (CSN)
greater than 9, 50-80 weight% of a medium coking coal having ash
content (dry basis) in the range of 14 -33 weight %, volatile matter
(dry basis) in the range of 22-26 weight%, Crucible Swelling Number
(CSN) in the range of 5-6 and maximum fluidity in the range of 20-
1505 dial division per minute (ddpm), 35-45 weight % of a hard
coking coal having ash content (dry basis) in the range of 8-12 weight
%, volatile matter (dry basis) in the range of 20-25 weight%, Crucible
Swelling Number in the range of 6-9 and Maximum fluidity in the

range of 200 - 2000 dial division per minute (ddpm).
The process of developing the blend design may further include using
different sources of the organo-refined coal, the medium coking coal
and the hard coking coal.
In an embodiment of the current invention, two different types of
organo-refined coals were used. Organo-refined coal A was extracted
from tailngs coal, which is generated as rejects from the froth flotation
process whereas organo-refined coal B was extracted from a thermal
coal. These coals were first characterized for their chemical,
rheological and petrographical properties. Before sample preparation
for characterization the coal samples were dried to remove the extra
moisture. The properties of the organo-refined coals used in the
current invention are given in the Table 1 below:


The organo-refined coals with properties as provided in the table 1,
were blended with the medium coking coal and high coking coal. The
properties of the medium coking coal and high coking coals used in the
current invention are given in table 2 below:
Table 2: Chemical and Rheological Properties of medium coking
coal and high coking coal used for blending

The coal properties were determined using standard known state of
the art test used for coal characterization.

Ash determination: Ash is determined by following Indian standard D
3174-11. 1 g of 250 mm size sample is taken to a weighed capsule.
Then the sample is placed in a cold muffle furnace and heated
gradually at such a rate that the temperature reached 450°C to 500°C
by 1 h. At the end of the 2 h it will reach 950°C. After cooling the
weight of the sample is measured and ash is calculated by weight
difference method.
Volatile matter (VM) determination: Ash was determined by following
ASTM standard D 3175-11. In this test 1 g of 250 mm size sample was
taken in a covered platinum crucible and heated inside a furnace at
950°C for 7 min. The VM was calculated by weight difference method.
Crucible swelling number (CSINQ: Crucible swelling number test was
done by following ASTM D720-91 (2010). In which 1 g of sample (-
0.212 mm size) was taken inside a translucent squat shaped silica
crucible and the sample was leveled by tapping the crucible 12 times.
The crucible was covered with a lid and heated under standard
conditions, either by a special type of gas burner or muffle furnace.
After the test the shape of coke button was compared with a standard
chart and accordingly, the crucible swelling number (0 to 9) was
determined.

Fluidity: This test was done following ASTM. D2639-08 This test was
performed in a constant torque Gieseler plastometer. 5 g sample of -
0.425 mm particle size was packed around a stirrer in a cylindrical
steel crucible (21.5mm ID x 35 mm length). The crucible along with
the stirrer and the sample was immersed in a solder bath which was
heated at a constant rate of 3°C/min. A constant torque of 40 g inch
was applied on the stirrer which remains stationary at the beginning
and starts rotating as the coal becomes plastic and again stops, when
the coal resolidifies into a coke mass. The speed of stirrer was noted at
1 min intervals as dial divisions per minute (ddpm). The data are
reported in terms of maximum fluidity.
Petrography of coal: This was done by following ASTM standard D
2797M-lla, D2798-11 a and D 2799- 1. For microscopic studies 5 kg
coke sample was crushed to minus 3 mm size and by using coning and
quartering method 100 g sample was prepared and mounted on
carnauba wax. The mounted sample was polished using silicon carbide
coated grinding papers of 320, 400, 600 grids respectively, followed by
buffing on blazer cloth using alumina polishing compounds (1.0 and
0.3 mm). The polished specimen was dried using an air dryer prior to
microscopic studies. The microscopic studies were done by Leica
DMS4000 microscope along with QWin software.

Different blend designs were developed using coals as described and
illustrated in table 1 and table 2. As evident from figure 1 (Petrography
study), the organo-refined coal or organic extracts are bitumen type in
nature, having low mineral matter and high swelling capabilities.
Characterization study shows that organo-refined coal has low ash
content and high swelling characteristics. Keeping these properties in
mind, blends were designed in a way so as to incorporate more of the
less fluidic coal and replace the expensive prime hard coking coal.
Carbonization tests
The developed blends were tested by conducting carbonization test.
The carbonization tests were conducted in the 7-kg Carbolite test
oven, under stamp charging conditions using a standard procedure.
Coals from different sources as given in table 1 and table 2 were taken
for blending in weight percentage and water was added to the coal
blend to obtain the desired value of moisture content (around 9.5-
10%). The coal cake was made inside a cardboard box keeping the
bulk density of 1150 kg/m3. Base tests were done with 100% of the
two individual coals identified (hard coking and medium coking. Before
charging the coal cake into the oven, it was ensured that the empty
oven temperature is 900±5°C. After 5 h of carbonisation time, the hot
coke was pushed out and quenched with water. The coke samples

were then tested for their coke strength after reaction (CSR) and coke
reactivity indices (CRI).
Coke Characterization
Coke samples were characterized for their proximate analysis following ASTM
standard D 3172-07 a. Coke strength after reaction (CSR) and a coke reactivity
test (CRI) were done following the Nippon Steel Corporation (NSC) method
(ASTM D5341 - 99(2010) el Standard Test Method for Measuring Coke Reactivity
Index (CRI) and Coke Strength After Reaction (CSR)).
In which 200 g coke of 19-21mm size was heated in a reaction tube (78mm
diameter x210mm length) at 1100°C for two hours during which CO2 was passed
at 5 l/min. The percentage loss in weight of coke during the above reaction is
reported as the CRI. This reacted coke is further tested by rotating in a I drum
(127mm diameter x725mm length) for 30 minutes at a speed of 20 rpm. The
coke is then screened on a 10mm sieve and the percent of +10mm fraction is
reported as the CSR.
Various blend designs were designed and tested as given in table 3
below. These blends were then tested using carbonization test and
coke characterizations tests as described above. The blends were
designed to evaluate the impact of organo-refined coals and hence,
the weight percentage ratio of organo-refined coals was varied from 5-
20 weight percentage.

Figure 2 represents the CSR parameter of different blends. Addition of
the organo-refined coal results in improvement of CSR and CRI.
Further, the blend design as per the current invention has substituted
a significant fraction of high coking coal and medium coking coal with
organo-refined coals. Organo-refined coal forms stronger bonds in the
coal blend due to the presence of more active sites or side chains.
Hence, it helps in modifying the coke making process by increasing the
fluidity of the coal blend through enhancing its plastic temperature
range during carbonization process to produce good quality coke.

WE CLAIM
1. A coal blend for use in blast furnace, the coal blend comprising:
5-20 weight percentage of one or more organo-refined coals
having ash content (dry basis) in the range of 9 -10 weight %,
volatile matter (dry basis) in the range of 30-34 weight%, and
Crucible Swelling Number (CSN) greater than 9;
50-80 weight% of one or more medium coking coals having ash
content (dry basis) in the range of 14 -33 weight %, volatile
matter (dry basis) in the range of 22-26 weight%, Crucible
Swelling Number (CSN) in the range of 5-6 and maximum
fluidity in the range of 20-1505 dial division per minute (ddpm);
and
35-45 weight % of a hard coking coal having ash content (dry
basis) in the range of 8-12 weight %, volatile matter (dry basis)
in the range of 20-25 weight%, Crucible Swelling Number in the
range of 6-9 and maximum fluidity in the range of 200 -2000
dial division per minute (ddpm).
2. The coal blend as claimed in claim 1, wherein the one or more
organo-refined coals are extracted from thermal coal and
tailings.

3. The coal blend as claimed in claim 1, wherein the coke strength
(CSR) of the coke is in the range of 48-55.
4. The coal blend as claimed in claim 1, wherein the coke reactivity
indices (CRI) of the coke is in the range of 33-39.
5. The coal blend as claimed in claim 1, wherein the one or more
medium coking coal is having 32.36 weight % ash content (dry
basis), 22.58 weight% volatile matter (dry basis), 5 Crucible
Swelling Number (CSN) and maximum fluidity equal to 20 dial
division per minute (ddpm).
6. The coal blend as claimed in claim 1, wherein the one or more
medium coking coal is having 14.63 weight % ash content (dry
basis), 25.10 weight% volatile matter (dry basis), 5.5 Crucible
Swelling Number (CSN) and maximum fluidity equal to 1505 dial
division per minute (ddpm).
7. The coal blend as claimed in claim 1, wherein the one or more
organo-refined coking coal is having 9.76 weight % ash content
(dry basis), 30.18 weight% volatile matter (dry basis), and
Crucible Swelling Number (CSN) greater than 9.
8. The coal blend as claimed in claim 1, wherein the one or more
organo-refined coking coal is having 9.71 weight % ash content

(dry basis), 33.69 weight% volatile matter (dry basis), and
Crucible Swelling Number (CSN) greater than 9.
9. The coal blend as claimed in claim 1, wherein the hard coking
coal is having 8 weight % ash content (dry basis), 21 weight%
volatile matter (dry basis), 7 Crucible Swelling Number (CSN)
and Maximum fluidity equal tol356 Dial division per minute
(ddpm).

ABSTRACT

The invention relates to a coal blend for use in blast furnace, the coal blend
comprising: 5-20 weight percentage of one or more organo-refined coals having
ash content (dry basis) in the range of 9 -10 weight %, volatile matter (dry
basis) in the range of 30-34 weight%, and Crucible Swelling Number (CSN)
greater than 9; 50-80 weight% of one or more medium coking coals having ash
content (dry basis) in the range of 14 -33 weight %, volatile matter (dry basis) in
the range of 22-26 weight%, Crucible Swelling Number (CSN) in the range of 5-6
and maximum fluidity in the range of 20-1505 dial division per minute (ddpm);
and 35-45 weight % of a hard coking coal having ash content (dry basis) in the
range of 8-12 weight %, volatile matter (dry basis) in the range of 20-25
weight%, Crucible Swelling Number in the range of 6-9 and maximum fluidity in
the range of 200 -2000 dial division per minute (ddpm).