Page 437 - Advanced Mine Ventilation

406 Advanced Mine Ventilation

The concentration of CO in Rg is defined as:

ðCOÞs
ðCOÞ ¼ 100 (24.4)
Rg
Rg
where (CO)s is the concentration of CO in the original gas sample in percent.
Let us call (CO) Rg=Rg,R 1 .
Hence,

ðCOÞ ðCOÞs
Rg
R 1 ¼ 100 ¼ 2 100 (24.5)
Rg Rg

Rg
Based on experimental data, R 1 appears to be a function of only [7] and can
O 2
be expressed as:
1=2

Rg
R 1 ¼ 150 (24.6)
O 2
The upper limit of Rg is

1=2
Rg
R 1 ¼ 300 (24.7)
O 2
Eq. (24.7) is mostly used for safety.
Taking a logarithm on both sides of Eq. (24.7):

1 Rg
[nR 1 ¼ [n 300 [n (24.8)
2 O 2

A plot of Eq. (24.8) is shown in Fig. 24.1.
The Litton Ratio is defined as the ratio of R 1 (Eq. 24.5) derived from sealed area gas
sample to the upper limit of R 1 shown in Eq. (24.7) or:

1 ðCOÞs
R ¼ (24.9)
3 Rg 3=2 $O 2 1=2
If this value is greater than 1.00, ambient temperatures have not been reached.
Smoldering coal combustion at above-ambient temperature is likely to be in progress.
This condition is unsafe for mine entry or reopening of seals. If the ratio is less than
1.00 and continues to decline, then it is safe to assume that the fire is dead and ambient
equilibrium has been achieved. Table 24.2 shows some field data to illustrate the
conclusion [5].