Note: Descriptions are shown in the official language in which they were submitted.
1063060
The present inyention rel~tes to an improvement in the
method for manu~acturing a high-strength formed coke in a slight mutual
agglomeration using a horizontal slot type coke oven battery, such coke
being especially useful for blast furnaces.
A method is now known for the purpose of improving the coke
quality and the productivity, in manufacturing a coke for blast furnace
using a conventional, i.e., a horizontal slot type coke oven battery.
Such known method comprises charging briquettes produced by forming r
blended raw material coal fines by a compression forming machine (herein-
after referred to as "~ormed coal"), into the horizontal slot-type coke
oven battery thus carbonizing the formed coal to produce a coke~
According to this method, a coke which is especially useful in a
blast furnace is produced either by charging a formed coal and coal fines after r
mixing into a horizontal slot type coke oven battery, charging a formed coal
and coal fines alternately in horizontal layers into a horizontal slot type coke i
oven battery, or charging a formed coal only into a horizontal slot type coke _
oven battery; and then carbonizing the raw materials thus charged. ~
~'
In the aforementioned method, in charging a formea coal
and coal fines in combination into a horizontal slot type coke oven
battery, pieces of formed coal should be completely agglomerated with
surrounding coal fines during the process of carbonizatian. For this
purpose, it is necessary to use raw material coals having a somewhat high
fluidity in carbonizing, and this not only imposes certain limits on the
range of selection and blending of raw materiaI coals used. but also
necessitates troublesom charging practices into the horizontal slot type
.
coke oven battery.
When only a formed coal is charged into a horizontal slot
type coke oven battery, wide range of selection and blending of raw
materlal coals uaed, i~ available and the charging into a horizontal
slot type coke oven battery i8 also easy. In this case, however, the
operation of the horizontal slot type coke oven battery is problematic.
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More specific~lly? ~ith ~ ~iew to facilltat~ng discharge of an already
carbonized for~ed coal ~hereinafter referred to ~s "formed coke~, it is
necessary that pieces of ~ormed coke should be mutually agglomerated.
On the other hand, however, a formed coke mutually aggiomerated too
firmly remains in the agglomerated state even after discharging, and is
not separated into pieces, It is therefore desirable that a formed coke
produced by chargIng only a formed coal into a horizontal slot type coke
oven battery, being in a ~utually agglomerated state at the time of
discharging, should 6e only slightly agglomerated so as to permit easy
separation into pieces after discharging. In a horizontal slot type coke
oven battery, however, the heating rate differs between the zone near
the oven walls and the central zone. If the blend~ng ratio of raw
material coals is decided on the basis of the central zone, pleces of
formed coke in the zone near the oven walls are mutuahly agglomerated
too firmly, and remain in the agglomerated state even after discharging,
not permitting separation into pieces, A blending ratio of raw material
coals not causing mutual agglomeration of a formed coke, if adopted to
avoid the aforementioned drawback, leads to a lower strength of the formed
coke. If, on the contrary, the blending ratio of raw material coals is
decided on the basls of the zone near the oven walls, pieces of formed
coke in the central zone are not mutually agglomerated, thus making it
difficult to discharge the produced coke.
For the purpose of obtaining a formed coke in mutual agglo-
meration as mentioned above, a method has been proposed, which comprises
charging only a formed coal produced by blending raw material coal fines
so a6 to give a coking index of 80 to 88 into a horizontal slot type coke
oven battery and carbonizing said formed coal. According to this method,
however, it i8 not always possible to obtain a satisfactory formed coke
in a slight mutual agglomeration. The coking index is defined a6 an
index calculated by ~L~_~ x 100, where:
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~063060
A The amount of oversize coke (g) obtained by
sleving through a 35 mesh screen a coke produced
through carbonization of a mixture consisting
of a coal fine with a size of not more than 65
mesh in an amount of 1 g and a coke breeze with
a size of 48 to 65 mesh in an amount of 9 g in
a crucible at 950 + 20C for 7 minutes; and
B: The amount of oversize coke (g) obtained by
sieving further through a 48 mesh screen the
undersize coke obtained through the 35 mesh
screen.
An object of one broad aspect of the present ~`
invention is therefore to provide an improvement in a method
for manufacturing a high-strength formed coke for blast
furnace in a slight mutual agglomeration using only a formed
coal comprising low-grade raw material coals in a horizontal
slot type coke oven battery. r
In accordance with a broad aspect of the present
invention, an improvement is provided in a method for manufacturing
a high-strength formed coke in a slight mutual agglomeration
solely from formed coal in a conventional horizontal type coke
oven battery, which comprises sieving a plurality of different
types of raw material coal fines to a size not exceeding 1.5 mm.,
mixing the plurality of different types of raw material coal
fines thus sieved with a binder, forming same to produce a
formed coal, charglng only the formed coal into the coke oven
battery, and then carbonizing the formed coal in the coke oven
:
battery under conventional carbonizing conditions to produce
a formed coke, the improvement which comprises: blending
~30 the plurality of different types of coal fines after the sieving
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step to form a mixture of coal fines so as to satisfy the
following conditions: (a) AP index: 75 at the minimum, ,.
(b) Mean maximum reflectance. 1.20% at the minimum, and (c)
A [dilatation] - [contraction] value of from -2% to +5% when
carbonized under conventional conditions in the coke oven
battery at a heating rate of 5C./min. (350 - 600C.);
whereby the formed coke has a percentage of co-agglomeration
within a range of from 40 to 90%.
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--` 1063060
~ Y ~ iant of this ~spect, the fo~med coal is formed
into b~iquettes each having a groove on the uppe~ and the lo~er surface
thereof, respectively.
In the accompanying drawings,
Figure 1 is a graph illustrating the relation between the
size of raw material coal fines ~as abgclssa~ for formed coal and the
degree of co-agglomeration of a formed coke ~as ordinate~;
Figure 2 i5 a graph illustrating, in terms of the coke
strength, the relation between the mean maximum reflectance (as abscissa2
and the AP index of blended raw material coal fines (as ordinate);
Figure 3 is a graph illustrating the relating bet~een the
value [dilatation] - [contsaction] of a formed coal in coking (as
abscissa) and the percentage of co-agglomeration of a formed coke (as
ordinate);
Pigures 4 (a) and (b) are sectional Yiews of conyentional
molds used for producing a formed coal; and
Figures 4 (c) and (d) are sectional views of more desirable
molds for use in the method of an aspect of the present invention.
The inventors conducted an intensive study on the method
for manufacturing a formed coke using a conventional, l.e., a horizontal
slot type coke oven battery, and found as a result the possibility of
obtaining a high-strength formed coke for blast furnace in a slight
mutual agglomeration by: sieving raw material coal fines to a size not
exceeding 1.5 mm; blending the raw material coal fines thus sieved so as
to satisfy the following conditions:
~a) AP index: 75 at the minimum,
(b) Mean maximum reflectance: 1.20 % at the minimu~,
and
(c) lDilatation] - [contraction] in carbonizing at a
hea~ti~g ~ate of 5C~min, (35Q - 6QQC): -2X to
+5 %;
mixing the blented raw material coal fines thus obtained by adding a
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binder, and fo~ing the s~me in a compre~sion fomming machine to
produce a formed coal; and then, charging the formed coal thus obtained
~nto a horizontal slot type coke oven battery, and carbonizing the same.
In an aspect of the present invention, the size of biended
ra~ material coal fines Por formed coal is limited to 1.5 mm and below
in view of the relation between the size of blended raw material coal
fines and the degree of co-agglomeration of formed coke shown in Figure 1.
The degree of co-agglomeration as herein employed ig defined as an index
representing the degree of mutual agglomeration between pieces of formed
coke. This value is expressed by 3 in the case where, in carbonizing
only a formed coal into a formed coke, the pieces of formed coke are
mutually agglomerated firmly and a force applled to separate pieces of
said formed coke would result, not in the separation at agglomeration
interfaces, but in the breakout of individual pieces of the formed coke.
The value ia expressed by 0 in the case where the pieces of formed coke
mutually agglomerated are separated at agglomeration interfaces by the
application of a relatively small force, Figures 1.0, 1.5 and 3,Q
indicated on the abscissa of Figure 1 mean that the size of the blended
raw material coal fines does not exceed 1.0 mm, 1.5 mm and 3.0 mm,
respectlvely.
As mentioned above, both a too firm mutual agglomeration and
the non-mutual-agglomeration are not desirable for a formed coke. The
degree of co-agglomeration is preferably under 1, and more preferably Q,
In an aspect of the present invention, a degree of co-agglomeration of
this order is referred to as a slight co-agglomeration. As is clear from
Figure 1, in terms of the AP index described later, a size of raw material
coal fines not exceeding 1.5 mm leads to a degree of co-agglomeration of
formed coke of as low as under 1 or even 0 in most cases, thus leading
to a desirable slight co-agglomeration of a formed coke.
Al~o in an aspect of the present ~nyention, the AP index is
limited to 75 at the min i , and the mean maximum reflectance, to 1.20 ~
at the minimum, in view of the relation between the mean maximum reflectance
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. 1063060
and the AP index of blended ~aw ~te~i~l coal fines, shown in Figure 2
with regard to the st~en~th DIl5 of a formed coke~ ~ ;
The AP index, an abbreviation of the Agglomeration PropertY
Index, of blended raw material coal fines, herein employed, is defined
as a percentage obtained by: crushing a coal sample in an amount of 35 g
to a size not exceeding l mm; producing a formed coal by adding a lO wt.% .
binder and by forming the mixture in a compression forming machine under
a pressure of 300 kg/cm2; charging said formed coal in an experimental
coke oven at an oven temperature of 500C and carbonizing the same to a !
final temperature of 900C to produce a formed coke in a briquette form; ~r
putting the formed coke thus obtained into a small-sized drum (200 mm dia.
x 70 mm long, S0 r.p.m.); after turning said drum l,000 times, sieving the
formed coke through a 3 mm screen; and calculating the ratio of the
oversize coke weight to the formed coke weight before sieving. This AP
index is a property which has been created by the inventors. The mean
maximum reflectance is obtained by: crushing a coal sample to a size not ~ ;
exceeding 20 mesh; freezing the crushed coal sample with an acrylic resin
and polishing same; and measuring the reflectance of light of the vitrinite
in an oil in compliance with ASTM-2797-69T and 2798-69T.
It is in general desirable that a coke for a blast furnace
should bave a coke strength DIl50 of at least 92Ø As is evident from
Figure 2, in an aspect of this invention a formed coke having a coke
strength DIl5 of at least 92.0 is obtained only when using a formed coal
produced from blended raw material coal fines having an AP index of at
least 751and a mean maximum reflectance of at least 1.20 %. The results
of measurement shown in Figure 2 refer to a case where a formed coke was
produced by carbonizing a formed coal under the following conditions:
Size of blended raw material coal fines: 1.5 mm
at the maximum,
Amount of binde~: lO ~t,X (C/H: 0,72), and r---
Heating rate: 5.5C/min. (400 - 600C).
- In an aspect of the present invention, furthermore, tbe value
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1063060
[dilatation] - [cont~action] of a formed coal in carbonizing at a
heating rate of 5C~in, (350 - 600C) is limited to a range from -2 % to ~ -
+5 %, in view of the relation between the value [dilatation] of a formed
coal in carbonizing and the percentage of co-agglomeration of a formed
coke shown in Figure 3. The percentage of co-agglomeration herein employ-
ed is defined as a percentage representing the state of mutual agglomera- ~ -
tion between pieces of a formed coke produced by carbonizing only a
formed coal, with 100 % for the case in which all the pieces of formed
coke are mutually agglomerated, and with 0 % for the case with no mutual
agglomeration between the pieces of formed coke. The value [dllatation] -
[contraction] as used in various aspects of the present invention is in
conformity to DIN-51739. _
As mentioned above, pieces of a formed coke should preferably
be in a slight mutual agglomeration, and a formed coke in this preferable
slight mutual agglomeration is obtained when said percentage of co-agglomer-
ation is within the range from 40 to 90 %. In other words, a formed coke
with a degree of co-agglomeratlon of under 1 or re preferably of 0 is
obtained when said percentage of co-agglomeration is within the range ~
from 40 to 90 %. As is clear from Figure 3, when using a formed coal ~s
with a value [dilatation] - [contraction] in the range from -2 % to +5 %
in carbonizing, the percentage of co-agglomeration of formed coke lies
within the range from 40 to 90 %. The results of measurement shown in
Figure 3 refer to a case where a formed coke was produced by carbonizing
a formed coke under the following conditions: !
Size of blended raw material coal fines: 1.5 mm _
at the maximum,
Amount of binder: 10 wt.% (C/H: 0.72~, and
Heating rate: 5.5C/min. (350 - 600C).
.~,
U8ually, two ~emi-sphe~ical mold8 as shown in the 8ectional ~
views of Flgure 4(a) ~nd (b) are conventionally e~ployed for producing r
a formet coal. The possibility was however found to obtain the following
favorable merits:
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1063060
(1~ MechAn~c~l strength of a ~o~ed coal and a formed
coke are not impa~red;
(2? In a horizontal slot type coke oven battery, the
larger contact area between pieces of a formed
coke permits easier discharge of coke even with
a low degree of co-agglomeration of the formed
coke; and
~3) In charging a formed coke into a blast furnace,
the permeability resistance is smaller than in a
conventional formed coke. In addition, the more
active convection heat conduction in carbonizing
a formed coal in a horizontal slot type coke oven
battery leads to a smaller difference in the
carbonizing conditions in the oven width direc-
tion than in a conventional one,
by using two molds having a ridge at the center as shown in the sectional
views of Figure 4(c) and (d), and by producing pieces of formed coal in
the form of briquettes each having a groove on the upper and the lower
surfaces, respectively.
Now, certain aspects of the present invention is described
further in detail with reference to some embodiments.
EXAMPLE 1
Raw material coal fines having a size not exceeding 1.5 mm
were blended as follows:
Black Water Coal: 20%
Big Ben Coal: 25%, and
Kuznetsk OS Coal: 55%
to obtain blended raw material coal fines presenting an AP index of 90.0,
a mean maximum reflectance of 1,35 ~, a value ~dilatation] - [contraction]
3Q in carb~nlzing at a heating rate of 5C~min, (350 - 600C) of ~2 X, an
ash, content of 8.5 % and a volatile matter content of 23.8 Z. Sait
blended raw material coal fines were mixed by adding a 10 wt.% binder
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--` 1063060
and ~or~ed in a compression forming machine under a pressure of 3Q0 kg/cm
to produce a formed coal. The formed coal was charged into a horizontal
slot type coke oven battery, and carbonized into a formed coke. The formed
coke thus obtained showed a coke strength DI35 of 92.0 and was in a very
good slight mutual agglomeration with a degree of co-agglomeration of 0.
EXAMPLE 2
Raw material coal Pines with a size not exceeding 1~5 mm were
blended as follows:
Black Water Coal: 20~, -
Sprague MH Coal: 25%,
Watson Coal: 15%.
Kuzunetsk OS Coal: 30% ,and
Petroleum Coke 10%
to obtain blended raw material coal fines havinR an AP index of 87.7, a
mean maximum reflectance of 1.49%, a value [dilatation] - [contraction] in
carbonizin~ at a heatin~ rate of 5C/min. (350 - 600C) of 3 %, an ash
content of 11.4 %, and a volatile matter content 21.4 %. Then, a formed
coal was produced in the same manner as in Example 1, and a formed coke
was manufactured by carbonizing said formed coal. The formed coke thus
obtained showed a coke strength D~3~ o 92.3 and was in very good slight
mutual agglomeration with a degree of co-agglomeration of 0.
According to aspects of the present invention, as described
in detail above, it is possible to manufacture a formed coke having a coke
strength necessary for blast furnace and in slight mutual agglomeration
to a desirable extent, in a horizontal slot type coke oven battery, from
low-grade raw material coal fine6, thus providing industrially useful
effects.
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