FIELD OF THE INVENTION
The present invention relates to a method for improving coke strength after
reactivity. More particularly the invention relates to a method for improving
metallurgical coke strength at high temperature by carbonization of different
types of coal being in stamp condition adaptable to blast furnace use.
BACKGROUND OF THE INVENTION
In recent years, blast furnaces of larger volume have come into use and the
requirements for higher coke strength have become important. The large blast
furnaces have undergone considerable changes in coke properties in the lower
furnace regions. With the increased use of Pulverized Coal Injection,
improvement in hot coke strength is inescapable for efficient and consistent
performance in the furnace.
The prior art teaches reactivity test that measures the loss in weight of coke
sample due to the solution loss reaction, followed by the tumbler strength of the
reacted coke strength. The test has been widely adopted and commonly the 'I"
test which refer the shape of the tumbler drum is used to measure Coke
Strength after reaction (CSR). In the known test procedure, 200 gm of 20±1 mm
coke placed in a tube (78mm diameter by 230mm length) is reacted at a
temperature of 1100 ±5°C in a stream of CO2 at a flow rate of 5 l/m for two
hours. The reacted residue after cooling in nitrogen is weighted, and coke
reactivity index is calculated as follow:

The reacted coke is tested for strength by tumbling it in an I DRUM (130 mm
diameter X 700 mm length), rotating at 20 r.p.m for 30 minutes. The tumbled
coke is screen on a 10mm sieve and the coke strength after reaction is
calculated as:

Efforts for increasing coke CSR center around selection of coal blend proportions
and coal composition; and carbonization parameters. Considering the actual
operating conditions at the batteries, the carbonization parameters are totally
independent and with the practical range of these variables, CSR is not affected
greatly. Accordingly, the known testing specification, the flue temperature and
coking time have less effect on CSR than does coal composition. It has been
reported that CSR depends about 70% on the coals and about 30% on the
operating factors such as flue temperature and soaking time. However, for stamp
charged coke, stamping treatment of coal charge to achieve stipulated bulk
density may be relevant for production of high CSR Coke, since the bulk density
would influence porosity and properties of the cell wall of the resultant coke and
consequently its CSR.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an improved process in a
stamp charging procedure for producing metallurgical coke with coke strength
after reactivity greater than seventy from a coal blend.
Another object of the invention is to propose an improved process in a stamp
charging procedure for producing metallurgical coke with coke strength after
reactivity greater than seventy from a coal blend, the produced coke being
capable to act as cement.
SUMMARY OF THE INVENTION
For the purpose of the present invention, one or more of Coals Grizzly Creek,
Standard hard coking cola, Premium semi hard coking coal, Elkview semi hard
coking coal West Bokaro coal, Semisoft coking coal, lamadoba coal, Bhelatand
coal, Hail Creek, Downson Coal, have been used.
Preparation of the coal comprises crushing in hammer mill and testing of
crushing fineness with help of 3.2 mm screen. The homogenization of charge is
done manually. All tests are carried out maintaining at least ten percent moisture
in the blend.
The coal/coal blend is charged into an electrically heated 7 kg. carbolite oven
(370 L X115 W X305 H) mm and then carbonized at flue temperature around
1000°C under stamp charging conditions. The heating rate and the carbonization
time are kept identical for all the tests.
Carbonization tests are carried out in the 7 kg oven on a single type of coal like
Grizzly Creek, Standard hard coking coal, Premium semi hard coking coal,
Elkview semi hard coking coal West Bokaro coal, Semisoft coking coal, Jamadoba
coal, Blair Athol, Hail Creek, Downson Coal and the blends containing varying
proportions of these coal.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 is a graph showing a relation between total Iron Content of coal and
CSR of stamp charged coke
Figure 2 is a graph showing a relations between CaO Content of coal and CSR of
stamp charge Coke
Figure 3 is a graph showing a relation between SiO2 Content of coal and CSR of
stamp charged Coke
Figure 4 is a graph showing a relation between MgO Content of coal and CSR of
stamp charged coke
Figure 5 is a graph showing a relation between AI2O3 of coal and CSR of stamp
charged coke
Figure 6 is a graph showing a relation between TiO2 Content of coal and CSR of
stamp charged Coke
Figure 7 is a graph showing a relation between Basicity Index of coal ash and
CSR of stamp charged Coke
Figure 8 is a graph showing a relation between inertinite of coal and CSR of
stamp charged Coke
Figure 9 is a graph showing a relation between Fluidity range of coal and CSR of
stamp charged coke
Table 1 : summarizes the results of coke made with 100% single coal in 7Kg
Carbolite oven. The ash, V.M, Ro and CSN varied in the range, 7.75 - 15.4%,
20.0-28.8%, 0.85-1.22 AND 2-8 respectively.
Table 2 shows the results of coal blend carbonization tests carried out in 7Kg
Carbolite oven.
DETAIL DESCRIPTION OF THE INVENTION
The blending of coals in order to obtain greater than seventy CSR are prepared
considering different parameters such as basicity index, inertinite content,
temperature range, ash, volatile matter, Ro, and results of single coal
carbonization tests.
Inventors have studied, particularly, relationship between ash constituents,
basicity index, inertinite of coal and temperature range of fluidity of coal with
coke CSR in stamp charging condition.
The ash content and chemical composition of the coal ash have powerful
influence on CSR of coke. The basicity Index has been defined as follow:
Basicity Index = (Na20+K20+MgO+CaO+Fe203)/(AI203+Si02)
The numerator corresponds to the basic oxides in ash and denominator to acid
oxide.
Coke formation begins with bonding of coal particles upon heating. Coal particles
contain variety of petrographic components and behaviors of each type of
petrographic components differ considerably. There are two types of
petrographic components namely reactive component and inert component.
Reactive component soften and melt upon but inert components do not soften
and melts upon heating. In the coking process, lumps coke formed when
particles are bonded with each other as inert components are wrapped in
reactive that have soften.
In the coke making process the coal must provide a phase that also eventually
acts as cement. An optimum amount of fluidity is required by coal blends to
make good cake.
As a result, following phenomenon are established (1) ash constituents are
although weakly related to CSR but for producing coke CSR greater than seventy
it is necessary to maintain Fe(T)<0.6%,CaO<0.4°/o SiO2>5% MgO<03%
AI203>2.5% and Ti02 in the range of 0.1-0.2% (2) The coke CSR can be
obtained from basicity Index <0.2 (3) For producing CSR grater than seventy, it
is necessary to select a blend which has less than 30%(by volume) inert
component (4) The minimum fluidity range should be 90oC. Based on such
observations, the inventors have (Table : 2) produced coke with CSR greater
than 58 which is equivalent to 70 in Coke Plant and positive lateral dilation in the
range of 6.29-10%. In stamp charging condition lateral dilation greater than
8.25% in laboratory oven gives higher wall pressure in coke plant, therefore, in
stamp charging such type of blend should not be used in old ovens.
WE CLAIM
1. An improved process in a stamp charging procedure for producing
metallurgical coke with coke strength after reactivity greater than seventy
from a coal blend having ash and Volatile substances in the range of 10.2-
12.75% and 20.45-24.75% respectively, wherein coal blends are prepared
from blendable, none coking and prime coking coal, wherein a
reflectance-in-oii (RO), and coal strength after reaction (CSR) value of the
coal blend varies in the range of 1.077-1.25 and 4-6.5 respectively, and
wherein a basicity index coal blend is less than 0.2.
2. The process as claimed in claim 1, wherein inert component of said coal
blend is less than 30(volume %).
3. The process as claimed in claim 1, wherein a minimum fluidity range of
the coal blend is about 90oC.
4. An improved process in a stamp charging procedure for producing
metallurgical coke with coke strength after reactivity greater than seventy
from a coal blend, as substantially described and illustrated herein with
reference to the accompanying drawings.

This invention relates to an improved process in a stamp charging procedure for
producing metallurgical coke with coke strength after reactivity greater than
seventy from a coal blend having ash and Volatile substances in the range of
10.2-12.75% and 20.45-24.75% respectively, wherein coal blends are prepared
from blendable, none coking and prime coking coal, wherein a reflectance-in-oil
(RO), and coal strength after reaction (CSR) value of the coal blend varies in the
range of 1.077-1.25 and 4-6.5 respectively, and wherein a basicity index coal
blend is less than 0.2.