Page 50 - New Trends In Coal Conversion

18 New Trends in Coal Conversion

methods for the analysis of coal have been developed to define the quality of the ma-
terial through chemical, petrographic, and empirical determinations. These enable the
producer to monitor variations in the quality of the product and the purchaser to assess
the suitability of marketed coal for specific process tests (Pajares and Díez, 2014).
As described in Ward and Su arez-Ruiz (2008) and in Pajares and Díez (2014), the
basic chemical parameters of a coal are moisture (knowledge of the total moisture con-
tent of a coal is essential for commercial activities), ash, volatile matter, and fixed car-
bon percentages, as determined by proximate analysis, and carbon, hydrogen,
nitrogen, sulfur, and oxygen contents obtained from an ultimate chemical analysis
(Fig. 1.10). Other analyses that may be carried out include determining the forms of
sulfur present in the coal (pyritic, sulphate, organic) and the carbon (or CO 2 ) content
derived from the carbonates. The chlorine content, which is mainly associated with
inorganic salts, and the phosphorous content can also be determined. Relatively
high proportions of chlorine in coals may give rise to corrosion during its utilization.
As for the phosphorous content, this is an undesirable element in coals to be used in the
steel industry.
Coal ash may be analyzed to determine the major and minor metal oxide content,
and the amount of certain trace elements, some of which could be potentially hazard-
ous, may also be evaluated. The ash composition influences coal (and ash) behavior
during its combustion in boilers where slagging and fouling can result. Large amounts
of iron, calcium, sodium, and potassium oxides can result in ashes with low ash fusion
temperatures. In coking coals, sodium and potassium oxides should not exceed a

Proximate analysis Petrographic analysis
Moisture Maceral composition
Ash Vitrinite reflectance
Volatile matter
Fixed C Swelling and caking
Elemental analysis Free-swelling index
Audibert-Arnu dilatometry
C, H, N, S, O
Ruhr dilatometry
Coal Gieseler plasticity
Ash composition
Sapozhnikov test
Roga test
Ash fusibility G caking index test
Gray-king assay
Fischer assay
Total moisture Coking pressure
Koppers test
Sole heated-oven test
Calorific value Movable wall oven
Size analysis Grindability
Hardgrove
Figure 1.10 Analysis and test for coal characterization.
Modified from Pajares, J.A., Díez, M.A., 2014. Coal and coke. In: Reedijk, J. (Ed.).
Encyclopedia reference module in chemistry, molecular sciences and chemical engineering.
Elsevier, Waltham, MA. 22 pp.