Page 187 - Advances In Productive, Safe, and Responsible Coal Mining

166 Advances in Productive, Safe, and Responsible Coal Mining

value, increased sulfur and mercury contents, and increased transportation costs on a
MMBTU basis, as shown in the following computations:
Cost impact of higher ash content (lower heating value)
Cleaned seam-only ash content¼10% (12,960BTU/lb)
Increase in ash content due to OSD¼8%
Ash content with OSD¼10 1.08¼10.8% (12,845BTU/lb)
6
BTU reduction in 1ton of clean coal¼2000 (12,960 12,845)/10 ¼0.23MMBTU
Cost of BTU reduction¼0.23 $1.50¼$0.35/ton of clean coal
Increase in ash content in 1ton of clean coal¼0.008tons
Increased cost of transportation¼0.008tons $7/ton¼$0.06/ton of clean coal

Cost impact of higher sulfur content
Cleaned seam-only sulfur content¼2%
Increase in sulfur content due to OSD¼1.9%
Sulfur content with OSD¼2 1.019¼2.038%
Sulfur increase in 1ton of clean coal¼0.00038tons
Cost of sulfur increase¼0.00038 $390¼$0.15/ton of clean coal

Cost impact of higher mercury content
Cleaned seam-only Hg content¼0.10ppm
Increase in Hg content due to OSD¼3.8%
Hg content with OSD¼0.1 1.038¼0.1038ppm
6
Hg increase in 1ton of clean coal¼2000 (0.1038–0.1)/10 ¼0.0000076lbs
Cost of Hg increase¼0.0000076 $32,000¼$0.24/ton of clean coal

9.3.2.1 Overall cost impact due to quality impacts of OSD mining

The above cost impact computations add up to $0.79 per ton of clean coal. Considering
that coal preparation plants in Illinois average around 65% yield, the overall cost of
quality impacts translates into $1.22 per ton of ROM coal. Separating this cost into roof
and floor components is accomplished by realizing that ash- and transportation-related
impacts are applicable to both roof and floor dilution, which average 13.5% and 8.0%,
respectively (see Table 9.2, wt% column), while sulfur- and trace-element-related
impacts are associated primarily with roof OSD. This leads to the determination that
the cost of quality impacts is higher for roof OSD ($5.09 per ton of roof dilution versus
$1.26 per ton of floor dilution). From a purely economic perspective, this finding leads
to the recommendation that if mining height considerations require cutting out of seam
material, floor strata should be mined before roof strata.

9.3.2.2 Summary of OSD cost impacts
Overall, cost impact modeling results are shown in Table 9.4. Fig. 9.3 provides a
graphic representation of the same data. As noted previously, mining, processing,
and waste disposal cost estimates are taken from data generated in previously cited
studies [10, 11, 14]. Quality impact cost estimates developed by Patwardhan [2] were
described in the previous section of this chapter.