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134 Advanced Mine Ventilation

Table 9.5 Regression Analysis of Data on Respirable Dust Index (RDI)

Partial Correlation
Independent Variable Regression Coefficient Coefficient
Fixed carbon (DAF) 0.7138 0.4192
Fusain 0.1909 0.3924
Ash 0.1676 0.3473
Intercept 0.0204

fusain content, and ash percentage were the most significant independent variables in
that order. The results of regression analysis were as shown in Table 9.5.
Hence, log RDI ¼ 0.0204e0.1676 Ash þ0.7138 Fix C þ 0.1909 Fusain
Taking antilog on both sides:

0:714 0:191
0:95ðFixCÞ $ðFusainÞ
RDI ¼ (9.3)
0:168
ðAshÞ
where RDI ¼ Percentage yield of respirable dust; FixC ¼ Percentage fixed carbon
content (dry ash-free basis); Fusain ¼ Percentage fusain content; Ash ¼ Percentage of
ash content (dry).
The standard error of estimate is 13.6%.

9.6 Results of Similar, Subsequent Studies

Nearly 25 years after the original work done by Thakur [2], the same study was
repeated by Srikanth [7] and Jha [8]. Their findings were in agreement with Thakur
and reconfirmed all conclusions. A summary of their work is presented here for a
good comparison.

9.6.1 Srikanth’s Studies
Srikanth [7] used a jaw crusher to create 37 mm coal dust particles. Coal samples
were obtained from coal mines in addition to some samples from the same source
as Thakur’s samples. They used a Microtrac Standard Range Analyzer (SRA) and
Small Particle Analyser (SPA), which measured projected area (and hence diameter)
using laser scattering and diffraction, respectively. The data were combined and
plotted on a RosineRammler graph (discussed in Chapter 8). Their main findings
were as follows:

1. Higher rank coals produced more total dust (<15 mm) and respirable dust (<7 mm). Semian-
thracite coal produced 3.7 times more total dust and 4.2 times more respirable dust compared
with high-volatile bituminous coal.