Coal Composition, Coal Plasticity, and Coke Strength Page: 15
This report is part of the collection entitled: Technical Report Archive and Image Library and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
Table 6.--Statistics for best correlations between coke strength and coal composition or coal plasticity or both i
Correlations between coal Correlations between coke
composition and coke Correlations between coal strength and combination cf
strength plasticity and coke strength ccal composition and coal
plasticity
Two- Three- Four- Twc- Three-variable Four- Three-variable Four-variable
variable variable variable variable variable
s-inch tumbler index:
Correlation coefficient 2-.................... 0. 597 0. 607 0. 610 0. 471 0. 519 0. 560 3 0. 515, 4 0. 599 0. 616
Standard error <f estimate ........... 4. 6 4. 6 4. 6 5.1 4.0 4. 4 34.5, 44.7 4.1
1-inch tumbler index:
Ccrrelaticn coefficient 2--.......------ . 790 .790 .813 .737 3.777,4.785 .823 .816 .851
Standard error of estimate_ 9.0 9. 1 8.7 10.4 9.44 9. 6 8.8 8.6 8. 1
1--inch shatter index:
Correlation coefficient 2 _ .................. . 698 .726 .761 .674 .743 .646 .706 3. 701, 4. 776
Standard error of estimate --------------- 7.3 7.1 6.7 7.7 7.0 6.5 7.3 a 6.1, 4 6.81 Summarized from tables 2, 3, 5, and 8-12.
2 Multiple correlation coefficient for the three- and four-variable cor-
relations.
average chemical structure of a polymeric system
mainly composed of aromatic and hydroaromatic
hydrocarbons should be examined. The aromatic
and hydroaromatic nature of coal 17 has been well
established (32, 46, 69, 94).
In a mixture of aromatic and hydroaromatic hy-
drocarbons, whether they are polymers or simple
compounds, the lower the atomic H/C is, the more
aromatic or the less hydroaromatic the average
hydrocarbon of the mixture should be. The decrease
of atomic H/C from decalin to naphthalene may
serve as an example for pure compounds. In the
same mixture, a lower atomic H/C may also mean
a higher degree of condensation of the average hy-
drocarbon, as in the case of naphthalene to pyrene
or coronene. Furthermore, for similar hydrocarbons
with the same number of rings, those which are
more condensed have smaller molecular weight and
therefore need more moles to make up a certain
weight-percent. As a result, the average aroma-
ticity of the mixture may increase and the average
hydroaromaticity may decrease. The difference in
atomic H/C is small between aromatic hydrocar-
bons with a different number of rings, for example,
only 0.276 between naphthalene and coronene. But
it is much larger between aromatic hydrocarbons
and their hydroaromatics, for example, 1.000 be-
tween naphthalene and decalin, or between any
pericondensed aromatic hydrocarbon and its per-
hydrocompound. Hence, the aromatic-hydroaro-
matic structure should play a larger role in the
atomic H/C change than the degree of condensa-
tion of the hydrocarbons. Polymeric hydrocarbon
systems may differ in aromaticity and/or in degree
of condensation from one system to another. The
polymer in each system may 'be made of the same
or similar fundamental units.
1? For coals with 82.5 to 90.0 percent carbon on dry, min-
eral-matter-free basis, less than 5 of 100 carbon atoms in the
average molecule are paraffinic and in side chains (S3).3 Best equation based on lowest standard error of estimate.
4 Best equation based on highest multiple correlation coefficient.
Based on the relation between atomic H/C and
the average aromaticity or hydroaromaticity of a
mixture of aromatic and hydroaromatic hydro-
carbons, the increase of coke-strength indices with
decreasing atomic H/C of the parent coal may
mean an increase of the indices with increasing
aromaticity or decreasing hydroaromaticity of the
average coking-coal molecule. Coal is considered
here as a mixture of polymeric molecules with
fundamental units of similar aromatic and hydro-
aromatic structures. The term "average molecule,"
whether of coal or of coke, refers to a hypothetical
molecule that has the average composition of these
units.
The dependence of coke strength upon the aro-
maticity of the average parent-coal molecule indi-
cates that the aromatic-hydroaromatic structure of
the coking-coal molecules may result in coke mole-
cules with a combination of binding forces that
affects the strength of the coke. Such binding
forces should be attributed to chemical bonds be-
tween atoms and van der Waals forces between
molecules. Crystalline structure may have only small
effects, if any, on the strength of 9000 C. cokes
from bituminous coals; these cokes are mainly
amorphous.
The regression coefficient signs for calorific value,
oxygen, volatile matter, and atomic O/C and H/O
in the linear correlations with coke-strength indices
also lend support to the hypothesis that coke
strength depends on the aromaticity of the parent
coal. Calorific value, which mainly depends on the
carbon content of coal, should have the same re-
gression coefficient sign as carbon. Oxygen and
volatile matter, both of which decrease with in-
creasing carbon (figs. 1-2), should have an op-
posite sign from that of carbon. Atomic O/C should
have the same sign as oxygen because the sign for
carbon is positive. Similarly, atomic H/O should
have a positive sign because signs for both hydro-
gen and oxygen are negative. All these signs are
15
Upcoming Pages
Here’s what’s next.
Search Inside
This report can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Report.
Wu, W. R. K. & Frederic, W. H. Coal Composition, Coal Plasticity, and Coke Strength, report, Date Unknown; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc12806/m1/19/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.