FIELD OF INVENTION
The present invention relates to a method for maximum utilization of heat altered
coal (Jhama) in coke making adaptable to blast furnace input material.
BACK GROUND OF THE INVENTION
Coal affected by igneous intrusion is a common phenomenon all over the world.
Such coals are known by various names such as geological coke, natural coke,
cinder coke etc. In India it is known as jhama. Jhama being partially carbonized
is expected to loose all its coking properties and also, difficult washability
characteristics due to more uniform distribution of mineral matters in the partially
carbonized coal matrix. This makes its large scale utilisation, especially, coke
making challenging. Present invention emphasized to make utilisation maximum
quantity of Jhama coal as a component of coal blend in the coke making.
In India, a large amount of thermally metamorphosed coal Ghama) has been
found near the Damodar Valley coalfields in Jharia, which is a part of lower
Gondwana coalfields. In general, igneous intrusions cause dramatic changes in
vitrinite reflectance, mineralogy and geochemistry of the coal seams. Depending
upon the intensity of alteration, jhama coal can be demarcated in categories like
highly affected and moderately affected. In the Indian coal scenario Jharia
coalfield occupies a special status as this is the only storehouse of prime coking
coal and has been meeting the coking coal needs of the country for over a
century. In Jharia, major part of the reserve of coking coal is altered due to
igneous intrusion (Figure 1). For example, the total insitu reserve of jhama at
Jharia Division of Tata Steel is 154.10 million tonne wherein the extractable
reserve is only 8.64 million tonne till date. Some preliminary studies have been
done in past for beneficiation of moderately and highly affected jhama coal. The
presence of jhama causes the estimation of the quality and quantity of coal in
any area or seam to be problematical because of the coal's heterogeneous
alteration and compact nature. Many attempts were made to overcome the
various difficulties, but very few systematic characterizations were done earlier.
Hence, proper industrial utilization of heat affected coal could not be made till
now.
There have been developments which directed toward the use of low grade/non
coking coal in the production of blast furnace metallurgical coke. Among them
the most popular methods are comprise of use of different binder, briquetting etc.
An US Patent 4135983 of 1974 discloses coking properties of coal to produce
blast furnace coke is improved by blending with a highly aromatic bituminous
substances obtained by heat treatment of hydrocarbons.
An US Patent 4100031 of 1978, discloses a teaching of a technique available
which involves addition of a binder to a coal for making briquettes which is
blended with about 40% or more of low grade coal.
An US patent 4178215 of 1979 and an US patent 4318779 of 1982 that disclosed
the methods for preparation of improved coke by adjusting the moisture content
of blend, briquetting and adding additives and caking material.
An US patent 4523927 of 1985 discloses another method of converting low rank
coal to high rank coal which has better quality in terms of heating value, moisture
content etc comprise of heat-treating coal for dehydrating the coal and distilling
off tar vaporizing the tar, and coating the heat-treated coal surface with the tar
vapor, whereby the coal surface is coated uniformly.
An US patent 5752993 of 1998 discloses a teaching of substitute of blast furnace
coke can be manufactured in the form of compressed briquette or other solid
from a reaction of fine carbonaceous material (such as coke breeze, coke files or
petroleum coke), a reactive tar or and polymetric binder.
An US patent 6033528 of 2000 discloses a teaching of a blast furnace coke is
produced by rapidly heating a coal blend having 10 to 30% by weight of a mon to
medium caking coal at a different rate to that of prime caking coal and the
charging the coke blend to the coke over.
An US patent 7497928 of 2009 discloses a teaching of another method of
metallurgical coke production process comprises rapidly drying coal particles in
an inert atmosphere, and maintaining the particles, once dry, in an inert
atmosphere. The dried particles are then compressed into a briquette without
addition of a binder.
The present invention emphasized on using moderate affected jhama coal in
coke making using some specific pre-carbonization techniques, adding some
additives ad by combination of both.
OBJECTS OF THE INVENTION
It is therefore, an object of the present invention to propose a method for
maximum utilisation of heat altered coal (Jhama) in coke making.
Another object of present invention is to propose a method for maximum
utilisation of heat altered coal (Jhama) is coke making which will save the
quantity of indigenous medium coking coal, prime coking coal and imported coal.
Further object of the present invention is to propose a method for maximum
utilisation heat altered coal (Jhama) in coke making which utilizes the unusable
heat alter coal (Jhama) Stock from the reservoir.
SUMMARY OF THE INVENTION:
The present invention is to utilisation of jhama coal for using in coke making. In
order to achieve this a pre-carbonization technique like groupwise crushing is
tested. In groupwjse crushing the constituents of coal blend categorized in
different groups. Each group is then crushed separately. Also addition of
additives like pitch, phenolic resin is found to improve the quality of coal. The
invention directs the optimum size range of jhama coal to which it should be
crushed for using effectively in coke making and also the use of phenolic resin for
further improvement of coke quality. Studies have been made in 7kg Carbolite
oven by using different amount of jhama coals are crushed in different size and
using different percentage of additives in it and carbonized in an oven. Resultant
cokes are then characterized for Coke Strength after Reaction (CSR).
BRIEF DESCRIPTION OF ACCOMPANYING DRAWING:
Figure 1 - Shows a geographical area of heat affected coals in Jharia.
Figure 2 - Shows a bar chart indication the improvement in coke CSR (Coke
Strength after Reaction)
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION:
Step 1: Characterization of jhama coal
In order to use jhama as one of component in coal blend for coke making, it was
characterized by some preliminary tests like proximate analysis, ultimate
analysis, fluidity, dilation, Hard grove grindability index, calorific value, crucible
swelling number and petrographic studies. Jhama coal is characterized with low
volatile matter, high ash content, high fixed carbon (>85%) and very low or nil
fluidity. Characterization results indicate that jhama has significant amount of
reactive material (reflectance of desired level) and it can also fulfill the
requirement of reactive in coal blend.
Step 2: Crushing of jhama coal in specific size range
The component of coal blend divided in two groups (i) Conventional component
and (ii) Jhama coal. Conventional component comprises indigenous medium
coking coal, prime coking coal and imported coal. The conventional blend
component to be used for making the coal blends were crushed to a fineness of
90% below 3.2mm. Where as jhama coal crushed separately to a fineness of
0.200 - 0.400mm and then mixed with other component in a ratio of 95-97%
conventional compound and 5-3% of Jhama coal.
Step 3: Additives
Additives like phenolic resin, pitch, molasses etc. were also added in some blend
in different proportion in order to find their influence.
Step 4: Carbonization test
The blend thus prepared is allowed to form a cake having a size of 34 cm x 90
cm x 27 cm under stamp charging. The blend thus formed is allowed for
carbonization in an oven in a temperature of 1100°C for period of 5 hrs charging
conditions using a standard procedure. A series of carbonization tests were
carried to study the influence of specific size crushing of jhama coal to the base
blend under stamp charging conditions and also to find out the effect of different
additives. The coke samples were tested for CSR and CRI.
Results
The results are summarized in Table 1. The results are given for three different
blend compositions (B1, B2, B3). In these three blend heat altered coal is crushed
in specific size. Improvement in coke CSR values observed in compare to base
blend where jhama is not crushed in that specific size. This is due to reduction of
heterogeneity among the component of coal blend. From experimental results it
is clear that when jhama coal is crushed around 0.200-0.400 mm it gives best
results. The addition of around 0.1% phenolic resin along with specific size
crushing of jhama gives best results. In that case jhama can be used up to 5%.
WE CLAIM
1. A method for maximum utilisation of heat altered coal (Jhama) for coke
making comprises the steps of.
crushing the heat altered coal (jhama) to covert a size of 0.200-
0.400 mm;
crushing the convention coal to covert a size of 90% below 3.2 mm;
mixing the heat altered coal (jhama) to conventional coal in the
proportion 3-5% and 97-95%;
Adding 0.1% phenolic resin binder to the blend;
making the blend in the form of a cake under stamp charging;
carbonization of the cake at a temperature of 1100°C for 5 hour in
an oven
characterized in that the crushing of Jhama reduces the heterogeneity
among the component of coal blend and increases the Coke Strength
value after Reaction(CSR).
2. The method as claimed in claim 1 wherein the size of the cake is 34cm x
90cm x 27cm.

The present invention relates to a method for maximum utilisation of heat altered
coal (Jhama) for coke making comprises the steps of crushing the heat altered
coal (jhama) to covert a size of 0.200-0.400 mm; crushing the convention coal to
covert a size of 90% below 3.2 mm; mixing the heat altered coal (Jhama) to
conventional coal in the proportion 3-5% and 97-95%; adding 0.1% phenolic
resin binder to the blend; making the blend in the form of a cake under stamp
charging and carbonization of the cake at a temperature of 1100°C for 5 hour in
an oven characterized in that the crushing of Jhama reduces the heterogeneity
among the component of coal blend and increases the Coke Strength value after
Reaction(CSR).