Gas Content: Analytical Method
The Analytical method is known as a simple method of indirectly estimating
the gas content of a coal seam, as it requires a small number of input
parameters. The formula used in the Analytical method is as follows:
Q=(100-% moisture -% ash)*1/100 *(0.75)[k(0.096 h)n– 0.14(1.8h/100+
1)]
Q = gas content, m3/t;
h = depth, m;
k & n = constants. The value of k varies from 5.7 to 20 cm3/g
and the n value ranges from 0.31 to 0.12 as shown in the following graph. The
values
of k & n can be obtained by using the ratio of fixed carbon to volatile matter
of coal in the seam. It can be seen that the estimate for the gas content using
this method is largely based on the saturation value for the coal and therefore
while this method is valid for large depths, it breaks down when it is applied
to seams lying at shallow depths.
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