FIELD OF THE INVENTION
The present invention relates to 'innovative blend designing for maximizing
addition of low ash carbonaceous constituents in stamp charge coal blend to
broaden the coal base' thereby, permitting the use of inferior coals and inerts
without impairing the coke quality. More particularly, the present invention
relates to a coal blend composition for maximizing utilization of inert
carbonaceous matters in a stamp charge coal blend.
BACKGROUND OF THE INVENTION
Stamp charging has been established as a versatile technology which not only
improves the coke properties that can be obtained from a given coal blend, but
also broadens the coal base for coke making and permitting the use of inferior
coals without impairing the coke quality. To produce high strength coke at
reasonable cost, the process of stamp charging is essential with 40-45% high
grade coals without sacrificing the coke quality.
It is known that adequate coke strength can be obtained at specific optimum
values of rank, petrographical properties and fluidity of the coal blend. These
optimum levels additionally depend on operating parameters and carbonization

technology, which is specific to every coke making installation. Once these
optimum levels are identified then, suitable blends need to be formulated with
proper selection of the constituent coals so as to have optimum coal blend
properties as mentioned above.
Low ash carbonaceous materials like petroleum coke and anthracite can be used
in the stamp charging coal blend so as to broaden the coal range and reduce the
overall cost of the stamp charging blend. The effect of these inerts on coke
structure have been widely studied and that their influence on the coke quality
appear to be related primarily to the effectiveness with which they are
incorporated into the coke structure and to the presence (or absence) of fissures.
The advantage with petroleum coke is that it is less likely to generate fissures,
and still improve the coke quality, if its incorporation results in thicker cell walls
and smaller pores. Hence, the use of these inerts calls for judicious selection of
other components of coal blend and optimization of the blend proportion.
The fluidity of coal blend plays an important role for producing high quality of
coke. If fluidity is too low, coke strength deteriorates due to poor adhesion
between particles, because there is not enough plastic material for binding the
inert phase. On the other hand, too high fluidity also produces lots of inherent
cracks in coke and makes it porous. Hence, a blend should have optimum fluidity
to produce a coke of good quality. The inerts have tendency to decrease the
overall fluidity of the blend.

OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a coal blend composition for
maximizing utilization of inert carbonaceous matters in a stamp charge coal
blend, which exhibits high fluidity.
Another object of the invention is to propose a coal blend composition for
maximizing utilization of inert carbonaceous matters in a stamp charge coal
blend, which allows assimilation of carbonaceous inert materials without
compromising the produced quality of coke.
A further object of the invention is to propose a coal blend composition for
maximizing utilization of inert carbonaceous matters in a stamp charge coal
blend, which reduces the production cost and increases the yield.
A still another object of the present invention is to propose a coal blend
composition for maximizing utilization of inert carbonaceous matters in a stamp
charge coal blend, which produces strength coke.
A still further object of the present invention is to propose a coal blend
composition for maximizing utilization of inert carbonaceous matters in a stamp
charge coal blend which controls expansion of the coke mass in the stamp
charge oven to avoid excessive swelling pressure and oven damage.

SUMMARY OF THE INVENTION
Accordingly there is provided a coal blend composition for maximizing utilization
of inert carbonaceous matters in a stamp charge coal blend. Thus, the present
invention demonstrates that low ash carbonaceous inerts like fluid coke and
anthracite can be used in the stamp charging blend to produce high quality coke
by using 20% coal having high fluidity in the stamp charging blend along with
other non-fluidic coking coals, up to 15% low ash carbonaceous inerts. The
addition of carbonaceous inerts not only improves the coke yield but also
enhances the coke quality. By the addition of these inerts, the coal component in
the normal base blend is reduced by 5 to 10% and that can be replaced by
medium coking coal of low cost. Hence, the overall cost of the coal blend will be
much less without sacrificing the coke quality.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 illustrates CSR (Coke Strength after Reaction) of coke for various
blends.
Figure 2 illustrates yield of coke for various blends.
Figure 3 illustrates effect of Mosaic texture on CSR.
Figure 4 illustrates effect of isotropic texture on CRI (Coke Reactivity Index).

DETAILED DESCRIPTION OF THE INVENTION
A selected illustrative embodiment of the present invention will be now described
with respect to the accompanying drawings and graphs.
The main objective of the present invention is to propose a stamp charge base
coal blend so as to have a high fluidity which could assimilate carbonaceous inert
materials for example, anthracite and petroleum coke without impairing the coke
quality. While optimizing the coal blend to get high strength coke it is also
necessary to control the expansion of the coke mass in the stamp oven to avoid
excessive swelling pressure and oven damage.
According to the invention, twp captive coals of prime and medium coking types
were used as components in the coal blends. Their properties are summarized in
Table - 1 . The Ind. Medium Coking coal exhibits fairly a reasonable maximum
fluidity (<3000 ddpm), but its use in the stamp charging blend is restricted due
to its high ash and volatile matter content. However, even this level of fluidity is
not good enough to assimilate inerts more than a certain limit. Therefore, it is
imperative to look for coals having low ash with high fluidity, sufficient enough to
digest maximum quantity of carbonaceous inerts.


Three coals viz. HF1, HF2 and HF3 having high fluidity were identified for
experimentation. The coals were tested for their chemical, rheological and

petrographical properties to assess their coking potentiality and compatibility. All
the results of these tests have been complied in Table 2.


Out of these coals, HF1 coal has got the highest maximum fluidity of 10551
ddpm, whereas HF2 and HF3 coals possess the maximum fluidity of 8775 ddpm
and 3026 ddpm respectively.
Three different types of carbonaceous inerts were also selected for incorporating
into the stamp charge coal blends.
One of the carbonaceous inerts is fluid ccoke which is basically a petroleum coke
that derives its name from its production method, namely in a fluidized bed
where the heavy residual oil is injected and cracks forming small round grains of
carbon, having fairly uniform size fractions in the range of 0.1-0.2 mm (fine
powder form). Fluid coke is characterized by its ultra low ash, very low volatile
matter (V.M.), ultra low phosphorous contents associated with high sulphur
content (<2%).
The other two inerts identified are Anthracites C and A from two different
sources. The properties of these inerts are given in Table 3.


In order to explore the possibilities of using these carbonaceous inerts in the
stamp charging coal blend and to access the influence of the same on coke
making, a series of carbonization tests were conducted in the 7-kg Carbolite test
oven under stamp charging condition (Wet Bulk Density of the coal cakes - 1150
kg/m3).
The first series of carbonization tests were carried out to study the effect of
addition of inerts like fluid coke and anthracite to the normal base blend
(Table 4). The second series of tests were done with suitably formulated blends
comprising the captive coals, high fluidity coals and the carbonaceous inerts
(Table 5).


The factors considered for designing the coal blends for the second series of
tests were
• Reduction in the cost of coal blend
• Increase in coke yield without deterioration in coke quality
• Safe carbonization with respect to wall pressure

• Note: Safe Lateral Expansion - 8.2 % max (as per 7-kg
Carbolite oven)
• Acceptable coke CSR -54 (min.) CSR in the 7-kg Carbolite
oven is equivalent to 65 CSR in commercial coke oven.
• (32 CRI in 7-kg Carbolite oven corresponds to 26 CRI in commercial
coke oven)
• *Base blend

The maximum lateral expansions of the coal mass which occurs normally at 60%
carbonization time were measured for all the tests. The samples of the resultant
coke were tested for ash content and high temperature strength characteristics
i.e. CSR and CRI.
The effect of addition of high fluidity coals were summed under:
• It was possible to reduce the high fluid coal component in the stamp
charging blend from 40% (Imp. Semi-soft coal) to 35% (High Fluidity
coals + Carbonaceous Inerts) and still produce coke with improved
strength characteristics.
• In all the tests, the CSR of coke improved at least by 2 points.
• The coke yield increased by 1.5 - 2.5% due to low V.M. content of the
blend.
• Coke ash level reduced by 2 - 3 points.
Figure 1 depicts the comparison of CSR values of all the results carried out in the
7-kg Carbolite oven. It shows that all the blends having inerts and high fluidity
coals resulted in high coke strength after reaction than that of the base blend.
Cokes produced from the blends containing fluid coke as carbonaceous inert
have the maximum increase in CSR (2. 5 and 8 in the figure 1). This is mainly
due to the fine particle size of fluid coke contributing to better assimilation during
carbonization. Fluid coke being very fine in size, get very easily dispersed in the
coal mass during the plastic/fluid state of carbonization and hence, blend
containing fluid coke have more increase in CSR than that of Anthracite (C) and

Anthracite (A). Blends having Anthracite (C) as inert have the lowest increase in
CSR (3, 6 and 9 in figure 1). This may perhaps be due to very high maturity level
of Anthracite (C) compared to Anthracite (A) as indicated by its Ro value. Blends
having HF1 (2, 3 and 4 in figure 1) have maximum capacity to assimilate
carbonaceous inerts compared to HF2 and HF3.
Figure 2 represents the gross coke yield values obtained in all the tests.
Compared to the base blend, the coke yields of all the test blends were higher,
although the maximum yield was obtained with coal blend containing fluid coke
(2, 5 and 8 in figure 2).
The microstructure characteristics could be explained as in general. Anthracite
and Fluid coke do not mix well with coal blend due to high melting temperature.
But addition of high fluidity coals to the base blend can bring about significant
improvement in the mixing pattern of these inerts. The coke made from the base
blend, as may be seen from the figure 3, is comparatively rich in isotropic carbon
indicating thereby the high reactivity nature of this coke against those cokes
made using Anthracite and Fluid Coke in combination with high fluidity coals.
Likewise, the CSR of the coke made using Anthracite and Fluid Coke in
combination with high fluidity coals are much higher than that of coke made
from base blend. It appears that presence of high fluidity coal improves the
plastic behavior of the coal blend, allowing the molecules to move more freely to
form better anisotropic texture. The anisotropic carbon forms are generally more
resistant in C02 gasification than the isotropic carbon form, hence, the increase
in anisotropic carbon and the decrease in isotropic carbon may be responsible for
an improvement in CSR.

The mosaic texture is predominant in all the coke samples of test blends in
comparison to those of base blend as can be seen from figure 3. This increase
in mosaic texture has contributed towards improving the coke strength in terms
CSR. It is also evident that the flow and lamellar texture together have negative
influence on CSR. It reveals that addition of fluid coke and anthracite has
contributed towards decreasing the flow and lamellar texture together, because
during the carbonization process mesophase coalesces with other spheres as the
pyrolitic process continues. Isotropic texture indicates the reactivity of
metallurgical coke as can be seen from figure 4. Coal blends in which fluid coke
and anthracite have been added in combination with high fluidity coals have
comparatively less isotropic texture than that of the base blends. Because of this,
the coke reactivity (CRI) of base blend is higher that of other blends containing
high fluidity coals and inerts as can be seen from figure 4.
Hence, the above findings indicate that low ash carbonaceous inerts in
combination with high fluidity coals can be used beneficially as a replacement for
the coal component presently being used in stamp charging blend. Such
materials when used in combination with high fluidity coals would result in higher
coke strength, higher coke yield and productivity.

WE CLAIM:
1. A coal blend composition for maximizing utilization of inert carbonaceous
matters in a stamp charge coal blend, comprising high fluidity coals in
admixture with low ash carbonaceous materials, wherein said high fluidity
coals have a range of fluidity from 3000 to 15000 ddpm and wherein said
low ash carbonaceous materials have fixed carbon content of more than
75%.
2. The coal blend composition as claimed in claim 1, wherein said low ash
carbonaceous materials can be selected from a group of inerts consisting
of Anthracite, Fluid Coke, and other materials used for stamp charge coke
making, having ash content of less than 15% and volatile matter content
less than 15%.
3. The coal blend composition as claimed in claim 1, wherein up to 15%
carbonaceous inerts can be used in the stamp charge coke making
process.
4. The coal blend composition as claimed in claim 1, wherein the maximum
swelling pressure should be within the allowable limit for known stamp
charging.

5. The coal blend composition as claimed in claim 1, wherein, the coke
strength after reaction(CSR) of the coke is more than that of the base
blend used for stamp charging.