Page 145 - Academic Press Encyclopedia of Physical Science and Technology 3rd Organic Chemistry

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Fuel Chemistry 255

TABLE II Compositional Analysis of Various Solid Fuels
Bituminous
Lignite, coal (hvAb), Anthracite,
Darco Subbituminous Upper Clarion Primrose Petroleum
Fuel component Wood a Peat a seam, TX b coal b seam b seam b Coke a

Moisture (as rec’d) 48.00 — 32.60 27.12 1.73 3.77 5.58
Volatile matter (d.b.) c 72.80 75.00 67.39 47.56 39.41 3.71 10.41
Fixed carbon (d.b.) 24.2 23.1 21.34 38.12 51.68 82.38 88.89
Ash (d.b) 3.00 2.70 11.27 14.32 8.91 13.91 0.71
Heating value (d.b) (Btu/lb) 9,030 8,650 11,375 10,842 13,390 12,562 15,033
Carbon 55.00 8,650 74.90 73.88 83.67 96.65 88.64
Hydrogen 5.77 5.60 4.58 6.28 5.33 1.25 3.56
Nitrogen 0.10 0.70 1.75 1.22 1.46 0.78 1.61
Sulfur 0.10 0.17 0.78 1.78 4.82 0.52 5.89
Oxygen 39.10 40.10 18.78 18.62 9.54 1.32 0.30
a
C, H, N, S, and O are given on a dry ash free basis.
b
C, H, N, S, and O are given on a dry mineral matter free basis.
c
Dry basis.
requires higher pressures and temperatures in excess of uses the dry, mineral matter-free volatile matter to classify
200 C. The higher temperatures are encountered when coals above the rank of medium volatile bituminous. For
◦
there is a magma nearby in the ground, and high lateral coals with greater than 69% volatile matter, the method
pressures are encountered where land masses collide lead- uses the moist (containing natural bed moisture but not
ing to the formation of mountains. Both of these scenarios surface moisture), mineral matter-free calorific value to
lead to the formation of anthracites. The nature of the con- classify coals below the rank of high volatile bituminous.
stituents in coal is related to the degree of coalification, The moisture content is obtained by heating an air-dried
the measurement of which is termed rank. Coals may be coal sample at 105–110 C under specified conditions un-
◦
classified according to (1) rank, based on the degree of til a constant weight is obtained. The moisture content, in
coalification; (2) type, based on megascopic and micro- general, increases with decreasing rank and ranges from 1
scopic observations (physical appearance) that recognize to 40% for the various ranks of coal. The moisture content
differences in the proportion and distribution of various is an important factor in both the storage and the utiliza-
macerals and minerals; and (3) grade, based on value for tion behavior of coals. The presence of moisture adds un-
a specific use. Typical properties of these solid fuels are necessary weight during transportation, reduces the avail-
shown in Table II. able heat consuming latent heat of vaporization, and poses

TABLE III Important Properties for Utilization
II. PROPERTIES FOR UTILIZATION
Property Factors affecting
Coals vary widely from place and to place, and sometimes
Compositional analysis Proximate analysis
even within a few feet in a particular seam because of
Ultimate analysis
the nature of the precursor material and the depositional
Heating value
environment. Therefore, coals and other solid fuels are
Grindability Coal rank
analyzed for certain important properties for utilization
Moisture
(summarized in Table III).
Ash
Coal rank is usually determined from an empirical anal-
Combustibility Proximate analysis
ysiscalledtheproximateanalysisandcalorificvalueorop-
Surface area
tical reflectance of vitrinite. The proximate analysis con-
Porosity
sists of determination of moisture, volatile matter, and ash
Petrographic Analysis
contents, and, by difference from 100%, the fixed car-
Inorganic constituents Associated with the organic structure
bon content of a coal. The American Society for Testing
Discrete inorganic minerals
and Materials (ASTM) method of classification of coals