FIELD OF THE INVENTION:-
The present invention relates to a method for improvement of mean size of coke
for stamp charge battery.
BACKGROUND OF THE INVENTION:-
Coke physical properties are of great importance for the blast furnace operation.
The importance of coke physical properties is linked to the need to support the
ferrous burden and to give a permeable matrix through which reducing gases
can flow and molten material can percolate in the lower part of blast furnace.
These physical properties are related to its size (mean and distribution) and its
resistance to breakage and abrasion. Proper sizing of furnace coke can
contribute to the increase in production of a blast furnace and to the lowering of
coke rates. Too small coke entails the formation of an impermeable inert central
core in the blast furnace whereas large mean size with a narrow size distribution
maintains adequate permeability. It was found from literature that coke size
affected by nature of coal, operational parameter and addition of additives.
With this background a lab scale study has been designed to find the effect of
some additives on coke size.
Objects of the invention:-

It is therefore the object of the present invention to propose a methodology
which increases the mean size of coke for stamp charge battery.
Another object of the present invention is to propose a method for improvement
of mean size of coke for stamping battery which increases the productivity of
Blast furnace.
SUMMARY OF THE INVENTION:-
The present invention is provided with a method for improvement of mean size
of coke for stamp charging battery. It comprises the steps of preparing a coal
blend by 45% medium coking coal, 15% prime coal and rest are semi soft and
other and adding pyroxenite to the blend as additive. The blend is crushed to a
fineness of 90% below 3.2 mm size and water is added to coal blend to obtain
the desired value of moisture content for making a coal cake. The coal cake is
then placed inside a cardboard box and charged in carbolite oven at a
temperature of 900 ± 5°C. After 5 hours the coal cake is pushed and quenched
in water. After drying the coke for 24 hrs the sample is subjected to 5 kg micum
drum for 100 revolutions. The stabilized coke is then screened through 80, 50,
30, and 10 mm square hole screen, from the data mean size is calculated.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF
THE INVENTION:-

Characterization of pyroxenite
In order to use pyroxenite in the coal blend for coke making, it was characterized
by chemical analysis. Pyroxenite is basically a group of important rock-forming
silicate minerals of variable composition, among which calcium, magnesium, and
iron-rich varieties predominate. Pyroxenite is used as a source of MgO in sinter
making. From chemical analysis data it was found that pyroxenite content
around 25% MgO, 48% SiO2, 8% CaO and 5% Fe. The composition of
pyroxenite is presented in Table 1. Pyroxenite was added to the blend in the size
range of 0.18-0.21 mm.
Carbonization Test
A number of carbonization tests were conducted in the 7-kg carbolite test oven,
under stamp charging conditions using a standard procedure established at R &
D, Tata Steel. The coal samples to be used for making the coal blends were
crushed to a fineness of 90% below 3.2 mm. Water was added to the coal blend
to obtain the desired value of moisture content. The coal cake was made inside a
cardboard box keeping the bulk density 1150 kg/m3. The coal blend contain 45%
medium coking coal, 15% prime coking coal and rest are semi soft and other.
Pyroxenite was added to the coal blend by replacing semi soft coal. It was added
in different proportion. The final coal cake thus made was charged into the
carbolite test oven. Before charging the coal cake into the oven, it was ensured
that the empty oven temperature is 900 ± 5°C. After 5 h of carbonization time,
the hot cake was pushed out and quenched with water. The series of
carbonization tests were carried out following the above mentioned procedure to
study the effect of different additives on coke size. The coke samples were
subjected to 5 kg micum drum test in order to get weighted average and m30.
Size analysis of coke sample
After quenching the coke is left for drying. Dry coke is then stabilized by rotating
(100 revolutions) in 5 kg micum drum. The stabilized coke is then subjected to
square hole screen (80 mm, 50 mm, 30 mm and 10 mm) and the mean size is
calculated from screen analysis data.
Results
Table 2 shows mean size value of coke samples. It was found that addition of
pyroxenite increases the mean size of coke in compare to base blend. Pyroxenite
may form additional bond with coal. Use of additives more than 0.5% is not
advisable due to swelling which can be harmful for oven wall.
WE CLAIM:-
1. A method for improvement of mean size of coke for stamp charging
battery comprising the steps of:-
- preparing a coal blend by 45% medium coking coal, 15% prime coal
and rest are semi soft and other;
- adding pyroxenite to the blend as additive;
- crushing the coal blend to a fineness of 90% below 3.2 mm size;
- adding water to coal blend to obtain the desired value of moisture
content;
- making a coal cake by placing inside a cardboard box;
- charging the coal cake into carbolite test oven at a temperature of 900
± 5°C for 5 hours;
- quenching the hot cake in water;
- drying the coke after taking out from water;
- testing the dry coke sample to 5 kg micum drum test (100
revolutions);
- screening the stabilized coke through 80, 50, 30, and 10 mm square
hole screen and mean size is calculated which is 39.05 mm.
2. The method as claimed in claim 1, wherein chemical compositions of
pyroxenite are
Cr2O3 - 0.890%
TiO2 - 0.057%
Al2O3 - 1.580%
MnO-0.110%
MgO - 24.850%
SiO2 - 48.030%
CaO - 8.310%
Fe (T) - 4.820%
3. The method as claimed in claim 1, wherein the bulk density of coal cake is
1150 kg/m3.
4. The method as claimed in claim 1, wherein the optimize size of Pyroxenite
is 0.18-0.21 mm.
5. The method as claimed in claim 1, wherein the maximum 0.4% of
pyroxenite can be added to the blend.

The present invention is provided with a method for improvement of mean size
of coke for stamp charging battery. It comprises the steps of preparing a coal
blend by 45% medium coking coal, 15% prime coal and rest are semi soft and
other and adding pyroxenite to the blend as additive. The blend is crushed to a
fineness of 90% below 3.2 mm size and water is added to coal blend to obtain
the desired value of moisture content for making a coal cake. The coal cake is
then placed inside a cardboard box and charged in carbolite oven at a
temperature of 900 ± 5°C. After 5 hours the coal cake is pushed and quenched
in water. After drying the coke for 24 hrs the sample is subjected to 5 kg micum
drum for 100 revolutions. The stabilized coke is then screened through 80, 50,
30, and 10 mm square hole screen, from the data mean size is calculated.